ExploRing Persistence in Financial Time Series

Edited by W. Härdle, Z. Hlávka, and S. Klinke</p

Thyroid and pituitary gland development from hatching through metamorphosis of a teleost flatfish, the Atlantic halibut

Fish larval development, not least the spectacular process of flatfish metamorphosis, appears to be under complex endocrine control, many aspects of which are still not fully elucidated. In order to obtain data on the functional development of two major endocrine glands, the pituitary and the thyroid, during flatfish metamorphosis, histology, immunohistochemistry and in situ hybridization techniques were applied on larvae of the Atlantic halibut (Hippoglossus hippoglossus), a large, marine flatfish species, from hatching through metamorphosis. The material was obtained from a commercial hatchery. Larval age is defined as day-degrees (D =accumulated daily temperature from hatching). Sporadic thyroid follicles are first detected in larvae at 142 D (27 days post-hatch), prior to the completion of yolk sack absorption. Both the number and activity of the follicles increase markedly after yolk sack absorption and continue to do so during subsequent development. The larval triiodothyronine (T3) and thyroxine (T4) content increases, subsequent to yolk absorption, and coincides with the proliferation of thyroid follicles. A second increase of both T3 and T4 occurs around the start of metamorphosis and the T3 content further increases at the metamorphic climax. Overall, the T3 content is lower than T4. The pituitary gland can first be distinguished as a separate organ at the yolk sack stage. During subsequent development, the gland becomes more elongated and differentiates into neurohypophysis (NH), pars distalis (PD) and pars intermedia (PI). The first sporadic endocrine pituitary cells are observed at the yolk sack stage, somatotrophs (growth hormone producing cells) and somatolactotrophs (somatolactin producing cells) are first observed at 121 D (23 days post-hatch), and lactotrophs (prolactin producing cells) at 134 D (25 days post-hatch). Scarce thyrotrophs are evident after detection of the first thyroid follicles (142 D ), but coincident with a phase in which follicle number and activity increase (260 D ). The somatotrophs are clustered in the medium ventral region of the PD, lactotrophs in the anterior part of the PD and somatolactotrophs are scattered in the mid and posterior region of the pituitary. At around 600 D , coinciding with the start of metamorphosis, somatolactotrophs are restricted to the interdigitating tissue of the NH. During larval development, the pituitary endocrine cells become more numerous. The present data on thyroid development support the notion that thyroid hormones may play a significant role in Atlantic halibut metamorphosis. The time of appearance and the subsequent proliferation of pituitary somatotrophs, lactotrophs, somatolactotrophs and thyrotrophs indicate at which stages of larval development and metamorphosis these endocrine cells may start to play active regulatory roles.This work has been carried out within the projects ‘‘Endocrine Control as a Determinant of Larval Quality in Fish Aquaculture’’ (CT-96-1422) and ‘‘Arrested development: The Molecular and Endocrine Basis of Flatfish Metamorphosis’’ (Q5RS-2002-01192), with financial support from the Commission of the European Communities. However, it does not necessarily reflect the Commission’s views and in no way anticipates its future policy in this area. This project was further supported by the Swedish Council for Agricultural and Forestry Research and Pluriannual funding to CCMAR by the Portuguese Science and Technology Council

The effect of culture on Corporate Governance Practices in Nigeria

This study focuses on the effect of culture on the application of corporate governance practices in Nigeria. Corporate governance has been receiving serious attention in emerging markets over the past two decades. But relatively little attention has been given to the study on corporate governance in a country study. The current situations in Nigerian public and private sectors such as the corporate scandal resulting from Lever Brothers Nigeria plc, Siemens, Shell, Halliburton, and Cadbury Nigeria plc, have shown that the issue of fraud, corruption, and corporate scandals cannot be overlooked. Most top management, as this study argues, bring in beliefs acquired from their early childhood into their senior management roles and responsibilities. This study adopts a grounded theory and reports on the effect of culture on the implementation of corporate governance in Nigeria. Based on the interview with 32 staffs, this study identifies the effect of culture that shapes corporate governance and they include abuse of power by top management, weak legal framework, poor recruitment and ineffective control. Although having efficient corporate governance is worth pursuing, this depends on the power of top management, the strength of internal control procedures and the legal framework put in place by management

A framework for robust estimation of beta using information fusion approach

WOS: 000444687500021In terms of financial management, the precise estimation of the beta of a financial asset is of vital importance. Beta is the measure of the relationship between the return of an asset or a portfolio and the market return and means the systematic risk within the scope of the Capital Asset Pricing Model. In general, it is known that the distribution of returns is significantly non-normal with thick-tail and skewness features. The ordinary least square (OLS) estimator that focuses on the centre of a distribution loses its effectiveness in such cases as the divergence of the distribution from normality, the presence of outliers, and heteroscedasticity. Quantile regression (QR), which is regarded as a non-parametric method, shows robustness against the specified phenomena. QR reveals the information carried by the distribution in tails as the returns focus on the whole of distribution. This means different beta for each percentile requiring investigation, and causes the problem of fusion of this information. Ordered Weighted Averaging (OWA) operators can merge the information coming from different percentiles at a required orness level depending on the attitude of the investor towards the risk. This study also suggests the use of OWA operators in addition to different quantile combination techniques used in the literature. As a result of the analysis performed based on Borsa Istanbul (Istanbul Stock Exchange) data, it was shown that OWA operators have a performance that is comparable to OLS and quantile combination techniques

Dynamic generation of hypotheses: Mandelbrot, Soros and far-from-equilibrium

t In this paper I argue that the effective way to account for the behavior of stock market prices is to put in use a dynamic approach—bottom-up, local, nonaxiomatic, heuristic. To this end, I provide an analysis of the generation of four main hypotheses used to explain stock market prices (SMP). In particular I show how the means of generating these hypotheses is essential to assessing their efficiency and plausibility. In formulating a hypothesis, a selection of features of SMP is made for incorporation in a theory. This selection may be expressed mathematically in most of the cases. An examination of these means of generation can show us why some of these hypotheses are successful and efficient and some not, and can also shed light on the extent to which a particular hypothesis can be usefully applied. Thus the study of the means of generation of hypotheses will offer us a guide to formulating new hypotheses in a reliable and cogent fashion