X-rays from Superbubbles in the Large Magellanic Cloud IV: The Blowout Structure of N44

We have used optical echelle spectra along with ROSAT and ASCA X-ray spectra to test the hypothesis that the southern portion of the N44 X-ray bright region is the result of a blowout structure. Three pieces of evidence now support this conclusion. First, the filamentary optical morphology corresponding with the location of the X-ray bright South Bar suggests the blowout description (Chu et al 1993). Second, optical echelle spectra show evidence of high velocity (~90 km/sec) gas in the region of the blowout. Third, X-ray spectral fits show a lower temperature for the South Bar than the main superbubble region of Shell 1. Such a blowout can affect the evolution of the superbubble and explain some of the discrepancy discussed by Oey & Massey (1995) between the observed shell diameter and the diameter predicted on the basis of the stellar content and Weaver et al.'s (1977) pressure-driven bubble model.Comment: 15 pages, LaTeX + psfig, 1 tex file, 2 sty files, 7 PS files, also available at: http://www.astro.washington.edu/gene/papers/papers.htm

Phenyl radical + propene: a prototypical reaction surface for aromatic-catalyzed 1,2-hydrogen-migration and subsequent resonance-stabilized radical formation

The C[subscript 9]H[subscript 11] potential energy surface (PES) was experimentally and theoretically explored because it is a relatively simple, prototypical alkylaromatic radical system. Although the C[subscript 9]H[subscript 11] PES has already been extensively studied both experimentally (under single-collision and thermal conditions) and theoretically, new insights were made in this work by taking a new experimental approach: flash photolysis combined with time-resolved molecular beam mass spectrometry (MBMS) and visible laser absorbance. The C[subscript 9]H[subscript 11] PES was experimentally accessed by photolytic generation of the phenyl radical and subsequent reaction with excess propene (C[subscript 6]H[subscript 5] + C[subscript 3]H[subscript 6]). The overall kinetics of C[subscript 6]H[subscript 5] + C[subscript 3]H[subscript 6] was measured using laser absorbance with high time-resolution from 300 to 700 K and was found to be in agreement with earlier measurements over a lower temperature range. Five major product channels of C[subscript 6]H[subscript 5] + C[subscript 3]H[subscript 6] were observed with MBMS at 600 and 700 K, four of which were expected: hydrogen (H)-abstraction (measured by the stable benzene, C[subscript 6]H[subscript 6], product), methyl radical (CH[subscript 3])-loss (styrene detected), H-loss (phenylpropene isomers detected) and radical adduct stabilization. The fifth, unexpected product observed was the benzyl radical, which was rationalized by the inclusion of a previously unreported pathway on the C[subscript 9]H[subscript 11] PES: aromatic-catalysed 1,2-H-migration and subsequent resonance stabilized radical (RSR, benzyl radical in this case) formation. The current theoretical understanding of the C[subscript 9]H[subscript 11] PES was supported (including the aromatic-catalyzed pathway) by quantitative comparisons between modelled and experimental MBMS results. At 700 K, the branching to styrene + CH[subscript 3] was 2-4 times greater than that of any other product channel, while benzyl radical + C[subscript 2]H[subscript 4] from the aromatic-catalyzed pathway accounted for ∼10% of the branching. Single-collision conditions were also simulated on the updated PES to explain why previous crossed molecular beam experiments did not see evidence of the aromatic-catalyzed pathway. This experimentally validated knowledge of the C[subscript 9]H[subscript 11] PES was added to the database of the open-source Reaction Mechanism Generator (RMG), which was then used to generalize the findings on the C[subscript 9]H[subscript 11] PES to a slightly more complicated alkylaromatic system.Think Global Education Trus

Nontrivial dependence of dielectric stiffness and SHG on dc bias in relaxors and dipole glasses

Dielectric permittivity and Second Harmonic Generation (SHG) studies in the field-cooled mode show a linear dependence of dielectric stiffness (inverse dielectric permittivity) on dc bias in PMN-PT crystals and SHG intensity in KTaO$_{3}$:Li at small Li concentrations. We explain this unusual result in the framework of a theory of transverse, hydrodynamic-type, instability of local polarization.Comment: 5 figure

X-ray Emission from Wind Blown Bubbles. III. ASCA SIS Observations of NGC6888

We present ASCA SIS observations of the wind-blown bubble NGC6888. Owing to the higher sensitivity of the SIS for higher energy photons compared to the ROSAT PSPC, we are able to detect a T ~ 8x10^6 K plasma component in addition to the T ~ 1.3x10^6 K component previously detected in PSPC observations. No significant temperature variations are detected within NGC6888. Garcia-Segura & Mac Low's (1995) analytical models of WR bubbles constrained by the observed size, expansion velocity, and mass of the nebular shell under-predict the stellar wind luminosity, and cannot reproduce simultaneously the observed X-ray luminosity, spectrum, surface brightness profile, and SIS count rate of NGC6888's bubble interior. The agreement between observations and expectations from models can be improved if one or more of the following ad hoc assumptions are made: (1) the stellar wind luminosity was weaker in the past, (2) the bubble is at a special evolutionary stage and the nebular shell has recently been decelerated to 1/2 of its previous expansion velocity, and (3) the heat conduction between the hot interior and the cool nebular shell is suppressed. Chandra and XMM-Newton observations with high spatial resolution and high sensitivity are needed to determine accurately the physical conditions NGC6888's interior hot gas for critical comparisons with bubble models.Comment: 24 pages, 6 figures; accepted for Astrophysical Journal, Nov 1, 2005 issu

Regulation of Collagen Gene Expression in Cutaneous Diseases With Dermal Fibrosis: Evidence for Pretranslational Control

Dermal fibrosis, characterized by collagen accumulation, is the hallmark of several cutaneous diseases. To examine the mechanisms of collagen deposition in fibrotic skin diseases, fibroblast cultures were established from the skin of patients with progressive systemic sclerosis, morphea, scleredema, familial cutaneous collagenoma, connective tissue nevi of the collagen type, or keloids; these patients served as prototypes of fibrotic skin diseases with varying clinical features and potentially different etiologic factors. Collagen production was assayed by the synthesis of [3H]hydroxyproline, and types I and III procollagen messenger RNA (mRNA) levels were determined by dot blot hybridizations using human type I and type III procollagen-specific cDNA probes. The collagen production in fibroblast cultures from the fibrotic diseases was increased up to 6-fold over the controls, and a relatively good correlation between the collagen production and type I collagen mRNA. levels was noted. The type I/III procollagen mRNA ratio in control fibroblast cultures was 5.9 ± 1.6 (mean ± SD). The corresponding ratio in keloid cell culture was markedly increased, while slightly decreased values were noted in the case of morphea and familial cutaneous collagenoma; the values in other cultures were within the normal range. The results suggest that procollagen production in fibroblast cultures derived from fibrotic skin diseases reflects elevated levels of the corresponding procollagen mRNA. The increased mRNA abundance, suggesting pretranslational control, may result from enhanced transcriptional activity of the corresponding gene or alternatively reflects increased stability of the mRNA molecule

Modulation of Ionotropic Glutamate Receptors and Acid-Sensing Ion Channels by Nitric Oxide

Ionotropic glutamate receptors (iGluR) are ligand-gated ion channels and are densely expressed in broad areas of mammalian brains. Like iGluRs, acid-sensing ion channels (ASIC) are ligand (H+)-gated channels and are enriched in brain cells and peripheral sensory neurons. Both ion channels are enriched at excitatory synaptic sites, functionally coupled to each other, and subject to the modulation by a variety of signaling molecules. Central among them is a gasotransmitter, nitric oxide (NO). Available data show that NO activity-dependently modulates iGluRs and ASICs via either a direct or an indirect pathway. The former involves a NO-based and cGMP-independent post-translational modification (S-nitrosylation) of extracellular cysteine residues in channel subunits or channel-interacting proteins. The latter is achieved by NO activation of soluble guanylyl cyclase, which in turn triggers an intracellular cGMP-sensitive cascade to indirectly modulate iGluRs and ASICs. The NO modification is usually dynamic and reversible. Modified channels undergo significant, interrelated changes in biochemistry and electrophysiology. Since NO synthesis is enhanced in various neurological disorders, the NO modulation of iGluRs and ASICs is believed to be directly linked to the pathogenesis of these disorders. This review summarizes the direct and indirect modifications of iGluRs and ASICs by NO and analyzes the role of the NO-iGluR and NO-ASIC coupling in cell signaling and in the pathogenesis of certain related neurological diseases

Design of MARQUIS2: study protocol for a mentored implementation study of an evidence-based toolkit to improve patient safety through medication reconciliation.

BackgroundThe first Multi-center Medication Reconciliation Quality Improvement Study (MARQUIS1) demonstrated that implementation of a medication reconciliation best practices toolkit decreased total unintentional medication discrepancies in five hospitals. We sought to implement the MARQUIS toolkit in more diverse hospitals, incorporating lessons learned from MARQUIS1.MethodsMARQUIS2 is a pragmatic, mentored implementation QI study which collected clinical and implementation outcomes. Sites implemented a revised toolkit, which included interventions from these domains: 1) best possible medication history (BPMH)-taking; 2) discharge medication reconciliation and patient/caregiver counseling; 3) identifying and defining clinician roles and responsibilities; 4) risk stratification; 5) health information technology improvements; 6) improved access to medication sources; 7) identification and correction of real-time discrepancies; and, 8) stakeholder engagement. Eight hospitalists mentored the sites via one site visit and monthly phone calls over the 18-month intervention period. Each site's local QI team assessed opportunities to improve, implemented at least one of the 17 toolkit components, and accessed a variety of resources (e.g. implementation manual, webinars, and workshops). Outcomes to be assessed will include unintentional medication discrepancies per patient.DiscussionA mentored multi-center medication reconciliation QI initiative using a best practices toolkit was successfully implemented across 18 medical centers. The 18 participating sites varied in size, teaching status, location, and electronic health record (EHR) platform. We introduce barriers to implementation and lessons learned from MARQUIS1, such as the importance of utilizing dedicated, trained medication history takers, simple EHR solutions, clarifying roles and responsibilities, and the input of patients and families when improving medication reconciliation