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81.
The International Atomic Energy Agency Marine Environmental Laboratory (IAEA-MEL) conducted an intercomparison exercise for
the “Trace elements and methyl mercury in fish scallop: IAEA-452” in 2009. The Neutron Activation Analysis (NAA) laboratory
at PINSTECH, Pakistan took part in this exercise. Comparison with the IAEA results showed that of the 18 elements reported
to the IAEA 7 had unacceptable z-scores while the data for two elements was questionable (2< |z-score| <3). Upon investigation it was discovered that the large number of elements having unacceptable z-scores was due to human error and the greater difficulty in analyzing biological samples which have low amounts of trace
elements. Therefore selection of values corresponding to matrix matched reference materials (RMs), such as IAEA-436 and IAEA-407,
and to non-interfering peaks the results obtained became comparable to the IAEA results with only the result for As having
|z-score|> 3. 相似文献
82.
A. A. Qureshi A. Sultan A. Rashid M. Ali A. Waheed S. Manzoor M. A. Baloch Matiullah S. Batool H. A. Khan 《Journal of Radioanalytical and Nuclear Chemistry》2012,293(3):955-963
Mount Arafat is a sacred place for Muslims. It has been classified as a granodiorite rock which mainly consists of feldspar and quartz, muscovite, etc. During the Hajj and Umra, Muslims visit this holly place and stay there for some time. In order to study the geology and thermal history as well as to assess the radiological hazards due to the presence of primordial radionuclides, systematic studies using petrographic, fission track dating and γ-spectrometric (HPGe) techniques were carried out. Our study yielded fission track age of 9.13 ± 1.05 Ma of the Mount Arafat granodiorite. Rifting, magmatism, volcanism and sea floor spreading that resulted in the formation of Red Sea seems may have altered the original age of the Arafat granodiorite under study to 9.13 ± 1.05 Ma. Measured radioactivity concentrations due to 226Ra, 232Th and 40K were found to be 10.75 ± 3.92, 29.21 ± 4.34 and 664.49 ± 7.45 Bq kg?1, respectively. From the measured radioactivity, gamma index (Iγ) and radium equivalent (Raeq) were calculated as 0.402 and 103.23 Bq kg?1 whereas outdoor external dose (Dout) and annual effective dose (Eout) were estimated to be 40.30 nGyh?1 and 0.045 mSvy?1 respectively. All the above mentioned values are well below the recommended limits. The Mount Arafat thus does not pose any radiological health hazard to the general public. 相似文献
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85.
Mostafa A.A. Mahmoud Shimaa E. Waheed 《Journal of the Egyptian Mathematical Society》2012,20(1):20-27
In this work, the effects of slip velocity on the flow and heat transfer for an electrically conducting micropolar fluid over a permeable stretching surface with variable heat flux in the presence of heat generation (absorption) and a transverse magnetic field are investigated. The governing partial differential equations describing the problem are converted to a system of non-linear ordinary differential equations by using the similarity transformation, which is solved numerically using the Chebyshev spectral method. The effects of the slip parameter on the flow, micro-rotation and temperature profiles as well as on the local skin-friction coefficient, the wall couple stress and the local Nusselt number are presented graphically. The numerical results of the local skin-friction coefficient, the wall couple stress and the local Nusselt number are given in a tabular form and discussed. 相似文献
86.
Canted antiferromagnetic and optical properties of nanostructures of Mn2O3 prepared by hydrothermal synthesis
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Qurat-ul-ain Javed Wang Feng-Ping M.Yasir Rafique Arbab Mohammad toufiq M.Zubair Iqbal 《中国物理 B》2012,(11):443-449
We have reported new magnetic and optical properties of Mn2O3 nanostructures.The nanostructures have been synthesized by the hydrothermal method combined with the adjustment of pH values in the reaction system.The particular characteristics of the nanostructures have been analyzed by employing X-Ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive X-ray(EDX) analysis,transmission electron microscopy(TEM),high resolution transmission electron microscopy(HRTEM),Raman spectroscopy(RS),UV-visible spectroscopy,and the vibrating sample magnetometer(VSM).Structural investigation manifests that the synthesized Mn2O3 nanostructures are orthorhombic crystal.Magnetic investigation indicates that the Mn2O3 nanostructures are antiferromagnetic and the antiferromagnetic transition temperature is at TN=83 K.Furthermore,the Mn2O3 nanostructures possess canted antiferromagnetic order below the Neel temperature due to spin frustration,resulting in hysteresis with large coercivity(1580 Oe) and remnant magnetization(1.52 emu/g).The UV-visible spectrophotometry was used to determine the transmittance behaviour of Mn2O3 nanostructures.A direct optical band gap of 1.2 eV was acquired by using the Davis-Mott model.The UV-visible spectrum indicates that the absorption is prominent in the visible region,and transparency is more than 80% in the UV region. 相似文献
87.
Fractional differential equations are widely applied in physics, chemistry as well as engineering fields. Therefore, approximating
the solution of differential equations of fractional order is necessary. We consider the quadratic polynomial spline function
based method to find approximate solution for a class of boundary value problems of fractional order. We derive a consistency
relation which can be used for computing approximation to the solution for this class of boundary value problems. Convergence
analysis of the method is discussed. Four numerical examples are included to illustrate the practical usefulness of the proposed
method. 相似文献
88.
This work deals with the influence of thermal radiation on the problem of the mixed convection thin film flow and heat transfer of a micropolar fluid past a moving infinite vertical porous flat plate with a slip velocity.The fluid viscosity and the thermal conductivity are assumed to be the functions of temperature.The equations governing the flow are solved numerically by the Chebyshev spectral method for some representative value of various parameters.In comparison with the previously published work,the excellent agreement is shown.The effects of various parameters on the velocity,the microrotation velocity,and the temperature profiles,as well as the skin-friction coefficient and the Nusselt number,are plotted and discussed. 相似文献
89.
S. Waheed S. Rahman K. P. Gill 《Journal of Radioanalytical and Nuclear Chemistry》2009,279(3):725-731
Instrumental neutron activation analysis (INAA) have been used to determine As, Br, Hg, Sb and Se in combination with atomic
absorption spectrometry (AAS) as a complementary technique for the quantification of Cd and Pb in jaggery, brown sugar, white
sugar and molasses. All sugar cane products were collected from the local sugar cane industry of Pakistan. The highest concentration
of these potentially toxic elements was quantified in molasses; however, molasses together with jaggery, brown sugar and white
sugar contains trace amounts of all of these elements. Due to very low concentration of Cd it could only be detected in molasses.
To evaluate the percentage contribution of these elements in the sugar cane products to the weekly recommended values, intakes
on weekly consumption of 100 g of each item have also been calculated which follow the pattern Br>Se>Pb>Hg>As>Sb. The elevated
Br contents may be attributed to the use of Br-containing chemicals for fumigation; however, these contents are well within
the tolerance levels. The estimated weekly intake of all toxic elements is very low indicating that sugar cane products can
be safely ingested as part of the diets. 相似文献
90.