Taurek, numbers and probabilities

In his paper, “Should the Numbers Count?" John Taurek imagines that we are in a position such that we can either save a group of five people, or we can save one individual, David. We cannot save David and the five. This is because they each require a life-saving drug. However, David needs all of the drug if he is to survive, while the other five need only a fifth each.Typically, people have argued as if there was a choice to be made: either numbers matter, in which case we should save the greater number, or numbers don't matter, but rather there is moral value in giving each person an equal chance of survival, and therefore we should toss a coin. My claim is that we do not have to make a choice in this way. Rather, numbers do matter, but it doesn't follow that we should always save the greater number. And likewise, there is moral value in giving each person an equal chance of survival, but it doesn't follow that we should always toss a coin.In addition, I argue that a similar approach can be applied to situations in which we can save one person or another, but the chances of success are different

Hosting Byzantine Fault Tolerant Services on a Chord Ring

In this paper we demonstrate how stateful Byzantine Fault Tolerant services may be hosted on a Chord ring. The strategy presented is fourfold: firstly a replication scheme that dissociates the maintenance of replicated service state from ring recovery is developed. Secondly, clients of the ring based services are made replication aware. Thirdly, a consensus protocol is introduced that supports the serialization of updates. Finally Byzantine fault tolerant replication protocols are developed that ensure the integrity of service data hosted on the ring.Comment: Submitted to DSN 2007 Workshop on Architecting Dependable System

A Peer-to-Peer Middleware Framework for Resilient Persistent Programming

The persistent programming systems of the 1980s offered a programming model that integrated computation and long-term storage. In these systems, reliable applications could be engineered without requiring the programmer to write translation code to manage the transfer of data to and from non-volatile storage. More importantly, it simplified the programmer's conceptual model of an application, and avoided the many coherency problems that result from multiple cached copies of the same information. Although technically innovative, persistent languages were not widely adopted, perhaps due in part to their closed-world model. Each persistent store was located on a single host, and there were no flexible mechanisms for communication or transfer of data between separate stores. Here we re-open the work on persistence and combine it with modern peer-to-peer techniques in order to provide support for orthogonal persistence in resilient and potentially long-running distributed applications. Our vision is of an infrastructure within which an application can be developed and distributed with minimal modification, whereupon the application becomes resilient to certain failure modes. If a node, or the connection to it, fails during execution of the application, the objects are re-instantiated from distributed replicas, without their reference holders being aware of the failure. Furthermore, we believe that this can be achieved within a spectrum of application programmer intervention, ranging from minimal to totally prescriptive, as desired. The same mechanisms encompass an orthogonally persistent programming model. We outline our approach to implementing this vision, and describe current progress.Comment: Submitted to EuroSys 200

Promoting Component Reuse by Separating Transmission Policy from Implementation

In this paper we present a methodology and set of tools which assist the construction of applications from components, by separating the issues of transmission policy from component definition and implementation. This promotes a greater degree of software reuse than is possible using traditional middleware environments. Whilst component technologies are usually presented as a mechanism for promoting reuse, reuse is often limited due to design choices that permeate component implementation. The programmer has no direct control over inter-address-space parameter passing semantics: it is fixed by the distributed application's structure, based on the remote accessibility of the components. Using traditional middleware tools and environments, the application designer may be forced to use an unnatural encoding of application level semantics since application parameter passing semantics are tightly coupled with the component deployment topology. This paper describes how inter-address-space parameter passing semantics may be decided independently of component implementation. Transmission policy may be dynamically defined on a per-class, per-method or per-parameter basis.Comment: Submitted to ICDCS 200

The Effect of PIN Reduction in Populus: The Search for the Missing Phenotype

The plant hormone auxin is involved in virtually every aspect of plant growth and development. Because of its vital role in plant physiology, it is transported through controlled mechanisms. The PIN family of efflux carrier proteins are highly involved in this transport, shuttling molecules of auxin from cell to cell. This PIN-driven transport of auxin guides the differentiation of plant vasculature. In this study, I used a clonally-propagated line of the woody plant species Populus tremula x alba that had been genetically altered to induce an RNAi response against genes coding for the PIN proteins. These plants were shown to have reduced auxin transport rates, however, there was no difference when compared to wild-type in the external phenotype. First, reduction of PIN gene expression was confirmed in this Populus line through qRT-PCR, having been reduced by nearly 80% in shoot apices and over 90% in developing xylem. But despite this reduction of auxin transport, there was still no observable phenotype. It was then considered that this phenotype may be revealed if auxin transport rates were altered in localized areas of a single plant. Thus, this line of Populus was then used in reciprocal grafting experiments, in which RNAi line plants and wild-type plants were used alternatively as either scions or rootstocks. This resulted in whole plants with localized areas of reduced auxin transport. qRT-PCR was conducted on the scion and rootstocks of these plants to confirm that the RNAi signal is not graft transmissible, PIN expression in the RNAi plant segments having been reduced by over 65%, regardless of position (scion or rootstock). The vascular anatomy was then analyzed above and below the graft site. Again, regardless of the position of the RNAi line plant segment, digital image analysis revealed negligible difference in vessel size and distribution within developing xylem. These results may speak to the efficiency of homeostatic auxin mechanisms, which may have regulated the alterations in auxin transport such that the phenotype remained consistent with wild-type

Humanizing the Dragon

Peer Choice Award Winne

Towards Adaptable and Adaptive Policy-Free Middleware

We believe that to fully support adaptive distributed applications, middleware must itself be adaptable, adaptive and policy-free. In this paper we present a new language-independent adaptable and adaptive policy framework suitable for integration in a wide variety of middleware systems. This framework facilitates the construction of adaptive distributed applications. The framework addresses adaptability through its ability to represent a wide range of specific middleware policies. Adaptiveness is supported by a rich contextual model, through which an application programmer may control precisely how policies should be selected for any particular interaction with the middleware. A contextual pattern mechanism facilitates the succinct expression of both coarse- and fine-grain policy contexts. Policies may be specified and altered dynamically, and may themselves take account of dynamic conditions. The framework contains no hard-wired policies; instead, all policies can be configured.Comment: Submitted to Dependable and Adaptive Distributed Systems Track, ACM SAC 200

THE INFLUENCE INCLUSIVE LITERATURE CIRCLES WITH MULTICULTURAL LITERATURE HAS ON THE SELF-EFFICACIES OF 4TH GRADE STUDENTS WITH DISABILITIES

This study seeks to determine what happens to fourth grade students with disabilities reading self-efficacies when they participate in inclusive literature circles with multicultural literature. The purpose of this teacher research was to investigate strategies to improve reading self-efficacies of students with disabilities, investigating what would happen if students with disabilities were placed heterogeneously with their peers while reading books with characters with disabilities and how that influenced their reading self-efficacies. Four students with a disability were integrated with their general education peers in their inclusive classroom to participate in literature circles for four weeks. The multicultural books were books that contained characters with disabilities. Baseline data from the Reader Self-Perception Scale (RSPS) was used to assess students\u27 self-perceptions in reading. When analyzing the data, the three major themes within the study are: (1) Students\u27 perceptions of disabilities and how they changed throughout the literature meetings; (2) Students made connections to the text through representation of their experiences; and (3) Students had an increased engagement and belief in their ability. The results suggest that over time, inclusive literature circles with multicultural texts can slightly improve the reading self-efficacies of students with disabilities

The Implications of ACE Science: A Call to Respond

In “The Implications of ACE Science: A Call to Respond,” Valerie Norcross employs a professional format for writing in the field of psychology. Her essay cites studies linking Adverse Childhood Experiences (ACEs) with higher mortality rates due to a range of causes. Norcross explains some of the scientific theories for why childhood traumas contribute to shorter life expectancies. She describes efforts to screen children for ACEs and interventions for diminishing the long-term detrimental health effects of ACEs