19672 research outputs found
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Catalytic conversion of microcrystalline cellulose to nanocellulose using iron oxide catalysts
Get PDFCatalytic conversion of microcrystalline cellulose (MCC) to nanocellulose involves a one-pot homogeneous reaction carried out by the cleavage of β-1,4-glycosidic bonds within the cellulose network. Through this work, the synergistic combination of ultrasonication and catalyst has been proved to be effective in the controlled depolymerisation process of cellulose. Iron oxide being a Lewis acid catalyst has been used to abstract the single electron from the electron-rich C-O bond in cellulose. The iron oxide, maghemite (γ-Fe2O3) shows the highest activity as determined by the increase of crystallinity index (CrI%) from 80.62% to 85.63%. The other phases of iron oxide also showed catalytic activity with hematite (Fe2O3) at 84.05% and magnetite (Fe3O4) at 83.39%. Morphology and particle size analysis clearly show that the nanocellulose have been obtained in the range 78 nm to 220 nm due to the structural dimension measurement of both thickness (diameter) & length. Spectroscopy analysis via Fourier transform infrared and Raman shows no changes to the functional group, hence the chemical composition and integrity of cellulose remains intact. Nanocellulose suspension obtained using maghemite exhibited the highest colloidal stability and surface tension making it more suitable for application
A Comparative Study of Structural and Ethanol Gas Sensing Properties of Pure, Nickel and Palladium Doped SnO2 Nanorods Synthesised by the Hydrothermal Method
No full textSnO2 nanostructures are usually modified with some metal dopants in order to improve its gas sensing properties. In this work, pure tin oxide (SnO2), nickel (Ni) doped SnO2 (Ni:SnO2) and palladium (Pd) doped SnO2 (Pd:SnO2) nanorods were successfully synthesised via hydrothermal method at low temperature (180°C) without templates or further calcination. All the samples were systematically analysed using X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). The sensor response (R = R0/Rg) towards 1000 ppm ethanol gas was investigated using nitrogen gas as a carrier gas. XRD results confirmed that all samples consisted of rutile tetragonal-shaped SnO2. It was found that the average diameter of nanorods formed in Ni:SnO2 and Pd:SnO2 were decreased to ~6 nm and ~10 nm, compared with nanorods formed in pure SnO2 (~25 nm). The gas sensing results indicated that the sensor properties of SnO2 were enhanced after the doping process. At 450°C, the Pd:SnO2 nanorod sensor recorded the highest response value towards 1000 ppm ethanol gas which is 15 times higher than pure SnO2 nanorods. Interestingly, all samples showed similar response time, ~ 40 s. However, pure SnO2 and Ni:SnO2 nanorods sensors exhibited longer recovery time compared to Pd:SnO2 nanorods. Pd:SnO2 nanorods recorded only 12 min of almost 100% recovery. It is proposed that Pd:SnO2 sensor could be a promising candidate for the detection of ethanol gas. © Penerbit Universiti Sains Malaysia, 2019
Morphometric Analysis of Craniodental Characters of the House Rat, Rattus rattus (Rodentia: Muridae) in Peninsular Malaysia
No full textRattus rattus which is believed to be native to India is easily found in all continents of the world. With the absence of R. rattus from lineage I and the presence of lineage IV in Southeast Asia, little is known about how rodent morphology varies biogeographically. We evaluate the skull morphometrics in the population of R. rattus in Peninsular Malaysia and examine the intraspecific variation of the skull by assessing 20 craniodental characters of 130 R. rattus specimens. After observing the correlation matrix, highly correlated characters were removed and the remaining 14 craniodental characters were analysed using the conventional morphometrics method via univariate and multivariate statistics. We assessed the impact of age, sex and geographical factors (latitude, longitude and precipitation) on craniodental size. Male and female specimens were analysed separately since statistically significant sexual dimorphism was present. Males showed greater craniodental measurements compared to females. Three distinct age groups (C2, C3 and C4) were visible in the principal component analysis (PCA) and canonical variate analysis (CVA) plots for male and female specimens. Ages C2 and C3 shared similarities in craniodental measurements while C4 showed variability compared to C2 and C3. None of the geographical factors studied showed statistical significance for both male and female R. rattus. The results obtained from this study could potentially be a yardstick to observe if similar variations in craniodental traits are present in R. rattus from other countries in the Southeast Asian region. © 2019 Penerbit Universiti Kebangsaan Malaysia. All rights reserved
Screening of rickettsia sp. In ticks (acari: Ixodidae) collected from small mammals in three recreational forests in Selangor, Malaysia
No full textRickettsia is a gram-negative, non-motile, and obligate intracellular bacterium that usually associated with arthropods vectors such as ticks, fleas, lice and mites. These bacteria have the ability to cause diseases in humans, however, in Malaysia, knowledge on the prevalence and distribution of these bacteria mainly focused on humans and information of these bacteria in small mammal hosts is limited. Thus, this study aims to investigate the presence of Rickettsia sp. in the DNA of tick’s samples collected from small mammals in three different recreational forests in Selangor, Malaysia. Sampling was conducted in which 200 cage traps were set up randomly along streams and forest trails for five nights. A total of 106 fully engorged and adult ticks were collected from 23 individuals of seven small mammals host species. All samples were tested for Rickettsia bacteria based on polymerase chain reaction (PCR) using partial 17-kDa antigen gene. The PCR results obtained from this study showed no infestation of Rickettsia sp. in all tick samples. Our findings revealed that none of the tick samples from these forests’ sites were infected with Rickettsia pathogen, however, more intense and extensive surveillance for Rickettsia sp. from other tick species is still necessary for greater geographical areas across Malaysia. © 2019, Universiti Kebangsaan Malaysia Press. All rights reserved
Impact of addition of two ether additives with high speed diesel- Calophyllum Inophyllum biodiesel blends on NOx reduction in CI engine
No full textThe objective of this work was to compare the effect of diethyl ether (DEE) and methyl tertiary-butyl ether (MTBE) addition to biodiesel and diesel blends on diesel engine. The ethers concentration have been varied in proportion of 5% and 10% on volume basis with biodiesel by keeping the diesel concentration as 50% for all ternary blends preparation. Experimental results revealed that D50-B45-DEE5 ternary blend has shown 5.3% increase in thermal efficiency compared to other ternary blends. On the other hand, D50-B45-MTBE5 and D50-B45-DEE ternary blends have reduced CO emission by 8.1% and 14.8% respectively when compared to high speed diesel fuel. Furthermore, the D50-B40-DEE10 blend and D50-B40-MTBE10 reduce the NOx emission by 32% and 8.8% when compared to HSD at maximum load condition. Significant reduction is noted in HC emission for all ether added ternary blends than that of HSD and biodiesel fuels. However, the smoke emission is decreased marginally for D50-B45-DEE5 than that of HSD fuel. Finally, it is evident that both the DEE and MTBE could be used as viable additive with diesel or biodiesel in binary and ternary forms for diesel engine applications. © 2019 Elsevier Lt
Career Consultation as an Intervention Strategy in Alleviating Family’s Mental Health: A Case Study on Students with Disabilities
No full textRelevant information is critical in assisting families and teachers to help students with disabilities in planning their careers appropriate for their capabilities and abilities. Having the correct information and understanding will alleviate the psychological burden faced by family members in dealing with children with special educational needs. This study aimed to explore the knowledge and understanding of parents with special needs on the job marketability of their children. This qualitative study was conducted with 11 multi-case multi-site families of special education students. The consultation process for phase one involved consultations conducted by special education teacher trainees. The second phase of consultation and collaborative process involved students and special education students with undergraduate education guidance and counselling. The verbatim data were analysed using NVivo 11. The study showed that families still lack knowledge in the marketability of their special needs children particularly due to the limited information channel. The findings showed that knowledge on job marketability can help the parents plan their special needs children’s job marketability, which in turn, would directly contribute to the family wellbeing
Getting to know low-light images with the Exclusively Dark dataset
No full textLow-light is an inescapable element of our daily surroundings that greatly affects the efficiency of our vision. Research works on low-light imagery have seen a steady growth, particularly in the field of image enhancement, but there is still a lack of a go-to database as a benchmark. Besides, research fields that may assist us in low-light environments, such as object detection, has glossed over this aspect even though breakthroughs-after-breakthroughs had been achieved in recent years, most noticeably from the lack of low-light data (less than 2% of the total images) in successful public benchmark datasets such as PASCAL VOC, ImageNet, and Microsoft COCO. Thus, we propose the Exclusively Dark dataset to elevate this data drought. It consists exclusively of low-light images captured in visible light only, with image and object level annotations. Moreover, we share insightful findings in regards to the effects of low-light on the object detection task by analyzing the visualizations of both hand-crafted and learned features. We found that the effects of low-light reach far deeper into the features than can be solved by simple “illumination invariance”. It is our hope that this analysis and the Exclusively Dark dataset can encourage the growth in low-light domain researches on different fields. The dataset can be downloaded at https://github.com/cs-chan/Exclusively-Dark-Image-Dataset
A Novel Temperature-Insensitive Hydrostatic Liquid-Level Sensor Using Chirped FBG
No full textA novel half-bonded chirped fiber Bragg grating on a natural rubber diaphragm has been proposed to enhance the sensitivity and to compensate the temperature effects of a hydrostatic liquid-level sensor. This innovative fabrication method is resulted in the narrowing of the bandwidth with the hydrostatic pressure sensitivity recorded at-253 pm/kPa and water column sensitivity at-0.0253 nm/cm. The bandwidth modulation measurement was insensitive to temperature variations when compared with center wavelength modulation measurement. Furthermore, the proposed hydrostatic liquid-level sensor is compatible with a low-cost photodetector
Ferroelectric polarization promoted bulk charge separation for highly efficient CO2 photoreduction of SrBi4Ti4O15
No full textFast recombination of photogenerated charge carriers in bulk remains the major obstacle for photocatalysis nowadays. Developing ferroelectrics directly as photoactive semiconducting catalysts may be promising in view of the strong ferroelectric polarization that induces the anisotropic charge separation. Here, we report a ferroelectric layered perovskite SrBi4Ti4O15 as a robust photocatalyst for efficient CO2 reduction. In the absence of co-catalysts and sacrificial agents, the annealed SrBi4Ti4O15 nanosheets with the strongest ferroelectricity cast a prominent photocatalytic CO2 reduction activity for CH4 evolution with a rate of 19.8 μmol h−1 g−1 in the gas-solid reaction system, achieving an apparent quantum yield (AQY) of 1.33% at 365 nm, outperforming most of the reported photocatalysts. The ferroelectric hysteresis loop, piezoresponse force microscopy (PFM) and ns-level time-resolved fluorescence spectra uncover that the outstanding CO2 photoreduction activity of SrBi4Ti4O15 mainly stems from the strong ferroelectric spontaneous polarization along [100] direction, which allows efficient bulk charge separation along opposite direction. DFT calculations also disclose that both electrons and holes show the smallest effective masses along a axis, verifying the high mobility of charge carriers facilitated by ferroelectric polarization. This study suggests that the traditionally semiconducting ferroelectric materials that have long been studied as ferro/piezoelectric ceramics now may be powerfully applied in the photocatalytic field to deal with the growing energy crisis
A new species of the Simulium (Simulium) variegatum species-group (Diptera: Simuliidae) from Thailand
No full textA new species of black fly, Simulium (Simulium) luculentum, is described from specimens collected in Thailand, and is assigned to the Simulium variegatum species-group of the subgenus Simulium Latreille. This new species is distinguished from most members of this species group in the female by the mid femur and tibia entirely yellowish; and in the pupa by the gill with six filaments, which are somewhat inflated basally. This species represents the fifth member of the S. variegatum species-group recorded from Thailand