Semisynthetic Enzymes Are New Catalysts: Enzymes may be the ultimate catalysts, especially if their specificities can be changed by chemical modification     

Maugh TH 《Science (New York, N.Y.)》1984,223(4632):154-156

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Effect of photoperiod on gonadotrophin concentrations in domestic turkeys     

Patricia M. M. Godden  C. G. Scanes 《British poultry science》1977,18(6):687-694

1. Circulating immunoreactive luteinising hormone (LH) and follicle stimulating hormone (FSH) concentrations have been measured during photoperiodically‐induced changes in the reproductive state of turkeys.

2. In a period of sexual quiescence on short photoperiods (6L : 18D) LH concentrations were higher during the hours of darkness in both sexes.

3. Transfer to long photoperiods (16L : 8D) stimulated a rapid increase in LH and FSH concentrations. This was maintained for between 2 to 3 months when the concentrations of both gonadotrophins decreased as the birds became photorefractory.

4. Return to short photoperiods had no immediate effect on the concentrations of LH and FSH in females. The concentration of LH was increased during the 3rd week of short photoperiods when the hens were moulting.

5. LH concentrations fluctuated during the ovulatory cycle and were highest about 6 h before ovulation.  相似文献   

Views defended by debater          下载免费PDF全文

Hulland TJ 《The Canadian veterinary journal. La revue veterinaire canadienne》1977,18(7):200

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Hydrolysed feather protein as a source of amino acids for broilers     

R. MaCalpine  C. G. Payne 《British poultry science》1977,18(3):265-273

1. The inclusion of 25 g hydrolysed feather meal (HFM) in each kilogram of diet (floor experiment) and 60 g/kg (cage experiment) did not depress performance.

2. Chemical tests indicated 72.5% of the total lysine in HFM was available.

3. Total lysine concentration of 11.3 g/kg diet maximised performance during the period 0 to 34 d.

4. Reduction in dietary methionine content during the period 0 to 34 d from 4.2 g/kg to 3.2 g/kg did not depress performance on diets containing 60 g HFM/kg.

5. The results indicate that at least 57% by weight of the total sulphur amino acid requirement of broilers can be provided by cystine.  相似文献   

The hen's egg: Relationship of mean strain energy at shell fracture to shell compression speed,the nature of the compressing body and the location on the shell of the point of contact     

T. C. Carter 《British poultry science》1977,18(2):205-211

1. The mean energy, E_f, required for fracture of an egg shell at its equator by a flat plate is known to depend on shell compression speed, v_m, for speeds in the range 20 μm/s to 2.lb5 mm/s; analysis of published data shows that E_f bears a linear relationship to log (v_m ) throughout the industrially important speed range from 20 μm/s to 1.lb1 m/s, increasing from 1.lb3 to 5.lb0 mJ.

2. At lower speeds down to 2 μm/s E_f is constant.

3. E_f is reduced if the flat plate is replaced by a sphere or cylinder; the greater its curvature, the smaller E_f.

4. E_f for the narrow pole is greater and for the broad pole smaller than that for the equator but these differences may be due in part to . systematic differences in shell thickness as well as curvature.  相似文献   

Life below the ross ice shelf, antarctica     

Lipps JH  Ronan TE  Delaca TE 《Science (New York, N.Y.)》1979,203(4379):447-449

Samples and observations under 420 meters of ice and 430 kilometers from the open sea on the Ross Ice Shelf at a water depth of 597 meters revealed an unusual assemblage of benthic organisms. Scavenging amphipods, an isopod, and fish were present but a living infauna was absent. The observations may be accounted for by sampling or spatial bias, or by extremely low or fluctuating trophic resources.  相似文献   

The dynamics of estuaries     

Cheng RT 《Science (New York, N.Y.)》1979,203(4377):260

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Energy resources available to the United States, 1985 to 2000     

Hayes ET 《Science (New York, N.Y.)》1979,203(4377):233-239

Energy and the gross national product have grown hand in hand at 3 to 3(1/2) percent a year for almost 40 years. Our energy growth is slowing down and will sentially level off in the 1990's. Our production of oil and gas passed a peak in the early 1970's, and there is no resource base to justify predictions of increased yields. Coal is the only fossil fuel capable of increased production. There are serious doubts that our uranium resources can support a large light-water reactor program. Finding rates for petroleum, natural gas, and uranium are less than half of what they were 20 years ago.  相似文献   

Decoding nonverbal behavior     

Mayo C 《Science (New York, N.Y.)》1979,205(4413):1370

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The dead sea is alive and, well..     

Maugh TH 《Science (New York, N.Y.)》1979,205(4402):178

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