1,037 research outputs found

    A bone grease processing station at the Mitchell Prehistoric Indian Village: archaeological evidence for the exploitation of bone fats

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    © Association for Environmental Archaeology 2015. Author's accepted manuscript version deposited in accordance with SHERPA RoMEO guidelines. The definitive version is available at http://www.maneyonline.com/doi/abs/10.1179/1749631414Y.0000000035.Recent excavations at the Mitchell Prehistoric Indian Village, an Initial Middle Missouri site in Mitchell, South Dakota have revealed a large, clay-lined feature filled with fractured and fragmented bison bones. Fracture and fragmentation analysis, along with taphonomic evidence, suggests that the bones preserved within the feature represent evidence of prehistoric bone marrow and bone grease exploitation. Further, the character of the feature suggests that it served as a bone grease processing station. Bone fat exploitation is an activity that is frequently cited as a causal explanation for the nature of many fractured and fragmented bone assemblages in prehistory, and zooarchaeological assemblages have frequently been studied as evidence of bone fat exploitation. The Mitchell example provides some of the first direct, in-situ archaeological evidence of a bone grease processing feature, and this interpretation is sustained by substantial analytical evidence suggesting bone fat exploitation. This new evidence provides a clearer concept of the nature of bone fat exploitation in prehistory as well as an indication of the scale and degree to which bone grease exploitation occurred at the Mitchell site. Finally, this research demonstrates the importance of careful zooarchaeological and taphonomic analysis for the interpretation of both artifactual remains as well as archaeological features

    Structure and Colors of Diffuse Emission in the Spitzer Galactic First Look Survey

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    We investigate the density structure of the interstellar medium using new high-resolution maps of the 8 micron, 24 micron, and 70 micron surface brightness towards a molecular cloud in the Gum Nebula, made as part of the Spitzer Space Telescope Galactic First Look Survey. The maps are correlated with 100 micron images measured with IRAS. At 24 and 70 micron, the spatial power spectrum of surface brightness follows a power law with spectral index -3.5. At 24 micron, the power law behavior is remarkably consistent from the 0.2 degree size of our maps down to the 5 arcsecond spatial resolution. Thus, the structure of the 24 micron emission is self-similar even at milliparsec scales. The combined power spectrum produced from Spitzer 24 micron and IRAS 25 micron images is consistent with a change in the power law exponent from -2.6 to -3.5. The decrease may be due to the transition from a two-dimensional to three-dimensional structure. Under this hypothesis, we estimate the thickness of the emitting medium to be 0.3 pc.Comment: 13 Pages, 3 Figures, to be published in Astrophysical Journal Supplement Series (Spitzer Special Issue), volume 154. Uses aastex v5.

    Evaluation of rate law approximations in bottom-up kinetic models of metabolism.

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    BackgroundThe mechanistic description of enzyme kinetics in a dynamic model of metabolism requires specifying the numerical values of a large number of kinetic parameters. The parameterization challenge is often addressed through the use of simplifying approximations to form reaction rate laws with reduced numbers of parameters. Whether such simplified models can reproduce dynamic characteristics of the full system is an important question.ResultsIn this work, we compared the local transient response properties of dynamic models constructed using rate laws with varying levels of approximation. These approximate rate laws were: 1) a Michaelis-Menten rate law with measured enzyme parameters, 2) a Michaelis-Menten rate law with approximated parameters, using the convenience kinetics convention, 3) a thermodynamic rate law resulting from a metabolite saturation assumption, and 4) a pure chemical reaction mass action rate law that removes the role of the enzyme from the reaction kinetics. We utilized in vivo data for the human red blood cell to compare the effect of rate law choices against the backdrop of physiological flux and concentration differences. We found that the Michaelis-Menten rate law with measured enzyme parameters yields an excellent approximation of the full system dynamics, while other assumptions cause greater discrepancies in system dynamic behavior. However, iteratively replacing mechanistic rate laws with approximations resulted in a model that retains a high correlation with the true model behavior. Investigating this consistency, we determined that the order of magnitude differences among fluxes and concentrations in the network were greatly influential on the network dynamics. We further identified reaction features such as thermodynamic reversibility, high substrate concentration, and lack of allosteric regulation, which make certain reactions more suitable for rate law approximations.ConclusionsOverall, our work generally supports the use of approximate rate laws when building large scale kinetic models, due to the key role that physiologically meaningful flux and concentration ranges play in determining network dynamics. However, we also showed that detailed mechanistic models show a clear benefit in prediction accuracy when data is available. The work here should help to provide guidance to future kinetic modeling efforts on the choice of rate law and parameterization approaches

    Formation and interactions of cold and ultracold molecules: new challenges for interdisciplinary physics

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    Progress on researches in the field of molecules at cold and ultracold temperatures is reported in this review. It covers extensively the experimental methods to produce, detect and characterize cold and ultracold molecules including association of ultracold atoms, deceleration by external fields and kinematic cooling. Confinement of molecules in different kinds of traps is also discussed. The basic theoretical issues related to the knowledge of the molecular structure, the atom-molecule and molecule-molecule mutual interactions, and to their possible manipulation and control with external fields, are reviewed. A short discussion on the broad area of applications completes the review.Comment: to appear in Reports on Progress in Physic

    Measurement of Rapidity Distribution for High Mass Drell-Yan ee Pairs at CDF

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    We report on the first measurement of the rapidity distribution dsigma/dy over nearly the entire kinematic region of rapidity for e^+e^- pairs in the Z-boson region of 66116 GeV/c^2. The data sample consists of 108 pb^{-1} of ppbar collisions at \sqrt{s}=1.8 TeV taken by the Collider Detector at Fermilab during 1992--1995. The total cross section in the ZZ-boson region is measured to be 252 +- 11 pb. The measured total cross section and d\sigma/dy are compared with quantum chromodynamics calculations in leading and higher orders.Comment: 7 pages, 3 figures. Submitted to Physical Review Letter

    Determination of no-observed effect level (NOEL)-biomarker equivalents to interpret biomonitoring data for organophosphorus pesticides in children

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    <p>Abstract</p> <p>Background</p> <p>Environmental exposure to organophosphorus pesticides has been characterized in various populations, but interpretation of these data from a health risk perspective remains an issue. The current paper proposes biological reference values to help interpret biomonitoring data related to an exposure to organophosphorus pesticides in children for which measurements of alkylphosphate metabolites are available.</p> <p>Methods</p> <p>Published models describing the kinetics of malathion and chlorpyrifos in humans were used to determine no-observed effect level – biomarker equivalents for methylphosphates and ethylphosphates, respectively. These were expressed in the form of cumulative urinary amounts of alkylphosphates over specified time periods corresponding to an absorbed no-observed effect level dose (derived from a published human exposure dose) and assuming various plausible exposure scenarios. Cumulative amounts of methylphosphate and ethylphosphate metabolites measured in the urine of a group of Quebec children were then compared to the proposed biological reference values.</p> <p>Results</p> <p>From a published no-observed effect level dose for malathion and chlorpyrifos, the model predicts corresponding oral biological reference values for methylphosphate and ethylphosphate derivatives of 106 and 52 nmol/kg of body weight, respectively, in 12-h nighttime urine collections, and dermal biological reference values of 40 and 32 nmol/kg of body weight. Out of the 442 available urine samples, only one presented a methylphosphate excretion exceeding the biological reference value established on the basis of a dermal exposure scenario and none of the methylphosphate and ethylphosphate excretion values were above the obtained oral biological reference values, which reflect the main exposure route in children.</p> <p>Conclusion</p> <p>This study is a first step towards the development of biological guidelines for organophophorus pesticides using a toxicokinetic modeling approach, which can be used to provide a health-based interpretation of biomonitoring data in the general population.</p

    Search for New Particles Decaying to Dijets at CDF

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    We have used 106 pb^-1 of data collected with the Collider Detector at Fermilab to search for new particles decaying to dijets. We exclude at the 95% confidence level models containing the following new particles: axigluons and flavor universal colorons with mass between 200 and 980 GeV/c, excited quarks with mass between 80 and 570 GeV/c^2 and between 580 and 760 GeV/c^2, color octet technirhos with mass between 260 and 480 GeV/c^2, W' bosons with mass between 300 and 420 GeV/c^2, and E_6 diquarks with mass between 290 and 420 GeV/c^2.Comment: 18 pages, 4 figures, 1 table. Submitted to Physical Review D Rapid Communications. Postscript file of paper is also available at http://www-cdf.fnal.gov/physics/pub97/cdf3276_dijet_search_prd_rc.p

    Measurement of the lepton charge asymmetry in W-boson decays produced in p-pbar collisions

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    We describe a measurement of the charge asymmetry of leptons from W boson decays in the rapidity range 0 enu, munu events from 110+/-7 pb^{-1}of data collected by the CDF detector during 1992-95. The asymmetry data constrain the ratio of d and u quark momentum distributions in the proton over the x range of 0.006 to 0.34 at Q2 \approx M_W^2. The asymmetry predictions that use parton distribution functions obtained from previously published CDF data in the central rapidity region (0.0<|y_l|<1.1) do not agree with the new data in the large rapidity region (|y_l|>1.1).Comment: 13 pages, 3 tables, 1 figur

    Search for a Technicolor omega_T Particle in Events with a Photon and a b-quark Jet at CDF

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    If the Technicolor omega_T particle exists, a likely decay mode is omega_T -> gamma pi_T, followed by pi_T -> bb-bar, yielding the signature gamma bb-bar. We have searched 85 pb^-1 of data collected by the CDF experiment at the Fermilab Tevatron for events with a photon and two jets, where one of the jets must contain a secondary vertex implying the presence of a b quark. We find no excess of events above standard model expectations. We express the result of an exclusion region in the M_omega_T - M_pi_T mass plane.Comment: 14 pages, 2 figures. Available from the CDF server (PS with figs): http://www-cdf.fnal.gov/physics/pub98/cdf4674_omega_t_prl_4.ps FERMILAB-PUB-98/321-

    Observation of Hadronic W Decays in t-tbar Events with the Collider Detector at Fermilab

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    We observe hadronic W decays in t-tbar -> W (-> l nu) + >= 4 jet events using a 109 pb-1 data sample of p-pbar collisions at sqrt{s} = 1.8 TeV collected with the Collider Detector at Fermilab (CDF). A peak in the dijet invariant mass distribution is obtained that is consistent with W decay and inconsistent with the background prediction by 3.3 standard deviations. From this peak we measure the W mass to be 77.2 +- 4.6 (stat+syst) GeV/c^2. This result demonstrates the presence of two W bosons in t-tbar candidates in the W (-> l nu) + >= 4 jet channel.Comment: 20 pages, 4 figures, submitted to PR
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