Ensuring quality in classroom assessments

How can teachers make classroom-based assessments more valid, reliable, and fair? Shilpi Banerjee shares some guiding principles to help teachers design quality classroom-based assessments and use their results effectively

Magneto-dielectric effect in Pb(Zr_0·52Ti_0·48)O₃ filled nanoporous Ni_0·5Zn_0·5Fe₂O₄ composite

Nanoporous Ni0·5Zn0·5Fe2O4 particles of diameter, ~ 9·5 nm, were synthesized by citric acid assisted thermal decomposition in an autoclave. The BET surface area measured was 80 m2 g − 1 and the average pore diameter was 2·5 nm. By soaking the particles in a suitable precursor solution and then subjecting them to a heat treatment at 923 K for 3 h, Pb(Zr0·52Ti0·48)O3 was grown within the nanopores. X-ray and electron diffraction studies confirmed the presence of both these phases. The nanocomposites showed ferromagnetic behaviour over the temperature range 2–300 K. No ferroelectric hysteresis loop could be found which was consistent with the earlier theoretical prediction of loss of ferroelectricity below a critical thickness of 2·4 nm. Good magneto-dielectric response of the order of 7% at a magnetic field of 9 kOe was recorded for the present system. This is believed to arise due to a negative magnetostriction coefficient of Ni0·5Zn0·5Fe2O4 which exerted a compressive strain on Pb(Zr0·52Ti0·48)O3 thereby lowering the tetragonality in its crystal structure

Teaching-learning when schools reopen : a diagnostic approach

Schools in India have been closed from March 2020. Children have had no face-to-face interactions with teachers or peers since then. In the past one-and-ahalf years, various models of online education have been tried out. Studies conducted to estimate the efficacy of these models revealed the vast inequities and divides in access to technology and the internet and the gross inadequacy of online mediums in imparting any true learning. (UNICEF, 2020, Azim Premji University, Myths of Online Education, 2020). Practitioners and parents across the country have raised concerns over the limitations of online medium in providing personalised attention to children’s academic and socio-emotional needs, which, in turn, form the basis for any meaningful learning. It comes as no surprise to us that the majority of school-going children have not only not had any significant learning, but they have also been engulfed in the scenario of ‘learning loss,’ or ‘academic regression’, which as we understand it, is the phenomenon of forgetting previously learned concepts

Multi-functional Behaviour of Eu2O3 Embedded 3D Mesoporous Silica Template KIT-6

Rare-earth (RE) oxide embedded ordered mesoporous silica have been successfully prepared via a solution impregnation method. The structure and physical property of the nanocomposites (NCs) were studied by low-angle X-ray diffraction, Transmission Electron Microscopy (TEM), Photoluminescence (PL) and magnetic measurement. The NCs exhibited the room temperature  transition emission due to the presence of Eu3+ ions. Also the NC system showed a room temperature weak ferromagnetism due to the large oxygen vacancy present in the system. Photoluminescence, magnetic property and large surface area, make these NCs ideal multi-functional materials, which will have potential applications in the field of bio-medicine and drug-delivery. These kinds of nanocomposites are promising candidates for fabrication of various environment friendly smart devices

Immense Magnetodielectric Effect in Eu2O3-Mesoporous Silica Nanocomposites

Nanodimentional Eu2O3 was developed inside the channels of silica with mesoporus structure, which have5 nm pore diameter. At room temperature, such nanocomposite showed a large magnetodielectric coefficient of around 70% upon application of magnetic field of 1 Tesla at a frequency 1 kHz. The dielectric loss was quite low in spite of the fact that Eu2O3 is conducting in nature. This was achieved because of a scarcelydispensed Eu2O3species inside silica, which is highly resistive in nature. This method of nanocomposite formation gives rise to the fabrication of devices with high magnetodielectric coefficients

Sensing behaviour of some nanocomposite systems

Silver nanoparticles of diameters 3.4 to 13.2 nm grown at the interfaces between silicate glass and some oxide crystallites exhibited about six orders of magnitude reduction in resistivity for a relative humidity change from 25% to 80%. Sn-SnO2 nano core-shell structure prepared within a gel-derived silica glass film by electrodeposition technique followed by heat treatment showed large change in resistivity as a function of humidity. The resistivity also changed due to gas flow of CO2, C2H5OH and NO2, respectively. The latter arose because of reduction/oxidation of Sn4+/Sn2+ species present at the shell layer of the nanostructures. Nickel nanosheets of thickness ~0.6 nm grown within the interlayer spaces of Na-4 mica crystallites showed a change of dielectric permittivity (5%) for an applied magnetic field of 1.2 Tesla. An inhomogeneous model was used to explain this behavior. Two dimensional CuO phase was grown within the channels of diameter ~5 nm of mesoporous SiO2 structure. A magnetodielectric (MD) parameter M.D. of 4.4% was obtained in this case. BaTiO3 nanoparticles of diameter ~25 nm having pores with diameter 10 nm showed multiferroic behavior which arose due to the presence of oxygen vacancies as a result of large surface area present. An M.D. parameter of 11% was found. Similarly mesoporous LiNbO3 of 10 nm diameter showed an M.D. parameter of ~4.5% at a magnetic field 1 Tesla. A giant magnetocapacitance effect with a value of 44% at 1.5 T was observed in nickel zinc ferrite (NZF) impregnated mesoporous silica. A magnetocapacitance of 51% at magnetic field 1.7 T was found in the case of nanocomposites comprising of iron ion containing silica based nanoglass and mesoporous silica. In the last two examples the behavior was explained on the basis of Catalan model of space-charge polarization with extracted values of magnetoresistance of the NZF and nanoglass phases being 58%

An Antibody to the Tetraspan Membrane Protein CD9 Promotes Neurite Formation in a Partially α3β1 Integrin-Dependent Manner

The tetraspan cell surface glycoprotein, CD9, has been implicated in cellular signaling during growth and differentiation in the hematopoietic and nervous systems. Because CD9 expression is induced early in development in sensory and sympathetic neuroblasts, we investigated the role of CD9 in neurite outgrowth. We plated dissociated cells from neonatal sympathetic ganglia on immobilized anti-CD9 antibodies or antibodies against other cell surface molecules. We show here that B2C11, an anti-CD9 antibody that has been shown previously to activate Schwann cells in vitro, promotes robust neurite outgrowth from sympathetic neurons that is greater than that on other antibody surfaces and is comparable to neurite outgrowth on a collagen substratum. In addition, B2C11 causes dramatic morphological changes in neurons and glia from dissociated ganglia, including a flattening of these cells. Because CD9 interacts with integrins in many cell types including Schwann cells, and specifically with the α3β1 integrin in some cells, we tested whether the effect of B2C11 on neurite outgrowth is mediated by this integrin. An anti-α3β1 antibody, Ralph 3–1, attenuates the extent of neurite outgrowth on B2C11 and collagen, but not on laminin. Because the α3β1 integrin has been shown to mediate neurite outgrowth on different substrates, these results provide a functional significance for the CD9-α3β1 interaction; downstream signaling may be activated by this cis interaction on the cell surface in response to external cues that promote neurite outgrowth