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Ayano Chiba, Masanori Inui, Yukio Kajihara, Kazuhiro Fuchizaki, Ryo Akiyama
A pressure-induced structural change of a polymer isotactic poly(4-methyl-1-pentene) (P4MP1) in the melted state at 270 °C has been investigated by high-pressure in situ x-ray diffraction, where high pressures up to 1.8 kbar were applied using helium gas. The first sharp diffraction peak (FSDP) position of the melt shows a less pressure dependence than that of the normal compression using a solid pressure transmitting medium. The contraction using helium gas was about 10% at 2 kbar, smaller than about 20% at the same pressure using a solid medium...
May 21, 2017: Journal of Chemical Physics
Govindjee, John C Munday, George C Papageorgiou
We present here a Tribute to Frederick Yi-Tung Cho (1939-2011), an innovative and ingenious biophysicist and an entrepreneur. He was one of the 4 earliest PhD students [see: Cederstrand (1965)-Carl Nelson Cederstrand; coadvisor: Eugene Rabinowitch; Papageorgiou (1968)-George C. Papageorgiou (coauthor of this paper); and Munday (1968)-John C. Munday Jr. (also a coauthor of this paper)] of one of us (Govindjee) in Biophysics at the University of Illinois at Urbana-Champaign (UIUC) during the late 1960s (1963-1968)...
May 18, 2017: Photosynthesis Research
Yusuke Seki, Toshiyuki Takayanagi, Motoyuki Shiga
Ring-polymer molecular dynamics (RPMD) simulations have been performed to understand the photoexcitation dynamics of an Ag atom embedded in a low-temperature cluster consisting of 500 helium atoms, after the electronic excitation 5p (2)P1/2 ← 5p (2)S1/2 and 5p (2)P3/2 ← 5p (2)S1/2 of the Ag atom. Along the RPMD trajectory the time evolution of electronic wavefunction within the spin-orbit (2)P manifold is calculated, whereby the time-dependent Schrödinger equation and the RPMD equation of motion are coupled, using the à la Ehrenfest mean field approach...
May 16, 2017: Physical Chemistry Chemical Physics: PCCP
Nikolas Kaltsoyannis
The geometries and electronic structures of molecular ions featuring He atoms complexed to actinide cations are explored computationally using density functional and coupled cluster theories. A new record coordination number is established, as AcHe17(3+) , ThHe17(4+) , and PaHe17(4+) are all found to be true geometric minima, with the He atoms clearly located in the first shell around the actinide. Analysis of AcHen(3+) (n=1-17) using the quantum theory of atoms in molecules (QTAIM) confirms these systems as having closed shell, charge-induced dipole bonding...
May 16, 2017: Angewandte Chemie
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
Jiann C Yang, Edward Hnetkovsky, Doris Rinehart, Marco Fernandez, Felix Gonzalez, Joseph Borowsky
This paper summarizes the small scale thermal exposure test results of the performance of metallic and polymeric O-ring seals typically used in radioactive material transportation packages. Five different O-ring materials were evaluated: Inconel/silver, ethylene-propylene diene monomer (EPDM), polytetrafluoroethylene (PTFE), silicone, butyl, and Viton. The overall objective of this study is to provide test data and insights to the performance of these Oring seals when exposed to beyond-design-basis temperature conditions due to a severe fire...
April 2017: Polymer Testing
Uenderson Araujo-Barbosa, Elena Peña-Vazquez, Maria Carmen Barciela-Alonso, Sergio Luis Costa Ferreira, Ana Maria Pinto Dos Santos, Pilar Bermejo-Barrera
This work proposes the use of high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry (HPLC-ICP-MS) for simultaneous speciation of arsenic and chromium in iron supplements used for the treatment of anemia. The sample preparation procedure recommended for the total determination of arsenic and chromium was established using acid digestion in a microwave assisted oven. For speciation analysis, however, the microwave-assisted extraction procedure involved the use of water as extraction solvent at 90°C for 30min...
August 1, 2017: Talanta
O El-Atwani, J E Nathaniel, A C Leff, K Hattar, M L Taheri
Crystal defects generated during irradiation can result in severe changes in morphology and an overall degradation of mechanical properties in a given material. Nanomaterials have been proposed as radiation damage tolerant materials, due to the hypothesis that defect density decreases with grain size refinement due to the increase in grain boundary surface area. The lower defect density should arise from grain boundary-point defect absorption and enhancement of interstitial-vacancy annihilation. In this study, low energy helium ion irradiation on free-standing iron thin films were performed at 573 K...
May 12, 2017: Scientific Reports
Adrien Maniquet, Nicolas Bruyer, Guy Raffin, Franck Baco-Antionali, Claire Demesmay, Vincent Dugas, Jérôme Randon
80% vinyltrimethoxysilane-based hybrid silica monoliths (80-VTMS), which have been initially developed for separation in reversed-phase liquid chromatography, have been investigated in high pressure gas chromatography separations (carrier gas pressure up to 60bar) and compared to silica monolithic columns. The behavior of both silica and 80-VTMS monolithic columns was investigated using helium, nitrogen and carbon dioxide as carrier gas. The efficiency of 80-VTMS monolithic columns was shown to vary differently than silica monolithic columns according to the temperature and the carrier gas used...
May 2, 2017: Journal of Chromatography. A
Wei-Zhong Han, Jian Zhang, Ming-Shuai Ding, Lan Lv, Wen-Hong Wang, Guang-Heng Wu, Zhi-Wei Shan, Ju Li
The intriguing phenomenon of metal superelasticity relies on stress-induced martensitic transformation (SIMT), which is well-known to be governed by developing cooperative strain accommodation at multiple length scales. It is therefore scientifically interesting to see what happens when this natural length scale hierarchy is disrupted. One method is producing pillars that confine the sample volume to micrometer length scale. Here we apply yet another intervention, helium nanobubbles injection, which produces porosity on the order of several nanometers...
May 10, 2017: Nano Letters
Marek E Schmidt, Anto Yasaka, Masashi Akabori, Hiroshi Mizuta
The recent technological advance of the gas field ion source (GFIS) and its successful integration into systems has renewed the interest in the focused ion beam (FIB) technology. Due to the atomically small source size and the use of light ions, the limitations of the liquid metal ion source are solved as device dimensions are pushed further towards the single-digit nanometer size. Helium and neon ions are the most widely used, but a large portfolio of available ion species is desirable, to allow a wide range of applications...
May 10, 2017: Microscopy and Microanalysis
Masahiro Kawasaki, Tadashi Nobuchi, Yuta Nakafushi, Masateru Nose, Masateru Shibata, Peng Li, Makoto Shiojiri
Plant anatomy was examined for two clarinet reeds made out of Arundo donax by different means of microscopy: light microscopy, low-energy secondary electron scanning electron microscopy (SEM), backscattered electron SEM, and helium ion microscopy (HiM). The local indentation hardness HIT and Young's modulus EIT of different tissues on their cross sections were measured. A vascular bundle (Vb) (HIT  = 60-100 MPa, EIT  = 1,500-2,000 MPa) that includes soft tissues of phloem and xylem and a vascular bundle sheath (Bs) (HIT  = 300-500 MPa, EIT  = ∼7,000 MPa) form a pipe of the strong string along the longitudinal direction of the cane...
May 9, 2017: Microscopy Research and Technique
Shane R Ellis, Huong T Pham, Marc In Het Panhuis, Adam J Trevitt, Todd W Mitchell, Stephen J Blanksby
Reaction products from the ozonolysis of unsaturated lipids at gas-liquid interfaces have the potential to significantly influence the chemical and physical properties of organic aerosols in the atmosphere. In this study, the gas-phase dissociation behavior of lipid secondary ozonides is investigated using ion-trap mass spectrometry. Secondary ozonides were formed by reaction between a thin film of unsaturated lipids (fatty acid methyl esters or phospholipids) with ozone before being transferred to the gas phase as [M + Na](+) ions by electrospray ionization...
May 8, 2017: Journal of the American Society for Mass Spectrometry
K Sivsivadze, M Jokhadze, P Tushurashvili, T Murtazashvili, N Imnadze
A simple, rapid, selective, sensitive gas chromatography-mass spectrometry (GC-MS/MS) method was developed and validated for the determination of clozapine in human blood. For isolation was used solid phase extraction. The calibration standards range was 5-1500ng/mL. Analysis was carried out on a gas chromatograph Agilent 7000A Quadrupole GC-MS/MS. GC run conditions - capillary column HP-5MS, 30m × 0.25mm, coated with a 0.25μm film, column temperature from 50°C to 305°C with an increase of 10°C/min; the injection port and the transfer line temperature were 310°C; carrier gas - helium at flow rate of 1...
March 2017: Georgian Medical News
Adrien Savoyant, Hatim Alnoor, Olivier Pilone, Omer Nur, Magnus Willander
Zinc oxide (ZnO) nanorods grown by the low-temperature (90°C) aqueous chemical method with different cobalt concentration within the synthesis solution (from 0% to 15%), are studied by electron paramagnetic resonance (EPR), just above the liquid helium temperature. The anisotropic spectra of substitutional Co2+ reveal a high crystalline quality and orientation of the NRs, as well as the probable presence of a secondary disordered phase of ZnO:Co. The analysis of the EPR spectra indicates that the disappearance of the paramagnetic native core-defect (CD) at g~1...
May 5, 2017: Nanotechnology
Jing Li, Markus Holzmann, Ivan Duchemin, Xavier Blase, Valerio Olevano
The helium atom is the simplest many-body electronic system provided by nature. The exact solution to the Schrödinger equation is known for helium ground and excited states, and it represents a benchmark for any many-body methodology. Here, we check the ab initio many-body GW approximation and the Bethe-Salpeter equation (BSE) against the exact solution for helium. Starting from the Hartree-Fock method, we show that the GW and the BSE yield impressively accurate results on excitation energies and oscillator strength, systematically improving the time-dependent Hartree-Fock method...
April 21, 2017: Physical Review Letters
Ruben Bartali, Michal Otyepka, Martin Pykal, Petr Lazar, Victor Micheli, Gloria Gottardi, Nadhira Laidani
The interaction of the confined gas with solid surface immersed in water is a common theme of many important fields such as; self-cleaning surface, gas storage, and sensing. For that reason, we investigated the gas-graphite interaction in the water medium. The graphite surface was prepared by mechanical exfoliation of highly oriented pyrolytic graphite (HOPG). The surface chemistry and morphology were studied by X-ray photoelectron spectroscopy and atomic force microscopy, respectively. The surface energy of HOPG was estimated by contact angle measurements, using the Owens-Wendt method...
May 5, 2017: ACS Applied Materials & Interfaces
Vitaly L Sushkevich, Dennis Palagin, Marco Ranocchiari, Jeroen A van Bokhoven
Direct functionalization of methane in natural gas remains a key challenge. We present a direct stepwise method for converting methane into methanol with high selectivity (~97%) over a copper-containing zeolite, based on partial oxidation with water. The activation in helium at 673 kelvin (K), followed by consecutive catalyst exposures to 7 bars of methane and then water at 473 K, consistently produced 0.204 mole of CH3OH per mole of copper in zeolite. Isotopic labeling confirmed water as the source of oxygen to regenerate the zeolite active centers and renders methanol desorption energetically favorable...
May 5, 2017: Science
Yi Xin, Maurizio Cereda, Stephen Kadlecek, Kiarash Emami, Hooman Hamedani, Ian Duncan, Jennia Rajaei, Liam Hughes, Natalie Meeder, Joseph Naji, Harrilla Profka, Brian J Bolognese, Joseph P Foley, Patricia L Podolin, Rahim R Rizi
During lung-inflation, airspace dimensions are affected non-linearly by both alveolar expansion and recruitment, potentially confounding the identification of emphysematous lung by hyperpolarized helium-3 diffusion magnetic resonance imaging (HP MRI). This study aimed to characterize lung inflation over a broad range of inflation volume and pressure values in two different models of emphysema, as well as in normal lungs. Elastase-treated rats (n=7) and healthy controls (n=7) were imaged with HP MRI. Gradual inflation was achieved by incremental changes to both inflation volume and airway pressure...
May 4, 2017: American Journal of Physiology. Lung Cellular and Molecular Physiology
Felix C Horn, Helen Marshall, Guilhem J Collier, Richard Kay, Salman Siddiqui, Christopher E Brightling, Juan Parra-Robles, Jim M Wild
Purpose To assess the magnitude of regional response to respiratory therapeutic agents in the lungs by using treatment response mapping (TRM) with hyperpolarized gas magnetic resonance (MR) imaging. TRM was used to quantify regional physiologic response in adults with asthma who underwent a bronchodilator challenge. Materials and Methods This study was approved by the national research ethics committee and was performed with informed consent. Imaging was performed in 20 adult patients with asthma by using hyperpolarized helium 3 ((3)He) ventilation MR imaging...
May 4, 2017: Radiology
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