1,026 research outputs found

    Emission spectrum of quasi-resonant laterally coupled quantum dots

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    We calculate the emission spectrum of neutral and charged excitons in a pair of laterally coupled InGaAs quantum dots with nearly degenerate energy levels. As the interdot distance decreases, a number of changes take place in the emission spectrum which can be used as indications of molecular coupling. These signatures ensue from the stronger tunnel-coupling of trions as compared to that of neutral excitons.Comment: 7 pages, 7 figure

    Multi-objective optimization of a bottoming Organic Rankine Cycle (ORC) of gasoline engine using swash-plate expander

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    This paper presents a mathematical model of a bottoming Organic Rankine Cycle coupled to a 2 l turbocharged gasoline engine to optimize the cycle from a thermo-economic and sizing point of view. These criteria were optimized with different cycle values. Therefore, a methodology to optimize the ORC coupled to Waste Heat Recovery systems in vehicle applications is presented using a multiobjective optimization algorithm. Multi-objective optimization results show that the optimum solution depend on the importance of each objective to the final solution. Considering thermo-economic criteria as the main objective, greater sizes will be required. Considering sizing criteria as the main objective, higher thermo-economic parameters will be obtained. Therefore, in order to select a single-solution from the Pareto frontier, a multiple attribute decision-making method (TOPSIS) was implemented in order to take into account the preferences of the Decision Maker. Considering the weight factors 0.5 for Specific Investment Cost (SIC), 0.3 for the area of the heat exchangers (Atot) and 0.2 for Volume Coefficient (VC) and the boundaries of this particular application, the result is optimized with values of 0.48 m2 (Atot), 2515 /kW (SIC) and 2.62 MJ/m3 (VC). Moreover, the profitability of the project by means of the Net Present Value and the Payback has been estimated.This work is part of a research project called "Evaluation of bottoming cycles in IC engines to recover waste heat energies" funded by a National Project of the Spanish Government with reference TRA2013-46408-R. Authors want to acknowledge the "Apoyo para la investigacion y Desarrollo (PAID)" grant for doctoral studies (FPI S2 2015 1067). Authors acknowledge to ModeFRONTIER (ESTECO) because its support.Galindo, J.; Climent, H.; Dolz Ruiz, V.; Royo-Pascual, L. (2016). Multi-objective optimization of a bottoming Organic Rankine Cycle (ORC) of gasoline engine using swash-plate expander. Energy Conversion and Management. 126:1054-1065. https://doi.org/10.1016/j.enconman.2016.08.053S1054106512

    Petrography and mineralogy of the white marble and black stone of Göktepe (Mugla, Turkey) used in antiquity: New data for provenance determination

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    The discovery near Göktepe (Mugla province, Western Turkey) of an ancient quarrying site of white marbles and black stones has recently been reported by some authors. Assigning the provenance of stone from ancient artifacts to Göktepe is currently possible mainly thanks to chemical, EPR and MGS data. Petrographic description, which many researchers use to characterize ancient marbles, is still incomplete. Several thin sections of both types of stone were thus examined in this study, and also used for cathodoluminescence analysis. As the rock is >99% calcite, trace minerals could only be detected in some samples by XRD analysis of insoluble residues after acetic acid attack. Data on strontium and manganese contents and carbon and oxygen isotopes were also recorded, for better understanding of some petrographic features. A new method of grain size characterization was tentatively introduced to improve the description of grain size variability in the white marble. Microstructure and grain size measurements on thin sections of this marble identify two petrographic varieties: the first is extremely fine with signs of dynamic recrystallization, and the second exhibits texture and MGS similar to those of Carrara marble. Statuary samples of white marble from Villa Adriana (Tivoli, Rome), preliminarily assigned in a previous study partly to Carrara and partly to Göktepe quarry, are reconsidered here. A certain degree of variability was found in the structures and textures in the thin sections of the Göktepe black stone. It may have undergone transformations at an advanced stage of diagenesis. One important source of this variability seems to be a fluid alteration event, revealed by both isotopic and chemical data and trace mineral assemblages

    Immunospecific Antibody Concentration in Egg Yolk of Chickens Orally Immunised with Varying Doses of Bovine Serum Albumin and the Mucosal Adjuvant, RhinoVax®, using Different Immunization Regimes

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    Antibody harvested from eggs of immunised chickens, IgY, has proven to be a non-invasive alternative to  antibodies purified from serum of mammals. Taking the non-invasive concept further, the development of  oral immunization techniques combined with IgY harvest from chicken eggs may subsequently eliminate  all regulated procedures from polyclonal antibody production. In the present study, we report the effects of  varying the temporal administration mode of the antigen (immunogen) comparing dosing on three consecutive  days with dosing on five consecutive days, and of incorporating a mucosal adjuvant. Two antigen  doses were compared: 30 mg bovine serum albumin (BSA) and 300 mg BSA, with and without the mucosal  adjuvant, RhinoVax®, administered to laying chickens. The egg yolk of chickens dosed with BSA in combination  with 20% RhinoVax®, contained significantly higher concentrations of immunospecific IgY than  did egg yolks of chickens fed with BSA without adjuvant. The most efficient dose in the RhinoVax®-treated  groups was 300 mg BSA regardless of whether the chickens were initially immunised daily for three or  five days. A 3-day dosing regime with BSA alone also induced immunospecific IgY production. This study  confirms that RhinoVax® is an efficient oral adjuvant. It also demonstrates the efficacy of daily immunizations  on three or five consecutive days on immunospecific IgY production. The chickens received oral  booster immunizations one and two months after the initial immunization. No real effect could be recorded  after the second and third immunization, although the study did provide some evidence of memory  based on an optimum IgY concentration recorded after the 2nd immunization.

    Cohomological tautness for Riemannian foliations

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    In this paper we present some new results on the tautness of Riemannian foliations in their historical context. The first part of the paper gives a short history of the problem. For a closed manifold, the tautness of a Riemannian foliation can be characterized cohomologically. We extend this cohomological characterization to a class of foliations which includes the foliated strata of any singular Riemannian foliation of a closed manifold

    Allelic and genotypic frequencies of ASIP and MC1R genes in four West African sheep populations

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    In West Africa, consumers pay a major attention on the coat colour of the sheep due to religious and cultural reasons. White coated individuals reach selling prices up to three-fold higher than black coated sheep. The aim of this study was to ascertain the genotypic and allelic frequencies of MC1R and ASIP genes in order to assess possible implementation of breeding programmes focusing on the increase of the white coated sheep frequencies. A total of 113 individuals belonging to three Burkina Faso sheep breeds (Burkina-Sahel, Djallonké and Mossi) and one Niger sheep breed (Touareg) were genotyped for the MC1R and ASIP genes. The wild allele of the ASIP gene (Awt; 54.30%) was the most frequent in the four West African sheep, particularly in Burkina-Sahel (85%) and Touareg breeds (80%). The dominant black ED allele was not identified in Burkina-Sahel and Touareg. Most of the analysed individuals were homozygous for wild MC1R allele (E+/E+) with 100, 73.5, 59 and 100% frequency in Burkina-Sahel, Djallonké, Mossi and Touareg, respectively. The Awt/Awt was the most frequent genotype on the ASIP gene in the four West African breeds (80.53%). No individuals were homozygous for the deletion (allele Adel). Although, no routine methods for detection of the genetic basis of the recessive black coat colour patterns can be easily implemented, the current results suggest the feasibility of a selection programme aiming at decreasing the frequencies of the dominant black ED allele in Burkina Faso sheep breeds.Key words: Sheep, coat colour, MC1R gene, ASIP gene, Burkina Faso, Niger

    Active yellow pages: a pipelined resource management architecture for wide-area network computing

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    This paper describes a novel, pipelined resource management architecture for computational grids. The design is based on two key realizations. One is that resource management involves a sequence of tasks that is best handled by a pipeline. As shown in the paper, this approach results, in a scalable architecture for decentralized scheduling. The other realization is that static aggregation of resources for improved scheduling is inadequate in wide-area computing environments because the needs of users and jobs change with both, location and time. The described architecture addresses this problem by dynamically aggregating resources in a manner that continuously optimizes system response. This is accomplished by way of an active yellow pages directory that allows aggregation constraints to be (re)defined on the fly. An initial prototype of the active yellow pages service has been deployed in the PUNCH network computing environment. Experiences with the production PUNCH system and preliminary results from controlled experiments indicate that the active yellow pages service performs well.Peer Reviewe

    Tautness for riemannian foliations on non-compact manifolds

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    For a riemannian foliation F\mathcal{F} on a closed manifold MM, it is known that F\mathcal{F} is taut (i.e. the leaves are minimal submanifolds) if and only if the (tautness) class defined by the mean curvature form κμ\kappa_\mu (relatively to a suitable riemannian metric μ\mu) is zero. In the transversally orientable case, tautness is equivalent to the non-vanishing of the top basic cohomology group Hn(M/F)H^{^{n}}(M/\mathcal{F}), where n = \codim \mathcal{F}. By the Poincar\'e Duality, this last condition is equivalent to the non-vanishing of the basic twisted cohomology group Hκμ0(M/F)H^{^{0}}_{_{\kappa_\mu}}(M/\mathcal{F}), when MM is oriented. When MM is not compact, the tautness class is not even defined in general. In this work, we recover the previous study and results for a particular case of riemannian foliations on non compact manifolds: the regular part of a singular riemannian foliation on a compact manifold (CERF).Comment: 18 page

    Diamagnetic and paramagnetic shifts in self-assembled InAs lateral quantum dot molecules

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    We uncover the underlying physics that explains the energy shifts of discrete states of individual InAs lateral quantum dot molecules (LQDMs) as a function of magnetic fields applied in the Faraday geometry. We observe that ground states of the LQDM exhibit a diamagnetic shift while excited states exhibit a paramagnetic shift. We explain the physical origin of the transition between these two behaviors by analyzing the molecular exciton states with effective mass calculations. We find that charge carriers in delocalized molecular states can become localized in single QDs with increasing magnetic field. We further show that the net effects of broken symmetry of the molecule and Coulomb correlation lead to the paramagnetic response.NSF DMR-0844747 DMR 1309989 GV VALi+d Grant APOSTD/2013/052 NRF of Korea 2011-C0030821/2013R1A1A1007118 MINECO Project CTQ2011-2732

    Angle-resolved photoemission study and first principles calculation of the electronic structure of GaTe

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    The electronic band structure of GaTe has been calculated by numerical atomic orbitals density-functional theory, in the local density approximation. In addition, the valence-band dispersion along various directions of the GaTe Brillouin zone has been determined experimentally by angle-resolved photoelectron spectroscopy. Along these directions, the calculated valence-band structure is in good concordance with the valence-band dispersion obtained by these measurements. It has been established that GaTe is a direct-gap semiconductor with the band gap located at the Z point, that is, at Brillouin zone border in the direction perpendicular to the layers. The valence-band maximum shows a marked \textit{p}-like behavior, with a pronounced anion contribution. The conduction band minimum arises from states with a comparable \textit{s}- \textit{p}-cation and \textit{p}-anion orbital contribution. Spin-orbit interaction appears to specially alter dispersion and binding energy of states of the topmost valence bands lying at Γ\Gamma. By spin-orbit, it is favored hybridization of the topmost \textit{p}z_z-valence band with deeper and flatter \textit{px_x}-\textit{py_y} bands and the valence-band minimum at Γ\Gamma is raised towards the Fermi level since it appears to be determined by the shifted up \textit{px_x}-\textit{py_y} bands.Comment: 7 text pages, 6 eps figures, submitted to PR
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