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https://www.readbyqxmd.com/read/28550814/determination-of-equilibrium-structures-of-bromothymol-blue-revealed-by-using-quantum-chemistry-with-an-aid-of-multivariate-analysis-of-electronic-absorption-spectra
#1
Toru Shimada, Takeshi Hasegawa
The pH dependent chemical structures of bromothymol blue (BTB), which have long been under controversy, are determined by employing a combined technique of multivariate analysis of electronic absorption spectra and quantum chemistry. Principle component analysis (PCA) of the pH dependent spectra apparently reveals that only two chemical species are adequate to fully account for the color changes, with which the spectral decomposition is readily performed by using augmented alternative least-squares (ALS) regression analysis...
May 19, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28550747/investigation-of-solvation-of-iron-nanoclusters-in-ionic-liquid-1-butyl-1-1-1-trimethylammonium-methane-sulfonate-using-molecular-dynamics-simulations-effect-of-cluster-size-at-different-temperatures
#2
Mohsen Abbaspour, Hamed Akbarzadeh, Parnian Yousefi, Mohammad Razmkhah
The systems composed of metal nanoclusters in ionic liquids are relevant for applications in lubrication, electrochemical devices, catalysis, and chemical processes. The mechanism of solvation and interactions of these systems are not understood at present. In this work, we have simulated iron nanoclusters with different sizes in ionic liquid 1-butyl-1,1,1-trimethylammonium methane sulfonate [N1114][C1SO3] at two temperatures (300 and 500K) and at atmospheric pressure. We have investigated the effects of cluster size and the temperature on some of the thermodynamics, structural and dynamical properties of the systems...
May 21, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28550376/development-of-an-amber-compatible-transferable-force-field-for-poly-ethylene-glycol-ethers-glymes
#3
Nathalia S V Barbosa, Yong Zhang, Eduardo R A Lima, Frederico W Tavares, Edward J Maginn
An all-atom force field consistent with the general AMBER force field (GAFF) format for poly(ethylene glycol) dimethyl ether (diglyme or G2) was developed by fitting to experimental liquid densities and dielectric constants. Not surprisingly, the new force field gives excellent agreement with experimental liquid phase densities and dielectric constants over a wide temperature range. Other dynamic and thermodynamic properties of liquid G2 such as its self-diffusion coefficient, shear viscosity, and vaporization enthalpy were also calculated and compared to experimental data...
June 2017: Journal of Molecular Modeling
https://www.readbyqxmd.com/read/28549064/chemomechanical-regulation-of-myosin-ic-cross-bridges-deducing-the-elastic-properties-of-an-ensemble-from-single-molecule-mechanisms
#4
Florian Berger, A J Hudspeth
Myosin Ic is thought to be the principal constituent of the motor that adjusts mechanical responsiveness during adaptation to prolonged stimuli by hair cells, the sensory receptors of the inner ear. In this context myosin molecules operate neither as filaments, as occurs in muscles, nor as single or few molecules, as characterizes intracellular transport. Instead, myosin Ic molecules occur in a complex cluster in which they may exhibit cooperative properties. To better understand the motor's remarkable function, we introduce a theoretical description of myosin Ic's chemomechanical cycle based on experimental data from recent single-molecule studies...
May 26, 2017: PLoS Computational Biology
https://www.readbyqxmd.com/read/28548517/experimental-determination-of-%C3%AE-s-for-finite-nuclear-matter
#5
Debasish Mondal, Deepak Pandit, S Mukhopadhyay, Surajit Pal, Balaram Dey, Srijit Bhattacharya, A De, Soumik Bhattacharya, S Bhattacharyya, Pratap Roy, K Banerjee, S R Banerjee
We present, for the first time, simultaneous determination of shear viscosity (η) and entropy density (s) and thus, η/s for equilibrated nuclear systems from A∼30 to A∼208 at different temperatures. At finite temperature, η is estimated by utilizing the γ decay of the isovector giant dipole resonance populated via fusion evaporation reaction, while s is evaluated from the nuclear level density parameter (a) and nuclear temperature (T), determined precisely by the simultaneous measurements of the evaporated neutron energy spectra and the compound nuclear angular momenta...
May 12, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28548507/bloch-waves-in-minimal-landau-gauge-and-the-infinite-volume-limit-of-lattice-gauge-theory
#6
Attilio Cucchieri, Tereza Mendes
By exploiting the similarity between Bloch's theorem for electrons in crystalline solids and the problem of Landau gauge fixing in Yang-Mills theory on a "replicated" lattice, we show that large-volume results can be reproduced by simulations performed on much smaller lattices. This approach, proposed by Zwanziger [Nucl. Phys. B412, 657 (1994)NUPBBO0550-321310.1016/0550-3213(94)90396-4], corresponds to taking the infinite-volume limit for Landau-gauge field configurations in two steps: first for the gauge transformation alone, while keeping the lattice volume finite, and second for the gauge-field configuration itself...
May 12, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28548172/a-theoretical-study-on-anion-sensing-mechanism-of-multi-phosphonium-triarylboranes-intramolecular-charge-transfer-and-configurational-changes
#7
Haamid R Bhat, Prakash C Jha
The binding selectivity and recognition mechanism of a series of mono-, di- and triphosphonium substituted triarylboranes: (4-(dimesitylboryl)-3,5-dimethylphenyl)phosphonium ([Mes2BAr(P)](+), 1), 1,1'-mesitylboranediylbis(3,5-dimethylphenyl)phosphonium ([MesBAr(P)2](2+), 2) and 1,1',1''-boranetriyltris(3,5-dimethylphenyl)phosphonium ([BAr(P)3](3+), 3) where Ar(P) = 4-(H3P)-2,6-Me2-C6H2, for various anions has been investigated by employing density functional theory (DFT) and time dependent-density functional theory (TD-DFT) methods...
May 26, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28547121/a-precise-method-for-processing-data-to-determine-the-dissociation-constants-of-polyhydroxy-carboxylic-acids-via-potentiometric-titration
#8
Kaixuan Huang, Yong Xu, Wen Lu, Shiyuan Yu
The thermodynamic dissociation constants of xylonic acid and gluconic acid were studied via potentiometric methods, and the results were verified using lactic acid, which has a known pKa value, as a model compound. Solutions of xylonic acid and gluconic acid were titrated with a standard solution of sodium hydroxide. The determined pKa data were processed via the method of derivative plots using computer software, and the accuracy was validated using the Gran method. The dissociation constants associated with the carboxylic acid group of xylonic and gluconic acids were determined to be pKa1 = 3...
May 25, 2017: Applied Biochemistry and Biotechnology
https://www.readbyqxmd.com/read/28547007/rapid-self-healing-and-anion-selectivity-in-metallosupramolecular-gels-assisted-by-fluorine-fluorine-interactions
#9
Leticia Arnedo-Sánchez, Nonappa, Sandip Bhowmik, Sami Hietala, Rakesh Puttreddy, Manu Lahtinen, Luisa De Cola, Kari Rissanen
Simple ML2 [M = Fe(ii), Co(ii), Ni(ii)] complexes obtained from a perfluoroalkylamide derivative of 4-aminophenyl-2,2',6,2'-terpyridine spontaneously, yet anion selectively, self-assemble into gels, which manifest an unprecedented rapid gel strength recovery, viz. self-healing, and thermal rearrangement in aqueous dimethyl sulfoxide. The key factor for gelation and rheological properties emerges from the fluorine-fluorine interactions between the perfluorinated chains, as the corresponding hydrocarbon derivative did not form metallogels...
May 26, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28545847/sources-and-behaviour-of-nitrogen-compounds-in-the-shallow-groundwater-of-agricultural-areas-poyang-lake-basin-china
#10
Evgeniya Soldatova, Natalia Guseva, Zhanxue Sun, Valeriy Bychinsky, Pascal Boeckx, Bai Gao
Nitrogen contamination of natural water is a typical problem for various territories throughout the world. One of the regions exposed to nitrogen pollution is located in the Poyang Lake basin. As a result of agricultural activity and dense population, the shallow groundwater of this area is characterised by a high concentration of nitrogen compounds, primarily NO3(-), with the concentration varying from 0.1mg/L to 206mg/L. Locally, high ammonium content occurs in the shallow groundwater with low reduction potential Eh (<100mV)...
May 17, 2017: Journal of Contaminant Hydrology
https://www.readbyqxmd.com/read/28545260/thermostabilization-of-the-uronate-dehydrogenase-from-agrobacterium-tumefaciens-by-semi-rational-design
#11
Teresa Roth, Barbara Beer, André Pick, Volker Sieber
Aldaric acids represent biobased 'top value-added chemicals' that have the potential to substitute petroleum-derived chemicals. Until today they are mostly produced from corresponding aldoses using strong chemical oxidizing agents. An environmentally friendly and more selective process could be achieved by using natural resources such as seaweed or pectin as raw material. These contain large amounts of uronic acids as major constituents such as glucuronic acid and galacturonic acid which can be converted into the corresponding aldaric acids via an enzyme-based oxidation using uronate dehydrogenase (Udh)...
December 2017: AMB Express
https://www.readbyqxmd.com/read/28544966/antibacterial-property-and-biocompatibility-of-chitosan-poly-vinyl-alcohol-zno-cs-pva-zno-beads-as-an-efficient-adsorbent-for-cu-ii-removal-from-aqueous-solution
#12
Jiao Xu, Yaping Zhang, Yuvaraja Gutha, Weijiang Zhang
The feasibility of using chitosan/Poly(vinyl alcohol)/ZnO beads (CS/PVA/ZnO) as an adsorbent for removal of Cu(II) ions from aqueous solutions was studied in a batch method. The developed adsorbent material was characterized by XRD, FTIR, SEM and TEM analysis. Pure ZnO shows the characteristic peaks at (100), (002), (101), (102), (110), (103), (200) and (112) that were in good agreement with wurtzite ore having hexagonal lattice structure. Antibacterial properties and biocompatibility of the CS/PVA/ZnO was tested...
May 11, 2017: Colloids and Surfaces. B, Biointerfaces
https://www.readbyqxmd.com/read/28544453/black-tungsten-nitride-as-metallic-photocatalyst-for-overall-water-splitting-operable-at-up-to-765-nm
#13
Yu Lei Wang, Ting Nie, Yu Hang Li, Xue Lu Wang, Li Rong Zheng, Ai Ping Chen, Xue Qing Gong, Huagui Yang
Semiconductor photocatalysts are hardly to be employed for overall water splitting beyond 700 nm, owing to both thermodynamic aspects and activation barriers. Metallic materials as photocatalysts are known to overcome this limitation through interband transitions for creating electron-hole pairs, however, the application of metallic photocatalysts for overall water splitting has never been fulfilled. Here we report, for the first time, that the black tungsten nitride can be employed as metallic photocatalyst for overall water splitting at wavelengths of up to 765 nm...
May 19, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28543768/an-efficient-pd-catalyzed-regio-and-stereoselective-carboxylation-of-allylic-alcohols-with-formic-acid
#14
Yao Fu, Rui Shang, Ming-Chen Fu, Wan-Min Cheng
Formic acid is efficiently used as a C1 source to directly carboxylate allylic alcohols in the presence of a low loading of palladium catalyst and acetic anhydride as additive to afford β,γ-unsaturated carboxylic acids with excellent chemo-, regio-, and stereoselectivity. The reaction proceeds through a carbonylation process with in situ-generated carbon monoxide (CO) under mild conditions, avoiding the use of high-pressure gaseous CO. A bisphosphine ligand that has a large bite angle (4,5-bis(diphenylphosphino)-9,9-dimethylxanthene) was found to be uniquely effective for this transformation...
May 25, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28542229/thermodynamic-framework-to-assess-low-abundance-dna-mutation-detection-by-hybridization
#15
Hanny Willems, An Jacobs, Wahyu Wijaya Hadiwikarta, Tom Venken, Dirk Valkenborg, Nadine Van Roy, Jo Vandesompele, Jef Hooyberghs
The knowledge of genomic DNA variations in patient samples has a high and increasing value for human diagnostics in its broadest sense. Although many methods and sensors to detect or quantify these variations are available or under development, the number of underlying physico-chemical detection principles is limited. One of these principles is the hybridization of sample target DNA versus nucleic acid probes. We introduce a novel thermodynamics approach and develop a framework to exploit the specific detection capabilities of nucleic acid hybridization, using generic principles applicable to any platform...
2017: PloS One
https://www.readbyqxmd.com/read/28542191/spontaneous-cortical-activity-is-transiently-poised-close-to-criticality
#16
Gerald Hahn, Adrian Ponce-Alvarez, Cyril Monier, Giacomo Benvenuti, Arvind Kumar, Frédéric Chavane, Gustavo Deco, Yves Frégnac
Brain activity displays a large repertoire of dynamics across the sleep-wake cycle and even during anesthesia. It was suggested that criticality could serve as a unifying principle underlying the diversity of dynamics. This view has been supported by the observation of spontaneous bursts of cortical activity with scale-invariant sizes and durations, known as neuronal avalanches, in recordings of mesoscopic cortical signals. However, the existence of neuronal avalanches in spiking activity has been equivocal with studies reporting both its presence and absence...
May 24, 2017: PLoS Computational Biology
https://www.readbyqxmd.com/read/28541955/synthesis-of-the-modified-nanofiber-as-a-nanoadsorbent-and-its-dye-removal-ability-from-water-isotherm-kinetic-and-thermodynamic
#17
Niyaz Mohammad Mahmoodi, Zahra Mokhtari-Shourijeh, Asieh Ghane-Karade
In this paper, poly(vinyl alcohol) (PVA) nanofiber was prepared and modified by diethylenetriamine (DETA) and ethylenediamine (EDA) in the presence of glutaraldehyde (GA). Dye removal ability of the modified nanofiber (PVA/DETA/EDA/GA) as a nanoadsorbent from water was studied. Fourier transform Infrared (FTIR) and scanning electron microscopy (SEM) were used to investigate the characteristics of the modified nanofiber. Direct Red 23 (DR23) and Direct Blue (DB78) were used. The effect of operational parameters such as pH, initial dye concentration, contact time, temperature and adsorbent dosage on dye removal was studied...
May 2017: Water Science and Technology: a Journal of the International Association on Water Pollution Research
https://www.readbyqxmd.com/read/28541953/application-of-black-walnut-juglans-nigra-husk-for-the-removal-of-lead-ii-ion-from-aqueous-solution
#18
O S Lawal, O S Ayanda, O O Rabiu, K O Adebowale
The biosorption characteristics of Pb (II) ions from aqueous solution using black walnut (Juglans nigra) seed husk (WSH) biomass were investigated using batch adsorption techniques. The effects of pH, contact time, initial Pb (II) ion concentration, and temperature were studied. The Langmuir, Freundlich and Temkin isotherms were used to analyze the equilibrium data. It was found that the adsorption of Pb (II) ions onto WSH was best described by the Freundlich adsorption model. Biosorption kinetics data were tested using the pseudo-first order and pseudo-second order models, and it was observed that the kinetics data fitted the pseudo-second order model...
May 2017: Water Science and Technology: a Journal of the International Association on Water Pollution Research
https://www.readbyqxmd.com/read/28541945/application-of-scallop-shell-fe3o4-nanoparticles-for-the-removal-of-cr-vi-from-aqueous-solutions
#19
Azita Mohagheghian, Robabeh Vahidi-Kolur, Melina Pourmohseni, Jae-Kyu Yang, Mehdi Shirzad-Siboni
In this study, removal of Cr(VI) by Scallop shell-Fe3O4 nanoparticles was investigated with variation of pH, adsorbent dosage, initial Cr(VI) concentration, ionic strength and temperature. Coating of Fe3O4 nanoparticles onto Scallop shell was identified by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. The maximum adsorption was observed at pH 3. Removal efficiency of Cr(VI) was increased with increasing adsorbent dosage, but was decreased with increasing initial Cr(VI) concentration and temperature...
May 2017: Water Science and Technology: a Journal of the International Association on Water Pollution Research
https://www.readbyqxmd.com/read/28541703/molecular-origin-of-the-vibrational-structure-of-ice-ih
#20
Daniel R Moberg, Shelby C Straight, Christopher Knight, Francesco Paesani
An unambiguous assignment of the vibrational spectra of ice Ih remains a matter of debate. This study demonstrates that an accurate representation of many-body interactions between water molecules, combined with an explicit treatment of nuclear quantum effects through many-body molecular dynamics (MB-MD), leads to a unified interpretation of the vibrational spectra of ice Ih in terms of the structure and dynamics of the underlying hydrogen-bond network. All features of the infrared and Raman spectra in the OH stretching region can be unambiguously assigned by taking into account both the symmetry and the delocalized nature of the lattice vibrations as well as the local electrostatic environment experienced by each water molecule within the crystal...
May 26, 2017: Journal of Physical Chemistry Letters
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