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radiation chemistry

John Mark Cline, Greg Dugan, John Daniel Bourland, Donna L Perry, Joel D Stitzel, Ashley A Weaver, Chen Jiang, Artak Tovmasyan, Kouros Owzar, Ivan Spasojevic, Ines Batinic-Haberle, Zeljko Vujaskovic
Radiation injury to the lung is the result of acute and chronic free radical formation, and there are currently few effective means of mitigating such injury. Studies in rodents indicate that superoxide dismutase mimetics may be effective in this regard; however, studies in humans or large animals are lacking. We hypothesized that post-exposure treatment with the lipophilic mitochondrial superoxide dismutase mimetic, MnTnHex-2-PyP5+ (hexyl), would reduce radiation-induced pneumonitis and fibrosis in the lungs of nonhuman primates...
March 7, 2018: Antioxidants (Basel, Switzerland)
Jan Chalabala, Frank Uhlig, Petr Slavicek
Ionization in the condensed phase and molecular clusters leads to a complicated chain of processes with coupled electron-nuclear dynamics. It is difficult to describe such dynamics with conventional nonadiabatic molecular dynamics schemes since the number of states swiftly increases as the molecular system grows. It is therefore attractive to use a direct electron and nuclear propagation such as the real-time time-dependent density functional theory (RT-TDDFT). Here we report a RT-TDDFT benchmark study on simulations of singly and doubly-ionized states of a water monomer and dimer as a prototype for more complex processes in a condensed phase...
March 7, 2018: Journal of Physical Chemistry. A
George Rhoderick, Michael Edwin Kelley, Walter R Miller, James E Norris, Jennifer Carney, Lyn Gameson, Christina Cecelski, Kimberly Harris, Cassie Goodman, Abneesh Srivastava, Joseph T Hodges
There are many gas phase compounds present in the atmosphere that effect and influence the earth's climate. These compounds absorb and emit radiation, a process which is the fundamental cause of the greenhouse effect. The major greenhouse gases in the earth's atmosphere are carbon dioxide, methane, nitrous oxide and ozone. Some halocarbons are also strong greenhouse gases and are linked to stratospheric ozone depletion. Hydrocarbons and monoterpenes are precursors and contributors to atmospheric photochemical processes which leads to the formation of particulates and secondary photo oxidants such as ozone leading to photochemical smog...
March 2, 2018: Analytical Chemistry
J Eric Nielsen, Steven Pawson, Andrea Molod, Benjamin Auer, Arlindo M da Silva, Anne R Douglass, Bryan Duncan, Qing Liang, Michael Manyin, Luke D Oman, William Putman, Susan E Strahan, Krzysztof Wargan
NASA's Goddard Earth Observing System (GEOS) Earth System Model (ESM) is a modular, general circulation model (GCM), and data assimilation system (DAS) that is used to simulate and study the coupled dynamics, physics, chemistry, and biology of our planet. GEOS is developed by the Global Modeling and Assimilation Office (GMAO) at NASA Goddard Space Flight Center. It generates near-real-time analyzed data products, reanalyses, and weather and seasonal forecasts to support research targeted to understanding interactions among Earth System processes...
December 2017: Journal of Advances in Modeling Earth Systems
Eranezhuth Wasan Awin, Abhijeet Lale, Kollamala Chellappan Nair Hari Kumar, Umit Bilge Demirci, Samuel Bernard, Ravi Kumar
Titania (TiO₂) is considered to have immense potential as a photocatalyst, the anatase phase in particular. There have been numerous attempts to push the limits of its catalytic activity to higher wavelengths to harness the visible electromagnetic radiation. Most of the investigations till date have been restricted to fine-tuning the bandgap by doping, control of defect chemistry at the surface and several to first principle simulations either with limited success or success at the cost of complexities in processing...
March 1, 2018: Materials
Dominika Borek, Raquel Bromberg, Johan Hattne, Zbyszek Otwinowski
A method of analysis is presented that allows for the separation of specific radiation-induced changes into distinct components in real space. The method relies on independent component analysis (ICA) and can be effectively applied to electron density maps and other types of maps, provided that they can be represented as sets of numbers on a grid. Here, for glucose isomerase crystals, ICA was used in a proof-of-concept analysis to separate temperature-dependent and temperature-independent components of specific radiation-induced changes for data sets acquired from multiple crystals across multiple temperatures...
March 1, 2018: Journal of Synchrotron Radiation
Hao Jiang, Izabela Szlufarska
It is known that grain boundaries (GBs) provide sinks for defects induced into a solid by irradiation. At the same time radiation can change the atomic structure and chemistry of GBs, which in turn impacts the ability of GBs to continue absorbing defects. Although a number of studies have been reported for tilt GBs acting as defect sinks, the questions of how twist GBs evolve to absorb non-equilibrium concentrations of defects and whether GBs saturate as defect sinks for typical irradiation conditions have remained largely unanswered...
February 27, 2018: Scientific Reports
Christian van der Linde, Wai Kit Tang, Chi-Kit Siu, Martin K Beyer
A significant fraction of nitrate in the troposphere is formed in the reactions of HNO3 with the carbonate radical anion CO3 ˙- and the mono- and dihydrated species CO3 ˙- (H2 O)1,2 . A reaction mechanism was proposed in earlier flow reactor studies, which is investigated here in more detail by quantum chemical calculations and experimental reactivity studies of mass selected ions under ultra-high vacuum conditions. Bare CO3 ˙- forms NO3 - (OH˙) as well as NO3 - , with a total rate coefficient of 1.0 × 10-10 cm3 s-1 ...
February 23, 2018: Physical Chemistry Chemical Physics: PCCP
Sara Khademi, Saeed Sarkar, Sharmin Kharrazi, Seyed Mohammad Amini, Ali Shakeri-Zadeh, Mohammad Reza Ay, Hossein Ghadiri
Increasing attention has been focused on the use of nanostructures as contrast enhancement agents in medical imaging, especially in computed tomography (CT). To date, gold nanoparticles (GNPs) have been demonstrated to have great potential as contrast agents for CT imaging. This study was designed to evaluate any effect on X-ray attenuation that might result from employing GNPs with a variety of shapes, sizes, surface chemistries, and concentrations. Gold nanorods (GNRs) and spherical GNPs were synthesized for this application...
January 2018: Physica Medica: PM
Colin R Gregson, Gregory P Horne, Robin M Orr, Simon M Pimblott, Howard E Sims, Robin J Taylor, Kevin J Webb
The yield of molecular hydrogen, as a function of nitric acid concentration, from the α-radiolysis of aerated nitric acid and its mixtures with sulfuric acid containing plutonium or americium has been investigated. Comparison of experimental measurements with predictions of a Monte Carlo radiation track chemistry model shows that, in addition to scavenging of the hydrated electron, its precursor, and the hydrogen atom, the quenching of excited state water is important in controlling the yield of molecular hydrogen...
February 22, 2018: Journal of Physical Chemistry. B
Emeric Bron, Chloé Daudon, Jérôme Pety, François Levrier, Maryvonne Gerin, Pierre Gratier, Jan H Orkisz, Viviana Guzman, Sébastien Bardeau, Javier R Goicoechea, Harvey Liszt, Karin Öberg, Nicolas Peretto, Albrecht Sievers, Pascal Tremblin
Context: Previous attempts at segmenting molecular line maps of molecular clouds have focused on using position-position-velocity data cubes of a single molecular line to separate the spatial components of the cloud. In contrast, wide field spectral imaging over a large spectral bandwidth in the (sub)mm domain now allows one to combine multiple molecular tracers to understand the different physical and chemical phases that constitute giant molecular clouds (GMCs). Aims: We aim at using multiple tracers (sensitive to different physical processes and conditions) to segment a molecular cloud into physically/chemically similar regions (rather than spatially connected components), thus disentangling the different physical/chemical phases present in the cloud...
February 2018: Astronomy and Astrophysics
Michael V Accardi, Oreola Donini, Adam Rumage, Alexis Ascah, Julius Haruna, Mylène Pouliot, Kim Bujold, Hai Haung, Wieslaw Wierzbicki, John Stamatopoulos, Houman Naraghi, Thomas Measey, Simon Authier
PURPOSE: Characterization of a novel partial body irradiation (PBI) shielding strategy in nonhuman primates (NHP; rhesus macaques), aimed at protecting the oral cavity, with respect to various gastrointestinal (GI-ARS) syndrome parameters as well as buccal ulceration development. MATERIALS AND METHODS: NHPs were irradiated using a Cobalt-60 gamma source, in a single uniform dose, ranging from 9-13 Gy and delivered at 0.60-0.80 Gy min -1 . Animals were either partially shielded via oral cavity shielding (PBI OS ) or underwent total body irradiation (TBI)...
February 15, 2018: International Journal of Radiation Biology
Sarah Freeman, David Lee, Ling Ling Lim, Agnieszka Maria Skowron, Ruben Rodriguez De Leon
Aviation emits pollutants that affect climate, including CO2 and NOx; NOx indirectly so, through the formation of tropospheric ozone and reduction of ambient methane. To improve the fuel performance of engines, combustor temperatures and pressures often increase, increasing NOx emissions. Conversely, combustor modifications to reduce NOx may increase CO2. Hence, a technology tradeoff exists, which also translates to a tradeoff between short lived climate forcers and a long-lived greenhouse gas, CO2. Moreover, the NOx-O3-CH4 system responds in a non-linear manner, according to both aviation emissions and background NOx...
February 8, 2018: Environmental Science & Technology
Marek Piątkowski, Łukasz Janus, Julia Radwan-Pragłowska, Dariusz Bogdał, Dalibor Matysek
A new type of promising chitosan beads with advanced properties were obtained under microwave radiation according to Green Chemistry principles. Biomaterials were prepared using chitosan as raw material and glutamic acid/1,5-pentanodiol mixture as crosslinking agents. Additionally beads were modified with Tilia platyphyllos extract to enhance their antioxidant properties. Beads were investigated over their chemical structure by FT-IR analysis. Also their morphology has been investigated by SEM method. Additionally swelling capacity of the obtained hydrogels was determined...
February 1, 2018: Colloids and Surfaces. B, Biointerfaces
Xin Xu, Long-Quan Xu, Tao Xiong, Tao Chen, Ya-Wei Liu, Lin-Fan Zhu
The generalized oscillator strengths for the valence-shell excitations of A2Σ+, C2Π, and D2Σ+ electronic-states of nitric oxide have been determined at an incident electron energy of 1500 eV with an energy resolution of 70 meV. The optical oscillator strengths for these transitions have been obtained by extrapolating the generalized oscillator strengths to the limit that the squared momentum transfer approaches to zero, which give an independent cross-check to the previous experimental and theoretical results...
January 28, 2018: Journal of Chemical Physics
Jun Ma, Furong Wang, Mehran Mostafavi
Oxidation reactions by radicals constitute a very important class of chemical reactions in solution. Radiation Chemistry methods allow producing, in a controlled way, very reactive oxidizing radicals, such as OH•, CO₃•-, NO₃•, SO₄•-, and N₃•. Although the radical cation of water, H₂O•+, with a very short lifetime (shorter than 1 ps) is the precursor of these radicals in aqueous solutions, its chemistry is usually known to be limited to the reaction of proton transfer by forming OH• radical...
January 26, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Matthew James Abplanalp, Sándor Góbi, Alexandre Bergantini, Andrew M Turner, Ralf I Kaiser
Complex organic molecules are ubiquitous in star- and planet-forming regions as well as on comets such as on 67P/Churyumov-Gerasimenko, but their origins have remained largely unexplained until now. Here, we report the first laboratory detection of distinct C3H8O (propanol, methyl ethyl ether) and C4H8O (n-butanal, i-butanal) isomers formed within interstellar analog ices through interaction with ionizing radiation. This study reveals that complex organics with propyl (C3H7) and butyl (C4H9) groups can be synthesized easily in deep space and may act as key evolutionary tracers of a cosmic ray driven non-equilibrium chemistry in low temperature interstellar ices at 10 K...
January 22, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Raoul Wolf, Jan-Erik Thrane, Dag Olav Hessen, Tom Andersen
Concentrations of dissolved organic matter (DOM) are increasing in a large number of lakes across the Northern hemisphere. This browning serves a dual role for biota by protecting against harmful ultraviolet radiation, while also absorbing photosynthetically active radiation. The photochemical activation of DOM and subsequent formation of reactive oxygen species (ROS) is a potentially harmful side effect, but can be difficult to measure directly in situ. In this study, we combine a data set of physico-chemical properties from 71 Nordic lakes with in vitro ROS formation quantum yields to predict ROS formations across a representative boreal ecosystem gradient...
April 1, 2018: Water Research
Xudong Shi, Kai Gao, Hao Huang, Ran Gao
Pretargeted immuno-PET imaging based on the bioorthogonal chemistry between 18F-labeled Reppe anhydride derivatives and tetrazine conjugates of the EGFR-specific monoclonal antibodies cetuximab and panitumumab was performed. This pretargeting approach yielded high target-to-nontarget ratios. Furthermore, due to the fast clearance rate of the PET probe, the overall radiation burden to nontarget tissues was also substantially decreased.
January 16, 2018: Bioconjugate Chemistry
Łukasz Szeleszczuk, Dariusz Maciej Pisklak, Monika Zielińska-Pisklak
Glycine is a common amino acid with relatively complex chemistry in solid state. Although several polymorphs (α, β, δ, γ, ε) of crystalline glycine are known, for NMR spectroscopy the most important is a polymorph, which is used as a standard for calibration of spectrometer performance and therefore it is intensively studied by both experimental methods and theoretical computation. The great scientific interest in a glycine results in a large number of crystallographic information files (CIFs) deposited in Cambridge Structural Database (CSD)...
January 5, 2018: Journal of Computational Chemistry
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