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Relatively little attention has been paid to integrating gaseous N(2)O generated by wastewater treatment into overall reactive nitrogen (Nr) pollution reduction. We propose that there is potential for substantial reductions in N(2)O emissions through the addition of denitrification processes to existing nitrifying wastewater treatment plants (WWTPs), which are designed to lower ammonia levels but currently do not reduce overall Nr. In addition to providing the benefit of reducing total nitrogen concentrations in the effluent, this kind of WWTP upgrade has been demonstrated to reduce energy consumption and fossil CO(2) emissions. We show that the creation of a greenhouse gas (GHG) crediting system for the wastewater sector could provide a potentially sizable economic incentive on the order of $10 million to $600 million per year in the U.S. for upgrading of nitrifying WWTPs that results in N(2)O reductions, with an ancillary benefit of another $30-100 million per year from electricity savings. Even if biological nitrogen removal (BNR) treatment were mandated by existing and future water quality regulations, a GHG crediting system could still be created to promote BNR design and operation that drive N(2)O emissions below a baseline to even lower levels. In this case GHG credits could offset around 0.5-70% of the operating and maintenance cost for the BNR.  相似文献
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《》2006,16(3):403-410
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Activins, as members of the transforming growth factor-beta superfamily, control and orchestrate many physiological processes and are vital for the development, growth and functional integrity of most tissues, including the pituitary. Activins produced by pituitary cells work in conjunction with central, peripheral, and other local factors to influence the function of gonadotropes and maintain a normal reproductive axis. Follistatin, also produced by the pituitary, acts as a local buffer to bind activin and modulate its bioactivity. On the other hand, inhibins of gonadal origin provide an endocrine feedback signal to antagonize activin signaling in cells that express the inhibin co-receptor, betaglycan, such as gonadotropes. This review highlights the pituitary roles of activin and the mechanisms through which these actions are modulated by inhibin and follistatin.  相似文献
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Local breeds are rarely subject to modern selection techniques; however, selection programs will be required if local breeds are to remain a viable livelihood option for farmers. Selection in small populations needs to take into account accurate inbreeding control. Optimum contribution selection (OCS) is efficient in controlling inbreeding and maximizes genetic gain. The current paper investigates genetic progress in simulated dairy cattle populations from 500 to 6,000 cows undergoing young bull selection schemes with OCS compared with truncation selection (TS) at an annual inbreeding rate of 0.003. Selection is carried out for a dairy trait with a base heritability of 0.3. A young bull selection scheme was used because of its simplicity in implementation. With TS, annual genetic gain from 0.111 standard deviation units with 500 cows increases rapidly to 0.145 standard deviation units with 4,000 cows. Then, genetic gain increases more slowly up to 6,000 cows. At the same inbreeding rate, OCS produces higher genetic progress than TS. Differences in genetic gain between OCS and TS vary from to 2 to 6.3%. Genetic gain is also improved by increasing the number of years that males can be used as sires of sires. When comparing OCS versus TS at different heritabilities, we observe an advantage of OCS only at high heritability, up to 8% with heritability of 0.9. By increasing the constraint on inbreeding, the difference of genetic gain between the 2 selection methods increases in favor of OCS, and the advantage at the inbreeding rate of 0.001 per generation is 6 times more than at the inbreeding rate of 0.003. Opportunities exist for selection even in dairy cattle populations of a few hundred females. In any case, selection in local breeds will most often require specific investments in infrastructure and manpower, including systems for accurate data recording and selection skills and the presence of artificial insemination and breeders organizations. A cost-benefit analysis is therefore advisable before considering the implementation of selection schemes in local dairy cattle breeds.  相似文献
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Cross contamination of foodborne pathogens from raw meats to ready-to-eat foods has caused a number of foodborne outbreaks. The cross contamination and transfer rates of Salmonella enterica from chicken to lettuce under various food-handling scenarios were determined. The following scenarios were tested: in scenario 1, cutting board and knife used to cut chicken (106 CFU/g) were also used for cutting lettuce, without washing; in scenario 2, cutting board and knife were washed with water separately after cutting chicken, and subsequently used for cutting lettuce; and in scenario 3, cutting board and knife were thoroughly washed with soap and hot water after cutting chicken, and before cutting lettuce. In each scenario, cutting board, knife, chicken and lettuce were sampled for population of S. enterica. For scenario 1, both before and after cutting lettuce, the cutting board and knife each had about 2 logs CFU/cm2 of S. enterica, respectively. The cut lettuce had about 3 logs CFU/g of S. enterica. In scenario 2, fewer organisms (0.5–2.4 logs CFU/g or cm2) were transferred. The transfer rates in both scenarios ranged from 0.02 to 75%. However, in scenario 3, <1 log CFU/g or cm2 organisms were detected on lettuce, cutting board or knife, after washing and cutting lettuce. This shows that the FDA recommended practice for cleaning cutting boards is effective in removing S. enterica and preventing cross contamination.  相似文献
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Peptic hydrolysate with angiotensin I-converting enzyme (ACE) inhibitory activity was prepared from Acetes chinensis . The 3 kDa ultrafiltration filtrates (UF-IV) of the desalted hydrolysate exerted a potent ACE inhibitory activity with IC50 being 0.67 mg mL−1. The fractions with molecular weight located between 611 and 240 Da achieved a total percentage of 63.6% in the UF-IV, with a mean peptide length of about 5.6–2.1. Gastrointestinal digestions were simulated on the hydrolysate and UF-IV and addressed their effect on the ACE inhibitory activity. The ACE inhibitory activity of the UF-IV could survive or be maintained in active form by simulated gastrointestinal digestion. Furthermore, the UF-IV exerted potent antihypertensive effect after oral administrations were given to spontaneously hypertensive rats (SHR) at a dose of 900 mg kg−1 body weight. In conclusion, the UF-IV could serve as useful antihypertensive peptides in the prevention and treatment of hypertension and other associated disorders.  相似文献
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