Heat treatment as a route to tailor the yield-damping properties in A356 alloys

A356 is a common industrial alloy due to its relatively good mechanical properties, reduced weight and capability be casted into complex structures. However, in order to display good static mechanical properties (e.g.elevated yield strength) it must be heat treated (usually T6), therefore, compromising its dynamic properties (e.g. damping ratio). This study analyses the role of such heat treatments in the overall microstructure of A356 poured in ceramic block, associating the morphology transformations with the internal mechanisms that enhance yield strength and reduce damping. It is suggested that these variables display an inverse proportionality and a linear model is determined for the design of alloys with tailored yield/damping by the use of different artificial ageing times.Supported by the project iRAIL Innovation in Railway Systems and Technologies Doctoral Programme funds and by national funds through FCT - Portuguese Foundation for Science and Technology and was developed on the aim of the Doctoral grant PD/ BD/114096/2015

Sequential star formation in IRAS 06084-0611 (GGD 12-15): From intermediate-mass to high-mass stars

Context. The formation and early evolution of high- and intermediate-mass stars towards the main sequence involves the interplay of stars in a clustered and highly complex environment. To obtain a full census of this interaction, the Formation and Early evolution of Massive Stars (FEMS) collaboration studies a well-selected sample of 10 high-mass star-forming regions. Aims. In this study we examine the stellar content of the high-mass star-forming region centered on IRAS 06084-0611 in the Monoceros R2 cloud. Methods. Using the near-infrared H- and K-band spectra from the VLT/SINFONI instrument on the ESO Very Large Telescope (VLT)and photometric near-infrared NTT/SOFI, 2MASS and Spitzer/IRAC data, we were able to determine the spectral types for the most luminous stars in the cluster. Results. Two very young and reddened massive stars have been detected by SINFONI: a massive Young Stellar Object (YSO) con- sistent with an early-B spectral type and a Herbig Be star. Furthermore, stars of spectral type G and K are detected while still in the Pre-Main Sequence (PMS) phase. We derive additional properties such as temperatures, extinctions, radii and masses. We present a Hertzsprung-Russell diagram and find most objects having intermediate masses between \sim1.5-2.5 M\odot. For these stars we derive a median cluster age of \sim4 Myr. Conclusions. Using Spitzer/IRAC data we confirm earlier studies that the younger class 0/I objects are centrally located while the class II objects are spread out over a larger area, with rough scale size radii of \sim0.5 pc and \sim1.25 pc respectively. Moreover, the presence of a massive YSO, an ultracompact H ii region and highly reddened objects in the center of the cluster suggest a much younger age of < 1 Myr. A possible scenario for this observation would be sequential star formation along the line of sight; from a cluster of intermediate-mass to high-mass stars.Comment: 14 pages, 10 figures, 2 tables. Astronomy and Astrophysic

Vibration damping and acoustic behavior of PU-filled non-stochastic aluminum cellular solids

Aluminum-based cellular solids are promising lightweight structural materials considering their high specific strength and vibration damping, being potential candidates for future railway vehicles with enhanced riding comfort and low fuel consumption. The filling of these lattices with polymer-based (i.e., polyurethane) foams may further improve the overall vibration/noise-damping without significantly increasing their density. This study explores the dynamic (i.e., frequency response) and acoustic properties of unfilled and polyurethane-filled aluminum cellular solids to characterize their behavior and explore their benefits in terms of vibration and noise-damping. It is shown that polyurethane filling can increase the vibration damping and transmission loss, especially if the infiltration process uses flexible foams. Considering sound reflection, however, it is shown that polyurethane filled samples (0.27–0.30 at 300 Hz) tend to display lower values of sound absorption coefficient relatively to unfilled samples (0.75 at 600 Hz), is this attributed to a reduction in overall porosity, tortuosity and flow resistivity. Foam-filled samples (43–44 dB at 700–1200 Hz) were shown to be more suitable to reduce sound transmission rather than reflection than unfilled samples (21 dB at 700 Hz). It was shown that the morphology of these cellular solids might be optimized depending on the desired application: (i) unfilled aluminum cellular solids are appropriate to mitigate internal noises due to their high sound absorption coefficient; and (ii) PU filled cellular solids are appropriate to prevent exterior noises and vibration damping due to their high transmission loss in a wide range of frequencies and vibration damping.This work was supported by Fundação para a Ciência e a Tecnologia FCT under the research Doctoral Grant PD/BD/114096/2015, project UIDP/04077/2020 and UIDB/04436/2020, and Stimulus of Scientific Employment Application CEECIND/03991/2017

Influence of arterial mechanical properties on carotid blood flow: comparison of CFD and FSI studies

Carotid artery blood flow is studied to compare models with rigid and elastic walls. Considering a patient-specific geometry and transient boundary conditions. In the case of rigid walls, only the fluid (blood) behavior is considered, in a typical Computational Fluid Dynamics study. With the elastic walls, the reciprocal influence of both fluid and solid (blood and artery) are taken into account, constituting a Fluid-Structure Interaction study. Further more, the study of the influence of mechanical properties of the artery, which become stiffer with the progression of atherosclerosis, on blood flow is also presented, an innovative approach relative to the work done in this field. Results show that the carotid sinus is the preferential zone to develop atherosclerosis, given its low values of Time-Averaged Wall Shear Stress. Additionally, it is fundamental to consider the arterial wall as elastic bodies, given that the rigid model overestimates the flow velocity and Wall Shear Stress. On the different mechanical properties of the vessel, its influence is minimal in the Time-Averaged Wall Shear Stress profiles. However, given the results of the displacement and velocity profiles, their inclusion in blood flow simulations in stenosed arteries should be considered.This work was supported by FEDER funds through the COMPETE program with the reference project PTDC/SEM-TEC/3827/2014. Additionally, this work is supported by FCT with the reference projects UID/EEA/04436/2019, UID/CEC/00319/2019 and UID/EMS/04077/2019

Design and development of a new approach to wrist rehabilitation

Wrist injuries are a very common type of pathology that can compromise most daily tasks. Conventional therapy is dependent on the availability of physiotherapists as well as devices designed for this purpose. Conventional devices do not accompany the patient throughout their rehabilitation process, requiring their constant replacement. Vibratory therapies emerged in recent years and have demonstrated several benefits in this area. However, there are few vibratory devices designed for wrist rehabilitation. In this paper, we propose two different portable and active models for wrist rehabilitation based on vibratory therapy for wrist rehabilitation. The first model has a cylindrical shape and the second model has a dumbbell shape. The results obtained showed that vibratory therapy can assist the wrist rehabilitation because it promoted improvements in joint amplitude gain in all wrist movements. Furthermore, the second device demonstrated higher joint gains than the first device. In addition, the results obtained from the measurement of accelerations demonstrate that the natural frequencies of both devices are adequate for wrist and forearm rehabilitation as well as the mode of vibration. There are differences between what the simulations predicted and what was obtained in practice in terms of natural frequency values.- (undefined

Dimensionality and Factorial Invariance of Religiosity Among Christians and the Religiously Unaffiliated: A Cross-Cultural Analysis Based on the International Social Survey Programme

We present a study of the dimensionality and factorial invariance of religiosity for 26 countries with a Christian heritage, based on the 1998 and 2008 rounds of the International Social Survey Programme (ISSP) Religion survey, using both exploratory and multi-group confirmatory factor analyses. The results of the exploratory factor analysis showed that three factors, common to Christian and religiously unaffiliated respondents, could be extracted from our initially selected items and suggested the testing of four different three-factor models using multi-group confirmatory factor analysis. For the model with the best fit and measurement invariance properties, we labeled the three resulting factors as “Beliefs in afterlife and miracles”, “Belief and importance of God” and “Religious involvement.” The first factor is measured by four items related to the Supernatural Beliefs Scale (SBS-6); the second by three items related to belief in God and God’s perceived roles as a supernatural agent; and the third one by three items with the same structure found in previous cross-cultural analyses of religiosity using the European Values Survey (ESS) and also by belief in God. Unexpectedly, we found that one item, belief in God, cross-loaded on to the second and third factors. We discussed possible interpretations for this finding, together with the potential limitations of the ISSP Religion questionnaire for revealing the structure of religiosity. Our tests of measurement invariance across gender, age, educational degree and religious (un)affiliation led to acceptance of the hypotheses of metric- and scalar-invariance for these groupings (units of analysis). However, in the measurement invariance tests across the countries, the criteria for metric invariance were met for twenty-three countries only, and partial scalar invariance was accepted for fourteen countries only. The present work shows that the exploration of large multinational and cross-cultural datasets for studying the dimensionality and invariance of social constructs (in our case, religiosity) yields useful results for cross-cultural comparisons, but is also limited by the structure of these datasets and the way specific items are coded

Risk Factors Associated with Falls among Nursing Home Residents: A Case-Control Study

Introduction: To identify factors predictive of falls and enable appropriate management of fall risk it is necessary to understand the behaviour and health conditions of older adults living in nursing homes. Objective: This study had two main objectives. The first was to find significant predictors for falls in older adults living in nursing homes. The second main goal was to build a predictive model to find the best predictors for falls. Methods: Out of 56 nursing homes with the same legal statute, 25 agreed to participate. The sample was randomly selected and only the independent or slight/ moderately dependent participants were included in the study (n = 325). Results: There was a mean of 1.47 ± 0.99 falls (range from 1 to 7) per resident in nursing homes. By using the t test and odds ratio analysis, ten factors related to falls were identified. Through the binary logistic regression, a model was tested identifying four robust predictors: static balance, resorting to emergency services, polypharmacy, and an independent self-care profile. Conclusions: The present study replicated the main results of contemporary research on the risk factors of falls. More importantly, it suggests that the self-care profile model should be taken into account in future studies and early interventions. It is crucial to implement preventive measures consistent with safer environments and to establish an individual plan for integrated activities according to older adults’ health needs.Para identificar os fatores preditivos de quedas e permitir a gestão adequada do seu risco, é necessário compreender o comportamento e as condições clínicas dos idosos. Objetivos: Este estudo teve dois objetivos principais. O primeiro foi encontrar preditores para quedas em idosos que vivem em estruturas residenciais para idosos. O segundo objetivo principal foi construir um modelo preditivo para encontrar os melhores preditores de quedas. Métodos: De um total de 56 estruturas residenciais para idosos contactados, com o mesmo enquadramento legal, 25 aceitaram participar. A amostra foi selecionada aleatoriamente e apenas os participantes independentes ou com um compromisso leve/moderado foram incluídos no estudo (n = 325). Resultados: Registou- se uma média de 1.47 ± 0.99 quedas (variando entre 1 a 7) por participante. Por meio do teste t e da análise de odds ratio, foram identificados dez fatores relacionados com as quedas. Através da regressão logística binária, foi testado um modelo identificando quatro preditores robustos: equilíbrio estatístico, recurso a serviços de emergência, polifarmácia e perfil de autocuidado independente. Conclusões: O presente estudo replicou os principais resultados de pesquisas contemporâneas sobre os fatores de risco para quedas. Mais importante ainda, sugere que o modelo de perfil de autocuidado deve ser levado em consideração em estudos futuros e intervenções precoces. É fundamental implementar medidas preventivas condizentes com ambientes mais seguros e estabelecer um plano individual de atividades integradas de acordo com as necessidades de saúde dos idosos.info:eu-repo/semantics/publishedVersio

A novel rescue maneuver for a distal dislodged lumen-apposing metal stent (LAMS): "LAMS-in-LAMS" technique

Introduction: the appearance of the lumen-apposing metal stent (LAMS) has meant an authentic revolution. To date, the results are promising but it is necessary to note the technical incidents and LAMS-related complications. Case report: an EUS-transmural guided drainage using a HotAXIOS was planned for a 36-year-old man with oral intolerance due to a voluminous walled-off necrosis. The distal flange was left in the collection, but a total distal malposition occurred during the proximal flange delivery, despite correct apposition with visualization of the black mark. A rescue technique was performed inserting a second LAMS over-the-guidewire salvaging the initial failed transmural drainage. Discussion: This case is a reminder that in similar scenarios, extreme tension of the echoendoscope can cause a malfunction of the AXIOS stent delivery system, and lead to a total distal malposition. This "LAMS-in-LAMS" technique is feasible, effective, and a very helpful rescue technique in cases of dislodged LAMS

Implementação de um dispositivo multivibracional para auxiliar à remoção de dentes e raízes

A corrente prática de extração dentária é realizada recorrendo a instrumentos rígidos num processo que implica elevadas forças mecânicas e, consequentemente, um pósoperatório doloroso para os pacientes. O presente trabalho apresenta as fases de conceção e desenvolvimento de um instrumento capaz de atuar na fase mais crítica do processo, com a indução de vibração a altas frequências, prevendo-se a diminuição da força necessária para efetuar a extração, bem como os danos provocados pelo procedimento atualmente realizado.info:eu-repo/semantics/publishedVersio

Implementation of a multivibrational medical device to assist the removal of teeth and roots

The current practice of tooth extraction is performed using rigid instruments in a process involving high mechanical strength and thus a painful postoperative for patients. In this sense, this work presents the stages of design and development of an instrument capable of acting in the most critical stage of tooth extraction process, the luxation phase, with the induction of vibration at high frequencies, so it is expected to decrease the force required to perform the extraction as well as the damage caused by the currently used procedure. The instrument used by the professional dentist in luxation phase is the dental elevator. So, it was selected and purchased a standard straight elevator to perform the operations necessary for the development of the vibrating elevator. Vibration induction was performed by a system with a piezoelectric actuator. The placement of the whole vibration system was designed to reduce the number of operations to perform to the original instrument as well as maintain the most of his ergonomic shape. Thus, the system was placed inside of the instrument handle to fulfill the aims above. The vibration system behavior was also study through simulation in COMSOL Multiphysics and a theoretical simulation. Through tests it was intended to provide an environment similar to a tooth extraction procedure, using a pig's head as model to which was perform the process of luxation and extraction of teeth of his jaw with the device developed and with or without its vibration system. During the tests, it was difficult to understand the influence of the vibration system in the process. However, tests had great difficulty once the model has significant anatomical differences comparing to Human teeth and roots. However, it is estimated that this vibration can assist the depth penetration of the device between the tooth and the alveolar bone allowing the easier placement of the instrument and an easier lifting of the tooth. The oscillation in this region may also lead to its elevation. These facts indicate that the process is being facilitated, reducing the force applied and the duration of the process when using vibration.info:eu-repo/semantics/publishedVersio