Dressed atom versus exciton polariton: From Rabi oscillations to the Fermi Golden rule

We rederive the dressed atom and the exciton polariton within the {\it same} framework to make clear that their difference only comes from the number of electrons available for photoexcitations. Using it, we analytically show how the time dependence of the photon number transforms from an oscillating behavior (at the stimulated or vacuum Rabi frequency) to an exponential decay (identical for atom and semiconductor) when the excited state lifetime decreases. Although the matter ground state is in both cases coupled by monochromatic photons {\it not to a continuum but to a discrete state}, this decay yet follows a kind of Fermi Golden rule. The energy conservation it contains, is however conceptually different

Almost Sure Stabilization for Adaptive Controls of Regime-switching LQ Systems with A Hidden Markov Chain

This work is devoted to the almost sure stabilization of adaptive control systems that involve an unknown Markov chain. The control system displays continuous dynamics represented by differential equations and discrete events given by a hidden Markov chain. Different from previous work on stabilization of adaptive controlled systems with a hidden Markov chain, where average criteria were considered, this work focuses on the almost sure stabilization or sample path stabilization of the underlying processes. Under simple conditions, it is shown that as long as the feedback controls have linear growth in the continuous component, the resulting process is regular. Moreover, by appropriate choice of the Lyapunov functions, it is shown that the adaptive system is stabilizable almost surely. As a by-product, it is also established that the controlled process is positive recurrent

Preference erosion and multilateral trade liberalization

Because of concern that OECD tariff reductions will translate into worsening export performance for the least developed countries, trade preferences have proven a stumbling block to developing country support for multilateral liberalization. The authors examine the actual scope for preference erosion, including an econometric assessment of the actual utilization and the scope for erosion estimated by modeling full elimination of OECD tariffs, and hence full most-favored-nation liberalization-based preference erosion. Preferences are underutilized due to administrative burden-estimated to be at least 4 percent on average-reducing the magnitude of erosion costs significantly. For those products where preferences are used (are of value), the primary negative impact follows from erosion of EU preferences. This suggests the erosion problem is primarily bilateral rather than a WTO-based concern.Free Trade,Economic Theory&Research,Trade Policy,Trade and Regional Integration,Rules of Origin

Modeling and Dimensioning Ground Heat Exchangers Principles: Influence of the soil's thermal proprieties

International audienceIn the context of energy crisis and global warming, heating buildings with the solar energy stored in the soil rep- resents a very interesting alternative. Moreover, cooling buildings can also use the soil damping capacity. This paper presents our reflexion about the modeling and dimensioning of the ground heat exchanger part of ground-coupled heat pumps (GCHP). After a physical overview of the ground heat exchanger, we extract from analytical solutions practical consequences of the soil damping behavior and limits that provide guidelines for the dimensioning. We then question the default values of the numerical tools thermal parameters used for the simulation of GCHP. We illustrate this issue through a TRNSYS dynamic simulation of GCHP, demonstrating that soil's thermal parameters have a strong impact on the results. Finally, we give some perspectives for the determination of soil's characteristics in situ, but indirectly, thanks to geophysical prospection methods as ground penetrating radar, electromagnetic induction, or electrical resistivity tomography.Dans un contexte de crise e ́nerge ́tique et de re ́chauffement climatique, le chauffage des baˆtiments graˆce a` l'e ́nergie solaire stocke ́e dans le sol est un principe inte ́ressant. De plus, les sondes ge ́othermiques utilise ́es pour extraire la chaleur du sol permettent aussi de l'y re ́injecter, et donc de refroidir les baˆtiments graˆce a` l'inertie thermique du sol. Cet article pre ́sente nos re ́flexions sur la mode ́lisation et le dimensionnement des e ́changeurs thermiques en faible profondeur couple ́s a` des pompes a` chaleur (PAC ge ́othermique). Apre`s une pre ́sentation de la physique sous-jacente aux e ́changeurs thermiques et des me ́thodes de re ́solution analytiques et nume ́riques, nous soulignons l'importance des valeurs des parame`tres thermiques du sol utilise ́es par les outils nume ́riques pour simuler les PAC ge ́othermiques. Nous illustrons cette question a` partir de re ́sultats de simulation dynamique TRNSYS : ceux-ci sont fortement influence ́s par les valeurs de conductivite ́ thermique du sol. Enfin, nous pre ́sentons un e ́tat de l'art des mesures de ces parame`tres thermiques in situ et sugge ́rons quelques me ́thodes ge ́ophysiques pour les de ́terminer indirectement, parmi lesquelles le ge ́oradar, l'induction e ́lectromagne ́tique et la tomographie e ́lectrique. La forte empreinte de la teneur en eau sur la thermique des sols permettrait en effet d'estimer leurs caracte ́ristiques thermiques via des mesures de conductivite ́ e ́lectrique ou de permittivite ́ die ́lectrique, elles aussi relie ́es a` la teneur en eau du milieu

Design of a simulation environment for laboratory management by robot organizations

This paper describes the basic concepts needed for a simulation environment capable of supporting the design of robot organizations for managing chemical, or similar, laboratories on the planned U.S. Space Station. The environment should facilitate a thorough study of the problems to be encountered in assigning the responsibility of managing a non-life-critical, but mission valuable, process to an organized group of robots. In the first phase of the work, we seek to employ the simulation environment to develop robot cognitive systems and strategies for effective multi-robot management of chemical experiments. Later phases will explore human-robot interaction and development of robot autonomy

Analysis of the meiotic segregation in intergeneric hybrids of tilapias

Tilapia species exhibit a large ecological diversity and an important propensity to interspecific hybridisation. This has been shown in the wild and used in aquaculture. However, despite its important evolutionary implications, few studies have focused on the analysis of hybrid genomes and their meiotic segregation. Intergeneric hybrids between Oreochromis niloticus and Sarotherodon melanotheron, two species highly differentiated genetically, ecologically, and behaviourally, were produced experimentally. The meiotic segregation of these hybrids was analysed in reciprocal second generation hybrid (F2) and backcross families and compared to the meiosis of both parental species, using a panel of 30 microsatellite markers. Hybrid meioses showed segregation in accordance to Mendelian expectations, independent from sex and the direction of crosses. In addition, we observed a conservation of linkage associations between markers, which suggests a relatively similar genome structure between the two parental species and the apparent lack of postzygotic incompatibility, despite their important divergence. These results provide genomics insights into the relative ease of hybridisation within cichlid species when prezygotic barriers are disrupted. Overall our results support the hypothesis that hybridisation may have played an important role in the evolution and diversification of cichlids