The debris disk - terrestrial planet connection

The eccentric orbits of the known extrasolar giant planets provide evidence that most planet-forming environments undergo violent dynamical instabilities. Here, we numerically simulate the impact of giant planet instabilities on planetary systems as a whole. We find that populations of inner rocky and outer icy bodies are both shaped by the giant planet dynamics and are naturally correlated. Strong instabilities -- those with very eccentric surviving giant planets -- completely clear out their inner and outer regions. In contrast, systems with stable or low-mass giant planets form terrestrial planets in their inner regions and outer icy bodies produce dust that is observable as debris disks at mid-infrared wavelengths. Fifteen to twenty percent of old stars are observed to have bright debris disks (at wavelengths of ~70 microns) and we predict that these signpost dynamically calm environments that should contain terrestrial planets.Comment: Contribution to proceedings of IAU 276: Astrophysics of Planetary System

Receiving Aphasia Intervention in a Virtual Environment: The Participants’ Perspective

Background: Digital technology is making an increasing contribution to aphasia therapy. However applications of virtual reality are rare. EVA Park is a virtual island developed with and for people with aphasia. It is a multi-user environment, which enables people with aphasia to interact with support workers, therapists and each other. The first study to use EVA Park in aphasia rehabilitation demonstrated significant gains in functional communication. This paper augments the findings of that study, by reporting results from qualitative interviews conducted with the 20 study participants. Aims: This study aimed to determine the views of participants about the intervention that they received in EVA Park, and the impacts of that intervention. Long-term retrospective views were also explored. Methods & Procedures: Participants took part in 1:1, semi-structured interviews two weeks before (Entry) and to weeks after (Exit) the intervention. Questions focussed on activities undertaken by participants, communication, changes since the stroke and uses of technology. Exit interviews additionally explored participants’ views and experiences of EVA Park and any perceived impacts of the intervention. A sub-set of 5 participants was interviewed at least one year later, to explore long term recollections of the EVA Park intervention and any perceived long term impacts. Interview data were transcribed and subject to framework analysis. Outcomes & Results: The thematic framework comprised 10 parent themes and 33 sub-themes. Following ‘affect’, the largest single theme related to EVA Park, with 636 coded references. Comments were overwhelmingly positive. EVA Park intervention was strongly associated with fun and enjoyment. Participants particularly valued their relationship with the support workers who delivered the intervention. The virtual locations and activities in EVA Park were also appreciated, together with the contact with other participants. Perceived impacts related to communication, activity, computer use and confidence. Most participants in the long term interviews described maintained impacts. Conclusions: These interview results indicate that the first intervention delivered in EVA Park was highly acceptable to participants and perceived as beneficial. They augment the findings of our experimental study and suggest that EVA Park could be a valuable addition to the resources available to practising clinician

Time-Dependent Density Functional Theory of Open Quantum Systems in the Linear-Response Regime

Time-Dependent Density Functional Theory (TDDFT) has recently been extended to describe many-body open quantum systems (OQS) evolving under non-unitary dynamics according to a quantum master equation. In the master equation approach, electronic excitation spectra are broadened and shifted due to relaxation and dephasing of the electronic degrees of freedom by the surrounding environment. In this paper, we develop a formulation of TDDFT linear-response theory (LR-TDDFT) for many-body electronic systems evolving under a master equation, yielding broadened excitation spectra. This is done by mapping an interacting open quantum system onto a non-interacting open Kohn-Sham system yielding the correct non-equilibrium density evolution. A pseudo-eigenvalue equation analogous to the Casida equations of usual LR-TDDFT is derived for the Redfield master equation, yielding complex energies and Lamb shifts. As a simple demonstration, we calculate the spectrum of a C$^{2+}$ atom in an optical resonator interacting with a bath of photons. The performance of an adiabatic exchange-correlation kernel is analyzed and a first-order frequency-dependent correction to the bare Kohn-Sham linewidth based on Gorling-Levy perturbation theory is calculated.Comment: 18 pages, 4 figure

Medidas experimentales de desplazamientos micrométricos basadas en vórtices ópticos

In this work, a system for measuring micrometer-displacements based on the characteristics of optical vortices is presented. In the proposal, a binary vortex-producing lens (BVPL) programmed to generate optimized optical vortices is transversally displaced from the optical axis, inducing perturbations on the optical characteristics of the vortices that are used as transduction parameters. Specifically, the method proposed theoretically by Anzolin et al. [18], which is based on the asymmetry of the intensity patterns of the off-axis optical vortices, is studied experimentally by using BVPLs. Experimental implementation is completely described and compared with theoretical results, likewise, metrological characteristics of the experimental metrological system are analyzed. Based on the results, we experimentally confirm the possibility of creating high sensitivity metrological systems by using optical vortices, opening the door for new vortex metrology techniques.En este trabajo, un sistema para medir desplazamientos micrométricos basados en las características de vórtices ópticos es presentado. En la propuesta, una lente productora de vórtices binaria (BVPL) programada para generar vórtices ópticos optimizados es desplazada transversalmente del eje óptico, induciendo perturbaciones en las características ópticas de los vórtices que son usadas como parámetros de transducción. Específicamente, el método propuesto por Anzolín et al [18], el cuál es basado en la asimetría de los patrones de intensidad de los vórtices ópticos fuera del eje, es estudiado experimentalmente usando BVPLs. Se describe completamente la implementación experimental y se compara con los resultados teóricos, así mismo, se analizan características metrológicas del sistema metrológico experimental. En base a los resultados, confirmamos experimentalmente la posibilidad de crear sistemas metrológicos de alta sensibilidad utilizando vórtices ópticos, abriendo la puerta para nuevas técnicas de metrología de vórtices.Centro de Investigaciones Óptica

Assembling the puzzle of superconducting elements: A Review

Superconductivity in the simple elements is of both technological relevance and fundamental scientific interest in the investigation of superconductivity phenomena. Recent advances in the instrumentation of physics under pressure have enabled the observation of superconductivity in many elements not previously known to superconduct, and at steadily increasing temperatures. This article offers a review of the state of the art in the superconductivity of elements, highlighting underlying correlations and general trends.Comment: Review, 10 pages, 11 figures, 97 references; to appear in Superc. Sci. Techno

Medidas experimentales de desplazamientos micrométricos basadas en vórtices ópticos

In this work, a system for measuring micrometer-displacements based on the characteristics of optical vortices is presented. In the proposal, a binary vortex-producing lens (BVPL) programmed to generate optimized optical vortices is transversally displaced from the optical axis, inducing perturbations on the optical characteristics of the vortices that are used as transduction parameters. Specifically, the method proposed theoretically by Anzolin et al. [18], which is based on the asymmetry of the intensity patterns of the off-axis optical vortices, is studied experimentally by using BVPLs. Experimental implementation is completely described and compared with theoretical results, likewise, metrological characteristics of the experimental metrological system are analyzed. Based on the results, we experimentally confirm the possibility of creating high sensitivity metrological systems by using optical vortices, opening the door for new vortex metrology techniques.En este trabajo, un sistema para medir desplazamientos micrométricos basados en las características de vórtices ópticos es presentado. En la propuesta, una lente productora de vórtices binaria (BVPL) programada para generar vórtices ópticos optimizados es desplazada transversalmente del eje óptico, induciendo perturbaciones en las características ópticas de los vórtices que son usadas como parámetros de transducción. Específicamente, el método propuesto por Anzolín et al [18], el cuál es basado en la asimetría de los patrones de intensidad de los vórtices ópticos fuera del eje, es estudiado experimentalmente usando BVPLs. Se describe completamente la implementación experimental y se compara con los resultados teóricos, así mismo, se analizan características metrológicas del sistema metrológico experimental. En base a los resultados, confirmamos experimentalmente la posibilidad de crear sistemas metrológicos de alta sensibilidad utilizando vórtices ópticos, abriendo la puerta para nuevas técnicas de metrología de vórtices.Centro de Investigaciones Óptica

Specific heat and magnetization study on single crystals of a frustrated, quasi one-dimensional oxide: Ca3Co2O6

Specific heat and magnetization measurements have been carried out under a range of magnetic fields on single crystals of Ca3Co2O6. This compound is composed of Ising magnetic chains that are arranged on a triangular lattice. The intrachain and interchain couplings are ferromagnetic and antiferromagnetic, respectively. This situation gives rise to geometrical frustration, that bears some similarity to the classical problem of a two-dimensional Ising triangular antiferromagnet. This paper reports on the ordering process at low-T and the possibility of one-dimensional features at high-T.Comment: 7 pages, 6 figures, accepted for publication in PR

Complex brain circuits studied via simultaneous and permanent detection of three transported neuroanatomical tracers in the same histological section.

Experimental neuroanatomical tracing methods lie at the basis of the study of the nervous system. When the scientific question is relatively straightforward, it may be sufficient to derive satisfactory answers from experiments in which a single neuroanatomical tracing method is applied. In various scientific paradigms however, for instance when the degree of convergence of two different projections on a particular cortical area or subcortical nucleus is the subject of study, the application of single tracing methods can be either insufficient or uneconomical to solve the questions asked. In cases where chains of projections are the subjects of study, the simultaneous application of two tracing methods or even more may be compulsory. The present contribution focuses on combinations of several neuroanatomical tract-tracing strategies, enabling in the end the simultaneous, unambiguous and permanent detection of three transported markers according to a three-color paradigm. A number of combinations of three tracers or of two tracers plus the immunocytochemical detection of a neuroactive substance can be conceived; we describe several of these combinations implemented by us using the present multitracer protocol

Experimental loophole-free violation of a Bell inequality using entangled electron spins separated by 1.3 km

For more than 80 years, the counterintuitive predictions of quantum theory have stimulated debate about the nature of reality. In his seminal work, John Bell proved that no theory of nature that obeys locality and realism can reproduce all the predictions of quantum theory. Bell showed that in any local realist theory the correlations between distant measurements satisfy an inequality and, moreover, that this inequality can be violated according to quantum theory. This provided a recipe for experimental tests of the fundamental principles underlying the laws of nature. In the past decades, numerous ingenious Bell inequality tests have been reported. However, because of experimental limitations, all experiments to date required additional assumptions to obtain a contradiction with local realism, resulting in loopholes. Here we report on a Bell experiment that is free of any such additional assumption and thus directly tests the principles underlying Bell's inequality. We employ an event-ready scheme that enables the generation of high-fidelity entanglement between distant electron spins. Efficient spin readout avoids the fair sampling assumption (detection loophole), while the use of fast random basis selection and readout combined with a spatial separation of 1.3 km ensure the required locality conditions. We perform 245 trials testing the CHSH-Bell inequality $S \leq 2$ and find $S = 2.42 \pm 0.20$. A null hypothesis test yields a probability of $p = 0.039$ that a local-realist model for space-like separated sites produces data with a violation at least as large as observed, even when allowing for memory in the devices. This result rules out large classes of local realist theories, and paves the way for implementing device-independent quantum-secure communication and randomness certification.Comment: Raw data will be made available after publicatio