Electrical properties and thermal expansion of cordierite and cordierite-mullite materials

Commercially available cordierite and mullite powders were used to obtain cordierite and composite materials with mullite content up to 65 wt.% by attrition milling, uniaxial pressing and sintering. The employed cordierite powders were the coarse, medium and fine single granulometric fractions and the binary mixtures of them with 30, 50 and 70 wt.% of the smaller size component. Mullite powder employed in composites was a 7 h-attrition milled one. The dielectric constant (), dielectric loss tangent (tan δ), resistivity (ρ) and thermal expansion coefficient () were measured. The influence of the porosity, mullite and glassy phase contents and grain size in the electrical parameters was analyzed. The thermal expansion coefficient as a function of the composition was studied.     

Radiation-induced grafting of functional acrylic monomers onto polyethylene and polypropylene films using acryloyl chloride

Summary Radiation-induced graft polymerization of acryloyl chloride onto films of polyolefins (polyethylene and polypropylene) using gamma radiation was investigated in order to establish a convenient method to obtain polymer films grafted with polyacrylic esters. Grafting was carried out by three different methods; (i) direct irradiation of film in monomer solution (ii) vapor phase irradiation method, and (iii) pre-irradiation in air. The effects of monomer concentration, radiation dose and methods of grafting, on the formation of grafted polyolefins are reported in this paper. Received: 5 April 2000/Revised version: 17 November 2000/Accepted: 20 November 2000     

Studies on diacetylenic vinyl compounds

The thermal and radiation polymerization of phenyl-4-vinylphenylbutadiyne(PVPB) in the solid state was investigated. Both soluble and insoluble products were formed. The amount of insoluble fractions increased with increase in the conversion. The soluble polymers were partially crystalline but the insoluble polymers were amorphous. The molecular weights of soluble polymers were mostly less than 2000. The weight retention of the insoluble polymers obtained by the UV irradiation was very high being more than 80% at 1000°C, while the polymers obtained thermally or by gamma irradiation lost considerable amounts at 600°C.     

Fate of steroid hormones and endocrine activities in swine manure disposal and treatment facilities

Manure may contain high concern endocrine-disrupting compounds (EDCs) such as steroid hormones, naturally produced by pigs, which are present at μg L⁻¹ levels. Manure may also contain other EDCs such as nonylphenols (NP), polycyclic aromatic hydrocarbons (PAHs) and dioxins. Thus, once manure is applied to the land as soil fertilizer these compounds may reach aquifers and consequently living organisms, inducing abnormal endocrine responses. In France, manure is generally stored in anaerobic tanks prior spreading on land; when nitrogen removal is requested, manure is treated by aerobic processes before spreading. However, little is known about the fate of hormones and multiple endocrine-disrupting activities in such manure disposal and treatment systems. Here, we determined the fate of hormones and diverse endocrine activities during manure storage and treatment by combining chemical analysis and in vitro quantification of estrogen (ER), aryl hydrocarbon (AhR), androgen (AR), pregnane-X (PXR) and peroxysome proliferator-activated γ (PPARγ) receptor-mediated activities. Our results show that manure contains large quantities of hormones and activates ER and AhR, two of the nuclear receptors studied. Most of these endocrine activities were found in the solid fraction of manure and appeared to be induced mainly by hormones and other unidentified pollutants. Hormones, ER and AhR activities found in manure were poorly removed during manure storage but were efficiently removed by aerobic treatment of manure.     

The Protective Effect of Pumpkin and Fermented Whey Mixture against AFB1 and OTA Immune Toxicity In Vitro. A Transcriptomic Approach

Scope

The aim of the study is to investigate in Jurkat cells the possible beneficial effect of pumpkin (P) and fermented milk whey (FW) mixture against aflatoxin B1 (AFB1) and ochratoxin A (OTA) induced alterations in gene expression profile.

Methods and results

Human T cells are exposed for 7 days to digested bread extracts containing P-FW mixture along with AFB1 and OTA, individually and in combination. The results of RNA sequencing show that AFB1 P-FW exposure resulted in 34 differentially expressed genes (DEGs) while 3450 DEGs are found in OTA P-FW exposure and 3264 DEGs in AFB1-OTA P-FW treatment. Gene ontology analysis reveals biological processes and molecular functions related to immune system and inflammatory response. Moreover, PathVisio analysis points to eicosanoid signaling via lipoxygenase as the main pathway altered by AFB1 P-FW exposure whereas interferon signaling is the most affected pathway after OTA P-FW and AFB1-OTA P-FW treatments.

Conclusions

The mitigation of genes and inherent pathways typically associated with the inflammatory response suggest not only the anti-inflammatory and protective role of P-FW mixture but also their possible application in food industry to counteract AFB1 and OTA toxic effects on human and animal health.     

Asparagine quantification in cellular culture media using copper modified carbon nanotubes composite electrodes

Direct quantification of Asparagine (Asp) in a Streptomyces sp. M7 (SM7) culture medium was performed using multi-wall carbon nanotubes composite electrodes modified with copper microparticles (CNTPE-Cu). A sensitive and fast response is achieved at CNTPE-Cu after additions of SM7 cultures supernatant, without interference of the culture medium components. This response allows determining the Asp concentration as a function of the bacteria growth. The results reveal that the SM7 bacteria consume Asp as a carbon and nitrogen sources in the absence of another carbon source such as glucose.     

Studies on salts of amine‐containing polymers with benzoic acids. III. Poly(N,N‐dimethylaminoethyl methacrylate‐g‐polyethylene) with benzoic acids

Poly(N,N‐dimethylaminoethyl methacrylate) [poly(DMAEMA)] was grafted onto a commercial polyethylene film by means of γ‐irradiation, and the grafted films were reacted with various liquid‐crystal‐forming benzoic acids. When polymeric salts consisting only of poly(DMAEMA) and the benzoic acids were heated, dissociation of salts was observed, but with poly(DMAEMA) grafted onto polyethylene films, salt dissociation or crystallization of dissociated acids could be avoided, and interesting morphologies, including liquid‐crystal phases, were observed for the systems of benzoic acids–poly(DMAEMA‐g‐polyethylene). © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 972–978, 2000     

New Interpenetrating Polymer Networks of N-isopropylacrylamide/ N-acryloxysuccinimide: Synthesis and Characterization

Interpenetrating polymer networks (IPNs) based on poly (N-isopropylacrylamide), PNIPAAm, and poly (N-acryloxysuccinimide), PNAS, were prepared by a sequential method; the PNIPAAm which was polymerized and crosslinked by gamma irradiation, was swelled in a solution of PNAS/polylysine, which function as crosslinking agent for this monomer and as anchoring element of vesicles. The thermosensitivity properties (limit swelling time, lower critical solution temperature (LCST) and water retention), chemical composition (FTIR and elemental analysis), thermal properties (DSC and TGA) and morphology (SEM) were studied to characterize the IPNs.     

From the synthesis and characterization of methacrylated fatty acid based precursors to shape memory polymers

Fatty acid based precursors were synthesized by a one‐step reaction from oleic or lauric acids and glycidyl methacrylate to be used later in polymer formulations. Different times of reaction, amounts of catalyst and initial ratios of reactants were evaluated, obtaining conversions higher than 0.9 for the best conditions. The monomers obtained are interesting alternatives to synthetics since they combine low cost with environmental advantages (i.e. higher bio‐carbon content). These polymeric precursors were reacted separately in cationic and free radical polymerizations with styrene (50 wt%) to evaluate their potential as greener monomers. The lauric acid precursor and free radical polymerization were the alternatives that produced elastomeric materials with higher glass transition temperatures and storage moduli. These results were related to the lesser plasticizing effect of the shorter fatty acid chain, in comparison with that of the oleic acid based monomer, and to a lower free volume in the formed structure during curing. Moreover, all the obtained polymers exhibited shape memory properties that can be activated by temperature changes. © 2018 Society of Chemical Industry     

Gamma-ray induced crosslinking of polynorbornene and its copolymer containing a stabilizing group

Summary The gamma-ray induced, solid state crosslinking of polynorbornene(PolyNB) and its copolymer was studied. PolyNB degradates when irradiated in air, but it is readily crosslinked in vacuum. Homopolymer and copolymers containing a stabilizing group, 3,5-di-tert-butyl-4-hydroxybenzoyloxy group, were resistant to crosslinking showing induction periods before crosslinking. The irradiated PolyNB showed an ESR signal due to the allyl radical, and the polymer containing the hydroxybenzoyloxy group showed a signal due to the quinolic radical.