Excited states of exciton-polariton condensates in 2D and 1D harmonic traps

We present a theoretical description of Bogolyubov-type excitations of exciton-polariton Bose-Einstein condensates (BECs) in semiconductor microcavities. For a typical two-dimensional (2D) BEC we focus on two limiting cases, the weak-and strong-coupling regimes, where a perturbation theory and the Thomas-Fermi approximation, respectively, are valid. We calculate integrated scattering intensity spectra for probing the collective excitations of the condensate in both considered limits. Moreover, in relation to recent experiments on optical modulation allowing localization of condensates in a trap with well-controlled shape and dimensions, we study the quasi-one-dimensional (1D) motion of the BEC inmicrowires and report the corresponding Bogolyubov excitation spectrum. We show that in the 1D case the characteristic polariton-polariton interaction constant is expressed as g(1) = 3 lambda N/(2L(y)) (lambda is the 2D polariton-polariton interaction parameter in the cavity, N the number of the particles, and L-y the wire cavity width). We reveal some interesting features for 2D and 1D Bogolyubov spectra for both repulsive (lambda > 0) and attractive (lambda < 0) interactions.Fundação para a Ciência e a Tecnologia (FCT) - Portuguese Foundation for Science and Technology Grants: PTDC-FIS-113199-2009, PEst-C/FIS/UI0607/2013CNPq, FAPESP, BrazilRussian Ministry of Education and Science 11.G34.31.006

Сравнительное исследование фармакокинетики и биораспределения карбазольного соединения CBL0100 в составе различных топических лекарственных форм на морских свинках

An experimental drug CBL0100 is developed as an antifungal agent for topical application. In order to assess the effect of composition of the formulation on transdermal absorption, a comparative absorption study of its pharmacokinetics and biodistribution after a single topical application on the guinea pigs' skin. Two different formulations of CBL0100 (prototypes of final dosage forms for topical applications) - cream emulsion and polyethylene glycol vehicles with a content of active substance 1, 0,2 and 0,02% mass. in each of these formulations were used in the study. CBL0100 concentration in blood plasma and homogenates of organs and tissues of animals was analyzed by HPLC - MS/MS. During the preliminary blood-to-plasma partitioning in vitro experiment it was determined that CBL0100 is found mostly in the cell fraction of the blood, which, based upon the pharmacokinetic curves shape affects elimination from plasma. It was revealed that after a single topical application active compound enters the systemic circulation and intensively distributed into the spleen, liver, kidneys and lungs of guinea pigs. At the same time, its content in the muscular tissue and the heart is negligible; CBL0100 moderately penetrates into the brain. In general, it was shown that the emulsion composition provides improved bioavailability of CBL0100 compared to the polyethylene glycol composition.Экспериментальный препарат CBL0100 разрабатывается в качестве противогрибкового средства для местного применения. Для оценки влияния состава лекарственной формы на трансдермальное всасывание было проведено сравнительное исследование его фармакокинетики и биораспределения после однократного нанесения на кожу морских свинок. В исследовании использовали две различные прописи CBL0100 (прототипы готовых лекарственных форм для топических аппликаций) - крема на эмульсионной (ЭМ) и полиэтиленгликолевой (ПЭГ) основах с содержанием активного вещества 1, 0,2 и 0,02% по массe. Концентрацию активного вещества в плазме крови и гомогенатах органов и тканей животных определяли методом ВЭЖХ-МС/ МС. В предварительном эксперименте по изучению распределения CBL0100 между плазмой и клеточными компонентами крови in vitro установлено, что исследуемое соединение преимущественно обнаруживается в клеточной фракции крови, что, судя по форме фармакокинетических кривых, влияет на скорость его элиминации из плазмы. Показано, что после однократного накожного нанесения крема CBL0100 проникает в системный кровоток и интенсивно распределяется в селезёнку, печень, почки и лёгкие морских свинок. В то же время его содержание в мышечной ткани и сердце незначительно; в мозг CBL0100 проникает умеренно. Установлено, что пропись на ЭМ основе обеспечивает повышенную по сравнению ПЭГ основой биодоступность CBL0100

International experience and FDI location choices of Chinese firms: The moderating effects of home country government support and host country institutions

We examine the extent to which Chinese government support of foreign direct investment (FDI) projects and host country institutional environments interact with prior entry experience by Chinese firms, and how this interrelationship affects FDI undertaken by Chinese firms. We hypothesize that home country government support and well-established host country institutions enhance organizational capabilities to take risks in FDI. As such, they reduce the need to accumulate experiential knowledge and capabilities relating to entering host countries based on prior entry experience in a particular country when undertaking follow-up investment projects. Using a unique, hand-collected panel data set of Chinese publicly listed firms during 2002–2009, we find that home government support and well-developed host country institutions reduce the importance of prior entry experience and significantly increase the likelihood of FDI entry into a host country. Further, from our subsample analyses we identify differences between entering developed and developing host countries in terms of the impact of home country government support and quality of host country institutions. Our findings help explain the puzzle concerning why emerging economy firms have rapidly internationalized in a short period of time and do not follow the pattern predicted by classical IB theories

Electronic properties and phase transitions in low-dimensional semiconductors

We present the first review of the current state of the literature on electronic properties and phase transitions in TlX and TlMX2 (M = Ga, In; X = Se, S, Te) compounds. These chalcogenides belong to a family of the low-dimensional semiconductors possessing chain or layered structure. They are of significant interest because of their highly anisotropic properties, semi- and photoconductivity, non-linear effects in their I-V characteristics (including a region of negative differential resistance), switching and memory effects, second harmonic optical generation, relaxor behavior and potential applications for optoelectronic devices. We review the crystal structure of TlX and TlMX2 compounds, their transport properties under ambient conditions, experimental and theoretical studies of the electronic structure, transport properties and semiconductor-metal phase transitions under high pressure, and sequences of temperature-induced structural phase transitions with intermediate incommensurate states. Electronic nature of the ferroelectric phase transitions in the above-mentioned compounds, as well as relaxor behavior, nanodomains and possible occurrence of quantum dots in doped and irradiated crystals is discussed.Comment: 70 pages, 38 figure

EXECUTIVE PAY AND PERFORMANCE IN PORTUGUESE LISTED COMPANIES

This essay analyses the relationship between corporate governance practices and Chief Executive Officer (CEO) wages from a sample of Portuguese listed companies over the period from 2002-2011. The relationship between CEO total compensation and shareholders return, firm characteristics, CEO characteristics, board of directors and shareholders characteristics is analysed. It is found that firm specific factors accounts for the majority of the variance in total CEO pay, while firm performance accounts for less than 5%. It is also found that the CEO characteristics, board of directors’ structures, and shareholders features are related with the CEO pay. The policy implications of these results are then derived

Exciton-polariton laser diodes

Despite their name polariton lasers do not rely on stimulated emission of cavity photons. The less stringent threshold conditions are the cause that bosonic polariton lasers can outperform standard lasers in terms of their threshold currents. The part-light and part-matter quasiparticles called polaritons, can undergo a condensation process into a common energy state. The radiated light from such a system shares many similarities with the light emitted from a conventional photon laser, even though the decay of the polaritons out of the finite lifetime cavity is a spontaneous process. We discuss properties of polariton condensates in GaAs based microcavities. The system’s response to an external magnetic field is used as a reliable tool to distinguish between polariton laser and conventional photon laser. In particular, we will discuss the realization of an electrically pumped polariton laser, which manifests a major step towards the exploitation of polaritonic devices in the real world.Published versio

Exciton-polariton lasers in magnetic fields

Polariton lasers do not rely on stimulated emission of cavity photons, which sets stringent conditions on the threshold current in a conventional laser. Indeed, it has been demonstrated in optically pumped systems, that bosonic polariton lasers can outperform standard lasers in terms of their threshold power. The polaritons, which are part light and part matter quasiparticles, can undergo a condensation process into a common energy state. The radiated light from such a system shares many similarities with the light emitted from a conventional photon laser, even though the decay of the polaritons is a spontaneous process. We discuss properties of polariton lasers and condensates in GaAs based microcavities. Special emphasis is given to the system’s response to an applied magnetic field. We introduce the magnetic field interactions as a reliable tool to distinguish a polariton laser from a conventional photon laser device. In particular, we will discuss the first successful realization of an electrically pumped polariton laser, which marks a promising step towards the exploitation of polaritonic devices in the real world. We believe that our work can be extended to devices operated at room temperature by transferring the technology to large bandgap semiconductors, or even to GaAs samples with a modified layer design.Published versio