The influence of hilly terrain on canopy-atmosphere carbon dioxide exchange

Topography influences many aspects of forest-atmosphere carbon exchange; yet only a small number of studies have considered the role of topography on the structure of turbulence within and above vegetation and its effect on canopy photosynthesis and the measurement of net ecosystem exchange of CO2 (N-ee) using flux towers. Here, we focus on the interplay between radiative transfer, flow dynamics for neutral stratification, and ecophysiological controls on CO2 sources and sinks within a canopy on a gentle cosine hill. We examine how topography alters the forest-atmosphere CO2 exchange rate when compared to uniform flat terrain using a newly developed first-order closure model that explicitly accounts for the flow dynamics, radiative transfer, and nonlinear eco physiological processes within a plant canopy. We show that variation in radiation and airflow due to topography causes only a minor departure in horizontally averaged and vertically integrated photosynthesis from their flat terrain values. However, topography perturbs the airflow and concentration fields in and above plant canopies, leading to significant horizontal and vertical advection of CO2. Advection terms in the conservation equation may be neglected in flow over homogeneous, flat terrain, and then N-ee = F-c, the vertical turbulent flux of CO2. Model results suggest that vertical and horizontal advection terms are generally of opposite sign and of the same order as the biological sources and sinks. We show that, close to the hilltop, F-c departs by a factor of three compared to its flat terrain counterpart and that the horizontally averaged F-c-at canopy top differs by more than 20% compared to the flat-terrain case.

Detecting intraday periodicities with application to high frequency exchange rates

Many recent papers have documented periodicities in returns, return volatility, bid–ask spreads and trading volume, in both equity and foreign exchange markets. We propose and employ a new test for detecting subtle periodicities in time series data based on a signal coherence function. The technique is applied to a set of seven half-hourly exchange rate series. Overall, we find the signal coherence to be maximal at the 8-h and 12-h frequencies. Retaining only the most coherent frequencies for each series, we implement a trading rule that is based on these observed periodicities. Our results demonstrate in all cases except one that, in gross terms, the rules can generate returns that are considerably greater than those of a buy-and-hold strategy, although they cannot retain their profitability net of transactions costs. We conjecture that this methodology could constitute an important tool for financial market researchers which will enable them to detect, quantify and rank the various periodic components in financial data better.

Evaluating forecasts from SETAR models of exchange rates

We consider the forecasting performance of two SETAR exchange rate models proposed by Kräger and Kugler [J. Int. Money Fin. 12 (1993) 195]. Assuming that the models are good approximations to the data generating process, we show that whether the non-linearities inherent in the data can be exploited to forecast better than a random walk depends on both how forecast accuracy is assessed and on the ‘state of nature’. Evaluation based on traditional measures, such as (root) mean squared forecast errors, may mask the superiority of the non-linear models. Generalized impulse response functions are also calculated as a means of portraying the asymmetric response to shocks implied by such models.

Medieval foreign exchange: a time series analysis

This chapter applies rigorous statistical analysis to existing datasets of medieval exchange rates quoted in merchants’ letters sent from Barcelona, Bruges and Venice between 1380 and 1310, which survive in the archive of Francesco di Marco Datini of Prato. First, it tests the exchange rates for stationarity. Second, it uses regression analysis to examine the seasonality of exchange rates at the three financial centres and compares them against contemporary descriptions by the merchant Giovanni di Antonio da Uzzano. Third, it tests for structural breaks in the exchange rate series.

Linear and non-linear (non-)forecastability of high-frequency exchange rates

This paper forecasts Daily Sterling exchange rate returns using various naive, linear and non-linear univariate time-series models. The accuracy of the forecasts is evaluated using mean squared error and sign prediction criteria. These show only a very modest improvement over forecasts generated by a random walk model. The Pesaran–Timmerman test and a comparison with forecasts generated artificially shows that even the best models have no evidence of market timing ability.

Can physical exercise during gestation attenuate the effects of a maternal perinatal low-protein diet on oxygen consumption in rats?

A protocol of physical exercise, based on maximal oxygen uptake ((V) over dot(O2max)), for female rats before and during pregnancy was developed to evaluate the impact of a low-protein diet on oxygen consumption during gestation and growth rate of the offspring. Virgin female Wistar rats were divided into four groups as follows: untrained (NT, n = 5); trained (T, n = 5); untrained with low-protein diet (NT+LP, n = 5); and trained with low-protein diet (T+LP, n = 5). Trained rats were submitted to a protocol of moderate physical training on a treadmill over a period of 4 weeks (5 days week(-1) and 60 min day(-1), at 65% of (V) over dot(O2max)). At confirmation of pregnancy, the intensity and duration of the exercise was reduced. Low-protein groups received an 8% casein diet, and their peers received a 17% casein diet. The birthweight and growth rate of the pups up to the 90th day were recorded. Oxygen consumption ((V) over dot(O2)), CO(2) production and respiratory exchange ratio (RER) were determined using an indirect open-circuit calorimeter. Exercise training increased. (V) over dot(O2max) by about 20% when compared with the initial values (45.6 +/- 1.0 ml kg(-1) min(-1)). During gestation, all groups showed a progressive reduction in the resting (V) over dot(O2) values. Dams in the NT+LP group showed lower values of resting (V) over dot(O2) than those in the NT group. The growth rate of pups from low-protein-fed mothers was around 50% lower than that of their respective controls. The T group showed an increase in body weight from the 60th day onwards, while the NT+LP group presented a reduced body weight from weaning onwards. In conclusion, physical training attenuated the impact of the low- protein

Impactos da votalidade cambial na atividade de turismo receptivo: novos desenhos de contratos

De 2002 a 2006 a moeda nacional brasileira, o real, vem sofrendo crescente valorização, tendência que afeta negativamente o setor exportativo no Brasil. Este trabalho refere-se o impacto desta valorização numa indústria específica do setor de exportação, a de turismo receptivo. São destacados os modelos de contratos atuais e analisada a proposição de um novo modelo de contrato, fechado em moeda nacional para as vendas internacionais, visando minimizar o risco cambial inerente à atividade. Os resultados indicam que a adoção deste novo modelo contratual eliminaria o risco cambial da parte da cadeia de distribuição situada no território nacional, trocando este por risco de demanda em função da flutuação do preço para o cliente final.

An overview of some historical brazilian macroeconomic series and some open questions

This paper presents an overview of the Brazilian macroeconomy by analyzing the evolution of some specific time series. The presentation is made through a sequence of graphs. Several remarkable historical points and open questions come up in the data. These include, among others, the drop in output growth as of 1980, the clear shift from investments to government current expenditures which started in the beginning of the 80s, the notable way how money, prices and exchange rate correlate in an environment of permanently high inflation, the historical coexistence of high rates of growth and high rates of inflation, as well as the drastic increase of the velocity of circulation of money between the 70s and the mid-90s. It is also shown that, although net external liabilities have increased substantially in current dollars after the Real Plan, its ratio with respect to exports in 2004 is practically the same as the one existing in 1986; and that residents in Brazil, in average, owed two more months of their final income (GNP) to abroad between 1995-2004 than they did between 1990 and 1994. Variance decompositions show that money has been important to explain prices, but not output (GDP).

The Brazilian 1994 stabilization plan: an analytical view

The Real Plan has succeeded in stabilizing the Brazilian inflation. The consumer price inflation has been reduced from 11260 percent per year, in June 1994, to an estimate of 8 percent in 1997. The lower inflation resulted in a remarkable income distribution, and in an increased private consumption. The plan managed to control the inflationary effects of the increased demand with some traditional measures: A more liberalized economy, a moving (and overvalued) exchange rate band, high interest rate differentials, and a tight domestic credit policy. The government has, so far failed to accomplish the fiscal adjustment. The price stabilization has largely depended on the current account deficit. However, macroeconomic indicators do not present reasons for concern about the current account sustainability, in the medium-run. The economy may be trapped in a low-growth vicious cycle, represented by a stop-and-go trend, due to the two-way endogencity between domestic saving and growth. Economic growth depends on policies in increase the public sector saving, to secure the privatization of the State enterprises, and to promote investments. The major problem for the government action is, as always, in the political sphere. Approximately 80 percent of the Central Government net revenue are allocated to the social sectors. Consequently, the fiscal reform will hue to deal with the problem of re-designing the public sector’s intervention in the social area. Most probably, it will be inevitable to cut the social area budget. This is politically unpleasant.

Interesse, ideologia & incompetência: a guerra do Iraque e o segundo consenso de Washington

Este projeto continua a avançar o programa de pesquisa que relaciona desenvolvimento econômico e democracia: pretende-se neste projeto dar um passo adiante e examinar como a democracia, uma vez consolidada como fruto do desenvolvimento capitalista, se torna ela própria um fator de desenvolvimento, particularmente quando ela deixa de ser uma mera democracia de elites para se tornar uma democracia de sociedade civil, na qual o debate público passa a ser um elemento central.

Ensaios em econometria aplicada

This thesis has three chapters. Chapter 1 explores literature about exchange rate pass-through, approaching both empirical and theoretical issues. In Chapter 2, we formulate an estate space model for the estimation of the exchange rate pass-through of the Brazilian Real against the US Dollar, using monthly data from August 1999 to August 2008. The state space approach allows us to verify some empirical aspects presented by economic literature, such as coe cients inconstancy. The estimates o ffer evidence that the pass-through had variation over the observed sample. The state space approach is also used to test whether some of the "determinants" of pass-through are related to the exchange rate pass-through variations observed. According to our estimates, the variance of the exchange rate pass-through, monetary policy and trade ow have infuence on the exchange rate pass-through. The third and last chapter proposes the construction of a coincident and leading indicator of economic activity in the United States of America. These indicators are built using a probit state space model to incorporate the deliberations of the NBER Dating Cycles Committee regarding the state of the economy in the construction of the indexes. The estimates o ffer evidence that the NBER Committee weighs the coincident series (employees in nonagricultural payrolls, industrial production, personal income less transferences and sales) di fferently way over time and between recessions. We also had evidence that the number of employees in nonagricultural payrolls is the most important coincident series used by the NBER to de fine the periods of recession in the United States.

Temporal aggregation and bandwidth selection in estimating long memory

This paper reinterprets results of Ohanissian et al (2003) to show the asymptotic equivalence of temporally aggregating series and using less bandwidth in estimating long memory by Geweke and Porter-Hudak’s (1983) estimator, provided that the same number of periodogram ordinates is used in both cases. This equivalence is in the sense that their joint distribution is asymptotically normal with common mean and variance and unity correlation. Furthermore, I prove that the same applies to the estimator of Robinson (1995). Monte Carlo simulations show that this asymptotic equivalence is a good approximation in finite samples. Moreover, a real example with the daily US Dollar/French Franc exchange rate series is provided.

A importância de um índice de volatilidade para o mercado brasileiro

Este trabalho objetiva analisar a importância de um índice de volatilidade implícita para o mercado brasileiro. Por ser conhecida como uma medida das expectativas futuras dos investidores, diversos estudos, principalmente na literatura estrangeira, tem consegui extrair importantes informações quanto às mudanças na volatilidade implícita com a chegada de novos dados sobre a economia. Analisando as opções de juros (IDI) e de dólar, este trabalho verifica que informações de dados macroeconômicos impactam a volatilidade. Os resultados demonstram que as expectativas quanto ao mercado de juros são impactadas por diversos dados, porém o mesmo não acontece com o mercado de dólar, a qual se demonstrou ser impactada somente por intervenções do Banco Central via colocação de swaps. Por fim, o trabalho conclui que existem varáveis não transacionáveis que explicam as variações na volatilidade implícita, mostrando que as volatilidades implícitas das opções possuem bastantes informações quanto às expectativas.

Volatilidade cambial e regimes de câmbio

Regimes de câmbio flutuante têm sido amplamente adotados desde 1973. De acordo com muitos estudos empíricos, esses regimes têm manifestado maiores volatilidades do que os regimes de câmbio fixo adotados após a Segunda Guerra Mundial. Contudo, desde começo dos anos 1970, muitos países têm adotado diferentes tipos de regimes de câmbio flutuante, desde completamente livres a flutuantes administrados, assim como uma ampla variedade de regimes de câmbio rígido. O objetivo deste trabalho é verificar se a volatilidade cambial está estatisticamente associada a esses diferentes regimes de câmbio. Utilizando a classificação cambial de facto de Reinhart e Rogoff (2004), nossa pesquisa aponta que regimes de câmbio com algum tipo de rigidez cambial são menos voláteis que regimes de câmbio com flutuação livre (freely floating); além disso, aponta que regimes cambiais em períodos de instabilidade monetária são ainda mais voláteis. Verificou-se ainda, que crises cambiais são significativas e responsáveis por maior volatilidade cambial, enquanto outros tipos de crises não se mostram estatisticamente significantes. Um terceiro resultado importante é o de que a abertura comercial e a abertura financeira não apresentaram significância estatística.

Estimando a taxa de juros real neutra brasileira via modelo DSGE

Este trabalho objetiva estimar uma série trimestral para a taxa de juros real neutra brasileira via modelo de Equilíbrio Geral Dinâmico Estocástico (DSGE), para o período compreendido entre o primeiro trimestre de 2000 e o último de 2011. O modelo representa uma economia fechada, com famílias maximizando utilidade do tipo CRRA, firmas maximizando lucro em um mercado de concorrência imperfeita e um governo com política fiscal de orçamento equilibrado e regra de política monetária à la Taylor, em um contexto de rigidez de preços. Neste arcabouço, a taxa de juros real neutra foi calculada com base nos choques de produtividade e de gastos de governo, que foram considerados os mais relevantes para a economia brasileira. Adicionalmente, analisou-se o impacto dos choques de produtividade e gastos do governo sobre a taxa neutra, assim como seu comportamento ao longo do período estimado e sua sensibilidade a calibragens alternativas. Por fim, ao comparar o comportamento do hiato de taxa de juros vis-à-vis à inflação, encontramos correlações negativas de 56% e 83% para todo o período estimado e para uma amostra mais recente (do primeiro trimestre de 2006 até o último de 2011), respectivamente, indicando certa consistência na série obtida.