A survey on the inverse integrating factor

The relation between limit cycles of planar differential systems and the inverse integrating factor was first shown in an article of Giacomini, Llibre and Viano appeared in 1996. From that moment on, many research articles are devoted to the study of the properties of the inverse integrating factor and its relationwith limit cycles and their bifurcations. This paper is a summary of all the results about this topic. We include a list of references together with the corresponding related results aiming at being as much exhaustive as possible. The paper is, nonetheless, self-contained in such a way that all the main results on the inverse integrating factor are stated and a complete overview of the subject is given. Each section contains a different issue to which the inverse integrating factor plays a role: the integrability problem, relation with Lie symmetries, the center problem, vanishing set of an inverse integrating factor, bifurcation of limit cycles from either a period annulus or from a monodromic ω-limit set and some generalizations.

Decoding auditory EEG responses in healthy and clinical populations: A comparative study.

BACKGROUND: Analyses of brain responses to external stimuli are typically based on the means computed across conditions. However in many cognitive and clinical applications, taking into account their variability across trials has turned out to be statistically more sensitive than comparing their means. NEW METHOD: In this study we present a novel implementation of a single-trial topographic analysis (STTA) for discriminating auditory evoked potentials at predefined time-windows. This analysis has been previously introduced for extracting spatio-temporal features at the level of the whole neural response. Adapting the STTA on specific time windows is an essential step for comparing its performance to other time-window based algorithms. RESULTS: We analyzed responses to standard vs. deviant sounds and showed that the new implementation of the STTA gives above-chance decoding results in all subjects (in comparison to 7 out of 11 with the original method). In comatose patients, the improvement of the decoding performance was even more pronounced than in healthy controls and doubled the number of significant results. COMPARISON WITH EXISTING METHOD(S): We compared the results obtained with the new STTA to those based on a logistic regression in healthy controls and patients. We showed that the first of these two comparisons provided a better performance of the logistic regression; however only the new STTA provided significant results in comatose patients at group level. CONCLUSIONS: Our results provide quantitative evidence that a systematic investigation of the accuracy of established methods in normal and clinical population is an essential step for optimizing decoding performance.

Sähkökäyttöisen konejärjestelmän vuorovaikutteinen simulointi

Työn tavoitteena oli toteuttaa simulointimalli, jolla pystytään tutkimaan kestomagnetoidun tahtikoneen aiheuttaman vääntömomenttivärähtelyn vaikutuksia sähkömoottoriin liitetyssä mekaniikassa. Tarkoitus oli lisäksi selvittää kuinka kyseinen simulointimalli voidaan toteuttaa nykyaikaisia simulointiohjelmia käyttäen. Saatujen simulointitulosten oikeellisuus varmistettiin tätä työtä varten rakennetulla verifiointilaitteistolla. Tutkittava rakenne koostui akselista, johon kiinnitettiin epäkeskotanko. Epäkeskotankoon kiinnitettiin massa, jonka sijaintia voitiin muunnella. Massan asemaa muuttamalla saatiin rakenteelle erilaisia ominaistaajuuksia. Epäkeskotanko mallinnettiin joustavana elementtimenetelmää apuna käyttäen. Mekaniikka mallinnettiin dynamiikan simulointiin tarkoitetussa ADAMS –ohjelmistossa, johon joustavana mallinnettu epäkeskotanko tuotiin ANSYS –elementtimenetelmäohjelmasta. Mekaniikan malli siirrettiin SIMULINK –ohjelmistoon, jossa mallinnettiin myös sähkökäyttö. SIMULINK –ohjelmassa mallinnettiin sähkökäyttö, joka kuvaa kestomagnetoitua tahtikonetta. Kestomagnetoidun tahtikoneen yhtälöt perustuvat lineaarisiin differentiaaliyhtälöihin, joihin hammasvääntömomentin vaikutus on lisätty häiriösignaalina. Sähkökäytön malli tuottaa vääntömomenttia, joka syötetään ADAMS –ohjelmistolla mallinnettuun mekaniikkaan. Mekaniikan mallista otetaan roottorin kulmakiihtyvyyden arvo takaisinkytkentänä sähkömoottorin malliin. Näin saadaan aikaiseksi yhdistetty simulointi, joka koostuu sähkötoimilaitekäytöstä ja mekaniikasta. Tulosten perusteella voidaan todeta, että sähkökäyttöjen ja mekaniikan yhdistetty simulointi on mahdollista toteuttaa valituilla menetelmillä. Simuloimalla saadut tulokset vastaavat hyvin mitattuja tuloksia.

From bird to sparrow: Learning-induced modulations in fine-grained semantic discrimination.

Recognition of environmental sounds is believed to proceed through discrimination steps from broad to more narrow categories. Very little is known about the neural processes that underlie fine-grained discrimination within narrow categories or about their plasticity in relation to newly acquired expertise. We investigated how the cortical representation of birdsongs is modulated by brief training to recognize individual species. During a 60-minute session, participants learned to recognize a set of birdsongs; they improved significantly their performance for trained (T) but not control species (C), which were counterbalanced across participants. Auditory evoked potentials (AEPs) were recorded during pre- and post-training sessions. Pre vs. post changes in AEPs were significantly different between T and C i) at 206-232ms post stimulus onset within a cluster on the anterior part of the left superior temporal gyrus; ii) at 246-291ms in the left middle frontal gyrus; and iii) 512-545ms in the left middle temporal gyrus as well as bilaterally in the cingulate cortex. All effects were driven by weaker activity for T than C species. Thus, expertise in discriminating T species modulated early stages of semantic processing, during and immediately after the time window that sustains the discrimination between human vs. animal vocalizations. Moreover, the training-induced plasticity is reflected by the sharpening of a left lateralized semantic network, including the anterior part of the temporal convexity and the frontal cortex. Training to identify birdsongs influenced, however, also the processing of C species, but at a much later stage. Correct discrimination of untrained sounds seems to require an additional step which results from lower-level features analysis such as apperception. We therefore suggest that the access to objects within an auditory semantic category is different and depends on subject's level of expertise. More specifically, correct intra-categorical auditory discrimination for untrained items follows the temporal hierarchy and transpires in a late stage of semantic processing. On the other hand, correct categorization of individually trained stimuli occurs earlier, during a period contemporaneous with human vs. animal vocalization discrimination, and involves a parallel semantic pathway requiring expertise.

Tietojärjestelmän kehittäminen markkinaehtoisten sähkösopimusten hallintaan

Tässä työssä toteutettiin Lappeenrannan Energia Oy:lle tietojärjestelmäratkaisu, jolla yritys kykenee helposti ja vaivattomasti hallitsemaan asiakkaiden dynaamiset sähkösopimukset. Työn teoriaosa antaa lukijalle kattavan kuvan tietojärjestelmien kehitysprosessista, sekä esittelee työmenetelmiä ja mahdollisia ongelmia. Myös sähkömarkkinoista esitellään kompakti tietopaketti lukijalle, jotta toteutusosan asiat olisivat selkeämpiä. Käytännön osuus esittelee Lappeenrannan Energia Oy:n dynaamisten sähkösopimusten nykyistä toimintamallia ja uuden toteutettavan tietojärjestelmän vaatimukset. Uuden järjestelmän tavoitteena oli tuoda yritykselle kilpailuetua, parantamalla työn tehokkuutta ja sopimuksien hallintaa. Uusi tietojärjestelmä käydään läpi ominaisuuksittain, jotta saadaan hyvä kokonaiskäsitys sen kaikista ominaisuuksista. Työ käsittää siis toteutuksen aina suunnitteluasteelta lopputulokseen asti. Myös tulevaisuuden kehityksen ensiaskeleet esitellään työn lopuksi.

Distinct roles of NMDA receptors at different stages of granule cell development in the adult brain.

NMDA receptor (NMDAR)-dependent forms of synaptic plasticity are thought to underlie the assembly of developing neuronal circuits and to play a crucial role in learning and memory. It remains unclear how NMDAR might contribute to the wiring of adult-born granule cells (GCs). Here we demonstrate that nascent GCs lacking NMDARs but rescued from apoptosis by overexpressing the pro-survival protein Bcl2 were deficient in spine formation. Insufficient spinogenesis might be a general cause of cell death restricted within the NMDAR-dependent critical time window for GC survival. NMDAR loss also led to enhanced mushroom spine formation and synaptic AMPAR activity throughout the development of newborn GCs. Moreover, similar elevated synapse maturation in the absence of NMDARs was observed in neonate-generated GCs and CA1 pyramidal neurons. Together, these data suggest that NMDAR operates as a molecular monitor for controlling the activity-dependent establishment and maturation rate of synaptic connections between newborn neurons and others.

Kunnallisen palveluyksikön toimintojen kehittäminen ja kustannusten

Työn tavoitteena on sisäisen palveluyksikön prosessikuvauksien kautta kehittää nykyistä toimintaa, laskea tuotettujen palveluiden yksikkökustannuksia ja arvioida palkitsemisen vaikutusta sisäisten tukipalveluiden tuottamisen tehostamiseen Nurmijärven kunnassa. Toimintolaskennalla saadaan aikaiseksi tuotetuille palveluille kustannukset ja tuotehinnoittelu. Tällä saadaan aikaan lähes aiheuttamisperiaatteen mukainen kustannusten kohdistaminen. Lisäksi työssä arvioidaan kustannusten kautta saavutettavaa toiminnan tehokkuutta. Työssä haastateltiin yksikön henkilökuntaa, minkä tuloksena saatiin toiminnasta prosessikuvaukset. Toimintolaskennassa tiedot kerättiin eri järjestelmistä ja yksikössä mitattiin työtehtävien hoitoon käytettyä aikaa. Kannusteiden vaikutuksista järjestettiin kolmen organisaation tietotekniikkayksiköiden henkilökunnalle kysely sekä yksikön esimiehet haastateltiin. Haastattelun avulla selvitettiin palkitsemisen nykytilannetta ja tulevaisuuden kehittämismahdollisuuksia. Tuloksena saatiin tukipalveluhinnasto, jolla toteutettiin sisäisten kustannusten kohdistaminen organisaatiossa. Tukipalveluprosessien kuvaamisen tuloksena saatiin toimenpide-ehdotuksia toteutukseen ja lisäkehittämishankkeita. Työntekijöiden kannustekyselyn tuloksena rahapalkitsemisen lisäksi nousi esiin esimiehen antaman palautteen arvostus sekä oman osaamisen kehittäminen.

Commodity Price Driven Risk Management from Viewpoint of High Grade Steel Alloys

The study of price risk management concerning high grade steel alloys and their components was conducted. This study was focused in metal commodities, of which nickel, chrome and molybdenum were in a central role. Also possible hedging instruments and strategies for referred metals were studied. In the literature part main themes are price formation of Ni, Cr and Mo, the functioning of metal exchanges and main hedging instruments for metal commodities. This section also covers how micro and macro variables may affect metal prices from the viewpoint of short as well as longer time period. The experimental part consists of three sections. In the first part, multiple regression model with seven explanatory variables was constructed to describe price behavior of nickel. Results were compared after this with information created with comparable simple regression model. Additionally, long time mean price reversion of nickel was studied. In the second part, theoretical price of CF8M alloy was studied by using nickel, ferro-chrome and ferro-molybdenum as explanatory variables. In the last section, cross hedging possibilities for illiquid FeCr -metal was studied with five LME futures. Also this section covers new information concerning possible forthcoming molybdenum future contracts as well. The results of this study confirm, that linear regression models which are based on the assumption of market rationality, are not able to reliably describe price development of metals at issue. Models fulfilling assumptions for linear regression may though include useful information of statistical significant variables which have effect on metal prices. According to the experimental part, short futures were found to incorporate the most accurate information concerning the price movements in the future. However, not even 3M futures were able to predict turning point in the market before the faced slump. Cross hedging seemed to be very doubtful risk management strategy for illiquid metals, because correlations coefficients were found to be very sensitive for the chosen time span.

Learning Robot Motions from Visual Sensing

Learning from demonstration becomes increasingly popular as an efficient way of robot programming. Not only a scientific interest acts as an inspiration in this case but also the possibility of producing the machines that would find application in different areas of life: robots helping with daily routine at home, high performance automata in industries or friendly toys for children. One way to teach a robot to fulfill complex tasks is to start with simple training exercises, combining them to form more difficult behavior. The objective of the Master’s thesis work was to study robot programming with visual input. Dynamic movement primitives (DMPs) were chosen as a tool for motion learning and generation. Assuming a movement to be a spring system influenced by an external force, making this system move, DMPs represent the motion as a set of non-linear differential equations. During the experiments the properties of DMP, such as temporal and spacial invariance, were examined. The effect of the DMP parameters, including spring coefficient, damping factor, temporal scaling, on the trajectory generated were studied.

Henkilöauton korin mallintaminen virtuaalitestejä varten

Nykyään auton korien tuotekehitysprosessissa jää hyvin vähän aikaa korin rakenteiden optimointiin. Rakenteiden optimointi tehdään virtuaalitestauksen avulla siten, että yhdellä elementtimallilla tehdään erilaisia testejä ja optimoidaan useita omaisuuksia samanaikaisesti. Tässä tutkimuksessa tavoitteena on kehittää auton korin FEM-malli, jolla voidaan suorittaa mahdollisimman monta erilaista virtuaalitestiä. Rakennetun mallin toimivuutta testattiin tekemällä sille ympäriajoturvallisuustesti ja saatuja tuloksia verrattiin oikean auton testiin.

Animal models of prenatal immune challenge and their contribution to the study of schizophrenia: a systematic review

Prenatal immune challenge (PIC) in pregnant rodents produces offspring with abnormalities in behavior, histology, and gene expression that are reminiscent of schizophrenia and autism. Based on this, the goal of this article was to review the main contributions of PIC models, especially the one using the viral-mimetic particle polyriboinosinic-polyribocytidylic acid (poly-I:C), to the understanding of the etiology, biological basis and treatment of schizophrenia. This systematic review consisted of a search of available web databases (PubMed, SciELO, LILACS, PsycINFO, and ISI Web of Knowledge) for original studies published in the last 10 years (May 2001 to October 2011) concerning animal models of PIC, focusing on those using poly-I:C. The results showed that the PIC model with poly-I:C is able to mimic the prodrome and both the positive and negative/cognitive dimensions of schizophrenia, depending on the specific gestation time window of the immune challenge. The model resembles the neurobiology and etiology of schizophrenia and has good predictive value. In conclusion, this model is a robust tool for the identification of novel molecular targets during prenatal life, adolescence and adulthood that might contribute to the development of preventive and/or treatment strategies (targeting specific symptoms, i.e., positive or negative/cognitive) for this devastating mental disorder, also presenting biosafety as compared to viral infection models. One limitation of this model is the incapacity to model the full spectrum of immune responses normally induced by viral exposure.

Optimizing the Performance of a Heat Exchanger Network

This research is the continuation and a joint work with a master thesis that has been done in this department recently by Hemamali Chathurangani Yashika Jayathunga. The mathematical system of the equations in the designed Heat Exchanger Network synthesis has been extended by adding a number of equipment; such as heat exchangers, mixers and dividers. The solutions of the system is obtained and the optimal setting of the valves (Each divider contains a valve) is calculated by introducing grid-based optimization. Finding the best position of the valves will lead to maximization of the transferred heat in the hot stream and minimization of the pressure drop in the cold stream. The aim of the following thesis will be achieved by practicing the cost optimization to model an optimized network.

Age-related changes in ERPs associated with context-based and response-based interference

Age-related differences in information processing have often been explained through deficits in older adults' ability to ignore irrelevant stimuli and suppress inappropriate responses through inhibitory control processes. Functional imaging work on young adults by Nelson and colleagues (2003) has indicated that inferior frontal and anterior cingulate cortex playa key role in resolving interference effects during a delay-to-match memory task. Specifically, inferior frontal cortex appeared to be recruited under conditions of context interference while the anterior cingulate was associated with interference resolution at the stage of response selection. Related work has shown that specific neural activities related to interference resolution are not preserved in older adults, supporting the notion of age-related declines in inhibitory control (Jonides et aI., 2000, West et aI., 2004b). In this study the time course and nature of these inhibition-related processes were investigated in young and old adults using high-density ERPs collected during a modified Sternberg task. Participants were presented with four target letters followed by a probe that either did or did not match one of the target letters held in working memory. Inhibitory processes were evoked by manipulating the nature of cognitive conflict in a particular trial. Conflict in working memory was elicited through the presentation of a probe letter in immediately previous target sets. Response-based conflict was produced by presenting a negative probe that had just been viewed as a positive probe on the previous trial. Younger adults displayed a larger orienting response (P3a and P3b) to positive probes relative to a non-target baseline. Older adults produced the orienting P3a and 3 P3b waveforms but their responses did not differentiate between target and non-target stimuli. This age-related change in response to targetness is discussed in terms of "early selection/late correction" models of cognitive ageing. Younger adults also showed a sensitivity in their N450 response to different levels of interference. Source analysis of the N450 responses to the conflict trials of younger adults indicated an initial dipole in inferior frontal cortex and a subsequent dipole in anterior cingulate cortex, suggesting that inferior prefrontal regions may recruit the anterior cingulate to exert cognitive control functions. Individual older adults did show some evidence of an N450 response to conflict; however, this response was attenuated by a co-occurring positive deflection in the N450 time window. It is suggested that this positivity may reflect a form of compensatory activity in older adults to adapt to their decline in inhibitory control.

Approches générales de résolution pour les problèmes multi-attributs de tournées de véhicules et confection d'horaires

Thèse réalisée en cotutelle entre l'Université de Montréal et l'Université de Technologie de Troyes

Study of histone H3 lysine 56 deacetylation in saccharomyces cerevisiae

Chez la levure Saccharomyces cerevisiae, l'acétylation de l'histone H3 sur la lysine 56 (H3K56ac) est présente sur les histones néo-synthétisées déposées derrière les fourches de réplication et est essentielle pour préserver la viabilité cellulaire en réponse au dommage à l'ADN. La désacétylation d'H3K56 sur l'ensemble du génome catalysée par Hst3 et Hst4 et a lieu en phase G2 ou M. H3K56ac est une lame à double tranchant. L'absence d'H3K56ac rend les cellules sensibles aux dommages à l'ADN. En revanche, un excès d'acétylation d'H3K56 dans un mutant hst3Δ hst4Δ a des conséquences encore plus sévères tels que la thermo-sensibilité, l'hypersensibilité aux agents génotoxiques, l'instabilité génomique ainsi qu'une courte durée de vie réplicative. Les désacétylases Hst3 et Hst4 sont étroitement régulées au cours du cycle cellulaire afin de permettre à l'H3K56ac d'exercer son rôle en réponse aux dommages à l'ADN tout en évitant les conséquences néfastes de l'hyperacétylation d'H3K56. Dans cette thèse, nous avons identifié la machinerie moléculaire responsable de la dégradation de Hst3. De plus, nous avons exploré les raisons pour lesquelles l'absence de désacétylation donne lieu aux phénotypes du mutant hst3Δ hst4Δ. Au chapitre 2, nous démontrons que la dégradation d'Hst3 peut être complétée avant l'anaphase. Ceci suggère que la désacétylation de H3K56 a lieu durant une courte fenêtre du cycle cellulaire se situant entre la complétion de la phase S et la métaphase. De plus, nous avons identifié deux sites de phosphorylation d'Hst3 par la kinase cycline-dépendante 1 (Cdk1) et démontré que ces évènements de phosphorylation conduisent à la dégradation d'Hst3 in vivo. Nous avons aussi démontré que l'ubiquityltransférase Cdc34 et l'ubiquitine ligase SCFCdc4 sont requises pour la dégradation d'Hst3. Finalement, nous avons montré que la phosphorylation d'Hst3 par la kinase mitotique Clb2-Cdk1 peut directement entraîner l'ubiquitylation d'Hst3 par SCFCdc4 in vitro. Au chapitre 3, nous avons étudié les mécanismes moléculaires sous-jacents à la sensibilité extrême du mutant hst3Δ hst4Δ aux agents qui endommagent l'ADN. Nous avons établi qu'en raison de la présence anormale d'H3K56ac devant les fourches de réplication, le mutant hst3Δ hst4Δ exhibe une forte perte de viabilité lorsqu'exposé au méthyl méthanesulfonate (MMS) durant un seul passage à travers la phase S. Nous avons aussi découvert que, malgré le fait que le point de contrôle de réponse aux dommages à l'ADN est activé normalement dans le mutant hst3Δ hst4Δ, ce mutant est incapable de compléter la réplication de l'ADN et d'inactiver le point de contrôle pour une longue période de temps après exposition transitoire au MMS. L'ensemble de nos résultats suggère que les lésions à l'ADN induites par le MMS dans le mutant hst3Δ hst4Δ causent une forte perte de viabilité parce que ce mutant est incapable de compléter la réplication de l'ADN après une exposition transitoire au MMS. Dans la deuxième section du chapitre 3, nous avons employé une approche génétique afin d'identifier de nouveaux mécanismes de suppression de deux phénotypes prononcés du mutant hst3Δ hst4Δ. Nous avons découvert que la délétion de plusieurs gènes impliqués dans la formation de frontières entre l'hétérochromatine et de l'euchromatine atténue les phénotypes du mutant hst3Δ hst4Δ sans réduire l'hyperacétylation d'H3K56. Nos résultats indiquent aussi que l'abondante acétylation de l'histone H4 sur la lysine 16 (H4K16ac) est néfaste au mutant hst3Δ hst4Δ. Ce résultat suggère un lien génétique intriguant entre l'acétylation d'H3K56 et celle d'H4K16. L'existence de ce lien était jusqu'à présent inconnu. Nous avons identifié un groupe de suppresseurs spontanés où H3K56ac est indétectable, mais la majorité de nos suppresseurs ne montrent aucune réduction flagrante d'H3K56ac ou d'H4 K16ac par rapport aux niveaux observés dans le mutant hst3Δ hst4Δ. Une étude plus approfondie de ce groupe de suppresseurs est susceptible de mener à la découverte de nouveaux mécanismes génétiques ou épigénétiques permettant d'éviter les conséquences catastrophiques de l'hyperacétylation d'H3K56 chez le mutant hst3Δ hst4Δ. En résumé, cette thèse identifie la machinerie moléculaire responsable de la dégradation d'Hst3 (une désacétylase d'H3K56) durant une fenêtre de temps situées entre la fin de la phase S et la métaphase. Nos résultats permettent aussi d'expliquer pourquoi la dégradation d'Hst3 précède le début de la phase S durant laquelle l'acétylation d'H3K56 s'accumule derrière les fourches de réplication afin d'exercer son rôle de mécanisme de défense contre le dommage à l'ADN. De plus, nous avons identifié plusieurs suppresseurs qui permettent de contourner le rôle important d'Hst3 et Hst4 en réponse au dommage à l'ADN. Plusieurs suppresseurs révèlent un lien génétique inattendu entre deux formes abondantes d'acétylation des histones chez Saccharomyces cerevisiae, soit H3K56ac et H4K16ac.