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Luis M Sesé
The problem of the equilibrium triplet structures in fluids with quantum behavior is discussed. Theoretical questions of interest to the real space structures are addressed by studying the three types of structures that can be determined via path integrals (instantaneous, centroid, and total thermalized-continuous linear response). The cases of liquid para-H2 and liquid neon on their crystallization lines are examined with path-integral Monte Carlo simulations, the focus being on the instantaneous and the centroid triplet functions (equilateral and isosceles configurations)...
March 14, 2018: Journal of Chemical Physics
Michael M Linden, J Philipp Wagner, Bastian Bernhardt, Marcus A Bartlett, Wesley D Allen, Peter R Schreiner
Disentangling internal and external effects is a key requirement for understanding conformational tunneling processes. Here we report the s-trans/s-cis tunneling rotamerization of carbonic acid monomethyl ester (1) under matrix isolation conditions and make comparisons to its parent carbonic acid (3). The observed tunneling rate of 1 is temperature independent in the 3-20 K range and accelerates when using argon instead of neon as the matrix material. The methyl group increases the effective half-life (τeff) of the energetically disfavored s-trans-conformer from 3-5 h for 3 to 11-13 h for 1...
March 15, 2018: Journal of Physical Chemistry Letters
Javier Vicente-Tejedor, Miguel Marchena, Laura Ramírez, Diego García-Ayuso, Violeta Gómez-Vicente, Celia Sánchez-Ramos, Pedro de la Villa, Francisco Germain
Light causes damage to the retina (phototoxicity) and decreases photoreceptor responses to light. The most harmful component of visible light is the blue wavelength (400-500 nm). Different filters have been tested, but so far all of them allow passing a lot of this wavelength (70%). The aim of this work has been to prove that a filter that removes 94% of the blue component may protect the function and morphology of the retina significantly. Three experimental groups were designed. The first group was unexposed to light, the second one was exposed and the third one was exposed and protected by a blue-blocking filter...
2018: PloS One
Vikram Sundar, David Gelbwaser-Klimovsky, Alán Aspuru-Guzik
Modeling nuclear quantum effects is required for accurate molecular dynamics (MD) simulations of molecules. The community has paid special attention to water and other biomolecules that show hydrogen bonding. Standard methods of modeling nuclear quantum effects like Ring Polymer Molecular Dynamics (RPMD) are computationally costlier than running classical trajectories. A force-field functor (FFF) is an alternative method that computes an effective force field which replicates quantum properties of the original force field...
March 12, 2018: Journal of Physical Chemistry Letters
D A Orwig, P Boucher, I Paynter, E Saenz, Z Li, C Schaaf
Contemporary terrestrial laser scanning (TLS) is being used widely in forest ecology applications to examine ecosystem properties at increasing spatial and temporal scales. Harvard Forest (HF) in Petersham, MA, USA, is a long-term ecological research (LTER) site, a National Ecological Observatory Network (NEON) location and contains a 35 ha plot which is part of Smithsonian Institution's Forest Global Earth Observatory (ForestGEO). The combination of long-term field plots, eddy flux towers and the detailed past historical records has made HF very appealing for a variety of remote sensing studies...
April 6, 2018: Interface Focus
Milanpreet Kaur, Ravinder Singh Sawhney, Derick Engles
Using the smallest non-classical fullerene, we investigate the impact of endohedral fullerene molecules on the quantum transport through molecular junctions, and then compared this with the pure C20 -based molecular junction. By employing the density functional theory combined with the non-equilibrium Green's function, we contemplated different electronic parameters, namely, density of states, transmission coefficient, energy levels, molecular orbitals, conduction gaps, electron density and their charge transfer...
March 4, 2018: Journal of Molecular Modeling
Sheng-Lung Chou, Jen-Iu Lo, Yu-Chain Peng, Hsiao-Chi Lu, Bing-Ming Cheng, J F Ogilvie
Irradiation at 173 or 143 nm of samples of16 O2 or18 O2 in solid Ne near 4 K produced many new spectral lines in absorption and emission from the mid-infrared to the near-ultraviolet regions. The major product was ozone, O3 , that was identified with its mid-infrared and near-ultraviolet absorption lines. Oxygen atoms were formed on photolysis of O2 and stored in solid neon until the temperature of a sample was increased to 9 K, which enabled their migration and combination to form O3 and likely also O2 . O2 in five excited states and O in two excited states detected through the emission spectra indicate that complicated processes occurred in solid Ne after far-ultraviolet excitation...
March 2, 2018: Physical Chemistry Chemical Physics: PCCP
Stephanie L Fitzpatrick, Lawrence J Appel, Bethany Bray, Neon Brooks, Victor J Stevens
BACKGROUND: We have demonstrated previously that patterns of behavioral adherence in the first 6 months of behavioral lifestyle interventions were associated with significant weight loss at 18 months. In this article, we extend this work to examine patterns of behavioral adherence over 18 months and to explore baseline demographic and psychosocial predictors. METHOD: Latent class analysis was applied separately to the Weight Loss Maintenance and PREMIER trials data to examine patterns of adherence to the following recommendations: (1) consuming ≥9 servings of fruits and vegetables per day, (2) ≤25% of energy from total fat, (3) ≤7% energy from saturated fat, and (4) ≥180 minutes of moderate-to-vigorous physical activity per week...
February 1, 2018: Health Education & Behavior: the Official Publication of the Society for Public Health Education
Luciana Mara Fé Gonçalves, Maria de Nazaré Paula da Silva, Adalberto Luis Val, Vera Maria Fonseca de Almeida-Val
Two Amazonian closely related tetras - cardinal Paracheirodon axelrodi and green neon P. simulans - were artificially acclimatized to environmental chambers mimicking future climate change scenarios (mild, moderate and extreme), using a microcosm facility. P. simulans survived (100%) to all scenarios after 30 days exposure, while P. axelrodi presented decreasing survival percentages according to environmental severity. These differences may be the reflection of distinct natural acclimatization to microhabitats between the species, which differ in thermal conditions...
February 19, 2018: Genetics and Molecular Biology
Gernot Frenking, Lili Zhao, Israel Fernandez, Robert Berger, Mingfei Zhou, Dandan Jiang
BaCO+ and BaCO- were and isolated in a low-temperature neon matrix. The observed C-O stretching wavenumber for BaCO+ of 1911.2 cm-1 is the most red-shifted value measured for any metal carbonyl cations, indicating strong π backdonation of electron density from Ba+ to CO. Quantum chemical calculations indicate that BaCO+ has a 2 ground state, which correlates with the 2D(5d1) excited state of Ba+ that comprises significant Ba+(5dπ1)→CO(* LUMO) backbonding, letting the BaCO+ complex behave like a conventional transition-metal carbonyl...
February 12, 2018: Angewandte Chemie
Stephan Prinz, Maximilian Schnitzenbaumer, Dionysios Potamianos, Marcel Schultze, Sebastian Stark, Matthias Häfner, Catherine Y Teisset, Christoph Wandt, Knut Michel, Reinhard Kienberger, Birgitta Bernhardt, Thomas Metzger
We present an optical parametric chirped pulse amplifier (OPCPA) delivering CEP-stable ultrashort pulses with 7 fs, high energies of more than 1.8 mJ and high average output power exceeding 10 W at a repetition rate of 6 kHz. The system is pumped by a picosecond regenerative thin-disk amplifier and exhibits an excellent long-term stability. In a proof-of-principle experiment, high harmonic generation is demonstrated in neon up to the 61st order.
January 22, 2018: Optics Express
Christoph Binder, Nicholas Longford, Chris Gale, Neena Modi, Sabita Uthaya
BACKGROUND: The optimal nutritional regimen for preterm infants, including those that develop necrotising enterocolitis (NEC), is unknown. OBJECTIVE: The objective here was to evaluate body composition at term in infants following NEC, in comparison with healthy infants. The primary outcome measure was non-adipose tissue mass (non-ATM). METHODS: We compared body composition assessed by magnetic resonance imaging at term in infants born <31 weeks of gestational age that participated in NEON, a trial comparing incremental versus immediate delivery of parenteral amino acids on non-ATM, and SMOF versus intralipid on intrahepatocellular lipid content...
January 23, 2018: Neonatology
Arif Ali Chishti, Christa Baumstark-Khan, Kristina Koch, Waldemar Kolanus, Sebastian Feles, Bikash Konda, Abid Azhar, Luis F Spitta, Bernd Henschenmacher, Sebastian Diegeler, Claudia Schmitz, Christine E Hellweg
Nuclear factor kappaB (NF-κB) is a central transcription factor in the immune system and modulates cell survival in response to radiotherapy. Activation of NF-κB was shown to be an early step in the cellular response to ultraviolet A (UVA) and ionizing radiation exposure in human cells. NF-κB activation by the genotoxic stress-dependent sub-pathway after exposure to different radiation qualities had been evaluated to a very limited extent. In addition, the resulting gene expression profile, which shapes the cellular and tissue response, is unknown...
January 25, 2018: Radiation Research
Hamza Shakeel, Haoyan Wei, Joshua M Pomeroy
We report precise experimental values of the enthalpy of sublimation (ΔHs ) of quenched condensed films of neon (Ne), nitrogen (N2), oxygen (O2), argon (Ar), carbon dioxide (CO2), krypton (Kr), xenon (Xe), and water (H2O) vapor using a single consistent measurement platform. The experiments are performed well below the triple point temperature of each gas and fall in the temperature range where existing experimental data is very limited. A 6 cm2 and 400 µm thick double paddle oscillator (DPO) with high quality factor (Q ≈ 4 × 105 at 298K) and high frequency stability (33 parts per billion) is utilized for the measurements...
March 2018: Journal of Chemical Thermodynamics
A E El-Raie, H E Hassan, A A Abd El-Rahman, R A Shaimaa
The authenticity of honey is great importance for commercial and health reasons. Adulteration of honey bee with cheaper sweetening materials has been used. The objectives of this study were: 1) To evaluate the quality of honey bee according to physicochemical characteristics, 2) To estimate the transmission property of prediction of honey using visible laser technique, and 3) Possibility of adulteration of honey bee according to high transmission intensity of laser beam through Clover honey bee. Helium-neon (He-Ne) laser in the visible light with wavelengths 632...
January 20, 2018: Journal of the Science of Food and Agriculture
Zongfang Wu, Agata Płucienik, Felix E Feiten, Matthias Naschitzki, Walter Wachsmann, Sandy Gewinner, Wieland Schöllkopf, Volker Staemmler, Helmut Kuhlenbeck, Hans-Joachim Freund
Vibrational action spectroscopy employing infrared radiation from a free-electron laser has been successfully used for many years to study the vibrational and structural properties of gas phase aggregates. Despite the high sensitivity of this method no relevant studies have yet been conducted for solid sample surfaces. We have set up an experiment for the application of this method to such targets, using infrared light from the free-electron laser of the Fritz Haber Institute. In this Letter, we present first results of this technique with adsorbed argon and neon atoms as messengers...
September 29, 2017: Physical Review Letters
Piotr Aleksander Guńka, Michał Hapka, Michael Hanfland, Maciej Dranka, Grzegorz Chałasiński, Janusz Zachara
Investigations into the helium permeation of arsenolite, the cubic, molecular arsenic(III) oxide polymorph As₄O₆, were carried out in order to understand how and why arsenolite helium clathrate As₄O₆∙2He is formed. High-pressure synchrotron X-ray diffraction experiments on arsenolite single crystals revealed that the permeation of helium into non-porous arsenolite depends on the time during which the crystal is subjected to high pressure and on the crystal history. The single crystal was totally transformed into As₄O₆·2He within 45 h under 5 GPa...
January 17, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
André Kristopher Eckhardt, Dennis Gerbig, Peter R Schreiner
Although frequently employed, heavy atom kinetic isotope effects (KIE) have not been reported for quantum mechanical tunneling reactions. Here we examine the secondary KIE through 13C substitution of the carbene atom in methylhydroxycarbene (H3C-C̈-OH) in its [1,2]H tunneling shift reaction to acetaldehyde (H3C-CHO). Our study employs matrix isolation IR spectroscopy in various inert gases and quantum chemical computations. Depending on the choice of the matrix host gas the KIE varies within a range of 1.0 in xenon and 1...
January 10, 2018: Journal of Physical Chemistry. A
K Uno, T Jitsuno
We developed a longitudinally excited N2 laser with a simple driver circuit and a simple power supply. The N2 laser consisted of a 20 cm-long glass tube with an inner diameter of 2.5 mm, a normal stable resonator formed by flat mirrors, a variable transformer, a neon sign transformer, a spark gap, and a 200 pF capacitance. The N2 laser produced a laser pulse with an energy of 379 nJ and a pulse width of 7.5 ns at a repetition rate of 100 Hz. The laser beam was circular and had a Gaussian profile with a correlation factor of 0...
December 2017: Review of Scientific Instruments
Friethjof Theel, Antonia Karamatskou, Robin Santra
The Hartree-Fock method is an important approximation for the ground-state electronic wave function of atoms and molecules so that its usage is widespread in computational chemistry and physics. The Hartree-Fock method is an iterative procedure in which the electronic wave functions of the occupied orbitals are determined. The set of functions found in one step builds the basis for the next iteration step. In this work, we interpret the Hartree-Fock method as a dynamical system since dynamical systems are iterations where iteration steps represent the time development of the system, as encountered in the theory of fractals...
December 2017: Chaos
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