Bilal Nsouli

RBS and HIRBS studies of nanostructured AgSiO2 sol–gel thin coatings

In the present work, composite AgSiO2 thin coatings, containing metal nanoparticles, were prepared on glass substrates by the sol–gel route. The coatings were thermally treated in oxidative and reductive conditions up to 500 C for metal nanoparticle formation. The coating structure and the nanoparticle formation were studied by atomic force microscopy and Rutherford backscattering spectroscopy (RBS) techniques. In the case of RBS, 1.4 MeV 4 He þ ions were used for all samples, and low energy 16 O and 12 C ions in selected ones (heavy ion RBS, HIRBS), in order to improve the depth resolution for the profiling of the metal component. The antibacterial activity against Escherichia coli is examined by antibacterial drop test. The coatings exhibited a high antibacterial activity, which was enhanced with the increase of the metal concentration and was reduced with the increase of the particle size of the metal nanoparticles. The possible correlation between the layer interdiffusion after the thermal treatment and the antibacterial activity is examined and analyzed. Although further studies are required, RBS and HIRBS seem to be excellent tools for the quality control in the production of sol–gel thin coatings. 2002 Elsevier Science B.V. All rights reserved.

Formation of lipid oxidation and isomerization products during processing of nuts and sesame seeds.

The aim of the present study was to quantify some nutritional and safety quality parameter changes that take place in nuts (roasting) and sesame seeds (dehulling, roasting, milling, and sterilization) during processing. Such evaluation was based on chemical analysis of various indicators of lipid alteration in raw and processed pistachios, almonds, peanuts, and tahina. Lipid oxidation was assessed by the evolution of lipid oxidation products including hydroperoxides, p-anisidine, and thiobarbituric acid reactive substances, as well as carboxymethyllysine (CML) and trans fatty acids (tFAs). All these parameters were significantly affected by the different processing stages, especially by roasting and sterilization (tahina). Nut roasting and sesame heat treatment increased the primary (hydroperoxides) and secondary (aldehydic compounds) lipid oxidation products, with the p-anisidine value reaching 6-11.5 and thiobarbituric acid reactive substances 3-5 mg/kg (equiv of malondialdehyde) in the different end products. In addition, roasting led to the formation of CML (between 12.7 and 17.7 ng/mg) and tFAs (between 0.6 and 0.9 g/100 g) in nuts and tahina, which were absent in the raw material. Roasting parameters appear as the critical factor to control to limit the CML and tFA formation in the final product.

Determination of natural and artificial radioactivity in soil at North Lebanon province

The concentrations of natural and artificial radionuclides at 57 sampling locations along the North Province of Lebanon are reported. The samples were collected from uncultivated areas in a region not previously reported. The samples were analyzed by gamma spectrometers with High Purity Germanium detectors of 30% and 40% relative efficiency. The activity concentrations of primordial naturally occurring radionuclides of (238)U, (232)Th, and (40)K varied between 4-73 Bq kg(-1), 5-50 Bq kg(-1), and 57-554 Bq kg(-1) respectively. The surface activity concentrations due to the presence of these radionuclides were calculated and Kriging-geostatistical method was used to plot the obtained data on the Lebanese radioactive map. The results for (238)U, (232)Th, and (40)K ranged from 0.2 kBq m(-2) to 9 kBq m(-2), from 0.2 kBq m(-2) to 3 kBq m(-2), and from 3 kBq m(-2) to 29 kBq m(-2) respectively. For the anthropogenic radionuclides, the activity concentrations of (137)Cs founded in soil ranged from 2 Bq kg(-1) to 113 Bq kg(-1), and the surface activity concentration from 0.1 kBq m(-2) to 5 kBq m(-2). The total absorbed gamma dose rates in air from natural and artificial radionuclides in these locations were calculated. The minimum value was 6 nGy h(-1) and the highest one was 135 nGy h(-1) with an average of 55 nGy h(-1) in which the natural terrestrial radiation contributes in 99% and the artificial radionuclides mainly (137)Cs contributes only in 1%. The total effective dose calculated varied in the range of 7 μSv y(-1) and 166 μSv y(-1) while the average value was 69 μSv y(-1) which is below the permissible limit 1000 μSv y(-1).

Fluorine determination in human healthy and carious teeth using the PIGE technique

Abstract The purpose of this study is to determine and compare the fluorine concentration in human teeth from two different populations, living in the Portuguese quite isolated islands of Acores: S. Miguel and Terceira. Both populations have similar dietary habits, similar occupational activities, mostly rural, and the age of both populations is more or less the same, around 40 years. No chronic diseases were registered in any of the donors. The two groups are exposed to different levels of fluorine in drinking water. Terceira island has moderate fluorine concentration levels (1–2 μg g−1) while S. Miguel island is known for the high fluorine concentration levels in its water (>3 μg g −1 ), especially in one area known as Furnas. Thirty-three teeth, 17 healthy and 16 carious without restoration (14 incisors and canines, 7 premolars and 12 molars), were collected and analyzed for the determination of fluorine concentration in the dentine region, using the nuclear reaction 19 F ( p , αγ ) 16 O . The teeth were cross-sectioned along the vertical plane and polished, in order to obtain a smooth and plane surface of about 1 mm thickness. In this work an association between caries prevalence and fluorine content of drinking water is discussed and the variation of fluorine concentration among different types of teeth (canines and incisors, premolars, molars) and physical state (carious and non-carious) is examined.

Microstructural characterization of chromium oxide thin films grown by remote plasma assisted pulsed laser deposition

In this work, we investigate the use of Remote Plasma Assisted PLD for the growth of chromium oxide thin films. In an attempt to enhance oxygen incorporation in the growing layers, laser ablation takes place in an activated oxygen background that contains atomic oxygen as well as excited oxygen molecules, thereby creating growth conditions that are inaccessible by reactive PLD. All films were grown on Si (100) substrates by ablating a pure Cr2O3 target using a KrF excimer laser. The micro-structural analysis of the grown layers was achieved using Infra- Red Spectroscopy, X-Ray Diffraction, Atomic Force Microscopy and Rutherford Back- Scattering. It is found that films deposited under remote plasma conditions show a predominance of the higher oxidation states of chromium while the antiferromagnetic Cr2O3 phase is mostly present in films grown in an O2 ambient. The effect of substrate temperature on the microstructure of the films was also studied. At low substrate temperatures (<350°C), the films have an amorphous microstructure with elongated rod-like features that could indicate the formation of the CrO2 phase. With increasing temperature up to 450oC, the structure of the films reverts to a crystalline Cr2O3 phase as inferred from the appearance of the corresponding peaks in the XRD spectra and from the narrowing of the infra-red absorption bands.

On the phosphorus characterization in thin SiO2 (P,B) CVD layer deposited onto a silicon substrate by PIXE

Abstract In this work the capability of the PIXE technique to monitor a rapid and accurate quantification of P in thin SiO 2 (P,B) CVD layers (400 nm) deposited onto silicon substrate is discussed. In order to improve the sensitivity for P determination, a systematic study was undertaken using protons and helium ion beams at different energies using different thickness of Kapton X-ray absorbers. 600 keV proton or 1.5 MeV helium under normal incidence, using 146 μm Kapton as X-ray absorber, permits an accurate quantification of P with high sensitivity within few minutes of acquisition time. This sensitivity is highly improved when using grazing incidence angles (e.g. 80°), thus 1 MeV protons can be easily used. Finally, the PIXE results show that the phosphorus concentration in the CVD layer varies linearly with the percentage of the phosphine gas used in the CVD gas mixture.

Ion beam analysis and PD-MS as new analytical tools for quality control of pharmaceuticals: comparative study from fluphenazine in solid dosage forms.

In order to evaluate the potential of accelerator based analytical techniques ((particle induced X-ray emission (PIXE), particle induced gamma-ray emission (PIGE), and particle desorption mass spectrometry (PD-MS)) for the analysis of commercial pharmaceutical products in their solid dosage form, the fluphenazine drug has been taken as a representative example. It is demonstrated that PIXE and PIGE are by far the best choice for quantification of the active ingredient (AI) (certification with 7% precision) from the reactions induced on its specific heteroatoms fluorine and sulfur using pellets made from original tablets. Since heteroatoms cannot be present in all types of drugs, the PD-MS technique, which makes easily the distinction between AI(s) and excipients, has been evaluated for the same material. It is shown that the quantification of AI is obtained via the detection of its protonated molecule. However, calibration curves have to be made from the secondary ion yield variations since matrix effects of various nature are characteristics of such mixtures of heterogeneous materials (including deposits from soluble components). From the analysis of solid tablets, (either transformed into pellets and even as received), it is strongly suggested that the physical state of the grains in the mixture is a crucial parameter in the ion emission and accordingly for the calibration curves. As a result of our specific (but not optimized) conditions the resulting precision is <17% with an almost linear range extending from 0.04 to 7.87 mg of AI in a tablet made under the manufacturer conditions (the commercial drug product is labeled at 5 mg).

Use of PIXE analysis technique for the study of Beirut amphora production in the Roman period

Ion Beam Analysis techniques were developed and utilized for applications in the domain of archeology at the accelerator laboratory of the Lebanese Atomic Energy Commission. The characterization of Beirut kiln materials, mainly amphorae ceramics from the Roman period, was done using PIXE technique. In two runs with 1 and 3 MeV protons, we measured 20 major and trace elements. Consequently, a classification based on the elemental composition and on multivariate statistical techniques of some 70 ceramic objects was obtained providing the first step of a Lebanese database for future studies. Furthermore, the analysis of carrot amphorae found in Gaul (south of France) showed that some of them were of Beirut products and hence emphasized the role of Beirut city in the Mediterranean trade in the Roman period.

Investigation of norflurazon pesticide photodegradation using plasma desorption time‐of‐flight mass spectrometry analysis

We have previously demonstrated that PD-TOFMS (plasma desorption time-of-flight mass spectrometry) analysis is a powerful technique for the in situ analysis of pesticides deposited or adsorbed on solid materials. With the aim of producing reproducible data on the modification of a pesticide under controlled photodegradation conditions, we have now undertaken a study where both the substrate and the pesticide are well characterized. This is the case for norflurazon deposited onto an aluminium substrate, in particular regarding the reproducibility of preparation of the samples and the change with time of their chemical composition. Degradation parameters have been derived from the variation in yield of ions representative of the molecule and of its breakdown products and, particularly, from the time required for 50% dissipation of their initial concentration (DT50). DT50 values ranging between 1 and 10 h have been found. An interpretation of the degradation process is proposed from the decay of other ions. As expected, the degradation is faster when the UV sunlight is unfiltered (a factor of 3.8 for the molecule, and around 5 for the breakdown products).

Set-up, optimization and first set of samples at the radiocarbon laboratory in Lebanon

A new radiocarbon laboratory has been established recently at the Lebanese Atomic Energy Commission. This laboratory consists of benzene synthesis line and a low background liquid scintillation counter, Tri-Carb 3180 TR/SL for measurements with Bismuth Germanate (BGO) guard detector. The effectiveness of the benzene line was tested firstly by preparing benzene from a wood sample after carbide and acetylene receiving. Normalization and standardization of the liquid scintillation counter was carried out, as well as the Factor of Merit (E2/B) was determined for three different counting regions. To assure accuracy and reliability of results, reference materials were used. Based on z-score and u-score evaluation, as well as Student’s t-test, acceptable data were obtained from travertine and wood samples available through the International Atomic Energy Agency (IAEA-C2 and IAEA-C5), and humic acid (U) and murex shell (R) from the Fifth International Radiocarbon Intercomparison (VIRI). After that, a preliminary study was done, which is the base for future research in order to assess the anthropogenic impact and degree of environmental pollution in terms of radiocarbon isotope ratio (Δ14C) deduced from the Percent Modern Carbon or PMC. This work represents the results of four reference materials and those of five green grass samples. The Δ14C of green grass samples collected from two different clean zones were found to be 50‰ and 52‰, while the values of those collected from different polluted zones were 23‰, 7‰ and 15‰.