723,439 research outputs found
An analysis of the possible thermal emission at radio frequencies from an evolved supernova remnant HB 3 (G132.7 + 1.3): revisited
It has recently been reported that some of the flux density values for an
evolved supernova remnant (SNR) HB 3 (G132.7 + 1.3) are not accurate. In this
work we revised an analysis of the possible thermal emission at radio
frequencies from the SNR HB 3 using the recently published, corrected, flux
density values. A model including a sum of non-thermal (purely synchrotron) and
thermal (bremsstrahlung) component is applied for fitting integrated radio
spectrum of the SNR. The contribution of thermal component in total volume
emissivity at was estimated to be . The ambient
density was also estimated to be for the
. Again, we obtained the relatively significant
presence of thermal emission at radio frequencies from the SNR so we could
support interaction between SNR HB 3 and adjacent molecular cloud associated
with the H {\sc ii} region W3. Our model estimates for thermal component
contribution to total volume emissivity at and ambient density
are similar to those obtained earlier (, ). It is clear that the corrected flux density values do not
change the basic conclusions.Comment: 6 pages, 1 figur
A financial analysis of born-global firms: evidence from Spain
From the beginning of the 1970s to the present day, significant changes have taken place in the competitive and organizational
behavior of small and medium-sized companies (SMEs). Recently, some of these factors have applied more
intensively, and this has given rise to growth in the number of new companies that undertake overseas operations almost
immediately (known as born globals).
The phenomenon of early internationalization is relatively recent, so there are still many aspects that need to be studied.
The objective of this study is to contribute to the scarce empirical literature existing in Spain on this topic, by providing
evidence on the possible differences in character of the born-global firms compared with the rest of exporting
companies. To this end, the focus of the study is on the analysis of variables such as the size and sector of activity of
these companies, and their principal economic and financial magnitudes.
A sample of 1,324 Spanish SMEs that were exporting in 2007 was surveyed; of this total approximately 12% identified
themselves as having adopted early internationalization.
The results obtained indicate that the born-global firms are, on average, smaller; they are classified mostly to the services
sector; and they are much more leveraged than the rest of Spanish SMEs that export
The C-terminal extension of the beta 7 subunit and activator complexes stabilize nascent 20 S proteasomes and promote their maturation
The eukaryotic 20 S proteasome is formed by dimerization of two precursor complexes containing the maturation factor Ump1. beta 7/Pre4 is the only one of the 14 subunits forming the 20 S proteasome that is absent from these precursor complexes in Saccharomyces cerevisiae. Increased expression of Pre4 leads to a reduction in the level of precursor complex, indicating that Pre4 incorporation into these complexes is rate-limiting for their dimerization. When we purified these precursor complexes, we observed co-purification of Blm10, a large protein known to attach to the alpha ring surface of proteasomes. In contrast to single mutants lacking either Blm10 or the C-terminal extension of Pre4, a mutant lacking both grew extremely poorly, accumulated very high levels of precursor complexes, and was impaired in beta subunit maturation. The effect of blm10 Delta on proteasome biogenesis is modest, apparently because the 19 S regulatory particle is capable of substituting for Blm10, as long as precursor complex dimers are stabilized by the Pre4Cterminus. We found that a mutation (sen3/rpn2) affecting the Rpn2 subunit inhibits attachment of the 19 S activator to the 20 S particle or its precursors. Although the sen3 mutation alone had no apparent effect on precursor complex dimerization and active site maturation, the sen3 blm10 double mutant was impaired in these processes. Together these data demonstrate that Blm10 and the 19 S activator have a partially redundant function in stabilizing nascent 20 S proteasomes and in promoting their activation.info:eu-repo/semantics/publishedVersio
Intermediate-Mass-Elements in Young Supernova Remnants Reveal Neutron Star Kicks by Asymmetric Explosions
The birth properties of neutron stars yield important information on the
still debated physical processes that trigger the explosion and on intrinsic
neutron-star physics. These properties include the high space velocities of
young neutron stars with average values of several 100 km/s, whose underlying
"kick" mechanism is not finally clarified. There are two competing
possibilities that could accelerate NSs during their birth: anisotropic
ejection of either stellar debris or neutrinos. We here present new evidence
from X-ray measurements that chemical elements between silicon and calcium in
six young gaseous supernova remnants are preferentially expelled opposite to
the direction of neutron star motion. There is no correlation between the kick
velocities and magnetic field strengths of these neutron stars. Our results
support a hydrodynamic origin of neutron-star kicks connected to asymmetric
explosive mass ejection, and they conflict with neutron-star acceleration
scenarios that invoke anisotropic neutrino emission caused by particle and
nuclear physics in combination with very strong neutron-star magnetic fields.Comment: 24 pages, 12 figures, accepted for publication in The Astrophysical
Journa
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