12,645 research outputs found

    Multifractal Scaling of Thermally-Activated Rupture Processes

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    We propose a ``multifractal stress activation'' model combining thermally activated rupture and long memory stress relaxation, which predicts that seismic decay rates after mainshocks follow the Omori law ∼1/tp\sim 1/t^p with exponents pp linearly increasing with the magnitude MLM_L of the mainshock and the inverse temperature. We carefully test this prediction on earthquake sequences in the Southern California Earthquake catalog: we find power law relaxations of seismic sequences triggered by mainshocks with exponents pp increasing with the mainshock magnitude by approximately 0.1−0.150.1-0.15 for each magnitude unit increase, from p(ML=3)≈0.6p(M_L=3) \approx 0.6 to p(ML=7)≈1.1p(M_L=7) \approx 1.1, in good agreement with the prediction of the multifractal model.Comment: four pages and 2 figure

    Positronium oscillations to Mirror World revisited

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    We present a calculation of the branching ratio of orthopositronium decay into an invisible mode, which is done in the context of Mirror World models, where ordinary positronium can disappear from our world due to oscillation into its mirror twin. In this revision we clarify some formulas and approximations used previously, correct them at some places, add new effects relevant for a feasible experiment and finally perform a combined analysis. We include into consideration various effects due to external magnetic and electric fields, collisions with cavity walls and scattering off gas atoms in the cavity. Oscillations of the Rydberg positroniums are also considered. To perform a numerical estimates in a realistic case we wrote computer code, which can be adopted in any experimental setup. Its work is illustrated with an example of a planned positronium experiment within the AEgIS project.Comment: 23 pages, 4 figures, typos corrected, references added, published versio

    Development of a high-altitude airborne dial system: The Lidar Atmospheric Sensing Experiment (LASE)

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    The ability of a Differential Absorption Lidar (DIAL) system to measure vertical profiles of H2O in the lower atmosphere was demonstrated both in ground-based and airborne experiments. In these experiments, tunable lasers were used that required real-time experimenter control to locate and lock onto the atmospheric H2O absorption line for the DIAL measurements. The Lidar Atmospheric Sensing Experiment (LASE) is the first step in a long-range effort to develop and demonstrate an autonomous DIAL system for airborne and spaceborne flight experiments. The LASE instrument is being developed to measure H2O, aerosol, and cloud profiles from a high-altitude ER-2 (extended range U-2) aircraft. The science of the LASE program, the LASE system design, and the expected measurement capability of the system are discussed

    Total 4He Photoabsorption Cross Section Revisited: Correlated HH versus Effective Interaction HH

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    Two conceptually different hyperspherical harmonics expansions are used for the calculation of the total 4He photoabsorption cross section. Besides the well known method of CHH the recently introduced effective interaction approach for the hyperspherical formalism is applied. Semi-realistic NN potentials are employed and final state interaction is fully taken into account via the Lorentz integral transform method. The results show that the effective interaction leads to a very good convergence, while the correlation method exhibits a less rapid convergence in the giant dipole resonance region. The rather strong discrepancy with the experimental photodisintegration cross sections is confirmed by the present calculations.Comment: LaTeX, 7 pages, 3 ps figure

    Phase Coexistence Near a Morphotropic Phase Boundary in Sm-doped BiFeO3 Films

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    We have investigated heteroepitaxial films of Sm-doped BiFeO3 with a Sm-concentration near a morphotropic phase boundary. Our high-resolution synchrotron X-ray diffraction, carried out in a temperature range of 25C to 700C, reveals substantial phase coexistence as one changes temperature to crossover from a low-temperature PbZrO3-like phase to a high-temperature orthorhombic phase. We also examine changes due to strain for films greater or less than the critical thickness for misfit dislocation formation. Particularly, we note that thicker films exhibit a substantial volume collapse associated with the structural transition that is suppressed in strained thin films

    Cmah-dystrophin deficient mdx mice display an accelerated cardiac phenotype that is improved following peptide-PMO exon skipping treatment

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    Duchenne muscular dystrophy (DMD) is caused by loss of dystrophin protein, leading to progressive muscle weakness and premature death due to respiratory and/or cardiac complications. Cardiac involvement is characterized by progressive dilated cardiomyopathy, decreased fractional shortening and metabolic dysfunction involving reduced metabolism of fatty acids—the major cardiac metabolic substrate. Several mouse models have been developed to study molecular and pathological consequences of dystrophin deficiency, but do not recapitulate all aspects of human disease pathology and exhibit a mild cardiac phenotype. Here we demonstrate that Cmah (cytidine monophosphate-sialic acid hydroxylase)-deficient mdx mice (Cmah−/−;mdx) have an accelerated cardiac phenotype compared to the established mdx model. Cmah−/−;mdx mice display earlier functional deterioration, specifically a reduction in right ventricle (RV) ejection fraction and stroke volume (SV) at 12 weeks of age and decreased left ventricle diastolic volume with subsequent reduced SV compared to mdx mice by 24 weeks. They further show earlier elevation of cardiac damage markers for fibrosis (Ctgf), oxidative damage (Nox4) and haemodynamic load (Nppa). Cardiac metabolic substrate requirement was assessed using hyperpolarized magnetic resonance spectroscopy indicating increased in vivo glycolytic flux in Cmah−/−;mdx mice. Early upregulation of mitochondrial genes (Ucp3 and Cpt1) and downregulation of key glycolytic genes (Pdk1, Pdk4, Ppara), also denote disturbed cardiac metabolism and shift towards glucose utilization in Cmah−/−;mdx mice. Moreover, we show long-term treatment with peptide-conjugated exon skipping antisense oligonucleotides (20-week regimen), resulted in 20% cardiac dystrophin protein restoration and significantly improved RV cardiac function. Therefore, Cmah−/−;mdx mice represent an appropriate model for evaluating cardiac benefit of novel DMD therapeutics

    Potash Studies on Burley Tobacco in Owen County, Kentucky

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    Since the late 1970\u27s, farmers in the Wheatley Community of Owen county have reported seeing potassium (K) deficiency on tobacco during the growing season. Most of them had been following University of Kentucky fertilizer recommendations for burley production. Analyses of cured leaf samples from one such crop in 1980 confirmed K deficiency. It was decided that the problem warranted conducting some field experiments in order to define the problem and hopefully develop a solution. Consequently, we located a field on the Harold Malcomb farm near Wheatly, that tested low in soil K and designed a field experiment with the objectives of (1) testing the effectiveness of UK soil test recommendations for potash, (2) testing K rates applied pre-plant, sidedressed, and in combination, and (3) since soil Zinc (Zn) levels were low, we also decided to test for a tobacco yield response to fertilizer Zn. Subsequently, K studies were conducted in different fields of the Malcomb farm during 1981, 1984, 1985, 1986, and i987, and in a field on the Steve Simpson farm near New Columbus in 1986. The following report summarizes what we learned

    Automated Harvesting of Burley Tobacco II. Evaluation of System Performance

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    A prototype system for fully automated harvesting of burley tobacco has been developed and tested. Three years of field testing has shown that mechanical losses associated with the system were only slightly higher than via conventional methods. The system performed reliably at a sustained harvesting rate of approximately 1.4 ha/day (3.4 acre/day), while indicating that a rate of 2 ha/day (5 acre/day) should be easily achievable. The system is operated by two workers and reduces conventional labor requirement by approximately 80-85%

    Automated Harvesting of Burley Tobacco I. System Development

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    A fully automated system for harvesting and handling mature buriey tobacco has been developed. This article identifies the operations essential to this harvesting concept and describes the development of the mechanisms by which they were accomplished. The system detaches, inverts and places mature plants into portable holders for air curing under waterproof covering without requiring any manual handling of the crop. Manual labor currently required to harvest buriey tobacco would be reduced by 80-85% and the system would eliminate the drudgery associated with manual handling. The harvesting system has an approximate capacity of 1.4 to 2.0 ha/day (3.5 to 5.0 ac/day) and is operated by two workers
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