41,850 results match your criteria Astronomy & Geophysics[Journal]


Nonadiabatic Molecular Dynamics Study of the Relaxation Pathways of Photoexcited Cyclooctatetraene.

J Phys Chem Lett 2021 Jun 15:5716-5722. Epub 2021 Jun 15.

Physics and Chemistry of Materials, Theoretical Division, Los Alamos National Laboratory, Los Alamos 87545, New Mexico, United States.

In the current study, we present nonadiabatic (NAMD) and adiabatic molecular dynamics simulations of the transition-state dynamics of photoexcited cyclooctatetraene (COT). The equilibrium-state structure and absorption spectra are analyzed using the semiempirical Austin Model 1 potential. The NAMD simulations are obtained by a surface-hopping algorithm. Read More

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Nonlesional diffusely abnormal appearing white matter in clinically isolated syndrome: Prevalence, association with clinical and MRI features, and risk for conversion to multiple sclerosis.

J Neuroimaging 2021 Jun 15. Epub 2021 Jun 15.

Department of Radiology, University of British Columbia, Vancouver, British Columbia, Canada.

Background And Purpose: While diffusely abnormal white matter (DAWM) is a nonlesional MRI abnormality identified in ∼25% of patients with multiple sclerosis (MS), it has yet to be investigated in patients at an earlier disease stage, namely clinically isolated syndrome (CIS). The goals of this study were to (1) determine the prevalence of DAWM in patients with a CIS suggestive of MS, (2) evaluate the association between DAWM and demographic, clinical, and MRI features, and (3) evaluate the prognostic significance of DAWM on conversion from CIS to MS.

Methods: One hundred and forty-two CIS participants were categorized into DAWM and non-DAWM groups at baseline and followed for up to 24 months or until MS diagnosis. Read More

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Changes in the geometry of modern daily disposable soft contact lenses during wear.

Sci Rep 2021 Jun 14;11(1):12460. Epub 2021 Jun 14.

Division of Ophthalmology and Optometry, Department of Ophthalmology, Collegium Medicum, Nicolaus Copernicus University, ul. Ujejskiego 75, 85-168, Bydgoszcz, Poland.

The geometry of contact lenses can be altered by wear but determining the changes that occur in soft contact lenses (SCLs) is challenging. This study aimed to investigate the shape alterations of daily disposable SCLs after wear using swept-source optical coherence tomography (SS-OCT). Forty-five eyes with myopia of - 3. Read More

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Strong interaction between interlayer excitons and correlated electrons in WSe/WS moiré superlattice.

Nat Commun 2021 Jun 14;12(1):3608. Epub 2021 Jun 14.

Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, NY, USA.

Heterobilayers of transition metal dichalcogenides (TMDCs) can form a moiré superlattice with flat minibands, which enables strong electron interaction and leads to various fascinating correlated states. These heterobilayers also host interlayer excitons in a type-II band alignment, in which optically excited electrons and holes reside on different layers but remain bound by the Coulomb interaction. Here we explore the unique setting of interlayer excitons interacting with strongly correlated electrons, and we show that the photoluminescence (PL) of interlayer excitons sensitively signals the onset of various correlated insulating states as the band filling is varied. Read More

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Multiple fermion scattering in the weakly coupled spin-chain compound YbAlO.

Nat Commun 2021 Jun 14;12(1):3599. Epub 2021 Jun 14.

Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA.

The Heisenberg antiferromagnetic spin-1/2 chain, originally introduced almost a century ago, is one of the best studied models in quantum mechanics due to its exact solution, but nevertheless it continues to present new discoveries. Its low-energy physics is described by the Tomonaga-Luttinger liquid of spinless fermions, similar to the conduction electrons in one-dimensional metals. In this work we investigate the Heisenberg spin-chain compound YbAlO and show that the weak interchain coupling causes Umklapp scattering between the left- and right-moving fermions and stabilizes an incommensurate spin-density wave order at q = 2k under finite magnetic fields. Read More

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Manipulating nonadiabatic conical intersection dynamics by optical cavities.

Chem Sci 2019 Dec 12;11(5):1290-1298. Epub 2019 Dec 12.

Department of Chemistry, Physics and Astronomy, University of California Irvine CA 92697 USA

Optical cavities hold great promise to manipulate and control the photochemistry of molecules. We demonstrate how molecular photochemical processes can be manipulated by strong light-matter coupling. For a molecule with an inherent conical intersection, optical cavities can induce significant changes in the nonadiabatic dynamics by either splitting the pristine conical intersections into two novel polaritonic conical intersections or by creating light-induced avoided crossings in the polaritonic surfaces. Read More

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December 2019

Water-induced formation of an alkali-ion dimer in cryptomelane nanorods.

Chem Sci 2020 Apr 29;11(19):4991-4998. Epub 2020 Apr 29.

Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory Upton NY 11973 USA

Tunneled metal oxides such as α-MnO (hollandite) have proven to be compelling candidates for charge-storage materials in high-density batteries. In particular, the tunnels can support one-dimensional chains of K ions (which act as structure-stabilizing dopants) and HO molecules, as these chains are favored by strong H-bonds and electrostatic interactions. In this work, we examine the role of water molecules in enhancing the stability of K-doped α-MnO (cryptomelane). Read More

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Room temperature crystallization of amorphous polysiloxane using photodimerization.

Chem Sci 2020 Feb 28;11(11):3081-3088. Epub 2020 Feb 28.

Department of Chemistry, University of British Columbia Vancouver BC Canada V6T 1Z1

Bulk crystallization in flexible polymeric systems is difficult to control due to the random orientation of the chains. Here we report a photo cross-linking strategy that results in simultaneous cross-linking and crystallization of polysiloxane chains into millimeter sized leaf-like polycrystalline structures. Polymers containing pendant anthracene groups are prepared and undergo [4+4] photocycloaddition under 365 nm irradiation at room temperature. Read More

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February 2020

Bilayer graphene in strong ultrafast laser fields.

J Phys Condens Matter 2021 Jun 14. Epub 2021 Jun 14.

Georgia State University, Center for Nano-Optics (CeNo) and Department of Physics and Astronomy, Atlanta, Georgia, 30303, UNITED STATES.

We theoretically investigate the interaction of an ultrastrong femtosecond-long linearly polarized optical pulse with AB-stacked bilayer graphene. The pulse excite electrons from the valence into the conduction band, resulting in finite conduction band population. Such a redistribution of electrons results in the generation of current which can be manipulated by the angle of incidence of the pulse. Read More

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Rapid microstructural plasticity in the cortical semantic network following a short language learning session.

PLoS Biol 2021 Jun 14;19(6):e3001290. Epub 2021 Jun 14.

Center of Functionally Integrative Neuroscience, Aarhus University, Aarhus, Denmark.

Despite the clear importance of language in our life, our vital ability to quickly and effectively learn new words and meanings is neurobiologically poorly understood. Conventional knowledge maintains that language learning-especially in adulthood-is slow and laborious. Furthermore, its structural basis remains unclear. Read More

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Correction: Water-induced formation of an alkali-ion dimer in cryptomelane nanorods.

Chem Sci 2020 Jul 2;11(27):7266. Epub 2020 Jul 2.

Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory Upton NY 11973 USA

[This corrects the article DOI: 10.1039/D0SC01517B.]. Read More

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Investigations of Molecular Optical Properties Using Quantum Light and Hong-Ou-Mandel Interferometry.

J Am Chem Soc 2021 Jun 14. Epub 2021 Jun 14.

Department of Chemistry, University of Michigan, 930 N University Ave., Ann Arbor, Michigan 48109, United States.

Entangled photon pairs have been used for molecular spectroscopy in the form of entangled two-photon absorption and in quantum interferometry for precise measurements of light source properties and time delays. We present an experiment that combines molecular spectroscopy and quantum interferometry by utilizing the correlations of entangled photons in a Hong-Ou-Mandel (HOM) interferometer to study molecular properties. We find that the HOM signal is sensitive to the presence of a resonant organic sample placed in one arm of the interferometer, and the resulting signal contains information pertaining to the light-matter interaction. Read More

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Prenatal stress dysregulates resting-state functional connectivity and sensory motifs.

Neurobiol Stress 2021 Nov 27;15:100345. Epub 2021 May 27.

Department of Neuroscience, Canadian Centre for Behavioural Neuroscience, University of Lethbridge, Lethbridge, AB, Canada, T1K 3M4.

Prenatal stress (PS) can impact fetal brain structure and function and contribute to higher vulnerability to neurodevelopmental and neuropsychiatric disorders. To understand how PS alters evoked and spontaneous neocortical activity and intrinsic brain functional connectivity, mesoscale voltage imaging was performed in adult C57BL/6NJ mice that had been exposed to auditory stress on gestational days 12-16, the age at which neocortex is developing. PS mice had a four-fold higher basal corticosterone level and reduced amplitude of cortical sensory-evoked responses to visual, auditory, whisker, forelimb, and hindlimb stimuli. Read More

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November 2021

Attenuation coefficient estimation in Fourier-domain OCT of multi-layered phantoms.

Biomed Opt Express 2021 May 15;12(5):2744-2758. Epub 2021 Apr 15.

Department of Imaging Physics, Delft University of Technology, 2628 CJ, Delft, The Netherlands.

Optical properties, such as the attenuation coefficients of multi-layer tissue samples, could be used as a biomarker for diagnosis and disease progression in clinical practice. In this paper, we present a method to estimate the attenuation coefficients in a multi-layer sample by fitting a single scattering model for the OCT signal to the recorded OCT signal. In addition, we employ numerical simulations to obtain the theoretically achievable precision and accuracy of the estimated parameters under various experimental conditions. Read More

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Machine learning-based LIBS spectrum analysis of human blood plasma allows ovarian cancer diagnosis.

Biomed Opt Express 2021 May 2;12(5):2559-2574. Epub 2021 Apr 2.

School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China.

Early-stage screening and diagnosis of ovarian cancer represent an urgent need in medicine. Usual ultrasound imaging and cancer antigen CA-125 test when prescribed to a suspicious population still require reconfirmations. Spectroscopic analyses of blood, at the molecular and atomic levels, provide useful supplementary tests when coupled with effective information extraction methods. Read More

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Diagnostic prospects and preclinical development of optical technologies using gold nanostructure contrast agents to boost endogenous tissue contrast.

Chem Sci 2020 Jul 14;11(33):8671-8685. Epub 2020 Jul 14.

School of Physics and Astronomy, University of Exeter Exeter EX4 4QL UK

Numerous developments in optical biomedical imaging research utilizing gold nanostructures as contrast agents have advanced beyond basic research towards demonstrating potential as diagnostic tools; some of which are translating into clinical applications. Recent advances in optics, lasers and detection instrumentation along with the extensive, yet developing, knowledge-base in tailoring the optical properties of gold nanostructures has significantly improved the prospect of near-infrared (NIR) optical detection technologies. Of particular interest are optical coherence tomography (OCT), photoacoustic imaging (PAI), multispectral optoacoustic tomography (MSOT), Raman spectroscopy (RS) and surface enhanced spatially offset Raman spectroscopy (SESORS), due to their respective advancements. Read More

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Elevated metallothionein expression in long-lived species mediates the influence of cadmium accumulation on aging.

Geroscience 2021 Jun 11. Epub 2021 Jun 11.

Advanced Technology Center for Aging Research, IRCCS INRCA, 60121, Ancona, Italy.

Cadmium (Cd) accumulates with aging and is elevated in long-lived species. Metallothioneins (MTs), small cysteine-rich proteins involved in metal homeostasis and Cd detoxification, are known to be related to longevity. However, the relationship between Cd accumulation, the role of MTs, and aging is currently unclear. Read More

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A time-course Raman spectroscopic analysis of spontaneous in vitro microcalcifications in a breast cancer cell line.

Lab Invest 2021 Jun 11. Epub 2021 Jun 11.

School of Physics and Astronomy, University of Exeter, Exeter, UK.

Microcalcifications are early markers of breast cancer and can provide valuable prognostic information to support clinical decision-making. Current detection of calcifications in breast tissue is based on X-ray mammography, which involves the use of ionizing radiation with potentially detrimental effects, or MRI scans, which have limited spatial resolution. Additionally, these techniques are not capable of discriminating between microcalcifications from benign and malignant lesions. Read More

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Phasor-based hyperspectral snapshot microscopy allows fast imaging of live, three-dimensional tissues for biomedical applications.

Commun Biol 2021 Jun 11;4(1):721. Epub 2021 Jun 11.

Laboratory for Fluorescence Dynamics, University of California, Irvine, CA, USA.

Hyperspectral imaging is highly sought after in many fields including mineralogy and geology, environment and agriculture, astronomy and, importantly, biomedical imaging and biological fluorescence. We developed ultrafast phasor-based hyperspectral snapshot microscopy based on sine/cosine interference filters for biomedical imaging not feasible with conventional hyperspectral detection methods. Current approaches rely on slow spatial or spectral scanning limiting their application in living biological tissues, while faster snapshot methods such as image mapping spectrometry and multispectral interferometry are limited in spatial and/or spectral resolution, are computationally demanding, and imaging devices are very expensive to manufacture. Read More

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Detecting functional connectivity disruptions in a translational pediatric traumatic brain injury porcine model using resting-state and task-based fMRI.

Sci Rep 2021 Jun 11;11(1):12406. Epub 2021 Jun 11.

Department of Physics and Astronomy, Franklin College of Arts and Sciences, University of Georgia, 500 D.W. Brooks Drive Rm 119, Athens, GA, 30602, USA.

Functional magnetic resonance imaging (fMRI) has significant potential to evaluate changes in brain network activity after traumatic brain injury (TBI) and enable early prognosis of potential functional (e.g., motor, cognitive, behavior) deficits. Read More

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Recurrent neural network-based acute concussion classifier using raw resting state EEG data.

Sci Rep 2021 Jun 11;11(1):12353. Epub 2021 Jun 11.

Djavad Mowafaghian Centre for Brain Health, University of British Columbia, Vancouver, BC, V6T 1Z3, Canada.

Concussion is a global health concern. Despite its high prevalence, a sound understanding of the mechanisms underlying this type of diffuse brain injury remains elusive. It is, however, well established that concussions cause significant functional deficits; that children and youths are disproportionately affected and have longer recovery time than adults; and that individuals suffering from a concussion are more prone to experience additional concussions, with each successive injury increasing the risk of long term neurological and mental health complications. Read More

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Real-time imaging of cellular forces using optical interference.

Nat Commun 2021 06 11;12(1):3552. Epub 2021 Jun 11.

SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, UK.

Important dynamic processes in mechanobiology remain elusive due to a lack of tools to image the small cellular forces at play with sufficient speed and throughput. Here, we introduce a fast, interference-based force imaging method that uses the illumination of an elastic deformable microcavity with two rapidly alternating wavelengths to map forces. We show real-time acquisition and processing of data, obtain images of mechanical activity while scanning across a cell culture, and investigate sub-second fluctuations of the piconewton forces exerted by macrophage podosomes. Read More

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Asymmetric Rydberg blockade of giant excitons in Cuprous Oxide.

Nat Commun 2021 Jun 11;12(1):3556. Epub 2021 Jun 11.

Experimentelle Physik 2, Technische Universität Dortmund, Dortmund, Germany.

The ability to generate and control strong long-range interactions via highly excited electronic states has been the foundation for recent breakthroughs in a host of areas, from atomic and molecular physics to quantum optics and technology. Rydberg excitons provide a promising solid-state realization of such highly excited states, for which record-breaking orbital sizes of up to a micrometer have indeed been observed in cuprous oxide semiconductors. Here, we demonstrate the generation and control of strong exciton interactions in this material by optically producing two distinct quantum states of Rydberg excitons. Read More

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Electromagnetic power of lightning superbolts from Earth to space.

Nat Commun 2021 Jun 11;12(1):3553. Epub 2021 Jun 11.

Météorage, Pau, France.

Lightning superbolts are the most powerful and rare lightning events with intense optical emission, first identified from space. Superbolt events occurred in 2010-2018 could be localized by extracting the high energy tail of the lightning stroke signals measured by the very low frequency ground stations of the World-Wide Lightning Location Network. Here, we report electromagnetic observations of superbolts from space using Van Allen Probes satellite measurements, and ground measurements, and with two events measured both from ground and space. Read More

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Malus-metasurface-assisted polarization multiplexing.

Light Sci Appl 2020 Jun 12;9(1):101. Epub 2020 Jun 12.

School of Physics & Astronomy, University of Birmingham, Birmingham, B15 2TT, UK.

Polarization optics plays a pivotal role in diffractive, refractive, and emerging flat optics, and has been widely employed in contemporary optical industries and daily life. Advanced polarization manipulation leads to robust control of the polarization direction of light. Nevertheless, polarization control has been studied largely independent of the phase or intensity of light. Read More

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Exact Real-Time Longitudinal Correlation Functions of the Massive XXZ Chain.

Phys Rev Lett 2021 May;126(21):210602

Department of Physics, Faculty of Science, Shizuoka University, Ohya 836, Suruga, Shizuoka, Japan.

We apply a recently developed thermal form factor expansion method to evaluate the real-time longitudinal spin-spin correlation functions of the spin-1/2 XXZ chain in the antiferromagnetically ordered regime at zero temperature. An analytical result incorporating all types of excitations in the model is obtained, without any approximations. This allows for the accurate calculation of the real-time correlations in this strongly interacting quantum system for arbitrary distances and times. Read More

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Hidden Silicon-Vacancy Centers in Diamond.

Phys Rev Lett 2021 May;126(21):213601

Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA.

We characterize a high-density sample of negatively charged silicon-vacancy (SiV^{-}) centers in diamond using collinear optical multidimensional coherent spectroscopy. By comparing the results of complementary signal detection schemes, we identify a hidden population of SiV^{-} centers that is not typically observed in photoluminescence and which exhibits significant spectral inhomogeneity and extended electronic T_{2} times. The phenomenon is likely caused by strain, indicating a potential mechanism for controlling electric coherence in color-center-based quantum devices. Read More

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