HST and VLT investigations of the fragments of comet C/1999 S4 (LINEAR)     

Weaver HA  Sekanina Z  Toth I  Delahodde CE  Hainaut OR  Lamy PL  Bauer JM  A'Hearn MF  Arpigny C  Combi MR  Davies JK  Feldman PD  Festou MC  Hook R  Jorda L  Keesey MS  Lisse CM  Marsden BG  Meech KJ  Tozzi GP  West R 《Science (New York, N.Y.)》2001,292(5520):1329-1333

At least 16 fragments were detected in images of comet C/1999 S4 (LINEAR) taken on 5 August 2000 with the Hubble Space Telescope (HST) and on 6 August with the Very Large Telescope (VLT). Photometric analysis of the fragments indicates that the largest ones have effective spherical diameters of about 100 meters, which implies that the total mass in the observed fragments was about 2 x 10(9) kilograms. The comet's dust tail, which was the most prominent optical feature in August, was produced during a major fragmentation event, whose activity peaked on UT 22.8 +/- 0.2 July 2000. The mass of small particles (diameters less than about 230 micrometers) in the tail was about 4 x 10(8) kilograms, which is comparable to the mass contained in a large fragment and to the total mass lost from water sublimation after 21 July 2000 (about 3 x 10(8) kilograms). HST spectroscopic observations during 5 and 6 July 2000 demonstrate that the nucleus contained little carbon monoxide ice (ratio of carbon monoxide to water is less than or equal to 0.4%), which suggests that this volatile species did not play a role in the fragmentation of C/1999 S4 (LINEAR).  相似文献   

SOME PHYSICAL ASPECTS OF A RECENT ANALYSIS OF THE EARTH'S MAGNETIC FIELD     

Bauer LA 《Science (New York, N.Y.)》1923,58(1494):113-115

  相似文献   

Diminished response of Werner's syndrome fibroblasts to growth factors PDGF and FGF   总被引：3，自引：0，他引：3  

E A Bauer  N Silverman  D F Busiek  A Kronberger  T F Deuel 《Science (New York, N.Y.)》1986,234(4781):1240-1243

Patients with Werner's syndrome, an autosomal recessive disorder, undergo an accelerated aging process that leads to premature death. Fibroblasts from such patients typically grow poorly in culture. Here it is shown that fibroblasts from a patient with Werner's syndrome have a markedly attenuated mitogenic response to platelet-derived growth factor (PDGF) and fibroblast growth factor (FGF). In contrast, they have a full mitogenic response to fetal bovine serum. Both PDGF binding and receptor numbers per cell are unaltered. The Werner's syndrome cells express high constitutive levels of collagenase in vitro. Although PDGF enhances collagenase expression through increased levels of hybridizable collagenase messenger RNA in normal skin fibroblasts, no induction of collagenase occurs in the Werner's syndrome fibroblasts. Moreover, the failure to respond to this agonist effect of PDGF is not restored by fetal bovine serum. The data suggest that failure of one or more PDGF-mediated pathways in Werner's syndrome cells may contribute to the phenotypic expression of the disorder.  相似文献   

Vascular smooth muscle: aerobic glycolysis linked to sodium and potassium transport processes   总被引：7，自引：0，他引：7  

R J Paul  M Bauer  W Pease 《Science (New York, N.Y.)》1979,206(4425):1414-1416

Under aerobic conditions, glucose is primarily catabolized by vascular smooth muscle to lactate, in spite of an adequate oxidative capacity. Although this is often considered to be indicative of some nonspecific metabolic insufficiency, there is evidence that aerobic glycolysis is specifically coupled to sodium and potassium transport processes, whereas oxidative metabolism is couple to contracticle energy requirements.  相似文献   

Ionosphere of venus: first observations of the effects of dynamics on the dayside ion composition     

Taylor HA  Brinton HC  Bauer SJ  Hartle RE  Cloutier PA  Michel FC  Daniell RE  Donahue TM  Maehl RC 《Science (New York, N.Y.)》1979,203(4382):755-757

Bennett radio-frequency ion mass spectrometers have returned the first in situ measurements of the Venus dayside ion composition, including evidence of pronounced structural variability resulting from a dynamic interaction with the solar wind. The ionospheric envelope, dominated above 200 kilometers by O(+), responds dramatically to variations in the solar wind pressure, Which is observed to compress the thermal ion distributions from heights as great as 1800 kilometers inward to 280 kilometers. At the thermal ion boundary, or ionopause, the ambient ions are swept away by the solar wind, such that a zone of accelerated suprathermnal plasma is encountered. At higher altitudes, extending outward on some orbits for thousands of kilometers to the bows shock, energetic ion currents are detected, apparently originating from the shocked solar wind plasma. Within the ionosphere, observations of pass-to-pass differences in the ion scale heights are indicative of the effects of ion convection stimlulated by the solar wind interaction.  相似文献   

DNA rearrangement and altered RNA expression of the c-myb oncogene in mouse plasmacytoid lymphosarcomas   总被引：51，自引：0，他引：51  

J F Mushinski  M Potter  S R Bauer  E P Reddy 《Science (New York, N.Y.)》1983,220(4599):795-798

Three types of tumors termed plasmacytomas (ABPC's), lymphosarcomas (ABLS's), and plasmacytoid lymphosarcomas (ABPL's) arise in BALB/c mice treated with pristane and Abelson murine leukemia virus (A-MuLV). While most ABPC's and BLS's contain integrated A-MuLV proviral genome and synthesize the v-abl RNA, most ABPL's do not. The ABPL tumors were examined for the expression of other oncogenes that may be associated with their transformed state, in the absence of transforming virus. These tumors expressed abundant c-myb RNA of unusually large size and showed DNA rearrangements of the c-myb locus.  相似文献   

Visually guided reaching in infant monkeys after restricted rearing   总被引：4，自引：0，他引：4  

R Held  J A Bauer 《Science (New York, N.Y.)》1967,155(763):718-720

Infant macaques were reared from birth in an apparatus which pre cluded sight of their body parts. At 35 days postpartum one hand was exposed to view. Visual fixation of this hand was insistent and prolonged; visually guided reaching was poor, but it improved during ten succeeding hours of exposure. Little concomitant improvement occurred in the reaching of the unexposed hand.  相似文献   

MAGNETIC WORK OF THE UNITED STATES COAST AND GEODETIC SURVEY PLANNED FOR JULY 1, 1902, TO JUNE 30, 1903     

Bauer LA 《Science (New York, N.Y.)》1902,16(405):555-556

  相似文献   

A PLEA FOR TERRESTRIAL AND COSMICAL PHYSICS     

Bauer LA 《Science (New York, N.Y.)》1909,29(745):566-570

  相似文献   

THE BROADER ASPECTS OF RESEARCH IN TERRESTRIAL MAGNETISM     

Bauer LA 《Science (New York, N.Y.)》1911,33(837):41-54

  相似文献