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991.
A high-performance liquid chromatographic (HPLC) method for the simultaneous determination of prednisolone acetate (PA), prednisolone (PO), prednisone (PN), cortisone and hydrocortisone in swine plasma is described. Extraction of the steroid mixture from swine plasma with dexamethasone as internal standard was accomplished by solid-phase extraction (SPE) or the more traditional liquid-liquid extraction (LLE) techniques. These compounds were analyzed by normal-phase HPLC with ultraviolet detection. Although a detectable sensitivity of 5 ng/ml is achieved by the SPE technique, the practical sensitivity is established as 10 ng/ml. Conversely, the practical sensitivity is 5 ng/ml for all compounds by the LLE technique. Calibration curves were found to be linear between 10 and 500 ng/ml by the SPE technique and between 5 and 100 ng/ml by the LLE technique. The average recovery of the steroids PA, PO and PN at 20 ng/ml is between 70 and 90%. PA is stable for up to 3 h in swine plasma at room temperature (22 degrees C) but is completely converted to PO within 24 h. PA is stable in swine plasma in an ice bath for over 24 h. The usefulness of this analytical technique is demonstrated by the intraperitoneal administration of 125 mg of PA to swine and the quantitative determination of PA, PO and PN in the plasma as a function of time. 相似文献
992.
Migration and clustering of lattice defects after implantation of111In in Al and subsequent annealing at temperatures in the range from 80 to 800 K were investigated applying the DPAC technique. The effects of implantation dose, implantation temperature, laser irradiation, and plastic deformation were studied. The measurements on plastically deformed Al were complemented by positron lifetime measurements. We observed four In-defect clusters that can be flagged by well-defined hyperfine interaction parameters, and we determined their symmetry properties by using single-crystal samples. Important conclusions are: (i) monovacancies are not trapped by In-atoms, (ii) small In-defect clusters are formed by direct trapping of divacancies and/or trivacancies, and (iii) extended In-defect clusters are very stable and anneal in the temperature range 600–700 K. Consequences for the interpretation of other measurements on dilute Al(In) alloys are discussed.On leave from Tata Institute of Fundamental Research, Homi Bhabha Road, Bombay 400 005, India. 相似文献
993.
994.
The notion of a Weyl module, previously defined for the untwisted affine algebras, is extended here to the twisted affine algebras. We describe an identification of the Weyl modules for the twisted affine algebras with suitably chosen Weyl modules for the untwisted affine algebras. This identification allows us to use known results in the untwisted case to compute the dimensions and characters of the Weyl modules for the twisted algebras. 相似文献
995.
Optimal Advertising and Pricing in a New-Product Adoption Model 总被引:3,自引:0,他引:3
A model of new-product adoption is proposed that incorporates price and advertising effects. An optimal control problem that
uses the model as its dynamics is solved explicitly to obtain the optimal price and advertising effort over time. The model
has a great potential to be used in obtaining solutions and insights in a variety of differential game settings.
The authors thank Anshuman Chutani for help with the figures. 相似文献
996.
We have carried out very accurate density measurements (with a precision of ±5 × 10-5g cm-3) near the smectic A-nematic transition in binary mixtures of 4-n-nonyl-4'-cyanobiphenyl (9CB) and 4-n-decyl-4'-cyanobiphenyl (10CB). The transition crosses over from second to first order as the temperature range of the nematic phase decreases. For mixtures with the shortest nematic range the data deviate noticeably from a single power law behaviour. Such a deviation is an indication of the first order nature of the transition. Very good fits to a single power law have been obtained for pure 9CB and the x = 0·04 mixture where x is the mole fraction of 10CB in 9CB. The critical exponent obtained from the power law fitting has enabled us to locate the tricritical point to be very close to x=0·04, which is in agreement with the results obtained previously by high resolution calorimetric [1] and X-ray scattering studies [2]. 相似文献
997.
Thermoluminescence (TL) of LiNaSO4:Eu phosphor, irradiated with 24 and 48 MeV 7Li ions at different fluences in the range 5×109-1×1012 ion/cm2, has been studied. The samples from the same batch were also exposed to γ-rays from a Cs137 source for comparative studies. The TL glow curves of the materials, irradiated with 7Li ions, have similar structures to that of γ-irradiated sample. They have a simple structure with a prominent peak at 412 K along with small one at around 481 K. The intensity ratios of 412-481 K peaks have been observed to increase with fluence increasing, while that of γ-irradiated sample shows a reverse trend. This could be attributed to the changes in the recombination center populations due to 7Li ions, that have been implanted inside the matrix of LiNaSO4:Eu, during irradiation and might also act as a source for new trapping and luminescent centers. The implantation has been confirmed by TRIM calculations. The penetration depths (where the ion comes to rest) are found to be 145 and 463 μm corresponding to 24 and 48 MeV ion beam energies, respectively, which are less than the thickness of the sample chips (∼800 μm). The efficiencies of LiNaSO4:Eu to 24 and 48 MeV 7Li ions measured relative to γ-rays of Cs137 are found to be 0.007 and 0.024, respectively. Theoretical analysis of the glow curves of the samples irradiated by 7Li ions and γ-rays were done by glow curve deconvolution method to determine trapping parameters of various peaks. The experimentally observed linearity/sublinearity has been discussed in the frame of track interaction model. Photoluminescence studies in the 7Li ions irradiated and un-irradiated samples show that europium ions have incorporated in the host in their divalent (emission at 440 nm) as well as trivalent (emissions at 594, 615 and 700 nm) forms. The intensities of the emission bands of these ions have been observed to increase with fluence increasing. 相似文献
998.
999.
Bert Vanhaecht Jan Devroede Rudolph Willem Monique Biesemans Wyjayanthi Goonewardena Sanjay Rastogi Sven Hoffmann Philip G. Klein Cor E. Koning 《Journal of polymer science. Part A, Polymer chemistry》2003,41(13):2082-2094
Copolyamides 2.14/piperazine.14 with variable built‐in ratios of 1,2‐ethylenediamine (1,2‐EDA) and piperazine (pip) were synthesized by solution polycondensation. The built‐in ratio of both diamine comonomers was determined with solution 13C NMR analysis. The gradual replacement of 1,2‐EDA units by cycloaliphatic pip units in polyamide 2.14 resulted in a progressively decreased melting (Tm) and crystallization temperature of the obtained copolyamides. Apparently, the Tm raising effect of the incorporation of rigid cycloaliphatic moieties is overruled by the simultaneous Tm reduction caused by a decreasing hydrogen‐bond density. Indications for cocrystallization of 2.14 and pip.14 repeating units were obtained by the thermal analysis of copolyamides 2.14/pip.14 and of a blend of both homopolyamides. A preliminary wide‐angle X‐ray diffraction study pointed to the same conclusion. Solid‐state NMR spectroscopy was used to investigate the influence of the composition on the percentage of the rigid phase of the copolyamides and delivered additional indications for cocrystallization. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2082–2094, 2003 相似文献
1000.
S. Bhaskar Reddy K. Prasad Rao M.S. Ramachandra Rao 《Applied Physics A: Materials Science & Processing》2007,89(4):1011-1015
Single phase Sr substituted BaZr0.1Ti0.9O3 (also known as BZT) ceramics with a formula Ba1-xSrxZr0.1Ti0.9O3 (x=0.10, 0.20, 0.30, 0.40 and 0.50) are prepared using a solid state reaction of mixed oxides at 1250 °C for 15 h. Analysis
of XRD patterns of the ceramic powders show that Sr substitutes into Ba sites and reduces the lattice parameter. The powders
are sintered at 1600 °C for 6 h to investigate the microstructure and functional properties. It is found that strontium substitution
significantly modifies the microstructure and greatly influences the dielectric properties. The increase in Sr content reduces
the ceramic grain size and results in spherical grains. With an increase in Sr content, the Curie temperature is lowered,
and the relative permittivity maximum is increased and broadened. In Ba1-xSrxZr0.1Ti0.9O3 with x=0.30, the relative permittivity reached a maximum of 26600 and with further increase of Sr content, the relative permittivity
is lowered and the phase transition is found to be broad and diffused. The ferroelectric hysteresis characteristics are discussed
in detail.
PACS 77.84.-s; 77.80.Bh; 77.22.Ch; 77.84.Dy; 77.22.-d 相似文献