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https://www.readbyqxmd.com/read/27918613/defining-the-radiation-chemistry-during-liquid-cell-electron-microscopy-to-enable-visualization-of-nanomaterial-growth-and-degradation-dynamics
#1
T J Woehl, P Abellan
We present a critical review of methods for defining the chemical environment during liquid cell electron microscopy investigation of electron beam induced nanomaterial growth and degradation. We draw from the radiation chemistry and liquid cell electron microscopy literature to present solution chemistry and electron beam-based methods for selecting the radiolysis products formed and their relative amount during electron irradiation of liquid media in a transmission electron microscope. We outline various methods for establishing net oxidizing or net reducing reaction environments and propose solvents with minimal overall production of radicals under the electron beam...
December 5, 2016: Journal of Microscopy
https://www.readbyqxmd.com/read/27910853/holographic-free-electron-light-source
#2
Guanhai Li, Brendan P Clarke, Jin-Kyu So, Kevin F MacDonald, Nikolay I Zheludev
Recent advances in the physics and technology of light generation via free-electron proximity and impact interactions with nanostructures (gratings, photonic crystals, nano-undulators, metamaterials and antenna arrays) have enabled the development of nanoscale-resolution techniques for such applications as mapping plasmons, studying nanoparticle structural transformations and characterizing luminescent materials (including time-resolved measurements). Here, we introduce a universal approach allowing generation of light with prescribed wavelength, direction, divergence and topological charge via point-excitation of holographic plasmonic metasurfaces...
December 2, 2016: Nature Communications
https://www.readbyqxmd.com/read/27878166/mechanism-of-excited-state-deactivation-of-indan-1-ylidene-and-fluoren-9-ylidene-malononitriles
#3
Leandro A Estrada, Antonio Francés-Monerris, Igor Schapiro, Massimo Olivucci, Daniel Roca-Sanjuán
Herein, we report complementary computational and experimental evidence supporting the existence, for indan-1-ylidene malononitrile and fluoren-9-ylidene malononitrile, of a non-radiative decay channel involving double bond isomerisation motion. The results of UV-Vis transient absorption spectroscopy highlight that the decay takes place within hundreds of picoseconds. In order to understand the related molecular mechanism, photochemical reaction paths were computed by employing multiconfigurational quantum chemistry...
November 23, 2016: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27865670/radiation-damage-to-neuronal-cells-simulating-the-energy-deposition-and-water-radiolysis-in-a-small-neural-network
#4
Oleg V Belov, Munkhbaatar Batmunkh, Sébastien Incerti, Oidov Lkhagva
Radiation damage to the central nervous system (CNS) has been an on-going challenge for the last decades primarily due to the issues of brain radiotherapy and radiation protection for astronauts during space travel. Although recent findings revealed a number of molecular mechanisms associated with radiation-induced impairments in behaviour and cognition, some uncertainties exist in the initial neuronal cell injury leading to the further development of CNS malfunction. The present study is focused on the investigation of early biological damage induced by ionizing radiations in a sample neural network by means of modelling physico-chemical processes occurring in the medium after exposure...
November 16, 2016: Physica Medica: PM
https://www.readbyqxmd.com/read/27858299/detection-of-free-thiols-and-fluorescence-response-of-phycoerythrin-chromophore-after-ultraviolet-b-radiation-stress
#5
Vinod K Kannaujiya, Rajeshwar P Sinha
The chemistry of thiol-chromophore linkage plays a central role in the nature of fluorescence of phycoerythrin (PE). Interaction of thiol and chromophore is crucial for the energy transfer, redox signal and inhibition of oxidative damage. In the present investigation the effects of ultraviolet-B radiation on an emission fluorescence intensity and wavelength shift in PE due to interaction between thiol and chromophore by remarkable strategy of detection technique was studied. Purification of PE was done by using a gel permeation and ion exchange chromatography that yielded a quite high purity index (6...
November 17, 2016: Journal of Fluorescence
https://www.readbyqxmd.com/read/27806579/cerium-oxide-based-nanozymes-redox-phenomenon-at-biointerfaces
#6
Sanjay Singh
Cerium oxide nanoparticles (nanoceria) are known to exhibit enzymelike activity, such as biological catalase, oxidase, superoxide dismutase, and peroxidase enzymelike activities. Catalytically active nanoceria offer several advantages over natural enzymes, such as controlled synthesis at low cost, tunable catalytic activities, as well as high stability against stringent physiological conditions. Exploiting these properties, several biomedical applications, such as biosensing, immunoassay, drug delivery, radiation protection, and tissue engineering, have been maneuvered...
November 2, 2016: Biointerphases
https://www.readbyqxmd.com/read/27802722/laboratory-von-h%C3%A3-mos-x-ray-spectroscopy-for-routine-sample-characterization
#7
Zoltán Németh, Jakub Szlachetko, Éva G Bajnóczi, György Vankó
High energy resolution, hard X-ray spectroscopies are powerful element selective probes of the electronic and local structure of matter, with diverse applications in chemistry, physics, biology, and materials science. The routine application of these techniques is hindered by the complicated and slow access to synchrotron radiation facilities. Here we propose a new, economic, easily operated laboratory high resolution von Hámos type X-ray spectrometer, which offers rapid transmission experiments for X-ray absorption and is also capable of recording X-ray emission spectra...
October 2016: Review of Scientific Instruments
https://www.readbyqxmd.com/read/27788014/effect-of-conjugation-pathway-in-metal-free-room-temperature-dual-singlet-triplet-oled-emitters
#8
Wolfram Ratzke, Lisa Schmitt, Hideto Matsuoka, Christoph Bannwarth, Marius Retegan, Sebastian Bange, Philippe Klemm, Frank Neese, Stefan Grimme, Olav Schiemann, John Mark Lupton, Sigurd Höger
Metal-free dual singlet-triplet OLED emitters can provide direct insight into spin statistics - spin correlations and spin relaxation phenomena - through a comparison of fluorescence to phosphorescence intensity. Remarkably, such materials can also function at room temperature, exhibiting phosphorescence lifetimes of several milliseconds. Using electroluminescence, quantum chemistry and electron paramagnetic resonance, we investigate the effect of conjugation pathway on radiative and non-radiative relaxation of the triplet state in phenazine-based compounds and demonstrate that the contribution of the phenazine n* excited state is crucial to enabling phosphorescence...
October 27, 2016: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/27782638/perspective-accurate-ro-vibrational-calculations-on-small-molecules
#9
Jonathan Tennyson
In what has been described as the fourth age of quantum chemistry, variational nuclear motion programs are now routinely being used to obtain the vibration-rotation levels and corresponding wavefunctions of small molecules to the sort of high accuracy demanded by comparison with spectroscopy. In this perspective, I will discuss the current state-of-the-art which, for example, shows that these calculations are increasingly competitive with measurements or, indeed, replacing them and thus becoming the primary source of data on key processes...
September 28, 2016: Journal of Chemical Physics
https://www.readbyqxmd.com/read/27779879/multi-scale-modelling-of-the-gamma-radiolysis-of-nitrate-solutions
#10
Gregory Peter Horne, Thomas Ashley Donoclift, Howard Sims, Robin Orr, Simon M Pimblott
A multi-scale modelling approach has been developed for the extended timescale long-term radiolysis of aqueous systems. The approach uses a combination of stochastic track structure and track chemistry as well as deterministic homogeneous chemistry techniques and involves four key stages; radiation track structure simulation, the subsequent physicochemical processes, nonhomogeneous diffusion-reaction kinetic evolution, and homogeneous bulk chemistry modelling. The first three components model the physical and chemical evolution of an isolated radiation chemical track and provide radiolysis yields, within the extremely low dose isolated track paradigm, as the input parameters for a bulk deterministic chemistry model...
October 25, 2016: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/27757825/erratum-to-application-of-radiation-chemistry-to-some-selected-technological-issues-related-to-the-development-of-nuclear-energy
#11
Krzysztof Bobrowski, Konrad Skotnicki, Tomasz Szreder
No abstract text is available yet for this article.
December 2016: Topics in Current Chemistry (Journal)
https://www.readbyqxmd.com/read/27754503/acoustofluidic-coating-of-particles-and-cells
#12
Bugra Ayan, Adem Ozcelik, Hunter Bachman, Shi-Yang Tang, Yuliang Xie, Mengxi Wu, Peng Li, Tony Jun Huang
On-chip microparticle and cell coating technologies enable a myriad of applications in chemistry, engineering, and medicine. Current microfluidic coating technologies often rely on magnetic labeling and concurrent deflection of particles across laminar streams of chemicals. Herein, we introduce an acoustofluidic approach for microparticle and cell coating by implementing tilted-angle standing surface acoustic waves (taSSAWs) into microchannels with multiple inlets. The primary acoustic radiation force generated by the taSSAW field was exploited in order to migrate the particles across the microchannel through multiple laminar streams, which contained the buffer and coating chemicals...
October 18, 2016: Lab on a Chip
https://www.readbyqxmd.com/read/27733899/the-spatial-distribution-of-complex-organic-molecules-in-the-l1544-pre-stellar-core
#13
Izaskun Jiménez-Serra, Anton I Vasyunin, Paola Caselli, Nuria Marcelino, Nicolas Billot, Serena Viti, Leonardo Testi, Charlotte Vastel, Bertrand Lefloch, Rafael Bachiller
The detection of complex organic molecules (COMs) toward cold sources such as pre-stellar cores (with T<10 K), has challenged our understanding of the formation processes of COMs in the interstellar medium. Recent modelling on COM chemistry at low temperatures has provided new insight into these processes predicting that COM formation depends strongly on parameters such as visual extinction and the level of CO freeze out. We report deep observations of COMs toward two positions in the L1544 pre-stellar core: the dense, highly-extinguished continuum peak with A V ≥30 mag within the inner 2700 au; and a low-density shell with average A V ~7...
October 10, 2016: Astrophysical Journal. Letters
https://www.readbyqxmd.com/read/27731989/real-time-studies-of-iron-oxalate-mediated-oxidation-of-glycolaldehyde-as-a-model-for-photochemical-aging-of-aqueous-tropospheric-aerosols
#14
Daniel A Thomas, Matthew M Coggon, Hanna Lignell, Katherine Ann Schilling, Xuan Zhang, Rebecca H Schwantes, Richard C Flagan, John H Seinfeld, Jesse Lee Beauchamp
The complexation of iron (III) with oxalic acid in aqueous solution yields a strongly absorbing chromophore that undergoes efficient photodissociation to give iron (II) and the carbon dioxide anion radical. Importantly, iron (III) oxalate complexes absorb near-UV radiation (λ > 350 nm), providing a potentially powerful source of oxidants in aqueous tropospheric chemistry. Although this photochemical system has been studied extensively, the mechanistic details associated with its role in the oxidation of dissolved organic matter within aqueous aerosol remain largely unknown...
October 12, 2016: Environmental Science & Technology
https://www.readbyqxmd.com/read/27730379/influence-of-microhydration-on-the-structures-and-proton-induced-charge-transfer-in-rna-intermediates
#15
M C Bacchus-Montabonel, F Calvo
Solvation effects are of major interest in the context of radiation damage, due to their potential applications in cancer therapy. Reliable modeling of the solvent is, however, quite challenging, and numerous studies have been devoted to isolated biomolecules and stepwise-hydrated molecules in which the amount of solvent is controlled one molecule at a time. The influence of stepwise hydration on radiation damage is investigated here using the example of proton-induced charge transfer in two biomolecular targets...
November 2016: Journal of Molecular Modeling
https://www.readbyqxmd.com/read/27714271/radiation-damage-to-single-stranded-oligonucleotide-trimers-labelled-with-5-iodopyrimidines
#16
Kinga Westphal, Konrad Skotnicki, Krzysztof Bobrowski, Janusz Rak
The radiolysis of deoxygenated aqueous solution containing trimeric oligonucleotides labelled with iodinated pyrimidines and Tris-HCl as the hydroxyl radical scavenger leads to electron attachment to the halogenated bases that mainly results in single strand breaks. The iodinated trimers are 2-fold more sensitive to solvated electrons than the brominated oligonucleotides, which is explained by the barrier-free dissociation of the iodinated base anions. The present study fills the literature gap concerning the chemistry triggered by ionizing radiation in the iodinated pyrimidines incorporated into DNA...
October 4, 2016: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/27702448/laser-ablation-coupled-with-dapne-nsi-ms-applied-to-redacted-documents
#17
Vivian Huynh, Zachary J Sasiene, Phillip M Mach, Teresa D Golden, Guido F Verbeck
Laser ablation has been applied to redacted documents, where the text has been concealed by other ink. This technique strips the redacting ink revealing the text that was once redacted. Once removed, a nanomanipulation technique is used to extract the ink of the underlying text where mass spectrometry is then implemented to analyze its ink chemistry. In order to facilitate microscopy with direct analyte-probed nanoextraction coupled to nanospray ionization mass spectrometry (DAPNe-NSI-MS), laser ablation must be executed prior to ink extraction...
September 2016: Science & Justice: Journal of the Forensic Science Society
https://www.readbyqxmd.com/read/27669357/surface-chemistry-of-semiconducting-quantum-dots-theoretical-perspectives
#18
Svetlana V Kilina, Patrick K Tamukong, Dmitri S Kilin
Colloidal quantum dots (QDs) are near-ideal nanomaterials for energy conversion and lighting technologies. However, their photophysics exhibits supreme sensitivity to surface passivation and defects, of which control is problematic. The role of passivating ligands in photodynamics remains questionable and is a focus of ongoing research. The optically forbidden nature of surface-associated states makes direct measurements on them challenging. Therefore, computational modeling is imperative for insights into surface passivation and its impact on light-driven processes in QDs...
October 18, 2016: Accounts of Chemical Research
https://www.readbyqxmd.com/read/27668950/merging-structural-information-from-x-ray-crystallography-quantum-chemistry-and-exafs-spectra-the-oxygen-evolving-complex-in-psii
#19
Petko Chernev, Ivelina Zaharieva, Emanuele Rossini, Artur Galstyan, Holger Dau, Ernst-Walter Knapp
Structural data of the oxygen-evolving complex (OEC) in photosystem II (PSII) determined by X-ray crystallography, quantum chemistry (QC), and extended X-ray absorption fine structure (EXAFS) analyses are presently inconsistent. Therefore, a detailed study of what information can be gained about the OEC through a comparison of QC and crystallographic structure information combined with the information from range-extended EXAFS spectra was undertaken. An analysis for determining the precision of the atomic coordinates of the OEC by QC is carried out...
October 12, 2016: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/27643620/mechanisms-of-radiation-induced-degradation-of-cfcl3-and-cf2cl2-in-noble-gas-matrixes-an-evidence-for-hot-ionic-channels-in-the-solid-phase
#20
Ekaterina S Shiryaeva, Daniil A Tyurin, Vladimir I Feldman
The X-ray-induced transformations of simple chlorofluorocarbons (CFCl3 and CF2Cl2) in solid noble-gas matrixes (Ne, Ar, Kr, and Xe) at 7 K were studied in order to elucidate basic mechanisms of the radiation-chemical degradation with possible implications for stratospheric and extraterrestrial ice chemistry. The decomposition of parent molecules and formation of products were monitored by FTIR spectroscopy, and the identification was supported by ab initio calculations at the CCSD(T) level. It was shown that the ionic reaction channels were predominating in most cases (except for CF2Cl2/Xe system)...
October 13, 2016: Journal of Physical Chemistry. A
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