Position-sensitive silicon strip detector characterization using particle beams

Silicon strip detectors are fast, cost-effective and have an excellent spatial resolution. They are widely used in many high-energy physics experiments. Modern high energy physics experiments impose harsh operation conditions on the detectors, e.g., of LHC experiments. The high radiation doses cause the detectors to eventually fail as a result of excessive radiation damage. This has led to a need to study radiation tolerance using various techniques. At the same time, a need to operate sensors approaching the end their lifetimes has arisen. The goal of this work is to demonstrate that novel detectors can survive the environment that is foreseen for future high-energy physics experiments. To reach this goal, measurement apparatuses are built. The devices are then used to measure the properties of irradiated detectors. The measurement data are analyzed, and conclusions are drawn. Three measurement apparatuses built as a part of this work are described: two telescopes measuring the tracks of the beam of a particle accelerator and one telescope measuring the tracks of cosmic particles. The telescopes comprise layers of reference detectors providing the reference track, slots for the devices under test, the supporting mechanics, electronics, software, and the trigger system. All three devices work. The differences between these devices are discussed. The reconstruction of the reference tracks and analysis of the device under test are presented. Traditionally, silicon detectors have produced a very clear response to the particles being measured. In the case of detectors nearing the end of their lifefimes, this is no longer true. A new method benefitting from the reference tracks to form clusters is presented. The method provides less biased results compared to the traditional analysis, especially when studying the response of heavily irradiated detectors. Means to avoid false results in demonstrating the particle-finding capabilities of a detector are also discussed. The devices and analysis methods are primarily used to study strip detectors made of Magnetic Czochralski silicon. The detectors studied were irradiated to various fluences prior to measurement. The results show that Magnetic Czochralski silicon has a good radiation tolerance and is suitable for future high-energy physics experiments.

Methods in general model localization

The aim of this study was to evaluate and test methods which could improve local estimates of a general model fitted to a large area. In the first three studies, the intention was to divide the study area into sub-areas that were as homogeneous as possible according to the residuals of the general model, and in the fourth study, the localization was based on the local neighbourhood. According to spatial autocorrelation (SA), points closer together in space are more likely to be similar than those that are farther apart. Local indicators of SA (LISAs) test the similarity of data clusters. A LISA was calculated for every observation in the dataset, and together with the spatial position and residual of the global model, the data were segmented using two different methods: classification and regression trees (CART) and the multiresolution segmentation algorithm (MS) of the eCognition software. The general model was then re-fitted (localized) to the formed sub-areas. In kriging, the SA is modelled with a variogram, and the spatial correlation is a function of the distance (and direction) between the observation and the point of calculation. A general trend is corrected with the residual information of the neighbourhood, whose size is controlled by the number of the nearest neighbours. Nearness is measured as Euclidian distance. With all methods, the root mean square errors (RMSEs) were lower, but with the methods that segmented the study area, the deviance in single localized RMSEs was wide. Therefore, an element capable of controlling the division or localization should be included in the segmentation-localization process. Kriging, on the other hand, provided stable estimates when the number of neighbours was sufficient (over 30), thus offering the best potential for further studies. Even CART could be combined with kriging or non-parametric methods, such as most similar neighbours (MSN).

Sneutrino-antisneutrino oscillations at colliders

Modern elementary particle physics is based on quantum field theories. Currently, our understanding is that, on the one hand, the smallest structures of matter and, on the other hand, the composition of the universe are based on quantum field theories which present the observable phenomena by describing particles as vibrations of the fields. The Standard Model of particle physics is a quantum field theory describing the electromagnetic, weak, and strong interactions in terms of a gauge field theory. However, it is believed that the Standard Model describes physics properly only up to a certain energy scale. This scale cannot be much larger than the so-called electroweak scale, i.e., the masses of the gauge fields W^+- and Z^0. Beyond this scale, the Standard Model has to be modified. In this dissertation, supersymmetric theories are used to tackle the problems of the Standard Model. For example, the quadratic divergences, which plague the Higgs boson mass in the Standard model, cancel in supersymmetric theories. Experimental facts concerning the neutrino sector indicate that the lepton number is violated in Nature. On the other hand, the lepton number violating Majorana neutrino masses can induce sneutrino-antisneutrino oscillations in any supersymmetric model. In this dissertation, I present some viable signals for detecting the sneutrino-antisneutrino oscillation at colliders. At the e-gamma collider (at the International Linear Collider), the numbers of the electron-sneutrino-antisneutrino oscillation signal events are quite high, and the backgrounds are quite small. A similar study for the LHC shows that, even though there are several backrounds, the sneutrino-antisneutrino oscillations can be detected. A useful asymmetry observable is introduced and studied. Usually, the oscillation probability formula where the sneutrinos are produced at rest is used. However, here, we study a general oscillation probability. The Lorentz factor and the distance at which the measurement is made inside the detector can have effects, especially when the sneutrino decay width is very small. These effects are demonstrated for a certain scenario at the LHC.

Cliffordin analyysi ja sovelluksia

Cliffordin algebrat ovat äärellisulotteisia reaali- tai kompleksikertoimisia algebroja, jotka yleistävät kvaterneja ja kompleksilukuja. Näitä algebroja on kutsuttu myös geometrisiksi algebroiksi. Tässä tutkielmassa tarkastellaan analyysiä Cliffordin algebroilla ja sen sovelluksia. Analyysi tässä tarkoittaa sitä, että tarkastellaan Cliffordin algebraarvoisia funktioita, jotka omaavat erikseen määriteltyjä sileysominaisuuksia. Sovelluskohteina ovat osittaisdifferentiaaliyhtälöt ja reuna-arvo-ongelmat. Menetelmät ovat klassisia kompleksianalyysin menetelmiä. Tutkielmassa esitellään Cliffordin algebrat yleisille neliömuodollisille avaruuksille. Keskeisiä algebrallisia ominaisuuksia ovat Frobeniuksen teoreema ja perusoperaatiot. On yleisesti tunnettua, että kvaterneilla voidaan esittää kolmiulotteisen ja neljäulotteisen avaruuden rotaatiot. Tutkielmassa esitellään, miten Cliffordin ryhmiä, jotka ovat Cliffordin algebrojen osajoukkoja, käytetään useamman ulottuvuuden rotaatioiden esityksessä. Toinen sovelluskohde on Möbius-kuvausten esittäminen Vahlenin matriiseilla. Tutkielman toisessa osiossa määritellään monogeeniset funktiot erään Diracin operaattorin nollaratkaisuina. Monogeenisten funktioiden pääominaisuus on Cauchyn integraalikaava. Välittömiä seurauksia ovat esimerkiksi potenssisarjakehitelmät, analyyttisuus, Liuvillen teoreema ja muut klassisen kompleksianalyysin tuloksien yleistykset. Toisaalta monet kompleksianalyysin tulokset eivät yleisty. Esimerkiksi monogeenisten funktioiden tulo ei ole yleisesti ottaen monogeeninen. Potenssisarjat voidaan esittää monogeenisten polynomeiden avulla. Esitämme kannan monogeenisten polynomien avaruudelle käyttäen CK-laajennusta. Cauchyn ytimen ominaisuuksien avulla tarkastelemme Diracin operaattorin reuna-arvo-ongelmia ja nk. D-ongelmaa. Käyttäen Rungen lauseen yleistystä osoitamme D-ongelman yleisen ratkaistavuuden. Toisaalta reuna-arvo-ongelman ratkaistavuus karakterisoidaan käyttäen Cauchyn ytimen reuna-arvo-ominaisuuksia ja hyppyrelaatioita. Keskeinen sovellus tuloksille on aikaharmonisen Maxwellin yhtälön reuna-arvo-ongelmien tarkastelu. Mielenkiintoista on myös, miten Diracin operaattori linearisoi Laplacen operaattorin ja aalto-operaattorin. Toisaalta Diracin operaattorin avulla voidaan ilmaista Maxwellin yhtälöt tiiviissä muodossa. Muita tuloksia tutkielmassa ovat meromorfifunktioiden määritelmä ja Mittag-Lefflerin lause. Tutkielman lopuksi tarkastellaan lyhyesti harmonisten funktioiden ja monogeenisten funktioiden suhdetta. Jokainen harmoninen funktio on jonkin monogeenisen funktion reaaliosa. Tosin monogeeninen funktio ei ole yksikäsitteisesti määrätty sen reaaliosan avulla.

Lower Gastrointestinal Microbiota in Health and Irritable Bowel Syndrome : Characterisation and Effect of Probiotic Intervention

The human gastrointestinal (GI) microbiota is a complex ecosystem that lives in symbiosis with its host. The growing awareness of the importance of the microbiota to the host as well as the development of culture-free laboratory techniques and computational methods has enormously expanded our knowledge of this microbial community. Irritable bowel syndrome (IBS) is a common functional bowel disorder affecting up to a fifth of the Western population. To date, IBS diagnosis has been based on GI symptoms and the exclusion of organic diseases. The GI microbiota has been found to be altered in this syndrome and probiotics can alleviate the symptoms, although clear links between the symptoms and the microbiota have not been demonstrated. The aim of the present work was to characterise IBS related alterations in the intestinal microbiota, their relation to IBS symptoms and their responsiveness to probiotic theraphy. In this thesis research, the healthy human microbiota was characterised by cloning and sequencing 16S rRNA genes from a faecal microbial community DNA pool that was first profiled and fractionated according to its guanine and cytosine content (%G+C). The most noticeable finding was that the high G+C Gram-positive bacteria (the phylum Actinobacteria) were more abundant compared to a corresponding library constructed from the unfractionated DNA pool sample. Previous molecular analyses of the gut microbiota have also shown comparatively low amounts of high G+C bacteria. Furthermore, the %G+C profiling approach was applied to a sample constructed of faecal DNA from diarrhea-predominant IBS (IBS-D) subjects. The phylogenetic microbial community comparison performed for healthy and IBS-D sequence libraries revealed that the IBS-D sample was rich in representatives of the phyla Firmicutes and Proteobacteria whereas Actinobacteria and Bacteroidetes were abundant in the healthy subjects. The family Lachnospiraceae within the Firmicutes was especially prevalent in the IBS-D sample. Moreover, associations of the GI microbiota with intestinal symptoms and the quality of life (QOL) were investigated, as well as the effect of probiotics on these factors. The microbial targets that were analysed with the quantitative real-time polymerase chain reaction (qPCR) in this study were phylotypes (species definition according to 16S rRNA gene sequence similarity) previously associated with either health or IBS. With a set of samples, the presence or abundance of a phylotype that had 94% 16S rRNA gene sequence similarity to Ruminococcus torques (R. torques 94%) was shown to be associated with the severity of IBS symptoms. The qPCR analyses for selected phylotypes were also applied to samples from a six-month probiotic intervention with a mixture of Lactobacillus rhamnosus GG, L. rhamnosus Lc705, Propionibacterium freudenreichii ssp. shermanii JS and Bifidobacterium breve Bb99. The intervention had been previously reported to alleviate IBS symptoms, but no associations with the analysed microbiota representatives were shown. However, with the phylotype-specific assays applied here, the abundance of the R. torques 94% -phylotype was shown to be lowered in the probiotic-receiving group during the probiotic supplementation, whereas a Clostridium thermosuccinogenes 85% phylotype, previously associated with a healthy microbiota, was found to be increased compared to the placebo group. To conclude, with the combination of methods applied, higher abundance of Actinobacteria was detected in the healthy gut than found in previous studies, and significant phylum-level microbiota alterations could be shown in IBS-D. Thus, the results of this study provide a detailed overview of the human GI microbiota in healthy subjects and in subjects with IBS. Furthermore, the IBS symptoms were linked to a particular clostridial phylotype, and probiotic supplementation was demonstrated to alter the GI microbiota towards a healthier state with regard to this and an additional bacterial phylotype. For the first time, distinct phylotype-level alterations in the microbiota were linked to IBS symptoms and shown to respond to probiotic therapy.

Modelling vacuum arcs : from plasma initiation to surface interactions

A better understanding of vacuum arcs is desirable in many of today's 'big science' projects including linear colliders, fusion devices, and satellite systems. For the Compact Linear Collider (CLIC) design, radio-frequency (RF) breakdowns occurring in accelerating cavities influence efficiency optimisation and cost reduction issues. Studying vacuum arcs both theoretically as well as experimentally under well-defined and reproducible direct-current (DC) conditions is the first step towards exploring RF breakdowns. In this thesis, we have studied Cu DC vacuum arcs with a combination of experiments, a particle-in-cell (PIC) model of the arc plasma, and molecular dynamics (MD) simulations of the subsequent surface damaging mechanism. We have also developed the 2D Arc-PIC code and the physics model incorporated in it, especially for the purpose of modelling the plasma initiation in vacuum arcs. Assuming the presence of a field emitter at the cathode initially, we have identified the conditions for plasma formation and have studied the transitions from field emission stage to a fully developed arc. The 'footing' of the plasma is the cathode spot that supplies the arc continuously with particles; the high-density core of the plasma is located above this cathode spot. Our results have shown that once an arc plasma is initiated, and as long as energy is available, the arc is self-maintaining due to the plasma sheath that ensures enhanced field emission and sputtering. The plasma model can already give an estimate on how the time-to-breakdown changes with the neutral evaporation rate, which is yet to be determined by atomistic simulations. Due to the non-linearity of the problem, we have also performed a code-to-code comparison. The reproducibility of plasma behaviour and time-to-breakdown with independent codes increased confidence in the results presented here. Our MD simulations identified high-flux, high-energy ion bombardment as a possible mechanism forming the early-stage surface damage in vacuum arcs. In this mechanism, sputtering occurs mostly in clusters, as a consequence of overlapping heat spikes. Different-sized experimental and simulated craters were found to be self-similar with a crater depth-to-width ratio of about 0.23 (sim) - 0.26 (exp). Experiments, which we carried out to investigate the energy dependence of DC breakdown properties, point at an intrinsic connection between DC and RF scaling laws and suggest the possibility of accumulative effects influencing the field enhancement factor.

Early Growth and Later Health, Focus on Metabolic Syndrome, Obesity and Physical Activity

The Developmental Origins of Health and Disease Hypothesis proposes that adverse health outcomes in adult life are in part programmed during fetal life and infancy. This means that e.g. restricted nutrition during pregnancy programmes the offspring to store fat more effectively, to develop faster and to reach puberty earlier. These adaptations are beneficial in terms of short term survival. However, in developed countries these adaptations often lead to an increased risk of obesity and metabolic disturbances in later life, due to a mismatch between the prenatal and postnatal environment. This thesis aimed to study the role of early growth in people who are obese as adults, but metabolically healthy as well as in those who are normal in weight but metabolically obese. Other study aims were to assess whether physical activity and cardiorespiratory fitness are programmed early in life. The role of socioeconomic status in the development of obesity from a life course setting was also studied. These studies included 2003 men and women born in Helsinki between 1934 and 1944 with detailed information of their prenatal and childhood growth as well as living conditions. They participated in the detailed clinical examination during the years 2001-2004. A sub-group of the subjects participated in the UKK Institute 2-kilometre walk test. Metabolic syndrome was defined according to the 2005 criteria of the International Diabetes Federation. Among the obese men and women 20 % were metabolically healthy. Those with metabolic syndrome did not differ in birth size compared to the healthy ones, but by two years of age, they were lighter and thinner, and remained so up to 11 years. The period when changes in BMIs were predictive of the metabolic syndrome was from birth to 7 years. Of the normal weight individuals 17 % were metabolically obese. Again, there were no differences in birth size. However, by the age 7 years, those men who later developed metabolic syndrome were thinner. Gains in BMI during the first two years of life were protective of the syndrome. Children who were heavier, and especially taller, were more physically active, exercised with higher intensity and had higher cardiorespiratory fitness in their adult life than those who were shorter and thinner as children. Lower educational attainment and lower adult social class were associated with obesity in both men and women. Childhood social class was inversely associated with body mass index only in men while lower household income was associated with higher BMI in women. These results support the role of early life factors in the development of metabolic syndrome and adult life style. Early detection of risk factors predisposing to these conditions is highly relevant from a public health point of view.

Desorptio/fotoionisaatio ilmanpaineessa takavarikoitujen huumausaineiden, steroidien ja räjähdysaineiden tutkimuksessa

Tutkimuksen tarkoituksena oli selvittää desorptio/fotoionisaatio ilmanpaineessa tekniikan (engl. desorption atmospheric pressure photoionization, DAPPI) soveltuvuutta rikosteknisen laboratorion näytteiden analysointiin. DAPPI on nopea massaspektrometrinen ionisaatiotekniikka, jolla voidaan tutkia yhdisteitä suoraan erilaisilta pinnoilta. DAPPI:ssa käytetään lämmitettyä mikrosirua, joka suihkuttaa höyrystynyttä liuotin- ja kaasuvirtausta kohti näytettä. Näytteen pinnan komponentit desorboituvat lämmön vaikutuksesta, jonka jälkeen ionisoituminen tapahtuu VUV-lampun emittoimien fotonien avulla.DAPPI:lla tutkittiin takavarikoituja huumausaineita, anabolisia steroideja ja räjähdysaineita sekä niiden jäämiä erilaisilta pinnoilta. Lisäksi kartoitettiin DAPPI:n mahdollisuuksia ja rajoituksia erilaisille näytematriiseille ilman näytteiden esikäsittelyä. Takavarikoitujen huumausaineiden tutkimuksessa analysoitiin erilaisia tabletteja, jauheita, kasvirouheita, huumekasveja (khat, oopium, kannabis) ja sieniä. Anabolisia steroideja tunnistettiin tableteista sekä ampulleista, jotka sisälsivät öljymäistä nestettä. Jauheet ripoteltiin kaksipuoliselle teipille ja analysoitiin siltä. Muut näytteet analysoitiin sellaisenaan ilman minkäänlaista esikäsittelyä, paitsi nestemäisten näytteiden kohdalla näyte pipetoitiin talouspaperille, joka analysoitiin DAPPI:lla. DAPPI osoittautui nopeaksi ja yksinkertaiseksi menetelmäksi takavarikoitujen huumausaineiden ja steroidien analysoimisessa. Se soveltui hyvin rikoslaboratorion erityyppisten näytteiden rutiiniseulontaan ja helpotti erityisesti huumekasvien ja öljymäisten steroidiliuosten tutkimusta. Massaspektrometrin likaantuminen pystyttiin ehkäisemään säätämällä näytteen etäisyyttä sen suuaukosta. Likaantumista ei havaittu huolimatta näytteiden korkeista konsentraatioista ja useita kuukausia jatkuneista mittauksista. Räjähdysaineiden tutkimuksessa keskityttiin seitsemän eri räjähdysaineen DAPPI-MS-menetelmän kehitykseen; trinitrotolueeni (TNT), nitroglykoli (NK), nitroglyseriini (NG), pentriitti (PETN), heksogeeni (RDX), oktogeeni (HMX) ja pikriinihappoä Nämä orgaaniset räjähteet ovat nitraattiyhdisteitä, jotka voidaan jakaa rakenteen puolesta nitroamiineihin (RDX ja HMX), nitroaromaatteihin (TNT ja pikriinihappo) sekä nitraattiestereihin (PETN, NG ja NK). Menetelmäkehityksessä räjähdysainelaimennokset pipetoitiin polymetyylimetakrylaatin (PMMA) päälle ja analysoitiin siitä. DAPPI:lla tutkittiin myäs autenttisia räjähdysainejäämiä erilaisista matriiseista. DAPPI:lla optimoitiin jokaiselle räjähdysaineelle sopiva menetelmä ja yhdisteet saatiin näkymään puhdasaineina. Räjähdysainejäämien analysoiminen erilaisista rikospaikkamateriaaleista osoittautui haastavammaksi tehtäväksi, koska matriisit aiheuttivat itsessään korkean taustan spektriin, josta räjähdysaineiden piikit eivät useimmiten erottuneet tarpeeksi. Muut desorptioionisaatiotekniikat saattavat soveltua paremmin haastavien räjähdysainejäämien havaitsemiseksi.

Identification of collagenolytic MMP networks as potential biomarkers in progressive chronic periodontitis subjects and MMP-8 null allele model

Chronic periodontitis results from a complex aetiology, including the formation of a subgingival biofilm and the elicitation of the host s immune and inflammatory response. The hallmark of chronic periodontitis is alveolar bone loss and soft periodontal tissue destruction. Evidence supports that periodontitis progresses in dynamic states of exacerbation and remission or quiescence. The major clinical approach to identify disease progression is the tolerance method, based on sequential probing. Collagen degradation is one of the key events in periodontal destructive lesions. Matrix metalloproteinase (MMP)-8 and MMP-13 are the primary collagenolytic MMPs that are associated with the severity of periodontal inflammation and disease, either by a direct breakdown of the collagenised matrix or by the processing of non-matrix bioactive substrates. Despite the numerous host mediators that have been proposed as potential biomarkers for chronic periodontitis, they reflect inflammation rather than the loss of periodontal attachment. The aim of the present study was to determine the key molecular MMP-8 and -13 interactions in gingival crevicular fluid (GCF) and gingival tissue from progressive periodontitis lesions and MMP-8 null allele mouse model. In study (I), GCF and gingival biopsies from active and inactive sites of chronic periodontitis patients, which were determined clinically by the tolerance method, and healthy GCF were analysed for MMP-13 and tissue inhibitor of matrix metalloproteinases (TIMP)-1. Chronic periodontitis was characterised by increased MMP-13 levels and the active sites showed a tendency of decreased TIMP-1 levels associated with increments of MMP-13 and total protein concentration compared to inactive sites. In study (II), we investigated whether MMP-13 activity was associated with TIMP-1, bone collagen breakdown through ICTP levels, as well as the activation rate of MMP-9 in destructive lesions. The active sites demonstrated increased GCF ICTP levels as well as lowered TIMP-1 detection along with elevated MMP-13 activity. MMP-9 activation rate was enhanced by MMP-13 in diseased gingival tissue. In study (III), we analysed the potential association between the levels, molecular forms, isoenzyme distribution and degree of activation of MMP-8, MMP-14, MPO and the inhibitor TIMP-1 in GCF from periodontitis progressive patients at baseline and after periodontal therapy. A positive correlation was found for MPO/MMP-8 and their levels associated with progression episodes and treatment response. Because MMP-8 is activated by hypochlorous acid in vitro, our results suggested an interaction between the MPO oxidative pathway and MMP-8 activation in GCF. Finally, in study (IV), on the basis of the previous finding that MMP-8-deficient mice showed impaired neutrophil responses and severe alveolar bone loss, we aimed to characterise the detection patterns of LIX/CXCL5, SDF-1/CXCL12 and RANKL in P. gingivalis-induced experimental periodontitis and in the MMP-8-/- murine model. The detection of neutrophil-chemoattractant LIX/CXCL5 was restricted to the oral-periodontal interface and its levels were reduced in infected MMP-8 null mice vs. wild type mice, whereas the detection of SDF-1/CXCL12 and RANKL in periodontal tissues increased in experimentally-induced periodontitis, irrespectively from the genotype. Accordingly, MMP-8 might regulate LIX/CXCL5 levels by undetermined mechanisms, and SDF-1/CXCL12 and RANKL might promote the development and/or progression of periodontitis.

Diasporakysymyksiä kansainvälisessä yhteisössä. Esimerkkinä Venäjän politiikka ja lapsikiistat Suomessa.

Pro gradu -tutkielmassani tarkastelen diasporia ja niihin kohdistuvaa kansainvälistä sääntelyä. Diasporilla tarkoitan valtion rajojen ulkopuolella asuvia ihmisiä, joilla on jokin, esimerkiksi etninen tai kieliside tuohon valtioon. Valtiolla puolestaan voi olla jokin intressi suhteessa diasporaansa. Diasporiin liittyvät kysymykset ovat ajankohtaisia globaalissa maailmassa, jossa ihmisillä on entistä enemmän mahdollisuuksia pitää siteitä yllä useampaan kuin yhteen valtioon. Diasporien ohella kirjallisuudessa puhutaan myös kin-state -problematiikasta, kun viitataan valtioiden harjoittamaan politiikkaan, joka pyrkii vaikuttamaan toisen valtion alueella asuvien tai oleskelevien ihmisten asemaan. Tutkimuksen teoreettinen viitekehys on englantilaisen koulukunnan ajatus kansainvälisestä yhteisöstä ja sille keskeisistä primaari-instituutioista, kuten valtiosuvereniteetti ja kansainvälinen oikeus. Se, miten valtio politiikassaan suhtautuu instituutioihin, kertoo valtion suhteesta kansainväliseen yhteisöön yleensä. Instituutioita voidaan puolestaan tarkastella tiettyjen kapea-alaisempien normien, sekundaari-instituutioiden, valossa. Edellä mainittuna sekundaari-instituutiona esitellään tutkielmassa se kansainvälinen normisto, joka vaikuttaa diasporien asemaan valtioiden välisessä politiikassa. Normisto perustuu Yhdistyneiden kansakuntien, Euroopan neuvoston ja ETYJ:n sopimuksiin ja suosituksiin. Kansainvälisen oikeuden lähtökohta on, ettei valtio voi puuttua diasporakseen katsomiensa ihmisten asemaan toisessa valtiossa edes ääritapauksessa, jossa asuinvaltio epäonnistuu tehtävässään suojella toisen valtion kansalaisia tai vähemmistöjään. Reagointivastuu on kansainvälisellä yhteisöllä – vaikka interventiota ulkomailla olevien kansalaisten suojelemiseksi onkin suoritettu sekä kylmän sodan aikana että sen jälkeen. Interventiot eivät ole diasporapolitiikan ainoa muoto ja monilla valtioilla onkin niin sanottuja diasporalakeja, joiden puitteissa ne voivat vaikuttaa diasporiensa asemaan. Koulutukseen ja kulttuuriin liittyvä tuki on eurooppalaisissa suosituksissa katsottu hyväksyttäväksi, mutta muiden tukimuotojen ulottamista diasporiin tulee harkita ja soveltaa vain erityistapauksissa, jos politiikalla on valtion toimivallan ulkopuolella vaikuttavia seurauksia. Tutkimus näyttää, että diasporakysymysten sääntely on kansainvälisessä yhteisössä vielä osin määrittelemätöntä sekä altista valtioiden tulkinnoille. Esimerkkinä valtioiden tulkinnoista ja niiden harjoittamasta diasporapolitiikasta tarkastellaan Venäjän federaation politiikkaa, sillä Venäjän ulkopolitiikassa esillä pidetty kiinnostus suojella ulkomailla olevia kansalaisia ja maanmiehiä on herättänyt myös kansainvälistä huomiota. Venäjän politiikan tarkastelu luo kontekstin, jossa tutkielman varsinaista kiinnostuksenkohdetta, Suomen venäläisen diasporan asemaa, on mahdollista tarkastella. Tutkimusaineistoa ovat Venäjän johdon lausunnot liittyen viimeaikaisiin Suomen ja Venäjän välisiin nk. lapsikiistoihin. Teoriaohjaava sisällönanalyysi aineistosta esittää, että vaikka vihjeitä politiikassa yleisesti esiintyvästä nk. suojelupuheesta on havaittavissa myös Suomen venäläisen vähemmistön asemaan liittyen, ei Venäjä lapsikiistoissa kuitenkaan suoraan loukannut Suomen suvereniteettia tai kansainvälistä oikeutta. Tiettyjen puhetapojen ja esimerkiksi lapsiasiamies Astahovin toiminnan voidaan kuitenkin tulkita olevan kansainvälisen normiston vastaisia ja siten myös loukkaavan suvereniteettia ja kansainvälisen oikeuden henkeä. Teoreettisen viitekehyksen tehtävä oli ensisijaisesti antaa näkökulmia aineiston tarkasteluun. Venäjän politiikan suhde suvereniteettiin ja kansainväliseen oikeuteen suhteessa tässä tarkasteltuun politiikkakysymykseen kertoo kuitenkin myös Venäjän asemasta kansainvälisen yhteisön jäsenenä. Diasporanormistoon sitoutuminen osoittaa Venäjän sitoutuneen ainakin periaatteellisella tasolla solidaristiseen, yhteisiä normeja jakavaan kansainväliseen yhteisöön – toisaalta Venäjän viime vuosien politiikka kuitenkin osoittaa Venäjän samalla haastavan myös pluralistisille yhteisöille keskeisiä valtiosuvereniteetin ja kansainvälisen oikeuden noudattamisen periaatteita. Tärkeimmät lähteet: Buzan (2004), Brubakers (1995), Hannikainen (2000), Holsti (2004), Gazzini (2005), Gray (2000), Kántor ym. (2004), Sheffer (2003), Shevel (2010 ja 2011), Turner ja Otsuki (2010) ja Zevelev (2001 ja 2008).