Identification of fullerene-like CdSe nanoparticles from optical spectroscopy calculations

Semiconducting nanoparticles are the building blocks of optical nanodevices as their electronic states, and therefore light absorption and emission, can be controlled by modifying their size and shape. CdSe is perhaps the most studied of these nanoparticles, due to the efficiency of its synthesis, the high quality of the resulting samples, and the fact that the optical gap is in the visible range. In this article, we study light absorption of CdSe nanostructures with sizes up to 1.5 nm within density functional theory. We study both bulk fragments with wurtzite symmetry and novel fullerene-like core-cage structures. The comparison with recent experimental optical spectra allows us to confirm the synthesis of these fullerene-like CdSe clusters

Development of liquid xenon detectors for medical imaging

In the present paper, we report on our developments of liquid xenon detectors for medical imaging, positron emission tomography and single photon imaging, in particular. The results of the studies of several photon detectors (photomultiplier tubes and large area avalanche photodiode) suitable for detection of xenon scintillation are also briefly described.Comment: 13 pages, 5 figures, presented on the International Workshop on Techniques and Applications of Xenon Detectors (Xenon01), ICRR, Univ. of Tokyo, Kashiwa, Japan, December 3-4, 2001 (submitted to proceedings

Mode-coupling and the pygmy dipole resonance in a relativistic two-phonon model

A two-phonon version of the relativistic quasiparticle time blocking approximation (RQTBA-2) represents a new class of many-body models for nuclear structure calculations based on the covariant energy density functional. As a fully consistent extension of the relativistic quasiparticle random phase approximation (RQRPA), the two-phonon RQTBA implies a fragmentation of nuclear states over two-quasiparticle and two-phonon configurations. This leads, in particular, to a splitting-out of the lowest 1$^-$ state as a member of the two-phonon $[2^+\otimes3^-]$ quintuplet from the RQRPA pygmy dipole mode, thus establishing a physical mixing between these three modes. The inclusion of the two-phonon configurations in the model space allows to describe the positions and the reduced transition probabilities of the lowest 1$^-$ states in isotopes $^{116,120}$Sn as well as the low-energy fraction of the dipole strength without any adjustment procedures. The model is also applied to the low-lying dipole strength in neutron-rich $^{68,70,72}$Ni isotopes. Recent experimental data for $^{68}$Ni are reproduced fairly well

Introduction: consumption and its works

Though fairly recent as a research topic in the Portuguese anthropology context, contemporary material culture and consumption practices have been intensely scrutinized since the 1980s by all social sciences in many academic contexts, generating a plurality of debates that necessarily inspired and influenced the four papers presented in this collection.1 Despite this legacy, they however challenged us to reflect on a classical discussion that, even if always present in the field of contemporary material culture, did not gain primacy or much visibility in the empirical approaches to the field. Through their particular themes and specific approaches, and tough primarily focused on consumption practices, all four papers in this collection come across, and therefore make visible, instances of bridging, of encounter and of juxtaposition between consumption and what is sometimes identified as its opposite practice: work and production.info:eu-repo/semantics/publishedVersio

Spin filtering in nanowire directional coupler

The spin transport characteristics of a nanowire directional electronic coupler have been evaluated theoretically via a transfer matrix approach. The application of a gate field in the region of mixing allows for control of spin current through the different leads of the coupler via the Rashba spin-orbit interaction. The combination of spin-orbit interaction and applied gate voltages on different legs of the coupler give rise to a controllable modulation of the spin polarization. Both structural factors and field strength tuning lead to a rich phenomenology that could be exploited in spintronic devices.Comment: 9 pages, 4 figure

Functional turnover and community assemblage during tropical forest succession

Changes in species composition during the succession of ecological communities potentially reflect the differential effects of environmental filters and limiting similarity on structuring communities. As ecological succession can represent community assembly in action, understanding how successional time affects the functional and phylogenetic structure of communities can reveal the influence of different factors on the assembly process. We analysed functional patterns of multiple traits related to the succession of tropical forests to answer if there are trait convergence and/or divergence with regeneration age, and if functional and phylogenetic diversity can be predicted by forest age. We compiled checklists from studies of 23 successional forests in Brazilian Atlantic Forest, ranging from 4 to 120 years old. We also compiled functional traits for a total of 355 species. We analysed the data by a method that includes scaling-up trait-based data to the community level and matrix correlations of multiple traits. We built linear models to show the relationship between each trait and diversity (taxonomic, functional and phylogenetic) with successional time. We found no phylogenetic signal at the species pool and metacommunity levels, but significant trait divergence (tree guild, leaf slenderness, leaf area, pollination entomophilous generalist and pollination by vertebrate) and trait convergence (arboreal habitus, tree guild, leaf compoundness, pollination entomophilous generalist) patterns related to the successional gradient. Also, functional diversity increased during succession, with a significant increase in leaf slenderness and zoochoric dispersal and decrease in tree guild. Phylogenetic diversity also increased along the successional gradient. We found that the communities in the studied successional gradient are structured by both environmental (measured by trait convergence) and biotic (measured by trait divergence) filtering. The species turnover and diversification at taxonomic level are followed by well-defined patterns of trait turnover, revealing that community assembly is constrained by environmental filters at the beginning and by limiting similarity at the advanced stages of the succession

Positioning Airbnb and Fairbnb in the sharing-exchange continuum

Many organizations are positioning themselves as part of the sharing economy due to positive connotations associated with the sharing concept. Recognizing that many of these organizations represent the sharing economy to varying degrees, this study selected two organizations – Airbnb and Fairbnb, to analyze the extent to which they serve as examples of the sharing economy. A content analysis was undertaken to identify the position of each organization on a continuum, ranging from pure sharing to pure exchange characteristics. The analysis reveals that overall Fairbnb may be a stronger example of the sharing economy than Airbnb.info:eu-repo/semantics/acceptedVersio

On a generalized gravitational Aharonov-Bohm effect

A massless spinor particle is considered in the background gravitational field due to a rotating body. In the weak field approximation it is shown that the solution of the Weyl equations depend on the angular momentum of the rotating body, which does not affect the curvature in this approximation. This result may be looked upon as a generalization of the gravitational Aharonov-Bohm effect.Comment: 10 pages, LATEX fil

Frustrated multiband superconductivity

We show that a clean multiband superconductor may display one or several phase transitions with increasing temperature from or to frustrated configurations of the relative phases of the superconducting order parameters. These transitions may occur when more than two bands are involved in the formation of the superconducting phase and when the number of repulsive interband interactions is odd. These transitions are signalled by slope changes in the temperature dependence of the superconducting gaps.Comment: 5 pages, 3 figure