Showing papers by "State University of Campinas published in 1992"

Positive Solutions of Semilinear Elliptic Systems

Abstract: We investigate the existence of positive solutions of a Dirich let problem for the system \( - \Updelta u = f(v),\,\Updelta v = g(u) \) in a bounded convex domain Ω of \( {\mathbb{R}}^{N} \) with smooth boundary. In particular L ∞ a priori bounds are obtained in the same spirit as in De Figueiredo—Lions—Nussbaum [7].

The in vitro effect of glass-ionomer cement restoration on enamel subjected to a demineralization and remineralization model.

Abstract: The purpose of this in vitro study was to evaluate differences in initiation and progression of carieslike lesions around restorations in enamel. A demineralization/remineralization cycling model was used to induce experimental secondary caries around cavities restored with glass-ionomer cement or composite resin. The effects of these materials were compared by microhardness profiles. The results indicated that glass-ionomer cement showed potential value as a restorative material for the prevention or reversal of caries in enamel adjacent to restorations, even in situations of high cariogenic challenge.

Strict Monotonicity of Eigenvalues and Unique Continuation

Abstract: In this paper, we show that the strict mononicity of the eigen-values of an uniformly elliptic operator of second order is equivalent to a unique continuation property.

The most powerful scintillator supernovae detector: LVD

Abstract: The Large Volume Detector (LVD) in the Gran Sasso underground Laboratory is a multipurpose detector consisting of a large volume of liquid scintillator interleaved with limited streamer tubes. In this paper we discuss its power to study low-energy cosmic neutrinos. The results show that the first LVD tower (368 tons of liquid scintillator) is well suited to detect neutrinos from gravitational stellar collapses within all of our Galaxy over a wide range of burst duration (up to a few hundred seconds). No burst candidates have been observed in the first two months of data taking.

Ca2+ transport by digitonin-permeabilized Leishmania donovani. Effects of Ca2+, pentamidine and WR-6026 on mitochondrial membrane potential in situ

Abstract: The use of low concentrations of digitonin allowed the quantitative determination of the mitochondrial membrane potential of Leishmania donovani promastigotes in situ using safranine O. L. donovani mitochondria were able to build up and retain a membrane potential of a value comparable with that of mammalian mitochondria. The response of promastigotes mitochondrial membrane potential to phosphate, carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone (FCCP), valinomycin and Ca2+ indicates that these mitochondria behave similarly to vertebrate mitochondria with regard to the properties of their electrochemical proton gradient. When L. donovani promastigotes were permeabilized with digitonin in a reaction medium containing MgATP, succinate and 3.5 microM free Ca2+, they lowered the medium Ca2+ concentration to the submicromolar level (0.05-0.1 microM). The presence of 1 microM-FCCP decreased by about 75% the initial rate of Ca2+ sequestration by these permeabilized cells. This FCCP-insensitive Ca2+ uptake, probably by the endoplasmic reticulum, was completely inhibited by 500 microM-vanadate. On the other hand, when vanadate instead of FCCP was present, the initial rate of Ca2+ accumulation was decreased by about 25% and the Ca2+ set point was increased to 0.7 microM. The succinate-dependence and FCCP-and Ruthenium Red-sensitivity of the Ca2+ uptake detected in the presence of vanadate indicate that this uptake is probably by the mitochondria. This interpretation was further supported by the Ruthenium Red-sensitive decrease in the mitochondrial membrane potential caused by Ca2+ addition. The anti-leishmanial cationic drugs pentamidine and WR-6026 also induced a rapid collapse of the mitochondrial inner membrane potential of L. donovani promastigotes.

Partial Purification and Characterization of Lysine-Ketoglutarate Reductase in Normal and Opaque-2 Maize Endosperms

Abstract: Lysine-ketoglutarate reductase catalyzes the first step of lysine catabolism in maize (Zea mays L.) endosperm. The enzyme condenses l-lysine and α-ketoglutarate into saccharopine using NADPH as cofactor. It is endosperm-specific and has a temporal pattern of activity, increasing with the onset of kernel development, reaching a peak 20 to 25 days after pollination, and there-after decreasing as the kernel approaches maturity. The enzyme was extracted from the developing maize endosperm and partially purified by ammonium-sulfate precipitation, anion-exchange chromatography on DEAE-cellulose, and affinity chromatography on Blue-Sepharose CL-6B. The preparation obtained from affinity chromatography was enriched 275-fold and had a specific activity of 411 nanomoles per minute per milligram protein. The native and denaturated enzyme is a 140 kilodalton protein as determined by polyacrylamide gel electrophoresis. The enzyme showed specificity for its substrates and was not inhibited by either aminoethyl-cysteine or glutamate. Steady-state product-inhibition studies revealed that saccharopine was a noncompetitive inhibitor with respect to α-ketoglutarate and a competitive inhibitor with respect to lysine. This is suggestive of a rapid equilibrium-ordered binding mechanism with a binding order of lysine, α-ketoglutarate, NADPH. The enzyme activity was investigated in two maize inbred lines with homozygous normal and opaque-2 endosperms. The pattern of lysine-ketoglutarate reductase activity is coordinated with the rate of zein accumulation during endosperm development. A coordinated regulation of enzyme activity and zein accumulation was observed in the opaque-2 endosperm as the activity and zein levels were two to three times lower than in the normal endosperm. Enzyme extracted from L1038 normal and opaque-2 20 days after pollination was partially purified by DEAE-cellulose chromatography. Both genotypes showed a similar elution pattern with a single activity peak eluted at approximately 0.2 molar KCL. The molecular weight and physical properties of the normal and opaque-2 enzymes were essentially the same. We suggest that the Opaque-2 gene, which is a transactivator of the 22 kilodalton zein genes, may be involved in the regulation of the lysine-ketoglutarate reductase gene in maize endosperm. In addition, the decreased reductase activity caused by the opaque-2 mutation may explain, at least in part, the elevated concentration of lysine found in the opaque-2 endosperm.

Chevron osteotomy for hallux valgus.

Abstract: A retrospective study of the Chevron osteotomy procedure for hallux valgus was carried out on 112 patients (168 feet) with an average age of 39.7 years (range 19 to 61 years). The average follow-up was 4.4 years (range 13 months to 7.5 years). The preoperative diagnosis was symptomatic hallux valgus. The average preoperative intermetatarsal 1-2 angle was 15.5 degrees (range 11 degrees to 18 degrees) and the hallux valgus angle was 28.1 degrees (range 21 degrees to 42 degrees). The operation was effective in improving symptoms, cosmesis, and function and in decreasing the deformity.

Orofacial manifestations of the systemic mycoses

Abstract: Aspergillosis, cryptococcosis and zygomycosis (mucormycosis) are overall the most common systemic mycoses but histoplasmosis is particularly endemic in parts of central USA and other areas worldwide. Orofacial lesions caused by systemic mycoses have rarely been reported in the past though they have been recorded particularly in outdoor workers from geographic areas with a high prevalence of infection and occasionally in immunocompromised individuals. Increasing world-wide travel, and the dramatic increase in numbers of immunocompromised persons, especially those with human immunodeficiency virus (HIV) disease, have been responsible for an increase in reports and other studies of orofacial disease in systemic mycoses and new opportunists are now being recognized. Those in Oral Medicine and Pathology must now be aware of the possibility of a systemic mycosis as the cause of chronic oral ulceration, chronic maxillary sinus infection, or bizarre mouth lesions, especially in patients with HIV disease, lymphoproliferative disorders, or diabetes mellitus, or in those who have been in endemic areas. Diagnosis and management should be undertaken in consultation with a physician with appropriate expertise, as pulmonary and other systemic infection may well be present. This paper reviews the eight main systemic mycoses.

Linguagem - atividade constitutiva

Abstract: This paper was written in memory of Professor Carlos Franchi, whose linguistic thought has influenced resesearchers in this country for almost two generations. It deals with one of Franchi’s seminal ideas, namely that the main role of language is a constitutive rather than a representative one. The paper elaborates on it in semantic terms, assuming that this constitutive role has to do with knowledge. The first part of the paper describes several accounts of the relation between language and knowledge that, to my opinion, misrepresent Franchi’s views. Among these are not only the structuralist idea that “we are spoken by the code”, but also the belief that language determines perception and thinking (Whorf) and the idea that language is crucially involved in abstraction (Schaff). In the second part of the paper, I point to some semantic processes (which I have called monitoring, creation of non-conventional objects and heuristics and subvertion) where language has an active role in changing our received conception of the world. Key-words: Carlos Franchi, language as a constitutive activity, whorf, language and thought.

Studies of surface and interface segregation in polymer blends by secondary ion mass spectrometry

Abstract: Dynamic secondary ion mass spectrometry (SIMS) has recently been employed to obtain high resolution depth profiles in polymer blend thin films and is now regarded as a key probe of surface and interfacial segregation in these systems. Segregation phenomena strongly impact blend properties such as adhesion, friction and weatherability. The strengths and limitations of the SIMS polymer profiling technique are described and contrasted with the complementary techniques of forward recoil elastic scattering (FRES) and neutron reflectivity (NR). The procedures developed for sample preparation and data acquisition are discussed. Experimental results for the effect of incident O2 + energy and angle on depth resolution and sputtering rate in polystyrene (PS) are presented. Ongoing SIMS studies of model blend systems are described: Segregation from dPS (deuterated)/PS blends to vacuum and Si interfaces is examined as a function of the molecular weight of the blend components and preparation of the Si substrate, reve...

Bigger ant colonies reduce herbivory and herbivore residence time on leaves of an ant-plant: Azteca muelleri vs. Coelomera ruficornis on Cecropia pachystachya.

Abstract: The effect of defence force size in colonies of the ant Azteca muelleri on the time spent to localize, attack and expel the specialized herbivorous beetle Coelomera ruficornis from Cecropia pachystachya bushes was studied in an area of Atlantic forest in northeastern Brazil. Our results show that Azteca muelleri expel Coelomera ruficornis from Cecropia pachystachya and that the number of ants leaving a colony (defence force size) is negatively correlated with the residence time of an adult beetle on the plant. Colonies with larger defence forces recruited larger numbers of ants, resulting in faster herbivore discovery (r 2=0.80; n=17; P<0.001) and reduced herbivore residence time on a leaf (r 2=0.79 n=23; P<0.001) before being driven off by the ants. We also found a negative and significant relationship between herbivore damage on leaves and ant colony size (r 2=0.28; n=17; P<0.05). We conclude that larger colonies have more individuals available to patrol a plant and recruit defenders toward herbivores. This reduces the time spent to locate and expel susceptible herbivores from the plant. Since the plant probably benefits from reduced herbivory and the plant provides food for the ants, the association between Azteca muelleri and Cecropia pachystachya appears mutualistic.

Predation on palm nuts (Syagrus romanzoffiana) by squirrels (Sciurus ingrami) in south-east Brazil

Abstract: Although Terborgh (1986) suggested that palm nuts are a 'keystone plant resource' for frugivore communities in tropical forests, few studies exist on seed ecology of palm fruit crop (Bradford & Smith 1977, Pifiero etal. 1984, Vandermeer et ali. 1979). Janzen (1983) suggested that seed predators have a major impact on the structure of plant communities in tropical forests. Squirrels are regarded as important seed dispersers and seed predators (Glanz et ail. 1982, Janzen 1972) depending on the habitat and the fruit availability. These rodents frequently consume hard nuts and their distribution may be related to the distribution of food sources such as palms (Glanz 1982). This paper investigates the utilization of the fruits of the 'geriva', ySyagrus romnanZoffiana (Cham.) Glassmnan by squirrels in a tropical upland semideciduous forest in south-east Brazil. Field observations were made from August 1988 to May 1990 in the 250 ha Santa Genebra Reserve in Campinas (22? 49' S, 470 07' W), Sao Paulo State, Brazil. The climate of the region is characterized by one dry (April to September) and one rainy (October to March) season; annual rainfall during the study period was 1366 mm. The feeding assemblage that utilizes Sjyagruis fruits in Santa Genebra is composed of squirrels Seiinrus ingrami Thomas, a small species about 34 cm in length (H. Bergallo, unpub.), capuchin monkeys Cebus apella Linne and brown howler monkeys Aloucattafiusca Ihering. &yagrus rotinanzofJiana is a common palmi in semideciduous forests in south-east Brazil (H. F. Leitao-Filho, pers. comm.). The fruit is an ovoid drupe 2.5 cm in diameter, with a soft exocarp and woody endocarp. Individuals of this species produce fruit all the year round, each plant producing two bunches at a timie.

Host specificity and seed dispersal of Psittacanthus robustus (Loranthaceae) in south-east Brazil

Abstract: Psittacanthus robustus (Loranthaceae) is a Neotropical mistletoe which grows mainly on species of Vochysiaceae in Brazilian ‘cerrado’ regions. Its parasitizing pattern involves: (a) the height and the aspect of the crown of the host-plants; (b) the presence of sticky substance in the fruits of the parasite; and (c) the feeding behaviour and habitat selection of the dispersal agent, the swallowtanager Tersina viridis viridis. The feeding behaviour of this bird on fruits of P. robustus facilitates seed release and seedling establishment; its foraging habit and habitat selection account for high concentrations of the parasites on their preferred host-plants.

The use of optimal foraging theory in the understanding of fishing strategies: A case from Sepetiba Bay (Rio de Janeiro State, Brazil)

Abstract: The community of Gamboa is located on Itacuruca Island, Sepetiba Bay (State of Rio de Janeiro, Brazil) and includes 26 families, mostly of artisanal fishermen who use paddled or motor canoes, and encircling nets for fishing. In this study, predictions from optimal foraging theory (patch model), in particular of patch residence time, are compared to the observed behavior of fishermen on fishing trips. Fishermen's strategies differ depending on their intended prey. They spend more time in patches and use fewer patches for shrimp than for fish. Gamboa's fishermen tend to leave a patch later than predicted by the model. The difficulty in evaluating stock availability, the comparatively few patches available for shrimp, and the competitive aspects of fishing contribute to the explanation of this behavior.