Phase-separation phenomena in solutions of poly(2,6-dimethyl-1,4-phenylene oxide). III. Pulse-induced critical scattering of solutions in toluene

For the polymer-solvent system poly(phenylene oxide) in toluene the mechanism and kinetics of crystallization have been studied with the Pulse Induced Critical Scattering technique. It was found that after a delay-time the growth mechanism was diffusion controlled. The delay-time is thought to be connected with the nucleation of the crystallites and it disappeared in the seeded crystallizations studied. After incomplete melting of crystallites the first stages of growth resemble a condensation reaction

Adsorbent filled membranes for gas separation. Part 1. Improvement of the gas separation properties of polymeric membranes by incorporation of microporous adsorbents

The effect of the introduction of specific adsorbents on the gas separation properties of polymeric membranes has been studied. For this purpose both carbon molecular sieves and zeolites are considered. The results show that zeolites such as silicate-1, 13X and KY improve to a large extent the separation properties of poorly selective rubbery polymers towards a mixture of carbon dioxide/methane. Some of the filled rubbery polymers achieve intrinsic separation properties comparable to cellulose acetate, polysulfone or polyethersulfone. However, zeolite 5A leads to a decrease in permeability and an unchanged selectivity. This is due to the impermeable character of these particles, i.e. carbon dioxide molecules cannot diffuse through the porous structure under the conditions applied. Using silicate-1 also results in an improvement of the oxygen/nitrogen separation properties which is mainly due to a kinetic effect. Carbon molecular sieves do not improve the separation performances or only to a very small extent. This is caused by a mainly dead-end (not interconnected) porous structure which is inherent to their manufacturing process

Preparation of zeolite filled glassy polymer membranes

The incorporation of zeolite particles in the micrometer range into polymeric matrices was investigated as a way to improve the gas separation properties of the polymer materials used in the form of membranes. The adhesion between the polymer phase and the external surface of the particles appeared to be a major problem in the preparation of such membranes when the polymer is in the glassy state at room temperature. Various methods were investigated to improve the internal membrane structure, that is, surface modification of the zeolite external surface, preparation above the glass-transition temperature, and heat treatment. Improved structures were obtained as observed by scanning electron microscopy, but the influence on the gas separation properties was not in agreement with the observed structural improvements

Bezinklagen: een bron van mineralen

Veel varkensbedrijven kampen met het zogenaamde 'Minas-gat' op hun Minas-aangifte. Uit onderzoek op Praktijkcentrum Rosmalen blijkt dat hoge fosfaat- en stikstofgehalten van de bezinklagen in de mestput een belangrijke oorzaak vormen van het achterblijven van mineralen op het bedrijf. Het is van belang te voorkomen dat de mest bezinkt en de putten goed leeg te zuige

Recent advances in the formation of phase inversion membranes made from amorphous or semi-crystalline polymers

Structural characteristics in membranes formed by diffusion induced phase separation processes are discussed. Established theories on membrane formation from ternary systems can be extended to describe the effects of high or low molecular weight additives. A mechanism for the formation of nodular structures in the top layer of ultrafiltration membranes is presented. In the last part structures arising from polymer crystallization during immersion precipitation are discussed

Effectiviteit van ventilatie in afdelingen voor gespeende biggen

De ventilatie-effectiviteit was bij grondkanaalventilatie het hoogst en bij plafondventilatie ongeveer even hoog als bij deurventilatie

MINAS: een verfijnd systeem?

Op de Praktijkcentra voor de varkenshouderij Sterksel, Raalte en Rosmalen zijn de MINAS-boekhoudingen geanalyseerd op de effecten van verschillen in de voorraden voer en mest, en van afwijkingen in de bepalingen van het mineralengehalte in aangevoerd voer en afgevoerde mest. Door voorraadeffecten en onnauwkeurigheden in de bepalingen van de aan- en afvoer van mineralen is het mogelijk dat een varkenshouder heffing moet betalen, terwijl mest en dieren zijn afgevoerd volgens de regels. Om de spreiding in de MINAS-aangifte voor fosfaat en stikstof en de mogelijke heffing te bepalen werd een statistische analyse uitgevoerd voor een bedrijf met 237 zeugen en een bedrijf met 2000 vleesvarken

Ringonderzoek MINAS-laboratoria

In dit ringonderzoek is gekeken naar de verschillen tussen de analyseresultaten van gelijkwaardige mestmonsters. Ook is nagegaan wat de financiële gevolgen voor een varkenshouder kunnen zijn door de variatie in de analyseresultate

Tweefasenvoedering tijdens de dracht

Op het Praktijkcentrum Sterksel wordt onderzocht wat het effect is van tweefasenvoedering tijdens de dracht op reproductie, gezondheid en berekende mineralenuitscheiding van zeugen. Het onderzoek start met nuldeworps-zeugen die vervolgens vier worpen gevolgd worden

LC-MS proteomics analysis of the iInsulin/IGF-1-deficient Caenorhabditis elegans daf-2(e1370) mutant reveals extensive restructuring of intermediary metabolism

The insulin/IGF-1 receptor is a major known determinant of dauer formation, stress resistance, longevity, and metabolism in Caenorhabditis elegans. In the past, whole-genome transcript profiling was used extensively to study differential gene expression in response to reduced insulin/IGF-1 signaling, including the expression levels of metabolism-associated genes. Taking advantage of the recent developments in quantitative liquid chromatography mass spectrometry (LC-MS)-based proteomics, we profiled the proteomic changes that occur in response to activation of the DAF-16 transcription factor in the germline-less glp-4(bn2);daf-2(e1370) receptor mutant. Strikingly, the daf-2 profile suggests extensive reorganization of intermediary metabolism, characterized by the upregulation of many core intermediary metabolic pathways. These include glycolysis/gluconeogenesis, glycogenesis, pentose phosphate cycle, citric acid cycle, glyoxylate shunt, fatty acid beta-oxidation, one-carbon metabolism, propionate and tyrosine catabolism, and complexes I, II, III, and V of the electron transport chain. Interestingly, we found simultaneous activation of reciprocally regulated metabolic pathways, which is indicative of spatiotemporal coordination of energy metabolism and/or extensive post-translational regulation of these enzymes. This restructuring of daf-2 metabolism is reminiscent to that of hypometabolic dauers, allowing the efficient and economical utilization of internal nutrient reserves and possibly also shunting metabolites through alternative energy-generating pathways to sustain longevity