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991.
Kvapil Josef Kvapil Jiří Blažek K. Zikmund J. Autrata R. Schauer P. 《Czechoslovak Journal of Physics》1980,30(2):185-192
The luminescence intensity of Yttrium aluminium garnet activated by the Ce3+ (YAGCe3+) under cathode-ray excitation depends on the preparation method and content of some dopants. Samples containing Fe, Pt, Ir or some colour centre, respectively, show relatively low luminescence. The maximum luminescence intensity was obtained with the Czochralski method grown single crystals in 98% Ar+2% H2 atmosphere which were sensitized by oxygen annealing followed by treatment at 1500 °C in molybdenum container using a wet hydrogen atmosphere. 相似文献
992.
J. Rybníček 《Czechoslovak Journal of Physics》1980,30(12):1307-1314
The variations in time of mass spectra of ions, extracted from the hollow-cathode discharge in the regime of the intensive sputtering of the cathode material were measured. The mass spectrum changes in time conspicuously. From the results of measurements a distinct anisotropy of ion beam is inferred. The discharge turns into a metal-ions regime.The helpful discussions with Dr. J. Musil are gratefully acknowledged. 相似文献
993.
Maurício Vieira Kritz 《Bulletin of the Brazilian Mathematical Society》1980,11(2):217-236
In this work the initial value problem for the equation $$u_t + \beta u_x + yf(u)_x - \delta u_{xxt} = g,\forall x \in R, \forall t \in [0,T],$$ with periodic boundary conditions is interpreted in the sense of periodic distributions and studied via fixed point arguments. Weak solutions exist iff∈C 0 (R) andg∈L ∞(L 2(0,1)). Moreover, regularity inf, g and the initial data implies regularity of solutions. 相似文献
994.
The interdiffusion in the Co-Ni system has been investigated in the temperature range of 950 to 1150 °C, by means of diffusion specimens of pure Co and Ni. The concentration curvesN(x, t) obtained with the aid of an JXA-3 A JEOL electron microprobe were evaluated using the smoothing cubic spline method by means of the Boltzmann-Matano equation. The obtained interdififusion coefficient values ¯D increase with the increasing Ni concentration and satisfy the Arrhenius equation at temperaturesH 990 °C. At lower temperatures the influence of high diffusivity paths may be effective, resulting in higher ¯D values. No expressive influence of atomic (Ni3Co) or magnetic order on the interdiffusion has been detected. The activation enthalpyH values were found almost concentration independent. A Kirkendall effect study has been carried out with positive results which are presented in Part II of this paper. A new method for the determination of diffusants concentration in the Kirkendall plane was proposed. With the use of this method and of Darken equations the intrinsic diffusion coefficients were calculated. These results are given in Part III. 相似文献
995.
In this paper an approximative procedure to determine of the most probable model of oxide film originating at thermal oxidation of GaAs single-crystal samples within the temperature range 480–530 °C is proposed. It is shown that the system presented is more complicated if compare with that presumed previously. 相似文献
996.
dos Reis EO Vianna-Jorge R Suarez-Kurtz G Lima EL Azevedo Dde A 《Rapid communications in mass spectrometry : RCM》2005,19(12):1666-1674
A sensitive and specific assay for detection of busulfan in human plasma was developed. The assay is based on rapid isolation of busulfan by liquid-liquid extraction with ethyl acetate, and detection by high-performance liquid chromatography with electrospray ionization and tandem mass spectrometry. 1,6-Bis(methanesulfonyloxy)hexane, a synthesized analogue of busulfan, was used as the internal standard (IS). The acquisition was performed in the multiple reaction monitoring mode; busulfan and the IS were detected with no interferences from plasma matrix. The method was linear over the range 5-2500 ng mL(-1), with r2 > 0.99 and a run time of only 3.5 min. The intra- and inter-assay precisions were in the ranges 2.1-11.9% and 3.2-10.1%, respectively, and the intra- and inter-assay accuracies were 92.2-107.6% and 94.7-104.1%, respectively. The absolute recoveries were 82.0% (20 ng mL(-1)), 90.6% (1000 ng mL(-1)) and 80.0% (2000 ng mL(-1)) for busulfan, and 89.1% for the IS (1000 ng mL(-1)). The limits of detection and quantification were 2 and 5 ng mL(-1), respectively. The validated method was successfully applied to analyze plasma samples obtained from six adults receiving doses of 1 mg kg(-1) in a conditioning regimen prior to bone marrow transplantation. A marked intra-patient variation in busulfan concentrations during the steady state was observed, which limits the application of pharmacokinetic modeling and suggests that continuous therapeutic monitoring is necessary for adequate individualized dosing. In this regard, the present assay brings important advantages relative to other methods described in the literature, i.e., it is highly specific and simple to perform, with a rapid chromatographic run time (3.5 min), and the whole procedure can be completed in 4-5 h, which would permit dose corrections after the third dose allowing earlier and better dosing adjustments towards the target level of busulfan. 相似文献
997.
Becerra R Bowes SJ Ogden JS Cannady JP Almond MJ Walsh R 《The journal of physical chemistry. A》2005,109(6):1071-1080
Time-resolved kinetic studies of the reaction of silylene, SiH2, generated by laser flash photolysis of phenylsilane, have been carried out to obtain rate constants for its bimolecular reaction with NO. The reaction was studied in the gas phase over the pressure range 1-100 Torr in SF6 bath gas at five temperatures in the range 299-592 K. The second-order rate constants at 10 Torr fitted the Arrhenius equation log(k/cm3 molecule(-1) s(-1)) = (-11.66 +/- 0.01) + (6.20 +/- 0.10 kJ mol(-1))/RT ln 10 The rate constants showed a variation with pressure of a factor of ca. 2 over the available range, almost independent of temperature. The data could not be fitted by RRKM calculations to a simple third body assisted association reaction alone. However, a mechanistic model with an additional (pressure independent) side channel gave a reasonable fit to the data. Ab initio calculations at the G3 level supported a mechanism in which the initial adduct, bent H2SiNO, can ring close to form cyclo-H2SiNO, which is partially collisionally stabilized. In addition, bent H2SiNO can undergo a low barrier isomerization reaction leading, via a sequence of steps, ultimately to dissociation products of which the lowest energy pair are NH2 + SiO. The rate controlling barrier for this latter pathway is only 16 kJ mol(-1) below the energy of SiH2 + NO. This is consistent with the kinetic findings. A particular outcome of this work is that, despite the pressure dependence and the effects of the secondary barrier (in the side reaction), the initial encounter of SiH2 with NO occurs at the collision rate. Thus, silylene can be as reactive with odd electron molecules as with many even electron species. Some comparisons are drawn with the reactions of CH2 + NO and SiCl2 + NO. 相似文献
998.
J. Hernández-Borges M. A. Rodríguez-Delgado F. J. García-Montelongo 《Chromatographia》2006,63(3-4):155-160
Several improvements in sample pretreatment for the determination of organic pollutants (i.e. n-alkanes, polycyclic aromatic hydrocarbons, PAHs) in marine biota (mussels) are presented. The use of liquid nitrogen and
homogenization of the samples are shown to be an alternative to the time consuming liophilization step required for the analysis
of biota samples. Microwave-assisted hydrolysis and extraction are combined to isolate organic pollutants (19 n-alkanes and 27 PAHs) from biota matrices. Experimental design (ED) and artificial neural networks (ANNs) were used to optimize
the experimental conditions. NIST-CRM 2978 was used to test the validity of the developed method which shows a good agreement
with certified values. 相似文献
999.
V. Manríquez C. Díaz G. González I. Brito 《Journal of Thermal Analysis and Calorimetry》1996,46(6):1875-1880
Benzenesulfenamides with the formula R-S-N-(R)2 (R=C6H5 andR=NC4H8O, C7H7 and C6H11) and their chromium carbonyl complexes were studied by means of TG and mass spectrometric methods. The thermal behaviour of the compounds the stabilities of free sulfenamides are lower than those observed for the corresponding chromium carbonyl complexes. Combined thermogravimetry — mass spectrometry results suggest that the fragmentation mechanism of the carbonyl complexes involves cleavage of the Cr-S and Cr-CO bonds while that of sulfenamide depends mainly on the dissociation rates of the NR2 groups.This work was partially supported by the Departamento técnico de Investigation of the Universidad de Chile, Grant Q3280/9324. 相似文献
1000.
Summary A general definition of reaction graphs is presented. For a pair of isomeric molecular graphs
and
, related by a chemical transformation
, the reaction graph
is determined using a maximal common subgraph defined for vertex mapping
. A binary operation defined for graphs constructed over the same vertex set enables us to decompose the reaction graph
into the sum of prototype reaction graphs. A decomposition of an overall reaction graph can be advantageously used for the construction of a reaction network. An oriented path in this network beginning at
and ending at
corresponds to a breakdown of the transformation
into a sequence of intermediates. 相似文献