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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 9, 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
Mustafa Bashir M Jawad, Kristian Kofoed
The aim of this article is to investigate the latest knowledge of the aetiology, pathogenesis and treatment of mucosal malignant melanomas (MMM) in the gastrointestinal tract (GIT) and urogenital organs. MMM constitute 1.4% of all melanomas with an incidence rate in USA of 2.2 per million a year. MMM in the GIT occur mostly in the anal canal and rectum, but can also occur in the small intestine, gallbladder and the large intestine, though very rarely. Melanomas can occur in almost any part of the urinary tract...
February 27, 2017: Ugeskrift for Laeger
Shingo Ohira, Masaru Isono, Yoshihiro Ueda, Takero Hirata, Reiko Ashida, Hidenori Takahashi, Masayoshi Miyazaki, Masaaki Takashina, Masahiko Koizumi, Teruki Teshima
OBJECTIVE: The volume of targets to which a high radiation dose can be delivered is limited for pancreatic radiotherapy. We assessed changes in movements of pancreatic tumours between simulation and treatment and determined compensatory margins. METHODS: For 23 patients, differences in implanted fiducial marker motion magnitude (MMM) and mean marker position (MMP) between four-dimensional CT and cone-beam CT were measured. Subsequently, residual uncertainty was simulated after no action level (NAL) and extended no action level (eNAL) protocols were adopted...
April 2017: British Journal of Radiology
Kunihiro Kihou, Hirotaka Nishiate, Atsushi Yamamoto, Chul-Ho Lee
As-based Zintl compounds Ba1-xKxZn2As2 were prepared by solid-state reaction followed by hot pressing. Ba1-xKxZn2As2 (x ≤ 0.02) crystallizes in the α-BaCu2S2-type structure (space group Pnma) upon cooling from 900 °C, whereas it crystallizes in the ThCr2Si2-type structure (space group I4/mmm) for x ≥ 0.04. The lattice thermal conductivities are almost equivalent for both crystal structures with relatively low values of 0.8-1.1 W/mK at 773 K. The values are comparable to those of Sb-based Zintl compounds, though Ba1-xKxZn2As2 consists of As atoms, which are lighter than Sb atoms...
March 2, 2017: Inorganic Chemistry
Fan Sun, Zhongnan Guo, Ning Liu, Kun Lin, Da Wang, Wenxia Yuan
A single crystal of a new layered telluride KFeCuTe2 has been successfully synthesized by the self-flux method, which is formed by intercalating K in the parent telluride Fe1+xCuTe2. This new compound crystallizes in the space group I4/mmm with the interstitial Fe in pristine Fe1+xCuTe2 completely removed after K intercalation. X-ray photoelectron spectroscopy (XPS) shows that after intercalation, the valence of Fe switched from a mixture of +2 and +3 to the single trivalent one. The KFeCuTe2 is a Mott semiconductor (Eg = 1...
March 14, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
M M Kutluev, I L Pulin, A Ya Ryakhov, K S Mochalov, R R Farkhutdinov
AIM: To investigate the feasibility of using biological markers for determining the optimal timing to repeat lithotripsy of urinary stones. MATERIALS AND METHODS: This was a prospective, randomized, single-center cohort study of 100 patients randomized into 4 groups. Patients of group I (n=46), II (n=20), III (n=18) and IV (n=16) were used contact lithotripsy (URS), ESWL, PNL, combined lithotripsy. In all patients, before surgery and at 1, 7, 14, 20 days after lithotripsy, iron-induced urine chemiluminescence was measured to determine the level of reactive oxygen species (ROS) and concentration of medium-mass molecules (MMM) in urine...
December 2016: Urologii︠a︡
Juan Wang, Jinxiang Zhou, Yogender K Gowtham, Sarah W Harcum, Scott M Husson
This contribution describes strategies to purify monoclonal antibodies from Chinese hamster ovary (CHO) cell culture supernatant using newly designed multimodal membranes (MMMs). The MMMs were used for the capture step purification of human IgG1 following a size-exclusion desalting column to remove chaotropic salts that interfere with IgG binding. The MMM column attained higher dynamic binding capacity than a Protein A resin column at an equivalent residence time of 1 min. The two step MMM chromatography process achieved high selectivity for capturing hIgG1 from the CHO cell culture supernatant, though the desalting step resulted in product dilution...
March 1, 2017: Biotechnology Progress
Zeba Haque, Gohil Singh Thakur, Rangasamy Parthasarathy, Birgit Gerke, Theresa Block, Lukas Heletta, Rainer Pöttgen, Amish G Joshi, Ganesan Kalai Selvan, Sonachalam Arumugam, Laxmi Chand Gupta, Ashok Kumar Ganguli
We have synthesized two new Eu-based compounds, EuSr2Bi2S4F4 and Eu2SrBi2S4F4, which are derivatives of Eu3Bi2S4F4, an intrinsic superconductor with Tc = 1.5 K. They belong to a tetragonal structure (SG: I4/mmm, Z = 2), similar to the parent compound Eu3Bi2S4F4. Our structural and (151)Eu Mössbauer spectroscopy studies show that, in EuSr2Bi2S4F4, Eu-atoms exclusively occupy the crystallographic 2a-sites. In Eu2SrBi2S4F4, 2a-sites are fully occupied by Eu-atoms and the other half of Eu-atoms and Sr-atoms together fully occupy 4e-sites in a statistical distribution...
February 28, 2017: Inorganic Chemistry
Ehsan Ghasemi Estahbanati, Mohammadreza Omidkhah, Abtin Ebadi Amooghin
In this research, Pebax1657 as an organic phase and silver nanoparticles as an inorganic phase were used for preparation of binary mixed matrix membranes (MMMs). Silver nanoparticles as a filler could enter the polymer chains and enhance the gas permeability by increasing the fractional free volume of membranes. Afterward, ternary MMMs were fabricated by addition of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) ionic liquid, in order to have better polymer/filler adhesion and eliminate interfacial defects and nonselective voids...
March 22, 2017: ACS Applied Materials & Interfaces
Matthias Weil
ABSTRACT: The reversible phase transition of Pb8F14I2 is of continuous type and takes place at about 107 °C as monitored by temperature-dependent single crystal and powder X-ray diffraction measurements, optical microscopy, and differential scanning calorimetry. The low-temperature ferroelastic phase crystallizes in the orthorhombic crystal system (23 °C, Bmmb, Z = 2, a = 6.0699(6) Å, b = 6.0165(6) Å, c = 25.077(2) Å, 1487 structure factors, 41 parameter, R(F(2) ) = 0...
2017: Monatshefte Für Chemie
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