More is the Same; Phase Transitions and Mean Field Theories

This paper looks at the early theory of phase transitions. It considers a group of related concepts derived from condensed matter and statistical physics. The key technical ideas here go under the names of "singularity", "order parameter", "mean field theory", and "variational method". In a less technical vein, the question here is how can matter, ordinary matter, support a diversity of forms. We see this diversity each time we observe ice in contact with liquid water or see water vapor, "steam", come up from a pot of heated water. Different phases can be qualitatively different in that walking on ice is well within human capacity, but walking on liquid water is proverbially forbidden to ordinary humans. These differences have been apparent to humankind for millennia, but only brought within the domain of scientific understanding since the 1880s. A phase transition is a change from one behavior to another. A first order phase transition involves a discontinuous jump in a some statistical variable of the system. The discontinuous property is called the order parameter. Each phase transitions has its own order parameter that range over a tremendous variety of physical properties. These properties include the density of a liquid gas transition, the magnetization in a ferromagnet, the size of a connected cluster in a percolation transition, and a condensate wave function in a superfluid or superconductor. A continuous transition occurs when that jump approaches zero. This note is about statistical mechanics and the development of mean field theory as a basis for a partial understanding of this phenomenon.Comment: 25 pages, 6 figure

Executive Incentive Schemes in Initial Public Offerings: The Effects of Multiple-Agency Conflicts and Corporate Governance

Combining a behavioral agency perspective with research on multiple-agency conflicts, this article examines factors affecting the implementation of equity-based incentive schemes in initial public offerings (IPOs). With a unique sample of U.K. IPO companies between the years 1998 and 2002, it shows that conditional (performance-related) incentive schemes are negatively associated with share ownership and board power of the IPO’s founding directors. However, the retained ownership of venture capital firms is positively associated with the probability of conditional incentive schemes. Board independence weakly effects on the toughness of executive compensation. The article’s interesting findings suggest a number of avenues for a future analysis of the governance development process in threshold firms

Effect of Tissue Processing on Assessment of Endoscopic Intestinal Biopsies in Dogs and Cats

Background: Prior studies failed to detect significant association between hypoalbuminemia and small intestinal lesions. Hypothesis: Use of pictorial templates will enhance consistency of interpathologist interpretation and identification of intestinal lesions associated with hypoalbuminemia. Animals: Tissues from 62 dogs and 25 cats examined as clinical cases at 7 referral veterinary practices in 4 countries. Methods: Retrospective, observational study. Histopathology slides from sequential cases undergoing endoscopic biopsy were examined by 4 pathologists by pictorial templates. Changes for 9 microscopic features were recorded as normal, mild, moderate or severe, and 2- and 4-point scales were tested for consistency of interpretation. Logistic regression models determined odds ratios (OR) of histologic lesions being associated with hypoalbuminemia while k statistics determined agreement between pathologists on histologic lesions. Results: There was poor agreement (k= -0.013 to 0.3) between pathologists, and institution of origin of slides had effect (k = 1.0 for 3 of 4 lesions on slides from Institution 5) on agreement between pathologists on selected histologic features. Using 2 point as opposed to 4-point grading scale increased agreement between pathologists (maximum k = 0.69 using 4-point scale versus maximum k = 1.0 using 2-point scale). Significant association (P = .019\u2013 .04; 95% OR = 3.14\u201310.84) between lacteal dilation and hypoalbuminemia was found by 3 pathologists. Conclusions and Clinical Importance: Substantial inconsistency between pathologists remains despite use of pictorial template because of differences in slide processing. Distinguishing between mild and moderate lesions might be important source of the disagreement among pathologists