Shearing effects on the breathing mechanism of a cracked beam section in bi-axial flexure

The main purpose of this paper is to complete the works presented by Andrieux and Varé (2002) and El Arem et al. (2003) by taking into account the effects of shearing in the constitutive equations of a beam cracked section in bi-axial flexure. The paper describes the derivation of a lumped cracked beam model from the three-dimensional formulation of the general problem of elasticity with unilateral contact conditions on the crack lips. Properties of the potential energy and convex analysis are used to reduce the three-dimensional computations needed for the model identification, and to derive the final form of the elastic energy that determines the nonlinear constitutive equations of the cracked transverse section. We aim to establish a relation of behavior between the applied forces and the resulting displacements field vectors, which is compatible with the beams theory in order to allow the model exploitation for shafts dynamics analysis. The approach has been applied to the case of a cracked beam with a single crack covering the half of its circular cross section.     

Photoluminescence and thermoluminescence properties of SnO2 nanoparticles embedded in Li20-K20-B203 with Cu-doping

Cu-doped borate glass co-doped with SnO2 nanoparticles is fabricated by melt quenching. The structure and morphology of the samples are examined by X-ray diffraction and field emission scanning electron microscopy. Up-conversion enhancement is observed in the photoluminescence （PL） and thermolumines- cence （TL） intensities of the glass. PL emission spectra are identified in the blue and green regions, and a fourfold increase in emission intensity may be observed in the presence of embedded SnO2 nanoparticles. The glow curve is recorded at 215℃, and fourfold increases in TL intensity are obtained by addition of 0.1 mol% SnO2 nanoparticles to the glass. Higher TL responses of the samples are observed in the energy range of 15-100 KeV. At energy levels greater than -0.1 MeV, however, flat responses are obtained. The activation energy and frequency factor of the second-order kinetic reaction are calculated by the peak shape method.     

Novel Potentiometric Sensors for Determination of Melatonin and Oxomemazine in Biological Samples and in Pharmaceutical Formulations

Simple, selective and accurate sensors were developed for the determination of melatonin and oxomemazine in biological samples (urine) and in pharmaceutical preparations. Potentiometric measurements were based on bismus tetraiodate‐drug ion‐pair as novel electroactive materials incorporating a plasticized PVC membrane with o‐nitrophenyl octyl ether or dioctyl phthalate. Each sensor was conditioned for at least two days in 0.1 M drug solution before use. It exhibited fast and stable Nernstian response for melatonin and oxomemazine over the concentration range of 1.0×10^?6–1.0×10^?2 M and 1.0×10^?5–1.0×10^?2 M, pH range of 3.0–6.5 and 3.5–6.0 for melatonin and oxomemazine sensors, respectively. Results with an average recovery not more than 101 % and a mean standard deviation less than 1.0 % of the nominal were obtained for the four sensors. The sensors showed reasonable selectivity towards investigated drugs in presence of many cations.     

Studies on cryoprotectant toxicity to zebrafish (Danio rerio) ovarian tissue fragments

Cryopreservation of ovarian tissue is a viable alternative to cryopreservation of oocytes and embryos in many species but it has not been studied in fish. Selection of cryoprotectant is an important step in designing cryopreservation protocols. In order to identify the optimum cryoprotectant (CPA) in a suitable concentration for zebrafish ovarian tissue cryopreservation, studies on toxicities of five commonly used cryoprotectants methanol, ethanol, dimethyl sulfoxide (DMSO), ethylene glycol (EG) and propylene glycol (PG) were carried out. Experiments were conducted on ovarian tissue fragments consisting of stage I and stage II ovarian follicles. Ovarian tissue fragments were incubated in 90% L-15 medium (pH 9) containing 1-4M cryoprotectants for 30min at 22°C. Three different tests were used to assess ovarian tissue fragment viability: trypan blue (TB) staining, fluorescein diacetate (FDA) combined with propidium iodide (PI) staining and adenosine 5′- triphosphate (ATP) assay. Results from these tests showed that ATP assay was more sensitive than FDA+PI or TB staining for assessing cryoprotectant toxicity to follicles in tissue fragments. Methanol and ethanol were the least toxic cryoprotectants tested. Cryoprotectant toxicity increased in the order of methanol/ethanol, DMSO, PG and EG. Ethanol was used for zebrafish ovarian tissue for the first time and the results showed that the effect of methanol and ethanol on ovarian tissue fragments were comparable. As methanol has been shown to be the most effective cryoprotectant for zebrafish ovarian follicles in our laboratory, the use of ethanol will also be considered in assisting future freezing protocol design. The present study also showed that stage II ovarian follicles are more sensitive to cryoprotectant treatment than stage I follicles in tissue fragments. The results obtained in this study provided useful information for ovarian tissue fragment cryopreservation protocol design in the future.     

Aromatic poly(amide-ether)s containing naphthalene and methylene unites

1,5-Naphthene dioxy diacetic acid was synthesized from the reaction of 1,5-naphthalene diol and chloroacetic acid. It was used then as a bi-functiona l monomer in polycondensation reaction with aromatic diamines in the presence of tripnenylphosphite to produce poly(amide-ether)s. All the obtained polymers were characterized by IR and elemental analysis; their solubility behaviour was evaluated in polar organic solvents as well as in concentrated H₂SO₄. The extent of thermal stability and phase transitions of poly(amide- ether)s were investigated by thermogravimetric analysis and differential scanning calorimetry respectively; while the morphology was estimated by X-ray powder diffraction patterns. Besides, the fu-fu stacking character of polymer chain interactions in the solid state was confirmed by absorption spectra of solid thin films.     

Evaluation of chromatographic and spectroscopic methods for the analysis of petroleum-derived compounds in the environment

Summary Analytical protocols have been adapted for the study of hydrocarbons at the trace level in the environment. Various samples, including sediments and biota, were collected from the Kuwaiti environment, treated according to the protocol and analyzed by chromatographic and spectroscopic methods. The methods used were synchronous scanning fluorescence spectroscopy (SSFS); high-performance liquid chromatography (HPLC) on C18 reversed-phase and NH2 normal-phase columns with UV and fluorescence detectors; gas chromatography on fused-silica capillary columns (GC) with flame ionization detector (FID), mass spectrometer (MS) and flame photometric detector (FPD); and high-resolution molecular spectrofluorimetry in Shpol'skii matrix at 10 K (HRSS). The different methods were found to give complementary information. SSFS was useful for fast evaluation and preliminary assessment of oil pollution during extended programs; it permitted sample selection for deeper analyses but, when applied to biota, needed special care in the clean-up procedure. GC/FID, was used to analyze saturated and ethylenic compounds and was useful for obtaining information on the origin of hydrocarbons but inconvenient for analyzing the aromatic fraction. GC/FPD was difficult to use with sediment samples and yielded little information on biota samples, although it did permit confirmation of high oil contamination in some examples. HPLC on a normal-phase column with UV and fluorescence detectors was useful for the fractionation of samples and for the separation of different families of aromatic compounds according to aromatic carbon number. GC/MS was used to quantify polycyclic aromatic hydrocarbons (PAHs) of less than four cycles but was not sensitive enough for PAHs of higher molecular weight. HRSS, however, was useful for the quantification of heavy PAHs and was also faster, could be automated, and gave accurate results. However, in an oil-pollution study, it must be backed up by the other techniques. In fact, no single analytical technique was found to be sufficient, and only judicious combinations of the tested techniques yielded adequate information on the origin of hydrocarbons in the environment.     

Mössbauer Studies of Nanosize CuFe2O4 Particles

⁵⁷Fe Mössbauer spectra of pulsed-laser deposited (PLD) films of CoFe₂O₄ of 0.3 µm thickness is investigated using transmission geometry is reported. Mössbauer parameters were determined for the tetrahedral (A) and octahedral (B) sites. The PLD processed films gave measurable spectra with no visible evidence of clustering or multiple phases present. Results on the films agreed with those of the bulk material. The films exhibited magnetic hyperfine and quadruple splittings similar to that of bulk CoFe₂O₄. This work demonstrates that measurable transmission Mössbauer spectra may be obtained for PLD deposited CoFe₂O₄ thick films.     

Genetic diversity and haplotype structure of 21 Y‐STRs,including nine noncore loci,in South Tunisian Population: Forensic relevance

Y chromosome STRs (Y‐STRs) are being used frequently in forensic laboratories. Previous studies of Y‐STR polymorphisms in different groups of the Tunisian population identified low levels of diversity and discrimination capacity (DC) using various commercial marker sets. This definitely limits the use of such systems for Y‐STRs genotyping in Tunisia. In our investigation on South Tunisia, 200 unrelated males were typed for the 12 conventional Y‐STRs included in the PowerPlex® Y System. Additional set of nine noncore Y‐STRs including DYS446, DYS456, DYS458, DYS388, DYS444, DYS445, DYS449, DYS710, and DYS464 markers were genotyped and evaluated for their potential in improving DC. Allele frequency, gene diversity, haplotype diversity (HD), and DC calculation revealed that DYS464 was the most diverse marker followed by DYS710 and DYS449 markers. The standard panel of 12 Y‐STRs (DC = 80.5%) and the nine markers were combined to obtain DC of 99%. Among the 198 different haplotypes observed, 196 haplotypes were unique (HD = 99.999). Out of the nine noncore set, six Y‐STRs (DYS458, DYS456, DYS449, DYS710, DYS444, and DYS464) had the greatest impact on enhancing DC. Our data provided putative Y‐STRs combination to be used for genetic and forensic applications.