Infrared echoes near the supernova remnant Cassiopeia A     

Krause O  Rieke GH  Birkmann SM  Le Floc'h E  Gordon KD  Egami E  Bieging J  Hughes JP  Young ET  Hinz JL  Quanz SP  Hines DC 《Science (New York, N.Y.)》2005,308(5728):1604-1606

Two images of Cassiopeia A obtained at 24 micrometers with the Spitzer Space Telescope over a 1-year time interval show moving structures outside the shell of the supernova remnant to a distance of more than 20 arc minutes. Individual features exhibit apparent motions of 10 to 20 arc seconds per year, independently confirmed by near-infrared observations. The observed tangential velocities are at roughly the speed of light. It is likely that the moving structures are infrared echoes, in which interstellar dust is heated by the explosion and by flares from the compact object near the center of the remnant.  相似文献   

Photoperiod manipulation of insect diapause: a method of pest control?   总被引：3，自引：0，他引：3  

D K Hayes  W N Sullivan  M Z Oliver  M S Schechter 《Science (New York, N.Y.)》1970,169(943):382-383

Extension of day length by artificial light in selected field plots in the fall prevented 76 percent of European corn borer [Ostrinia nubilalis (Hübner)] larvae and 70 percent of codling moth [Laspeyresia pomonella (L.)] larvae from entering diapause. Nondiapausing insects cannot survive rigorous winter conditions.  相似文献   

Hypertensive action of 18-hydroxydeoxycorticosterone   总被引：2，自引：0，他引：2  

J T Oliver  M K Birmingham  A Bartova  M P Li  T H Chan 《Science (New York, N.Y.)》1973,182(118):1249-1251

18-Hydroxydeoxycorticosterone is an adrenal steroid hormone causing salt and water retention and is secreted in greatly increased amounts in response to the pituitary hormone adrenocorticotropic hormone. Its production is abnormally high in some forms of hypertension in man and rat. Direct proof that 18-hydroxydeoxycorticosterone is capable of causing hypertension is present. Daily subcutaneous injections of 200 micrograms, a low physiological dose, significantly increase the blood pressure of unilaterally nephrectomized saline-treated rats after 2 weeks. This strengthens the hypothesis that 18-hydroxydeoxycorticosterone contributes to the etiology of hypertension, possibly by a mechanism involving stressinduced release of adrenocorticotropic hormone.  相似文献   

Hepatic glucose sensing via the CREB coactivator CRTC2   总被引：1，自引：0，他引：1  

Dentin R  Hedrick S  Xie J  Yates J  Montminy M 《Science (New York, N.Y.)》2008,319(5868):1402-1405

Chronic hyperglycemia contributes to the development of diabetes-associated complications. Increases in the concentration of circulating glucose activate the hexosamine biosynthetic pathway (HBP) and promote the O-glycosylation of proteins by O-glycosyl transferase (OGT). We show that OGT triggered hepatic gluconeogenesis through the O-glycosylation of the transducer of regulated cyclic adenosine monophosphate response element-binding protein (CREB) 2 (TORC2 or CRTC2). CRTC2 was O-glycosylated at sites that normally sequester CRTC2 in the cytoplasm through a phosphorylation-dependent mechanism. Decreasing amounts of O-glycosylated CRTC2 by expression of the deglycosylating enzyme O-GlcNAcase blocked effects of glucose on gluconeogenesis, demonstrating the importance of the HBP in the development of glucose intolerance.  相似文献   

Amygdalar and hippocampal theta rhythm synchronization during fear memory retrieval     

Seidenbecher T  Laxmi TR  Stork O  Pape HC 《Science (New York, N.Y.)》2003,301(5634):846-850

The amygdalohippocampal circuit plays a pivotal role in Pavlovian fear memory. We simultaneously recorded electrical activity in the lateral amygdala (LA) and the CA1 area of the hippocampus in freely behaving fear-conditioned mice. Patterns of activity were related to fear behavior evoked by conditioned and indifferent sensory stimuli and contexts. Rhythmically synchronized activity at theta frequencies increased between the LA and the CA1 after fear conditioning and became significant during confrontation with conditioned fear stimuli and expression of freezing behavior. Synchronization of theta activities in the amygdalohippocampal network represents a neuronal correlate of conditioned fear, apt to improve neuronal communication during memory retrieval.  相似文献   

Atmospheric lines in the solar spectrum     

Oliver JE 《Science (New York, N.Y.)》1887,9(206):33-34

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Prevention of vaginal SHIV transmission in rhesus macaques through inhibition of CCR5   总被引：1，自引：0，他引：1  

Lederman MM  Veazey RS  Offord R  Mosier DE  Dufour J  Mefford M  Piatak M  Lifson JD  Salkowitz JR  Rodriguez B  Blauvelt A  Hartley O 《Science (New York, N.Y.)》2004,306(5695):485-487

Topical agents, such as microbicides, that can protect against human immunodeficiency virus (HIV) transmission are urgently needed. Using a chimeric simian/human immunodeficiency virus (SHIV SF162), which is tropic for the chemokine receptor CCR5, we report that topical application of high doses of PSC-RANTES, an amino terminus-modified analog of the chemokine RANTES, provided potent protection against vaginal challenge in rhesus macaques. These experimental findings have potentially important implications for understanding vaginal transmission of HIV and the design of strategies for its prevention.  相似文献   

Electron tunneling through organic molecules in frozen glasses     

Wenger OS  Leigh BS  Villahermosa RM  Gray HB  Winkler JR 《Science (New York, N.Y.)》2005,307(5706):99-102

Reaction rates extracted from measurements of donor luminescence quenching by randomly dispersed electron acceptors reveal an exponential decay constant of 1.23 per angstrom for electron tunneling through a frozen toluene glass (with a barrier to tunneling of 1.4 electron volts). The decay constant is 1.62 per angstrom (the barrier, 2.6 electron volts) in a frozen 2-methyl-tetrahydrofuran glass. Comparison to decay constants for tunneling across covalently linked xylyl (0.76 per angstrom) and alkyl (1.0 per angstrom) bridges leads to the conclusion that tunneling between solvent molecules separated by approximately 2 angstroms (van der Waals contact) is 20 to 50 times slower than tunneling through a comparable length of a covalently bonded bridge. Our results provide experimental confirmation that covalently bonded pathways can facilitate electron flow through folded polypeptide structures.  相似文献   

Evolution of oxygen secretion in fishes and the emergence of a complex physiological system     

Berenbrink M  Koldkjaer P  Kepp O  Cossins AR 《Science (New York, N.Y.)》2005,307(5716):1752-1757

We have reconstructed the events that led to the evolution of a key physiological innovation underpinning the large adaptive radiation of fishes, namely their unique ability to secrete molecular oxygen (O2). We show that O2 secretion into the swimbladder evolved some 100 million years after another O2-secreting system in the eye. We unravel the likely sequence in which the functional components of both systems evolved. These components include ocular and swimbladder countercurrent exchangers, the Bohr and Root effects, the buffering power and surface histidine content of hemoglobins, and red blood cell Na+/H+ exchange activity. Our synthesis reveals the dynamics of gains and losses of these multiple traits over time, accounting for part of the huge diversity of form and function in living fishes.  相似文献   

Embedded nanostructures revealed in three dimensions     

Arslan I  Yates TJ  Browning ND  Midgley PA 《Science (New York, N.Y.)》2005,309(5744):2195-2198

Nanotechnology creates a new challenge for materials characterization because device properties now depend on size and shape as much as they depend on the traditional parameters of structure and composition. Here we show that Z-contrast tomography in the scanning transmission electron microscope has been developed to determine the complete three-dimensional size and shape of embedded structures with a resolution of approximately 1 cubic nanometer. The results from a tin/silicon quantum dot system show that the positions of the quantum dots and their size, shape, structure, and formation mechanism can be determined directly. These methods are applicable to any system, providing a unique and versatile three-dimensional visualization tool.  相似文献