Wave reflection at a free interface in an anisotropic pyroelectric medium with nonclassical thermoelasticity

In this paper, the well-established two-dimensional mathematical model for linear pyroelectric materials is employed to investigate the reflection of waves at the boundary between a vacuum and an elastic, transversely isotropic, pyroelectric material. A comparative study between the solutions of (a) classical thermoelasticity, (b) Cattaneo–Lord–Shulman theory and (c) Green–Lindsay theory equations, characterised by none, one and two relaxation times, respectively, is presented. Suitable boundary conditions are considered in order to determine the reflection coefficients when incident elasto–electro–thermal waves impinge the free interface. It is established that, in the quasi-electrostatic approximation, three different classes of waves: (1) two principally elastic waves, namely a quasi-longitudinal Primary (qP) wave and a quasi-transverse Secondary (qS) wave; and (2) a mainly thermal (qT) wave. The observed electrical effects are, on the other hand, a direct consequence of mechanical and thermal phenomena due to pyroelectric coupling. The computed reflection coefficients of plane qP waves are found to depend upon the angle of incidence, the elastic, electric and thermal parameters of the medium, as well as the thermal relaxation times. The special cases of normal and grazing incidence are also derived and discussed. Finally, the reflection coefficients are computed for cadmium selenide observing the influence of (1) the anisotropy of the material, (2) the electrical potential and (3) temperature variations and (4) the thermal relaxation times on the reflection coefficients

COMPARATIVE PHYTOCHEMICAL AND BIOLOGICAL INVESTIGATION OF FIVE GLYCINE MAX (L.) MERRILL GENOTYPES

Objective: Soybean (Glycine max L. Merrill) is the world’s most important consumed seed legume. The objectives of the present study were to determine the variability in phytochemical composition and biological activities between five genotypes of G. max. Methods: Lipoidal matters were determined using glucose (GLC). Amino acids were detected by the amino acid analyzer. The phytoconstituents present within each ethanol extract was investigated by gas chromatography-mass spectrometry. The amount of total phenolics, flavonoids, and tannins was analyzed using a spectrophotometric technique, based on Folin–Ciocalteu reagent, aluminum chloride colorimetric assay, and the modified vanillin hydrochloric acid method, respectively. Quercetin, catechin, and gallic acid were used as standard compounds, respectively. Isoflavones content were detected by high-performance liquid chromatography (HPLC)/photodiode array (PDA). The radical scavenging and antioxidant capacity of the genotypes using different in vitro analytical assays such as 2,2-diphenyl,1-picryl hydrazyl, 2,2’-Azino-bis(3-ethylbenzothiazoline-6-sulphonic acid, reducing power, metal chelating, and ferric reducing anti-oxidant power. Butyl hydroxyl toluene and trolox were used as the reference antioxidant radical scavenger compounds. Antitumor activity was evaluated by detecting the viability of Ehrlich ascites carcinoma cells on four different concentrations (1–5 mg/mL). Results: GLC analysis showed the high value of total unsaturated fatty acids and 16 amino acids including glutamic acid with the highest concentration. The variation between genotypes according to their chemical composition of the aldehydes, esters, ketones, alcoholics, and carboxylic content were reported. HPLC/PDA referred to the presence of daidzein, genistein, and in all genotypes. Conclusion: The results confirm the higher value of phytoconstituents of the genotype Giza 35 and Giza 21 as well as their better bioactivity

Numerical Computations of Radial Vibrations of Axially Polarized Piezoelectric Circular Cylinder

Influence of the initial stresses on the frequency equation and the natural frequencies for radial vibrations of axially polarized piezoelectric circular cylinder have been taken into account. The mechanical boundary conditions correspond to those of stress free lateral surfaces while the electrical boundary conditions correspond to those of open and short circuit are considered. The satisfaction of the boundary conditions lead to the frequency equation, in the form of determinant involving Bessel functions, have been taken into consideration. The roots of the frequency equations give the values of the characteristic circular frequency parameters of the first three modes for various geometries. These roots are numerically computed and programmed for numerical evaluation by ''Bisection Method Iterations Technique (BMIT)'' and presented graphically for various thickness of the circular cylinder and for different values of the initial stress. The effect of the initial stress on the natural frequencies are illustrated graphically for a transversely isotropic piezoelectric martial PZT?4 circular cylinder. It is found that both the thickness of the circular cylinder and the initial stress have a substantial effect on the dispersion behavior. The results obtained in this paper may be applied to the vibrations of annular accelerometers operating in the radial shear mode. Also, they have theoretical basis application and have meaningful design for piezoelectric probes and electro-acoustic devices in the nondestructive evaluation. Keywords: Piezoelectricity, frequency equation, Transverse surface waves, Initial stress, Hexagonal crystals

Effect on the energy market of the potential switching to heat pumps for space heating

The main subject of this work is to understand what could happen in the Italian electricity market if a given share of building heating demand had switched from gas to electricity heating devices. The objective is to define the optimal share to switch in terms of minimization of environmental (CO2) emissions. The effects of such switching on the national energy system are analyzed from the financial point of view, depending also on the heating habits of final users. An hourly simulation of the electricity market has been performed by means of a bid stack model (BIDSM) developed at University of Genoa, calculating market prices, power plant generation typology, fuel consumption and global CO2 emissions. All the data are averaged on a national basis and results are reported for two different time schedule of heating requirements of the final users. In each case, the total energy consumption is fixed, and local "degree days" and location energy needs are considered. It seems that the use of heat pumps for building heating is a real option and that the user habits has a little impact on optimal share of switching from gas to heat pumps, at least concerning CO2 emission minimization

Variability and inheritance of okra leaf- shape of cotton cv. Sudac-k in different genetic backgrounds

   Okra leaf- shape is an important trait in cotton. Sudac-k is the only cotton variety with okra leaf type in the Sudan. The objectives of the study were to analyze the inheritance of the okra leaf of Sudac-k and its expression in different genetic backgrounds. The experiment was carried out for two seasons (2004/05 and 2005/06) and one off-season in 2006 at Gezira Research Farm of the Agricultural Research Corporation (ARC), Wad Medani, Sudan. The plant material consisted of Sudac-k and nine different varieties; B-pima, Barakat-90, G.S, Maryoud, Shambat-B, Acala-M, Acala-H, Barac (67) B and Albar (57)12. Eighteen reciprocal F1s were produced between Sudac-k and respective cultivars. In the second season, F2 ҆s, backcrosses and F3 plants were (Sudac-k X Albar (57)12). At maturity, individual plants were visually scored according to the leaf-shape into okra and normal leaf shape. Okra leaf morphology, lobe length, width and angle were measured in fully expanded 5- lobed leaf. It was observed that the okra leaf of Sudac-k had deep sinuses and narrow lobes while in F1 ҆ s, the sinuses were shorter and the lobes were broader. The okra leaf started at seedling stage with three lobes at the 3rd to 4th node and reached a maximum of 5 lobes at node 6 to 8 in Sudac-k, F1 plants and their progenies. Chi-square test for the segregation of leaf type in F2 indicated no significant differences among all F1 ҆ s between Sudac-k and the varieties in the distribution of okra and normal which followed the ratio of 1:2:1. This indicates that the okra leaf trait is conditioned by a single partially dominant gene. Significant differences were observed among the F1 hybrids for the expression of leaf lobing depth, lobe width and angle, indicating the effect of the genetic background on the expression of these parameters. The information will be useful in designing strategy for breeding of cotton varieties with suitable size of okra leaf to maximize its utilization in integrated insect pest management

Torsional vibrations of nonhomogeneous magnetostrictive elastic circular cylinder

This paper is concerned with the torsional vibrations of a nonhomogeneous magnetostrictive elastic cylinder. The cylinder is subjected to the action of a circumferential magnetic field produced by an axial current of constant density and the deformation of a magnetostrictive cylinder is produced by a constant longitudinal magnetic field. The frequency equation is determined, and the displacement and stress components are numerically calculated with graphical presentations

The Antiviral Drug Valacyclovir Successfully Suppresses Salivary Gland Hypertrophy Virus (SGHV) in Laboratory Colonies of Glossina pallidipes

Many species of tsetse flies are infected with a virus that causes salivary gland hypertrophy (SGH) symptoms associated with a reduced fecundity and fertility. A high prevalence of SGH has been correlated with the collapse of two laboratory colonies of Glossina pallidipes and colony maintenance problems in a mass rearing facility in Ethiopia. Mass-production of G. pallidipes is crucial for programs of tsetse control including the sterile insect technique (SIT), and therefore requires a management strategy for this virus. Based on the homology of DNA polymerase between salivary gland hypertrophy virus and herpes viruses at the amino acid level, two antiviral drugs, valacyclovir and acyclovir, classically used against herpes viruses were selected and tested for their toxicity on tsetse flies and their impact on virus replication. While long term per os administration of acyclovir resulted in a significant reduction of productivity of the colonies, no negative effect was observed in colonies fed with valacyclovir-treated blood. Furthermore, treatment of a tsetse colony with valacyclovir for 83 weeks resulted in a significant reduction of viral loads and consequently suppression of SGH symptoms. The combination of initial selection of SGHV-negative flies by non-destructive PCR, a clean feeding system, and valacyclovir treatment resulted in a colony that was free of SGH syndromes in 33 weeks. This is the first report of the use of a drug to control a viral infection in an insect and of the demonstration that valacyclovir can be used to suppress SGH in colonies of G. pallidipes

CHEMICAL COMPOSITION AND BIOLOGICAL ACTIVITIES OF TWO SOLANUM TUBEROSUM CULTIVARS GROWN IN EGYPT

Objective: This paper reports a comparative study based on the chemical composition, antioxidant and therapeutic effect of two Egyptian cultivars of Solanum tuberosum; Baraka (STB) and Alpha (STA) on hepatic functions and oxidative stress in alloxan (ALX)-treated rats.Methods: The potential of cultivars as a source of natural antioxidants were explored using five in vitro assays, and the results were compared with butylated hydroxyl toluene and Trolox. The modulator role of cultivars was assessed by determining its effect on oxidative stress measured by lipid peroxide (LPO) levels, serum aminotransferases and on antioxidative enzymatic activities of glutathione transferases, malondialdehyde, nitric oxide, catalase, superoxide dismutase, and glutathione peroxidase. In addition, histological examinations of liver, kidney, pancreas and spleen were carried out to confirm the biochemical changes of the diabetic group of rats non-treated and treated with STB, STA and glibenclamide as standard drug.Results: Our findings demonstrated variations in antioxidant activities of each cultivar. An increase in LPO, aminotransferases levels was observed in the ALX-induced diabetic rats. Administration of each cultivar for four w caused a significant reduction in LPO, serum aminotransferases levels in the ALX-induced diabetic rats. Furthermore, a significant improvement in the activities of all the investigated antioxidant enzymes was marked. In addition, the total content of phenolics, flavonoids, anthocyanins, tannins, and alkaloids were varied in each cultivar.Conclusion: STB evidenced remarkable bioactivity compared to that exhibited by STA. Moreover, three known compounds, previously not isolated from Solanum genus, were obtained from the methylene chloride fraction of STB.Â