Friedreich's ataxia: the vicious circle hypothesis revisited

Friedreich's ataxia, the most frequent progressive autosomal recessive disorder involving the central and peripheral nervous systems, is mostly associated with unstable expansion of GAA trinucleotide repeats in the first intron of the FXN gene, which encodes the mitochondrial frataxin protein. Since FXN was shown to be involved in Friedreich's ataxia in the late 1990s, the consequence of frataxin loss of function has generated vigorous debate. Very early on we suggested a unifying hypothesis according to which frataxin deficiency leads to a vicious circle of faulty iron handling, impaired iron-sulphur cluster synthesis and increased oxygen radical production. However, data from cell and animal models now indicate that iron accumulation is an inconsistent and late event and that frataxin deficiency does not always impair the activity of iron-sulphur cluster-containing proteins. In contrast, frataxin deficiency appears to be consistently associated with increased sensitivity to reactive oxygen species as opposed to increased oxygen radical production. By compiling the findings of fundamental research and clinical observations we defend here the opinion that the very first consequence of frataxin depletion is indeed an abnormal oxidative status which initiates the pathogenic mechanism underlying Friedreich's ataxia

EVALUACIÓN PARA LA GENERACIÓN DE ENERGÍA ELÉCTRICA, EN BASE A BIOGÁS PRODUCIDO POR LA BOSTA DE CERDO EN LA GRANJA RICO CERDO F&G. SAC EN LA CLAKE DISTRITO DE REQUE – CHICLAYO-LAMBAYEQUE.

En esta investigación tecnológica cuasi-experimental se evaluó la generación de energía eléctrica, en base a biogás producido por la bosta de cerdo en la granja Rico Cerdo F&G S.A.C. en la Clake Distrito de Reque – Chiclayo- Lambayeque. Para el desarrollo de esta investigación se estimó el volumen de bosta de cerdo y el volumen de agua utilizada en el lavado de los galpones, posteriormente se seleccionó el tiempo de retención adecuado para el tipo de materia prima, seguidamente se calculó el volumen de diseño del biodigestor, calculando luego las cantidades de biogás y metano producido por la bosta de cerdo, de acuerdo a los parámetros ya obtenidos se calcularon las cantidades de energía y potencia eléctrica. El volumen de bosta fue evaluado por la clasificación de cerdos según su edad y sexo obteniendo como resultado 21.230 m3 de bosta diarios, la evaluación del volumen del agua de lavado, fue mediante el caudal utilizado durante el día, obteniendo un volumen de 23.4m3, posteriormente se eligió el tiempo de retención para un estiércol de cerdo liquido obteniendo 25 días de retención obteniendo el volumen máximo de diseño del biodigestor equivalente a 1606.7106m3. De acuerdo al volumen de diseño del biodigestor y a las condiciones de la granja, fue seleccionado el biodigestor tipo laguna cubierta. De acuerdo a la evaluación de la bosta, la producción del biogás es de 891.696m3/día, la cual producirá una energía de 1765.557Kwh, esta energía será utilizada las 24 horas del día, obteniendo una potencia de diseño de 88.278Kw, por otro lado en el análisis económico se obtuvo un VAN equivalente a s/.1139677.950 y un TIR equivalente a 68%, lo que determinó que la producción de energía eléctrica en base a biogás producida por la bosta de cerdo es factible.Tesi

NiP/SiC composite coatings: the effects of particles on the electrochemical behaviour

NiP/SiC (17 at.% P) composite coatings were prepared by electrodeposition from a Brenner type plating bath containing SiC particles. Cyclic voltammetry and immersion time were used to evaluate the electrochemical behaviour of these coatings. The results showed that the presence of SiC particles in NiP alloy increased corrosion properties, because the exposed area of the metallic matrix was reduced due to its recovering by SiC particles. However, the current densities developed by the NiP/SiC composite coatings increased with increasing amount of incorporated particles, and such effect is more remarkable for small particles, after heat treatment and when the systems are polarized

Impacts of the use of SIC semiconductors in actuations systems

Driven by customers’ demands to improve aircraft performance on one hand, while ensuring compliance to ACARE (Advisory Council for Aeronautics Research in Europe) environmental requirements for 2020 on the other, the aircraft industry has been pushing toward the concept of More Electric Aircraft (MEA) for the last ten years or so. One of the main challenges associated to the More Electric Aircraft is thus to increase drastically the power density of electrical power systems, such as electromechanical chains applied to actuation systems, without compromising on reliability. This paper explains the advantages of using Wide Bandgap (WBG) semiconductors made of Silicon Carbide (SiC) in the power converters that are used in an electromechanical chain as well as the associated drawbacks when it comes to EMI and partial discharge, which are mainly related to high dv/dt and overvoltage during commutation. It also shows the development of a generic electromechanical chain platform at the Institut de Recherche Technologique (IRT) Saint-Exupéry and all related research. This platform is being designed in order to test different technologies composing an electromechanical chain (SiC transistors, passive filters, cables, innovative motor) and to evaluate the impact of the use of such technologies

Circadian variation in the circumstances of delivery in a population at low obstetric risk

While circadian variations in birth and perinatal mortality rates have previously been described in the literature, the reasons behind these observed rhythms remain unclear. The principal hypothetical causes include variations in obstetric practices and an association between the time of birth and biological parameters. In order to explore this issue we analysed the distribution patterns for time and day of birth, as well as circadian variations in maternal characteristics, obstetric practices and neonatal risk in a population at low obstetric risk. The study population included 685 low-risk pregnant women consecutively admitted at an early stage of labour to six maternity units. The results showed hourly variations in the birth rate and circadian variations in obstetric practices that might explain the hourly pattern observed for the birth rate. By contrast, the frequency of a positive neonatal risk indicator was uniform across all time categories in this population at low obstetric ris

Metrology with Atom Interferometry: Inertial Sensors from Laboratory to Field Applications

Developments in atom interferometry have led to atomic inertial sensors with extremely high sensitivity. Their performances are for the moment limited by the ground vibrations, the impact of which is exacerbated by the sequential operation, resulting in aliasing and dead time. We discuss several experiments performed at LNE-SYRTE in order to reduce these problems and achieve the intrinsic limit of atomic inertial sensors. These techniques have resulted in transportable and high-performance instruments that participate in gravity measurements, and pave the way to applications in inertial navigation.Comment: 7 pages, 5 figure

Review on VUV to MIR absorption spectroscopy of atmospheric pressure plasma jets

Absorption spectroscopy (AS) represents a reliable method for the characterization of cold atmospheric pressure plasma jets. The method's simplicity stands out in comparison to competing diagnostic techniques. AS is an in situ, non-invasive technique giving absolute densities, free of calibration procedures, which other diagnostics, such as laser-induced fluorescence or optical emission spectroscopy, have to rely on. Ground state densities can be determined without the knowledge of the influence of collisional quenching. Therefore, absolute densities determined by absorption spectroscopy can be taken as calibration for other methods. In this paper, fundamentals of absorption spectroscopy are presented as an entrance to the topic. In the second part of the manuscript, a review of AS performed on cold atmospheric pressure plasma jets, as they are used e.g. in the field of plasma medicine, is presented. The focus is set on special techniques overcoming not only the drawback of spectrally overlapping absorbing species, but also the line-of-sight densities that AS usually provides or the necessity of sufficiently long absorption lengths. Where references are not available for measurements on cold atmospheric pressure plasma jets, other plasma sources including low-pressure plasmas are taken as an example to give suggestions for possible approaches. The final part is a table summarizing examples of absorption spectroscopic measurements on cold atmospheric pressure plasma jets. With this, the paper provides a 'best practice' guideline and gives a compendium of works by groups performing absorption spectroscopy on cold atmospheric pressure plasma jets

Trade-off between Losses and EMI Issues in Three-Phase SiC Inverters for Aircraft Applications

Power converters will only be effectively used in future aircrafts if they are compact, efficient and reliable. All these aspects can be improved by the use of disruptive technology such as the so-called Wide Bandgap (WBG) semiconductors made of Silicon Carbide (SiC) or Gallium Nitride (GaN). These components can switch much faster than their silicon counterpart, which can reduce converter losses and also decrease differential mode filter given the increase of switching frequency. However, such a fast commutation increases Electromagnetic Interference (EMI) issues in the converter and loads connected to it. This paper shows the approach developed at the French Institute of Technology (IRT) Saint-Exupery, in order to evaluate the trade-offs between losses and EMI issues of three-phase inverters used in future aircraft applications. Given the voltage DC bus of 540V, SiC MOSFETs are investigated and experimental results show the impact of these components on losses and EMI for different parameters

Ergodicity and Slowing Down in Glass-Forming Systems with Soft Potentials: No Finite-Temperature Singularities

The aim of this paper is to discuss some basic notions regarding generic glass forming systems composed of particles interacting via soft potentials. Excluding explicitly hard-core interaction we discuss the so called `glass transition' in which super-cooled amorphous state is formed, accompanied with a spectacular slowing down of relaxation to equilibrium, when the temperature is changed over a relatively small interval. Using the classical example of a 50-50 binary liquid of N particles with different interaction length-scales we show that (i) the system remains ergodic at all temperatures. (ii) the number of topologically distinct configurations can be computed, is temperature independent, and is exponential in N. (iii) Any two configurations in phase space can be connected using elementary moves whose number is polynomially bounded in N, showing that the graph of configurations has the `small world' property. (iv) The entropy of the system can be estimated at any temperature (or energy), and there is no Kauzmann crisis at any positive temperature. (v) The mechanism for the super-Arrhenius temperature dependence of the relaxation time is explained, connecting it to an entropic squeeze at the glass transition. (vi) There is no Vogel-Fulcher crisis at any finite temperature T>0Comment: 10 pages, 9 figures, submitted to PR

Unshielded Cable modeling for Conducted Emissions Issues in Electrical Power Drive Systems

In power electronics applications, high frequency models for cables are necessary to understand EMI issues in pulsewidth modulation drives. This paper shows the approach developed at the French Institute of Technology (IRT) Saint-Exupery, in order to take account of the frequency dependency of unshielded power cables per-unit-length parameters for EMC simulations. Fast, predictive models are compared to different shapes numerical models. The method was applied to unshielded two and three wires cables. Finally, common mode (CM) emissions modeling is proposed to predict the CM noise currents, which are the most disturbing in any variable-speed drive systems. The modeling principle is to consider the complete CM circuit as a chain of quadripolar matrices