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891.
Nita Salina Abu Bakar Zal U’yun Wan Mahmood Ahmad Saat 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(1):315-323
In the present study, the depositions of 210Po were assessed in the surface soil and some mosses species found in the area around coal fired power plant using radiochemical deposition and alpha spectrometry counting system. The purposes of the study were to determine activity concentrations of 210Po in mosses and surface soil collected around coal-fired power plant in relation to trace the potential source of 210Po and to identify most suitable moss species as a bio-indicator for 210Po deposition. In this study, different species of mosses, Orthodontium imfractum, Campylopus serratus and Leucobryum aduncum were collected in May 2011 at the area around 15 km radius from Tanjung Bin coal-fired power plant located in Pontian, Johor. The 210Po activity concentrations in mosses and soil varied in the range 102 ± 4 to 174 ± 8 Bq/kg dry wt. and 37 ± 2 to 184 ± 8 Bq/kg dry wt., respectively. Corresponding highest activity concentration of 210Po observed in L. aduncum, therefore, this finding can be concluded this species was the most suitable as a bio-indicator for 210Po deposition. On the other hand, it is clear the accumulation of 210Po in mosses might be supplied from various sources of atmospheric deposition such as coal-fired power plant operation, industrial, plantation, agriculture and fertilizer activities, burned fuel fossil and forest; and other potential sources. Meanwhile, the main source of 210Po in surface soil is supplied from the in situ deposition of radon decay and its daughters in the soil itself. 相似文献
892.
Guan‐Yeow Yeap Tiang‐Chuan Hng Wan Ahmad Kamil Mahmood Masato M. Ito Yamashita Youhei Yoichi Takanishi 《Liquid crystals》2013,40(9):979-986
A series of eight liquid crystalline compounds, N,N′‐bis[(2‐hydroxy‐4‐alkoxyphenyl)methylene]benzene‐1,4‐diamines, has been synthesized and characterized. These homologous compounds differ in the length of terminal alkyl group C n H2n+1 wherein n is an even number ranging from 4 to 18. The spectroscopic techniques, FTIR, 1H NMR and 13C NMR, were employed to characterize the molecular structure. The transition temperatures of all the title compounds and their mesophases were studied by differential scanning calorimetry and polarizing microscopy. All the compounds were smectogenic, exhibiting both tilted and non‐tilted molecular orientation in their smectic phases. Further investigation to ascertain the anisotropic nature of subphases within the smectogenic region was carried out using X‐ray diffraction. 相似文献
893.
Parviz Rashidi-Ranjbar Ahmad Khoramabadi-zad Mahmood Roohi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1):229-238
Abstract The conformation of the heterocyclic eight-membered ring in 16H-dinaphtho and 12H-dibenzo [d,g][1,3,2]dioxasilocine was investigated in solution by 1H NMR spectroscopy. The barrier to ring inversion in the 16H-dinaphtho compound 3a was found to be 8.6±0.2 Kcal/mol and for the 12 H-dibenzo compound 4a, 8±0.2 Kcal/mol. Molecular mechanics calculations show three energy minima conformations for both compounds, boat chair(BC), twist boat(TB) and twist boat boat(TBB). Twist boat form is estimated to be the global minimum for the dibenzo compounds while TBB is the global conformation of the dinaphtho compounds. The result of molecular mechanics calculations are supported by analysis of the 1H-NMR spectra. 相似文献
894.
Mahmood Tajbakhsh Majid. M. Heravi Setareh Habibzadeh 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):361-364
Primary and secondary trimethylsilyl ethers are efficiently and rapidly converted to their corresponding carbonyl compounds with supported potassium ferrate under microwave irradiation in solventless system. 相似文献
895.
Majid M. Heravi Mahmood Tajbakhsh Setareh Habibzadeh Mitra Ghassemzadeh 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):2299-2302
An environmentally benign, efficient, and mild methodology for the cleavage of phenylhydrazones using potassium ferrate under microwave irradiation in solvent-free conditions is described. 相似文献
896.
Majid M. Heravi Fatemeh Derikvand Hossein A. Oskooie Rahim Hekmat Shoar Mahmood Tajbakhsh 《合成通讯》2013,43(3):513-517
An efficient and convenient method for the oxidation of thiols mediated by silica‐supported bis (trimethylsilyl) chromate (BTSC) in acetonitrile is reported. 相似文献
897.
ω-N,N-Dihydroxyethyl aminopropylpolymethylhydrosiloxane (DAPS) a monotelechelic polydimethylsiloxane with a diol-end group, which is used to prepare polyurethane surfactant, was successfully synthesized. The preparation included four steps, which are hydroxyl protection, alkylation, hydrosilylation, and deprotection. Then, a novel silicone-based polyurethane surfactant was prepared by the addition polymerization of isophorone diisocyanate to DAPS, polypropylene glycol, and methanol and was used in the preparation of polystyrene by emulsion polymerization. The DAPS was characterized by FTIR, 1H NMR, 13C NMR and elemental analysis. The results showed that each step was successfully carried out and the targeted products were synthesized in all cases. 相似文献
898.
Mahmood Mollaei Gharehajlu Yousef Darmani Saadan Zokaei 《Wireless Personal Communications》2014,79(2):1455-1470
Recently, IEEE 802.11 wireless ad-hoc networks become popular due to their flexibility and lack of infrastructure. Also they can easily be set up and almost available anywhere and anytime. Most researches which evaluate performance of these type of networks suppose saturation condition for the sake of analytical simplicity. However, most recent applications have \(ON/OFF\) property that causes unsaturation condition. In order to have that condition, each node is modeled by a \(M/G/1\) Markov model and has Poisson distribution as its packet arrival model. Based on these assumptions, average and variance of service time are analyzed accurately. Delay as an important QoS parameter in time critical applications, is analyzed precisely in this paper. Computing service time variance ables us to evaluate average packet delay by Pollaczek–Khinchin equation. It also helps us to estimate probability density function of its service time. To prove our analytic results, extensive simulations have been done, which show that the analytical and simulation results match perfectly. 相似文献
899.
A new mode of transport is described that was capable of high-resolution separation of superparamagnetic materials from complex mixtures based on their size. Laminar flow and a rotating external magnetic field were applied to superparamagnetic beads assembled on a semiperiodic micromagnet array. Beads at the edge of the micromagnet array oscillated in-phase with the external magnetic field with an amplitude that decreased with increasing frequency, ω, until they reached an immobilization frequency, ω(i), where the beads stopped moving. Laminar flow along the edge of the array could be tuned to sweep the beads for which ω < ω(i) downstream at a velocity that increased with size while leaving beads for which ω > ω(i) undisturbed. Flow-enhanced nonlinear magnetophoresis (F-NLM) promises to enable multiple superparamagnetc bead types to be used in the fractionation of cells and implementation of diagnostic assays. 相似文献
900.
Zaharudin?AhmadEmail author Zal?U’yun?Wan Mahmood Hidayah?Shahar Mei?Wo?Yii Ahmad?Sanadi?Abu Bakar 《Journal of Radioanalytical and Nuclear Chemistry》2011,287(1):329-334
Large volumes of surface seawater samples were collected from thirty locations in the Exclusive Economic Zone (EEZ) of the
east coast Peninsular Malaysia on June 2008 to study the activity concentrations of 137Cs. The results will serve as additional information to the existing baseline data and is very useful for monitoring fresh
input of anthropogenic radionuclide into Malaysian marine environment. In this study, the activity concentrations of 137Cs were determined using co-precipitation technique, followed by Gamma Spectrometry measurement. The mean activity concentration
of 137Cs ranged between 3.40 and 5.89 Bq/m3. Higher activity concentrations were observed at the coastal and towards the south of Peninsular Malaysia and were aligned
with the high turbidity. These may due to the rapid diffusion of 137Cs from suspended particulates and fine sediments into surface seawater. The activity concentrations of 137Cs observed in this study were slightly higher than the concentrations reported in seawater at the Straits of Malacca, Vietnam
and Philippines. This might be because the study area received more input of 137Cs that originated from global fallout and then deposited on land which later being transported subsequently into the coastal
zone due to siltation and erosion processes. It could also be attributed to the intrusion of river waters containing higher
concentrations of 137Cs. 相似文献