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91.
92.
M Kostrzewa BW Krings MJ Dixon K Eppelt A K?hler DL Grady D Steinberger ND Fairweather RK Moyzis AP Monaco U Müller 《Canadian Metallurgical Quarterly》1998,6(3):266-274
The disposition of S-2-[4-(3-methyl-2-thienyl)phenyl]propionic acid (CAS 155680-07-2, S-MTPPA, code: M-5011) was studied after oral administration to rats, dogs and monkeys using the 14C-labeled drug. After oral dosing, S-MTPPA was well absorbed from the gastrointestinal tract, to the extent of 97.7% in rats. The concentration of S-MTPPA in rat plasma reached a peak (Cmax: 13.07 micrograms/ml) at 15 min (tmax) after dosing and declined with a half-life (t1/2) of 2.5 h. The values of the parameters tmax, Cmax and t1/2 for dogs were 30 min, 26.2 micrograms/ml and 7.0 h, and those for monkeys were 15 min, 12.8 micrograms/ml and 3.0 h, respectively. The radioactivity was widely distributed in tissues and almost completely excreted in urine and feces within 48 h after oral administration to rats. The excretion of radioactivity in bile, urine and feces within 48 h after oral administration of 14C-S-MTPPA to bile duct-cannulated rats amounted to 75.0, 18.6 and 1.4% of the dose, respectively. The drug was metabolized mainly by oxidation of the thiophenyl moiety and by glucuronidation of the carboxyl group in rats and monkeys. The major urinary and fecal metabolite in dogs was identified as the taurine conjugate of MTPPA. 相似文献
93.
The weak physical gelation of cellulose acetate propionate-butyl butyrate solutions as a result of the in-situ decomposition of iron pentacarbonyl complexes was explored. Viscometry and infrared spectroscopy were used to monitor the iron pentacarbonyl decomposition reaction progress and its effect on viscosity. Changes in viscosity in of the cellulosic fluids in general and gelation in particular were found to be dependent upon the environment in which the Fe(CO)5 decompositions occurred. Systems under inert atmospheres exhibited a marked increase in viscosity, while systems under oxidative atmospheres exhibited a general decrease in viscosity. We propose a hypothesis that explains the dependence of the viscosity of these cellulosic fluids as a function of the environmental conditions during the precursor decomposition. Under nitrogen atmospheres, zero-valent nanoparticles with highly reactive surfaces are synthesized, which form weak, transient bonds with the cellulosic polymer. The iron particles, under these circumstances, serve as weak bridges between adjacent polymer chains. Conversely, the primary particles synthesized under an oxidative atmosphere are metal oxides, which are less attractive to the polymer chain and, therefore, do not yield such bridges. This work demonstrates the capability to apply a simple method to control the viscosity of cellulose ester fluids. 相似文献
94.
The biodegradation of pentachlorophenol (PCP) was tested in a three phase protocol. Phase I involved acclimation; phase II allowed determintion of biodegradation kinetics through use of continuous stirred tank reactors (CSTR) operated at solids retention times of 3.2, 7.8, 12.8 and 18.3 days; phase III assessed the importance of volatilization and sorption in PCP removal and evaluated the extent of biodegradation. Over the range of SRT's studied, PCP was found to be biodegradable with first order kinetics; the rate constant (μm/Ks) had a value of 0.0017 l μg−1d−1. The minimum concentration of PCP attainable in a CSTR was found to be 27 μg l−1. Additional studies suggested that the full relationship between the PCP degradation rate and the PCP concentration followed an inhibition-type function, with the maximum rate occurring at a PCP concentration of around 350 μg l−1. Radioisotopic studies revealed that PCP was mineralized by the culture, with the liberation of CO2 and the incorporation of carbon into cell material. Neither volatilization nor sorption removed significant amounts of PCP from the reactors. 相似文献
95.
M Kaefer JE Audia N Bruchovsky RL Goode KC Hsiao IY Leibovitch JH Krushinski C Lee CP Steidle DM Sutkowski BL Neubauer 《Canadian Metallurgical Quarterly》1996,58(2):195-205
Each amino acid is represented by a vector of numerical measurements for the attributes of volume, area, hydrophilicity, polarity, hydrogen bonding, shape, and charge. Inter-residue distances are then calculated according to common metrics, and we introduce a new clustering objective function derived from information-theoretic considerations. The arguments of the function are the inter-object distances of the things to be clustered: in this case the amino acids. By means of approximating the solution of an integer programming problem, then, the residues are partitioned into clusters. The clusters obtained are compared with groups obtained in substitution/mutation studies and found to be similar. Thus, probably the strongest and most objective evidence to date is supplied for believing that physico-chemical properties account for the viability of substitutions and that the important similarities/differences are explained by a relatively small and simple set of properties. 相似文献
96.
Dos Santos OF Rodrigues SC Sipahi GM Scolfaro LM da Silva EF 《Nanoscale research letters》2011,6(1):175
The electrical conductivity σ has been calculated for p-doped GaAs/Al0.3Ga0.7As and cubic GaN/Al0.3Ga0.7N thin superlattices (SLs). The calculations are done within a self-consistent approach to the theory by means of a full six-band Luttinger-Kohn Hamiltonian, together with the Poisson equation in a plane wave representation,
including exchange correlation effects within the local density approximation. It was also assumed that transport in the SL
occurs through extended minibands states for each carrier, and the conductivity is calculated at zero temperature and in low-field
ohmic limits by the quasi-chemical Boltzmann kinetic equation. It was shown that the particular minibands structure of the
p-doped SLs leads to a plateau-like behavior in the conductivity as a function of the donor concentration and/or the Fermi
level energy. In addition, it is shown that the Coulomb and exchange-correlation effects play an important role in these systems,
since they determine the bending potential. 相似文献
97.
High‐Temperature Neutron Diffraction,Raman Spectroscopy,and First‐Principles Calculations of Ti3SnC2 and Ti2SnC
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Grady W. Bentzel Michael Naguib Nina J. Lane Sven C. Vogel Volker Presser Sylvain Dubois Jun Lu Lars Hultman Michel W. Barsoum El'ad N. Caspi 《Journal of the American Ceramic Society》2016,99(7):2233-2242
Herein, we report—for the first time—on the additive‐free bulk synthesis of Ti3SnC2. A detailed experimental study of the structure of the latter together with a secondary phase, Ti2SnC, is presented through the use of X‐ray diffraction (XRD), and high‐resolution transmission microscopy (HRTEM). A previous sample of Ti3SnC2, made using Fe as an additive and Ti2SnC as a secondary phase, was studied by high‐temperature neutron diffraction (HTND) and XRD. The room‐temperature crystallographic parameters of the two MAX phases in the two samples are quite similar. Based on Rietveld analysis of the HTND data, the average linear thermal expansion coefficients of Ti3SnC2 in the a and c directions were found to be 8.5 (2)·10?6 K?1 and 8.9 (1)·10?6 K?1, respectively. The respective values for the Ti2SnC phase are 10.1 (3)·10?6 K?1 and 10.8 (6)·10?6 K?1. Unlike other MAX phases, the atomic displacement parameters of the Sn atoms in Ti3SnC2 are comparable to those of the Ti and C atoms. When the predictions of the atomic displacement parameters obtained from density functional theory are compared to the experimental results, good quantitative agreement is found for the Sn atoms. In the case of the Ti and C atoms, the agreement is more qualitative. We also used first principles to calculate the elastic properties of both Ti2SnC and Ti3SnC2 and their Raman active modes. The latter are compared to experiment and the agreement was found to be good. 相似文献
98.
BACKGROUND & AIMS: The molecular mechanisms underlying pancreatitis are largely unknown. The goal of this study was to identify an early genetic event that correlated with pancreatitis. METHODS: Differential display of messenger RNAs (mRNAs) was conducted on normal pancreas vs. those of animals with secretagogue-induced pancreatitis. Northern blots from normal animals and animals with experimental acute pancreatitis were probed with cloned complementary DNAs for chemokines. Pancreatitis was induced with cerulein and by retrograde injection of bile salts. Immunocytochemistry was used to identify the source of chemokine expression. Pyrrolidine dithiocarbamate was tested for effects on chemokine expression and pancreatitis. RESULTS: A differentially amplified band was consistently observed early after cerulein hyperstimulation. This band was identified as a portion of the mob-1 gene, an alpha-chemokine. Northern analysis indicated that mRNAs for mob-1 and another chemokine, mcp-1, were induced after cerulein hyperstimulation in vivo. mob-1 mRNA was also induced by retrograde injection of bile salts and by cerulein in acinar cells in vitro. mob-1 protein was localized to exocrine cells in pancreata of diseased animals. Pyrrolidine dithiocarbamate inhibited both chemokine gene expression and early inflammatory characteristics of pancreatitis. CONCLUSIONS: Chemokines are induced in acinar cells by treatments that induce pancreatitis and may play an important role in the early stages of the disease. 相似文献
99.
Dietary conjugated linoleic acid normalizes impaired glucose tolerance in the Zucker diabetic fatty fa/fa rat 总被引:2,自引:0,他引:2
KL Houseknecht JP Vanden Heuvel SY Moya-Camarena CP Portocarrero LW Peck KP Nickel MA Belury 《Canadian Metallurgical Quarterly》1998,244(3):678-682
Conjugated linoleic acid (CLA) is a naturally occurring fatty acid which has anti-carcinogenic and anti-atherogenic properties. CLA activates PPAR alpha in liver, and shares functional similarities to ligands of PPAR gamma, the thiazolidinediones, which are potent insulin sensitizers. We provide the first evidence that CLA is able to normalize impaired glucose tolerance and improve hyperinsulinemia in the pre-diabetic ZDF rat. Additionally, dietary CLA increased steady state levels of aP2 mRNA in adipose tissue of fatty ZDF rats compared to controls, consistent with activation of PPAR gamma. The insulin sensitizing effects of CLA are due, at least in part, to activation of PPAR gamma since increasing levels of CLA induced a dose-dependent transactivation of PPAR gamma in CV-1 cells cotransfected with PPAR gamma and PPRE X 3-luciferase reporter construct. CLA effects on glucose tolerance and glucose homeostasis indicate that dietary CLA may prove to be an important therapy for the prevention and treatment of NIDDM. 相似文献
100.