Showing papers by "Federal University of Rio de Janeiro published in 1996"

Attitude control without angular velocity measurement: a passivity approach

Abstract: It is well known that the linear feedback of the quaternion of the attitude error and the angular velocity globally stabilizes the attitude of a rigid body. In this note, we show that the angular velocity feedback can be replaced by a nonlinear filter of the quaternion, thus removing the need for direct angular velocity measurement. In contrast to other approaches, this design exploits the inherent passivity of the system; a model-based observer reconstructing the velocity is not needed. An application of the proposed scheme is illustrated for the robot control problem. Simulation results are included to illustrate the theoretical results.

Os pronomes cosmológicos e o perspectivismo ameríndio

Abstract: This study discusses the meaning of Amerindian "perspectivism": the ideas in Amazonian cosmologies concerning the way in which humans, animals, and spirits see both themselves and other world beings. Such ideas suggest the possibility of a redefinition of the classical categories of "nature", "culture", and "supernature" based on the concept of perspective or point of view. The study argues in particular that the antinomy between two characterizations of indigenous thought - on the one hand "ethnocentrism", which would deny the attributes of humanity to humans from other groups, and on the other hand "animism", which would extend such qualities to beings from other species - can be resolved if one considers the difference between the spiritual and corporal aspects of beings.

Sub-Poissonian processes in quantum optics

Abstract: The author reviews methods for generating sub-Poissonian light and related concepts. This light has energy fluctuations reduced below the level which corresponds to a classical Poissonian process (shot-noise level). After an introduction to the concept of nonclassical light, an overview is given of the main methods of quantum-noise reduction. Sub-Poissonian processes are exemplified in different areas of optics, ranging from single-atom resonance fluorescence to nonlinear optics, laser physics, and cavity quantum electrodynamics. Emphasis is placed on the conceptual foundations, and on developments in laser theory that lead to the possibility, already demonstrated experimentally, of linewidth narrowing and sub-Poissonian light generation in lasers and masers. The sources of quantum noise in these devices are analyzed, and four noise-suppression methods are discussed in detail: regularization of the pumping, suppression of spontaneous-emission noise, nonadiabatic evolution of the atomic variables, and twin-beam generation.

Calculation of area of stabilometric signals using principal component analysis

Abstract: In stabilometry, the sway of the human body in an upright posture is studied by monitoring the displacement of its centre of pressure in the lateral (x) and anterio-posterior (y) directions. The area covered by this trace has been defined as that of an ellipse fitted to the data. Conventionally, its angle of inclination is found through linear regression (LR) on the data in the x - y plane. In the present paper, principal component analysis (PCA) is proposed as providing a more suitable basis for the estimation of angle and area. Results of simulations and stabilometric tests confirm large differences between area and angle estimates obtained by regression of x over y, and y over x, with PCA generally agreeing with either one or the other of the LRs. The PCA technique is therefore recommended as an improved basis for measuring area and inclination of stabilograms, or similar data sets. Keywords: body balance, stabilometry, signal processing, principal component analysis

Tuning and test of fragmentation models based on identified particles and precision event shape data

Abstract: Event shape and charged particle inclusive distributions are measured using 750000 decays of the Z to hadrons from the DELPHI detector at LEP. These precise data allow a decisive confrontation with models of the hadronization process. Improved tunings of the JETSET, ARIADNE and HERWIG parton shower models and the JETSET matrix element model are obtained by fitting the models to these DELPHI data as well as to identified particle distributions from all LEP experiments. The description of the data distributions by the models is critically reviewed with special importance attributed to identified particles.

Phenotypic and Genotypic Characterization of Atypical Lactococcus garvieae Strains Isolated from Water Buffalos with Subclinical Mastitis and Confirmation of L. garvieae as a Senior Subjective Synonym of Enterococcus seriolicida

Abstract: During a survey of bacterial agents that cause subclinical mastitis in water buffalos, we isolated several strains of gram-positive cocci that appeared to be enterococci except that they grew very slowly at 45°C and grew slowly in broth containing 6.5% NaCl. On the basis of the results of conventional physiologic tests, these strains were identified as Enterococcus durans. However, none of the strains reacted with the AccuProbe Enterococcus genetic probe. The whole-cell protein profiles of these organisms were compared with the profiles of Enterococcus and Lactococcus reference strains. Apart from minor quantitative differences, the mastitis isolates had indistinguishable protein profiles that were similar to the profiles of the Lactococcus garvieae and Enterococcus seriolicida type strains. The results of DNA relatedness studies performed by using the hydroxy-apatite method at 55 and 70°C indicated that all of the mastitis isolates were related to the type strain of L. garvieae at the species level, despite the fact that they exhibited several uncommon phenotypic characteristics (growth at 45°C, growth in broth containing 6.5% NaCl, and failure to produce acid from mannitol and sucrose). The high levels of DNA relatedness between strains of L. garvieae and E. seriolicida demonstrated that these taxa are members of a single species. Since L. garvieae is a senior synonym of E. seriolicida, L. garvieae should be retained as the species name and strain ATCC 43921 should remain the type strain of this species.

O dois e seu múltiplo: reflexões sobre o perspectivismo em uma cosmologia tupi

Abstract: A partir da caca de porco do mato, este artigo e um ensaio etnografico sobre uma nocao indigena de ponto de vista, aplicada ao campo das relacoes entre o humano e o animal, na cosmologia de um povo Tupi, os Juruna. Alem de revelar a complexidade particular dessas relacoes, a nocao de ponto de vista permite mostrar como a nocao de duplo e irredutivel a nocao de alma, como "natureza" e "sobrenatureza" sao efeitos de perspectivas, e como, finalmente, a caca se insere em uma estrutura espaco-temporal bilinear multipla, evocadora dos "labirintos" que os Juruna desenham na pele.

Activation of C-H and C-C Bonds by an Acidic Zeolite: A Density Functional Study

Abstract: Density functional theory is used to determine transition states and the corresponding energy barriers of the reactions related to C−H bond activation of hydrogen exchange and dehydrogenation of ethane catalyzed by a protonated zeolite as well as hydride transfer between methanol and a methoxide (CH3-zeolite) species. Additionally the C−C bond activation involved in the acid catalyzed cracking reaction of ethane was investigated. The computed activation barriers are 118 for hydrogen exchange, 202 for hydride transfer, 292 for cracking and finally 297 for dehydrogenation, all in kilojoules per mole. For the cracking reaction, two different transition states with the same activation barrier have been obtained, dependent on the approach of the ethane molecule to the zeolite cluster. A study of the relation between acidity and the structure of the zeolite shows that the transition state for the hydrogen exchange reaction is rather covalent and its geometry resembles the well-known carbonium ion, while the oth...

Detection of extracellular proteases from microorganisms on agar plates

Abstract: We present herein an improved assay for detecting the presence of extracellular proteases from microorganisms on agar plates Using different substrates (gelatin, BSA, hemoglobin) incorporated into the agar and varying the culture medium composition, we were able to detect proteolytic activities from Pseudomonas aeruginosa, Micrococcus luteus and Serratia marcescens as well as the influence that these components displayed in the expression of these enzymes For all microorganisms tested we found that in agar-BHI or yeast extract medium containing gelatin the sensitivity of proteinase detection was considerably greater than in BSA-agar or hemoglobin-agar However, when BSA or hemoglobin were added to the culture medium, there was an increase in growth along with a marked reduction in the amount of proteinase production In the case of M luteus the incorporation of glycerol in BHI or yeast extract gelatin-agar induced protease liberation Our results indicate that the technique described here is of value for detecting extracellular proteases directly in the culture medium, by means of a qualitative assay, simple, inexpensive, straight forward method to assess the presence of the proteolytic activity of a given microorganism colony with great freedom in substrate selection

Neurofilament protein is differentially distributed in subpopulations of corticocortical projection neurons in the macaque monkey visual pathways

Abstract: Previous studies of the primate cerebral cortex have shown that neurofilament protein is present in pyramidal neuron subpopulations displaying specific regional and laminar distribution patterns. In order to characterize further the neurochemical phenotype of the neurons furnishing feedforward and feedback pathways in the visual cortex of the macaque monkey, we performed an analysis of the distribution of neurofilament protein in corticocortical projection neurons in areas V1, V2, V3, V3A, V4, and MT. Injections of the retrogradely transported dyes Fast Blue and Diamidino Yellow were placed within areas V4 and MT, or in areas V1 and V2, in 14 adult rhesus monkeys, and the brains of these animals were processed for immunohistochemistry with an antibody to nonphosphorylated epitopes of the medium and heavy molecular weight subunits of the neurofilament protein. Overall, there was a higher proportion of neurons projecting from areas V1, V2, V3, and V3A to area MT that were neurofilament protein-immunoreactive (57-100%), than to area V4 (25-36%). In contrast, feedback projections from areas MT, V4, and V3 exhibited a more consistent proportion of neurofilament protein-containing neurons (70-80%), regardless of their target areas (V1 or V2). In addition, the vast majority of feedback neurons projecting to areas V1 and V2 were located in layers V and VI in areas V4 and MT, while they were observed in both supragranular and infragranular layers in area V3. The laminar distribution of feedforward projecting neurons was heterogeneous. In area V1, Meynert and layer IVB cells were found to project to area MT, while neurons projecting to area V4 were particularly dense in layer III within the foveal representation. In area V2, almost all neurons projecting to areas MT or V4 were located in layer III, whereas they were found in both layers II-III and V-VI in areas V3 and V3A. These results suggest that neurofilament protein identifies particular subpopulations of corticocortically projecting neurons with distinct regional and laminar distribution in the monkey visual system. It is possible that the preferential distribution of neurofilament protein within feedforward connections to area MT and all feedback projections is related to other distinctive properties of these corticocortical projection neurons.

About the house: Lévi-Strauss and Beyond

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Biotechnological Applications of the Disaccharide Trehalose

Abstract: Trehalose is a disaccharide present in a variety of anhydrobiotic organisms which have the ability to promptly resume their metabolism after addition of water. It has been successfully used as a nontoxic cryoprotectant of enzymes, membranes, vaccines, animal and plant cells and organs for surgical transplants. It has been predicted that trehalose can also be used as an ingredient for dried and processed food. Therefore, the recent biotechnological applications of trehalose have imposed the standardization of methods for its production, as well as for its specific quantification.

Identification of Single and Dual Infections with Distinct Subtypes of Human Immunodeficiency Virus Type 1 by Using Restriction Fragment Length Polymorphism Analysis

Abstract: The simultaneous presence of multiple HIV-1 subtypes has become common in communities with the growth of the pandemic. As a consequence, the potentiality for an increased frequency of HIV-1 mixed infections caused by viruses of distinct subtypes could be expected. Thus, there is a need to estimate the prevalence and geographic distribution of infections caused by viruses of a singular subtype as well as coinfections caused by two or more HIV-1 strains of distinct subtypes. To address this need, we have developed a genetic method based on restriction fragment length polymorphism (RFLP) to screen for these two types of infections within infected populations. In this assay, restriction enzymes may be used to predict the phylogroup of HIV-1 infected samples. A 297 bp pol fragment spanning the entire viral protease gene and a 311 bp fragment of the p24 gag region are used for this analysis. The viral regions are amplified by nested PCR using DNA templates from uncultured peripheral blood mononuclear cells (PBMC) or virus culture. Classification of HIV-1 strains to well defined subtypes B, D, F, and A/C is done by sequential endonuclease restriction analysis of a PCR amplified-protease gene followed by analysis of the p24 gag region. The electrophoretic migration patterns visualized by ethidium bromide staining or by radiolabeled probes are then determined on a 10% polyacrylamide gel. In infections caused by viruses of a singular subtype, a single restriction pattern is detected, whereas in multiple infections caused by two or more viral strains of different subtypes, the combination of different digestion patterns are observed in infected individuals. Using this methodology we have screened for genetic variations in HIV-1 proviral DNA from thirty-three Brazilian samples. Our RFLP procedure classified thirty-two samples as single infections caused by viruses of subtypes B (31) and F (1), and one sample as dual infection caused by distinct viral strains. Subsequent sequence and phylogenetic analysis of the viral protease gene in lymphocytes of all these patients confirmed our RFLP findings in single infections, and demonstrated the existence of two distinct HIV-1 strains of subtypes F and D in a patient which lymphocytes showed the simultaneous presence of two different digestion patterns. As up to now, single infections caused by subtype D variants were not identified in Brazil, our data provide the first evidence of subtype D HIV-1 in this country. Because sequencing of HIV proviral DNA is not particularly practical for large-scale molecular epidemiological studies, the protease/gag-based RFLP screening method will be useful to predict the phylogroup of HIV-1, and to identify multiple infections caused by HIV-1 strains of distinct subtypes. We believe that this information is crucial for both evaluation of the HIV-1/AIDS pandemic and intervention strategies.

Isobutane/2-butene alkylation on zeolite beta: Influence of post-synthesis treatments

Abstract: The influence of the framework and extraframework composition of zeolite beta on its activity, selectivity, and deactivation behavior during the alkylation of isobutane with 2-butene has been studied by submitting a H-beta sample to different post-synthesis treatments. The parent Hβ sample was prepared by calcination, conventional NH4+ exchange, and further calcination of a commercial TEA-beta. These treatments were seen to produce some framework dealumination with formation of dispersed cationic extraframework aluminum (EFAL) species. The Hβ was then dealuminated by two chemical treatments (hydrochloric acid and ammonium hexafluorosilicate) and by steam calcination, the former procedures leading to almost EFAL-free catalysts. Furthermore, Hβ was also treated with the required amount of ammonium hexafluorosilicate (HFS) in order to remove EFAL species generated during the activation of the parent TEA-beta sample. The catalysts were characterized by XRD, N2 adsorption-desorption isotherms,27Al and29Si MAS-NMR, XPS, and IR spectroscopy with adsorption-desorption of pyridine. In general, dealumination of Hβ leads to less active, selective, and stable catalysts for isobutane/butene alkylation. The chemically dealuminated EFAL-free catalysts were much more active than the steamed sample, which was attributed to the presence of both cationic EFAL compensating framework charge and condensed type EFAL blocking acid sites in the latter catalyst. Furthermore, elimination of EFAL in Hβ by HFS treatment also decreased the alkylation activity of the zeolite, suggesting a synergistic effect of dispersed cationic EFAL species with framework hydroxyls of Hβ to form Bronsted acid sites of enhanced acid strength.

Thalidomide, a current teratogen in South America

Abstract: Thalidomide, mainly used for the treatment of leprosy, is a current teratogen in South America, and it is reasonable to assume that at present this situation is affecting many births in underdeveloped countries. Moreover, the potential re-marketing of thalidomide for the treatment of a large variety of diseases may extend the problem to the developed world. When the drug is available, the control of its intake during early pregnancy is very difficult since most pregnancies are unintended. The ongoing occurrence of thalidomide embryopathy cases went undetected by the ECLAMC, due to several factors: (1) low populational coverage through this monitoring system; (2) pre-existence of the teratogen with its effects present in both baseline (expected) and monitored (observed) materials; and (3) lack of a defined phenotype to be monitored. Thus, if thalidomide re-enters the market throughout the world, due to the wide range of new applications, occurrence of phocomelia alone might not be sufficient to detect its effects. By a case-reference approach, the ECLAMC registered 34 thalidomide embryopathy cases born in South America after 1965 whose birthplaces correspond to endemic areas for leprosy. Phocomelia was found in five of eleven fully described cases. Thus, phocomelia alone is neither specific nor sufficient to serve as a suitable phenotype to survey the teratogenic effects of thalidomide. Therefore, a thalidomide-like phenotype, defined as any bilateral upper and/or lower limb reduction defect of the preaxial and/or phocomelia types, should be included in the routine surveillance of birth defects in all programmes.

Emergence of high-level mupirocin resistance in methicillin-resistant Staphylococcus aureus isolated from Brazilian university hospitals.

Abstract: Surveillance for methicillin-resistant Staphylococcus aureus (MRSA) was implemented in Rio de Janeiro and Uberlândia University Hospitals, which had different policies on use of mupirocin. One hundred fourteen multiresistant MRSA strains were isolated from 62 patients. Mupirocin resistance was observed in 63% of strains in Rio de Janeiro, where there was extensive use of topical mupirocin, and 6.1% in Uberlândia, where its use was rare.

The long-term treatment of social phobia with moclobemide.

Abstract: Patients meeting the social phobia criteria of the revised third edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-III-R) on the DSM-III-R Structured Clinical Interview (n = 101) entered a long-term moclobemide treatment study. These patients were treated for 2 years with moclobemide (phase I) followed by drug withdrawal, in most cases abruptly (phase II). Those who relapsed entered phase III for a further period of 2 years of treatment. During phase I 40 patients (39.6%) withdrew due to inefficacy or relapse. Two patients were removed from the study because of other diagnoses (borderline or schizophreniform). At the end of phase I the remaining patients (58.4%) were rated as not ill (45.5%) or minimally ill (11.9%). Effort was taken to achieve the maximum dose of moclobemide (750 mg/day) and the mean (+/-SD) dose was 723.3 +/- 67.7 mg/day (month 21). A marked decrease in symptoms in the patients who responded was recorded on the Liebowitz Scale for Social Phobia, Clinical Global Impressions. Hamilton Anxiety Scale and Hamilton Depression Scale. Non-response was mainly associated with co-morbidity, especially alcohol abuse, axis II disorders, and a history of major depression or secondary dysthymia. The drug was well tolerated; the more frequent side effects were mild and occurred mainly in the first 2 months of phase I, including nausea, headaches or insomnia. In phase II there was a relapse rate of 88% and 51 patients entered phase III; these patients are still being treated.