Surface chemistry of fibres and vessel elements in chemical and recycled pulps

Den viktigaste råvaran i papperstillverkning är pappersmassa. Massan innehåller (ved)fibrer men också finmaterial och andra typers (ved)celler, så som kärlceller. Hur dessa komponenter beter sig under arkformationen i pappersmaskinen eller hur de bidrar till egenskaperna hos det färdiga pappret avgörs till stor del av massakomponenternas ytkemiska sammansättning, fysiska struktur och mängden joniserbara grupper på ytan. I denna avhandling studerades ytegenskaperna hos fraktionerade kemiska massor och returfibermassor med avancerade analystekniker. Rester av avfärgningskemikalier identifierades på både returfibrer och på kärlceller. Dessa kan påverka arkformationen och arkstyrkan på returfiberpapper. Kärlcellernas cellväggsstruktur visade sig skilja sig från fibrernas. Resultaten kan främja utvecklingen av returfiberprosessen och användningen av kärlcellsrika lövvedsmassor.Paperin tärkein raaka-aine on (puu)kuitumassa. Massa sisältää kuitujen lisäksi hienoainesta ja muita kasvisoluja, kuten putkilosoluja. Näiden massakomponenttien ulkopintojen kemiallinen koostumus, rakenne ja pintavaraus määrittävät paljolti sen, miten komponentit käyttäytyvät paperikoneen arkinmuodostuksessa sekä sen miten ne vaikuttavat valmiin paperin ominaisuuksiin. Tässä väitöstyössä tutkittiin fraktioitujen sellujen ja uusiomassojen pintaominaisuuksia uudenaikaisilla analyysitekniikoilla. Uusiokuiduista ja putkilosoluista löydettiin mm. siistausainejäämiä, jotka voivat vaikuttaa uusiopaperin arkinmuodostukseen ja arkkilujuuteen. Putkilosolujen soluseinämän rakenne osoittautui eroavan kuidun seinämän rakenteesta. Tulokset voivat edistää uusiokuituprosessin kehittämistä ja putkilosolupitoisten lehtipuumassojen käytettävyyttä

INTERACTIONS BETWEEN CATIONIC POLYELECTROLYTE AND PULP FINES

Papermaking pulps are a mixture of fibres, fibre fragments, and small cells (parenchyma or ray cells), usually called pulp fines. The interactions between pulp fines and a cationic copolymer of acrylamide and acryloxyethyltrimethyl ammonium chloride were investigated based on solid-liquid isotherms prepared under different turbulence, and subsequent advanced surface characterization using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The surface charge and surface area of pulp fine substrates were measured by methylene blue sorption-XPS analysis and nitrogen adsorption combined with mercury porosimetry, respectively. The driving force behind polyelectrolyte adsorption was the amount of the surface anionic charge, whereas surface area appeared to be of less importance. Based on a comparison of solid-liquid and XPS sorption isotherms, different polyelectrolyte conformations were suggested, depending on the types of fines: A flatter conformation and partial cell-wall penetration of polyelectrolytes on kraft fines from freshly prepared pulp, and a more free conformation with extended loops and tails on lignocellulosic fines from recycled pulp. Additionally, ToF-SIMS imaging proved that recycled pulp fines contained residual de-inking chemicals (primarily palmitic acid salts) that possibly hinder the electrostatic interactions with polyelectrolytes

Etude du mouvement dans les épreuves projectives à la lumière d'un cas de myasthénie gravis

International audienc

Home-based exercise in autoimmune myasthenia gravis: A randomized controlled trial

International audienceThe tolerance of exercise and its effects on quality of life in myasthenia gravis are not currently backed up by strong evidence. The aim of this study was to determine whether exercise as an adjunct therapy is well tolerated and can improve health-related quality of life (HRQoL) in stabilized, generalized autoimmune myasthenia gravis (gMG). We conducted a parallel-group, multi-center prospective RCT using computer-generated block randomization. Adults with stabilized, gMG, and no contra-indication to exercise, were eligible. Participants received usual care alone or usual care and exercise. The exercise intervention consisted of 3-weekly 40 min sessions of an unsupervised, moderate-intensity home rowing program over 3 months. The primary endpoint was the change in HRQoL from randomization to postintervention. Assessor-blinded secondary endpoints were exercise tolerance and effects on clinical, psychological and immunological status. Of 138 patients screened between October 2014 and July 2017, 45 were randomly assigned to exercise (n = 23) or usual care (n = 20). Although exercise was well tolerated, the intention-to-treat analysis revealed no evidence of improved HRQoL compared to usual care (MGQOL-15-F; mean adjusted between-groups difference of-0.8 points, 95%CI-5.4 to 3.7). Two patients hospitalized for MG exacerbation were from the usual care group