46,159 results match your criteria Astronomy Reports[Journal]

Energy Conversion in Polyelectrolyte Hydrogels.

ACS Macro Lett 2015 Aug 3;4(8):857-861. Epub 2015 Aug 3.

Department of Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, United States.

Using extensive molecular dynamics simulations of polyelectrolyte hydrogels we demonstrate that, on deformation, these hydrogels adjust their deformed state predominantly by altering electrostatic interactions between their charged groups rather than excluded-volume and bond energies. On deformation, due to the hydrogel's inherent tendency to preserve electroneutrality in its interior, the translational entropy of counterions decreases and the total electrostatic energy becomes more attractive. This result is valid for a wide range of compression ratios and Bjerrum lengths. Read More

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Fast Nanorod Diffusion through Entangled Polymer Melts.

ACS Macro Lett 2015 Sep 20;4(9):952-956. Epub 2015 Aug 20.

Department of Physics and Astronomy, University of Sheffield, Sheffield, United Kingdom.

Nanorod diffusion in polymer melts is faster than predicted by the continuum model (CM). Rutherford backscattering spectrometry is used to measure the concentration profile of titanium dioxide (TiO) nanorods ( = 43 nm, = 5 nm) in a polystyrene (PS) matrix having molecular weights () from 9 to 2000 kDa. In the entangled regime, the tracer diffusion coefficients () of TiO decrease as the , whereas the CM predicts ∼ using the measured zero-shear viscosity of TiO(1 vol %): PS() blends. Read More

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September 2015

Anisotropic Polymer Conformations in Aligned SWCNT/PS Nanocomposites.

ACS Macro Lett 2015 Sep 13;4(9):916-920. Epub 2015 Aug 13.

Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia 19104-6272, United States.

Polymer radii of gyration in isotropic single-walled carbon nanotube (SWCNT)/polymer nanocomposites were previously found to increase with increasing SWCNT concentration. Here, the SWCNTs in nanocomposites were aligned by melt fiber spinning, and the polymer chain conformations were found to be anisotropic. Using SAXS and SANS, the anisotropic SWCNT meshes were found to have smaller mesh sizes in the direction perpendicular to the alignment direction than along the alignment direction. Read More

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September 2015

Polymer Looping Is Controlled by Macromolecular Crowding, Spatial Confinement, and Chain Stiffness.

ACS Macro Lett 2015 Feb 21;4(2):202-206. Epub 2015 Jan 21.

Institute for Physics and Astronomy, University of Potsdam, 14476 Potsdam-Golm, Germany.

We study by extensive computer simulations the looping characteristics of linear polymers with varying persistence length inside a spherical cavity in the presence of macromolecular crowding. For stiff chains, the looping probability and looping time reveal wildly oscillating patterns as functions of the chain length. The effects of crowding differ dramatically for flexible versus stiff polymers. Read More

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February 2015

Plastic Deformation Mechanisms of Semicrystalline and Amorphous Polymers.

ACS Macro Lett 2015 Feb 14;4(2):147-150. Epub 2015 Jan 14.

Université Grenoble Alpes, UJF Liphy, F38041 Grenoble, France.

We use large-scale molecular dynamics simulations to investigate plastic deformation of semicrystalline polymers with randomly nucleated crystallites. The strain-softening regime is dominated by deformation of crystallites via reorientation of chain-folded lamellae toward the tensile axis, fragmentation of largest crystalline domains, and a partial loss of crystallinity. The strain-hardening regime coincides with unfolding of chains and recrystallization as a result of strain-induced chain alignment. Read More

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February 2015

σ Phase Formed in Conformationally Asymmetric AB-Type Block Copolymers.

ACS Macro Lett 2014 Sep 2;3(9):906-910. Epub 2014 Sep 2.

Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, Canada L8S 4M1.

The stability of various spherical phases formed in conformationally asymmetric AB diblock and architecture asymmetric AB miktoarm block copolymers is investigated using self-consistent field theory. Both the conformational and architecture asymmetries are unified into a parameter of conformationally asymmetric degree, ε. We find that a complex spherical phase, the σ phase, becomes stable and its phase region expands between bcc and hexagonal phases as increasing ε. Read More

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September 2014

Fast Polymer Diffusion through Nanocomposites with Anisotropic Particles.

ACS Macro Lett 2014 Sep 22;3(9):886-891. Epub 2014 Aug 22.

Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States.

Polymer nanocomposites (PNCs) have characteristic length scales associated with both the nanoparticles (i.e., size and interparticle distance) and the polymer molecules (i. Read More

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September 2014

Reply to "Marine abundance and its prehistoric past in the Baltic".

Nat Commun 2022 May 20;13(1):2824. Epub 2022 May 20.

School of Geography, Politics and Sociology, Newcastle University, Newcastle upon Tyne, UK.

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Machine learning-based event recognition in SiFi Compton camera imaging for proton therapy monitoring.

Phys Med Biol 2022 May 20. Epub 2022 May 20.

Faculty of Physics, Astronomy and Applied Computer Science, Jagiellonian University in Krakow, ul. prof. Stanisława Łojasiewicza 11, Krakow, 30-348, POLAND.

Objective: Online monitoring of dose distribution in proton therapy is currently being investigated with the detection of prompt gamma (PG) radiation emitted from a patient during irradiation. The SiPM and scintillation Fiber based Compton Camera (SiFi-CC) setup is being developed for this aim.

Approach: A machine learning approach to recognize Compton events is proposed, reconstructing the PG emission profile during proton therapy. Read More

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Phage delivered CRISPR-Cas system to combat multidrug-resistant pathogens in gut microbiome.

Biomed Pharmacother 2022 May 17;151:113122. Epub 2022 May 17.

KIIT School of Biotechnology, KIIT University, Bhubaneswar 751024, Odisha, India. Electronic address:

The Host-microbiome interactions that exist inside the gut microbiota operate in a synergistic and abnormal manner. Additionally, the normal homeostasis and functioning of gut microbiota are frequently disrupted by the intervention of Multi-Drug Resistant (MDR) pathogens. CRISPR-Cas (CRISPR-associated protein with clustered regularly interspersed short palindromic repeats) recognized as a prokaryotic immune system has emerged as an effective genome-editing tool to edit and delete specific microbial genes for the expulsion of bacteria through bactericidal action. Read More

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Structural features of interfacially adsorbed acyl-l-carnitines.

J Colloid Interface Sci 2022 May 7;623:368-377. Epub 2022 May 7.

Biological Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK. Electronic address:

Hypothesis: Acyl-l-carnitines (CLCs) are potentially important as biosurfactants in drug delivery and tissue engineering due to their good biocompatibility. However, little is currently known about the basic interfacial behavior underlying their technological applications. Following our previous characterization of their solution aggregation and adsorption at the air/water interface, this work examines how they adsorb at the hydrophilic solid/liquid interface. Read More

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Copper(I)-Pyrazolate Complexes as Solid-State Phosphors: Deep-Blue Emission through a Remote Steric Effect.

J Am Chem Soc 2022 May 20. Epub 2022 May 20.

Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United States.

We describe a novel manifestation of rigidochromic behavior in a series of tetranuclear Cu(I)-pyrazolate (Cupz) macrocycles, with implications for solid-state luminescence at deep-blue wavelengths (<460 nm). The Cupz emissions are remarkably sensitive to structural effects far from the luminescent core: when 3,5-di--butylpyrazoles are used as bridging ligands, adding a C4 substituent can induce a blue shift of more than 100 nm. X-ray crystal and computational analyses reveal that C4 units influence the conformational behavior of adjacent -butyl groups, with a subsequent impact on the global conformation of the Cupz complex. Read More

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Constraining the ^{30}P(p, γ)^{31}S Reaction Rate in ONe Novae via the Weak, Low-Energy, β-Delayed Proton Decay of ^{31}Cl.

Phys Rev Lett 2022 May;128(18):182701

Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA.

The ^{30}P(p,γ)^{31}S reaction plays an important role in understanding the nucleosynthesis of A≥30 nuclides in oxygen-neon novae. The Gaseous Detector with Germanium Tagging was used to measure ^{31}Cl β-delayed proton decay through the key J^{π}=3/2^{+}, 260-keV resonance. The intensity I_{βp}^{260}=8. Read More

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Quantum Metrological Power of Continuous-Variable Quantum Networks.

Phys Rev Lett 2022 May;128(18):180503

Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois 60637, USA.

We investigate the quantum metrological power of typical continuous-variable (CV) quantum networks. Particularly, we show that most CV quantum networks provide an entanglement to quantum states in distant nodes that enables one to achieve the Heisenberg scaling in the number of modes for distributed quantum displacement sensing, which cannot be attained using an unentangled probe state. Notably, our scheme only requires local operations and measurements after generating an entangled probe using the quantum network. Read More

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Electron Spin Resonance of the Interacting Spinon Liquid.

Phys Rev Lett 2022 May;128(18):187202

Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, USA.

We report experimental verification of the recently predicted collective modes of spinons, stabilized by backscattering interaction, in a model quantum spin chain material. We exploit the unique geometry of uniform Dzyaloshinskii-Moriya interactions in K_{2}CuSO_{4}Br_{2} to measure the interaction-induced splitting between the two components of the electron spin resonance (ESR) response doublet. From that we directly determine the magnitude of the "marginally irrelevant" backscattering interaction between spinons for the first time. Read More

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Regulation of Alfvén Eigenmodes by Microturbulence in Fusion Plasmas.

Phys Rev Lett 2022 May;128(18):185001

College of Engineering, University of Wisconsin, Madison, Wisconsin 53706, USA.

Global gyrokinetic simulations of mesoscale reversed shear Alfven eigenmodes (RSAE) excited by energetic particles (EP) in fusion plasmas find that RSAE amplitude and EP transport are much higher than experimental levels at nonlinear saturation, but quickly diminish to very low levels after the saturation if background microturbulence is artificially suppressed. In contrast, in simulations coupling micro-meso scales, the RSAE amplitude and EP transport decrease drastically at the initial saturation but later increases to the experimental levels in the quasisteady state with bursty dynamics due to regulation by thermal ion temperature gradient (ITG) microturbulence. The quasisteady state EP transport is larger for a stronger microturbulence. Read More

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Trainability of Dissipative Perceptron-Based Quantum Neural Networks.

Phys Rev Lett 2022 May;128(18):180505

Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.

Several architectures have been proposed for quantum neural networks (QNNs), with the goal of efficiently performing machine learning tasks on quantum data. Rigorous scaling results are urgently needed for specific QNN constructions to understand which, if any, will be trainable at a large scale. Here, we analyze the gradient scaling (and hence the trainability) for a recently proposed architecture that we call dissipative QNNs (DQNNs), where the input qubits of each layer are discarded at the layer's output. Read More

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Edge Reconstruction of a Time-Reversal Invariant Insulator: Compressible-Incompressible Stripes.

Phys Rev Lett 2022 May;128(18):186801

School of Physics and Astronomy, Tel Aviv University, Tel Aviv 6997801, Israel.

Two-dimensional (2D) topological electronic insulators are known to give rise to gapless edge modes, which underlie low energy dynamics, including electrical and thermal transport. This has been thoroughly investigated in the context of quantum Hall phases, and time-reversal invariant topological insulators. Here we study the edge of a 2D, topologically trivial insulating phase, as a function of the strength of the electronic interactions and the steepness of the confining potential. Read More

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Channel Coupling Dynamics of Deep-Lying Orbitals in Molecular High-Harmonic Generation.

Phys Rev Lett 2022 May;128(18):183202

Institute of Applied Physics and Computational Mathematics, P.O. Box 8009, Beijing 100088, China.

Investigation on structures in the high-harmonic spectrum has provided profuse information of molecular structure and dynamics in intense laser fields, based on which techniques of molecular ultrafast dynamics imaging have been developed. Combining ab initio calculations and experimental measurements on the high-harmonic spectrum of the CO_{2} molecule, we find a novel dip structure in the low-energy region of the harmonic spectrum which is identified as fingerprints of participation of deeper-lying molecular orbitals in the process and decodes the underlying attosecond multichannel coupling dynamics. Our work sheds new light on the ultrafast dynamics of molecules in intense laser fields. Read More

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Topological Space-Time Crystal.

Yang Peng

Phys Rev Lett 2022 May;128(18):186802

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

We introduce a new class of out-of-equilibrium noninteracting topological phases: the topological space-time crystals. These are time-dependent quantum systems that do not have discrete spatial translation symmetries but instead are invariant under discrete space-time translations. Similar to the Floquet-Bloch systems, the space-time crystals can be described by a frequency-domain-enlarged Hamiltonian, which is used to classify topologically distinct space-time crystals. Read More

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Chemistry of a Light Impurity in a Bose-Einstein Condensate.

Phys Rev Lett 2022 May;128(18):183401

Max-Planck-Institut für Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching, Germany.

Similar to an electron in a solid, an impurity in an atomic Bose-Einstein condensate (BEC) is dressed by excitations from the medium, forming a polaron quasiparticle with modified properties. This impurity can also undergo chemical recombination with atoms from the BEC, a process resonantly enhanced when universal three-body Efimov bound states cross the continuum. To study the interplay between these phenomena, we use a Gaussian state variational method able to describe both Efimov physics and arbitrarily many excitations of the BEC. Read More

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Eigenstate Thermalization Hypothesis and Its Deviations from Random-Matrix Theory beyond the Thermalization Time.

Phys Rev Lett 2022 May;128(18):180601

Department of Physics, University of Osnabrück, D-49076 Osnabrück, Germany.

The eigenstate thermalization hypothesis explains the emergence of the thermodynamic equilibrium in isolated quantum many-body systems by assuming a particular structure of the observable's matrix elements in the energy eigenbasis. Schematically, it postulates that off-diagonal matrix elements are random numbers and the observables can be described by random matrix theory (RMT). To what extent a RMT description applies, more precisely at which energy scale matrix elements of physical operators become truly uncorrelated, is, however, not fully understood. Read More

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Computational investigations on target-site searching and recognition mechanisms by thymine DNA glycosylase during DNA repair process.

Acta Biochim Biophys Sin (Shanghai) 2022 May 25. Epub 2022 May 25.

Key Laboratory of Systems Biomedicine (Ministry of Education), Shanghai Center for Systems Biomedicine, Shanghai Jiao Tong University, Shanghai 200240, China.

DNA glycosylase, as one member of DNA repair machineries, plays an essential role in correcting mismatched/damaged DNA nucleotides by cleaving the N-glycosidic bond between the sugar and target nucleobase through the base excision repair (BER) pathways. Efficient corrections of these DNA lesions are critical for maintaining genome integrity and preventing premature aging and cancers. The target-site searching/recognition mechanisms and the subsequent conformational dynamics of DNA glycosylase, however, remain challenging to be characterized using experimental techniques. Read More

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Electron transport through a (terpyridine)ruthenium metallo-surfactant containing a redox-active aminocatechol derivative.

Dalton Trans 2022 May 20. Epub 2022 May 20.

Department of Chemistry, Wayne State University, Detroit, MI 48202, USA.

Aiming to develop a new class of metallosurfactants with unidirectional electron transfer properties, a (terpyridine) ruthenium complex containing a semiquinone derivative L, namely [Ru(L)(L)Cl]PF (1), was synthesized and structurally characterized as a solid and in solution. The electronic and redox behaviour of 1 was studied experimentally as well as by means of DFT methods, and is indicative of significant orbital mixing and overlap between metal and ligands. The complex forms stable Pockels-Langmuir films at the air-water interface and allows for the formation of thin films onto gold electrodes to prepare nanoscale Au|LB 1|Au junctions for current-voltage (/) analysis. Read More

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Urban hierarchy and spatial diffusion over the innovation life cycle.

R Soc Open Sci 2022 May 4;9(5):211038. Epub 2022 May 4.

ELKH Centre for Economic and Regional Studies, Agglomeration and Social Networks Lendület Research Group, Budapest 1097, Hungary.

Successful innovations achieve large geographical coverage by spreading across settlements and distances. For decades, spatial diffusion has been argued to take place along the urban hierarchy. Yet, the role of geographical distance was difficult to identify in hierarchical diffusion due to missing data on spreading events. Read More

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Long-Range Ionic and Short-Range Hydration Effects Govern Strongly Anisotropic Clay Nanoparticle Interactions.

J Phys Chem C Nanomater Interfaces 2022 May 3;126(18):8143-8151. Epub 2022 May 3.

Thomas Young Centre and London Centre for Nanotechnology, 17-19 Gordon Street, London WC1H 0AH, U.K.

The aggregation of clay particles in aqueous solution is a ubiquitous everyday process of broad environmental and technological importance. However, it is poorly understood at the all-important atomistic level since it depends on a complex and dynamic interplay of solvent-mediated electrostatic, hydrogen bonding, and dispersion interactions. With this in mind, we have performed an extensive set of classical molecular dynamics simulations (included enhanced sampling simulations) on the interactions between model kaolinite nanoparticles in pure and salty water. Read More

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Quantification of the Landscape for Revealing the Underlying Mechanism of Intestinal-Type Gastric Cancer.

Chong Yu Jin Wang

Front Oncol 2022 3;12:853768. Epub 2022 May 3.

Department of Chemistry and of Physics and Astronomy, State University of New York at Stony Brook, Stony Brook, NY, United States.

Gastric cancer is a daunting disease with a tragic impact on global health. It is the fourth most common cancer and has become the second most frequent cause of cancer death in recent times. According to the Lauren classification, gastric cancer can be classified into two types: intestinal and diffuse. Read More

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Evaluation of the Radiation Shielding Properties of a Tellurite Glass System Modified with Sodium Oxide.

Materials (Basel) 2022 Apr 27;15(9). Epub 2022 Apr 27.

Physics Department, Faculty of Science, King Khalid University, Abha 61413, Saudi Arabia.

In this study, the X-ray and gamma attenuation characteristics and optical properties of a synthesized tellurite-phosphate-sodium oxide glass system with a composition of (85 - x)TeO-10PO-xNaO mol% (where x = 15, 20, and 25) were evaluated. The glass systems we re fabricated by our research group using quenching melt fabrication. The shielding parameters of as-synthesized systems, such as the mass attenuation coefficient (MAC), linear attenuation coefficient (LAC), effective atomic number (Z), half-value layer (HVL), tenth value layer (TVL), mean free path (MFP), and effective electron density (N) in a wide energy range between 15 keV and 15 MeV, were estimated using well-known PHY-X/PSD software and recently developed MIKE software. Read More

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Pulse Broadening Effects on Ranging Performance of a Laser Altimeter with Return-to-Zero Pseudorandom Noise Code Modulation.

Sensors (Basel) 2022 Apr 25;22(9). Epub 2022 Apr 25.

Korea Astronomy and Space Science Institute, Daejeon 34055, Korea.

A laser altimeter using code modulation techniques receives a backscattered pulse wider than the transmitted rectangular pulse when scanning a rough or sloped target surface. This leads to degrading the ranging performance in terms of signal-to-noise ratio (SNR) and detection probability. Unlike the pulsed techniques, little work has focused on the pulse broadening effect of the code modulation techniques. Read More

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Monitoring Various Bioactivities at the Molecular, Cellular, Tissue, and Organism Levels via Biological Lasers.

Sensors (Basel) 2022 Apr 20;22(9). Epub 2022 Apr 20.

State Key Laboratory of Advanced Optical Communication Systems and Networks, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China.

The laser is considered one of the greatest inventions of the 20th century. Biolasers employ high signal-to-noise ratio lasing emission rather than regular fluorescence as the sensing signal, directional out-coupling of lasing and excellent biocompatibility. Meanwhile, biolasers can also be micro-sized or smaller lasers with embedded/integrated biological materials. Read More

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