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 extraction of naturally occurring compounds is one of the fastest-growing industries because of its benefits against its synthetic analogs. Environmental protection must require the use of natural products instead of chemicals to minimize pollution. Thus, this investigation studies the use of some natural product, as curcumin, as naturally occurring acid‐base indicators. Curcumin can be used as acid-base indicators since it was found that it possesses pH-dependent solubility. Curcumin, the major active component of turmeric, Curcuma longa (Zingiberaceae), is used as a spice in curry and as a coloring agent in yellow mustards, cosmetics, pharmaceuticals, and hair dyes. In this research, the main compound colored rhizome of turmeric (Curcuma longa) cultivated in Mérida, Venezuela, is extracted: Curcumin (C₂₁H₂₀O₆) (1E,6E)-1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione, in a yield of 3.42% after 8 hours of extraction using soxhlet extractor system with organic solvents (hexane and ethanol). The thin-layer chromatography and column performed separation and purification using a mobile phase, a mixture of chloroform-hexane 3:2. The dye was characterized by spectroscopic analysis of visible ultraviolet (UV-Vis) and infrared (IR), in addition to his studio in steering sensitivity as an acid-base indicator. This dye is useful as an acid-base indicator in strong acid-strong base volumes and did not require large amounts of it as it has high sensitivity. The results indicate that curcumin as an acid-base indicator allows the development of new standards in different chemistry fields that require this type of analysis.

E-selectin, as identified (CD62E), is expressed on endothelial cells after stimulation with inflammation cytokines. β-Thalassemia diseases (βT) and early diagnosis are of utmost significance in the entire world population. This study was performed in the Thalassemia Center of the Al-Zahraa Educational Hospital in Al-Najaf Province, Iraq, on sixty-nine with β-thalassemia (54 βT major and 15 βT Intermedia) aged 8-40 years who transfused blood. Compared to 20 healthy volunteers as a control group. In both βT patients and healthy groups were assessed serum E-selectin levels. It was investigated the relationship with RBC, Hb, PCV, WBC, PLT, BMI, splenic status, iron, and ferritin levels. The results revealed a significant (P<0.05) decreased values of HB, RBC, P.C.V, and BMI. In contrast, values of WBC, PLT, Iron, and Ferritin were significantly increased in βT patients as compared to the healthy control groups. A significant (P<0.05) increase in serum E- Selectin level in βT patients (20.55±0.47) ng/ml to compare with the healthy group (9.16±0.50) ng/ml. Furthermore, it was a significant decrease in groups of βT major (19.87±0.42) ng/ml more than in βT intermedia (23±1.42) ng/ml. E-Selectin revealed a significant increase (P<0.05) in progress age and associated with splenectomies and underweight groups compared to splenectomies and the normal weight groups, respectively. Also, E-Selectin levels significantly positively correlated with WBC, PLT value, iron, and Ferritin levels. However, it was no significant with RBC, PCV, Hb. As a conclusion from this study, E- Selectin is an important biomarker in β-thalassemia patients can be identified as the complications associated with iron overload, inflammatory process, and endothelial dysfunction in βT disease.