Evaporation waves in superheated dodecane

We have observed propagating adiabatic evaporation waves in superheated liquid dodecane, C_(12)H_(26). Experiments were performed with a rapid decompression apparatus at initial temperatures of 180–300°C. Saturated dodecane in a tube was suddenly depressurized by rupturing a diaphragm. Motion pictures and still photographic images, and pressure and temperature data were obtained during the evaporation event that followed depressurization. Usually, a front or wave of evaporation started at the liquid free surface and propagated into the undisturbed regions of the metastable liquid. The evaporation wave front moved with a steady mean velocity but the front itself was unstable and fluctuating in character. At low superheats, no waves were observed until a threshold superheat was exceeded. At moderate superheats, subsonic downstream states were observed. At higher superheats, the downstream flow was choked, corresponding to a Chapman–Jouguet condition. At the most extreme superheat tested, a vapour content of over 90% was estimated from the measured data, indicating a nearly complete evaporation wave. Our results are interpreted by modelling the evaporation wave as a discontinuity, or jump, between a superheated liquid state and a two-phase liquid–vapour downstream state. Reasonable agreement is found between the model and observations; however, there is a fundamental indeterminacy that prevents the prediction of the observed wave speeds

Changing a school organization: A private school case study

Due to contextual demands, organizations face the constant need to adjust and adapt in order to maintain their stability. School organizations are not an exception and have to answer to these demands to guarantee their quality, efficacy and sustainability. Very little literature has addressed the school as organizations. However, analysing the educational environment from an organizational point of view could allow a better understanding on why school organizations change and how they strive for educational efficiency. This paper focuses on the main results of an organizational diagnosis aimed to identify the needs for a planned change intervention in a school based on a private charitable organization. Because an organizational diagnosis is a complex process, the choice of a theoretical model is critical, as it determines the type of information to be collected, it guides the interpretation of that information, and defines the course of action. In this project, we have taken Nadler and Tushman’s Organizational Congruence Model (1980) as a basic guideline. This model assumes the organization as a whole system, whose performance is contingent on the congruent adjustment level between their primary components. Therefore, we searched for incongruent sources, with special focus on the strategy and the fitness of the processes under internal and external environment pressure and demands. In order to get a wider vision of the organization, we carried out an organizational diagnosis using methodological triangulation, with qualitative and quantitative procedures. Following an action-research methodological framework, results of data analysis were debated with the participants and the school director. Data collection started by analyzing the school documentation, followed by individual interviews with the school director and general director. Subsequently, questionnaires intended to assess the organizational culture were applied to the school staff. A focus group was also carried out to understand the way the individuals respond to each others perceptions and how they construct shared meaning. The use of this method also served to involve the organizational members in the change process. Finally, an adapted force-field analysis has been conducted to enhance the participants’ willingness and commitment to the change process and to mitigate the resistance associated to it. Results show that a perceived need for change exists. Specifically, participants’ wish for a clearer school strategy aligned with the mission of the organization in which it is integrated. Moreover, results indicate the need for organizational changes towards a more appropriate resource distribution, a non-bureaucratic culture that may foster potential innovation, the implementation of a regular practice of feedback on work practices, and the enhancement of the organizational communication between departments. As orientation for change, we recommend an incremental change process, based on a cooperative thinking approach on the strategy and objectives of the school, and using the current review of the school main documents as a chance to redefine the management strategy. Furthermore, effective ways to assess and publicize school outcomes, and a systematic practice of performance assessment are also needed.info:eu-repo/semantics/acceptedVersio

Effects of the transfer design on post-training performance in elearning

Training in organizations is considered as a key factor for organizational development, and a tool for improving individual and organizational performance. However, training is only effective if knowledge and skills acquired during training are applied to the job, i.e., if the learning outcomes are transferred to workplace. Past research on the transfer of training has focused on various individual, group and organizational factors that before, during, and after training affect the probability that the acquired skills and knowledge are actually implemented in the workplace. Given the extant literature on the design of transfer, practitioners and training managers are prone to focus mostly on the training design itself and on the post-training procedures to enhance transfer. In order to contribute for studying the whole transfer processes in training activities, the main goal of this paper is to contribute for clarifying the effects of the design of learning transfer before and during eLearning training sessions. Results from an experimental study (N=115) show that the presence (vs. absence) of metacognitive orientations for transfer (design) before and during an e-learning. Session maximizes the effective transfer of learning. Specifically, participants who were instructed to mentally simulate a task in which they applied the skills learned in the training session performed better than those of the control group. This effect is moderated by perception of utility of training, in the sense that individuals who anticipated and mentally simulated task, and simultaneously perceived a greater utility of training, showed the highest performance. These results seem to highlight the importance of metacognitive dimension in the design of the transfer of learning, and especially of mental rehearsal of the use of skills and knowledge acquired in training.The practical implications of these results for enhancing the level of training transfer to the workplace are also discussed.info:eu-repo/semantics/acceptedVersio

Piezoelectric actuators for bone mechanical stimulation: exploring the concept.

Arthroplasty is liable to cause intense changes on strain levels and distribution in the boné surrounding the implant, namely stress shielding. Several solutions have been proposed for this, namely design variations and development of controlled-stiffness implants. A new approach to this problem, with potential application to other orthopaedic problems and other medical fields, would be the development of smart implants integrating systems for bone mechanical stimulation. Ideally, the implant should presente sensing capability and the ability to maintain physiological levels of strain at the implant interface. Piezoelectric materials’ huge potential as a mean to produce direct mechanical stimulation lies on the possibility of producing stimuli at a high range of frequencies and in multiple combinations. The present in vitro and preliminary in vivo studies were a first step towards the validation of the concept

Reprogramming of avian neural crest axial identity and cell fate

Neural crest populations along the embryonic body axis of vertebrates differ in developmental potential and fate, so that only the cranial neural crest can contribute to the craniofacial skeleton in vivo. We explored the regulatory program that imbues the cranial crest with its specialized features. Using axial-level specific enhancers to isolate and perform genome-wide profiling of the cranial versus trunk neural crest in chick embryos, we identified and characterized regulatory relationships between a set of cranial-specific transcription factors. Introducing components of this circuit into neural crest cells of the trunk alters their identity and endows these cells with the ability to give rise to chondroblasts in vivo. Our results demonstrate that gene regulatory circuits that support the formation of particular neural crest derivatives may be used to reprogram specific neural crest–derived cell types

Establishing neural crest identity: a gene regulatory recipe

The neural crest is a stem/progenitor cell population that contributes to a wide variety of derivatives, including sensory and autonomic ganglia, cartilage and bone of the face and pigment cells of the skin. Unique to vertebrate embryos, it has served as an excellent model system for the study of cell behavior and identity owing to its multipotency, motility and ability to form a broad array of cell types. Neural crest development is thought to be controlled by a suite of transcriptional and epigenetic inputs arranged hierarchically in a gene regulatory network. Here, we examine neural crest development from a gene regulatory perspective and discuss how the underlying genetic circuitry results in the features that define this unique cell population