Turbulence theory     

Lumley JL 《Science (New York, N.Y.)》1991,253(5020):686

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Atomic and molecular manipulation with the scanning tunneling microscope     

Stroscio JA  Eigler DM 《Science (New York, N.Y.)》1991,254(5036):1319-1326

The prospect of manipulating matter on the atomic scale has fascinated scientists for decades. This fascination may be motivated by scientific and technological opportunities, or from a curiosity about the consequences of being able to place atoms in a particular location. Advances in scanning tunneling microscopy have made this prospect a reality; single atoms can be placed at selected positions and structures can be built to a particular design atom-by-atom. Atoms and molecules may be manipulated in a variety of ways by using the interactions present in the tunnel junction of a scanning tunneling microscope. Some of these recent developments and some of the possible uses of atomic and molecular manipulation as a tool for science are discussed.  相似文献   

Continuing exclusions     

Strober MH 《Science (New York, N.Y.)》1991,254(5030):445-446

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Response     

Kaper JB  Mobley HL 《Science (New York, N.Y.)》1991,254(5030):358

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Ocular chemistry     

Adler AJ 《Science (New York, N.Y.)》1991,253(5024):1153

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Collections and causes     

Maienschein J 《Science (New York, N.Y.)》1991,254(5034):1050

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Despite reports of its death, the big bang is safe     

Waldrop MM 《Science (New York, N.Y.)》1991,251(4991):272-273

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Estimation of the relative bioavailability of copper sources in chicks fed on conventional dietary amounts     

M. A. Zanetti  P. R. Henry  C. B. Ammerman  R. D. Miles 《British poultry science》1991,32(3):583-588

1. Tissue accumulation of Cu from dietary additions of 0, 5, 10, or 20 mg/kg Cu as reagent grade Cu acetate and feed grade Cu carbonate was determined in day‐old chicks fed on conventional maize‐soyabean meal starter diets (5.41 mg/kg Cu as‐fed basis) for 3 weeks.

2. Average daily food intake, daily weight gain and food conversion were similar among treatments.

3. There were linear increases in plasma and liver Cu concentrations (P< 0.01) as dietary Cu increased.

4. Bioavailability of Cu as carbonate was 0.66 that of Cu in the acetate based on the multiple regression slope ratio of liver Cu concentration on added dietary Cu. Although responses for the two Cu sources did not differ significantly, the relative bioavailability of the Cu carbonate was similar (0.66 vs 0.68) to that obtained in an earlier study (Ledoux et al., 1991) with greater dietary Cu contents (150, 300 and 450 mg/kg) in which the slopes of the equations representing the two sources differed (P<0.05).  相似文献   

Book reviews     

Ron G. Board  M. H. Maxwell  A. H. Sykes 《British poultry science》1991,32(4):885-888

The Avian Egg: Chemistry & Biology, by R. W. Burley and D. V. Vadehra, 1989. v+472 pp. illustrated. New York. John Wiley & Sons. £66.70. ISBN 0–471–849952.

A Colour Atlas of Avian Anatomy, by J. McLelland. 1990. 127 pp. illustrated. London, Wolfe Publishing Ltd. £30. ISBN 0–7234–1575–7.

The Tropical Agriculturalist—Poultry, by A. J. Smith, 1990. vi + 218 pp. CTA/Macmillan, London. ISBN 0–333–52306–7.  相似文献   

The possible role of methionine in the detoxification of faba bean (Vicia faba L.) tannins in chick diets     

C. N. Wareham  J. Wiseman  D. J. A. Cole  J. Craigon 《British poultry science》1991,32(5):1017-1026

1. A metabolism trial was designed to investigate the role of methionine as a specific detoxifying agent of the condensed tannins present in faba beans (Vicia faba L.).

2. A 5 x 5 factorial approach was employed where 5 concentrations of dietary methionine were obtained (ranging from 3.9 to 12.15 g/kg diet dry matter) by the addition of DL‐methionine, and 5 concentrations of condensed tannins (ranging from 0.5 to 19.7 g/kg diet dry matter) by altering the ratio of tannin‐free and tannin‐containing faba bean hulls added to a basal diet.

3. The intake of condensed tannins had a significant, depressive effect on apparent available nitrogen (P< 0.001) and nitrogen corrected apparent metabolisable energy (AME_n ) (P< 0.001). There was no interaction between methionine and tannin (P>0.05). Thus the depressive effect of tannin was independent of methionine levels in the diet.

4. Methionine does not act as a specific detoxifier of faba bean condensed tannins.  相似文献