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John V Seeley, Nicolaas E Schimmel, Stacy K Seeley
A fluidic device called the multi-mode modulator (MMM) has been developed for use as a comprehensive two-dimensional gas chromatography (GC x GC) modulator. The MMM can be employed in a wide range of capacities including as a traditional heart-cutting device, a low duty cycle GC x GC modulator, and a full transfer GC x GC modulator. The MMM is capable of producing narrow component pulses (widths <50ms) while operating at flows compatible with high resolution chromatography. The sample path of modulated components is confined to the interior of a joining capillary...
June 13, 2017: Journal of Chromatography. A
Yanchao Wang, Sheng Wang, Yunwei Zhang, Jian Lv, Yue Chen, Weitao Zheng, Yanming Ma
It has been widely believed that SrO2, a typical alkaline earth metal peroxide, should adopt the tetrahedral CaC2-type structure (space group I4/mmm) at ambient pressure. Here we report a monoclinic structure (space group C2c), as predicted from first-principles swarm structure searching simulations, is energetically more favorable than the CaC2-type structure at ambient pressure and low temperature, while the I4/mmm structure is only stable at high pressure (>20 GPa) or elevated temperature conditions. A key difference between these structures is the distinct orientation of peroxide ions...
June 9, 2017: Inorganic Chemistry
Lulu Liu, Huijuan Sun, Cai-Zhuang Wang, Wen-Cai Lu
In this work, the crystal structures of YH3 and YH4 at high pressure (100 to 250 GPa) have been explored using a genetic algorithm combined with first-principles calculations. New structures of YH3 with space group symmetries of P21/m and I4/mmm were predicted. The electronic structures and the phonon dispersion properties of various YH3 and YH4 structures at different temperatures and pressures were investigated. Among YH3 phases, the P21/m structure of YH3 was found to have a relatively high superconducting transformation temperature Tc of 19 K at 120 GPa, which is reduced to 9 K at 200 GPa...
June 9, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Rupan Preet Kaur, Ravinder Singh Sawhney, Derick Engles
The transport properties of beryllium doped anthracene molecular junction are investigated using density functional non-equillibrium Green's function method. The equilibrium conductance of anthracene Metal-molecule-Metal (MmM) junction increases by approximately 77% by adding beryllium impurity to it. The electronic transport characteristics under both zero bias as well as finite bias are explored of such molecular junction. We observe novel attributes such as molecular rectification and NDR behavior for the molecular junction under consideration...
May 26, 2017: Journal of Molecular Graphics & Modelling
Željka Pezer, Amanda G Chung, Robert C Karn, Christina M Laukaitis
The Androgen-binding protein (Abp) gene region of the mouse genome contains 64 genes, some encoding pheromones that influence assortative mating between mice from different subspecies. Using CNVnator and quantitative PCR, we explored copy number variation in this gene family in natural populations of Mus musculus domesticus (Mmd) and M. m. musculus (Mmm), two subspecies of house mice that form a narrow hybrid zone in Central Europe. We found that copy number variation in the center of the Abp gene region is very common in wild Mmd, primarily representing the presence/absence of the final duplications described for the mouse genome...
May 29, 2017: Genome Biology and Evolution
Chun Hai Wang, Brendan J Kennedy, André L Menezes de Oliveira, Julia Polt, Kevin Steven Knight
In this work we synthesized BaTaO2N and SrTaO2N using a two-step high-temperature solid-state reaction method and analysed the structural distortions, relative to the ideal cubic perovskite structure, according to group theory. From a complete distortion analysis/refinement using high-resolution neutron diffraction data in the temperature range 8 to 613 K, we identified tetragonal structures for BaTaO2N [P4/mmm (No. 123)] and SrTaO2N [I4/mcm (No. 140)]. In contrast to an anion-disordered cubic perovskite (Pm \overline{3}m No...
June 1, 2017: Acta Crystallographica Section B, Structural Science, Crystal Engineering and Materials
Gnu Nam, Woongjin Choi, Junsu Lee, Seong-Ji Lim, Hongil Jo, Kang Min Ok, Kyunghan Ahn, Tae-Soo You
The Zintl phase solid-solution Ca11-xYbxSb10-yGez (0 ≤ x ≤ 9; 0 ≤ y ≤ 3; 0 ≤ z ≤ 3) system with the cationic/anionic multisubstitution has been synthesized by molten Sn metal flux and arc-melting methods. The crystal structure of the nine title compounds were characterized by both powder and single-crystal X-ray diffractions and adopted the Ho11Ge10-type structure with the tetragonal space group I4/mmm (Z = 4, Pearson Code tI84). The overall isotypic structure of the nine title compounds can be illustrated as an assembly of three different types of cationic polyhedra sharing faces with their neighboring polyhedra and the three-dimensional cage-shaped anionic frameworks consisting of the dumbbell-shaped Sb2 units and the square-shaped Sb4 or (Sb/Ge)4 units...
May 30, 2017: Inorganic Chemistry
M Gutiérrez, M López-González, F Sánchez, A Douhal
Light harvesting is a natural phenomenon that scientists try to mimic in artificial systems. Having this in mind, attention has been focused on using new smart-materials for photonics. Herein, we report on the photobehaviour of a Zr-NDC MOF (NDC = dimethyl 2,6-naphthalenedicarboxylate) and its composite material, Coumarin153@Zr-NDC, embedded within a polymeric membrane of poly[bisphenol A carbonate-co-4,4'-(3,3,5-trimethylcyclohexylidene)diphenol carbonate] (PC). For the mixed matrix membrane (MMM) Zr-NDC/PC, we observed interparticle excimer-like formation, taking place in times shorter than 15 ps and giving rise to a red-shifted broad emission band...
May 30, 2017: Physical Chemistry Chemical Physics: PCCP
Nudrat Tasneem, Edgar A Samaniego, Connie Pieper, Enrique C Leira, Harold P Adams, David Hasan, Santiago Ortega-Gutierrez
Neurocritical care patients are at risk of developing secondary brain injury from inflammation, ischemia, and edema that follows the primary insult. Recognizing clinical deterioration due to secondary injury is frequently challenging in comatose patients. Multimodality monitoring (MMM) encompasses various tools to monitor cerebral metabolism, perfusion, and oxygenation aimed at detecting these changes to help modify therapies before irreversible injury sets in. These tools include intracranial pressure (ICP) monitors, transcranial Doppler (TCD), Hemedex™ (thermal diffusion probe used to measure regional cerebral blood flow), microdialysis catheter (used to measure cerebral metabolism), Licox™ (probe used to measure regional brain tissue oxygen tension), and continuous electroencephalography...
2017: Critical Care Research and Practice
Hiromu Saito, Akira Uchida, Soichiro Watanabe
Three-bladed propeller-shaped triple [5]helicene was synthesized using eliminative and oxidative photocyclization reactions, which proceeded in 37 and 63% yields, respectively. Chromatographic purification gave a mixture of diastereomers, and the PPM and PMM isomers were gradually converted to the thermodynamically more stable PPP and MMM isomers at room temperature. The activation parameters for the racemization of the PPP and MMM isomers were determined, and the structure of the triple [5]helicene was determined by X-ray crystallographic analysis...
May 19, 2017: Journal of Organic Chemistry
Christopher G Morris, Nicholas M Jacques, Harry G W Godfrey, Tamoghna Mitra, Detlev Fritsch, Zhenzhong Lu, Claire A Murray, Jonathan Potter, Tom M Cobb, Fajin Yuan, Chiu C Tang, Sihai Yang, Martin Schröder
The identification of preferred binding domains within a host structure provides important insights into the function of materials. State-of-the-art reports mostly focus on crystallographic studies of empty and single component guest-loaded host structures to determine the location of guests. However, measurements of material properties (e.g., adsorption and breakthrough of substrates) are usually performed for a wide range of pressure (guest coverage) and/or using multi-component gas mixtures. Here we report the development of a multifunctional gas dosing system for use in X-ray powder diffraction studies on Beamline I11 at Diamond Light Source...
April 1, 2017: Chemical Science
Quanchen Feng, Shu Zhao, Yu Wang, Jun-Cai Dong, Wenxing Chen, Dongsheng He, Dingsheng Wang, Jun Yang, Yuanmin Zhu, Hailiang Zhu, Lin Gu, Zhi Li, Yuxi Liu, Rong Yu, Jun Li, Yadong Li
Improving the catalytic selectivity of Pd catalysts is of key importance for various industrial processes and remains a challenge so far. Given the unique properties of single-atom catalysts, isolating contiguous Pd atoms into single-Pd-site with another metal to form intermetallic structures is an effective way to endow Pd with high catalytic selectivity and to stabilize the single site with the intermetallic structures. Based on density functional theory modeling, we demonstrate that (110) surface of Pm-3m PdIn with single-atom Pd sites shows high selectivity for semi-hydrogenation of acetylene, whereas (111) surface of P4/mmm Pd3In with Pd trimer sites shows low selectivity...
May 14, 2017: Journal of the American Chemical Society
Zhong-Li Liu, Hong Jia, Rui Li, Xiu-Lu Zhang, Ling-Cang Cai
We discovered several new energetically competitive structures of NbSe2 using the multi-algorithm collaborative (MAC) crystal structure prediction algorithm combined with the density functional theory. It was found that the coordination number of Nb in NbSe2 is increased from 6 to 7, and then to 8 with increasing pressure. Furthermore, it was unexpected that an Se atom would be squeezed to the center of a cage formed by 12 other Se atoms and then have 12-fold coordination when the pressure was increased to 130...
May 24, 2017: Physical Chemistry Chemical Physics: PCCP
Weiwei Xie, Michał J Winiarski, Tomasz Klimczuk, R J Cava
Following the predictions of total energy calculations, a tetragonal SrMn2P2 phase is proposed and successfully formed under high pressure. At ambient pressure, SrMn2P2 adopts the primitive trigonal La2O3 structure type (space group P3[combining macron]m1). However, the results of total energy calculations indicate that SrMn2P2 should be more stable in the tetragonal ThCr2Si2 structure type (space group I4/mmm) than in its known trigonal structure, thus motivating our synthetic experiments. Guided by these calculations, a new tetragonal polymorph of SrMn2P2 was found under the relatively mild conditions of 5 GPa applied pressure at a temperature of 900 °C through the transformation of the ambient pressure trigonal form...
May 30, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Yongliang Guo, Cun Yu, Jun Lin, Changying Wang, Cuilan Ren, Baoxing Sun, Ping Huai, Ruobing Xie, Xuezhi Ke, Zhiyuan Zhu, Hongjie Xu
Thorium-carbon systems have been thought as promising nuclear fuel for Generation IV reactors which require high-burnup and safe nuclear fuel. Existing knowledge on thorium carbides under extreme condition remains insufficient and some is controversial due to limited studies. Here we systematically predict all stable structures of thorium dicarbide (ThC2) under the pressure ranging from ambient to 300 GPa by merging ab initio total energy calculations and unbiased structure searching method, which are in sequence of C2/c, C2/m, Cmmm, Immm and P6/mmm phases...
April 6, 2017: Scientific Reports
D H Ryan, Ming Yue, C B Boyer, X B Liu, Qingmei Lu, Hongguo Zhang, Chenhui Li, Manli Wang, Z Altounian
Neutron powder diffraction patterns measured above T C have been used to determine the location of the excess Mn in MnxGa (1.15 ≤ x ≤ 1.8). This information has then been used to constrain the fits to neutron powder diffraction patterns measured at ambient temperature and so determine unambiguously the Mn moments in this system. We find that Mn randomly occupies the two Ga sites (2a and 2b) in the I4/mmm structure and propose that it is more appropriate to use a simpler structure based on the P4/mmm space group with a reduced unit cell...
April 5, 2017: Scientific Reports
Naoya Matsumoto, Alu Konno, Yasushi Ohbayashi, Takashi Inoue, Akiyuki Matsumoto, Kenji Uchimura, Kenji Kadomatsu, Shigetoshi Okazaki
We demonstrate that high-quality images of the deep regions of a thick sample can be obtained from its surface by multi-focal multiphoton microscopy (MMM). The MMM system incorporates a spatial light modulator to separate the excitation beam into a multi-focal excitation beam and modulate the pre-distortion wavefront to correct spherical aberration (SA) caused by a refractive index mismatch between the immersion medium and the biological sample. When fluorescent beads in transparent epoxy resin were observed using four SA-corrected focal beams, the fluorescence signal of the obtained images was ~52 times higher than that obtained without SA correction until a depth of ~1100 μm, similar to the result for single-focal multiphoton microscopy (SMM)...
March 20, 2017: Optics Express
Janina Dechnik, Jorge Gascon, Christian Doonan, Christoph Janiak, Christopher James Sumby
Research into extended porous materials such as metal-organic frameworks (MOFs) and porous organic frameworks (POFs), and their molecular analogues, metal-organic polyhedra (MOPs) and porous organic cages (POCs), has blossomed over the last decade. Given their chemical and structural mutability and notable porosity, MOFs have been proposed as novel adsorbents for industrial gas separations. In this context they have also been identified as promising filler components for high-performance mixed matrix membranes (MMMs)...
April 4, 2017: Angewandte Chemie
A P Pikul, M Samsel-Czekała, G Chajewski, T Romanova, A Hackemer, R Gorzelniak, P Wiśniewski, D Kaczorowski
Motivated by the recent discovery of exotic superconductivity in YFe2Ge2 we undertook reinvestigation of formation and physical properties of yttrium-based 1:2:2 silicides. Here we report on syntheses and crystal structures of the YTE 2Si2 compounds with TE  =  Cr, Co, Ni, Rh, Pd and Pt, and their low-temperature physical properties measurements, supplemented by results of fully relativistic full-potential local-orbital minimum basis band structure calculations. We confirm that most of the members of that family crystallize in a tetragonal ThCr2Si2-type structure (space group I4/mmm) and have three-dimensional Fermi surface, while only one of them (YPt2Si2) forms with a closely-related primitive CaBe2Ge2-type unit cell (space group P4/nmm) and possess quasi-two-dimensional Fermi surface sheets...
March 21, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Neil R Poulter, Aletta E Schutte, Maciej Tomaszewski, Daniel T Lackland
Raised blood pressure is the biggest single contributing risk factor to death and the burden of disease worldwide. However, international data suggest that fewer than half of those with hypertension are aware of their condition. In May 2017, the International Society of Hypertension and the World Hypertension League are leading a global initiative - May Measurement Month (MMM) - to raise awareness of the importance of screening. MMM will be a cross-sectional survey of men and women aged ≥18 who have not had their BP measured since 30 April 2016...
May 2017: Journal of Hypertension
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