Latex on Glass: an Appropriate Model for Cartilage-Lubrication Studies?

Latex versus glass has frequently been used as a model system for the investigation of natural lubrication mechanisms, despite its significant differences from articular cartilage pairings. The differences in surface chemistry account for its different behavior in terms of protein adsorption and lubrication. While cartilage is well known for its protein resistance, most proteins present in synovial fluid can non-specifically adsorb onto latex or glass. We have investigated latex-versus-glass lubrication by means of pin-on-disk tribometry in the presence of synovial-fluid proteins and glycoproteins, focusing on the influence of the glass-cleaning procedure on friction. In order to simulate the effects of possible contamination of glass in previous studies, both hydrophilic and hydrophobic glass substrates were tested. Albumin was shown to impair lubrication (in comparison to PBS) when latex was slid against both types of glass surface, whereas bovine synovial fluid (BSF) and alpha-1-acid glycoprotein (AGP) impaired the lubrication of latex versus hydrophilic glass and improved the lubrication of latex versus hydrophobic glass. Protein adsorption on the surfaces was monitored by means of fluorescence imaging and optical waveguide lightmode spectroscopy (OWLS), which revealed a faster and greater amount of adsorption of AGP on hydrophobic surfaces than on hydrophilic ones. The influence of surface chemistry on the friction behavior of BSF and on the adsorption of AGP suggests that it plays a role in determining the relative amounts of adsorbed synovial fluid proteins. When BSF is used as a lubricant in the latex-versus-hydrophobic-glass system, more of the AGP, relative to albumin, appears to adsorb on both surfaces, counteracting the negative effect of albumin on friction. It therefore seems that latex on glass, while displaying nominal similarities to cartilage on cartilage under certain conditions, is not a useful model system. Moreover, surface contamination of the glass can play a major role in determining the results.     

Fractal fragmentation of rocks within sturzstroms: insight derived from physical experiments within the ETH geotechnical drum centrifuge

An investigation of the behaviour and energy budget of sturzstroms has been carried out using physical, analytical and numerical modelling techniques. Sturzstroms are rock slides of very large volume and extreme run out, which display intensive fragmentation of blocks of rock due to inter-particle collisions within a collisional flow. Results from centrifugal model experiments provide strong arguments to allow the micro-mechanics and energy budget of sturzstroms to be described quantitatively by a fractal comminution model. A numerical experiment using a distinct element method (DEM) indicates rock mass and boundary conditions, which allow an alternating fragmenting and dilating dispersive regime to evolve and to sustain for long enough to replicate the spreading and run out of sturzstroms without needing to resort to peculiar mechanism. The fragmenting spreading model supported here is able to explain the run out of a fluid-absent granular flow beyond the travel distance predicted by a Coulomb frictional sliding model. This, and its strong relation to internal fragmentation, suggests that a sturzstrom constitutes a landslide category of its own. This study provides a novel framework for the understanding the physics of such sturzstroms.     

Conceptual approaches to wellbeing in buildings: a scoping review

ABSTRACT

Several industry-led initiatives in various countries demonstrate a new interest in wellbeing and buildings. This paper adopts a scoping review method aiming to establish the most prevalent and insightful definitions and dimensions of wellbeing in buildings applied in the recent published literature. The paper adopts a two-step method for identifying and categorizing the conceptual approaches to wellbeing encountered in the current literature. First, an overview is presented of the term ‘wellbeing’ and its development over time. Second, the broad wellbeing categories identified are further refined and complemented via a deductive approach, drawing the final set of conceptual themes informed by the papers reviewed in this study. Nine themes were identified, two of which deductively emerged from the papers included in this study: environmental satisfaction/comfort and cognitive performance/productivity. The findings emphasize the heterogeneity of conceptual approaches to research concerning ‘wellbeing in buildings’, an ambiguity between wellbeing outcomes or determinants, and the need for greater clarity on the relative contributions of different wellbeing dimensions to overall individual or population wellbeing. Based on these findings, future work could be carried out to provide guidance on how to evaluate claims of evidence-based building design which foster individual or population wellbeing.     

Ozone Gas Antifungal Effect on Extruded Dog Food Contaminated with Aspergillus flavus

ABSTRACT

Decontamination of Aspergillus flavus spores in inoculated extruded food (Standard and Super-Premium types), through ozone (O₃) gas, was investigated at different concentrations (40 and 60 µmol/mol) and times (30, 60, and 120 min) of exposure. The gas antifungal efficiency, humidity, and lipid stability were evaluated before and after treatments. O₃ reduced A. flavus spores of the extruded food, on both types (p < 0.05). The highest reduction (98.3%) was observed for both food types, when gas was applied for 120 min, regardless of the O₃ concentration. Regarding humidity and peroxide index, there was no difference, either prior to or after the gas application for all treatments conditions. O₃ gas can be an efficient method for fungi spores’ contamination control during commercialization of extruded food in open bags exposed to the environment.     

Exploring the Potential and the Boundaries of the Rolling Horizon Technique for the Management of Reservoir Systems with over-Year Behaviour

The paper presents a set of experiments on the Rolling Horizon Technique (RHT), applied to the management of a multi-reservoir, multipurpose water resources system with over-year behaviour. In the RHT, decisions on releases from reservoirs are taken for a number of time steps ahead (the Forecasting Horizon – FH) through an optimization model, based on the present water availability in reservoirs and on some forecasts of future inflows over the FH. Only the decision concerning the first time step (the current month) is then implemented, as new information on reservoir levels and forecasts becomes available so that the process can start again with updated information. The paper investigates how the quality of forecasts and the length of the FH impact on the effectiveness of the decisions taken. The evaluation exercise is carried out in two different demand scenarios considering some deficit-related indices, such as TSSD, the Sum of Squared Standardized Deficits, over an Operation Horizon (OH) of forty years. The scenarios are designed to evaluate the role of different demand levels (corresponding to higher/lower stress) on system’s behaviour. Results show that in systems with over-year behaviour, effective forecasts (here simulated through the best possible: actually occurred inflows from the current month up to the end of water year) seem to add little value to system’s operation compared to the most naive forecast (average monthly values), especially in contexts characterized by high pressure on resources. Where there is less pressure on resources, good-quality forecasts are more effective to improve operation. A FH of 24 months seems to enhance significantly system’s performances compared to a FH of 12 months, while FHs longer than two years produce no improvements in system’s performances. The paper also tries to define the limits of a finite-horizon operation technique such as the RHT by benchmarking it with an idealistic release schedule obtained by a model that performs allocation with Perfect Foresight over the whole Operation Horizon.     

Self-diffusion of silicon in TiSi2 competing phases by tight-binding molecular dynamics

Tight-binding (TB) potentials allow for a straightforward separation of the binding and repulsive contributions in the total energy. This issue can be used in molecular dynamics runs to correlate the local atomic structure to the diffusion paths and the activation energies of silicon mobility in TiSi₂, which is the most common material for metallisations and local interconnects in microelectronic devices. In this work we focus on the self-diffusion process at high temperature and a relation between the crystal structures and the diffusion paths for the two competing phases is drawn.     

N-Glycans in Immortalized Mesenchymal Stromal Cell-Derived Extracellular Vesicles Are Critical for EV–Cell Interaction and Functional Activation of Endothelial Cells

Mesenchymal stromal cell-derived extracellular vesicles (MSC-EV) are widely considered as a cell-free therapeutic alternative to MSC cell administration, due to their immunomodulatory and regenerative properties. However, the interaction mechanisms between EV and target cells are not fully understood. The surface glycans could be key players in EV–cell communication, being specific molecular recognition patterns that are still little explored. In this study, we focused on the role of N-glycosylation of MSC-EV as mediators of MSC-EV and endothelial cells’ interaction for subsequent EV uptake and the induction of cell migration and angiogenesis. For that, EV from immortalized Wharton’s Jelly MSC (iWJ-MSC-EV) were isolated by size exclusion chromatography (SEC) and treated with the glycosidase PNGase-F in order to remove wild-type N-glycans. Then, CFSE-labelled iWJ-MSC-EV were tested in the context of in vitro capture, agarose-spot migration and matrigel-based tube formation assays, using HUVEC. As a result, we found that the N-glycosylation in iWJ-MSC-EV is critical for interaction with HUVEC cells. iWJ-MSC-EV were captured by HUVEC, stimulating their tube-like formation ability and promoting their recruitment. Conversely, the removal of N-glycans through PNGase-F treatment reduced all of these functional activities induced by native iWJ-MSC-EV. Finally, comparative lectin arrays of iWJ-MSC-EV and PNGase-F-treated iWJ-MSC-EV found marked differences in the surface glycosylation pattern, particularly in N-acetylglucosamine, mannose, and fucose-binding lectins. Taken together, our results highlight the importance of N-glycans in MSC-EV to permit EV–cell interactions and associated functions.