A contribution to the measurement of permittivity with theshort-circuited line method

The elimination of the ambiguity in the short-circuited line method for determining the dielectric permittivity by measuring the change in the position of the minimum for two similar frequencies is studied. This quantity is used to uniquely determine the coefficients of an algebraic equation with a single physical solution. Ambiguity may or may not be removed depending on the dielectric characteristics of the sample and on the value of the ratio sample thickness/wavelength. The former are not known a priori and the latter is an experimental parameter, which can be varied. The influence of this parameter on the elimination of ambiguity is studied. Finally the analysis is compared to results of measurements on several organic liquids     

Regulation of mevalonate 5-pyrophosphate decarboxylase in HeLa cells. Inhibition of enzymatic protein synthesis by serum lipoproteins

Mevalonate 5-pyrophosphate decarboxylase (EC 4.1.1.33) has been considered as a secondary site of regulation of cholesterogenesis. Because of this, we have studied the regulation of decarboxylase in HeLa cells by serum lipoproteins in the cell culture medium. A first group of experiments was performed with cells grown in Eagle's medium with 10% foetal calf serum. The specific activity of decarboxylase was increased when whole foetal calf serum was replaced with lipoprotein-poor serum. This increase was clearly reduced in the presence of cycloheximide. Addition of serum lipoproteins to a medium containing lipoprotein-poor serum led to a clear decrease in the decarboxylase activity. An identical decrease was observed after the addition of lipoproteins alone or in combination with cycloheximide. These results suggest for the first time that the effect of serum lipoproteins on decarboxylase activity should be a decrease in the rate of enzymatic protein synthesis, and corroborate the important role of reactions other than those catalysed by 3-hydroxy-3-methylglutaryl-CoA reductase in the regulation of cholesterogenesis.     

Calmodulin is involved in membrane depolarization-mediated survival of motoneurons by phosphatidylinositol-3 kinase- and MAPK-independent pathways

In the present work, we find that the elevation of extracellular K+ concentration promotes the survival of chick spinal cord motoneurons in vitro deprived of any neurotrophic support. This treatment induces chronic depolarization of the neuronal plasma membrane, which activates L-type voltage-dependent Ca2+ channels, resulting in Ca2+ influx and elevation of the cytosolic free Ca2+ concentration. Pharmacological reduction of intracellular free Ca2+ or withdrawal of extracellular Ca2+ reversed the effects of depolarization on survival. The intracellular Ca2+ response to membrane depolarization developed as an initial peak followed by a sustained increase in intracellular Ca2+ concentration. The depolarizing treatment caused tyrosine phosphorylation of mitogen-activated protein kinase (MAPK) without involving tyrosine kinase receptor activation. The calmodulin antagonist W13 inhibited the survival-promoting effect induced by membrane depolarization but not the tyrosine phosphorylation of MAPK. Moreover, depolarization did not induce phosphatidylinositol-3 kinase (PI-3K) phosphorylation in our cells, and the PI-3K inhibitor wortmannin did not suppress the survival-promoting effect of K+ treatment. These results suggest that calmodulin is involved in calcium-mediated survival of motoneurons through the activation of PI-3K- and MAPK-independent pathways.     

Nonlinearly Weighted First‐order Regression for Denoising Monte Carlo Renderings

We address the problem of denoising Monte Carlo renderings by studying existing approaches and proposing a new algorithm that yields state‐of‐the‐art performance on a wide range of scenes. We analyze existing approaches from a theoretical and empirical point of view, relating the strengths and limitations of their corresponding components with an emphasis on production requirements. The observations of our analysis instruct the design of our new filter that offers high‐quality results and stable performance. A key observation of our analysis is that using auxiliary buffers (normal, albedo, etc.) to compute the regression weights greatly improves the robustness of zero‐order models, but can be detrimental to first‐order models. Consequently, our filter performs a first‐order regression leveraging a rich set of auxiliary buffers only when fitting the data, and, unlike recent works, considers the pixel color alone when computing the regression weights. We further improve the quality of our output by using a collaborative denoising scheme. Lastly, we introduce a general mean squared error estimator, which can handle the collaborative nature of our filter and its nonlinear weights, to automatically set the bandwidth of our regression kernel.     

On the Barriers to Adaption to Less Water under Climate Change: Policy Choices in Mediterranean Countries

Barriers and constraints to adapting water resources management to climate change in the Mediterranean region are analysed in this paper. First, we analysed the risks to the water resources sector derived from climate change. We then identified the main objective of water adaptation measures: ensuring there is enough water for food, for people, and for ecosystems. This implies visions about availability - being sufficient water -, accessibility - both physical and economic access -, and adequacy - being safe for ecosystems and human consumption. A portfolio of local and collective actions to adapt water management for agriculture to climate change in Mediterranean countries is presented. Adaptation strategies included improved efficiency, optimisation of governance, enhancement of participation, development of risk-based choices, and economic instruments. Finally, the paper categorised the constraints to implement the measures, give specific examples about these issues and also quantify their impact. When considering constraints and opportunities to implement these water management practices, any environmental policy regulating their adoption should be based on recommending the use of extension and training to local actors on the application of the practices.     

Effect of a risk factor in convoy merging manoeuvres considering uncertainty in travelling times

Cooperative guiding, and especially in convoys, for automated, non-contaminating transport units is a line of research for sustainable urban transport. In this paper we propose a strategy for facilitating the merging manoeuvre between independent units travelling in a transport scenario (usually a city) and a convoy following a pre-defined peripheral trajectory in the same scenario. The proposal consists of an inexpensive computational cost algorithm, which is able to calculate the optimal merging point and the efficient route to reach it. An optimal merging node is the one on the periphery which minimises the merging time. In addition to the complexity of the problem is the uncertainty associated to travelling times, as is habitual in a real urban setting. Sources of uncertainty include weather conditions, the effect of the zone (proximity to centres of social services or cultural interest), the day and time on traffic density, etc. All this justifies the variability in the time taken by any vehicle moving along a section in the transport scenario.In order to delimit the randomness inherent to the problem, the authors incorporate a novel “risk factor” parameter, which conditions the solution. This risk factor limits the probability of a convoy reaching the merging node before the pursuer (failed merging manoeuvre).The possibility of having the travelling experiences from any unit moving in the transport scenario means that the statistics (mean and variance) associated to the expected travelling times can be updated dynamically. This task is executed in a remote centre which communicates with all the units in the transport scenario. This dynamic updating means that the objectives (optimal merging node and efficient routing) can be re-evaluated, and makes it possible to adapt to the changing conditions of the transport scenario, each time the pursuing unit reaches an intermediate node.In order to validate the algorithm described in this paper and evaluate the effect of the aforementioned novel risk factor, we have tested them on a simulated transport scenario using Player/Stage. The results and conclusions are also shown.     

A new iterative mutually coupled hybrid GA–PSO approach for curve fitting in manufacturing

Fitting data points to curves (usually referred to as curve reconstruction) is a major issue in computer-aided design/manufacturing (CAD/CAM). This problem appears recurrently in reverse engineering, where a set of (possibly massive and noisy) data points obtained by 3D laser scanning have to be fitted to a free-form parametric curve (typically a B-spline). Despite the large number of methods available to tackle this issue, the problem is still challenging and elusive. In fact, no satisfactory solution to the general problem has been achieved so far. In this paper we present a novel hybrid evolutionary approach (called IMCH-GAPSO) for B-spline curve reconstruction comprised of two classical bio-inspired techniques: genetic algorithms (GA) and particle swarm optimization (PSO), accounting for data parameterization and knot placement, respectively. In our setting, GA and PSO are mutually coupled in the sense that the output of one system is used as the input of the other and vice versa. This coupling is then repeated iteratively until a termination criterion (such as a prescribed error threshold or a fixed number of iterations) is attained. To evaluate the performance of our approach, it has been applied to several illustrative examples of data points from real-world applications in manufacturing. Our experimental results show that our approach performs very well, being able to reconstruct with very high accuracy extremely complicated shapes, unfeasible for reconstruction with current methods.