Study Some of Optical and Thermoluminescence Properties of Muscovite Mica Exposed to Ultraviolet Radiation

Thermoluminescence properties of ultraviolet-irradiated muscovite sample from Egypt have been studied. One TL peak is observed in the natural material around 190 14鈩?/m:t>"> . A linear response curve to ultraviolet radiation was obtained over the exposure time ranging from 15min to 75 min. A fading study over a period of 15 days shows that the UV-exposed aliquots faded by 27% when exposed for 150 min. The optical direct band gap decreased closely from 3.2eV to 3.1eV after irradiation which means improving crystallinity. Urbach energy decreased from 1.9eV to 1.8eV after irradiation shows less structural disorder. These results further indicate the potential of muscovite as a phosphor in retrospective dosimetry and TL dating. Keywords: Muscovite, optical properties, thermoluminescence properties,ultraviolet-irradiation

Late Miocene karst system at Sheikh Abdallah, between Bahariya and Farafra, Western Desert, Egypt : Implications for palaeoclimate and geomorphology

The extensive spelean deposits in the Western Desert of Egypt at Crystal Mountain (Gebel Bellorat) are considered to be 11-10 Ma, confirming the 'Vallesian' estimate made by Heissig (1982). Several new faunal elements have been discovered including anurans, snakes, soricids, bats, galagids, hystricids and glirids. This fauna indicates that the region was appreciably more humid 11-10 Ma than it is today, with at least 750 mm and possibly as much as 1,200 mm mean annual rainfall. The role of karst processes in the development of the oases of the Western Desert that may have been underestimated by previous researchers is emphasized

Detection of minor and trace elements in powdered milk

Passive gamma ray spectrometry and neutron capture prompt gamma activation analysis (PGAA) were used to investigate powdered cow's milk samples [termed optimal (1), optimal (2) and optimal (3)] collected from local markets in the city of Cairo, Egypt. Standard material with a total average activity of 0.830 ± 0.2 μCi and a certified reference material [IAEA (A-14)] were used to study the accuracy of a passive multi-gamma ray measurement method. Three powdered milk samples of the same geometry and volume were used in this analysis. The specific activity of 226Ra ranged from 24.5 ± 2.1 to 114 ± 1.2 Bq/kg, 232Th from 8 ± 1 to 14 ± 1.2 Bq/kg and 40K from 444 ± 28 to 1826.1 ± 3.1 Bq/kg, all of which were higher than the activities corresponding to the United Nations Scientific Committee on the Effect of Atomic Radiation (UNSCEAR) (50, 50 and 500 Bq/kg for 226Ra, 232Th and 40K, respectively). The average dose rate at 1 cm for 40K ranged from 8.21E−02 ± 0.12 to 3.3E−1 ± 0.22 mSv/h/cm. We also showed that 208Tl81, 212Pb82 and 212Bi83 should be considered products of thorium. k0-PGAA was carried out using an integrated and calibrated prompt gamma ray system with a neutron flux of 106 n/cm2 per second. The thermal to epithermal neutron flux ratio (f) and cadmium ratio were measured using a thin gold foil technique (ration = 160). Different Cl concentrations were prepared as standards for k0-PGAA. The elemental concentrations of Na, Mg, Al, Ca, Mn, Fe, Cu, Ga, Zn, As, Se, Cs, Cd, In, Th and I were measured in the three powdered milk samples. The mean ± standard deviation ranges of the elements were as follows: Na = 1069 ± 49–1583 ± 53 ppm, Mg = 347 ± 13.64–385 ± 16.71 ppm, Al = 45 ± 1.30–72 ± 2.40 ppm, Fe = 5500 ± 110–7123 ± 130 ppm, Zn = 107 ± 3–123 ± 6 ppm, Ca = 4200 ± 72–5483 ± 81 ppm, Mn = 1269 ± 69–1784 ± 72 ppm, Pr = 1.7 ± 0.02–2.6 ± 0.07 ppm, Ga = 265 ± 5–293 ± 8 ppm, Cu = 57 ± 0.5–64 ± 0.9 ppm, In = 1000± 38.64–1574 ± 41.34 ppm, Cd = 6.1 ± 2.71–12.6 ± 4.11 ppm, I = 53 ± 0.09–62 ± 1.18 ppm, Cs = 4 ± 1.56–11 ± 4.22 ppm, As = 26 ± 0.66–29 ± 0.89 ppm, Se = 126 ± 4.8–144 ± 5.7 ppm, Th = 47 ± 1.0–78 ± 6.0 ppm

Late Miocene karst system at Sheikh Abdallah, between Bahariya and Farafra, Western Desert, Egypt : Implications for palaeoclimate and geomorphology

The extensive spelean deposits in the Western Desert of Egypt at Crystal Mountain (Gebel Bellorat) are considered to be 11-10 Ma, confirming the 'Vallesian' estimate made by Heissig (1982). Several new faunal elements have been discovered including anurans, snakes, soricids, bats, galagids, hystricids and glirids. This fauna indicates that the region was appreciably more humid 11-10 Ma than it is today, with at least 750 mm and possibly as much as 1,200 mm mean annual rainfall. The role of karst processes in the development of the oases of the Western Desert that may have been underestimated by previous researchers is emphasized

Biological control of Sclerotinia minor using a chitinolytic bacterium and actinomycetes

Isolates of 85 bacteria and 94 streptomycete and 35 nonstreptomycete actinomycetes were obtained from a lettuce-growing field in Al-Ain, United Arab Emirates, on colloidal chitin agar, and screened for their ability to produce chitinase. Twenty-three bacteria and 38 streptomycete and 15 nonstreptomycete actinomycete isolates produced high levels of chitinase and were examined in vitro for their ability to suppress the growth of Sclerotinia minor, a pathogen causing basal drop disease of lettuce. The three most suppressive isolates were examined further for their production of β-1,3-glucanase and antifungal activity as well as their ability to colonize the roots and rhizosphere of lettuce in vitro and in planta. The three isolates, Serratia marcescens, Streptomyces viridodiasticus and Micromonospora carbonacea, significantly reduced the growth of S. minor in vitro, and produced high levels of chitinase and β-1,3-glucanase. Streptomyces viridodiasticus also produced antifungal metabolite(s) that significantly reduced the growth of the pathogen in vitro. When the pathogen was presented as the sole carbon source, all three isolates caused extensive hyphal plasmolysis and cell wall lysis. Serratia marcescens and St. viridodiasticus were competent to varying degrees in colonizing the roots of lettuce seedlings after 8 days on agar plates and the rhizosphere within 14 days in pots, with their competency being superior to that of M. carbonacea. All three isolates, individually or in combination, were antagonistic to S. minor and significantly reduced incidence of disease under controlled glasshouse conditions