32,585 results match your criteria Astronomy And Astrophysics Review[Journal]


Role of nuclear RNA in regulating chromatin structure and transcription.

Curr Opin Cell Biol 2019 Apr 19;58:120-125. Epub 2019 Apr 19.

MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, UK. Electronic address:

The importance of three-dimensional chromatin organisation in genome regulation has never been clearer. But in spite of the enormous technological advances to probe chromatin organisation in vivo, there is still a lack of mechanistic understanding of how such an arrangement is achieved. Here we review emerging evidence pointing to an intriguing role of nuclear RNA in shaping large-scale chromatin structure and regulating genome function. Read More

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http://dx.doi.org/10.1016/j.ceb.2019.03.007DOI Listing

Conformal Prediction Based on Raman Spectra for the Classification of Chinese Liquors.

Appl Spectrosc 2019 Apr 22:3702819831017. Epub 2019 Apr 22.

1 School of Science, Jiangnan University, Wuxi, China.

This work extends the conventional back-propagation neural network (BPNN) to the classification of Chinese liquors of different flavors according to their Raman spectra. Conformal prediction is applied to assign reliable confidence measures for each classification and support an effective framework to make the machine learning on classification trustable. The BPNN can be used to predict the flavors of Chinese liquors according to their Raman spectra, and a classification rate of 88. Read More

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http://dx.doi.org/10.1177/0003702819831017DOI Listing

Transport Evidence for Sulfur Vacancies as the Origin of Unintentional n-Type Doping in Pyrite FeS.

ACS Appl Mater Interfaces 2019 Apr 22. Epub 2019 Apr 22.

Department of Chemical Engineering and Materials Science , University of Minnesota , Minneapolis , Minnesota 55455 , United States.

Pyrite FeS has long been considered a potential earth-abundant low-cost photovoltaic material for thin-film solar cells but has been plagued by low power conversion efficiencies and open-circuit voltages. Recent efforts have identified a lack of understanding and control of doping, as well as uncontrolled surface conduction, as key roadblocks to the development of pyrite photovoltaics. In particular, while n-type bulk behavior in unintentionally doped single crystals and thin films is speculated to arise from sulfur vacancies (V), proof remains elusive. Read More

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http://dx.doi.org/10.1021/acsami.9b01335DOI Listing

Structure of the Current Sheet in the 11 July 2017 Electron Diffusion Region Event.

J Geophys Res Space Phys 2019 Feb 27;124(2):1173-1186. Epub 2019 Feb 27.

Space Science Center University New Hampshire Durham NH USA.

The structure of the current sheet along the Magnetospheric Multiscale (MMS) orbit is examined during the 11 July 2017 Electron Diffusion Region (EDR) event. The location of MMS relative to the X-line is deduced and used to obtain the spatial changes in the electron parameters. The electron velocity gradient values are used to estimate the reconnection electric field sustained by nongyrotropic pressure. Read More

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http://dx.doi.org/10.1029/2018JA026028DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6472497PMC
February 2019

Transport and Loss of Ring Current Electrons Inside Geosynchronous Orbit During the 17 March 2013 Storm.

J Geophys Res Space Phys 2019 Feb 1;124(2):915-933. Epub 2019 Feb 1.

Los Alamos National Laboratory Los Alamos NM USA.

Ring current electrons (1-100 keV) have received significant attention in recent decades, but many questions regarding their major transport and loss mechanisms remain open. In this study, we use the four-dimensional Versatile Electron Radiation Belt code to model the enhancement of phase space density that occurred during the 17 March 2013 storm. Our model includes global convection, radial diffusion, and scattering into the Earth's atmosphere driven by whistler-mode hiss and chorus waves. Read More

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http://dx.doi.org/10.1029/2018JA026031DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6472511PMC
February 2019

Evaluating Single Spacecraft Observations of Planetary Magnetotails With Simple Monte Carlo Simulations: 2. Magnetic Flux Rope Signature Selection Effects.

J Geophys Res Space Phys 2018 Dec 22;123(12):10124-10138. Epub 2018 Dec 22.

Department of Physics and Astronomy University of Southampton Southampton UK.

A Monte Carlo method of investigating the effects of placing selection criteria on the magnetic signature of in situ encounters with flux ropes is presented. The technique is applied to two recent flux rope surveys of MESSENGER data within the Hermean magnetotail. It is found that the different criteria placed upon the signatures will preferentially identify slightly different subsets of the underlying population. Read More

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http://dx.doi.org/10.1029/2018JA025959DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6472627PMC
December 2018

Evaluating Single-Spacecraft Observations of Planetary Magnetotails With Simple Monte Carlo Simulations: 1. Spatial Distributions of the Neutral Line.

J Geophys Res Space Phys 2018 Dec 22;123(12):10109-10123. Epub 2018 Dec 22.

Department of Physics and Astronomy University of Southampton Southampton UK.

A simple Monte Carlo model is presented that considers the effects of spacecraft orbital sampling on the inferred distribution of magnetic flux ropes, generated through magnetic reconnection in the magnetotail current sheet. When generalized, the model allows the determination of the number of orbits required to constrain the underlying population of structures: It is able to quantify this as a function of the physical parameters of the structures (e.g. Read More

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http://dx.doi.org/10.1029/2018JA025958DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6472645PMC
December 2018

Compositional Variations in the Vicinity of the Lunar Crust-Mantle Interface From Moon Mineralogy Mapper Data.

J Geophys Res Planets 2018 Dec 27;123(12):3220-3237. Epub 2018 Dec 27.

Faculty of Science, Vrije Universiteit Amsterdam Amsterdam The Netherlands.

Moon Mineralogy Mapper spectroscopic data were used to investigate the mineralogy of a selection of impact craters' central peaks or peak rings, in order to characterize the lunar crust-mantle interface, and assess its lateral and vertical heterogeneity. The depth of origin of the craters' central peaks or peak rings was calculated using empirical equations, and compared to Gravity Recovery and Interior Laboratory crustal thickness models to select craters tapping within +10/-20 km of the crust-mantle interface. Our results show that plagioclase is widely detected, including in craters allegedly sampling lower crustal to mantle material, except in central peaks where Low-Calcium Pyroxene was detected. Read More

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http://dx.doi.org/10.1029/2018JE005744DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6472644PMC
December 2018

The Melting Column as a Filter of Mantle Trace-Element Heterogeneity.

Geochem Geophys Geosyst 2018 Dec 28;19(12):4694-4721. Epub 2018 Dec 28.

Bullard Laboratories, Department of Earth Sciences University of Cambridge Cambridge UK.

The observed variability of trace-element concentration in basaltic lavas and melt inclusions carries information about heterogeneity in the mantle. The difficulty is to disentangle the contributions of source heterogeneity (i.e. Read More

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http://doi.wiley.com/10.1029/2018GC007880
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http://dx.doi.org/10.1029/2018GC007880DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6472646PMC
December 2018

Scanning Microwave Microscopy of Vital Mitochondria in Respiration Buffer.

IEEE MTTS Int Microw Symp 2018 Jun 20;2018:115-118. Epub 2018 Aug 20.

Integrated Nanosystems Research Facility, University of California, Irvine, Irvine, CA 92697, USA.

We demonstrate imaging using scanning microwave microscopy (SMM) of vital mitochondria in respiration buffer. The mitochondria are isolated from cultured HeLa cells and tethered to a solid graphene support. The mitochondria are kept vital (alive) using a respiration buffer, which provides nutrients to sustain the Krebs cycle. Read More

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http://dx.doi.org/10.1109/MWSYM.2018.8439645DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6469850PMC

Fast Diffusion of Ultrarelativistic Electrons in the Outer Radiation Belt: 17 March 2015 Storm Event.

Geophys Res Lett 2018 Oct 25;45(20):10874-10882. Epub 2018 Oct 25.

Department of Physics University of Minnesota, Twin Cities Minneapolis MN USA.

Inward radial diffusion driven by ULF waves has long been known to be capable of accelerating radiation belt electrons to very high energies within the heart of the belts, but more recent work has shown that radial diffusion values can be highly event-specific, and mean values or empirical models may not capture the full significance of radial diffusion to acceleration events. Here we present an event of fast inward radial diffusion, occurring during a period following the geomagnetic storm of 17 March 2015. Ultrarelativistic electrons up to ∼8 MeV are accelerated in the absence of intense higher-frequency plasma waves, indicating an acceleration event in the core of the outer belt driven primarily or entirely by ULF wave-driven diffusion. Read More

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http://dx.doi.org/10.1029/2018GL079786DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6472651PMC
October 2018

An in-situ approach for preparing atom probe tomography specimens by xenon plasma-focussed ion beam.

Ultramicroscopy 2019 Apr 12;202:121-127. Epub 2019 Apr 12.

SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, UK.

A method for the rapid preparation of atom probe tomography (APT) needles using a xenon plasma-focussed ion beam (FIB) instrument is presented and demonstrated on a test sample of Ti-6Al-4V alloy. The method requires significantly less operator input than the standard lift-out protocol, is site-specific and produces needles with minimal ion-beam damage; electron microscopy indicated the needle's surface amorphised/oxidised region to be less than 2 nm thick. The resulting needles were routinely analysable by APT, confirming the expected microstructure and showing negligible Xe contamination. Read More

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http://dx.doi.org/10.1016/j.ultramic.2019.04.005DOI Listing

Thermofield theory for finite-temperature quantum chemistry.

J Chem Phys 2019 Apr;150(15):154109

Department of Physics and Astronomy, Rice University, Houston, Texas 77005-1892, USA.

Thermofield dynamics has proven to be a very useful theory in high-energy physics, particularly since it permits the treatment of both time- and temperature-dependence on an equal footing. We here show that it also has an excellent potential for studying thermal properties of electronic systems in physics and chemistry. We describe a general framework for constructing finite temperature correlated wave function methods typical of ground state methods. Read More

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http://dx.doi.org/10.1063/1.5089560DOI Listing

Bulk viscosity of CO from Rayleigh-Brillouin light scattering spectroscopy at 532 nm.

J Chem Phys 2019 Apr;150(15):154502

Laboratory for Aero and Hydrodynamics, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Leeghwaterstraat 29, 2628CB Delft, The Netherlands.

Rayleigh-Brillouin scattering spectra of CO were measured at pressures ranging from 0.5 to 4 bars and temperatures from 257 to 355 K using green laser light (wavelength 532 nm, scattering angle of 55.7°). Read More

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http://dx.doi.org/10.1063/1.5093541DOI Listing

On the numerical solution of the exact factorization equations.

J Chem Phys 2019 Apr;150(15):154112

Department of Physics and Astronomy, Hunter College and the City University of New York, 695 Park Avenue, New York, New York 10065, USA.

The exact factorization (EF) approach to coupled electron-ion dynamics recasts the time-dependent molecular Schrödinger equation as two coupled equations, one for the nuclear wavefunction and one for the conditional electronic wavefunction. The potentials appearing in these equations have provided insight into non-adiabatic processes, and new practical non-adiabatic dynamics methods have been formulated starting from these equations. Here, we provide a first demonstration of a self-consistent solution of the exact equations, with a preliminary analysis of their stability and convergence properties. Read More

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http://dx.doi.org/10.1063/1.5090802DOI Listing

Amino acid conformations control the morphological and chiral features of the self-assembled peptide nanostructures: Young investigators perspective.

J Colloid Interface Sci 2019 Apr 6;548:244-254. Epub 2019 Apr 6.

State Key Laboratory of Heavy Oil Processing and Centre for Bioengineering and Biotechnology, China University of Petroleum (East China), 66 Changjiang West Road, Qingdao, China. Electronic address:

Hypothesis: A variety of nanostructures with different chiral features can be self-assembled from short peptides with highly similar sequences. We hypothesize that these supramolecular nanostructures are ruled by the constituent amino acid residues which adopt their conformations under the influence of intra-/inter-molecular interactions during peptide self-assembly.

Approach: Through reviewing recent advances in the self-assembly of short peptides and focusing on the relationship between amino acid conformations, peptide secondary structures and intra-/inter-molecular interactions within the supramolecular architectures, we aim to rationalize the complex interactive processes involved in the self-assembly of short, designed peptides. Read More

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http://dx.doi.org/10.1016/j.jcis.2019.04.019DOI Listing

Neuroimaging Evidence for Right Orbitofrontal Cortex Differences in Adolescents With Emotional and Behavioral Dysregulation.

J Am Acad Child Adolesc Psychiatry 2019 Apr 17. Epub 2019 Apr 17.

University of Vermont, Burlington; Vermont Center on Behavior and Health, University of Vermont, Burlington.

Objective: To characterize the structural and functional neurobiology of a large group of adolescents exhibiting a behaviorally and emotionally dysregulated phenotype.

Method: Age 14 adolescents from the IMAGEN study were investigated. Latent class analysis (LCA) on the Strengths and Difficulties Questionnaire (SDQ) was used to identify a class of individuals with elevated behavioral and emotional difficulties ("dysregulated"; n=233) who were compared to a matched sample from a low symptom class (controls, n=233). Read More

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https://linkinghub.elsevier.com/retrieve/pii/S08908567193026
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http://dx.doi.org/10.1016/j.jaac.2019.01.021DOI Listing
April 2019
1 Read

4D flow imaging with 2D-selective excitation.

Magn Reson Med 2019 Apr 19. Epub 2019 Apr 19.

Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany.

Purpose: 4D flow MRI permits to quantify non-invasively time-dependent velocity vector fields, but it demands long acquisition times. 2D-selective excitation allows to accelerate the acquisition by reducing the FOV in both phase encoding directions. In this study, we investigate 2D-selective excitation with reduced FOV imaging for fast 4D flow imaging while obtaining correct velocity quantification. Read More

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http://dx.doi.org/10.1002/mrm.27769DOI Listing

One Precursor but Two Types of Graphene Nanoribbons: On-Surface Transformations of 10,10'-Dichloro-9,9'-bianthryl on Ag(111).

J Phys Chem C Nanomater Interfaces 2019 Apr 25;123(14):8892-8901. Epub 2019 Mar 25.

Debye Institute for Nanomaterials Science, Utrecht University, PO Box 80000, 3508 TA Utrecht, The Netherlands.

On-surface synthesis has emerged in the last decade as a method to create graphene nanoribbons (GNRs) with atomic precision. The underlying premise of this bottom-up strategy is that precursor molecules undergo a well-defined sequence of inter- and intramolecular reactions, leading to the formation of a single product. As such, the structure of the GNR is encoded in the precursors. Read More

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http://dx.doi.org/10.1021/acs.jpcc.8b12209DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6463537PMC
April 2019
1 Read

The cosmic drama that helped to build the Milky Way.

Authors:

Nature 2019 Apr;568(7753):436

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http://dx.doi.org/10.1038/d41586-019-01226-2DOI Listing

Forging tools for refining predicted protein structures.

Proc Natl Acad Sci U S A 2019 Apr 18. Epub 2019 Apr 18.

Center for Theoretical Biological Physics, Rice University, Houston, TX 77030;

Refining predicted protein structures with all-atom molecular dynamics simulations is one route to producing, entirely by computational means, structural models of proteins that rival in quality those that are determined by X-ray diffraction experiments. Slow rearrangements within the compact folded state, however, make routine refinement of predicted structures by unrestrained simulations infeasible. In this work, we draw inspiration from the fields of metallurgy and blacksmithing, where practitioners have worked out practical means of controlling equilibration by mechanically deforming their samples. Read More

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http://www.pnas.org/lookup/doi/10.1073/pnas.1900778116
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http://dx.doi.org/10.1073/pnas.1900778116DOI Listing
April 2019
1 Read

Carrier lifetimes of >1 μs in Sn-Pb perovskites enable efficient all-perovskite tandem solar cells.

Science 2019 Apr 18. Epub 2019 Apr 18.

National Renewable Energy Laboratory, Golden, CO 80401, USA.

All-perovskite-based polycrystalline thin-film tandem solar cells have the potential to deliver efficiencies of > 30%. However, the performance of all-perovskite-based tandem devices have been limited by the lack of high-efficiency, low-band-gap Sn-Pb mixed-perovskite solar cells (PSCs). We report on using guanidinium thiocyanate (GuaSCN) to dramatically improve the structural and optoelectronic properties of Sn-Pb mixed, low-band-gap (~1. Read More

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http://www.sciencemag.org/lookup/doi/10.1126/science.aav7911
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http://dx.doi.org/10.1126/science.aav7911DOI Listing
April 2019
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Controlled Hydrothermal Growth and Li Storage Performance of 1D VO Nanobelts with Variable Vanadium Valence.

Nanomaterials (Basel) 2019 Apr 17;9(4). Epub 2019 Apr 17.

Department of Physics, School of Physics and Astronomy, Yunnan University, Kunming 650504, China.

One-dimensional (1D) vanadium oxide nanobelts (VO NBs) with variable V valence, which include VO·HO NBs, VO (B) NBs and VO NBs, were prepared by a simple hydrothermal treatment under a controllable reductive environment and a following calcination process. Electrochemical measurements showed that all these VO NBs can be adopted as promising cathode active materials for lithium ion batteries (LIBs). The Li storage mechanism, charge transfer property at the solid/electrolyte interface and Li diffusion characteristics for these as-synthesized 1D VO NBs were systematically analyzed and compared with each other. Read More

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http://dx.doi.org/10.3390/nano9040624DOI Listing

Classical stochastic systems with fast-switching environments: Reduced master equations, their interpretation, and limits of validity.

Phys Rev E 2019 Mar;99(3-1):032121

Theoretical Physics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, United Kingdom.

We study classical Markovian stochastic systems with discrete states, coupled to randomly switching external environments. For fast environmental processes we derive reduced dynamics for the system itself, focusing on corrections to the adiabatic limit of infinite timescale separation. We show that this can lead to master equations with bursting events. Read More

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http://dx.doi.org/10.1103/PhysRevE.99.032121DOI Listing

Experimental and numerical observation of dark and bright breathers in the band gap of a diatomic electrical lattice.

Phys Rev E 2019 Mar;99(3-1):032206

Department of Mathematics and Statistics, University of Massachusetts, Amherst, Massachusetts 01003, USA.

We observe dark and bright intrinsic localized modes (ILMs), also known as discrete breathers, experimentally and numerically in a diatomic-like electrical lattice. The experimental generation of dark ILMs by driving a dissipative lattice with spatially homogenous amplitude is, to our knowledge, unprecedented. In addition, the experimental manifestation of bright breathers within the band gap is also novel in this system. Read More

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http://dx.doi.org/10.1103/PhysRevE.99.032206DOI Listing

Twist-bend coupling and the statistical mechanics of the twistable wormlike-chain model of DNA: Perturbation theory and beyond.

Phys Rev E 2019 Mar;99(3-1):032414

Department of Physics and Astronomy, and Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, USA.

The simplest model of DNA mechanics describes the double helix as a continuous rod with twist and bend elasticity. Recent work has discussed the relevance of a little-studied coupling G between twisting and bending, known to arise from the groove asymmetry of the DNA double helix. Here the effect of G on the statistical mechanics of long DNA molecules subject to applied forces and torques is investigated. Read More

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http://dx.doi.org/10.1103/PhysRevE.99.032414DOI Listing

Diffusion of size bidisperse spheres in dense granular shear flow.

Phys Rev E 2019 Mar;99(3-1):032902

Institute of Process Equipment, Zhejiang University, Hangzhou 310027, China.

Diffusion is an important particle behavior in granular flow. Although granular diffusion has been studied for decades, the diffusion of size bidisperse particles has not been well understood. In this paper, discrete element method simulations with the Lees-Edwards boundary condition are performed to quantify the relation between the diffusion coefficient (D) and flow parameters for size bidisperse spheres in dense granular flow. Read More

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http://dx.doi.org/10.1103/PhysRevE.99.032902DOI Listing

Analog cosmology with two-fluid systems in a strong gradient magnetic field.

Phys Rev E 2019 Mar;99(3-1):031101

School of Mathematical Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom.

We propose an experiment combining fluid dynamics and strong magnetic field physics to simulate cosmological scenarios. Our proposed system consists of two immiscible, weakly magnetized fluids moved through a strong gradient magnetic field. The diamagnetic and paramagnetic forces thus generated amount to a time-dependent effective gravity, which allows us to precisely control the propagation speed of interface waves. Read More

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http://dx.doi.org/10.1103/PhysRevE.99.031101DOI Listing

Reply to "Comment on 'Lagrangian formulation and symmetrical description of liquid dynamics' ".

Authors:
K Trachenko

Phys Rev E 2019 Mar;99(3-2):036103

School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom.

We make three remarks in reply to the comment by Bryk, Duviryak, and Mryglod (BDM) [Bryk, Duviryak, and Mryglod, Phys. Rev. E 99, 036102 (2019)10. Read More

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http://dx.doi.org/10.1103/PhysRevE.99.036103DOI Listing

Exact decomposition of homoclinic orbit actions in chaotic systems: Information reduction.

Phys Rev E 2019 Mar;99(3-1):032212

Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164-2814, USA.

Homoclinic and heteroclinic orbits provide a skeleton of the full dynamics of a chaotic dynamical system and are the foundation of semiclassical sums for quantum wave packets, coherent states, and transport quantities. Here, the homoclinic orbits are organized according to the complexity of their phase-space excursions, and exact relations are derived expressing the relative classical actions of complicated orbits as linear combinations of those with simpler excursions plus phase-space cell areas bounded by stable and unstable manifolds. The total number of homoclinic orbits increases exponentially with excursion complexity, and the corresponding cell areas decrease exponentially in size as well. Read More

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https://link.aps.org/doi/10.1103/PhysRevE.99.032212
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http://dx.doi.org/10.1103/PhysRevE.99.032212DOI Listing
March 2019
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Closure for the Ornstein-Zernike equation with pressure and free energy consistency.

Phys Rev E 2019 Mar;99(3-1):032130

Department of Physics and Astronomy, California State University Northridge, 18111 Nordhoff Street, Northridge, California 91330, USA.

The Ornstein-Zernike (OZ) integral equation theory is a powerful approach to simple liquids due to its low computational cost and the fact that, when combined with an appropriate closure equation, the theory is thermodynamically complete. However, approximate closures proposed to date exhibit pressure or free energy inconsistencies that produce inaccurate or ambiguous results, limiting the usefulness of the Ornstein-Zernike approach. To address this problem, we combine methods to enforce both pressure and free energy consistency to create a new closure approximation and test it for a single-component Lennard-Jones fluid. Read More

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http://dx.doi.org/10.1103/PhysRevE.99.032130DOI Listing

Nonequilibrium phase transition in an open quantum spin system with long-range interaction.

Phys Rev E 2019 Mar;99(3-1):032131

CCSS, CTP and Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea.

We investigate a nonequilibrium phase transition in a dissipative and coherent quantum spin system using the quantum Langevin equation and mean-field theory. Recently, the quantum contact process (QCP) was theoretically investigated using the Rydberg antiblockade effect, in particular, when the Rydberg atoms were excited in s states so that their interactions were regarded as being between the nearest neighbors. However, when the atoms are excited to d states, the dipole-dipole interactions become effective, and long-range interactions must be considered. Read More

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http://dx.doi.org/10.1103/PhysRevE.99.032131DOI Listing

Resolution of the sign problem for a frustrated triplet of spins.

Authors:
Itay Hen

Phys Rev E 2019 Mar;99(3-1):033306

Information Sciences Institute, University of Southern California, Marina del Rey, California 90292, USA and Department of Physics and Astronomy, Center for Quantum Information Science & Technology, University of Southern California, Los Angeles, California 90089, USA.

We propose a mechanism for solving the "negative sign problem"-the inability to assign non-negative weights to quantum Monte Carlo configurations-for a toy model consisting of a frustrated triplet of spin-1/2 particles interacting antiferromagnetically. The introduced technique is based on the systematic grouping of the weights of the recently developed off-diagonal series expansion of the canonical partition function [Phys. Rev. Read More

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http://dx.doi.org/10.1103/PhysRevE.99.033306DOI Listing

Characteristic times in the standard map.

Phys Rev E 2019 Mar;99(3-1):032203

Research Center for Astronomy, Academy of Athens Soranou Efesiou 4, GR-115 27 Athens, Greece.

We study and compare three characteristic times of the standard map: the Lyapunov time t_{L}, the Poincaré recurrence time t_{r}, and the stickiness (or escape) time t_{st}. The Lyapunov time is the inverse of the Lyapunov characteristic number (L) and in general is quite small. We find empirical relations for the L as a function of the nonlinearity parameter K and of the chaotic area A. Read More

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http://dx.doi.org/10.1103/PhysRevE.99.032203DOI Listing

Model reduction methods for population dynamics with fast-switching environments: Reduced master equations, stochastic differential equations, and applications.

Phys Rev E 2019 Mar;99(3-1):032122

Theoretical Physics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, United Kingdom.

We study stochastic population dynamics coupled to fast external environments and combine expansions in the inverse switching rate of the environment and a Kramers-Moyal expansion in the inverse size of the population. This leads to a series of approximation schemes, capturing both intrinsic and environmental noise. These methods provide a means of efficient simulation and we show how they can be used to obtain analytical results for the fluctuations of population dynamics in switching environments. Read More

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http://dx.doi.org/10.1103/PhysRevE.99.032122DOI Listing

Machine learning of phase transitions in the percolation and XY models.

Phys Rev E 2019 Mar;99(3-1):032142

C. N. Yang Institute for Theoretical Physics and Department of Physics and Astronomy, State University of New York at Stony Brook, Stony Brook, New York 11794-3840, USA.

In this paper, we apply machine learning methods to study phase transitions in certain statistical mechanical models on the two-dimensional lattices, whose transitions involve nonlocal or topological properties, including site and bond percolations, the XY model, and the generalized XY model. We find that using just one hidden layer in a fully connected neural network, the percolation transition can be learned and the data collapse by using the average output layer gives correct estimate of the critical exponent ν. We also study the Berezinskii-Kosterlitz-Thouless transition, which involves binding and unbinding of topological defects, vortices and antivortices, in the classical XY model. Read More

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http://dx.doi.org/10.1103/PhysRevE.99.032142DOI Listing

Porous iron material for TcO- and ReO- sequestration from groundwater under ambient oxic conditions.

J Hazard Mater 2019 Apr 9;374:177-185. Epub 2019 Apr 9.

Hӧganäs Environmental Solutions LLC, Cary, NC, 27513, USA.

Technetium-99 (Tc) is a major contaminant at nuclear power plants and several US Department of Energy sites. Its most common aqueous species, pertechnetate (TcO), is very mobile in the environment, and currently there are no effective technologies for its sequestration. In this work, a porous iron (pFe) material was investigated for TcO and perrhenate (ReO) sequestration from artificial groundwater. Read More

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https://linkinghub.elsevier.com/retrieve/pii/S03043894193045
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http://dx.doi.org/10.1016/j.jhazmat.2019.04.030DOI Listing
April 2019
2 Reads

Molecular machinery providing copper bioavailability for spermatozoa along the epididymial tubule in mouse.

Biol Reprod 2019 Feb 19. Epub 2019 Feb 19.

Department of Genetics and Evolution, Institute of Zoology and Biomedical Research, Jagiellonian University, Kraków, Poland.

Progressive functional maturation of spermatozoa is completed during the transit of these cells through the epididymis, a tubule structure connecting a testicle to a vas deferens. Epididymal epithelial cells by means of their secretory and absorptive functions determine a highly specialized luminal microenvironment containing multiple organic and inorganic components. The latter include copper ions, which due to their redox properties are indispensable for critical homeostatic processes occurring in spermatozoa floating in different part of epididymis but can be potentially toxic. Read More

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https://academic.oup.com/biolreprod/advance-article/doi/10.1
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http://dx.doi.org/10.1093/biolre/ioz028DOI Listing
February 2019
2 Reads

Computational study of the mixed B-site perovskite SmBCoO (B = Mn, Fe, Ni, Cu) for next generation solid oxide fuel cell cathodes.

Phys Chem Chem Phys 2019 Apr 18. Epub 2019 Apr 18.

Department of Chemistry, University College London, WC1H 0AJ, London, UK. and School of Chemistry, Cardiff University, Main Building, Park Place, CF10 3AT, Cardiff, UK.

SmCoO3 is a promising perovskite material for the next generation of intermediate temperature solid oxide fuel cells (SOFC), but its potential application is directly linked to, and dependent on, the presence of dopant ions. Doping on the Co-site is suggested to improve the catalytic and electronic properties of this cathode material. Fe, Mn, Ni, and Cu have been proposed as possible dopants and experimental studies have investigated and confirmed the potential of these materials. Read More

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http://dx.doi.org/10.1039/c9cp00995gDOI Listing

Magnetic moment inversion at giant flux jump: dynamical property of critical state in type-II superconductors.

Sci Rep 2019 Apr 17;9(1):6233. Epub 2019 Apr 17.

Institute of Physics, Polish Academy of Sciences, Aleja Lotników 32/46, PL-02668, Warsaw, Poland.

Experimental evidence of tremendous magnetic moment dynamical inversion, from metastable trapping state to the state with essentially the same moment oriented in the opposite direction, appearing during giant flux jump connected to thermomagnetic avalanche process in superconducting YBaCuO single crystal, is presented. Magnetization inversion takes place in the system, without thermal contact between sample and sample holder, with a tremendous stored energy once the avalanche process is completed in quasi-adiabatic conditions. A model of magnetic moment inversion, caused by the jump between two metastable states of superconductor with the same energy storage, is presented and discussed in terms of the critical state with peculiar evolution of the critical-current spatial distribution. Read More

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http://www.nature.com/articles/s41598-019-42699-5
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http://dx.doi.org/10.1038/s41598-019-42699-5DOI Listing
April 2019
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Moon mapper, Sun spotter: the astonishing Thomas Harriot.

Authors:
Georgina Ferry

Nature 2019 Apr;568(7752):311-312

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http://dx.doi.org/10.1038/d41586-019-01174-xDOI Listing

Needle-like structures discovered on positively charged lightning branches.

Nature 2019 Apr 17;568(7752):360-363. Epub 2019 Apr 17.

ASTRON, Netherlands Institute for Radio Astronomy, Dwingeloo, The Netherlands.

Lightning is a dangerous yet poorly understood natural phenomenon. Lightning forms a network of plasma channels propagating away from the initiation point with both positively and negatively charged ends-called positive and negative leaders. Negative leaders propagate in discrete steps, emitting copious radio pulses in the 30-300-megahertz frequency band that can be remotely sensed and imaged with high spatial and temporal resolution. Read More

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http://www.nature.com/articles/s41586-019-1086-6
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http://dx.doi.org/10.1038/s41586-019-1086-6DOI Listing
April 2019
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Tunable spin-state bistability in a spin crossover molecular complex.

J Phys Condens Matter 2019 Apr 17. Epub 2019 Apr 17.

Department of Physics and Astronomy and Center for Materials Research and Analysis, University of Nebraska- Lincoln, Jorgensen Hall, 855 North 16th Str., NE 68588-0299, Lincoln, 68588-0299, UNITED STATES.

The spin crossover (SCO) transitions at both the surface and over the entire volume of the [Fe{H<sub>2</sub>B(pz)<sub>2</sub>}<sub>2</sub>(bipy)] polycrystalline films on Al2O3 substrates have been studied, where pz = pyrazol-1-yl and bipy = 2,2'-bipyridine. For [Fe{H<sub>2</sub>B(pz)<sub>2</sub>}<sub>2</sub>(bipy)] films of hundreds of nm thick, magnetometry and x-ray absorption spectroscopy measurements show thermal hysteresis in the SCO transition with temperature, although the transition in bulk [Fe{H2B(pz)2}2(bipy)] occurs in a non-hysteretic fashion at 157 K. While the size of the crystallites in those films are similar, the hysteresis becomes more prominent in thinner films, indicating a significant effect of the [Fe{H<sub>2</sub>B(pz)<sub>2</sub>}<sub>2</sub>(bipy)]/Al<sub>2</sub>O<sub>3</sub> interface. Read More

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http://iopscience.iop.org/article/10.1088/1361-648X/ab1a7d
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http://dx.doi.org/10.1088/1361-648X/ab1a7dDOI Listing
April 2019
1 Read
2.346 Impact Factor

Extracellular DNA Provides Structural Integrity to a Micrococcus luteus Biofilm.

Langmuir 2019 Apr 17. Epub 2019 Apr 17.

Department of Physics and Astronomy , The University of Sheffield , Hounsfield Road , Sheffield S3 7RH , U.K.

Force spectroscopy was used to show that extracellular DNA (eDNA) has a pre-eminent structural role in a biofilm. The adhesive behavior of extracellular polymeric substances to poly(ethylene terephthalate), a model hydrophobic surface, was measured in response to their degradation by hydrolytic enzymes known for their biofilm dispersion potential: DNaseI, protease, cellulase, and mannanase. Only treatment with DNaseI significantly decreased the adhesive force of the model bacterium Micrococcus luteus with the surface, and furthermore this treatment almost completely eliminated any components of the biofilm maintaining the adhesion, establishing a key structural role for eDNA. Read More

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http://dx.doi.org/10.1021/acs.langmuir.9b00297DOI Listing

Mineralogy, Structure, and Habitability of Carbon-Enriched Rocky Exoplanets: A Laboratory Approach.

Astrobiology 2019 Apr 17. Epub 2019 Apr 17.

2 Department of Earth Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands.

Carbon-enriched rocky exoplanets have been proposed to occur around dwarf stars as well as binary stars, white dwarfs, and pulsars. However, the mineralogical make up of such planets is poorly constrained. We performed high-pressure high-temperature laboratory experiments ( = 1-2 GPa,  = 1523-1823 K) on chemical mixtures representative of C-enriched rocky exoplanets based on calculations of protoplanetary disk compositions. Read More

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http://dx.doi.org/10.1089/ast.2018.1930DOI Listing

Silicene-supported TiO nanostructures: a theoretical study of electronic and optical properties.

Phys Chem Chem Phys 2019 Apr 17. Epub 2019 Apr 17.

Department of Physics, Michigan Technological University, Houghton, MI 49931, USA.

Titania (TiO2) is a material of choice for energy-related applications, such as photovoltaics and photocatalysis. The presence of a large band gap and fast electron-hole recombination occurring in the lattice significantly reduce the material's quantum efficiency, and therefore limit industrial-scale applications. In this article, we investigate whether silicene can be a viable substrate for TiO2 nanostructures in photocatalytic applications. Read More

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http://xlink.rsc.org/?DOI=C9CP00894B
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http://dx.doi.org/10.1039/c9cp00894bDOI Listing
April 2019
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Porous Silicon as a Platform for Radiation Theranostics Together with a Novel RIB-Based Radiolanthanoid.

Contrast Media Mol Imaging 2019 12;2019:3728563. Epub 2019 Mar 12.

Department of Chemistry, University of Helsinki, FI-00014 Helsinki, Finland.

Mesoporous silicon (PSi) is biocompatible and tailorable material with high potential in drug delivery applications. Here, we report of an evaluation of PSi as a carrier platform for theranostics by delivering a radioactive ion beam- (RIB-) based radioactive lanthanoid into tumors in a mouse model of prostate carcinoma. Thermally hydrocarbonized porous silicon (THCPSi) wafers were implanted with Dy at the facility for radioactive ion beams ISOLDE located at CERN, and the resulting [Dy]THCPSi was postprocessed into particles. Read More

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http://dx.doi.org/10.1155/2019/3728563DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6434306PMC

Generation of spatiotemporally tailored terahertz wavepackets by nonlinear metasurfaces.

Nat Commun 2019 Apr 16;10(1):1778. Epub 2019 Apr 16.

Department of Physical Electronics, School of Electrical Engineering, Tel-Aviv University, 6997801, Tel Aviv, Israel.

The past two decades have witnessed an ever-growing number of emerging applications that utilize terahertz (THz) waves, ranging from advanced biomedical imaging, through novel security applications, fast wireless communications, and new abilities to study and control matter in all of its phases. The development and deployment of these emerging technologies is however held back, due to a substantial lack of simple methods for efficient generation, detection and manipulation of THz waves. Recently it was shown that uniform nonlinear metasurfaces can efficiently generate broadband single-cycle THz pulses. Read More

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http://dx.doi.org/10.1038/s41467-019-09811-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6467996PMC