Electrical and thermal properties of chalcogenide glass system Se75Ge25−x Sb x

The dc and thermal conductivities of five different compositions of the chalcogenide glass system Se₇₅Ge_25–x Sb _x have been studied in a temperature range below T _g. The dc conductivity results indicate that each composition has a single activation energy in the considered temperature range. The coefficient of thermal conductivity increased linearly with temperature below T _g for the compositions investigated. The increase of Sb content in the chalcogenide glass system leads to an increased coefficient of electrical conductivity , an increased coefficient of thermal conductivity , and to a decreased activation energy E and pre-exponential factor ₀. The observed compositional dependencies of and E have been correlated with the increase of weak bond density and the decrease of covalent bond density in the structure of the compositions investigated with increasing Sb content at the expense of Ge content. The decrease in ₀ and the increase in has been, respectively, correlated with the decrease in mobility and the increase in phonon velocity.     

Efficient removal of iodine and chromium as anionic species from radioactive liquid waste using prepared iron oxide nanofibers

Journal of Radioanalytical and Nuclear Chemistry - Three synthetic hematite (SH) materials as iron oxides nanofibers were prepared and applied for the removal of 51Cr and radioiodine (131I) as...     

Ultrasonic characterization of heavy metal TeO2–WO3–PbO glasses below room temperature

The longitudinal ultrasonic attenuation measurements have been made using pulse echo method at fundamental frequencies of 2, 4, 6 and 8 MHz in 20WO₃–(80−x) TeO₂–xPbO ternary tellurite glasses (x=10, 12.5, 15, 17.5 and 20 mol%) in the temperature range 160–280 K. The results showed the presence of a broad peak which shifts to higher temperature with increasing frequency. The ultrasonic attenuation peaks suggest that the experimental behavior is controlled by thermally activated structural relaxations. The internal friction, acoustic activation energy, deformation potential, relaxation strength, number of loss centers and density of state have been calculated both as a function of temperature and PbO content. The acoustic activation energy was found to decrease from 0.156 to 0.135 eV with the increase of PbO content. The results showed that both the number of loss centers and their activation energy decrease with the atomic ring size. An increase in the density of state is observed with addition of PbO content at the same frequency in the whole range of temperature which is associated with structural units formed when PbO is added.     

Electrical and thermal properties of Ge40S60 films

Films of the composition Ge₄₀S₆₀ have been studied in the temperature range of 313–423 K for electrical conductivity, and 293–373 K for thermal conductivity. The dc conductivity results indicate a single value activation energy of 0.863 eV for the conductivity in the applied temperature range. The thermal conductivity coefficient increases linearly with temperature at a thickness of d=0.311 cm. It was found that the investigated samples show a memory effect. The threshold switching voltage was found to increase linearly with film thickness. Moreover, the threshold voltage decreases exponentially with temperature. The data are analysed using a thermal model for the switching process.     

Rho-kinase inhibitors from adlay seeds

Rho-kinase enzymes are one of the most important targets recently identified in our bodies. Several lines of evidence indicate that these enzymes are involved in many diseases and cellular disorders. ROCK inhibitors may have clinical applications for cancer, hypertension, glaucoma, etc. Our study aims to identify the possible involvement of Rho-kinase inhibition to the multiple biological activities of adlay seeds and provide a rationale for their folkloric medicines. Hence, we evaluated Rho-kinase I and II inhibitory activity of the ethanol extract and 28 compounds derived from the seeds. A molecular docking assay was designed to estimate the binding affinity of the tested compounds with the target enzymes. The results of our study suggest a possible involvement of Rho-kinase inhibition to the multiple biological activities of the seeds. Furthermore, the results obtained with the tested compounds revealed some interesting skeletons as a scaffold for design and development of natural Rho-kinase inhibitors.     

Pulsatile Flow of Blood through a Porous Mediumunder Periodic Body Acceleration

Pulsatile flow of blood through a porous medium has been studied studied underthe influence of body acceleration. With the help of Laplace and finite Hankeltransforms, analytic expressions for axial velocity, fluid acceleration, flow rate,and shear stress have been obtained.     

Star‐Shaped Polyaromatic Ethers Coordinated to Redox‐Active Cyclopentadienyliron Moieties

This communication is focused on the controlled design of star‐shaped aromatic ethers with pendent cyclopentadienyliron moieties. A trimetallic core was prepared, which was then reacted with a number of oligomeric ether complexes to give star‐shaped polymers with six, nine, twelve and fifteen pendent cationic cyclopentadienyliron moieties. Cyclic voltammetric studies showed reduction of the iron centers between –0.99 and –1.41 V. Thermogravimetric analysis showed that loss of the metallic moieties occurred between 225 and 284°C.     

SPE and HPLC monitoring of 17-β-estradiol in Egyptian aquatic ecosysetms

Solid-phase extraction and HPLC methods are described for monitoring of 17-β-estradiol residues in Egyptian aquatic ecosystems (water, fish, mollusks, sediment, and drinking water) at the Nile River, Suez Canal region, and northeast of Egypt. Molecular imprinted polymer was prepared and used in extraction. High performance liquid chromatography (HPLC) columns used were Supelcosil C₁₈ and Nucleosil C₁₈. The mobile phases used were different combinations of water and acetonitrile. The concentration of 17-β-estradiol in water, aquatic animals, and sediment samples were of 265.13–7988.12 µg/L, 0.503–96.167, and 0.775–11.884 µg/kg, respectively. Marine lake was contained with high levels of 17-β-estradiol (P < 0.05). Similarly, the Nile River downstream showed high levels of 17-β-estradiol. The detected concentrations in mollusks were significantly higher than those detected in fish. Tilapia fish did not show 17-β-estradiol. Contrarily, low concentrations were detected in the rivulet streams supplied by the Nile River. Besides, 17-β-estradiol was also detected in the sediments at low levels. Detection of 17-β-estradiol in the Egyptian ecosystems attracted attention toward heavy reliance on some esterogenic medicinal products in Egypt. The monitoring of 17-β-estradiol in other water bodies was recommended. Besides, the development of methodologies of bioremediation to eliminate 17-β-estradiol from the Egyptian and other water resources of the world was also suggested.     

Essential oil composition of the aerial parts of fresh and air-dried Salvia palaestina Benth. (Lamiaceae) growing wild in Jordan

The composition of the essential oil of fresh and air-dried Salvia palaestina Benth. (Lamiaceae) growing wild in Jordan has been studied using gas chromatography-mass spectrometry analysis. The essential oils of fresh and air-dried S. palaestina were mainly composed of sesquiterpene hydrocarbons (52.66% and 65.98%, respectively). The major component detected in the oils of fresh and dry S. palaestina was germacrene D (21.18% and 26.02%, respectively). Air drying resulted in a general increase of sesquiterpene hydrocarbons and a great decrease in the percentage of monoterpene hydrocarbons.     

Effect of annealing on the optical properties of In2Te3 thin films

2 Te₃ thin films of different thickness were prepared in a vacuum of 10^-5 Torr onto glass and quartz substrates held at about 300 K during the deposition process. X-ray diffraction analysis showed that the prepared samples in bulk or as-deposited thin-film forms were in an amorphous state. On annealing at 573 K, films have a β-phase polycrystalline structure. Transmittance and reflectance measurements in the spectral range of 400–2500 nm for films deposited onto quartz substrates were used to calculate the optical constants (the refractive index n, the absorption index k and the absorption coefficient α) for In₂Te₃ films, either as-deposited or annealed at different temperatures. The refractive index has anomalous behavior in the region of the fundamental absorption edge. The allowed optical transitions were found to be nondirect transitions, with an optical gap of 1.02 eV for the samples under test. The effect of annealing on the optical gap is interpreted in terms of the density of states proposed by Mott and Davis. Received: 22 June 1997/Accepted: 9 July 1997