Electron transfer in the nonadiabatic regime: Crossover from quantum-mechanical to classical behaviour

We study nonadiabatic electron transfer within the biased spin-boson model. We calculate the incoherent transfer rate in analytic form at all temperatures for a power law form of the spectral density of the solvent coupling. In the Ohmic case, we present the exact low temperature corrections to the zero temperature rate for arbitrarily large bias energies between the two redox sites. Both for Ohmic and non-Ohmic coupling, we give the rate in the entire regime extending from zero temperature, where the rate depends significantly on the detailed spectral behaviour, via the crossover region, up to the classical regime. For low temperatures, the rate shows characteristic quantum features, in particular the shift of the rate maximum to a bias value below the reorganization energy, and the asymmetry of the rate around the maximum. We study in detail the gradual extinction of the quantum features as temperature is increased.Comment: 17 pages, 4 figures, to be published in Chem. Phy

Decay of correlations in the dissipative two-state system

We study the equilibrium correlation function of the polaron-dressed tunnelling operator in the dissipative two-state system and compare the asymptoptic dynamics with that of the position correlations. For an Ohmic spectral density with the damping strength $K=1/2$, the correlation functions are obtained in analytic form for all times at any $T$ and any bias. For $K<1$, the asymptotic dynamics is found by using a diagrammatic approach within a Coulomb gas representation. At T=0, the tunnelling or coherence correlations drop as $t^{-2K}$, whereas the position correlations show universal decay $\propto t^{-2}$. The former decay law is a signature of unscreened attractive charge-charge interactions, while the latter is due to unscreened dipole-dipole interactions.Comment: 5 pages, 5 figures, to be published in Europhys. Let

Determining ethylene group disorder levels in κ\kappa-(BEDT-TTF)2_2Cu[N(CN)2_2]Br

We present a detailed structural investigation of the organic superconductor $\kappa$-(BEDT-TTF)$_2$Cu[N(CN)$_2$]Br at temperatures $T$ from 9 to 300 K. Anomalies in the $T$ dependence of the lattice parameters are associated with a glass-like transition previously reported at $T_g$ = 77 K. From structure refinements at 9, 100 and 300 K, the orthorhombic crystalline symmetry, space group {\it Pnma}, is established at all temperatures. Further, we extract the $T$ dependence of the occupation factor of the eclipsed conformation of the terminal ethylene groups of the BEDT-TTF molecule. At 300 K, we find 67(2) %, with an increase to 97(3) % at 9 K. We conclude that the glass-like transition is not primarily caused by configurational freezing-out of the ethylene groups

Charge transfer and coherence dynamics of tunnelling system coupled to a harmonic oscillator

We study the transition probability and coherence of a two-site system, interacting with an oscillator. Both properties depend on the initial preparation. The oscillator is prepared in a thermal state and, even though it cannot be considered as an extended bath, it produces decoherence because of the large number of states involved in the dynamics. In the case in which the oscillator is intially displaced a coherent dynamics of change entangled with oscillator modes takes place. Coherency is however degraded as far as the oscillator mass increases producing a increasingly large recoherence time. Calculations are carried on by exact diagonalization and compared with two semiclassical approximations. The role of the quantum effects are highlighted in the long-time dynamics, where semiclassical approaches give rise to a dissipative behaviour. Moreover, we find that the oscillator dynamics has to be taken into account, even in a semiclassical approximation, in order to reproduce a thermally activated enhancement of the transition probability

Parameter Mismatches and Perfect Anticipating Synchronization in bi-directionally coupled external cavity laser diodes

We study perfect chaos synchronization between two bi-directionally coupled external cavity semiconductor lasers and demonstrate for the first time that mismatches in laser photon decay rates can explain the experimentally observed anticipating time in synchronization.Comment: Latex 4 page

Higher Spin Gauge Theory and Holography: The Three-Point Functions

In this paper we calculate the tree level three-point functions of Vasiliev's higher spin gauge theory in AdS4 and find agreement with the correlators of the free field theory of N massless scalars in three dimensions in the O(N) singlet sector. This provides substantial evidence that Vasiliev theory is dual to the free field theory, thus verifying a conjecture of Klebanov and Polyakov. We also find agreement with the critical O(N) vector model, when the bulk scalar field is subject to the alternative boundary condition such that its dual operator has classical dimension 2.Comment: 90 pages, 5 figures; v4, minor changes in the introductio

Review of HIV-Related Cytopathology

Exfoliative and aspiration cytologies play a major role in the management of patients with human immunodeficiency virus infection. Common cytology samples include cervicovaginal and anal Papanicolaou tests, fine needle aspirations, respiratory specimens, body fluids, Tzanck preparations, and touch preparations from brain specimens. While the cytopathologists need to be aware of specific infections and neoplasms likely to be encountered in this setting, they should be aware of the current shift in the pattern of human immunodeficiency virus-related diseases, as human immunodeficiency virus patients are living longer with highly active antiretroviral therapy and suffering fewer opportunistic infections with better antimicrobial prophylaxis. There is a rise in nonhuman immunodeficiency virus-defining cancers (e.g., anal cancer, Hodgkin's lymphoma) and entities (e.g., gynecomastia) from drug-related side effects. Given that fine needle aspiration is a valuable, noninvasive, and cost-effective tool, it is frequently employed in the evaluation and diagnosis of human immunodeficiency virus-related diseases. Anal Papanicolaou tests are also increasing as a result of enhanced screening of human immunodeficiency virus-positive patients for cancer. This paper covers the broad spectrum of disease entities likely to be encountered with human immunodeficiency virus-related cytopathology

Magneto-structural properties of the layered quasi-2D triangular-lattice antiferromagnets Cs2_2CuCl4−x_{4-x}Brx_x for x{x} = 0,1,2 and 4

We present a study of the magnetic susceptibility $\chi_{mol}$ under variable hydrostatic pressure on single crystals of Cs$_2$CuCl$_{4-x}$Br$_x$. This includes the border compounds \textit{x} = 0 and 4, known as good realizations of the distorted triangular-lattice spin-1/2 Heisenberg antiferromagnet, as well as the isostructural stoichiometric systems Cs$_2$CuCl$_{3}$Br$_1$ and Cs$_2$CuCl$_{2}$Br$_2$. For the determination of the exchange coupling constants $J$ and $J^{\prime}$, $\chi_{mol}$ data were fitted by a $J-J^{\prime}$ model \cite{Schmidt2015}. Its application, validated for the border compounds, yields a degree of frustration $J^{\prime}$/$J$ = 0.47 for Cs$_2$CuCl$_3$Br$_1$ and $J^{\prime}$/$J$ $\simeq$ 0.63 - 0.78 for Cs$_2$CuCl$_2$Br$_2$, making these systems particular interesting representatives of this family. From the evolution of the magnetic susceptibility under pressure up to about 0.4\,GPa, the maximum pressure applied, two observations were made for all the compounds investigated here. First, we find that the overall energy scale, given by $J_c = (J^2$ + $J^{\prime 2}$)$^{1/2}$, increases under pressure, whereas the ratio $J^{\prime}$/$J$ remains unchanged in this pressure range. These experimental observations are in accordance with the results of DFT calculations performed for these materials. Secondly, for the magnetoelastic coupling constants, extraordinarily small values are obtained. We assign these observations to a structural peculiarity of this class of materials

Quantum Hall Resistance Overshoot in 2-Dimensional Electron Gases - Theory and Experiment

We present a systematical experimental investigation of an unusual transport phenomenon observed in two dimensional electron gases in Si/SiGe heterostructures under integer quantum Hall effect (IQHE) conditions. This phenomenon emerges under specific experimental conditions and in different material systems. It is commonly referred to as Hall resistance overshoot, however, lacks a consistent explanation so far. Based on our experimental findings we are able to develop a model that accounts for all of our observations in the framework of a screening theory for the IQHE. Within this model the origin of the overshoot is attributed to a transport regime where current is confined to co-existing evanescent incompressible strips of different filling factors.Comment: 26 pages, 10 figure

Psychopathological Course Typology in Schizophrenia Spectrum Disorders: A Heuristic Approach in a Sample of 100 Patients

Background: Despite several previous attempts at subtyping schizophrenia, a typology that reflects neurobiological knowledge and reliably predicts course and outcome is lacking. We applied the system-specific concept of the Bern Psychopathology Scale (BPS) to generate a course typology based on three domains: language, affectivity, and motor behaviour. Sampling and Methods: A cohort of 100 patients with schizophrenia or schizoaffective disorders according to DSM-IV criteria underwent psychopathological assessment, and all their available medical records were retrospectively analysed on the basis of the BPS. Results: Overall, 39% of the patients showed dominant abnormalities in only one domain, 37% in two domains, and 24% in all three domains. The motor domain was affected in the majority of patients (76%), followed by affectivity (63%) and language (46%). Eighty-six percent of patients showed a bipolar course pattern in at least one domain. Conclusions: In a retrospective analysis of 100 patient records we described system-specific course patterns of schizophrenia by using a neurobiologically informed psychopathological assessment. The results showed a surprisingly high proportion of bipolar courses and a pattern of pure and mixed subtypes, which speaks for an overlap of domains with regards to psychopathological symptoms. A limitation of this heuristic and retrospective approach is that it was largely based on clinical judgement. Prospective studies with more rigorous threshold definitions are needed to clarify the neurobiological and clinical implications of the proposed reorganization of psychotic disorders. (C) 2016 S. Karger AG, Base