排序方式: 共有33条查询结果,搜索用时 15 毫秒
1.
2.
3.
ABSTRACT Inter‐industry employment shifts were largely responsible for changes in the income distribution in the Pittsburgh region during the 1980s. Kernel density estimators were used, together with decomposition techniques developed by DiNardo et al. (1996 ) to show that industry shifts were responsible for over 90 percent of the earnings reductions at some points on the earnings distribution. Most of the losses at the lower end of the distribution occurred in the early 1980s as the economy plunged into a deep recession. The recovery in the later part of the decade brought little improvement as earnings in the lower part of the distribution continued to fall with the increase in employment of part‐time workers in the low‐wage trade and service sectors. 相似文献
4.
5.
A Ortega‐Pacheco M Jiménez‐Coello E Gutiérrez‐Blanco KY Acosta‐Viana E Guzmán‐Marín MA Zavala‐Sánchez NE Montalvo‐Beltrán MS Pérez‐Gutiérrez 《Reproduction in domestic animals》2010,45(6):1126-1129
Papaya seeds (Carica papaya Linn) have been found to have a significant effect on sperm characteristics in some mammals, including humans, but no studies have investigated the effects on dogs. In the present study, a significant decrease in sperm concentration was observed in a group of dogs treated with extracts from washed papaya seeds, but no decrease was observed in the group of dogs treated with non‐washed seeds. An important effect of extract components from washed seeds such as fatty acids is probably involved in the reduction of sperm production because of Sertoli cell damage, as has been suggested for langur monkeys. Dilution of the active components in the non‐washed papaya seeds or interference with some of the components may reduce the expected effect on spermatogenesis. This first report on the effects of a chloroformic extract of papaya seeds in dogs suggests that an increased dose is necessary to achieve azoospermia. 相似文献
6.
7.
8.
BACKGROUND: Evidence suggesting that a diet high in fruits and vegetables may be beneficial to bone health has sparked interest in the potential benefit of a vegetarian diet. However, other studies have raised a question regarding the adequacy of protein in such a diet. OBJECTIVE: The aim of the present study was to take a whole foods approach in examining the effects of foods high in protein on the risk of wrist fracture (WF) in a cohort with a significant proportion consuming a meat-free diet. DESIGN: A cohort study of women who completed two lifestyle surveys 25 years apart. SUBJECTS: One thousand eight hundred and sixty-five peri- and postmenopausal women at the time of the first survey. RESULTS: There was a significant interaction between meat consumption and foods high in vegetable protein. Among vegetarians, those who consumed the least vegetable protein intake were at highest risk for fracture. However, increasing levels of plant-based high-protein foods decreased WF risk, with a 68% reduction in risk (hazard ratio (HR) = 0.32, 95% confidence interval (CI) 0.13-0.79) in the highest intake group. Among those with lowest vegetable protein consumption, increasing meat intake decreased the risk of WF, with the highest consumption decreasing risk by 80% (HR = 0.20, 95% CI 0.06-0.66). CONCLUSIONS: The finding that higher consumption frequencies of foods rich in protein were associated with reduced WF supports the importance of adequate protein for bone health. The similarity in risk reduction by vegetable protein foods compared with meat intake suggests that adequate protein intake is attainable in a vegetarian diet. 相似文献
9.
Beeson TD Mastracchio A Hong JB Ashton K Macmillan DW 《Science (New York, N.Y.)》2007,316(5824):582-585
The asymmetric alpha-addition of relatively nonpolar hydrocarbon substrates, such as allyl and aryl groups, to aldehydes and ketones remains a largely unsolved problem in organic synthesis, despite the wide potential utility of direct routes to such products. We reasoned that well-established chiral amine catalysis, which activates aldehydes toward electrophile addition by enamine formation, could be expanded to this important reaction class by applying a single-electron oxidant to create a transient radical species from the enamine. We demonstrated the concept of singly occupied molecular orbital (SOMO) activation with a highly selective alpha-allylation of aldehydes, and we here present preliminary results for enantioselective heteroarylations and cyclization/halogenation cascades. 相似文献
10.