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https://www.readbyqxmd.com/read/29339305/modelling-ros-formation-in-boreal-lakes-from-interactions-between-dissolved-organic-matter-and-absorbed-solar-photon-flux
#1
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...
January 11, 2018: Water Research
https://www.readbyqxmd.com/read/29338219/pretargeted-immuno-pet-based-on-bioorthogonal-chemistry-for-imaging-egfr-positive-colorectal-cancer
#2
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
https://www.readbyqxmd.com/read/29315751/does-the-choice-of-the-crystal-structure-influence-the-results-of-the-periodic-dft-calculations-a-case-of-glycine-alpha-polymorph-gipaw-nmr-parameters-computations
#3
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
https://www.readbyqxmd.com/read/29283671/photobiological-effects-at-earth-s-surface-following-a-50%C3%A2-pc-supernova
#4
Brian C Thomas
We investigated the potential biological impacts at Earth's surface of stratospheric O3 depletion caused by nearby supernovae known to have occurred about 2.5 and 8 million years ago at about 50 pc distance. New and previously published atmospheric chemistry modeling results were combined with radiative transfer modeling to determine changes in surface-level solar irradiance and biological responses. We find that UVB irradiance is increased by a factor of 1.1 to 2.8, with large variation in latitude, and seasonally at high-latitude regions...
December 28, 2017: Astrobiology
https://www.readbyqxmd.com/read/29260851/structure-property-relations-in-giant-semiconductor-nanocrystals-opportunities-in-photonics-and-electronics
#5
Fabiola Navarro-Pardo, Haiguang Zhao, Zhiming M Wang, Federico Rosei
Semiconductor nanocrystals exhibit size-tunable absorption and emission ranging from the ultraviolet (UV) to the near-infrared (NIR) spectral range, high absorption coefficient, and high photoluminescence quantum yield. Effective surface passivation of these so-called quantum dots (QDs) may be achieved by growing a shell of another semiconductor material. The resulting core/shell QDs can be considered as a model system to study and optimize structure/property relations. A special case consists in growing thick shells (1...
December 20, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/29246047/synthesis-of-complex-organic-molecules-in-simulated-methane-rich-astrophysical-ices
#6
Sasan Esmaili, Andrew D Bass, Pierre Cloutier, Léon Sanche, Michael A Huels
It has been proposed that organic molecules required for life on earth may be formed by the radiation processing of molecular ices in space environments, e.g., within our solar system. Such processes can be studied in the laboratory with surface science analytical techniques and by using low-energy electron (LEE) irradiation to simulate the effects of the secondary electrons that are generated in great abundance whenever ionizing radiation interacts with matter. Here we present new measurements of 70 eV LEE irradiation of multilayer films of CH4, 18O2, and CH4/18O2 mixtures (3:1 ratio) at 22 K...
December 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/29240421/photochemistry-of-fe-h2o-adducts-in-argon-matrices-a-combined-experimental-and-theoretical-study-in-the-mid-ir-and-uv-visible-regions
#7
Vincent Deguin, Joëlle Mascetti, Aude Simon, Nadia Ben Amor, Christian Aupetit, Sandra Latournerie, Jennifer Anna Noble
The photochemistry of Fe:H2O adducts is of interest in fields as diverse as catalysis and astrochemistry. Industrially, iron can be used as a catalyst to convert H2O to H2, while in the interstellar medium it may be an important component of dust grains, influencing the chemistry on their icy surfaces. This study consisted of the deposition and spectral characterisation of binary systems of atomic iron with H2O in cryogenic argon matrices. In this way, we were able to obtain information about the interaction of the two species; we observed the formation of adducts of iron monomers and dimers with water molecules in the mid-IR and UV-visible spectral domains...
December 14, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29221417/l-edge-spectroscopy-of-dilute-radiation-sensitive-systems-using-a-transition-edge-sensor-array
#8
Charles J Titus, Michael L Baker, Sang Jun Lee, Hsiao-Mei Cho, William B Doriese, Joseph W Fowler, Kelly Gaffney, Johnathon D Gard, Gene C Hilton, Chris Kenney, Jason Knight, Dale Li, Ronald Marks, Michael P Minitti, Kelsey M Morgan, Galen C O'Neil, Carl D Reintsema, Daniel R Schmidt, Dimosthenis Sokaras, Daniel S Swetz, Joel N Ullom, Tsu-Chien Weng, Christopher Williams, Betty A Young, Kent D Irwin, Edward I Solomon, Dennis Nordlund
We present X-ray absorption spectroscopy and resonant inelastic X-ray scattering (RIXS) measurements on the iron L-edge of 0.5 mM aqueous ferricyanide. These measurements demonstrate the ability of high-throughput transition-edge-sensor (TES) spectrometers to access the rich soft X-ray (100-2000 eV) spectroscopy regime for dilute and radiation-sensitive samples. Our low-concentration data are in agreement with high-concentration measurements recorded by grating spectrometers. These results show that soft-X-ray RIXS spectroscopy acquired by high-throughput TES spectrometers can be used to study the local electronic structure of dilute metal-centered complexes relevant to biology, chemistry, and catalysis...
December 7, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/29215277/review-of-the-scientific-understanding-of-radioactive-waste-at-the-u-s-doe-hanford-site
#9
Reid A Peterson, Edgar C Buck, Jaehun Chun, Richard C Daniel, Daniel L Herting, Eugene S Ilton, Gregg J Lumetta, Sue B Clark
This paper reviews the origin and chemical and rheological complexity of radioactive waste at the U.S. Department of Energy Hanford Site. The waste, stored in underground tanks, was generated via three distinct processes over decades of plutonium extraction operations. Although close records were kept of original waste disposition, tank-to-tank transfers and conditions that impede equilibrium complicate our understanding of the chemistry, phase composition, and rheology of the waste. Tank waste slurries comprise particles and aggregates from nano to micron scales, with varying densities, morphologies, heterogeneous compositions, and complicated responses to flow regimes and process conditions...
December 7, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/29196935/serial-femtosecond-crystallography-at-the-sacla-breakthrough-to-dynamic-structural-biology
#10
REVIEW
Eiichi Mizohata, Takanori Nakane, Yohta Fukuda, Eriko Nango, So Iwata
X-ray crystallography visualizes the world at the atomic level. It has been used as the most powerful technique for observing the three-dimensional structures of biological macromolecules and has pioneered structural biology. To determine a crystal structure with high resolution, it was traditionally required to prepare large crystals (> 200 μm). Later, synchrotron radiation facilities, such as SPring-8, that produce powerful X-rays were built. They enabled users to obtain good quality X-ray diffraction images even with smaller crystals (ca...
December 1, 2017: Biophysical Reviews
https://www.readbyqxmd.com/read/29188145/a-three-dimensional-spatial-mapping-approach-to-quantify-fine-scale-heterogeneity-among-leaves-within-canopies
#11
Jenna L Wingfield, Lauren G Ruane, Joshua D Patterson
Premise of the study: The three-dimensional structure of tree canopies creates environmental heterogeneity, which can differentially influence the chemistry, morphology, physiology, and/or phenology of leaves. Previous studies that subdivide canopy leaves into broad categories (i.e., "upper/lower") fail to capture the differences in microenvironments experienced by leaves throughout the three-dimensional space of a canopy. Methods: We use a three-dimensional spatial mapping approach based on spherical polar coordinates to examine the fine-scale spatial distributions of photosynthetically active radiation (PAR) and the concentration of ultraviolet (UV)-absorbing compounds (A300) among leaves within the canopies of black mangroves (Avicennia germinans)...
November 2017: Applications in Plant Sciences
https://www.readbyqxmd.com/read/29171952/dynamics-of-radical-ions-of-hydroxyhexafluoroisopropyl-substituted-benzenes
#12
Kazumasa Okamoto, Naoya Nomura, Ryoko Fujiyoshi, Kikuo Umegaki, Hiroki Yamamoto, Kazuo Kobayashi, Takahiro Kozawa
Fluorination of the resist materials is one of the effective methods to enhance the energy deposition of extreme-ultraviolet (EUV) light for fabrications of the next-generation semiconductor devices. Dynamics of radical ions is important for radiation-chemistry of resist materials using EUV and electron beam lithography. Here, we studied dynamics of the radical anions and cations of benzenes with one or two 2-hydroxyhexafluoroisopropyl group (HFABs) using radiolysis techniques. Formation of dimer radical cation was observed only in mono-substituted benzene solutions in 1,2-dichloroethane...
November 24, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29151472/-fricke-gel-dosimeters
#13
Takuya Maeyama
Fricke gel dosimeters are based on the aqueous ferrous sulfate solution that has been used as a reliable chemical dosimeter for more than 90 years. The amount of radiation-induced oxidation of ferrous ions to ferric ions could be evaluated three-dimensionally via optical computed tomography (OCT) or magnetic resonance imaging (MRI). Three-dimensional dosimetry is expected to be a useful tool, in particular, for the verification of complex radiation dose planning in advanced radiation cancer therapy. Compared with other 3D gel dosimeters, there are several problems such as retention of dose distribution or dose sensitivity; however, they can easily be prepared in a chemistry laboratory...
2017: Japanese Journal of Medical Physics
https://www.readbyqxmd.com/read/29142326/complex-organic-molecules-in-strongly-uv-irradiated-gas
#14
S Cuadrado, J R Goicoechea, J Cernicharo, A Fuente, J Pety, B Tercero
We investigate the presence of complex organic molecules (COMs) in strongly UV-irradiated interstellar molecular gas. We have carried out a complete millimetre (mm) line survey using the IRAM 30 m telescope towards the edge of the Orion Bar photodissociation region (PDR), close to the H2 dissociation front, a position irradiated by a very intense far-UV (FUV) radiation field. These observations have been complemented with 8.5″ resolution maps of the H2CO JKa,Kc = 51,5 → 41,4 and C(18)O J = 3 → 2 emission at 0...
July 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/29141565/radio-modulatory-potential-ofcaffeic-acid-phenethyl-ester-a-therapeutic-perspective
#15
Km Anjaly, Ashu Tiku
Use of natural agents is an upcoming area of research in cancer biology. Caffeic acid phenethyl ester has received great attention because of its therapeutic potential in various conditions including cancer. It is an active/abundant component of propolis. Propolis is a honey bee hive product produced by bees using their enzyme-rich digestive secretions on resinous mix, bee wax and pollen from plants. It is used to protect the beehive against bacteria and other infections.Although a lot of work has been done on chemotherapeutic aspects of CAPE, its role as a radiomodulator is yet to be delineated...
November 13, 2017: Anti-cancer Agents in Medicinal Chemistry
https://www.readbyqxmd.com/read/29139511/radiation-chemistry-of-solid-acetone-in-the-interstellar-medium-a-new-dimension-to-an-old-problem
#16
R L Hudson
A laboratory investigation of acetone, an interstellar and cometary molecule, has produced new results concerning its decomposition in a radiation environment. Mid-infrared spectroscopy has been used to follow amorphous acetone's destruction by ionizing radiation (1 MeV protons) at 20 K. Radiation products identified are the CH4, CO, and CO2 usually made in such experiments, along with ketene, allene, and the acetonyl radical, all identified here for the first time in irradiated solid acetone. Evidence for the reduction product 2-propanol was suggestive, but a firm identification could not be made either for it or for the C2 hydrocarbons (i...
November 15, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29129050/metal-free-cycloaddition-chemistry-driven-pretargeted-radioimmunotherapy-using-%C3%AE-particle-radiation
#17
Manan Shah, Xiuli Zhang, Raffaella Rossin, Marc S Robillard, Darrell Fisher, Tyler Bueltmann, Freek J M Hoeben, Thomas Quinn
The pretargeted radioimmunotherapy approach (PRIT) decouples the administration of tumor targeting monoclonal antibodies (mAb) from that of the radiolabeled ligand. This multi-step strategy allows delivery of high doses of radiation to tumor cells while minimizing non-specific normal tissue irradiation. In this study, we evaluated the potential of pretargeted α-particle radioimmunotherapy based on inverse electron demand Diels-Alder reaction (IEDAA) between trans-cyclooctene (TCO) and tetrazine (Tz). Two tetrazine based chelators, DOTA-Tz and TCMC-Tz, were synthesized and compared for their radiolabeling efficiency with 212Pb, radiochemical stability and in-vivo pharmacokinetics...
November 12, 2017: Bioconjugate Chemistry
https://www.readbyqxmd.com/read/29125605/synchrotron-radiation-in-situ-x-ray-absorption-fine-structure-and-in-situ-x-ray-diffraction-analysis-of-a-high-performance-cobalt-catalyst-towards-the-oxygen-reduction-reaction
#18
Haiying Qin, Longxia Lin, Junkang Jia, Huangliang Ni, Yan He, Juan Wang, Aiguo Li, Zhenguo Ji, Jiabin Liu
Transition metal-based composites are one of the most important electrocatalysts because of their rich redox chemistry. The reaction kinetics of a redox couple is dependent on the chemical valence and is a key issue in electrocatalytic performance. In this study, a metallic Co catalyst was synthesized by pyrolyzing Co(OH)2. The effect of the chemical valence of Co on the oxygen reduction reaction (ORR) was investigated by comparing the electrocatalytic properties of three Co-based catalysts containing Co(0), Co(2+), and Co(3+)...
November 22, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29075688/at-the-crossroad-of-photochemistry-and-radiation-chemistry-formation-of-hydroxyl-radicals-in-diluted-aqueous-solutions-exposed-to-ultraviolet-radiation
#19
Kateřina Tomanová, Martin Precek, Viliam Múčka, Luděk Vyšín, Libor Juha, Václav Čuba
Formation yields of ˙OH radicals were precisely determined in aqueous solutions of coumarin-3-carboxylic acid and ferrous sulfate (i.e., Fricke dosimeter) exposed to 253.7 nm radiation delivered from a continuous source. Quantum yield of ˙OH radicals was determined as ∼0.08, i.e., roughly one out of twelve photons, efficiently absorbed in UV-illuminated solutions, produced one ˙OH radical. Energetically, a water molecule should undergo a correlated action of at least two 4.9 eV photons delivering enough energy for direct H-OH dissociation (5...
November 8, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29067367/a-general-method-for-the-inclusion-of-radiation-chemistry-in-astrochemical-models
#20
Christopher N Shingledecker, Eric Herbst
In this paper, we propose a general formalism that allows for the estimation of radiolysis decomposition pathways and rate coefficients suitable for use in astrochemical models, with a focus on solid phase chemistry. Such a theory can help increase the connection between laboratory astrophysics experiments and astrochemical models by providing a means for modelers to incorporate radiation chemistry into chemical networks. The general method proposed here is targeted particularly at the majority of species now included in chemical networks for which little radiochemical data exist; however, the method can also be used as a starting point for considering better studied species...
October 25, 2017: Physical Chemistry Chemical Physics: PCCP
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