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https://www.readbyqxmd.com/read/28346740/are-various-sigma-hole-bonds-steered-by-the-same-mechanisms
#1
Slawomir Janusz Grabowski, W Andrzej Sokalski
Representative Lewis acid - Lewis base complexes linked by tetrel, pnicogen, chalcogen and halogen bonds have been studied within the Quantum Theory of Atoms in Molecules (QTAIM) approach and the Hybrid Variation-Perturbation Theory (HVPT) in order to analyse possible relationships between these sigma-hole dimers. Results obtained at the MP2/aug-cc-pVTZ level indicate numerous correlations similar to hydrogen bonded systems.
March 27, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28345728/embedding-1d-or-2d-cobalt-carboxylate-substrates-in-3d-coordination-polymers-exhibiting-slow-magnetic-relaxation-behaviors-crystal-structures-high-field-epr-and-magnetic-studies
#2
Nannan Mao, Biquan Zhang, Fan Yu, Xi Chen, Gui-Lin Zhuang, Zhenxing Wang, Zhongwen Ouyang, Tianle Zhang, Bao Li
By utilizing well-designed bifunctional ligands derived from 1H-imidazole-4,5-dicarboxylic acid, magnetic coordination polymers (CPs) that exhibit slow magnetic relaxation at the low temperature regions were constructed and further structurally characterized. In 1, 1D cobalt-carboxyl chains were stabilized in the final structure. In contrast, by adjusting the length of the substituted arms on imidazole-4,5-dicarboxylic acid, a novel 3D CP, 2 containing 2D 6(3) cobalt-carboxyl layer was obtained. A combination of Quantum Monte Carlo (QMC) simulations and the first-principles Density functional theory (DFT) calculations showed that compound 2 features weak ferro- and antiferro-magnetic coupling mechanisms with two different super-exchange paths of -/+/- for syn-anti carboxylate bridges and -/-/- for syn-syn carboxylate bridges...
March 27, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28344506/characteristics-of-the-new-phase-in-cdt
#3
J Ambjørn, J Gizbert-Studnicki, A Görlich, J Jurkiewicz, N Klitgaard, R Loll
The approach of Causal Dynamical Triangulations (CDT), a candidate theory of nonperturbative quantum gravity in 4D, turns out to have a rich phase structure. We investigate the recently discovered bifurcation phase [Formula: see text] and relate some of its characteristics to the presence of singular vertices of very high order. The transition lines separating this phase from the "time-collapsed" B-phase and the de Sitter phase [Formula: see text] are of great interest when searching for physical scaling limits...
2017: European Physical Journal. C, Particles and Fields
https://www.readbyqxmd.com/read/28342373/using-quantum-chemical-modeling-and-calculations-for-evaluation-of-cellulose-potential-for-estrogen-micropollutants-removal-from-water-effluents
#4
Amin Ghasemi, Milad Asgarpour Khansary, Azam Marjani, Saeed Shirazian
This paper is devoted to investigate the suitability of cellulose for estrogens micropollutants removal from water effluent. For this purpose, the sorption of eight estrogens including Estradiol, Estrone, Testosterone, Progesterone, Estriol, Mestranol, Ethinylestradiol and Diethylstilbestrol were investigated. The charge density profiles and sorption curves were obtained and discussed using quantum chemical calculations where the Accelrys Materials Studio software and COSMO-SAC model were employed. The geometry optimization of compound molecule and energy minimizations was performed using the Dmol3 Module and density functional theory of generalized gradient approximate and Volsko-Wilk-Nusair functional...
March 3, 2017: Chemosphere
https://www.readbyqxmd.com/read/28342352/mechanochemical-mechanism-of-rapid-dechlorination-of-hexachlorobenzene
#5
Shanshan Deng, Shaoguo Kang, Nannan Feng, Jianxin Zhu, Bo Yu, Xiaofeng Xie, Jing Chen
Recent researches indicate that mechanochemical treatment (MCT) is a promising method to degrade the environmental hazards, especially in the area of persistent organic pollutants (POPs) disposal. However, the mechanochemical dechlorination mechanism of POPs still needs to be further verified. In this mechanochemical process, hexachlorobenzene (HCB) was chosen as a model pollutant with aluminum and alumina (Al+Al2O3) powders as the co-milling regents. Both of the intermediate analysis and quantum chemical calculations were adopted to elucidate the free radical dechlorination mechanism of HCB...
March 12, 2017: Journal of Hazardous Materials
https://www.readbyqxmd.com/read/28339250/de-sitter-space-as-a-resonance
#6
Jonathan Maltz, Leonard Susskind
A quantum mechanical formulation of de Sitter cosmological spacetimes still eludes string theory. In this Letter we conjecture a potentially rigorous framework in which the status of de Sitter space is the same as that of a resonance in a scattering process. We conjecture that transition amplitudes between certain states with asymptotically supersymmetric flat vacua contain resonant pole characteristic metastable intermediate states. A calculation employing constrained instantons illustrates this idea.
March 10, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28339222/holographic-duals-for-five-dimensional-superconformal-quantum-field-theories
#7
Eric D'Hoker, Michael Gutperle, Christoph F Uhlemann
We construct global solutions to type IIB supergravity with 16 residual supersymmetries whose space-time is AdS_{6}×S^{2} warped over a Riemann surface. Families of solutions are labeled by an arbitrary number L≥3 of asymptotic regions, in each of which the supergravity fields match those of a (p,q) five-brane, and may therefore be viewed as near-horizon limits of fully localized intersections of five-branes in type IIB string theory. These solutions provide compelling candidates for holographic duals to a large class of five-dimensional superconformal quantum field theories which arise as nontrivial UV fixed points of perturbatively nonrenormalizable Yang-Mills theories, thereby making them more directly accessible to quantitative analysis...
March 10, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28338625/-r-aloesaponol-iii-8-methyl-ether-from-eremurus-persicus-a-novel-compound-against-leishmaniosis
#8
Daniela Rossi, Karzan Mahmood Ahmed, Raffaella Gaggeri, Serena Della Volpe, Lauretta Maggi, Giuseppe Mazzeo, Giovanna Longhi, Sergio Abbate, Federica Corana, Emanuela Martino, Marisa Machado, Raquel Varandas, Maria do Céu Sousa, Simona Collina
Leishmaniosis is a neglected tropical disease which affects several millions of people worldwide. The current drug therapies are expensive and often lack efficacy, mainly due to the development of parasite resistance. Hence, there is an urgent need for new drugs effective against Leishmania infections. As a part of our ongoing study on the phytochemical characterization and biological investigation of plants used in the traditional medicine of western and central Asia, in the present study, we focused on Eremurus persicus root extract in order to evaluate its potential in the treatment of leishmaniosis...
March 24, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28338329/evidence-for-electron-hole-pair-excitation-in-the-associative-desorption-of-h2-and-d2-from-au-111
#9
Quan Shuai, Sven Kaufmann, Daniel J Auerbach, Dirk Schwarzer, Alec M Wodtke
The dissociative adsorption reaction of hydrogen on noble metals is believed to be well-described within the Born-Oppenheimer approximation. In this work, we have experimentally derived translational energy distributions for selected quantum states of H2 and D2 formed in associative desorption reactions at a Au(111) surface. Using the principle of detailed balance, we compare our results to theory carried out at the same level of sophistication as was done for the reaction on copper. The theory predicts translational excitation that is much higher than is seen in experiment and fails to reproduce the experimentally observed isotope effect...
March 27, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28334526/an-unusual-non-emissive-behavior-of-rubrene-j-aggregates-a-rare-violation
#10
Nikhil Aggarwal, Archita Patnaik
Structure - property correlations in Rubrene (RB) colloidal J-aggregates were unravelled by steady state and time resolved spectroscopy in conjunction with excited state density functional calculations. The RB J-aggregate with a slippage angle θ = 30.4(0), estimated from the monomeric transition dipole moment directions, exhibited a broad FWHM of 1073 cm(-1) and a 5 nm red shifted absorption band carrying a transition dipole moment (M ⃗_(λagg )= 1.80 D) almost equivalent to the monomeric dye (M ⃗_(λmon )=1...
March 23, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28333163/universality-of-schmidt-decomposition-and-particle-identity
#11
Stefania Sciara, Rosario Lo Franco, Giuseppe Compagno
Schmidt decomposition is a widely employed tool of quantum theory which plays a key role for distinguishable particles in scenarios such as entanglement characterization, theory of measurement and state purification. Yet, its formulation for identical particles remains controversial, jeopardizing its application to analyze general many-body quantum systems. Here we prove, using a newly developed approach, a universal Schmidt decomposition which allows faithful quantification of the physical entanglement due to the identity of particles...
March 23, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28330413/molecular-dynamic-simulation-and-dft-study-on-the-drug-dna-interaction-crocetin-as-an-anticancer-and-dna-nanostructure-model
#12
Ebrahim Azarhazin, Mohammad Izadyar, Mohammad Reza Housaindokht
In this research, the interaction of Crocetin as an anticancer drug and a Dickerson DNA has been investigated. 25 ns molecular dynamic simulations of Crocetin and DNA composed of twelve base pairs and a sequence of d(CGCGAATTCGCG)2 were done in water. Three definite parts of the B-DNA were considered in analyzing the best interactive site from the thermodynamic point of view. Binding energy analysis showed that van der Waals interaction is the most important part related to the reciprocal O and H atoms of the Crocetin and DNA...
March 22, 2017: Journal of Biomolecular Structure & Dynamics
https://www.readbyqxmd.com/read/28330356/grand-canonical-electronic-density-functional-theory-algorithms-and-applications-to-electrochemistry
#13
Ravishankar Sundararaman, William A Goddard, Tomas A Arias
First-principles calculations combining density-functional theory and continuum solvation models enable realistic theoretical modeling and design of electrochemical systems. When a reaction proceeds in such systems, the number of electrons in the portion of the system treated quantum mechanically changes continuously, with a balancing charge appearing in the continuum electrolyte. A grand-canonical ensemble of electrons at a chemical potential set by the electrode potential is therefore the ideal description of such systems that directly mimics the experimental condition...
March 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28330340/cooperative-enhancement-of-the-nonlinear-optical-response-in-conjugated-energetic-materials-a-td-dft-study
#14
Andrew E Sifain, Loza F Tadesse, Josiah A Bjorgaard, David E Chavez, Oleg V Prezhdo, R Jason Scharff, Sergei Tretiak
Conjugated energetic molecules (CEMs) are a class of explosives with high nitrogen content that posses both enhanced safety and energetic performance properties and are ideal for direct optical initiation. As isolated molecules, they absorb within the range of conventional lasers. Crystalline CEMs are used in practice, however, and their properties can differ due to intermolecular interaction. Herein, time-dependent density functional theory was used to investigate one-photon absorption (OPA) and two-photon absorption (TPA) of monomers and dimers obtained from experimentally determined crystal structures of CEMs...
March 21, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28327567/quantum-locality-in-game-strategy
#15
Carlos A Melo-Luna, Cristian E Susa, Andrés F Ducuara, Astrid Barreiro, John H Reina
Game theory is a well established branch of mathematics whose formalism has a vast range of applications from the social sciences, biology, to economics. Motivated by quantum information science, there has been a leap in the formulation of novel game strategies that lead to new (quantum Nash) equilibrium points whereby players in some classical games are always outperformed if sharing and processing joint information ruled by the laws of quantum physics is allowed. We show that, for a bipartite non zero-sum game, input local quantum correlations, and separable states in particular, suffice to achieve an advantage over any strategy that uses classical resources, thus dispensing with quantum nonlocality, entanglement, or even discord between the players' input states...
March 22, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28327381/the-enhancing-effect-of-a-cation-%C3%AF-interaction-on-the-cooperativity-of-halogen-bonds-a-computational-study
#16
Mehdi D Esrafili, Soheila Asadollahi
In this work, we investigate the effect of a cation-π interaction on the cooperativity of X⋯N halogen bonds in PhX⋯NCX⋯NH3 complexes, where Ph=phenyl and X=Cl, Br, I. Molecular geometries and interaction energies of the resulting complexes are studied at the MP2/aug-cc-pVDZ(-PP) computational level. The mechanism of the cooperativity between halogen bonds is analyzed using parameters derived from the noncovalent index, quantum theory of atoms in molecules and natural bond orbital methodologies. It is found that the divalent cations (Be(2+), Mg(2+)) have a larger influence on the cooperativity of halogen bonds than monovalent ones (Li(+), Na(+))...
March 2, 2017: Journal of Molecular Graphics & Modelling
https://www.readbyqxmd.com/read/28326054/dynamical-constants-and-time-universals-a-first-step-toward-a-metrical-definition-of-ordered-and-abnormal-cognition
#17
REVIEW
Mark A Elliott, Naomi du Bois
From the point of view of the cognitive dynamicist the organization of brain circuitry into assemblies defined by their synchrony at particular (and precise) oscillation frequencies is important for the correct correlation of all independent cortical responses to the different aspects of a given complex thought or object. From the point of view of anyone operating complex mechanical systems, i.e., those comprising independent components that are required to interact precisely in time, it follows that the precise timing of such a system is essential - not only essential but measurable, and scalable...
2017: Frontiers in Psychology
https://www.readbyqxmd.com/read/28325048/photoinduced-single-and-multiple-electron-dynamics-processes-enhanced-by-quantum-confinement-in-lead-halide-perovskite-quantum-dots
#18
Dayton Jon Vogel, Andrei Kryjevski, Talgat M Inerbaev, Dmitri S Kilin
Methyl-ammonium lead iodide perovskite (MAPbI3) is a promising material for photovoltaic devices. A modification of the MAPbI3 into confined nanostructures is expected to further increase efficiency of solar energy conversion. Photo-excited dynamic processes in a MAPbI3 quantum dot (QD) have been modeled by many-body perturbation theory and nonadiabatic dynamics. A photoexcitation is followed by either exciton cooling (EC), its radiative (RR) or non-radiative recombination (NRR), or multi-exciton generation (MEG) processes...
March 21, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28321655/quantum-chemical-nmr-ft-ir-and-esi-ms-studies-of-complexes-of-colchicine-with-zn-ii
#19
Wojciech Jankowski, Joanna Kurek, Piotr Barczyński, Marcin Hoffmann
Colchicine is a tropolone alkaloid from Colchicinum autumnale. It shows antifibrotic, antimitotic, and anti-inflammatory activities, and is used to treat gout and Mediterranean fever. In this work, complexes of colchicine with zinc(II) nitrate were synthesized and investigated using DFT, (1)H and (13)C NMR, FT IR, and ESI MS. The counterpoise-corrected and uncorrected interaction energies of these complexes were calculated. We also calculated their (1)H, (13)C NMR, and IR spectra and compared them with the corresponding experimentally obtained data...
April 2017: Journal of Molecular Modeling
https://www.readbyqxmd.com/read/28320909/theoretical-and-computational-studies-of-non-equilibrium-and-non-statistical-dynamics-in-the-gas-phase-in-the-condensed-phase-and-at-interfaces
#20
Riccardo Spezia, Emilio Martínez-Nuñez, Saulo Vazquez, William L Hase
In this Introduction, we show the basic problems of non-statistical and non-equilibrium phenomena related to the papers collected in this themed issue. Over the past few years, significant advances in both computing power and development of theories have allowed the study of larger systems, increasing the time length of simulations and improving the quality of potential energy surfaces. In particular, the possibility of using quantum chemistry to calculate energies and forces 'on the fly' has paved the way to directly study chemical reactions...
April 28, 2017: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
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