Dielectric Elastomer Actuator biased by Magnetorheological Elastomer with Permanent Magnet

Dielectric elastomer actuators have become one of the most important smart material transducers in recent times. One of the crucial aspects in this field is the application of bias to find the best operating conditions. The basic task is to find the proper bias configuration to obtain a wide range of displacements in the actuator. In the literature, various biases, such as mechanical springs, permanent magnets, or pneumatic springs, are studied. In our work, the magnetorheological elastomer is applied to build a novel bias that ensures a wide range of displacement. Because of the softness and the compliant chemical structure, the magnetorheological elastomer can be easily integrated with the dielectric elastomer actuator. The magnetorheological elastomer as a bias for a dielectric elastomer actuator is verified in the series of experiments. Finally, the discussion on the advantages and disadvantages of the new bias type is performed

Nonlinear analysis of the ripping head power time series

We investigate the power of a ripping head in the process of concrete cutting. Using nonlinear embedding methods we study the corresponding time series obtained during the cutting process. The calculated maximal Lyapunov exponent indicates the exponential divergence typical for chaotic or stochastic systems. The recurrence plots technique has been used to get nonlinear process statistics for identification and description of nonlinear dynamics, lying behind the cutting process

APPLICATION OF NEURAL NETWORKS IN PREDICTION OF TENSILE STRENGTH OF ABSORBABLE SUTURES

The paper presents results of research on neural network application in fore-casting the tensile strength of two types of sutures. The preliminary research was conducted in order to establish the accuracy of the proposed method and will be used for formulating further research areas. The neu-ral network enabled evaluation of suture material degradation after 3-to-6-days’ exposure to Ringer’s solution. The encountered problems regarding inaccuracies show that developing a single model for sutures may be difficult or impossible. Therefore future research should be conducted for a single type of sutures only and require applying additional parameters for the neural network

Global Surgery – Informing National Strategies for Scaling Up Surgery in Sub-Saharan Africa

Abstract Surgery has the potential to address one of the largest, neglected burdens of disease in low- and middle-income countries (LMICs), especially in sub-Saharan Africa (SSA). The Lancet Commission on Global Surgery (LCoGS) has provided a blueprint for a systems approach to making safe emergency and elective surgery accessible and affordable and has started to enable African governments to develop national surgical plans. This editorial outlines an important gap, which is the need for surgical systems research, especially at district hospitals which are the first point of surgical care for rural communities, to inform the implementation of country plans. Using the Lancet Commission as a starting point and illustrated by two European Union (EU) funded research projects, we point to the need for implementation research to develop and evaluate contextualised strategies. As illustrated by the case study of Zambia, coordination by global and external stakeholders can enable governments to lead national scale-up of essential surgery, supported by national partners including surgical specialist associations

Inhibition of thrombin generation by simvastatin and lack of additive effects of aspirin in patients with marked hypercholesterolemia

AbstractOBJECTIVESTo assess the effects of aspirin compared with simvastatin on thrombin generation in hypercholesterolemic men, and to establish whether the reduction of elevated blood cholesterol by simvastatin would affect the action of aspirin on thrombin formation.BACKGROUNDAspirin inhibits thrombin formation, but its performance is blunted in hypercholesterolemia. By virtue of altering lipid profile, statins could be expected to influence thrombin generation.METHODSThirty-three men, aged 34 to 61 years, with minimal or no clinical symptoms, serum total cholesterol >6.5 mmol/liter and serum triglycerides <4.6 mmol/liter, completed the study consisting of three treatment phases. First, they received 300 mg of aspirin daily for two weeks (phase I), which was then replaced by simvastatin at the average dose of 24 mg/d for three months (phase II). In phase III, aspirin, 300 mg/day, was added for two weeks to simvastatin, the dose of which remained unchanged. Thrombin generation was assessed: 1) in vivo, by measuring levels of fibrinopeptide A (FPA) and prothrombin fragment 1+2 (F1+2) in venous blood; and 2) ex vivo, by monitoring the rates of increase of FPA and F1+2 in blood emerging from standardized skin incisions of a forearm. A mathematical model was used to describe the kinetics of thrombin formation at the site of microvascular injury.RESULTSTwo-week treatment with aspirin had no effect on thrombin markers in vivo, while ex vivo it depressed the total amount of thrombin formed, though not the reaction rate. After simvastatin treatment, serum cholesterol decreased by 31% and LDL cholesterol by 42%, while thrombin generation became markedly depressed. In venous blood, FPA was significantly reduced. Concomitantly, the initial thrombin concentration and total amount of thrombin generated decreased significantly. Addition of aspirin to simvastatin (phase III) had no further effect on any of these parameters.CONCLUSIONSIn men with hypercholesterolemia, lowering serum cholesterol level by a three-month simvastatin treatment is accompanied by a marked reduction of thrombin generation both at basal conditions in venous blood and after activation of hemostasis by microvascular injury. Once blood cholesterol became reduced, adding aspirin to simvastatin did not enhance dampening of thrombin formation

Critical shortage of capacity to deliver safe paediatric surgery in sub-Saharan Africa: evidence from 67 hospitals in Malawi, Zambia, and Tanzania

IntroductionPaediatric surgical care is a significant challenge in Sub-Saharan Africa (SSA), where 42% of the population are children. Building paediatric surgical capacity to meet SSA country needs is a priority. This study aimed to assess district hospital paediatric surgical capacity in three countries: Malawi, Tanzania and Zambia (MTZ).MethodsData from 67 district-level hospitals in MTZ were collected using a PediPIPES survey tool. Its five components are procedures, personnel, infrastructure, equipment, and supplies. A PediPIPES Index was calculated for each country, and a two-tailed analysis of variance test was used to explore cross-country comparisons.ResultsSimilar paediatric surgical capacity index scores and shortages were observed across countries, greater in Malawi and less in Tanzania. Almost all hospitals reported the capacity to perform common minor surgical procedures and less complex resuscitation interventions. Capacity to undertake common abdominal, orthopaedic and urogenital procedures varied—more often reported in Malawi and less often in Tanzania. There were no paediatric or general surgeons or anaesthesiologists at district hospitals. General medical officers with some training to do surgery on children were present (more often in Zambia). Paediatric surgical equipment and supplies were poor in all three countries. Malawi district hospitals had the poorest supply of electricity and water.ConclusionsWith no specialists in district hospitals in MTZ, access to safe paediatric surgery is compromised, aggravated by shortages of infrastructure, equipment and supplies. Significant investments are required to address these shortfalls. SSA countries need to define what procedures are appropriate to national, referral and district hospital levels and ensure that an appropriate paediatric surgical workforce is in place at district hospitals, trained and supervised to undertake these essential surgical procedures so as to meet population needs

Nonlinear analysis of the ripping head power time series

We investigate the power of a ripping head in the process of concrete cutting. Using nonlinear embedding methods we study the corresponding time series obtained during the cutting process. The calculated maximal Lyapunov exponent indicates the exponential divergence typical for chaotic or stochastic systems. The recurrence plots technique has been used to get nonlinear process statistics for identification and description of nonlinear dynamics, lying behind the cutting process

Nonlinear analysis of the ripping head power time series

We investigate the power of a ripping head in the process of concrete cutting. Using nonlinear embedding methods we study the corresponding time series obtained during the cutting process. The calculated maximal Lyapunov exponent indicates the exponential divergence typical for chaotic or stochastic systems. The recurrence plots technique has been used to get nonlinear process statistics for identification and description of nonlinear dynamics, lying behind the cutting process