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Water equilibrium

Jeanne Dollinger, Veronika J Schacht, Caroline Gaus, Sharon Grant
Surfactants have the potential to modify the environmental behavior of hydrophobic pesticides leading to an enhanced or reduced mobility risk. This risk is often overlooked in registration procedures due to a lack of suitable methodologies to quantify the transport potential of pesticides with surfactants. In this study we present a novel methodology designed to study the surfactant facilitated transport of pesticides under controlled equilibrium and dynamic hydrologic conditions. Using this methodology, we investigated the risk of chlorpyrifos enhanced mobility for two common surfactant application practices in agrosystems: pesticide spraying and irrigation with waste water...
June 14, 2018: Chemosphere
Arash Asfaram, Mehrorang Ghaedi, Hamedreza Javadian, Alireza Goudarzi
A simple, rapid, and efficient method of dispersive micro solid phase extraction (D-μ-SPE) combined with UV-Vis spectrophotometry via ultrasound-assisted (UA) was applied for the determination and preconcentration of quercetin in extract of watercress (Nasturtium officinale), fruit juice and water samples. The sorbent in this method was synthesized by doping copper and sulfide into the tetragonal structure of SnO2 -nanoparticles (Cu- and S- @SnO2 -NPs) and subsequently loading it on activated carbon (AC). The D-μ-SPE parameters with direct effect on the extraction efficiency of the targeted analyte, such as sample pH, volume of eluent, sorbent mass and ultrasound time were optimized using central composite design method...
October 2018: Ultrasonics Sonochemistry
Jacob Carlson Miner, Angel Enrique García
Monovalent salt solutions have strongly coupled interactions with biopolymers, from large polyelectrolytes to small RNA oligomers. High salt concentrations have been known to induce transitions in the structure of RNA, producing non-canonical configurations and even driving RNA to precipitate out of solution. Using all-atom molecular dynamics simulations, we model a monovalent salt species (KCL) at high concentrations (0.1-3m) and calculate the equilibrium distributions of water and ions around a small tetraloop-forming RNA oligomer in a variety of structural arrangements: folded A-RNA (canonical) and Z-RNA (non-canonical) tetraloops and unfolded configurations...
June 14, 2018: Journal of Chemical Physics
Martin Svoboda, Martin Lísal
To address a high salinity of flow-back water during hydraulic fracturing, we use molecular dynamics (MD) simulations and study the thermodynamics, structure, and diffusion of concentrated aqueous salt solution in clay nanopores. The concentrated solution results from the dissolution of a cubic NaCl nanocrystal, immersed in an aqueous NaCl solution of varying salt concentration and confined in clay pores of a width comparable to the crystal size. The size of the nanocrystal equals to about 18 Å which is above a critical nucleus size...
June 14, 2018: Journal of Chemical Physics
Marc P Coons, John M Herbert
Widely used continuum solvation models for electronic structure calculations, including popular polarizable continuum models (PCMs), usually assume that the continuum environment is isotropic and characterized by a scalar dielectric constant, ε. This assumption is invalid at a liquid/vapor interface or any other anisotropic solvation environment. To address such scenarios, we introduce a more general formalism based on solution of Poisson's equation for a spatially varying dielectric function, ε(r). Inspired by nonequilibrium versions of PCMs, we develop a similar formalism within the context of Poisson's equation that includes the out-of-equilibrium dielectric response that accompanies a sudden change in the electron density of the solute, such as that which occurs in a vertical ionization process...
June 14, 2018: Journal of Chemical Physics
Leandra S Boucheron, Jacob T Stanley, Yeling Dai, Siheng Sean You, Christopher T Parzyck, Suresh Narayanan, Alec R Sandy, Zhang Jiang, Mati Meron, Binhua Lin, Oleg G Shpyrko
We experimentally probed the stress relaxation of a monolayer of iron oxide nanoparticles at the water-air interface. Upon drop-casting onto a water surface, the nanoparticles self-assembled into islands of two-dimensional hexagonally close packed crystalline domains surrounded by large voids. When compressed laterally, the voids gradually disappeared as the surface pressure increased. After the compression was stopped, the surface pressure (as measured by a Wilhelmy plate) evolved as a function of the film aging time with three distinct timescales...
May 2018: Physical Review. E
David Steinmetz, Benoit Creton, Veronique Lachet, Bernard Rousseau, Carlos Nieto-Draghi
In this work, liquid-liquid systems are studied by means of coarse-grained Monte Carlo simulations (CG-MC) and Dissipative Particle Dynamics (DPD). A methodology is proposed to reproduce liquid-liquid equilibrium (LLE) and to provide variation of interfacial tension (IFT) as a function of the solute concentration. A key step is the parameterization method based on the use of Flory-Huggins parameter between DPD beads to calculate solute/solvent interactions. Parameters are determined using a set of experimental compositional data of LLE following four different approaches...
June 15, 2018: Journal of Chemical Theory and Computation
Kun Wang, Patrice Chartrand
This paper presents a quantitative thermodynamic description for water, hydrogen fluoride and hydrogen dissolutions in cryolite-base molten salts, which is of technological importance to the Hall-Héroult electrolytic aluminum extraction cell. The Modified Quasichemical Model in the Quadruplet Approximation (MQMQA), as used to treat a large variety of molten salt systems, was adopted to thermodynamically describe the present liquid phase; all solid solutions were modeled using the Compound Energy Formalism (CEF); the gas phase was thermodynamically treated as an ideal mixture of all possible species...
June 15, 2018: Physical Chemistry Chemical Physics: PCCP
Franz Pirolt, Otto Glatter, Gregor Trimmel
Monoglycerides form lipophilic liquid-crystalline phases when mixed with water. The corresponding liquid-crystalline nanostructures coexist with excess water, which is a necessary condition for the formation of internally nanostructured dispersed particles. These nanostructures can comprise bicontinuous cubic phases, inverted hexagonal phases, and inverted micellar cubic phases. The dispersed particles are therefore named cubosomes, hexosomes, or micellar cubosomes. Such dispersions are usually stabilized by hydrophilic high-molecular-weight tri-block copolymers...
June 14, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Marcello Sega, Pál Jedlovszky
Thermodynamic temperature is a scalar. However, the connection with the kinetic energy tensor in statistical mechanics leaves open the possibility to define a tensorial temperature. This concept has sometimes been used to simulate isothermal conditions in out-of-equilibrium systems. Here, we show, by studying a sessile water droplet, that a tensorial temperature leads to the wrong thermodynamics, or, in other words, the equilibrium isothermal ensemble generated using a tensorial temperature is not the canonical one, with interfacial free energies that can differ up to 40% from the correct ones...
June 14, 2018: Physical Chemistry Chemical Physics: PCCP
Sandra L Berry, Brendan Mackey
Here we sought a biologically meaningful, climate variable that captures water-energy availability and is suitable for high resolution (250 m × 250 m) modelling of the fraction of photosynthetically active radiation intercepted by the sunlit canopy (F V ) derived from a 10-year (July 2000 - June 2010) time series of Moderate Resolution Imaging Spectroradiometer (MODIS) Normalized difference vegetation index (NDVI) satellite imagery for Australia. The long-term mean annual evaporation deficit, and mean annual water availability indices all yielded strong linear relationships with mean F V ([Formula: see text], %)...
June 13, 2018: Scientific Reports
Roc Matheu, Abolfazl Ghaderian, Laia Francas, Petko Chernev, Mehmed Ertem, Jordi Benet-Buchholz, Victor Batista, Michael Haumann, Carolina Gimbert-Suriñach, Xavier Sala, Antoni Llobet
The Ru complex [RuII(bda-κ-N2O2)(N-NH2)2], 1, (bda2- = (2,2'-bipyridine)-6,6'-dicarboxylate; N-NH2 = 4-(pyridin-4-yl)aniline) is used as a synthetic intermediate to prepare Ru-bda complexes that contain the NO+, acetonitrile (MeCN) or H2O ligands at oxidation states II and III. Complex 1 reacts with excess NO+ to form a Ru complex where the aryl amine ligands N-NH2 in 1 are transformed into diazonium salts (N-N2+ = 4-(pyridin-4-yl)benzenediazonium)) together with the formation of a new Ru-NO group at the equatorial zone, to generate [RuII(bda-κ-N2O)(NO)(N-N2)2]3+, 23+...
June 13, 2018: Chemistry: a European Journal
Hongjuan Geng
Cellulose/N,N'-methylene bisacrylamide/graphene oxide hydrogels were prepared by mixing cellulose with N,N'-methylene bisacrylamide (MBA) and graphene oxide (GO) in NaOH/urea aqueous solution. Two states of hydrogels, i.e. the freshly prepared hydrogels and the hydrogels at swelling equilibrium state in deionized water, were prepared. The gelation time, mechanical properties, transparency, texture properties and water retention ratio of the hydrogels were investigated. Results showed that the cellulose solution showed obvious MBA and GO induced gelation behaviors...
September 15, 2018: Carbohydrate Polymers
Kyuma Suzuki, Shun Watanabe, Yumi Yuasa, Yasunori Yamashita, Hajime Arai, Hideki Tanaka, Toshihiro Kuge, Masanobu Mori, Kin-Ichi Tsunoda, Seiichi Nohara, Yuichi Iwasaki, Yoshitaka Minai, Yukiko Okada, Seiya Nagao
Understanding ecosystem dynamics of radionuclides is necessary to ensure effective management for food safety. The Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident on March 11, 2011 released large amounts of radiocesium (134 Cs and 137 Cs) and contaminated the environment across eastern Japan. In this study, we aimed to elucidate the temporal dynamics of 137 Cs in the aquatic ecosystem of Lake Onuma on Mt. Akagi. The effective ecological half-life (Teff ) of 137 Cs in fishes, western waterweed (Elodea nuttallii), seston (phytoplankton and zooplankton), and lake water was estimated using survey data of 137 Cs concentration collected from 2011 to 2016, and single- and two-component decay function models (SDM and TDM, respectively)...
May 1, 2018: Science of the Total Environment
Meshal Alzaid, Abu M N Taufique, Salim A Thomas, Clay Carufel, John M Harris, Alex J B Waters, Amal Altayyar, Sylvio May, Erik K Hobbie
Macroscopic single-wall carbon nanotube (SWCNT) films of nanoscale thickness have significant potential for an array of applications that demand thin, transparent, conductive coatings. Using macroscopic micrometer-thick polystyrene sheets as a reference, we characterize the elastic response of freestanding multifunctional SWCNT nanosheets possessing both exceptionally high Young's modulus and good durability. Thin SWCNT films (20 nm to 200 nm thick) asymmetrically 'doped' with dilute concentrations of super-paramagnetic colloids were suspended in ethanol as freestanding nanosheets...
June 11, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Jakub Krajniak, Zidan Zhang, Sudharsan Pandiyan, Eric Nies, Giovanni Samaey
We develop novel parallel algorithms that allow molecular dynamics simulations in which byproduct molecules are created and removed because of the chemical reactions during the molecular dynamics simulation. To prevent large increases in the potential energy, we introduce the byproduct molecules smoothly by changing the non-bonded interactions gradually. To simulate complete equilibrium reactions, we allow the byproduct molecules attack and destroy created bonds. Modeling of such reactions are, for instance, important to study the pore formation due to the presence of e...
June 11, 2018: Journal of Computational Chemistry
Joel Mensah, Irina Delidovich, Peter J C Hausoul, Laurent Weisgerber, Wolfgang Schrader, Regina Palkovits
The isomerization of glucose to fructose is a crucial interim step in the processing of biomass to renewable fuels and chemicals. This study investigates the copper catalyzed glucose-fructose-isomerization in water focusing on insights into the roles of dissolved copper species. Depending on the pH, the thermodynamic equilibrium is shifted towards one or a few copper species namely Cu2+, Cu(OH)+, and Cu(OH)2. According to thermodynamics, the highest concentration of Cu(OH)+ is found at pH 5.3 for which also the highest fructose yield of 19% is achieved...
June 9, 2018: ChemSusChem
Hélène Bureau, Laurent Remusat, Imène Esteve, Daniele L Pinti, Pierre Cartigny
Natural diamonds contain mineral and fluid inclusions that record diamond growth conditions. Replicating the growth of inclusion-bearing diamonds in a laboratory is therefore a novel diagnostic tool to constrain the conditions of diamond formation in Earth's lithosphere. By determining the carbon isotopic fractionation during diamond growth in fluids or melts, our laboratory experiments revealed that lithospheric monocrystalline and fibrous and coated diamonds grow similarly from redox reactions at isotopic equilibrium in water and carbonate-rich fluids or melts, and not from native carbon...
June 2018: Science Advances
Amel Benatallah, Faissal Ghozlane, Michel Marie
Objective: This study was conducted to evaluate the effect of water restriction (WR) on physiological and blood parameters on lactating dairy cows reared under Mediterranean climate. Methods: The trial lasted 16 days preceded by two weeks of adaptation to the experimental condition in spring 2014 on 6 dairy cows in mid-lactation. These cows were watered at will for 4 days (W100) (hydration period), then split into 2 groups, one group has received 25% and the other 50% of water compared to their mean water consumption during the hydration period; then rehydrated for 4 days...
May 31, 2018: Asian-Australasian Journal of Animal Sciences
Ayana Hirono, Taro Toyota, Kouichi Asakura, Taisuke Banno
Micrometer-sized self-propelled oil droplets under a far-from-equilibrium condition have drawn much attention because of their potential as a dynamic model for the chemical machinery in living organisms. In order to clarify the effect of interactions between the system components (surfactant, oil, and water) on the locomotion mode of droplets, we investigated the behaviors of oil droplets composed of n-heptyloxybenzaldehyde (HBA) in solutions of cationic surfactants having or not-having an ester or an ether linkage...
June 7, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
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