397 research outputs found
The phase relation between sunspot numbers and soft X-ray flares
To better understand long-term flare activity, we present a statistical study
on soft X-ray flares from May 1976 to May 2008. It is found that the smoothed
monthly peak fluxes of C-class, M-class, and X-class flares have a very
noticeable time lag of 13, 8, and 8 months in cycle 21 respectively with
respect to the smoothed monthly sunspot numbers. There is no time lag between
the sunspot numbers and M-class flares in cycle 22. However, there is a
one-month time lag for C-class flares and a one-month time lead for X-class
flares with regard to sunspot numbers in cycle 22. For cycle 23, the smoothed
monthly peak fluxes of C-class, M-class, and X-class flares have a very
noticeable time lag of one month, 5 months, and 21 months respectively with
respect to sunspot numbers. If we take the three types of flares together, the
smoothed monthly peak fluxes of soft X-ray flares have a time lag of 9 months
in cycle 21, no time lag in cycle 22 and a characteristic time lag of 5 months
in cycle 23 with respect to the smoothed monthly sunspot numbers. Furthermore,
the correlation coefficients of the smoothed monthly peak fluxes of M-class and
X-class flares and the smoothed monthly sunspot numbers are higher in cycle 22
than those in cycles 21 and 23. The correlation coefficients between the three
kinds of soft X-ray flares in cycle 22 are higher than those in cycles 21 and
23. These findings may be instructive in predicting C-class, M-class, and
X-class flares regarding sunspot numbers in the next cycle and the physical
processes of energy storage and dissipation in the corona.Comment: 8 pages, 3 figures, Accepted for publication in Astrophysics & Space
Scienc
Statistical properties of the GALEX spectroscopic stellar sample
The GALEX General Data Release 4/5 includes 174 spectroscopic tiles, obtained
from slitless grism observations, for a total of more than 60,000 ultraviolet
spectra. We have determined statistical properties of the sample of GALEX
stars. We have defined a suitable system of spectroscopic indices, which
measure the main mid-UV features at the GALEX low spectral resolution and we
have employed it to determine the atmospheric parameters of of stars in the
range 4500<Teff<9000 K. Our preliminary results indicate that the sample is
formed by a majority of main sequence F- and G-type stars, with metallicity
[M/H]>-1 dex.Comment: 9 pages, 9 figures, accepted for publication in Astrophysics & Space
Science, UV universe special issu
Culture, Embodiment and Genes: Unravelling the Triple Helix
Much recent work stresses the role of embodiment and action in thought and reason, and celebrates the power of transmitted cultural and environmental structures to transform the problem-solving activity required of individual brains. By apparent contrast, much work in evolutionary psychology has stressed the selective fit of the biological brain to an ancestral environment of evolutionary adaptedness, with an attendant stress upon the limitations and cognitive biases that result. On the face of it, this suggests either a tension or, at least, a mismatch, with the symbiotic dyad of cultural evolution and embodied cognition. In what follows, we explore this mismatch by focusing on three key ideas: cognitive niche construction; cognitive modularity; and the existence (or otherwise) of an evolved universal human nature. An appreciation of the power and scope of the first, combined with consequently more nuanced visions of the latter two, allow us to begin to glimpse a much richer vision of the combined interactive potency of biological and cultural evolution for active, embodied agents
Supersymmetry Without Prejudice at the LHC
The discovery and exploration of Supersymmetry in a model-independent fashion
will be a daunting task due to the large number of soft-breaking parameters in
the MSSM. In this paper, we explore the capability of the ATLAS detector at the
LHC ( TeV, 1 fb) to find SUSY within the 19-dimensional
pMSSM subspace of the MSSM using their standard transverse missing energy and
long-lived particle searches that were essentially designed for mSUGRA. To this
end, we employ a set of k previously generated model points in the
19-dimensional parameter space that satisfy all of the existing experimental
and theoretical constraints. Employing ATLAS-generated SM backgrounds and
following their approach in each of 11 missing energy analyses as closely as
possible, we explore all of these k model points for a possible SUSY
signal. To test our analysis procedure, we first verify that we faithfully
reproduce the published ATLAS results for the signal distributions for their
benchmark mSUGRA model points. We then show that, requiring all sparticle
masses to lie below 1(3) TeV, almost all(two-thirds) of the pMSSM model points
are discovered with a significance in at least one of these 11 analyses
assuming a 50\% systematic error on the SM background. If this systematic error
can be reduced to only 20\% then this parameter space coverage is increased.
These results are indicative that the ATLAS SUSY search strategy is robust
under a broad class of Supersymmetric models. We then explore in detail the
properties of the kinematically accessible model points which remain
unobservable by these search analyses in order to ascertain problematic cases
which may arise in general SUSY searches.Comment: 69 pages, 40 figures, Discussion adde
Energy Release During Slow Long Duration Flares Observed by RHESSI
Slow Long Duration Events (SLDEs) are flares characterized by long duration
of rising phase. In many such cases impulsive phase is weak with lack of
typical short-lasting pulses. Instead of that smooth, long-lasting Hard X-ray
(HXR) emission is observed. We analysed hard X-ray emission and morphology of
six selected SLDEs. In our analysis we utilized data from RHESSI and GOES
satellites. Physical parameters of HXR sources were obtained from imaging
spectroscopy and were used for the energy balance analysis. Characteristic time
of heating rate decrease, after reaching its maximum value, is very long, which
explains long rising phase of these flares.Comment: Accepted for publication in Solar Physic
Interaction of quasilocal harmonic modes and boson peak in glasses
The direct proportionality relation between the boson peak maximum in
glasses, , and the Ioffe-Regel crossover frequency for phonons,
, is established. For several investigated materials . At the frequency the mean free path of the
phonons becomes equal to their wavelength because of strong resonant
scattering on quasilocal harmonic oscillators. Above this frequency phonons
cease to exist. We prove that the established correlation between
and holds in the general case and is a direct consequence of
bilinear coupling of quasilocal oscillators with the strain field.Comment: RevTex, 4 pages, 1 figur
Hypertension in Canada: Past, Present, and Future
Canada has an extremely successful hypertension detection and treatment program. The aim of this review was to highlight the historic and current infrastructure and initiatives that have led to this success, and the outlook moving forward into the future. We discuss the evolution of hypertension awareness and control in Canada; contributions made by organizations such as the Canadian Hypertension Society, Blood Pressure Canada, and the Canadian Hypertension Education Program; the amalgamation of these organizations into Hypertension Canada; and the impact that Hypertension Canada has had on hypertension care in Canada. The important contribution that public policy and advocacy can have on prevention and control of blood pressure in Canada is described. We also highlight the importance of population-based strategies, health care access and organization, and accurate blood pressure measurement (including ambulatory, home, and automated office modalities) in optimizing hypertension prevention and management. We end by discussing how Hypertension Canada will move forward in the near and longer term to address the unmet residual risk attributable to hypertension and associated cardiovascular risk factors. Hypertension Canada will continue to strive to enhance hypertension prevention and control rates, thereby improving the quality of life and cardiovascular outcomes of Canadians, while at the same time creating a hypertension care model that can be emulated across the world
Parity nonconservation in deuteron photoreactions
We calculate the asymmetries in parity nonconserving deuteron
photodisintegration due to circularly polarized photons gamma+d to n+p with the
photon laboratory energy ranging from the threshold up to 10 MeV and the
radiative capture of thermal polarized neutrons by protons n+p to gamma+d. We
use the leading order electromagnetic Hamiltonian neglecting the smaller
nuclear exchange currents. Comparative calculations are done by using the
Reid93 and Argonne v18 potentials for the strong interaction and the DDH and
FCDH "best" values for the weak couplings in a weak one-meson exchange
potential. A weak NDelta transition potential is used to incorporate also the
Delta(1232)-isobar excitation in the coupled-channels formalism.Comment: 14 pages, 13 figures (18 eps files), LaTeX2
Anisotropy at the end of the cosmic ray spectrum?
The starburst galaxies M82 and NGC253 have been proposed as the primary
sources of cosmic rays with energies above eV. For energies \agt
10^{20.3} eV the model predicts strong anisotropies. We calculate the
probabilities that the latter can be due to chance occurrence. For the highest
energy cosmic ray events in this energy region, we find that the observed
directionality has less than 1% probability of occurring due to random
fluctuations. Moreover, during the first 5 years of operation at Auger, the
observation of even half the predicted anisotropy has a probability of less
than to occur by chance fluctuation. Thus, this model can be subject
to test at very small cost to the Auger priors budget and, whatever the outcome
of that test, valuable information on the Galactic magnetic field will be
obtained.Comment: Final version to be published in Physical Review
Phenomenology of Randall-Sundrum Black Holes
We explore the phenomenology of microscopic black holes in the
Randall-Sundrum (RS) model. We consider the canonical framework in which both
gauge and matter fields are confined to the brane and only gravity spills into
the extra dimension. The model is characterized by two parameters, the mass of
the first massive graviton , and the curvature of the RS
anti-de Sitter space. We compute the sensitivity of present and future cosmic
ray experiments to various regions of and and compare with that
of Runs I and II at the Tevatron. As part of our phenomenological analysis, we
examine constraints placed on by AdS/CFT considerations.Comment: Version to appear in Physical Review D; contains additional analysis
on sensitivity of OW
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