Search

The COVID-19 pandemic has caused a massive disruption in the way traditional higher education institutions deliver their courses. Unlike transitions from face-to-face teaching to blended, online or flipped classroom in the past, changes in emergency remote teaching –a temporary shift of instructional delivery to an alternate remote delivery mode due to crisis circumstances– happen suddenly and in an unplanned way. This study analyzes the move to emergency remote teaching at the School of Telecommunication Engineering (Universidad Politecnica de Madrid), and the impact of organizational aspects related to unplanned change, instruction-related variables –class size, synchronous/asynchronous delivery– and use of digital supporting technologies, on students' academic performance. Using quantitative data of academic records across all (N = 43) courses of a bachelor's degree programme in Telecommunication Engineering and qualitative data from a questionnaire delivered to all (N = 43) course coordinators, the research also compares the academic results of students during the COVID-19 pandemic with those of previous years. The results of this case study show an increase in students' academic performance in emergency remote teaching, and support the idea that organizational factors may contribute to successful implementation of emergency remote teaching; the analysis does not find differences across courses with different class sizes or delivery modes. The study further explores possible explanations for the results of the analysis, considering organizational, individual and instruction-related aspects.

Electron beam lithography is a well-established tool suitable for the modification of substrate surface chemistry. It therefore follows that the deposition and self-assembly of nanoparticles on a surface can be directed using this method. This work explores the effect of electron dose on the electron beam lithographic patterning of self-assembled monolayers (SAMs) on gold surfaces. Electron beam irradiation of the sample induces conversion of the SAM terminal functional aromatic nitro (NO2) moieties to aromatic amino (NH2) moieties. The cationic NH2 functionalised regions direct the site-specific assembly of anionic citrate-passivated gold nanoparticles in aqueous solution at pH 4.5. Control of nanoparticle attachment to the SAM is demonstrated over the exposure range 5000–125,000 uC/cm2. Overexposure led to significant numbers of secondary electrons reaching the surface, causing conversion of functional aromatic moieties outside of the regions irradiated, which reduced feature quality and regional selectivity of adsorption.

Tb x Fe 1− x thin films deposited by sputtering on Mo were investigated structurally and magnetically. The microstructure consists of TbFe 2 nanoparticles embedded in an amorphous matrix, and the Tb content can be correlated with an increase in the volume of these nanoparticles. Similar microstructure and behavior were found when TbFe 2 was deposited on glass and on a Pt buffer layer. Nevertheless, thermal treatments promote a different effect, depending on the mechanical stiffness of the buffer layer. The layers deposited on Mo, a rigid material, show crystalline TbFe 2 together with α-Tb phase upon thermal treatment. In contrast, TbFe 2 does not crystallize properly on Pt, a material with a lower stiffness than Mo. Intermediate results were observed on the film deposited on glass. Experimental results show the impact of the buffer stiffness on the crystallization process. Moreover, the formation of α-Tb appears to be fundamental to crystallized TbFe 2 on layers deposited on rigid buffers.

Some important improvements in magnetostrictive piezoelectric sensors have been obtained by applying an alternating current to the ferromagnetic amorphous ribbon. First, we present a way to minimize the hysteresis in these devices using a demagnetizing current through the magnetic sample. Second, the current, at a frequency half that of the longitudinal piezoelectric resonance, is used to induce size changes in the high-magnetostriction amorphous ribbon, and these changes, which depend on the external magnetic field, can be read by the piezoelectric support. Then, with this configuration, it is not necessary to have a coil for the detection of a magnetic field.

A new working configuration for magnetostrictive-piezoelectric magnetic sensors is presented. In this configuration, the excitation is caused using an electrical current flowing through the ferromagnetic sample and the induced signal is sensed in the piezoelectric support as an electrical voltage. This new idea allows a magnetic field detection without any coil and opens a possibility for a future miniaturisation of the sensor.

The magnetic ground state of antiferromagnetically coupled Gd/Fe multilayers and the evolution of in-plane domain walls is modelled with micromagnetics. The twisted state is characterised by a rapid decrease of the interface angle with increasing magnetic field. We found that for certain ratios M(Fe):M(Gd), the twisted state is already present at low fields. However, the magnetic ground state is not only determined by the ratio M(Fe):M(Gd) but also by the thicknesses of the layers, that is the total moments of the layer. The dependence of the magnetic ground state is explained by the amount of overlap of the domain walls at the interface. Thicker layers suppress the Fe aligned and the Gd aligned state in favour of the twisted state. Whereas ultrathin layers exclude the twisted state, since wider domain walls can not form in these ultrathin layers.

Magnetic domain-wall patterns in magnetostatically coupled bilayers separated by a non-magnetic interlayer have been studied for different anisotropy configurations. A numerical treatment is presented for the case of a parallel anisotropy axis between magnetic layers for samples with thicknesses of 1000Afor the magnetic layers and 100Afor the interlayer. For these thicknesses coupled Neel walls appear with a similar structure to that found in previous works on thinner films except for the much higher magnetic poles found at the interlayer boundary surfaces. Samples of Fe 20 Ni 80 /Cu/Fe 20 Ni 80 of 500/200/500Athickness have been grown whilst uniaxial anisotropies were induced in the magnetic layers with the perpendicular easy axis directions between them. Bitter observations show that coupling between domain walls also exists in samples with the non-parallel magnetic anisotropy axis in both layers.