Browsing by Issue Date, starting with "2021-07-28"
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- Effects of a Dynamic Leading Edge on a Plunging AirfoilPublication . Camacho, Emanuel; Neves, Fernando M. S. P.; Marques, Flávio D.; Barata, Jorge M M; Silva, AndréThe dynamics of oscillating airfoils are of great interest in many research areas such as rotor dynamics and biomimetics. The results reported in this research provide an insight into the mechanics of birds’ leading edge and how the dynamic curvature of the airfoil can highly benefit the aerodynamic and propulsive performance, especially at high angles of attack. The main goal of the current work is to numerically investigate the influence of a deflecting leading edge on the propulsive coefficients and flowfield created by a plunging airfoil at a Reynolds number of 1.4 × 104 and a constant Strouhal number of 0.15 with different ( k, ℎ) combinations. Employing a RANS approach with the proposed NACA0012-IK30 airfoil, results show that dynamically deflecting the leading edge significantly improves the propulsive efficiency of the airfoil by either reducing the required power or improving the thrust production. The outcomes regarding the propulsive efficiency show a considerable increase of up to 92% when the higher nondimensional amplitude was considered.
- Optimization of the GSH-Mediated Formation of Mesoporous Silica-Coated Gold Nanoclusters for NIR Light-Triggered Photothermal ApplicationsPublication . Fernandes, Natanael; Rodrigues, Ana Carolina Félix; Diogo, Duarte de Melo; Correia, I.J.; Moreira, AndréCancer light-triggered hyperthermia mediated by nanomaterials aims to eliminate cancer cells by inducing localized temperature increases to values superior to 42 C, upon irradiation with a laser. Among the different nanomaterials with photothermal capacity, the gold-based nanoparticles have been widely studied due to their structural plasticity and advantageous physicochemical properties. Herein, a novel and straightforward methodology was developed to produce gold nanoclusters coated with mesoporous silica (AuMSS), using glutathione (GSH) to mediate the formation of the gold clusters. The obtained results revealed that GSH is capable of triggering and control the aggregation of gold nanospheres, which enhanced the absorption of radiation in the NIR region of the spectra. Moreover, the produced AuMSS nanoclusters mediated a maximum temperature increase of 20 C and were able to encapsulate a drug model (acridine orange). In addition, these AuMSS nanoclusters were also biocompatible with both healthy (fibroblasts) and carcinogenic (cervical cancer) cells, at a maximum tested concentration of 200 g/mL. Nevertheless, the AuMSS nanoclusters’ NIR light-triggered heat generation successfully reduced the viability of cervical cancer cells by about 80%. This confirms the potential of the AuMSS nanoclusters to be applied in cancer therapy, namely as theragnostic agents.
- Development of cationic polymeric nanoparticles for plasmid DNA vaccine deliveryPublication . Nunes, Renato Pereira; Sousa, Ângela Maria Almeida de; Simaite, AivaCancer is the second most prevalent cause of death in the world and does not yet have a universal cure. Human papillomavirus (HPV) is among the main carcinogenic pathogens and its infection is related to several cancers, such as cervical and oropharyngeal cancers. Cervical cancer is the 4th largest cause of cancer in women worldwide. Nowadays it is considered one of the most common public health issue, principally in middle-aged women group, especially in less developed countries. The two major infectious papillomavirus genotypes are HPV16 and HPV18, and they are considered to be the most oncogenic and responsible for more than 70% of cervical cancers. Among the HPV virus oncoproteins the E7 oncoprotein inhibits the activity of the retinoblastoma protein (pRb), leading to a deregulation of the cell cycle and consequent uncontrolled growth of cells. Vaccination is considered to be the greatest contribution to global public health interventions of the latest centuries. The evolution and consequent contribution of vaccines are responsible for an impressive increase in general life expectancy. However, the current vaccines against the HPV do not have a therapeutic effect when the patient is already infected. This means that the vaccine can only prevent the infection by the HPV, but cannot treat or revert cancers induced by pre-existing and persistent HPV infections. In this way, DNA vaccines can be a promising solution for the effective treatment of HPV-infected individuals, since they can induce preventive and therapeutic immune responses. In order to be effective, the naked DNA needs to be internalized into the eukaryotic cell nucleus without degradation and the target gene expression is also dependent on the non-degradation of the DNA molecule. However, the internalization efficiency is low, due to the repulsion of the DNA by the membrane. Intramuscular delivery is one of the main routes for DNA vaccine administration. Nevertheless, it requires large amounts of the DNA administered and external stimulation to encourage the internalization of the DNA into the eukaryotic cells. In this work, we consider biocompatible drug delivery systems that can protect, carry and help the cellular internalization of DNA vaccines. This can lead to alternative and less invasive administration routes, such as intranasal administration. In this context, Chitosan (CS) polyplexes using sodium tripolyphosphate (TPP) as a crosslinker were designed and prepared using the ionotropic gelation method. Several parameters that may affect the systems formulation were investigated, including different TPP and CS volumes and concentrations, DNA concentrations, flow rate speed addition of TPP/DNA/pDNA solution. These nanocarriers were characterized in terms of size, surface charge, encapsulation efficiency, morphology, stability and cellular viability exploring two different cell lines. Ultimately, the verification of cell internalization and consequent target gene expression encoded in the DNA vaccine was also verified by reverse transcription polymerase chain reaction (RT-PCR) and reverse transcription-quantitative real-time. The results showed that the variation of parameters allowed to overcome an ordinary challenge regarding the CS systems achieving monodisperse nanoparticles (NPs) with good size, bellow 200 nm and encapsulation efficiency higher than 60%. The nanoparticles analyzed by scanning electron microscopy (SEM) present spherical or oval shapes in nano sizes. Stability studies demonstrated that the polyplexes are able to protect encapsulated DNA from serine proteases, trypsin, DMEM-F12 medium supplemented with 10% of fetal bovine serum, and Dulbecco´s Modified Eagle´s Medium with High Glucose (DMEM-HG) supplemented with 10% not inactivated fetal bovine serum. Resazurin assay showed that the systems are biocompatible supporting that no cytotoxicity is induced. In addition, the PCR and RT-qPCR results showed that produced nanoparticles have the desired and intended effect, showing that they are suitable for cell uptake, internalization, and gene expression. In conclusion, the presented results revealed that the CS-TPP-pDNA polyplexes are suitable as a good nanocarrier for plasmid DNA vaccine delivery.
- Avaliação objetiva e subjetiva dos sinais elétricos aplicados na estimulação elétrica nervosa transcutâneaPublication . Araújo, Ana Beatriz da Silva; Calado, Maria do Rosario AlvesA estimulação elétrica é utilizada regularmente por fisioterapeutas, sendo usualmente indicada para o alívio da dor. A estimulação elétrica nervosa transcutânea é uma terapêutica não invasiva, que através de um estimulador externo, faz circular uma corrente elétrica que atravessa os elétrodos que estão colocados na superfície da pele. Em 1965, Melzack e Wall forneceram uma justificação fisiológica para os efeitos analgésicos da eletroestimulação. Propuseram a teoria de controlo do portão. De acordo com esta teoria, a ativação de fibras aferentes de grande diâmetro, fibras A-beta, provoca a ativação local de mecanismos inibitórios no corno dorsal da medula espinhal causando a inibição pré-sináptica das fibras aferentes nociceptivas, fibras A-delta e C, provocando um alívio da dor. A TENS aplica uma corrente de baixa frequência quando comparada a todo o espectro de frequências de corrente elétrica disponíveis para uso terapêutico, e pode ser classificada em quatro modalidades: convencional, acupuntura, burst e breve-intenso. Este estudo teve como objetivo avaliar, numa pequena amostra de indivíduos, a experiência dolorosa que a TENS pode provocar e os seus efeitos térmicos, recorrendo a uma escala numérica da dor e à termografia, respetivamente.
- Computational Analysis of High-Pressure Nitrogen Jets from Transcritical to Supercritical Gas-Like ConditionsPublication . Magalhães, Leandro; Silva, André; Barata, Jorge M MA fluid is considered to be in a supercritical state if its pressure and temperature are above their critical point values, which can be regarded as identifiers of pure fluid. However, in the thrust chamber of liquid rocket engines, the propellant mixture is a reality, which albeit being injected at supercritical conditions, can lead to local transcritical behavior, meaning that the mixture temperature can have values below its critical point condition. As such, an accurate numerical solver aiming at characterizing the flow inside the combustion chamber of liquid rocket engines needs to replicate transcritical behavior. The present study is focused on the analysis of nitrogen jets under transcritical and supercritical conditions. While a greater approximation to the experiments is obtained for the tested supercritical conditions, insights are obtained into transcritical behavior and the transition between transcritical and supercritical jet behavior.