On the damped frequency response of a finite-element model of the cat eardrum

This article presents frequency responses calculated using a three-dimensional finite-element model of the cat eardrum that includes damping. The damping is represented by both mass-proportional and stiffness-proportional terms. With light damping, the frequency responses of points on the eardrum away from the manubrium display numerous narrow minima and maxima, the frequencies and amplitudes of which are different for different positions on the eardrum. The frequency response on the manubrium is smoother than that on the eardrum away from the manubrium. Increasing the degree of damping smooths the frequency responses both on the manubrium and on the eardrum away from the manubrium. The overall displacement magnitudes are not significantly reduced even when the damping is heavy enough to smooth out all but the largest variations. Experimentally observed frequency responses of the cat eardrum are presented for comparison with the model results.     

Growth of single crystals of copper and their thermal profile estimation

Copper crystals have been grown by Czochralski technique in a 6-bar argon gas environment. X-ray analysis shows that these are single crystals and are strain-free. A slight pressure environment that is truly hydrostatic seems to improve the quality of the crystals. Thermal profile estimation results show that the values of temperature which decrease upto the neck region are same in magnitude as those measured during the experiments and that necking improves the thermal profile and, consequently, the crystal quality. No facet formation has been observed in these crystals.     

Synthesis and characterization of myristic acid capped silver nanoparticles

Reduction of silver myristate (AgMy) under mild thermal reaction conditions in a dipolar aprotic solvent i.e. N, N-dimethylformamide (DMF) has been carried out. UV–visible absorption measurements of dried and re-dispersible brown flocculants showed broad features of surface plasmon resonance (SPR) due to silver nanoparticles. The freshly isolated particles showed absorption bands at 414 and 485 nm, respectively, due to inter-particle coupling or clustering of silver ions and silver atoms. X-ray diffraction (XRD) pattern of fcc zero-valent silver resulted in crystallite size of about 10 nm. Scanning electron microscopy (SEM) revealed formation of rod shaped silver with increasing reaction temperature. Thermal analysis (TGA) showed about 10% weight loss due to organic capping.     

Toxicity and the cardiovascular activity of organotin compounds: a review

A comprehensive review on toxicity of organotin compounds including sources of their intake and mode of action, and cardiovascular activity of organotin compounds is presented. Further research to develop novel useful organotin compounds having hypertensive activity needs to be carried out. Copyright © 2008 John Wiley & Sons, Ltd.     

Speciation and Multinuclear NMR Spectroscopic Studies of Di- and Trimethyltin(IV) Moieties with MESNA in Aqueous Medium

The interaction of Me₂Sn(IV)²⁺ and Me₃Sn(IV)⁺ with a prodrug, sodium 2-mercaptoethane sulfonate (HSCH₂CH₂SO₃Na, MESNA) abbreviated as (HL), has been studied potentiometrically in aqueous solution (I = 0.1 mol·L^?1 KNO₃, 298 K). The concentration distribution of various species formed in the solution was studied with changes in pH (~3–11). A strong coordination of MESNA with metal through the S atom of thiol group has been found. In the Me₂Sn(IV)–HL system, the species [Me₂Sn(L)]⁺ (53.1–75.6%) is predominant at acidic pH (3.73 ± 0.02) and the species [Me₂Sn(L)₂OH]^? (29.4–38.5%) is predominant at basic pH (10.32 ± 0.08). In contrast, for the Me₃Sn(IV)⁺ system, [Me₃SnL] (37.0–57.4%) is the major species at pH 7.65 ± 0.03 and [Me₃Sn(OH)] (49.9–67.2%) and [Me₃Sn(L)(OH)]^? (30.2–46.5%) are the major species at pH 11.05 ± 0.01. However, at physiological pH (7.01 ± 0.32), in both (1:1) and (1:2) Me₂Sn(IV)–HL systems, the species [Me₂Sn(L)(OH)] (67.2–89.9%) is predominant, whereas for Me₃Sn(IV)–HL (1:1) and (1:2) systems, [Me₃Sn(OH)] (53.5%) and [Me₃SnL] (56.8%) are the respective predominant species. In order to characterize the possible geometry of the proposed complex species, multinuclear (¹H, ¹³C and ¹¹⁹Sn) NMR studies were carried out at different pHs. No polymeric species were detected in the experimental pH range.     

Similarity solutions for the flow behind an exponential shock in a non-ideal gas

Similarity solutions for the flow of a non-ideal gas behind a strong exponential shock driven out by a piston (cylindrical or spherical) moving with time according to an exponential law are obtained. Similarity solutions exist only when the surrounding medium is of constant density. Solutions are obtained, in both the cases, when the flow between the shock and the piston is isothermal or adiabatic. It is found that the assumption of zero temperature gradient brings a profound change in the density distribution as compare to that of the adiabatic case. Effects of the non-idealness of the gas on the flow-field between the shock and the piston are investigated. The variations of density-ratio across the shock and the location of the piston with the parameter of non-idealness of the gas are also obtained.     

Large amplitude response of circular plates on elastic foundations

The von Kármán type partial differential equations governing non-linear dynamic behaviour of circular plates resting on Winkler and Pasternak elastic foundations have been analysed analytically. The space and time-wise integrations have been carried out employing the Chebyshev polynomials and implicit Houbolt techniques, respectively. The influence of foundation parameters K and G on the large amplitude response of circular plates subjected to step function loads has been studied for both the clamped immovable as well as simply supported immovable edge conditions. Foundation parameters K and G have been determined for the minimax central response. For all values of K,values of G should be between 30 and 40 for the clamped circular plates and the value of G should be a maximum for the simply supported circular plates.