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https://www.readbyqxmd.com/read/28529962/picosecond-sulfur-k-edge-x-ray-absorption-spectroscopy-with-applications-to-excited-state-proton-transfer
#1
Benjamin E Van Kuiken, Matthew R Ross, Matthew L Strader, Amy A Cordones, Hana Cho, Jae Hyuk Lee, Robert W Schoenlein, Munira Khalil
Picosecond X-ray absorption (XA) spectroscopy at the S K-edge (∼2.4 keV) is demonstrated and used to monitor excited state dynamics in a small organosulfur molecule (2-Thiopyridone, 2TP) following optical excitation. Multiple studies have reported that the thione (2TP) is converted into the thiol (2-Mercaptopyridine, 2MP) following photoexcitation. However, the timescale and photochemical pathway of this reaction remain uncertain. In this work, time-resolved XA spectroscopy at the S K-edge is used to monitor the formation and decay of two transient species following 400 nm excitation of 2TP dissolved in acetonitrile...
July 2017: Structural Dynamics (Melville, N.Y.)
https://www.readbyqxmd.com/read/28524689/facile-anhydrous-proton-transport-on-hydroxyl-functionalized-graphane
#2
Abhishek Bagusetty, Pabitra Choudhury, Wisssam A Saidi, Bridget Derksen, Elizabeth Gatto, J Karl Johnson
Graphane functionalized with hydroxyl groups is shown to rapidly conduct protons under anhydrous conditions through a contiguous network of hydrogen bonds. Density functional theory calculations predict remarkably low barriers to diffusion of protons along a 1D chain of surface hydroxyls. Diffusion is controlled by the local rotation of hydroxyl groups, a mechanism that is very different from that found in 1D water wires in confined nanopores or in bulk water. The proton mean square displacement in the 1D chain was observed to follow Fickian diffusion rather than the expected single-file mobility...
May 5, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28524679/transition-from-collisional-to-collisionless-regimes-in-interpenetrating-plasma-flows-on-the-national-ignition-facility
#3
J S Ross, D P Higginson, D Ryutov, F Fiuza, R Hatarik, C M Huntington, D H Kalantar, A Link, B B Pollock, B A Remington, H G Rinderknecht, G F Swadling, D P Turnbull, S Weber, S Wilks, D H Froula, M J Rosenberg, T Morita, Y Sakawa, H Takabe, R P Drake, C Kuranz, G Gregori, J Meinecke, M C Levy, M Koenig, A Spitkovsky, R D Petrasso, C K Li, H Sio, B Lahmann, A B Zylstra, H-S Park
A study of the transition from collisional to collisionless plasma flows has been carried out at the National Ignition Facility using high Mach number (M>4) counterstreaming plasmas. In these experiments, CD-CD and CD-CH planar foils separated by 6-10 mm are irradiated with laser energies of 250 kJ per foil, generating ∼1000  km/s plasma flows. Varying the foil separation distance scales the ion density and average bulk velocity and, therefore, the ion-ion Coulomb mean free path, at the interaction region at the midplane...
May 5, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28524664/nam-tms-mechanism-of-%C3%AE-amino-acid-n-carboxyanhydride-polymerization-a-dft-study
#4
Tianwen Bai, Jun Ling
The normal amine mechanism via proton transferring route (NAM-H) is widely accepted for synthesis of polypeptides with nonionic initiators. Besides proton, trimethylsilyl (TMS) group transferring process has been found in living/controlled polymerization initiated by N-TMS amine in experiments but the corresponding mechanism has never been proposed yet. In this work, we employed density functional theory (DFT) with solvation model to investigate the details of TMS-transfer mechanism, defined as NAM-TMS, for ring-opening polymerization of α-amino acid N-carboxyanhydride...
May 19, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28521106/first-principles-models-for-biological-light-harvesting-phycobiliprotein-complexes-from-cryptophyte-algae
#5
Mi Kyung Lee, Ksenia B Bravaya, David F Coker
There have been numerous efforts, both experimental and theoretical, that have attempted to parameterize model Hamiltonians to describe excited state energy transfer in photosynthetic light harvesting systems. The Frenkel exciton model, with its set of electronically coupled two level chromophores that are each linearly coupled to dissipative baths of harmonic oscillators, has become the workhorse of this field. The challenges to parameterizing such Hamiltonians have been their uniqueness, and physical interpretation...
May 18, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28520813/pancreatic-fat-content-by-magnetic-resonance-imaging-in-subjects-with-prediabetes-diabetes-and-controls-from-a-general-population-without-cardiovascular-disease
#6
Sophia D Heber, Holger Hetterich, Roberto Lorbeer, Christian Bayerl, Jürgen Machann, Sigrid Auweter, Corinna Storz, Christopher L Schlett, Konstantin Nikolaou, Maximilian Reiser, Annette Peters, Fabian Bamberg
BACKGROUND/OBJECTIVE: Despite the relevance of pancreatic fat content in the development of metabolic diseases, its association with impaired glucose metabolism, diabetes, and other adipose tissue compartments remains unclear. Thus, we determined differences in pancreatic fat content by magnetic resonance imaging (MRI) between subjects with prediabetes, diabetes, and normal controls in a cohort from the general population. METHODS: Subjects without history of cardiovascular disease with established diabetes or prediabetes as well as normal controls were included and underwent whole-body MRI on a 3T scanner...
2017: PloS One
https://www.readbyqxmd.com/read/28520778/texture-analysis-using-proton-density-and-t2-relaxation-in-patients-with-histological-usual-interstitial-pneumonia-uip-or-nonspecific-interstitial-pneumonia-nsip
#7
Maria T A Buzan, Andreas Wetscherek, Claus Peter Heussel, Michael Kreuter, Felix J Herth, Arne Warth, Hans-Ulrich Kauczor, Carmen Monica Pop, Julien Dinkel
OBJECTIVES: The purpose of our study was to assess proton density (PD) and T2 relaxation time of usual interstitial pneumonia (UIP) and nonspecific interstitial pneumonia (NSIP) and to evaluate their utility in differentiating the two patterns. Furthermore, we aim to investigate whether these two parameters could help differentiate active-inflammatory and stable-fibrotic lesions in NSIP. METHODS: 32 patients (mean age: 69 years; M:F, 1:1) with pathologically proven disease (UIP:NSIP, 1:1), underwent thoracic thin-section multislice CT scan and 1...
2017: PloS One
https://www.readbyqxmd.com/read/28517014/n-atom-transfer-via-thermal-or-photolytic-activation-of-a-co-azido-complex-with-a-pnp-pincer-ligand
#8
V Vreeken, L Baij, B de Bruin, M A Siegler, J I van der Vlugt
Thermal or photolytic activation of well-defined mononuclear [Co(N3)(PNP)] (PNP = 2,2'-bis(diisopropylphosphino)-4,4'-ditolylamido) results in the structurally characterized dinuclear species [Co(μ-N;κ(3)-P,N,N-PN(P)N)]2 (3), with two N-bridging phosphiniminato bridgeheads. Density Functional Theory (DFT) calculations indicate the intermediacy of a mononuclear cobalt-nitrido complex, followed by N-migratory insertion into a Co-P bond. Reaction of 3 with two equiv. HCl leads to rupture of the dimer with formation of mononuclear [CoCl(PN(P)N(H))] (4) by protonation of the N-bridges...
May 18, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28516989/the-effect-of-anions-on-the-electrochemical-properties-of-polyaniline-for-supercapacitors
#9
Ji Xing, Maoying Liao, Chi Zhang, Min Yin, Dongdong Li, Ye Song
To investigate the effect of anions on the electrochemical properties of polyaniline (PANI) for supercapacitors, electrochemical performance tests of PANI with different dopant anions were carried out in the corresponding acid solutions by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) methods. In particular, ionic fluxes and solvent molecules involved in redox processes can be analyzed by the electrochemical quartz crystal microbalance (EQCM) technique and discriminated by simultaneously recording cyclic voltammograms and mass changes during redox switching...
May 18, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28512786/a-single-molecular-and-gate-operated-with-two-orthogonal-switching-mechanisms
#10
Na Zhang, Wai-Yip Lo, Anex Jose, Zhengxu Cai, Lianwei Li, Luping Yu
Single-molecular electronics is a potential solution to nanoscale electronic devices. While simple functional single-molecule devices such as diodes, switches, and wires are well studied, complex single-molecular systems with multiple functional units are rarely investigated. Here, a single-molecule AND logic gate is constructed from a proton-switchable edge-on gated pyridinoparacyclophane unit with a light-switchable diarylethene unit. The AND gate can be controlled orthogonally by light and protonation and produce desired electrical output at room temperature...
May 17, 2017: Advanced Materials
https://www.readbyqxmd.com/read/28507672/mechanism-of-photocatalytic-water-oxidation-on-small-tio2-nanoparticles
#11
Mikko Muuronen, Shane M Parker, Enrico Berardo, Alexander Le, Martijn A Zwijnenburg, Filipp Furche
We present the first unconstrained nonadiabatic molecular dynamics (NAMD) simulations of photocatalytic water oxidation by small hydrated TiO2 nanoparticles using Tully surface hopping and time-dependent density functional theory. The results indicate that ultrafast electron-proton transfer from physisorbed water to the photohole initiates the photo-oxidation on the S1 potential energy surface. The new mechanism readily explains the observation of mobile hydroxyl radicals in recent experiments. Two key driving forces for the photo-oxidation reaction are identified: localization of the electron-hole pair and stabilization of the photohole by hydrogen bonding interaction...
March 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28505758/machine-learning-applied-to-proton-radiography-of-high-energy-density-plasmas
#12
Nicholas F Y Chen, Muhammad Firmansyah Kasim, Luke Ceurvorst, Naren Ratan, James Sadler, Matthew C Levy, Raoul Trines, Robert Bingham, Peter Norreys
Proton radiography is a technique extensively used to resolve magnetic field structures in high-energy-density plasmas, revealing a whole variety of interesting phenomena such as magnetic reconnection and collisionless shocks found in astrophysical systems. Existing methods of analyzing proton radiographs give mostly qualitative results or specific quantitative parameters, such as magnetic field strength, and recent work showed that the line-integrated transverse magnetic field can be reconstructed in specific regimes where many simplifying assumptions were needed...
April 2017: Physical Review. E
https://www.readbyqxmd.com/read/28505623/effect-of-a-low-rank-denoising-algorithm-on-quantitative-magnetic-resonance-imaging-based-measures-of-liver-fat-and-iron
#13
Brian C Allen, Felix Lugauer, Dominik Nickel, Lubna Bhatti, Randa A Dafalla, Brian M Dale, Tracy A Jaffe, Mustafa R Bashir
PURPOSE: This study aimed to assess the effect of a low-rank denoising algorithm on quantitative magnetic resonance imaging-based measures of liver fat and iron. MATERIALS AND METHODS: This was an institutional review board-approved, Health Insurance Portability and Accountability Act-compliant, retrospective analysis of 42 consecutive subjects who were imaged at 3T using a multiecho gradient echo sequence that was reconstructed using the multistep adaptive fitting algorithm to obtain quantitative proton density fat fraction (PDFF) and R2* maps (original maps)...
May 2017: Journal of Computer Assisted Tomography
https://www.readbyqxmd.com/read/28504972/temperature-dependent-spectroscopic-and-excited-state-dynamics-of-3-hydroxychromones-with-electron-donor-and-acceptor-substituents
#14
Alan Szalai, Luciana Giordano, Verónica M Sánchez, Teresa D Z Atvars, Marcelo Faleiros, Elizabeth Jares-Erijman, Pedro F Aramendía
We have studied the photophysical and photochemical behavior of three compounds derived from 3-hydroxychromone (3-HC), capable of undergoing excited state proton transfer (ESIPT). The compounds have two substituents, located in positions 2 and 7, one on each ring of the 3-HC heterocycle. The substituent pattern shows different electron donating and acceptor features. The compounds were studied by absorption and emission spectroscopy, steady state anisotropy, and time resolved emission spectroscopy (TRES) as a function of temperature...
May 15, 2017: Methods and Applications in Fluorescence
https://www.readbyqxmd.com/read/28504642/ion-recombination-correction-factor-in-scanned-light-ion-beams-for-absolute-dose-measurement-using-plane-parallel-ionisation-chambers
#15
Severine Rossomme, Julian Horn, Stephan Brons, Oliver Jaekel, Andrea Mairani, Mario Ciocca, Vincent Floquet, Francesco Romano, Diana Rodriguez Garcia, Stefaan Vynckier, Hugo Palmans
Based on international reference dosimetry protocols for light-ion beams, a correction factor (<i>k<sub>s</sub></i>) has to be applied to the response of a plane-parallel ionisation chamber, to account for recombination of negative and positive charges in its air cavity before these charges can be collected on the electrodes. In this work, <i>k<sub>s</sub></i> for IBA PPC40 Roos-type chambers is investigated in four scanned light-ion beams (proton, helium, carbon and oxygen)...
May 15, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28500667/magnetic-resonance-neurography-and-diffusion-tensor-imaging-of-the-peripheral-nerves-in-patients-with-cmt-type-1a
#16
Michael Vaeggemose, Signe Vaeth, Mirko Pham, Steffen Ringgaard, Uffe B Jensen, Hatice Tankisi, Niels Ejskjaer, Sabine Heiland, Henning Andersen
INTRODUCTION: Investigation of peripheral neuropathies by magnetic resonance neurography (MRN) may provide increased diagnostic accuracy when performed in combination with diffusion tensor imaging (DTI). The aim of this study was to evaluate DTI in the detection of neuropathic abnormalities in Charcot-Marie-Tooth-type-1A (CMT1A). METHODS: MR imaging of the sciatic and tibial nerves, including MRN and DTI, was prospectively performed in 15 CMT1A patients and 30 healthy-controls (HC)...
May 13, 2017: Muscle & Nerve
https://www.readbyqxmd.com/read/28499816/tumor-ablation-using-low-intensity-ultrasound-and-sound-excitable-drug
#17
Ching-Hsuan Tung, Myung Shin Han, Young Kim, Jianjun Qi, Brian E O'Neill
The cell membrane is a semi-fluid container that defines the boundary of cells, and provides an enclosed environment for vital biological processes. A sound excitable drug (SED) that is non-cytotoxic to cells is developed to disrupt the plasma membrane under gentle ultrasound insonation, 1MHz, 1W/cm(2). The frequency and power density of insonation are within the physical therapy and medical imaging windows; thus the applied ultrasound is safe and not harmful to tissues. The insertion of SEDs into the plasma membrane is not toxic to cells; however, the intruding SEDs weaken the membrane's integrity...
May 10, 2017: Journal of Controlled Release: Official Journal of the Controlled Release Society
https://www.readbyqxmd.com/read/28498679/observation-of-the-isovector-giant-monopole-resonance-via-the-28-si-10-be-10-b-1-74%C3%A2-%C3%A2-mev-reaction-at-100%C3%A2-%C3%A2-amev
#18
M Scott, R G T Zegers, R Almus, Sam M Austin, D Bazin, B A Brown, C Campbell, A Gade, M Bowry, S Galès, U Garg, M N Harakeh, E Kwan, C Langer, C Loelius, S Lipschutz, E Litvinova, E Lunderberg, C Morse, S Noji, G Perdikakis, T Redpath, C Robin, H Sakai, Y Sasamoto, M Sasano, C Sullivan, J A Tostevin, T Uesaka, D Weisshaar
The (^{10}Be,^{10}B^{*}[1.74  MeV]) charge-exchange reaction at 100  AMeV is presented as a new probe for isolating the isovector (ΔT=1) nonspin-transfer (ΔS=0) response of nuclei, with ^{28}Si being the first nucleus studied. By using a secondary ^{10}Be beam produced by fast fragmentation of ^{18}O nuclei at the NSCL Coupled Cyclotron Facility, applying the dispersion-matching technique with the S800 magnetic spectrometer to determine the excitation energy in ^{28}Al, and performing high-resolution γ-ray tracking with the Gamma-Ray Energy Tracking In-beam Nuclear Array (GRETINA) to identify the 1022-keV γ ray associated with the decay from the 1...
April 28, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28498678/mechanisms-and-origins-of-chemo-and-regioselectivities-of-ru-ii-catalyzed-decarboxylative-c-h-alkenylation-of-aryl-carboxylic-acids-with-alkynes-a-computational-study
#19
Jing-Lu Yu, Shuo-Qing Zhang, Xin Hong
The mechanisms and chemo- and regioselectivities of Ru(II)-catalyzed decarboxylative C-H alkenylation of aryl carboxylic acids with alkynes were investigated with density functional theory (DFT) calculations. The catalytic cycle involves sequential carboxylate-directed C-H activation, alkyne insertion, decarboxylation and protonation. The facile tether-assisted decarboxylation step directs the intermediate toward the desired decarboxylative alkenylation, instead of typical annulation and double alkenylation pathways...
May 22, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28497835/revealing-the-electrophilicity-of-n-ac-indoles-with-fecl3-a-mechanistic-study
#20
Rodolphe Beaud, Raj Kumar Nandi, Alejandro Perez-Luna, Régis Guillot, Didier Gori, Cyrille Kouklovsky, Nour-Eddine Ghermani, Vincent Gandon, Guillaume Vincent
Herein, we report a mechanistic exploration of the unusual FeCl3-mediated hydroarylation of N-Ac indoles. Electron density topology analysis of a crystal, in situ IR monitoring, Hammett and Taft studies as well as DFT computations allowed us to determine that activation of acetyl with FeCl3 and of the C2[double bond, length as m-dash]C3 bond with a proton is involved.
May 12, 2017: Chemical Communications: Chem Comm
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