On the Munn-Silbey approach to polaron transport with off-diagonal coupling

Improved results using a method similar to the Munn-Silbey approach have been obtained on the temperature dependence of transport properties of an extended Holstein model incorporating simultaneous diagonal and off-diagonal exciton-phonon coupling. The Hamiltonian is partially diagonalized by a canonical transformation, and optimal transformation coefficients are determined in a self-consistent manner. Calculated transport properties exhibit substantial corrections on those obtained previously by Munn and Silbey for a wide range of temperatures thanks to a numerically exact evaluation and an added momentum-dependence of the transformation matrix. Results on the diffusion coefficient in the moderate and weak coupling regime show distinct band-like and hopping-like transport features as a function of temperature.Comment: 12 pages, 6 figures, accpeted in Journal of Physical Chemistry B: Shaul Mukamel Festschrift (2011

Impact of molecular quadrupole moments on the energy levels at organic heterojunctions

The functionality of organic semiconductor devices crucially depends on molecular energies, namely the ionisation energy and the electron affinity. Ionisation energy and electron affinity values of thin films are, however, sensitive to film morphology and composition, making their prediction challenging. In a combined experimental and simulation study on zinc-phthalocyanine and its fluorinated derivatives, we show that changes in ionisation energy as a function of molecular orientation in neat films or mixing ratio in blends are proportional to the molecular quadrupole component along the p-p-stacking direction. We apply these findings to organic solar cells and demonstrate how the electrostatic interactions can be tuned to optimise the energy of the charge-transfer state at the donor-acceptor interface and the dissociation barrier for free charge carrier generation. The confirmation of the correlation between interfacial energies and quadrupole moments for other materials indicates its relevance for small molecules and polymers.We thank Beatrice Beyer for providing F4ZnPc and F16ZnPc. M.S. acknowledges financial support by the German Research Foundation (DFG) through the project MatWorldNet LE-747/44-1. F.O. would like to thank the DFG for financial support (project OR-349/1). The TDCF setup in Potsdam was partially financed by the DFG through INST 336/94-1 FUGG. This work was supported by the German Federal Ministry for Education and Research (BMBF) grant InterPhase (FKZ 13N13661) and through the InnoProfile project "Organische p-i-n Bauelemente 2.2" (03IPT602X). Moreover, the project received funding from the NMP-20-2014-"Widening materials models" programme under Grant Agreement No. 646259 (MOSTOPHOS). K.L. is a fellow of the Canadian Institute for Advanced Research (CIFAR). We gratefully acknowledge grants for computing time from the Zentrum fur Informationsdienste und Hochleistungsrechnen Dresden (ZIH). The X-ray scattering experiments were performed on beamline ID3 at the European Synchrotron Radiation Facility (ESRF), Grenoble, France. We are grateful to Maciej Jankowski for providing assistance at beamline ID3. We acknowledge support by the Open Access Publication Funds of the SLUB/TU Dresden

Finite size effects on transport coefficients for models of atomic wires coupled to phonons

We consider models of quasi-1-d, planar atomic wires consisting of several, laterally coupled rows of atoms, with mutually non-interacting electrons. This electronic wire system is coupled to phonons, corresponding, e.g., to some substrate. We aim at computing diffusion coefficients in dependence on the wire widths and the lateral coupling. To this end we firstly construct a numerically manageable linear collision term for the dynamics of the electronic occupation numbers by following a certain projection operator approach. By means of this collision term we set up a linear Boltzmann equation. A formula for extracting diffusion coefficients from such Boltzmann equations is given. We find in the regime of a few atomic rows and intermediate lateral coupling a significant and non-trivial dependence of the diffusion coefficient on both, the width and the lateral coupling. These results, in principle, suggest the possible applicability of such atomic wires as electronic devices, such as, e.g., switches.Comment: 9 pages, 5 figures, accepted for publication in Eur. Phys. J.

Identifying the Azobenzene/Aniline reaction intermediate on TiO2-(110) : a DFT Study

Density functional theory (DFT) calculations, both with and without dispersion corrections, have been performed to investigate the nature of the common surface reaction intermediate that has been shown to exist on TiO2(110) as a result of exposure to either azobenzene (C6H5N═NC6H5) or aniline (C6H5NH2). Our results confirm the results of a previous DFT study that dissociation of azobenzene into two adsorbed phenyl imide (C6H5N) fragments, as was originally proposed, is not energetically favorable. We also find that deprotonation of aniline to produce this surface species is even more strongly energetically disfavored. A range of alternative surface species has been considered, and while dissociation of azobenzene to form surface C6H4NH species is energetically favored, the same surface species cannot form from adsorbed aniline. On the contrary, adsorbed aniline is much the most stable surface species. Comparisons with experimental determinations of the local adsorption site, the Ti–N bond length, the molecular orientation, and the associated C 1s and N 1s photoelectron core level shifts are all consistent with the DFT results for adsorbed aniline and are inconsistent with other adsorbed species considered. Possible mechanisms for the hydrogenation of azobenzene required to produce this surface species are discussed

Multidrug- and extensively drug-resistant tuberculosis

We evaluated risk factors and treatment outcomes associated with multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis (TB) in Germany in 2004–2006. In 177 (4%) of 4,557 culture-positive TB cases, Mycobacterium tuberculosis isolates were identified as MDR TB; an additional 7 (0.15%) met criteria for XDR TB. Of these 184 patients, 148 (80%) were born in countries of the former Soviet Union. In patients with XDR TB, hospitalization was longer (mean ± SD 202 ± 130 vs. 123 ± 81 days; p = 0.015) and resistance to all first-line drugs was more frequent (36% vs. 86%; p = 0.013) than in patients with MDR TB. Seventy-four (40%) of these 184 patients received treatment with linezolid. Treatment success rates ranged from 59% for the entire cohort (59% for MDR TB and 57% for XDR TB) to 87% for those with a definitive outcome (n = 125; 89% for MDR TB and 80% for XDR TB). Extensive drug susceptibility testing and availability of second- and third-line drugs under inpatient management conditions permit relatively high treatment success rates in MDR- and XDR TB

Neural Correlates of Speech Processing in Prelingually Deafened Children and Adolescents with Cochlear Implants

Prelingually deafened children with cochlear implants stand a good chance of developing satisfactory speech performance. Nevertheless, their eventual language performance is highly variable and not fully explainable by the duration of deafness and hearing experience. In this study, two groups of cochlear implant users (CI groups) with very good basic hearing abilities but non-overlapping speech performance (very good or very bad speech performance) were matched according to hearing age and age at implantation. We assessed whether these CI groups differed with regard to their phoneme discrimination ability and auditory sensory memory capacity, as suggested by earlier studies. These functions were measured behaviorally and with the Mismatch Negativity (MMN). Phoneme discrimination ability was comparable in the CI group of good performers and matched healthy controls, which were both better than the bad performers. Source analyses revealed larger MMN activity (155–225 ms) in good than in bad performers, which was generated in the frontal cortex and positively correlated with measures of working memory. For the bad performers, this was followed by an increased activation of left temporal regions from 225 to 250 ms with a focus on the auditory cortex. These results indicate that the two CI groups developed different auditory speech processing strategies and stress the role of phonological functions of auditory sensory memory and the prefrontal cortex in positively developing speech perception and production

Exploring CEvNS with NUCLEUS at the Chooz Nuclear Power Plant

Coherent elastic neutrino-nucleus scattering (CE$\nu$NS) offers a unique way to study neutrino properties and to search for new physics beyond the Standard Model. Nuclear reactors are promising sources to explore this process at low energies since they deliver large fluxes of (anti-)neutrinos with typical energies of a few MeV. In this paper, a new-generation experiment to study CE$\nu$NS is described. The NUCLEUS experiment will use cryogenic detectors which feature an unprecedentedly low energy threshold and a time response fast enough to be operated in above-ground conditions. Both sensitivity to low-energy nuclear recoils and a high event rate tolerance are stringent requirements to measure CE$\nu$NS of reactor antineutrinos. A new experimental site, denoted the Very-Near-Site (VNS) at the Chooz nuclear power plant in France is described. The VNS is located between the two 4.25 GW$_{\mathrm{th}}$ reactor cores and matches the requirements of NUCLEUS. First results of on-site measurements of neutron and muon backgrounds, the expected dominant background contributions, are given. In this paper a preliminary experimental setup with dedicated active and passive background reduction techniques is presented. Furthermore, the feasibility to operate the NUCLEUS detectors in coincidence with an active muon-veto at shallow overburden is studied. The paper concludes with a sensitivity study pointing out the promising physics potential of NUCLEUS at the Chooz nuclear power plant

Long-Term Follow-Up of the Intergroup Exemestane Study

Purpose: The Intergroup Exemestane Study, an investigator-led study of 4,724 postmenopausal patients with early breast cancer (clinical trial information: ISRCTN11883920), has previously demonstrated that a switch from adjuvant endocrine therapy after 2 to 3 years of tamoxifen to exemestane was associated with clinically relevant improvements in efficacy. Here, we report the final efficacy analyses of this cohort. Patients and Methods: Patients who remained disease free after 2 to 3 years of adjuvant tamoxifen were randomly assigned to continue tamoxifen or switch to exemestane to complete a total of 5 years of adjuvant endocrine therapy. Given the large number of non–breast cancer–related deaths now reported, breast cancer–free survival (BCFS), with censorship of intercurrent deaths, was the primary survival end point of interest. Analyses focus on patients with estrogen receptor-positive or unknown tumors (n = 4,599). Results: At the time of the data snapshot, median follow-up was 120 months. In the population that was estrogen receptor positive or had unknown estrogen receptor status, 1,111 BCFS events were observed with 508 (22.1%) of 2,294 patients in the exemestane group and 603 (26.2%) of 2,305 patients in the tamoxifen group. The data corresponded to an absolute difference (between exemestane and tamoxifen) at 10 years of 4.0% (95% CI, 1.2% to 6.7%), and the hazard ratio (HR) of 0.81 (95% CI, 0.72 to 0.92) favored exemestane. This difference remained in multivariable analysis that was adjusted for nodal status, prior use of hormone replacement therapy, and prior chemotherapy (HR, 0.80; 95% CI, 0.71 to 0.90; P < .001). A modest improvement in overall survival was seen with exemestane; the absolute difference (between exemestane and tamoxifen) at 10 years in the population that was estrogen receptor positive or had unknown estrogen receptor status was 2.1% (95% CI, −0.5% to 4.6%), and the HR was 0.89 (95% CI, 0.78 to 1.01; P = .08). For the intention-to-treat population, the absolute difference was 1.6% (95% CI, −0.9% to 4.1%); the HR was 0.91 (95% CI, 0.80 to 1.03, P = .15). No statistically significant difference was observed in the proportion of patients who reported a fracture event in the post-treatment period. Conclusion: The Intergroup Exemestane Study and contemporaneous studies have established that a strategy of switching to an aromatase inhibitor after 2 to 3 years of tamoxifen can lead to sustained benefits in terms of reduction of disease recurrence and breast cancer mortality

Biology and conservation of freshwater bivalves : past, present and future perspectives

Freshwater bivalves have been highly threatened by human activities, and recently their global decline has been causing conservational and social concern. In this paper, we review the most important research events in freshwater bivalve biology calling attention to the main scientific achievements. A great bias exists in the research effort, with much more information available for bivalve species belonging to the Unionida in comparison to other groups. The same is true for the origin of these studies, since the publishing pattern does not always correspond to the hotspots of biodiversity but is concentrated in the northern hemisphere mainly in North America, Europe and Russia, with regions such as Africa and Southeast Asia being quite understudied. We also summarize information about past, present and future perspectives concerning the most important research topics that include taxonomy, systematics, anatomy, physiology, ecology and conservation of freshwater bivalves. Finally, we introduce the articles published in this Hydrobiologia special issue related with the International Meeting on Biology and Conservation of Freshwater Bivalves held in 2012 in Braganc¸a, Portugal.We would like to express our gratitude to our sponsors and institutions, especially to the Polytechnic Institute of Braganca for all the logistic support. We acknowledge all keynote speakers, authors, session chairpersons and especially to all attendees whose contributions were fundamental for the success of this meeting. We would also like to thank all referees of this special issue and to Koen Martens, Editor-in-Chief of Hydrobiologia, for all the valuable comments and suggestions. The chronogram was built with the help of the expert opinion of fellow colleagues Rafael Araujo, Arthur Bogan, Kevin Cummings, Dan Graf, Wendell Haag, Karl-Otto Nagel and David Strayer to whom we are very grateful. The authors acknowledge the support provided by Portuguese Foundation for Science and Technology (FCT) and COMPETE funds-projects CONBI (Contract: PTDC/AAC-AMB/117688/2010) and ECO-IAS (Contract: PTDC/AAC-AMB/116685/2010), and by the European Regional Development Fund (ERDF) through the COMPETE, under the project "PEst-C/MAR/LA0015/2011"