From caging to rouse dynamics in polymer melts with intramolecular barriers: a critical test of the mode coupling theory

By means of computer simulations and solution of the equations of the mode coupling theory (MCT),we investigate the role of the intramolecular barriers on several dynamic aspects of nonentangled polymers. The investigated dynamic range extends from the caging regime characteristic of glass-formers to the relaxation of the chain Rouse modes. We review our recent work on this question,provide new results, and critically discuss the limitations of the theory. Solutions of the MCT for the structural relaxation reproduce qualitative trends of simulations for weak and moderate barriers. However, a progressive discrepancy is revealed as the limit of stiff chains is approached. This dis-agreement does not seem related with dynamic heterogeneities, which indeed are not enhanced by increasing barrier strength. It is not connected either with the breakdown of the convolution approximation for three-point static correlations, which retains its validity for stiff chains. These findings suggest the need of an improvement of the MCT equations for polymer melts. Concerning the relaxation of the chain degrees of freedom, MCT provides a microscopic basis for time scales from chain reorientation down to the caging regime. It rationalizes, from first principles, the observed deviations from the Rouse model on increasing the barrier strength. These include anomalous scaling of relaxation times, long-time plateaux, and nonmonotonous wavelength dependence of the mode correlators.

The challenges of building theory by combining lenses

The article presents a discussion of foundational issues in the field of management science, focusing on advances in management theory and research. The metaphor of explanatory lenses is used as a rubric to illustrate the theoretical challenges involved in elucidating the interrelationships of various factors in organizational behavior. The importance of clarifying such interrelationships is emphasized, from the standpoint of editing scholarly papers on such topics for publication. Topics discussed include communication and psychology in management, economics, and behavioral finance.

The role of intramolecular barriers on the glass transition of polymers: computer simulations versus mode coupling theory

We present computer simulations of a simple bead-spring model for polymer melts with intramolecular barriers. By systematically tuning the strength of the barriers, we investigate their role on the glass transition. Dynamic observables are analyzed within the framework of the mode coupling theory (MCT). Critical nonergodicity parameters, critical temperatures, and dynamic exponents are obtained from consistent fits of simulation data to MCT asymptotic laws. The so-obtained MCT λ-exponent increases from standard values for fully flexible chains to values close to the upper limit for stiff chains. In analogy with systems exhibiting higher-order MCT transitions, we suggest that the observed large λ-values arise form the interplay between two distinct mechanisms for dynamic arrest: general packing effects and polymer-specific intramolecular barriers. We compare simulation results with numerical solutions of the MCT equations for polymer systems, within the polymer reference interaction site model (PRISM) for static correlations. We verify that the approximations introduced by the PRISM are fulfilled by simulations, with the same quality for all the range of investigated barrier strength. The numerical solutions reproduce the qualitative trends of simulations for the dependence of the nonergodicity parameters and critical temperatures on the barrier strength. In particular, the increase in the barrier strength at fixed density increases the localization length and the critical temperature. However the qualitative agreement between theory and simulation breaks in the limit of stiff chains. We discuss the possible origin of this feature.

Thermodynamic stability of nanosized multicomponent bubbles/droplets: The square gradient theory and the capillary approach

Formation of nanosized droplets/bubbles from a metastable bulk phase is connected to many unresolved scientific questions. We analyze the properties and stability of multicomponent droplets and bubbles in the canonical ensemble, and compare with single-component systems. The bubbles/droplets are described on the mesoscopic level by square gradient theory. Furthermore, we compare the results to a capillary model which gives a macroscopic description. Remarkably, the solutions of the square gradient model, representing bubbles and droplets, are accurately reproduced by the capillary model except in the vicinity of the spinodals. The solutions of the square gradient model form closed loops, which shows the inherent symmetry and connected nature of bubbles and droplets. A thermodynamic stability analysis is carried out, where the second variation of the square gradient description is compared to the eigenvalues of the Hessian matrix in the capillary description. The analysis shows that it is impossible to stabilize arbitrarily small bubbles or droplets in closed systems and gives insight into metastable regions close to the minimum bubble/droplet radii. Despite the large difference in complexity, the square gradient and the capillary model predict the same finite threshold sizes and very similar stability limits for bubbles and droplets, both for single-component and two-component systems.

Osakeyhtiön sivuuttaminen, kohdistamisongelmana tulonsaaja - OY vs. osakas

Tutkielman tavoitteena on tutkia veronkiertosäännöksen eli VML 28 §:n soveltamista sivuutettaessa osakeyhtiö verotuksessa. Tutkielma on rajattu tapauksiin, joissa osakeyhtiön tuloa on sivuutettu ja verotettu osakkaan palkkatulona. Tutkielma muodostuu lähinnä kirjallisuuteen ja lainsäädäntöön perustuvista teoriaosista sekä oikeuskäytäntöön pohjautuvasta tutkimusosasta. Tutkimus on oikeusdogmaattinen, eli tarkoituksena on selvittää voimassa olevan lainsäädännön sisältö. Tutkimuksessa on käyty läpi korkeimman hallinto-oikeuden ja hallinto-oikeuksien päätöksiä ja selvitetty näiden avulla kriteerejä, joita voidaan pitää tunnusmerkkeinä vallitsevasta palkkasuhteesta. Tämä saattaa johtaa verotuksessa osakeyhtiön tulon sivuuttamiseen. Päätös osakeyhtiön sivuuttamisesta tehdään kuitenkin aina kokonaisarvioinnin perusteella. Päätöksen lopputulokseen vaikuttaa kuitenkin merkittävästi mm. osakeyhtiön toimeksiantajien lukumäärä. Mikäli toimeksisaaja työskentelee hyvin samankaltaisissa olosuhteissa kuin toimeksiantajan työntekijät, voidaan osakeyhtiö verotuksessa sivuuttaa, mikäli tilanne tulee esille esim. verotarkastuksen yhteydessä.

Epäasianmukainen verontorjunta ympäristöverotuksessa

Epäasianmukaisella verontorjunnalla kannustintyyppisten ympäristöverojen yhteydessä tarkoitetaan sitä, että veron määrä vähenee ilman ympäristön tilan paranemista. Tutkimuksessa selvitetään, millaisia epäasianmukaisia verontorjuntakeinoja ympäristöveroihin liittyy, kuinka paljon niissä on kyse lainsäädäntöteknisistä valinnoista sekä lainsäädännön puutteellisuudesta ja kuinka ympäristöverotusta voitaisiin mahdollisesti parantaa. Esitys painottuu normatiiviseen sääntelyteoriaan eli siihen, minkälainen ohjauskeino tai sääntely palvelee parhaiten tietyn yhteiskuntapoliittisen päämäärän saavuttamista. Päästöt ovat usein suorassa suhteessa tuotteen ominaisuuksiin, mutta ympäristöverot eivät. Ongelmalliseksi muodostuvat lisäksi veronalennukset, kuten veroporrastukset ja veron palautukset. Nämä kannustavat epäasianmukaiseen verontorjuntaan, kuten yritysjärjestelyihin, hamstraukseen ja esimerkiksi jätteiden sijoittamiseen kaatopaikkojen ulkopuolelle. Epäasianmukaista verontorjuntaa voidaan ehkäistä muun muassa kiristämällä rangaistuksia, tiedottamalla, kaventamalla normaaliverokohtelun ja lievennetyn verokohtelun eroa sekä verotuksen kohdetta muuttamalla. Tärkeintä tulevaisuudessa olisi kuitenkin keskittyä kansainväliseen yhteistyöhön ja ympäristöverotuksen yhdenmukaistamiseen.

Versatility of field theory motivated nuclear effective Lagrangian approach

We analyze the results for infinite nuclear and neutron matter using the standard relativistic mean field model and its recent effective field theory motivated generalization. For the first time, we show quantitatively that the inclusion in the effective theory of vector meson self-interactions and scalar-vector cross-interactions explains naturally the recent experimental observations of the softness of the nuclear equation of state, without losing the advantages of the standard relativistic model for finite nuclei.

Theory of mind impairment in patients with behavioural variant fronto-temporal dementia (bv-FTD) increases caregiver burden.

BACKGROUND: Theory of mind (ToM), the capacity to infer the intention, beliefs and emotional states of others, is frequently impaired in behavioural variant fronto-temporal dementia patients (bv-FTDp); however, its impact on caregiver burden is unexplored. SETTING: National Institute of Neurological Disorders and Stroke, National Institutes of Health. SUBJECTS: bv-FTDp (n = 28), a subgroup of their caregivers (n = 20) and healthy controls (n = 32). METHODS: we applied a faux-pas (FP) task as a ToM measure in bv-FTDp and healthy controls and the Zarit Burden Interview as a measure of burden in patients' caregivers. Patients underwent structural MRI; we used voxel-based morphometry to examine relationships between regional atrophy and ToM impairment and caregiver burden. RESULTS: FP task performance was impaired in bv-FTDp and negatively associated with caregiver burden. Atrophy was found in areas involved in ToM. Caregiver burden increased with greater atrophy in left lateral premotor cortex, a region associated in animal models with the presence of mirror neurons, possibly involved in empathy. CONCLUSION: ToM impairment in bv-FTDp is associated with increased caregiver burden.

Participação da radiologia nas perícias necroscópicas de baleados realizadas no Instituto Médico-Legal do Rio de Janeiro

OBJETIVO: Este trabalho aborda as conseqüências de laudos necroscópicos incompletos de baleados, nos casos em que não foi possível o uso de recursos radiológicos para localizar os projéteis de arma de fogo. MATERIAIS E MÉTODOS: Foram analisados 8.185 laudos necroscópicos do Instituto Médico-Legal Afrânio Peixoto, Rio de Janeiro, RJ, referentes à demanda total de cadáveres no período de 1º de janeiro a 31 de dezembro de 2001, dos quais 3.122 casos corresponderam a necropsias de baleados. RESULTADOS: Desses casos, 309 corpos foram sepultados contendo ainda, no seu interior, projéteis de arma de fogo, podendo suscitar futuras indagações judiciais. No mesmo período foram solicitadas 23 exumações, 12 delas com a finalidade de recolher projéteis. Foram calculados os gastos relacionados à realização de necropsias de baleados - R$ 996,85 - e custos alusivos à realização de exumações com a finalidade de recolher projéteis de arma de fogo - R$ 1.155,40, visando a estabelecer o montante financeiro que poderia ser poupado pelos cofres públicos, a ser alocado para finalidades outras, se a perícia médico-legal de baleados, no exame inicial, obtivesse sucesso. CONCLUSÃO: Os resultados permitiram concluir que todos os atos necroscópicos de baleados devem seguir protocolos específicos, uma vez que perícias incompletas exigem exumação posterior, com gastos adicionais desnecessários.

Proportionality and Party Success in Europe

This thesis consists of four articles and an introductory section. The main research questions in all the articles are about proportionality and party success in Europe, at European, national or district levels. Proportionality in this thesis denotes the proximity of seat shares parties receive compared to their respective vote shares, after the electoral system’s allocation process. This proportionality can be measured through numerous indices that illustrate either the overall proportionality of an electoral system or a particular election. The correspondence of a single party’s seat shares to its vote shares can also be measured. The overall proportionality is essential in three of the articles (1, 2 and 4), where the system’s performance is studied by means of plots. In article 3, minority party success is measured by advantage-ratios that reveal single party’s winnings or losses in the votes to seat allocation process. The first article asks how proportional are the European parliamentary (EP) electoral systems, how do they compare with results gained from earlier studies and how do the EP electoral systems treat different sized parties. The reasons for different outcomes are looked for in explanations given by traditional electoral studies i.e. electoral system variables. The countries studied (EU15) apply electoral systems that vary in many important aspects, even though a certain amount of uniformity has been aspired to for decades. Since the electoral systems of the EP elections closely resemble the national elections, the same kinds of profiles emerge as in the national elections. The electoral systems indeed treat the parties differentially and six different profile types can be found. The counting method seems to somewhat determine the profile group, but the strongest variables determining the shape of a countries’ profile appears to be the average district magnitude and number of seats allocated to each country. The second article also focuses on overall proportionality performance of an electoral system, but here the focus is on the impact of electoral system changes. I have developed a new method of visualizing some previously used indices and some new indices for this purpose. The aim is to draw a comparable picture of these electoral systems’ changes and their effects. The cases, which illustrate this method, are four elections systems, where a change has occurred in one of the system variables, while the rest remained unchanged. The studied cases include the French, Greek and British European parliamentary systems and the Swedish national parliamentary system. The changed variables are electoral type (plurality changed to PR in the UK), magnitude (France splitting the nationwide district into eight smaller districts), legal threshold (Greece introducing a three percent threshold) and counting method (d’Hondt was changed to modified Sainte-Laguë in Sweden). The radar plots from elections after and before the changes are drawn for all country cases. When quantifying the change, the change in the plots area that is created has also been calculated. Using these radar plots we can observe that the change in electoral system type, magnitude, and also to some extent legal threshold had an effect on overall proportionality and accessibility for small parties, while the change between the two highest averages counting method had none. The third article studies the success minority parties have had in nine electoral systems in European heterogeneous countries. This article aims to add more motivation as to why we should care how different sized parties are treated by the electoral systems. Since many of the parties that aspire to represent minorities in European countries are small, the possibilities for small parties are highlighted. The theory of consociational (or power-sharing) democracy suggests that, in heterogeneous societies, a proportional electoral system will provide the fairest treatment of minority parties. The OSCE Lund Recommendations propose a number of electoral system features, which would improve minority representation. In this article some party variables, namely the unity of the minority parties and the geographical concentration of the minorities were included among possible explanations. The conclusions are that the central points affecting minority success were indeed these non-electoral system variables rather than the electoral system itself. Moreover, the size of the party was a major factor governing success in all the systems investigated; large parties benefited in all the studied electoral systems. In the fourth article the proportionality profiles are again applied, but this time to district level results in Finnish parliamentary elections. The level of proportionality distortion is also studied by way of indices. The average magnitudes during the studied periodrange from 7.5 to 26.2 in the Finnish electoral districts and this opens up unequal opportunities for parties in different districts and affects the shape of the profiles. The intra-country case allows the focus to be placed on the effect of district magnitude, since all other electoral systems are kept constant in an intra-country study. The time span in the study is from 1962 to 2007, i.e. the time that the districts have largely been the same geographically. The plots and indices tell the same story, district magnitude and electoral alliances matter. The district magnitude is connected to the overall proportionality of the electoral districts according to both indices, and the profiles are, as expected, also closer to perfect proportionality in large districts. Alliances have helped some small parties to gain a much higher seat share than their respective vote share and these successes affect some of the profiles. The profiles also show a consistent pattern of benefits for the small parties who ally with the larger parties.

What can ecosystems learn? Expanding evolutionary ecology with learning theory.

BACKGROUND: The structure and organisation of ecological interactions within an ecosystem is modified by the evolution and coevolution of the individual species it contains. Understanding how historical conditions have shaped this architecture is vital for understanding system responses to change at scales from the microbial upwards. However, in the absence of a group selection process, the collective behaviours and ecosystem functions exhibited by the whole community cannot be organised or adapted in a Darwinian sense. A long-standing open question thus persists: Are there alternative organising principles that enable us to understand and predict how the coevolution of the component species creates and maintains complex collective behaviours exhibited by the ecosystem as a whole? RESULTS: Here we answer this question by incorporating principles from connectionist learning, a previously unrelated discipline already using well-developed theories on how emergent behaviours arise in simple networks. Specifically, we show conditions where natural selection on ecological interactions is functionally equivalent to a simple type of connectionist learning, 'unsupervised learning', well-known in neural-network models of cognitive systems to produce many non-trivial collective behaviours. Accordingly, we find that a community can self-organise in a well-defined and non-trivial sense without selection at the community level; its organisation can be conditioned by past experience in the same sense as connectionist learning models habituate to stimuli. This conditioning drives the community to form a distributed ecological memory of multiple past states, causing the community to: a) converge to these states from any random initial composition; b) accurately restore historical compositions from small fragments; c) recover a state composition following disturbance; and d) to correctly classify ambiguous initial compositions according to their similarity to learned compositions. We examine how the formation of alternative stable states alters the community's response to changing environmental forcing, and we identify conditions under which the ecosystem exhibits hysteresis with potential for catastrophic regime shifts. CONCLUSIONS: This work highlights the potential of connectionist theory to expand our understanding of evo-eco dynamics and collective ecological behaviours. Within this framework we find that, despite not being a Darwinian unit, ecological communities can behave like connectionist learning systems, creating internal conditions that habituate to past environmental conditions and actively recalling those conditions. REVIEWERS: This article was reviewed by Prof. Ricard V Solé, Universitat Pompeu Fabra, Barcelona and Prof. Rob Knight, University of Colorado, Boulder.