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41.
The occurrence of hemispherical corroding pits in metal surfaces has been known for many years, and qualitative explanations have been given to explain the phenomenon in terms of passivation at the uncorroded flat surface. However, the quantitative solution of potential distribution in such a system, which would be necessary for a test of experimental data, has not been made. The problem is complicated by the discontinuity in surface flux at the edge of the pit. The flux normal to the surface inside the pit can be assumed constant over the whole surface since the pit remains hemispherical during corrosion. However, at the pit edge the normal flux is abruptly reduced to zero, and the planar surface acts essentially as an insulator. 相似文献
42.
K. M. Hanson G. S. Cunningham R. J. McKee 《International journal of imaging systems and technology》1997,8(6):506-512
Deformable geometric models can be used in the context of Bayesian analysis to solve ill-posed tomographic reconstruction problems. The uncertainties associated with a Bayesian analysis may be assessed by generating a set of random samples from the posterior, which may be accomplished using a Markov Chain Monte Carlo (MCMC) technique. We demonstrate the combination of these techniques for a reconstruction of a two-dimensional object from two orthogonal noisy projections. The reconstructed object is modeled in terms of a deformable geometrically defined boundary with a uniform interior density yielding a nonlinear reconstruction problem. We show how an MCMC sequence can be used to estimate uncertainties in the location of the edge of the reconstructed object. © 1997 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 8, 506–512, 1997 相似文献
43.
Calmodulin-dependent protein kinase II (Cam kinase II) is known to desensitise epidermal growth factor receptor (HER-1) tyrosine kinase activity by a process involving phosphorylation at serines 1046/47 in the cytoplasmic tail. We have developed an experimental system to investigate phosphorylation of the related HER-2/c-erbB2 proto-oncogene utilising purified Cam kinase II and recombinant glutathione-S-transferase (GST) fusion proteins. The cDNA for rat Cam kinase II-alpha was transfected into human embryonic kidney (HEK) 293 fibroblasts and the expressed protein purified to homogeneity by calmodulin-agarose affinity chromatography. A GST fusion protein comprising residues 1126-1255 of HER-2 was phosphorylated by purified Cam kinase II, in contrast to a GST protein comprising residues 1005-1125. Phosphoamino-acid analysis and site-directed mutagenesis indicated that HER-2 was phosphorylated on a single site at threonine-1172 which resides within a consensus Cam kinase II phosphorylation site (RAKT). HER-2 (threonine-1172-alanine), in the form of a ligand-inducible chimaera HER-1/2, was co-transfected into HEK-293 fibroblasts with a constitutively active form of Cam kinase II, followed by in vivo labelling of these cells with 32 P-orthophosphate. Immunoprecipitation of ligand-activated receptors followed by two-dimensional phosphopeptide mapping indicated that threonine-1172 in HER-2 is a newly identified in vivo site which can be hyper-phosphorylated by constitutively active Cam kinase II. In addition, when over-expressed in HEK-293 fibroblasts, HER-1/2 (threonine-1172-alanine) showed a defect in desensitisation and underwent a more sustained EGF-induced receptor autophosphorylation compared to wild-type HER-1/2. 相似文献
44.
In Alberta, cellulitis condemnations average 0.5% and are among the highest in Canada. Presently, all cellulitis-affected birds are condemned for fear of systemic infections and public health implications. In a slaughterhouse sample of 102 birds condemned with cellulitis, Escherichia coli was isolated from 83.3% of the lesions. All hearts were cultured and from 11.2% E. coli was recovered. Gross lesions of perihepatitis, infected oviducts, and arthritis were found in 11.2%, 6.7%, and 2.9% of the birds, respectively. Serotyping suggested that visceral infection occurs independent of cellulitis in at least half of the cases. There was no correlation between microscopic visceral lesions and positive bacterial cultures. Two E. coli isolates of serogroup 0157 produced no toxin and neither isolate produced CS31A, F107, or F1845 fimbriae. Cellulitis lesions ranged from 0.55 to 218.9 cm2. All lesions under 16 cm2 and 64% of lesions up to 48 cm2 were considered suitable for trimming. 相似文献
45.
RL Quigley KH Bannister MW Chisdak FL Reitknecht 《Canadian Metallurgical Quarterly》1996,62(2):570-571
Airway control and protection, in any operation, is the first priority. The presence of a T-Y stent in the proximal airway can complicate this fundamental principle. Here we describe an effective and safe technique for positive-pressure single-lung ventilation via a T-Y stent for a lung lobectomy. 相似文献
46.
Complementary medications appear to be gaining popularity among cancer patients. When we surveyed 143 advanced cancer patients attending an outpatient pain and symptom clinic at a regional cancer centre as to their use of complementary medications and nutritional supplements, we found 37% (53/143) to be making use of complementary medications. Users tended to be younger (mean age 53.3 years) and have a preference for purchase from health stores, with 61% of complementary medications being bought there. Health store staff were the primary recommenders for both men and women and especially for those over 60 years of age. Of the 197 complementary medications purchased, 78 (39.6%) were herbs, 67 (32.5%) were vitamins, 13 (6.6%) were minerals, 21 (10.7%) were other medications including shark cartilage, and 21 (10.7%) could not be identified. Both anticancer effect and the promotion of well-being were prominent among the stated reasons for using these medications. 相似文献
47.
OBJECTIVE: To determine the efficacy of genetic testing of individuals presenting with features possibly indicative of von Hippel-Lindau (VHL) disease, regardless of other relevant family and clinical details. SETTING AND PARTICIPANTS: Between September 1994 and December 1997, 16 unrelated individuals were referred to Genetic Services of Western Australia by local clinicians and by similar genetic services in other States, for VHL gene mutation analysis because of clinical manifestations suggestive of the diagnosis. METHODS: The subjects were investigated by screening for mutations in the polymerase chain reaction products of the three VHL gene exons using single-stranded conformational polymorphism analysis (SSCP). If no mutations were detected the exons were sequenced, and if no variations were found DNA was examined by Southern analysis for germinal rearrangements. RESULTS: Mutations in the VHL gene were detected in eight of 16 individuals (50%), including 3 individuals with no family history suggestive of VHL disease. Five mutations were detected by SSCP, two by gene sequencing and one by Southern analysis. Each mutation occurred only in a single family and three had not been previously reported. CONCLUSION: Genetic screening of individuals presenting with clinical features suggestive of VHL facilitates confirmation of the diagnosis, accurate genetic counselling and surveillance of at-risk family members. The necessity for costly and time-consuming screening programs can be reduced and screening directed at those carrying the mutation. Our low stringency criteria are justified for screening for VHL mutations. 相似文献
48.
ETR1 represents a prototypical ethylene receptor. Homologues of ETR1 have been identified in Arabidopsis as well as in other plant species, indicating that ethylene perception involves a family of receptors and that the mechanism of ethylene perception is conserved in plants. The amino-terminal half of ETR1 contains a hydrophobic domain responsible for ethylene binding and membrane localization. The carboxyl-terminal half of the polypeptide contains domains with homology to histidine kinases and response regulators, signaling motifs originally identified in bacteria. The putative histidine kinase domain of ETR1 was expressed in yeast as a fusion protein with glutathione S-transferase and affinity purified. Autophosphorylation of the purified fusion protein was observed on incubation with radiolabeled ATP. The incorporated phosphate was resistant to treatment with 3 M NaOH, but was sensitive to 1 M HCl, consistent with phosphorylation of histidine. Autophosphorylation was abolished by mutations that eliminated either the presumptive site of phosphorylation (His-353) or putative catalytic residues within the kinase domain. Truncations were used to delineate the region required for histidine kinase activity. An examination of cation requirements indicated that ETR1 requires Mn2+ for autophosphorylation. These results demonstrate that higher plants contain proteins with histidine kinase activity. Furthermore, these results indicate that aspects of ethylene signaling may be regulated by changes in histidine kinase activity of the receptor. 相似文献
49.
The North Central Cancer Treatment Group designed a phase II trial to assess the efficacy and toxicity of topotecan in patients with unresectable malignant pleural mesothelioma. Twenty-two previously untreated patients with unresectable pleural mesothelioma and good performance status (Eastern Cooperative Oncology Group performance status 0, 1, or 2) were enrolled on this trial from October 1993 through July 1994. Nineteen men and three women, median age 66 years (range, 44-78 years), were treated with topotecan 1.5 mg/m2 intravenously over 30 minutes daily for 5 days at 3-week intervals until toxicity, progression of disease, or a patient decided to discontinue treatment. There were seven patients with measurable disease and 15 with evaluable disease; all were assessable for response and toxicity. A total of 113 cycles of treatment were given, for a median of three cycles (range, 1-26 cycles). Myelosuppression was the most frequent toxicity. Eighteen of 21 patients (86%) experienced grade 3 or 4 neutropenia during the initial treatment cycle. The median neutrophil nadir was 0.5 x 10(3)/microl (range, 0.1-1.6 x 10(3)/microl), and the median platelet nadir was 127 x 10(3)/microl (range, 18-460 x 10(3)/microl). Other toxicities more than grade 2 included malaise (two patients), and anorexia, infection, fever, pulmonary, and cardiac in one patient each. There were no objective responses, and 18 patients had stable disease for a median of 74 days. The median survival for all patients was 230 days, with 23% alive at 1 year. Topotecan as administered in this trial is reasonably well tolerated; however, the response rate was insufficient to warrant additional study in pleural mesothelioma. 相似文献
50.
RC Wood KL MacDonald KE White CW Hedberg M Hanson MT Osterholm 《Canadian Metallurgical Quarterly》1993,270(24):2935-2939
OBJECTIVE: To assess the presence of antibody to hepatitis B surface antigen (anti-HBs) at postvaccination testing in Minnesota health care workers receiving recombinant hepatitis B vaccines, and to identify risk factors for lacking anti-HBs following hepatitis B vaccination. DESIGN: Retrospective cohort study. SETTING: Ten acute care hospitals in Minnesota. PARTICIPANTS: A total of 595 health care workers who had received hepatitis B vaccine (Recombivax HB or Engerix-B) between June 1987 and December 1991 and who underwent postvaccination testing for anti-HBs within 6 months after receiving the third dose of vaccine. MAIN OUTCOME MEASURE: Presence or absence of anti-HBs following hepatitis B vaccination. RESULTS: Five variables were independently associated with lacking anti-HBs by multivariate analysis: vaccine brand, smoking status, gender, age, and body mass index. Stratifying by vaccine brand demonstrated that age (P = .01), body mass index (P < .01), and smoking status (P < .01) were associated with lacking anti-HBs only for Recombivax HB recipients; and gender (P = .03) was associated with lacking anti-HBs only for Engerix-B recipients. After controlling for smoking status, age, gender, and body mass index, recipients of Recombivax HB were more likely to lack anti-HBs than recipients of Engerix-B (relative risk, 2.3; 95% confidence interval, 1.1 to 4.7; P = .02). CONCLUSIONS: Results indicate that certain populations of health care workers are at increased risk of not responding to hepatitis B vaccination. Further studies evaluating immunogenicity of currently available recombinant hepatitis B vaccines in persons at high risk for primary vaccine failure are needed. 相似文献