Error analysis of photoelasticity in fracture mechanics

An error analysis of the use of photoelasticity in the study of fracture problems is attempted. In particular, it was desired to determine the optimum regions of data collection and to ascertain the sensitivity of the extractedK ₁ andK ₂ values to errors in such parameters as crack-tip position and fringe location. Experiments were performed on both Mode 1 and Mixed Mode cases and the results compared with the error analysis     

Directional Preferences of Approach of Nucleophiles to Sulfonium Ions

An analysis of the crystal environments of sulfonium ions shows that short nonbonded contacts (secondary bonds) to sulfur tend to occur along the extensions of the C-S primary bonds. Non-bonded contacts to the C (a)-atoms of sulfonium ions are not especially short and do not show any striking directional preference, except in sulfonium ions derived from methionine where a specific intramolecular interaction between a carboxyl O-atom and the C (γ)-atom may represent an incipient stage of the internal nucleophilic displacement leading to formation of homoserine and mercaptan.     

Defining International Market Opportunities via Wishart's Mode Analysis

Generally, companies selling overseas do not select foreign markets systematically. This paper introduces the concepts of a market concentration strategy and an optimum portfolio of markets as a basis for planning foreign markets. It is shown how numerical classification procedures can operationalize these strategy concepts. Wishart's mode analysis is illustrated as an effective tool for solving this problem.     

Protein deformation of lipid hybrid bilayer membranes studied by sum frequency generation vibrational spectroscopy

Structural deformations of lipid hybrid bilayer membranes induced by signal peptideless (SPL) proteins have been studied for the first time using the inherently surface specific nonlinear optical technique of sum frequency generation vibrational spectroscopy. Specifically, deformations of 1,2-distearoylphosphatidylglycerol(DSPG) membranes induced by interaction with FGF-1, a SPL protein which is released asa function of cellular stress through a nonclassical pathway, have been investigated. FGF-1 was found to induce lipid alkyl chain deformations in previously highly ordered DSPG membranes at the extremely low concentration of 1 nM at 60 degrees C. The deformation process was shown to exhibit a degree of reversibility upon removal of the protein by rinsing with buffer solution.     

Hydrogen-bonded cubanes in the crystal structure of 2,6-di(Pr(i))aniline hydrochloride and their inorganic analogues [M(2+)(2,6-di(Pr(i))C6H5N(2-))]4 (M = Sn, Pb)

The crystal structure of 2,6-di(Pr(i))aniline hydrochloride contains hydrogen-bonded cubanes analogous to those in the complexes [M(2+)(2,6-di(Pr(i))C6H5N(2-))]4, M = Sn, Pb.     

Highly optimized tolerance: robustness and design in complex systems

Highly optimized tolerance (HOT) is a mechanism that relates evolving structure to power laws in interconnected systems. HOT systems arise where design and evolution create complex systems sharing common features, including (1) high efficiency, performance, and robustness to designed-for uncertainties, (2) hypersensitivity to design flaws and unanticipated perturbations, (3) nongeneric, specialized, structured configurations, and (4) power laws. We study the impact of incorporating increasing levels of design and find that even small amounts of design lead to HOT states in percolation.     

Clean reconstructed InAs(1 1 1) A and B surfaces using chemical treatments and annealing

Well-ordered clean InAs(1 1 1) A and B surfaces have been prepared using HCl-isopropanol solutions and characterized using low-energy electron diffraction and photoemission spectroscopy. The as-treated surfaces are covered by a layer containing arsenic and small amounts of InCl_x. Annealing induces desorption of the overlayer and reveals (2 × 2) and (1 × 1) structures on the A and B surfaces, respectively. For both surfaces, the surface components of the In 4d and As 3d reveal a charge transfer from the electropositive surface indium to the electronegative surface arsenic. The major advantage of this preparation method over conventional thermal cleaning is a significant reduction in the annealing temperature (≈250 °C) thereby avoiding anion evaporation.