927 research outputs found
Breaking stress of neutron star crust
The breaking stress (the maximum of the stress-strain curve) of neutron star
crust is important for neutron star physics including pulsar glitches, emission
of gravitational waves from static mountains, and flares from star quakes. We
perform many molecular dynamic simulations of the breaking stress at different
coupling parameters (inverse temperatures) and strain rates. We describe our
results with the Zhurkov model of strength. We apply this model to estimate the
breaking stress for timescales ~1 s - 1 year, which are most important for
applications, but much longer than can be directly simulated. At these
timescales the breaking stress depends strongly on the temperature. For
coupling parameter <200, matter breaks at very small stress, if it is applied
for a few years. This viscoelastic creep can limit the lifetime of mountains on
neutron stars. We also suggest an alternative model of timescale-independent
breaking stress, which can be used to estimate an upper limit on the breaking
stress.Comment: 5 pages, 2 figures. Accepted for publication in MNRAS Letter
It is time to rethink tactics in the fight against malaria
April 25 marks World Malaria Day, an opportunity for those who work to defeat the illness, to review progress and renew commitments. After a decade of steady success, this year’s commemoration of the date is also an opportunity to reconsider current approaches and assess the state of the science needed to keep pace in the global effort to combat malaria
X-band microwave generation caused by plasma-sheath instability
It is well known that oscillations at the electron plasma frequency may
appear due to instability of the plasma sheath near a positively biased
electrode immersed in plasma. This instability is caused by transit-time
effects when electrons, collected by this electrode, pass through the sheath.
Such oscillations appear as low-power short spikes due to additional ionization
of a neutral gas in the electrode vicinity. Herein we present first results
obtained when the additional ionization was eliminated. We succeeded to prolong
the oscillations during the whole time a positive bias was applied to the
electrode. These oscillations could be obtained at much higher frequency than
previously reported (tens of GHz compared to few hundreds of MHz) and power of
tens of mW. These results in combination with presented theoretical estimations
may be useful, e.g., for plasma diagnostics.Comment: 12 pages, 7 figure
Total absorption of an electromagnetic wave by an overdense plasma
We show both theoretically and experimentally that an electromagnetic wave
can be totally absorbed by an overdense plasma when a subwavelength diffraction
grating is placed in front of the plasma surface. The absorption is due to
dissipation of surface plasma waves (plasmons-polaritons) that have been
resonantly excited by the evanescent component of the diffracted
electromagnetic wave. The developed theoretical model allows one to determine
the conditions for the total absorption.Comment: To be published in PR
Infections associated with eating seed sprouts: an international concern.
Recent outbreaks of Salmonella and Escherichia coli O157:H7 infections associated with raw seed sprouts have occurred in several countries. Subjective evaluations indicate that pathogens can exceed 107 per gram of sprouts produced from inoculated seeds during sprout production without adversely affecting appearance. Treating seeds and sprouts with chlorinated water or other disinfectants fails to eliminate the pathogens. A comprehensive approach based on good manufacturing practices and principles of hazard analysis and critical control points can reduce the risk of sprout-associated disease. Until effective measures to prevent sprout-associated illness are identified, persons who wish to reduce their risk of foodborne illness from raw sprouts are advised not to eat them; in particular, persons at high risk for severe complications of infections with Salmonella or E. coli O157:H7, such as the elderly, children, and those with compromised immune systems, should not eat raw sprouts
Broad-band polarization-independent total absorption of electromagnetic waves by an overdense plasma
We have shown both experimentally and theoretically that
polarization-independent broad-band absorption of electromagnetic waves by an
overdense plasma, caused by surface plasmon-polaritons (SPP) excitation, can be
achieved due to combination of two factors: a non-zero angle of incidence and a
two-dimensional circular diffraction grating placed at a properly chosen
distance in front of the plasma boundary. Direct detection of SPP has been
achieved for the first time using a miniature antenna imbedded in the plasma.Comment: considerably broadened versio
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