Electronic Microscopy Laboratory

Campinas, Brazil

Electronic Microscopy Laboratory

Campinas, Brazil
Time filter
Source Type

Goncalves R.V.,University of Sao Paulo | Vono L.L.R.,University of Sao Paulo | Wojcieszak R.,CNRS Laboratory of Catalysis and Solid State Chemistry | Dias C.S.B.,Brazilian Synchrotron Light Laboratory (LNLS) | And 3 more authors.
Applied Catalysis B: Environmental | Year: 2017

The transformation of CO2 into CO through the reverse water gas shift (RWGS) reaction is very sensitive to the metal particle size and metal-support interactions. Indeed, large metallic particles or aggregates tend to produce more methane than CO. In this context, magnetron sputtering deposition was explored here for the preparation of highly dispersed nickel catalyst supported on silica. The Ni catalyst prepared for 30 min of sputtering time contains 2.4 wt% of Ni, small metal particles size (2.3 nm) and controlled composition (77% Ni, 23% Ni oxides). In-situ XANES under RWGS reaction conditions indicates reduction of nickel in the temperature range from 250 to 500 °C. The conversion of CO2 into CO through the RWGS reaction was close to the thermodynamic equilibrium values for 1:1 and 1:4 (CO2:H2) gas composition at temperature as high as 800 °C. CO was produced continuously for 40 h at 660 °C without significant drop of activity. The overall catalytic performance was superior to that of a classical catalyst prepared by incipient wetness impregnation, as evidenced by the higher activity at T > 600 °C and stability for a long time on stream. © 2017 Elsevier B.V.

Stroppa D.G.,Electronic Microscopy Laboratory | Stroppa D.G.,University of Campinas | Zagonel L.F.,Electronic Microscopy Laboratory | Montoro L.A.,Electronic Microscopy Laboratory | And 3 more authors.
ChemPhysChem | Year: 2012

This work presents an overview of high-resolution scanning transmission electron microscopy (HRSTEM) techniques and exemplifies the novel quantitative characterization possibilities that have emerged from recent advances in these methods. The synergistic combination of atomic resolution imaging and spectroscopy provided by HRSTEM is highlighted as a unique feature that can provide a comprehensive analytical description of material properties at the nanoscale. State-of-the-art high-angle annular dark field and annular bright field examples are depicted as well as the use of X-ray energy-dispersive spectroscopy and electron energy-loss spectroscopy for probing samples properties at the atomic scale. In addition, promising techniques such as cathodoluminescence, confocal HRSTEM, and diffraction mapping are introduced. The presented examples and results indicate that HRSTEM-related techniques are fundamental tools for comprehensive assessment of properties at the atomic scale. Probing atoms: An overview of high-resolution scanning transmission electron microscopy (HRSTEM) techniques is given (see picture). Current advances suggest that HRSTEM-related techniques are fundamental tools for comprehensive assessment of properties at the atomic scale. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Khaleel N.,St Johns Medical College | Ravindranath R.,St Johns Medical College | Chandrasekhar Sagar B.K.,Electronic Microscopy Laboratory | Andrade C.,National Institute of Mental Health and Neuro Sciences
Indian Journal of Psychiatry | Year: 2013

Background: In animal models, stress and depression are associated with excitatory changes in the amygdala; this aberrant neuroplasticity may represent increased fear learning, explaining the anxiety, fear, and related symptoms that characterize clinical depression. Materials and Methods: In a pilot investigation, we treated adult, male, Wistar rats with sham electroconvulsive shocks (ECS; n=3), low-dose ECS (10 mC; n=3), and high-dose ECS (60 mC; n=3). The rats were sacrificed 1 month after the last of 6 once-daily ECS and, after dissection, sections of the basolateral amygdala were examined using transmission electron microscopy under low (×11,000) and high (×30,000) magnification. Results: In each group, 4 fields were examined under low magnification and 6 fields under high magnification. The number of excitatory synapses and the ratio of excitatory to inhibitory synapses were both numerically lower with ECS than with sham ECS, and the effect was stronger in the high-dose ECS group (statistical analyses were not performed because this was a pilot study). Conclusions: By reducing the number of excitatory synapses and the ratio of excitatory to inhibitory synapses, ECT (especially high-dose ECT) may reduce stress-induced excitatory changes in the amygdala. These changes may help explain a part of the benefits observed with ECT in conditions such as depression and post-traumatic stress disorder.

Nista S.V.G.,University of Campinas | Bettini J.,Electronic Microscopy Laboratory | Mei L.H.I.,University of Campinas
Carbohydrate Polymers | Year: 2015

Electrospinning of mucoadhesive membranes is a new and promising field of investigation in the pharmaceutical and biomedical area. The present study explored the electrospinning of two mucoadhesive polymers, chitosan and alginate, to form a core-shell type nanofibers for future applications as controlled drug delivery. Due to the charged functional groups present in these natural polysaccharides, they can complex to yield various nanodevices to be used in controlled release of several active ingredients. In this work, the core-shell type coaxial nanofibers formation was evidenced by the aid of transmission electron microscopy (TEM). Other characterization techniques as scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Infrared spectroscopy (FTIR) and X-ray diffraction (XRD), strongly suggest the formation of different molecular structures of the membranes obtained by the complexation of chitosan and alginate. Swelling rate and weight loss tests followed by SEM analyses confirmed that the nanofiber structure of these membranes were kept even after incubating them for 24 h in water. The results of this work confirmed that core-shell nanofibers made of chitosan and alginate polycomplex is possible to be obtained with success. © 2015 Elsevier Ltd. All rights reserved.

Ospina C.A.,Brazilian Center for Physical Research | Ospina C.A.,Electronic Microscopy Laboratory | Terra J.,Brazilian Center for Physical Research | Ramirez A.J.,Electronic Microscopy Laboratory | And 3 more authors.
Colloids and Surfaces B: Biointerfaces | Year: 2012

High-resolution transmission electron microscopy (HRTEM) and ab initio quantum-mechanical calculations of electronic structure were combined to investigate the structure of the hydroxyapatite (HA) (0. 1. 0) surface, which plays an important role in HA interactions with biological media. HA was synthesized by in vitro precipitation at 37 °C. HRTEM images revealed thin elongated rod nanoparticles with preferential growth along the [0. 0. 1] direction and terminations parallel to the (0. 1. 0) plane. The focal series reconstruction (FSR) technique was applied to develop an atomic-scale structural model of the high-resolution images. The HRTEM simulations identified the coexistence of two structurally distinct terminations for (0. 1. 0) surfaces: a rather flat Ca(II)-terminated surface and a zig-zag structure with open OH channels. Density functional theory (DFT) was applied in a periodic slab plane-wave pseudopotential approach to refine details of atomic coordination and bond lengths of Ca(I) and Ca(II) sites in hydrated HA (0. 1. 0) surfaces, starting from the HRTEM model. © 2011 Elsevier B.V.

Mogili N.V.V.,University of Limerick | Mogili N.V.V.,Electronic Microscopy Laboratory | Tanner D.A.,University of Limerick | Nakahara S.,University of Limerick
Strain | Year: 2016

Strained superlattices (SSLs) are typically found inside the p-n junction area of semiconductor devices and consist of very thin alternating layers of different material. There exists a small lattice mismatch between these materials which results in localised strain, as in the case of germanium-silicon/silicon SSLs. Strain measurements using a convergent beam electron diffraction (CBED) technique inside a transmission electron microscope (TEM) have indicated that the strain measured normal to these germanium-silicon/silicon SSLs varies almost sinusoidally, in spite of theoretical predictions which indicate a much sharper change in strain between these layers. A theoretical formulation involving an elasticity solution has been developed to predict the strain inside these SSL structures. The comparison of theoretical and experimental results clearly quantifies the effect of beam size on the spatial resolution of CBED measurements. Given that beam size is critically dependent on the spot size of the beam, the convergence angle, the specimen thickness and the position of the focused plane, these parameters are all clearly accounted for in the theoretical predictions. © 2016 Wiley Publishing Ltd.

Darouich S.,Electronic Microscopy Laboratory | Goucha R.,Charles Nicolle Hospital | Jaafoura M.H.,Electronic Microscopy Laboratory | Zekri S.,Electronic Microscopy Laboratory
Ultrastructural Pathology | Year: 2011

Membranoproliferative glomerulonephritis with isolated C3 deposits (MPGNC3) is an uncommon condition characterized by overt glomerular C3 deposits in the absence of immunoglobulins and intramembranous dense deposits. Here the authors describe the clinical and morphological features of primary MPGNC3 in a 13-year-old boy and critically review the previously published cases. The patient presented with nephrotic syndrome and microscopic hematuria. Blood tests revealed very low circulating C3 levels. The renal biopsy exhibited subendothelial, subepithelial, and mesangial deposits, with C3 but not immunoglobulins seen on immunofluorescence. This case and the review of the literature indicate that the serum complement profile with decreased levels of C3 and normal levels of classical pathway components together with glomerular deposits containing exclusively complement C3 is highly suggestive of alternative pathway activation. The diagnosis of acquired and/or genetic complement abnormalities in some cases supports that complement dysregulation is implicated in the pathogenesis of MPGNC3. Such data show great promise to provide new therapy strategies based on modulation of the complement system activity. Copyright © 2011 Informa Healthcare USA, Inc.

Darouich S.,Electronic Microscopy Laboratory | Darouich S.,Charles Nicolle Hospital | Goucha R.,Charles Nicolle Hospital | Jaafoura M.H.,Electronic Microscopy Laboratory | And 3 more authors.
Ultrastructural Pathology | Year: 2011

Obesity-related glomerulopathy (ORG) is a secondary form of focal segmental glomerulosclerosis (FSGS) occurring in obese patients with a body-mass index higher than 30 kg/m 2. It is typically manifested by nephrotic-range proteinuria without full nephrotic syndrome, and progressive renal insufficiency. Characteristic morphologic features include the consistent presence of glomerulomegaly, predominance of perihilar variant of FSGS, and the relatively mild fusion of visceral epithelial cell foot processes. The concept of podocyte depletion as a driver of the glomerular scarring in obesity-associated FSGS is well documented. The underlying mechanisms are likely to be related in part to the oxidative stress and the impairment of the integrity of the slit diaphragm and cell adhesion resulting mainly from angiotensin II and transforming growth factor-β. These proapoptotic cytokines are upregulated in obesity in response to insulin resistance, compensatory hyperinsulinemia and glomerular hyperfiltration-hypertension mediated mechanical stress. This review is designed to discuss the clinicopathologic features of obesity-associated FSGS, with a focus on the podocyte injury, which is involved in the onset and progression of the glomerulosclerotic process. Ultrastructural glomerular lesions are documented. © 2011 Informa Healthcare USA, Inc.

Anderson S.R.,Electronic Microscopy Laboratory | Esposito D.,Protein Expression Laboratory | Gillette W.,Protein Expression Laboratory | Zhu J.Y.,U.S. Department of Agriculture | And 2 more authors.
Tappi Journal | Year: 2014

Traditional cellulose nanocrystal (CNC) production methods use harsh chemicals, are energetically expensive, and result in a hydrophilic sulfate surface chemistry with limited utility. Enzymatic production of CNCs is a less expensive alternative production method that eliminates the need for harsh chemicals and requires much less energy for mechanical fibrillation and heating. Furthermore, enzymes that selectively degrade the amorphous regions of cellulose fibers, and do not significantly digest the crystalline areas, result in CNCs that retain a hydroxyl group surface chemistry. Retention of hydroxyl groups allows for easier chemical manipulation, and thus an expanded commercial potential. Here we show that cellulase from Aspergillus niger is capable of producing CNC and microfibrillated cellulose (MFC) from well-solubilized kraft pulp feedstock with minimal processing, and that a chimeric cellulase partially digests kraft pulp and live wood feedstock. Additionally, we show that as a feedstock source, milled pulp from bug-killed dead and downed trees has significantly reduced energy requirements to process the feedstock into elementary fibers and MFCs when compared to live wood feedstock sources.

PubMed | Environmental Toxicology Laboratory, Cell Biology Laboratory, Jagiellonian University and Electronic Microscopy Laboratory
Type: Journal Article | Journal: Particle and fibre toxicology | Year: 2016

There is growing evidence that exposure to titanium dioxide nanoparticles (TiO2 NPs) could be harmful. Previously, we have shown that TiO2 NPs induces endothelial cell dysfunction and damage in glial cells. Considering that inhaled particles can induce systemic effects and the evidence that nanoparticles may translocate out of the lungs, we evaluated whether different types of TiO2 NPs can induce the expression of receptors for adhesion molecules on monocytes (U937 cell line). We evaluated the role of reactive oxygen spices (ROS) on these effects.The expression of receptors for early (sLe(x) and PSGL-1) and late (LFA-1, VLA-4 and V3) adhesion molecules was evaluated in U937 cells on a time course (3-24h) using a wide range of concentrations (0.001-100g/mL) of three types of TiO2 NPs (<25nm anatase, 50nm anatase-rutile or<100nm anatase). Cells exposed to TNF were considered positive controls, and unexposed cells, negative controls. In some experiments we added 10 molar of N-acetylcysteine (NAC) to evaluate the role of ROS.All tested particles, starting at a concentration of 0.03g/mL, induced the expression of receptors for early and late adhesion molecules. The largest increases were induced by the different molecules after 3h of exposure for sLe(x) and PSGL-1 (up to 3-fold of the positive controls) and after 18h of exposure for LFA-1, VLA-4 and V3 (up to 2.5-fold of the positive controls). Oxidative stress was observed as early as 10min after exposure, but the maximum peak was found after 4h of exposure. Adhesion of exposed or unexposed monocytes to unexposed or exposed endothelial cells was tested, and we observed that monocytes cells adhere in similar amounts to endothelial cells if one of the two cell types, or both were exposed. When NAC was added, the expression of the receptors was inhibited.These results show that small concentrations of particles may activate monocytes that attach to endothelial cells. These results suggest that distal effects can be induced by small amounts of particles that may translocate from the lungs. ROS play a central role in the induction of the expression of these receptors.

Loading Electronic Microscopy Laboratory collaborators
Loading Electronic Microscopy Laboratory collaborators