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

Picocyanobacteria distribution in the Ebro Estuary (Spain)

The stratified estuary of the Ebro River is located on the Mediterranean coast of Spain. From samples obtained in 6 sampling campaigns between July 1999 and February 2000 from the last 18 km of Ebro River, the abundance of picocyanobacteria was estimated by epifluorescence microscopy. The abundance of picocyanobacteria reached 93.7 x106 cells L–1 in the river mouth (station R1) below the surface, in October 1999. In deeper layers of salt wedge area stations (near the river mouth), we could observe higher concentrations of marine cyanobacteria. This study offers comments about the abundance and distribution in cyanobacteria

Switching the sign of Josephson current through Aharonov-Bohm interferometry

We investigate the DC Josephson effect in a superconductor-normal metal-superconductor junction where the normal region consists of a ballistic ring. We show that a fully controllable $\pi$-junction can be realized through the electro-magnetostatic Aharonov-Bohm effect in the ring. The sign and the magnitude of the supercurrent can be tuned by varying the magnetic flux and the gate voltage applied to one arm, around suitable values. The implementation in a realistic set-up is discussed.Comment: 4 pages, 3 figure

A Case of Singular Geotechnical Failure for Industrial Structures in the Peruvian Andes

During the rainy season of 1982, foundation distress was occurred at several recently completed and still incomplete structures of an important mine project located in the Peruvian Andes. When the tailings thickener was tested an unexpected settlement started, some cracking was observed in the slab, and the central pier settled and tilted. The nature of the distress suggested the failure occurred as the result of the combined effect of a long term seepage under the bearing foundation soil and due to its different degree of compaction. This paper presents the characteristics of these problems as both foundation and fill materials, the probably failure mechanisms and a discussion of geotechnical design criteria to solving them

Flow regimes study within the Strait of Gibraltar using a high-performance numerical model

A three-dimensional sigma coordinate free-surface high-performance model is used to investigate the flow regimes within the Strait of Gibraltar. High performances are achieved through a directive-based, MPI-like, parallelization of the code, obtained using SMS tool. The model makes use of a coastal-following, curvilinear orthogonal grid, that includes the Gulf of Cadiz and the Alboran Sea, reaching very high resolution in the Strait. Four experiments with different initial salinity conditions representing the present and possible future climate conditions over the Mediterranean basin have been performed. Model results, analysed by means of the three-layer composite Froude number theory, have shown two different possible regimes within the strait; for the present climate condition the strait is subjected to a sub-maximal regimewhilefor possible future climate conditions a maximal regime can be reached

Living on the Edge: Settlement Patterns by the Symbiotic Barnacle \u3cem\u3eXenobalanus globicipitis\u3c/em\u3e on Small Cetaceans

The highly specialized coronulid barnacle Xenobalanus globicipitis attaches exclusively on cetaceans worldwide, but little is known about the factors that drive the microhabitat patterns on its hosts. We investigate this issue based on data on occurrence, abundance, distribution, orientation, and size of X. globicipitis collected from 242 striped dolphins (Stenella coeruleoalba) that were stranded along the Mediterranean coast of Spain. Barnacles exclusively infested the fins, particularly along the trailing edge. Occurrence, abundance, and density of X. globicipitis were significantly higher, and barnacles were significantly larger, on the caudal fin than on the flippers and dorsal fin. Barnacles were found more frequently and in greater numbers on the dorsal rather than ventral side of the caudal fin and on the central third of dorsal and ventral fluke surfaces. Nearly all examined individuals attached with their cirral fan oriented opposite to the fluke edge. We suggest that X. globicipitis may chemically recognize dolphins as a substratum, but fins, particularly the flukes, are passively selected because of creation of vortices that increase contact of cyprids with skin and early survival of these larvae at the corresponding sites. Cyprids could actively select the trailing edge and orient with the cirri facing the main direction of flow. Attachment on the dorsal side of the flukes is likely associated with asymmetrical oscillation of the caudal fin, and the main presence on the central segment of the flukes could be related to suitable water flow conditions generated by fluke performance for both settlement and nutrient filtration

Modelling the Canes Venatici I dwarf spheroidal galaxy

The aim of this work is to find a progenitor for Canes Venatici I (CVn I), under the assumption that it is a dark matter free object that is undergoing tidal disruption. With a simple point mass integrator, we searched for an orbit for this galaxy using its current position, position angle, and radial velocity in the sky as constraints. The orbit that gives the best results has the pair of proper motions $\mu_\alpha$ = -0.099 mas yr$^{-1}$ and $\mu_\delta$ = -0.147 mas yr$^{-1}$, that is an apogalactic distance of 242.79 kpc and a perigalactic distance of 20.01 kpc. Using a dark matter free progenitor that undergoes tidal disruption, the best-fitting model matches the final mass, surface brightness, effective radius, and velocity dispersion of CVn I simultaneously. This model has an initial Plummer mass of 2.47 x $10^7$ M$_\odot$ and a Plummer radius of 653 pc, producing a remnant after 10 Gyr with a final mass of 2.45 x 10$^5$ M$_\odot$, a central surface brightness of 26.9 mag arcsec$^{-2}$, an effective radius of 545.7 pc, and a velocity dispersion with the value 7.58 km s$^{-1}$. Furthermore, it is matching the position angle and ellipticity of the projected object in the sky.Comment: 11 pages, 14 figures, accepted by A&

Anthocyanins are Key Regulators of Drought Stress Tolerance in Tobacco

Abiotic stresses will be one of the major challenges for worldwide food supply in the near future. Therefore, it is important to understand the physiological mechanisms that mediate plant responses to abiotic stresses. When subjected to UV, salinity or drought stress, plants accumulate specialized metabolites that are often correlated with their ability to cope with the stress. Among them, anthocyanins are the most studied intermediates of the phenylpropanoid pathway. However, their role in plant response to abiotic stresses is still under discussion. To better understand the effects of anthocyanins on plant physiology and morphogenesis, and their implications on drought stress tolerance, we used transgenic tobacco plants (AN1), which over-accumulated anthocyanins in all tissues. AN1 plants showed an altered phenotype in terms of leaf gas exchanges, leaf morphology, anatomy and metabolic profile, which conferred them with a higher drought tolerance compared to the wild-type plants. These results provide important insights for understanding the functional reason for anthocyanin accumulation in plants under stress