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Chemical evolution

Song Zhang, Jiajia Liu, Karla Hernandez Ruiz, Rong Tu, Meijun Yang, Qizhong Li, Ji Shi, Haiwen Li, Lianmeng Zhang, Takashi Goto
In this study, we demonstrated the chemical vapor deposition (CVD) of vertically standing molybdenum disulfide (MoS₂) nanosheets, with an unconventional combination of molybdenum hexacarbonyl (Mo(CO)₆) and 1,2-ethanedithiol (C₂H₆S₂) as the novel kind of Mo and S precursors respectively. The effect of the distance between the precursor’s outlet and substrates (denoted as d ) on the growth characteristics of MoS₂, including surface morphology and nanosheet structure, was investigated. Meanwhile, the relationship between the structure characteristics of MoS₂ nanosheets and their catalytic performance for hydrogen evolution reaction (HER) was elucidated...
April 20, 2018: Materials
Ol'ha O Brovarets', Dmytro M Hovorun
In this Review we have summarized and generalized the results of the investigation of the microstructural mechanisms of the tautomerisation by the counter movement of the protons along the neighboring intermolecular H-bonds in 22 biologically important pairs of nucleotide bases in the framework of the original method, which allows to trace the evolution of the physico-chemical parameters, that characterize these processes along the intrinsic reaction coordinate (IRC). It was demonstrated the performance of the introduction of the conception of the key points (KPs) (from nine to five, depending on the symmetry and nature of system), which exhaustively characterize the flow of the tautomerisation processes...
April 20, 2018: Journal of Biomolecular Structure & Dynamics
Martin E Lidell
Adapting to the cold extrauterine environment after birth is a great challenge for the newborn. Due to their high surface area-to-volume ratio, infants tend to lose more heat to the environment as compared to adults. In addition, human newborns lack sufficiently developed skeletal muscle mass to maintain body temperature through shivering thermogenesis, an important source of heat in cold-exposed adults. Evolution has provided humans and other placental mammals with brown adipose tissue (BAT), a tissue that converts chemically stored energy, in the form of fatty acids and glucose, into heat through non-shivering thermogenesis...
April 20, 2018: Handbook of Experimental Pharmacology
Shijing Xu, Jingyao Wang, Jiazhong Wu, Qingjie Liu, Chengzhen Sun, Bofeng Bai
Oil wettability in the water-oil-rock systems is very sensitive to the evolution of surface charges on the rock surfaces induced by the adsorption of ions and other chemical agents in water flooding. Through a set of large-scale molecular dynamics simulations, we reveal the effects of surface charge on the oil contact angles in an ideal water-decane-silicon dioxide system. The results show that the contact angles of oil nano-droplets have a great dependence on the surface charges. As the surface charge density exceeds a critical value of 0...
April 19, 2018: Nanoscale Research Letters
Xingqun Zheng, Lishan Peng, Li Li, Na Yang, Yanjun Yang, Jing Li, Jianchuan Wang, Zidong Wei
The transition-metal compounds (MX) have gained wide attention as hydrogen evolution reaction (HER) electrocatalysts; however, the interaction between the non-metallic atom (X) and the metal atom (M) in MX, and the role of X in the enhanced catalytic activity of MX, are still ambiguous. In this work, we constructed a simple model [X/Ni(100)] to decipher the contribution of X towards enhancing the catalytic activity of NiX, which allows us to accurately predict the trend in HER catalytic activity of NiX based on the easily accessible physico-chemical characteristics of X...
February 21, 2018: Chemical Science
Shawna A Foo, Dione Deaker, Maria Byrne
The impact of ocean acidification on marine invertebrate eggs and consequences for sperm chemotaxis are unknown. In the sea urchins Heliocidaris tuberculata and H. erythrogramma , with small (93µm) and large (393µm) eggs, respectively, we documented the effect of decreased pH on the egg jelly coat, an extracellular matrix that increases target size for sperm and contains sperm attracting molecules. In near future conditions (pH 7.8, 7.6) the jelly coat of H. tuberculata decreased by 11 and 21%, reducing egg target size by 9 and 17%, respectively...
April 19, 2018: Journal of Experimental Biology
Zenghua Chang, Jiantao Wang, Zhaohui Wu, Min Gao, Shuaijin Wu, Shigang Lu
Silicon is a promising material for anodes in energy storage devices. However, excessive growth of solid electrolyte interphase (SEI) caused by the severe volume change during the (de)lithiation processes lead to a dramatic capacity fading. Here we report a super-concentrated electrolyte composed of Lithium bis(fluorosulfonyl)imide (LiFSI) and propylene carbonate (PC) with a molar ratio of 1 to 2 to improve the cycling performance of silicon nano particles (SiNPs). The SiNP electrode shows a remarkably improved cycling performance with an initial delithiation capacity of ca...
April 19, 2018: ChemSusChem
Rosa María Pereñiguez Rodríguez, Davide Ferri
Combinations of perovskite-type oxides with transition and precious metals exhibit the remarkable self-regenerable property that could be exploited for numerous practical applications. The objective of the present work was to study the reversibility of structural changes of perovskite-type oxides under cyclic reducing/oxidizing atmosphere by taking advantage of the reducibility of LaCoO3. LaCoO3±δ and LaCo0.8Cu0.2O3±δ were prepared by ultrasonic spray combustion and were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS) and temperature programmed reduction (TPR)...
April 19, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Sheng-Yi Xie, Luhong Wang, Fuyang Liu, Xian-Bin Li, Ligang Bai, Vitali B Prakapenka, Zhonghou Cai, Ho-Kwang Mao, ShengBai Zhang, Haozhe Liu
Understanding how the structures of a crystal behave under compression is a fundamental issue both for condensed matter physics and geoscience. Traditional description of crystal as the stacking of unit-cell with special symmetry has gained much success on the analysis of physical properties. Unfortunately, it's hard to reveal the relationship between the compressed phases. Taking the family of metal dioxides (MO2) as an example, the structural evolution, subject to fixed chemical formula and highly confined space, often appears as a set of random and uncorrelated events...
April 18, 2018: Journal of Physical Chemistry Letters
Yuri S Djikaev, Eli Ruckenstein
We study some thermodynamic aspects of the activation of aqueous organic aerosols into cloud droplets considering the aerosols to consist of liquid solution of water and hydrophilic and hydrophobic organic compounds, taking into account the presence of reactive species in the air. The hydrophobic (surfactant) organic molecules on the surface of such an aerosol can be processed by chemical reactions with some atmospheric species; this affects the hygroscopicity of the aerosol and hence its ability to become a cloud droplet either via nucleation or via Köhler activation...
April 18, 2018: Journal of Physical Chemistry. A
Chengxi Huang, Jian Zhou, Kaiming Deng, Erjun Kan, Puru Jena
In spite of decades of research, a fundamental understanding of the unusual magnetic behavior of small Mn clusters remains a challenge. Experiments show that Mn2 is antiferromagnetic while small clusters containing up to five Mn atoms are ferromagnetic with magnetic moments of 5 µB/atom, and become ferrimagnetic as they grow further. Theoretical studies based on density functional theory (DFT), on the other hand, find Mn2 to be ferromagnetic, with ferrimagnetic order setting in at different sizes that depend upon the computational methods used...
April 18, 2018: Journal of Physical Chemistry. A
Zhuohao Xiao, Xin-Yuan Sun, Xiuying Li, Yongqing Wang, Zhiqiang Wang, Bowei Zhang, Xianglin Li, Ze Xiang Shen, Lingbing Kong, Yizhong Huang
Theoretically, the accomplishment of phase transformation requires sufficient energy to overcome the barriers of structure rearrangements. Transition of an amorphous to crystalline structure is implemented traditionally by heating at high temperatures. However, phase transformation under ambient condition without involving external energy has not been reported. Here, we demonstrate that phase transformation of GeO2 glass to nanocrystals can be triggered at ambient condition when subjected to aqueous environments...
April 18, 2018: Nano Letters
Joey A Lussier, Fabian J Simon, Pamela S Whitfield, Kalpana Singh, Venkataraman Thangadurai, Mario Bieringer
Solid oxide fuel cells (SOFCs) are solid-state electrochemical devices that directly convert chemical energy of fuels into electricity with high efficiency. Because of their fuel flexibility, low emissions, high conversion efficiency, no moving parts, and quiet operation, they are considered as a promising energy conversion technology for low carbon future needs. Solid-state oxide and proton conducting electrolytes play a crucial role in improving the performance and market acceptability of SOFCs. Defect fluorite phases are some of the most promising fast oxide ion conductors for use as electrolytes in SOFCs...
April 17, 2018: Inorganic Chemistry
Francesca Di Maria, Francesco Lodola, Elena Zucchetti, Fabio Benfenati, Guglielmo Lanzani
Artificially enhancing light sensitivity in living cells allows control of neuronal paths or vital functions avoiding the wiring associated with the use of stimulation electrodes. Many possible strategies can be adopted for reaching this goal, including the direct photoexcitation of biological matter, the genetic modification of cells or the use of opto-bio interfaces. In this review we describe different light actuators based on both inorganic and organic semiconductors, from planar abiotic/biotic interfaces to nanoparticles, that allow transduction of a light signal into a signal which in turn affects the biological activity of the hosting system...
April 17, 2018: Chemical Society Reviews
Wen Zhu, Wei Gan, Zahir Muhammad, Changda Wang, Chuanqiang Wu, Hengjie Liu, Daobin Liu, Ke Zhang, Qun He, Hongliang Jiang, Xusheng Zheng, Zhe Sun, Shuangming Chen, Li Song
Few-layer ternary FePS3 nanosheets, prepared via chemical vapor transport synthesis and ball-milling exfoliation, exhibit excellent electrocatalytic performance for the oxygen evolution reaction in an alkaline medium. Combined with first principles calculations, our X-ray spectroscopy and HRTEM results clearly reveal that the introduction of in-plane defects in FePS3 layers after exfoliation and formation of a FePS3-FeOOH heterostructure during the OER process largely contribute to the catalytic activity enhancement...
April 16, 2018: Chemical Communications: Chem Comm
Gregory W Stull, Melanie Schori, Douglas E Soltis, Pamela S Soltis
PREMISE OF THE STUDY: Our current understanding of flowering plant phylogeny provides an excellent framework for exploring various aspects of character evolution through comparative analyses. However, attempts to synthesize this phylogenetic framework with extensive morphological data sets have been surprisingly rare. Here, we explore character evolution in Asteridae (asterids), a major angiosperm clade, using an extensive morphological data set and a well-resolved phylogeny. METHODS: We scored 15 phenotypic characters (spanning chemistry, vegetative anatomy, and floral, fruit, and seed features) across 248 species for ancestral state reconstruction using a phylogenetic framework based on 73 plastid genes and the same 248 species...
April 14, 2018: American Journal of Botany
Keon Mook Seong, Brad S Coates, May R Berenbaum, John M Clark, Barry R Pittendrigh
BACKGROUND: Cytochrome P450 monooxygenases (P450s) are involved in the biosynthesis of endogenous intracellular compounds and the metabolism of xenobiotics, including chemical insecticides. We investigated the structural and expression level variance across all P450 genes with respect to the evolution of insecticide resistance under multigenerational DDT selection. RESULTS: RNA-seq and reverse transcriptase quantitative PCR indicated that the transcript levels of seven P450 genes were significantly up-regulated and three P450 genes were down-regulated in the DDT-resistant strain 91-R, as compared to the control strain 91-C...
April 15, 2018: Pest Management Science
Dagmar R D'hooge
The beneficial use of computer simulations to track the microstructural evolution of individual species is highlighted in view of macromolecular engineering and design, considering two case studies on catalytic polymerization, and both "low" (<100) and "high" (>100) chain lengths, that is, i) atom transfer radical copolymerization of n-butyl acrylate and styrene aiming at the synthesis of functional macrospecies of "identical' chain length; and ii) chain shuttling polymerization of ethylene and 1-octene toward the production of segmented block copolymers with "soft" and "hard" segments...
April 14, 2018: Macromolecular Rapid Communications
Zhiyong Gong, Yong-Le Pan, Gorden Videen, Chuji Wang
The study of physical and chemical properties of a microscopic object, such as a single particle, is made possible using optical trapping (OT) technology combined with other measuring techniques. Here we show a universal optical trap combined with Raman spectroscopy (RS) and microscopy imaging for single-particle studies. The universal optical trap is constructed using two counter-propagating hollow beams and is able to stably levitate single particles of a wide range of properties, such as transparent or absorbing materials, organic (polymers, bioaerosols, etc...
August 22, 2018: Analytica Chimica Acta
Chong-Yu Liao, Ying-Cai Feng, Gang Li, Xiao-Min Shen, Shi-Huo Liu, Wei Dou, Jin-Jun Wang
The citrus red mite, Panonychus citri , a major citrus pest distributed worldwide, has evolved severe resistance to various classes of chemical acaricides/insecticides including pyrethroids. It is well known that the resistance to pyrethroids is mainly caused by point mutations of voltage-gated sodium channel gene in a wide range of pests. However, increasing number of evidences support that pyrethroids resistance might also be resulted from the integrated mechanisms including metabolic mechanisms. In this study, firstly, comparative analysis of RNA-seq data showed that multiple detoxification genes, including a GSTs gene PcGSTd1 , were up-regulated in a fenpropathrin-resistant population compared with the susceptible strain (SS)...
2018: Frontiers in Physiology
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