Showing papers by "Universidade Federal de Minas Gerais published in 1999"

Cryptographic distinguishability measures for quantum-mechanical states

Abstract: This paper, mostly expository in nature, surveys four measures of distinguishability for quantum-mechanical states. This is done from the point of view of the cryptographer with a particular eye on applications in quantum cryptography. Each of the measures considered is rooted in an analogous classical measure of distinguishability for probability distributions: namely, the probability of an identification error, the Kolmogorov distance, the Bhattacharyya coefficient, and the Shannon (1948) distinguishability (as defined through mutual information). These measures have a long history of use in statistical pattern recognition and classical cryptography. We obtain several inequalities that relate the quantum distinguishability measures to each other, one of which may be crucial for proving the security of quantum cryptographic key distribution. In another vein, these measures and their connecting inequalities are used to define a single notion of cryptographic exponential indistinguishability for two families of quantum states. This is a tool that may prove useful in the analysis of various quantum-cryptographic protocols.

The zero-inflated Poisson model and the decayed, missing and filled teeth index in dental epidemiology

Abstract: For frequency counts, the situation of extra zeros often arises in biomedical applications. This is demonstrated with count data from a dental epidemiological study in Belo Horizonte (the Belo Horizonte caries prevention study) which evaluated various programmes for reducing caries. Extra zeros, however, violate the variance–mean relationship of the Poisson error structure. This extra-Poisson variation can easily be explained by a special mixture model, the zero-inflated Poisson (ZIP) model. On the basis of the ZIP model, a graphical device is presented which not only summarizes the mixing distribution but also provides visual information about the overall mean. This device can be exploited to evaluate and compare various groups. Ways are discussed to include covariates and to develop an extension of the conventional Poisson regression. Finally, a method to evaluate intervention effects on the basis of the ZIP regression model is described and applied to the data of the Belo Horizonte caries prevention study.

A new proposal to adjust Moran's I for population density

Abstract: We analyse the effect of using prevalence rates based on populations with different sizes in the power of spatial independence tests. We compare the well known spatial correlation Moran's index to three indexes obtained after adjusting for population density, one proposed by Oden, another proposed by Waldhor, and a third proposed by us in this paper. We find an effect of spatially correlated populations in the type I error probability on the test based on Moran's and Waldhor's indexes. We conclude also that the test proposed by Oden is powerful to test risk heterogeneity, but it has disadvantages when the interest is solely on the spatial correlation of morbidity risks. In this latter case, we recommend using our proposed test which is more powerful than the usual Moran's index applied directly to the rates.

GR3J: a daily watershed model with three free parameters

Abstract: This paper describes a new empirical watershed model, the prime feature of which is its parsimony. It involves only three free parameters, a characteristic unparalleled by continuous process models able to work on a wide array of catchments. In spite of its crude simplicity, it achieved, on average, worthwhile results on a set of 140 French catchments and overwhelmingly outperformed a linear model involving 16 parameters. It performed roughly as well as a conceptual model with five free parameters, derived from the well-known TOPMODEL.

The Central Siberian Origin for Native American Y Chromosomes

Abstract: Y chromosomal DNA polymorphisms were used to investigate Pleistocene male migrations to the American continent. In a worldwide sample of 306 men, we obtained 32 haplotypes constructed with the variation found in 30 distinct polymorphic sites. The major Y haplotype present in most Native Americans was traced back to recent ancestors common with Siberians, namely, the Kets and Altaians from the Yenissey River Basin and Altai Mountains, respectively. Going further back, the next common ancestor gave rise also to Caucasoid Y chromosomes, probably from the central Eurasian region. This study, therefore, suggests a predominantly central Siberian origin for Native American paternal lineages for those who could have migrated to the Americas during the Upper Pleistocene.

Measurement of the de Broglie Wavelength of a Multiphoton Wave Packet

Abstract: A fourth-order Young interference experiment was done to demonstrate a practical way to measure the de Broglie wavelength of a two-photon wave packet. A two-photon collinear beam is generated by type-II spontaneous parametric down-conversion. By modifying the transverse field profile of the pump laser beam that generates the two-photon beam we demonstrate that it is possible to measure the de Broglie wavelength of the single-photon constituents of the two-photon wave packet, the de Broglie wavelength of the two-photon wave packet as a whole and an ill defined intermediate de Broglie wavelength between the two cases.

Instrumental Analysis Study of Iron Species Biosorption by Sargassum Biomass

Abstract: The mechanism of iron uptake by the dry biomass of the brown seaweed Sargassum fluitans was investigated at the molecular level using different instrumental techniques. Transmission electron microscopy (TEM) and the chemical microanalysis by electron dispersive spectroscopy (EDS) of the biomass exposed to iron solutions confirmed the deposition of the metal mainly in the cell wall. The analysis of the Fe(II)-exposed biomass by X-ray photoelectron spectroscopy (XPS) indicated the presence of Fe in two states of oxidation in the biomass exposed to ferrous iron solution, whereas only Fe(III) was present in ferric iron-exposed biomass, suggesting a partial oxidation of Fe(II) when in contact with the biomass. In both Fe(II)- and Fe(III)-exposed samples, XPS indicated iron complexation with sulfate groups in the biomass. The FTIR analysis of metal-loaded biomass samples revealed the chelating character of the ion complexation to carboxyl groups as well as the complexation of Fe(III) with sulfur of sulfonate gr...

As licenciaturas e as novas políticas educacionais para a formação docente

Abstract: Neste artigo sao apresentadas reflexoes e analises a respeito das recentes politicas educacionais para a formacao docente no Brasil. O foco sao as diferentes questoes que envolvem os cursos de licenciatura no pais, principalmente, a partir da aprovacao da Lei de Diretrizes e Bases da Educacao Nacional (lei no 9.394/96). Mais especificamente, sao discutidos os modelos de formacao docente - subjacentes as formulacoes atuais e a serem implementadas -, as demandas para a formacao profissional resultantes das mudancas na educacao basica brasileira, o locus da preparacao de professores e o processo de construcao das diretrizes curriculares para as licenciaturas.

Reproductive phenology of sympatric taxa of Chamaecrista (Leguminosae) in Serra do Cipó, Brazil

Abstract: Reproductive phenology of 13 sympatric taxa of Chamaecrista in three sections was surveyed at Serra do Cipo, south-east Brazil. Mean abundance of flowers and fruits per plant and mean number of aborted, predated, and surviving seeds per fruit were estimated. Monthly average number of developed seeds per fruit multiplied by the monthly mean number of fruits per plant gave the monthly average number of seeds produced by a plant of each taxon. Five types of phenological behaviour were differentiated by cluster analyses according to the season during which each species produced most of its mature seeds. This behaviour was related to the taxonomic section to which the taxa belong, to plant architecture, to geographical range, to seed predation and to local climatic seasonality. Herbs were more affected by variation in rainfall than shrubs and trees. Two species did not show any clear seasonal behaviour. Widespread taxa produced most of their mature seeds in the rainy season or immediately after it, and all but one of the narrowly distributed species produced most of their mature seeds in the dry season or in the transition from dry to rainy season. Seed predation is probably not an important selective force affecting reproductive phenology of larger taxa, while the smaller taxa seemed too constrained by abiotic factors for biotic factors to influence their phenology significantly.

β-Chemokines Enhance Parasite Uptake and Promote Nitric Oxide-Dependent Microbiostatic Activity in Murine Inflammatory Macrophages Infected with Trypanosoma cruzi

Abstract: In the present study, we describe the ability of Trypanosoma cruzi trypomastigotes to stimulate the synthesis of b-chemokines by macrophages. In vivo infection with T. cruzi led to MIP-1a, RANTES, and JE/MCP1 mRNA expression by cells from peritoneal inflammatory exudate. In addition, in vitro infection with T. cruzi resulted in expression of b-chemokine MIP-1a, MIP-1b, RANTES, and JE mRNA by macrophages. The expression of the b-chemokine MIP-1a, MIP-1b, RANTES, and JE proteins by murine macrophages cultured with trypomastigote forms of T. cruzi was confirmed by immunocytochemistry. Interestingly, macrophage infection with T. cruzi also resulted in NO production, which we found to be mediated mainly by b-chemokines. Hence, treatment with anti-b-chemokine-specific neutralizing antibodies partially inhibited NO release by macrophages incubated with T. cruzi parasites. Further, the addition of the exogenous b-chemokines MIP-1a, MIP-1b, RANTES, and JE/MCP-1 induced an increased T. cruzi uptake, leading to enhanced NO production and control of parasite replication in a dose-dependent manner. L-NMMA, a specific inhibitor of the Larginine‐NO pathway, caused a decrease in NO production and parasite killing when added to cultures of macrophages stimulated with b-chemokines. Among the b-chemokines tested, JE was more potent in inhibiting parasite growth, although it was much less efficient than gamma interferon (IFN-g). Nevertheless, JE potentiates parasite killing by macrophages incubated with low doses of IFN-g. Together, these results suggest that in addition to their chemotactic activity, murine b-chemokines may also contribute to enhancing parasite uptake and promoting control of parasite replication in macrophages and may play a role in resistance to T. cruzi infection.

The Role of MIP in Lens Fiber Cell Membrane Transport

Abstract: MIP has been hypothesized to be a gap junction protein, a membrane ion channel, a membrane water channel and a facilitator of glycerol transport and metabolism. These possible roles have been indirectly suggested by the localization of MIP in lens gap junctional plaques and the properties of MIP when reconstituted into artificial membranes or exogenously expressed in oocytes. We have examined lens fiber cells to see if these functions are present and whether they are affected by a mutation of MIP found in CatFr mouse lens. Of these five hypothesized functions, only one, the role of water channel, appears to be true of fiber cells in situ. Based on the rate of volume change of vesicles placed in a hypertonic solution, fiber cell membrane lipids have a low water permeability (pH2O) on the order of 1 micron/sec whereas normal fiber cell membrane pH2O was 17 micron/sec frog, 32 micron/sec rabbit and 43 micron/sec mouse. CatFr mouse lens fiber cell pH2O was reduced by 13 micron/sec for heterozygous and 30 micron/sec for homozygous mutants when compared to wild type. Lastly, when expressed in oocytes, the pH2O conferred by MIP is not sensitive to Hg2+ whereas that of CHIP28 (AQP1) is blocked by Hg2+. The fiber cell membrane pH2O was also not sensitive to Hg2+ whereas lens epithelial cell pH2O (136 micron/sec in rabbit) was blocked by Hg2+. With regard to the other hypothesized roles, fiber cell membrane or lipid vesicles had a glycerol permeability on the order of 1 nm/sec, an order of magnitude less than that conferred by MIP when expressed in oocytes. Impedance studies were employed to determine gap junctional coupling and fiber cell membrane conductance in wild-type and heterozygous CatFr mouse lenses. There was no detectable difference in either coupling or conductance between the wild-type and the mutant lenses.

Chagas' disease diagnosis: comparative analysis of parasitologic, molecular, and serologic methods.

Abstract: During the course of chronic chagasic infection, low parasitemia levels prevent parasite detection by current techniques such as hemoculture and xenodiagnosis. Since serologic tests have sensitivity but lack specificity, molecular assays based on the polymerase chain reaction (PCR) have been proposed as alternative tools for parasite detection in individuals with chronic Chagas' disease. A variable degree of PCR efficiency has been reported in the literature and illustrates the need for further evaluation of large numbers of chagasic patients. In this study, we compared an optimized PCR technique with hemoculture and complement-mediated lysis (CoML) in 113 individuals from or living in endemic areas of Brazil who had conventional serologic results that were either positive, negative, or inconclusive. The PCR amplification yielded positive results in 83.5% (66 of 79) of individuals with positive serology, 47.6% (10 of 21) with negative serology, and 46.2% (6 of 13) with inconclusive serology. Of 10 patients with negative serology and positive PCR result, eight (80%) had positive CoML, indicating that they could have been chagasic but were not mounting immune responses. The PCR results were also positive for all individuals who had positive hemoculture, for 37 individuals with negative hemoculture and positive serology, and for two of six individuals with inconclusive serology and negative hemoculture. Thirteen individuals living in nonendemic areas who had negative serology were used as a negative control group: 100% had negative PCR results. Our results show that the optimized PCR protocol used here was very sensitive in detecting the presence of Trypanosoma cruzi in chronic chagasic patients. The PCR and CoML results were well correlated in all of the groups studied, which suggests that our PCR protocol may be effective in the evaluation of cure in patients who receive anti-parasite treatment.

Persistent Sydenham's chorea.

Abstract: BACKGROUND Sydenham's chorea (SC) occurs in 26% of patients with rheumatic fever (RF). Despite usually being described as a self-limited condition, few reports indicate that SC may persist in rare subjects. OBJECTIVE To investigate the proportion of subjects with SC lasting more than 2 years and if clinical features differentiate patients with SC with a duration of less than 2 years (Group 1) from those with SC lasting more than 2 years (Group 2). METHODS Prospective assessment of all patients with SC seen at our service from July 1993 through March 1998 analyzing the following: gender; age at onset; frequency of arthritis, carditis, family history of RF and SC; topographic distribution; and chorea severity on a 0–4 scale. RESULTS Thirty-two patients (19 female, 13 male) were studied. In Group 1 (16 subjects, 50%) the follow-up period was 36.2 ± 20.0 months; 50% were female; age at onset was 10.9 ± 2.6 years; arthritis and carditis were present in 37.5% and 31.2%, respectively; family history of SC was reported by 18.7%; hemichorea was seen in 25.8% of subjects; and the mean intensity of chorea was 2.60.8. In Group 2, with a follow-up period of 34.1 ± 18.9 months, 68.8% were female; age at onset was 9.3 ± 3.9 years; arthritis and carditis were diagnosed in 18.7% and 50%, respectively; no patient reported a family history of SC; hemichorea was observed in 6.2% of subjects; and the mean intensity of chorea was 2.8 ± 0.5. No difference was statistically significant. CONCLUSIONS SC persists in half of our patients. Female gender, possibly related to endocrine factors, as well as the presence of carditis, indicating a more severe disease, may be risk factors for a longer duration of SC.

Pharmacological modulation of secondary mediator systems–cyclic AMP and cyclic GMP–on inflammatory hyperalgesia

Abstract: 1. The objective of the present paper was to evaluate the relevance of neuronal balance of cyclic AMP and cyclic GMP concentration for functional regulation of nociceptor sensitivity during inflammation. 2. Injection of PGE2 (10-100 ng paw-1) evoked a dose-dependent hyperalgesic effect which was mediated via a cyclic AMP-activated protein kinase (PKA) inasmuch as hyperalgesia was blocked by the PKA inhibitor H89. 3. The PDE4 inhibitor rolipram and RP73401, but not PDE3 and PDE5 inhibitors potentiated the hyperalgesic effects of PGE2. The hyperalgesic effect of dopamine was also enhanced by rolipram. Moreover, rolipram significantly potentiated hyperalgesia induced by carrageenan, bradykinin, TNF alpha, IL-1 beta, IL-6 and IL-8. This suggests that neuronal cyclic AMP mediates the prostanoid and sympathetic components of mechanical hyperalgesia. Moreover, in the neuron cyclic AMP is mainly metabolized by PDE4. 4. To examine the role of the NO/cyclic GMP pathway in modulating mechanical hyperalgesia, we tested the effects of the soluble guanylate cyclase inhibitor, ODQ. This substance counteracts the inhibitory effects of the NO donor, SNAP, on the hyperalgesia induced by PGE2. 5. The ODQ potentiated hyperalgesia induced by carrageenan, bradykinin, TNF alpha, IL-1 beta, IL-6 and IL-8. In contrast, ODQ had no significant effect on the hyperalgesia induced by PGE2 and dopamine. This indicates that the hyperalgesic cytokines may activate soluble guanylate cyclase, which down-regulate the ability of these substances to cause hyperalgesia. This event appears not to be mediated by prostaglandin or dopamine. 6. In conclusion, the results presented in this paper confirm an association between (i) hyperalgesia and elevated levels of cyclic AMP as well as (ii) antinociception and elevated levels of cyclic GMP. The intracellular levels of cyclic AMP that enhance hyperalgesia are controlled by the PDE4 isoform and appear to result in activation of protein kinase A whereas the intracellular levels of cyclic GMP results from activation of a soluble guanylate cyclase.

Variation in Short Tandem Repeats Is Deeply Structured by Genetic Background on the Human Y Chromosome

Abstract: Eleven biallelic polymorphisms and seven short-tandem-repeat (STR) loci mapping on the nonrecombining portion of the human Y chromosome have been typed in men from northwestern Africa. Analysis of the biallelic markers, which represent probable unique events in human evolution, allowed us to characterize the stable backgrounds or haplogroups of Y chromosomes that prevail in this geographic region. Variation in the more rapidly mutating genetic markers (STRs) has been used both to estimate the time to the most recent common ancestor for STR variability within these stable backgrounds and to explore whether STR differentiation among haplogroups still retains information about their phylogeny. When analysis of molecular variance was used to study the apportionment of STR variation among both genetic backgrounds (i.e., those defined by haplogroups) and population backgrounds, we found STR variability to be clearly structured by haplogroups. More than 80% of the genetic variance was found among haplogroups, whereas only 3.72% of the genetic variation could be attributed to differences among populations-that is, genetic variability appears to be much more structured by lineage than by population. This was confirmed when two population samples from the Iberian Peninsula were added to the analysis. The deep structure of the genetic variation in old genealogical units (haplogroups) challenges a population-based perspective in the comprehension of human genome diversity. A population may be better understood as an association of lineages from a deep and population-independent gene genealogy, rather than as a complete evolutionary unit.

[Dynamics of institutionalization of older adults in Belo Horizonte, Brazil].

Abstract: OBJETIVO: O processo de envelhecimento populacional brasileiro tem sido acompanhado por transformacoes epidemiologicas e sociais que, em outros paises, aumentaram a demanda por instituicoes de longa permanencia. Nesse sentido, desenvolveu-se estudo sobre dinâmica da institucionalizacao de idosos atraves da analise da oferta de leitos e caracteristicas demograficas dos residentes em asilos. METODOS: Foi realizado levantamento dos asilos de idosos do Municipio de Belo Horizonte, MG. Foram registradas datas de nascimento e admissao de 1.128 residentes de 33 dos 40 asilos em funcionamento no municipio. A lotacao foi calculada atraves da capacidade informada e da taxa de institucionalizacao, segundo dados da Pesquisa Nacional por Amostra de Domicilios (PNAD). RESULTADOS: As taxas de institucionalizacao de idosos (65+) do municipio foram 0,9% (mulheres) e 0,3% (homens). A lotacao mediana dos asilos era de 92%. Dentre os 1.128 residentes arrolados (92,5% do total), as mulheres (81%) apresentavam maiores medias de idade (76,4 x 70,4 anos; p=0,00) e estada (5,6 x 4,5 anos; p=0,01). DISCUSSAO/CONCLUSOES: Elevada lotacao, listas de espera nos asilos filantropicos (85% do total) e rigidos criterios para admissao (metade recusava idosos demenciados ou dependentes) sugerem que a baixa taxa de institucionalizacao se deve a escassez de vagas. A predominância de idosas reflete a prevalencia de viuvas ou separadas na comunidade (66% contra 76% de homens casados). A proporcao de homens adultos (31% < 65 anos) sugere dificuldade de se auto-sustentarem apos a viuvez. Elevada taxa de mortalidade (24% durante 20 meses de acompanhamento de amostra aleatoria de 263 residentes), incompativel com o rigor dos criterios de admissao, determina a baixa mediana de estada (3 anos). Os dados refletem o anacronismo de um sistema nao direcionado a manutencao dos idosos em seus proprios domicilios.

Dissipative dynamics of the Jaynes-Cummings model in the dispersive approximation: Analytical results

Abstract: We present the time evolution of a two-level atom interacting dispersively with an electromagnetic field in a dissipative cavity. We investigate the influence of dissipation on the entanglement of the two subsystems $(\mathrm{atom}+\mathrm{field}).$ Simple but realistic, the model displays several nontrivial quantum features, which emerge when an environment is taken into account: the cavity is shown to have practically no influence in the coherence properties of the field from the qualitative point of view. On the other hand, although the atom is not directly coupled to the cavity modes, its coherent properties are strongly influenced by dissipation both qualitatively as well as quantitatively.

Ovarian follicular atresia in two teleost species: a histological and ultrastructural study

Abstract: Follicular atresia is a common phenomenon in vertebrate ovaries involving the oocyte and the follicular wall degeneration. Female Astyanax bimaculatus lacustris and Leporinus reinhardti were kept in aquaculture cages inside tanks from February 1994 to January 1995 for the study of the characteristics of different stages of follicular atresia. Histological and ultrastructural analysis demonstrated similarities in the degenerative events and in the resorption of oocytes in both species. Degradation of organelles, such as mitochondria, cortical alveoli, and annulate lamellae occurred in the peripheral ooplasm during the initial stage of the process. Follicle cells showed marked phagocytic activity with digestive vacuoles, myelin figures, and lipofuscin granules during the intermediate and advanced stages of follicular atresia. Granulocytes were in activity during the final stage of follicle resorption. The duration of follicular atresia was 4 months in Leporinus reinhardti and 7 months in Astyanax bimaculatus lacustris. When submitted to induced reproduction in December 1995, 50-60% of the females of both species responded to induced spawning, indicating the recovery of gonadal activity. It is suggested that, in captive conditions, follicular atresia is shorter in total-spawning fishes when compared to those showing partial spawning, and that it has no apparent deleterious effects on induced reproduction in the subsequent cycle.

Evaluation of enzyme-linked immunosorbent assay for the diagnosis of Helicobacter pylori infection in children from different age groups with and without duodenal ulcer.

Abstract: Background:Although enzyme-linked immunosorbent assay (ELISA) is highly sensitive and specific for the diagnosis of Helicobacter pylori infection in adults, their performance in children is still controversial.Methods:A second-generation ELISA was used to evaluate the IgG response to H. pylo

Criteria of Chagas disease cure

Abstract: The investigation of the rational etiological treatment of Chagas disease, through controlled clinical trials, only began around half a century after the discovery of the disease. This resulted from a meeting held in Rio de Janeiro, in 1962, between a number of Brazilian researchers and representatives from the pharmaceutical industry (Anais 1962). Two facts were then known: (1) nitrofuran compounds are active against Trypanosoma cruzi: (2) long course administration of nitrofurazone prevents the development of experimental infection in mouse. At that meeting, we had the opportunity of discussing methods of evaluation of therapeutic efficacy. We discarded clinical criteria, due to the slow natural evolution of the disease. Furthermore, since the main objective of specific therapy is the eradication of the causative organism, the criterion of cure should be the proof of the elimination of T. cruzi, demonstrated in practice by the post-therapeutic consistent negative parasitological and serological tests, at that time, respectively, xenodiagnosis (XD) and complement fixation (CF). In the years following the landmark 1962 meeting, we examined, at the University Hospital and private practice, in Belo Horizonte, MG, Brasil, 2,405 Chagas disease patients, 47 with the acute and 2,358 with various chronic forms (Table I). We performed several controlled clinical trials, with nitrofurazone, l-furaltadone, nifurtimox, benznidazole, ketoconazole, among other drugs. In addition, new diagnostic tests were introduced: hemoculture (HC), quantitative indirect immunofluorescence test (IF), quantitative indirect hemagglutination test (HA) and complement mediated lysis (CoML). IMMUNE RESPONSE

Liposomes: from biophysics to the design of peptide vaccines

Abstract: Liposomes (lipid-based vesicles) have been widely studied as drug delivery systems due to their relative safety, their structural versatility concerning size, composition and bilayer fluidity, and their ability to incorporate almost any molecule regardless of its structure. Liposomes are successful in inducing potent in vivo immunity to incorporated antigens and are now being employed in numerous immunization procedures. This is a brief overview of the structural, biophysical and pharmacological properties of liposomes and of the current strategies in the design of liposomes as vaccine delivery systems.