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排序方式: 共有3722条查询结果,搜索用时 11 毫秒
41.
K. G. Savin I. P. Golubeva Yu. V. Prokopenko 《Radioelectronics and Communications Systems》2016,59(5):229-236
A new method for calculating the frequency and power characteristics of different modes of a microwave metal-dielectric resonator has been proposed. The results of measurements of experimental specimens are presented that are in good agreement with calculation results. The relationships of the frequency and power characteristics of a resonator as a function of its geometrical and electrophysical parameters were obtained by using the method of partial regions. A high sensitivity of the main mode resonant frequency to the thickness of air inhomogeneity was detected. In this case the introduction of inhomogeneity increases the resonator Q-factor. Thus, the proposed design can be used as a high-Q tunable resonator. 相似文献
42.
JS Smythe FA Spring B Gardner SF Parsons PA Judson DJ Anstee 《Canadian Metallurgical Quarterly》1995,85(10):2929-2936
This report describes the production and characterization of 13 rodent monoclonal antibodies to the human erythrocyte anion transport protein AE1 (syn. band 3). Eleven antibodies (4 murine and 7 rat) recognize epitopes dependent on the integrity of the third extracellular loop of the protein. Two antibodies (1 murine and 1 rat) recognize epitopes on the N-terminal cytoplasmic domain. Quantitative binding studies using radioiodinated IgG and Fab fragments of antibodies to extracellular epitopes on AE1 ranged from 77,000 to 313,000 (IgG) and from 241,000 to 772,000 (Fab) molecules bound at saturation. The results indicate that the epitopes recognized by different antibodies vary in their accessibility and suggest that there is heterogeneity in the organization of individual AE1 molecules in the red blood cell membrane. Quantitative binding studies on South East Asian ovalocytes using several antibodies to AE1 and an anti-Wrb show a marked reduction in the number of antibody molecules bound at saturation. These results are consistent with the existence of highly cooperative interactions between transmembrane domains of AE1 in normal erythrocytes and the disruption of these interactions in the variant AE1 found in South East Asian ovalocytes. 相似文献
43.
SH Kaufmann D Peereboom CA Buckwalter PA Svingen LB Grochow RC Donehower EK Rowinsky 《Canadian Metallurgical Quarterly》1996,88(11):734-741
BACKGROUND: Topotecan (TPT) is a topoisomerase I poison that exhibits antineoplastic activity. Analysis of the cytotoxic effects of combinations of TPT and other anticancer agents has been limited. PURPOSE: We assessed the cytotoxic effects produced by combinations of TPT and other antineoplastic agents in experiments involving multiple human cancer cell lines of diverse histologic origins. METHODS: The cytotoxic effects of various antimetabolites (fluorouracil, methotrexate, or cytarabine), antimicrotubule agents (vincristine or paclitaxel [Taxol]), DNA alkylating agents (melphalan, bis[chloroethyl]nitrosourea [BCNU], or 4-hydroperoxycyclophosphamide [4HC]), and a DNA-platinating agent (cisplatin), alone and in combination with TPT, were measured in clonogenic (i.e., colony-forming) assays. HCT8 ileocecal adenocarcinoma, A549 non-small-cell lung carcinoma, NCI-H82ras(H) lung cancer, T98G glioblastoma, and MCF-7 breast cancer cell lines were used in these assays. The data were analyzed by the median effect method, primarily under the assumption that drug mechanisms of action were mutually nonexclusive (i.e., completely independent of one another). For each level of cytotoxicity (ranging from 5% to 95%), a drug combination index (CI) was calculated. A CI less than 1 indicated synergy (i.e., the effect of the combination was greater than that expected from the additive effects of the component agents), a CI equal to 1 indicated additivity, and a CI greater than 1 indicated antagonism (the effect of the combination was less than that expected from the additive effects of the component agents). RESULTS: When the mechanisms of drug action were assumed to be mutually nonexclusive, virtually all CIs for combinations of TPT and either antimetabolites or antimicrotubule agents revealed cytotoxic effects that were less than additive. The CIs calculated at low-to-intermediate levels of cytotoxicity for combinations of TPT and the DNA alkylating agents melphalan, BCNU, and 4HC also showed drug effects that were less than additive; in most cases, however, nearly additive or even synergistic effects were observed with these same drug combinations at high levels of cytotoxicity (i.e., at > or = 90% inhibition of colony formation). Results obtained with combinations of TPT and cisplatin varied according to the cell line examined. With A549 cells, less than additive effects were seen at low-to-intermediate levels of cytotoxicity, and more than additive effects were seen at high levels of cytotoxicity. With NCI-H82ras(H) cells, synergy was observed over most of the cytotoxicity range. CONCLUSIONS AND IMPLICATIONS: TPT cytotoxicity appears to be enhanced more by combination with certain DNA-damaging agents than by combination with antimetabolites or antimicrotubule agents. Interactions between TPT and other drugs can vary depending on the cell type examined. Further investigation is required to determine the basis of the observed effects and to determine whether these in vitro findings are predictive of results obtained in vivo. 相似文献
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46.
VS Caviness DN Kennedy C Richelme J Rademacher PA Filipek 《Canadian Metallurgical Quarterly》1996,6(5):726-736
Volumetric magnetic resonance image (MRI)-based morphometry was performed on the brains of 30 normal children (15 males and 15 males) with a mean age of 9 years (range 7-11 years). This age range lies in a late but critical phase of brain growth where not volumetric increment will be small but when the details of brain circuity are being fine-tuned to support the operations of the adult brain. The brain at this age is 95% the volume of the adult brain. The brain of the female child is 93% the volume of the male child. For more than 95% of brain structures, the volumetric differences in male and female child brain are uniformly scaled to the volume difference of the total brain in the two sexes. Exceptions to this pattern of uniform scaling are the caudate, hippocampus and pallidum, which are disproportionately larger in female than male child brain, and the amygdala, which is disproportionately smaller in the female child brain. The patterns of uniform scaling are generally sustained during the final volumetric increment in overall brain size between age 7-11 and adulthood. There are exceptions to this uniform scaling of child to adult brain, and certain of these exceptions are sexually dimorphic. Thus, with respect to major brain regions, the cerebellum in the female but not the male child is already at adult volume while the brainstem in both sexes must enlarge more than the brain as a whole. The collective subcortical gray matter structures of the forebrain of the female child are already at their adult volumes. The volumes of these same structures in the male child, by contrast, are greater than their adult volumes and, by implication, must regress in volume before adulthood. The volume of the central white matter, on the other hand, is disproportionately smaller in female than male child brain with respect to the adult volumes of cerebral central white matter. By implication, relative volumetric increase of cerebral central white matter by adulthood must be greater in the female than male brain. The juxtaposed progressive and regressive patterns of growth of brain structures implied by these observations in the human brain have a soundly established precedent in the developing rhesus brain. There is emerging evidence that sexually dimorphic abnormal regulation of these terminal patterns of brain development are associated with gravely disabling human disorders of obscure etiology. 相似文献
47.
AA Bakova BD Brondz OA Fedorkina VA Gusev AI Gordienko IuS Krivoshein IuL Krivorutchenko TG Prokopenko IA Popov 《Canadian Metallurgical Quarterly》1994,39(4):187-189
The possibilities of using influenza A (Leningrad) 385/80 (H3N2) virus matrix protein-specific FITC-labeled D8 monoclonal antibodies in immunofluorescence assays were investigated. The virus antigen accumulation was detected in chorioallantoic cells of chick embryos. Exhibiting the type-specific properties, the fluorescent antibodies stain the perinuclear space, cytoplasmic membrane, and granular structures in the cytoplasm of infected cells. The haemagglutination test tires in the corresponding specimens were at least 1:16. 相似文献
48.
We present an HPLC method for the determination of amino acids in plasma. The method is based on automated precolumn derivatization of amino acids with o-phthalaldehyde, separation of the derivatives by reversed-phase chromatography, and quantification by fluorescence detection. Complete separation was achieved within 12 min. Total analysis time, including derivatization, chromatography, and reequilibration of the column, was 17 min. The assay was linear from 5 to 800 mumol/L for all amino acids. Recovery of amino acids added to plasma samples was 96-106%, except for tryptophan (89%). Within-run precision (CV) was 1.8-6.4%, and between-run precision was 2.1-7.2%. The method can be used for determining primary amino acids in plasma and cerebrospinal fluid. The simple sample preparation and short analysis time make the method particularly suitable for routine analysis of large series of samples. 相似文献
49.
Effect of vitamin A supplementation on diarrhoea and acute lower-respiratory-tract infections in young children in Brazil 总被引:1,自引:0,他引:1
ML Barreto LM Santos AM Assis MP Araújo GG Farenzena PA Santos RL Fiaccone 《Canadian Metallurgical Quarterly》1994,344(8917):228-231
A beneficial effect of periodic vitamin A supplementation on childhood mortality has been demonstrated, but the effect on morbidity is less clear. We investigated the effect of vitamin A supplementation on diarrhoea and acute lower-respiratory-tract infections (ALRI) in children from northeastern Brazil in a randomised, double-blind, placebo-controlled community trial. 1240 children aged 6-48 months were assigned vitamin A or placebo every 4 months for 1 year. They were followed up at home three times a week, and data about the occurrence and severity of diarrhoea and ALRI were collected. Any child with cough and respiratory rate above 40 breaths per min was visited by a paediatrician. The overall incidence of diarrhoea episodes was significantly lower in the vitamin-A-supplemented group than in the placebo group (18.42 vs 19.58 x 10(-3) child-days; rate ratio 0.94 [95% Cl 0.90-0.98]). The benefit of supplementation was greater as regards severe episodes of diarrhoea; the incidence was 20% lower in the vitamin A group than in the placebo group (rate ratio 0.80 [0.65-0.98]). With the standard definition of diarrhoea (> or = 3 liquid or semi-liquid stools in 24 h) the effect of vitamin A on mean daily prevalence did not reach significance, but as the definition of diarrhoea was made more stringent (increasing number of stools per day), a significant benefit became apparent, reaching for diarrhoea with 6 or more liquid or semi-liquid stools in 24 h a 23% lower prevalence. We found no effect of vitamin A supplementation on the incidence of ALRI. The reduction in severity of diarrhoea may be the most important factor in the lowering of mortality by vitamin A supplementation. 相似文献
50.