Identification and analysis of chunks in software projects

Most software systems undergo continuous change in different phases of their lifecycle such as development or maintenance. Ideally, such changes should correspond to a system\u27s modular design. However, some changes span across more than one component thereby resulting in discrepancies between design and implementation. In such cases, making a change to one component requires changes to other components leading to an increase in time and effort to make changes to a software system as it evolves. This thesis investigates: 1) an approach to observe how components change together by identifying tightly coupled changes known as chunks, 2) whether there are any trends in how chunks evolve over time, and 3) whether chunks can help identify design issues in a software system. In this work, a family of algorithms is proposed to identify independently changing chunks from change data obtained from mining version history repositories of three large software systems - Moodle, Eclipse, and Company-X. A comprehensive analysis of certain characteristics of the resulting chunks is conducted. In addition, evolution of chunks with respect to size in terms of number of files within a chunk, and percentage of changes crossing a chunk are studied. Lastly, a pragmatic interpretation of the results to identify necessary code refactoring or system redesign is presented. The findings of this work show that the percentage correlation of a chunk decreases with an increase in the number of inter-component or subsystem couplings. We also observed that there is no association between chunk size and percentage correlation. Identifying chunks that merge helps in a better understanding of the inconsistencies between how a system is designed for change and how it is actually changed, and to identify areas of a system that require refactoring or redesign. Additionally, identifying stable chunks can provide insights into how size and percentage correlation of the corresponding empirical components change over time

Obstructing mucocele of the cystic duct after transplantation of the liver

A tension mucocele was created in three hepatic homografts by ligating a low-lying cystic duct during transplant cholecystectomy and by incorporating its outflow end into the anastomosis of the common hepatic duct to the recipient common duct or Roux limb of jejunum. The consequent complication of obstruction of the biliary tract that necessitated reoperation and excision of the mucocele in all three patients can be avoided by the simple expedient of completely removing the cystic duct when feasible or providing egress to the secretion of the cystic duct as described

Orthotopic liver transplantation for alcoholic cirrhosis.

Fifteen patients with Laennec's cirrhosis underwent orthotopic liver transplantation between 1963 and the end of 1979. The first eight patients died perioperatively or within two months, but four of the next seven patients had long survival; three are still alive after 11 to 14 years. After the introduction of cyclosporine therapy, 41 more patients with alcoholic cirrhosis were treated with liver transplantation from 1980 to June 1987. The one-year survival is 73.2%, and, after one to three years, 28 (68%) of the recipients are living. Of the 35 patients in the combined old and new series who lived for six months or longer, only two returned to alcohol abuse. Social and vocational rehabilitation has been the rule in these recipients who were selected primarily because of urgency of need, because they or their families insisted on treatment, and because they and their families thereby committed themselves to long-standing programs of alcoholism care

Cadaveric renal transplantation at the University of Pittsburgh: a two and one-half-year experience with the point system.

From January 1, 1986 to July 30, 1988, 530 consecutive cadaver kidney transplantations were performed with patient selection by a point system that took into account time awaiting an organ, donor-recipient matching, degree of presensitization, and some less important factors. The effect of the system was to diminish judgmental factors in case selection which in the past, had probably operated to the disadvantage of "undesirable" potential recipients, including older ones. Primary 1-year graft survival (74%) and graft survival after retransplantation (71%) were lower than in the earlier time. However, the results with triple-drug therapy using CsA, AZA and P demonstrated 88% 1-year graft survival for primary graft recipients and 74% in highly sensitized patients, with comparable patient mortality. These latter observations provide some assurance that the concepts of equitable access and efficient utilization of a scarce resource are not mutually exclusive

Heat Transfer in Surface-Cooled Objects Subject to Microwave Heating

Several investigators in microwave bioeffects research have exposed biological preparations to intense microwave fields, while at the same time cooling the sample with flowing water. We examine the heat transfer characteristics of this situation, to estimate the maximum temperature increase and thermal time constants that might be encountered in such an experiment. The sample is modeled as a uniform sphere, cylinder, or slab subject to uniform heating, which is located in an unbounded coolant flow. The heat transfer is determined by the Biot and Reynolds numbers (which reflect the geometry, fluid flow, and material thermal properties of the system) the temperature rise is governed by the heat conduction equation coupled with external convection. The results are expressed in terms of nondimensional quantities, from which the thermal response of a heated object of arbitrary size can be determined. At low coolant flow rates, the maximum temperature rise can be biologically significant, even for relatively small objects (of millimeter radius) exposed to moderate levels of microwave energy (with a SAR of ca. 100 mW/g). The results are valid also where the coolant is a gas or a liquid different from water, the only restriction being on the Reynolds number of the flow