Showing papers by "University of Lisbon published in 1989"
TL;DR: In this paper, the authors present a formal analysis of the incentives for cost reduction under a regime of price-cap regulation and show that a marginal reduction in the price cap increases the regulated firm's investment in cost reduction.
Abstract: In this article, we present a formal analysis of the incentives for cost reduction under a regime of price-cap regulation. We assume price-cap regulation establishes a ceiling below which a monopolist has complete price flexibility, while prices above the ceiling are subject to cost-based regulation. Our main conclusions are that a marginal reduction in the price cap increases the regulated firm’s investment in cost reduction. However, very low price caps might destroy investment incentives completely. Therefore, investment is a discontinuous function of the price-cap level.
199 citations
TL;DR: A new percentile reinforcement schedule suited to study pattern variability was developed and tested, whose main feature was the relative dissociation it provided between the variability requirement defining criterional responses and overall probability of reinforcement.
Abstract: The present investigation developed and tested a new percentile reinforcement schedule suited to study pattern variability, whose main feature was the relative dissociation it provided between the variability requirement defining criterional responses and overall probability of reinforcement. In a discrete-trials procedure, pigeons produced patterns of four pecks on two response keys. If the pattern emitted on the current trial differed from the N preceding patterns, reinforcement was delivered with probability mu. The schedule continuously adjusted the criterion N such that the probability of a criterional response, estimated from the subject's recent behavior, was always constant. In these circumstances, the criterion corresponded to an invariant percentile in the distribution of recent responses. Using a between-subjects design, Experiment 1 manipulated the variability requirement--the percentile--while keeping overall reinforcement probability constant. The degree of variability varied directly with the requirement. In addition, an inverse relationship existed between the requirement and within-group variance. Experiment 2 manipulated probability of reinforcement while maintaining the variability requirement constant. No consistent relationship was found between variability and reinforcement probability. A tentative hypothesis was advanced ascribing the operant conditioning of behavioral variability to a process of probability-dependent selection.
114 citations
TL;DR: There was a significant interaction between target type and word structure: Detections were more numerous when the target coincided with the first syllable of the target-bearing word than when it did not.
Abstract: A total of 40 unschooled Portuguese adults, either illiterates or ex-illiterates, were presented auditorily with short sentences and asked to detect the occurrence of a word initiated by a specified syllable-sized target. The target was either CV or CVC, and the target-bearing word was initiated by either a CV or a CVC syllable. The dependent variable was the number of correct detections. Ex-illiterates performed better than illiterates. There was a significant interaction between target type and word structure: Detections were more numerous when the target coincided with the first syllable of the target-bearing word than when it did not. This effect is similar to the one obtained by Mehler, Dommergues, Frauenfelder, and Segui (1981) in a reaction-time study with French literate subjects, and shows evidence of a syllabification procedure. The fact that this syllable effect is obtained with illiterate subjects, regardless of their overall performance, suggests that the development of a syllabifica...
71 citations
Journal Article•
TL;DR: In this paper, the authors present new estimates of gross domestic product, which extend the quantitative basis and the time-span of previous estimates, and discuss the conclusions that can be drawn from the estimates presented in the first part, and the perspectives they open for research on Portuguese economic history of the XlXth and XXth centuries.
Abstract: Introduction The time has come for a thorough revision of the existing knowledge about Portuguese economic growth in the XlXth and XXth centuries. Several texts published in the 1980's have provided a lot of data and much seminal discussion. However, retrospective national accounts estimates and conflicting theses have flourished in a rather chaotic way, and an attempt at synthesis may be welcome for future debate. This paper tries to provide such a synthesis. Its first part presents new estimates of gross domestic product, which extend the quantitative basis and the time-span of previous estimates. Its second part discusses the conclusions that can be drawn from the estimates presented in the first part, and the perspectives they open for research on Portuguese economic history of the XlXth and XXth centuries.
56 citations
TL;DR: The results demonstrate that La RNPs are localized in clusters of interchromatin granules, both in Triton X-100-extracted and DNase-digested nuclei, suggesting a role for nuclear actin in anchorage of snRNPs.
54 citations
TL;DR: Rhythms of larval release of the most abundant decapod crustaceans in the Mira Estuary, Portugal, were observed based on plankton samples made over consecutive ebbing tides during one lunar cycle in June 1986, suggesting that the larval-releasing activity is connected to the hour of the high tide rather than to tidal amplitude.
Abstract: Rhythms of larval release of the most abundant decapod crustaceans in the Mira Estuary, Portugal, were observed based on plankton samples made over consecutive ebbing tides during one lunar cycle in June 1986. Most species showed a semi-lunar rhythm of larval release, centered on crepuscular high tides around the quarter moons. The study suggests that the larval-releasing activity is connected to the hour of the high tide rather than to tidal amplitude.
50 citations
TL;DR: The larval and post-larval development of Percnon gibbesi, from a combination of laboratory-reared and plankton-caught material, is described, and larval characters within the Plagusiinae are discussed.
Abstract: The larval and post-larval development of Percnon gibbesi, from a combination of laboratory-reared and plankton-caught material, is described, and larval characters within the Plagusiinae are discussed. The synonymy of Percnon and Pluteocaris is established.
38 citations
TL;DR: In this article, the reduction of Mn(II) to manganese amalgam at the mercury thin film wall-jet disc electrode and the oxidation of MnO 2 at glassy carbon and platinum wall-Jet electrodes are investigated.
37 citations
TL;DR: In this paper, the authors present an experimental method for the characterization of MOS power switching transistors that does not involve technological parameters that are not available to designers and is based on the time-domain analysis of the commutation performance of the transistor when constant current are injected into its terminals.
Abstract: The authors present an experimental method for the characterization of MOS power switching transistors that does not involve technological parameters that are not available to designers. The method is based on the time-domain analysis of the commutation performance of the transistor when constant current are injected into its terminals. The analysis of the time-domain waveforms and the knowledge of the internal structure of the MOS devices are sufficient for the evaluation of the transistor capacitances. It is then possible to introduce a simple large-signal model for power MOSFETs that is particularly well suited to the analysis of circuits using the MOS transistor in commutation (e.g., switching power converters or high-efficiency power amplifiers). The authors also present the model implementation in the SPICE 2 program. Comparison between results obtained experimentally and by computer simulation for several circuits confirms the accuracy of the proposed method. >
37 citations
01 Dec 1989
TL;DR: There is evidence supporting the hypothesis that trisomy 21 patients have an increase in free radical reactions and lipoperoxidation susceptibility, and the possible association between oxidative stress and cortical lens damage in DS patients is assessed.
Abstract: Previous studies have suggested that free radicals and related species play a role in lens damage. The molecules involved may include proteins, lipids and DNA. Focal cortical changes and cortical liquefaction have been reported in patients with Down's syndrome over the age of 15 years. There is evidence supporting the hypothesis that trisomy 21 patients have an increase in free radical reactions and lipoperoxidation susceptibility. This could be due to an increase in the H2O2 generation catalysed by CuZn SOD although the activity of other gene products coded for on chromosome 21 cannot be excluded. Thiobarbituric acid reactive products were measured in human erythrocytes of nine DS patients and nine age-matched controls. There was a significant increase in the first group (21.0 +/- 2.3 nmol MDA/g Hb vs 16.4 +/- 2.9 nmol MDA/g Hb; p less than or equal to 0.01). In plasma, however, TBA products and antioxidant levels (ascorbic acid, tocopherol and uric acid) were not significantly different. Further studies should be carried out, namely through the use of more specific and sensitive methods, to assess the possible association between oxidative stress and cortical lens damage in DS patients.
35 citations
TL;DR: Fetal skeletal malformations that affect calcified and non-calcified bone tissue as a result of gestational zinc deficiency in rats are identified and the effect of maternal ZD in fetal bone calcification is assessed.
Abstract: Zinc deficiency (ZD) is teratogenic in rats, and fetal skeletal defects are prominent. This study identifies fetal skeletal malformations that affect calcified and non-calcified bone tissue as a result of gestational zinc deficiency in rats, and it assesses the effect of maternal ZD in fetal bone calcification. Pregnant Sprague-Dawley rats (180-250 g) were fed 1) a control diet (76.4 micrograms Zn/g diet) ad libitum (group C), 2) a zinc-deficient diet (0 microgram/g) ad libitum (group ZD), or 3) the control diet pair-fed to the ZD rats (group PF). On day 21 of gestation, laparotomies were performed. Fetuses were weighed, examined for external malformations, and stained in toto with a double-staining technique for the study of skeletal malformations. Maternal and fetal tissues were used for Zn, Mg, Ca, and P determinations. Gross external malformations were present in 97% of the ZD fetuses. No external malformations were found in fetuses from groups C and PF. Ninety-one percent of cleared ZD fetuses had multiple skeletal malformations, whereas only 3% of the fetuses of group PF had skeletal defects; no skeletal malformations were found in fetuses from group C. Some of the skeletal malformations described in the ZD fetuses, mainly affecting non-calcified bone, were not mentioned in previous reports, thus stressing the importance of using double-staining techniques. Examination of stained fetuses and counting of ossification centers revealed important calcification defects in ZD fetuses. These effects were confirmed by lower Ca and P concentrations in fetal bone with alteration of the Ca:P ratio.
TL;DR: In the recently ovulated oocytes, fertilized eggs and early embryos from the golden hamster, networks of cytokeratin filaments extended throughout the cortical and perinuclear regions, while aggregates progressively disappeared.
TL;DR: Five flavonoids and an acetophenone derivative were isolated from Artemisia campestris subsp.
TL;DR: In this paper, the general features of the dimensional reduction scheme for multi-dimensional spaces of the type M4 × S/R were studied and the properties of the scalar potentials of the reduced theories were investigated and an effective method of explicit calculation of these potentials was elaborated.
Abstract: We study the general features of the dimensional reduction scheme for multi-dimensional spaces of the type M4 × S/R, S/R being a symmetric coset space. The properties of the scalar potentials of the reduced theories are investigated and an effective method of explicit calculation of these potentials is elaborated. We consider also a wide class of embeddings of Lie subalgebras into simple Lie algebras resulting in reduced theories of physical interst.
TL;DR: In this article, the aeromagnetic anomaly map for mainland Portugal shows a clear zonation correlated with the main structural units of the Hercynian foldbelt, and the limits of these zones are in agreement with those described by geologists except for the western border of the CIZ which does not have any magnetic signature.
TL;DR: In this paper, the authors presented new absolute measurements of thermal conductivity and of the thermal diffusivity of gaseous argon obtained with a transient hot-wire instrument.
Abstract: This paper presents new absolute measurements of the thermal conductivity and of the thermal diffusivity of gaseous argon obtained with a transient hot-wire instrument. We measured seven isotherms in the supercritical dense gas at temperatures between 157 and 324 K with pressures up to 70 MPa and densities up to 32 mol · L−1 and five isotherms in the vapor at temperatures between 103 and 142 K with pressures up to the saturation vapor pressure. The instrument is capable of measuring the thermal conductivity with an accuracy better than 1% and thermal diffusivity with an accuracy better than 5%. Heat capacity results were determined from the simultaneously measured values of thermal conductivity and thermal diffusivity and from the density calculated from measured values of pressure and temperature from an equation of state. The heat capacities presented in this paper, with a nominal accuracy of 5%, prove that heat capacity data can be obtained successfully with the transient hot wire technique over a wide range of fluid states. The technique will be invaluable when applied to fluids which lack specific heat data or an adequate equation of state.
TL;DR: In this article, the authors report the first time tunneling tranport on vertical μc Si/a / a ǫ 6CyOz heterostructures produced in a Two consecutive Decomposition and Deposition Chamber system where a Negative Differential Conductance is observed even at room temperature.
Abstract: In this paper we report by the first time tunneling tranport on vertical μc Si / a SixCyOz : H / μc Si ( μc a μc ) heterostructures produced in a Two consecutive Decomposition and Deposition Chamber system where a Negative Differential Conductance is observed even at room temperature. Giant bias anomalies are observed, that decrease with temperature. Tunneling spectroscopy data are also reported for samples measured at low temperatures. A qualitative information of the recorded data is obtained and related with main features of the heterostructure. Nevertheless in this stage is hard to take quantitative information.
TL;DR: It cannot rule out that the MRSA Lisbon isolates are a homogeneous group of strains that might have a common origin, and seem to be different from MRSA recently isolated in other countries, butAntimicrobial susceptibilities and genetic analysis showed that resistance to penicillin, methiillin, erythromycin (inducible phenotype), tetracycline, gentamicin, tobramycin, kanamycin, streptomycin, neomycin and
TL;DR: Putting the external quarks on shell, it is found that the corresponding flavor-changing S-matrix elements are not renormalized, i.e., the sum of all counterterms vanishes.
Abstract: The flavor-changing amplitudes \ensuremath{\gamma}${q}_{i}$${q}_{j}$ and ${\mathrm{Zq}}_{i}$${q}_{j}$ are computed for off-shell particles and without approximations. The calculations are done in the 't Hooft\char21{}Feynman gauge, and the on-shell renormalization scheme is used. The Ward-Slavnov-Taylor identities are derived and used to check the results. Putting the external quarks on shell, we found that the corresponding flavor-changing S-matrix elements are not renormalized, i.e., the sum of all counterterms vanishes. Using the renormalization scheme proposed by Sirlin the meaning of this cancellation is clarified.
TL;DR: In this article, the consistency of a nonparametric estimator of bivariate extreme value distributions is established, which is similar to the consistency established in this paper, but different.
01 Jan 1989
TL;DR: A large class of mathematical models for phase change problems in thermo-diffusion phenomena belong to the family of the so-called Stefan problems, after the Austrian mathematical-physicist Joseph Stefan, who, exactly one century ago, published a series of papers on some of these problems as discussed by the authors.
Abstract: A large class of mathematical models for phase change problems in thermo-diffusion phenomena belong to the family of the so-called Stefan problems, after the Austrian mathematical-physicist Joseph Stefan, who, exactly one century ago, published a series of papers on some of these problems [St]. However, the first work on this type of problems seems to be due to Lame and Clapeyron [LC] and since then they have interested a large number of mathematicians.
TL;DR: The formation of the maleimide ring depended on the orientation and substitution of HO-3' and the reaction was analogous of showdomycin.
Journal Article•
TL;DR: In this article, the authors report the theoretical chronoamperometric response for a ring electrode of finite size, and compare the experimental response to that of a disk electrode, showing that the response of the ring electrode approaches mass transport conditions close to those for the final steady state at times which are short compared to those at which the steady state is reached for disks of similar radii.
TL;DR: Rutin (quercetin-3-O-rutinoside) was shown to be a competitive inhibitor for faecalase, whereas no inhibitory activity could be found for salivase.
TL;DR: Although intended for children who are not malnourished, the European ORS should have an adequate potassium concentration, namely the same concentration as found in WHO-ORS.
Abstract: Clinical trials testing different oral rehydration solutions (ORS) are reviewed. The effects of individual components and their concentrations are analysed in order to establish margins of safety for the composition of the ideal ORS for children in Europe. Glucose is the solute of choice for ORS and concentrations of 70-140 mmol/l are adequate. Glucose may be replaced by sucrose or glucose polymers. "Low" sodium concentrations (35-60 mmol/l) are advised for rehydration and maintenance in acute non-cholera diarrhoea, for children of all ages, including neonates, and for any degree of dehydration except shock. Although intended for children who are not malnourished, the European ORS should have an adequate potassium concentration (20-30 mmol/l), namely the same concentration as found in WHO-ORS. Chloride concentration depends upon other constituents of ORS, namely sodium and potassium, but the range of 30-90 mmol/l is considered to be adequate. Base or base precursors are not required for correction of acidosis except in the severe cases that always need intravenous replacement. A relatively low osmolality seems advisable.
TL;DR: A subdural electrode was designed and constructed with 3 pairs of contacts to make 3 dipoles that well approximate the expected magnetic behavior for a current dipole and can be used clinically to test localization capabilities of magnetoencephalography.
TL;DR: In this paper, the forms of the overpotential-time response to controlled current experiments at finite disk electrodes were discussed, and compared to experimental results obtained at disk microelectrodes.
TL;DR: Azelaic acid: Pharmacology, toxicology and mechanism of action in acne was discussed in this paper, where it was shown that Azelaic acids are effective in removing acne lesions.
Abstract: (1989). Azelaic acid: Pharmacology, toxicology and mechanism of action in acne. Journal of Dermatological Treatment: Vol. 1, No. sup1, pp. 11-15.