In this study a 2D cubic chamber model filled with paraffin is analyzed with and without the inclusion of magnetic Fe3O4 nanoparticles at concentrations of 0.5, 1, 1.5 and 2 wt%, and an external magnetic field of intensities 0.005, 0.01, 0.015 and 0.02 T. It is ascertained that adding magnetic nanoparticles leads the horizontal temperature gradient to be reduced owing to increments in thermal conductivity. Additionally, this feature is found to be accelerated by applying an external magnetic field, which shapes highly conductive cluster formations of nanoparticles. However, since the increase in nanoparticle concentration and magnetic intensity increases the composite viscosity, there is an optimum configuration while applying both schemes. As such, the addition of 1 wt% nanoparticles provides the best results, as the melting time is reduced up to 25% compared to pure paraffin. Meanwhile, the melting time of a 1 wt% nanoparticle-containing phase change material (PCM) in the presence of an external magnetic field is improved up to 24% compared to the case with no external magnetic field. Also, the heat transfer coefficient of a 1 wt% nanoparticle-containing PCM both with and without an external magnetic field is also staggeringly enhanced compared to pure paraffin. Good correspondence with experimental data was achieved.
Dependence of the linear discriminant analysis on location and scale weakens its performance when predicting class under the presence of homogeneous covariance matrices for the candidate classes. Further, outlying samples render the method to suffer from higher rates of misclassification. In this study, we propose the minimization approximation cost classification (MACC) method that accounts for some specific cost function 23.9. The theoretical derivation is made to find an optimal linear hyperplane θ, which yields maximum separation between the dichotomous groups. Real-life data and simulations were used to validate the method against the standard classifiers. Results show that the proposed method is more efficient and outperforms the standard methods when the data are crowded at the class boundaries.
ABSTRACT Aflatoxin contamination in food commodities is a major food safety concern all over the world. These aflatoxins are a group of carcinogenic secondary metabolites produced by some fungi belonging to Aspergillus section Flavi. To minimize the level of aflatoxins in food commodities, a wide range of preand post-harvest procedures have been employed. In this study, aqueous extracts of 13 medicinal herbs were assessed for their ability to detoxify aflatoxin B1 (AFB1), the most potent and commonly occurring carcinogen in foods. Among them, herbal extracts of Hybanthus enneaspermus, Eclipta prostrata and Centella asiatica exhibited over 70% detoxification of AFB1. The degradation of AFB1 upon treatment with these herbal extracts was confirmed by liquid chromatography–mass spectrometry analysis. Two fractions (Rf 0.75 and 0.87) purified from H. enneaspermus by using thin-layer chromatography displayed in vitro AFB1-detoxifying properties. Gas chromatography–mass spectrometry analysis of the active fractions revealed the presence of linalool and bornyl acetate as the major components suggesting possible involvement of volatile compounds of H. enneaspermus in the detoxification of AFB1. To our knowledge, this is the first report on the detoxification of AFB1 by H. enneaspermus, E. prostrata and C. asiatica aqueous extracts.
The Education and Learning Capital Model (ELCM), based on the Actiotope Model of Giftedness was used as a framework to explain the current practices dedicated to serve gifted education. This article addresses the status quo of gifted education in Oman according to the ELDM. The model comprised ten components including action learning capital, economic education capital, cultural education capital, social educational capital, infrastructure education capital, organismic learning capital, telic learning capital, episodical learning capital, and attentional learning capital. Questions related to these ten elements were answered by analyzing reports from the Ministry of Education (MoE) and royal decrees that serve the education of gifted students. Also, interviews were conducted with gifted students, teachers, and administrators, and parents of gifted students to consolidate the answers to the ten questions based on the ELCM. The article concluded with some recommendations and suggestions of supporting gifted education in Oman.
Single-phased Ru3+-doped LaFeO3 nanocrystalline particles (6-70 nm), with nominal compositions of LaFe1-xRuxO3 (x = 0.00, 0.015, 0.03, 0.05 and 0.08), were prepared using mechano-synthesis at temperatures that are ca. 400 °C- 700 °C lower than those used to synthesize cation-doped LaFeO3 conventionally. The Ru3+ ions are found to substitute exclusively for the Fe3+ ones at the octahedral sites of the perovskite-related structure. The lattice parameters of all samples are suggestive of a weak Jahn-Teller-like distortion as opposed to the normal distortion of orthorhombic perovskites. 57Fe Mössbauer measurements for all samples show the Fe3+ ions to be in high-spin state implying that the observed lattice distortion is due to particle-size surface-induced disorder rather than the electronic degeneracy associated with the normal Jahn-Teller distortion. The decrease in the Mössbauer hyperfine magnetic fields with increasing Ru3+ content is attributed mainly to particle size reduction rather than the cationic substitution of Fe3+ by the Ru3+. A monotonic decrease of the optical band gap from 2.17 eV (x = 0.00) to 1.79 eV (x = 0.08) was observed, revealing how doping with Ru3+ affects the optical absorption of the LaFeO3 nanoparticles.
Background Unilateral otitis media with effusion in adult patient is considered alarming finding needing a detailed examination of the nasopharynx. The lesions in this area ranged from benign to more destructive malignant pathologies. Lipoma as a cause of obstruction is an extremely rare entity. We are reporting a case of eustachian tube lipoma presented with refractory otitis media with effusion. This is an extremely rare location of such entity and to the best of our knowledge, this is the third case reported in the world literature of eustachian tube lipoma after 2 cases published in 2011 and 2016 respectively. However, this is the first case reported in the literature of eustachian tube sialolipoma. Case presentation We are reporting a 27-year-old male who presented to our outpatient department with a complain of unilateral ear block, hearing loss, and intermittent tinnitus. Clinical evaluation revealed unilateral otitis media with effusion that was confirmed by pure tone audiogram and tympanometry. Computed tomography and magnetic resonance imaging were obtained showed a lesion originating in the eustachian tube area protruding in the nasopharynx. Surgical removal was successful with complete recovery. Conclusions Unilateral otitis media with effusion necessitate nasal endoscopic examination to rule-out lesions at the nasopharynx. This is the first case of sialolipoma in eustachian tube in the literature. Endoscopic removal is usually successful with uneventful short recovery period.
This study aims to review the concept of constructability and evaluate the level of implementation of constructability practices in the construction industry in Muscat Governorate. One hundred and ninety questionnaires were distributed, and 85 complete responses were received, including 10 from owners (12%), 64 from consultants (75%) and 11 from the contractors (13%). The results showed that owners, consultants, and contractors recognize, support, and practice constructability efforts. 45% of the respondents said that constructability efforts typically begin in preconstruction planning, which shows a positive awareness that constructability efforts must start at the earliest stage of a project’s life cycle. In addition, 60% of the respondents indicated that they performed constructability by following a constructability procedure during the design stage. All the respondents agreed that constructability implementation obstacles continued to exist in construction projects in Muscat and the cost and time associated with the implementation of constructability review practices are the most dominant obstacles. Although constructability has been recognized in Muscat’s construction industry, the level of constructability awareness and improvement in cost and time estimation and quality requirements are developing.
The total annual emission due to fossil fuel and agro waste stubble burning is 36.73 teragrams CO2 equivalent. Many international organizations focus on alternative energy sources such as biofuel production. In the recent past, biofuel production has gathered pace and increased dramatically, with the USA and Brazil topping the list for bioethanol production. Recent advancements in pre-treatment technologies include the use of ionic liquids and deep eutectic solvents. In this review, many recent advancements on pre-treatment technology of biomass have been discussed. This review also emphasizes on the recent advancements made in the field of saccharification technology. Bioethanol production from cellulosic biomass is facilitated by a complex set of enzymes mainly endoglucanase, exoglucanase and ß-glucosidase apart from other auxillary enzymes and accessory protiens. In this review, multiple approaches have been explored which enhance biofuel production such as developing cellulose degrading microbial consortia and genetically modified microbes. This study also highlights the importance of bioethanol production with reference to climate change concerns, advances in technologies and future perspectives.
Owing to the necessity of precise calculations in gas hydrates systems comprised of novel environmentally friendly materials such as natural amino acids (NAAs), as well as their blends with ionic liquids (ILs), alcohols, and salts, the present study reports a new method concerning the water activity computation coupled with the van der Waals-Platteeuw (vdW-P) model. The developed activity model consists of two terms, namely Free-Volume modification of the Flory-Huggins (FVFH) equation taking into account the molecular (short-range) interactions, and the extended Debye-Hückel (EDH) equation considering the ionic (long-range) interactions. The model's performance is then assessed against a comprehensive databank (11 NAAs, 9 blends, 475 data points) collected from open literature and data of 3 gaseous hydrate formers (CH4, CO2, and natural gas). The overall deviation of the determined gas hydrates dissociation temperatures for the whole databank is found to be 0.40 K (0.14%), while the most significant individual deviation does not exceed 1.76%, proving the remarkable performance of the developed calculation procedure. Not only does not the model benefit from parameter regression, but it also offers accurate predictions in the complex systems of the inhibitors’ blends. When NAAs are employed solely (409 data points), the deviations of the model results from real data of gas hydrates dissociation temperatures are 0.39 K. On the other hand, in the presence of NAAs mixtures with ILs, alcohols, and salts (66 data points), which represent highly complex systems, the deviation is 0.41 K.
Such a significant standpoint is the development of environmentally safe materials that any improvement in this regard is currently state of the art. Accordingly, this study aims to develop a precise calculation procedure based on solution thermodynamic regulations to determine hydrate dissociation conditions in the complex systems comprised of gaseous hydrate formers and sugar-derived materials aqueous solutions. The developed methodology employs free-volume modification of the Flory-Huggins model for water activity calculation and then modified van der Waals-Platteeuw approach for hydrate dissociation conditions modeling in the intended systems. To this end, 29 systems of 11 hydrate formers, 11 sugar-derived compounds, and 528 data points are appraised, the results of which indicate the AARDs (%) of 0.13 (AAD = 0.35 K) and 4.66 (AAD = 0.15 MPa) in predicting hydrate dissociation conditions when the best strategy is employed to determine interaction parameters. The impressive performance of the method in representing the experimental data of the hydrate systems is reflected in the accomplishment of accurate water activity calculation. Green hydrate inhibition strategy and enriching sugar-derived products are the systems that can benefit from the achievements of this study.
Fossil fuels comprising coal, crude oil, and natural gas are non-renewable and greatly harmful to the environment. Hydrogen, on the other hand, is both sustainable and environmentally friendly. However, due to its light weight and gaseous nature, it presents challenging problems of its storage, and the practical hydrogen storage is perhaps the biggest hurdle in the success of the hydrogen economy on a large scale. Hydrogen can be stored in a variety of physical and chemical methods. Each storage technique has its own advantages and disadvantages. It is the subject of this study to review the hydrogen storage strategies and to survey the recent developments in the field.
Model analysis for piperazine (PZ) activated sodium sarcosinate (Na-Sar) for CO2 capture and sequestration for environmental sustainability is challenging and required in-depth analysis. Here, we performed experiments and developed a model for correlating physical properties such as density, refractive index, surface tension, and viscosity of PZ activated Na-Sar for CO2 capture. Physical properties were investigated at different temperatures from 298.15 to 333.15 K and different mass fractions (w1 + w2) of aqueous blends of PZ + Na-Sar were used (0.02 + 0.10, 0.05 + 0.10, 0.10 + 0.10, 0.02 + 0.20, 0.05 + 0.20, 0.10 + 0.20, 0.02 + 0.30, 0.05 + 0.30, and 0.10 + 0.30). All physical properties decreased as temperature increased; however, as PZ in Na-Sar solutions increased, physical properties tended to increase. Refractive index, density, and surface tension showed a linear relationship, while viscosity showed an exponential behavior with the temperature. Empirical correlations were established for all measured properties as a function of temperature and solvent concentration. The correlations showed that the experimentally measured and correlated values were in good agreement. These properties are not available in the literature and are important for the designing of gas–liquid absorption systems. This work can be a useful contribution towards the global efforts to mitigate CO2 from various industrial streams.
We enriched several bacterial consortia from oilfield samples and investigated them for heavy crude oil biocatalytic upgrading potential. SARA (Saturates, Asphaltenes, Resins, Aromatics) analysis of heavy oil treated with one bacterial consortium (designated as 5C) revealed up to 127% increase in the saturates fraction, accompanied by 54% decrease in the aromatics fraction. The asphaltene content was reduced by 52% and the resins increased by 87%. SimDist analysis revealed a better average recovery of fractions from the biotreated oil (up to 86%) compared to the non-treated oil (71%), and the biotreated oil from one culture was fully recovered. While Ni and V contents were mostly higher (up to 125%) in the biotreated oil compared to untreated controls, sulfur content marginally dropped (up to 3.5%) after biotreatment. Illumina-MiSeq amplicon sequencing uncovered source-dependent variations in the composition of the bacterial consortia, with Proteobacteria, Actinobacteria, Bacteroidia and Bacilli as the most abundant in all cultures (≥98.7% of total sequences). The structure of the bacterial consortia shifted with time, revealing different members potentially involved in the bioupgrading process. In the 5C culture, Achromobacter and Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium appeared to be key players. It can be inferred that biocatalytic hydrocarbon redistribution in the biotreated oil improved distillation efficiency.
This study identified distinctive profiles of Omani teachers related to their motivation to leave the teaching (MLT) occupation and estimated differences in teachers’ job satisfaction across the estimated profiles. Data on 1625 Omani teachers were analyzed using unconditional and conditional latent profile analysis. The results revealed three latent profiles, including (1) quitters (i.e., teachers with a high level of MLT), (2) moderately engaged teachers (i.e., teachers with a moderate level of MLT), and (3) highly engaged teachers (i.e., teachers with a low level of MLT). Gender and two particular age groups significantly predicted profile membership, allowing for the identification of the characteristics of teachers within each profile.
This study evaluates the effect of renewable, non-renewable energy consumption and economic growth on unemployment rate across 51 US states over the period 1977–2017. We applied a fixed effect model and a Seemingly Unrelated Regression Equations (SURE) model, which allows for an unknown form of cross-sectional dependence and slope heterogeneity. While the results of the fixed effects model indicate the negative and positive effects of non-renewable and renewable energy consumption on the unemployment rate, respectively, mixed results were received by employing SURE model at the state level. By allowing for slope heterogeneity, the results of the SURE model confirm that the non-renewable and renewable energy consumption only have job-creating effects in 19 and 6 out of 51 states, respectively. The renewable energy consumption has pro-unemployment effect in 20 states.
This paper examines the quantile relationships between the Saudi Riyal (SAR) exchange rate pressure, CDS spreads, total reserve assets, and oil prices. Using the available monthly data ranging from 2008 to 2018, and employing the error correction model, the results show a negative and significant relationship between the long-run coefficient of the SAR exchange rate pressure and the long run coefficients of both the CDS and the oil price. However, the long run coefficient of the foreign reserves is statistically insignificant, thus indicating that exchange rate pressure, CDS spread and oil price variables are cointegrated. As for the short-run coefficients, we find that the lag SAR pressure affects the current pressure. Moreover, the short-run coefficient of the foreign reserves affects negatively the SAR pressure. Using the quantile ARDL (QARDL) model, we find a significant relationship particularly in the extreme quantiles, regardless of the level or the log level series. Under the long-run coefficients, the positive (negative) relationship characterizes the nexus of the reserves-pressure and the oil-pressure (oil pressure). As for the short-run coefficients, we find that an increase in the lag SAR pressures contributes to the current pressure across all quantiles, whereas an increase in the reserves reduces the pressure in the extreme quantiles. These results have important implications for policy makers.
The G7 countries consist of some of the world's most developed nations which have economically flourished over the years. However, alongside such robust economic performances, the environmental qualities in these countries have rather aggravated to raise deep concerns among the stakeholders. Hence, this study is designed to empirically examine the environmental effects of nuclear and renewable energy consumption, economic complexity, and economic growth in the G7 countries for the period between 1995 and 2016. To ensure novelty, this study considers carbon footprints along with carbon dioxide emissions to measure environmental quality in the context of the G7 nations. The results reveal that although nuclear energy consumption is effective in mitigating carbon dioxide emissions and carbon footprints in the long run, renewable energy consumption degrades the environment in the G7 countries. Besides, the results also reveal that the G7 countries can transform their production processes in an environmentally friendly manner provided they can undergo a clean transition in energy use. Finally, economic growth is evidenced to be detrimental for the environment since higher economic growth levels are seen to boost both carbon dioxide emission and carbon footprint levels. Therefore, in line with the findings, this study recommends the G7 countries to significantly enhance their nuclear and renewable energy consumption levels, increase their economic complexity indices, and integrate environmental welfare policies within their economic growth strategies.
In this paper, we are concerned with a nonmatching grid mixed finite-elements–finite-differences approximation (FEM-FD) method of overlapping nonlinear multiplicative Schwarz iterations for nonlinear elliptic PDEs. By means of a geometric convergence result in L∞ for the nonlinear Schwarz iterations and a Lipschitz property with respect to the data of both the FEM and FD solutions of the corresponding linear PDE problems, we derive an L∞ error estimate on each subdomain between the discrete nth Schwarz iterate and the true solution of the nonlinear PDE.
Biocrusts covering drylands account for major fractions of terrestrial biological nitrogen fixation and release large amounts of gaseous reactive nitrogen (Nr) as nitrous acid (HONO) and nitric oxide (NO). Recent investigations suggested that aerobic and anaerobic microbial nitrogen transformations occur simultaneously upon desiccation of biocrusts, but the spatio-temporal distribution of seemingly contradictory processes remained unclear. Here, we explore small-scale gradients in chemical concentrations related to structural characteristics and organism distribution. X-ray microtomography and fluorescence microscopy revealed mixed pore size structures, where photoautotrophs and cyanobacterial polysaccharides clustered irregularly in the uppermost millimeter. Microsensor measurements showed strong gradients of pH, oxygen, and nitrite, nitrate, and ammonium ion concentrations at micrometer scales in both vertical and lateral directions. Initial oxygen saturation was mostly low (∼30%) at full water holding capacity, suggesting widely anoxic conditions, and increased rapidly upon desiccation. Nitrite concentrations (∼6 to 800 μM) and pH values (∼6.5 to 9.5) were highest around 70% WHC. During further desiccation they decreased, while emissions of HONO and NO increased, reaching maximum values around 20% WHC. Our results illustrate simultaneous, spatially separated aerobic and anaerobic nitrogen transformations, which are critical for Nr emissions, but might be impacted by future global change and land management.
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