Construction and performance characteristics of a rapid discharge TEA CO2 laser

A novel excitation technique is described for molecular gas lasers. A specially constructed electrode configuration is activated by a rapid Marx generator. A very homogeneous selfsustained discharge can be obtained although no separate preionization source is present. The construction is applied to a CO2 system. Details of the operating characteristics are given. We found the maximum energy production to be over 60 J per liter and a small-signal gain of 6% per cm could be reached

Experimental determination of the electron-avalanche and the electron-ion recombination coefficient

The electron-ion recombination coefficient γ and the avalanche coefficient δ = (α − a) · vd, where α and a are the ionizat ion and attachment coefficients respectively and vd the drift velocity of the electrons, have been experimentally determined in a self-sustained CO2-laser system (1:1:3 mixture) as a function of the E/N value. For low voltages we found the expected decrease of the recombination coefficient for increasing E/N values. However, it appears that for larger voltage the recombination coefficient increases sharply for increasing E/N values. The measurements of δ show a much smaller value than expected from theoretical calculations. This must be explained by a lower value of the electron-energy distribution function for higher energies, which may be consistent with our measured high recombination probability for electrons having high energy

A 5 cm single-discharge CO2 laser having high power output

A single-discharge self-sustained CO2 laser has been constructed with a gap distance of 5 cm. The system has a very simple construction; it produces a very uniform discharge with an output power of 50 Joules per liter for a CO2 : N2 : He = 1 : 1 : 3 mixture. The efficiency can be as high as 19%

Kinetic modelling of a self-sustained TEA CO2 laser

Recently new experimental values for the electron-ion recombination and the avalanche coefficients have been obtained. The results have been used to predict the time behaviour of the laser current and voltage. Excellent agreement between theory and experiment could be obtained

Strategic evaluation study on child-centred community development - Synthesis report

This strategic formative evaluation was carried out by Wageningen International Capacity Development & Institutional Change (CD&IC) programme from May to September 2009. The evaluation aims to obtain insight into the understanding of CCCD within Plan, and to learn more about the factors that favour or obstruct the implementation of Child Centred Community Development (CCCD) in practice. Suggestions on improving CCCD as an approach to development are provided, as well as an analysis of capacity development needs for CCCD implementation. This evaluation report is a product of Phase I of the complete anticipated evaluation trajectory. Phase II will most likely include an international workshop around the findings of Phase I. The findings of Phase I will contribute to the track record for the MFS II application to the Dutch Ministry of Foreign Affairs which Plan Netherlands is currently preparing. The study comprised a desk research stage, which reviewed relevant Plan documentation as well as consultations with key stakeholders within Plan worldwide. During this stage face to face interviews were conducted in Plan IH office in Woking, and at NLNO in Amsterdam. Other interviews with stakeholders in ROs and NOs were done using Skype. Furthermore two field studies were conducted in Kenya and Bangladesh. Given the fact that the topic of the study is broad, it is limited to analysis of the wider issues pertaining to CCCD rather than in-depth detailed analysis of these issues

A novel platform for the production of nonhydroxylated gelatins based on the methylotrophic yeast Hansenula polymorpha

The use of yeast as a host for heterologous expression of proteins that are normally derived from animal tissue is a promising way to ensure defined products that are devoid of potential harmful animal side products. Here we report on the production and secretion of a custom-designed gelatin, Hu3–His8, by the yeast Hansenula polymorpha. We observed that Hu3–His8 was poorly secreted by the heterologous Saccharomyces cerevisiae invertase secretion signal. In contrast, the S. cerevisiae mating factor α prepro sequence efficiently directed secretion into the culture medium. However, at higher copy numbers, intracellular accumulation of Hu3–His8 precursors occurred. Overproduction of Erv29p, a protein required for packaging of the glycosylated pro-α factor into COPII vesicles, did not improve gelatin secretion in the multicopy strain. Previously, H. polymorpha was reported to hydroxylate proline residues in gelatinous sequences. In contrast, we were unable to detect hydroxyprolines in the secreted Hu3–His8. Also, we failed to identify a gene encoding prolyl-4-hydroxylase in the H. polymorpha genome.