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41.
Zal U’yun Wan Mahmood Zaharudin Ahmad Mohd Izwan Abd. Adziz Che Abd Rahim Mohamed Abdul Kadir Ishak 《Journal of Radioanalytical and Nuclear Chemistry》2010,285(2):365-372
Thorium activity concentrations were measured in seven marine sediment cores taken from Sabah-Sarawak coast on 2004 by using
a gravity box corer. Collected sediments were generally homogenous mud which contained much more mixture of silt and clay
compared to sand and relatively low content of organic carbon (i.e. less than 5% at all sampling stations). The results found
that activity concentrations of 230Th, 232Th and ratios of 230Th/232Th were ranged from 6.5–20.4 Bq/kg dry wt., 6.8–27.8 Bq/kg dry wt. and 0.69–0.92, respectively. It seem that, 232Th activity concentrations are slightly higher than 230Th at all sampling stations and both radionuclides were generally high at Sabah compared to Sarawak coastal waters. 230Th activity concentrations in sediment core appear to be correlated with the activity concentrations of 232Th at some sampling station. These indicating both radionuclides were supplied from the same of environment and source origin
of detrital from terrestrial and shallower water. The low 230Th/232Th activity ratio which is less than unity suggesting that 232Th was actively and rapidly regenerated compared to 230Th from 234U. It also can be attributed to less efficiently scavenge of 230Th onto particles prior deposited at the marine sediment bed. 相似文献
42.
The adsorption of 2,4-dichlorophenoxyacetic acid (2,4-D) on organophilic sepiolite (dodecylammonium sepiolite, DAS) was studied as a function of solution concentration and temperature. The observed adsorption rates were found to be equal to the first-order kinetics. The rate constants were calculated for temperatures ranging between 25 and 40 degrees C at constant concentration. The adsorption energies, E, and adsorption capacity, q(m), for 2,4-D adsorption on organophilic sepiolite was estimated using the Dubinin-Radushkevic equation. Thermodynamic parameters (Deltag(a), Deltah(a), Deltas(a)) were determined by a new approximation from the isotherm of 2,4-D adsorption on DAS. Also, DeltaS(0) and DeltaH(0) values were calculated from the van't Hoff equation. These isotherms were modeled according to the Freundlich and Dubinin-Radushkevic adsorption equations. The amount of adsorption of this herbicide on organophilic sepiolite was found to be dependent on the relative energies of adsorbent-adsorbate, adsorbate-solvent, and adsorbate-adsorbate interaction. 相似文献
43.
Nur Farha Shaafi Mohd Fakhrul Zamani Kadir Shujahadeen B. Aziz 《Molecular Crystals and Liquid Crystals》2019,693(1):57-65
AbstractQuantum confined structure-based solar cell is promising two folds increment of the maximum theoretical photovoltaic conversion efficiency i.e., > 60% in comparison with that of the bulk analogs e.g., silicon-based and dye sensitized solar cell (ca. 32% of maximum theoretical efficiency). The key to the significant increment is the ability of the fluorophore to exhibit multiple exciton generation upon absorption photon with sufficient energy. Small size of lead chalcogenides (PbS, PbSe, PbTe) crystals have been reported and proven experimentally could exhibit this unique property. We have investigated few clusters of narrow bandgap lead chalcogenides nanocrystals i.e., (PbS)n, (PbSe)n and (PbTe)n; which n?=?4 - 80. The cluster models were optimized using quantum chemical calculations to the lowest energy geometry at B3LYP/lanl2dz level of theory. The predicted realistic (PbS)80, (PbSe)50, and (PbTe)74 clusters with the size, and bandgap of 4.58?nm (2.00?eV), 4.03?nm (1.51?eV), and 4.84?nm (1.55?eV) are smaller than that of their exciton Bohr radius i.e., 5.01, 13.1, and 24.8?nm respectively. Therefore, the occurrence of multi exciton generation in the clusters is hypothesized upon absorption of photon with Ephoton = 2Eg. 相似文献
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We review new methodologies for glucose sensing from our laboratories based on the specific biological interactions between Con A, dextran-coated gold nanoparticles and glucose, and the interactions between dextran, glucose, and boronic-acid capped silver nanoparticles in solution. Our new approaches promise new tunable glucose sensing platforms. Dextran-coated gold nanoparticles were aggregated with the addition of Con A resulting in increase an in absorbance of nanoparticles at 650 nm, where the post-addition of glucose caused the dissociation of the aggregates and thus a decrease in the absorbance at 650 nm. The interaction of glucose and dextran with boronic acid-capped silver nanoparticles in solution resulted in enhanced luminescence intensity cumulatively due to surface-enhanced fluorescence and the decrease in absorbance at 400 nm, with an increase in absorbance at 640 nm. Lifetime measurements were used to distinguish the contribution from the surface-enhanced fluorescence. TEM was employed to assess the aggregation of nanoparticles. 相似文献
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48.
O. A. Bég S. S. Motsa A. Kadir T. A. Bég M. N. Islam 《Journal of Engineering Thermophysics》2016,25(4):576-599
Laminar natural convection plume of a microstructural non-Newtonian fluid along a vertical surface about a line heat source in a saturated high permeability porous medium is studied. The transformed non-linear boundary value problem is solved numerically using a rigorously tested SQLM algorithm, which combines a spectral collocationmethod with the quasilinearization method (QLM). The effects of Grashof number, Prandtl number, Darcy number and Eringen micropolar rheological material parameters are examined. Excellent stability and convergence of the spectral method is demonstrated. Validation of solutions with the Keller box finite difference is included. Applications of the study arise in geological (petroleum) fluid dynamics. 相似文献
49.
Two systems (salted and plasticized) of starch–chitosan blend-based electrolytes incorporated with ammonium chloride (NH4Cl) are prepared via solution cast technique. The incorporation of 25 wt% NH4Cl has maximized the room temperature conductivity of the electrolyte to (6.47?±?1.30)?×?10?7 S cm?1. Conductivity is enhanced to (5.11?±?1.60)?×?10?4 S cm?1 on addition of 35 wt% glycerol. The temperature dependence of conductivity for all electrolytes is Arrhenian, and the value of activation energy (E a ) decreases with increasing conductivity. Conductivity is found to be influenced by the number density (n) and mobility (μ) of ions. The complexation between the electrolytes components is proven by Fourier transform infrared analysis. The relaxation time (t r ) for selected electrolytes is found to decrease with increasing conductivity and temperature. Conduction mechanism for the highest conducting electrolyte in salted and plasticized systems is determined by employing Jonscher’s universal power law. 相似文献
50.
Polymer electrolyte system based on poly(vinyl alcohol) (PVA)-chitosan blend doped with ammonium bromide (NH4Br) has been prepared by solution cast method. Fourier transform infrared (FTIR) spectroscopy analysis confirms the complexation between salt and polymer host. The highest ionic conductivity obtained at room temperature is (7.68?±?1.24)?×?10?4 S cm?1 for the sample comprising of 30 wt% NH4Br. X-ray diffraction (XRD) patterns reveal that PVA-chitosan with 30 wt% NH4Br exhibits the most amorphous structure. Thermogravimetric analysis (TGA) reveals that the electrolytes are stable until ~260 °C. The conductivity variation can also be explained by field emission scanning electron microscopy (FESEM) study. Dielectric properties of the electrolytes follow non-Debye behavior. The conduction mechanism of the highest conducting electrolyte can be represented by the correlated barrier hopping (CBH) model. From linear sweep voltammetry (LSV) result, the highest conducting electrolyte is electrochemically stable at 1.57 V. 相似文献