<p>Diss. (sammanfattning) Umeå : Universitet, 1992, Härtill 4 uppsatser</p> / digitalisering@umu

Viruses infecting bacteria (phages) are the most abundant and ubiquitous entities on Earth and likely critical to any ecosystem, as they influence nutrient cycling, mortality and evolution. Ultimately, their impact depends on whether phage—host interactions lead to intracellular phage coexistence (temperate phage) or cell death (lytic phage). Temperate phages in the lysogenic cycle replicate their genome (either integrated into the host chromosome or extrachromosomally), until induced to become lytic, when they create and release progeny via cell lysis. While knowledge on lytic versus lysogenic outcomes is vast, it largely derives from few model systems that underrepresent natural diversity. Further, less is known about the efficiency of phage—host interactions and the regulation of optimal versus sub-optimal lytic infections, which are predicted as relevant under environmental (nutrients, temperature) and host (availability, density) conditions that are common in the ocean. In this dissertation I characterize the phage—host interactions in a new marine model system, phage ϕ38:1 and its Cellulophaga baltica bacterial host, member of the ubiquitous Bacteroidetes phylum. First, I show ϕ38:1’s ability to infect numerous, genetically similar strains of the C. baltica species, two of which display contrasting infection outcomes–lytic versus sub-optimally lytic or lysogenic on the original versus alternative hosts, respectively. Second, I collaboratively apply new gene marker-based approaches (phageFISH and geneELISA) to study ϕ38:1’s infection at the single-cell level and show that it is sub-optimal on the alternative host, rather than lysogenic. Third, I collaboratively develop whole-genome transcriptome datasets for ϕ38:1 infecting both, the optimal and sub-optimal hosts, to characterize the cellular response to infection and hypothesize potential transcriptional and post-transcriptional regulation of the sub-optimal infection. Together, these findings advance our knowledge of naturally-occurring phage—host interactions with a focus on nearly-unstudied sub-optimal infections.

Στην παρούσα εργασία ασχοληθήκαμε με το φαινόμενο του Ιανουαρίου και την επίδρασή του στις χρηματιστηριακές αγορές επτά επιλεγμένων χωρών, της Γερμανίας, της Ελλάδας, της Αυστρίας, του Ιταλίας, της Αγγλίας, της Ρωσίας και της Ολλανδίας. Το φαινόμενο του Ιανουαρίου (January effect) αποτελεί ένα είδος εποχιακής ανωμαλίας και ημερολογιακού φαινομένου, που επηρεάζει τις τάσεις που παρατηρούνται στην χρηματιστηριακή αγορά και τις αγορές τίτλων κάθε αρχή νέους έτους. Οι ερμηνείες που έχουν δοθεί από την ακαδημαϊκή κοινότητα για την εμφάνιση του January effect ποικίλουν και θα μελετηθούν στο κυρίως μέρος της διπλωματικής εργασίας. Συγκεντρώνοντας και μελετώντας την διεθνή βιβλιογραφία για το συγκεκριμένο φαινόμενο, καθώς επίσης διάφορες μελέτες περιπτώσεων σε διαφορετικές χρηματιστηριακές αγορές και σε συνδυασμό με τη χρήση του στατιστικού πακέτου ανάλυσης e-views, καταφέραμε να εμβαθύνουμε στο φαινόμενο και να διακρίνουμε την έντασή τους στις προαναφερθείσες χώρες. Τα σημαντικότερα ευρήματα παρουσιάζονται στο δεύτερο κεφάλαιο της παρούσας πτυχιακής εργασίας, μετά τη βιβλιογραφική ανασκόπηση. / -

Intro: 80 percent of the Swedish population own shares. This makes Sweden the leading country in private investment in securities. It can be difficult for the private investor to know where, when and which security to invest in. The strategies are as ambivalent as the stock markets fluctuations. If the investor prefers to refrain from investing money himself, there are brokers who carry out these types of services. Brokers use complex calculations and analytical tools to reach the best investment strategies. Their results are based on historic data from public information. According to the theory of the efficient market hypothesis, it is not possible to generate excessive returns on investments which are based on publicly available information. Purpose: The study aims to assess if stock recommendations published in a business newspaper have any value for investors, who hopes to generate high returns. Methodology: Since the data is quantitative, a deductive method is used to comprehend the results. Investments are divided into two fictive portfolios where one portfolio follows a passive investment strategy whilst in the other, active investments based on public information are made. A one-sample t-test is used to obtain the statistics for answering the hypothetical questions. Theoretical: The primary theory for the essay is the theory of efficient market hypothesis, perspectives but also passive investment strategies and the random walk hypothesis are being touched upon. Empirical: A study has been conducted of recommendations with the recomendations foundations found on DI.se between 01.01.2005 and 31.12.2006, as the study objects. Theprimary sources have been DI.se and the NASDAQ OMX. The results from the data are solely products of my own empirical findings. Conclusion: The results signify a large difference between a passive and an active investment strategy, although the statistical results indicates no significancy.

In this thesis, portfolio optimisation is used to evaluate if a specific sample of portfolios have a higher risk level or lower expected return, compared to what may be obtained through optimisation. It also compares the return of optimised portfolios with the return of the original portfolios. The risk analysis software Aegis Portfolio Manager developed by Barra is used for the optimisations. With the expected return and risk level used in this thesis, all portfolios can obtain a higher expected return and a lower risk. Over a six-month period, the optimised portfolios do not consistently outperform the original portfolios and therefore it seems as though the optimisation do not improve the return of the portfolios. This might be due to the uncertainty of the expected returns used in this thesis.

Formal methods provide means for rigorously specifying the desired behaviour of a hardware or software system, making a precise model of its actual behaviour, and then verifying whether that actual behaviour corresponds to the specification.<br><br> My habiliation thesis reports on various contributions to this realm, where my main interest has been on algorithmic aspects. This is motivated by the observation that asymptotic worst-case complexity, often used to characterize the difficulty of algorithmic problems, is only loosely related to the difficulty encountered in solving those problems in practice.<br><br> The two main types of system I have been working on are pushdown systems and Petri nets. Both are fundamental notions of computation, and both offer, in my opinion, particularly nice opportunities for combining theory and algorithmics.<br><br> Pushdown systems are finite automata equipped with a stack; since the height of the stack is not bounded, they represent a class of infinite-state systems that model programs with (recursive) procedure calls. Moreover, we shall see that specifying authorizations is another, particularly interesting application of pushdown systems.<br><br> While pushdown systems are primarily suited to express sequential systems, Petri nets model concurrent systems. My contributions in this area all concern unfoldings. In a nutshell, the unfolding of a net N is an acyclic version of N in which loops have been unrolled. Certain verification problems, such as reachability, have a lower complexity on unfoldings than on general Petri nets.

This thesis studies data structures in the word-RAM and bitprobe models, with an emphasis on space efficiency. In the word-RAM model of computation the space cost of a data structure is measured in terms of the number of w-bit words stored in memory, and the cost of answering a query is measured in terms of the number of read, write, and arithmetic operations that must be performed. In the bitprobe model, like the word-RAM model, the space cost is measured in terms of the number of bits stored in memory, but the query cost is measured solely in terms of the number of bit accesses, or probes, that are performed. First, we examine the problem of succinctly representing a partially ordered set, or poset, in the word-RAM model with word size Theta(lg n) bits. A succinct representation of a combinatorial object is one that occupies space matching the information theoretic lower bound to within lower order terms. We show how to represent a poset on n vertices using a data structure that occupies n^2/4 + o(n^2) bits, and can answer precedence (i.e., less-than) queries in constant time. Since the transitive closure of a directed acyclic graph is a poset, this implies that we can support reachability queries on an arbitrary directed graph in the same space bound. As far as we are aware, this is the first representation of an arbitrary directed graph that supports reachability queries in constant time, and stores less than n choose 2 bits. We also consider several additional query operations. Second, we examine the problem of supporting range queries on strings of n characters (or, equivalently, arrays of n elements) in the word-RAM model with word size Theta(lg n) bits. We focus on the specific problem of answering range majority queries: i.e., given a range, report the character that is the majority among those in the range, if one exists. We show that these queries can be supported in constant time using a linear space (in words) data structure. We generalize this result in several directions, considering various frequency thresholds, geometric variants of the problem, and dynamism. These results are in stark contrast to recent work on the similar range mode problem, in which the query operation asks for the mode (i.e., most frequent) character in a given range. The current best data structures for the range mode problem take soft-Oh(n^(1/2)) time per query for linear space data structures. Third, we examine the deterministic membership (or dictionary) problem in the bitprobe model. This problem asks us to store a set of n elements drawn from a universe [1,u] such that membership queries can be always answered in t bit probes. We present several new fully explicit results for this problem, in particular for the case when n = 2, answering an open problem posed by Radhakrishnan, Shah, and Shannigrahi [ESA 2010]. We also present a general strategy for the membership problem that can be used to solve many related fundamental problems, such as rank, counting, and emptiness queries. Finally, we conclude with a list of open problems and avenues for future work.

The ongoing search for energy conservation in built structures and during the construction process prompted this thesis work to explore the use of sustainable technologies for floor heating systems. The thesis work explores the use of thermoplastic material as a sustainable substitute material for future floor heating systems. Concrete materials are presently used extensively for floor heating systems. Thermoplastic materials are seldom used for floor heating and the primary focus of this thesis is to explore the suitability & adaptability of thermoplastics as an innovative energy saving floor heating material. A thorough study of energy demands and the impact on environment due to greenhouse gas emissions has been done. Thermoplastic materials are environmental friendly and light weight. They exhibit high thermal conductivity which is favourable for the floor heating systems. A design technique has been developed for the use of thermoplastic materials as an energy efficient floor heating material. The present technique creates a new modular floor heating system. The design technique uses thermoplastic material of size 2.4m x1.2m with embedded electric heaters. Thermoplastic foam panels act as a single building block. A numerical simulation has been carried out to study the heat transfer characteristics of the proposed material. Limited experiments were conducted to verify the validity of the simulation results. The results from the experiments indicate good agreement with simulation results. The energy savings from the thermoplastic floor heating systems have been compared with that of electrical floor heating systems. The adaptability of the new floor heating system in terms of energy savings and cost benefit analysis is also discussed. / sustainable floor heating system

Reducing the energy consumption of available resources is still a problem to be solved in Wireless Sensor Networks (WSNs). Many types of existing routing protocols are developed to save power consumption. In these protocols, cluster-based routing protocols are found to be more energy efficient. A cluster head is selected to aggregate the data received from root nodes and forwards these data to the base station in cluster-based routing. The selection of cluster heads should be efficient to save energy. In our proposed protocol, we use static clustering for the efficient selection of cluster heads. The proposed routing protocol works efficiently in large as well as small areas. For an optimal number of cluster head selection we divide a large sensor field into rectangular clusters. Then these rectangular clusters are further grouped into zones for efficient communication between cluster heads and a base station. We perform MATLAB simulations to observe the network stability, throughput, energy consumption, network lifetime and the number of cluster heads. Our proposed routing protocol outperforms in large areas in comparison with the LEACH, MH-LEACH, and SEP routing protocols.

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