Numerical simulation of exciton dynamics in Cu2O at ultra low temperatures within a potential trap

We have studied theoretically the relaxation behaviour of excitons in cuprous oxide (Cu2O) at ultra low temperatures when excitons are confined within a potential trap by solving numerically the Boltzmann equation. As relaxation processes, we have included in this paper deformation potential phonon scattering, radiative and non-radiative decay and Auger decay. The relaxation kinetics has been analysed for temperatures in the range between 0.3K and 5K. Under the action of deformation potential phonon scattering only, we find for temperatures above 0.5K that the excitons reach local equilibrium with the lattice i.e. that the effective local temperature is coming down to bath temperature, while below 0.5K a non-thermal energy distribution remains. Interestingly, for all temperatures the global spatial distribution of excitons does not reach the equilibrium distribution, but stays at a much higher effective temperature. If we include further a finite lifetime of the excitons and the two-particle Auger decay, we find that both the local and the global effective temperature are not coming down to bath temperature. In the first case we find a Bose-Einstein condensation (BEC) to occur for all temperatures in the investigated range. Comparing our results with the thermal equilibrium case, we find that BEC occurs for a significantly higher number of excitons in the trap. This effect could be related to the higher global temperature, which requires an increased number of excitons within the trap to observe the BEC. In case of Auger decay, we do not find at any temperature a BEC due to the heating of the exciton gas

Hard rock seismic exploration of ore deposits in Australia

We present an overview of the developments and achievements, over the past four years in the application of seismic reflection methods for mineral exploration in Australia. We show that seismic methods can be successfully used to delineate exceptionally complex hard rock environment in Australia providing that the acquisition parameters and data processing strategy are adequate for the task. Moreover methodologies for the direct targeting of specific ore reserves as well as rock identification from seismic data are discussed

Diagnostic aspects of gonorrhoea

In 1971 an investigation into the epidemiological, clinical, bacteriological and therapeutic aspects of gonorrhoea was started in collaboration with the Bacteriological Laboratory of the University Hospital/Medical Faculty Rotterdam. Jn the framework of this investigation, the data were recorded on optically readable forms. These forms could be processed to punched cards and fed to a computer for storage and processing, and could also be used as such for filing purposes. Jn order to make efficient use of these forms, it now became necessary to standardize the questioning technique used for collection of the epidemiological data, and the methods of clinical examination, bacteriological investigation and treatment. This thesis deals with a part of the data covered by the abovementioned investigation - mainly those parts relating to the diagnostic aspects of gonorrhoea. However, in order to place these aspects in the total framework of the investigation and in order to allow better comprehension of further publications resulting from this thesis, a full description is given of the methods of examination, treatment and follow-up (Chapter I ) , the methods of bacteriological investigation (Chapter II) and the registration and processing of the data (Chapter III). The epidemiological data on the gonorrhoea patients covered by this investigation are also summarized (Chapter IV)

A comparative study of the democratization process in Kenya, Malawi and Zambia during the 1990s.

Thesis (M.A.

Consumer attitudes towards organic versus conventional food with specific quality attributes

This paper describes the findings from a consumer survey conducted as part of the EU-funded research project QualityLowInputFood (QLIF). The objective was to segment occasional organic consumers with regard to their preferences for organic, conventional and conventional-plus products, i.e., conventional products with a specific attribute that also applies to organic products. In other words, these conventional-plus products are placed between organic and conventional food products. In addition, we aimed at analysing differences between consumer segments regarding their price sensitivity and attitudes towards food. The survey used choice experiments to investigate occasional organic consumer preferences for the different types of products. In subsequent standardized face-to-face interviews we collected data on consumer attitudes towards food that could explain the observed preferences. The attitudes were summarized in attitude factors, using factor analysis. The responses from the interviews and choice experiments were analysed by latent class models. These econometric models were used to identify segments within a group of individuals for their preference structure and to relate membership in each segment to consumer characteristics. Two segments of occasional organic consumers were identified. Consumers in segment 1 strongly preferred organic products and were less price sensitive. Furthermore, consumers in this segment showed a significantly higher level of agreement with most of the investigated attitude factors than consumers in segment 2. The latter consisted of consumers who were significantly more price sensitive and preferred conventional-plus and conventional products rather than organic products. Communicating quality attributes represents a promising marketing tool of product differentiation and information for both organic and conventional food marketers. The price sensitivity of parts of occasional organic consumers suggests that the perceived price-performance ratio of organic products needs to be increased by targeted pricing and communication strategies integrating product-relevant information. If not, conventional-plus products, representing a cheaper alternative, might be preferred by parts of the occasional organic consumers

Positivity of Lyapunov exponents for a continuous matrix-valued Anderson model

We study a continuous matrix-valued Anderson-type model. Both leading Lyapunov exponents of this model are proved to be positive and distinct for all ernergies in $(2,+\infty)$ except those in a discrete set, which leads to absence of absolutely continuous spectrum in $(2,+\infty)$. This result is an improvement of a previous result with Stolz. The methods, based upon a result by Breuillard and Gelander on dense subgroups in semisimple Lie groups, and a criterion by Goldsheid and Margulis, allow for singular Bernoulli distributions

Single Proton Knock-Out Reactions from 24,25,26F

The cross sections of the single proton knock-out reactions from 24F, 25F, and 26F on a 12C target were measured at energies of about 50 MeV/nucleon. Ground state populations of 6.6+-.9 mb, 3.8+-0.6 mb for the reactions 12C(24F,23O) and 12C(25F,24O) were extracted, respectively. The data were compared to calculations based on the many-body shell model and the eikonal theory. In the reaction 12C(26F,25O) the particle instability of 25O was confirmed