X-ray diffraction study of cadmium hydroxyapatite

Solid solutions of cadmium and calcium hydroxyapatite [Ca10−x Cdx (PO4)6 (OH)2 (0 ≤ x ≤ 10)] were synthesized by a wet process in a basic medium. The lattice dimensions of these compounds vary linearly with the atom percent cadmium. The distribution of the calcium and cadmium ions between two non- equivalent crystallographic sites, (1) and (2), were determined by the Rietveld method. The site-occupancy factors of atoms indicate a slight preference of cadmium for site (2) in the apatite structure

Synthesis of functionalized alkenes via Knoevenagel condensation using Marine Fish Scales as a new efficient and eco-friendly catalyst

The preparation of Marine Fish Scales (MFS) and its analog doped with NaNO3 (NaNO3/MFS) as new catalysts was discussed in this work. Then, these materials were characterized by ATG/ATD, X-ray diffraction, SEM, EDX, and IR spectrophotometer. The MFSand NaNO3/MFS can be used as eco-friendly catalysts for the Knoevenagel condensation and led to the functionalized alkenes in high yields with short reaction time. The tests show that 100 mg is the optimum mass, as well as the suitable solvent, is ethanol for the condensation of Knoevenagel. These parameters led to excellent yields (between 87 % and 99 % using NaNO3/MFS). These catalysts can be also reused for several times

THE ACTIVITY CONCENTRATIONS AND HAZARD INDICES IN SEDIMENT SAMPLES FROM THE AFRICAN COASTS

In this work we have been interested in a compilation of data covering the period from 2000 to present of radionuclide activity concentrations in estuary or marine sediments of the African continent. So, we included three radionuclides as the most representative of natural radioactivity (226Ra, 232Th and 40K) in sediment samples taken from 20 coastal areas, by considering the Atlantic Ocean (Nigeria, Ghana, Morocco and Canary Islands), the Mediterranean Sea (Spain and Egypt) and the Red Sea (Egypt). Therefore, we have relied on scientific publications as well as on our own results.Moreover, to characterize the potential radiation dose to humans resulting from exposure to sediment natural radioactivity, eight radiological hazard indices were estimated: Total Absorbed Dose Rate in air (D), Annual Effective Dose Equivalent (AEDE), Annual Gonadal Dose Equivalent (AGDE), Radium Equivalent Activity (Raeq), External Hazard Index (Hex), Internal Hazard Index (Hin), Gamma Index (Ig) and Excess Lifetime Cancer Risk (ELCR).The highest activity concentrations were found in sediment samples in Atlantic Ocean, especially in one site in Nigeria with a great exceed of the World Wide Average concentrations of 226Ra, 232Thand 40K, which are 35, 30 and 400 Bq Kg-1 respectively.Also, the calculation of the eight radiological hazard indices indicated significant radiological risks always in the same site in Nigeria in Atlantic Ocean

Study of the mechanical behavior of leaded copper by scratch test and nanoindentation

Copper-lead was investigated by scratch tests under two set of experiments conditions: at progressive loads (0 – 200 N) and at two different constant loads (20 – 30 N). These tests were made to assess the adhesion properties to determine the critical normal load of copper- lead journal bearings material. The morphologies of material after scratches are synthesized by optical microscope. Nanoindentation studies of copper-lead provide the possibility of examining a variety of mechanical events due to porosity and pre-existing defects in material. The resulting data are analyzed in terms of load–displacement curves and various comparative parameters, such as hardness and Young’s modulus

Evaluating Quasi-Periodic Variations in the γ\gamma-ray Lightcurves of Fermi-LAT Blazars

The detection of periodicities in light curves of active galacticnuclei (AGN) could have profound consequences for our understanding of the nature and radiation physics of these objects. At high energies (HE; E>100 MeV) 5 blazars (PG 1553+113,PKS 2155-304, 0426-380, 0537-441, 0301-243) have been reported to show year-like quasi-periodic variations (QPVs) with significance >3 sig. As these findings are based on few cycles only, care needs to be taken to properly account for random variations which can produce intervals of seemingly periodic behaviour. We present results of an updated timing analysis for 6 blazars (adding PKS 0447-439), utilizing suitable methods to evaluate their long term variability properties and to search for QPVs in their light curves. We generate gamma-ray light curves covering almost 10 years, study their timing properties and search for QPVs using the Lomb-Scargle Periodogram and the Wavelet Z-transform. Extended Monte Carlo simulations are used to evaluate the statistical significance. Comparing their probability density functions (PDFs), all sources (except PG 1553+113) exhibit a clear deviation from a Gaussian distribution, but are consistent with being log-normal, suggesting that the underlying variability is of a non-linear, multiplicative nature. Apart from PKS 0301-243 the power spectral density for all investigated blazars is close to flicker noise (PL slope -1). Possible QPVs with a local significance ~ 3 sig. are found in all light curves (apart from PKS 0426-380 and 0537-441), with observed periods between (1.7-2.8) yr. The evidence is strongly reduced, however, if evaluated in terms of a global significance. Our results advise caution as to the significance of reported year-like HE QPVs in blazars. Somewhat surprisingly, the putative, redshift-corrected periods are all clustering around 1.6 yr. We speculate on possible implications for QPV generation.Comment: 12 pages, 13 figure

Classification of N=2 supersymmetric CFT_{4}s: Indefinite Series

Using geometric engineering method of 4D $\mathcal{N}=2$ quiver gauge theories and results on the classification of Kac-Moody (KM) algebras, we show on explicit examples that there exist three sectors of $\mathcal{N}=2$ infrared CFT$_{4}$s. Since the geometric engineering of these CFT$_{4}$s involve type II strings on K3 fibered CY3 singularities, we conjecture the existence of three kinds of singular complex surfaces containing, in addition to the two standard classes, a third indefinite set. To illustrate this hypothesis, we give explicit examples of K3 surfaces with H$_{3}^{4}$ and E$_{10}$ hyperbolic singularities. We also derive a hierarchy of indefinite complex algebraic geometries based on affine $A_{r}$ and T$$ algebras going beyond the hyperbolic subset. Such hierarchical surfaces have a remarkable signature that is manifested by the presence of poles.Comment: 12 pages, 2 figure