44,500 research outputs found

    Designers manual for circuit design by analog/digital techniques Final report

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    Manual for designing circuits by hybrid compute

    One-electron spectral functions of the attractive Hubbard model at intermediate coupling

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    We calculate the one-electron spectral function of the attractive-U Hubbard model in two dimensions. We work in the intermediate coupling and low density regime and evaluate analytically the self-energy. The results are obtained in a framework based on the self-consistent T-matrix approximation. We also calculate the chemical potential of the bound pairs as a function of temperature. On the basis of this calculation we analyze the low-temperature resistivity and specific heat in the normal state of this system. We compare our results with recent beautiful tunneling experiments in the underdoped regime of HTSC-materials.Comment: 2 pages, LT22 Conference paper, phbauth and elsart style files include

    The Infrared Nucleus of the Wolf-Rayet Galaxy Henize 2-10

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    We have obtained near-infrared images and mid-infrared spectra of the starburst core of the dwarf Wolf-Rayet galaxy He 2-10. We find that the infrared continuum and emission lines are concentrated in a flattened ellipse 3-4'' or 150 pc across which may show where a recent accretion event has triggered intense star formation. The ionizing radiation from this cluster has an effective temperature of 40,000 K, corresponding to 30M⊙30M_\odot stars, and the starburst is 0.5−1.5×1070.5-1.5 \times 10^7 years old.Comment: 17 pages Latex, 7 postscript figures, 1 postscript table, accepted to A

    Spin lifetimes and strain-controlled spin precession of drifting electrons in zinc blende type semiconductors

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    We study the transport of spin polarized electrons in n-GaAs using spatially resolved continuous wave Faraday rotation. From the measured steady state distribution, we determine spin relaxation times under drift conditions and, in the presence of strain, the induced spin splitting from the observed spin precession. Controlled variation of strain along [110] allows us to deduce the deformation potential causing this effect, while strain along [100] has no effect. The electric field dependence of the spin lifetime is explained quantitatively in terms of an increase of the electron temperature.Comment: 5 pages, 6 figure

    Experimental determination of cosmic ray charged particle intensity profiles in the atmosphere

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    Absolute cosmic-ray free air ionization and charged particle fluxes and dose rates throughout the atmosphere were measured on a series of balloon flights that commenced in 1968. Argon-filled ionization chambers equipped with solid-state electrometers, with different gas pressures and steel wall thicknesses, and a pair of aluminum-wall Gm counters have provided the basic data. These data are supplemented by measurements with air-filled and tissue equivalent ionization chambers and a scintillation spectrometer. Laboratory experiments together with analyses of the theoretical aspects of the detector responses to cosmic radiation indicate that these profiles can be determined to an overall accuracy of + or - 5 percent

    R116C mutation of cationic trypsinogen in a Turkish family with recurrent pancreatitis illustrates genetic microheterogeneity of hereditary pancreatitis

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    Hereditary pancreatitis is due to heterozygosity for gain-of-function mutations in the cationic trypsinogen gene which result in increased levels of active trypsin within pancreatic acinar cells and autodigestion of the pancreas. The number of disease-causing defects is generally considered to be low. To gain further insight into the molecular basis of this disorder, DNA sequence analysis of all five exons was performed in 109 unrelated patients with idiopathic chronic pancreatitis in order to determine the variability of the underlying mutations. Two German females and one German male were carriers of the most common N291 and R122H mutations (trypsinogen numbering system). In a Turkish proband, an arginine (CGT) to cysteine (TGT) substitution at amino acid position 116 was identified. Family screening demonstrated that the patient had inherited the mutation from his asymptomatic father and that he had transmitted it to both of his children, his daughter being symptomatic since the age of 3 years. In addition, a German male was found to be a heterozygote for a D100H (GAC-->CAC) amino acid replacement. Our data provide evidence for genetic heterogeneity of hereditary pancreatitis. The growing number of cationic trypsinogen mutations is expected to change current mutation screening practices for this disease

    Simulations of the Galaxy Cluster CIZA J2242.8+5301 I: Thermal Model and Shock Properties

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    The giant radio relic in CIZA J2242.8+5301 is likely evidence of a Mpc sized shock in a massive merging galaxy cluster. However, the exact shock properties are still not clearly determined. In particular, the Mach number derived from the integrated radio spectrum exceeds the Mach number derived from the X-ray temperature jump by a factor of two. We present here a numerical study, aiming for a model that is consistent with the majority of observations of this galaxy cluster. We first show that in the northern shock upstream X-ray temperature and radio data are consistent with each other. We then derive progenitor masses for the system using standard density profiles, X-ray properties and the assumption of hydrostatic equilibrium. We find a class of models that is roughly consistent with weak lensing data, radio data and some of the X-ray data. Assuming a cool-core versus non-cool-core merger, we find a fiducial model with a total mass of 1.6×1015 M⊙1.6 \times 10^{15}\,M_\odot, a mass ratio of 1.76 and a Mach number that is consistent with estimates from the radio spectrum. We are not able to match X-ray derived Mach numbers, because even low mass models over-predict the X-ray derived shock speeds. We argue that deep X-ray observations of CIZA J2242.8+5301 will be able to test our model and potentially reconcile X-ray and radio derived Mach numbers in relics.Comment: 19 pages, 19 figure

    Near-infrared spectropolarimetry of a delta-spot

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    Sunspots harboring umbrae of both magnetic polarities within a common penumbra (delta-spots) are often but not always related to flares. We present first near-infrared (NIR) observations (Fe I 1078.3 nm and Si I 1078.6 nm spectra) obtained with the Tenerife Infrared Polarimeter (TIP) at the Vacuum Tower Telescope (VTT) in Tenerife on 2012 June 17, which afford accurate and sensitive diagnostics to scrutinize the complex fields along the magnetic neutral line of a delta-spot within active region NOAA 11504. We examine the vector magnetic field, line-of-sight (LOS) velocities, and horizontal proper motions of this rather inactive delta-spot. We find a smooth transition of the magnetic vector field from the main umbra to that of opposite polarity (delta-umbra), but a discontinuity of the horizontal magnetic field at some distance from the delta-umbra on the polarity inversion line. The magnetic field decreases faster with height by a factor of two above the delta-umbra. The latter is surrounded by its own Evershed flow. The Evershed flow coming from the main umbra ends at a line dividing the spot into two parts. This line is marked by the occurrence of central emission in the Ca II 854.2 nm line. Along this line, high chromospheric LOS-velocities of both signs appear. We detect a shear flow within the horizontal flux transport velocities parallel to the dividing line.Comment: 4 pages, will appear as Letter in Astronomy & Astrophysic
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