No abstract

No abstract

Exposure of 10-d-old spinach (Spinacea oleracea L.) plants to excess (500 µM) concentrations of Co, Ni, Cu, Zn and Cd in sand culture inhibited growth, induced toxicity symptoms, oxidative damage and changes in the antioxidant defense system. The severity of the metal-induced effects varied with the metals and the duration of exposure to excess supply of the metals. Each metal induced chlorosis. In addition, excess Co, Ni and Cd also produced metal specific toxic effects. Excess supply of each metal caused lipid peroxidation (TBARS). Their effectiveness in producing oxidative damage was in the order: Ni > Co > Cd > Cu >Zn. Of all the metals, Ni was also most effective in lowering the concentration of the chloroplast pigments (Chl, Car). While each metal increased the concentration of ascorbate and activated the key enzymes of the ascorbate-glutathione cycle, excess Cd and Zn were more effective in this regard. Each metal increased the activity of SOD and POD and decreased the activity of CAT. Enhancement in SOD activity and inhibition of CAT activity suggested high build-up of H 2 O 2 , possibly the main cause of oxidative stress, induced in response to excess supply of the heavy metals.

In this letter, design of compact size rat‐race coupler (RRC), based on impedance‐controlled simple transmission line structure is proposed for predetermined harmonic suppression. The present approach has the advantage that within the fabrication limit of high‐impedance lines, a large number of harmonics are suppressed. Design guidelines are provided. Theoretical predictions are verified by implementing a prototype microstrip RRC, with upto twelfth harmonic of the operating frequency suppressed along with 75% size reduction compared with the conventional RRC. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 30–34, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24832

No abstract

In this paper, ultrasonic properties like ultrasonic attenuation, sound velocities, acoustic coupling constants and thermal relaxation time have been studied in hexagonal structured metals Gadolinium (Gd), Terbium (Tb), Dysprosium (Dy), Holmium (Ho), Erbium (Er) and Thulium (Tm) along unique axis at room temperature. For the evaluations of ultrasonic properties, second-and third-order elastic constants have been computed also. The peculiar behavior of these metals is found at 55° due their least thermal relaxation time and highest Debye average velocity. Dy is more ductile, stable, perfect metal in comparison to other chosen metals due to its lowest value of attenuation. So we predict that Dy is most suitable lanthanide metals for material science and engineering.

No abstract

Abstract:The ultrasonic attenuation in thulium monochalcogenides TmX (X =S, Se and Te) has been studied theoretically with a modified Mason's approach in the temperature range 100 K to 300 K along 100 , 110 and 111 crystallographic directions. The thulium monochalcogenides have attracted a lot of interest due to their complex physical and chemical characteristics. TmS, TmSe and TmTe are trivalent metal, mixed valence state, and divalent semiconductor, respectively. Coulomb and Born-Mayer potential is applied to evaluate the second-and third-order elastic constants. These elastic constants are used to compute ultrasonic parameters such as ultrasonic velocities, thermal relaxation time, and acoustic coupling constants that, in turn, are used to evaluate ultrasonic attenuation. A comparison of calculated ultrasonic parameters with available theoretical/experimental physical parameters gives information about classification of these materials.