The importance of modelling assumptions when analysing the dynamic response of a masonry railway viaduct

© 2018 The International Masonry Society (IMS). The masonry viaduct at Marsh Lane is an important part of the railway network near Leeds, UK, dating from the 1860s. However, deterioration has resulted in notable deflections under train loads, which have concerned asset managers. Coupled with uncertainty regarding the true structural behaviour under serviceability conditions, this has led to detailed monitoring of the viaduct. This paper summarises the main conclusions of the monitoring installation before focusing on the evaluation of computational modelling of the viaduct, through comparison of modelling and monitoring results. In the monitoring scheme, fibre-optic cables containing Fibre-Bragg Gratings allowed measurement of dynamic in-plane barrel strains while digital image correlation captured displacements using commercial video cameras. The results illuminated a complicated three-dimensional dynamic response under train loading and highlighted the importance of interaction between adjacent spans. Separately, rail loading of the viaduct was simulated with a series of finite element models, each with increasing levels of complexity, to establish the relative stiffness contributions of various structural components. These models were then compared to detailed measurements from the real viaduct so that their validity could be evaluated. This approach revealed the impact of some common modelling assumptions and permitted assessment of nonlinear contributions to structural behaviour

The effects of wind on the loading and vibration of stone pinnacles

© 2016 International Masonry Society. All rights reserved. Following the collapse of a tympanum pinnacle at Beverley Minster in Yorkshire, a research project was undertaken to investigate the wind forces which act on stone pinnacles. A survey was conducted and the most common failure modes were identified, which highlighted the importance of dynamic forces in addition to the static drag force. Further, the potential impact of decorative crockets on these forces was of interest. Both static and dynamic forces on pinnacles were investigated through a series of wind tunnel tests. The results demonstrate the relative magnitude of these forces, and that the decorative crockets do appreciably affect both the drag force and wind-induced vibration. The experimental data was used to derive general relationships for wind forces acting on stone pinnacles for potential use in engineering practice

ENHANCING EXERCISE PERFORMANCE THROUGH ISCHAEMIC PRECONDITIONING

Ischaemic preconditioning (IPC) is an intervention whereby brief intermittent ischaemic episodes are induced in a limb (usually 4x5-minute arterial occlusion bouts, interspersed with 5-minutes of reperfusion) either at the site of interest (IPC), or at a distance from the site of interest (Remote; RIPC). Although originally linked to cardiology, recently studies have investigated the effects of IPC administered on a limb prior to exercise with some showing improvements in exercise performance. The overarching aim of the present thesis was to investigate how to optimise IPC to further enhance exercise performance. The optimal protocol of IPC on exercise performance was quantified by manipulating: 1. the number of cycles, 2. amount of muscle tissue, and 3. local vs Remote occlusion, which were applied in a randomized counterbalanced order in study 1 (Chapter 3). IPC dose, location and occlusion area differed prior to a 375 KJ time trial (TT) performance in 12 trained men. The traditional 4x5-min IPC stimulus resulted in the fastest TT time compared to SHAM [17 secs (90% CI: 0, 34 secs); P=0.097], but there was no benefit of applying a greater number of cycles [5 secs (-35, 26 secs); P=0.49] or employing unilateral IPC [18 secs (-11, 48 secs, P=0.29]. Local versus Remote cuff placement did not result in changes in TT time [0 secs (-16, 16 secs; P>0.9]. Overall, regardless of location, the 4x5-minute dose seemed to provide the most benefit to exercise performance. The ability of IPC to enhance exercise capacity may be mediated through altering exercise-induced blood flow and/or vascular function. Study 2 (Chapter 4) investigated the blood flow response to exercise, using ultrasound, when exercise was preceded by a control (SHAM) condition, or either local or Remote (R)IPC in eighteen recreationally trained males. Vascular 4 function tests were also performed before SHAM and (R)IPC and at the end of exercise. IPC resulted in enlarged brachial artery diameter during exercise [0.016 cm (0.003 to 0.03 cm); P=0.016] compared to RIPC, but blood flow during exercise was similar between conditions. No changes in post-exercise vascular function were observed between conditions. Therefore, enhanced vasodilation following local (but not Remote) IPC, when performed prior to exercise, does not translate into increased blood flow during exercise nor impact post-exercise vascular function. IPC could alleviate deleterious muscle damage responses after exercise-induced muscle damage (EIMD; often lasting <72 hours). Study 3 (Chapter 5) investigated whether IPC could negate eccentric exercise-induced reductions in torque production. Eleven recreationally trained males completed 200 repetitions of maximal eccentric contractions when preceded by IPC or SHAM performed in a randomized order, separated by a 9-week washout period. Muscle function tests were performed after IPC/SHAM prior to eccentric exercise and at 1-hour, 24-hours, 48-hours & 72-hours post-EIMD. Venous blood samples were taken at all time points. Greater maximal [15.2 N.m-1 (6.2 to 24.1); P=0.006] and mean [13.3 N.m-1 (5.3 to 21.3); P=0.007] torque production during a fixed angle voluntary maximal voluntary contraction (MVC) task and during a 60 deg·sec-1 [10.1 (4.9 to 15.3); P=0.002 & 9.8 N.m-1 (6.1 to 13.5; P<0.005] isokinetic task were evident after IPC versus SHAM prior to eccentric exercise (EIMD). This was maintained throughout the (72-hour) muscle damage window. Lower cytokine (IL-6 and IL-1ra) were reported after IPC versus SHAM (P<0.002, respectively). IPC resulted in greater overall HSP-27 & 32 levels (P<0.01) whilst HSP-72 was lower (P=0.001) versus SHAM. Therefore, IPC can enhance maximal torque production during isokinetic dynamometry, before and after muscle damaging exercise and induce advantageous extracellular stress responses to EIMD in humans. 5 Study 4 employed IPC in a practical exercise-priming model, that aimed to maximise repeated sprint ability (RSA). Eleven trained cyclists performed 4 experimental visits in a repeated measures design. The “traditional” 4x5-minute local IPC (IPC) dose was compared to a SHAM condition (20 mmHg). IPC or SHAM were performed on two separate visits, each combined with either passive muscle heating (HEAT) on two visits, or thermoneutral (non-heated) insulation on two visits, prior to an “all out” repeated sprint task (10x6-second sprints with 24-seconds of recovery). There were no meaningful changes in 10x6-second average [12 (-7 to 31) watts; P=0.28] or peak [6 (-14 to 26) watts; P=0.62] power output following IPC versus SHAM. Additionally, no benefit was observed when muscle temperature was elevated in combination with IPC [5 (-14 to 19) watts; P=0.67], or separately to IPC [9 (-9 to 28); P=0.4] versus SHAM. Overall, it appears that IPC, nor (the combination of) muscle heating can positively impact RSA performance in trained cyclists versus a SHAM condition. The findings from this thesis suggest that using a “traditional” dose of 4x5-minute cycles, either on the legs or the arms, promote performance enhancements in aerobic tasks such as cycling TT performance. These potential performance improvements are likely not resultant from increased limb blood flow. IPC can also enhance muscle function following muscle damaging exercise and induce advantageous extracellular stress responses to EIMD. Nevertheless, IPC alone or when combined with local muscle heating likely has no meaningful enhancements in repeated sprint cycling performance. The findings from this thesis may help athletes to establish a better understanding of how IPC can be used prior to exercise

Microscopic dynamics in liquid metals: the experimental point of view

The experimental results relevant for the understanding of the microscopic dynamics in liquid metals are reviewed, with special regards to the ones achieved in the last two decades. Inelastic Neutron Scattering played a major role since the development of neutron facilities in the sixties. The last ten years, however, saw the development of third generation radiation sources, which opened the possibility of performing Inelastic Scattering with X rays, thus disclosing previously unaccessible energy-momentum regions. The purely coherent response of X rays, moreover, combined with the mixed coherent/incoherent response typical of neutron scattering, provides enormous potentialities to disentangle aspects related to the collectivity of motion from the single particle dynamics. If the last twenty years saw major experimental developments, on the theoretical side fresh ideas came up to the side of the most traditional and established theories. Beside the raw experimental results, therefore, we review models and theoretical approaches for the description of microscopic dynamics over different length-scales, from the hydrodynamic region down to the single particle regime, walking the perilous and sometimes uncharted path of the generalized hydrodynamics extension. Approaches peculiar of conductive systems, based on the ionic plasma theory, are also considered, as well as kinetic and mode coupling theory applied to hard sphere systems, which turn out to mimic with remarkable detail the atomic dynamics of liquid metals. Finally, cutting edges issues and open problems, such as the ultimate origin of the anomalous acoustic dispersion or the relevance of transport properties of a conductive systems in ruling the ionic dynamic structure factor are discussed.Comment: 53 pages, 41 figures, to appear in "The Review of Modern Physics". Tentatively scheduled for July issu

Distributed dynamic fibre-optic strain monitoring of the behaviour of a skewed masonry arch railway bridge

AbstractSkewed masonry arch railway bridges are common, yet their structural behaviour under typical working loads, along with gradual changes in behaviour due to degradation, can be difficult to determine. This paper aims to address this problem through detailed monitoring of a damaged, skewed masonry arch railway bridge in the UK, which was recently repaired. A comprehensive Structural Health Monitoring system was installed, including an array of fibre-optic Fibre Bragg Grating (FBG) sensors to provide distributed sensing data across a large portion of the bridge. This FBG monitoring data is used, in this paper, to investigate the typical dynamic structural response of the skewed bridge in detail, and to quantify the sensitivity of this response to a range of variables. It is observed that the dynamic bridge response is sensitive to the time of day, which is a proxy for passenger loading, to the train speed, and to temperature. It is also observed that the sensitivity of the response to these variables can be local, in that the response can differ throughout the bridge and be affected by existing local damage. Identifying these trends is important to distinguish additional damage from other effects. The results are also used to evaluate some typical assumptions regarding bridge behaviour, which may be of interest to asset engineers working with skewed masonry arch bridges.</jats:p

'I found myself a despicable being!':Medical students face disturbing moral dilemmas

CONTEXT: The psychological realm of medical students` moral experiences is explored tangentially in medical education literature, often in the context of ethics or professionalism education. This study deepens our understanding by (1) investigating the nature of moral dilemmas experienced at the onset of clinical practice, (2) exploring students` emotional response to these dilemmas, and (3) examining how students perceive the influence of these dilemmas on their professional development. METHODS: This is a cross-sectional qualitative study carried out in 2017 that applied Thematic Template Analysis to individual interviews performed with last-year medical students. The interviews followed the drawing of a Rich Picture representing moral dilemmas experienced by medical students at the onset of clinical practice. RESULTS: Moral dilemmas have four intertwined dimensions. The first relates to students` struggle to prioritize, balance and apply conflicting moral values; the second comprises the clash between students` inner motivation and the external constraints that limit the moral action; the third refers to the conflict between students' current attitudes with the desired/idealized attitudes of the doctor they intend to become; the forth corresponds to weighting conflicting ethical principles during the moral decision. Students` emotional responses are intense, long-lasting, and with a remarkable residue effect, particularly when the moral decision does not align with their moral beliefs. Moral dilemmas are impactful experiences that affect the professional development of medical students and can culminate in both detachment or growth in moral courage. CONCLUSION: Moral dilemmas are memorable, complex, and emotionally intense experiences that impact the professional development of medical students. Understanding students` moral dilemmas can help educators to devise pedagogical activities to anticipate and reflect on these experiences. These activities should happen under the guidance of a non-judgmental facilitator, capable of listening and legitimating students' thoughts and feelings while providing insights to nurture their professional development

Effects of oxidized lipids (4,5 (E)-epoxy-2(E)-heptenal and 4,5 (E)-epoxy-2 (E) -decenal) and lysine reaction products on zinc and calcium utilization: assays in Caco-2 cells

The influence of the presence of brown products from the reaction between two oxidized lipids (4,5 (E)-epoxy-2(E)-heptenal, EH, and 4,5 (E)-epoxy-2 (E)-decenal, ED) and lysine (EH-L and ED-L) on zinc and calcium utilization was studied, and compared with a fructosyl-lysine mixture (F-L). Assays were carried out in Caco-2 cells grown in bicameral chambers. The Zn transported across the cell monolayer was significantly lower in the presence of the EH-L, ED-L and F-L samples, specially with EH-L. Significant decreases in Zn uptake were also observed, with no differences between samples. However, calcium transport was not modified. Thus, the assayed lipid-aminoacid brown products seem to have negative effects on Zn availability, whereas Ca availability appears to be unaffected.Se estudió la influencia de la presencia de productos obtenidos en la reacción de dos lípidos oxidados (4,5(E)-epoxy-2(E)- heptenal, EH, y 4,5(E)-epoxy-2(E)-decenal, ED) con el aminoácido lisina (EH-L y ED-L), sobre la absorción de zinc y calcio, comparándolos frente a una mezcla de fructosil-lisina (F-L). Los ensayos se realizaron con células Caco-2 sembradas en placas bicamerales. La adición de las muestras EH-L, ED-L y F-L al medio de cultivo supuso una reducción significativa en el Zn transportado a través de la monocapa de células, mucho más marcada ante la presencia de EH-L. También se redujo significativamente la captación celular de Zn, sin diferencias entre las distintas muestras ensayadas. Sin embargo, el transporte de Ca no se vio modificado. Por lo tanto, los productos pardos lípido-aminoacídicos ensayados parecen afectar negativamente la disponibilidad del Zn, sin tener efectos notables sobre la del Ca.Peer reviewe

Time-of-day variation on performance measures in repeated-sprint tests: A systematic review.

The lack of standardization of methods and procedures have hindered agreement in the literature related to time-of-day effects on repeated sprint performance and needs clarification. Therefore, the aim of the present study was to investigate and systematically review the evidence relating to time-of-day based on performance measures in repeated-sprints. The entire content of PubMed (MEDLINE), Scopus, SPORTDiscus® (via EBSCOhost) and Web of Science was searched. Only experimental research studies conducted in male adult participants aged ≥18yrs, published in English before June 2019 were included. Studies assessing repeated-sprints between a minimum of two time-points during the day (morning versus evening) were deemed eligible. The primary search revealed that a total of 10 out of 112 articles were considered eligible and subsequently included. Seven articles were deemed strong and three moderate quality. Eight studies found repeated-sprint performance across the first, first few, or all sprints, to increase in favor of the evening. The magnitude of difference is dependent on the modality and the exercise protocol used. The non-motorized treadmill established an average 3.5–8.5% difference in distance covered, average and peak velocity, and average power, across all sprints in three studies and in peak power in two studies. In cycling, power output differed across all sprints by 6.0% in one study and 8.0% for the first sprint only in five studies. All four studies measuring power decrement values (i.e. rate of fatigue) established differences up to 4.0% and two out of five studies established total work to be significantly higher by 8.0%. Repeated-sprint performance is affected by time-of-day with greater performance in the late/early afternoon. The magnitude is dependent on the variable assessed and the mode of exercise. There is a clear demand for more rigorous investigations which control factors that specifically relate to investigations of time-of-day and are specific to the sport of individuals