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# Quantum theory

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#1
Ko Takase, Keiichi Noguchi, Koji Nakano
Chiral spiro polycyclic aromatic compounds with thiophene and/or thiophene S,S-dioxide units were synthesized as a new family of circularly polarized luminescence (CPL) materials. Oxidation of the thiophene unit to its S,S-dioxide provided significant changes in photophysical properties such as much higher fluorescence quantum yield and positive solvatochromism in photoluminescence spectra. Density functional theory calculations qualitatively demonstrated the observed absorption properties. The prepared chiral spiro compounds exhibit intense CPL signals with a relatively large dissymmetry factor for small organic molecules...
September 19, 2017: Organic Letters
#2
Felix A Faber, Luke Hutchison, Bing Huang, Justin Gilmer, Samuel S Schoenholz, George E Dahl, Oriol Vinyals, Steven Kearnes, Patrick F Riley, O Anatole von Lilienfeld
We investigate the impact of choosing regres- sors and molecular representations for the construction of fast machine learning (ML) models of thirteen electronic ground-state properties of organic molecules. The performance of each regressor/representation/property combination is assessed using learning curves which report out- of-sample errors as a function of training set size with up to ∼118k distinct molecules. Molecular structures and properties at hybrid density functional theory (DFT) level of theory come from the QM9 database [Ramakrishnan et al, Scientific Data 1 140022 (2014)] and include enthalpies and free energies of atomization , HOMO/LUMO energies and gap, dipole moment, polarizability, zero point vibrational energy, heat capacity and the highest fundamental vibrational frequency...
September 19, 2017: Journal of Chemical Theory and Computation
#3
Sushil Ranjan Bhatta, Bijan Mondal, Gonela Vijaykumar, Arunabha Thakur
A unique turn-on fluorescent device based on a ferrocene-aminonaphtholate derivative specific for Hg(2+) cation was developed. Upon binding with Hg(2+) ion, the probe shows a dramatic fluorescence enhancement (the fluorescence quantum yield increases 58-fold) along with a large red shift of 68 nm in the emission spectrum. The fluorescence enhancement with a red shift may be ascribed to the combinational effect of C═N isomerization and an extended intramolecular charge transfer (ICT) mechanism. The response was instantaneous with a detection limit of 2...
September 19, 2017: Inorganic Chemistry
#4
William H Sulis
Walter Freeman III pioneered the application of nonlinear dynamical systems theories and methodologies in his work on mesoscopic brain dynamics.Sadly, mainstream psychology and psychiatry still cling to linear correlation based data analysis techniques, which threaten to subvert the process of experimentation and theory building. In order to progress, it is necessary to develop tools capable of managing the stochastic complexity of complex biopsychosocial systems, which includes multilevel feedback relationships, nonlinear interactions, chaotic dynamics and adaptability...
October 2017: Nonlinear Dynamics, Psychology, and Life Sciences
#5
Ewa Pastorczak, Jun Shen, Michal Hapka, Piotr Piecuch, Katarzyna Pernal
Non-covalent interactions between molecules with stretched intramonomer covalent bonds are a fascinating, yet little studied area. This shortage of information stems largely from the inability of most of the commonly used computational quantum chemistry methods to accurately describe weak long-range and strong non-dynamic correlations at the same time. In this work, we propose a geminal-based approach, abbreviated as EERPA-GVB, capable of describing such systems in a robust manner using relatively inexpensive computational steps...
September 18, 2017: Journal of Chemical Theory and Computation
#6
Dimitrios Maganas, Serena DeBeer, Frank Neese
In this work, a new protocol for the calculation of valence-to-core resonant X-ray emission (VtC RXES) spectra is introduced. The approach is based on the previously developed restricted open configuration interaction with singles (ROCIS) method and its parametrized version, based on a ground-state Kohn-Sham determinant (DFT/ROCIS) method. The ROCIS approach has the following features: (1) In the first step approximation, many-particle eigenstates are calculated in which the total spin is retained as a good quantum number...
September 18, 2017: Inorganic Chemistry
#7
REVIEW
Bruno Marchal
After reviewing the basic of theology of Universal Numbers/Machines, as detailed in (Marchal, 2007), I illustrate how that body of thought might be used to shed some light upon the apparent dichotomy in Eastern/Western spirituality. This paper relies entirely on my previous inter-disciplinary work in mathematical logic, computer science and machine's theology, where "theology" is used here in the sense of Plato: it is the truth, or the "truth-theory" (in the sense of logicians) about a machine that the machine can either deduce from some of its primitive beliefs, or can be intuited in some sense that eventually is made clear through the modal logic of machine self-reference...
September 14, 2017: Progress in Biophysics and Molecular Biology
#8
Chuntao Wang, Xiaoxiao Luo, Zehui Jia
The control of linkage and charge state between biomolecules and metals represents a key issue for the architect of bioactive systems. In this paper, the linkage, charge state and layer of L-Cysteine (L-Cys) self-assembled films were handled on copper surfaces at pH=6.86. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed to measure the film quality and the details of self-assembled progress. X-ray photoelectron spectroscopy (XPS) and quantum chemical calculations of density functional theory (DFT) were used to characterize the linkage, charge state and layer of the L-Cys molecules on copper surfaces...
September 7, 2017: Colloids and Surfaces. B, Biointerfaces
#9
Ying Su, Xuejiao Chen, Wenyu Ji, Qinghui Zeng, Zhongyuan Ren, Zisheng Su, Lei Liu
CsPbX3 (X = Cl, Br, I) perovskite quantum dots (PQDs) have been intensively investigated on photoelectric devices due to their superior optical properties. To date, the stability of CsPbX3 PQDs is still an open challenge. The previous mixed-halide CsPbX3 PQDs were generally obtained via the anion-exchange method at 40 °C. Here, the single- and mixed-halide CsPbX3 PQDs are synthesized at high temperature via the hot injection technique. The surface ligands could thus be strongly coordinated onto the surface of the PQDs, which dramatically improve the optical properties of the PQDs...
September 15, 2017: ACS Applied Materials & Interfaces
#10
Francisco Wellery Nunes Silva, Eduardo Cruz-Silva, Mauricio Terrones, Humberto Terrones, E B Barros
Quantum molecular dynamics (QMD) and density functional theory (DFT) are employed in this work in order to study the structural and electronics properties of carbon, Boron Nitride or hybrid BNC nanoshells (BNCNSs). The studied nanoshells can be formed by stacking two zigzag graphene nanoribbons (zGNRs), two zigzag Boron Nitride nanoribbons (zBNNRs) or one zigzag graphene nanoribbon on a Boron Nitride nanoribbon. In all cases only one of the edges of the ribbon is passivated, while the other one is left unpassivated...
September 15, 2017: Nanotechnology
#11
Niclas S Mueller, Sebastian Heeg, Patryk Kusch, Etienne Gaufrès, Nathalie Y-W Tang, Uwe Hübner, Richard Martel, Aravind Vijayaraghavan, Stephanie Reich
We isolated the plasmonic contribution to surface-enhanced Raman scattering (SERS) and found it to be much stronger than expected. Organic dyes encapsulated in single-walled carbon nanotubes are ideal probes for quantifying plasmonic enhancement in a Raman experiment. The molecules are chemically protected through the nanotube wall and spatially isolated from the metal, which prevents enhancement by chemical means and through surface roughness. The tubes carry molecules into SERS hotspots, thereby defining molecular position and making it accessible for structural characterization with atomic-force and electron microscopy...
#12
Tamiru Teshome, Ayan Datta
The electronic structures of novel heterostructures namely graphene-Au van der Waals (vdW) interfaces have been studied using Density Functional Theory. The dispersion-corrected PBE-D2 and PBE-D3 functionals perform well in describing the phonon spectrum and binding energies. Ab-initio molecular dynamics simulations reveal that the van der Waals framework is able to survive large out of plane motions till 1200K. Beyond T = 1200K a transition of the quasiplanar Au into 3D-cluster like structure is observed. Novel dielectric capacitors consisting of two-dimensional, h-BN layers placed between graphene and Au is designed based on such 2D Au-graphene interfaces...
September 15, 2017: ACS Applied Materials & Interfaces
#13
Sitichoke Amnuanpol
Double-stranded DNA (dsDNA) undergoes a structural transition to single-stranded DNA (ssDNA) in many biologically important processes such as replication and transcription. This strand separation arises in response either to thermal fluctuations or to external forces. The roles of ions are twofold, shortening the range of the interstrand potential and renormalizing the DNA elastic modulus. The dsDNA-to-ssDNA transition is studied on the basis that dsDNA is regarded as a bound state while ssDNA is regarded as an unbound state...
September 14, 2017: Journal of Biological Physics
#14
Zhi Gao, Sjoerd N Vogels, Matthieu Besemer, Tijs Karman, Gerrit C Groenenboom, Ad Van der Avoird, Sebastiaan Y T van de Meerakker
We present state-to-state differential cross sections for collisions of NO molecules (X(2)Π1/2, j=1/2f) with para-H2 and ortho-D2 molecules, at a collision energy of 510 and 450 cm(-1), respectively. The angular scattering distributions for various final states of the NO radical are measured with high resolution using a crossed molecular beam apparatus that employs the combination of Stark deceleration and velocity map imaging. Rotational rainbows as well as diffraction oscillations are fully resolved in the scattering images...
September 14, 2017: Journal of Physical Chemistry. A
#15
M Widelicka, K Pogorzelec-Glaser, A Pietraszko, P Ławniczak, R Pankiewicz, A Łapiński
The crystal structure of 1H-pyrazol-2-ium hydrogen oxalate has been studied at 100 K. It consists of two-dimensional layers built with one-dimensional chains that contain pyrazolium and oxalate acids bonded by N-HO and O-HO hydrogen bonds. According to the X-ray data and the Quantum Theory of Atoms in Molecules, it was shown that weak and moderate hydrogen bonds are present in the crystal at room temperature. The thermal stability was studied with the DSC, TGA, and DTG methods: three endothermic peaks are observed at 384, 420, and 469 K...
September 14, 2017: Physical Chemistry Chemical Physics: PCCP
#16
Ramona Kositzki, Stefan Mebs, Nils Schuth, Nils Leidel, Lennart Schwartz, Michael Karnahl, Florian Wittkamp, Daniel Daunke, Andreas Grohmann, Ulf-Peter Apfel, Frédéric Gloaguen, Sascha Ott, Michael Haumann
Synthetic diiron compounds of the general formula Fe2(μ-S2R)(CO)n(L)6-n (R = alkyl or aromatic groups; L = CN(-) or phosphines) are versatile models for the active-site cofactor of hydrogen turnover in [FeFe]-hydrogenases. A series of 18 diiron compounds, containing mostly a dithiolate bridge and terminal ligands of increasing complexity, was characterized by X-ray absorption and emission spectroscopy in combination with density functional theory. Fe K-edge absorption and Kβ main-line emission spectra revealed the varying geometry and the low-spin state of the Fe(i) centers...
September 14, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
#17
Weilin Du, Lei Liao, Li Yang, Aimiao Qin, Aihui Liang
Stable water-soluble copper sulfide(Cu2S) quantum dots(QDs) with near-infrared emission were synthesized using N-acetyl-L-cysteine(NAC) as a modifier in aqueous solution and nitrogen atmosphere at room temperature. The product was characterized by TEM, XRD, XPS, FT-IR, FL and UV-VIS spectrometers. Effects of preparation conditions such as pH values, the molar ratio of reactants, temperature, and metal ions on the fluorescence properties of Cu2S QDs were discussed. Under optimal conditions, the prepared Cu2S QDs with average diameter about 2-5 nm show a near-infrared emission at 770 nm with the excitation wavelength of 466 nm, and have a good detection sensitivity for ions of Hg(2+), Ag(+) and Au(3+), based on the characteristic of fluorescence quenching...
September 13, 2017: Scientific Reports
#18
Ya-Jie Wu, Ning Li, Jing He, Su-Peng Kou
In this paper, we present a study on the repulsive Haldane-Hubbard model with spin-rotation symmetry in square lattices by deriving non-linear $\sigma$ model for magnetic states. It is found that a chiral spin liquid state as the ground state of the correlated system exists in the $\mathcal{C}=2$ topological spin-density wave proposed by Y.-J. Wu \textit{et al.} [J. Phys.: Condens. Matter \textbf{28}, 115602 (2016)], of which the low energy physics can be determined by the Chern-Simons-Hopf gauge field theory...
September 13, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
#19
B G de Sousa, J I N Oliveira, E L Albuquerque, U L Fulco, V E Amaro, C A G Blaha
Many species of bacteria involved in degradation of n-alkanes have an important constitutional metabolic enzyme, the alkane hydroxylase called AlkB, specialized in the conversion of hydrocarbons molecules that can be used as carbon and/or energy source. This enzyme plays an important role in the microbial degradation of oil, chlorinated hydrocarbons, fuel additives, and many other compounds. A number of these enzymes has been biochemically characterized in detail because the potential of alkane hydroxylases to catalyse high added-value reactions is widely recognized...
September 1, 2017: Journal of Molecular Graphics & Modelling
#20
Raghavender Medishetty, Lydia Nemec, Venkatram Nalla, Sebastian Henke, Marek Samoc, Karsten Reuter, Roland A Fischer
Multi-photon absorption (MPA) is among the most prominent nonlinear optical (NLO) effects and has applications, for example in telecommunications, defense, photonics and bio-medicines. Established MPA materials include dyes, quantum dots, organometallics and conjugated polymers, most often dispersed in solution. We demonstrate how metal-organic frameworks (MOFs), a novel NLO solid-state materials class, can be designed for exceptionally strong MPA behavior. MOFs consisting of zirconium- and hafnium-oxo-clusters and featuring a chromophore linker based on the tetraphenylethene (TPE) molecule exhibit record high two-photon absorption (2PA) cross section values, up to 3600 GM...
September 12, 2017: Angewandte Chemie
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