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排序方式: 共有1042条查询结果,搜索用时 218 毫秒
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R Kneen NG Pham T Solomon TM Tran TT Nguyen BL Tran J Wain NP Day TH Tran CM Parry NJ White 《Canadian Metallurgical Quarterly》1998,27(4):845-850
PURPOSE: To review the University of Florida experience in treating ependymomas, analyze prognostic factors, and provide treatment recommendations. METHODS AND MATERIALS: Forty-one patients with ependymoma and no metastases outside the central nervous system received postoperative radiotherapy with curative intent between 1966 and 1989. Ten patients had supratentorial lesions, 22 had infratentorial lesions, and 9 had spinal cord lesions. All patients had surgery (stereotactic biopsy, subtotal resection, or gross total resection). Most patients with high-grade lesions received radiotherapy to the craniospinal axis. Low-grade intracranial lesions received more limited treatment. Spinal cord lesions were treated using either partial spine or whole spine fields. RESULTS: Of 32 intracranial tumors, 21 recurred, all at the primary site; no spinal cord tumors recurred. Overall 10-year survival rates were 51% (absolute) and 46% (relapse-free); by tumor site: spinal cord, 100%; infratentorial, 45%; supratentorial, 20% (p = 0.002). On multivariate analysis, tumor site was the only factor that influenced absolute survival (p = 0.0004); other factors evaluated included grade, gender, age, duration of symptoms, resection extent, primary tumor dose, treatment field extent, surgery-to-radiotherapy interval, and days under radiotherapy treatment. CONCLUSIONS: Patients with supratentorial or infratentorial tumors receive irradiation, regardless of grade. Craniospinal-axis fields are used when spinal seeding is radiographically or pathologically evident. Spinal cord tumors are treated using localized fields to the primary site if not completely resected. Failure to control disease at the primary site remains the main impediment to cure. 相似文献
23.
MC Lipman D Stobbs S Madge R Miller MA Johnson 《Canadian Metallurgical Quarterly》1998,114(1):284-290
STUDY OBJECTIVES: Asymptomatic HIV-infected individuals are increasingly recruited for studies involving invasive procedures such as bronchoscopy. We sought to determine the response to and outcome of a request for a research bronchoscopy in HIV-positive individuals with no respiratory disease, and whether this would adversely affect future decisions to have a medically indicated bronchoscopy. DESIGN AND SETTING: Prospective, semistructured, questionnaire-based study in a London teaching hospital HIV outpatient clinic. PARTICIPANTS: One hundred and seven consecutive HIV-infected eligible individuals. Thirty-one healthy volunteers served as a control group for the subjective response to bronchoscopy. MAIN OUTCOME MEASURES: Subjects' attitudes and responses to requests for bronchoscopy and subsequent behavior when they required medically indicated bronchoscopy. RESULTS: Seventy-five patients (70%) agreed to the procedure in principle, predominantly for altruistic reasons. Thirty-nine subjects underwent bronchoscopy. Five percent found it worse than expected; and 79% agreed to another research bronchoscopy (performed in 11 subjects approximately 2 years later). All patients said they would undergo bronchoscopy again for diagnostic purposes (required in seven during the study). When compared to a healthy volunteer population within the same study, postbronchoscopy symptoms were similar in frequency although somewhat different in nature. Subjects felt that a clear explanation of what was involved enhanced their participation in this research. CONCLUSIONS: Invasive research procedures such as bronchoscopy can be performed and are repeatable in a healthy HIV-infected population. Performance of procedures for research purposes does not appear to adversely affect future health-care decisions. 相似文献
24.
TH Kim WC Bowen DB Stolz D Runge WM Mars GK Michalopoulos 《Canadian Metallurgical Quarterly》1998,244(1):93-104
The present study has examined the distribution of axons of differing sizes in the optic pathway of the ground squirrel. Axon diameters were measured from electron micrographs at various locations across sections of the optic nerve and tract, and total distributions and numbers were estimated. In both the nerve and tract, roughly 1.2 million optic axons were present. The population of optic axons had a unimodal size distribution, peaking at 0.9 microm in diameter and having an extended tail toward larger diameters. Local axon diameter distributions in the optic tract indicated distinct (though partially overlapping) axon diameter classes, including one of fine sizes peaking at 0.8-0.9 microm, a second of medium sizes peaking around 1.7-1.8 microm, and a third composed of the larger fibers with diameters up to 4.8 microm. The fine-caliber axons were found at all locations in the tract, and were the only axons present immediately adjacent to the pia, while the medium- and coarse-caliber axons were found at deeper locations. Curiously, the larger axons were found primarily in the medial parts of the tract, where axons from the dorsal retina normally course. A similarly restricted distribution of the larger axons was observed in the dorsotemporal parts of the optic nerve, suggesting that this difference in the tract may relate to an asymmetric distribution of ganglion cells on the retina giving rise to these axons. Measurements of axonal size taken within the optic fiber layer in dorsal and ventral parts of the retina confirmed this asymmetry, consistent with previous demonstrations of soma size differences in the dorsal versus ventral retina. The partial segregation of axons by size in the optic tract of the ground squirrel then reflects both the asymmetric distribution of retinal ganglion cell classes and the chronotopic reordering of optic axons that occurs within the chiasmatic region. 相似文献
25.
蜕变测试和断言检查的比较与实验研究 总被引:1,自引:0,他引:1
在软件测试中,测试预言是一种用于检查程序在测试中是否正常运行的机制.然而在某些实际情况下,还无法制定测试预言或者难以有效地应用测试预言.针对此类测试预言问题,蜕变测试于近年应运而生,但蜕变测试的效率问题还没有被充分地加以研究.作者用控制实验的方法研究了使用蜕变测试的成本及效率,进而将蜕变测试和常用的断言检查两种方法的错误检测率和时间成本进行了比较和分析.实验结果表明,相比于断言检查方法,蜕变测试具有检测到更多错误的潜力.通过分析蜕变测试的效率和性能,与断言测试相比,蜕变测试的错误检测率更高效而效率有待提高,可适用于较为粗粒度的测试需求. 相似文献
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27.
L. T. LINDELL O. STEINVALL M. JONSSON TH. CLAESSON 《International journal of remote sensing》2013,34(5):629-642
Secchi disk depth was recorded in the field all along the Swedish coastline and compared with LANDSAT data. Chromaticity analysis was applied in the evaluation to allow for Sun angle and atmospheric corrections. The data were used to study the relative nutrient and solids loading situations around the Swedish coast and as a basis for the applicability of laser bathymetry for water depth soundings 相似文献
28.
LUC SARRAZIN THéRèSE SCHEMBRI PIERRE REBOUILLON 《The International journal of environmental studies》2013,70(4):413-425
A selective method for determining polycyclic aromatic hydrocarbons (PAHs) in sediments using solid‐phase extraction and RP‐HPLC with fluorescence and UV detection is described. The complete analytical method is used to surface sediments from the creek of Cortiou (France). Sewage from the urban area of Marseille is delivered to the creek. PAH levels in sediments (µg/g) range between 2.251 µg/g (for the benzo(a)anthracene) and 0.001 µg/g. The flux of pollution provided by the outfall is preferentially oriented from East to West by the Liguro‐Provenalcal current. The significant values are mainly confined on a perimeter of 2 km around the outfall. The phenanthrene/anthracene and fluoranthene/pyrene ratios indicate pyrolytic and petrogenic contamination. The particulate size observations concerning the sediments show that oxygenated sandy zones, where eliminating mechanisms (desorption, biodegradation) take place, are mainly located on the Chêvres plateau and around Jarre, Plane and Riou Islands. 相似文献
29.
Oil-in-water emulsions stabilized with nonionic emulsifiers change to water-in-oil emulsions as the temperature rises when the hydrophilic and lipophilic properties of the mixed emulsifier are just balanced. Preparation above the phase inversion temperature followed by rapid cooling yields emulsions that exhibit very fine droplet size and extreme long-term stability. Cosmetic emulsions were prepared by this phase inversion temperature (PIT) method using typical raw materials such as polar oils, e.g. decyl oleate, 2-octyl dodecanol or isopropyl myristate, and nonionic emulsifiers, e.g. ceteareth-12 or polyoxyethylene eicosyl/docosyl ether combined with cetostearyl alcohol as a co-emulsifier. The phase inversion temperature was measured as a function of the oil polarity and the concentration of mixed emulsifier. The relationship between phase inversion temperature, droplet size and emulsion stability was investigated. In addition, self-bodying agents such as cetostearyl alcohol or monoglycerides were added to these thin, fine disperse emulsions to adjust the consistency. The influence of these ingredients on phase inversion temperature, droplet size, yield value and emulsion stability was studied. 相似文献
30.
FRANÇOIS DES ROSIERS MARIUS THÉRIAULT YAN KESTENS PAUL VILLENEUVE 《Housing Studies》2007,22(6):945-964
This paper investigates the effect of environmental features on house values while focusing on the interactions between landscaping attributes and home buyers' profile. The originality of this study rests on the assumption that, while neighbourhood characteristics translate into distinct sub-markets and primarily set the structure of house prices, individual home buyers' preferences, under specific market conditions, also affect values. The study benefits from two distinct, although related data sets on the single-family segment of Quebec City's housing market: while landscaping features were obtained via an extensive field survey of houses sold between 1993 and 2000, a detailed phone survey of related homeowners' family status, age and income profiles is being conducted since 2000. Findings suggest that household profile and structure do shape landscaping preferences and that utility patterns of homeowners may be best understood by looking at interactions between the two sets of variables. Considering that population aging is a major issue for economic and social planners, such a conclusion should be accounted for in housing policy design. 相似文献