Showing papers by "University of Lisbon published in 1984"

Depolarized light scattering of heavy water, and hydrogen bond dynamics

Abstract: We measured the depolarized Rayleigh scattering of heavy water from 70°C down to -13°C. The spectra were analysed and show a low frequency component. Both the intensity and the width of this line are temperature dependent. The characteristic time associated with the width has an Arrhenius behaviour with an activation energy of 2·5 kcal mol-1. The intensity has a quadratic shape with a maximum around 50°C. We interpret these results as a manifestation of the hydrogen-bond dynamics and propose a mechanism for the breaking of H-bonds through the librational movements. Comparisons are made with theoretical models and molecular dynamics simulations.

Penultimate limiting forms in extreme value theory

Abstract: Let {X n}n≧1 be a sequence of independent, identically distributed random variables. If the distribution function (d.f.) ofM n=max (X 1,…,X n), suitably normalized with attraction coefficients {αn}n≧1(αn>0) and {b n}n≧1, converges to a non-degenerate d.f.G(x), asn→∞, it is of interest to study the rate of convergence to that limit law and if the convergence is slow, to find other d.f.'s which better approximate the d.f. of(M n−bn)/an thanG(x), for moderaten. We thus consider differences of the formF n(anx+bn)−G(x), whereG(x) is a type I d.f. of largest values, i.e.,G(x)≡Λ(x)=exp (-exp(−x)), and show that for a broad class of d.f.'sF in the domain of attraction of Λ, there is a penultimate form of approximation which is a type II [Ф α(x)=exp (−x−α), x>0] or a type III [Ψ α(x)= exp (−(−x)α), x<0] d.f. of largest values, much closer toF n(anx+bn) than the ultimate itself.

Phage-types and susceptibility to 26 antibiotics of nosocomial strains of Acinetobacter isolated in Portugal.

Abstract: Sixty-two strains of Acinetobacter calcoaceticus isolated from pathological samples or from the environment in several hospitals in Lisbon, were studied by means of two complementary phage-typing s...

Trade and Financial Interdependence Under Flexible Exchange Rates: The Pacific Area

Abstract: This paper analyses policy interdependence under flexible exchange rates and its implications for middle-income countries in the Pacific area. In the first part of the paper, the consequences of strategic behavior among industrial countries are illustrated by means of a simple diagram. It is argued that in the absence of incentives to coordinate macroeconomic policies among major countries, exchange rates will tend to be volatile. Evidence on the world value of the dollar in the flexible rate period is then presented and interpreted.The second part describes exchange rate policies in the Pacific area. It is found that the widespread policy of pegging to the U.S. dollar has implied occasional large devaluations against the numeraire (Korea, Taiwan, Thailand, Philippines and Indonesia). An alternative, which requires higher Pacific trade and financial interdependence than the one prevailing during the last decade, would be a joint float along the lines of the policies seemingly pursued by Malaysia and Singapore.The two-country macroeconomic model presented in the Appendix can be used to assess the costs and benefits of policy coordination both at the world and at the regional level.

The Centre-Periphery Model and Industrial Development in Portugal:

Abstract: A critique of the use of the centre-periphery model in explanation of intranational regional development based upon Marxist and neo-Marxist economic theory is presented. Seemingly different approaches use the same basic explanatory structure. The history and structure of the model arc discussed, followed by a theoretical and epistemological critique of the explanatory content. Empirical evidence for key economic variables in the industrial sector in Portugal is presented, which casts further doubt upon the validity of the model. Portugal exhibits an apparent centre-periphery structure in patterns of regional industrial development, but closer analysis reveals that underlying patterns found in these key variables do not conform.

Two Test Statistics for Choice of Univariate Extreme Models

Abstract: Asymptotic properties of the statistic proposed by Gum-bel. Wn = {max(Xi) − med(Xi)}/{med(Xi) −min(Xi)}, are obtained for testing the shape parameter k = 0, in von Mises-Jenkinson form. Similar results are obtained for a ratio of variances test statistic modified from one suggested by Jenkinson. Comparison is made; as could be expected Gumbel statistic turns out to be the better one.

Bounds on light scalar particles from nuclear decays

Abstract: We examine two experiments done by Kohler, Watson, and Becker to search for the emission of light scalar particles in the nuclear ${0}^{+}$-${0}^{+}$ transitions and their subsequent decay into ${e}^{+}{e}^{\ensuremath{-}}$. We show that the $^{4}\mathrm{He}$ experiment is not sensitive to this search, due to the large proton-decay width of the ${0}^{+}$ state of $^{4}\mathrm{He}$. Thus, scalar masses between 1.03 and 5.84 MeV only are excluded at the Higgs-boson-like coupling, via the $^{16}\mathrm{O}$ experiment.

Concomitants in a Multidimensional Extreme Model

Abstract: Ordering of multivariate data is referred, with special emphasis to induced ordering, where the order statistics of a marginal sample together with their concomitants are considered.

The differential integration of the rural family

Abstract: This paper is concerned with the principle of the differential integration of the rural family, illustrated by means of a comparison between the social reproduction of the family farm in England and the pequenoproprietario household in Portugal. The comparison is developed in terms of a cultural model of the family in each case. In the English example, this appears to involve a partitioning of identity (especially on the part of the in-marrying wife) within the family and kinship system. In the Portuguese case, there is a suspension of identity of family members who are absent in space and in time. In both cases the idea of the family works as a unificatory device. It is for this very reason that critical attention should be given to the distinction between folk construct and analytical concept. Resume Le principc de ľ integration differentielle de la famille runic est illustre dans cet article a travers la comparaison de la reproduction sociale de ľ exploitation familiale en Angleterre ? une part et de la petite exploitation 2u Portugal. Au dela de ce principe la comparaison porte sur le modele culturcl familial de chacun de ces cas. Dans le cas anglais, lc modele culturel implique une separation ? identite (surtout dans le cas de la femme qui se marie) entre la famille et la parente. Dans le cas portuguais il s'agit ? une suspension ? identite des membres de la famille qui sont eloignes dans le temps ou dans Pcspace. Mais dans les deux cas ľ idee de famille fonctionne comme un mecanisme unificatcur. Ce dernier constat conduit a insister sur la distinction qui doit etre faitc entre la notion commune de famille et le concept scientifique. Kurzfassung Dieser Beitrag befasst sich mit dem Prinzip der differentiellen Integration der landlichen Familie, dargestellt an Hand eines Vergleichs zwischen der sozialen Reproduktion des Familienbetriebes in England und des Haushaltes von Kleineigentumcrn in Portugal. Der Verglcich wird nach Entwicklung eines Kulturmodells der Familie fur jedes Land durch-fgefuhrt. Dies scheint im Falle Englands cine Teilung der Identitat (insbesondcre bei der einheiratenden Ehcfrau) innerhalb der Familie und der Verwandtschaftssystems einzu-schliessen. Im Falle von Portugal kann cine Aufhcbung der Identitat von solchen Familienmitgliedern, die in raumlicher und zcitlicher Entfernung leben, festgestellt werden. In beiden Fallen wirkt die Idee der Familie als cine Einhcit stiftende Einrichtung. Aus genau diesem Grunde sollte der Unterscheidung zwischen volkstumlichen Vorstellungen und analytischen Konzeptcn kritische Aufmerksamkeit gewidmet werden.

/sup 3/He D-state effects in the /sup 1/H(d,. gamma. )/sup 3/He reaction

Abstract: The tensor analyzing powers of the $^{1}\mathrm{H}(\stackrel{\ensuremath{\rightarrow}}{d},\ensuremath{\gamma})^{3}\mathrm{He}$ reaction initiated by a polarized beam are studied using the Sasakawa wave function for the three-body bound state and neglecting initial state interactions. Good agreement is obtained with recent ${A}_{\mathrm{yy}}$ data taken at ${E}_{\ensuremath{\gamma}}=14.66$ MeV. It is shown that at low energy the tensor analyzing powers are sensitive to the asymptotic region of the bound state wave function and can be used to determine the asymptotic $\frac{D}{S}$ state ratio, $\ensuremath{\eta}$, in $^{3}\mathrm{He}$.

Lattice Location Studies on Hafnium, Thallium and Lead Implanted Magnesium Single Crystals

Abstract: The lattice location of hafnium, thallium and lead implanted into magnesium crystals has been studied using the Rutherford backscattering channeling technique with the 1.2 MeV 4He+ beam of the Van de Graaff - accelerator of LNETI – Sacavem. The results showed complete substitutionality for the hafnium implantation.This position was not affected by annealing at 300°C. For lead and thallium it was found that only a fraction of the implanted ions occupy substitutional lattice sites. After a similar annealing treatment all the implanted ions are observed at random positions. It will be shown that these data are in good agreement with recent predictions of Sood (4) and Singh and Zunger (5). However, they cannot be explained with the extended Miedema scheme (1,2).

Strongly N-normal lattices

Abstract: The main purpose of this work is to characterize subvarieties of algebras with a distributive lattice reduct, by studying the partial order of their set of filters.

Determination of Zinc, Iron and Aluminium in Halophytic Species of the River Sado Estuary—Portugal, by Atomic Absorption Spectrometry

Abstract: In our research emphasis is placed upon bioaccumulation of Zn, Fe and Al by salt marsh vegetation of coastal areas of River Sado estuary.

Trade and Financial Interdependence Under Flexible Exchange Rates: The Pacific Area

Abstract: This paper analyses policy interdependence under flexible exchange rates and its implications for middle-income countries in the Pacific area. In the first part of the paper, the consequences of strategic behavior among industrial countries are illustrated by means of a simple diagram. It is argued that in the absence of incentives to coordinate macroeconomic policies among major countries, exchange rates will tend to be volatile. Evidence on the world value of the dollar in the flexible rate period is then presented and interpreted.The second part describes exchange rate policies in the Pacific area. It is found that the widespread policy of pegging to the U.S. dollar has implied occasional large devaluations against the numeraire (Korea, Taiwan, Thailand, Philippines and Indonesia). An alternative, which requires higher Pacific trade and financial interdependence than the one prevailing during the last decade, would be a joint float along the lines of the policies seemingly pursued by Malaysia and Singapore.The two-country macroeconomic model presented in the Appendix can be used to assess the costs and benefits of policy coordination both at the world and at the regional level.

A note on Pólya’s theorem

Abstract: The class of extended Polya functions O = {f: f is a continuous real valued real function, f(-t) = f(t) = f(0) I [0,1], limt?8 f(t) = c I [0,1] and f(|t|) is convex} is a convex set. Its extreme points are identified, and using Choquet's theorem it is shown that f I O has an integral representation of the form f(|t|) = ?08 max{0, 1-|t|y} dG(y), where G is the distribution function of some random variable Y. As on the other hand max{0, 1-|t|y} is the characteristic function of an absolutely continuous random variable X with probability density function f(x) = (2p)-1(x/2)-2sin2(x/2), we conclude that f is the characteristic function of the absolutely continuous random variable Z = XY, X and Y independent. Hence, any f I O is a characteristic function. This proof sheds an interesting light upon Polya's sufficient condition for a given function to be a characteristic function

Training elementary school teachers to use computers: With emphasis on Logo

Abstract: For the past two summers we have taught a twoweek "computer camp" for teachers of grades one through seven. The teachers, who were paired by grade level (one pair at each computer), spent approximately three hours each day in "class" at an Apple II + microcomputer and averaged another two hours a day in individual practice. Participants were selected on a first-come, first-served basis in response to announcements sent to area schools. The most recent camp session included eleven elementary and four middle school teachers and was taught by a university faculty member and four graduate assistants in the mathematics education department.

In vitro activity of ceftazidime and other beta-lactam antibiotics against nosocomial strains of Pseudomonas aeruginosa

Abstract: The in vitro sensitivity of 300 nosocomial strains of Pseudomonas aeruginosa to ceftazidime was compared with their sensitivities to eleven other beta-lactam antibiotics. Concentrations of 2 mg/l of ceftazidime were sufficient to inhibit all of the strains tested including the carbenicillin-resistant ones. Ceftazidime shows considerably greater activity against Ps. aeruginosa than the other beta-lactam antibiotics.