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21.
Nadia Abdullah Abd Rahim Abu Talib Helmey Ramdhaney Mohd Saiah Abdul Aziz Jaafar Mohamad Amran Mohd Salleh 《Experimental Thermal and Fluid Science》2009,33(4):561-578
Thermochromic liquid crystals (TLCs) have been widely employed by researchers in heat transfer and fluid flow communities as a reliable and non-intrusive temperature measurement tool due to their unique optical properties such as birefringence, optical activity, circular dichroism and selective reflection of colours in the visible spectrum as function of temperature. The use of narrowband TLCs are attractive for temperature and heat transfer measurements due to their higher precision in temperature measurements and due to the fact that narrowband TLCs are less affected by variations in illumination-viewing angles and illumination disturbances. Narrowband TLCs have been used with full intensity-matching methods to provide robust image processing for measurements of thermal parameters in transient heat transfer tests. Calibration of narrowband TLCs is necessary in order to obtain the intensity-temperature relationship of the TLCs. Film thickness is one of the factors which affects calibrations of TLCs. In this research, film thicknesses of 10, 20, 30, 40 and 50 μm were investigated on green intensity-based calibrations of R35C1W TLC during heating and cooling. Results showed an increase in magnitude of peak green intensity with increasing film thickness, with a percentage increase of nearly 18% when film thickness increased from 10 to 50 μm. Results also showed an inconsistent shift in temperature at which peak green intensity occurs, with a maximum shift of 0.40 °C, suggesting that film thickness effects may be insignificant for narrowband TLCs compared with wideband TLCs. A theoretical method for estimating the volume of TLC coating required to achieve a desired film thickness has also been described in this paper, based on the surface area and dry solids content of the TLC. The method is easily implemented and applicable for sprayable TLC coatings. 相似文献
22.
Rahman RN Tejo BA Basri M Rahman MB Khan F Zain SM Siahaan TJ Salleh AB 《Applied biochemistry and biotechnology》2004,118(1-3):11-20
Candida rugosa lipase was modified via reductive alkylation to increase its hydrophobicity to work better in organic solvents. The free
amino group of lysines was alkylated using propionaldehyde with different degrees of modification obtained (49 and 86%). Far-ultraviolet
circular dichroism (CD) spectroscopy of the lipase in aqueous solvent showed that such chemical modifications at the enzyme
surface caused a loss in secondary and tertiary structure that is attributed to the enzyme unfolding. Using molecular modeling,
we propose that in an aqueous environment the loss in protein structure of the modified lipase is owing to disruption of stabilizing
salt bridges, particularly of surface lysines. Indeed, molecular modeling and simulation of a salt bridge formed by Lys-75
to Asp-79, in a nonpolar environment, suggests the adoption of a more flexible alkylated lysine that may explain higher lipase
activity in organic solvents on alkylation. 相似文献
23.
M. Y. A. Rahman A. A. Umar L. Roza M. M. Salleh 《Journal of Solid State Electrochemistry》2012,16(12):3947-3952
The morphology of photovoltaic material is able to influence of the performance of photoelectrochemical cell. Polyvinylpyrrolidone (PVP), cetyltrimethylammonium bromide (CTAB), and hexamethylenetetramine (HMT) surfactant were used to modify the morphology nanostructure of TiO2 films by a simple technique, namely, liquid phase deposition during their growth process. It was found that the untreated surfactant TiO2 film produces the morphology with the mixture nanosphere and nanoflower. The film treated with PVP, CTAB, and HMT produce the nanostructure shape of nanoflower, nanowire, and nanorod, respectively. These TiO2 samples were utilized as photovoltaic materials in a photoelectrochemical cell of ITO/TiO2/electrolyte/platinum. It was found that the photovoltaic parameters such as short-circuit current density (J sc), open-circuit voltage (V oc) and fill factor are influenced by the morphology in terms of shape and particle size of the TiO2 nanostructure. The cell utilizing the TiO2 nanowire treated with PVP possesses the highest J sc and V oc of 0.100 mAcm?2 and 0.44 V. The length of the TiO2 nanowire is 6?±?2 nm, while the cell with the untreated surfactant TiO2 sample demonstrates the lowest performance. It was also found that the J sc and V oc increase with the decrease in the length of the TiO2 nanostructures. The smallest length of TiO2 possesses the best interfacial contact at TiO2/electrolyte containing iodide/triiodide redox couple. Thus, the redox reaction is optimized at this interface. 相似文献
24.
Fumio Hosoi Yasushi Aoki Miyuki Hagiwara Hideki Omichi M. Mat. Salleh 《辐射效应与固体损伤》2013,168(1-4):351-354
Abstract Substituting metallic or rare-earth atoms or removing O in the superconductor YBa2Cu3O7 usually has a strong effect on the superconducting properties. We have made extensive XAFS studies on Co, Fe, Ni, Zn, Gd, and Pr substituted materials including some thin film samples. In nearly all cases, significant distortions are found. Although the lattice constant change is small (< 0.05 Å) the local distortions can be significant larger (~ 0.1 to 0.3 Å). The observed large local distortions of the lattice together with a change in the charge distribution at a site indicate that the interior of the unit cell is easily distorted. The correlation of a strong Tc suppression with large local distortions suggests that distortions of the nearby layers must play a significant role in models for superconductivity in high Tc materials. 相似文献
25.
Dariush Khezrimotlagh Shaharuddin Salleh Zahra Mohsenpour 《The Journal of the Operational Research Society》2014,65(5):694-707
This paper provides a new structure in data envelopment analysis (DEA) for assessing the performance of decision making units (DMUs). It proposes a technique to estimate the DEA efficient frontier based on the Arash Method in a way different from the statistical inferences. The technique allows decisions in the target regions instead of points to benchmark DMUs without requiring any more information in the case of interval/fuzzy DEA methods. It suggests three efficiency indexes, called the lowest, technical and highest efficiency scores, for each DMU where small errors occur in both input and output components of the Farrell frontier, even if the data are accurate. These efficiency indexes provide a sensitivity index for each DMU and arrange both inefficient and technically efficient DMUs together while simultaneously detecting and benchmarking outliers. Two numerical examples depicted the validity of the proposed method. 相似文献
26.
Ng Sook Han Mohd. Basyaruddin Abd. Rahman Raja Noor Zaliha Raja Abd. Rahman Abu Bakar Salleh Zahariah Ismail 《Journal of Dispersion Science and Technology》2013,34(10):1428-1433
Palm oil esters (POEs) are wax esters derived from palm oil and cis-9-octadecen-1-ol. The excellent wetting behaviour of the esters without the oily feel make them have great potentials in the manufacture of cosmeceutical and pharmaceutical products. However, little is known about their phase behaviors in ternary systems. The purpose of this investigation was to construct phase diagram of the POEs and mixed surfactants and to consequently select nanoemulsions composition for further studies. The preparation and characterization of oil-in-water nanoemulsions stabilized by hydrocolloid gums were then studied. Two types of nonionic surfactants were selected, namely Tween 80 (T80) and Span 80 (S80). Ternary phase diagram of POEs:Tocotrienol/T80:S80 (80:20)/water system was constructed at 25.0 ± 0.5°C. The emulsification properties of 2 hydrocolloids gum (xanthan gum, carbopol ultrez 20 copolymer) were investigated. Gum dispersions were prepared in water (0.8%) and emulsified with 30% oil using a Polytron homogenizer. The flow curve of the emulsions always exhibited shear thinning behavior and obeys the power law viscosity. The emulsions with carbopol ultrez 20 copolymer was the most stable emulsions which composed of very small oil droplets (50% < 142.43 nm) with a narrow size distribution. 相似文献
27.
Shakri Natasa Mohd Salleh Wan Mohd Nuzul Hakimi Wan Khamis Shamsul 《Chemistry of Natural Compounds》2021,57(6):1114-1115
Chemistry of Natural Compounds - 相似文献
28.
Basri M Samsudin S Ahmad MB Razak CN Salleh AB 《Applied biochemistry and biotechnology》1999,81(3):205-217
Lipase from Candida rugosa was immobilized by entrapment on poly(N-vinyl-2-pyrrolidone-co-2-hydroxyethyl methacrylate)(poly[VP-co-HEMA]) hydrogel, and divinylbenzene was the crosslinking agent.
The immobilized enzymes were used in the esterification reaction of oleic acid and butanol in hexane. The activities of the
immobilized enzymes and the leaching ability of the enzyme from the support with respect to the different compositions of
the hydrogels were investigated. The thermal, solvent, and storage stability of the immobilized lipases was also determined.
Increasing the percentage of composition of VP from 0 to 90, which corresponds to the increase in the hydrophilicity of the
hydrogels, increased the activity of the immobilized enzyme. Lipase immobilized on VP(%):HEMA(%) 90∶10 exhibited the highest
activity. Lipase immobilized on VP(%):HEMA(%) 50∶50 showed the highest thermal, solvent, storage, and operational stability
compared to lipase immobilized on other compositions of hydrogels as well as the native lipase. 相似文献
29.
Khayoon WS Saad B Salleh B Ismail NA Abdul Manaf NH Abdul Latiff A 《Analytica chimica acta》2010,679(1-2):91-97
The development of a reversed phase high performance liquid chromatography fluorescence method for the determination of the mycotoxins fumonisin B(1) and fumonisin B(2) by using silica-based monolithic column is described. The samples were first extracted using acetonitrile:water (50:50, v/v) and purified by using a C(18) solid phase extraction-based clean-up column. Then, pre-column derivatization for the analyte using ortho-phthaldialdehyde in the presence of 2-mercaptoethanol was carried out. The developed method involved optimization of mobile phase composition using methanol and phosphate buffer, injection volume, temperature and flow rate. The liquid chromatographic separation was performed using a reversed phase Chromolith(?) RP-18e column (100 mm × 4.6 mm) at 30 °C and eluted with a mobile phase of a mixture of methanol and phosphate buffer pH 3.35 (78:22, v/v) at a flow rate of 1.0 mL min(-1). The fumonisins separation was achieved in about 4 min, compared to approximately 20 min by using a C(18) particle-packed column. The fluorescence excitation and emission were at 335 nm and 440 nm, respectively. The limits of detections were 0.01-0.04 μg g(-1) fumonisin B(1) and fumonisin B(2), respectively. Good recoveries were found for spiked samples (0.1, 0.5, 1.5 μg g(-1) fumonisins B(1) and B(2)), ranging from 84.0 to 106.0% for fumonisin B(1) and from 81.0 to 103.0% for fumonisin B(2). Fifty-three samples were analyzed including 39 food and feeds and 14 inoculated corn and rice. Results show that 12.8% of the food and feed samples were contaminated with fumonisin B(1) (range, 0.01-0.51 μg g(-1)) and fumonisin B(2) (0.05 μg g(-1)). The total fumonisins in these samples however, do not exceed the legal limits established by the European Union of 0.8 μg g(-1). Of the 14 inoculated samples, 57.1% contained fumonisin B(1) (0.16-41.0 μg g(-1)) and fumonisin B(2) (range, 0.22-50.0 μg g(-1)). Positive confirmation of selected samples was carried out using liquid chromatography-tandem mass spectrometry, using triple quadrupole analyzer and operated in the multiple reaction monitoring mode. 相似文献
30.