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Search Results: 1 - 10 of 325294 matches for " S. S. Arafat "
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Study of the Structural and Electrical Properties of Cr-Doped BiFeO3 Ceramic  [PDF]
S. S. Arafat, S. Ibrahim
Materials Sciences and Applications (MSA) , 2017, DOI: 10.4236/msa.2017.810051
Abstract: Multiferroic BiFe1-xCrxO3 (x = 0.2 and 0.4) ceramics were synthesized in a single phase. The effects of Cr3+ substitution on the crystal structure, dielectric permittivity and leakage current were investigated. Preliminary X-ray structural studies revealed that the samples had a rhombohedral perovskite crystal structure. The dielectric constant ε' significantly increased while the dielectric loss tanδ was substantially decreased with the increase in Cr3+ substitution. The temperature effect on the dielectric properties exhibited an anomaly corresponding to magneto-electric coupling in the samples and was shifted to lower temperatures with the increase in Cr3+ substitution. The leakage current density also reduced in magnitude with the increase in the Cr3+ substitution.
Internet-Based Spectral Database for Different Land Covers in Egypt  [PDF]
S. M. Arafat, E. Farg, M. Shokr, G. Al-Kzaz
Advances in Remote Sensing (ARS) , 2013, DOI: 10.4236/ars.2013.22012

The spectral signatures of natural objects in the visible and near-infrared spectral range are influenced by the object’s physical and biochemical properties. These signatures can be compiled in a database and used to retrieve information of land cover types and their physical composition from actual hyperspectral observations. This paper describes development process of hyperstectral database of reflectance from different land cover types in Egypt. It has been compiled from data obtained using a ground-based spectroradiometer system that covers the spectral range from 350 to 2500 nm at 1 nm resolution. The database is accessible through a website http://www.spectraldb.narss.sci.eg/spectral, where the system includes also metadata that describes the site environment and measurement processes. The system provides flexible mechanisms and friendly interfaces to allow accessing the database by the non-specialized people, whereas spectral data can be sorted by sites, species or selected environmental parameters. The system presents sample results from different vegetation and soil covers. Development of such a database is essential for different remote sensing applications, satellite’s calibrations, data dissemination and linkage with other databases for scientific researches purposes.

Gene therapy for carcinoma of the breast: Pro-apoptotic gene therapy
Jesús Gómez-Navarro, Waleed Arafat, Jialing Xiang
Breast Cancer Research , 1999, DOI: 10.1186/bcr27
Abstract: The highly orchestrated form of cell death known as apoptosis goes awry to some extent in most cancers. Increasingly, a general theme in cancer pathophysiology is the development of a defect in the function of pro-apoptotic molecules, such as p53, that commonly prepare the cell for apoptosis whenever cell proliferation or DNA damage is induced; lack of these molecules therefore deprives the cell of a critical safety mechanism [1]. Alternatively, a functional excess of anti-apoptotic molecules, such as Bcl-2, may also occur in tumors. In each case, the result is an imbalance that favors the inappropriate survival of tumor cells. The mechanisms involved and their components are attractive therapeutic targets because the tumor cell is totally dependent on them for its survival, and appears typically to have a higher sensitivity to the induction of apoptosis than normal tissues [1,2]. In addition, restoring or enhancing the capacity to undergo apoptosis may, in some cases, be a crucial event that renders tumors sensitive to classical anticancer agents, such as those used in chemotherapy [3,4**] and radiotherapy [5,6]. The present review discusses the most common genetic alterations that alter apoptosis regulation in breast cancer, and the initial gene-based approaches that have been explored to overcome them with therapeutic intent.There is a multitude of critical steps during the pathogenesis of cancer in which avoidance of programmed cell death assures the progression, and maintenance, of the malignant phenotype (Fig. 1) [7,8*,9,10]. Early during tumor progression, defects in apoptosis allow the survival of the cancer cell despite the existence of DNA damage and cell-cycle dysregulation. This severe breaking of a basic DNA housekeeping action contributes to the genetic instability that characterizes cancer, and thus initiates and sustains a spiral of further and further genetic aberrations that endow tumor cells with extraordinary capacities and adaptability. In fact,
Gas Sensors Based on One Dimensional Nanostructured Metal-Oxides: A Review
M. M. Arafat,B. Dinan,Sheikh A. Akbar,A. S. M. A. Haseeb
Sensors , 2012, DOI: 10.3390/s120607207
Abstract: Recently one dimensional (1-D) nanostructured metal-oxides have attracted much attention because of their potential applications in gas sensors. 1-D nanostructured metal-oxides provide high surface to volume ratio, while maintaining good chemical and thermal stabilities with minimal power consumption and low weight. In recent years, various processing routes have been developed for the synthesis of 1-D nanostructured metal-oxides such as hydrothermal, ultrasonic irradiation, electrospinning, anodization, sol-gel, molten-salt, carbothermal reduction, solid-state chemical reaction, thermal evaporation, vapor-phase transport, aerosol, RF sputtering, molecular beam epitaxy, chemical vapor deposition, gas-phase assisted nanocarving, UV lithography and dry plasma etching. A variety of sensor fabrication processing routes have also been developed. Depending on the materials, morphology and fabrication process the performance of the sensor towards a specific gas shows a varying degree of success. This article reviews and evaluates the performance of 1-D nanostructured metal-oxide gas sensors based on ZnO, SnO2, TiO2, In2O3, WOx, AgVO3, CdO, MoO3, CuO, TeO2 and Fe2O3. Advantages and disadvantages of each sensor are summarized, along with the associated sensing mechanism. Finally, the article concludes with some future directions of research.
Improvement of Nitrogen Fertilizer Efficiency with Nitrification Inhibitors in Lowland Rice
S.M. Arafat,A. Abd El-Galil,M. Abu Seeda
Pakistan Journal of Biological Sciences , 1999,
Abstract: Rice is a very responsive crop to nitrogen, but the efficiency of the N-fertilizers is low. Greenhouse experiment has been conducted to evaluate some synthetic (N-serve) and natural (neem cake and waste tea) nitrification inhibitors to improve fertilizer efficiency and reduce N-losses in rice fields. Nitrogen was applied as urea and ammonium sulfate at a rate of 60mg/Kg soil. Results revealed that addition of inhibitors with both N fertilizer caused a significantly increase in both grain and straw yields rice, addition of 0.04 per cent neem cake with both urea and as gave the highest grain and straw yields of rice while the waste tea gave the lowest. The percentage increase of total yield with urea + inhibitor treatments ranged between 5.8 per cent to 26 per cent when compared with urea alone, 26 per cent increase was recorded for 0.04 per cent neem cake treatment and 22.4 per cent for N-serve, while 5.8 per cent was recorded for 0.04 per cent waste tea treatment. Also, the percentage increase in total rice yield over AS alone was 14.4 per cent and 25.6 per cent for 0.02 per cent and 0.04 per cent neem cake treatments respectively, while was 8.8 per cent for N-serve treatment. Results also showed that neem cake combined with both urea and AS was more effectiveness on N-uptake especially at applied rate (0.04 per cent ). The percentage increase in total N-uptake over urea alone was 31 per cent , 29 per cent and 5 per cent for 0.04 per cent neem cake, N-serve and 0.04 per cent waste tea respectively. On the other hand, the percentage increase of total N-uptake over all as alone was 29 per cent and 15 per cent for 0.04 per cent and 0.02 per cent neem cake treatments respectively, while, the waste tea a very low increase in total N-uptake. N-recovery by rice plant increased from 285 to 513 mg N/pot as a result of addition of inhibitors, as well as an improved in the utilization efficiency of N from urea and AS fertilizers was recorded.
Three Cladosporium spp. As Promising Biological Control Candidates for Controlling Whiteflies (Bemisia spp.) In Egypt
N. F. Abdel-baky,Arafat,S. Nehal,A.H. Abdel-salam
Pakistan Journal of Biological Sciences , 1998,
Abstract: Three species of entomopathogenic fungi, Cladosporium uredinicola, C. cladosporioides, and C. chlorocephalum, were found attacking whiteflies (Bemisia spp.) in Mansoura region, Dakahlia Governorate, Egypt. Their prevalence on Bemisia infesting seven plant hosts varied from 10.0 to 28.0% according to the plant host. The morphology of these three fungi and their infection symptoms is discussed. Attempts were made to initiate artificial infections in different stages of a laboratory culture of Bemisia spp. Results indicated that eggs were infected at a lower percentage (14 to 28%), whereas the hatching rate of eggs recorded a higher percentage (56%). Pathogenicity effect on nymphs and adults were very high ( 88%) and varied according to the spore concentrations and periods after infection. Laboratory studies revealed that C. uredinicola gave the highest infection percentages, followed by C. cladosporioides and C. chlorocephalum. Light regime studies showed that the three species of the fungus were more aggressive on Bemisia under a diurnal light regime than under continuous darkness.
In vivo Antinociceptive Activity of Leaf Extract of Crinum asiaticum and Phytochemical Analysis of the Bioactive Fractions
M.Z. Asmawi,O.M. Arafat,S. Amirin,I.M. Eldeen
International Journal of Pharmacology , 2011,
Abstract: Crinum asiaticum is a perennial bulbous herb native to tropical South-eastern Asia. The plant is useful in Asian and African traditional medicine as an analgesic agent. This report aimed to investigate the antinociceptive effects of leaf extracts of Crinum asiaticum on rats and to highlight the major chemical groups of the bioactive fractions. Powdered leaf of Crinum asiaticum was sequentially extracted using petroleum ether, chloroform and methanol. The extracts were investigated for their antinociceptive activity on rats using the carrageenan-induced paw hyperalgesia method. Pain threshold response was measured by applying pressure on the rat's paw using analgesy-meter. Oedema was induced by injection of 0.1 mL 1% (w/v) carrageenan dissolved in normal saline into the footpad of the right hind paw of the rat and allowed to develop. The test samples were administered orally in a dose of 1000, 500 and 250 mg kg-1 (10 mL kg-1). Rats administered orally with vehicle were used as negative group. Indomethacin (1 mg kg-1) was used as positive control. After 4 h, the pain threshold of each rat was measured. The best activity was shown by the chloroform extracts at the dose of 250 mg kg-1 (n = 4-5 in each group; p<0.05), followed by the methanol extracts. No activity was observed with the petroleum ether extract (1000 mg kg-1). Indomethacin was used as positive control (1 mg kg-1). Phytochemical screening of the active fractions indicated the presence of alkaloids, coumarins, glycosides, triterpenes and flavonoids. The results obtained support the reported uses of the plant as traditional analgesic agent.
Bioadhesive Controlled Metronidazole Release Matrix Based on Chitosan and Xanthan Gum
Ala’a F. Eftaiha,Nidal Qinna,Iyad S. Rashid,Mayyas M. Al Remawi,Munther R. Al Shami,Tawfiq A. Arafat,Adnan A. Badwan
Marine Drugs , 2010, DOI: 10.3390/md8051716
Abstract: Metronidazole, a common antibacterial drug, was incorporated into a hydrophilic polymer matrix composed of chitosan xanthan gum mixture. Hydrogel formation of this binary chitosan-xanthan gum combination was tested for its ability to control the release of metronidazole as a drug model. This preparation (MZ-CR) was characterized by in vitro, ex vivo bioadhesion and in vivo bioavailability study. For comparison purposes a commercial extended release formulation of metronidazole (CMZ) was used as a reference. The in vitro drug-release profiles of metronidazole preparation and CMZ were similar in 0.1 M HCl and phosphate buffer pH 6.8. Moreover, metronidazole preparation and CMZ showed a similar detachment force to sheep stomach mucosa, while the bioadhesion of the metronidazole preparation was higher three times than CMZ to sheep duodenum. The results of in vivo study indicated that the absorption of metronidazole from the preparation was faster than that of CMZ. Also, MZ-CR leads to higher metronidazole C max and AUC relative to that of the CMZ. This increase in bioavailability might be explained by the bioadhesion of the preparation at the upper part of the small intestine that could result in an increase in the overall intestinal transit time. As a conclusion, formulating chitosan-xanthan gum mixture as a hydrophilic polymer matrix resulted in a superior pharmacokinetic parameters translated by better rate and extent of absorption of metronidazole.
A Study of Students and Teachers' Preferences and Attitudes towards Correction of Classroom Written Errors in Saudi EFL Context
Arafat Hamouda
English Language Teaching , 2011, DOI: 10.5539/elt.v4n3p128
Abstract: It is no doubt that teacher written feedback plays an essential role in teaching writing skill. The present study, by use of questionnaire, investigates Saudi EFL students' and teachers' preferences and attitudes towards written error corrections. The study also aims at identifying the difficulties encountered by teachers and students during the feedback process. The questionnaire findings reveal that both teachers and students have positive attitudes towards written error correction. The study also shows that while teachers and students share such common preferences as the importance of error correction and the types of errors, there are considerable discrepancies as to the techniques of error correction. For instance, students favor the overall correction, whereas most teachers do not. However, the results show that students prefer teacher correction to peer and self-correction. Moreover, both the teachers and students have encountered a number of difficulties, so suggestions have been investigated so as to deal with the problems.
Sex Steroids and Breast Cancer: An Overview  [PDF]
Zeina Nahleh, Juan E. Arenas, Arafat Tfayli
Journal of Cancer Therapy (JCT) , 2013, DOI: 10.4236/jct.2013.44097

Sex steroids, also known as sex hormones are synthesized naturally by the gonads (ovaries or testes). The two main classes of sex steroids, androgens and estrogens, are crucial hormones for the proper development and function of the body; they regulate sexual differentiation, the secondary sex characteristics, and sexual habits. They are also well known to influence many common cancers, especially hormonally driven cancers such as breast and prostate cancer. In this report, we review the association of sex steroids with cancer and the potential use of endocrine manipulation in cancer therapy as well as the limitations and challenges faced in this field.

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