Identifying A Unifying Mechanism for the Implementation of Concurrency Abstractions on Multi-Language Virtual Machines

Supporting all known abstractions for concurrent and parallel programming in a virtual machines (VM) is a futile undertaking, but it is required to give programmers appropriate tools and performance. Instead of supporting all abstractions directly, VMs need a unifying mechanism similar to \textttINVOKEDYNAMIC for JVMs. Our survey of parallel and concurrent programming concepts identifies concurrency abstractions as the ones benefiting most from support in a VM. Currently, their semantics is often weakened, reducing their engineering benefits. They require a mechanism to define flexible language guarantees. Based on this survey, we define an ownership-based meta-object protocol as candidate for VM support. We demonstrate its expressiveness by implementing actor semantics, software transactional memory, agents, CSP, and active objects. While the performance of our prototype confirms the need for VM support, it also shows that the chosen mechanism is appropriate to express a wide range of concurrency abstractions in a unified way

BIAXIAL-STRAIN EFFECT ON EXCITONIC TRANSITIONS E(0) AND E(0)+DELTA(0) IN THE TEMPERATURE-RANGE 4.5-200 K AND ZEEMAN SPLITTING IN ZNSE/GAAS EPILAYERS

International audienceIdentification of heavy-hole and light-hole excitonic transitions is made by reflectivity and magnetocircular dichroism in strained metal-organic vapor-phase-epitaxy-grown ZnSe/GaAs epilayers with a thickness range between 0.10 and 0.78 mum at 4.5 K. The observed splitting of the exciton transitions due to the lattice mismatch is constant up to 200 K. It is explained by the very small variation (< 2%) of the lattice mismatch strain in this temperature range. Zeeman splitting of \+/- 3/2, +/- 1/2] and \+/- 1/2, -/+ 1/2] transitions are measured at 5.5 T and effective g values g3/2 = -0. 24 and g1/2 = 0. 5 7 are determined

BIAXIAL-STRAIN EFFECT ON EXCITONIC TRANSITIONS E(0) AND E(0)+DELTA(0) IN THE TEMPERATURE-RANGE 4.5-200 K AND ZEEMAN SPLITTING IN ZNSE/GAAS EPILAYERS

International audienceIdentification of heavy-hole and light-hole excitonic transitions is made by reflectivity and magnetocircular dichroism in strained metal-organic vapor-phase-epitaxy-grown ZnSe/GaAs epilayers with a thickness range between 0.10 and 0.78 mum at 4.5 K. The observed splitting of the exciton transitions due to the lattice mismatch is constant up to 200 K. It is explained by the very small variation (< 2%) of the lattice mismatch strain in this temperature range. Zeeman splitting of \+/- 3/2, +/- 1/2] and \+/- 1/2, -/+ 1/2] transitions are measured at 5.5 T and effective g values g3/2 = -0. 24 and g1/2 = 0. 5 7 are determined

Optimization and optical studies of ZnCdSe-ZnSe heterostructures grown by MOVPE

International audienceGraded index-separate confinement heterostructures (GRIN-SCH) based on ZnCdSe and ZnSe wide band gap semiconductors have been grown by low pressure MOVPE on (100) GaAs substrates. First, we have paid attention to the growth of thick ZnCdSe layers. A first study is carried out using selenium hydride, dimethyl cadmium and two dimethylzinc adducts as Se, Cd and Zn precursor respectively. This combination leads to intense prereactions and poor layer morphology. To limit this problem we have then used the tetrahydrothiophene:dimethylcadmium adduct. GRIN-SCH structures grown using the two Cd metalorganics are studied using photoluminescence. We have made a detailed study on the influence of the temperature on the carrier trapping and detrapping in the structures

LOW-PRESSURE MOVPE GROWTH OF ZNSE, ZNTE, AND ZNSE/ZNTE STRAINED-LAYER SUPERLATTICES

International audienceZnSe and ZnTe single-crystal layers have been grown onto {100} GaAs substrates by low- pressure metalorganic vapor-phase epitaxy (LP-MOVPE) using the triethylamine-dimethylzinc adduct [DMZn(NEt3)] as the zinc precursor. The selenium and tellurium precursors were H2Se (5% in H-2) and di-isopropyltellurium (DiPTe), respectively. These two semiconductors have been grown with different VI/II molar ratios, at different growth temperatures, and with an overall growth pressure ranging from 40 to 400 Torr. Optimal growth parameters have been determined by optical means for the two materials. This information was then used to grow ZnTe/ZnSe strained-layer superlattices. We have studied structures grown on both ZnSe and ZnTe relaxed buffer layers which display a drastic dependence of the Stokes shift between photoluminescence and the optical bandgap on the nature of the buffer layer. Growth interruptions have been used to optimize the optical properties of the superlattices. Theoretical modeling of superlattice band structures has been performed using results of optical and structural characterizations. Observations of zone center transitions as well as excitons associated with the miniband dispersion of the superlattices are reported, in agreement with the theoretical calculation

Optical properties of GaN epilayers on sapphire

International audienceThe optical properties of GaN epilayers grown by metal-organic vapor-phase epitaxy on (0001)-oriented sapphire are investigated by means of photoluminescence, reflectance, and differential spectroscopy. We obtain quantitative information about the intrinsic or extrinsic nature of the 2 and 300 K photoluminescence features. From detailed investigations of the reflectance properties of these layers we can quantify the residual strain field in these layers and determine the GaN deformation potentials. Comparison of these values with quantities measured on other semiconductors with wurtzite symmetry is also addressed. Last we utilize photoreflectance spectroscopy to measure exciton binding energies

Tritium in saliva measurements used for monitoring of exposed workers

Simultaneous measurement of tritium in urine and saliva in exposed workers reveals differences in the kinetic fate of this radioelement in these two bodily fluids. During two years, four cases of accidental exposure, affecting seven workers, were used for these bioassays. Since the concentration of tritium increases much faster in saliva than in urine, a ratio estimated at 1 to 30 at about 30 minutes after contamination occurs, it is possible to consider saliva assay as an alternative to urine assay, which is more common practice today

OPTICAL-PROPERTIES AND RECOMBINATION PROCESSES IN (ZN,CD)SE GRADED-INDEX SEPARATE-CONFINEMENT HETEROSTRUCTURES

International audienceGraded Index Separate Confinement Heterostructures have been grown by MOVPE using (Zn,Cd)Se and ZnSe wide bandgap semiconductors. These structures are composed of a deep Zn1-xCdxSe (x<0.23%) central well embedded between two thick (Zn, Cd)Se graded layers within which the cadmium composition varies from 0 up to 10% on one side of the well, and from 10 down to 0% on the other side. Both carriers and photon confinement occur in such structures making them suitable for blue-green stimulated emission. Reflectance and photoreflectance data, taken at 2K on a series of samples of different designs allowed us to observe excitonic transitions up to the third quantum number. The structures exhibit a strong photoluminescence line due to the recombination of the carriers in the quantum well. The photoluminescence intensity is analyzed as a function of the temperature and displays a strong thermal quenching. This quenching is due to an increase of the non-radiative recombinations through defects at low temperature and to the thermal escape of the carriers above 40-60K. The value of the activation energy for thermal escape shows that this mechanism is unipolar and concerns the heavy holes

SimParc, un jeu sérieux pour la gestion participative des espaces protégés pour la conservation de la biodiversité et l'inclusion sociale

International audienceThe objective of this paper is to reflect on our experience in a serious game research project, named SimParc, about multi-agent support for participatory management of protected areas for biodiversity conservation and social inclusion. Our project has a clear filiation with the MAS-RPG (Multi-Agent-Simulation – Role-Playing Games) methodology developed by the ComMod action-research community about participatory management of renewable resources, where multi-agent simulation (MAS) computes the dynamics of the resources and role-playing game (RPG) represents the actions and dialogue between stakeholders about the resources. Meanwhile, we have explored some specific directions, such as: dialogue support for negotiation; argumentation-based decision making and its explanation; technical assistance to the players based on viability modeling. In fact, in our project multi-agent based simulation focuses on the negotiation process itself, performed by human players and some artificial participants/agents, rather than on the simulation of the resources dynamics. Meanwhile, as we will see, we have also reintroduced the modeling of the socioecosystem dynamics, but as a local technical assistance/analysis tool for the players and not as a global system modeling. In this proposed chapter, we aim at discussing the rationales for these specificities and for the whole project, as well as summarizing the architecture of our prototype system, current results and experience produced and, last but not the least, lessons learned and prospects for future works