An Ogden-like iteration lemma for rational power series

Summary An Ogden-like iteration lemma for languages that are support of rational power series is proved; it is a generalization of Jacob's iteration lemma. The new bound we obtain is much smaller than the one of Jacob and does no more depend on the cardinality of the alphabet. The proof consists in studying how pseudo-regular matrices appear as subproducts of long products of square matrices.     

Integration and enhancement of low-level signals from air-pollution monitoring sensors

In this paper, we have demonstrated how signal enhancement techniques would be advantageous in the low-level analysis of air pollutants. We have further shown what type of signal-to-noise gain may be expected from an off-the-shelf, inexpensive run-of-the-mill mercury monitor. As long as an evoked response time constant is introduced into the measuring system, noise of a random nature may be reduced to such an extent that trace signals, buried deep in the electrical background, may be reliably measured. If we couple this type of analysis to a multi-parameter mercury analyzer, contributing factors may be evaluated⁸. This will result in a more efficient system application.We have also reported a manner in which evoked response time is related to instrument onset time. However, there are other methods for obtaining an evoked response. Of note is the use of wavelength in the enhancement of spectrophotometric signals.⁹ In additional work now being carried out in our laboratory, there are indications that it is possible to relate this type of processing to SO₂ analyzing systems using conductometry.     

Factors affecting the concentrations of cadmium, zinc, copper and lead in the sediments of the Vesdre River

The main factors influencing Cd, Zn, Cu and Pb concentrations in the sediments of the highly polluted Vesdre River (eastern Belgium) have been investigated. Only negative correlations were demonstrated between the clay content and heavy metals. The composition of the clay minerals could partially explain this paradox. However, the pretreatment of the minerals might influence the geochemical data obtained from analysis. Iron-hydroxides and phosphates seem to be the main sinks for Pb, Cd and Zn whereas organic components might play a less important role.     

Approximating the inverse of a matrix for use in iterative algorithms on vector processors

Most iterative techniques for solving the symmetric positive-definite systemAx=b involve approximating the matrixA by another symmetric positive-definite matrixM and then solving a system of the formMz=d at each iteration. On a vector machine such as the CDC-STAR-100, the solution of this new system can be very time consuming. If, however, an approximationM ^?1 can be given toA ^?1, the solutionz=M ^?1 d can be computed rapidly by matrix multiplication, a fast operation on the STAR. Approximations using the Neumann expansion of the inverse ofA give reasonable forms forM ^?1 and are presented. Computational results using the conjugate gradient method for the “5-point” matrixA are given.     

Polaromicrotribometric study of polyphenylene oxide film formation on metal electrodes by electrolysis of disubstituted phenols

The anodic oxidation of numerous disubstituted phenols has been studied in a base and alcohol media using various metals (Fe, Cu, Ni, Cr, Ti, Zn, Au, Pt) as electrodes. For 2,6-dimethylphenol, the passivity phenomenon shown by simultaneous recording of the current/potential and friction/potential curves (polaromicrotribometry) is explained by formation on the electrode of a thin, insulating film of polyphenylene oxide (PPO) whose chemical nature has been recognized by multiple reflection ir spectroscopy. The measured physical characteristics of this film (thickness, adherence, hydrophobicity, coefficient of friction...) indicate its possible interest as a protective coating for metallic surfaces.     

The Exact Maximum Likelihood-Based Test for Fractional Cointegration: Critical Values,Power and Size

The exact maximum likelihood (EML) procedure can be used as a residual-based test of the hypothesis of no cointegration against the alternative of fractional cointegration. Since the corresponding asymptotic properties have not yet been established, this paper provides simulated critical values, power and size relating to the EML-based test for fractional cointegration. Monte Carlo simulations indicate that the simulated density of the EML-based test is shifted to the left compared to the standard normal distribution and exhibits a strong excess of kurtosis in the absence of autoregressive components in the regression residuals. The power and size comparison indicates that the EML-based test is more powerful than other fractional cointegration tests (Lo, Lobato-Robinson and Geweke and Porter-Hudak) in small and medium sample sizes. Moreover, by simulating integrated time series with AR(1), and respectively MA(1), disturbances, it is shown that, whatever the sample size, the EML-based test exhibits the lowest size distortions for positive AR(1) and negative MA(1) coefficients, respectively.JEL classifications: C15; C22     

Time-varying, 3-D echocardiography using a fast-rotating probe

A fast continuous rotating ultrasound scan-head transducer was used to perform three-dimensional (3-D) echocardiography with 2-D images acquired during a single cardiac cycle. The 3-D images were reconstructed by interpolating 2-D data acquired with the probe. Two experiments were carried out to validate the image reconstructions. A dynamic cardiac phantom was used as a known reference to compare the minimal and maximal volumes estimated manually on the reconstructed 3-D images. The left ventricle (LV) volume of 30 healthy volunteers also were estimated using a semiautomatic ellipse approach and compared to measurements obtained with standard 2-D examination. Results showed a good agreement between 3-D and reference measurements.     

A unified theory of market partitioning: an integration of resource-partitioning and sunk cost theories

Our objective was to integrate a sociological and an economictheory of market partitioning into a unifying framework: GlennCarroll’s resource-partitioning and John Sutton’ssunk cost theories, respectively. In so doing, two importanttheory fragments from organizational ecology and industrialorganization are integrated in an attempt to understand theantecedents and consequences of so-called dual market structures.A dual market structure features high concentration and highdensity, two market structure conditions that in most extanttheory are thought to be unrelated. We argue that both theoryfragments are highly complementary, offering different storiesabout the evolution of competition that produce similar marketstructure outcomes. In terms of the competitive strategies andorganizational forms involved, however, the accounts of dualmarket structure evolution in the resource-partitioning andsunk cost theories are very different. This is instrumentalin developing a dynamic theory of Porterian strategic management.We use these insights to reinterpret existing evidence, discussinga series of well-known industry studies.