395 research outputs found
Positive cross-correlations induced by ferromagnetic contacts
Due to the Fermionic nature of carriers, correlations between electric
currents flowing through two different contacts attached to a conductor present
a negative sign. Possibility for positive cross-correlations has been
demonstrated in hybrid normal/superconductor structures under certain
conditions. In this paper we show that positive cross-correlations can be
induced, if not already present, in such structures by employing ferromagnetic
leads with magnetizations aligned anti-parallel to each other. We consider
three-terminal hybrid structures and calculate the mean-square correlations of
current fluctuations as a function of the bias voltage at finite temperature.Comment: 6 pages, 5 figures; accepted version by PRB, figures replace
Phenomenological Tests of Supersymmetric A_4 Family Symmetry Model of Neutrino Mass
Recently Babu, Ma and Valle proposed a model of quark and lepton mixing based
on symmetry. Within this model the lepton and slepton mixings are
intimately related. We perform a numerical study in order to derive the slepton
masses and mixings in agreement with present data from neutrino physics. We
show that, starting from three-fold degeneracy of the neutrino masses at a high
energy scale, a viable low energy neutrino mass matrix can indeed be obtained
in agreement with constraints on lepton flavour violating
and decays. The resulting slepton spectrum must necessarily
include at least one mass below 200 GeV which can be produced at the LHC. The
predictions for the absolute Majorana neutrino mass scale eV
ensure that the model will be tested by future cosmological tests and
searches.
Rates for lepton flavour violating processes
in the range of sensitivity of current
experiments are typical in the model, with BR(\mu \to e \gamma) \gsim
10^{-15} and the lower bound BR. To first
approximation, the model leads to maximal leptonic CP violation in neutrino
oscillations.Comment: 23 pages, 7 figure
Gender Differences in HIV and Hepatitis C Related Vulnerabilities Among Aboriginal Young People Who Use Street Drugs in Two Canadian Cities
Objectives: Vulnerability to HIV and Hepatitis C virus (HCV) infection for indigenous populations worldwide must be contextualized in experiences of current and past trauma. Aboriginal women entrenched in poverty face further gender-specific harms which place them at increased risk for HIV infection.
Methods: This study was cross-sectional and based on a community-based sample of Aboriginal young people (Métis, Abo- riginal, First Nations, Inuit, and non-status Indians) between the ages of 14 and 30 years who used injection or non-injection non- cannabis illegal drugs (street drugs) in the previous month. Between October 2003 and July 2005, 543 participants living in either Vancouver or Prince George, Canada, were recruited by word of mouth, posters, and street outreach. Young people in the study completed a questionnaire administered by Aboriginal interviewers. Female participants (n D 262) were compared to male participants (n D 281) with respect to sociodemographics, trauma, sexual risk variables, and drug use patterns. Trained nurses drew blood samples for HIV and HCV antibodies and provided pre- and post-test counseling.
Results: Proportions positive for HIV and HCV were significantly higher among young women. HIV was 13.1% [9.5, 17.7] in women compared to 4.3% [2.5, 7.4] in men, and HCV was 43.6% [37.6, 49.8] in women as compared to 25.4% [20.5, 30.9] in men. When the analysis was restricted to young people who reported injection drug use, the proportions positive for HIV and HCV remained significantly higher among young women. Experiences of forced sex were reported by 70% of young women compared to 29% of young men, p \u3c 0:001, while the median age of first forced sex was 6-years-old for both men and women.
Discussion: The results of the final model indicated that HIV had been associated with residing in Vancouver, having injected for longer, and sexual abuse, but not being female. However, this gendered analysis demonstrated that a greater proportion of young women were experiencing sexual abuse, and sexual abuse was asso- ciated with HIV positive status. Harm reduction and drug treatment programs are urgently required that target women at a young age and address complex traumatic experiences associated with childhood sexual abuse
Inverse Scattering at a Fixed Quasi-Energy for Potentials Periodic in Time
We prove that the scattering matrix at a fixed quasi--energy determines
uniquely a time--periodic potential that decays exponentially at infinity. We
consider potentials that for each fixed time belong to in space. The
exponent 3/2 is critical for the singularities of the potential in space. For
this singular class of potentials the result is new even in the
time--independent case, where it was only known for bounded exponentially
decreasing potentials.Comment: In this revised version I give a more detailed motivation of the
class of potentials that I consider and I have corrected some typo
The properties of Brightest Cluster Galaxies in the SDSS DR6 adaptive matched filter cluster catalogue
We study the properties of Brightest Cluster Galaxies (BCGs) drawn from a
catalogue of more than 69000 clusters in the SDSS DR6 based on the adaptive
matched filter technique (AMF, Szabo et al., 2010). Our sample consists of more
than 14300 galaxies in the redshift range 0.1-0.3. We test the catalog by
showing that it includes well-known BCGs which lie in the SDSS footprint. We
characterize the BCGs in terms of r-band luminosities and optical colours as
well as their trends with redshift. In particular, we define and study the
fraction of blue BCGs, namely those that are likely to be missed by either
colour-based cluster surveys and catalogues. Richer clusters tend to have
brighter BCGs, however less dominant than in poorer systems. 4-9% of our BCGs
are at least 0.3 mag bluer in the g-r colour than the red-sequence at their
given redshift. Such a fraction decreases to 1-6% for clusters above a richness
of 50, where 3% of the BCGs are 0.5 mag below the red-sequence. A preliminary
morphological study suggests that the increase in the blue fraction at lower
richnesses may have a non-negligible contribution from spiral galaxies. We show
that a colour selection based on the g-r red-sequence or on a cut at colour u-r
>2.2 can lead to missing the majority of such blue BCGs. We also extend the
colour analysis to the UV range by cross-matching our catalogue with publicly
available data from Galex GR4 and GR5. We show a clear correlation between
offset from the optical red-sequence and the amount of UV-excess. Finally, we
cross-matched our catalogue with the ACCEPT cluster sample (Cavagnolo et al.,
2009), and find that blue BCGs tend to be in clusters with low entropy and
short cooling times. That is, the blue light is presumably due to recent star
formation associated to gas feeding by cooling flows. (abridged)Comment: 15 pages, 15 figures, submitted to MNRA
Light-flavor sea-quark distributions in the nucleon in the SU(3) chiral quark soliton model (I) -- phenomenological predictions --
Theoretical predictions are given for the light-flavor sea-quark
distributions including the strange quark ones on the basis of the flavor SU(3)
version of the chiral quark soliton model. Careful account is taken here of the
SU(3) symmetry breaking effects due to the mass difference between the strange
and nonstrange quarks. This effective mass difference between the
strange and nonstrange quarks is the only one parameter necessary for the
flavor SU(3) generalization of the model. A particular emphasis of study is put
on the {\it light-flavor sea-quark asymmetry} as exemplified by the observables
as well as on the {\it particle-antiparticle asymmetry} of
the strange quark distributions represented by etc. As for the unpolarized
sea-quark distributions, the predictions of the model seem qualitatively
consistent with the available phenomenological information provided by the NMC
data for , the E866 data for , the CCFR data and Barone et al.'s fit for etc. The
model is shown to give several unique predictions also for the spin-dependent
sea-quark distribution, such that and , although the verification
of these predictions must await more elaborate experimental investigations in
the near future.Comment: 36 pages, 20 EPS figures. The revised version accepted for
publication in Phys. Rev. D. The title has been changed, and the body of the
paper has been divided into two pieces, i.e.. the present one which discusses
the main phenomenological predictions of the model and the other one which
describes the detailed formulation of the flavor SU(3) chiral quark soliton
model to predict light-flavor quark and antiquark distribution functions in
the nucleo
Supersymmetric mass spectra and the seesaw type-I scale
We calculate supersymmetric mass spectra with cMSSM boundary conditions and a
type-I seesaw mechanism added to explain current neutrino data. Using
published, estimated errors on SUSY mass observables for a combined LHC+ILC
analysis, we perform a theoretical analysis to identify parameter
regions where pure cMSSM and cMSSM plus seesaw type-I might be distinguishable
with LHC+ILC data. The most important observables are determined to be the
(left) smuon and selectron masses and the splitting between them, respectively.
Splitting in the (left) smuon and selectrons is tiny in most of cMSSM parameter
space, but can be quite sizeable for large values of the seesaw scale,
. Thus, for very roughly GeV hints for type-I
seesaw might appear in SUSY mass measurements. Since our numerical results
depend sensitively on forecasted error bars, we discuss in some detail the
accuracies, which need to be achieved, before a realistic analysis searching
for signs of type-I seesaw in SUSY spectra can be carried out.Comment: 17 pages, 7 figure
Energy dependent counting statistics in diffusive superconducting tunnel junctions
We present an investigation of the energy dependence of the full charge
counting statistics in diffusive
normal-insulating-normal-insulating-superconducting junctions. It is found that
the current in general is transported via a correlated transfer of pairs of
electrons. Only in the case of strongly asymmetric tunnel barriers or energies
much larger than the Thouless energy is the pair transfer uncorrelated. The
second cumulant, the noise, is found to depend strongly on the applied voltage
and temperature. For a junction resistance dominated by the tunnel barrier to
the normal reservoir, the differential shot noise shows a double peak feature
at voltages of the order of the Thouless energy, a signature of an ensemble
averaged electron-hole resonance.Comment: 8 pages, 5 figure
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