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B B Wu, H M Zheng, Y Q Ding, W J Liu, H L Lu, P Zhou, L Chen, Q Q Sun, S J Ding, David W Zhang
Growing high-quality and uniform dielectric on black phosphorus is challenging since it is easy to react with O2 or H2O in ambient. In this work, we have directly grown Al2O3 on BP using plasma-enhanced atomic layer deposition (PEALD). The surface roughness of BP with covered Al2O3 film can reduce significantly, which is due to the removal of oxidized bubble in BP surface by oxygen plasma. It was also found there is an interfacial layer of PO x in between amorphous Al2O3 film and crystallized BP, which is verified by both X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) measurements...
December 2017: Nanoscale Research Letters
Zhenhua Lin, Olivier Tillement, Marie-Genevieve Blanchin, Vivek Jindal, Agnès Vinsot, Romain V H Dagnelie, Virginie Blin, Yanick Lettry, Benoit Hautefeuille
Long term in situ diffusion experiments in the Callovian-Oxfordian mudstone (France) are designed in the context of nuclear waste management. β-emitters HTO and (36)Cl radiotracers are representative of neutral and anionic species in these experiments. Studies have been carried out to design an in situ beta monitoring system in order to quantify tracer migration in the rock pore water over time. The development, design and calibration of β-emitter radiation sensors were performed. An optimised geometry was calculated for the detection chamber of (36)Cl in solution (Ø×L=30×2mm(2)) via Monte-Carlo N-Particle transport simulation tools...
April 1, 2017: Applied Radiation and Isotopes
Daan C Swarts, John van der Oost, Martin Jinek
The CRISPR-associated protein Cas12a (Cpf1), which has been repurposed for genome editing, possesses two distinct nuclease activities: endoribonuclease activity for processing its own guide RNAs and RNA-guided DNase activity for target DNA cleavage. To elucidate the molecular basis of both activities, we determined crystal structures of Francisella novicida Cas12a bound to guide RNA and in complex with an R-loop formed by a non-cleavable guide RNA precursor and a full-length target DNA. Corroborated by biochemical experiments, these structures reveal the mechanisms of guide RNA processing and pre-ordering of the seed sequence in the guide RNA that primes Cas12a for target DNA binding...
April 20, 2017: Molecular Cell
Shunsuke Kobayashi, Craig A J Fisher, Akihide Kuwabara, Yoshio Ukyo, Yuichi Ikuhara
The spatial distribution of Li ions in a lithium iron phosphate (Li1-xFePO4) single crystal after chemical delithiation is quantitatively investigated using Fe M2,3-edge and valence electron energy loss (EEL) spectroscopy techniques. Li contents between those of end-member compositions LiFePO4 and FePO4 are found to correspond to reproducible changes in Fe M2,3-edge and valence EEL spectra across an interface between LiFePO4 and FePO4 regions. Quantitative analysis of these changes is used to estimate the local valence states of Fe ions, from which the Li concentration in the intermediate phase can be deduced...
April 18, 2017: Microscopy
Hein J E M Janssens, Jaap Fransen, Matthijs Janssen, Tuhina Neogi, H Ralph Schumacher, Tim L Jansen, Nicola Dalbeth, William J Taylor
Objective.: To test the performance of the 2015 ACR-EULAR gout classification criteria against presence of SF MSU crystals in a primary healthcare population. Methods.: The criteria were applied to an existing dataset of consecutive patients with monoarthritis presenting to Dutch family physicians; all patients underwent microscopic SF analysis by design. The data had been prospectively collected to develop a diagnostic decision rule for gout in 2010. Diagnostic performance was assessed by calculating area under the receiver operating characteristic curve, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and constructing calibration plots for the full version of the criteria (including SF analysis results of all patients) and the clinical-only version (not including SF analysis results)...
April 20, 2017: Rheumatology
S Prokhorenko, Y Nahas, L Bellaiche
Homotopy theory and first-principles-based effective Hamiltonian simulations are combined to investigate the stability of topological defects in proper ferroelectric crystals. We show that, despite a nearly trivial topology of the order parameter space, these materials can exhibit stable topological point defects in their tetragonal polar phase and stable topological line defects in their orthorhombic polar phase. The stability of such defects originates from a novel mechanism of topological protection related to finite-temperature fluctuations of local dipoles...
April 7, 2017: Physical Review Letters
Ioan B Magdău, Graeme J Ackland
We show that the isotope effect leads to a completely different spectroscopic signal in hydrogen-deuterium mixtures, compared to pure elements that have the same crystal structure. This is particularly true for molecular vibrations, which are the main source of information about the structure of high-pressure hydrogen. Mass disorder breaks translational symmetry, meaning that vibrations are localized almost to single molecules, and are not zone-center phonons. In mixtures, each observable infrared (IR) peak corresponds to a collection of many such molecular vibrations, which have a distribution of frequencies depending on local environment...
April 7, 2017: Physical Review Letters
D J Voneshen, H C Walker, K Refson, J P Goff
The suppression of transverse phonons by liquidlike diffusion in superionic conductors has been proposed as a means to dramatically reduce thermal conductivity in thermoelectric materials [H. Lui et al. Nat. Mater. 11, 422 (2012)NMAACR1476-112210.1038/nmat3273]. We have measured the ion transport and lattice dynamics in the original phonon-liquid electron-crystal Cu_{2}Se using neutron spectroscopy. We show that hopping time scales are too slow to significantly affect lattice vibrations and that the transverse phonons persist at all temperatures...
April 7, 2017: Physical Review Letters
A Srinivasan, D S Miserev, K L Hudson, O Klochan, K Muraki, Y Hirayama, D Reuter, A D Wieck, O P Sushkov, A R Hamilton
We investigate the relationship between the Zeeman interaction and the inversion-asymmetry-induced spin-orbit interactions (Rashba and Dresselhaus SOIs) in GaAs hole quantum point contacts. The presence of a strong SOI results in the crossing and anticrossing of adjacent spin-split hole subbands in a magnetic field. We demonstrate theoretically and experimentally that the anticrossing energy gap depends on the interplay between the SOI terms and the highly anisotropic hole g tensor and that this interplay can be tuned by selecting the crystal axis along which the current and magnetic field are aligned...
April 7, 2017: Physical Review Letters
B B Zhou, X Liu, H R Guo, X L Zeng, X F Chen, H P Chung, Y H Chen, M Bache
We show that a temporal soliton can induce resonant radiation by three-wave mixing nonlinearities. This constitutes a new class of resonant radiation whose spectral positions are parametrically tunable. The experimental verification is done in a periodically poled lithium niobate crystal, where a femtosecond near-IR soliton is excited and resonant radiation waves are observed exactly at the calculated soliton phase-matching wavelengths via the sum- and difference-frequency generation nonlinearities. This extends the supercontinuum bandwidth well into the mid IR to span 550-5000 nm, and the mid-IR edge is parametrically tunable over 1000 nm by changing the three-wave mixing phase-matching condition...
April 7, 2017: Physical Review Letters
Ryo Ozawa, Satoru Hayami, Yukitoshi Motome
Magnetic Skyrmions are swirling spin textures with topologically protected noncoplanarity. Recently, Skyrmions with the topological number of unity have been extensively studied in both experiment and theory. We here show that a Skyrmion crystal with an unusually high topological number of two is stabilized in itinerant magnets at a zero magnetic field. The results are obtained for a minimal Kondo lattice model on a triangular lattice by an unrestricted large-scale numerical simulation and variational calculations...
April 7, 2017: Physical Review Letters
Jin Chen, Qian Zhang, Weitong Ren, Wenfei Li
Despite considerable effort, elucidating allostery of large macromolecular assemblies at a molecular level in solution remains technically challenging due to its structural complexity. Here we have employed an approach combining amide backbone hydrogen/deuterium exchange coupled with mass spectrometry, fluorescence spectroscopy and molecular simulations to characterize allosteric patterns of chaperonin GroEL, a ~800 kDa tetradecamer from E. coli. Using available crystal structures of GroEL, we quantitatively map out GroEL allosteric changes in solution by resolving exchange behaviors of 133 overlapping proteolytic peptides with more than 95% sequence coverage...
April 21, 2017: Journal of Physical Chemistry. B
Benjamin Schammé, Xavier Monnier, Nicolas Couvrat, Laurent Delbreilh, Valérie Dupray, Eric Dargent, Gérard Coquerel
In this article, we study the physicochemical transformations of crystalline Quinidine upon high-energy milling. The investigations have been achieved by classical, high performance and fast scanning calorimetry combined with broadband dielectric spectroscopy and X-ray powder diffraction. As evolution of crystalline Quinidine with time of milling revealed a prominent sub-Tg cold-crystallization phenomenon, independent and complementary analytical techniques were implemented. Fast scanning calorimetry was performed for the first time on a milled pharmaceutical compound to postpone the crystallization event to higher temperatures...
April 21, 2017: Journal of Physical Chemistry. B
Sophie Langis-Barsetti, Thierry Maris, James D Wuest
Derivatives of 2,1,3-benzothiadiazole (1) are widely used in many areas of science and are particularly valuable as components of active layers in various thin-film optoelectronic devices. Even more effective benzothiadiazoles are likely to result if a deeper understanding of their preferred patterns of molecular association can be acquired. To provide new insight, we have analyzed the structures of compounds in which multiple benzothiadiazole units are attached to well-defined planar and nonplanar molecular cores...
April 21, 2017: Journal of Organic Chemistry
Ji-Kun Li, Jing Dong, Chuan-Ping Wei, Song Yang, Ying-Nan Chi, Yan-Qing Xu, Chang-Wen Hu
Six alkoxohexavanadate-based Cu- or Co-POVs [Cu(dpa)(acac)(H2O)]2[V6O13(OMe)6] (1), [Cu(phen)(acac)(MeOH)]2[V6O13(OMe)6] (2), [Co(dpa)(acac)2]2[V6O13(OMe)6]·2MeOH (3), [Co(phen)(acac)2]2[V6O13(OMe)6] (4), [Cu(dpa)(acac)]2[V(IV)2V(V)4O12(OMe)7] (5), and [Cu(dpa)(acac)(MeOH)]2[V(IV)2V(V)4O11(OMe)8] (6) (POV = polyoxovanadate; dpa = 2,2'-dipyridine amine; phen = 1,10-phenanthroline; acac = acetylacetone anion) have been synthesized by controlling the reaction conditions and characterized by single-crystal X-ray diffraction and powder X-ray diffraction analyses, FT-IR spectroscopy, element analyses, and X-ray photoelectron spectroscopy...
April 21, 2017: Inorganic Chemistry
Rebecca Faye Alford, Andrew Leaver-Fay, Jeliazko R Jeliazkov, Matthew J O'Meara, Frank P DiMaio, Hahnbeom Park, Maxim V Shapovalov, P Douglas Renfrew, Vikram Khipple Mulligan, Kalli Kappel, Jason W Labonte, Michael Steven Pacella, Richard Bonneau, Philip Bradley, Roland L Dunbrack, Rhiju Das, David Baker, Brian Kuhlman, Tanja Kortemme, Jeffrey J Gray
Over the past decade, the Rosetta biomolecular modeling suite has informed diverse biological questions and engineering challenges ranging from interpretation of low-resolution structural data to design of nanomaterials, protein therapeutics, and vaccines. Central to Rosetta's success is the energy function: a model parameterized from small molecule and X-ray crystal structure data used to approximate the energy associated with each biomolecule conformation. This paper describes the mathematical models and physical concepts that underlie the latest Rosetta Energy Function, REF15...
April 21, 2017: Journal of Chemical Theory and Computation
Lisa Suntrup, Sinja Klenk, Johannes Klein, Sebastian Sobottka, Biprajit Sarkar
Bidentate ligands containing at least one triazole or triazolylidene (mesoionic carbene, MIC) unit are extremely popular in contemporary chemistry. One reason for their popularity is the similarities as well as differences in the donor/acceptor properties that these ligands display in comparison to their pyridine or other N-heterocyclic carbene counterparts. We present here seven rhenium(I) carbonyl complexes where the bidentate ligands contain combinations of pyridine/triazole/triazolylidene. These are the first examples of rhenium(I) complexes with bidentate 1,2,3-triazol-5-ylidene-containing ligands...
April 21, 2017: Inorganic Chemistry
Patrick J Quinlivan, Gerard Parkin
X-ray diffraction studies demonstrate that crystals of the carbodiphosphorane, (Ph3P)2C, obtained from solutions in benzene, exhibit a linear P-C-P interaction. This observation is in contrast to the highly bent structures that have been previously reported for this molecule, thereby providing experimental evidence that the coordination geometry at zerovalent carbon may be very flexible. Density functional theory calculations support the experimental observations by demonstrating that the energy of (Ph3P)2C varies relatively little over the range 130-180°...
April 21, 2017: Inorganic Chemistry
Ortal Lidor-Shalev, Nikolaos Pliatsikas, Yacov Cramiel, Panos Patsalas, Yitzhak Mastai
In this article, we describe an advance approach for the fabrication of chiral metal-oxide nanofilms. Our approach is based on the atomic layer deposition of titania and alumina nanofilms onto cellulose microfibers, used as chiral templates, leading to the formation of chiral nanofilms with a spatial fibrous structure. The chiral nanofilms were extensively characterized by X-ray photoelectron spectroscopy and high-resolution electron microscopy. The chiral property of the produced titania nanofilms was studied by enantioselective adsorption experiments using circular-dichroism spectroscopy and chiral high-performance liquid chromatography...
April 21, 2017: ACS Nano
Masoumeh Meskinfam Langroudi, Masoud Giahi Saravani, Azita Nouri
BACKGROUND: Different methods have been used to prepare bone-like composites from inorganic nanoparticles embedded in polymeric matrixes to obtain the properties and structures required for bone fillers. METHODS: Bone-like nano-hydroxyapatite (nHA) was synthesized using a biomimetic method, with polyvinylpyrrolidone (PVP) as template and sodium dodecyl sulfate (SDS) as surfactant. RESULTS: The results demonstrated the formation of HA composites and showed that polymer and surfactant as the polymer capsule can be properly used to control the size, shape, morphology and dispersion of HA crystals...
April 11, 2017: Journal of Applied Biomaterials & Functional Materials
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