School of Biological and Physical Science

Effect of waterlogging on growth and development of selected green gram varieties

Wed, 25 Jun 2025 00:00:00 GMT

Effect of waterlogging on growth and development of selected green gram varieties Ochar, Samson Onyango; Sikuku, Phoebe Anyango; Onyango, John Collins This experiment studied the effect of waterlogging on growth and development of selected green gram varieties so as to recommend to farmers the variety that can withstand waterlogging. The seeds of the three selected green gram varieties were planted in 10 litre capacity pots that were arranged in completely randomised design. Waterlogging was induced at vegetative stage; 21 days after sowing (DAS) by dipping 10 litre pots in larger 20 litre pots and maintaining standing water at 3cm above the soil level for 3days (T3), 6 days (T6) and 9 days (T9). Control (T0) was achieved by watering the pots with 500ml of water per day. Net assimilation rate, transpiration rate and stomatal conductance were measured using LI-COR 680 portable photosynthesis systems. Chlorophyll content was determined using the Arnon method. The measurements were taken from three plant samples per variety regularly throughout the study period. KAT 00301 and KAT 00309 maintained a significantly high net assimilation rate, stomatal conductance and chlorophyll content than KAT 00308 under waterlogging treatments. KAT 00308 was more vulnerable to waterlogging. The variety wilted and died under prolonged waterlogging but KAT 00301 and KAT 00309 survived though with reduced yield. Both small and commercial green gram farmers should plant KAT 00301 and KAT 00309 to minimise losses due to waterlogging.

Management of microbial keratitis by private pharmacies in Uganda: a study of knowledge, attitude, and practice.

Mon, 27 Jan 2025 00:00:00 GMT

Management of microbial keratitis by private pharmacies in Uganda: a study of knowledge, attitude, and practice. Abel Ebong, Simon Arunga, Tara B Mtuy, Angela Meric Birungi, John Onyango, Gilbert Arinda, Francis Orishaba, Teddy Kwaga, Rita Kageni, David Macleod, Reena Yadav, Sandip Das Sanyam, Jeremy J Hoffman, Abeer HA Mohamed Ahmed, Astrid Leck, Mathew J Burton To determine the knowledge, attitude, and practice of pharmacy attendants in the management of microbial keratitis.

Facilitators and barriers of Community Case management of Malaria implementation in Homabay, Busia and Kakamega Counties, Kenya

Thu, 21 Aug 2025 00:00:00 GMT

Facilitators and barriers of Community Case management of Malaria implementation in Homabay, Busia and Kakamega Counties, Kenya Sheila Lumumba, Albino Luciani, Bryson Sifuma, Dennis Kinyua, George Gikunda, Norah Ogutu, John Onyango, Diana Mukami, Colleta Kiilu, Saida Kassim, Yvonne Opanga, George Githuka Community Case management of malaria (CCMm) is a strategy used in malaria-endemic areas to reduce malaria morbidity and mortality. CCMm involves providing malaria diagnosis and treatment within the community by trained community health volunteers (CHVs). While evidence suggests CCMm is effective in combating the disease burden at the community level, it isn’t without challenges. This study assesses facilitators of and barriers to uptake of CCMm. https://doi.org/10.1371/journal.pone.0329709

In vitro, ex vivo, and in silico studies of phytochemicals from the stem bark of Bischofia javanica

Sat, 14 Jun 2025 00:00:00 GMT

In vitro, ex vivo, and in silico studies of phytochemicals from the stem bark of Bischofia javanica Awas, Erick Okoth; Midiwo, O.Jacob; Omosa, Leonidah Kerubo.et.al The stem bark extract of Bischofia javanica, used in traditional Kenyan medicine afforded nine compounds named, santin (1), ermanin (2), rhamnocitrin (3), kumatakenin (4), abyssinone V-4′-methyl ether (5), β-sitosterol (6), betulinic acid (7), friedelin (8) and 1-methyl-1,10-phenanthrolin-1-ium (9). Structural elucidation was performed based on spectroscopic and spectrometric analyses, and the data were compared with those reported in the literature. The natural origin of 1-methyl-1,10-phenanthrolin-1-ium (9) in the plant kingdom is reported here for the first time. Ermanin (2) showed selective in vitro antiplasmodial activity with IC50 = 0.05 μM, while 1-methyl-1,10-phenanthrolinium (9) exhibited potent antiplasmodial activity with IC50 values of 1.56 μM (in vitro), and 1.20 μM (ex vivo). Furthermore, molecular docking studies revealed that 1-methyl-1,10-phenanthrolinium (9) could be considered a potential lead compound for future antimalarial drugs.

Diazinon residues levels in farm-gate Brassica oleracea var. acephala of Kimira-Oluch smallholder farm improvement project, Kenya

Wed, 28 May 2025 00:00:00 GMT

Diazinon residues levels in farm-gate Brassica oleracea var. acephala of Kimira-Oluch smallholder farm improvement project, Kenya Oromo, George Odoyo; Owuor, Philip Okinda; Kwach, Bowa; Otieno, Peter Diazinon insecticide, though associated with human health impacts, is popularly used in the production of Brassica oleracea var. acephala (kale) at the Kimira-Oluch Smallholder Farmers Improvement Project (KOSFIP), Kenya. Diazinon controls insect pests that lower quality and profitability of produce. The preharvest interval of diazinon in kale is 12 days which may not be observed by farmers with inadequate appreciation of Good Agricultural Practices (GAP). Since the extent of GAPs adoption at KOSFIP has not been evaluated, it remains unclear whether diazinon residues levels in kale of KOSFIP could be a health risk to the consumers. Diazinon residues levels and corresponding health risks in farm-gate kale at KOSFIP were determined. Cross-sectional survey based on snowball sampling identified 40 farms applying diazinon on the vegetable. Triplicate samples were collected from each farm for residue analysis, using the QuEChERS method, and LC-ESI-MS/MS analysis. Standard normal distribution function f(z) revealed 78% of farm-gate samples had detectable residual diazinon levels and 70% were above the Codex MRL of 0.05 mg/kg. Continued application of diazinon on kale at KOSFIP is exposing consumers to short-term health risks. Efforts must be intensified to ensure GAP are adopted. The estimated farm-gate samples with health risk indices for children and adults (HRIc and HRIA) >1.0 were 64% and 26%, respectively. The residual levels are therefore potential health risks to both children and adults. Farm-gate residual levels and resultant partial HRI were comparatively higher than findings of most previous studies. Inappropriate label PHI and malpractices against GAP may be responsible for high residual levels. There should be regular surveillance and trainings of farmers on GAP for sustainable production of kale in the Lake Victoria region. Use of diazinon on kale should be discouraged and intensive routine pesticide residue screening be enhanced for conventional vegetable produce. https://doi.org/10.1371/journal.pone.0310586

Exploring Rabi Oscillations, Maximally Entangled States and Perfect Teleportation in the Anti-Jaynes-Cummings Interaction: Insights into Quantum Dynamics and Entanglement Applications

Mon, 11 Nov 2024 00:00:00 GMT

Exploring Rabi Oscillations, Maximally Entangled States and Perfect Teleportation in the Anti-Jaynes-Cummings Interaction: Insights into Quantum Dynamics and Entanglement Applications Mayero, Christopher; Omolo, Joseph Akeyo This study presents a method for producing maximally entangled qubit states, also known as entangled anti-polariton qubit states, in the anti-Jaynes-Cummings interaction mechanism. We show that, in an initial vacuum-field, the time evolution of entanglement in the anti-Jaynes-Cummings interaction process takes the same form as in the Jaynes-Cummings interaction process, and that Rabi oscillations in a cavity mode in the anti-Jaynes-Cummings interaction process occur in the reverse sense relative to the Jaynes-Cummings interaction process. We demonstrate quantum teleportation of an atomic quantum state using the created anti-polariton qubit state as one of the initial qubits. We accomplish a perfect maximal teleportation fidelity of unity by employing an entanglement swapping procedure. URI: http://archive.article4submit.com/id/eprint/3041

Effect of the extended π-surface and N-butyl substituents of imidazoles on their reactivity, electrochemical behaviours and biological interactions of corresponding Pt(II)-CNC carbene complexes: exploring DFT and docking interactions†

Fri, 05 Jul 2024 00:00:00 GMT

Effect of the extended π-surface and N-butyl substituents of imidazoles on their reactivity, electrochemical behaviours and biological interactions of corresponding Pt(II)-CNC carbene complexes: exploring DFT and docking interactions† Onunga, O.Daniel; Jaganyi, Deogratius; Robinson, Ross; Mambanda, Allen In this study, we synthesised and characterised three C^N^C pincer (N-heterocyclic carbene)-type tridentate ligands, namely, 2,6-bis[(3-methylimidazolium-1-yl)methyl]pyridine dibromide (L1), 2,6-bis[(3-methylbenzimidazolium-1-yl)methyl]pyridine dibromide (L2) and 2,6-bis[(3-butylimidazolium-1-yl)methyl]pyridine dibromide (L3), and their corresponding six-membered chelates with Pt(II) to form PtL1–PtL3 complexes, namely, 2,6-bis[(3-methylimidazolium-1-yl)methyl]pyridinechloroplatinum(II) tetrafluoroborate (PtL1), 2,6-bis[(3-methylbenzimidazol-1-yl)methyl]pyridinechloroplatinum(II) tetrafluoroborate (PtL2) and 2,6-bis[(3-butylimidazol-1-yl)methyl]pyridinechloroplatinum(II) tetrafluoroborate (PtL3). Substitution kinetics using thiourea nucleophiles (tu, dmtu and tmtu), structural properties through theoretical DFT, biological interactions with DNA/BSA, electrochemical behaviors using cyclic voltammetry and docking simulations for Pt(II) C^N^C pincer complexes were investigated. The extended π surface of benzimidazole (PtL2) caused σ-donation in cis-Pt–C bonds, while N-butyl arms (PtL3) on the bis(3-methylimidazolium-1-yl)pyridine C^N^C pincer ligand had a steric influence on the labile ligand, leading to an increasing order of chloride substitution as follows: PtL3 < PtL2 < PtL1. The nucleophile's reactivity order is in accordance with its bulkiness, and the order is tu > dmtu > tmtu. Reactivity trends were justified by the trends in theoretical DFT data. Strong cis σ-donor ligands prevent the co-coordination of the spectator ligand. Large negative entropy of activation (ΔS#) and positive enthalpy of activation (ΔH#) support a limiting associative substitution mechanism. Biological interactions of PtL1–PtL3 with CT-DNA and BSA complexes were confirmed using spectroscopic and cyclic voltammetry (CV) titrations, and the data obtained established moderate-to-strong binding affinities. Complexes bind to CT-DNA mainly via the groove mode and to a lesser extent via intercalation, whereas they insert into the upper protein cleft of BSA. Electrochemistry results also established the groove binding mode of interaction, and −ΔG values affirmed the binding process as spontaneous. Molecular docking simulations of PtL1–PtL3 with CT-DNA and BSA corroborated with groove binding being the main binding mode.

Slowing the reactivity of dicyclometalated Pd (II) complexes through the 2, 6-bis (N-heterocyclic carbene) pyridine (C^ N^ C) non-leaving ligands: kinetic and computational study

Wed, 21 Aug 2024 00:00:00 GMT

Slowing the reactivity of dicyclometalated Pd (II) complexes through the 2, 6-bis (N-heterocyclic carbene) pyridine (C^ N^ C) non-leaving ligands: kinetic and computational study Onunga, O.Daniel; Jaganyi, Deogratius; Mambanda, Allen In this study, the kinetic and mechanistic studies of the substitution of chloride ligand of [(chloro)(2,6-bis(N-heterocyclic carbene)pyridine)Pd(II)]BF4 complexes, namely Pd1, Pd2, Pd3 and Pd4, by thiourea nucleophiles viz Tu, Dmtu and Tmtu were investigated. The rate of chloride substitution of dicyclometalated complexes was monitored in aqueous media containing 20 mM LiCl using stopped-flow spectrophotometry as a function of concentration and temperature under pseudo-first-order conditions. The kinetic data fitted to the pseudo-first-order rate law, kobs = k2[Nu]. The rate of chloride substitution decreased in the order Pd1 ˃ Pd2 ˃ Pd4 ˃ > Pd3. The reactivity of Pd1 was lower by two orders of magnitude compared to [Pd(terpy)Cl]+ (terpy = terpyridine). Both complexes have strong π-acceptor non-leaving ligands that promote efficient back bonding of charge into the aromatic bis(NHC) chelates of its non-leaving ligand. Contrastingly, the lutidine-bridged complexes, (Pd2-4) form 6-membered and non-aromatic bis(NHC) chelates which cause steric influence on either side of the square plane. Their substituents also impart additional steric effects and σ-inductive effects in the rings. The combined effect significantly lowers rates of substitution. Consequently, Pd3 was the least reactive. The substitution mechanism is associative since no evidence of a mechanistic change over to the dissociative substitution was observed, despite the complexes coordinated with tridentates with two cis-σ-bound carbon donors. The article can be accessed in full via:https://link.springer.com/journal/11243/aims-and-scope

Tuning the structural and mechanical properties of SiC-Li and SiC-Na alloys for aerospace application: an ab initio study

Mon, 04 Nov 2024 00:00:00 GMT

Tuning the structural and mechanical properties of SiC-Li and SiC-Na alloys for aerospace application: an ab initio study Otieno, Ochieng Victor; Ongwen, Nicholas; Otieno, Calford Aluminum (Al) and its alloys are popular in the aerospace industry due to their high strength-to-weight ratio, corrosion resistance, and ductility. However, these properties (extreme ductility and malleability) can compromise corrosion resistance, making them susceptible to dents and scratches. Silicon Carbide (SiC) is a promising alternative to Al and it alloys due to its higher Youngs modulus and excellent wear resistance, although it has the drawbacks of brittleness and higher density. This study investigated the structural and mechanical properties of SiC alloyed with lithium (SiC-Li) or sodium (SiC-Na) using ab initio calculations with the aim of tuning the structural and mechanical properties of SiC. Modeling was done using Burai software, which offers a friendly graphical user interface for Quantum ESPRESSO, thus facilitating the creation of input files, visualization of crystal structures and analysis of results. The results from this study showed that the addition of Li and Na lowered the density as well as the mechanical properties of SiC but still being favorably better than those of Al and its alloys, suggesting that the modeled alloys could potentially replace the traditional Al and its alloys in the aerospace industry. Further experimental studies are needed to validate these findings and to explore the possibility of simultaneous alloying of SiC with both Li and Na for enhanced performance.

First principles investigation of elastic, electronic and thermoelectric properties of lead-free Cs–X–I (X= Pb, Gd, Nd, Y) perovskites

Thu, 31 Oct 2024 00:00:00 GMT

First principles investigation of elastic, electronic and thermoelectric properties of lead-free Cs–X–I (X= Pb, Gd, Nd, Y) perovskites Alruqi, Adel Bandar; Ongwen, Nicholas Ogada Perovskites have become the center of recent research for their possible application in perovskite solar cells, owing to their desirable optical and electronic properties, flexibility, tunability, and low–cost fabrication. Most of the perovskites are however made of lead, which is a highly poisonous element. It is therefore necessary to seek alternative perovskites for this application that are less toxic. This study investigated the elastic, electronic, and thermoelectric properties of Cs–X–I (X = Pb, Gd, Nd, and Y) as possible replacements to the leaded CsPbI3 due to their less toxic nature. The density functional theory was utilized in the computations, with quantum espresso and BoltzTrap packages. The results showed that all the materials were structurally stable. The computed mechanical properties also showed that all the other materials had better elastic constants compared to those of CsPbI3. CsPbI3 was observed to exhibit the lowest band gap, unlike the others. Moreover, the other materials possessed higher elastic constants, electrical conductivities, and lowest thermal conductivities, which are highly needed in the perovskite solar cells. However, an experimental treatment needs to be done on the studied structures in order to confirm the properties obtained in this work.