Hearnshaw on burt     

Cronbach LJ 《Science (New York, N.Y.)》1979,206(4425):1392-1394

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Science and the politics of development     

Carey WD 《Science (New York, N.Y.)》1979,205(4413):1339

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Measurement of fluctuating magnetic gradients originating from oceanic internal waves     

Podney W  Sager R 《Science (New York, N.Y.)》1979,205(4413):1381-1382

Fluctuating magnetic gradients over oceans come from electric currents flowing in seawater arising from its motions across the earth's magnetic field. Gradients of 0.3 to 0.6 picoteslas per meter for each meter of internal wave displacement have been measured at frequencies of 2 to 5 millihertz with a superconductive magnetic gradiometer supported 7 meters above the surface of water 18 meters deep about 1.5 kilometers offshore from San Diego, California.  相似文献   

Extraction and analysis of organic cations from Acid solution with strong electric fields and mass spectrometry     

Ligon WV 《Science (New York, N.Y.)》1979,204(4389):198-200

High electric fields have been used to extract organic cations from solutions of small organic molecules in polyphosphoric acid. The cations have been analyzed by mass spectrometry. Production of ions by this method is shown to be related to ease of protonation by acid rather than to ionization potential.  相似文献   

Dollar-a-Gallon Gas Fuels Metric Conversion     

Broad WJ 《Science (New York, N.Y.)》1979,205(4411):1113

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Energy R & d fueled by few countries     

Broad WJ 《Science (New York, N.Y.)》1979,206(4425):1384-1385

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Environmentalists chide carter     

Carter LJ 《Science (New York, N.Y.)》1979,205(4405):471

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Nuclear physics     

McVoy KW 《Science (New York, N.Y.)》1979,205(4405):486-487

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Effect of different patterns of food restriction from different ages on growth and efficiency of broilers     

W. J. Yule  D. E. Fuelling 《British poultry science》1979,20(3):273-279

1. The effect of restricted feeding on performance and carcass characteristics of broilers was determined in three experiments.

2. In the first experiment, removal of food for 8 h/d from 42 to 56 d of age significantly improved food conversion efficiency of broilers on deep litter. Removal of food for 16 h/d or on alternate days tended to cause slower growth and also improved conversion efficiency.

3. In the second experiment, denial of food for 8 h/d did not significantly affect either growth rate or conversion efficiency of caged broilers. Denial of food on alternate days, from 28 d of age, depressed food intake and growth rate. Food restriction decreased dressing percentage regardless of the age of introduction. With 32, 40 or 48 h food denial each 72 h there was a large depression in growth rate and dressing percentage. Carcass dry matter was also less, indicating less carcass fat, when food was denied for 48 h each 72 h.

4. In the third experiment, growth rate of broilers on deep litter was significantly improved by denying food for 8 h/d from 28 d of age, and was significantly depressed by food denial on alternate days. This depression was significantly more severe if restriction started at 28 d rather than at 42 d of age. Conversion efficiency was not significantly improved by denial for 8 h/d.

5. In the last two experiments conversion efficiency was much worse in severe restriction.  相似文献   

Effect of light,vitamin d and dietary phosphorus on egg‐shell quality late in the pullet laying year     

A. L. Yannakopoulos  T. R. Morris 《British poultry science》1979,20(3):337-342

1. Eighteen diets supplying all combinations of three phosphorus contents (3.1, 4.0 and 4.8 g non‐phytate P/kg) and six vitamin D supplements (37.5 or 150 μg cholecalciferol/kg; or 16 or 24 μg 25‐hydroxy‐cholecalciferol/kg; or 37.5 μg cholecalciferol/kg with either 16 or 24 μg 25‐hydroxycholecalciferol/kg) were fed to 2 880 pullets of two stocks from 64 to 74 weeks of age. The birds were housed in eight light‐proof rooms, four of which had 24‐h light‐dark cycles (16L : 8D) and four had 28‐h cycles (20L : 8D).

2. The dietary treatments had no significant effect upon food intake, egg output, shell thickness, shell deformation or specific gravity of the eggs.

3. The 28‐h cycle reduced mean rate of lay by 4.5%, increased egg weight by 5.8% and increased shell thickness by 9.4%. The proportion of eggs with shell faults revealed on candling was reduced from 4.1 % to 2.8%.

4. It is concluded from this and other sources that decreasing dietary phosphorus or modifying vitamin D supplements may sometimes lead to increases in shell thickness of the order of 1 to 2%, but that these changes are unlikely to result in a measurable reduction in the proportion of cracked eggs late in the laying year.

5. A 28‐h light‐dark cycle results in a longer and more uniform interval between consecutive ovipositions and thus gives reliable increases in shell thickness which are large enough to reduce the proportion of cracked eggs in many practical situations. Whether it is profitable to use an ahemeral cycle will depend upon the relative prices paid for eggs of different sizes.  相似文献