19672 research outputs found
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Immobilization of cross-linked tannase enzyme on multiwalled carbon nanotubes and its catalytic behavior
No full textImmobilization of cross-linked tannase on pristine multiwalled carbon nanotubes (MWCNT) was successfully performed. Cross-linking of tannase molecules was made through glutaraldehyde. The immobilized tannase exhibited significantly improved pH, thermal, and recycling stability. The optimal pH for both free and immobilized tannase was observed at pH 5.0 with optimal operating temperature at 30°C. Moreover, immobilized enzyme retained greater biocatalytic activities upon 10 repeated uses compared to free enzyme in solution. Immobilization of tannase was accomplished by strong hydrophobic interaction most likely between hydrophobic amino acid moieties of the glutaraldehyde-cross-linked tannase to the MWCNT
Investigation of cerium-139 radioisotope adsorption by conducting polymer composite
No full textCerium is an abundant rare earth element, with several stable and radioactive isotopes. Due to its numerous industrial applications, cerium radioisotopes are common components of liquid radioactive wastes. We investigated the removal of 139Ce radionuclide from wastewater by adsorption using composite of polypyrrole with wood sawdust, as a model for other cerium radioisotopes. The composite material was characterized by Brunauer–Emmett–Teller, field emission scanning electron microscopy and Fourier transform infrared spectroscopy techniques. Effects of pH, initial ion concentration and temperature on the uptake amount of 139Ce were investigated by batch adsorption. The results indicated that the uptake amount of cerium ion increased with a rise in pH to optimum value of 8.0 and contact time of 120 min. The pseudo-second-order kinetics was found to best fit the kinetic data, while the isotherm data showed a good fit to both the Langmuir and Freundlich models. The maximum sorption capacity of 6.57 ± 0.54 mg/g was estimated by the Langmuir model. Thermodynamic studies indicated that the adsorption is feasible, spontaneous and endothermic in nature. The radiation hardness of polymer composite was also investigated by exposing it to 60Co gamma source. Irradiation had practically no significant effect on the sorption performance of as-prepared polymer composite
A Novel Diamond Ring Fiber-Based Surface Plasmon Resonance Sensor
No full textWe propose a highly sensitive novel diamond ring fiber (DRF)-based surface plasmon resonance (SPR) sensor for refractive index sensing. Chemically active plasmonic material (gold) layer is coated inside the large cavity of DRF, and the analyte is infiltrated directly through the fiber instead of selective infiltration. The light guiding properties and sensing performances are numerically investigated using the finite element method (FEM). The proposed sensor shows a maximum wavelength and amplitude interrogation sensitivity of 6000 nm/RIU and 508 RIU−1, respectively, over the refractive index range of 1.33–1.39. Additionally, it also shows a sensor resolution of 1.67 × 10−5 and 1.97 × 10−5 RIU by following the wavelength and amplitude interrogation methods, respectively. The proposed diamond ring fiber has been fabricated following the standard stack-and-draw method to show the feasibility of the proposed sensor. Due to fabrication feasibility and promising results, the proposed DRF SPR sensor can be an effective tool in biochemical and biological analyte detection
Fragility Curves of Regular and Irregular Moment-Resisting Concrete and Steel Frames
No full textThis study presents the fragility curves of regular and irregular moment-resisting frames using different heights, materials, and ground motion records. The concrete and steel frames used in this study differed in terms of height, namely, 3, 6, and 9 stories. Each type of frame was designed based on Eurocode 2 and Eurocode 3 with the aid of Eurocode 8 for earthquake loading. Incremental dynamic analysis (IDA) was conducted for the three selected ground motion records using SAP2000 software as the main tool. The IDA curves were compared to the five levels of the limit state of FEMA 356: operational phase (OP), immediate occupancy, damage control, life safety, and collapse prevention (CP). Based on the analysis of fragility curves, irregular frames exhibited a higher probability of reaching OP and CP levels compared with regular frames
Demarcation energy properties of regenerated fiber Bragg grating sensors in few-mode fibers
No full textIn this work, thermal regeneration of fiber Bragg gratings inscribed in single-mode fibers, two-mode step index fibers and four-mode step index fibers is performed, where the single-mode fibers are used as the reference in the analysis. Specifically, we investigate the behavior of the thermal decay, recovery and eventually the permanent erasure of the gratings in the temperature range from 25 to 1300°C. In the domain of demarcation energy, the thermal responses of the gratings can be normalized and they share similar characteristic curves despite the different temperature ramping rates used in the annealing treatment. It is found that the demarcation energy at the regeneration point and the attempt-to-escape frequency for each grating can be associated with the confinement factors of the fibers. The finding in this work has provided a new insight in the manufacture of regenerated fiber Bragg grating sensors by using few-mode fibers for multiparameter sensing in high temperature environments
The effect of 10 days of intermittent fasting on Wingate anaerobic power and prolonged high-intensity time-to-exhaustion cycling performance
No full textMany physically active individuals have undertaken intermittent fasting to reduce their daily caloric intake. However, abstaining from meals for a specific length of time may lead to the acute disturbance of highly carbohydrate-dependent exercise performance. The purpose of this study was to observe the effect of 10 days of intermittent fasting on high-intensity type exercises, Wingate anaerobic (WT) and prolonged high-intensity time-to-exhaustion (HIT) cycling test. Twenty participants were randomised into an intermittent fasting (FAS) and a control group (CON). One day after baseline data collection on Day-0 where participants consumed their recommended daily caloric intake (FAS = 2500 ± 143 kcal day−1; CON = 2492 ± 20 kcal day−1) served over a course of five meals, the FAS group consumed only four meals where 40% was restricted by the omission of lunch (FAS = 1500 ± 55 kcal day−1). This diet was then continued for 10 days. Data on exercise performance and other dependent variables were collected on Day-2, -4, -6, -8 and -10. A reduction in WT power in the FAS group was observed on Day-2 (821.74 ± 66.07 W) compared to Day-0 (847.63 ± 95.94 W) with a moderate effect size (p <.05, ES = 0.4), while HIT time-to-exhaustion performance declined over the 10 days with a trend of recovery from a large to a minimum effect size (p <.05, ES = 0.8–0.3). Body weight and triglyceride were consistently reduced in the FAS group (p <.01). The present study suggests that intermittent fasting must exceed 10 days to ensure that high-intensity performance does not deteriorate because this length of time seems to be required for effective adaptation to the new dietary regimen
Effect of the Poly L-lactic Acid Coating on the Corrosion of Magnesium in Hank's Solution
No full texto control the corrosion rate, the Magnesium (Mg) was coated with poly (l-lactic acid) (PLLA) using electrospinning technique. The effectiveness of the PLLA coating on the high purity Magnesium (HP Mg) and alloy AZ91 were tested in Hank’s solution immersion test. The corrosion behaviour of Mg coated PLLA was studied through hydrogen evolution, weight loss and scanning electron microscope (SEM) before, during and after samples were immersed. The solution was maintained at pH 7 by bubbling CO2 gas. The results showed that surface treatment on Mg by coating with PLLA had reduced the rate of corrosion during the immersion test. The PLLA coating was also characterized and the coating adhesion was evaluated
Theoretical and experimental studies on a Q-switching operation in an erbium-doped fiber laser using vanadium oxide as saturable absorber
No full textWe introduce theoretical analysis for a passively Q-switching operation in an erbium-doped fiber laser (EDFL) with a saturable absorber (SA). Peak power, repetition rate, and pulse duration have been calculated as functions of pump power and cavity length. The simulation results are compared with the passively Q-switched EDFL demonstrated using vanadium oxide (V2O5) as SA. The nonlinear saturable absorption of the V2O5-SA is characterized by a modulation depth of 7% with a saturation intensity of 71 MW cm-2. This is the first demonstration of a fiber laser based on a V2O5-SA that introduces new opportunity for photonic applications. The introduced theoretical model could be highly useful for understanding and improving Q-switched EDFLs based on a SA
Prevalence and factors associated with poor sleep quality among secondary school teachers in a developing country
No full textThis study aimed to determine the prevalence and factors associated with poor sleep quality among secondary school teachers in the state of Selangor, Malaysia. This was a cross sectional study, conducted in two phases. Phase I tested the reliability of the Pittsburgh Sleep Quality Index in the Malay language (M-PSQI), whereas Phase II determined the prevalence and factors associated with poor sleep quality where a total of 1,871 secondary school teachers were studied. Participants were recruited using multistage sampling. Self-administered questionnaire was used to collect data on socio-demographic and teaching characteristics, comorbidities and characteristics of sleep. The M-PSQI was used to measure sleep quality. The Depression Anxiety Stress Scale-21 was used to measure mental health status. Results showed that the M-PSQI had a good internal consistency and moderate reliability. The prevalence of poor sleep quality was 61 (95% CI: 54–67)%. Total teaching hours/day, depression and stress were significantly associated with poor sleep quality in the univariate analysis, while only stress (OR 1.04; 95% CI 1.02–1.05%) remained significant in the multivariate analyses. In conclusion, stress level of the secondary school teachers should be reduced to improve sleep quality
Seasonality, habitat type and locality influenced bird assemblage structure in Nigeria
No full textThis is the first report of the avian assemblage in the study area of Dutse, Nigeria. In addition to recording bird species, the effects of season, dominant vegetation structure, locality and anthropogenic activities on bird abundance, species richness and diversity were investigated. Using the point transect method, 264 points on 48 km of transect were used to count birds between 06:30 and 11:00 from August 2015 to February 2016. A total of 122 bird species of 41 families were recorded. Highest bird species richness was recorded in Warwade, highest abundance in Model, and highest diversity in Malamawa. The dry season and woodland habitat showed higher bird species richness, abundance and diversity than the wet season and shrubland habitat. Tree density was more important in increasing bird abundance than shrub density. Small-scale anthropogenic activities and habitat modification, such as farming, grazing, wood removal and human interference did not appear to have impacted the birds; however, loss of high tree-density woodland habitats may pose a major threat to the bird community in Dutse. The presence of birds of concern in the area suggests the need for conservation efforts of avifauna and as well as the forested habitats in Dutse