Introductory lectures to loop quantum gravity

We give a standard introduction to loop quantum gravity, from the ADM variables to spin network states. We include a discussion on quantum geometry on a fixed graph and its relation to a discrete approximation of general relativity.Comment: Based on lectures given at the 3eme Ecole de Physique Theorique de Jijel, Algeria, 26 Sep -- 3 Oct, 2009. 52 pages, many figures. v2 minor corrections. To be published in the proceeding

On Barriers in State and Input Constrained Nonlinear Systems

In this paper, the problem of state and input constrained control is addressed, with multidimensional constraints. We obtain a local description of the boundary of the admissible subset of the state space where the state and input constraints can be satisfied \emph{for all times}. This boundary is made of two disjoint parts: the subset of the state constraint boundary on which there are trajectories pointing towards the interior of the admissible set or tangentially to it; and a barrier, namely a semipermeable surface which is constructed via a minimum-like principle.Comment: 36 pages, 8 figures, submitte

Making Homes in Limbo: Embodied Virtual “Homes” in Prolonged Conditions of Displacement

This special issue makes an original contribution to our understanding of the meaning of home by introducing the idea of the constellation of HOME-Home-home and homemaking practices where these are not necessarily foreseen, in contexts of displacement. In this article, I argue that we need to distinguish between humanitarian-driven understandings of “protracted refugee situations” and peoplecentred experiences of “prolonged conditions of displacement.” I show how the papers in the special issue bring to the fore inconsistencies between state-centred perspectives and people-centred meanings of the “constellation of homes.” Lastly, I examine the significance of other spaces where home may be made during prolonged displacements: the virtual space. I conclude by suggesting that we need to examine in greater depth the complex relationship between the dwelling, home, and homemaking practices when these occur in material and de-territorialized virtual spaces.Ce numéro spécial de Refuge apporte une contribution originale à la façon dont nous concevons l’idée de «domicile» en postulant la constellation triadique de DOMICILE-Domicile-domicile ainsi que les pratiques reliées à l’établissement d’un domicile dans des contextes parfois inattendus, en ce qui concerne les situations de déplacement. Dans cet article, j’avance qu’il faut distinguer entre les conceptions humanitaires reliées aux «situations de réfugiés prolongés» et les expériences en «conditions prolongées de déplacement» axées sur les individus. Je montre comment les articles dont le numéro spécial est composé font ressortir les désaccords inhérents entre les perspectives étatiques et les conceptions expérientielles des individus autour de cette «constellation» triadique de «domicile». En dernier lieu, je me penche sur l’importance d’autres espaces qui pourraient servir de contexte à l’établissement d’un domicile en situation de déplacement prolongé, notamment l’espace virtuel. Pour conclure, je propose qu’on réexamine en profondeur la relation complexe entre les pratiques de logement, de domicile, et d’établissement de domicile dans leur actualisation matérielle ainsi que dans le contexte d’espaces virtuels déterritorialisés

Divergent discourses, children and forced migration

Experiences of refugee, internally displaced and migrant children in different contexts (such as post-conflict and resettlement) are often considered separately, yet closer analysis points to the existence of commonalities across transnational locations and a need to articulate the ways in which global systems, state policies and migration processes impact on the lives of these children. Current discourses, policies and practices towards forced migrant children show that there are divergent and at times conflicting constructions of childhood and migration, and implicitly reveal the positions that these children occupy in relation to the nation-state system. In this article we focus on the existence of common divergent discourses that emerge from contexts in the global North and South, including Rwanda, Uganda, Ireland and the United Kingdom, where we have carried out research with children forced to move. Our overall aim is to re-politicise the position of child and youth forced migration through an analysis of three sets of divergent or ambivalent discourses: a) forced-migrant children as product of and threat to the nation-state; b) ‘visible’ and ‘invisible’ children; and c) the ‘psychological’ and the ‘political’ child

“Refugee Voices,” New Social Media and Politics of Representation: Young Congolese in the Diaspora and Beyond

This article examines the role of new social media in the articulation and representation of the refugee and diasporic “voice.” The article problematizes the individualist, de-politicized, de-contextualized, and aestheticized representation of refugee/diasporic voices. It argues that new social media enable refugees and diaspora members to exercise agency in managing the creation, production, and dissemination of their voices and to engage in hybrid (on- and offline) activism. These new territories for self-representation challenge our conventional understanding of refugee/diaspora voices. The article is based on research with young Congolese living in the diaspora, and it describes the Geno-cost project created by the Congolese Action Youth Platform (CAYP) and JJ Bola’s spoken-word piece, “Refuge.” The first shows agency in the creation of analytical and activist voices that promote counter-hegemonic narratives of violence in the eastern Democratic Republic of Congo, while the second is an example of aesthetic expressions performed online and offline that reveal agency through authorship and ownership of one’s voice. The examples highlight the role that new social media play in challenging mainstream politics of representation of refugee/diaspora voices.Cet article étudie le rôle des nouveaux médias sociaux dans la politique de la représentation de la « voix » des réfugiés et de la diaspora. Il propose une problématisation des approches trop souvent dépoliticisées, uniformisées et individualisées à la représentation des « voix des réfugiés et de la diaspora ». Il soutient que les nouveaux médias sociaux permettent aux réfugies d’exercer leur propre volonté d’agir en gérant la création, la production et la dissémination de récits alternatifs et en s’engageant dans un militantisme hybride (en ligne ainsi que hors ligne). Ces nouveaux lieux d’auto-représentation mettent en question nos conceptions conventionnelles des voix des réfugiés et de la diaspora. En se basant sur la recherche parmi de jeunes Congolais faisant partie de la diaspora au Royaume-Uni, l’article décrit le projet geno-cost développé par le Congolese Action Youth Platform (CAYP), ainsi que la création poétique orale intitulée « Refuge » de JJ Bola. Le premier exemple étudie l’exercice de la volonté d’agir qui se manifeste dans le développement de voix analytiques et militantes qui appuient des récits anti-hégémoniques concernant les causes et les solutions du conflit prolongé en République démocratique du Congo, alors que le deuxième exemple représente une instance d’expression politique et esthétique performée en ligne ainsi que hors ligne qui démontre la volonté d’agir par l’entremise de la création et la possession de sa propre voix. Effectivement, ces exemples soulignent le rôle que jouent les nouveaux médiassociaux pour contrer les politiques conventionnelles de représentation en matière de voix des réfugiés et de ceux qui font partie de la diaspora

The lafargeholcim merger, a merger of (implied) interests

The project title is: The LafargeHolcim Merger, a Merger of (Implied) Interests. This work project is a case study about the merger that created the world’s biggest cement company, LafargeHolcim. It is focused on the pre-deal situation and the long negotiations that led to the merger, with attention too to the poor share price performance after the merger. Questions regarding governance, deal rationale, merger of equals, transaction ratios and multiples are the main subjects developed

Laser-induced Field Emission from Tungsten Tip: Optical Control of Emission Sites and Emission Process

Field-emission patterns from a clean tungsten tip apex induced by femtosecond laser pulses have been investigated. Strongly asymmetric field-emission intensity distributions are observed depending on three parameters: (1) the polarization of the light, (2) the azimuthal and (3) the polar orientation of the tip apex relative to the laser incidence direction. In effect, we have realized an ultrafast pulsed field-emission source with site selectivity of a few tens of nanometers. Simulations of local fields on the tip apex and of electron emission patterns based on photo-excited nonequilibrium electron distributions explain our observations quantitatively. Electron emission processes are found to depend on laser power and tip voltage. At relatively low laser power and high tip voltage, field-emission after two-photon photo-excitation is the dominant process. At relatively low laser power and low tip voltage, photoemission processes are dominant. As the laser power increases, photoemission from the tip shank becomes noticeable.Comment: 12 pages, 12 figures, submitted to Physical Review

Produção de ésteres metílicos com acetato de metila supercrítico em reator tubular

Orientadora : Profa. Dra. Fernanda de CastilhosOrientadora : Profa. Dra. Camila da SilvaDissertação (mestrado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Engenharia de Alimentos. Defesa: Curitiba, 13/04/2012Bibliografia: fls. 80-89ResumoResumo: Os métodos de produção de biodiesel que utilizam o álcool como reagente da reação produzem glicerina como subproduto. Com o aumento mundial da produção de biodiesel, houve um excesso da produção de glicerina, o que levou a sua desvalorização no mercado. Uma alternativa para o processo de produção de biodiesel é a substituição do álcool por acetato de metila. Neste processo é produzido como subproduto da reação, a triacetina, que é considerada um aditivo do biodiesel. Ao contrário dos métodos convencionais de produção de biodiesel, a transesterificação supercrítica não utiliza catalisador e não é afetada pela presença de ácidos graxos livres e água, sendo considerada uma alternativa promissora. O objetivo deste trabalho foi investigar a produção de biodiesel, em condições supercríticas por transesterificação não catalítica utilizando acetato de metila, avaliar a estabilidade dos ésteres metílicos do meio reacional e avaliar o efeito da transferência de massa sobre o rendimento da reação. Neste trabalho, foram usados dois tipos de óleo (soja e macaúba) que apresentam diferentes teores de ácidos graxos livres. Avaliou-se a influência da temperatura, da razão molar e o tempo de residência, sobre o rendimento em ésteres metílicos de ácidos graxos para as reações conduzidas em reator tubular de leito fixo. Os resultados demonstraram que a composição do óleo afetou significativamente a produção de biodiesel. Os melhores rendimentos de ésteres metílicos de ácidos graxos foram obtidos na reação com óleo de macaúba após 45 minutos de reação, na temperatura de 325 °C, pressão de 200 bar, com razão mássica óleo de macaúba: acetato de metila 1:5. Verificou-se também que o óleo de soja em condições acima de 350 °C e longos tempos de residência apresentam elevados graus de decomposição dos constituintes do meio reacional, obtendo níveis de decomposição superiores a 50 % na temperatura de 375 °C.Abstract: The methods of producing biodiesel using the alcohol as the reaction reagent produce glycerol by product. With increased global production of biodiesel, there was an excess production of glycerin, which led to its devaluation in the market. An alternative process for the production of biodiesel is to replace the alcohol is methyl acetate. This process is produced as a byproduct of the reaction, triacetin, which is considered an additive for biodiesel. Unlike conventional methods of biodiesel production, supercritical transesterification catalyst does not use and is not affected by the presence of free fatty acids and water, is considered a promising alternative. The objective of this study was to investigate the production of biodiesel in supercritical conditions by non-catalytic transesterification using methyl acetate, to evaluate the stability of the methyl esters of the reaction medium and to evaluate the effect of mass transfer on the reaction yield. In this work, we used two types of oil (soybean and macauba) that exhibit different levels of free fatty acids. We evaluated the effect of temperature, molar ratio and the residence time on the yield of methyl esters of fatty acids for reactions conducted in fixed bed tubular reactor. The results showed that the oil composition significantly affected the production of biodiesel. The best yields of the fatty acid methyl esters were obtained on reaction with oil macauba after 45 minutes of reaction, at a temperature of 325 ° C, pressure 200 bar, with mass ratio of oil macauba: methyl acetate 1:5. It was also soybean oil in a position above 350 ° C and long residence times have high degrees of decomposition of the constituents of the reaction, resulting decomposition levels above 50% at a temperature of 375 ° C

El aprendizaje de los estudiantes en tiempos de pandemia y pospandemia : Virtualidad y presencialidad. Facultad de Psicología. UNLP

Durante los años 2020-2021, la pandemia por la enfermedad de coronavirus (COVID-19) produjo modificaciones impactantes en el sistema educativo obligando a estudiantes y docentes a mudar readecuadar sus prácticas a un formato obligado de educación a distancia, determinado por las posibilidades tecnológicas. Los estudiantes que culminaron su educación secundaria en el año 2019 e ingresaron a la Facultad en el 2020, vivieron la inédita experiencia de la virtualización de su proceso de enseñanza-aprendizaje. La pregunta es cómo se caracteriza el aprendizaje de esos estudiantes durante el tiempo de la virtualidad de pandemia y de la presencialidad en pospandemia. Se busca realizar un aporte a la comprensión de dichas particularidades y su posible impacto sobre el proceso de enseñanza aprendizaje de estos estudiantes. El estudio se centra en los estudiantes de la materia Estadística Aplicada a la Psicología, de la carrera de Psicología, de la UNLP, cursantes en 2021 y en 2022. La modalidad elegida para realizar este TFI es una indagación exploratoria mediante una metodología con diseño cuantitativa que pueda caracterizar a los estudiantes y sus aprendizajes, realizados en la modalidad virtual y, posteriormente, en la presencialidad. Cada uno de esos estudiantes de las cohortes constituye una unidad de análisis del problema planteado. Se buscó realizar un acercamiento empírico mediante la estrategia de recolección de datos a través de una encuesta. La información recolectada permitió realizar una mejor comprensión sobre el tema. Cada modalidad de cursada, virtual o presencial, tiene sus particularidades y características. Ambas grupos son diferentes en tanto la modalidad de cursada pero no se han podido establecer pruebas empíricas de diferencias en el modo de adquirir conocimientos. Lo distintivo y la singular diferencia entre esos dos escenarios observados está en la dimensión vincular de ambos tipo de cursada; hay una diferencia marcada entre las cohortes y se aloja en la dimensión relacional siendo este plano uno de los pilares de la enseñanza y de la permanencia de estudiantes en la Universidad. La corroboración de que los vínculos interpersonales presenciales impregnan la experiencia estudiantil positivamente y resultan ser irreemplazables, insustituibles, es el aporte de este estudio para los abordajes pedagógicos del cuerpo docente de la cátedra.Facultad de Psicologí

Cognitive processing and body balance in elderly subjects with vestibular dysfunction

Abnormal body balance and cognitive dysfunction may develop in elderly patients with chronic vestibular dysfunction. AIM: To evaluate the relationship between cognitive processing and body balance in elderly patients with chronic peripheral vestibular disease. Type of Study: Cross-sectional. METHODS: Seventy-six patients (> 60 years) with chronic peripheral vestibular dysfunction and dizziness for more than three months were enrolled. The tests for investigating body balance were: the Berg Balance Scale (BBS), Dynamic Gait Index (DGI), Timed Up and Go Test (TUGT) Timed Up and Go Test modified (TUGTm); the Mini Mental State Examination (MMSE), Test Clock (RT,) and Verbal Fluency Test (VF) were applied for assessing cognition. RESULTS: The mean age was 69.03 years (SD=6.21 years); most were female (82.9%). There was a significant negative correlation between the MMSE and the TUGT (ρ=-0.312; p=0.01), MMSE and TUGTm (ρ=-0.306; p=0.01), FV and TUGT (ρ=-0.346; p=0.01), and FV and TUGTm (ρ=-0.536; p=0.01); there was a significant positive correlation between the TR and BBS (ρ=0.343; p=0.01), TR and DGI (ρ=0.298; p=0.01), FV and BBS (ρ=0.299; p=0.01), and FV and DGI (ρ=0.306; p=0.01). CONCLUSION: Elderly patients with chronic peripheral vestibular disease and worse performance in body balance tests have functional impairment in cognitive skills.Idosos com disfunção vestibular crônica podem apresentar alteração do equilíbrio corporal e disfunção cognitiva. OBJETIVO: Avaliar a relação entre o processamento cognitivo e o equilíbrio corporal de idosos com vestibulopatia periférica crônica. Forma de Estudo: Transversal. MATERIAL E MÉTODO: O estudo incluiu 76 pacientes (> 60 anos), com disfunção vestibular periférica crônica, com queixa de tontura há mais de três meses. Os testes utilizados para investigar o equilíbrio corporal foram: Berg Balance Scale (BBS), Dynamic Gait Index (DGI), Timed Up and Go Test (TUGT) e Timed Up Go Test modificado (TUGTm) e para a avaliação cognitiva utilizou-se Mini Exame do Estado Mental (MEEM), Teste do Relógio (TR) e Teste de Fluência Verbal (FV). RESULTADOS: A média etária dos pacientes foi de 69,03 anos (DP=6,21 anos), sendo a maioria feminina (82,9%). Observou-se correlação negativa significante entre o MEEM e TUGT (ρ=-0,312; p=0,01), MEEM e TUGTm (ρ=-0,306; p=0,01), FV e TUGT (ρ=-0,346; p=0,01) e FV e TUGTm (ρ=-0,536; p=0,01); e correlação positiva significante entre TR e BBS (ρ=0,343; p=0,01), TR e DGI (ρ=0,298; p=0,01), FV e BBS (ρ=0,299; p=0,01), e FV e DGI (ρ=0,306; p=0,01). CONCLUSÃO: Idosos com vestibulopatia periférica crônica com pior desempenho no equilíbrio corporal funcional apresentam prejuízo nas habilidades cognitivas.UNIFESP Programa de Pós-Graduação em Neurologia e NeurociênciasUniversidade Bandeirante de São Paulo Programa de Mestrado em Reabilitação do Equilíbrio Corporal e Inclusão SocialUNIFESP, Programa de Pós-Graduação em Neurologia e NeurociênciasSciEL