Purpose
The lateral ligament complex of the ankle has been extensively studied. Recently an anatomical study described a connection between anterior talofibular ligament inferior fascicle (ATFLif) ...and calcaneofibular ligament (CFL). The applicability and the mechanical role of these connections have not yet been studied and need to be clarified. The purpose of this study is to evaluate the connection between ATFLif and CFL through a dynamic measurement analysis.
Methods
An anatomical study was performed in 13 fresh-frozen below-the-knee ankle specimens. Each specimen was dissected in a protocolized manner until the lateral ligaments were exposed. A complete injury to both ATFL’s fascicles was created in the proximal third of the ligament. A displacement transducer specifically design was inserted in the CFL and in the lateral part of the calcaneus to test its lengthening. A traction of 1 kg weight (9.8 N) was applied to ATFLif while the transducer measured the lengthening that this force created in the CFL.
Results
A total of 13 ankle specimens were carefully dissected. One specimen with signals of a prior traumatic injury of the ATFLif was excluded. A total of 12 specimens were included, 7 females and 5 males with an average age of 74 years (52–88 years). The right ankle was dissected in 6 specimens.
ATFL was identified as a two-fascicled ligament in all cases. The fibers connecting the ATFLif and CFL were observed in all specimens. The displacement transducer showed lengthening in the CFL in all measurements with a median of 0.59 mm (SD ± 0.34).
Conclusion
Connecting fibers between ATFLif and CFL are robust enough to transmit tension from one structure to the other. In the case of associated proximal lesions of the ATFLif and CFL, ligaments repair with a single suture may be considered. This can be applied in surgical procedures in patients with lateral ankle instability.
In tissue engineering, scaffolds can be obtained by means of 3D printing. Different structures are used in order to reduce the stiffness of the solid material. The present article analyzes the ...mechanical behavior of octet-truss microstructures. Three different octet structures with strut radii of 0.4, 0.5, and 0.6 mm were studied. The theoretical relative densities corresponding to these structures were 34.7%, 48.3%, and 61.8%, respectively. Two different values for the ratio of height (H) to width (W) were considered, H/W = 2 and H/W = 4. Several specimens of each structure were printed, which had the shape of a square base prism. Compression tests were performed and the elasticity modulus (E) of the octet-truss lattice-structured material was determined, both, experimentally and by means of Finite Element Methods (FEM). The greater the strut radius, the higher the modulus of elasticity and the compressive strength. Better agreement was found between the experimental and the simulated modulus of elasticity results for H/W = 4 than for H/W = 2. The octet-truss lattice can be considered to be a promising structure for printing in the field of tissue engineering.
In this work, experimental and numerical analyses of repairs on carbon fiber reinforced epoxy (CFRE) substrates, with CFRE and aluminum alloy doublers typical of aircraft structures, are presented. ...The substrates have a bridge gap of 12.7 mm (simulated crack), repaired with twin doublers joined with riveted, adhesive bonded, and hybrid joints. The performance of the repairs using different doubler materials and joining techniques are compared under static loading. The experimental results show that riveted joints have the lowest strength, while adhesive bonded joints have the highest strength, irrespective of the doubler material. Finite element analysis (FEA) of the studied joints is also performed using commercial FEA tool Abaqus. In the FEA model, point-based fasteners are used for the rivets, and a cohesive zone contact model is used to simulate the adhesive bond. The FEA results indicate that the riveted joints have higher tensile stresses on the metal doublers compared to the composite doublers. As per the failure modes, interestingly, for hybrid joints using composite doublers, the doublers fail due to net-section failure, while, for hybrid joints using metal doublers, it is the composite substrate that fails due to net-section failure. This suggests vulnerability of the composite structures to mechanical fastener holes. Lastly, the Autodesk Helius composite tool is used for prediction of first-ply failure and ply load distribution, and for progressive failure analysis of the composite substrate.
Understanding the immune response to the SARS-CoV-2 virus is critical for efficient monitoring and control strategies. The ProHEpic-19 cohort provides a fine-grained description of the kinetics of ...antibodies after SARS-CoV-2 infection with an exceptional resolution over 17 months. We established a cohort of 769 healthcare workers including healthy and infected with SARS-CoV-2 in northern Barcelona to determine the kinetics of the IgM against the nucleocapsid (N) and the IgG against the N and spike (S) of SARS-CoV-2 in infected healthcare workers. The study period was from 5 May 2020 to 11 November 2021.We used non-linear mixed models to investigate the kinetics of IgG and IgM measured at nine time points over 17 months from the date of diagnosis. The model included factors of time, gender, and disease severity (asymptomatic, mild-moderate, severe-critical) to assess their effects and their interactions. 474 of the 769 participants (61.6%) became infected with SARS-CoV-2. Significant effects of gender and disease severity were found for the levels of all three antibodies. Median IgM(N) levels were already below the positivity threshold in patients with asymptomatic and mild-moderate disease at day 270 after the diagnosis, while IgG(N and S) levels remained positive at least until days 450 and 270, respectively. Kinetic modelling showed a general rise in both IgM(N) and IgG(N) levels up to day 30, followed by a decay with a rate depending on disease severity. IgG(S) levels remained relatively constant from day 15 over time.
The objective of this research is to characterise the material poly lactic acid (PLA), printed by fused deposition modelling (FDM) technology, under three loading conditions-tension, compression and ...bending-in order to get data that will allow to simulate structural components. In the absence of specific standards for materials manufactured in FDM technology, characterisation is carried out based on ASTM International standards D638, D695 and D790, respectively. Samples manufactured with the same printing parameters have been built and tested; and the tensile, compressive and flexural properties have been determined. The influences of the cross-sectional shape and the specimen length on the strength and elastic modulus of compression are addressed. By analysing the mechanical properties obtained in this way, the conclusion is that they are different, are not coherent with each other, and do not reflect the bimodular nature (different behaviour of material in tension and compression) of this material. A finite element (FE) model is used to verify these differences, including geometric non-linearity, to realistically reproduce conditions during physical tests. The main conclusion is that the test methods currently used do not guarantee a coherent set of mechanical properties useful for numerical simulation, which highlights the need to define new characterisation methods better adapted to the behaviour of FDM-printed PLA.
The process of international migration causes a situation of vulnerability in people's health and greater difficulty in coping with disease. Furthermore, the adversities suffered during migration can ...trigger reactive signs of stress and cause anxious, depressive, confusional and somatic symptoms. This article studies the relationships between psychosocial risk, psychological distress and somatization in immigrants from four communities: Maghrebis, Sub-Saharans, South Americans and South Asian. A cross-sectional study was carried out with questionnaires on 602 immigrants who were surveyed in the primary care centers of an urban area of Catalonia. The instruments used were the Demographic Psychosocial Inventory (DPSI), the Brief Symptom Inventory (BSI) and the Somatic Symptom Inventory (SSI). The average psychosocial risk obtained was 0.35, with the highest values in the Sub-Saharan community. Psychological distress showed a mean value of 0.66, with the Sub-Saharan community scoring the lowest in all dimensions except depression. The average somatization values were 1.65, with the Sub-Saharan community scoring the least. The female gender is a risk factor for somatization and psychological distress. Perceived psychosocial risk is a predictor of psychological distress, but not somatization, suggesting that the use of more adaptive coping strategies could minimize the effect of the migration process on somatizations.
•The beam-upright connections of racks play a relevant role in their seismic capacity.•This work supplements a previously-conducted testing campaign on such connections.•In those tests, different ...weld paths were compared, looking for ductile break modes.•In this paper, numerical simulations are performed in order to deepen the tests observations.•The influence of the weld paths on the connection stiffness, stress elastic distribution, and yielding onset is studied.
This paper presents numerical simulations of a suite of cantilever seismic tests of speed-lock connections between beam and upright members of adjustable pallet rack systems. The tested specimens differ in the endplate-to-beam weld beads geometric configuration; the experimental results show that each weld configuration leads to different behavior, significantly affecting the connection capacity and ductility. As a result, the performed numerical simulations aim to better understand and deepen these observations. Special attention is paid to the initial (elastic) behavior of the tested assembly, albeit the stress redistribution after the first yielding has also been studied and found to be relevant. The numerical results are satisfactory compared with the experimental ones, and specific remarks are derived. This work is a part of a broader research effort aimed to improve the dissipative seismic behavior of racks; such research activity involves also upright-base plate connections testing, advanced numerical simulation, and proposal of rack ductility behavior factors.
This paper presents seismic cantilever monotonic and cyclic tests of speed-lock (boltless) beam-to-upright connections of adjustable pallet rack systems; the objective of the monotonic tests is to ...obtain the bounds that are employed to define the loading protocol of the subsequent cyclic tests. The beam-to-upright connections consist of welding the beam to an intermediate end-plate (L-shaped) that, in its turn, is linked to the upright through a hooked assembly. The performed experiments investigate the connections hysteretic behavior, as it contributes to the rack lateral strength, stiffness, and ductility. More precisely, the main objective of this research is to propose a new strengthened design of the weld beads geometric configuration. This design is oriented for the connection failure not to arise in the weld, but the hooked assembly. This shift is expected to increase the connection ductility; in this sense, specimens with traditional and novel weld geometric designs are tested. In most of the tests performed, the results confirm that the new weld design leads to more ductile failure modes; preliminary evaluations state that the ductility increase might be sufficient to absorb most of the input seismic energy. On the other hand, tests are conducted according to two loading protocols: the traditional one by following European regulations and a new strategy proposed by Prof. Castiglioni accounting for the influence of gravity loads. Comparison between their results shows that the Castiglioni approach is more demanding and seems to reproduce the actual seismic behavior of racks better.
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•The beam-upright connections play a relevant role in their seismic capacity.•Their cyclic behavior, given its complexity, needs to be investigated by testing.•This paper presents cyclic tests on boltless beam-upright connections of racks.•Different welding strategies are compared aiming to redistribute the stresses and improve the ductility.•The influence of the testing protocol is also investigated.
The behaviour of various aircraft lap joint repair configurations is investigated experimentally and numerically under static loading. The lap joints consist of aluminium alloy (AA) 2024-T3 ...substrates repaired with twin single-sided AA 2024-T3 or Carbon Fibre Reinforced Epoxy (CFRE) doublers. Pure riveted, pure bonded and hybrid (riveted and bonded) joints of metal–metal and metal–composite configurations are investigated. From experimental results, joints with adhesive bond showed nearly 5 times higher average strength than pure riveted joints, while hybrid joints performed better than riveted and bonded joints because of higher stiffness. On the other hand, hybrid metal–metal joint has 70% higher average strength compared to hybrid metal–composite joint. Rivet-shear has caused failure of riveted joints, and adhesive failure is observed in pure bonded joints. Hybrid joints with metal doublers have failed initially due to adhesive failure and later rivet shear. Interestingly, net-section failure is observed in composite doublers with breakage of doublers due to the presence of holes in the doublers. Experimental results are complimented with numerical analysis using commercial finite element code ABAQUS. Load–displacement curves obtained from the numerical results are in good agreement with experiments with a marginal error of 2%. In addition to load–displacement curves, a detailed stress analysis is performed numerically on metal–metal and metal-composite joints under riveted, bonded and hybrid configurations to study stress distribution on substrate and doublers. Numerical analysis showed hybrid and bonded joints have lower stresses in substrate and doublers compared to the riveted joints. Bonded joints have smoother load transfer due to the adhesive spread over a larger area. And finally, Stress Intensity Factors (SIFs) are performed numerically for unreinforced and reinforced metal substrate with crack length of 1, 5 and 10 mm with metal and composite doublers under riveted and bonded configuration. For crack of 10 mm, 35% reduction in SIFs is observed for reinforced substrate with bonded metal or composite doublers compared to unreinforced cracked substrate.
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