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21.
J Christensen-Dalsgaard W Dappen SV Ajukov ER Anderson HM Antia S Basu VA Baturin G Berthomieu B Chaboyer SM Chitre AN Cox P Demarque J Donatowicz WA Dziembowski M Gabriel DO Gough DB Guenther JA Guzik JW Harvey F Hill G Houdek CA Iglesias AG Kosovichev JW Leibacher P Morel CR Proffitt J Provost J Reiter EJ Rhodes FJ Rogers IW Roxburgh MJ Thompson RK Ulrich 《Science (New York, N.Y.)》1996,272(5266):1286-1292
Data from the Global Oscillation Network Group (GONG) project and other helioseismic experiments provide a test for models of stellar interiors and for the thermodynamic and radiative properties, on which the models depend, of matter under the extreme conditions found in the sun. Current models are in agreement with the helioseismic inferences, which suggests, for example, that the disagreement between the predicted and observed fluxes of neutrinos from the sun is not caused by errors in the models. However, the GONG data reveal subtle errors in the models, such as an excess in sound speed just beneath the convection zone. These discrepancies indicate effects that have so far not been correctly accounted for; for example, it is plausible that the sound-speed differences reflect weak mixing in stellar interiors, of potential importance to the overall evolution of stars and ultimately to estimates of the age of the galaxy based on stellar evolution calculations. 相似文献
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在内蒙古阿拉善荒漠区选择过牧和禁牧两种不同干扰条件下的样地,运用标志重捕法和Jolly-seber模型,于2005年~2007年,对三趾跳鼠(Dipus sagitta)种群数量动态进行了连续3年的专门研究.结果表明:3年中三趾跳鼠种群数量的波动较大,其变动经历了低谷-上升-高峰-下降4个时期,该种的数量变动存在一定规律;同一年中不同干扰条件的种群数量差异明显,3a中种群第1次数量高峰均为过牧区>禁牧区,其种群年平均数量及第2次数量高峰均为禁牧区>过牧区. 相似文献
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G Pugliesi SC Scolari FS Mesquita M Maturana Filho ER Araújo D Cardoso JN Sales I Martin M Sá Filho CM Bertan M Binelli 《Reproduction in domestic animals》2014,49(4):e35-e39
This short communication reports the impact of endometrial biopsies, uterine flushings and follicular fluid aspiration procedures at day 6 post artificial insemination (AI) on pregnancy rates. In Experiment 1, cows were timed AI (TAI) and assigned to the following treatment groups: control (n = 37), uterine flushing (n = 35) and endometrial biopsy (n = 38). On day 30 post AI, pregnancy rates were 40.5%, 33% and 28.5%, respectively (p > 0.1). Pregnancy rate on day 60 was lower (p < 0.004) in flushed cows than in the controls. In Experiment 2, oestrus was detected and cows were assigned to flushing (n = 32) or biopsy (n = 33) treatments 6 days after AI, which resulted in pregnancy rates of 31% and 36%, respectively (p > 0.1). In Experiment 3, cows were, 6 days after TAI, randomly assigned to the following treatments: control (n = 84) or aspiration of the largest follicle (n = 73). Pregnancy rates on day 30 post AI were 63.5% for the control group and 53% for the aspirated group (p > 0.1). In conclusion, uterine flushing and endometrial biopsy negatively affect pregnancy rates, but neither procedure can be considered to be incompatible with pregnancy maintenance. Follicular aspiration during pregnancy does not interact with pregnancy success. The amount and quality of samples obtained are compatible with the use of cellular and molecular analysis of uterine variables from cows that failed or succeeded on maintaining pregnancy. 相似文献
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Nitrogen mineralization and crop uptake from surface-applied leaves of green manure species on a tropical volcanic-ash soil 总被引:3,自引:0,他引:3
Juan Cobo Edmundo Barrios Donald C. Kass Richard Thomas 《Biology and Fertility of Soils》2002,36(2):87-92
Leaves of nine green manure (GM) species were surface applied to a tropical volcanic-ash soil at a rate of 100 kg N ha-1 in order to evaluate their N-fertilizer value in a glasshouse experiment. GM treatments were compared to urea at two rates, 50 kg N ha-1 (FN50) and 100 kg N ha-1 (FN100), and to a control with no fertilizer application (FN0). Two weeks after treatment application, upland rice seedlings were sown in order to conduct N uptake studies. Soil volumetric moisture content was maintained close to 50%. In general, soil showed an initial increase in inorganic N followed by a rapid decline with time. After 2 weeks of evaluation FN100, FN50 and leaves of Mucuna pruriens var. Tlaltizapan and Indigofera constricta presented higher values of inorganic N (157-109 mg N kg-1 soil); while, FN0 and leaves of Mucuna deerengianum, Cratylia argentea and Calliandra calothyrsus presented lower values (75-89 mg N kg-1 soil). N recovery by rice, at 20 weeks after planting, was highest for FN100 (59.9%) followed by Canavalia brasiliensis (54.6%), Calliandra calothyrsus (47.4%) and M. pruriens var. IITA-Benin (32.4%); while, M. pruriens var. Tlaltizapan, FN50, Tithonia diversifolia and I. constricta presented lower N uptake (13-20%). Significant relationships were found between some quality parameters of GM evaluated (i.e. total N, fibers, lignin and polyphenol content), soil N availability and rice N uptake. These results suggest that GM that decomposed and released N slowly resulted in high N uptake when they were used at pre-sowing in a tropical volcanic-ash soil. 相似文献
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水氮耦合对棉花干物质积累及产量的影响 总被引:1,自引:0,他引:1
【目的】研究水氮耦合对棉花干物质积累及产量影响。【方法】大田试验采用裂区试验设计,设置灌溉量与施肥量2个调控因子,其中灌溉量为主区,施肥量为副区,均设置3个梯度,灌溉量依次为2 250(低灌量)、3 450(中灌量,传统经验灌溉量CK)、4 650 m3/hm2,(高灌溉量)分别以W1、W2和W3表示;施肥量(折合纯氮)依次为0(空白)、300(中等施氮量,传统经验施氮量CK)、600 kg/hm2(高施氮量,200%CK),分别以N1、N2和N3表示。【结果】灌溉量和施肥量对植株生长和产量构成有一定促进作用,提高灌溉量和施肥量均能显著提高株高、叶片数和结铃率。在对干物质积累方面提高灌溉量可显著提高干物质积累总量,而提高施肥量主要促进了干物质更早的向经济器官积累。通过提高灌溉量可增产23.2%~31.4%,通过增施氮肥可显著增产12.5%~17.6%。【结论】水氮耦合对棉花单铃重、籽棉产量和皮棉产量均有显著的调控作用。水氮优化策略能够提高资源利用效率,降低水肥投入,产量稳定。 相似文献
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基于能值-生态足迹修正模型的区域可持续发展研究——以江苏省南通市为例 总被引:1,自引:1,他引:0
在系统分析能值—生态足迹模型缺陷的基础上,通过增加人工投入指标,统一能值密度以及引入折能/折标系数对其进行了修正,并采用修正后的模型对江苏省南通市1996—2010年的可持续发展水平进行了测算。结果表明:(1)1996—2010年间南通市人均生态足迹由0.65hm2增长到0.90hm2,主要是由能源消费量的增加引起的;(2)同期南通市人均生态承载力由0.51hm2增长到0.81hm2,这主要是由农、畜产品产量提高和水电开发力度加大引起的,而通过劳务和资金投入提高承载力的空间很大;(3)1996—2010年南通市一直处于生态赤字状态,可持续性评价指数也都在0.5以上,区域发展处于不可持续状态。为进一步缩小生态承载力与生态足迹之间的差距,应采取以下措施:引导重点行业和企业节能降耗,大力发展新能源;加大农业科技投入,继续提高农产品产量;重视人力资源的投入,促使经济发展方式向技术密集型和资本密集型转变。 相似文献
30.
Cletos Mapiye Tyler D Turner John A Basarab Vern S Baron Jennifer L Aalhus Michael ER Dugan 《畜牧与生物技术杂志(英文版)》2014,(1):98-105
Background: The current study evaluated the subcutaneous fatty acid(FA) composition of calf- and yearling-fed stee with or without growth promoting implants. Crossbred steers(n = 112; 267 ± 5.0 kg) of the same contemporary group were allocated to one of four production system and implant strategy based treatments in a completely randomized design with a 2 × 2 factorial arrangement of treatments.Results: There were no interactions(P 0.05) between production systems and growth promoting implants for the total and individual subcutaneous FA. Yearling as opposed to calf finishing reduced(P 0.05) subcutaneous proportions of C20:3n-6, trans(t)12-18:1, C14:0, several minor cis-monounsaturated FA(c-MUFA; c9-14:1, c11-16:1,c11-18:1, c12-18:1, c13-18:1, c9-20:1 and c11-20:1), and increased(P 0.05) subcutaneous proportions of t11c15-18:2,total and individual branched-chain FA. Subcutaneous fat from steers implanted with growth promotants had higher(P 0.05) proportions of total polyunsaturated FA(PUFA), total n-6 PUFA, C18:2n-6 and individual t-18:1isomers(t6 to t10) compared to non-implanted steers.Conclusions: Overall, current findings show that production systems and growth promotants led to only minor differences in subcutaneous FA composition of beef steers. 相似文献