Patient Retention in Antiretroviral Therapy Programs in Sub-Saharan Africa: A Systematic Review

Paper published in PLoS Medicine in 2007.

Meanings of the Sabbath for Worship in the Seventh-Day Adventist Church

This study investigates the meanings and significance of the seventh-day Sabbath for worship in the Seventh-day Adventist Church. In recent years, both the day and concept of Sabbath have attracted ecumenical attention, but the focus of scholarship has been placed on Sunday as the Lord's Day or Sabbath with little consideration given to the seventh-day Sabbath. In contrast, this project examines the seventh-day Sabbath and worship on that day from theological, liturgical, biblical and historical perspectives. Although not intended as an apology for Seventh-day Adventist practices, the work does strive to promote a critical and creative conversation with other theological and liturgical traditions in order to promote mutual, ecumenical understanding. Historical research into the origins and nature of the principal day for weekly Christian worship provides a starting point for discussion on Sabbath. Reconsideration of the relationship between Judaism and early Christianity in recent studies suggests that the influence of Judaism lasted longer than previously supposed, thereby prolonging the developmental process of Sabbath (seventh day) to Sunday. A possible coexistence of Sabbath and Sunday in early Christianity offers an alternative to perspectives that dichotomize Sabbath and Sunday from Christian antiquity onward, and thus for the Seventh-day Adventist Church, suggests biblical and historical validity for their Sabbath worship practice. Recent theological perspectives on Sabbath and Sunday are examined, particularly those of Karl Barth, Jürgen Moltmann and Pope John Paul II. While all three of these theologians stress the continuity of Sabbath and Sunday and speak mainly to a theology of Sunday, they do highlight the significance of Sabbath—which is relevant to an interpretation of seventh-day Sabbath worship. The study concludes that the seventh-day Sabbath is significant for worship in the Seventh-day Adventist Church because it symbolizes the relationship between God and human beings, reminds humanity of the creating and redeeming God who acts in history, and invites persons to rest and fellowship with God on a day sanctified by God.

The Gospel Worship Service Presents Unique Challenges for Chaplains: A Primer on Leading a Gospel Service in the Air Force

This project examines the challenges military chaplains face when leading Gospel services in the United States Air Force in both domestic and deployed locations. It argues that some chaplains assigned to Gospel services do not have the ministry skills set to lead them effectively. Through quantitative and qualitative research methods involving surveys of 30 military chaplains, lay leaders and parishioners, and follow-up interviews to explore critical issues identified by leaders and congregants alike, this project develops a Gospel service manual. This instructional primer outlines the historical evolution of the Gospel service and addresses its integral elements of worship and challenges that chaplains need to understand to meet the worship needs of multicultural and ecumenical military congregations.

OS Support for Portable Bulk Synchronous Parallel Programs

Predictability -- the ability to foretell that an implementation will not violate a set of specified reliability and timeliness requirements -- is a crucial, highly desirable property of responsive embedded systems. This paper overviews a development methodology for responsive systems, which enhances predictability by eliminating potential hazards resulting from physically-unsound specifications. The backbone of our methodology is the Time-constrained Reactive Automaton (TRA) formalism, which adopts a fundamental notion of space and time that restricts expressiveness in a way that allows the specification of only reactive, spontaneous, and causal computation. Using the TRA model, unrealistic systems – possessing properties such as clairvoyance, caprice, infinite capacity, or perfect timing -- cannot even be specified. We argue that this "ounce of prevention" at the specification level is likely to spare a lot of time and energy in the development cycle of responsive systems -- not to mention the elimination of potential hazards that would have gone, otherwise, unnoticed. The TRA model is presented to system developers through the Cleopatra programming language. Cleopatra features a C-like imperative syntax for the description of computation, which makes it easier to incorporate in applications already using C. It is event-driven, and thus appropriate for embedded process control applications. It is object-oriented and compositional, thus advocating modularity and reusability. Cleopatra is semantically sound; its objects can be transformed, mechanically and unambiguously, into formal TRA automata for verification purposes, which can be pursued using model-checking or theorem proving techniques. Since 1989, an ancestor of Cleopatra has been in use as a specification and simulation language for embedded time-critical robotic processes.

Hidden Type Variables and Conditional Extension for More Expressive Generic Programs

Generic object-oriented programming languages combine parametric polymorphism and nominal subtype polymorphism, thereby providing better data abstraction, greater code reuse, and fewer run-time errors. However, most generic object-oriented languages provide a straightforward combination of the two kinds of polymorphism, which prevents the expression of advanced type relationships. Furthermore, most generic object-oriented languages have a type-erasure semantics: instantiations of type parameters are not available at run time, and thus may not be used by type-dependent operations. This dissertation shows that two features, which allow the expression of many advanced type relationships, can be added to a generic object-oriented programming language without type erasure: 1. type variables that are not parameters of the class that declares them, and 2. extension that is dependent on the satisfiability of one or more constraints. We refer to the first feature as hidden type variables and the second feature as conditional extension. Hidden type variables allow: covariance and contravariance without variance annotations or special type arguments such as wildcards; a single type to extend, and inherit methods from, infinitely many instantiations of another type; a limited capacity to augment the set of superclasses after that class is defined; and the omission of redundant type arguments. Conditional extension allows the properties of a collection type to be dependent on the properties of its element type. This dissertation describes the semantics and implementation of hidden type variables and conditional extension. A sound type system is presented. In addition, a sound and terminating type checking algorithm is presented. Although designed for the Fortress programming language, hidden type variables and conditional extension can be incorporated into other generic object-oriented languages. Many of the same problems would arise, and solutions analogous to those we present would apply.