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Chemical evolution

Peyman Sakhaii, Bojan Bohorc, Wolfgang Bermel
A new experiment for recording double quantum spectra is introduced. The 2D DQ NMR experiment yields phase sensitive spectra with double quantum frequencies in F1 . The appearance of remote peaks is vastly suppressed by using a small flip angle double quantum excitation and reconversion. Pulse sequences and phase sensitive processing are discussed. The complexity of the SQ antiphase magnetization given in larger proton spin networks could be reduced by using the option of band selective decoupling during the preparation period...
May 24, 2018: Journal of Magnetic Resonance
Maddaly Ravi, Aswathy S Lal, S Kauser Begum
Premature chromosome condensation (PCC) involves induction of near-chromosome-like morphology to interphase chromatin. Experimental induction of PCC was achieved by somatic cell hybridization (SCH), an approach which evolved into a chemical-induction process. PCC presents most probably the only way in which cytogenetic assessment of damages can be analyzed in special situations such as availability of limited numbers of sample cells and for cells which have lost their ability to divide. Initial experiments on PCC were reported in late 1960s and the technique has evolved into one with wide range of applications owing to its increased efficiency in detecting primary DNA damages...
June 8, 2018: Mutation Research
Mohammed Rehaan Chandan, Nilanjon Naskar, Anuja Das, Rabibrata Mukherjee, Gopalakrishna Pillai Harikrishnan
Several interfacial phenomena are active during polymeric foaming, the dynamics of which significantly influence terminal stability, cell structure and in turn the thermo-mechanical properties of temporally evolved foam. Understanding these dynamics is important in achieving desired foam properties. Here, we introduce a method to simultaneously portray the time evolution of bubble growth, lamella thinning and Plateau border drainage, occurring during reactive polymeric foaming. In this method, we initially conduct bulk and surface shear rheology under polymerizing and non-foaming conditions...
June 15, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Fabrizio Cleri, Fabio Landuzzi, Ralf Blossey
Double strand breaks (DSB) in the DNA backbone are the most lethal type of defect induced in the cell nucleus by chemical and radiation treatments of cancer. However, little is known about the outcomes of damage in nucleosomal DNA, and on its effects on damage repair. We performed microsecond-long molecular dynamics computer simulations of nucleosomes including a DSB at various sites, to characterize the early stages of the evolution of this DNA lesion. The damaged structures are studied by the essential dynamics of DNA and histones, and compared to the intact nucleosome, thus exposing key features of the interactions...
June 14, 2018: PLoS Computational Biology
Justice N A Tettey, Conor Crean, Susan C Ifeagwu, Martin Raithelhuber
The phenomenon of new psychoactive substances (NPS), which came to the attention of the wider international community at the beginning of the 2010s, has been unprecedented in terms of the sheer number of substances, their rate of emergence, chemical diversity, and range of pharmacological effects. In particular, the chemical diversity has been a challenge to promoting a better understanding of the NPS market - a fundamental requirement for effective policy decisions and interventions. This manuscript highlights the significant chemical diversity of NPS and describes an alternative, complementary, and pragmatic classification based on pharmacological effects, which aligns NPS to traditional controlled drugs and enhances understanding of the phenomenon...
June 13, 2018: Handbook of Experimental Pharmacology
Sepehr Hamzehlouia, Shaffiq A Jaffer, Jamal Chaouki
Natural gas is a robust and environmentally friendlier alternative to oil resources for energy and chemicals production. However, gas is distributed globally within shales and hydrates, which are generally remote and difficult reserves to produce. The accessibility, transportation, and distribution, therefore, bring major capital costs. With today's low and foreseen low price of natural gas, conversion of natural gas to higher value-added chemicals is highly sought by industry. Dry reforming of methane (DRM) is a technology pathway to convert two critical greenhouse gas components, CH4 and CO2 , to syngas, a commodity chemical feedstock...
June 12, 2018: Scientific Reports
J González-Romero, M E Lucas-Borja, P A Plaza-Álvarez, J Sagra, D Moya, J De Las Heras
Wildfire has historically been an alteration factor in Mediterranean basins. Despite Mediterranean ecosystems' high resilience, wildfire accelerates erosion and degradation processes, and also affects soil functionality by affecting nutrient cycles and soil structure. In semi-arid Mediterranean basins, check dams are usually built in gullies and channels after fire as a measure against soil erosion. Although check dams have proven efficient action to reduce erosion rates, studies about how they affect soil functionality are lacking...
June 9, 2018: Science of the Total Environment
Marialuisa Aufiero, Ryan Gilmour
The axioms of stereoelectronic theory constitute an atlas to navigate the contours of molecular space. All too rarely lauded, the advent and development of stereoelectronic theory has been one of organic chemistry's greatest triumphs. Inevitably, however, in the absence of a comprehensive treatise, many of the field's pioneers do not receive the veneration that they merit. Rather their legacies are the stereoelectronic pillars that persist in teaching and research. This ubiquity continues to afford practitioners of organic chemistry with an abundance of opportunities for creative endeavor in reaction design, in conceiving novel activation modes, in preorganizing intermediates, or in stabilizing productive transition states and products...
June 12, 2018: Accounts of Chemical Research
Miroslav Krepl, Jennifer Vögele, Holger Kruse, Elke Duchardt-Ferner, Jens Wöhnert, Jiri Sponer
The neomycin sensing riboswitch is the smallest biologically functional RNA riboswitch, forming a hairpin capped with a U-turn loop-a well-known RNA motif containing a conserved uracil. It was shown previously that a U→C substitution of the eponymous conserved uracil does not alter the riboswitch structure due to C protonation at N3. Furthermore, cytosine is evolutionary permitted to replace uracil in other U-turns. Here, we use molecular dynamics simulations to study the molecular basis of this substitution in the neomycin sensing riboswitch and show that a structure-stabilizing monovalent cation-binding site in the wild-type RNA is the main reason for its negligible structural effect...
June 9, 2018: Nucleic Acids Research
Kai-Ti Chu, Yu-Chiao Liu, Min-Wen Chung, Agus Riyanto Poerwoprajitno, Gene-Hsiang Lee, Ming-Hsi Chiang
The intrinsic catalytic property of a Fe-S complex toward H2 evolution was investigated in a wide range of acids. The title complex exhibited catalytic events at -1.16 and -1.57 V (vs Fc+ /Fc) in the presence of trifluoromethanesulfonic acid (HOTf) and trifluoroacetic acid (TFA), respectively. The processes corresponded to the single reduction of the Fe-hydride-S-proton and Fe-hydride species, respectively. When anilinium acid was used, the catalysis occurred at -1.16 V, identical with the working potential of the HOTf catalysis, although the employment of anilinium acid was only capable of achieving the Fe-hydride state on the basis of the spectral and calculated results...
June 12, 2018: Inorganic Chemistry
Vlastimil Mazánek, Hindia Nahdi, Jan Luxa, Zdeněk Sofer, Martin Pumera
In the last decade, layered materials and their 2D counterparts, such as graphene, transition metal chalcogenides or black phosphorus, have been tested for their electrocatalytic properties. The main application is in the hydrogen evolution reaction (HER) and the oxygen reduction reaction (ORR), in which layered materials could possibly replace platinum. Although platinum offers both the lowest overpotential and the highest current density, it is also expensive and rare and has little tolerance to passivation...
June 12, 2018: Nanoscale
Evgeniy V Skopin, Laetitia Rapenne, Hervé Roussel, Jean-Luc Deschanvres, Elisabeth Blanquet, Gianluca Ciatto, Dillon D Fong, Marie-Ingrid Richard, Hubert Renevier
InGaAs is one of the III-V active semiconductors used in modern high-electron-mobility transistors or high-speed electronics. ZnO is a good candidate material to be inserted as a tunneling insulator layer at the metal-semiconductor junction. A key consideration in many modern devices is the atomic structure of the hetero-interface, which often ultimately governs the electronic or chemical process of interest. Here, a complementary suite of in situ synchrotron X-ray techniques (fluorescence, reflectivity and absorption) as well as modeling is used to investigate both structural and chemical evolution during the initial growth of ZnO by atomic layer deposition (ALD) on In0...
June 12, 2018: Nanoscale
Ling Pang, Xuemei Zhang, Shaopeng Wu, Yong Ye, Yuanyuan Li
The properties of asphalt pavement are damaged under the effects of moisture. The pH value and salt concentration of water are the key factors that affect the chemical and rheological properties of asphalt during moisture damage. Four kinds of water solutions, including distilled water, an acidic solution, alkaline solution and saline solution were used to investigate the effects of aqueous solute compositions on the chemical and rheological properties of asphalt. Thin-layer chromatography with flame ionization detection (TLC-FID), Fourier transform infrared (FTIR) spectroscopy and dynamic shear rheometer (DSR) were applied to investigate the components, chemistry and rheology characteristics of asphalt specimens before and after water solute exposure...
June 11, 2018: Materials
Matthew Joseph Crane, Xuezhe Zhou, E James Davis, Peter Pauzauskie
A vast range of insulating, semiconducting, and metallic nanomaterials have been studied over the past several decades with the aim of understanding how continuous-wave or pulsed laser radiation can influence their chemical functionality and local environment. Many fascinating observations have been made during laser irradiation including, but not limited to, the superheating of solvents, mass-transport-mediated morphology evolution, photodynamic therapy, morphology dependent resonances, and a range of phase transformations...
June 11, 2018: Chemistry, An Asian Journal
Chenxi Wei, Sihao Xia, Hai Huang, Yuwei Mao, Piero Pianetta, Yijin Liu
Functional materials and devices are usually morphologically complex and chemically heterogeneous. Their structures are often designed to be hierarchical because of the desired functionalities, which usually require many different components to work together in a coherent manner. The lithium ion battery, as an energy storage device, is a very typical example of this kind of structure. In a lithium ion battery, the cathode, anode, and separator are soaked in a liquid electrolyte, facilitating the back and forward shuttling of the lithium ions for energy storage and release...
June 11, 2018: Accounts of Chemical Research
Tong Yang, Yang Bao, Wen Xiao, Jun Zhou, Jun Ding, Yuan Ping Feng, Kian Ping Loh, Ming Yang, Shijie Wang
Molybdenum disulfide has been demonstrated as a promising catalyst for hydrogen evolution reactions (HER). However, its performance is limited by fractional active edge sites and the strong dependence on hydrogen coverage. In this study, we find an enhanced HER performance in a two-dimensional sub-stoichiometric molybdenum sulfide. Both first-principles calculations and experimental results demonstrate that the basal plane is catalytically active towards HER as evidenced by an optimum Gibbs free energy and a low reaction overpotential...
June 11, 2018: ACS Applied Materials & Interfaces
Matthias Driess, Carsten Walter, Prashanth Menezes, Holger Dau, Stefan Loos
The development of inexpensive, earth abundant and bioinspired oxygen evolution (water oxidation) electrocatalysts that are easily accessible and scalable is a principal requirement regarding the feasibility of water splitting for large-scale chemical energy storage. Here we present a unique, versatile and scalable approach to fabricate manganese oxide films starting from single layers to multi-layers, with controlled thickness and high reproducibility. The resulting MnOx films are comprised of small nanostructures that are assembled closely, in form of porous sponge-like layers...
June 11, 2018: ChemSusChem
Wei Shi, Xiuxia Zhao, Jianrui Feng, Jing Liu, Guangming Yang, Guichang Wang, Peng Cheng
Photocatalytic water splitting for hydrogen production using sustainable sunlight is a promising alternative to industrial hydrogen production. However, the scarcity of highly active, recyclable, inexpensive photocatalysts impedes the development of photocatalytic hydrogen evolution reaction (HER) schemes. Herein, a metal-organic framework (MOF)-template strategy was developed to prepare non-noble metal cocatalyst/solid solution heterojunction NiS/ZnxCd1-xS with superior photocatalytic HER activity. By adjusting the doping metal concentration in MOFs, the chemical compositions and bandgaps of the heterojunctions can be fine-tuned, and the light absorption capacity and photocatalytic activity were further optimized...
June 10, 2018: Angewandte Chemie
Jeffrey W Bullard, John Hagedorn, M Tyler Ley, Qinang Hu, Wesley Griffin, Judith E Terrill
Advances in nano-computed X-ray tomography (nCT), nano X-ray fluorescence spectrometry (nXRF), and high-performance computing have enabled the first direct comparison between observations of three-dimensional nanoscale microstructure evolution during cement hydration and computer simulations of the same microstructure using HydratiCA. nCT observations of a collection of triclinic tricalcium silicate (Ca3 SiO5 ) particles reacting in a calcium hydroxide solution are reported and compared to simulations that duplicate, as nearly as possible, the thermal and chemical conditions of those experiments...
April 2018: Journal of the American Ceramic Society
Sloane L English, Jay G Forsythe
RATIONALE: Depsipeptides, or peptides with a mixture of amide and ester linkages, may have evolved into peptides on primordial Earth. Previous studies on depsipeptides utilized electrospray ionization - ion mobility - quadrupole time-of-flight (ESI-IM-QTOF) tandem mass spectrometry; such analysis was thorough yet time-consuming. Here, a complementary matrix-assisted laser desorption/ionization - time-of-flight (MALDI-TOF) approach was optimized for rapid characterization of depsipeptide length and monomer composition...
June 9, 2018: Rapid Communications in Mass Spectrometry: RCM
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