6,681 research outputs found
Superfluid-insulator transitions of two-species Bosons in an optical lattice
We consider a realization of the two-species bosonic Hubbard model with
variable interspecies interaction and hopping strength. We analyze the
superfluid-insulator (SI) transition for the relevant parameter regimes and
compute the ground state phase diagram for odd filling at commensurate
densities. We find that in contrast to the even commensurate filling case, the
superfluid-insulator transition occurs with (a) simultaneous onset of
superfluidity of both species or (b) coexistence of Mott insulating state of
one species and superfluidity of the other or, in the case of unit filling, (c)
complete depopulation of one species. The superfluid-insulator transition can
be first order in a large region of the phase diagram. We develop a variational
mean-field method which takes into account the effect of second order quantum
fluctuations on the superfluid-insulator transition and corroborate the
mean-field phase diagram using a quantum Monte Carlo study.Comment: 12 pages, 11 figure
Learning a Static Analyzer from Data
To be practically useful, modern static analyzers must precisely model the
effect of both, statements in the programming language as well as frameworks
used by the program under analysis. While important, manually addressing these
challenges is difficult for at least two reasons: (i) the effects on the
overall analysis can be non-trivial, and (ii) as the size and complexity of
modern libraries increase, so is the number of cases the analysis must handle.
In this paper we present a new, automated approach for creating static
analyzers: instead of manually providing the various inference rules of the
analyzer, the key idea is to learn these rules from a dataset of programs. Our
method consists of two ingredients: (i) a synthesis algorithm capable of
learning a candidate analyzer from a given dataset, and (ii) a counter-example
guided learning procedure which generates new programs beyond those in the
initial dataset, critical for discovering corner cases and ensuring the learned
analysis generalizes to unseen programs.
We implemented and instantiated our approach to the task of learning
JavaScript static analysis rules for a subset of points-to analysis and for
allocation sites analysis. These are challenging yet important problems that
have received significant research attention. We show that our approach is
effective: our system automatically discovered practical and useful inference
rules for many cases that are tricky to manually identify and are missed by
state-of-the-art, manually tuned analyzers
MicroRNA in autoimmunity and autoimmune diseases
MicroRNAs (miRNAs) are small conserved non-coding RNA molecules that post-transcriptionally regulate gene expression by targeting the 3′ untranslated region (UTR) of specific messenger RNAs (mRNAs) for degradation or translational repression. miRNA-mediated gene regulation is critical for normal cellular functions such as the cell cycle, differentiation, and apoptosis, and as much as one-third of human mRNAs may be miRNA targets. Emerging evidence has demonstrated that miRNAs play a vital role in the regulation of immunological functions and the prevention of autoimmunity. Here we review the many newly discovered roles of miRNA regulation in immune functions and in the development of autoimmunity and autoimmune disease. Specifically, we discuss the involvement of miRNA regulation in innate and adaptive immune responses, immune cell development, T regulatory cell stability and function, and differential miRNA expression in rheumatoid arthritis and systemic lupus erythematosus
Salt stress induced ion accumulation, ion homeostasis, membrane injury and sugar contents in salt-sensitive rice (Oryza sativa L. spp. indica) roots under isoosmotic conditions
Excess salt induced ionic and osmotic stresses that disturbed metabolism and led to reduction of plant development. Previous studies reported that sugars in stressed plants were involved in stress tolerance. However, the role of sugars in salt-stressed plants against only ionic effects is still unclear. The objective of this research was to investigate accumulation and homeostasis of ions, membrane injury, water content, growth characters and sugar contents in roots, in-response to salt stress under iso-osmotic conditions. Salt-sensitive rice, Pathumthani1 (PT1) was grown on MS culture medium for 7 days and was adjusted to salt stress under iso-osmotic conditions (-1.75 ± 0.20 MPa) by mannitol for 4 days. An increase in NaCl increased Na+ and Na+:K+ in PT1 roots leading to increased membrane injury, while the water content was decreased. Additionally, growth characters, including number, length, fresh weight and dry weight of roots, were inhibited. Sugar accumulations in PT1 roots were enhanced by increases in NaCl. The increase in Na+ was positively related to total soluble sugars, resulting in an osmotic adjustment of the membrane that maintained water availability. The accumulation of sugars in PT1 roots may be a primary salt-defense mechanism and may function as an osmotic control.Key words: Mannitol, membrane injury, oligosaccharides, sodium ion, potassium ion, sodium chloride
Speedy Transactions in Multicore In-Memory Databases
Silo is a new in-memory database that achieves excellent performance and scalability on modern multicore machines. Silo was designed from the ground up to use system memory and caches efficiently. For instance, it avoids all centralized contention points, including that of centralized transaction ID assignment. Silo's key contribution is a commit protocol based on optimistic concurrency control that provides serializability while avoiding all shared-memory writes for records that were only read. Though this might seem to complicate the enforcement of a serial order, correct logging and recovery is provided by linking periodically-updated epochs with the commit protocol. Silo provides the same guarantees as any serializable database without unnecessary scalability bottlenecks or much additional latency. Silo achieves almost 700,000 transactions per second on a standard TPC-C workload mix on a 32-core machine, as well as near-linear scalability. Considered per core, this is several times higher than previously reported results.Engineering and Applied Science
Branes in the plane wave background with gauge field condensates
Supersymmetric branes in the plane wave background with additional constant
magnetic fields are studied from the world-sheet point of view. It is found
that in contradistinction to flat space, boundary condensates on some maximally
supersymmetric branes necessarily break at least some supersymmetries. The
maximally supersymmetric cases with condensates are shown to be in one to one
correspondence with the previously classified class II branes.Comment: LaTeX, 31 pages, no figures; v2: references added, some typos
correcte
High Performance Electrocatalysts Based on Pt Nanoarchitecture for Fuel Cell Applications
Fuel cells, converting chemical energy from fuels into electricity directly without the need for combustion, are promising energy conversion devices for their potential applications as environmentally friendly, energy efficient power sources. However, to take fuel cell technology forward towards commercialization, we need to achieve further improvements in electrocatalyst technology, which can play an extremely important role in essentially determining cost-effectiveness, performance, and durability. In particular, platinum- (Pt-) based electrocatalyst approaches have been extensively investigated and actively pursued to meet those demands as an ideal fuel cell catalyst due to their most outstanding activity for both cathode oxygen reduction reactions and anode fuel oxidation reactions. In this review, we will address important issues and recent progress in the development of Pt-based catalysts, their synthesis, and characterization. We will also review snapshots of research that are focused on essential dynamics aspects of electrocatalytic reactions, such as the shape effects on the catalytic activity of Pt-based nanostructures, the relationships between structural morphology of Pt-based nanostructures and electrochemical reactions on both cathode and anode electrodes, and the effects of composition and electronic structure of Pt-based catalysts on electrochemical reaction properties of fuel cells.</jats:p
Mg(, )Na reaction study for spectroscopy of Na
The Mg(, )Na reaction was measured at the Holifield
Radioactive Ion Beam Facility at Oak Ridge National Laboratory in order to
better constrain spins and parities of energy levels in Na for the
astrophysically important F()Ne reaction rate
calculation. 31 MeV proton beams from the 25-MV tandem accelerator and enriched
Mg solid targets were used. Recoiling He particles from the
Mg(, )Na reaction were detected by a highly segmented
silicon detector array which measured the yields of He particles over a
range of angles simultaneously. A new level at 6661 5 keV was observed in
the present work. The extracted angular distributions for the first four levels
of Na and Distorted Wave Born Approximation (DWBA) calculations were
compared to verify and extract angular momentum transfer.Comment: 11 pages, 6 figures, proceedings of the 18th International Conference
on Accelerators and Beam Utilization (ICABU2014
Critical Behaviour of Superfluid He in Aerogel
We report on Monte Carlo studies of the critical behaviour of superfluid
He in the presence of quenched disorder with long-range fractal
correlations. According to the heuristic argument by Harris, uncorrelated
disorder is irrelevant when the specific heat critical exponent is
negative, which is the case for the pure He. However, experiments on helium
in aerogel
have shown that the superfluid density critical exponent changes. We
hypothesize that this is a cross-over effect due to the fractal nature of
aerogel. Modelling the aerogel as an incipient percolating cluster in 3D and
weakening the bonds at the fractal sites, we perform XY-model simulations,
which demonstrate an increase in from
for the pure case to an apparent value of in the presence of
the fractal disorder, provided that the helium correlation length does not
exceed the fractal correlation length.Comment: 4 pages, RevTex, 3 postscript figures, LaTeX file and figures have
been uuencoded
Estimation the Performance of Solar Fiber Optic Lighting System after Repairing the Glass Fiber Cables in a South Korean Residential Building
The solar fiber optic lighting system consists of the solar ray concentrating apparatus, the tracking control, lighting transmission and emission parts. This system was installed on a 20-storey apartment building in South Korea. Many residents had concerns about its long-term maintenance. The most common maintenance difficulties are sun tracking problems and damaged glass fiber cables. Sometimes fiber optic lighting systems should not be repaired with splices. Splicing glass fiber cables often results in decreased system efficiency and further cable damage. In this study, the cost of replacing the cables was prohibitive; hence, the drop in efficiency of the damaged cables was answered by repairing through splicing. These damaged cables were repaired by specially process of cutting and polishing. Results showed that the luminous intensity ratio improved by 0.391%, though this was still lower than the recommended guideline of 0.725%. Accordingly, on average 55% of luminous intensity was increased
- …