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radiation chemistry

Andrew J Rushby, Martin Johnson, Benjamin J W Mills, Andrew J Watson, Mark W Claire
The potential habitability of an exoplanet is traditionally assessed by determining whether its orbit falls within the circumstellar "habitable zone" of its star, defined as the distance at which water could be liquid on the surface of a planet (Kopparapu et al., 2013 ). Traditionally, these limits are determined by radiative-convective climate models, which are used to predict surface temperatures at user-specified levels of greenhouse gases. This approach ignores the vital question of the (bio)geochemical plausibility of the proposed chemical abundances...
May 2018: Astrobiology
Sophie Nowak, Sandra Lafon, Sandrine Caquineau, Emilie Journet, Benoit Laurent
Mineral dust aerosols, produced by wind erosion in arid regions and semi-arid surfaces, are important components of the atmosphere that affect the Earth radiative budget, atmospheric chemistry and biogeochemical cycles. Dust aerosol particles are composed of a complex mixture of various minerals, mainly clays, calcite, quartz, feldspars and iron oxides. The nature and the relative abundance of the minerals are key parameters to evaluate mineral dust environmental impacts. Strong limitations remain to quantify the mineralogical composition of dust particles, mainly due to the low mass of in-situ collected dust particle samples...
August 15, 2018: Talanta
Craig Meiers, Amy Taylor, Brian Geller, Beau Toskich
Background: Hepatic metastatectomy and ablation are associated with prolonged survival, but not all lesions are anatomically amenable to these therapies. We evaluated safety and initial efficacy of segmental ablative transarterial radioembolization, or radiation segmentectomy (RS), as a treatment for hepatic metastases. Methods: A single institution retrospective analysis was performed of patients with hepatic metastases, determined unamenable to resection by a multidisciplinary tumor board, treated with RS from 2015-2017...
April 2018: Journal of Gastrointestinal Oncology
Md Jakaria, Duk-Yeon Cho, Md Ezazul Haque, Govindarajan Karthivashan, In-Su Kim, Palanivel Ganesan, Dong-Kug Choi
Thymoquinone (TQ) is an active ingredient isolated from Nigella sativa and has various pharmacological activities, such as protection against oxidative stress, inflammation, and infections. In addition, it might be a potential neuropharmacological agent because it exhibits versatile potential for attenuating neurological impairments. It features greater beneficial effects in toxin-induced neuroinflammation and neurotoxicity. In various models of neurological disorders, it demonstrates emergent functions, including safeguarding various neurodegenerative diseases and other neurological diseases, such as stroke, schizophrenia, and epilepsy...
2018: Oxidative Medicine and Cellular Longevity
Yanyang Chen, Yasaman Jami-Alahmahdi, Kiran Sagar Unikela, Graham J Bodwell, Travis D Fridgen
1,1,9,9-Tetramethyl[9](2,11)teropyrenophane (TM9TP), a belt-shaped molecule, has a sizable cavity that molecules or ions could occupy. In this study, the question of whether TM9TP forms gas phase ion-molecule complexes with metal cations (K+, Rb+, Cs+) situated inside or outside the TM9TP cavity was addressed using both experimental and computational methods. Complexes were trapped in a Fourier transform ion cyclotron resonance mass spectrometer and their structures were explored by some novel physical chemistry/mass spectrometry methods...
May 9, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Shady S Hassan, Gwilym A Williams, Amit K Jaiswal
Pretreatment of lignocellulosic biomass to overcome its intrinsic recalcitrant nature prior to the production of valuable chemicals has been studied for nearly 200 years. Research has targeted eco-friendly, economical and time-effective solutions, together with a simplified large-scale operational approach. Commonly used pretreatment methods, such as chemical, physico-chemical and biological techniques are still insufficient to meet optimal industrial production requirements in a sustainable way. Recently, advances in applied chemistry approaches conducted under extreme and non-classical conditions has led to possible commercial solutions in the marketplace (e...
April 25, 2018: Bioresource Technology
Marcus Seidel, Xiao Xiao, Syed A Hussain, Gunnar Arisholm, Alexander Hartung, Kevin T Zawilski, Peter G Schunemann, Florian Habel, Michael Trubetskov, Vladimir Pervak, Oleg Pronin, Ferenc Krausz
Spectroscopy in the wavelength range from 2 to 11 μm (900 to 5000 cm-1 ) implies a multitude of applications in fundamental physics, chemistry, as well as environmental and life sciences. The related vibrational transitions, which all infrared-active small molecules, the most common functional groups, as well as biomolecules like proteins, lipids, nucleic acids, and carbohydrates exhibit, reveal information about molecular structure and composition. However, light sources and detectors in the mid-infrared have been inferior to those in the visible or near-infrared, in terms of power, bandwidth, and sensitivity, severely limiting the performance of infrared experimental techniques...
April 2018: Science Advances
Jose Asuncion Ramos-Mendez, Joseph Perl, Jan Schuemann, Aimee Louise McNamara, Harald Paganetti, Bruce A Faddegon
Simulation of water radiolysis and the subsequent chemistry provides important information on the effect of ionizing radiation on biological material. The Geant4 Monte Carlo toolkit has added chemical processes via the Geant4-DNA project. The TOPAS tool simplifies the modeling of complex radiotherapy applications with Geant4 without requiring advanced computational skills, extending the pool of users. Thus, a new extension to TOPAS, TOPAS-nBio, is under development to facilitate the configuration of track-structure simulations as well as water radiolysis simulations with Geant4-DNA for radiobiological studies...
April 26, 2018: Physics in Medicine and Biology
Tolga N V Karsili, Mark A Fennimore, Spiridoula Matsika
The elementary synthesis of prebiotic molecules has attracted vast attention in recent years. Due to their rich surface chemistry and lack of suitable atmosphere, comets represent an important host for such synthesis, especially since they are routinely irradiated with short wavelength electromagnetic radiation and energetic cosmological electrons. Using high-level electronic structure theory, we present the details of the reactivity associated with the electron-impact induced prebiotic synthesis of ethylene glycol (a carbohydrate building block) from elementary methanol...
April 25, 2018: Physical Chemistry Chemical Physics: PCCP
Tomás Bosco, Mónica Beatriz Bertiller, Analía Lorena Carrera
Assessing the ability of key species to cope with environmental stresses in disturbed areas is an important issue for recovery of degraded arid ecosystem. Our objective was to evaluate the effect of soil moisture, exposure to UV radiation, and presence/absence of litter with different chemistry on soil N, recruitment and biomass of seedlings of perennial grass (Poa ligularis and Nassella tenuis) and evergreen shrub species (Atriplex lampa and Larrea divaricata) in denuded areas. We carried out a microcosm experiment with soil blocks (28 cm depth) sowed with seeds of the target species, subjected to different levels of litter type (perennial grass-evergreen shrub mixture, evergreen shrub mixture, and no litter), UV radiation (near ambient and reduced UV), and soil water (high: 15-25% and low 5-15%)...
April 16, 2018: Journal of Environmental Management
Drew C Baird, Garrett J Meyers, Jocelyn S Hu
Testicular cancer is the most common solid tumor among males 15 to 34 years of age, with an estimated 8,850 new cases and 410 deaths during 2017 in the United States. With effective treatment, the overall five-year survival rate is 97%. Risk factors for testicular cancer include undescended testis (cryptorchidism), personal or family history of testicular cancer, age, ethnicity, and infertility. The U.S. Preventive Services Task Force recommends against routine screening in asymptomatic men. Men with symptoms should receive a complete history and physical examination...
February 15, 2018: American Family Physician
Yupeng He, Shifeng Hou, Liqiong Yang, Fang Zhang, Guizheng Zou
Tunable optics and electronics of II-VI nanocrystals (NCs) is mainly achieved in the traditional size-dependent strategy. Herein, adjustable triggering energy, intensity, and even spectrum for reductive-oxidation electrochemiluminescence (ECL) from highly-passivated CdTe/CdS NCs of the same size are achieved via decorating NCs with counterions, which proves surface chemistry can bring out varied electrostatic interaction between surface vacancies and electrochemically injected carriers for adjustable electrochemical redox induced radiative charge-transfer...
April 17, 2018: Chemistry: a European Journal
Patricia M Valdespino-Castillo, Ping Hu, Martín Merino-Ibarra, Luz M López-Gómez, Daniel Cerqueda-García, Roberto González-De Zayas, Teresa Pi-Puig, Julio A Lestayo, Hoi-Ying Holman, Luisa I Falcón
Microbialites are modern analogs of ancient microbial consortia that date as far back as the Archaean Eon. Microbialites have contributed to the geochemical history of our planet through their diverse metabolic capacities that mediate mineral precipitation. These mineral-forming microbial assemblages accumulate major ions, trace elements and biomass from their ambient aquatic environments; their role in the resulting chemical structure of these lithifications needs clarification. We studied the biogeochemistry and microbial structure of microbialites collected from diverse locations in Mexico and in a previously undescribed microbialite in Cuba...
2018: Frontiers in Microbiology
Sukrit Ranjan, Zoe R Todd, John D Sutherland, Dimitar D Sasselov
A key challenge in origin-of-life studies is understanding the environmental conditions on early Earth under which abiogenesis occurred. While some constraints do exist (e.g., zircon evidence for surface liquid water), relatively few constraints exist on the abundances of trace chemical species, which are relevant to assessing the plausibility and guiding the development of postulated prebiotic chemical pathways which depend on these species. In this work, we combine literature photochemistry models with simple equilibrium chemistry calculations to place constraints on the plausible range of concentrations of sulfidic anions (HS- , HSO3 - , SO3 2- ) available in surficial aquatic reservoirs on early Earth due to outgassing of SO2 and H2 S and their dissolution into small shallow surface water reservoirs like lakes...
April 8, 2018: Astrobiology
Pau Armengol, Lasse Spörkel, Ricard Gelabert, Miquel Moreno, Walter Thiel, José M Lluch
We report quantum mechanical/molecular mechanical non-adiabatic molecular dynamics simulations on the electronically excited state of green fluorescent protein mutant S65T/H148D. We examine the driving force of the ultrafast (τ < 50 fs) excited-state proton transfer unleashed by absorption in the A band at 415 nm and propose an atomistic description of the two dynamical regimes experimentally observed [Stoner Ma et al., J. Am. Chem. Soc., 2008, 130, 1227]. These regimes are explained in terms of two sets of successive dynamical events: first the proton transfers quickly from the chromophore to the acceptor Asp148...
April 5, 2018: Physical Chemistry Chemical Physics: PCCP
Connor Slagle, Douglas H Thamm, Elissa K Randall, Mark Andrew Borden
Interest in the use of targeted microbubbles for ultrasound molecular imaging (USMI) has been growing in recent years as a safe and efficacious means of diagnosing tumor angiogenesis and assessing response to therapy. Of particular interest are cloaked microbubbles, which improve specificity by concealing the ligand from blood components until they reach the target vasculature, where the ligand can be transiently revealed for firm receptor-binding by ultrasound acoustic radiation force pulses. Herein, a bio-orthogonal "click" conjugation chemistry is introduced to decorate the surface of cloaked 4-5 μm diameter microbubbles as part of a sterile and reproducible production process...
April 4, 2018: Bioconjugate Chemistry
Eric Maimon, Amram Samuni, Sara Goldstein
Hydroxamic acids (RC(O)NHOH) form a class of compounds, which display interesting chemical and biological properties The chemistry of RC(O)NHOH) is associated with one- and two-electron oxidations forming the respective nitroxide radical (RC(O)NHO•) and acyl nitroso (RC(O)N=O), respectively, which are relatively unstable species. In the present study the kinetics and mechanism of •NO2 reaction with nitroxide radicals derived from acetohydroxamic acid, suberohydroxamic acid, benzohydroxamic acid and suberoylanilide hydroxamic acid have been studied in alkaline solutions...
April 2, 2018: Journal of Physical Chemistry. A
Bin Wang, Jacquelyn Shuman, Herman H Shugart, Manuel T Lerdau
Air quality is closely associated with climate change via the biosphere because plants release large quantities of volatile organic compounds (VOC) that mediate both gaseous pollutants and aerosol dynamics. Earlier studies, which considered only leaf physiology and simply scale up from leaf-level enhancements of emissions, suggest that climate warming enhances whole forest VOC emissions, and these increased VOC emissions aggravate ozone pollution and secondary organic aerosol formation. Using an individual-based forest VOC emissions model-UVAFME-VOC-that simulates system-level emissions by explicitly simulating forest community dynamics to the individual tree level, ecological competition among the individuals of differing size and age, and radiative transfer and leaf function through the canopy, we find that climate warming only sometimes stimulates isoprene emissions (the single largest source of non-methane hydrocarbon) in a southeastern US forest...
March 30, 2018: Ecological Applications: a Publication of the Ecological Society of America
Marie-Christine Bacchus-Montabonel
The formation of the building blocks of life and how they could survive under harsh astrophysical environments remains an open question of prebiotic chemistry. Effectively, ion bombardments or intense UV radiation may drive the destruction of prebiotic compounds. The possible role of sulfur in such processes is addressed here for the first time, by comparing directly proton-induced charge transfer for sulfur containing molecules and that for related COMs. The proton collision on mercaptoacetonitrile HSCH2C[triple bond, length as m-dash]N conformers has thus been investigated theoretically in a wide impact energy range modelling various astrophysical environments and compared to related COMs, namely HCN oligomers, in order to exhibit qualitative tendencies...
April 4, 2018: Physical Chemistry Chemical Physics: PCCP
Stefanie Klein, Marc Wegmann, Luitpold V R Distel, Winfried Neuhuber, Carola Kryschi
Silicon nanoparticles with sizes between were synthesized through wet-chemistry procedures using diverse phase transfer reagents. On the other hand, the preparation of iron-doped silicon nanoparticles was carried out using the precursor Na4 Si4 containing 5% Fe. Biocompatibility of all silicon nanoparticle samples was achieved by surface-stabilizing with (3-aminopropyl)triethoxysilane. These surface structures provided positive surface charges which facilitated electrostatic binding to the negatively charged biological membranes...
April 15, 2018: Biochemical and Biophysical Research Communications
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