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Topic: Kinetic fractionation

	SAHRA - Isotopes
		Isotope fractionation occurs because the bond energy of each isotope is slightly different, with heavier isotopes having stronger bonds and slower reaction rates.
		Equilibrium fractionation describes isotopic exchange reactions that occur between two different phases of a compound at a rate that maintains equilibrium, as with the transformation of water vapor to liquid precipitation.Although the process is in equilibrium, the rate of these exchanges is different so that the result is an enrichment of one of the isotopes.
		Kinetic fractionation is fractionation that is unidirectional, where equilibrium is not attained.
	www.sahra.arizona.edu /programs/isotopes/types/stable.html (499 words)

	USGS -- Isotope Tracers -- Resources -- Isotope Geochemistry
		As a consequence of fractionation processes, waters and solutes often develop unique isotopic compositions (ratios of heavy to light isotopes) that may be indicative of their source or of the processes that formed them.
		The magnitude of the fractionation depends on the reaction pathway utilized and the relative energies of the bonds being severed and formed by the reaction.
		Kinetic fractionation factors are typically described in terms of enrichment or discrimination factors; these are defined in various ways by different researchers.
	wwwrcamnl.wr.usgs.gov /isoig/res/funda.html (1607 words)

	SAHRA - Isotopes
		equilibrium fractionation - fractionation that occurs between two different phases that are in equilibrium, e.g., the transformation of water vapor to liquid precipitation.
		kinetic fractionation - fractionation that is unidirectional, where equilibrium is not attained.
		This type of fractionation applies to evaporation of surface waters and to most biogeochemical reactions, where the light isotope is faster reacting and becomes concentrated in the products.
	www.sahra.arizona.edu /programs/isotopes/glossary/index.html (1121 words)

	[No title] (Site not responding. Last check: 2007-10-18)
		Kinetic fractionation factors for 18O derived empirically from a variety of isotope studies of plant water compare favourably with fractionation factors estimated from theoretical consideration of leaf energy balance and boundary layer dynamics.
		Kinetic fractionation during evapotranspiration is sensitive to the nature of the boundary layer, which is controlled by leaf size and morphology.
		Improved characterization of kinetic effects during evapotranspiration has implications for isotopic study of plant water use, and for constraining interpretations of paleoclimate based on the isotopic composition of plant tissues.
	io.uwinnipeg.ca /~wbuhay/gcapaper.htm (229 words)

	Ch2
		Kinetic effects are affected by the surface temperature, wind speed (shear at the water surface), salinity, and most importantly, humidity.
		Humidity h is 0% and temperature is 25anddeg;C. As the fraction of water remaining approaches 0, a Rayleigh distillation causes an exponential increase in the heavy isotopes.
		However, the isotopic composition of the water vapour is controlled by a combination of kinetic fractionation during primary evaporation (humidity less than 100%) and mixing of vapour masses in the atmosphere.
	www.science.uottawa.ca /~eih/ch2/ch2.htm (3624 words)

	Fundamental & Exploratory Research Program: Research Summary
		Kinetic Fractionation of LITHIUM Isotopes by Diffusion in Water
		In particular, the kinetic fractionation of isotopes during diffusion, though understood for gaseous systems, is not well characterized and understood for condensed systems such as liquid water or silicate melts.
		In the simple case of diffusion of a monatomic gaseous species in an isothermal gas, the ratio of the diffusivities for two isotopes of an element is proportional to the square root of the inverse ratio of the isotope masses.
	www-esd.lbl.gov /research_sums_02-03/fundamental_research/christensen.html (277 words)

	isotope
		There is much more fractionation between hydrogen and deuterium (one of which is twice as heavy than the other), than we see in oxygen, where the difference in mass is only (18-16)/16 = 1/8.
		In nature, isotope fractionation occurs during chemical reactions such as the precipitation of calcite and physical processes such as evaporation and condensation.
		There are additional effects on the hydrogen and oxygen isotopic fractionation in polar ice that do result from the direct effect of the temperature: there is kinetic fractionation of oxygen and hydrogen within growing ice crystals - how fast the water molecules containing different isotopes move into the crystal.
	ethomas.web.wesleyan.edu /ees123/isotope.htm (2658 words)

	Chapter 6: Isotope fractionation corrections
		Isotope fractionation is the physical phenomenon which causes changes in the relative abundance of isotopes due to their differences in mass.
		A kinetic isotope effect occurs when one isotope reacts more rapidly than the other in an irreversible system or a system in which the products are swept away from the reactants before they have an opportunity to come to equilibrium.
		When there is isotope fractionation, however, the flux of the heavy tracer and the tracee are not equal and thus flux derived from the kinetic analysis of the tracer is not equal to that of the tracee.
	www.unu.edu /Unupress/food2/UID05E/uid05e0e.htm (1855 words)

	Chapter 2: Fundamentals of Isotope Geochemistry
		Kinetic fractionations, especially unidirectional ones, are usually larger than the equilibrium fractionation factor for the same reaction in most low-temperature environments.
		This is because the curves in Figure 2.5 were calculated using both an equilibrium fractionation for the phase change and a kinetic fractionation (Equation 2.20) for the diffusion of water vapor across the water-atmosphere interface (Gat and Gonfiantini, 1981).
		is an additional diffusive (kinetic) isotope fractionation which results from the different diffusivities of the water molecules of various isotopic compositions in the liquid-air boundary layer (i.e., an additional fractionation caused by diffusion across the humidity gradient between the "equilibrium vapor layer" and the turbulently mixed vapor sublayer on Figure 2.6).
	wwwrcamnl.wr.usgs.gov /isoig/isopubs/itchch2.html (13621 words)

	Polymer Applications of SCF - Phasex Corporation
		Narrow fractions of polyethylene and its copolymers are desired for many reasons e.g., for GPC calibration standards, properties evaluation, kinetics studies or catalyst performance analysis.
		DSC thermograms of the thirteen LLDPE fractions separated by side chain branching are shown in the figure on the right and are compared with the DSC of the parent polymer.
		The CITREF fractions of polyethylene are useful for the overall evaluation of the polymerization process, the narrow fractions providing quantitative information on kinetic profiles, and catalyst life and performance (mols monomer/mol of active catalyst).
	www.phasex4scf.com /supercritical_markets/supercritical_fluids_polymers.htm (1421 words)

	paleoxiso
		If conditions are not normalized, isotopic fractionation during dissolution will vary from sample to sample and all our data will just show that one day it was warmer in the lab than another day, or something else that we are not interested in.
		Isotope fractionation is the partial separation of isotopes of the same element during physical (e.g., evaporation) or chemical (e.g., precipitation reaction) processes.
		Kinetic isotopic fractionation occurs when the rates of processes differ between isotopic species (as a result of molecules with the lighter isotope moving faster).
	ethomas.web.wesleyan.edu /ees123/paleoxiso.htm (2739 words)

	a11d in fm98
		This type of fractionation violates the common rule of mass dependence, and is therefore referred to as mass independent fractionation.
		Equilibrium fractionation is opposite in sign to the experimentally determined kinetic fractionation factor for HCl volatilization.
		Using the measured fractionation factor extrapolated to stratospheric temperatures, $\delta$ $^{37}$Cl values for stratospheric gas phase HCl are calculated to be approximately -3 to -6 per mil.
	www.agu.org /cgi-bin/SFgate/SFgate?&listenv=table&multiple=1&range=1&directget=1&application=fm98&database=/data/epubs/wais/indexes/fm98/fm98&maxhits=200&="A11D" (1841 words)

	Contra Rb-Sr dating
		Because of fractionation during diffusion, the element is slightly isotopically heavier on the high-concentration side of the boundary, and slightly isotopically lighter on the low-concentration side of the boundary.
		Moreover, were the repetitive isotopic fractionation on the same material to occur on a volumetric scale commensurate with a large fraction of the Earth’s mantle and/or crust, then appreciable amounts of the chemical elements with considerably-altered isotopic ratios would result.
		The calculated fractionation factors, based on the atomic-mass differences of about 4, 2, and 1 between the indicated strontium isotopes, and a β value of 0.1, are 1.0084, 1.0045, and 1.0020, respectively.
	www.answersingenesis.org /tj/v15/i1/dating.asp (7005 words)

	Stable Isotope Fractionation of Tetrachloroethene during Reductive Dechlorination by Sulfurospirillum multivorans and ...
		an increase in isotope fractionation was observed with a decrease
		is the fractionation factor of the biochemical reaction.
		Carbon isotope fractionation during microbial dechlorination of trichloroethene, cis-dichloroethene, and vinyl chloride: implications for assessment of natural attenuation.
	aem.asm.org /cgi/content/full/71/7/3413 (4207 words)

	Center for Isotope Geochemistry @ Berkeley Lab
		This research involves measurements of the isotopic fractionation of various dissolved species due to diffusion in silicate and aqueous fluids.
		The goal is to understand the phenomenon of kinetic isotopic fractionation by diffusion in condensed media, and the implications for the structure and behavior of dissolved complexes.
		We are investigating isotopic fractionation of other elements, including K and the noble gases, during diffusion in water and across semi-permeable membranes.
	esd.lbl.gov /CIG/research/isotope_fraction.html (244 words)

	Center for Isotope Geochemistry @ Berkeley Lab
		This research involves measurements of the isotopic fractionation of various dissolved species due to diffusion in silicate and aqueous fluids.
		The goal is to understand the phenomenon of kinetic isotopic fractionation by diffusion in condensed media, and the implications for the structure and behavior of dissolved complexes.
		We are investigating isotopic fractionation of other elements, including K and the noble gases, during diffusion in water and across semi-permeable membranes.
	www-esd.lbl.gov /CIG/research/isotope_fraction.html (244 words)

	Skidmore et al.(2004)Éæé (Site not responding. Last check: 2007-10-18)
		Kinetic isotopic fractionation during carbonate dissolution in laboratory experiments: implications for detection of microbial CO signatures using Â
		The fractionation factor for this kinetic isotopic effect is defined as Ã
		This difference is most likely due to the preferential dissolution of highly reactive ultra-fine particles with damaged surfaces that are common in subglacial sediments.
	home.hiroshima-u.ac.jp /er/ES_W_R101.html (273 words)

	IGAC \| Biogenic aerosol formation in the boreal forest (BIOFOR)
		As a rule of thumb, isotope fractionation is larger for the lighter elements and thus, the greatest isotope variations occur for hydrogen.
		The mass dependence of isotope fractionation in chemical reactions according to transition state calculations and equilibrium calculations is mainly the result of differences in the normal vibrational frequencies for the individual isotopic species [Kaye, 1987].
		It seems clear now that the anomalous fractionation in ozone formation is not caused by a "mass independent" symmetry selection processes, but rather by some unknown parameter in the three body collision process that depends strongly on the masses of the atoms and molecules involved.
	www.igac.noaa.gov /newsletter/16/mass-new.php (3604 words)

	Dissertaion Alexander Heuser - 6. Evolutionary Control on Ca Isotope Fractionation Factors
		This lets me hypothesize that the fractionation factors α are not constant throughout time rather than dependent on relative changes of the individual calcification process of the species.
		In contrast to other isotope systems like boron, oxygen and carbon Ca isotope fractionation may be very sensitive to changes of the calcium carbonate precipitation mechanism because it is controlled by kinetic isotope fractionation rather than by equilibrium fractionation (Heumann and Lieser, 1973; O'Neil et al., 1986, Gussone et al., 2003).
		Isotope fractionation of C and O isotopes is relatively large when these molecules form in a distinct bulk solution.
	www.alexheuser.de /diss/chapter6.php (1438 words)

	Stanford Oceans Seminar Series (Site not responding. Last check: 2007-10-18)
		Stable isotope ratios (D/H) of biochemicals relate to the D/H of environmental water available to organisms, in spite of kinetic isotopic fractionation that typically causes D-depletion in organic hydrogen relative to water hydrogen.
		Changes in the D/H ratio of sedimentary organic matter (SOM) during thermal maturation have been difficult to interpret because the effects of hydrogen exchange and kinetic fractionations are confounded in natural samples.
		Experimental and field data document a progressive increase in the D/H ratio of most organic hydrogen at the bulk and molecular levels with increasing thermal maturity, and suggest that the transfer of hydrogen from water to organic matter is the most important mechanism leading to those changes.
	pangea.stanford.edu /research/Oceans/Seminar/schimmelmann.html (182 words)

	The 1988 Shroud of Turin Radiocarbon Tests Reconsidered
		If kinetic isotopic fractionation effects are present, then the lighter isotopic compounds will diffuse faster and further than compounds containing the heaver isotope.
		It is from this quantum mechanical effect that temperature-dependent equilibrium isotopic fractionation arises and its inverse relationship with temperature is observed.
		The fire to which the Shroud was exposed in 1532 appears to be a workable candidate for inducing both kinetic isotopic reactions and, also, potentially incomplete equilibrium reactions that may have resulted from the rapid temperature drop and water vapor environment associated with the quenching of the heated Shroud reliquary with water.
	members.aol.com /turin99/radiocarbon-b.htm (2477 words)

	CiteULike: Pathway of CH4 formation in anoxic rice field soil and rice roots determined by 13C-stable isotope ... (Site not responding. Last check: 2007-10-18)
		Comparison with radiotracer and/or inhibitor studies constrained the kinetic fractionation factors used for calculation.
		The fractionation factors for the conversion of CO2 to CH4 and of acetate to CH4 were on the order of alpha = 1.07 (epsilon = -70%) and epsilon > or = - 20%, respectively.
		The results demonstrate that there is quite some variability in pathways of CH4 production, and also indicate that isotopic fractionation factors may be different in different habitats and change with time.
	www.citeulike.org /article/115184 (485 words)

	Fractionation and kinetic properties of rat liver and kidney methionine adenosyltransferase isozymes. (Site not responding. Last check: 2007-10-18)
		Fractionation and kinetic properties of rat liver and kidney methionine adenosyltransferase isozymes.
		It has a L-methionine concentration required for half-maximal velocity [S0.5(Met)] of 8 microM and a molecular weight of 120 000 and is strongly inhibited by Adomet.
		MAT-I shows Michaelis-Menten kinetics with a Km (L-methionine) of 41 microM and a molecular weight of 208 000 and is slightly inhibited by S-adenosyl-L-methionine (Adomet).
	www.pdg.cnb.uam.es /UniPub/iHOP/gp/4303689.html (195 words)

	Fogel.gl.ciw.edu
		Fractionation of the stable isotopes of oxygen during respiration by plants--the basis of a new technique to estimate partitioning to the alternative path, in Molecular, Biochemical and Physiological Aspects of Plant Respiration, H. Lambers and L.H.W. van der Plas, eds., pp.
		Kinetic fractionation of stable nitrogen isotopes during amino acid transamination.
		Isotope fractionation of nitrogen and carbon in the synthesis of amino acids by microorganisms.
	fogel.gl.ciw.edu /index.php?&menuid=7 (2515 words)

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