Abstract: Despite substantial policy efforts made by the French government to reduce dependence on pesticides, farming practices are only changing slowly. This paper analyses the socio-economic trade-offs that 110 farmers are currently facing in the transition to agro-ecological practices. A mixed-method approach – a quantitative discrete choice experiment (DCE) and qualitative interviews – was set up to understand these farmers' motivations and perspectives, and how policy can improve to accompany them on the road to low chemical input farming. Results of the DCE indicate that the majority of the farmers in our sample are keen to change practices but are at a loss as to how this can be done, as a number of preferences for this transition came out as inconclusive. Qualitative interviews with a representative sample of the farmers that took part in the DCE complemented this result by illustrating a deep uncertainty for the future and a disconnect felt between authorities and themselves as a group. We argue that this uncertainty contributed to a lack of clear-cut solutions established through the DCE. The indepth discussions with farmers illustrated the wish for concrete and local policy measures based on farmers' networks and peer support.

Abstract: Regenerative life support systems (RLSS) will play a vital role in achieving self-sufficiency during long-distance space travel. Urine conversion into a liquid nitrate-based fertilizer is a key process in most RLSS. This study describes the effects of simulated microgravity (SMG) on Comamonas testosteroni, Nitrosomonas europaea, Nitrobacter winogradskyi and a tripartite culture of the three, in the context of nitrogen recovery for the Micro-Ecological Life Support System Alternative (MELiSSA). Rotary cell culture systems (RCCS) and random positioning machines (RPM) were used as SMG analogues. The transcriptional responses of the cultures were elucidated. For CO2-producing C. testosteroni and the tripartite culture, a PermaLifeTM PL-70 cell culture bag mounted on an in-house 3D-printed holder was applied to eliminate air bubble formation during SMG cultivation. Gene expression changes indicated that the fluid dynamics in SMG caused nutrient and O2 limitation. Genes involved in urea hydrolysis and nitrification were minimally affected, while denitrification-related gene expression was increased. The findings highlight potential challenges for nitrogen recovery in space.

Abstract: To get better performance from inductively coupled plasma (ICP)-based methods, it is informative to study the properties of the ICP under different conditions. Annemie Bogaerts and Maryam Aghaei at the University of Antwerp, Belgium, are using computational modeling to examine how various properties of the ICP, such as gas flow path lines and velocity, temperature changes, and ionization effects, are affected by numerous factors, such as the gas flow rates of injector and auxiliary gas, applied power, and even the very presence of a mass spectrometry (MS) sampler. They have also applied their models to study particle transport through the ICP. Using their developed model, it is now possible to predict optimum conditions for specific analyses. Bogaerts and Aghaei spoke to us about this work.

Abstract: In the manufacturing of multi-Vt FinFET transistors, the gate material deposited in the nano-spaces left by the removed dummy gate must be etched back in mask-defined wafer areas. Etch conformality is a necessary condition for the control of under-etch at the boundary between areas defined by masking. We studied the feasibility of TiN etching by APM (ammonia peroxide mixture, also known as SC1) in nano-confined volumes representative of FinFET transistors of the 7 nm node and below, namely nanotrenches with 1-D confinement and nanoholes with 2-D confinement. TiN etching was characterized for rate and conformality using different electron microscopy techniques. Etching in closed nanotrenches was conformal, starting and progressing all along the 2-D seam, with a rate that was 38% higher compared to a planar film. Etching in closed nanoholes proved also to be conformal and faster than planar films, but with a delay to open the 1-D seam that seemed to depend strongly on small variations in the hole diameter. However, holes between the fins at the bottom of the removed dummy gate, are not circular and do present 2-D seams that should lend themselves for an easier start of conformal etching as compared to the circular nanoholes used in this study. Finally, to explain the higher etch rate observed in nano-confined features, concentrations of ions in nanoholes were calculated taking the overlap of electrostatic double layers (EDL) into account. With negatively charged TiN walls, as measured by streaming potential on planar films, ammonium was the dominant ion in nanoholes. As no chemical reaction proposed in the literature for TiN etching matched with this finding, we proposed that the formation of ammine complexes, dissolving the formed Ti oxide, was the rate-determining step.

Abstract: Very uniform and well shaped Mn3O4 nano-octahedra are synthesized using a simple hydrothermal method under the help of polyethylene glycol (PEG200) as a reductant and shape-directing agent. The nano-octahedra formation mechanism is monitored. The shape and crystal orientation of the nanoparticles is reconstructed by scanning electron microscopy and electron tomography, which reveals that the nano-octahedra only selectively expose {101} facets at the external surfaces. The magnetic testing demonstrates that the Mn3O4 nano-octahedra exhibit anomalous magnetic properties: the Mn3O4 nano-octahedra around 150 nm show a similar Curie temperature and blocking temperature to Mn3O4 nanoparticles with 10 nm size because of the vertical axis of [001] plane and the exposed {101} facets. With these Mn3O4 nano-octahedra as a catalyst, the photodecomposition of rhodamine B is evaluated and it is found that the photodecomposition activity of Mn3O4 nano-octahedra is much superior to that of commercial Mn3O4 powders. The anomalous magnetic properties and high superior photodecomposition activity of well shaped Mn3O4 nano-octahedra should be related to the special shape of the nanoparticles and the abundantly exposed {101} facets at the external surfaces. Therefore, the shape preference can largely broaden the application of the Mn3O4 nano-octahedra.

Abstract: The wearable revolution is already present in society through numerous gadgets. However, the contest remains in fully deployable wearable (bio)chemical sensing. Its use is constrained by the energy consumption which is provided by miniaturized batteries, limiting the autonomy of the device. Hence, the combination of materials and engineering efforts to develop sustainable energy management is paramount in the next generation of wearable self-powered electrochemical devices (WeSPEDs). In this direction, this review highlights for the first time the incorporation of innovative energy harvesting technologies with top-notch wearable self-powered sensors and low-powered electrochemical sensors toward battery-free and self-sustainable devices for health and wellbeing management. First, current elements such as wearable designs, electrochemical sensors, energy harvesters and storage, and user interfaces that conform WeSPEDs are depicted. Importantly, the bottlenecks in the development of WeSPEDs from an analytical perspective, product side, and power needs are carefully addressed. Subsequently, energy harvesting opportunities to power wearable electrochemical sensors are discussed. Finally, key findings that will enable the next generation of wearable devices are proposed. Overall, this review aims to bring new strategies for an energy-balanced deployment of WeSPEDs for successful monitoring of (bio)chemical parameters of the body toward personalized, predictive, and importantly, preventive healthcare.

Abstract: According to the World Health Organization, about 422 million people worldwide have diabetes, with 1.5 million deaths directly attributed each year. Therefore, there is still a need to effectively monitor glucose in diabetic patients for proper management. Recently, wearable patches based on microneedle (MN) sensors provide minimally invasive analysis of glucose through the interstitial fluid (ISF) while exhibiting excellent correlation with blood glucose. Despite many advances in wearable electrochemical sensors, long-term stability and continuous monitoring remain unsolved challenges. Herein, we present a highly stable electrochemical biosensor based on a redox mediator bilayer consisting of Prussian blue and iron-nickel hexacyanoferrate to increase the long-term stability of the readout coupled with a hollow MN array as a sampling unit for ISF uptake. First, the enzymatic biosensor is developed by using affordable screen-printed electrodes (SPE) and optimized for long-term stability fitting the physiological range of glucose in ISF (i.e., 2.5–22.5 mM). In parallel, the MN array is assessed for minimally invasive piercing of the skin. Subsequently, the biosensor is integrated with the MN array leaving a microfluidic spacer that works as the electrochemical cell. Interestingly, a microfluidic channel connects the cell with an external syringe to actively and rapidly withdraw ISF toward the cell. Finally, the robust MN sensing patch is characterized during in vitro and ex vivo tests. Overall, affordable wearable MN-based patches for the continuous monitoring of glucose in ISF are providing an advent in wearable devices for rapid and life-threatening decision-making processes.

Abstract: We show that the angular range of the transmission through magnetic barrier structures can be efficiently controlled in single-layer and bilayer graphenes and this renders the structures efficient wavevector filters. As the number of magnetic barriers increases, this range shrinks, the gaps in the transmission versus energy become wider, and the conductance oscillates with the Fermi energy.

Abstract: The scattering of a Gaussian wave packet in armchair and zigzag graphene edges is theoretically investigated by numerically solving the time-dependent Schrodinger equation for the tight-binding model Hamiltonian. Our theory allows us to investigate scattering in reciprocal space, and depending on the type of graphene edge we observe scattering within the same valley, or between different valleys. In the presence of an external magnetic field, the well-known skipping orbits are observed. However, our results demonstrate that in the case of a pseudomagnetic field, induced by nonuniform strain, the scattering by an armchair edge results in a nonpropagating edge state.

Abstract: Dynamics of electron wave-packets is studied using the continuum Dirac model in a graphene geometric diode where the propagation of the wave packet is favored in certain direction due to the presence of geometric constraints. Clear rectification is obtained in the THz frequency range with the maximum rectification level of 3.25, which is in good agreement with recent experiments on graphene ballistic diodes. The rectification levels are considerably higher for systems with narrower channels. In this case, the wave packet transmission probabilities and rectification rate also strongly depend on the energy of the incident wave packet, as a result of the quantum nature of energy levels along such channels. These findings can be useful for fundamental understanding of the charge carrier dynamics in graphene geometry diodes.

Abstract: This piece of work is twofold. First, the time evolution of wave-packets in 2D systems is analyzed by the Split-Operator technique in three different scenarios: in multilayer phosphorene, the transient oscillations in the time-dependent average of position and momentum were observed due to the zitterbewegung effect, and the wave packet propagates non-uniformly along the space deforming itself into an elliptical shape. These results were corroborated by the Green’s function formalism except for large values of the wave-vector and long times; in 2D semiconductor quantum wires (QWs) with anisotropic effective masses and different angle orientations with respect to the anisotropic axis. We have shown that the greater this angle, the smaller is the energy levels spacing implying in an increase of the accessible electronic states. Additionally, for non-null magnetic field, the quantum Hall edge states are significantly affected by the edge orientation. In the anisotropic case damped oscillations in the average values of velocity in both x and y directions where obtained. Theses oscillations are originated by the QW geometry but also from subwavepackets with different momentum orientations, whereas for isotropic QWs the wavepacket disperses without splitting; in the third scenario the split-operator technique was used to study the Landau levels, the wave packet trajectories and velocities of electrons in graphene at low-energy regime described by a modified Dirac equation where the momentum-operator is written in a generalized form as result of applying the position-dependent translation operator formalism (PDTO). In the second part of this thesis, the electronic and tunneling properties of α − T3 lattices were studied. Electrons in these lattices behave analogous to integer-spin Dirac Fermions. The presence of a third atomic site in the unit cell leads to a flat band in the energy spectrum, providing unique electronic and tunneling properties. The presence of a super-periodic potential and the inclusion of symmetry-breaking terms results in deviations of the atomic equivalence between the atomic sites affecting the Dirac points and the band-gap. Small deviations in the equivalence between the atomic sites and the number of barriers change the transmission properties in these lattices. Additionally, new tunneling regions are possible by adjusting the symmetry between the atomic sites and affect the omnidirectional total transmission called super-Klein tunneling observed in these lattices. We compare those results to the tunneling probabilities through regions where the energy spectrum changes from linear with a middle flat band to a hyperbolic dispersion.