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Topic: Decay constant

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Exponential decay

Nikolai Kapustin

	Radioactive Half-Life
		The radioactive half-life for a given radioisotope is a measure of the tendency of the nucleus to "decay" or "disintegrate" and as such is based purely upon that probability.
		The predictions of decay can be stated in terms of the half-life, the decay constant, or the average lifetime.
		The rate of radioactive decay is typically expressed in terms of either the radioactive half-life, or the radioactive decay constant.
	hyperphysics.phy-astr.gsu.edu /hbase/nuclear/halfli2.html (464 words)

	Exponential decay - Wikipedia, the free encyclopedia
		(The notation λ for the decay constant is a remnant of the usual notation for an eigenvalue.
		If the decaying quantity is the number of discrete elements of a set, it is possible to compute the average length of time for which an element remains in the set.
		In a sample of a radionuclide that undergoes radioactive decay to a different state, the number of atoms in the original state follows exponential decay as long as the remaining number of atoms is large.
	en.wikipedia.org /wiki/Decay_constant (1164 words)

	Radioactive decay - Wikipedia, the free encyclopedia
		Decay is said to occur in the parent nucleus and produces a daughter nucleus.
		Of the commonly occurring forms of radioactive decay, the only one that changes the number of aggregate protons and neutrons (nucleons) contained in the nucleus is alpha emission, which reduces it by four.
		On the premise that radioactive decay is truly random (rather than merely chaotic), it has been used in hardware random-number generators and is an invaluable tool in estimating the absolute ages of geological materials and young organic matter.
	en.wikipedia.org /wiki/Radioactive_decay (1972 words)

	Exponential decay Summary
		(The notation λ for the decay constant is a remnant of the usual notation for an eigenvalue.
		If the decaying quantity is the number of discrete elements of a set, it is possible to compute the average length of time for which an element remains in the set.
		In a sample of a radionuclide that undergoes radioactive decay to a different state, the number of atoms in the original state follows exponential decay as long as the remaining number of atoms is large.
	www.bookrags.com /Exponential_decay (1599 words)

	[No title] (Site not responding. Last check: 2007-10-17)
		The decay of an atom of a radioactive isotope to an atom of a stable daughter element occurs spontaneously.
		Because decay is a spontaneous occurrence, it is not known precisely when a specific atom of a radioactive isotope will decay to a daughter atom.
		The decay constant is a probability that, over a given amount of time, an atom of an isotope will decay into an atom of its daughter.
	cse.cosm.sc.edu /hses/AbsolDat/pages/decay.htm (222 words)

	Time constant - Wikipedia, the free encyclopedia
		Other examples include time constant used in control systems for integral and derivative action controllers, which are often pneumatic, rather than electrical.
		The resistance across the membrane is a function of the number of open ion channels and the capacitance is a function of the properties of the lipid bilayer.
		The larger a time constant is, the slower the rise or fall of the potential of neuron.
	en.wikipedia.org /wiki/Time_constant (462 words)

	[No title] (Site not responding. Last check: 2007-10-17)
		Because the decay rate is a measure of probability, the value of a decay constant is between 0 and 1.
		Because it is a quantity of change measured over a period of time, the decay constant is also considered to be the decay rate of an isotope.
		Decay constants are determined by detecting energy that is released during decay of a known amount of pure sample.
	cse.cosm.sc.edu /hses/AbsolDat/pages/mordecay.htm (297 words)

	Carbon 14: Constant Rate
		It has been found, for example, that decay constants are the same at a temperature of 2000 degrees C or at a temperature of 186 degrees C and are the same in a vacuum or under a pressure of several thousand atmospheres.
		Under certain environmental conditions, the decay characteristics of C-14, Co-60, and Ce-137, all of which decay by beta emission, do deviate slightly from the ideal random distribution predicted by current theory [Anderson, 1972; Anderson and Spangler, 1973], but changes in the decay constants have not been detected.
		Because this type of decay involves a particle outside the nucleus, the decay rate may be affected by variations in the electron density near the nucleus of the atom.
	www.infidels.org /library/modern/dave_matson/young-earth/carbon-14/constant_rate.html (1183 words)

	Half Life and Radioactive Decay
		Transmutation describes a process by which the nucleus of a radioactive atom undergoes decay into an atom with a different number of protons, until such time as a stable nucleus is produced.
		An alpha particle (i.e., a helium nucleus) is released during alpha decay of a radioactive substance.
		In beta decay, the beta particle released originated in the nucleus of the atom, not in the electron orbital.
	library.thinkquest.org /27948/decay.html (417 words)

	Atoms - the inside story. Using the decay equation.
		The number decaying will still be 12% of the total but it is fewer than in the first instance because there are fewer nuclei to decay.
		The chance of decaying in one second is less than the decay constant because the rate of decay gets less during the second as there are fewer nuclei to decay.
		For example, if we were to choose a time interval of 0.5 second and a decay constant of 2, then the chance of decaying in the time inteval would be 1 – i.e.
	www.schoolscience.co.uk /content/5/physics/particles/partich4pg3.html (758 words)

	Search ScienceWorld
		Exponential decay is the decrease in a quantity N according to the law N(t)==N_0e^(-lambdat) for a parameter t and constant lambda (known as the decay constant), where e^x is the exponential function and N_0==N(0) is the initial value.
		\tau\equiv 1/\lambda is the mean lifetime of a decaying particle, frequently called simply the "lifetime." Equations of this type describe phenomena such as radioactive decay of nuclei and the current in a CR circuit.
		The following table summarizes decay modes due to different fundamental forces, together with the particles mediating the decay and the approximate half-life for decay.
	scienceworld.wolfram.com /search/index.cgi?as_q=Decay (424 words)

	Photon Decay in Red Shift
		By the twenties, conjecture that wave decay might be the cause of Hubble Red Shift had been submerged under wartime developments including the use of Doppler shift in both sonar and radar to determine target speeds.
		Interest in wave decay was precluded by further war and atomic energy until the Soviet launch of the orbital Sputnik Earth satellite in 1957.
		A tentative abstract form would include the two constants h and c, and perhaps something which is related to the current values of the variables of wavelength, frequency, momentum, wavenumber, wavetime and energy.
	www.eskimo.com /~mikel137/index.htm (944 words)

	How to Change Nuclear Decay Rates (Site not responding. Last check: 2007-10-17)
		For most nuclides that decay by electron capture or internal conversion, most of the time, the probability of grabbing or converting an electron is also insensitive to the environment, as the innermost electrons are the ones most likely to get grabbed/converted.
		Alpha decay and spontaneous fission might also be affected by changes in the electron density near the nucleus, for a different reason.
		All told, the existence of changes in radioactive decay rates due to the environment of the decaying nuclei is on solid grounds both experimentally and theoretically.
	www.weburbia.demon.co.uk /physics/decay_rates.html (1067 words)

	Radioactive decay and Specific Activity (Site not responding. Last check: 2007-10-17)
		Radioactive decay is a first-order process that is specified by a decay constant that is characteristic for each isotope.
		Basically, the decay constant is the fraction of radioactive atoms that decay in a small unit of time.
		Another way to view the decay constant is the half-life which is the time required for half of the original number of atoms to decay.
	www.mun.ca /biochem/courses/3107/Topics/rad_decay.html (331 words)

	How to Change Nuclear Decay Rates (Site not responding. Last check: 2007-10-17)
		For most nuclides that decay by electron capture or internal conversion, most of the time, the probability of grabbing or converting an electron is also insensitive to the environment, as the innermost electrons are the ones most likely to get grabbed/converted.
		Alpha decay and spontaneous fission might also be affected by changes in the electron density near the nucleus, for a different reason.
		All told, the existence of changes in radioactive decay rates due to the environment of the decaying nuclei is on solid grounds both experimentally and theoretically.
	math.ucr.edu /home/baez/physics/ParticleAndNuclear/decay_rates.html (1170 words)

	decay - Definitions from Dictionary.com
		Decay, decompose, disintegrate, rot imply a deterioration or falling away from a sound condition.
		Rot is sometimes synonymous with decay, but often, like putrefy, stresses offensiveness to the sense of smell: The food left on the counter began to rot.
		The study of particle decay is fundamental to subatomic physics.
	dictionary.reference.com /browse/decay (984 words)

	Physics 30: Atomic Physics - Half-Life and Radioactive Decay
		The decay constant is a measure of the rate at which the nuclide releases radioactive emissions.
		Recognize that the decay constant is a measure of the rate of radioactive decay.
		Recognize that the expressed relationships for the radioactive decay are based on statistics and probability, and on the examination of the behaviour of a large number of individual situations.
	www.sasked.gov.sk.ca /docs/physics/u8b3phy.html (1434 words)

	Baylor University \|\| Geology Department \|\| Are decay constants actually constant?
		The answer is that the decay constants used in the dating of geological materials are effectively constant and invariant to external forces.
		The effect of beta decay is that a neutron is converted to a proton within an atom's nucleus, accompanied by the ejection of an electron and an antineutrino from the atom.
		Heavier radiogenic elements may undergo alpha decay, in which two protons and two neutrons are ejected from the nucleus, reducing the atomic number by 2 and the atomic mass number by 4.
	www.baylor.edu /geology/index.php?id=26725 (563 words)

	Modeling the Probability for Proton Decay (Site not responding. Last check: 2007-10-17)
		The experimental search for proton decay was undertaken because of the implications of the grand unification theories.
		The probability for observing a proton decay can be estimated from the nature of particle decay and the application of Poisson statistics.
		For a small sample, the observation of a proton decay is infinitesmal, but suppose we consider the volume of protons represented by the Super Kameokande neutrino detector in Japan.
	hyperphysics.phy-astr.gsu.edu /hbase/particles/protondec.html (312 words)

	Effective Delayed Neutron Precursor Decay Constant
		The decay constant of a precursor is simply the fraction of an initial number of the precursor atoms that decays in a given unit time.
		During an up-power transient, however, the shorter-lived precursors decaying at any given instant were born at a higher power level (or flux level) than the longer-lived precursors decaying at the same instant.
		The longer-lived precursors decaying at a given instant were born at a higher power level (or flux level) than the shorter-lived precursors decaying at that instant.
	www.tpub.com /doenuclearphys/nuclearphysics81.htm (576 words)

	1 Nucleosynthesis and nuclear decay
		where 8 is the constant of proportionality, which is characteristic of the radionuclide in question and is called the decay constant (expressed in units of reciprocal time).
		When using radioactive decay to measure the ages of rocks we must apply the classic principle of uniformitarianism (Hutton, 1788), by assuming that the decay constant of the parent radionuclide has not changed during the history of the Earth.
		Because radioactive decay is a property of the nucleus, which is shielded from outside influence by orbital electrons, it is very unlikely that physical conditions influence " or $ decay, but electron capture decay could be affected.
	www.onafarawayday.com /Radiogenic/Ch1/Ch1-4.htm (1297 words)

	Radioactive Decay
		My question: is the rate of decay a constant no matter what the current atmospheric conditions are, in other words would the rate of decay be different on a different planet due to differences in gravity, atmosphere,temperature or whatever differences there are.
		The rate of decay of a radioactive element is not a constant.
		While carbon 14 decay is independent of the environment it is in, if we are going to use it for dating, we need to have a reference.
	www.newton.dep.anl.gov /askasci/phy99/phy99x43.htm (790 words)

	Articles / Impact / Consequences of Time Dependent Nuclear Decay Indices on Half Lives - Institute for Creation Research
		indicated that the nuclear decay parameter, l, was a constant.
		The fundamental assumption made is that the decay of an atom is independent of the age of that atom.
		Dudley rejects the idea that radioactive decay is completely spontaneous and instead hypothesizes that neutrinos from the neutrino sea, which has been suggested by others, trigger radioactive decay.
	www.icr.org /index.php?module=articles&action=view&ID=200 (1555 words)

	Curves of Increasing Growth
		In general y=A + Bx where A is an initial value and a positive B is an additive growth constant while a negative B is a subtractive decay constant.
		A number of asymmetries derive from the fact that power-law dynamics are relative to where you are at on the x axis raised to a fixed power, while exponential dynamics are relative to a fixed starting value raised to a power that varies with the x axis.
		In the plots, exponentials are the lower curve in growth but the middle in decay; power laws are the lower curve in decay but the middle in growth.
	eclectic.ss.uci.edu /~drwhite/Anthro179a/power-and-exponential.html (587 words)

	Exponential decay law
		It was shown very early on that decay is a random process: this gives rise to an exponential decay law.
		The decay of (a particular state of) a nucleus is determined by one number, the decay constant
		The probability is thus independent of time, it is independent of the age of a particular nucleus and is the same for all nuclei in the same state (i.e.
	www.phy.uct.ac.za /courses/phy300w/np/ch1/node30.html (442 words)

	Plate Rotation (Site not responding. Last check: 2007-10-17)
		Elements such as uranium, thorium, and plutonium are observed to emit particles and thereby undergo radioactive decay.
		Radioactive decay is an exponential process such that half of the parent element will decay to the daughter element in a set amount of time (known as the half-life).
		The primary elements in the decay series are shown with their relative abundances as individual bars, such that initially the parent element has an abundance of 1e10 atoms.
	www.mines.utah.edu /~ggapps/radiation/radiation.html (425 words)

	Topic 3
		The radioactive decay constant is defined as the
		However some very unstable nuclides decay in microseconds, so the decay constant would have to be “per nanosecond”.
		Notice that the horizontal axis is calibrated in periods of time in which the decay goes from an initial value to half that value.
	www.antonine-education.co.uk /Physics_A2/Module_5/Topic_3/TOPIC_3.HTM (893 words)

	Radiometric dating falsely assumes rates are constant - EvoWiki
		Radioactive decay constants depend finally on several fundamental constants which are today often believed to be fine-tuned.
		Because different physical forces are involved in varying proportions in the different decay modes, it is very unlikely that all radiometric techniques would be affected in exactly the same way by a change in decay rates.
		A significant change in decay rates should therefore show up in significant conflict between the results from different radiometric techniques, which is not the case.
	wiki.cotch.net /index.php/Radiometric_dating_falsely_assumes_rates_are_constant (580 words)

	What is weight decay?
		Whereas decay using the sum of squared weights tends to shrink the large coefficients more than the small ones, weight elimination tends to shrink the small coefficients more, and is therefore more useful for suggesting subset models (pruning).
		One approach to choosing the decay constant is to train several networks with different amounts of decay and estimate the generalization error for each; then choose the decay constant that minimizes the estimated generalization error.
		A fundamental problem with weight decay is that different types of weights in the network will usually require different decay constants for good generalization.
	www.faqs.org /faqs/ai-faq/neural-nets/part3/section-6.html (657 words)

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