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Thomas Sandberg, Christian Weinberger, Didem Şen Karaman, Jessica M Rosenholm
The interaction between disulfiram (Antabus®) and silica was studied experimentally by adsorption from apolar solvent onto highly porous silica material (Santa Barbara Amorphous material-3, SBA-3) with large surface area. The adsorption isotherm was fitted to the Langmuir model by accounting two different affinities contributing to the overall behavior, which were attributed to two different types of silanol groups (i.e. geminal and vicinal) present on amorphous silica surfaces. This assumption was supported by theoretical calculations...
December 28, 2017: Journal of Pharmaceutical Sciences
Sara V Tadayon, Elizabeth S Foreman, Craig Murray
Reactions of the simplest Criegee intermediate (CH2OO) with a series of alcohols have been studied in a flash photolysis flow reactor. Laser photolysis of diiodomethane at 355 nm in the presence of molecular oxygen was used to produce CH2OO, and the absolute number densities were determined as a function of delay time from analysis of broadband transient absorption spectra obtained using a pulsed LED. The kinetics for the reactions of CH2OO with methanol, ethanol, and 2-propanol were measured under pseudo-first-order conditions at 295 K, yielding rate constants of (1...
December 29, 2017: Journal of Physical Chemistry. A
Olga Dmitrieva
The present study seeks to answer the question of whether consonant duration is perceived differently across consonants of different manners of articulation and in different contextual environments and whether such differences may be related to the typology of geminates. The results of the cross-linguistic identification experiment suggest higher perceptual acuity in labeling short and long consonants in sonorants than in obstruents. Duration categories were also more consistently and clearly labeled in the intervocalic than in the preconsonantal environment, in the word-initial than in the word-final position, and after stressed vowels than between unstressed vowels...
March 1, 2017: Language and Speech
Ayelén Florencia Crespi, Agustin Jesus Byrne, Daniel Vega, Ana Karina Chattah, Gustavo Alberto Monti, Juan Manuel Lázaro-Martínez
The stability of gem-diol forms in imidazolecarboxaldehyde isomers was studied by solid-state nuclear magnetic resonance (ss-NMR) combined with single-crystal X-ray diffraction studies. These methodologies also allowed determining the factors governing the occurrence of such rare functionalization in carbonyl moieties. Results indicated that the position of the carbonyl group is the main factor that governs the generation of geminal diols, having a clear and direct effect on hydration, since, under the same experimental conditions, only 36% of 5-imidazolecarboxaldehydes and 5% of 4-imidazolecarboxaldehydes were hydrated, as compared to 2-imidazolecarboxaldehydes, with which a 100% hydration was achieved...
December 20, 2017: Journal of Physical Chemistry. A
Zhitian Liu, Linhua Zhang, Ming Shao, Yao Wu, Di Zeng, Xiang Cai, Jiashun Duan, Xiaolu Zhang, Xiang Gao
The geometries of perylene diimides(PDI) based acceptors is important for improving the phase separation and charge transport in organic solar cells. In order to finely tune the geometry, diphenyl, spiro-fluorene and benzene were used as the core moiety to construct quasi-3D nonfullerene acceptors based on PDI building blocks. The molecular geometries, energy levels, optical properties, photovoltaic properties and exciton kinetics were systematically studied. The structure-performance relationship was discussed as well...
December 18, 2017: ACS Applied Materials & Interfaces
Yukihide Ishibashi, Miya Arinishi, Tetsuro Katayama, Hiroshi Miyasaka, Tsuyoshi Asahi
Femtosecond excited-state dynamics of fullerene-C60 nanoparticles (nC60) having a mean size of 50 nm dispersed in pure water was studied by means of femtosecond transient absorption spectroscopy. The intermolecular charge-transfer (CT) excited state in solid C60 was directly and firstly observed by femtosecond 350 nm and 420 nm excitations, and its intrinsic lifetime of 0.35 ps was found. The CT excited state relaxed to the locally excited S1 state and excimers or directly to the ground state through geminate charge recombination...
December 12, 2017: Physical Chemistry Chemical Physics: PCCP
D J Srivastava, P Florian, J H Baltisberger, P J Grandinetti
The dependence of a 29Si geminal J coupling across the inter-tetrahedral linkage on local structure was examined using first-principles DFT calculations. The two main influences on 2JSi-O-Si were found to be a primary dependence on the linkage Si-O-Si angle and a secondary dependence on mean Si-O-Si linkage of the two coupled 29Si nuclei. An analytical expression describing these dependences was proposed and used to develop an approach for relating the correlated pair of 2JSi-O-Si coupling and mean 29Si isotropic chemical shift to the linkage Si-O-Si angle and the mean Si-O-Si angle of the two coupled 29Si nuclei...
December 11, 2017: Physical Chemistry Chemical Physics: PCCP
Renato Piai Pereira, Rodrigo Ravazzi, Rogério Vieira Silva, Eduardo Nunes, João Milton Rocha Gusmão, Paulo Sérgio Flores Campos
Gemination aka twinning and fusion, are rare occurrences in posterior mandibular teeth, often requiring endodontic and surgical treatment for functional, orthodontic or cosmetic reasons. The diagnosis and design of a precise treatment plan in cases involving double teeth are in most cases challenging. The purpose of this case report is to describe a successful multidisciplinary treatment protocol for a double tooth. Upon completion of the endodontic, restorative and orthodontic treatments, the clinical and radiographic three-year follow-up revealed that the rest of the transected premolar showed evidence of healing of the supporting tissues and satisfactory cosmetic result...
2017: Iranian Endodontic Journal
Majid Moosavi, Fatemeh Khashei, Elaheh Sedghamiz
In this work, the structural and dynamical properties of two imidazolium-based geminal dicationic ionic liquids (GDILs), i.e. [Cn(mim)2][NTf2]2 with n = 3 and 5, have been studied to obtain a fundamental understanding of the molecular basis of the macroscopic and microscopic properties of the bulk liquid phase. To achieve this purpose, molecular dynamics (MD) simulation, density functional theory (DFT) and atoms in molecule (AIM) methods were used. Interaction energies, charge transfers and hydrogen bonds between the cation and anions of each studied GDIL were investigated by DFT calculations and also AIM...
December 6, 2017: Physical Chemistry Chemical Physics: PCCP
Zhen Lei Song, Yuebao Zhang, Qianyou Guo, Ji Lu, Xianwei Sun, Qiang Pu, Yanjun Cao, Zhiwen Chu, Lu Gao
Convergent total synthesis of bryostatin 8 has been accomplished via an organosilane-based strategy. The C ring is constructed stereoselectively through geminal bis(silane)-based [1,5]-Brook rearrangement, and the B ring through geminal bis(silane)-based Prins cyclization, efficiently joining the northern and southern parts of the molecule.
December 6, 2017: Angewandte Chemie
Hung-Cheng Chen, Andrew R Cook, Sadayuki Asaoka, Jeffery S Boschen, Theresa L Windus, John R Miller
Geminate recombination of 24 radical anions (M˙-) with solvated protons (RH2+) was studied in tetrahydrofuran (THF) with pulse radiolysis. The recombination has two steps: (1) diffusion of M˙- and RH2+ together to form intimate (contact and solvent separated) ion pairs, driven by Coulomb attraction; (2) annihilation of anions due to proton transfer (PT) from RH2+ to M˙-. The non-exponential time-dependence of the geminate diffusion was determined. For all molecules protonated on O or N atoms the subsequent PT step is too fast (<0...
December 1, 2017: Physical Chemistry Chemical Physics: PCCP
N Rivas, G Moriena, L Domenianni, J H Hodak, E Marceca
We performed femtosecond transient absorption (TA) experiments to monitor the solvation dynamics of charge-transfer-to-solvent (CTTS) electrons originating from UV photoexcitation of ammoniated iodide in close proximity to the counterions. Solutions of KI were prepared in liquid ammonia and TA experiments were carried out at different temperatures and densities, along the liquid-gas coexistence curve of the fluid. The results complement previous femtosecond TA work by P. Vöhringer's group in neat ammonia via multiphoton ionization...
November 24, 2017: Physical Chemistry Chemical Physics: PCCP
Kara M Kapnas, Benjamin W Toulson, Elizabeth S Foreman, Sarah A Block, J Grant Hill, Craig Murray
Photolysis of geminal diiodoalkanes in the presence of molecular oxygen has become an established route to the laboratory production of several Criegee intermediates, and such compounds also have marine sources. Here, we explore the role that the trihaloalkane, chlorodiiodomethane (CHI2Cl), may play as a photolytic precursor for the chlorinated Criegee intermediate ClCHOO. CHI2Cl has been synthesized and its UV absorption spectrum measured; relative to that of CH2I2 the spectrum is shifted to longer wavelength and the photolysis lifetime is calculated to be less than two minutes...
November 21, 2017: Physical Chemistry Chemical Physics: PCCP
Yasunari Tamai, Yeli Fan, Vincent O Kim, Kostiantyn Ziabrev, Akshay Rao, Stephen Barlow, Seth R Marder, Richard H Friend, S Matthew Menke
Rapid, long-range charge separation in polymer-fullerene organic solar cells (OSCs) enables electrons and holes to move beyond their Coulomb capture radius and overcome geminate recombination. Understanding the nature of charge generation and recombination mechanisms in efficient, nonfullerene-acceptor-based OSCs are critical to further improve device performance. Here we report charge dynamics in an OSC using a perylene diimide (PDI) dimer acceptor. We use transient absorption spectroscopy to track the time evolution of electroabsorption caused by the dipolar electric field generated between electron-hole pairs as they separate after ionization at the donor-acceptor interface...
November 17, 2017: ACS Nano
Prabhat Kumar Singh, Ankur Awasthi
Photo-induced intermolecular excited-state proton transfer (ESPT) reactions are ubiquitous in chemistry and biology. ESPT reactions are extremely sensitive to the nature of water molecules in its microenvironment and thus serve as a sensitive reporter for the water structure and dynamics in a system. Herein, the photo-induced intermolecular ESPT reaction of 8-Hydroxy pyrene-1, 3, 5-trisulfonic acid (HPTS, also known as Pyranine) has been investigated in various DMSO-water mixtures using steady-state and time-resolved emission spectroscopy...
November 14, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Mei Lu, Yijin Su, Pengyi Zhao, Xiaohan Ye, Yi Cai, Xiaodong Shi, Eric Masson, Fengyao Li, J Larry Campbell, Hao Chen
Gold-catalyzed alkyne hydration was studied using in-situ reacting mass spectrometry (MS) technology. By monitoring the reaction process in solution under different conditions (regular and very diluted catalyst concentrations, different pHs) and examining the reaction occurrence in the early reaction stage (1-2 ms after mixing) with MS, we collected a series of experimental evidence to support that the bisgold complex is a key reaction intermediate. Furthermore, both experimental and computational studies confirmed that the σ,π-bisgold complexes are not active intermediate toward nucleophilic addition...
November 13, 2017: Chemistry: a European Journal
Donna Erickson
No abstract text is available yet for this article.
October 2017: Journal of the Acoustical Society of America
Rafael Gallo, Anees Ahmad, Gustavo Metzker, Antonio Carlos Bender Burtoloso
A one-pot alkylation-halogenation of ketosulfoxonium ylides in the presence of alkylhalides is described. The method furnishes several gem-difunctionalized haloketones (an alkyl and F, Cl, Br, or I) in good yields. Replacing alkyhalides with a mixture of electrophilic halogen species and various halide anions led to gem-dihalogenated ketones containing a combination of the same or two different halogens. Kinetic isotopic effects as well as reaction kinetic experiments give insight to the mechanism of these reactions...
October 27, 2017: Chemistry: a European Journal
Jie Yu, Li-Min Fu, Long-Jiang Yu, Ying Shi, Peng Wang, Zheng-Yu Wang-Otomo, Jian-Ping Zhang
Carotenoids (Cars) in bacterial photosynthesis are known as accessory light harvesters and photoprotectors. Recently, the singlet fission (SF) reaction initiated by Car photoabsorption has been recognized to be an effective excitation deactivation channel disfavoring the light harvesting function. Since the SF reaction and the triplet sensitization reaction underlying photoprotection both yield triplet excited state Cars ((3)Car*), their contribution to the overall (3)Car* photoproduction are difficult to disentangle...
November 8, 2017: Journal of the American Chemical Society
Joshua K G Karlsson, Owen J Woodford, Roza Al-Aqar, Anthony Harriman
Erythrosine, a popular food dye, undergoes fast O2-sensitive bleaching in water when subjected to visible light illumination. In dilute solution, erythrosine undergoes photobleaching via first-order kinetics, where the rate of bleaching depends critically on the rate of photon absorption and on the concentration of dissolved oxygen. Kinetic studies indicate that this inherent bleaching is augmented by self-catalysis at higher concentrations of erythrosine and on long exposure times. Under the conditions used, bleaching occurs by way of geminate attack of singlet molecular oxygen on the chromophore...
November 1, 2017: Journal of Physical Chemistry. A
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