5,204 research outputs found
The spectral evolution of impulsive solar X-ray flares
The time evolution of the spectral index and the non-thermal flux in 24
impulsive solar hard X-ray flares of GOES class M was studied in RHESSI
observations. The high spectral resolution allows for a clean separation of
thermal and non-thermal components in the 10-30 keV range, where most of the
non-thermal photons are emitted. Spectral index and flux can thus be determined
with much better accuracy than before. The spectral soft-hard-soft behavior in
rise-peak-decay phases is discovered not only in the general flare development,
but even more pronounced in subpeaks. An empirically found power-law dependence
between the spectral index and the normalization of the non-thermal flux holds
during the rise and decay phases of the emission peaks. It is still present in
the combined set of all flares. We find an asymmetry in this dependence between
rise and decay phases of the non-thermal emission. There is no delay between
flux peak and spectral index minimum. The soft-hard-soft behavior appears to be
an intrinsic signature of the elementary electron acceleration process.Comment: 10 pages, 7 figures. Accepted for publication by A&
A Comment on âIs Information Systems a Science?â
In this paper, we respond to McBrideâs (2018) paper on whether information systems is a science. We first argue that information systems is indeed a science in that it draws from and creates knowledge in a form similar to many different disciplines, including psychology, sociology, mathematics, economics, computer science, and engineering. We counter the flawed logic of methodical extremists who believe that their approach represents the best or only path to knowledge. Specifically, we argue that many different methods of inquiry and discovery are appropriate in information systems and that each has its strengths and weaknesses
Recommended from our members
AQP2 is Necessary for Vasopressin- and Forskolin-Mediated Filamentous Actin Depolymerization in Renal Epithelial Cells
Remodeling of the actin cytoskeleton is required for vasopressin (VP)âinduced aquaporin 2 (AQP2) trafficking. Here, we asked whether VP and forskolin (FK)âmediated Fâactin depolymerization depends on AQP2 expression. Using various MDCK and LLCâPK1 cell lines with different AQP2 expression levels, we performed Fâactin quantification and immunofluorescence staining after VP/FK treatment. In MDCK cells, in which AQP2 is delivered apically, VP/FK mediated Fâactin depolymerization was significantly correlated with AQP2 expression levels. A decrease of apical membrane associated Fâactin was observed upon VP/FK treatment in AQP2 transfected, but not in untransfected cells. There was no change in basolateral actin staining under these conditions. In LLCâPK1 cells, which deliver AQP2 basolaterally, a significant VP/FK mediated decrease in Fâactin was also detected only in AQP2 transfected cells. This depolymerization response to VP/FK was significantly reduced by siRNA knockdown of AQP2. By immunofluorescence, an inverse relationship between plasma membrane AQP2 and membraneâassociated Fâactin was observed after VP/FK treatment again only in AQP2 transfected cells. This is the first report showing that VP/FK mediated Fâactin depolymerization is dependent on AQP2 protein expression in renal epithelial cells, and that this is not dependent on the polarity of AQP2 membrane insertion
B743: Primary Health Care and the Developmentally Disabled: An Analysis of the Normalization Principle in the State of Maine
At the time of publication, there existed an estimated group of 10 million American people defined as developmentally disabled. Stimulated in part by the often observed dehumanizing environment of institutional arrangement for the mentally disabled, the search for more humane treatment and management alternative has pointed in the direction of what has been termed \u27 normalization.
In 1969, the Danish Mental Retardation Service defined normalization as \u27\u27 letting the mentally retarded obtain an existence as close to normal as possible.
The focus of this study is on barriers to the normalization principle in the provision of primary health care to the developmentally disabled in the State of Maine. Possible barriers include attitudes toward the developmentally disabled, accessibility and quality of community based services, and lack of viable coordination mechanisms. Since 1971, the Maine Department of Mental Health and Corrections has made a concerted effort to encourage services based upon the principle of normalization. As pressures for normalization intensify, it seems warranted that those community-based structures which carry out the concept be examined as to their receptivity and the feasibility of further efforts in this direction. Although the principle of normalization has demonstrated its usefulness and potential, it is not without its limitations (Mesibov 1976). This study made no attempt to examine these limitations of the principle itself.https://digitalcommons.library.umaine.edu/aes_bulletin/1127/thumbnail.jp
On Silicon Group Elements Ejected by Supernovae Type Ia
There is compelling evidence that the peak brightness of a Type Ia supernova
is affected by the electron fraction Ye at the time of the explosion. The
electron fraction is set by the aboriginal composition of the white dwarf and
the reactions that occur during the pre explosive convective burning. To date,
determining the makeup of the white dwarf progenitor has relied on indirect
proxies, such as the average metallicity of the host stellar population. In
this paper, we present analytical calculations supporting the idea that the
electron fraction of the progenitor systematically influences the
nucleosynthesis of silicon group ejecta in Type Ia supernovae. In particular,
we suggest the abundances generated in quasi nuclear statistical equilibrium
are preserved during the subsequent freezeout. This allows one to potential
recovery of Ye at explosion from the abundances recovered from an observed
spectra. We show that measurement of 28Si, 32S, 40Ca, and 54Fe abundances can
be used to construct Ye in the silicon rich regions of the supernovae. If these
four abundances are determined exactly, they are sufficient to recover Ye to 6
percent. This is because these isotopes dominate the composition of
silicon-rich material and iron rich material in quasi nuclear statistical
equilibrium. Analytical analysis shows that the 28Si abundance is insensitive
to Ye, the 32S abundance has a nearly linear trend with Ye, and the 40Ca
abundance has a nearly quadratic trend with Ye. We verify these trends with
post-processing of 1D models and show that these trends are reflected in model
synthetic spectra.Comment: Submitted to the Ap
Replication research: opportunities, experiences and challenges
Replication is one of the main principles of the scientific method. In the physical sciences, new knowledge is often not considered valid until the original study has been replicated in other labs and the original results are not refuted Replication will either improve confidence in our research findings or identify important boundary conditions. Replications also enhance various scientific processes and offer methodical and educational improvements. The purpose of this panel is twofold. First, to explore the opportunities for scientific development that replication research enables by reflecting on the experiences of encouraging, doing, and publishing replication studies. Second, to explore the various challenges that replication research raises about its value to individual scholars as well as to our collective understanding of phenomena within the information systems field
Clinical and hemodynamic follow-up of left ventricular to aortic conduits in patients with aortic stenosis
To assess the long-term results of left ventricular outflow tract reconstruction utilizing an apical left ventricular to aortic valved (porcine) conduit the clinical and hemodynamic data were reviewed from 24 patients who had placement of an apico-aortic conduit. Eighteen of the patients are asymptomatic and taking no cardiac medications. Three patients were reoperated on, one patient 1.5 years after his original operation for subacute bacterial endocarditis and two patients 3 to 4 years after their original operation for severe conduit valve insufficiency. None of the patients is taking anticoagulants and no thromboembolic events have occurred. Postoperative catheterization has been performed 1 to 1.5 years (mean 1.2) after repair in 15 of 21 patients. The rest left ventricular outflow tract gradient has decreased from 102.5 ± 20 mm Hg preoperatively to 14.8 ± 9.9 mm Hg postoperatively (probability [p] < 0.001). Some degree of conduit obstruction was demonstrated by catheter passage in 11 of the 15 patients. In these 11 patients, the obstruction occurred at three distant sites: at the egress of the left ventricle in 9, at the porcine valve in 5 and at the aortic to conduit junction in 1. Isometric exercise in five and supine bicycle exercise in six patients increased the left ventricular outflow tract gradient by 2.5 ± 1.1 and 20.8 ± 11.8 mm Hg, respectively, despite an increase in cardiac index of 1 ± 0.3 and 3.7 ± 0.4 liters/min per m2, respectively. The data suggest that a left ventricular to aortic conduit is an effective form of therapy for severe left ventricular outflow tract obstruction
Multi-wavelength analysis of high energy electrons in solar flares: a case study of August 20, 2002 flare
A multi-wavelength spatial and temporal analysis of solar high energy
electrons is conducted using the August 20, 2002 flare of an unusually flat
(gamma=1.8) hard X-ray spectrum. The flare is studied using RHESSI, Halpha,
radio, TRACE, and MDI observations with advanced methods and techniques never
previously applied in the solar flare context. A new method to account for
X-ray Compton backscattering in the photosphere (photospheric albedo) has been
used to deduce the primary X-ray flare spectra. The mean electron flux
distribution has been analysed using both forward fitting and model independent
inversion methods of spectral analysis. We show that the contribution of the
photospheric albedo to the photon spectrum modifies the calculated mean
electron flux distribution, mainly at energies below 100 keV. The positions of
the Halpha emission and hard X-ray sources with respect to the current-free
extrapolation of the MDI photospheric magnetic field and the characteristics of
the radio emission provide evidence of the closed geometry of the magnetic
field structure and the flare process in low altitude magnetic loops. In
agreement with the predictions of some solar flare models, the hard X-ray
sources are located on the external edges of the Halpha emission and show
chromospheric plasma heated by the non-thermal electrons. The fast changes of
Halpha intensities are located not only inside the hard X-ray sources, as
expected if they are the signatures of the chromospheric response to the
electron bombardment, but also away from them.Comment: 26 pages, 9 figures, accepted to Solar Physic
- âŠ