排序方式: 共有37条查询结果,搜索用时 46 毫秒
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Beaulieu JP Bennett DP Fouqué P Williams A Dominik M Jørgensen UG Kubas D Cassan A Coutures C Greenhill J Hill K Menzies J Sackett PD Albrow M Brillant S Caldwell JA Calitz JJ Cook KH Corrales E Desort M Dieters S Dominis D Donatowicz J Hoffman M Kane S Marquette JB Martin R Meintjes P Pollard K Sahu K Vinter C Wambsganss J Woller K Horne K Steele I Bramich DM Burgdorf M Snodgrass C Bode M Udalski A Szymański MK Kubiak M Wieckowski T Pietrzyński G Soszyński I Szewczyk O Wyrzykowski L 《Nature》2006,439(7075):437-440
In the favoured core-accretion model of formation of planetary systems, solid planetesimals accumulate to build up planetary cores, which then accrete nebular gas if they are sufficiently massive. Around M-dwarf stars (the most common stars in our Galaxy), this model favours the formation of Earth-mass (M(o)) to Neptune-mass planets with orbital radii of 1 to 10 astronomical units (au), which is consistent with the small number of gas giant planets known to orbit M-dwarf host stars. More than 170 extrasolar planets have been discovered with a wide range of masses and orbital periods, but planets of Neptune's mass or less have not hitherto been detected at separations of more than 0.15 au from normal stars. Here we report the discovery of a 5.5(+5.5)(-2.7) M(o) planetary companion at a separation of 2.6+1.5-0.6 au from a 0.22+0.21-0.11 M(o) M-dwarf star, where M(o) refers to a solar mass. (We propose to name it OGLE-2005-BLG-390Lb, indicating a planetary mass companion to the lens star of the microlensing event.) The mass is lower than that of GJ876d (ref. 5), although the error bars overlap. Our detection suggests that such cool, sub-Neptune-mass planets may be more common than gas giant planets, as predicted by the core accretion theory. 相似文献
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Wave acceleration of electrons in the Van Allen radiation belts 总被引:1,自引:0,他引:1
Horne RB Thorne RM Shprits YY Meredith NP Glauert SA Smith AJ Kanekal SG Baker DN Engebretson MJ Posch JL Spasojevic M Inan US Pickett JS Decreau PM 《Nature》2005,437(7056):227-230
The Van Allen radiation belts are two regions encircling the Earth in which energetic charged particles are trapped inside the Earth's magnetic field. Their properties vary according to solar activity and they represent a hazard to satellites and humans in space. An important challenge has been to explain how the charged particles within these belts are accelerated to very high energies of several million electron volts. Here we show, on the basis of the analysis of a rare event where the outer radiation belt was depleted and then re-formed closer to the Earth, that the long established theory of acceleration by radial diffusion is inadequate; the electrons are accelerated more effectively by electromagnetic waves at frequencies of a few kilohertz. Wave acceleration can increase the electron flux by more than three orders of magnitude over the observed timescale of one to two days, more than sufficient to explain the new radiation belt. Wave acceleration could also be important for Jupiter, Saturn and other astrophysical objects with magnetic fields. 相似文献
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C. Franzini T. Cianci P. Lenzi J. P. Libert J. A. Horne P. L. Parmeggiani 《Cellular and molecular life sciences : CMLS》1986,42(6):604-606
Summary In young rabbits the slope of the temperature in the deep cervical region close to brown adipose tissue increased during desynchronized sleep at low ambient temperature. No increase occurred at neutral ambient temperature. In control rabbits (after disappearance of brown adipose tissue), the slope of deep cervical temperature did not increase during desynchronized sleep at low or neutral ambient temperatures.Preliminary data were reported at the Association des Physiologistes, Réunion de Poitiers, 20–23 June 1983.Acknowledgments. We wish to thank Giuseppe Mancinelli and Leonida Sabattini for technical assistance. This work was supported by a grant from the Consiglio Nazionale delle Ricerche, Rome. J.P.L. wishes to thank NATO for partial financial support during his stay at the Physiology Department in Bologna. 相似文献
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Human slow wave sleep: a review and appraisal of recent findings, with implications for sleep functions, and psychiatric illness. 总被引:4,自引:0,他引:4
J Horne 《Experientia》1992,48(10):941-954
Recent findings concerning human slow wave sleep (hSWS-stages 3 + 4; delta EEG activity) are critically reviewed. Areas covered include the significance of the first hSWS cycle; hSWS in extended sleep; relationship between hSWS, prior wakefulness and sleep loss; hSWS influence on sleep length; problems with hSWS deprivation; influence of the circadian rhythm; individual differences in hSWS, especially, age, gender and constitutional variables such as physical fitness and body composition. Transient increases in hSWS can be produced by increasing both the quality and quantity of prior wakefulness, with an underlying mechanism perhaps relating to the waking level of brain metabolism. Whilst there may also be thermoregulatory influences on hSWS, hypotheses that energy conservation and brain cooling are major roles for hSWS are debatable. hSWS seems to offer some form of cerebral recovery, with the prefrontal cortex being particularly implicated. The hSWS characteristics of certain forms of major psychiatric disorders may well endorse this prefrontal link. 相似文献
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C. H. W. Horne R. S. Patrick R. N. M. Macsween A. R. Henderson 《Cellular and molecular life sciences : CMLS》1972,28(3):306-307
Résumé L'albumine intracellulaire a été démontrée dans le foie de rats par une technique d'immunofluorescence. Il y a une réduction significative du nombre des cellules fluorescentes dans les foies des animaux souffrant de cirrhose produite par le CCl4. 相似文献
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Drago J McColl CD Horne MK Finkelstein DI Ross SA 《Cellular and molecular life sciences : CMLS》2003,60(7):1267-1280
Neuronal nicotinic acetylcholine receptors are ligand-gated ion channels that subserve a
range of functions in the brain and peripheral nervous system. They are pentamers variously composed
of (2– 10) and subunits
( 2– 4). Pharmacological and ligand-binding
studies have shown that the different subunits vary in their distribution and channel properties, but
precise delineation of the in vivo function of individual subunits has been hampered by lack of
subunit-specific antagonists. The development of transgenic mice with targeted deletions
of specific subunits (knockout mice) or mutations in critical receptor domains (knockin mice)
has extended understanding of nicotinic receptors, revealing that some subunits are necessary for
viability, whereas others mediate modulatory effects on learning and memory, locomotion,
anxiety, nociception, dopaminergic neurotransmission, seizure threshold, development of the visual
system and autonomic function. In some cases, studies of transgenic mice have confirmed expectations
derived from pharmacological and expression studies, but in other cases, compensation by related
subunits has revealed a degree of functional redundancy not predicted by previous approaches.Received 19 September 2002; received after revision 12 November 2002; accepted 11 December 2002 相似文献
29.
In young rabbits the slope of the temperature in the deep cervical region close to brown adipose tissue increased during desynchronized sleep at low ambient temperature. No increase occurred at neutral ambient temperature. In control rabbits (after disappearance of brown adipose tissue), the slope of deep cervical temperature did not increase during desynchronized sleep at low or neutral ambient temperatures. 相似文献
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C. H. W. Horne A. W. Thomson C. B. J. Hunter V. van Heyningen D. L. Deane C. M. Steel 《Cellular and molecular life sciences : CMLS》1979,35(3):411-412
Summary 2-PAG is present on the surface of mononuclear blood leucocytes and can be demonstrated predominantly on B-lymphocytes and monocytes. Pretreatment of cells with antibody to 2-PAG leads to a marked reduction in Fc-rosette formation. Competitive blocking experiments with specific antisera reveal a particularly close asociation between 2-PAG and MLR (mixed leucocyte reaction) determinants on the cell surface. These findings suggest one mechanism whereby 2-PAG may modify cell-mediated immune responses. 相似文献