Análise da viabilidade celular de um monobiofilme de Streptococcus mutans após exposição a colutórios bucais presentes no mercado brasileiro

Este estudo tem como propósito analisar a eficácia de diferentes formulações de antissépticos bucais presentes no mercado brasileiro sobre um monobiofilme de Streptococcus mutans (ATCC 25175). O experimento foi realizado expondo as amostras às formulações por 1 minuto. Os biofilmes foram desenvolvidos semeando as cepas em tubos de ensaio contendo meio de cultura TSB acrescido de 1% de sacarose por 7 dias, com trocas de meio a cada 48 horas. A amostra foi dividida em grupos: monobiofilme tratado com solução contendo clorexidina (controle positivo); monobiofilme tratado com solução contendo óleos essenciais; monobiofilme tratado com solução contendo triclosan; biofilme tratado com solução contendo triclosan acrescido de cloreto de zinco; monobiofilme tratado com solução contendo cloreto de cetilpiridínio; monobiofilme tratado com solução salina fisiológica estéril (controle negativo). Para a análise do efeito pós antibiotico, as cepas foram removidas e plaqueadas imediatamente após a exposição e após 2 horas de crescimento em meio TSB. A média do crescimento bacteriano foi convertida em unidades formadoras de colônia (UFC) para análise. Para analizar a capacidade de recolonização as cepas foram inoculadas em TSB acrescido de sacarose por 48hs. os valores submetidos à análise estatística pelo teste t-student e ANOVA com modificação de Tukey e Dunnett. Os resultados nos permitem concluir que: todos os grupos tratados com antissépticos apresentaram redução das concentrações de microrganismos viáveis em relação ao controle negativo, nos dois tempos analizados. As formulações contendo triclosan e óleos essenciais não apresentaram diferença nem relação ao controle positivo e nem entre eles mesmos, também nos dois tempos. As formulações de antissépticos, contendo clorexidina, óleos essenciais, triclosan podem alterar a capacidade de recolonização do monobiofilme, neste modelo.

Biossorção de vanádio pela macroalga marinha Sargassum filipendula

Muitos biossorventes naturais têm sido pesquisados por possuírem baixo custo e apresentarem propriedades ligantes, como é o caso da macroalga marinha Sargassum filipendula (S. filipendula) que vem sendo utilizada como material biossorvente no processo de biossorção de metais pesados. No presente trabalho a alga marrom foi utilizada para estudos realizados em batelada, onde se determinou o pH ideal de biossorção de vanádio, a relação sólido/líquido ideal e a importância da velocidade de agitação. O estudo cinético e de equilíbrio dos íons metálicos também foram realizados em bateladas nas seguintes condições de ensaio: (1) 0,10 g de biomassa, 25,0 mL de solução de vanádio igual a 18,0 mg L-1, temperatura 25,0 C e 150 rpm de agitação; (2) 0,10 g de biomassa, 25,0 mL de solução de vanádio igual a 36,0 mg L-1, temperatura 25,0 C e 150 rpm de agitação. A melhor condição para biossorção de vanádio foi encontrada para 36,0 mg L-1 e pH= 2,0. O estudo cinético de biossorção de vanádio mostrou que o modelo de segunda ordem descreve melhor os dados experimentais em 36,0 mg L-1 (R2= 0,9825). O estudo de equilíbrio mostrou um perfil crescente de remoção de vanádio. A melhor eficiência de captação dos íons de vanádio foi de 61,0 % para Co= 40,0 mg L-1 em pH= 2,0. Os dados experimentais da isoterma de vanádio mostraram-se mais adequados ao modelo de Langmuir para pH= 2,0, Os parâmetros de equilíbrio calculados a partir do modelo de Langmuir (b, qmax ) 0,009 e 43,3 mg/g, respectivamente, corroboram melhor para a interpretação dos resultados quando comparados com o modelo de Freundlich (kF, n) 1,56 e 2,41, visto que o coeficiente de correlação é maior para Langmuir

Quantifying Earthquake Collapse Risk of Tall Steel Moment Frame Buildings Using Rupture-to-Rafters Simulations

There is a sparse number of credible source models available from large-magnitude past earthquakes. A stochastic source model generation algorithm thus becomes necessary for robust risk quantification using scenario earthquakes. We present an algorithm that combines the physics of fault ruptures as imaged in laboratory earthquakes with stress estimates on the fault constrained by field observations to generate stochastic source models for large-magnitude (Mw 6.0-8.0) strike-slip earthquakes. The algorithm is validated through a statistical comparison of synthetic ground motion histories from a stochastically generated source model for a magnitude 7.90 earthquake and a kinematic finite-source inversion of an equivalent magnitude past earthquake on a geometrically similar fault. The synthetic dataset comprises of three-component ground motion waveforms, computed at 636 sites in southern California, for ten hypothetical rupture scenarios (five hypocenters, each with two rupture directions) on the southern San Andreas fault. A similar validation exercise is conducted for a magnitude 6.0 earthquake, the lower magnitude limit for the algorithm. Additionally, ground motions from the Mw7.9 earthquake simulations are compared against predictions by the Campbell-Bozorgnia NGA relation as well as the ShakeOut scenario earthquake. The algorithm is then applied to generate fifty source models for a hypothetical magnitude 7.9 earthquake originating at Parkfield, with rupture propagating from north to south (towards Wrightwood), similar to the 1857 Fort Tejon earthquake. Using the spectral element method, three-component ground motion waveforms are computed in the Los Angeles basin for each scenario earthquake and the sensitivity of ground shaking intensity to seismic source parameters (such as the percentage of asperity area relative to the fault area, rupture speed, and risetime) is studied.

Under plausible San Andreas fault earthquakes in the next 30 years, modeled using the stochastic source algorithm, the performance of two 18-story steel moment frame buildings (UBC 1982 and 1997 designs) in southern California is quantified. The approach integrates rupture-to-rafters simulations into the PEER performance based earthquake engineering (PBEE) framework. Using stochastic sources and computational seismic wave propagation, three-component ground motion histories at 636 sites in southern California are generated for sixty scenario earthquakes on the San Andreas fault. The ruptures, with moment magnitudes in the range of 6.0-8.0, are assumed to occur at five locations on the southern section of the fault. Two unilateral rupture propagation directions are considered. The 30-year probabilities of all plausible ruptures in this magnitude range and in that section of the fault, as forecast by the United States Geological Survey, are distributed among these 60 earthquakes based on proximity and moment release. The response of the two 18-story buildings hypothetically located at each of the 636 sites under 3-component shaking from all 60 events is computed using 3-D nonlinear time-history analysis. Using these results, the probability of the structural response exceeding Immediate Occupancy (IO), Life-Safety (LS), and Collapse Prevention (CP) performance levels under San Andreas fault earthquakes over the next thirty years is evaluated.

Furthermore, the conditional and marginal probability distributions of peak ground velocity (PGV) and displacement (PGD) in Los Angeles and surrounding basins due to earthquakes occurring primarily on the mid-section of southern San Andreas fault are determined using Bayesian model class identification. Simulated ground motions at sites within 55-75km from the source from a suite of 60 earthquakes (Mw 6.0 − 8.0) primarily rupturing mid-section of San Andreas fault are considered for PGV and PGD data.

Report of an investigation of a plan of elimination of grade crossings on the A.T. & S.F. Ry. in the city of Pasadena, California

The problem of the Atchison, Topeka, and Santa Fe railroad in Pasadena is a very dynamic one, as is readily recognized by engineers, city officials, and laymen. The route of the railroad was first laid out in the eighties and because of certain liberal concessions granted by the City of Pasadena, the right-of-way was located through Pasadena, despite the fact that the grade coming into the city either from Los Angeles or San Bernardino was enormous. Some years later, other transcontinental routes of the Santa Fe out of Los Angles were sought, and a right-of-way was obtained by way of Fullerton and Riverside to San Bernardino, where this route joins the one from Los Angeles through Pasadena. This route, however, is ten miles longer than the one through Pasadena, which means a considerable loss of time in a short diversion of approximately only sixty miles in length.

Kinetics and mechanisms of adsorption of Escherichia coli bacteriophage T_4 to activated carbon

A study was conducted on the adsorption of Escherichia coli bacteriophage T₄ to activated carbon. Preliminary adsorption experiments were also made with poliovirus Type III. The effectiveness of such adsorbents as diatomaceous earth, Ottawa sand, and coconut charcoal was also tested for virus adsorption.

The kinetics of adsorption were studied in an agitated solution containing virus and carbon. The mechanism of attachment and site characteristics were investigated by varying pH and ionic strength and using site-blocking reagents.

Plaque assay procedures were developed for bacteriophage T₄ on Escherichia coli cells and poliovirus Type III on monkey kidney cells. Factors influencing the efficiency of plaque formation were investigated.

The kinetics of bacteriophage T₄ adsorption to activated carbon can be described by a reversible second-order equation. The reaction order was first order with respect to both virus and carbon concentration. This kinetic representation, however, is probably incorrect at optimum adsorption conditions, which occurred at a pH of 7.0 and ionic strength of 0.08. At optimum conditions the adsorption rate was satisfactorily described by a diffusion-limited process. Interpretation of adsorption data by a development of the diffusion equation for Langmuir adsorption yielded a diffusion coefficient of 12 X 10^-8 cm²/sec for bacteriophage T₄. This diffusion coefficient is in excellent agreement with the accepted value of 8 X 10^-8 cm²/sec. A diffusion-limited theory may also represent adsorption at conditions other than the maximal. A clear conclusion on the limiting process cannot be made.

Adsorption of bacteriophage T₄ to activated carbon obeys the Langmuir isotherm and is thermodynamically reversible. Thus virus is not inactivated by adsorption. Adsorption is unimolecular with very inefficient use of the available carbon surface area. The virus is probably completely excluded from pores due to its size.

Adsorption is of a physical nature and independent of temperature. Attraction is due to electrostatic forces between the virus and carbon. Effects of pH and ionic strength indicated that carboxyl groups, amino groups, and the virus's tail fibers are involved in the attachment of virus to carbon. The active sites on activated carbon for adsorption of bacteriophage T₄ are carboxyl groups. Adsorption can be completely blocked by esterifying these groups.

Emissões de compostos orgânicos voláteis de um aterro controlado e o potencial formador de ozônio

O presente estudo teve como objetivo quantificar as emissões de Compostos Orgânicos Voláteis do Aterro Controlado Morro do Céu localizado na cidade de Niterói, Rio de Janeiro, Brasil. Para tanto, vinte amostras foram coletadas, usando uma bomba de ar operada a bateria durante dois dias de dezembro de 2009. Uma câmara de fluxo cilíndrica de PVC de 30L foi inserida 5 cm no solo do aterro, e as amostras foram coletadas através de uma válvula na parte superior da câmera. Os resultados indicaram um valor de 1.980 Kg Km-2 h-1. O modelo Gaussiano de dispersão atmosférica ISCST3 foi utilizado para calcular a difusão e transporte dos poluentes a fim de estimar as concentrações de COV no bairro, usando dados topográficos, meteorológicos e de emissões. Valores de 525 μg m-3 de COV foram encontrados a 500 metros do aterro. As emissões do aterro foram usadas em conjunto com dados meteorológicos, utilizando o modelo de trajetória OZIPR e o mecanismo químico SAPRC para demonstrar o impacto na formação do ozônio troposférico na região. É conhecido que o ozônio é formado pela reação entre COV, NOx e luz solar. A contribuição de valores elevados de COV provenientes das emissões do aterro conduzirá a uma nova situação com valores mais elevados de ozônio na região. Os resultados da modelagem indicaram um aumento maior que 1000% nos níveis de ozônio na região do aterro, se comparado com a modelagem do ozônio para a região metropolitana do Rio de Janeiro. Os resultados mostram ser necessário que maior atenção seja dada à política de gerenciamento de RSU no Brasil, incluindo a escolha adequada para o local de instalação, o monitoramento da área durante e após o período de operação e técnicas mais adequadas de disposição dos resíduos sólidos urbanos

Model systems for the study of drug hypersensitivity

I. It was not possible to produce anti-tetracycline antibody in laboratory animals by any of the methods tried. Tetracycline protein conjugates were prepared and characterized. It was shown that previous reports of the detection of anti-tetracycline antibody by in vitro-methods were in error. Tetracycline precipitates non-specifically with serum proteins. The anaphylactic reaction reported was the result of misinterpretation, since the observations were inconsistent with the known mechanism of anaphylaxis and the supposed antibody would not sensitize guinea pig skin. The hemagglutination reaction was not reproducible and was extremely sensitive to minute amounts of microbial contamination. Both free tetracyclines and the conjugates were found to be poor antigens.

II. Anti-aspiryl antibodies were produced in rabbits using 3 protein carriers. The method of inhibition of precipitation was used to determine the specificity of the antibody produced. ε-Aminocaproate was found to be the most effective inhibitor of the haptens tested, indicating that the combining hapten of the protein is ε-aspiryl-lysyl. Free aspirin and salicylates were poor inhibitors and did not combine with the antibody to a significant extent. The ortho group was found to participate in the binding to antibody. The average binding constants were measured.

Normal rabbit serum was acetylated by aspirin under in vitro conditions, which are similar to physiological conditions. The extent of acetylation was determined by immunochemical tests. The acetylated serum proteins were shown to be potent antigens in rabbits. It was also shown that aspiryl proteins were partially acetylated. The relation of these results to human aspirin intolerance is discussed.

III. Aspirin did not induce contact sensitivity in guinea pigs when they were immunized by techniques that induce sensitivity with other reactive compounds. The acetylation mechanism is not relevant to this type of hypersensitivity, since sensitivity is not produced by potent acetylating agents like acetyl chloride and acetic anhydride. Aspiryl chloride, a totally artificial system, is a good sensitizer. Its specificity was examined.

IV. Protein conjugates were prepared with p-aminosalicylic acid and various carriers using azo, carbodiimide and mixed anhydride coupling. These antigens were injected into rabbits and guinea pigs and no anti-hapten IgG or IgM response was obtained. Delayed hypersensitivity was produced in guinea pigs by immunization with the conjugates, and its specificity was determined. Guinea pigs were not sensitized by either injections or topical application of p-amino-salicylic acid or p-aminosalicylate.

I. Studies on bacteriophage DNA's and minicircular DNA's in M. lysodeikticus and E. coli 15. II. Flow dichroism of DNA solutions

Part I

Chapter 1.....A physicochemical study of the DNA molecules from the three bacteriophages, N1, N5, and N6, which infect the bacterium, M. lysodeikticus, has been made. The molecular weights, as measured by both electron microscopy and sedimentation velocity, are 23 x 10⁶ for N5 DNA and 31 x 10⁶ for N1 and N6 DNA's. All three DNA's are capable of thermally reversible cyclization. N1 and N6 DNA's have identical or very similar base sequences as judged by membrane filter hybridization and by electron microscope heteroduplex studies. They have identical or similar cohesive ends. These results are in accord with the close biological relation between N1 and N6 phages. N5 DNA is not closely related to N1 or N6 DNA. The denaturation T_m of all three DNA's is the same and corresponds to a (GC) content of 70%. However, the buoyant densities in CsCl of Nl and N6 DNA's are lower than expected, corresponding to predicted GC contents of 64 and 67%. The buoyant densities in Cs₂SO₄ are also somewhat anomalous. The buoyant density anomalies are probably due to the presence of odd bases. However, direct base composition analysis of N1 DNA by anion exchange chromatography confirms a GC content of 70%, and, in the elution system used, no peaks due to odd bases are present.

Chapter 2.....A covalently closed circular DNA form has been observed as an intracellular form during both productive and abortive infection processes in M. lysodeikticus. This species has been isolated by the method of CsC1-ethidium bromide centrifugation and examined with an electron microscope.

Chapter 3.....A minute circular DNA has been discovered as a homogeneous population in M. lysodeikticus. Its length and molecular weight as determined by electron microscopy are 0.445 μ and 0.88 x 10⁶ daltons respectively. There is about one minicircle per bacterium.

Chapter 4.....Several strains of E. coli 15 harbor a prophage. Viral growth can be induced by exposing the host to mitomycin C or to uv irradiation. The coliphage 15 particles from E. coli 15 and E, coli 15 T^- appear as normal phage with head and tail structure; the particles from E. coli 15 TAU are tailless. The complete particles exert a colicinogenic activity on E.coli 15 and 15 T^-, the tailless particles do not. No host for a productive viral infection has been found and the phage may be defective. The properties of the DNA of the virus have been studied, mainly by electron microscopy. After induction but before lysis, a closed circular DNA with a contour length of about 11.9 μ is found in the bacterium; the mature phage DNA is a linear duplex and 7.5% longer than the intracellular circular form. This suggests the hypothesis that the mature phage DNA is terminally repetitious and circularly permuted. The hypothesis was confirmed by observing that denaturation and renaturation of the mature phage DNA produce circular duplexes with two single-stranded branches corresponding to the terminal repetition. The contour length of the mature phage DNA was measured relative to φX RFII DNA and λ DNA; the calculated molecular weight is 27 x 10⁶. The length of the single-stranded terminal repetition was compared to the length of φX 174 DNA under conditions where single-stranded DNA is seen in an extended form in electron micrographs. The length of the terminal repetition is found to be 7.4% of the length of the nonrepetitious part of the coliphage 15 DNA. The number of base pairs in the terminal repetition is variable in different molecules, with a fractional standard deviation of 0.18 of the average number in the terminal repetition. A new phenomenon termed "branch migration" has been discovered in renatured circular molecules; it results in forked branches, with two emerging single strands, at the position of the terminal repetition. The distribution of branch separations between the two terminal repetitions in the population of renatured circular molecules was studied. The observed distribution suggests that there is an excluded volume effect in the renaturation of a population of circularly permuted molecules such that strands with close beginning points preferentially renature with each other. This selective renaturation and the phenomenon of branch migration both affect the distribution of branch separations; the observed distribution does not contradict the hypothesis of a random distribution of beginning points around the chromosome.

Chapter 5....Some physicochemical studies on the minicircular DNA species in E. coli 15 (0.670 μ, 1.47 x 10⁶ daltons) have been made. Electron microscopic observations showed multimeric forms of the minicircle which amount to 5% of total DNA species and also showed presumably replicating forms of the minicircle. A renaturation kinetic study showed that the minicircle is a unique DNA species in its size and base sequence. A study on the minicircle replication has been made under condition in which host DNA synthesis is synchronized. Despite experimental uncertainties involved, it seems that the minicircle replication is random and the number of the minicircles increases continuously throughout a generation of the host, regardless of host DNA synchronization.

Part II

The flow dichroism of dilute DNA solutions (A₂₆₀≈0.1) has been studied in a Couette-type apparatus with the outer cylinder rotating and with the light path parallel to the cylinder axis. Shear gradients in the range of 5-160 sec.^-1 were studied. The DNA samples were whole, "half," and "quarter" molecules of T4 bacteriophage DNA, and linear and circular λb₂b₅c DNA. For the linear molecules, the fractional flow dichroism is a linear function of molecular weight. The dichroism for linear A DNA is about 1.8 that of the circular molecule. For a given DNA, the dichroism is an approximately linear function of shear gradient, but with a slight upward curvature at low values of G, and some trend toward saturation at larger values of G. The fractional dichroism increases as the supporting electrolyte concentration decreases.

An investigation of the stresses and deflections of swept plates

The problem in this investigation was to determine the stress and deflection patterns of a thick cantilever plate at various angles of sweepback.

The plate was tested at angles of sweepback of zero, twenty, forty, and sixty degrees under uniform shear load at the tip, uniformly distributed load and torsional loading.

For all angles of sweep and for all types of loading the area of critical stress is near the intersection of the root and trailing edge. Stresses near the leading edge at the root decreased rapidly with increase in angle of sweep for all types of loading. In the outer portion of the plate near the trailing edge the stresses due to the uniform shear and the uniformly distributed load did not vary for angles of sweep up to forty degrees. For the uniform shear and the uniformly distributed loads for all angles of sweep the area in which end effect is pronounced extends from the root to approximately three quarters of a chord length outboard of a line perpendicular to the axis of the plate through the trailing edge root. In case of uniform shear and uniformly distributed loads the deflections near the edge at seventy-five per cent semi-span decreased with increase in angle of sweep. Deflections near the trailing edge under the same loading conditions increased with increase in angle of sweep for small angles and then decreased at the higher angles of sweep. The maximum deflection due to torsional loading increased with increase in angle of sweep.

Resistência à infiltração de glicose de quatro cimentos reparadores

O presente estudo teve como objetivo comparar a qualidade do selamento promovido por 3 cimentos reparadores endodônticos: Ceramicrete, iRoot-BP Plus e BioAggregate, com o ProRoot MTA branco, utilizando o modelo de infiltração de glicose sob pressão. 64 incisivos centrais superiores, recém-extraídos e sem tratamento endodôntico foram selecionados. A instrumentação do canal radicular foi realizada em todos os dentes com brocas Gates-Glidden e limas K-Flexofile (Dentsply Maillefer, Ballaigues Suíça), 1mm aquém do ápice. A patência foraminal foi confirmada a cada instrumento usado. Os dentes tiveram suas coroas removidas padronizando-os em 15mm de comprimento. Foi realizada apicetomia a 3mm do ápice e o preparo da cavidade retrógrada com o auxílio do ultrassom Various 350 (NSKNakanishi Inc., Tóquio, Japão) e da ponta E32D (NSKNakanishi Inc., Tóquio, Japão). As raízes foram distribuídas, randomicamente, em quatro grupos experimentais (n=15): G1Ceramicrete, G2iRoot BP Plus, G3BioAggregate e G4ProRoot MTA branco. Como controle negativo (n=2) foram utilizados dentes hígidos, e como controle positivo (n=2), dentes acessados e com patência confirmada. Os cimentos reparadores foram manipulados seguindo as recomendações do fabricante e inseridos na cavidade retrógrada utilizando a mesma ponta ultrassônica usada no preparo. As amostras foram mantidas na presença de umidade por 72h para o completo endurecimento dos materiais. As raízes foram montadas em um dispositivo de dupla-câmara selada para a infiltração da glicose. Foram utilizados 0,75ml de solução de glicose a 1Mol/L na câmara superior e 0,75ml de água destilada na câmara inferior. Os dispositivos foram conectados a um sistema de distribuição de pressão, que permitiu a infiltração de 32 amostras em uma mesma etapa. A solução de glicose foi forçada apicalmente sob uma pressão de 15psi durante 1 hora. Uma alíquota de 10l foi coletada da câmara inferior para quantificar a glicose infiltrada. A concentração de glicose foi determinada com o auxílio do Kit GlucoseHK (Megazyme, Wicklow, Irlanda) e de um espectrofotômetro de luz visível (Campsec M330, Cambridge, Reino Unido) em um comprimento de onda de 340nm. O teste não-paramétrico Kruskal-Wallis e o teste Dunns foram utilizados na análise estatística. Os resultados encontrados demonstraram que houve diferença significativa entre os grupos experimentais (p=0,0036). O BioAggregate apresentou a maior concentração de glicose-1,85(g/L), seguido do ProRoot MTA-1,2; IRoot BP-0,85 e Ceramicrete-0,75. Não houve diferença entre os três novos cimentos reparadores e o material padrão-ouro (p>0,05). Não houve diferença entre Ceramicrete e iRoot BP Plus (p>0,05), porém estes foram estatisticamente diferentes do BioAggregate (p<0,05). Diante dos resultados obtidos, pode-se concluir que: nenhum dos cimentos testados foi capaz de promover selamento hermético; os três novos cimentos testados não revelaram o mesmo padrão de selamento; os três novos cimentos testados revelaram um padrão de selamento semelhante a do ProRoot MTA branco; e o Ceramicrete e o iRoot BP Plus apresentaram padrão de selamento superior em comparação com o BioAggregate.

Biossorção de tório com emprego de Sargassum filipendula

Com o aumento do rigor para descarte de efluentes contaminado com metais pesados, as pesquisas têm se intensificado na busca de métodos de remoção, que tragam bons resultados de captação dos metais, aliado a um baixo custo. O uso de biomassas como bactérias, fungos e algas marinhas como material adsorvente, tem se apresentado como uma alternativa, principalmente para soluções com baixo teor de metais. Neste trabalho, a alga marinha Sargassum filipendula foi avaliada na sua capacidade de remoção do metal tório de uma solução sintética e do efluente dos laboratórios de análises ambientais do IRD. A cinética desta biossorção foi estudada em regime de batelada e o equilíbrio foi alcançado com 180 min de reação. Dois modelos cinéticos foram utilizados nesta avaliação, um de primeira ordem e um modelo de pseudo segunda ordem, tendo o modelo de segunda ordem apresentado um melhor ajuste dos dados. Na avaliação da capacidade máxima de captação do tório pela biomassa marinha em regime de batelada, foi construída a isoterma que apresentou um perfil crescente na captação alcançando um máximo de 2,59 mol/g. Os modelos de Langmuir e Freundlich foram utilizados para ajustar os dados da isoterma, tendo apresentado maior correlação com os dados o modelo de Langmuir, resultando num valor de captação máxima calculado pelo modelo de 2,92 mol/g. A capacidade de remoção do metal tório da alga Sargassum filipendula também foi avaliada em regime contínuo. Um estudo de altura crítica de leito foi realizado preenchendo-se uma coluna com diferentes massas de alga correspondendo a diferentes alturas de leito. A concentração de tório residual foi quantificada na solução de saída e a menor concentração na saída foi alcançada com 40 cm de leito ou 96 g de biomassa. Após este estudo um sistema contínuo com duas colunas, com 96 g de biomassa cada, e uma bomba peristáltica foi utilizado para o tratamento do efluente real do IRD, contendo não apenas o metal tório, mas outros metais como urânio, cálcio, cromo, ferro, chumbo, etc. Cento e cinco litros de efluente foram tratados numa concentração de 6 mg/L, a concentração do efluente de saída foi de 3,75 mg/L. A caracterização do efluente quanto aos metais presentes foi realizada em ICP-MS, os resultados demonstraram que não houve competição pelos sítios ligantes da biomassa entre o tório e os demais metais. Além disso, alguns metais como cálcio, ferro e magnésio, tiveram um aumento na concentração de saída indicando a presença do mecanismo de troca iônica na biossorção do tório por Sargassum filipendula

O problema do ethos científico no novo modo de produção da ciência contemporânea

Nosso trabalho tem como objetivo central mostrar que as mudanças ocorridas no modo de produção da ciência contemporânea possuem implicações, tanto para os aspectos sociológicos da ciência quanto para os seus princípios filosóficos, que ainda apontam para uma necessidade de uma análise da relação entre ciência e sociedade. Baseamos nossa tese no trabalho desenvolvido pelo físico e epistemólogo da ciência John Michael Ziman F. R. S. (1925-2005), que defende que as mudanças ocorridas nos últimos 60 anos, relacionadas a uma nova forma de organizar, gerir e financiar a prática científica, i.e., a uma nova forma de prática científica, levaram ao surgimento de uma ciência pós-acadêmica ou pós-industrial. Sua consequência mais grave é a incorporação de um novo ethos científico, que tem como base princípios gerenciais, em detrimento do ethos mertoniano, cujo objetivo principal seria a manutenção de princípios que foram histórica e socialmente defendidos pelos cientistas em um ideal de ciência acadêmica, tais como os de objetividade, busca da verdade e autonomia, ainda que como ideais reguladores. Contudo, mostraremos que Ziman não adere à interpretação tradicional do ethos mertoniano, que o associa a uma epistemologia fundacionista. Além disso, ele reformula, seguindo as novas filosofia e sociologia da ciência, os ideais epistêmicos preconizados pelas tendências positivistas e neopositivistas, em especial a noção da objetividade. Para Ziman, a ciência ainda produz conhecimento confiável, pois possui um mecanismo cooperativo de produção, que tem como base a crítica entre os pares.

Advanced Monte Carlo Simulation and Machine Learning for Frequency Domain Optical Coherence Tomography

Optical Coherence Tomography(OCT) is a popular, rapidly growing imaging technique with an increasing number of bio-medical applications due to its noninvasive nature. However, there are three major challenges in understanding and improving an OCT system: (1) Obtaining an OCT image is not easy. It either takes a real medical experiment or requires days of computer simulation. Without much data, it is difficult to study the physical processes underlying OCT imaging of different objects simply because there aren't many imaged objects. (2) Interpretation of an OCT image is also hard. This challenge is more profound than it appears. For instance, it would require a trained expert to tell from an OCT image of human skin whether there is a lesion or not. This is expensive in its own right, but even the expert cannot be sure about the exact size of the lesion or the width of the various skin layers. The take-away message is that analyzing an OCT image even from a high level would usually require a trained expert, and pixel-level interpretation is simply unrealistic. The reason is simple: we have OCT images but not their underlying ground-truth structure, so there is nothing to learn from. (3) The imaging depth of OCT is very limited (millimeter or sub-millimeter on human tissues). While OCT utilizes infrared light for illumination to stay noninvasive, the downside of this is that photons at such long wavelengths can only penetrate a limited depth into the tissue before getting back-scattered. To image a particular region of a tissue, photons first need to reach that region. As a result, OCT signals from deeper regions of the tissue are both weak (since few photons reached there) and distorted (due to multiple scatterings of the contributing photons). This fact alone makes OCT images very hard to interpret.

This thesis addresses the above challenges by successfully developing an advanced Monte Carlo simulation platform which is 10000 times faster than the state-of-the-art simulator in the literature, bringing down the simulation time from 360 hours to a single minute. This powerful simulation tool not only enables us to efficiently generate as many OCT images of objects with arbitrary structure and shape as we want on a common desktop computer, but it also provides us the underlying ground-truth of the simulated images at the same time because we dictate them at the beginning of the simulation. This is one of the key contributions of this thesis. What allows us to build such a powerful simulation tool includes a thorough understanding of the signal formation process, clever implementation of the importance sampling/photon splitting procedure, efficient use of a voxel-based mesh system in determining photon-mesh interception, and a parallel computation of different A-scans that consist a full OCT image, among other programming and mathematical tricks, which will be explained in detail later in the thesis.

Next we aim at the inverse problem: given an OCT image, predict/reconstruct its ground-truth structure on a pixel level. By solving this problem we would be able to interpret an OCT image completely and precisely without the help from a trained expert. It turns out that we can do much better. For simple structures we are able to reconstruct the ground-truth of an OCT image more than 98% correctly, and for more complicated structures (e.g., a multi-layered brain structure) we are looking at 93%. We achieved this through extensive uses of Machine Learning. The success of the Monte Carlo simulation already puts us in a great position by providing us with a great deal of data (effectively unlimited), in the form of (image, truth) pairs. Through a transformation of the high-dimensional response variable, we convert the learning task into a multi-output multi-class classification problem and a multi-output regression problem. We then build a hierarchy architecture of machine learning models (committee of experts) and train different parts of the architecture with specifically designed data sets. In prediction, an unseen OCT image first goes through a classification model to determine its structure (e.g., the number and the types of layers present in the image); then the image is handed to a regression model that is trained specifically for that particular structure to predict the length of the different layers and by doing so reconstruct the ground-truth of the image. We also demonstrate that ideas from Deep Learning can be useful to further improve the performance.

It is worth pointing out that solving the inverse problem automatically improves the imaging depth, since previously the lower half of an OCT image (i.e., greater depth) can be hardly seen but now becomes fully resolved. Interestingly, although OCT signals consisting the lower half of the image are weak, messy, and uninterpretable to human eyes, they still carry enough information which when fed into a well-trained machine learning model spits out precisely the true structure of the object being imaged. This is just another case where Artificial Intelligence (AI) outperforms human. To the best knowledge of the author, this thesis is not only a success but also the first attempt to reconstruct an OCT image at a pixel level. To even give a try on this kind of task, it would require fully annotated OCT images and a lot of them (hundreds or even thousands). This is clearly impossible without a powerful simulation tool like the one developed in this thesis.

I. The structure and properties of closed circular duplex DNA. II. Chemically interacting systems at equilibrium in a buoyant density gradient

I. The binding of the intercalating dye ethidium bromide to closed circular SV 40 DNA causes an unwinding of the duplex structure and a simultaneous and quantitatively equivalent unwinding of the superhelices. The buoyant densities and sedimentation velocities of both intact (I) and singly nicked (II) SV 40 DNAs were measured as a function of free dye concentration. The buoyant density data were used to determine the binding isotherms over a dye concentration range extending from 0 to 600 µg/m1 in 5.8 M CsCl. At high dye concentrations all of the binding sites in II, but not in I, are saturated. At free dye concentrations less than 5.4 µg/ml, I has a greater affinity for dye than II. At a critical amount of dye bound I and II have equal affinities, and at higher dye concentration I has a lower affinity than II. The number of superhelical turns, τ, present in I is calculated at each dye concentration using Fuller and Waring's (1964) estimate of the angle of duplex unwinding per intercalation. The results reveal that SV 40 DNA I contains about -13 superhelical turns in concentrated salt solutions.

The free energy of superhelix formation is calculated as a function of τ from a consideration of the effect of the superhelical turns upon the binding isotherm of ethidium bromide to SV 40 DNA I. The value of the free energy is about 100 kcal/mole DNA in the native molecule. The free energy estimates are used to calculate the pitch and radius of the superhelix as a function of the number of superhelical turns. The pitch and radius of the native I superhelix are 430 Å and 135 Å, respectively.

A buoyant density method for the isolation and detection of closed circular DNA is described. The method is based upon the reduced binding of the intercalating dye, ethidium bromide, by closed circular DNA. In an application of this method it is found that HeLa cells contain in addition to closed circular mitochondrial DNA of mean length 4.81 microns, a heterogeneous group of smaller DNA molecules which vary in size from 0.2 to 3.5 microns and a paucidisperse group of multiples of the mitochondrial length.

II. The general theory is presented for the sedimentation equilibrium of a macromolecule in a concentrated binary solvent in the presence of an additional reacting small molecule. Equations are derived for the calculation of the buoyant density of the complex and for the determination of the binding isotherm of the reagent to the macrospecies. The standard buoyant density, a thermodynamic function, is defined and the density gradients which characterize the four component system are derived. The theory is applied to the specific cases of the binding of ethidium bromide to SV 40 DNA and of the binding of mercury and silver to DNA.

O uso da Técnica de Oscilações Forçadas na análise da mecânica ventilatória de indivíduos portadores de silicose classificados em diferentes graus de obstrução

O termo silicose refere-se ao processo de fibrose pulmonar causado pela inalação de poeira contendo sílica. É uma doença ocupacional, incurável, que se inicia nas vias aéreas distais e pode progredir independente do término da exposição. Os testes de função pulmonar, apesar de não serem utilizados como ferramenta diagnóstica para silicose, são amplamente empregados para acompanhar longitudinalmente esses indivíduos. Estudos recentes sugerem que a Técnicas de Oscilações Forçadas (FOT) pode ser aplicada para detecção de alterações pulmonares precoces em indivíduos com silicose. Contudo, existem poucos estudos descrevendo as alterações de mecância respiratória associada com a silicose através da FOT. Neste contexto, os objetivos deste estudo são: (1) analisar as alterações de mecânica respiratória de indivíduos portadores de silicose com diferentes graus de obstrução e (2) avaliar a capacidade da FOT em detectar alterações na função pulmonar decorrentes da silicose. Trata-se de um estudo transversal controlado com avaliação de casos prevalentes, tendo como unidade de avaliação o indivíduo. Os exames realizados incluíram medidas de espirometria e FOT. Foi selecionado um total de 67 indivíduos, 46 portadores de silicose e 21 sadios, caracterizando o grupo controle. Os indivíduos com diagnóstico de silicose foram divididos em três grupos classificados de acordo com o nível de obstrução sugerido pela espirometria. Essa classificação resultou em três categorias: Indivíduos normais ao exame espirométrico (NE), n= 12; com distúrbio ventilatório obstrutivo leve (DVOL), n=22; com distúrbio ventilatório obstrutivo moderado ou acentuado (DVOMA), n= 12. Todos os indivíduos realizaram exames da FOT para análise das propriedades resistivas e reativas do sistema respiratório. Posteriormente aos exames da FOT os indivíduos foram submetidos à espirometria. Considerando os grupos divididos a partir da espirometria, os parâmetros resistivos e reativos e a impedância do sistema respiratório em 4Hz (Z4Hz) se modificaram significativamente com a progressão da distúrbio obstrutivo. Na análise do poder diagnóstico da FOT os parâmetros R0, Rm, Rsr4 e |Z4Hz| mostraram-se precisos para identificar as modificações de mecânica respiratória em pacientes com silicose apresentando distúrbio ventilatório obstrutivo leve. Para distúrbio ventilatório obstrutivo moderado e acentuado todos os parâmetros analisados apresentaram habilidade para identificar essas alterações. Na análise entre o grupo controle e normal ao exame, nenhum parâmetro da FOT apresentou valor de acurácia adequado para uso clínico. Esses resultados são coerentes com as alterações fisiopatológicas relacionadas à silicose, confirmando o potencial da FOT na avaliação das modificações de mecânica respiratória em doentes com silicose.