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https://www.readbyqxmd.com/read/28338703/theoretical-investigation-of-proton-collisions-on-prebiotic-candidates-hydrogen-cyanide-polymers
#1
Marie-Christine Bacchus-Montabonel
One of the major concerns in prebiotic chemistry is the formation and destruction routes of prebiotic compounds in space. As detected for a long time, hydrogen cyanide (HCN) has been suggested to be a feedstock molecule at the origin of life driving easy oligomerization, in particular to form adenine. This may focus on its first oligomers because its dimer cyanomethanimine was recently observed in star-forming regions, or its trimer aminomalononitrile. With regard to the assumption of an extra-terrestrial origin of life, the stability of such species under ultraviolet radiation or in ion-collisions is an open question...
March 24, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28336860/light-emission-intensities-of-luminescent-y%C3%A2-o%C3%A2-eu-and-gd%C3%A2-o%C3%A2-eu-particles-of-various-sizes
#2
Jens Adam, Wilhelm Metzger, Marcus Koch, Peter Rogin, Toon Coenen, Jennifer S Atchison, Peter König
There is great technological interest in elucidating the effect of particle size on the luminescence efficiency of doped rare earth oxides. This study demonstrates unambiguously that there is a size effect and that it is not dependent on the calcination temperature. The Y₂O₃:Eu and Gd₂O₃:Eu particles used in this study were synthesized using wet chemistry to produce particles ranging in size between 7 nm and 326 nm and a commercially available phosphor. These particles were characterized using three excitation methods: UV light at 250 nm wavelength, electron beam at 10 kV, and X-rays generated at 100 kV...
January 25, 2017: Nanomaterials
https://www.readbyqxmd.com/read/28327297/first-proof-of-bismuth-oxide-nanoparticles-as-efficient-radiosensitisers-on-highly-radioresistant-cancer-cells
#3
Callum Stewart, Konstantin Konstantinov, Sally McKinnon, Susanna Guatelli, Michael Lerch, Anatoly Rosenfeld, Moeava Tehei, Stéphanie Corde
This study provides the first proof of the novel application of bismuth oxide as a radiosensitiser. It was shown that on the highly radioresistant 9L gliosarcoma cell line, bismuth oxide nanoparticles sensitise to both kilovoltage (kVp) or megavoltage (MV) X-rays radiation. 9L cells were exposed to a concentration of 50μg.mL(-1) of nanoparticle before irradiation at 125kVp and 10MV. Sensitisation enhancement ratios of 1.48 and 1.25 for 125kVp and 10MV were obtained in vitro, respectively. The radiation enhancement of the nanoparticles is postulated to be a combination of the high Z nature of the bismuth (Z=83), and the surface chemistry...
November 2016: Physica Medica: PM
https://www.readbyqxmd.com/read/28323482/constraints-on-the-early-terrestrial-surface-uv-environment-relevant-to-prebiotic-chemistry
#4
Sukrit Ranjan, Dimitar D Sasselov
The UV environment is a key boundary condition to abiogenesis. However, considerable uncertainty exists as to planetary conditions and hence surface UV at abiogenesis. Here, we present two-stream multilayer clear-sky calculations of the UV surface radiance on Earth at 3.9 Ga to constrain the UV surface fluence as a function of albedo, solar zenith angle (SZA), and atmospheric composition. Variation in albedo and latitude (through SZA) can affect maximum photoreaction rates by a factor of >10.4; for the same atmosphere, photoreactions can proceed an order of magnitude faster at the equator of a snowball Earth than at the poles of a warmer world...
March 2017: Astrobiology
https://www.readbyqxmd.com/read/28298101/acetonitrile-cluster-solvation-in-a-cryogenic-ethane-methane-propane-liquid-implications-for-titan-lake-chemistry
#5
L René Corrales, Thomas D Yi, Samantha K Trumbo, David Shalloway, Jonathan I Lunine, David A Usher
The atmosphere of Titan, Saturn's largest moon, exhibits interesting UV- and radiation-driven chemistry between nitrogen and methane, resulting in dipolar, nitrile-containing molecules. The assembly and subsequent solvation of such molecules in the alkane lakes and seas found on the moon's surface are of particular interest for investigating the possibility of prebiotic chemistry in Titan's hydrophobic seas. Here we characterize the solvation of acetonitrile, a product of Titan's atmospheric radiation chemistry tentatively detected on Titan's surface [H...
March 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28285158/catalytic-topological-insulator-bi2se3-nanoparticles-for-in-vivo-protection-against-ionizing-radiation
#6
Xiao-Dong Zhang, Yaqi Jing, Shasha Song, Jiang Yang, Jun-Ying Wang, Xuhui Xue, Yuho Min, Gyeongbae Park, Xiu Shen, Yuan-Ming Sun, Unyong Jeong
Bi2Se3 nanoparticles (NPs) have attracted wide interests in biological and medical applications. Layer-like Bi2Se3 with high active surface area is promising for free radical scavenging. Here, we extended the medical applications of Bi2Se3 NPs further to in vivo protection against ionizing radiation based on their superior antioxidant activities and electrocatalytic properties. It was found that Bi2Se3 NPs can significantly increase the surviving fraction of mice after exposure of high-energy radiation of gamma ray...
March 8, 2017: Nanomedicine: Nanotechnology, Biology, and Medicine
https://www.readbyqxmd.com/read/28262861/dense-ionization-and-subsequent-non-homogeneous-radical-mediated-chemistry-of-femtosecond-laser-induced-low-density-plasma-in-aqueous-solutions-synthesis-of-colloidal-gold
#7
Hakim Belmouaddine, Minghan Shi, Paul-Ludovic Karsenti, Ridthee Meesat, Léon Sanche, Daniel Houde
The "cold" low density plasma channels generated by the filamentation of powerful femtosecond laser pulses in aqueous solutions constitute a source of dense ionization. Here, we probed the radiation-assisted chemistry of water triggered by laser ionization via the radical-mediated synthesis of nanoparticles in gold chloride aqueous solutions. We showed that the formation of colloidal gold originates from the reduction of trivalent ionic gold initially present in solution by the reactive radicals (e.g. hydrated electrons) produced upon the photolysis of water...
March 6, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28260804/spatial-distribution-of-fir-rotationally-excited-ch-and-oh-emission-lines-in-the-orion-bar-pdr
#8
A Parikka, E Habart, J Bernard-Salas, J R Goicoechea, A Abergel, P Pilleri, E Dartois, C Joblin, M Gerin, B Godard
CONTEXT: The methylidyne cation (CH(+)) and hydroxyl (OH) are key molecules in the warm interstellar chemistry, but their formation and excitation mechanisms are not well understood. Their abundance and excitation are predicted to be enhanced by the presence of vibrationally excited H2 or hot gas (~500-1000 K) in photodissociation regions with high incident FUV radiation field. The excitation may also originate in dense gas (> 10(5) cm(-3)) followed by nonreactive collisions with H2, H, and electrons...
March 2017: Astronomy and Astrophysics
https://www.readbyqxmd.com/read/28238734/drug-releasing-nanoplatforms-activated-by-alternating-magnetic-fields
#9
REVIEW
Damien Mertz, Olivier Sandre, Sylvie Bégin-Colin
The use of an alternating magnetic field (AMF) to generate non-invasively and spatially a localized heating from a magnetic nano-mediator has become very popular these last years to develop magnetic hyperthermia (MH) as a promising therapeutic modality already used in the clinics. AMF has become highly attractive this last decade over others radiations, as AMF allows a deeper penetration in the body and a less harmful ionizing effect. In addition to pure MH which induces tumor cell death through local T elevation, this AMF-generated magneto-thermal effect can also be exploited as a relevant external stimulus to trigger a drug release from drug-loaded magnetic nanocarriers, temporally and spatially...
February 24, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28216663/the-importance-of-pollen-chemistry-in-evolutionary-host-shifts-of-bees
#10
Maryse Vanderplanck, Nicolas J Vereecken, Laurent Grumiau, Fabiana Esposito, Georges Lognay, Ruddy Wattiez, Denis Michez
Although bee-plant associations are generally maintained through speciation processes, host shifts have occurred during evolution. Understanding shifts between both phylogenetically and morphologically unrelated plants (i.e., host-saltation) is especially important since they could have been key processes in the origin and radiation of bees. Probably far from being a random process, such host-saltation might be driven by hidden constraints associated with plant traits. We selected two clades of oligolectic bees (i...
February 20, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28210619/a-useful-tool-as-a-medical-checkup-in-a-general-population-bioelectrical-impedance-analysis
#11
Mika Enomoto, Hisashi Adachi, Ako Fukami, Eita Kumagai, Sachiko Nakamura, Yume Nohara, Shoko Kono, Erika Nakao, Nagisa Morikawa, Tomoko Tsuru, Akiko Sakaue, Yoshihiro Fukumoto
Accumulation of visceral fat leads to metabolic syndrome and increases risks of cerebro-cardiovascular diseases, which should be recognized and improved at the early stage in general population. Accurate measurement of visceral fat area (VFA) is commonly performed by the abdominal cross-sectional image measured by computed tomography scan, which is, however, limited due to the radiation exposure. The bioelectrical impedance analysis (OMRON, HDS-2000 DUALSCAN(R)) has been recently developed to measure VFA, which is more easily accessible modality...
2017: Frontiers in Cardiovascular Medicine
https://www.readbyqxmd.com/read/28182184/surface-plasmon-polariton-induced-hot-carrier-generation-for-photocatalysis
#12
Wonmi Ahn, Daniel C Ratchford, Pehr E Pehrsson, Blake S Simpkins
Non-radiative plasmon decay in noble metals generates highly energetic carriers under visible light irradiation, which opens new prospects in the fields of photocatalysis, photovoltaics, and photodetection. While localized surface plasmon-induced hot carrier generation occurs in diverse metal nanostructures, inhomogeneities typical of many metal-semiconductor plasmonic nanostructures hinder predictable control of photocarrier generation and therefore reproducible carrier-mediated photochemistry. Here, we generate traveling surface plasmon polaritons (SPPs) at the interface between a noble metal/titanium dioxide (TiO2) heterostructure film and aqueous solution, enabling simultaneous optical and electrochemical interrogation of plasmon-mediated chemistry in a system whose resonance may be continuously tuned via the incident optical excitation angle...
February 9, 2017: Nanoscale
https://www.readbyqxmd.com/read/28165081/vibrational-branching-ratios-and-radiative-lifetimes-in-the-laser-cooling-of-albr
#13
Yufeng Gao, Mingjie Wan
The feasibility of laser cooling of the AlBr molecule is investigated using ab initio quantum chemistry. Potential energy curves, permanent dipole moments, and transition dipole moments for the ground state X(1)Σ(+) and the first two excited states (a(3)Π and A(1)Π) are calculated using the multi-reference configuration interaction plus Davidson corrections (MRCI+Q) method with the ACVQZ basis set; the spin-orbit coupling effects are also taken into account in electronic structure calculations at the MRCI level...
February 6, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28151534/targeted-nanoparticles-for-tumour-radiotherapy-enhancement-the-long-dawn-of-a-golden-era
#14
Elisabetta Gargioni, Florian Schulz, Annette Raabe, Susanne Burdak-Rothkamm, Thorsten Rieckmann, Kai Rothkamm
Despite considerable progress in (I) our understanding of the aetiopathology of head and neck cancer and (II) the precise delivery of radiotherapy, long-term survival rates for many patients with head and neck cancer remain disappointingly low. Over the past years, gold nanoparticles (NP) have emerged as promising radiation dose enhancers. In a recent study published in Nanoscale, Popovtzer et al. have used gold NP coated with an antibody against the epidermal growth factor receptor (EGFR) in an attempt to enhance radiation-induced tumour cell killing in a head and neck cancer xenograft model...
December 2016: Annals of Translational Medicine
https://www.readbyqxmd.com/read/28140563/abrupt-size-partitioning-of-multimodal-photoluminescence-relaxation-in-monodisperse-silicon-nanocrystals
#15
Samuel L Brown, Joseph B Miller, Rebecca J Anthony, Uwe R Kortshagen, Andrei Kryjevski, Erik K Hobbie
Intrinsic constraints on efficient photoluminescence (PL) from smaller alkene-capped silicon nanocrystals (SiNCs) put limits on potential applications, but the root cause of such effects remains elusive. Here, plasma-synthesized colloidal SiNCs separated into monodisperse fractions reveal an abrupt size-dependent partitioning of multilevel PL relaxation, which we study as a function of temperature. Guided by theory and simulation, we explore the potential role of resonant phonon interactions with "minigaps" that emerge in the electronic density of states (DOS) under strong quantum confinement...
February 28, 2017: ACS Nano
https://www.readbyqxmd.com/read/28138685/actinide-ion-extraction-using-room-temperature-ionic-liquids-opportunities-and-challenges-for-nuclear-fuel-cycle-applications
#16
Prasanta Kumar Mohapatra
Studies on the extraction of actinide ions from radioactive feeds have great relevance in nuclear fuel cycle activities, mainly in the back end processes focused on reprocessing and waste management. Room temperature ionic liquid (RTIL) based diluents are becoming increasingly popular due to factors such as more efficient extraction vis-à-vis molecular diluents, higher metal loading, higher radiation resistance, etc. The fascinating chemistry of the actinide ions in RTIL based solvent systems due to complex extraction mechanisms makes it a challenging area of research...
January 31, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28134238/charge-transfer-to-ground-state-ions-produces-free-electrons
#17
D You, H Fukuzawa, Y Sakakibara, T Takanashi, Y Ito, G G Maliyar, K Motomura, K Nagaya, T Nishiyama, K Asa, Y Sato, N Saito, M Oura, M Schöffler, G Kastirke, U Hergenhahn, V Stumpf, K Gokhberg, A I Kuleff, L S Cederbaum, K Ueda
Inner-shell ionization of an isolated atom typically leads to Auger decay. In an environment, for example, a liquid or a van der Waals bonded system, this process will be modified, and becomes part of a complex cascade of relaxation steps. Understanding these steps is important, as they determine the production of slow electrons and singly charged radicals, the most abundant products in radiation chemistry. In this communication, we present experimental evidence for a so-far unobserved, but potentially very important step in such relaxation cascades: Multiply charged ionic states after Auger decay may partially be neutralized by electron transfer, simultaneously evoking the creation of a low-energy free electron (electron transfer-mediated decay)...
January 30, 2017: Nature Communications
https://www.readbyqxmd.com/read/28124034/low-fouling-and-functional-poly-carboxybetaine-coating-via-a-photo-crosslinking-process
#18
Hsiu-Wen Chien, Po-Hsiu Cheng, Shao-Yung Chen, Jiashing Yu, Wei-Bor Tsai
Antifouling modification technology is developed for many biomedical applications such as blood-contact devices and biosensors. In this work, a photo-reactive polymer containing zwitterionic carboxybetaine groups was prepared by copolymerization of two kinds of methacrylic acids with carboxybetaine and azidoaniline. The carboxybetaine moiety is for low fouling and the azidophenyl moiety is for photo-crosslinking. The synthesized copolymers were coated onto polymeric substrates, and then covalently immobilized on the substrates by exposure to UV radiation...
January 26, 2017: Biomaterials Science
https://www.readbyqxmd.com/read/28088137/forces-on-nuclei-moving-on-autoionizing-molecular-potential-energy-surfaces
#19
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
#20
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
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