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991.
By adapting noise filtering to individual pulse intervals, the Preloaded Filter (PLF) pulse processor (1) combines high resolution with optimum throughput efficiency. As a consequence, its output pulse interval distribution contains strong non-random components which render conventional ADC dead-time correction an impossibility. Quantitative correction of dead-time and pileup losses of the PLF processor may be achieved, however, with the Virtual Pulse Generator (2), together with a new, distribution-independent method of measuring ADC losses which is based on a pulse counting technique.  相似文献   
992.
2-(-Oximinoethyl)-2-methylthiirane was obtained by the reaction of 3,4-dibromo-3-methyl-2-butanone oxime with sodium sulfide. At the same time, the O-carbamoyl derivative of the ,-dibromo oxime was converted to the corresponding substituted ,-unsaturated oxime under the same conditions. Thiirane oxime, like its O-carbamoyl derivative, underwent the desulfuration that is characteristic for thirranes under the influence of tributylphosphine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 751–753, June, 1982.  相似文献   
993.
The principles and techniques of dynamic light scattering (DLS) are outlined and its application to the study of suspensions of interacting colloidal particles is discussed. We show how, under appropriate conditions, DLS can measure long-time collective and self-diffusion coefficients as well as study short-time motions (characterized by the cumulants). These theoretical considerations are illustrated by experimental data. Finally, we discuss the relevance of certain characteristic timescales to theories of the diffusion of interacting particles.  相似文献   
994.
The construction and analytical applications of an improved liquid-membrane electrode for salicylate are described. Tests of various combinations of symmetrical tetraalkylammonium salicylates and solvents showed that the best liquid ion-exchanger was tetraoctylammonium salicylate in p-nitrocumene. Electrode response is Nernstian down to 2 × 10?5 M. Major interferences are perchlorate and periodate; the working pH range is 6–9. The electrode is useful for direct potentiometric determinations of salicylate in pharmaceutical preparations.  相似文献   
995.
It was derived theoretically that a sharp end-point of this spectrophotometrical titration is defined, in order of importance, by: 1. *KC ? *KI (numerically speaking, log*KC*KI should be at least 4); 2. *KI being large (numerically e.g. 104-105); this is already reached by choosing a high pH; 3. it being low; 4. mt being as high as possible.  相似文献   
996.
Serum for reference pools of in vivo polychlorinated biphenyls (PCBs) was obtained from four goats that had received one dose (100 mg kg-1) of a selected technical Aroclor (AR) (1016, 1242, 1254 or 1260) and were allowed to recover for 30 d. These pools were used to assess the differences in an analytical method that determines and quantifies PCBs using packed-column gas chromatography (PCGC) (quantified on the basis of mean mass percent. data for grouped PCB peaks) and capillary-column gas chromatography (CCGC) (quantified on the basis of percent. composition data for specific congeners). With CCGC, results were statistically significantly different (p less than or equal to 0.0002) from results with PCGC for ARs 1016, 1242 and 1254 but not for AR 1260 (p = 0.23). When comparing these gas chromatographic methods using bovine serum spiked in vitro with the same ARs at 17-25 p.p.b., it was found that the methods were not statistically significantly different for any of the ARs (p = 0.30-0.92). Levels of serum PCB determined by the two methods for 12 persons, divided into two groups according to exposure, were compared using the paired t-test. Group 1 consisted of three persons with dietary and/or environmental exposure; one with dietary and/or environmental exposure in addition to occupational exposure dating back 20 years. Group 2 consisted of eight persons with recent occupational exposure.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
997.
998.
The CD of saturated iridoids containing a 2.9-dioxatricyclo[4.3.1.03,7] decan skeleton derived from valepotriates is determined by the acetal chromophore. For the less symmetric ring system of 1,6-anhydro hexapyranoses the sign of this CD is predictable. The vicinal effect for enones and diketones in this series is appreciable. A new rule for the correlation between the CD around 190–205 nm of enol ethers and their absolute conformation is given; the same reasoning is applicable to explain the known rules for cisoid and transoid vinyl cyclo-propanes.  相似文献   
999.
Luminescence of Eu2+ Ions in Fluosilicates MSiF6 (M = Sr, Ba) A pure f → f emission is detected in Eu2+ doped SrSiF6 and BaSiF6. Because of the strong ionic bonding of europium a large gap occurs between the bottom of the 5d band and the 6P7/2 emission level (3000 cm?1 at 300 K). The emission is very intense under low pressure mercury excitation and decreases slowly with temperature.  相似文献   
1000.
Pyridinium salts     
New 4- (benzazol-2-yl)pyridinium salts have been synthesized. Their reduction in a neutral medium with sodium tetrahydroborate has given 2-(1,2,5,6-tetrahydropyridin-4-yl)benzazoles. The catalytic hydrogenation of the latter leads to piperidine derivatives which have also been synthesized by an independent route.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 104–107, January, 1974.  相似文献   
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