Comparison of sample crystallinity determination methods by X-ray diffraction for challenging cellulose I materials

Cellulose crystallinity assessment is important for optimizing the yield of cellulose products, such as bioethanol. X-ray diffraction is often used for this purpose for its perceived robustness and availability. In this work, the five most common analysis methods (the Segal peak height method and those based on peak fitting and/or amorphous standards) are critically reviewed and compared to two-dimensional Rietveld refinement. A larger () and more varied collection of samples than previous studies have presented is used. In particular, samples () with low crystallinity and small crystallite sizes are included. A good linear correlation () between the five most common methods suggests that they agree on large-scale crystallinity differences between samples. For small crystallinity differences, however, correlation was not seen for samples that were from distinct sample sets. The least-squares fitting using an amorphous standard shows the smallest crystallite size dependence and this method combined with perpendicular transmission geometry also yielded values closest to independently obtained cellulose crystallinity values. On the other hand, these values are too low according to the Rietveld refinement. All analysis methods have weaknesses that should be considered when assessing differences in sample crystallinity.Peer reviewe

Radiologisen kuvantamisen ympäristöjalanjälki

Lääketieteessä on totuttu lähtemään Aristoteleen ajatuksesta, että tärkeintä on yrittää olla aiheuttamatta haittaa potilaalle. Yhä tärkeämpää on kuitenkin yrittää välttää myös ympäristölle koituvaa haittaa. Terveydenhuollolla, kuten kaikella ihmisen toiminnalla, on omat ympäristövaikutuksensa. Ilmastoon vaikuttavien kasvihuonekaasujen päästöjen lisäksi ilmaan, maaperään ja vesistöihin päätyy monia haitallisia aineita.</p

Hierarchical structure and dynamics of plant cell wall studied using x-rays

The interest in wood and its main constituent, cellulose, is growing continuously. This can be explained by the demands of sustainable development and the extending scope of applications enabled by novel materials like nanocrystalline cellulose. Outstanding mechanical properties are one of the main reasons for the usability of wood. However, details on the ultrastructure of wood cell wall are still lacking, and thus also the origin for the mechanical properties is partly unknown. The various properties of plant materials arise from their hierarchical structure. Thus information at several size scales is needed for revealing the structure-function relationships. In this study, the structure of plant cell wall and cellulose based materials was characterized from the micro- to nanometer scale: using x-ray microtomography, the three-dimensional cellular structure was revealed and using x-ray scattering methods, the nanostructure was investigated. In the cell wall, parallel cellulose chains form microfibrils, which are partially crystalline and embedded in an amorphous hemicellulose-lignin matrix. The orientation, width and length of the crystalline parts of microfibrils vary between the plant species and materials. In this thesis, the cellulose structure was characterized in various plant species, and the effects due to drying, chemical pulping and acid hydrolysis were determined. It was found that the properties of the amorphous matrix played a role in all the effects studied. The wide spectrum of the samples, including native cotton, flax, bamboo, various wood species, pulp, microcrystalline and nanofibrillated cellulose (MCC, NFC), enabled interesting comparisons. It was observed, that in tension wood, pulp, MCC, and NFC, the cellulose crystallite width was significantly larger than in native normal wood. The high cellulose content and lack of lignin were typical for all the samples with a larger crystallite width. It was also found that the lateral and longitudinal order of the cellulose chains in crystallites was higher in never-dried wood compared to the corresponding air-dried samples. This indicated that the moisture had impact on the structures formed by crystalline cellulose although the water molecules can not enter the crystallites. One of the objects of the thesis was the study of the cellulose structure of oak from the Swedish warship Vasa. The results gave information on the preservation of the historically important wood throughout the centuries at the bottom of the sea.Kiinnostus puuta ja sen pääainesosaa, selluloosaa, kohtaan kasvaa jatkuvasti. Tämä johtuu sekä kestävän kehityksen asettamista vaatimuksista että laajentuvista sovellusmahdollisuuksista, joita uudet selluloosapohjaiset materiaalit tarjoavat. Puun erinomaiset mekaaniset ominaisuudet ovat yksi tärkeimmistä syistä sen suosioon eri käyttökohteissa. Puusoluseinän rakenne ei ole täysin tunnettu, joten mekaanisten ominaisuuksien alkuperääkään ei ole kyetty täysin selittämään. Kasvimateriaalien ominaisuudet perustuvat niiden hierarkkiseen rakenteeseen. Siksi tutkimustietoa tarvitaan useissa kokoluokissa, jotta rakenteen ja ominaisuuksien yhteydet pystytään havaitsemaan. Tässä työssä puun ja selluloosamateriaalien rakenteita tarkasteltiin mikrometritasolta nanometritasolle: röntgenmikrotomografialla selvitettiin näytteen kolmiulotteinen rakenne mikrometrin tarkkuudella, ja röntgensirontamenetelmät paljastivat nanorakenteen. Soluseinässä selluloosaketjut muodostavat osittain kiteisiä selluloosamikrofibrillejä, jotka ovat hemiselluloosan ja ligniinin muodostamassa amorfisessa matriisissa. Tässä työssä tarkasteltiin selluloosakiteiden rakennetta eri kasvilajeissa ja seurattiin kuivumisen, sellunkeiton ja happohydrolyysin aikaansaamia muutoksia. Amorfisen matriisin ominaisuuksien havaittiin vaikuttavan kaikissa tutkituissa reaktioissa. Tutkimukseen sisältyvien näytteiden moninaisuus, mukaan lukien puuvilla, pellava, bambu, useat eri puulajit, sellu, mikrokiteinen ja nanofibrilloitu selluloosa, mahdollisti mielenkiintoisten vertailujen tekemisen. Vetopuussa, sellussa, nano- ja mikrokiteisessä selluloosassa havaittiin, että selluloosakiteen leveys oli suurempi kuin tavallisessa puussa. Näitä näytteitä yhdistivät korkea selluloosapitoisuus ja alhainen ligniinipitoisuus. Työssä havaittiin myös, että selluloosakiteissä selluloosaketjut olivat paremmin järjestyneitä sekä ketjujen pitkittäiseen että poikittaiseen suuntaan luonnollisessa kosteudessa säilytetyssä puunäytteessä kuin vastaavassa kuivassa näytteessä. Tämä viittaa siihen, että puun kosteuspitoisuudella on merkitystä kiteisen selluloosan muodostamiin rakenteisiin vaikka vesimolekyylit eivät pääse tunkeutumaan itse kiteisiin. Yksi tutkimuskohteista oli historiallisen ruotsalaisen Vasa-laivan tammen selluloosarakenteet. Röntgensirontatulokset antoivat tietoa historiallisesti arvokkaan puunäytteen soluseinän rakenteiden säilymisestä läpi merenpohjassa vietettyjen vuosisatojen

Seurantaraportoinnin laatu : käyttäjänäkökulma

Siirretty Doriast

Aural Multitasking in Personal Media Devices

Henkilökohtaisten medialaitteiden (personal media device, PMD) käyttö liikenteessä saattaa johtaa onnettomuuksiin. Tämä johtuu kyseisten laitteiden käytön aikana tapahtuvasta visuaalisen huomiokyvyn jakamisesta laitteen ja ympäristön välillä. Tämä diplomityö käsittelee äänenvaraista monikäyttöä (auditory multitasking) PMD-laitteissa käyttäen lähtökohtanaan äänikäyttöliittymiä. äänenvarainen monikäyttö viittaa useiden samanaikaisten tehtävien suorittamiseen käyttäen ääntä ensisijaisena modaliteettina. Jotta tähän tavoitteiseen päästäisiin, on ratkaistava useita perustavanlaatuisia ongelmia monilähteisen ääni-informaation esittämiseen ja interaktioon liittyen. Tämä diplomityö koostuu kolmesta aiheesta. Ensimmäinen aihe esittelee eleisiin perustuvan ohjaustavan äänikäyttöliittymille. Ohjain käyttää äänentunnistusta neljän haptisen eleen luokitteluun. Tästä johtuen ohjainta voidaan käyttää esimerkiksi taskun läpi. Toinen aihepiiri esittelee monikerroksisen äänikäyttöliittymän, joka hyödyntää ns. ympäristöön sulautuvien näyttöjen (ambient display) ideoita ja luo henkilökohtaisen, kerrostetun äänimaiseman. Tarkoituksena on luoda äänimaisema, jossa käyttäjä pystyy keskittämään huomiokykynsä haluamaansa äänivirtaan. Kyseisessä toteutuksessa äänilähteet jaotellaan etu- ja taustakerroksiin niiden prioriteettien perusteella. Viimeinen aihe esittelee nopean head-related transfer function -pohjaisen (HRTF) tilaäänijärjestelmän personalisointimetodin. Metodi voidaan toteuttaa äänipelinä ja se ei vaadi kuulokkeiden lisäksi erillisiä laitteita.The use of personal media devices (PMDs) in traffic can lead to safety critical situations. This is due to divided visual attention between the device and the interface. This thesis considers the use of auditory interfaces for multitasking in PMDs. Aural multitasking refers to performing several simultaneous tasks by using sound as the primary display modality. In order to create such an eyes-free multitasking interface, the problems of presenting information from various sound sources and issues regarding the interaction must be solved. This thesis consists of three distinct topics. The first topic presents a gesture controller for auditory interfaces. The controller uses acoustic classification to recognize four tactile gestures and it can be operated for example through a pocket. The second topic presents a multilayer auditory interface. The multilayer interface incorporates ideas from ambient displays and creates a personal, layered, soundscape that enables auditory attention managing. The method divides the information and tasks into foreground and background streams according to their priorities. The last topic presents a rapid head-related transfer function (HRTF) personalization method for PMD usage. The method is implemented as an auditory game and it does not require additional accessories besides the headphones

Longitudinal analysis of the quality of orthodontic treatment outcome and stability of occlusal traits

Objectives To assess the quality and stability of orthodontic treatment outcome relative to the initial malocclusion. Material and methods The study was performed in one public health care clinic in Finland. Study subjects comprised 51 orthodontic patients (age range 12.7-18.7 years). Pre-treatment medical records and lateral skull radiographs were analysed for malocclusion type. The main reasons for orthodontic treatment were mandibular retrognathia, Class II distal bite, deep bite and crowding. At the end of a retention phase (Examination 1), the quality of treatment outcome was assessed using the occlusal morphology and function index (OMFI) and patients were asked about treatment satisfaction. Stability of occlusal traits and patient satisfaction were re-evaluated after a two-year follow-up (Examination 2). Occlusal characteristics descriptive statistics were performed. Results At Examination 1, all six morphological criteria for acceptability were fulfilled by 76% and all functional criteria by 82% of the patients. All OMFI criteria were met by 67% of the patients. At Examination 2, 68% of the patients fulfilled all morphological and 82% all functional criteria of acceptability. At Examination 2, all the OMFI criteria were still met by 64% of the patients and 92% expressed satisfaction with own occlusion. The main reasons for unacceptability were deficiencies in canine relationship and overbite, in addition to functional protrusion interferences. Conclusions In the evaluated health care clinic, patient satisfaction and the quality of treatment outcome were high. However, deep bite showed a tendency for relapse.Peer reviewe

Ultrastructural X-ray scattering studies of tropical and temperate hardwoods used as tonewoods

The structure of hardwoods representing eight tropical and five temperate species was characterized from the atomistic level up to the cellular level using X-ray scattering, X-ray microtomography and light microscopy. The species were chosen for this study based on their popularity as tonewoods. The ultrastructure of wood cell walls, including crystallite size, orientation and close-range order of cellulose microfibrils were determined by small- and wide-angle X-ray scattering (SAXS, WAXS). The SAXS patterns were interpreted by using an analytical model of cylinden packed in a hexagonal close-range order with paracrystalline distortion. The values for the cylinder diameters given by this model were compared to the average crystallite widths obtained by WAXS using the Scherrer equation. In six out of z6 samples, all of these representing tropical species used especially in fretboard parts of electric guitars, large differences between these two sizes were obtained. The WAXS and microscopy results of these samples corresponded to tension wood structures. These comparisons and interpretations of SAXS results have not been previously presented for any tropical hardwoods, especially related to those containing tension wood tissue. The importance of the ultrastructural characterization was highlighted in this study in the case of tropical hardwood samples.Peer reviewe

Tear Film Lipid Layer Structure : Self-Assembly of O-Acyl-omega-hydroxy Fatty Acids and Wax Esters into Evaporation-Resistant Monolayers

In healthy eyes, the tear film lipid layer (TFLL) is considered to act as an evaporation resistant barrier, which prevents eyes from drying. Seeking to understand the mechanisms behind the evaporation resistance of the TFLL, we studied mixtures of lipid layer wax esters and O-acyl-omega-hydroxy fatty acids. Analyzing their self-assembly and biophysical properties led to new discoveries concerning the structure and function of the TFLL. We discovered how these lipids self-assemble at the air-water interface and form an efficient antievaporative barrier, demonstrating for the first time how the interaction of different tear film lipid species can improve the evaporation resistance compared with individual lipid classes on their own. These results provide a potential mechanism for the evaporation resistance of the lipid layer. In addition, the results serve as a base for the future development of improved dry eye treatments and other applications where the evaporation of water represents a significant challenge.Peer reviewe

Inversion of crystallization rates in miscible block copolymers of poly(lactide)-block-poly(2-sopropyl-2-oxazoline)

Miscible block copolymers (BCPs) are rarely studied. When one or both components of such BCPs are semi-crystalline polymers, strong effects on the crystallization behavior can be expected. We present a study of 18 miscible BCPs comprised of poly(lactide) (PLLA, semi-crystalline and PDLLA, amorphous) and poly(2-isopropyl-2-oxazoline) (PiPOx, semi-crystalline) with PiPOx volume fractions of 0.14 <phi(PiPOx) <0.82. All BCPs exhibit a single glass transition and form a homogeneous melt. Mixing has a plasticizing effect on PiPOx and increases its crystallization rates (DSC). In contrast, the crystallization rates of PLLA are dramatically reduced, or in most cases entirely prevented. During isothermal crystallization at 130 degrees C, the crystallization rates of the BCPs were inverted in comparison with those of the parent homopolymers. Crystallization drives the BCPs to phase separate and the formed crystalline structure is that of the parent homopolymers. The fast crystallization of PiPOx confines the observed superstructure. The BCPs were studied on multiple length scales - from the atomic level (WAXS, IR spectroscopy) to the meso level (AFM, SAXS) and the macroscopic superstructure (polarized optical microscopy). A mechanism of the structure evolution is presented.Peer reviewe

Radiologisten tutkimusten luokittelulle on monta käyttötarkoitusta

On tärkeää, että koko maassa on käytössä yhteneväiset radiologiset nimikkeet ja koodisto. Kanta-arkiston käyttöönotto korostaa luokituksen merkitystä.Peer reviewe