Comment on "Magnetic response of Disordered Metallic Rings: Large Contributions of Far Levels"

Comment on cond-mat/0205390; PRL 90, 026805 (2003

Sum rules for spin-Hall conductivity cancelation

It has been shown recently that the universal dc spin conductivity of two-dimensional electrons with a Rashba spin-orbit interaction is canceled by vertex corrections in a weak scattering regime. We prove that the zero bulk spin conductivity is an intrinsic property of the free-electron Hamiltonian and scattering is merely a tool to reveal this property in terms of the diagrammatic technique. When Zeeman energy is neglected, the zero dc conductivity persists in a magnetic field. Spin conductivity increases resonantly at the cyclotron frequency and then decays towards the universal value.Comment: 4 pages, 1 figur

Crossover from diffusive to non-diffusive dynamics in the two-dimensional electron gas with Rashba spin-orbit coupling

We present the calculation of the density matrix response function of the two-dimensional electron gas with Rashba spin-orbit interaction, which is applicable in a wide range of parameters covering the diffusive and non-diffusive, the dirty and the clean limits. A description of the crossover between the different regimes is thus provided as well. On the basis of the derived microscopic expressions we study the propagating charge and spin-polarization modes in the clean, non-diffusive regime, which is accessible in the modern experiments.Comment: 8 pages, 6 figures, a considerable extension of the first versio

Spin-orbit coupling in a Quantum Dot at high magnetic field

We describe the simultaneous effects of the spin-orbit (SO) perturbation and a magnetic field $B$ on a disk shaped quantum dot (QD). {As it is known the} combination of electrostatic forces among the $N$ electrons confined in the QD and the Pauli principle can induce a spin polarization when $B$ (applied in the direction orthogonal to the QD) is above a threshold value. In the presence of an electric field parallel to $B$, coupled to the spin $S$ by a Rashba term, we demonstrate that a symmetry breaking takes place: we can observe it by analyzing the splitting of the levels belonging to an unperturbed multiplet. We also discuss the competitive effects of the magnetic field, the SO perturbation and the electron electron interaction, in order to define the hierarchy of the states belonging to a multiplet. We demonstrate how this hierarchy depends on the QD's size. We show the spin texture due to the combined effects of the Rashba effect and the interaction responsible for the polarization.Comment: 8 pages, 3 figures, PACS: 73.21.La,71.15.Mb,75.75.+

Integer Spin Hall Effect in Ballistic Quantum Wires

We investigate the ballistic electron transport in a two dimensional Quantum Wire under the action of an electric field ($E_y$). We demonstrate how the presence of a Spin Orbit coupling, due to the uniform electric confinement field gives a non-commutative effect as in the presence of a transverse magnetic field. We discuss how the non commutation implies an edge localization of the currents depending on the electron spins also giving a semi-classical spin dependent Hall current. We also discuss how it is possible obtain a quantized Spin Hall conductance in the ballistic transport regime by developing the Landauer formalism and show the coupling between the spin magnetic momentum and the orbital one due to the presence of a circulating current.Comment: 7 pages, 5 figures, accepted for publication in Phys. Rev. B, PACS: 72.25.-b, 72.10.-d, 72.15.Rn, 73.23.-b, 71.10.P

Modeling the Daily Variations of the Coronal X-ray Spectral Irradiance with Two Temperatures and Two Emission Measures

The Miniature X-ray Solar Spectrometer (MinXSS-1) CubeSat observed solar X-rays between 0.5 and 10 keV. A two-temperature, two-emission measure model is fit to each daily averaged spectrum. These daily average temperatures and emission measures are plotted against the corresponding daily solar 10.7 cm radio flux (F10.7) value and a linear correlation is found between each that we call the Schwab Woods Mason (SWM) model. The linear trends show that one can estimate the solar spectrum between 0.5 keV and 10 keV based on the F10.7 measurement alone. The cooler temperature component of this model represents the quiescent sun contribution to the spectra and is essentially independent of solar activity, meaning the daily average quiescent sun is accurately described by a single temperature (1.70 MK) regardless of solar intensity and only the emission measure corresponding to this temperature needs to be adjusted for higher or lower solar intensity. The warmer temperature component is shown to represent active region contributions to the spectra and varies between 5 MK to 6 MK. GOES XRS-B data between 1-8 Angstroms is used to validate this model and it is found that the ratio between the SWM model irradiance and the GOES XRS-B irradiance is close to unity on average. MinXSS-1 spectra during quiescent solar conditions have very low counts beyond around 3 keV. The SWM model can generate MinXSS-1 or DAXSS spectra at very high spectral resolution and with extended energy ranges to fill in gaps between measurements and extend predictions back to 1947

Connecting biodiversity monitoring with soil inventory information - A Swiss case study

Switzerland is one of the first countries in the world to monitor its biological diversity. The Federal Office for the environment (FOEN), triggered by the Rio world summit, initiated 1995 a program for this purpose called Biodiversity Monitoring in Switzerland (BDM). According to the Convention on Biological Diversity various biodiversity targets were defined and the action plan strategy biodiversity Switzerland serves to implement these strategic goals. Unfortunately, up to very recently, soil was not part of these considerations. In the Swiss biodiversity monitoring system a core indicator, species diversity in habitats, is designed to document changes in species diversity of vascular plants and mosses in Switzerland’s major habitats. Together with the current land use and general metadata like elevation, slope, exposition and geology these data are stored in a central database. Since 2001 the totally 1’600 sites based on a regular grid (6 by 4 km) are resampled in a 5 years interval. In the third sampling campaign (2011-2015) the setting was broadened by taking soil samples at all locations possible. At each site 4 replicates 0-20 cm were taken to provide predictions on plot scale variability. All samples were prepared in the laboratory of the Swiss Soil Monitoring Network. Exploratory data analyses for pH, soil organic carbon and nitrogen revealed distinct patterns according to land use as well as to altitude; pH decreases from colline to alpine zones. Furthermore, regional analyses show enormous differences between the northern and southern side of the Alps. Connecting measured soil parameters with the outcome of the BDM survey enables to determine the impact of environmental conditions on species diversity of vascular plants and mosses as well as on soil-plant interactions. Therefore, connecting measured soil inventory data and plant and moss diversity information provide a clear added value to the Biodiversity Monitoring in Switzerland

The Energetic Costs of Cellular Computation

Cells often perform computations in response to environmental cues. A simple example is the classic problem, first considered by Berg and Purcell, of determining the concentration of a chemical ligand in the surrounding media. On general theoretical grounds (Landuer's Principle), it is expected that such computations require cells to consume energy. Here, we explicitly calculate the energetic costs of computing ligand concentration for a simple two-component cellular network that implements a noisy version of the Berg-Purcell strategy. We show that learning about external concentrations necessitates the breaking of detailed balance and consumption of energy, with greater learning requiring more energy. Our calculations suggest that the energetic costs of cellular computation may be an important constraint on networks designed to function in resource poor environments such as the spore germination networks of bacteria.Comment: 9 Pages (including Appendix); 4 Figures; v3 corrects even more typo