Urban agriculture in Senegal: effect of wastewater on the agronomical performance and hygienic quality of tomato and lettuce

The use of wastewater in urban agriculture has gained a lot of interest in Senegal. The aim of this works was to assess the effect of wastewater on the agronomical performance of two vegetable crops and the hygienic threats as compared to tap water. We also compared the effect of irrigation mode and the addition of fertilizers. Results showed that there were no significant differences between the two irrigation modes. Thesturdiness at 2 months had a positive effect on the number of plant (tomato) at the harvest, the yield and fruit average weight. Considering the following parameters studied (overall yield, corrected yield, number of fruit per treatment and fruit average size, there were significant differences between plants (lettuce) treated with tap water and those treated with wastewater. In a chemical point of view, samples from aspersion and draining watering mode treatments were similar in term of their content in heavy metals. On the lettuce, results showed a low presence of worms on crop watered with wastewater. On the other hand, lettuce watered with theaspersion technique contents much more germs of pathogens than those watered in draining mode. As for tomato, there was a total absence of worms and other pathogenic germs in both irrigation modes. This studysuggests that use of wastewater in horticulture with a moderate fertilization and taking into account soil chemistry could be gainful to urban farmers. The study addresses the issue of preliminary studies on the wastewater and soil quality before deciding on the adequate crop to grow

Effects of post-deposition vacuum annealing on film characteristics of p-type Cu2_{2}O and its impact on thin film transistor characteristics

Annealing of cuprous oxide (Cu$_{2}$O) thin films in vacuum without phase conversion for subsequent inclusion as the channel layer in p-type thin film transistors (TFTs) has been demonstrated. This is based on a systematic study of vacuum annealing effects on the sputtered p-type Cu$_{2}$O as well as the performance of TFTs on the basis of the crystallographic, optical, and electrical characteristics. It was previously believed that high-temperature annealing of Cu$_{2}$O thin films would lead to phase conversion. In this work, it was observed that an increase in vacuum annealing temperature leads to an improvement in film crystallinity and a reduction in band tail states based on the X-ray diffraction patterns and a reduction in the Urbach tail, respectively. This gave rise to a considerable increase in the Hall mobility from 0.14 cm$^{2}$/V·s of an as-deposited film to 28 cm$^{2}$/V·s. It was also observed that intrinsic carrier density reduces significantly from 1.8 × 1016 to 1.7 × 10$^{13}$ cm$^{-3}$ as annealing temperature increases. It was found that the TFT performance enhanced significantly, resulting from the improvement in the film quality of the Cu$_{2}$O active layer: enhancement in the field-effect mobility and the on/off current ratio, and a reduction in the off-state current. Finally, the bottom-gate staggered p-type TFTs using Cu$_{2}$O annealed at 700 °C showed a field-effect mobility of ∼0.9 cm$^{2}$/V·s and an on/off current ratio of ∼3.4 × 102.This work was supported by the Engineering and Physical Sciences Research Council under Grant No. EP/M013650/1. G.R. acknowledges the support of the Cambridge Trusts

Self-cleaning on a higher order mode in ytterbium-doped multimode fiber with parabolic profile

We experimentally demonstrate polarization-dependent Kerr spatial beam self-cleaning into the LP11 mode of an Ytterbium-doped multimode optical fiber with parabolic gain and refractive index profiles

Optimisation of amorphous zinc tin oxide thin film transistors by remote-plasma reactive sputtering

The influence of the stoichiometry of amorphous zinc tin oxide (a-ZTO) thin films used as the semiconducting channel in thin film transistors (TFTs) is investigated. A-ZTO has been deposited using remote-plasma reactive sputtering from zinc:tin metal alloy targets with 10%, 33%, and 50% Sn at. %. Optimisations of thin films are performed by varying the oxygen flow, which is used as the reactive gas. The structural, optical, and electrical properties are investigated for the optimised films, which, after a post-deposition annealing at 500 °C in air, are also incorporated as the channel layer in TFTs. The optical band gap of a-ZTO films slightly increases from 3.5 to 3.8 eV with increasing tin content, with an average transmission ∼90% in the visible range. The surface roughness and crystallographic properties of the films are very similar before and after annealing. An a-ZTO TFT produced from the 10% Sn target shows a threshold voltage of 8 V, a switching ratio of 10$^8$, a sub-threshold slope of 0.55 V dec$^{-1}$, and a field effect mobility of 15 cm$^2$ V$^{-1}$ s$^{-1}$, which is a sharp increase from 0.8 cm$^2$ V$^{-1}$ s$^{-1}$ obtained in a reference ZnO TFT. For TFTs produced from the 33% Sn target, the mobility is further increased to 21 cm$^2$ V$^{-1}$ s$^{-1}$, but the sub-threshold slope is slightly deteriorated to 0.65 V dec$^{-1}$. For TFTs produced from the 50% Sn target, the devices can no longer be switched off (i.e., there is no channel depletion). The effect of tin content on the TFT electrical performance is explained in the light of preferential sputtering encountered in reactive sputtering, which resulted in films sputtered from 10% and 33% Sn to be stoichiometrically close to the common Zn$_2$SnO$_4$ and ZnSnO$_3$ phases.Engineering and Physical Sciences Research Council (Grant ID: EP/M013650/1

Nonlinear polarization dynamics of Kerr beam self-cleaning in a GRIN multimode optical fiber

We experimentally study polarization dynamics of Kerr beam self-cleaning in a graded-index multimode optical fiber. We show that spatial beam cleaning is accompanied by nonlinear polarization rotation, and a substantial increase of the degree of linear polarization.Comment: 5 pages, 6 figure

Dynamics of high-energy multimode Raman solitons

The dynamics of high-energy Raman solitons in graded-index multimode fibers is both numerically and experimentally investigated. The propagation of high-power pulses produces nonlinear losses, that quench up to 80% of the fiber transmission. In such a regime, several solitons arising from the fission of ultra-short femtosecond pulses manifest unique features: pulse width, Raman self-frequency shift and soliton order remain nearly constant over a broad range of energies

Spatial beam self-cleaning and supercontinuum generation with Yb-doped multimode graded-index fiber taper based on accelerating self-imaging and dissipative landscape

We experimentally demonstrate spatial beam self-cleaning and supercontinuum generation in a tapered Ytterbium-doped multimode optical fiber with parabolic core refractive index profile when 1064 nm pulsed beams propagate from wider (122 µm) into smaller (37 µm) diameter. In the passive mode, increasing the input beam peak power above 20 kW leads to a bell-shaped output beam profile. In the active configuration, gain from the pump laser diode permits to combine beam self-cleaning with supercontinuum generation between 520-2600 nm. By taper cut-back, we observed that the dissipative landscape, i.e., a non-monotonic variation of the average beam power along the MMF, leads to modal transitions of self-cleaned beams along the taper length

Dynamical and Thermodynamic Elements of Modeled Climate Change at the East African Margin of Convection

We propose a dynamical interpretation of model projections for an end-of-century wetting in equatorial East Africa. In the current generation of global climate models, increased atmospheric moisture content associated with warming is not the dominant process explaining the increase in rainfall, as the regional circulation is only weakly convergent even during the rainy seasons. Instead, projected wetter future conditions are generally consistent with the El Niño-like trend in tropical Pacific sea surface temperatures in climate models. In addition, a weakening in moisture convergence over the adjacent Congo Basin and Maritime Continent cores of convection results in the weakening of near-surface winds, which increases moisture advection from the Congo Basin core toward the East African margin. Overall confidence in the projections is limited by the significant biases in simulation of the regional climatology and disagreement between observed and modeled tropical Pacific sea surface temperature trends to date