Journal of Mathematical and Fundamental Sciences

Carbon Nanodots as Complexing Agent in the Formation of Lead(II) Sulfide Thin Films via Direct Deposition of Lead(II) Sulfide Powder

Thu, 31 Aug 2023 00:00:00 +0700

This study reveals for the first time the formation of lead(II) sulfide (PbS) thin films via direct deposition of PbS powder using carbon nanodots (Cdots) as a complexing agent. The chemical bath deposition (CBD) technique was utilized and the Cdots’ mass was varied, i.e., (in g) 3, 5, 7, and 9. The Cdots were prepared from the waste of a rice noodle production home industry via the low-temperature carbonization method. The Cdots were characterized using UV-Vis spectrophotometry, showing absorption peaks at 275 nm and 325 nm; PL, showing an emission peak at 500 nm with cyan luminescence; XRD, showing several peaks, indicating an incomplete carbonization process; FTIR, indicating the existence of C=C, C-H, C-O, and O-H functional groups; HRTEM, revealing the sizes of the Cdots in the range of 2 nm to 6 nm; and SEM, showing a smooth morphology of the Cdots’ surface. The thin films obtained were smooth with higher XRD peaks and better material distribution compared to pure PbS thin film. The band gap measurement indicated that the increase of the PbS band gap was caused by the increase of the Cdots’ mass. Hence, the thin films’ band gap may be tuned using the Cdots’ mass.

Magnetoresistance Features at the Magnetic Field-Induced Phase Transition in FeRh Thin Films

Tue, 12 Sep 2023 00:00:00 +0700

The causes of the appearance of first-order magnetic phase transitions remain a mystery. FeRh alloy is a classical material where a first-order magnetic phase transition occurs. The authors of this article studied the phase transition from the antiferromagnetic state to the ferromagnetic state in FeRh alloy. Comparison of the magnetometry and transport properties results allowed us to determine a number of differences in the mechanisms of the phase evolution during magnetic field and temperature induced transition. This article notes the priority of the rearrangement of the micromagnetic structure of the ferromagnetic phase as a result of the induction of a phase transition by a magnetic field. The main feature of the magnetic field induced phase transition compared to the temperature induced one is the change in the micromagnetic structure of the ferromagnetic phase. The growth of a ferromagnetic phase with less scattering fields leads to asymmetric behavior when a phase transition is induced near the metastable state. We also focused on the importance of taking into account the effect of magnetostriction when analyzing the evolution of the phase transition, which leads to the irreversibility of the phase transition near a zero magnetic field.

Modelling the Impact of Decomposed Disease-Induced Dead Cashew Plants on Fusarium Wilt Dynamics in South-Eastern Tanzania

Fatu Chilinga, Alfred K. Hugo — Wed, 04 Oct 2023 00:00:00 +0700

Cashew Fusarium wilt disease transmitted by Fusarium oxysporum is dangerous and destroys many cashew plants in Tanzania. The effect of this disease leads households and the government to experience a decrease in overall cashew production and income due to this disease’s capacity to harm cashew plants. This study aimed to ascertain the role of Fusarium wilt-decayed disease-induced dead plants in spreading the disease among cashew plants. A mathematical model was created based on the dynamics of the disease and a stability analysis was conducted using theories of ordinary differential equations. Data from two regions in Tanzania, Lindi, and Mtwara, were used in model fitting and parameter estimation. Additionally, the parameters were estimated using maximum likelihood estimation (MLE). The outcome suggests that the disease’s prevalence and spread increase during an outbreak as decomposed diseased-induced dead plants contribute to the saturation of chlamydospores in the soil.