Showing papers by "University of Coimbra published in 1983"
TL;DR: In vitro and in vivo tests of a new commercial fluorophotometer showed that the instrument is capable of measuring fluorescein concentrations of 1 to 1,000 ng/mL accurately and performed superiorly when compared with other existing fluorideophotometers.
Abstract: • In vitro and in vivo tests of a new commercial fluorophotometer showed that the instrument is capable of measuring fluorescein concentrations of 1 to 1,000 ng/mL accurately The in vivo estimate of the spread functions of the lens and chorioretinal peaks yielded values of about 1% and 05% 3 and 6 mm, respectively, from the peak Pigmentation did not influence the chorioretinal spread function Reproducibility in vivo was evaluated to be 12% Furthermore, when compared with other existing fluorophotometers, the new instrument performed superiorly
99 citations
TL;DR: The microscopic features suggest that the proliferating trichilemmal cyst must be considered an hamartoma of the terminal hair follicle, not only related to the isthmic segment of the outer root sheath but with some differentiation towards the infundibular and matricial segments.
Abstract: Fourteen cases (9 female, 5 male) of proliferating trichilemmal cysts are reported. The patients age-range was 40-80, 12 being over 60. The cysts wee present for 2-50 years and enlarged in the months or years before the observation. Seven were ulcerated. In 4 with multiple lesions both proliferating and ordinary trichilemmal cysts were present. The histological features were typical in all but one patient (evolution towards squamous cell carcinoma?) with some variation from lesion to lesion and from area to area in the same tumour. The microscopic features suggest that the proliferating trichilemmal cyst must be considered an hamartoma of the terminal hair follicle, not only related to the isthmic segment of the outer root sheath but with some differentiation (smaller and more variable) towards the infundibular and matricial segments. The tumour is likely to be a proliferating trichilemmal cyst from the beginning and not a peculiar evolution of an ordinary, pre-existant, trichilemmal cyst.
91 citations
TL;DR: Several methods of data analysis permit improved evaluation of the blood-retinal barrier (BRB) by vitreous fluorophotometry and an algorithm for artifact correction was tested in vivo in situations in which large artifacts are expected.
Abstract: Several methods of data analysis permit improved evaluation of the blood-retinal barrier (BRB) by vitreous fluorophotometry. With the use of an algorithm for artifact correction, tested in vivo in situations in which large artifacts are expected, artifacts were reduced to less than the equivalent of 1 ng/mL in normal eyes 3 mm from the chorioretinal and lens peaks. A procedure developed to evaluate the lens transmittance was found to have a 12% reproducibility. In addition, the anterior and posterior sources of leakage could be separated by choosing the appropriate time of measurement after injection of the dye. Moreover, a procedure to estimate quantitatively the inward permeability of the BRB yielded a preliminary estimate of 7.2 X 10(-8) cm/s in normal subjects.
65 citations
TL;DR: A working hypothesis for the pathogenesis of diabetic retinopathy is presented and vitreous fluorophotometry has shown that a disturbance of the blood-retinal barrier appears in diabetic eyes before any lesion is clinically visible in the fundus.
Abstract: A review of the pathologic picture of diabetic retinopathy shows that available clinical methods of examination demonstrate the alteration of the blood-retinal barrier (leakage), microaneurysms, capillary closure, preferential channels, preretinal neovascularization and gross extravascular lesions. All of these changes may be shown by fluorescein angiography. The value of this method, however, is fundamentally related to the morphologic demonstration of these lesions and not their quantification. Quantitative evaluation of retinal involvement in diabetes is needed in order to delineate more clearly its natural history, criteria for prognosis, and effect of treatment. Vitreous fluorophotometry, a quantitative and sensitive method of evaluating the permeability of the blood-retinal barrier, has opened new perspectives for the evaluation of retinal involvement in diabetes. Vitreous fluorophotometry has shown that a disturbance of the blood-retinal barrier, possibly functional, appears in diabetic eyes before any lesion is clinically visible in the fundus, and that there is a close correlation between the severity of the vascular lesions and higher vitreous fluorophotometry readings. Recent studies also indicate an interesting correlation with metabolic control, particularly, glycosylated hemoglobin levels and insulin treatment. Finally, on the basis of these findings a working hypothesis for the pathogenesis of diabetic retinopathy is presented.
51 citations
TL;DR: In this article, the simulation of a combined wind-solar- hydro system for electric power generation, with energy storage facilities, was described, and a simple multivariable weather model, including the wind speed, the solar radiation and the rainfall, was developed.
Abstract: This paper describes the simulation of a combined wind-solar- hydro system for electric power generation, with energy storage facilities. A simple multivariable weather model, including the wind speed, the solar radiation and the rainfall, was developed. This model is * used with the Monte Carlo simulation method to evaluate the reliability of the mixed generating system. Different percentages of wind and solar generation capacities were tried as well as the tilt of the solar arrays.
47 citations
TL;DR: The results suggest that synaptic membrane vesicles isolated from sheep brain cortex synaptosomes possess mechanisms for Na+/Ca2+ exchange and ATP‐dependent Ca2+ uptake, whose activity may be regulated by monovalent cations, specifically K+, at physiological concentrations.
Abstract: Two Ca2+ transport systems were investigated in plasma membrane vesicles isolated from sheep brain cortex synaptosomes by hypotonic lysis and partial purification. Synaptic plasma membrane vesicles loaded with Na+ (Na+i) accumulate Ca2+ in exchange for Na+, provided that a Na+ gradient (in leads to out) is present. Agents that dissipate the Na+ gradient (monensin) prevent the Na+/Ca2+ exchange completely. Ca2+ accumulated by Na+/Ca2+ exchange can be released by A 23187, indicating that Ca2+ is accumulated intravesicularly. In the absence of any Na+ gradient (K+i-loaded vesicles), the membrane vesicles also accumulate Ca2+ owing to ATP hydrolysis. Monovalent cations stimulate Na+/Ca2+ exchange as well as the ATP-dependent Ca2+ uptake activity. Taking the value for Na+/Ca2+ exchange in the presence of choline chloride (external cation) as reference, other monovalent cations in the external media have the following effects: K+ or NH4+ stimulates Na+/Ca2+ exchange; Li+ or Cs+ inhibits Na+/Ca2+ exchange. The ATP-dependent Ca2+ transport system is stimulated by increasing K+ concentrations in the external medium (Km for K+ is 15 mM). Replacing K+ by Na+ in the external medium inhibits the ATP-dependent Ca2+ uptake, and this effect is due more to the reduction of K+ than to the elevation of Na+. The results suggest that synaptic membrane vesicles isolated from sheep brain cortex synaptosomes possess mechanisms for Na+/Ca2+ exchange and ATP-dependent Ca2+ uptake, whose activity may be regulated by monovalent cations, specifically K+, at physiological concentrations.
46 citations
TL;DR: In this article, the ion=interaction equation is used to calculate the mean activity coefficients for the saturated aqueous mixtures, NaCl+Na2SO4 and NaCl +MgCl2.
Abstract: The ion=interaction equation is used to calculate the mean activity coefficients for the saturated aqueous mixtures, NaCl+Na2SO4 and NaCl+MgCl2. A comparison between these values with those obtained from solubility shows a good agreement over a wide temperature range as well as at high ionic strengths for both mixed systems.
45 citations
TL;DR: The results indicate that diffusion alone does not account for the outward flow of fluorescein in the vitreous, and the possible underlying factors and significance of these findings are discussed.
Abstract: • The permeability of the blood-vitreous barrier to fluorescein passing out of the vitreous does not necessarily equal the permeability to fluorescein passing into it. We calculated the ratio between the outward and inward permeability coefficients of the blood-vitreous barrier in eight normal men who ingested 3-g of sodium fluorescein. The calculation was based on the ratio between the serum free fluorescein and the vitreous fluorescein concentrations (as determined by fluorophotometry) when the net transport across the barrier was zero. The outward permeability to fluorescein was 31 ± 18 times (mean ± SD) the inward permeability. To our knowledge, this article provides the first direct evidence for a specialized transport mechanism in humans whereby fluorescein is removed from the vitreous into the blood. The malfunction of this process may be important in human disease. Pharmacologic manipulation of this process may be possible.
44 citations
TL;DR: In this article, the activity coefficients for saturated aqueous KCl, CsCl and mixtures of NaCl with each of these electrolytes are calculated from solution properties using the ion interaction model as well as from the solubility.
Abstract: The activity coefficients for saturated aqueous KCl, CsCl and mixtures of NaCl with each of these electrolytes are calculated from solution properties using the ion interaction model as well as from the solubility. The agreement between the two sets of results for both single and mixed electrolytes is, in general, good when it is considered that the saturated solution molatities are often much higher than those whose properties were used in the evaluation of the ion interaction parameters. Also, for pure KCl (aq) the agreement is good up to 300°C, an extrapolation 50°C above the range of data on which the equations were based.
28 citations
TL;DR: In this article, measurements of the Fano factor and the mean energy to make an ion pair were made for several mixtures of krypton and xenon using the proportional scintillation method.
14 citations
TL;DR: In this article, the basic properties of self-quenching streamers in a proportional counter with a thick anode wire are investigated and the influence of mixing benzene and triethylamine to argon-isobutane mixtures is studied regarding thresholds for streamer production, pulse shapes and dead time.
Abstract: The basic properties of self-quenching streamers in a proportional counter with a thick anode wire are investigated In particular, the influence of mixing benzene and triethylamine to argon-isobutane mixtures is studied regarding thresholds for streamer production, pulse shapes and dead time There is a lowering of the high voltage threshold for streamer production associated with low concentrations of triethylamine and benzene Higher concentrations of benzene increase that thre? shold Triethylamine leads to narrower pulses Stable operation is observed for a much broader range of high voltages than in the absence of photoionization vapours
TL;DR: In this paper, a PAC experiment was performed on a181HfTa sample which contained ∼ 0.1 at. 1 at. 2 at. 3 at. 4 at. 5 at. 6 at.
Abstract: A PAC experiment was performed on a181HfTa sample which contained ∼ 0. 1 at.
oxygen and ∼1 at.
hydrogen. At low temperature a new quadrupole interaction withν
Q=470 MHz, η=0.95 was found. This interaction is attributed to an O-H complex. At 55 K this interaction disappears and the well known oxygen frequency shows up, indicating a breakup of the O-H pair at 55 K. With deuterium instead of hydrogen the same frequency but a different (105 K) breakup temperature was found.
TL;DR: In this paper, an unidimensional Monte Carlo method was used to calculate secondary scintillation (electroluminescence) intensity in xenon gas proportional SCintillation counters, and other transport parameters like electron drift time, average number of collisions, efficiency for light production and induced charge pulse amplitude were calculated.
Abstract: An unidimensional Monte Carlo method is used to calculate the secondary scintillation (electroluminescence) intensity in xenon gas proportional scintillation counters. Other transport parameters like electron drift time, average number of collisions, efficiency for light production and induced charge pulse amplitude are also calculated. The values obtained agree well with the experimental data available.
TL;DR: The most sensitive part of the Ramaman spectra in this respect is formed by the frequency changes occurring in the 1400-1700 cm−1 region and the changes in the relative intensity of some bands associated either with C-F or C-C stretching vibrations as mentioned in this paper.
Abstract: Raman spectroscopy is shown to be a useful method for structure and conformation analysis in fluorinated surfactants (perfluoro decanoic acid and its lithium, sodium and ammonium salts). The most sensitive part of the spectra in this respect is formed by the frequency changes occurring in the 1400–1700 cm−1 region and the changes in the relative intensity of some bands associated either with C-F or C-C stretching vibrations. The successive increase in the degree of disorder at transitions into liquid crystalline and micellar phases can be seen from a decrease in the 1370/1300 cm−1 intensity ratio.
TL;DR: In this article, the perturbation felt by181Hf probes in a 181HfTa lattice loaded with 30 at% hydrogen was observed by PAC as a function of temperature.
Abstract: The perturbation felt by181Hf probes in a181HfTa lattice loaded with 30 at% hydrogen was observed by PAC as a function of temperature. Three different interactions were identified: 1) ΝQ1=433 (6) MHz, η=0.45 2) ΝQ2=142 (9) MHz, η=0.9, and 3) ΝQ≃0, σ=4–14 Μ−1 which are attributed to the Β−, e− and α-phase in TaH system, respectively.
TL;DR: Post-probenecid HVA levels suggest that there are distinct forms of parkinsonism and could predict the response to L-DOPA therapy.
Abstract: Determinations of CSF HVA before and after Probenecid administration were made in 41 patients with Parkinson's disease. The means of HVA concentration were lower than those of controls but no correlation with clinical data was found. A negative correlation was demonstrated between post-probenecid HVA levels and subsequent score improvement with L-DOPA at 3,6 and 12 months. Post-probenecid HVA levels suggest that there are distinct forms of parkinsonism and could predict the response to L-DOPA therapy.
TL;DR: In this paper, a characterization of the invariant factors of an integral matrix as approximation numbers is given, similar to the one known for the singular values of complex matrices, which is used to prove some recent results on invariant factorizations.
[...]
TL;DR: The Raman spectra of mixed cyrstals containing Mn(CO) 5 X (X = Cl, Br) and Re(CO 5 X′ (X′ = Br, Cl) show band broadening and both band weakening and enhancement in the ca. 1975 cm −1 region as discussed by the authors.
TL;DR: In this paper, an algorithm for ranking paths in acyclic networks is presented, initialized with the determination of the shortest tree, which is placed in a candidate list, at each step the tree for which is minimal the distance of the path between two specified nodes is removed from list.
Abstract: In this paper an algorithm for ranking paths in acyclic networks is presented. The algorithm is initialized with the determination of the shortest tree, which is placed in a candidateList. At each step the tree for which is minimal the distance of the path between two specified nodes is removed fromList. Some adjacent trees of the removed one are generated and placed inList in such a way that repetitions are avoided. This method is repeated until the desired paths have been determined.
The computational complexity of the algorithm is studied too.
In dieser Arbeit wird ein Algorithmus zur Ermittlung nachstbester Wege in zyklenfreien Netzen dargestellt. Das Verfahren beginnt mit der Bestimmung eines kurzesten Baumes, der auf eine Kandidatenliste gesetzt wird. Mit jedem Schritt wird ein Baum von der Kandidatenliste entfernt, dessen zugehoriger Weg zwischen Netzanfang und -ende minimal ist. Anschlieβend werden jeweils benachbarte Baume des soeben entfernten Baumes erzeugt und derart in die Liste aufgenommen, daβ Wiederholungen ausgeschlossen sind. Diese Vorgehensweise wiederholt sich, bis alle gewunschten Wege ermittelt sind. Auch die Komplexitat des Verfahrens wird untersucht.
TL;DR: It is suggested that the cations increase the [3H]spiperone binding by either exposing more binding sites, by preventing denaturation or by increasing the solubility of [ 3H]Spiperone in the membrane phase, or by a combination of these processes.
TL;DR: In this paper, a compilation of the previous experimental data arising mainly from work related with the gas proportional scintillation counter is made, and these data are compared with the calculated results.
01 Jan 1983
TL;DR: The results of fatigue crack propagation tests carried out on steel rectangular hollow sections with fillet welded gusset plates are reported in this article, where the crack propagation data was obtained on the lateral sides of the tubes subjected to plane bending.
Abstract: The results of fatigue crack propagation tests carried out on steel rectangular hollow sections with fillet welded gusset plates are reported. The crack propagation data was obtained on the lateral sides of the tubes subjected to plane bending. Crack initiation was studied with the scanning electron microscope and a fracture surface analysis was made using the same technique. It was found that crack initiation in thin walled tubes depends basically on three factors: (i) The stress concentration in the tube corners, (ii) The surface ripple in the weldment and (iii) The level of porosity in the weld. Further work is necessary to draw more definitive conclusions on the influence of the factors.
TL;DR: In this article, daily measurements of pH and conductivity of rainwater at Coimbra, Portugal in the period between autumn 1978 to autumn 1980 are reported, and a seasonal variation of 1.2 pH units was found for the acidity with the highest average pH in autumn and the lowest in summer.
Abstract: Daily measurements of pH and conductivity of rainwater at Coimbra, Portugal in the period between autumn 1978 to autumn 1980 are reported. The average conductivity is 26 μΩ- -1 cm -1 and the average pH is 4.75. Neutral salt contribution to conductivity is significant and is highest in autumdwinter. Correlations between neutral salt conductivity and wind direction were found. pH values have a large dispersion and more than 30% of the samples had a pH (5.0. A seasonal variation of 1.2 pH units was found for the acidity with the highest average pH in autumn and the lowest in summer. A bimodal pH frequency distribution was found for the winter and spring seasons with a minimum frequency ranging from 5.7 to 5.3 pH units. DOI: 10.1111/j.1600-0889.1983.tb00026.x
01 Jan 1983
TL;DR: A quick method for making multistate characters out of continuous measurements is described, following the intuitive method used by taxonomists, which is a kind of discriminant function analysis.
Abstract: A quick method for making multistate characters out of continuous measurements is described. Following the intuitive method used by taxonomists, which is a kind of discriminant function analysis, we looked for gaps and dips in the frequency curve.
TL;DR: In this article, the excess Gibbs energy of a mixture of two molecularly simple components which are completely miscible in the solid state was estimated for a particular case of argon-methane.
TL;DR: In this paper, a class of hybrid formulae suitable for the numerical integration of stiff systems of first order ordinary differential equations is presented, which are defined in a predictor-corrector mode and contain an off-step pointxn+v, which is distinct from the points defined by the step used.
Abstract: A class of hybrid formulae suitable for the numerical integration of stiff systems of first order ordinary differential equations is presented. These formulae are defined in a predictor-corrector mode and contain an off-step pointxn+v, which is distinct from the points defined by the step used. The parameterv is examined in an attempt to obtain better stability properties and higher order formulae of one step only. We obtain order five and eitherA-stability or stiff-stability according to the values ofv used. Some numerical results are presented.