Complexes of dipolar excitons in layered quasi-two-dimensional nanostructures

We discuss neutral and charged complexes (biexciton and trion) formed by indirect excitons in layered quasi-two-dimensional semiconductor heterostructures. Indirect excitons -- long-lived neutral Coulomb-bound pairs of electrons and holes of different layers -- have been known for semiconductor coupled quantum wells and are recently reported for van der Waals heterostructures such as bilayer graphene and transition metal dichalcogenides. Using the configuration space approach, we derive the analytical expressions for the trion and biexciton binding energies as functions of the interlayer distance. The method captures essential kinematics of complex formation to reveal significant binding energies, up to a few tens of meV for typical interlayer distances ~3-5 A, with the trion binding energy always being greater than that of the biexciton. Our results can contribute to the understanding of more complex many-body phenomena such as exciton Bose-Einstein condensation and Wigner-like electron-hole crystallization in layered semiconductor heterostructures.Comment: 10 pages, 4 figures, 105 references. arXiv admin note: text overlap with arXiv:1605.0234

The brand image of Malta as a tourism destination: a case study in public relations and corporate communication practice

Place branding and country branding are evolving concepts, which continue to engage attention. This paper reviews the conceptual foundation of place branding and its application to public relations and corporate communication practices in the island state of Malta, a popular tourist destination in the centre of the Mediterranean Sea. The Maltese authorities use communication practices to develop Brand Malta and the study shows how the image of Malta is used to position its offer in the valuable UK market. Tourism is vital to the Maltese economy and the authorities need to create a favourable image and a strong brand. A number of interviews were carried out with representatives from the Malta brand promoter, Malta Tourism Authority (MTA) to establish the brand strategies and communications approaches adopted for rebranding and repositioning in the market. In addition two tour operators were contacted, who specialize in promoting Malta, to illustrate the practices of the private sector and their coordination with the Maltese authorities. The findings are analysed in accordance with the theoretical frameworks featured in the literature. The studies show that Malta has achieved some success in developing and sustaining the brand in a competitive tourism market. Niche propositions and added value have been important. A coherent approach to public relations and a corporate communication rationale do provide a strategic framework which helps competitiveness and sustains overall value

Transport of indirect excitons in ZnO quantum wells

We report on spatially- and time-resolved emission measurements and observation of transport of indirect excitons in ZnO/MgZnO wide single quantum wells

Use of contraceptives by Roma women from Plovdiv region

Introduction: The share of unwanted pregnancies and voluntary abortions among women from Central and Eastern Europe is still quite high, and Bulgaria is no exception to this statistic. This might be accounted for by the low frequency of use of contraceptives or their improper use. Our country is home to a variety of ethnic groups, with Roma being one of the most numerous, ranking third in population behind Bulgarians and Turks. This determines the influence of this ethnic group on the demographic indicators of the country. Aim: To study the knowledge of contraceptive use and the frequency of use of contraceptive methods and means among Roma women from the Plovdiv region and the factors influencing it. Materials and methods: This cross-sectional survey was conducted among 70 Roma women via structured, anonymous interviews in 2019. Statistical data analysis was performed using non-parametric methods, descriptive and correlation analyses. Results: The main method of preventing unwanted pregnancies for the Roma is the interrupted intercourse. The husband and his mother influence the decision to use contraception. Higher education and financial security have a positive effect on the frequency of contraceptive use. Conclusions: Reproductive behaviour among Roma is largely determined by their ethnic traditions. Characteristic features were observed, such as early marriages, early sexual intercourse, short pro- and intergenetic interval. Roma women have little knowledge of the various methods and means of preventing unwanted pregnancies. The frequency of contraceptive use is very low

Optical polarization grating in semiconductors induced by exciton-polaritons

A scattering-state approach is proposed to study the propagation of extremely short optical pulses through semiconductor heterostructures. The formalism is applied to the propagation of exciton polaritons: Our simulated experiments predict the formation of an exciton-induced polarization grating when the light pulse is resonant with the excitonic transition, and suggest proper physical conditions for its experimental detection. Moreover, our analysis of the polariton transport in thick semiconductor layers reveals a decrease of the average polariton group velocity as a function of time, which we ascribe to a re-emission—reabsorption of light by excitons

Retrieval of snow properties from the Sentinel-3 Ocean and Land Colour Instrument

The Sentinel Application Platform (SNAP) architecture facilitates Earth Observation data processing. In this work, we present results from a new Snow Processor for SNAP. We also describe physical principles behind the developed snow property retrieval technique based on the analysis of Ocean and Land Colour Instrument (OLCI) onboard Sentinel-3A/B measurements over clean and polluted snow fields. Using OLCI spectral reflectance measurements in the range 400–1020 nm, we derived important snow properties such as spectral and broadband albedo, snow specific surface area, snow extent and grain size on a spatial grid of 300 m. The algorithm also incorporated cloud screening and atmospheric correction procedures over snow surfaces. We present validation results using ground measurements from Antarctica, the Greenland ice sheet and the French Alps. We find the spectral albedo retrieved with accuracy of better than 3% on average, making our retrievals sufficient for a variety of applications. Broadband albedo is retrieved with the average accuracy of about 5% over snow. Therefore, the uncertainties of satellite retrievals are close to experimental errors of ground measurements. The retrieved surface grain size shows good agreement with ground observations. Snow specific surface area observations are also consistent with our OLCI retrievals. We present snow albedo and grain size mapping over the inland ice sheet of Greenland for areas including dry snow, melted/melting snow and impurity rich bare ice. The algorithm can be applied to OLCI Sentinel-3 measurements providing an opportunity for creation of long-term snow property records essential for climate monitoring and data assimilation studies—especially in the Arctic region, where we face rapid environmental changes including reduction of snow/ice extent and, therefore, planetary albedo.publishedVersio

Investigation of the Role of Mitochondrial DNA in Multiple Sclerosis Susceptibility

Several lines of evidence suggest that mitochondrial genetic factors may influence susceptibility to multiple sclerosis. To explore this hypothesis further, we re-sequenced the mitochondrial genome (mtDNA) from 159 patients with multiple sclerosis and completed a haplogroup analysis including a further 835 patients and 1,506 controls. A trend towards over-representation of super-haplogroup U was the only evidence for association with mtDNA that we identified in these samples. In a parallel analysis of nuclear encoded mitochondrial genes, we also found a trend towards association with the complex I gene, NDUFS2. These results add to the evidence suggesting that variation in mtDNA and nuclear encoded mitochondrial genes may contribute to disease susceptibility in multiple sclerosis

mdm2 gene amplification is associated with luminal breast cancer progression in humanized PDX mice and a worse outcome of estrogen receptor positive disease

Estrogen receptor-positive breast cancer is a highly prevalent but heterogeneous disease among women. Advanced molecular stratification is required to enable individually most efficient treatments based on relevant prognostic and predictive biomarkers. First objective of our study was the hypothesis-driven discovery of biomarkers involved in tumor progression upon xenotransplantation of Luminal breast cancer into humanized mice. The second objective was the marker validation and correlation with the clinical outcome of Luminal breast cancer disease within the GeparTrio trial. An elevated mdm2 gene copy number was associated with enhanced tumor growth and lung metastasis in humanized tumor mice. The viability, proliferation and migration capacity of inherently mdm2 positive breast cancer cells in vitro were significantly reduced upon mdm2 knockdown or anti-mdm2 targeting. An mdm2 gain significantly correlated with a worse DFS and OS of Luminal breast cancer patients, albeit it was also associated with an enhanced preoperative pathological response rate. We provide evidence for an enhanced Luminal breast cancer stratification based on mdm2. Moreover, mdm2 can potentially be utilized as a therapeutic target in the Luminal subtype