Solar-grade silicon prepared by carbothermic reduction of silica

An advanced carbothermic reduction (ACR) process was developed to produce solar grade (SC) silicon from high purity silica and carbon. Preparation of starting materials and operation of the arc furnace to product high purity silicon is described. Solar cells prepared from single crystal SG-Si had efficiencies of up to 12.3% practically identical to cells made from electronic grade silicon. The ACR process is not in the pilot stage for further evaluation

Connecting Angular Momentum and Galactic Dynamics: The complex Interplay between Spin, Mass, and Morphology

The evolution and distribution of the angular momentum of dark matter (DM) halos have been discussed in several studies over the past decades. In particular, the idea arose that angular momentum conservation should allow to infer the total angular momentum of the entire DM halo from measuring the angular momentum of the baryonic component, which is populating the center of the halo, especially for disk galaxies. To test this idea and to understand the connection between the angular momentum of the DM halo and its galaxy, we use the Magneticum simulations. We successfully produce populations of spheroidal and disk galaxies self-consistently. Thus, we are able to study the dependence of galactic properties on their morphology. We find that (1) the specific angular momentum of stars in disk and spheroidal galaxies as a function of their stellar mass compares well with observational results; (2) the specific angular momentum of the stars in disk galaxies is slightly smaller compared to the specific angular momentum of the cold gas, in good agreement with observations; (3) simulations including the baryonic component show a dichotomy in the specific stellar angular momentum distribution when splitting the galaxies according to their morphological type (this dichotomy can also be seen in the spin parameter, where disk galaxies populate halos with slightly larger spin compared to spheroidal galaxies); (4) disk galaxies preferentially populate halos in which the angular momentum vector of the DM component in the central part shows a better alignment to the angular momentum vector of the entire halo; and (5) the specific angular momentum of the cold gas in disk galaxies is approximately 40 percent smaller than the specific angular momentum of the total DM halo and shows a significant scatter.Comment: 25 pages, accepted by ApJ, www.magneticum.or

Protoneutron stars in the Brueckner-Hartree-Fock approach and finite-temperature kaon condensation

We study the properties of hot neutrino-trapped beta-stable stellar matter using an equation of state of nuclear matter within the Brueckner-Hartree-Fock approach including three-body forces, combined with a standard chiral model for kaon condensation at finite temperature. The properties of (proto)neutron stars are then investigated within this framework.Comment: 10 pages, 5 figures, 2 tables, PRC in pres

The degradation of MgB2 under ambient environment

The superconductivities of samples prepared by several procedures were found to degrade under ambient environment. The degradation mechanism was studied by measuring the change of surface chemical composition of dense MgB2 pellets (prepared by hot isostatic pressure, HIPed) under atmospheric exposure using X-ray Photoelectron Spectroscopy (XPS). Results showed that samples with poor connectivity between grains and with smaller grain sizes degrade with time when exposed to ambient conditions. In these samples, the Tc did not change with time, but the superconducting transition became broader and the Meissner fraction decreased. In contrast, our well-sintered and the HIPed samples remained stable for several months under ambient condition. The degradation was found to be related to surface decomposition as observed by XPS. We observed the formation of oxidized Mg, primarily in the form of a Mg hydroxide, the increase of C and O contents, and the reduction of B concentration in the surface layer of MgB2 samples.Comment: 15 pages, 3 figure

The cosmic growth of the active black hole population at 1<z<2 in zCOSMOS, VVDS and SDSS

We present a census of the active black hole population at 1<z<2, by constructing the bivariate distribution function of black hole mass and Eddington ratio, employing a maximum likelihood fitting technique. The study of the active black hole mass function (BHMF) and the Eddington ratio distribution function (ERDF) allows us to clearly disentangle the active galactic nuclei (AGN) downsizing phenomenon, present in the AGN luminosity function, into its physical processes of black hole mass downsizing and accretion rate evolution. We are utilizing type-1 AGN samples from three optical surveys (VVDS, zCOSMOS and SDSS), that cover a wide range of 3 dex in luminosity over our redshift interval of interest. We investigate the cosmic evolution of the AGN population as a function of AGN luminosity, black hole mass and accretion rate. Compared to z = 0, we find a distinct change in the shape of the BHMF and the ERDF, consistent with downsizing in black hole mass. The active fraction or duty cycle of type-1 AGN at z~1.5 is almost flat as a function of black hole mass, while it shows a strong decrease with increasing mass at z=0. We are witnessing a phase of intense black hole growth, which is largely driven by the onset of AGN activity in massive black holes towards z=2. We finally compare our results to numerical simulations and semi-empirical models and while we find reasonable agreement over certain parameter ranges, we highlight the need to refine these models in order to match our observations.Comment: 31 pages, 28 figures, accepted for publication in MNRA

Transpolyacetylene chains in hydrogenated amorphous carbon films free of nanocrystalline diamond

The microstructure of distributed electron cyclotron resonance plasma-deposited hydrogenated amorphous carbon films (a-C:H) was investigated using electron diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy. Experimental evidence of the existence of transpolyacetylene (TPA) chains in a-C:H films free of nanocrystalline diamond is presented. The values of the mean bond angles and lengths and first neighbor numbers are consistent with the TPA data. The Raman spectra were fitted using the G and D bands and the bands centered at 1140, 1233, and 1475 cm(-1) assigned to TPA chains modes. The relative intensity of the latter decreases while hydrogen content decreases. A significant sp(2)-CH olefinic mode contribution to the infrared stretching band is observed for the low-density films (similar to1.2 g/cm(3)). TPA chains growth is enhanced when ion current density and energy decrease. (C) 2003 American Institute of Physics. (DOI: 10.1063/1.1538349

Purification and analytical characterization of an anti- CD4 monoclonal antibody for human therapy

A purification process for the monclonal anti-CD4 antibody MAX.16H5 was developed on an analytical scale using (NH&SO, precipitation, anion-exchange chromatography on MonoQ or Q-Sepharose, hydrophobic interaction chromatography on phenyl- Sepharose and gel filtration chromatography on Superdex 200. The purification schedule was scaled up and gram amounts of MAX.16H5 were produced on corresponding BioPilot columns. Studies of the identity, purity and possible contamination by a broad range of methods showed that the product was highly purified and free from contaminants such as mouse DNA, viruses, pyrogens and irritants. Overall, the analytical data confirm that the monoclonal antibody MAX.16H5 prepared by this protocol is suitable for human therapy

Specific Heat of a Fractional Quantum Hall System

Using a time-resolved phonon absorption technique, we have measured the specific heat of a two-dimensional electron system in the fractional quantum Hall effect regime. For filling factors $\nu = 5/3, 4/3, 2/3, 3/5, 4/7, 2/5$ and 1/3 the specific heat displays a strong exponential temperature dependence in agreement with excitations across a quasi-particle gap. At filling factor $\nu = 1/2$ we were able to measure the specific heat of a composite fermion system for the first time. The observed linear temperature dependence on temperature down to $T = 0.14$ K agrees well with early predictions for a Fermi liquid of composite fermions.Comment: 4 pages, 4 figures (version is 1. resubmission: Added a paragraph to include the problems which arise by the weak temperature dependence at \nu = 1/2, updated affiliation

Shearing Interferometer for Quantifying the Coherence of Hard X-Ray Beams

We report a quantitative measurement of the full transverse coherence function of the 14.4 keV x-ray radiation produced by an undulator at the Swiss Light Source. An x-ray grating interferometer consisting of a beam splitter phase grating and an analyzer amplitude grating has been used to measure the degree of coherence as a function of the beam separation out to 30 m. Importantly, the technique provides a model-free and spatially resolved measurement of the complex coherence function and is not restricted to high resolution detectors and small fields of view. The spatial characterization of the wave front has important applications in discovering localized defects in beam line optics