Showing papers by "Universidade Federal de Minas Gerais published in 2007"

Studying Disorder in Graphite-Based Systems by Raman Spectroscopy

Abstract: Raman spectroscopy has historically played an important role in the structural characterization of graphitic materials, in particular providing valuable information about defects, stacking of the graphene layers and the finite sizes of the crystallites parallel and perpendicular to the hexagonal axis Here we review the defect-induced Raman spectra of graphitic materials from both experimental and theoretical standpoints and we present recent Raman results on nanographites and graphenes The disorder-induced D and D′ Raman features, as well as the G′-band (the overtone of the D-band which is always observed in defect-free samples), are discussed in terms of the double-resonance (DR) Raman process, involving phonons within the interior of the 1st Brillouin zone of graphite and defects In this review, experimental results for the D, D′ and G′ bands obtained with different laser lines, and in samples with different crystallite sizes and different types of defects are presented and discussed We also present recent advances that made possible the development of Raman scattering as a tool for very accurate structural analysis of nano-graphite, with the establishment of an empirical formula for the in- and out-of-plane crystalline size and even fancier Raman-based information, such as for the atomic structure at graphite edges, and the identification of single versus multi-graphene layers Once established, this knowledge provides a powerful machinery to understand newer forms of sp2 carbon materials, such as the recently developed pitch-based graphitic foams Results for the calculated Raman intensity of the disorder-induced D-band in graphitic materials as a function of both the excitation laser energy (Elaser) and the in-plane size (La) of nano-graphites are presented and compared with experimental results The status of this research area is assessed, and opportunities for future work are identified

Estudos de revisão sistemática: um guia para síntese criteriosa da evidência científica

Abstract: Systematic review studies: a guide for careful synthesis of the scientific evidence Introduction: Aggregation of research evidence to guide clinical practice is one of the main reasons for conducting studies that provide a synthesis of the literature, but it is not the only reason. Systematic reviews are designed to be methodical, explicit and replicable. Such studies may help to guide project development, by indicating new directions for further investigations and identifying which research methods have been used within a given area. Methods: Systematic reviews require straightforward questions, search strategy definition, establishment of study inclusion and exclusion criteria and careful analysis of the selected literature. The development process for reviews of this type includes characterization of each selected study, evaluation of their quality, identification of important concepts, comparison of statistical analyses used and conclusions regarding what the literature tells us about a specific intervention. Such reviews also suggest problems/questions that need further investigation. Systematic review studies follow the structure of original articles. Conclusion: Good systematic reviews are important resources, in the light of the accelerated growth of scientific information. These studies help in producing syntheses of the evidence available in the literature on specific interventions, and may help clinicians and researchers in their work process.

Localization systems for wireless sensor networks

Abstract: Monitoring applications define an important class of applications used in wireless sensor networks In these applications the network perceives the environment and searches for event occurrences (phenomena) by sensing different physical properties, such as temperature, humidity, pressure, ambient light, movement, and presence (for target tracking) In such cases the location information of both phenomena and nodes is usually required for tracking and correlation purposes In this work we summarize most of the concepts related to localization systems for WSNs as well as how to localize the nodes in these networks (which allows the localization of phenomena) By dividing the localization systems into three distinct components -distance/angle estimation, position computation, and localization algorithm - besides providing a didactic viewpoint, we show that these components can be seen as subareas of the localization problem that need to be analyzed and studied separately

Information fusion for wireless sensor networks: Methods, models, and classifications

Abstract: Wireless sensor networks produce a large amount of data that needs to be processed, delivered, and assessed according to the application objectives. The way these data are manipulated by the sensor nodes is a fundamental issue. Information fusion arises as a response to process data gathered by sensor nodes and benefits from their processing capability. By exploiting the synergy among the available data, information fusion techniques can reduce the amount of data traffic, filter noisy measurements, and make predictions and inferences about a monitored entity. In this work, we survey the current state-of-the-art of information fusion by presenting the known methods, algorithms, architectures, and models of information fusion, and discuss their applicability in the context of wireless sensor networks.

What is the Impact of International Remittances on Poverty and Inequality in Latin America

Abstract: Workers' remittances have become a major source of income for developing countries. However, little is still known about their impact on poverty and inequality. Using a large cross-country panel dataset, the authors find that remittances in Latin American and Caribbean (LAC) countries have increased growth and reduced inequality and poverty. These results are robust to the use of different instruments that attempt to correct for the potential endogeneity of remittances. Household survey-based estimates for 10 LAC countries confirm that remittances have negative albeit relatively small inequality and poverty-reducing effects, even after imputations for the potential home earnings of migrants.

Photon-blockade-induced Mott transitions and XY spin models in coupled cavity arrays

Abstract: We propose a physical system where photons could exhibit strongly correlated effects. We demonstrate how a Mott-insulator phase of atom-photon excitations (polaritons) can arise in an array of individually addressable coupled electromagnetic cavities when each of these cavities is coupled resonantly to a single two-level system (atom, quantum dot, or Cooper pair). This Mott phase is characterized by the same integral number of net polaritonic excitations with photon blockade providing the required repulsion between the excitations in each site. Detuning the atomic and photonic frequencies suppresses this effect and induces a transition to a photonic superfluid. Finally, on resonance the system can straightforwardly simulate the dynamics of many-body spin systems.

Angiotensin-(1-7) Through Receptor Mas Mediates Endothelial Nitric Oxide Synthase Activation via Akt-Dependent Pathways

Abstract: Angiotensin-(1-7) [Ang-(1-7)] causes endothelial-dependent vasodilation mediated, in part, by NO release. However, the molecular mechanisms involved in endothelial NO synthase (eNOS) activation by Ang-(1-7) remain unknown. Using Chinese hamster ovary cells stably transfected with Mas cDNA (Chinese hamster ovary-Mas), we evaluated the underlying mechanisms related to receptor Mas-mediated posttranslational eNOS activation and NO release. We further examined the Ang-(1-7) profile of eNOS activation in human aortic endothelial cells, which constitutively express the Mas receptor. Chinese hamster ovary-Mas cells and human aortic endothelial cell were stimulated with Ang-(1-7; 10(-7) mol/L; 1 to 30 minutes) in the absence or presence of A-779 (10(-6) mol/L). Additional experiments were performed in the presence of the phosphatidylinositol 3-kinase inhibitor wortmannin (10(-6) mol/L). Changes in eNOS (at Ser1177/Thr495 residues) and Akt phosphorylation were evaluated by Western blotting. NO release was measured using both the fluorochrome 2,3-diaminonaphthalene and an NO analyzer. Ang-(1-7) significantly stimulated eNOS activation (reciprocal phosphorylation/dephosphorylation at Ser1177/Thr495) and induced a sustained Akt phosphorylation (P<0.05). Concomitantly, a significant increase in NO release was observed (2-fold increase in relation to control). These effects were blocked by A-779. Wortmannin suppressed eNOS activation in both Chinese hamster ovary-Mas and human aortic endothelial cells. Our findings demonstrate that Ang-(1-7), through Mas, stimulates eNOS activation and NO production via Akt-dependent pathways. These novel data highlight the importance of the Ang-(1-7)/Mas axis as a putative regulator of endothelial function.

Comparison of general exercise, motor control exercise and spinal manipulative therapy for chronic low back pain: A randomized trial

Abstract: Practice guidelines recommend various types of exercise and manipulative therapy for chronic back pain but there have been few head-to-head comparisons of these interventions. We conducted a randomized controlled trial to compare effects of general exercise, motor control exercise and manipulative therapy on function and perceived effect of intervention in patients with chronic back pain. Two hundred and forty adults with non-specific low back pain 3months were allocated to groups that received 8weeks of general exercise, motor control exercise or spinal manipulative therapy. General exercise included strengthening, stretching and aerobic exercises. Motor control exercise involved retraining specific trunk muscles using ultrasound feedback. Spinal manipulative therapy included joint mobilization and manipulation. Primary outcomes were patient-specific function (PSFS, 3-30) and global perceived effect (GPE, -5 to 5) at 8weeks. These outcomes were also measured at 6 and 12months. Follow-up was 93% at 8weeks and 88% at 6 and 12months. The motor control exercise group had slightly better outcomes than the general exercise group at 8weeks (between-group difference: PSFS 2.9, 95% CI: 0.9-4.8; GPE 1.7, 95% CI: 0.9-2.4), as did the spinal manipulative therapy group (PSFS 2.3, 95% CI: 0.4-4.2; GPE 1.2, 95% CI: 0.4-2.0). The groups had similar outcomes at 6 and 12months. Motor control exercise and spinal manipulative therapy produce slightly better short-term function and perceptions of effect than general exercise, but not better medium or long-term effects, in patients with chronic non-specific back pain.

Urban as a determinant of health

Abstract: Cities are the predominant mode of living, and the growth in cities is related to the expansion of areas that have concentrated disadvantage. The foreseeable trend is for rising inequities across a wide range of social and health dimensions. Although qualitatively different, this trend exists in both the developed and developing worlds. Improving the health of people in slums will require new analytic frameworks. The social-determinants approach emphasizes the role of factors that operate at multiple levels, including global, national, municipal, and neighborhood levels, in shaping health. This approach suggests that improving living conditions in such arenas as housing, employment, education, equality, quality of living environment, social support, and health services is central to improving the health of urban populations. While social determinant and multilevel perspectives are not uniquely urban, they are transformed when viewed through the characteristics of cities such as size, density, diversity, and complexity. Ameliorating the immediate living conditions in the cities in which people live offers the greatest promise for reducing morbidity, mortality, and disparities in health and for improving quality of life and well being.

Regional climate change over eastern Amazonia caused by pasture and soybean cropland expansion

Abstract: [1] Field observations and numerical studies revealed that large scale deforestation in Amazonia could alter the regional climate significantly, projecting a warmer and somewhat drier post-deforestation climate. In this study we employed the CPTEC-INPE AGCM to assess the effects of Amazonian deforestation on the regional climate, using simulated land cover maps from a business-as-usual scenario of future deforestation in which the rainforest was gradually replaced by degraded pasture or by soybean cropland. The results for eastern Amazonia, where changes in land cover are expected to be larger, show increase in near-surface air temperature, and decrease in evapotranspiration and precipitation, which occurs mainly during the dry season. The relationship between precipitation and deforestation shows an accelerating decrease of rainfall for increasing deforestation for both classes of land use conversions. Continued expansion of cropland in Amazonia is possible and may have important consequences for the sustainability of the region's remaining natural vegetation.

Chemokines in Oral Inflammatory Diseases: Apical Periodontitis and Periodontal Disease

Abstract: The inflammatory oral diseases are characterized by the persistent migration of polymorphonuclear leukocytes, monocytes, lymphocytes, plasma and mast cells, and osteoblasts and osteoclasts. In the last decade, there has been a great interest in the mediators responsible for the selective recruitment and activation of these cell types at inflammatory sites. Of these mediators, the chemokines have received particular attention in recent years. Chemokine messages are decoded by specific receptors that initiate signal transduction events, leading to a multitude of cellular responses, including chemotaxis and activation of inflammatory and bone cells. However, little is known about their role in the pathogenesis of inflammatory oral diseases. The purpose of this review is to summarize the findings regarding the role of chemokines in periapical and periodontal tissue inflammation, and the integration, into experimental models, of the information about the role of chemokines in human diseases.

Polymyxin B as inhibitor of LPS contamination of Schistosoma mansoni recombinant proteins in human cytokine analysis

Abstract: Recombinant proteins expressed in Escherichia coli vectors are generally contaminated with endotoxin. In this study, we evaluated the ability of Polymyxin B to neutralize the effect of LPS present as contaminant on Schistosoma mansoni recombinant proteins produced in E. coli in inducing TNF-α and IL-10. Peripheral blood mononuclear cells from individuals chronically infected with S. mansoni were stimulated in vitro with recombinant Sm22.6, Sm14 and P24 antigens (10 μg/mL) in the presence of Polymyxin B (10 μg/mL). The levels of cytokines were measured using ELISA. There was greater than 90 % reduction (p < 0.05) in the levels of TNF-α and IL-10 when Polymyxin B was added to the cultures stimulated with LPS. In cultures stimulated with S. mansoni recombinant proteins in the presence of Polymyxin B, a reduction in the levels of TNF-α and IL-10 was also observed. However, the percentage of reduction was lower when compared to the cultures stimulated with LPS, probably because these proteins are able to induce the production of these cytokines by themselves. This study showed that Polymyxin B was able to neutralize the effect of endotoxin, as contaminant in S. mansoni recombinant antigens produced in E. coli, in inducing TNF-α and IL-10 production.

Plant communities on ironstone outcrops: a diverse and endangered Brazilian ecosystem

Abstract: Mountain areas are recognized centres of endemism and diversity on account of their isolation and altitudinal diversity. In tropical regions, mountain tops usually stand as islands of xeric vegetation among mesophytic assemblages. Unlike the vegetation growing on other rock outcrops lithologies, such as inselbergs (granite/gneiss) or campos rupestres (quartz/arenite), ironstone outcrop plant communities still lack systematic studies in Brazil. These outcrops (locally known as canga) share most of the characteristics of other rock outcrops, such as isolation and edapho-climatic harshness, but differ in that they are the object of opencast mining, and thus subjected to irrecoverable degradation. In addition, they are expected to harbour metal-tolerant and hyperaccumulator plant species. A botanical survey of two ironstone outcrop locations in the most important mining region of southeastern Brazil, the Iron Quadrangle, revealed a high within-site (138 and 160 species per site), and between-site diversity (only 27% of common species), totaling 64 families and 234 species among basal families and eudicots (154 species), monocots (68 species), and ferns (12 species). Canga crusts are rich in dicots, several of which play an important role in community structuring, together with the more usual monocot aggregations. Distinct plant communities are found associated to different microhabitats within the iron crust, depending primarily on the amount of soil and moisture retention in the different microtopographies. The environmental uniqueness, high diversity, lack of studies and rapid destruction of these ecosystems pose an immediate challenge for their conservation.

Consumer attitudes toward counterfeits: a review and extension

Abstract: – The purpose of this research is to propose and test a model that integrates the main predictors of consumers' attitude and behavioral intentions toward counterfeits; to help companies understand the main factors influencing consumer behavior toward counterfeits and create effective anti‐piracy strategies., – An integrated model is proposed following the studies by Ang et al. and Huang et al. A survey with 400 consumers was conducted in the Brazilian market and the Structural Equation Modeling technique was used to test the hypothesized relationships., – The main contribution of the paper is to show that consumer intentions to buy counterfeited products are dependent on the attitudes they have toward counterfeits, which in turn are more influenced by perceived risk, whether consumers have bought a counterfeit before, subjective norm, integrity, price‐quality inference and personal gratification. The paper reinforces the mediator role of attitude in the relationship between these antecedents and behavioral intentions. Moreover, previous experience with counterfeits consumption does not have a direct effect on behavioral intentions, but only an indirect effect through attitude., – The paper contributes to inform policy makers and managers of brands about the main predictors of consumer's attitudes toward counterfeits. In this way, ads intended to discourage consumption of counterfeits could use the perceived risk as the main message appeal., – This paper investigates the key antecedents and consequences of consumer attitudes toward counterfeits by integrating and testing two recent models dealing with this subject in the marketing literature.

Probing the electronic structure of bilayer graphene by Raman scattering

Abstract: The electronic structure of bilayer graphene is investigated from a resonant Raman study of the ${G}^{\ensuremath{'}}$ band using different laser excitation energies. The values of the parameters of the Slonczewski-Weiss-McClure model for bilayer graphene are obtained from the analysis of the dispersive behavior of the Raman features, and reveal the difference of the effective masses of electrons and holes. The splitting of the two TO phonon branches in bilayer graphene is also obtained from the experimental data. Our results have implications for bilayer graphene electronic devices.

Activation of TLR2 and TLR4 by Glycosylphosphatidylinositols Derived from Toxoplasma gondii

Abstract: GPIs isolated from Toxoplasma gondii , as well as a chemically synthesized GPI lacking the lipid moiety, activated a reporter gene in Chinese hamster ovary cells expressing TLR4, while the core glycan and lipid moieties cleaved from the GPIs activated both TLR4- and TLR2-expressing cells. MyD88, but not TLR2, TLR4, or CD14, is absolutely needed to trigger TNF-α production by macrophages exposed to T. gondii GPIs. Importantly, TNF-α response to GPIs was completely abrogated in macrophages from TLR2/4-double-deficient mice. MyD88 −/− mice were more susceptible to death than wild-type (WT), TLR2 −/− , TLR4 −/− , TLR2/4 −/− , and CD14 −/− mice infected with the ME-49 strain of T. gondii . The cyst number was higher in the brain of TLR2/4 −/− , but not TLR2 −/− , TLR4 −/− , and CD14 −/− , mice, as compared with WT mice. Upon infection with the ME-49 strain of T. gondii , we observed no decrease of IL-12 and IFN-γ production in TLR2-, TLR4-, or CD14-deficient mice. Indeed, splenocytes from T. gondii -infected TLR2 −/− and TLR2/4 −/− mice produced more IFN-γ than cells from WT mice in response to in vitro stimulation with parasite extracts enriched in GPI-linked surface proteins. Together, our results suggest that both TLR2 and TLR4 receptors may participate in the host defense against T. gondii infection through their activation by the GPIs and could work together with other MyD88-dependent receptors, like other TLRs or even IL-18R or IL-1R, to obtain an effective host response against T. gondii infection.

Magnetospheric accretion-ejection processes in the classical T Tauri star AA Tauri

Abstract: Context. Accretion and ejection are complex and related processes that vary on various timescales in young stars. Aims. We intend to investigate the accretion and outflow dynamics and their interaction from observations of the classical T Tauri star AA Tau. Methods. From a long time series of high resolution (R = 115 000) HARPS spectra and simultaneous broad-band photometry, we report new evidence for magnetospheric accretion as well as ejection processes in the nearly edge-on classical T Tauri star AA Tau. Results. AA Tau’s light curve is modulated with a period of 8.22 d. The recurrent luminosity dips are due to the periodic occultation of the central star by the magnetically-warped inner disk edge located at about 9 R� . Balmer line profiles exhibit a clear rotational modulation of high-velocity redshifted absorption components with a period of 8.22 days as well, with a maximum strength when the main accretion funnel flow passes through the line of sight. At the same time, the luminosity of the system decreases by about 1 mag, indicative of circumstellar absorption of the stellar photosphere by the magnetically-warped, corotating inner disk edge. The photospheric and He I radial velocities also exhibit periodic variations, and the veiling is modulated by the appearance of the accretion shock at the bottom of the accretion funnel. Diagnostics of hot winds and their temporal behaviour are also presented. Conclusions. The peculiar geometry of the young AA Tau system (nearly edge-on) allows us to uniquely probe the acretion-ejection region close to the star. We find that most spectral and photometric diagnostics vary as expected from models of magneticallychannelled accretion in young stars, with a large scale magnetosphere tilted by 20 ◦ onto the star’s spin axis. We also find evidence for time variability of the magnetospheric accretion flow on a timescale of a few rotational periods.

Third and fourth optical transitions in semiconducting carbon nanotubes.

Abstract: We have studied the optical transition energies of single-wall carbon nanotubes over broad diameter (0.7–2.3 nm) and energy (1.26 –2.71 eV) ranges, using their radial breathing mode Raman spectra. We establish the diameter and chiral angle dependence of the poorly studied third and fourth optical transitions in semiconducting tubes. Comparative analysis between the higher lying transitions and the first and second transitions show two different diameter scalings. Quantum mechanical calculations explain the result showing strongly bound excitons in the first and second transitions and a delocalized electron wave function in the third transition. In carbon nanotubes [1], quantum confinement is responsible for 1D van Hove singularities in the electronic density of states and unusually strong many-body (electron-electron and electron-hole) interactions [2]. Current understanding of the photophysical properties of semiconducting carbon nanotubes [2 –7] are based mostly on experimental results for the first (E S ) and second (E S ) optical transitions (S superscript stands for semiconducting, while M will be used for metallic tubes), based on a set of fewer than 40 SWNTs (characterized by their (n, m) indices [1]) in the diameter range from 0.7 to 1.3 nm [8– 13]. Efforts have been made to extend these results to larger diameter tubes, and to establish the third (E S ) and fourth (E S ) transitions [14,15]. E S and E S are important for the optics of large diameter semiconducting single-wall carbon nanotubes (SWNTs), since for dt > 1: 3n m, E S is already in the infrared range [8–11]. Here we measure the optical properties of SWNTs over broad diameter (0.7–2.3 nm) and energy (1.26 –2.71 eV) ranges. We probe over 200 different SWNT species, about 378 different optical transition energies, going up to the fourth optical transition of semiconducting SWNTs, thus establishing the (n, m) dependence of the poorly studied E S and E S transitions. Surprisingly, we find that E S and E S follow a different (blue-shifted) diameter scaling when compared with E S and E S . These results are supported by electronic structure calculations showing that E S and E S are described by bound exciton states, whereas the E S transitions correspond to a delocalized exciton or to an unbound electron-hole pair. The sample consists of as-grown vertically aligned SWNTs, synthesized by the chemical vapor deposition method from alcohol, on top of a quartz substrate. Transmission Electron Microscopy shows a rather homogeneous sample formed by isolated SWNTs and very small

Impulsive behavior in adults with attention deficit/ hyperactivity disorder: Characterization of attentional, motor and cognitive impulsiveness

Abstract: Attention-deficit/hyperactivity disorder (ADHD) is characterized by inattention and/or hyperactivity/impulsivity. Impulsivity persists in adults with ADHD and might be the basis of much of the impairment observed in the daily lives of such individuals. The objective of this study was to address the presence, and more importantly, the three dimensions of impulsivity: attentional, non-planning and motor, in how they may relate to neuropsychological mechanisms of impulse control. We studied a sample of 50 adults with ADHD and 51 healthy comparison controls using the Barratt Impulsivity Scale Version 11 (BIS), and neuropsychological tasks, namely the Continuous Performance Task (CPT-II) and the Iowa Gambling Task (IGT). The ADHD group showed more signs of impulsivity on the three dimensions of BIS, committed more errors of omission and commission on the CPT-II, and made more disadvantageous choices on the IGT. These results support the existence of deficits related to three components of impulsivity: motor, cognitive, and attentional among adults with ADHD. Most importantly, this study also highlights the complementary nature of self-report questionnaires and neuropsychological tasks in the assessment of impulsivity in ADHD adults. (JINS, 2007, 13, 693–698.)

The impact of remittances on poverty and human capital: evidence from Latin American household surveys.

Abstract: This paper explores the impact of remittances on poverty, education, and health in 11 Latin American countries using nationally representative household surveys and making an explicit attempt to account for one of the inherent costs associated with migration-the potential income that the migrant may have made at home. The main findings of the study are the following: (1) regardless of the counterfactual used remittances appear to lower poverty levels in most recipient countries; (2) yet despite this general tendency, the estimated impacts tend to be modest; and (3) there is significant country heterogeneity in the poverty reduction impact of remittances' flows. Among the aspects that have been identified in the paper that may lead to varying outcomes across countries are the percentage of households reporting remittances income, the share of remittances of recipient households belonging to the lowest quintiles of the income distribution, and the relative importance of remittances flows with respect to GDP. While remittances tend to have positive effects on education and health, this impact is often restricted to specific groups of the population.

Raman Spectroscopy of Carbon Nanotubes in 1997 and 2007

Abstract: Over the last 10 years, carbon nanotubes have offered a unique system for the study of Raman spectra in one-dimensional systems, and at the same time Raman spectroscopy has provided a widely used and powerful tool for the characterization of single walled carbon nanotubes (SWNTs). The 10 year history of Raman scattering in SWNTs is reviewed here and future prospects for the field are discussed.

Angiotensin-(1-7) counterregulates angiotensin II signaling in human endothelial cells.

Abstract: Angiotensin (Ang)-(1-7), acting through the Mas receptor, opposes the actions of Ang II. Molecular mechanisms for this are unclear. Here we sought to determine whether Ang-(1-7) influences Ang II signaling in human endothelial cells, focusing specifically on Src homology 2-containing inositol phosphatase 2 (SHP-2) and its interaction with c-Src. Ang II-induced phosphorylation of c-Src, extracellular signal regulated kinase (ERK)1/2, and SHP-2 and activation of NAD(P)H oxidase were assessed in the absence and presence of Ang-(1-7) (10(-6) mol/L, 15 minutes) by immunoblotting and lucigenin-enhanced chemiluminescence, respectively. (D-Ala(7))-Ang I/II (1-7) (Ang fragment 1-7 receptor antagonist) was used to block Ang-(1-7) effects. Association between SHP-2 and c-Src was assessed by immunoprecipitation/immunoblotting studies. Ang II significantly increased activation of c-Src, ERK1/2, and NAD(P)H oxidase and reduced phosphorylation of SHP-2 (P<0.05) in human endothelial cells. These effects were abrogated in cells pre-exposed to Ang-(1-7). Ang fragment 1-7 receptor antagonist pretreatment blocked the negative modulatory actions of Ang-(1-7) on Ang II-induced signaling. Ang-(1-7) alone did not significantly alter phosphorylation of c-Src, ERK1/2, and SHP-2 and had no effect on basal activity of NAD(P)H oxidase. SHP-2 and c-Src were physically associated in the basal state. This association was increased by Ang-(1-7) and blocked by Ang fragment 1-7 receptor antagonist. Our findings demonstrate that, in human endothelial cells, Ang-(1-7) negatively modulates Ang II/Ang II type 1 receptor-activated c-Src and its downstream targets ERK1/2 and NAD(P)H oxidase. We also show that SHP-2-c-Src interaction is enhanced by Ang-(1-7). These phenomena may represent a protective mechanism in the endothelium whereby potentially deleterious effects of Ang II are counterregulated by Ang-(1-7).

Measuring the absolute Raman cross section of nanographites as a function of laser energy and crystallite size

Abstract: In this paper, the dependence of the differential Raman cross section $\ensuremath{\beta}$ of the $D$, $G$, ${D}^{\ensuremath{'}}$, and ${G}^{\ensuremath{'}}$ bands of nanographites on the excitation laser energy and also on the crystallite size is reported. We show that ${\ensuremath{\beta}}_{G}$ is proportional to the fourth power of the excitation laser energy $({E}_{l})$, as predicted by the Raman scattering theory. For the bands which arise from the double-resonance mechanism ($D$, ${D}^{\ensuremath{'}}$, and ${G}^{\ensuremath{'}}$), the differential cross section does not depend on ${E}_{l}$, explaining the strong dependence of the ratio ${I}_{D}∕{I}_{G}$ on the excitation laser energy ${E}_{l}$ used in the Raman experiment. The ${L}_{a}$ dependence of $D$ and ${D}^{\ensuremath{'}}$ band differential cross sections is measured, confirming that the proportionality ${I}_{D}∕{I}_{G}\ensuremath{\propto}{L}_{a}^{\ensuremath{-}1}$ originates from the strong dependence of ${\ensuremath{\beta}}_{D}$ on the inverse of the crystallite size. In the ${G}^{\ensuremath{'}}$ band case, the data show that its differential cross section increases with the increasing crystallite size ${L}_{a}$, following an opposite behavior when compared with the disorder induced $D$ and ${D}^{\ensuremath{'}}$ bands. An analysis on the dependence of the full width at half maximum $(\ensuremath{\Gamma})$ of the $D$, $G$, ${D}^{\ensuremath{'}}$, and ${G}^{\ensuremath{'}}$ bands on the crystallite size ${L}_{a}$ of nanographites is performed, showing that the phonon lifetime is proportional to the crystallite size.

A escola "faz" as juventudes? Reflexões em torno da socialização juvenil

Abstract: This text discusses the relationships between schooling and youth and the place of schools in the socialization of contempo- rary youth, especially in what regards young people from lower

Exciton Photophysics of Carbon Nanotubes

Abstract: The goal of this chapter is to review the importance of excitons to single-wall carbon nanotube (SWNT) optics. We have developed the presentation for both researchers in the SWNT field who want to learn more about the unusual aspects of SWNT exciton photophysics and researchers more knowledgeable about the physics of excitons, but not about SWNT physics. Excitons in SWNTs are special because graphite has two energy bands at the Fermi energy related to time-reversal symmetry and because SWNTs are actually one dimensional. This review discusses both theoretical and experimental points of view, thus aiming to provide a summary of the most important work in the field, as well as to identify open questions.