奶牛产酸乳诊治

由于营养供给不合理,导致的泌乳奶牛发生瘤胃酸中毒,而出现产酸乳现象。本研究通过营养调整,结合药物治疗法,有效地防止了奶牛产酸乳的现象。     

Bacterial inoculants for rice: effects on nutrient uptake and growth promotion

Beneficial soil bacteria are able to colonize plant root systems promoting plant growth and increasing crop yield and nutrient uptake through a variety of mechanisms. These bacteria can be an alternative to chemical fertilizers without productivity loss. The objectives of this study were to test bacterial inoculants for their ability to promote nutrient uptake and/or plant growth of rice plants subjected to different rates of chemical fertilizer, and to determine whether inoculants could be an alternative to nitrogen fertilizers. To test the interaction between putatively beneficial bacteria and rice plants, field experiments were conducted with two isolates: AC32 (Herbaspirillum sp.) and UR51 (Rhizobium sp.), and different nitrogen fertilization conditions (0%, 50%, and 100% of urea). Satisfactory results were obtained in relation to the nutrient uptake by plants inoculated with both isolates, principally when the recommended amount of nitrogen fertilizer was 50% reduced. These bacterial strains were unable to increase plant growth and grain yield when plants were subjected to the high level of fertilization. This study indicated that the tested inoculant formulations can provide essential nutrients to plants, especially when the levels of nitrogen fertilizers are reduced.     

Exciton storage in semiconductor self-assembled quantum dots

Storage and retrieval of excitons were demonstrated with semiconductor self-assembled quantum dots (QDs). The optically generated excitons were dissociated and stored as separated electron-hole pairs in coupled QD pairs. A bias voltage restored the excitons, which recombined radiatively to provide a readout optical signal. The localization of the spatially separated electron-hole pair in QDs was responsible for the ultralong storage times, which were on the order of several seconds. The present limits of this optical storage medium are discussed.     

A quantum dot single-photon turnstile device

Quantum communication relies on the availability of light pulses with strong quantum correlations among photons. An example of such an optical source is a single-photon pulse with a vanishing probability for detecting two or more photons. Using pulsed laser excitation of a single quantum dot, a single-photon turnstile device that generates a train of single-photon pulses was demonstrated. For a spectrally isolated quantum dot, nearly 100% of the excitation pulses lead to emission of a single photon, yielding an ideal single-photon source.     

办公室计算机的日常维护

办公室计算机日常使用时简单的软硬件维护和操作,从而使计算机发挥出它的最大性能,更好的满足工作需要.     

Is Semen Analysis Useful to Predict the Odds that the Sperm will Meet the Egg?

Any mammalian spermatozoon that achieves successful in vivo fertilization has to perform almost perfectly in many disparate functions and overcome a series of obstacles imposed by the female reproductive tract. This implies that during formation in the testis and epididymis, the spermatozoa did not incur any morphological, metabolic, immunological or genetic abnormalities. Given that the spermatozoa are such highly differentiated cells, this means that every cellular compartment must not only be intact but must also respond appropriately to intracellular and extracellular signals. Assuming that a spermatozoon possesses this level of perfection, and is able to reach and penetrate an oocyte, it can only be regarded as 'fertile' if the DNA it carries is intact and able to sustain embryonic development. Although the proportion of inseminated spermatozoa that meet these criteria is vanishingly small, the female reproductive tract applies stringent selection criteria during sperm transport and, as a result, the probability of conception around the time of ovulation is very high. If laboratory tests of semen quality could approach the efficacy of the female reproductive tract, it would be possible to predict the odds of spermatozoa meeting the egg; however, this is not possible at present. In this article, I suggest a simple model to illustrate how a battery of laboratory tests could eventually be used to make these predictions.     

园林土方工程施工中要注意的七个问题

园林土方工程施工与园林地形改造的需要有很大的关系,其施工方法可有人力施工、机械化和半机械化施工等.土方调配、施工准备、施工排水与降水、土方开挖与填筑、土方的填筑等方面都是施工中需要严格关注和把控的.     

Studies on the efficacy of deltamethrin applied to cattle for the control of tsetse flies (Glossina spp.) in southern Africa

Summary The tsetse fly (Glossina spp.) inhabits 11 million km² of Africa (Greekmore, 1989) where it is responsible for the transmission of trypanosomosis to man and animals. Because of its slow rate of reproduction, with females producing only four to five pupae per annum, control of the tsetse fly is the best means of controlling trypanosomosis. A number of different methods have been and are used but, whilst successes have been achieved, a long term solution has not been found.

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Resumen La mosca tsetsé (Glossina spp.) infesta 11 millones de km² (Greekmore, 1989) donde es responsable de la transmisión de tripanosomiasis al hombre y animales. Debido a la baja tasa de reproducción de la mosca (cuatro a cinco pupas por a?o), el control de la mosca per se es el método más efectivo, habiendose obtenido algún éxito, sin encontrer todavía una solución a largo plazo.

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Résumé La tsé-tsé (Glossina spp.) occupe 11 millions de km² du sol africain (Greekmore, 1989) et elle est responsable de la transmission de la trypanosomose chez l'homme et les animaux. En raison de son taux lent de reproduction (les femelles ne produisent que 4 à 5 larves par an) la luttre contre la tsétsé est la meilleure méthode pour combattre la trypanosomose. On a utilisé, et on utilise encore, de nombreuses techniques variées et bien que des succès aient été obtenus, aucune solution à long terme n'a encore été trouvée.