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Search Results: 1 - 10 of 469186 matches for " Ahmed A. Moustafa "
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Levodopa Enhances Reward Learning but Impairs Reversal Learning in Parkinson's Disease Patients
Ahmed A. Moustafa
Frontiers in Human Neuroscience , 2011, DOI: 10.3389/fnhum.2010.00240
Motor and cognitive changes in normal aging
Ahmed A. Moustafa
Frontiers in Aging Neuroscience , 2014, DOI: 10.3389/fnagi.2014.00331
Freezing of gait and response conflict in Parkinson's disease: computational directions
Ahmed A. Moustafa
Frontiers in Computational Neuroscience , 2014, DOI: 10.3389/fncom.2014.00007
The Effect of Incorporation of Ferrite Nano-particles on Compressive Strength and Re-sistivity of Self-Compacting Concrete  [PDF]
Mohamed A. Ahmed, Yehia A. Hassanean, Kamal A. Assaf, Moustafa A. Shawkey
Open Journal of Civil Engineering (OJCE) , 2015, DOI: 10.4236/ojce.2015.51013
Abstract: Mn-Ferrite nanoparticles were prepared using citrate auto combustion method. The prepared sample was characterized by X-ray diffraction (XRD), HRTEM and BET to measure the particle diameter and the surface area of the prepared sample. The data of XRD clarified that the sample was formed in single phase spinel structure without any extra peaks indicating non-existence of any secondary phase. The HRTEM micrograph indicated that the particles were in an agglomerated state due to the absence of surfactant and high magnetic properties of Mn-Ferrite nanoparticles. The mechanical properties were measured at different ratios of nano-Ferrite to concrete. The obtained values of mercury intrusion porosimetry (MIP) indicated that the addition of Mn-Ferrite nanoparticles increased the compressive strength and decreased the total intrusion volume. This was due to the rapid consuming of Ca(OH)2 which was formed during hydration of Portland cement especially at early ages due to the high reactivity of MnFe2O4 nanoparticles. Moreover, MnFe2O4 nanoparticles recovered the particle packing density of the blended cement, leading to a reduced volume of pores in the cement paste.
Study of Electroslag Remelted and Nitrogen Containing High Speed Tool Steel M41  [PDF]
S. A. El Badry, Hossam Halfa, A. Ahmed, A. G. Moustafa
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2010, DOI: 10.4236/jmmce.2010.91001
Abstract: Mossbauer Effect (ME) spectra, microstructure and hardness of some alloyed and conventional AISI M41 high speed tool steel samples produced by induction furnace as well as after doing electro-slag refining (ESR) process under different slag compositions have been investigated. The obtained ME spectra for all samples could be analyzed to a singlet and three sextets. The appeared singlet in the conventional steel and that alloyed with nitrogen as well as two refined samples using electro-slag remelting 1 and 2 (ESR1, M41N and ESR2, M41N) can be attributed to γ–austenite phase, while the singlet that appeared in the refined sample 3 (ESR3, M41N) can be attributed to some iron nitride of the form ( ε-Fe2N). In the refined sample, which does not contain nitrogen, γ–austenite phase cannot be found and some α-Fe2O3 was detected. The observed three sextets were attributed to three different magnetic martensite phases. It appeared also that some transformations in between the three martensite phases and between martensite and austenite take place, and all these changes were thoroughly discussed. It is interesting to state that the obtained ME results are in agreement with those obtained from optical microscopy and micro-hardness measurements.
Synthesis and Anticancer Activity of Some New S-Glycosyl and S-Alkyl 1,2,4-Triazinone Derivatives
Hosam A. Saad,Ahmed H. Moustafa
Molecules , 2011, DOI: 10.3390/molecules16075682
Abstract: A series of S-glycosyl and S-alkyl derivatives of 4-amino-3-mercapto-6-(2-(2-thienyl)vinyl)-1,2,4-triazin-5(4H)-one (1) were synthesized using different halo compounds such as preacetylated sugar bromide, 4-bromobutylacetate, 2-acetoxyethoxy-methyl bromide, 3-chloropropanol, 1,3-dichloro-2-propanol, epichlorohydrin, allyl bromide, propargyl bromide, phthalic and succinic acids in POCl3. The structures of the synthesized compounds have been deduced from their elemental analysis and spectral (IR, 1H-NMR, and 13C-NMR) data. Some of the synthesized compounds were screened as anticancer agents. Significant anticancer activities were observed in vitro for some members of the series, and compounds 4-Amino-3-(3-hydroxypropylthio)-6-(2-(2-thienyl)vinyl)-1,2,4-triazin-5(4H)-one (12) and 3-(4-Oxo-3-(2-(2-thienyl)vinyl)-4H-[1,3,4]thiadiazolo-[2,3-c][1,2,4]tr-iazin-7-yl)propanoic acid (18) are active cytotoxic agents against different cancer cell lines.
Numerical Investigation of the Geometric Phase and Entropy Squeezing for a Two-Level System in the Presence of Decoherence Terms  [PDF]
Moustafa M. Salama, Ahmed O. Elnubi, Sayed Abdel-Khalek, Mohamed A. El-Sayed
Journal of Electromagnetic Analysis and Applications (JEMAA) , 2013, DOI: 10.4236/jemaa.2013.59057

In this paper, we have presented the numerical investigation of the geometric phase and field entropy squeezing for a two-level system interacting with coherent field under decoherence effect during the time evolution. The effects of the initial state setting and atomic dissipation damping parameter on the evolution of the geometric phase and entropy squeezing have been examined. We have reported some new results related to the periodicity and regularity of geometric phase and entropy squeezing.

Synthesis and Analgesic Activity of Some New Pyrazoles and Triazoles Bearing a 6,8-Dibromo-2-methylquinazoline Moiety
Hosam A. Saad,Nermen A. Osman,Ahmed H. Moustafa
Molecules , 2011, DOI: 10.3390/molecules161210187
Abstract: 2-(6,8-Dibromo-2-methylquinazolin-4-yloxy)-acetohydrazide (4) was prepared by the reaction of 6,8-dibromo-2-methylbenzo-[d][1,3]oxazin-4-one with formamide to afford quinazolinone 2, followed by alkylation with ethyl chloroacetate to give the ester 3. Treatment of ester 3 with hydrazine hydrate and benzaldehyde afforded 4 and styryl quinazoline 5. The hydrazide was reacted with triethyl orthoformate, acetylacetone and ethyl acetoacetate and benzaldehyde derivatives to afford the corresponding pyrazoles 6, 7, 9 and hydrazone derivatives 10a-c. Cyclization of hydrazones 10a-c with thioglycolic acid afforded the thiazole derivatives 11a-c. Reaction of the hydrazide with isothiocyanate derivatives afforded hydrazinecarbothioamide derivatives 12a-c, which cyclized to triazole-3-thiols and thiadiazoles 13a-c and 14a-c, respectively. Fusion of the hydrazide with phthalimide afforded the annelated compound 1,2,4-triazolo[3,4-a]isoindol-5-one (15). The newly synthesized compounds were characterized by their spectral (IR, 1H-, 13C-NMR) data. Selected compounds were screened for analgesic activity.
Time representation in reinforcement learning models of the basal ganglia
Samuel J. Gershman,Ahmed A. Moustafa,Elliot A. Ludvig
Frontiers in Computational Neuroscience , 2013, DOI: 10.3389/fncom.2013.00194
Abstract: Reinforcement learning models have been influential in understanding many aspects of basal ganglia function, from reward prediction to action selection. Time plays an important role in these models, but there is still no theoretical consensus about what kind of time representation is used by the basal ganglia. We review several theoretical accounts and their supporting evidence. We then discuss the relationship between reinforcement learning models and the timing mechanisms that have been attributed to the basal ganglia. We hypothesize that a single computational system may underlie both reinforcement learning and interval timing—the perception of duration in the range of seconds to hours. This hypothesis, which extends earlier models by incorporating a time-sensitive action selection mechanism, may have important implications for understanding disorders like Parkinson's disease in which both decision making and timing are impaired.
Potato Disc Bioassay and Cytotoxic Effect of Leptadenia pyrotechnica: Comparative Study of Diverse Extracts
Amal M. Youssef Moustafa,Ahmed I. Khodair,Mahmoud A. Saleh
Pakistan Journal of Biological Sciences , 2011,
Abstract: Comparative acute toxicity studies of the latex and sequential extracts of Leptadenia pyrotechnica (Forsk.) Decne (Asclepiadaceae) were recorded using brine shrimp. The higher toxicities were exhibited in latex; methanol, methanol/dichloromethane (1:1), defatted methanol/dichloromethane (1:1), defatted methanol and dichloromethane extracts. The other extracts; aqueous, alkaloids, ethyl acetate and n-butanol exhibited less toxicities compared with the other extracts. The estimated LC50 and its 95% confidence limits for these extracts expressed in ppm were: methanol, latex 18.84 (11.22-31.61), methanol/dichloromethane 19.95 (7.76-53.70), defatted methanol/dichloromethane 21.38 (7.24-63.10), defatted methanol 28.19 (16.27-48.81) and dichloromethane 30.90 (11.75-79.43). The anti-tumor activities; potato disc assays of methanol, ethyl acetate and alkaloids extracts showed good activities as anti-tumor agent which represented-49.30,-43.20 an -33.60%, respectively. While latex and aqueous extract represented-30.80 and-28.17%, respectively.
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