scispace - formally typeset
Search or ask a question

Showing papers by "Universidade Federal de Minas Gerais published in 2001"


Journal ArticleDOI
TL;DR: Evidence is presented that Trypanosoma cruzi-derived GPI anchors and GIPLs trigger CD25 expression on Chinese hamster ovary-K1 cells transfected with CD14 and Toll-like receptor-2 (TLR-2), but not wild-type (TLr-2-deficient) Chinese hamsters ovary cells, which may initiate host innate defense mechanisms and inflammatory response during protozoan infection.
Abstract: Glycosylphosphatidylinositol (GPI) anchors and glycoinositolphospholipids (GIPLs) from parasitic protozoa have been shown to exert a wide variety of effects on cells of the host innate immune system. However, the receptor(s) that are triggered by these protozoan glycolipids has not been identified. Here we present evidence that Trypanosoma cruzi-derived GPI anchors and GIPLs trigger CD25 expression on Chinese hamster ovary-K1 cells transfected with CD14 and Toll-like receptor-2 (TLR-2), but not wild-type (TLR-2-deficient) Chinese hamster ovary cells. The protozoan-derived GPI anchors and GIPLs containing alkylacylglycerol and saturated fatty acid chains or ceramide were found to be active in a concentration range of 100 nM to 1 microM. More importantly, the GPI anchors purified from T. cruzi trypomastigotes, which contain a longer glycan core and unsaturated fatty acids in the sn-2 position of the alkylacylglycerolipid component, triggered TLR-2 at subnanomolar concentrations. We performed experiments with macrophages from TLR-2 knockout and TLR-4 knockout mice, and found that TLR-2 expression appears to be essential for induction of IL-12, TNF-alpha, and NO by GPI anchors derived from T. cruzi trypomastigotes. Thus, highly purified GPI anchors from T. cruzi parasites are potent activators of TLR-2 from both mouse and human origin. The activation of TLR-2 may initiate host innate defense mechanisms and inflammatory response during protozoan infection, and may provide new strategies for immune intervention during protozoan infections.

579 citations


Journal ArticleDOI
TL;DR: The double resonance Raman process provides new assignments for the dispersive and nondispersive features observed in the Raman spectra of disordered graphite and carbon nanotubes, some features having been incorrectly assigned previously, or not assigned at all.
Abstract: The phonon dispersion relations of graphite can be probed over a wide range of the Brillouin zone by double resonance Raman spectroscopy. The double resonance Raman process provides us with new assignments for the dispersive and nondispersive features observed in the Raman spectra of disordered graphite and carbon nanotubes, some features having been incorrectly assigned previously, or not assigned at all.

543 citations


Journal ArticleDOI
TL;DR: In this paper, it is assumed that coeval Paramirim and Sangha aulacogens played a key role by making room for the Aracuai-West-Congo Basin.

395 citations


Journal ArticleDOI
TL;DR: DNA polymorphisms in the nonrecombining portion of the Y-chromosome are examined to investigate the contribution of distinct patrilineages to the present-day white Brazilian population, which agrees with the known history of the peopling of Brazil since 1500.
Abstract: We examined DNA polymorphisms in the nonrecombining portion of the Y-chromosome to investigate the contribution of distinct patrilineages to the present-day white Brazilian population. Twelve unique-event polymorphisms were typed in 200 unrelated males from four geographical regions of Brazil and in 93 Portuguese males. In our Brazilian sample, the vast majority of Y-chromosomes proved to be of European origin. Indeed, there were no significant differences when the haplogroup frequencies in Brazil and Portugal were compared by means of an exact test of population differentiation. Y-chromosome typing was quite sensitive in the detection of regional immigration events. Distinct footprints of Italian immigration to southern Brazil, migration of Moroccan Jews to the Amazon region, and possible relics of the 17th-century Dutch invasion of northeast Brazil could be seen in the data. In sharp contrast with our mtDNA data in white Brazilians, which showed that ⩾60% of the matrilineages were Amerindian or African, only 2.5% of the Y-chromosome lineages were from sub-Saharan Africa, and none were Amerindian. Together, these results configure a picture of strong directional mating between European males and Amerindian and African females, which agrees with the known history of the peopling of Brazil since 1500.

343 citations


Journal ArticleDOI
17 Nov 2001-BMJ
TL;DR: In two antenatal interviews, preferences regarding type of delivery were nearly identical among public and private patients and strongly favoured vaginal births Contrary to popular belief, middle and upper class women in Brazil do not want to deliver by caesarean section.
Abstract: Objective: To assess and compare the preferences of pregnant women in the public and private sector regarding delivery in Brazil Design: Face to face structured interviews with women who were interviewed early in pregnancy, about one month before the due date, and about one month post partum Setting: Four cities in Brazil Participants: 1612 pregnant women: 1093 public patients and 519 private patients Main outcome measures: Rates of delivery by caesarean section in public and private institutions; women9s preferences for delivery; timing of decision to perform caesarean section Results: 1136 women completed all three interviews; 476 women were lost to follow up (376 public patients and 100 private patients) Despite large differences in the rates of caesarean section in the two sectors (222/717 (31%) among public patients and 302/419 (72%) among private patients) there were no significant differences in preferences between the two groups In both antenatal interviews, 70-80% in both sectors said they would prefer to deliver vaginally In a large proportion of cases (237/502) caesarean delivery was decided on before admission: 48/207 (23%) in women in the public sector and 189/295 (64%) in women in the private sector Conclusions: The large difference in the rates of caesarean sections in women in the public and private sectors is due to more unwanted caesarean sections among private patients rather than to a difference in preferences for delivery High or rising rates of caesarean sections do not necessarily reflect demand for surgical delivery What is already known on this topic In Brazil, one quarter of all women deliver in the private sector The rate of caesarean deliveries in the private sector is extremely high (70%) and more than twice that in the public sector, where rates have recently fallen due to a new policy Previous studies in which women were interviewed after birth showed that a substantial proportion of private patients who have caesarean sections would have preferred normal delivery What this study adds In two antenatal interviews, preferences regarding type of delivery were nearly identical among public and private patients and strongly favoured vaginal births Contrary to popular belief, middle and upper class women in Brazil do not want to deliver by caesarean section

294 citations


Journal ArticleDOI
TL;DR: Indocyanine green staining of the ILM appears to be a safe and useful adjunct in vitreous surgery for macular hole repair, and there was no clinical or fluorescein angiographic evidence of ICG toxicity.

278 citations


Journal ArticleDOI
TL;DR: Specific yeast communities vectored by beetles, drosophilids, and bees that visit ephemeral flowers, mostly in the genus Hibiscus and in the families Convolvulaceae and Cactaceae, in the Neotropical, Nearctic, and Australian biogeographic regions are studied.
Abstract: We studied specific yeast communities vectored by beetles, drosophilids, and bees that visit ephemeral flowers, mostly in the genus Hibiscus and in the families Convolvulaceae and Cactaceae, in the Neotropical, Nearctic, and Australian biogeographic regions. The communities consist mostly of yeasts in four clades centered around the genera Metschnikowia, Kodamaea, Wickerhamiella, and Starmerella. The largest geographic discontinuity occurs as a function of the nitidulid beetle species that dominate the non-pollinator insect visitors of the flowers. This partitions the New World, where the dominant beetle is in the genus Conotelus, from the Australian biogeographic region, dominated by species of Aethina. Distinct but sympatric insects may also carry radically different yeast communities.

261 citations


Journal ArticleDOI
TL;DR: The results suggest that the antiarrhythmogenic effect of low concentrations of Ang-(1-7) is mediated by a specific receptor and that release of endogenous prostaglandins contributes to the alleviation of reversible and/or irreversible ischemia-reperfusion injury.
Abstract: In this study we evaluate the effects of angiotensin-(1-7) on reperfusion arrhythmias in isolated rat hearts. Rat hearts were perfused according to Langendorff technique and maintained in heated (37+/-1 degrees C) and continuously gassed (95% O(2)/5% CO(2)) Krebs-Ringer solution at constant pressure (65 mm Hg). The electrical activity was recorded with an ECG (bipolar). Local ischemia was induced by coronary ligation for 15 minutes. After ischemia, hearts were reperfused for 30 minutes. Cardiac arrhythmias were defined as the presence of ventricular tachycardia and/or ventricular fibrillation after the ligation of the coronary artery was released. Angiotensin II (0.20 nmol/L, n=10) produced a significant enhancement of reperfusion arrhythmias. On the other hand, Ang-(1-7) presented in the perfusion solution (0.22 nmol/L, n=11) reduced incidence and duration of arrhythmias. The antiarrhythmogenic effects of Ang-(1-7) was blocked by the selective Ang-(1-7) antagonist A-779 (2 nmol/L, n=9) and by indomethacin pretreatment (5 mg/kg IP, n=8) but not by the bradykinin B(2) antagonist HOE 140 (100 nmol/L, n=10) or by L-NAME pretreatment (30 mg/kg IP, n=8). These results suggest that the antiarrhythmogenic effect of low concentrations of Ang-(1-7) is mediated by a specific receptor and that release of endogenous prostaglandins.by Ang-(1-7) contributes to the alleviation of reversible and/or irreversible ischemia-reperfusion injury.

241 citations


Journal ArticleDOI
TL;DR: A perturbation theory of the static response of insulating crystals to homogeneous electric fields that combines the modem theory of polarization (MTP) with the variation-perturbation framework is developed at the unrestricted order of perturbations in this article.
Abstract: A perturbation theory of the static response of insulating crystals to homogeneous electric fields that combines the modem theory of polarization (MTP) with the variation-perturbation framework is developed at unrestricted order of perturbation. First, we address conceptual issues related to the definition of such a perturbative approach. In particular, in our definition of an electric-field-dependent energy functional for periodic systems, the position operator appearing in the perturbation term is replaced by a Berry-phase expression, along the lines of the MTP. Moreover, due to the unbound nature of the perturbation, a regularization of the Ferry-phase expression for the polarization is needed in order to define a numerically stable variational procedure. Regularization is achieved by means of discretization, which can be performed either before or after the perturbation expansion. We compare the two possibilities and apply them to a model tight-binding Hamiltonian. Lowest-order as well as generic formulas are presented for the derivatives of the total energy, the normalization condition, the eigenequation, and the Lagrange parameters.

216 citations


Journal ArticleDOI
TL;DR: A cross-sectional survey was carried out on 3702 boys and girls aged 9-14 years, attending public and private primary schools in Belo Horizonte, Brazil, showing that the prevalence of dental injuries increased from 8% at the age of 9 years to 13.6% at 12 and 16.1% at 14 years.
Abstract: A cross-sectional survey was carried out on 3702 boys and girls aged 9-14 years, attending public and private primary schools in Belo Horizonte, Brazil. A multi-stage sampling technique using an equal probability scheme was adopted to select the children. The response rate for the total sample was 97%. Dental examinations were carried out by one dentist (MISC). Intra-examiner agreement was very good. The prevalence of dental injuries increased from 8% at the age of 9 years to 13.6% at 12 and 16.1% at 14 years. Adjusted results showed that children from high socio-economic backgrounds were 1.4 (95% CI = 1.15-1.79) times more likely to present with a dental injury than children with low SES. Boys were 1.7 times (95% CI = 1.41-2.16) more likely to have dental injuries than girls. Children with an overjet size greater than 5.0 mm were 1.37 times (95% CI = 1.06-1.80) more likely to have a dental injury than children with an overjet size equal or lower than 5.0 mm. Finally, children with an adequate lip coverage were 0.56 times (95% CI = 0.44-0.72) less likely to have a traumatic dental injury than those with inadequate lip coverage.

214 citations


Journal ArticleDOI
TL;DR: Gait analysis revealed that the 10 week training resulted in significant increases in gait speed associated with improvements in walking patterns as determined by increases in selected kinematic and kinetic measures.
Abstract: The purpose of this study was to evaluate the impact of a combined program of muscle strengthening and physical conditioning on gait performance in subjects with chronic stroke, using a single group pre- and post-test design. Thirteen subjects were recruited for the 10-week program (3 days/week), which consisted of warm-up, aerobic exercises, lower extremity muscle strengthening and cool-down. Data from cinematographic film and a force plate obtained during multiple walking trials were used in a four-segment kinetic model to yield spatiotemporal, kinematic and kinetic variables. Gait analysis revealed that the 10 week training resulted in significant increases in gait speed associated with improvements in walking patterns as determined by increases in selected kinematic and kinetic measures. After training, subjects were able to generate higher levels of powers and demonstrated increases in positive work performed by the ankle plantar flexor and hip flexor/extensor muscles.

Journal ArticleDOI
TL;DR: In this article, the authors presented two numerical models to simulate the transient and steady state behavior of a vapor compression refrigeration system, where the condenser and the evaporator were divided into a number of control volumes.
Abstract: This work presents two numerical models to simulate the transient and steady state behavior of a vapor compression refrigeration system. The condenser and the evaporator were divided into a number of control volumes. Time dependent partial differential equations system was obtained from the mass, energy and momentum balances for each control volume. As the expansion valve and the compressor both have very small thermal inertia, the steady state models were applied for these components. Transient and steady state models numerical predictions were compared and good agreement was found. Further simulations were performed with the objective of verifying the possibility of controlling the refrigeration system and the superheating of the refrigerant in the evaporator outlet by varying the compressor speed and the throttling valve sectional area. The results indicate that the proposed models can be used to formulate an algorithm for controlling a refrigeration system.

Journal ArticleDOI
TL;DR: X-ray absorption fine structure spectroscopy and density functional calculations were used to determine the structural model of arsenic surface complex on gibbsite mineral in this paper, which showed that As(V) forms an inner sphere bidentate binuclear complex on the surface of Al oxyhydroxyl octaedra.

Journal ArticleDOI
TL;DR: The results suggest that the level of IFN-gamma deficiency is a major determinant of the site of reactivation of T. cruzi infection in immunocompromised host.
Abstract: The role of cytokines in the control of tissue parasitism and pathogenesis of experimental Chagas’ disease was investigated. Wild-type and different cytokine as well as inducible nitric oxide synthase (iNOS) knockout mice were infected with the Colombian strain of Trypanosoma cruzi, and the kinetics of tissue parasitism, inflammatory reaction, parasitemia, and mortality were determined. We demonstrate the pivotal role of the interleukin (IL)-12/interferon (IFN)-γ/iNOS axis and the antagonistic effect of IL-4 in controlling heart tissue parasitism, inflammation, and host resistance to acute infection with T. cruzi. Further, the heart and central nervous system were shown the main sites of reactivation of T. cruzi infection in mice lacking functional genes for IFN-γ and IL-12, respectively. Our results also show that in contrast to IFN-γ knockout (KO) mice, splenocytes from IL-12 KO mice infected with T. cruzi produced low levels of IFN-γ upon stimulation with antigen. Consistently, high levels of anti-T. cruzi IgG2a antibodies were detected in the sera from IL-12 KO, but not from IFN-γ KO mice, infected with the Colombian strain of T. cruzi. Thus, our results suggest that the level of IFN-γ deficiency is a major determinant of the site of reactivation of T. cruzi infection in immunocompromised host.

Journal ArticleDOI
TL;DR: A model for the evolution of the male lineages of South Amerindians that involves differential patterns of genetic drift and gene flow is proposed, consistent with the linguistic and cultural diversity of South America, the environmental heterogeneity of the continent, and the available paleoecological data.
Abstract: The geographic structure of Y-chromosome variability has been analyzed in native populations of South America, through use of the high-frequency Native American haplogroup defined by the DYS199-T allele and six Y-chromosome-linked microsatellites (DYS19, DYS389A, DYS389B, DYS390, DYS391, and DYS393), analyzed in 236 individuals. The following pattern of within- and among-population variability emerges from the analysis of microsatellite data: (1) the Andean populations exhibit significantly higher levels of within-population variability than do the eastern populations of South America; (2) the spatial-autocorrelation analysis suggests a significant geographic structure of Y-chromosome genetic variability in South America, although a typical evolutionary pattern could not be categorically identified; and (3) genetic-distance analyses and the analysis of molecular variance suggest greater homogeneity between Andean populations than between non-Andean ones. On the basis of these results, we propose a model for the evolution of the male lineages of South Amerindians that involves differential patterns of genetic drift and gene flow. In the western part of the continent, which is associated with the Andean area, populations have relatively large effective sizes and gene-flow levels among them, which has created a trend toward homogenization of the gene pool. On the other hand, eastern populations-settled in the Amazonian region, the central Brazilian plateau, and the Chaco region-have exhibited higher rates of genetic drift and lower levels of gene flow, with a resulting trend toward genetic differentiation. This model is consistent with the linguistic and cultural diversity of South Amerindians, the environmental heterogeneity of the continent, and the available paleoecological data.

Journal ArticleDOI
TL;DR: Findings support a new subgroup of postinfectious autoimmune inflammatory disorders associated with Group A β hemolytic streptococcus, abnormal basal ganglia imaging, and elevated ABGA.
Abstract: Antibasal ganglia antibodies (ABGA) are associated with Sydenham's chorea and pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections. We present 10 patients with acute disseminated encephalomyelitis (ADEM) associated with Group A beta hemolytic streptococcal infection. The clinical phenotype was novel, with 50% having a dystonic extrapyramidal movement disorder, and 70% a behavioral syndrome. None of the patients had rheumatic fever or Sydenham's chorea. Enzyme-linked immunosorbent assay, Western immunoblotting, and immunohistochemistry were used to detect ABGA. Neurological (n = 40) and streptococcal (n = 40) controls were used for comparison. Enzyme-linked immunosorbent assay results showed significantly elevated ABGA in the patients with poststreptococcal ADEM. Western immunoblotting demonstrated ABGA reactivity to three dominant protein bands of 60, 67, or 80 kDa; a finding not reproduced in controls. Fluorescent immunohistochemistry demonstrated specific binding to large striatal neurones, which was not seen in controls. Streptococcal serology was also significantly elevated in the poststreptococcal ADEM group compared with neurological controls. Magnetic resonance imaging studies showed hyperintense basal ganglia in 80% of patients with poststreptococcal ADEM, compared to 18% of patients with nonstreptococcal ADEM. These findings support a new subgroup of postinfectious autoimmune inflammatory disorders associated with Group A beta hemolytic streptococcus, abnormal basal ganglia imaging, and elevated ABGA.

Journal ArticleDOI
TL;DR: The results corroborate the hypothesis that predicts that habitat stress is the main factor generating the patterns of galling insect richness in Brazilian savannas.
Abstract: Five hypotheses were tested to explain the pattern of galling insect species richness in four neotropical savanna physiognomies, 'canga ', 'campo sujo', 'cerrado' s. st., and 'cerradao', that occur in Minas Gerais, southeastern Brazil. We found 125 species of galling insects on 80 host plant species. The increase of plant species richness explained 35% of the variation in galling insect richness, corroborating the plant species richness hypothesis. Most of the galling species occurred on trees, followed by shrubs, and herbs. However, the difference in mean number of galls was only statistically significant between herbs and trees, corroborating partially the plant structural complexity hypothesis. A significant relationship was observed between galling species richness and density of herbs, and shrubs, corroborating partially the resource concentration hypothesis. Galling insect richness showed a negative correlation with magnesium, potassium, and zinc on soil, corroborating the soil fertility hypothesis. The content of magnesium, potassium, iron and CTC (T) explained 72% of the variation in galling insect richness. Plant family size positively influenced galling insect richness, corroborating the plant family size hypothesis. Overall, the results corroborate the hypothesis that predicts that habitat stress is the main factor generating the patterns of galling insect richness in Brazilian savannas.

Journal ArticleDOI
30 Sep 2001
TL;DR: In this article, a three-phase line-interactive uninterruptible power supply (UPS) system with series-parallel active power line conditioning capabilities, using a synchronous reference frame (SRF) based controller, is presented.
Abstract: This paper presents a three-phase line-interactive uninterruptible power supply (UPS) system with series-parallel active power-line conditioning capabilities, using a synchronous reference frame (SRF) based controller, which allows an effective power factor correction, load harmonic current suppression and output voltage regulation. The three-phase UPS system is composed of two active power filter topologies. The first one is a series active power filter, which works as a sinusoidal current source in phase with the input voltage. The other is a parallel active power filter, which works as a sinusoidal voltage source in phase with the input voltage, providing to the load a regulated and sinusoidal voltage with low total harmonic distortion (THD). Operation of a three-phase phase-locked loop (PLL) structure, used in the proposed line-interactive UPS implementation, is presented and experimentally verified under distorted utility conditions. The control algorithm using SRF method and the active power flow through the UPS system are described and analytically studied. Design procedures, digital simulations and experimental results for a prototype are presented to verify the good performance of the proposed three-phase line-interactive UPS system.

Journal ArticleDOI
TL;DR: A detailed analysis of the correlation between structure and proinflammatory activity by Trypanosoma cruzi‐derived GPI anchors is provided and the implications in resistance and pathogenesis during the infection with T. cruzi are discussed.
Abstract: A strong activation of macrophages is observed during acute infection with Trypanosoma cruzi. Little is known, however, about the parasite molecules that are responsible for this early acti- vation of innate immunity. Recent studies have shown the stimulatory activity of protozoan-de- rived glycosylphosphatidylinositol (GPI) anchors on cultured macrophages. In this review, we pro- vide a detailed analysis of the correlation between structure and proinflammatory activity by T. cruzi- derived GPI anchors. We also cover the studies that have identified the Toll-like receptor 2 as a functional GPI receptor and have partially charac- terized signaling pathways triggered by T. cruzi- derived GPI anchors, which lead to the synthesis of proinflammatory cytokines in macrophages. Fi- nally, we discuss the implications of these findings in resistance and pathogenesis during the infection with T. cruzi. J. Leukoc. Biol. 70: 467-477; 2001.

Journal ArticleDOI
TL;DR: Although there was no significant association between 23S rDNA mutations and the vacA andcagA status, clarithromycin-susceptible strains more often contained mixed vacA genotypes, indicating the presence of multiple H. pylori strains.
Abstract: Helicobacter pylori strains from 299 patients were tested in six laboratories in different countries Macrolide susceptibility of the strains was determined by agar dilution (174%) or the epsilometer test (826%) Mutations in the 23S ribosomal DNA (rDNA) that are associated with macrolide resistance were analyzed by PCR and reverse hybridization (PCR-line probe assay [LiPA]) This method identifies A2115G, G2141A, A2142G, A2142C, A2142T, A2143G, and A2143C mutations in the 23S rDNA vacA s-region (s1a, s1b, s1c, and s2) and m-region (m1, m2a, and m2b) genotypes and cagA status were also determined using another PCR-LiPA system Of the 299 strains investigated by MIC testing, 130 (435%) were resistant and 169 (565%) were susceptible to clarithromycin Of the 130 resistant strains, 127 (977%) contained 23S rDNA mutations, whereas 167 (988%) of the 169 susceptible strains contained wild-type sequences The predominant mutations were A2143G (452%) and A2142G (333%) Twenty-eight (198%) strains contained multiple 23S rDNA mutations Only five resistant strains contained the A2142C mutation (three of these in combination with the A2142G mutation), and the A2115G, G2141A, A2142T, and A2143C mutations were not found MICs of clarithromycin for the A2142G mutant strains were significantly higher than MICs for the A2143G strains Although there was no significant association between 23S rDNA mutations and the vacA and cagA status, clarithromycin-susceptible strains more often contained mixed vacA genotypes, indicating the presence of multiple H pylori strains In conclusion, our data confirmed the very strong association between 23S rDNA mutations and macrolide resistance and showed that the PCR-LiPA permits accurate and reliable diagnosis of macrolide resistance in H pylori

Journal ArticleDOI
01 Jan 2001
TL;DR: The main goal of the STS curriculum is to provide scientific and technological literacy for students so they can act as citizens and participate on decision making on the perspective of social responsibility.
Abstract: The main goal of the STS curriculum is to provide scientific and technological literacy for students so they can act as citizens and participate on decision making on the perspective of social responsibility. This paper discusses this educational goal and provides a review of the literature about its implications for science education. It also reflects on the National High School Curriculum related to the same objectives.

Journal ArticleDOI
TL;DR: Leung et al. as mentioned in this paper compared managers from 24 nations/territories at the ecological or sample mean level, as opposed to the individual participant level, in order to draw more definitive conclusions about nation differences.
Abstract: There has been increasing interest in cross-national research that attempts to understand differences and similarities among employees from different cultures and nations. One of the basic issues of concern to organizational researchers is the health and well-being of employees, and it has been viewed as both a response to the work environment and as an affect-related antecedent of other employee outcomes such as job performance or turnover. Employee control beliefs and perceptions have been linked to well-being and play an important role (Ganster and Fusilier, 1989; Spector, 1982). Although there is a tremendous amount of research at the individual level relating control and other variables to well-being, most has been done in the USA and a handful of western nations, and most has targeted the individual employee. Our study compared managers from 24 nations/territories at the ecological or sample mean level (Leung and Bond, 1989), as opposed to the individual participant level, in order to draw more definitive conclusions about nation differences.

Journal ArticleDOI
TL;DR: In this paper, an analysis of age, metal abundance, and positional data on populous clusters in the Small Magellanic Cloud (SMC) with the ultimate aim of determining the line-of-sight (LOS) depth of the SMC by using these clusters as proxies is presented.
Abstract: We present an analysis of age, metal abundance, and positional data on populous clusters in the Small Magellanic Cloud (SMC) with the ultimate aim of determining the line-of-sight (LOS) depth of the SMC by using these clusters as proxies. Our data set contains 12 objects and is limited to clusters with the highest-quality data for which the ages and abundances are best known and can be placed on an inter- nally consistent scale. We have analyzed the variation of the clustersproperties with position on the sky and with line-of-sight depth. Based on this analysis, we draw the following conclusions: (1) The obser- vational data indicate that the eastern side of the SMC (facing the Large Magellanic Cloud) contains younger and more metal-rich clusters as compared with the western side. This is not a strong correlation because our data set of clusters is necessarily limited, but it is suggestive and warrants further study. (2) Depending on how the reddening is computed to our clusters, we —nd a mean distance modulus that ranges from to 18.82 ^ 0.05. (3) The intrinsic ^1 p LOS depth of the SMC (m ( M) 0 \ 18.71 ^ 0.06 populous clusters in our study is between D6 and D12 kpc, depending primarily on whether we adopt the Burstein & Heiles reddenings or those from Schlegel et al. (4) Viewing the SMC as a triaxial galaxy with declination, right ascension, and LOS depth as the three axes, we —nd axial ratios of approximately 1:2:4. Taken together, these conclusions largely agree with those of previous investigators and under- score the utility of populous star clusters as probes of the structure of the Small Magellanic Cloud.

Journal ArticleDOI
TL;DR: In this paper, the authors used Resonant Raman scattering (RRS) measurements made with a tunable laser to study the shape of the joint density of electronic states (JDOS) of isolated single-wall carbon nanotubes (SWNTs).
Abstract: Resonant Raman scattering (RRS) measurements made with a tunable laser provide a highly reliable technique to study the shape of the joint density of electronic states (JDOS) of isolated single-wall carbon nanotubes (SWNTs). RRS can be used to determine the energy value for the one-dimensional (1D) van Hove singularities of a SWNT with a precision better than 5 meV, thereby providing important information that could be used for subsequent measurements on this same SWNT. With RRS, the measured width of the JDOS is on the order of $\ensuremath{\sim}0.1\ensuremath{-}1.0\mathrm{meV},$ further demonstrating that SWNTs really provide a remarkably good model for 1D mesoscopic systems.

Proceedings ArticleDOI
01 Sep 2001
TL;DR: Experimental results show that the two-level cache is superior, and that it allows increasing the maximum number of queries processed per second by a factor of three, while preserving the response time.
Abstract: We present an e ective caching scheme that reduces the computing and I/O requirements of a Web search engine without altering its ranking characteristics. The novelty is a two-level caching scheme that simultaneously combines cached query results and cached inverted lists on a real case search engine. A set of log queries are used to measure and compare the performance and the scalability of the search engine with no cache, with the cache for query results, with the cache for inverted lists, and with the two-level cache. Experimental results show that the two-level cache is superior, and that it allows increasing the maximum number of queries processed per second by a factor of three, while preserving the response time. These results are new, have not been reported before, and demonstrate the importance of advanced caching schemes for real case search engines.

Journal ArticleDOI
TL;DR: In this paper, two series of zirconia-hydroxyapatite composites, Z4H6 and Z6H4 with 40 and 60 vol.% of the ZIRconia content respectively, were prepared by powder uniaxial pressing at 700 MPa and sintering in air at 1200-1500°C for 3 h.

Journal ArticleDOI
TL;DR: The results suggest that the regulatory roles of IFN-gamma and TNF-alpha on chemokine expression may play a crucial role in the modulation of the inflammatory response during T. cruzi infection and mediate resistance to infection.
Abstract: Infection with Trypanosoma cruzi causes a strong inflammatory reaction at the inoculation site and, later, in the myocardium. The present study investigates the role of cytokines as modulators of T. cruzi -induced chemokine expression in vivo and in vitro . In macrophage cultures, although the stimulation with interferon (IFN)-γ increases the expression of IP-10, it blocks KC expression. Tumor necrosis factor (TNF)-α, on the other hand, potentiates KC, IP-10, macrophage inflammatory protein-1α, and JE/monocyte chemotatic protein-1 expression. Interleukin-10 and transforming growth factor-β inhibited almost all chemokines tested. The role of IFN-γ and TNF-α in chemokine modulation during infection was investigated in T. cruzi -infected IFN-γ-deficient (GKO) or TNF-R1/p55-deficient (p55−/−) mice. The expression of chemokines detected in the inoculation site correlated with the infiltrating cell type observed. Although GKO mice had a delayed and intense neutrophilic infiltrate correlating with the expression of KC and macrophage inflammatory protein-2, none of the above was observed in p55−/− mice. The detection of infiltrating T cells, Mig, and IP-10 in the myocardium was observed in wild-type and p55−/−, but not in GKO mice. Together, these results suggest that the regulatory roles of IFN-γ and TNF-α on chemokine expression may play a crucial role in the modulation of the inflammatory response during T. cruzi infection and mediate resistance to infection.

Proceedings ArticleDOI
21 May 2001
TL;DR: An architecture for tightly coupled multi-robot coordination that is well suited to cooperative manipulation tasks is proposed and the experimental implementation and demonstration in a cooperative transportation task, in which two and three heterogeneous robots cooperate to carry a large object in an environment containing obstacles.
Abstract: Proposes an architecture for tightly coupled multi-robot coordination that is well suited to cooperative manipulation tasks. At all times, a robot is identified as a leader, while the others are designated as followers. The assignment of roles and the coordination between the robots is guaranteed by communication protocols and control algorithms. The key feature is the flexibility that allows changes in leadership and assignment of roles during the execution of a task. We describe the experimental implementation and demonstration in a cooperative transportation task, in which two and three heterogeneous robots cooperate to carry a large object in an environment containing obstacles.

Journal ArticleDOI
TL;DR: For instance, this article found that dyslexics performed significantly worse than both their chronological age (CA) and reading age (RA) controls in reading and reading ability at both age levels.
Abstract: This study tested the predictions of thephonological and double deficit hypotheses byexperimentally examining speech perception,phoneme awareness, lexical retrieval (serialand discrete), articulatory speed, and verbalSTM in school age child (N = 35) and adolescent(N = 36) dyslexics, and both chronological age(CA) and reading age (RA) controls. Theresults confirmed the findings of previousstudies of a deficit in phoneme awareness indevelopmental dyslexia. At both age levels,dyslexics performed significantly more poorlythan both their CA and RA controls. Althoughdeficits in the other processes investigated,particularly in rapid serial naming, were alsoapparent, they were not as clear-cut as thedeficit in phoneme awareness. In general,definite evidence of a deficit in rapid serialnaming was limited to the more severelyimpaired dyslexics. Furthermore, although rapidserial naming contributed independent variationto various literacy skills, its contributionwas modest relative to the contribution ofphoneme awareness, regardless of whether theliteracy skill relied more or less heavily onphonological or orthographic coding skills. Further analyses suggested that variation inrapid serial skill is particularly importantfor fluent reading of text, whereas phonemeawareness is particularly important for thedevelopment of the ability to read byphonologically recoding letters or groups ofletters in words into their phonological codes.This explains the relatively strongcontribution of phoneme awareness to readingand spelling ability in general. In sum, thephonological hypothesis offers a moreparsimonious account of the present resultsthan the double deficit hypothesis.

Journal ArticleDOI
TL;DR: In this paper, a method was developed for atom transfer radical polymerization (ATRP) synthesis of a nanocomposite consisting of dispersed, nanosized hard particles in a thermoplastic matrix.
Abstract: A method was developed for atom transfer radical polymerization (ATRP) synthesis of a nanocomposite consisting of dispersed, nanosized hard particles in a thermoplastic matrix. Octafunctional cubic silsesquioxanes were used as a platform to synthesize 8-arm star poly(methyl methacrylate) (PMMA) via ATRP. The cubic silsesquioxane, octakis(hydridodimethylsiloxy)octasilsesquioxane (Q8M8H), was converted to either octakis(2-bromo-2-methylpropionoxypropyldimethylsiloxy)octasilsesquioxane (OBPS) or the octaethylbenzyl chloride analogue. The bromo ester was successfully employed as an ATRP initiator using CuCl as catalyst, leading to formation of PMMA arms with controlled molecular weights and hence to nanocomposites with essentially complete control of dispersion and solids loading. The catalyst and initiator concentrations were demonstrated to affect the molecular weight distribution and the occurrence of star−star coupling caused by inevitable termination reactions.