The z>4 Quasar Population Observed by Chandra and XMM-Newton

The current status of our Chandra and XMM-Newton project on high-redshift (z>4) quasars is briefly reviewed. We report the main results obtained in the last few years for the detected quasars, along with a few (~10%) intriguing cases where no detection has been obtained with Chandra snapshot observations.Comment: 4 pages, to appear in the proceedings of 'Multiwavelength AGN surveys' (Cozumel, December 8-12 2003), ed. R. Maiolino and R. Mujic

Entry corridor definition and SM/RCS deorbit requirements for Apollo block 1 earth orbit missions. Project Apollo

Entry corridor definition and SM reaction control system for Apollo Block 1 earth orbit mission

Integrating hot and cool intelligences: Thinking Broadly about Broad Abilities

Although results from factor-analytic studies of the broad, second-stratum abilities of human intelligence have been fairly consistent for decades, the list of broad abilities is far from complete, much less understood. We propose criteria by which the list of broad abilities could be amended and envision alternatives for how our understanding of the hot intelligences (abilities involving emotionally-salient information) and cool intelligences (abilities involving perceptual processing and logical reasoning) might be integrated into a coherent theoretical framework

Pressure and isotope effect on the anisotropy of MgB2_{2}

We analyze the data for the pressure and boron isotope effect on the temperature dependence of the magnetization near $T_{c}$. Invoking the universal scaling relation for the magnetization at fixed magnetic field it is shown that the relative shift of $T_{c}$, induced by pressure or boron isotope exchange, mirrors essentially that of the anisotropy. This uncovers a novel generic property of anisotropic type II superconductors, inexistent in the isotropic case. For MgB$_{2}$ it implies that the renormalization of the Fermi surface topology due to pressure or isotope exchange is dominated by a mechanism controlling the anisotropy.Comment: 7 pages, 3 figure

The X-ray Properties of the Most-Luminous Quasars from the Sloan Digital Sky Survey

Utilizing 21 new Chandra observations as well as archival Chandra, ROSAT, and XMM-Newton data, we study the X-ray properties of a representative sample of 59 of the most optically luminous quasars in the Universe (M_i~~-29.3 to -30.2) spanning a redshift range of z~~1.5-4.5. Our full sample consists of 32 quasars from the Sloan Digital Sky Survey (SDSS) Data Release 3 (DR3) quasar catalog, two additional objects in the DR3 area that were missed by the SDSS selection criteria, and 25 comparably luminous quasars at z>~4. This is the largest X-ray study of such luminous quasars to date. By jointly fitting the X-ray spectra of our sample quasars, excluding radio-loud and broad absorption line (BAL) objects, we find a mean X-ray power-law photon index of Gamma=1.92^{+0.09}_{-0.08} and constrain any neutral intrinsic absorbing material to have a mean column density of N_H<~2x10^{21} cm^{-2}. We find, consistent with other studies, that Gamma does not change with redshift, and we constrain the amount of allowed Gamma evolution for the most-luminous quasars. Our sample, excluding radio-loud and BAL quasars, has a mean X-ray-to-optical spectral slope of a_ox=-1.80+/-0.02, as well as no significant evolution of a_ox with redshift. We also comment upon the X-ray properties of a number of notable quasars, including an X-ray weak quasar with several strong narrow absorption-line systems, a mildly radio-loud BAL quasar, and a well-studied gravitationally lensed quasar.Comment: 18 pages (emulateapj), 11 figures. Accepted for publication in The Astrophysical Journa

Excitation Induced Dephasing in Semiconductor Quantum Dots

A quantum kinetic theory is used to compute excitation induced dephasing in semiconductor quantum dots due to the Coulomb interaction with a continuum of states, such as a quantum well or a wetting layer. It is shown that a frequency dependent broadening together with nonlinear resonance shifts are needed for a microscopic explanation of the excitation induced dephasing in such a system, and that excitation induced dephasing for a quantum-dot excitonic resonance is different from quantum-well and bulk excitons.Comment: 6 pages, 4 figures. Extensively revised text, two figures change

Comment on "Fano Resonance for Anderson Impurity Systems"

In a recent Letter, Luo et al. (Phys. Rev. Lett. 92, 256602 (2004)) analyze the Fano line shapes obtained from scanning tunneling spectroscopy (STS) of transition metal impurities on a simple metal surface, in particular of the Ti/Au(111) and Ti/Ag(100) systems. As the key point of their analysis, they claim that there is not only a Fano interference effect between the impurity d-orbital and the conduction electron continuum, as derived in Ujsaghy et al. (Phys. Rev. Lett. 85, 2557 (2000)), but that the Kondo resonance in the d-electron spectral density has by itself a second Fano line shape, leading to the experimentally observed spectra. In the present note we point out that this analysis is conceptually incorrect. Therefore, the quantitative agreement of the fitted theoretical spectra with the experimental results is meaningless.Comment: 1 page, no figures. Accepted for publication in PRL; revised version uploaded on November 18th, 200