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https://www.readbyqxmd.com/read/29334685/observation-of-a-phononic-quadrupole-topological-insulator
#1
Marc Serra-Garcia, Valerio Peri, Roman Süsstrunk, Osama R Bilal, Tom Larsen, Luis Guillermo Villanueva, Sebastian D Huber
The modern theory of charge polarization in solids is based on a generalization of Berry's phase. The possibility of the quantization of this phase arising from parallel transport in momentum space is essential to our understanding of systems with topological band structures. Although based on the concept of charge polarization, this same theory can also be used to characterize the Bloch bands of neutral bosonic systems such as photonic or phononic crystals. The theory of this quantized polarization has recently been extended from the dipole moment to higher multipole moments...
January 15, 2018: Nature
https://www.readbyqxmd.com/read/29334460/multiple-stimuli-responses-of-stereo-isomers-of-aie-active-ethynylene-bridged-and-pyridyl-modified-tetraphenylethene
#2
Zhaoyang Wang, Xiao Cheng, Anjun Qin, Haoke Zhang, Jing Zhi Sun, Ben Zhong Tang
Luminescent molecules with aggregation-induced emission (AIE) property, or AIE-gens are typical stimuli-responsive materials and many AIE-gens have shown luminescent responses to mechano-, thermo-, electro-, vapo- and/or solvato-stimulus, but the detailed structure-property relationship has been addressed for only few of them. Here, we report a tetraphenylethene (TPE) derivative with pyridyl modifiers and ethynylene bridges. The (Z)- and (E)-isomers are clearly purified and both of them are AIE-active and demonstrate multiple luminescent responses to external stimuli...
January 15, 2018: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/29334459/development-of-charmm-compatible-force-field-parameters-for-cobalamin-and-related-cofactors-from-quantum-mechanical-calculations
#3
Anna Pavlova, Jerry M Parks, James C Gumbart
Corrinoid cofactors such as cobalamin are used by many enzymes and are essential for most living organisms. Therefore, there is broad interest in investigating cobalamin-protein interactions with molecular dynamics simulations. Previously developed parameters for cobalamins are based mainly on crystal structure data. Here, we report CHARMM-compatible force field parameters for several corrinoids developed from quantum mechanical calculations. We provide parameters for corrinoids in three oxidation states, Co3+, Co2+ and Co1+, and with various axial ligands...
January 15, 2018: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/29334457/new-mechanism-for-ferroelectricity-in-the-perovskite-ca2-xmnxti2o6-synthesized-by-spark-plasma-sintering
#4
Zongyao Li, Yujin Cho, Xiang Li, Xinyu Li, Akihisa Aimi, Yoshiyuki Inaguma, Jose Antonio Alonso, Maria Teresa Fernandez-Diaz, Jiaqiang Yan, Michael C Downer, Graeme Henkelman, John B Goodenough, Jianshi Zhou
Perovskite oxides hosting ferroelectricity are particularly important materials for modern technologies. The ferroelectric transition in the well-known oxides BaTiO3 and PbTiO3 is realized by softening of a vibration mode in the cubic perovskite structure. For most perovskite oxides, octahedral-site tilting systems are developed to accommodate the bonding mismatch due to a geometric tolerance factor t = (A-O)/[√2(B-O)] < 1. In the absence of cations having lone-pair electrons, e.g. Bi3+ and Pb2+, all simple and complex A-site and B-site ordered perovskite oxides with a t < 1 show a variety of tilting systems and none of them become ferroelectric...
January 15, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29334394/substitution-of-the-laser-borane-anti-b18h22-with-pyridine-a-structural-and-photophysical-study-of-some-unusually-structured-macropolyhedral-boron-hydrides
#5
Michael G S Londesborough, Jiří Dolanský, Tomáš Jelínek, John D Kennedy, Ivana Císařová, Robert D Kennedy, Daniel Roca-Sanjuán, Antonio Francés-Monerris, Kamil Lang, William Clegg
Reaction of anti-B18H221 with pyridine in neutral solvents gives sparingly soluble B16H18-3',8'-Py23a as the major product (ca. 53%) and B18H20-6',9'-Py22 (ca. 15%) as the minor product, with small quantities of B18H20-8'-Py 4 (ca. 1%) also being formed. The three new compounds 2, 3a and 4 are characterized by single-crystal X-ray diffraction analyses and by multinuclear multiple-resonance NMR spectroscopy. Compound 2 is of ten-vertex nido:ten-vertex arachno two-atoms-in-common architecture, long postulated for a species with borons-only cluster constitution, but previously elusive...
January 15, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/29334146/self-assembled-ag-mxa-superclusters-with-structure-dependent-mechanical-properties
#6
Xiaoyun Qin, Dan Luo, Zhenjie Xue, Qian Song, Tie Wang
The low elastic modulus and time-consuming formation process represent the major challenges that impede the penetration of nanoparticle superstructures into daily life applications. As observed in the molecular or atomic crystals, more effective interactions between adjacent nanoparticles would introduce beneficial features to assemblies enabling optimized mechanical properties. Here, a straightforward synthetic strategy is showed that allows fast and scalable fabrication of 2D Ag-mercaptoalkyl acid superclusters of either hexagonal or lamellar topology...
January 15, 2018: Advanced Materials
https://www.readbyqxmd.com/read/29334101/semiconductor-metal-structural-phase-transformation-in-mote2-monolayers-by-electronic-excitation
#7
Aravind Krishnamoorthy, Lindsay Bassman, Rajiv K Kalia, Aiichiro Nakano, Fuyuki Shimojo, Priya Vashishta
Optical modulation of the crystal structure and materials properties is an increasingly important technique for functionalization of two-dimensional and layered semiconductors, where traditional methods like chemical doping are ineffective. Controllable transformation between the semiconducting (H) and semimetallic (T') polytypes of transition metal chalcogenide monolayers is of central importance to two-dimensional electronics, and thermally-driven and strain-driven examples of this phase transformation have been previously reported...
January 15, 2018: Nanoscale
https://www.readbyqxmd.com/read/29333938/structure-based-engineering-to-restore-high-affinity-binding-of-an-isoform-selective-anti-tgf%C3%AE-1-antibody
#8
Dana M Lord, Julie J Bird, Denise M Honey, Annie Best, Anna Park, Ronnie R Wei, Huawei Qiu
Metelimumab (CAT192) is a human IgG4 monoclonal antibody developed as a TGFβ1-specific antagonist. It was tested in clinical trials for the treatment of scleroderma but later terminated due to lack of efficacy. Subsequent characterization of CAT192 indicated that its TGFβ1 binding affinity was reduced by ∼50-fold upon conversion from the parental single-chain variable fragment (scFv) to IgG4. We hypothesized this result was due to decreased conformational flexibility of the IgG that could be altered via engineering...
January 15, 2018: MAbs
https://www.readbyqxmd.com/read/29333680/cellulose-based-biomimetics-and-their-applications
#9
REVIEW
Ana P C Almeida, João P Canejo, Susete N Fernandes, Coro Echeverria, Pedro L Almeida, Maria H Godinho
Nature has been producing cellulose since long before man walked the surface of the earth. Millions of years of natural design and testing have resulted in cellulose-based structures that are an inspiration for the production of synthetic materials based on cellulose with properties that can mimic natural designs, functions, and properties. Here, five sections describe cellulose-based materials with characteristics that are inspired by gratings that exist on the petals of the plants, structurally colored materials, helical filaments produced by plants, water-responsive materials in plants, and environmental stimuli-responsive tissues found in insects and plants...
January 15, 2018: Advanced Materials
https://www.readbyqxmd.com/read/29333351/understanding-the-effect-of-the-dianhydride-structure-on-the-properties-of-semiaromatic-polyimides-containing-a-biobased-fatty-diamine
#10
Arijana Susa, Johan Bijleveld, Marianella Hernandez Santana, Santiago J Garcia
In this work we report the effect of the hard block dianhydride structure on the overall properties of partially biobased semiaromatic polyimides. For the study, four polyimides were synthesized using aliphatic fatty dimer diamine (DD1) as the soft block and four different commercially available aromatic dianhydrides as the hard block: 4,4'-(4,4'-isopropylidenediphenoxy) bis(phthalic anhydride) (BPADA), 4,4'-oxidiphthalic anhydride (ODPA), 4,4'-(Hexafluoroisopropylidene) diphthalic anhydride (6FDA), and 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA)...
January 2, 2018: ACS Sustainable Chemistry & Engineering
https://www.readbyqxmd.com/read/29332600/finding-novel-anti-carcinomas-compounds-by-targeting-sfrp4-through-molecular-modeling-docking-and-dynamic-simulation-studies
#11
M Hassan, M Azhar, Q Abbas, H Reza, A A Moustafa, S Shahzadi, Z Ashraf, S Y Seo
BACKGROUND: Secreted frizzled-related protein 4 (SFRP4) is a glycoprotein that act as a competitor of both canonical and non-canonical Wnt pathways. SFRP4 is mostly expressed in ovary and played a significant role as a target molecule to cure ovarian carcinoma. OBJECTIVE: Multiple chemical agonists are being used to cure ovary melanoma. We are interested to theoretically analyze the compounds through computational approaches for their inhibitory effects against SFRP4...
January 11, 2018: Current Computer-aided Drug Design
https://www.readbyqxmd.com/read/29332593/facile-synthesis-crystal-structure-dft-calculation-and-biological-activities-of-4-2-fluorophenyl-3-3-methoxybenzyl-1h-1-2-4-triazol-5-4h-one-5
#12
Muhammad Saleem, Muhammad Rafiq, Yeon Ki Jeong, Dae Won Cho, Chong-Hyeak Kim, Sung-Yum Seo, Chang-Shik Choi, Seong-Karp Hong, Ki-Hwan Lee
BACKGROUND: In the past few decades, the design, synthesis and characterization of novel heterocyclic compounds with auspicious biological profile received the considerable attention of scientific community. Among them, the small and simple organic molecular backbone like triazole moiety have broad spectrum of applications in the medicinal as well as diagnostic areas. OBJECTIVE: The objective of present study was the synthesis, characterization and exploration of biological profile of 4-(2-fluorophenyl)-3-(3-methoxybenzyl)-1H-1,2,4-triazol-5(4H)-one (5)...
January 12, 2018: Medicinal Chemistry
https://www.readbyqxmd.com/read/29332382/cu2i2se6-a-metal-inorganic-framework-wide-bandgap-semiconductor-for-photon-detection-at-room-temperature
#13
Wenwen Lin, Constantinos C Stoumpos, Oleg Y Kontsevoi, Zhifu Liu, Yihui He, Sanjib Das, Yadong Xu, Kyle M McCall, Bruce W Wessels, Mercouri G Kanatzidis
Cu2I2Se6 is a new wide-bandgap semiconductor with high stability and great potential towards hard radiation and photon detection. Cu2I2Se6 crystallizes in the rhombohedral R3 ̅m space group with a density of d = 5.287 g·cm-3 and a wide bandgap Eg of 1.95 eV. First-principles electronic band structure calculations at the density functional theory level indicate an indirect bandgap and a low electron effective mass me* of 0.32. The congruently melting compound was grown in centimeter-size Cu2I2Se6 single crystals using a vertical Bridgman method...
January 14, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29331933/combined-effects-of-ag-and-uio-66-for-removal-of-elemental-mercury-from-flue-gas
#14
Songjian Zhao, Dongyao Chen, Haomiao Xu, Jian Mei, Zan Qu, Ping Liu, Yong Cui, Naiqiang Yan
The zirconium metal-organic framework material UiO-66 was doped with Ag nanoparticles and investigated for the removal of elemental mercury (Hg0) in flue gas. Physical and chemical characterization of the adsorbents showed that adding Ag did not change the crystal structure and morphology of the UiO-66. Ag doping can improve the redox activity of UiO-66, and the adsorbent exhibited high thermal stability and surface area. Hg0 removal experiments indicated that UiO-66 exhibited the higher performance compared with P25 and activated carbon, and the addition of Ag exhibited a significant synergistic effect with the UiO-66, which had highest Hg0 adsorption capacity (3...
January 9, 2018: Chemosphere
https://www.readbyqxmd.com/read/29331778/synthesis-of-a-novel-narrow-band-gap-iron-ii-iii-oxide-titania-silver-silicate-nanocomposite-as-a-highly-efficient-and-stable-visible-light-driven-photocatalyst
#15
Huiping Chen, Nan Chen, Chuanping Feng, Yu Gao
Ag6Si2O7, a visible light-driven photocatalyst, has attracted considerable attention owing to its enormous environmental remediation potential. In this work, a magnetic iron(II,III) oxide/titania/silver silicate (Fe3O4/TiO2/Ag6Si2O7) nanocomposite was synthesized by anchoring TiO2 and Ag6Si2O7 on the surface of Fe3O4 nanoparticles. The morphology, crystal structure, as well as the spectroscopic, magnetic, and photocurrent properties of the as-prepared Fe3O4/TiO2/Ag6Si2O7 nanocomposite were studied. Methylene blue (MB) was used for evaluating the photocatalytic performance under simulated visible light...
January 6, 2018: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/29331739/determination-of-atomic-scale-chemical-composition-at-semiconductor-heteroepitaxial-interfaces-by-high-resolution-transmission-electron-microscopy
#16
C Wen, Y J Ma
The determination of atomic structures and further quantitative information such as chemical compositions at atomic scale for semiconductor defects or heteroepitaxial interfaces can provide direct evidence to understand their formation, modification, and/or effects on the properties of semiconductor films. The commonly used method, high-resolution transmission electron microscopy (HRTEM), suffers from difficulty in acquiring images that correctly show the crystal structure at atomic resolution, because of the limitation in microscope resolution or deviation from the Scherzer-defocus conditions...
January 8, 2018: Micron: the International Research and Review Journal for Microscopy
https://www.readbyqxmd.com/read/29331609/structure-of-the-bacillus-anthracis-dtdp-l-rhamnose-biosynthetic-pathway-enzyme-dtdp-%C3%AE-d-glucose-4-6-dehydratase-rfbb
#17
Trevor Gokey, Andrei S Halavaty, George Minasov, Wayne F Anderson, Misty L Kuhn
Many bacteria require L-rhamnose as a key cell wall component. This sugar is transferred to the cell wall using an activated donor dTDP-L-rhamnose, which is produced by the dTDP-L-rhamnose biosynthetic pathway. We determined the crystal structure of the second enzyme of this pathway dTDP-α-D-glucose 4,6-dehydratase (RfbB) from Bacillus anthracis. Interestingly, RfbB only crystallized in the presence of the third enzyme of the pathway RfbC; however, RfbC was not present in the crystal. Our work represents the first complete structural characterization of the four proteins of this pathway in a single Gram-positive bacterium...
January 10, 2018: Journal of Structural Biology
https://www.readbyqxmd.com/read/29331120/on-the-mechanical-stability-of-the-body-centered-cubic-phase-and-the-emergence-of-a-metastable-ci16-phase-in-classical-hard-sphere-solids
#18
Vadim B Warshavsky, David M Ford, Peter A Monson
The stability of the body-centered cubic (bcc) solid phase of classical hard spheres is of intrinsic interest and is also relevant to the development of perturbation theories for bcc solids of other model systems. Using canonical ensemble Monte Carlo, we simulated systems initialized in a perfect bcc lattice at various densities in the solid region. We observed that the systems rapidly evolved into one of four structures that then persisted for the duration of the simulation. Remarkably, one of these structures was identified as cI16, a cubic crystalline structure with 16 particles in the unit cell, which has recently been observed experimentally in lithium and sodium solids at high pressures...
January 14, 2018: Journal of Chemical Physics
https://www.readbyqxmd.com/read/29330606/the-associations-of-poor-psychiatric-well-being-among-incarcerated-men-with-injecting-drug-use-histories-in-victoria-australia
#19
Reece Cossar, Mark Stoové, Stuart A Kinner, Paul Dietze, Campbell Aitken, Michael Curtis, Amy Kirwan, James R P Ogloff
BACKGROUND: Dual substance dependence and psychiatric and psychological morbidities are overrepresented in prison populations and associated with reoffending. In the context of an increasing prison population in Australia, investigating the needs of vulnerable people in prison with a dual diagnosis can help inform in-prison screening and treatment and improve prison and community service integration and continuation of care. In this study we quantified psychiatric well-being in a sample of people in prison with a history of injecting drug use in Victoria, Australia, and identified factors associated with this outcome...
January 13, 2018: Health & Justice
https://www.readbyqxmd.com/read/29330549/excellent-room-temperature-deformability-in-high-strain-rate-regimes-of-magnesium-alloy
#20
Hidetoshi Somekawa, Alok Singh, Ryoji Sahara, Tadanobu Inoue
Magnesium and its alloys have the lowest density among structural metallic materials; thus, this light-weight metal has great potential for reducing the weight, for example, of vehicles and trains. However, due to its crystal structure, deformability is poor; in particular, under compressive stress. In this study, we modified magnesium with bismuth as an alloying element, which has the characteristics of being likely to form precipitates instead of grain boundary segregation. The Mg-Bi binary alloy showed excellent deformability and high absorption of energy in high-strain rate regimes at room temperature via contribution of grain boundary sliding...
January 12, 2018: Scientific Reports
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