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https://www.readbyqxmd.com/read/28088137/forces-on-nuclei-moving-on-autoionizing-molecular-potential-energy-surfaces
#1
Nimrod Moiseyev
Autoionization of molecular systems occurs in diatomic molecules and in small biochemical systems. Quantum chemistry packages enable calculation of complex potential energy surfaces (CPESs). The imaginary part of the CPES is associated with the autoionization decay rate, which is a function of the molecular structure. Molecular dynamics simulations, within the framework of the Born-Oppenheimer approximation, require the definition of a force field. The ability to calculate the forces on the nuclei in bio-systems when autoionization takes place seems to rely on an understanding of radiative damages in RNA and DNA arising from the release of slow moving electrons which have long de Broglie wavelengths...
January 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28079196/ultra-fast-charge-migration-competes-with-proton-transfer-in-the-early-chemistry-of-h2o%C3%AB
#2
Furong Wang, Uli Schmidhammer, Aurélien de La Lande, Mehran Mostafavi
Oxidation by the ultra-short lived radical cation of water, H2O˙(+), can potentially take place at the interface of water and numerous heterogeneous systems involved in radiation therapy, energy and environmental industries. The oxidation processes induced by H2O˙(+) can be mimicked in highly concentrated solutions where the nearest neighbors of H2O˙(+) may be molecules other than water. The reactivity of H2O˙(+) and D2O˙(+) is probed in hydrogenated and deuterated sulfuric acid solutions of various concentrations...
January 12, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28068078/enriching-nanoparticles-via-acoustofluidics
#3
Zhangming Mao, Peng Li, Mengxi Wu, Hunter Bachman, Nicolas Mesyngier, Xiasheng Guo, Sheng Liu, Francesco Costanzo, Tony Jun Huang
Focusing and enriching submicrometer and nanometer scale objects is of great importance for many applications in biology, chemistry, engineering, and medicine. Here, we present an acoustofluidic chip that can generate single vortex acoustic streaming inside a glass capillary through using low-power acoustic waves (only 5 V is required). The single vortex acoustic streaming that is generated, in conjunction with the acoustic radiation force, is able to enrich submicrometer- and nanometer-sized particles in a small volume...
January 9, 2017: ACS Nano
https://www.readbyqxmd.com/read/28067515/plutonium-and-americium-alpha-radiolysis-of-nitric-acid-solutions
#4
Gregory Peter Horne, Colin R Gregson, Howard E Sims, Robin M Orr, Robin J Taylor, Simon M Pimblott
The yield of HNO2, as a function of absorbed dose and HNO3 concentration, from the α-radiolysis of aerated HNO3 solutions containing plutonium or americium has been investigated. There are significant differences in the yields measure from solutions of the two different radionuclides. For 0.1 mol dm-3 HNO3 solutions the radiolytic yield of HNO2 produced by americium α-decay is below the detection limit, whereas for plutonium α-decay the yield is considerably greater than that found previously for γ-radiolysis...
January 9, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28063356/nanoparticles-for-radiooncology-mission-vision-challenges
#5
REVIEW
Leoni A Kunz-Schughart, Anna Dubrovska, Claudia Peitzsch, Alexander Ewe, Achim Aigner, Samuel Schellenburg, Michael H Muders, Silke Hampel, Giuseppe Cirillo, Francesca Iemma, Rainer Tietze, Christoph Alexiou, Holger Stephan, Kristof Zarschler, Orazio Vittorio, Maria Kavallaris, Wolfgang J Parak, Lutz Mädler, Suman Pokhrel
Cancer is one of the leading non-communicable diseases with highest mortality rates worldwide. About half of all cancer patients receive radiation treatment in the course of their disease. However, treatment outcome and curative potential of radiotherapy is often impeded by genetically and/or environmentally driven mechanisms of tumor radioresistance and normal tissue radiotoxicity. While nanomedicine-based tools for imaging, dosimetry and treatment are potential keys to the improvement of therapeutic efficacy and reducing side effects, radiotherapy is an established technique to eradicate the tumor cells...
December 14, 2016: Biomaterials
https://www.readbyqxmd.com/read/28048349/we-h-bra-04-biological-geometries-for-the-monte-carlo-simulation-toolkit-topasnbio
#6
A McNamara, J Perl, P Piersimoni, J Ramos-Mendez, B Faddegon, K Held, H Paganetti, J Schuemann
PURPOSE: New advances in radiation therapy are most likely to come from the complex interface of physics, chemistry and biology. Computational simulations offer a powerful tool for quantitatively investigating radiation interactions with biological tissue and can thus help bridge the gap between physics and biology. The aim of TOPAS-nBio is to provide a comprehensive tool to generate advanced radiobiology simulations. METHODS: TOPAS wraps and extends the Geant4 Monte Carlo (MC) simulation toolkit...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047744/we-a-201-01-memorial-introduction
#7
C Marshall
: Chris Marshall: Memorial Introduction Donald Edmonds Herbert Jr., or Don to his colleagues and friends, exemplified the "big tent" vision of medical physics, specializing in Applied Statistics and Dynamical Systems theory. He saw, more clearly than most, that "Making models is the difference between doing science and just fooling around [ref Woodworth, 2004]". Don developed an interest in chemistry at school by "reading a book" - a recurring theme in his story. He was awarded a Westinghouse Science scholarship and attended the Carnegie Institute of Technology (later Carnegie Mellon University) where his interest turned to physics and led to a BS in Physics after transfer to Northwestern University...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047091/we-a-201-02-modern-statistical-modeling
#8
A Niemierko
: Chris Marshall: Memorial Introduction Donald Edmonds Herbert Jr., or Don to his colleagues and friends, exemplified the "big tent" vision of medical physics, specializing in Applied Statistics and Dynamical Systems theory. He saw, more clearly than most, that "Making models is the difference between doing science and just fooling around [ref Woodworth, 2004]". Don developed an interest in chemistry at school by "reading a book" - a recurring theme in his story. He was awarded a Westinghouse Science scholarship and attended the Carnegie Institute of Technology (later Carnegie Mellon University) where his interest turned to physics and led to a BS in Physics after transfer to Northwestern University...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28046871/su-f-t-676-measurement-of-hydroxyl-radicals-in-radiolized-water-systems
#9
Z Ouyang, G Strack, E Sajo, W Ngwa
PURPOSE: Hydroxyl radicals can be produced within tissue by radiation therapy, and they are largely responsible for DNA damage and cell killing. Coumarin-3-carboxylic acid (3-CCA) and crystal violet are reported to react with hydroxyl radicals and can be used for fluorescence and absorbance measurements, respectively. This study assesses the ability of hydroxyl measurement for both 3-CCA and crystal violet in radiolized water systems in order to provide dosimetric information in radiation chemistry and radiation biology experiments...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28046561/we-a-201-00-anne-and-donald-herbert-distinguished-lectureship-on-modern-statistical-modeling
#10
Joseph Deasy
: Chris Marshall: Memorial Introduction Donald Edmonds Herbert Jr., or Don to his colleagues and friends, exemplified the "big tent" vision of medical physics, specializing in Applied Statistics and Dynamical Systems theory. He saw, more clearly than most, that "Making models is the difference between doing science and just fooling around [ref Woodworth, 2004]". Don developed an interest in chemistry at school by "reading a book" - a recurring theme in his story. He was awarded a Westinghouse Science scholarship and attended the Carnegie Institute of Technology (later Carnegie Mellon University) where his interest turned to physics and led to a BS in Physics after transfer to Northwestern University...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28017738/validation-of-the-radiobiology-toolkit-topas-nbio-in-simple-dna-geometries
#11
Aimee McNamara, Changran Geng, Robert Turner, Jose Ramos Mendez, Joseph Perl, Kathryn Held, Bruce Faddegon, Harald Paganetti, Jan Schuemann
Computational simulations offer a powerful tool for quantitatively investigating radiation interactions with biological tissue and can help bridge the gap between physics, chemistry and biology. The TOPAS collaboration is tackling this challenge by extending the current Monte Carlo tool to allow for sub-cellular in silico simulations in a new extension, TOPAS-nBio. TOPAS wraps and extends the Geant4 Monte Carlo simulation toolkit and the new extension allows the modeling of particles down to vibrational energies (∼2eV) within realistic biological geometries...
December 22, 2016: Physica Medica: PM
https://www.readbyqxmd.com/read/28013121/radiopharmaceutical-chemistry-of-targeted-radiotherapeutics-part-4-strategies-for-211-at-labeling-at-high-activities-and-radiation-doses-of-211-at-%C3%AE-particles
#12
Oscar R Pozzi, Michael R Zalutsky
INTRODUCTION: Alpha particles are radiation of high energy and short range, properties that can lead to radiolysis-mediated complications in labeling chemistry at the high radioactivity levels required for clinical application. In previous papers in this series, we have shown that radiation dose has a profound effect on the astatine species that are present in the labeling reaction and their suitability for the synthesis of N-succinimidyl 3-[(211)At]astatobenzoate. The purpose of this study was to evaluate the effects of adding N-chlorosuccinimide (NCS) to the methanol solution used for initial isolation of (211)At after distillation, a process referred to as (211)At stabilization, on (211)At chemistry after exposure to high radiation doses...
December 10, 2016: Nuclear Medicine and Biology
https://www.readbyqxmd.com/read/28009563/development-of-synchrotron-x-ray-micro-tomography-under-extreme-conditions-of-pressure-and%C3%A2-temperature
#13
M Álvarez-Murga, J P Perrillat, Y Le Godec, F Bergame, J Philippe, A King, N Guignot, M Mezouar, J L Hodeau
X-ray tomography is a non-destructive three-dimensional imaging/microanalysis technique selective to a wide range of properties such as density, chemical composition, chemical states and crystallographic structure with extremely high sensitivity and spatial resolution. Here the development of in situ high-pressure high-temperature micro-tomography using a rotating module for the Paris-Edinburgh cell combined with synchrotron radiation is described. By rotating the sample chamber by 360°, the limited angular aperture of ordinary high-pressure cells is surmounted...
January 1, 2017: Journal of Synchrotron Radiation
https://www.readbyqxmd.com/read/28009542/oh-cleavage-from-tyrosine-debunking-a-myth
#14
Charles S Bury, Ian Carmichael, Elspeth F Garman
During macromolecular X-ray crystallography experiments, protein crystals held at 100 K have been widely reported to exhibit reproducible bond scission events at doses on the order of several MGy. With the objective to mitigate the impact of radiation damage events on valid structure determination, it is essential to correctly understand the radiation chemistry mechanisms at play. OH-cleavage from tyrosine residues is regularly cited as amongst the most available damage pathways in protein crystals at 100 K, despite a lack of widespread reports of this phenomenon in protein crystal radiation damage studies...
January 1, 2017: Journal of Synchrotron Radiation
https://www.readbyqxmd.com/read/28009541/x-ray-radiation-damage-to-biological-macromolecules-further-insights
#15
Elspeth F Garman, Martin Weik
Despite significant progress made over more than 15 years of research, structural biologists are still grappling with the issue of radiation damage suffered by macromolecular crystals which is induced by the resultant radiation chemistry occurring during X-ray diffraction experiments. Further insights into these effects and the possible mitigation strategies for use in both diffraction and SAXS experiments are given in eight papers in this volume. In particular, damage during experimental phasing is addressed, scavengers for SAXS experiments are investigated, microcrystals are imaged, data collection strategies are optimized, specific damage to tyrosine residues is reexamined, and room temperature conformational heterogeneity as a function of dose is explored...
January 1, 2017: Journal of Synchrotron Radiation
https://www.readbyqxmd.com/read/28008187/the-millimeter-iram-30-m-line-survey-toward-ik-tau
#16
L Velilla Prieto, C Sánchez Contreras, J Cernicharo, M Agúndez, G Quintana-Lacaci, V Bujarrabal, J Alcolea, C Balança, F Herpin, K M Menten, F Wyrowski
AIMS: We aim to investigate the physical and chemical properties of the molecular envelope of the oxygen-rich AGB star IK Tau. METHODS: We carried out a millimeter wavelength line survey between ~79 and 356 GHz with the IRAM-30 m telescope. We analysed the molecular lines detected in IK Tau using the population diagram technique to derive rotational temperatures and column densities. We conducted a radiative transfer analysis of the SO2 lines, which also helped us to verify the validity of the approximated method of the population diagram for the rest of the molecules...
January 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/28001448/following-the-interstellar-history-of-carbon-from-the-interiors-of-stars-to-the-surfaces-of-planets
#17
L M Ziurys, D T Halfen, W Geppert, Y Aikawa
The chemical history of carbon is traced from its origin in stellar nucleosynthesis to its delivery to planet surfaces. The molecular carriers of this element are examined at each stage in the cycling of interstellar organic material and their eventual incorporation into solar system bodies. The connection between the various interstellar carbon reservoirs is also examined. Carbon has two stellar sources: supernova explosions and mass loss from evolved stars. In the latter case, the carbon is dredged up from the interior and then ejected into a circumstellar envelope, where a rich and unusual C-based chemistry occurs...
December 2016: Astrobiology
https://www.readbyqxmd.com/read/27995274/emergence-of-life-on-earth-a-physicochemical-jigsaw-puzzle
#18
REVIEW
Jan Spitzer
We review physicochemical factors and processes that describe how cellular life can emerge from prebiotic chemical matter; they are: (1) prebiotic Earth is a multicomponent and multiphase reservoir of chemical compounds, to which (2) Earth-Moon rotations deliver two kinds of regular cycling energies: diurnal electromagnetic radiation and seawater tides. (3) Emerging colloidal phases cyclically nucleate and agglomerate in seawater and consolidate as geochemical sediments in tidal zones, creating a matrix of microspaces...
January 2017: Journal of Molecular Evolution
https://www.readbyqxmd.com/read/27994676/pre-clinical-evaluation-of-a-novel-class-of-anti-cancer-agents-the-pyrrolo-1-5-benzoxazepines
#19
REVIEW
L M Greene, S Butini, G Campiani, D C Williams, D M Zisterer
Microtubules are currently ranked one of the most validated targets for chemotherapy; with clinical use of microtubule targeting agents (MTAs) extending beyond half a century. Recent research has focused on the development of novel MTAs to combat drug resistance and drug associated toxicities. Of particular interest are compounds structurally different to those currently used within the clinic. The pyrrolo-1, 5-benzoxazepines (PBOXs) are a structurally distinct novel group of anti-cancer agents, some of which target tubulin...
2016: Journal of Cancer
https://www.readbyqxmd.com/read/27973843/reevaluation-of-neptunium-nitric-acid-radiation-chemistry-by-multiscale-modeling
#20
G P Horne, T S Grimes, B J Mincher, S P Mezyk
Multiscale modeling has been used to quantitatively reevaluate the radiation chemistry of neptunium in a range of aerated nitric acid solutions (0.1-6.0 mol dm(-3)). Exact calculation of initial radiolytic yields accounting for changes in radiation track chemistry was found to be crucial for reproducing experimental data. The γ irradiation induces changes in the Np(VI)/Np(V) oxidation-state distribution, predominantly driven by reactions involving HNO2, H2O2, NO2(•), and NO3(•) from the radiolysis of aqueous nitric acid...
December 15, 2016: Journal of Physical Chemistry. B
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