Lattice relaxation around arsenic and selenium in CdTe

We have investigated the lattice relaxation around impurity atoms at the anion sublattice in CdTe, such as As acting as acceptor and Se which is isovalent to Te, with fluorescence detected EXAFS. We experimentally verify the lattice relaxation with a bond length being reduced by 8% around the As atom as inferred indirectly from ab-initio calculations of the electric field gradient in comparison with the measured value in a PAC experiment (S. Lany et al., Phys. Rev. B 62, R2259 (2000)). In the case of the isovalent impurity atom Se, the bond length is similarly reduced as determined experimentally by EXAFS and by model calculations with the density functional theory implemented in the WIEN97 program. In contrast to this inward relaxation, preliminary calculations for Br in CdTe, the next element in the series As, Se, and Br, which acts as donor at the Te sublattice, indicate an increase in bond length, an interesting prediction waiting for experimental verification

Experimental verification of calculated lattice relaxations around impurities in CdTe

We have measured the lattice distortion around As acceptor and Br donor in CdTe with fluorescence detected X ray absorption spectroscopy. We could experimentally verify the lattice relaxation with a bond length reduction of 8 around the As atom as inferred indirectly from ab initio calculations of the electric field gradient performed with the WIEN97 package in comparison with the measured value in a Perturbed Angular Correlation experiment as recently reported. We have complemented our own calculations of relaxation with WIEN97 with calculations using the FHI96md pseudo potential program which allows the use of larger super cell sizes. Encouraged by the good agreement between experiment and model calculation for As in CdTe as well as similarly for the isovalent Se in CdTe, we extended our investigation to Br in CdTe, where the electric field gradient has also been measured, and could not only verify the derived lattice expansion around Br with our EXAFS analysis but additionally observe fractions of Br in the A center as well as in a DX center configuratio

Gaming with eutrophication: Contribution to integrating water quantity and quality management at catchment level

The Metropolitan Region of Sao Paulo (MRSP) hosts 18 million inhabitants. A complex system of 23 interconnected reservoirs was built to ensure its water supply. Half of the potable water produced for MRSP's population (35 m3/s) is imported from a neighbour catchment, the other half is produced within the Alto Tietê catchment, where 99% of the population lives. Perimeters of land use restriction were defined to contain uncontrolled urbanization, as domestic effluents were causing increasing eutrophication of some of these reservoirs. In the 90's catchment committees and sub committees were created to promote discussion between stakeholders and develop catchment plans. The committees are very well structured "on paper". However, they are not very well organised and face a lack of experience. The objective of this work was to design tools that would strengthen their discussion capacities. The specific objective of the AguAloca process was to integrate the quality issue and its relation to catchment management as a whole in these discussions. The work was developed in the Alto Tietê Cabeceiras sub-catchment, one of the 5 sub catchments of the Alto-Tietê. It contains 5 interconnected dams, and presents competitive uses such as water supply, industry, effluent dilution and irrigated agriculture. A RPG was designed following a companion modelling approach (Etienne et al., 2003). It contains a friendly game-board, a set of individual and collective rules and a computerized biophysical model. The biophysical model is used to simulate water allocation and quality processes at catchment level. It articulates 3 modules. A simplified nutrient discharge model permits the estimation of land use nutrient exportation. An arc-node model simulates water flows and associated nutrient charges from one point of the hydrographical network to another. The Vollenweider model is used for simulating specific reservoir dynamics. The RPG allows players to make individual and collective decisions related to water allocation and the management of its quality. Impacts of these decisions are then simulated using the biophysical model. Specific indicators of the game are then updated and may influence player's behaviour (actions) in following rounds. To introduce discussions on the management of water quality at a catchment level, an issue that is rarely explicitly dealt with, four game sessions were implemented involving representatives of basin committees and water and sanitation engineers. During the game session, the participants took advantage of the water quality output of the biophysical model to test management alternatives such as rural sewage collection or effluent dilution. The biophysical model accelerated calculations of flows and eutrophication rates that were then returned to the game board with explicit indicators of quantity and quality. Players could easily test decisions impacting on qualitative water processes and visualize the simulation results directly on the game board that was representing a friendly, virtual and simplified catchment. The Agualoca game proved its ability to turn complex water processes understandable for a non totally initiated public. This experience contributed to a better understanding of multiple-use water management and also of joint management of water quality and quantity. (Résumé d'auteur

First principles calculations of tetragonal FeX X S, Se, Te Magnetism, hyperfine interaction, and bonding

Magnetic ground states, local crystallographic environment of Fe, and hyperfine interaction parameters in tetragonal FeX X S, Se, Te are investigated by means of density functional theory DFT calculations using augmented plane waves plus local orbitals APW lo method. We use several different mag netic configurations to evaluate the magnetic and electronic properties of this system, as well as the hyperfine interaction parameters at Fe lattice site. The results obtained for the ground state collinear anti ferromagnetic arrangement relatively well reproduce the quadruple splitting and isomer shifts from the available Mössbauer measurements. The Bader s atoms in molecule charge density analysis indicates bonding of closed shell type and a sizable charge transfer from Fe to X . The system properties are sensitive to the structural optimization of the position of the chalcogen atom with respect to the iron plan

Higher Twist Distribution Amplitudes of the Nucleon in QCD

We present the first systematic study of higher-twist light-cone distribution amplitudes of the nucleon in QCD. We find that the valence three-quark state is described at small transverse separations by eight independent distribution amplitudes. One of them is leading twist-3, three distributions are twist-4 and twist-5, respectively, and one is twist-6. A complete set of distribution amplitudes is constructed, which satisfies equations of motion and constraints that follow from conformal expansion. Nonperturbative input parameters are estimated from QCD sum rules.Comment: 29 pages, 4 figures, eqn in (3.19) corrected, table 3 accordingly changed, some typos fixe

Topical inflammasome inhibition with disulfiram prevents irritant contact dermatitis

Background: The pathogenesis of contact dermatitis, a common inflammatory skin disease with limited treatment options, is held to be driven by inflammasome activation induced by allergens and irritants. We here aim to identify inflammasome-targeting treatment strategies for irritant contact dermatitis. Methods: A high content screen with 41,184 small molecules was performed using fluorescent Apoptosis associated speck-like protein containing a CARD (ASC) speck formation as a readout for inflammasome activation. Hit compounds were validated for inhibition of interleukin (IL)-1β secretion. Of these, the approved thiuramdisulfide derivative disulfiram was selected and tested in a patch test model of irritant contact dermatitis in 25 healthy volunteers. Topical application of disulfiram, mometasone or vehicle was followed by application of sodiumdodecylsulfate (SDS) for 24 h each. Eczema induction was quantified by mexameter and laser speckle imaging. Corneocyte sampling of lesional skin was performed to assess inflammasome-mediated cytokines IL-1β and IL-18. Results: Disulfiram induced a dose-dependent inhibition of ASC speck formation and IL-1β release in cellular assays in vitro. In vivo, treatment with disulfiram, but not with vehicle and less mometasone, inhibited SDS-induced eczema. This was demonstrated by significantly lower erythema and total perfusion values assessed by mexameter and laser speckle imaging for disulfiram compared to vehicle (p < 0.001) and/or mometasone (p < 0.001). Also, corneocyte IL-18 levels were significantly reduced after application of disulfiram compared to vehicle (p < 0.001). Conclusion: We show that disulfiram is a dose-dependent inhibitor of inflammasome pathway activation in vitro and inhibitor of SDS-induced eczema in vivo. Topical application of disulfiram represents a potential treatment option for irritant contact dermatitis

Survey of electronic properties and local structures around Fe in selected multinary chalcogenides

Paper presents detailed studies of local and electronic structure around Fe in Cd0.97Fe0.03Te, Cd0.98Fe0.02Te0.97Se0.03 and Cd0.99Fe0.01Te0.91S0.09 multinary chalcogenides by means of X ray absorption fine structure XAFS , X ray magnetic circular dichroism XMCD and electron paramagnetic resonance EPR measurements. In addition, electronic consequences of Fe incorporation into CdTe semiconductor host were studied by means of first principles calculations. In order to improve accuracy of the calculated total energies, the band gaps and the band edge positions, special attention is paid to the treatment of exchange correlation interaction and the description of highly localized Fe 3d states. Also, the Bader theory of the topological properties of the electron charge density is used to access details of the nature, strength and distribution of the next nearest neighbour bonds. Local and electronic structure around Fe in Cd0.97Fe0.03Te and Cd0.98Fe0.02Te0.97Se0.03 systems have been found to exhibit similar characteristics, since the first coordination sphere around Fe comprises four Te atoms located at approximately the same distance. In Cd0.99Fe0.01Te0.91S0.09 system, however, local bimodal distribution of distances has been revealed, with one Fe Te bond replaced with much shorter Fe S bond, resulting in much stronger crystal field. Along with the crystal field effect, the spin orbit interaction has proven to play decisive role in determining the nature of Fe doped CdTe systems. While the systems with higher Fe concentrations 25 at. are intrinsic insulators, in systems with only 3.125 at. Fe one spin channel contributes to the density of states at the Fermi level, which makes them suitable for spin selective electronic transport application

Long-lived states in synchronized traffic flow. Empirical prompt and dynamical trap model

The present paper proposes a novel interpretation of the widely scattered states (called synchronized traffic) stimulated by Kerner's hypotheses about the existence of a multitude of metastable states in the fundamental diagram. Using single vehicle data collected at the German highway A1, temporal velocity patterns have been analyzed to show a collection of certain fragments with approximately constant velocities and sharp jumps between them. The particular velocity values in these fragments vary in a wide range. In contrast, the flow rate is more or less constant because its fluctuations are mainly due to the discreteness of traffic flow. Subsequently, we develop a model for synchronized traffic that can explain these characteristics. Following previous work (I.A.Lubashevsky, R.Mahnke, Phys. Rev. E v. 62, p. 6082, 2000) the vehicle flow is specified by car density, mean velocity, and additional order parameters $h$ and $a$ that are due to the many-particle effects of the vehicle interaction. The parameter $h$ describes the multilane correlations in the vehicle motion. Together with the car density it determines directly the mean velocity. The parameter $a$, in contrast, controls the evolution of $h$ only. The model assumes that $a$ fluctuates randomly around the value corresponding to the car configuration optimal for lane changing. When it deviates from this value the lane change is depressed for all cars forming a local cluster. Since exactly the overtaking manoeuvres of these cars cause the order parameter $a$ to vary, the evolution of the car arrangement becomes frozen for a certain time. In other words, the evolution equations form certain dynamical traps responsible for the long-time correlations in the synchronized mode.Comment: 16 pages, 10 figures, RevTeX

Virtual unfolding of folded papyri

The historical importance of ancient manuscripts is unique since they provide information about the heritage of ancient cultures. Often texts are hidden in rolled or folded documents. Due to recent improvements in sensitivity and resolution, spectacular disclosures of rolled hidden texts were possible by X-ray tomography. However, revealing text on folded manuscripts is even more challenging. Manual unfolding is often too risky in view of the fragile condition of fragments, as it can lead to the total loss of the document. X-ray tomography allows for virtual unfolding and enables non-destructive access to hidden texts. We have recently demonstrated the procedure and tested unfolding algorithms on a mockup sample. Here, we present results on unfolding ancient papyrus packages from the papyrus collection of the Musée du Louvre, among them objects folded along approximately orthogonal folding lines. In one of the packages, the first identification of a word was achieved, the Coptic word for “Lord”