排序方式: 共有18条查询结果,搜索用时 15 毫秒
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M. Tufail M. Asghar M. Akram Sabiha Javied K. Khan S. A. Mujahid 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(2):1085-1096
Natural radioactivity in the environment may change with time due to human activities, chemical and biological changes. From the view of radiation risk to population, the knowledge of natural radioactivity levels and the measurement of collective radiation dose received by the population is very vital. Radiological constraints on soil of thickly populated Peshawar basin in northern Pakistan were assessed through radiometric assay. Soil samples collected from different locations of four districts of this basin were analysed using an HPGe gamma spectrometer. Activity concentrations of 40K, 226Ra and 232Th in these samples was 648 ± 121 (421–996), 45 ± 7 (32–60) and 59 ± 7 (46–72) Bq kg?1, respectively that followed lognormal distribution. The average concentrations of primordial radionuclides were found to be higher than that reported for the worldwide soil. Radium equivalent activity and gamma index derived from these activity concentrations were lesser than their respective limits. The average absorbed dose rate and the annual effective dose for both indoor and outdoor cases were found to be higher than the values given in the UNSCEAR 2000 report. The results of the present study were compared with those for other locations of Pakistan along with that for the world. The radiological impact of the measured data was evaluated using hazard assessment models. A thoughtful discussion of the above mentioned evaluation is also given. 相似文献
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M. G. M. Khan N. Ahmad Sabiha Khan 《Journal of Mathematical Modelling and Algorithms》2009,8(4):409-423
The method of choosing the best boundaries that make strata internally homogeneous, given some sample allocation, is known
as optimum stratification. In order to make the strata internally homogeneous, the strata are constructed in such a way that
the strata variances should be as small as possible for the characteristic under study. In this paper the problem of determining
optimum strata boundaries (OSB) is discussed when strata are formed based on a single auxiliary variable with a varying measurement
cost per units across strata. The auxiliary variable considered in the problem is a size variable that holds a common model
for a whole population. The OSB are achieved effectively by assuming a suitable distribution of the auxiliary variable and
creating strata by cutting the range of the distribution at optimum points. The problem of finding the OSB, which minimizes
the variance of the estimated population mean under a weighted stratified balanced sampling, is formulated as a mathematical
programming problem (MPP). Treating the formulated MPP as a multistage decision problem, a solution procedure using dynamic
programming technique is developed. A numerical example using a hospital population data is presented to illustrate the computational
details of the solution procedure. A software program coded in JAVA is written to carry out the computation. The distribution
of the auxiliary variable in this example is considered to be continuous with an exponential density function. 相似文献
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In this paper, we classify static spherically symmetric (SS) perfect fluid space-times via conformal vector fields (CVFs) in f(T) gravity. For this analysis, we first explore static SS solutions by solving the Einstein field equations in f(T) gravity. Secondly, we implement a direct integration technique to classify the resulting solutions. During the classification, there arose 20 cases. Studying each case thoroughly, we came to know that in three cases the space-times under consideration admit proper CVFs in f(T) gravity. In one case, the space-time admits proper homothetic vector fields, whereas in the remaining 16 cases either the space-times become conformally flat or they admit Killing vector fields. 相似文献
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Achat S Tomao V Madani K Chibane M Elmaataoui M Dangles O Chemat F 《Ultrasonics sonochemistry》2012,19(4):777-786
The possibility to improve the nutritional value of olive oil by enriching it in phenolic compounds from olive leaves (e.g., oleuropein) by ultrasonic maceration was studied. The experimental design used led to the following optimal extraction conditions: ultrasonic power of 60 W, temperature of 16 °C and sonication duration of 45 min. The high total phenolic content (414.3 ± 3.2 mg of oleuropein equivalent/kg of oil), oleuropein (111.0 ± 2.2 mg/kg of oil) and α-tocopherol (55.0 ± 2.1 g/kg of oil) concentrations obtained by optimized ultrasound-assisted extraction (UAE) proved the efficiency of this process when compared with the conventional solid-liquid extraction. Histochemical analyses showed that this efficiency is due to specific alteration of the phenol-containing leaf structures. Furthermore, the radical-scavenging activity of the processed oil (DPPH test) and its stability toward lipid autoxidation (heating test) confirmed its enrichment in antioxidants. Sensory evaluation of the enriched olive oil showed a slight increase in bitterness but an overall acceptability. Finally, the enriched olive oil was characterized by clear green color (L∗, a∗, b∗ parameters). 相似文献
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Muhammad Waqas Huai-Min Chen Guang-Xiong Peng Abd Al Karim Haj Ismail Muhammad Ajaz Zafar Wazir Ramoona Shehzadi Sabiha Jamal Atef AbdelKader 《Entropy (Basel, Switzerland)》2021,23(10)
We used the blast wave model with the Boltzmann–Gibbs statistics and analyzed the experimental data measured by the NA61/SHINE Collaboration in inelastic (INEL) proton–proton collisions at different rapidity slices at different center-of-mass energies. The particles used in this study were , , , , and . We extracted the kinetic freeze-out temperature, transverse flow velocity, and kinetic freeze-out volume from the transverse momentum spectra of the particles. We observed that the kinetic freeze-out temperature is rapidity and energy dependent, while the transverse flow velocity does not depend on them. Furthermore, we observed that the kinetic freeze-out volume is energy dependent, but it remains constant with changing the rapidity. We also observed that all three parameters are mass dependent. In addition, with the increase of mass, the kinetic freeze-out temperature increases, and the transverse flow velocity, as well as kinetic freeze-out volume decrease. 相似文献
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Sabiha Parveen Mohd. Sajid Ali Hamad A. Al-Lohedan Sartaj Tabassum 《Molecules (Basel, Switzerland)》2021,26(21)
Lysozyme is often used as a model protein to study interaction with drug molecules and to understand biological processes which help in illuminating the therapeutic effectiveness of the drug. In the present work, in vitro interaction studies of 1-{(2-hydroxyethyl)amino}-2-amino-1,2-dideoxy-d-glucose triphenyl tin (IV) (GATPT) complex with lysozyme were carried out by employing various biophysical methods such as absorption, fluorescence, and circular dichroism (CD) spectroscopies. The experimental results revealed efficient binding affinity of GATPT with lysozyme with intrinsic binding (Kb) and binding constant (K) values in the order of 105 M−1. The number of binding sites and thermodynamic parameters ΔG, ΔH, and ΔS at four different temperatures were also calculated and the interaction of GATPT with lysozyme was found to be enthalpy and entropy driven. The CD spectra revealed alterations in the population of α–helical content within the secondary structure of lysozyme in presence of GATPT complex. The morphological analysis of the complex with lysozyme and lysozyme-DNA condensates was carried out by employing confocal and SEM studies. Furthermore, the molecular docking studies confirmed the interaction of GATPT within the larger hydrophobic pocket of the lysozyme via several non-covalent interactions. 相似文献
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Noreen Sajjad Raha Orfali Shagufta Perveen Sabiha Rehman Aeysha Sultan Taslim Akhtar Arif Nazir Gulzar Muhammad Tahir Mehmood Safina Ghaffar Areej Al-Taweel Muhammad I. Jilani Munawar Iqbal 《Molecules (Basel, Switzerland)》2022,27(10)
Biodiesel is considered a sustainable alternative to petro-diesel owing to several favorable characteristics. However, higher production costs, primarily due to the use of costly edible oils as raw materials, are a chief impediment to its pecuniary feasibility. Exploring non-edible oils as raw material for biodiesel is an attractive strategy that would address the economic constraints associated with biodiesel production. This research aims to optimize the reaction conditions for the production of biodiesel through an alkali-catalyzed transesterification of Tamarindus indica seed oil. The Taguchi method was applied to optimize performance parameters such as alcohol-to-oil molar ratio, catalyst amount, and reaction time. The fatty acid content of both oil and biodiesel was determined using gas chromatography. The optimized conditions of alcohol-to-oil molar ratio (6:1), catalyst (1.5% w/w), and reaction time 1 h afforded biodiesel with 93.5% yield. The most considerable contribution came from the molar ratio of alcohol to oil (75.9%) followed by the amount of catalyst (20.7%). In another case, alcohol to oil molar ratio (9:1), catalyst (1.5% w/w) and reaction time 1.5 h afforded biodiesel 82.5% yield. The fuel properties of Tamarindus indica methyl esters produced under ideal conditions were within ASTM D6751 biodiesel specified limits. Findings of the study indicate that Tamarindus indica may be chosen as a prospective and viable option for large-scale production of biodiesel, making it a substitute for petro-diesel. 相似文献
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Zhiliang Wang Lei Zhang Tobias U. Schülli Yang Bai Sabiha Akter Monny Aiju Du Lianzhou Wang 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(49):17768-17773
Metal oxides are an important family of semiconductors for effective photoelectrodes in solar‐to‐chemical energy conversion. Defect engineering, such as modification of oxygen vacancy density, has been extensively applied in tailoring the optoelectric properties of photoelectrodes. Very limited attention has been paid to the influence of metal vacancies. Herein, we study metal vacancies in a typical CuO photocathode for photoelectrochemical (PEC) water splitting. The Cu vacancies can improve the charge carrier concentration, and facilitate the charge separation and transfer in the CuO photocathode. By changing the O2 partial pressure, the density of Cu vacancies can be tuned, which leads to improved PEC performance. The CuO photocathode prepared in pure O2 exhibits a 100 % photocurrent increase compared to that prepared in air. The promotion effect of Cu vacancies on the PEC is also observed in other Cu based photocathodes, showing the generic role of metal vacancies in efficient photocathodes. 相似文献