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排序方式: 共有173条查询结果,搜索用时 15 毫秒
1.
The authors studied the content of volatile N-nitrosamines (NA) in the most common sausage products. It was established that the total content of NA in sausage products is not high and ranges from trace amounts up to 10 micrograms/kg product. The allowable doses of nitrite in the sausage manufacture being low, no relationship was discovered between the content of NA and residual nitrite in meat products. 相似文献
2.
To identify the predictive factors for testicular sperm extraction (TESE) and to understand the pathology associated with TESE, we carried out a prospective study in 40 consecutive men with azoospermia due to primary gonadal failure. The main outcome measure was the retrieval of at least one testicular spermatozoon. Endocrine and biophysical profiles, testicular histology, Johnsen score and testicular spermatids were used as predictors of sperm extraction. Spermatogenesis was quantified with the Johnsen score. A variable pattern of spermatogenesis was common, being present in 20 (50%) patients. Visualisation of testicular spermatids on testicular histology showed a strong association with TESE (P < 0.0001). Statistically significant differences were detected in plasma follicle stimulating hormone (FSH) and testicular volume between patients who had hypospermatogenesis and Sertoli cell-only or maturation arrest. There were no significant differences in Johnsen score, biophysical and endocrine profiles between the groups with successful and failed TESE. However, a statistically significant trend occurred with changes in histological pattern [chi2 for trend, P = 0.001; Pearson's coefficient (r) = 0.6], Johnsen score (P = 0.022; r = 0.5), testicular volume (P = 0.01; r = 0.5) and plasma FSH concentrations (P = 0.044; r = 0.4), albeit to a limited degree. Difference in the interpretation of histological patterns with different assessors was observed. The type of occupation or risk factors for azoospermia showed no association with testicular pathology or TESE. Variable histological patterns in different tubules in the same individual may explain the poor correlation of TESE with endocrine and biophysical profiles, Johnsen score and histological pattern. Differences in the amount of tissue used for TESE and histopathology, and misinterpretation of testicular histology rather than failure to quantify spermatogenesis may explain the poor correlation between histological patterns and TESE. Testicular spermatids predicted TESE. However, considerable overlap in values means that no single variable can provide a perfect discrimination between the groups with successful and failed TESE. 相似文献
3.
The distribution of microamounts of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y nitrates between aqueous HNO3 solutions and fullerene black impregnated with diphenyl(dibutylcarbamoylmethyl)phosphine oxide (L) was studied. The influence exerted on the efficiency of REE recovery by the HNO3 concentration in the aqueous phase and concentration of L in the sorbent phase was examined. The degree of REE recovery increases on adding HClO4 to the aqueous phase. 相似文献
4.
A. V. Vodopyanov M. Yu. Glyavin S. V. Golubev A. G. Luchinin S. V. Razin M. I. Safronova A. V. Sidorov A. P. Fokin 《Technical Physics Letters》2017,43(2):186-189
We have measured the density of plasma (electron concentration) in discharge maintained in inhomogeneous argon flow under the action of high-power pulsed radiation of gyrotron (frequency, 0.67 THz; power 40 kW; pulse duration, 20–30 μs) in a range of background gas pressures in the discharge chamber from 10–3 to 300 Torr. The electron concentration at low pressures (10–3 to 7 Torr) was determined using Starkeffect induced broadening of the Hα atomic emission line (656.3 nm) of hydrogen present in discharge as a small impurity in residual gases. The maximum observed Stark broadening of the Hα line corresponded to a plasma density on the order of 2 × 1016 cm–3, which exceeded the critical value for the given frequency of radiation sustaining the discharge. At background pressures above 7 Torr, the plasma density was estimated from analysis of the spatiotemporal patterns and waveforms of discharge glow in the visible spectral range. These estimations gave electron concentrations on the level of (1–2) × 1015 cm–3. 相似文献
5.
ABSTRACT A method and a device for determination of the effective diffusion coefficient of active solvents in composite polymeric materials (CPM) based on cellulose derivatives are proposed and examined. This method accounts for anomalous mass transfer phenomena, considerable shrinkage and changes of sorption capacity of the CPM specimen allowing selection of the rational technological regime. Results of experimental studies on diffusion of acetone and ethanol in cellulose nitrate with various degrees of substitution are given as examples. 相似文献
6.
R. V. Shafigulin A. V. Bulanova P. P. Purygin A. V. Konstantinov I. A. Safronova 《Protection of Metals and Physical Chemistry of Surfaces》2011,47(6):773-777
Some physicochemical regularities of the sorption of azole derivatives of benzoic acid in the course of reversed-phase high-performance
liquid chromatography are discussed. Single- and multiparameter dependences of the retention factor on physicochemical properties
of sorbate molecules are obtained. 相似文献
7.
Unmodified and hybrid membranes based on Nafion and carbon nanotubes have been synthesized by hot pressing from a mixture of polymer and dopant powders. The water uptake, ionic conductivity under different conditions, and diffusion permeability of the membranes for HCl and methanol solutions have been studied. The hybrid membranes are characterized by high water uptake and proton conductivity in contact with water and low diffusion permeability for hydrochloric acid solution. In contact with water, the conductivity of the samples modified with 1 wt % carbon nanotubes is 0.070 S/cm; the diffusion permeability of a 0.1 M HCl solution is 2.43 × 10–7 cm2/s. 相似文献
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