Thermodynamically consistent Langevin dynamics with spatially correlated noise predicts frictionless regime and transient attraction effect

While the origin of temporal correlations in Langevin dynamics have been thoroughly researched, the understanding of Spatially Correlated Noise (SCN) is rather incomplete. In particular, very little is known about the relation between friction and SCN. In this article, we derive the formal formula for the spatial correlation function in the particle-bath interactions. This expression shows that SCN is the inherent component of binary mixtures, originating from the effective (entropic) interactions. Further, employing this spatial correlation function, we postulate the thermodynamically consistent Langevin equation driven by SCN and the adequate Fluctuation-Dissipation Relation. The thermodynamical consistency is achieved by introducing the spatially variant friction coefficient, which can be also derived analytically. This coefficient exhibits a number of intriguing properties, e.g. the singular behavior for certain interaction types. Eventually, we apply this new theory to the system of two charged particles in the presence of counter-ions. Such particles interact via the screened-charge Yukawa potential and the inclusion of SCN leads to the emergence of the anomalous frictionless regime. In this regime the particles can experience active propulsion leading to the transient attraction effect. This effect suggests a non-equilibrium mechanism facilitating the molecular binding of the like-charged particles.Comment: expanded and revised version resubmitted to Phys. Rev.

Beam Performance of Tracking Detectors with Industrially Produced GEM Foils

Three Gas-Electron-Multiplier tracking detectors with an active area of 10 cm x 10 cm and a two-dimensional, laser-etched orthogonal strip readout have been tested extensively in particle beams at the Meson Test Beam Facility at Fermilab. These detectors used GEM foils produced by Tech-Etch, Inc. They showed an efficiency in excess of 95% and spatial resolution better than 70 um. The influence of the angle of incidence of particles on efficiency and spatial resolution was studied in detail.Comment: 8 pages, 9 figures, accepted by Nuclear Instruments and Methods in Physics Research

Self-Assembly of \u3cem\u3eEscherichia coli\u3c/em\u3e MutL and Its Complexes with DNA

The Escherichia coli MutL protein regulates the activity of several enzymes, including MutS, MutH, and UvrD, during methyl-directed mismatch repair of DNA. We have investigated the self-association properties of MutL and its binding to DNA using analytical sedimentation velocity and equilibrium. Self-association of MutL is quite sensitive to solution conditions. At 25 °C in Tris at pH 8.3, MutL assembles into a heterogeneous mixture of large multimers. In the presence of potassium phosphate at pH 7.4, MutL forms primarily stable dimers, with the higher-order assembly states suppressed. The weight-average sedimentation coefficient of the MutL dimer in this buffer (s̅20,w) is equal to 5.20 ± 0.08 S, suggesting a highly asymmetric dimer (f/fo = 1.58 ± 0.02). Upon binding the nonhydrolyzable ATP analogue, AMPPNP/Mg2+, the MutL dimer becomes more compact (s̅20,w = 5.71 ± 0.08 S; f/fo = 1.45 ± 0.02), probably reflecting reorganization of the N-terminal ATPase domains. A MutL dimer binds to an 18 bp duplex with a 3′-(dT20) single-stranded flanking region, with apparent affinity in the micromolar range. AMPPNP binding to MutL increases its affinity for DNA by a factor of ∼10. These results indicate that the presence of phosphate minimizes further MutL oligomerization beyond a dimer and that differences in solution conditions likely explain apparent discrepancies in previous studies of MutL assembly

Towards ultra-high resolution 3D reconstruction of a whole rat brain from 3D-PLI data

3D reconstruction of the fiber connectivity of the rat brain at microscopic scale enables gaining detailed insight about the complex structural organization of the brain. We introduce a new method for registration and 3D reconstruction of high- and ultra-high resolution (64 $\mu$m and 1.3 $\mu$m pixel size) histological images of a Wistar rat brain acquired by 3D polarized light imaging (3D-PLI). Our method exploits multi-scale and multi-modal 3D-PLI data up to cellular resolution. We propose a new feature transform-based similarity measure and a weighted regularization scheme for accurate and robust non-rigid registration. To transform the 1.3 $\mu$m ultra-high resolution data to the reference blockface images a feature-based registration method followed by a non-rigid registration is proposed. Our approach has been successfully applied to 278 histological sections of a rat brain and the performance has been quantitatively evaluated using manually placed landmarks by an expert.Comment: 9 pages, Accepted at 2nd International Workshop on Connectomics in NeuroImaging (CNI), MICCAI'201

Sustainable Water Management in the Southwestern United States: Reality or Rhetoric?

Background: While freshwater sustainability is generally defined as the provisioning of water for both people and the environment, in practice it is largely focused only on supplying water to furnish human population growth. Symptomatic of this is the state of Arizona, where rapid growth outside of the metropolitan Phoenix-Tucson corridor relies on the same groundwater that supplies year-round flow in rivers. Using Arizona as a case study, we present the first study in the southwestern United States that evaluates the potential impact of future population growth and water demand on streamflow depletion across multiple watersheds. Methodology/Principal Findings: We modeled population growth and water demand through 2050 and used four scenarios to explore the potential effects of alternative growth and water management strategies on river flows. Under the base population projection, we found that rivers in seven of the 18 study watersheds could be dewatered due to municipal demand. Implementing alternative growth and water management strategies, however, could prevent four of these rivers from being dewatered. Conclusions/Significance: The window of opportunity to implement water management strategies is narrowing. Because impacts from groundwater extraction are cumulative and cannot be immediately reversed, proactive water management strategies should be implemented where groundwater will be used to support new municipal demand. Our approach provides a low-cost method to identify where alternative water and growth management strategies may have the most impact, and demonstrates that such strategies can maintain a continued water supply for both people and the environment

An experimental survey of the production of alpha decaying heavy elements in the reactions of 238^{238}U +232^{232}Th at 7.5-6.1 MeV/nucleon

The production of alpha particle decaying heavy nuclei in reactions of 7.5-6.1 MeV/nucleon $^{238}$U +$^{232}$Th has been explored using an in-beam detection array composed of YAP scintillators and gas ionization chamber-Si telescopes. Comparisons of alpha energies and half-lives for the observed products with those of the previously known isotopes and with theoretically predicted values indicate the observation of a number of previously unreported alpha emitters. Alpha particle decay energies reaching as high as 12 MeV are observed. Many of these are expected to be from decay of previously unseen relatively neutron rich products. While the contributions of isomeric states require further exploration and specific isotope identifications need to be made, the production of heavy isotopes with quite high atomic numbers is suggested by the data.Comment: 12 pages, 12 figure

Comparison of the rheological properties of polyamide-6 and its nanocomposites with montmorillonite obtained by melt intercalation

Each varying parameter which can contribute to the quality of final products plays an important role in the processing of polymer nanomaterials. Rheological properties are useful in proper formulation of new polyamide-6 (PA-6) based materials and selecting processing parameters. However, the measured rheological properties depend strongly on the sample preparation method, humidity regulation, and time-temperature history during the measurement and not least on the kind of rheometer being used. The results of the preliminary investigation show the changes in visco-elastic properties of two types of PA-6 and their nanocomposites with montmorilonite