, Parides MK, Curtis AB, Kaufman ES, Davidenko JM, Shinn TS, Fontaine JM. Microvolt T wave alternans ... signal processing techniques are required to detect TWA. Microvolt T wave Alternans MTWA Microvolt T wave ... millionth of a volt. Microvolt T wave alternans is defined as an alternation in the morphology of the T wave ... imperceptible alternans at the microvolt level and susceptibility to arrhythmias and showed alternans ... Method, which allowed measurement of alternans at the level of one microvolt. Clinical Significance Microvolt T wave alternans testing acts as a risk stratifier between patients who need implantable ... T, Schloss EJ, Waller T, Chung E, Menon S, Nallamothu BK, Chan PS. Microvolt T wave alternans identifies ... to a more invasive electrophysiology EP study ref name medscape.com Noninvasive Microvolt ... Bigger. Microvolt T Wave Alternans Distinguishes Between Patients Likely and Patients Not Likely to Benefit ... method for measuring Microvolt T wave Alternans has been approved for reimbursement by Medicare, as well ... issued by CMS, Microvolt T wave Alternans diagnostic testing is covered for the evaluation of patients ... Determination NCD for Microvolt T Wave Alternans MTWA url https www.cms.gov medicare coverage database ... www.cambridgeheart.com Cambridge Heart Manufacturer of Microvolt T wave Alternans Systems http www.gehealthcare.com ... more details
orphan date April 2010 Image SX 117 Front and in case.jpg thumb 200px right Hallicrafters SX 117 The Hallicrafters SX 117 was a radio communications receiver manufactured by the Hallicrafters company in the 1960s. Description The SX 117 was a triple conversion intermediate frequency receiver designed to cover the 10 meter band 10 meter to 80 meter band 80 meter amateur radio bands with an additional band switch setting for WWV radio station WWV on 10 MHz . The first and third conversion oscillators were crystal controlled. The second was variable from 6 to 6.5 MHz. Introduced in 1962 at a price of 379.95, it had a product detector for Single sideband modulation SSB , a notch filter, and selectable bandwidth of 0.5, 2.5, and 5 KHz . In addition to the ham bands, general coverage was possible for most frequencies in 500 kHz segments from 85 kHz to 30 MHz with appropriate crystals. For frequencies below 3 MHz, the HA 10 LF MF converter was an optional accessory costing 24.95. The receiver featured 13 vacuum tube s plus Solid state electronics solid state rectifiers and a noise limiter. ref http www.dxing.com rx sx115.htm DXing.com Hallicrafters SX 117 ref Specifications Input Voltage 105 125 A.C. 50 60 cycles. Power Consumption 70W. Sensitivity listed .5 to 1 Microvolt. Audio Output Impedance 3.2 ohms or 500 ohms. Audio Output Power 3.2 Ohms 3.5 W.P.P. Antenna impedance 50 75 Ohm Unbalanced. ref http www.dxing.com rx sx115.htm DXing.com Hallicrafters SX 117 ref Gallery gallery Image SX117 Back.jpg Hallicrafters SX 117 receiver back view. Image Underside SX 117.jpg Hallicrafters SX 117 receiver underchassis view. Image Top SX 117.jpg Hallicrafters SX 117 receiver top view. gallery See also Communications receiver Hallicrafters Vintage amateur radio References Reflist External links http www.rigpix.com hallicrafter sx117.htm SX 117 General Information , RigPix.com http www.rigpix.com hallicrafter sx117 manual.pdf SX 117 Operators and Service Manu ... more details
Image Popcorn noise graph.png thumb Graph of burst noise Burst noise is a type of electronic noise that occurs in semiconductors. It is also called popcorn noise , impulse noise , bi stable noise , or random telegraph signal RTS noise. It consists of sudden step like transitions between two or more discrete voltage or current levels, as high as several hundred microvolt s, at random and unpredictable times. Each shift in offset voltage or current often lasts from several milliseconds to seconds, and sounds like popcorn popping if hooked up to an audio speaker. ref http www.stanford.edu bipin research Noise.pdf page 11 Random Telegraph Signal Review of Noise in Semiconductor Devices and Modeling of Noise in Surrounding Gate MOSFET, Bipin Rajendran ref Popcorn noise was first observed in early point contact diode s, then re discovered during the commercialization of one of the first semiconductor operational amplifier op amps the 709. ref name intersil http www.intersil.com data an an519.pdf Operational Amplifier Noise Prediction Intersil Application Note ref No single source of popcorn noise is theorized to explain all occurrences, however the most commonly invoked cause is the random trapping and release of charge carrier s at thin film interfaces or at defect sites in bulk semiconductor crystal. In cases where these charges have a significant impact on transistor performance such as under an MOS gate or in a bipolar base region , the output signal can be substantial. These defects can be caused by manufacturing processes, such as heavy ion implantation , or by unintentional side effects such as surface contamination. ref http www.ti.com lit an slva043b slva043b.pdf Noise Analysis In Operational Amplifier Circuits Texas Instruments application report ref ref http web.mit.edu klund www CMOSnoise.pdf page 9 Noise Sources in Bulk CMOS Kent H. Lundberg ref Individual op amps can be screened for popcorn noise with peak detector circuits, to minimize the amount of noise i ... more details
A microphone preamplifier is a sound engineer sound engineering device that prepares a microphone electrical signal signal to be processed by other equipment. Microphone signals are normally too weak to be transmitted to units such as mixing console s and sound recording recording device s. dubious Weak signals date January 2011 Preamplifiers increase a microphone signal to line level i.e. the level of signal strength required by such devices by providing stable gain while preventing induced noise that would otherwise distort the signal. ref Ballou, 1987, pp. 506 507. ref The microphone preamplifiers are colloquially called microphone preamp , mic preamp , preamp not to be confused with a control amplifier in high fidelity high fidelity reproduction equipment , mic pre and pre . Technical details The output voltage on a dynamic microphone may be very low, typically in the 0 to 100 microvolt range. A microphone preamplifier increases that level by up to 70 Decibel dB , to approximately 0 to 10 volts. This stronger signal is used to drive equalization circuitry within an audio mixer, to drive external audio effects, and to sum with other signals to create an audio mix for audio recording and for live sound . In use A microphone is a transducer and, as such, is the source of much of the coloration of an audio mix. Most audio engineer s would assert that a microphone preamplifier also affects the sound quality of an audio mix. A preamplifier might load the microphone with low impedance, forcing the microphone to work harder and so change its tone quality. A preamplifier might add coloration for adding a different characteristic than the audio mixer s built in preamplifiers. Some microphones must be used in conjunction with a preamplifier to function properly e.g.Condenser microphones or date January 2011 Some preamplifiers exist as one part of a channel strip , which can include other kinds of audio recording devices such as Dynamic range compression compressor s, Equal ... more details
Image BiofeedbackHeadband2.jpg thumb right 200px A Example of a biofeedback headband front view and back view for use in measuring and reduction of bruxism subconscious teeth clenching and grinding and tension headaches A biofeedback headband is a self contained biofeedback unit which is worn on the head and held in place by an elastic strap. Biofeedback headbands are most often used for controlling bruxism during sleep, but can also be used during the day. Clenching is sensed through electromyography EMG by picking up microvolt level muscle signals from the temporalis muscles through black conductive rubber sensor pads which contact the user s forehead and temples when the unit is worn. Modern biofeedback headbands track clenching and grinding activity as well as providing biofeedback. After a night of use, the user can read out of the unit both the number of clenching incidents detected, and the total amount of clenching time accumulated through the night. Biofeedback headbands may also be used to reduce tension headaches and migraines which are caused by bruxism or excessive tightening of frontalis muscle . History The first biofeedback headband was invented by Lee Weinstein, in 1998, and patented in September, 2000. ref cite web url http www.wikipatents.com US Patent 6117092 bruxism biofeedback apparatus and method title Bruxism Biofeedback Method and Apparatus publisher WikiPatents.com date 2000 09 12 ref Advances were made in the following year and patented in August, 2001. ref cite web url http www.wikipatents.com US Patent 6270466 bruxism biofeedback apparatus and method including acoustic transducer title Bruxism Biofeedback Apparatus and Medhod Including Acoustic Transducer publisher WikiPatents.com date 2001 08 07 ref The first headband commercially available for use in the reduction or elimination of bruxism was introduced by BruxCare at the Boston Convention and Exhibition Center Yankee Dental Congress in Boston , in February 2001. These early units had ... more details
Unreferenced date December 2009 A broadcast range also listening range or listening area for radio , or viewing range or viewing area for television is the service area that a broadcasting broadcast station or other transmission radio transmission covers via radio wave s or possibly infrared light , which is closely related . It is generally the area in which a station s signal strength is sufficient for most receiver radio receiver s to decode it, however this also depends on electromagnetic interference interference from other stations. Legal definitions The primary service area is the area served by a station s strongest signal. The city grade contour is 70 dB decibel s relative to one microvolt per meter of signal strength or 3.16mV m millivolts per meter for FM stations in the United States , according to Federal Communications Commission FCC regulations. This is also significant in broadcast law , in that a station must cover its city of license within this area, except for non commercial educational and low power broadcasting low power stations. The legally protected range of a station extends beyond this range, out to the point where signal strength is expected to be 1mV m for most stations in North America , though for List of North American broadcast station classes AM class B1 stations it is 0.7mV m, and as low as 0.5mV m for full class B stations the maximum allowed in densely population populate d areas of both Canada and the U.S. . Practical application In reality, radio propagation changes along with the weather and tropospheric ducting , and occasionally along with other upper atmospheric phenomena like sunspot s and even meteor shower s. Thus, while a broadcasting authority might fix the range to an area with exact Boundary topology boundaries defined as a series of Euclidean vector vector s , this is rarely if ever true. When a broadcast reaches well outside of its intended range due to anomalous propagation unusual conditions , DXing is possible. ... more details
In telecommunications , particularly in radio , signal strength refers to the magnitude of the electric field at a reference point that is a significant distance from the transmitting antenna. It may also be referred to as received signal level or field strength . Typically, it is expressed in voltage per length or Transmitter power output signal power received by a reference antenna. Nominal power High powered transmissions, such as those used in broadcasting , are expressed in Decibel dB millivolt s per metre dBmV m . For very low power systems, such as mobile phone s, signal strength is usually expressed in Decibel dB microvolt s per metre dB V m or in decibel s above a reference level of one Watt unit milliwatt dBm . In broadcasting terminology, 1 mV m is 1000 V m or 60 Decibel Radio power, energy, and field strength dB often written dBu . Examples 100 dB or 100 mV m blanketing interference may occur on some receivers 60 dB or 1.0 mV m frequently considered the edge of a radio station s protected area in North America 40 dB or 0.1 mV m the minimum strength at which a station can be received with acceptable quality on most receivers Relationship to average radiated power The electric field strength at a specific point can be determined from the power delivered to the transmitting antenna, its geometry and radiation resistance. Consider the case of a center fed half wave dipole antenna in Free space optical communication free space math scriptstyle L lambda 2 math . If constructed from thin conductors, the current distribution is essentially sinusoidal and the radiating electric field is given by Image lambdaover2 antenna.jpg frame Current distribution on antenna of length math scriptstyle L math equal to one half wavelength math scriptstyle lambda 2 math . math E theta r jI circ over 2 pi varepsilon circ c , r cos left scriptstyle pi over 2 cos theta right over sin theta e j left omega t kr right math where math scriptstyle theta math is the angle between th ... more details
refimprove date November 2007 Thermoelectric effect cTopic Principles The thermopower , or thermoelectric power also called the Seebeck coefficient of a material is a measure of the magnitude of an induced thermoelectric voltage in response to a temperature difference across that material. ref name Blundell Concepts in Thermal Physics , by Katherine M. Blundell http books.google.com books?id v2W5ha0E D4C&pg PA393&dq thermopower seebeck&lr &ei nLQ7Ss2uI4uwkASkzpS6BQ Weblink through Google books ref The thermopower has units of volt s per kelvin V K , ref name Blundell although it is more often given in microvolt s per kelvin V K . Thermo power is a misnomer. What is called thermo power would be more correctly dubbed thermoelectric sensitivity as it measures the voltage or electric potential not the electric power induced in response to a temperature difference. Note that the unit of thermopower V K is different from the unit of power watt s . The phenomenon quantified by thermopower is called the Seebeck effect . The Seebeck effect and two related phenomena the Peltier effect and Thomson effect are together called the thermoelectric effect . Physics of thermopower main Thermoelectric effect Classically, an applied temperature difference causes charged carriers in the material, whether they are electrons or Electron hole holes , to diffuse from the hot side to the cold side, similar to a gas that expands when heated. Mobile charged carriers migrating to the cold side leave behind their oppositely charged and immobile nuclei at the hot side thus giving rise to a thermoelectric voltage thermoelectric refers to the fact that the voltage is created by a temperature difference . Since a separation of charges also creates an electric field, the buildup of charged carriers onto the cold side eventually ceases at some maximum value since there exists an equal amount of charged carriers drifting back to the hot side as a result of the electric field at equilibrium. Only an in ... more details
relative to 1 microvolt. Widely used in television and aerial amplifier specifications. 60 dB V 0 ... dB V m electric field strength relative to 1 microvolt per meter . Often used to specify the signal ... more details
Interventions infobox Name Evoked potential Image Caption ICD10 ICD9 MeshID D005071 OtherCodes An evoked potential or evoked response is an electrical potential recorded from the nervous system of a human or other animal following presentation of a Stimulus physiology stimulus , as distinct from spontaneous potentials as detected by electroencephalography EEG or electromyography EMG . Evoked potential amplitude s tend to be low, ranging from less than a microvolt to several microvolts, compared to tens of microvolts for EEG, millivolts for EMG, and often close to a volt for Electrocardiogram ECG . To resolve these low amplitude potentials against the background of ongoing EEG, ECG, EMG, and other biological signals and ambient noise, signal averaging is usually required. The signal is time locked to the stimulus and most of the noise occurs randomly, allowing the noise to be averaged out with averaging of repeated responses. ref Cite book title Spehlmann s Evoked Potential Primer author Karl E. Misulis, Toufic Fakhoury year 2001 publisher Butterworth heinemann isbn 0 7506 7333 8 ref Signals can be recorded from cerebral cortex , brain stem , spinal cord and Peripheral nervous system peripheral nerve s. Usually the term evoked potential is reserved for responses involving either recording from, or stimulation of, central nervous system structures. Thus evoked compound motor action potentials CMAP or sensory nerve action potentials SNAP as used in nerve conduction study nerve conduction studies NCS are generally not thought of as evoked potentials, though they do meet the above definition. Sensory evoked potentials Sensory evoked potentials SEP are recorded from the central nervous system following stimulation of sense organ s for example, visual evoked potentials elicited by a flashing light or changing pattern on a monitor ref name osheaetal O Shea, R. P., Roeber, U., & Bach, M. 2010 . Evoked potentials Vision. In E. B. Goldstein Ed. , Encyclopedia of Perception Vol ... more details
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