247 research outputs found

    Is Phaseolus vulgaris Leucoagglutinin (PHA-L) a Useful Marker for Labeling Neural Grafts?

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    The lectin Phaseolus vulgaris leucoagglutinin (PHA-L) has come into wide use as an anterograde neuroanatomical tracer. The ability of this lectin to fill entire neurons and remain in place over long periods suggested it might be an ideal marker for donor cells to be grafted into hosts for long survival periods. We have used the lectin PHA-L to mark fetal rat olfactory bulb (OB) cells prior to grafting into host rat OBs. Hosts were sacrificed at various times up to 9 weeks after grafting, and tissue was immunohistochemically processed for PHA reactivity. After 2 and 4 weeks survival, sparse patterns of labeled cells were observed within the host OBs. However, after 9 weeks survival, few if any labeled cells were visible within host tissue. We conclude that PHA-L may be a less than satisfactory marker for fetal rat cells (other than astrocytes) which are to be identified in host tissue after a period of several weeks

    A thermophysical study of the melting process in alkyl chain metal n-alkanoates: The thallium (I) series

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    The peculiar thermal behavior of the thallium(I) n-alkanoates series (consisting in several transitions between polymorphic and mesomorphic phases) in comparison with other metallic n-alkanoates series is stated. The allowance of highly accurate adiabatic heat capacity data permits a study of the CH2CH2 contributions to the lattice heat capacity curve at low temperature. Moreover, in this series an anomalous gradual enhancement of the lattice heat capacity has been interpreted from vibrational spectroscopy results as a noncooperative effect due to the internal hindered rotation of the alkyl chain (formation of gauche defects, even in the solid state). The thermodynamics of the “stepwise melting process” from the totally ordered solid at low temperature to the isotropic liquid is based on a revised lattice heat-capacity curve. This was used to evaluate the energy and entropy not only of the clear first order transitions present in the series but also of the described noncooperative effect. The CH2CH2 enthalpy and entropy contribution for this series is estimated and a comparison with the published values for other series is carried out. Moreover, the texture of the mesophases is revealed by polarized light microscopy. © 1999 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69602/2/JCPSA6-111-8-3590-1.pd

    The thermodynamics of ammonium scheelites IV. Heat capacity of ammonium metaperiodate NH4IO4 from 8 to 324 K

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    The heat capacity of the scheelite salt ammonium metaperiodate, NH4IO4, was measured from 8 to 324 K using adiabatic calorimetry. The heat capacity against temperature curve shows an excess with a maximum around 200 K as is typical of other ammonium scheelites. A small peak in the curve near 270 K resulted from melting a saturated aqueous solution trapped in the lattice. Values of the standard molar thermodynamic quantities for NH4IO4 are presented up to 320 K. Values for Cp, mo(298.15 K)/R, [Delta]0TSmo(298.15 K)/R, and [Phi]mo(298.15 K, 0)/R are (18.58+/-0.02), (23.03+/-0.04), and (11.20+/-0.02), respectively.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26984/1/0000551.pd

    The thermodynamics of ammonium scheelites V. Heat capacity of deuterated ammonium metaperiodate ND4IO4 from 8 to 329 K

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    The heat capacity of the scheelite salt: deuterated ammonium metaperiodate, ND4IO4, was measured from 8 to 329 K using adiabatic calorimetry. The heat capacity against temperature curve shows a broad maximum with a peak around 200 K which is typical of other ammonium scheelites. A small peak in the curve around 275 K resulted from fusion of a saturated D2O salt solution trapped in the lattice. Values of the standard molar thermodynamic quantities for ND4IO4 are presented up to 330 K.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/26999/1/0000566.pd

    Charged pion form factor between Q2Q^2=0.60 and 2.45 GeV2^2. I. Measurements of the cross section for the 1{^1}H(e,eâ€Čπ+e,e'\pi^+)nn reaction

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    Cross sections for the reaction 1{^1}H(e,eâ€Čπ+e,e'\pi^+)nn were measured in Hall C at Thomas Jefferson National Accelerator Facility (JLab) using the CEBAF high-intensity, continous electron beam in order to determine the charged pion form factor. Data were taken for central four-momentum transfers ranging from Q2Q^2=0.60 to 2.45 GeV2^2 at an invariant mass of the virtual photon-nucleon system of WW=1.95 and 2.22 GeV. The measured cross sections were separated into the four structure functions σL\sigma_L, σT\sigma_T, σLT\sigma_{LT}, and σTT\sigma_{TT}. The various parts of the experimental setup and the analysis steps are described in detail, including the calibrations and systematic studies, which were needed to obtain high precision results. The different types of systematic uncertainties are also discussed. The results for the separated cross sections as a function of the Mandelstam variable tt at the different values of Q2Q^2 are presented. Some global features of the data are discussed, and the data are compared with the results of some model calculations for the reaction 1{^1}H(e,eâ€Čπ+e,e'\pi^+)nn.Comment: 26 pages, 23 figure

    Measurements of Deuteron Photodisintegration up to 4.0 GeV

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    The first measurements of the differential cross section for the d(gamma,p)n reaction up to 4.0 GeV were performed at Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab. We report the cross sections at the proton center-of-mass angles of 36, 52, 69 and 89 degrees. These results are in reasonable agreement with previous measurements at lower energy. The 89 and 69 degree data show constituent-counting-rule behavior up to 4.0 GeV photon energy. The 36 and 52 degree data disagree with the counting rule behavior. The quantum chromodynamics (QCD) model of nuclear reactions involving reduced amplitudes disagrees with the present data.Comment: 5 pages (REVTeX), 1 figure (postscript

    Separated Response Function Ratios in Exclusive, Forward pi^{+/-} Electroproduction

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    The study of exclusive π±\pi^{\pm} electroproduction on the nucleon, including separation of the various structure functions, is of interest for a number of reasons. The ratio RL=σLπ−/σLπ+R_L=\sigma_L^{\pi^-}/\sigma_L^{\pi^+} is sensitive to isoscalar contamination to the dominant isovector pion exchange amplitude, which is the basis for the determination of the charged pion form factor from electroproduction data. A change in the value of RT=σTπ−/σTπ+R_T=\sigma_T^{\pi^-}/\sigma_T^{\pi^+} from unity at small −t-t, to 1/4 at large −t-t, would suggest a transition from coupling to a (virtual) pion to coupling to individual quarks. Furthermore, the mentioned ratios may show an earlier approach to pQCD than the individual cross sections. We have performed the first complete separation of the four unpolarized electromagnetic structure functions above the dominant resonances in forward, exclusive π±\pi^{\pm} electroproduction on the deuteron at central Q2Q^2 values of 0.6, 1.0, 1.6 GeV2^2 at WW=1.95 GeV, and Q2=2.45Q^2=2.45 GeV2^2 at WW=2.22 GeV. Here, we present the LL and TT cross sections, with emphasis on RLR_L and RTR_T, and compare them with theoretical calculations. Results for the separated ratio RLR_L indicate dominance of the pion-pole diagram at low −t-t, while results for RTR_T are consistent with a transition between pion knockout and quark knockout mechanisms.Comment: 6 pages, 3 figure

    A Study of the Quasi-elastic (e,e'p) Reaction on 12^{12}C, 56^{56}Fe and 97^{97}Au

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    We report the results from a systematic study of the quasi-elastic (e,e'p) reaction on 12^{12}C, 56^{56}Fe and 197^{197}Au performed at Jefferson Lab. We have measured nuclear transparency and extracted spectral functions (corrected for radiation) over a Q2^2 range of 0.64 - 3.25 (GeV/c)2^2 for all three nuclei. In addition we have extracted separated longitudinal and transverse spectral functions at Q2^2 of 0.64 and 1.8 (GeV/c)2^2 for these three nuclei (except for 197^{197}Au at the higher Q2^2). The spectral functions are compared to a number of theoretical calculations. The measured spectral functions differ in detail but not in overall shape from most of the theoretical models. In all three targets the measured spectral functions show considerable excess transverse strength at Q2^2 = 0.64 (GeV/c)2^2, which is much reduced at 1.8 (GeV/c)2^2.Comment: For JLab E91013 Collaboration, 19 pages, 20 figures, 3 table

    Determination of the pion charge form factor for Q^2=0.60-1.60 GeV^2

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    The data analysis for the reaction H(e,e' pi^+)n, which was used to determine values for the charged pion form factor Fpi for values of Q^2=0.6-1.6 GeV^2, has been repeated with careful inspection of all steps and special attention to systematic uncertainties. Also the method used to extract Fpi from the measured longitudinal cross section was critically reconsidered. Final values for the separated longitudinal and transverse cross sections and the extracted values of Fpi are presented.Comment: 11 pages, 6 figure
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