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排序方式: 共有8294条查询结果,搜索用时 15 毫秒
31.
RA Bayoumi MS Nur-E-Kamal M Tadayyon KK Mohamed BH Mahboob MM Qureshi MS Lakhani MO Awaad J Kaeda TJ Vulliamy L Luzzatto 《Canadian Metallurgical Quarterly》1996,46(3):136-141
Operational skills involved in controlling a motor vehicle were measured in two groups of very healthy elderly drivers and a young control group to test the hypothesis that there are age-related declines in operational performance that may influence driver safety. An actual behind-the-wheel, standardized road test was employed using a motor vehicle equipped with sensors to record speed, braking activity, and lane position, as well as direction and magnitude of front-wheel and eye-movement excursions. The data from these sensors were used as dependent measures of operational performance. Older drivers made fewer steering and eye-movement excursions and drifted across the center line more frequently than the young control group. Younger drivers drove significantly faster and executed more braking applications than did their older counterparts. The motor-vehicle operational performance of older healthy drivers was related to visual-spatial attentional declines and the useful field of vision associated with the normal aging process. 相似文献
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首先通过电炉—LF精炼炉—VD精炼炉—包内球化的工艺路线获得了足够的优质铁液,然后通过选取合适的分型面、设置合理的浇注系统、设计专用的冷铁、安放足够大的保温冒口和上表面加大加工余量来去除夹渣等措施,成功生产了具有厚大断面的大型球墨铸铁铸件。 相似文献
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根据企业特点 ,在贯彻ISO90 0 2标准中 ,建立健全设备管理机构及制度体系 ,提高企业设备管理水平 ,建立设备台帐等提出了几点看法 相似文献
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We examined the effects of different cytokine combinations and culture conditions on the expansion and modulation of cell surface antigens of CD34+ derived dendritic cells (DCs), the most efficient antigen-presenting cells capable of stimulating resting T cells in the primary immune response. Cells with a dendritic morphology and expressing HLA-DR, CD1a, S100 and CD83 were maximally expanded under serum-free conditions with the addition of SCF, GM-CSF, TNF-alpha, TGF-beta and Flt-3 ligand (fold increase of CD1a+ cells = 102 +/- 32 after 2 weeks of culture). CD34+ cells were also grown under continuous flow conditions in an artificial capillary system: after 14d of culture, the expansion in the total cell number was lower than that of the static cultures (3.3 +/- 2 v 18.9 +/- 4) but the percentage of CD1a+/CD83+/ CD80+ cells was considerably higher, whereas the CD14+ cells were significantly reduced (8.9 +/- 2 v 26 +/- 13). In continuous perfusion cultures, low levels of DC precursors and of LTC-IC were still present up to day 14. The DCs generated under flow conditions stimulated the mixed leucocyte reaction (MLR) more than the cells grown in static cultures. By electron microscopy, cells grown in the continuous flow system showed an increased number of large cells with numerous dendritic processes and abundant multilamellar complexes. The cells expanded under these conditions were sorted on the basis of their light-scatter properties into two fractions: one containing a predominance of CD1a+/S100+/ CD8 3+/CD80+/CD14- 'large cells' with great internal complexity (mature DCs); the second including 'small cells' either CD33+/CD14+, CD33+/CD15+ or CD33+/CD13-/CD14. The DCs generated and selected with this method are therefore particularly well suited for immunotherapeutic protocols. 相似文献
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Effect of routine screening for Down's syndrome on the significance of isolated fetal hydronephrosis
OBJECTIVE: To determine the risk of Down's syndrome in fetuses with isolated hydronephrosis at 18-23 weeks in an unselected general population after routine screening for Down's syndrome, using first trimester nuchal translucency measurement and second trimester maternal serum biochemistry. POPULATION: All pregnant women undergoing a routine 18-23 week ultrasound scan, from a population who had been offered screening for Down's syndrome. SETTING: A district general hospital serving a low risk obstetric population. METHODS: Prospective study of all routine 18-23 weeks ultrasound scans. The prevalence of isolated hydronephrosis and Down's syndrome was determined and the relative risk for Down's syndrome was calculated for different ultrasound findings. RESULTS: 10,971 women were scanned at 18-23 weeks during the study period. Down's syndrome was diagnosed in 14 of 20 cases before this stage using first trimester nuchal translucency measurement and second trimester maternal serum biochemistry. Isolated fetal hydronephrosis was diagnosed in 423 pregnancies (3.9%); none of these pregnancies were affected by Down's syndrome. The relative risk for Down's syndrome was 0.18 (95% CI 0.06-0.53) for women with a normal scan (n = 9983). When multiple ultrasound markers were found (n = 565), the relative risk for Down's syndrome was 2.00 (95% CI 0.18-22.10) and 9.00 (95% CI 1.14-71.30) for all other aneuploidies. CONCLUSION: The finding of isolated fetal hydronephrosis does not significantly increase the age-related risk for Down's syndrome. The presence of multiple ultrasound markers is associated with an increased risk of aneuploidies other than Down's syndiome. These findings are explained by the reduced prevalence of Down's syndrome as a result of prior screening and diagnosis of this condition. 相似文献
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为提升雄安新区应对气候变化和急性冲击灾害的适应能力,建设高韧性高弹性的城市水系统,实现新区水系统的安全运行与可持续发展,构建了基于不确定性的雄安新区城市水系统安全保障技术.该技术包括水系统的风险源识别、风险综合评价和风险管理策略3部分.在应对气候变化方面,提出了"气候变化模拟预估—气候变化增量分析—水系统影响风险分析"的技术框架、不同精度的气候变化增量分析方法,以及分层级的城市水系统气候变化影响与风险分析方法.在应对急性冲击方面,提出了有效识别城市水系统面临的急性冲击风险源识别方法,以及急性冲击灾害多情景多灾种风险分析方法.在安全保障机制方面,提出了建立雄安新区水系统应急预案体系的要求,以及区域协同、综合应对、专业负责和网格化管理的"城市-组团-社区"三级风险管控机制. 相似文献