Crystallographic orientation inhomogeneity and crystal splitting in biogenic calcite

The calcitic prismatic units forming the outer shell of the bivalve Pinctada margaritifera have been analysed using scanning electron microscopy–electron back-scatter diffraction, transmission electron microscopy and atomic force microscopy. In the initial stages of growth, the individual prismatic units are single crystals. Their crystalline orientation is not consistent but rather changes gradually during growth. The gradients in crystallographic orientation occur mainly in a direction parallel to the long axis of the prism, i.e. perpendicular to the shell surface and do not show preferential tilting along any of the calcite lattice axes. At a certain growth stage, gradients begin to spread and diverge, implying that the prismatic units split into several crystalline domains. In this way, a branched crystal, in which the ends of the branches are independent crystalline domains, is formed. At the nanometre scale, the material is composed of slightly misoriented domains, which are separated by planes approximately perpendicular to the c-axis. Orientational gradients and splitting processes are described in biocrystals for the first time and are undoubtedly related to the high content of intracrystalline organic molecules, although the way in which these act to induce the observed crystalline patterns is a matter of future research

The role of mathematics for physics teaching and understanding

That mathematics is the “language of physics” implies that both areas are deeply interconnected, such that often no separation between “pure” mathematics and “pure” physics is possible. To clarify their interplay a technical and a structural role of mathematics can be distinguished. A thorough understanding of this twofold role in physics is also important for shaping physics education especially with respect to teaching the nature of physics. Herewith the teachers and their pedagogical content knowledge play an important role. Therefore we develop a model of PCK concerning the interplay of mathematics and physics in order to provide a theoretical framework for the views and teaching strategies of teachers. In an exploratory study four teachers from Germany and four teachers from Israel have been interviewed concerning their views and its transfer to teaching physics. Here we describe the results from Germany. Besides general views and knowledge held by all or nearly all teachers we also observe specific individual focus depending on the teachers’ background and experiences. The results fit well into the derived model of PCK

A superconducting levitation transport model system for dynamical and didactical studies

Superconducting levitation transport systems might become very attractive in the near future due to various reasons. The realisation of contactless systems allows e.g. extended maintenance-free operation with high efficiency since such a system only needs energy for cooling and propulsion. We established a small superconducting levitation transport model system called "SupraTrans Mini" consisting of permanent magnetic rails and a levitated vehicle including four YBCO-bulk samples in a cryostat. The rail system consists of an oval shaped loop (2.90 m x 1.44 m), which was build up from individual linear and curved track modules. Inside the vehicle position variations of the superconductors are possible. By means of velocity, acceleration and temperature measurements different dynamical aspects of our complex levitation system can be investigated. We also show the broad applicability of the experimental setup for didactical studies in physics

A superconducting levitation transport model system for dynamical and didactical studies

Superconducting levitation transport systems might become very attractive in the near future due to various reasons. The realisation of contactless systems allows e.g. extended maintenance-free operation with high efficiency since such a system only needs energy for cooling and propulsion. We established a small superconducting levitation transport model system called "SupraTrans Mini" consisting of permanent magnetic rails and a levitated vehicle including four YBCO-bulk samples in a cryostat. The rail system consists of an oval shaped loop (2.90 m x 1.44 m), which was build up from individual linear and curved track modules. Inside the vehicle position variations of the superconductors are possible. By means of velocity, acceleration and temperature measurements different dynamical aspects of our complex levitation system can be investigated. We also show the broad applicability of the experimental setup for didactical studies in physics

The Randomized Shortened Dental Arch Study: Tooth Loss

The evidence concerning the management of shortened dental arch (SDA) cases is sparse. This multi-center study was aimed at generating data on outcomes and survival rates for two common treatments, removable dental prostheses (RDP) for molar replacement or no replacement (SDA). The hypothesis was that the treatments lead to different incidences of tooth loss. We included 215 patients with complete molar loss in one jaw. Molars were either replaced by RDP or not replaced, according to the SDA concept. First tooth loss after treatment was the primary outcome measure. This event occurred in 13 patients in the RDP group and nine patients in the SDA group. The respective Kaplan-Meier survival rates at 38 months were 0.83 (95% CI: 0.74-0.91) in the RDP group and 0.86 (95% CI: 0.78-0.95) in the SDA group, the difference being non-significant

Branching patterns of the foetal popliteal artery

Background: The objective of the study is to evaluate the popliteal artery topography and the origin variability of its branches in human foetuses at the gestational age of from 4 to 9 months. The basis for the analysis are direct observations of classic anatomic dissections of the popliteal fossa. Possible dimorphic and bilateral differen- ces, as well as the gestational age variability at the foetal period, were considered. A typology of popliteal artery branches will be made on the basis of the studies.  Materials and methods: The research material of this study comprises 231 foetuses (including 116 males and 115 females). The foetuses were divided into five 28-day age classes. The vessels of the lower extremity were injected with LBSK 5545 latex through the femoral artery. The bilateral dissection of the po- pliteal artery along with its branches was performed. No visible malformations were found in the research material, and the foetuses came from spontaneous abortions and premature births.  Results and Conclusions: Ten per cent of the cases featured the variations of popliteal artery terminal branches. Three most commonly seen variations are the trifurcation, anterior tibial-peroneal trunk, and high terminal division of the po- pliteal artery. The most common course of the superior muscular branches is that there are two large branches which are distributed from the popliteal artery at the height of the knee joint cavity and they do not distribute cutaneous branches. Sural branches are also present as two large vessels without cutaneous branches. The genicular anastomosis branches that run on their own are a typical topographic system of these branches.

Development of a device to simulate tooth mobility

Objectives: The testing of new materials under simulation of oral conditions is essential in medicine. For simulation of fracture strength different simulation devices are used for test set-up. The results of these in vitro tests differ because there is no standardization of tooth mobility in simulation devices. The aim of this study is to develop a simulation device that depicts the tooth mobility curve as accurately as possible and creates reproducible and scalable mobility curves. Materials and methods: With the aid of published literature and with the help of dentists, average forms of tooth classes were generated. Based on these tooth data, different abutment tooth shapes and different simulation devices were designed with a CAD system and were generated with a Rapid Prototyping system. Then, for all simulation devices the displacement curves were created with a universal testing machine and compared with the tooth mobility curve. With this new information, an improved adapted simulation device was constructed. Results: A simulations device that is able to simulate the mobility curve of natural teeth with high accuracy and where mobility is reproducible and scalable was developed

Design of Polymer-Embedded Heterogeneous Fenton Catalysts for the Conversion of Organic Trace Compounds

Advanced oxidation processes are the main way to remove persistent organic trace compounds from water. For these processes, heterogeneous Fenton catalysts with low iron leaching and high catalytic activity are required. Here, the preparation of such catalysts consisting of silica-supported iron oxide (Fe2O3/SiOx) embedded in thermoplastic polymers is presented. The iron oxide catalysts are prepared by a facile sol–gel procedure followed by thermal annealing (calcination). These materials are mixed in a melt compounding process with modified polypropylenes to stabilize the Fe2O3 catalytic centers and to further reduce the iron leaching. The catalytic activity of the composites is analyzed by means of the Reactive Black 5 (RB5) assay, as well as by the conversion of phenol which is used as an example of an organic trace compound. It is demonstrated that embedding of silica-supported iron oxide in modified polypropylene turns the reaction order from pseudo-first order (found for Fe2O3/SiOx catalysts), which represents a mainly homogeneous Fenton reaction, to pseudo-zeroth order in the polymer composites, indicating a mainly heterogeneous, surface-diffusion-controlled process

Quantum Theory contents insertion in High School curricula

A inovação científica e tecnológica do século XX foi esmagadora. Contudo, a nossa experiência docente permite-nos afirmar que as aprendizagens na escola secundária estão longe de acompanhar a evolução que se verifica na sociedade atual. No entanto, já estão a ser incluídos alguns conteúdos de Física Moderna nos currículos oficiais de vários países, parecendo evidenciar uma preocupação em atualizar a preparação dos jovens para o mundo que os rodeia. Neste artigo relatamos um estudo que fizemos acerca dos currículos de Física de alguns países, sobretudo no que diz respeito à Teoria Quântica, a grande invenção do século XX, tentando identificar os conteúdos selecionados e a maneira como estes se integram nas orientações curriculares gerais.In the XXth century, scientific and technological innovation has been overwhelming. Our teaching profession lead us to believe that studies in High Schools do not follow the evolution of ideas that characterizes our modern society. However, some contents of Modern Physics are already included in the official curricula of several countries, which seem to be worried about the improvement of today’s youth training. In this paper we report a study made about Physics’ curricula in several countries, emphasizing Quantum Theory issues, the biggest invention of the XXth century, trying to identify the selected subjects selected and the way they fit into general curricula orientations