SOUTHERN JOURNAL OF SCIENCES

Background: MQ-series gas sensors belong to the metal oxide semiconductor (MOS) family of sensors that can sense the presence of many gases. These sensors find their application in gas alarm systems as key components. While necessary sensor circuit output voltage value for alarm point in a stand-alone gas alarm system is desirable, but what exact combination of the sensor circuit parameters is required? Hitherto, the determination of these circuit parameters has not been given much attention in the research community. Aim: the purpose of this work is to explore a structured graphical approach of determination of MQ series gas sensor circuit parameters for a stand-alone gas alarm system that yields desired sensor circuit output voltage value for the alarm point; the main objective of the study was to develop mathematical model equations that relate the: (i) sensor resistance (RS) with the gas concentration (x) and the sensor resistance at standard calibration concentration of the sensor base gas in the clean air (Ro) and (ii) sensor circuit output voltage (VRL), load resistance (RL) and sensor resistance (RS). It is expected from the model equations developed that graphical correlations of the sensor circuits parameters will be generated. Using these graphs for a particular case of an MQ-4 gas sensor under the influence of LPG, the parameters that yield desired sensor circuit output voltage of 2V for 1000 ppm of LPG alarm point will be determined. Methods: Model equations were developed for the sensor dynamics, and based on these model equations, graphs for the determination of required sensor parameters were plotted for a case of MQ-4 gas sensor response to LPG. Results and Discussion: The results yielded optimal values for R_O,R_S and R_L of 20 kΩ, 30 kΩ and 20 kΩ respectively, for alarm settings of 1000 ppm and a desired sensor circuit output voltage of 2 V. Based on determined parameters, the calibration equation for determination of best concentration value for a given value of emulated LPG concentration was developed. Using the method proposed in this study makes the process of determining the MQ-series gas sensor circuit parameters less cumbersome as their value can easily be obtained from the resulting graphs. Conclusions: a structured graphical approach for determination of MQ-series gas sensor circuit parameters for alarm points in a stand-alone gas alarm system showed that using MQ-4 gas sensor and LPG as the target gas, and for a sensor circuit output voltage of 2 V for alarm point at 1000 ppm of LPG, the corresponding value of R_O, R_S and R_L obtained were 20 kΩ, 30 kΩ, and 20 kΩ respectively. Hence, a structured graphical approach is suitable for determining MQ series gas sensor circuit parameters for a stand-alone gas alarm system under the influence of its associated gases.

The pre-sowing treatment of scarlet sage (Salvia splendens Ker Gawl.) seeds with 4-methyl-2-piperidin1-yl-pyrimidine-5-carboxylic acid at concentrations of 0.01, 0.05, and 0.1% proved to have an obvious inhibiting effect. Prior to sowing, the seeds of Salvia splendens were soaked in a water suspension of 4-methyl-2-piperidin-1-yl-pyrimidine-5-carboxylic acid and 4-methyl-2-morpholin-4-pyrimidine-5-carboxylic acid with concentrations of 0.01%, 0.05%, and 0.1% for 18 hours. On the 42nd day of the experiment, the seedlings, having been preliminarily hardened for 12 days, were removed from the greenhouse and planted on the field. The pre-sowing treatment of Salvia splendens seeds with 4-methyl-2-morpholin-4-pyrimidine-5-carboxylic acid proved to have the inhibiting effect at concentrations of 0.01 and 0.05%. The height of the seedlings decreased by 13.3-43.7%. It was revealed that 4-methyl-2-piperidin-1-yl-pyrimidine-5-carboxylic acid at concentrations of 0.01, 0.05, and 0.1% decreased the growth of the seedlings by 30.4-43.7%, and 4-methyl-2-morpholin-4-pyrimidine-5-carboxylic acid at concentrations of 0.01 and 0.05% decreased the growth of the seedlings by13.3-22.2%. By contrast, the effect of pyrimidinecarboxylic acids on seed germination and plant height of another annual flower – spreading marigold (Tagetes patula L.) was stimulating. It was investigated some different concentrations from 0.01 to 0.05 %. The same concentrations of identical compounds were tested, but effects from them were opposite for Tagetes patula, and Salvia splendens seedlings. Сonsequently, the species-specific effect of pyrimidinecarboxylic acids on seed germination and plant height for ornamental grasses takes place. Therefore,4-methyl-2-piperidin-1-yl-pyrimidine-5-carboxylic acid and 4-methyl-2-morpholin4-pyrimidine-5-carboxylic acid are recommended as growth retardants for Salvia splendens. 

Background: Coronavirus Disease-2019 (COVID-19) appears in individuals asymptomatically and in various symptomatic forms. Symptomatic diversity can result in diagnosis failures, hospitalization, admission to intensive care, multi-organ failure, and death. The causes and risk factors of the severity of disease symptoms are uncertain. This uncertainty can only be resolved by elucidating the effects of host genes and genetic variations on different phenotypes. Aim: This review aimed to emphasize the importance of large-scale genotype-phenotype correlation studies in elucidating the phenotypic diversity in COVID-19 disease. Methods: All publications related to Phenome-Wide Association Study (PheWAS) in the PubMed database were searched. PheWAS studies applied to COVID-19 patients have been identified. In addition, studies applied to the genome-wide association study (GWAS)- Electronic health records (EHRs) data and additionally matched to the gene expression data were systematically reviewed. The latest PheWAS methodology and its importance in Large-scale genotype-phenotype correlations are discussed within the context of published COVID-19 studies. Results: According to our PubMed search data, there are few PheWAS studies on COVID-19 disease. This review explains the use of PheWAS studies applied to health records and GWAS data, and colocalization studies applied to expression quantitative trait locus (eQTL) analysis to understand the phenotypic variability of COVID-19. Discussion; Although there is a very limited number of PheWAS studies on COVID-19 diseases, these studies have obtained important data. At the current stage, there is a need for such studies in COVID-19 research. Conclusions: PheWAS is an ideal method for large-scale genotype-phenotype correlation studies that can reveal genetic diversity and phenotypic diversity in the pathophysiology of the disease.