369 research outputs found
Simulating Electron Transport and Synchrotron Emission in Radio Galaxies: Shock Acceleration and Synchrotron Aging in Axis-Symmetric Flows
We introduce a simple and economical but effective method for including
relativistic electron transport in multi-dimensional simulations of radio
galaxies. The method is designed to follow explicitly diffusive acceleration at
shocks, and, in smooth flows 2nd order Fermi acceleration plus adiabatic and
synchrotron cooling. We are able to follow both the spatial and energy
distributions of the electrons, so that direct synchrotron emission properties
can be modeled in time-dependent flows for the first time.
Here we present first results in the form of some axis-symmetric MHD
simulations of Mach 20 light jet flows. These show clearly the importance of
nonsteady terminal shocks that develop in such flows even when the jet inflow
is steady. As a result of this and other consequences of the fundamentally
driven character of jets, we find complex patterns of emissivities and
synchrotron spectra, including steep spectral gradients in hot spots, islands
of distinct spectra electrons within the lobes and spectral gradients coming
from the dynamical histories of a given flow element rather than from
synchrotron aging of the embedded electrons. In addition, spectral aging in the
lobes tends to proceed more slowly than one would estimate from regions of high
emissivity.Comment: 30 pages of Latex generated text plus 7 figures in gif format.
Accepted for publication in the Astrophysical Journal. High resolution
postscript figures available through anonymous ftp at
ftp://ftp.msi.umn.edu/pub/users/twj/RGje
Bcl-2 protein family: Implications in vascular apoptosis and atherosclerosis
Apoptosis has been recognized as a central component in the pathogenesis of atherosclerosis, in addition to the other human pathologies such as cancer and diabetes. The pathophysiology of atherosclerosis is complex, involving both apoptosis and proliferation at different phases of its progression. Oxidative modification of lipids and inflammation differentially regulate the apoptotic and proliferative responses of vascular cells during progression of the atherosclerotic lesion. Bcl-2 proteins act as the major regulators of extrinsic and intrinsic apoptosis signalling pathways and more recently it has become evident that they mediate the apoptotic response of vascular cells in response to oxidation and inflammation either in a provocative or an inhibitory mode of action. Here we address Bcl-2 proteins as major therapeutic targets for the treatment of atherosclerosis and underscore the need for the novel preventive and therapeutic interventions against atherosclerosis, which should be designed in the light of molecular mechanisms regulating apoptosis of vascular cells in atherosclerotic lesions
Consensus standards for acquisition, measurement, and reporting of intravascular optical coherence tomography studies
Objectives: The purpose of this document is to make the output of the International Working Group for Intravascular Optical Coherence Tomography (IWG-IVOCT) Standardization and Validation available to medical and scientific communities, through a peer-reviewed publication, in the interest of improving the diagnosis and treatment of patients with atherosclerosis, including coronary artery disease. Background: Intravascular optical coherence tomography (IVOCT) is a catheter-based modality that acquires images at a resolution of ∼10 μm, enabling visualization of blood vessel wall microstructure in vivo at an unprecedented level of detail. IVOCT devices are now commercially available worldwide, there is an active user base, and the interest in using this technology is growing. Incorporation of IVOCT in research and daily clinical practice can be facilitated by the development of uniform terminology and consensus-based standards on use of the technology, interpretation of the images, and reporting of IVOCT results. Methods: The IWG-IVOCT, comprising more than 260 academic and industry members from Asia, Europe, and the United States, formed in 2008 and convened on the topic of IVOCT standardization through a series of 9 national and international meetings. Results: Knowledge and recommendations from this group on key areas within the IVOCT field were assembled to generate this consensus document, authored by the Writing Committee, composed of academicians who have participated in meetings and/or writing of the text. Conclusions: This document may be broadly used as a standard reference regarding the current state of the IVOCT imaging modality, intended for researchers and clinicians who use IVOCT and analyze IVOCT data
The Volcanic Hazard Maps Database:an initiative of the IAVCEI Commission on Volcanic Hazards and Risk
In this work we present the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) Commission on Volcanic Hazards and Risk (CVHR) Volcanic Hazard Maps Database and the accompanying volcanichazardmaps.org website. Using input from a series of IAVCEI CVHR Working Group on Hazard Mapping workshops, we developed a classification scheme and terminology framework for categorizing, discussing, naming, and searching for hazard maps. ≥ The database and website aim to serve as a resource for the volcanology community to explore how different aspects of hazard map development and design have been addressed in different countries, for different hazard processes, and for different intended purposes and audiences. Additionally, they act as a tool for presenting hazard map options to stakeholder groups and serve as a learning resource that can be incorporated into educational materials and training courses. In this work, we present the database and website, discuss the classification scheme, explore the enormous diversity of hazard maps, and suggest ways that the database and website can be used by the volcanic hazard mapping community.</p
A Potassium Metal-Organic Framework based on Perylene- 3,4,9,10-tetracarboxylate as Sensing Layer for Humidity Actuators
We have synthesized a novel three-dimensional metal-organic-framework (MOF) based on the
perylene-3,4,9,10-tetracarboxylate linker and potassium as metallic centre. We report the formation
of this K-based MOF using conventional routes with water as solvent. This material displays intense
green photoluminescence at room temperature, and displays an aggregation dependent quenching.
Correlation of the optical properties with the crystalline packing was confirmed by DFT calculations. We
also demonstrate its potential to build humidity actuators with a reversible and reproducible response,
with a change of 5 orders of magnitudes in its impedance at about 40% relative humidity (RH). This
3D-MOF is based on an interesting perylene derivative octadentate ligand, a moiety with interesting
fluorescent properties and known component in organic semiconductors. To the best of our knowledge,
this is the first time to build such a printed and flexible actuator towards humidity with a reversible
response, enabling precise humidity threshold monitoring.This work was supported by the Junta de Andalucía (FQM-1484, and FQM-195). Red Guipuzcoana de Ciencia,
Tecnología e Innovación (OF188/2017) and University of the Basque Country (GIU14/01, EHUA16/32). BB
acknowledges funding by RyC-2012–10381 contract and computational resources provided by the RES and
Alhambra supercomputing facilities. This work was also supported by the German Research Foundation (DFG)
and the Technical University of Munich within the Open Access Publishing Funding Programme
Positive Regulation by GABABR1 Subunit of Leptin Expression through Gene Transactivation in Adipocytes
Background: The view that c-aminobutyric acid (GABA) plays a functional role in non-neuronal tissues, in addition to an inhibitory neurotransmitter role in the mammalian central nervous system, is prevailing, while little attention has been paid to GABAergic signaling machineries expressed by adipocytes to date. In this study, we attempted to demonstrate the possible functional expression of GABAergic signaling machineries by adipocytes. Methodology/Principal Findings: GABAB receptor 1 (GABABR1) subunit was constitutively expressed by mouse embryonic fibroblasts differentiated into adipocytes and adipocytic 3T3-L1 cells in culture, as well as mouse white adipose tissue, with no responsiveness to GABA BR ligands. However, no prominent expression was seen with mRNA for GABA BR2 subunit required for heteromeric orchestration of the functional GABABR by any adipocytic cells and tissues. Leptin mRNA expression was significantly and selectively decreased in adipose tissue and embryonic fibroblasts, along with drastically reduced plasma leptin levels, in GABA BR1-null mice than in wild-type mice. Knockdown by siRNA of GABA BR1 subunit led to significant decreases in leptin promoter activity and leptin mRNA levels in 3T3-L1 cells. Conclusions/Significance: Our results indicate that GABABR1 subunit is constitutively expressed by adipocytes to primarily regulate leptin expression at the transcriptional level through a mechanism not relevant to the function as a partner o
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