RF Energy Deposition in a Heterogeneous Model of Man: Near-Field Exposures

The electric field strength was measured in a full-scale heterogeneous model of man exposed in the near field of resonant dipoles. The model was comprised of skull, spinal cord, rib cage, all other major bones, brain, lung, and muscle tissue. Electrical properties of these simulated tissues were the same as respective live tissue properties at test frequencies of 160, 350, and 915 MHz. The rates of energy absorption were calculated on the basis of the measured field strengths and tissue conductivities. Patterns of the energy deposition are compared for two orientations of the antennas with respect to the body. Also the results for the heterogeneous model are compared to data for homogeneous model having average tissue electrical properties.     

Comparison of the Adhesive Shear Modulus in Bulk and Bonded States

A method is proposed for determining the in situ shear modulus of a structural adhesive from a sandwich beam loaded in 3-point bending in which the adhesive is contained as a thin layer. Expressions for calculating the elastic shear modulus of the adhesive layer from compliance data on the beam are derived, and experimental tests to validate the theory are conducted. To verify the test results, tensile tests are also conducted, and the shear modulus for bulk adhesive is determined using the constitutive equation for an isotropic material relating tensile modulus and Poisson's ratio to shear modulus.

However, the bulk shear modulus as traditionally determined from a tensile test was up to an order of magnitude greater than the in situ shear modulus obtained from the 3-point bend test. A finite element simulation and sensitivity study replicated the experimental results of the 3-point bend tests, and showed that using the shear modulus obtained from the tensile tests would result in significant errors in predicting material and joint behavior. In addition, torsion tests were conducted on bonded cylinders to measure directly the shear modulus. The shear modulus from the torsion test was in agreement with the in situ modulus obtained from the 3-point bend test. This combined experimental-computational approach validated the 3-point bend test as a means to determine the in situ adhesive shear modulus. Finally, micrographs of the interface of the 3-point bend specimen indicated that adhesion occurred by the extension of adhesive pillars to the surface of the adherends. This pillaring phenomenon may have resulted in a lack of bonding along significant portions of the interface, and may explain the compliance of the 3-point bend specimens and, subsequently, the lower shear modulus. The repeatability of the experiments and the substantiation of the results of the experiments by finite element analysis suggest that this pillaring phenomenon may be a mechanism of adhesion.     

Grooming behavior and competitive dominance in the albino rat.

Compared dominance in 28 male Wistar rats manifested in water competition under 2 levels of deprivation, with grooming activity in a nondeprived state. While competitive dominance was significantly related to motivational level, grooming emerged as a more stable indicator of social ascendance and did not require prior manipulation of a biological state. Implications of this observation for broader aspects of social motivation are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of the Adhesive Shear Modulus in Bulk and Bonded States

A method is proposed for determining the in situ shear modulus of a structural adhesive from a sandwich beam loaded in 3-point bending in which the adhesive is contained as a thin layer. Expressions for calculating the elastic shear modulus of the adhesive layer from compliance data on the beam are derived, and experimental tests to validate the theory are conducted. To verify the test results, tensile tests are also conducted, and the shear modulus for bulk adhesive is determined using the constitutive equation for an isotropic material relating tensile modulus and Poisson's ratio to shear modulus.

However, the bulk shear modulus as traditionally determined from a tensile test was up to an order of magnitude greater than the in situ shear modulus obtained from the 3-point bend test. A finite element simulation and sensitivity study replicated the experimental results of the 3-point bend tests, and showed that using the shear modulus obtained from the tensile tests would result in significant errors in predicting material and joint behavior. In addition, torsion tests were conducted on bonded cylinders to measure directly the shear modulus. The shear modulus from the torsion test was in agreement with the in situ modulus obtained from the 3-point bend test. This combined experimental-computational approach validated the 3-point bend test as a means to determine the in situ adhesive shear modulus. Finally, micrographs of the interface of the 3-point bend specimen indicated that adhesion occurred by the extension of adhesive pillars to the surface of the adherends. This pillaring phenomenon may have resulted in a lack of bonding along significant portions of the interface, and may explain the compliance of the 3-point bend specimens and, subsequently, the lower shear modulus. The repeatability of the experiments and the substantiation of the results of the experiments by finite element analysis suggest that this pillaring phenomenon may be a mechanism of adhesion.