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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 3243-3248 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Mixtures of acetone/methanol, acetonitrile/methanol, and acetone/acetonitrile over their whole composition range were studied with infrared and far-infrared (THz) spectroscopy. Experimental spectra of all mixtures were obtained below 120 cm−1, and spectra of methanolic mixtures were also measured from 400 to 1000 cm−1. The mixtures display ideal absorption spectra below 120 cm−1, contrasting with significant nonidealities in the absorption of aqueous mixtures in the same frequency range. Dramatic changes as a function of composition were found in methanolic mixtures at higher frequencies. The high frequency librational band of methanol, centered at 670 cm−1, shifts to substantially lower frequencies upon dilution, indicating marked changes in the librational motion of the hydroxyl hydrogen of methanol. This band is a sensitive probe of the hydrogen bonding environment experienced by methanol molecules. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 3249-3260 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Molecular dynamics simulations have been used to study mixtures of acetone/methanol, acetonitrile/methanol, and acetone/acetonitrile over their entire composition range. Using the effective pair potentials of the neat liquids, the simulations reproduce much of the experimental spectra presented in the previous paper [D. S. Venables, A. Chiu, and C. A. Schmuttenmaer, J. Chem. Phys. 113, 3243 (2000)]. In addition to the total dipole spectra, autocorrelation functions and their corresponding spectra were calculated for the single dipole moment as well as the translational and rotational velocities of each component in the mixtures. Radial and spatial distribution functions, hydrogen bonding, and methanol chain formation in the mixtures were also analyzed. The red-shift of the high frequency librational band is attributed to methanol chains breaking up into shorter segments, and to hydrogen bonding between methanol and co-solvent molecules. Methanol molecules have a strong tendency to reside in chains, even at low methanol concentrations, and hydrogen bonding is the primary determinant of structure in the mixtures. © 2000 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 11222-11236 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Binary mixtures of water with acetone, acetonitrile, and methanol over their entire range of compositions have been studied spectroscopically and by using molecular dynamics (MD) simulations. We report absorption coefficients and indices of refraction over a frequency range from 3 to 55 cm−1, and from 400 to 1200 cm−1. The far-infrared absorption of the mixtures is substantially less than that for ideal mixtures, and Debye time constants calculated from the spectra are longer for the real than for the ideal mixtures. Significant composition dependence is observed in the high frequency librational spectra of the mixtures, and is reproduced by the MD simulations. Single dipole and angular velocity spectra are also reported, as are detailed changes in the hydrogen bonding environment in the mixtures. There is a loss of tetrahedral water structure on mixing, yet water molecules have a strong tendency to aggregate, especially in the acetone and acetonitrile mixtures. Spatial distribution functions are reported for the acetone/water system. © 2000 American Institute of Physics.
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  • 4
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Carbonate concretions in the Lower Carboniferous Caton Shale Formation contain diagenetic pyrite, calcite and barite in the concretion matrix or in different generations of septarian fissures. Pyrite was formed by sulphate reduction throughout the sediment before concretionary growth, then continued to form mainly in the concretion centres. The septarian calcites show a continuous isotopic trend from δ13C=−28·7‰ PDB and δ18O=−1·6‰ PDB through to δ13C=−6·9‰ PDB and δ18O=−14·6‰ PDB. This trend arises from (1) a carbonate source initially from sulphate reduction, to which was added increasing contributions of methanogenic carbonate; and (2) burial/temperature effects or the addition of isotopically light oxygen from meteoric water. The concretionary matrix carbonates must have at least partially predated the earliest septarian cements, and thus used the same carbonate sources. Consequently, their isotopic composition (δ13C=−12·0 to −10·1‰ PDB and δ18O=−5·7 to −5·6‰ PDB) can only result from mixing a carbonate cement derived from sulphate reduction with cements containing increasing proportions of carbonate from methanogenesis and, directly or indirectly, also from skeletal carbonate. Concretionary growth was therefore pervasive, with cements being added progressively throughout the concretion body during growth. The concretions contain barite in the concretion matrix and in septarian fissures. Barite in the earlier matrix phase has an isotopic composition (δ34S=+24·8‰ CDT and δ18O=+16·4‰ SMOW), indicating formation from near-surface, sulphate-depleted porewaters. Barites in the later septarian phase have unusual isotopic compositions (δ34S=+6 to +11‰ CDT and δ18O=+8 to +11‰ SMOW), which require the late addition of isotopically light sulphate to the porewaters, either from anoxic sulphide oxidation (using ferric iron) or from sulphate dissolved in meteoric water. Carbon isotope and biomarker data indicate that oil trapped within septarian fissures was derived from the maturation of kerogen in the enclosing sediments.
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  • 5
    ISSN: 1432-2072
    Keywords: Pharmacokinetics ; Bioavailability ; Drug absorption ; Benzodiazepines ; Diazepam ; Ethanol ; Drug interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Six healthy male or female volunteers ingested a single 5-mg tablet of diazepam with a typical ethanol-containing cocktail (1.5 ounces of 80-proof vodka plus 4 ounces of orange juice plus ice) or with a similar ethanol-free mixture (4 ounces of orange juice plus ice) in the fasting state on two occasions separated by at least 1 week. Diazepam concentrations in multiple plasma samples drawn from 15 min to 24 h after each dose were determined by electron-capture gas-liquid chromatography. Mean values of pharmacokinetic variables for diazepam taken without and with ethanol, respectively, were: peak plasma diazepam concentration, 221 vs. 208 ng/ml; time of peak concentration, 0.79 vs. 1.79 h after dosing (P〈0.1); apparent lag time prior to start of absorption, 16.5 vs. 26.2 min; apparent first-order absorption half-life, 19.3 vs. 34.6 min. The completeness of diazepam absorption, judged by the area under the 24-h plasma concentration curve, was nearly identical for the two conditions. Thus, coadministration of diazepam with the ethanol cocktail tended to slow the rate of diazepam absorption, but did not influence the completeness of absorption. Pharmacodynamic synergism of ethanol and diazepam, if it exists, cannot be attributed to enhancement of the rate or completeness of diazepam absorption.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 16 (1979), S. 73-74 
    ISSN: 1432-1041
    Keywords: cephalexin ; absorption ; elimination ; acutely ill patients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-8744
    Keywords: lorazepam ; benzodiazepines ; pharmacokinetics ; drug accumulation ; antipyrine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Six healthy volunteers participated in single- and multiple-dose pharmacokinetic studies of oral lorazepam. Following single 4-mg oral doses, peak plasma lorazepam concentrations ranging from 40 to 70 ng/ml were reached within 3 hr of the dose. Values of absorption half-life averaged 25min (range 10.3–42.7min), and elimination half-life (t 1/2β ) averaged 14.2 hr (range 8.4–23.9 hr). During 15 consecutive days of 3 mg per day administered in divided doses, accumulation to the steady-state condition was complete within several days of the initiation of therapy. Values of accumulation half-life (mean 21.1 hr) were slightly longer than t 1/2β , and the two were not well correlated. Observed accumulation ratios (mean 1.88) were very close to those predicted from the single-dose study (mean 1.77), but the correlation between the two (r=0.51) was not significant in the small sample size. “Washout” half-life values (mean 14.9 hr) were highly correlated with t 1/2β (r=0.92). Clearance of a single intravenous dose of antipyrine determined prior to the multiple- dose lorazepam study (mean 0.86 ml/min/kg) was essentially identical to that determined after the study (mean 0.87 ml/min/kg). Overall, the rate and extent of lorazepam accumulation during multiple dosage were reasonably well predicted by the single-dose kinetic study. However, accurate prediction for any specific individual was not always achieved. Stimulation or inhibition by lorazepam of its own clearance probably does not explain imprecise prediction, since single-dose t 1/2β .
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 183 (1975), S. 517-521 
    ISSN: 0003-276X
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: This study focuses on the confusion in existing literature concerning the presence of smooth muscle in the capsule and trabeculae of lymphnodes. Human and bovine nodes from several anatomical areas and several individuals of each species were examined by conventional light, electron and fluorescence microscopy. Smooth muscle cells, independent of blood vessels, were demonstrated in the trabeculae and capsules of lymph nodes of both species examined by all three techniques. The need for further study on the function of these cells is indicated.
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  • 9
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/article
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