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Topic: Conduction


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  conduction - Encyclopedia.com
conduction transfer of heat or electricity through a substance, resulting from a difference in temperature between different parts of the substance, in the case of heat, or from a difference in electric potential, in the case of electricity.
In solids, electric current consists of a flow of electrons; as in the case of heat conduction, metals are better conductors of electricity because of their greater free-electron density, while nonmetals, such as rubber, are poor conductors and may be used as electrical insulators, or dielectrics.
The role of sensory nerve conduction study of the palmar cutaneous nerve in the diagnosis of carpal tunnel syndrome in patients with polyneuropathy
www.encyclopedia.com /doc/1E1-conducton.html   (1462 words)

  
 Heat conduction
Gradient heat transport depends on three quantities: the conductivity of the material, the cross-sectional area of the material, and the spatial gradient of temperature.
The larger the conductivity, gradient,and/or cross-section, the faster the heat flows.
In this experiment, the flow of heat through a collection of conductive bars which vary in cross-section is simulated.
www.jhu.edu /~virtlab/conduct/conduct.htm   (339 words)

  
  AllRefer.com - conduction (Physics) - Encyclopedia
conduction, transfer of heat or electricity through a substance, resulting from a difference in temperature between different parts of the substance, in the case of heat, or from a difference in electric potential, in the case of electricity.
Conduction of electricity consists of the flow of charges as a result of an electromotive force, or potential difference.
In solids, electric current consists of a flow of electrons; as in the case of heat conduction, metals are better conductors of electricity because of their greater free-electron density, while nonmetals, such as rubber, are poor conductors and may be used as electrical insulators, or dielectrics.
reference.allrefer.com /encyclopedia/C/conducton.html   (508 words)

  
 MDA / Quest Vol 7 No 5 /Simply Stated . . .
A nerve is actually a bundle of axons, cables that conduct action potentials from one end of a nerve cell (or neuron) to the other.
NCV measures action potentials conducted by axons, so doctors use it for diagnosing diseases that primarily affect nerve function, such as different forms of Charcot-Marie-Tooth disease (CMT).
Conduction speed is influenced by a coating around axons, called myelin.
www.mdausa.org /publications/Quest/q75ss.html   (866 words)

  
 MedlinePlus Medical Encyclopedia: Nerve conduction velocity
Nerve conduction velocity (NCV) is a test of the speed of signals through a nerve.
Often the nerve conduction test is followed by electromyography (EMG) which involves needles being placed into the muscle and you contracting that muscle.
Conduction block (the impulse is blocked somewhere along the nerve pathway)
www.nlm.nih.gov /medlineplus/ency/article/003927.htm   (558 words)

  
 Nerve conduction studies   (Site not responding. Last check: )
The conduction velocity (CV) is calculated by dividing the length of the nerve segment between the two stimulation points by the difference between the proximal and distal latency [12].
A Conduction block is the failure of an action potential to propagate throughout the length of a structurally intact axon.
The conduction velocity (CV) is calculated by dividing the length of the nerve segment from the stimulus point to the recording point by the positive peak latency.
www.med.ege.edu.tr /~norolbil/2000/NBD10900.html   (6684 words)

  
 Heat conduction - Wikipedia, the free encyclopedia
The law of heat conduction, also known as Fourier's law, states that the time rate of heat flow Q through a slab (or a portion of a perfectly insulated wire, as shown in the figure) is proportional to the gradient of temperature difference:
A is the transversal surface area, Δx is the thickness of the body of matter through which the heat is passing, k is a conductivity constant dependent on the nature of the material and its temperature, and ΔT is the temperature difference through which the heat is being transferred.
R-value is the unit for heat resistance, the reciprocal of the conductance.
en.wikipedia.org /wiki/Newton%27s_law_of_cooling   (443 words)

  
 ** H E A T **   (Site not responding. Last check: )
The law says that the heat conducted through a cross section is proportional to the negative of the temperature.The proportionally constant is called the thermal conductivity of the materials.
It depends on 3 things, the conductivity of the material, the area of the cross section and the spatial gradient of temperature.If the gradient or cross section is large, the heat will flow or be conducted faster.
The relative conductivity of the differing cross sectional bars is measured along the x axis taking and time into account in a function that is expressed as c(x).In the experiment heat is conducted through the bar and the cross section of the bar has to be determined.
library.thinkquest.org /C001300/gather/principles/conduction.html   (492 words)

  
 Conduction
Heat conduction (as opposed to electrical conduction) is the flow of internal energy from a region of higher temperature to one of lower temperature by the interaction of the adjacent particles (atoms, molecules, ions, electrons, etc.) in the intervening space.
Conductivities vary for material being greatest for metallic solids, lower for nonmetallic solids, very low for liquids, and extremely low for gases.
Using copper in the base would increase the rate at which heat was transferred from the flames or heating element to the food, while using stainless steel on the sides would reduce the rate at which heat was lost from the food to the environment.
hypertextbook.com /physics/thermal/conduction   (1161 words)

  
 Nerve conduction study Summary
A nerve conduction study (NCS) is a test commonly used to evaluate the function, especially the ability of electrical conduction, of the motor and sensory nerves of the human body.
Nerve conduction studies are used mainly for evaluation of paresthesias (numbness, tingling, burning) and/or weakness of the arms and legs.
This also evaluates conduction between the limb and the spinal cord, but in this case, the afferent impulses (those going towards the spinal cord) are in sensory nerves while the efferent impulses (those coming from the spinal cord) are in motor nerves.
www.bookrags.com /Nerve_conduction_study   (1560 words)

  
 Charging by Conduction
Charging by conduction involves the contact of a charged object to a neutral object.
When the process of charging by conduction is complete, the electroscope acquires an excess negative charge due to the movement of electrons onto it from the metal sphere.
And if a conducting pathway is made between an electron and an excess proton, one can be certain that there is likely an electron which would be willing to take the pathway.
www.glenbrook.k12.il.us /gbssci/phys/Class/estatics/u8l2c.html   (2474 words)

  
 Normal impulse conduction
The conduction system within the heart is very important because it permits a rapid and organized depolarization of ventricular myocytes that is necessary for the efficient generation of pressure during systole.
The conduction of electrical impulses throughout the heart, and particularly in the specialized conduction system, is strongly influenced by autonomic nerve activity.
Because conduction velocity depends on the rate of tissue depolarization, which is related to the slope of phase 0 of the action potential, conditions (or drugs) that alter phase 0 will affect conduction velocity.
www.cvphysiology.com /Arrhythmias/A003.htm   (775 words)

  
 Electrical conduction Summary
The third form of conduction occurs in metals where the electrons exist as a "cloud" that can be moved easily in an electric field.
Conduction is well-described by Ohm's Law, which states that the current is proportional to the applied electric field.
Thermionic emission occurs when the thermal energy exceeds the metal's work function, while field emission occurs when the electric field at the surface of the metal is high enough to cause tunneling, which results in the ejection of free electrons from the metal into the vacuum.
www.bookrags.com /Electrical_conduction   (1542 words)

  
 Bagatellen: Conduction in Improvised Music - The London Improvisers Orchestra
With the conduction of large improvising ensembles, the interpretation of a composition is dispensable.
Conduction becomes reduced to two or three essential characteristics – the technical ability to clearly express intent to large numbers of people while they are playing, and the extent to which the conductor is able to, or wishes to, impose their personality on the ensemble.
Conduction is the process whereby various hand signals or other signs are used to direct responses from members of the orchestra.
www.bagatellen.com /archives/features/000095.html   (5268 words)

  
 Nerve Conduction Study Information on Healthline
A nerve conduction study is a test that measures the movement of an impulse through a nerve after the deliberate stimulation of the nerve.
The ability of a nerve to swiftly and properly transmit an impulse down its length, and to pass on the impulse to the adjacent nerve or to a connection muscle in which it is embedded, is vital to the performance of many activities in the body.
The nerve conduction study, which was devised in the 1960s, can detect the loss of nerve function due to these injuries, and, from the nature of the nerve signal pattern that is produced, offer clues as to the nature of the problem.
www.healthline.com /galecontent/nerve-conduction-study   (844 words)

  
 Altered impulse conduction
Depolarization decreases the action potential amplitude and rate of depolarization (phase 0 slope is decreased), both of which decrease the velocity of action potential conduction or completely stop the conduction of action potentials (i.e., conduction block).
Conduction blocks can also be caused, especially at the AV node, by excessive vagal activation or because of drugs that reduce conduction such as beta-blockers and calcium-channel blockers.
Conduction blocks can occur at the AV node, bundle of His, or bundle branches as shown in the figure.
www.cvphysiology.com /Arrhythmias/A008b.htm   (418 words)

  
 Conduction System
The heart's conduction system consists of the sinoatrial node, the atrioventricular node, internodal fasiculus, and the atrioventricular bundle, which divides into right and left branches.
The function of these cells is to initiate and conduct action potentials that are responsible for the contraction of the working cells.
The cause of this slow conduction through the atrioventricular bundle is partly due to the small fiber size as compared to normal atrial muscle fibers.
oak.cats.ohiou.edu /~jr888793/conduction.html   (1724 words)

  
 Heat Transfer
Conduction is heat transfer by means of molecular agitation within a material without any motion of the material as a whole.
If one end of a metal rod is at a higher temperature, then energy will be transferred down the rod toward the colder end because the higher speed particles will collide with the slower ones with a net transfer of energy to the slower ones.
Convection is heat transfer by mass motion of a fluid such as air or water when the heated fluid is caused to move away from the source of heat, carrying energy with it.
230nsc1.phy-astr.gsu.edu /hbase/thermo/heatra.html   (441 words)

  
 General Conduction Theory in Heat Transfer
This equation determines the heat flux vector q for a given temperature profile T and thermal conductivity k.
The temperature profile within a body depends upon the rate of its internally-generated heat, its capacity to store some of this heat, and its rate of thermal conduction to its boundaries (where the heat is transfered to the surrounding environment).
is related to the thermal conductivity k, the specific heat c, and the density
www.efunda.com /formulae/heat_transfer/conduction/overview_cond.cfm   (232 words)

  
 Thermal Physics Unit 6 - Transfer of Heat (1)
There are three means of heat transfer; conduction, convection and radiation.
Conduction is the transfer of heat through a medium, such as a solid, where the heat is transferred from molecule to molecule (or electron to electron) but there is no bulk transport of the molecules through the medium.
where the constant of proportionality K is known as the coefficient of thermal conductivity, and is equal to the rate of heat flow per unit area for a temperature gradient of 1° per unit length.
www.shef.ac.uk /physics/teaching/phy001/unit6.html   (625 words)

  
 THE MERCK MANUAL OF GERIATRICS, Ch. 91, Arrhythmias and Conduction Disturbances
Intrinsic conduction system disease and acute disorders affecting the conduction system (eg, MI, digitalis toxicity) are more common among the elderly than among younger persons.
Widespread age-related histologic changes in the conduction system may contribute to the striking age-related increase in the incidence of bradyarrhythmias and conduction disturbances.
The increase in PR interval is due to a delay that is proximal to the His bundle; conduction time from the His bundle to the ventricle appears to be unrelated to age.
www.merck.com /mrkshared/mmg/sec11/ch91/ch91c.jsp   (1655 words)

  
 Conduction
The flow of heat by conduction occurs via collisions between atoms and molecules in the substance and the subsequent transfer of kinetic energy.
This transfer of kinetic energy from the hot to the cold side is called a flow of heat through conduction.
Materials which have a high thermal conductivity have, by definition, a low thermal resistance - they are poor heat insulators.
theory.uwinnipeg.ca /mod_tech/node75.html   (403 words)

  
 Nerve Conduction Studies
The nerve conduction study stimulates specific nerves and records their ability to send the impulse to the muscle.
Nerve conduction studies show whether the nerves transmit electrical impulses to the muscles or up the sensory nerves at normal speeds (conduction velocities).
Slower conduction velocities may also be caused by injury or damage to a nerve (such as carpal tunnel syndrome) or group of nerves (such as Guillain-Barré syndrome or post-polio syndrome).
www.csmc.edu /7080.html   (368 words)

  
 BioMed Central | Full text | Diagnostic properties of nerve conduction tests in population-based carpal tunnel syndrome
Nerve conduction tests are commonly used in the assessment of patients with numbness, tingling and pain in the hands.
The nerve conduction tests were done using the Kimura technique [9] that utilizes anatomical landmarks and included measurements of median nerve distal motor latency, long finger-wrist sensory latency, and sensory conduction velocity in the forearm, wrist-palm, and palm-digit segments, as well as ulnar nerve small finger-wrist sensory latency.
The low positive predictive value for nerve conduction testing is not unusual in a disease with a prevalence rate of less than 5% [8] in the general population.
www.biomedcentral.com /1471-2474/4/9   (4346 words)

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