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https://www.readbyqxmd.com/read/29142326/complex-organic-molecules-in-strongly-uv-irradiated-gas
#1
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
#2
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
#3
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
#4
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
#5
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 10, 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
#6
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
#7
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
https://www.readbyqxmd.com/read/29059055/quantum-yield-in-polymer-wrapped-single-walled-carbon-nanotubes-a-computational-model
#8
Dejan M Djokić, Aranya Goswami
Quantum yield in polymer wrapped single walled carbon nanotubes (SWCNTs) has been computationally investigated using a 2D model of exciton decay with non-radiative channels due to the diffusive motion across the nanotube surface. Beside the role of SWCNT's ends as the exciton quenchers, we have considered the influence of the wrapping polymer through its chemistry and wrapping angle. The model has been solved exactly for zero-angle wrapping, a particular case when the polymer interfaces the nanotube along its axis...
October 23, 2017: Nanotechnology
https://www.readbyqxmd.com/read/29057870/plasmonic-tunnel-junctions-for-single-molecule-redox-chemistry
#9
Bart de Nijs, Felix Benz, Steven J Barrow, Daniel O Sigle, Rohit Chikkaraddy, Aniello Palma, Cloudy Carnegie, Marlous Kamp, Ravishankar Sundararaman, Prineha Narang, Oren A Scherman, Jeremy J Baumberg
Nanoparticles attached just above a flat metallic surface can trap optical fields in the nanoscale gap. This enables local spectroscopy of a few molecules within each coupled plasmonic hotspot, with near thousand-fold enhancement of the incident fields. As a result of non-radiative relaxation pathways, the plasmons in such sub-nanometre cavities generate hot charge carriers, which can catalyse chemical reactions or induce redox processes in molecules located within the plasmonic hotspots. Here, surface-enhanced Raman spectroscopy allows us to track these hot-electron-induced chemical reduction processes in a series of different aromatic molecules...
October 20, 2017: Nature Communications
https://www.readbyqxmd.com/read/29017126/short-term-facilitation-of-microbial-litter-decomposition-by-ultraviolet-radiation
#10
Yang Lin, Steven D Karlen, John Ralph, Jennifer Y King
Solar radiation plays an important role in carbon cycling by increasing the decomposition rates of plant litter and soil organic matter (i.e. photodegradation). Previous work suggests that exposure to radiation can facilitate microbial decomposition of litter by altering litter chemistry and consequently litter degradability (i.e. photopriming). However, it remains unclear to what extent photopriming contributes to litter decomposition processes and on what timescale photopriming operates. We conducted laboratory experiments to compare the effects of UV photopriming at two temporal scales (months versus days)...
February 15, 2018: Science of the Total Environment
https://www.readbyqxmd.com/read/28992690/atmospheric-chemistry-of-e-and-z-cf3ch%C3%A2-chf-hfo-1234ze-oh-reaction-kinetics-as-a-function-of-temperature-and-uv-and-ir-absorption-cross-sections
#11
María Antiñolo, Iván Bravo, Elena Jiménez, Bernabé Ballesteros, José Albaladejo
We report here the rate coefficients for the OH reactions (kOH) with E-CF3CH═CHF and Z-CF3CH═CHF, potential substitutes of HFC-134a, as a function of temperature (263-358 K) and pressure (45-300 Torr) by pulsed laser photolysis coupled to laser-induced fluorescence techniques. For the E-isomer, the existing discrepancy among previous results on the T dependence of kOH needs to be elucidated. For the Z-isomer, this work constitutes the first absolute determination of kOH. No pressure dependence of kOH was observed, while kOH exhibits a non-Arrhenius behavior: kOH(E) = [Formula: see text] and kOH(Z) = [Formula: see text] cm(3) molecule(-1) s(-1), where uncertainties are 2σ...
October 20, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28990403/redox-potential-and-ros-mediated-nanomedicines-for-improving-cancer-therapy
#12
Sterling Glass, Laura Gonzalez Fajardo, Andre Beringhs, Xiuling Lu
SIGNIFICANCE: The overabundance of reactive oxygen species (ROS) and antioxidants in cancer cells represents a challenge for therapeutic intervention, while also providing an opportunity for the development of new strategies to improve clinical therapeutic outcomes. Recent Advances: Nanotechnology has advanced tremendously in recent decades and now offers many potential opportunities to leverage altered redox status to improve conventional therapies. Highly tunable nanoparticle delivery systems have shown great promise for improving: 1) chemotherapy via selective redox-sensitive drug release in tumor cells and limited systemic toxicity; 2) photodynamic therapy via enhancing photoactivation and/or ROS production; and 3) radiation therapy via enhancing ROS production...
October 7, 2017: Antioxidants & Redox Signaling
https://www.readbyqxmd.com/read/28972622/untangling-the-methane-chemistry-in-interstellar-and-solar-system-ices-toward-ionizing-radiation-a-combined-infrared-and-reflectron-time-of-flight-analysis
#13
Matthew J Abplanalp, Brant M Jones, Ralf I Kaiser
Pure methane (CH4/CD4) ices were exposed to three ionizing radiation sources at 5.5 K under ultrahigh vacuum conditions to compare the complex hydrocarbon spectrum produced across several interstellar environments. These irradiation sources consisted of energetic electrons to simulate secondary electrons formed in the track of galactic cosmic rays (GCRs), Lyman α (10.2 eV; 121.6 nm) photons simulated the internal VUV field in a dense cloud, and broadband (112.7-169.8 nm; 11.0-7.3 eV) photons which mimic the interstellar ultra-violet field...
October 3, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28970624/k-and-l-edge-x-ray-absorption-spectroscopy-xas-and-resonant-inelastic-x-ray-scattering-rixs-determination-of-differential-orbital-covalency-doc-of-transition-metal-sites
#14
Michael L Baker, Michael W Mara, James J Yan, Keith O Hodgson, Britt Hedman, Edward I Solomon
Continual advancements in the development of synchrotron radiation sources have resulted in X-ray based spectroscopic techniques capable of probing the electronic and structural properties of numerous systems. This review gives an overview of the application of metal K-edge and L-edge X-ray absorption spectroscopy (XAS), as well as K resonant inelastic X-ray scattering (RIXS), to the study of electronic structure in transition metal sites with emphasis on experimentally quantifying 3d orbital covalency. The specific sensitivities of K-edge XAS, L-edge XAS, and RIXS are discussed emphasizing the complementary nature of the methods...
August 15, 2017: Coordination Chemistry Reviews
https://www.readbyqxmd.com/read/28949933/quantum-yield-in-polymer-wrapped-single-walled-carbon-nanotubes-a-computational-model
#15
Dejan Djokic, Aranya Goswami
Quantum yield in polymer wrapped Single Walled Carbon Nanotubes (SWCNTs) has been computationally investigated using a $2D$ model of exciton decay with non-radiative channels due to the diffusive motion across the nanotube surface. Beside the role of SWCNT's ends as the exciton quenchers, we have considered the influence of the wrapping polymer through its chemistry and wrapping angle. The model has been solved exactly for zero-angle wrapping, a particular case when the polymer interfaces the nanotube along its axis...
September 26, 2017: Nanotechnology
https://www.readbyqxmd.com/read/28942484/characteristics-and-trends-on-global-environmental-monitoring-research-a-bibliometric-analysis-based-on-science-citation-index-expanded
#16
Di Zhang, Hui-Zhen Fu, Yuh-Shan Ho
A bibliometric analysis based on the Science Citation Index Expanded from Web of Science was carried out to provide insights into research activities and trends of the environmental monitoring from 1993 to 2012. Study emphases covered publication outputs, language, categories, journals, countries/territories, institutions, words, and hot issues. The results indicated that the annual output of environmental monitoring publications increased steadily. The environmental sciences and analytical chemistry were the two most common categories...
September 24, 2017: Environmental Science and Pollution Research International
https://www.readbyqxmd.com/read/28936278/modulating-the-catalytic-activity-of-cerium-oxide-nanoparticles-with-the-anion-of-the-precursor-salt
#17
Swetha Barkam, Julian Ortiz, Shashank Saraf, Nicholas Eliason, Rameech Mccormack, Soumen Das, Ankur Gupta, Craig Neal, Alex Petrovici, Cameron Hanson, Michael D Sevilla, Amitava Adhikary, Sudipta Seal
In this work, we tested our hypothesis that surface chemistry and antioxidant properties of cerium nanoparticles (CNPs) are affected by presence of counterions. We first employed various precursor cerium (III) (Ce(III)) salts with different counterions (acetate, nitrate, chloride, sulfate) to synthesize CNPs following the same wet chemical methodology. Electron spin resonance (ESR) studies provided evidence for the formation of radicals from counterions (e.g., NO3•(2-) from reduction of NO3(-) in CNPs synthesized from Ce(III) nitrate)...
September 14, 2017: Journal of Physical Chemistry. C, Nanomaterials and Interfaces
https://www.readbyqxmd.com/read/28910515/chiral-kagome-lattices-from-on-surface-synthesized-molecules
#18
Tao Wang, Qitang Fan, Lin Feng, Zhijie Tao, Jianmin Huang, Huanxin Ju, Qian Xu, Shanwei Hu, Junfa Zhu
Kagome lattices have attracted much attention due to their potential applications in spin-frustrated magnetism and host-guest chemistry. Examples toward the fabrication of 2D Kagome lattices reported previously have a common feature that the precursor molecules were typically structurally intact on surface with no chemical reactions accompanied. Herein, with the combined synchrotron radiation photoelectron spectroscopy (SRPES) and scanning tunneling microscopy (STM), we demonstrated that two types of chiral Kagome lattices from on-surface synthesized organometallic compounds were fabricated, which are known as intermediates of Glaser coupling on silver single crystal surfaces...
September 14, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28905949/electronic-and-molecular-structure-relations-in-diiron-compounds-mimicking-the-fefe-hydrogenase-active-site-studied-by-x-ray-spectroscopy-and-quantum-chemistry
#19
Ramona Kositzki, Stefan Mebs, Nils Schuth, Nils Leidel, Lennart Schwartz, Michael Karnahl, Florian Wittkamp, Daniel Daunke, Andreas Grohmann, Ulf-Peter Apfel, Frédéric Gloaguen, Sascha Ott, Michael Haumann
Synthetic diiron compounds of the general formula Fe2(μ-S2R)(CO)n(L)6-n (R = alkyl or aromatic groups; L = CN(-) or phosphines) are versatile models for the active-site cofactor of hydrogen turnover in [FeFe]-hydrogenases. A series of 18 diiron compounds, containing mostly a dithiolate bridge and terminal ligands of increasing complexity, was characterized by X-ray absorption and emission spectroscopy in combination with density functional theory. Fe K-edge absorption and Kβ main-line emission spectra revealed the varying geometry and the low-spin state of the Fe(i) centers...
September 26, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28901132/regioselectivity-of-the-oh-radical-addition-to-uracil-in-nucleic-acids-a-theoretical-approach-based-on-qm-mm-simulations
#20
Juan Aranda, Antonio Francés-Monerris, Iñaki Tuñón, Daniel Roca-Sanjuán
Oxidation of nucleic acids is ubiquitous in living beings under metabolic impairments and/or exposed to external agents such as radiation, pollutants, or drugs, playing a central role in the development of many diseases mediated by DNA/RNA degeneration. Great efforts have been devoted to unveil the molecular mechanisms behind the OH radical additions to the double bonds of nucleobases; however, the specific role of the biological environment remains relatively unexplored. The present contribution tackles the study of the OH radical addition to uracil from the gas phase to a full RNA macromolecule by means of quantum-chemistry methods combined with molecular dynamics simulations...
September 28, 2017: Journal of Chemical Theory and Computation
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