On an upper bound for the arithmetic self-intersection number of the dualizing sheaf on arithmetic surfaces

Vegeu el resum a l'inici del document del fitxer adjunt

Intermediate asymptotics beyond homogeneity and self-similarity: long time behavior for [formula]

"Vegeu el resum a l'inici del document del fitxer adjunt."

Choosing how to choose: self-stable majority rules and constitutions

Constitutional arrangements affect the decisions made by a society. We study how this effect leads to preferences of citizens over constitutions; and ultimately how this has a feedback that determines which constitutions can survive in a given society. Constitutions are stylized here, to consist of a voting rule for ordinary business and possibly different voting rule for making changes to the constitution. We deffine an equilibrium notion for constitutions, called self-stability, whereby under the rules of a self-stable constitution, the society would not vote to change the constitution. We argue that only self-stable constitutions will endure. We prove that self-stable constitutions always exist, but that most constitutions (even very prominent ones) may not be self-stable for some societies. We show that constitutions where the voting rule used to amend the constitution is the same as the voting rule used for ordinary business are dangerously simplistic, and there are (many) societies for which no such constitution is self-stable rule. We conclude with a characterization of the set of self-stable constitutions that use majority rule for ordinary business.

Self-selection consistent functions

This paper studies collective choice rules whose outcomes consist of a collection of simultaneous decisions, each one of which is the only concern of some group of individuals in society. The need for such rules arises in different contexts, including the establishment of jurisdictions, the location of multiple public facilities, or the election of representative committees. We define a notion of allocation consistency requiring that each partial aspect of the global decision taken by society as a whole should be ratified by the group of agents who are directly concerned with this particular aspect. We investigate the possibility of designing envy-free allocation consistent rules, we also explore whether such rules may also respect the Condorcet criterion.

Preparació i caracterització de materials mesoporosos en sistemes tensioactius

Estudi elaborat a partir d’una estada a la Universitat Nacional de Yokohama des de maig fins a mitjans de juny del 2006. S'ha estudiat el comportament fàssic i la preparació de sílica mesoporosa pels nous tensioactius fluorats d'estructura C8F17SO2(C3H7)N(C2H4O)nH (abreujat C8F17(EO)n. El tensioactiu C8F17(EO)n forma micel•les allargades i cristalls líquids en aigua, i per tant pot ser adequat per a la preparació de materials mesoporosos. Sílica mesoestructurada es va preparar pel mètode de precipitació per autoagregació cooperativa. Un estudi sistemàtic es va realitzar, investigant la influència de les concentracions de tensioactiu i precursor (TEOS), l’efecte del pH i de la longitud de cadena de poliòxid d’etilè. Els materials es van caracteritzar per raigs X a angle petit (SAXS), sorció de nitrògen i TEM. Els materials obtinguts presenten diàmetres de por petits i parets de por gruixudes. A més, aquests materials posseeixen altes superfícies específiques, que s’han obtingut emprant concentracions de tensioactiu petites, produint parets de por robustes sense microporositat significativa. La superfície específica es manté durant el procés de calcinació, malgrat un petit encongiment degut a l’entrecreuament de la sílica. Els materials de sílica obtinguts han mostrat ser significativament més robustos que altres materials similars descrits a la bibliografia, com la sílica MCM-41.

The causal relationship between Individual’s choice behavior and self-reported satisfaction: the case of residential mobility in the EU

One of the most persistent and lasting debates in economic research refers to whether the answers to subjective questions can be used to explain individuals’ economic behavior. Using panel data for twelve EU countries, in the present study we analyze the causal relationship between self-reported housing satisfaction and residential mobility. Our results indicate that: i) households unsatisfied with their current housing situation are more likely to move; ii) housing satisfaction raises after a move, and; iii) housing satisfaction increases with the transition from being a renter to becoming a homeowner. Some interesting cross-country differences are observed. Our findings provide evidence in favor of use of subjective indicators of satisfaction with certain life domains in the analysis of individuals’ economic conduct.

Point-occurrence self-similarity in crackling-noise systems and in other complex systems

It has been recently found that a number of systems displaying crackling noise also show a remarkable behavior regarding the temporal occurrence of successive events versus their size: a scaling law for the probability distributions of waiting times as a function of a minimum size is fulfilled, signaling the existence on those systems of self-similarity in time-size. This property is also present in some non-crackling systems. Here, the uncommon character of the scaling law is illustrated with simple marked renewal processes, built by definition with no correlations. Whereas processes with a finite mean waiting time do not fulfill a scaling law in general and tend towards a Poisson process in the limit of very high sizes, processes without a finite mean tend to another class of distributions, characterized by double power-law waiting-time densities. This is somehow reminiscent of the generalized central limit theorem. A model with short-range correlations is not able to escape from the attraction of those limit distributions. A discussion on open problems in the modeling of these properties is provided.

Could cell membranes produce acoustic streaming? Making the case for synechococcus self-propulsion

Sir James Lighthill proposed in 1992 that acoustic streaming occurs in the inner ear, as part of the cochlear amplifier mechanism. Here we hypothesize that some of the most ancient organisms use acoustic streaming not only for self-propulsion but also to enhance their nutrient uptake. We focus on a motile strain of Synechococcus, a yanobacteria whose mechanism for self-propulsion is not known. Molecular motors could work like piezoelectric transducers acting on the crystalline structure surrounding the outer cell membrane. Our calculations show that a traveling surface acoustic wave (SAW)could account for the observed velocities. These SAW waves will also produce a non-negligible Stokes layer surrounding the cell: motion within this region being essentially chaotic. Therefore, an AS mechanism would be biologically advantageous, enhancing localized diffusion processes and consequently, chemical reactions. We believe that acoustic streaming, produced by nanometer scale membrane vibrations could be widespread in cell biology. Other possible instances are yeast cells and erythrocytes. Flows generated by acoustic streaming may also be produced by silica coated diatoms along their raphe. We note that microelectromechanical (MEMS) acoustic streaming devices were first introduced in the 1990’s. Nature may have preceded this invention by 2.7 Gyr.

Territorial autonomy and self-determination conflicts: opportunity and willingness cases from Bolivia, Niger, and Thailand

The paradox of autonomy is about whether self-rule accommodates or exacerbates armed conflict. This study attempts to unpack the puzzle examining the effectiveness of territorial autonomy as a state response to self-determination conflicts throughout the world. It challenges the conflict-inducing features of autonomy arguing that territorial autonomy can mitigate armed conflict by channeling group grievances into peaceful forms of protest. Thus, this study aims at arriving at a comprehensive theory that identifies which factors are responsible for violent escalation of conflicts grounded in self-determination demands. By using the concepts of opportunity structures and willingness dimension, this study shows that conflict escalation only takes place when minorities with greater bargaining power vis-à-vis the center, in contexts of high levels of economic inequality within dyad, are mobilized around autonomy and separatist demands.

GREC CLÀSSIC : curs d'autoaprenentatge introductori

GREC CLÀSSIC. Curs d’autoaprenentatge introductori. Dos anys. El curs consta de tretze lliçons i d’una gramàtica estructurada en quatre blocs: 1. Alfabet i diacrítics, fenòmens fonètics. 2. Morfologia nominal. 3. Morfologia verbal. 4. Infinitius i participis. Sintaxi de les oracions. L’estructura de les lliçons, excepte la primera que inclou l’alfabet, combina qüestions de morfologia nominal i verbal o de morfologia i sintaxi, tal com acostumen a fer els mètodes d’aprenentatge de les llengües modernes. Cada lliçó formula els seus objectius específics, desenvolupa la seva part de continguts i conclou amb uns exercicis pràctics d’autocorrecció. La Gramàtica, per la seva banda, està organitzada com un manual elemental de llengua grega on la persona que segueixi el curs pot ampliar la seva formació i consultar els dubtes. Parts complementàries: presentació on es formulen els objectius, la metodologia i les instruccions concretes per a seguir el curs; terminologia on s’ordenen alfabèticament els conceptes gramaticals emprats en el curs; avaluació final per tal que, més enllà dels exercicis de cada lliçó, hom pugui comprovar si ha assolit els coneixements previstos o si, en cas de no arribar-hi, ha de reforçar algunes lliçons o parts de les mateixes abans de tornar a fer l’avaluació; lèxic, ordenat alfabèticament per tal que hom pugui conèixer el significat dels mots emprats en el curs sense necessitat de consultar un diccionari. A la part d’avaluació hi ha també una enquesta per tal que les persones que segueixin el curs en facin una valoració i ens permetin corregir els seus dèficits o mancances. El projecte 2007MQD00178 ha continuat ampliant els dossiers electrònics, els exercicis autoavaluatius del seu web www.ub.edu/filologiagrega/electra i ha dedicat una part important de la seva tasca a elaborar els continguts i els programes de les assignatures dels dos primers cursos del nou grau de Filologia Clàssica.

Higher education as formation of the self and citizenship: an ethnography of the University Students from Amman, Jordan

My interest in higher education and citizenship in the Middle East at large and in Jordan in particular is fostered by some of the reflections Eickelman proposed (1992). Being a quite recent phenomenon, intimately linked with the more general topic of state formation it seemed to me more suitable to study it in a little country with a recent history (a field study left almost unexplored until now as far as Jordan is concerned, to the best of my knowledge, since Antoun 1994 focuses on the migration as a quest for higher education). The process of state formation in Jordan is quite studied. I thus intended to study the higher education policies as an attempt both to create a national citizenry and more recently as a way of controlling the more problematic part of the population (youth, which constitutes more than the double of the population. See UNDP and Ministry of Planning 2000). How do the young students enter the university system, and in which way does this system work? How is this system designed, in order to retain social control of the students (since they are usually perceived to be a factor of social and political instability, as in Iran or in Egypt)? Is there any significant difference between different faculties? And if so, why? My conclusions at this stage are that the university system is an integral part of the survival of the regime. The system works quite well, and Jordan has one of the best educational position in the region. Yet there are important distinctions to be made: the access to the better faculties is socially selective while the less valued faculties are left to the poorer and less wealthy youth. This results in a different treatment of the students and of the courses that I analysed. In the better faculties the teaching standards are quite high, and the relationship between professors and students is almost on a same-level base, while in the less privileged faculties the opposite is true. Thus we can observe a concrete politics of divide et impera intended to split the youth in two. For the more privileged there are some freedoms, both within and outside classes, designed I guess at forging them as autonomous individuals. On the opposite the less privileged are kept under tight control, even if also these students are a privileged category among youth at large.

A mi què m'expliques?

Els alumnes i les alumnes de primer cicle d'ESO s'enfronten amb les dificultats de la nova etapa i la necessitat de demostrar les seves competències lingüístiques, quant al redactat i la correcció en l'elaboració de textos diversos. Les noves tecnologies de la informació i la comunicació poden ajudar (i han de propiciar-ho) a desenvolupar aquestes capacitats, i han de ser un element motivador perquè els nois i les noies sentin la necessitat de crear produccions escrites pròpies, adequades lingüísticament, coherents i amb les idees ben organitzades.És necessari, a més, que l'avaluació d'aquestes tasques els serveixi per millorar l'expressió en llengua catalana, gramaticalment i ortogràficament, tot ajudant-los a establir sistemes d'autocorrecció i rectificació d'errors.L'exposició pública (en un mitjà com el d'internet) de les seves obres hauria de reblar l'aspecte de la motivació en la creació d'escrits, de manera que els aporti noves expectatives de comunicació i els animi a participar de l'espai virtual que els ofereix aquesta finestra oberta al món. El meu treball té la intenció de ser un projecte educatiu per aconseguir una millora en l'expressió escrita dels alumnes del primer curs d'ESO amb l'ajuda de les eines de les Tecnologies de la Informació i la Comunicació.

Determinants of the educational use of digital learning materials: The mediating role of self-efficacy, perceived norm and attitude

Initiatives to stimulate the development and propagation of open educational resources (OER) need a sufficiently large community that can be mobilized to participate in this endeavour. Failure to achieve this could lead to underuse of OER. In the context of the Wikiwijs initiative a large scale survey was undertaken amongst primary and secondary school teachers to explore possible determinants of the educational use of digital learning materials (DLMs). Basing on the Integrative Model of Behaviour Prediction it was conjectured that self-efficacy, attitude and perceived norm would take a central role in explaining the intention to use DLMs. Several other predictors were added to the model as well whose effects were hypothesized to be mediated by the three central variables.All conjectured relationships were found using path analysis on survey data from 1484 teachers. Intention to DLMs was most strongly determined by self-efficacy, followed by attitude. ICT proficiency was in its turn the strongest predictor of self-efficacy. Perceived norm played only a limited role in the intention to use DLMs. Concluding, it seems paramount for the success of projects such as Wikiwijs to train teachers in the use of digital learning materials and ICT (e.g. the digital blackboard) and to impact on their attitude.

Using self organizing maps on compositional data

Self-organizing maps (Kohonen 1997) is a type of artificial neural network developedto explore patterns in high-dimensional multivariate data. The conventional versionof the algorithm involves the use of Euclidean metric in the process of adaptation ofthe model vectors, thus rendering in theory a whole methodology incompatible withnon-Euclidean geometries.In this contribution we explore the two main aspects of the problem:1. Whether the conventional approach using Euclidean metric can shed valid resultswith compositional data.2. If a modification of the conventional approach replacing vectorial sum and scalarmultiplication by the canonical operators in the simplex (i.e. perturbation andpowering) can converge to an adequate solution.Preliminary tests showed that both methodologies can be used on compositional data.However, the modified version of the algorithm performs poorer than the conventionalversion, in particular, when the data is pathological. Moreover, the conventional ap-proach converges faster to a solution, when data is \well-behaved".Key words: Self Organizing Map; Artificial Neural networks; Compositional data