Response     

Badilescu S 《Science (New York, N.Y.)》1994,264(5163):1342-1343

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Seeing the nuclei of active galaxies     

Kinney AL 《Science (New York, N.Y.)》1994,263(5143):40-42

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A formation mechanism for catalytically grown helix-shaped graphite nanotubes     

Amelinckx S  Zhang XB  Bernaerts D  Zhang XF  Ivanov V  Nagy JB 《Science (New York, N.Y.)》1994,265(5172):635-639

The concept of a spatial-velocity hodograph is introduced to describe quantitatively the extrusion of a carbon tubule from a catalytic particle. The conditions under which a continuous tubular surface can be generated are discussed in terms of this hodograph, the shape of which determines the geometry of the initial nanotube. The model is consistent with all observed tubular shapes and explains why the formation process induces stresses that may lead to "spontaneous" plastic deformation of the tubule. This result is due to the violation of the continuity condition, that is, to the mismatch between the extrusion velocity by the catalytic particle, required to generate a continuous tubular surface, and the rate of carbon deposition.  相似文献   

Variation in plasma cholesterol concentration over time in the domestic fowl     

L. M. Hall  J. C. McKay 《British poultry science》1994,35(4):631-634

1. Variations in the concentration of plasma cholesterol available to the developing oocyte over a three week period in Gallus domesticus are described.

2. There are small changes in concentration between weeks for individual birds, but no changes between consecutive days within weeks or times within days.

3. It is recommended that future attempts to assess the relationship between variation in blood and yolk cholesterol concentrations estimate blood cholesterol concentration from two samples taken a week apart.  相似文献   

Effects of faba bean tannins on the growth and histological structure of the intestinal tract and liver of chicks and rats     

L. T. Ortiz  C. Alzueta  J. Trevino  M. Castano 《British poultry science》1994,35(5):743-754

1. Diets containing a freeze‐dried tannin extract from faba beans (Vicia faba L.) at concentrations of 0, 8 and 16 g/kg were fed to growing chicks and rats.

2. Chicks fed on the tannin‐containing diets exhibited a high mortality and significant decreases in body‐weight as well as lower food intakes and higher food intake:weight gain ratios (P<0.01). In rats there was no mortality but the growth and food intake were adversely affected (P< 0.05).

3. Histological changes occurred in the ileal mucosa of chicks. Atrophy and shortening of villi with distortion of their architecture were observed. Similar histological disorders but less pronounced were also found in rats.

4. Histopathology of the liver of both chicks and rats showed an hydropic degeneration of hepatocytes, clearly more severe in the former than in the latter.  相似文献   

Corruption scandal reaches academe     

Biggin S 《Science (New York, N.Y.)》1994,266(5187):965

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The Structure of Nature's Solvent: Water     

Colson SD  Dunning TH 《Science (New York, N.Y.)》1994,265(5168):43-44

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The entrepreneurial twist     

Panem S 《Science (New York, N.Y.)》1994,263(5151):1299

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Environmental test case     

Humphrey SR 《Science (New York, N.Y.)》1994,265(5174):976-977

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Even a robot cricket always gets her mate     

Bains S 《Science (New York, N.Y.)》1994,266(5192):1809

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