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Water equilibrium

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https://www.readbyqxmd.com/read/28437020/deactivation-of-a-cobalt-catalyst-for-water-reduction-via-valence-tautomerism
#1
Claudio N Verani, Habib Baydoun, Shivnath Mazumder, H Bernhard Schlegel
The activity of the water reduction catalyst [CoIII(L1)(pyr)2]PF6 (1), where (L1)-2 is a bis-amido pyridine ligand and pyr is pyrrolidine, is investigated. Catalyst 1 has an overpotential of 0.54 V and a high observed TOF of 23 min-1, albeit for a relatively short time. Considering the significant activity of 1 and aiming to improve catalyst design, a detailed structural and electronic study is performed to understand the mechanisms of deactivation. Experimental and theoretical evidence support that the metal-reduced [CoI(L1)]- is in tautomeric equilibrium with the ligand-reduced [CoII(L1●)]- species...
April 24, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28435965/conformational-and-hydration-properties-modulate-ice-recognition-by-type-i-antifreeze-protein-and-its-mutants
#2
Sandipan Chakraborty, Biman Jana
The mechanism of ice recognition by antifreeze protein (AFP) is a topic of recent interest. Here, using equilibrium simulations and free energy calculations, we provide structural rationale to the observed experimental anomalies on type I AFP (wfAFP isoform HPLC6) and its mutants as well as probe the molecular origin of ice recognition by them. Our results clearly demonstrate that the interplay between the conformational and hydration properties dictates the ice binding ability of type I AFP and its mutants...
April 24, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28435950/solvent-free-on-surface-synthesis-of-boroxine-cof-monolayers
#3
Saskia Spitzer, Atena Rastgoo-Lahrood, Klaus Macknapp, Viktoria Ritter, Stefan Sotier, Wolfgang M Heckl, Markus Lackinger
A protocol is proposed for the solvent-free on-surface synthesis of covalent organic framework monolayers by condensation of diboronic acids. Monomers are vapor-deposited and water is used for equilibrium regulation. Samples are characterized on progressively smaller length scales by light microscopy, Scanning Electron Microscopy, and Scanning Tunneling Microscopy.
April 24, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28434231/charge-and-film-drainage-of-colliding-oil-drops-coated-with-non-ionic-surfactant-c12e5
#4
Srinivas Mettu, Joseph D Berry, Raymond Riley Dagastine
Interaction forces between colliding tetradecane drops were measured in the presence of non-ionic surfactant penta-ethylene-glycol-mono-dodecyl-ether (C12E5). The force behavior was measured in the range of pre-micellar compositions of non-ionic surfactant in various salt solutions and was consistent with the presence of a surface charge even though the surfactant was non-ionic in nature. The surface potential of the oil drops was found to decrease with increase in C12E5 concentration. The measured electrophoretic mobilities and zeta potentials of emulsified tetradecane drops also decreased with an increase in C12E5 concentration...
April 22, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28433176/novel-hydroxyethyl-chitosan-cellulose-scaffolds-with-bubble-like-porous-structure-for-bone-tissue-engineering
#5
Yaping Wang, Junmin Qian, Na Zhao, Ting Liu, Weijun Xu, Aili Suo
Hydrogels fabricated from natural polysaccharides may serve as ideal scaffolds for tissue engineering because of their similarity to the extracellular matrices. In this study, novel hydrogel scaffolds with bubble-like porous structure were prepared from hydroxyethyl chitosan (HECS) and cellulose (CEL) by a combination of chemical crosslinking, particle-leaching using silicon dioxide particles as porogen and freeze-drying method. The morphology, compression stress-strain curves, wettability, and swelling and rheological behaviors of the HECS/CEL scaffolds were characterized by SEM, mechanical test, contact angle measurement and rheometer...
July 1, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/28433157/enhanced-mechanical-properties-of-chitosan-nanodiamond-composites-by-improving-interphase-using-thermal-oxidation-of-nanodiamond
#6
Zahra Delavar, Akbar Shojaei
Polymer composite films based on chitosan (CS) and nanodimaond (ND) were prepared using solution casting method. ND with variable contents of carboxylic functional group was prepared using thermal oxidation at temperature of 420°C under air atmosphere at various durations of 1.5 and 4.5h. The interfacial interaction between NDs and CS and morphological evolution of CS in presence of NDs were investigated by Fourier transform infrared (FTIR), differential scanning calorimeter (DSC) and X-ray diffraction (XRD) analyses...
July 1, 2017: Carbohydrate Polymers
https://www.readbyqxmd.com/read/28433040/predicting-miscibility-of-binary-liquids-from-small-cluster-qce-calculations
#7
Johannes Ingenmey, Michael von Domaros, Barbara Kirchner
The quantum cluster equilibrium method is applied to model binary systems of molecular solvents. We minimize the computational effort as well as the experimental input and present the results obtained for the completely miscible acetonitrile/acetone, benzene/acetone, and water/acetone systems, as well as for the hardly miscible water/benzene system. Only clusters of sizes up to n = 3 are applied and these are optimized employing the low-cost functional PBEh-3c. The thermodynamic functions of the pure liquids are in reasonable agreement with experiments...
April 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28431965/origin-of-nanodroplet-formation-upon-dissolution-of-an-amorphous-solid-dispersion-a-mechanistic-isotope-scrambling-study
#8
Anura S Indulkar, Jan E Waters, Huaping Mo, Yi Gao, Shweta A Raina, Geoff G Z Zhang, Lynne S Taylor
It has been observed that certain amorphous solid dispersions (ASDs), upon dissolution, generate drug-rich amorphous nanodroplets. These nanodroplets, present as a dispersed phase, can potentially enhance oral bioavailability of poorly soluble drugs by serving as a drug reservoir that efficiently feeds the continuous aqueous solution phase following absorption of drug. The purpose of this study was to probe the formation mechanism of the nanodroplets. The model system studied was nifedipine (NFD) formulated as an ASD with hydroxypropyl methylcellulose E5 Premium LV (HPMC-E5) or polyvinylpyrrolidone/vinyl acetate (PVPVA)...
April 18, 2017: Journal of Pharmaceutical Sciences
https://www.readbyqxmd.com/read/28431384/sediment-and-salinity-effects-on-the-bioaccumulation-of-sulfamethoxazole-in-zebrafish-danio-rerio
#9
Y Chen, J L Zhou, L Cheng, Y Y Zheng, J Xu
The dynamic distribution of a widely used antibiotic sulfamethoxazole between water, sediment and aquatic organisms (zebrafish) was studied in microcosms. Sulfamethoxazole concentrations in water were gradually reduced, while in sediment and zebrafish gradually increased, suggesting active adsorption and bioaccumulation processes occurring. The presence of sediment particles and their interactions with water reduced the bioaccumulation of sulfamethoxazole in zebrafish by 13-28%. The sediment of smaller particle size with more organic carbon content and higher surface area, adsorbed sulfamethoxazole more extensively and decreased its bioaccumulation most significantly...
April 14, 2017: Chemosphere
https://www.readbyqxmd.com/read/28429011/drop-transport-and-positioning-on-lubricant-impregnated-surfaces
#10
Jian Hui Guan, Élfego Ruiz-Gutiérrez, Ben Bin Xu, David Wood, Glen McHale, Rodrigo Ledesma-Aguilar, Gary George Wells
We demonstrate the transport and positioning of water droplets on macro-patterned lubricant-impregnated surfaces. The macro-patterning produces menisci features in the impregnating liquid layer which interact with a droplet via a capillary mechanism similar to the Cheerios effect. These interactions control the droplet motion and positioning on an otherwise completely slippery surface. We present experimental results using a V-shape channel geometry as a model system. The interaction between deformations on the lubricant layer induced by the droplet and the underlying V-shape geometry leads to both local and global equilibrium positions for the droplet within the channel...
April 21, 2017: Soft Matter
https://www.readbyqxmd.com/read/28419977/investigation-of-as-v-removal-from-acid-mine-drainage-by-iron-hydr-oxide-modified-zeolite
#11
Pfano Mathews Nekhunguni, Nikita Tawanda Tavengwa, Hlanganani Tutu
In this work, the synthesis of iron (hydr) oxide modified zeolite was achieved through precipitation of iron on the zeolite. The structure and surface morphology of iron (hydr) oxide modified zeolite (IHOMZ) was studied by scanning electron microscopy (SEM), coupled with an energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared (FT-IR) spectra. The efficiency of IHOMZ was then investigated through batch technique for the extraction of As(V) from mine waste water. The optimum parameters for maximum As(V) adsorption were: an initial As(V) concentration (10 mg L(-1)), adsorbent dosage (3...
April 15, 2017: Journal of Environmental Management
https://www.readbyqxmd.com/read/28418442/network-analysis-and-percolation-transition-in-hydrogen-bonded-clusters-nitric-acid-and-water-extracted-by-tributyl-phosphate
#12
Michael J Servis, David T Wu, Jenifer C Braley
Extraction of polar molecules by amphiphilic species results in a complex variety of clusters whose topologies and energetics control phase behavior and efficiency of liquid-liquid separations. A computational approach including quantum mechanical vibrational frequency calculations and molecular dynamics simulation with intermolecular network theory is used to provide a robust assessment of extractant and polar solute association through hydrogen bonding in the tributyl phosphate (TBP)/HNO3/H2O/dodecane system for the first time...
April 18, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28414171/the-effects-of-water-on-degradation-of-the-zirconia-resin-bond
#13
C Chen, Y Chen, Z Lu, M Qian, H Xie, F R Tay
OBJECTIVES: 10-methacryloyloxydecyldihydrogenphosphate (MDP) containing primers improve bonding of yttria-stabilised tetragonal zirconia (Y-TZP) to methacrylate resins. The present study investigated the role played by water in the deterioration of MDP-mediated zirconia-resin bonds. METHODS: Grit-blasted Y-TZP plates were conditioned with two MDP primers and bonded with resin for shear bond strength (SBS) testing. Additional bonded plates were aged hydrothermally and compared with unaged Y-TZP after 24hours of water-storage or 6 months of water/acid/alkali-storage...
April 13, 2017: Journal of Dentistry
https://www.readbyqxmd.com/read/28413952/building-new-bridges-between-in-vitro-and-in-vivo-in-early-drug-discovery-where-molecular-modeling-meets-systems-biology
#14
Robert A Pearlstein, Daniel J J McKay, Viktor Hornak, Callum Dickson, Andrei Golosov, Tyler Harrison, Camilo Velez-Vega, José Duca
Cellular drug targets exist within networked function generating systems whose constituent molecular species undergo dynamic interdependent non-equilibrium state transitions in response to specific perturbations (i.e. inputs). Cellular phenotypic behaviors are manifest through the integrated behaviors of such networks. However, in vitro data are frequently measured and/or interpreted with empirical equilibrium or steady state models (e.g. Hill, Michaelis-Menten, Briggs-Haldane) relevant to isolated target populations...
April 14, 2017: Current Topics in Medicinal Chemistry
https://www.readbyqxmd.com/read/28413882/consequences-of-surface-oxophilicity-of-ni-ni-co-and-co-clusters-on-methane-activation
#15
Weifeng Tu, Mireille Ghoussoub, Chandra Veer Singh, Ya-Huei Cathy Chin
This study describes a new C-H bond activation pathway during CH4-CO2 reactions on oxophilic Ni-Co and Co clusters, unlike those established previously on Ni clusters. The initial C-H bond activation remains as the sole kinetically relevant step on Ni-Co, Ni, and Co clusters, but their specific reaction path varies. On Ni clusters, C-H bond activation occurs via an oxidative addition step that involves a three center (H3C∙∙∙*∙∙∙H)(‡) transition state, during which a Ni atom inserts into the C-H bond and donates its electron density into the C-H bond anti-bonding orbital...
April 17, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28411553/cerium-dioxide-nanoparticles-possess-anti-inflammatory-properties-in-the-conditions-of-the-obesity-associated-nafld-in-rats
#16
Nazarii Kobyliak, Oleksandr Virchenko, Tetyana Falalyeyeva, Maryana Kondro, Tetyana Beregova, Petro Bodnar, Oleksandr Shcherbakov, Rostyslav Bubnov, Martin Caprnda, Delian Delev, Jan Sabo, Peter Kruzliak, Luis Rodrigo, Radka Opatrilova, Mykola Spivak
BACKGROUND: Obesity is a risk factor for non-alcoholic fatty liver disease (NAFLD). The disease is associated with impairment of pro/antioxidant equilibrium and the inflammation in liver tissue. The aim of the work was to investigate the anti-inflammatory properties of the nanocrystalline cerium dioxide (nCeO2) on the rat model of NAFLD associated with monosodium glutamate (MSG)-induced obesity. METHODS: The study was carried out on three groups of rats: control, MSG- and MSG+nCeO2...
April 12, 2017: Biomedicine & Pharmacotherapy, Biomédecine & Pharmacothérapie
https://www.readbyqxmd.com/read/28410497/anesthetics-mechanism-on-a-dmpc-lipid-membrane-model-insights-from-molecular-dynamics-simulations
#17
Marzieh Saeedi, Alexander P Lyubartsev, Seifollah Jalili
To provide insight into the molecular mechanisms of local anesthetic action, we have carried out an extensive investigation of two amide type local anesthetics, lidocaine and articaine in both charged and uncharged forms, interacting with DMPC lipid membrane. We have applied both standard molecular dynamics simulations and metadynamics simulations to provide a detailed description of the free energy landscape of anesthetics embedded in the lipid bilayer. The global minimum of the free energy surface (equilibrium position of anesthetics in the lipid membrane) occurred around 1nm of the bilayer center...
March 29, 2017: Biophysical Chemistry
https://www.readbyqxmd.com/read/28407589/transport-of-anionic-azo-dyes-from-aqueous-solution-to-gemini-surfactant-modified-wheat-bran-synchrotron-infrared-molecular-interaction-and-adsorption-studies
#18
Yan Zhang, Guohe Huang, Chunjiang An, Xiaying Xin, Xia Liu, Maya Raman, Yao Yao, Wenxia Wang, Mukesh Doble
From the view of economic efficiency and technology sustainability, biomass adsorbent has a high potential for pollution control. In the present study, the performance of gemini 12-2-12 surfactant-modified wheat bran (MWB) for the removal of anionic azo dyes from aqueous solution was investigated. A new insight was gained into the modification mechanism through synchrotron-assisted infrared analysis and molecular interaction simulation. The equilibrium and kinetic studies for the adsorption of Acid Red 18 (AR-18), Acid Orange 7 (AO-7) and Acid Black 1 (AB-1) on MWB were conducted...
April 10, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28406193/breathing-modes-of-kolumbo-submarine-volcano-santorini-greece
#19
Evangelos Bakalis, Theo J Mertzimekis, Paraskevi Nomikou, Francesco Zerbetto
Submarine volcanoes, such as Kolumbo (Santorini, Greece) are natural laboratories for fostering multidisciplinary studies. Their investigation requires the most innovative marine technology together with advanced data analysis. Conductivity and temperature of seawater were recorded directly above Kolumbo's hydrothermal vent system. The respective time series have been analyzed in terms of non-equilibrium techniques. The energy dissipation of the volcanic activity is monitored by the temperature variations of seawater...
April 13, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28406007/uranium-in-water-adsorption-over-nh2-functionalized-ordered-silica
#20
Jeremie Huynh, Ruben Palacio, Fariba Safizadeh, Grégory Lefèvre, Michael Descostes, Lilian Eloy, Nadia Guignard, Julie Rousseau, Sebastien Royer, Emmanuel Tertre, Isabelle Batonneau-Gener
This work goes inside the understanding of U(VI) adsorption mechanism over amino-functionalized mesoporous silica SBA-15 and highlights its high efficiency in aqueous media for U(VI) removal and preconcentration. The samples were synthesized and functionalized by both grafting and co-condensation methods, using different alkyl substituted amine groups, and were characterized by XRD, N2 physisorption, FT-IR spectroscopy and Elemental C-H-N-S analyses. The properties for U(VI) adsorption were evaluated under discontinuous conditions, with effect of several parameters (initial pH, contact time, initial U(VI) concentration, functionalization method and organic moiety composition) determined...
April 13, 2017: ACS Applied Materials & Interfaces
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