Dissipation-induced long-range order in the one-dimensional Bose-Hubbard model

Understanding the stability of strongly correlated phases of matter when coupled to environmental degrees of freedom is crucial for identifying the conditions under which these states may be observed. Here, we focus on the paradigmatic one-dimensional Bose-Hubbard model, and study the stability of the Luttinger liquid and Mott insulating phases in the presence of local particle exchange with site-independent baths of non-interacting bosons. We perform a numerically exact analysis of this model by adapting the recently developed wormhole quantum Monte Carlo method for retarded interactions to a continuous-time formulation with worm updates; we show how the wormhole updates can be easily implemented in this scheme. For an Ohmic bath, our numerical findings confirm the scaling prediction that the Luttinger-liquid phase becomes unstable at infinitesimal bath coupling. We show that the ensuing phase is a long-range ordered superfluid with spontaneously-broken U(1) symmetry. While the Mott insulator remains a distinct phase for small bath coupling, it exhibits diverging compressibility and non-integer local boson occupation in the thermodynamic limit. Upon increasing the bath coupling, this phase undergoes a transition to a long-range ordered superfluid. Finally, we discuss the effects of super-Ohmic dissipation on the Luttinger-liquid phase. Our results are compatible with a stable dissipative Luttinger-liquid phase that transitions to a long-range ordered superfluid at a finite system-bath coupling.Comment: 16 pages, 15 figure

Avaliação de diferentes técnicas de análise de sistemas eléctricos com formas de onda não-sinusoidais

Uma das áreas de grande prioridade no âmbito das redes eléctricas tem sido a da filtragem ou compensação de harmónicos. Para além das técnicas clássicas de compensação usando filtros passivos, o avanço dos dispositivos de estado sólido tem vindo a afirmar a utilização de filtros activos, série e paralelos. Este trabalho faz a análise e avaliação de alguns dos principais algoritmos – teoria p-q de Akagi, método FBD de Depenbrock, método do referencial síncrono ou da transformação de Park, método da tensão instantânea de Staudt, e método de decomposição de correntes de Czarnecki –, para análise de sistemas eléctricos com formas de onda não-sinusoidiais. Foram utilizados o Matlab/Simulink e Power System Blockset como ferramentas de simulação de sistemas eléctricos com um filtro activo controlado por esses métodos, fazendo-se a análise e comparação dos resultados obtidos

Active filters for power quality improvement

This paper deals with problems related with harmonics in power system networks. Several international standards issued to control power quality problems are briefly described and some important methods to analyse electrical circuits with non-sinusoidal waveforms are introduced and evaluated. One of these methods - the p-q theory - was used to implement the control algorithm of a shunt active filter, which is also described in this paper as an application example. The filter can compensate for harmonic currents, power factor and load unbalance. Both simulation and experimental results are presented, showing that good dynamic and steady state response can be achieved with this approach

Lower urinary tract and bowel dysfunction in spinocerebellar ataxias

Background: Little information is available in spinocerebellar ataxias (SCAs) regarding pelvic organ symptoms. The aim of this study was to characterize the lower urinary tract (LUT) and bowel dysfunction in autosomal dominant spinocerebellar ataxias. Methods: Patients with confirmed SCAs attending a tertiary care service were approached about LUT and bowel complaints, and completed validated questionnaires: urinary symptom profile (USP), QualiveenShort form, International Prostate Symptom Score, and Neurogenic Bowel Dysfunction Score. SCA3 and SCA7 patients with urological complaints additionally underwent urodynamic studies (UDS). Patients’ characterization included demographic, clinical (Scale for the Assessment and Rating of Ataxia (SARA), Inventory of Non-Ataxia Signs (INAS)), and genetic variables. Descriptive and comparative analyses were performed. Results: Fifty-one patients participated: SCA1 (n = 4), SCA2 (n = 11), SCA3 (n = 13), SCA6 (n = 17), and SCA7 (n = 6). The prevalence of self-reported LUT symptoms was 60.8% (n = 31), whereas LUT symptoms was reported in 86.3%(n = 44) using the USP. Both storage and voiding symptoms were reported, urinary frequency and urgency being the most frequent (n = 34, 68%). Although LUT symptoms were most often classed as mild (n = 27, 61.4%), they impacted QoL in 38 patients (77.6%). Of these, 21 (55.3%) were not on pharmacological treatment for urinary dysfunction. Most common abnormalities in UDS (n = 14) were detrusor overactivity (storage phase) and detrusor underactivity (voiding phase). Bowel symptoms were less common (31.4%, n = 16) and of mild severity. Conclusion: LUT symptoms are prevalent in SCA patients and impact QoL, whereas bowel symptoms tend to be mild. These symptoms are overlooked by patients and physicians due to the complexity of neurological involvement in SCA, and therefore a multidisciplinary management approach should be adopted

Parent's reports of lexical and grammatical aspects of toddlers's language in European Portuguese: developmental trends, age and gender differences

The results from a large-scale study on toddlers’ language acquisition in European Portuguese are presented. Toddlers’ lexical and grammatical competencies were assessed using the MacArthur–Bates Communicative Development Inventory: Words and Sentences. The results, based on 3012 reports completed by parents, indicate an increase in the lexical size and on five measures of grammatical development (production of regular morphology, irregular morphology, over-regularizations, mean length of utterances and sentence complexity) across age groups. A main effect of gender was found for lexical size, production of regular and irregular morphology, production of over-regularizations and sentence complexity, with girls obtaining overall higher scores than boys. All lexical and grammatical development measures are positively correlated, even after controlling for age and gender effects. These findings are discussed in terms of their consistency with those obtained for other languages.CiPsi - Psychology Research Centre, Uminho (UID/PSI/ 01662/2013), PortugalCIEC – Research Centre on Child Studies, IE, UMinho (FCT R&D unit 317), Portugalinfo:eu-repo/semantics/publishedVersio

The Economic Adjustment Program for Portugal : assessing welfare impact in a heterogeneous-agent framework

The sovereign debt crisis, triggered by the 2007-08 global financial cri- sis, has affected several European Union (EU) countries, leading to unprecedented financial assistance programs. In May 2011, the Portuguese Government set an agreement with the Troika (a supranational institution composed by the European Commission (EC), the European Central Bank (ECB) and the International Monetary Fund (IMF)), through which, in exchange for external help, the Portuguese author- ities committed to an Economic Adjustment Program (EAP). In order to assess the impacts of the EAP on welfare and, in particular, on inequality, this paper simulates the debt consolidation strategy proposed by the Troika using a general equilibrium model with heterogeneous agents. The model enables to explore the impacts of the fiscal adjustment on the endogenous cross-section distribution of income, wealth and welfare. Our results predict a positive net welfare gain, despite the existence of sig- nificant transition costs in terms of output losses and inequality, especially during the first years of implementation. Overall, the net positive welfare gains are biased towards the poorer, which means that the consolidation plan will be, in the end, equality-enhancing. These results reflect the instruments involved in the consolida- tion strategy: productive and unproductive expenditure cuts combined with a slight increase in social transfers. Furthermore, the simulation predicts a positive impact on the Portuguese net foreign asset (NFA) position. Assuming this prediction is correct, this strongly supports the motivation for the adoption of the Economic Adjustment Program which considers the large external indebtedness of Portugal as a central issue in the economic diagnosis.info:eu-repo/semantics/publishedVersio

Homeschooling and the criticism of school: hybridisms and educational (dis)continuities

Desde os anos 1960, o homeschooling apresenta dinâmicas de crescimento atualizadas nos diagnósticos da crise do capitalismo e dos sistemas educativos. Por ser praticado por famílias próximas do progressismo libertário, do cristianismo conservador ou de outras inspirações axiológicas, a abordagem investigativa presente neste texto pressupôs romper com uma visão unívoca e alheia à sua diversidade e aos diferentes graus de (in)formalidade dos quotidianos educativos de crianças e de jovens que caracterizam este fenómeno educativo. Procura-se captar as especificidades do ensino doméstico (ED) em Portugal e a sua crescente expressão social e educacional e reflete-se sobre os sentidos das aprendizagens que ele encerra. Conclui-se que o ED parece ser contrário aos horizontes formativos da criança segundo o interesse da sociedade, sendo omisso sobre o seu papel na emancipação dos sujeitos. Confrontam-se a escola e o seu modo de funcionamento a partir do racional do ED, à procura de novas epistemologias e de novas linhas de pesquisa.Since the 1960s, homeschooling has shown growth dynamics updated by the diagnosis of the crisis of capitalism and of educational systems. Because it is practiced by families close to libertarian progressivism, conservative Christianity, or other axiological inspirations, this paper’s approach sought to break with a univocal conception alien to its diversity and to the different degrees of (in)formality of the children’s and young people’s educational daily lives inherent to this educational practice. Therefore, this paper seeks to understand the specificities of Portuguese homeschooling and its increasing social and educational expression, and to reflect on the meanings of the learning it entails. Being unclear about its role on the emancipation of the subjects, homeschooling seems to be contrary to the educational horizons of the child according to the interests of the whole society. This paper confronts school and its way of functioning with the homeschooling rationale in order to search for new epistemologies and new lines of research.info:eu-repo/semantics/publishedVersio

Testing and Assessment in an International Context: Cross- and Multi-cultural Issues

Globalisation, increase of migration flows, and the concurrent worldwide competitiveness impose rethinking of testing and assessment procedures and practices in an international and multicultural context. This chapter reviews the methodological and practical implications for psychological assessment in the field of career guidance. The methodological implications are numerous and several aspects have to be considered, such as cross-cultural equivalence or construct, method, and item bias. Moreover, the construct of culture by itself is difficult to define and difficult to measure. In order to provide non-discriminatory assessment, counsellors should develop their clinical cross-cultural competencies, develop more specific intervention strategies, and respect cultural differences. Several suggestions are given concerning translation and adaptation of psychological instruments, developing culture specific measures, and the use of these instruments. More research in this field should use mixed methods, multi-centric designs, and consider emic and etic psychological variables. A multidisciplinary approach might also allow identifying culture specific and ecological meaningful constructs. Non-discriminatory assessment implies considering the influence and interaction of personal characteristics and environmental factors

Chromosome copy number changes carry prognostic information independent of KIT/PDGFRA point mutations in gastrointestinal stromal tumors

<p>Abstract</p> <p>Background</p> <p>Oncogenic point mutations in <it>KIT </it>or <it>PDGFRA </it>are recognized as the primary events responsible for the pathogenesis of most gastrointestinal stromal tumors (GIST), but additional genomic alterations are frequent and presumably required for tumor progression. The relative contribution of such alterations for the biology and clinical behavior of GIST, however, remains elusive.</p> <p>Methods</p> <p>In the present study, somatic mutations in <it>KIT </it>and <it>PDGFRA </it>were evaluated by direct sequencing analysis in a consecutive series of 80 GIST patients. For a subset of 29 tumors, comparative genomic hybridization was additionally used to screen for chromosome copy number aberrations. Genotype and genomic findings were cross-tabulated and compared with available clinical and follow-up data.</p> <p>Results</p> <p>We report an overall mutation frequency of 87.5%, with 76.25% of the tumors showing alterations in <it>KIT </it>and 11.25% in <it>PDGFRA</it>. Secondary <it>KIT </it>mutations were additionally found in two of four samples obtained after imatinib treatment. Chromosomal imbalances were detected in 25 out of 29 tumors (86%), namely losses at 14q (88% of abnormal cases), 22q (44%), 1p (44%), and 15q (36%), and gains at 1q (16%) and 12q (20%). In addition to clinico-pathological high-risk groups, patients with <it>KIT </it>mutations, genomic complexity, genomic gains and deletions at either 1p or 22q showed a significantly shorter disease-free survival. Furthermore, genomic complexity was the best predictor of disease progression in multivariate analysis.</p> <p>Conclusions</p> <p>In addition to <it>KIT/PDGFRA </it>mutational status, our findings indicate that secondary chromosomal changes contribute significantly to tumor development and progression of GIST and that genomic complexity carries independent prognostic value that complements clinico-pathological and genotype information.</p