Chemical modification of the photoluminescence quenching of porous silicon     

Lauerhaas JM  Sailor MJ 《Science (New York, N.Y.)》1993,261(5128):1567-1568

The photoluminescence of porous silicon can be quenched by adsorbates, and the degree of quenching can be tuned by chemical derivatization of the porous silicon surface. Thus, as-prepared porous silicon has a hydrophobic, hydrogen-terminated surface, and the photoluminescence is strongly quenched by ethanol and weakly quenched by water. Mild chemical oxidation (iodine followed by hydrolysis) produces a hydrophilic porous silicon surface. Photoluminescence from this hydrophilic material is quenched to a lesser extent by ethanol and to a greater extent by water, relative to the original surface. This demonstrates that the visible luminescence from porous silicon is highly surface-sensitive, and the surface interactions can be tuned by specific chemical transformations.  相似文献   

Plasma astrophysics     

Begelman MC 《Science (New York, N.Y.)》1993,260(5108):705

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AAAS's Red Scare     

Berdick M 《Science (New York, N.Y.)》1993,261(5118):145-146

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Other books of interest     

Gresshoff PM 《Science (New York, N.Y.)》1993,262(5142):2071-2072

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The horse tree     

McKenna MC 《Science (New York, N.Y.)》1993,260(5111):1156-1157

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Genotypic differences in speed and magnitude of response to ahemeral lighting     

M. M. Shanawany  P. S⊘rensen  F. Pirchner 《British poultry science》1993,34(5):881-886

1. The paper compares between three genetically different lines in their egg weight and shell thickness response to a 28‐h cycle.

2. The response in shell thickness to ahemeral lighting was more rapid (2.2 d) than for egg weight (4.2 d).

3. Differences between genotypes were evident in both the speed and magnitude of response.

4. Overall, egg weight and shell thickness on the 28‐h cycle were 7% and 8% greater than on 24 h.

5. The allometric increase indicates that the increase in shell weight was on average 14% more than the increase in egg weight.  相似文献   

Monitoring pregnancy losses in small dairy herds     

Lemire GE  Stalheim PS  Lemire MR  Tiemann M  Verdon L 《The Canadian veterinary journal. La revue veterinaire canadienne》1993,34(1):33-35

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Metastatic chondrosarcoma and subcutaneous granulomas in a grey rat snake (Elaphe obsoleta obsoleta)          下载免费PDF全文

Honour SM  Ayroud M  Wheler C 《The Canadian veterinary journal. La revue veterinaire canadienne》1993,34(4):238-240

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Food intake adjustments of chicks: Short term reactions of genetic stocks to deficiencies in lysine,methionine or tryptophan     

D. O. Noble  M. L. Picard  E. A. Dunnington  G. Uzu  A. S. Larsen  P. B. Siegel 《British poultry science》1993,34(4):725-735

1. Growth, food intake, and food preference were measured in two experimental lines (White Rocks and White Leghorns) of chickens fed diets varying in content of lysine, methionine, or tryptophan. Diet A was balanced in all amino acids, while the remaining 6 diets were moderately ( ～ 30%) or slightly ( ～ 15%) deficient in either lysine, methionine, or tryptophan relative to NRC recommendations for broiler diets.

2. Body weight and food utilisation efficiency of White Leghorns at 10 d of age were not affected by diet, whereas the lower concentrations of lysine and methionine depressed these traits in White Rocks.

3. Tryptophan deficiency reduced food intake of White Leghorns, but not White Rocks.

4. With choice feeding of balanced and deficient diets from day 10 to 16, preferences between the diets were minimal for White Leghorns, whereas for White Rocks there was an almost immediate preference for the balanced diet, followed by lack of preference or preference for the deficient diet.

5. Apparently for some genetic stocks there is rapid adjustment to deficiencies in these amino acids with overconsumption, followed by compensation for preference of the balanced diet. The response, however, will vary depending on the deficient amino acid.  相似文献   

Radioactive waste at ward valley     

Grossman CM 《Science (New York, N.Y.)》1995,269(5231):1653-1655

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