Cinemática e dinâmica das cames

As cames ou ressaltos (ou ainda excêntricos) são acessórios mecânicos destinados a transformar rotações em movimentos rectilíneos, ou mesmo noutras rotações de amplitude geralmente limitada. As suas aplicações são bastante conhecidas sobretudo na indústria automóvel, com incidência nos motores a 4 tempos, onde as válvulas de admissão e escape são comandadas por excêntricos ou cames. Esta monografia descreve os princípios cinemáticos e dinâmicos do funcionamento das cames

Parto Diferido em Gravidez Gemelar Bicoriônica: um Caso com 154 Dias de Latência

Premature delivery often complicates multifetal pregnancies, placing neonates at risk of serious morbidity and mortality. In select cases, preterm birth of one sibling may not require delivery of the remaining fetus(es), which may remain in utero for a delayed-interval delivery, consequently improving neonatal morbidity and mortality. Currently, there is no consensus on the best protocol for the optimal management of these cases. We report one case of delayed-interval delivery of a dichorionic pregnancy assisted in our center. In this case, prophylactic cerclage, tocolytic therapy and administration of broad-spectrum prophylactic antibiotics enabled delivery at 37 weeks, corresponding to 154 days of latency, which is, to our knowledge, the longest interval described in the literature. The attempt to defer the delivery of the second fetus in peri-viability is an option that should be offered to parents after counseling, providing that the clinical criteria of eligibility are fulfilled. The correct selection of candidates, combined with the correct performance of procedures, as well as fetal and maternal monitoring and early identification of complications increase the probability of success of this type of delivery.info:eu-repo/semantics/publishedVersio

Mathematical estimation of axial length increment in the control of myopia progression

This study aims to evaluate the existing mathematical approach for the theoretical estimation of axial length (AL) in a cross-sectional study, developing a new mathematical model and testing it in a longitudinal sample. Many professionals do not have a device to measure the AL due to clinic space and cost of equipment. However, this parameter plays an important role in the assessment of myopia progression to monitor treatment effects with myopia control strategies. First, a cross-sectional study based on the mathematical equation proposed by Morgan was performed. The AL was estimated based on the mean values of keratometry and spherical equivalent in 1783 subjects (52% female), aged 14.6 ± 4.6 years (6 to 25 years), of whom 738 were myopic, 770 emmetropic and 275 hyperopic. On average, the AL estimated with the Morgan formula was 0.25 ± 0.48 mm larger than the real AL value (95% limits of agreement: +0.70 to −1.20 mm). The study by gender, ametropia, type of astigmatism and age showed statistically significant differences between the real AL and predicted AL_Morgan (r > 0.750, spearman). Based on the previous sample, a multiple linear regression was applied, and a new mathematical model was proposed. The model was tested on a longitudinal sample of 152 subjects whose mean age was 13.3 ± 3.1 years (9 to 24 years) and of whom 96 were female (64%). The sample consisted of 46 myopes, 82 emmetropes and 24 hyperopes. The longitudinal study of the differences in axial length at one year between the models showed no statistically significant differences and that the mathematical equations are valid for estimating differences in axial increment for ages between 9 and 24 years, despite errors in the predicted value for axial length.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UIDB/04650/2020 at Center of Physics, UMinho, and predoctoral grant SFRH/BD/136684/2018 to A.A.-d.-S

Comentário a “O papel da oxigenoterapia hiperbárica nas úlceras retais secundárias à terapêutica com árgon-plasma”

Dear Editor, We read with great interest the paper by Laranjo et al. [1] entitled “The Effect of Hyperbaric Oxygen Therapy on Rectal Ulcers after Argon Plasma Coagulation.” The authors reported the case of a patient with chronic radiation proctitis, who developed rectal ulcers after endoscopic treatment with argon plasma coagulation (APC) and was successfully treated with hyperbaric oxygen therapy (HBO). Although it is well established that HBO therapy is an effective alternative treatment for patients with radiation-induced rectal ulcers and severe chronic proctitis [2, 3], its application has not been described as a treatment option in APC-induced rectal ulcers. We acknowledge the authors’ awareness of HBO as an option for complications induced by conventional chronic proctitis treatments and we would like to share our experience on this particular matter. A 72-year-old female patient was admitted to our Emergency Department with rectal bleeding, acute anal pain, and iron deficiency anemia (hemoglobin 10.7 g/dL). She had a past medical history of endometrial carcinoma treated with radio- and brachytherapy 2 years before. Total colonoscopy revealed multiple bleeding rectal radiation-induced telangiectasias. Medical treatment with topical salicylates and sucralfate for 8 months was unsuccessful and APC therapy (45 W; 1.5 L/min gas flow) every 4 weeks was initiated. The patient was submitted to a total of 6 APC sessions, with an overall endoscopic improvement between the first and third sessions. However, amidst the fourth and sixth APC sessions, the patient developed multiple APC-induced ulcers and an ulcerated stenosis of the distal rectum.info:eu-repo/semantics/publishedVersio

Liquidity and the multiscaling properties of the volume traded on the stock market

We investigate the correlation properties of transaction data from the New York Stock Exchange. The trading activity f(t) of each stock displays a crossover from weaker to stronger correlations at time scales 60-390 minutes. In both regimes, the Hurst exponent H depends logarithmically on the liquidity of the stock, measured by the mean traded value per minute. All multiscaling exponents tau(q) display a similar liquidity dependence, which clearly indicates the lack of a universal form assumed by other studies. The origin of this behavior is both the long memory in the frequency and the size of consecutive transactions.Comment: 7 pages, 3 figures, submitted to Europhysics Letter

Anterior and posterior corneal elevation after orthokeratology and standard and customized LASIK surgery

Purpose: To quantify the changes in the elevation topography of the front and back corneal surfaces after three different refractive treatments for correcting myopia with standard and custom laser in situ keratomileusis (LASIK) and orthokeratology using corneal refractive therapy.Methods: We evaluated 20 eyes undergoing orthokeratology for correction of myopia spherical equivalent (mean +/- SD=-3.41 +/- 0.76 D), 18 eyes undergoing custom LASIK surgery (mean +/- SD=-4.14 +/- 0.89 D), and 23 eyes undergoing standard LASIK (mean +/- SD=23.61 +/- 0.67 D). The values of front and back corneal surfaces were derived by using Pentacam (Oculus, Inc. GmbH, Wetzlar, Germany) before and at least 3 months after each treatment, in the center of the cornea and 4 points to each side of the horizontal meridian at intervals of 1 mm.Results: Corneal elevation data before treatment were not statistically different between patients in either group (P>0.070, for back and front elevation). After treatment, both surgical procedures significantly increased the positive value of the front elevation beyond an area of 6 mm. The opposite trend was found within the central 5 mm of the cornea, presenting a statistically significant decrease in elevation (P0.285).Conclusions: Differences in front corneal elevation changes between LASIK and orthokeratology reveal a much different mechanism for producing corneal power subtraction. The back corneal surface does not suffer significant changes after surgical and nonsurgical treatments for the correction of myopia.Supported by a grant from the Science and Technology Foundation (FCT) of the Ministry of Science and Superior Education (MCES) (European Social Funding). Doctoral Fellowship (AQ) number SFRH/BD/61768/2009

Hybrid moulds : the use of combined techniques for the rapid manufacturing of injection moulds

"Virtual modeling and rapid manufacturing : advanced research in virtual and rapid prototyping : proceedings of the 2nd International Conference on Advanced Research and Rapid Prototyping, Leiria, Portugal, 28 September - 1 October, 2005 (VR@P 2005)". ISBN 0-415-39062-1Injection moulding is the major polymer processing technique. The mould is a key element of this process and its characteristics have a key importance on the parts produced. The fabrication of products with higher added value, especially in terms of production time and costs, is essential for the success of the mouldmaking industry within a global competitive environment. This paper presents the concept of hybrid mould, a recent concept for injection moulding of prototype and short series. Direct and indirect rapid tooling technologies can be used for the fabrication of these moulds. Hence, new design guidelines need to be defined to produce these moulds as well to assess its performance. Epoxy tooling and selective laser sintering are the two rapid tooling technologies explored to produce inserts for hybrid-moulds. This work studies the fabrication of hybrid-moulds through these rapid tooling technologies, as well its mechanical and thermal behaviour.(undefined

BIOMECHANICS OF THE PENALTY STROKE IN ROLLER HOCKEY

This paper describes a preliminary study on the biomechanics of the shot in roller hockey. This is a Portuguese sport having a most extensive prize list, where Portugal has been 15 times world champion, 20 European champions in senior male competition and won three world championships in senior female. Despite this impressive collection of titles, hockey continues to be the lesser studied sport, concretely regarding studies on biomechanics. The influence of sports equipment in the athlete’s performance and a detailed analysis of the main technical gestures had not motivated yet the researchers for detailed studies to enable their optimization. The purpose of this study was to characterize the mechanical properties of the stick (Aleu) and its influence on the shot power