Welding of Sheet metal using Modified short arc MIG/MAG welding process

In this research work, the results of an investigation dealing with welding of sheet metals with diverse air gap using FastROOT modified short arc welding method and short circuit MAG welding processes have been presented. Welding runs were made under different conditions and, during each run, the different process parameters were continuously monitored. It was found that maximum welding speed and less HAZ are reached under specific welding conditions with FastROOT method with the emphasis on arc stability. Welding results show that modified short arc exhibits a higher electrode melting coefficient and with virtually spatter free droplet transition. By adjusting the short circuit duration the penetration can be controlled with only a small change in electrode deposition. Furthermore, by mixing pulsed MIG welding with modified arc welding the working envelope of the process is greatly extended allowing thicker material sections to be welded with improved weld bead aesthetics. FastROOT is a modified short arc welding process using mechanized or automated welding process based on dip transfer welding, characterized by controlled material deposition during the short circuit of the wire electrode to the workpiece.

“IT’S ALL RIGHT”. Multimodal rightward spatial bias modified by age and praxis

The general goal of the present work was to study whether spatial perceptual asymmetry initially observed in linguistic dichotic listening studies is related to the linguistic nature of the stimuli and/or is modality-specific, as well as to investigate whether the spatial perceptual/attentional asymmetry changes as a function of age and sensory deficit via praxis. Several dichotic listening studies with linguistic stimuli have shown that the inherent perceptual right ear advantage (REA), which presumably results from the left lateralized linguistic functions (bottom-up processes), can be modified with executive functions (top-down control). Executive functions mature slowly during childhood, are well developed in adulthood, and decline as a function of ageing. In Study I, the purpose was to investigate with a cross-sectional experiment from a lifespan perspective the age-related changes in top-down control of REA for linguistic stimuli in dichotic listening with a forced-attention paradigm (DL). In Study II, the aim was to determine whether the REA is linguistic-stimulus-specific or not, and whether the lifespan changes in perceptual asymmetry observed in dichotic listening would exist also in auditory spatial attention tasks that put load on attentional control. In Study III, using visual spatial attention tasks, mimicking the auditory tasks applied in Study II, it was investigated whether or not the stimulus-non-specific rightward spatial bias found in auditory modality is a multimodal phenomenon. Finally, as it has been suggested that the absence of visual input in blind participants leads to improved auditory spatial perceptual and cognitive skills, the aim in Study IV was to determine, whether blindness modifies the ear advantage in DL. Altogether 180-190 right-handed participants between 5 and 79 years of age were studied in Studies I to III, and in Study IV the performance of 14 blind individuals was compared with that of 129 normally sighted individuals. The results showed that only rightward spatial bias was observed in tasks with intensive attentional load, independent of the type of stimuli (linguistic vs. non-linguistic) or the modality (auditory vs. visual). This multimodal rightward spatial bias probably results from a complex interaction of asymmetrical perceptual, attentional, and/or motor mechanisms. Most importantly, the strength of the rightward spatial bias changed as a function of age and augmented praxis due to sensory deficit. The efficiency of the performance in spatial attention tasks and the ability to overcome the rightward spatial bias increased during childhood, was at its best in young adulthood, and decreased as a function of ageing. Between the ages of 5 and 11 years probably at first develops movement and impulse control, followed by the gradual development of abilities to inhibit distractions and disengage attention. The errors especially in bilateral stimulus conditions suggest that a mild phenomenon resembling extinction can be observed throughout the lifespan, but especially the ability to distribute attention to multiple targets simultaneously decreases in the course of ageing. Blindness enhances the processing of auditory bilateral linguistic stimuli, the ability to overcome a stimulus-driven laterality effect related to speech sound perception, and the ability to direct attention to an appropriate spatial location. It was concluded that the ability to voluntarily suppress and inhibit the multimodal rightward spatial bias changes as a function of age and praxis due to sensory deficit and probably reflects the developmental level of executive functions.

Genetically Determined Hypometabolism in Alzheimer’s Disease and Midlife Risk Factors for Cognitive Impairment

The role of genetic factors in the pathogenesis of Alzheimer’s disease (AD) is not completely understood. In order to improve this understanding, the cerebral glucose metabolism of seven monozygotic and nine dizygotic twin pairs discordant for AD was compared to that of 13 unrelated controls using positron emission tomography (PET). Traditional region of interest analysis revealed no differences between the non-demented dizygotic co-twins and controls. In contrast, in voxel-level and automated region of interest analyses, the non-demented monozygotic co-twins displayed a lower metabolic rate in temporal and parietal cortices as well as in subcortical grey matter structures when compared to controls. Again, no reductions were seen in the non-demented dizygotic co-twins. The reductions seen in the non-demented monozygotic co-twins may indicate a higher genetically mediated risk of AD or genetically mediated hypometabolism possibly rendering them more vulnerable to AD pathogenesis. With no disease modifying treatment available for AD, prevention of dementia is of the utmost importance. A total of 2 165 at least 65 years old twins of the Finnish Twin Cohort with questionnaire data from 1981 participated in a validated telephone interview assessing cognitive function between 1999 and 2007. Those subjects reporting heavy alcohol drinking in 1981 had an elevated cognitive impairment risk over 20 years later compared to light drinkers. In addition, binge drinking was associated with an increased risk even when total alcohol consumption was controlled for, suggesting that binge drinking is an independent risk factor for cognitive impairment. When compared to light drinkers, also non-drinkers had an increased risk of cognitive impairment. Midlife hypertension, obesity and low leisure time physical activity but not hypercholesterolemia were significant risk factors for cognitive impairment. The accumulation of risk factors increased cognitive impairment risk in an additive manner. A previously postulated dementia risk score based on midlife demographic and cardiovascular factors was validated. The risk score was found to well predict cognitive impairment risk, and cognitive impairment risk increased significantly as the score became higher. However, the risk score is not accurate enough for use in the clinic without further testing.

Adsorption of hydrogen sulfide by modified cellulose nano/microcrystals

Hydrogen sulfide is toxic and hazardous pollutant. It has been under great interest for past few years because of all the time tighten environmental regulations and increased interest of mining. Hydrogen sulfide gas originates from mining and wastewater treatment systems have caused death in two cases. It also causes acid rains and corrosion for wastewater pipelines. The aim of this master thesis was to study if chemically modified cellulose nanocrystals could be used as adsorbents to purify hydrogen sulfide out from water and what are the adsorption capacities of these adsorbents. The effects of pH and backgrounds on adsorption capacities of different adsorbents are tested. In theoretical section hydrogen sulfide, its properties and different purification methods are presented. Also analytical detection methods for hydrogen sulfide are presented. Cellulose nano/microcrystals, properties, application and different modification methods are discussed and finally theory of adsorption and modeling of adsorption is shortly discussed. In experimental section different cellulose nanocrystals based adsorbents are prepared and tested at different hydrogen sulfide concentrations and in different conditions. Result of experimental section was that the highest adsorption capacity at one component adsorption had wet MFC/CaCO3. At different pH the adsorption capacities of adsorbents changed quite dramatically. Also change of hydrogen sulfide solution background did have effect on adsorption capacities. Although, when tested adsorbents’ adsorption capacities are compared to those find in literatures, it seems that more development of MFC based adsorbents is needed.

Membrane properties of structurally modified ceramides : effects on lipid lateral distribution and sphingomyelin-interactions in artificial bilayer membranes

Ceramides comprise a class of sphingolipids that exist only in small amounts in cellular membranes, but which have been associated with important roles in cellular signaling processes. The influences that ceramides have on the physical properties of bilayer membranes reach from altered thermodynamical behavior to significant impacts on the molecular order and lateral distribution of membrane lipids. Along with the idea that the membrane physical state could influence the physiological state of a cell, the membrane properties of ceramides have gained increasing interest. Therefore, membrane phenomena related to ceramides have become a subject of intense study both in cellular as well as in artificial membranes. Artificial bilayers, the so called model membranes, are substantially simpler in terms of contents and spatio-temporal variation than actual cellular membranes, and can be used to give detailed information about the properties of individual lipid species in different environments. This thesis focuses on investigating how the different parts of the ceramide molecule, i.e., the N-linked acyl chain, the long-chain sphingoid base and the membrane-water interface region, govern the interactions and lateral distribution of these lipids in bilayer membranes. With the emphasis on ceramide/sphingomyelin(SM)-interactions, the relevance of the size of the SMhead group for the interaction was also studied. Ceramides with methylbranched N-linked acyl chains, varying length sphingoid bases, or methylated 2N (amide-nitrogen) and 3O (C3-hydroxyl) at the interface region, as well as SMs with decreased head group size, were synthesized and their bilayer properties studied by calorimetric and fluorescence spectroscopic techniques. In brief, the results showed that the packing of the ceramide acyl chains was more sensitive to methyl-branching in the mid part than in the distal end of the N-linked chain, and that disrupting the interfacial structure at the amide-nitrogen, as opposed to the C3-hydroxyl, had greater effect on the interlipid interactions of ceramides. Interestingly, it appeared that the bilayer properties of ceramides could be more sensitive to small alterations in the length of the long-chain base than what was previously reported for the N-linked acyl chain. Furthermore, the data indicated that the SM-head group does not strongly influence the interactions between SMs and ceramides. The results in this thesis illustrate the pivotal role of some essential parts of the ceramide molecules in determining their bilayer properties. The thesis provides increased understanding of the molecular aspects of ceramides that possibly affect their functions in biological membranes, and could relate to distinct effects on cell physiology.

From the seeds of rediscovered texts come new fields of inquiry

Kirjallisuusarvostelu

Surface characterization of chemically modified fiber, wood and paper

Inorganic-organic sol-gel hybrid coatings can be used for improving and modifying properties of wood-based materials. By selecting a proper precursor, wood can be made water repellent, decay-, moisture- or UV-resistant. However, to control the barrier properties of sol-gel coatings on wood substrates against moisture uptake and weathering, an understanding of the surface morphology and chemistry of the deposited sol-gel coatings on wood substrates is needed. Mechanical pulp is used in production of wood-containing printing papers. The physical and chemical fiber surface characteristics, as created in the chosen mechanical pulp manufacturing process, play a key role in controlling the properties of the end-use product. A detailed understanding of how process parameters influence fiber surfaces can help improving cost-effectiveness of pulp and paper production. The current work focuses on physico-chemical characterization of modified wood-based materials with surface sensitive analytical tools. The overall objectives were, through advanced microscopy and chemical analysis techniques, (i) to collect versatile information about the surface structures of Norway spruce thermomechanical pulp fiber walls and understand how they are influenced by the selected chemical treatments, and (ii) to clarify the effect of various sol-gel coatings on surface structural and chemical properties of wood-based substrates. A special emphasis was on understanding the effect of sol-gel coatings on the water repellency of modified wood and paper surfaces. In the first part of the work, effects of chemical treatment on micro- and nano-scale surface structure of 1st stage TMP latewood fibers from Norway spruce were investigated. The chemicals applied were buffered sodium oxalate and hydrochloric acid. The outer and the inner fiber wall layers of the untreated and chemically treated fibers were separately analyzed by light microscopy, atomic force microscopy and field-emission scanning electron microscopy. The selected characterization methods enabled the demonstration of the effect of different treatments on the fiber surface structure, both visually and quantitatively. The outer fiber wall areas appeared as intact bands surrounding the fiber and they were clearly rougher than areas of exposed inner fiber wall. The roughness of the outer fiber wall areas increased most in the sodium oxalate treatment. The results indicated formation of more surface pores on the exposed inner fiber wall areas than on the corresponding outer fiber wall areas as a result of the chemical treatments. The hydrochloric acid treatment seemed to increase the surface porosity of the inner wall areas. In the second part of the work, three silane-based sol-gel hybrid coatings were selected in order to improve moisture resistance of wood and paper substrates. The coatings differed from each other in terms of having different alkyl (CH3–, CH3-(CH2)7–) and fluorocarbon (CF3–) chains attached to the trialkoxysilane sol-gel precursor. The sol-gel coatings were deposited by a wet coating method, i.e. spraying or spreading by brush. The effect of solgel coatings on surface structural and chemical properties of wood-based substrates was studied by using advanced surface analyzing tools: atomic force microscopy, X-ray photoelectron spectroscopy and time-of-flight secondary ion spectroscopy. The results show that the applied sol-gel coatings, deposited as thin films or particulate coatings, have different effects on surface characteristics of wood and wood-based materials. The coating which has a long hydrocarbon chain (CH3-(CH2)7–) attached to the silane backbone (octyltriethoxysilane) produced the highest hydrophobicity for wood and wood-based materials.

Bio-ethanol valorization towards C4s including 1-butanol over metal modified alumina and zeolite catalysts

Bio-ethanol has been used as a fuel additive in modern society aimed at reducing CO2-emissions and dependence on oil. However, ethanol is unsuitable as fuel supplement in higher proportions due to its physico-chemical properties. One option to counteract the negative effects is to upgrade ethanol in a continuous fixed bed reactor to more valuable C4 products such as 1-butanol providing chemical similarity with traditional gasoline components. Bio-ethanol based valorization products also have other end-uses than just fuel additives. E.g. 1-butanol and ethyl acetate are well characterised industrial solvents and platform chemicals providing greener alternatives. The modern approach is to apply heterogeneous catalysts in the investigated reactions. The research was concentrated on aluminium oxide (Al2O3) and zeolites that were used as catalysts and catalyst supports. The metals supported (Cu, Ni, Co) gave very different product profiles and, thus, a profound view of different catalyst preparation methods and characterisation techniques was necessary. Additionally, acidity and basicity of the catalyst surface have an important role in determining the product profile. It was observed that ordinary determination of acid strength was not enough to explain all the phenomena e.g. the reaction mechanism. One of the main findings of the thesis is based on the catalytically active site which originates from crystallite structure. As a consequence, the overall evaluation of different by-products and intermediates was carried out by combining the information. Further kinetic analysis was carried out on metal (Cu, Ni, Co) supported self-prepared alumina catalysts. The thesis gives information for further catalyst developments aimed to scale-up towards industrially feasible operations.

Modified nano- and microcellulose based adsorption materials in water treatment

In recent decades, industrial activity growth and increasing water usage worldwide have led to the release of various pollutants, such as toxic heavy metals and nutrients, into the aquatic environment. Modified nanocellulose and microcellulose-based adsorption materials have the potential to remove these contaminants from aqueous solutions. The present research consisted of the preparation of five different nano/microcellulose-based adsorbents, their characterization, the study of adsorption kinetics and isotherms, the determination of adsorption mechanisms, and an evaluation of adsorbents’ regeneration properties. The same well known reactions and modification methods that were used for modifying conventional cellulose also worked for microfibrillated cellulose (MFC). The use of succinic anhydride modified mercerized nanocellulose, and aminosilane and hydroxyapatite modified nanostructured MFC for the removal of heavy metals from aqueous solutions exhibited promising results. Aminosilane, epoxy and hydroxyapatite modified MFC could be used as a promising alternative for H2S removal from aqueous solutions. In addition, new knowledge about the adsorption properties of carbonated hydroxyapatite modified MFC as multifunctional adsorbent for the removal of both cations and anions ions from water was obtained. The maghemite nanoparticles (Fe3O4) modified MFC was found to be a highly promising adsorbent for the removal of As(V) from aqueous solutions due to its magnetic properties, high surface area, and high adsorption capacity . The maximum removal efficiencies of each adsorbent were studied in batch mode. The results of adsorption kinetics indicated very fast removal rates for all the studied pollutants. Modeling of adsorption isotherms and adsorption kinetics using various theoretical models provided information about the adsorbent’s surface properties and the adsorption mechanisms. This knowledge is important for instance, in designing water treatment units/plants. Furthermore, the correspondence between the theory behind the model and properties of the adsorbent as well as adsorption mechanisms were also discussed. On the whole, both the experimental results and theoretical considerations supported the potential applicability of the studied nano/microcellulose-based adsorbents in water treatment applications.

Studies on membrane properties of cholesterol and 3-beta modified sterol analogs

Cholesterol (Chol) is an important lipid in cellular membranes functioning both as a membrane fluidity regulator, permeability regulator and co-factor for some membrane proteins, e.g. G-protein coupled receptors. It also participates in the formation of signaling platforms and gives the membrane more mechanical strenght to prevent osmotic lysis of the cell. The sterol structure is very conserved and already minor structural modifications can completely abolish its membrane functions. The right interaction with adjacent lipids and the preference of certain lipid structures over others are also key factors in determining the membrane properties of cholesterol. Because of the many important properties of cholesterol it is of value to understand the forces and structural properties that govern the membrane behavior of this sterol. In this thesis we have used established fluorescence spectroscopy methods to study the membrane behavior of both cholesterol and some of its 3β-modified analogs. Using several fluorescent probes we have established how the acyl chain order of the two main lipid species, sphingomyelin (SM) and phosphatidylcholine (PC) affect sterol partitioning as well as characterized the membrane properties of 3β-aminocholesterol and cholesteryl phosphocholine. We concluded that cholesterol prefers SM over PC at equal acyl chain order, indicating that other structural properties besides the acyl chain order are important for sphingomyelin-sterol interactions. A positive charge at the 3β position only caused minor changes in the sterol membrane behavior compared to cholesterol. A large phosphocholine head group caused a disruption in membrane packing together with other membrane lipids with large head groups, but was also able to form stable fluid bilayers together with ceramide and cholesterol. The Ability of the large head group sterol to form bilayers together with ceramide was further explored in the last paper where cholesteryl phosphocholine/ceramide (Chol-PC/Cer) complexes were successfully used to transfer ceramide into cultured cells.

Hävittäjäohjaajan kognitiivisen kuormituksen tason mittaaminen NASA-Task Load Index ja Modified Cooper-Harper -mittareilla F/A-18 virtuaalisimulaattorissa

F/A-18-monitoimihävittäjän ohjaajan tehtävän kognitiiviset vaatimukset ovat korkeat. Kognitiivisen kuormituksen taso vaikuttaa hävittäjäohjaajan suoritustasoon ja subjektiivisiin tun-temuksiin. Yerkesin ja Dodsonin periaatteen mukaisesti erittäin matala tai erittäin korkea kuormituksen taso laskee suoritustasoa. Optimaalinen kuormituksen taso ja suoritustaso saa-vutetaan jossain ääripäiden välillä. Hävittäjäohjaajan kognitiivisen kuormituksen tasoon vaikuttaa lentotehtävän suorittamiseen vaadittava henkinen ponnistelu. Vaadittavan ponnistelun taso riippuu tehtävien vaatimustasosta ja määrästä, tehtäviin käytettävissä olevasta ajasta sekä yksilöllisistä ominaisuuksista. Tutkimuksessa mitattiin kognitiivisen kuormituksen tasoa subjektiivisen arvioinnin menetelmällä NASA-TLX (National Aeronautics and Space Administration - Task Load Index) ja MCH (Modified Cooper-Harper) -mittareilla. Tutkimuksessa selvitettiin mittareiden havaintoarvojen muutosta, sensitiivisyyttä ja yhdenmukaisuutta kognitiivisen kuormituksen tason muuttuessa. Tutkimuksen mittauksiin osallistui 35 Suomen ilmavoimien aktiivisessa palveluksessa olevaa F/A-18-monitoimihävittäjäohjaajaa. Koehenkilöiden lentotuntien keskiarvo F/A-18-monitoimihävittäjällä oli 598 tuntia ja keskihajonta 445 tuntia. Koehenkilöiden tehtävänä oli lentää F/A-18-virtuaalisimulaattorilla 11 ILS (Instrument Landing System) -mittarilähestymistä eri aloitusetäisyyksiltä kiitotien kynnyksestä. Kognitiivisesti kuormitta-van mittarilähestymistehtävän aikana kuormituksen tasoa nostettiin lisätehtävillä ja vähentä-mällä tehtäviin käytettävissä olevaa aikaa. Koehenkilöitä pyydettiin ponnistelemaan mahdollisimman paljon tehtävien suorittamisen aikana hyvän suoritustason ylläpitämiseksi. Tulosten perusteella mittareiden havaintoarvot muuttuivat kognitiivisen kuormituksen tason muuttuessa. Käytettävissä olevan ajan vaikutus kognitiivisen kuormituksen tasoon oli tilastollisesti erittäin merkitsevä. Mittarit olivat sensitiivisiä kognitiivisen kuormituksen tason muutokselle ja antoivat yhdenmukaisia havaintoarvoja.

Analytics for the modified kraft pulps

Tämän diplomityön tavoitteena on kehittää sopiva analyyttinen menetelmä muokatun kraft-sellukuidun substituutioasteen (DS) kvantitatiivista määrittämistä varten. Muokkauksella tarkoitetaan tässä yhteydessä joko kovalenttisesti tai adsorption avulla tapahtuvaa molekyylin kiinnittymistä sellukuidun pinnalle. Työn kirjallisuusosuudessa käsitellään lyhyesti eri muokkaustapoja ja yhdisteitä joiden avulla voidaan saavuttaa haluttuja ominaisuuksia sellusta valmistetuille lopputuotteille. Lisäksi kirjallisuusosuudessa käydään läpi käyttötarkoitukseen soveltuvimpia suoria ja epäsuoria analyysimenetelmiä. Analyysimenetelmistä kaikkein lupaavimpia testattiin työn kokeellisessa osassa. Diplomityön kokeellisessa osassa keskityttiin kehittämään muokatulle sellulle kvantitatiivista menetelmää DS:n määrittämiseksi Fourier-muunnos infrapuna-vaimennettu kokonaisheijastus (FTIR-ATR) spektrometrillä. Kirjallisuuskatsauksessa ei löytynyt yhtään dokumentoitua tutkimusta, jossa FTIR-ATR menetelmää olisi käytetty muokatun sellukuidun kvantitatiiviseen tutkimukseen. Muiden analyysimenetelmien, kuten alkuaineanalyysin, termogravimetrisen analyysin (TGA) ja valomikroskopian avulla pyrittiin tuottamaan lisätietoa muokkauksesta. Kvantitatiivisen FTIR-ATR menetelmän kehitykseen käytetyt muokatut sellukuidut olivat selluloosa-asetaattia ja selluloosa betainaattia. Saatujen tulosten perusteella muokattujen sulfiitti- ja kraft sellukuitujen DS:n kvantitatiivinen määrittäminen on mahdollista FTIR-ATR menetelmällä. Vähäinen kalibrointipisteiden määrä vaikeutti tarkan analyysimenetelmän tekemistä. Kehitetyn menetelmän suurimpina ongelmina olivat kiinteiden näytteiden heterogeenisyys sekä mahdollisten epäpuhtauksien tunnistaminen. Jatkotutkimusten avulla kehitettyä menetelmää on kuitenkin mahdollista käyttää muokattujen sellukuitujen jatkuvaan analysointiin selluteollisuudessa.

A modified nominal stress method for fatigue assessment of steel plates with thermally cut edges

Thermal cutting methods, are commonly used in the manufacture of metal parts. Thermal cutting processes separate materials by using heat. The process can be done with or without a stream of cutting oxygen. Common processes are Oxygen, plasma and laser cutting. It depends on the application and material which cutting method is used. Numerically-controlled thermal cutting is a cost-effective way of prefabricating components. One design aim is to minimize the number of work steps in order to increase competitiveness. This has resulted in the holes and openings in plate parts manufactured today being made using thermal cutting methods. This is a problem from the fatigue life perspective because there is local detail in the as-welded state that causes a rise in stress in a local area of the plate. In a case where the static utilization of a net section is full used, the calculated linear local stresses and stress ranges are often over 2 times the material yield strength. The shakedown criteria are exceeded. Fatigue life assessment of flame-cut details is commonly based on the nominal stress method. For welded details, design standards and instructions provide more accurate and flexible methods, e.g. a hot-spot method, but these methods are not universally applied to flame cut edges. Some of the fatigue tests of flame cut edges in the laboratory indicated that fatigue life estimations based on the standard nominal stress method can give quite a conservative fatigue life estimate in cases where a high notch factor was present. This is an undesirable phenomenon and it limits the potential for minimizing structure size and total costs. A new calculation method is introduced to improve the accuracy of the theoretical fatigue life prediction method of a flame cut edge with a high stress concentration factor. Simple equations were derived by using laboratory fatigue test results, which are published in this work. The proposed method is called the modified FAT method (FATmod). The method takes into account the residual stress state, surface quality, material strength class and true stress ratio in the critical place.