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Now showing items 613-632 of 26145
• (Helsingfors universitet, 2013)
• (1980)
• (1998)
• (Helsingin yliopisto, 2014)
• (Helsingin yliopisto, 2004)
• (2002)
• (Helsingin yliopisto, 2008)
Diet is a major player in the maintenance of health and onset of many diseases of public health importance. The food choice is known to be largely influenced by sensory preferences. However, in many cases it is unclear whether these preferences and dietary behaviors are innate or acquired. The aim of this thesis work was to study the extent to which the individual differences in dietary responses, especially in liking for sweet taste, are influenced by genetic factors. Several traits measuring the responses to sweetness and other dietary variables were applied in four studies: in British (TwinsUK) and Finnish (FinnTwin12 and FinnTwin16) twin studies and in a Finnish migraine family study. All the subjects were adults and they participated in chemosensory measurements (taste and smell tests) and filled in food behavior questionnaires. Further, it was studied, whether the correlations among the variables are mediated by genetic or environmental factors and where in the genome the genes influencing the heritable traits are located. A study of young adult Finnish twins (FinnTwin16, n=4388) revealed that around 40% of the food use is attributable to genetic factors and that the common, childhood environment does not affect the food use even shortly after moving from the parents home. Both the family study (n=146) and the twin studies (British twins, n=663) showed that around half of the variation in the liking for sweetness is inherited. The same result was obtained both by the chemosensory measurements (heritability 41-49%) and the questionnaire variables (heritability 31-54%). By contrast, the intensity perception of sweetness or the responses to saltiness were not influenced by genetic factors. Further, a locus influencing the use-frequency of sweet foods was identified on chromosome 16p. A closer examination of the relationships among the variables based on 663 British twins revealed that several genetic and environmental correlations exist among the different measures of liking for sweetness. However, these correlations were not very strong (range 0.06-0.55) implying that the instruments used measure slightly different aspects of the phenomenon. In addition, the assessment of the associations among responses to fatty foods, dieting behaviors, and body mass index in twin populations (TwinsUK n=1027 and FinnTwin12 n=299) showed that the dieting behaviors (cognitive restraint, uncontrolled eating, and emotional eating) mediate the relationship between obesity and diet. In conclusion, the work increased the understanding of the background variables of human eating behavior. Genetic effects were shown to underlie the variation of many dietary traits, such as liking for sweet taste, use of sweet foods, and dieting behaviors. However, the responses to salty taste were shown to be mainly determined by environmental factors and thus should more easily be modifiable by dietary education, exposure, and learning than sweet taste preferences. Although additional studies are needed to characterize the genetic element located on chromosome 16 that influences the use-frequency of sweet foods, the results underline the importance of inherited factors on human eating behavior.
• (Helsingin yliopisto, 2011)
This thesis is concerned with the area of vector-valued Harmonic Analysis, where the central theme is to determine how results from classical Harmonic Analysis generalize to functions with values in an infinite dimensional Banach space. The work consists of three articles and an introduction. The first article studies the Rademacher maximal function that was originally defined by T. Hytönen, A. McIntosh and P. Portal in 2008 in order to prove a vector-valued version of Carleson's embedding theorem. The boundedness of the corresponding maximal operator on Lebesgue-(Bochner) -spaces defines the RMF-property of the range space. It is shown that the RMF-property is equivalent to a weak type inequality, which does not depend for instance on the integrability exponent, hence providing more flexibility for the RMF-property. The second article, which is written in collaboration with T. Hytönen, studies a vector-valued Carleson's embedding theorem with respect to filtrations. An earlier proof of the dyadic version assumed that the range space satisfies a certain geometric type condition, which this article shows to be also necessary. The third article deals with a vector-valued generalizations of tent spaces, originally defined by R. R. Coifman, Y. Meyer and E. M. Stein in the 80's, and concerns especially the ones related to square functions. A natural assumption on the range space is then the UMD-property. The main result is an atomic decomposition for tent spaces with integrability exponent one. In order to suit the stochastic integrals appearing in the vector-valued formulation, the proof is based on a geometric lemma for cones and differs essentially from the classical proof. Vector-valued tent spaces have also found applications in functional calculi for bisectorial operators. In the introduction these three themes come together when studying paraproduct operators for vector-valued functions. The Rademacher maximal function and Carleson's embedding theorem were applied already by Hytönen, McIntosh and Portal in order to prove boundedness for the dyadic paraproduct operator on Lebesgue-Bochner -spaces assuming that the range space satisfies both UMD- and RMF-properties. Whether UMD implies RMF is thus an interesting question. Tent spaces, on the other hand, provide a method to study continuous time paraproduct operators, although the RMF-property is not yet understood in the framework of tent spaces.
• (2015)
We show that the embedding of a matrix game in a mechanistic population dynamical model can have important consequences for the evolution of how the game is played. In particular, we show that because of this embedding evolutionary branching and multiple evolutionary singular strategies can occur, which is not possible in the conventional theory of matrix games. We show that by means of the example of the hawk-dove game.
• (2012)
Amenabilitet är ett begrepp som förekommer inom teorin för både lokalt kompakta grupper och Banach algebror. Forskningen kring translations-invarianta mått under första halvan av 1900-talet ledde till definitionen av amenabla lokalt kompakta grupper. En lokalt kompakt grupp $G$ kallas för amenabel om det finns en positiv linjär funktional med normen 1 i $L^\infty(G)^*$ som är vänster-invariant i förhållandet till den givna gruppoperationen. Under samma tidsperiod utvecklades teorin för Hochschild kohomologi för Banach algebror. En Banach algebra $A$ kallas för amenabel om den första Hochschild kohomologigruppen $H^1(A,X^*)=\{0\}$ för varje dual Banach $A$-bimodule $X^*$, d.v.s. om varje kontinuerlig derivation $D:A\rightarrow X^*$ är en inre derivation. År 1972 bevisade B. E. Johnson att gruppalgebran $L^1(G)$ för en lokalt kompakt grupp $G$ är amenabel om och endast om $G$ är amenabel. Detta resultat rättfärdigar terminologin amenabel Banach algebra. I denna pro gradu-avhandling presenterar vi grundteorin för amenabla Banach algebror och ger ett bevis till Johnsons teorem. ************************ Amenability is a notion that occurs in the theory of both locally compact groups and Banach algebras. The research on translation-invariant measures during the first half of the 20th century led to the definition of amenable locally compact groups. A locally compact group $G$ is called amenable if there is a positive linear functional of norm 1 in $L^\infty(G)^*$ that is left-invariant with respect to the given group operation. During the same time the theory of Hochschild cohomology for Banach algebras was developed. A Banach algebra $A$ is called amenable if the first Hochschild cohomology group $H^1(A,X^*)=\{0\}$ for all dual Banach $A$-bimodules $X^*$, that is, if every continuous derivation $D:A\rightarrow X^*$ is inner. In 1972 B. E. Johnson proved that the group algebra $L^1(G)$ for a locally compact group $G$ is amenable if and only if $G$ is amenable. This result justifies the terminology amenable Banach algebra. In this Master's thesis we present the basic theory of amenable Banach algebras and give a proof of Johnson's theorem.
• (Helsingin yliopisto, 2013)