From laterally modulated two-dimensional electron gas towards artificial graphene

Cyclotron resonance has been measured in far-infrared transmission of GaAs/Al$_x$Ga$_{1-x}$As heterostructures with an etched hexagonal lateral superlattice. Non-linear dependence of the resonance position on magnetic field was observed as well as its splitting into several modes. Our explanation, based on a perturbative calculation, describes the observed phenomena as a weak effect of the lateral potential on the two-dimensional electron gas. Using this approach, we found a correlation between parameters of the lateral patterning and the created effective potential and obtain thus insights on how the electronic miniband structure has been tuned. The miniband dispersion was calculated using a simplified model and allowed us to formulate four basic criteria that have to be satisfied to reach graphene-like physics in such systems

Accuracy of Semiclassical Methods for Shape Invariant Potentials

We study the accuracy of several alternative semiclassical methods by computing analytically the energy levels for many large classes of exactly solvable shape invariant potentials. For these potentials, the ground state energies computed via the WKB method typically deviate from the exact results by about 10%, a recently suggested modification using nonintegral Maslov indices is substantially better, and the supersymmetric WKB quantization method gives exact answers for all energy levels.Comment: 7 pages, Latex, and two tables in postscrip

Quantum superconductor-metal transition

We consider a system of superconducting grains embedded in a normal metal. At zero temperature this system exhibits a quantum superconductor-normal metal phase transition. This transition can take place at arbitrarily large conductance of the normal metal.Comment: 13 pages, 1 figure include

Two-dimensional photonic crystal slab with embedded silicon nanocrystals: Efficient photoluminescence extraction:

A two-dimensional photonic crystal (PhC) slab was fabricated from a luminescent planar waveguide, formed by a (800 nm thick) layer of silicon nanocrystals (SiNCs) embedded in a polished silica plate. Dimensions of the PhC were designed so that light emitted by SiNCs under excitation with an external UV source can, during its propagation in the layer, interact with the periodicity and be Bragg-diffracted into air. This approach leads to up to 8-fold vertical extraction enhancement of SiNCs luminescence from the PhC slab compared to the bare planar layer. Results of the experiment are supported by the computer simulation. (C) 2013 AIP Publishing LLC

Captive breeding of Margaritifera auricularia (Spengler, 1793) and its conservation importance

Margaritifera auricularia is one of the most endangered freshwater mussels (Bivalvia, Unionida) in the world. Since 2013, the abundance of this species in the Ebro River basin (Spain) has sharply declined, driving the species to the verge of regional extinction. Therefore, any management measures that might facilitate the recovery of this species would be essential for its conservation. During 2014–2016, captive breeding of M. auricularia allowed the production of >106 juveniles, out of which 95% were released into the natural environment, and 5% were grown in the laboratory under controlled conditions. The aim of this experimental work was to establish the best culture conditions for the survival and growth of M. auricularia juveniles in the laboratory. The experiment was divided into two phases: phase I, in which juveniles recently detached from fish gills were cultured in detritus boxes until they reached a shell length of 1 mm; and phase II, in which these specimens were transferred to larger aquaria to grow up to 3–4 mm. The best experimental conditions for juvenile survival and growth corresponded to treatments in glass containers at a density of 0.2 ind. L−1, using river water, with added substrate and detritus, enriched with phytoplankton, and avoiding extra aeration. The highest survival and growth rates attained, respectively, values of c. 60% at 100 days and 2.56 mm in shell length at 30–32 weeks. This is the first study to report on the long‐term survival and growth of juvenile M. auricularia in the laboratory, providing essential information in order to implement future conservation measures addressed at reinforcing the natural populations of this highly threatened species in European water bodies.This project was funded by the Government of Aragón, Department of Rural Development and Sustainability and carried out by the Environmental Service Department of SARGA. Special thanks go to Manuel Alcántara, Miguel Ángel Muñoz, Ester Ginés, Carlos Catalá, and Juan Pablo de la Roche, who were involved in the project. The authors appreciate the work of the reviewer and editor who improved the quality of the manuscript. The Aragón's forest rangers are thanked for their assistance during fieldwork

Development and validation of a repharsed phase- HPLC method for simultaneous determination of rosiglitazone and glimepiride in combined dosage forms and human plasma

<p>Abstract</p> <p>Background</p> <p>Rosiglitazone (ROZ) and glimepiride (GLM) are antidiabetic agents used in the treatment of type 2 diabetes mellitus. A survey of the literature reveals that only one spectrophotometric method has been reported for the simultaneous determination of ROS and GLM in pharmaceutical preparations. However the reported method suffers from the low sensitivity, for this reason, our target was to develop a simple sensitive HPLC method for the simultaneous determination of ROZ and GLM in their combined dosage forms and plasma.</p> <p>Results</p> <p>A simple reversed phase high performance liquid chromatographic (RP-HPLC) method was developed and validated for the simultaneous determination of Rosiglitazone (ROS) and Glimepiride (GLM) in combined dosage forms and human plasma. The separation was achieved using a 150 mm × 4.6 mm i.d., 5 μm particle size Symmetry^®C18 column. Mobile phase containing a mixture of acetonitrile and 0.02 M phosphate buffer of pH 5 (60: 40, V/V) was pumped at a flow rate of 1 mL/min. UV detection was performed at 235 nm using nicardipine as an internal standard. The method was validated for accuracy, precision, specificity, linearity, and sensitivity. The developed and validated method was successfully used for quantitative analysis of Avandaryl™ tablets. The chromatographic analysis time was approximately 7 min per sample with complete resolution of ROS (t_R= 3.7 min.), GLM (t_R= 4.66 min.), and nicardipine (t_R, 6.37 min). Validation studieswas performed according to ICH Guidelines revealed that the proposed method is specific, rapid, reliable and reproducible. The calibration plots were linear over the concentration ranges 0.10-25 μg/mL and 0.125-12.5 μg/mL with LOD of 0.04 μg/mL for both compounds and limits of quantification 0.13 and 0.11 μg/mL for ROS and GLM respectively.</p> <p>Conclusion</p> <p>The suggested method was successfully applied for the simultaneous analysis of the studied drugs in their co-formulated tablets and human plasma. The mean percentage recoveries in Avandaryl™ tablets were 100.88 ± 1.14 and 100.31 ± 1.93 for ROS and GLM respectively. Statistical comparison of the results with those of the reference method revealed good agreement and proved that there were no significant difference in the accuracy and precision between the two methods respectively. The interference likely to be introduced from some co-administered drugs such as glibenclamide, gliclazide, metformine, pioglitazone and nateglinide was investigated.</p

Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC

The uncertainty on the calorimeter energy response to jets of particles is derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the calorimeter response to single isolated charged hadrons is measured and compared to the Monte Carlo simulation using proton-proton collisions at centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009 and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter response to specific types of particles (positively and negatively charged pions, protons, and anti-protons) is measured and compared to the Monte Carlo predictions. Finally, the jet energy scale uncertainty is determined by propagating the response uncertainty for single charged and neutral particles to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3% for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table, submitted to European Physical Journal

Hunt for new phenomena using large jet multiplicities and missing transverse momentum with ATLAS in 4.7 fb−1 of s√=7TeV proton-proton collisions

Results are presented of a search for new particles decaying to large numbers of jets in association with missing transverse momentum, using 4.7 fb−1 of pp collision data at s√=7TeV collected by the ATLAS experiment at the Large Hadron Collider in 2011. The event selection requires missing transverse momentum, no isolated electrons or muons, and from ≥6 to ≥9 jets. No evidence is found for physics beyond the Standard Model. The results are interpreted in the context of a MSUGRA/CMSSM supersymmetric model, where, for large universal scalar mass m 0, gluino masses smaller than 840 GeV are excluded at the 95% confidence level, extending previously published limits. Within a simplified model containing only a gluino octet and a neutralino, gluino masses smaller than 870 GeV are similarly excluded for neutralino masses below 100 GeV