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The Interacting Boson Approximation model, IBA-1, has been used in studying the nuclear structure of [sup.154,156]Dy. The excited positive and negative parity states, potential energy surfaces, V([beta], [gamma]), electromagnetic transition probabilities, B(E1), B(E2), back bending, staggering effect, [DELTA]I = 1, and electric monopole strength, X(E0/E2), were calculated successfully. The calculated values are compared to the available experimental data and show reasonable agreement. The energy and electromagnetic transition probabilities ratios as well as the contour plot of the potential energy surfaces show that the [sup.156]Dy nucleus is an X(5) candidate., 1 Introduction The nuclear shape and shape phase transitions in the rare earth dysprosium isotopes have been investigated by many authors theoretically and experimentally. Theoretically, analytical solution of the Bohr [...]

The isotope composition of zinc (Zn) was determined in settling particles collected monthly over a year in the hypolimnion of the eutrophic Lake Greifen (Switzerland) in order to explore the potential of this novel isotope system as a proxy for biogeochemical processes in aqueous environments. Significant variation in [delta][sup.66][Zn.sub.JMC3_0749L] of 0.9[per thousand] (where [delta][sup.66][Zn.sub.JMC3_0749L] = [[{[sup.66]Zn : [sup.64]Zn}.sub.sample]/[{[sup.66]Zn : [sup.64]Zn}.......sub.JMC3-0749L] - 1] x 1000) was found throughout the seasonal cycle of productivity. The most negative [delta][sup.66][Zn.sub.JMC3_0749L] values (down to -0.66[per thousand] [+ or -] 0.08[per thousand]) were observed during the productive summer period from June to September, when the Zn in the settling particles was predominantly associated with organic material, and when Zn concentrations in the epilimnion were lowest. This observation is likely explained with preferential uptake of the light Zn isotopes during algal growth. During the other months, the Zn in the sediment traps showed higher [delta][sup.66]Zn values, reflecting increasing contributions of anthropogenic or lithogenic components. The average isotopic signature of the settling particles during the autumn-winter-spring period (~-0.2[per thousand] for [delta][sup.66][Zn.sub.JMC3.0749L]) was somewhat lower than typical for anthropogenic and natural sources, and this possibly reflects the effect of the preferential adsorption of lighter dissolved Zn isotopes onto the settling particles. We suggest that Rayleigh fractionation plays a minor role in controlling the isotopic composition of the settling particles in the lake. Our work demonstrates the presence of an obvious seasonal cycle in [delta][sup.66]Zn, and this suggests that Zn isotopes can be employed to study nutrient utilization and other biogeochemical processes in lakes and other aquatic environments.

Abstract We report the first palaeodietary stable isotope study of humans and animals from an East Polynesian archaeological site. The Hanamiai Dune in the Marquesas Islands of French Polynesia has [...]

Nuclear structure of [sup.230-238]U isotopes hav been studied in the frame work of the interacting boson approximation model (IBM - 1). The contour plot of the potential energy surfaces, V(β, [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.forsciint.2008.01.006 Byline: Erica Taylor (a), James F. Carter (b), Jenny C. Hill (b), Carolyn Morton (a), Niamh Nic Daeid (c), Richard Sleeman (b) Keywords: Plastic materials; Polyethylene; Plastic bag examination; Birefringence; Isotope ratio; Isotope ratio mass spectrometry (IRMS) Abstract: Plastic bags are frequently used to package drugs, explosives and other contraband. There exists, therefore, a requirement in forensic casework to compare bags found at different locations. This is currently achieved almost exclusively by the use of physical comparisons such as birefringence patterns. This paper discusses some of the advantages and shortcomings of this approach, and presents stable isotope ratio mass spectrometry (IRMS) as a supplementary tool for effecting comparisons of this nature. Carbon and hydrogen isotopic data are presented for sixteen grip-seal plastic bags from a wide range of sources, in order to demonstrate the range of values which is likely to be encountered. Both isotopic and physical comparison (specifically birefringence) techniques are then applied to the analysis of rolls of bags from different manufacturing lots from a leading manufacturer. Both approaches are able to associate bags from a common production batch. IRMS can be applied to small fragments which are not amenable to physical comparisons, and is able to discriminate bags which could be confused using birefringence patterns alone. Similarly, in certain cases birefringence patterns discriminate bags with similar isotopic compositions. The two approaches are therefore complementary. When more than one isotopically distinct region exists within a bag (e.g. the grip-seal is distinct from the body) the ability to discriminate and associate bags is greatly increased. Author Affiliation: (a) Faculty of Applied Sciences, University of the West of England, Frenchay Campus, Coldharbour Lane, Bristol BS16 1QY, UK (b) Mass Spec Analytical Ltd., Building 20F, Golf Course Lane, Filton, Bristol BS99 7AR, UK (c) Centre for Forensic Science, Department of Pure and Applied Chemistry, University of Strathclyde, Royal College, 204 George Street, Glasgow G1 1XW, UK Article History: Received 22 May 2007; Revised 3 January 2008; Accepted 9 January 2008

The Sr, S, O and C isotope database of marine carbonates contains over 55,000 published isotope values of low-Mg calcite from diagenetically little altered Phanerozoic fossil shells as well as samples of whole rocks and calcite cements of Ordovician to Archean age. Carbon and oxygen isotope data for the shell material are divided into habitat subsets (high-, mid-, low-latitude and deep sea), and whole rock data are separated by mineralogy into calcite/dolomite subsets. Trend, correlation, wavelet, and spectral analyses on Ganssian-filtered isotope records were applied to detect and quantify similarities and patterns in temporal records with the following results: (1) Oxygen isotope trends from the 'high-latitude' and 'deep-sea' habitats are almost indistinguishable through the last 115 Ma, consistent with the existence of the 'oceanic conveyor belt' throughout this interval; (2) All oxygen isotope habitat records show a strong, coherent 30-45 Ma (~ 38 Ma) cyclicity throughout the Cretaceous and the Cenozoic (3) Up to 70% of the multi-million year variability in the [delta][sup.18]O record of the last 115 Ma can be simulated by the following equation: [delta][sup.18]O([per thousand]) = 0.64 sin(2[pi]t/120 Ma + 0.9) + X sin (2[pi]t/38.3 Ma + 1.1) with X ranging from 0.4-0.6 [per thousand] for the 'low-', 'high-latitude' and 'deep-sea' habitats, to 0.8 [per thousand] for the 'mid-latitude' realm. (1) A ~ 120 [+ or -] 20 Ma cycle occurs in the Paleozoic and Neoproterozoic 6180 record, consistent with paleoclimate variability as interpreted from sedimentological and faunal records. (2) The offset of [delta][sup.13]C values between 'deep water' and 'high-latitude' vs. surficial habitats at lower latitudes is consistent with the operation of a biological pump in the oceans since at least the Cretaceous. (3) Sr and S isotope records exhibit a ~ 60-70 Ma cyclicity throughout the Phanerozoic. Keywords: isotopes; databases; oxygen; carbon; Strontium; sulfur

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.forsciint.2007.03.001 Byline: F. Roelofse (a), U.E. Horstmann (b) Keywords: Isotope ratio mass spectrometry (IRMS); Carbonate; Dolomite; Carbon; Stable isotopes Abstract: The application of isotope ratio mass spectrometry (IRMS) in forensic science to establish the provenance of a range of questioned substances including soils, drugs, explosives, currency, ivory and rhino horn has been widely documented. The present study wishes to highlight the applicability of IRMS and specifically stable carbon IRMS in determining the provenance of a carbonate rock that was switched for nickel metal exported from South Africa to Israel. The technique employed effectively argued against a South African origin for the rock whilst simultaneously supporting an Israeli origin, enabling investigators to focus their attention accordingly. The study represents the first documented instance known to the authors where IRMS has been employed in the forensic geo-location of a rock. Author Affiliation: (a) Council for Geoscience, Private Bag X112, Pretoria 0001, South Africa (b) iThemba Labs Gauteng (Environmental Isotope Group), Private Bag 11, Wits 2050, South Africa Article History: Received 17 August 2006; Revised 1 March 2007; Accepted 1 March 2007

The transmission spectra of two CO isotopic variants, i.e., [sup.12]CO and [sup.13]CO, are measured with a recently developed widely tunable THz source. The pure rotational transition lines of J = 6 [right arrow] 7, 10 [right arrow] 11, 11 [right arrow] 12, 12 [right arrow] 13, and 13 [right arrow] 14 have been identified in the spectra. The transition frequencies and the rotational constant of each CO isotopic variant are also presented. Experimental results indicate that the difference of the rotational constants between the two isotopic variants can be used to reliably differentiate [sup.12]CO and [sup.13]CO. Compared with the measurements made by using a Fourier transform infrared spectrometer, our tunable THz source has produced approximately the same accuracies for measuring transition frequencies or determining rotational constants. OCIS codes: 300.6390, 300.6270.

A procedure was developed to accurately measure the W isotopic compositions of iron meteorites with a precision of better than [+ or -] 0.1 [member of] on [member of][sup.182]W and [member of][sup.184]W (normalized to [sup.186]W/[sup.183]W). Purification of W was achieved through a two-step, ion-exchange procedure. In most cases, the yield is better than 80%, and purified W solutions are clear of matrix elements and direct isobars of W. The final W solutions were analyzed using a Micromass Isoprobe multicollector inductively coupled plasma mass spectrometer (MC-ICPMS). Tests performed on mixtures of terrestrial standards and meteorite samples demonstrate that the method is accurate and that [member of][sup.182]W variations as small as ~0.1 [member of] can be detected. Analyses of three different aliquots of the Gibeon (IVA) iron meteorite obtained over a period of 6 months show identical [member of][sup.182]W values with a weighted mean of 3.38 [+ or -] 0.05, consistent with literature data for 1VA iron meteorites, and indicating that the metal-silicate differentiation event in its parent body was either contemporaneous with or slightly postdated (by up to ~2.5 My) the formation of refractory inclusions. We demonstrate our ability to measure [member of][sup.184]W accurately and precisely (within [+ or -] 0.1 [member of]), which is useful for characterizing cosmogenic and nucleosynthetic effects that may be present in iron meteorites. We also report for the first time measurements of [member of][sup.180]W, albeit with large error bars (< [+ or -] 4 [member of], in most cases).

The isotopic distribution in mass spectroscopy is described for identifying pure compounds, being able to distinguish molecular fragments by masses. Punnett squares are familiar, easy to compute, and often graphical which makes helpful to students and the relative distribution of isotopic combination is easily generated for even isotopic distribution can be correlated with the peak heights.

Southern California and southern Nevada contain abundant lead zinc deposits with strikingly different characteristics. On the west, the Darwin Terrane contains abundant Jurassic and Cretaceous intrusions surrounded by lead zinc skarn and replacement deposits rich in pyrite and manganese minerals. The Tecopa Terrane is east of the Darwin Terrane and contains some lead deposits that are hosted by the Proterozoic Noonday Dolomite. These lead deposits have no consistent relation to igneous rocks; they contain mainly galena, and are devoid of pyrite and manganese minerals. Other skarn and vein deposits in the Ivanpah and Tecopa districts are more closely associated with igneous rocks. Mississippi Valley type lead zinc deposits are present still farther to the east in the Goodsprings Terrane in Nevada. These deposits are hosted by breccias formed below the Mississippian Pennsylvanian unconformity and are unrelated to igneous rocks. Deposits in the Darwin Terrane have lead isotopic signatures that lie along a mantle-sediment mixing line indicating that they formed in a continental arc setting analogous to that for the plutons in the Sierra Nevada batholith [Chen, J.H. and Tilton, G.R., 1991. Application of lead and strontium isotopic relationships to the petrogenesis of granitoid rocks, central Sierra Nevada batholith, California. Geological Society of America Bulletin 103, 439-447]. Encroachment of this continental arc on the North American continent in the eastern part of the Darwin Terrane resulted in a lead isotopic signature that is like that of the strongly contaminated plutons [Chen, J.H. and Tilton, G.R., 1991. Application of lead and strontium isotopic relationships to the petrogenesis of granitoid rocks, central Siena Nevada batholith, California. Geological Society of America Bulletin 103, 439-447]. Many deposits from the Inyo Mountains on east side of the Owens Valley have lead isotopic signatures that reflect this encroachment. To the east in the Tecopa Terrane, encroachment of the continental arc on the Mojave crust resulted in partial melting of 1.7 Ga amphibolite and granulite facies rocks to produce the plutons and mineral deposits associated with plutons in this terrane. Lead from deposits in this terrane hosted in the Proterozoic Noonday Dolomite and associated rocks have a lead isotope signature that reflects hydrothermal circulation of fluids in the Mojave supracrustal rocks. The boundary between the Darwin Terrane and the Tecopa Terrane lies just west of the Ash Valley--Panamint Range Fault and is bounded by the Towne Fault on the north and the Garlock Fault on the south. Lead isotopic data from the Goodsprings district in southwestern Nevada, east of the Tecopa Terrane, form a 1.45 Ga linear array that is indicative of Mississippi Valley type mineralization. Although we have no independent evidence of the timing of the tectonic events that formed these deposits, it is likely that all formed as a result of the Mesozoic collision of the Panthalassen crust with the North American continent. Keywords: lead isotope: lead zinc deposits: Basra and Range: metallogeny

We studied planktonic community structure and isotopic composition using compound-specific [sup.13]C analysis of phospholipid-derived fatty acids (PLFA) along the Scheldt estuary during a spring bloom. A comprehensive set of other carbon cycle parameters was also determined. Based on dissolved carbon dioxide and oxygen concentrations and primary and bacterial secondary production, the trophic status of the estuary changed from strongly net heterotrophic in the upper to net autotrophic in the lower estuary. Concentrations of algal PLFA and pigments and microscopic identifications of dominant phytoplankton revealed the same trend: a mixed community of green algae and diatoms dominated the freshwater phytoplankton and there was a major diatom bloom at intermediate salinities. Bacterial biomass (also based on PLFA) was much lower for the diatom bloom in the lower estuary than in the net heterotrophic upper estuary. Carbon isotopic ratios of the main diatom marker PLFA. 20: 5[omega]3, were mainly related to changes in [[dealta.sup.13]C values of dissolved inorganic carbon and showed a residual variation of ~5 [per thousand], which is probably related to changes in growth conditions along the estuary. The green algal marker 18: 3[omega]3 was much more depleted in [sup.13]C than the diatom markers, suggesting that these two main pbytoplankton groups use a different inorganic carbon source or carbon dioxide fixation mechanism. Isotopic ratios of the different bacterial PLFA detected were very similar and ranged between -30 [per thousand] and -21 [per thousand]. They closely tracked [[delta].sup.13]C values in particulate organic carbon (POC), indicating that POC or material with the same [sup.13]C signature was the main bacterial carbon substrate. In the lower, marine side of the estuary, isotope ratios of bacterial and algal PLFA were similar, suggesting a coupling between primary production and bacterial consumption of organic matter. However. [[delta].sup.13]C values of bacterial PLFA in the upper estuary were enriched compared with algal PLFA t between 6 [per thousand] and 15 [per thousand]), indicating an uncoupled algal-bacterial system with allochthonous subsidies, such as terrestrial C3 organic matter or sewage supporting bacterial growth.

Oxygen, carbon, and strontium isotope variations in vein-filling calcite and quartz cements and their host rocks are used to elucidate the origin, spatial and temporal evolution, and migration pathways of fluids in the detachment Nuncios fold complex, northeastern Mexico. The folded Mesozoic sedimentary sequence contains two regional paleohydrostratigraphic units separated by a unit of low permeability. Two main generations of cements are present in both paleohydrostratigraphic units. Distinct differences exist between [[delta].sup.18]O, [[delta].sup.13]C, [sup.87]Sr/[sup.86]Sr, and fluid-inclusion temperatures of early vein-filling cements in the lower and the upper units. These differences, together with a strong correspondence between early cement and host-rock [[delta].sup.18]O and [[delta].sup.13]C values, suggest that early diagenetic fluids were compartmentalized between the two units. Late vein-filling cements have isotopic compositions and fluid-inclusion temperatures that converge to similar values, indicating a change to open fluid flow between the lower and upper units. We hypothesize that the fluid history of the Nuncios fold complex evolved in two main stages: (1) burial diagenesis and early folding, during which fluids were confined within individual units, and (2) late-stage folding, during which increased deformation associated with fold tightening caused the expulsion of fluid from the lower unit into the upper unit. Keywords: fluid migration, evaporite, isotopes, detachment fold, Sierra Madre Oriental.

Significant variability in [[delta].sup.34][S.sub.pyrite] values in Neoproterozoic sedimentary rocks has been attributed to the evolution of nonphotosynthetic sulfide-oxidizing bacteria and the advent of sulfur disproportionation reactions in response to Earth's evolving redox chemistry. We analyzed trace sulfate in carbonates from South Australia and Namibia and reconstructed the sulfur isotope evolution of seawater sulfate. Comparison of our [[delta].sup.34][S.sub.sulfate] record with published [[delta].sup.34][S.sub.pyrite] data from the same or equivalent successions indicates that [[delta].sup.34][S.sub.sulfate] - [[delta].sup.34][S.sub.pyrite] ([[DELTA].sup.34]S) rose gradually through the second half of the Neoproterozoic and fluctuated coincident with episodes of glaciation, but did not exceed 46 [per thousand] before ca. 580 Ma. Large variability in [[delta].sup.34][S.sub.pyrite] in the Neoproterozoic can be explained as a consequence of low sulfate concentrations and rapidly fluctuating [[delta].sup.34][S.sub.sulfate] in seawater rather than the onset of sulfur disproportionation reactions mediated by nonphotosynthetic sulfide-oxidizing bacteria. Keywords: Neoproterozoic, sulfate, [[delta].sup.34]S, South Australia, Namibia.

The Hf isotope composition of rutile in mica-amphibole-rutile-ilmenite-diopside (MARID) xenoliths from the Kimberley area of South Africa has been analyzed in situ by laser ablation microprobe--multicollector--inductively coupled plasma mass spectrometry to investigate metasomatic processes in the lithospheric mantle. The [sup.176]Hf/[sup.177]Hf ratio shows a wide range, from 0.2811 to 0.2858 ([[epsilon].sub.Hf] = -55 to +110); much of this range is found within single samples and even within single grains. We suggest that the MARID rutiles initially resulted from the interaction of an asthenospheric melt with ancient depleted harzburgitic mantle with low [sup.176]Hf/[sup.177]Hf ratios ( Keywords: MARID xenoliths, mantle rutile, hafnium isotopes, mantle xenoliths, kimberlitic metasomatism, South Africa lithosphere.

Spatial geochemical variations of Quaternary lavas erupted along the northern segment of the Kamchatka arc are used to trace changes in magma generation across the subducting Pacific slab edge. The late Pleistocene-Holocene lavas of the northern end of the Central Kamchatka depression north of the Pacific slab edge show strong enrichment in high field strength elements and light rare earth elements, relatively unradiogenic strontium and lead but radiogenic neodymium isotope ratios, and oxygen isotope compositions similar to those of mid-oceanic-ridge basalts. These geochemical characteristics are distinct from the southern Central Kamchatka depression volcanoes located above the subducting Pacific slab. Extensive fluid-triggered mantle melting dominates magma genesis beneath the largest Kamchatka volcanoes in the south, whereas low-degree decompression melting of the Pacific asthenospheric mantle is the major magma generation process north of the Pacific slab edge. Quaternary detachment of the subducted Pacific plate fragment resulted in the influx of fertile mantle beneath Kamchatka. We propose that upwelling and southward flow of this hotter, more fertile mantle is the main reason for recent magmatism in northern Kamchatka and for the exceptional productivity of the Central Kamchatka depression volcanoes (Klyuchevskoy and Sheveluch), the most active arc volcanoes on Earth. Keywords: Kamchatka arc, slab edge, subduction, trace element geochemistry, Sr-Nd-Pb-O isotopes, Klyuchevskoy, Sheveluch.

We present the results of oxygen isotope and electronmicroprobe analyses of sphaerosiderites obtained from Cretaceous paleosols in Iowa. The sphaerosiderite [[delta].sup.18]O values record Cretaceous meteoric groundwater chemistry and an overall waning of brackish groundwater inundation during alluvial-plain aggradation and soil genesis. We focus on horizons that precipitated from freshwater, in which [[delta].sup.18]O values ranging from -3.3[per thousand] to -6.8[per thousand] relative to the Peedee belemnite standard are interpreted to record variations in the Cretaceous atmospheric hydrologic cycle. During relative sea-level highstands, moisture was derived from the Cretaceous Western Interior Seaway, whereas during lowstands, when the seaway narrowed and occasionally withdrew from the Midcontinent, the dominance of hemispheric-scale atmospheric moisture transport initiated in the tropical Tethys Ocean led to decreased precipitation rates. These processes did not operate like a switch, but rather as a continuum of competing moisture sources and mechanisms of transport between the nearby epicontinental sea and the distant tropics. The sphaerosiderite data demonstrate (1) temporal variation in the intensity of hemispheric-scale atmospheric moisture transport and (2) long-term amplification of the global hydrologic cycle marked by extreme [sup.18]O depletion at the AlbianCenomanian boundary. Keywords: Cretaceous, Dakota Formation, paleosols, sphaerosiderite, oxygen isotopes.

The reduced partition function ratios (RPFRs) of Li(super +) (Solv)(sub n) clusters with different values were calculated to investigate the solvent effect of the isotopic effect of the lithium. The RPFR is dependent mainly on the number of solvent molecules in the first shell, and the size dependence of the RPFR plateaus at n=4.

The growth of accelerator mass spectrometry as a tool for quantitative isotope ratio analysis in the biosciences necessitates high-throughput sample preparation. A method has been developed to convert C[O.sub.2] obtained from carbonaceous samples to solid graphite for highly sensitive and precise [sup.14]C quantification. Septa-sealed vials are used along with commercially available disposable materials, eliminating sample cross contamination, minimizing complex handling, and keeping per sample costs low. Samples containing between 0.25 and 10 mg of total carbon can be reduced to graphite in ~4 h in routine operation. Approximately 150 samples per 8-h day can be prepared by a single technician.

An assumption inherent in isotope dilution methodologies is that of homogeneous distribution of label. This assumption may not hold, however because of mass transfer limitations in most soil systems. The effects of mass transfer limitations on isotope dilution in soil aggregates with radii up to 0.36 cm were examined using spherical diffusion-reaction models designed to simulate [sup.15]N[H.sub.4.sup.+] isotope dilution experiments measuring gross production and consumption of N[H.sub.4.sup.+] across a 24-h period. Equations that described transport and reaction of N[H.sub.4.sup.+] assumed Fickian diffusion, linear, equilibrium adsorption, zero-order production of natural abundance [sup.15]N, and either pseudo-first-order or zero-order consumption of N[H.sub.4.sup.+]. In the case of pseudo-first-order consumption, rate calculations were sensitive to the adsorption coefficient (emphasizing the need to interpret results as apparent rates), but not to other transport parameters. In the case of zero-order consumption, both production and consumption rates were always underestimated. Errors increased as aggregate size increased and as effective diffusivity decreased. Increasing the consumption to production rate ratio increased the error in production rate estimates. Allowing the applied label to diffuse into soil aggregates for 24 h prior to initial time sampling decreased errors by a factor of about three (to

Simultaneous dual isotope imaging ([sup.99m]TC/[sup.123]I) has potential clinical applications but has not been implemented in the clinic. The aim of this work was to design an artificial neural network (ANN) for crosstalk and scatter correction using a smaller number of energy windows (8) than we had previously proposed (26) to allow implementation on some clinical cameras, and to validate our approach using realistic Monte Carlo simulations and anthropomorphic brain phantom acquisitions. Monte Carlo simulations of dual isotope SPECT studies of a digital brain phantom and physical acquisitions of the striatal brain phantom were used to validate our approach. Corrected projections were reconstructed using an iterative ordered subsets expectation maximization (OSEM) algorithm that modeled nonuniform attenuation and variable collimator response in the projector/backprojector. Results: In Monte Carlo simulations, ANN26 and ANN8 yielded similarly accurate quantitation of [sup.123]I activity (bias < 7%) in all brain structures. An asymmetric windowing method (AW) yielded accurate estimation in the striata (bias < 7%) but not in other brain structures. The estimation bias of [sup.99m]Tc primary activity was Index Terms--Artificial neural networks, attenuation correction, brain single photon emission compted tomography (SPECT), crosstalk correlation, dual isotope imaging, iterative reconstruction, ordered subsets expectation maximization (OSEM), scatter correction.

We have developed a new technique in which a solid reagent, cobalt(III) fluoride, is used to prepare oxygen gas for isotope ratio measurement from water derived either from direct injection or from the pyrolysis of solid samples. The technique uses continuous flow, isotope ratio monitoring, gas chromatography/mass spectrometry (irmGC/ MS) to measure the [[delta].sup.18]O and [[delta].sup.17]O of the oxygen gas. Water from appropriate samples is evolved by a procedure of stepped pyrolysis (0-1000 [degrees] C, typically in 50 [degrees] C increments) under a flowing stream of helium carrier gas. The method has considerable advantages over others used for water analysis in that it is quick; requires only small samples, typically 1-50 mg of whole rock samples (corresponding to ~0.2 [micro]mol of [H.sub.2]O); and the reagent is easy and safe to handle. Reproducibility in isotope ratio measurement obtained from pyrolysis of samples of a terrestrial solid standard are [[delta].sup.18]O [+ or -] 0.54, [[delta].sup.17]O [+ or -] 0.33, and [[DELTA].sup.17]O [+ or -] 0.10 [per thousand], 1 [sigma] in all cases. The technique was developed primarily for the analysis of meteorites, and the efficiency of the method is illustrated herein by results from water standards, solid reference materials, and a sample of the Murchison CM2 meteorite.

We present a rapid and selective method to increase the volatility of tyrosine and phenylalanine without adding derivative C for high-precision gas chromatography--continuous-flow isotope ratio mass spectrometry (GCC--IRMS) based on enzymatic decarboxylation to yield alkylamines and evaluated for [sup.15]N isotopic integrity. Purified tyrosine and phenylalanine were converted to tyramine and phenethylamine by tyrosine and phenylalanine decarboxylases, respectively. GC separation was achieved using a thick stationary phase (5-[micro]m) capillary column. Recoveries were 95 [+ or -] 2%. The reproducibility of [delta][sup.15]N of tyramine and phenethylamine measured by GCC--IRMS averaged SD([delta][sup.15]N) = 0.33 [per thousand]. The absolute differences between [delta][sup.15]N of amino acids measured by elemental analyzer-IRMS and the alkylamines measured by GCC--IRMS was not significant. Phenethylamine and tyramine prepared from a mixture of 18 amino acids were extracted by ethanol with 95% recovery, and analysis yielded clean chromatograms and equivalent precision. These data indicate that enzymatic decarboxylation of phenylalanine and tyrosine is a convenient method to increase their volatility for continuous-flow isotopic analysis without introducing extraneous C or significant isotopic fractionation.

Research has been conducted on the [1,7]-hydrogen shift in substituted 1,3,5-heptatrienes. The use of the density functional calculations in investigating this shift is described and the results indicate the presence of the tunneling in thermal antarafacial [1,7]-hydrogen shift reactions.

Research has been conducted on the sacoglossans which have a potential for carbon acquisition from plastid photosynthesis. The estimate of the fraction of sacoglossan carbon supplied by the kleptoplastid photosynthesis has been suggested based on the stable carbon isotopes' mass balance at the natural abundance level.

Byline: Tomislav P. Zivkovic (1) Keywords: vibrational isotope effect; harmonic approximation; stretching and bending vibrations; out-of-plane vibrations; deuterated bromoethenes Abstract: Linear (planar) molecules A and B which are identical except for isotopic substitutions at the atomic sites I are considered. Stretching (bending, out-of-plane) frequencies [omega].sub.k and normal modes [psi].sub.k of the isotopically perturbed molecule B are expressed in terms of stretching (bending, out-of-plane) frequencies I1/2.sub.i and the corresponding normal modes I|.sub.i of the unperturbed molecule A. Complete specification of the unperturbed normal modes is not required. All that is needed are stretching (bending, out-of-plane) amplitudes a(c)I|[I|.sub.i]aa of the normal modes I|.sub.i at those sites I that are affected by isotopic substitution. The rule which interlaces frequencies [omega].sub.k of molecule A with frequencies I1/2.sub.i of molecule B is derived. Given two isotopic molecules A and B .sub.I that differ by a single isotopic substitution at site I, the inversion relation is derived. This relation expresses unperturbed stretching (bending, out-of-plane) amplitudes at the site I in terms of stretching (bending, out-of-plane) frequencies of molecules A and B .sub.I. As an example, out-of-plane vibrations of deuterated bromoethene were considered. In the simplest method 12 out-of-plane frequencies of four polydeuterated bromoethenes were calculated from 12 out-of-plane frequencies of bromoethene and three monodeuterated bromoethenes. Standard deviation of thus calculated frequencies from experimental frequencies is I=2.74 cm.sup.-1. In another method, 15 out-of-plane frequencies of four polydeuterated bromoethenes and selected monodeuterated bromoethene are calculated from 9 out-of-plane frequencies of bromoethene and the remaining two monodeuterated bromoethenes. Depending on which monodeuterated bromoethene is selected (1-, cis- or trans-), standard deviation of thus obtained frequencies from experimental frequencies is I1=2.84 cm.sup.-1, Ic=2.96 cm.sup.-1 and It=2.72 cm.sup.-1. Author Affiliation: (1) RuAer Boskovic Institute, P.O.B. 180, HR-10002, Zagreb, Croatia Article History: Registration Date: 08/10/2004

Isotopic fractionation in three species of basidiomycete species using different sources of sugar in their ecosystem environment is presented. Results show that the fungi differentially fractionate sucrose derived from C(sub)3 and C(sub)4 in a taxon-specific manner and that the fractionation is sensitive to the nonrandom distribution of the stable isotope.

The diet of juvenile pink shrimp (Farfantepenaeus duorarum Burkenroad, previously Penaeus duorarum) from Long Key Bight, Florida Keys, was studied using stomach content examination, pigment measurements, and stable isotope ([[delta].sup.13]C and [[delta].sup.15]N) analysis. Samples were taken over approximately 24 h on four occasions from December 1997 to June 1998. Juvenile F. duorarum fed nocturnally, the main prey being the seagrass shrimp Thor floridanus (Decapoda: Caridea: Hippolytidae), which accounted for 34% of the stomach content volume. Other common components of the diet were bivalves (mainly Tellina sp.) with 15% volume, calcareous algae (8%), plant detritus (5%), copepods (3%), and seagrass fragments (2%). Pigment concentrations (chlorophyll a plus phaeopigments) in F. duorarum stomachs ranged from 7 to 73 mg [l.sup.-1] or 40 to 310 ng [stomach.sup.-1]. The exponential gastric evacuation rate was determined experimentally at 1.3 [+ or -] 0.5 [h.sup.-1] Daily rations (in percent body weight) calculated from time series of stomach fullness ranged between 11 and 16% [d.sup.-1]. Total consumption by the population (in wet weight) ranged between 0.05 and 0.3 g [m.sup.-2] [d.sup.-1]. Stable isotope measurements confirmed that T. floridanus was the main food source for F. duorarum, [[delta].sup.13]C-values of whole animals of both species were identical at -10.0 [+ or -] 1.6 [per thousand] PDB. [[delta].sup.15]N-values of both species were also not significantly different (pooled mean: 5.9 [+ or -] 1.7 [per thousand]). Stomach contents of wild-caught F. duorarum and stomach contents of F. duorarum fed T. floridanus also showed similar stable isotope values.

Research has been conducted on the soybean lipoxygenase-1. Experiments have demonstrated that elimination reaction and enzyme inactivation produce large kinetic isotope effects.