On formal aspects of the epistemic approach to paraconsistency

This paper reviews the central points and presents some recent developments of the epistemic approach to paraconsistency in terms of the preservation of evidence. Two formal systems are surveyed, the basic logic of evidence (BLE) and the logic of evidence and truth (LET J ), designed to deal, respectively, with evidence and with evidence and truth. While BLE is equivalent to Nelson’s logic N4, it has been conceived for a different purpose. Adequate valuation semantics that provide decidability are given for both BLE and LET J . The meanings of the connectives of BLE and LET J , from the point of view of preservation of evidence, is explained with the aid of an inferential semantics. A formalization of the notion of evidence for BLE as proposed by M. Fitting is also reviewed here. As a novel result, the paper shows that LET J is semantically characterized through the so-called Fidel structures. Some opportunities for further research are also discussed

The Effect of social security, demography and technology on retirement

This article investigates the causes in the reduction of labor force participation ofthe old. We argue that the changes in social security policy, in technology and indemography may account for most of the changes in retirement over the second partof the last century in the U.S. economy. We develop a dynamic general equilibriummodel with endogenous retirement that embeds social security legislation. The modelis able to match very closely the increase in the retirement rate of males aged 65 andolder. It also quanti es the isolated impact on retirement and on the solvency of thesocial security system of the di¤erent factors. The model suggests that technologicaland demographic changes had a strong in uence on retirement, so that it would haveincreased signi cantly even if the social security rules had not changed. However, asthe latter became much more generous in the past, changes in social security policycan account not only for a sizeable part of the expansion of retirement, but also for themost of the observed increase in the social security expenses as a share of GDP.

Recovery operators, paraconsistency and duality

There are two foundational, but not fully developed, ideas in paraconsistency, namely, the duality between paraconsistent and intuitionistic paradigms, and the introduction of logical operators that express meta-logical notions in the object language. The aim of this paper is to show how these two ideas can be adequately accomplished by the Logics of Formal Inconsistency (LFIs) and by the Logics of Formal Undeterminedness (LFUs). LFIs recover the validity of the principle of explosion in a paraconsistent scenario, while LFUs recover the validity of the principle of excluded middle in a paracomplete scenario. We introduce definitions of duality between inference rules and connectives that allow comparing rules and connectives that belong to different logics. Two formal systems are studied, the logics mbC and mbD, that display the duality between paraconsistency and paracompleteness as a duality between inference rules added to a common core– in the case studied here, this common core is classical positive propositional logic (CPL + ). The logics mbC and mbD are equipped with recovery operators that restore classical logic for, respectively, consistent and determined propositions. These two logics are then combined obtaining a pair of logics of formal inconsistency and undeterminedness (LFIUs), namely, mbCD and mbCDE. The logic mbCDE exhibits some nice duality properties. Besides, it is simultaneously paraconsistent and paracomplete, and able to recover the principles of excluded middle and explosion at once. The last sections offer an algebraic account for such logics by adapting the swap-structures semantics framework of the LFIs the LFUs. This semantics highlights some subtle aspects of these logics, and allows us to prove decidability by means of finite non-deterministic matrices

Use of bone plates and screws to manage chronic mandibular dislocation

Different treatment modalities are described in literature to treat mandibular recurrent dislocation, including intra- capsular esclerosant injections, articular eminence reduction, soft tissues suture to limit condilar movement, and grafts or implants to create mechanical interference, like zygomatic arch down fracture or articular eminence in- crease by bone plates. In this paper, a patient with mandibular recurrent dislocation episodes were eliminated after bilateral fixation of bone plates to the lateral sur-face of the zygomatic arch to restrict mandibular movements. One arm of the plate was extended me-dially just below the articular eminence and fixed at lateral zygomatic arch portion by two screws. The surgical technique is described and 24 months follow-up period is demonstrate with excellent recovery and functional activities. The temporomandibular joint (TMJ) function was unimpeded and no recu-rrence of condilar dislocation was observed. We concluded that this technique is safe and efficient to hinder dislocations of mandible, preserve the TMJ initial characteristics, and prevent abnormal condi-lar movements over the eminenc

The Effect of Social Security, Demography and Technology on Retirement

This article investigates the causes in the reduction of labor force participation ofthe old. We argue that the changes in social security policy, in technology and indemography may account for most of the changes in retirement over the second partof the last century in the U.S. economy. We develop a dynamic general equilibriummodel with endogenous retirement that embeds social security legislation. The modelis able to match very closely the increase in the retirement rate of males aged 65 andolder. It also quanti es the isolated impact on retirement and on the solvency of thesocial security system of the di¤erent factors. The model suggests that technologicaland demographic changes had a strong in uence on retirement, so that it would haveincreased signi cantly even if the social security rules had not changed. However, asthe latter became much more generous in the past, changes in social security policycan account not only for a sizeable part of the expansion of retirement, but also for themost of the observed increase in the social security expenses as a share of GDP.

Explorando a função polinomial quadrática com Winplot

O uso da tecnologia tem tomado, cada vez mais, uma posição de relevância no cenário educacional. Segundo os Parâmetros Curriculares Nacionais (1998), a utilização de recursos tecnológicos traz significativas contribuições a fim de repensar o processo de ensino e aprendizagem. Para melhor compreender o papel da tecnologia no desenvolvimento dos estudantes construímos uma tarefa piloto que foi aplicada em duas instituições escolares das redes pública e privada. Para analisar essa atividade escolhemos as abordagens teóricas em termos de quadros de Douady (1984) e níveis de conhecimento esperados dos estudantes de Robert (1997). Os estudantes que participaram da atividade já eram capazes de mobilizar conhecimentos sobre equações do segundo grau e representação gráfica de uma função, o que facilitou a interpretação e o estudo da função quadrática. O trabalho com o software permitiu revisitar conhecimentos supostos disponíveis ou pelo menos mobilizáveis ao se introduzir a nova noção

Globalization and the Industrial Revolution

This paper argues that trade specialization played an indispensable role in supportingthe Industrial Revolution, allowing the economy to shift resources to the manufacturewithout facing food and raw materials shortage. In our arti cial economy, there are twosectors agriculture and manufacture and the economy is initially closed and under aMalthusian trap. In this economy the industrial revolution entails a transition towards adynamic Heckscher-Ohlin economy. The model reproduces the main stylized facts of thetransition to modern growth and globalization. We show that two-sectors closed-economymodels cannot explain the fall in the value of land relative to wages observed in the 19thcentury and that the transition in this case is much longer than that observed allowingfor trade.