Computationally Efficient Methods for MDL-Optimal Density Estimation and Data Clustering

The Minimum Description Length (MDL) principle is a general, well-founded theoretical formalization of statistical modeling. The most important notion of MDL is the stochastic complexity, which can be interpreted as the shortest description length of a given sample of data relative to a model class. The exact definition of the stochastic complexity has gone through several evolutionary steps. The latest instantation is based on the so-called Normalized Maximum Likelihood (NML) distribution which has been shown to possess several important theoretical properties. However, the applications of this modern version of the MDL have been quite rare because of computational complexity problems, i.e., for discrete data, the definition of NML involves an exponential sum, and in the case of continuous data, a multi-dimensional integral usually infeasible to evaluate or even approximate accurately. In this doctoral dissertation, we present mathematical techniques for computing NML efficiently for some model families involving discrete data. We also show how these techniques can be used to apply MDL in two practical applications: histogram density estimation and clustering of multi-dimensional data.

Huellas de Eros y Thánatos en la narrativa de Diamela Eltit : La palabra en movimiento en el juego entre tropos, metáforas y deconstrucciones lingüísticas

Väitöskirja analysoi espanjan kielen dekonstruktioita ruumiin metaforista ja troopeista koostuvassa aineistossa chileläisen kirjailijan Diamela Eltitin (1949 -) neljässä romaanissa: Lumpérica (1983), Vaca sagrada (1991), El infarto del alma (1994) ja Los trabajadores de la muerte (1998). Näkökulma on kielen muutoksessa Eltitin proosassa 1980- ja 1990-luvuilla alkaen kokeellisesta huippuvaiheesta 1983, jolloin hän julkaisi esikoisromaaninsa Lumpérica. Tutkimus korostaa Eltitin romaanien historiallista arvoa, kirjallisuuden tapaa murtaa kielen rakenteita ja sitä miten tämä murros kytkeytyy taideteoreettiseen muutokseen kulttuuridiskursseissa. Tutkimus tarkastelee Eltitin kehityskaarta kenraali Augusto Pinochetin sotilasvallankaappauksesta 1973 halki sotilashallituksen kauden (1973-1990) aina kansalaisyhteiskunnan vahvistumiseen ja vuoteen 1998. Tutkimus analysoi ruumiin troopeista ja metaforista koostuvaa tutkimusaineistoa lingvistiikan, kirjallisuustieteen, historian ja sukupuolen tutkimuksen monitieteisessä viitekehyksessä. Sen vuoksi väitöskirja liittyy espanjalaisen filologian, yleisen kirjallisuustieteen, Latinalaisen Amerikan tutkimuksen ja naistutkimuksen oppiaineisiin. Kolme tärkeintä oppiteoreettista runkoa ovat lingvistinen strukturalismi, dekonstruktio ja feministiset kirjallisuusteoriat. Dekonstruktiivinen lähestymistapa tekstiin korostaa kielen merkityksen muodostumisen filosofista perustaa. Se pyrkii selvittämään, miten merkitys muodostuu kirjoittajan, tekstin ja lukijan välillä. Tekstikritiikki koostuu semanttisesta ja dekonstruktiivisesta tekstianalyysistä, jonka metodologisen mallin perusta on tanskalaisen kielitieteilijän Louis Hjelmslevin (1899-1965) kielitieteellinen malli. Väitös ei käytä mallia suoraan, vaan soveltaa sitä kaunokirjallisuuden tutkimukseen. Oppiteoreettisen viitekehyksen osalta tutkimus sijoittuu strukturalismin ja poststrukturalismin murrokseen. Tutkimus korostaa Eltitin radikaalia muotokieltä ja teatraalisuutta, hänen kielensä visuaalisuutta ja ruumiin metaforien eroottista jännitettä, mikä ilmenee mm. falloksen metaforaksi tulkitun hehkuvan valon kuvissa romaanissa Lumpérica. Vanhat kreikkalaiset myytit Éros ja Thánatos kasvavat esille länsimaisen taidehistorian perinteestä ja kontekstualisoituvat uusiksi kielikuviksi Chilen kirjallisessa maaperässä. Ne muodostavat Eltitin taiteellisen tuotannon pysyvän aihepiirin ja luovat teoksiin synkkää ja karua virettä sekä tummia ja eroottisia sävyjä. Tutkimus osoittaa, että Eltit dekonstruoi kieltä, mutta dekonstruktiot eivät ole jatkuvia eivätkä samanlaisia kaikissa romaaneissa. Kielellisten dekonstruktioiden variaatio on laaja eikä Eltit murra kielen syntaktisia ja morfologisia rakenteita kaikissa teksteissään. Tutkimuksen perusteella väitän, että Eltitin kirjoituksesta puhuttaessa useat tutkijat käyttävät epämääräisesti dekonstruktio-termiä. Useiden tutkijoiden toteamus dekonstruktiosta Diamela Eltitin kirjallisessa tuotannossa pysyvänä piirteenä on epätäsmällinen. Sen sijaan dekonstruktiivinen kirjoitus tarkoittaa Eltitillä laajasti vaihtelevaa lähestymistapaa kieleen, mikä ilmenee kehityslinjana hänen tuotannossaan ja eri tavoin jokaisessa teoksessa.

Post-industrial Intervention : An Activity-Theoretical Expedition Tracing the Proximal Development of Forms of Conducting Interventions

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Boundaries in Action : An Activity-theoretical Study of Development, Learning, and Change in Health Care Organization for Patients with Multiple and Chronic Illnesses

This study examines boundaries in health care organizations. Boundaries are sometimes considered things to be avoided in everyday living. This study suggests that boundaries can be important temporally and spatially emerging locations of development, learning, and change in inter-organizational activity. Boundaries can act as mediators of cultural and social formations and practices. The data of the study was gathered in an intervention project during the years 2000-2002 in Helsinki in which the care of 26 patients with multiple and chronic illnesses was improved. The project used the Change Laboratory method that represents a research assisted method for developing work. The research questions of the study are: (1) What are the boundary dynamics of development, learning, and change in health care for patients with multiple and chronic illnesses? (2) How do individual patients experience boundaries in their health care? (3) How are the boundaries of health care constructed and reconstructed in social interaction? (4) What are the dynamics of boundary crossing in the experimentation with the new tools and new practice? The methodology of the study, the ethnography of the multi-organizational field of activity, draws on cultural-historical activity theory and anthropological methods. The ethnographic fieldwork involves multiple research techniques and a collaborative strategy for raising research data. The data of this study consists of observations, interviews, transcribed intervention sessions, and patients' health documents. According to the findings, the care of patients with multiple and chronic illnesses emerges as fragmented by divisions of a patient and professionals, specialties of medicine and levels of health care organization. These boundaries have a historical origin in the Finnish health care system. As an implication of these boundaries, patients frequently experience uncertainty and neglect in their care. However, the boundaries of a single patient were transformed in the Change Laboratory discussions among patients, professionals and researchers. In these discussions, the questioning of the prevailing boundaries was triggered by the observation of gaps in inter-organizational care. Transformation of the prevailing boundaries was achieved in implementation of the collaborative care agreement tool and the practice of negotiated care. However, the new tool and practice did not expand into general use during the project. The study identifies two complementary models for the development of health care organization in Finland. The 'care package model', which is based on productivity and process models adopted from engineering and the 'model of negotiated care', which is based on co-configuration and the public good.

High-density lipoprotein 17beta-estradiol fatty acyl esters and phytoestrogens : Impact on reverse cholesterol transport and women's cardiovascular health

Reverse cholesterol transport (RCT) is an important function of high-density lipoproteins (HDL) in the protection of atherosclerosis. RCT is the process by which HDL stimulates cholesterol removal from peripheral cells and transports it to the liver for excretion. Premenopausal women have a reduced risk for atherosclerosis compared to age-matched men and there exists a positive correlation for serum 17β-estradiol (E2) and HDL levels in premenopausal women supporting the role of E2 in atherosclerosis prevention. In premenopausal women, E2 associates with HDL as E2 fatty acyl esters. Discovery of the cellular targets, metabolism, and assessment of the macrophage cholesterol efflux potential of these HDL-associated E2 fatty acyl esters were the major objectives of this thesis (study I, III, and IV). Soy phytoestrogens, which are related to E2 in both structure and function, have been proposed to be protective against atherosclerosis but the evidence to support these claims is conflicting. Therefore, another objective of this thesis was to assess the ability of serum from postmenopausal women, treated with isoflavone supplements (compared to placebo), to promote macrophage cholesterol efflux (study II). The scope of this thesis was to cover the roles that HDL-associated E2 fatty acyl esters have in the cellular aspects of RCT and to determine if soy isoflavones can also influence RCT mechanisms. SR-BI was a pivotal cellular receptor, responsible for hepatic and macrophage uptake and macrophage cholesterol efflux potential of HDL-associated E2 fatty acyl esters. Functional SR-BI was also critical for proper LCAT esterification activity which could impact HDL-associated E2 fatty acyl ester assembly and its function. In hepatic cells, LDL receptors also contributed to HDL-associated E2 fatty acyl esters uptake and in macrophage cells, estrogen receptors (ERs) were necessary for both HDL-associated E2 ester-specific uptake and cholesterol efflux potential. HDL-containing E2 fatty acyl esters (E2-FAE) stimulated enhanced cholesterol efflux compared to male HDL (which are deficient in E2) demonstrating the importance of the E2 ester in this process. To support this, premenopausal female HDL, which naturally contains E2, showed greater macrophage cholesterol efflux compared to males. Additionally, hepatic and macrophage cells hydrolyzed the HDL-associated E2 fatty acyl ester into unesterified E2. This could have important biological ramifications because E2, not the esterified form, has potent cellular effects which may influence RCT mechanisms. Lastly, soy isoflavone supplementation in postmenopausal women did not modulate ABCA1-specific macrophage cholesterol efflux but did increase production of plasma pre-β HDL levels, a subclass of HDL. Therefore, the impact of isoflavones on RCT and cardiovascular health needs to be further investigated. Taken as a whole, HDL-associated E2 fatty acyl esters from premenopausal women and soy phytoestrogen treatment in postmenopausal women may be important factors that increase the efficiency of RCT through cellular lipoprotein-related processes and may have direct implications on the cardiovascular health of women.

Associations of gene polymorphisms and nutrition with calcium homeostasis and bone mineral density : Studies on skeletal nutrigenetics

Heredity explains a major part of the variation in calcium homeostasis and bone strength, and the susceptibility to osteoporosis is polygenetically regulated. Bone phenotype results from the interplay between lifestyle and genes, and several nutritional factors modulate bone health throughout life. Thus, nutrigenetics examining the genetic variation in nutrient intake and homeostatic control is an important research area in the etiology of osteoporosis. Despite continuing progress in the search for candidate genes for osteoporosis, the results thus far have been inconclusive. The main objective of this thesis was to investigate the associations of lactase, vitamin D receptor (VDR), calcium sensing receptor (CaSR) and parathyroid hormone (PTH) gene polymorphisms and lifestyle factors and their interactions with bone health in Finns at varying stages of the skeletal life span. Markers of calcium homeostasis and bone remodelling were measured from blood and urine samples. Bone strength was measured at peripheral and central bone sites. Lifestyle factors were assessed with questionnaires and interviews. Genetic lactase non-persistence (the C/C-13910 genotype) was associated with lower consumption of milk from childhood, predisposing females in particular to inadequate calcium intake. Consumption of low-lactose milk and milk products was shown to decrease the risk for inadequate calcium intake. In young adulthood, bone loss was more common in males than in females. Males with the lactase C/C-13910 genotype may be more susceptible to bone loss than males with the other lactase genotypes, although calcium intake predicts changes in bone mass more than the lactase genotype. The BsmI and FokI polymorphisms of the VDR gene were associated with bone mass in growing adolescents, but the associations weakened with age. In young adults, the A986S polymorphism of the calcium sensing receptor gene was associated with serum ionized calcium concentrations, and the BstBI polymorphism of the parathyroid gene was related to bone strength. The FokI polymorphism and sodium intake showed an interaction effect on urinary calcium excretion. A novel gene-gene interaction between the VDR FokI and PTH BstBI gene polymorphisms was found in the regulation of PTH secretion and urinary calcium excretion. Further research should be carried out with more number of Finns at varying stages of the skeletal life span and more detailed measurements of bone strength. Research should concern mechanisms by which genetic variants affect calcium homeostasis and bone strength, and the role of diet-gene and gene-gene interactions in the pathogenesis of osteoporosis.

Factors affecting farmland prices in Finland

The purpose of the study was to analyse factors affecting the differences in land prices between regions. The key issue was to find out the policy effects on farmland prices. In addition to comprehensive literature review, a theoretical analysis as well as modern panel and spatial econometric techniques were utilized. The study clearly pointed out the importance of taking into account the possible spatial dependence. The data were exceptionally large, comprising more than 6 000 observations. Thus, it allowed a thorough econometric estimation including the possibility to take into account the spatial nature of the data. This study supports the view that there are many other factors that affect farmland prices besides pure agricultural returns. It was also found that the support clearly affects land prices. However, rather than assuming the discount rates for support and market returns to be similar, the rough analysis refers to the discount rate for support being a little lower. If this were true it would indicate that farmers rely more on support income than market returns. The results support the view presented in literature that land values are more responsive to government payments when these payments are perceived to be permanent. An important result of this study is that the structural differences between regions and the structural change in agriculture seemed to have a considerable role in affecting land prices. Firstly, the present structure affects the competition in the land market: the more dense farms are in the region the more there are potential buyers, and the land price increases. Secondly, the change in farm structure (especially in animal husbandry) connected to the policy changes that increase area-based support affects land prices. The effect comes from two sources. Growing farms need more land for the manure, and the proportion of retiring farmers may be lower. The introduction of the manure density variable proved to be an efficient way to aggregate the otherwise very difficult task of taking into account the environmental pressure caused by structural change in animal husbandry. Finally, infrastructure also has a very important role in determining the price level of agricultural land. If other industries are prospering in the surrounding area, agricultural viability also seems to improve. The non-farm opportunities offered to farm families make continuing and developing farming more tempting.