Spectral Properties and Local Density of States of Disordered Quantum Hall Systems with Rashba Spin-Orbit Coupling

We theoretically investigate the spectral properties and the spatial dependence of the local density of states (LDoS) in disordered two-dimensional electron gases (2DEG) in the quantum Hall regime, taking into account the combined presence of electrostatic disorder, random Rashba spin-orbit in- teraction, and finite Zeeman coupling. To this purpose, we extend a coherent-state Green's function formalism previously proposed for spinless 2DEG in the presence of smooth arbitrary disorder, that here incorporates the nontrivial coupling between the orbital and spin degrees of freedom into the electronic drift states. The formalism allows us to obtain analytical and controlled nonperturbative expressions of the energy spectrum in arbitrary locally flat disorder potentials with both random electric fields and Rashba coupling. As an illustration of this theory, we derive analytical microscopic expressions for the LDoS in different temperature regimes which can be used as a starting point to interpret scanning tunneling spectroscopy data at high magnetic fields. In this context, we study the spatial dependence and linewidth of the LDoS peaks and explain an experimentally-noticed correlation between the spatial dispersion of the spin-orbit splitting and the local extrema of the potential landscape.Comment: 18 pages, 5 figures; typos corrected and Sec. IV A rewritten; published versio

The complete mitochondrial genome of Yarrowia lipolytica

We here report the complete nucleotide sequence of the 47.9 kb mitochondrial (mt) genome from the obligate aerobic yeast Yarrowia lipolytica. It encodes, all on the same strand, seven subunits of NADH: ubiquinone oxidoreductase (ND1-6, ND4L), apocytochrome b (COB), three subunits of cytochrome oxidase (COX1, 2, 3), three subunits of ATP synthetase (ATP6, 8 and 9), small and large ribosomal RNAs and an incomplete set of tRNAs. The Y. lipolytica mt genome is very similar to the Hansenula wingei mt genome, as judged from blocks of conserved gene order and from sequence homology. The extra DNA in the Y. lipolytica mt genome consists of 17 group 1 introns and stretches of A+Trich sequence, interspersed with potentially transposable GC clusters. The usual mould mt genetic code is used. Interestingly, there is no tRNA able to read CGN (arginine) codons. CGN codons could not be found in exonic open reading frames, whereas they do occur in intronic open reading frames. However, several of the intronic open reading frames have accumulated mutations and must be regarded as pseudogenes. We propose that this may have been triggered by the presence of untranslatable CGN codons. This sequence is available under EMBL Accession No. AJ307410

The many facets of polyelectrolytes and oppositely charged macroions complex formation

A review. Various models of the complex formation between polyelectrolyte chains and oppositely charged macroions are reviewed. In recent years, a great deal of knowledge of the multitude of possible polyelectrolyte conformations at the macroion surface has been accumulated, which consequently has led to increasing interest in using such complexes in the design of nanomaterials. This review focuses on key studies relating to the effects of various physico-chem. parameters on complex formation and areas for future research are identified

Dielectric discontinuity effects on the adsorption of a linear polyelectrolyte at the surface of a neutral nanoparticle

The formation of complexes between nanoparticles and polyelectrolytes is a key process for the control of the reactivity of manufd. nanoparticles and rational design of core shell nanostructures. In this work, we investigate the influence of the nanoparticle dielec. const. on the adsorption of a linear charged polymer (polyelectrolyte) at the surface of a neutral nanoparticle. The polyelectrolyte linear charge d., as well as the image charges in the nanoparticle due to the dielec. discontinuity, is taken into account. Monte Carlo simulations are used to predict the adsorption/desorption limits and system properties. Effects of the nanoparticle size and polyelectrolyte length are also investigated. The polyelectrolyte is found adsorbed on the nanoparticle when the dielec. const. of the nanoparticle is greater than the dielec. const. of the medium. Attractive interactions induced by the presence of opposite sign image charges are found strong enough to adsorb the polyelectrolyte showing that the reaction field contribution has to be considered. The affinity between the polyelectrolyte and the nanoparticle is found to increase in magnitude by increasing the nanoparticle size and dielec. const. The reaction field magnitude is also found to depend in a nonlinear way from the polyelectrolyte length

Effects of surface site distribution and dielectric discontinuity on the charging behavior of nanoparticles. A grand canonical Monte Carlo study

The surface site distribution and the dielec. discontinuity effects on the charging process of a spherical nanoparticle (NP) have been investigated. It is well known that electrostatic repulsion between charges on neighboring sites tends to decrease the effective charge of a NP. The situation is more complicated close to a dielec. breakdown, since here a charged site is not only interacting with its neighbors but also with its own image charge and the image charges of all its neighbors. Coexistence of opposite charges, titrn. sites positions, and pH dependence are systematically studied using a grand canonical Monte Carlo method. A Tanford and Kirkwood approach has been applied to describe the interaction potentials between explicit discrete ampholytic charging sites. Homogeneous, heterogeneous and patch site distributions were considered to reproduce the titrn. site distribution at the solid/soln. interface of natural NPs. Results show that the charging process is controlled by the balance between Coulomb interactions and the reaction field through the solid-liq. interface. They also show that the site distribution plays a crucial role in the charging process. In patch distributions, charges accumulate at the perimeter of each patch due to finite size effects. When homogeneous and heterogeneous distributions are compared, three different charging regimes are obtained. In homogeneous and heterogeneous (with quite low polydispersity indexes) distributions, the effects of the NP dielec. const. on Coulomb interactions are counterbalanced by the reaction field and in this case, the dielec. breakdown has no significant effect on the charging process. This is not the case in patch distributions, where the dielec. breakdown plays a crucial role in the charging process

Ultrahigh finesse Fabry-Perot superconducting resonator

We have built a microwave Fabry-Perot resonator made of diamond-machined copper mirrors coated with superconducting niobium. Its damping time (Tc = 130 ms at 51 GHz and 0.8 K) corresponds to a finesse of 4.6 x 109, the highest ever reached for a Fabry-Perot in any frequency range. This result opens novel perspectives for quantum information, decoherence and non-locality studies

Tree canopy density thresholds for improved forests cover estimation in protected areas of Madagascar

The rich endemic biodiversity of Madagascar is concentrated in different types of natural forests primarily conserved within the network of protected areas (PAs). Since 1990, remote sensing has been utilized to monitor forest cover. The latest forest cover map generated using these techniques provides accurate estimates of natural forest cover within the PAs network. However, the standardized application of Tree Canopy Density (TCD), as used in global assessments of forest cover, yields erroneous estimates for different forest types in Madagascar because the standard TCD cannot be globally applied to all types of forests. Our study aims to utilize global remote sensing data at the scale of PAs to identify specific TCD thresholds for individual PAs. Starting from the year 2000 data, the application of these thresholds will allow us to estimate deforestation in subsequent years at reduced costs. We used the official PA boundaries, a reliable forest cover map at the national scale, and the TCDs published at a global scale to infer the values of TCD to be applied in each PA. The standard TCD threshold above 30% overestimates humid and dry forests and underestimates dry spiny forests in Madagascar. Our specific TCD thresholds inferred for each PA accurately estimate the forest cover in the vast majority of PAs. Using these specific TCD thresholds will allow for improved monitoring of forest cover within the network of PAs. The methodology detailed here can also be applied in other geographic regions, and future improvements in data on forest cover—both remotely sensed and field-collected—will enhance our ability to estimate forest cover and its changes over time