11,365 research outputs found

    Development of \u3ci\u3eOrius Insidiosus\u3c/i\u3e (Hemiptera: Anthocoridae) in Relation to Temperature

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    A developmental threshold of lO.3°C and a thermal constant of 307 day-degrees C were estimated for a Wisconsin population of Orius insidiosus (Say) (Hemiptera: Anthocoridae) by rearing eggs and nymphs at various constant temperatures

    Variations and trends in state nursing facility capacity: 1978-93.

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    The demand for nursing facility (NF) beds has been growing with the aging of the population and many other factors. As the need for nursing home care grows, the Nation's capacity to provide such care is the subject of increasing concern. This article examines licensed NFs and beds, presenting data on trends from 1978-93. Measures of the adequacy of NF beds in States are examined over time, including the ratio of beds per aged population, occupancy rates, and State official's opinions of the adequacy of supply. State and regional variations are shown over time, and we speculate on the factors which may be associated with the variation

    Triple-Pomeron Matrix Model for Dispersive Corrections to Nucleon-Nucleus Total Cross Section

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    Dispersive corrections to the total cross section for high-energy scattering from a heavy nucleus are calculated using a matrix model, based on the triple-Pomeron behavior of diffractive scattering from a single nucleon, for the cross section operator connecting different states of the projectile nucleon . Energy-dependent effects due to the decrease in longitudinal momentum transfers and the opening of more channels with increasing energy are included. The three leading terms in an expansion in the number of inelastic transitions are evaluated and compared to exact results for the model in the uniform nuclear density approximation for the the scattering of nucleons from Pb^{208} for laboratory momenta ranging from 50 to 200 GeV/c.Comment: 16 pages, 2 figures, RevTex

    A simple method for detection of mitochondrial DNA polymorphisms

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    Polymorphisms were identified in mtDNA of Heterobasidion annosum by digesting total genomic DNA with HaeIII, CfoI, or MspI, which recognize the restriction sites GGCC, GCGC, and CCGG, respectively. Most DNA was digested to fragments of less than 2 kb, while AT-rich fragments of 1.7 to 17 kb stood out as bands of uniform intensity after ethidium bromide staining. These fragments hybridized to mtDNA probes and were inherited in a uniparental fashion

    Temperature dependence of instantons in QCD

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    We investigate the temperature dependence of the instanton contents of gluon fields, using unquenched lattice QCD and the cooling method. The instanton size parameter deduced from the correlation function decreases from 0.44fm below the phase-transition temperature TcT_c (150\approx 150MeV) to 0.33fm at 1.3 TcT_c. The instanton charge distribution is Poissonian above TcT_c, but it deviates from the convoluted Poisson at low temperature. The topological susceptibility decreases rapidly below TcT_c, showing the apparent restoration of the U(1)AU(1)_A symmetry already at TTcT \approx T_c.Comment: 8 pages TEX, 3 Postscript figures available at http://www.krl.caltech.edu/preprints/MAP.htm

    The Formation of the First Stars II. Radiative Feedback Processes and Implications for the Initial Mass Function

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    We consider the radiative feedback processes that operate during the formation of the first stars, including the photodissociation of H_2, Ly-alpha radiation pressure, formation and expansion of an HII region, and disk photoevaporation. These processes may inhibit continued accretion once the stellar mass has reached a critical value, and we evaluate this mass separately for each process. Photodissociation of H_2 in the local dark matter minihalo occurs relatively early in the growth of the protostar, but we argue this does not affect subsequent accretion since by this time the depth of the potential is large enough for accretion to be mediated by atomic cooling. However, neighboring starless minihalos can be affected. Ionization creates an HII region in the infalling envelope above and below the accretion disk. Ly-alpha radiation pressure acting at the boundary of the HII region is effective at reversing infall from narrow polar directions when the star reaches ~20-30Msun, but cannot prevent infall from other directions. Expansion of the HII region beyond the gravitational escape radius for ionized gas occurs at masses ~50-100Msun, depending on the accretion rate and angular momentum of the inflow. However, again, accretion from the equatorial regions can continue since the neutral accretion disk has a finite thickness and shields a substantial fraction of the accretion envelope from direct ionizing flux. At higher stellar masses, ~140Msun in the fiducial case, the combination of declining accretion rates and increasing photoevaporation-driven mass loss from the disk act to effectively halt the increase in the protostellar mass. We identify this process as the mechanism that terminates the growth of Population III stars... (abridged)Comment: 31 pages, including 10 figures, accepted to Ap

    The interpretation of the field angle dependence of the critical current in defect-engineered superconductors

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    We apply the vortex path model of critical currents to a comprehensive analysis of contemporary data on defect-engineered superconductors, showing that it provides a consistent and detailed interpretation of the experimental data for a diverse range of materials. We address the question of whether electron mass anisotropy plays a role of any consequence in determining the form of this data and conclude that it does not. By abandoning this false interpretation of the data, we are able to make significant progress in understanding the real origin of the observed behavior. In particular, we are able to explain a number of common features in the data including shoulders at intermediate angles, a uniform response over a wide angular range and the greater discrimination between individual defect populations at higher fields. We also correct several misconceptions including the idea that a peak in the angular dependence of the critical current is a necessary signature of strong correlated pinning, and conversely that the existence of such a peak implies the existence of correlated pinning aligned to the particular direction. The consistency of the vortex path model with the principle of maximum entropy is introduced.Comment: 14 pages, 7 figure

    Calorons in Weyl Gauge

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    We demonstrate by explicit construction that while the untwisted Harrington-Shepard caloron AμA_\mu is manifestly periodic in Euclidean time, with period β=1T\beta=\frac{1}{T}, when transformed to the Weyl (A0=0A_0=0) gauge, the caloron gauge field AiA_i is periodic only up to a large gauge transformation, with winding number equal to the caloron's topological charge. This helps clarify the tunneling interpretation of these solutions, and their relation to Chern-Simons numbers and winding numbers.Comment: 10 pages, 10 figures, a sign typo in equation 27 is correcte

    Calorons and localization of quark eigenvectors in lattice QCD

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    We analyze the localization properties for eigenvectors of the Dirac operator in quenched lattice QCD in the vicinity of the deconfinement phase transition. Studying the characteristic differences between the Z_3 sectors above the critical temperature T_c, we find indications for the presence of calorons.Comment: 4 pages, 4 figure

    Calorons, instantons and constituent monopoles in SU(3) lattice gauge theory

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    We analyze the zero-modes of the Dirac operator in quenched SU(3) gauge configurations at non-zero temperature and compare periodic and anti-periodic temporal boundary conditions for the fermions. It is demonstrated that for the different boundary conditions often the modes are localized at different space-time points and have different sizes. Our observations are consistent with patterns expected for Kraan - van Baal solutions of the classical Yang-Mills equations. These solutions consist of constituent monopoles and the zero-modes are localized on different constituents for different boundary conditions. Our findings indicate that the excitations of the QCD vacuum are more structured than simple instanton-like lumps.Comment: Remarks added. To appear in Phys. Rev.
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