A model to design light emitting diodes matrix driven by constant current source

It is always desirable to operate LEDs within its designed maximum temperature for maximized life. For LEDs driven by a constant current source it is possible to improve LED life by putting more LEDs in parallel to share current and reduce temperature, but the cost would increase. This paper proposes a general LED model to estimate the relationship between temperature, operating current, luminous flux, life and reliability of light emitting diodes. This model can direct LED matrix design with respect to the required parameters. The model would help lighting designers to consider the driving current and number of LED in a lamp matrix in order to achieve the desired light flux, efficacy and life with desired cost. A method involved power electronic technique is proposed to form a dynamic matrix that can response to the changing ambient temperature. This allows the engineer to build the real desired matrix flexibly.published_or_final_versio

Distribution of carbon monoxide-producing neurons in human colon and in Hirschsprung's disease patients

Hirschsprung's disease (HSCR) is characterized by the absence of ganglion cells and impaired relaxation of the gut. Nitric oxide (NO) and, more recently, carbon monoxide (CO) have been identified as inhibitory neurotransmitters causing relaxation. A deficiency in NO has been reported in aganglionic gut; we hypothesized that CO could also be involved in impaired gut motility in HSCR. The aim of the study was to determine the distribution of CO-and NO-producing enzymes in the normal and aganglionic gut. We performed laser capture microdissection, reverse transcription-polymerase chain reaction, and immunohistochemistry on colon biopsies of normal controls (n = 9) and patients with HSCR (n = 10). The mRNA expression of heme oxygenase-2 (HO-2), immunoreactivities of HO-2 and NO synthase, was determined and compared. Results show a high level of expression of HO-2 mRNA localized in the myenteric plexus. Expression of HO-2 mRNA was also detected in the mucosa, submucosa, and muscular layer. Down-regulation of HO-2 mRNA expression was detected in the aganglionic colon. Immunoreactivities of HO-2 and NO synthase were localized mainly to the ganglion plexus and to nerve fibers within the muscle in the control colons and normoganglionic colons. HO-2-containing neurons were more abundant than NO synthase-containing neurons in the myenteric plexus. Nearly all of the NO synthase-containing neurons also contained HO-2. HO-2 and NO synthase were selectively absent in the myenteric and submucosal regions and in the muscle of the aganglionic colon. Our findings suggest involvement of both CO and NO in the pathophysiology of HSCR. Copyright 2002, Elsevier Science (USA). All rights reserved.postprin

Sonic hedgehog regulates the proliferation, differentiation, and migration of enteric neural crest cells in gut

Enteric neural crest cells (NCCs) migrate and colonize the entire gut and proliferate and differentiate into neurons and glia of the enteric nervous system in vertebrate embryos. We have investigated the mitogenic and morphogenic functions of Sonic hedgehog (Shh) on enteric NCCs in cell and organ culture. Enteric NCCs expressed Shh receptor Patched and transcripts encoding the Shh signal transducer (Gli1). Shh promoted the proliferation and inhibited the differentiation of NCCs. The pro-neurogenic effect of glial cell line-derived neurotrophic factor (GDNF) on NCCs was abolished by Shh. In gut explants, NCCs migrated from the explants onto the adjacent substratum if GDNF was added, whereas addition of Shh abolished this migration. Neuronal differentiation and coalescence of neural crest-derived cells into myenteric plexuses in explants was repressed by the addition of Shh. Our data suggest that Shh controls the proliferation and differentiation of NCCs and modulates the responsiveness of NCCs toward GDNF inductions.published_or_final_versio

A γA-Crystallin Mouse Mutant Secc with Small Eye, Cataract and Closed Eyelid

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CHANDRA DETECTION OF A NEW DIFFUSE X-RAY COMPONENT FROM THE GLOBULAR CLUSTER 47 TUCANAE

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Tracking down the migration of mouse neural crest cells

During early embryonic development, cell migration is one of the most important morphogenetic processes. Neural crest cells arise from the dorsal part of the neural tube and migrate along different pathways to numerous locations where they differentiate into a variety of tissues. In the mouse, studies of neural crest cell migration have been difficult partly because of the absence of specific markers which can label neural crest cells throughout their migration from their origin to the site of differentiation. Nevertheless, the use of different experimental strategies involving extrinsic, intrinsic or genetic cell markers has already led to a good understanding of this migration. In our studies, extrinsic markers such as wheat germ agglutinin-gold conjugates and DiI and genetic markers including Hoxb2-lacZ and green fluorescent protein have been employed in tracing migrating neural crest cells. The labelling procedures and the strength and weaknesses of the tracing methods are reviewed herein. Copyright © 2003 S. Karger AG, Basel.published_or_final_versio

Search for pulsed γ-ray emission from globular cluster M28

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Exploring the X-ray and γ-ray properties of the redback millisecond pulsar PSR J1723-2837

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Orbital-phase-dependent γ-ray Emissions from the Black Widow Pulsar

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Pulsed γ-ray emission from magnetar 1E 2259+586

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