Analysis of reinforced concrete structures with occurrence of discrete cracks at arbitrary positions

A nonlinear analysis of in-plane loaded plates is presented, which eliminates the disadvantages of the smeared crack approach. The elements used and the computational method are discussed. An example is shown in which one or more discrete cracks are dominant

An extendable modular endoprosthetic system for bone tumour management in the leg

A modular endoprosthetic system has been developed at the Groningen University Hospital and the University of Twente. The system can bridge a defect resulting from the resection of a malignant bone tumour which has developed around the knee joint of a child. Since the other healthy leg continues to grow, the system includes an element whose length can be adjusted non-invasively by using an external magnetic field. In addition to this lengthening element, there are one hip and two knee components, connectors of various lengths, and fixation elements. The paper describes the elements of the modular endoprosthetic system. Tables are created by means of which the elemental composition of such an endoprosthesis can be determined for each individual patient

Novel mutations in PIEZO1 cause an autosomal recessive generalized lymphatic dysplasia with non-immune hydrops fetalis.

Generalized lymphatic dysplasia (GLD) is a rare form of primary lymphoedema characterized by a uniform, widespread lymphoedema affecting all segments of the body, with systemic involvement such as intestinal and/or pulmonary lymphangiectasia, pleural effusions, chylothoraces and/or pericardial effusions. This may present prenatally as non-immune hydrops. Here we report homozygous and compound heterozygous mutations in PIEZO1, resulting in an autosomal recessive form of GLD with a high incidence of non-immune hydrops fetalis and childhood onset of facial and four limb lymphoedema. Mutations in PIEZO1, which encodes a mechanically activated ion channel, have been reported with autosomal dominant dehydrated hereditary stomatocytosis and non-immune hydrops of unknown aetiology. Besides its role in red blood cells, our findings indicate that PIEZO1 is also involved in the development of lymphatic structures

Extramuscular myofascial force transmission alters substantially the acute effects of surgical aponeurotomy: assessment by finite element modeling

Effects of extramuscular myofascial force transmission on the acute effects of aponeurotomy were studied using finite element modeling and implications of such effects on surgery were discussed. Aponeurotomized EDL muscle of the rat was modeled in two conditions: (1) fully isolated (2) with intact extramuscular connections. The specific goal was to assess the alterations in muscle length-force characteristics in relation to sarcomere length distributions and to investigate how the mechanical mechanism of the intervention is affected if the muscle is not isolated. Major effects of extramuscular myofascial force transmission were shown on muscle length-force characteristics. In contrast to the identical proximal and distal forces of the aponeurotomized isolated muscle, substantial proximo-distal force differences were shown for aponeurotomized muscle with extramuscular connections (for all muscle lengths F dist > F prox after distal muscle lengthening). Proximal optimal length did not change whereas distal optimal length was lower (by 0.5 mm). The optimal forces of the aponeurotomized muscle with extramuscular connections exerted at both proximal and distal tendons were lower than that of isolated muscle (by 15 and 7%, respectively). The length of the gap separating the two cut ends of the intervened aponeurosis decreases substantially due to extramuscular myofascial force transmission. The amplitude of the difference in gap length was muscle length dependent (maximally 11.6% of the gap length of the extramuscularly connected muscle). Extramuscular myofascial force transmission has substantial effects on distributions of lengths of sarcomeres within the muscle fiber populations distal and proximal to the location of intervention: (a) Within the distal population, the substantial sarcomere shortening at the proximal ends of muscle fibers due to the intervention remained unaffected however, extramuscular myofascial force transmission caused a more pronounced serial distribution towards the distal ends of muscle fibers. (b) In contrast, extramuscular myofascial force transmission limits the serial distribution of sarcomere lengths shown for the aponeurotomized isolated muscle in the proximal population. Fiber stress distributions showed that extramuscular myofascial force transmission causes most sarcomeres within the aponeurotomized muscle to attain lengths favorable for higher force exertion. It is concluded that acute effects of aponeurotomy on muscular mechanics are affected greatly by extramuscular myofascial force transmission. Such effects have important implications for the outcome of surgery performed to improve impeded function since muscle in vivo is not isolated both anatomically and mechanically

Opportunities to Learn Mathematics Pedagogy and Connect Classroom Learning to Practice: A Study of Future Teachers in the United States and Singapore

In this study, we conducted secondary analyses using the TEDS-M database to explore future mathematics specialists teachers’ opportunities to learn (OTL) how to teach mathematics. We applied latent class analysis techniques to differentiate among groups of prospective mathematics specialists with potentially different OTL mathematics pedagogy within the United States and Singapore. Within the United States, three subgroups were identified: (a) Comprehensive OTL, (b) Limited OTL, and (c) OTL Mathematics Pedagogy. Within Singapore, four subgroups were identified: (a) Comprehensive OTL, (b) Limited Opportunities to Connect Classroom Learning with Practice, (c) OTL Mathematics Pedagogy, and (d) Basic OTL. Understanding the opportunities different prospective teachers had to learn from and their experiences with different components of instructional practice in university and practicum settings has implications for teacher preparation programs

Design of an intramedullary leg lengthening device with a shape memory actuator

The procedure and the external fixator for lengthening long bones was developed by G.A. Ilizarov in the late 1960’s. This technique has, despite its proven abilities for leg lengthening and correction of angular deformities, some considerable disadvantages for the patients. Discomfort, infections and restricted weight bearing are some reasons for the development of a completely intramedullary device for leg lengthening. The device developed at the Laboratory of Biomechanical Engineering, University of Twente, is a telescopic intramedullary nail with a maximum diameter of 13 mm, which can be lengthened with 0.5 mm steps induced by a shape memory alloy actuator. The electrical energy for the actuator is supplied from outside the body by inductive coupling of two solenoid coils. Internally, the electrical energy is transformed to thermal energy by Thermofoils and Peltier‐elements