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https://www.readbyqxmd.com/read/28432960/molecular-dynamic-simulations-on-tkx-50-rdx-cocrystal
#1
Shuling Xiong, Shusen Chen, Shaohua Jin
Dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50) is a newly synthesized energetic material with excellent comprehensive properties. Cyclotrimethylenetrinitramine (RDX) is currently one of the most widely used energetic materials in the world. TKX-50 and RDX supercell models and TKX-50/RDX cocrystal model were constructed based on their crystal cell parameters and the formation mechanism of cocrystal, respectively, then they were simulated by molecular dynamics (MD) simulations. The maximum trigger bond (NNO2) length(Lmax), binding energy (Ebind), radial distribution function (RDF), cohesive energy density(CED) and mechanical properties were simulated at different temperatures based on the simulated equilibrium structures of the models...
March 19, 2017: Journal of Molecular Graphics & Modelling
https://www.readbyqxmd.com/read/28432770/chiral-separation-of-aryloxyphenoxy-propionate-herbicides-in-a-permethyl-%C3%AE-cyclodextrin-based-column-influence-of-temperature-and-mobile-phase-composition-on-enantioselectivity
#2
Ester Lubomirsky, Héctor Di Loreto, Juan M Padró, Cecilia B Castells
We used a permethyl-β-cyclodextrin chiral stationary phase under reversed-phase conditions for the chiral separation of four aryloxyphenoxy-propionate herbicides (fenoxaprop-p-ethyl, quizalofop-p-ethyl and tefuryl and haloxyfop-p-methyl) with mixtures of methanol, ethanol, 2-propanol, n-propanol, tert-butanol, or acetonitrile and water as mobile phases and investigated the influence of mobile phase composition and column temperature (from 0 to 50 °C) on the separation. The retention factors (k) and selectivity factors (α) of all the herbicides investigated decreased with increasing temperature...
April 22, 2017: Electrophoresis
https://www.readbyqxmd.com/read/28432354/structural-and-functional-analysis-of-lysozyme-after-treatment-with-dielectric-barrier-discharge-plasma-and-atmospheric-pressure-plasma-jet
#3
Sooho Choi, Pankaj Attri, Inhwan Lee, Jeongmin Oh, Ji-Hye Yun, Ji Hoon Park, Eun Ha Choi, Weontae Lee
The variation in the biological function of proteins plays an important role in plasma medicine and sterilization. Several non-thermal plasma sources with different feeding gases are used worldwide for plasma treatment, including dielectric barrier discharge (DBD) and atmospheric-pressure plasma jet (APPJ) as the most commonly used sources. Therefore, in the present work, we used both DBD and APPJ plasma sources with N2 and air as feeding gases to evaluate the effects on the structural, thermodynamic, and activity changes of enzymes...
April 21, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28431946/relationship-between-calorimetric-profiles-and-differential-melting-curves-for-natural-dnas
#4
Chun-Ling Chang, Alexander S Fridman, Roger M Wartell, Chin-Kun Hu, Dmitri Y Lando
Many experiments demonstrate that regions with higher GC-content in natural DNAs unwind at higher temperatures adsorbing more heat than equivalently sized regions with lower GC-content. This simple observation implies that normalized calorimetric melting profiles (calorimetric cDMCs) will not be equivalent differential melting curves (DMCs). We propose simple expressions for long natural and random DNA sequences to reciprocally convert DMCs and corresponding calorimetric cDMCs. The expressions are confirmed by the Poland-Fixman-Freire method and an approach based upon mixtures of homopolymeric duplexes...
April 18, 2017: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/28431312/melatonin-charge-transfer-complex-with-2-3-dichloro-5-6-dicyano-1-4-benzoquinone-molecular-structure-dft-studies-thermal-analyses-evaluation-of-biological-activity-and-utility-for-determination-of-melatonin-in-pure-and-dosage-forms
#5
Gehad G Mohamed, Maher M Hamed, Nadia G Zaki, Mohamed M Abdou, Marwa El-Badry Mohamed, Abanoub Mosaad Abdallah
A simple, accurate and fast spectrophotometric method for the quantitative determination of melatonin (ML) drug in its pure and pharmaceutical forms was developed based on the formation of its charge transfer complex with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as an electron acceptor. The different conditions for this method were optimized accurately. The Lambert-Beer's law was found to be valid over the concentration range of 4-100μgmL(-1) ML. The solid form of the CT complex was structurally characterized by means of different spectral methods...
April 4, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28431217/reduced-graphene-oxide-as-an-effective-adsorbent-for-removal-of-malachite-green-dye-plausible-adsorption-pathways
#6
Kanika Gupta, Om P Khatri
Efficient removal of malachite green (MG) dye from simulated wastewater is demonstrated using high surface area reduced graphene oxide (rGO). The plausible interaction pathways between MG dye and rGO are deduced from nanostructural features (HRTEM) of rGO and spectroscopic analyses (FTIR and Raman). The high surface area (931m(2)⋅gm(-1)) of rGO, π-π interaction between the aromatic rings of MG dye and graphitic skeleton, and electrostatic interaction of cationic centre of MG dye with π-electron clouds and negatively charged residual oxygen functionalities of rGO collectively facilitate the adsorption of MG dye on the rGO...
April 12, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28430500/thermalization-and-return-to-equilibrium-on-finite-quantum-lattice-systems
#7
Terry Farrelly, Fernando G S L Brandão, Marcus Cramer
Thermal states are the bedrock of statistical physics. Nevertheless, when and how they actually arise in closed quantum systems is not fully understood. We consider this question for systems with local Hamiltonians on finite quantum lattices. In a first step, we show that states with exponentially decaying correlations equilibrate after a quantum quench. Then, we show that the equilibrium state is locally equivalent to a thermal state, provided that the free energy of the equilibrium state is sufficiently small and the thermal state has exponentially decaying correlations...
April 7, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28430435/cu-in-halide-perovskite-cihp-solar-absorbers
#8
Xin-Gang Zhao, Dongwen Yang, Yuanhui Sun, Tianshu Li, Lijun Zhang, Liping Yu, Alex Zunger
The long-term chemical instability and the presence of toxic Pb in otherwise stellar solar absorber APbX3 made of organic molecules on the A site and halogens for X have hindered their large-scale commercialization. Previously explored ways to achieve Pb-free halide perovskites involved replacing Pb(2+) with other similar M(2+) cations in ns(2) electron configuration, e.g., Sn(2+) or by Bi(3+) (plus Ag(+)), but unfortunately this showed either poor stability (M = Sn) or weakly absorbing oversized indirect gaps (M = Bi), prompting concerns that perhaps stability and good optoelectronic properties might be contraindicated...
April 21, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28430420/a-thorium-chalcogenolate-series-generated-by-atom-insertion-into-thorium-carbon-bonds
#9
Nicholas S Settineri, Mary E Garner, John Arnold
A new thorium monoalkyl complex, Th(CH2SiMe3)(L3) (L = MeC(N(i)Pr)2) (2), undergoes insertion of chalcogen atoms resulting in a series of thorium chalcogenolate complexes, Th(ECH2SiMe3)(L3) (E = S, SS, Se, Te; 5-8). Complex 6 represents the first alkyl disulfide thorium species and illustrates the ability of 2 to undergo controllable, stoichiometric atom insertion. All complexes have been characterized by (1)H and (13)C NMR spectroscopy, FTIR, EA, and melting point, and in the case of 1, 2, and 4-8, X-ray crystallography...
April 21, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28430199/control-over-differentiation-of-a-metastable-supramolecular-assembly-in-one-and-two-dimensions
#10
Tomoya Fukui, Shinnosuke Kawai, Satoko Fujinuma, Yoshitaka Matsushita, Takeshi Yasuda, Tsuneaki Sakurai, Shu Seki, Masayuki Takeuchi, Kazunori Sugiyasu
Molecular self-assembly under kinetic control is expected to yield nanostructures that are inaccessible through the spontaneous thermodynamic process. Moreover, time-dependent evolution, which is reminiscent of biomolecular systems, may occur under such out-of-equilibrium conditions, allowing the synthesis of supramolecular assemblies with enhanced complexities. Here we report on the capacity of a metastable porphyrin supramolecular assembly to differentiate into nanofibre and nanosheet structures. Mechanistic studies of the relationship between the molecular design and pathway complexity in the self-assembly unveiled the energy landscape that governs the unique kinetic behaviour...
May 2017: Nature Chemistry
https://www.readbyqxmd.com/read/28430195/a-stable-compound-of-helium-and-sodium-at-high-pressure
#11
Xiao Dong, Artem R Oganov, Alexander F Goncharov, Elissaios Stavrou, Sergey Lobanov, Gabriele Saleh, Guang-Rui Qian, Qiang Zhu, Carlo Gatti, Volker L Deringer, Richard Dronskowski, Xiang-Feng Zhou, Vitali B Prakapenka, Zuzana Konôpková, Ivan A Popov, Alexander I Boldyrev, Hui-Tian Wang
Helium is generally understood to be chemically inert and this is due to its extremely stable closed-shell electronic configuration, zero electron affinity and an unsurpassed ionization potential. It is not known to form thermodynamically stable compounds, except a few inclusion compounds. Here, using the ab initio evolutionary algorithm USPEX and subsequent high-pressure synthesis in a diamond anvil cell, we report the discovery of a thermodynamically stable compound of helium and sodium, Na2He, which has a fluorite-type structure and is stable at pressures >113 GPa...
May 2017: Nature Chemistry
https://www.readbyqxmd.com/read/28430134/on-the-morphology-of-group-ii-metal-fluoride-nanocrystals-at-finite-temperature-and-partial-pressure-of-hf
#12
Zeinab Kaawar, Stefan Mahn, Erhard Kemnitz, Beate Paulus
We have investigated the bulk and surface properties of the group II metal fluorides CaF 2 , SrF 2 and BaF 2 using periodic density functional theory (DFT) calculations and surface thermodynamics. Our bulk results show that the best agreement with experiment is achieved with the B3LYP and PBE functionals. We determined the relative importance of the low index surfaces in vacuum and found that an fluoride microcrystal exposes only the (111) surface in which the undercoordinated cations are sevenfold coordinated...
April 21, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28430106/atomic-motions-in-the-layered-copper-pseudochalcogenide-cuncn-indicative-of-a-quantum-spin-liquid-scenario
#13
Andrei L Tchougreeff, Ralf Stoffel, Andreas Houben, Philipp Jacobs, Richard Dronskowski, Matej Pregelj, Andrej Zorko, Denis Arcon, Oksana Zaharko
We explore the thermodynamic properties of the layered copper(II) carbodiimide CuNCN by heat-capacity measurements and investigate the corresponding thermal atomic motions by means of neutron powder diffraction as well as inelastic neutron scattering. The experiments are complemented by a combination of density-functional calculations, phonon analysis and analytic theory. The existence of a soft flexural mode-bending of the layers, characteristic for the material structure-is established in the phonon spectrum of CuNCN by giving characteristic temperature-dependent contributions to the heat capacity and atomic displacement parameters...
April 21, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28429932/thermodynamics-of-the-thermal-denaturation-of-acid-molten-globule-state-of-cytochrome-c-indicate-a-reversible-high-temperature-oligomerization-process
#14
Shigeyoshi Nakamura, Tomonori Saotome, Akiko Nakazawa, Masao Fukuda, Yutaka Kuroda, Shun-Ichi Kidokoro
In this study, we performed differential scanning calorimetry (DSC) and pressure perturbation calorimetry (PPC) analysis of the thermal transition of cytochrome c from an acidic molten globule (MG) state with the protein concentrations of 0.5-18.2 mg/mL. DSC profiles were highly reversible and showed clear protein-concentration dependence, indicating that reversible oligomerization occurred accompanying the thermal transition from the MG state. The DSC and PPC data required at least a six-state model including three new oligomeric states: dimer (I2), trimer (I3), and tetramer (I4) in addition to the three monomeric states previously characterized...
April 21, 2017: Biochemistry
https://www.readbyqxmd.com/read/28429787/heat-temperature-and-clausius-inequality-in-a-model-for-active-brownian-particles
#15
Umberto Marini Bettolo Marconi, Andrea Puglisi, Claudio Maggi
Methods of stochastic thermodynamics and hydrodynamics are applied to a recently introduced model of active particles. The model consists of an overdamped particle subject to Gaussian coloured noise. Inspired by stochastic thermodynamics, we derive from the system's Fokker-Planck equation the average exchanges of heat and work with the active bath and the associated entropy production. We show that a Clausius inequality holds, with the local (non-uniform) temperature of the active bath replacing the uniform temperature usually encountered in equilibrium systems...
April 21, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28429451/a-strong-cis-effect-in-an-imidazole-imidazolium-substituted-alkene
#16
Dayne C Georgiou, Mohammad A Haghighatbin, Conor F Hogan, Michael S Scholz, James N Bull, Evan J Bieske, David J D Wilson, Jason L Dutton
We report the first example of an alkene with two carbon-bound substituents (imidazole and imidazolium rings) where the Z-isomer has a greater thermodynamic stability than the E-isomer which persists in both the gas phase and in solution. Theoretical calculations, solution fluorescence spectroscopy and gas-phase ion mobility mass spectrometry studies confirm the preference for the Z-isomer, the stability of which is traced to a non-covalent interaction between the imidazole lone pair and the imidazolium ring...
April 21, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28428126/interactions-of-tetracyclines-with-ovalbumin-the-main-allergen-protein-from-egg-white-spectroscopic-and-electrophoretic-studies
#17
Maria Dayanne de A Dantas, Humberto de Araújo Tenório, Thiago Inácio B Lopes, Hugo Juarez V Pereira, Anita J Marsaioli, Isis M Figueiredo, Josué Carinhanha Caldas Santos
The interactions of tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC) with ovalbumin (OVA), the main allergen protein of egg white, were investigated by molecular spectroscopy and electrophoresis at three pH conditions (1.5, 4.6 and 7.4). Molecular and synchronous fluorescence, UV-vis spectroscopy, electrophoresis and (1)H NMR were used to study the interaction process. Tetracyclines interact with ovalbumin fluorescence by a static quenching mechanism with non-fluorescent complex formation changing the native protein structure...
April 17, 2017: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/28427941/elongation-affinity-activation-barrier-and-stability-of-a%C3%AE-42-oligomers-fibrils-in-physiological-saline
#18
Roberto A Rodriguez, Liao Y Chen, Germán Plascencia-Villa, George Perry
Amyloid-beta (Aβ) peptides, Aβ40 and the more neurotoxic Aβ42, have been the subject of many research efforts for Alzheimer's disease. In two recent independent investigations, the atomistic structure of Aβ42 fibril has been clearly established in the S-shaped conformation consisting of three β-sheets stabilized by salt bridges formed between the Lys28 sidechain and the C-terminus of Ala42. This structure distinctively differs from the long-known structure of Aβ40 in the β-hairpin shaped conformation consisting of two β-sheets...
April 17, 2017: Biochemical and Biophysical Research Communications
https://www.readbyqxmd.com/read/28427899/energy-and-information-flows-in-biological-systems-bioenergy-transduction-of-v1-atpase-rotary-motor-and-dynamics-of-thermodynamic-entropy-in-information-flows
#19
REVIEW
Ichiro Yamato, Takeshi Murata, Andrei Khrennikov
We classify research fields in biology with respect to flows of materials, energy, and information. We investigate energy transducing mechanisms in biology, using as a representative the typical molecular rotary motor V1-ATPase from a bacterium Enterococcus hirae. The structures of several intermediates of the rotary motor are described and the molecular mechanism of the motor converting chemical energy into mechanical energy is discussed. Comments and considerations on the information flows in biology, especially on the thermodynamic entropy in quantum physical and biological systems, are presented in section 3 in a biologist friendly manner...
April 17, 2017: Progress in Biophysics and Molecular Biology
https://www.readbyqxmd.com/read/28427643/improving-the-enzymolysis-efficiency-of-potato-protein-by-simultaneous-dual-frequency-energy-gathered-ultrasound-pretreatment-thermodynamics-and-kinetics
#20
Yu Cheng, Yun Liu, Juan Wu, Prince Ofori Donkor, Ting Li, Haile Ma
The thermodynamics and kinetics of traditional and simultaneous dual frequency energy-gathered ultrasound (SDFU) assisted enzymolysis of potato protein were investigated to get the knowledge of the mechanisms on the SDFU's promoting efficiency during enzymolysis. The concentration of potato protein hydrolysate and parameters of thermodynamic and kinetic during traditional and SDFU assisted enzymolysis were determined. The results showed that potato protein hydrolysate concentration of SDFU assisted enzymolysis was higher than traditional enzymolysis at the hydrolysis time of 60min (p<0...
July 2017: Ultrasonics Sonochemistry
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