The role and uses of technologies in mathematics classrooms: Between challenge and modus Vivendi

Abstract

Drawing support from theoretical frameworks, this article analyses the role and uses of technology in the teaching of mathematics, with specific reference to the complexity of integrating technology into teaching. Four aspects are discussed here: the changes that technology brings about in classroom mathematical activity, the difficulties students encounter in solving problems in a technology‐rich environment, the evaluation of potential assignments and the creation of conditions appropriate for learning, and the difficulties faced by teachers who use technology in deciding when and how to intervene. This analysis is illustrated by examples taken primarily from dynamic geometry, but similar analyses could be conducted for computerized environments of other kinds.     

Structure of waterborne coatings by electrochemical impedance spectroscopy and a thermostimulated current method: influence of fillers

Electrochemical impedance spectroscopy (EIS) was coupled with a thermostimulated current (TSC) method to investigate the effect of fillers on the barrier properties of an epoxy-polyamido amine waterborne coating on a 2024 aluminium alloy. Four systems were studied: a clear coat and three pigmented coatings (with and without chromates). The results obtained by TSC highlight the specific action of chromates which decrease the molecular mobility (hardening) of the coating by comparison with neutral fillers. This has been explained by the high polarity of chromates that enhances interactions with the binder. Impedance measurements carried out for free-standing films and for coated aluminium alloy have corroborated the role of chromates on the barrier properties of the coating which remain high as a function of exposure time in a 0.5 M NaCl solution. TSC was also used to measure the glass transition temperature (T_g) of the hydrated systems. T_g was significantly decreased when the coatings were hydrated due to a strong plasticization effect induced by water uptake. For the different systems, we conclude that the weak barrier properties of the films (attached films) or the decrease of the barrier properties with time (free-standing films) were linked to the variation of the glass transition temperature by water uptake.     

In Vitro and In Vivo Characterization of PLLA-316L Stainless Steel Electromechanical Devices for Bone Tissue Engineering—A Preliminary Study

Bone injuries represent a major social and financial impairment, commonly requiring surgical intervention due to a limited healing capacity of the tissue, particularly regarding critical-sized defects and non-union fractures. Regenerative medicine with the application of bone implants has been developing in the past decades towards the manufacturing of appropriate devices. This work intended to evaluate medical 316L stainless steel (SS)-based devices covered by a polymer poly (L-lactic acid) (PLLA) coating for bone lesion mechanical and functional support. SS316L devices were subjected to a previously described silanization process, following a three-layer PLLA film coating. Devices were further characterized and evaluated towards their cytocompatibility and osteogenic potential using human dental pulp stem cells, and biocompatibility via subcutaneous implantation in a rat animal model. Results demonstrated PLLA-SS316L devices to present superior in vitro and in vivo outcomes and suggested the PLLA coating to provide osteo-inductive properties to the device. Overall, this work represents a preliminary study on PLLA-SS316L devices’ potential towards bone tissue regenerative techniques, showing promising outcomes for bone lesion support.     

Diffusion of semi‐flexible polyelectrolyte through nanochannels

The diffusion of sodium polystyrene sulfonate through polycarbonate nanochanels was studied in salt‐free dilute aqueous solution. A stronger molecular weight dependence of diffusion was observed compared to free diffusion in dilute solution. Scaling exponentials relating polymer size to diffusivity were between Flory's theory (D_eff ∝ N^?0.6) and Rouse's model (D_eff ∝ N^?1), revealing a crossover regime from 3‐D diffusion to 1‐D diffusion. Diffusion was less hindered for the polyelectrolyte (D_eff/D₀), than for a rigid sphere, when the polymer/channel size ratio exceeded 0.2. This is attributed to elongated chains with reduced frictional hindrance. Simulation of the confined diffusion based on an elongated cigar model gave D ∝ N^?1 ${R_{\rm t}^{2/3}}$ while the experimental results agree with D ∝ N^?0.94${R_{\rm t}^{ 2/3}}$ . For charged polyelectrolytes, the transition to 1‐D diffusion therefore begins before the polymer radius of gyration exceeds the channel size contrary to model assumptions. We attribute this to the charged nature of the polyelectrolytes causing extended chain conformations. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

An accurate real-time PCR test for the detection and quantification of cauliflower mosaïc virus (CaMV): applicable in GMO screening

Maher Chaouachi and Marie Noelle Fortabat are contributed equally to this work.     

Optical and physical properties of stratospheric aerosols from balloon measurements in the visible and near-infrared domains. II. Comparison of extinction,reflectance, polarization,and counting measurements

The physical properties of stratospheric aerosols can be retrieved from optical measurements involving extinction, radiance, polarization, and counting. We present here the results of measurements from the balloonborne instruments AMON, SALOMON, and RADIBAL, and from the French Laboratoire de Météorologie Dynamique and the University of Wyoming balloonborne particle counters. A cross comparison of the measurements was made for observations of background aerosols conducted during the polar winters of February 1997 and January-February 2000 for various altitudes from 13 to 19 km. On the one band, the effective radius and the total amount of background aerosols derived from the various sets of data are similar and are in agreement with pre-Pinatubo values. On the other hand, strong discrepancies occur in the shapes of the bimodal size distributions obtained from analysis of the raw measurement of the various instruments. It seems then that the log-normal assumption cannot fully reproduce the size distribution of background aerosols. The effect ofthe presence of particular aerosols on the measurements is discussed, and a new strategy for observations is proposed.     

From conceptual modelling to requirements engineering

Conceptual modelling is situated in the broader view of information systems requirements engineering. Requirements Engineering (RE) explores the objectives of different stakeholders and the activities carried out by them to meet these objectives in order to derive purposeful system requirements and therefore lead to better quality systems, i.e., systems that meet the requirements of their users. Thus RE product models use concepts for modelling these instead of concepts like data, process, events, etc., used in conceptual models. Since the former are more stable than the latter, requirements engineering manages change better. The paper gives the rationale for extending traditional conceptual models and introduces some RE product models. Furthermore, in contrast to conceptual modelling, requirements engineering lays great stress on the engineering process employed. The paper introduces some RE process models and considers their effect on tool support. This revised version was published online in June 2006 with corrections to the Cover Date.     

A virucidal face mask based on the reverse-flow reactor concept for thermal inactivation of SARS-CoV-2

While facial coverings reduce the spread of SARS-CoV-2 by viral filtration, masks capable of viral inactivation by heating can provide a complementary method to limit transmission. Inspired by reverse-flow chemical reactors, we introduce a new virucidal face mask concept driven by the oscillatory flow of human breath. The governing heat and mass transport equations are solved to evaluate virus and CO₂ transport. Given limits imposed by the kinetics of SARS-CoV-2 thermal inactivation, human breath, safety, and comfort, heated masks may inactivate SARS-CoV-2 to medical-grade sterility. We detail one design, with a volume of 300 ml at 90°C that achieves a 3-log reduction in viral load with minimal impedance within the mask mesh, with partition coefficient around 2. This is the first quantitative analysis of virucidal thermal inactivation within a protective face mask, and addresses a pressing need for new approaches for personal protective equipment during a global pandemic.     

Real-Time Photobleaching and Stable Operation at 204 mW of a Tm : ZBLAN Blue Fiber Laser

We report the observation of a stable output power of 204 mW in a Tm³⁺ : ZBLAN upconversion blue fiber laser, which we believe to be the highest reported to date as being stable in the long term. For the first time, we also present results of the dynamics of a real-time photobleaching of the color centers by an external laser source during laser oscillation. The dependence of the photoinduced absorption on the photobleaching power is also investigated. The total average photoinduced absorption was estimated at 2.7 dB/m     

Constructing the Lyee method with a method engineering approach

This paper proposes an Evolution driven ME approach aiming to support the evolution of an existing method (the As–Is method) in order to obtain a new method (the To–Be method) better adapted to a given engineering situation and/or satisfying new methodogical requirements. The proposed approach is used in order to evolve the existing Lyee method into a Lyee user driven method.¹