Browsing by Title
Now showing items 4610-4629 of 33005
-
(2020)Taustaa: Pään ja kaulan alueen syövät ovat tiettyjen sijaintikohtien osalta melko huonoennusteisia. Hoitotuloksia yritetään parantaa kehittämällä hoitomuotoja sekä lyhentämällä sekä diagnostista että hoitoviivettä. Lisäksi pyritään vaikuttamaan muun muassa etiologisiin tekijöihin. Näiden syöpien tunnettuja riskitekijöitä ovat alkoholin suurkulutus, runsas tupakointi sekä ihmisen papilloomavirusinfektio. D-vitamiinitason on todettu aiemmissa havainnoivissa tutkimuksissa assosioituvan käänteisesti muun muassa yleisen syöpäriskin sekä suolistosyöpäriskin kanssa. Kirjallisuudessa on tähän liittyen tutkimuksia myös pään ja kaulan alueen syövän suhteen. Tavoitteet: Systemaattisen katsauksen tavoitteena oli selvittää nykyinen käsitys D-vitamiinin roolista pään ja kaulan alueen syövälle altistavana tekijänä sekä D-vitamiinipitoisuuden vaikutuksesta kyseisten syöpien hoitotulokseen. Systemaattinen katsaus tehtiin Ovid Medline -, Pubmed-, ja Scopus-tietokannoissa. Katsaukseen hyväksyttiin tutkimukset, joissa tutkittavat sairastivat pään ja kaulan alueen syöpää sekä heiltä oli mitattu 25-OH-D₂-pitoisuudet. Tutkimukset rajattiin englanninkielisiin julkaisuihin. Valikoitujen tutkimusten ulkopuolelle suljettiin syövän hoitoon sekä eläinkokeisiin keskittyvät ja solutason tutkimukset. Tulokset: Tarkasteltuja tutkimuksia oli 276, joista valikoitui lopulta 13 tutkimusta. Pään ja kaulan alueen syöpiä sairastavilla potilailla on selkeästi matalammat D-vitamiinipitoisuudet terveisiin verrokkeihin verrattuna. D-vitamiinin yhteydestä syöpäriskiin löytyi ristiriitaisia tuloksia, sekä D-vitamiinin roolia puoltavia että kumoavia tutkimuksia oli yhtä paljon. D-vitamiinilla ei havaittu yhteyttä kuolleisuuteen, mutta sen epäillään assosioituvan pidemmän hoidonjälkeisen elossaoloajan kanssa sekä suojaavan mukosiitilta ja lihaskadolta. Johtopäätelmät: Tulosten perusteella D-vitamiinin roolista on tähän mennessä hyvin ristiriitaisia tuloksia pään ja kaulan alueen syöpien altistavana tekijänä, eikä pelkkien havainnoivien tutkimusten perusteella voida päätellä syy-yhteyksiä. Tutkielman aiheesta tarvitaan satunnaistettuja kontrolloituja tutkimuksia, jotta saadaan vahvempaa näyttöä ja voidaan tarvittaessa luoda uusia ravintosuosituksia tämän alueen syöpäpotilaille.
-
(2010)Johdanto: Ikääntyessä iholla tapahtuva D-vitamiininmuodostus heikkenee ja lihakset ja luusto haurastuvat. Heikko lihaskunto on yhteydessä kaatumisriskiin, ja kaatuminen on yleisin syy vanhusten murtumiin. Monissa tutkimuksissa on osoitettu, että luustovaikutustensa lisäksi D-vitamiinilla on vaikutuksia luurankolihakseen. D-vitamiinihoidon on osoitettu vähentävän kaatumisia, mikä saattaa osin selittyä parantuneen tasapainon kautta. Joissakin tutkimuksissa on havaittu heikko tilastollinen yhteys Dvitamiinin ja kroonisen kivun välillä. D-vitamiinin puutokseen liitettyjä kipuja on esitetty luustoperäisiksi, mutta D-vitamiinin lihasvaikutukset huomioiden ne saattavat olla ainakin osin lihasperäisiä. Tavoitteet: Tämän poikkileikkaustutkimuksen tavoitteena oli tutkia, onko seerumin 25-hydroksi-Dvitamiinipitoisuus (25OHD) yhteydessä lihastoimintoihin itsenäisesti kotona asuvilla reumatauteja sairastavilla yli 50-vuotiailla. Hypoteesina oli, että D-vitamiinin puutos on yhteydessä heikentyneisiin neuromuskulaarisiin lihastoimintoihin, joita tässä tutkimuksessa mitattiin tasapainon perusteella. Aineisto ja menetelmät: Tutkimukseen rekrytoitiin yli 50-vuotiaita, koska tässä kohderyhmässä lihastoimintojen heikentymisen ja D-vitamiinin puutoksen odotettiin olevan yleisiä. Tutkittavien tuli kuitenkin olla kohtalaisen hyväkuntoisia, jotta he jaksaisivat fyysiset testit ja tutkimuksen mahdollisesti aiheuttaman henkisen rasituksen. Siksi lihastoimintojen ongelmia kuvaamaan valittiin polymyalgia rheumaticaa sairastavia, itsenäisesti kotona asuvia ihmisiä. Tutkimukseen osallistui myös joitakin yli 50- vuotiaita fibromyalgiaa ja nivelreumaa sairastavia henkilöitä. Seerumin 25OHD-pitoisuus määritettiin EIA-menetelmällä (IDS, UK). D-vitamiinin yhteyttä tutkittiin tasapainoon (Rombergin vakio tasapainolevyllä) ja lihasvoimaan (puristusvoima molempien käsien parhaan tuloksen keskiarvona, jalkojen nopeusvoima hyppylevyllä), kipuun ja toimintakykyyn. Tilastomenetelminä käytettiin ristiintaulukointia, t-testiä, lineaarista regressiota, logistista regressiota ja Pearsonin korrelaatiota. Tulokset: Tutkimukseen osallistui 47 henkilöä, joista viisi oli miehiä. Potilaat olivat 53-81 -vuotiaita (keski-ikä 70 v) ja hieman ylipainoisia (BMI 28). 25OHD oli keskimäärin 64 nmol/l. Ravitsemustila oli keskimäärin hyvä (MNA-pisteet 24). 25OHD oli alle 50 nmol/l 32 %:lla ja vastaavasti alle 75 nmol/l 74 %:lla tutkittavista. Potilaista 83 % käytti D-vitamiinivalmistetta. 25OHD korreloi positiivisesti ravitsemustilan (MNA) ja käänteisesti tasapainon ja kiputiheyden kanssa. 25OHD, ikä, sukupuoli ja MNA-pisteet selittivät 13,9 % (adjusted r2) huojunnan vaihtelusta ja 14,5 % (r2 Cox & Snell) kiputiheyden vaihtelusta. Ainoastaan 25OHD-pitoisuudella oli tilastollisesti merkitsevä itsenäinen selitysosuus huojuntaan (p = 0,024) ja kiputiheyteen (p = 0,045). Niillä, joilla 25OHD oli vähintään 75 nmol/l, oli 83 % pienempi riski kärsiä päivittäisestä kivusta kuin niillä, joilla 25OHD-pitoisuus oli alle 75 nmol/l. Lihasvoimalla, lihasmassalla ja kivun voimakkuudella ei havaittu yhteyttä D-vitamiinistatukseen. Johtopäätökset: Tässä tutkimuksessa reumatauteja sairastavien yli 50-vuotiaiden potilaiden matalat 25OHD-pitoisuudet olivat yhteydessä tasapainovaikeuksiin ja päivittäisiin kipuihin. Lihasmassa ja lihasvoima eivät olleet yhteydessä D-vitamiinistatukseen. Löydösten pohjalta olisi tulevaisuudessa tarpeen tutkia tarkemmin D-vitamiinikorvaushoidon vaikutuksia tasapainomittareihin ja kiputiheyteen.
-
(2015)Målet med denna studie var att undersöka sambandet mellan D-vitaminhalten i blodet och riskfaktorer för det metabola syndromet. Dessa faktorer är hypertension, bukfetma, hyperglykemi och dyslipidemi. Det har i många studier framkommit ett samband mellan dessa och en D-vitaminhalt på under 50 nmol/l. I denna studie analyseras att material som består av en D-vitaminmätning från år 2007 och mätning av de olika riskfaktorerna från åren 2012-2013. Materialet är en del av Helsinki Birth Cohort Study (HBCS) materialet. Analysen av materialet visar att D-vitaminbrist med stor sannolikhet är kopplat till det metabola syndromets olika riskfaktorer.
-
(2017)Detta arbete är en litteraturstudie vars syfte är att undersöka vetenskapliga artiklar för att ta reda på hur D-vitamin påverkar parodontala vävnaden och om det finns belägg för att D-vitamin har en positiv effekt på parodontala hälsan. D-vitamin är ett prohormon som reglerar immunförsvaret och kroppens absorption av kalcium och fosfor. Parodontit är en kronisk inflammatorisk sjukdom som bryter ner tänders stödjevävnad samt käkarnas alveolarben och ger upphov till tandlossning. Denna studie letar i den vetenskapliga litteraturen om det finns kausalitets samband mellan D-vitaminbrist och parodontit eftersom båda tillstånden är skelettala och inflammatoriska sjukdomar. Både parodontit och D-vitaminbrist är vanligt förekommande i den finska befolkningen. Detta arbete är baserat på litteratursökning i PubMed, Melinda, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews och internet hemsidan terveysportti.fi. Litteraturgranskningens resultat är att sambandet mellan D-vitamin halten i serum och parodontal infektion är svag. Populations studier visar att D-vitamin brist har försumbar gynnsam effekt på parodontal infektion. Däremot har D-vitamin i teorin positiv effekt på alveolarbenets mineraldensitet och immunförsvar. Denna studie visar att D-vitaminbrist kan vara orsaken till ett svagt parodontologiskt behandlingssvar om andra starkare parodontologiska riskfaktorer är uteslutna.
-
(2023)This thesis deals with how meaningful landscapes are created through experiences in everyday life. As European governments seek to implement the European Landscape Convention into policy, landscapes and their relationships with its inhabitants must be understood on a more fundamental level. In addition to understanding how meaningful landscapes are created, this thesis also sheds light on the relationships between landscapes and social and societal change. Landscape here is then more than a simple scenery or representation; it is temporal and dynamic and the context of our dwelling. Two related but different landscapes in the Southwest Finland archipelago are studied through the application of the phenomenological approach. The first centres around the former ironworks town of Dalsbruk, including the surrounding region of Dragsfjärd. The second centres around Hitis village in the Hitis archipelago. Special attention is also given to the Purunpää nature conservation area in Dragsfjärd as it relates to changing attitudes regarding the landscape. Material collected during two months of fieldwork includes interviews with 11 people, informal discussions, first-person observations, and archival materials in the form of historical photographs and factory magazines from Dalsbruk provided by the town’s ironworks museum. By combining the dwelling perspective at the core of the phenomenological approach to landscapes with a historical, political and environmental context in the form of an environmental history of the region, the process of the landscape’s becoming is revealed and the various meanings that it holds for people are illuminated. Not only has the landscape had an enormous effect on where settlements have been founded, it has also shaped the livelihoods of its inhabitants. At the same time generation after another has left their mark on the landscape, shaping the way people today relate to it. This study covers how the physical landscape embodies the social hierarchies of previous generations as a materialisation of their dwelling. It deals with how stories and place names make landscapes and places meaningful for the local population by evoking a shared history and identity of a place. Additionally, subjective memories and experiences affect how people perceive the landscape and how different people find it to be meaningful. This has an impact on how both the past and future of a place or landscape is imagined, leading to the conclusion that they are always contested. Landscapes in the Archipelago Sea region are revealed to be filled with values and meanings far beyond the aesthetic.
-
(2014)Goals. The purpose of this study was to examine, whether the dynamicity of pitch has an effect on duration perception in synthetic auditory stimuli and if the effect, if observed, is dependent on first language. Furthermore, it was of interest to see, if mother tongue has an effect to the way static auditory stimuli are perceived. The effect of dynamic pitch on duration perception is a topic little researched and the results obtained are contradictory which is why this thesis is relevant. The duration discrimination abilities of Finnish and Chinese people have not been compared to each other before, so this thesis has some new information to offer about the perception of duration. Method. The research consisted of different kinds of behavioral tests, which measured the ability to discriminate the differences between two auditory stimuli. Two alternative forced choice method was used in all the experiments. In the first experiment the discrimination ability was measured in stimuli which only differed in duration. In the second experiment the stimuli were dynamic and in the third experiment the stimuli only differed in pitch. There were altogether 30 subjects, 15 of which Finnish and 15 Mandarin Chinese speakers. The answers of the subjects were analyzed with logistic linear regression models fit for multiple variables. Results and conclusions. According to the results mother tongue does have an effect to the answers given and the dynamicity of pitch does lengthen the perceived duration. The effect of language background was also apparent in static stimuli although the significance was marginal. It is nevertheless possible to conclude from the results that the perception of duration between Finnish and Mandarin Chinese speakers does differ from each other. The research on the effect of dynamic pitch on duration perception needs to be continued. Further research is especially needed over the conventions of perceiving natural auditory stimuli and the perception of pitch when tied to a linguistic context.
-
(2017)Peliäänet ovat pelaajalle tarkoitettuja ääniä, joita peliohjelmisto toistaa suorituksen aikana. Työssä tarkastellaan ja arvioidaan erilaisten peliäänien kehityksen piirteitä ja vertaillaan mahdollisia ratkaisumenetelmiä keskenään. Työssä hyödynnettiin kirjallisia lähteitä ja työn osana toteutettiin yksinkertainen peliäänimoottori. Moottorin käytön helppoutta eri skenaarioissa arvioitiin sanallisesti. Vertailu toteutusmentelmien välillä suoritettiin käyttäen lähteistä löytyvää tietoa, sekä kokemuspohjaa olemassa olevien ratkaisujen käytöstä ja peliäänimoottorin toteutuksesta. Vertailussa todettiin eri ratkaisumenetelmien sopivan tiettyyn pelinkehitystilanteisiin paremmin ja toisiin huonommin. Itse kehitettävät pelimoottoriratkaisut sopivat hyvin tilanteisiin, joissa kehitettävä alusta on suorituskyvyltään rajattu tai peliäänimoottorin vaatimukset edellyttävät toimintoja, joita olemassa olevissa ratkaisuissa ei ole. Vastaavasti olemassaolevat ratkaisut sopivat hyvin suurempiin projekteihin, joissa peliäänien avulla tavoitellaan realistisuutta
-
(2023)Maatalouden rakennemuutos ja liiketoimintaympäristön muuttuminen edellyttävät nykypäivän maatiloilta uudenlaisia kyvykkyyksiä. Miksi toiset tilat selviävät muutoksessa paremmin kuin toiset tilat? Strategiatutkimus lähestyy kysymystä käyttäen selittäjänä dynaamisten kyvykkyyksien teoriaa. Kyvykkyyksien avulla selvitetään, miten maatilayrittäjä aistii muutoksen liiketoimintaympäristössään ja miten hän tarttuu havaittuun muutokseen miettien tilansa jatkuvaa uudistamista. Tutkimuksessa haastateltiin seitsemää yrittäjää, joiden päätuotantosuuntana oli emolehmät. Yrittäjät olivat päätoimisia yrittäjiä tai emolehmätuotanto oli eriytetty tilan muista toiminnoista, joten tuotannon kannattavuuden arvioiminen oli konkreettisempaa. Teemahaastatteluna toteutetut haastattelut tehtiin kyselylomakkeen pohjalta, joka oli muotoiltu Teecen (2007b) ajatusten perustalle dynaamisista kyvykkyyksistä. Miten tunnistetaan, tartutaan sekä otetaan muutos käytäntöön suomalaisilla emolehmätiloilla. Yrittäjän päätöksiin tutkimuksessa vaikuttivat tilan resurssit, strategia sekä yrittäjän oma arvomaailma tilan historiaan kytkettynä. Yrittäjät olivat kyllä avoimia uudelle, keräsivät tietoa toimintaympäristöstään sisä- ja ulkopuolelta mutta käytännön toteutuksen suhteen monella tilalla oli parannettavaa. Pitkän- ja lyhyen aikavälin suunnitelmia olisi hyvä tehdä myös paperille asti. Tavoitteena tutkielmassa ei ole tehdä yleistettäviä päätelmiä emolehmätuotannon johtamistavoista. Tulosten avulla voidaan havainnoida vain, miten pieni määrä emolehmätiloja tekee päätöksiä tuotantonsa suhteen. Tulevaisuuden tutkimuksissa tulisikin perehtyä laajemmin dynaamisten kyvykkyyksien vaikutuksiin yleensä maatilojen johtamisessa.
-
(2017)This thesis summarises the adaptive bitrate streaming technology called Dynamic Adaptive Streaming over HTTP, also named as MPEG-DASH, as it is developed by the Moving Picture Experts Group. The thesis introduces and summarises MPEG-DASH standard, including the content of the standard, Profiles from MPEG and DASH Industry Forum, and an evaluation of the standard. The thesis then analyses the MPEG-DASH system and provides related research papers. It is organized into three different parts based on the workflow of the whole system, including the hosted Media Presentation Description file and video Segments in server, network infrastructures and DASH clients. In the end, the thesis discusses about the adoptions of the MPEG-DASH system in different industries, including Broadband, Broadcast, Mobile and 3D.
-
(2022)Sulfuric acid has a central role in atmospheric chemistry, as it is considered to have a significant contribution in cloud formation and acid rain. In the gas phase, hydrolysis of SO3 catalysed by a single water molecule is contemplated to be the primary pathway to form sulfuric acid in the atmosphere. However, in previous studies it has been calculated that when the hydrolysis reaction is catalysed by a formic acid (FA) molecule, the potential energy barrier is significantly lower than for the water molecule catalysed reaction. In this work, the role of dynamic and steric effects for both reactions were studied through ab initio molecular dynamics (AIMD) collision simulations. The simulations were done by either colliding FA or a water molecule with SO3-H2O complex or a water dimer with the SO3-molecule. Altogether 230 trajectories were calculated at PBE/6-311+G(2pd,2df) level of theory, 70 for the collision of a water dimer and SO3, and 80 for both the collision of a water molecule or FA with SO3-H2O. The collision of FA with SO3-H2O led to the formation of sulfuric acid in 5 % of the simulations, whereas for the collision of a water molecule with SO3-H2O the reaction does not occur within the simulation time. Additionally, the SO3-H2O-FA pre-reactive complex formed in the simulations is shown to be more stable, most likely due to a less constrained ring structure. The collision of a water dimer with SO3 most commonly leads to the formation of SO3-H2O, and either sticking or evading of the second water molecule of the dimer. Based on the simulation results, strictly in terms of dynamic and steric effects, the FA-catalysed mechanism seems to be favored over the H2O-catalysed one
-
(2024)Food waste is a global problem which has economic, environmental, and social impacts. More than 30% of food intended for human consumption is lost or wasted annually which amounts to a billion tons of food and $ 940 billion in economic losses every year. Traditional "best before" dates and "use by" dates cause confusion among the consumers. The static nature of traditional best before dates and use by dates and absence of any digital label cause enormous amount of food waste. Insufficient consumer knowledge about several types of labeling dates causes rejections of expired food products which are still safe for human consumption. The aim of this research is to understand how consumers would select and evaluate food products that are close to the best-before day and when the food is expired but the sensors would say it is still good. In this research, a survey is conducted to see if the dynamic best before label sensor creates any additional value to the consumers related to the expiry date. Choice-based conjoint (CBC) analysis is used to determine how consumers value the dynamic best before label. The result of the study shows that consumers are more likely to buy a product if dynamic label is used in the packaging. The results of initial research are quite promising, but future researchers can study further by increasing samples sizes to get more data and by calculating willingness to pay (WTP). Finnish food companies can also investigate further to see how the introduction of dynamic labelling system works in practice in Finland and contribute to fight against food waste.
-
(2022)Currency risk is an important yet neglected consideration for investors holding internationally diversified investment portfolios. The foreign exchange market is an extremely liquid and efficient market, with daily transaction volumes exceeding the equivalent of several trillion euros. International investors have to decide upon the level of exposure on various currency risks typically by hedging some or all of the underlying currency exposure with currency derivative contracts. The currency overlay refers to an approach where the aggregate currency exposure from the investment portfolio is managed with a separate derivatives strategy, aimed at improving the overall portfolio’s risk adjusted returns. In this thesis, we develop a novel systematic, data-driven approach to manage the currency risk of investors holding diversified bond-equity portfolios, accounting for both risk minimization and expected returns maximization objectives on the portfolio level. The model is based upon modern portfolio theory, leveraging findings from prior literature in covariance modelling and expected currency returns. The focus of this thesis is in ensuring efficient risk diversification through the use of accurate covariance estimates fed by high-frequency data on exchange rates, bonds and equity indexes. As to the expected returns estimate, we identify purchasing power parity (PPP) and carry signals as credible alternatives to improve the expected risk-adjusted returns of the strategy. A block bootstrap simulation methodology is used to conduct empirical tests on different specifications of the developed dynamic overlay model. We find that dynamic risk-minimizing strategies significantly decrease portfolio risk relative to either unhedged or fully hedged portfolios. Using high-freqency data based returns covariance estimates is likely to improve portfolio diversification relative to a simple daily data-based estimator. The empirical results are much less clear in terms of risk adjusted returns. We find tentative evidence that the tested dynamic strategies improve risk adjusted returns. Due to the limited data sample used in this study, the findings regarding expected returns are highly uncertain. Nevertheless, considering evidence from prior research covering much longer time-horizons, we expect that both the risk-minimizing and returns maximizing components of the developed model are likely to improve portfolio-level risk adjusted returns. We recommend using the developed model as an input to support the currency risk management decision for investors with globally diversified investment portfolios, along with other relevant considerations such as solvency or discretionary market views.
-
(2011)In recent years, thanks to developments in information technology, large-dimensional datasets have been increasingly available. Researchers now have access to thousands of economic series and the information contained in them can be used to create accurate forecasts and to test economic theories. To exploit this large amount of information, researchers and policymakers need an appropriate econometric model.Usual time series models, vector autoregression for example, cannot incorporate more than a few variables. There are two ways to solve this problem: use variable selection procedures or gather the information contained in the series to create an index model. This thesis focuses on one of the most widespread index model, the dynamic factor model (the theory behind this model, based on previous literature, is the core of the first part of this study), and its use in forecasting Finnish macroeconomic indicators (which is the focus of the second part of the thesis). In particular, I forecast economic activity indicators (e.g. GDP) and price indicators (e.g. consumer price index), from 3 large Finnish datasets. The first dataset contains a large series of aggregated data obtained from the Statistics Finland database. The second dataset is composed by economic indicators from Bank of Finland. The last dataset is formed by disaggregated data from Statistic Finland, which I call micro dataset. The forecasts are computed following a two steps procedure: in the first step I estimate a set of common factors from the original dataset. The second step consists in formulating forecasting equations including the factors extracted previously. The predictions are evaluated using relative mean squared forecast error, where the benchmark model is a univariate autoregressive model. The results are dataset-dependent. The forecasts based on factor models are very accurate for the first dataset (the Statistics Finland one), while they are considerably worse for the Bank of Finland dataset. The forecasts derived from the micro dataset are still good, but less accurate than the ones obtained in the first case. This work leads to multiple research developments. The results here obtained can be replicated for longer datasets. The non-aggregated data can be represented in an even more disaggregated form (firm level). Finally, the use of the micro data, one of the major contributions of this thesis, can be useful in the imputation of missing values and the creation of flash estimates of macroeconomic indicator (nowcasting).
-
(2014)Operating System-level Virtualization is virtualization technology based on running multiple isolated userspace instances, commonly referred to as containers, on top of a single operating system kernel. The fundamental difference compared to traditional virtualization is that the targets of virtualization in OS-level virtualization are kernel resources, not hardware. OS-level virtualization is used to implement Bring Your Own Device (BYOD) policies on contemporary mobile platforms. Current commercial BYOD solutions, however, don't allow for applications to be containerized dynamically upon user request. The ability to do so would greatly improve the flexibility and usability of such schemes. In this work we study if existing OS-level virtualization features in the Linux kernel can meet the needs of use cases reliant on such dynamic isolation. We present the design and implementation of a prototype which allows applications in dynamic isolated domains to be migrated from one device to another. Our design fits together with security features in the Linux kernel, allowing the security policy influenced by user decisions to be migrated along with the application. The deployability of the design is improved by basing the solution on functionality already available in the mainline Linux kernel. Our evaluation shows that the OS-level virtualization features in the Linux kernel indeed allow applications to be isolated in a dynamic fashion, although known gaps in the compartmentalization of kernel resources require trade-offs between the security and interoperability to be made in the design of such containers.
-
(2021)WebAssembly (WASM) is a binary instruction format for a stack-based virtual machine originally designed for the Web but also capable of being run on outside of the browser contexts. The WASM binary format is designed to be fast to transfer, load and execute. WASM programs are designed to be safe to execute by running them in a memory safe sandboxed environment. Combining dynamic linking with WebAssembly could allow the creation of adaptive modular applications that are cross-platform and sandboxed but still fast to execute and load. This thesis explores implementing dynamic linking in WebAssembly. Two artifacts are presented: a dynamic linking runtime prototype which exposes a POSIX-like host function interface for modules and an Android GUI interfacing prototype built on top of the runtime. In addition the results of measurements which were performed on both artefacts are presented. Dynamic linking does improve the memory usage and the startup time of applications when only some modules are needed. However if all modules are needed immediately then dynamic linked applications. perform worse than statically linked applications. Based on the results, dynamically linking WebAssembly modules could be a viable technology for PC and Android. The poor performance of A Raspberry Pi in the measurements indicates that dynamic linking might not be viable for resource contrained system especially if applications are performance critical.
-
(2024)Wood construction has been increasing globally and engineered wood products (EWPs), such as Cross Laminated Timber (CLT), have had a major part in it. Increasing wood construction could help decrease the carbon footprint of the construction sector, since wood can be sustainably sourced and wood products store carbon. To use wood in construction in a more extensive way, its properties and behaviour as a construction material must be known. Wood has many properties of which moisture has a great impact on other properties, such as strength. Too high moisture can also cause problems, such as fungal growth, on its own. Therefore, it is important to monitor the moisture levels and understand the factors affecting them. In this study, the wood moisture content (MC) of CLT wall elements was monitored with resistance-based moisture meters from the manufacturing plant, through transportation and construction of a building at the Hyytiälä forestry station in Finland. There were sensors in five locations around the building and they all measured MC in three different depths inside the wall. The objective was to see how, where and when did the MC change within the CLT elements. The data was analysed with statistical tests and presented through various types of graphs. The results showed that variation within the data was large, approximately from 8% to 16%. On average the MC was at its highest near the surface of the CLT elements, after the protective canopy was removed. Two measuring locations on the opposite sides of the building had consistently higher MC than in the other measuring locations. The MC stayed below FSP (Fibre saturation point) throughout the monitoring period and, therefore, the risk for moisture induced damage is very low.
-
(2013)The subject of our research is the behavior of the economy in response to monetary and technology shocks. To understand these issues we use a Dynamic Money-in-the-Utility-Function framework. We implement a non-separable property of the utility function that implies non-neutrality of real money balances. We construct a toy theoretic model with two representative agents who maximize their functions subject to constraints. We analytically solve the model using a method of log-linearization around the steady state and obtain the system of linear equations. We analyze the response of economic equilibrium with respect to implemented shocks using a method of undetermined coefficients and solve a system of linear difference expectation equations. In addition to analytical solution we also present Impulse Response Functions of the model. We compute the impacts of monetary and technology shocks on the model and find that in case of a positive monetary shock expected inflation effect dominates the liquidity effect, while in case of a positive productivity shock income effect dominates substitution effect. The findings regarding the impact of a technology shock contradict the theory of real business cycles that predicts the domination of substitution effect over the income effect
-
(2020)We consider a so-called principal-agent problem, where our aim is to construct an optimal contract that maximises utilities for the contractor, the principal, and for the effort-exerting party, the agent. In our setting, the time-horizon of the contract is infinite, and the agent receives a continuously paid compensation for exerting effort. Our main goal is to establish a problem introduced in Sannikov (2008) and characterise an optimal contract by restricting the menu of feasible contracts, an approach inspired by Cvitanic et. al. (2018) We begin with an extensive literature review, where we review the continuous-time principal-agent problems and further motivate the scope of this thesis. We start from the notable article Holmström et. al. (1987), and we progress towards the works Williams (2008), Sannikov (2008) and Cvitanic et. al. (2018) Following the review, we construct the problem and lay the mathematical foundations for it. We focus on a new benchmark setting, adapted from Sannikov (2008) and Cvitanic et. al. (2018). We first define the so-called controlled state equation, and construct the canonical probability space. Then, we introduce then impose few assumptions regarding the core concepts, and identify the problems of the agent and the principal and characterise their objective functions. After characterising the problem, we characterise the optimal contract and show that the optimal contract maximises the principal's profit. We characterise the difference function of Sannikov (2008) to the agent's optimisation problem, and then follow Cvitanic et. al. (2018) on the reduction of the problem. The reduction is done by restricting the possible menu of contracts and thus reduce the non-standard problem to a dynamic programming problem. We introduce the corresponding Hamiltonian functionals, together with the value functions to the both principal and the agent. Furthermore, we introduce a family restricted processes, which we show to characterise the optimal contract. We finish with showing that the optimal contract exists even with the notion of retirement. Having completed the main technical contribution, that is, having solved for the optimal contract, we briefly discuss the results and their implications against previous literature. Additionally, we discuss the possible extensions to our research.
-
(2016)Dynamic scoring is an approach, which strives to take into account the effects that public policy changes and changes in the law have on the macroeconomic variables. Scoring is an estimate of the effects the policy change is expected to bring. Compared to the traditional approach, dynamic scoring offers more information of the effects, but does this with increased uncertainty. In their paper “Dynamic scoring: A back-of-the-envelope guide” (2006) N. Gregory Mankiw and Matthew Weinzierl use neoclassical growth model, or Ramsey growth model, to examine how large a part of capital and labor income tax cuts pay for themselves by inducing higher economic growth, i.e. the size of the dynamic feedback effect. Their focus is on the changes of tax revenue. They use first a basic model with Cobb-Douglas production and inelastic labor supply, then relax those assumptions for a more general Ramsey model and then in turn include parameters allowing for finite horizon households, imperfect competition, and externalities to capital investment. Depending on the model used, the dynamic feedback effect varies from model to model, for a capital tax cut from 50 to 74 percent and for a labor income tax cut from zero (with inelastic labor supply) to 21 percent. This thesis extends the Mankiw–Weinzierl model by including a tax on consumption to examine how this affects the dynamic feedback effect. In all the models, there is an increase in the dynamic feedback effect: depending on the model used, it varies for a capital tax cut from 60 to 87 percent and for a labor income tax cut from zero (with inelastic labor supply) to 25 percent. The values of some of the key parameters, namely the constant-consumption elasticity of labor supply and the elasticity of substitution between capital and labor, and the tax rates are revised as well. This further increases the dynamic feedback effect all along the line, in some cases even suggesting a capital tax cut to more than compensate the static revenue loss. Including a tax on consumption into the models increases the dynamic feedback effect, working into the same direction as rising the initial rates of capital and labor income taxes. Using alternative tax rates and values of the key parameters also has a significant impact on the size of the dynamic feedback effect.
-
(2023)Intestinal epithelium is capable of rapid regeneration, which is associated with transient changes in cellular identity. Some of these changes involve an enrichment of fetal-like gene expression and simultaneous suppression of adult stem cell signature. Interestingly, the upregulation of fetal-like marker Stem cell antigen 1 (Sca1) is modulated by extracellular matrix (ECM) which is known to guide epithelial cells during regeneration. Our recently published decellularized small intestinal ECM (iECM) system retains the composition and topology of natural ECM. This makes it an attractive system for ex vivo studies addressing regeneration. This thesis aimed to gain insight into the fetal-like identity and its dynamics using an ex vivo iECM system. Intriguingly, Sca1 expressing cells on iECM displayed migratory features, such as a leading edge and changes in nuclear morphology. Curiously, these features are typical for epithelial cells during development. Furthermore, based on marker gene expression during iECM re-epithelization, fetal-like state was upregulated while adult stem cell state was downregulated, revealing a gradually emerging inverse correlation. Additionally, data suggests that circadian rhythms may have a role in modulating the fetal-like state. iECM from an active-state mice indicated a reduced capability to induce fetal-like identity and overall re-epithelization compared to the rest-state iECM. The results of this thesis suggest further potential of iECM system in studying emergence of fetal-like state during re-epithelization and circadian rhythm impact on it.
Now showing items 4610-4629 of 33005