A coherent picture of water at extreme negative pressure.

International audienceLiquid water at atmospheric pressure can be supercooled to 41 C (ref. 1) and superheated to C302 C (ref. 2). Experiments involving fluid inclusions of water in quartz suggest that water is capable of sustaining pressures as low as 140 MPa before it breaks by cavitation3. Other techniques, for which cavitation occurs consistently at around 30MPa (ref. 4), produce results that cast doubt on this claim. Here we reproduce the fluid-inclusion experiment, performing repeated measurements on a single sample--a method used in meteorology5, bioprotection6 and protein crystallization7, but not yet in liquid water under large mechanical tension. The resulting cavitation statistics are characteristic of a thermally activated process, and both the free energy and the volume of the critical bubble are well described by classical nucleation theory when the surface tension is reduced by less than 10%, consistent with homogeneous cavitation. The line of density maxima of water at negative pressure is found to reach 922:8 kgm3 at around 300 K, which further constrains its contested phase diagram

Socratic dialogue and teacher-pupil interaction

The aim of this quasi experimental research involving an experimental and a control group was to answer the question whether a course in the Socratic Dialogue in Nelson-Heckmann tradition would have any effects on content area student teachers’ beliefs and interactional behaviour with second language pupils. We consider the question partly positively answered. The course did not seem to have any effects on the teachers’ beliefs about communication as measured by a teacher belief survey, but it did have effects on their interactional behaviour. However, the first half of the answer can further be nuanced by the answer to the specific question regarding the effects of the course in the Socratic Dialogue on the student teachers’ statements on learning. As it is, after the course, the spontaneous statements on learning were more participation oriented. Regarding the nature of the effects on the student teachers’ interactional behaviour with second language pupils, the teachers asked more open-ended questions, slowed down the pace of the dialogue, explicitly invited the pupils to contribute and allowed them more time to express themselves. Also, they paid more attention to language. The microanalysis of the interaction in the teacher-pupil learning dialogues where the teacher’s interactional behaviour had changed, displayed change patterns pointing to an increase in interactional space for the pupil and in open question sequences containing a greater variety and frequency of metalinguistic sequences. In the course of the research, three instruments were developed. The first was the Socratic Dialogue assessment form. It may be considered a successful attempt at defining the Socratic Dialogue and its main features. It was developed in the cooperation with four experienced Socratic Dialogue facilitators and one Socratic Dialogue theoretician. Its inter-observer reliability was good. The second instrument was a teacher belief survey. Drawing on two metaphors for learning (Sfard, 1998) it comprised the two corresponding scales along which teachers’ beliefs about communication in general and in learning and instructions in particular were measured. Its reliability was satisfactory as was its construct validity. The third instrument was the teacher-pupil-learning-dialogue scoring scheme which captured the teacher’s scaffolding behaviour on 8 features. The instrument was found reliable for two observers. Each of the three instruments could be seen as presenting a theoretical contribution to the study of the Socratic Dialogue, teacher beliefs and interactional scaffolding by framing one or more of their respective aspects

PhD Research Proposal: How does Socratic Dialogue as developed by Nelson and Heckmann influence the reflective skills in student teachers?

I intend to do an action research on how I can improve educating teachers by means of training them in reflective skills through Socratic Dialogue. In order to be able to meet demands posed to student teachers by the recently introduced changes in higher professional education in the Netherlands and also the didactics of new learning introduced at junior vocational education, they need to develop into Self-Directed Learners. We should help them equip themselves with more than just the necessary reflective skills. We should induce and facilitate the birth of genuine need to reflect. They should leave this education able to make justified choices for learning in their professional careers. And they should leave with a genuine curiosity and interest in other ways of thinking than their own. Having realized the importance and value of an open dialogue they will become self-conscious thinkers and practitioners who know how to learn to look and wonder about what they see. In the present situation, the students are asked to reflect on all sorts of items and situations connected with their study career and their school practice. Various models are offered to them (Korthagen, Hendriksen) in the hope that by reflecting, they will learn how to reflect. And they certainly do, to a certain extent. But what this extent is and how long it will be perpetrated after they leave the school is less certain. But the genuine need to reflect remains untouched upon. This can be done by means of training in Socratic Dialogue and training in facilitating one

Wyznaczanie stałych elastyczności tkanin o splocie płóciennym korzystając z testów rozciągania w różnych kierunkach

In this paper the values of elastic constants of woven fabrics for different angles of extension direction were analysed. Four types of fabric samples of different raw material composition and the same type of weave were tested under tensile forces in seven directions oriented with a 15° increment with respect to the weft direction. The elasticity modulus and Poisson’s ratio of the woven fabrics were determined experimentally in a laboratory. Based on the experimentally obtained values, theoretically calculated elastic constants for arbitrarily chosen fabric directions were calculated. A good agreement between the experimental results and values of the elastic constants calculated was shown, hence the theoretical equations can be used with high accuracy to calculate the elastic constants of fabric in various directions. Therefore the measurements need to be undertaken when the tensile force is acting on the fabric only in the warp, weft and at an angle of 45°.W pracy przeanalizowano stałe elastyczności tkanin rozciąganych pod różnymi kątami. Badano próbki wykonane z różnych materiałów ale o tym samym splocie. Próbki rozciągano w kierunkach o przesunięciu co 150 licząc od kierunku wątku. Badano moduł elastyczności i współczynnik Poissona. Testy przeprowadzono w warunkach laboratoryjnych. Korzystając z wyników eksperymentów przeprowadzono teoretyczne obliczenia stałych elastyczności dla wybranych kierunków rozciągania. Stwierdzono dobrą zgodność wyników, dzięki czemu można wyciągnąć wniosek, że zastosowane wzory mogą służyć do obliczeń stałych elastyczności z dużą dokładnością. Dlatego pomiary takie powinny być przeprowadzane jeżeli siły rozciągające tkaninę działają tylko w kierunku osnowy, wątku i pod kątem 45 stopni

Student teachers' self-dialogues, peer dialogues, and supervisory dialogues in placement teaching

Item does not contain fulltext17 p

Impact of in-service Master of Education programmes on teachers and their working environment

In these uncertain times, politicians and society have been voicing high expectations from teacher education asking for evidence of added value and impact on the student. In this study a longitudinal mixed-methods approach was used to determine the impact of in-service Master of Education programmes on teachers (N = 1,917) and their work environment in the Netherlands. The results of online surveys were explained by means of realist evaluation using focus-group and in-depth interviews. The study shows that Master of Education programmes had an impact on professional and pedagogical skills of teachers, and in some cases also on their work environment. A two-tier mechanism is proposed: the Master’s programmes provide teachers with more indepth knowledge about teaching and learning and a more critical stance through inquiry and research. Consequently, some teachers contribute to a culture of inquiry in their schools, provided that the schools facilitate them in new roles