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Search Results: 1 - 10 of 714397 matches for " M. A. Tantawy "
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Effect of High Temperatures on the Microstructure of Cement Paste  [PDF]
M. A. Tantawy
Journal of Materials Science and Chemical Engineering (MSCE) , 2017, DOI: 10.4236/msce.2017.511004
Abstract: The microstructural and compositional changes within the cement paste exposed to high temperatures were monitored by XRD, FTIR, TGA/DTA and SEM techniques to understand the nature of decomposition of C-S-H gel and the associated physicomechanical properties of thermally damaged cement paste. OPC paste (w/c ratio 0.27) was hydrated for 28 days then fired up to 750°C for 2 hours (heating rate 10°C/min). The relative mass percent of calcium hydrates and portlandite was estimated by calculations derived from TGA results. Beyond 450°C, the percentage of portlandite sharply diminishes and C-S-H progressively decomposes into C2S and C3S until complete loss of calcium hydrates content occurs at 750°C. An increase of the total porosity, severe loss in mechanical strength and propagation of harmful cracks occurs. The thermal shock as a result of cooling of the heated cement paste and the rehydration of lime enhance the propagation of harmful cracks.
Throughput Estimation with Noise Uncertainty for Cyclostationary Feature Detector in Cognitive Radio Network  [PDF]
Mohsen M. Tantawy
Wireless Engineering and Technology (WET) , 2015, DOI: 10.4236/wet.2015.62003
Abstract: Cognitive Radio Networks (CRNs) are recognized as the enabling technology for improving the future bandwidth utilization. In CRNs secondary users are allowed to utilize the frequency bands of primary users when these bands are not currently being used. The secondary users are required to sense the radio frequency environment. The lower the probability of false alarm, the more chances the channel can be reused and the higher the achievable throughput for the secondary network. The main contribution of this paper is to formulate the sensing-throughput-noise uncertainty tradeoff for cyclostationary feature detection. Computer simulations have shown that for a 1 MHz channel, when the sensing duration is 2% of total time, the spectrum will get 99% probability of detection regardless of 50% noise uncertainty.
Effect of Transmission Control Protocol on Limited Buffer Cognitive Radio Relay Node  [PDF]
Mohsen M. Tantawy
Communications and Network (CN) , 2015, DOI: 10.4236/cn.2015.73013
Abstract: Transmission Control Protocol (TCP) is the most important transport layer protocol being used nowadays. It suffers from many problems over mobile networks especially over Cognitive Radio (CR). CR is one of the latest mobile technologies that brings its own share of problems for TCP. The buffer overflow for CR secondary network relay node can affect the performance of TCP. The contribution of this paper is the novel cross-layer model being used to evaluate the effect of the TCP congestion control on the secondary relay node buffer size in Cognitive Radio Network (CRN). The performance has been assessed by buffer overflow probability.
Amphetamine Versus Non Amphetamine-Related First Episode Psychosis in Saudi Arabian Patients  [PDF]
Ehab Said EL Desoky, Ashraf M A El-Tantawy, Yasser M. Raya, Abdulhameed Al-Yahya
Pharmacology & Pharmacy (PP) , 2011, DOI: 10.4236/pp.2011.23013
Abstract: Background: Amphetamines are illicit psychostimulant drugs that can induce psychotic symptoms. Very few studies have been conducted in Kingdom of Saudi Arabia (SA) on amphetamine abuse and related psychosis. Recently, the pattern of amphetamine abuse in SA showed a significant trend of increased frequency. Objectives: To investigate the extent of amphetamine abuse in a sample of Saudi patients hospitalized for first episode of acute psychosis. Also, to compare in that sample between amphetamine psychosis and other psychoses regarding demographic data, premorbid personality and symptoms profile. Method: 106 patients with acute psychosis were hospitalized and screening of urine for amphetamine was conducted for all. Patients’ psychiatric evaluation included interviewing, and ICD-10 criteria for personality disorders. 30 healthy subjects were also included for comparison with patients. Results: 34/106 of psychotic patients (32%) were positive for amphetamine in urine (≥ 1000 ng/ml). The frequency of personality disorders was significantly higher (P < 0.01) in the patients (54/106; 51%) compared with healthy subjects (6/30; 20%). Also, the incidence of personality disorders was significantly higher (P < 0.01) in amphetamine positive psychosis (25/34; 73.5%) compared with amphetamine negative psychosis (29/72; 40%). Cluster B personality disorders particularly the antisocial and borderline were significantly higher in amphetamine positive psychosis (13/34; 38%) compared with amphetamine negative psychoses (6/72; 8%). The symptom profile showed significant difference between amphetamine positive and amphetamine negative psychosis as regards ideas of reference (50% vs. 14%), suspiciousness (44% vs. 11%), suicidal ideation (38% vs. 23%), paranoid delusions (29% vs. 17%) and increased pulse or blood pressure (29% vs. 7%) respectively. Conclusion: Screening of amphetamine in urine among patients with first episode of acute psychosis can help and support the clinical distinction of amphetamine psychosis from other types of psychosis. This is therapeutically critical since the line of treatment may be different between the two types of psychoses.
Phenetic Analysis of Morphological and Molecular Traits in Acanthaceae Juss  [PDF]
Usama K. Abdel-Hameed, Mohamed E. Tantawy, Mohamed A. Salim, Magdy M. Mourad, Ishak F. Ishak
Journal of Biosciences and Medicines (JBM) , 2015, DOI: 10.4236/jbm.2015.33004
Abstract:

Acanthaceae has received considerable taxonomic attention at the familial, subfamilial, tribal and subtribal levels. Several different infra-familial classifications have been proposed for the Acanthaceae, but no taxonomic consensus has yet been reached. The main objective of the present study is to throw light on the phenetic relationships and to explore the contribution of morphological and molecular characters in systematics of Acanthaceae. The morphological data viz. macromorphology, stomatography, lamina architecture and ISSR profiles of 30 Egyptian acanthaceous taxa were investigated. The phenetic analysis using NTSYS-PC version 2.02 software based on 55 potentially informative morphological and molecular characters indicated that the used morphological and ISSR criteria is likely to be useful and valuable taxonomic traits. The morphological characters and ISSR aspects of all the studied species produced a phenogram that showed two series; one of them had two subseries, the first one comprised only three taxa while the second divided into two clusters, each contained two groups. The delimitation and the membership of the studied taxa clearly merit additional study using more criteria. The phenetic analysis of both morphological and molecular attributes clarified the segregation of genus Avicennia as a distinct identity away from Acanthaceae. Acanthus mollis & A. montanus are isolated in its own series that comparable to tribe Acantheae of the current taxonomic systems. The studied species of Thunbergia are gathered its own subseries that comparable to tribe Thunbergiae and Ruellia in its own group that comparable to tribe Ruellieae.

Phytosociological Studies on the Wild Mesembryanthemum Species in Egypt 1. Quantitative Analysis of the Representative Communities
F. M. El Shayeb,H. El Tantawy,A. El Kholi
Journal of Biological Sciences , 2002,
Abstract: Communities of Mesembryanthemum species were studied quantitatively. Surveys were carried out in five habitats supporting M. crystallinum, four habitats supporting M. forsskaolii and six habitats supporting M. nodiflorum. Vegetation analysis of the community types included (density, frequency, cover area, relative density, relative frequency, relative cover, fresh weight and biomass) of each species. Results indicated that M. crystallinum and M. forsskaolii had higher densities than M. nodiflorum, while M. nodiflorum and M. crystallinum had higher biomass than M. forsskaolii. Results also showed highest cover for M. crystallinum and lowest for M. nodiflorum.
Evaluation of the Pozzolanic Activity of Sewage Sludge Ash
M. A. Tantawy,A. M. El-Roudi,Elham M. Abdalla,M. A. Abdelzaher
ISRN Chemical Engineering , 2012, DOI: 10.5402/2012/487037
Abstract:
Fire Resistance of Sewage Sludge Ash Blended Cement Pastes
M. A. Tantawy,A. M. El-Roudi,Elham M. Abdalla,M. A. Abdelzaher
Journal of Engineering , 2013, DOI: 10.1155/2013/361582
Abstract: The aim of the present study is to investigate the hydration characteristics and the fire resistance of sewage sludge ash blended cement pastes by the determination of compressive strength, bulk density, and total porosity in addition to XRD and SEM techniques. Sewage sludge ash modifies the hydration of cement because of its pozzolanic reaction with portlandite favoring the formation of crosslinked fibrous calcium silicate of low Ca/Si ratio. Hence, it was concluded that thermal damage of cement pastes after the exposure to high treatment temperatures (i.e., crack formation and loss of mechanical properties) was effectively reduced with sewage sludge as content up to 20?wt% because of that the presence of crosslinked fibrous calcium silicate strengthens the cement matrix. 1. Introduction Sewage water is the collection of wastewater effluents from domestic, hospital, commercial, and industrial establishments. The objective of the sewage treatment is to produce treated sewage water and sewage sludge suitable for safe discharge into the environment or reuse [1]. International environmental protection agencies recommended that incineration is an attractive disposal method of sewage sludge [2]. Sewage sludge ash has been used as an additive in the production of construction materials [3], mortars [4], and concrete [5]. The exposure of concrete to high temperatures as in an accidental fire of buildings leads to an undesirable structural quality deterioration [6]. Previous studies illustrate that hardened cement paste plays a key role in high temperatures deterioration process. The main damage mechanisms that discuss the deterioration of concrete at elevated temperatures are thermal mismatch, decomposition of hydrates, coarsening of pore structure, and pore pressure effects [7]. Siliceous aggregates expand around 575°C as a result of the α-β quartz inversion, whereas cement paste shrinks above 200°C [8]. This thermal mismatch (i.e., expansion of siliceous aggregate and shrinkage of cement paste matrix) causes a considerable tension at the aggregate-matrix interface leading eventually to interface fracture and cracking [9]. The decomposition of hydrates occurs during the thermal damage of cementitious materials including the decomposition of ettringite, C-S-H, and carboaluminate hydrates at 180–450°C and portlandite at 425–580°C [10]. The decomposition of portlandite damages the C-S-H. The decomposition of hydrates decreases stiffness and strength of cementitious materials. Volume reduction of the hydrated phases because of the loss of bound water leads to air
Evaluation of the Pozzolanic Activity of Sewage Sludge Ash
M. A. Tantawy,A. M. El-Roudi,Elham M. Abdalla,M. A. Abdelzaher
ISRN Chemical Engineering , 2012, DOI: 10.5402/2012/487037
Abstract: Raw sewage sludge was characterized by XRD, FTIR, SEM, and TGA techniques and incinerated in temperature range 650–950°C for 2?h. The effect of incineration temperature on the microstructure and pozzolanic activity of the resultant ash was investigated by techniques mentioned above as well as Chapelle test. It was concluded that incineration of sewage sludge affects the microstructure and pozzolanic activity of the resultant ash. During incineration at temperatures lower than 800°C, amorphous silica captures fixed carbon resulting from incomplete combustion conditions whereas at higher temperatures crystallization of amorphous silica was enhanced. Hydration products formed from hydrothermal treatment of silica fume with lime is amorphous whereas that of sewage sludge ash is fibrous. Hence, incineration of sewage sludge ash must be optimized at 800°C to preserve the pozzolanic activity of the resultant ash. 1. Introduction Sewage is the collection of wastewater effluents from domestic, hospital, commercial, industrial establishments, and rain water. The objective of sewage treatment is to produce treated sewage water and sewage sludge suitable for safe discharge into the environment or reuse [1]. The most common treatment options for sewage sludge include anaerobic digestion, aerobic digestion, and composting. Choice of the treatment method depends on the amount of sludge and other site-specific conditions [2]. Sewage sludge tends to accumulate heavy metals existing in the wastewater. The composition of sewage sludge and its content of heavy metals vary widely depending on the sludge origins and treatment options [3]. In past decades, sewage sludge was primarily disposed to landfills and seawaters [4]. Space limitations on existing landfills and increasing environmental concerns such as groundwater pollution from landfill leachate, odor emission and soil contamination have prompted the investigation of alternative disposal routes [5]. Sewage sludge has been used in agriculture as fertilizer and soil amendment [6]. However heavy metals such as Zn, Cu, Ni, Cd, Pb, Hg, and Cr are principal elements restricting the use of sludge for agricultural purposes [3]. The solidification/stabilization of sewage sludge in cementitious matrix has been evaluated [7]. Sewage sludge adversely affects durability of concrete, mainly due to the organic material which retards setting and heavy metals which interfere with the hardening reactions [8]. Hence, sewage sludge addition in concrete was limited to 10?wt.% and the solidified concrete was recommended for use in certain
Somatosensory Evoked Potential for Detection of Subclinical Neuropathy in Egyptian Children with Acute Lymphoblastic Leukaemia
A.A.G. Tantawy,S.M. Hassanein,A.A.M. Adly,O.M. Saeed
Pakistan Journal of Biological Sciences , 2010,
Abstract: To evaluate neurological changes developing during paediatric Acute Lymphoblastic Leukaemia (ALL) therapy clinically and through electrophysiological Study of Somatosensory Evoked Potentials (SSEPs) changes in different phases of therapy. Thirty five-ALL patients with age range from 3-14 years were included compared to 30 healthy controls. History, neurological examination, complete blood counts, cytological examination of bone marrow aspirate and cerebrospinal fluid with Measurement of Serum Methotrexate (MTX) were done. The SSEPs were performed and patients subjected to another SSEP with measurement of serum MTX level before and 10 days after intra-thecal injection (IMTX). Clinical neurological findings in patients after induction were depressed deep tendon reflexes (43.3%), hypotonia (28.6%), lost pain sensation (28.6%), muscle weakness (17.1%) and movement disorders (17.1%). Percentage of delayed SSEPs after induction were at levels of brachial plexus (28.6%), spinal cord (68.6%), cortical conduction (31.4%), ERB-N13 Inter Peak Latency (IPL) (74.3%) and N13-N20 IPL (17.1%) in the studied patients. Significant prolonged latency of N13 (p = 0.005), N20 (p = 0.04) and IPL of ERB-N 13 (p = 0.005), N13-N20 (p = 0.01), Inter-Side Difference (ISD) of N13 (p = 0.01), ERB-N13 (p = 0.02) and N13-N20 (p = 0.03) after induction compared to values at diagnosis. Significant positive correlation were found between serum MTX after IMTX with N13-N20 IPL (p = 0.01), N20 ISD (p = 0.03) with significant prolongation in N20 latency, N13-N20 IPL and ISD of N20 compared to values before injection. ALL patients have prolonged latency of SSEPs at cervical cord and cortical levels which increased after IMTX due to axonal injury throughout the cord. SSEPs could be an early diagnostic tool for subclinical neuropathy.
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