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排序方式: 共有134条查询结果,搜索用时 46 毫秒
41.
Ginther DK Schaffer WT Schnell J Masimore B Liu F Haak LL Kington R 《Science (New York, N.Y.)》2011,333(6045):1015-1019
We investigated the association between a U.S. National Institutes of Health (NIH) R01 applicant's self-identified race or ethnicity and the probability of receiving an award by using data from the NIH IMPAC II grant database, the Thomson Reuters Web of Science, and other sources. Although proposals with strong priority scores were equally likely to be funded regardless of race, we find that Asians are 4 percentage points and black or African-American applicants are 13 percentage points less likely to receive NIH investigator-initiated research funding compared with whites. After controlling for the applicant's educational background, country of origin, training, previous research awards, publication record, and employer characteristics, we find that black applicants remain 10 percentage points less likely than whites to be awarded NIH research funding. Our results suggest some leverage points for policy intervention. 相似文献
42.
An ultrastructural study of pollen-derived plants and normal microspore development indicates that chloroplasts and mitochondria are physically altered during microsporogenesis. These changes appear to debilitate the organelle so that only chloroplasts and mitochondria of the female parent are contributed to the offspring. 相似文献
43.
Addition of extracts of bean cotyledon or hypocotyl or of a coconut-water preparation to roots grown from excised bean hypocotyls markedly increased the number of nodules, while removal of part of the hypocotyl tissue reduced the number. The active morphogenetic substance in the coconut water has been partially purified. 相似文献
44.
AE Pashitski A Gurevich AA Polyanskii DC Larbalestier A Goyal ED Specht DM Kroeger JA DeLuca JE Tkaczyk 《Science (New York, N.Y.)》1997,275(5298):367-369
Magneto-optical imaging was used to visualize the inhomogeneous penetration of magnetic flux into polycrystalline TlBa2Ca2Cu3Ox films with high critical current densities, to reconstruct the local two-dimensional supercurrent flow patterns and to correlate inhomogeneities in this flow with the local crystallographic misorientation. The films have almost perfect c-axis alignment and considerable local a- and b-axis texture because the grains tend to form colonies with only slightly misaligned a and b axes. Current flows freely over these low-angle grain boundaries but is strongly reduced at intermittent colony boundaries of high misorientation. The local (<10-micrometer scale) critical current density Jc varies widely, being up to 10 times as great as the transport Jc (scale of approximately 1 millimeter), which itself varies by a factor of about 5 in different sections of the film. The combined experiments show that the magnitude of the transport Jc is largely determined by a few high-angle boundaries. 相似文献
45.
Harman-Fetcho JA Hapeman CJ McConnell LL Potter TL Rice CP Sadeghi AM Smith RD Bialek K Sefton KA Schaffer BA Curry R 《Journal of agricultural and food chemistry》2005,53(15):6040-6048
Climate and soil conditions in South Florida along with an extensive canal system facilitate movement of agricultural pesticides into surface waters. In a two-year study (2002-2004) of the currently used pesticides in South Florida, atrazine, endosulfan, metolachlor, chlorpyrifos, and chlorothalonil were the most frequently detected in the canals and in Biscayne Bay, with average concentrations of 16, 11, 9.0, 2.6, and 6.0 ng/L, respectively. Concentrations of atrazine and chlorpyrifos were highest near corn production. Chlorothalonil and endosulfan concentrations were highest near vegetable production, with no clear trend for metolachlor, which is used on multiple crops. Concentration data were used to calculate an aquatic life hazard potential for the planting period (November) versus the harvest period (March). This analysis indicated that a higher hazard potential occurs during harvest, primarily from the use of endosulfan. These data will also serve to document canal conditions prior to implementation of the Comprehensive Everglades Restoration Plan (CERP). 相似文献
46.
47.
Harry S. Paris Ron Cohen Menahem Edelstein Yosef Burger Yohanan Ma‘oz Arthur A. Schaffer 《Genetic Resources and Crop Evolution》2013,60(5):1629-1640
Over the past century, Israel was a focal point for the improvement of local cucurbit landraces and introduction of cucurbit germplasm. Some improved open-pollinated cucurbit cultivars developed in Israel became established as market types of considerable economic importance far beyond its borders. The origin and history of these cultivars is not widely known and therefore the purpose of the present work was to collect and compare the records relevant to the development of these cultivars, and to describe them more fully. The four economically most important cultivars originated through mass-selection by amateur breeders and were named after their respective farming communities. The ‘Bet Alfa’ cucumber (Cucumis sativus) was selected from a local landrace and introduced in 1936. The ‘Malali’ watermelon (Citrullus lanatus) originated as a rogue in a local landrace and was commercialized around 1940. The ‘Ananas Yoqne‘am’ melon (Cucumis melo) was selected from a local landrace and commercialized around 1950. The ‘Ha‘Ogen’ melon was selected from a cultivar introduced from Hungary and commercialized in the 1950s. The outstanding fruit quality of these four cultivars resulted in their widespread planting in Israel and neighboring countries. Moreover, the quality of the cucumber and melon cultivars inspired successive improvements, notably introgression of disease resistance and development of hybrids, by Israeli breeder-geneticists. The ever-increasing demand for their high-quality fruits established as international market types the Bet Alfa cucumber, the Ananas Yoqne‘am melon, and the Ha‘Ogen melon and its derivative, the Galia melon, and each is intensively bred today by local and multinational seed companies. 相似文献
48.
Schaffer PA Charles JB Tzipory L Ficociello JE Marvel SJ Barrera J Spraker TR Ehrhart EJ 《Veterinary pathology》2012,49(5):771-774
Lymphoma in the left femoral nerve of a 10-year-old English Cocker Spaniel caused complete paralysis of the affected limb. Neoplastic cells were immunopositive for CD79a and Pax5 and negative for CD3. Neoplastic cells were in multiple lymph nodes and one kidney but spared bone marrow. The clinical and histologic features in this case resemble those of the rare human condition of neurolymphomatosis. 相似文献
49.
K. W. Migliaccio B. Schaffer Y. C. Li E. Evans J. H. Crane R. Muñoz-Carpena 《Irrigation Science》2008,27(1):57-66
Many of the best management practices (BMPs) that are recommended for agricultural producers have not been scientifically
evaluated for their conservation benefits considering the soil, climate, and hydrology of the proposed application location.
The goal of this study was to compare royal palm (Roystonea elata) production in south Florida, USA, using tensiometer automated irrigation and reduced soil applications of nitrogen (N) and
phosphorus (P), to that of traditional grower practices considering water savings, nutrient inputs, crop yield, crop nutrient
status, soil nutrient status, and economic analyses. The study consisted of six treatments: (1) control (i.e., a grower irrigation
rate and N and P fertilizer rates); (2) irrigation system automated to irrigate when soil water suction exceeded 5 kPa and
the grower N and P rates; (3) irrigation system automated to irrigate when soil water suction exceeded 15 kPa and the grower
N and P rates; (4) irrigation system automated to irrigate when soil water suction exceeded 15 kPa and 50% of the grower N
and P rates; (5) the grower irrigation rate and 75% of the grower N and P rates; and (6) the grower irrigation rate and 50%
of the grower N and P rates. Irrigation water volume applied, plant diameters, and plant heights were measured periodically
throughout the study and plant tissue samples and soil samples were collected periodically for analysis of N and P content.
Significant differences among treatments were only observed for the irrigation water volume applied. Automating the irrigation
system to irrigate at soil suction exceeding 5 and 15 kPa resulted in 75 and 96% less water applied, respectively, than traditional
irrigation scheduling practices used by a grower. Economic analyses suggested that all treatments would result in financial
savings ranging from 7 to 34% per ha considering a 5-year, 2 ha investment. Thus, automating irrigation based on soil water
suction for palm production in southern Florida, USA and similar locations will result in more sustainable agricultural production
systems by benefiting the environment (less nutrients and water applied) and the grower (lower cost). 相似文献
50.
Filipe Selau Carlos Naihana Schaffer Robson Andreazza Lawrence A Morris Marino José Tedesco Cácio Luiz Boechat 《Communications in Soil Science and Plant Analysis》2018,49(3):319-333
Irrigation with treated wastewaters can improve nutrient levels and yield of crops planted on degraded soils. This study evaluated how irrigation with treated industrial wastewater affected biomass production and nutrition of maize plants and physio-chemical properties of a degraded soil. The experiment was conducted in a greenhouse using PVC columns. Treatments consisted of 8 treatments irrigated with clean water and increasing doses of N and P, and 8 treatments with 4 proportions of wastewater irrigation (25%, 50%, 75% and 100% v/v). In general, maize biomass did not differ between irrigation water sources. Differences were largely associated with N nutrition. We observed increases in concentrations of N, P, K, S, Mn, Na, Cu, and Zn in tissue of maize under irrigation with wastewater. The addition of treated wastewater increased the P and Na concentrations, and EC values in the soil without affecting clay dispersion in water. An associated economic analysis indicated that wastewater irrigation would not be economically feasible without including environmental benefits. In southern Brazil, the proportion of irrigation water that is wastewater should not exceed 50%. 相似文献