Groundwater contamination     

Bredehoeft JD  Usselman TM 《Science (New York, N.Y.)》1984,224(4655):1292

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Effects of pretreatment conditions on ammonium and nitrate uptake by Douglas-fir seedlings     

Rygiewicz PT  Bledsoe CS 《Tree physiology》1986,1(2):145-150

Effects of pretreatment solutions containing varying concentrations of calcium, potassium, ammonium and nitrate were evaluated by measuring fluxes of the same ions during a subsequent 4-hour uptake by Douglas-fir seedlings. Maximal rate of ammonium uptake (11 microeq g(-1) root dry weight h(-1)) was about 5 times faster than that of nitrate (2 microeq g(-1) root dry weight h(-1)). Ammonium uptake was most rapid after pretreatment with low potassium levels and was unaffected by ammonium pretreatment. Nitrate uptake was most rapid after pretreatment with high levels of nitrate and low levels of potassium. Calcium uptake was greater when nitrate replaced ammonium as the N source. High calcium pretreatment levels depressed subsequent calcium uptake or resulted in calcium release in both ammonium and nitrate experiments. Potassium efflux occurred with both N sources, but the release was less during nitrate uptake than during ammonium uptake. Efflux of potassium is probably associated with the high potassium status of the seedlings and the exchange between potassium and other cations. High levels of potassium in the pretreatment solutions enhanced potassium efflux and caused a reduction in the subsequent rates of uptake of both ammonium and nitrate. Length of pretreatment and seedling size generally did not affect uptake rates.  相似文献   

Venus: detailed mapping of maxwell montes region     

Alexandrov YN  Crymov AA  Kotelnikov VA  Petrov GM  Rzhiga ON  Sidorenko AI  Sinilo VP  Zakharov AI  Akim EL  Basilevski AT  Kadnichanski SA  Tjuflin YS 《Science (New York, N.Y.)》1986,231(4743):1271-1273

From October 1983 to July 1984, the north hemisphere of Venus, from latitude 30 degrees to latitude 90 degrees , was mapped by means of the radar imagers and altimeters of the spacecraft Venera 15 and Venera 16. This report presents the results of the radar mapping of the Maxwell Montes region, one of the most interesting features of Venus' surface. A radar mosaic map and contour map have been compiled.  相似文献   

Influence of site and variety on starch,hemicellulose and cellulose composition of wheats and their digestibilities by adult cockerels     

Margaret Longstaff  J. M. McNab 《British poultry science》1986,27(3):435-449

1. It has been shown that both the variety of wheat and the environment under which growth took place influenced the quantities of starch and cell wall carbohydrate contents of wheat.

2. The different varieties of wheat investigated contained different proportions of water‐soluble to water‐insoluble hemicelluloses.

3. By comparison of the arabinose to xylose ratios it was concluded that water‐soluble and insoluble arabinoxylans of wheat were branched to the same degree.

4. Starch from six wheat varieties grown in the U.K. was very well digested by adult cockerels and true metabolisable energy values of the wheats were high.

5. Small amounts of cell wall carbohydrates were digested by adult cockerels.  相似文献   

Effects of evisceration and storage temperature on changes in meat quality of traditional farm‐fresh Turkeys     

T. C. Grey  G. C. Mead  Nerys M. Griffiths  J. M. Jones 《British poultry science》1986,27(3):463-470

1. Conditions affecting the keeping quality of traditional farm‐fresh turkeys were investigated.

2. Storage of uneviscerated Wrolstad turkeys at 4 °C for 10 days caused no statistically significant changes in meat flavour or texture.

3. During further storage at —2 °C, however, there was a slight but significant change in flavour, which became more marked with time in birds which had been eviscerated after the initial period at 4 °C.

4. Both eviscerated and uneviscerated birds became slightly tougher during storage.

5. Initial holding at 4 °C increased the numbers of psychrotrophic bacteria on the skin by about 10³ but subsequent changes at — 2 °C were slight for uneviscerated birds.

6. Eviscerated carcases had higher counts than uneviscerated birds after storage at — 2 °C and, although ‘off’ odours were not detected, spoilage appeared to be imminent at the end of the 20‐d period.  相似文献   

Book reviews     

P. A. L. Wight  G. C. Perry 《British poultry science》1986,27(3):511-514

Birds Their Structure and Function, By A. S. King and J. McLelland, 1984. 2nd ed. 334 pp. illustrated. London, Baillière Tindall. £9.50. ISBN 0 7020 0872 9.

Proceedings of the 2nd European Symposium on Poultry Welfare, 1985. 360 pp. illustrated. German Branch of the World's Poultry Science Association, Celle, Institut für Kleintierzucht.  相似文献   

Age of the earliest african anthropoids     

Fleagle JG  Bown TM  Obradovich JD  Simons EL 《Science (New York, N.Y.)》1986,234(4781):1247-1249

The earliest fossil record of African anthropoid primates (monkeys and apes) comes from the Jebel Qatrani Formation in the Fayum depression of Egypt. Reevaluation of both geologic and faunal evidence indicates that this formation was deposited in the early part of the Oligocene Epoch, more than 31 million years ago, earlier than previous estimates. The great antiquity of the fossil higher primates from Egypt accords well with their primitive morphology compared with later Old World higher primates. Thus, the anthropoid primates and hystricomorph rodents from Fayum are also considerably older than the earliest higher primates and rodents from South America.  相似文献   

Mathematical physics: gravitational physics of stellar and galactic systems     

DE Zeeuw T 《Science (New York, N.Y.)》1986,232(4751):778-779

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Ice-nucleating bacteria     

Lindemann J  Warren GJ  Suslow TV 《Science (New York, N.Y.)》1986,231(4738):536

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The benefits of zootherapy          下载免费PDF全文

Sanderson T 《The Canadian veterinary journal. La revue veterinaire canadienne》1986,27(5):229

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