Automorphisms of quantum matrices

We study the automorphism group of the algebra \oqmn of $n \times n$ generic quantum matrices. We provide evidence for our conjecture that this group is generated by the transposition and the subgroup of those automorphisms acting on the canonical generators of \oqmn by multiplication by scalars. Moreover, we prove this conjecture in the case when $n=3$.Comment: 15 pages; to appear in Glasgow Mathematical Journa

Spin-Phonon Coupling in Iron Pnictide Superconductors

The magnetic moment in the parent phase of the iron-pnictide superconductors varies with composition even when the nominal charge of iron is unchanged. We propose the spin-lattice coupling due to the magneto-volume effect as the primary origin of this effect, and formulate a Landau theory to describe the dependence of the moment to the Fe-As layer separation. We then compare the superconductive critical temperature of doped iron pnictides to the local moment predicted by the theory, and suggest that the spin-phonon coupling may play a role in the superconductivity of this compound

Occupational Disorder as the Origin of Flattening of the Acoustic Phonon Branches in the Clathrate Ba8_{8}Ga16_{16}Ge30_{30}

In the search for high-performance thermoelectrics, materials such as clathrates have drawn attention due to having both glass-like low phonon thermal conductivity and crystal-like high electrical conductivity. Ba$_{8}$Ga$_{16}$Ge$_{30}$ (BGG) has a loosely bound guest Ba atom trapped inside rigid Ga/Ge cage structures. Avoided crossings between acoustic phonons and the flat guest atom branches have been proposed to be the source of the low lattice thermal conductivity of BGG. Ga/Ge site disorder with Ga and Ge exchanging places in different unit cells has also been reported. We used time-of-flight neutron scattering to measure the complete phonon spectrum in a large single crystal of BGG and compared these results with predictions of density functional theory to elucidate the effect of the disorder on heat-carrying phonons. Experimental results agreed much better with the calculation assuming the disorder than with the calculation assuming the ordered configuration. Although atomic masses of Ga and Ge are nearly identical, we found that disorder strongly reduces phonon group velocities, which significantly reduces thermal conductivity. Our work points at a new path towards optimizing thermoelectrics.Comment: 6 pages, 3 figure

The 180 Degree Turn: Finding the Human Side of Mandated Counseling

This article discusses how cultural changes in the United States led to an emergence of a number of mandated treatments intended to address the specific concerns of substance abuse, sexual abuse, and domestic violence. A brief history of interventions for each of the respective fields is described and a trend toward more humanistic treatment methods is noted. The similarities between the Person-Centered Approach and current trends in these fields are explained

Spin Excitations in BaFe1.84Co0.16As2 Superconductor Observed by Inelastic Neutron Scattering

Superconductivity appears to compete against the spin-density-wave in Fe pnictides. However, optimally cobalt doped samples show a quasi-two-dimensional spin excitation centered at the (0.5, 0.5, L) wavevector, "the spin resonance peak", that is strongly tied to the onset of superconductivity. By inelastic neutron scattering on single crystals we show the similarities and differences of the spin excitations in BaFe1.84Co0.16As2, with respect to the spin excitations in the high-temperature superconducting cuprates. As in the cuprates the resonance occurs as an enhancement to a part of the spin excitation spectrum which extends to higher energy transfer and higher temperature. However, unlike in the cuprates, the resonance peak in this compound is asymmetric in energy.Comment: 12 pages, 6 figures; PACS # 74.70.-b, 74.20.Mn, 78.70.Nx, 74.25.Ha; corrected discussion of figures in tex

A new role for organometallic reactions in organic synthesis in industry

Abstract -Organometallic compounds are coming to play a significant role as catalysts and reagents for the synthesis of organic compounds in high technology industry. Some examples involving C-C bond formation include alkylation of chloronaphthoquinones and halobenzenes, a titanium-mediated cyclization of diynes, and a simultaneous alkylation and ring closure of hexenedioates to give cyclopentanone derivatives. Transition metal imides provide convenient reagents for C-N bond formation in a new synthesis of allylic amines