140 research outputs found

    Exploring double skin façade as strategy for achieving thermal comfort in proposed mixed use office complex Kano, Nigeria

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    Thermal comfort can be defined as a state of mind which a human feels neither too hot nor too cold. Thermal discomfort in the case of hot humid climates, becomes a great threat to our livelihood and thermal comfort in offices in general. The ability of designers to harness and use the building envelope make life much better and livable is of great importance. This research seeks to use Double skin façade as a strategy for improving indoor thermal comfort by testing the air gap between the double skins. Climate and Weather readings were obtained and used to simulate and check the effect of Double skin façade in improving indoor thermal comfort in office complex. Double skin facade has been suggested by many researchers as a possible alternative technique for improving indoor thermal comfort. The double skin facade study in this research involved computer simulation using Emissions Control Optimization TEChnology (ECOTEC). The result of the final base case model shows that double skin façade can increase the indoor thermal comfort in a building and the wider the air gap, the higher the thermal comfort by showing the hours of comfort and discomfort to the simulated office building. The other important factor is that it can continuously induce the flow of natural ventilation, regardless of the available wind outside of the office complex building. This effect is significant toward improving the thermal comfort performance in the office complex through passive natural ventilation

    Phytochemical screening and thin layer chromatographic profile of Nauclea diderrichii leaf extracts

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    The present study investigates the phytochemicals and thin layer chromatographic profile ofNauclea diderrichii (Rubiaceae) leaf extracts. Phytochemical in the hexane, ethyl acetate andmethanol extracts were determined using standard chemical tests. Thin layer chromatographictechniques were carried out using various solvent systems of varying polarity on these extracts.Preliminary phytochemical screening revealed the presence of alkaloids, glycosides, saponins,phenolic compounds, tannins, phytosterols, carbohydrates, flavonoids and terpenoids. Furtherscreening using thin layer chromatographic technique on the N. diderrichii leaf extracts alsorevealed different phytochemical compounds with different Rf values. The results obtained inpresent study indicated that Nauclea diderrichii leaf is a rich source of phytochemicals. This could justifies the use of plant species in traditional medicine for treatment of various diseases.Keywords: Nauclea diderrichii, Rubiaceae Leaf extracts, Phytochemicals, Retention factor, TLC

    Evaluation of Antibacterial Potency of Endophytic Fungi Isolated from Mentha piperita

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    The Mentha piperita is an aromatic perennial herb, a member of the family Lamiaceae (Labiatae) that produces creeping stolons, growing in the range of 45 to 80 cm tall. Fungal endophytes reside in the healthy plant tissues to produce several metabolic products such as plants growth hormones, anti-phagocytes to biological feeding, medicinal ingredients, and many products of biological activities. Hence, they are regarded as a reservoir of active metabolites for the development of novel drugs. Although, many endophytic fungi have been reported from different plants, reports on fungal endophytes from M. piperita are very limited. In this study, fungal endophytes from the leaf and stem of M. piperita were successfully evaluated for their potential antibacterial properties. Healthy leaves of the peppermint were prepared and cultured on potato dextrose agar (PDA) plates for 5 to 7 days at 28 oC until fungal colonies appeared. Fifteen (15) fungal isolates were identified based on cultural and morphological characteristics and had six (6) rapid growing species, namely Aspergillus fumigatus, Rhizopus arrhizus, Aspergillus flavus, Fusarium oxysporum, Aspergillus niger, Alternaria alternate which were selected and evaluated their crude metabolites against c using agar well diffusion method. The susceptibility study showed a remarkable in vitro antibacterial activity of the fungal crude metabolites against all the test bacteria which increased with an increased incubation time of 7, 14 and 21 days incubation. However, the fungi displayed maximal zone of growth inhibition after 21 days of incubation. In conclusion, fungal endophytes were isolated from M. piperita and evaluated in vitro antibacterial activity of their crude metabolites against the test bacterial isolates

    Performance comparison of heuristic algorithms for task scheduling in IaaS cloud computing environment

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    Cloud computing infrastructure is suitable for meeting computational needs of large task sizes. Optimal scheduling of tasks in cloud computing environment has been proved to be an NP-complete problem, hence the need for the application of heuristic methods. Several heuristic algorithms have been developed and used in addressing this problem, but choosing the appropriate algorithm for solving task assignment problem of a particular nature is difficult since the methods are developed under different assumptions. Therefore, six rule based heuristic algorithms are implemented and used to schedule autonomous tasks in homogeneous and heterogeneous environments with the aim of comparing their performance in terms of cost, degree of imbalance, makespan and throughput. First Come First Serve (FCFS), Minimum Completion Time (MCT), Minimum Execution Time (MET), Maxmin, Min-min and Sufferage are the heuristic algorithms considered for the performance comparison and analysis of task scheduling in cloud computing

    A Closer Look at Precision Hard Turning of AISI4340: Multi-Objective Optimization for Simultaneous Low Surface Roughness and High Productivity

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    This article reports an extended investigation into the precision hard turning of AISI 4340 alloy steel when machined by two different types of inserts: wiper nose and conventional round nose. It provides a closer look at previously published work and aims at determining the optimal process parameters for simultaneously minimizing surface roughness and maximizing productivity. In the mathematical models developed by the authors, surface roughness at different cutting speeds, depths of cut and feed rates is treated as the objective function. Three robust multi-objective techniques, (1) multi-objective genetic algorithm (MOGA), (2) multi-objective Pareto search algorithm (MOPSA) and (3) multi-objective emperor penguin colony algorithm (MOEPCA), were used to determine the optimal turning parameters when either the wiper or the conventional insert is used, and the results were experimentally validated. To investigate the practicality of the optimization algorithms, two turning scenarios were used. These were the machining of the combustion chamber of a gun barrel, first with an average roughness (Ra) of 0.4 µm and then with 0.8 µm, under conditions of high productivity. In terms of the simultaneous achievement of both high surface quality and productivity in precision hard turning of AISI 4340 alloy steel, this work illustrates that MOPSA provides the best optimal solution for the wiper insert case, and MOEPCA results are the best for the conventional insert. Furthermore, the results extracted from Pareto front plots show that the wiper insert is capable of successfully meeting both the requirements of Ra values of 0.4 µm and 0.8 µm and high productivity. However, the conventional insert could not meet the 0.4 µm Ra requirement; the recorded global minimum was Ra = 0.454 µm, which reveals the superiority of the wiper compared to the conventional insert

    Seroprevalence of SARS-CoV-2 antibody among individuals aged above 15 years and residing in congregate settings in Dire Dawa city administration, Ethiopia

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    Background Determining the extent of seropositivity of SARS-CoV-2 antibody has the potential to guide prevention and control efforts. We aimed to determine the seroprevalence of SARS-CoV-2 antibody among individuals aged above15 years and residing in the congregate settings of Dire Dawa city administration, Ethiopia. Method We analyzed COVID-19 seroprevalence data on 684 individuals from a community based cross-sectional survey conducted among individuals aged above 15 years and residing in congregate settings in Dire Dawa from June 15 to July 30, 2020. Data were collected using interview and blood sample collection. Participants were asked about demographic characteristics, COVID-19 symptoms, and their practice of preventive measures. Seroprevalence was determined using SARS-CoV-2 IgG test. Bivariate and multivariate multilevel mixed effects logistic regression model was fitted and statistical significance was set at p value < 0.05. Result The estimated SARS-CoV-2 seroprevalence was 3.2% (95 % CI 2.0–4.8) in the study region with no differences by age and sex but considerable differences were observed by self-reported practice of COVID-19 preventive measures. The cluster effect is not significant (P = 0.396) which has suggested no evidence of heterogeneity in SARS-CoV-2 seroprevalence among the clusters. The odds of SARS-CoV-2 antibody seroprevalence were higher for individuals who were employed and work by moving from home to work area (AOR; 9.73 95% CI 2.51, 37.68), reported of not wearing facemasks when leaving home (AOR; 6.4 95% CI 2.30, 17.66) and did not practice physical distancing measures (AOR; 10 95% CI 3.01, 33.20) compared to their counterparts, respectively. Our estimated seroprevalence of SARS-CoV-2 among participants who reported not to have practiced social distancing measures was 12.8 (95% CI, 7.0, 19) and 1.5 (95% CI, 0.5, 2.5) among those who reported of practicing them. More than 80% of study participants reported of implementing infection prevention measures (face masks and physical distancing recommendations). Conclusion The detected SARS-CoV-2 seroprevalence among the study participants was low at the time of the survey indicating higher proportion of population yet to be infected. COVID-19 preventive measures were associated with reduced seroprevalence and should be promoted to avoid transmission to the uninfected majority

    Adhesion characteristics of solution treated environmental dust

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    Environmental dust is modified towards self-cleaning applications under the gravitational influence. Dust particles are collected in the local area of Dammam in Saudi Arabia and they are treated with a dilute hydrofluoric acid solution. The changes in chemical and adhesion characteristics of the dust particles prior and after the solution treatment are analyzed. Force of adhesion and work required to remove dust from hydrophobic and hydrophilic glass surfaces are assessed, separately, for solution treated and collected dust. We show that aqueous hydrofluoric acid solution treatment modifies some dust components while causing the formation of submicron cracks and nano/submicron porous/pillars like textures on the dust particles. The texture generated on dust surfaces after the solution treatment has a great influence on dust adhesion characteristics. Hence, the solution treated dust particles result in lower adhesion on hydrophobic and hydrophilic glass surfaces as compared to that of untreated dust. The gravitational force enables to remove solution treated dust from inclined glass surfaces, which becomes more apparent for hydrophobic surfaces.The study was supported by King Fahd University of Petroleum and Minerals (KFUPM) through Projects# IN171001 and King Abdullah City for Atomic and Renewable Energy (K.A.CARE) to accomplish this work

    Identification and quantification of phenolic compounds in bambangan (Mangifera pajang Kort.) peels and their free radical scavenging activity.

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    Phenolic compounds and antioxidant capacity of acidified methanolic extract prepared from fully ripe bambangan (Mangifera pajang K.) peel cultivated in Sarawak, Malaysia, were analyzed. The total phenolic content (98.3 mg GAE/g) of bambangan peel powder (BPP) was determined by the Folin-Ciocalteu method. BPP showed a strong potency of antioxidant activity and was consistent with that of BHT and vitamin C as confirmed by the DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity and FRAP (ferric-reducing antioxidant power) assays. Gallic acid, p-coumaric acid, ellagic acid, protocatechuic acid, and mangiferin were the major compounds among the 16 phenolics that have been identified and quantified in M. pajang peels with 20.9, 12.7, 7.3, 5.4, and 4.8 mg/g BPP, respectively. Peak identities were confirmed by comparing their retention times, UV-vis absorption spectra, and mass spectra with authentic standards. The 16 phenolic compounds identified in M. pajang K. using HPLC-DAD and TSQ-ESI-MS are reported here for the first time
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