Work domain analysis and intelligent transport systems: Implications for vehicle design

This article presents a Work Domain Analysis (WDA) of the road transport system in Victoria, Australia. A series of driver information requirements and tasks that could potentially be supported through the use of Intelligent Transport Systems (ITS) are then extracted from the WDA. The potential use of ITS technologies to circumvent these information gaps and provide additional support to drivers is discussed. It is concluded that driver information requirements are currently not entirely satisfied by contemporary vehicle design and also that there are a number of driving tasks that could be further supported through the provision of supplementary systems within vehicles

Metodos para el manejo de enfermedades de pastos tropicales en Sur America

Durante la decada pasada, varias enfermedades de plantas forrajeras tropicales ocasionan perdidas considerables en America del Sur. Casi todas lasenfermedades han ocurrido en praderas de leguminosas nativas promisorias, en regiones de produccion de pastos, mientras que las gramineas introducidas de Africa han tenido pocos problemas de enfermedades. El significado de esta diferencia es discutible. El posible manejo de enfermedades en praderas tropicales incluye control quimico y biologico, control natural a traves de saneamiento, asociacion estrategica, manejo de praderas y resistencia. El saneamiento a traves de la quema y asociacion estrategica ha mostrado potencial para el manejo de enfermedades de plantas forrajeras tropicales. Aunque la resistencia se considera como el metodo de manejo de enfermedades mas practico, su origen parece estar modificado por las caracteristicas de los ecosistemas de las praderas tropicales en America del Sur. (Extracto

Calcium Spikes in Epithelium: study on Drosophila early embryos

International audienceCalcium ion acts in nearly every aspect of cellular life. The versatility and specificity required for such a ubiquitous role is ensured by the spatio-temporal dynamics of calcium concentration variations. While calcium signal dynamics has been extensively studied in cell cultures and adult tissues, little is known about calcium activity during early tissue morphogenesis. We monitored intracellular calcium concentration in Drosophila gastrula and revealed single cell calcium spikes that were short-lived, rare and showed strong variability among embryos. We quantitatively described the spatio-temporal dynamics of these spikes and analyzed their potential origins and nature by introducing physical and chemical perturbations. Our data highlight the inter-and intra-tissue variability of calcium activity during tissue morphogenesis

Axial localization of luminophores by partial coherence interferometry

We propose a solution for increasing the axial resolution of confocal microscopes. In the experimental set-up described in this paper an interference phenomenon between two counterpropagating beams is used to determine the axial position of a luminophore. The optical path difference between the two waves, which is related to the position of the luminophore, is recovered thanks to a second interferometer by using partial coherence interferometry demodulation technique. The proposed solution can find applications in biology for localizing with nanometric resolution a small number of tagged species

Location of sugars in multilamellar membranes at low hydration

Severe dehydration is lethal for most biological species. However, there are a number of organisms which have evolved mechanisms to avoid damage during dehydration. One of these mechanisms is the accumulation of small solutes (e.g. sugars), which have been shown to preserve membranes by inhibiting deleterious phase changes at low hydration. Specifically, sugars reduce the gel to fluid phase transition temperatures of model lipid/water mixtures. However, there is a debate about the precise mechanism, the resolution of which hinges on the location of the sugars. In excess water, it has been observed using contrast variation SANS that the sugar concentration in the excess phase is higher than in the interlamellar region [Deme and Zemb, J. Appl. Crystallog. 33 (2000) 569]. This raises two questions regarding the location of the sugars at low hydrations: first, does the system phase separate to give a sugar/water phase in equilibrium with a lipid/water/sugar lamellar region (with different sugar concentrations); and second, is the sugar in the interlamellar region uniformly distributed, or does it concentrate preferentially either in close proximity to the lipids, or towards the center of the interbilayer region. In this paper we present the preliminary results of measurements using contrast variation SANS to determine the location of sugars in lipid/water mixtures

Freeze avoidance: a dehydrating moss gathers no ice

Using cryo-SEM with EDX fundamental structural and mechanical properties of the moss Ceratodon purpureus (Hedw.) Brid. were studied in relation to tolerance of freezing temperatures. In contrast to more complex plants, no ice accumulated within the moss during the freezing event. External ice induced desiccation with the response being a function of cell type; water-filled hydroid cells cavitated and were embolized at -4 ºC while parenchyma cells of the inner cortex exhibited cytorrhysis, decreasing to ~20% of their original volume at a nadir temperature of -20 ºC. Chlorophyll fluorescence showed that these winter acclimated mosses displayed no evidence of damage after thawing from -20 ºC while GCMS showed that sugar concentrations were not sufficient to confer this level of freezing tolerance. In addition, differential scanning calorimetry showed internal ice nucleation occurred in hydrated moss at ~ -12 ºC while desiccated moss showed no evidence of freezing with lowering of nadir temperature to -20 ºC. Therefore the rapid dehydration of the moss provides an elegantly simple solution to the problem of freezing; remove that which freezes

Quantitative study on the effects of sugars on membrane phase transitions - preliminary investigations

It is well known that sugars and other small solutes can reduce the temperature at which membranes undergo the fluid-gel phase transition at low hydration. The mechanisms for this are now well understood [Bryant et al. Abstract No. 85]. Naively, one might expect that this ability would be a direct function of sugar concentration, and that the effects should increase as the amount of sugar increases. However, the real situation is more complex. Previous work [K.L. Koster, Y.P. Lei, M. Anderson, S. Martin, G. Bryant, Biophys. J. 78 (2000) 1932–1946.] has shown that there are two distinct mechanisms for reduction in the transition temperature: first, if the sugar concentration is too low to form a glass, then the transition temperature can be reduced to (at best) the full hydration value; and second, if a glass forms, the transition temperature can be depressed to a fixed value, largely independent of sugar concentration. However, to the authors’ knowledge there has been no systematic study of the membrane transition temperature as a function of sugar/lipid ratio and level of hydration. In this paper we present the results of such a study. We show that in the absence of a glass, the reduction in the membrane phase transition temperature reaches a maximum value at a limiting sugar:lipid ratio. Beyond that value, the addition of further sugar no longer alters the membrane phase transition temperature. We explain these results in terms of hydration forces between membranes, and comment on the implications of these results for the prevention of damage to membranes during dehydration

Effects of sugars on lipid bilayers during dehydration - SAXS/WAXS measurements and quantitative model

We present an X-ray scattering study of the effects of dehydration on the bilayer and chain-chain repeat spacings of dipalmitoylphosphatidylcholine bilayers in the presence of sugars. The presence of sugars has no effect on the average spacing between the phospholipid chains in either the fluid or gel phase. Using this finding, we establish that for low sugar concentrations only a small amount of sugar exclusion occurs. Under these conditions, the effects of sugars on the membrane transition temperatures can be explained quantitatively by the reduction in hydration repulsion between bilayers due to the presence of the sugars. Specific bonding of sugars to lipid headgroups is not required to explain this effect