Orientador: Fernando Galembeck / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-15T06:51:39Z (GMT). No. of bitstreams: 1 SilvaeSouza_CristianeAparecida_D.pdf: 8520514 bytes, checksum: 17e73481eda5f744b4ec360be3455823 (MD5) Previous issue date: 2009 / Resumo: A morfologia de filmes compósitos preparados com fosfato de alumínio e látexes de poli(metacrilato de metila-co-acrilato de butila) e de poli(estireno-co-acrilato de butila) foi caracterizada por técnicas de microscopia eletrônica de transmissão e de varredura (TEM, SEM) e por técnicas de microscopia de varredura por sonda (AFM, DPFM). O grau de opacidade (razão de contraste) e os cálculos de coeficiente de espalhamento das partículas de fosfato de alumínio nos filmes compósitos foram obtidos através dos espectros de refletância. As micrografias das superfícies de desbaste dos filmes compósitos mostraram espaços vazios entre os agregados de partículas de fosfato de alumínio dispersos pela matriz polimérica. A adesão entre os agregados de partículas de fosfato de alumínio e polímero é muito boa nas interfaces de contato. A refletância dos filmes compósitos varia amplamente, dependendo da concentração das partículas de fosfato de alumínio, assim como da sua forma de uso em pó ou em dispersão e da dimensão dos espaços vazios entre os agregados de partículas. Os resultados das medidas óticas de opacidade mostraram que os filmes compósitos mais opacos foram os obtidos com fosfato de alumínio na forma de pó e com a dimensão dos vazios entre os agregados de partículas na mesma ordem de grandeza que o comprimento de onda da luz na região do visível (400 a 700 nm). Os coeficientes de espalhamento dos filmes de fosfato de alumínio/poli(estireno-co-acrilato de butila) foram calculados empiricamente usando o modelo de Kubelka-Munk e os resultados mostraram que os vazios contidos nos agregados de partículas de fosfato de alumínio justificam a opacidade dos filmes. O filme mais opaco, com razão de contraste de 88 %, apresentou ampla distribuição de dimensão dos vazios com média numérica igual a 650 nm. Além disso, os valores obtidos dos coeficientes de espalhamento experimentais são muito próximos dos coeficientes de espalhamento estimados pela teoria de Mie. A eficiência de espalhamento, predita pela teoria de Mie, de uma bolha de ar rodeada por fosfato de alumínio com diâmetro médio de 650 nm é apenas 12 % menor que a eficiência de espalhamento de uma partícula de dióxido de titânio, no seu diâmetro ótimo de 350 nm, dispersa no mesmo meio / Abstract: Composite films prepared with aluminum phosphate and latex of poly(methyl methacrylate-co-butyl acrylate) and poly(styrene-co-butyl acrylate) were characterized by electronic microscopy (TEM, SEM) and by different techniques of scanning probe microscopy (AFM, DPFM). Opacity (contrast ratio) and light scattering coefficients of composite films were obtained from reflectance spectra. SEM and TEM micrographs from composite films trimmed surfaces or thin cuts showed voids within aluminum phosphate particle aggregates. The adhesion between aluminum phosphate particle aggregates and polymer is very good at contact interfaces. Composite films reflectance changes widely, depending on void diameters, on aluminum phosphate particle concentration, as well as its use in the form of powder or dispersion. Opacity results showed that the most opaque composite films were obtained with aluminum phosphate powder and with void diameters in the same order of magnitude as the wavelength of light in the visible region (400 to 700 nm). Scattering coefficients of aluminum phosphate/poly(styrene-co-butyl acrylate) films were calculated empirically using the Kubelka-Munk model and the results showed that the observed voids account for films opacity. The most opaque composite film shows contrast ratio equal to 88 % and a broad distribution of void diameters, peaking at ca. 650 nm. Film scattering coefficient of the observed voids was calculated using Mie theory to evaluate their contribution to film opacity showing that the measured and estimated values are in reasonable agreement. The Mie calculations show that scattering efficiency for air trapped within the phosphate particles dispersed in polymer latex is in excess of 4 units in the 650 nm diameter range, which is only 12 % lower than the calculated values for optimum size TiO2 particles (350 nm) dispersed in the same polymer / Doutorado / Físico-Química / Doutor em Ciências

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No. of bitstreams: 1 flaviavitaljanuzzi.pdf: 3423606 bytes, checksum: 57861685b0ccc18a4cb7382012422482 (MD5) Previous issue date: 2017-12-19 / PROQUALI (UFJF) / Um fundo de investimento (FI) é considerado opaco se as informações sobre a volatilidade dos seus retornos são incompreensíveis e inacessíveis para a grande parte dos atuais e potenciais cotistas, conforme Sato (2014). Tal fenômeno se agrava quando o gestor utiliza ativos complexos para estruturar a carteira do fundo. São considerados complexos, segundo Brunnermeier, Oehmke e Jel (2009), aqueles que apresentam estruturas de fluxo de caixa que não podem ser facilmente compreendidas e projetadas pelo investidor, tais como os derivativos, por exemplo. Com base nessa perspectiva, este estudo avaliou se um aumento na opacidade dos fundos multimercados, ocasionado pelo maior posicionamento do seu patrimônio líquido em derivativos, esteve associado a uma variação no nível de risco, no retorno ajustado ao risco e no fluxo de recursos dos fundos multimercado brasileiros, sob três perspectivas, considerando: a) a amostra total (capítulo 4); b) apenas o segmento de FI’s que cobra taxa de performance, o que viabilizou a análise de uma possível ocorrência de conflitos de agência entre gestores e cotistas (capítulo 5), e c) o grupo de fundos alavancados e não alavancados (capítulo 6). No capítulo 4, foi constatada uma associação positiva entre a posição em derivativos e variações no risco e uma relação negativa entre derivativos e desempenho (em termos mensais e anuais). No geral, evidenciou-se que derivativos estiveram relacionados à captação de forma negativa apenas no que se refere ao segmento de investidores qualificados. No entanto, verificou-se que fundos categorizados como do tipo “Estratégia” pela ANBIMA1 (todos admitem alavancagem) atraíram mais recursos financeiros quando direcionados a investidores não qualificados. No que se refere ao capítulo 5, não foi identificado, de forma geral, problemas de agência entre gestores e investidores, no entanto, conflitos de interesses foram observados dentro do segmento de fundos alavancados destinados a cotistas não qualificados. Por fim, no capítulo 6, obtiveram-se resultados condizentes com a teoria de torneio proposta por Brown, Harlow e Starks (1996). Ao incorporar o uso de derivativos, verificou-se que FI’s alavancados perdedores (ou seja aqueles que se situaram nos menores percentis de rentabilidade em pelo menos um semestre), ampliam seu investimento nesses ativos opacos, o que elevou tanto o risco total quanto a exposição do FI a oscilações econômicas (risco sistemático) e a retornos negativos (risco downside). Cabe ressaltar, contudo, que uma contrapartida de maior retorno ajustado não foi necessariamente oferecida pelo gestor ao cotista desse fundo perdedor. / A fund is considered opaque if the information related to its volatility and return is not comprehended and/or available for a considerable number of current and potential unitholders(Sato, 2014). This phenomenon becomes worse when managers use complex assets to structure their fund’s portfolio. Complex assets are defined by Brunnermeier, Oehmke and Jel (2009), as those whose payoffs cannot be understood or even forecasted by investors, such as, derivatives. Considering these ideas, this study analyzed if the increase in hedge fund opacity, caused by the greater position of its net worth in derivatives, was associated with the variation of the risk level, the adjusted return and the flow of resources in Brazilian hedge funds. Three perspectives were investigated: a) the total sample (chapter 4); b) only the segment of hedge funds that charge performance fees which allowed the analysis of potential agency problems between unitholders and managers (chapter 5); c) the group of leveraged and unleveraged funds (chapter 6). In summary, in chapter 4 it was found a positive association between derivatives and the risk variation, and a negative relation between derivatives and performance (in the long and short terms). In general, there is evidence that derivatives were related to inflows in a negative way only in the segment of qualified investors. Nonetheless, it was observed that funds classified as “Strategy” by ANBIMA (i.e. those in which leverage operations are allowed) attracted more financial resources when they were directed to non-qualified investors. With regard to chapter 5, agency problems between mangers and investors were not identified; however, conflicts of interest were identified in the leveraged funds directed to non-qualified unitholders. Finally, specifically for chapter 6, the results were consistent with the tournament theory proposed by Brown, Harlow and Starks (1996). By incorporating the derivative usage in the analysis I verified that loser funds able to leverage, characterized by those that were in the lower percentile of return in some semesters, amplified their investments in opaque assets. It resulted in an increase of the total risk, the economic exposure (systematic risk) and the occurrence of negative returns (downside risk). Yet it is important to highlightthat unitholders of loser funds do not receive higher adjusted return as compensation for the higher risk faced.

A estabilidade de cor é crucial para o sucesso de qualquer tipo de restauração estética, pois a alteração de cor das resinas é o maior motivo para as trocas das restaurações anteriores. O objetivo desse trabalho foi avaliar similaridade de cor, sua estabilidade e opacidade de três compósitos diretos (TPH - Dentsply; Charisma - Heraus Kulzer; Concept - Vigodent) protegidos com selantes de superfície (Fortify e Biscover - Bisco) e cianoacrilato (Super Bonder - Loctite Henkel). Para cada compósito foram obtidos 40 corpos-deprova que foram divididos em 4 grupos, segundo o tipo de proteção recebida:Grupo 1 - sem selantes (controle); Grupo 2 - cianoacrilato; Grupo 3 - selante Fortify e Grupo 4 - selante Biscover. Os corpos-de-prova tiveram sua cor e opacidade avaliadas (Espectrofotômetro PCB 6087 BYK GARDNER) sendo, em seguida, submetidos a envelhecimento artificial acelerado (EAA - Sistema C-UV, Comexim) por 384 horas. Após esse período, foram feitas as medidas finais de cor e opacidade. Foram realizadas análises em Microscopia Eletrônica de Varredura (MEV - Jeol JSM 7500 - SII, Sony, Tokyo, Japan) para verificação da modificação superficial dos corpos-de-prova, antes e após envelhecimento. Verificou-se que os compósitos não apresentaram os mesmos valores para as coordenadas L*, a* e b*, antes do EAA. Todos os compósitos, independentes da cobertura de superfície, apresentaram alteração de cor após o EAA considerada clinicamente inaceitável (ΔE>=3,3). A alteração na opacidade foi pequena para os grupos protegidos, sendo que os melhores resultados foram conseguidos com o selante Fortify. As superfícies analisadas por MEV protegidas com selantes de superfície apresentaram maior lisura superficial que quando protegidas com cianoacrilato, tanto antes quanto após EAA. Concluiu-se que matizes iguais de compósitos não apresentaram similaridade de cor entre as marcas comerciais avaliadas. Além disso, selantes de superfície comerciais não foram efetivos na manutenção da cor dos compósitos, entretanto auxiliam na manutenção da opacidade. / The color stability is crucial for the success of any type of aesthetic restoration because color alteration of composite resins is the main reason for the replacement of restorations in anterior teeth. The purpose of the study was to evaluate the color similarity, stability and opacity of three direct resin composites (TPH - Dentsply; Charisma - Heraus Kulzer; Concept - Vigodent) protected with surface sealant (Fortify and Biscover - Bisco) and cyanoacrylate (Super Bonder - Loctite Henkel). Forty specimens were done for each composite and divided into 4 groups (n=10) according to the surface protection: G1 - without sealant; G2 - cianoacrilate; G3 - Fortify and G4 - Biscover. The specimens had their color and opacity evaluated by reflection spectrophotometry (Spectrophotometer PCB 6087 BYK GARDNER) and were sequentially submitted to the accelerated artificial aging (AAA - C-UV System, Comexim) for 384 hours. After this period, final color and opacity measurements were made. Scanning Electron Microscopy (SEM - Jeol JSM 7500 - SII, Sony, Tokyo, Japan) were accomplished to verify the specimens\' alteration before and after the artificial aging. It were verified that composites did not present the same values for L*, a* and b* coordinates before AAA. All composites, regardless of the surface coat, presented color alteration after AAA considered clinically unacceptable (ΔE>3.3). The opacity alteration was small for the protected groups, and the best results were achieved with Fortify sealant. The surfaces analyzed by SEM protected with sealant displayed higher superficial smoothness than those protected with cyanocrylate before and after the AAA. It were concluded that composite resins of the same shade did not present color similarity among the testes products. Besides, surface sealants were not effective in maintaining composite color, but aid to maintain the opacity.

Made available in DSpace on 2014-08-20T14:30:14Z (GMT). No. of bitstreams: 1 Dissertacao_Cari_Maristela_Pieper.pdf: 422459 bytes, checksum: 06736de352d724ef840d5461683237cd (MD5) Previous issue date: 2012-12-19 / The aim of this study was to evaluate the ability of two ceramic opaque masking applied in different thicknesses in a metallic substrate. 80 Ni-Cr (High Bond) metalic discs were fabricated, each with 1.6 mm diameter and 1 mm thickness, by lost wax technique. After disks obtaining, they were divided into 8 groups (n = 10) and opaque ceramic (Noritake) "paste" (groups 1 to 4) and "powder" (groups 5 to 8) was applied with a camel hair brush and distilled water. The opaque layers were machined with aluminum oxide burs to achieve the following thickness: G1 = G5 and 0.10 mm thick; G2 and G6 = 0.15 mm; G3 and G7 = 0.20 mm and G4 and G8 = 0.30 mm thick. Than opaque dentin ceramic was applied (two sintering cicles, totaling 0.7 mm) and glazed. The color was evaluated with the aid of a portable spectrocolorimeter (Konica - Minolta CR-10), which registered the color of specimens in the CIE L*a*b* scale. The absolute values of L *, a * and b * were statistically analyzed as isolated variables.The &#916;E were also analyzed, considering the mean values of L * a * b * in the control group (G4) as reference values. Once data showed normality and homogeneity, it were applied 2-way ANOVA and Tukey s complementary test, when needed, with p < 5%. Results: Powder opaque presented statistically significant greater values in (L*) and (&#916;E) and the reverse happened to other two variables. Analysing opaque thickness, values may be grouped as followed: (L*) variable: (0,10mm = 0,15mm) < (0,20mm = 0,30mm); (a*) variable: (0,10mm) < (0,15mm = 0,20mm) < (0,30mm); (b*) variable showed no statistically significant differences; (&#916;E) variable: (0,10mm) < (0,15mm = 0,20mm = 0,30mms). It could be concluded that paste and powder opaque have different behavior and all thickness, except 0,10 mm, may be used without significant color change / O objetivo deste estudo foi avaliar a capacidade de mascaramento de duas cerâmicas opacas aplicadas em espessuras diferentes num substrato metálico. Para isso foram confeccionados 80 discos metálicos de Ni-Cr (High Bond) com 16 mm de diâmetro e 1mm de espessura, através da técnica da cera perdida. Após a obtenção dos discos estes foram divididos em 8 grupos (n=10) e foi aplicada a cerâmica opaca (Noritake) em pasta (grupos de 1 à 4) e em pó (grupos de 5 à 8) com pincel de pêlo de camelo e água destilada. As camadas opacas foram usinadas com pontas de óxido de alumínio até atingirem as seguintes espessuras: G1 e G5 = 0,10mm de espessura; G2 e G6 = 0,15mm; G3 e G7 = 0,20mm e G4 e G8 = 0,30mm de espessura. Após, foi aplicada cerâmica de dentina opaca (em dois ciclos de sinterização totalizando 0,7mm), e em seguida à sinterização foi realizado o glaze final.A avaliação da cor foi realizada com o auxílio do Espectrocolorímetro portátil (Konica - Minolta CR-10), que registrou a cor dos 80 corpos de prova metalocerâmicos nos eixos da escala CIE - L*, a* b* após o ciclo de glaze. Os valores absolutos de L*, a* e b* dos grupos foram analisados estatísticamente como variáveis isoladas. Também foi analisado o valor da variável &#916;E, sendo que os valores médios de L* a* e b* do grupo controle (G4) foram considerados como os valores de referência para os cálculos do &#916;a, &#916;b, &#916;L e &#916;E dos demais grupos. Após constatada normalidade e homogeneidade dos dados foi aplicada análise de variância para dois fatores de variação (2-way ANOVA) e teste complementar de Tukey ambos para p<5%. Resultados: O opaco em pó apresentou valores maiores estaticamente significantes nas variáveis (L*) e (&#916;E), ocorrendo o inverso nas outras duas variáveis.Quanto à espessura de opaco, os valores podem ser agrupados da seguinte forma, segundo os testes complementares aplicados: variável (L*): (0,10mm = 0,15mm) < (0,20mm = 0,30mm); variável (a*): (0,10mm) < (0,15mm = 0,20mm) < (0,30mm); variável (b*): não houveram diferenças estatisticamente significantes; variável (&#916;E): (0,10mm) < (0,15mm = 0,20mm = 0,30mm). Conclui-se que houve diferença entre os tipos de opaco em pasta e em pó e que todas as espessuras testadas, exceto a de 0,10 mm, podem ser usadas sem alteração significativa da cor

In the first essay I examine the relation between firm advertising and tax aggressiveness. Advertising increases firm visibility in both the product and the financial market. While investors would appreciate more tax savings, they are aware of the negative impact of tax aggressiveness on consumers’ views of the firm and hence its competitive positions in the product market. We find that firms that spend more on advertising have fewer tax sheltering activities, lower book-tax differences, and higher cash effective tax rates. Specifically, an increase of 1% on Advertisingi,t (ADVGPi,t), the firm pays an additional tax of $0.70 million ($10.92 million). However, the negative impact of advertising on tax aggressiveness becomes weaker (and even reverses) for firms having great transparency, more public scrutiny, or strong external monitoring. We control for endogeneity using propensity score matching and an instrumental variable approach. Our findings are consistent with the argument that advertising enhances corporate reputation and is an important determinant in firms’ tax planning. In the second essay I document a significant increase in opportunistic insider trades when retail investors are paying greater attention to the stock. Using Google SVI to proxy for their level of attention, we find that a higher (lower) SVI on a stock is associated with more insider sales (purchases) of the stock and greater abnormal returns on the sales (purchases). A value-weighted long-short portfolio mimicking insider trades would earn an abnormal return of 1.19% per month (14.28% per year), excluding transaction costs. We also fund that the SVI-related insider traders tend to be non-independent directors who have long tenures but no senior executive positions in their firm and the firm tends to exhibit weaker governance, lower reputation, and poorer social responsibility. Our results are more pronounced for lottery-type stocks but are weaker for stocks with large attention of local investors. Interestingly, the risk of SEC investigation and litigation is lower on SVI-related insider sales and this type of sales actually rises following an increase in news releases of SEC enforcement action. Overall, certain insiders appear to engage in trades to take advantage of variations of retail investors’ attention to their stock.

Une propriété d'un objet est dite opaque pour un observateur si celui-ci ne peut déduire que la propriété est satisfaite sur la base de l'observation qu'il a de cet objet. Supposons qu'un certain de nombre de propriétés (appelées secrets) soient attachées à chaque intervenant d'un système, nous dirons alors que le système lui-même est opaque si chaque secret d'un observateur lui est opaque : il ne peut percer aucun des secrets qui lui ont été attachés. L'opacité a été étudié préalablement dans le contexte des systèmes à événements discrets où différents jeux d'hypothèses ont pu être identifiés pour lesquels on pouvait d'une part décider de l'opacité d'un système et d'autre part développer des techniques pour diagnostiquer et/ou forcer l'opacité. Cette thèse constitue la première contribution au problème de l'opacité des artefacts d'un système à flots de tâches (système workflow). Notre propos est par conséquent de formaliser ce problème en dégageant les hypothèses qui doivent être posées sur ces systèmes pour que l'opacité soit décidable. Nous indiquons quelques techniques pour assurer l'opacité d'un système. / A property (of an object) is opaque to an observer when he or she cannot deduce the property from its set of observations. If each observer is attached to a given set of properties (the so-called secrets), then the system is said to be opaque if each secret is opaque to the corresponding observer. Opacity has been studied in the context of discrete event dynamic systems where technique of control theory were designed to enforce opacity. This thesis is the first attempt to formalize opacity of artifacts in data-centric workflow systems. We motivate this problem and give some assumptions that guarantee the decidability of opacity. Some techniques for enforcing opacity are indicated.

Les propriétés radiatives sont d'une importance cruciale lors de l'étude des plasmas astrophysiques et de fusion, particulièrement dans des conditions hors équilibre thermodynamique local (hors-ETL). C'est pourquoi nous avons développé un modèle collisionnel-radiatif, capable de calculer les propriétés radiatives en toutes conditions de température et de densité. Nous avons intégré à ce modèle de nouveaux facteurs de Gaunt développés par nous-mêmes. Ces facteurs permettent d'obtenir des sections efficaces des processus atomiques plus précis que les formules classiques et semi-empiriques, nécessaires au calcul des populations atomiques. Ils ont été obtenus en utilisant des méthodes sophistiquées, telles que les méthodes distorted-wave et generelized-line-strength, à l'aide du code FAC. Dans le but de valider nos résultats, nous les avons comparés dans un premier temps, aux calculs de Hill et Rose d'un plasma composé d'un mélange de carbone et de 5% de silicium, dans des conditions ETL et hors-ETL. Les résultats sont très satisfaisants, aussi bien à l'ETL qu'hors-ETL. Nous avons aussi comparé nos résultats à la transmission mesurée par Xiong et al. d'un plasma de silicium à Te = 72 eV et Ne = 1.3 x 10²¹ cm⁻³. Là encore, nous obtenons un bon accord. Cependant, on constate la présence de quelques écarts au niveau du décalage spectral de certaines raies, ainsi que l'absence de certaines transitions. Cette absence peut s'expliquer par certaines configurations électroniques manquantes dans le calcul de structure atomique. Nous nous sommes aussi intéressés à l'absorption d'un mélange de carbone et de 5% de germanium avec un nombre restreint de configurations électroniques. Nous avons exploré l'effet d'interaction de configurations ainsi que l'effet d'un champ radiatif. Nous avons également déduit des lois permettant de calculer rapidement les lois de Planck et de Rosseland. Ces lois concernent pour le moment le carbone, le silicium et le germanium, pour Te entre 250 et 350 eV et Ne entre 2 et 8 x 10²³ cm⁻³. / The radiative properties are of utmost importance when studying astrophysical and ICF plasmas, particularly in non local thermodynamic equilibrium conditions. This is the reason why we have developed a collisional-radiative model that enables us to calculate the radiative properties of plasmas under any temperature and density conditions. We developed and implemented new Gaunt factors to the CR model. These factors greatly improve the precision when calculating the cross sections of the microscopic processes. These cross sections are required to calculate the populations of the atomic levels. We obtained these new factors by using the distorted-wave and generalized line strength methods of the Flexible Atomic Code (FAC).In order to validate our new-developed CR model, we compared our results to those of Hill and Rose, of a plasma composed of carbon and 5% silicon, in LTE and NLTE conditions. We obtained satisfactory results in both conditions. We also compared our results to the experimental transmission measured by Xiong et al., of a pure silicon plasma, with Te = 72 eV et Ne = 1.3 x 10²¹ cm⁻³. Again, we obtained results that are in good agreement with the measured spectrum. However, we noticed some discrepancies in the line shift of some lines, and some missing transitions. This can be explained by the absence of certain electronic configurations in the calculation of the atomic structure with the Cowan atomic code.We also explored the absorption of a plasma composed of carbon and 5% germanium with a restricted number of electronic configurations. We investigated the effect of configuration interaction and the effect of the radiative field. We also developed new laws that predict the Planck and Rosseland mean opacities very quickly. For the time being, these laws work for carbon, silicon and germanium, with Te between 250 and 350 eV, and Ne between entre 2 et 8x10²³ cm⁻³.

No description available.

This thesis is concerned with effects of spin polarization in neutron stars. In particular, we focus on static and dynamic properties of dense neutron matter. We use two different kind of potential to perform our studies: the phenomenological two-body Argonne V$8$' potential plus the three-body Urbana IX force and a modern local version of chiral effective potential up to next-to-next-to-leading order (N$2$LO). Estimates are calculated for the neutrino mean free path in partially spin-polarized neutron matter starting from Quantum Monte Carlo (QMC) simulations and using mean-field approaches to compute the response function in the longitudinal and transverse channel. We also compute magnetic susceptibility of dense neutron matter from accurate QMC calculations of partially spin-polarized systems. Twist-averaged boundary conditions (TABC) have been implemented to reduce finite-size effects. In the results, we also account for the theoretical uncertainty coming from the chiral expansion scheme. These results may play a role in studying high-energy phenomena such as neutron star mergers and supernova explosions, although they have been computed only at T$=0$ K.

In a town in northern Norway, the sailors on whale-watching boats meet whales in their daily work. Many have up to 30 years’ experience in locating the whales, through sight or submerged microphones, and in positioning the boats in non-intrusive ways that respect the whales’ life in the open water. But in spite of this continued, long-lasting contact, the sailors agree that there is not much that can be known about the whales. This study, based on interviews to the five seamen of one whale-watching company, explores the resources on which the sailors can draw to make sense of the underwater beings they interact with. Departing from the ontological paradigm that sees the world as made up of overlapping realities, the author draws on different aspects of multispecies theory to explore how anthropomorphism, technology, and kinship are key elements that make up the sailors’ relational ontology with whales. This is analysed in the light of the doctrine of opacity, which posits that it is not necessary to know the mind of others to have successful relations. This study hopes to further the exploration of topics within maritime anthropology, and to contribute to a better understanding of human/underwater beings that leads to the preservation of their environment.