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This paper presents a workable vapour compression system (VCS) for evaluating the performance of a refrigeration system with an integrated condenser that uses a long-term alternative refrigerant to halocarbon as a heat transfer medium (R600a). India's refrigeration system uses halocarbon refrigerants due to their excellent thermophysical and thermodynamic properties. Greenhouse gas emissions from halocarbon refrigerants and fossil fuel combustion contribute to global warming that engenders climate change and the deterioration of the ecosystem. The halocarbon refrigerant was discontinued based on high global warming potential. The system was investigated under various ambient temperatures of 16, 20, 24, and 28 °C (oC). The performance of the VCS was analyzed using the parameters of coefficient performance, compressor work, and pull-down time (PDT). The experimental result shows that the vapour compression system obtained its best PDT, enhanced coefficient of performance, and energy reduction when the ambient temperature was 20 °C.

Modulation of molecular features of metal free organic dyes is important to present sensitizers with competing electronic and optical properties for dye sensitized solar cells (DSSCs). The D-A2-π-A1 molecular design based on phenothiazine skeleton (D) connected with benzothiadiazole (A2) linked with furan π-spacer and acceptor unit of cynoacrylic acid (A1) were fabricated and examined theoretically for possible use as DSSCs. Density functional theory (DFT) and time dependent density functional theory TDDFT were used to study the effect of additional donors on the photophysical properties of the dyes. Eight (8) different donor subunits were introduced at C7 of phenoxazine based dye skeleton to extend the π-conjugation, lower HOMO-LUMO gap (Eg) and improve photo-current efficiency of the dye sensitizer. All the dye sensitizers (except P3 and P4) exhibited capability of injecting electrons into the conduction band of the semiconductor (TiO2) and regenerated via redox potential (I−/I3-) electrode. Attachment of 2-hexylthiophene (P2) remarkably lowered the Eg, extended π-electron delocalization, hence, gives higher absorption wavelength (λmax) at 752 nm. The donor subunit containing 2-hexylthiophene (P2) presented the best chemical hardness, open circuit voltage (Voc), and other comparable electronic properties, making P2 the best DSSC candidate amongst the optimized dyes. The reported dyes would be interesting for further experimental research.

Abstracts: This work used quantum chemical method via DFT to calculate molecular descriptors for the development of QSAR model to predict bioactivity (IC50- 50% inhibition concentration) of the selected 1, 2, 3-triazole-pyrimidine derivatives against receptor (human gastric cancer cell line, MGC-803). The selected molecular parameters were obtained by B3LYP/6-31G∗∗. QSAR model linked the molecular parameters of the studied compounds to their cytotoxicity and reproduced their observed bioactivities against MGC-803. The calculated IC50 tailored the observed IC50 and greater than standard compound, 5-fluorouracil, suggesting that the developed QSAR model reproduced the observed bioactivity. Statistical analyses (including R2, CV. R2 and Ra2 gave 0.950, 0.970 and 0.844 respectively) revealed a very good fitness. Molecular docking studies revealed the hydrogen bonding with the amino acid residues in the binding site, as well as ligand conformations which are essential feature for ligand-receptor interactions. Therefore, the methods used in this study are veritable tools that can be employed in pharmacological and medicinal chemistry researches in designing better drugs with improve potency.

Gastric cancer as a dreaded disease which occurs in the digestive system of human being remain a threat to the medical world. Bioactivity of series of designed and synthesized molecular compounds containing triazole and pyrimidine moieties were subjected to quantum chemical calculations using B3LYP/6-31+G∗. The calculated molecular descriptors such as the EHOMO (eV), ELUMO (eV), band gap (eV), chemical hardness (η), global nucleophilicity, dipole moment (Debye), chemical potential, log P, molecular weight (amu) and Ovality. The descriptors that describe anti-gastric cancer activity of the studied compounds were used for QSAR analysis using SPSS and Gretl software packages for multiple linear regression (MLR), XLSTAT for partial least square (PLS) and MATLAB for artificial neural network (ANN). The methods (MLR, PLS, and ANN) were predictive. Nevertheless, ANN performed better than MLR and PLS. More so, molecular docking study was executed on the studied compounds and gastric cancer cell line (PDB ID: 4oum); the docking studies showed that 2-(1-(2-(3-benzyl-5-(benzylthio)-3H-[1,2,3]triazolo[4,5-d]pyrimidin-7-yl)hydrazono)ethyl)phenol (A22) having the lowest binding affinity (-8.40 kcal/mol); this was correlated to the observed inhibitory activity of the compound against gastric cancer. Thus, it showed better inhibition than other studied compounds. The amino acid residues that were involved in stabilizing A22 in the active site of the 4oum are: VAL-9, ALA-10, THR-49, ASN-48, PRO-47 and TYR-46. Also, a good relationship was observed between the calculated binding affinity and the observed inhibition concentration (IC50).