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Water equilibrium

Guojun Yao, Xu Jing, Chang Liu, Peng Wang, Xueke Liu, Yinzhu Hou, ZhiQiang Zhou, Donghui Liu
Bullfrog, as a kind of amphibians, can be easily exposed to varied pollutants in the environment for the reason of its habitats and highly permeable skin. We investigated the degradation kinetics and residues of α-cypermethrin in bullfrog by two different methods of administration for the environmental monitoring the behavior of one of the most used pesticides in the amphibians. The oral administration and water exposure of α-cypermethrin on bullfrog was studied in this work. α-Cypermethrin and its main metabolites of cis-3-(2',2-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (cis-DCCA) and 3-phenoxybenzoic acid (3-PBA), which have been determined that having correlation with a number of epidemic diseases, were detected simultaneously...
March 17, 2017: Ecotoxicology and Environmental Safety
Paola D'Angelo, Valentina Migliorati, Alessandra Serva, Riccardo Spezia
A diluted solution of Ce(NO₃)₃ in the protic ionic liquid (IL) ethylammonium nitrate (EAN) is investigated using molecular dynamics (MD) simulations and extended X-ray absorption fine structure (EXAFS) spectroscopy. For the first time polarizable effects are included in the MD force field to describe a heavy metal ion in a protic IL, but, unlike water, they are found to be unessential. The CeIII ion first solvation shell is formed by nitrate ions arranged in an icosahedral structure, and an equilibrium between monodentate and bidentate ligands is present in the solution...
March 20, 2017: Chemistry: a European Journal
Razi Epsztein, Michael Beliavski, Sheldon Tarre, Michal Green
The implementation of hydrogenotrophic denitrification is limited due to safety concerns, poor H2 utilization and low solubility of H2 gas with the resulting low transfer rate. The current paper presents the main research work conducted on a pressurized hydrogenotrophic reactor for denitrification that was recently developed. The reactor is based on a new concept suggesting that a gas-liquid equilibrium is achieved in the closed headspace of denitrifying reactor, further produced N2 gas is carried out by the effluent and gas purging is not required...
March 15, 2017: Journal of Environmental Management
Juhua Yu, Shiming Ding, Jicheng Zhong, Chengxin Fan, Qiuwen Chen, Hongbin Yin, Lei Zhang, Yinlong Zhang
Sediment dredging is an effective restoration method to control the internal phosphorus (P) loading of eutrophic lakes. However, the core question is that the real mechanism of dredging responsible for sediment internal P release still remains unclear. In this study, we investigated the P exchange across the sediment-water interface (SWI) and the internal P resupply ability from the sediments after dredging. The study is based on a one-year field simulation study in Lake Taihu, China, using a Rhizon soil moisture sampler, high-resolution dialysis (HR-Peeper), ZrO-Chelex diffusive gradients in thin film (ZrO-Chelex DGT), and P fractionation and adsorption isotherm techniques...
March 16, 2017: Science of the Total Environment
Felix Schulze-Zachau, Björn Braunschweig
Air/water interfaces were modified by oppositely charged poly(sodium 4-styrenesulfonate) (NaPSS) and hexadecyltrimethylammonium bromide (CTAB) polyelectrolyte/surfactant mixtures and were studied on a molecular level with vibrational sum-frequency generation (SFG), tensiometry, surface dilatational rheology and ellipsometry. In order to deduce structure property relations, our results on the interfacial molecular structure and lateral interactions of PSS(-)/CTA(+) complexes were compared to the stability and structure of macroscopic foam as well as to bulk properties...
March 20, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Fabian Christoph Fischer, Luise Henneberger, Maria König, Kai Bittermann, Lukas Linden, Kai-Uwe Goss, Beate I Escher
High-throughput in vitro bioassays are becoming increasingly important in the risk characterization of anthropogenic chemicals. Large databases gather nominal effect concentrations (Cnom) for diverse modes of action. However, the biologically effective concentration can substantially deviate due to differences in chemical partitioning. In this study, we modeled freely dissolved (Cfree), cellular (Ccell), and membrane concentrations (Cmem) in the Tox21 GeneBLAzer bioassays for a set of neutral and ionogenic organic chemicals covering a large physicochemical space...
March 19, 2017: Chemical Research in Toxicology
Lee-Ping Wang, Keri A McKiernan, Joseph Gomes, Kyle A Beauchamp, Teresa Head-Gordon, Julia E Rice, William C Swope, Todd J Martínez, Vijay S Pande
The increasing availability of high-quality experimental data and first-principles calculations creates opportunities for developing more accurate empirical force fields for simulation of proteins. We developed the AMBER-FB15 protein force field by building a high-quality quantum chemical data set consisting of comprehensive potential energy scans and employing the ForceBalance software package for parameter optimization. The optimized potential surface allows for more significant thermodynamic fluctuations away from local minima...
March 17, 2017: Journal of Physical Chemistry. B
Ines M Hauner, Antoine Deblais, James K Beattie, Hamid Kellay, Daniel Bonn
The surface tension of water is an important parameter for many biological or industrial processes, and roughly a factor of three higher than that of non-polar liquids such as oils, which is usually attributed to hydrogen bonding and dipolar interactions. Here we show by studying the formation of water drops that the surface tension of a freshly created water surface is even higher (~ 90 mNm(-1)) than under equilibrium conditions (~ 72 mNm(-1)) with a relaxation process occurring on a long timescale (~ 1 ms)...
March 16, 2017: Journal of Physical Chemistry Letters
Hui Liu, Fu Chen, Huiyong Sun, Dan Li, Tingjun Hou
By means of estimators based on nonequilibrium work, equilibrium free energy differences or potentials of mean force (PMFs) of a system of interest can be computed from biased molecular dynamics (MD) simulations. The approach, however, is often plagued by slow conformational sampling and poor convergence, especially when the solvent effects are taken into account. Here, as a possible way to alleviate the problem, several widely-used implicit solvent models, which are derived from the analytic generalized Born (GB) equation and implemented in the AMBER suite of programs, were employed in free energy calculations based on nonequilibrium work and evaluated for their abilities to emulate explicit water...
March 15, 2017: Journal of Chemical Theory and Computation
Alexandra Bourgouin, Nicolas Varfalvy, Louis Archambault
Out-of-field dose depends on multiple factors, making peripheral dosimetry complex. Only a few dosimeters have the required features for measuring peripheral dose. Plastic scintillator dosimeters (PSDs) offer numerous dosimetric advantages as required for out-of-field dosimetry. The purpose of this study is to determine the potential of using PSD as a surface peripheral dosimeter. Measurements were performed with a parallel-plate ion chamber, a small volume ion chamber, and with a PSD. Lateral-dose measurements (LDM) at 0...
September 2016: Journal of Applied Clinical Medical Physics
Mizuho Yabushita, Peng Li, Kathleen A Durkin, Hirokazu Kobayashi, Atsushi Fukuoka, Omar K Farha, Alexander Katz
The molecular origins of adsorption of lignin-derived phenolics to metal-organic framework NU-1000 are investigated from aqueous solution, as well as in competitive mode with glucose present in the same aqueous mixture. A comparison of adsorption equilibrium constants (Kads) for phenolics functionalized with either carboxylic acid or aldehyde substituents demonstrated only a slight increase (less than a factor of 6) for the former according to both experiments and calculations. This small difference in Kads between aldehyde and carboxylic-acid substituted adsorbates is consistent with the pyrene unit of NU-1000 as the adsorption site, rather than the zirconia nodes, while at saturation coverage, the adsorption capacity suggests multiple guests per pyrene...
March 15, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Horacio Poblete, Ingrid Miranda-Carvajal, Jeffrey Comer
Understanding the interaction of carbon nanomaterials with proteins is essential for determining the potential effects of these materials on health and in the design of biotechnology based on them. Here we leverage explicit-solvent molecular simulation and multidimensional free-energy calculations to investigate how adsorption to carbon nanomaterial surfaces affects the conformational equilibrium of alanine dipeptide, a widely used model of protein backbone structure. We find that the two most favorable structures of alanine dipeptide on graphene (or large carbon nanotubes) correspond to the two amide linkages lying in the same plane, flat against the surface, rather than the nonplanar α-helix-like and β-sheet-like conformations that predominate in aqueous solution...
March 14, 2017: Journal of Physical Chemistry. B
Jing Xu, Barbara J Finlayson-Pitts, R Benny Gerber
Understanding the properties of atmospheric particles made of several components is a very challenging problem. In this paper, we perform quantum chemical calculations for small multicomponent clusters of atmospheric relevance that incorporate methanesulfonic acid (MSA), methylamine (MA), oxalic acid (OxA), and water (H2O). Potential correlations between theoretical predictions of proton transfer in the small clusters and findings of recent experiments on formation of particles of detectable sizes (>2 nm) from the same components are studied...
March 17, 2017: Journal of Physical Chemistry. A
Orsolya Dömötör, Veronika F S Pape, Nóra V May, Gergely Szakács, Éva A Enyedy
Complex formation processes of [Ru(η(6)-p-cymene)(H2O)3](+) and [Rh(η(5)-C5Me5)(H2O)3](+) organometallic cations with 8-hydroxyquinoline (HQ) ligands were studied in aqueous solution by the combined use of (1)H NMR spectroscopy, UV-visible spectrophotometry and pH-potentiometry. Solution stability, chloride ion affinity and lipophilicity of the complexes were characterized together with the in vitro cytotoxicity against a pair of cancer cell lines, responsive and resistant to classic chemotherapy. The solid phase structure of the [Rh(η(5)-C5Me5)(8-quinolinolato)(Cl)] complex was characterized by single-crystal X-ray diffraction analysis...
March 13, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
Laura A Richards, Daniel Magnone, Chansopheaktra Sovann, Chivuth Kong, Sebastian Uhlemann, Oliver Kuras, Bart E van Dongen, Christopher J Ballentine, David A Polya
Arsenic contamination of groundwaters in South and Southeast Asia is a major threat to public health. In order to better understand the geochemical controls on the mobility of arsenic in a heavily arsenic-affected aquifer in northern Kandal Province, Cambodia, key changes in inorganic aqueous geochemistry have been monitored at high vertical and lateral resolution along dominant groundwater flow paths along two distinct transects. The two transects are characterized by differing geochemical, hydrological and lithological conditions...
March 9, 2017: Science of the Total Environment
Shan Hua, Ji-Lai Gong, Guang-Ming Zeng, Fu-Bing Yao, Min Guo, Xiao-Ming Ou
Organochlorine pesticides (OCPs) in sediment were a potential damage for humans and ecosystems. The aim of this work was to determine the effectiveness of carbon materials remedy hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethanes (DDTs) in sediment. Two different carbon materials including activated carbon (AC) and multi-walled carbon nanotubes (MWCNTs) were used in the present research. Sediment treated with 2 wt% AC and MWCNTs after 150 d contact showed 97%, and 75% reduction for HCH, and 93% and 59% decrease for DDTs in aqueous equilibrium concentration, respectively...
March 1, 2017: Chemosphere
Munmun Banerjee, Nirjhar Bar, Ranjan Kumar Basu, Sudip Kumar Das
Cr(VI) is a toxic water pollutant, which causes cancer and mutation in living organisms. Adsorption has become the most preferred method for removal of Cr(VI) due to its high efficiency and low cost. Peanut and almond shells were used as adsorbents in downflow fixed bed continuous column operation for Cr(VI) removal. The experiments were carried out to scrutinise the adsorptive capacity of the peanut shells and almond shells, as well as to find out the effect of various operating parameters such as column bed depth (5-10 cm), influent flow rate (10-22 ml min(-1)) and influent Cr(VI) concentration (10-20 mg L(-1)) on the Cr(VI) removal...
March 10, 2017: Environmental Science and Pollution Research International
Sayiter Yıldız, Mehmet Çekim, Turgay Dere
In this study, biosorption of Cu(2+) and Ni(2+) ions to tobacco stalks was investigated under different operational conditions. The effects of the initial pH, ion concentrations, temperature, and duration of contact and adsorbent dosage were determined in the batch experiments. Chemical oxygen demand (COD) analyses were also performed to identify the possible negative effects of the sorbent throughout biosorption process. The sorption capacities of this sorbent were predicted by use of the equilibrium and kinetic models...
March 10, 2017: Applied Biochemistry and Biotechnology
Dan Hu, Xiaodong Wan, Xiaohui Li, Jianguo Liu, Chunhua Zhou
In this study, a novel, effective and environment-friendly methods was used to prepare poly-l-lysine (PLL)-functionalized magnetic Fe3O4-(GO-MWCNTs) hybrid composite with large surface area and abundant hydroxyl and amino groups. The as-prepared PLL-Fe3O4-(GO-MWCNTs) nanocomposite was systematically characterized by FT-IR, XRD, TGA, SEM, TEM, VSM and EDX. The PLL-Fe3O4-(GO-MWCNTs) hybrid composite exhibited excellent adsorption performance for the removal of a dye (tartrazine) and a heave metal (Pb(II)). The result showed that adsorption of Pb(II) reached equilibrium in 30min and adsorption of tartrazine reached equilibrium in approximately 60min...
March 7, 2017: International Journal of Biological Macromolecules
Chaofan Ding, Yuanling Sun, Yanhui Wang, Jianbo Li, Yanna Lin, Weiyan Sun, Chuannan Luo
A simple chemical bonding method to synthesize magnetic cellulose-poly(dopamine) (Fe3O4@CMC@PDA) was reported. The adsorption behaviors of resorcinol in aqueous solution on Fe3O4@CMC@PDA were systematically investigated. As the results shown that, with the advantage of high surface area, abundant hydroxyl and amino groups of Fe3O4@CMC@PDA, and the magnetic property of Fe3O4, the resorcinol can be easily and rapidly extracted from the water by magnetic attraction under investigation. The adsorption equilibrium of Fe3O4@CMC@PDA for resorcinol corresponded with Freundlich isotherm, and the novel adsorbent exhibited better resorcinol removal efficiency in solutions with low pH...
March 7, 2017: International Journal of Biological Macromolecules
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