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

Ariswan Ariswan — 2023-08-31

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

Aleksei S. Komlev — 2023-09-12

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 — 2023-10-04

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.

The Modified Double Sampling Coefficient of Variation Control Chart

Fachrur Rozi — 2023-10-04

The concept of monitoring the coefficient of variation has gained significant interest in quality control, particularly in situations where the mean and standard deviation of a process are not constant. This study modified the procedure of the previous double sampling chart for monitoring the coefficient of variation, developed by Ng et al. in 2018. Instead of using only information from the second sample, here, information from both samples is used. The probability properties of the out-of-control signal and run length of this chart are presented. To evaluate the chart’s performance, the optimal design and a comparison with the previous double sampling control chart using average run-length criteria are described. It was found that the modified double sampling chart has better performance and is more efficient compared to the previous chart, especially when the total sample size is smaller. As a study case, the application of this chart is illustrated using real data from a molding process. This confirmed that the modified double sampling chart improved performance in detecting out-of-control signals. Thus, the modified chart is recommended to be applied in industry.

Computational Study of Nocardiotide-A Analogues in the Development of Technetium-99m Radiopeptides for Cancer Imaging for Targeting Somatostatin Receptor 2

Rizky Juwita Sugiharti — 2023-10-07

Nocardiotide-A (cWIWLVA) is a cyclic peptide with significant cytotoxicity against several cancer cells. The present research aimed to design a radiopeptide based on nocardiotide-A analogues to be labeled by technetium-99m targeting SSTR2, which is the most widely expressed receptor in several types of human cancers and used as radiopeptide target. Nocardiotide-A analogues were individually designed by replacing valine at the lead compound with lysine, arginine, histidine, asparagine, and glutamine, and this was simulated by molecular dynamics using AMBER18. A molecular docking using AutoDock 4.2 was performed and evaluated to understand the effect of chelation of technetium-99m on ^99mTc-HYNIC-EDDA and ^99mTc-HYNIC-tricine on the binding affinity of nocardiotide-A analogues. The molecular dynamics simulation confirmed that the designed nocardiotide-A-based peptides were stable in the binding pocket of SSTR2 for 200 ns. Moreover, the nocardiotide-A-based radiopeptides are able to interact with residues Q102, D122, Q126, and N276 by building hydrogen bonds, which are essential binding residues in SSTR2. The molecular docking simulation revealed that the best docking parameter is exhibited by ^99mTc/EDDA/HYNIC-cWIWLNA and ^99mTc/tricine/HYNIC-cWIWLNA with a binding free energy of –12.59 kcal/mol and –8.96 kcal/mol, respectively. Taken together, nocardiotide-A-based radiopeptides are prospective to be further developed for cancer imaging targeting SSTR2.