Low-dislocation-density GaN from a single growth on a textured substrate

The density of threading dislocations (TD) in GaN grown directly on flat sapphire substrates is typically greater than 10{sup 9}/cm{sup 2}. Such high dislocation densities degrade both the electronic and photonic properties of the material. The density of dislocations can be decreased by orders of magnitude using cantilever epitaxy (CE), which employs prepatterned sapphire substrates to provide reduced-dimension mesa regions for nucleation and etched trenches between them for suspended lateral growth of GaN or AlGaN. The substrate is prepatterned with narrow lines and etched to a depth that permits coalescence of laterally growing III-N nucleated on the mesa surfaces before vertical growth fills the etched trench. Low dislocation densities typical of epitaxial lateral overgrowth (ELO) are obtained in the cantilever regions and the TD density is also reduced up to 1 micrometer from the edge of the support regions

Classical Loop Actions of Gauge Theories

Since the first attempts to quantize Gauge Theories and Gravity in the loop representation, the problem of the determination of the corresponding classical actions has been raised. Here we propose a general procedure to determine these actions and we explicitly apply it in the case of electromagnetism. Going to the lattice we show that the electromagnetic action in terms of loops is equivalent to the Wilson action, allowing to do Montecarlo calculations in a gauge invariant way. In the continuum these actions need to be regularized and they are the natural candidates to describe the theory in a ``confining phase''.Comment: LaTeX 14 page

Integratible Process for Fabrication of Fluidic Microduct Networks on a Single Wafer

We present a microelectronics fabrication compatible process that comprises photolithography and a key room temperature SiON thin film plasma deposition to define and seal a fluidic microduct network. Our single wafer process is independent of thermo-mechanical material properties, particulate cleaning, global flatness, assembly alignment, and glue medium application, which are crucial for wafer fusion bonding or sealing techniques using a glue medium. From our preliminary experiments, we have identified a processing window to fabricate channels on silicon, glass and quartz substrates. Channels with a radius of curvature between 8 and 50 {micro}m, are uniform along channel lengths of several inches and repeatable across the wafer surfaces. To further develop this technology, we have begun characterizing the SiON film properties such as elastic modulus using nanoindentation, and chemical bonding compatibility with other microelectronic materials

Triad representation of the Chern-Simons state in quantum gravity

We investigate a triad representation of the Chern-Simons state of quantum gravity with a non-vanishing cosmological constant. It is shown that the Chern-Simons state, which is a well-known exact wavefunctional within the Ashtekar theory, can be transformed to the real triad representation by means of a suitably generalized Fourier transformation, yielding a complex integral representation for the corresponding state in the triad variables. It is found that topologically inequivalent choices for the complex integration contour give rise to linearly independent wavefunctionals in the triad representation, which all arise from the one Chern-Simons state in the Ashtekar variables. For a suitable choice of the normalization factor, these states turn out to be gauge-invariant under arbitrary, even topologically non-trivial gauge-transformations. Explicit analytical expressions for the wavefunctionals in the triad representation can be obtained in several interesting asymptotic parameter regimes, and the associated semiclassical 4-geometries are discussed. In restriction to Bianchi-type homogeneous 3-metrics, we compare our results with earlier discussions of homogeneous cosmological models. Moreover, we define an inner product on the Hilbert space of quantum gravity, and choose a natural gauge-condition fixing the time-gauge. With respect to this particular inner product, the Chern-Simons state of quantum gravity turns out to be a non-normalizable wavefunctional.Comment: Latex, 30 pages, 1 figure, to appear in Phys. Rev.

Extended Loops: A New Arena for Nonperturbative Quantum Gravity

We propose a new representation for gauge theories and quantum gravity. It can be viewed as a generalization of the loop representation. We make use of a recently introduced extension of the group of loops into a Lie Group. This extension allows the use of functional methods to solve the constraint equations. It puts in a precise framework the regularization problems of the loop representation. It has practical advantages in the search for quantum states. We present new solutions to the Wheeler-DeWitt equation that reinforce the conjecture that the Jones Polynomial is a state of nonperturbative quantum gravity.Comment: 12pp, Revtex, no figures, CGPG-93/12-

Evaluación inmunológica. Hepatitis viral tipo B. Pre y post refuerzo en trabajadores de la salud. Policlínico 5 de septiembre. Año 2003 - 2004 Immunological assessment. Viral type-B hepatitis: pre and post-reinforcement to the health workers. “5 de s

Tomando en consideración la importancia del problema de salud ocasionado por el Virus de la Hepatitis Tipo B (V.H.B), así como lo orientado por el Ministerio de Salud Pública (MINSAP) en el Programa contra la Hepatitis Viral Tipo B, hemos estudiado el cumplimiento del esquema de vacunación, en trabajadores de la Salud (T.S), la respuesta inmune en ellos y la forma de intervenir para incrementar dicha respuesta en los que hayan tenido irregularidades y lo necesiten. En estos casos se realizó la aplicación de una dosis de 20 microgramos de la Vacuna Heberbiovac HB midiendo la cantidad de anticuerpos (Ac) antes y l mes después del refuerzo. El número de trabajadores pesquisados fue de 41 detectándose irregularidades (2 dosis) en el 31%. Se demostró menor seroprotección e hiperespuesta cuando solo se administraron 2 dosis. En estos trabajadores donde se utilizó el refuerzo se incrementó la respuesta inmune. Los no seroprotegidos en el pesquisaje inicial no alcanzaron valores de hipe respuesta coincidiendo con edad > 44 años. Se recomienda incrementar la cultura de buenas prácticas en nuestro sector desde el punto de vista Biológico y Educativo. Palabras clave: PROBLEMAS DE SALUD, RESPUESTA INMUNE, TRABAJADORES DE LA SALUD. ABSTRACT Considering the importance of the health problem by viral type B hepatitis (V.H.B.) as well as the guideline of Public Health Ministry (MINSAP) in the program anti type B viral hepatitis it was studied the fulfilment of vaccination scheme in health workers, the immune response in those patients with abnormalities and those that needed it. In such cases a dose of 20 microgramus of Heberbiovac Vaccine HB was applied measuring the antibodies (Ac) before and one month after the reinforcing doses, the immunological response was increased. No-serum protected patients in the initial study did not reach hyperresponse values coinciding with age over 44. it is recommended to increase the good practices in our sectors from the biological and educational points of view. Key words: HEALTH PROBLEMS, IMMUNE RESPONSE, HEALTH WORKERS

Evaluación inmunológica. Hepatitis viral tipo B. Pre y post refuerzo en trabajadores de la salud. Policlínico 5 de septiembre. Año 2003 - 2004 Immunological assessment. Viral type-B hepatitis: pre and post-reinforcement to the health workers. “5 de s

Tomando en consideración la importancia del problema de salud ocasionado por el Virus de la Hepatitis Tipo B (V.H.B), así como lo orientado por el Ministerio de Salud Pública (MINSAP) en el Programa contra la Hepatitis Viral Tipo B, hemos estudiado el cumplimiento del esquema de vacunación, en trabajadores de la Salud (T.S), la respuesta inmune en ellos y la forma de intervenir para incrementar dicha respuesta en los que hayan tenido irregularidades y lo necesiten. En estos casos se realizó la aplicación de una dosis de 20 microgramos de la Vacuna Heberbiovac HB midiendo la cantidad de anticuerpos (Ac) antes y l mes después del refuerzo. El número de trabajadores pesquisados fue de 41 detectándose irregularidades (2 dosis) en el 31%. Se demostró menor seroprotección e hiperespuesta cuando solo se administraron 2 dosis. En estos trabajadores donde se utilizó el refuerzo se incrementó la respuesta inmune. Los no seroprotegidos en el pesquisaje inicial no alcanzaron valores de hipe respuesta coincidiendo con edad > 44 años. Se recomienda incrementar la cultura de buenas prácticas en nuestro sector desde el punto de vista Biológico y Educativo. Palabras clave: PROBLEMAS DE SALUD, RESPUESTA INMUNE, TRABAJADORES DE LA SALUD. ABSTRACT Considering the importance of the health problem by viral type B hepatitis (V.H.B.) as well as the guideline of Public Health Ministry (MINSAP) in the program anti type B viral hepatitis it was studied the fulfilment of vaccination scheme in health workers, the immune response in those patients with abnormalities and those that needed it. In such cases a dose of 20 microgramus of Heberbiovac Vaccine HB was applied measuring the antibodies (Ac) before and one month after the reinforcing doses, the immunological response was increased. No-serum protected patients in the initial study did not reach hyperresponse values coinciding with age over 44. it is recommended to increase the good practices in our sectors from the biological and educational points of view. Key words: HEALTH PROBLEMS, IMMUNE RESPONSE, HEALTH WORKERS

The Extended Loop Group: An Infinite Dimensional Manifold Associated with the Loop Space

A set of coordinates in the non parametric loop-space is introduced. We show that these coordinates transform under infinite dimensional linear representations of the diffeomorphism group. An extension of the group of loops in terms of these objects is proposed. The enlarged group behaves locally as an infinite dimensional Lie group. Ordinary loops form a subgroup of this group. The algebraic properties of this new mathematical structure are analized in detail. Applications of the formalism to field theory, quantum gravity and knot theory are considered.Comment: The resubmited paper contains the title and abstract, that were omitted in the previous version. 42 pages, report IFFI/93.0