1,837 research outputs found

    Preliminary Analysis of SOHO/STEREO Observations of Sungrazing Comet ISON (C/2012 S1) Around Perihelion

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    We present photometric and morphological analysis of the behavior of sungrazing comet C/2012 S1 ISON in SOHO and STEREO images around its perihelion on 2013 November 28.779 UT. ISON brightened gradually November 20-26 with a superimposed outburst on November 21.3-23.5. The slope of brightening changed about November 26.7 and was significantly steeper in SOHO's orange and clear filter images until November 27.9 when it began to flatten out, reaching a peak about November 28.1 (rH∼17R⊙r_H{\sim}17 R_\odot), then fading before brightening again from November 28.6 (rH∼5R⊙r_H{\sim}5 R_\odot) until disappearing behind the occulting disc. ISON brightened continuously as it approached perihelion while visible in all other telescopes/filters. The central condensation disappeared about November 28.5 and the leading edge became progressively more elongated until perihelion. These photometric and morphological behaviors are reminiscent of the tens of meter sized Kreutz comets regularly observed by SOHO and STEREO and strongly suggest that the nucleus of ISON was destroyed prior to perihelion. This is much too small to support published gas production rates and implies significant mass loss and/or disruption in the days and weeks leading up to perihelion. No central condensation was seen post-perihelion. The post-perihelion lightcurve was nearly identical in all telescopes/filters and fell slightly steeper than rH−2r_H^{-2}. This implies that the brightness was dominated by reflected solar continuum off of remnant dust in the coma/tail and that any remaining active nucleus was <10 m in radius.Comment: Accepted by ApJL; 11 pages of text (pre-print style), 3 figures, 1 tabl

    Development of Peptoid-Based Ligands for the Removal of Cadmium from Biological Media.

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    Cadmium poisoning poses a serious health concern due to cadmiums increasing industrial use, yet there is currently no recommended treatment. The selective coordination of cadmium in a biological environment-i.e. in the presence of serum ions, small molecules, and proteins-is a difficult task. To address this challenge, a combinatorial library of peptoid-based ligands has been evaluated to identify structures that selectively bind to cadmium in human serum with minimal chelation of essential metal ions. Eighteen unique ligands were identified in this screening procedure, and the binding affinity of each was measured using metal titrations monitored by UV-vis spectroscopy. To evaluate the significance of each chelating moiety, sequence rearrangements and substitutions were examined. Analysis of a metal-ligand complex by NMR spectroscopy highlighted the importance of particular residues. Depletion experiments were performed in serum mimetics and human serum with exogenously added cadmium. These depletion experiments were used to compare and demonstrate the ability of these peptoids to remove cadmium from blood-like mixtures. In one of these depletion experiments, the peptoid sequence was able to deplete the cadmium to a level comparable to the reported acute toxicity limit. Evaluation of the metal selectivity in buffered solution and in human serum was performed to verify minimal off-target binding. These studies highlight a screening platform for of the identification of metal-ligands that are capable of binding in a complex environment. They additionally demonstrate the potential utility of biologically-compatible ligands for the treatment of heavy metal poisoning

    That\u27s freakin\u27 sweet: The collecting of Family Guy

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    The animated series Family Guy (1999-2006) has been cancelled twice and resurrected twice mainly because of the efforts of viewers. It is worth asking, however; why has Family Guy attained a level of fanaticism that repeatedly rescues it from permanent cancellation? Arguably, the Family Guy audience is made up predominantly of members of generation y and as such, the way they view the program and their relationship to it will differ to that of previous generations. In short, Family Guy was cancelled due to poor ratings, however, these ratings were a result of erratic scheduling that was not conducive to the establishment of a strong audience base. This encouraged viewers to look beyond the television for information relating to Family Guy (i.e. air dates or missed episodes) and to discuss the show in general, creating an \u27imagined community\u27 online. The establishment of community whilst facilitating organized protests to have the series continued in times of cancellation does not explain why viewers have gone to this extreme. Popular culture is becoming increasingly complex, and it is possible to suggest that Family Guy is more complex than previous animated series. The way in which Family Guy is constructed may appear unusual to some, yet to members of generation y who are familiar with this style of animated series (having grown up with children\u27s series similar to it during the 1990s) it appears to be a natural progression from previous series. As a result they identify strongly with the series and perhaps even view it as something produced for them. This level of identification and the series history of being cancelled has led to the collection of episodes and information (namely quotes) around Family Guy. The collection of knowledge is indicative of the level of importance viewers place in the series and it becomes necessary for the maintenance of friendships. Labeling downloaded episodes as a collection is problematic as they constitute a vastly different type of collectable to material items. It is suggested, that this is a result of rigid and possibly outmoded perceptions of collectables and collecting and, that the term collecting should be considered as covering different forms of collecting and different levels of involvement on the part of the collector

    The Nucleus of Comet 10P/Tempel 2 in 2013 and Consequences Regarding Its Rotational State: Early Science from the Discovery Channel Telescope

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    We present new lightcurve measurements of Comet 10P/Tempel 2 carried out with Lowell Observatory's Discovery Channel Telescope in early 2013 when the comet was at aphelion. These data represent some of the first science obtained with this new 4.3-m facility. With Tempel 2 having been observed to exhibit a small but ongoing spin-down in its rotation period for over two decades, our primary goals at this time were two-fold. First, to determine its current rotation period and compare it to that measured shortly after its most recent perihelion passage in 2010, and second, to disentangle the spin-down from synodic effects due to the solar day and the Earth's orbital motion and to determine the sense of rotation, i.e. prograde or retrograde. At our midpoint of 2013 Feb 24, the observed synodic period is 8.948+/-0.001 hr, exactly matching the predicted prograde rotation solution based on 2010 results, and yields a sidereal period of the identical value due to the solar and Earth synodic components just canceling out during the interval of the 2013 observations. The retrograde solution is ruled out because the associated sidereal periods in 2010 and 2013 are quite different even though we know that extremely little outgassing, needed to produce torques, occurred in this interval. With a definitive sense of rotation, the specific amounts of spin-down to the sidereal period could be assessed. The nominal values imply that the rate of spin-down has decreased over time, consistent with the secular drop in water production since 1988. Our data also exhibited an unexpectedly small lightcurve amplitude which appears to be associated with viewing from a large, negative sub-Earth latitude, and a lightcurve shape deviating from a simple sinusoid implying a highly irregularly shaped nucleus.Comment: Accepted by AJ; 12 pages of text (pre-print style), 3 tables, 2 figure

    Numerical modelling of particulate and fibre reinforced composites

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    This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This thesis presents research into the micromechanical modelling of composite materials using numerical techniques. Composite materials are generally examined from two points of view: macromechanics and micromechanics, owing to their inherent heterogeneous nature. In this research, the material behaviour is examined on a microscopic scale, as the properties of interest, i.e. strength and toughness, are dependent on local phenomena. In general, the strength and toughness of composite materials are not as well understood as the simpler elastic properties, because in many cases the modes of failure under a given system of external load are not predictable in advance. Previous research in this field has typically involved specially designed experiments, theoretical/statistical studies, or the use of numerical models. In this study, advanced implementations of numerical methods in continuum mechanics, i.e. the boundary element and the finite element methods are employed to gain a greater understanding of composite behaviour. The advantage of using numerical methods, as opposed to experimental studies, is that the geometric and material characteristics can be investigated parametrically, in addition to the reduced time and expense involved. However, to model the complete behaviour of real composites is still not possible, due to the degree of complexity and uncertainty involved in modelling the various mechanisms of damage and failure, etc. and also due to the immense computational cost. Therefore, simplified models must be employed which are limited by their assumptions. For the preliminary studies within this thesis, geometrically simplified models are presented to provide an understanding of the influence of embedding second phase inclusions on the local stress fields, and also to validate the numerical techniques with readily available analytical solutions. These models are then extended to accommodate additional phenomena, such as inclusion interaction, spatial inclusion arrangement, material formulation, i.e. consisting of two- and three-phases of various material properties. The influence of such factors on the local stress concentrations, which play an important role in determining the strength of the composite, is analysed through a series of parametric studies. The localised toughening of composites is also considered through novel investigations into the interaction between a propagating crack with inclusions and microcracks. Through the development of the numerical models a more realistic representation of composite behaviour is achieved, which in tum, provides an improved knowledge of the factors that control strength and toughness. Such information is invaluable to composite material designers, who presently rely heavily on experimental studies to develop composite materials.This study is funded by the UK Engineering and Physical Sciences Research Council (EPSRC)

    Folk Polyphony Goes Viral: Televised Singing Competitions and the Play of Authenticity in the Republic of Georgia

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    Televised talent competitions have become a global phenomenon, and Georgia is no exception. While such programs usually feature pop-rock repertoire that is often sung in English, numerous performances of traditional folk polyphony have been featured on shows like Georgia’s Got Talent. I examine three diverse case studies, unpacking what each one reveals about the contested understandings of authenticity, heritage, tradition, and folk music in Georgia today, particularly in relation to gender. Debates over the definitions of these terms often mask struggles over power relations at varying scales.&nbsp;Les concours de talents télévisés sont devenus un phénomène mondial, et la Géorgie n’y fait pas exception. Mais tandis que ces programmes mettent en général à l’honneur un répertoire pop-rock qui est la plupart du temps chanté en anglais, des spectacles tels que « La Géorgie a un incroyable talent » ont souvent montré des performances de polyphonie traditionnelle. J’examine ici trois études de cas et ce que chacune révèle de contradictions quant aux conceptions de l’authenticité, du patrimoine, de la tradition et de la musique traditionnelle en Géorgie aujourd’hui, en particulier en relation avec le genre. Les débats qui portent sur la définition de ces termes dissimulent souvent des conflits au sujet de relations de pouvoir à diverses échelles
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