American University in Cairo

About: American University in Cairo is a education organization based out in Cairo, Egypt. It is known for research contribution in the topics: Population & Context (language use). The organization has 2472 authors who have published 5339 publications receiving 73741 citations.

Effect of cold work and annealing on the structure and characteristics of NiTi alloy

Abstract: A hot rolled NiTi alloy (50.7 at.% Ni) was subjected to cold rolling with reductions of 20%, 30% and 40%. Some of the 40% cold rolled samples were then annealed at 400 °C, 500 °C, 600 °C and 700 °C. X-ray results and microstructural analysis show that increasing the percent of cold rolling causes an increase in the volume fraction of martensite, which results in an increase in recoverable strain, tensile strength and hardness. On the other hand, this eliminates the superelasticity plateau and results in a reduction in ductility and shape memory recovery. After an initial sharp decrease in superelasticity with cold rolling, further increase in cold rolling results in relative improvement in the superelasticity. Annealing on the other hand causes a significant increase in austenite volume fraction, leading to a decrease in hardness and superelasticity in the temperature range of 400 °C–500 °C. Recrystallization starts at 500 °C and grains grow with annealing at higher temperatures while hardness and superelasticity increase.The results of this work indicate that it is best to use the NiTi alloy in the as hot rolled condition if maximum SME is desired. Cold rolled NiTi would be preferable if high strength, hardness and acceptable recoverable strains are desirable.

Effect of sex, size, and age of commensal rat hosts on the infestation parameters of their ectoparasites in a rural area of Egypt.

Abstract: The present study was carried out in the Bilbeis area, Sharqiya Governorate, Egypt. A total of 127 male and 115 female black rats Rattus rattus and 124 male and 153 female Norway rats R. norvegicus was collected during the study period. A total of 20,643 and 40,997 ectoparasites was recovered from R. rattus and R. norvegicus, respectively. Three common mite species were recovered from both rat hosts: Ornithonyssus bacoti, Radfordia ensifera, and Laelaps nuttalli. Three common flea species were also recovered from both rat hosts: Echidnophaga gallinacea, Leptopsylla segnis, and Xenopsylla cheopis. Polyplax spinulosa was the only louse species that infested both rat hosts. Rats that lived more than 12 mo formed about 24 and 14% of the populations of the black and Norway rats, respectively. The prevalences and general indices of many ectoparasites were significantly higher on males than on females of both rat hosts. Seasonal differences in prevalences and general indices of many ectoparasites were recorded between the 2 sexes of both rat species. Prevalences and general indices of most ectoparasites on both rat species showed a tendency to increase with increasing size and age of rat hosts. The type and degree of correlation between prevalences and general indices on the one hand and each of body size and age on the other hand differed among the species of ectoparasites.

Internal Control Quality, Egyptian Standards on Auditing and External Audit Delays: Evidence from the Egyptian Stock Exchange

Abstract: This paper examines the impact of internal control quality (ICQ) on external audit delays as proxied by the auditor component of audit report lag (A-ARL) and the effect of the adoption of the Egyptian Standards on Auditing (ESA) on this relationship in the Egyptian context. Using a balanced panel data of 344 firm-year observations spanning from 2007 to 2010, we hypothesise and empirically find the following. First, ICQ represents a key determinant of timely disclosure, as it contributes significantly to the reduction of A-ARL. Second, the adoption of the ESA has significantly contributed to the improvement of audit practices by reducing A-ARL. Third, the adoption of ESA has also strengthened the relationship between A-ARL and ICQ for the post-adoption period of these standards. Additional analysis is conducted to examine the impact of industry characteristics on the relationship between ICQ and A-ARL and the association remains significant regardless of the sector considered. In order to make a more informative analysis, we examine the effect of ICQ on the management component of audit report lag (M-ARL) and we document a positive association between both variables. The results contribute to the literature dealing with the relation between A-ARL and ICQ by shedding light on the importance of ICQ in audit practices in an emerging country characterised by weak legal enforcement and a high level of secrecy. Findings also have policy implications for Egyptian standard-setters with respect to the development of internal auditing standards.

Tunability and Sensing Properties of Plasmonic/1D Photonic Crystal.

Abstract: Gold/one-dimensional photonic crystal (Au/1D-PC) is fabricated and applied for sensitive sensing of glucose and different chemical molecules of various refractive indices. The Au layer thickness is optimized to produce surface plasmon resonance (SPR) at the right edge of the photonic band gap (PBG). As the Au deposition time increased to 60 sec, the PBG width is increased from 46 to 86 nm in correlation with the behavior of the SPR. The selectivity of the optimized Au/1D-PC sensor is tested upon the increase of the environmental refractive index of the detected molecules. The resonance wavelength and the PBG edges increased linearly and the transmitted intensity increased nonlinearly as the environment refractive index increased. The SPR splits to two modes during the detection of chloroform molecules based on the localized capacitive coupling of Au particles. Also, this structure shows high sensitivity at different glucose concentrations. The PBG and SPR are shifted to longer wavelengths, and PBG width is decreased linearly with a rate of 16.04 A/(μg/mm3) as the glucose concentration increased. The proposed structure merits; operation at room temperature, compact size, and easy fabrication; suggest that the proposed structure can be efficiently used for the biomedical and chemical application.