Interpolation formula for the electrical conductivity of nonideal plasmas

On the basis of a quantum-statistical approach to the electrical conductivity of nonideal plasmas we derive analytical results in the classical low-density regime, in the degenerate Born limit, and for the contribution of the Debye-Onsager relaxation effect. These explicit results are used to construct an improved interpolation formula of the electrical conductivity valid in a wide range of temperature and density which allows to compare with available experimental data of nonideal plasmas.Comment: 7 pages, 1 tabl

Assessment and reduction of insect infestation of cured fish in South East Asia, with laboratory studies on Chrysomya raegacephala (fab.), a principal causative agent

A survey of cured fish establishments in 5 countries of South East Asia, revealed that cured fish is a nutritionally and economically important commodity in the region and that insect infestation, in particular blowfly infestation during processing and dermestid beetle infestation during storage, are major causes of losses in cured fish. Many processors have responded by illegally applying household and agricultural insecticides to their fish. Field investigations in Indonesia and Thailand, identified Chrysomya megacephala (Fab.) as the most widespread cause of infestation during processing. Lucilia caprina (Wied.) was also a common cause of infestation. Dermestes maculatus (Degeer), D. carnivorus (Fab.), D. ater (Degeer) and Piophila casei (L.), were the most common causes of infestation during storage. These species were able to tolerate the relatively high salt concentrations of the processed fish. Field infestation reduction trials, demonstrated that salting the fish for an extended period failed to provide protection against insect infestation. Guarding the salting tank with a closely fitting lid, prevented blowfly infestation during salting. Flyscreens were found to reduce blowfly infestation during drying, but the design used, presented practical difficulties and was not acceptable to the processor. The pyrethroid insecticide Fastac (alphacypermethrin), prevented blowfly infestation during processing at concentrations as low as 0.00.3% and had a marked repellent effect against blowflies at a concentration of 0.001%. Fastac, applied at a concentration of 0.006%, protected fish against dermestid beetle infestation and damage. Fastac residues in fish treated with a 0.006% dip decreased to less than 2 rag/kg after drying and 1 week's storage. The pyrethroid insecticide deltamethrin, prevented insect infestation during processing and storage, when applied as a 0.003% dip before drying. The FAO/WHO approved insecticide piriraiphos-methyl, reduced blowfly infestation and prevented damage during processing and reduced dermestid beetle infestation during storage, when applied as a 0.03% dip before drying. This treatment resulted in residues, after processing, that were within the FAO/WHO maximum residue limit of 10 mg/kg.Spray applications of pirimiphos-methyl, at dosages of 5-20 mg/kg and deltaraethrin, at dosages of 1-3 mg/kg, were effective in reducing dermestid beetle infestation of smoked fish during storage. Laboratory investigations demonstrated that C. megacephala produced similar numbers of male and female offspring and that there was no difference between the mortalities of the 2 sexes. Female flies greatly outnumbered male flies at the processing site. Mean lifespans of C. megacephala cage populations ranged from 47-54 days and the maximum survival time ranged from 80-98 days. C. megacephala eggs matured within 3 weeks of adult emergence and the mean egg count for the adult female flies was 221.The presence of C. megacephala eggs on fish, stimulated oviposition by C. megacephala and freshly laid eggs were found to have a higher stimulatory effect than eggs which had been previously boiled. Fish being salted exerted a marked, differential attractive effect on gravid, female flies. When presented with fish of a range of salt concentrations, C. megacephala preferentially oviposited on the fish with the lowest salt concentration. In the absence of choice, C. megacephala readily oviposited on fish with relatively high salt contents of 30-40% (dwb). A feeding medium salt content of 33.8% was necessary to significantly reduce larval growth rate and salt contents in excess of 39.5% were necessary to obtain high larval mortalities. Salt contents of up to 39.5% had no effect on pupal mortality

Analytic expression for Taylor-Couette stability boundary

We analyze the mechanism that determines the boundary of stability in Taylor-Couette flow. By simple physical argument we derive an analytic expression to approximate the stability line for all radius ratios and all speed ratios, for co- and counterrotating cylinders. The expression includes viscosity and so generalizes Rayleigh's criterion. We achieve agreement with linear stability theory and with experiments in the whole parameter space. Explicit formulae are given for limiting cases.Comment: 6 pages (LaTeX with REVTEX) including 4 figures (Postscript) Revised, discussion of two additional references. See also http://staff-www.uni-marburg.de/~esse

Polariton effects in the dielectric function of ZnO excitons obtained by ellipsometry

This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in Appl. Phys. Lett. 96, 031904 (2010) and may be found at https://doi.org/10.1063/1.3284656.The complex dielectric tensor of ZnO in the regime of the excitonic transitions is determined with ellipsometry and analyzed concerning the quantization of the electromagnetic field in terms of coupled polariton-eigenmodes. Negative sections in the real part indicate the significant formation of polaritons for the dipole-allowed excitons of the three upper valence-bands Γ7,Γ9,Γ7. The transverse-longitudinal splittings which separate the upper polariton branch from the lower branch, corresponding to the k-vector of the used light, are deduced precisely for each subband. Mainly for E∥c, additional absorption peaks are observed at the longitudinal B-exciton and closely above. One is considered to be a mixed-mode and the other is seen as a consequence of interference effects in an exciton free surface layer which is also visible in reflectance anisotropy spectroscopy.EC/FP7/218570/EU/MULTIFUNCTIONAL NANOMATERIALS CHARACTERISATION EXPLOITING ELLIPSOMETRY and POLARIMETRY/NANOCHAR

A proposal for relative time petri nets

Copyright © 2005, IEEEPetri nets are a graph-based modelling formalism which has been widely used for the formal specification and analysis of concurrent systems. A common analysis technique is that of state space exploration (or reachability analysis). Here, every possible reachable state of the system is generated and desirable properties are evaluated for each state. This approach has the great advantage of conceptual simplicity, but the great disadvantage of being susceptible to state space explosion, where the number of states is simply too large for exhaustive exploration. Many reduction techniques have been suggested to ameliorate the problem of state space explosion. In the case of timed systems, the state space is infinite, unless analysis is restricted to a bounded time period. In this paper, we present a Petri net formalism based on the notion of relative time (as opposed to the traditional approach of dealing with absolute time). The goal is to derive a finite state space for timed systems which have repeating patterns of behaviour, even though time continues to advance indefinitely.Joseph Kuehn, Charles Lakos, Robert Esse

Component-based design and analysis: a case study

©2003 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.In this paper, we introduce a component-based design methodology and present a practical analysis approach that makes use of the modular nature of component-based designs to alleviate the state space explosion problem, a well-known obstacle to system verification. In addition, the approach is illustrated by application to a non-trivial case study: the production cell. It is shown that not only the basic consistency property, viz. the freedom from unexpected reception and deadlock, but also other important safety properties in the design can be proved.Yan Jin, Charles Lakos, Robert Esse

Report on a visit to Indonesia to conduct a review of the post harvest fisheries sector

A review of post-harvest fisheries in Indonesia was undertaken for the Overseas Development Administration, by a fisheries technologist, a biologist, and an economist, during a five week visit in June and July 1988. The terms of reference were: to review post-harvest fisheries and donors' activities in the sector, and to identify a strategy for future ODA inputs. The marine fishery is the most important in terms of value, followed by tambak aquaculture (mostly shrimps and milkfish), and the inland capture fishery. Most of the harvest is sold in the domestic market as wet fish, dried fish, and pindang (fish cooked in brine). Exports of frozen shrimp, from the tambaks and the marine fishery, are becoming increasingly important. Additionally, there are exports of wet fish on ice to Singapore. The team considered that the greatest problem facing the sector is overfishing of the South Java Sea, resulting in operational fishing grounds being located at an ever increasing distance from the main markets on Java. This poses a challenge to resource management, both pre- and post-harvest. The former requiring resource surveys, and the latter, the identification of low-cost improvements to on-board handling, to ensure the supply of fish to Java's predominantly low income population. A study encompassing these aspects is proposed by the EC in collaboration with France; ODNRI, in consultation with ODA HO, will liase with the French technical agency (ORSTOM) to determine whether complementary inputs from ODNRI would be useful. A second area in which action is proposed is in reducing losses from insect infestation of sun-dried fish. Dried fish is an important protein source for low-income groups in Indonesia, and an area in which ODA could make an effective contribution. The use of household insecticides on drying fish in Indonesia has been widely publicised and the practice banned. The problem persists though, and the team recommends a follow-up programme to an existing project. The existing project has provided training to the staff of provincial quality control laboratories in loss assessment and reduction, including the use of a safe (and approved) insecticide - Minawet. Financial analysis of the use of Minawet and adoption trials will be undertaken during the final stages of the existing project. Subject to satisfactory results from these, a large-scale extension project is proposed, aimed at adoption of Minawet by fish processors. An additional element will be the provision of the necessary training and equipment in pesticide residue analysis, for the National Centre for Quality Control and Fish Processing

Excitonic - vibronic coupled dimers: A dynamic approach

The dynamical properties of exciton transfer coupled to polarization vibrations in a two site system are investigated in detail. A fixed point analysis of the full system of Bloch - oscillator equations representing the coupled excitonic - vibronic flow is performed. For overcritical polarization a bifurcation converting the stable bonding ground state to a hyperbolic unstable state which is basic to the dynamical properties of the model is obtained. The phase space of the system is generally of a mixed type: Above bifurcation chaos develops starting from the region of the hyperbolic state and spreading with increasing energy over the Bloch sphere leaving only islands of regular dynamics. The behaviour of the polarization oscillator accordingly changes from regular to chaotic.Comment: uuencoded compressed Postscript file containing text and figures. In case of questions, please, write to [email protected]

Femtosecond study of the interplay between excitons, trions, and carriers in (Cd,Mn)Te quantum wells

We present an absorption study of the neutral and positively charged exciton (trion) under the influence of a femtosecond, circularly polarized, resonant pump pulse. Three populations are involved: free holes, excitons, and trions, all exhibiting transient spin polarization. In particular, a polarization of the hole gas is created by the formation of trions. The evolution of these populations is studied, including the spin flip and trion formation processes. The contributions of several mechanisms to intensity changes are evaluated, including phase space filling and spin-dependent screening. We propose a new explanation of the oscillator strength stealing phenomena observed in p-doped quantum wells, based on the screening of neutral excitons by charge carriers. We have also found that binding heavy holes into charged excitons excludes them from the interaction with the rest of the system, so that oscillator strength stealing is partially blockedComment: 4 pages, 4 figure