A Predictive Model for the Growth/No Growth Boundary of Zygosaccharomyces bailii at 7?°C and Conditions Mimicking Acidified Sauces

The spoilage potential of Zygosaccharomyces bailii has been widely recognized within the food industry. However, few data are available on the growth characteristics of this yeast at low temperature and in the absence of chemical preservatives. In this study, the growth/no growth boundary of Z. bailii was defined at refrigeration temperature (7?°C) and at conditions relevant to high-sugar, low-pH foods (such as ketchup and salad dressing), i.e. pH?3.0?C5.0 (five levels), a _w 0.93?C0.97 (five levels) and acetic acid concentration 0?C2.5% (v/v; six levels). Yeast growth was followed during 90?days by optical density measurements, and logistic regression models were used to describe the data. Acetic acid had a significant effect on the relation between a _w and NaCl concentration and this interaction had important consequences for the model development. When data were modelled as a function of a _w or NaCl concentration, a stimulatory effect by acetic acid was observed. In contrast, as a function of (toxic) Na⁺ ions, no evidence was found of such a phenomenon. These results indicate that in cases where the relationship between a _w and solute concentration is not straightforward such as in the presence of acid preservatives, one must be critical towards the interpretation of data and correspondingly, the development of predictive models. On a practical note, the developed models, especially the one incorporating Na⁺ ions, may be used (1) to assess the stability of shelf-stable acidified foods stored under chilled conditions after opening or (2) to formulate new additive-free products intended for storage at 7?°C.     

Development of photocatalytic efficient Ti-based nanotubes and nanoribbons by conventional and microwave assisted synthesis strategies

Titanate nanotubes were prepared via a hydrothermal treatment of TiO₂ powders (Riedel De Haen) in a basic solution. Morphology and structure of the prepared samples were characterized by high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), XRD, FT-Raman spectroscopy, nitrogen sorption and DSC. The photocatalytic activity was evaluated by photocatalytic oxidation of rhodamine 6G. Trititanate nanotubes (TTNT) with inner pore diameters between 4 and 4.2 nm and surface areas up till 360 m²/g could be synthesized. The synthesis route was modified by introduction of a calcination step, by applying a lower hydrothermal temperature and microwave irradiation in order to increase the photocatalytic activity of the porous photoactive nanotubular materials. Calcination and a softer hydrothermal treatment led to the formation of anatase without affecting the surface area and nanotubular shape of the samples. In this way, the photocatalytic activity of the original trititanate nanotubes could be significantly increased. By making use of microwave assisted synthesis, the photocatalytic activity can also be increased due to the presence of anatase. However, by applying microwave synthesis, a different structure was obtained, nanoribbons (NR) instead of nanotubes, resulting in a decrease in surface area and porosity.     

Advanced manufacturing concepts for crystalline silicon solar cells

An overview is given concerning current industrial technologies, near future improvements and medium term developments in the field of industrially implementable crystalline silicon solar cell fabrication. The paper proves that considerable improvements are still possible, both in efficiency and in production cost. The paper also proves that a lot of effort is being put worldwide on thinner substrates and on thin-film crystalline silicon cells deposited on cheap carriers, in order to save in substrate cost and in order to gain more independence from availability problems of silicon feedback     

Power handling of the bulk tungsten divertor row at JET: First measurements and comparison to the GTM thermal model

The design of the tile assemblies of the bulk tungsten divertor row in JET was improved in the course of several experiments as far as the power and energy performances are concerned: many prototypes were exposed to high heat fluxes in several electron and ion beam facilities during the development phase. These experiments were carried out in parallel with extensive modelling of the complete tungsten tile assembly in the so-called Global Thermal Model (GTM). The goal was to understand the heat flow from the plasma-facing surface through the supporting structure down to the base plate of the JET MkII divertor sufficiently to be able to later interpret operational data from the torus. Temperatures measured in the torus are in good agreement (?10/+15%) with the model. Some characteristic times show stronger deviations, with no incidence on the highest temperature at all times.