Perron-Frobenius operators and representations of the Cuntz-Krieger algebras for infinite matrices

In this paper we extend work of Kawamura, see kawamura, for Cuntz-Krieger algebras O_A for infinite matrices A. We generalize the definition of branching systems, prove their existence for any given matrix A and show how they induce some very concrete representations of O_A. We use these representations to describe the Perron-Frobenius operator, associated to an nonsingular transformation, as an infinite sum and under some hypothesis we find a matrix representation for the operator. We finish the paper with a few examples.Comment: 16 pages, 2 figure

On Exact Algorithms for Permutation CSP

In the Permutation Constraint Satisfaction Problem (Permutation CSP) we are given a set of variables $V$ and a set of constraints C, in which constraints are tuples of elements of V. The goal is to find a total ordering of the variables, $\pi\ : V \rightarrow [1,...,|V|]$, which satisfies as many constraints as possible. A constraint $(v_1,v_2,...,v_k)$ is satisfied by an ordering $\pi$ when $\pi(v_1)<\pi(v_2)<...<\pi(v_k)$. An instance has arity $k$ if all the constraints involve at most $k$ elements. This problem expresses a variety of permutation problems including {\sc Feedback Arc Set} and {\sc Betweenness} problems. A naive algorithm, listing all the $n!$ permutations, requires $2^{O(n\log{n})}$ time. Interestingly, {\sc Permutation CSP} for arity 2 or 3 can be solved by Held-Karp type algorithms in time $O^*(2^n)$, but no algorithm is known for arity at least 4 with running time significantly better than $2^{O(n\log{n})}$. In this paper we resolve the gap by showing that {\sc Arity 4 Permutation CSP} cannot be solved in time $2^{o(n\log{n})}$ unless ETH fails

Quantum photon correlations at the single atom level in free space

In this project, we present a novel approach to calculate and engineer the photon correlations emerging from the interference between an input field and the field scattered by an atom in free space. Historically, it has been difficult to observe robust quantum correlations in the total field, as the inefficient atom-light coupling in free space usually causes the scattered field to be small in comparison to the input. To overcome this issue, we propose the use of separate pump and probe beams, where the former effectively enhances the atomic emission to be comparable to the probe. Additionally, we elucidate the physical origin of the non-classical correlations predicted, by studying the transient atomic state after the measurement of a photon

Illuminating the charged leptons in the proton

The description of the structure of proton is fundamental in order to describe the standard model processes at the LHC as well as for the searching of New Physics. Quantum fluctuations imply the presence of photons and leptons inside the proton, which admit a parton distribution function (PDF). Although the lepton PDFs are expected to be small, its presence opens new production mechanisms. In order to explore the lepton - induced processes at the LHC, a precise determination of the leptonic content of the proton is needed. In this paper we propose to constrain the content of charged leptons inside the proton through the study of the QED Compton scattering in ultraperipheral proton - nucleus collisions at the LHC. We estimate the total cross sections and associated distributions considering different models for the lepton PDFs and distinct lepton flavours. We demonstrate that a future experimental analysis of this process is feasible and that it can be used to constrain the content of electrons, muons and taus inside the proton.Comment: 10 pages, 3 figures, 1 table. Improved version to be published in PR

The nZEBs in the near Future: Overview of definitions and guidelines towards existing plans for increasing nZEBs

Zero-energy performance buildings have gained significant attention since the publication in 2010 of the recast of the EPBD recast which requires all new buildings to become nearly zero-energy by 2020. Buildings are requested to meet higher levels of energy performance and to explore more the alternative energy supply systems available locally on a cost-efficiency basis. Since the directive does not specify minimum or maximum harmonized requirements as well as details of energy performance calculation framework, it is up to the member states to define the exact meaning of “high energy performance” and “amount of energy from renewable sources” according to their own local conditions and strategic interests. Nearly zero-energy building (nZEB) performance derives from net zero-energy concept (Net ZEB) which in case of buildings is usually defined as a high energy performance building that over a year is energy neutral. The successful implementation of such an ambitious target, however, needs to be planned out diligently. The critical steps are a) a correct picture about the existing state and trends, b) clear definitions and targets, c) dynamic building codes and energy efficient technologies and d) rules for testing and verification. The nZEBs or NetZEBs built in the near future therefore may play a critical role in implementing any ambitious plan as its success on long-term relies on setting best practice examples, in addition of the supporting policies and initiatives. The purpose of this paper is to review existing definitions, terms and policies on strategic planning of nZEBs at national and international level

Inclusão Social de Pessoas Cegas: treinamento no uso de leitor de tela

Anais do 35º Seminário de Extensão Universitária da Região Sul - Área temática: EducaçãoA ação de extensão apresentada neste trabalho teve por objetivo principal ofertar treinamento no uso do leitor de tela NVDA para pessoas cegas. Essa ação de extensão foi proposta para atender uma demanda apresentada pela comunidade. A metodologia envolveu ministrar um questionário inicial, definir o conteúdo programático do treinamento e a equipe executora, realizar um estudo dirigido como forma de preparação, fazer reuniões para discussão das técnicas de ensino e do material de apoio e preparar o laboratório. O treinamento promoveu uma introdução ao uso do computador para os participantes. O conhecimento adquirido, aliado a alguma prática regular, contribui para permitir a inclusão social e autonomia dos participantes. O treinamento ofereceu a oportunidade para a participação de seis alunos de graduação em atividades de extensão universitári

Does pain affect the development of tolerance during opioid treatment?

Opioidtolerans innebär att dos-responskurvan är förskjuten åt höger. Det krävs en högre dos för att uppnå samma effekt som tidigare efter att toleransutveckling har uppstått. Tolerans utvecklas efter första administreringen och kan kvarstå under lång tid. Därför är det förvånande att flera studier ifrån kliniska situationer på humansidan visar att tolerans vid opioidbehandling många gånger är ringa eller uteblir. Syftet med den här studien är att undersöka betydelsen av smärta för toleransutveckling vid opioidbehandling samt om toleransutveckling skiljer sig åt mellan olika opioider. När opioidreceptorn har aktiverats av en agonist fosforlyseras den vilket leder till att den bli desensitierad. Fosforlyserade receptorer kan sedan endocyteras och antingen brytas ned eller resensitieras. Olika opioider har varierande förmåga att stimulera de aktiverade opioidreceptorerna till endocytos och resensitiering. Många av de opioider som används kliniskt stimulerar obetydligt till endocytos. Morfin och buprenorfin stimulerar i princip inte alls de aktiverade opioidreceptorerna till endocytos medan fentanyl och metadon gör det till viss del. Det går att minska toleransutveckligen genom att administrera morfin tillsammans med en låg dos av en annan opioid med bättre endocytosstimulerande förmåga. Morfin tillsammans med små doser metadon, fentanyl eller etorfin har visats ge en ökad endocytosaktivitet och minskad toleransutveckling. Vid smärta frisätts endogena opioider, så kallade endorfiner. Endorfinerna har en stark endocytosstimulerande effekt, och skulle kunna förklara en lägre grad av toleransutveckling vid opioidbehandling i samband med smärta. Toleransutvecklingen skiljer sig åt vid behandling med olika opioider i närvaro av smärta. Möjligen på grund av att olika opioider har varierande förmåga att stimulera till endocytos och resensitiering av opioidreceptorn. Vid behandling med fentanyl ses en högre grad av toleransutveckling än för behandling med morfin eller oxykodon. Behandling med metadon ger lägre grad av toleransutveckling än behandling med morfin. När toleransutvecklingen vid smärta har jämförts med toleransutvecklingen utan smärta är resultaten motsägelsefulla. Morfin är den opioid som studerats mest i samband med smärta och toleransutveckling. En del studier har visat på en minskad tolerans medan andra har visat att toleransutvecklingen ökar. Metoderna för att framkalla tolerans och för att mäta toleransutvecklingen har varierat mellan de olika studierna vilket gör det svårt att jämföra och väga resultat mot varandra. Slutsatsen är att viss evidens finns för att olika opioider troligtvis har varierande förmåga att framkalla toleransutveckling. Däremot är resultaten motsägelsefulla angående smärtas betydelse för toleransutveckling i samband med opioidbehandling. Det finns viss evidens för att smärta kan ge en minskad toleransutveckling mot morfin, men konsensus saknas.Opioid tolerance denote a shift of the dose - response curve to the right, meaning a higher dose will be required to achieve the same effect after the development of tolerance has occurred. Tolerance develops after first administration of an opioid and can persist for a long time. Therefore, it is surprising that several studies in the clinical setting show tolerance development during opioid therapy often is minor or absent. The purpose of this study is to examine the role of pain in development of tolerance during opioid therapy and investigate whether the development of tolerance differs between opioids. When the opioid receptor is activated by an agonist it will be phosphorylated causing a desensitized receptor. Endocytosis of the desensitized receptor may lead to the receptor either being down regulated or resensitized. Different opioids have varying ability to stimulate the activated opioid receptors to endocytosis and resensitizing. Many of the opioids that are used in the clinical setting stimulate endocytosis insignificantly. Morphine and buprenorphine almost lack the ability to stimulate activated opioid receptors to endocytosis while fentanyl and methadone do to some degree. Several studies have shown it is possible to reduce the development of tolerance by administering morphine together with a low dose of another opioid with better ability to stimulate endocytosis. Morphine along with a small dose of methadone, fentanyl or etorphine has been shown to provide increased endocytosis and reduced development of tolerance. During pain the endogenous opioids are released – the endorphins. Endorphins have a strong ability to stimulate endocytosis, and therefore they could be one of the reasons behind a reduced tolerance development during opioid therapy associated with pain. Comparative studies have shown that the development of tolerance differed between different opioids. This is supported by observations in a retrospective clinical study and by several studies showing that different opioids have varying abilities to stimulate endocytosis and resensitizing of the opioid receptor. The development of tolerance in the presence of pain has been compared to the development of tolerance without pain in several studies - with inconsistent results. Morphine is the best studied opioid in connection with pain on the development of tolerance. Some studies have shown a decreased tolerance development while others have shown an increased development of tolerance. Methods for inducing tolerance and for measuring development of tolerance have varied from study to study, which might explain some of the differences. While there is some evidence supporting the theory that pain has significance for the development of tolerance to morphine the inconsistence makes it impossible to draw a general conclusion regarding the impact of pain on development of tolerance. However I came to the conclusion that there is a difference in development of tolerance between different opioids. Fentanyl seems to develop tolerance at a higher rate than morphine or oxycodone while methadone seems to develop tolerance at a lower rate than morphine