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排序方式: 共有1177条查询结果,搜索用时 15 毫秒
991.
A study was undertaken to compare beta-glucuronidase-positive Escherichia coli counts produced by the ISO-GRID hydrophobic grid membrane filter method using SD-39 agar (test method) with those produced by AOAC Official Method 990.11, an existing ISO-GRID method using lactose monensin glucuronate agar and buffered MUG agar (reference method). The methods were evaluated using 21 food products, with three independent lots of five replicate samples analyzed per product by both methods. The test and reference methods were statistically equivalent for 19 of the 21 products; frozen, raw ground lamb produced significantly higher counts using the reference method, whereas counts obtained from cottage cheese were significantly higher using the SD-39 agar-based method. 相似文献
992.
The aims of the present study were: (1) to evaluate BODIPY forskolin as a suitable fluorescent marker for membrane adenylyl cyclase (AC) in living enteric neurons of the guinea-pig ileum; (2) to test the hypothesis that AC is distributed in several subpopulations of enteric neurons; (3) to test the hypothesis that the distribution of AC in the myenteric plexus is not unique to AH/Type 2 neurons. BODIPY forskolin was used to assess the co-distribution of AC in ganglion cells expressing the specific calcium-binding proteins (CaBPs), calretinin, calbindin-D28, and s-100. Cultured cells or tissues were incubated with 10 microM BODIPY forskolin for 30 min and fluorescent labeling was monitored by using laser scanning confocal microscopy. BODIPY forskolin stained the cell soma, neurites, and nerve varicosities of Dogiel Type I or II neurons. About 99% of myenteric and 27% of submucous ganglia contained labeled neurons. About 14% of myenteric and 3% of submucous glia with immunoreactivity for s-100 protein displayed BODIPY forskolin fluorescence. BODIPY forskolin differentially labeled myenteric neurons immunoreactive for calbindin-D28 (80%) and calretinin (17%). The majority (63%) of BODIPY forskolin-labeled myenteric neurons displayed no immunoreactivity for either CaBP. In submucous ganglia, the dye labeled 44.6% of calretinin-immunoreactive neurons, representing 21% of all labeled neurons; it also labeled varicose nerve fibers running along blood vessels. AC thus exists in myenteric Dogiel type II/AH neurons, enteric cholinergic S/Type 1 neurons, and other unidentified non-cholinergic S/Type 1 neurons. Our data also support the hypothesis that AC is expressed in distinct functional subpopulations of AH and S neurons in enteric ganglia, and show that BODIPY forskolin is a suitable marker for AC in immunofluorescence co-distribution studies involving living cells or tissues. 相似文献
993.
JV Spencer WW Newcomb DR Thomsen FL Homa JC Brown 《Canadian Metallurgical Quarterly》1998,72(5):3944-3951
The herpes simplex virus type 1 (HSV-1) capsid is a T=16 icosahedral shell that forms in the nuclei of infected cells. Capsid assembly also occurs in vitro in reaction mixtures created from insect cell extracts containing recombinant baculovirus-expressed HSV-1 capsid proteins. During capsid formation, the major capsid protein, VP5, and the scaffolding protein, pre-VP22a, condense to form structures that are extended into procapsids by addition of the triplex proteins, VP19C and VP23. We investigated whether triplex proteins bind to the major capsid-scaffold protein complexes as separate polypeptides or as preformed triplexes. Assembly products from reactions lacking one triplex protein were immunoprecipitated and examined for the presence of the other. The results showed that neither triplex protein bound unless both were present, suggesting that interaction between VP19C and VP23 is required before either protein can participate in the assembly process. Sucrose density gradient analysis was employed to determine the sedimentation coefficients of VP19C, VP23, and VP19C-VP23 complexes. The results showed that the two proteins formed a complex with a sedimentation coefficient of 7.2S, a value that is consistent with formation of a VP19C-VP23(2) heterotrimer. Furthermore, VP23 was observed to have a sedimentation coefficient of 4.9S, suggesting that this protein exists as a dimer in solution. Deletion analysis of VP19C revealed two domains that may be required for attachment of the triplex to major capsid-scaffold protein complexes; none of the deletions disrupted interaction of VP19C with VP23. We propose that preformed triplexes (VP19C-VP23(2) heterotrimers) interact with major capsid-scaffold protein complexes during assembly of the HSV-1 capsid. 相似文献
994.
A special selection of the Euler angles is made, according to which one axis of the rotating coordinate system is related to the center of mass of electrons. The hierarchy of the hyperspherical coordinates R, α, and θ allows sequential quantization with respect to these variables to be performed. The complex structure of the potential with respect to the R coordinate leads to the use of a quasi-classical approximation. The energy spectrum of doubly excited S-states of a He atom is determined. The results are compared to other published data. 相似文献
995.
A. L. Musatov Yu. V. Gulyaev K. R. Izrael’yants E. F. Kukovitskii N. A. Kiselev O. Yu. Maslennikov I. A. Guzilov A. B. Ormont E. G. Chirkova 《Journal of Communications Technology and Electronics》2007,52(6):714-716
A compact X-ray tube with a field emitter based on carbon nanotubes is developed. Over a long time interval, the X-ray tube maintains an anode current of 300 μA, an anode voltage of 10 kV, and the stable characteristics of the field emitter. 相似文献
996.
M. A. Kiselev 《Journal of Computer and Systems Sciences International》2007,46(5):815-825
An approach to synthesis of aircraft control algorithms minimizing the time of executing a turn is proposed. The specific feature of the approach is that the algorithms are developed without analytical solution of the optimal control problem, which causes considerable difficulties for such complex technical system as an aircraft. 相似文献
997.
E. P. Bernard R. E. Bogtnev V. V. Khmelenko V. Kiryukhin S. I. Kiselev D. M. Lee 《Journal of Low Temperature Physics》2004,134(1-2):169-174
Impurity-helium solids created by injecting deuterium atoms and molecules into superfluid 4He have been studied via electron spin resonance (ESR) and x-ray diffraction methods. We measured the g-factor, the hyperfine constant and the spin-lattice relaxation time of D atoms in D-D2-He solids. These measurements show that D atoms are mainly stabilized in D2 clusters. Using an x-ray method we found the size of D2 clusters to be ~90Å in diameter and the densities of D2 molecules in the samples to be of order 2.5?1021 cm?3 . The highest average concentration of D atoms achieved in D-D2-He solids was ~1.5?1018 cm?3 . The local concentrations of D atoms within D2 clusters is found to be large (~2?1019 cm?3). 相似文献
998.
V. A. Andrianov A. Bleile P. Egelhof S. Kraft A. Kiseleva O. Kiselev H. J. Meier J. P. Meier 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2004,520(1-3):84-86
The energy resolution of calorimetric low-temperature detectors for heavy ions has been analyzed. It is shown that the contribution of base line noise is small. The energy resolution is determined by intrinsic fluctuations of the detector signal. An incomplete energy thermalization during the stopping process of the heavy ion, the dependence of signal shape on impact position and fluctuations of the Al-TES thermometer response are considered as main sources of detector line broadening. Test measurements with 5 MeV -particles are presented. 相似文献
999.
DJ Ahnen P Feigl G Quan C Fenoglio-Preiser LC Lovato PA Bunn G Stemmerman JD Wells JS Macdonald FL Meyskens 《Canadian Metallurgical Quarterly》1998,58(6):1149-1158
We assessed Ki-ras mutations by single-strand conformation polymorphism followed by DNA sequencing, p53 expression by immunohistochemistry, ploidy status, and S-phase fraction in 66 stage II and 163 stage III colon cancer patients enrolled on a randomized trial of surgery followed by observation or adjuvant levamisole or 5-fluorouracil (5FU) plus levamisole (Intergroup Trial 0035) to see whether these factors were independently associated with survival or with differential effects of adjuvant therapy. A Cox proportional hazards survival model was used to describe marker effects and therapy by marker interactions, with adjustment for the clinical covariates affecting survival. A Bonferroni adjustment was used to account for multiple testing. Mutation of the Ki-ras gene was found in 41% of the cancers and was associated with a poor prognosis in stage II but not stage III. In stage II, 7-year survival was 86% versus 58% in those with wild type versus Ki-ras mutations. After adjustment for treatment and clinical variables, the hazard ratio (HR) for death was 4.5; 95% confidence interval (CI), 1.7-12.1 (P = 0.012). p53 overexpression was found in 63% of cancers and was associated with a favorable survival in stage III but not stage II. Seven-year survival in stage III was 56% with p53 overexpression versus 43% with no p53 expression (HR, 2.2; 95% CI, 1.3-3.6; P = 0.012). Aneuploidy was more common in stage III than in stage II (66 versus 47%; P = 0.009) but was not independently related to survival in either group. The proliferative rate was greater in aneuploid than in diploid cancers but was not related to survival. There was no benefit of adjuvant therapy in stage II nor in any of the stage II subgroups defined by mutational status. In stage III, adjuvant therapy with 5FU plus levamisole improved 7-year survival in patients with wild-type Ki-ras (76 versus 44%; HR, 0.4; 95% CI, 0.2-0.8) and in those without p53 overexpression (64 versus 26%; HR, 0.3; 95% CI, 0.1-0.7). Adjuvant therapy did not benefit those with Ki-ras mutations or p53 overexpression. The effects of adjuvant therapy did not differ according to ploidy status or proliferative rate. Ki-ras mutation is a significant risk factor for death in stage II, and the absence of p53 expression is a significant risk factor for death in stage III colon cancer after adjustment for treatment and clinical covariates. Exploratory analyses suggest that patients with stage III colon cancer with wild-type Ki-ras or no p53 expression benefit from adjuvant 5FU plus levamisole, whereas those with Ki-ras mutations or p53 overexpression do not. An independent study will be required to determine whether response to adjuvant therapy in colon cancer depends on mutational status. 相似文献
1000.
A. B. Konovalov A. N. Kiselev V. V. Vlasov 《Pattern Recognition and Image Analysis》2006,16(2):249-255
Spatial resolution of computed tomography using two modified algebraic reconstruction algorithms is studied theoretically
and experimentally for the case when several projections are recorded. A simple setup with gamma rays recording on a screened
photographic film is used for registration of X-ray projections. A standard phantom with periodic spatial structures in the
form of cylindrical rods is irradiated, its cross section is reconstructed, and the modulation transfer function is estimated.
It is shown that the multiplicative algebraic reconstruction technique optimizing the entropy provides a better resolution
(about 1.5 mm for four projections). 相似文献