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101.
102.
103.
Dr. K. Löns 《Zeitschrift für Physik A Hadrons and Nuclei》1968,215(1):1-16
Differential cross sections for direct pair production by electrons with total energiesE 0=5.511 and 32 MeV in copper are calculated in lowest order of pertubation theory and Born approximation, including the matrix elements of the electron exchange effect. Integration over particle angles and — in the case ofE 0=32 MeV — over the energy of one outgoing electron was performed numerically on an IBM 7044 computer by using Gaussian quadrature formulas in FORTRAN-programs. The results forE 0=5.511 MeV show a severe reduction of the differential cross section due to the exchange effect, while the results for 32 MeV are in fairly good agreement with the pair production experiment performed byCriegee in 1959. 相似文献
104.
Mössbauer spectroscopy and X-ray diffraction measurements have been done on (Ti1–x
Nb
x
)Fe2 compounds in order to investigate the effect of Nb on the magnetic properties of TiFe2. The experimental results show that Nb enters the lattice by filling Ti sites, thereby forming a continuous phase over the whole range of Nb concentrations. The Mössbauer spectra at 80 K fitted with a magnetic hyperfine field distribution show a continuous decrease of the average magnetic hyperfine field with increasing Nb concentration, as well as several different magnetic configurations forx0.3. 相似文献
105.
Capps KL McLaughlin EM Murray AW Aldus CF Wyatt GM Peck MW van Amerongen A Ariëns RM Wichers JH Baylis CL Wareing DR Bolton FJ 《Journal of AOAC International》2004,87(1):68-77
An interlaboratory study was conducted for the validation of 3 methods for the detection of all verotoxin-producing Escherichia coli (VTEC) in foods. The methods were a multi-analyte 1-step lateral flow immunoassay (LFIA) for detection of E. coli O157 and verotoxin (VT); an enzyme-linked immunosorbent assay targeted against VT1, VT2, and VT2c (VT-ELISA); and a polymerase chain reaction (PCR) method for detection of VT genes (VT-PCR). Aliquots (25 g or 25 mL) of 4 food types (raw minced [ground] beef, unpasteurized milk, unpasteurized apple juice [cider], and salami) were individually inoculated with low numbers (<9 to 375 cells/25 g) of 6 test strains of E. coli (serogroups O26, O103, O111, O145, and O157) with differing VT-producing capabilities. Five replicates for each test strain and 5 uninoculated samples were prepared for each food type. Fourteen participating laboratories analyzed samples using the LFIA, 9 analyzed the samples by ELISA, and 9 by PCR. The LFIA for O157 and VT had a specificity (correct identification of negative samples) of 92 and 94%, respectively, and a sensitivity (correct identification of positive samples) of 94 and 55%, respectively. The VT-ELISA and VT-PCR had a specificity of 98 and 99%, respectively, and a sensitivity of 89 and 72%, respectively. 相似文献
106.
Alise Babre Andis Kalvāns Konrāds Popovs Inga Retiķe Aija Dēliņa Rein Vaikmäe 《Isotopes in environmental and health studies》2016,52(6):706-725
A new data set of δ2H and δ18O in the groundwater from the central part of the Baltic Artesian Basin is presented. The hydrogeological section is subdivided into stagnation, slow exchange and active exchange zones. Na–Ca–Cl brine found at the deepest part – the stagnation zone – is characterized by δ18O values above ?5?‰ and δ2H values approaching ?40?‰ with respect to Vienna Standard Mean Ocean Water. The slow exchange zone where waters of mostly intermediate salinity reside is characterized by δ18O values around ?11.7?‰ and δ2H values around ?85.3?‰. Mean δ18O and δ2H values of the fresh groundwater in the active water exchange zone are ?11.1 and ?79.9?‰, respectively. Characteristically, the groundwater in the active and slow exchange zone is isotopically more depleted compared with the precipitation values observed, and the depletion increases with depth down to the level where strongly enriched brines are encountered. 相似文献
107.
Jānis Cīrulis 《Linear and Multilinear Algebra》2016,64(8):1498-1508
Star partial order was initially introduced for semigroups and rings with (proper) involution. In particular, this order has recently been studied on Rickart *-rings. It is known that the star order in such rings can be characterized by conditions not involving involution explicitly. Owing to these characterizations, the order can be extended to certain special Rickart rings named strong in the paper; this extension is the objective of the paper. The corresponding order structure of strong Rickart rings is studied more thoroughly. In particular, the most significant lattice properties of star-ordered Rickart *-rings are successfully transferred to strong Rickart rings; also several new results are obtained. 相似文献
108.
Temporal Control of Gelation and Polymerization Fronts Driven by an Autocatalytic Enzyme Reaction 下载免费PDF全文
Elizabeth Jee Dr. Tamás Bánsági Jr. Dr. Annette F. Taylor Prof. John A. Pojman 《Angewandte Chemie (International ed. in English)》2016,55(6):2127-2131
Chemical systems that remain kinetically dormant until activated have numerous applications in materials science. Herein we present a method for the control of gelation that exploits an inbuilt switch: the increase in pH after an induction period in the urease‐catalyzed hydrolysis of urea was used to trigger the base‐catalyzed Michael addition of a water‐soluble trithiol to a polyethylene glycol diacrylate. The time to gelation (minutes to hours) was either preset through the initial concentrations or the reaction was initiated locally by a base, thus resulting in polymerization fronts that converted the mixture from a liquid into a gel (ca. 0.1 mm min?1). The rate of hydrolytic degradation of the hydrogel depended on the initial concentrations, thus resulting in a gel lifetime of hours to months. In this way, temporal programming of gelation was possible under mild conditions by using the output of an autocatalytic enzyme reaction to drive both the polymerization and subsequent degradation of a hydrogel. 相似文献
109.
110.
A well known chaotic mapping in symbol space is a shift mapping.However,other chaotic mappings in symbol space exist too.The basic change is to consider the process not only at a set of times which are equally spaced,say at unit time apart(a shift mapping),but at a set of times which are not equally spaced,say if the unit time can not be fixed.The increasing mapping as a generalization of the shift mapping and the k-switch mapping are introduced.The increasing and k-switch mappings are chaotic. 相似文献