10 research outputs found

    Selluloosan nanokiteet: ominaispiirteet, kidemuokkaus, ja uudet valmistustavat

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    This thesis focused on how the properties of cellulose nanocrystals (CNCs) are affected by crystal lattice modification and crystal surface modification. In addition, developing new production methods were examined from the point of view of the limitations of the common production methods and the effect of the native environment and characteristics of cellulose. In order to investigate new production methods, hurdles in the current production methods, mechanical treatment and CNC isolation, were probed by omitting the hydrolysis step. Microcrystalline cellulose (MCC) was disintegrated to CNC via introduction of charged units by TEMPO-mediated oxidation and mechanical forces caused by sonication. However, the yields for the product fraction containing majority of the CNCs, alongside with some larger particles, remained low at 10-20% unlike what has been reported for nanofibrillated cellulose (NFC). The possible reason for the low yield of disintegration could be the limitations of the sufficient particle size upon sonication. On the other hand, the introduction of carboxylic groups on the particle surface could have resulted in additional hydrogen bonding between the particles since carboxylic groups are capable of forming more hydrogen bonds than the hydroxyl group. Additionally, TEMPO-mediated oxidation resulted in intriguing properties for the smaller particles that were produced and isolated. The porosity of the smaller particles, showed a distinct lack of larger pores that were present in larger TEMPO-oxidized particles and the untreated MCC. A possible explanation was suspected to be the hydrogen bonds created between the particles in combination of particle cleavage at the sites of the larger pores during disintegration. The bonding between CNCs was also examined by hydrophobization of the CNCs by silylation. The CNCs were first produced via acid vapour hydrolysis, which allows the CNC to remain in the fibrillar matrix of the hydrolysed cellulose microfibril (CMF) until dispersed into a medium. The silylated CNCs were disintegrated into a hydrophobic medium, toluene, and examined with TEM, which revealed that the end-to-end interactions of the CNCs were undisturbed by the hydrophobic medium, and the silylated CNCs were observed to stay in nanowire-like formations similar to the native CMF shape. However, the degree of polymerisation (DP) had reached the levelling-off DP, and therefore the formations were considered to consist of end-to-end associated CNCs. Furthermore, the effect of polymorph transition from cellulose I to III induced by complexation with ethylenediamine to CNC morphology was examined. When the polymorph transition was performed in dispersion, the dimensions of the CNCs remained unchanged. By contrast, when the polymorph transition was performed on CNCs immobilized on a surface, the crystal width decreased by half. It was hypothesized that the bonding between the CNC and the substrate caused frustration in the crystal lattice causing the outermost layer to be exfoliated.Tässä työssä tutkittiin, miten kidehilan ja kidepinnan muokkaaminen vaikuttavat selluloosananokiteiden (CNC) ominaisuuksiin. Lisäksi uusien tuotantomenetelmien kehittämistä tutkittiin arvioimalla tavallisimpien tuotantomenetelmien rajoitteita sekä CNC:n ominaispiirteiden ja luonnollisen ympäristön fibrillimatriisissa vaikutusta saantoon, hajottamalla mikrokiteisen selluloosan (MCC) partikkeleita. MCC hajotettiin tuomalla varautuneita ryhmiä kiteen pinnoille TEMPO-katalysoidulla hapetuksella ja altistamalla se ultraäänellä aiheutetuille mekaanisille voimille. CNC:t sisältäneiden tuotefraktioiden saannot pysyivät kuitenkin alhaisina (10 - 20%) toisinkuin on raportoitu selluloosan nanokuiduille (NFC). Syy vähäiseen saantoon saattoi olla sonikaation rajoittuneisuus menetelmänä. Toisaalta TEMPO-katalysoitu hapettuminen on voinut lisätä hiukkasten välistä vetysitoutumista tuomalla karboksyyliryhmiä partikkelien pinnoille, sillä karboksyyliryhmä pystyy muodostamaan kaksi vetysidosta toisin kuin yhteen vetysidokseen kykenevät hydroksyyliryhmät. Silti TEMPO-välitteinen hapettuminen johti erikoisiin ominaisuuksiin pienempikokoisille partikkeleille. Pienempien partikkelien huokoskokojakaumassa ei ollut merkkejä suurempien huokosten olemassaolosta, vaikka näitä esiintyi suurempien TEMPO-hapettuneiden partikkelien ja muokkaamattoman MCC:n huokoskokojakaumassa. Tähän ovat syynä luultavasti karboksyylihappojen aikaan saamat vetysidokset sekä partikkelien pilkkoutuminen suurempien huokosten kohdalta. CNC:den välistä sidosta tarkasteltiin myös hydrofoboimalla CNC:tä silylointireaktion kautta. CNC:t valmistettiin ensin happohöyryhydrolyysillä, joka jättää CNC:t hydrolysoidun selluloosamikrofibrillin (CMF) fibrillimatriisiin, kunnes matriisi hajotetaan dispergoimalla se liuottimeen. Kun silyloidut CNC:t hajautettiin hydrofobiseen liuottimeen eli tolueeniin ja tutkittiin elektronimikroskoopilla (TEM), paljastivat TEM-kuvat, että hydrofobinen liuotin ei ollut häirinnyt CNC:iden päiden välisiä vuorovaikutuksia, ja silyloitujen CNC:iden havaittiin pysyvän nanolankamaisissa muodostelmissa kuten CMF. Polymerointiasteen (DP) määritys kuitenkin varmisti hydrolyysin tapahtuneen, joten muodostumien voitiin katsoa koostuvan päästä päähän liittyneistä CNC:stä. Lisäksi tarkasteltiin polymorfin muunnoksen vaikutusta CNC:n morfologiaan kun selluloosa I kidemuoto muunnettiin selluloosa III muotoon etyleenidiamiini-kompleksaation kautta. Kun polymorfimuunnos tehtiin dispersiossa, CNC:iden mittasuhteet pysyivät muuttumattomina. Kun taas polymorfimuunnos tehtiin pinnalle kiinnitetyille CNC:lle, kiteet kapenivat puoleen alkuperäisestä. Oletettavasti sitoutuminen CNC:n ja substraatin välillä aiheuttivat pingottumista kidehilassa, jolloin CNC:n ulommat kerrokset pääsivät kuoriutumaan

    Käyttäjälähtöinen suunnittelu digitaalisissa peleissä

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    Pelisuunnittelijoiden tulee tuntea ja ymmärtää pelaajiensa tarpeita sekä pelaamisen motivaatioita, jos he haluavat pelinsä mahdollisimman laajan asiakaskunnan saataville. Tämä voidaan saavuttaa käyttäjälähtöisellä suunnittelulla. Tässä kandidaatintutkielmassa tarkasteltiin digitaalisten pelien käyttäjälähtöistä suunnittelua. Tutkielman tavoitteena oli selvittää digitaalisten pelien käytettävyyteen, saavutettavuuteen ja pelaajatyyppeihin liittyviä tekijöitä. Tutkielma toteutettiin systemaattisena kirjallisuuskatsauksena. Tutkielman aineistona oli vertaisarvioituja artikkeleita sekä alan kirjallisuutta, joita haettiin hyödyntämällä tietokantahakuja ja lumipallo-otantamenetelmää. Kirjallisuuskatsauksesta käy ilmi, että saavuttaakseen laajan asiakaskunnan digitaalisten pelien suunnittelussa tulee huomioida käytettävyystekijöitä, kuten pelaajilla käytössä olevaa laitteistoa, pelin oppimiskäyrää, pelin pelattavuutta ja pelin tapaa käsitellä pelaajan tekemiä virheitä. Saavutettavuutta voidaan puolestaan lisätä huomioimalla monipuolisesti niin visuaalisia, auditiivisia, kognitiivisia kuin motorisia rajoitteita. Näiden lisäksi pelin houkuttelevuutta voidaan lisätä huomioimalla erilaisia pelaajatyyppejä, jotka ovat tapa määritellä erilaisia pelaamisen motivaatioita.To create games for a wide customer-base game designers need to understand needs and motivations of different kinds of players. User-centred design is a way to achieve this kind of understanding. This bachelor's thesis examines user-centred design of digital games. The aim of the thesis is to investigate factors related to the usability, accessibility, and player types of digital games. The thesis was conducted as a systematic literature review. The material of the thesis consisted of peer-reviewed articles and literature in the gaming field, which were searched using database searches and snowball sampling method. The literature review shows that to reach a wide customer base, the design of digital games must consider usability factors such as the hardware used by players, the learning curve of the game, the games playability and the way the game handles players failures. Accessibility, in turn, can be increased by con-sidering players visual, auditory, cognitive, and motor limitations. In addition to these, the appeal of the game can be increased by considering different types of players, which are a way of determining different motivations for playing

    Quenching of fluorescence of pyrene with polymeric quenchers

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    In this study polymeric fluorescence quenchers were studied. The focus was on the quenching efficiency assessed with Stern-Volmer -plotting. Poly(4-vinylpyridine) and poly(nitrostyrene), poly(allylamine) and two other polymers were used as quenchers. Measurements with other than poly(nitrostyrene) were conducted in DMF. The measurements in aqueous solutions were conducted with different pH and with water and methanol as solvents for the pyrene. Using methanol as the solvent for pyrene made possible variation of pyrene concentration. Poly(4-vinylpyridine) was found to be an excellent quencher of fluorescence in aqueous solutions at pH 3.5, as was also poly(nitrostyrene) in DMF solutions. The Stern-Volmer -plot showed linear dependency of intensity ratio to quencher concentration, whereas the other polymeric quenchers tested showed downwards curvature implying that perhaps the polymer conformation prevents the fluorophore quencher interactions. Also the quenching of fluorescence was found to be independent of pH

    Surface-induced Frustration in Solid State Polymorphic Transition of Native Cellulose Nanocrystals

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    International audienceThe presence of an interface generally influences crystallization of polymers from melt or from solution. Here, by contrast, we explore the effect of surface immobilization in a direct solid state polymorphic transition on individual cellulose nanocrystals (CNCs), extracted from a plant-based origin. The conversion from native cellulose I to cellulose III crystal occurred via a host-guest inclusion of ethylene diamine inside the crystal. 60% reduction in CNC width (height) in atomic force microscopy images suggested that when immobilized on a flat modified silica surface, the stresses caused by the inclusion or the subsequent regeneration resulted in exfoliation, hypothetically between the van der Waals bonded sheets within the crystal. Virtually no changes in dimensions were visible when the polymorphic transition was performed to non-immobilized CNCs in bulk dispersion. With reservations and by acknowledging the obvious dissimilarities, the exfoliation of cellulose crystal sheets can be viewed as analogous to exfoliation of 2D structures like graphene from a van der Waals stacked solid. Here, the detachment is triggered by an inclusion of a guest molecule inside a host cellulose crystal and the stresses caused by the firm attachment of the CNC on a solid substrate, leading to detachment of molecular sheets or stacks of sheets

    Nicotine-Morphine Interactions At α4β2 α7 And α3 Nicotinic Acetylcholine Receptors

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    Nicotine and opioids share several behavioral and rewarding properties. Although both opioids and nicotine have their own specific mechanism of action, there is empirical and experimental evidence of interactions between these drugs. We studied receptor-level interactions of nicotine and morphine at α4β2, α7 and α3 nicotinic acetylcholine receptors. [ 3H]epibatidine displacement was used to determine if morphine binds competitively to nicotinic acetylcholine receptors. Functional interactions of morphine and nicotine were studied with calcium fluorometry and 86Rb+ efflux assays. Morphine displaced [ 3H]epibatidine from nicotinic agonist binding sites in all cell lines studied. The Ki values for morphine were 13.2 μM in SH-EP1-hα4β2 cells, 0.16 μM and 126 μM in SH-SY5Y cells and 43.7 μM in SH-EP1-hα7 cells. In SH-EP1-hα4β2 cells expressing α4β2 nicotinic acetylcholine receptors, morphine acted as a partial agonist of 86Rb+ efflux comparable to cytisine (with EC50 values of 53.3 μM for morphine and 5.38 μM for cytisine). The effect of morphine was attenuated concentration-dependently by the nicotinic antagonist mecamylamine. In the SH-SY5Y cell line expressing several subtypes of nicotinic acetylcholine receptors morphine had an inhibitory effect on nicotine induced 86Rb+ ion efflux mediated by α3 nicotinic acetylcholine receptors. These results suggest that morphine acts as a partial agonist at α4β2 nicotinic acetylcholine receptors and as a weak antagonist at α3 nicotinic acetylcholine receptors. © 2013 Elsevier B.V. All rights reserved
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