3,697 research outputs found

    OSETI with STACEE: A Search for Nanosecond Optical Transients from Nearby Stars

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    We have used the STACEE high-energy gamma-ray detector to look for fast blue-green laser pulses from the vicinity of 187 stars. The STACEE detector offers unprecedented light-collecting capability for the detection of nanosecond pulses from such lasers. We estimate STACEE's sensitivity to be approximately 10 photons per square meter at a wavelength of 420 nm. The stars have been chosen because their characteristics are such that they may harbor habitable planets and they are relatively close to Earth. Each star was observed for 10 minutes and we found no evidence for laser pulses in any of the data sets.Comment: 38 pages, 12 figures. Accepted for publication in Astrobiolog

    Observations of the BL Lac Object 3C 66A with STACEE

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    We present the analysis and results of recent high-energy gamma-ray observations of the BL Lac object 3C 66A conducted with the Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE). During the 2003-2004 observing season, STACEE extensively observed 3C 66A as part of a multiwavelength campaign on the source. A total of 33.7 hours of data was taken on the source, plus an equivalent-duration background observation. After cleaning the data set a total of 16.3 hours of live time remained, and a net on-source excess of 1134 events was seen against a background of 231742 events. At a significance of 2.2 standard deviations this excess is insufficient to claim a detection of 3C 66A, but is used to establish flux upper limits for the source.Comment: Accepted for publication in the Astrophysical Journa

    Framing Ethnic Variations in Alcohol Outcomes from Biological Pathways to Neighborhood Context

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    Background Health disparities research seeks to eliminate disproportionate negative health outcomes experienced in some racial/ethnic minority groups. This brief review presents findings on factors associated with drinking and alcohol‐related problems in racial/ethnic groups. Methods Those discussed are as follows: (i) biological pathways to alcohol problems, (ii) gene × stress interactions, (iii) neighborhood disadvantage, stress, and access to alcohol, and (iv) drinking cultures and contexts. Results These factors and their interrelationships are complex, requiring a multilevel perspective. Conclusions The use of interdisciplinary teams and an epigenetic focus are suggested to move the research forward. The application of multilevel research to policy, prevention, and intervention programs may help prioritize combinations of the most promising intervention targets

    EXITE/IPC observations of SN1987A and southern targets

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    The Energetic X-ray Imaging Telescope Experiment (EXITE) was developed to a flight-ready status and conducted two flights (May 18, 1988, and May 8-10, 1989) from Alice Springs, Australia, as part of the campaigns to observe the supernova SN1987A. The basic operation of the detector and gondola systems in the laboratory was tested on the first flight and found to meet expected performance values. A bizarre 'balloon tape' insulation problem, however, prevented normal telescope pointing on the first flight so no data on SN1987A or other targets were obtained. Following a successful second EXITE flight from Ft. Sumner, NM, in October 1988, the experiment was flown again on a successful 30 hour flight as part of the final 1989 supernova campaign. A second x-ray imaging experiment from MSFC was also flown (piggy-back) for this third flight. Good data were obtained on the supernova and a variety of high priority galactic targets, and final analysis is still in progress. Preliminary results from this flight are presented

    Expression of the neural cell adhesion molecule NCAM in endocrine cells

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    We examined the expression of the neural cell adhesion molecule NCAM in a number of endocrine tissues of adult rat and in an endocrine tumor cell line. NCAM was found by immunoelectron microscopy to be present on the surface of all endocrine cells in the three lobes of the hypophysis, although staining was relatively less intense in the intermediate lobe, and in pancreatic islets. Pituicytes, hypophyseal glial cells, were also labeled for NCAM. A rat insulinoma cell line (RIN A2) also expressed NCAM as judged by immunocytochemistry. Analysis of NCAM antigenic determinants (Mr 180, 140, and 120 KD) revealed large variations in the relative proportions of NCAM polypeptides present in the different tissues. Although all tissues and cell lines expressed NCAM-140, NCAM-180 was not detected in the adenohypophysis, pancreas, or adrenal medulla, and NCAM-120 was found in none of the endocrine tissues or cell lines except at low levels in the neurohypophysis. The tumor cell line expressed significant levels of NCAM-180, which was most abundant in the neurohypophysis. These results show that NCAM expression appears to be a general property of endocrine cells, although the antigenic composition differs markedly from that in brain tissue. These data are discussed with regard to the embryological origins of the different endocrine tissues, and possible functional implications are suggested

    The Serotonin Transporter Polymorphism (5-HTTLPR) and Alcohol Problems in Heavy Drinkers: Moderation by Depressive Symptoms.

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    Heavy alcohol use in young adults has been prospectively associated with a host of psychosocial and alcohol-related problems. Recent studies have supported the interaction between serotonin transporter polymorphism and adverse environmental factors, as a predictor of alcohol use and the development of alcohol dependence. The current study examined the role of depressive symptoms in combination with the serotonin transporter polymorphism as a predictor of alcohol use and alcohol-related problems. Results revealed a significant genotype by depressive symptom interaction, such that heavier alcohol use was associated with depressive symptoms in L allele homozygotes but not among S allele carriers. These results remained significant after controlling for ethnicity and gender effects. These findings extend the emerging literature supporting 5-HTTLPR genotype as a risk factor for alcohol-related problems in the context of co-occurring symptoms of depression

    LANDSAT-4 sensor performance

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    Preflight and in-orbit sensor and data measurements indicate that TM meets or exceeds most specifications. Measured spectral band edges meet instrument specifications in 12 out of 14 cases; there is ample dynamic range. The signal-to-noise ratio exceeds specifications, except for band 3, channel 4; and band 7 channel 7 is very noisy but still meets specifications. The modulation transfer function of channel 4, band 2, is smaller than specified. Registration errors between the primary focal plane (PFP) and the cold focal plane (CFP) are about 0.75 pixels along-scan and 0.2 pixels across scan. Forward and reverse scan discontinuities, are well within ground-processing capabilities to rectify. Instrument gain variability, up to 7% for band 5, requires use of the internal calibration (IC) system to assure radiometric accuracy. Preliminary applications evaluation of image contents indicates that TM provides much better definition of edges than MSS
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