Read by QxMD icon Read

Quantum theory

Danillo Valverde, Zélia Maria da Costa Ludwig, Célia Regina da Costa, Valdemir Ludwig, Herbert C Georg
At physiological conditions, myriads of biomolecules (e.g., amino acids, peptides, and proteins) exist predominantly in the zwitterionic structural form and their biological functions will result in these conditions. However these geometrical structures are inaccessible energetically in the gas phase, and at this point, stabilization of amino-acids in physiological conditions is still under debate. In this paper, the electronic properties of a glycine molecule in the liquid environment were studied by performing a relaxation of the glycine geometry in liquid water using the free energy gradient method combined with a sequential quantum mechanics/molecular mechanics approach...
January 14, 2018: Journal of Chemical Physics
Hong-Hao Tu
We show that rational conformal field theories in 1+1 dimensions on a Klein bottle, with a length L and width β, satisfying L≫β, have a universal entropy. This universal entropy depends on the quantum dimensions of the primary fields and can be accurately extracted by taking a proper ratio between the Klein bottle and torus partition functions, enabling the characterization of conformal critical theories. The result is checked against exact calculations in quantum spin-1/2 XY and Ising chains.
December 29, 2017: Physical Review Letters
Tao Liu, Alexander A Penin
We study the high-energy fixed-angle Sudakov limit of the scattering amplitudes suppressed by the leading power of the quark mass in perturbative quantum chromodynamics. We prove the factorization and perform all-order resummation of the double-logarithmic radiative corrections which determine the asymptotic behavior of the amplitudes. In contrast to the Sudakov logarithms, the mass-suppressed double-logarithmic corrections are induced by soft quark exchange. The structure of the corrections and the asymptotic behavior of the amplitudes in this case crucially depend on the color flow in a given process and are determined by the eikonal color charge nonconservation...
December 29, 2017: Physical Review Letters
Tong Li, Jian-Guo Zhang
Metal hydrazineboranes (MHBs), as a kind of new hydrogen storage materials, show the excellent hydrogen storage per-formance and the dehydrogenation property. Herein, we designed multiple dehydrogenation pathways to compare with each other and indicated the metal-controlled effect. Quantum chemistry theory is used to calculate the crystal structure for determining the molecular structure. With the increasing of the metal radius, the energy difference of the isomers also increases. The dehydrogenation pathways of Lithium hydrazineborane (PathA) and Sodium hydrazineborane (PathB) show the totally similar to each other in the dehydrogenation process despite the energy barrier, as well as the comparison Path of A' (for LiHB) and B' (for NaHB)...
January 11, 2018: Journal of Physical Chemistry. A
Chen Chen, Le Fang, Jihua Zhang, Guodong Zhao, Wei Ren
We explored the possibility of increasing the interfacial carrier quantum confinement, mobility and conductivity in the (LaAlO3)n/(BaTiO3)n superlattices by thickness regulation using the first-principles electronic structure calculations. Through constructing two different interfacial types of LaAlO3/BaTiO3 superlattices, we discovered that the LaO/TiO2 interface is preferred from cleavage energy consideration. We then studied the electronic characteristics of two-dimensional electron gas (2DEG) produced at the LaO/TiO2 interface in the LaAlO3/BaTiO3 superlattices via spin-polarized density functional theory calculations...
January 11, 2018: Scientific Reports
K V Shulga, E Il'ichev, M V Fistul, I S Besedin, S Butz, O V Astafiev, U Hübner, A V Ustinov
Quantum theory is expected to govern the electromagnetic properties of a quantum metamaterial, an artificially fabricated medium composed of many quantum objects acting as artificial atoms. Propagation of electromagnetic waves through such a medium is accompanied by excitations of intrinsic quantum transitions within individual meta-atoms and modes corresponding to the interactions between them. Here we demonstrate an experiment in which an array of double-loop type superconducting flux qubits is embedded into a microwave transmission line...
January 11, 2018: Nature Communications
Chaoyu Song, Feng-Ren Fan, Ningning Xuan, Shenyang Huang, Guowei Zhang, Chong Wang, Zhengzong Sun, Hua Wu, Hugen Yan
Due to the strong quantum confinement effect, few-layer γ-InSe exhibits a layer-dependent bandgap, spanning the visible and near infrared regions, and thus recently draws tremendous attention. As a two-dimensional material, the mechanical flexibility provides an additional tuning knob for the electronic structures. Here, for the first time, we engineer the band structures of few-layer and bulk-like InSe by uniaxial tensile strain, and observe salient shift of photoluminescence (PL) peaks. The shift rate of the optical gap is approximately 90-100 meV per 1% strain for 4- to 8-layer samples, which is much larger than that for the widely studied MoS2 monolayer...
January 11, 2018: ACS Applied Materials & Interfaces
Jan P Unsleber, Thomas Dresselhaus, Kevin Klahr, David Schnieders, Michael Böckers, Dennis Barton, Johannes Neugebauer
We present the new quantum chemistry program Serenity. It implements a wide variety of functionalities with a focus on subsystem methodology. The modular code structure in combination with publicly available external tools and particular design concepts ensures extensibility and robustness with a focus on the needs of a subsystem program. Several important features of the program are exemplified with sample calculations with subsystem density-functional theory, potential reconstruction techniques, a projection-based embedding approach and combinations thereof with geometry optimization, semi-numerical frequency calculations and linear-response time-dependent density-functional theory...
January 10, 2018: Journal of Computational Chemistry
Haiqing Zhao, Chang-Shui Yu
Coherence is the most fundamental quantum feature of the nonclassical systems. The understanding of coherence within the resource theory has been attracting increasing interest among which the quantification of coherence is an essential ingredient. A satisfactory measure should meet certain standard criteria. It seems that the most crucial criterion should be the strong monotonicity, that is, average coherence doesn't increase under the (sub-selective) incoherent operations. Recently, the Tsallis relative α entropy has been tried to quantify the coherence...
January 10, 2018: Scientific Reports
André Kristopher Eckhardt, Dennis Gerbig, Peter R Schreiner
Although frequently employed, heavy atom kinetic isotope effects (KIE) have not been reported for quantum mechanical tunneling reactions. Here we examine the secondary KIE through 13C substitution of the carbene atom in methylhydroxycarbene (H3C-C̈-OH) in its [1,2]H tunneling shift reaction to acetaldehyde (H3C-CHO). Our study employs matrix isolation IR spectroscopy in various inert gases and quantum chemical computations. Depending on the choice of the matrix host gas the KIE varies within a range of 1.0 in xenon and 1...
January 10, 2018: Journal of Physical Chemistry. A
Ashlesha Patil, Dipankar Saha, Swaroop Ganguly
We propose a technologically feasible one-dimensional double barrier resonant tunneling diode (RTD) as electronic nose, inspired by the vibration theory of biological olfaction. The working principle is phonon-assisted inelastic electron tunneling spectroscopy (IETS), modeled here using the Non-Equilibrium Green Function formalism for quantum transport. While standard IETS requires low-temperature operation to obviate the thermal broadening of spectroscopic peaks, we show that quantum confinement in the well of the RTD provides electron energy filtering in this case and could thereby allow room-temperature operation...
January 9, 2018: Scientific Reports
Daniel Moreno, Maria Gonzalez-Miquel, Victor R Ferro, Jose Palomar
Zwitterions ionic liquids (ZIs) are compounds in which both counterions are covalently tethered, conferring them with unique characteristics; however, most of their properties are still unknown, remaining a bottleneck to exploit practical applications. Herein, molecular and fluid properties of ZIs and their mixtures are explored by means of quantum chemical analysis based on density functional theory (DFT) and COSMO-RS method, and compared against homologous ILs, to provide a comprehensive overview on the effect of the distinct structures on their physicochemical and thermodynamic behavior...
January 7, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
James S M Anderson, Paul W Ayers
Generalizing our recent work on relativistic generalizations of the quantum theory of atoms in molecules, we present the general setting under which the principle of stationary action for a region leads to open quantum subsystems. The approach presented here is general and works for any Hamiltonian, and when a reasonable Lagrangian is selected, it often leads to the integral of the Laplacian of the electron density on the region vanishing as a necessary condition for the zero-flux surface. Alternatively, with this method, one can design a Lagrangian that leads to a surface of interest (though this Lagrangian may not be, and indeed probably will not be, "reasonable")...
January 9, 2018: Journal of Computational Chemistry
Stefan Gullatz, Matthew Gildersleeve
Jung's paper 'Synchronicity - an acausal connecting principle', defining the phenomenon as a 'meaningful' coincidence depending on archetypal activation, was published in 1952, together with a conceptually related piece by physicist and Nobel Laureate Wolfgang Pauli entitled, 'The influence of archetypal ideas on the scientific theories of Kepler'. Slavoj Žižek, in The Indivisible Remainder: On Schelling and Related Matters, suggests that, in contrast to any notion of a 'pre-modern Jungian harmony', the main lesson of quantum physics was that not only was the psychoanalytic, empty subject of the signifier constitutively out-of-joint with respect to the world, but that the Real in itself was already incomplete, out-of-joint, 'not-all'...
February 2018: Journal of Analytical Psychology
Sławomir J Grabowski
MP2/aug-cc-pVTZ calculations were performed for complexes linked by hydrogen bonds. Three types of proton donating species were taken into account: H2O, CCl3H, and H3O+. These calculations are supported by the natural bond orbital (NBO) method and the quantum theory of atoms in molecules (QTAIM) approach. Numerous correlations between parameters of H-bonded systems were found. The most important are those which show the response of the system on the H-bond formation; for example, the increase of polarization of the A-H bond correlates with the strength of the hydrogen bond...
January 8, 2018: Journal of Molecular Modeling
Jacob Shamblin, Maximilian Heres, Haidong Zhou, Joshua Sangoro, Maik Lang, Joerg Neuefeind, J A Alonso, Steven Johnston
Many-body effects produce deviations from the predictions of conventional band theory in quantum materials, leading to strongly correlated phases with insulating or bad metallic behavior. One example is the rare-earth nickelates RNiO3, which undergo metal-to-insulator transitions (MITs) whose origin is debated. Here, we combine total neutron scattering and broadband dielectric spectroscopy experiments to study and compare carrier dynamics and local crystal structure in LaNiO3 and NdNiO3. We find that the local crystal structure of both materials is distorted in the metallic phase, with slow, thermally activated carrier dynamics at high temperature...
January 8, 2018: Nature Communications
Geng Chen, Nati Aharon, Yong-Nan Sun, Zi-Huai Zhang, Wen-Hao Zhang, De-Yong He, Jian-Shun Tang, Xiao-Ye Xu, Yaron Kedem, Chuan-Feng Li, Guang-Can Guo
Improving the precision of measurements is a significant scientific challenge. Previous works suggest that in a photon-coupling scenario the quantum fisher information shows a quantum-enhanced scaling of N2, which in theory allows a better-than-classical scaling in practical measurements. In this work, utilizing mixed states with a large uncertainty and a post-selection of an additional pure system, we present a scheme to extract this amount of quantum fisher information and experimentally attain a practical Heisenberg scaling...
January 8, 2018: Nature Communications
Alexander Kandratsenka, Hongyan Jiang, Yvonne Dorenkamp, Svenja M Janke, Marvin Kammler, Alec M Wodtke, Oliver Bünermann
The Born-Oppenheimer approximation (BOA) provides the foundation for virtually all computational studies of chemical binding and reactivity, and it is the justification for the widely used "balls and springs" picture of molecules. The BOA assumes that nuclei effectively stand still on the timescale of electronic motion, due to their large masses relative to electrons. This implies electrons never change their energy quantum state. When molecules react, atoms must move, meaning that electrons may become excited in violation of the BOA...
January 8, 2018: Proceedings of the National Academy of Sciences of the United States of America
Vladimir A Gritsenko, Timofey V Perevalov, Vitaliy A Voronkovskii, Andrei A Gismatulin, Vladimir N Kruchinin, Vladimir Sh Aliev, Vladimir A Pustovarov, Igor P Prosvirin, Yakov Roizin
Optical and transport properties of nonstoichiometric tantalum oxide thin films grown by ion beam sputtering were investigated in order to understand the dominant charge transport mechanisms and reveal the nature of traps. The TaOx films content was analyzed by X-ray photoelectron spectroscopy and by quantum-chemistry simulation. From the optical absorption and photoluminescence measurements and density functional theory simulations, it was concluded that the 2.75 eV blue luminescence excited in a TaOx by 4...
January 8, 2018: ACS Applied Materials & Interfaces
M S A Abdel-Mottaleb, M Saif, M S Attia, M M Abo-Aly, Sarah N Mobarez
A number of novel lanthanide (Gd3+, Sm3+, and Tb3+) complexes of the 1',3'-dihydro-8-methoxy-1',3',3'-trimethyl-6-nitrospiro[2H-1-benzopyran-2,2'-(2H)-indole] (spiropyran; SP), a widely studied molecular photoswitch, were investigated. Comparative spectroscopic (absorption and fluorescence) and kinetic investigations of the stimulated photochromic and solvatochromic behavior were carried out in different media. SP embedded in a rigid thin film of poly(methylmethacrylate) might be exploited profitably as an optical sensor for the identification of a solvent's nature...
January 8, 2018: Photochemical & Photobiological Sciences
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"