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Hui Chen, Thomas Pope, Zhuoyan Wu, Dongfei Wang, Lei Tao, De-Liang Bao, Wende Xiao, Jun-Long Zhang, Yu-Yang Zhang, Shi-Xuan Du, Song Gao, Sokrates T Pantelides, Werner A Hofer, Hong-Jun Gao
The quantum efficiency or the rate of conversion of incident photon to free electron in photosynthesis is known to be extremely high. It has long been thought that the origin of this efficiency are molecular vibrations leading to a very fast separation of electrons and holes within the involved molecules. However, molecular vibrations are commonly in the range above 100 meV, which is too high for excitations in an ambient environment. Here, we analyze experimental spectra of single organic molecules on metal surfaces at ~ 4 K, which often exhibit a pronounced dip...
July 20, 2017: Nano Letters
Ismael Galván, Alberto Jorge, María García-Gil
Vibrations in covalent bonds affect electron delocalization within molecules, as reported in polymers. If synthesized by living cells, the electron delocalization of polymers affects the stabilization of cellular free radicals, but biomolecular vibration has never been considered a potential source of cytotoxicity. Here we show that the vibrational characteristics of natural pheomelanin and eumelanin contribute to feather color expression in four poultry breeds with different melanin-based pigmentation patterns, but only the vibrational characteristics of pheomelanin are related to the production of reactive oxygen species (ROS) in the mitochondria of melanocytes and to systemic levels of cellular oxidative stress and damage...
July 20, 2017: Integrative Biology: Quantitative Biosciences From Nano to Macro
Yong-Tao Ma, Xinyou Ma, Anyang Li, Hua Guo, Li Yang, Jiaxu Zhang, William L Hase
Direct dynamics simulations were performed to study the SN2 double inversion mechanism SN2-DI, with retention of configuration, for the F(-) + CH3I reaction. Previous simulations identified a transition state (TS) structure, i.e. TS0, for the SN2-DI mechanism, including a reaction path. However, intrinsic reaction coordinate (IRC) calculations from TS0 show it is a proton transfer (PT) TS connected to the F(-)HCH2I SN2 pre-reaction complex and the FHCH2I(-) proton transfer post-reaction complex. Inclusion of TS0 in the SN2-DI mechanism would thus involve non-IRC atomistic dynamics...
July 20, 2017: Physical Chemistry Chemical Physics: PCCP
Sayan Mondal, Mrinalini Puranik
We report deep UV initiated excited state dynamics of the canonical nucleobase adenine (Ade) through Resonance Raman (RR) intensity analysis. RR spectra of Ade at excitation wavelengths throughout the Bb absorption band in the 210-230 nm wavelength range are measured and subsequently converted to scattering cross-sections. The time-dependent wave packet (TDWP) formalism has been employed for self-consistent simulations of the resulting wavelength dependent Raman excitation profiles (REP) and absorption spectrum of Ade...
July 20, 2017: Physical Chemistry Chemical Physics: PCCP
P Sundaram, V Manivannan, R Padmanaban
Initial state-selected and energy resolved channel-specific reaction probabilities, integral cross sections and thermal rate constants of the H((2)S) + CH(+)(X(1)Σ(+)) reaction are calculated within the coupled states approximation by a time-dependent wave packet propagation method. The new ab initio global potential energy surface (PES) of the electronic ground state (1 (2)A') of the system, recently reported by Li et al. [J. Chem. Phys., 2015, 142, 124302], is employed for this purpose. All partial wave contributions up to the total angular momentum J = 60 are considered to obtain the converged integral reaction cross section up to a collision energy of 1...
July 20, 2017: Physical Chemistry Chemical Physics: PCCP
Laurent Bonnet, Joaquin Espinosa-Garcia
The OH + CHD3 reaction is among the largest one ever studied at the high-resolution level permitted by imaging techniques [B. Zhang et al., J. Phys. Chem. A, 2005, 109, 8989]. This process involves eighteen configuration space coordinates, which are large enough to make exact quantum scattering calculations beyond reach. Moreover, freezing some degrees-of-freedom in order to render these calculations feasible may lead to unrealistic predictions. However, we have found it possible to reproduce for the first time the pair-correlated measurements of Zhang et al...
July 20, 2017: Physical Chemistry Chemical Physics: PCCP
S van den Wildenberg, B Mignolet, R D Levine, F Remacle
The coupled electronic-nuclear coherent dynamics induced by a short strong VUV fs pulse in the low excited electronic states of HCN is probed by transient absorption spectroscopy with a second weaker fs UV pulse. The nuclear time-dependent Schrodinger equation is solved on a 2D nuclear grid with several electronic states with a Hamiltonian including the dipole coupling to the pump and the probe electric fields. The two internal nuclear coordinates describe the motion of the light H atom. There is a band of several excited electronic states at about 8 eV above the ground state (GS) that is transiently accessed by the pump pulse...
July 20, 2017: Physical Chemistry Chemical Physics: PCCP
Kun Zhang, Zhaojian Yang
Rotating machinery is often subjected to variable loads during operation. Thus, monitoring and identifying different load types is important. Here, five typical load types have been qualitatively studied for a rotor system. A novel load category identification method for rotor system based on vibration signals is proposed. This method is a combination of ensemble empirical mode decomposition (EEMD), energy feature extraction, and back propagation (BP) neural network. A dedicated load identification test bench for rotor system was developed...
July 20, 2017: Sensors
Sen Lin, Lili Liu, Yong Yang, Wei Zhang, Meng Xu, Kuangfei Lin
In this paper, the amine-functionalized magnetite hollow nanospheres (AMHNs), prepared through a facile one-pot synthesis, were used as heavy metal ion adsorbents, whose morphology and physicochemical features were exploring by transmission electron microscopy, vibrating sample magnetometer, X-ray diffraction and Fourier-transform infrared analyses. Its adsorption performances for Pb(2+), Cu(2+), Zn(2+), Ni(2+) and Cd(2+) were studied in detail. The adsorption increased with the increase of initial pH value of the solution and could be obviously affected by ionic strength...
July 2017: Water Science and Technology: a Journal of the International Association on Water Pollution Research
Tobias Garling, Yujin Tong, Tamim Darwish, Martin Wolf, R Kramer Campen
Surfaces whose macroscopic properties can be switched by light are potentially useful in a wide variety of applications. One such promising application is electrochemical sensors that can be gated by optically switching the electrode <i>on</i> or <i>off</i>. One way to make such a switchable electrode is by depositing a self-assembled monolayer of bistable, optically switchable molecules onto an electrode surface. Quantitative application of any such sensor requires understanding how changes in interfacial field affect the composition of photostationary states, <i>i...
July 20, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Marie-Paule Pileni
The spontaneous assembly of uniform-sized globular entities into ordered arrays is a universal phenomenon observed for objects with diameters spanning a broad range of length scales. These extend from the atomic scale (10(-8) cm), through molecular and macromolecular scales with proteins, synthetic low polymers, and colloidal crystals (∼10(-6) cm), to the wavelength of visible light (∼10(-5) cm). The associated concepts of sphere packing have had an influence in diverse fields ranging from pure geometrical analysis to architectural models or ideals...
July 20, 2017: Accounts of Chemical Research
Bret Pasch, Isao T Tokuda, Tobias Riede
Functional changes in vocal organ morphology and motor control facilitate the evolution of acoustic signal diversity. Although many rodents produce vocalizations in a variety of social contexts, few studies have explored the underlying production mechanisms. Here, we describe mechanisms of audible and ultrasonic vocalizations (USVs) produced by grasshopper mice (genus Onychomys). Grasshopper mice are predatory rodents of the desert that produce both loud, long-distance advertisement calls and USVs in close-distance mating contexts...
July 26, 2017: Proceedings. Biological Sciences
Genkuan Ren, Xinlong Wang, Penghui Huang, Benhe Zhong, Zhiye Zhang, Lin Yang, Xiushan Yang
Porous magnetite nanoparticles were successfully synthesized by reduction of titanium residue with pyrite under nitrogen protection, and characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, vibrating sample magnetometer, X-ray photoelectron spectroscope, zeta potential and Brunauer-Emmett-Teller method. The XRD analysis confirmed the formation of porous magnetite nanoparticles with single spinel structure. The SEM image demonstrated that porous magnetite nanoparticles displayed spherical shape with the average diameter of ~51nm...
July 13, 2017: Science of the Total Environment
Maria Grazia Benedetti, Gennaro Boccia, Lorenzo Cavazzuti, Elena Magnani, Elisabetta Mariani, Alberto Rainoldi, Roberto Casale
Quadriceps weakness has been associated with knee osteoarthritis (OA). High-frequency localized muscle vibration (LMV) has been proposed recently for quadriceps strengthening in patients with knee OA. The purpose of this study was (a) to investigate the clinical effectiveness of high-frequency LMV on quadriceps muscle in patients with knee OA and (b) to disentangle, by means of surface electromyography (sEMG), the underlying mechanism. Thirty patients, aged between 40 and 65 years, and clinically diagnosed with knee OA were included in this randomized, controlled, single-blinded pilot study...
July 18, 2017: International Journal of Rehabilitation Research. Revue Internationale de Recherches de Réadaptation
Chantal Triscoli, Ilona Croy, Susann Steudte-Schmiedgen, Håkan Olausson, Uta Sailer
INTRODUCTION: The present study explores whether long-lasting pleasant touch has positive effects on the stress response, reward sensitivity, mood, and interoceptive awareness. METHODS: 40 participants received either 35minutes of brush stroking targeting C-tactile fibres (CT) or vibration on the forearm, and rated pleasantness and intensity. Prior and after, stress response (cortisol and heart rate variability), reward sensitivity, mood and interoceptive awareness were measured...
July 16, 2017: Biological Psychology
Lucca Kühner, Mario Hentschel, Ute Zschieschang, Hagen Klauk, Jochen Vogt, Christian Huck, Harald Giessen, Frank Neubrech
Spectroscopic infrared chemical imaging is ideally suited for label-free and spatially resolved characterization of molecular species, but often suffers from low infrared absorption cross sections. Here, we overcome this limitation by utilizing confined electromagnetic near-fields of resonantly excited plasmonic nanoantennas, which enhance the molecular absorption by orders of magnitude. In the experiments, we evaporate microstructured chemical patterns of C60 and pentacene with nanometer thickness on top of homogeneous arrays of tailored nanoantennas...
May 26, 2017: ACS Sensors
Jae Yoon Shin, Steven A Yamada, Michael D Fayer
Supported ionic liquid membranes (SILMs) are porous membranes impregnated with ionic liquids (ILs) and used as advanced carbon capture materials. Here, two-dimensional infrared (2D IR) and IR polarization selective pump-probe (PSPP) spectroscopies were used to investigate CO2 reorientation and spectral diffusion dynamics in SILMs. The SILM contained 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonly)imide in the poly(ether sulfone) membrane with average pore size of ~350 nm. Two ensembles of CO2 were observed in the SILM, one in the IL phase in the membrane pores and the other in the supporting membrane polymer...
July 19, 2017: Journal of the American Chemical Society
Evgeny Loginov, Luis F Gomez, Boris G Sartakov, Andrey F Vilesov
Ethane core - silver shell clusters consisting of several thousand particles have been assembled in helium droplets upon capture of first ethane molecules, followed by Ag atoms. The composite clusters were studied via infrared laser spectroscopy in the range of C-H stretching vibrations of ethane molecules. The spectra show the splitting of the vibrational bands, which was assigned to different environment of the molecules, such as in contact or devoid of a contact with Ag atoms. The analysis of the band intensities for different number of trapped ethane molecules and Ag atoms indicates that the composite clusters consist of ethane core covered with small Ag clusters having different degree of submergence on the surface...
July 19, 2017: Journal of Physical Chemistry. A
Woongmo Sung, Zaure Avazbaeva, Doseok Kim
Interfacial water reorientation caused by charged Langmuir monolayers consisting of primary fatty amine (ODA) and cationic lipid having quaternary amine headgroup (DPTAP) were investigated by interface-selective vibrational sum-frequency generation spectroscopy. For DPTAP monolayer, initially large sum-frequency intensity from interfacial water OH band decreased steadily by increasing monovalent salt (NaCl, NaI) concentration due to counterion adsorption. On the other hand, ODA/water exhibited significantly smaller sum-frequency intensity than DPTAP/water implying only small portion of protonated amine group (-NH3+) initially existed...
July 19, 2017: Journal of Physical Chemistry Letters
Kiharu Abe, Kim Hyeon-Deuk
Achieving a direct nonequilibrium simulation for hydrogen systems has been quite challenging because nuclear quantum effects (NQEs) have to be taken into account. We directly simulated nonequilibrium hydrogen molecules under a temperature gradient with the recently developed nonempirical molecular dynamics method, which describes nonspherical hydrogen molecules with the NQEs. We found dynamical ordering purely induced by heat flux, which should be distinguished from static ordering like orientational alignment, as decelerated translational motions and enhanced intensity of H-H vibrational power spectra despite the little structural ordering...
July 20, 2017: Journal of Physical Chemistry Letters
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