Supergravity duals of gauge theories from F(4) gauged supergravity in six dimensions

We construct supergravity solutions dual to twisted field theories that are the worldvolume theories of D4-branes wrapped on 2, 3-cycles, and NS-fivebranes on 3-cycles. We first obtain the solutions for the Romans' six-dimensional gauged supergravity theories and then up-lift them to ten dimensions. In particular, we find solutions for field configurations with either non-Abelian fields or B-fields being excited. One of these solutions, in the massless case, is up-lifted to the massless type IIA string theory. This is the first example of such a kind. The cases studied provide new examples of the AdS/CFT duality involving twisted field theories.Comment: 26 pages, 3 figures, minor changes and references added to match the published versio

Metal-insulator transition in the quarter- filled frustrated checkerboard lattice

We study the electronic structure and correlations in the geometrically frustrated two dimensional checkerboard lattice. In the large U limit considered here we start from an extended Hubbard model of spinless fermions at half-filling. We investigate the model within two distinct Green's function approaches: In the first approach a single-site representation decoupling scheme is used that includes the effect of nearest neighbor charge fluctuations. In the second approach a cluster representation leading to a 'multiorbital' model is investigated which includes intra-cluster correlations exactly and those between clusters on a mean field basis. It is demonstrated that with increasing nearest-neighbor Coulomb interaction V both approaches lead to a metal-insulator transition with an associated 'Mott-Hubbard' like gap caused by V. Within the single site approach we also explore the possibility of charge order. Furthermore we investigate the evolution of the quasiparticle bands as funtion of V

Submicrometric Films of Surface-Attached Polymer Network with Temperature-Responsive Properties

Temperature-responsive properties of surface-attached poly(N-isopropylacrylamide) (PNIPAM) network films with well-controlled chemistry are investigated. The synthesis consists of cross-linking and grafting preformed ene-reactive polymer chains through thiol--ene click chemistry. The formation of surface-attached and cross-linked polymer films has the advantage of being wellcontrolled without any caution of no-oxygen atmosphere or addition of initiators. PNIPAM hydrogel films with same cross-link density are synthesized on a wide range of thickness, from nanometers to micrometers. The swelling-collapse transition with temperature is studied by using ellipsometry, neutron reflectivity, and atomic force microscopy as complementary surface-probing techniques. Sharp and high amplitude temperature-induced phase transition is observed for all submicrometric PNIPAM hydrogel films. For temperature above LCST, surface-attached PNIPAM hydrogels collapse similarly but without complete expulsion of water. For temperature below LCST, the swelling of PNIPAM hydrogels depends on the film thickness. It is shown that the swelling is strongly affected by the surface attachment for ultrathin films below $\sim$150 nm. For thicker films above 150 nm (to micrometers), surface-attached polymer networks with the same cross-link density swell equally. The density profile of the hydrogel films in the direction normal to the substrate is confronted with in-plane topography of the free surface. It results that the free interface width is much larger than the roughness of the hydrogel film, suggesting pendant chains at the free surface.Comment: in Langmuir, American Chemical Society, 2015, LANGMUIR, 31 (42), pp.11516-1152

Suppressed silicide formation in FePt thin films by nitrogen addition

Copyright © 2013 Elsevier. NOTICE: this is the author’s version of a work that was accepted for publication in Journal of Magnetism and Magnetic Materials. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Magnetism and Magnetic Materials Vol. 331 (2013), DOI: 10.1016/j.jmmm.2012.11.045FePt and FePtN thin films have been prepared on silicon substrates by the relatively new deposition technique known as High Target Utilization Sputtering. Films were annealed post-deposition at temperatures up to 800 °C in order to induce the high-anisotropy L10 phase. The FePt films initially showed an improvement in magnetic properties with annealing temperature, but for annealing above around 400 °C the magnetic properties deteriorated markedly. The magnetic properties of the FePtN films, however, continued to improve with increasing annealing temperature, right up to the maximum temperature applied of 800 °C. Analysis by X-ray diffraction revealed the formation of iron and platinum silicides in FePt films above 400 °C, but that such silicides are absent from the FePtN at all annealing temperatures except 800 °C. This behavior is attributed to the nitrogen in FePtN films reacting preferentially with the silicon in the substrate to form silicon nitride, thus suppressing the formation of platinum and iron silicides. Thus, by introducing nitrogen during the deposition of FePt films on Si substrates the formation of deleterious silicides appears to be suppressed during thermal treatment, thereby offering protection against silicon pollution.Plasma Quest Lt

Strategies for Teaching Information Literacy to English Language Learners

Academic librarians are encountering a growing number of English Language Learners (ELLs) every day, as our classrooms have become more linguistically diverse every year. In this dramatically changing environment, academic librarians are expected to meet the needs of increasingly diverse students speaking multiple languages. The purpose of this paper is to present widely used teaching strategies to support ELLs based on an exhaustive literature review. Study also suggests collaboration among ESL or classroom instructors and librarians to enhance semester-long learning experience

Interplay of plasma-induced and fast thermal nonlinearities in a GaAs-based photonic crystal nanocavity

We investigate the nonlinear response of GaAs-based photonic crystal cavities at time scales which are much faster than the typical thermal relaxation rate in photonic devices. We demonstrate a strong interplay between thermal and carrier induced nonlinear effects. We have introduced a dynamical model entailing two thermal relaxation constants which is in very good agreement with experiments. These results will be very important for Photonic Crystal-based nonlinear devices intended to deal with practical high repetition rate optical signals.Comment: 10 pages, 8 figures, Phys Rev A (accepted