Commercializing the laboratory: Faculty patenting and the open science environment

This paper investigates the relationship between patenting and publication of research results by university faculty members. Our study adds to the limited evidence on this topic with an empirical investigation based on a panel data set for a broad sample of university researchers. Results suggest that publication and patenting are complementary, not substitute, activities for faculty members. This is not consistent with recent concerns regarding deleterious effects of patenting on the research output of faculty members. Average citations to publications, however, appear to decline for repeat patenters, suggesting either a decrease in quality or restrictions on use associated in patent protection

BeppoSAX Observations of the Maser Sy2 Galaxy: ESO103-G35

We have made BeppoSAX observations of the Seyfert 2/1.9 galaxy ESO103-G35, which contains a nuclear maser source and is known to be heavily absorbed in the X-rays. Analysis of the X-ray spectra observed by SAX in October 1996 and 1997 yields a spectral index 0.74+/-0.07, typical of Seyfert galaxies and consistent with earlier observations of this source. The strong, soft X-ray absorption has column density 1.79E(23)/cm^2, again consistent with earlier results. The best fitting spectrum is that of a power law with a high energy cutoff at 29+/-10 keV, a cold, marginally resolved Fe Kalpha line with EW 290 eV (1996) and a mildly ionized Fe K-edge at 7.37 keV. The Kalpha line and cold absorption are consistent with origin in a accretion disk/torus through which our line-of-sight passes at a radial distance of $\sim 50$ pc. The Fe K-edge is mildly ionized suggesting the presence of ionized gas probably in the inner accretion disk, close to the central source or in a separate warm absorber. The data quality is too low to distinguish between these possibilities but the edge-on geometry implied by the water maser emission favors the former. Comparison with earlier observations of ESO103-G35 shows little/no change in spectral parameters while the flux changes by factors of a few on timescales of a few months. The 2--10 keV flux decreased by a factor of 2.7 between Oct 1996 and Oct 1997 with no detectable change in the count rate >20 keV suggesting a constant or delayed response reflection component. The high energy cutoff is lower than the typical 300keV values seen in Seyfert galaxies. A significant subset of similar sources would affect current models of the AGN contribution to the cosmic X-ray background which generally assume a high energy cutoff of 300 keV.Comment: 22 pages, postscript file, accepted for publication in Ap

Numerical study of a superconductor-insulator transition in a half-filled Hubbard chain with distant transfers

The ground state of a one-dimensional Hubbard model having the next-nearest neighbor hopping (t') as well as the nearest-neighbor one (t) is numerically investigated at half-filling. A quantum Monte Carlo result shows a slowly decaying pairing correlation for a sizeable interaction strength $(U \leq 2t)$, while the system is shown to become insulating for yet larger $U>U_C\sim 3t$ from a direct evaluation of the charge gap with the density-matrix renormalization group method. The results are consistent with Fabrizio's recent weak-coupling theory which suggests a transition from a superconductor into an insulator at a finite U.Comment: 4 pages, RevTeX, uses epsf.sty and multicol.st

Spanning Trees and bootstrap reliability estimation in correlation based networks

We introduce a new technique to associate a spanning tree to the average linkage cluster analysis. We term this tree as the Average Linkage Minimum Spanning Tree. We also introduce a technique to associate a value of reliability to links of correlation based graphs by using bootstrap replicas of data. Both techniques are applied to the portfolio of the 300 most capitalized stocks traded at New York Stock Exchange during the time period 2001-2003. We show that the Average Linkage Minimum Spanning Tree recognizes economic sectors and sub-sectors as communities in the network slightly better than the Minimum Spanning Tree does. We also show that the average reliability of links in the Minimum Spanning Tree is slightly greater than the average reliability of links in the Average Linkage Minimum Spanning Tree.Comment: 17 pages, 3 figure

Phase diagram of the half-filled Hubbard chain with next-nearest-neighbor hopping

We investigate the ground-state phase diagram of the half-filled one-dimensional Hubbard model with next-nearest-neighbor hopping using the Density-Matrix Renormalization Group technique as well as an unrestricted Hartree-Fock approximation. We find commensurate and incommensurate disordered magnetic insulating phases and a spin-gapped metallic phase in addition to the one-dimensional Heisenberg phase. At large on-site Coulomb repulsion $U$, we make contact with the phase diagram of the frustrated Heisenberg chain, which has spin-gapped phases for sufficiently large frustration. For weak $U$, sufficiently large next-nearest-neighbor hopping $t_2$ leads to a band structure with four Fermi points rather than two, producing a spin-gapped metallic phase. As $U$ is increased in this regime, the system undergoes a Mott-Hubbard transition to a frustrated antiferromagnetic insulator

Interplay of Orbital Degeneracy and Superconductivity in a Molecular Conductor

We study electron propagation in a molecular lattice model. Each molecular site involves doubly degenerate electronic states coupled to doubly degenerate molecular vibration, leading to a so--called E-e type of Jahn-Teller Hamiltonian. For weak electron-phonon coupling and in the anti-adiabatic limit we find that the orbital degeneracy induces an intersite pairing mechanism which is absent in the standard non-degenerate polaronic model. In this limit we analyse the model in the presence of an additional on-site repulsion and we determine, within BCS mean field theory, the region of stability of superconductivity. In one dimension, where powerful analytical techniques are available, we are able to calculate the phase diagram of the model both for weak and for strong electron-phonon coupling.Comment: 11 pages, REVTEX style, 3 compressed figures adde

Dielectric catastrophe at the Mott transition

We study the Mott transition as a function of interaction strength in the half-filled Hubbard chain with next-nearest-neighbor hopping t' by calculating the response to an external electric field using the Density Matrix Renormalization Group. The electric susceptibility chi diverges when approaching the critical point from the insulating side. We show that the correlation length xi characterizing this transition is directly proportional to fluctuations of the polarization and that chi ~ xi^2. The critical behavior shows that the transition is infinite-order for all t', whether or not a spin gap is present, and that hyperscaling holds.Comment: 4 pages, 4 eps figures, REVTe

Evolution of Hot Gas and Dark Halos in Group-Dominant Elliptical Galaxies: Influence of Cosmic Inflow

We study the complete dynamical evolution of hot interstellar gas in massive elliptical galaxies born into a simple flat universe beginning with an overdense perturbation. Within the turn-around radius dark matter flows in a self-similar fashion into a stationary Navarro-Frenk-White halo and the baryonic gas shocks. After a few gigayears, when enough gas accumulates within the accretion shock, the de Vaucouleurs stellar system is constructed and the energy from Type II supernovae is released. The stars and dark halo are matched to NGC 4472. Gas continues to enter the galaxy by secondary infall and by stellar mass loss based on a Salpeter IMF. After about 13 Gyrs the temperature and density distribution in the hot gas agree quite well with the hot interstellar gas observed in NGC 4472. As a result of supernova-driven outflow, the present day baryonic fraction has a deep minimum in the outer galactic halo. When relatively gas-rich, X-ray luminous models are spatially truncated at early times, simulating tidal events that may have occurred during galaxy group dynamics, the current locus of truncated models lies just along the $L_x$, X-ray size correlation among well-observed ellipticals, providing another striking confirmation of our simple model of elliptical evolution.Comment: 16 pages in AASTEX LaTeX with 14 figures; accepted by Astrophysical Journa

Resonant Absorption in the AGN spectra emerging from photoionized gas: differences between steep and flat ionizing continua

We present photoionization models accounting for both photoelectric and resonant absorption. Resonance absorption lines from C, O, Ne, Mg, Si S and Fe between 0.1 and 10 keV are treated. In particular we consider the complex of almost 60 strong Fe L absorption lines around 1 keV. We calculate profiles, intensities and equivalent widths of each line, considering both Doppler and natural broadening mechanisms. Doppler broadening includes a term accounting for turbulence of the gas along the line of sight. We computed spectra transmitted by gas illuminated by drastically different ionizing continua and compared them to spectra observed in flat X-ray spectrum, broad optical emission line type 1 AGN, and steep X-ray spectrum, narrow optical emission line type 1 AGN. We show that the $\sim 1$ keV absorption feature observed in moderate resolution X-ray spectra of several Narrow Line Seyfert 1 galaxies can be explained by photoionization models, taking into account for resonance absorption, without requiring relativistic outflowing velocities of the gas, if the physical properties of these absorbers are close to those found in flat X-ray spectrum Seyfert 1 galaxies.Comment: 22 pages, 10 figures. Accepted for publication on Ap