Honeycomb structures display extraordinary stiffness-to-weight ratio when loaded in the out-of-plane direction. When realized using thermoplastic polyurethane (TPU), the structures offer the ...potential for repeatable and high specific energy absorption. Varying the cell size and wall thickness of TPU honeycombs facilitates changes in stiffness magnitude, though affords only modest capacity to alter the shape of the stress-strain curve. 3D printing facilitates advanced design exploration, beyond that of straight walls. Origami fold patterns have demonstrated the ability to influence the buckling behavior of tubular structures. Here we demonstrate the incorporation of origami folds into square honeycombs. The fold parameters facilitate significant tailoring of the stress-strain curve, allowing a range of profiles from quasi-rectangular to quasi-linear to be achieved; such structures can find applications in situation-specific energy absorption scenarios.
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•A method was developed to introduce origami fold patterns into square honeycombs.•The origami honeycombs were realized via 3D printing in thermoplastic polyurethane.•The crushing behavior of the origami honeycombs was studied via finite element analysis and experimental compression testing.•Varying the origami fold parameters allows significant tailoring of the honeycomb stress-strain response.•Absorption efficiencies as high as 0.49 were experimentally demonstrated, which rivals that of rigid polyurethane foams.
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•Elastomeric pre-buckled circular honeycombs were additively manufactured and tested under static and dynamic loading.•Variable mechanical behaviour can be achieved through informed ...selection of pre-buckled design feature’s aspect ratio.•Periodic boundary condition finite element represents a method to accurate and computationally efficient simulation.
Selective laser sintering has been used to manufacture different structural variations of a pre-buckled circular honeycomb. The mechanical behaviour of these structures has been examined under both quasi-static and dynamic impact loading. Pre-buckled circular honeycombs with aspect ratios e = 0.8 and e = 0.6 were compared to a traditional, straight-walled honeycomb. It has been found that the mechanical behaviour of the honeycomb can be tailored to yield different mechanical responses. Principally, decreasing the aspect ratio reduced the stress at yield, as well as the total energy absorbed until densification, however, this alleviated the characteristic stress-softening response of traditional honeycombs under static and dynamic conditions. When subjected to multiple cycles of loading, a stabilised response was observed. The numerical response closely agreed with the experimental results. A simplified, periodic boundary condition model also closely agreed with the experimental results whilst alleviating computational run time by nominally 75%. The numerical full factorial parameter design sweep identified a broad range of mechanical behaviour. This represents a valuable tool to identify optimal design configurations for future impact mitigating applications.
BackgroundPerforming high-quality chest compressions during cardiopulmonary resuscitation (CPR) requires achieving of a target depth, release force, rate and duty cycle.ObjectiveThis study evaluates ...whether ‘real time’ feedback could improve infant CPR performance in basic life support-trained (BLS) and lay rescuers. It also investigates whether delivering rescue breaths hinders performing high-quality chest compressions. Also, this study reports raw data from the two methods used to calculate duty cycle performance.MethodologyBLS (n=28) and lay (n=38) rescuers were randomly allocated to respective ‘feedback’ or ‘no-feedback’ groups, to perform two-thumb chest compressions on an instrumented infant manikin. Chest compression performance was then investigated across three compression algorithms (compression only; five rescue breaths then compression only; five rescue breaths then 15:2 compressions). Two different routes to calculate duty cycle were also investigated, due to conflicting instruction in the literature.ResultsNo-feedback BLS and lay groups demonstrated <3% compliance against each performance target. The feedback rescuers produced 20-fold and 10-fold increases in BLS and lay cohorts, respectively, achieving all targets concurrently in >60% and >25% of all chest compressions, across all three algorithms. Performing rescue breaths did not impede chest compression quality.ConclusionsA feedback system has great potential to improve infant CPR performance, especially in cohorts that have an underlying understanding of the technique. The addition of rescue breaths—a potential distraction—did not negatively influence chest compression quality. Duty cycle performance depended on the calculation method, meaning there is an urgent requirement to agree a single measure.
Introduction and hypothesis
The objective of the study was to reveal the way we treat vaginal mesh complications in a trained referral center.
Methods
This is a retrospective review of all patients ...who underwent surgical removal of transvaginal mesh for mesh-related complications during a 5-year period.
Results
Eighty-three patients underwent 104 operations including 61 complete mesh removal, 14 partial excision, 15 section of sub-urethral sling, and five laparoscopies. Main indications were erosion, infection, granuloma, incomplete voiding, and pain. Fifty-eight removals occurred more than 2 years after the primary mesh placement. Mean operation time was 21 min, and there were two intraoperative and ten minor postoperative complications. Stress urinary incontinence (SUI) recurred in 38% and cystocele in 19% of patients.
Conclusions
In a trained center, mesh removal was found to be a quick and safe procedure. Mesh-related complications may frequently occur more than 2 years after the primary operation. Recurrence was mostly associated with SUI and less with genital prolapse.
Whole-crop rye harvested before maturity represents a valuable forage for silage production. Due to the scarcity of data on fermentation characteristics and aerobic stability (ASTA) and the lack of ...information on mycotoxin formation during aeration of early-cut rye (ECR) silage after silo opening, we evaluated the effects of different additive types and compositions. Wilted forage was treated with various biological and chemical additives, ensiled in 1.5-L glass jars and stored for 64 days. Fermentation pattern, yeast and mould counts and ASTA were determined at silo opening. In total 34 mycotoxins were analysed in wilted forage and in silage before and after 240 h of air exposure. Chemical additives caused the lowest dry matter (DM) losses during fermentation accompanied with the lowest ethanol production and the highest water-soluble carbohydrate concentration. Aerobic deterioration, which started within two days after silo opening in silage left untreated and inoculated with homofermentative lactic acid bacteria, was prevented by the combined use of hetero- and homofermentative lactic acid bacteria and the chemical additive containing sodium nitrite, hexamethylene tetramine and potassium sorbate. Moreover, these two additives largely restricted the formation of the mycotoxin roquefortine C to < 0.05 mg kg−1 DM after aeration, whereas untreated silage contained 85.2 mg kg−1 DM.
Skin tribology in sport MacFarlane, Maxwell James; Theobald, Peter
Biosurface and biotribology,
September 2021, 2021-09-00, 20210901, 2021-09-01, Letnik:
7, Številka:
3
Journal Article
Recenzirano
Odprti dostop
This review describes the principles of skin friction and wear for the benefit of sports scientists, engineers and clinicians. Skin exhibits complex behaviour, defying tribological laws for dry ...contact; hence, its friction and wear characteristics are affected by sliding speed, normal load, and contact area. Some sports seek to increase skin friction to enhance performance; however, this needs to be offset against injury risk given that skin abrades when slid across a rough and hard surface, delaminates when slid across a smooth and hard surface, and chafes or blisters when repeatedly rubbed against some fabrics. Whilst skin interactions can both define and hinder athlete performance, there exists a need to better understand skin biomechanics to optimise the balance of risk versus reward.
Thermoplastic elastomers (TPE) are commonly used to fabricate structures for application in repeatable, energy absorption environments. The emergence of additive manufacturing (AM) means scope now ...exists to design and build complex TPE components that can mechanically outperform traditionally manufactured equivalents. The ability to efficiently characterize these new TPE AM materials is, however, a barrier preventing wider industrial uptake. This study aims to establish a novel pathway for efficiently characterizing materials used in transient, dynamic applications, to ultimately enable accurate finite element (FE) simulation. A laser sintered TPE powder was characterised by performing low, intermediate and high rate uniaxial tension tests, plus planar and equibiaxial loading states. These data demonstrated significantly different behaviour across strain rates and deformation modes, necessitating fit of an augmented hyperelastic and linear viscoelastic model. FE software was then used to calibrate material model coefficients, with their validity evaluated by comparing the simulated and experimental behaviour of the material in isolated (uniaxial tensile) and mixed modal (lattice-based impact) deformation states. Close correlation demonstrated this novel approach efficiently generated valid material model coefficients, removing a barrier to industry adopting these materials. This creates opportunity to exploit these new technologies for the design optimization and fabrication of high-performance components.
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•Established a novel pathway to efficiently calibrate a material model for additively manufactured thermoplastic elastomers•New pathway is the first that captures the hyperelastic and linear viscoelastic behaviour within a dynamic environment•Validity demonstrated by comparing the experimental and simulated behaviour of a lattice structure at high strain-rates•Introduction of this pathway to efficient characterisation of this AM material type removes a barrier to use industry
To analyze the socio-residential factors associated with extremely and very preterm deliveries occurring in non-level 3 maternity units in France.
This is a population-based observational ...retrospective study using national hospital data from 2012 to 2014. A generalized estimating equations regression model was used to study the characteristics of women who delivered very preterm and the socio-residential risk factors for not delivering in a level 3 maternity unit at 24-31+6d weeks of gestation.
Among deliveries resulting in live births and without contraindication to in-utero transfer, we identified 9198 extremely or very preterm deliveries; 2122 (23.1%) of these were managed in a non-level 3 unit. Our study showed that young maternal age (women under 20 years at delivery) was associated with the risk of giving birth prematurely in a non-level 3 maternity, and particularly in a level 1 maternity unit (adjusted relative risk, 1.53; 95% CI 1.09-2.16). Living more than 30 minutes away from the closest level 3 unit increased the risk of delivering very preterm in a level 1 or 2 unit. Living in an urban area or urban periphery increased the risk of giving birth in a level 2 maternity unit (adjusted relative risk, 1.53; 95% CI 1.28-1.83 and 1.42; 95% CI 1.17-1.71, respectively).
This study shows that young pregnant women living more than 30 minutes from a level 3 hospital have an increased risk of delivering in a maternity unit that is not equipped to deal with premature births. The risk also increases with an urban place of residence when the delivery occurs in a level 2 unit. A clearer understanding of the population at risk of delivering prematurely in a non-level 3 maternity could lead to improvements in structuring healthcare to encourage earlier management and better support.
Background Morbidity and mortality remain high following infant cardiac arrest. Optimal cardiopulmonary resuscitation (CPR) is therefore imperative. Objective Comparison of two-thumb (TT) and ...two-finger (TF) infant chest compression technique compliance with international recommendations. Design Randomised cross-over experimental study. Methods Twenty-two certified Advanced Paediatric Life Support (APLS) instructors performed 2 min continuous TT and TF chest compressions on an instrumented infant CPR manikin. Compression depth (CD), release force (RF), compression rate (CR) and duty cycles (DCs) were recorded. Quality indices were developed to calculate the proportion of compressions that complied with internationally recommended targets, and an overall quality index was used to calculate the proportion that complied with all four targets. Results Mean CD was 33 mm and 26 mm (p<0.001; target ≥36.7 mm), mean RF was 0.8 kg and 0.2 kg (p<0.001; target <2.5 kg), mean CR was 128/min and 131/min (p=0.052; target 100–120/min) and mean DCs was 61% and 53% (p<0.001; target 30–50%) for the TT and TF techniques, respectively. With the exception of RF, the majority of compressions failed to comply with targets. The TT technique improved median CD compliance (6% vs 0% (p<0.001)), while the TF technique improved median DC compliance (23% vs 0% (p<0.001)). Overall compliance with all four targets was <1% for both techniques (p=0.14). Conclusions Compliance of APLS instructors with current international recommendations during simulated infant CPR is poor. The TT technique provided improved CD compliance, while the TF technique provided superior DC compliance. If this reflects current clinical practice, optimisation of performance to achieve international recommendations during infant CPR is called for.
To estimate the prevalence of menorrhagia in women in Reunion Island using the Higham score, to evaluate self-reporting as an alternative diagnostic method, and to study women's level of knowledge ...about menorrhagia and its impact on their quality of life.
This was a descriptive, cross-sectional observational study involving 185 adult women with menstrual periods living in Reunion Island. Women volunteered to answer an online self-questionnaire proposed by healthcare professionals from January to May 2023 in Reunion Island. They completed a general information questionnaire, the Higham score, a menorrhagia knowledge questionnaire and a menstrual quality of life questionnaire.
The prevalence of menorrhagia in the sample was 48.1% using the Higham score and 46.5% using self-report. Women's level of knowledge about menorrhagia is still insufficient, given the significant impact on quality of life during menstruation among those suffering from this symptom.
The prevalence of menorrhagia in our sample of women on Reunion Island is high. Measures need to be taken to break the taboos surrounding menstruation, promote menstrual education and foster a better understanding by women of menstrual pathologies, particularly menorrhagia. Early detection of this symptom would enable faster treatment and avoid complications and adverse effects on quality of life.
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