Y. Badr

Biosynthesis of Gold Nanoparticles Using Pseudomonas Aeruginosa

Pseudomonas aeruginosa were used for extracellular biosynthesis of gold nanoparticles (Au NPs). Consequently, Au NPs were formed due to reduction of gold ion by bacterial cell supernatant of P. aeruginos ATCC 90271, P. aeruginos (2) and P. aeruginos (1). The UV‐Vis. and fluorescence spectra of the bacterial as well as chemical prepared Au NPs were recorded. Transmission electron microscopy (TEM) micrograph showed the formation of well‐dispersed gold nanoparticles in the range of 15–30 nm. The process of reduction being extracellular and may lead to the development of an easy bioprocess for synthesis of Au NPs.

A new real-time retinal tracking system for image-guided laser treatment

A new system is proposed for tracking sensitive areas in the retina for computer-assisted laser treatment of choroidal neovascularization (CNV). The system consists of a fundus camera using red-free illumination mode interfaced to a computer that allows real-time capturing of video input. The first image acquired is used as the reference image and utilized by the treatment physician for treatment planning. A grid of seed contours over the whole image is initiated and allowed to deform by splitting and/or merging according to preset criteria until the whole vessel tree is demarcated. Then, the image is filtered using a one-dimensional Gaussian filter in two perpendicular directions to extract the core areas of such vessels. Faster segmentation can be obtained for subsequent images by automatic registration to compensate for eye movement and saccades. An efficient registration technique is developed whereby some landmarks are detected in the reference frame then tracked in the subsequent frames. Using the relation between these two sets of corresponding points, an optimal transformation can be obtained. The implementation details of proposed strategy are presented and the obtained results indicate that it is suitable for real-time location determination and tracking of treatment positions.

Comparitive study of structure changes with temperature in univalent and divalent ionic nitrate crystals

Abstract The temperature dependence of the d.c. resistivity and dielectric constant of polycrystalline samples of Pb(NO 3 ) 2 , Ba(NO 3 ) 2 and Sr(NO 3 ) 2 were found to show anomalies in the high temperature region. In addition, sharp peaks were obtained in both differential thermal analysis (DTA) and thermomechanical analysis (TMA) curves in the same temperature range. The observed anomalies were attributed to orientational disorder of the nitrate group leading to an order-disorder phase transition which is reported here for the first time. A comparison is made between the role of NO 3 − ions in both the divalent and univalent nitrates, taking NaNO 3 as representative. The TMA curve for Sr(NO 3 ) 2 showed a pronounced peak at 325°C. This peak was related to a sudden increase in the expansion coefficient associated with the rotation of the NO 3 − group leading to a solid state phase transformation. Energy diagrams describing the conduction mechanism and showing a fractionization of energy barriers in the case of divalent nitrates are introduced.

Characterization of gamma irradiated polyethylene films by DSC and X‐ray diffraction techniques

The effect of gamma radiation on the thermal behavior and crystalline structure of low density polyethylene (LDPE) has been investigated using differential scanning calorimetry (DSC) and X-ray diffraction techniques (XRD). Gamma irradiation was carried out in atmospheric air to a maximum dose of 883 kGy. DSC results of the heating run from room temperature up to 150 °C showed that the melting temperature (Tm), and onset temperature of LDPE film decrease linearly with increasing irradiation dose. However, upon cooling LDPE film from 150 °C to room temperature, the crystallization temperature (Tc) and onset temperature were found to decrease non-linearly with increasing irradiation dose up to 500 kGy and then tended to level off. The change in heat of fusion (ΔHf) with irradiation dose was found to proceed with different behaviour, two stages, with a kink at irradiation dose of about 500 kGy, being observed. This suggests the occurrence of degradation and crosslinking at low and high doses, respectively. However, parameters of the X-ray diffraction pattern such as number of diffraction patterns, peak position (2θ) and width of the diffraction pattern, support the results of DSC measurements. © 2000 Society of Chemical Industry

Production of fertile transgenic wheat plants by laser micropuncture

A modified, non-damaging, protocol for the production of fertile transgenic wheat (Triticum aestivum L. cultivar Giza 164) plants by laser micropuncture was developed. The new homemade setup secures the transformation of as many as 60 immature embryo-derived calli (10000 cells each) in less than one hour using a UV excimer laser with two dimensional translation stages, a suitable computer program and a proper optical system. Five-day-old calli were irradiated by a focused laser microbeam to puncture momentarily made self-healing holes ( approximately 0.5 microm) in the cell wall and membrane to allow uptake of the exogenous DNA. The plant expression vector pAB6 containing bar gene as a selectable marker for the herbicide bialaphos resistance and GUS (uidA) gene as a reporter gene was used for transformation. No selection pressure was conducted during the four-week callus induction period. Induced calli were transferred to a modified MS medium with 1 mg l(-1) bialaphos for regeneration, followed by selection on 2 mg l(-1) bialaphos for rooting. Three regenerated putative transgenic events were evaluated for the integration and stable expression of both genes and results indicated that this modified procedure of laser-mediated transformation can be successfully used in transforming wheat.

Structural and Photoluminescence Behaviors of Nano-Structure Thin Film and Bulk Silica Gel Derived Glasses

Nano-structure bulk and thin film silica gel derived glasses were prepared by sol-gel technique. Both samples were derived from the same precursor and subjected to the same heat-treatment regime. Structural information about prepared samples are obtained by analyzing the XRD patterns and TEM micrographs. The bulk samples phase changes from amorphous to ∝-crystoballite at higher temperature (1300°C) than that in the thin film (500°C). The crystallite size depends to a large extent on the heat-treatment temperature. Bulk sample heat treated at 1400°C was as small as 10.4 nm. Thin film samples show higher response to heat-treatment temperature than the bulk samples, where the film is denser, has smaller pores and seems more homogeneous at lower temperature than bulk sample as revealed by SEM. The observed Raman spectra for bulk and thin film samples are in accordance with that of the ∝-crystoballite. The Raman peak intensity is higher for thin film than bulk samples. The photoluminescence PL measurements for bulk samples show a broad intense peak at 532 nm combined with three weak peaks at longer wavelength 587, 635 and 666 nm. The PL peak intensity shows a reasonable decrease with increasing the heat-treatment temperature while the peak position shifted slightly to a lower wavelength. While the thin film samples show a unique peak at wavelength = 523 nm. The appearance of PL bands are interpreted on the light of non-bridged oxygen hole center as well as the structure defects.

On the low temperature phase transition in (NH4)2SO4

Abstract An ultracryostat and multidecameter were used to determine the temperature dependence of the dielectric constant ϵ′ and dielectric loss ϵ″ over a wide range of frequencies of single crystals and polycrystalline samples of (NH 4 ) 2 SO 4 in the region of the low temperature phase transition. A sharp increase was observed in the values of ϵ′ and ϵ″ at about −50°C. In addition, a dielectric dispersion was detected and found to be more pronounced in the high temperature phase. This dispersion was attributed to piezoelectric resonance. The observed sudden increase in the values of the dielectric constant and dielectric loss below − 50°C was attributed to the ferroelectric nature of the low temperature phase of (NH 4 ) 2 SO 4 . A DTA thermogram showed a sharp peak at − 50°C which indicated that the phase transition is one of first order type. A TMA thermogram showed that this transformation was associated with a rapid increase in the expansion coefficient. Such an increase in the lattice parameter might be attributed to the enhanced rotation of electric dipoles associated with the distorted NH 4 + and SO 4 2− ions. The distortion of both the ammonium and sulfate ions in addition to their expected orientational motion are suggested to be responsible for the ferroelectric behaviour of ammonium sulfate below −50°C. A transition to a metastable hexagonal state at about −40°C is thought to occur, and this transformation is found to be irreversible.

VUV emission from a novel DBD-based radiation source

In all previous works on the dielectric barrier discharge (DBD), the authors used two electrodes separated by one or more dielectric layers and a gas-filled gap between them. In this work a new DBD design is investigated, using ring electrodes (two or four) on the outside of a dielectric tube. The discharge inside the tube occurs as a result of the application of RF power (13.56 MHz). The VUV emission under high-pressure conditions for different gas mixtures is studied. VUV emission at 130.3 and 121.5 nm (Lyman-α) is obtained by using an argon–oxygen mixture, and an argon (or neon)–hydrogen mixture, respectively. The emission spectra, the power density, the total power, the lifetime and the stability will be discussed.

IR and DTA studies of high-temperature phase transition in lithium-ammonium sulphate

Abstract The temperature dependence of the IR absorption spectra of LiNH 4 SO 4 in the region of the internal vibrational modes showed, in addition to the main peak v 3 (a) = 1120 cm −1 , a shoulder v 3 (a) = 1117 cm −1 . This shoulder was attributed to vibrations of the SO 2− 4 ions in the disordered orientations. The intensity of this shoulder was found to increase with temperature. Calculation of the energy activating the process of disorder in LiNH 4 SO 4 at different temperatures showed that it decreases as the temperature increases. The mechanism of the high-temperature order-disorder phase transition is explained. DTA studies were found to confirm the proposed mechanism.

Diagnostic of human teeth using photoacoustic response

Laser-induced photoacoustic spectroscopy (LIPS) can be used to measure trace-element concentration in materials, down to parts-per-million. In this paper we investigate the use of laser-induced photoacoustic response in carious teeth detection. First, we found the Q-switched Nd:YAG laser of a wavelength of 1064 nm to produce detectable response in teeth. Then, we implemented two detection techniques using a piezoelectric transducer and Michelson Interferometer. The accurately detected response of a tooth sample by the piezoelectric transducer was analyzed using spectral analysis. However, in dentistry we do not necessarily mead an exact quantitative measurement; thus we designed a more physically realizable system that measures the acoustically-induced surface displacement using Michelson Interferometer. Monitoring this surface displacement we were able to determine the physical and optical properties of the tooth sample which could be used as a basis in diagnostics. The responses obtained by both detectors were equally confined to the categorization of a carious tooth from a normal one.