2,978 research outputs found

    A resource survey of the coastal lands from Vlaming Head to Tantabiddi Well, West Cape Range region

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    The report comprise four parts; a brief review of the area\u27s climate, discussion of the geomorphology of the major landform units, an assessment of the potential erosion hazards of the surveyed landforms, and recommendations for development

    Cosmic Strings from Supersymmetric Flat Directions

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    Flat directions are a generic feature of the scalar potential in supersymmetric gauge field theories. They can arise, for example, from D-terms associated with an extra abelian gauge symmetry. Even when supersymmetry is broken softly, there often remain directions in the scalar field space along which the potential is almost flat. Upon breaking a gauge symmetry along one of these almost flat directions, cosmic strings may form. Relative to the standard cosmic string picture based on the abelian Higgs model, these flat-direction cosmic strings have the extreme Type-I properties of a thin gauge core surrounded by a much wider scalar field profile. We perform a comprehensive study of the microscopic, macroscopic, and observational characteristics of this class of strings. We find many differences from the standard string scenario, including stable higher winding mode strings, the dynamical formation of higher mode strings from lower ones, and a resultant multi-tension scaling string network in the early universe. These strings are only moderately constrained by current observations, and their gravitational wave signatures may be detectable at future gravity wave detectors. Furthermore, there is the interesting but speculative prospect that the decays of cosmic string loops in the early universe could be a source of ultra-high energy cosmic rays or non-thermal dark matter. We also compare the observational signatures of flat-direction cosmic strings with those of ordinary cosmic strings as well as (p,q) cosmic strings motivated by superstring theory.Comment: 58 pages, 16 figures, v2. accepted to PRD, added comments about baryogenesis and boosted decay products from cusp annihilatio

    Rapid and quantitative determination of hexanal in cooked muscle foods

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    A simple and rapid method was developed to quantify hexanaJ in cooked muscle foods. The method involves extraction of the 2,4-dinitrophenylhydrazones of carbonyls with hexane and their separation by reversed-phased high performance liquid chromatography. The method compared well with the classical thiobarbituric acid test. The method was successfully used to quantify hexana) in cooked beef and pork burgers during storage at 4 °C for up to 1 week as well as in cooked turkey burgers after diet supplementation with vitamin E. After 7 days' storage at 4 °C, the contents of hexanal increased from 0.71 to 22.50 μ.mol/kg in beef burgers, from 0.89 to 32.7S μmol / kg in pork burgers and from 1.31 to S2.16 μmol / kg in turkey burgers (20 mg vitamin E per kg feed). Supplementation of turkey feeds with 600 mg Yitamin E per kg resulted in a 24% reduction in hexanal content in cooked turkey burgers after storage for 7 days at 4 °C, compared to the control (unsupplemented) group

    Statins in Acute Coronary Syndromes Do the Guideline Recommendations Match the Evidence?

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    On the basis of the evidence obtained from observational studies, randomized controlled trials and their meta-analyses, current guidelines recommend initiating high-dose statin therapy pre-discharge regardless of the baseline low-density lipoprotein (LDL) level in patients with acute coronary syndromes (ACS). Careful review of the evidence indicates that early initiation of high-dose statin therapy reduces recurrent ischemia and may reduce revascularization, but does not confer benefit in terms of hard clinical outcomes such as death or myocardial infarction in any of the randomized controlled trials, and may be associated with increased liver and muscle-related adverse outcomes leading to increased withdrawal and suboptimal long-term adherence. A mortality benefit is apparent in pooled analyses of randomized controlled trials only at long-term (24-month) but not short-term (4-month) follow-up. The critical role of the timing of initiation of therapy (early vs. late) on the benefit-risk profile of statin treatment has not been systematically assessed. It is unclear whether the clinical benefits are attributable to lipid-lowering or lipid-lowering–independent effects. Finally, an optimal LDL threshold for initiating treatment or target LDL level for treatment in ACS remains yet to be defined. On the basis of these observations, and despite a compelling pathophysiologic rationale, the justification for current Class I, Level of Evidence: A recommendation for statin therapy in patients with ACS remains open to question

    Proton Lifetime and Baryon Number Violating Signatures at the LHC in Gauge Extended Models

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    There exist a number of models in the literature in which the weak interactions are derived from a chiral gauge theory based on a larger group than SU(2)_L x U(1)_Y. Such theories can be constructed so as to be anomaly-free and consistent with precision electroweak measurements, and may be interpreted as a deconstruction of an extra dimension. They also provide interesting insights into the issues of flavor and dynamical electroweak symmetry breaking, and can help to raise the mass of the Higgs boson in supersymmetric theories. In this work we show that these theories can also give rise to baryon and lepton number violating processes, such as nucleon decay and spectacular multijet events at colliders, via the instanton transitions associated with the extended gauge group. For a particular model based on SU(2)_1 x SU(2)_2, we find that the B+LB+L violating scattering cross sections are too small to be observed at the LHC, but that the lower limit on the lifetime of the proton implies an upper bound on the gauge couplings.Comment: 36 page

    Microwave Backscatter and Attenuation Dependence of Leaf Area Index for Flooded Rice Fields

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    Wetlands are important for their role in global climate as a source of methane and other reduced trace gases. As part of an effort to determine whether radar is suitable for wetland vegetation monitoring, we have studied the dependence of microwave backscatter and attenuation on leaf area index (LAI) for flooded rice fields. We find that the radar return from a flooded rice field does show dependence on LAI. In particular, the C-band VV cross section per unit area decreases with increasing LAI. A simple model for scattering from rice fields is derived and fit to the observed HH and VV data. The model fit provides insight into the relation of backscatter to LAI and is also used to calculate the canopy path attenuation as a function of LAI

    GALEX FUV Observations of Comet C/2004 Q2 (Machholz): The Ionization Lifetime of Carbon

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    We present a measurement of the lifetime of ground state atomic carbon, C(^3P), against ionization processes in interplanetary space and compare it to the lifetime expected from the dominant physical processes likely to occur in this medium. Our measurement is based on analysis of a far ultraviolet (FUV) image of comet C/2004 Q2 (Machholz) recorded by the Galaxy Evolution Explorer (GALEX) on 2005 March 1. The bright CI 1561 A and 1657 A multiplets dominate the GALEX FUV band. We used the image to create high S/N radial profiles that extended beyond one million km from the comet nucleus. Our measurements yielded a total carbon lifetime of 7.1 -- 9.6 x 10^5 s (scaled to 1 AU). Which compares favorably to calculations assuming solar photoionization, solar wind proton change exchange and solar wind electron impact ionization are the dominant processes occurring in this medium and that comet Machholz was embedded in the slow solar wind. The shape of the CI profiles inside 3x10^5 km suggests that either the CO lifetime is shorter than previously thought and/or a shorter-lived carbon-bearing parent molecule, such as CH_4 is providing the majority of the carbon in this region of the coma of comet Machholz.Comment: 26 pages, 6 figures, accepted for publication in the Astrophysical Journa

    Immunolocalization of KATP channel subunits in mouse and rat cardiac myocytes and the coronary vasculature.

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    BACKGROUND: Electrophysiological data suggest that cardiac KATP channels consist of Kir6.2 and SUR2A subunits, but the distribution of these (and other KATP channel subunits) is poorly defined. We examined the localization of each of the KATP channel subunits in the mouse and rat heart. RESULTS: Immunohistochemistry of cardiac cryosections demonstrate Kir6.1 protein to be expressed in ventricular myocytes, as well as in the smooth muscle and endothelial cells of coronary resistance vessels. Endothelial capillaries also stained positive for Kir6.1 protein. Kir6.2 protein expression was found predominantly in ventricular myocytes and also in endothelial cells, but not in smooth muscle cells. SUR1 subunits are strongly expressed at the sarcolemmal surface of ventricular myocytes (but not in the coronary vasculature), whereas SUR2 protein was found to be localized predominantly in cardiac myocytes and coronary vessels (mostly in smaller vessels). Immunocytochemistry of isolated ventricular myocytes shows co-localization of Kir6.2 and SUR2 proteins in a striated sarcomeric pattern, suggesting t-tubular expression of these proteins. Both Kir6.1 and SUR1 subunits were found to express strongly at the sarcolemma. The role(s) of these subunits in cardiomyocytes remain to be defined and may require a reassessment of the molecular nature of ventricular KATP channels. CONCLUSIONS: Collectively, our data demonstrate unique cellular and subcellular KATP channel subunit expression patterns in the heart. These results suggest distinct roles for KATP channel subunits in diverse cardiac structures
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