GaN micro-light-emitting diode arrays with monolithically integrated sapphire microlenses

A microdisk light emitting diode (micro-LED) with a monolithically integrated microlens array was demonstrated. The capability of the lenses in concentrating light emitted from microdisk LEDs was also demonstrated. The focal lengths of the microlenses were determined to be around 44 νm. The emission pattern of the LED emitters was found to be altered by the optical properties of the microlenses. The light emitted by the hybrid device was also found to be less divergent than a broad-area device.published_or_final_versio

InGaN nano-ring structures for high-efficiency light emitting diodes

A technique based on the Fresnel diffraction effect for the fabrication of nano-scale site-controlled ring structures in InGaN/GaN multi-quantum well structures has been demonstrated. The ring structures have an internal diameter of 500 nm and a wall width of 300 nm. A 1 cm-1 Raman shift has been measured, signifying substantial strain relaxation from the fabricated structure. The 9 nm blueshift observed in the cathodoluminescence spectra can be attributed to band filling and/or screening of the piezoelectric field. A light emitting diode based on this geometry has been demonstrated. © 2005 American Institute of Physics.published_or_final_versio

Vegetation Cover Analysis of Hazardous Waste Sites in Utah and Arizona Using Hyperspectral Remote Sensing

This study investigated the usability of hyperspectral remote sensing for characterizing vegetation at hazardous waste sites. The specific objectives of this study were to: (1) estimate leaf-area-index (LAI) of the vegetation using three different methods (i.e., vegetation indices, red-edge positioning (REP), and machine learning regression trees), and (2) map the vegetation cover using machine learning decision trees based on either the scaled reflectance data or mixture tuned matched filtering (MTMF)-derived metrics and vegetation indices. HyMap airborne data (126 bands at 2.3 x 2.3 m spatial resolution), collected over the U. S. Department of Energy uranium processing sites near Monticello, Utah and Monument Valley, Arizona, were used. Grass and shrub species were mixed on an engineered disposal cell cover at the Monticello site while shrub species were dominant in the phytoremediation plantings at the Monument Valley site. Regression trees resulted in the best calibration performance of LAI estimation (R-2 > 0.80. The use of REPs failed to accurately predict LAI (R-2 < 0.2). The use of the MTMF-derived metrics (matched filter scores and infeasibility) and a range of vegetation indices in decision trees improved the vegetation mapping when compared to the decision tree classification using just the scaled reflectance. Results suggest that hyperspectral imagery are useful for characterizing biophysical characteristics (LAI) and vegetation cover on capped hazardous waste sites. However, it is believed that the vegetation mapping would benefit from the use of higher spatial resolution hyperspectral data due to the small size of many of the vegetation patches (<1 m) found on the sites.open111

The Equivalence Theorem for Chiral Lagrangians

In this work we derive the version of the Equivalence Theorem that applies when the symmetry breaking sector of the Standard Model is described by a general chiral lagrangian. The demonstration is valid for renormalized fields for any value of the gauge parameter (in $R_{\xi}$ gauges) and any parametrization of the coset space. It is based in the absence of gauge anomalies which makes it possible to build an (anti)-BRS invariant chiral lagrangian in terms of the renormalized fields and therefore to use the corresponding Ward identities to obtain the theorem.Comment: 18 pages, LaTeX, FT/UCM/2/94 (We have corrected some errata

On the Equivalence Theorem in the χPT\chi PT Description of the Symmetry Breaking Sector of the Standard Model

We develop an alternative formulation of the symmetry breaking sector of the Standard Model as a gauged non-linear sigma model (NLSM) following the philosophy of the Chiral lagrangian approach, which is the only compatible with all the experimental and theoretical constraints. We derive the BRS symmetry of the model and the corresponding quantum lagrangian, which is a generalization of the standard Faddeev-Popov method, in a way which is covariant with respect to the reparametrizations of the coset space of the NLSM. Then we use the BRS invariance of the quantum lagrangian to state the Equivalence Theorem for the renormalized $S$-matrix elements calculated as a chiral expansion.Comment: LaTeX. Final version as it will appear in Nuclear Physics B (1994

Subaru FOCAS Spectroscopic Observations of High-Redshift Supernovae

We present spectra of high-redshift supernovae (SNe) that were taken with the Subaru low resolution optical spectrograph, FOCAS. These SNe were found in SN surveys with Suprime-Cam on Subaru, the CFH12k camera on the Canada-France-Hawaii Telescope (CFHT), and the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope (HST). These SN surveys specifically targeted z>1 Type Ia supernovae (SNe Ia). From the spectra of 39 candidates, we obtain redshifts for 32 candidates and spectroscopically identify 7 active candidates as probable SNe Ia, including one at z=1.35, which is the most distant SN Ia to be spectroscopically confirmed with a ground-based telescope. An additional 4 candidates are identified as likely SNe Ia from the spectrophotometric properties of their host galaxies. Seven candidates are not SNe Ia, either being SNe of another type or active galactic nuclei. When SNe Ia are observed within a week of maximum light, we find that we can spectroscopically identify most of them up to z=1.1. Beyond this redshift, very few candidates were spectroscopically identified as SNe Ia. The current generation of super red-sensitive, fringe-free CCDs will push this redshift limit higher.Comment: 19 pages, 26 figures. PASJ in press. see http://www.supernova.lbl.gov/2009ClusterSurvey/ for additional information pertaining to the HST Cluster SN Surve

A global fit of ππ\pi\pi and πK\pi K elastic scattering in ChPT with dispersion relations

We apply the one-loop results of the $SU(3)_L\times SU(3)_R$ ChPT suplemented with the inverse amplitude method to fit the available experimental data on $\pi\pi$ and $\pi K$ scattering. With esentially only three parameters we describe accurately data corresponding to six different channels, namely $(I,J)=(0,0), (2,0), (1,1), (1/2,0), (3/2,0)$ and $(1/2,1)$. In addition we reproduce the first resonances of the $(1,1)$ and $(1/2,1)$ channel with the right mass corresponding to the $\rho$ and the $K^*(892)$ particles.Comment: 19 pages, 5 figures available on request, FT/UCM/10/9

Personal and professional challenges in the management of deliberate self-poisoning patients in rural Sri Lanka: a qualitative study of rural hospital doctors' experiences and perceptions

Background. Deliberate self-poisoning is a major public heath issue in developing countries. In rural Sri Lanka deliberate self-poisoning is one of the leading causes of hospital death. The majority of patients with poisoning present to rural hospitals for initial treatment that are staffed by non-specialist and often relatively junior doctors. The treatment of self-poisoning patients poses numerous clinical challenges and further difficulties are experienced if patients are uncooperative and aggressive, intoxicated with alcohol or suffering mental illness. Previous research in developed countries has examined self-poisoning patients and their treatment but little is know about self-poisoning patient care in the context of rural health provision in developing countries. This study provides the first focused exploration of the experiences and perceptions of primary care rural hospital doctors in Sri Lanka toward the treatment of self-poisoning patients. Methods. Semi-structured in-depth interviews were conducted with fifteen doctors from rural hospitals in the North Central Province, Sri Lanka. All interviews were recorded and transcribed and subject to thematic analysis. Results. Participating doctors did perceive that treating self-poisoning patients in a primary care rural hospital as potentially confidence-building. However, resource issues such as the lack of medication, equipment and staffing were seen as important challenges to treating self-poisoning patients. Other challenges identified included disparity with community and other staff members regarding expectations of care, a sense of professional isolation and a lack of continuing education programs. Conclusion. Addressing professional isolation through educational and trainee programs for doctors and reducing the variance in expectations between professional groups and the community has the potential to improve delivery of care for self-poisoning patients

Mapping and identification of candidate loci responsible for Peromyscus hybrid overgrowth

Crosses between two recently diverged rodent species of the genus Peromyscus result in dramatic parent-of-origin effects on growth and development. P. maniculatus females crossed with P. polionotus males yield growth-retarded conceptuses, whereas the reciprocal cross results in overgrowth and lethality. These hybrid effects are particularly pronounced in the placenta. We previously detected linkage to two regions of the genome involved in the overgrowth effects. One locus, termed Peal, is a paternally expressed autosomal locus mapping to a domain whose house mouse equivalent contains several clusters of imprinted genes. The other locus, termed Mexl, maps to a gene-poor region of the X chromosome. Here we use an advanced intercross line to verify and narrow the regions of linkage and identify candidate genes for Mexl and Peal. While we have previously shown that Mexl affects both pre-and postnatal growth, we show here that Peal affects only prenatal growth. Utilizing criteria such as mutant phenotypes and allelic expression, we identify the loci encoding the homeobox protein Esx1 and the zinc-finger protein Pw1/Peg3 as candidates. Both loci exhibit expression changes in the hybrids