Vibration of elliptic cylindrical shells: higher order shell theory.

The equations for the free vibration of an elliptic cylindrical shell of constant thickness were derived using a Ritz approach. A higher order shell theory is employed that includes the effects of shear deformation, rotary inertia, and symmetric and antisymmetric thickness stretch deformations. The frequency-wavenumber spectrum has seven branches: flexural, extensional, torsional, two thickness shear, and two thickness stretch. The resulting seven coupled algebraic equations are symmetric and positive definite. The shell has a constant thickness, h, finite length, L, and is "simply supported" at its ends, (z=0,L), where z is the axial coordinate. The elliptic cross-section is defined by the shape parameter, a, and the half-length of the major axis, l. The modal solutions are expanded in a doubly infinite series of comparison functions in terms of circular functions in the angular and axial coordinates. Numerical results for the natural frequencies were obtained for two values of h/l and L/l, and various shape parameters, including the limiting case of a simply supported cylindrical shell (a approximately 100).

Introducing nanochemoprevention as a novel approach for cancer control: proof of principle with green tea polyphenol epigallocatechin-3-gallate.

Chemoprevention, especially through the use of naturally occurring phytochemicals capable of impeding the process of one or more steps of carcinogenesis process, is a promising approach for cancer management. Despite promising results in preclinical settings, its applicability to humans has met with limited success largely due to inefficient systemic delivery and bioavailability of promising chemopreventive agents. Here, we introduce the concept of nanochemoprevention, which uses nanotechnology for enhancing the outcome of chemoprevention. We encapsulated green tea polyphenol epigallocatechin-3-gallate (EGCG) in polylactic acid-polyethylene glycol nanoparticles and observed that encapsulated EGCG retains its biological effectiveness with over 10-fold dose advantage for exerting its proapoptotic and angiogenesis inhibitory effects, critically important determinants of chemopreventive effects of EGCG in both in vitro and in vivo systems. Thus, this study could serve as a basis for the use of nanoparticle-mediated delivery to enhance bioavailability and limit any unwanted toxicity of chemopreventive agents, such as EGCG.

Vibration of prolate spheroidal shells with shear deformation and rotatory inertia: axisymmetric case.

This paper presents the derivation of the equations for nonaxisymmetric motion of prolate spheroidal shells of constant thickness. The equations include the effect of distributed mechanical surface forces and moments. The shell theory used in this derivation includes three displacements and two thickness shear rotations. Thus, the effects of membrane, bending, shear deformation, and rotatory inertia are included in this theory. The resulting five coupled partial differential equations are self-adjoint and positive definite. The frequency-wave-number spectrum has five branches, two acoustic and three optical branches representing flexural, extensional, torsional, and two thickness shear. For the case of axisymmetric motion, these were computed for various spheroidal shell eccentricities and thickness-to-length ratios for a large number of modes. The axisymmetric dynamic response for damped shells of various eccentricities and thicknesses under point and ring surface forces are presented.