Dalla prospettiva di studente a quella di docente

The contribution describes the laboratory of Didactics of the first year of the degree course for primary school teacher training. The lab was activated with the aim of approaching prospective teachers to a professional vision. Such change has fostered the participation in laboratory activities in which the student reflects on his/her own vision about teaching and learning by building a metaphor-collage that reifies his/her vision of teaching and in which the student analyzes videos. Such activity, in alternationwith lectures of the course in General didactics, create situations of structural coupling, that is, it lets students articulate, thanks to the interaction with the “dispositf” in which act, a personal perspective that dialogues with the “savy knowledge”.Il contributo descrive il laboratorio di Didattica generale del primo anno del corso di laurea in Scienze della formazione primaria attivato con la finalità di avviare nei futuri insegnanti una visione professionale. Tale cambiamento è favorito dalla partecipazione ad attività laboratoriali in cui lo studente riflettesulla propria visione di insegnamento e apprendimento costruendo un collagemetafora che reifica la propria immagine di insegnamento e analizzando video. Tali attività, intervallandosi con le lezioni frontali del corso di didattica generale, creano situazioni di accoppiamento strutturale, ovvero consentono allo studente, grazie all’interazione con il dispositivo in cui opera, di articolare un proprio punto di vista che dialoga con il “sapere sapiente”

ELECTRICAL CHARACTERIZATION OF THE FORWARD CURRENTVOLTAGE OF AL IMPLANTED 4H-SIC PIN DIODES

ABSTRACTIn this work,theforward current-voltagecharacteristics of n-type Al implanted 4H-SiC pin diodeshave been investigatedexperimentally and by mean of numerical simulations in the 298-378K temperature range. Our simulations were performedusing proprietary simulations software. The model parameters to be calibrated in the simulation are the electron and holeminority carriers lifetimes.The measured forward I-V characteristics showed two differentbehaviour, the leaky behaved andwell behaved diode. The later diodes were considered for simulation comparison.Employing temperature-dependent carrierlifetimes as a fitting parameter, the simulation indicates that drift layer and bulk carrier lifetime ranging from 10ns to 50ns. Weachieved a good agreement between simulations and measured data. The measured and the simulated forward characteristicsindicate an ideality factor of about1.3for the region 2.5V-2.78Vand 2.14 in the low injection region. Activation energies ofabout 1.61eV and 2.51eVare obtained respectively which are in good agreement with the expected values.KEYWORDS: p-i-n diode, silicon carbide, silvaco, device simulation, lifetimes

The Tumor Suppressor PRDM5 Regulates Wnt Signaling at Early Stages of Zebrafish Development

PRDM genes are a family of transcriptional regulators that modulate cellular processes such as differentiation, cell growth and apoptosis. Some family members are involved in tissue or organ maturation, and are differentially expressed in specific phases of embryonic development. PRDM5 is a recently identified family member that functions as a transcriptional repressor and behaves as a putative tumor suppressor in different types of cancer. Using gene expression profiling, we found that transcriptional targets of PRDM5 in human U2OS cells include critical genes involved in developmental processes, and specifically in regulating wnt signaling. We therefore assessed PRDM5 function in vivo by performing loss-of-function and gain-of-function experiments in zebrafish embryos. Depletion of prdm5 resulted in impairment of morphogenetic movements during gastrulation and increased the occurrence of the masterblind phenotype in axin+/− embryos, characterized by the loss of eyes and telencephalon. Overexpression of PRDM5 mRNA had opposite effects on the development of anterior neural structures, and resulted in embryos with a shorter body axis due to posterior truncation, a bigger head and abnormal somites. In situ hybridization experiments aimed at analyzing the integrity of wnt pathways during gastrulation at the level of the prechordal plate revealed inhibition of non canonical PCP wnt signaling in embryos overexpressing PRDM5, and over-activation of wnt/β-catenin signaling in embryos lacking Prdm5. Our data demonstrate that PRDM5 regulates the expression of components of both canonical and non canonical wnt pathways and negatively modulates wnt signaling in vivo

Analysis of 4H-SiC MOSFET with distinct high-k/4H-SiC interfaces under high temperature and carrier-trapping conditions

In this work, the reliability of different oxide/4H-SiC interfaces under high temperature and carrier-trapping conditions are investigated carefully. In more detail, the carrier-trapping and temperature effects are considered in the electrical characterization of a low breakdown 4H-SiC-based MOSFET by using in turn SiO2, Si3N4, AlN, Al2O3, Y2O3 and HfO2 as gate dielectric. A gate oxide with a high relative permittivity notably improves the transistor performance. In addition, HfO2 assures the MOSFET best immunity behaviors. The obtained results are explained in terms of the carrier channel mobility, device on-state resistance, and oxide electric field. By using HfO2, however, an increased gate leakage current is calculated. This drawback is overcome by inserting a thin interfacial layer (2 nm-thick) in the HfO2/4H-SiC MOS structure. In particular, two alternative gate stacked dielectrics, involving either SiO2 or Al2O3, have proven their effectiveness in preserving the transistor on-state figures of merit while limiting the gate leakage current in the whole explored gate voltage range. To support the prediction capabilities of the presented modeling analysis, the simulations results are compared with experimental data from literature resulting in a good agreement. Low power MOSFETs are used in several applications for which reliability and durability are as critical as performance. For example, referring to power optimizers for photovoltaic (PV) modules, which fall under the low-load and low-voltage category of DC–DC converters, these devices significantly increase the energy generated by each single PV module operating under harsh conditions and stressing environments. In addition, they have to ensure high reliability over the long term of operation

Improving the efficiency of a-Si:H/c-Si thin heterojunction solar cells by using both antireflection coating engineering and diffraction grating

In this paper, we present an analytical study of the impact of light trapping and multilayer antireflection coating (ARC) on the electrical characteristics of n(a-Si:H)/i(a-Si:H)/p(c-Si)/p+(C-Si) heterojunction solar cells with intrinsic thin layer (SHJ). The developed analytical model considers a triangular texture morphology of the solar cell top surface and a double ARC layer. This model serves as a fitness function to optimize the device reliability against the interfacial traps using Grey Wolf optimization approach (GWO). The optimized solar cell reveals a high short circuit current I SC = 47.9 mA, an open circuit voltage V OC = 0.56 V, fill factor FF = 74.72% and a conversion efficiency improvement in the order of 30% over conventional planar solar cells efficiency. Not only the optimized SHJ solar cell exhibits higher performance in terms of figure of merits, but also shows superior interfacial traps reliability at the amorphous/crystalline interface. This reliability enhancement is due to a better surface texture control and intrinsic thin film layer tuning provided by GWO approach

Temperature and SiO2/4H-SiC interface trap effects on the electrical characteristics of low breakdown voltage MOSFETs

The temperature and carrier-trapping effects on the electrical characteristics of a 4H silicon carbide (4H-SiC) metal–oxide–semiconductor field effect transistor (MOSFET) dimensioned for a low breakdown voltage (BVDS) are investigated. Firstly, the impact of the temperature is evaluated referring to a fresh device (defects-free). In particular, the threshold voltage (Vth), channel mobility (µch), and on-state resistance (RON) are calculated in the temperature range of 300 K to 500 K starting from the device current–voltage characteristics. A defective MOSFET is then considered. A combined model of defect energy levels inside the 4H-SiC bandgap (deep and tail centers) and oxide-fixed traps is taken into account referring to literature data. The simulation results show that the SiO2/4H-SiC interface traps act to increase RON, reduce µch, and increase the sensitivity of Vth with temperature. In more detail, the deep-level traps in the mid-gap have a limited effect in determining RON once the tail traps contributions have been introduced. Also, for gate biases greater than about 2Vth (i.e., VGS > 12 V) the increase of mobile carriers in the inversion layer leads to an increased screening of traps which enhances the MOSFET output current limiting the RON increase in particular at low temperatures. Finally, a high oxide-fixed trap density meaningfully influences Vth (negative shifting) and penalizes the device drain current over the whole explored voltage range

OP\uc9EN & ReForm : Observation des Pratiques \uc9ducatives et des pratiques ENseignantes de la Recherche \ue0 la Formation

Les objectifs de la structure f\ue9d\ue9rative sont les suivants : - donner une plus grande visibilit\ue9 aux recherches r\ue9alis\ue9es par les \ue9quipes de la structure f\ue9d\ue9rative et \ue0 leurs applications (publications, colloques, valorisation d\u2019outils d\u2019\ue9valuation et de formation) - permettre aux unit\ue9s partenaires de confronter les approches, concepts, d\ue9marches et m\ue9thodologies utilis\ue9es afin de d\ue9velopper des projets de recherche collaborative pluridisciplinaire ; - favoriser les interactions entre les unit\ue9s afin de d\ue9velopper des projets de recherche \ue0 dimension internationale dans le domaine de l\u2019\ue9ducation, de l\u2019enseignement et de la formation professionnelle ; - contribuer au d\ue9veloppement de partenariats avec les professionnels de mani\ue8re \ue0 diffuser les apports de la recherche dans la formation professionnelle initiale et continue. La structure f\ue9d\ue9rative comprend 18 unit\ue9s de recherche dont 10 unit\ue9s en co-tutelle avec Nantes et 7 unit\ue9s partenaires Actuellement, le r\ue9seau OP\uc9EN & ReForm est en mesure de d\ue9velopper des collaborations avec le regroupement de 8 facult\ue9s de recherche et de 4 chaires de recherche au sein de l\u2019IRP\uc9 de Sherbrooke (Institut de recherche sur les pratiques \ue9ducatives), la facult\ue9 d\u2019\ue9ducation de Macerata et de Bari (Italie) et avec l\u2019ULB de Bruxelles