1,106 research outputs found
Considerable enhancement of the critical current in a superconducting film by magnetized magnetic strip
We show that a magnetic strip on top of a superconducting strip magnetized in
a specified direction may considerably enhance the critical current in the
sample. At fixed magnetization of the magnet we observed diode effect - the
value of the critical current depends on the direction of the transport
current. We explain these effects by a influence of the nonuniform magnetic
field induced by the magnet on the current distribution in the superconducting
strip. The experiment on a hybrid Nb/Co structure confirmed the predicted
variation of the critical current with a changing value of magnetization and
direction of the transport current.Comment: 6 pages, 7 figure
Anomalous state of a 2DEG in vicinal Si MOSFET in high magnetic fields
We report the observation of an anomalous state of a 2D electron gas near a
vicinal surface of a silicon MOSFET in high magnetic fields. It is
characterised by unusual behaviour of the conductivities and
, which can be described as a collapse of the Zeeman spin
splitting accompanied by a large peak in and an anomalous peak in
. It occurs at densities corresponding to the position of the
Fermi level above the onset of the superlattice mini-gap inherent to the
vicinal system. The range of fields and densities where this effect exists has
been determined, and it has been shown that it is suppressed by parallel
magnetic fields
Correlation effects during liquid infiltration into hydrophobic nanoporous mediums
Correlation effects arising during liquid infiltration into hydrophobic
porous medium are considered. On the basis of these effects a mechanism of
energy absorption at filling porous medium by nonwetting liquid is suggested.
In accordance with this mechanism, the absorption of mechanical energy is a
result expenditure of energy for the formation of menisci in the pores on the
shell of the infinite cluster and expenditure of energy for the formation of
liquid-porous medium interface in the pores belonging to the infinite cluster
of filled pores. It was found that in dependences on the porosity and,
consequently, in dependences on the number of filled pores neighbors, the
thermal effect of filling can be either positive or negative and the cycle of
infiltration-defiltration can be closed with full outflow of liquid. It can
occur under certain relation between percolation properties of porous medium
and the energy characteristics of the liquid-porous medium interface and the
liquid-gas interface. It is shown that a consecutive account of these
correlation effects and percolation properties of the pores space during
infiltration allow to describe all experimental data under discussion
Partitioning heritability by functional annotation using genome-wide association summary statistics
Recent work has demonstrated that some functional categories of the genome contribute disproportionately to the heritability of complex diseases. Here we analyze a broad set of functional elements, including cell type-specific elements, to estimate their polygenic contributions to heritability in genome-wide association studies (GWAS) of 17 complex diseases and traits with an average sample size of 73,599. To enable this analysis, we introduce a new method, stratified LD score regression, for partitioning heritability from GWAS summary statistics while accounting for linked markers. This new method is computationally tractable at very large sample sizes and leverages genome-wide information. Our findings include a large enrichment of heritability in conserved regions across many traits, a very large immunological disease-specific enrichment of heritability in FANTOM5 enhancers and many cell type-specific enrichments, including significant enrichment of central nervous system cell types in the heritability of body mass index, age at menarche, educational attainment and smoking behavior
Chiral Modulations in Curved Space I: Formalism
The goal of this paper is to present a formalism that allows to handle
four-fermion effective theories at finite temperature and density in curved
space. The formalism is based on the use of the effective action and zeta
function regularization, supports the inclusion of inhomogeneous and
anisotropic phases. One of the key points of the method is the use of a
non-perturbative ansatz for the heat-kernel that returns the effective action
in partially resummed form, providing a way to go beyond the approximations
based on the Ginzburg-Landau expansion for the partition function. The
effective action for the case of ultra-static Riemannian spacetimes with
compact spatial section is discussed in general and a series representation,
valid when the chemical potential satisfies a certain constraint, is derived.
To see the formalism at work, we consider the case of static Einstein spaces at
zero chemical potential. Although in this case we expect inhomogeneous phases
to occur only as meta-stable states, the problem is complex enough and allows
to illustrate how to implement numerical studies of inhomogeneous phases in
curved space. Finally, we extend the formalism to include arbitrary chemical
potentials and obtain the analytical continuation of the effective action in
curved space.Comment: 22 pages, 3 figures; version to appear in JHE
Adiabatic description of nonspherical quantum dot models
Within the effective mass approximation an adiabatic description of
spheroidal and dumbbell quantum dot models in the regime of strong dimensional
quantization is presented using the expansion of the wave function in
appropriate sets of single-parameter basis functions. The comparison is given
and the peculiarities are considered for spectral and optical characteristics
of the models with axially symmetric confining potentials depending on their
geometric size making use of the total sets of exact and adiabatic quantum
numbers in appropriate analytic approximations
Mutational re-modeling of di-aspartyl intramembrane proteases: uncoupling physiologically-relevant activities from those associated with Alzheimer\u27s disease
The intramembrane proteolytic activities of presenilins (PSEN1/PS1 and PSEN2/PS2) underlie production of beta-amyloid, the key process in Alzheimer\u27s disease (AD). Dysregulation of presenilin-mediated signaling is linked to cancers. Inhibition of the gamma-cleavage activities of PSENs that produce Abeta, but not the epsilon-like cleavage activity that release physiologically essential transcription activators, is a potential approach for the development of rational therapies for AD. In order to identify whether different activities of PSEN1 can be dissociated, we designed multiple mutations in the evolutionary conserved sites of PSEN1. We tested them in vitro and in vivo assays and compared their activities with mutant isoforms of presenilin-related intramembrane di-aspartyl protease (IMPAS1 (IMP1)/signal peptide peptidase (SPP)). PSEN1 auto-cleavage was more resistant to the mutation remodeling than the epsilon-like proteolysis. PSEN1 with a G382A or a P433A mutation in evolutionary invariant sites retains functionally important APP epsilon- and Notch S3- cleavage activities, but G382A inhibits APP gamma-cleavage and Abeta production and a P433A elevates Abeta. The G382A variant cannot restore the normal cellular ER Ca(2+) leak in PSEN1/PSEN2 double knockout cells, but efficiently rescues the loss-of-function (Egl) phenotype of presenilin in C. elegans. We found that, unlike in PSEN1 knockout cells, endoplasmic reticulum (ER) Ca(2+) leak is not changed in the absence of IMP1/SPP. IMP1/SPP with the analogous mutations retained efficiency in cleavage of transmembrane substrates and rescued the lethality of Ce-imp-2 knockouts. In summary, our data show that mutations near the active catalytic sites of intramembrane di-aspartyl proteases have different consequences on proteolytic and signaling functions
Interacting circular nanomagnets
Regular 2D rectangular lattices of permalloy nanoparticles (40 nm in
diameter) were prepared by the method of the electron lithography. The
magnetization curves were studied by Hall magnetometry with the compensation
technique for different external field orientations at 4.2K and 77K. The shape
of hysteresis curves indicates that there is magnetostatic interaction between
the particles. The main peculiarity is the existence of remanent magnetization
perpendicular to easy plain. By numerical simulation it is shown, that the
character of the magnetization reversal is a result of the interplay of the
interparticle interaction and the magnetization distribution within the
particles (vortex or uniform).Comment: 16 pages, 8 figure
Flux Modulations seen by the Muon Veto of the GERDA Experiment
The GERDA experiment at LNGS of INFN is equipped with an active muon veto.
The main part of the system is a water Cherenkov veto with 66~PMTs in the water
tank surrounding the GERDA cryostat. The muon flux recorded by this veto shows
a seasonal modulation. Two effects have been identified which are caused by
secondary muons from the CNGS neutrino beam (2.2 %) and a temperature
modulation of the atmosphere (1.4 %). A mean cosmic muon rate of /(sm) was found in good agreement with other experiments at
LNGS at a depth of 3500~meter water equivalent.Comment: 7 pages, 6 figure
The geography of recent genetic ancestry across Europe
The recent genealogical history of human populations is a complex mosaic
formed by individual migration, large-scale population movements, and other
demographic events. Population genomics datasets can provide a window into this
recent history, as rare traces of recent shared genetic ancestry are detectable
due to long segments of shared genomic material. We make use of genomic data
for 2,257 Europeans (the POPRES dataset) to conduct one of the first surveys of
recent genealogical ancestry over the past three thousand years at a
continental scale. We detected 1.9 million shared genomic segments, and used
the lengths of these to infer the distribution of shared ancestors across time
and geography. We find that a pair of modern Europeans living in neighboring
populations share around 10-50 genetic common ancestors from the last 1500
years, and upwards of 500 genetic ancestors from the previous 1000 years. These
numbers drop off exponentially with geographic distance, but since genetic
ancestry is rare, individuals from opposite ends of Europe are still expected
to share millions of common genealogical ancestors over the last 1000 years.
There is substantial regional variation in the number of shared genetic
ancestors: especially high numbers of common ancestors between many eastern
populations likely date to the Slavic and/or Hunnic expansions, while much
lower levels of common ancestry in the Italian and Iberian peninsulas may
indicate weaker demographic effects of Germanic expansions into these areas
and/or more stably structured populations. Recent shared ancestry in modern
Europeans is ubiquitous, and clearly shows the impact of both small-scale
migration and large historical events. Population genomic datasets have
considerable power to uncover recent demographic history, and will allow a much
fuller picture of the close genealogical kinship of individuals across the
world.Comment: Full size figures available from
http://www.eve.ucdavis.edu/~plralph/research.html; or html version at
http://ralphlab.usc.edu/ibd/ibd-paper/ibd-writeup.xhtm
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