Estudo da viabilidade operacional do processo de soldagem MAG com alimentação adicional de arame frio

Este trabalho apresenta um estudo experimental da viabilidade operacional, econômica, geométrica e da qualidade da solda com o uso do processo intitulado MAG-CW (Metal Active Gas–Cold Wire); entendido como: processo de soldagem MAG com adição de arame frio ou não energizado. Neste contexto, para o desenvolvimento deste trabalho utilizou-se os processos de soldagem MAG e o MAG-CW, sendo utilizados arames consumíveis sólidos de 1,2 mm de diâmetro, da classe AWS E-70S6 e o dióxido de carbono puro, CO², como gás de proteção com vazão de 17 l/min, para os dois processos empregados. A soldagem automatizada foi realizada com o auxílio de uma fonte eletrônica ajustada em CC⁺, no modo tensão constante e interfaceada a um microcomputador. Para ambos os processos, os cordões de solda foram depositados sobre corpos de prova de aço carbono SAE 1020 medindo 76x155x12,7 mm, com passes em simples deposição, na posição plana puxando e empurrando o arco voltaico. Para o processo MAG-CW adicionouse o arame frio, na região do arco elétrico, por um sistema de alimentação auxiliar de arame de forma seqüencial Tandem e Twin, também, na posição plana. As variáveis de influência foram a Velocidade de Alimentação do Arame-Eletrodo, VAE, que variou em três níveis: 6, 7,5 e 9 m/min, respectivamente, a Velocidade de Alimentação de Arame Frio, VAF, que também variou em três níveis, sendo: 3, 4 e 5 m/min combinadas com VAE. As variáveis de resposta para a avaliação experimental foram a estabilidade do arco elétrico, as características econômicas, as características geométricas e a qualidade superficial do cordão de solda. Os resultados mostraram satisfatória estabilidade do arco, bem como, elevada produção em relação ao processo MAG e bom aspecto superficial das soldas. Neste sentido, o processo MAG-CW, quando comparado ao processo MAG, foi superior na taxa de fusão (TF) em 57% para a VAE igual a 6 m/min, 59 % para VAE igual a 7,5 m/min e de 53 % para a VAE igual a 9 m/min. Observou-se, ainda, que o mesmo ocorreu para a taxa de deposição (TD) aumentando em todos os níveis de velocidade: 62% para a VAE na condição igual a 6 m/min e 7,5 m/min e de 57 % para a VAE na condição igual a 9 m/min. A boa performance no aumento das taxas obtidas pelo processo MAG-CW demonstra vantagem, com maior evidência no desempenho destas características, em função da adição de arame frio ao arco.

Avaliação, por extensometria, da deformação superficial no substrato de retenção dos implantes gerada por próteses fixas implanto suportadas em função do cantilever

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Desenvolvimento de equipamento multifuncional portátil de baixo custo para determinações fotométricas, turbidimétricas, nefelométricas e fluorimétricas

Pós-graduação em Química - IQ

A simple and portable instrument for determination of captopril in pharmaceutical formulations

Objective: This article describes the application and the performance of a cheap, simple and portable device that can be used for colorimetric quantitative determination of captopril (CPT) in pharmaceutical preparations. Methods: The sensor is a light detector resistor (LDR) placed into a black PTFE cell and coupled to a low cost multimeter (Ohmmeter). The instrument has been tested and is easy and fast to use. The quantitative study is based mainly on reduction of ammonium molybdate by captopril, in the presence of sulphuric acid, producing a green-yellow compound (max 407 nm). The calibration curves were obtained by plotting the electric resistance of the LDR against the CPT concentration on the range of 4.60 x 10-4 to 1.84 x 10-3 mol l-1 with a good coefficient of determination (R2 = 0.9962). Results: Statistical analysis of the obtained results showed no significant difference between the proposed methodology and the official reported method as evident from the t-test and variance ratio at 95% confidence level. Conclusion: The results of this study demonstrate that the instrument can be used for simple, accurate, precise, fast, in situ and low-cost colorimetric analysis of captopril in pharmaceuticals products.

Avaliação de um sensor de resistencia eletrica e sua correlação com atributos do solo

The electrical measures of the soil have been used as variables that correlate with its characteristics. This study aimed at developing an electrical capacitance sensor of low cost, to evaluate its performance on the field and verify the correlation between the measurements of electrical capacitance with physical properties (sand, silt and clay) and chemical properties of soil (pH, MO, P resin, H + Al, K, Ca, Mg, SB, CTC and V%) and the moisture content. The data sampling was performed at the farm named "Capão da Onça" which belongs to the State University of Ponta Grossa. The samples collection was conducted in an area of approximately 13 hectares, totalizing 81 samples. In each sampling the electrical capacitance of the soil was measured. After the sensor withdrawal, soil samples were collected and sent to be analysed in the laboratory of the College of Agronomics Science of the Paulista State University. The measuring instrument used to collect data on electric capacitance of the soil a digital multimeter was used. The data were submitted to the analysis of correlation and regression. The developed system presented a low cost and it was capable to measuring variation of the electrical capacitance of the soil. The obtained measures satisfactorily correlated with the levels of clay and sand, and weakly with the moisture content. This had demonstrated the possibility to use a sensor to verify the soil texture in not homogeneous areas. The measures of the electrical capacitance of the soil obtained by the sensor had significantly correlated with the soil attributes: calcium, magnesium, pH, SB and CTC. These results had demonstrated the possibility to use a sensor for soil fertility control.

Integrazione della riduzione della mobilità respiratoria nel trattamento radiante esterno conformazionale

Several methods to reduce respiratory-induced motion have been described in literature, with the goal of increasing accuracy of treatment to minimize normal tissue toxicity or increase dose to the target volume. We analyzed two different techniques of respiratory gating: the deep inspiration breath hold technique and the respiratory gating using the Real-time Position Management (RPM) system. The first method is a self-gating technique in which radiation treatment take place during a phase of breath-holding. The second technique use a reflective marker placed on the patient’s anterior surface. The motion of the marker is tracked using a camera interfaced to a computer. The gating thresholds are set when the tumor is in the desired portion of the respiratory cycle. These thresholds determine when the gating system turns the treatment beam on and off. We compared both techniques with a standard external radiation treatment. The dosimetric analysis has led to considerable advantage of these methods compared to the external radiation treatment, particularly in reducing the dose to the lung.

A hybrid technology for parallel recording of single ion channels

Hybrid technologies, thanks to the convergence of integrated microelectronic devices and new class of microfluidic structures could open new perspectives to the way how nanoscale events are discovered, monitored and controlled. The key point of this thesis is to evaluate the impact of such an approach into applications of ion-channel High Throughput Screening (HTS)platforms. This approach offers promising opportunities for the development of new classes of sensitive, reliable and cheap sensors. There are numerous advantages of embedding microelectronic readout structures strictly coupled to sensing elements. On the one hand the signal-to-noise-ratio is increased as a result of scaling. On the other, the readout miniaturization allows organization of sensors into arrays, increasing the capability of the platform in terms of number of acquired data, as required in the HTS approach, to improve sensing accuracy and reliabiity. However, accurate interface design is required to establish efficient communication between ionic-based and electronic-based signals. The work made in this thesis will show a first example of a complete parallel readout system with single ion channel resolution, using a compact and scalable hybrid architecture suitable to be interfaced to large array of sensors, ensuring simultaneous signal recording and smart control of the signal-to-noise ratio and bandwidth trade off. More specifically, an array of microfluidic polymer structures, hosting artificial lipid bilayers blocks where single ion channel pores are embededed, is coupled with an array of ultra-low noise current amplifiers for signal amplification and data processing. As demonstrating working example, the platform was used to acquire ultra small currents derived by single non-covalent molecular binding between alpha-hemolysin pores and beta-cyclodextrin molecules in artificial lipid membranes.

Polimeri tiofenici funzionali e loro applicazioni nel fotovoltaico

Recentemente, sempre più attenzione è stata rivolta all' utilizzo di coloranti organici come assorbitori di luce per la preparazione di strati fotoattivi in celle solari organiche (OPV). I coloranti organici presentano un'elevata abilità nella cattura della luce solare grazie all'elevato coefficiente di estinzione molare e buone proprietà fotofisiche. Per questi motivi sono eccellenti candidati per l'incremento della conversione fotoelettrica in OPV. In questa tesi viene descritta una nuova strategia per l'incorporazione di derivati porfirinici in catena laterale a copolimeri tiofenici. Gli studi svolti hanno dimostrato che poli(3-bromoesil)tiofene può essere variamente funzionalizzato con idrossitetrafenilporfirina (TPPOH), per l'ottenimento di copolimeri utilizzabili come materiali p-donatori nella realizzazione di OPV. I copolimeri poli[3-(6-bromoesil)tiofene-co-(3-[5-(4-fenossi)-10,15,20-trifenilporfirinil]esil tiofene] P[T6Br-co-T6TPP] contenenti differenti quantità di porfirina, sono stati sintetizzati sia con metodi non regiospecifici che regiospecifici, con lo scopo di confrontarene le proprietà e di verificare se la strutture macromolecolare che presenta una regiochimica di sostituzione sempre uguale, promuove o meno il trasporto della carica elettrica, migliorando di conseguenza l'efficienza. E' stato inoltre effettuato un ulteriore confronto tra questi derivati e derivati simili P[T6H-co-T6TPP] che non contengono l'atomo di bromo in catena laterale con lo scopo di verificare se l'assenza del gruppo reattivo, migliora o meno la stabilità termica e chimica dei film polimerici, agendo favorevolmete sulle performance dei dispositivi fotovoltaici. Tutti i copolimeri sono stati caratterizzati con differenti tecniche: spettroscopia NMR, FT-IR e UV-Vis, analisi termiche DSC e TGA, e GPC. Le celle solari Bulk Heterojunction, preparate utilizzando PCBM come materiale elettron-accettore e i copolimeri come materilai elettron-donatori, sono state testate utilizzando un multimetro Keithley e il Solar Simulator.

Validation of the Swiss Monte Carlo Plan for a static and dynamic 6 MV photon beam

Monte Carlo (MC) based dose calculations can compute dose distributions with an accuracy surpassing that of conventional algorithms used in radiotherapy, especially in regions of tissue inhomogeneities and surface discontinuities. The Swiss Monte Carlo Plan (SMCP) is a GUI-based framework for photon MC treatment planning (MCTP) interfaced to the Eclipse treatment planning system (TPS). As for any dose calculation algorithm, also the MCTP needs to be commissioned and validated before using the algorithm for clinical cases. Aim of this study is the investigation of a 6 MV beam for clinical situations within the framework of the SMCP. In this respect, all parts i.e. open fields and all the clinically available beam modifiers have to be configured so that the calculated dose distributions match the corresponding measurements. Dose distributions for the 6 MV beam were simulated in a water phantom using a phase space source above the beam modifiers. The VMC++ code was used for the radiation transport through the beam modifiers (jaws, wedges, block and multileaf collimator (MLC)) as well as for the calculation of the dose distributions within the phantom. The voxel size of the dose distributions was 2mm in all directions. The statistical uncertainty of the calculated dose distributions was below 0.4%. Simulated depth dose curves and dose profiles in terms of [Gy/MU] for static and dynamic fields were compared with the corresponding measurements using dose difference and γ analysis. For the dose difference criterion of ±1% of D(max) and the distance to agreement criterion of ±1 mm, the γ analysis showed an excellent agreement between measurements and simulations for all static open and MLC fields. The tuning of the density and the thickness for all hard wedges lead to an agreement with the corresponding measurements within 1% or 1mm. Similar results have been achieved for the block. For the validation of the tuned hard wedges, a very good agreement between calculated and measured dose distributions was achieved using a 1%/1mm criteria for the γ analysis. The calculated dose distributions of the enhanced dynamic wedges (10°, 15°, 20°, 25°, 30°, 45° and 60°) met the criteria of 1%/1mm when compared with the measurements for all situations considered. For the IMRT fields all compared measured dose values agreed with the calculated dose values within a 2% dose difference or within 1 mm distance. The SMCP has been successfully validated for a static and dynamic 6 MV photon beam, thus resulting in accurate dose calculations suitable for applications in clinical cases.

Beamlet based direct aperture optimization for MERT using a photon MLC

PURPOSE A beamlet based direct aperture optimization (DAO) for modulated electron radiotherapy (MERT) using photon multileaf collimator (pMLC) shaped electron fields is developed and investigated. METHODS The Swiss Monte Carlo Plan (SMCP) allows the calculation of dose distributions for pMLC shaped electron beams. SMCP is interfaced with the Eclipse TPS (Varian Medical Systems, Palo Alto, CA) which can thus be included into the inverse treatment planning process for MERT. This process starts with the import of a CT-scan into Eclipse, the contouring of the target and the organs at risk (OARs), and the choice of the initial electron beam directions. For each electron beam, the number of apertures, their energy, and initial shape are defined. Furthermore, the DAO requires dose-volume constraints for the structures contoured. In order to carry out the DAO efficiently, the initial electron beams are divided into a grid of beamlets. For each of those, the dose distribution is precalculated using a modified electron beam model, resulting in a dose list for each beamlet and energy. Then the DAO is carried out, leading to a set of optimal apertures and corresponding weights. These optimal apertures are now converted into pMLC shaped segments and the dose calculation for each segment is performed. For these dose distributions, a weight optimization process is launched in order to minimize the differences between the dose distribution using the optimal apertures and the pMLC segments. Finally, a deliverable dose distribution for the MERT plan is obtained and loaded back into Eclipse for evaluation. For an idealized water phantom geometry, a MERT treatment plan is created and compared to the plan obtained using a previously developed forward planning strategy. Further, MERT treatment plans for three clinical situations (breast, chest wall, and parotid metastasis of a squamous cell skin carcinoma) are created using the developed inverse planning strategy. The MERT plans are compared to clinical standard treatment plans using photon beams and the differences between the optimal and the deliverable dose distributions are determined. RESULTS For the idealized water phantom geometry, the inversely optimized MERT plan is able to obtain the same PTV coverage, but with an improved OAR sparing compared to the forwardly optimized plan. Regarding the right-sided breast case, the MERT plan is able to reduce the lung volume receiving more than 30% of the prescribed dose and the mean lung dose compared to the standard plan. However, the standard plan leads to a better homogeneity within the CTV. The results for the left-sided thorax wall are similar but also the dose to the heart is reduced comparing MERT to the standard treatment plan. For the parotid case, MERT leads to lower doses for almost all OARs but to a less homogeneous dose distribution for the PTV when compared to a standard plan. For all cases, the weight optimization successfully minimized the differences between the optimal and the deliverable dose distribution. CONCLUSIONS A beamlet based DAO using multiple beam angles is implemented and successfully tested for an idealized water phantom geometry and clinical situations.

Measurements of jet vetoes and azimuthal decorrelations in dijet events produced in pp collisions at √s = 7 TeV using the ATLAS detector

Additional jet activity in dijet events is measured using pp collisions at ATLAS at a centre-of-mass energy of 7 TeV, for jets reconstructed using the anti-kt algorithm with radius parameter R=0.6. This is done using variables such as the fraction of dijet events without an additional jet in the rapidity interval bounded by the dijet subsystem and correlations between the azimuthal angles of the dijets. They are presented, both with and without a veto on additional jet activity in the rapidity interval, as a function of the mean transverse momentum of the dijets and of the rapidity interval size. The double differential dijet cross section is also measured as a function of the interval size and the azimuthal angle between the dijets. These variables probe differences in the approach to resummation of large logarithms when performing QCD calculations. The data are compared to POWHEG, interfaced to the PYTHIA 8 and HERWIG parton shower generators, as well as to HEJ with and without interfacing it to the ARIADNE parton shower generator. None of the theoretical predictions agree with the data across the full phase-space considered; however, POWHEG+PYTHIA 8 and HEJ+ARIADNE are found to provide the best agreement with the data.These measurements use the full data sample collected with the ATLAS detector in 7 TeV pp collisions at the LHC and correspond to integrated luminosities of 36.1 pb−1 and 4.5 fb−1 for data collected during 2010 and 2011 respectively.

Measurement of dijet cross sections in pp collisions at 7 TeV centre-of-mass energy using the ATLAS detector

Double-differential dijet cross-sections measured in pp collisions at the LHC with a 7TeV centre-of-mass energy are presented as functions of dijet mass and half the rapidity separation of the two highest-pT jets. These measurements are obtained using data corresponding to an integrated luminosity of 4.5 fb−1, recorded by the ATLAS detector in 2011. The data are corrected for detector effects so that cross-sections are presented at the particle level. Cross-sections are measured up to 5TeV dijet mass using jets reconstructed with the anti-kt algorithm for values of the jet radius parameter of 0.4 and 0.6. The cross-sections are compared with next-to-leading-order perturbative QCD calculations by NLOJet++ corrected to account for non-perturbative effects. Comparisons with POWHEG predictions, using a next-to-leading-order matrix element calculation interfaced to a partonshower Monte Carlo simulation, are also shown. Electroweak effects are accounted for in both cases. The quantitative comparison of data and theoretical predictions obtained using various parameterizations of the parton distribution functions is performed using a frequentist method. In general, good agreement with data is observed for the NLOJet++ theoretical predictions when using the CT10, NNPDF2.1 and MSTW 2008 PDF sets. Disagreement is observed when using the ABM11 and HERAPDF1.5 PDF sets for some ranges of dijet mass and half the rapidity separation. An example setting a lower limit on the compositeness scale for a model of contact interactions is presented, showing that the unfolded results can be used to constrain contributions to dijet production beyond that predicted by the Standard Model.

Characterization of the Axial Jet Separator with a CO2/Helium Mixture: Toward GC-AMS Hyphenation

Development of interfaces for sample introduction from high pressures is important for real-time online hyphenation of chromatographic and other separation devices with mass spectrometry (MS) or accelerator mass spectrometry (AMS). Momentum separators can reduce unwanted low-density gases and introduce the analyte into the vacuum. In this work, the axial jet separator, a new momentum interface, is characterized by theory and empirical optimization. The mathematical model describes the different axial penetration of the components of a jetgas mixture and explains the empirical results for injections of CO2 in helium into MS and AMS instruments. We show that the performance of the new interface is sensitive to the nozzle size, showing good qualitative agreement with the mathematical model. Smaller nozzle sizes are more preferable due to their higher inflow capacity. The CO2 transmission efficiency of the interface into a MS instrument is ~14% (CO2/helium separation factor of 2.7). The interface receives and delivers flows of ~17.5 mL/min and ~0.9 mL/min, respectively. For the interfaced AMS instrument, the ionization and overall efficiencies are 0.7-3% and 0.1-0.4%, respectively, for CO2 amounts of 4-0.6 µg C, which is only slightly lower compared to conventional systems using intermediate trapping. The ionization efficiency depends on to the carbon mass flow in the injected pulse and is suppressed at high CO2 flows. Relative to a conventional jet separator, the transmission efficiency of the axial jet separator is lower, but its performance is less sensitive to misalignments.

A dual resonance, image -guided, volume localization technique for magnetic resonance spectroscopy

An interleaved, dual resonance, volume localization technique for $\sp1$H/$\sp{31}$P magnetic resonance spectroscopy has been designed, implemented on a 2 T imager/spectrometer, and verified with phantom studies.^ Localization techniques, including several single voxel techniques and spectroscopic imaging, were implemented, and studies were performed to compare the efficiency of each sequence of $\sp1$H/$\sp{31}$P spectral acquisitions. The sequence chosen was a hybrid of the stimulated echo single voxel technique and the spectroscopic imaging technique.^ Water suppression during the $\sp1$H spectral acquisitions was accomplished by the use of three narrow bandwidth RF saturation pulses in combination with three spoiler gradients. The spoiler gradient amplitudes were selected on the basis of a numerical solution of the Bloch equations. A post-acquisition water suppression algorithm was used to minimize any residual water signal.^ For interleaved $\sp1$H/$\sp{31}$P acquisitions, a dual resonance RF coil was constructed and interfaced to the existing RF detection system via a custom-designed dual resonance transcoupler and switching system. Programmable attenuators were incorporated to allow for changes in receiver and transmitter attenuation "on the fly".^ To provide the rapidly switched gradient fields required for the $\sp1$H/$\sp{31}$P acquisitions, an actively screened gradient coil system was designed and implemented. With this system, gradient field rise times on the order of 100 $\mu$s were obtained. These rapid switching times were necessary for minimizing intrasequence delays and for improving localization quality and water suppression efficiency.^ The interleaved $\sp1$H/$\sp{31}$P volume localization technique was tested using a two-compartment phantom. Analysis of the data showed that the spectral contamination was less than three percent. One-to-one spatial correspondence of the $\sp1$H and $\sp{31}$P spectra was verified and allowed for direct correlation of the spectral data with a standard magnetic resonance image. ^

Dissolved inorganic carbon isotopes in pore waters of ODP Leg 204 sediments

Isotopic characterization of carbon in the dissolved inorganic carbon (DIC) pool is fundamental for a wide array of scientific studies directly related to gas hydrate research. In order to generate integrated and internally consistent data of d13C of DIC in pore waters from Hydrate Ridge, we used the modern continuous flow technology of a GasBench II automated sampler interfaced to a gas source stable isotope mass spectrometer for the rapid determination (~80 samples/day) of d13C DIC in small-volume water samples. The overall precision of this technique is conservatively estimated to be better than ±0.15 per mil (1 sigma), which is similar to the precision of methods in current use. Here we present the data generated from Ocean Drilling Program Leg 204 pore water samples.