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Huijin Li, Dedong Han, Liqiao Liu, Junchen Dong, Guodong Cui, Shengdong Zhang, Xing Zhang, Yi Wang
This letter demonstrates bi-layer channel Al-doped ZnO/ZnO thin film transistors (AZO/ZnO TFTs) via atomic layer deposition process at a relatively low temperature. The effects of annealing in oxygen atmosphere at different temperatures have also been investigated. The ALD bi-layer channel AZO/ZnO TFTs annealed in dry O2 at 300 °C exhibit a low leakage current of 2.5 × 10(-13)A, I on/I off ratio of 1.4 × 10(7), subthreshold swing (SS) of 0.23 V/decade, and high transmittance. The enhanced performance obtained from the bi-layer channel AZO/ZnO TFT devices is explained by the inserted AZO front channel layer playing the role of the mobility booster...
December 2017: Nanoscale Research Letters
Jennifer Bridwell-Rabb, Aoshu Zhong, He G Sun, Catherine L Drennan, Hung-Wen Liu
Oxetanocin A (OXT-A) is a potent antitumour, antiviral and antibacterial compound. Biosynthesis of OXT-A has been linked to a plasmid-borne Bacillus megaterium gene cluster that contains four genes: oxsA, oxsB, oxrA and oxrB. Here we show that both the oxsA and oxsB genes are required for the production of OXT-A. Biochemical analysis of the encoded proteins, a cobalamin (Cbl)-dependent S-adenosylmethionine (AdoMet) radical enzyme, OxsB, and an HD-domain phosphohydrolase, OxsA, reveals that OXT-A is derived from a 2'-deoxyadenosine phosphate in an OxsB-catalysed ring contraction reaction initiated by hydrogen atom abstraction from C2'...
March 27, 2017: Nature
Sören Zint, Daniel Ebeling, Tobias Schlöder, Sebastian Ahles, Doreen Mollenhauer, Hermann A Wegner, Andre Schirmeisen
The in-depth knowledge about on-surface reaction mechanisms is crucial for the tailor-made design of covalently bonded organic frameworks, for applications such as nanoelectronic or -optical devices. Latest developments in atomic force microscopy, which rely on functionalizing the tip with single CO molecules at low temperatures allow to image molecular systems with submolecular resolution. Here, we are using this technique to study the complete reaction pathway of the on-surface Ullmann-type coupling between bromotriphenylene molecules on a Cu(111) surface...
March 27, 2017: ACS Nano
Slawomir Janusz Grabowski, W Andrzej Sokalski
Representative Lewis acid - Lewis base complexes linked by tetrel, pnicogen, chalcogen and halogen bonds have been studied within the Quantum Theory of Atoms in Molecules (QTAIM) approach and the Hybrid Variation-Perturbation Theory (HVPT) in order to analyse possible relationships between these sigma-hole dimers. Results obtained at the MP2/aug-cc-pVTZ level indicate numerous correlations similar to hydrogen bonded systems.
March 27, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Jinlong Gong, Xinhe Bao
Surface and interfacial catalysis plays a vital role in chemical industries, electrochemistry and photochemical reactions. The challenges of modern chemistry are to optimize the chemical reaction processes and understand the detailed mechanism of chemical reactions. Since the early 1960s, the foundation of surface science systems has allowed the study of surface and interfacial phenomena on atomic/molecular level, and thus brought a number of significant developments to fundamental and technological processes, such as catalysis, material science and biochemistry, just to name a few...
March 27, 2017: Chemical Society Reviews
Georg Dorn, Alexander Leitner, Julien Boudet, Sébastien Campagne, Christine von Schroetter, Ahmed Moursy, Ruedi Aebersold, Frédéric H-T Allain
Ribonucleoproteins (RNPs) are key regulators of cellular function. We established an efficient approach, crosslinking of segmentally isotope-labeled RNA and tandem mass spectrometry (CLIR-MS/MS), to localize protein-RNA interactions simultaneously at amino acid and nucleotide resolution. The approach was tested on polypyrimidine tract binding protein 1 and U1 small nuclear RNP. Our method provides distance restraints to support integrative atomic-scale structural modeling and to gain mechanistic insights into RNP-regulated processes...
March 27, 2017: Nature Methods
Jean Comtet, Antoine Niguès, Vojtech Kaiser, Benoit Coasne, Lydéric Bocquet, Alessandro Siria
Room-temperature ionic liquids (RTILs) are new materials with fundamental importance for energy storage and active lubrication. They are unusual liquids, which challenge the classical frameworks of electrolytes, whose behaviour at electrified interfaces remains elusive, with exotic responses relevant to their electrochemical activity. Using tuning-fork-based atomic force microscope nanorheological measurements, we explore here the properties of confined RTILs, unveiling a dramatic change of the RTIL towards a solid-like phase below a threshold thickness, pointing to capillary freezing in confinement...
March 27, 2017: Nature Materials
Te Han, Dongxiang Jiang, Xiaochen Zhang, Yankui Sun
Rotating machinery is widely used in industrial applications. With the trend towards more precise and more critical operating conditions, mechanical failures may easily occur. Condition monitoring and fault diagnosis (CMFD) technology is an effective tool to enhance the reliability and security of rotating machinery. In this paper, an intelligent fault diagnosis method based on dictionary learning and singular value decomposition (SVD) is proposed. First, the dictionary learning scheme is capable of generating an adaptive dictionary whose atoms reveal the underlying structure of raw signals...
March 27, 2017: Sensors
Uksu Kim, Noboru Morita, Deug Lee, Martin Jun, Jeong Woo Park
Pulse electrochemical nanopatterning (PECN), a non-contact scanning probe lithography (NC-SPL) process using ultrashort voltage pulses, is based primarily on an electrochemical machining (ECM) process using localized electrochemical oxidation between a sharp tool tip and the sample surface. In this study, nanoscale oxide patterns were formed on silicon Si (100) wafer surfaces via electrochemical surface nanopatterning, by supplying external pulsed currents through non-contact atomic force microscopy. Nanoscale oxide width and height were controlled by modulating the applied pulse duration...
March 27, 2017: Nanotechnology
Maya Narayanan Nair, Irene Palacio, Arlensiú Celis, Alberto Zobelli, Alexandre Gloter, Stefan Kubsky, Jean-Philippe Turmaud, Matthew Conrad, Claire Berger, Walter de Heer, Edward Henry Conrad, Amina Taleb-Ibrahimi, Antonio Tejeda
The epitaxial graphene buffer layer on the Si face of hexagonal SiC shows a promising band gap, which precise origin remains to be understood. In this work, we correlate the electronic to the atomic structure of the buffer layer by combining angle resolved photoemission spectroscopy (ARPES), scanning tunneling microscopy (STM) and high-resolution scanning transmission electron microscopy (HR-STEM). We show that the band structure in the buffer has an electronic periodicity related to the structural periodicity observed in STM images and published X-ray diffraction...
March 27, 2017: Nano Letters
Navjeet Ahalawat, Rajesh Kumar Murarka
The AMP-activated protein kinase (AMPK), a central enzyme in the regulation of energy homeostasis, is an important drug target for type 2 diabetes, obesity and cancer. Binding of adenosine nucleotides to the regulatory γ-subunit tightly regulates the activity of this enzyme. Though recent crystal structures of AMPK have provided important insights into the allosteric activation of AMPK, molecular details of the regulatory mechanism of AMPK activation is still elusive. Here, we have performed extensive all-atom molecular dynamics (MD) simulations and shown that the kinase domain (KD) and γ-subunit comes closer resulting in a more compact heterotrimeric AMPK complex in AMP-bound state compared to the ATP-bound state...
March 27, 2017: Journal of Physical Chemistry. B
James A Graham, Jonathan W Essex, Syma Khalid
Development of coarse-grained (CG) molecular dynamics models is often a laborious process which commonly relies upon approximations to similar models, rather than systematic parametrisation. PyCGTOOL automates much of the construction of CG models via calculation of both equilibrium values and force constants of internal coordinates directly from atomistic molecular dynamics simulation trajectories. The derivation of bespoke parameters from atomistic simulations improves the quality of the CG model compared to the use of generic parameters derived from other molecules, while automation greatly reduces the time required...
March 27, 2017: Journal of Chemical Information and Modeling
Rui Sun, Olaseni Sode, James F Dama, Gregory A Voth
The protein mediated hydrolysis of nucleoside triphosphates such as ATP or GTP is one of the most important and challenging biochemical reactions in nature. The chemical environment (water structure, catalytic metal, and amino acid residues) adjacent to the hydrolysis site contains hundreds of atoms, usually greatly limiting the amount of the free energy sampling that one can achieve from computationally demanding electronic structure calculations such as QM/MM simulations. Therefore, the combination of QM/MM molecular dynamics with the recently developed Transition-tempered Metadynamics (TTMetaD), an enhanced sampling method that can provide a high-quality free energy estimate at an early stage in a simulation, is an ideal approach to address the biomolecular nucleoside triphosphate hydrolysis problem...
March 27, 2017: Journal of Chemical Theory and Computation
Anastasia V Rudik, Vladislav M Bezhentsev, Alexander V Dmitriev, Dmitry S Druzhilovskiy, Alexey A Lagunin, Dmitry A Filimonov, Vladimir V Poroikov
A new freely available web-application MetaTox ( for prediction of xenobiotic's metabolism and calculation toxicity of metabolites based on the structural formula of chemicals has been developed. MetaTox predicts metabolites, which are formed by nine classes of reactions (aliphatic and aromatic hydroxylation, N- and O-glucuronidation, N-, S- and C-oxidation, and N- and O-dealkylation). The calculation of probability for generated metabolites is based on analyses of "structure-biotransformation reactions" and "structure-modified atoms" relationships using a Bayesian approach...
March 27, 2017: Journal of Chemical Information and Modeling
Timothy A Su, Haixing Li, Rebekka S Klausen, Nathaniel T Kim, Madhav Neupane, James L Leighton, Michael L Steigerwald, Latha Venkataraman, Colin Nuckolls
This Account provides an overview of our recent efforts to uncover the fundamental charge transport properties of Si-Si and Ge-Ge single bonds and introduce useful functions into group 14 molecular wires. We utilize the tools of chemical synthesis and a scanning tunneling microscopy-based break-junction technique to study the mechanism of charge transport in these molecular systems. We evaluated the fundamental ability of silicon, germanium, and carbon molecular wires to transport charge by comparing conductances within families of well-defined structures, the members of which differ only in the number of Si (or Ge or C) atoms in the wire...
March 27, 2017: Accounts of Chemical Research
Bartosz Błasiak, Casey H Londergan, Lauren J Webb, Minhaeng Cho
The vibrational frequency of a chosen normal mode is one of the most accurately measurable spectroscopic properties of molecules in condensed phases. Accordingly, infrared absorption and Raman scattering spectroscopy have provided valuable information on both distributions and ensemble-average values of molecular vibrational frequencies, and these frequencies are now routinely used to investigate structure, conformation, and even absolute configuration of chemical and biological molecules of interest. Recent advancements in coherent time-domain nonlinear vibrational spectroscopy have allowed the study of heterogeneous distributions of local structures and thermally driven ultrafast fluctuations of vibrational frequencies...
March 27, 2017: Accounts of Chemical Research
Papatya Kaner, Xiaoran Hu, Samuel W Thomas, Ayse Asatekin
In this study, we present a novel self-cleaning, photoresponsive membrane that is capable of removing pre-deposited foulant layers upon changes in surface morphology in response to UV or visible light irradiation while maintaining stable pore size and water permeance. These membranes were prepared by creating thin film composite (TFC) membranes by coating a porous support membrane with a thin layer of novel comb-shaped graft copolymers at two side-chain lengths featuring polyacrylonitrile (PAN) backbones and photoreactive side-chains, synthesized by atom transfer radical polymerization (ATRP)...
March 27, 2017: ACS Applied Materials & Interfaces
Kirstin Casdorff, Tobias Keplinger, Herve Bellanger, Benjamin Michen, Silke Sch N, Ingo Burgert
The adhesion behavior of polyelectrolyte multilayers consisting of poly-(diallyldimethylammonium chloride), PDDA, and poly(styrene sulfonate), PSS, towards a silicon AFM tip was studied during their build-up on wood, a chemically heterogeneous, micrometer rough biomaterial and compared with a nanometer rough substrate, namely quartz. The Atomic Force Microscopy based force mapping approach generated high resolution topography-, and adhesion maps within the first bilayers, which point toward a homogeneous layer-by-layer build-up on the biomaterial surface, and therefore indicate an even charge distribution...
March 27, 2017: ACS Applied Materials & Interfaces
Bartlomiej Wiendlocha, SunPhil Kim, Yeseul Lee, Bin He, Gloria Lehr, Mercouri G Kanatzidis, Donald T Morelli, Joseph P Heremans
The Eu atoms in Pb1-xEuxSe have long been assumed to be divalent. We show that p-type doping of this magnetic semiconductor alloy with Na can modify the effective Eu valence: a mixed, Eu(2+)-Eu(3+) state appears in Pb1-x-yEuxNaySe at particular values of y. Magnetization, carrier concentration, resistivity, and thermopower of Pb1-x-yEuxNaySe are reported for a number of samples with different x and y. A pronounced increase in thermopower at a given carrier concentration was identified and attributed to the presence of enhanced ionized impurity scattering...
March 27, 2017: Physical Chemistry Chemical Physics: PCCP
Ryota Okuno, Minayo Yamaguchi, Hideki Fujiwara
We report the first preparation of a symmetric tetrathiafulvalene (TTF)-pyridyl thiolato zinc(ii) complex in which two TTF parts connect to the central zinc atom through pyridines and thiolates. We also discuss the crystal structure analysis and physical properties of the complex, especially photocurrent generations measured on its thin-film sample and single crystal.
March 27, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
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