1,221 research outputs found

    The brightness distribution of IRC +10216 at 11 microns

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    The brightness distribution of IRC +10216 at a wavelength of 11 microns was measured in detail using a spatial interferometer. This brightness distribution appears to have azimuthal symmetry; an upper limit of 1.1 may be set to the ellipticity at 11 microns if the object has a major axis oriented either along or perpendicular to the major axis of the optical image. The radial distribution shows both compact and extended emission. The extended component, which is due to thermal emission from circumstellar dust, contributes 91% of the total flux and has a 1/e diameter of 0.90 minutes. The tapered shape of this component is consistent with a l/r squared dust density dependence. The compact component is unresolved (less than 0.2 minutes in diameter) and represents emission from the central star seen through the circumstellar envelope

    Variations in the spatial distribution of 11 Micron radiation from omicron Ceti

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    The spatial distribution of 11 micron radiation from omicron Ceti was observed at various phases of its light cycle using a stellar interferometer. Changes were seen which can be attributed to variation in the strength of thermal emission from circumstellar dust relative to the stellar continuum at 11 microns. These changes are shown to be correlated with the changes in luminosity of micron Ceti in such a way that dust grain emission at 11 microns was increased more than the continuum during the period of maximum luminosity. The degree of the change in dust grain emission implies that the maximum dust temperature is in the range of 500 K to 700 K during minimum stellar luminosity

    Spatial heterodyne interferometry of VY Canis Major's, alpha Orionis, alpha Scorpii, and R leonis at 11 microns

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    Using the technique of heterodyne interferometry, measurements were made of the spatial distribution of 11 micron radiation from four late type stars. The circumstellar shells surrounding VY Canis Majoris, alpha Orionis, and alpha Scorpii were resolved, whereas that of R Leonis was only partially resolved at a fringe spacing of 0.4 sec

    The impact of phosphorus inputs from small discharges on designated freshwater sites

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    Natural England, with a contribution from the Broads Authority, commissioned the Centre for Ecology & Hydrology (CEH) in 2009 to conduct a review of the potential risk posed by small domestic discharges, such as from septic tanks, to freshwater SSSIs. The particular focus of this work was the risk of phosphorus (P) pollution to sites that are vulnerable to hyper-eutrophication

    Plastic Deformation, Wrinkling, and Recovery in Microgel Multilayers

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    Microgel multi-layer films assembled from anionic particles and linear polycation were prepared on elastomeric substrates and their self-healing properties studied. Dried films were imaged in situ during mechanical deformation and were determined to undergo plastic deformation in response to linear strain, leading to film buckling upon strain relaxation. Hydration leads to rapid reorganization of the film building blocks, permitting recovery of the film to the undamaged state. Additionally, films were determined to heal in the presence of high relative humidity environments, suggesting that film swelling and hydration is a major factor in the restoration of film integrity, and that full immersion in solvent is not required for healing. Films prepared from microgels with lower levels of acid content and/or polycation length, factors strongly connected to the charge density and presumably the connectivity of the film, also display self-healing characteristics

    Extracting Information from Adaptive Control Experiments

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    Optical control of chemical reactivity is achieved through the use of photonic reagents, that is, “shaped” ultrafast optical pulses created using a pulse shaper. It has been demonstrated in a number of molecular systems that these pulses can effectively guide the system into a desired final state. Effective pulses are often found through an experimental search involving thousands of individual measurements. An examination of the pulses tested in these experiments can reveal the pulse features responsible for control and also the underlying molecular dynamics. In this article we review attempts to extract information from optical control experiments using adaptive learning algorithms to search the available parameter space, and we discuss how these kinds of experiments can be used to achieve and understand multiphoton optical control.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91361/1/397_ftp.pd

    Adolescents and Sexual Risk-Taking: The Interplay of Constraining Relationship Beliefs, Healthy Sex Attitudes, and Romantic Attachment Insecurity

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    Introduction: Although sexual exploration during adolescence may be perceived as normative, many adolescents who are sexually active are likely to engage in risky sexual behaviors detrimental to their well-being. The present study examined the influence of insecure attachment (anxious and avoidant dimensions), healthy sex attitudes, and constraining relationship beliefs on the following sexual risk indicators: age at first sex, number of sexual partners, condom use, length of time knowing sexual partners, seriousness of relationship, and frequency of sex. Methods: Cross-sectional data from two cohorts recruited one year apart for a five-year project were analyzed. Adolescents were public high school students from a Southern state in the USA (cohort 1: N = 878, 51.1% females, M = 16.50 years old; cohort 2: N = 759, 46.9% females, M = 15.78 years old). Results: Across both cohorts, healthy sex attitudes were related to having sex for the first time at an older age, having less sexual partners in a lifetime, and knowing one’s sexual partner longer. High scores on the avoidant attachment dimension were related to less commitment to the relationship. This dimension also was related to holding lower scores on healthy sex attitudes, which in turn was related to having more sexual partners and knowing one’s sexual partner for a shorter time. Although not replicated, higher endorsement of constraining relationship beliefs was associated with inconsistent condom use and greater sex frequency. Conclusion: Findings suggests that attachment insecurity, healthy sex attitudes, and constraining relationship beliefs work together to influence adolescent sexual risks

    Coyote, Canis latrans - Rio Grande Turkey, Meleagris gallopavo intermedia, Interactions

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    Coyotes (Canis latrans) are widely known to be predators of Wild Turkeys (Meleagris gallopauo sspp.). We describe two observations of single Coyotes coming within 10 m of feeding Wild Turkey flocks without attempting to predate them in Stevens County, Kansas. We relate these observations to Coyote predation on turkeys and mobbing behavior

    Optical properties of metal nanoparticles with no center of inversion symmetry: observation of volume plasmons

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    We present theoretical and experimental studies of the optical response of L-shaped silver nanoparticles. The scattering spectrum exhibits several plasmon resonances that depend sensitively on the polarization of the incident electromagnetic field. The physical origin of the resonances is traced to different plasmon phenomena. In particular, a high energy band with unusual properties is interpreted in terms of volume plasmon oscillations arising from the asymmetry of a nanoparticle.Comment: 14 pages, 5 figures. Physical Review B, 2007, accepte
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