Effect of ethanol on the growth of Clostridium botulinum

Model broth studies were carried out to investigate the effect of ethanol on the growth of proteolytic (group I) strains of Clostridium botulinum. Ethanol extended the pathogen's lag phase, decreased its exponential growth rate, and decreased its final level of growth in the stationary phase. In all cases, botulinum neurotoxin production was associated with growth. Micrographs of C. botulinum cultures grown at 37 degrees C in trypticase peptone glucose yeast extract (TPGY) broths containing 2 and 4% ethanol showed elongation of vegetative cells and interference with cell division. The inhibition of growth and toxin production at the ethanol level predicted (5.5%, wt/wt) was confirmed by microscopy and by the mouse bioassay. A subsequent study was carried out to determine the combined effect of ethanol (0 to 8% [wt/wt]), water activity (aw; 0.953 to 0.997), and pH (6.2 to 8.2) on the probability of the growth of and neurotoxin production by proteolytic strains of C. botulinum (10(3) spores per ml). Growth and neurotoxin production occurred in 1 to 3 days in TPGY broths without ethanol (0%) and in 2 to 4 days in broths containing 2% ethanol regardless of the aw or pH levels (P < 0.005). Growth and neurotoxin production were delayed by an ethanol concentration of 4% ethanol and completely inhibited by a concentration of 6%. At an ethanol concentration of 4%, the probability of growth and toxin production over 365 days (Pt) was influenced by aw and pH. After 365 days, the maximum probability of growth and toxin production (Pmax) was 1 for all but one combination. However, tau, the time it took for 50% of all eventually positive replicates for any given combination of barriers to show growth and/or turbidity, ranged from <3 to 229 days. All tubes of TPGY broths that showed no growth after 365 days were subcultured in fresh TPGY broths. In all cases, growth and toxin production occurred within 24 h at 37 degrees C, indicating the reversible (sporostatic and/or bacteriostatic) effect of ethanol on C. botulinum.     

Protactinium-231: A new radionuclide for AMS

For the first time, an AMS system was used to determine concentrations of the actinide Protactinium-231. ²³¹Pa has widespread applications in the earth sciences. It can be used for U-series disequilibrium dating, and ²³¹Pa is an important tracer in Paleoceanography. The Pa isotopes were measured with the compact ETH/PSI-AMS facility TANDY operating at about 300 kV. The linearity of the AMS is documented with two standard-dilution experiments and first measurements of natural samples from very different climate archives are presented. Our results show that it is possible to determine ²³¹Pa amounts in the lower femtogram (1 fg = 10⁻¹⁵ g) range with the TANDY. In natural samples, ²³¹Pa concentrations between 1 and 4 pg/g (1 pg = 10⁻¹² g) were measured with an average total error of 3% (one sigma). The average over all reproducibility of these first measurements was better than 2% with clear potential for improvement.     

Capsosomes with Multilayered Subcompartments: Assembly and Loading with Hydrophobic Cargo

Therapeutic artificial cells or organelles are nanoengineered vehicles that are expected to substitute for missing or lost cellular function. The creation of capsosomes, polymer carrier capsules containing liposomal subcompartments, is a promising approach towards constructing such therapeutic devices using the layer‐by‐layer assembly method. Herein, the assembly of intact, nonaggregated capsosomes containing multiple liposome layers is reported. It is also further demonstrated that thiocoraline, a hydrophobic model peptide with antitumor activity, can be efficiently loaded into the membrane of the liposomal subcompartments of the capsosomes. Cell viability assays verify the activity of the trapped antitumor cargo. It is also shown that pristine capsosomes do not display inherent cytotoxic effects. The ability to tune the number of liposome layers and hence the drug loading in capsosomes as well as their noncytotoxicity provide new opportunities for the creation of therapeutic artificial cells and organelles.     

Impact of synchrotron radiation on fuel cell operation in imaging experiments

For the clarification of water transport mechanisms in operating fuel cells, synchrotron radiation computed tomography (SR-CT) was applied. A novel fuel cell has been designed that exposes the entire active area (7 mm²) to the SR beam while at the same time allowing for full fuel cell operation during the imaging experiment. This micro fuel cell has been qualified successfully prior to the SR imaging experiments. The cell voltage was 600 mV at 0.2 A cm⁻² (open circuit voltage, OCV > 950 mV) and the operation was stable for hours. However, under SR beam exposition for in situ imaging, severe cell performance degradation within minutes has been reproducibly observed. Even after the SR beam had been switched-off cell operation remained irreversibly degraded whilst OCV could be recovered. Preliminary results indicate a higher degradation sensitivity of the cathode side of the cell. Apparently, the unique setup of the experiment which exposes an operating fuel cell with the entire active area to the SR beam reveals otherwise unnoticeable degradation mechanisms. It may have to be concluded that the very same materials degrade heavily during beam exposure that are subject of the imaging investigation. Consequently, the applicability of SR imaging to study water transport in porous fuel cell materials has to be revisited critically. This publication describes the observations made during fuel cell operation under SR beam exposure and discuss potential mechanisms that may cause beam-induced performance degradation.     

A diagnosis-based approach for tire-road forces and maximum friction estimation

A new approach to estimate vehicle tire forces and road maximum adherence is presented. Contrarily to most of the previous works on this subject, it is not an asymptotic observer-based estimation, but a combination of elementary diagnosis tools and new algebraic techniques for filtering and estimating derivatives of noisy signals. In a first step, instantaneous friction and lateral forces will be computed within this framework. Then, extended braking stiffness concept is exploited to detect which braking efforts allow to distinguish a road type from another. A weighted Dugoff model is used during these ‘distinguishable’ intervals to estimate the maximum friction coefficient. Very promising results have been obtained in noisy simulations and real experimentations for most of the driving situations.     

Exhaust hood for steam turbines-single-flow arrangement

In the past, increased attention was given to the development of an optimal shape for the inlet part of LP turbine casings in SKODA POWER. A double-flow design is typically used for high power output turbines. An optimized shape for the internal diffuser has been found, which transforms the kinetic energy of steam into increased pressure, thus effectively increasing the thermodynamic efficiency of the stage. Some conclusions have been drawn from laboratory experiments, others derived directly from on-site measurements at power plants. The conclusions from the development of double-flow turbines form the basis for the design of the single-flow turbine arrangement. Single-flow design is typically used for lower output turbines. There are still some limitations in applying this arrangement. The designer needs to resolve the bearing position and how to ensure access to them. Reinforcing the ribs and supports are used, therefore, to ensure the rigidity of the entire casing. The optimization of the single-flow diffuser shape is therefore the subject of the study presented below.