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proton density

Yingying Li, Ke Ye, Per E M Siegbahn, Rong-Zhen Liao
The design and synthesis of biomimetic Mn complexes to catalyze oxygen evolution is a very appealing goal since water oxidation in nature employs manganese. A mononuclear Mn complex 1 [LMnII(H2O)2]2+ (L=Py2N(tBu)2) was recently reported to catalyze water oxidation electrochemically with an applied potential of 1.23 V at pH=12.2 in aqueous solution. Density functional calculations have here been performed to elucidate the mechanism of water oxidation promoted by this catalyst. The calculations showed that 1 can readily lose two protons and one electron with the production of 2 [LMnIII(OH)2]+, which then undergoes two sequential proton-coupled electron transfer processes to afford 4 [LMnVOO]+...
December 7, 2016: ChemSusChem
Akihiro Okamoto, Yoshihide Tokunou, Junki Saito
Outer-membrane c-type cytochrome (OM c-Cyt) complexes in several genera of iron-reducing bacteria, such as Shewanella and Geobacter, are capable of transporting electrons from the cell interior to extracellular solids as a terminal step of anaerobic respiration. The kinetics of this electron transport has implications for controlling the rate of microbial electron transport during bioenergy or biochemical production, iron corrosion, and natural mineral cycling. Herein, we review the findings from in-vivo and in-vitro studies examining electron transport kinetics through single OM c-Cyt complexes in Shewanella oneidensis MR-1...
2016: Biophysics and Physicobiology
Xiaohong Duan, Jin Liu, Xueni Zheng, Zhe Wang, Yanli Zhang, Ying Hao, Tielin Yang, Hongwen Deng
Vacuolar-type H (+)-ATPase (V-ATPase) is a highly conserved, ancient enzyme that couples the energy of ATP hydrolysis to proton transport across vesicular and plasma membranes of eukaryotic cells. Previously reported mutations of various V-ATPase subunits are associated with increased bone density. We now show that haploinsufficiency for the H subunit of the V1 domain (ATP6V1H) is associated with osteoporosis in humans and mice. A genome-wide SNP array analysis of 1625 Han Chinese found that 4 of 15 tag SNPs (26...
2016: Theranostics
Brian P Setzler, Zhongbin Zhuang, Jarrid A Wittkopf, Yushan Yan
Fuel cells are the zero-emission automotive power source that best preserves the advantages of gasoline automobiles: low upfront cost, long driving range and fast refuelling. To make fuel-cell cars a reality, the US Department of Energy has set a fuel cell system cost target of US$30 kW(-1) in the long-term, which equates to US$2,400 per vehicle, excluding several major powertrain components (in comparison, a basic, but complete, internal combustion engine system costs approximately US$3,000). To date, most research for automotive applications has focused on proton exchange membrane fuel cells (PEMFCs), because these systems have demonstrated the highest power density...
December 6, 2016: Nature Nanotechnology
Denisa Geffertová, Syed Tahir Ali, Veronika Šolínová, Marcela Krečmerová, Antonín Holý, Zdeněk Havlas, Václav Kašička
Capillary electrophoresis (CE) and quantum mechanical density functional theory (DFT) were applied to the investigation of the acid-base and electromigration properties of important compounds: newly synthesized derivatives of 5-azacytosine - analogs of efficient antiviral drug cidofovir. These compounds exhibit a strong antiviral activity and they are considered as potential new antiviral agents. For their characterization and application, it is necessary to know their acid-base properties, particularly the acidity constants (pKa) of their ionogenic groups (the basic N(3) atom of the triazine ring and the acidic phosphonic acid group in the alkyl chain)...
November 29, 2016: Journal of Chromatography. A
Ahmed Taki Eddine Ardjani, Sidi Mohamed Mekelleche
In the present work, the molecular structure and the antioxidant activity of 4-(5-chloro-2-hydroxyphenylamino)-4-oxobut-2-enoic acid (A) and its derivatives (B-E) have been studied at the B3LYP/6-31++G(2d,2p) computational level. The obtained results indicate that the hydrogen atom transfer (HAT mechanism) is thermodynamically more favored in gas phase; whereas, the sequential proton loss-electron transfer (SPLET mechanism) is more preferred in polar solvents. The antioxidant activity of compounds A-E is also analyzed by the calculation of atomic spin densities, chemical hardnesses, dipole moments, and lipophilicity indexes...
December 2016: Journal of Molecular Modeling
A Ligia Focsan, Lowell D Kispert
In an organized assembly in Arabidopsis thaliana plant, proton loss from the radical cation of zeaxanthin (Zea(+)) was found to occur under intense illumination, a possible component in photoprotection. A stable neutral radical is formed because of the favorable proton loss at C4(4') position(s) of the terminal ends of Zea(+) that extends the unpaired spin density distribution (notation Zea(4) or Zea(4') by symmetry). Proton loss from the radical cation of β-carotene (β-car(+)) to available proton acceptors was also detected in a PSII sample upon irradiation...
November 19, 2016: Journal of Photochemistry and Photobiology. B, Biology
Nathan Diehl, Margaret M Johnson
OBJECTIVE: The objective of our study was to define the prevalence of osteoporosis and osteopenia in patients with noncystic fibrosis bronchiectasis (NCFB). METHODS: We conducted a retrospective chart review of all patients with physician-diagnosed NCFB evaluated at Mayo Clinic Florida between January 1, 2011 and June 3, 2013. RESULTS: A total of 113 patients with physician-diagnosed NCFB and confirmatory findings on computed tomography scan were identified...
December 2016: Southern Medical Journal
Charlie C Park, Phirum Nguyen, Carolyn Hernandez, Ricki Bettencourt, Kimberly Ramirez, Lynda Fortney, Jonathan Hooker, Ethan Sy, Mosab H Alquiraish, Mark A Valasek, Emily Rizo, Lisa Richards, David Brenner, Claude B Sirlin, Rohit Loomba
BACKGROUND & AIMS: Magnetic-resonance-imaging (MRI) techniques and ultrasound-based transient elastography (TE) can be used in noninvasive diagnosis of fibrosis and steatosis in patients with nonalcoholic fatty liver disease (NAFLD). We performed a prospective study to compare the performance of magnetic resonance elastography (MRE) vs TE for in diagnosis of fibrosis, and MRI-based proton density fat fraction (MRI-PDFF) analysis vs TE-based controlled attenuation parameter (CAP) for diagnosis of steatosis in patients undergoing biopsy to assess NAFLD...
October 27, 2016: Gastroenterology
W J Capecchi, J K Anderson, P J Bonofiglo, J Kim, S Sears
The neutron emissivity profile in the Madison Symmetric Torus is being reconstructed through the use of a collimated neutron detector. A scintillator-photomultiplier tube (PMT) system is employed to detect the fusion neutrons with the plasma viewing volume defined by a 55 cm deep, 5 cm diameter aperture. Effective detection of neutrons from the viewing volume is achieved through neutron moderation using 1300 lbs of high density polyethylene shielding, which modeling predicts attenuates the penetrating flux by a factor of 10(4) or more...
November 2016: Review of Scientific Instruments
N V Kabadi, H Sio, V Glebov, M Gatu Johnson, A MacPhee, J A Frenje, C K Li, F Seguin, R Petrasso, C Forrest, J Knauer, H G Rinderknecht
The particle-time-of-flight (pTOF) detector at the National Ignition Facility (NIF) is used routinely to measure nuclear bang-times in inertial confinement fusion implosions. The active detector medium in pTOF is a chemical vapor deposition diamond. Calibration of the detectors sensitivity to neutrons and protons would allow measurement of nuclear bang times and hot spot areal density (ρR) on a single diagnostic. This study utilizes data collected at both NIF and Omega in an attempt to determine pTOF's absolute sensitivity to neutrons...
November 2016: Review of Scientific Instruments
Xiao Ding Zhang, Guo Jun Yang, Yi Ding Li, Tao Wei, Xiaozhong He, Liang Chao Zhao, Zhuo Zhang, Chaofan Ma, Xiaoguo Jiang, Jinshui Shi
Lens focused proton radiograph on thin objects is demonstrated using an 11-MeV proton cyclotron at China Academy of Engineering Physics. The proton beam exiting from the tested objects is focused onto the image plane by a magnetic lens system mitigating image blur caused by multiple Coulomb scattering. Both simulations and experiments show that clear images can be obtained with a lens system for the objects with thickness up to 2.7 × 10(-2) g/cm(2) and the error for the areal density measurement is measured to be less than 2...
November 2016: Review of Scientific Instruments
A Netepenko, W U Boeglin, D S Darrow, R Ellis, M J Sibilia
Detection of charged fusion products, such as protons and tritons resulting from D(d, p) t reactions, can be used to determine the position and time dependent fusion reaction rate profile in spherical tokamak plasmas with neutral beam heating. We have developed a prototype instrument consisting of 6 ion-implanted-silicon surface barrier detectors combined with collimators in such a way that each detector can accept 3 MeV protons and 1 MeV tritons and thus provides a curved view across the plasma cross section...
November 2016: Review of Scientific Instruments
M Gauthier, J B Kim, C B Curry, B Aurand, E J Gamboa, S Göde, C Goyon, A Hazi, S Kerr, A Pak, A Propp, B Ramakrishna, J Ruby, O Willi, G J Williams, C Rödel, S H Glenzer
We report on the successful operation of a newly developed cryogenic jet target at high intensity laser-irradiation. Using the frequency-doubled Titan short pulse laser system at Jupiter Laser Facility, Lawrence Livermore National Laboratory, we demonstrate the generation of a pure proton beam a with maximum energy of 2 MeV. Furthermore, we record a quasi-monoenergetic peak at 1.1 MeV in the proton spectrum emitted in the laser forward direction suggesting an alternative acceleration mechanism. Using a solid-density mixed hydrogen-deuterium target, we are also able to produce pure proton-deuteron ion beams...
November 2016: Review of Scientific Instruments
A M Rasmus, A U Hazi, M J-E Manuel, C C Kuranz, S R Klein, P X Belancourt, J R Fein, M J MacDonald, R P Drake, B B Pollock, J Park, G J Williams, H Chen
Ultra-intense short pulse lasers incident on solid targets (e.g., thin Au foils) produce well collimated, broad-spectrum proton beams. These proton beams can be used to characterize magnetic fields, electric fields, and density gradients in high energy-density systems. The LLNL-Imaging Proton Spectrometer (L-IPS) was designed and built [H. Chen et al., Rev. Sci. Instrum. 81, 10D314 (2010)] for use with such laser produced proton beams. The L-IPS has an energy range of 50 keV-40 MeV with a resolving power (E/dE) of about 275 at 1 MeV and 21 at 20 MeV, as well as a single spatial imaging axis...
November 2016: Review of Scientific Instruments
Tia E Plautz, V Bashkirov, V Giacometti, R F Hurley, R P Johnson, P Piersimoni, H F-W Sadrozinski, R W Schulte, A Zatserklyaniy
PURPOSE: To evaluate the spatial resolution of proton CT using both a prototype proton CT scanner and Monte Carlo simulations. METHODS: A custom cylindrical edge phantom containing twelve tissue-equivalent inserts with four different compositions at varying radial displacements from the axis of rotation was developed for measuring the modulation transfer function (MTF) of a prototype proton CT scanner. Two scans of the phantom, centered on the axis of rotation, were obtained with a 200 MeV, low-intensity proton beam: one scan with steps of 4°, and one scan with the phantom continuously rotating...
December 2016: Medical Physics
Paolo Farace, Roberto Righetto, Sylvain Deffet, Arturs Meijers, Francois Vander Stappen
PURPOSE: To introduce a fast ray-tracing algorithm in pencil proton radiography (PR) with a multilayer ionization chamber (MLIC) for in vivo range error mapping. METHODS: Pencil beam PR was obtained by delivering spots uniformly positioned in a square (45 × 45 mm(2) field-of-view) of 9 × 9 spots capable of crossing the phantoms (210 MeV). The exit beam was collected by a MLIC to sample the integral depth dose (IDDMLIC). PRs of an electron-density and of a head phantom were acquired by moving the couch to obtain multiple 45 × 45 mm(2) frames...
December 2016: Medical Physics
Christoph Alexander Bauer, Andreas Hansen, Stefan Grimme
The fractional occupation number weighted density (FOD) analysis is explored as a general theoretical diagnostic for complicated electronic structures. Its main feature is to provide robustly and fast the information where 'hot' (strongly correlated and chemically active) electrons are localized in a molecule. We demonstrate its usage in four different prototypical applications: (i) As a new and fast measure for the biradical character of polycyclic aromatic hydrocarbons, (ii) for the selection of active orbital spaces in multiconfigurational or complete active space self consistent field (MCSCF/CASSCF) treatments, (iii) as a possibility to consistently describe molecular energy landscapes in regions with varying biradical character as exemplified by partial double bond torsions, and (iv) as a powerful visualization method for static electron correlation effects in large biomolecules in connection with an efficient semi-empirical tight-binding molecular orbital scheme...
December 1, 2016: Chemistry: a European Journal
C Athira, Raghavan B Sunoj
Metallic salts as well as protic additives are widely employed in transition metal catalyzed C-H bond functionalization reactions to improve the efficiency of catalytic protocols. In one such example, ZnCl2 and pivalic acid are used as additives in a palladium catalyzed synthesis of isoxazolone from a readily available benzohydroxamic acid under one pot conditions. In this article, we present some important mechanistic insights into the role of ZnCl2 and pivalic acid, gained by using density functional theory (M06) computations...
November 30, 2016: Organic & Biomolecular Chemistry
Bishwajit Ganguly, Abul Kalam Biswas
This study reports for the first time that compounds of Ge (II) can function as superbases. Two B(N=PiPr3)2 groups attached to a germanium (II) center show a gas phase proton affinity of 296.2 kcal/mol, close to the range of a hyperbase as revealed by B3LYP-D3/6-31G(2d,p) level of theory. These DFT calculations showed better agreement of geometrical parameters for the reported stable germylene compound 1 than previously reported calculations at the B3LYP/6-31G(2d,p) and PBE/DZP level of theory. A systematic study performed with different substitutions of Ge(II) revealed that such system can achieve basicity close to a hyperbase...
November 30, 2016: Chemistry: a European Journal
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