46,230 results match your criteria Astronomy Letters-A Journal Of Astronomy And Space Astrophysics[Journal]


Enhanced Chemical Sensing with Multiorder Coherent Raman Scattering Spectroscopic Dephasing.

Anal Chem 2022 May 27. Epub 2022 May 27.

Interdisciplinary Center for Quantum Information, Zhejiang Province Key Laboratory of Quantum Technology and Device, and Department of Physics, Zhejiang University, Hangzhou, Zhejiang 310028 China.

Molecular vibrational spectroscopy is widely used in various sensing and imaging applications, providing intrinsic information at the molecular level. Nonlinear optical interactions using ultrashort laser pulses facilitate the selective coherent excitation of molecular vibrational modes by focusing energy into specific molecular bonds, boosting the signal level for multiple orders of magnitude. The dephasing of such coherence, which is susceptible to the local molecular environment, however, is often neglected. Read More

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Real-space observation of fluctuating antiferromagnetic domains.

Sci Adv 2022 May 27;8(21):eabj9493. Epub 2022 May 27.

Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854, USA.

Magnetic domains play a fundamental role in physics of magnetism and its technological applications. Dynamics of antiferromagnetic domains is poorly understood, although antiferromagnets are expected to be extensively used in future electronic devices wherein it determines the stability and operational speed. Dynamics of antiferromagnets also features prominently in the studies of topological quantum matter. Read More

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Shape and interaction decoupling for colloidal preassembly.

Sci Adv 2022 May 27;8(21):eabm0548. Epub 2022 May 27.

Department of Chemical Engineering, Delft University of Technology, 2629 HZ Delft, the Netherlands.

Creating materials with structure that is independently controllable at a range of scales requires breaking naturally occurring hierarchies. Breaking these hierarchies can be achieved via the decoupling of building block attributes from structure during assembly. Here, we demonstrate, through computer simulations and experiments, that shape and interaction decoupling occur in colloidal cuboids suspended in evaporating emulsion droplets. Read More

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CeO-Zn Nanocomposite Induced Superoxide, Autophagy and a Non-Apoptotic Mode of Cell Death in Human Umbilical-Vein-Derived Endothelial (HUVE) Cells.

Toxics 2022 May 16;10(5). Epub 2022 May 16.

King Abdullah Institute for Nanotechnology, King Saud University, Riyadh 11451, Saudi Arabia.

In this study, a nanocomposite of cerium oxide-zinc (CeO-Zn; 26 ± 11 nm) based on the antioxidant rare-earth cerium oxide (CeO) nanoparticles (NPs) with the modifier zinc (Zn) was synthesized by sintering method and characterized. Its bio-response was examined in human umbilical-vein-derived endothelial (HUVE) cells to get insight into the components of vascular system. While NPs of CeO did not significantly alter cell viability up to a concentration of 200 µg/mL for a 24 h exposure, 154 ± 6 µg/mL of nanocomposite CeO-Zn induced 50% cytotoxicity. Read More

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How Pioneer Transcription Factors Search for Target Sites on Nucleosomal DNA.

J Phys Chem B 2022 May 27. Epub 2022 May 27.

Department of Physics and Astronomy, Rice University, Houston, Texas 77005, United States.

All major biological processes start after protein molecules known as transcription factors detect specific regulatory sequences on DNA and initiate genetic expression by associating to them. But in eukaryotic cells, much of the DNA is covered by nucleosomes and other chromatin structures, preventing transcription factors from binding to their targets. At the same time, experimental studies show that there are several classes of proteins, called "pioneer transcription factors", that are able to reach the targets on nucleosomal DNA; however, the underlying microscopic mechanisms remain not well understood. Read More

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Effect of Strongly Magnetized Electrons and Ions on Heat Flow and Symmetry of Inertial Fusion Implosions.

Phys Rev Lett 2022 May;128(19):195002

Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.

This Letter presents the first observation on how a strong, 500 kG, externally applied B field increases the mode-two asymmetry in shock-heated inertial fusion implosions. Using a direct-drive implosion with polar illumination and imposed field, we observed that magnetization produces a significant increase in the implosion oblateness (a 2.5× larger P2 amplitude in x-ray self-emission images) compared with reference experiments with identical drive but with no field applied. Read More

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Tunneling Magnetoresistance in Noncollinear Antiferromagnetic Tunnel Junctions.

Phys Rev Lett 2022 May;128(19):197201

School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, 430074 Wuhan, China.

Antiferromagnetic (AFM) spintronics has emerged as a subfield of spintronics driven by the advantages of antiferromagnets producing no stray fields and exhibiting ultrafast magnetization dynamics. The efficient method to detect an AFM order parameter, known as the Néel vector, by electric means is critical to realize concepts of AFM spintronics. Here, we demonstrate that noncollinear AFM metals, such as Mn_{3}Sn, exhibit a momentum dependent spin polarization which can be exploited in AFM tunnel junctions to detect the Néel vector. Read More

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Evidence of Large Recoil Velocity from a Black Hole Merger Signal.

Phys Rev Lett 2022 May;128(19):191102

LIGO Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.

The final black hole left behind after a binary black hole merger can attain a recoil velocity, or a "kick," reaching values up to 5000  km/s. This phenomenon has important implications for gravitational wave astronomy, black hole formation scenarios, testing general relativity, and galaxy evolution. We consider the gravitational wave signal from the binary black hole merger GW200129_065458 (henceforth referred to as GW200129), which has been shown to exhibit strong evidence of orbital precession. Read More

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Bogoliubov-Born-Green-Kirkwood-Yvon Hierarchy and Generalized Hydrodynamics.

Phys Rev Lett 2022 May;128(19):190401

Kadanoff Center for Theoretical Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, Illinois 60637, USA.

We consider fermions defined on a continuous one-dimensional interval and subject to weak repulsive two-body interactions. We show that it is possible to perturbatively construct an extensive number of mutually compatible conserved charges for any interaction potential. However, the contributions to the densities of these charges at second order and higher are generally nonlocal and become spatially localized only if the potential fulfils certain compatibility conditions. Read More

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Observation of the Decay Λ_{b}^{0}→Λ_{c}^{+}τ^{-}ν[over ¯]_{τ}.

Phys Rev Lett 2022 May;128(19):191803

Institute for High Energy Physics NRC Kurchatov Institute (IHEP NRC KI), Protvino, Russia, Protvino, Russia.

The first observation of the semileptonic b-baryon decay Λ_{b}^{0}→Λ_{c}^{+}τ^{-}ν[over ¯]_{τ}, with a significance of 6.1σ, is reported using a data sample corresponding to 3  fb^{-1} of integrated luminosity, collected by the LHCb experiment at center-of-mass energies of 7 and 8 TeV at the LHC. The τ^{-} lepton is reconstructed in the hadronic decay to three charged pions. Read More

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Bound on Eigenstate Thermalization from Transport.

Authors:
Anatoly Dymarsky

Phys Rev Lett 2022 May;128(19):190601

Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506, USA and Skolkovo Institute of Science and Technology, Skolkovo Innovation Center, Moscow, Russia, 143026.

We show that macroscopic thermalization and transport impose constraints on matrix elements entering the eigenstate thermalization hypothesis (ETH) ansatz and require them to be correlated. It is often assumed that the ETH reduces to random matrix theory (RMT) below the Thouless energy scale. We show that this conventional picture is not self-consistent. Read More

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Tests of Lepton Universality Using B^{0}→K_{S}^{0}ℓ^{+}ℓ^{-} and B^{+}→K^{*+}ℓ^{+}ℓ^{-} Decays.

Phys Rev Lett 2022 May;128(19):191802

Institute for High Energy Physics NRC Kurchatov Institute (IHEP NRC KI), Protvino, Russia, Protvino, Russia.

Tests of lepton universality in B^{0}→K_{S}^{0}ℓ^{+}ℓ^{-} and B^{+}→K^{*+}ℓ^{+}ℓ^{-} decays where ℓ is either an electron or a muon are presented. The differential branching fractions of B^{0}→K_{S}^{0}e^{+}e^{-} and B^{+}→K^{*+}e^{+}e^{-} decays are measured in intervals of the dilepton invariant mass squared. The measurements are performed using proton-proton collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 9  fb^{-1} . Read More

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Self-Lensing Flares from Black Hole Binaries: Observing Black Hole Shadows via Light Curve Tomography.

Phys Rev Lett 2022 May;128(19):191101

Department of Astronomy, Columbia University, 550 W 120th Street, New York, New York 10027, USA.

Supermassive black hole (BH) binaries are thought to produce self-lensing flares (SLFs) when the two BHs are aligned with the line of sight. If the binary orbit is observed nearly edge-on, we find a distinct feature in the light curve imprinted by the relativistic shadow around the background ("source") BH. We study this feature by ray tracing in a binary model and predict that 1% of the current binary candidates could show this feature. Read More

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X-ray Digital Radiography and Computed Tomography.

J Imaging 2022 Apr 21;8(5). Epub 2022 Apr 21.

Istituto di Scienze e Tecnologie Chimiche "Giulio Natta" SCITEC-CNR, Via dell' Elce di Sotto 8, 06123 Perugia, Italy.

In recent years, X-ray imaging has rapidly grown and spread beyond the medical field; today, it plays a key role in diverse research areas [... Read More

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Non-Markovian diffusion of excitons in layered perovskites and transition metal dichalcogenides.

Phys Chem Chem Phys 2022 May 27. Epub 2022 May 27.

RAIC Center, Skolkovo Institute of Science and Technology, 121205, Moscow, Russia.

The diffusion of excitons in perovskites and transition metal dichalcogenides shows clear anomalous, subdiffusive behaviour in experiments. In this paper we develop a non-Markovian mobile-immobile model which provides an explanation of this behaviour through paired theoretical and simulation approaches. The simulation model is based on a random walk on a 2D lattice with randomly distributed deep traps such that the trapping time distribution involves slowly decaying power-law asymptotics. Read More

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Topological Disentanglement Dynamics of Torus Knots on Open Linear Polymers.

ACS Macro Lett 2019 May 3;8(5):576-581. Epub 2019 May 3.

Department of Physics and Astronomy, University of Padova, Via Marzolo 8, I-35131 Padova, Italy.

We simulate and study the topological disentanglement occurring when torus knots reach the ends of a semiflexible open polymer (decay into simpler knots or unknotting). Through a rescaling procedure and the application of appropriate boundary conditions, we show that the full unknotting process can be understood in terms of point-like particles representing essential crossings, diffusing on the support [0, 1]. We address the bending and configurational free energy drives on the diffusion process, together with the scaling properties of the effective diffusion and friction coefficients. Read More

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3D printed protein-based robotic structures actuated by molecular motor assemblies.

Nat Mater 2022 May 26. Epub 2022 May 26.

Max Planck Institute of Biochemistry, Martinsried, Germany.

Upscaling motor protein activity to perform work in man-made devices has long been an ambitious goal in bionanotechnology. The use of hierarchical motor assemblies, as realized in sarcomeres, has so far been complicated by the challenges of arranging sufficiently high numbers of motor proteins with nanoscopic precision. Here, we describe an alternative approach based on actomyosin cortex-like force production, allowing low complexity motor arrangements in a contractile meshwork that can be coated onto soft objects and locally activated by ATP. Read More

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Economic significance of biofilms: a multidisciplinary and cross-sectoral challenge.

NPJ Biofilms Microbiomes 2022 May 26;8(1):42. Epub 2022 May 26.

National Biofilms Innovation Centre & School of Biological Sciences, University of Southampton, Southampton, UK.

The increasing awareness of the significance of microbial biofilms across different sectors is continuously revealing new areas of opportunity in the development of innovative technologies in translational research, which can address their detrimental effects, as well as exploit their benefits. Due to the extent of sectors affected by microbial biofilms, capturing their real financial impact has been difficult. This perspective highlights this impact globally, based on figures identified in a recent in-depth market analysis commissioned by the UK's National Biofilms Innovation Centre (NBIC). Read More

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Some minimal notes on notation and minima: A comment on "How particular is the physics of the free energy principle?" by Aguilera, Millidge, Tschantz, and Buckley.

Phys Life Rev 2022 May 16;42:4-7. Epub 2022 May 16.

Department of Mathematics, Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3651, USA; VERSES Research Lab and Spatial Web Foundation, Los Angeles, CA 90016, USA. Electronic address:

We comment on a technical critique of the free energy principle in linear systems by Aguilera, Millidge, Tschantz, and Buckley, entitled "How Particular is the Physics of the Free Energy Principle?" Aguilera and colleagues identify an ambiguity in the flow of the mode of a system, and we discuss the context for this ambiguity in earlier papers, and their proposal of a more adequate interpretation of these equations. Following that, we discuss a misinterpretation in their treatment of surprisal and variational free energy, especially with respect to their gradients and their minima. In sum, we argue that the results in the target paper are accurate and stand up to rigorous scrutiny; we also highlight that they, nonetheless, do not undermine the FEP. Read More

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Enhanced photoacoustic imaging in tissue-mimicking phantoms using polydopamine-shelled perfluorocarbon emulsion droplets.

Ultrason Sonochem 2022 May 18;86:106041. Epub 2022 May 18.

School of Physics and Astronomy, Monash University, Clayton, VIC 3800, Australia. Electronic address:

The current work features process parameters for the ultrasound (25 kHz)-assisted fabrication of polydopamine-shelled perfluorocarbon (PDA/PFC) emulsion droplets with bimodal (modes at 100-600 nm and 1-6 µm) and unimodal (200-600 nm) size distributions. Initial screening of these materials revealed that only PDA/PFC emulsion droplets with bimodal distributions showed photoacoustic signal enhancement due to large size of their optically absorbing PDA shells. Performance of this particular type of emulsion droplets as photoacoustic agents were evaluated in Intralipid®-India ink media, mimicking the optical scattering and absorbanceof various tissuetypes. Read More

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Unusual Magnetic Features in Two-Dimensional FeGeTe Induced by Structural Reconstructions.

J Phys Chem Lett 2022 May 26:4877-4883. Epub 2022 May 26.

Department of Physics and Astronomy, Uppsala University, Box-516, 75120 Uppsala, Sweden.

Recent experiments on FeGeTe suggested the presence of a symmetry breaking of its conventional crystal structure. Here, using density functional theory calculations, we elucidate that the stabilization of the (√3 × √3)30° supercell structure is caused by the swapping of Fe atoms occurring in the monolayer limit. The swapping to the vicinity of Te atoms is facilitated by the spontaneous occurrence of Fe vacancy and its low diffusion barrier. Read More

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Myriam P. Sarachik: Extraordinary physicist, indomitable spirit, enduring legacy.

Proc Natl Acad Sci U S A 2022 May 26;119(22):e2204151119. Epub 2022 May 26.

Department of Physics and Astronomy, Amherst College, Amherst, MA 01002.

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Long-lifetime spin excitations near domain walls in 1T-TaS.

Proc Natl Acad Sci U S A 2022 May 26;119(22):e2121740119. Epub 2022 May 26.

Department of Physics, University of Illinois Urbana-Champaign, Urbana, IL 61801.

SignificanceThere is an intense ongoing search for two-level quantum systems with long lifetimes for applications in quantum communication and computation. Much research has been focused on studying isolated spins in semiconductors or band insulators. Mott insulators provide an interesting alternative platform but have been far less explored. Read More

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Implied but unseen Belknap Press, 2022. 376 pp.

Science 2022 May 26;376(6596):926. Epub 2022 May 26.

The reviewer is Astronomer Royal for Scotland and is at the Institute for Astronomy, University of Edinburgh, Edinburgh, UK, and the German Centre for Cosmological Lensing, Ruhr-University Bochum, Bochum, Germany.

A journalist probes dark matter and those who study it. Read More

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A microfluidic system that replicates pharmacokinetic (PK) profiles in vitro improves prediction of in vivo efficacy in preclinical models.

PLoS Biol 2022 May 26;20(5):e3001624. Epub 2022 May 26.

Oncology Safety, Clinical Pharmacology & Safety Sciences, BioPharmaceuticals R&D, AstraZeneca, Boston, Massachusetts, United States of America.

Test compounds used on in vitro model systems are conventionally delivered to cell culture wells as fixed concentration bolus doses; however, this poorly replicates the pharmacokinetic (PK) concentration changes seen in vivo and reduces the predictive value of the data. Herein, proof-of-concept experiments were performed using a novel microfluidic device, the Microformulator, which allows in vivo like PK profiles to be applied to cells cultured in microtiter plates and facilitates the investigation of the impact of PK on biological responses. We demonstrate the utility of the device in its ability to reproduce in vivo PK profiles of different oncology compounds over multiweek experiments, both as monotherapy and drug combinations, comparing the effects on tumour cell efficacy in vitro with efficacy seen in in vivo xenograft models. Read More

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Structural differences in adolescent brains can predict alcohol misuse.

Elife 2022 May 26;11. Epub 2022 May 26.

Department of Psychiatry and Psychotherapy, Charité - Universitätsmedizin Berlin, Berlin, Germany.

Alcohol misuse during adolescence (AAM) has been associated with disruptive development of adolescent brains. In this longitudinal machine learning (ML) study, we could predict AAM significantly from brain structure (T1-weighted imaging and DTI) with accuracies of 73 - 78% in the IMAGEN dataset (n ~1182). Our results not only show that structural differences in brain can predict AAM, but also suggests that such differences might precede AAM behavior in the data. Read More

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Antibiotic Resistance via Bacterial Cell Shape-Shifting.

mBio 2022 May 26:e0065922. Epub 2022 May 26.

Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA.

Bacteria have evolved to develop multiple strategies for antibiotic resistance by effectively reducing intracellular antibiotic concentrations or antibiotic binding affinities, but the role of cell morphology in antibiotic resistance remains poorly understood. By analyzing cell morphological data for different bacterial species under antibiotic stress, we find that bacteria increase or decrease the cell surface-to-volume ratio depending on the antibiotic target. Using quantitative modeling, we show that by reducing the surface-to-volume ratio, bacteria can effectively reduce the intracellular antibiotic concentration by decreasing antibiotic influx. Read More

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Chain Ends and the Ultimate Strength of Polyethylene Fibers.

ACS Macro Lett 2016 Mar 5;5(3):263-267. Epub 2016 Feb 5.

Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, United States.

We use large scale molecular dynamics (MD) simulations to determine the tensile yield mechanism of orthorhombic polyethylene (PE) crystals with finite chains spanning 10-10 carbons in length. We find the yield stress σ saturates for long chains at 6.3 GPa, agreeing well with experiments. Read More

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Graphene Oxide as a Radical Initiator: Free Radical and Controlled Radical Polymerization of Sodium 4-Vinylbenzenesulfonate with Graphene Oxide.

ACS Macro Lett 2016 Feb 19;5(2):199-202. Epub 2016 Jan 19.

Department of Chemistry and Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37916-1600, United States.

The free radical and controlled radical polymerization of sodium 4-vinylbenzenesulfonate using graphene oxide as a radical initiator was studied. This work demonstrates that graphene oxide can initiate radical polymerization in an aqueous solution without any additional initiator. Poly(sodium 4-vinylbenzenesulfonate) obtained via reversible addition-fragmentation chain transfer polymerization had a controlled molecular weight with a very narrow polydispersity ranging between 1. Read More

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February 2016