Polymers pushing Polymers: Polymer Mixtures in Thermodynamic Equilibrium with a Pore

We investigate polymer partitioning from polymer mixtures into nanometer size cavities by formulating an equation of state for a binary polymer mixture assuming that only one (smaller) of the two polymer components can penetrate the cavity. Deriving the partitioning equilibrium equations and solving them numerically allows us to introduce the concept of "polymers-pushing-polymers" for the action of non-penetrating polymers on the partitioning of the penetrating polymers. Polymer partitioning into a pore even within a very simple model of a binary polymer mixture is shown to depend in a complicated way on the composition of the polymer mixture and/or the pore-penetration penalty. This can lead to enhanced as well as diminished partitioning, due to two separate energy scales that we analyse in detail.Comment: 10 pages, 6 figure

Evidence for νμ→ντ\nu_\mu \to \nu_\tau appearance in the CNGS neutrino beam with the OPERA experiment

The OPERA experiment is designed to search for $\nu_{\mu} \rightarrow \nu_{\tau}$ oscillations in appearance mode i.e. through the direct observation of the $\tau$ lepton in $\nu_{\tau}$ charged current interactions. The experiment has taken data for five years, since 2008, with the CERN Neutrino to Gran Sasso beam. Previously, two $\nu_{\tau}$ candidates with a $\tau$ decaying into hadrons were observed in a sub-sample of data of the 2008-2011 runs. Here we report the observation of a third $\nu_\tau$ candidate in the $\tau^-\to\mu^-$ decay channel coming from the analysis of a sub-sample of the 2012 run. Taking into account the estimated background, the absence of $\nu_{\mu} \rightarrow \nu_{\tau}$ oscillations is excluded at the 3.4 $\sigma$ level.Comment: 9 pages, 5 figures, 1 table

Magic Angle Spinning Nuclear Magnetic Resonance Characterization of Voltage-Dependent Anion Channel Gating in Two-Dimensional Lipid Crystalline Bilayers

The N-terminus of the voltage-dependent anion channel (VDAC) has been proposed to contain the mechanistically important gating helices that modulate channel opening and closing. In this study, we utilize magic angle spinning nuclear magnetic resonance (MAS NMR) to determine the location and structure of the N-terminus for functional channels in lipid bilayers by measuring long-range 13C–13C distances between residues in the N-terminus and other domains of VDAC reconstituted into DMPC lipid bilayers. Our structural studies show that the distance between A14 Cβ in the N-terminal helix and S193 Cβ is ∼4–6 Å. Furthermore, VDAC phosphorylation by a mitochondrial kinase at residue S193 has been claimed to delay mitochondrial cell death by causing a conformational change that closes the channel, and a VDAC-Ser193Glu mutant has been reported to show properties very similar to those of phosphorylated VDAC in a cellular context. We expressed VDAC-S193E and reconstituted it into DMPC lipid bilayers. Two-dimensional 13C–13C correlation experiments showed chemical shift perturbations for residues located in the N-terminus, indicating possible structural perturbations to that region. However, electrophysiological data recorded on VDAC-S193E showed that channel characteristics were identical to those of wild type samples, indicating that phosphorylation of S193 does not directly affect channel gating. The combination of NMR and electrophysiological results allows us to discuss the validity of proposed gating models

Determination of the muon charge sign with the dipolar spectrometers of the OPERA experiment

The OPERA long-baseline neutrino-oscillation experiment has observed the direct appearance of $\nu_\tau$ in the CNGS $\nu_\mu$ beam. Two large muon magnetic spectrometers are used to identify muons produced in the $\tau$ leptonic decay and in $\nu_\mu^{CC}$ interactions by measuring their charge and momentum. Besides the kinematic analysis of the $\tau$ decays, background resulting from the decay of charmed particles produced in $\nu_\mu^{CC}$ interactions is reduced by efficiently identifying the muon track. A new method for the charge sign determination has been applied, via a weighted angular matching of the straight track-segments reconstructed in the different parts of the dipole magnets. Results obtained for Monte Carlo and real data are presented. Comparison with a method where no matching is used shows a significant reduction of up to 40\% of the fraction of wrongly determined charges.Comment: 10 pages. Improvements in the tex

Emulsion sheet doublets as interface trackers for the OPERA experiment

New methods for efficient and unambiguous interconnection between electronic counters and target units based on nuclear photographic emulsion films have been developed. The application to the OPERA experiment, that aims at detecting oscillations between mu neutrino and tau neutrino in the CNGS neutrino beam, is reported in this paper. In order to reduce background due to latent tracks collected before installation in the detector, on-site large-scale treatments of the emulsions ("refreshing") have been applied. Changeable Sheet (CSd) packages, each made of a doublet of emulsion films, have been designed, assembled and coupled to the OPERA target units ("ECC bricks"). A device has been built to print X-ray spots for accurate interconnection both within the CSd and between the CSd and the related ECC brick. Sample emulsion films have been extensively scanned with state-of-the-art automated optical microscopes. Efficient track-matching and powerful background rejection have been achieved in tests with electronically tagged penetrating muons. Further improvement of in-doublet film alignment was obtained by matching the pattern of low-energy electron tracks. The commissioning of the overall OPERA alignment procedure is in progress.Comment: 19 pages, 19 figure

Measurement of the atmospheric muon charge ratio with the OPERA detector

The OPERA detector at the Gran Sasso underground laboratory (LNGS) was used to measure the atmospheric muon charge ratio in the TeV energy region. We analyzed 403069 atmospheric muons corresponding to 113.4 days of livetime during the 2008 CNGS run. We computed separately the muon charge ratio for single and for multiple muon events in order to select different energy regions of the primary cosmic ray spectrum and to test the charge ratio dependence on the primary composition. The measured charge ratio values were corrected taking into account the charge-misidentification errors. Data have also been grouped in five bins of the "vertical surface energy". A fit to a simplified model of muon production in the atmosphere allowed the determination of the pion and kaon charge ratios weighted by the cosmic ray energy spectrum.Comment: 14 pages, 10 figure

The detection of neutrino interactions in the emulsion/lead target of the OPERA experiment

The OPERA neutrino detector in the underground Gran Sasso Laboratory (LNGS) was designed to perform the first detection of neutrino oscillations in appearance mode through the study of $\nu_\mu\to\nu_\tau$ oscillations. The apparatus consists of an emulsion/lead target complemented by electronic detectors and it is placed in the high energy long-baseline CERN to LNGS beam (CNGS) 730 km away from the neutrino source. Runs with CNGS neutrinos were successfully carried out in 2007 and 2008 with the detector fully operational with its related facilities for the emulsion handling and analysis. After a brief description of the beam and of the experimental setup we report on the collection, reconstruction and analysis procedures of first samples of neutrino interaction events

Магнитно-резонансная трактография: возможности и ограничения метода, современный подход к обработке данных

Purpose: systematization of the knowledge about diffusion tensor magnetic resonance tomography; analysis of literature related to current limitations of this method and possibilities of overcoming these limitations.Materials and methods. We have analyzed 74 publications (6 Проанализировано 74 публикации (6 Russian, 68 foreign), published in the time period from 1986 to 2021years.  More, than half of these articles were published in the last ten years, 19 studies-in the time period from 2016 to 2021years.Results. In this article we  represent the physical basis of diffusion weighted techniques of magnetic resonance tomography, principles of obtaining diffusion weighted images and diffusion tensor, cover the specific features of the probabilistic and deterministic approaches of the diffusion tensor MRI data processing, describe methods of evaluation of the diffusion characteristics of tissues in clinical practice. Article provides a thorough introduction to the reasons of existing limitations of diffusion tensor MRI and systematization the main developed approaches of overcoming these limitations, such as multi-tensor model, high angular resolution diffusion imaging, diffusion kurtosis visualization. The article consistently reviews the stages of data processing of diffusion tensor magnetic resonance tomography (preprocessing, processing and post processing). We also describe the special aspects of the main approaches to the quantitative data analysis of diffusion tensor magnetic resonance tomography (such as analysis of the region of interest, analysis of the total data amount, quantitative tractography).Conclusion. Magnetic resonance tractography is a unique technique for noninvasive in vivo visualization of brain white matter tracts and assessment of the structural integrity of their constituent axons. In the meantime this technique, which has found applications in numerous pathologies of central nervous system, has a number of significant limitations, and the main of them are the inability to adequately visualize the crossing fibers and the relatively low reproducibility of the results. Standardization of the data postprocessing algorithms, further upgrading of the magnetic resonance scanners and implementation of the alternative tractography methods have the potential of partially reducing of the current limitations.Цель исследования. Систематизация знаний о диффузионной тензорной магнитно-резонансной томографии; анализ литературы, касающейся существующих на сегодняшний момент ограничений метода и возможностей их преодоления.Материал и методы. Проанализировано 74 публикации (6 отечественных, 68 зарубежных), вышедших в свет в период с 1986 по 2021 год. Более половины работ было опубликовано в последнее десятилетие, 19 работ – в период с 2016 по 2021 год.Результаты. В статье изложены физические основы диффузионных методик магнитно-резонансной томографии, принципы получения диффузионно-взвешенных изображений и диффузионного тензора, отражены особенности вероятностного и детерминистского подходов к обработке данных диффузионной тензорной МРТ, а также методы оценки диффузионных характеристик тканей в клинической практике. Подробно рассмотрены причины имеющихся ограничений диффузионной тензорной МРТ, а также систематизированы основные разработанные приемы преодоления этих ограничений, таких как мультитензорная модель, диффузионная визуализация высокого углового разрешения, диффузионная спектральная визуализация, диффузионная куртозисная визуализация. Последовательно рассмотрены этапы обработки данных диффузионной тензорной магнитно-резонансной томографии (препроцессинг, процессинг и постпроцессинг). Отражены особенности основных подходов к количественному анализу данных диффузионной тензорной магнитно-резонансной томографии (таких как анализ области интереса, анализ всего объема данных, количественная трактография).Заключение. Магнитно-резонансная трактография – уникальная методика неинвазивной прижизненной визуализации проводящих путей головного мозга и оценки структурной целостности составляющих их аксонов, нашедшая применение при многих заболеваниях центральной нервной системы. В то же время эта методика имеет ряд существенных ограничений, основными из которых являются невозможность адекватной визуализации перекрещивающихся волокон и относительно низкая воспроизводимость результатов. Стандартизация алгоритмов постпроцессинга данных, дальнейшее совершенствование магнитнорезонансных томографов и внедрение альтернативных методов трактографии потенциально способны частично нивелировать имеющиеся в настоящее время недостатки