396 research outputs found
New Interstellar Dust Models Consistent with Extinction, Emission, and Abundance Constraints
We present new interstellar dust models which have been derived by
simultaneously fitting the far-ultraviolet to near-infrared extinction, the
diffuse infrared (IR) emission and, unlike previous models, the elemental
abundance constraints on the dust for different interstellar medium abundances,
including solar, F and G star, and B star abundances. The fitting problem is a
typical ill-posed inversion problem, in which the grain size distribution is
the unknown, which we solve by using the method of regularization. The dust
model contains various components: PAHs, bare silicate, graphite, and amorphous
carbon particles, as well as composite particles containing silicate, organic
refractory material, water ice, and voids. The optical properties of these
components were calculated using physical optical constants. As a special case,
we reproduce the Li & Draine (2001) results, however their model requires an
excessive amount of silicon, magnesium, and iron to be locked up in dust: about
50 ppm (atoms per million of H atoms), significantly more than the upper limit
imposed by solar abundances of these elements, about 34, 35, and 28 ppm,
respectively. A major conclusion of this paper is that there is no unique
interstellar dust model that simultaneously fits the observed extinction,
diffuse IR emission, and abundances constraints.Comment: 70 pages, 23 figures, accepted for publication in the Astrophysical
Journal Supplemen
Effect of the Boron Addition on the structure of the Ni-Mn-Co-In alloys
Series of Ni45:5xCo4:5Mn36:6In13:4Bx (at.%, x = 0, 0.05, 0.1, 0.5, 1.0) polycrystalline magnetic shape memory
alloys produced by the induction melting were examined in terms of the structure and transition temperatures.
The structure of the alloys was determined by the X–ray diffraction and transmission electron microscopy. Scanning
electron microscopy and electron backscattering diffraction techniques were applied to obtain the microstructure
and texture of alloys. Boron addition promotes nucleation of the second Co–rich and In–poor phase as well as
causes decrease of the martensitic transformation temperatures
An Analysis of the Shapes of Interstellar Extinction Curves. VI. The Near-IR Extinction Law
We combine new HST/ACS observations and existing data to investigate the
wavelength dependence of NIR extinction. Previous studies suggest a power-law
form, with a "universal" value of the exponent, although some recent
observations indicate that significant sight line-to-sight line variability may
exist. We show that a power-law model provides an excellent fit to most NIR
extinction curves, but that the value of the power, beta, varies significantly
from sight line-to-sight line. Therefore, it seems that a "universal NIR
extinction law" is not possible. Instead, we find that as beta decreases, R(V)
[=A(V)/E(B-V)] tends to increase, suggesting that NIR extinction curves which
have been considered "peculiar" may, in fact, be typical for different R(V)
values. We show that the power law parameters can depend on the wavelength
interval used to derive them, with the beta increasing as longer wavelengths
are included. This result implies that extrapolating power law fits to
determine R(V) is unreliable. To avoid this problem, we adopt a different
functional form for NIR extinction. This new form mimics a power law whose
exponent increases with wavelength, has only 2 free parameters, can fit all of
our curves over a longer wavelength baseline and to higher precision, and
produces R(V) values which are consistent with independent estimates and
commonly used methods for estimating R(V). Furthermore, unlike the power law
model, it gives R(V)'s that are independent of the wavelength interval used to
derive them. It also suggests that the relation R(V) = -1.36 E(K-V)/E(B-V) -
0.79 can estimate R(V) to +/-0.12. Finally, we use model extinction curves to
show that our extinction curves are in accord with theoretical expectations.Comment: To appear in the Astrophysical Journa
Ethical issues of decision making and communication in health care: An intercultural and interfaith perspective
The purpose of this research was to elucidate the main ethical issues that arise during decision-making and medical communication influenced by interfaith and intercultural differences. The statistical analysis of information retrieved from the United Nations official web site, as well as the analysis of secondary data taken from the literature sources, were applied to achieve the goal set. The outcomes of the study reveal that in Germany, Russia, and the United States, ethical problems in decision-making and communication in healthcare exist since the cultures and faiths of these countries’ populations vary. Moreover, beliefs become more diverse due to the increasing number of migrants and medical tourists. It was found what ethical peculiarities of a particular religion can affect decision-making and communication during the provision of medical services to patients undergoing treatment in Germany, Russia, or the US. The results of the research can be applied in the scientific studies on ethical issues that arise in healthcare, as well as in the process of setting diagnosis, providing preventive care, treatment, transplantation, and euthanasia. © 2021 Journal of Pharmaceutical Negative Result
Light Scattering from Volcanic-Sand Particles in Deposited and Aerosol Form
The light-scattering properties of volcanic sand collected in Iceland are studied here to characterize the sand particles and develop a reference for future remote-sensing observations. While such sand is common in Iceland, the smaller-size fraction can be readily transported by winds and found in the atmosphere at distant locations. The sand appears dark when deposited on a surface due to the high optical absorption of the material. Therefore, atmospheric regions containing such particles during a dust storm may absorb sunlight considerably, causing redistribution of solar energy. Here, we measure the angular scattered-light intensity and degree of linear polarization from the sand. This is done with two experimental apparatuses, the Cosmic Dust Laboratory (CoDuLab) at the Institute de Astrofísica de Andalucía (IAA) and the goniospectropolarimeter (FIGIFIGO) at the Finnish Geospatial Research Institute (FGI). Two scattering-scenarios of practical interest for remote-sensing applications are considered: (1) single sand-particles suspended in aerosol as an optically thin cloud, and (2) the same particles deposited on a substrate. We also model the measurements with the discrete dipole approximation to estimate the complex-valued refractive index m, where we find that m ≈ 1.6 + 0.01i at λ = 647 nm. Lastly, we present a comparative analysis of the polarimetric response of the sand particles with that reported in the literature for carbon-soot, another highly absorbing atmospheric contaminant. © 2019.This research was partially supported by the Academy of Finland Project no. 260027 and the COST Action MP1104 “Polarization as a tool to study the Solar System and beyond”. NZ acknowledges Magnus Ehrnrooth Foundation for the research travel support. This work also has been partially supported by contracts AYA2015-67152-R and RTI2018-095330-B-I00 . We thank P. Dagsson Waldhauserová, O. Arnalds, A. Virkkula, O. Meinander, and J. Svensson for their help obtaining the samples and for relevant discussions. We acknowledge the use of imagery provided by services from NASA's Global Imagery Browse Services (GIBS), part of NASA's Earth Observing System Data and Information System (EOSDIS). We also would like to thank reviewers for their constructive reviews
Selective 5HT3 antagonists and sensory processing: A systematic review
Ondansetron is a selective serotonin (5HT3) receptor antagonist that is under evaluation as an adjunctive treatment for schizophrenia, and a novel treatment for hallucinations in Parkinson’s disease. Ondansetron reverses sensory gating deficits and improves visuoperceptual processing in animal models of psychosis, but it is unclear to what extent preclinical findings have been replicated in humans. We systematically reviewed human studies that evaluated the effects of ondansetron and other 5HT3 receptor antagonists on sensory gating deficits or sensory processing. Of 11 eligible studies, eight included patients with schizophrenia who were chronically stable on antipsychotic medication; five measured sensory gating using the P50 suppression response to a repeated auditory stimulus; others included tests of visuoperceptual function. Three studies in healthy participants included tests of visuoperceptual and sensorimotor function. A consistent and robust finding (five studies) was that ondansetron and tropisetron (5HT3 antagonist and α7-nicotinic receptor partial agonist) improved sensory gating in patients with schizophrenia. Tropisetron also improved sustained visual attention in non-smoking patients. There was inconsistent evidence of the effects of 5HT3 antagonists on other measures of sensory processing, but interpretation was limited by the small number of studies, methodological heterogeneity and the potential confounding effects of concomitant medication in patients. Despite these limitations, we found strong evidence that selective 5HT3 antagonists (with or without direct α7-nicotinic partial agonist effects) improved sensory gating. Future studies should investigate how this relates to potential improvement in neurocognitive symptoms in antipsychotic naive patients with prodromal or milder symptoms, in order to understand the clinical implications
Perspectives on Interstellar Dust Inside and Outside of the Heliosphere
Measurements by dust detectors on interplanetary spacecraft appear to
indicate a substantial flux of interstellar particles with masses exceeding
10^{-12}gram. The reported abundance of these massive grains cannot be typical
of interstellar gas: it is incompatible with both interstellar elemental
abundances and the observed extinction properties of the interstellar dust
population. We discuss the likelihood that the Solar System is by chance
located near an unusual concentration of massive grains and conclude that this
is unlikely, unless dynamical processes in the ISM are responsible for such
concentrations. Radiation pressure might conceivably drive large grains into
"magnetic valleys". If the influx direction of interstellar gas and dust is
varying on a ~10 yr timescale, as suggested by some observations, this would
have dramatic implications for the small-scale structure of the interstellar
medium.Comment: 13 pages. To appear in Space Science Review
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