Structural numerical analysis of a branched modular stent-graft for aneurysms encompassing all zones of the aortic arch.

The development of stent-grafts for the total repair of aneurysms in the aortic arch is still a technical challenge due mainly to the anatomical complexity of this region. Research performed here structurally evaluated a modular branched stent-graft for aneurysms encompassing all zones of the aortic arch by means of numerical simulations using fluid-structure interaction. The geometric domain obtained by means of computed tomography was subjected to physiological boundary conditions. The blood was modelled as non-Newtonian by the Carreau model, and the arterial wall was modelled as anisotropic hyperelastic by the Holzapfel model. The material adopted for the stents was Nitinol, and expanded polytetrafluoroethylene (ePTFE) was used for the graft. A comparison of the structural behaviour of the aneurysmal aortic arch before and after stent-graft implantation was performed. The numerical flow model was experimentally verified in vitro on a representative test bench of blood flow in the aortic arch. The stent-graft was shown to minimally modify arterial wall dynamics and was not susceptible to migration and endoleak. Peak stresses and strains were found in the stents and graft, respectively, while the stresses in the aneurysm sac were significantly reduced, of the order of 97.5%, due to the isolation of the arterial wall by the stent-graft.

Comparative study between 1-way and 2-way coupled fluid-structure interaction in numerical simulation of aortic arch aneurysms.

Hemodynamic forces are related to pathological variations of the cardiovascular system, and numerical simulations for fluid-structure interaction have been systematically used to analyze the behavior of blood flow and the arterial wall in aortic aneurysms. This paper proposes a comparative analysis of 1-way and 2-way coupled fluid-structure interaction for aortic arch aneurysm. The coupling models of fluid-structure interaction were conducted using 3D geometry of the thoracic aorta from computed tomography. Hyperelastic anisotropic properties were estimated for the Holzapfel arterial wall model. The rheological behavior of the blood was modeled by the Carreau-Yasuda model. The results showed that the 1-way approach tends to underestimate von Mises stress, displacement, and strain over the entire cardiac cycle, compared to the 2-way approach. In contrast, the behavior of the variables of flow field, velocity, wall shear stress, and Reynolds number when coupled by the 1-way model was overestimated at the systolic moment and tends to be equal at the diastolic moment. The quantitative differences found, especially during the systole, suggest the use of 2-way coupling in numerical simulations of aortic arch aneurysms due to the hyperelastic nature of the arterial wall, which leads to a strong iteration between the fluid and the arterial wall.

Impact of pivoting bite tip on bite force measurement tests.

OBJECTIVE: Present a gnathodynamometer design that increases patient comfort, precision, and/or ease for the operator during bite force tests. MATERIALS AND METHODS: A bite tip capable of pivoting 180° was tested on senior dental students in a double-blind trial. The tests were performed in teeth 11 and 16 with the bite tip on the long axis of the clamp and at an angle of 90° to the clamp. The sample was composed of 24 students, 13 males and 11 females, randomly divided into two groups: the operator group (OP), which was composed of 12 students, 7 males and 5 females, and the test group (TI), which was composed of 12 students, 6 males and 6 females. The operator and participants were asked to evaluate comfort and precision/ease in positioning the bite tip by attributing scores from 0 (total discomfort) to 10 (total comfort) during the test. RESULTS: No difference was noted in tooth 11 (P > 0.05). In tooth 16, there was a statistically significant improvement (P < 0.01) for the participants tested and the operator using the pivoting bite tip. CONCLUSIONS: The pivoting bite tip showed no difference in the comfort of the participants and operator precision when testing incisors; however, the tip showed a difference for both conditions in the molar region. The gnathodynamometer geometry showed good results in participant comfort and operator precision when used in bite force tests of the incisors and molars. Further investigations are needed to confirm whether these improvements influence the mean value and maximum bite force measurement. CLINICAL RELEVANCE: Bite force measurement is a method for obtaining important data to check the functional conditions of the stomatognathic system. With the aging of the world population, it has become important to check the quality of life during aging. The pivoting bite tip improves the comfort and precision of bite tests for the participants tested and for the operator, respectively.

Efficacy of ultrasound vector flow imaging in tracking omnidirectional pulsatile flow.

BACKGROUND: Ultrasound vector flow imaging (VFI) shows potential as an emerging non-invasive modality for time-resolved flow mapping. However, its efficacy in tracking multidirectional pulsatile flow with temporal resolvability has not yet been systematically evaluated because of the lack of an appropriate test protocol. PURPOSE: We present the first systematic performance investigation of VFI in tracking pulsatile flow in a meticulously designed scenario with time-varying, omnidirectional flow fields (with flow angles from 0° to 360°). METHODS: Ultrasound VFI was performed on a three-loop spiral flow phantom (4 mm diameter; 5 mm pitch) that was configured to operate under pulsatile flow conditions (10 ml/s peak flow rate; 1 Hz pulse rate; carotid pulse shape). The spiral lumen geometry was designed to simulate recirculatory flow dynamics observed in the heart and in curvy blood vessel segments such as the carotid bulb. The imaging sequence was based on steered plane wave pulsing (-10°, 0°, +10° steering angles; 5 MHz imaging frequency; 3.3 kHz interleaved pulse repetition frequency). VFI's pulsatile flow estimation performance and its ability to detect secondary flow were comparatively assessed against flow fields derived from computational fluid dynamics (CFD) simulations that included consideration of fluid-structure interactions (FSI). The mean percentage error (MPE) and the coefficient of determination (R2 ) were computed to assess the correspondence of the velocity estimates derived from VFI and CFD-FSI simulations. In addition, VFI's efficacy in tracking pulse waves was analyzed with respect to pressure transducer measurements made at the phantom's inlet and outlet. RESULTS: Pulsatile flow patterns rendered by VFI agreed with the flow profiles computed from CFD-FSI simulations (average MPE: -5.3%). The shape of the VFI-measured velocity magnitude profile generally matched the inlet flow profile. High correlation exists between VFI measurements and simulated flow vectors (lateral velocity: R2  = 0.8; axial velocity R2  = 0.89; beam-flow angle: R2  = 0.98; p < 0.0001 for all three quantities). VFI was found to be capable of consistently tracking secondary flow. It also yielded pulse wave velocity (PWV) estimates (5.72 ± 1.02 m/s) that, on average, are within 6.4% of those obtained from pressure transducer measurements (6.11 ± 1.15 m/s). CONCLUSION: VFI can consistently track omnidirectional pulsatile flow on a time-resolved basis. This systematic investigation serves well as a quality assurance test of VFI.

Caeski: an assistive technology for the communication of persons with deafblindness.

PURPOSE: Caeski is a keyboard with 12 vibrating keys that connects to an application via smartphone. This assistive technology aims to facilitate the communication of persons with deafblindness in presential contexts or with people who can be anywhere in the world. The purpose is to present this assistive technology and analyse the viability of its use through tests with eleven persons with deafblindness. MATERIALS AND METHODS: The study design consisted of ten days of testing with eleven persons with deafblindness and five interpreters who had the function of passing the information about the content of the tests. RESULTS: The tests showed that most participants were able to communicate through Caeski. In addition, the tests showed the need to add the function of repeating the reception of information via vibration to confirm the understanding. The results demonstrated the need for more training time to improve the learning of accented words and long sentences. Therefore, training time and previous contact with technological devices are factors that influence the result of the tests. CONCLUSION: The use of Caeski is feasible and as future perspectives, this assistive technology can be used in association with similar assistive technologies such as Perkins Machine and Braille Line, preventing possible tactile overloads. In addition, can be applied in the educational context, from literacy to university. Studies with longer training time should be conducted to confirm the results. The implications for rehabilitation:Social interactions, presential and online, with deafblind and non-deafblind persons anywhere in the world.Literacy and cognitive development of persons with deafblindness.Digital inclusion for occupational, school or academic contexts.

In vitro evaluation of physical and chemical parameters involved in aPDT of Aggregatibacter actinomycetemcomitans.

Periodontitis is an infectious disease characterized by the destruction of supporting tissues. Antimicrobial photodynamic therapy (aPDT) has been proposed as an improved method for eliminating microorganisms. Its efficiency depends on the correct use of physical and chemical parameters. Thus, these parameters and their relations were evaluated in this study with the purpose of establishing lethal conditions for combating bacterial agents. Diode lasers and light-emitting diodes (LEDs) were characterized to evaluate the absorption profile and resonance of methylene blue (MB) and toluidine blue O (TBO). The relations between light energy density and photosensitizer absorption were determined. Two methodologies were used to evaluate the effects of aPDT against Aggregatibacter actinomycetemcomitans. LED light exhibited a broad emission spectrum with a peak light wavelength of 637 nm and 99% purity. The resonance intensity of MB was higher with diode laser irradiation, and TBO showed higher resonance intensity with LED irradiation. There was no difference in the absorption profile of photosensitizers using diode lasers or LEDs, and variations in power density did not result in an increasing or decrease in light absorption. A. actinomycetemcomitans was susceptible to photodynamic processes. Emission spectra and peak light wavelengths of light sources combined with the absorption profiles of photosensitizers were the main parameters involved in determining the efficiency of photodynamic effects. Power density did not alter the light absorption of photosensitizers. The association between adequate irradiation characteristics and photosensitizer absorption results in complete inactivation of A. actinomycetemcomitans. In addition, the bactericidal effect was not altered by an increase in energy densities.

Validation of the Brazilian Version of the RMS Tactile Scale (B-RMS-TS).

This study aimed to validate the Brazilian version of the RMS Tactile Scale (B-RMS-TS) in children and adolescents with visual impairment. Ten visually impaired children and adolescents between 10 and 17 years old of an Educational Center for Visually Impaired People answered the verbalized Dental Anxiety Scale (DAS), and the DAS in Braille to evaluate their dental anxiety levels. B-RMS-TS construct validity was assessed by convergent and discriminant validity. Convergent validity was tested in two ways: Pearson's correlation between the B-RMS-TS and the overall anxiety question; Pearson's correlation between B-RMS-TS and verbalized DAS and DAS in Braille. B-RMS-TS reliability was measured by internal consistency (Cronbach's alfa and McDonald's omega) and test-retest reliability (ICC). B-RMS-TS was moderately correlated to the overall anxiety question (r=0.493;p=0.147). B-RMS-TS showed excellent correlation with verbalized DAS (r=0.971;p<0.001) and DAS in Braille (r=0.934;p<0.011). B-RMS-TS was able to discriminate dental anxiety levels between male and female (p=0.008). The B-RMS-TS demonstrated excellent reliability (Cronbach's alpha=0.661, McDonald's omega=0.700 and ICC=0.987; 95%CI=0.817-0.999). B-RMS-TS is valid and reliable to measure dental anxiety levels in Brazilian children and adolescents with visual impairment.

Phototherapy (cluster multi-diode 630 nm and 940 nm) on the healing of pressure injury: A pilot study.

The therapeutic benefits of LED in wound care have been reported since the 1990s. Nevertheless, studies directly related to the effects of LED phototherapy on the venous and arterial circulation and the healing process of pressure injuries are scarce in literature. Thus, the aim of this study was to evaluate the efficacy of a LED phototherapy prototype in participants with pressure injuries. In this pilot study 15 participants were randomized into three therapeutic groups. The experimental groups received applications of 630 and 940 nm LED three times a week for 8 weeks, with a dose of 6 J/cm2 in Group I. In group II, a dose of 8 J/cm2 in addition to the standard treatment. Group III (control group) received only daily standard treatment which consisted of cleaning the lesioned area with physiological solution, followed by application of an alginate hydrogel dressing over a period of 8 weeks. Pressure injuries were photographed and the area was measured by the Quantikov® image analyzer software. There was no statistically significant difference (p > 0.05) between the three groups when assessing the initial lesion area. At the end of 2 months, the median and interquartile ranges of the injuries were 5.90 (0.79-9.5) cm2 for group I, 0.54 (0.47-1.16) cm2 for group II and 26.76 (17.25-41.05) for group III. There was a statistically significant difference between treatment types (I x III and II x III) for pressure injuries over the 21 sessions. However, there was no significant difference between groups I x II that received different doses of LED phototherapy. The initial hypothesis was supported given that the combination of two wavelengths in the LED phototherapy with different doses may be helpful in accelerating the healing of pressure injuries.

Validation of the Brazilian Version of the RMS Tactile Scale (B-RMS-TS)

Abstract This study aimed to validate the Brazilian version of the RMS Tactile Scale (B-RMS-TS) in children and adolescents with visual impairment. Ten visually impaired children and adolescents between 10 and 17 years old of an Educational Center for Visually Impaired People answered the verbalized Dental Anxiety Scale (DAS), and the DAS in Braille to evaluate their dental anxiety levels. B-RMS-TS construct validity was assessed by convergent and discriminant validity. Convergent validity was tested in two ways: Pearson's correlation between the B-RMS-TS and the overall anxiety question; Pearson's correlation between B-RMS-TS and verbalized DAS and DAS in Braille. B-RMS-TS reliability was measured by internal consistency (Cronbach's alfa and McDonald's omega) and test-retest reliability (ICC). B-RMS-TS was moderately correlated to the overall anxiety question (r=0.493;p=0.147). B-RMS-TS showed excellent correlation with verbalized DAS (r=0.971;p<0.001) and DAS in Braille (r=0.934;p<0.011). B-RMS-TS was able to discriminate dental anxiety levels between male and female (p=0.008). The B-RMS-TS demonstrated excellent reliability (Cronbach's alpha=0.661, McDonald's omega=0.700 and ICC=0.987; 95%CI=0.817-0.999). B-RMS-TS is valid and reliable to measure dental anxiety levels in Brazilian children and adolescents with visual impairment.

Resumo Este estudo objetivou validar a versão brasileira da escala tátil RMS (B-RMS-TS) em crianças e adolescentes com deficiência visual. Dez crianças e adolescentes deficientes visuais entre 10 e 17 anos de idade de um Centro Educacional para Pessoas Deficientes Visuais responderam a Dental Anxiety Scale (DAS) verbalizada, e a DAS em Braille para avaliar seus níveis de ansiedade odontológica. A validade de construto da B-RMS-TS foi avaliada pela validade convergente e discriminante. A validade convergente foi testada em duas maneiras: correlação de Pearson entre a B-RMS-TS e a questão geral de ansiedade; correlação de Pearson entre a B-RMS-TS e a DAS verbalizada e a DAS em Braille. A confiabilidade da B-RMS-TS foi mensurada pela consistência interna (alfa de Cronbach e ômega de McDonald).) e confiabilidade teste-reteste (CCI). A B-RMS-TS foi correlacionada moderadamente à questão geral de ansiedade (r=0,493;p=0,147). A B-RMS-TS mostrou correlação excelente com a DAS verbalizada (r=0,971;p<0,001) e com a DAS em Braille (r=0,934;p<0,011). A B-RMS-TS foi capaz de discriminar níveis de ansiedade odontológica entre meninos e meninas (p=0,008). A B-RMS-TS demonstrou confiabilidade excelente (alfa de Cronbach=0,661, ômega de McDonald=0,700 e CCI=0,987; 95%IC=0,817-0,999). A B-RMS-TS é válida e confiável para mensurar níveis de ansiedade odontológica em crianças e adolescentes brasileiros com deficiência visual.

Influence of hemodialysis blood flow rate on the thrombogenic potential in patients with central venous catheters.

In this study we apply methods to determine the tendency for thrombus formation in different central venous catheters (CVC) models associated with flow rate variation. To calculate the thrombogenic potential, we proposed a new numerical model of the platelet lysis index (PLI) equation. To compare the results of PLI and flow rate in different models of catheters, numerical calculations were performed on three different tips of CVC. The results showed that the PLI increases as a power function of the flow rate independent of the type of CVC. This study evidenced that the higher the blood flow rate used in the catheter, the greater the potential for thrombus formation. The PLI computed at the catheter outlet presented higher values when compared to the values computed at the vein outlet indicating that the blood flow through the CVC arterial lumen presents a proportionally larger thrombogenic potential when compared to the blood flow that leaves the vein towards the atrium. This finding may have consequences for clinical practice, since there is no specific flow value recommended in the catheter when the hemodialysis machine is turned on, and with this equation it was possible to demonstrate the thrombogenic potential that the flow rate can possibly offer.

Activated platelets in central venous catheters: a flow cytometry and numerical simulation approach

The central venous catheter that is inserted in patients undergoing hemodialysis can cause hemodynamic instability and trigger complications such as thrombus formation. The objective of this study was to investigate hemostatic and numerical influences on thrombus formation in patients undergoing hemodialysis with a central venous catheter. Participants were assigned to three groups: I: clinical and laboratorial healthy individuals matched by sex and age (controls); II: participants after one month of insertion of the catheter and III: participants after 4 months of insertion of the catheter. Platelet activation was investigated by GPIIb/IIIa and p-selectin expressions using flow cytometry. A three-dimensional model of the catheter was constructed in the numerical simulation for the calculation of partial differential equation of a platelet activation model. A significant difference was detected by the expression of p-selectin comparing the group I (33.42 ± 4.74), group II (40.79 ± 5.54) and group III(51.00 ± 7.21) (p < 0.0001). The median values for GPIIb/IIIa were 10426 (10029-10721), 13921 (13412-15652) and 19946 (18714-21815) after catheter insertion (p < 0.0001), for groups I, II and III, respectively. Excluding the first arterial orifice, venous orifices tend to have greater platelet activation when compared to the other arterial orifices. The results of this study showed the influence of arterial and venous lateral orifices in stimulating the development of thrombi associated with the activation of platelet markers the longer the catheter was used.

Resistance to fracture of intraradicular posts made of biological materials.

BACKGROUND: The aim was to analyze the fracture resistance of human teeth treated endodontically and restored with posts made of bovine dentin, human dentin, or glass fiber, and to evaluate the fracture pattern. METHODS: Cylindrical posts of 1.5 mm in diameter cemented to the roots of human maxillary canines presented a length of 15 mm, cervical diameter of 5-5.5 mm in the mesiodistal direction, and 7-7.5 mm in the vestibule-palatal direction. The groups studied were: Group I-10 glass fiber posts; Group II-10 human dentin posts; Group III-10 bovine dentin posts (self-adhesive resin cement); and Group IV-10 bovine dentin posts (resin-modified glass-ionomer cements). The coronal part of tooth was restored with a standardized core build-up using composite. All of the groups were submitted to a compression force test and the resistance to fracture was verified using a universal testing machine. The fracture pattern was likewise evaluated. RESULTS: The values of resistance to fracture were: 723.3N in group I, 561.5N in group II, 556.6N in group III, and, 613.27N in group IV. However, no statistically significant difference was observed among the groups. The fractures in groups I and II were most commonly found in the middle/apical third and were considered irreparable. For restored teeth in group III, half of the fractures appeared in the cervical third and were reparable. In group IV, all of the fractures were reparable, with the majority in the cervical thirds. CONCLUSION: Bovine dentin can be used as intraradicular post to substitute human dentin and glass fiber posts. The greater the malleability of the post, the greater the chances of survival of the teeth when subjected to fracture testing.

Overall indexes of coordination in front crawl swimming.

The aim of this study was to propose a group of parameters able to quantify not only arm coordination but also inter limb coordination. These include the well know index of coordination with the relative duration of the stroke phases and two new parameters: the Index of synchronization (Ids) between arms and legs actions; and the Index of inter limb coordination (IdIC) calculated as the relative foot position during successive arm stroke phases. These parameters were compared between experts and amateur swimmers in a maximal front crawl sprint. The influence of arm stroke in leg kick parameters was also assessed, comparing the full stroke condition with a condition without arms actions. Sixty-five per cent of expert swimmers used synchronized limb actions while 95% of amateur swimmers used non-synchronized limb motions. These synchronized expert swimmers also converged towards a specific coordination pattern between foot position and arm stroke phases. In the condition without arms, both groups changed kick rate and amplitude. The present study reveals the interdependency of arms and legs actions and the importance of coordination and synchronization between limbs. Therefore, the proposed group of overall indexes of coordination provides a more complete marker for the analysis of swimming technique.

Effect of the expression of CD62P and thrombin generation on patients using central venous catheters for hemodialysis.

The formation of thrombi in medical devices that come into contact with blood is a common cause of increased morbidity and mortality. Prolonged use of central venous catheters (CVCs) may cause high infection rates or compromise CVC patency due to thrombus development. In this study, we sought insights into possible changes in the hemostatic system during prolonged use of inserted CVCs for hemodialysis by assessing platelets by CD62P and CD41a expression and the potential for thrombin generation (TG). This study included patients with chronic renal failure who were undergoing hemodialysis three times a week using a CVC, and healthy subjects as controls. The participants were distributed into three groups: Group 1: clinically and laboratorially healthy individuals matched by sex and age to the patients (controls); Group II: patients who had completed 1 month of CVC insertion; and Group III: the same patients after they had completed 4 months of CVC insertion. Platelet activation analysis and TG evaluation were performed using blood samples obtained through two different accesses, that is, through a peripheral vein and directly from the CVC lumen. The data showed platelet activation and an increase in the generation of thrombin, particularly after 4 months of CVC use. The results also indicated that insertion of the catheter into the blood stream stimulated the intrinsic rather than the extrinsic pathway. Taken together, the data showed a direct relationship between the use of CVCs in hemodialysis patients and a state of hypercoagulability, most likely associated with endothelial damage and the contact of the medical device with blood components such as platelets and coagulation factors.

Development of esthetic prosthesis for a patient with severe stigmatizing facial lesions due to cancer: a pilot study.

PURPOSE: Severe physical facial deformities due to surgical interventions can have significant psychosocial consequences to patient's relationships with friends and family and thus, has a considerable impact on their quality of life. We have developed a 3D prosthesis for a 56-year-old woman diagnosed with epidermoid carcinoma at the right hemiface, to improve her quality of life. METHODS: The patient started radiotherapy with modulated intensity. To deal with the advance of the process, a maxilectomy of supra structure with modified radical cervical emptying on the right hemiface was performed. Reconstruction of areas surgically affected by the displacement of islands of skin and muscle (flaps) from healthy regions was initiated. Although the procedure occurred without intercurrences, the patient developed necrosis and loss of the myocutaneous flap. After the removal of the flap, the esthetic result of the treatment was evident causing exposure of subcutaneous and granulation tissues. RESULTS: A computational model was used to develop a 3D structure of the affected area and then used to construct the prosthesis. The prosthesis was applied over the affected area, and the patient was able see her face on the mirror for the first time in years. The patient was grateful and hopeful. CONCLUSION: We have found that the application of this new technology greatly improves the social interaction of patients with deformities due to surgical interventions.

Indirect sinusoidal vibrations induces an acute increase in explosive strength.

The purpose of this study was to examine the acute effect of indirect vibration on neuromuscular responses and fatigue resistance (electromyographic activity - EMG and force) during isometric exercise. Nineteen healthy men (age=22.4±2.7years; body mass=76.4±12.9kg, height=175±6.7cm) performed isometric elbow flexion exercises in three experimental treatments: only isometric exercise (control - CON); isometric exercise with the addition of sinusoidal vibrations (SVE1; frequency=20Hz, displacement=3.55±0.54mm); and isometric exercise with the addition of sinusoidal vibrations with frequency variation (SVE2; frequency=20±3Hz, displacement=3.6±0.8mm). The peak of the rate of EMG rise (RER) and the root mean square of biceps brachii during the first 200ms (RMS200bic) were significantly higher in SVE1 (RMS200bic, 25.57±11.70%MVC; RER, 266.91±130.16%MVCs-1) than CON (RMS200bic, 19.31±8.19%MVC; RER, 169.15±65.98%MVCs-1). Regarding force, in SVE1, compared to CON, significant increases were observed in peak of rate of force development (CON, 643.96±192.57N/s; SVE1, 845.54±292.84N/s), rate of force development in the first 200ms (CON, 382.92±138,63N/s; SVE1, 501.09±147.46N/s), and impulse in 200ms (CON, 8.56±3.56Ns; SVE1, 11.67±4.45Ns). The addition of indirect sinusoidal vibrations during exercise induced increases in the rate of force development (explosive strength), without affecting the peak force (maximal strength) and the ability to sustain strength production.

Determination of a quantitative parameter to evaluate swimming technique based on the maximal tethered swimming test.

The aim of this study was to propose a new force parameter, associated with swimmers' technique and performance. Twelve swimmers performed five repetitions of 25 m sprint crawl and a tethered swimming test with maximal effort. The parameters calculated were: the mean swimming velocity for crawl sprint, the mean propulsive force of the tethered swimming test as well as an oscillation parameter calculated from force fluctuation. The oscillation parameter evaluates the force variation around the mean force during the tethered test as a measure of swimming technique. Two parameters showed significant correlations with swimming velocity: the mean force during the tethered swimming (r = 0.85) and the product of the mean force square root and the oscillation (r = 0.86). However, the intercept coefficient was significantly different from zero only for the mean force, suggesting that although the correlation coefficient of the parameters was similar, part of the mean velocity magnitude that was not associated with the mean force was associated with the product of the mean force square root and the oscillation. Thus, force fluctuation during tethered swimming can be used as a quantitative index of swimmers' technique.

Quantification and Analysis of Leaflet Flutter on Biological Prosthetic Cardiac Valves.

The use of porcine or bovine pericardium biological cardiac valves has as its main disadvantage a relatively short lifespan, with failures due to calcification and fatigue. Increasing these valves' durability constitutes a great challenge. An understudied phenomenon is the effect of flutter, an oscillation of the leaflets that can cause regurgitation and accelerate calcification and fatigue. As a starting point to study how to reduce or prevent these oscillations, a method was developed to quantify the flutter frequencies occurring at the point of the valve's full opening. On a test bench that simulates the heart flow, the cusp behaviors of eight biological valves were filmed with a high speed camera at 2000 frames per second at different flow rates and motion capture software obtained the frequencies and amplitudes of the vibrations of each leaflet. Oscillations in the range of 200 Hz with average amplitudes of 0.4 mm were found; larger nominal diameter valves obtained lower values, and bovine pericardial valves had superior performance compared to porcine valves. A dimensionless analysis was performed to find a relationship between the geometric and mechanical properties of the valves with the critical speed of the onset of fluttering. This relationship inspired a method to predict whether flutter will occur in the bioprosthesis. This method is a new tool for the consideration of maximizing the life of prosthetic valves.

Numerical simulation of heat transfer in a canine knee joint in thermal neutrality: analysis of the influence of different values of blood perfusion and considerations of the blood perfusion rate / Simulação numérica da transferência de calor na articulação do joelho canino em neutralidade térmica: análises das influências dos diferentes valores de perfusão sanguínea e das considerações da taxa de perfusão sanguínea

This study aimed to simulate heat transfer in thermal equilibrium in the canine knee joint. We analyzed the impact of different values of blood perfusion available in the literature and considered blood perfusion rates. The geometric models of canine knee joints were created from a photographic record of a cross section of an anatomical part. Two geometric models were developed: one without the epidermis and one with the epidermis. A heat diffusion equation was used to model the heat transfer phenomenon. Numerical simulations of the canine knee in a thermal neutrality condition were performed using the ANSYS-CFX® program. The simulation results were compared with experimental in vivo data. The smaller percentage differences between the experimental and simulated in vivo results were found in simulations that used the blood flow rate as a function of temperature. The computer simulation proved to be a good alternative to evaluate the temperature of biological tissues.

O presente trabalho visa simular a transferência de calor, em equilíbrio térmico, na articulação do joelho canino e analisar o impacto dos diferentes valores de perfusão sanguínea disponíveis na literatura e das considerações da taxa de perfusão sanguínea. Os modelos geométricos da articulação do joelho canino foram criados com base em um registro fotográfico de um corte transversal de uma peça anatômica. Foram desenvolvidos dois modelos geométricos: 1- sem epiderme e 2 ­ com epiderme. A equação de difusão de calor foi utilizada para modelar o fenômeno de transferência de calor. As simulações numéricas do joelho canino na condição de neutralidade térmica foram realizadas utilizando o programa ANSYS-CFX®. Os resultados da simulação foram comparados com os dados experimentais in vivo. As menores diferenças percentuais, entre o experimento in vivo e os resultados simulados, foram encontradas nas simulações que utilizaram a taxa de perfusão sanguínea em função da temperatura. A simulação computacional mostrou-se uma boa alternativa para avaliar a temperatura dos tecidos biológicos.

Análise da validade dos parâmetros absolutos e relativos para o cálculo da potência anaeróbia no RAST / Analysis of the absolute and relative parameters validity for anaerobic power output in RAST

O objetivo do presente estudo foi analisar a validade dos parâmetros de potência absolutos e relativos do Running-based Anaerobic Sprint Test (RAST) com base no teste de Wingate (WAnT). Doze voluntários do sexo masculino com idade de 25,50 anos (± 2,32) realizaram os testes RAST e WAnT. Foram observados valores significativos (p < 0,01) de correlação para a potência máxima absoluta (r = 0,76) e para a potência média absoluta (r = 0,74) dos testes, entretanto, os valores relativos apresentaram correlações não significativas (r = 0,54 e 0,27 respectivamente). Todos os parâmetros analisados apresentaram diferenças significativas (p < 0,01) na comparação entre WAnT e RAST. Desta forma, os resultados sugerem que apenas os parâmetros de potência absoluta do RAST são válidos. Assim ao aplicar o RAST para avaliação e/ou prescrição de treinamento, ou em pesquisas científicas, devem ser usados preferencialmente os parâmetros absolutos do teste.

The aim of the present study was to analyze the absolute and relative parameters validity for Running-based Anaerobic Sprint Test (RAST) based on Wingate test (WAnT). Twelve male volunteers aged 25.50 ± 2.32 years old performed both RAST and WAnT. Significant (p < 0.01) correlation values for the absolute maximum power (r = 0.76) and mean absolute power (0.74) was found but the relative mean values did not showed significant correlations for both maximum (r = 0.54) and average power output (r = 0.27). Significant differences (p < 0.01) between WAnT and RAST were found for all assessed parameters. Therefore, the results of the present study suggest that the RAST should be used with caution for prescription training and evaluation, and acquisition of scientific data. The results also suggest that only the absolute parameters of the test are good predictors of anaerobic power.