19672 research outputs found
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Effect of Aspect Ratio on Natural Convection in a Porous Wavy Cavity
No full textThe present study analyzes natural convective flow and heat transfer in a wavy cavity saturated with porous medium. The sidewalls of the cavity are maintained at constant temperatures where higher temperature is applied on the vertical left wall while the wavy right wall is cooled at a lower temperature. The remaining top and bottom walls are taken to be adiabatic. The Darcy model is adopted for the fluid flow through the porous medium. The governing equations and boundary conditions are solved using the finite difference method over a range of cavity aspect ratios, wavy wall amplitudes, number of undulations and Darcy–Rayleigh numbers. The waviness of the cavity enhances the heat transfer inside the cavity, and the heat transfer rate is more enhanced when the aspect ratio of the cavity is close to 1. The study is applicable to the design of solar heating systems and geothermal reservoirs
Enhancing biomass and lipid productions of microalgae in palm oil mill effluent using carbon and nutrient supplementation
No full textMicroalgae are a promising feedstock for biofuel generation. Economical and effective mass cultivation is essential for greater feasibility in microalgal-based biofuel full applications. The present study reported on cultivation of Chlorella sorokiniana CY-1 in palm oil mill effluent (POME) under photoautotrophic and mixotrophic cultivation. Enhancement of biomass and lipid productions were carried out by using glucose, urea and glycerol supplementations. Mixotrophic cultivation was more effective than photoautotrophic condition. Glycerol addition exhibited greater microalgae growth performance compared to supplementing glucose or urea. Biomass (1.68 g L−1) and lipid (15.07%) production were highest in POME medium with combinations of 200 mg L−1 urea, glucose and glycerol supplementation. Chlorella sorokiniana CY-1 grown in POME with glucose and glycerol supplementation gave considerably comparable yields as in all supplements-added POME medium. Ideal fatty acids compositions shown in urea and glycerol supplemented-POME medium though lower biomass production obtained. The pollutant remediation efficiencies attained were 63.85% COD, 91.54% TN and 83.25% TP in all supplements-added medium. The estimated net energy ratio was 0.55 and nutrient cost could be reduced up to 76%. Cheap and effective carbon and nutrients supplementation is essential to minimize the economic impact and maximize yields in commercial scale microalgae cultivation for biofuel production and environmental sustainability
Waste to energy: the effects of Pseudomonas sp. on Chlorella sorokiniana biomass and lipid productions in palm oil mill effluent
No full textMicroalgae are recognised as promising feedstock for biofuel production. The feasibility in commercial scale microalgae cultivation could be enhanced by incorporating palm oil mill effluent (POME) as culture medium, for greater biomass growth and lipid production, together with POME bioremediation. The polluting POME is generated massively in Malaysia. POME contains high concentrations of carbon and nutrients, thus it is suitable to be applied for microalgae cultivation. The approach on waste to energy should be advanced. We studied the effects of applying Pseudomonas sp. on Chlorella sorokiniana CY-1 cultivation in POME. Pseudomonas sp. was found effective in POME decolourisation prior to C. sorokiniana CY-1 cultivation. Yet, microalgae biomass and lipid productions were higher in the non-decolourised POME. Pseudomonas sp. was as well-being co-cultivated with C. sorokiniana CY-1 in ratios of microalgae versus bacteria of 1:1; 2:1 and 1:2. Biomass of 2.04 g L−1 and biomass productivity of 185.71 mg L−1 d−1 were attained in ratio of 1:1. Interestingly, the lipid content exhibited was excellent (16.04%), and about twofold higher than other ratios and the control (without bacteria). Fatty acids compositions were dominated by C16:0 (32.49%), C18:1 (24.06%) and C18:2 (20.28%), which were desirable fatty acids for biodiesel production. Effective POME bioremediation achieved with chemical oxygen demand, total nitrogen and total phosphorus removal of 53.7, 55.6 and 77.3%, respectively. Co-cultivation of microalgae and bacteria can be applied in the POME treatment plant. This allows satisfactory biomass and excellent lipid yields for biofuel production, as well as effective wastewater bioremediation
Troponin T monitoring to detect myocardial injury after noncardiac surgery: a cost–consequence analysis
No full textBackground: Myocardial injury after noncardiac surgery (MINS) is a mostly asymptomatic condition that is strongly associated with 30-day mortality; however, it remains mostly undetected without systematic troponin T monitoring. We evaluated the cost and consequences of postoperative troponin T monitoring to detect MINS. Methods: We conducted a model-based cost-consequence analysis to compare the impact of routine troponin T monitoring versus standard care (troponin T measurement triggered by ischemic symptoms) on the incidence of MINS detection. Model inputs were based on Canadian patients enrolled in the Vascular Events in Noncardiac Surgery Patients Cohort Evaluation (VISION) study, which enrolled patients aged 45 years or older undergoing inpatient noncardiac surgery. We conducted probability analyses with 10 000 iterations and extensive sensitivity analyses. Results: The data were based on 6021 patients (48% men, mean age 65 [standard deviation 12] yr). The 30-day mortality rate for MINS was 9.6%. We determined the incremental cost to avoid missing a MINS event as 1309). Conclusion: The costs associated with a troponin T monitoring program to detect MINS were moderate. Based on the estimated incremental cost per health gain, implementation of postoperative troponin T monitoring seems appealing, particularly in patients at high risk for MINS
A Qualitative Study of Young Men Who Have Sex With Men and Multilevel Factors Related to HIV Risks in Malaysia
No full textYoung men who have sex with men (YMSM) are a group at high risk for HIV infection, yet no research has been conducted to understand this population in Malaysia. Semistructured interviews from a combination of YMSM aged 18–25 (n = 20) and local service providers of sexual health services (n = 4) were conducted from May to June 2015. Thematic analysis was used to identify common themes in participant responses from transcripts. Participants reported societal and internalized homophobia, an absence of sex education and difficulty accessing confidential HIV testing. This study provides insights into how homophobia in Malaysian society influences individual risk behavior for HIV in Malaysian YMSM, and makes practical suggestions for more effective HIV prevention in this population
Modelling the information-seeking behaviour of international students in their use of social media in Malaysia
No full textIntroduction. The understanding of the information-seeking behaviour of international students using social media is limited. Therefore, the purpose of this research is to model the information-seeking behaviour of international students when they use social media to find information. Method. A mixed method approach was employed to collect data from the literature. Semi-structured interviews were conducted with twenty international students of different demographic backgrounds and with eleven staff members who work with international students. Questionnaires were distributed to 205 international students from four universities in Malaysia. Analysis. Using the literature review and empirical data, we propose a model of the information-seeking behaviour of international students who use social media, as validated and verified from the questionnaire. Results. The information-seeking activities were identified as informal searching, deciding, interacting, following, verifying and saving. The sources were search engines, social media and face-to-face settings. However, social media are more dominant than search engines and face-to-face communication. The questionnaire validated the proposed model and demonstrated that demographic variables exert a significant effect on the information-seeking behaviour of international students as they use social media. Conclusion. This research enhances the previous models of information-seeking behaviour by adding the role of social media and provides valuable insights for international students, universities and higher-education institutions
Synthesis of Bimetallic Gold-Silver (Au-Ag) Nanoparticles for the Catalytic Reduction of 4-Nitrophenol to 4-Aminophenol
No full textBimetallic gold-silver nanoparticles as unique catalysts were prepared using seed colloidal techniques. The catalytic capabilities of the nanoparticles were ascertained in the reduction of 4-nitrophenol to 4-aminophenol in the presence of sodium borohydride. Our results clearly showed that the rate of 4-NP reduction to 4-AP increased with a corresponding decrease in the diameter of the bimetallic NPs. The Au-Ag nanoparticles prepared with 5.0 mL Au seed volume indicated higher reduction activity, which was approximately 1.2 times higher than that of 2.0 mL Au seed volume in the reductive conversion of 4-NP to 4-AP. However, the monometallic NPs showed relatively less catalytic activity in the reductive conversion of 4-NP to 4-AP compared to bimetallic Au-Ag nanoparticles. Our studies also reinforced the improved catalytic properties of the bimetallic Au-Ag nanoparticles structure with a direct impact of the size or diameter and relative composition of the bimetallic catalytic nanoparticles
Tailoring electronics structure, electrical and magnetic properties of synthesized transition metal (Ni)-doped ZnO thin film
No full textImproving Zinc Oxide (ZnO) conductivity is in dire need due to its major shortcoming of high resistivity as a result of low carrier concentration. In this work, ZnO was doped with a transition metal, Nickel (Ni) in different concentrations (1 mol%, 2 mol%, 3 mol%, and 4 mol%) and the influence of Ni concentrations in ZnO thin film in term of electrical, electronic structure as well as magnetic properties were investigated. ZnO thin films with Ni-doping were successfully produced via a sol-gel spin coating method. High-Resolution Transmission Electron Microscopy (HR-TEM) image observed for 3 mol% Ni:ZnO thin film shows clear and coherent lattice fringes in hexagonal shape with the amorphous structure inside. The resistivity of Ni:ZnO films show to decrease with the addition of Ni-doping down to 1.7 × 10−1 Ω cm, whilst the conductivity and the carrier concentration improved from 0.28 Sm-1 to 5.87 Sm-1 and 2.23 × 1014 cm−3 to 485.14 × 1014 cm−3 respectively. Thermal dependence activation energy (Ea) of ZnO thin film is found to be 1.3 eV and increases up to 15.1 eV above 373 K. X-ray Photoemission Spectroscopy/Ultraviolet Photoemission Spectroscopy (XPS/UPS) spectra indicate that Ni-doped ZnO induced more surface defects and native defects in the ZnO system. In addition to that, photoluminescence spectra show that Vo and Zni induced shallow donor in the system. Finally, via Vibrating Sample Magnetometery (VSM) measurement, it is revealed that the ferromagnetism of Ni:ZnO might be induced by the co-existence of Vo and Zni defects. These results may open an attractive path to tailor Ni-doping in ZnO system to act as potential candidates for the optoelectronic and spintronic applications
Reduced red blood cell deformability in Plasmodium knowlesi malaria
No full textThe simian parasite Plasmodium knowlesi can cause severe and fatal human malaria. However, little is known about the pathogenesis of this disease. In falciparum malaria, reduced red blood cell deformability (RBC-D) contributes to microvascular obstruction and impaired organ perfusion. In P knowlesi infection, impaired microcirculatory flow has been observed in Macaca mulatta (rhesus macaques), unnatural hosts who develop severe and fatal disease. However, RBC-D has not been measured in human infection or in the natural host M fascicularis (long-tailed macaques). Using ektacytometry, we measured RBC-D in adults with severe and non-severe knowlesi and falciparum malaria and in healthy controls. In addition, we used micropipette aspiration to determine the relative stiffness of infected RBCs (iRBCs) and uninfected RBCs (uRBCs) in P knowlesi-infected humans and M fascicularis Ektacytometry demonstrated that RBC-D overall was reduced in human knowlesi malaria in proportion to disease severity, and in severe knowlesi malaria, it was comparable to that of severe falciparum malaria. RBC-D correlated inversely with parasitemia and lactate in knowlesi malaria and HRP2 in falciparum malaria, and it correlated with hemoglobin nadir in knowlesi malaria. Micropipette aspiration confirmed that in humans, P knowlesi infection increased stiffness of both iRBCs and uRBCs, with the latter mostly the result of echinocytosis. In contrast, in the natural host M fascicularis, echinocyte formation was not observed, and the RBC-D of uRBCs was unaffected. In unnatural primate hosts of P knowlesi, including humans, reduced deformability of iRBCs and uRBCs may represent a key pathogenic mechanism leading to microvascular accumulation, impaired organ perfusion, and anemia
Transformation of biomass into carbon nanofiber for supercapacitor application – A review
No full textThis paper starts with a review on challenges and need of improved supercapacitor application, which is then followed by advantages of biomass compared with other materials for use in supercapacitor application. The conversion of biomass into carbon nanofiber using different techniques was extensively reviewed for its advantages and limitations. It was revealed that the materials currently used are yet to be fully sustainable or feasible for energy storage application. In contrast, biomass represents a widely available and sustainable material to be converted into carbon nanofiber for energy storage application. Different techniques were employed for carbon nanofiber production to achieve different objectives, comprising high product yield, feasible diameter adjustment, low electric consumption, and shorter production time. Nevertheless, it was revealed that many key properties of the biomass-derived carbon nanofiber have yet to be fully investigated, as there are still knowledge gaps to be filled for each technique. Thus, more studies are needed to broaden the existing understanding in the key parameters of different techniques in order to develop a highly desirable carbon nanofiber from biomass for sustainable energy storage application