Matalan syntyvyyden syitä ja seurauksia julkisen eläkejärjestelmän ylläpidon ja uudistamisen näkökulmasta

Viime vuosikymmeninä teollistuneissa OECD-maissa yksi suurimmista väestöllisistä muutoksista on tapahtunut syntyvyydessä. Sotien jälkeen syntyneiden suurten ikäluokkien jälkeen useissa teollistuneissa maissa väestönkasvun trendi on ollut laskeva, mikä puolestaan on johtanut kasvavaan huoleen matalan syntyvyyden sosioekonomisista seurauksista. Matala syntyvyyden taso on monissa kehittyneissä maissa luonut varjon valtion ylläpitämän sosiaaliturvajärjestelmän ylle ja sen rahoituspohjan heikentyminen on kasvattanut huolta järjestelmän tulevaisuudesta. Myös muun muassa viime vuosikymmenten taloudelliset taantuma-ajat, väestön ikärakenteessa ja työmarkkinoilla tapahtuneet muutokset, sekä väestön ikääntyminen ja veronmaksajien väheneminen ovat luoneet uudenlaiset paineet julkisen sosiaaliturva- ja eläkejärjestelmän ylläpidolle ja rahoittamiselle. Mietittäessä puolestaan syitä syntyvyyden madaltumiseen viime vuosikymmeninä, ovat tutkimukset osoittaneet, etteivät talous- ja sosiaalijärjestelmien rakenne sekä niissä tapahtuneet muutokset ole olleet tässä muutoksessa merkityksettömiä. Verotuksella ja valtion myöntämillä sosiaalituilla on osoitettu olevan vaikutus yksilön lapsenhankinta- ja myös perheenmuodostamispäätökseen. Tässä tutkielmassa tutkimuksen kohteena ovat matala syntyvyys, sekä sen syyt ja seuraukset taloustieteellisestä näkökulmasta. Tutkielman tarkoituksena on selvittää matalan syntyvyyden ja perheen perustamisen sekä jakojärjestelmäisen eläkejärjestelmän välistä yhteyttä, ja löytää todisteita siitä, millaisia kannustimia julkisella eläkejärjestelmällä syntyvyyden suhteen on. Li-säksi tutkielmassa perehdytään julkisen eläkejärjestelmän tulevaisuuteen väestöllisten haastei-den edessä, ja tarkastellaan järjestelmän uudistamismahdollisuuksia. Matalaa syntyvyyttä tarkastellaan muun muassa väestöllisen transition teorian avulla. Matalan syntyvyyden ja jakojärjestelmäisen eläkejärjestelmän suhdetta tutkitaan Zhangin ja Zhangin (2007) matemaattisella mallinnuksella, jonka avulla saadaan selville, että julkisen eläkejärjes-telmän käyttö sosiaalisen hyvinvoinnin optimoinnissa on pääomainvestointien ulkoisvaikutusten myötä oikeutettua, ja että järjestelmällä ja sitä rahoittavalla tuloverolla on negatiivinen vaikutus syntyvyyteen, mikäli vanhemmat preferoivat lastensa laadullisia, hyvinvointiin liittyviä ominai-suuksia niiden lukumäärään. Perheen perustamisen ja eläkejärjestelmän suhdetta puolestaan tarkastellaan Ehrlichin ja Kimin (2007) tutkimuksen pohjalta. Ehrlichin ja Kimin tutkimuksen tulos on, että julkista eläkejärjestel-mää rahoittavan tuloveron ja sen korottamisen vaikutus syntyvyyteen ja perheen perustamiseen on negatiivinen. Julkisen eläkejärjestelmän viittä eri uudistamisvaihtoehtoa ja niiden hyvinvointi-vaikutuksia käsitellään tutkielmassa pääosin Attanasion, Kitaon ja Violanten (2007) mallin avul-la. Jokaisella reformilla on Attanasion, Kitaon ja Violanten mukaan erilaisia makrotaloudellisia vaikutuksia, joita tarkastellaan tutkielmassa pääosin sanallisesti ja graafisesti, sekä eri tutkimus-ten tuloksia vertailemalla. Tutkielmassa käsite syntyvyys rinnastetaan taloustieteellisessä mielessä lasten kysynnäksi, ja sitä tutkitaan pääosin makrotaloudellisesta näkökulmasta. Kaikki tutkielmassa käytettävät matemaattiset mallit ovat limittäisten sukupolvien malleja ja julkisella eläkejärjestelmällä viitataan jakojärjestelmäiseen, pay-as-you-go -eläkejärjestelmään.

Achievement and Social Strategies and the Cumulation of Positive and Negative Experiences During Young Adulthood

These longitudinal studies focused on investigating young adults during transition into a new educational environment. The aims were to examine: (1) what kinds of achievement and social strategies young adults deploy, (2) whether the deployment of these strategies predicts people's success in their studies, their life events, their peer relationships, and their well-being, (3) whether young adults' success in dealing with educational transition (e.g. success in studies, life events, peer relationships and well-being) predict changes in their strategies and well-being, and (4) the associations between young adults' social strategies, interpersonal behaviour, person perception, and their peer relationships and satisfaction with them. The participants were students from Helsinki university and from two vocational institutes (the numbers ranging between 92 and 303). The results revealed that achievement and social strategies contributed to individuals' success in dealing with both the academic and interpersonal challenges of a new environment. Social strategies were also associated with online interpersonal behaviour and person perception, which mediated their impact on peer relationships. Achievement and social strategies changed as a result of environmental feedback. However, they also showed high stability, forming reciprocal and cumulative associations with the feedback the individuals received about their success in dealing with educational transition: the use of functional strategies, such as optimistic, defensive-pessimistic and planning-oriented strategies, increased their success, which in turn enhanced their well-being and further deployment of functional strategies. The opposite was true in the case of dysfunctional strategies, such as self-handicapping and avoidance. Key words : Achievement strategies, social strategies, transition, young adults, life events, sociometric status, social behaviour, person perception, well-being.

Radiation effects in supported nanoparticles

Nanotechnology applications are entering the market in increasing numbers, nanoparticles being among the main classes of materials used. Particles can be used, e.g., for catalysing chemical reactions, such as is done in car exhaust catalysts today. They can also modify the optical and electronic properties of materials or be used as building blocks for thin film coatings on a variety of surfaces. To develop materials for specific applications, an intricate control of the particle properties, structure, size and shape is required. All these depend on a multitude of factors from methods of synthesis and deposition to post-processing. This thesis addresses the control of nanoparticle structure by low-energy cluster beam deposition and post-synthesis ion irradiation. Cluster deposition in high vacuum offers a method for obtaining precisely controlled cluster-assembled materials with minimal contamination. Due to the clusters small size, however, the cluster-surface interaction may drastically change the cluster properties on deposition. In this thesis, the deposition process of metal and alloy clusters on metallic surfaces is modelled using molecular dynamics simulations, and the mechanisms influencing cluster structure are identified. Two mechanisms, mechanical melting upon deposition and thermally activated dislocation motion, are shown to determine whether a deposited cluster will align epitaxially with its support. The semiconductor industry has used ion irradiation as a tool to modify material properties for decades. Irradiation can be used for doping, patterning surfaces, and inducing chemical ordering in alloys, just to give a few examples. The irradiation response of nanoparticles has, however, remained an almost uncharted territory. Although irradiation effects in nanoparticles embedded inside solid matrices have been studied, almost no work has been done on supported particles. In this thesis, the response of supported nanoparticles is studied systematically for heavy and light ion irradiation. The processes leading to damage production are identified and models are developed for both types of irradiation. In recent experiments, helium irradiation has been shown to induce a phase transformation from multiply twinned to single-crystalline nanoparticles in bimetallic alloys, but the nature of the transition has remained unknown. The alloys for which the effect has been observed are CuAu and FePt. It is shown in this thesis that transient amorphization leads to the observed transition and that while CuAu and FePt do not amorphize upon irradiation in bulk or as thin films, they readily do so as nanoparticles. This is the first time such an effect is demonstrated with supported particles, not embedded in a matrix where mixing is always an issue. An understanding of the above physical processes is essential, if nanoparticles are to be used in applications in an optimal way. This thesis clarifies the mechanisms which control particle morphology, and paves way for the synthesis of nanostructured materials tailored for specific applications.

Fertility in Namibia : Changes in fertility levels in North-Central Namibia 1960-2001, including an assessment of the impact of HIV

The aim of this study was to estimate the development of fertility in North-Central Namibia, former Ovamboland, from 1960 to 2001. Special attention was given to the onset of fertility decline and to the impact of the HIV epidemic on fertility. An additional aim was to introduce parish registers as a source of data for fertility research in Africa. Data used consisted of parish registers from Evangelical Lutheran congregations, the 1991 and 2001 Population and Housing Censuses, the 1992 and 2000 Namibia Demographic and Health Surveys, and the HIV sentinel surveillances of 1992-2004. Both period and cohort fertility were analysed. The P/F ratio method was used when analysing census data. The impact of HIV infection on fertility was estimated indirectly by comparing the fertility histories of women who died at an age of less than 50 years with the fertility of other women. The impact of the HIV epidemic on fertility was assessed both among infected women and in the general population. Fertility in the study population began to decline in 1980. The decline was rapid during the 1980s, levelled off in the early 1990s at the end of war of independence and then continued to decline until the end of the study period. According to parish registers, total fertility was 6.4 in the 1960s and 6.5 in the 1970s, and declined to 5.1 in the 1980s and 4.2 in the 1990s. Adjustment of these total fertility rates to correspond to levels of fertility based on data from the 1991 and 2001 censuses resulted in total fertility declining from 7.6 in 1960-79 to 6.0 in 1980-89, and to 4.9 in 1990-99. The decline was associated with increased age at first marriage, declining marital fertility and increasing premarital fertility. Fertility among adolescents increased, whereas the fertility of women in all other age groups declined. During the 1980s, the war of independence contributed to declining fertility through spousal separation and delayed marriages. Contraception has been employed in the study region since the 1980s, but in the early 1990s, use of contraceptives was still so limited that fertility was higher in North-Central Namibia than in other regions of the country. In the 1990s, fertility decline was largely a result of the increased prevalence of contraception. HIV prevalence among pregnant women increased from 4% in 1992 to 25% in 2001. In 2001, total fertility among HIV-infected women (3.7) was lower than that among other women (4.8), resulting in total fertility of 4.4 among the general population in 2001. The HIV epidemic explained more than a quarter of the decline in total fertility at population level during most of the 1990s. The HIV epidemic also reduced the number of children born by reducing the number of potential mothers. In the future, HIV will have an extensive influence on both the size and age structure of the Namibian population. Although HIV influences demographic development through both fertility and mortality, the effect through changes in fertility will be smaller than the effect through mortality. In the study region, as in some other regions of southern Africa, a new type of demographic transition is under way, one in which population growth stagnates or even reverses because of the combined effects of declining fertility and increasing mortality, both of which are consequences of the HIV pandemic.

Geochemistry of the sheeted dike complex at Pito Deep

Alteration of sheeted dikes exposed along submarine escarpments at the Pito Deep Rift (NE edge of the Easter microplate) provides constraints on the crustal component of axial hydrothermal systems at fast spreading mid-ocean ridges. Samples from vertical transects through the upper crust constrain the temporal and spatial scales of hydrothermal fluid flow and fluid-rock reaction. The dikes are relatively fresh (average extent of alteration is 27%), with the extent of alteration ranging from 0 to >80%. Alteration is heterogeneous on scales of tens to hundreds of meters and displays few systematic spatial trends. Background alteration is amphibole-dominated, with chlorite-rich dikes sporadically distributed throughout the dike complex, indicating that peak temperatures ranged from <300°C to >450°C and did not vary systematically with depth. Dikes locally show substantial metal mobility, with Zn and Cu depletion and Mn enrichment. Amphibole and chlorite fill fractures throughout the dike complex, whereas quartz-filled fractures and faults are only locally present. Regional variability in alteration characteristics is found on a scale of <1-2 km, illustrating the diversity of fluid-rock interaction that can be expected in fast spreading crust. We propose that much of the alteration in sheeted dike complexes develops within broad, hot upwelling zones, as the inferred conditions of alteration cannot be achieved in downwelling zones, particularly in the shallow dikes. Migration of circulating cells along rides axes and local evolution of fluid compositions produce sections of the upper crust with a distinctive character of alteration, on a scale of <1-2 km and <5-20 ka.

Magnetophotoresistance in Pr 1–x CaxMnO3 Thin Films

In this work, a colossal magnetoresistive (CMR) Pr1−xCaxMnO3 (PCMO) man- ganite thin films and polycrystalline samples were studied with the main focus on the properties of the insulator to metal Mott phase transition. The polycrystalline PCMO samples were fabricated with the solid state reaction method. The polycrystalline sam- ples were further processed into the epitaxial thin films with the pulsed laser deposition method (PLD). The structural and magnetic properties of the samples were systemat- ically investigated and the thin films samples were further investigated with magneto- transport measurement where the thin films response to illumination was also studied. After the successful synthesis of polycrystalline PCMO samples with varying x = between 0.0 - 0.5, the magnetic characterization of the samples showed rich magnetic properties having the signatures of the magnetic phase coexistence of antiferromag- netic (AFM) and ferromagnetic (FM) ordering and cluster glass behaviour. With the increased doping concentration from x = 0.3 to 0.5, the AFM charge-order (CO) phase started to form up being strongest on the sample x = 0.5. This AFM CO phase could be melted with the high external magnetic field at temperatures below Neel’s tempera- ture TN inducing an irreversible first order metamagnetic AFM to FM phase transition. The strength of the AFM CO phase decreased with decreasing Ca concentration and increasing temperature. The polycrystalline PCMO samples with Ca concentrations of 0.3 - 0.5, showing metamagnetic behaviour, were selected for the fabrication of the thin film samples. The films were grown using two different in situ oxygen treatment temperatures at 500 ◦C and 700 ◦C in the PLD system. The films with x = 0.4 and 0.5 showed weaker AFM CO phase with greatly reduced melting fields when compared to polycrystalline samples. Also, the robustness of the AFM CO phase was further decreased in thin films with the lower oxygen treatment temperature of 500 ◦C. The magneto-transport measurements made on the thin films showed that the melting of AFM CO phase was connected to CMR effect where the increasing magnetic field induced an insulator to metal phase transition, which reduces the resistivity of the film around nine orders of magnitude. The use of illumination during the magneto-transport measurements showed a vari- ety of intriguing phenomena including magnetophotoresistance. The illumination had a huge effect to the insulator to metal transition (IMT) reducing the transition magnetic field significantly. Moreover, by magnetically biasing the thin films with the constant external magnetic field, the IMT could be induced by switching on the illumination.