Spin currents in superconductors

It is argued that experiments on rotating superconductors provide evidence for the existence of macroscopic spin currents in superconductors in the absence of applied external fields. Furthermore it is shown that the model of hole superconductivity predicts the existence of such currents in all superconductors. In addition it is pointed out that spin currents are required within a related macroscopic (London-like) electrodynamic description of superconductors recently proposed. The spin current arises through an intrinsic spin Hall effect when negative charge is expelled from the interior of the metal upon the transition to the superconducting state

The Multi-Wavelength Tully-Fisher relation with spatially resolved HI kinematics

In this paper we investigate the statistical properties of the Tully-Fisher relation for a sample of 32 galaxies with measured distances from the Cepheid period-luminosity relation and/or TRGB stars. We take advantage of panchromatic photometry in 12 bands (from FUV to 4.5 $\mu$m) and of spatially resolved HI kinematics. We use these data together with three kinematic measures ($W^{i}_{50}$, $V_{max}$ and $V_{flat}$) extracted from the global HI profiles or HI rotation curves, so as to construct 36 correlations allowing us to select the one with the least scatter. We introduce a tightness parameter $\sigma_{\perp}$ of the TFr, in order to obtain a slope-independent measure of the goodness of fit. We find that the tightest correlation occurs when we select the 3.6 $\mu$m photometric band together with the $V_{flat}$ parameter extracted from the HI rotation curve.Comment: 16 pages, 16 figures, accepted for publication in MNRAS, minor changes due to proof correction

Crystallization study by transmission electron microscopy of SrTiO3 thin films prepared by plasma-assisted ALD

The crystallization behavior of thin strontium titanate (SrTiO3, STO) films with ~15 nm thickness was studied by Transmission Electron Microscopy (TEM). Amorphous STO films with [Sr]/([Sr]+[Ti]) ratio ranging from 0.50 to 0.63 were deposited at 350°C by plasma-assisted ALD and subsequently treated by rapid thermal annealing in flowing N2 for crystallization. Different temperatures and annealing durations were employed to fully characterize the crystallization process. TEM analysis showed that transrotational crystals were formed and evidenced the influence of the STO composition and of the thermal budget applied on the grain size, crack and void formation. In particular, Sr-rich layers ([Sr]/([Sr]+[Ti] = 0.59) showed a finer crystalline structure which was imputed to a higher nucleation probability at the onset of the crystallization process. Crystallization into the perovskite structure was confirmed for all the film compositions studied. By tuning the STO composition and the thermal budget of the annealing step it was demonstrated that it is possible to control the microstructure of the crystallized film as a further step in optimizing the STO film properties

Electrodynamics of superconductors

An alternate set of equations to describe the electrodynamics of superconductors at a macroscopic level is proposed. These equations resemble equations originally proposed by the London brothers but later discarded by them. Unlike the conventional London equations the alternate equations are relativistically covariant, and they can be understood as arising from the 'rigidity' of the superfluid wave function in a relativistically covariant microscopic theory. They predict that an internal 'spontaneous' electric field exists in superconductors, and that externally applied electric fields, both longitudinal and transverse, are screened over a London penetration length, as magnetic fields are. The associated longitudinal dielectric function predicts a much steeper plasmon dispersion relation than the conventional theory, and a blue shift of the minimum plasmon frequency for small samples. It is argued that the conventional London equations lead to difficulties that are removed in the present theory, and that the proposed equations do not contradict any known experimental facts. Experimental tests are discussed.Comment: Small changes following referee's and editor's comments; to be published in Phys.Rev.

Effects of large-scale wetland loss on network connectivity of the Rainwater Basin, Nebraska

Context The Rainwater Basin region in south-central Nebraska supports a complex network of spatiallyisolated wetlands that harbor diverse floral and faunal communities. Since European settlement, many wetlands have been lost from the network, which has increased distances among remaining wetlands. As a result, populations of wildlife species with limited dispersal capabilities may have become isolated and face greater local extinction risks. Objectives We compared the pre-European settlement and current extent of the Rainwater Basin network to assess the effects of wetland losses on network connectivity for a range of maximum dispersal distances. Methods We constructed network models for a range of maximum dispersal distances and calculated network metrics to assess changes in network connectivity and the relative importance of individual wetlands in regulating flow. Results Since European settlement, the number of wetlands in the Rainwater Basin has decreased by[90%. The average distance to the nearest neighboring wetland has increased by 150% to * 1.2 km, and the dispersal distance necessary to travel throughout the whole network has increased from 3.5 to 10.0 km. Last, relative importance of individual wetlands depended on the maximum dispersal distance. Which wetlands to preserve to maintain connectivity might therefore depend on the dispersal capabilities of the species or taxa of interest. Conclusions To preserve a broad range of biodiversity, conservation efforts should focus on preserving dense clusters of wetlands at fine spatial scales to maintain current levels of network connectivity, and restoring connections between clusters to facilitate long-range dispersal of species with limited dispersal capabilities

Morphologies and stellar populations of galaxies in the core of Abell 2218

SUMMARIZED ABSTRACT: We present a study of the stellar populations and morphologies of galaxies in the core of the galaxy cluster Abell 2218. Integral field spectroscopy was obtained using PMAS/[email protected] CAHA to obtain a complete flux limited sample of cluster members within its field-of-view (~74"X64"). In addition of 31 galaxies with known redshifts in the outer regions, we built up a final sample of 59 spectroscopically confirmed cluster members. Multiban photometry and detailed morphologies were obtained using deep images taken with the HST/ACS camera in the BVRI and z-bands. The CM diagram shows that the E-type galaxies cover the range of brighter and redder colors. A large fraction of spiral galaxies ($\sim$50%) is found. They cover a wide range in colors. This result, together with the distributions of ages, metallicities and masses, indicates that E-type galaxies are more massive and have older stellar populations, while L-type galaxies are less massive and have a wider range of stellar Our results agree with a proposed two-step scenario for the evolution of galaxies in clusters. In addition, an extremely blue merging galaxy system is found at the core, with the nominal redshift of the cluster.Comment: 29 pages, 17 figures, accepted for publishing in MNRAS. (HST/ACS composite image: http://www.caha.es/sanchez/abell2218/BRI_big.jpg

The line-of-sight warp of the spiral galaxy ESO 123-G23

We present 3-D modelling of the distribution and kinematics of the neutral hydrogen in the spiral galaxy ESO 123-G23. The optical appearance of this galaxy is an almost perfectly edge-on disk, while the neutral hydrogen is found to extend vertically out to about 15 kpc on either side of the galactic plane. The HI layer and the major features of the HI data cube can be successfully explained by a model dominated by a strong (about 30 degrees) line-of-sight warp. Other models were tried, including a flare model and a two-component model, but they clearly do not reproduce the data. This is the first unambiguous detection of a galactic warp that has the maximum deviation from the central plane almost along the line-of-sight. No evidence for the presence of any companion galaxy is found in the HI data cube. Line-of-sight warps in edge-on galaxies are probably frequent, but escape detection as they are too weak. Moreover they may easily be mistaken as flares or 'thick disks'. A 3-D modelling of the HI layer as the one presented here is needed in order to distinguish between these possibilities.Comment: 5 pages, 5 figures, accepted by A&

PMAS: The Potsdam Multi Aperture Spectrophotometer. II. The Wide Integral Field Unit PPak

PPak is a new fiber-based Integral Field Unit (IFU), developed at the Astrophysical Institute Potsdam, implemented as a module into the existing PMAS spectrograph. The purpose of PPak is to provide both an extended field-of-view with a large light collecting power for each spatial element, as well as an adequate spectral resolution. The PPak system consists of a fiber bundle with 331 object, 36 sky and 15 calibration fibers. The object and sky fibers collect the light from the focal plane behind a focal reducer lens. The object fibers of PPak, each 2.7 arcseconds in diameter, provide a contiguous hexagonal field-of-view of 74 times 64 arcseconds on the sky, with a filling factor of 60%. The operational wavelength range is from 400 to 900nm. The PPak-IFU, together with the PMAS spectrograph, are intended for the study of extended, low surface brightness objects, offering an optimization of total light-collecting power and spectral resolution. This paper describes the instrument design, the assembly, integration and tests, the commissioning and operational procedures, and presents the measured performance at the telescope.Comment: 14 pages, 21 figures, accepted at PAS

Applying infrared thermography to soil surface temperature monitoring: Case study of a high-resolution 48 h survey in a vineyard (Anadia, Portugal)

The soil surface albedo decreases with an increasing biochar application rate as a power decay function, but the net impact of biochar application on soil temperature dynamics remains to be clarified. The objective of this study was to assess the potential of infrared thermography (IRT) sensing by monitoring soil surface temperature (SST) with a high spatiotemporal and thermal resolution in a scalable agricultural application. We monitored soil surface temperature (SST) variations over a 48 h period for three treatments in a vineyard: bare soil (plot S), 100% biochar cover (plot B), and biochar-amended topsoil (plot SB). The SST of all plots was monitored at 30 min intervals with a tripod-mounted IR thermal camera. The soil temperature at 10 cm depth in the S and SB plots was monitored continuously with a 5 min resolution probe. Plot B had greater daily SST variations, reached a higher daily temperature peak relative to the other plots, and showed a faster rate of T increase during the day. However, on both days, the SST of plot B dipped below that of the control treatment (plot S) and biochar-amended soil (plot SB) from about 18:00 onward and throughout the night. The diurnal patterns/variations in the IRT-measured SSTs were closely related to those in the soil temperature at a 10 cm depth, confirming that biochar-amended soils showed lower thermal inertia than the unamended soil. The experiment provided interesting insights into SST variations at a local scale. The case study may be further developed using fully automated SST monitoring protocols at a larger scale for a range of environmental and agricultural applications