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Environmental Analysis of Sustainable and Traditional Cooling and Lubrication Strategies during Machining Processes
No full textDue to rising demands of replacing traditional cooling strategies with sustainable cooling strategies, the development of sustainable strategies such as minimum quantity lubrication (MQL) of nano-cutting fluids (NCFs) is on the rise. MQL of NCFs has received a lot of attention due to its positive impact on machining process efficiency. However, environmental and human health impacts of this strategy have not been fully investigated yet. This work aims to investigate the impacts of MQL of molybdenum disulfide (MoS2), multi-walled carbon nanotubes (MWCNTs), titanium dioxide (TiO2), and aluminum oxide (Al2O3) NCFs by employing a cradle-to-gate type of life cycle assessment (LCA). Besides, this paper provides a comparison of the impacts and machining performance when utilizing MQL of NCFs with other cooling strategies such as traditional flood cooling (TFC) of conventional cutting fluids and MQL of vegetable oils. It was found that NCFs have higher impacts than conventional cutting fluids and vegetable oils. The impacts of TiO2-NCF and MoS2-NCF were lower than the impacts of MWCNTs-NCF and Al2O3-NCF. MQL of NCFs presented higher impacts by 3.7% to 35.4% in comparison with the MQL of vegetable oils. TFC of conventional CFs displayed the lowest impact. However, TFC of conventional cutting fluids is contributing to severe health problems for operators. MQL of vegetable oils displayed higher impacts than TCFs of conventional cutting fluids. However, vegetable oils are considered to be environmentally friendly. According to the findings, the MQL of vegetable oils is the most sustainable strategy for machining processes with associated low/medium cutting temperatures. While MQL of TiO2 and MoS2 NCFs are the sustainable strategy for machining processes associated with high cutting temperatures
Antiamoebic activity of plant‑based natural products and their conjugated silver nanoparticles against Acanthamoeba castellanii (ATCC 50492)
No full textAcanthamoeba spp. are the causative agent of Acanthamoeba keratitis and granulomatous amoebic encephalitis (GAE). The current options to treat Acanthamoeba infections have limited success. Silver nanoparticles show antimicrobial effects and enhance the efficacy of their payload at the specific biological targets. Natural folk plants have been widely used for treating diseases as the phytochemicals from several plants have been shown to exhibit amoebicidal effects. Herein, we used natural products of plant or commercial sources including quercetin (QT), kolavenic acid (PGEA) isolated from plant extracts of Polyalthia longifolia var pendula and crude plant methanolic extract of Caesalpinia pulcherrima (CPFLM) as antiacanthamoebic agents. Furthermore, these plant-based materials were conjugated with silver nanoparticles (AgNPs) to determine the effects of the natural compounds and their nanoconjugates against a clinical isolate of A. castellanii from a keratitis patient (ATCC 50492) belonging to the T4 genotype. The compounds were conjugated with AgNPs and characterized by using ultraviolet visible spectrophotometry and atomic force microscopy. Quercetin coated silver nanoparticles (QT-AgNPs) showed characteristic surface plasmon resonance band at 443 nm and the average size distribution was found to be around 45 nm. The natural compounds alone and their nanoconjugates were tested for the viability of amoebae, encystation and excystation activity against A. castellanii. The natural compounds showed significant growth inhibition of A. castellanii while QT-AgNPs specifically exhibited enhanced antiamoebic effects as well as interrupted the encystation and excystation activity of the amoebae. Interestingly, these compounds and nanoconjugates did not exhibit in vitro cytotoxic effects against human cells. Plant-based compounds and extracts could be an interesting strategy in development of alternative therapeutics against Acanthamoeba infections.Sunway Universit
Land Use/Land Cover Changes Impact on Groundwater Level and Quality in the Northern Part of the United Arab Emirates
No full textThis study aims to develop an integrated approach for mapping and monitoring land use/land cover (LULC) changes and to investigate the impacts of LULC changes and population growth on groundwater level and quality using Landsat images and hydrological information in a Geographic information system (GIS) environment. All Landsat images (1990, 2000, 2010, and 2018) were classified using a support vector machine (SVM) and spectral analysis mapper (SAM) classifiers. The result of validation metrics, including precision, recall, and F1, indicated that the SVM classier has a better performance than SAM. The obtained LULC maps have an overall accuracy of more than 90%. Each pair of enhanced LULC maps (1990–2000, 2000–2010, 2010–2018, and 1990–2018) were used as input data for an image difference algorithm to monitor LULC changes. Maps of change detection were then imported into a GIS environment and spatially correlated against the spatiotemporal maps of groundwater level and groundwater quality. The results also show that the approximate built-up area increased from 227.26 km2 (1.39%) to 869.77 km2 (7.41%), while vegetated areas (farmlands, parks and gardens) increased from about 76.70 km2 (0.65%) to 290.70 km2 (2.47%). The observed changes in LULC are highly linked to the depletion in groundwater level and quality across the study area from the Oman Mountains to the coastal areas.American University of Sharja
Green Synthesis of Encapsulated Copper Nanoparticles Using a Hydroalcoholic Extract of Moringa oleifera Leaves and Assessment of Their Antioxidant and Antimicrobial Activities
No full textThe synthesis of metal nanoparticles using plant extracts is a very promising method in green synthesis. The medicinal value of Moringa oleifera leaves and the antimicrobial activity of metallic copper were combined in the present study to synthesize copper nanoparticles having a desirable added-value inorganic material. The use of a hydroalcoholic extract of M. oleifera leaves for the green synthesis of copper nanoparticles is an attractive method as it leads to the production of harmless chemicals and reduces waste. The total phenolic content in the M. oleifera leaves extract was 23.0 ± 0.3 mg gallic acid equivalent/g of dried M. oleifera leaves powder. The M. oleifera leaves extract was treated with a copper sulphate solution. A color change from brown to black indicates the formation of copper nanoparticles. Characterization of the synthesized copper nanoparticles was performed using ultraviolet-visible light (UV-Vis) spectrophotometry, Fourier-transform infrared (FTIR) spectrometry, high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The synthesized copper nanoparticles have an amorphous nature and particle size of 35.8-49.2 nm. We demonstrate that the M. oleifera leaves extract and the synthesized copper nanoparticles display considerable antioxidant activity. Moreover, the M. oleifera leaves extract and the synthesized copper nanoparticles exert considerable anti-bacterial activity against Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, and Enterococcus faecalis (MIC values for the extract: 500, 250, 250, and 250 µg/mL; MIC values for the copper nanoparticles: 500, 500, 500, and 250 µg/mL, respectively). Similarly, the M. oleifera leaves extract and the synthesized copper nanoparticles exert relatively stronger anti-fungal activity against Aspergillus niger, Aspergillus flavus, Candida albicans, and Candida glabrata (MIC values for the extract: 62.5, 62.5, 125, and 250 µg/mL; MIC values for the copper nanoparticles: 125, 125, 62.5, and 31.2 µg/mL, respectively). Our study reveals that the green synthesis of copper nanoparticles using a hydroalcoholic extract of M. oleifera leaves was successful. In addition, the synthesized copper nanoparticles can be potentially employed in the treatment of various microbial infections due to their reported antioxidant, anti-bacterial, and anti-fungal activities.Government of Indi
Optimization of a Confined Jet Geometry to Improve Film Cooling Performance Using Response Surface Methodology (RSM)
No full textThis study investigates the interrelated parameters affecting heat transfer from a hot gas flowing on a flat plate while cool air is injected adjacent to the flat plate. The cool air forms an air blanket that shield the flat plate from the hot gas flow. The cool air is blown from a confined jet and is simulated using a two-dimensional numerical model under three variable parameters; namely, blowing ratio, jet angle and density ratio. The interrelations between these parameters are evaluated to properly understand their effects on heat transfer. The analyses are conducted using ANSYS-Fluent, and the performance of the air blanket is reported using local and average adiabatic film cooling effectiveness (AFCE). The interrelation between these parameters and the AFCE is established through a statistical method known as response surface methodology (RSM). The RSM model shows that the AFCE has a second order relation with the blowing ratio and a first order relation with both jet angle and density ratio. Also, it is found that the highest average AFCE is reached at an injection angle of 30 degree, a density ratio of 1.2 and a blowing ratio of 1.8
Suppressing the Capacitor Voltage Fluctuations in Low Frequency Operation of Modular Multilevel Converters
No full textLowfrequency operation in the modular multilevel converters (MMCs) is enabled by applying a reference common mode voltage and circulating currents at a frequency much higher than the desired output frequency. The frequency of injected common-mode signals is limited for maintaining a good performance in the circulating current control. Firstly, this paper theoretically analyzes the effect of increasing the frequency of injected common-mode signals by evaluating the error between reference and actual circulating currents. Secondly, we introduce an additional parameter in the reference circulating current to enhance the suppression of MMC's capacitor voltage fluctuations. Intensive computer simulations are developed for a seven-level MMC driving a medium-voltage induction motor drive system to verify the circulating current error analysis and assess the capacitor voltage fluctuations. Finally, the proposed technique for suppressing the capacitor voltage fluctuations is experimentally validated on a 600-V three-level MMC feeding an inductive load. The voltage fluctuations are reduced by more than 50% (63.6%) when the proposed technique is applied with a high common-mode frequency.U.S. Department of Energ
Metronidazole conjugated magnetic nanoparticles loaded with amphotericin B exhibited potent effects against pathogenic Acanthamoeba castellanii belonging to the T4 genotype
No full textAcanthamoeba castellanii can cause granulomatous amoebic encephalitis and Acanthamoeba keratitis. Currently, no single drug has been developed to effectively treat infections caused by Acanthamoeba. Recent studies have shown that drugs conjugated with nanoparticles exhibit potent in vitro antiamoebic activity against pathogenic free-living amoebae. In this study, we have developed a nano drug delivery system based on iron oxide nanoparticles conjugated with metronidazole which were further loaded with amphotericin B to produce enhanced antiamoebic effects against Acanthamoeba castellanii. The results showed that metronidazole-nanoparticles-amphotericin B (Met-MNPs-Amp) significantly inhibited the viability of these amoebae as compared to the respective controls including drugs and nanoparticles alone. Met-MNPs-Amp exhibited IC₅₀ at 50 μg/mL against both A. castellanii trophozoites and cysts. Furthermore, these nanoparticles did not affect the viability of rat and human cells and showed safe hemolytic activity. Hence, the results obtained in this study have potential utility in drug development against infections caused by Acanthamoeba castellanii. A combination of drugs can lead to successful prognosis against these largely neglected infections. Future studies will determine the value of conjugating molecules with diagnostic and therapeutic potential to provide theranostic approaches against these serious infections.Sunway UniversityAmerican University of Sharja
Compound distributions for financial returns
No full textIn this paper, we propose six Student’s t based compound distributions where the scale parameter is randomized using functional forms of the half normal, Fréchet, Lomax, Burr III, inverse gamma and generalized gamma distributions. For each of the proposed distribution, we give expressions for the probability density function, cumulative distribution function, moments and characteristic function. GARCH models with innovations taken to follow the compound distributions are fitted to the data using the method of maximum likelihood. For the sample data considered, we see that all but two of the proposed distributions perform better than two popular distributions. Finally, we perform a simulation study to examine the accuracy of the best performing model
Investigation and Mathematical Modeling of Acoustic Release of Doxorubicin from Micelles
No full textA Master of Science thesis in Chemical Engineering by Youssef Ashraf Alhariri entitled, “Investigation and Mathematical Modeling of Acoustic Release of Doxorubicin from Micelles”, submitted in May 2020. Thesis advisors is Ghaleb Husseini and Rana Sabouni. Soft copy is available (Thesis, Approval Signatures, Completion Certificate, and AUS Archives Consent Form).Given the growing concern over the increasing number of people diagnosed with cancer and the high prevalence of unwanted side effects associated with chemotherapy on healthy tissues, this thesis aims to provide better, safer, and more effective treatment modalities. In this work, a targeted nanocarrier is loaded with an anti-cancer drug. Results of ultrasound release experiments are used to compare the response of different micellar types to acoustic waves. The investigated micelles include non-targeted micelles, folated micelles, micelles stabilized using an interpenetrating network of N,Ndiethylacrylamide, and micelles formed using PEO-b-poly(NIPAAm-co-HEMAlactaten). Acoustic release of the chemotherapeutic drug Doxorubicin (DOX) from micelles, was investigated using both 70-kHz and 80-kHz ultrasound at the following power densities: 0.76, 2.389, 2.546, 3.540, 5.013, 5.432, and 5.914 W/cm2. Next, mathematical modeling is applied to capture drug release kinetics from these nanovehicles. The investigated models are zero-order, first-order, Higuchi, Hixon- Crowell, Korsmeyer-Peppas, Weibull, Baker-Lonsdale, and Hopfenberg. Using statistics and the rate constants deduced, the effects of temperature, power density, and micellar type on drug release were investigated. Results showed that the release from folated micelles is slightly higher compared to release from non-folated micelles. This may be due to the conjugation of the folate moiety, which renders the micelles more sensitive to ultrasound (sonosensitive), by reducing their stability. Moreover, an increase in any of the experimental variables (mechanical index, temperature, or power density) leads to an increase in the percent of drug released. Finally, the Higuchi model provided the best fit to the experimental data, which means that the acoustic data available conform to this model’s assumptions and release mechanism. In conclusion, using micelles as drug delivery carriers and ultrasound as a trigger modality may reduce the side effects associated with chemotherapy.College of EngineeringDepartment of Chemical EngineeringMaster of Science in Chemical Engineering (MSChE
Characterization of PM₂̣ ₅ at a Traffic Site Using Several Integrated Analytical Techniques
Get PDFWe have conducted a comprehensive, year-long, sampling campaign for particulate matter (PM) at a site near a major highway, following standard protocols. Total mass, elemental and chemical composition of the fine fractions (PM₂ ̣₅) of particulates originating from traffic are determined using several complementary techniques. These complementary techniques include gravimetric analysis, X-ray fluorescence, scanning electron microscopy and energy dispersive spectroscopy, X-ray diffraction (XRD) and black carbon multiwavelength absorption. Conducting an enrichment factor analysis and correlation coefficient calculations on elements show that Si, Ca, Al, Fe, Ti, Mn, Mg, K, Na and Cr are of crustal origin, while P, Cl and V are enriched slightly from human activities. All other measured elements (Rb, Zr, Ba, Sr, S, Ni, Cu, Zn and Pb) have high enrichment factors and relate to anthropogenic sources. Sulfates in the form of mascagnite and koktaite had the largest contribution to PM₂ ̣₅ (43% of total PM concentration). Natural pollutants such as quartz, calcite, iron oxide and aluminum oxide originating from the crust also contribute to PM₂ ̣₅ eBC and elements such as Zn, Ba, Cu, Fe and S are related to traffic emissions such as exhaust emissions and tire, brakes and road erosion. Correlation coefficients and enrichment factor calculations helped identify elements that are related to natural emissions and those related to anthropogenic sources. Being an arid region, the PM₂ ̣₅ mass concentrations were found to be within or slightly above international air quality standards.American University of SharjahUniversity of Sharja