COINTEGRATION AND THE FORECAST ACCURACY OF VAR MODELS

This paper assesses the forecast performance of a set of VAR models under a growing number of restrictions. With a maximum forecast horizon of 12 years, we show that the farther the horizon is, the more structured and restricted VAR models have to be to produce accurate forecasts. Indeed, unrestricted VAR models, not subjected to integration or cointegration, are poor forecasters for both short and long run horizons. Differenced VAR models, subject to integration, are reliable predictors for one-step horizons but ineffectual for multi-step horizons. Cointegrated VAR models including appropriate structural breaks and exogenous variables, as well as being subjected to over-identifying theory consistent restrictions, are excellent forecasters for both short and long run horizons. Hence, to obtain precise forecasts from VAR models, proper specification and cointegration are crucial for whatever horizons are at stake, while integration is relevant only for short run horizons.VAR demand systems; structural breaks, exogenous regressors, integration; cointegration; forecast accuracy.

Testing Alternative Dynamic Systems for Modelling Tourism Demand

The goals in this paper are to contribute an empirical study of tourism demand dynamics, and to point out areas where the scrutiny of relationships between theoretical and empirical considerations are likely to produce new insights in this area of research. A flexible general form of a Dynamic Almost Ideal Demand System (DAIDS) is derived to analyse the UK tourism demand for its geographically proximate neighbours Portugal, Spain and France, in the period 1969-1997. Nested within the general dynamic structure are Deaton and Muellbauer’s static AIDS model itself, the partial adjustment model and the auto-regressive distributed lag model, which are tested against the general dynamic alternative. The empirical results obtained show that DAIDS is a data coherent and theoretically consistent model, providing evidence of the robustness of this methodology to conduct tourism demand analysis in a temporal context. Moreover, the dynamic model offers statistically strong evidence on the inadequacy of the orthodox static AIDS and the other restricted models to reconcile consistently data and theory within their formulations. Estimates for tourism price and expenditure elasticities are obtained, permitting a comparative analysis of the relative magnitudes and statistical relevance of long and short run sensitivity of the UK tourism demand to changes in its determinants.Tourism Demand, dynamic almost ideal system, partial adjustment system, autoregressive distributed lag system.

A classification of special 2-fold coverings

Starting with an O(2)-principal fibration over a closed oriented surface F_g, g>=1, a 2-fold covering of the total space is said to be special when the monodromy sends the fiber SO(2) = S^1 to the nontrivial element of Z_2. Adapting D Jonhson's method [Spin structures and quadratic forms on surfaces, J London Math Soc, 22 (1980) 365-373] we define an action of Sp(Z_2,2g), the group of symplectic isomorphisms of (H_1(F_g;Z_2),.), on the set of special 2-fold coverings which has two orbits, one with 2^{g-1}(2^g+1) elements and one with 2^{g-1}(2^g-1) elements. These two orbits are obtained by considering Arf-invariants and some congruence of the derived matrices coming from Fox Calculus. Sp(Z_2,2g) is described as the union of conjugacy classes of two subgroups, each of them fixing a special 2-fold covering. Generators of these two subgroups are made explicit.Comment: This is the version published by Geometry & Topology Monographs on 29 April 200

The opinion of Emilia Ferreiro on literacy

Com o objetivo de contribuir para a compreensão de um importante momento da história da alfabetização no Brasil, analisam-se aspectos do pensamento da pesquisadora Emilia Ferreiro (1937 – ) sobre alfabetização, com ênfase em suas concepções a respeito do processo de construção do conhecimento da língua escrita, por parte de crianças, que resultam de sua pesquisa sobre a psicogênese da língua escrita fundamentada na Epistemologia Genética de Jean Piaget e na Psicolinguística de Noam Chomsky e que tiveram significativa repercussão em nosso país, a partir de meados dos anos de 1980. O tema é abordado de uma perspectiva histórica, por meio da utilização de procedimentos de localização, reunião e ordenação da bibliografia disponível de e sobre Emilia Ferreiro e da análise da configuração textual do livro Psicogênese da língua escrita.With the aim of contributing to the comprehension of an important moment in Brazil’s literacy history, this paper analyzes aspects of Emilia Ferreiro’s (1937 - ) thoughts on literacy, emphasizing her theories about the process of constructing knowledge of written language by children. These theories are the result of her research on the psychogenesis of written language, based on Jean Piaget’s genetic epistemology and on Noam Chomsky’s psycholinguistics, both of which had significant repercussions in our country beginning in the mid 1980s. This paper’s topic is approached from a historical perspective through the process of locating, gathering and organizing the available bibliography by and about Emilia Ferreiro and analyzing the textual configuration of the book Psychogenesis of Written Language (Psicogênese da língua escrita)

Quadpack industries: a pe approach to the cosmetic packaging market - investment thesis and exit options

The thesis presents a private equity investment opportunity in Quad pack. Quad pack is a Spanish-based manufacturing company focusing on the production of packaging for cosmetics. The work presents an overview of the company as well as the markets in which it operates. It is then proposed a value creation strategy, a business plan and an LBO model finishing with the exit strategy and a due diligence. Finally, a small reflection about the role of private equity on the packaging market is included

Mundicenter : the struggle to survive in a saturated market

In 2013, Mundicenter, one of the subsidiaries of the Portuguese Group Alves Ribeiro received a wake-up call when the results of 2012 came up. This company operated in the malls development industry, a complex and highly saturated market facing a period of great macro- economic and internal market changes, jeopardizing its 30 years of existence. This company ended up in a position where a revolutionary decision was needed to survive. Managers had to decide between keep doing damage control and follow the holding’s preferences or proceed to a strategy restructuring involving a high investment in a critical period, going against the Group conservative culture. These times were very difficult for the company’s managers that had two fronts to beat, first the internal culture and second the market conditions.Em 2013, na Mundicenter, uma das subsidiárias da empresa portuguesa Grupo Alves Ribeiro soou o alarme quando os resultados de 2012 saíram. Esta empresa estava inserida na indústria de desenvolvimento de centros comerciais, um mercado complexo e altamente saturado que atravessava um período de grande turbulência pautado por mudanças macroeconómicas e no mercado interno colocando em risco os seus 30 anos de existência. Esta empresa acabou vendo-se numa posição em que foi obrigada a tomar uma decisão de elevado risco para sobreviver. Os administradores tiveram de decidir entre continuar a fazer controlo de danos e seguir as políticas da empresa-mãe ou proceder a uma reestruturação estratégica envolvendo um elevado investimento numa época crítica, indo contra as práticas conservadoras do Grupo. Aqueles tempos foram caracterizados pelas dificuldades passadas pelos gestores da empresa que tinha de lutar em duas frentes diferentes, pela primeira vez a cultura interna e segundo as condições de mercado

Effect of arginine vasopressin and ANP on intracellular pH and cytosolic free [Ca2+] regulation in MDCK cells

Effect of arginine vasopressin and ANP on intracellular pH and cytosolic free [Ca2+] regulation in MDCK cells.BackgroundThe effects of arginine vasopressin (AVP) on intracellular pH (pHi) are not clearly defined, and may vary with cell membrane surface and the hormonal doses being studied. Since cytosolic free calcium concentration ([Ca2+]i) has an important effect on cellular H+ extrusion and it was shown that AVP increases [Ca2+]i while atrial natriuretic peptide (ANP) reduces it, there may be some interaction between AVP and ANP during the regulation of pHi.MethodsThe effects of AVP and/or ANP on pHi and [Ca2+]i were investigated in Madin-Darby canine kidney (MDCK) cells by the fluorescent probes BCECF-AM and Fluo 4-AM, respectively. The pHi recovery rate was examined in the first two minutes following the acidification of pHi with a NH4Cl pulse.ResultsAVP (10-12 or 10-9 mol/L) stimulated the rate of the Na+-dependent pHi recovery, but AVP (10-6 mol/L) impaired it. At the apical membrane surface, specific V1 or V2 receptor antagonists did not alter the effects of AVP. At the basolateral membrane surface, the V1 antagonist returned both the stimulatory and inhibitory effects of AVP to control levels, and the V2 antagonist converted the inhibitory effect of AVP to a stimulatory effect. ANP (10-6 mol/L) or dimethyl-BAPTA-AM (50 μmol/L) impaired both the stimulatory and inhibitory effects of AVP. AVP increased [Ca2+]i in a dose-dependent manner. ANP or dimethyl-BAPTA-AM decreased [Ca2+]i, and the subsequent addition of AVP caused only a partial recovery of [Ca2+]i.ConclusionsThe results are compatible with stimulation of the Na+/H+ exchanger by increases of [Ca2+]i in the lower range (at 10-12 or 10-9 mol/L AVP, via basolateral V1 receptors) and inhibition at high [Ca2+]i levels (at 10-6 mol/L AVP, via basolateral V1 and V2 receptors). ANP, by impairing the path causing the increase in [Ca2+]i, blocks both the stimulatory and inhibitory effects of AVP on Na+-dependent pHi recovery