Quantum dot emission from site-controlled ngan/gan micropyramid arrays

InxGa1−xN quantum dots have been fabricated by the selective growth of GaN micropyramid arrays topped with InGaN/GaN quantum wells. The spatially, spectrally, and time-resolved emission properties of these structures were measured using cathodoluminescence hyperspectral imaging and low-temperature microphotoluminescence spectroscopy. The presence of InGaN quantum dots was confirmed directly by the observation of sharp peaks in the emission spectrum at the pyramid apices. These luminescence peaks exhibit decay lifetimes of approximately 0.5 ns, with linewidths down to 650 me

A theory driven analysis of the effective QED coupling at MZM_Z

An evaluation of the effective QED coupling at the scale M_Z is presented. It employs the predictions of perturbative QCD for the cross section of electron positron annihilation into hadrons up to order \alpha_s^2, including the full quark mass dependence, and of order \alpha_s^3 in the high energy region. This allows to predict the input for the dispersion relations over a large part of the integration region. The perturbative piece is combined with data for the lower energies and the heavy quark thresholds. The result for the hadronic contribution to the running of the coupling \Delta\alpha^{(5)}_{\rm had}(M_Z^2)= (277.5 \pm 1.7)\times 10^{-4} leads to (\alpha(M_Z^2))^{-1}=128.927 \pm 0.023. Compared to previous analyses the uncertainty is thus significantly reduced.Comment: 9 pages (Latex); minor error in result for charm threshold region fixed; final result unchange

Process studies of odour emissions from effluent ponds using machine-based odour measurement

Replicable experimental studies using a novel experimental facility and a machine-based odour quantification technique were conducted to demonstrate the relationship between odour emission rates and pond loading rates. The odour quantification technique consisted of an electronic nose, AromaScan A32S, and an artificial neural network. Odour concentrations determined by olfactometry were used along with the AromaScan responses to train the artificial neural network. The trained network was able to predict the odour emission rates for the test data with a correlation coefficient of 0.98. Time averaged odour emission rates predicted by the machine-based odour quantification technique, were strongly correlated with volatile solids loading rate, demonstrating the increased magnitude of emissions from a heavily loaded effluent pond. However, it was not possible to obtain the same relationship between volatile solids loading rates and odour emission rates from the individual data. It is concluded that taking a limited number of odour samples over a short period is unlikely to provide a representative rate of odour emissions from an effluent pond. A continuous odour monitoring instrument will be required for that more demanding task

The whiteflies (Hemiptera: Aleyrodidae) of Europe and the Mediterranean Basin

The whitefly fauna of Europe and the Mediterranean Basin comprises 56 species that are considered to be native or naturalized, accommodated within 25 genera. Presented here are a check-list, an identification key to puparia, and a brief account of each species including its distribution and host-plant range. The puparium of each species is illustrated. One new nomenclatural combination (Aleuroclava similis, from Aleurotuberculatus) and two new synonymies (Parudamoselis kesselyakiwith Ceraleurodicus varus, Asterobemisia nigrini with A. paveli) are proposed. Three nominal species (Aleurodes capreae, A. fraxini, and Aleyrodes campanulae) are here treated as nomina dubia. Species which, in the study area, have only been recorded from glasshouses are discussed. Four additional species, not yet recorded from the region, are included in the discussion, two of them because a particular quarantine risk is perceived and two because they are notifiable pests in European Union quarantine legislatio

Exotic Bound State Production at Hadron Colliders

Hadronic production of nonrelativistic boundstates of $b^{\prime}$ or isosinglet quarks D with suppressed weak decays is investigated for LHC and SSC energies. QCD corrections to production and decay rates are incorporated. Large rates for final states from $\eta_{b^{\prime}}\rightarrow HZ$ are predicted.Comment: 7 pages and 13 figures (figures not includes, can be sent upon request), TTP93-1

Width and dual width of subsets in polynomial association schemes

AbstractThe width of a subset C of the vertices of a distance-regular graph is the maximum distance which occurs between elements of C. Dually, the dual width of a subset in a cometric association scheme is the index of the “last” eigenspace in the Q-polynomial ordering to which the characteristic vector of C is not orthogonal. Elementary bounds are derived on these two new parameters. We show that any subset of minimal width is a completely regular code and that any subset of minimal dual width induces a cometric association scheme in the original. A variety of examples and applications are considered

Natural polymorphism in the thrombospondin-related adhesive protein of Plasmodium falciparum

We have developed a typing system using natural sequence variation in the thrombospondin-related adhesive protein (TRAP) gene of Plasmodium falciparum. This method permits a haplotype to be assigned to any particular TRAP gene. We have applied this method to a hospital-based, case control-study in Mali. Previous sequence variation and conservation in TRAP has been confirmed. Particular TRAP haplotypes can be used as geographic hallmarks. Because of the high level of conflict between characters, we have examined the phylogenetic relationships between parasites using a network approach. Having received patient samples from urban and periurban areas of Bamako, the majority of haplotypes were closely related and distinct from TRAP sequences present in other continents. This suggests that the structure of TRAP can only tolerate a limited number of sequence variations to preserve its function but that this is sufficient to allow the parasite to evade the host's immune system until a long-lived immune response can be maintained. It may also reflect host genetics in that certain variants may escape the host immune response more efficiently than others. For vaccine design, sequences from the major regional variants may need to be considered in the production of effective subunit vaccines

On a class of embeddings of massive Yang-Mills theory

A power-counting renormalizable model into which massive Yang-Mills theory is embedded is analyzed. The model is invariant under a nilpotent BRST differential s. The physical observables of the embedding theory, defined by the cohomology classes of s in the Faddeev-Popov neutral sector, are given by local gauge-invariant quantities constructed only from the field strength and its covariant derivatives.Comment: LATEX, 34 pages. One reference added. Version published in the journa