Karimat El-Sayed

Structural and anisotropic thermal expansion correlation of Li2ZrO3 at different temperatures

Structural and thermal expansion studies of Li2ZrO3 were carried out by recording X-ray powder diffraction patterns at five temperatures, 82, 198, 300, 423 and 573 K. The Rietveld refinement method was used for the analysis. There were large anisotropic changes in the lattice parameters as a function of temperature, slight changes in the fractional coordinates of the different atoms, and anisotropic changes in the interatomic distances between the different cations. The correlation of these anisotropies with the structure is considered.

Structural, microstructural, magnetic and electrical properties of diluted magnetic Se1−xMnx

Polycrystalline Se1?xMnx (x?=?0.01, 0. 03 and 0.05) samples were prepared by solid state reaction. The x-ray analysis using Rietveld method revealed the presence of two phases in the Se1?xMnx matrix; the Se phase and MnSe phase. The magnetization measurement showed three peaks at; 270, 160 and 150?K. The two peaks at 150?K and 160?K are due to antiferromagnetic transition, but the peak at 270?K is due to magnetic structural phase transition. The ac conductivity was measured under vacuum in the temperature range 77?493?K and frequency range 50?Hz?100?kHz. The ac conductivity results showed that samples Se0.99Mn0.01 and Se0.97Mn0.03 follow the overlapping large polaron tunnelling model, while sample Se0.95Mn0.05 follows the correlated barrier hopping model. The barrier height Wm is getting smaller by increasing the localization defects centres, caused by increasing the Mn per cent. Accordingly the Se0.95Mn0.o5 sample has the smallest Wm and consequently the largest ac conductivity, dielectric constant (?1) and dielectric loss (?2). The dielectric constant is three orders higher than those of pure Se element. The temperature dependence of ?1 and ?2 revealed anomaly peaks at nearly room temperature, caused by the structural phase transition. The antiferromagnetic and the high dielectric properties of the studied samples make them a good material for electromagnetic devices that can be used in many applications.

Women in Physics in Egypt: The Status and Needs of Female Physics Students

Information is provided on a number of issues: the percentage of female students enrolled in physics in higher education, the percentage of women who earned BSc degrees in physics from Egyptian universities, and the percentage of women academic staff members in different universities and institutions relative to staff members in other fields of science. The results of a survey that features the ideas of female physics students are presented. The Africa and the Middle East Regional Conference on Women in Physics held in Egypt in 2007 is discussed.

Getting Women Into the Physics Leadership Structure Nationally and Internationally

The underrepresentation of women among physicists around the world, especially in leadership positions, has broad implications for industries and government agencies with a strong need for a technologically educated workforce. The dearth of women physicists in academia exacerbates the situation in that female students lack exposure to successful women in the field. Three years ago, an international group of women met for a round table discussion at the First IUPAP International Conference on Women in Physics and discussed the importance of having women in leadership positions. They shared their experiences and successes, and drew up and reported a set of recommendations addressing the preparation of women for leadership, the selection process, and the responsibilities of institutions. They acknowledged that implementation of their recommendations would differ among countries. At the Second IUPAP International Conference on Women in Physics an international group of women met again to review, revise, and m...

The effect of the partial substitution of sulfur on the structural and microstructural properties of selenium

.These discrepancies are being discussed in terms of the peak shifts in both the amorphous andcrystalline state, the percentage of sulfur compositional variations, and finally in terms of theprobable site occupancy of the sulfur atoms in the selenium structure.

Effect of partial substitution of Cr or Mn for Ga or Fe on crystal-structure and microstructures of GaFeO3

Gallium iron oxide GaFeO 3 and the substituted GaFeO 3 with Cr and Mn, i.e., Ga(Fe 0.95 M e 0.05 )O 3 , and (Ga 0.95 M e 0.05 )FeO 3 ; M e =Cr and Mn, have been synthesized and investigated by X-ray powder diffraction. The refined structural parameters of the considered samples using the Rietveld technique showed a considerable distortion in the polyhedron around different cations, which may have an effect on the piezoelectricity of the studied samples. There are also changes in the interatomic distances between different cations, which may have a direct influence on the ferromagnetic properties of the samples. Crystallite size and microstrain are anisotropic and the largest along the b axis, which may be responsible for the piezoelectricity. The correlations between all these changeable parameters will be discussed.

Women in physics in Egypt: Challenges and progress

The statistics concerning the enrollment of physics students of both genders showed a slight regression between 2005 and 2010. Alternatively, the enthusiasm of female students and graduates is obvious in their progressive achievements. A survey conducted on a random sample of female students in preparatory and secondary schools revealed several points of weakness in physics teaching at these stages of education. The responses of the students and teachers are analyzed and presented together with relevant suggestions.

Women are Needed to Change the Face of Physics (abstract)

God created men and women differently so we can integrate with each other for the sake of the Earth’s inhabitants, and form families that are the fundamental building blocks of healthy and prosperous nations. The world around us is full of many challenges (environment, energy, health, food). Physicists are able to contribute strongly in solving most of these challenges; moreover, physicists can help promote in the welfare and economic development of all nations. Advancing in physics understanding is an exciting intellectual challenge that benefits from the diverse and complementary approaches taken by both women and men. Accordingly, women are needed to change the face of physics. We have to encourage and attract them, beginning with the education of girls, scholarships, help balancing family and career, and positions of influence for women. These measures are discussed.

Crystal Structure Determination and Biological Activity of C20H20O6 and C19H16O6Br2 (abstract)

Crystal structures for methyl 2‐(3‐(3,4‐dimethoxyphenyl)‐1‐1oxopropan‐2‐yl) benzoate (C20H20O6) and methyl 4‐bromo‐3‐(2‐bromo‐4,5‐dimethoxyphenyl)‐1‐oxoisochroman‐4‐carboxylate (C19H16O6Br2) were prepared and characterized by single‐crystal x‐ray diffraction technique to establish their three‐dimensional structures. Both were crystallized from acetone by a slow evaporation method. The results showed that the first crystal (C20H20O6) is monoclinic with space group P21, lattice parameters a = 7.8839 (4)A, b = 8.1087 (4)A, c = 14.4840 (10)A, β = 97.447 (2)°, V = 918.13 (9)A3, Z = 2, and Dx = 1.289 g/m3. The final discrepancy factor is R = 0.034 for 2,917 significant reflections. The second crystal (C19H16O6Br2) is monoclinic with space group P21/c, lattice parameters 20.1043 (7)A, b = 8.7046 (2)A, c = 11.0497 (3)A, β = 97.0923 (11)°, V = 1918.90 (10)A3, Z = 4, and Dx = 1.690 g/m3. The final discrepancy factor is R = 0.064 for 9,619 significant reflections. Projection of structure, connectivity of the molecul...

Crystal structure of two biologically active biphenyl derivatives

Figure 1 Diffraction data for the compounds: 2-ethyl-2,4,5-trimethyl2H-1,3-thiazine-6(3H)-thione (I) and 2-phenyl-1,2,6,7tetra hydrocyclopenta[d][1,3]thiazine-4(5H)-thione (II) were collected on a Rigaku AFC7S diffractometer using the programs CrystalClear [5] for the data collection and cell refinement, CrystalStructure [6] for the data reduction, and SHELX97 [7] for the structure solution and refinement. The solution of their crystal structures found 1 fragment (12 non-hydrogen atoms) for compound (I) and 2 fragments (32 non-hydrogen atoms) for compound (II). The molecular packings consist of zig-zag chains with hydrogen bonds of the type N-H∙∙∙S with gaph symbols [C(6)]S for (I), [C2(12)] S1 and [C 2 2(12)]S3 for (II). Finally, the molecular structures obtained by X-ray single diffraction are compared with the ones optimized by solid state DFTB calculations [8].