Journal of Mathematical and Fundamental Sciences
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Slater-Pauling-like Behavior of Spin Hall Conductivity in Pt-based Superlattices
Full text linkThe intrinsic spin Hall effect in the bulk systems of late transition metals (Os, Ir, Pt, and Au) as well as the Pt-based superlattices were investigated by using first-principle calculations. By comparing the computed spin Hall conductivities of Pt−M superlattices (M=Os, Ir, and Au) with different compositions and those obtained from atomic bulk composition, we saw that the spin Hall conductivities (SHCs) follow the behavior described by the Slater-Pauling curve, the maximum of which is at pure Pt bulk. From the examination of the band structures of the considered systems, we found that the origin of this behavior comes from the variation of the band structures as a direct consequence of the change of the number of electrons and hybridization effects
Optimal Control and Cost Effectiveness Analysis of SIRS Malaria Disease Model with Temperature Variability Factor
Full text linkIn this study, we proposed and analyzed the optimal control and cost-effectiveness strategies for malaria epidemics model with impact of temperature variability. Temperature variability strongly determines the transmission of malaria. Firstly, we proved that all solutions of the model are positive and bounded within a certain set with initial conditions. Using the next-generation matrix method, the basic reproductive number at the present malaria-free equilibrium point was computed. The local stability and global stability of the malaria-free equilibrium were depicted applying the Jacobian matrix and Lyapunov function respectively when the basic reproductive number is smaller than one. However, the positive endemic equilibrium occurs when the basic reproductive number is greater than unity. A sensitivity analysis of the parameters was conducted; the model showed forward and backward bifurcation. Secondly, using Pontryagin’s maximum principle, optimal control interventions for malaria disease reduction are described involving three control measures, namely use of insecticide-treated bed nets, treatment of infected humans using anti-malarial drugs, and indoor residual insecticide spraying. An analysis of cost-effectiveness was also conducted. Finally, based on the simulation of different control strategies, the combination of treatment of infected humans and insecticide spraying was proved to be the most efficient and least costly strategy to eradicate the disease
Purely Data-driven Exploration of COVID-19 Pandemic After Three Months of the Outbreak
Full text linkMany research studies have been carried out to understand the epidemiological characteristics of the COVID-19 pandemic in its early phase. The current study is yet another contribution to better understand the disease properties by parameter estimation based on mathematical SIR epidemic modeling. The authors used Johns Hopkins University’s dataset to estimate the basic reproduction number of COVID-19 for five representative countries (Japan, Germany, Italy, France, and the Netherlands) that were selected using cluster analysis. As byproducts, the authors estimated the transmission, recovery, and death rates for each selected country and carried out statistical tests to see if there were any significant differences
Microwave-Assisted Claisen-Schmidt Condensation Reaction of Ethyl p-methoxycinnamate to Synthesize p-Methoxystyryl Ketone Derivatives and Evaluate Anti-inflammatory Activity of Synthetic Products
Full text linkThe rhizome of Kaempferia galanga has been known to contain ethyl p-methoxycinnamate (EPMC) (1) as a main component, which has anti-inflammatory properties. Previously we have reported the structural modification of EPMC (1) to form another ester, nitrostyrene, and cinnammamide derivatives and then studied their structure-activity relationships as anti-inflammatory agent. In continuing our research, in this paper, we report the microwave-assisted Claisen-Schmidt condensation of EPMC (1) to synthesize a series of p-methoxystyryl ketones followed by a study of their anti-inflammatory activity. The reaction begins with microwave-assisted cleavage oxidation of hydrolyzed product of EPMC, p-methoxycinnamic acid (2) with Ca(NO3)2 for the synthesis of p-methoxybenzaldehyde (3). Furthermore, 3 was reacted with acetophenone, ethyl methyl ketone and acetone via microwave-assisted Claisen-Schmidt condensation for the synthesis of (E)-1-(4-methoxyphenyl)-3-phenylprop-2-en-1-one (5a) (E)-1-(4-methoxyphenyl)pent-1-en-3-one (5b) and (E)-4-(4-methoxyphenyl)but-3-en-2-one (5c), respectively. The reaction products were characterized using spectroscopic techniques and were then tested for anti-inflammatory activity using in vitro anti-denaturation of protein assay. It was found that converting EPMC (1) to 5a and 5b reduced anti-inflammatory activity, while 5c retained anti-denaturation activity with an IC50 of 72.8 µg/ml
Designing Aquifer Model for the Banks of the Serayu River, Sokawera, Somagede, Banyumas, Indonesia by Means of 1D-Electrical Resistivity Data
Full text linkA geoelectric survey using the 1D-electrical resistivity method was applied to design a groundwater aquifer model for the banks of the Serayu River in Sokawera Village, Somagede District, Banyumas Regency, Indonesia. The aim of this research was to identify the characteristics of aquifers in the research area based on resistivity log data. Acquisition, modeling, and interpretation of resistivity data were carried out and the results were lithological logs at seven sounding points. Correlation between the lithological logs resulted in a hydrostratigraphic model. This model is composed of several hydrological units, i.e. shallow aquifer, aquitard, and deep aquifer. The shallow aquifers are composed of sandy clay (10.81-18.21 Wm) and clayey sand (3.04-7.43 Wm) with a depth of groundwater from the water table to 27.51 m. The deep aquifers are composed of sandstone with variation of porosity (2.24-12.04 Wm) at a depth of more than 54.98 m. Based on this model, potential shallow aquifers were estimated to be at sounding points Sch-5, Sch-6, and Sch-7. This hydrostratigraphic model shows that the two types of aquifers are separated by an aquitard layer, allowing groundwater infiltration from the shallow aquifer to the deep aquifer and vice versa. Moreover, the Serayu riverbanks in this research area are estimated to be a groundwater discharge area