8,460 research outputs found

    The fate of non-trivial entanglement under gravitational collapse

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    We analyse the evolution of the entanglement of a non-trivial initial quantum field state (which, for simplicity, has been taken to be a bipartite state made out of vacuum and the first excited state) when it undergoes a gravitational collapse. We carry out this analysis by generalising the tools developed to study entanglement behaviour in stationary scenarios and making them suitable to deal with dynamical spacetimes. We also discuss what kind of problems can be tackled using the formalism spelled out here as well as single out future avenues of research.Comment: 9 pages, 2 figures. v2: Added Journal reference and small changes to match published versio

    Fine Structure of Open Shell Diatomic Molecules in Combined Electric and Magnetic Fields

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    We present a theoretical study of the impact of an electric field combined with a magnetic field on the rotational dynamics of open shell diatomic molecules. Within the rigid rotor approximation, we solve the time-independent Schr\"odinger equation including the fine-structure interactions and the \Lambda-doubling effects. We consider three sets of molecule specific parameters and several field regimes and investigate the interplay between the different interactions identifying the dominant one. The possibility of inducing couplings between the spin and rotational degrees of freedom is demonstrated.Comment: 11 pages, 16 figure

    An MS-CASPT2 Study of the Photodecomposition of 4- Methoxyphenyl Azide. Role of Internal Conversion and Intersystem Crossing

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    Aryl azides photochemistry is strongly dependent on the substituent relative position, as has been studied by time resolved resonant Raman (TR3) spectroscopy for 4-methoxyphenyl azide and its isomer 3-methoxyphenyl azide. When irradiated at 266 nm, the former results in 4,4’-dimethoxyazobenzene whereas the latter forms 1,2-didehydroazepine. It is proposed that the key step of the reactions is the formation of a nitrene derivative. Recently, it has been proposed by us that nitrenes might have a relevant role in the Surface-Enhanced Raman Scattering (SERS) of p-aminothiophenol, however, the molecular mechanism is not well known in neither of these cases. Therefore, we studied the photodecomposition of 4-methoxyphenyl azide using multiconfigurational self-consistent field methods (MC-SCF) with the CAS-SCF and MS-CASPT2 approximations and calculated the resonant Raman spectra of the relevant species using a multi-state version of Albrecht’s vibronic theory. The results propose that the reaction follows a two steps sequence after irradiation at 266 nm: an intersystem crossing 21A’/23A’’ which decays through a 21A’/21A’’ conical intersection producing molecular nitrogen and triplet 4-methoxyphenyl nitrene in its ground state.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

    Frequency shift on the potential-dependent surface-enhanced Raman scattering of pyridine: simplified models for metal and solvent effects

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    The electronic structure of adsorbates is altered when it interacts with a surface, modifying the properties of both entities and giving rise to interesting phenomena related to heterogeneous catalysis or molecular electronics. If such surface is a metallic substrate, the electrode potential can be used to tune this interaction. Potential-dependent Surface-Enhanced Raman Scattering (SERS) is a particularly useful technique to study the induced effects on the molecule when the metal-adsorbate surface complex is formed, as the observed frequency shifts of the vibrational modes can provide information about it. However, from the computational point of view, these systems are difficult to model, because the macroscopic metal cannot be modelled easily using quantum mechanics. As an approach, we propose a simple model using silver atomic wires with different size and charge bonded to the molecule (AgnPyq, n = 2,3,5,7 and q = 0 and ±1 for n even and odd, respectively) which has been developed by the group and provides a good description of the effect of the electrode potential on the chemical enhancement mechanism of SERS.1-3 Electronic calculations were performed using Density Functional Theory (DFT). In order to study the frequency shifts, solvent effects have been taken into account by using the Polarizable Continuum Model (PCM). We have used three different functionals (B3LYP, PW91 and M06HF) and two basis sets (LANL2DZ for all atoms and LANL2DZ for Ag and 6-31G(d) for C,N,H) and, in all cases, a good agreement is achieved in terms of amplitude and trend of the frequency shift for most of the vibrational modes, especially when solvent interactions are included. The method was extended to other metals and solvents giving results in agreement with the available experimental data.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

    Charge Transfer mechanism in the Surface Enhanced Raman Scattering of 2,2'-bipyridine recorded on a silver electrode

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    Nowadays, Surface Enhanced Raman Spectroscopy (SERS) has become a powerful technique to investigate the electronic structure of surface-molecule hybrid systems due to the huge enhancement of the Raman signal. It is established that the origin of this enhancement has two main contributions; the electromagnetic (EM), related to surface plasmons, and the chemical mechanism, due to resonant charge transfer (CT) processes between the adsorbate and the metal. With the aim to investigate the SERS-CT of bipyridine and to identify charge transfer process, the spectra were recorded on silver electrode by using three different wavelengths (473, 532 and 785 nm) in a range from 0.0 up to -1.4 V electrode potential. The electrode potential was modelled in the calculations with atomic silver wires of different size and charge attached to the BPy molecule (AgnBPyq, with q = 0 for n = 2 and q = ±1 for n = 3, 5, 7) and were computed with Density Functional Theory (DFT). Although BPy shows a trans conformation in solution, a cis conformation was chosen for its chelating properties. The results indicate that the intensification of the ~1550 cm-1 band at negative potentials is due the Franck-Condon factors related to the resonant CT process from the metal to the BPy molecule.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

    Spatial productivity spillovers across Spanish municipalities

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    Whilst a great deal of e¤ort has been dedicated to identification of agglomeration effects on labour productivity, the measurement of spatial productivity spillovers is a question that has been addressed only occasionally along the New Economic Geography literature. We estimate agglomeration effects, nonetheless conditioned to the possible existence of spatial productivity spillovers across Spanish municipalities in year 2001. To this respect, we find that agglomeration effects are in the same order of magnitude than thoseencountered when measured in the standard way. Further, these agglomeration efects coexist with very strong spatial productivity spillovers in a close neighbourhood of 10 km. Finally, these spatial e¤ects are shown to quickly diminish as distance increases.IV estimation, elevation, spatial externalities, productivity, neighbourhood, Spain

    Measuring cortical connectivity in Alzheimer's disease as a brain neural network pathology: Toward clinical applications

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    Objectives: The objective was to review the literature on diffusion tensor imaging as well as resting-state functional magnetic resonance imaging and electroencephalography (EEG) to unveil neuroanatomical and neurophysiological substrates of Alzheimer’s disease (AD) as a brain neural network pathology affecting structural and functional cortical connectivity underlying human cognition. Methods: We reviewed papers registered in PubMed and other scientific repositories on the use of these techniques in amnesic mild cognitive impairment (MCI) and clinically mild AD dementia patients compared to cognitively intact elderly individuals (Controls). Results: Hundreds of peer-reviewed (cross-sectional and longitudinal) papers have shown in patients with MCI and mild AD compared to Controls (1) impairment of callosal (splenium), thalamic, and anterior–posterior white matter bundles; (2) reduced correlation of resting state blood oxygen level-dependent activity across several intrinsic brain circuits including default mode and attention-related networks; and (3) abnormal power and functional coupling of resting state cortical EEG rhythms. Clinical applications of these measures are still limited. Conclusions: Structural and functional (in vivo) cortical connectivity measures represent a reliable marker of cerebral reserve capacity and should be used to predict and monitor the evolution of AD and its relative impact on cognitive domains in pre-clinical, prodromal, and dementia stages of AD. (JINS, 2016, 22, 138–163

    The European Map of Job Flows

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    The European Map of Job Flows (EMJF) is a term used to denote a dataset of meso- and macro-level variables describing different aspect of labour mobility within national labour markets in Europe. In this paper, EMJF is centred on the notion of job “flows”, namely the changes in the level of employment at different breakdowns and levels of aggregation. EMJF is very rich in information content due to the wide variety of possible breakdown of the data and in this sense it is a “map” mostly in the virtual sense, namely, that it is not possible to visualise in the form of geographic maps all the wealth of available information. In terms of its value as a research product and tool, EMJF is mostly an intermediate product in the sense that it is a convenient means to organise the relevant information, which could subsequently be used for different analytical and research purposes. It provides both for cross-sections/snapshots of job flows at different point in time but also it allows their assessment and analysis over longer periods of time. In this sense, EMJF can be widely used for various types of labour-market analysis and research. EMJF’s visual components can also be a convenient tool for policy makers dealing with labour market policies at different level (regional, national or supra-national) in the decision-making process. Here we present a Compilation of a EMJF on the basis of firm-level data In this sense the job flows are built up on the basis of firm-level data for individual countries, following a common methodology. We adopt an approach of establishing such a EMJF on the basis of the AMADEUS dataset developed by the consultancy Bureau van Dijk. The dataset in its most extended version contains balance sheet data and ownership data for almost 14 million firms from 43 different European countries (September 2009 update). For many EU countries the dataset has in principle access to the entire universe of firms which have to report a balance sheet. In terms of countries, the geographic coverage of AMADEUS encompasses information for all the 27 members of the European Union (albeit with different qualities in terms of national coverage) as well as other 16 European countries that complete the geographical and political definition of the continent. Another interesting feature of the database is given by the detailed definition of a firm's location, with data available on the region (NUTS2) and the city in which the firm operates. This project deliverable presents the main results from the final stage of MICRO-DYN work on the EMJF. It discusses the approach to building the EMJF on the basis of AMADEUS data and illustrates the analytical potential of the EMJF as a research tool with a range of Europe-wide analytical exercises. Probably the most important outcome of this research effort is the demonstrated capability to perform meta-analysis at the European level of important labour market characteristics on the basis of firm-level data.job flows, europe, labor market, microdata
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