1. Field of the Invention
This invention relates to a method and apparatus for displaying fluorescence information, wherein excitation light is irradiated to a region of interest in a living body, intrinsic fluorescence produced by an intrinsic dye in the living body is detected, and information in accordance with characteristics of the intrinsic fluorescence is displayed.
2. Description of the Related Art
There have heretofore been proposed fluorescence information displaying techniques utilizing characteristics such that, in cases where excitation light having wavelengths falling within an excitation wavelength range for an intrinsic dye in a living body is irradiated to the living body, an intensity of fluorescence produced by the intrinsic dye in the living body varies for normal tissues and diseased tissues. With the proposed fluorescence information displaying techniques, excitation light having predetermined wavelengths is irradiated to a region of interest in a living body, the fluorescence produced by an intrinsic dye in the living body is detected, and the location and the infiltration range of diseased tissues are displayed as a fluorescence image.
Ordinarily, when excitation light is irradiated to a region of interest in a living body, the fluorescence having a high intensity is produced by normal tissues, and the fluorescence having a low intensity is produced by diseased tissues. Therefore, by measurement of the fluorescence intensity, a judgment as to the state of a disease is capable of being made.
Basically, apparatuses for displaying fluorescence information comprise excitation light irradiating means for irradiating excitation light, which has wavelengths falling within an excitation wavelength range for an intrinsic dye in a living body, to the living body, imaging means for detecting fluorescence produced by the intrinsic dye in the living body and forming a fluorescence image of the living body, and image displaying means for receiving the output from the imaging means and displaying the fluorescence image. In many cases, the apparatuses for displaying fluorescence information take on the form built in endoscopes, which are inserted into the body cavities, colposcopes, operating microscopes, or the like.
However, the aforesaid apparatuses for displaying fluorescence information have the problems described below. Specifically, since a region in a living body has protrusions and recesses, the distance between the light source of the excitation light irradiating means and the region of interest in the living body is not uniform. Therefore, ordinarily, the irradiance of the excitation light at the living body portion, which is exposed to the excitation light, is non-uniform. The intensity of fluorescence is approximately in proportion to the irradiance of the excitation light, and the irradiance of the excitation light at the portion, which is exposed to the excitation light, is in inverse proportion to the square of the distance between the light source of the excitation light irradiating means and the portion, which is exposed to the excitation light. Accordingly, the problems occur in that diseased tissues, which are located close to the light source, produce the fluorescence having a higher intensity than the intensity of the fluorescence produced by normal tissues, which are located remote from the light source. The problems also occur in that the intensity of the fluorescence from normal tissues, which are located at a position inclined with respect to the excitation light, becomes markedly low. Thus if the irradiance of the excitation light is non-uniform, the intensity of the fluorescence will vary in accordance with the level of the irradiance of the excitation light, and therefore an error will often be made in the judgment of the state of a disease.
A fluorescence imaging technique has been proposed in, for example, xe2x80x9cFluorescence Imaging of Early Lung Cancer,xe2x80x9d Annual International Conference of the IEEE Engineering in Medicine and Biology Society, Vol. 12, No. 3, 1990. With the proposed technique, the fluorescence, which is produced by an intrinsic dye in an region of interest in a living body when the region of interest is exposed to excitation light, is separated into an intensity of the green wavelength region (hereinbelow referred to as the xe2x80x9cgreen region intensity Gxe2x80x9d) and an intensity of the red wavelength region (hereinbelow referred to as the xe2x80x9cred region intensity Rxe2x80x9d). An image operation is then performed in accordance with division of the red region intensity R and the green region intensity G by each other, and the results of the division are displayed. The proposed technique utilizes the findings in that the spectrum of the fluorescence produced by normal tissues is different from the spectrum of the fluorescence produced by diseased tissues. Specifically, when the spectrum of the fluorescence, which is produced by the intrinsic dye at normal tissues in the living body, and the spectrum of the fluorescence, which is produced by the intrinsic dye at diseased tissues in the living body, are compared with each other, in particular, the intensity of the green region of the spectrum obtained from the diseased tissues is markedly lower than the intensity of the green region of the spectrum obtained from the normal tissues. Therefore, the degree of reduction in the intensity of the green region intensity G of the fluorescence, which is produced from the diseased tissues, as compared with the intensity of the green region intensity G of the fluorescence produced from the normal tissues, is markedly higher than the degree of reduction in the intensity of the red region intensity R of the fluorescence, which is produced from the diseased tissues, as compared with the intensity of the red region intensity R of the fluorescence produced from the normal tissues. Therefore, only the fluorescence from the diseased tissues can be specifically extracted by the division of R/G and can be displayed as an image.
Specifically, with the proposed technique, the term of the fluorescence intensity depending upon the distance between the excitation light source and the region of interest in the living body and the distance between the region of interest in the living body and the fluorescence receiving means is canceled, and information reflecting only the difference in fluorescence spectrum pattern is obtained.
However, heretofore, research has not been conducted sufficiently with respect to a combination of detection wavelengths, at which the difference between the pattern of a fluorescence spectrum obtained from normal tissues and the pattern of a fluorescence spectrum obtained from diseased tissues occurs markedly. Therefore, there have been the problems in that a desirable combination of detection wavelengths cannot be presented with numerical values.
The primary object of the present invention is to provide a method of displaying fluorescence information, wherein fluorescence components having two different wavelengths are extracted from fluorescence, the two different wavelengths having been specified with numerical values as an appropriate combination of detection wavelengths, at which a difference between a pattern of a fluorescence spectrum obtained from normal tissues and a pattern of a fluorescence spectrum obtained from diseased tissues occurs markedly, light intensities of the extracted fluorescence components are detected, and information in accordance with a ratio between the light intensities of the extracted fluorescence components is displayed with a high reliability.
Another object of the present invention is to provide a method of displaying fluorescence information, wherein fluorescence components having wavelengths falling within a certain wavelength region are extracted from fluorescence, the certain wavelength region having been specified with numerical values as an appropriate detection wavelength region, at which a difference between a fluorescence intensity of fluorescence produced from normal tissues and a fluorescence intensity of fluorescence produced from diseased tissues occurs markedly, a light intensity of the extracted fluorescence components is detected, and information in accordance with the detected light intensity is displayed with a high reliability.
The specific object of the present invention is to provide an apparatus for carrying out the method of displaying fluorescence information.
The present invention provides a first method of displaying fluorescence information, comprising the steps of:
i) irradiating excitation light to a measuring site in a living body, the excitation light causing the measuring site to produce fluorescence,
ii) detecting light intensity of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a predetermined wavelength region containing 480 nm,
iii) detecting light intensity of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a predetermined wavelength region containing either one of 630 nm and 700 nm, and
iv) displaying information in accordance with a ratio between the two detected light intensities.
The present invention also provides a first apparatus for displaying fluorescence information, comprising:
i) excitation light irradiating means for irradiating excitation light to a measuring site in a living body, the excitation light causing the measuring site to produce fluorescence,
ii) first fluorescence intensity detecting means for detecting light intensity of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a predetermined wavelength region containing 480 nm,
iii) second fluorescence intensity detecting means for detecting light intensity of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a predetermined wavelength region containing either one of 630 nm and 700 nm, and
iv) displaying means for displaying information in accordance with a ratio between the light intensity, which has been detected by the first fluorescence intensity detecting means, and the light intensity, which has been detected by the second fluorescence intensity detecting means.
The first apparatus for displaying fluorescence information in accordance with the present invention should preferably be modified such that the first fluorescence intensity detecting means comprises:
first wavelength selecting means for selecting the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within the predetermined wavelength region containing 480 nm, and
first light intensity detecting means for detecting the light intensity of the fluorescence components having been selected by the first wavelength selecting means, and
the second fluorescence intensity detecting means comprises:
second wavelength selecting means for selecting the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within the predetermined wavelength region containing either one of 630 nm and 700 nm, and
second light intensity detecting means for detecting the light intensity of the fluorescence components having been selected by the second wavelength selecting means.
Also, the first apparatus for displaying fluorescence information in accordance with the present invention should more preferably be modified such that the first wavelength selecting means selects the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within the predetermined wavelength region of 480 nmxc2x1at most 70 nm, and
the second wavelength selecting means selects the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within the predetermined wavelength region of either one of 630 nmxc2x1at most 70 nm and 700 nmxc2x1at most 70 nm.
Further, in the first apparatus for displaying fluorescence information in accordance with the present invention, the excitation light should preferably have wavelengths falling within the range of 380 nm to 420 nm, which range is apart from the characteristic peak light intensity of the fluorescence produced from normal tissues of the living body. Furthermore, in the first apparatus for displaying fluorescence information in accordance with the present invention, the excitation light irradiating means should preferably be a GaN type of semiconductor laser.
The first apparatus for displaying fluorescence information in accordance with the present invention may be constituted so as to two-dimensionally detect a fluorescence image. Alternatively, the first apparatus for displaying fluorescence information in accordance with the present invention may be constituted so as to detect the fluorescence intensity with respect to each point at a site in the living body.
Also, in the first apparatus for displaying fluorescence information in accordance with the present invention, by way of example, each of the first wavelength selecting means and the second wavelength selecting means may be constituted so as to extract the fluorescence components, which have wavelengths falling within the predetermined wavelength region, with a dichroic mirror, or the like. Alternatively, each of the first wavelength selecting means and the second wavelength selecting means may be constituted so as to extract the fluorescence components, which have wavelengths falling within the predetermined wavelength region, in a time division mode by changing over an optical filter, or the like. As another alternative, in cases where a fluorescence image is to be detected two-dimensionally, each of the first wavelength selecting means and the second wavelength selecting means may be constituted so as to extract the fluorescence components, which have wavelengths falling within the predetermined wavelength region, by utilizing-a mosaic filter formed by connecting optical filters with one another in a mosaic pattern.
Further, in the first apparatus for displaying fluorescence information in accordance with the present invention, the displaying means may employ one of various displaying techniques. For example, the displaying means may be constituted so as to display the ratio between the light intensity of the fluorescence components, which have wavelengths falling within the predetermined wavelength region containing 480 nm, and the light intensity of the fluorescence components, which have wavelengths falling within the predetermined wavelength region containing either one of 630 nm and 700 nm, on a monitor, with a printer, or the like. Alternatively, the displaying means may be constituted so as to alter the tint or the luminance of the displayed color in accordance with the ratio between the two light intensities.
The present invention further provides a second method of displaying fluorescence information, comprising the steps of:
i) irradiating excitation light to a measuring site in a living body, the excitation light causing the measuring site to produce fluorescence,
ii) detecting light intensity B of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a wavelength region of 480 nmxc2x1at most 70 nm and at least containing 450 nm to 480 nm, and
iii) displaying information in accordance with the light intensity B.
The present invention still further provides a third method of displaying fluorescence information, comprising the steps of:
i) irradiating excitation light to a measuring site in a living body, the excitation light causing the measuring site to produce fluorescence,
ii) detecting light intensity W of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within an entire measurement wavelength region,
iii) detecting at least one light intensity selected from among:
light intensity Bxe2x80x2 of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a wavelength region of 480 nmxc2x1at most 70 nm and at least containing 450 nm to 480 nm,
light intensity R1 of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a wavelength region of 630 nmxc2x1at most 70 nm and at least containing 600 nm to 630 nm, and
light intensity R2 of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a wavelength region of 700 nmxc2x1at most 70 nm and at least containing 700 nm to 710 nm, and
iv) displaying information in accordance with a ratio between the at least one selected light intensity and the light intensity W.
The present invention also provides a fourth method of displaying fluorescence information, comprising the steps of:
i) irradiating excitation light to a measuring site in a living body, the excitation light causing the measuring site to produce fluorescence,
ii) detecting light intensity B of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a wavelength region of 480 nmxc2x1at most 70 nm and at least containing 450 nm to 480 nm,
iii) detecting light intensity W of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within an entire measurement wavelength region,
iv) detecting at least one light intensity selected from among:
light intensity Bxe2x80x2 of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a wavelength region of 480 nmxc2x1at most 70 nm and at least containing 450 nm to 480 nm,
light intensity R1 of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a wavelength region of 630 nmxc2x1at most 70 nm and at least containing 600 nm to 630 nm, and
light intensity R2 of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a wavelength region of 700 nmxc2x1at most 70 nm and at least containing 700 nm to 710 nm, and
v) displaying information in accordance with the light intensity B and a ratio between the at least one light intensity, which is selected from among the light intensities Bxe2x80x2, R1, and R2, and the light intensity W.
In the third and fourth methods of displaying fluorescence information in accordance with the present invention, in cases where the light intensity Bxe2x80x2 is detected as the at least one light intensity, the light intensity Bxe2x80x2 may be the light intensity of the fluorescence components having wavelengths falling within the wavelength region identical with the wavelength region of the fluorescence components, whose light intensity is detected as the light intensity B. Alternatively, the light intensity Bxe2x80x2 may be the light intensity of the fluorescence components having wavelengths falling within the wavelength region different from the wavelength region of the fluorescence components, whose light intensity is detected as the light intensity B. In the former cases, instead of the light intensity Bxe2x80x2 being detected besides the light intensity B, the light intensity B may be employed as the light intensity Bxe2x80x2. The term xe2x80x9cdetecting light intensity Bxe2x80x2 xe2x80x9d as used herein also includes the cases where the light intensity B is employed as the light intensity Bxe2x80x2.
The present invention further provides a second apparatus for displaying fluorescence information, comprising:
i) excitation light irradiating means for irradiating excitation light to a measuring site in a living body, the excitation light causing the measuring site to produce fluorescence,
ii) first light intensity detecting means for detecting light intensity B of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a wavelength region of 480 nmxc2x1at most 70 nm and at least containing 450 nm to 480 nm, and
iii) fluorescence information displaying means for displaying information in accordance with the light intensity B having been detected by the first light intensity detecting means.
The present invention still further provides a third apparatus for displaying fluorescence information, comprising:
i) excitation light irradiating means for irradiating excitation light to a measuring site in a living body, the excitation light causing the measuring site to produce fluorescence,
ii) second light intensity detecting means for detecting light intensity W of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within an entire measurement wavelength region,
iii) at least one light intensity detecting means selected from among:
third light intensity detecting means for detecting light intensity Bxe2x80x2 of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a wavelength region of 480 nmxc2x1at most 70 nm and at least containing 450 nm to 480 nm,
fourth light intensity detecting means for detecting light intensity R1 of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a wavelength region of 630 nmxc2x1at most 70 nm and at least containing 600 nm to 630 nm, and
fifth light intensity detecting means for detecting light intensity R2 of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a wavelength region of 700 nmxc2x1at most 70 nm and at least containing 700 nm to 710 nm, and
iv) fluorescence information displaying means for displaying information in accordance with a ratio between the light intensity, which has been detected by the at least one selected light intensity detecting means, and the light intensity W.
The present invention also provides a fourth apparatus for displaying fluorescence information, comprising:
i) excitation light irradiating means for irradiating excitation light to a measuring site in a living body, the excitation light causing the measuring site to produce fluorescence,
ii) first light intensity detecting means for detecting light intensity B of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a wavelength region of 480 nmxc2x1at most 70 nm and at least containing 450 nm to 480 nm,
iii) second light intensity detecting means for detecting light intensity W of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within an entire measurement wavelength region,
iv) at least one light intensity detecting means selected from among:
third light intensity detecting means for detecting light intensity Bxe2x80x2 of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a wavelength region of 480 nmxc2x1at most 70 nm and at least containing 450 nm to 480 nm,
fourth light intensity detecting means for detecting light intensity R1 of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a wavelength region of 630 nmxc2x1at most 70 nm and at least containing 600 nm to 630 nm, and
fifth light intensity detecting means for detecting light intensity R2 of fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a wavelength region of 700 nmxc2x1at most 70 nm and at least containing 700 nm to 710 nm, and
v) fluorescence information displaying means for displaying information in accordance with the light intensity B and a ratio between the light intensity, which has been detected by the at least one selected light intensity detecting means, and the light intensity W.
In the third and fourth apparatuses for displaying fluorescence information in accordance with the present invention, in cases where the third light intensity detecting means is provided as the at least one light intensity detecting means, the third light intensity detecting means may be identical with the first light intensity detecting means. Alternatively, the third light intensity detecting means may be different from the first light intensity detecting means. In the former cases, instead of the third light intensity detecting means being provided besides the first light intensity detecting means, the first light intensity detecting means may be utilized as the third light intensity detecting means. The term xe2x80x9ccomprising third light intensity detecting meansxe2x80x9d as used herein also includes the cases where the first light intensity detecting means is utilized as the third light intensity detecting means.
The second, third, and fourth apparatuses for displaying fluorescence information in accordance with the present invention should preferably be modified such that the light intensity detecting means comprises an image sensor for two-dimensionally detecting the fluorescence produced by the measuring site and forming a fluorescence image, and wavelength selecting means for selecting the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a desired wavelength region.
Also, the second, third, and fourth apparatuses for displaying fluorescence information in accordance with the present invention may be modified such that the light intensity detecting means is provided with fluorescence acquiring means for acquiring the fluorescence, which is produced by a single point at a site in the living body.
Further, in the second, third, and fourth apparatuses for displaying fluorescence information in accordance with the present invention, the excitation light should preferably have wavelengths falling within the range of 380 nm to 420 nm, which range is apart from the characteristic peak light intensity of the fluorescence produced from normal tissues of the living body. Furthermore, in the second, third, and fourth apparatuses for displaying fluorescence information in accordance with the present invention, the excitation light irradiating means should preferably be a GaN type of semiconductor laser.
Furthermore, in the second, third, and fourth apparatuses for displaying fluorescence information in accordance with the present invention, the fluorescence information displaying means may employ one of various displaying techniques. For example, in cases where the light intensity of the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within a predetermined wavelength region containing 480 nm, and the light intensity of the fluorescence components of the fluorescence, which fluorescence components have wavelengths falling within the entire measurement wavelength region, are detected and the information in accordance with the ratio between the two detected light intensities are displayed, the fluorescence information displaying means may be constituted so as to display the ratio between the two detected light intensities on a monitor, with a printer, or the like. Alternatively, the fluorescence information displaying means may be constituted so as to alter the tint or the luminance of the displayed color in accordance with the ratio between the two detected light intensities.
The first method of displaying fluorescence information and the first apparatus for displaying fluorescence information in accordance with the present invention have the effects described below.
When the excitation light is irradiated to living body tissues, the living body tissues are excited by the excitation light and produce the fluorescence having a spectrum illustrated in FIG. 5. It is assumed that the thus produced fluorescence results from superposition of the fluorescence produced by various kinds of intrinsic dyes in the living body, such as FAD, collagen, fibronectin, and porphyrin. FIG. 5 shows typical fluorescence spectra of the fluorescence produced from normal tissues and the fluorescence produced from diseased tissues, which fluorescence spectra have been measured by the inventors.
As illustrated in FIG. 5, the level and the pattern of the spectrum of the fluorescence vary for the normal tissues and the diseased tissues. The level of the fluorescence produced from the normal tissues is high as a whole, and the level of the fluorescence produced from the diseased tissues is low as a whole. The fluorescence spectrum obtained from the normal tissues has a peak spectral intensity at a region in the vicinity of 480 nm, which region is a blue region. The fluorescence spectrum obtained from the diseased tissues has a peak spectral intensity at a region in the vicinity of 630 nm, which region is a red region, and a peak spectral intensity at a region in the vicinity of 700 nm.
FIG. 6 is a graph showing a distribution of ratios of spectral intensities at respective wavelengths of a fluorescence spectrum, which is obtained from normal tissues, to a spectral intensity of an entire measurement wavelength region width, which spectral intensity is taken as 1, and a distribution of ratios of spectral intensities at respective wavelengths of a fluorescence spectrum, which is obtained from diseased tissues, to a spectral intensity of the entire measurement wavelength region width, which spectral intensity is taken as 1. As illustrated in FIG. 6, the distributions of the spectral intensity ratios more clearly manifest the difference between the pattern of the fluorescence spectrum of the fluorescence produced from the normal tissues and the pattern of the fluorescence spectrum of the fluorescence produced from the diseased tissues.
In accordance with FIG. 5 and FIG. 6, the inventors studied about an appropriate combination of detection wavelengths, at which the difference between the pattern of the fluorescence spectrum obtained from the normal tissues and the pattern of the fluorescence spectrum obtained from the diseased tissues occurs markedly.
As a result, it has been found that, in cases where the light intensity at the wavelength region in the vicinity of 480 nm and the light intensity at the wavelength region in the vicinity of 630 nm or in the vicinity of 700 nm are detected, the ratio between the two detected light intensities markedly represents the difference between the pattern of the fluorescence spectrum obtained from the normal tissues and the pattern of the fluorescence spectrum obtained from the diseased tissues.
Specifically, the light intensity at the predetermined wavelength region containing 480 nm, at which a high light intensity is obtained characteristically from the normal tissues, and the light intensity at the predetermined wavelength region containing 630 nm or 700 nm, at which a high light intensity is obtained characteristically from the diseased tissues, are detected from the fluorescence having been detected from the measuring site, whose tissue state is unknown. Also, the information in accordance with the ratio between the two detected light intensities is displayed. In such cases, a person, who sees the displayed information, is capable of presuming whether the tissues at the measuring site are the normal tissues or the diseased tissues.
As described above, with the first method of displaying fluorescence information and the first apparatus for displaying fluorescence information in accordance with the present invention, the excitation light is irradiated to the measuring site in the living body, the excitation light causing the measuring site to produce the fluorescence. Also, the light intensity of the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within the predetermined wavelength region containing 480 nm, is detected. Further, the light intensity of the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within the predetermined wavelength region containing either one of 630 nm and 700 nm. Thereafter, the information in accordance with the ratio between the two detected light intensities is displayed. Therefore, with the first method of displaying fluorescence information and the first apparatus for displaying fluorescence information in accordance with the present invention, the information having enhanced reliability is capable of being displayed.
In the first apparatus for displaying fluorescence information in accordance with the present invention, the first fluorescence intensity detecting means may comprise the first wavelength selecting means for selecting the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within the predetermined wavelength region containing 480 nm, and the first light intensity detecting means for detecting the light intensity of the fluorescence components having been selected by the first wavelength selecting means. Also, the second fluorescence intensity detecting means may comprise the second wavelength selecting means for selecting the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within the predetermined wavelength region containing either one of 630 nm and 700 nm, and the second light intensity detecting means for detecting the light intensity of the fluorescence components having been selected by the second wavelength selecting means. With the thus modified first apparatus for displaying fluorescence information in accordance with the present invention, the light intensity at each of the predetermined wavelength regions is capable of being detected easily.
Also, from the results of analysis made on the fluorescence spectra illustrated in FIG. 5 and FIG. 6, it has been found that, if the width of the predetermined wavelength region containing 480 nm is broader than 480 nmxc2x170 nm, the ratio of the light intensity at the predetermined wavelength region detected from the diseased tissues to the light intensity at the predetermined wavelength region detected from the normal tissues will become high. Further, it has been found that, if the width of the predetermined wavelength region containing 630 nm is broader than 630 nm xc2x170 nm, or if the width of the predetermined wavelength region containing 700 nm is broader than 700 nmxc2x170 nm, the ratio of the light intensity at the predetermined wavelength region detected from the diseased tissues to the light intensity at the predetermined wavelength region detected from the normal tissues will become low. Therefore, with the first apparatus for displaying fluorescence information in accordance with the present invention, wherein the first wavelength selecting means selects the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within the predetermined wavelength region of 480 nm xc2x1at most 70 nm, and the second wavelength selecting means selects the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within the predetermined wavelength region of either one of 630 nmxc2x1at most 70 nm and 700 nmxc2x1at most 70 nm, the light intensity ratio having reliability enhanced even further is capable of being obtained.
Further, with the first apparatus for displaying fluorescence information in accordance with the present invention, wherein the excitation light has wavelengths falling within the range of 380 nm to 420 nm that is apart from the region in the vicinity of 480 nm, at which the light intensity of the fluorescence produced from the normal tissues becomes characteristically high, the fluorescence having the fluorescence spectrum of a desirable pattern is capable of being produced, and therefore the reliability of the displayed information is capable of being enhanced. Furthermore, with the first apparatus for displaying fluorescence information in accordance with the present invention, wherein the GaN type of semiconductor laser is employed as the excitation light irradiating means, the size of the apparatus is capable of being kept small, and the cost of the apparatus is capable of being kept low.
The second, third, and fourth methods of displaying fluorescence information and the second, third, and fourth apparatuses for displaying fluorescence information in accordance with the present invention have the effects described below.
As illustrated in FIG. 5, the level and the pattern of the spectrum of the fluorescence vary for the normal tissues and the diseased tissues. The level of the intrinsic fluorescence produced from the normal tissues is high as a whole, and the level of the intrinsic fluorescence produced from the diseased tissues is low as a whole. The fluorescence spectrum obtained from the normal tissues has a peak spectral intensity at a region in the vicinity of 480 nm, which region is the blue region. However, at the region in the vicinity of 480 nm, only slight fluorescence is produced from the diseased tissues. From FIG. 5, it can be found that the wavelengths, at which the difference between the spectral intensity of the fluorescence spectrum obtained from the normal tissues and the spectral intensity of the fluorescence spectrum obtained from the diseased tissues occurs markedly, are the wavelengths in the vicinity of 480 nm, and the wavelength of 480 nm is desirable as the center wavelength of the detection wavelengths.
Also, in experiments made by the inventors and with respect to a plurality of patients, fluorescence spectra of the fluorescence produced from diseased tissues and the fluorescence produced from normal tissues located in the vicinity of the diseased tissues were detected. Thereafter, from each of the fluorescence spectra, light intensities at various measurement wavelength regions having different widths and having their centers at 480 nm were calculated. With respect to each of the widths of the measurement wavelength regions, the ratio of the light intensity of the fluorescence produced from the diseased tissues to the light intensity of the fluorescence produced from the normal tissues was calculated. From the calculations, the results shown in FIG. 11 were obtained.
From the results shown in FIG. 11, it can be found that, in cases where the width of the measurement wavelength region is at most 100 nm, i.e. in cases where the measurement wavelength region is 480 nm at most 50 nm, little change occurs in the ratio of the light intensity of the fluorescence produced from the diseased tissues to the light intensity of the fluorescence produced from the normal tissues. Also, it can be found that, in cases where the width of the measurement wavelength region is 150 nm, the ratio of the light intensity of the fluorescence produced from the diseased tissues to the light intensity of the fluorescence produced from the normal tissues becomes high and close to 1, and the contrast between the fluorescence produced from the normal tissues and the fluorescence produced from the diseased tissues becomes low. Therefore, it can be found desirable to extract the fluorescence components having wavelengths falling within the wavelength region width of at most 140 nm around the wavelength of 480 nm, i.e. the wavelengths falling within the wavelength region of 480 nmxc2x1at most 70 nm, at which wavelength region little increase occurs with the ratio of the light intensity of the fluorescence produced from the diseased tissues to the light intensity of the fluorescence produced from the normal tissues.
Further, from the results of experiments, it has been found that the wavelength corresponding to the peak spectral intensity in the fluorescence spectrum often varies slightly for different persons and different measuring sites in a single person, and therefore the light intensity at the wavelength region, which at least contains 450 nm to 480 nm, should be detected.
FIG. 6 shows the distribution of ratios of spectral intensities at respective wavelengths of the fluorescence spectrum, which is obtained from the normal tissues, to the spectral intensity of the entire measurement wavelength region width, which spectral intensity is taken as 1, and the distribution of ratios of spectral intensities at respective wavelengths of the fluorescence spectrum, which is obtained from the diseased tissues, to the spectral intensity of the entire measurement wavelength region width, which spectral intensity is taken as 1. In cases where the ratios of the spectral intensities at respective wavelengths of the fluorescence spectrum to the spectral intensity of the entire measurement wavelength region width are calculated, adverse effects of a difference in measurement conditions, such as a measurement distance, can be eliminated. Therefore, the distributions of the spectral intensity ratios manifest the difference between the pattern of the fluorescence spectrum of the fluorescence produced from the normal tissues and the pattern of the fluorescence spectrum of the fluorescence produced from the diseased tissues. The fluorescence spectrum obtained from the normal tissues has the peak spectral intensity at the region in the vicinity of 480 nm. The fluorescence spectrum obtained from the diseased tissues has the peak spectral intensity at the region in the vicinity of 630 nm, and the peak spectral intensity at the region in the vicinity of 700 nm.
In accordance with FIG. 6, the inventors studied about measurement wavelengths and measurement wavelength region width, at which the difference between the pattern of the fluorescence spectrum obtained from the normal tissues and the pattern of the fluorescence spectrum obtained from the diseased tissues occurs markedly. The study was made in the same manner as that described above and by setting the center wavelengths at 480 nm, 630 nm, and 700 nm. FIG. 12 shows the results obtained from experiments, in which the center wavelength was set at 480 nm, the measurement wavelength region width was set at various different values, the ratio of the light intensity of each measurement wavelength region width to the light intensity of the entire measurement wavelength region width was calculated with respect to each of the fluorescence produced from the normal tissues and the fluorescence produced from the diseased tissues, and the ratio of the thus calculated light intensity ratio for the diseased tissues to the thus calculated light intensity ratio for the normal tissues was calculated.
As a result, from the study made with the spectral intensity ratio distribution, as in the study made with the spectral intensity distribution, in cases where the center wavelength is 480 nm, it has been found desirable to extract the fluorescence components having wavelengths falling within the wavelength region width of at most 140 nm around the wavelength of 480 nm, i.e. the wavelengths falling within the wavelength region of 480 nmxc2x1at most 70 nm and at least containing 450 nm to 480 nm, at which wavelength region little increase occurs with the ratio of the light intensity of the fluorescence produced from the diseased tissues to the light intensity of the fluorescence produced from the normal tissues and the contrast between the fluorescence produced from the normal tissues and the fluorescence produced from the diseased tissues does not become low.
Also, though not shown, in cases where the center wavelength is set at 630 nm, it has been found desirable to extract the fluorescence components having wavelengths falling within the wavelength region of 630 nmxc2x1at most 70 nm and at least containing 600 nm to 630 nm. Further, in cases where the center wavelength is set at 700 nm, it has been found desirable to extract the fluorescence components having wavelengths falling within the wavelength region of 700 nmxc2x1at most 70 nm and at least containing 700 nm to 710 nm.
Specifically, the fluorescence components having the wavelengths falling within the wavelength region described above are extracted from the fluorescence having been detected from the measuring site, whose tissue state is unknown, and the light intensity of the extracted fluorescence components is detected. Also, the information in accordance with the detected light intensity is displayed. In such cases, a person, who sees the displayed information, is capable of accurately presuming whether the tissues at the measuring site are the normal tissues or the diseased tissues.
As described above, with the second method of displaying fluorescence information and the second apparatus for displaying fluorescence information in accordance with the present invention, the excitation light is irradiated to the measuring site in the living body, the excitation light causing the measuring site to produce the fluorescence. Also, the light intensity B of the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within the wavelength region of 480 nm xc2x1at most 70 nm and at least containing 450 nm to 480 nm, is detected. Further, the information in accordance with the light intensity B is displayed. Therefore, with the second method of displaying fluorescence information and the second apparatus for displaying fluorescence information in accordance with the present invention, the information having enhanced reliability is capable of being displayed.
With the third method of displaying fluorescence information and the third apparatus for displaying fluorescence information in accordance with the present invention, the excitation light is irradiated to the measuring site in the living body, the excitation light causing the measuring site to produce the fluorescence. Also, the light intensity W of the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within the entire measurement wavelength region, is detected. Further, at least one light intensity is detected, the at least one light intensity being selected from among the light intensity Bxe2x80x2 of the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within the wavelength region of 480 nmxc2x1at most 70 nm and at least containing 450 nm to 480 nm, the light intensity R1 of the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within the wavelength region of 630 nm xc2x1at most 70 nm and at least containing 600 nm to 630 nm, and the light intensity R2 of the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within the wavelength region of 700 nmxc2x1at most 70 nm and at least containing 700 nm to 710 nm. Furthermore, the information in accordance with the ratio between the at least one selected light intensity and the light intensity W is displayed. Therefore, with the third method of displaying fluorescence information and the third apparatus for displaying fluorescence information in accordance with the present invention, adverse effects of fluctuations in spectral intensity due to fluctuations in measurement conditions, such as the measurement distance and the measurement angle, are capable of being reduced, and the information having enhanced reliability, which represents the feature of the spectrum pattern, is capable of being displayed.
With the fourth method of displaying fluorescence information and the fourth apparatus for displaying fluorescence information in accordance with the present invention, the excitation light is irradiated to the measuring site in the living body, the excitation light causing the measuring site to produce the fluorescence. Also, the light intensity B of the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within the wavelength region of 480 nmxc2x1at most 70 nm and at least containing 450 nm to 480 nm, is detected. Further, the light intensity W of the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within the entire measurement wavelength region, is detected. Furthermore, at least one light intensity is detected, the at least one light intensity being selected from among the light intensity Bxe2x80x2 of the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within the wavelength region of 480 nmxc2x1at most 70 nm and at least containing 450 nm to 480 nm, the light intensity R1 of the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within the wavelength region of 630 nm xc2x1at most 70 nm and at least containing 600 nm to 630 nm, and the light intensity R2 of the fluorescence components of the fluorescence produced by the measuring site, which fluorescence components have wavelengths falling within the wavelength region of 700 nmxc2x1at most 70 nm and at least containing 700 nm to 710 nm. Also, the information in accordance with the light intensity B and the ratio between the at least one light intensity, which is selected from among the light intensities Bxe2x80x2, R1, and R2, and the light intensity W is displayed. Therefore, with the fourth method of displaying fluorescence information and the fourth apparatus for displaying fluorescence information in accordance with the present invention, the information having enhanced reliability, which represents the characteristics of the spectral intensity and the spectrum pattern, is capable of being displayed.
With the second, third, and fourth apparatuses for displaying fluorescence information in accordance with the present invention, wherein each of the light intensity detecting means is provided with the image sensor for two-dimensionally detecting the fluorescence produced by the measuring site and forming a fluorescence image, the information concerning the fluorescence over a wide range is capable of being displayed quickly.
With the second, third, and fourth apparatuses for displaying fluorescence information in accordance with the present invention, wherein each of the light intensity detecting means is provided with the fluorescence acquiring means for acquiring the fluorescence, which is produced by a single point at a site in the living body, the information concerning the fluorescence produced from a desired point at the site is capable of being displayed.
With the second, third, and fourth apparatuses for displaying fluorescence information in accordance with the present invention, wherein the excitation light has the wavelengths falling within the range of 380 nm to 420 nm that is apart from the region in the vicinity of 480 nm, at which region the light intensity of the fluorescence produced from normal tissues takes the characteristically large value, the fluorescence with the fluorescence spectrum in a desirable pattern is capable of being produced, and the reliability of the displayed information is capable of being enhanced. Furthermore, with the second, third, and fourth apparatuses for displaying fluorescence information in accordance with the present invention, wherein the GaN type of semiconductor laser is employed as the excitation light irradiating means, the size of the apparatus is capable of being kept small, and the cost of the apparatus is capable of being kept low.


This invention relates to a tape cassette having a case which is smaller, especially in thickness, than a conventional tape cassette and which can still accommodate a magnetic tape of the same width as can a conventional tape cassette, and to an adaptor for mounting such a tape cassette to a conventional tape recorder.
Among cassette tapes, the most widespread now in use are called compact cassettes, which contain a magnetic tape having a width of 3.8 mm and have a standardized shape and size, i.e. a length of 100 mm, a width of 64 mm and a thickness of 8.5 mm (FIG. 8).
A handy tape recorder for this type of compact cassette is rather small and lightweight. In fact, the latest model is only slightly larger than the cassette itself. In other words, further reduction in size of the hardware part of the tape recorder is almost impossible.
On the other hand, a micro-cassette is known which is extremely small (50 mm in length, 33 mm in width and 8 mm in thickness). But since its sound information recording capacity is smaller than a compact cassette and it cannot feed the tape stably due to its fragile build, its sound quality is considerably poor. Thus, tape recorders for micro-cassettes are not popular in spite of their compact size.
For the above reasons, it is essential, in attempting to realize a reduction in size of a tape cassette, not to impair the sound information recording capacity, not to impair the sound quality and to keep a sufficient strength of the cassette itself.
Also, it is desirable that such a small and thin tape cassette be capable of being recorded with and being replayed on a conventional compact cassette tape recorder.
Japanese Unexamined Patent Publication No. 56-98757 discloses a compact cassette in which a tape cassette is inserted in a case to protect its magnetic tape during transportation and which can be mounted on a tape recorder with the tape cassette received in the case.
Also, Japanese Examined Patent Publication No. 57-58752 discloses a solid type tape cassette having a solid interior except at some portions. It has an increased strength.


Field of the Invention
The present invention relates to a decorative cover for containers, and more particularly but not by way of limitation, to a decorative cover for flower pots and to methods for producing such decorative cover wherein the decorative cover contains design indicia to personalize or enhance the visual aesthetic effect of the decorative cover.


1. Field of the Invention
The present invention relates to a spark plug used for ignition in an internal combustion engine.
2. Description of the Related Art
FIG. 9 shows a conventional spark plug 300 used for ignition in an internal combustion engine, such as an automobile gasoline engine. The spark plug 300 is mounted on a cylinder head SH of an engine by a male-threaded portion 301a formed on an outer circumferential surface of a metallic shell 301. When the spark plug 300 is mounted on the cylinder head SH, a spark discharge gap g defined by a ground electrode 304 and a center electrode 303 is positioned within a combustion chamber BR and is adapted to ignite a fuel-air mixture. A hexagonal portion 305 (tool engagement portion) is formed on an outer circumferential surface of the metallic shell 301 and is adapted to tighten the male-threaded portion 301a by a tightening tool. The metallic shell 301 assumes a substantially cylindrical shape having a bore 306 for receiving an insulator 302 and is conventionally manufactured by cold plastic processing and machining. In many spark plugs, in order to improve manufacturing efficiency, a schematic profile and the bore 306 are formed by die forging, and a final profile including the male-threaded portion 301a is finished by machining. Since the metallic shell 301 has a thin-walled portion, the dimensions of the metallic shell 301 must be designed in consideration of a material flow during die forging; otherwise, a working defect is likely to occur.
With a recent tendency toward complication of engine head structure, space allocated around a valve for installation of the spark plug 300 is decreasing. Thus, the hexagonal portion 305 needs to be reduced to increase space for use on the head side. However, reducing the size of the hexagonal portion 305 causes the following problems.
(1) To prevent an excessive reduction in the wall thickness of the hexagonal portion 305 in association with a reduction in the size of the hexagonal portion 305, a diameter D1 of a portion (hereinafter referred to as xe2x80x9ca major-bore portionxe2x80x9d) 306a of the shell bore 306 must be reduced. Also, the outside diameter of the insulator 302 must be reduced accordingly. However, when a diameter D2 of a portion (hereinafter referred to as xe2x80x9can intermediate-bore portionxe2x80x9d) of the shell bore 306 corresponding to the male-threaded portion 301a is reduced, a forging punch becomes excessively thin, when the intermediate-bore portion 306b is formed by forging and thus may be damaged or may cause a working defect when a large working load is applied thereon. This problem arises particularly in the case when the male-threaded portion 301a has a long screw reach.
(2) A portion of the insulator 302 positioned within the major-bore portion 306a is formed into a flange portion 302e. When the metallic shell 306 is swaged onto the insulator 302, the flange portion 302e bears a swaging force. A metallic terminal 313 and a center electrode 303 are connected by a glass seal portion 315. In the step of the glass seal portion 315, the flange portion 302e bears a pressing force. In particular, the center electrode 303, a material powder of the glass seal portion 315, and the metallic terminal 313 are disposed within a through-hole formed in the insulator 302. Then the insulator 302 is inserted into a bore formed in a seat die such that the flange portion 302e rests on an inner seat portion formed on the wall of the bore. In this state, the entire insulator 302 is heated to a temperature equal to or higher than a glass softening point, and the metallic terminal 313 is pressed inwardly in the axial direction to press the material powder with the center electrode 303, thereby forming the glass seal portion 315. During this pressing process, the flange portion 302e bears a pressing force.
If the outside diameter of the insulator 302 is too small to meet the demand described above in (1), manufacturing the insulator 302 becomes very difficult. Therefore, there is a certain limit to a reduction in the outside diameter of the insulator 302. As the size of the hexagonal portion 305 is reduced, the diameter D1 of the major-bore portion 306a is reduced accordingly. Thus, the diameter of the flange portion 302e, which is accommodated within the major-bore portion 306a, is also reduced. Because of a reduction in the size of the hexagonal portion 305, the diameter of the flange portion 302e must be reduced because there is a certain limit to a reduction in the diameter of a portion of the insulator 302 other than the flange portion 302e (for example, a portion of the insulator 302 positioned within the intermediate-bore portion 306b; hereinafter referred to as xe2x80x9can intermediate-trunk portion 302axe2x80x9d). As a result, the amount of a projection of the flange portion 302e decreases, causing, for example, a decrease in the area of contact between the flange portion 302e and the seat portion of the seat die used in the step of forming the glass seal portion 315. Consequently, a load concentration causes breakage of the seat die or galling of the insulator 302 and the seat die.
(3) If the diameter of the intermediate-trunk portion 302a of the insulator 302 is reduced to meet the demand described above in (2), and also the diameter D2 of the intermediate-bore portion 306b of the metallic shell 306 is set to a rather large value to attain favorable workability during the process in (1), a gap is likely to be formed between the intermediate-bore portion 306b and the intermediate-trunk portion 302a of the insulator 302. The presence of this gap tends to cause an eccentric disposition of the insulator 302 within the metallic shell 301, potentially causing an impairment in spark plug performance (for example, lateral sparking).
An object of the present invention is to provide a spark plug capable of increasing the degree of freedom with respect to space around a cylinder head on which the spark plug is mounted, through reduction in the size of a tool engagement portion, such as a hexagonal portion, and capable of implementing the following:
(1) in spite of a reduction in the size of the tool engagement portion, a metallic shell can be manufactured efficiently and at high yield;
(2) during formation of a conductive glass seal layer or a resistor by use of a seat die, breakage or galling of the seat die is less likely to occur; and
(3) during incorporation of an insulator into the metallic shell, an eccentric disposition of the insulator within the metallic shell is less likely to occur.
To achieve the above object, the present invention provides a spark plug including an elongate center electrode, an insulator enclosing the center electrode, a metallic shell having open opposite ends and enclosing the insulator, the metallic shell having a male-threaded portion formed on a front-side outer circumferential surface of the metallic shell, and a tool engagement portion formed on the outer circumferential surface of the metallic shell at a rear side with respect to the male-threaded portion, the tool engagement portion projecting circumferentially outwardly, and a ground electrode connected to the metallic shell and defining a spark discharge gap in cooperation with the center electrode.
In the specification, the term xe2x80x9cfrontxe2x80x9d refers to a spark discharge gap side with respect to an axial direction of the center electrode, and the term xe2x80x9crearxe2x80x9d refers to a side opposite the front side.
The insulator has a stepped annular insulator-side engagement portion for engaging with an annular shell-side engagement portion projected inwardly from a portion of an inner surface of the metallic shell corresponding to the male-threaded portion, and |Axe2x88x92E|xe2x89xa61.5 mm, and 0.4xe2x89xa6(D2/E)2xe2x89xa60.6, where A is a dimension of the tool engagement portion represented by a diameter of an inscribed circle of a cross-sectional outline of the tool engagement portion, E is an effective diameter of the male-threaded portion, and D2 is an inner diameter of an intermediate-bore portion of the metallic shell located on a rear side with respect to the shell-side engagement portion.
According to the above-described structure, the dimension A of the tool engagement portion (for example, a hexagonal portion) is reduced with respect to the effective diameter E of the male-threaded portion such that |Axe2x88x92E| becomes not greater than 1.5 mm. Thus, the degree of freedom with respect to space around a cylinder head on which the spark plug is mounted can be increased. Even when available space around a valve for installation of the spark plug decreases due to complication of cylinder head structure, the spark plug can be easily mounted on the cylinder head. Although the outside diameter of the insulator decreases in association with a reduction in the size of the tool engagement portion, so long as 0.4xe2x89xa6(D2/E)2xe2x89xa60.6, the wall thickness of the male-threaded portion of the metallic shell falls within an appropriate range. Thus, during forging of the metallic shell, a forging punch is less susceptible to breakage and is less likely to cause a working defect. That is, the problem described previously in (1) is solved, and the metallic shell can be manufactured efficiently and at high yield.
More particularly, (D2/E)2 represents the ratio of the cross-sectional area of the intermediate-bore portion having the diameter D2 xe2x80x9cxcfx80(D2/2)2xe2x80x9d to the cross-sectional area of the male-threaded portion having the effective diameter E xe2x80x9cxcfx80(E/2)2.xe2x80x9d The smaller the value (D2/E)2 (i.e., the more the effective diameter E of the male-threaded portion increases with respect to the diameter D2 of the intermediate-bore portion), the greater the wall thickness of the male-threaded portion. When (D2/E)2 is less than 0.4, the wall thickness of the male-threaded portion becomes excessively large, causing an insufficient diameter of the intermediate-bore portion. As a result, when the intermediate-bore portion is to be formed through cold working, such as forging, a forging punch to be used becomes excessively thin and thus may be damaged or may cause a working defect when a large working load is imposed thereon. When (D2/E)2 is in excess of 0.6, the wall thickness of the male-threaded portion becomes excessively thin. As a result, formation of the male-threaded portion through cold working becomes difficult, and the formed male-threaded portion suffers insufficient strength. More preferably, (D2/E)2 ranges from 0.45 to 0.55.
A flange portion may be formed on the outer circumferential surface of the insulator on the rear side with respect to the stepped portion. In this case, preferably, d2/d1 is not greater than 0.75, where d1 is the outside diameter of the flange portion, and d2 is the outside diameter of an intermediate-trunk portion extending between the flange portion and the stepped portion. As mentioned previously in (2), in the case of reducing the outside dimension A of the tool engagement portion such that |Axe2x88x92E| is not greater than 1.5 mm, if the outside diameter of the intermediate-trunk portion becomes excessively small, manufacture of the insulator becomes very difficult. Also, a reduction in the size of the tool engagement portion unavoidably requires a reduction in the outside diameter of the flange portion. In other words, the diameter ratio d2/d1 between the intermediate-trunk portion and the flange portion tends to increase. As d2/d1 increases, the amount of projection of the flange portion from the outer circumferential surface of the intermediate-trunk portion decreases. As a result, as mentioned previously, the step of forming a glass seal portion is likely to involve breakage of a seat die or galling between the insulator and the seat die. Through employment of a d2/d1 of not greater than 0.7, the amount of projection of the flange portion becomes sufficiently large, thereby effectively preventing the above-mentioned problem associated with a reduction in the size of the tool engagement portion; i.e., solving the problem described previously in (2). More preferably, d2/d1 is not greater than 0.65. However, d2/d1 is excessively small, the intermediate-trunk portion becomes too thin for manufacture of the insulator. Therefore, in order to avoid such a problem, the value d2/d1 must be adjusted as adequate.
As mentioned previously in (3), if the diameter of the intermediate-bore portion is set to a rather large value in order to attain favorable workability of the metallic shell while the diameter of the intermediate-trunk portion of the insulator is decreased in association with a reduction in the size of the tool engagement portion, a gap is likely to be formed between the intermediate-bore portion of the metallic shell and the intermediate-trunk portion of the insulator. In the case of formation of such a gap, preferably, an eccentricity preventive portion is provided substantially concentrically with the intermediate-bore portion and the intermediate-trunk portion in such a manner as to partially fill the gap. In the step of incorporating the insulator into the metallic shell, the eccentricity preventive portion restricts lateral movement of the insulator; i.e., an eccentric disposition of the insulator within the metallic shell, thereby solving the problem described previously in (3).
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.


The use of soap dispensers for hand washing has now become widely known and accepted. Typically, such soap dispensers dispense a quantity of soap which is then worked into a lather by the user when combined with water on the hands. Recently, there has been a general acceptance of foam soap delivery systems. In such systems, liquid soap is combined with air, typically under force or pressure, and then driven through a mesh, screen or porous passage to finish or homogenize the soap into a uniform stable composition. In some systems, a mixing chamber is employed prior to the porous structure or passage in order to prepare a prefoam of randomly sized and spaced bubbles. The mixing chamber and porous passage are generally presented at a foamer head that is immediately adjacent the drive mechanism for the liquid and air. In general, these drive systems are typically pistons within cylinders or pumps to achieve the pressurization and drive of the liquid soap and air.
In the past, little attention has been given to the development of foamer heads that are adaptable for use in systems where the liquid soap source is remote from the dispensing head. Indeed, the prior art foamer heads have typically been of a rudimentary nature, with little regard for the specifics of the design or the configuration of the constituent elements. While the prior art foamer heads have generally been of a satisfactory nature, little attention has been given to the efficacy of soap foam generation to achieve a desired uniformity and integrity of the resulting foam. Moreover, where foam soap is to be dispensed from an area remote from the liquid soap source, the prior art has generally taught the generation of the foam close to the liquid soap source, with its subsequent delivery to a dispensing head remote from that source. However, such systems have generally proven to be problematic. It has been found that foam is difficult to drive for any distance through a conduit. Breakdown of the foam occurs, resulting in reduced volumes of soap being dispensed on each dispensing cycle, and with the ultimate dispensing of liquid soap globules. It has also been found that such remote delivery systems have resulted in extremely low output volumes on subsequent dispensing operations, and even total failures to dispense when the period of time between dispensing operations has been sufficient to allow the soap foam within the conduit to fully breakdown. Other problems have been evidenced with a “wet” foam output on subsequent dispensing operations, resulting from the breakdown of foam in the conduit into a liquid form.
In systems where the dispensing head is remote from the point of foam generation, it has been found that the liquid and/or air cylinders of this system have required careful design to ensure sufficient “suck-back” force on the return stroke of the dispensing operation to draw residual foam back away from the dispensing head to preclude drips and the like.
The remote dispensing heads referenced herein are typically present in what are referred to as counter-mount systems, in which the soap reservoir is maintained beneath the counter and the dispensing head is above the counter, the two being interconnected by conduits that are three or more feet in length. The problems of foam breakdown and suck-back failure are characteristic of such systems.
There is a need in the art for an improved soap foam generator, adaptable for use in any of a variety of delivery systems, and particularly in remote dispensing systems, such as counter-mount systems, in which the air and liquid sources are remote from the dispensing head.


The present invention relates to vehicle internal safety belts, and more particularly to a vehicle internal safety belt for folding one's head to the head-rest of the vehicle internal seat, which can also be alternatively used for holding one's legs together.
Conventionally, a vehicle internal seat is generally equipped with a safety belt for fastening on one's waist to firmly secure a person to a seat. However, even if a person is fastened to a vehicle internal seat by a safety belt, a person's head is still not protected and may be shaken to hit a window glass or some part inside a vehicle during vehicle collision or sudden braking of the vehicle. Further, there is no means available in a vehicle seat to bind one's legs together while one is sleeping in a vehicle internal seat. Because it is ungraceful to unintentionally open the two legs apart while a women is sleeping in a vehicle internal seat, a woman may be constantly in a state of anxiety while sleeping in a vehicle internal seat.


The present invention relates to azlactone activated polyalkylene oxides (PAO's) having improved hydrolytic stability, and to water-soluble polyalkylene oxide conjugates prepared therefrom.
The conjugation of water-soluble polyalkylene oxides with useful molecules such as proteins and polypeptides is well known. The coupling of peptides and polypeptides to polyethylene glycol (PEG) and similar water-soluble polyalkylene oxides is disclosed by U.S. Pat. No. 4,179,337 to Davis et al.
Davis et al. discloses that physiologically active polypeptides modified with PEG exhibit dramatically reduced immunogenicity and antigenicity. Also, the polyalkylene oxide conjugates, when injected into a living organism, have been shown to remain in the bloodstream considerably longer than the corresponding native proteins. Examples of such therapeutic protein conjugates include tissue plasminogen activator, insulin, interleukin II and hemoglobin. In addition, PAO's have also been conjugated to oligonucleotides. See, for example, U.S. Pat. No. 4,904,582.
To conjugate polyalkylene oxides, the hydroxyl end-groups of the polymer must first be converted into reactive functional groups. This process is frequently referred to as "activation" and the product is called an "activated polyalkylene oxide."
Until recently, covalent attachment of the polyalkylene oxide to an appropriate nucleophile was effected by activated polyalkylene oxides such as polyalkylene oxide succinoyl-N-hydroxysuccinimide ester, as disclosed by Abuchowski et al., Cancer Biochem. Biophys., 7, 175-86 (1984). This polyalkylene oxide derivative is desirable because it is reactive under mild conditions.
A shortcoming associated with this derivative, however, is the fact that it is relatively hydrolytically unstable when no nucleophile is present. Recently, in U.S. Pat. No. 5,122,614, polyalkylene oxide-N-succinimide carbonates were disclosed having improved hydrolytic stability over the polyalkylene oxide succinoyl succinates. Even so, the pH conditions necessary to deprotonate the .epsilon.-NH.sub.2 groups of polypeptide lysines for conjugation subject the activated polyalkylene oxide to hydrolysis. This does not affect the reaction end product, other than to reduce its yield. While reduced yields ordinarily affect product cost, the hydrolysis becomes even more costly for several reasons. Firstly, reaction mixtures cannot be prepared significantly in advance. Additional purification of the end product is required to remove the hydrolytic degradation products. Furthermore, the reduction in yield is compensated for by increasing the amount of activated polyalkylene oxide starting material. This increases the viscosity of the reaction mixture, thereby further increasing the processing cost, and potentially interferes with downstream purification of the polymer and conjugate.
A need exists, therefore, for polyalkylene oxides that are unreactive towards weak nucleophiles such as water but react readily with stronger nucleophiles such as polypeptides. While azlactones have been reported to react readily with amines and less readily with water, azlactone activated PAO's are unreported. Unsaturated azlactones, in particular, are not altered by long contact with water. See, Carter, Organic Reactions, Vol. III (Adams, ed., John Wiley & Sons, New York 1946) pp. 198-239. The disclosed unsaturated azlactones have the following structures ##STR1## in which R.sub.1 and R.sub.2 are independently selected from hydrogen, phenyl rings and lower alkyl moieties. R is the residue of an .alpha.-acyl amino acid.


Though the current invention is also applicable to lithographic processes as used in printing industry, the current invention is mainly concerned with lithography as applied in the production of electronic and electric devices, sensors, and the like. The characteristic length scale, i.e. the design rule of the relevant lithographic pattern is usually in the micron to submicron region. The manufacturing process of these devices is currently almost entirely dominated by methods based on optical or e-beam lithography.
Since the emergence of integrated circuits (ICs) and micromechanical devices, optical lithography has been crucial for the purpose of their mass production: Its convenience, parallel operation and resolution has created a huge market. Fabrication of devices with ever smaller dimensions, necessary to satisfy the demands of storage and computation, becomes increasingly problematic with visible light as processes steadily reach fundamental limits, predominantly set by diffraction. This realization triggered intense research in UV, X-ray, e-beam, and Scanning Probe (SP)
lithography. These methods deliver high resolution with varying success and their economics remain, at best, uncertain. Reasons for these uncertainties include limitations due to wavelength dependent phenomena, the slow writing speeds of e-beam and SP lithographies, and challenges in finding appropriate resists and masks.
A separate and related limitation of current lithographies is the complexity of processes required for modifying or altering a layer at regions defined by the desired lithographic pattern to be written; lithography today relies on bulk transfer of reactive material from the liquid or gas phase, or from a plasma using masks to protect the other regions of the substrate.
An alternative approach to lithography has been published by A. Kumar and G. M. Whitesides in : Appl. Phys. Lett. 1993, 63, 2002-2004. In this process, known as microcontact stamp lithography, stamps are fabricated by casting a replica in poly(dimethylsiloxane) (PDMS) of a master with a negative of the desired pattern. In the one known example of microcontact stamping used for lithography, the PDMS stamp is inked with an alkanethiol, hexadecanethiol, and transferred to gold by transient contact between the stamp and the gold substrate. The thiol covalently binds to the gold in an autophobic reaction: the thiol modifies the wettability of the gold substrate, preventing spread of the bulk liquid phase and thus confining the transferred monolayer to the region of contact between the raised regions of the elastomeric stamp and the substrate. The presence of these thiols allows subsequent lithographic processing of the gold using a cyanide/oxygen etch that selectively removes gold not protected by a monolayer of alkanethiol. Although this system allows reproductions of features in gold down to one micron, its scope remains limited to a special subset of useful materials, i.e. thiols and gold.
In all these lithographic processes, a number of agents are used which pose a considerable potential threat to the environment. Huge efforts are therefore taken to sufficiently protect workers within IC factories and the population living in their surrounding from a possible exposure to these agents. Immense resources are also invested for safely depositing the waste and remains of the IC manufacturing.
The object of the present invention is to avoid limitations in the type of reactions, materials transferred and range of substrates useful in contact based lithography and to demonstrate new strategies of direct processing of substrates without the intervening application of resists.
It is a further object of the inventions to improve the known lithographic processes by providing a method for modifying a surface at precisely determined positions. While being more convenient to apply, the new process should at least have a resolution comparable to state-of-the-art lithography. Another object of the invention is to restrict the amount of agents and material used in the lithographic process, in particular, hazardous waste generated by this process should be minimized.
As mentioned above, lithographic processes are also found in the field of printing. In particular, color printing is found to face similar problems concerning alignment during several separated printing steps as encountered in lithography for semiconductor devices. In four color printing the colors cyan, magenta, yellow and black are applied to four separate printing rollers that transfer the lithographic pattern to the paper in four separate printing steps. The alignment among those four printing steps limits the maximal resolution and quality of color images especially on cheap and low quality paper. Printing can either be done with poor alignment (.about.0.1 mm) and bad image quality on cheap paper or with better alignment (.about.0.01 mm) and better image quality on high quality paper. The rastering dimension has to be adapted to the alignment and consequently is >0.1 mm (<300 dpi) for low quality paper and>0.01 mm (<3000 dpi) for the paper with the highest quality. Photographic reproduction, on the other hand, can be carried out with grain sizes of the order of microns (<0.001 mm). Thus, high quality printing requires expensive equipment able to maintain tolerances of 10 microns over several meters.
It is therefore seen as another object of the invention to improve the conventional color printing procedure, in particular to facilitate the alignment procedure necessary to print several colors.


Exocrine glands are glands that release a secretion external to or at the surface of an organ by means of a canal or duct. Examples of exocrine glands include, among others, the mammary glands, prostate, liver, gall bladder, pancreas, kidneys, sweat glands, and salivary glands. Cancers of exocrine glands pose a major health problem, frequently resulting in death. Currently, cancers of the breast and prostate are among the leading causes of death among women and men, respectively.
The mature human breast comprises from six to nine major ducts, which emanate from the nipple, serially branch into ducts and terminate in lobuloalveolar structures (Russo et al., Lab. Invest. 62(3): 244–278 (1990)). This branching network of ducts is composed of epithelial cells in a supporting matrix of connective tissue and endothelial cells.
Tissues removed from the human female breast during surgery and autopsy have been examined in numerous studies directed to the nature and site of origin of neoplastic growth. Subgross sampling and histological confirmation have enabled pathological characterization of entire breasts, leading to the postulation of the existence of four major possible sites of origin of mammary carcinomas, namely ducts, terminal ducts, ductules, and acini (Russo et al., supra). Ductal origin is supported by the presence of more extensive epithelial proliferations, which are presumed to be preneoplastic, in surgically removed cancerous breasts as compared to nonmalignant breasts removed during autopsies (Russo et al., supra).
With a cumulative lifetime risk of a woman developing breast cancer estimated to be 1 in 9, there is an urgent need to develop therapeutic methods of treatment that are more effective, less invasive and accompanied by fewer side effects and prophylactic methods of treatment that are more effective than increased and intensified physical monitoring and far less extreme than radical mastectomy. In spite of the recent discovery of the heritable breast cancer susceptibility loci, BRCA1 (Miki et al., Science 266: 66–71 (1994)) and BRCA2, and other cancer susceptibility loci, and the increasing ability of physicians to identify women with elevated breast cancer risk, prophylactic methods are still currently limited to physical monitoring and prophylactic mastectomy.
In view of the above, it is an object of the present invention to provide a method of locally treating an exocrine gland prophylactically for disease. It is another object of the present invention to provide a method of locally treating an exocrine gland, in particular the mammary gland, prophylactically for cancer. Another object of the present invention is to provide a method of locally treating an exocrine gland therapeutically for disease. Yet another object of the present invention is to provide a method of locally treating a mammary gland therapeutically for cancer. Still yet another object of the present invention is to provide a method of locally treating a mammary gland both therapeutically and prophylactically for cancer. These and other objects and advantages, as well as additional inventive features, will become apparent from the detailed description provided herein.


The present invention relates to Caterpillar sidebooms used for pipelaying, and more particularly pertains to methods and apparatus for converting old, discontinued, mechanically-operated, low-drive, Caterpillar sidebooms into hydraulically-operated sidebooms, with minimal retrofitting.
It is well known in the art that crawler or tractor-type vehicles having an integrated, rigid maneuverable boom disposed on a side thereof are commonly used for pipelaying operations, i.e., for raising, carrying, and lowering heavy pipe. Referred to as "sidebooms," such vehicles must be capable of safely handling heavy pipe; indeed, there are sideboom models that have been constructed for handling pipe up to 200,000 pounds. Such sidebooms were mechanically-operated in their first incarnation and are now readily available from original equipment manufacturers in hydraulically-operated models.
An early development in the mechanical sideboom art is disclosed by Butterfield et al. in U.S. Pat. No. 3,785,503, wherein a plurality of planetary gears and concomitant shafts are used to drive the winch drums for each of the boom and the load. Primarily due to its inherent complicated, high-maintenance gearing system, no embodiments of the Butterfield sideboom was ever commercialized. A significant improvement in the pipelaying sideboom art would be a sideboom that eliminates all gears to accomplish transmission of power, i.e., that eliminates all mechanical connections between the engine and the winch system.
Other early developments in the sideboom art, albeit not applicable to pipelaying operations, per se, are taught in U.S. Pat. Nos. 2,909,290; and 3,329,283. More particularly, Nichols, in U.S. Pat. No. 2,909,290, teaches a farm tractor-mounted sideboom intended for lifting light loads typical on the farm. Of course, pipelaying operations demand sidebooms with lifting capacities up to 200,000 pounds. Similarly, Wade, in U.S. Pat. No. 3,329,283, teaches a snap mount sideboom configured to be foldable for reducing its prerequisite overhead clearance. Half of the Wade boom's height may be reduced and the folded boom portion secured to the tractor's side by using integral hooks and cable. Especially in view of the Wade sideboom having no counterweight, it should be evident to those skilled in the art that both Wade and Nichols are inapplicable to the rigors of pipelaying wherein not only a strong, firm boom structure is required, but also the framework of the sideboom must be sufficiently broad to provide a low enough center of gravity for stability and must include a counterweight to provide sufficient operational stability and safety. It will be readily understood by those skilled in the art that such attributes are not provided by conventional tractors.
Indicative of initial attempts to improve the sideboom art using hydraulics is an apparatus described by Stefanutti in U.S. Pat. No. 3,265,218. In particular, the use of hydraulically actuated booms and hoist assemblies is described, wherein hydraulic cylinders are used either inside or astride the boom to raise and lower the boom. As will be appreciated by those skilled in the art, the Stefanutti apparatus has not been widely accepted.
As taught by Vinton in U.S. Pat. No. 3,938,669, however, while the introduction of such hydraulically-operated sidebooms were anticipated to provide improvements associated with effectively and safely manipulating winches and cables through an operator's interfacing with clutches, brakes, and levers for controlling the position of the boom and for hoisting and lowering a load, such sidebooms failed to provide the prerequisite control and versatility. To attempt to remedy this deficiency in the art, Vinton discloses a hydraulic circuit that includes two separate sources of hydraulic fluid for controlling sideboom movement-related functions. One fluid source provides low volume hydraulic fluid for accomplishing not only precise, low-speed manipulation and control, but also for preventing anti-drift of both boom and hoist. The other fluid source provides high volume hydraulic fluid for providing high-speed operation of these movement and control functions. The plurality of control valves inherent in the Vinton circuit for controlling the hoist and the boom motors are operated via two levers. This apparatus also incorporates a hydraulic cylinder, instead of a drum/cable arrangement for controlling the boom; no drums or cables are involved in raising or lowering either the boom or the hook, except a short cable connected to the hook at the end of a hydraulic cylinder. As is well known by those skilled in the sideboom art, this methodology was a commercial failure.
As a further development in the sideboom art, Forsyth teaches in U.S. Pat. No. 5,332,110 a hydraulically-operated sideboom intended to prevent boom over-rotation, to impart positive drive to the boom and load winches, and to provide improved control over free fall and vertical kick-out. These safe operating features are particularly intended for pipelaying applications involving lifting and lowering of large pipes. Indicative of current Caterpillar tractors and sidebooms, embodiments taught by Forsyth are exclusively for newly manufactured hydraulically-operated high-drive tractors which are the antithesis of predecessor low-drive mechanically-operated Caterpillar tractors.
As will be appreciated by those skilled in the sideboom art, current Caterpillar hydraulically-operated high-drive sidebooms have a higher center of gravity but operate easier due to less controls than old, discontinued, mechanically-operated, low-drive, Caterpillar sidebooms. Such "high drive" models are constructed with an undercarriage that was introduced by Caterpillar in the early 1980's; the sprockets and drive mechanisms for the undercarriage are situated much higher off the ground than the previous conventional "low drive" system that was in effect from the inception of the original Caterpillar sideboom. More particularly, the Caterpillar low-drive sidebooms were discontinued from 1972 through 1986 as follows: model 572E was discontinued in 1972; model 572F was discontinued in 1975; model 572G was discontinued in 1986; model 583H was discontinued in 1974; model 583K was discontinued in 1986; model 594G was discontinued in 1975; and model 594H was discontinued in 1986. In addition, Caterpillar hydraulically-operated high-drive sidebooms are very expensive, and some models not only have inherent counterweight obstruction problems, but also are difficult to move from job-site to job-site. While the Forsyth disclosure teaches that his hydraulic pipelayer is adapted for mounting upon a conventional track-laying tractor (i.e., bulldozer), it is well known in the art that the main frame of a sideboom is constructed differently from that of a conventional tractor. In particular, unlike a conventional tractor which is constructed with an oscillating frame, a sideboom is constructed with a rigid frame of wider track gauge than a conventional tractor. Indeed, Caterpillar identifies such tractor and sideboom frames with different serial numbers series. Thus, to obtain the prerequisite performance demanded in the pipelaying art, a drawworks assembly must be mounted upon a frame capable of rigidity to accommodate the pivoting action of a sideboom typically positioned upon rough terrain, with the frame having a sufficiently wide track gauge for stability purposes.
As will be understood by practitioners in the art, a drawworks system built upon an old, discontinued, mechanically-operated, low-drive, Caterpillar sideboom--having significantly more controls than a conventional discontinued tractor--inherently suffers from a panoply of problems associated with the simultaneous use of a daunting ensemble of gear-shifting mechanisms, clutches, and brakes, all operated by 6 different hand controls to properly lift and manipulate heavy pipes under conditions generally characterized by unpredictable and adverse terrain. Pipeline construction companies constitute 95% of the users of this type of machinery. As will be appreciated by those conversant with the art, historically, such pipeline construction companies have had to choose between the newer high-drive sidebooms with herein before mentioned faults and high price or the older, discontinued Caterpillar sidebooms that are more economical but are more dangerous and are very difficult to operate. It should also be noted that, as the pipelaying industry continues to mature, the number of skilled sideboom operators has gradually diminished.
As should be evident to those skilled in the art, it would be advantageous for construction companies who are continuing to utilize older discontinued Caterpillar sidebooms to have the additional benefits of improved handling, safety, and efficiency. It would be also be advantageous for pipeline contractors to have the ability to expeditiously train low-drive Caterpillar sideboom operators and to simultaneously achieve a level of safety heretofore unmatched by any other sideboom system known in the art, regardless of design. Of course, it would be advantageous for pipelaying contractors to have the benefit of a Caterpillar sideboom that inherently avoids or mitigates the complex levers and the like associated with maneuvering a sideboom, and controlling the lifting and lowering of a pipe load.
Accordingly, these limitations and disadvantages of the prior art are overcome with the present invention, and improved means and techniques are provided which are useful for effectively and reliably utilizing old, discontinued, mechanically-operated, low-drive, Caterpillar sidebooms for pipelaying applications.


The present invention relates to telephone conference calls, and deals more particularly with conferencing an already-connected telephone call in a seamless manner that is transparent to the call participants.
When two people are participating in a telephone call, they may decide that it would be useful if one or more other persons were also participating. For example, the current call participants may be work colleagues who are discussing an urgent problem, and they might decide that one or more of their co-workers could provide valuable insight into the problem. Currently, the existing telephone call has to be terminated, and a new telephone call has to be initiated using a conference bridge.


The demand for e-commerce brings a unique set of challenges to network infrastructures. For example, one server may be inadequate to provide the required capacity and scalability to serve the increasing size of e-commerce transactions. Server load balancing (SLB) was developed to overcome this problem, where a number of servers (server farm) act as a single server and a special device (dispatcher) dispatches requests to servers in a manner that balances the load on all the servers in the server farm. Some SLB schemes may dispatch requests to the server having the least load, and other SLB schemes may dispatch requests to any server such that the network is optimized, for example. For purposes of simplicity, the server selected by any given SLB scheme is referred to herein as the “best server”.
In e-commerce transactions hosted on a website, however, SLB introduces a new problem. When a customer sends information to a website that utilizes an SLB scheme, the information is sent to the best server computed by the dispatcher, Server A, and stored locally on that server. For example, a customer of Amazon.com® selects books and places them in the shopping cart, and then decides to visit other areas of the site before purchasing. When the customer returns to the shopping cart, effectively to access state information (the state of previously stored information), the SLB scheme again computes the best server, this time Server B, to direct the customer's request to. Since the distribution of requests amongst the servers in the server farm may have changed since the customer's last request, the best server on the subsequent request is different from the best server on the first request. Consequently, the customer's information does not exist on Server B, and the shopping cart may be empty when the customer returns to it.
One current solution to this problem is to globally maintain state information, such that the state information can be accessed by any server in the server farm. For example, state information can be maintained in a special state server, or even one of the servers in the server farm. One of the disadvantages to this, however, is the latency associated with memory accesses by the servers, as well as dispatcher latency associated with storing state information.