Theory of Ion Neutralization at Metal Surfaces

This work will concentrate on the mechanisms that produce neutralized atoms upon scattering of ions from metal surfaces. Three mechanisms are usually considered for ion neutralization at metal surfaces. Those are: resonance tunneling; Auger neutralization and surface plasmon-mediated ion neutralization. The third mechanism, namely surface plasmon-mediated ion neutralization, was suggested and calculated by us in an earlier work, where a unitary transformation was introduced to the second quantized Hamiltonian. The atoms are described by a state orthogonal to all conduction band states of the metal. The transformation gave rise to an additional term in the matrix elements ''the orthogonalization term''. This theory of applying a unitary transformation to the second quantized Hamiltonian is applied to the resonance and Auger neutralization mechanisms. The orthogonalization correction to the neutralization rate is found to be important at small distances from the surface when, applied to the scattering of protons from aluminum surface.

Changes in the amount of proteins in seeds and stems cells of seedlings of Maize Plant (Zea mays L.) cultured in solutions of some heavy metal salts

The aim of this research is to determine the effect of some heavy metal ions on total protien metabolism in seeds and seedlings of maize plant (GHOTA 82) and study the changes in the morphological specifications of plant, after cultivating for 6 days in solutions at different concentrations of water and heavy metal ions Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+. The results showed that heavy metal ions have inhibitory effect on total protien metabolism, which decreased their amount in seedlings, While accumulated in the seeds. This inhibitory effect depends on the type and concentration of heavy metal ions. The results also showed morphological changes in the maize plant seedlings, which decreased their growth due to the effect of these ions.

Ni release from polished or PFM fired Ni-Cr dental casting alloys

Nickel metal may cause systemic toxicity and allergy The compatibility of dental casting alloys correlates with their release of elements .The aim of this study was to specify the relationship of the release of nickel from Ni- Cr dental alloys with their composition , and to determine the effects of thermal treatment of Ni-Cr alloys during porcelain firing process on the release of nickel . Ranging Five Ni-Cr alloys commonly used in clinical practice were used, They have different nickel percentage Ranging between ٥٩،٣ and ٨١ % , two of them containing beryllium .

Studying the absorbance of some painted metals for the direct light

In this research we studied and measured the response and absorbance for some metals (zinc, copper, iron, aluminum) which are exposed to the direct light and painted with black, which has a high absorbance and low emittance, and with different thicknesses (to obtain black bodies) with higher absorption. we took the measurement on the painted metals for each thickness of the paint in the laboratory first using tow lamps 30 watt and 100 watt to compare the absorption of these metals of the radiation from these two lamps with the absorption of the solar radiation and make sure that the absorption is similar of the two situations, then we took the measurements in AL- Kadmous Area which is 900m above sea level using direct solar radiation , and we found the relationship between the absorbance and the paint thickness.

دراسة مخبريّة للانطباق الحفافيّ لطريقتي صنع الجسور الزيركونيّة CAD\CAM و Slip-Casting

Recent development in dental materials had led to the fabrication of metal free fixed prosthodontics to improve the mechanical and aesthetic properties to restore posterior teeth depending on many techniques, therefore came the propose of this study to compare the marginal fit of Zirconia bridges made by CAD/CAM and Slip-Cast techniques. 30 Bridges were fabricated to restore missing first lower molar, they were divided into two groups (15 CAD\CAM, 15 Slip-Cast). The marginal fit was evaluated by measuring the thickness of light body silicone that made using Replica technique. Depending on T-test, the mean marginal discrepancy for CAD/CAM groups was 13.92μ and 11.30μ for Slip-Cast techniques. Therefore, it was concluded that the marginal fit of Slip-Cast techniques was significantly better than CAD/CAM techniques.