Oxygen adsorption on clean and oxygen precovered Cu(100)

Kuparipinnan hapettumisen alkuvaiheet ovat vielä nykyisin tutkijoille epäselviä. Kuitenkin, jotta hapettumisprosessia voitaisiin säädellä, on sangen tärkeää ymmärtää mistä varsinainen hapettuminen lähtee liikkeelle ja mitkä ovat hapettumisen seuraavat vaiheet. Tähän kysymykseen haetaan vastauksia tässä työssä käyttäen puhtaasti teoreettisia menetelmiä pinnan käsittelyssä. Aikaisempien teoreettisten ja kokeellisten tutkimusten välillä on pieni ristiriita liittyen hapen tarttumistodennäköisyyteen. Teoreettisten tutkimusten mukaan happi ei puhtaalle pinnalle tullessaan näe potentiaalivallia, mutta kokeelliset tutkimukset osoittavat sellaisen kuitenkin olevan. Tuohon ristiriitaan pureudutaan käyttäen aikaisemmista laskuista poikkeavaa kvanttimekaaniseen molekyylidynamiikkaan perustuvaa lähestymistapaa. Työssä havaitaan, että aikaisemmin yleisesti käytetty menetelmä hukkaa huomattavan määrän tietoa ja siten tutkijat eivät voi ainoastaan tyytyä tarkastelemaan kyseisellä menetelmällä saatuja tuloksia. Kuparipinnalle havaittiin, että korkeilla molekyylin kineettisen energian arvolla aikaisemmin suoritetut laskut hajottavista trajektoreista pitävät paikkansa, mutta matalilla kineettisen energian arvoilla molekyyli kohtaa erittäin voimakkaan ``steering'' vaikutuksen ja trajektorit joiden piti olla hajottavia johtavatkin molekulaariseen adsorptioon. Kun hapen konsentraatio pinnalla on suurempi kuin 0.5 ML, pinta rekonstruoituu. Myös rekonstruktion jälkeistä pintaa on tutkittu samanlaisilla menetelmillä kuin puhdasta pintaa. Rekonstruoituneelle pinnalle ei löydetty hajottavia trajektoreita ja havaittiin, että hapelle annetun kineettisen energian matalilla arvoilla myös tässä tapauksessa on erittäin voimakas ``steering'' vaikutus.

Jaakko Juteinin arkkikirjallisuutta

Numeroitu 22 vihkosen sarja runoja, virsiä, juomalauluja, mietelmiä ja muita pieniä kaunokirjallisia kirjoitelmia.

Studies of Eu- and Yb-induced Reconstructions on the Si(100) Surface

This thesis presents experimental studies of rare earth (RE) metal induced structures on Si(100) surfaces. Two divalent RE metal adsorbates, Eu and Yb, are investigated on nominally flat Si(100) and on vicinal, stepped Si(100) substrates. Several experimental methods have been applied, including scanning tunneling microscopy/spectroscopy (STM/STS), low energy electron diffraction (LEED), synchrotron radiation photoelectron spectroscopy (SR-PES), Auger electron spectroscopy (AES), thermal desorption spectroscopy (TDS), and work function change measurements (Δφ). Two stages can be distinguished in the initial growth of the RE/Si interface: the formation of a two-dimensional (2D) adsorbed layer at submonolayer coverage and the growth of a three-dimensional (3D) silicide phase at higher coverage. The 2D phase is studied for both adsorbates in order to discover whether they produce common reconstructions or reconstructions common to the other RE metals. For studies of the 3D phase Yb is chosen due to its ability to crystallize in a hexagonal AlB2 type lattice, which is the structure of RE silicide nanowires, therefore allowing for the possibility of the growth of one-dimensional (1D) wires. It is found that despite their similar electronic configuration, Eu and Yb do not form similar 2D reconstructions on Si(100). Instead, a wealth of 2D structures is observed and atomic models are proposed for the 2×3-type reconstructions. In addition, adsorbate induced modifications on surface morphology and orientational symmetry are observed. The formation of the Yb silicide phase follows the Stranski-Krastanov growth mode. Nanowires with the hexagonal lattice are observed on the flat Si(100) substrate, and moreover, an unexpectedly large variety of growth directions are revealed. On the vicinal substrate the growth of the silicide phase as 3D islands and wires depends drastically on the growth conditions. The conditions under which wires with high aspect ratio and single orientation parallel to the step edges can be formed are demonstrated.

Fractionation of wood hydrolysate by ultrafiltration membranes at high temperature

Ultrafiltration (UF) is already used in pulp and paper industry and its demand is growing because of the required reduction of raw water intake and the separation of useful compounds from process waters. In the pulp and paper industry membranes might be exposed to extreme conditions and, therefore, it is important that the membrane can withstand them. In this study, extractives, hemicelluloses and lignin type compounds were separated from wood hydrolysate in order to be able to utilise the hemicelluloses in the production of biofuel. The performance of different polymeric membranes at different temperatures was studied. Samples were analysed for total organic compounds (TOC), lignin compounds (UV absorption at 280 nm) and sugar. Turbidity, conductivity and pH were also measured. The degree of fouling of the membranes was monitored by measuring the pure water flux before and comparing it with the pure water flux after the filtration of hydrolysate. According to the results, the retention of turbidity was observed to be higher at lower temperature compared to when the filtrations were operated at high temperature (70 °C). Permeate flux increased with elevated process temperature. There was no detrimental effect of temperature on most of the membranes used. Microdyn-Nadir regenerated cellulose membranes (RC) and GE-Osmonics thin film membranes seemed to be applicable in the chosen process conditions. The Polyethersulphone (NF-PES-10 and UH004P) and polysulphone (MPS-36) membranes used were highly fouled, but they showed high retentions for different compounds.

Sydämen sulatuksia ihmiselle

Sisältö: Kehoitus armahtamaan kanssa-luotuja ; Ihmisen arwo ; Luotuen arwo ; Linnun pesä.

Exploring Adaptive Implementation of On-Chip Networks

As technology geometries have shrunk to the deep submicron regime, the communication delay and power consumption of global interconnections in high performance Multi- Processor Systems-on-Chip (MPSoCs) are becoming a major bottleneck. The Network-on- Chip (NoC) architecture paradigm, based on a modular packet-switched mechanism, can address many of the on-chip communication issues such as performance limitations of long interconnects and integration of large number of Processing Elements (PEs) on a chip. The choice of routing protocol and NoC structure can have a significant impact on performance and power consumption in on-chip networks. In addition, building a high performance, area and energy efficient on-chip network for multicore architectures requires a novel on-chip router allowing a larger network to be integrated on a single die with reduced power consumption. On top of that, network interfaces are employed to decouple computation resources from communication resources, to provide the synchronization between them, and to achieve backward compatibility with existing IP cores. Three adaptive routing algorithms are presented as a part of this thesis. The first presented routing protocol is a congestion-aware adaptive routing algorithm for 2D mesh NoCs which does not support multicast (one-to-many) traffic while the other two protocols are adaptive routing models supporting both unicast (one-to-one) and multicast traffic. A streamlined on-chip router architecture is also presented for avoiding congested areas in 2D mesh NoCs via employing efficient input and output selection. The output selection utilizes an adaptive routing algorithm based on the congestion condition of neighboring routers while the input selection allows packets to be serviced from each input port according to its congestion level. Moreover, in order to increase memory parallelism and bring compatibility with existing IP cores in network-based multiprocessor architectures, adaptive network interface architectures are presented to use multiple SDRAMs which can be accessed simultaneously. In addition, a smart memory controller is integrated in the adaptive network interface to improve the memory utilization and reduce both memory and network latencies. Three Dimensional Integrated Circuits (3D ICs) have been emerging as a viable candidate to achieve better performance and package density as compared to traditional 2D ICs. In addition, combining the benefits of 3D IC and NoC schemes provides a significant performance gain for 3D architectures. In recent years, inter-layer communication across multiple stacked layers (vertical channel) has attracted a lot of interest. In this thesis, a novel adaptive pipeline bus structure is proposed for inter-layer communication to improve the performance by reducing the delay and complexity of traditional bus arbitration. In addition, two mesh-based topologies for 3D architectures are also introduced to mitigate the inter-layer footprint and power dissipation on each layer with a small performance penalty.

Identification of extractives and polysaccharides as foulants in membrane filtration of pulp and paper mill effluents

The search for new renewable materials has intensified in recent years. Pulp and paper mill process streams contain a number of potential compounds which could be used in biofuel production and as raw materials in the chemical, food and pharmaceutical industries. Prior to utilization, these compounds require separation from other compounds present in the process stream. One feasible separation technique is membrane filtration but to some extent, fouling still limits its implementation in pulp and paper mill applications. To mitigate fouling and its effects, foulants and their fouling mechanisms need to be well understood. This thesis evaluates fouling in filtration of pulp and paper mill process streams by means of polysaccharide model substance filtrations and by development of a procedure to analyze and identify potential foulants, i.e. wood extractives and carbohydrates, from fouled membranes. The model solution filtration results demonstrate that each polysaccharide has its own fouling mechanism, which also depends on the membrane characteristics. Polysaccharides may foul the membranes by adsorption and/or by gel/cake layer formation on the membrane surface. Moreover, the polysaccharides interact, which makes fouling evaluation of certain compound groups very challenging. Novel methods to identify wood extractive and polysaccharide foulants are developed in this thesis. The results show that it is possible to extract and identify wood extractives from membranes fouled in filtration of pulp and paper millstreams. The most effective solvent was found to be acetone:water (9:1 v/v) because it extracted both lipophilic extractives and lignans at high amounts from the fouled membranes and it was also non-destructive for the membrane materials. One hour of extraction was enough to extract wood extractives at high amounts for membrane samples with an area of 0.008 m2. If only qualitative knowledge of wood extractives is needed a simplified extraction procedure can be used. Adsorption was the main fouling mechanism in extractives-induced fouling and dissolved fatty and resin acids were mostly the reason for the fouling; colloidal fouling was negligible. Both process water and membrane characteristics affected extractives-induced fouling. In general, the more hydrophilic regenerated cellulose (RC) membrane fouled less that the more hydrophobic polyethersulfone (PES) and polyamide (PA) membranes independent of the process water used. Monosaccharide and uronic acid units could also be identified from the fouled synthetic polymeric membranes. It was impossible to analyze all monosaccharide units from the RC membrane because the analysis result obtained contained degraded membrane material. One of the fouling mechanisms of carbohydrates was adsorption. Carbohydrates were not potential adsorptive foulants to the sameextent as wood extractives because their amount in the fouled membranes was found to be significantly lower than the amount of wood extractives.

The role of van der Waals interactions in the case of H2 adsorption on ruthenium (0001) surface

Computational material science with the Density Functional Theory (DFT) has recently gained a method for describing, for the first time the non local bonding i.e., van der Waals (vdW) bonding. The newly proposed van der Waals-Density Functional (vdW-DF) is employed here to address the role of non local interactions in the case of H2 adsorption on Ru(0001) surface. The later vdW-DF2 implementation with the DFT code VASP (Vienna Ab-initio Simulation Package) is used in this study. The motivation for studying H2 adsorption on ruthenium surface arose from the interest to hydrogenation processes. Potential energy surface (PES) plots are created for adsorption sites top, bridge, fcc and hcp, employing the vdW-DF2 functional. The vdW-DF yields 0.1 eV - 0.2 eV higher barriers for the dissociation of the H2 molecule; the vdW-DF seems to bind the H2 molecule more tightly together. Furthermore, at the top site, which is found to be the most reactive, the vdW functional suggests no entrance barrier or in any case smaller than 0.05 eV, whereas the corresponding calculation without the vdW-DF does. Ruthenium and H2 are found to have the opposite behaviors with the vdW-DF; Ru lattice constants are overestimated while H2 bond length is shorter. Also evaluation of the CPU time demand of the vdW-DF2 is done from the PES data. From top to fcc sites the vdW-DF computational time demand is larger by 4.77 % to 20.09 %, while at the hcp site it is slightly smaller. Also the behavior of a few exchange correlation functionals is investigated along addressing the role of vdW-DF. Behavior of the different functionals is not consistent between the Ru lattice constants and H2 bond lengths. It is thus difficult to determine the quality of a particular exchange correlation functional by comparing equilibrium separations of the different elements. By comparing PESs it would be computationally highly consuming.

Metsänhakkuiden vaikutukset merikotkan (Haliaeetus albicilla) pesintään

Suomen merikotkapopulaatio kasvaa ja levittäytyy saaristosta mantereen puolelle. Sen seurauksena tehometsätalouden intressit ja merikotkan pesimähabitaattien suojelutarve törmäävät yhä useammin. Tämän tutkimuksen tavoitteena oli tuottaa tuloksia, joiden perusteella voidaan laatia entistä tarkemmat ohjeet pesien huomioonottamisesta metsätaloustoimenpiteiden yhteydessä. Käytin tutkimusaineistona WWF:n merikotkatyöryhmän vuosittain keräämiä pesimätietoja sekä metsänkäyttöilmoituksista kokoamiani hakkuutietoja vuosilta 2000–2009. Tarkastelin yleistettyjen lineaaristen sekamallien avulla säteeltään 600-metrisen pesäalueen hakkuiden vaikutusta mm. pesinnän jatkumiseen samalla pesällä ja pesimäyritysten onnistumiseen. Havaitsin, että edellisvuoden pesinnän epäonnistuminen lisää merikotkien pesänvaihtotodennäköisyyttä, ja uudistushakkuuaukot pesäalueella lisäävät tätä epäonnistumisen jälkeistä pesänvaihtoherkkyyttä. Merikotkat ovat kuitenkin monissa tapauksissa pesineet ja myös onnistuneet pesinnässään hyvinkin lähellä hakkuuaukkoa. Pesäalueen hakkuut pesimäkauden ulkopuolella eivät siis haittaa ainakaan kaikkien merikotkayksilöiden pesinnän aloitusta tai pesimäyrityksen onnistumista. Uudistushakkuutapahtuma pesäalueella laskee vähintään suuntaa-antavasti samanaikaisen tai seuraavan pesinnän onnistumistodennäköisyyttä. Reviireillä, joiden ytimessä on hakkuita, pesinnän väliinjättövuosia on ainakin suuntaa-antavasti enemmän kuin hakkaamattomilla reviireillä. Hakkuiden haittavaikutuksista huolimatta poikastuotto on niilläkin reviireillä, joiden ytimessä on hakkuita, niin hyvä, että populaatio kasvaa. Nykyisen tasoinen hakkuuhäiriö ei siis uhkaa merikotkien suotuisan suojelun tasoa. Tutkimukseni perusteella pidän ELY-keskuksen käyttämää 50–100 metrin levyistä näkyvyyden mukaan sovellettavaa suojavyöhykettä sopivana pesimäkauden ulkopuolisille hakkuille. Varsinaisesti en saanut näyttöä tämänkään suojavyöhykkeen tarpeellisuudesta, mutta aineisto ei ollut edes sopiva näin lähellä pesää olevien hakkuiden vaikutusten tilastolliseen testaamiseen. Sen sijaan näyttää melko varmalta, että ainakaan isompi suojavyöhyke ei ole tarpeen merikotkan suotuisan suojelun tason varmistamiseksi. Hakkuuaineiston ajoitusongelmien vuoksi en voi ottaa kantaa pesimäkautisen suojavyöhykkeen leveyteen. Merikotkapopulaation kasvun myötä lajin uhanalaisluokitus saattaa lähivuosina muuttua, mikä vaikuttanee myös pesimähabitaattien suojaan lainsäädännössä. Siinäkin tilanteessa tämä tutkimus auttanee vapaaehtoisen suojelun toteutusta.

Spectroscopic Studies of III-V Semiconductor Materials for Improved Devices

Defects in semiconductor crystals and at their interfaces usually impair the properties and the performance of devices. These defects include, for example, vacancies (i.e., missing crystal atoms), interstitials (i.e., extra atoms between the host crystal sites), and impurities such as oxygen atoms. The defects can decrease (i) the rate of the radiative electron transition from the conduction band to the valence band, (ii) the amount of charge carriers, and (iii) the mobility of the electrons in the conduction band. It is a common situation that the presence of crystal defects can be readily concluded as a decrease in the luminescence intensity or in the current flow for example. However, the identification of the harmful defects is not straightforward at all because it is challenging to characterize local defects with atomic resolution and identification. Such atomic-scale knowledge is however essential to find methods for reducing the amount of defects in energy-efficient semiconductor devices. The defects formed in thin interface layers of semiconductors are particularly difficult to characterize due to their buried and amorphous structures. Characterization methods which are sensitive to defects often require well-defined samples with long range order. Photoelectron spectroscopy (PES) combined with photoluminescence (PL) or electrical measurements is a potential approach to elucidate the structure and defects of the interface. It is essential to combine the PES with complementary measurements of similar samples to relate the PES changes to changes in the interface defect density. Understanding of the nature of defects related to III-V materials is relevant to developing for example field-effect transistors which include a III-V channel, but research is still far from complete. In this thesis, PES measurements are utilized in studies of various III-V compound semiconductor materials. PES is combined with photoluminescence measurements to study the SiO2/GaAs, SiNx/GaAs and BaO/GaAs interfaces. Also the formation of novel materials InN and photoluminescent GaAs nanoparticles are studied. Finally, the formation of Ga interstitial defects in GaAsN is elucidated by combining calculational results with PES measurements.

Safety and outcome of coronary interventions with special reference to anticoagulation and stent type

University of Turku, Faculty of Medicine, Department of Cardiology and Cardiovascular Medicine, Doctoral Programme of Clinical Investigation, Heart Center, Turku University Hospital, Turku, Finland Division of Internal Medicine, Department of Cardiology, Seinäjoki Central Hospital, Seinäjoki, Finland Heart Center, Satakunta Central Hospital, Pori, Finland Annales Universitatis Turkuensis Painosalama Oy, Turku, Finland 2015 Antithrombotic therapy during and after coronary procedures always entails the challenging establishment of a balance between bleeding and thrombotic complications. It has been generally recommended to patients on long-term warfarin therapy to discontinue warfarin a few days prior to elective coronary angiography or intervention to prevent bleeding complications. Bridging therapy with heparin is recommended for patients at an increased risk of thromboembolism who require the interruption of anticoagulation for elective surgery or an invasive procedure. In study I, consecutive patients on warfarin therapy referred for diagnostic coronary angiography were compared to control patients with a similar disease presentation without warfarin. The strategy of performing coronary angiography during uninterrupted therapeutic warfarin anticoagulation appeared to be a relatively safe alternative to bridging therapy, if the international normalized ratio level was not on a supratherapeutic level. In-stent restenosis remains an important reason for failure of long-term success after a percutaneous coronary intervention (PCI). Drug-eluting stents (DES) reduce the problem of restenosis inherent to bare metal stents (BMS). However, a longer delay in arterial healing may extend the risk of stent thrombosis (ST) far beyond 30 days after the DES implantation. Early discontinuation of antiplatelet therapy has been the most important predisposing factor for ST. In study II, patients on long-term oral anticoagulant (OAC) underwent DES or BMS stenting with a median of 3.5 years’follow-up. The selective use of DESs with a short triple therapy seemed to be safe in OAC patients, since late STs were rare even without long clopidogrel treatment. Major bleeding and cardiac events were common in this patient group irrespective of stent type. In order to help to predict the bleeding risk in patients on OAC, several different bleeding risk scorings have been developed. Risk scoring systems have also been used also in the setting of patients undergoing a PCI. In study III, the predictive value of an outpatient bleeding risk index (OBRI) to identify patients at high risk of bleeding was analysed. The bleeding risk seemed not to modify periprocedural or long-term treatment choices in patients on OAC after a percutaneous coronary intervention. Patients with a high OBRI often had major bleeding episodes, and the OBRI may be suitable for risk evaluation in this patient group. Optical coherence tomography (OCT) is a novel technology for imaging intravascular coronary arteries. OCT is a light-based imaging modality that enables a 12–18 µm tissue axial resolution to visualize plaques in the vessel, possible dissections and thrombi as well as, stent strut appositions and coverage, and to measure the vessel lumen and lesions. In study IV, 30 days after titanium-nitride-oxide (TITANOX)-coated stent implantation, the binary stent strut coverage was satisfactory and the prevalence of malapposed struts was low as evaluated by OCT. Long-term clinical events in patients treated with (TITANOX)-coated bio-active stents (BAS) and paclitaxel-eluting stents (PES) in routine clinical practice were examined in study V. At the 3-year follow-up, BAS resulted in better long-term outcome when compared with PES with an infrequent need for target vessel revascularization. Keywords: anticoagulation, restenosis, thrombosis, bleeding, optical coherence tomography, titanium

GaN- ja AlGaN-puolijohteiden pintaominaisuuksista ja niiden muokkauksesta

Yhdistepuolijohde galliumnitridi (GaN) on energiatehokkaiden valkoisten ledien päämateriaali. GaN on kestävä materiaali; sillä on muun muassa alhainen säteilyreagointi ja suuri jännitekestävyys, minkä vuoksi GaN soveltuu hyvin myös maanpuolustus- ja avaruussovelluksiin. Sen iso energia-aukko mahdollistaa materiaalin käytön suurteho- ja suurtaajuussovelluksissa, ja sen suuri lämpökapasiteetti ja lämmönjohtavuuskyky avaavat edelleen uusia mahdollisuuksia materiaalin käytölle muun muassa tehovahvistimissa mikroaaltotaajuudella. GaN:ä käytetään myös sinisten ja violettien ledien valmistuksessa. Kun yhdisteeseen lisätään alumiinia, saadaan alumiinigalliumnitridin (AlGaN) energia-aukkoa ja muita ominaisuuksia säädeltyä alumiinin määrää muuttamalla. AlGaN-pintojen ominaisuuksia on tutkittu suhteellisen vähän, vaikka niiden merkitys kasvaa jatkuvasti kehitettäessä nanoteknologian sovelluksia. AlGaN-pintojen tutkiminen on tärkeää, koska monissa sovelluksissa juuri pinnat ja rajapinnat ovat huomattavassa asemassa laitteiden toiminnan kannalta. Pinnoilla sijaitseva atomien epäjärjestys, kidevirheet ja epäpuhtausatomit sekä atomien kemiallinen sidosympäristö kiinnostavat tutkijoita. Myös erilaisten pintakäsittelyjen vaikutusten tunteminen edellä mainittuihin ominaisuuksiin on tärkeää hyvien pintojen valmistuksen saavuttamiseksi. Tämän pro gradu -tutkielman on tarkoitus tutustua III–V-puolijohteiden GaN:n ja AlGaN:n pintaominaisuuksiin ja niiden muokkaukseen materiaalifysiikan pintatieteen menetelmillä. Mg-piristeisille Al0,5Ga0,5N-näytteille tehdyt LEED- ja STM-mittaukset osoittavat, että AlGaN-pinnat tarjoavat hyvän lähtökohdan bulkille tyypillisten ominaisuuksien tutkimiseen. XPS- ja SR-PES-mittaukset osoittavat, että Mg-piristys vaikuttaa aktivoituvan noin 700 °C:n lämmityksessä, ja näytteet sisältävät aiemmissa tutkimuksissa havaitun vedyn lisäksi happea ja hiiltä, jotka vaikuttavat magnesiumin aktivoitumiseen ja siitä syntyvään aukkokonsentraatioon. LEED-, STM- ja resistiivisyysmittaukset tukevat tehtyjä XPS- ja SR-PES-mittauksia. Al0,5Ga0,5N-näytteen energia-aukossa sijaitsevien aktiivisten vastaanottajatilojen määritettiin sijaitsevan 200–600 meV valenssivyön maksimin yläpuolella riippuen jälkilämmityksen kestosta.