Unified Communications Architecture Basics

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Cisco Unified Communications Architecture Basics

Table Of Contents

Cisco Unified Communications Architecture Basics

Voice over IP

Video over IP

Fax over IP

VoIP Protocols

Voice and Video Codecs

Voice- and Video-enabled Infrastructure

Quality of Service

High Availability

IP Multicast

Cisco Unified Communications Architecture Basics

This appendix provides a high-level overview of some of the basic architectural concepts and elements upon which the Cisco Unified Communications System is built.

Additional information regarding Voice over IP technologies is available at:

The Cisco Unified Communications System provides support for the transmission of voice, video, and data over a single, IP-based network, which enables companies to consolidate and streamline communications. The Cisco Unified Communications System is a key part of the Cisco Unified Communications Solution, which also includes network infrastructure, security, and network management products, wireless connectivity, third-party communications applications, and a lifecycle services approach for preparing, planning, designing, implementing, operating and optimizing (PPDIOO) the system.

The Cisco Unified Communications System leverages an existing IP infrastructure (built on the Open System Interconnection [OSI] reference model) and adds support for voice and video-related devices, features, and applications. Support for major signaling protocols, such as the Session Initiation Protocol (SIP), the Media Gateway Control Protocol (MGCP), and H.323 is provided, as is the ability to integrate with legacy voice and video networks.

Table A-1 shows the relationship between the OSI reference model and the voice and video protocols and functions of the Cisco Unified Communications System.

Table A-1 Voice and Video over IP in the OSI Reference Model

OSI Layer Number
OSI Layer Name

Unified IP Phone, Unified Personal Communicator, etc.

Video endpoint, Unified Video Advantage, etc.

H.261, H.263, H.264

Data Link

Frame Relay, ATM, Ethernet, PPP, MLP, and more

Following this model:

Layer 6—Digital signal processors (DSPs) compress/encode (decompress/decode) the voice or video signal using the chosen codec. The DSP then segments the compressed/encoded signal into frames and stores them into packets.

Layer 5—The packets are transported in compliance with a signaling protocol, such as Skinny Client Control Protocol (SCCP), H.323, MGCP, or SIP.

Layer 4—Signaling traffic (call setup and teardown) uses TCP as its transport medium.

Media streams use Real-time Transport Protocol (RTP) over UDP for the transport protocol. RTP is used because it inserts timestamps and sequence numbers in each packet to enable synchronization at the receiving end. UDP is used because TCP would introduce delays (due to acknowledgements) that are not easily tolerated by real-time traffic.

Layer 3—The IP layer provides routing and network-level addressing.

Layer 2—The data-link layer protocols control and direct the transmission of the information over the physical medium.

Voice over IP

In general, the components of a VoIP network fall into the following categories:

Infrastructure—Provides the foundation for the transmission of voice over an IP network. In addition to routers and switches, this includes the interfaces, devices, and features necessary to integrate VoIP devices, legacy PBX, voicemail, and directory systems, and to connect to other VoIP and legacy telephony networks. Typical products used to build the infrastructure include Cisco voice gateways (non-routing, routing, and integrated), Cisco IOS and Catalyst switches, and Cisco routers, as well as security devices, such as firewalls, virtual private networks (VPNs), and intrusion detection systems. In addition, Quality of Service (QoS), high-availability, and bandwidth provisioning (for WAN devices) should be deployed.

Call processing—Provides signaling and call control services from the time a call is initiated until the time a call is terminated. The call processing component also provides feature services, such as call transfer and forwarding capabilities. In the Cisco Unified Communications System, call processing is performed by Cisco Unified Communications Manager or Communications Manager Express.

Applications—Includes components that supplement the basic call processing to provide users with a complete suite of communications options. Applications in the Cisco Unified Communications System include Cisco Unity for voice messaging products, Cisco Unified MeetingPlace conference scheduling software, Cisco Emergency Responder, and applications that enhance the usability of the system and allow users to be more productive, such as the Cisco Unified Presence.

Voice-enabled endpoints—Includes IP phones, soft phones, wireless IP phones, and analog gateways, which provide access to the PSTN and enable interoperability with legacy telephony devices (such as a Plain Old Telephone System [POTS] phone). For IP phones and softphones, the supported protocols are SCCP, H.323, and SIP. For gateways, the supported protocols are SCCP, H.323, SIP, and MGCP.

For a more in depth discussion of Voice over IP, see Voice over IP Fundamentals from Cisco Press.

Video over IP

Typical IP videoconferencing components include:

Gateways—Performs translation between different protocols, audio encoding formats, and video encoding formats that may be used by the various standards. The Cisco Unified Videoconferencing gateways enable conferences using H.323, H.320, SCCP, or SIP endpoints.

Gatekeepers— Works with the call-processing component to provide management of H.323 endpoints. The gatekeeper handles all Registration, Admission, and Status (RAS) signaling, while the call-processing component handles all of the call signaling and media negotiations.

Conference bridges—Enables conferencing between three or more participants. Video endpoints are generally point-to-point devices, allowing only two participants per conversation. A conference bridge or multipoint conference unit (MCU) is required to extend a video conference to three or more participants.

Video-enabled endpoints—Includes stand-alone video terminals, IP phones with integrated video capabilities, and video conferencing software on a PC. These endpoints can be H.323, H.320, SCCP, or SIP.

For additional information about videoconferencing, see the IP Videoconferencing Solution Reference Network Design guide.

Fax over IP

Fax over IP enables the interworking of standard fax machines over packet-based networks. With fax over IP, the fax image is extracted from the analog signal and converted to digital data for transmission over the IP network.

The components of the Cisco Unified Communications System support three methods for transmitting fax over IP: real-time fax, store-and-forward fax, fax pass-through.

For real-time fax, Cisco supports Cisco fax relay and T.38 fax relay (from the International Telecommunications Union [ITU-T]). With this method, the DSP breaks down the fax tones from the sending fax machine into their specific frames (demodulation), transmits the information across the IP network using the fax relay protocol, and then converts the bits back into tones at the far side (modulation). The fax machines on either end send and receive tones as they would over the PSTN and are not aware that information is actually going across an IP network.

For store-and-forward fax, Cisco supports T.37 (from the ITU-T). With this method, the on-ramp gateway receives a fax from a traditional fax device and converts it into a Tagged Image File Format (TIFF) file attachment. The gateway then creates a standard Multipurpose Internet Mail Extension (MIME) e-mail message and attaches the TIFF file to the e-mail. The gateway forwards the e-mail, now called a fax mail, and its attachment to the messaging infrastructure of a designated Simple Mail Transport Protocol (SMTP) server.

Store-and-forward fax allows for fax transmissions to be stored and transmitted across a packet-based network in a bulk fashion, which allows faxes to use least-cost routing and enables faxes to be stored and transmitted when toll charges are more favorable. When using store-and-forward fax, however, the user must be willing to accept fax delays that range from seconds to hours, depending upon the particular method of deployment.

For fax pass-through, fax data is not demodulated or compressed for its transit through the packet network. With this method, the fax traffic is carried between the two gateways in RTP packets using an uncompressed format resembling the G.711 codec. The gateway does not distinguish fax calls from voice calls.

VoIP Protocols

For signaling and call control, the Cisco Unified Communications System supports the Cisco proprietary VoIP protocol, SCCP, as well as the major industry-standard protocols of H.323, SIP, and MGCP. These protocols can be categorized as using either a client-server or peer-to-peer model.

The client-server model is similar to that used in traditional telephony, in which in which dumb endpoints (telephones) are controlled by centralized switches. With a client-server model, the majority of the of the intelligence resides in the centralized call processing component, which handles the switching logic and call control, and with very little processing is done by the phone itself.

The advantages of the client-server model are that it centralizes management, provisioning, and call control; it simplifies call flows for replicating legacy voice features; it reduces the amount of memory and CPU required on the phone; and it is easier for legacy voice engineers to understand.

MGCP and SCCP are examples of client-server protocols.

The peer-to-peer model allows network intelligence to be distributed between the endpoints and call-control components. Intelligence in this instance refers to call state, calling features, call routing, provisioning, billing, or any other aspect of call handling. The endpoints can be VoIP gateways, IP phones, media servers, or any device that can initiate and terminate a VoIP call.

The advantages of the peer-to-peer model are that it is more flexible, more scalable, and more easily understood by engineers who are accustomed to running IP data networks.

SIP and H.323 are examples of peer-to-peer protocols.

Table A-2 Protocols Supported by Cisco Unified Communications Components

A proprietary protocol from Cisco Systems. SCCP uses the client-server model. Call control is provided by the Cisco Unified Communications Manager or Communications Manager Express. Unified IP Phones run a "skinny" client, which requires very little processing to be done by the phone itself.

SCCP is supported by all Cisco IP Phones, by Cisco Unified Video Advantage, by many third-party video endpoints, and by select Cisco gateways.

The recommendation from the ITU-T for multimedia communications over LANs. MGCP uses the client-server model and is used primarily to communicate with gateways.

MGCP provides easier configuration and centralized management. It is supported by most Cisco gateways.

A recommendation from the Internet Engineering Task Force (IETF) for multimedia communications over LANs. SIP uses the peer-to-peer model. Call control is provided through a SIP proxy or redirect server. In Cisco Unified Communications Manager, SIP call control is provided through a built-in back-to-back user agent (B2BUA).

SIP uses a simple messaging scheme and is highly scalable. It is supported by an increasing number of Cisco IP phones, by a number of third-party video endpoints, and on the trunk side of many Cisco gateways.

The recommendation from the ITU-T for multimedia communications over LANs. H.323 uses the peer-to-peer model. It is based on the Integrated Services Digital Network (ISDN) Q.931 protocol. Call control is provided through a gatekeeper.

H.323 provides robust support for interfaces and interoperates easily with PSTN and SS7. It is supported by a number of third-party video endpoints and by most Cisco gateways.

Voice and Video Codecs

As previously mentioned, codecs are used to encode and compress analog streams (such as voice or video) into digital signals that can then be sent across an IP network.

Tip As a general recommendation, if bandwidth permits, it is best use a single codec throughout the campus to minimize the need for transcoding resources, which can add complexity to network design.

Characteristics of a codec are as follows:

Codecs are either narrowband or wideband. Narrowband (used by traditional telephony systems) refers to the fact that the audio signals are passed in the range of 300-3500 Hz. With wideband, the audio signals are passed in the range of 50 to 7000 Hz. Therefore, a wideband codec allows for audio with richer tones and better quality.

The sampling rate (or frequency) corresponds to the number of samples taken per second, expressed in Hz or kHz. For digital audio, typical sampling rates are 8 kHz (narrowband), 16 kHz (wideband) and 32 kHz (ultra-wideband). For digital video, typical sampling rates are 50Hz (for Phase-Alternating Line, PAL, used largely in Western Europe) and 59.94 Hz (for National Television System Committee, NTSC, used largely in North America). Both rates are supported by all the video codec listed in Table A-3.

The compression ratio indicates the relative difference between the original size and the compressed size of the audio or video stream. Lower compression ratios yield better quality but require greater bandwidth. In general, low-compression codecs are best suited for voice over LANs and are capable of supporting DTMF and fax. High-compression codecs are better suited for voice over WANs.

The complexity refers to the amount of processing required to perform the compression. Codec complexity affects the call density—the number of calls reconciled on the DSPs. With higher codec complexity, fewer calls can be handled.

The components of the Cisco Unified Communications System support one or more of the audio and video codecs described in Table A-3.

Table A-3 Codecs Supported by Cisco Unified Communications Components

A narrowband audio codec defined by the ITU-T that provides toll-quality audio at 64 Kbps. It uses pulse code modulation (PCM) and samples audio at 8 kHz. G.711 supports two companding algorithms; mu-law (used in the US and Japan) and a-law (used in Europe and other parts of the world).

G.711 is a low-compression, medium-complexity codec.

A wideband audio codec defined by the ITU-T that provides high-quality audio at 32 to 64 Kbps. It uses Adaptive Differential PCM (ADPCM) and samples audio at 16 kHz.

G.722 is similar to G.711 in compression and complexity, but provides higher quality audio.

A wideband audio codec defined by the ITU-T that provides high-quality audio at 24 and 32 Kbps. It uses Modulated Lapped Transform (MLT) and samples audio at 16 kHz.

G.722.1 is a high-compression, low-complexity codec.It provides better quality than G.722 at lower bit-rates.

A narrowband audio codec defined by the ITU-T for videoconferencing that provides near toll-quality audio at 6.3 or 5.3 Kbps. It uses Algebraic Code Excited Linear Prediction (ACELP) and Multi Pulse-Maximum Likelihood Quantization (MP-MLQ) and samples audio at 8 kHz.

G.723.1 is a high-compression, high-complexity codec. However, the quality is slightly lower than that of G.711.

A narrowband codec defined by the ITU-T that provides toll-quality audio at 32 Kbps. It uses ADPCM and samples audio at 8 kHz.

G.726 is a medium-complexity codec. It requires half the bandwidth of G.711, while providing nearly the same quality. Note that G.726 supersedes G.723, but has no effect on G.723.1.

A narrowband codec defined by the ITU-T that provides near toll-quality audio at 16 Kbps. It uses Low Delay CELP (LD-CELP) and samples audio at 8 kHz.

G.728 is a high-compression, high-complexity codec.

A narrowband audio codec defined by the ITU-T that provides toll-quality audio at 8 Kbps. It uses Conjugate-Structure ACELP (CS-ACELP) and samples audio at 8 kHz.

G.729a is a high-compression, medium-complexity codec. The quality is lower than that of G.711 and it is not appropriate for DTMF, but it is good for situations where bandwidth is limited.

iLBC (internet Low Bitrate Codec)

A narrowband audio codec standardized by the IETF that provides better than toll-quality audio at either 13.33 or 15.2 Kbps. It uses block-independent linear-predictive coding (LPC) samples audio at 8 kHz.

iLBC provides higher basic quality than G.729 and is royalty free. It enables graceful speech quality degradation in a lossy network. This codec is suitable for real-time communications, streaming audio, archival, and messaging.

AAC (Advanced Audio Codec)

A wideband audio codec standardized by the Moving Pictures Experts Group (as MPEG-4 AAC). It provides high-quality audio at rates of 32 Kbps and above. It uses AAC-LD (low delay) samples audio at 20 kHz.

A wideband audio codec defined by the IETF as a MIME subtype. It provides reasonable quality audio at 256 Kbps. It is based on PMC and samples audio at 16 kHz.

GSM-FR (Global System for Mobile Communications- Full Rate)

An audio codec defined by the European Telecommunications Standards Institute (ETSI). It was originally designed for GSM digital mobile phone systems and provides somewhat less than toll-quality audio at 13 Kbps. It uses Regular Pulse Excitation with Long-Term Prediction (RPE-LTP) and samples audio at 8 kHz.

GSM-FR is a medium-complexity codec.

GSM-EFR (Enhanced Full Rate)

An audio codec defined by the ETSI for digital voice that provides toll-quality audio at 12.2 Kbps. It uses ACELP and samples audio at 8 kHz.

GSM-EFR is a high-complexity codec and provides better sound quality than GSM-FR.

QCELP (Qualcomm Code Excited Linear Prediction)

An audio codec defined by the Telecommunications Industry Association (TIA) for wideband spread spectrum digital communication systems that provides toll-quality audio at either 8 or 13 Kbps. As indicated by the name, it uses CELP and samples audio at 8 kHz.

QCELP is a high-complexity codec.

One of the first video codecs defined by the ITU-T. It was originally used for video over ISDN. It is designed to support data rates in multiples of 64 Kbps. H.261 supports Common Intermediate Format (CIF - 352 × 288) and QCIF (176 × 144) resolutions.

H.261 is similar to MPEG, however, H.261 requires significantly less computing overhead than MPEG for real-time encoding. Because H.261 uses constant bitrate encoding, it is better suited for use with relatively static video.

A video codec defined by the ITU-T as an improvement to H.261. It is used in H.323, H.320, and SIP networks. In addition to CIF and QCIF, H.263 supports SQCIF (128 x 96), 4CIF (704 x 576), and 16CIF (1408 x 1152) resolutions.

H.263 provides lower bitrate communication, better performance, and improved error recovery. It uses half pixel precision and variable bitrate encoding, which makes H.263 better suited to accommodate motion in video.

The next in the evolution of video codecs. It was defined by the ITU-T in conjunction with the MPEG (as MPEG-4 Part 10) and is designed to provide higher-quality video at lower bit rates.

H.264 provides better video quality, compression efficiency, and resilience to packet and data loss than that of H.263. It also makes better use of bandwidth, resulting in the ability to run more channels over existing systems.

Voice- and Video-enabled Infrastructure

By default, an IP data network transmits data based on the concept of "best effort." Depending on the volume of traffic and the bandwidth available, data networks can often experience delays. However, these delays are typically a matter of seconds (or fractions of seconds) and go unnoticed by users and applications, such as e-mail or file transfers. In the event of significant network congestion or minor route outages, receiving devices can wait and reorder any out-of-sequence packets and sending devices can simply resend any dropped packets.

Voice and video are very time-dependant media, which suffer greatly when subjected to the delays that data applications easily tolerate. In the event of significant congestion or outages, voice applications can only attempt to conceal dropped packets, often resulting in poor quality. Therefore, voice and video require an infrastructure that provides for smooth, guarenteed delivery.

A network infrastructure that transmits voice and video, especially that delivered in real-time, requires special mechanisms and technologies to ensure the safety and quality of the media as well as the efficient use of the network resources. In a voice- or video-enabled network, the following must be built into the infrastructure:

Quality of service

High availability

Voice security

Multicast capabilities

Quality of Service

Quality of Service (QoS) is defined as the measure of performance for a transmission system that reflects its transmission quality and service availability. The transmission quality of the network is determined by the following factors:

Loss—Also known as packet loss, is a measure of packets faithfully transmitted and received compared to the total number that were transmitted. Loss is expressed as the percentage of packets that were dropped.

Loss is typically a function of availability (see the "High Availability" section). If the network is Highly Available, then loss (during periods of non-congestion) would essentially be zero. During periods of congestion, however, QoS mechanisms can be employed to selectively determine which packets are more suitable to be dropped.

Delay—Also known as latency, is the finite amount of time it takes a packet to reach the receiving endpoint after being transmitted from the sending endpoint. In the case of voice, this equates to the amount of time it takes for sounds to leave the speaker's mouth and be heard in the listener's ear. This time period is termed the "end-to-end delay."

There are three types of delay:

Packetization delay—The time required to sample and encode analog voice signals and digitize them into packets.

Serialization delay—The time required to place the packet bits onto the physical media.

Propagation delay—The time required to transmit the packet bits across the physical media.

Delay Variation—Also known as interpacket delay, is the difference in the end-to-end delay between packets. For example, if one packet required 100 ms to traverse the network from the source-endpoint to the destination-endpoint and the following packet required 125 ms to make the same trip, then the delay variation would be calculated as 25 ms.

Each end station in a VoIP or Video over IP conversation has a jitter buffer. Jitter buffers are used to smooth out changes in arrival times of data packets containing voice. A jitter buffer is dynamic and adaptive, and can adjust for up to a 30 ms average change in arrival times of packets. If you have instantaneous changes in arrival times of packets that are outside of the capabilities of a jitter buffer's ability to compensate you will have jitter buffer over-runs and under-runs.

A jitter buffer under-run occurs when the arrival times of packets increases to the point where the jitter buffer has been exhausted and contains no packets to be processed by the DSPs when it is time to play out the next piece of voice or video.

A jitter buffer over-run occurs when packets containing voice or video arrive faster than the jitter buffer can dynamically resize itself to accommodate. When this happens, packets are dropped when it is time to play out the voice or video samples, resulting in degraded voice quality.

Cisco provides a QoS toolset that allows network administrators to minimize the effects of loss, delay, and delay variation. These tools (as shown in Figure A-1) enable the classification, scheduling, policing and shaping of traffic—the goal being to give preferential treatment to voice and video traffic.

Figure A-1 Cisco QoS Toolkit

Classification tools mark a frame or packet with a specific value. This marking (or remarking) establishes a trust boundary on which the scheduling tools depend.

Scheduling tools determine how a traffic exits a device. Whenever traffic enters a device faster than it can exit it (as with speed mismatches), then a point of congestion develops. Scheduling tools use various buffers to allow higher-priority traffic to exit sooner than lower priority traffic. This behavior is controlled by queueing algorithms, which are activated only when a devices is experiencing congestion and are deactivated when the congestion clears.

Policers and shapers are the oldest forms of QoS mechanisms. These tools have the same objectives—to identify and respond to traffic violations. Policers and shapers identify traffic violations in an identical manner; however, they respond differently to these violations. A policer typically drops traffic; a shaper typically delays the excess traffic using a buffer to hold packets and shape the flow when the data rate of the source is higher than expected.

For more information about QoS considerations and tools, see the Enterprise QoS Solution Reference Network Design Guide.

High Availability

The objective of high availability is to prevent or minimize network outages. This is particularly important in networks that carry voice and video. More than a single technology, high availability is an approach to implementing a mixture of policies, technologies, and inter-related tools to ensure end-to-end availability for services, clients, and sessions. High availability heavily on network redundancy and software availability.

Network redundancy depends on redundant hardware, processors, line cards, and links. The network should be designed so that it has no single points of failure for critical hardware (for example, core switches). Hardware elements, such as cards, should be "hot swappable," meaning they can be replaced without causing disruption to the network. Power supplies and sources should also be redundant.

Software availability depends on reliability-based protocols, such as Spanning Tree and Hot Standby Routing Protocol (HSRP). Spanning Tree, HSRP, and other protocols provide instructions to the network and/or to components of the network on how to behave in the event of a failure. Failure in this case could be a power outage, a hardware failure, or a disconnected cable. These protocols provide rules to reroute packets and reconfigure paths. The speed at which these rules are applied is called convergence. A converged network is one that, from a user standpoint, has recovered from a failure and can now process instructions and/or requests.

For more information about high availability, see Designing a Campus Network for High Availability.

As with important data traffic, voice (and often video) traffic on an IP network must be secured. In some cases, the same technologies that can be used to secure a data network are employed in a VoIP network. In other cases, unique technologies must be implemented. In both cases, one of the key objectives is to protect the voice or video stream without impacting the quality.

When securing the network, it is important to consider all possible areas of vulnerability. This means protecting the network from internal and external threats, securing internal and remote connectivity, and limiting network access to devices, applications, and users that can be trusted. Comprehensive security is achieved first by securing the network itself, and then by extending that security to endpoints and applications. For voice and video communications, security must protect four critical elements:

Network infrastructure—The switches, routers, and connecting links comprising the foundation network that carries all IP data, voice, and video traffic. This includes using tools such as:

Network intrusion detection and prevention systems

Voice- and video-enabled VPNs

VLAN segmentation

Port security

Access control server/user authentication and authorization

Dynamic Address Resolution Protocol (ARP) inspection

IP source guard and Dynamic Host Configuration Protocol (DHCP) snooping

Wireless security technologies, such as wired equivalent privacy (WEP) and Lightweight Extensible Authentication Protocol (LEAP)

Call processing systems—Servers and associated equipment for call management, control, and accounting. This includes using tools such as:

Digital certificates

Signed software images

Endpoints—IP phones, soft phones, video terminals, and other devices that connect to the IP Communications network. This includes using tools such as:

Digital certificates

Endpoint authentication

Secure RTP stream encryption

Switch port security

Virus protection and integrated Cisco Security Agent

Applications—User applications such as unified messaging, conferencing, customer contact, and custom tools that extend the capabilities of IP Communications systems. This includes using tools such as:

Secure management

Multilevel administration

Media encryption

Use of H.323 and SIP signaling

Hardened platform

Virus protection and integrated Cisco Security Agent

IP Multicast

IP multicast allows for a streamlined approach to delivering data to multiple hosts that need to receive the same data at the same time, such as with distance learning. With IP multicast, an audio or video stream can be sent from a single server to multiple endpoints. For example:

When configured for IP multicast services, Music-on-Hold (MoH) can stream the same audio file to multiple IP phones without the overhead of duplicating that stream one time for each phone on hold.

IP/TV allows for the streaming of audio, video, and slides to thousands of receivers simultaneously across the network. High-rate IP/TV streams that would normally congest a low-speed WAN link can be filtered to remain on the local campus network.

In contrast to unicast, which would send individual streams to each of the recipients, IP multicast simultaneously delivers a single stream of information to thousands of recipients, thereby reducing bandwidth consumption, as shown in Figure A-2.

Figure A-2 IP Multicast

Multicast packets are replicated in the network by Cisco routers and switches enabled with Protocol Independent Multicast (PIM) and other supporting multicast protocols. These routers create "distribution trees," which control the path that IP Multicast traffic takes through the network in order to deliver traffic to all the receivers.

For more information about IP multicast, see the Cisco Network Infrastructure IP Multicast Design Guide.

The components and technologies of the Cisco Unified Communications System and the enabling infrastructure work in concert to deliver converged voice, video, and data communications.

Figure A-3 Cisco Unified Communications System

The components and technologies employed in the infrastructure (such as QoS and IP Multicast) provide a secure, robust, reliable, and efficient foundation.

Building on the infrastructure, the gateways and call-processing components perform the necessary conversion, integration, and control functions to enable efficient, streamlined communications.

The applications augment the call processing to provide features an services required by users.

And the endpoints provide access to the network services and features—enabling users to make the most of their communications system and increase their productivity.


Cold Spring Harbor Laboratory
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NeuroscienceCSHL neuroscientists focus on understanding how neural activity and neural circuitry underlie behavior, and how disruptions in these circuits lead to neurological and neuropsychiatric disorders such as Alzheimer's disease, autism, schizophrenia and depression. These questions are addressed in two model systems—rodents and Drosophila—using molecular, cellular, genetic, developmental, theoretical, physiological and behavioral approaches.

Neuroscience research at CSHL is highly collaborative, and can be divided into three broad themes: sensory processing, cognition, and cognitive disorders.  The sensory processing group addresses basic questions about sensory representations (auditory, olfactory and visual) and decision-making. The cognition group uses the tools of modern neuroscience (genetic, molecular, physiology and imaging) to study the neural mechanisms underlying cognitive processes—including attention, memory and decision-making—that have traditionally been studied only in nonhuman and human primate models.  The cognitive disorder group builds on recent findings about the genetic basis of diseases like autism and schizophrenia to define how neural circuits and synaptic function are disrupted in these disorders. In addition, there is an effort to develop new anatomical methods to improve our understanding of brain circuits, connectivity and function.

Neuroscience researchers at CSHL:

Dinu Florin Albeanu - Neuronal circuits; sensory coding and synaptic plasticity; neuronal correlates of behavior; olfactory processing

Anne Churchland
- Decision-making; electrophysiology; sensory processing; vision; audition; neural computation; modeling; behavior

Joshua Dubnau - Learning, memory, genetics, behavior

Grigori Enikolopov - Stem cells; neurogenesis; development; signal transduction

Hiro Furukawa - Membrane proteins, X-ray crystallography, electrophysiology, neurodegenerative disease

Z. Josh Huang - Development and function of the GABAergic inhibitory circuitry in neocortex; cortical circuits; mouse genetics; developmental plasticity; neurogenomics; autism

Adam Kepecs - Decision-making; neural circuits; behavioral electrophysiology; theoretical neuroscience; neuroeconomics

Alexei Koulakov - Theoretical neurobiology; quantitative principles of cortical design; computer science; applied mathematics

Bo Li - Neuroscience; glutamatergic synapse; synaptic plasticity; schizophrenia; depression; rodent models of psychiatric disorders

Partha P. Mitra - Neuroinformatics; theoretical engineering; animal communications; neural prostheses; brain imaging; developmental linguistics

Pavel Osten - Neurobiology of autism and schizophrenia; gene expression-based mapping of brain activity; anatomical mapping of brain connectivity; high throughput microscopy

Stephen Shea - Olfaction; audition; communication behaviors; in vivo electrophysiology; individual recognition

Jessica Tollkuhn - Transcriptional regulation; chromatin; critical periods in neurodevelopment; steroid hormones and behavior

Glenn Turner - Neural coding; learning and memory; sensory processing; Drosophila; electrophysiology

Linda Van Aelst - Signal transduction; Ras & Rho proteins; tumorigenesis; neuronal development

Anthony Zador - Neural circuits; sensory processing, attention and decision making; attention; molecular tool development; connectomics

Yi Zhong - Neurophysiology; Drosophila; learning and memory; neurofibromatosis; signal transduction


A process in which a disagreement between two or more parties is resolved by impartial individuals, called arbitrators, in order to avoid costly and lengthy litigation.

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Kentuckians for Strong Leadership

Select cycle:

NOTE: This committee is a single-candidate super PAC in support of Mitch McConnell (R).

Outside Spending: Independent Expenditures, Electioneering Communication & Communication Costs by Targeted Candidate as of March 01, 2015:

Grand Total: $6,409,610
Total For Democrats: $0
Total Against Democrats: $6,409,610
Total For Republicans: $0
Total Against Republicans: $0

Our math: Why don't the numbers add up?
Grimes, AlisonDKY Senate$6,409,610$0$6,409,610Lost

Based on data released daily by the FEC on March 01, 2015.

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cystitis inflammation of the urinary bladder.
cysto- bladder; sac.
cystoscope an instrument for examining the urinary bladder and passages.
-cyte cell.
cyto- cell.
cytoplast the cytoplasmic structure of a cell.


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Bonzle Digital Atlas of Australia

Windiest places by mean windspeed in Victoria

Windiest places by mean windspeed in Victoria

See also: Windiest Places Now | Calmest places in Australia

RankingPlace NameAnnual Mean Windspeed at 3pm (km/h)
1Port Welshpool, VIC32.6 km/h
2Sandy Point, VIC32.6 km/h
3Ocean Grove-Barwon Heads, VIC31.6 km/h
4Mallacoota, VIC30.2 km/h
5Winchelsea, VIC23.3 km/h
6Lara, VIC23.3 km/h
7Bannockburn, VIC23.3 km/h
8Inverleigh, VIC23.3 km/h
9Geelong, VIC23.3 km/h
10Leopold, VIC23.3 km/h
11Moriac, VIC23.3 km/h
12Torquay, VIC23.3 km/h
13Anglesea, VIC23.3 km/h
14Aireys Inlet-Fairhaven, VIC23.3 km/h
15Cann River, VIC22.1 km/h
16Dinner Plain, VIC22.1 km/h
17Wandong-Heathcote Junction, VIC21.7 km/h
18Wallan, VIC21.7 km/h
19Sunbury, VIC21.7 km/h
20Diggers Rest, VIC21.7 km/h
21Bulla, VIC21.7 km/h
22Melton, VIC21.7 km/h
23Dunkeld, VIC21.4 km/h
24Hamilton, VIC21.4 km/h
25Penshurst, VIC21.4 km/h
26Balmoral, VIC21.4 km/h
27Portarlington, VIC21.3 km/h
28Indented Head, VIC21.3 km/h
29Clifton Springs, VIC21.3 km/h
30St Leonards, VIC21.3 km/h
31Drysdale, VIC21.3 km/h
32Queenscliff, VIC21.3 km/h
33St Andrews Beach, VIC21.3 km/h
34Rockbank, VIC21 km/h
35Werribee South, VIC21 km/h
36Little River, VIC21 km/h
37Beeac, VIC20.5 km/h
38Colac, VIC20.5 km/h
39Birregurra, VIC20.5 km/h
40Learmonth, VIC20.3 km/h
41Beaufort, VIC20.3 km/h
42Creswick, VIC20.3 km/h
43Miners Rest, VIC20.3 km/h
44Cardigan Village, VIC20.3 km/h
45Ballarat, VIC20.3 km/h
46Snake Valley, VIC20.3 km/h
47Mount Helen, VIC20.3 km/h
48Smythesdale, VIC20.3 km/h
49Buninyong, VIC20.3 km/h
50Linton, VIC20.3 km/h

Picture relating to Snug Falls - titled 'Snug Falls'Snug Falls Picture relating to Muttaburra - titled 'Muttaburra'Muttaburra Picture relating to Braddon - titled 'Brick cottages constructed around Doonkuna Street, Braddon.'Braddon Picture relating to Parliament House - titled 'Braddon and Reid area, from north - Old Parliament House in background.'Parliament House Picture relating to Lyndoch - titled 'Lyndoch Hotel'Lyndoch Picture relating to Barton - titled 'National Library, Kings Avenue, Barton.'Barton

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George Salmond

Our research involves multiple aspects of molecular microbiology including quorum sensing (QS), molecular pathogenesis in plant and animal pathogens, regulation and biosynthesis of antibiotics and other secondary metabolites, protein secretion systems, gas vesicles and flotation, bacteriophage exploitation, toxin-antitoxin systems and anti-viral abortive infection. We work on various Gram-negative enterobacteria, including the phytopathogen, Erwinia (Pectobacterium), Serratia species (which can be opportunistic human pathogens) Citrobacter rodentium (the murine pathogen) and a spectrum of phages infecting bacteria of fundamental, medical, agricultural or industrial biotechnology interest (including Pseudomonas and Streptomyces).

We are investigating the phenomenon of quorum sensing in which bacteria make small diffusible molecules (N-acyl homoserine lactones) as chemical communication signals reflecting cell population density status. The phenotypes regulated by quorum sensing include virulence, exoenzyme and antibiotic production, and gas vesicle organelle morphogenesis. We aim to understand molecular mechanisms involved in quorum sensing, and dissect their physiological role(s), evolution, and potential use in synthetic biology. We study the genetics and biochemistry of production of carbapenems, prodiginines and haterumalides/oocydins in enterobacteria such as  Erwinia (Pectobacterium), Dickeya, Serratia and other rhizosphere organisms. We use genetics, transcriptomics and proteomics to investigate the physiological impacts of environmental signaling in the regulation of virulence and antibiotic production in Erwinia and Serratia. We also investigate molecular processes involved in virulence factor secretion in Erwinia. We are exploiting new bacteriophages for the development of genetic tools in functional genomics. We are also studying phage abortive infection systems (with bifunctional toxin-antitoxin capacity) through which bacteria control the replication of their viral parasites. We are also investigating the morphogenesis of bacterial gas vesicles (flotation chambers) as intracellular organelles which develop in response to a quorum sensing morphogen and other environmental cues.

Lab members: Rita Monson, Miguel Angel Matilla Vazquez, Alison Rawlinson, Feng Rao, Chin Mei Lee, Xinzhe Fang, Josephine Hellberg

Key publications:


Double Take 'Toons: Gone But Not Forgotten

NPR Double Take revisits 2010.

Football Hall of Famer George Blanda, who was known as the "Grand Old Man," died at the age of 83. Blanda played for a record 26 seasons.

Legendary UCLA men's basketball coach John Wooden passed away at the age of 99. The "Wizard of Westwood" was a teacher and a mentor. His teams won 10 national titles and held the record for the longest winning streak of 88 games.

Sports Greats George Blanda and John Wooden are recalled by Randy Bish and Steve Greenberg.


Exhibition Of Korean works that reflects the country's modern art sensibilities

You can't really do justice to the ‘Korean Contemporary Spectrum' exhibition currently on at Lalit Kala Akademi in a single article. Just like you can't really take in all that the 150 paintings on display have to offer in a single viewing.

One of the largest expositions of Korean art in India to date, the exhibition presents a mind-boggling array of works representative of the lively contemporary art scene in Korea. The works cover a variety of styles and attitudes, painting a fascinating picture of a nation's modern artistic sensibilities.

Walk into the gallery, and you're greeted by vast, leisurely canvases and a profusion of distinctive imagery. On one hand, you have the idyllic landscapes, such as Jang Hye Sun's dreamy oil, ‘Fragrance of a lotus flower', Park Kwang Ho's gorgeous ink of the ‘First Snow' against gnarled trees, or Ryoo Myeong Ryeol's delicate ‘Pine tree'. On the other, you have the frenetic cityscapes, such as Kim Jong Hyun's traffic-filled lambda print ‘Landscape of a road crossing' or Seo Gi Hwan's densely packed sea of urban rooftops and skyscrapers, ‘Human landscape'.

The abstracts are equally striking, such as Lee So Yun's ‘A sonata in A minor', a beautifully textured mixed media work that's all glittering aqua and deep blue, or Lee Hye Ryun's eye-catching oil, ‘By sharpness', that's all gleaming shards of green glass against black. The play on colour ranges from bright and cheery, such as Oh Ku Sook's flower-covered ‘Festival' and fantastical, such as Jun Hyun Jung's ‘Remember', to dark and dystopian, such as Kim Hak Dae's nightmarish ‘The Circulation' or Lee Ji Hyun's ‘Coexistence 13'.

In total contrast to these free-flowing abstracts, you have the quiet, more traditional figuratives, such as Shin Dong Sook's ‘Emotion', depicting two introspective girls in Korean dress, or Kim Ha Na's rather touching oil of a Quasimodo-like gentle giant helping a damsel in distress in ‘Converse', and the delicate still-life paintings, such as Jeon Eui Sung's ‘Sentiment', depicting traditional urns, or Kwon Hyuk's oil ‘Jar', the broad canvas filled entirely with the soft curves of a single jar.

Then you have the determinedly modern works, such as Lee Jin Young's brightly coloured, graffiti-style acrylic, ‘The sensibility of today', or Shin Sang Cheol's mixed media work of a sleek, super-cool car – all shining metal and actual blinking lights – at a crosswalk, titled ‘Don't walk -2'. And that just about scratches the surface of what this unique exhibition – which covers two entire halls at the Akademi – has to offer.

(‘Korean Contemporary Spectrum' closes on Thursday.)


Sticky Fingers - How To Fly (STONER MUSIC)

How to fly ✌✨🌻 -Sticky Fingers
Love his dancing lol 💕 #dylanfrost #StickyFingers #howtofly

Image from Shelbs2 on Devian Art

As a young man training to become a pilot, the engineering behind an aircraft is quite intimidating. However, I’m a technology buff so I decided to use the most powerful tool known to man [the computer] to help resolve my curiosity. I began my research without the intention of going too far in depth on flight and airplane design the first day but enough at least begin in the right direction. I began with the basics and progressed with tidbits of information to further extend upon, all of which I’ve assimilated bellow for those who wish to explore more.

MATERIALS OF A PLANE: Aluminum is the most commonly used metal for planes, and it is the most preferred choice. even more than all other materials combined” due to its affordability and its strength to weight ratio. Other materials such as wood and composites are used as well but less frequently. The FAA released an information guide on the materials that can be used for a plane.

PLANE COMPONENTS: There are 21 basic parts that make up an airplane and 23 components can be found on an instrument panel. The FAA released a main components list and NASA offers a slightly more in depth lesson on all the mentioned parts.

AERODYNAMICS: Making the plane be able to fly can be one of the most daunting tasks in building a plane. To be able to make something that can fly takes well planned engineering and time. The main forces in flight are lift, drag, thrust, and gravity. If one can design the plane correctly, gravity will be countered by lift and down-force; also, drag will be countered by thrust. As simple as it may sound, going faster and building an efficient plane isn’t as simple as sticking some wings on something and taking off. Yet, with enough study, anyone can learn about flight and the science of flight. As for resources to learn about this wonderful science, NASA comes to the rescue again and provided a basic aerodynamics index for those who are interested in learning.

I hope the information I have provided can satisfy some mutual curiosity that others may hold as well. For learning how to fly the plane - buy a Private Pilot’s Manual, go to a local flight school, get your flight hours, then take a test. May the sky fare well to you. Adieu


Yoga Physiology

Yoga physiology, anatomy and movement science

News about the blog

The autonomic nervous system

How does heart rate variability fit into this?

So what can we take from these results?

Research review: The effects of bhastrika in the elderly, part 2

In this post, I’ll discuss some of the results of the study I described in my previous post. If you haven’t already done so, you should read that one before this.

To refresh your memory, Santaella and his colleagues studied the effects of bhastrika practice in elderly individuals (1). They tested several measures of respiratory function at the beginning of the study and again after four months of training. Those measures included forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and maximum expiratory and inspiratory pressures (PEmax, or MEP, and PImax, or MIP). Don’t worry about the abbreviations. Scientific research tends to read like acronym soup, but in general I’ll stick to the full names.

Breathe in as much as you can, then exhale out as much as possible. The amount of air you exhaled is your forced vital capacity.  You’ll never empty all the air out of your lungs, so vital capacity doesn’t represent your lungs’ total capacity, but it’s a good measure of their useable capacity.

The air that’s left in the lungs after a complete exhalation is called the residual volume. Residual air is important. It helps to maintain a moist, carbon dioxide-rich atmosphere in the lungs and allows for continual gas exchange even after you’ve exhaled.

Vital capacity is a function of the size of your lungs, which is correlated with the size of your body, particularly your height. It’s also a function of your age. As you grow older, your lungs lose elasticity and your chest becomes stiffer. This leaves more air trapped in the lungs, increasing the residual volume, which leads to a gradual decline in vital capacity.

Now do the same exercise, breathing in and out as much as possible, but try to exhale as quickly as you can. The amount of air you exhale within the first second is called forced expiratory volume in one second, or FEV1. You may have done this test in your doctor’s office. FEV1 is an important measure of the health of your lungs. If you’re healthy, you should be able to empty out 80% or more of your vital capacity in the first second. If you can’t, because there’s some obstruction to the air flow, it could be a sign of asthma, chronic bronchitis or emphysema.

Maximum inspiratory and expiratory pressures are self-explanatory. They are measures of the maximum pressure you can generate while inhaling and exhaling through a mouthpiece. Both of them are indirect measures of the strength of your respiratory muscles.

The elderly lose both muscle mass and strength as they age, a process called sarcopenia. Exercise does a lot to mitigate sarcopenia, but some loss seems to be inevitable. Not surprisingly, as the strength of the respiratory musculature declines, maximum inspiratory and expiratory pressures also decline. That can be a serious problem for the elderly when conditions such as pneumonia place an extra load on the respiratory muscles. Since vital capacity and respiratory pressures decline with age, anything that improves them would be good news for the elderly.

So, did bhastrika practice help? The results were mixed. Maximum inspiratory and expiratory pressures improved significantly in the bhastrika group. Forced vital capacity and FEV1 increased slightly in the bhastrika group, but the difference was not statistically significant. The control group remained essentially unchanged, despite the fact that they were also practicing yoga (but without the bhastrika practice).

Research has generally shown that you can’t improve vital capacity with exercise. (On land at least. Swimming does increase vital capacity, probably because of the greater resistance to breathing that water provides.)

Some research suggests that yoga practice can improve vital capacity, but there are enough weaknesses in those studies that I’m not convinced. Most of the evidence comes from uncontrolled studies on students who were teenagers or young adults (2, 3). Women don’t reach full vital capacity until around age 20. For men, it’s around age 25. Without a control group, it’s hard to know whether those young people’s vital capacity would have increased regardless of yoga training. One large uncontrolled study (3) of college students did find increases across the board, regardless of age and gender. That’s suggestive of a training effect, but aside from the lack of a control group, there was also enough room for error in the testing procedures that those results aren’t as compelling as they could be.

I’ve only found one controlled study (4) showing a link between improved vital capacity and yoga. Unfortunately, there were major differences in the composition of the experimental and control groups in that study, and no details about the selection process, so again, I’m cautious about the results.

Other studies have found no correlation between yoga practice and vital capacity. It would be nice if there were better-designed studies to answer the question, especially for mature adults, but for the time being I’m not convinced that yoga does much to increase vital capacity. If it does, my guess is that the effect is small, unless you’re young. In that respect Santaella’s results weren’t surprising.

On the other hand, maximum inspiratory and expiratory pressures are a function of muscle strength. You can strengthen muscles, so you’d expect those measures to improve with training, and, in fact they did in this study. Overall, there hasn’t been much research on this topic. What little there is suggests that yoga practice can increase inspiratory and expiratory pressures (5), although in one of those studies (6) the difference was not statistically significant.

The bhastrika practice in this current study consisted of rounds of kapalabhati followed by breath retentions incorporating bandhas. I’ve written about kapalabhati before. It’s a strengthening exercise for the expiratory musculature, specifically the transversus abdominis as well as other abdominal muscles.

Inhalation retentions, particularly using jalandhara bandha, strengthen the muscles of inspiration. Jalandhara bandha is the “net-holding lock,” sometimes called chin lock. It requires you to hold the ribcage in a lifted position while bringing your chin towards your sternum. At some point, I’ll write about the physiological rationale for jalandhara bandha, but for now I’ll just point out that maintaining the position of the ribcage necessitates a strong contraction of the external intercostals along with the scalenes and the diaphragm, all of which are muscles of inspiration.

So, for the elderly individuals in this study, bhastrika practice seems to have strengthened their respiratory muscles. I should point out one caveat, though. The researchers in this study tested their subjects first to make sure they were healthy, and did not include any with evidence of cardiovascular disease in the study. Both kapalabhati and breath retentions can affect blood pressure. Because high blood pressure is common in the elderly, I wouldn’t recommend that senior citizens practice them unless they have a physician’s approval.

In the next post in this series, I’ll discuss the findings relating to heart rate variability.

2. Joshi LN, et al. Effect of short term ‘Pranayam’ practice on breathing rate and ventilatory functions of lung. Indian J Physiol Pharmacol. 1992;36(2):105-8.

3. Birkel DA & Edgren L. Hatha yoga: Improved vital capacity of college students. Alternative Therapies in Health and Medicine. 2000;6(6): 55-63.

4. Makwana K. Effect of short term yoga practice on ventilatory function tests. Indian J Physiol Pharmacol. 1988;32(3):202-8.

5. Madanmohan, et al. Effect of six weeks yoga training on weight loss following step test, respiratory pressures, handgrip strength and handgrip endurance in young healthy subjects. Indian J Physiol Pharmacol. 2008;52(2):164-70.

6. de Godoy DV, et al. Yoga versus aerobic activity: effects on spirometry results and maximal inspiratory pressure. J Bras Pneumol. 2006;32(2):130-5.

Image from Wikipedia Commons

Self magazine interview

Research review: The effects of bhastrika in the elderly

Narisara’s question in response to my kapalabhati post inspired me to write about this recent study: Yoga respiratory training improves respiratory function and cardiac sympathovagal balance in elderly subjects: a randomised controlled trial. I thought it would serve both as an opportunity to explore some interesting aspects of physiology and as a primer on scientific research in general.

You don’t need to know anything about science to practice yoga. The ancient yogis didn’t. Their method was introspection. They discovered the effects of yogic practices through sustained attention to their own internal physical and mental states. Given how much variation there is between individuals, that’s probably still the best way for you to determine the effects of your own practice.

However, yoga and meditation also teach us how untrustworthy our interpretation of things can be. We see what we want to see. Patanjali describes it in the Yoga Sutras as viparyaya—misconception.

One of the fundamental ways we are primed by evolution to mis-conceive is to see causality where none exists. “I practiced headstand, and my headache went away, so headstand much have cured it.” Not necessarily. Just because two events are correlated doesn’t mean one caused the other. And even if it did, that doesn’t mean it would work for anyone else.

A lot of scientific studies simply find correlations. That’s particularly true in epidemiological research, where scientists look at large populations to discover things like “people who drink coffee have higher rates of depression.” (I’m just making that up. I don’t know if there’s any such study.) The media often report those studies with headlines like “Coffee causes depression.” Well does it? Maybe. But maybe not. We can’t tell, because it’s simply an association. Correlation doesn’t prove causality. At most, it can generate hypotheses, which then have to be tested.

From a scientific point of view, the only way to demonstrate causality is in a randomized controlled trial. Take two groups of randomized individuals, who—in theory—don’t differ in any significant way. Test each group at the beginning of the experiment, then give one group some sort of experimental treatment with the other group acting as a control. Re-test everybody at the end. Assuming that the only difference between the groups was the treatment you gave—which is a very big assumption—any change in the experimental group had to have come from the treatment. However, this process can go wrong in all sorts of ways, which is why one trial doesn’t prove much of anything. In fact, to be accurate, no amount of trials can prove anything. All a scientific trial can really do is disprove a hypothesis. There’s always the possibility that another, unidentified factor caused the results we see, and not the experimental treatment.

Hopefully, that wasn’t too basic an introduction to the scientific method, but, since I plan to periodically review yoga research here, I wanted to cover the background first. The main point is that scientific studies vary in quality. Unfortunately, much of the yoga-related scientific literature is not very compelling. Many studies are poorly designed, or else so poorly reported that it’s hard to interpret their results—which amounts to the same thing from a scientific point of view.

This study, however, was well designed and reported, so I’m hoping it can serve as an example of what to look for in scientific research. Plus, you don’t have to rely on the abstract. You can read the full text here. It’s free, unlike many studies that require you either to be a subscriber to the journal or to pay an exorbitant fee to read the full text.

Anyway, on to the study. Investigators in Brazil hypothesized that practicing “bhastrika” would improve respiratory and autonomic nervous system function in healthy senior citizens. I put “bhastrika” in quotes because, while the term comes up a lot in pranayama research, it seems every researcher uses it to mean something different—probably because different schools of yoga define it differently. In this case, they mean kapalabhati with surya bhedana: 45 kapalabhati breaths, followed by an inhalation through the right nostril, a retention with bandhas, and a long, slow exhalation. (There’s a video here.)

This was a randomized controlled trial, which is generally the highest quality study design you’ll find in yoga research. (You’ll almost never see “blind” or “double blind” randomized controlled trials, which are the scientific gold standard, because it’s pretty obvious whether you’re doing yoga or not. Some studies have had control groups do “sham” yoga as a way of blinding participants as to which group they’re in, but that’s generally unconvincing.)

The groups were small, with 15 participants in the experimental group and 14 in the control. Those are pretty typical numbers for exercise training studies, because it’s expensive and difficult to recruit larger groups.

On the other hand, if the groups are too small, a few random outliers could mask an effect that’s actually there, so researchers need enough participants to ensure what’s called statistical power. It’s a good sign in a study when the authors include an analysis of statistical power, as they do here.

The authors provide a flow chart that gives some insight into the difficulties of recruiting subjects for these kinds of studies. They began with a pool of 150 participants in a yoga program for the elderly. Only 76 people volunteered for the experiment. Of those, 46 were excluded for health reasons such as cardiovascular disease, or because they were taking medications which could affect the results. That left 30 people, or two groups of 15. (One person in the control group didn’t attend the required classes and was dropped from the experiment.)

The authors also list demographic and biochemical statistics for the two groups to show that there weren’t obvious significant differences between them. If there were big differences, say one group were significantly older or had more men or women, those could affect the results. Randomization is supposed to eliminate such differences, but it doesn’t always, so it’s a good sign when researchers check. Of course, there could be other important differences they overlooked, but nevertheless, it’s a good sign.

Everyone in the study participated in an hour-long yoga asana class twice a week for four months. The experimental group followed that up with an extra half-hour of training in bhastrika, while the control group did 30 more minutes of asana. The experimental group also practiced bhastrika twice a day on their own for 10 minutes at a time, recording the sessions in a diary to verify compliance.

Most yoga studies have focused on the effect of a comprehensive practice that often includes asana, pranayama and meditation, and even lifestyle and dietary changes. That’s useful because it tells us something about the overall benefits of a yoga practice, but it doesn’t say anything about what specific exercises do. Was it the asana or the meditation that made a difference? We don’t know.

To me, the most interesting aspect of this study is that the authors chose not to do that, instead opting to test the effects of one specific practice. Everyone, both the control and the experimental subjects, did essentially the same yoga practice. The difference was that the experimental group added bhastrika. Therefore, we can expect that any differences in the results we see between groups will—probably—be due to bhastrika.

Participants were tested at the beginning of the study and again at the end. Those tests included measures of respiratory function, autonomic nervous system balance, and quality of life. I’ll wait to describe those in more detail over the next couple of posts because I also want to explore some of the underlying physiology along the way.

Part two of this series will look at how the bhastrika practice affected participants’ respiratory function.

Hyperventilation: Why more isn’t necessarily better when in comes to breathing (Part 4)

This series on hyperventilation, or over-breathing, concludes with a look at kapalabhati, a yoga breathing technique that at first glance resembles hyperventilation.

The Sanskrit word kapalabhati means “skull-shining.” It’s one of my favorite practices. I often begin my day with it after using the neti pot. It leaves me feeling both mentally energized and calm–a very different feeling from the agitation that accompanies hyperventilation. And, in fact, despite appearances, kapalabhati isn’t hyperventilation, as long as it’s done properly.

To practice kapalabhati, sit in a comfortable, upright posture such as virasana or a stable cross-legged seat. Contract your abdomen swiftly and vigorously, expelling your breath through your nose while keeping your spine fairly vertical (this means you’ll mainly use the transversus abdominis muscle, whose job is to compress the abdominal contents). Immediately following the contraction, relax your abdominal muscles to let your belly drop, which will allow air to flow back into your lungs. As you get comfortable, you can build up to a fairly rapid pace, but keep the emphasis on the exhalation. Don’t try to inhale actively. Simply allow the inhalations to happen between exhalations.

Experienced practitioners can breathe as rapidly as two breaths per second during kapalabhati. That’s 10 times as fast as a typical quiet breathing rate of 12 breaths per minute. Intuitively, it seems likely that breathing that quickly would blow off significant amounts of CO2, but let’s look at it more closely.

To estimate the volume of air moving through the lungs, we’ll calculate “minute ventilation,” the amount of air you inhale (or exhale) per minute. The “average” person takes in about half a liter (500 ml) of air per breath during normal quiet breathing. This is called “tidal volume.” Multiplying tidal volume by breathing rate gives us his minute ventilation, in this case 6 liters (500 ml x 12 breaths per minute).

(I say “his” deliberately because these “average” figures are based on studies conducted years ago with subjects who were almost always young men. Often they were medical students, since poor students are about the only people willing to endure long experimental procedures for small stipends. Otherwise, they were generally soldiers, who probably had even less choice. Lung capacity depends on size, especially height, as well as age. Since these figures are for a young man of average height and weight for the time, if you’re female or older, or a small male, your actual lung volumes could be smaller. If you’re a big man, they will probably be larger.)

At 500 ml per breath and 120 breaths per minute you’d move 60 liters of air in and out every minute practicing kapalabhati. That’s 10 times normal minute ventilation–appropriate if you’re exercising vigorously, but a lot if you’re sitting still. Your abdominal muscles get a workout during kapalabhati, so your ventilation has to increase somewhat, but probably nothing like 60 liters per minute.

Fortunately, your actual tidal volume during kapalabhati is likely a lot less than 500 ml. Measured values range from 130 to 380 ml. (Keep in mind these numbers come from a mere handful of studies, each with very few subjects. There’s probably a large range of individual variability, so treat them as a rough approximation. But, in any case, they match my experience of kapalabhati as a shallow breath.)

Why is tidal volume lower during kapalabhati?

Normally when you inhale, the diaphragm contracts, pulling down on the bottom of the lungs to stretch them open. As the volume of the lungs increases, their internal pressure drops, and air flows in. Because the lungs are elastic, when the diaphragm stops contracting they recoil to their “resting volume,” driving up the pressure to move air out. (The lungs reach their resting volume when the forces that tend to pull them closed, including their own elasticity, are balanced by the forces that tend to pull them open. Those forces include the downward pull of gravity on the abdomen and the elastic recoil of the ribs, as well as the contraction of inspiratory muscles such as the diaphragm.)

Kapalabhati is different because it’s a non-diaphragmatic breath. When you exhale during kapalabhati, the abdominal muscles contract. They push the abdominal contents upward against the diaphragm, actively compressing the lungs and driving air out. You inhale not by contracting the diaphragm, but by relaxing the abdominal muscles. This causes the abdomen to drop. As gravity pulls the belly down, it also pulls the diaphragm’s central tendon and the base of the lungs down, creating the expansion that brings air in.

Because you’re breathing rapidly, your next exhale begins before your diaphragm has a chance to descend very far. The central tendon probably doesn’t even drop to where it would be at the end of a normal exhale, much less to where it would be after a normal diaphragmatic inhale.

Not only that, to allow the belly to move as freely as possible in kapalabhati, you need to stabilize the base of ribs. You can feel this when you practice kapalabhati by placing your hands on your lower ribs and noting how they don’t widen as they typically do when you breathe diaphragmatically. Because you’re missing the lateral expansion of the lungs that usually accompanies the downward pull on their base during a diaphragmatic inhale, tidal volume is reduced even further.

Another factor also keeps kapalabhati from becoming hyperventilation: only part of that tidal volume is actually involved in gas exchange. To understand why that is, we’ll look at the microscopic anatomy of the lungs.

Gas exchange takes place at the interface between tiny, gossamer-walled air sacs known as alveoli, which make up the bulk of the lung tissue, and the networks of capillaries that surround them. Capillaries are so narrow that red blood cells pass through single file, like customers funneled through a supermarket check-out line, and so thin-walled that oxygen and carbon dioxide can diffuse between the alveoli and the blood.

Lung and Diaphragm

Before air reaches the alveoli it must pass through an extensive network of tubing, from the nose or mouth through the throat, the trachea, and a series of smaller and smaller branching tubes within the lungs. If the alveolar-capillary interface is the checkout line where the business of breathing is transacted–oxygen for carbon dioxide–the airway is like the network of highways and local streets that conduct goods to and from the market.

Since the air that fills the tubing isn’t involved in gas exchange, that volume is called the anatomical dead space. It’s usually estimated at 150 ml. Thus, of the 500 ml taken in during a typical quiet breath, only 350 ml actually reaches the alveoli. At 12 breaths per minute, normal “alveolar ventilation” is 4.2 liters (12 x 350 ml), not the 6 liters that pass through the nostrils.

Alveolar ventilation rather than total ventilation determines how much CO2 gets expelled, so we’ll need to estimate that for kapalabhati. Arbitrarily splitting the difference between the high and low figures mentioned above for tidal volume during kapalabhati, we get an average of about 250 ml. Subtracting 150 ml of dead space gives us an estimate of 100 ml of alveolar ventilation per breath. 120 breaths per minute would yield 12 liters per minute.

That’s a rough guess, and the actual amounts could be very different for a particular individual, but it fits with laboratory observations. In the small number of studies on the subject, researchers have generally found that expired CO2 levels remain normal even during lengthy bouts of kapalabhati, at least for experienced practitioners. In addition, their cardiovascular parameters don’t reflect what you’d expect to see in hyperventilation. Whatever the increase in alveolar ventilation, it appears to match the body’s increased need for oxygen, and therefore production of CO2. That makes sense in light of the fact that most of the air moving in and out is simply filling and emptying the airway, without reaching the alveoli.

This also yields some insight into why it’s important to practice kapalabhati correctly, and, in particular, to try not to inhale actively. Just let the inhalations happen as you relax the belly between exhalations. Otherwise, you could drive alveolar ventilation too high, turning it into a true hyperventilating breath.

In my experience, this is typically why people feel lightheaded or dizzy during kapalabhati, and why some find it stressful–particularly those who are habitual paradoxical, or reverse, breathers. For them, because it’s difficult to relax the belly while inhaling, kapalabhati turns into a series of rapid forceful thoracic breaths. That’s much more likely to lead to hyperventilation than the series of sharp abdominal exhales that kapalabhati is meant to be.

Of course, it’s not easy to let go of trying to inhale. It requires trust that you will get enough air. But that might just be the most important reason to learn to do kapalabhati safely.

Frostell C, et al. Effects
of high-frequency breathing on pulmonary ventilation and gas exchange. J Appl Physiol: Respirat Environ Exercise Physiol. 55(6):1854-1861,1983

Karambelkar PV, et al. Some respiratory studies in respect of kapalabhati and voluntary hyperventilation. Yoga-Mimamsa. 21(1-2):54-58,1982

Miles WR. Oxygen consumption during three yoga-type breathing patterns. J Appl Physiol. 19(1):75-82, 1964

Wenger MA & Bagchi BK. Studies of autonomic functions of practitioners of yoga in India. Behav Sci. 6:312-23, 1961

Image: By National Cancer Institute ([1]) [Public domain], via Wikimedia Commons

Tadasana: finding the summit of the mountain

In many yoga styles tadasana—mountain pose—is the starting point of the practice. Settling into the pose, we search for the feeling of the height of a mountain by finding the broad base of a mountain in the feet.

The challenge of tadasana is that humans are not built like mountains. In fact, with our small base of support and high center of gravity we’re closer to upside-down mountains—more swaying palm trees than bottom-heavy heaps of rock. (Interestingly, the Sanskrit word tada can mean palm tree as well as mountain.)

This swaying like a palm tree, called postural sway, is normal. Balance is not static. It is dynamic, a continual falling away from and regaining of the center. The nervous system receives input from proprioceptors in joints and muscles, visual cues, as well as information from the vestibular system in the inner ears. It processes that information to form a continuously modified sense of where you are in space. When the brain senses that you have moved away from the center, it unconsciously initiates muscular contractions to bring the weight back over your feet.

Postural sway can be measured. Early researchers used techniques like attaching smoked paper to a subject’s head and having them stand under a marker suspended from the ceiling. The marker would record the subjects’ movements as they maintained their balance, tracing a scribbled pattern on the paper. Someone who swayed a lot would draw a larger scribble; someone who didn’t move so much, a smaller one.

The smaller the scribble, the less work it takes to balance, because when you are close to the center it is easy to regain it; the more you deviate, the more effort you need to come back. Imagine standing at the summit of a high peak. If you take a single step in any direction, it’s easy to return. But if you move even a dozen yards away, you might have to do some strenuous climbing to regain the top.

So the closer you hover around the center, the more ease you’ll find in tadasana and the less muscular effort it will require. But how do you find that center? Forcibly inhibiting postural sway won’t help. In fact it’ll only make balance more difficult, by decreasing your sensitivity.

The key is rather to develop keener awareness. Where are you tallest? Where is the summit of the mountain? At that point each of your joints will be centered, with your weight centered over your feet.

Bring your awareness to your feet. When the heels and the balls of the big and little toes are evenly grounded the ankle joints will be centered and the arches will lift. Pay particular attention to the firm pressure of the balls of the big toes into the earth. For many, they tend to slide out, collapsing the inner arch of the foot; for others, it’s difficult to ground them at all and the weight falls to the outside of the feet. Either way, the foundation of the pose will sink.

Notice how your pelvis sits on top of your femurs. It’s common for the pelvis to shift forward or to be tilted or tucked under, so that the hip sockets are no longer centered on top of the femur heads. With your hand on your head, shift your pelvis forward and backward, left and right, to find the sweet spot where your head is at its highest point. Then tilt and tuck the pelvis, feeling for where the hip joints are completely centered and you are tallest.

Sense how your neck rests on top of your thoracic spine. If the sternum is pulled down or forced up, C7 (the bottom cervical vertebra) will not be able to center itself and the neck will be dragged out of alignment.  Notice how your skull sits on top of the atlas (the top cervical vertebra). Is your chin tucked or tilting up? Where are you looking? At horizon level? Up or down? When your head is centered, it should be able to turn and move easily.

In fact, only from the center is it possible to move with ease in any direction. When you’re off center, your choices are limited. By finding the summit of the mountain in tadasana, you’ll discover a sense of relaxed readiness that will let you move into the rest of your practice more fluidly.

What does stretching do for you?

Hyperventilation: Why more isn’t necessarily better when in comes to breathing (Part 2)

This is part two of a series of posts devoted to the physiology of hyperventilation.

In part one of this series, I covered what might seem like a paradoxical outcome of hyperventilation—that breathing more than necessary actually reduces the amount of oxygen to the brain. In this installment, I’ll explore two more effects of over-breathing: involuntary muscle spasms while hyperventilating and long periods of apnea (not breathing) afterwards.

The muscle contractions I experienced were dramatic. My limbs took on a life of their own, flopping like fish as my hands and feet spasmed (a condition known as tetany), all without conscious volition. There are several hypotheses about why this happens, but the most widely accepted has to do with calcium levels in the bloodstream. As I mentioned earlier, when CO2 levels in the blood drop, pH rises. This alkaline shift causes changes in a blood-borne protein called albumin. Albumin then binds to calcium, reducing the amount of free calcium in circulation. This in turn causes peripheral nerves to become more excitable. These hair trigger nerves then fire repeatedly, sending signals to muscles that cause them to contract involuntarily.

After I quit hyperventilating, I found myself pausing for long periods after my exhalations, in a way that also felt involuntary. To my partner, it looked as if I had stopped breathing altogether. These periods of not breathing have been observed in many people after hyperventilation, but they are not easy to explain.

To understand why, let’s begin with what makes us breathe. Breathing rate is directly controlled by several regions within the brainstem, collectively called the respiratory center. The respiratory center, left to its own devices, generates a regular series of impulses along the phrenic nerve that cause the diaphragm (the main breathing muscle) to rhythmically contract and relax, in turn leading us to breathe in and out. However, the respiratory center doesn’t exist in isolation; it receives inputs from many other parts of the nervous system that alter that rhythm. Some inputs are excitatory, encouraging more frequent breathing; others inhibit breathing.

The primary inputs that stimulate breathing come from sensors known as chemoreceptors, which continuously sample the chemical composition of body fluids. Some chemoreceptors are sensitive to oxygen; when arterial oxygen levels decline, they trigger an inhale. Under normal circumstances, though, oxygen levels don’t drop low enough to stimulate these receptors. They are like a thermostat turned way down; they only click on when oxygen levels are very low, and thus serve more as a last resort than a day in, day out regulator of breathing.

Other chemoreceptors are sensitive to carbon dioxide levels. Those located in the brain stem are the primary regulators of breathing rate. Technically, they don’t sense carbon dioxide; rather they test the pH of the cerebrospinal fluid (the fluid bath the brain and spinal cord float in). However, since the prime determinant of cerebrospinal pH is the carbon dioxide level in the blood, it amounts to the same thing. These sensors are far more sensitive than oxygen sensors; even a small rise in CO2 levels will cause them to fire, sending a signal to the respiratory center to trigger an inhale. Thus, we could say that, by and large, we don’t breathe to take in oxygen, but to get rid of CO2.

There are many other inputs into the respiratory center as well, in particular from the cerebral cortex (the “executive office” of the brain, where conscious decisions are made) and the limbic system (a group of areas of the brain concerned with emotion). It’s not only physiology that determines breathing; emotions and conscious decisions play a role too.

For instance, you could choose not to breathe. Of course, you would soon find that your ability to control your breath in this way is limited. As CO2 levels rise, stimulation from the chemoreceptors will overpower signals from the “higher brain” and you’ll have no choice but to breathe. You can’t kill yourself by holding your breath. (An exception may be divers who hyperventilate before going underwater. Lowering CO2 levels beforehand allows them to hold their breath longer while diving. But if they don’t breathe when they need to, oxygen levels in the brain may drop so low that they lose consciousness and drown.)

This would seem to explain those long periods of suspension after the exhale when I gave up on hyperventilation: CO2 levels in my bloodstream had dropped so low that it took a while for them to build up high enough trigger another inhale. However, there is a problem with this answer. Chemoreceptors respond to increases in CO2; they are indifferent to decreases. In other words, they won’t cause you to stop breathing. This is why people who hyperventilate can continue to do so for long periods of time; there’s nothing to stop them, short of losing consciousness.

There are a lot of discrepancies in the research around this issue. Some studies have found periods of apnea common after hyperventilation; others have found the opposite. Some of this variation is likely due to the length of the period of hyperventilation being studied, with apneas being more common after long sessions than short. (This seems to lend credence to the mechanism I outlined above; the longer the period of hyperventilation, the more CO2 levels would be driven down.) However, even discounting that, there is a great deal of individual variation in how people respond to the aftermath of hyperventilation. Some react as I did, by ceasing breathing. Others don’t. And we still have the problem that there is no clearly explicable physiological reason why low CO2 levels should cause breathing to stop.

Of course, I was not a physiologically naive subject going in. I was aware that hyperventilation lowers CO2 levels, so perhaps at some level I made a conscious decision to stop breathing to bring them back to a normal range to restore blood flow to my fogged up brain. That’s a possibility, but to me, those periods of breath suspension felt involuntary, as if some unconscious part of the brain took over to restore my system to balance. I guess we have to leave it at that, until further research explains what happens.

In any case, not everyone will react to hyperventilation by stopping. Hyperventilation can continue for long periods, because the system of checks and balances that regulate internal conditions within the body don’t work well to restrain it. In fact, it’s possible that hyperventilation could become habitual for some individuals. In the next installment, I will look at what happens in that case.

Meah MS & Gardner WN. Post-hyperventilation apnoea in conscious humans. J Physiol. 477(Pt 3):527-38, 1994

Tawadrous FD & Eldridge FL. Posthyperventilation breathing patterns after active hyperventilation in man. J Appl Physiol. 37(3):353-6, 1974

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I have a two files (both are DAT file) on the computer. I have to write a
application which take the selected data from this file and selected data
from my database table and then generate a new file which contain all selected

What's the best way to do it. because this two (.DAT) file continuous change
at particular time so it also change final output file.

Any help is realy appreciate.


This review first appeared in the July 2009 issue of hifi & stereo magazine You can also read this review of the Hornmanufaktur Allegro in its original German version. We translated it through a syndication arrangement with our German colleagues. As is customary for our own reviews, the writer's signature at review's end shows an e-mail address should you have questions or wish to send feedback. All images contained in this review are the property of or Hornmanufaktur. - Ed.

Reviewer: Ralph Werner
Sources: Analog - deck - Acoustic Solid MPX; tone arm - Phonotools Vivid-Two, SME M2 12-inch; carts Denon DL-103, Ortofon MC Rondo Bronce, Shelter 201, Zu Audio DL-103; digital - CD player - HIFIAkademie cdPlayer; Computer & Co - Logitech Squeezebox, Readynas Duo NAS-Server, HP Notebook; D/A converter - Aqvox USB2DA-MKII, Benchmark DAC1 USB
Amplification: Phono - Aqvox 2 CI MKII; preamplifier - Octave HP 300 MK2; power amp - Electrocompaniet AW180 monos; integrated - KingRex T20, LUA 4040C, Myryad MXI 2080, Rega Elicit
Loudspeaker: Thiel SCS4, Zu Audio Druid mk4
... and various cables
Review component retail: €5,000/pr in Birch veneer

"For many years, Hornmanufaktur has built loudspeakers which don't conform to the usual hifi norms and fashion statements but to the frequency response of the human ear." That's how the firm whose bestselling Allegro model is today's focus puts it somewhere on their website. Without any fancy footwork on interpreting that statement, two consequences seem obvious. There's solid self-confidence at work to oppose the speaker mainstream (however you'd define that mainstream); and this maker relies more on trust in his own ears than measurement fetishism. Hence the slogan "Qui habet aures audiendi audiat". A biblical quote (Matthew 11,15) for an advert's punch line? This promised to get interesting.

The man behind Hornmanufaktur is Gerald Hüpfel, chef and developer of some pretty special speakers from Austria. His self confidence is echoed in his bio. An IT manager who enters the highly competitive loudspeaker arena better have gumption and specific skills. Hüpfel is quite the interdisciplinarian too. After completing electro technical and sound engineering studies to combine science and art, he studied musicology to focus on music theory and history. "This comprehensive background was a prerequisite to attack the design of musical playback equipment" puns Hüpfel who followed high-school with an engagement at conducting opera in Vienna..

Five years ago, he commenced horn manufacture less than 80km outside of Graz in the Southern Burgenland - back-loaded horns like today's Allegro. This type of design amplifies the lowest two octaves by funneling a woofer's rear wave through a horn. The Allegro is defined both by its rear horn and the use of a singular widebander. It's a 1-way, without crossover. The visually most distinctive element of this drive unit is its light beige color. It stems from a cellulose that's harvested from the Banaba plant, also a healing herb whose exceedingly long fibers are said to make for very stiff yet light membranes. To enhance their self-damping properties, the cones are liberally oiled which closes off the micro fibers' molecular pores. Afterwards natural lacquers increase overall stiffness but also lock in the oil to prevent migration. A close inspection confirms a "fibrous and oily" appearance..

As is quite common for the breed, this transducer combines two membranes. A 16.5cm diameter cone extends to ca. 12.500Hz whence the smaller 7cm whizzer cone takes over to improve treble with less beaming. With the Allegro, this whizzer attaches directly to the voice coil whereas the main cone couples to the whizzer via a damped bridge. At ca. 12.5kHz, this mechanical low-pass activates at about 12dB/octave and Hornmanufaktur refers to their solution as a "quasi coaxial transducer sans electrical filter". This mechanical high pass mirrors the back-loaded horn which loads the widebander in the lower octaves such as to seriously damp down excursions compared to 'normal' boxes. That reduces the front-firing output and is strategically countermanded by the 'virtual bass membrane' of the horn mouth which is driven by the cone's backside. Horn action covers about 40 to 120Hz while the separation between direct radiation and horn augmentation enters with a 24dB/octave angle.

To respond to a Physic drop-out's "whutza horn" quip, let's start basic and with radiation resistance. This determines a moving membrane's ratio of electrical to acoustical conversion in both sound pressure (gain) and air movement (loss). Conventional speakers suffer the latter particularly in the bass where losses exceed gain. Put differently, they move more hot air than create bass pressure. Naturally, frequency affects this ratio. The lower a tone, the more time the air has to evade the cone's excursion by escaping sideways rather than finding itself compressed. At higher frequencies, this reaction interval shrinks and both radiation resistance and acoustic gain increase.