DSpace Collection:

Nutrient budgets for sustained crop production in African soils: evidence from potato-grown soils in Tanzania

Fri, 01 Nov 2024 00:00:00 GMT

Title: Nutrient budgets for sustained crop production in African soils: evidence from potato-grown soils in Tanzania Authors: Aloo, Becky Nancy; Tripathi, Vishal; Makumba, Billy Amendi; Mbega, Ernest Rashid Abstract: Soil fertility is under pressure worldwide due to agricultural intensification to match food demand. In sub-Saharan Africa (SSA), the depletion of soil nutrients is the root cause of the widespread food insecurity. Therefore, there is a need to continually monitor soil nutrient levels to drive policies and management options for sustained food production. Compared to other crops, potato (Solanum tuberosum L.) is increasingly becoming significant for food and economic security in SSA. The crop is, however, a heavy nutrient feeder and withdraws hefty amounts of nutrients from the soil which can interfere with its sustained production. However, very few studies have assessed the soil fertility levels of potato-grown soils in different parts of SSA. This chapter includes a case study report from the investigation of the fertility status and associated physicochemical properties of potato-grown soils in various agro-ecological areas in Tanzania. Soil samples collected from 27 potato farmlands were sampled in nine districts and analyzed for pH, electrical conductivity at 25 °C (EC25), soluble salts (SS), particle size distribution, potassium, phosphorus, iron, nitrogen, zinc, organic matter (OM), and organic carbon (OC) using standard methods. The results revealed significant differences for fertility-related physicochemical properties like EC25 (P = 0.004), (%) SS (P = 0.004), (%) OC (P = 0.018), and (%) OM (P = 0.019) in the soils but there were no significant differences for the fertility status of soils across the different study areas. Significant (P < 0.05) correlations were also observed for different parameters. The study concluded that specific soil characteristics differed significantly while fertility was relatively consistent. These findings serve as a basis for comprehending the existing soil conditions and can inform future strategies for sustainable soil management to ensure optimal nutrient levels to support the continued productivity of potatoes in the region.

All optical polarization-based and DSP-Assisted distributed fiber sensor for earth mass movements caused by environmental factors

Sun, 01 Mar 2020 00:00:00 GMT

Title: All optical polarization-based and DSP-Assisted distributed fiber sensor for earth mass movements caused by environmental factors Authors: Kipnoo, Rotich E.K; Isoe, G.M.; Kiboi, Boiyo c; Kuja, S.; Waswa, , D.; Leitch, A.W.R. Abstract: Fiber optic sensors for industrial, consumer, medical and military applications have been reported. Their working principle is majorly based on non-linear optics. For the first time to our knowledge, we propose a cost-effective real time monitoring polarization-based digital signal processing (DSP)-assisted sensor that relies on linear optics for application in earth mass movements due to environmental factors. A sensitivity of 0.075 kg−1 is achieved. This is realized on an average SOP speed of 0.83°/s yielding 598° angular drift on its polarization changes. A sensing performance comparison of single mode fiber (SMF) and large effective area fiber (LEAF) fiber is reported.

Tunable Phase Shifters for 6G Beamforming Networks

Mon, 01 Jun 2026 00:00:00 GMT

Title: Tunable Phase Shifters for 6G Beamforming Networks Authors: Naibei, Victor Chepkech; Choge, Dismas; Jena, James; Waswa, David; Boiyo, Duncan Kiboi Abstract: The deployment of 6G network requires multiple number of antennas at the base station with multiple signals that undergo constructive interference to create thinner beams with more energy so as to mitigate path loss. This will support higher data rates, lower latency levels, and improved energy efficiency. This paper proposes a phase-shifting technology for beamforming that focuses radio energy to a specific user equipment, thus maximizing spectral efficiency. We present a novel approach of phase-shifting technology by generating tunable microwave pulses using the slicing-level technique in an optoelectronic oscillator (OEO) setup. Two laser sources undergo intensity and phase modulation using a well-characterized Mach–Zehnder modulator and a phase modulator. Modulating signals in the range of 100 kHz–13.3 MHz are used to generate microwave waveforms. Repetition-rate-tunable pulses are generated from the microwave waveforms using the slicing-level technique. Photonic-assisted tunable pulses generated have a pulse width ranging from 0.6 ns to 7.5 μs and a duty cycle ranging from 17% to 96% optimized for phase shifting (𝜑) of signals, with potential for multiple antenna elements, which act as time delays aimed at creating constructive interference of the beams that form a concentrated beam of energy. This work successfully creates phase shifters ranging from 14° to 299° that can be used to steer antennas for 6G network by controlling pointing angles at the antenna array terminals, which creates a multiplex transmission line as a linear combination of signals.

Valorization of shrimp shell waste into functional chitosan: recent advances, analytical challenges, and future perspectives

Wed, 01 Jul 2026 00:00:00 GMT

Title: Valorization of shrimp shell waste into functional chitosan: recent advances, analytical challenges, and future perspectives Authors: Bishir, Sadiq; Ramkat, Rose Chepchirchir; Makatiani, Jacqueline Kubochi; Njira, Njira Pili Abstract: The increasing accumulation of shrimp shell waste from seafood processing presents both an environmental challenge and an opportunity for sustainable biomass valorization within the circular bioeconomy. Chitosan, a biodegradable and biocompatible polysaccharide obtained through chitin deacetylation, has emerged as a versatile biomaterial with broad applications in biomedicine, agriculture, environmental remediation, food packaging, and advanced functional materials. This review critically evaluates recent advances in the production of chitosan from shrimp shell waste, emphasizing extraction technologies, quality determinants, structural characterization, and analytical evaluation. Conventional chemical extraction is critically compared with emerging green approaches, including microwave-, ultrasonic-, autoclave-, enzymatic-, fermentation-, and deep eutectic solvent-assisted processes, highlighting their effects on yield, degree of deacetylation, molecular weight, scalability, and environmental sustainability. Current characterization and analytical methods are comparatively assessed, with particular emphasis on the complementary role of 3,5-dinitrosalicylic acid (DNSA)-based assays for reducing-end quantification during chitosan depolymerization. The review further discusses advances in functionalized chitosan derivatives, nanocomposites, industrial translation, and sustainable production strategies while identifying standardization of extraction and analytical protocols as a critical requirement for improving reproducibility and facilitating commercial-scale production. Collectively, this review provides an integrated perspective on current progress, remaining challenges, and future research priorities for developing high-quality chitosan from shrimp shell waste.