Multímetro interfaceado de baixo custo para aquisição de dados

A digital multimeter (~U$ 240.00 on the national market) connected to a microcomputer by a RS-232 serial interface is proposed for data acquisition in equipment with analog output. Data are measured at the rate of 2 points per second and stored in text files by the software that accompanies the device, running in a Windows environment. The performance of the multimeter was verified by monitoring the transient signals generated in flow injection systems associated with fluorimetric, spectrophotometric and flame photometric detection. In addition, the performance of the proposed device was similar to that attained by employing an interface card with a 12-bit analog-to-digital converter for acquisition of the signals generated by a capillary electrophoresis equipment with oscillometric detection.

Circumsolar energetic particle distribution on 2011 November 3

Late on 2011 November 3, STEREO-A, STEREO-B, MESSENGER, and near-Earth spacecraft observed an energetic particle flux enhancement. Based on the analysis of in situ plasma and particle observations, their correlation with remote sensing observations, and an interplanetary transport model, we conclude that the particle increases observed at multiple locations had a common single source active region and the energetic particles filled a very broad region around the Sun. The active region was located at the solar backside (as seen from Earth) and was the source of a large flare, a fast and wide coronal mass ejection, and an EIT wave, accompanied by type II and type III radio-emission. In contrast to previous solar energetic particle events showing broad longitudinal spread, this event showed clear particle anisotropies at three widely separated observation points at 1AU, suggesting direct particle injection close to the magnetic footpoint of each spacecraft, lasting for several hours.We discuss these observations and the possible scenarios explaining the extremely broad particle spread for this event.

Butyltin speciation in sediments from Todos os Santos Bay (Bahia, Brazil) by GC-PFPD

Butyltin compounds were investigated in surface sediments from 17 stations in Todos os Santos Bay. Analytical conditions for organotin determination in marine sediments were optimized for GC with pulsed flame photometric detection. Detection limits were: 5.4 µg kg-1 for TBT; 0.2 µg kg-1 for DBT; and 2.1 µg kg-1 for MBT, using a 610-nm filter. In general, TBT concentrations were low and in the range of

Determinação de isotiocianato de benzila em Carica papaya utilizando cromatografia gasosa com detectores seletivos

In the present work, a method was developed and validated for the quantification of benzyl isothiocyanate (BITC) in the fruits of Carica papaya. The quantification of this compound was carried out by gas chromatography (GC) with selective detectors - nitrogen phosphorus detector (NPD) and flame photometric detector (FPD). The performance of these detectors showed a higher sensitivity of the NPD with a broader linear range of detection. The LOD/LOQ were 0.038/0.100 µg/mL for NPD and 5.78/19.29 µg/mL for FPD. The recovery of the method for BITC was 90,64%. An average value of BITC concentration in all the analyzed samples was 16,23 µg BITC/g.

Enseñar a convivir, enseñar a comunicarse = Teaching to live together, teaching to communicate

In this article we look at some of the questions related to the learning of how to live together so that we may then look more closely at the relative aspects of the learning of language. We insist on the importance of the not strictly linguistic aspects associated to the incorporation of children from immigrant families to the schools. From this point of view we underline the heterogeneous nature of the situation in which these children find themselves (in function with the social and professional situation of the family, of having been born here or not, and of having or not previous school experience in the community of origin etc). We also look at the necessary eradication of stereo types in the treating of this problem. We then discuss some strategies where there can be joint collaboration in the school for attaining these objectives

Estratégias de pré-concentração em eletroforese capilar: parte 2. Manipulação da velocidade da fase dispersa/secundária

This work describes CE preconcentration strategies based on the effect of manipulation of the disperse/secondary velocity. Introduced by Terabe et al. in 1984, micellar electrokinetic chromatography is a powerful separation approach that increases the usage of electrokinetic phenomena for the separation of nonionic compounds. The main disadvantage of MEKC is the low concentration sensitivity associated with the limited optical path length for on-capillary photometric detection and the limited volume of sample solution that can be injected. This paper compiles on-line concentration strategies for neutral analytes by sample stacking and sweeping in micellar electrokinetic chromatography.

Determinação da constante de dissociação (Ka) do captopril e da nimesulida: experimentos de química analítica para o curso de farmácia

This paper presents the determination of the dissociation constant (Ka) of captopril and nimesulide as contextualized experiments to teach chemical concepts to students of Pharmacy. Captopril is an antihypertensive drug, which presents high water-solubility and weak acid properties. The pKa of carboxylic acid group of captopril is 3.7. Nimesulide is a non-steroidal anti-inflammatory drug sparingly soluble in water. It is weakly acidic (pKa ≈ 6.5) because of its methanesulfonamide functional group. The pKa of captopril was determined by potentiometric titration with NaOH 2.0 x 10-2 moL L ¹. The pKa of nimesulide was determined by using spectrophotometry and photometric titration. The experimental values of pKa of both drugs are in very good agreement with those from literature

LOW COST ANALYZER FOR THE DETERMINATION OF PHOSPHORUS BASED ON OPEN-SOURCE HARDWARE AND PULSED FLOWS

The need for automated analyzers for industrial and environmental samples has triggered the research for new and cost-effective strategies of automation and control of analytical systems. The widespread availability of open-source hardware together with novel analytical methods based on pulsed flows have opened the possibility of implementing standalone automated analytical systems at low cost. Among the areas that can benefit from this approach are the analysis of industrial products and effluents and environmental analysis. In this work, a multi-pumping flow system is proposed for the determination of phosphorus in effluents and polluted water samples. The system employs photometric detection based on the formation of molybdovanadophosphoric acid, and the fluidic circuit is built using three solenoid micropumps. The detection is implemented with a low cost LED-photodiode photometric detection system and the whole system is controlled by an open-source Arduino Uno microcontroller board. The optimization of the timing to ensure the color development and the pumping cycle is discussed for the proposed implementation. Experimental results to evaluate the system behavior are presented verifying a linear relationship between the relative absorbance and the phosphorus concentrations for levels as high as 50 mg L-1.

Circular Spectropolarimetric Studies of DQ White Dwarfs

This thesis summarizes studies of a class of white dwarfs (WDs) called DQ WDs. White dwarfs are the remnants of ordinary stars like our Sun that have run out of nuclear fuel. WDs are classified according to the composition of their atmosphere and DQ WDs have an atmosphere made of helium and carbon. The carbon comes in either atomic or molecular form and in some cases the strong spectral absorption features cover the entire optical wavelength region. The research presented here utilizes spectropolarimetry, which is an observational technique that combines spectroscopy and polarization. Separately these allow to study the composition of a target and the inhomogeneous distribution of matter in the target. Put together they form a powerful tool to probe the physical properties in the atmosphere of a star. It is espacially good for detecting magnetic fields. The papers in this thesis describe efforts to do a survey of DQ white dwarfs with spectropolarimetry in order to search for magnetic fields in them. Paper I describes the discovery of a new magnetic cool DQ white dwarf, GJ841B. Initial modeling of molecular features on DQ WDs showed inconsistencies with observations. The first possible solution to this problem was stellar spots on these WDs. To investigate the matter, two DQ WDs were monitored for photometric variability that could arise from the presence of such spots. Paper II summarizes this short campaign and reports the negative results. Paper III reports observations of the rest of the objects in our survey. The paper includes the discovery of polarization from another cool DQ white dwarf, bringing the total of known magnetic cool DQs to three. Unfortunately the model used in this thesis cannot, in its present state, be used to model these objects nor are the observations of high enough spectroscopic resolution to do so.

Performance evaluation of 3D computer vision techniques

This work presents the implementation and comparison of three different techniques of three-dimensional computer vision as follows: • Stereo vision - correlation between two 2D images • Sensorial fusion - use of different sensors: camera 2D + ultrasound sensor (1D); • Structured light The computer vision techniques herein presented took into consideration the following characteristics: • Computational effort ( elapsed time for obtain the 3D information); • Influence of environmental conditions (noise due to a non uniform lighting, overlighting and shades); • The cost of the infrastructure for each technique; • Analysis of uncertainties, precision and accuracy. The option of using the Matlab software, version 5.1, for algorithm implementation of the three techniques was due to the simplicity of their commands, programming and debugging. Besides, this software is well known and used by the academic community, allowing the results of this work to be obtained and verified. Examples of three-dimensional vision applied to robotic assembling tasks ("pick-and-place") are presented.

Real-time Image-based RGB-D Camera Motion Tracking and Environment Mapping

In this work, image based estimation methods, also known as direct methods, are studied which avoid feature extraction and matching completely. Cost functions use raw pixels as measurements and the goal is to produce precise 3D pose and structure estimates. The cost functions presented minimize the sensor error, because measurements are not transformed or modified. In photometric camera pose estimation, 3D rotation and translation parameters are estimated by minimizing a sequence of image based cost functions, which are non-linear due to perspective projection and lens distortion. In image based structure refinement, on the other hand, 3D structure is refined using a number of additional views and an image based cost metric. Image based estimation methods are particularly useful in conditions where the Lambertian assumption holds, and the 3D points have constant color despite viewing angle. The goal is to improve image based estimation methods, and to produce computationally efficient methods which can be accomodated into real-time applications. The developed image-based 3D pose and structure estimation methods are finally demonstrated in practise in indoor 3D reconstruction use, and in a live augmented reality application.

Terpenoid transformations over gold catalysts

Nowadays biomass transformation has a great potential for the synthesis of value-added compounds with a wide range of applications. Terpenoids, extracted from biomass, are inexpensive and renewable raw materials which often have a biological activity and are widely used as important organic platform molecules in the development of new medicines as well as in the synthesis of fine chemicals and intermediates. At the same time, special attention is devoted to the application of gold catalysts to fine chemical synthesis due to their outstanding activity and/or selectivity for transformations of complex organic compounds. Conversion of renewable terpenoids in the presence of gold nanoparticles is one of the new and promising directions in the transformation of biomass to valuable chemicals. In the doctoral thesis, different kinds of natural terpenoids, such as α-pinene, myrtenol and carvone were selected as starting materials. Gold catalysts were utilized for the promising routes of these compounds transformation. Investigation of selective α-pinene isomerization to camphene, which is an important step in an industrial process towards the synthesis of camphor as well as other valuable substrates for the pharmaceutical industry, was performed. A high activity of heterogeneous gold catalysts in the Wagner-Meerwein rearrangement was demonstrated for the first time. Gold on alumina carrier was found to reach the α-pinene isomerization conversion up to 99.9% and the selectivity of 60-80%, thus making this catalyst very promising from an industrial viewpoint. A detailed investigation of kinetic regularities including catalyst deactivation during the reaction was performed. The one-pot terpene alcohol amination, which is a promising approach to the synthesis of valuable complex amines having specific physiological properties, was investigated. The general regularities of the one-pot natural myrtenol amination in the presence of gold catalysts as well as a correlation between catalytic activity, catalyst redox treatment and the support nature were obtained. Catalytic activity and product distribution were shown to be strongly dependent on the support properties, namely acidity and basicity. The gold-zirconia (Au/ZrO2) catalyst pretreated under oxidizing atmosphere was observed to be rather active, resulting in the total conversion of myrtenol and the selectivity to the corresponding amine of about 53%. The reaction kinetics was modelled based on the mechanistic considerations with the catalyst deactivation step incorporated in the mechanism. Carvone hydrogenation over a gold catalyst was studied with the general idea of investigating both the activity of gold catalysts in competitive hydrogenation of different functional groups and developing an approach to the synthesis of valuable carvone derivatives. Gold was found to promote stereo- and chemoselective carvone hydrogenation to dihydrocarvone with a predominant formation of the trans-isomer, which generally is a novel synthetic method for an industrially valuable dihydrocarvone. The solvent effect on the catalytic activity as well as on the ratio between trans- and cis-dihydrocarvone was evaluated.

A Model-Based Development and Verification Framework for Distributed System-on-Chip Architecture

The capabilities and thus, design complexity of VLSI-based embedded systems have increased tremendously in recent years, riding the wave of Moore’s law. The time-to-market requirements are also shrinking, imposing challenges to the designers, which in turn, seek to adopt new design methods to increase their productivity. As an answer to these new pressures, modern day systems have moved towards on-chip multiprocessing technologies. New architectures have emerged in on-chip multiprocessing in order to utilize the tremendous advances of fabrication technology. Platform-based design is a possible solution in addressing these challenges. The principle behind the approach is to separate the functionality of an application from the organization and communication architecture of hardware platform at several levels of abstraction. The existing design methodologies pertaining to platform-based design approach don’t provide full automation at every level of the design processes, and sometimes, the co-design of platform-based systems lead to sub-optimal systems. In addition, the design productivity gap in multiprocessor systems remain a key challenge due to existing design methodologies. This thesis addresses the aforementioned challenges and discusses the creation of a development framework for a platform-based system design, in the context of the SegBus platform - a distributed communication architecture. This research aims to provide automated procedures for platform design and application mapping. Structural verification support is also featured thus ensuring correct-by-design platforms. The solution is based on a model-based process. Both the platform and the application are modeled using the Unified Modeling Language. This thesis develops a Domain Specific Language to support platform modeling based on a corresponding UML profile. Object Constraint Language constraints are used to support structurally correct platform construction. An emulator is thus introduced to allow as much as possible accurate performance estimation of the solution, at high abstraction levels. VHDL code is automatically generated, in the form of “snippets” to be employed in the arbiter modules of the platform, as required by the application. The resulting framework is applied in building an actual design solution for an MP3 stereo audio decoder application.

INFLUENCE OF THE GLYPHOSATE FORMULATIONS ON WETTABILITY AND EVAPORATION TIME OF DROPLETS ON DIFFERENT TARGETS

ABSTRACTEfficiency of weed control can be increased if the herbicide formulation provides higher target coverage and evaporation time that enable an adequate distribution of herbicide on the target plant, allowing the absorption to continue even after the droplets evaporation. The aim of this research was to assess the influence of glyphosate formulations on the wetted area and evaporation time of droplets on different targets. Tests were conducted with droplets sizing from 500 μm containing three formulations of glyphosate (isopropylamine salt, ammonium salt and potassium salt) deposited on three surfaces, two leaves (Bidens pilosa and Cenchrus echinatus) and glass slides. Sequential images analyses were used to quantify the evaporation time and the wetted area. An experimental system was utilized that was composed of a droplet generator, a stereo microscope with a camera to capture images, as well as an environmental chamber controlled for temperature and relative humidity. The kind of glyphosate formulations and target surfaces are crucial in the wetted area and evaporation time. The isopropylamine salt decreased the wetted area and evaporation time when compared with ammonium salt and potassium salt for all the surfaces deposited on. Bidens pilosa allows an increased wetted area for all the glyphosate formulations when compared to Cenchrus echinatus and glass slides.

Solar Twins and Solar Analogues in Galactic Surveys.

The Sun is a crucial benchmark for how we see the universe. Especially when it comes to the visible range of the spectrum, stars are commonly compared to the Sun, as it is the most thoroughly studied star. In this work I have focussed on two aspects of the Sun and how it is used in modern astronomy. Firstly, I try to answer the question on how similar to the Sun another star can be. Given the limits of observations, we call a solar twin a star that has the same observed parameters as the Sun within its errors. These stars can be used as stand-in suns when doing observations, as normal night-time telescopes are not built to be pointed at the Sun. There have been many searches for these twins and every one of them provided not only information on how close to the Sun another star can be, but also helped us to understand the Sun itself. In my work I have selected _ 300 stars that are both photometrically and spectroscopically close to the Sun and found 22 solar twins, of which 17 were previously unknown and can therefore help the emerging picture on solar twins. In my second research project I have used my full sample of 300 solar analogue stars to check the temperature and metallicity scale of stellar catalogue calibrations. My photometric sample was originally drawn from the Geneva-Copenhagen-Survey (Nordström et al. 2004; Holmberg et al. 2007, 2009) for which two alternative calibrations exist, i.e. GCS-III (Holmberg et al. 2009) and C11 (Casagrande et al. 2011). I used very high resolution spectra of solar analogues, and a new approach to test the two calibrations. I found a zero–point shift of order of +75 K and +0.10 dex in effective temperature and metallicity, respectively, in the GCS-III and therefore favour the C11 calibration, which found similar offsets. I then performed a spectroscopic analysis of the stars to derive effective temperatures and metallicities, and tested that they are well centred around the solar values.