Adsorption studies on cellulose surfaces by combinations of interfacial techniques

In this work, the adsorption of various polymers on cellulose surfaces was studied in detail at molecular level. Special attention was paid on the interactions between renewable polysaccharides and different nanofibrillated cellulose (NFC) grades. Polymer or nanoparticle adsorption in aqueous medium was explored as a strategy to functionalize NFC. The role of pulp raw material and chemical pre-treatment on the NFC properties was clarified via indirect adsorption studies with ultrathin NFC films. Atomic force microscopy (AFM) -in different imaging and force detection modes-, quartz crystal microbalance with dissipation (QCM-D), Raman spectroscopy and surface plasmon resonance (SPR) were combined to carry out this research. The similar backbone having polysaccharides had natural affinity on NFC substrates. Comparison between NFC from different origin (hardwood vs. softwood), although of similar morphology, revealed differences in the conformation of adsorbed polysaccharide layer. The polysaccharide structure rather than NFC origin had more notable effect on adsorbed polysaccharide amount and layer properties. The attachment of the very thin (only few nm thick) polysaccharide layer was uniform without aggregates. They nevertheless were able to change the surface properties of cellulosic materials. One example was the lowered friction co-efficient with one polysaccharide (chitosan) determined for regenerated cellulose spheres in low pH aqueous solution. In addition, NFCs prepared after chemical pre-treatments were compared to unmodified NFC. Increasing the anionicity prevented the interfibril association by electrostatic repulsion. As a consequence the fibrillation efficiency was enhanced and very thin nanofibrils were achieved. The surface interactions were systematically probed and compared with different cationic counterparts using layer-by-layer (LbL)-technique. The high charged, chemically modified NFC behaved differently compared to low charged, unmodified NFC: they bound more water and the layer formation and stabilization was faster; and the adsorbed amount increased as the function of layer number. Nevertheless, multilayers could also be formed with the lower charged NFCs to some extent. Non-electrostatic interactions were significant between oppositely charged all-cellulosic materials. A considerable increase in adhesive forces during multilayer build-up due to high compressibility of the high charged NFC was also detected. The information obtained in this study for the interactions of emerging, renewable, bio-based materials can be used to create more sustainable material applications in the future

Looking for Razors and Needles in a Haystack: Multifaceted Analysis of Suicidal Declarations on Social Media—A Pragmalinguistic Approach

In this paper, we study language used by suicidal users on Reddit social media platform. To do that, we firstly collect a large-scale dataset of Reddit posts and annotate it with highly trained and expert annotators under a rigorous annotation scheme. Next, we perform a multifaceted analysis of the dataset, including: (1) the analysis of user activity before and after posting a suicidal message, and (2) a pragmalinguistic study on the vocabulary used by suicidal users. In the second part of the analysis, we apply LIWC, a dictionary-based toolset widely used in psychology and linguistic research, which provides a wide range of linguistic category annotations on text. However, since raw LIWC scores are not sufficiently reliable, or informative, we propose a procedure to decrease the possibility of unreliable and misleading LIWC scores leading to misleading conclusions by analyzing not each category separately, but in pairs with other categories. The analysis of the results supported the validity of the proposed approach by revealing a number of valuable information on the vocabulary used by suicidal users and helped to pin-point false predictors. For example, we were able to specify that death-related words, typically associated with suicidal posts in the majority of the literature, become false predictors, when they co-occur with apostrophes, even in high-risk subreddits. On the other hand, the category-pair based disambiguation helped to specify that death becomes a predictor only when co-occurring with future-focused language, informal language, discrepancy, or 1st person pronouns. The promising applicability of the approach was additionally analyzed for its limitations, where we found out that although LIWC is a useful and easily applicable tool, the lack of any contextual processing makes it unsuitable for application in psychological and linguistic studies. We conclude that disadvantages of LIWC can be easily overcome by creating a number of high-performance AI-based classifiers trained for annotation of similar categories as LIWC, which we plan to pursue in future work.journal articl

Päällystyspastan komponenttien vuorovaikutukset

Diplomityön tarkoituksena oli tutkia verhopäällystyksessä käytetyn päällystyspastan komponenttien vuorovaikutuksia keskittyen erityisesti pinta-aktiivisten aineiden vaikutuksiin. Kirjallisuusosassa esitellään verhopäällystyksen perusteet ja pastan komponentit sekä tarkastellaan pinta-aktiivisten aineiden vaikutuksia eri komponentteihin, päällystetyn paperin ominaisuuksiin sekä verhopäällystysprosessiin. Perinteisistä päällystystekniikoista poiketen verhopäällystyspastaan lisätään pinta-aktiivisia aineita, jotta pastan pintajännitys laskisi ja stabiilin verhon muodostuminen helpottuisi. Pinta-aktiivisen aineen adsorptio päällystyspigmenttiin riippuu sekä pigmenttilajista että käytetyn dispergointiaineen määrästä. Pinta-aktiiviset aineet vaikuttavat myös lateksin stabiilisuuteen. Liuenneella kalsiumionilla on haitallinen vaikutus erityisesti anionisia pinta-aktiivisia aineita sisältävän lateksin käyttäytymiseen. Pinta-aktiivisten aineiden vaikutusta päällystyspastan komponentteihin tutkittiin kahdella eri tavalla, adsorptiokokeilla ja mittaamalla eri komponenteilla päällystettyjen pintojen kosketuskulma kostutettaessa pinta vedellä tai vesi-kostutusvesiseoksella. Adsorptiota kaoliini-, kalsiumkarbonaatti- ja kipsipigmenttiin tutkittiin ns. serum replacement- kennolla. Adsorptiota havaittiin nonionisella pinta-aktiivisella aineella, erityisesti kalsiumkarbonaattiin. Valitettavasti tulokset eivät täysin vastaa kirjallisuusarvoja, eikä mittausmenetelmä ollut kovin luotettava ja toistettava. Kosketuskulmamittauksissa löydettiin eroja päällystekerroksen käyttäytymisissä. Kaoliini oli stabiilein kaikilla lateksi ja paksuntajalisäyksillä. Kalsiumkarbonaatti ei käyttäytynyt yhtä stabiilisti, mutta kipsi osoitti huomattavaa epästabiilisuutta, erityisesti tietyn anionisia pinta-aktiivisia sisältävän lateksin kanssa. Tämä ilmeni nopeana, yllättävänä laskuna veden kosketuskulmassa päällystekerroksen pinnalla. Mahdollisena syynä on kipsistä liukenevan kalsiumionin vaikutus anioniseen pinta-aktiiviseen aineeseen. Paksuntajan lisäys parantaa päällysteen stabiilisuutta jonkin verran, mutta ei täysin. Kaiken kaikkiaan, verhopäällystyspastan sisältämillä pinta-aktiivisilla aineilla todettiin olevan suuri vaikutus päällystekerroksen käyttäytymiseen pinnan kostuessa. Jos päällystekerros käyttäytyy epästabiilisti, voi se johtaa mahdollisesti ongelmiin painatuksessa

Spatial variability of mercury and polyunsaturated fatty acids in the European perch (Perca fluviatilis) - Implications for risk-benefit analyses of fish consumption

This study evaluated the spatial variability of risks and benefits of consuming fish from humic and clear lakes. Mercury in fish is a potential risk for human health, but risk assessment may be confounded by selenium, which has been suggested to counterbalance mercury toxicity. In addition to the risks, fish are also rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are known to be beneficial for cardiovascular health and brain cognitive function in humans. We found that the concentrations of EPA + DHA and mercury in European perch (Perca fluviatilis) vary spatially and are connected with lake water chemistry and catchment characteristics. The highest mercury concentrations and the lowest EPA + DHA concentrations were found in perch from humic lakes with high proportion of peatland (30–50%) in the catchment. In addition, the ratio of selenium to mercury in perch muscle was ≥1 suggesting that selenium may counterbalance mercury toxicity. The observed variation in mercury and EPA + DHA content in perch from different lakes indicate that the risks and benefits of fish consumption vary spatially, and are connected with lake water chemistry and catchment characteristics. In general, consumption of perch from humic lakes exposed humans to greater risks (higher concentrations of mercury), but provided less benefits (lower concentrations of EPA + DHA) than consumption of perch from clear lakes.final draftpeerReviewe

Spatial variability of mercury and polyunsaturated fatty acids in the European perch (Perca fluviatilis) - Implications for risk-benefit analyses of fish consumption

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