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Essam Hammam, Jalal Basahi, Iqbal Ismail, Ibrahim Hassan, Talal Almeelbi
The excited state hydrogen bonding dynamics of BBVN in hydrogen donating methanol solvent was explored at the TD-BMK/cc-pVDZ level of theory with accounting for the bulk environment effects at the polarizable continuum model (PCM). The heteroatoms of the BBVN laser dye form hydrogen bonds with four methanol molecules. In the formed BBVN-(MeOH)4 complex, the A-type hydrogen bond (N…HO), of an average strength of 25kJmol(-1), is twofold stronger than the B-type (O…HO) one. Upon photon absorption, the total HB binding energy increases from 78...
October 17, 2016: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Thomas W Ebbesen
The notion that light and matter states can be hybridized the way s and p orbitals are mixed is a concept that is not familiar to most chemists and material scientists. Yet it has much potential for molecular and material sciences that is just beginning to be explored. For instance, it has already been demonstrated that the rate and yield of chemical reactions can be modified and that the conductivity of organic semiconductors and nonradiative energy transfer can be enhanced through the hybridization of electronic transitions...
October 25, 2016: Accounts of Chemical Research
Christiane Kiske, Svenja Noerenberg, Miriam Ecker, Xingyue Ma, Tohru Taniguchi, Kenji Monde, Wolfgang Eisenreich, Karl-Heinz Engel
The absolute configurations of chiral β-mercaptoalkanones had been previously assigned on the basis of the 1H NMR anisotropy method using (S)-2-methoxy-2-(1-naphthyl)propionic acid ((S)-MαNP) as chiral auxiliary. This study presents a reinvestigation of the configurations of 4-mercapto-2-pentanone, 1, 4-mercapto-2-heptanone, 2, and 2-mercapto-4-heptanone, 3. Enantiomers of 1, 2 and 3 were obtained by lipase-catalyzed hydrolyses of the respective acetylthioalkanones. Upon derivatization with (S)-MαNP, the configurations of the reaction products were deduced on the basis of the order of the HPLC-elution of the diastereoisomeric thioesters assuming that the sector rule previously developed for secondary alcohols is also valid for thiols...
October 25, 2016: Journal of Agricultural and Food Chemistry
Jeffrey R Hawley, Prateek Kalra, Xiaokui Mo, Brian Raterman, Lisa D Yee, Arunark Kolipaka
PURPOSE: Previous studies of breast MR elastography (MRE) evaluated the technique at magnetic field strengths of 1.5 Tesla (T) with the breast in contact with the driver. The aim of this study is to evaluate breast stiffness measurements and their reproducibility using a soft sternal driver at 3T and compare the results with qualitative measures of breast density. MATERIALS AND METHODS: Twenty-two healthy volunteers each underwent two separate breast MRE scans in a 3T MRI...
October 25, 2016: Journal of Magnetic Resonance Imaging: JMRI
Mostafa Fakhraee, Mohammad Reza Gholami
The effects of ester addition on structural and dynamic properties of biodegradable ILs composed of the 1-(alkoxycarbonyl)-3-alkylimidazolium cation ([C1COOCnC1im](+), n = 1, 2, 4) coupled with [Br](-), [NO3](-), [BF4](-), [PF6](-), [TfO](-), and [Tf2N](-) are explored using the molecular dynamics (MD) simulations and quantum theory of atoms in molecules (QTAIM) at 400 K. Formation of the intramolecular H bonds between O atoms of the ester group and H atoms of the imidazolium ring as well as the nearest H atom of the alkyl chain to the ester group are disclosed from reduced density gradient (RDG) results...
October 25, 2016: Journal of Physical Chemistry. B
Benjamin E Arenas, Sébastien Gruet, Amanda L Steber, Barbara M Giuliano, Melanie Schnell
We report here further spectroscopic investigation of the astrochemically relevant molecule i-propyl cyanide. We observed and analysed the rotational spectra of the ground state of the molecule and ten vibrationally excited states with energies between 180-500 cm(-1). For this, we used a segmented W-band spectrometer (75-110 GHz) and performed the experiments under room temperature conditions. This approach thus provides access to high-resolution, pure rotational data of vibrational modes that occur in the far-infrared fingerprint region, and that can be difficult to access with other techniques...
October 25, 2016: Physical Chemistry Chemical Physics: PCCP
Xiaoshu Lü, Esa-Pekka Takala, Esko Toppila, Ykä Marjanen, Leena Kaila-Kangas, Tao Lu
Exposure to whole-body vibration (WBV) presents an occupational health risk and several safety standards obligate to measure WBV. The high cost of direct measurements in large epidemiological studies raises the question of the optimal sampling for estimating WBV exposures given by a large variation of exposure levels in real worksites. This paper presents a new approach to address this problem. A daily exposure to WBV was recorded for 9 to 24 days among 48 all-terrain vehicle drivers. Four datasets based on root mean squared recordings were obtained from the measurement...
October 25, 2016: Ergonomics
Pauline N Serrano, Hongxin Wang, Jason C Crack, Christopher Prior, Matthew I Hutchings, Andrew J Thomson, Saeed Kamali, Yoshitaka Yoda, Jiyong Zhao, Michael Y Hu, Ercan E Alp, Vasily S Oganesyan, Nick E Le Brun, Stephen P Cramer
The reaction of protein-bound iron-sulfur (Fe-S) clusters with nitric oxide (NO) plays key roles in NO-mediated toxicity and signaling. Elucidation of the mechanism of the reaction of NO with DNA regulatory proteins that contain Fe-S clusters has been hampered by a lack of information about the nature of the iron-nitrosyl products formed. Herein, we report nuclear resonance vibrational spectroscopy (NRVS) and density functional theory (DFT) calculations that identify NO reaction products in WhiD and NsrR, regulatory proteins that use a [4Fe-4S] cluster to sense NO...
October 25, 2016: Angewandte Chemie
Anupam P Vedurmudi, Bruce A Young, J Leo van Hemmen
In internally coupled ears (ICE), the displacement of one eardrum creates pressure waves that propagate through air-filled passages in the skull, causing a displacement of the opposing eardrum and vice versa. In this review, a thorough mathematical analysis of the membranes, passages, and propagating pressure waves reveals how internally coupled ears generate unique amplitude and temporal cues for sound localization. The magnitudes of both of these cues are directionally dependent. On the basis of the geometry of the interaural cavity and the elastic properties of the two eardrums confining it at both ends, the present paper reviews the mathematical theory underlying hearing through ICE and derives analytical expressions for eardrum vibrations as well as the pressures inside the internal passages, which ultimately lead to the emergence of highly directional hearing cues...
October 25, 2016: Biological Cybernetics
Eric K S Shim, Gleen F Chandra, S Pedireddy, Soo-Y Lee
Edible bird's nest (EBN) is made from the glutinous salivary secretion of highly concentrated mucin glycoprotein by swiftlets (genus Aerodramus or Collocalia) native to the Indo-Pacific region. The unique Raman spectrum of EBN has vibrational lines that can be assigned to peptides and saccharides in the glycoprotein, and it can be used to screen for adulteration. The common edible adulterants classified into two types. Type I adulterants, such as fish bladder, pork skin, karaya gum, coralline seaweed, agar strips, and tremella fungus, were solids which adhered externally on the surface of the EBN cement...
September 2016: Journal of Food Science and Technology
Simon T Thompson, H Henry Lamb, Bernard Delley, Stefan Franzen
Tetraamminepalladium(II) perrhenate, a double complex salt, has significant utility in PdRe catalyst preparation; however, the vibrational spectra of this readily prepared compound have not been described in the literature. Herein, we present the infrared (IR) and Raman spectra of tetraamminepalladium(II) perrhenate and several related compounds. The experimental spectra are complemented by an analysis of normal vibrational modes that compares the experimentally obtained spectra with spectra calculated using DFT (DMol(3))...
October 17, 2016: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
Kun Qian, Christoph Janott, Vedhas Pandit, Zixing Zhang, Clemens Heiser, Winfried Hohenhorst, Michael Herzog, Werner Hemmert, Bjoern Schuller
OBJECTIVE: Obstructive Sleep Apnea (OSA) is a serious chronic disease and a risk factor for cardiovascular diseases. Snoring is a typical symptom of OSA patients. Knowledge of the origin of obstruction and vibration within the upper airways is essential for a targeted surgical approach. Aim of this paper is to systematically compare different acoustic features, and classifiers for their performance in the classification of the excitation location of snore sounds. METHODS: Snore sounds from 40 male patients have been recorded during Drug-Induced Sleep Endoscopy, and categorized by ENT experts...
October 21, 2016: IEEE Transactions on Bio-medical Engineering
Z Hirjaková, H Šingliarová, D Bzdúšková, J Kimijanová, K Bučková, P Valkovič, F Hlavačka
The aim of the study was to evaluate the effect of surgical reconstruction of anterior cruciate ligament (ACL) on postural stability and responses to lower limb (LL) muscles vibrations. Centre of pressure (CoP) was measured in 17 subjects during stance on firm/foam surface with eyes open/closed and during unilateral vibrations of LL muscles (m. triceps surae - TS, m. quadriceps femoris - Q, m. quadriceps femoris and hamstrings simultaneously - QH). The measurements were performed: 1) preoperatively, 2) six weeks and 3) three months after the reconstruction...
October 24, 2016: Physiological Research
Hyun Jin Yang, Michael Trenary, Maki Kawai, Yousoo Kim
In contrast to conventional spectroscopic studies of adsorbates at high coverage that provide only spatially averaged information, we have characterized the laterally confined shuttling dynamics of a single molecule under the influence of intermolecular interactions by vibrational spectroscopy using a scanning tunneling microscope. The bridge sites on Pt(111) are only occupied by a CO molecule that is surrounded by four other CO molecules at on-top sites. The bridge-site CO undergoes laterally confined shuttling toward an adjacent on-top site to transiently occupy a metastable site, which is slightly displaced from the center of an on-top site through repulsive interaction with adjacent on-top CO molecules...
October 24, 2016: Journal of Physical Chemistry Letters
Pan-Pan Zhang, Alexander Eisfeld
Two-dimensional electronic spectroscopy has become an important experimental technique to obtain information on, e.g., electronic coherences in large molecular complexes or vibronic couplings. For the correct interpretation of two-dimensional spectra, however, detailed theoretical calculations are required. Reliable theoretical calculations are impeded by large system sizes and number of vibrational degrees of freedom that need to be explicitly taken into account. Here we demonstrate that a numerical approach based on a stochastic hierarchy of pure states (HOPS) does allow to calculate two-dimensional spectra, notwithstanding the stochasticity of our method...
October 24, 2016: Journal of Physical Chemistry Letters
B E Husic, D Schebarchov, D J Wales
We use the harmonic superposition approach to examine how a single atom substitution affects low-temperature anomalies in the vibrational heat capacity (CV) of model nanoclusters. Each anomaly is linked to competing solidlike "phases", where crossover of the corresponding free energies defines a solid-solid transition temperature (Ts). For selected Lennard-Jones clusters we show that Ts and the corresponding CV peak can be tuned over a wide range by varying the relative atomic size and binding strength of the impurity, but excessive atom-size mismatch can destroy a transition and may produce another...
October 24, 2016: Nanoscale
Pavel Zelenovskiy, Igor Kornev, Semen Vasilev, Andrei Kholkin
The elastic properties of the nanotubes of self-assembled aromatic dipeptide diphenylalanine are investigated by means of Raman spectroscopy and a mass-in-mass 1D model. Analysis of nanotubes' lattice vibrations reveals the essential contribution of the water in the nanochannel core of the tubes to the Young's modulus and high water mobility along the channel. Direct measurements of the Young's modulus performed by nanoindentation confirm the obtained results.
October 24, 2016: Physical Chemistry Chemical Physics: PCCP
Jiyuan Zheng, Lai Wang, Di Yang, Jiadong Yu, Xiao Meng, Zhibiao Hao, Changzheng Sun, Bing Xiong, Yi Luo, Yanjun Han, Jian Wang, Hongtao Li, Mo Li, Qian Li
In ultra-high sensitive APDs, a vibrate of temperature might bring a fatal decline of the multiplication performance. Conventional method to realize a temperature-stable APD focuses on the optimization of device structure, which has limited effects. While in this paper, a solution by reducing the carrier scattering rate based on an GaN/AlN periodically-stacked structure (PSS) APD is brought out to improve temperature stability essentially. Transport property is systematically investigated. Compared with conventional GaN homojunction (HJ) APDs, electron suffers much less phonon scatterings before it achieves ionization threshold energy and more electrons occupy high energy states in PSS APD...
October 24, 2016: Scientific Reports
Jacek Koput
The accurate potential energy surface of beryllium monohydroxide, BeOH, in its ground electronic state X 2A' has been determined from ab initio calculations using the coupled-cluster approach in conjunction with the correlation-consistent core-valence basis sets up to septuple-zeta quality. The higher-order electron correlation, scalar relativistic, and adiabatic effects were taken into account. The BeOH molecule was confirmed to be bent at equilibrium, with the BeOH angle of 141.2° and the barrier to linearity of 129 cm(-1) ...
October 24, 2016: Journal of Computational Chemistry
Reda Boulmène, Muthuramalingam Prakash, Majdi Hochlaf
Ab initio and DFT studies on CO2 interacting with different tautomers and isomers of triazole (TZ) are carried out to understand the adsorption mechanism and their mutual preferential sites. We used post Hartree-Fock methods (MP2, CCSD(T), and CCSD(T)-F12) and various DFTs (PBE, PBE0, M05-2X, and M11) with and without considering the dispersion correction for comparison. We determined hence the equilibrium structures, vibrational frequencies and binding energies of TZ-CO2 clusters and mapped their potential energy surfaces along the intermonomer coordinates...
October 24, 2016: Physical Chemistry Chemical Physics: PCCP
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