568 research outputs found
High energy scattering in 2+1 QCD
High energy scattering in 2+1 QCD is studied using the recent approach of
Verlinde and Verlinde. We calculate the color singlet part of the quark-quark
scattering exactly within this approach, and discuss some physical implication
of this result. We also demonstrate, by two independent methods, that
reggeization fails for the color singlet channel. We briefly comment on the
problem in 3+1 QCD.Comment: 20 pages, references adde
Irreversible and reversible modes of operation of deterministic ratchets
We discuss a problem of optimization of the energetic efficiency of a simple
rocked ratchet. We concentrate on a low-temperature case in which the
particle's motion in a ratchet potential is deterministic. We show that the
energetic efficiency of a ratchet working adiabatically is bounded from above
by a value depending on the form of ratchet potential. The ratchets with
strongly asymmetric potentials can achieve ideal efficiency of unity without
approaching reversibility. On the other hand we show that for any form of the
ratchet potential a set of time-protocols of the outer force exist under which
the operation is reversible and the ideal value of efficiency is also achieved.
The mode of operation of the ratchet is still quasistatic but not adiabatic.
The high values of efficiency can be preserved even under elevated
temperatures
K-string tensions at finite temperature and integrable models
It has recently been pointed out that simple scaling properties of Polyakov
correlation functions of gauge systems in the confining phase suggest that the
ratios of k-string tensions in the low temperature region is constant up to
terms of order T^3. Here we argue that, at least in a three-dimensional Z_4
gauge model, the above ratios are constant in the whole confining phase. This
result is obtained by combining numerical experiments with known exact results
on the mass spectrum of an integrable two-dimensional spin model describing the
infrared behaviour of the gauge system near the deconfining transition.Comment: 22 pages, 7 figures, 1 tabl
Influence of recirculation rate on the performance of a combined anaerobic-aerobic reactor applied to the removal of carbon and nitrogen from poultry slaughterhouse wastewater
The objective of this study was to evaluate a combined anaerobic-aerobic upflow fixed-bed reactor with liquid phase recirculation for the removal of nitrogen and organic matter from poultry slaughterhouse wastewater. The reactor performance was evaluated with a hydraulic retention time (HRT) of 11 h and three different recirculation rates (R=0.5; 1 and 2). The highest nitrogen removal efficiency value was obtained with an HRT of 11 h (6.8 h in the anaerobic zone and 4.2 h in the aerobic zone) and a recirculation rate of 2. In this condition, the total nitrogen removal efficiency was 69%, with effluent concentrations of 6 mg NH4+ L-1 and 12 mg NO3- L-1. For all tested conditions, there was good chemical oxygen demand (COD) removal, with efficiency above 95%. The effect of dilution and the favoring of mass transfer caused by the increase in the recirculation rate positively influenced reactor performance.Key words: Anaerobic degradation, nitrification, denitrification, combined reactor
Generalized stochastic Schroedinger equations for state vector collapse
A number of authors have proposed stochastic versions of the Schr\"odinger
equation, either as effective evolution equations for open quantum systems or
as alternative theories with an intrinsic collapse mechanism. We discuss here
two directions for generalization of these equations. First, we study a general
class of norm preserving stochastic evolution equations, and show that even
after making several specializations, there is an infinity of possible
stochastic Schr\"odinger equations for which state vector collapse is provable.
Second, we explore the problem of formulating a relativistic stochastic
Schr\"odinger equation, using a manifestly covariant equation for a quantum
field system based on the interaction picture of Tomonaga and Schwinger. The
stochastic noise term in this equation can couple to any local scalar density
that commutes with the interaction energy density, and leads to collapse onto
spatially localized eigenstates. However, as found in a similar model by
Pearle, the equation predicts an infinite rate of energy nonconservation
proportional to , arising from the local double commutator in
the drift term.Comment: 24 pages Plain TeX. Minor changes, some new references. To appear in
Journal of Physics
Risk of requiring a wheelchair in primary progressive multiple sclerosis: Data from the ORATORIO trial and the MSBase registry
Background and purpose: Reaching Expanded Disability Status Scale (EDSS) â„7.0 represents the requirement for a wheelchair. Here we (i) assess the effect of ocrelizumab on time to EDSS â„7.0 over the ORATORIO (NCT01194570) double-blind and extended controlled periods (DBP+ECP), (ii) quantify likely long-term benefits by extrapolating results, and (iii) assess the plausibility of extrapolations using an independent real-world cohort (MSBase registry; ACTRN12605000455662). Methods: Post hoc analyses assessing time to 24-week confirmed EDSS â„7.0 in two cohorts of patients with primary progressive multiple sclerosis (baseline EDSS 3.0â6.5) were investigated in ORATORIO and MSBase. Results: In the ORATORIO DBP+ECP, ocrelizumab reduced the risk of 24-week confirmed EDSS â„7.0 (hazard ratio = 0.54, 95% confidence interval [CI]: 0.31â0.92; p = 0.022). Extrapolated median time to 24-week confirmed EDSS â„7.0 was 12.1 and 19.2 years for placebo and ocrelizumab, respectively (7.1-year delay [95% CI: â4.3 to 18.4]). In MSBase, the median time to 24-week confirmed EDSS â„7.0 was 12.4 years. Conclusions: Compared with placebo, ocrelizumab significantly delayed time to 24-week confirmed wheelchair requirement in ORATORIO. The plausibility of the extrapolated median time to reach this milestone in the placebo group was supported by observed real-world data from MSBase. Extrapolated benefits for ocrelizumab over placebo could represent a truly meaningful delay in loss of ambulation and independence
A novel systems biology approach to evaluate mouse models of late-onset Alzheimer\u27s disease.
BACKGROUND: Late-onset Alzheimer\u27s disease (LOAD) is the most common form of dementia worldwide. To date, animal models of Alzheimer\u27s have focused on rare familial mutations, due to a lack of frank neuropathology from models based on common disease genes. Recent multi-cohort studies of postmortem human brain transcriptomes have identified a set of 30 gene co-expression modules associated with LOAD, providing a molecular catalog of relevant endophenotypes.
RESULTS: This resource enables precise gene-based alignment between new animal models and human molecular signatures of disease. Here, we describe a new resource to efficiently screen mouse models for LOAD relevance. A new NanoString nCounterÂź Mouse AD panel was designed to correlate key human disease processes and pathways with mRNA from mouse brains. Analysis of the 5xFAD mouse, a widely used amyloid pathology model, and three mouse models based on LOAD genetics carrying APOE4 and TREM2*R47H alleles demonstrated overlaps with distinct human AD modules that, in turn, were functionally enriched in key disease-associated pathways. Comprehensive comparison with full transcriptome data from same-sample RNA-Seq showed strong correlation between gene expression changes independent of experimental platform.
CONCLUSIONS: Taken together, we show that the nCounter Mouse AD panel offers a rapid, cost-effective and highly reproducible approach to assess disease relevance of potential LOAD mouse models
Exact boundary S-matrices of the supersymmetric sine-Gordon theory on a half line
Using the boundary Yang-Baxter equations and exact results on the bulk
-matrices, we compute exact boundary scattering amplitudes of the
supersymmetric sine-Gordon model with integrable boundary potentials.Comment: 15 pages, requires phyzzx.tex. Serious typo-errors are correcte
Genotyping-by-Sequencing and Ecological Niche Modeling Illuminate Phylogeography, Admixture, and Pleistocene Range Dynamics in Quaking Aspen (Populus Tremuloides)
Populus tremuloides is the widestâranging tree species in North America and an ecologically important component of mesic forest ecosystems displaced by the Pleistocene glaciations. Using phylogeographic analyses of genomeâwide SNPs (34,796 SNPs, 183 individuals) and ecological niche modeling, we inferred population structure, ploidy levels, admixture, and Pleistocene range dynamics of P. tremuloides, and tested several historical biogeographical hypotheses. We found three genetic lineages located mainly in coastalâCascades (cluster 1), eastâslope CascadesâSierra NevadasâNorthern Rockies (cluster 2), and U.S. Rocky Mountains through southern Canadian (cluster 3) regions of the P. tremuloides range, with tree graph relationships of the form ((cluster 1, cluster 2), cluster 3). Populations consisted mainly of diploids (86%) but also small numbers of triploids (12%) and tetraploids (1%), and ploidy did not adversely affect our genetic inferences. The main vector of admixture was from cluster 3 into cluster 2, with the admixture zone trending northwest through the Rocky Mountains along a recognized phenotypic cline (Utah to Idaho). Clusters 1 and 2 provided strong support for the âstableâedge hypothesisâ that unglaciated southwestern populations persisted in situ since the last glaciation. By contrast, despite a lack of clinal genetic variation, cluster 3 exhibited âtrailingâedgeâ dynamics from niche suitability predictions signifying complete northward postglacial expansion. Results were also consistent with the âinland dispersal hypothesisâ predicting postglacial assembly of Pacific Northwestern forest ecosystems, but rejected the hypothesis that Pacificâcoastal populations were colonized during outburst flooding from glacial Lake Missoula. Overall, congruent patterns between our phylogeographic and ecological niche modeling results and fossil pollen data demonstrate complex mixtures of stableâedge, refugial locations, and postglacial expansion within P. tremuloides. These findings confirm and refine previous genetic studies, while strongly supporting a distinct Pacificâcoastal genetic lineage of quaking aspen
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