Formulaçao de um elemento finito de cabo incorporando o efeito do atrito (Elemento de cabos escorregando)

O trabalho apresenta a formulacáo geometricamente exata e a implementaçao computacional de um elemento finito de cabo que permite o escorregamento em presenca de atrito. O novo elemento fornece procedimentos naturais para simular o processo de montagem e a resposta aos carregamentos de estruturas de cabos em geral, além de ter campos promissores de aplicaçáo no modelamento de estruturas de concreto protendido e no estudo de oscilaçoes auto-excitáveis. Resultados de exemplos elementares sáo discutidos.Peer Reviewe

Formulaçao de um elemento finito de cabo incorporando o efeito do atrito (Elemento de cabos escorregando)

O trabalho apresenta a formulacáo geometricamente exata e a implementaçao computacional de um elemento finito de cabo que permite o escorregamento em presenca de atrito. O novo elemento fornece procedimentos naturais para simular o processo de montagem e a resposta aos carregamentos de estruturas de cabos em geral, além de ter campos promissores de aplicaçáo no modelamento de estruturas de concreto protendido e no estudo de oscilaçoes auto-excitáveis. Resultados de exemplos elementares sáo discutidos.Peer Reviewe

Spatial revolute joints with clearances for dynamic analysis of multi-body systems

This paper presents a new technique for assessing the influence that clearance of spatial joints has on the kinematics and dynamics of multi-body systems. The technique is developed for the revolute joint in which the basic elements are the journal and bearing. Under certain working conditions, these two mechanical elements collide with each otherbeing the contact treated as coupled forces. The forces between each pair of contacting bodies are equal and opposite, and the magnitude and direction are calculated based on the positions and velocities of the bodies, as well as on the geometry of the joint. A continuous contact force model is used to evaluate the contact–impact force. The proposed methodology is developed in the framework of the multi-body systems formulation; therefore, the forces developed during the contact between the joint elements are introduced into the systems’ equations of motion as external forces. A double pendulum is used as a numerical example to show the application of the proposed methodology, being the efficiency of the developed methodologies discussed in the process of the results obtained.FEDER - Project POCTI/2001/EME/ 38281Fundação para a Ciência e a Tecnologia (FCT

Dynamic behaviour of planar rigid multi-body systems including revolute joints with clearance

This paper deals with a general methodology to assess the influence of the clearance size and the friction coefficient on the dynamic response of planar rigid multi-body systems including revolute joints with clearance. When there is a clearance in a revolute joint, impacts between the journal and the bearing can occur, and consequently, local deformations take place. The impact is internal and the response of the system is performed using a continuous contact force model. The friction effect because of the contact between joint elements is also included. The dynamic response of the systems is obtained numerically by solving the constraint equations and the contact-impact forces produced in the clearance joint, simultaneously with the differential equations of motion and a set of initial conditions. Numerical results for two simple mechanisms with revolute clearance joints are presented and discussed. In the present work, the clearance size and friction effects are analysed separately. Through the use of Poincaré maps, both periodic and chaotic responses of the systems are observed. The results predict the existence of the periodic or regular motion at certain clearance sizes and friction coefficients and chaotic or non-linear in other cases.FEDER - Project POCTI/2001/EME/38281Fundação para a Ciência e a Tecnologia (FCT

O elemento inconsciente na literatura e na filosofia (1921): tradução de Pedro Paulo Pimenta

Portuguese translation of: CORNFORD, Francis M. (1950). “The Unconscious Element in Literature and Philosophy (1921)”, In: The Unwritten Philosophy and Other Essays, edited by W. K. C. Guthrie, Cambridge: Cambridge University Press, pp. 1-13.Tradução em português de: CORNFORD, Francis M. (1950). “The Unconscious Element in Literature and Philosophy (1921)”, In: The Unwritten Philosophy and Other Essays, edited by W. K. C. Guthrie, Cambridge: Cambridge University Press, pp. 1-13

A study on dynamics of mechanical systems including joints with clearance and lubrication

In this work a methodology for the dynamical analysis of mechanical systems considering realistic joint characteristics, namely, joints with clearance and lubrication is presented. For the case of the joints with clearance modelled as a contact pair with dry contact, a technique using a continuous approach for the evaluation of the contact force is applied, in which the energy dissipation in form of hysteresis damping is considered. The friction forces are calculated using a modified Coulomb’s friction law. For the lubricated case, the hydrodynamic theory for dynamically loaded journal–bearings is used to compute the forces generated by lubrication action. The numerical results point out that the existence of dry joint clearances causes high peaks on the kinematic and dynamic system’s characteristics due to contact–impact forces when compared to those obtained with lubricated model. The performance of the lubricated joint is closer to that of an ideal joint.FEDER - Project POCTI/2001/EME/38281Fundação para a Ciência e a Tecnologia (FCT

Characterization of silicon photodiodes for diffuse reflectance signal extraction

Early detection of gastrointestinal (GI) can cers is one of most important concerns in medical field. Its detection at the earliest stage is crucial to increase the patient survival chances. Optical signals extraction and analysis, specifically diffuse reflectance and intrinsic fluorescence, may impr ove the ability to detect GI dysplasia, once some morphological and biochemical changes on the tissues (related with early cancer progre ssion) can modify these signals’ shape and intensity. The project under th is paper aims to develop a chip - sized spectros copy microsystem for the early detection of GI cancer. This paper presents the characterization of silicon photodiodes (n+/p - epilayer type) fabricated in a standard 0.7 μm CMOS process, with different dimensions. The main goal is to conclude which photodio de must be fabricated for the microsystem implementation, taking into account its capacity to extract the signals in the relevant spectral band (350 nm – 750 nm), not comprising the microsystem dimensions. With this study , it can be conclude d that the suit able photodiodes for the detection of those spectroscopic signals are the ones with 125 × 125 μm 2 or 100 × 100 μm 2 active area , once their quantum efficiency varies between 20% and 55%, approximately, above 450 nm. In spite of the low photodiod es quantum efficiency (lower than 20%) below 450 nm, the viability of using the 100 × 100 μm 2 photodiode to extract the diffuse reflectance signal, between 350 nm and 750 nm, was proven using a test phantom representative of a GI tissue.This work is funded by FEDER funds through the "Eixo I do Programa Operacional Fatores de Competitividade (POFC) QREN, projects reference COMPETE: FCOMP-01-0124-FEDER-020241 and FCOMP-01-124-FEDER-037291 (PEst-C/FIS/UI0607/2013) and by FCT – Fundação para a Ciência e a Tecnologia, project reference PTDC/EBB-EBI/120334/2010. S. Pimenta thanks the FCT for the SFRH/BD/87605/2012 PhD grant

Effects of light intensity on the distribution of anthocyanins in Kalanchoe brasiliensis Camb. and Kalanchoe pinnata (Lamk.) Pers

This paper compares two medicinal species of Kalanchoe, which are often used interchangeably by the population, regarding the distribution of anthocyanins under the influence of four luminosity levels for 6 months. For the morphoanatomical analysis, the 6th stem node of each plant was sectioned. Usual histochemical tests revealed the presence of anthocyanins by cross sections of the stems, petioles and leaf blades. The petioles and leaf blades were submitted to the extraction with acidified methanol, and the anthocyanins were quantified by spectrophotometric readings. At the macroscopic level, it was noticed for both species a higher presence of anthocyanins in stems and petioles of plants under full sunlight. The microscopy of K. brasiliensis stems evidenced the deposition of anthocyanins in the subjacent tissue to the epidermis and cortex, which increased with light intensity. In K. pinnata a subepidermal collenchyma was observed, which interfered in the visualization of anthocyanins. In petioles and leaf blades of K. brasiliensis the deposition of anthocyanins was peripheral, and in K. pinnata it was also throughout the cortex. The quantification of anthocyanins in petioles showed in 70% of light higher averages than in 25%, but in leaf blades there were no significant results. This study contributes to the pharmacognosy of Kalanchoe and it is sustained by the description of flavonoids as biological markers of the genus.Este trabalho compara duas espécies medicinais de Kalanchoe utilizadas muitas vezes de forma indiferenciada pela população, quanto à distribuição de antocianinas sob influência de quatro níveis de luminosidade por 6 meses. Para a análise morfoanatômica foi seccionado o 6 º nó do caule de cada planta. Testes histoquímicos clássicos evidenciaram a presença de antocianinas em cortes transversais dos caules, pecíolos e lâminas foliares. Os pecíolos e lâminas foliares foram submetidos à extração com metanol acidificado e as antocianinas foram quantificadas através de leituras espectrofotométricas. Observou-se em nível macroscópico nas duas espécies, maior presença de antocianinas nos caules e pecíolos das plantas sob luz plena. A microscopia de caules de K. brasiliensis evidenciou a deposição de antocianinas no tecido subjacente à epiderme e córtex, o que aumentou com a intensidade luminosa. Em K. pinnata, observou-se colênquima subepidérmico, o que interferiu na visualização de antocianinas. Nos pecíolos e lâminas foliares de K. brasiliensis, a deposição de antocianinas foi periférica e em K. pinnata, se deu também por todo o córtex. A quantificação de antocianinas dos pecíolos mostrou, em 70% de luminosidade, teores superiores aos obtidos em 25%, porém nas lâminas foliares não foram obtidos resultados significativos. Este trabalho contribui para a farmacognosia de Kalanchoe e sustenta-se pela descrição de flavonóides como marcadores biológicos do gênero

Nature of the constant factor in the relation between radial breathing mode frequency and tube diameter for single-wall carbon nanotubes

Resonance Raman scattering is used to determine the radial breathing mode (RBM) frequency (ωRBM) dependence on tube diameter (dt) for single-wall carbon nanotubes (SWNTs). We establish experimentally the ωRBM=227.0/dt as the fundamental relation for pristine SWNTs. All the other RBM values found in the literature can be explained by an upshift in frequency due mostly to van der Waals interaction between SWNTs and environment

Assessment of PCR in the detection of Leishmania spp in experimentally infected individual phlebotomine sandflies (Diptera: Psychodidae: Phlebotominae)

DNA amplification by the polymerase chain reaction (PCR) was applied in the investigation of the presence of Leishmania (Kinetoplastida: Trypanosomatidae) parasites in single phlebotomine sandflies. Three phlebotomine/parasite pairs were used: Lutzomyia longipalpis/Leishmania chagasi, Lutzomyia migonei/Leishmania amazonensis and Lutzomyia migonei/Leishmania braziliensis, all of them incriminated in the transmission of visceral or cutaneous leishmaniasis. DNA extraction was performed with whole insects, with no need of previous digestive tract dissection or pooling specimens. The presence of either mouse blood in the digestive tract of the sandflies or the digestive tract itself did not interfere in the PCR. Infection by as few as 10 Leishmania sp. per individual were sufficient for DNA amplification with genus-specific primers. Using primers for L. braziliensis and L. mexicana complexes, respectively, it was possible to discriminate between L. braziliensis and L. amazonensis in experimentally infected vectors (L. migonei).Neste trabalho avaliamos o uso da reação em cadeia da polimerase (PCR) na investigação da presença de parasitas Leishmania (Kinetoplastida:Trypanosomatidae) em flebotomíneos individuais. Para isso, foram utilizados três pares flebotomíneo/parasita: Lutzomyia longipalpis/Leishmania chagasi, Lutzomyia migonei/Leishmania amazonensis e Lutzomyia migonei/Leishmania braziliensis, todos eles incriminados na transmissão de leishmaniose cutânea ou visceral. O DNA total a ser amplificado foi extraído de flebotomíneos inteiros, contendo ou não o parasita, sem dissecção prévia do trato digestivo ou combinação de indivíduos. Conteúdos do trato digestivo de flebotomíneos, em especial sangue de camundongo, não interferiram na reação de amplificação. Dez parasitas Leishmania sp. por flebotomíneo foram suficientes para detecção com iniciadores gênero-específicos. Com a utilização de iniciadores para os complexos L. braziliensis e L. mexicana, respectivamente, foi possível discriminar entre L. braziliensis e L. amazonensis, em flebotomíneos infectados experimentalmente (L. migonei)