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https://www.readbyqxmd.com/read/28527296/performances-and-working-mechanism-of-a-novel-polycarboxylate-superplasticizer-synthesized-through-changing-molecular-topological-structure
#1
Xiao Liu, Jianan Guan, Guanghong Lai, Ziming Wang, Jie Zhu, Suping Cui, Mingzhang Lan, Huiqun Li
A novel star-shaped polycarboxylate superplasticizer (SPCE) was synthesized through a simple two-step method. (1)H Nuclear Magnetic Resonance ((1)H NMR) and Infrared Spectroscopy (IR) measurements were used for structural characterization. SPCE and comb-shaped polycarboxylate superplasticizer (CPCE) with same molecular weights were designed and synthesized. The cement paste containing SPCE exhibited better fluidity, fluidity retention, water reduction, 25% lower saturated dosage of PCE, 10% longer setting time, lower hydration heat, more delayed hydration heat evolution and lower amount of hydration products at early ages...
May 10, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28524743/nanoparticle-exposures-from-nano-enabled-toner-based-printing-equipment-and-human-health-state-of-science-and-future-research-needs
#2
Sandra Vanessa Pirela, John Martin, Dhimiter Bello, Philip Demokritou
Toner formulations used by laser printers (LP) and photocopiers (PC), collectively called "toner-based printing equipment" (TPE), are nano-enabled products (NEP) because they contain several engineered nanomaterials (ENM) that improve toner performance. It has been shown that during consumer use (printing), these ENM are released in the air, together with other semi-volatile organic nanoparticles, and newly formed gaseous co-pollutants such as volatile organic compounds (VOC). The aim of this review is to detail and analyze physico-chemical and morphological (PCM), as well as the toxicological properties of particulate matter (PM) emissions from TPE...
May 19, 2017: Critical Reviews in Toxicology
https://www.readbyqxmd.com/read/28524450/methylammonium-mediated-evolution-of-mixed-organic-cation-perovskite-thin-films-a-dynamic-composition-tuning-process
#3
Chongwen Li, Yuanyuan Zhou, Li Wang, Yue Chang, Yingxia Zong, Lioz Etgar, Guanglei Cui, Nitin P Padture, Shuping Pang
Methylammonium-mediated phase-evolution behavior of FA1-x MAx PbI3 mixed-organic-cation perovskite (MOCP) is studied. It is found that by simply enriching the MOCP precursor solutions with excess methylammonium cations, the MOCPs form via a dynamic composition-tuning process that is key to obtaining MOCP thin films with superior properties. This simple chemical approach addresses several key challenges, such as control over phase purity, uniformity, grain size, composition, etc., associated with the solution-growth of MOCP thin films with targeted compositions...
May 19, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28522885/dynamically-tunable-cell-culture-platforms-for-tissue-engineering-and-mechanobiology
#4
Koichiro Uto, Jonathan H Tsui, Cole A DeForest, Deok-Ho Kim
Human tissues are sophisticated ensembles of many distinct cell types embedded in the complex, but well-defined, structures of the extracellular matrix (ECM). Dynamic biochemical, physicochemical, and mechano-structural changes in the ECM define and regulate tissue-specific cell behaviors. To recapitulate this complex environment in vitro, dynamic polymer-based biomaterials have emerged as powerful tools to probe and direct active changes in cell function. The rapid evolution of polymerization chemistries, structural modulation, and processing technologies, as well as the incorporation of stimuli-responsiveness, now permit synthetic microenvironments to capture much of the dynamic complexity of native tissue...
February 2017: Progress in Polymer Science
https://www.readbyqxmd.com/read/28521711/mini-heme-proteins-designability-of-structure-and-diversity-of-functions
#5
Jagdish Rai
Natural heme proteins may have heme bound to poly-peptide chain as a cofactor via non-covalent forces or heme as a prosthetic group may be covalently bound to the proteins. Nature has used porphyrins in diverse functions like electron transfer, oxidation, reduction, ligand binding, photosynthesis, signaling, etc. by modulating its properties through diverse protein matrices. Synthetic chemists have tried to utilize these molecules in equally diverse industrial and medical applications due to their versatile electro-chemical and optical properties...
May 15, 2017: Current Protein & Peptide Science
https://www.readbyqxmd.com/read/28521336/chemical-ecology-of-antibiotic-production-by-actinomycetes
#6
Anne van der Meij, Sarah F Worsley, Matthew I Hutchings, Gilles P van Wezel
Actinomycetes are a diverse family of filamentous bacteria that produce a plethora of natural products relevant for agriculture, biotechnology and medicine, including the majority of the antibiotics we use in the clinic. Rather than as free-living bacteria, many actinomycetes have evolved to live in symbiosis with among others plants, fungi, insects and sponges. As a common theme, these organisms profit from the natural products and enzymes produced by the actinomycetes, for example, for protection against pathogenic microbes, for growth promotion or for the degradation of complex natural polymers such as lignocellulose...
May 1, 2017: FEMS Microbiology Reviews
https://www.readbyqxmd.com/read/28515776/hormonally-active-phytochemicals-and-vertebrate-evolution
#7
Max R Lambert, Thea M Edwards
Living plants produce a diversity of chemicals that share structural and functional properties with vertebrate hormones. Wildlife species interact with these chemicals either through consumption of plant materials or aquatic exposure. Accumulating evidence shows that exposure to these hormonally active phytochemicals (HAPs) often has consequences for behavior, physiology, and fecundity. These fitness effects suggest there is potential for an evolutionary response by vertebrates to HAPs. Here, we explore the toxicological HAP-vertebrate relationship in an evolutionary framework and discuss the potential for vertebrates to adapt to or even co-opt the effects of plant-derived chemicals that influence fitness...
June 2017: Evolutionary Applications
https://www.readbyqxmd.com/read/28515469/the-topobiology-of-chemical-elements-in-seabird-feathers
#8
Nicholas R Howell, Jennifer L Lavers, Sayaka Uematsu, David Paterson, Daryl L Howard, Kathryn Spiers, Martin D de Jonge, Tracey Hanley, Richard Garrett, Richard B Banati
The highly organized morphogenesis of bird feathers holds important phylo- and ontogenetic information on the evolution of birds, organogenesis, tissue regeneration, and the health status of individual animals. Altered topobiological patterns are regularly used as retrospective evidence for disturbed developmental trajectories due to the past exposure to environmental stressors. Using the most advanced high-resolution (5-70 µm) X-ray fluorescence microscopy (XFM), we describe in the feathers from three species of Procellariiformes hitherto unknown, depositions of elements (Zn, Ca, Br, Cu, Fe) that are independent of pigmentation or any underlying variation in density or polymer structure...
May 17, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28514900/a-qm-qtaim-detailed-look-at-the-watson-crick%C3%A2-wobble-tautomeric-transformations-of-the-2-aminopurine%C3%A2-pyrimidine-mispairs
#9
Ol'ha O Brovarets', Ivan S Voiteshenko, Horacio Pérez-Sánchez, Dmytro M Hovorun
This work is devoted to the careful QM/QTAIM analysis of the evolution of the basic physico-chemical parameters along the intrinsic reaction coordinate (IRC) of the biologically important 2AP∙T(WC)↔2AP∙T*(w) and 2AP·C*(WC)↔2AP·C(w) Watson-Crick(WC)↔wobble(w) tautomeric transformations obtained at each point of the IRC using original authors' methodology. Established profiles reflect the high similarity between the courses of these processes. Basing on the scrupulous analysis of the profiles of their geometric and electron-topological parameters it was established that the dipole-active WC↔w tautomerisations of the Watson-Crick-like 2AP∙T(WC) / 2AP·C*(WC) mispairs, stabilized by the two classical N3H···N1, N2H···O2 and one weak C6H···O4/N4 H-bonds, into the wobble 2AP∙T*(w)/ 2AP·C(w) base pairs, respectively, joined by the two classical N2H···N3 and O4/N4H···N1 H-bonds, proceed via the concerted stepwise mechanism through the sequential intrapair proton transfer and subsequent large-scale shifting of the bases relative each other, through the planar, highly stable, zwitterionic transition states stabilized by the participation of the four H-bonds - N1(+)H···O4(-)/N4(-), N1(+)H···N3(-), N2(+)H···N3(-) and N2(+)H···O2(-)...
May 18, 2017: Journal of Biomolecular Structure & Dynamics
https://www.readbyqxmd.com/read/28514632/a-waterborne-pursuit-deterrent-signal-deployed-by-a-sea-urchin
#10
Hannah Sheppard-Brennand, Alistair G B Poore, Symon A Dworjanyn
Selection by consumers has led to the evolution of a vast array of defenses in animals and plants. These defenses include physical structures, behaviors, and chemical signals that mediate interactions with predators. Some of the strangest defensive structures in nature are the globiferous pedicellariae of the echinoderms. These are small venomous appendages with jaws and teeth that cover the test of many sea urchins and sea stars. In this study, we report a unique use of these defensive structures by the collector sea urchin Tripneustes gratilla...
June 2017: American Naturalist
https://www.readbyqxmd.com/read/28514061/mapping-intermediate-degradation-products-of-poly-lactic-co-glycolic-acid-in-vitro
#11
Jian Li, Peter Nemes, Ji Guo
There is widespread interest in using absorbable polymers, such as poly(lactic-co-glycolic acid) (PLGA), as components in the design and manufacture of new-generation drug eluting stents (DES). PLGA undergoes hydrolysis to progressively degrade through intermediate chemical entities to simple organic acids that are ultimately absorbed by the human body. Understanding the composition and structure of these intermediate degradation products is critical not only to elucidate polymer degradation pathways accurately, but also to assess the safety and performance of absorbable cardiovascular implants...
May 17, 2017: Journal of Biomedical Materials Research. Part B, Applied Biomaterials
https://www.readbyqxmd.com/read/28513467/evolution-of-the-fermi-surface-of-bitecl-with-pressure
#12
Derrick VanGennep, Daniel Jackson, David Graf, Helmuth Berger, James J Hamlin
We report measurements of Shubnikov-de Haas oscillations in the giant Rashba semiconductor BiTeCl under applied pressures up to ~2.5 GPa. We observe two distinct oscillation frequencies, corresponding to the Rashba-split inner and outer Fermi surfaces. BiTeCl has a conduction band bottom that is split into two sub-bands due to the strong Rashba coupling, resulting in two spin-polarized conduction bands as well as a Dirac point. Our results suggest that the chemical potential lies above this Dirac point, giving rise to two Fermi surfaces...
May 17, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28511856/measurement-of-15-n-longitudinal-relaxation-rates-in-15-nh4-spin-systems-to-characterise-rotational-correlation-times-and-chemical-exchange
#13
D Flemming Hansen
Many chemical and biological processes rely on the movement of monovalent cations and an understanding of such processes can therefore only be achieved by characterising the dynamics of the involved ions. It has recently been shown that (15)N-ammonium can be used as a proxy for potassium to probe potassium binding in bio-molecules such as DNA quadruplexes and enzymes. Moreover, equations have been derived to describe the time-evolution of (15)N-based spin density operator elements of (15)NH4(+) spin systems...
June 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28507721/mo-6-activated-multimetal-oxygen-evolving-catalysts
#14
Peng Fei Liu, Shuang Yang, Li Rong Zheng, Bo Zhang, Hua Gui Yang
Water splitting is key to electrically-powered chemical fuel synthesis, but the slow kinetics of the oxygen evolution reaction (OER) hinder the wider promotion of such technology. Several first-row (3d) transition metal-based catalysts have been developed for the OER; however, these catalysts still require operating voltages that lie well above the fundamental thermodynamic potential. Here, we report high-valence metal molybdenum (Mo(6+)) modulated 3d metal (oxy)hydroxides. The obtained multimetal FeCoMo based OER catalysts require an overpotential of 277 mV to reach the current density of 10 mA cm(-2) on the glassy carbon electrode, and there was no evidence of degradation for about 40 hours of stability testing...
May 1, 2017: Chemical Science
https://www.readbyqxmd.com/read/28505826/steepest-entropy-ascent-nonequilibrium-quantum-thermodynamic-framework-to-model-chemical-reaction-rates-at-an-atomistic-level
#15
G P Beretta, Omar Al-Abbasi, M R von Spakovsky
The steepest entropy ascent (SEA) dynamical principle provides a general framework for modeling the dynamics of nonequilibrium (NE) phenomena at any level of description, including the atomistic one. It has recently been shown to provide a precise implementation and meaning to the maximum entropy production principle and to encompass many well-established theories of nonequilibrium thermodynamics into a single unifying geometrical framework. Its original formulation in the framework of quantum thermodynamics (QT) assumes the simplest and most natural Fisher-Rao metric to geometrize from a dynamical standpoint the manifold of density operators, which represent the thermodynamic NE states of the system...
April 2017: Physical Review. E
https://www.readbyqxmd.com/read/28504899/metabolic-diversity-and-novelties-in-the-oomycetes
#16
Howard S Judelson
The eukaryotic microbes called oomycetes include many important saprophytes and pathogens, with the latter exhibiting necrotrophy, biotrophy, or obligate biotrophy. Understanding oomycete metabolism is fundamental to understanding these lifestyles. Genome mining and biochemical studies have shown that oomycetes, which belong to the kingdom Stramenopila, secrete suites of carbohydrate- and protein-degrading enzymes adapted to their environmental niches and produce unusual lipids and energy storage compounds...
May 15, 2017: Annual Review of Microbiology
https://www.readbyqxmd.com/read/28504262/density-structure-of-earth-s-lowermost-mantle-from-stoneley-mode-splitting-observations
#17
Paula Koelemeijer, Arwen Deuss, Jeroen Ritsema
Advances in our understanding of Earth's thermal evolution and the style of mantle convection rely on robust seismological constraints on lateral variations of density. The large-low-shear-wave velocity provinces (LLSVPs) atop the core-mantle boundary beneath Africa and the Pacific are the largest structures in the lower mantle, and hence severely affect the convective flow. Here, we show that anomalous splitting of Stoneley modes, a unique class of free oscillations that are perturbed primarily by velocity and density variations at the core-mantle boundary, is explained best when the overall density of the LLSVPs is lower than the surrounding mantle...
May 15, 2017: Nature Communications
https://www.readbyqxmd.com/read/28504168/binding-efficacy-and-kinetics-of-chitosan-with-dna-duplex-the-effects-of-deacetylation-degree-and-nucleotide-sequences
#18
Yanmei Yang, Meng Guo, Rui Qian, Chang Liu, Xumin Zong, Yong-Qiang Li, Weifeng Li
The binding process of DNA duplex with various types of chitosan polymers were studied at atomic level through molecular dynamics simulations. The interaction kinetics and binding strength, complex morphology and DNA structure evolution were systematically accessed. The binding efficacy of chitosan to DNA reduces (both in complexation speed and binding strength) when deacetylation degree is decreased, because protonated amine groups on chitosan backbone are more prone to bind with DNA, especially the phosphate oxygen, through coulomb interaction...
August 1, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/28501570/electrocatalytic-properties-of-n-doped-graphite-felt-in-electro-fenton-process-and-degradation-mechanism-of-levofloxacin
#19
Xiaocheng Liu, Danxing Yang, Yaoyu Zhou, Jiachao Zhang, Lin Luo, Sijun Meng, Song Chen, Mengjiao Tan, Zhicheng Li, Lin Tang
The degradation of antibiotic levofloxacin was investigated by dimensionally stable anode as well as modified cathode using low-cost chemical reagents of hydrazine hydrate and ethanol for electro-Fenton in an undivided cell at pH 3.0 under room temperature. Comparison of unmodified and modified cathode was performed. The apparent rate constant of levofloxacin decay was found to be 0.2883 min(-1) for graphite felt-10 with the best performance at 200 mA, which is lower than graphite felt at 400 mA. The optimum modified cathode showed a significant improvement of complete mineralization of levofloxacin, reaching a 92% TOC removal at 200 mA for 480 min higher than unmodified one at twice the current...
May 6, 2017: Chemosphere
https://www.readbyqxmd.com/read/28500352/whole-mantle-convection-with-tectonic-plates-preserves-long-term-global-patterns-of-upper-mantle-geochemistry
#20
T L Barry, J H Davies, M Wolstencroft, I L Millar, Z Zhao, P Jian, I Safonova, M Price
The evolution of the planetary interior during plate tectonics is controlled by slow convection within the mantle. Global-scale geochemical differences across the upper mantle are known, but how they are preserved during convection has not been adequately explained. We demonstrate that the geographic patterns of chemical variations around the Earth's mantle endure as a direct result of whole-mantle convection within largely isolated cells defined by subducting plates. New 3D spherical numerical models embedded with the latest geological paleo-tectonic reconstructions and ground-truthed with new Hf-Nd isotope data, suggest that uppermost mantle at one location (e...
May 12, 2017: Scientific Reports
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