Characteristic Energy Losses with High Energy Electrons up to 2.5 MeV

Some aspects of the influence of the energy of the incident electrons in electron energy loss spectroscopy (EELS) are considered. It is shown that this method of analysis used in high voltage electron microscopy, permits one to observe, with a better edge jump ratio than at lower accelerating voltages, the characteristic edges. One important question is to eliminate artefacts in the counting and to record only electrons from the true spectrum. Some recent examples are given. One of them concerns extended energy loss fine structures (EXELFS). It seems high voltage electron microscopy (HVEM) could be very useful in this domain

Applications of yeast flocculation in biotechnological processes

A review on the main aspects associated with yeast flocculation and its application in biotechnological processes is presented. This subject is addressed following three main aspects – the basics of yeast flocculation, the development of “new” flocculating yeast strains and bioreactor development. In what concerns the basics of yeast flocculation, the state of the art on the most relevant aspects of mechanism, physiology and genetics of yeast flocculation is reported. The construction of flocculating yeast strains includes not only the recombinant constitutive flocculent brewer’s yeast, but also recombinant flocculent yeast for lactose metabolisation and ethanol production. Furthermore, recent work on the heterologous β-galactosidase production using a recombinant flocculent Saccharomyces cerevisiae is considered. As bioreactors using flocculating yeast cells have particular properties, mainly associated with a high solid phase hold-up, a section dedicated to its operation is presented. Aspects such as bioreactor productivity and culture stability as well as bioreactor hydrodynamics and mass transfer properties of flocculating cell cultures are considered. Finally, the paper concludes describing some of the applications of high cell density flocculation bioreactors and discussing potential new uses of these systems.Fundação para a Ciência e a Tecnologia (FCT) – PRAXIS XXI - BD11306/97

The Electronic Geophysical Year (eGY) and the World Data Center System

[1] The WDC system was created to archive and distribute data collected from the observational programs of the 1957-1958 International Geophysical Year. Originally established in the United States, Europe, Russia, and Japan, the WDC system has since expanded to other countries and to new scientific disciplines. The WDC system now includes over 51 Centers in 12 countries. The WDCs have been very successful over the last 50 years in meeting the needs of ICSU programs. However, in the next 50 years, the WDC system will need to evolve to accommodate the changing needs of ICSU and the global scientific community. Advances in information technology, as promoted by the electronic Geophysical Year, the implementation of new global scientific programs and the rapid increase in global, high-speed network connectivity will require the WDC system to adapt their current infrastructure, reorient their activities and implement new modes of operation. New requirements of existing ICSU programs like the IGBP, the activities of the new international science years (IPY, IHY, eGY, IYPE) and the implementation of the far reaching, long-term, Global Earth Observation System of Systems, will make new demands on the WDCs. The WDC system will respond by placing emphasis on modernizing its capabilities, expanding the WDCs into new disciplines, broadening the System geographically, especially into developing countries, and being more proactive in addressing new requirements from the ICSU and global scientific community. INDEX TERMS

MICROANALYSIS TECHNIQUE USING ELECTRON ENERGY LOSS SPECTROSCOPY IN HIGH VOLTAGE ELECTRON MICROSCOPY

En vue de l'utilisation de la spectroscopie de pertes d'énergie d'électrons à très haute tension, pour l e développement de la microanalyse, on étudie la variation du contraste des distributions caractéristiques d'ionisation du niveau K du carbone en fonction de l'énergie des électrons primaires (entre 0,3 et 1 MeV). Cette étude permet de conclure à un avantage des hautes tensions dans ce domaine.With the purpose of using EELS for the development of microanalysis, the variation of the jump-ratio at the carbon K-edge is studied as a function of the primary electron incident energy (0.3 - 1 MeV). This study shows an interest in using high accelerating voltage in that field

MICRO-ANALYSE DE CRISTAUX EN CROISSANCE SUR UNE SURFACE DE SILICIUM

Sur une surface de silicium, préalablement polie, chauffée dans un microscope électronique, nous avons fait croître des cristaux que nous avons observés et analysés.Crystals were grown on a polished silicon surface by heating in an electron microscope column. These crystals and their growths were studied by TEM and analysed by EELS, revealing structure and composition