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AbstractMononuclear trivalent lanthanide complexes with formula [Ln(L)(NO3)3] [in which L=4,4‐difluoro‐8‐(2′:2′′;6′′:2′′′‐terpyridin‐4′′‐yl)‐1,3,5,7‐tetramethyl‐2,6‐diethyl‐4‐bora‐3a,4a‐diaza‐s‐indacene (Boditerpy)] are reported for Ln=Yb, Nd, Er, La and Gd. According to the crystal structure of the Yb complex, the lanthanide ion is bound to the terdentate terpyridine and the inner coordination sphere of the nine‐coordinate lanthanide ion is completed by three bidentate nitrate anions. The coordination polyhedron can be described as a distorted tricapped antiprism. The terpyridine chelate is almost planar and tilted by nearly 60° from the indacene subunit. FT‐IR spectra confirm the bidentate binding mode of the nitrate anions for the other complexes. NMR and ES‐MS spectra (through characteristic isotopic patterns) confirm the chemical formulation. The complexes have high molar absorption coefficients in the visible spectral region (65 000 M−1 cm−1 at 529 nm) and display sizeable NIR luminescence (900 to 1600 nm, for Ln=Yb, Nd and Er), upon irradiation through the electronic state of the indacene moiety at 514 nm. Crystal‐field splitting was analysed at low temperature. The quantum yield of the Yb solution (10−4 M) in dichloromethane amounts to 0.31 %, corresponding to a sensitisation efficacy of the ligand of ca. 63 %.

Abstract Despite the remarkable potential for biogas production from livestock and organic wastes, the number of constructed biogas digesters for the continent is in the order of thousands and in case of Mauritania is lower than the number of the provinces. While majority of the existing digesters left far behind the expected efficiency, lack of a comprehensive economic assessment along with an efficient design questions their practical application. The present study introduced the first assessment to evaluate the biogas potential from livestock manures and waste from slaughterhouses in Northwest Africa (a case of Mauritania). Using ArcGIS® software, a database was conducted to build maps that show the amount of waste products, the potential of biogas, and equivalent amounts of energy. These were used to assess the potential of biogas and the corresponding potential energy for each geographical department in Mauritania. The results indicated that the southern provinces had the highest biogas potential with the maximum and the average values of 520 and 258.7 (±125.8) × 106 m3/year. On the other hand, the lowest biogas production potential (27.7 × 106 m3/year) was recorded for northern provinces with the maximum and the average values of 135 and 76.4 (±39.7) × 106 m3/year. The results showed that 63,579 × 106 kg of waste associated with livestock (cattle) and slaughterhouse applications were annually produced in the country. It was determined that this quantity could generate 2451 × 106 m3 of biogas per year, corresponding to an energy potential of 52,704 × 106 MJ/year. Considering the rapid depletion of conventional energy sources and the significance of biogas as a renewable fuel, a detailed feasibility analysis (for the biogas production in each province of Mauritania by means of community type fixed-dome digesters) was also performed in the scope of this study. The results of the comprehensive cost breakdown analysis revealed that the revenues obtained from sale of biogas-generated electricity and digested slurry (as fertilizer) could able to pay the initial investment within approximately 6.5 years without subsidy. The findings of this study, as the first of its own, could be used to comprehend how utilization of information such as slaughterhouse and livestock population, nutrition habitats, land-usage maps and geographic information system (GIS) can be employed to germinate a model for more comprehensive assessment of biogas production potential from livestock manure and slaughterhouse wastes, specifically in case of northern African countries. Moreover, in case of biogas plant, this model could be employed as a decision-making tool to identify the highly qualified location for construction of the biogas plant.

Please read abstract in the article. ; The South African Research Chairs Initiative of the Department of Science and Technology, the National Research Foundation of South Africa, the Organization for Women in Science for the Developing World (OWSD) and the University of Pretoria. ; https://www.elsevier.com/locate/est ; hj2023 ; Physics

One-dimensional solidification and melting of a slab with uniform volumetric energy generation is examined analytically. A sudden change in surface temperature triggers phase transformation and interface motion. Analytic solutions are obtained using a quasi-steady approximation. Unlike solidification, the melting case is characterized by a pure liquid phase and a mixture of solid and liquid at the fusion temperature. The solution is governed by a single energy generation parameter. Temperature profiles, interface location and steady state conditions are presented for solidification and melting. Results are applied to two examples: solidification of a nuclear material and melting of ice.

Nitrogen (N) doping of porous carbon materials is an effective strategy for enhancing the electrochemical performance of electrode materials. Herein, we report on ex-situ (post) nitrogen-doped porous carbons prepared using a biomass waste, peanut shell (PS) as a carbon source and melamine as the nitrogen source. The synthesis method involved a two-step mechanism, initial chemical activation of the PS using KOH and post N-doping of the activated carbon. The effect of the activating agent/precursor ratio and the ex-situ N-doping on the structural, textural, electrochemical properties of the porous carbons was studied. The ex-situ N-doped porous carbon with an optimum amount of KOH to PS exhibited the best capacitance performance with a specific surface area (SSA) of 1442 m2 g-1 and an enriched nitrogen content (3.2 at %). The fabricated symmetric device exhibited a 251.2 F g-1 specific capacitance per electrode at a gravimetric current of 1 A g-1 in aqueous electrolyte (2.5 M KNO3) at a wide cell voltage of 2.0 V. A specific energy of 35 Wh kg-1 with a corresponding specific power of 1 kW kg-1 at 1 A g-1 was delivered with the device still retaining up to 22 Wh kg-1 and a 20 kW kg-1 specific power even at 20 A g-1. Moreover, long term device stability was exhibited with an 83.2% capacity retention over 20 000 charge/discharge cycles and also a good rate capability after 180 h of floating at 5 A g-1. This great performance of the symmetric supercapacitor can be correlated to the surface porosity and post nitrogen-doping effect which increased the electrochemically-active sites resulting in a remarkable charge storage capability.

This work deals with the influence of envelope thickness and solar absorption on the time lag and the decrement factor. For this, a test cell of 1 m3 of volume is built with a material commonly used in construction in Senegal, the compressed earth brick stabilized with cement. The ambient-air temperature inside and outside of test cell and solar direct normal irradiance is measured. The test cell is modeled using EnergyPlus software. The comparison of experimental and theoretical ambient-air temperature puts out a great linear showing the reliability of the model. The time lag and the decrement factor are calculated using the air-sol equivalent temperature of the test cell and the inside ambient-air temperature. The time lag and decrement factor of the compressed stabilized earth brick envelope are respectively 0.22 and 6.6 h showing the good thermal inertia of those bricks. A parametric study is performed to determine the effect of envelope thickness and solar absorptivity on the time lag and decrement factor. The results show that the decrement factor decreases with envelope thickness while the time lag increases linearly and that an envelope thickness of 32 cm has a decrement factor of around zero with a maximum time lag of about 12 h for this type of material. The envelope’s solar absorption has a moderate effect on the decrement factor and time lag.

Abstract A novel optimized sizing and management strategy of a grid-connected hybrid photovoltaic (PV)-solar-battery-group system were proposed for the electrification of residential consumers in Northwest Africa (a case of Mauritania), and the influence of the state of the sky (clear, moderately overcast, and overcast) was analyzed according to the load flowing (LF) and the cycle charging (CC) strategies. In order to mitigate the pressure on the national grid, consolidate the consumer autonomy, minimize the cost of medium- and long-term consumption bills, and CO2-related emissions, a cartographic approach was conducted as the first attempt to map the electricity consumption potential for buildings in the city of Nouakchott (Mauritania) using a geo-referenced database. ArcGIS®, HOMER Pro®, and MATLAB® softwares were used for the establishment of the load profile, optimized sizing of the PV-batteries-group-grid system, and calculation of the lightness index, respectively. The LF strategy provided the best monitoring of the load throughout the day by minimizing the generator uptime. The techno-economic analysis revealed the values of cost of energy (COE) and net present cost (NPC) as follows: COE = $0.0549/kWh and NPC = $24,796 for the LF PV-batteries-grid strategy, COE = 0.0646 $/kWh and NPC = $23,380 for the CC PV-batteries-grid strategy, and COE = $0.17/kWh and NPC = $23,262 for the case of the grid on its own.