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Jeffrey L. Beynon David L. Hutchins Anthony J. Rubino Addison L. Lawrence Brian R. Chapman 《Journal of the World Aquaculture Society》1981,12(2):63-70
Birds can reduce production of shrimp in mariculture grow-out ponds through predation and competition for feed. This study involved weekly nocturnal enumeration of bird populations and observation of nocturnal avian habits on a series of 0.1 ha experimental ponds at the Texas A&M University Shrimp Mariculture Facility at Corpus Christi, Texas. Observations were conducted hourly from sunset to sunrise during October through December 1980. The rate of predation was evaluated every three hours by comparing the number of feeding attempts to the number of successful prey captures over a known time period. Gulls (Family Laridae) acted primarily as competitors for feed. Active feeding by gulls was restricted to daylight hours, consequently feed loss decreased when the feed was distributed at or after dusk. Major preadatory birds included herons and egrets (F. Ardeidae), migratory ducks (F. Anatidae), and, to a lesser extent, grebes (F. Podicipedidae) and shorebirds (Order Charadriiformes). Bird predation decreased pond production by 75% in some ponds. 相似文献
143.
The pear cultivars ‘Spadona Estiva’, ‘Coscia’, ‘Beurré Superfin’ and a ‘Bartlett’ clone of South African origin (termed ‘Bartlett Sport’) were tested on 5 quince rootstock types, 5 Pyrus species and on 5 or 30 cm long interstocks of the pear cultivars ‘Bergamotte Esperen’ and ‘Spadona Estiva’ on quince MA, while ‘Dr. Jules Guyot’ was used as an interstock on ‘Bartlett’ seedlings.At the age of 10 years only ‘Spadona Estiva’ showed no signs of decline on quince rootstocks, ‘Coscia’ showed moderate decline, while the remaining cultivars had already declined severely. When the trunk circumference of ‘Beurré Superfin’ trees on the various quince clones was taken as an indicator for the degree of graft incompatibility, a negative correlation was found between this parameter and cyanogenic glycoside content in the stem bark of ungrafted quince plants belonging to the same clones. Pear interstocks on quince MA rootstocks did in some cases increase crops compared to the same quince alone, but did not prevent the decline of ‘Beurré Superfin’ and Bartlett Sport' on quince.The most vigorous and most prolific rootstock was Pyrus betulaefolia. However, with ‘Spadona Estiva’ differences in vigor between the rootstocks were only small and crops on the Israeli quince CI 7 were similar to those on Pyrus betulaefolia, but fruit size was larger on quince. Cropping of this cultivar at the age of 4 years was closely related to the intensity of flowering, whereas with ‘Coscia’ this relation was much less evident.Leaf fall in autumn and the opening of the vegetative buds of ‘Beurré Superfin’ in spring were earlier on quince than on Pyrus rootstocks. 相似文献
144.
Papantoniou E Hammond EW Tsiami AA Scriven F Gordon MH Schofield JD 《Journal of agricultural and food chemistry》2003,51(4):1057-1063
Fractionation and reconstitution techniques were used to study the contribution of endogenous flour lipids to the quality of semisweet (Rich Tea-type) biscuits. Biscuit flour was defatted with chloroform and baked with bakery fat but without endogenous lipid addition. Semisweet biscuits baked from defatted flour were flatter, denser, and harder and showed collapse of gas cells during baking when compared with control biscuits. Defatted flour semisweet doughs exhibited a different rheological behavior from the control samples showing higher storage and loss moduli (G' and G' ' values), that is, high viscoelasticity. Functionality was restored when total nonstarch flour lipids were added back to defatted flour. Both the polar and nonpolar lipid fractions had positive effects in restoring flour quality, but the polar lipid fraction was of greatest benefit. Both fractions were needed for complete restoration of both biscuit quality and dough rheological characteristics. 相似文献
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Linden DJ 《Science (New York, N.Y.)》2003,301(5640):1682-1685
Neuroscientists have long sought to elucidate the molecular underpinnings of the memories needed to learn, for example, a motor task. In his Perspective, Linden discusses new work (Koekkoek et al.) suggesting that long-term depression in Purkinje cells mediated by protein kinase C signaling is responsible for motor memory in a task called associative eyelid conditioning. 相似文献
147.
Malakoff D 《Science (New York, N.Y.)》2003,301(5636):1034-1037
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Cole-Hamilton DJ 《Science (New York, N.Y.)》2003,299(5613):1702-1706
Homogeneous catalysts have many attractive properties, such as high selectivities. However, many homogeneous catalytic systems cannot be commercialized because of difficulties associated with separating the products from the catalyst. Recent approaches to tackling this problem are reviewed and compared. 相似文献