1. Field of the Invention
The present invention relates to a multi-directional switch, and particularly relates to, for example, a multi-directional switch in which on-off operation of multiple contacts is dependent on the pressing directions of the switch.
2. Description of the Prior Art
FIG. 1 is a perspective view showing an example of a hand-held type game playing apparatus using a conventional character moving switch which constitutes the background of the present invention. Referring to FIG. 1, a body 1 comprises a liquid crystal display plate 2. The liquid crystal plate 2 comprises a plurality of characters formed with transparent electrodes so that a predetermined character is displayed according to development of a game or in response to operation of character moving switches 4a to 4d. The characters 3a, 3b, 3c and 3d illustrated in the drawing are selectively displayed by operation of character moving switches 4a, 4b, 4c and 4d. More particularly, the character 3a is displayed responsive to operation of the character moving switch 4a, the character 3b is displayed responsive to operation of the character moving switch 4b, the character 3c is displayed responsive to operation of the character moving switch 4c and the character 3d is displayed responsive to operation of the character moving switch 4d. Accordingly, by operating optionally the character moving switches 4a to 4d, a display is made as if characters 3a to 3d were moving. The body 1 further comprises game switches 5 and 6 for giving instructions to start a game of different difficulty and a current time switch 7 for giving instructions to indicate the current time.
As described above, the conventional character moving switches 4a to 4d are provided corresponding to the characters 3a to 3d, that is, corresponding to the moving directions of the characters. The character moving switches 4a and 4b are provided in the vicinity of the left end of the body 1, and the character moving switches 4c and 4d are provided in the vicinity of the right end of the body 1. Accordingly, if one plays a game with a hand-held type game playing apparatus in his hands, the character moving switches 4a and 4b must be operated with the left hand, and the character moving switches 4c and 4d must be operated with the right hand. Thus, it is very difficult to operate two switches with one hand and other two switches with the other hand. As a result, one must take a great care in operation of the character moving switches 4a and 4d, which makes the game dull. On the other hand, if a larger number of character moving switches are provided to increase character moving directions, more variety will be given to the game, so that one will not easily get bored with it. Thus, in using conventional character moving switches, there is a disadvantage that either variety of a game or simplicity in operation must be disregarded.
In order to eliminate the above described disadvantage, the character moving switches 4a to 4d might be disposed collectively in a certain position in the body 1 so that one can operate them with one hand. However, such collective disposition will encounter another problem in that two or more than two character moving switches are often pressed simultaneously. Conversely, this means that the character moving switches 4a to 4d must be separated from each other with a certain distance. Accordingly, space for positioning the character moving switches 4a to 4d should be made larger, and consequently sufficient space cannot be provided for display of the liquid crystal display plate 2. As a result, the content of a game organized in the liquid crystal display plate 2 has to be limited.
In the foregoing, the disadvantage of character moving switches used in a hand-held type game playing apparatus was explained. However, the same disadvantages or problems as described above are also found in various conventional apparatus where control for selection of modes or moving directions is made by means of switches, if switches are provided corresponding to the modes or moving directions.


In the traditional client-server model, the majority of processing and data storage occurs at the client. In the emerging Software as a Service (“SaaS”) market, the majority of the processing occurs at the server and the data is centralized to take advantage of the connectivity the Internet provides. The power of the connectivity and information sharing is leading to massively scalable applications that support hundreds of thousands, up to hundreds of millions of users.
Massively scalable applications are creating many new challenges in managing user loads and storage systems in an automated fashion. One of theses challenges is the ability to accurately predict when capacity will be needed in data-heavy applications, such as email, file storage, and online back-up, and also in non-data heavy applications. Making this prediction is difficult because the limitations which can affect available overall load take many forms, including utilization of processor, memory, I/O load (comprising reads per second, writes per second, total transactions per second, and number of ports being utilized), network space, disk space, an application or applications, and power, and these forms are continually changing. Additionally, making this prediction is difficult because it is hard for an administrator to distinguish between a short-term load that can be reached due to a burst of activity and long-term growth that requires increased capacity. Administrators also do not have useful numbers on the different types of utilization of the server systems. As a result, administrators are often in a reactive mode when trying to address capacity concerns. Further, administrators do not have any methods for accurately assessing costs, such as the cost per user per service especially when multiple servers are required for a single service or for assessing whether to maximize the configuration of a server or purchase a new server to add capacity.


In recent years, along with a development of multimedia applications such as picture, audio and text, it has become general to handle all sorts of media in an integrated way. However, an information compression technique for data is dispensable for its storage and transmission since a digitalized picture contains an enormous amount of data. On the other hand, a standardization of compression techniques is also important for interoperating compressed picture data. The standards of picture compression techniques include H.261, H.263 established by the ITU (International Telecommunication Union) and MPEG (Moving Picture Experts Group)-1, MPEG-2 and MPEG-4 established by the ISO (International Organization for Standardization).
An inter-picture prediction which accompanies motion compensation can be cited as a technique shared among these moving picture coding methods. In the motion compensation based on these moving picture coding methods, a picture of an input image is divided into blocks, each of which has a predetermined size, and a predictive image is generated for each block using motion vectors, respectively indicating a motion between pictures. The following predictions are employed for the inter-picture prediction according to the MPEG: a forward prediction for a prediction using a single picture whose display time is earlier than that of a current picture to be coded; a backward prediction for a prediction using a single picture whose display time is later than that of the current picture; a bi-directional prediction for a prediction using two pictures, that is, one picture whose display time is earlier than the current picture and the other picture whose display time is later than that of the current picture (see reference, for example, ISO/IEC 14496-2:1999(E) Information technology—coding of audio-visual objects Part 2: Visual (1999-12-01) pp 150 7.6.7 Temporal prediction structure).
In the MPEG, a reference picture to be used is determined uniquely depending on the type of inter-picture prediction and an arbitrary reference picture cannot be selected. In the meantime, a bidirectional prediction which is expanded so that two arbitrary reference pictures can be selected out of a plurality of coded pictures stored in a picture memory regardless of the display time of the current picture is taken under the consideration in the H.264 which is presently under the process of standardization by the ITU.
FIG. 1 is a block diagram showing a structure of a moving picture coding apparatus according to the H.264. The conventional moving picture coding apparatus shown in FIG. 1 is an apparatus for executing a moving picture coding method which allows a selection of two arbitrary reference pictures from plural coded pictures when the inter-picture prediction is operated.
This moving picture coding apparatus includes, as shown in FIG. 1, a motion estimation unit 301, a pixel interpolation unit 102, a subtractor 103, a picture coding unit 104, a picture decoding unit 105, an adder 106, a variable length coding unit 302, a multi-picture buffer 108 and a switch 109.
The moving picture coding apparatus divides an inputted image data Img into blocks and performs processing for each of the blocks. The subtractor 103 subtracts a predictive image data Pred from the image data Img inputted to the moving picture coding apparatus and outputs it as residual data Res. The picture coding unit 104 performs picture coding processing such as orthogonal transformation and quantization on the inputted residual data Res and outputs it as coded residual data ERes including quantized orthogonal transformed coefficients. The picture decoding unit 105 performs picture decoding processing such as inverse quantization and inverse orthogonal transformation on the inputted coded residual data ERes and outputs it as decoded residual data DRes. The adder 106 adds the decoded residual data DRes to the predictive image data Pred and outputs it as reconstructed image data Recon. Out of the reconstructed image data Recon, the data having the possibility to be used for reference in the subsequent inter-picture prediction is stored in the multi-picture buffer 108.
Here, an interpolation prediction using two reference pictures performed by the conventional moving picture coding apparatus is described with reference to FIG. 2. FIG. 2 is a conceptual diagram of the interpolation prediction using plural reference pictures. Here, a picture Pic is a current picture to be coded. Pictures FwRef1˜FwRef3 represent coded pictures respectively having a display time earlier than that of the current picture whereas pictures BwRef1˜BwRef3 represent coded pictures respectively having a display time later than that of the current picture. A block Blk1 is predicted using pixel values in a reference block RefBlk11 included in the picture FwRef3 whose display time is earlier than that of the current picture Pic and pixel values in a reference block RefBlk12 included in the picture BwRef1 whose display time is later than that of the current picture Pic. A block Blk2 is predicted using pixel values in reference blocks RefBlk21 and RefBlk22 included in two pictures FwRef1 and FwRef2 respectively having a display time earlier than that of the current picture. A block Blk3 is predicted using pixel values in reference blocks RefBlk31 and RefBlk32 included in two pictures BwRef1 and BwRef2 respectively having a display time later than that of the current picture. Namely, a result of interpolating pixels in the areas corresponding to the two reference blocks using a predetermined method such as the one using an average value is considered to be a predictive image. The characteristics of the conventional moving picture coding apparatus is to perform prediction on a block-by-block basis using arbitrary two reference pictures as shown in FIG. 2. A method for predicting with the use of two arbitrary reference pictures as described above is called “plural reference picture interpolation prediction” hereinafter. The prediction method includes a method in which a block included in a single arbitrary picture is used directly as a predictive image and the intra-picture prediction other than the method of generating a predictive image using the pixel interpolation as described above, and it is possible to switch the prediction method on a block-by-block basis.
The motion estimation unit 301 determines a prediction type for the block, reference pictures and motion vectors to be used for inter-picture prediction performed on the inputted current block to be coded and outputs a prediction type PredType, reference picture numbers RefNo1, RefNo2, and motion vectors MV1, MV2. The motion estimation 301 outputs two picture numbers and two motion vectors since two reference pictures are selected when plural reference picture interpolation prediction is operated. Here, the multi-picture buffer 108 outputs a reference block RefBlk1 corresponding to the reference picture number RefNo1 and the motion vector MV1 and a reference block RefBlk2 corresponding to the reference picture number RefNo2 and the motion vector MV2. The pixel interpolation unit 102 performs interpolation for the pixels with respect to the two reference blocks RefBlk1 and RefBlk2 using average value and outputs it as-an interpolated block RefPol. On the other hand, in the case of using an inter-picture prediction other than a plural reference picture interpolation prediction, the motion estimation unit 301 selects a single reference picture, and therefore, outputs a single reference picture number RefNo1 and a single motion vector MV1. In this case, the multi-picture buffer 108 outputs a reference block RefBlk with respect to the reference picture number RefNo1 and the motion vector MV1.
When the prediction type determined by the motion estimation unit 301 indicates a plural reference picture interpolation prediction, the switch 109 is switched to a “1” side and the interpolated block RefPol is used as a predictive image data Pred. When the prediction type PredType indicates an inter-picture prediction other than a plural reference picture interpolation prediction, the switch SW11 is switched to a “0” side and the reference block RefBlk is used as a predictive image data Pred. The variable length coding unit 302 performs variable length coding on the coded residual data ERes, the prediction type PredType, the reference picture numbers RefNo1, RefNo2 and the motion vectors MV1, MV2 and then outputs them as coded moving picture data Str0.
FIG. 3 is a conceptual diagram of a data format of coded moving picture used by the conventional moving picture coding apparatus. Coded data equivalent to a single picture, Picture, is composed of coded data equivalent to a single block, Block, where each block composes a picture, and the like. Here, the coded data equivalent to a single block, Block, presents coded data of a block on which a plural reference picture interpolation prediction is performed, and includes the reference picture numbers RefNo1, RefNo2, the motion vectors MV1, MV2, with respect to the two reference pictures, the prediction mode PredType, and the like, in the coded data.
FIG. 4 is a block diagram showing a structure of the conventional moving picture decoding apparatus. The moving picture decoding apparatus includes, as shown in FIG. 4, a variable length decoding unit 601, a motion compensation unit 602, a picture decoding unit 404, an adder 405, a pixel interpolation unit 406, a multi-picture buffer 407 and a switch 408.
The variable length decoding unit 601 performs variable length decoding on the inputted coded image data Str0 and outputs the coded residual data ERes, the motion vectors MV1, MV2, the reference picture numbers RefNo1, RefNo2 and the prediction type PreType. The picture decoding unit 404 performs picture decoding processing such as inverse quantization and inverse orthogonal transformation on the inputted coded residual data ERes and outputs decoded residual data DRes. The adder 405 adds the decoded residual data DRes to the predictive image data Pred and outputs it as decoded image data DImg outside the moving picture decoding apparatus. The multi-picture buffer 407 stores the decoded image data DImg for inter-picture prediction.
The motion compensation unit 602 outputs reference picture numbers NRefNo1, NRefNo2 of the reference blocks necessary for inter-picture prediction according to the prediction type PredType as well as the motion vectors MV1, MV2 and instructs the multi-picture buffer 407 to output the reference blocks. When the prediction type PredType indicates a plural reference picture interpolation prediction, the multi-picture buffer 407 outputs the reference block RefBlk1 corresponding to the reference picture number NRefNo1 and the motion vector NMV1 as well as the reference block RefBlk2 corresponding to the reference picture number NRefNo2 and the motion vector NMV2. The pixel interpolation unit 406 interpolates the pixels in the two reference blocks RefBlk1 and RefBlk2 using the average value. On the other hand, when the prediction type PredType indicates an inter-picture prediction method other than a plural reference picture interpolation prediction, the multi-picture buffer 407 outputs the reference block RefBlk corresponding to the reference picture number NRefNo1 and the motion vector NMV1.
When the prediction type PreType indicates a plural reference picture interpolation prediction, the switch 408 is switched to a “0” side and an interpolated block RefPol is used as a predictive image data Pred. Thus, the moving picture decoding apparatus decodes the coded moving picture data Str0 through the processing described above and outputs it as decoded image data DImg.
Meanwhile, under the moving picture coding method based on the MPEG-4, a plural reference picture interpolation prediction method called “direct mode” is defined for a picture type, called “bidirectional predictive picture”, employing a plural reference picture interpolation prediction. It is defined as a method to abbreviate the motion vectors and the reference picture numbers included in the coded data of the block by calculating the motion vectors with respect to two reference pictures used for the generation of the predictive image by means of interpolation using the coded motion vectors.
FIG. 5 is an illustration for a case of using the direct mode defined in the MPEG-4. Here, a picture Pic represents a current picture to be coded, a picture Ref1 represents a reference picture whose display time is earlier than that of the current picture Pic and a picture Ref2 represents a reference picture whose display time is later than that of the current picture Pic whereas a block Blk represents a current block to be coded and a block Blk0 represents a block whose position is same as that of the current block Blk in the reference picture Ref2. A motion vector MV01 represents a forward reference motion vector using the picture Ref1 as a reference picture for coding the block Blk0, a motion vector MV1 represents a motion vector of the current block with respect to the reference picture Ref1, a motion vector MV2 represents a motion vector of the current block with respect to the reference picture Ref2, a block RefBlk1 represents a reference block to be referred to by the motion vector MV1 and a block RefBlk2 represents a reference block to be referred to by the motion vector MV2.
As for the two pictures to be used for reference by the current block Blk, the picture Ref2 whose display time is later than and is closest to the current picture is used as a backward reference picture whereas the picture Ref1, which has been used for reference by the block Blk0 at the time of coding, is used as a forward reference picture.
For the calculation of the motion vectors, it is assumed that either the motion is constant or no motions are found in comparing the pictures. Here, with an assumption that a differential value between the display time of the current picture Pic and that of the reference picture Ref1 is TRD1, a differential value between the display time of the reference picture Ref1 and that of the reference picture Ref2 is TRD2, and a differential value between the display time of the current picture Pic and that of the reference picture Ref2 is TRD3, the motion vectors MV1 and MV2 to be used for coding the current block can be calculated respectively using the following equations:MV1=MV01×(TRD1/TRD2)  (Equation A)MV2=−MV01×(TRD3/TRD2)  (Equation B)
Using the above method, the reference pictures and the motion vectors in the case of using a direct mode can be determined. The processing in the case of using a direct mode as described above, performed by the moving picture coding apparatus, is executed by the motion estimation unit 301 shown in the block diagram illustrating the conventional moving picture coding apparatus in FIG. 1. The processing for the case of using a direct mode described above, performed by the moving picture decoding apparatus, is executed by the motion compensation unit 602 shown in the block diagram illustrating the conventional moving picture decoding apparatus in FIG. 4.
When a moving picture, in which a motion between the pictures is small, is inter-picture coded, a predictive error between the pictures become very small and most of the coded residual data ERes become “0” by performing picture coding processing such as quantization. A case in which the entire coded residual data ERes resulted from the inter-picture prediction using the reference pictures and the motion vectors of the current block is “0” in the coding in which the motion vectors and the reference pictures are determined using a predetermined method without coding them, as in the case of using a direct mode as described above, is defined as one of the prediction types PredType called “skip mode”. In using a skip mode, only the prediction type PredType indicating the skip mode is transmitted, therefore, coding of a block requires a very small code amount. The efficiency of coding can be further improved by assigning variable length code that is shorter than other prediction types to this skip mode or by run-length coding the number of consecutive blocks used for the skip mode.
In the H.264 described above, “skip mode” is defined as a case in which the entire coded residual data equivalent to a single block obtained by the inter-picture prediction using a direct mode is assumed to be “0”. The following processing is performed when a block is coded using a skip mode by the moving picture coding apparatus shown in FIG. 1. The motion estimation unit 301 outputs the reference picture numbers RefNo1, RefNo2, the motion vectors MV1, MV2 as well as the prediction type PredType indicating a skip mode. The variable length coding unit 302 performs variable length coding only for the prediction type PredType and outputs it as coded moving picture data Str0 through the processing explained above, when the prediction type PredType indicates a skip mode. The following processing is performed when the coded data of the block coded using a skip mode is inputted to the moving picture decoding apparatus shown in FIG. 4. The variable length decoding unit 601 performs variable length decoding on the prediction type PredType. When the prediction type PredType indicates a skip mode, the motion compensation unit 602 outputs, through the processing operated in the case of direct mode explained above, the reference picture numbers NRefNo1, NRefNo2, the motion vectors NMV1, NMV2 as well as the prediction type PredType indicating a skip mode.
In the H.264 as described above, arbitrary reference pictures can be selected out of a plurality of coded pictures regardless of the display time of the current picture. However, the arbitrary reference pictures are selected by performing motion estimation for the plurality of the coded pictures in this case, therefore, the processing burden caused by the motion estimation becomes very large. The plural reference picture interpolation prediction also contains a problem of degrading the coding efficiency since it requires coding of reference picture numbers and motion vectors for every two reference pictures.
Furthermore, when inter-picture prediction is performed for a picture using a picture whose display time is later than that of the current picture as a reference picture, as in the case of bidirectional prediction described in the conventional technique, the picture has to be coded in an order different from a display order, which causes a delay. In a case of real time communication such as a videophone, bi-directional predictive pictures cannot be used because of the delay. In the H.264, however, two arbitrary reference pictures can be selected regardless of display order information, therefore, the delay caused by coding can be eliminated by performing a plural reference picture interpolation prediction with a selection of two pictures respectively having a display time which is earlier than that of the current picture. However, the picture whose display time is later than that of the current picture is not stored in the multi-picture buffer, therefore, the direct mode conventionally used for determining the motion vectors using the picture whose display time is later than that of the current picture as described above cannot be employed.


1. Field of the Invention
The present invention relates to integrated circuit lead frames and methods of production thereof. In particular, this invention relates to plastic lead frames with a conductive coating or material contained therein used for packaging integrated circuits and methods of manufacturing the same.
2. State of the Art
Integrated circuit (IC) chips are enclosed in plastic packages that provide protection from hostile environments and enable electrical interconnection to printed-circuit boards. During a manufacturing process, the IC chip is typically attached to a die paddle of a conventional lead frame or suspended from the lead fingers of a leads-over-chip (LOC) lead frame using an adhesive such as epoxy or double-sided tape, and subsequently encapsulated with a dense and rigid plastic by a transfer molding process. In essence, the lead frame forms the backbone of the molded plastic IC package.
Lead frames typically perform many functions such as: (1) a holding fixture that indexes with tool-transfer mechanisms as the package proceeds through various assembly operations, (2) a dam that prevents plastic from rushing out between leads during the molding operation, (3) a chip attach substrate, (4) a support matrix for the plastic, and (5) an electrical and thermal conductor from chip to board.
Traditionally, lead frames are fabricated from a strip of sheet metal by stamping or chemical milling operations. There are many different metal alloy compositions which are commercially available for producing lead frames. For example, Rao R. Tummala and Eugene J. Rymaszewski, "Microelectronics Packaging Handbook," Table 8-4, 1989, provide 16 different alloys available from 9 different manufacturers. Lead frame material selection depends on many factors such as cost, ease of fabrication, strength, thermal conductivity, and matched coefficient of thermal expansion (CTE). A close match of CTE between the silicon die and the lead frame is required to avoid chip fracture from differential expansion rates.
The most widely used metal for lead frame fabrication is Alloy 42 (42% Nickel-58% Iron). Alloy 42 has a CTE near silicon and good tensile strength properties. The disadvantage of Alloy 42 is that it has low thermal conductivity. Since the lead frame is the main conduit by which heat flows from the chip to the environment and printed circuit board, this can have a profound effect on the package thermal resistance after prolonged device operation.
A layered composite strip, such as copper-clad stainless steel, was developed to emulate the mechanical properties of Alloy 42 while increasing thermal conductivity. However, copper-clad stainless steel is somewhat more expensive to manufacture than Alloy 42. When manufacturing copper-clad stainless steel lead frames, the cladding is accomplished by high-pressure rolling of copper foil onto a stainless steel strip, followed by annealing the composite to form a solid-solution weld. While copper alloys provide good thermal conductivity and have a CTE near that of low-stress molding compounds, there is a substantial CTE mismatch with respect to silicon.
While numerous alloys have been developed to solve problems with thermal conductivity, CTE mismatch, and strength, other important factors such as ease of fabrication and cost have not improved as readily.
Conventional methods for making lead frames for integrated circuit devices are described in U.S. Pat. No. 3,440,027. The use of a plastic support structure in a method of forming metal lead frames is described in U.S. Pat. No. 4,089,733 (hereinafter the "'733" patent). The plastic support structure of the '733 patent solves the problem of deformed and misaligned lead fingers resulting from stress during the bonding process by supporting the lead fingers with a plastic structure. However, the '733 patent requires a metal lead frame in addition to the plastic support structure with its attendant costs. A method of manufacturing multi-layer metal lead frames is disclosed in U.S. Pat. No. 5,231,756 (hereinafter the "'756" patent). The '756 patent provides an improvement in aligning power and ground planes for use in a multi-layer lead frame where such planes are necessary. However, the number of steps required to manufacture such multi-layer lead frames will not solve the problem of decreasing costs. In short, none of these related art appear to disclose methods of producing low-cost lead frames made from materials not structurally based on metal.
Since packaged ICs are produced in high volumes, a small decrease in the cost per packaged IC can result in substantial savings overall. Accordingly, there is a need in the industry for a low-cost plastic lead frame with suitable characteristics for IC packaging.


In a storage device using a semiconductor memory or the like, error correction processing is performed in data decoding processing. There is a chien search as a method of specifying error locations of data in the error correction processing. In the chien search, exclusive-OR operations multiplying α to the power, which multiply coefficients of an error location polynomial (t-order or less) except for a constant term by α, α2, . . . , αt, and exclusive-OR operations, which obtain the sum of the respective results of the operations on a Galois field, are performed to specify error locations by searching roots. Since error locations are determined in every cycle in a chien search circuit, all the exclusive-OR operations are performed in one cycle. Meanwhile, it is possible to improve error correction capability by increasing the order of the Galois field or the order of the error location polynomial in the chien search circuit, but the number of stages of the exclusive-OR operations is increased.


Universal Serial Bus (USB) is an industry standard developed that defines the cables, connectors and communications protocols used in a bus for connection, communication, and power supply between electronic devices.
In many portable products, USB is often used both as a communication port and as a power delivery port to accommodate battery charging. For example, a standard USB 2.0 compliant port may provide a maximum power delivery of 7.5 W (5V at 1.5 A) to a dedicated charging port that may be used to recharge the battery of a portable device. However, as the battery capacities of portable devices are increasing, for example, from 5600 mAh to 8000 mAh and 10000 mAh, the charging time for these devices increases accordingly. For example, using a standard USB 2.0 compliant port, it takes about 2 hours and 40 minutes to recharge a 5600 mAh battery, but it takes 4 hours and 45 minutes to recharge a 10000 mAh.
Faster charging times may be achieved by increasing the charging current and/or charging voltage. USB Power Delivery (PD) specification specifies using certified PD aware USB cables with standard USB type A/B connectors to deliver up to 100 W of power at 20 V. USB PD requires the use of PD-aware cables. For example, PD-aware cables with USB-micro B/AB connectors may support a maximum power of up to 60 W at 20 V, 36 W at 12 V and 10 W at 5 V. Consequently, under new USB standards, currents up to 5 A and power up to 100 W may be transferred through power delivery aware cables.
USB specification requires specification on the electrical parameters for the USB cables. For example, USB specification requires that USB cables have an American Wire Gauge (AWG) rating of 24-26, and further require that micro-B connectors have less than 50 mΩs.
However, USB cables including PD-aware cables may not be able to safely handle the large currents. For example, the cables may become defective during use due to field stress. Additionally, some of the USB manufacturers may not have good quality control. The large power supplied through a defective USB can pose a significant safety risk. Similarly, due to backward compatibility, end users may not be aware of the necessity to use the newer PD-aware cables.


Cellular wireless networks commonly provide both voice and data capability. A data communications layer is typically overlaid onto the voice communications layer, while utilizing the same network. For example, cellular devices utilizing the global system for mobile communications (GSM) voice standard are able to use the general packet radio service (GPRS) layer of the network for data communications. In these systems, a cellular device must register separately for the voice and the data networks. Protocols for network selection and registration were designed for human users primarily using voice communications, and in some instances these protocols require manual reconfiguration if there is a problem with or a different selection is desired for the data network. However, a problem arises in the event that a manual configuration, correction, or other input is required to correct a problem with the data network and there is no one available to provide the manual configuration, correction, or other input.


With the advent of the Internet, email has become prevalent in digital communications. For example, email messages are exchanged on a daily basis to conduct business, to maintain personal contacts, to send and receive files, etc. Unfortunately, undesired email messages have also become prevalent with increased email traffic. Often, these email messages are unsolicited advertisements, which are often referred to as “junk mail” or “spam.” Currently, software applications exist, which remove some of the spam or junk mail from a recipient's email account, thereby reducing clutter in the recipient's email account. Some of these applications remove email messages that contain a particular text or content (e.g., large image files, etc.) that may indicate that the email message is spam or junk mail. Email messages that are determined to be spam or junk mail are then either removed (e.g., permanently deleted) or stored in a designated folder (e.g., “trash” folder, “junk mail” folder, etc.). Unfortunately, some of the algorithms used to detect spam or junk mail may be quite complicated and cumbersome. Due to the complexity of current anti-spam or antijunk-mail algorithms, a need exists in the industry for simpler solutions.


Modern high volume package delivery systems often include package conveying systems that accept packages from one or more loading stations, and transports the packages to a variety of output destinations such as chutes, bins, and subsequent conveyor systems.
One of the most conventional types of conveyors is a belt conveyor, which includes the use of an endless flexible belt which passes over at least two cylindrical rollers, one of which is a drive roller. Packages are placed atop the upwardly-directed "working" surface of the belt conveyor, and are transported in a generally straight direction from end of the conveyor to the other.
Although such conventional belt conveyors have advantages, including simplicity, they also have disadvantages in that they conventionally only provide a "straight-line" transporting feature. This can be restrictive to package delivery system designers who may have the need to move a package or other product from an origin through a tortuous, curved, path to a destination.
Therefore, it has been known in the prior art to provide flexible conveyor chains such as shown in U.S. Pat. No. 3,776,349 to Kampfer, entitled "Fabricated Conveyor Chain", which discloses the concept of providing a fabricated flexible conveyor chain, which includes a plurality of link units 11 linked together by a plurality of pivot pins 12. Although the pivot pins 12 provide a linking feature between the link units, they fit loosely enough within their mounting holes to allow sideward relative pivoting of the link units. A similar type of "hard pin" connection is disclosed in U.S. Pat. No. 3,262,550 to Kampfer, entitled "Conveyor Chain", in U.S. Pat. No. 2,884,118 to Williams, entitled "Articulator Conveyor Chain", and also in U.S. Pat. No. 5,176,247 to Counter et. al., entitled "Sideflexing Conveyor Chain including Low Centerline Hinge Pin".
Although such "hard pin" connection configurations as described above have their advantages, they have disadvantages in that they tend to be complex, expensive, noisy, and difficult to maintain. Furthermore, they tend to provide a multitude of hard "pinch points", which are disadvantageous when in a human workplace environment. A "smooth" but flexible conveyor configuration is disclosed in U.S. Pat. No. 4,084,687 to Lapeyre, entitled "Conveyor Having Resilient Conveying Surface", but this configuration appears to be quite complex, requiring the use of link members 20 which are linked to modules 20 to support and convey flexible members 32 supported thereon.
Therefore, there is a need in the art to provide a package conveyor system which can transport packages or other items along a tortuous path, yet is simple in construction, quiet in operation, and cost-effective to manufacture, operate, and maintain.


1. Field of the Invention
The present invention relates to an electrode of a plasma display panel (PDP). More particularly, the present invention relates to a technology for improving exposure latitude and imparting improved PDP quality by modifying a photo-patternable paste.
2. Technical Background
In PDP's, 1000 or more electrodes measuring 80 to 100 μm in width by 0.5 to 1.5 m in length are formed. These electrodes are preferred to be free of defects and have superior linearity. Silver is typically used for the conductive metal particles contained in the electrodes.
Photolithography has recently become widely used to form the electrodes in PDP. In this method, a photo-patternable paste is first coated. A pattern is then formed by exposing and developing a film composed of the photo-patternable paste. Accompanying the increased size of glass substrates in recent years, proximity exposure has come to be used during exposure. Proximity exposure refers to a system whereby exposure is carried out while providing a gap of several hundred micrometers between a photomask and the coated film to be exposed.
In the case of pattern formation using a photo-patternable paste, it is desirable to increase the process latitude. It is desirable to increase the degree of freedom of the exposure conditions. In the case of low process latitude, the pattern shape may change easily depending on the exposure conditions, or the width of the electrodes may become uneven. Photosensitivity to changes in the pattern shape depending on exposure conditions signifies a low degree of freedom, and may even lead to restrictions on the production process. When carrying out proximity exposure, in particular, the width of the electrode formed tends to be greater than the designed electrode width, resulting in the decrease of sharpness of image. Measures to avoid this decrease in sharpness are needed.
Japanese Patent Application Laid-open No. 2003-195487 discloses a technology in which an ultraviolet absorber is added for the purpose of forming a fine, sharp transparent electrode. According to this publication, addition of the ultraviolet absorber makes it possible to diminish scattering of exposure light within the paste. Examples of ultraviolet absorbers include azo-based dyes, amino ketone-based dyes, xanthene-based dyes, quinoline-based dyes, anthraquinone-based dyes, benzophenone-based dyes, diphenylcyanoacrylate-based dyes, triazine-based dyes and p-aminobenzoic acid-based dyes.
However, if a dye-based ultraviolet absorber like that disclosed in Japanese Patent Application Laid-open No. 2003-195487 is used, since the ultraviolet absorber itself absorbs light, the paste that is produced is also colored. In a process for producing a PDP using a conductive paste, defect inspections are frequently carried out using visible light to confirm the coated state of the paste. At this time, if a dye which absorbs visible light is contained in the paste, there is the possibility of locations where defects are not present being detected. In addition, if the absorbance of visible light changes as a result of adding an ultraviolet absorber, there is the risk of having a detrimental effect on the efficiency of the photoinitiator. For example, since some photoinitiators have an absorbance range in the vicinity of up to 450 nm, in the case of using such a photoinitiator, a change in the absorbance in that range also ends up having an effect on the reflection efficiency of the photoinitiator.


The present invention relates to image-forming optical systems. More particularly, the present invention relates to a decentered optical system with a reflecting surface having a power for use in optical apparatus using digital still cameras, film scanners, and endoscopes. a small-sized image pickup device, e.g. video cameras,
Recently, with the achievement of small-sized image pickup devices, image-forming optical systems for use in video cameras, digital still cameras, film scanners, endoscopes, etc. have also been demanded to be reduced in size and weight and also in cost.
In the general rotationally symmetric coaxial optical systems, however, optical elements are arranged in the direction of the optical axis. Therefore, there is a limit to the reduction in thickness of the optical systems. At the same time, the number of lens elements unavoidably increases because it is necessary to correct chromatic aberration produced by a rotationally symmetric refracting lens used in the optical systems. Therefore, it is difficult to reduce the cost in the present state of the art. Under these circumstances, there have recently been proposed optical systems designed to be compact in size by giving a power to a reflecting surface, which produces no chromatic aberration, and folding an optical path in the optical axis direction.
Japanese Patent Application Unexamined Publication (KOKAI) Number [hereinafter referred to as “JP(A)”] 7-333505 proposes to reduce the thickness of an optical system by giving a power to a decentered reflecting surface and thus folding an optical path. In an example thereof, however, the number of constituent optical members is as large as five, and actual optical performance is unclear. No mention is made of the configuration of the reflecting surface.
JP(A) 8-292371, 9-5650 and 9-90229 each disclose an optical system in which an optical path is folded by a single prism or a plurality of mirrors integrated into a single block, and an image is relayed in the optical system to form a final image. In these conventional examples, however, the number of reflections increases because the image is relayed. Accordingly, surface accuracy errors and decentration accuracy errors are transferred while being added up. Consequently, the accuracy required for each surface becomes tight, causing the cost to increase unfavorably. The relay of the image also causes the overall volumetric capacity of the optical system to increase unfavorably.
JP(A) 9-222563 discloses an example of an optical system that uses a plurality of prisms. However, because the optical system is arranged to relay an image, the cost increases and the optical system becomes large in size unfavorably for the same reasons as stated above.
JP(A) 9-211331 discloses an example of an optical system in which an optical path is folded by using a single prism to achieve a reduction in size of the optical system. However, the optical system is not satisfactorily corrected for aberrations.
JP(A) 8-292368, 8-292372, 9-222561, 9-258105 and 9-258106 all disclose examples of zoom lens systems. In these examples, however, the number of reflections is undesirably large because an image is relayed in a prism. Therefore, surface accuracy errors and decentration accuracy errors of reflecting surfaces are transferred while being added up, unfavorably. At the same time, the overall size of the optical system unavoidably increases, unfavorably.
JP(A) 10-20196 discloses an example of a two-unit zoom lens system having a positive front unit and a negative rear unit, in which the positive front unit comprises a prism of negative power placed on the object side of a stop and a prism of positive power placed on the image side of the stop. JP(A) 10-20196 also discloses an example in which the positive front unit, which comprises a prism of negative power and a prism of positive power, is divided into two to form a three-unit zoom lens system having a negative unit, a positive unit and a negative unit. However, the prisms used in these examples each have two transmitting surfaces and two reflecting surfaces, which are all independent surfaces. Therefore, a relatively wide space must be ensured for the prisms. In addition, the image plane is large in size in conformity to the Leica size film format. Accordingly, the prisms themselves become unavoidably large in size. Furthermore, because the disclosed zoom lens systems are not telecentric on the image side, it is difficult to apply them to image pickup devices such as CCDs. In either of the examples of zoom lens systems, zooming is performed by moving the prisms. Accordingly, the decentration accuracy required for the reflecting surfaces becomes tight in order to maintain the required performance over the entire zooming range, resulting in an increase in the cost.
When a general refracting optical system is used to obtain a desired refracting power, chromatic aberration occurs at an interface surface thereof according to chromatic dispersion characteristics of an optical element. To correct the chromatic aberration and also correct other ray aberrations, the refracting optical system needs a large number of constituent elements, causing the cost to increase. In addition, because the optical path extends straight along the optical axis, the entire optical system undesirably lengthens in the direction of the optical axis, resulting in an unfavorably large-sized image pickup apparatus.
In decentered optical systems such as those described above in regard to the prior-art, an imaged figure or the like is undesirably distorted and the correct shape cannot be reproduced unless the formed image is favorably corrected for aberrations, particularly rotationally asymmetric distortion.
Furthermore, in a case where a reflecting surface is used in a decentered optical system, the sensitivity to decentration errors of the reflecting surface is twice as high as that in the case of a refracting surface, and as the number of reflections increases, decentration errors that are transferred while being added up increase correspondingly. Consequently, manufacturing accuracy and assembly accuracy, e.g. surface accuracy and decentration accuracy, required for reflecting surfaces become even more strict.


The present invention relates to the activation of fluid bed oxidation catalysts. More particularly the present invention relates to the activation of fluid bed oxidation catalysts useful in the preparation of maleic anhydride from 4-carbon atom hydrocarbons, including n-butane.
Oxidation catalysts containing the mixed oxides of vanadium and phosphorus have been utilized to produce maleic anhydride from 4-carbon atom hydrocarbons, such as n-butane. Methods have been investigated for activating, or increasing the catalytic activity of these catalysts. It is taught in the literature to "condition" vanadium phosphate-containing maleic anhydride catalysts under the flow of a low level of hydrocarbon in air, such as 0.2 volume percent to 2 volume percent hydrocarbon in air at temperatures of 300.degree. C. to 600.degree. C., as in U.S. Pat. No. 4,171,316.
U.S. Pat. No. 3,985,775 discloses the preparation of vanadium phosphorus mixed oxide catalysts prepared by a method requiring heating the catalyst precursor at about 350.degree. C. to 410.degree. C. to drive off at least a portion of hydration, and then at a higher temperature. This method is taught as suitable for use in fixed bed operation.
Attempting to "condition" a fluid bed catalyst with low levels of hydrocarbon in air under normal operating conditions has been found to have little beneficial effect.
Activation procedures for fixed bed catalysts are not readily applicable for use with fluid bed catalysts. In fixed bed operation, a characteristic exotherm or hot spot is generated in the catalyst bed within the reactor vessel. A substantial portion of the total reaction takes place at this hot spot. The location of the hot spot is dependent upon the location of the oxygen and feed stock inlets, the dimensions of the vessel, and operating conditions such as flow rates, temperature and pressure. Fixed bed activation procedures generally may concentrate in the hot spot of the catalyst bed, having little effect on the remainder of the catalyst in the reactor.
In fluid bed operation, such a hot spot is not generated. Catalyst particles are not localized, but move throughout the reactor vessel, and substantially the entire portion of the catalyst within the reactor vessel contacts the feed to contribute to the reaction.


A critical response of the innate immune system to microbial infection is the ingestion, destruction and clearance of pathogens by activated phagocytic cells. Within their phagosomal compartments, macrophages generate an environment that is hostile to microbes via the production of reactive oxygen and nitrogen species, the elaboration of proteases, acidification of the phagosomal lumen and the export of iron.1,2 Unlike iron, copper (Cu) is not essential for many pathogens, although it is an essential trace element for mammals. In fact, Cu has been used for over a century as a microbiocidal agent for the elimination of human and plant pathogens.3 Moreover, Cu is critical for normal innate immune cell function and Cu deficiency in mammals renders the host susceptible to microbial pathogens. It is well documented that Cu levels rise dramatically in the serum of mammals during infection/inflammation and Cu accumulates at sites of inflammation, underscoring a specialized role for Cu in innate immunity.4,5 Consistent with a microbiocidal role for Cu in macrophages, phagosomal Cu concentrations rise dramatically in activated macrophages in parallel with increased expression of the Ctrl plasma membrane Cu importer and the Atp7A Cu pump on the phagosomal membrane.6, 7 Moreover, studies in both prokaryotic and fungal pathogens demonstrate the requirement for the Cu homeostasis machinery in resistance to macrophage killing.7, 8 Together, these studies provide compelling evidence for a critical role of Cu in microbiocidal activity of the host, which is countered by the Cu homeostasis machinery of invading bacterial and fungal pathogens.
Biocidal properties of Cu have been documented since ancient Egyptians used it for water and wound sterilization in 2400 B.C.9 The Bordeaux mixture of copper sulfate and lime has been used since 1880 as a fungicide for grapes and other plants,3 while metallic Cu surfaces, which likely release Cu ions upon bacterial contact, may reduce contamination in hospitals.10-12 Metallic Cu, Cu salts, and Cu compounds continue to be used to control bacterial, fungal, and algal growth in agricultural and healthcare settings where microbes exist in the environment.3 The environment of pathogenic microbes, however, is ultimately the infected host, and while Cu and its complexes have been used for so long as environmental antimicrobials, no approach to date has been effective at using Cu to fight infection in a mammalian host. A challenge in this area is to discover ways to deliver or reallocate Cu selectively to the site of infection or inflammation.4


Conventionally, there is a medicine dispensing device for dispensing blister packages having a configuration in which a blister package is conveyed with the help of a grip unit and cut by a cutter mechanism to enable retrieval of the required quantity of the package sheet (see Patent document 1, for example).
As another medicine dispensing device for dispensing blister packages, there is one having a configuration that enables retrieval of a blister package loaded inside a medicine cassette by sucking it with a suction member (see Patent document 2, for example).
However, in the medicine dispensing device disclosed in Patent Document 1, a grip unit is used for retrieving not only a fraction of the blister package but also one full blister package, and therefore, there is a problem of poor retrieving efficiency. Further, since the blister packages are stacked vertically, the space occupied in the height direction increases, and there is a problem that the quantity and type that can be accommodated is limited.
In the medicine dispensing device disclosed in Patent Document 2, it is not possible to dispense fraction of a blister package.


Plastic exterior products in a variety of colors and with a high quality sense of touch are increasingly popular for electronic parts, automobile parts and the like. Plastic exterior products can be formed of a resin composition including a thermoplastic resin and metal particles distributed therein to give a metal-like texture to the product.
Japanese Patent Laid-Open Publication Nos. 2001-262003 and 2007-137963 discuss adding metal particles to a plastic resin, but the metal-like texture did not appear in an actual experiment. Also, there is a problem in that a flow mark or a weld line is formed during an injection molding process.
Japanese Patent Laid-Open Publication No. 1995-196901 discusses adding a metal microplate having an average aspect ratio (average thickness/average particle diameter) of about 1/100 to about 1/8 obtained through a punching process to a resin to provide a metal-like texture. This process, however, is also limited by formation of a weld line.


Large quantities of glucose-containing syrups are manufactured by the enzymatic hydrolysis of corn starch. The first step of this process is usually accomplished by treating a starch-water mixture with an alpha-amylase enzyme at temperatures near the boiling point of water. A thermostable alpha-amylase is most efficient at these temperatures. For this reason, there is a great incentive to obtain a low-cost source of such a thermostable enzyme.
The alpha-amylases used commercially are produced by various microorganisms. It is known that these microorganisms contain genetic material which codes for the production of the enzymes by the organism. This genetic material is present in the form of deoxyribonucleic acid, hereafter referred to as DNA, within the cell.
Most genetic material in a bacterium exists as giant DNA molecules which are present as the chromosome of the cell. However, a certain amount of the genetic material may also be present in the form of smaller closed circular molecules of DNA, known as plasmids.
By techniques referred to as genetic engineering, it is possible to transfer a portion of the DNA from one organism to another. Various workers have attempted to use these techniques to develop microorganisms which are superior alpha-amylase producers.
One technique that has been used is to remove the total DNA, i.e., chromosomal plus plasmid DNA, from a microorganism known to produce an amylase. Fragments of this DNA are then linked with the DNA of a bacteriophage. The bacteriophage containing this combined DNA is used to infect another microorganism whereby it transfers this genetic material onto the chromosomal DNA of the microorganism. The cells of the infected organism that receive DNA containing an amylase gene in an active form become amylase producers. These cells can be selected and grown for further use.
An additional genetic engineering technique that has been used with thermostable alpha-amylases involves extracting the total DNA from a microorganism known to produce such amylases. Some fragments of the DNA are transformed into a new host microorganism whereby they are incorporated into the chromosome of the host microorganism. Any cells into which the DNA containing active amylase-coding genetic material has been introduced are then selected and grown.
It has now been found that DNA coding for a thermostable alpha-amylase can exist in a naturally-occurring plasmid. Furthermore, it has been found that such naturally-occurring genetic material containing a thermostable alpha-amylase coding gene can be combined directly with another plasmid, known as a plasmid vector, to give a synthetic plasmid, hereafter called a chimeric plasmid. This chimeric plasmid can be inserted into and multiplied in a new host microorganism. This permits the development of microorganisms that are superior alpha-amylase producers which can be grown readily on a commercial scale. It is to the use of the newly-discovered, naturally-occurring plasmids containing alpha-amylase genes, the formation of chimeric plasmids containing their genetic material, and the development of new microorganisms containing these chimeric plasmids, that the present invention is directed.


The desirability of improving the efficiency of combustion in a vehicle's engine has long been recognized. For instance, Lyons and McKone is U.S. Pat. No. 2,086,775, and again in U.S. Pat. No. 2,151,432, disclose a method for improving combustion efficiency in an internal combustion engine by adding to the fuel what is described as "relatively minute quantities" of catalytic organometallic compounds. The Lyons and McKone patents, though, are directed solely to internal combustion engines and do not address the problem of NO.sub.x emissions from diesel engines.
In a unique application of catalytic technology described in International Publication No. WO 86/03482 and U.S. Pat. No. 4,892,562, Bowers and Sprague teach the preparation of diesel fuel containing fuel soluble platinum group metal compounds at levels of from 0.01 to 1.0 parts per million (ppm). The Bowers and Sprague results were corroborated and refined by work of Kelso, Epperly, and Hart, described in "Effects of Platinum Fuel Additive on the Emissions and Efficiency of Diesel Engines," Society of Automotive Engineers (SAE) Paper No. 901,492, August 1990. Although the use of platinum group metal additives is effective, further nitrogen oxides reductions are still believed possible.
Moreover, in "Assessment of Diesel Particulate Control--Direct and Catalytic Oxidation," SAE Paper No. 81 0112, 1981, Murphy, Hillenbrand, Trayser, and Wasser have reported that the addition of catalyst metal to diesel fuel can improve the operation of a diesel trap. Among the catalysts disclosed is a platinum compound, albeit one containing chlorine, known to reduce catalyst effectiveness. In addition, the regeneration of a diesel trap by the use of a metallic additive which can include copper, nickel, cobalt, and, especially, iron, is discussed by Mueller, Wiedemann, Preuss and Schadlich in "Diesel Particulate Filter System With Additive Supported Regeneration," ATZ Automobiltechnische Zeitschift 91 (1989).
Other researchers have considered the use of water in oil emulsions for improving combustion efficiency in diesel engines. For instance, DenHerder, in U.S. Pat. No. 4,696,638, discusses such emulsions and indicates that the positive effects therefrom include "cleaner exhaust." Although the disclosure of Denherder refers to emulsions containing up to about 40% water, Denherder is primarily directed to emulsions having only up to about 10% water in the form of droplets having a diameter of about 1 to about 10 microns.
Furthermore, Wasser and Parry have reported in "Diesel Engine NO.sub.x Control: Selective Catalytic Reduction and Methanol Emission," EPRI/EPA Joint Symposium on Stationary NO.sub.x Control, New Orleans, La., March, 1987 that NO.sub.x reductions of up to 80%, which are the levels desired for effective emission control, can be achieved in diesel engines using water and oil emulsions. They found, though, that emulsions of at least 60% water in oil are necessary to achieve such reductions. Unfortunately, such high water ratios can lead to increased emissions of carbon monoxide (CO) and unburned hydrocarbons. In addition, such high water levels can also cause problems in emulsion stability and create corrosion and storage volume concerns.
Recently, Dainoff and Sprague, in U.S. patent application entitled "Process for Reducing Nitrogen Oxides Emissions and Improving the Combustion Efficiency of a Turbine:, Ser. No. 07/691,556, filed Apr. 25, 1991, have discovered that water-in-fuel oil emulsions up to about 50% water by weight are useful for reducing nitrogen oxides and particulate emissions from combustion turbines, but they do not address the usefulness of such emulsions in vehicle diesel engines.
There has been a great deal of study of processes and agents for reducing nitrogen oxides emissions from stationery sources, such as boilers, etc. Preferred among such processes are those referred to as selective, non-catalytic reduction (SNCR) NO.sub.x reducing processes. Such processes involve the introduction of a NO.sub.x reducing treatment agent into a combustion effluent to achieve reductions of nitrogen oxides of up to about 50% or greater by a gas phase free radical mediated reaction process. SNCR processes generally utilize a nitrogen containing treatment agent such as ammonia, urea, or other chemicals and compositions which can break down in the effluent to the amidozine radical, which is believed to be the moiety which reacts with and reduces nitrogen oxides to molecular nitrogen (N.sub.2).
Such processes are disclosed by, for instance, Lyon, in U.S. Pat. No. 3,900,554, Arand, Muzio, and Sotter, in U.S. Pat. No. 4,208,386, and Arand, Muzio, and Teixeira, in U.S. Pat. No. 4,325,924. Although effective at reducing nitrogen oxides in effluents from open flame combustion, it has been believed that at the temperatures and pressures which exist in diesel engines, the use of nitrogenous nitrogen oxides reducing agents in such processes may actually create NO.sub.x, thus exacerbating the problem.
Accordingly, a process and composition which is effective at substantially reducing the nitrogen oxides emissions from a diesel engine without the drawbacks of the prior art is extremely desirable.


P2 receptors have been generally categorized as either metabotropic nucleotide receptors or ionotropic receptors for extracellular nucleotides. Metabotropic nucleotide receptors (usually designated P2Y or P2Y.sub.n, where "n" is a subscript integer indicating subtype) are believed to differ from ionotropic receptors (usually designated P2X or P2X.sub.n) in that they are based on a different fundamental means of transmembrane signal transduction: P2Y receptors operate through a G protein-coupled system, while P2X receptors are ligand-gated ion channels. The ligand for these P2X receptors is ATP, and/or other natural nucleotides, for example, ADP, UTP, UDP, or synthetic nucleotides, for example 2-methylthioATP.
At least seven P2X receptors, and the cDNA sequences encoding them, have been identified to date. P2X.sub.1 cDNA was cloned from the smooth muscle of the rat vas deferens (Valera et al (1994) Nature 371:516-519) and P2X.sub.2 cDNA was cloned from PC12 cells (Brake et al. (1994) Nature 371:519-523). Five other P2X receptors have been found in cDNA libraries by virtue of their sequence similarity to P2X.sub.1 and P2X.sub.2 (P2X.sub.3 : Lewis et al. (1995) Nature 377:432-435, Chen et al. (1995) Nature 377:428-431; P2X.sub.4 : Buell et al. (1996) EMBO J. 15:55-62, Seguela et al. (1996) J. Neurosci. 16:448-455, Bo et al. (1995) FEBS Lett. 375:129-133, Soto et al. (1996) Proc. Natl. Acad. Sci. USA 93:3684-3688, Wang et al. (1996) Biochem. Biophys. Res. Commun.220:196-202; P2X.sub.5 : Collo et al. (1996) J. Neurosci. 16:2495-2507, Garcia-Guzman et al. (1996) FEBS Lett. 388:123-127; P2X.sub.6 : Collo et al. (1996), supra, Soto et al. (1996) Biochem. Biophys. Res. Commun. 223:456-460; P2X.sub.7 : Surprenant et al. (1996) Science 272:735-738). For a comparison of the amino acid sequences of rat P2X receptors see Buell et al. (1996) Eur. J. Neurosci. 8:2221-2228.
Native P2X receptors form rapidly activated, nonselective cationic channels that are activated by ATP. Rat P2X.sub.1 and rat P2X.sub.2 have equal permeability to Na.sup.+ and K.sup.+ but significantly less to Cs.sup.+. The channels formed by the P2X receptors generally have high Ca.sup.2+ permeability (P.sub.Ca /P.sub.Na.congruent.4). The cloned rat P2X.sub.1, P2X.sub.2 and P2X.sub.4 receptors exhibit the same permeability for Ca.sup.2+ observed with native receptors. However, the mechanism by which P2X receptors form an ionic pore or bind ATP is not known.
A variety of tissues and cell types, including epithelial, immune, muscle and neuronal, express at least one form of P2X receptor. The widespread distribution of P2X.sub.4 receptors in the rat central nervous system suggests a role for P2X.sub.4 -mediated events in the central nervous system. However, study of the role of individual P2X receptors is hampered by the lack of receptor subtype-specific agonists and antagonists. For example, one agonist useful for studying ATP-gated channels is .alpha.,.beta.-methylene-ATP (.alpha.,.beta.meATP). However, the P2X receptors display differential sensitivity to the agonist with P2X.sub.1 and P2X.sub.2 being .alpha.,.beta.meATP-sensitive and insensitive, respectively. Furthermore, binding of .alpha.,.beta.meATP to P2X receptors does not always result in channel opening. The predominant forms of P2X receptors in the rat brain, P2X.sub.4 and P2X.sub.6 receptors, cannot be blocked by suramin or PPADS. These two forms of the P2X receptor are also not activated by .alpha.,.beta.meATP and are, thus, intractable to study with currently available pharmacological tools.
A therapeutic role for P2 receptors has been suggested, for example, for cystic fibrosis (Boucher et al. (1995) in: Belardinelli et al. (eds) Adenosine and Adenine Nucleotides: From Molecular Biology to Integrative Physiology (Kluwer Acad., Norwell Mass.) pp 525-532), diabetes (Loubatieres-Mariani et al. (1995) in: Belardinelli et al. (eds), supra, pp 337-345), immune and inflammatory diseases (Di Virgilio et al. (1995) in: Belardinelli et al. (eds), supra, pp 329-335), cancer (Rapaport (1993) Drug Dev. Res. 28:428-431), constipation and diarrhea (Milner et al. (1994) in: Kamm et al. (eds.) Constipation and Related Disorders: Pathophysiology and Management in Adults and Children (Wrightson Biomedical, Bristol) pp 41-49), behavioral disorders such as epilepsy, depression and aging-associated degenerative diseases (Williams (1993) Drug. Dev. Res. 28:438-444), contraception and sterility (Foresta et al. (1992) J. Biol. Chem. 257:19443-19447), and wound healing (Wang et al. (1990) Biochim. Biophys. Res. Commun. 166:251-258).
Accordingly, there is a need in the art for specific agonists and antagonists for each P2X receptor subtype and, in particular, agents that will be effective in vivo, as well as for methods for identifying P2X receptor-specific agonist and antagonist compounds.


This invention relates to pneumatic tires and more particularly to a pneumatic tire having a wide reinforcing breaker or belt extending into an annular protuberance in the buttress region of the tire.
The tread reinforcement component commonly referred to as a belt or breaker is disposed between the tread and the carcass in the crown region of the tire. Typically, a breaker or belt is constructed of one or more plies of rubberized cord fabric. Each cord in the fabric is generally of a substantially non-extensible material such as metallic wires or strands, glass filaments, or rayon filaments. The cords within the breaker plies are oriented parallel to each other and substantially parallel to the plane of the beads and thus circumferentially of the tire, or at a small bias angle. In a single ply breaker construction, the small bias angle can be 0.degree.. Where the breaker is a multi-ply structure, however, the small bias angle is in the range of about 15.degree.-30.degree. with respect to the median equatorial plane of the tire, and may be oppositely disposed in successive plies.
The development of a reinforcing belt or breaker for use in pneumatic tires added a number of benefits to tires including considerable improvement to tire durability. On the other hand, the breaker also introduced some new problems of its own. The lateral edges of a breaker in a typical tire, due to their location between the tire tread and carcass at a position of continually changing stress, tend to separate from the carcass or themselves. Improper positioning of the breaker results in the uniformity problems of increased lateral force variation and conicity.
Another benefit of a reinforcing breaker is improved tread wear due to the greater stiffness imparted to the tire tread. Of course, this benefit is enhanced by utilizing a "flat" tread having no convex cross-sectional curvature so that the relative movement between the center portion of the tread and the axially outward portions is minimized thereby resulting in an even wear pattern. A serious drawback of a tread designed to have no convex cross-sectional curvature lies in the fact that a tire which is vulcanized with such a shape, when cured, may inflate to a concave tread cross-section rather than a flat cross-section. Elimination of this problem can be accomplished by constructing and vulcanizing the tire such that the tread has at least a small convex cross-sectional curvature, that is, a large crown radius ratio, when the cured tire is inflated to its rated inflation pressure.
In the detailed description of the invention following hereinafter, the cross-sectional curvature of the tread and breaker of the tire are discussed in terms of "crown radius ratio" and "crown radius." The term "crown radius" as used herein either with respect to the tread or breaker, means the radius of the arc of a circle which best approximates the arc of curvature of the tread surface or the breaker as the case may be of a tire. The crown radius is commonly determined by the formula ##EQU1## where "leg set" is the axial distance measured along a line tangent to the tread or breaker at its midpoint between the shoulders of the tread or edge of the breaker, or predetermined points axially equidistance inward of the shoulders or breaker edges. Shoulder drop is the perpendicular distance from the aforementioned tangent line to the tread shoulders or said predetermined points. In the case of a breaker, shoulder drop may be considered as the perpendicular distance between the line tangent to the breaker at its midpoint and the edges of the breaker. The "crown radius ratio" is the ratio of the crown radius of either the tread or breaker to the nominal cross-sectional width of the tire and as used herein is expressed in terms of percent.
Either a belted radial or a belted bias tire construction is suitable for use in the present invention. The radial type tire is, however, the preferred embodiment. A radial tire is inclusive of various tire constructions which typically comprise a carcass or body having one or more reinforcement plies of cord fabric extending from bead to bead wherein the cords in each ply are substantially radial in orientation, that is, the cords are oriented substantially normal to the beads and the crown centerline of the tire. In a single ply radial tire construction, the carcass cords normally have a 90.degree. bias angle, that is, in the unshaped carcass they extend perpendicular to the planes of the beads. In a two-ply radial tire construction, the cords in each carcass ply are parallel to the cords in the other carcass ply. However, the cords in each ply may be oriented at oppositely disposed angles of 70.degree. or more with respect to the median equatorial plane of the tire and thus the angle between cords in different plies is between 0.degree. and 40.degree.. In more than two ply radial ply tire constructions, similar cord arrangements in successive carcass plies is usually employed.
With regard to the prior art, U.S. Pat. No. 3,450,182 discloses a tire having a flat tread cross-section, wide protuberances extending beyond the width of the tire sidewalls, a tread surface in normal engagement with the ground between the lateral edges of the protuberances and a breaker extending laterally beneath the tread to positions adjacent the edges of the protuberances. This patent does not, however, disclose a breaker having its lateral edges removed from the stress area of contact by the tread with the ground or a convex cross-sectional tread curvature facilitating the manufacture of a tire. Moreover, the extreme lateral extension of the protuberances beyond the tire sidewall will result in a high degree of tread shoulder wear and breaker separation due to centrifugal force moving the protuberances radially outward during tire rotation.
In U.S. Pat. No. 2,477,754, an aircraft tire is shown in which a tread and breaker have a substantial convexly curved cross-section when the tire is inflated and the breaker has edges positioned within protuberances extending from the side of the tire. When this tire is loaded (but not impacted), the tread-ground contact area is in the crown area of the tread only and consequently the tread wear and traction of the tire will be relatively poor. Moreover, when the tire is subject to the normal type of impaction and very heavy loading which aircraft tires receive, the lateral edges of the breaker rotate through the tread-ground contact area to cause edge separation of the breaker. A further defect in the tire of U.S. Pat. No. 2,477,754 is that the circumferential breaker cords along the lateral sides of the breaker will carry the entire breaker load under deflection so that these breaker cords will break after a small amount of such use.


Collapsible tube squeezing devices for dispensing the contents of tubes containing toothpaste, hair creme, hand lotion, shoe polishing creme, glue, and the like are well known in the art. A review of the prior art devices shows that while such devices exist they have not received substantial user acceptance due to their expense, size, lack of universality, difficulties with operation and the necessity to use both of the operator's hands in emptying the contents of collapsible tubes.
The advent of collapsible tubes formed of plastic, rather than the well known metallic type collapsible tubes, has also presented additional problems which have rendered many pre-plastic tube squeezing devices unsuitable for their intended purposes particularly in regard to removal of the contents of the crown portion of such tubes. Crown portions of plastic collapsible tubes have a tendency to be substantially more rigid than metallic tubes which factor coupled with the resiliency of plastics often employed in the manufacture of plastic collapsible tubes necessitates that special measures be undertaken in order to completely empty such tubes.


The subject matter disclosed herein relates to a rotary device and, more particularly, to a rotary device with no-back and torque-limiting capabilities.
An aircraft utilizes actuation systems for control of aircraft flight surfaces. Such actuation systems transmit torque to actuators through torque transmission devices including torque tubes, gear boxes and bearing supports. If a disconnection failure occurs to a torque transmission device, a no-back will prevent a loss of position control for a given flight surface by grounding the resultant torque generated by airloads on the flight control surface to a structural ground and thereby lock the surface in a fixed position.
With such flight control actuation systems, it is often necessary to mitigate an overload condition generated by a structural jam. One method to accomplish overload mitigation is to have a torque limiting device within the actuation system such that the actuator output torque is limited by a mechanism within an actuator by transferring torque to structural ground if the limit is exceeded.


1. Field of the Invention
The invention relates to a digital switching stage having a differential amplifier with a first and a second differential amplifier branch; a first resistor which is connected in the first differential amplifier branch has a first terminal that is a terminal for a first supply potential and has a second terminal; and a first bipolar transistor which is connected in an emitter follower circuit with respect to the second terminal of the first resistor has an emitter which is connected to an output terminal.
Such a switching stage is shown in the literature, such as in an article by George R. Watson, entitled "Advances in Bipolar VLSI", in Proceedings of the IEEE, Vol. 78, No. 11, pp. 1706-1719, November 1990. An output of the switching stage is essentially capacitively loaded by a connecting line connected to it. At a positively oriented edge of the output signal, the current required to reverse the charge of the parasitic capacitance which is operative on the output side flows through the emitter follower transistor. That is, the charge reversing current is furnished at low impedance by the first supply potential source. At a negatively oriented output signal edge, the charge reversing current flows either through one additional current source or through the input of a further switching stage connected to the output side. The current is furnished at high impedance from a further supply potential source.
In order to achieve a high operating speed, the switching stages must have adequate driver capability and a high permanent current therefore flows through the additional current source or the following switching stage. The power loss is correspondingly high.
2. Summary of the Invention
It is accordingly an object of the invention to provide a digital switching stage with a current switch, which overcomes the hereinafore-mentioned disadvantages of the hereto-fore-known devices of this general type and which has a high processing speed and a low power loss.
With the foregoing and other objects in view there is provided, in accordance with the invention, a digital switching stage, comprising a differential amplifier having a first and a second differential amplifier branch; a terminal for a first supply potential, a terminal for a second supply potential, and an output terminal; a first resistor being connected in the first differential amplifier branch and having a first terminal and a second terminal, the first terminal being the terminal for the first supply potential; a first bipolar transistor being connected in an emitter follower circuit with respect to the second terminal of the first resistor and having an emitter being connected to the output terminal; a second bipolar transistor having a base and having a collector-to-emitter path being connected between the output terminal and the terminal for the second supply potential; and a second resistor being connected in the second differential amplifier branch and having a first terminal and a second terminal, the first terminal of the second resistor being connected to the output terminal, and the second terminal of the second resistor being connected to the base of the second bipolar transistor.
In the switching stage according to the invention, for both the leading and the trailing output signal edges, the charge reversing current of the parasitic capacitance that is operative on the output side is furnished at low impedance from the supply potential forces. The input and output signal levels are symmetrical to the supply potentials. In comparison with the conventional switching stage, the supply voltage is lower, so that the lower loss is further reduced thereby.
In accordance with another feature of the invention, there is provided a current source transistor having a collector-to-emitter path, the differential amplifier including a first and at least one second switching transistor having mutually coupled emitters being connected through the collector-to-emitter path of the current source transistor to the terminal for the second supply potential.
In accordance with a further feature of the invention, there is provided a voltage divider connected between the terminals for the supply potentials for supplying the base of the first switching transistor with a reference potential.
In accordance with an added feature of the invention, the voltage divider includes a first diode having an anode connected to the terminal for the first supply potential and having a cathode; a second diode having a cathode connected to the terminal for the second supply potential and having an anode; a first resistor connected between the cathode of the first diode and the base of the first switching transistor; and a second resistor connected between the base of the first switching transistor and the anode of the second diode.
In accordance with an additional feature of the invention, the base of the current source transistor is connected to the anode of the second diode.
In accordance with yet another feature of the invention, the first and second resistors of the voltage divider have the same given resistance.
In accordance with yet a further feature of the invention, the first and second resistors of the differential amplifier each have the same resistance being twice the given resistance.
In accordance with a concomitant feature of the invention, the resistance of the first resistor of the differential amplifier is greater than the resistance of the second resistor of the differential amplifier, and the resistances of the first and second resistors of the differential amplifier are each greater than twice the given resistance.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a digital switching stage with a current switch, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.


Cancer generally refers to one of a group of more than 100 diseases caused by the uncontrolled growth and spread of abnormal cells that can take the form of solid tumors, lymphomas, and non-solid cancers such as leukemia. Unlike normal cells, which reproduce until maturation is attained and then only as necessary for replacement, cancer cells grow and divide endlessly, crowding out nearby cells and eventually spreading to other parts of the body, unless their progression is stopped. Once cancer cells metastasize by leaving a tumor, they will travel through the bloodstream or lymphatic system to other parts of the body, where the cells begin multiplying and developing into new tumors. This sort of tumor progression makes cancer dangerously fatal. Although there have been great improvements in diagnosis, general patient care, surgical techniques, and local and systemic adjuvant therapies, most deaths from cancer are still due to metastases and other cancers that are resistant to conventional therapies including radiation and chemotherapy.
Radiation therapy is typically only effective for cancer treatment at early and middle stages of cancer, when cancer is localized, and not effective for late stage disease with metastasis. Chemotherapy can be effective at all stages of the disease, but there can be severe side effects, e.g. vomiting, low white blood cells, loss of hair, loss of weight and other toxic effects, to radiation therapy and chemotherapy. Because of such severe side effects, many cancer patients do not or cannot successfully complete a chemotherapy treatment regimen. The side effects of radiation and anticancer drugs can be viewed as resulting from poor target specificity. Anticancer drugs, typically administered intravenously or more rarely orally, circulate through most normal tissues of patients as well as the target tumors. If the drug is toxic to a normal cell, then this circulation will result in the death of normal cells, leading to side effects, and the more toxic the drug to normal cells, the more serious the side effects. Due to these and other problems, some highly cytotoxic chemotherapeutic agents, agents with nanomolar or sub-nanomolar IC50 values against cancer cells, have not been successfully developed into approved drugs.
Prodrugs have been investigated as a means to lower the unwanted toxicity or some other negative attribute of a drug without loss of efficacy. A prodrug is a drug that has been chemically modified to render it inactive but that, subsequent to administration, is metabolized or otherwise converted to the active form of the drug in the body. For example, in an effort to improve drug targeting, prodrugs have been developed that are activated under hypoxic conditions. Hypoxia creates a bioreductive environment, and certain anti-cancer agents have been converted into prodrugs that can be activated in such environments. See the reviews by Naylor et al., May 2001, Mini. Rev. Med. 1(1):17-29, and Denny, 2001, Eur. J. Med Chem. 36: 577-595. “Hypoxia” is a condition of low oxygen levels; most solid tumors larger than about 1 mm in diameter contain hypoxic regions (see the references Coleman, 1988, J. Nat. Canc. Inst. 80: 310; and Vaupel et al., Cancer Res. 49: 6449).
As a tumor grows, it requires a blood supply and thus the growth of new vasculature. The new vasculature that supports tumor growth is often highly unordered, leaving significant portions of the tumor under-vascularized and subject to intermittent vascular blockage. The vascular architecture of the tumor can contribute significantly to the cancer's ability to survive drug therapy in at least two different ways. First, if the drug must reach the cancer through the bloodstream, then not as much drug will reach the under-vascularized, hypoxic areas of the tumor. Second, to the extent the drug requires oxygen to be effective, then the drug will be less effective in the hypoxic regions of the tumor.
Conversely, however, the hypoxic environment is conducive to reductive events that can be used to generate reduced derivatives of a variety of chemical groups (see the reference Workman et al., 1993, Cancer and Metast. Rev. 12: 73-82), and bioreductive prodrug compounds have been developed to exploit such environments. These prodrugs include the antibiotics Mitomycin C (MMC) and Porfiromycin (POR), N-oxides such as Tirapazamine (TRZ; see the reference Zeeman et al., 1986, Inst. J. Radiot. Oncol. Biol. Phys. 12: 1239), quinones such as the indoloquinone E09 (see the reference Bailey et al., 1992, Int. J. Radiot. Oncol. Biol. Phys. 22: 649), cyclopropamitosenes (EP-A-0868137), and a tertiary amine-N-oxide analogue of Mitoxantrone (AQ4N) that is activated by cytochrome P450 3A4 (see the references Patterson, 1993, Cancer Metast. Rev. 12: 119; and Patterson, 1994, Biochem. Pharm. Oncol. Res. 6: 533).
Other bioreductively activated prodrug compounds include the nitroimidazole derivatives that have been reported to be useful in cancer radiotherapy as radio-sensitizing agents (see the patent publications EP312858 and WO91/11440) and potentiatiors of chemotherapeutic agents (see U.S. Pat. No. 4,921,963). Nitroimidazole has also been conjugated to the anti-cancer agent PARP 5-bromoisoquinolinone (see the reference Parveen et al., July 1999, Bioorg. Med. Chem. Lett., 9:2031-36). The nitroimidazole moiety itself is, however, somewhat cytotoxic to normal cells, because it undergoes redox cycling and generates superoxides under oxygenated conditions.
Bioreductively activated prodrug compounds that include a nitroimidazole linked to a variety of anti-neoplastic agents has been described in A 2-NITROIMIDAZOLE CARBAMATE PRODRUG OF 5-AMINO-1-(CHLOROMETHYL)-3-[5,6,7-TRIMETHOXYINDOL-2-YL)CARBONYL]-1,2-DIHYDRO-3H-BENZ[E]INDOLE (AMINO-SECO-CBI-TMI) FOR USE WITH ADEPT AND GDEPT, M. P. Hay et al., Bioorganic & Medicinal Chemistry Letters 9 (1999) 2237-2242, and PCT publication WO 00/64864. In all of the prodrugs described in these documents, the nitroimidazole is directly linked to a carbamate linker and the anti-neoplastic agent is protected at a nitrogen via a carbamate or at a carbon via an ester linkage.
Thus, there remains a need to provide drugs to treat cancer. Such drugs would be especially beneficial if they targeted cancer cells more effectively than current drugs and had fewer, less serious side effects. The present compounds and methods help meet this need.


Fiber optics communication systems require compact light emitting sources capable of generating single-mode, tunable, narrow linewidth radiation in the 1.3-1.56 .mu.m wavelength range. Some of the existing semiconductor lasers, for example, InGaAsP DFB lasers can meet requirements for high power and proper wavelength, but a high dynamic single mode yield is difficult to achieve. Conventional index coupled CFB lasers employing an index corrugation have an inherent problem in existence of two longitudinal modes with an equal threshold gain which results in poor single mode operation as shown, for example, in the article by H. Kogelnik and C. V. Shank "Coupled-Wave theory of distributed feedback lasers", J. Appl. Phys., vol. 43, no. 5, pp. 2327-2335, 1972. In complex coupled DFB lasers, a periodic optical gain or loss modulation in the presence or absence of conventional index corrugation along the laser cavity effectively breaks the mode degeneracy between the two Bragg modes around the stop band of the DFB lasers, and thus avoids a serious and inherent problem for conventional index coupled DFB lasers, as shown in publications by Y. Luo, Y. Nakano, K. Tada et al. "Purely gain-coupled distributed feedback semiconductor 35 lasers", Appl. Phys. Lett., vol. 56, pp. 1620-1622, 1990 and G. P. Li, T. Makino, R. Moore et al. "Partly gain-coupled 1.55 .mu.m strained layer multi-quantum well DFB lasers", IEEE J. Quantum Electronics, vol. QE-29, pp. 1736-1742, 1993. With introduction of even a small amount of gain or loss coupling, the dynamic single mode yield of complex coupled DFB lasers increases drastically, whether or not there is index coupling. It effectively provides lasing predominantly on a preferred and fixed Bragg mode among the two originally degenerate ones around a stop band, regardless of random distribution of unknown laser facet phases. In in-phase gain coupled DFB lasers, the higher index region within a grating period has a higher optical modal gain, resulting in lasing mainly of the right Bragg mode with the lasing wavelength longer than the Bragg wavelength. Both theory and experiments have confirmed this conclusion. For anti-phase loss coupled DFB lasers, the higher index region within a grating period experiences higher optical loss, resulting primarily in lasing of the left Bragg mode with the lasing wavelength shorter than the Bragg wavelength.
Previously known gain coupled or loss coupled DFB lasers utilize only one type of complex coupling which results in a high dynamic single mode yield for one of predetermined and dominant Bragg mode only. The random distribution of cleaved or HR-coated laser facets is usually the major reason why the opposite Bragg mode across the stop band sometimes actually lases as the dominant mode. Nevertheless, with an increase of complex coupling strength, the single mode yield increases quickly, and an excellent dynamic single mode behavior with a high side mode suppression ratio (SMSR) can be obtained, as reported in the publication by B. Borchert, K. David, B. Stegmuller et al. "1.55 .mu.m gain-coupled quantum-well distributed feedback lasers with high-single-mode yield and narrow linewidth", IEEE Photon. Technol. Lett., vol. 3, no. 11, pp. 955-957, 1991.
Complex coupled DFB lasers have been studied intensively by different scientific groups. It was shown that they constitute a good candidate for practical applications in fiber optics communication systems. Some of the achievements are reported in the following publications: W. T. Tsang, F. S. Choa, M. C. Wu et al. "Semiconductor distributed feedback lasers with quantum well superlattice gratings for index or gain-coupled feedback", Appl. Phys. Lett., vol. 60, pp. 2580-2582, 1992 and J. Hong, K. Leong, T Makino et al. "Impact of random facet phase on modal properties of partly gain-coupled DFB lasers", J. Selected Topics on Quantum Electronics, vol. 3, no. 2, pp. 555-568, 1997.
Nevertheless, a rapid advance in high speed and large capacity dense wavelength division multiplexing (DWDM) fiber optics systems has been constantly demanding semiconductor lasers having not only single mode properties but also a wide continuous tuning range for practical and cost effective applications. A number of techniques have been used in attempt to obtain a widely tunable DFB laser with dynamic single mode performance comparable with standard DFB laser generating at fixed wavelength. First, conventional index coupled tunable lasers followed by complex coupled lasers were tried. The latter appeared to be better in comparison with index coupled lasers because of maintaining good single mode properties within a wide wavelength tuning range. However, similar to other single contact DFB lasers, a wavelength range of complex coupled DFB lasers is limited either by the injection current or base temperature. A multi-sectional laser with separate electrodes for independent current injection was introduced next, providing an effective mode selection and phase control. Some of the experimental implementations of the idea are described in the following publications: Y. Yoshikuni, K. Oe, G. Motosugi, T. Matsuoka "Broad Wavelength tuning under single-mode oscillation with a multi-electrode distributed feedback laser", Electronic Lett., vol. 22, no. 22, pp. 1153-1154; I. Kim, R. C. Alferness, U. Koren et al. "Broadly tunable vertical-coupler filtered tensile-strained InGaAs/InGaAsP multiple quantum well laser", Appl. Phys. Lett., vol. 64, pp. 2764-2766, 1994; M. Oberg, S. Nilsson, K. Streubel et al. "74 nm wavelength tuning range of an InGaAsP/In vertical grating-assisted codirectional coupler laser with rear sampled grating reflector", IEEE Photonics Technol. Lett., vol. 5, pp. 735-737, 1993; H. Ishii, Y. Tohmori, Y. Yoshikuni et al. "Multiple-phase-shift super structure grating DBR lasers for broad wavelength tuning", IEEE Photonics Technol. Lett., vol. 5, pp. 613-615, 1993; M. Okai, I. F. Lealman, L. J. Rivers et al. "In-line Fabry-Perot optical waveguide filter with quasi-chirped gratings", Electron. Lett., vol. 32, pp. 108-109, 1996. When conventional index coupled DFB lasers are used in conjunction with multi-electrodes to achieve wider wavelength tuning range, current injection into two different electrodes of DFB lasers has to be well controlled and the current ratio among the electrodes needs to be precisely maintained. Due to the inherent Bragg mode degeneracy in conventional index coupled DFB lasers, each DFB section has its own stop band. The two Bragg modes around the related stop band compete equally for lasing as the dominant mode. Which one of the Bragg modes will tend to lase depends largely on the unknown grating facet phase and the injection currents in the two different sections. When two sections of the laser are biased independently, two pairs of Bragg modes, four in total, tend to compete against each other. Normally it results in a low SMSR or fast degradation of SMSR during the wavelength tuning within a certain current injection range. To overcome these problems, a complicated and tedious injection current control is normally required. As a result, a high yield device with a high SMSR, wide controlled tuning range and long term stable operation is difficult to obtain. Moreover, from device to device, the random facet phase usually causes a random distribution of lasing mode between the two pairs of degenerated Bragg modes, and the final single mode yield with a wide wavelength tuning range is low. Even if a preselected SMSR is initially high, it can degrade rapidly with a small injection current variation within a certain range due to the sensitivity of index coupled DFB lasers to initial phase variations.
Among other multi-sectional lasers, complex coupled lasers appear to be the best candidates for a wide range tuning. Complex coupled DFB lasers are preferably used as building blocks for tunable lasers to ensure a high SMSR and provide high single mode yield and a small degradation of SMSR over injection current variation. Nevertheless, the tuning range of these lasers is still limited which results in a continued demand for further increasing a tuning range of DFB lasers while maintaining other essential characteristics of the lasers, and development of effective methods of their operation.