58,070 research outputs found
Germanium and lead: Significant differences between meteoritic and photospheric abundances?
The order of the Galactic cosmic ray source (GCRS) composition in terms of first ionization potential (FIP) was examined. For most elements, the degree of volatility is (positively) correlated with the value of the FIP, so that it is not easy to distinguish a correlation of GCRS abundances anomalies with FIP from a correlation with volatility. Only a few permit to distinguish between the two kinds of ordering: if they are depleted relative to refractory metals, volatility must be relevant, if not, FIP is relevant. Among them Cu and Zn would seem to favor FIP. Among the best indicators are Ge and Pb. The abundance anomalies in GCRS are defined relative to a standard which, for the heavy elements concerned, is commonly taken as C1 Carbonaceous Chondrites. Photospheric abundances are more directly representative of the protosolar nebula, and hence of ordinary local galactic (LG) matter. The Ge and Pb reference abundance determinations in the Photosphere and in C1 meteorites are examined and their relevance to the problem with FIP vs. volatility in GCRs is discussed
Measurement of macroscopic plasma parameters with a radio experiment: Interpretation of the quasi-thermal noise spectrum observed in the solar wind
The ISEE-3 SBH radio receiver has provided the first systematic observations of the quasi-thermal (plasma waves) noise in the solar wind plasma. The theoretical interpretation of that noise involves the particle distribution function so that electric noise measurements with long antennas provide a fast and independent method of measuring plasma parameters: densities and temperatures of a two component (core and halo) electron distribution function have been obtained in that way. The polarization of that noise is frequency dependent and sensitive to the drift velocity of the electron population. Below the plasma frequency, there is evidence of a weak noise spectrum with spectral index -1 which is not yet accounted for by the theory. The theoretical treatment of the noise associated with the low energy (thermal) proton population shows that the moving electrical antenna radiates in the surrounding plasma by Carenkov emission which becomes predominant at the low frequencies, below about 0.1 F sub P
Recommended from our members
Oncogenic fusion protein BCR-FGFR1 requires the breakpoint cluster region-mediated oligomerization and chaperonin Hsp90 for activation.
Mutation and translocation of fibroblast growth factor receptors often lead to aberrant signaling and cancer. This work focuses on the t(8;22)(p11;q11) chromosomal translocation which creates the breakpoint cluster region (BCR) fibroblast growth factor receptor1 (FGFR1) (BCR-FGFR1) fusion protein. This fusion occurs in stem cell leukemia/lymphoma, which can progress to atypical chronic myeloid leukemia, acute myeloid leukemia, or B-cell lymphoma. This work focuses on the biochemical characterization of BCR-FGFR1 and identification of novel therapeutic targets. The tyrosine kinase activity of FGFR1 is required for biological activity as shown using transformation assays, interleukin-3 independent cell proliferation, and liquid chromatography/mass spectroscopy analyses. Furthermore, BCR contributes a coiled-coil oligomerization domain, also essential for oncogenic transformation by BCR-FGFR1. The importance of salt bridge formation within the coiled-coil domain is demonstrated, as disruption of three salt bridges abrogates cellular transforming ability. Lastly, BCR-FGFR1 acts as a client of the chaperonin heat shock protein 90 (Hsp90), suggesting that BCR-FGFR1 relies on Hsp90 complex to evade proteasomal degradation. Transformed cells expressing BCR-FGFR1 are sensitive to the Hsp90 inhibitor Ganetespib, and also respond to combined treatment with Ganetespib plus the FGFR inhibitor BGJ398. Collectively, these data suggest novel therapeutic approaches for future stem cell leukemia/lymphoma treatment: inhibition of BCR oligomerization by disruption of required salt bridges; and inhibition of the chaperonin Hsp90 complex
Dust detection by the wave instrument on STEREO: nanoparticles picked up by the solar wind?
The STEREO/WAVES instrument has detected a very large number of intense
voltage pulses. We suggest that these events are produced by impact ionisation
of nanoparticles striking the spacecraft at a velocity of the order of
magnitude of the solar wind speed. Nanoparticles, which are half-way between
micron-sized dust and atomic ions, have such a large charge-to-mass ratio that
the electric field induced by the solar wind magnetic field accelerates them
very efficiently. Since the voltage produced by dust impacts increases very
fast with speed, such nanoparticles produce signals as high as do much larger
grains of smaller speeds. The flux of 10-nm radius grains inferred in this way
is compatible with the interplanetary dust flux model. The present results may
represent the first detection of fast nanoparticles in interplanetary space
near Earth orbit.Comment: In press in Solar Physics, 13 pages, 5 figure
Quantum Chinos Game: winning strategies through quantum fluctuations
We apply several quantization schemes to simple versions of the Chinos game.
Classically, for two players with one coin each, there is a symmetric stable
strategy that allows each player to win half of the times on average. A partial
quantization of the game (semiclassical) allows us to find a winning strategy
for the second player, but it is unstable w.r.t. the classical strategy.
However, in a fully quantum version of the game we find a winning strategy for
the first player that is optimal: the symmetric classical situation is broken
at the quantum level.Comment: REVTEX4.b4 file, 3 table
Rubber friction on wet and dry road surfaces: the sealing effect
Rubber friction on wet rough substrates at low velocities is typically 20-30%
smaller than for the corresponding dry surfaces. We show that this cannot be
due to hydrodynamics and propose a novel explanation based on a sealing effect
exerted by rubber on substrate "pools" filled with water. Water effectively
smoothens the substrate, reducing the major friction contribution due to
induced viscoelastic deformations of the rubber by surface asperities. The
theory is illustrated with applications related to tire-road friction.Comment: Format Revtex 4; 8 pages, 11 figures (no color); Published on Phys.
Rev. B (http://link.aps.org/abstract/PRB/v71/e035428); previous work on the
same topic: cond-mat/041204
A multi-data source surveillance system to detect a bioterrorism attack during the G8 summit in Scotland
In 18 weeks, Health Protection Scotland (HPS) deployed a syndromic surveillance system to early-detect natural or intentional disease outbreaks during the G8 Summit 2005 at Gleneagles, Scotland. The system integrated clinical and non-clinical datasets. Clinical datasets included Accident and Emergency (A and E) syndromes, and General Practice (GPs) codes grouped into syndromes. Non-clinical data included telephone calls to a nurse helpline, laboratory test orders, and hotel staff absenteeism. A cumulative sum-based detection algorithm and a log-linear regression model identified signals in the data. The system had a fax-based track for real-time identification of unusual presentations. Ninety-five signals were triggered by the detection algorithms and four forms were faxed to HPS. Thirteen signals were investigated. The system successfully complemented a traditional surveillance system in identifying a small cluster of gastroenteritis among the police force and triggered interventions to prevent further cases
Asymmetric supernova remnants generated by Galactic, massive runaway stars
After the death of a runaway massive star, its supernova shock wave interacts
with the bow shocks produced by its defunct progenitor, and may lose energy,
momentum, and its spherical symmetry before expanding into the local
interstellar medium (ISM). We investigate whether the initial mass and space
velocity of these progenitors can be associated with asymmetric supernova
remnants. We run hydrodynamical models of supernovae exploding in the
pre-shaped medium of moving Galactic core-collapse progenitors. We find that
bow shocks that accumulate more than about 1.5 Mo generate asymmetric remnants.
The shock wave first collides with these bow shocks 160-750 yr after the
supernova, and the collision lasts until 830-4900 yr. The shock wave is then
located 1.35-5 pc from the center of the explosion, and it expands freely into
the ISM, whereas in the opposite direction it is channelled into the region of
undisturbed wind material. This applies to an initially 20 Mo progenitor moving
with velocity 20 km/s and to our initially 40 Mo progenitor. These remnants
generate mixing of ISM gas, stellar wind and supernova ejecta that is
particularly important upstream from the center of the explosion. Their
lightcurves are dominated by emission from optically-thin cooling and by X-ray
emission of the shocked ISM gas. We find that these remnants are likely to be
observed in the [OIII] lambda 5007 spectral line emission or in the soft
energy-band of X-rays. Finally, we discuss our results in the context of
observed Galactic supernova remnants such as 3C391 and the Cygnus Loop.Comment: 21 pages, 16 figure
- …