Interplay of rotational, relaxational, and shear dynamics in solid ⁴He

Using a high-sensitivity torsional oscillator (TO) technique, we mapped the rotational and relaxational dynamics of solid helium-4 ((4)He) throughout the parameter range of the proposed supersolidity. We found evidence that the same microscopic excitations controlling the torsional oscillator motions are generated independently by thermal and mechanical stimulation. Moreover, a measure for the relaxation times of these excitations diverges smoothly without any indication for a critical temperature or critical velocity of a supersolid transition. Finally, we demonstrated that the combined temperature-velocity dependence of the TO response is indistinguishable from the combined temperature-strain dependence of the solid's shear modulus. This implies that the rotational responses of solid (4)He attributed to supersolidity are associated with generation of the same microscopic excitations as those produced by direct shear strain.     

Induction of AIDS-like disease in macaque monkeys with T-cell tropic retrovirus STLV-III

The T-cell tropic retrovirus of macaque monkeys STLV-III has morphologic, growth, and antigenic properties indicating that it is related to HTLV-III/LAV, the etiologic agent of the acquired immune deficiency syndrome (AIDS) in humans. Four of six rhesus monkeys died within 160 days of STLV-III inoculation with a wasting syndrome, opportunistic infections, a primary retroviral encephalitis, and immunologic abnormalities including a decrease in T4+ peripheral blood lymphocytes. These data show that an immunodeficiency syndrome can be produced experimentally in a nonhuman primate by an agent from the HTLV-III/LAV group of retroviruses. The STLV-III-macaque system will thus provide a useful model for the study of antiviral agents and vaccine development for human AIDS.     

A region of the Herpesvirus saimiri genome required for oncogenicity

Herpesvirus saimiri naturally infects squirrel monkeys (Saimiri sciureus) without producing signs of disease; infection of other New World primates, however, results in a rapidly progressing, malignant, T-cell lymphoma. Results described in this report identify a region of the viral genome that is required for oncogenicity in owl monkeys (Aotus trivirgatus); this region is not required for replication of the virus. This is believed to be the first such genomic region identified in a herpesvirus system.     

Interactions between mitochondrial lipid oxidation and oxymyoglobin oxidation and the effects of vitamin E

Off-flavor and discoloration of meat products result from lipid oxidation and myoglobin (Mb) oxidation, respectively, and these two processes appear to be interrelated. The objective of this study was to investigate their potential interaction in mitochondria and the effects of mitochondrial alpha-tocopherol concentrations on lipid oxidation and metmyoglobin (MetMb) formation in vitro. The addition of ascorbic acid and ferric chloride (AA-Fe(3+)) increased ovine and bovine mitochondrial lipid oxidation when compared with their controls (p < 0.05); MetMb formation also increased with increased lipid oxidation relative to controls (p < 0.05). Reactions containing Mb and mitochondria with greater alpha-tocopherol concentrations demonstrated less lipid oxidation and MetMb formation than mitochondria with lower alpha-tocopherol concentrations. Greater mitochondrial alpha-tocopherol concentration was also correlated with increased mitochondrial oxygen consumption in vitro and with a more pronounced effect at pH 7.2 than at pH 5.6. Relative to controls, succinate addition to bovine mitochondria resulted in increased concentrations of ubiquinol 10 and alpha-tocopherol and decreased lipid and Mb oxidation (p < 0.05). Mitochondrial lipid oxidation was closely related to MetMb formation; both processes were inhibited by alpha-tocopherol in a concentration-dependent manner.     

Effects of birth weight and postnatal nutrition on neonatal sheep: IV. Organ growth

This study investigated effects of birth weight and postnatal nutrition on organ growth in neonatal lambs. Suffolk x (Finnsheep x Dorset) low- (mean +/- SD 2.29 +/- 0.34 kg, n = 28) and high- (4.84 +/- 0.45 kg, n = 20) birth-weight male lambs were studied. Lambs within each birth weight category were allocated to be individually grown rapidly (ad libitum fed, ADG 337 g, n = 20) or slowly (ADG 150 g, n = 20) on a liquid diet to live weights up to approximately 20 kg. All organs weighed less at birth in small than in large newborns (P < 0.001), except the adrenals (P = 0.10). At birth, as a percentage of empty body weight (EBW), small newborns had larger testes (0.14 vs. 0.10%, P = 0.023) and smaller thymus (0.17 vs. 0.37%, P = 0.009), and tended to have a larger heart (0.85 vs. 0.75%, P = 0.060) and a smaller spleen (0.10 vs. 0.14%, P = 0.054) than large newborns. During the first 2 to 3 wk postpartum, small newborns had greater fractional growth rates of organs than large newborns, most notably spleen, thymus, and liver. Postnatal growth of organs was more closely associated with EBW than age, except for lungs, testes, and stomach. At completion of rearing to 20 kg of live weight, small newborns had a spleen approximately 30% heavier than large newborns (P < 0.001). Testes weights were 37% and 24% greater in small newborns reared slowly and rapidly, respectively, compared with their high-birth-weight counterparts (P = 0.034). It was also evident that postnatal nutrition altered the mass of individual organs at the conclusion of the rearing period without affecting the combined weight of dissected organs. Slowly reared lambs had a larger pancreas (+27%, P = 0.002), stomach complex (+83%, P < 0.001), large intestine (+39%, P < 0.001), entire gastrointestinal tract (+18%, P = 0.002), and testes (+54%, P = 0.016) and tended to have a larger heart (+6%, P = 0.068) than their rapidly reared counterparts at 20 kg of live weight. Rapidly reared lambs had a larger thymus (+61%, P = 0.003), liver (+34%, P < 0.001), kidneys (+33%, P < 0.001), and small intestine (+17%, P < 0.001) and tended to have a larger thyroid (+13%, P = 0.054) at 20 kg of live weight than slowly reared lambs. The functional significance of the smaller thymus at birth and increase in spleen and testes weights at 20 kg of live weight in low- compared with high-birth-weight lambs warrants further investigation. It also remains to be established whether these differences at 20 kg of live weight persist.     

Searching the world wide Web

The coverage and recency of the major World Wide Web search engines was analyzed, yielding some surprising results. The coverage of any one engine is significantly limited: No single engine indexes more than about one-third of the "indexable Web," the coverage of the six engines investigated varies by an order of magnitude, and combining the results of the six engines yields about 3.5 times as many documents on average as compared with the results from only one engine. Analysis of the overlap between pairs of engines gives an estimated lower bound on the size of the indexable Web of 320 million pages.