Numerical study of the localization length critical index in a network model of plateau-plateau transitions in the quantum Hall effect

We calculate numerically the localization length critical index within the Chalker-Coddington (CC) model for plateau-plateau transitions in the quantum Hall effect. Lyapunov exponents have been calculated with relative errors on the order $10^{-3}$. Such high precision was obtained by considering the distribution of Lyapunov exponents for large ensembles of relatively short chains and calculating the ensemble average values. We analyze thoroughly finite size effects and find the localization length critical index $\nu= 2.517\pm 0.018$.Comment: 4 pages, 4 figure

Electrostatic tailoring of magnetic interference in quantum point contact ballistic Josephson junctions

The magneto-electrostatic tailoring of the supercurrent in quantum point contact ballistic Josephson junctions is demonstrated. An etched InAs-based heterostructure is laterally contacted to superconducting niobium leads and the existence of two etched side gates permits, in combination with the application of a perpendicular magnetic field, to modify continuously the magnetic interference pattern by depleting the weak link. For wider junctions the supercurrent presents a Fraunhofer-like interference pattern with periodicity h/2e whereas by shrinking electrostatically the weak link, the periodicity evolves continuously to a monotonic decay. These devices represent novel tunable structures that might lead to the study of the elusive Majorana fermions.Comment: 4.5 pages, 4 color figure

Mycobacterium bovis infections in Portugal: Spoligotyping and MIRU-VNTR typing of animal isolates

Tuberculosis is still one of the most important infectious diseases worldwide. Although human cases due to Mycobacterium bovis, the aetiological agent of bovine tuberculosis (bTB), considerably decreased in most industrialized countries, the possible zoonotic health hazard and the considerable economic losses it brings justify significant efforts to eradicate the disease in several countries. In Portugal, although a systematic slaughter policy of tuberculin reactive animals has been ongoing for several years, eradication is far from being achieved. In order to clarify possible infection sources and transmission routes, molecular typing of Portuguese M. bovis animal strains was undertaken. Two typing methods directed on potentially polymorphic genomic regions were chosen: Spoligotyping, a reverse line blot hybridization technique that evaluates the presence or absence of 43 oligonucleotide sequences in the Direct Repeat genomic region, and MIRU-VNTR (Mycobacterial Interspersed Repetitive Units- Variable Number Tandem Repeats) typing of 8 selected minisatellite like loci

Effective core potential ab initio calculations on main group heptoxides and large silicate systems

The ab initio molecular structures for several main group heptoxides (X2O7n-, n=0,2,4) are calculated using effective core potentials at the HF and DFT (B3LYP) levels. Particular attention is given to the X-O-X bond angle, as this structural parameter is a key feature for the study of both heptoxides and larger derivatives, such as polysilicate systems. The extent of the p-d interactions, which was found to be the main factor governing the magnitude of the X-O-X angle in transition metal heptoxides, does not play a significant role in the main group analogues.http://www.sciencedirect.com/science/article/B6TGT-40V4F3D-3/1/f26d56c6395122fcba007ed20f55868

Effect of a magnetic field on the two-phonon Raman scattering in graphene

We have studied, both experimentally and theoretically, the change of the so-called 2D band of the Raman scattering spectrum of graphene (the two-phonon peak near 2700 cm-1) in an external magnetic field applied perpendicular to the graphene crystal plane at liquid helium temperature. A shift to lower frequency and broadening of this band is observed as the magnetic field is increased from 0 to 33 T. At fields up to 5--10 T the changes are quadratic in the field while they become linear at higher magnetic fields. This effect is explained by the curving of the quasiclassical trajectories of the photo-excited electrons and holes in the magnetic field, which enables us (i) to extract the electron inelastic scattering rate, and (ii) to conclude that electronic scattering accounts for about half of the measured width of the 2D peak.Comment: 11 pages, 7 figure

Tuning the electron-phonon coupling in multilayer graphene with magnetic fields

Magneto Raman scattering study of the E$_{2g}$ optical phonons in multi-layer epitaxial graphene grown on a carbon face of SiC are presented. At 4.2K in magnetic field up to 33 T, we observe a series of well pronounced avoided crossings each time the optically active inter Landau level transition is tuned in resonance with the E$_{2g}$ phonon excitation (at 196 meV). The width of the phonon Raman scattering response also shows pronounced variations and is enhanced in conditions of resonance. The experimental results are well reproduced by a model that gives directly the strength of the electron-phonon interaction.Comment: 4 pages, 3 figure

Rhodoliths and rhodolith beds

Rhodolith (maërl) beds, communities dominated by free living coralline algae, are a common feature of subtidal environments worldwide. Well preserved as fossils, they have long been recognized as important carbonate producers and paleoenvironmental indicators. Coralline algae produce growth bands with a morphology and chemistry that record environmental variation. Rhodoliths are hard but often fragile, and growth rates are only on the order of mm/yr. The hard, complex structure of living beds provides habitats for numerous associated species not found on otherwise entirely sedimentary bottoms. Beds are degraded locally by dredging and other anthropogenic disturbances, and recovery is slow. They will likely suffer severe impacts worldwide from the increasing acidity of the ocean. Investigations of rhodolith beds with scuba have enabled precise stratified sampling that has shown the importance of individual rhodoliths as hot spots of diversity. Observations, collections, and experiments by divers have revolutionized taxonomic studies by allowing comprehensive, detailed collection and by showing the large effects of the environment on rhodolith morphology. Facilitated by in situ collection and calibrations, corallines are now contributing to paleoclimatic reconstructions over a broad range of temporal and spatial scales. Beds are particularly abundant in the mesophotic zone of the Brazilian shelf where technical diving has revealed new associations and species. This paper reviews selected past and present research on rhodoliths and rhodolith beds that has been greatly facilitated by the use of scuba

New approach addressing sustainability in urban areas using sustainable city models

A brief analysis of the environmental, social and economic paradigm of nowadays cities, allows reaching a simple conclusion: current cities are not sustainable. Considering this, it is very important to study the causes of cities problems and to develop city models implementing sustainability practices. There are a limited number of studies developing sustainable city models, but the scientific community lacks even more studies about the rehabilitation of current cities to implement these models. This work emerges with the objective of analysing how it is possible to implement sustainability practices in cities through the development of a sustainable city model and an urban rehabilitation plan. The development of sustainable city models is a very complex topic and the analysis of the literature shows that it is necessary to consider the relation between environmental and social aspects in the development of sustainable cities, while taking special concerns when considering the economic issues. It was also concluded that sustainable city models and rehabilitation plans should be subject to sustainability assessments and should consider the active participation of its inhabitants. In fact, a city can only be sustainable if its population is in harmony with the city model and we can only assess results by predicting and measuring performance levels.(undefined

Comprehensive transient-state study for CARMENES-NIR high thermal stability

CARMENES has been proposed as a next-generation instrument for the 3.5m Calar Alto Telescope. Its objective is finding habitable exoplanets around M dwarfs through radial velocity measurements (m/s level) in the near-infrared. Consequently, the NIR spectrograph is highly constraint regarding thermal/mechanical requirements. As a first approach, the thermal stability has been limited to \pm 0.01K (within year period) over a working temperature of 243K. This can be achieved by means of several temperature-controlled rooms. The options considered to minimise the complexity of the thermal design are here presented, as well as the transient-state thermal analyses realised to make the best choice