INDO-SCPT calculations of the solvent dependence of some carbon-proton spin-spin coupling constants

Summary A theoretical study of the effects of non-specific solute-solvent interactions on the directly bonded carbon-proton couplings¹ J(C–H), in acetaldehyde, acetone and acrylonitrile is presented. The solvent induced changes in these couplings calculated by an INDO-SCPT procedure incorporating a modified solvaton model are in satisfactory agreement with experiment and show significant improvement over the INDO-FPT calculations using the Klopman-Germer solvaton model.

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INDO-SCPT-Rechnungen der Lösungsmittelabhängigkeit einiger C-H-Kopplungskonstanten

Zusammenfassung Es wird eine theoretische Studie zu den nichtspezifischen Lösungsmittelwechselwirkungen auf die Spin-Spin-Kopplungen direkt aneinander gebundener C- und H-Atome von Acetaldehyd, Aceton und Acrylnitril vorgestellt. Die vom Solvens induzierten Änderungen der Kopplungskonstanten werden von der INDO-SCPT-Methode unter Verwendung eines modifizierten Solvationsmodells zufriedenstellend wiedergegeben. Die Übereinstimmung mit den experimentellen Daten ist besser als INDO-FPT-Rechnungen mit dem Klopmann-Germer-Solvaton-Modell.

     

1H,13C and19FNMR studies on the structure of the intramolecularly hydrogen bondedcis-enols of 2-trifluoroacetylcycloalkanones

Summary The¹H,¹³C and¹⁹F NMR spectra of some 2-trifluoroacetylcycloalkanones comprising five-, six-, seven-, and eight-membered ring systems have been studied. These systems have been shown by¹⁹F NMR spectroscopy to be over 90% enolized. The effects of ring size on the¹H,¹³C and¹⁹F chemical shifts and¹³C-¹⁹F coupling constants are discussed. The direction of enolization in these systems was investigated by¹H,¹³C and¹⁹F NMR spectroscopy and evidences were presented in favour of a dominant exocyclic enol form in the five- and an endocyclic enol form in the six-, seven- and eight-membered ring systems.

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¹H-,¹³C- und¹⁹F-NMR-Untersuchungen zur Struktur der intramolekularen Wasserstoffbindung in dencis-Enolen von 2-Trifluoracetylcycloalkanonen

Zusammenfassung Die¹H-,¹³C- und¹⁹F-NMR-Spektren einiger 2-Trifluoracetylcycloalkanone mit fünf-, sechs-, sieben- und achtgliedrigen Ringsystemen wurden untersucht. Mittels¹⁹F-NMR konnte über 90% Enolisierung nachgewiesen werden. Der Effekt der Ringgröße auf die chemischen Verschiebungen in den¹H-,¹³C- und¹⁹F-NMR-Spektren und auf die¹³C-¹⁹F-Kopplungskonstanten werden diskutiert. Die Enolisierungsrichtung dieser Systeme wurde unter Einsatz der NMR-Spektren untersucht: dabei ergab sich eine dominierende exocyclische Enolform für die Fünfringe und eine endocyclische Enolform für die sechs-, sieben- und achtgliedrigen Ringe.

     

Quantum algorithm for obtaining the energy spectrum of molecular systems

Simulating a quantum system is more efficient on a quantum computer than on a classical computer. The time required for solving the Schr?dinger equation to obtain molecular energies has been demonstrated to scale polynomially with system size on a quantum computer, in contrast to the well-known result of exponential scaling on a classical computer. In this paper, we present a quantum algorithm to obtain the energy spectrum of molecular systems based on the multiconfigurational self-consistent field (MCSCF) wave function. By using a MCSCF wave function as the initial guess, the excited states are accessible. Entire potential energy surfaces of molecules can be studied more efficiently than if the simpler Hartree-Fock guess was employed. We show that a small increase of the MCSCF space can dramatically increase the success probability of the quantum algorithm, even in regions of the potential energy surface that are far from the equilibrium geometry. For the treatment of larger systems, a multi-reference configuration interaction approach is suggested. We demonstrate that such an algorithm can be used to obtain the energy spectrum of the water molecule.     

Multi-scroll and multi-wing chaotic attractor generated with Julia process fractal

This paper proposes a general multi-scrolls and multi-wings attractor systems while combining in one hand, Julia’s process with Lorenz’s attractor and in another hand Julia’s process with two coupled Lorenz systems. We have also studied the combination of Julia’s process with the chaotic attractor system proposed in [1].     

Decay rates at low and high frequencies for a plate equation with feedback concentrated in interior curves

In this paper we study the stabilization of plate vibrations by means of piezoelectric actuators. In this situation the geometric control condition of Bardos, Lebeau and Rauch [6] is not satisfied. We prove that we have exponential stability for the low frequencies but not for the high frequencies. We give an explicit decay rate for regular initial data at high frequencies while clarifying the behavior of the constant which intervenes in this estimation there function of the frequency of cut n. The method used is based on some trace regularity which reduces stability to some observability inequalities for the corresponding undamped problem. Moreover, we show numerically at low frequencies, that the optimal location of the actuator is the center of the domain Ω.     

Decomposition of unitary matrices for finding quantum circuits: application to molecular Hamiltonians

Constructing appropriate unitary matrix operators for new quantum algorithms and finding the minimum cost gate sequences for the implementation of these unitary operators is of fundamental importance in the field of quantum information and quantum computation. Evolution of quantum circuits faces two major challenges: complex and huge search space and the high costs of simulating quantum circuits on classical computers. Here, we use the group leaders optimization algorithm to decompose a given unitary matrix into a proper-minimum cost quantum gate sequence. We test the method on the known decompositions of Toffoli gate, the amplification step of the Grover search algorithm, the quantum Fourier transform, and the sender part of the quantum teleportation. Using this procedure, we present the circuit designs for the simulation of the unitary propagators of the Hamiltonians for the hydrogen and the water molecules. The approach is general and can be applied to generate the sequence of quantum gates for larger molecular systems.     

The two-machine flowshop scheduling problem with sequence-independent setup times: New lower bounding strategies

The two-machine flowshop environment with sequence-independent setup times has been intensely investigated both from theoretical and practical perspectives in the scheduling literature. Nevertheless, very scant attention has been devoted to deriving effective lower bounding strategies. In this paper, we propose new lower bounds for the total completion time minimization criterion. These bounds are based on three relaxation schemes, namely the waiting time-based relaxation scheme, the single machine-based relaxation scheme, and the Lagrangian relaxation scheme. Extensive computational study carried on instances with up to 500 jobs reveals that embedding the waiting time-based bounding strategy within the Lagrangian relaxation framework yields the best performance while requiring negligible CPU time.     

Multipartite quantum entanglement evolution in photosynthetic complexes

We investigate the evolution of entanglement in the Fenna-Matthew-Olson (FMO) complex based on simulations using the scaled hierarchical equations of motion approach. We examine the role of entanglement in the FMO complex by direct computation of the convex roof. We use monogamy to give a lower bound for entanglement and obtain an upper bound from the evaluation of the convex roof. Examination of bipartite measures for all possible bipartitions provides a complete picture of the multipartite entanglement. Our results support the hypothesis that entanglement is maximum primary along the two distinct electronic energy transfer pathways. In addition, we note that the structure of multipartite entanglement is quite simple, suggesting that there are constraints on the mixed state entanglement beyond those due to monogamy.     

Time evolution of a single spin inhomogeneously coupled to an interacting spin environment

We study the time evolution of a single spin coupled by exchange interaction to an environment of interacting spin bath modeled by the XY Hamiltonian. By evaluating the spin correlator of the single spin, we observed that the decay rate of the spin oscillations strongly depends on the relative magnitude of the exchange coupling between the single spin and its nearest neighbor J(') and coupling among the spins in the environment J. The decoherence time varies significantly based on the relative coupling magnitudes of J and J('). The decay rate law has a Gaussian profile when the two exchange couplings are of the same order J(') approximately J but converts to exponential and then a power law as we move to the regimes of J(')>J and J(')相似文献