Fracture mechanics of cellular glass

The fracture mechanics of cellular glasses (for the structural substrate of mirrored glass for solr concentrator reflecting panels) are discussed. Commercial and developmental cellular glasses were tested and analyzed using standard testing techniques and models developed from linear fracture mechanics. Two models describing the fracture behavior of these materials were developed. Slow crack growth behavior in cellular glass was found to be more complex than that encountered in dense glasses or ceramics. The crack velocity was found to be strongly dependent upon water vapor transport to the tip of the moving crack. The existence of a static fatigue limit was not conclusively established, however, it is speculated that slow crack growth behavior in Region 1 may be slower, by orders of magnitude, than that found in dense glasses

Controlling Listeria monocytogenes on ready-to-eat poultry products using carboxymethylcellulose film coatings containing green tea extract (GTE) combined with nisin and malic acid

The ability to control Listeria monocytogenes on ready-to-eat poultry products using carboxymethyl-cellulose film coatings containing green tea extract (GTE), malic acid (M), nisin (N), and their combinations was evaluated. The antimicrobials (GTE: 1.0%, nisin: 10,000 IU/g, malic acid: 1.0%) were incorporated alone or in combination into a carboxymethyl cellulose film coating. Pre-inoculated, fully cooked chicken pieces (~1g, 1cm x 1cm x 1cm) were coated with the film solution. The coated chicken pieces were stored at 4°C and the inhibitory activity against Listeria monocytogenes was evaluated at 0, 7, 14, 21, and 28 days. The highest inhibitory activity was found in the sample containing GTE, nisin, and malic acid in combination with a reduction of 3.3 log CFU/mL. These data demonstrate that GTE—combined with nisin and malic acid and incorporated into a carboxymethyl-cellulose film coating, multiple-hurdle technology—is effective in inhibiting L. monocytogenes growth on fully cooked chicken pieces at 4°C. Research in the area of finding natural antimicrobials to aid in the prevention of food-borne illnesses is necessary to improve safety and shelf life of products such as ready-to-eat meats. This project provides an effective combination of natural anti-microbials to control L. monocytogenes in ready-to-eat chicken pieces

A methodology for exploiting parallelism in the finite element process

A methodology is described for developing a parallel system using a top down approach taking into account the requirements of the user. Substructuring, a popular technique in structural analysis, is used to illustrate this approach

Strong electron correlations in cobalt valence tautomers

We have examined cobalt based valence tautomer molecules such as Co(SQ)$_2$(phen) using density functional theory (DFT) and variational configuration interaction (VCI) approaches based upon a model Hamiltonian. Our DFT results extend earlier work by finding a reduced total energy gap (order 0.6 eV) between high temperature and low temperature states when we fully relax the coordinates (relative to experimental ones). Futhermore we demonstrate that the charge transfer picture based upon formal valence arguments succeeds qualitatively while failing quantitatively due to strong covalency between the Co 3$d$ orbitals and ligand $p$ orbitals. With the VCI approach, we argue that the high temperature, high spin phase is strongly mixed valent, with about 30 % admixture of Co(III) into the predominantly Co(II) ground state. We confirm this mixed valence through a fit to the XANES spectra. Moreover, the strong electron correlations of the mixed valent phase provide an energy lowering of about 0.2-0.3 eV of the high temperature phase relative to the low temperature one. Finally, we use the domain model to account for the extraordinarily large entropy and enthalpy values associated with the transition.Comment: 10 pages, 4 figures, submitted to J. Chem. Phy

Fermi-liquid effects in the gapless state of marginally thin superconducting films

We present low temperature tunneling density-of-states measurements in Al films in high parallel magnetic fields. The thickness range of the films, t=6-9 nm, was chosen so that the orbital and Zeeman contributions to their parallel critical fields were comparable. In this quasi-spin paramagnetically limited configuration, the field produces a significant suppression of the gap, and at high fields the gapless state is reached. By comparing measured and calculated tunneling spectra we are able to extract the value of the antisymmetric Fermi-liquid parameter G^0 and thereby deduce the quasiparticle density dependence of the effective parameter G^0_{eff} across the gapless state.Comment: 6 pages, 4 figure

Finite element for rotor/stator interactive forces in general engine dynamic simulation. Part 1: Development of bearing damper element

A general purpose squeeze-film damper interactive force element was developed, coded into a software package (module) and debugged. This software package was applied to nonliner dynamic analyses of some simple rotor systems. Results for pressure distributions show that the long bearing (end sealed) is a stronger bearing as compared to the short bearing as expected. Results of the nonlinear dynamic analysis, using a four degree of freedom simulation model, showed that the orbit of the rotating shaft increases nonlinearity to fill the bearing clearance as the unbalanced weight increases

Hyperspherical Harmonics, Separation of Variables and the Bethe Ansatz

The relation between solutions to Helmholtz's equation on the sphere $S^{n-1}$ and the [{\gr sl}(2)]^n Gaudin spin chain is clarified. The joint eigenfuctions of the Laplacian and a complete set of commuting second order operators suggested by the $R$--matrix approach to integrable systems, based on the loop algebra \wt{sl}(2)_R, are found in terms of homogeneous polynomials in the ambient space. The relation of this method of determining a basis of harmonic functions on $S^{n-1}$ to the Bethe ansatz approach to integrable systems is explained.Comment: 14 pgs, Plain Tex, preprint CRM--2174 (May, 1994

The Impact of Situational Constraints, Role Stressors, and Commitment on Employee Altruism

This study investigated relations between 3 work-related stressors (role ambiguity, role conflict, and organizational constraints) and altruistic behavior in the workplace. It was predicted that each stressor would be negatively related to altruism and that these relations would be moderated by affective commitment (AC). Data from 144 incumbent-supervisor dyads revealed that all 3 stressors; were weakly and negatively related to altruism. Two of these relationships were moderated by AC, although not as predicted. Organizational constraints were positively related to altruism among those reporting high levels of AC but negatively related among those reporting low levels of AC. The pattern was exactly opposite for role conflict. Implications of these findings are discussed

Dual Isomonodromic Deformations and Moment Maps to Loop Algebras

The Hamiltonian structure of the monodromy preserving deformation equations of Jimbo {\it et al } is explained in terms of parameter dependent pairs of moment maps from a symplectic vector space to the dual spaces of two different loop algebras. The nonautonomous Hamiltonian systems generating the deformations are obtained by pulling back spectral invariants on Poisson subspaces consisting of elements that are rational in the loop parameter and identifying the deformation parameters with those determining the moment maps. This construction is shown to lead to ``dual'' pairs of matrix differential operators whose monodromy is preserved under the same family of deformations. As illustrative examples, involving discrete and continuous reductions, a higher rank generalization of the Hamiltonian equations governing the correlation functions for an impenetrable Bose gas is obtained, as well as dual pairs of isomonodromy representations for the equations of the Painleve transcendents $P_{V}$ and $P_{VI}$.Comment: preprint CRM-1844 (1993), 28 pgs. (Corrected date and abstract.