Particles Spreading Phenomena in the Case of Glass Thermal Spraying

The spreading phenomena of particles during thermal spraying are quite difficult to observe given the kinetics of the process. In this work, the splat formation of glass and alumina is theoretically compared, showing that glass transition and low-thermal conductivity yield a higher ratio between cooling and flattening times, which strongly modifies their spreading behavior. Wipe tests show that splash—splat transition temperature can be modified by the glass composition and its subsequent hydrodynamic properties. The detection of peculiar remaining objects, such as fibers and wavelets shows the possibility of “freezing” some phenomena that are totally unobservable with crystalline oxides, except with high-velocity observations.     

Structure-property relationships for a series of polyimide copolymers with sulfonated pendant groups

A series of high molecular weight, sulfonated polyimide copolymers (8a-f) with controlled acid contents have been obtained using 2,2′-bis(4-sulfobenzyloxy)benzidine (14) prepared via a flexible synthetic route. This series of novel sulfonated polyimide membranes were found to possess higher hydrolytic stability than polyimides in which the sulfonic acid groups are bound directly to the polymer main chain. An in-depth analysis of conductivity data was also performed for 8 and compared to the results for Nafion^® (1), sulfonated poly(ether ether ketone) (2) and a main-chain sulfonated polyimide (3). In order to remove the influence of acid strength, the proton mobility value for 8 at infinite dilution was calculated and found to be 1.2(±0.6) × 10⁻³ cm² s⁻¹ V⁻¹. A catalyst-coated membrane (CCM)-MEA based on a polyimide incorporating 60% sulfonated monomer (8d) was found to exhibit comparable beginning-of-life fuel cell performance as a Nafion^®-based CCM MEA at 50 °C.     

Constrained Sintering of a Glass Ceramic Composite: I. Asymmetric Laminate

The camber of asymmetric laminates has been experimentally measured and predicted. Two cases are distinguished: (i) sintering of a viscous layer on a viscous substrate and (ii) sintering of a viscous layer on an elastic substrate. In the first case, particular attention is paid to the microstructure of the shrinking layer: a gradient in porosity as well as in pore size has been found along the thickness. Microstructural observations have been rationalized through an asymmetric stress state in the shrinking layer. In the second case, substrate cracking is predicted as function of Young's modulus and thickness ratio of the elastic substrate.     

In situ neutron diffraction measurement of strain relaxation in welds during heat treatment

Neutron diffraction (ND) is commonly used to investigate the stress redistribution before and after post-weld heat treatment (PWHT) in welded structures. However, there is a lack of information on the evaluations of strains during PWHT. The present work employed in situ ND to measure the relaxation of residual strains during conventional PWHT in multi-pass high-strength low-alloy steel welds. It was found that strain relaxation occurs principally during the heating stage of the heat treatment. The findings have important economic bearings and can be used to characterise comparable material combinations and optimise the PWHT process for high-strength low-alloy weld joints. This unique information also provides a valuable benchmark for the finite element modelling of this complex process.     

Some investigations into the optimal dimensional synthesis of parallel robots

In this paper, we will perform a comparison between two approaches of dimensional synthesis of parallel robots. The first one concerns the single-objective optimization approach; in this case, the dimensional synthesis is expressed by taking into account only one performance criterion but enables to get a final solution if it exists. The second one concerns the multi-objective optimization approach; it enables to simultaneously take into account several performance criteria. However, this approach appears to provide a set of solutions instead of a single expected final solution which should directly enable to carry out the structural synthesis. In fact, the search of a single final solution is postponed to a further step where the designers have to impose and/or restrict certain parameters. And we will establish if it is really necessary to make a multi-objective optimization approach or if a single-objective is sufficient to reach the objectives set in the specifications (user requirements). A discussion is proposed concerning the arising questions related to each approach and leading to the optimal dimensional synthesis. The PAR2 robot with two degree-of-freedom is used to exemplify the analysis and the comparison of the two approaches. The proposed comparison can be applied to any classes of parallel robots.     

Electrochemical surface nanopatterning by selective reductive desorption from mixed metal surfaces

We report on a novel strategy to the functionalisation of electrode surfaces based on the preparation and patterning of mixed metal electrodes using metal selective electrodesorption of a sacrificial alkanethiol. Plain palladium (Pd) and plain polycrystalline gold (poly-Au) electrodes were used initially to determine metal specific potential windows within which electrodesorption of the short alkanethiol mercaptoethanol could be achieved. We found that stripping of mercaptoethanol from gold was achieved at potentials lower than −0.800 V, whilst stripping from palladium was achieved at more positive potentials i.e. around −0.650 V. Mixed metal electrodes were prepared by electroplating for short period of times palladium onto poly-Au electrodes. The resulting surfaces were characterised electrochemically in 1 M H₂SO₄ and clearly exhibited reduction peaks for both gold and palladium oxide formation. The mixed metal electrodes were coated with mercaptoethanol, which was further selectively removed from Pd by cyclic voltammetry in NaOH in the Pd-specific potential window. The presence of bare Pd domains revealed following electrodesorption was confirmed by subsequently adsorbing the electroactive alkanethiol 6-ferrocenylhexanethiol onto the freshly revealed Pd. Cyclic voltamogramms exhibited sharp redox peaks that could only be attributed to the successful immobilisation of 6-ferrocenylhexanethiol onto fresh Pd domains. Control surfaces, i.e. MCE fully coated Pd/Poly-Au electrode, exposed to 6-ferrocenylhexanethiol did not exhibit significant voltammetric features, attesting to the efficient patterning of the mixed metal electrode by employing metal specific reductive desorption of short alkanethiols. The possibility to pattern electrode surfaces in such way will find application in the field of diagnostics, and also in heterogeneous catalysis where Pd-Au alloys have received an increased interest in the recent years.     

A new membrane bioreactor generation for wastewater treatment application: Strategy of membrane aeration management by sequencing aeration cycles

Polymem is developing in the past few years a new membrane bioreactor concept using external module membranes. The membranes are hollow fibers. They are housed in carters and work in outside/in filtration mode. Permanent air scouring is provided at the bottom of the module to control the accumulation of sludge on the membrane surface. In other words, the membrane carters look like bubble columns with hollow fiber membranes inside.The main advantages of this concept are the easy maintenance of the external modules; the total independence of the bioreactor from the membrane filtration part, which facilitates plant retrofitting and upgrading; the high membrane compacity (up to 500 m²/m3), and better efficiency of membrane air scouring thanks to a dedicated coarse bubbles aeration system inside the module vessel.The first part of this paper deals with the quantification of the specific aeration demand of the system. Aeration demand was compared to conventional MBR systems. The study shows that with this optimised geometry of module concept, the aeration flow rate is lowered compared with conventional processes.In the second part of this paper, an optimisation of the aeration demand was carried out by sequencing the cycle of aeration by incorporating a syncope in the aeration. Ratios of the time-on and time-off from 1/2 to 1/5 were tested for various instantaneous aeration flow rates. Impacts on both short term fouling and long term fouling were evaluated and quantified in terms of permeability decrease. The advantages of the location of the membrane in an external cylindrical carter have been demonstrated in terms of operating cost savings with a reduction of specific aeration demand for membranes scouring at 100 to 250 Nl/h m², which is half the classical consumption of the submerged MBR today.     

High-Fat Diet Aggravates Cerebral Infarct,Hemorrhagic Transformation and Neuroinflammation in a Mouse Stroke Model

Background: Stroke in context of type 2 diabetes (T2D) is associated with a poorer outcome than in non-diabetic conditions. We aimed at creating a new reproducible mouse model of stroke in impaired glucose tolerance conditions induced by high-fat diet. Methods: Adult C57BL6 mice were fed for 2 months with either normal diet (ND) or high-fat diet (HFD). We used a model of Middle Cerebral Artery Occlusion (MCAO) for 90 min. Oral Glucose Tolerance Test (OGTT) and Insulin Tolerance Test (ITT) were used to assess pre-diabetic status. Brain infarct volume, hemorrhagic transformation (HT) as well as systemic and cerebral inflammatory markers were evaluated. Results: HFD was associated with an increased body weight and glycemia following OGTT. The HFD group presented a significant increase in brain infarct volume (38.7 (IQR 30–46.7%) vs. 28.45 (IQR 21–30%); p = 0.016) and HT (HFD: 2 (IQR 1–5) vs. ND: 0 (IQR 0–1); p = 0.012) and higher levels of IL-6 and MCP-1 in infarcted hemisphere compared to the ND group. Conclusion: Two months of HFD in adult mice were sufficient to alter the lipid profile and the control of hyperglycemia. These metabolic perturbations were significantly associated with increased infarct volume and hemorrhagic complications.     

Novel TTLL5 Variants Associated with Cone-Rod Dystrophy and Early-Onset Severe Retinal Dystrophy

Variants of the TTLL5 gene, which encodes tubulin tyrosine ligase-like family member five, are a rare cause of cone dystrophy (COD) or cone-rod dystrophy (CORD). To date, only a few TTLL5 patients have been clinically and genetically described. In this study, we report five patients harbouring biallelic variants of TTLL5. Four adult patients presented either COD or CORD with onset in the late teenage years. The youngest patient had a phenotype of early onset severe retinal dystrophy (EOSRD). Genetic analysis was performed by targeted next generation sequencing of gene panels and assessment of copy number variants (CNV). We identified eight variants, of which six were novel, including two large multiexon deletions in patients with COD or CORD, while the EOSRD patient harboured the novel homozygous p.(Trp640*) variant and three distinct USH2A variants, which might explain the observed rod involvement. Our study highlights the role of TTLL5 in COD/CORD and the importance of large deletions. These findings suggest that COD or CORD patients lacking variants in known genes may harbour CNVs to be discovered in TTLL5, previously undetected by classical sequencing methods. In addition, variable phenotypes in TTLL5-associated patients might be due to the presence of additional gene defects.