7,290 research outputs found
Gamma-ray emission expected from Kepler's SNR
Nonlinear kinetic theory of cosmic ray (CR) acceleration in supernova
remnants (SNRs) is used to investigate the properties of Kepler's SNR and, in
particular, to predict the gamma-ray spectrum expected from this SNR.
Observations of the nonthermal radio and X-ray emission spectra as well as
theoretical constraints for the total supernova (SN) explosion energy E_sn are
used to constrain the astronomical and particle acceleration parameters of the
system. Under the assumption that Kepler's SN is a type Ia SN we determine for
any given explosion energy E_sn and source distance d the mass density of the
ambient interstellar medium (ISM) from a fit to the observed SNR size and
expansion speed. This makes it possible to make predictions for the expected
gamma-ray flux. Exploring the expected distance range we find that for a
typical explosion energy E_sn=10^51 erg the expected energy flux of TeV
gamma-rays varies from 2x10^{-11} to 10^{-13} erg/(cm^2 s) when the distance
changes from d=3.4 kpc to 7 kpc. In all cases the gamma-ray emission is
dominated by \pi^0-decay gamma-rays due to nuclear CRs. Therefore Kepler's SNR
represents a very promising target for instruments like H.E.S.S., CANGAROO and
GLAST. A non-detection of gamma-rays would mean that the actual source distance
is larger than 7 kpc.Comment: 6 pages, 4 figures. Accepted for publication in Astronomy and
Astrophysics, minor typos correcte
Rolling of asymmetric disks on an inclined plane
In a recent papers, Turner and Turner (2010 {\em Am. J. Phys.} {\bf 78}
905-7) and Jensen (2011 {\em Eur. J. Phys.} {\bf 32} 389-397) analysed the
motion of asymmetric rolling rigid bodies on a horizontal plane. These papers
addressed the common misconception that the instantaneous point of contact of
the rolling body with the plane can be used to evaluate the angular momentum
and the torque in the equation of motion
. To obtain the correct equation of motion,
the "phantom torque" or various rules that depend on the motion of the point
about which and are evaluated were discussed. In
this paper, I consider asymmetric disks rolling down an inclined plane and
describe the most basic way of obtaining the correct equation of motion; that
is, to choose the point about which and are
evaluated that is stationary in an inertial frame
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Glacier-Linked Eskers on Mars: Environments of Recent Wet-Based Glaciation From Numerical Models
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Evidence for Recent Wet-Based Crater Glaciation in Tempe Terra, Mars.
[Introduction]
Mars’ mid-latitudes host abundant putative debris-covered water-ice glaciers (viscous flow features; VFF). Eskers emerging from 110-150 Myr-old VFF in Phlegra Montes and Tempe Terra provide evidence for rare occurences of past, localized basal melting of their parent VFF, despite the cold climates of the late Amazonian (see this conf.). Eskers are sinuous ridges comprising glaciofluvial sediment deposited by meltwater flowing through tunnels within glacial ice.
Here, we describe a population of sinuous ridges emerging from VFF in an unnamed ~45 km-diameter crater (38.47 N, 72.43 W) in Tempe Terra, ~600 km from the VFF-linked esker identified by Butcher et al. We consider two working hypotheses for the formation of the sinuous ridges; that they are either (1) eskers formed by melting of the glaciers from which they emerge, or (2) topographically inverted fluvial channels which formed prior to glaciation of the crater. We present observations from preliminary geomorphic mapping of the crater to start to test those hypotheses
Sustainable consumption behaviours in P2P accommodation platforms: an exploratory study
This paper examines how sustainable consumption behaviours are assembled in peer-to-peer (P2P) platforms, based on four factors—services portfolio complexity, network membership, reputation and innovative practices—and its impact on P2P platform performance. Using data from one P2P accommodation platform in Romania and based on 2556 observations, we tested the research hypothesis using ordinary least squares regression. Specifically, services portfolio complexity positively influences sustainable consumption behaviours, while network membership has a negative influence. Services portfolio complexity has a positive influence on sustainable consumption behaviours when innovative practices are high. Finally, sustainable consumption behaviours positively influence P2P platform performance.
This is a post-peer-review, pre-copyedit version of an article published in Soft Computing. The final authenticated version is available online at: http://dx.doi.org/10.1007/s00500-020-04681-6
Shot noise in a diffusive F-N-F spin valve
Fluctuations of electric current in a spin valve consisting of a diffusive
conductor connected to ferromagnetic leads and operated in the giant
magnetoresistance regime are studied. It is shown that a new source of
fluctuations due to spin-flip scattering enhances strongly shot noise up to a
point where the Fano factor approaches the full Poissonian value.Comment: 5 pages, 3 figure
Dr. Favalli, et al. reply
We thank Dr. So, et al1 for the interest in our letter2 and for sharing the results about the coronavirus disease 2019 (COVID-19) in patients with systemic lupus erythematosus (SLE) in Hong Kong1 We agree that the quantification of the risk of infection with severe acute respiratory coronaviruses-2 (SARS-CoV-2) in patients with SLE is a major concern
Leaf pigments and wax as traits of heat tolerance in field pea
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