X-ray irradiation as an improvement technique for oxygen ordering and enrichment of YBa2Cu3O7 − x single crystals

The effects of X-ray irradiation on as-grown YBa₂Cu₃O_{7 – x} single crystals were investigated, in order to test the effects of radiation-induced defects during the subsequent annealing in O₂, and to verify if short-circuits for diffusion could be provided that improve the oxygen enrichment of the specimens. X-ray irradiation was found to have a favourable effect on the homogeneity of the oxygen enrichment of the samples, as stated by the high reproducibility of resistance measurements carried out on specimens grown, irradiated and annealed under the same conditions. Even if X-ray irradiation seems unable to determine a significant reduction of the time needed for annealing, and it could not consequently be regarded as a totally resolutive step during the production of high-quality monocrystalline superconductors, the observed homogenization of lattice oxygen distribution seems to be exploitable.     

Poly(vinyl alcohol)–lignin blended resin for cellulose‐based composites

Wood has limitations in strength because of its biostructural defects, including vessels. To overcome this limitation, composite materials can be innovated by breaking wood down into cellulose and lignin and reassembling them for bio‐originating strong structural materials. In this study, an ecofriendly resin was developed that was suitable for cellulose‐based composites. To overcome the low dimensional stability of lignin and to increase its interactions with cellulose, it was blended with poly(vinyl alcohol) (PVA). The PVA–lignin resin was characterized with scanning electron microscopy, Fourier transform infrared spectroscopy, thermal analysis, mechanical tensile testing, and lap‐shear joint testing. The adhesion properties of the PVA–lignin resin increased with increasing PVA content. PVA played the role of synthetic polymer and that of linker between the cellulose and lignin, like hemicellulose does in wood. The PVA–lignin resin exhibited a high miscibility, mechanical toughness, and good adhesion properties for nanocellulose composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46655.     

Synthesis,characterization, and antibacterial property of eco-friendly Ag/cellulose nanocomposite film

This paper reports silver/cellulose nanocomposite film and its antibacterial activity. A wet and porous cellulose film was served as support for silver nanoparticles synthesis by a hydrothermal method. Stable silver nanoparticles were synthesized using the cellulose film acting as both reducing and stabilizing agent without using any toxic chemicals. The characterization of the synthesized nanocomposite proves that silver nanoparticles are not only deposited over the cellulose surface but also nucleated and grew inside the cellulose film. Silver nanoparticle size and distribution were tuned to improve the antibacterial activity, and the synthesized nanocomposite film shows significant antibacterial action.     

A chance-constrained portfolio selection model with random-rough variables

Traditional portfolio selection (PS) models are based on the restrictive assumption that the investors have precise information necessary for decision-making. However, the information available in the financial markets is often uncertain. This uncertainty is primarily the result of unquantifiable, incomplete, imprecise, or vague information. The uncertainty associated with the returns in PS problems can be addressed using random-rough (Ra-Ro) variables. We propose a new PS model where the returns are stochastic variables with rough information. More precisely, we formulate a Ra-Ro mathematical programming model where the returns are represented by Ra-Ro variables and the expected future total return maximized against a given fractile probability level. The resulting change-constrained (CC) formulation of the PS optimization problem is a non-linear programming problem. The proposed solution method transforms the CC model in an equivalent deterministic quadratic programming problem using interval parameters based on optimistic and pessimistic trust levels. As an application of the proposed method and to show its flexibility, we consider a probability maximizing version of the PS problem where the goal is to maximize the probability that the total return is higher than a given reference value. Finally, a numerical example is provided to further elucidate how the solution method works.

     

Pitting Corrosion Within Bioreactors for Space Cell-Culture Contaminated by <Emphasis Type="Italic">Paenibacillus glucanolyticus</Emphasis>, a Case Report

Performing cell biology experiments in space imposes the use of hardware that essentially allows fluid exchange in a contained environment. Given the technical and logistical peculiarities, the limited opportunities and the high cost of access to space, a great effort during mission preparation of scientific studies is devoted to preventing loss of the experiment. The European Space Agency (ESA) requires, at the end of the preparation phase, the execution of an Experiment Sequence Test (EST), a dry-run version of the space experiment to check all procedures. At conclusion of the EST of our experiment ‘ENDO’ (ESA ILSRA-2009-1026), we found pitting corrosion of metal parts and biofilm formation within the cell-culture devices. The subsequent chemical (spectral assays), instrumental (OGP SmartScope) and microbiological (MALDI-TOF, 16S rRNA gene sequencing) investigations allowed the identification in contaminated material of Paenibacillus glucanolyticus, a ubiquitous, aerobic, facultative anaerobic, endospore forming, acid-producing, Gram-positive microorganism. A concurrence of P. glucanolyticus contamination and galvanic corrosion determined massive fouling, rust precipitation and damage to cells and cell-culture devices being, to our knowledge, the association between this microbe and corrosion never reported before in literature. As a consequence of the episode a critical procedure of experiment set up, i.e. hardware sterilization, was modified. The ENDO experiment was successfully launched to the International Space Station on September 2nd 2015 and returned to the PI laboratory on September 13th, with all cell culture samples in optimal condition.     

Secondary nanoparticle emissions during diesel particulate trap regeneration

Two nanostructured mixed oxide catalysts (the CoCr₂O₄ spinel and the LiCrO₂ delafossite) have been recently developed for diesel soot combustion. The catalysts have been deposited via in situ combustion synthesis over SiC wallflow trap by CTI (Salindres, F). Bench tests proved that, after soot loading, both the developed traps enable a faster and more complete regeneration at 550 °C than the non-catalysed trap. However, a specific study on the particles distribution after the SiC trap, carried out via SMPS analysis, showed that secondary nanoparticles (<20 nm) are emitted during the regeneration promoted by the highly-active CoCr₂O₄ catalytic trap, as opposed to the LiCrO₂-catalysed and the virgin counter parts. This phenomenon has been investigated vs. the regeneration temperature and some sampling conditions so as to draw preliminary indications on the nature of these undesired particles.     

Comparison of morphologies and mechanical properties of crosslinked epoxies modified by polystyrene and poly(methyl methacrylate)) or by the corresponding block copolymer polystyrene-b-poly(methyl methacrylate)

Polystyrene (PS, M_n=28,400, PI=1.07), poly(methyl methacrylate) (PMMA, M_n=88,600, PI=1.03), and PS (50,000)-b-PMMA (54,000) (PI=1.04), were used as modifiers of an epoxy formulation based on diglycidyl ether of bisphenol A (DGEBA) and m-xylylene diamine (MXDA). Both PS and PMMA were initially miscible in the stoichiometric mixture of DGEBA and MXDA at 80 °C, but were phase separated in the course of polymerization. Solutions containing 5 wt% of each one of both linear polymers exhibited a double phase separation. A PS-rich phase was segregated at a conversion close to 0.02 and a PMMA rich phase was phase separated at a conversion close to 0.2. Final morphologies, observed by scanning electron microscopy (SEM), consisted on a separate dispersion of PS and PMMA domains. A completely different morphology was observed when employing 10 wt% of PS-b-PMMA as modifier. PS blocks with M_n=50,000 were not soluble in the initial formulation. However, they were dispersed as micelles stabilized by the miscible PMMA blocks, leading to a transparent solution up to the conversion where PMMA blocks began to phase separate. A coalescence of the micellar structure into a continuous thermoplastic phase percolating the epoxy matrix was observed. The elastic modulus and yield stress of the cured blend modified by both PS and PMMA were 2.64 GPa and 97.2 MPa, respectively. For the blend modified by an equivalent amount of block copolymer these values were reduced to 2.14 GPa and 90.0 MPa. Therefore, using a block copolymer instead of the mixture of individual homopolymers and selecting an appropriate epoxy-amine formulation to provoke phase separation of the miscible block well before gelation, enables to transform a micellar structure into a bicontinuous thermoplastic/thermoset structure that exhibits the desired decrease in yield stress necessary for toughening purposes.     

Cs–V catalysts for the combustion of diesel particulate

Topics in Catalysis - The soot combustion process, promoted by some promising diesel particulate combustion catalysts based on Cs and V oxides (Cs2O, Cs3VO4, Cs4V2O7, Cs2O · V2O5, CsVO3,...     

Proof movie — A proof with the Boyer-Moore prover

This paper uses the Boyer-Moore prover for developing a proof of correctness for the implementation of a very small compiler. The polished version of the proof is included as an appendix. The major intent of the paper is to describe the process of proving using an automatic theorem prover.This paper presents work done when the author was employed at the University of Kiel, Germany. The research was partially funded by the Commission of the European Communities (CEC) under the ESPRIT programme in the field of Basic Research Action proj. no. 3104, ProCoS: Provably Correct Systems     

Photocatalytic degradation of aromatic sulfonates present in industrial percolates

Photocatalytic treatment in the presence of aqueous TiO₂ suspensions was applied to an aqueous percolate containing various hydrophilic aromatic pollutants, in particular naphthalene sulfonates. A preliminary feasibility study was accomplished on standards of pure compounds, for which a degradation rate trend inversely proportional to the sulfonation degree was found, demonstrating the important role played by the substrate adsorption on semiconductor particles. The evolution of primary processes, the abatement of TOC and the release of sulfate were monitored. Further experiments performed on samples of percolates taken from an abandoned industrial site demonstrated the suitability of photocatalysis for the effective destruction and mineralization of the investigated contaminants in these complex matrices after a few hours irradiation.