The Multifaceted Activity of the VirF Regulatory Protein in the Shigella Lifestyle

Shigella is a highly adapted human pathogen, mainly found in the developing world and causing a severe enteric syndrome. The highly sophisticated infectious strategy of Shigella banks on the capacity to invade the intestinal epithelial barrier and cause its inflammatory destruction. The cellular pathogenesis and clinical presentation of shigellosis are the sum of the complex action of a large number of bacterial virulence factors mainly located on a large virulence plasmid (pINV). The expression of pINV genes is controlled by multiple environmental stimuli through a regulatory cascade involving proteins and sRNAs encoded by both the pINV and the chromosome. The primary regulator of the virulence phenotype is VirF, a DNA-binding protein belonging to the AraC family of transcriptional regulators. The virF gene, located on the pINV, is expressed only within the host, mainly in response to the temperature transition occurring when the bacterium transits from the outer environment to the intestinal milieu. VirF then acts as anti-H-NS protein and directly activates the icsA and virB genes, triggering the full expression of the invasion program of Shigella. In this review we will focus on the structure of VirF, on its sophisticated regulation, and on its role as major player in the path leading from the non-invasive to the invasive phenotype of Shigella. We will address also the involvement of VirF in mechanisms aimed at withstanding adverse conditions inside the host, indicating that this protein is emerging as a global regulator whose action is not limited to virulence systems. Finally, we will discuss recent observations conferring VirF the potential of a novel antibacterial target for shigellosis

Thermo-Mechanical and Morphological Properties of Polymer Composites Reinforced by Natural Fibers Derived from Wet Blue Leather Wastes: A Comparative Study

The present work investigated the possibility to use wet blue (WB) leather wastes as natural reinforcing fibers within different polymer matrices. After their preparation and characterization, WB fibers were melt-mixed at 10 wt.% with poly(lactic acid) (PLA), polyamide 12 (PA12), thermoplastic elastomer (TPE), and thermoplastic polyurethane (TPU), and the obtained samples were subjected to rheological, thermal, thermo-mechanical, and viscoelastic analyses. In parallel, morphological properties such as fiber distribution and dispersion, fiber–matrix adhesion, and fiber exfoliation phenomena were analyzed through a scanning electron microscope (SEM) and energy-dispersive spectroscopy (EDS) to evaluate the relationship between the compounding process, mechanical responses, and morphological parameters. The PLA-based composite exhibited the best results since the Young modulus (+18%), tensile strength (+1.5%), impact (+10%), and creep (+5%) resistance were simultaneously enhanced by the addition of WB fibers, which were well dispersed and distributed in and significantly branched and interlocked with the polymer matrix. PA12- and TPU-based formulations showed a positive behavior (around +47% of the Young modulus and +40% of creep resistance) even if the not-optimal fiber–matrix adhesion and/or the poor de-fibration of WB slightly lowered the tensile strength and elongation at break. Finally, the TPE-based sample exhibited the worst performance because of the poor affinity between hydrophilic WB fibers and the hydrophobic polymer matrix

The Multifaceted Activity of the VirF Regulatory Protein in the Shigella Lifestyle

Shigella is a highly adapted human pathogen, mainly found in the developing world and causing a severe enteric syndrome. The highly sophisticated infectious strategy of Shigella banks on the capacity to invade the intestinal epithelial barrier and cause its inflammatory destruction. The cellular pathogenesis and clinical presentation of shigellosis are the sum of the complex action of a large number of bacterial virulence factors mainly located on a large virulence plasmid (pINV). The expression of pINV genes is controlled by multiple environmental stimuli through a regulatory cascade involving proteins and sRNAs encoded by both the pINV and the chromosome. The primary regulator of the virulence phenotype is VirF, a DNA-binding protein belonging to the AraC family of transcriptional regulators. The virF gene, located on the pINV, is expressed only within the host, mainly in response to the temperature transition occurring when the bacterium transits from the outer environment to the intestinal milieu. VirF then acts as anti-H-NS protein and directly activates the icsA and virB genes, triggering the full expression of the invasion program of Shigella. In this review we will focus on the structure of VirF, on its sophisticated regulation, and on its role as major player in the path leading from the non-invasive to the invasive phenotype of Shigella. We will address also the involvement of VirF in mechanisms aimed at withstanding adverse conditions inside the host, indicating that this protein is emerging as a global regulator whose action is not limited to virulence systems. Finally, we will discuss recent observations conferring VirF the potential of a novel antibacterial target for shigellosis

Thermal behaviour of ski-boot liners: effect of materials on thermal comfort in real and simulated skiing conditions

The choice of the appropriate material for the construction of ski-boot liners is of fundamental importance in order to achieve ergonomic comfort and high thermal insulation. In this work the effect on thermal comfort of different materials used for commercial ski-boot liners has been analysed. The thermal insulation and the moisture management of liners made of different materials have been tested both in a climatic chamber and in outdoor conditions using wireless sensors combined with infrared thermography. The results obtained show substantial differences in terms of thermal comfort between the liners in the same environmental conditions, showing that closed cell ethylene vinyl acetate foams provide the best thermal comfor

Ski Boot Soles Based on a Glass Fiber/Rubber Composite with Improved Grip on Icy Surfaces

Abstract A study on the effect of glass fibers/rubber composites on the grip on ice has been conducted in order to develop new materials for ski boot soles with increased grip in winter environments. The study has been conducted analyzing the friction of a composite material and of a ski boot sole containing an insert made of the composite material and comparing the results with those obtained using rubber and a thermoplastic elastomer. The analysis of the morphology of the composite surface, by Scanning Electron Microscopy, shows a homogenous distribution of glass fibers of approximately 10 μm of diameter in the rubber matrix. Moreover, the measure of the contact angle shows that the composite material has a higher water repellency compared to the rubber matrix. The measure of the coefficient of friction indicates a significant effect of the glass fibers on the grip on icy surfaces. The increased grip can be ascribed to the stiffness of the glass fibers that are able to have a mechanical grip on the ice surface and to the increased contact angle and water repellency of the composite that decrease the formation of a water layer below the sole

Thermal behaviour of ski-boot liners: effect of materials on thermal comfort in real and simulated skiing conditions

The choice of the appropriate material for the construction of ski-boot liners is of fundamental importance in order to achieve ergonomic comfort and high thermal insulation. In this work the effect on thermal comfort of different materials used for commercial ski-boot liners has been analysed. The thermal insulation and the moisture management of liners made of different materials have been tested both in a climatic chamber and in outdoor conditions using wireless sensors combined with infrared thermography. The results obtained show substantial differences in terms of thermal comfort between the liners in the same environmental conditions, showing that closed cell ethylene vinyl acetate foams provide the best thermal comfort

Super-heavy fermion material as metallic refrigerant for adiabatic demagnetization cooling

Low-temperature refrigeration is of crucial importance in fundamental research of condensed matter physics, as the investigations of fascinating quantum phenomena, such as superconductivity, superfluidity and quantum criticality, often require refrigeration down to very low temperatures. Currently, cryogenic refrigerators with $^3$He gas are widely used for cooling below 1 Kelvin. However, usage of the gas is being increasingly difficult due to the current world-wide shortage. Therefore, it is important to consider alternative methods of refrigeration. Here, we show that a new type of refrigerant, super-heavy electron metal, YbCo$_2$Zn$_{20}$, can be used for adiabatic demagnetization refrigeration, which does not require 3He gas. A number of advantages includes much better metallic thermal conductivity compared to the conventional insulating refrigerants. We also demonstrate that the cooling performance is optimized in Yb$_{1-x}$Sc$_x$Co$_2$Zn$_{20}$ by partial Sc substitution with $x\sim$0.19. The substitution induces chemical pressure which drives the materials close to a zero-field quantum critical point. This leads to an additional enhancement of the magnetocaloric effect in low fields and low temperatures enabling final temperatures well below 100 mK. Such performance has up to now been restricted to insulators. Since nearly a century the same principle of using local magnetic moments has been applied for adiabatic demagnetization cooling. This study opens new possibilities of using itinerant magnetic moments for the cryogen-free refrigeration

Transformations agricoles et agroalimentaires

À l’heure des robots et du numérique, la terre (habitat, agriculture, paysage, planète) et la nourriture (du corps et de l’âme) sont parmi les préoccupations majeures dans les espaces médiatiques et politiques. Le pétrole et l’abondance qui l’a accompagné nous avaient fait oublier qu’elles sont au fondement des sociétés humaines. La « crise alimentaire » de 2008, qui a secoué plusieurs continents, a rappelé aux gouvernements l’enjeu de la sécurité alimentaire. Après des décennies d’excédents, de baisse du prix des produits agricoles de base, la question de la valeur de la terre et de l’agriculture est de retour. La question de la santé et celle des droits humains prennent une place élargie tant dans les politiques publiques et dans la production de normes alimentaires. Des mouvements sociaux transnationaux s’emparent de la question de l’avenir de l’agriculture et de l’alimentation, et de celle de la « bonne vie ». Pour contribuer à cette réflexion sur l’avenir de la terre et de la nourriture, cet ouvrage étudie la socialisation de l’agriculture, c’est-à-dire sa prise en charge tant par les politiques agricoles (essentiellement nationales) que par l’organisation des marchés dans un cadre national et international. Il le fait en prenant un large recul et mobilise trois temporalités. La première est celle de la planète. La seconde, celle des régimes métaboliques, façons dont l’humanité à différents stades de développement, mobilise matériaux et énergie. La troisième est celle du capitalisme, avec la succession de systèmes hégémoniques (ce qui n’exclue pas de multiples polarités). Cet ouvrage réunit des recherches récentes d’économistes, de sociologues, d’historiens et d’agronomes, de différents pays, recherches qui ont en commun de concerner la place de l’agriculture dans l’évolution des capitalismes