Experimental work has already demonstrated that Al-doped ZnO nanostructures exhibit a higher response than the pure ZnO sample to CO gas and can detect it at sub-ppm concentrations. In this work, ...using density functional theory calculations (at B3LYP, M06-L, and B97D levels), we studied the effect of Al-doping on the sensing properties of a ZnO nanocluster. We investigated several doping and adsorption possibilities. This study explains the electrical behavior that has been obtained from the ZnO nanostructures upon the CO adsorption. There is a relationship between the HOMO–LUMO energy gap (E g) and the resistivity of the ZnO nanostructure. If a Zn atom of the ZnO nanocluster is replaced by an Al atom, a CO molecule can be adsorbed from its C-head on the doped site with ΔG of −5.0 kcal/mol at room temperature. In contrast to the pristine cluster, Al-doped ZnO cluster can detect CO molecules due to a significant decrease in the E g and thereby in the resistivity. We also found that the E g decreases by increasing the number of Al atom up to 4, and then it starts to increase by increasing the Al atoms with its trend analogous to the resistivity change in the experimental work.
By using density functional theory, we investigated the reactivity and electronic sensitivity of pristine and structurally manipulated BC2N nanotubes (BC2NNT) to a HCN molecule. It was mainly found ...that (i) the pristine BC2NNT can weakly adsorb the HCN with adsorption energy of −1.1 kcal/mol, and its electronic properties are not sensitive to HCN; (ii) doping the tube by an Al atom can largely improve its reactivity to HCN, but it does not have a significant effect on its sensitivity; (iii) B–B antisite defect on the tube wall can improve both reactivity and sensitivity of the tube to HCN; (iv) N–N antisite could improve neither the reactivity nor the sensitivity. Upon the adsorption of HCN on the B–B antisite defect, the HOMO–LUMO energy gap of the tube is significantly reduced from 2.23 to 1.82 eV and energy of 6.3 kcal/mol is released.
Atherosclerosis is a major etiology of cardiovascular disease that causes considerable mortality. Oxidized low-density lipoprotein (oxLDL) is a fundamental attributor to atherosclerosis. Therefore, ...there seems to be an essential place for antioxidant therapy besides the current treatment protocols for coronary heart disease. Polyphenols are a class of compounds with substantial antioxidant properties that have shown the ability to reduce LDL oxidation in preclinical studies. However, clinical evidence has not been as conclusive although offering many promising signs. This review aims to examine the trials that have evaluated how dietary intake of polyphenols in different forms might influence the oxidation of LDL. Lowering the circulating cholesterol, incorporation into LDL particles, and enhancing systemic antioxidant activity are among the main mechanisms of action for polyphenols for lowering oxLDL. On the other hand, the population under study significantly affects the impact on oxLDL, as the type of the supplement and phenolic content. To conclude, although the polyphenols might decrease inflammation and enhance endothelial function via lowering oxLDL, there are still many gaps in our knowledge that need to be filled with further high-quality studies.
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Bacterial Cellulose aerogels were prepared by solvent exchange and freeze-drying. They were used as the template for silver, copper oxide, and zinc oxide nanoparticles by the optimized amount of the ...corresponding salt and method. The as-prepared nanocomposites showed antibacterial activity against Klebsiella pneumonia (K) and Staphylococcus aureus (S) bacteria.
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In this work, porous bacterial cellulose aerogels (BCA) were prepared by 1-step (BCA-1) and 3-step (BCA-3) exchange of solvent inside the bacterial cellulose hydrogel (0.65 %) with tertiary butyl alcohol followed by freeze-drying. BCA-3 was used as a template for Ag, CuO, and ZnO nanoparticles by reducing the corresponding salt using sodium borohydride (NaBH4) as a reducer agent. The silver nanoparticles (Ag NPs) were grown onto the BCA-3 scaffold (Ag/BCA-3) by adjusting the amount of AgNO3 with two different processes. Similarly, CuO and ZnO cellulosic nanocomposites (CuO/BCA-3 and ZnO/BCA-3) were fabricated by the optimized amount (0.1 M) and method (method-2). Aerogel and metal nanoparticle composites were characterized by Brunauer-Emmett-Teller (BET); UV–visible spectrophotometry (UV–Vis); X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR); Scanning electron microscopy (SEM); Energy dispersive spectroscopy (EDS); and Transmission electron microscopy (TEM) analysis. Results showed that the web-like entangled structures of aerogels have specific surface areas as high as 87–97 m2g−1. Ag/BCA-3 and CuO/BCA-3 exhibited a spherical morphology of NPs with an average particle size of about 50 nm and 10 nm, respectively. ZnO/BCA-3 resulted in hexagonal morphology with around 50 nm. The metal nanocomposites showed antibacterial activity against Klebsiella pneumonia (gram-negative) and Staphylococcus aureus (gram-positive) bacteria.
In the present study, effects of salinity stress were evaluated in the leaves and roots of two pistachio cultivars (Badami-Rize-Zarand (BZ) and Badami-e-Sefid (BS)). In overall, salinity negatively ...affects growth of both cultivars with more pronounced effects on BS. The physiological reason of the reduction could be attributed to some extent to more depletion of photosynthetic pigment in BS. In both cultivars, salinity increased proline content. Moderate and high salinities increased the soluble sugar contents in BZ. In both cultivars, Na
+
content increased in plant organs with increasing Na
+
in the media. Salinity treatment decreased the Fe and Pi contents in BS cultivar, while they remained unchanged in BZ. These results show that BZ cultivar exhibits more tolerance to salinity stress than BS cultivar possibly by better growth performance, accumulating more osmolytes, lesser accumulation of toxic sodium ion and lower Na
+
/K
+
in the shoots as well as maintaining nutrient contents.
Product category management (PCM) plays a pivotal role in today's large stores. PCM manages to answer questions such as assortment planning (AP) and shelf space allocation (SSA). AP problem seeks to ...determine a list of products and suppliers, while SSA problem tries to design the layout of the selected products in the available shelf space. These problems aim to maximize the retailer sales under different constraints, such as limited purchasing budget, limited space of classes for displaying the products, and having at least a certain number of suppliers. This paper makes an attempt to develop an integrated mathematical model to optimize integrated AP, SSA, and inventory control problem for the perishable products. The objective of the model is to maximize the sales and retail profit, considering the costs of supplier contracting/selecting and ordering, assortment planning, holding, and procurement cost. GAMS BARON solver is hired to solve the proposed model in small and medium scales. However, because the problem is NP-hard, an evolutionary genetic algorithm (GA), and an efficient local search vibration damping optimization (VDO) algorithm are proposed. A real case study is considered to evaluate the effectiveness and capabilities of the model. Besides, some test problems of different sizes are generated and solved by the proposed metaheuristic solvers to confirm the efficient performance of proposed algorithms in solving large-scale instances.
•Icemaking process is studied via theoretical, numerical, and experimental analyses.•3D transient model is developed using enthalpy-porosity and volume of fluid models.•Setting the ice removal ...temperature at −8 °C reduces the solidification time by 18 %.•Daily ice production is increased by 20% at the optimal ice removal temperature.
Automatic icemakers are integrated into refrigerators to ensure a consistent ice supply and improve energy efficiency. Despite these advantages, a thorough investigation of the automatic icemaking process in domestic refrigerator-freezers is lacking in the literature. This study aims at assessing the performance of automatic icemaking process in a domestic freezer through detailed theoretical, numerical and experimental analyses. A simplistic zero-dimensional transient energy balance model is developed to investigate the heat transfer during different stages of the water solidification process. The convective heat transfer coefficient calculated from the theoretical analysis is used to inform the numerical model. A three-dimensional transient model is proposed to predict the temperature and density variation inside the ice cube modelled as a pyramid. The free surface flow is modelled using volume of fluid method, while enthalpy-porosity method is employed for the water freezing process. The results show a non-uniform temperature distribution throughout the solidification process and that the temperature of the outer frozen layers keeps decreasing with the solidification time. Experiments are conducted to measure the temperature variation of the ice cube. It is shown that the icemaking process is accelerated by around 18 % when the ice-removal temperature is set at −8°C instead of −12 °C, which is a conventional set temperature for ice remover in current domestic freezers.
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