Raman and infrared spectroscopy of Na<Subscript>0.5</Subscript>Bi<Subscript>0.5</Subscript>TiO<Subscript>3</Subscript> - BaTiO<Subscript>3</Subscript> ceramics

Lead-free Na_0.5Bi_0.5TiO₃ -BaTiO₃ ceramics have been prepared in the whole range of concentrations and studied at room-temperature by means of X-ray, Raman scattering and infrared techniques. X-ray measurements revealed rhombohedral, rhombohedral-tetragonal boundaries and tetragonal modifacations depending on the contents of BaTiO₃. The distinct changes of the Raman and infrared spectra with increasing of BaTiO₃ content, which were correlated with X-ray results, were observed. The broad phonon spectra indicated the disorder in the A site of Na_0.5Bi_0.5TiO₃ -BaTiO₃ system.     

Inhibitory action of aqueous coffee ground extracts on the corrosion of carbon steel in HCl solution

The effects of aqueous extracts of spent coffee grounds on the corrosion of carbon steel in a 1 mol L⁻¹ HCl were examined. Two methods of extraction were studied: decoction and infusion. The inhibition efficiency of C-steel in 1 mol L⁻¹ HCl increased as the extract concentration and temperature increased. The coffee extracts acted as a mixed-type inhibitor with predominant cathodic effectiveness. In this study, the adsorption process of components of spent coffee grounds extracts obeyed the Langmuir adsorption isotherm. The chlorogenic acids isolated do not seem to explain the corrosion inhibition observed during the use of the coffee extracts.     

Stoichiometry distribution of thin films deposited by laser ablation: Monte Carlo simulation

An expansion of a bi-component laser plume into a dilute background gas is simulated using a combined Monte Carlo simulation method. The effects of different types of collisions taking place during the transport of the ablated species on their distributions when arriving at a flat substrate are shown. Furthermore, we demonstrate that the film thickness distributions of both components and, hence, the final stoichiometry distribution, depend strongly on the incorporation probability of the species. This probability is expressed as a function of both deposited particle energy and the substrate absorbing properties. These studies can facilitate the comparison of the simulation results with experiments and are of particular interest for pulsed laser deposition (PLD) of multicomponent materials.     

FPGA realization of the LIRA neural classifier

Different types of neural networks can be used to classify images. We propose to apply LIRA (LImited Receptive Area) neural classifier to work with images. To accelerate the neural network functioning we propose a digital implementation of the LIRA neural classifier. We begin with a neuron design, and then continue with the neural network simulation. The advantage of neural network is its parallel structure and possibility of the training. FPGA (Field Programmable Gate Array) allows the implementation of these parallel algorithms in a single device. Speed of classification is one of the most important requirements in adaptive control systems based on computer vision. The contribution of this article is LIRA neural classifier implementation with FPGA for two classes to accelerate the training and recognition processes.     

Effect of X-rays on poly(vinylidene fluoride) in X-ray photoelectron spectroscopy

The polymer poly(vinylidene fluoride) (PVDF) was irradiated with X-rays produced by a nonmonochromatic (MgKα) source and the structural and electronic PVDF surface modifications were studied by X-ray photoelectron spectroscopy (XPS). Changes in the shape and intensity of the C_1s and F_1s lines show that a PVDF degradation consisting of the polymer defluorination takes place. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:2125–2129, 1998     

Off-axis and inline electron holography: Experimental comparison

Electron holography is a very powerful technique for mapping static electric and magnetic potentials down to atomic resolution. While electron holography is commonly considered synonymous with its off-axis variant in the high energy electron microscopy community, inline electron holography is widely applied in low-energy electron microscopy, where the realization of the off-axis setup is still an experimental challenge. This paper demonstrates that both inline and off-axis holography may be used to recover amplitude and phase shift of the very same object, in our example latex spheres of 90 and 200 nm in diameter, producing very similar results, provided the object does not charge under the electron beam.     

Seed morphoanatomy of the genus Passiflora L. (Passifloraceae) by scanning electron microscopy and light microscopy

Morphoanatomical analysis of seeds contributes to knowledge of the development of seedlings and identification of species, as well as supporting conservation studies. The conservation of the species belonging to the Passiflora genus is crucial due to of the threats to the genetic resources of these species. Thus, the objective of this study was to morphoanatomically characterize Passiflora seeds, verify possible injuries to the tissues after cryopreservation and thus contribute to the conservation strategies of the species of this genus. Initially, seeds of Passiflora coccinea, P. edulis, P. gibertii, P. maliformis, P. morifolia, P. setacea, P. suberosa, and P. tenuifila collected from the Passion Fruit Active Germplasm Bank of the Embrapa Cassava and Fruits research unit (Embrapa Mandioca e Fruticultura) were analyzed. Then, their length, width and thickness, shape of the base and tip, and ornamentations present on the body and edge of the seeds were evaluated. The seeds of the species were placed in cryotubes and immersed in liquid nitrogen to assess possible cryoinjuries. The tegument and tissues of the seeds were examined by scanning electron microscopy. The seeds had varied biometric data, with average values of 4.63 mm for length, 3.28 mm for width, and 1.51 mm for thickness. Six ornamentation types were observed: reticulate for the species P. coccinea; finely reticulate for P. edulis; foveolate reticulate for P. gibertii and P. setacea; alveolate reticulate for P. maliformis and P. tenuifila; coarsely reticulate for P. morifolia; and falsifoveolate reticulate for P. suberosa. Some seeds suffered tegument cracks due to the freezing in liquid nitrogen, but without physiological damages to the embryo and endosperm. The cryopreservation of the seeds in the presence of the tegument significantly reduced the cryoinjuries caused to the embryo. Cryopreservation can be promising for long-term conservation of passion fruit seeds.     

Ultrastructure of oocytes of the Urostreptus atrobrunneus (Diplopoda,Spirostreptida, Spirostreptidae): A potential urban centers plague

The knowledge of the process of egg formation is indispensable for understanding the mechanisms involved in the reproduction of different species. In this context, the objective of this work was to describe the ultrastructure of the oocytes of Urostreptus atrobrunneus (Spirostreptida), a potential plague of urban centers in different locations of São Paulo State. The lack of knowledge about the morphology, physiology, and the reproductive behavior of the species have hindered an effective control of it. The oocytes of U. atrobrunneus presented three development stages: young oocyte or type I; intermediary oocyte or type II; and mature oocyte or type III. During the oocyte development, the cytoplasm become filled with several globules of protein, drops of lipids, and sphaerocrystals, and it was not observed in many organelles in the oocytes with exception of mitochondria, abundant, principally in young oocytes. The vitelline membrane is also deposited in a discontinuous form and the chorion does not present differentiation of layers. The follicular epithelium alters its shape according to the development phase of the oocyte. Part of the vitellus is from exogenous origin and part is endogenous. Before this, only two studies about the ultrastructural analysis of the female germ cells of diplopods were published. Microsc. Res. Tech. © 2012 Wiley Periodicals, Inc.