Fault recovery in the reliable multicast protocol

The Reliable Multicast Protocol (RMP) provides a unique, group-based model for distributed programs that need to handle reconfiguration events at the application layer. This model, called membership views, provides an abstraction in which events such as site failures, network partitions, and normal join-leave events are viewed as group reformations. RMP provides access to this model through an application programming interface (API) that notifies an application when a group is reformed as the result of a some event. RMP provides applications with reliable delivery of messages using an underlying IP Multicast (12, 5) media to other group members in a distributed environment even in the case of reformations. A distributed application can use various Quality of Service (QoS) levels provided by RMP to tolerate group reformations. This paper explores the implementation details of the mechanisms in RMP that provide distributed applications with membership view information and fault recovery capabilities

Reliable multicast protocol specifications flow control and NACK policy

This appendix presents the flow and congestion control schemes recommended for RMP and a NACK policy based on the whiteboard tool. Because RMP uses a primarily NACK based error detection scheme, there is no direct feedback path through which receivers can signal losses through low buffer space or congestion. Reliable multicast protocols also suffer from the fact that throughput for a multicast group must be divided among the members of the group. This division is usually very dynamic in nature and therefore does not lend itself well to a priori determination. These facts have led the flow and congestion control schemes of RMP to be made completely orthogonal to the protocol specification. This allows several differing schemes to be used in different environments to produce the best results. As a default, a modified sliding window scheme based on previous algorithms are suggested and described below

Chirality in Bare and Passivated Gold Nanoclusters

Chiral structures have been found as the lowest-energy isomers of bare (Au$_{28}$ and Au$_{55}) and thiol-passivated (Au$_{28}(SCH$_{3})$_{16}$and Au$_{38}(SCH_{3})_{24}) gold nanoclusters. The degree of chirality existing in the chiral clusters was calculated using the Hausdorff chirality measure. We found that the index of chirality is higher in the passivated clusters and decreases with the cluster size. These results are consistent with the observed chiroptical activity recently reported for glutahione-passivated gold nanoclusters, and provide theoretical support for the existence of chirality in these novel compounds.Comment: 5 pages, 1 figure. Submitted to PR

Prevalence and predictors of HIV-related stigma among institutional- and community-based caregivers of orphans and vulnerable children living in five less-wealthy countries

<p>Abstract</p> <p>Background</p> <p>In the face of the HIV/AIDS epidemic that has contributed to the dramatic increase in orphans and abandoned children (OAC) worldwide, caregiver attitudes about HIV, and HIV-related stigma, are two attributes that may affect caregiving. Little research has considered the relationship between caregiver attributes and caregiver-reported HIV-related stigma. In light of the paucity of this literature, this paper will describe HIV-related stigma among caregivers of OAC in five less wealthy nations.</p> <p>Methods</p> <p>Baseline data were collected between May 2006 through February 2008. The sample included 1,480 community-based and 192 institution-based caregivers. Characteristics of the community-based and institution-based caregivers are described using means and standard deviations for continuous variables or counts and percentages for categorical variables. We fit logistic regression models, both for the full sample and separately for community-based and institution-based caregivers, to explore predictors of acceptance of HIV.</p> <p>Results</p> <p>Approximately 80% of both community-based and institution-based caregivers were female; and 84% of institution-based caregivers, compared to 66% of community-based caregivers, said that they would be willing to care for a relative with HIV. Similar proportions were reported when caregivers were asked if they were willing to let their child play with an HIV-infected child. In a multivariable model predicting willingness to care for an HIV-infected relative, adjusted for site fixed effects, being an institution-based caregiver was associated with greater willingness (less stigma) than community-based caregivers. Decreased willingness was reported by older respondents, while willingness increased with greater formal education. In the adjusted models predicting willingness to allow one's child to play with an HIV-infected child, female gender and older age was associated with less willingness. However, willingness was positively associated with years of formal education.</p> <p>Conclusions</p> <p>The caregiver-child relationship is central to a child's development. OAC already face stigma as a result of their orphaned or abandoned status; the addition of HIV-related stigma represents a double burden for these children. Further research on the prevalence of HIV-related acceptance and stigma among caregivers and implications of such stigma for child development will be critical as the policy community responds to the global HIV/AIDS orphan crisis.</p

Developing theory and practice: Creation of a Community of Practice through Action Research produced excellence in stroke care

The study was funded by a grant from the Special Trustees of the Trust. Copyright @ 2010 Informa UK, Ltd.This article has been made available through the Brunel Open Access Publishing Fund.This article has been made available through the Brunel Open Access Publishing Fund.Much emphasis is placed on expert knowledge like evidence-based stroke guidelines, with insufficient attention paid to processes required to translate this into delivery of everyday good care. This paper highlights the worth of creating a Community of Practice (CoP) as a means to achieve this. Drawing on findings from a study conducted in 2000/2002 of processes involved in establishing a nationally lauded high quality Stroke Unit, it demonstrates how successful development of a new service was linked to creation of a CoP. Recent literature suggests CoPs have a key in implementing evidence-based practice; this study supports this claim whilst revealing for the first time the practical knowledge and skills required to develop this style of working. Findings indicate that participatory and democratic characteristics of Action Research are congruent with the collaborative approach required for developing a CoP. The study is an exemplar of how practitioner researchers can capture learning from changing practice, thus contributing to evidence-based healthcare with theoretical and practical knowledge. Findings are relevant to those developing stroke services globally but also to those interested in evidencebased practice.This article is available through the Brunel Open Access Publishing Fund

Large‐scale calculations of excitation energies in coupled cluster theory : The singlet excited states of benzene

Algorithms for calculating singlet excitation energies in the coupled cluster singles and doubles (CCSD) model are discussed and an implementation of an atomic‐integral direct algorithm is presented. Each excitation energy is calculated at a cost comparable to that of the CCSD ground‐state energy. Singlet excitation energies are calculated for benzene using up to 432 basis functions. Basis‐set effects of the order of 0.2 eV are observed when the basis is increased from augmented polarized valence double‐zeta (aug‐cc‐pVDZ) to augmented polarized valence triple‐zeta (aug‐cc‐pVTZ) quality. The correlation problem is examined by performing calculations in the hierarchy of coupled cluster models CCS, CC2, CCSD, and CC3, as well as by using the CCSDR(3) perturbative triples corrections. The effect of triple excitations are less than 0.2 eV for all excitations except for the 2 1E2g state. The calculated excitation energies are compared with experiment and other theoretical [email protected]

Beyond belief: Strategic taboos and organizational identity in strategic agenda setting

A comprehensive strategic agenda matters for fundamental strategic change. Our study seeks to explore and theorize how organizational identity beliefs influence the judgment of strategic actors when setting an organization’s strategic agenda. We offer the notion of “strategic taboo” as those strategic options initially disqualified and deemed inconsistent with the organizational identity beliefs of strategic actors. Our study is concerned with how strategic actors confront strategic taboos in the process of setting an organization’s strategic agenda. Based on a revelatory inductive case study, we find that strategic actors engage in assessing the concordance of the strategic taboos with organizational identity beliefs and, more specifically, that they focus on key identity elements (philosophy; priorities; practices) when doing so. We develop a typology of three reinterpretation practices that are each concerned with a key identity element. While contextualizing assesses the potential concordance of a strategic taboo with an organization’s overall philosophy and purpose, instrumentalizing assesses such concordance with respect to what actors deem an organization’s priorities to be. Finally, normalizing explores concordance with respect to compatibility and fit with the organization’s practices. We suggest that assessing concordance of a strategic taboo with identity elements consists in reinterpreting collective identity beliefs in ways that make them consistent with what organizational actors deem the right course of action. This article discusses the implications for theory and research on strategic agenda setting, strategic change, a practice-based perspective on strategy, and on organizational identity. © The Author(s) 2014

Ab initio calculations for bromine adlayers on the Ag(100) and Au(100) surfaces: the c(2x2) structure

Ab initio total-energy density-functional methods with supercell models have been employed to calculate the c(2x2) structure of the Br-adsorbed Ag(100) and Au(100) surfaces. The atomic geometries of the surfaces and the preferred bonding sites of the bromine have been determined. The bonding character of bromine with the substrates has also been studied by analyzing the electronic density of states and the charge transfer. The calculations show that while the four-fold hollow-site configuration is more stable than the two-fold bridge-site topology on the Ag(100) surface, bromine prefers the bridge site on the Au(100) surface. The one-fold on-top configuration is the least stable configuration on both surfaces. It is also observed that the second layer of the Ag substrate undergoes a small buckling as a consequence of the adsorption of Br. Our results provide a theoretical explanation for the experimental observations that the adsorption of bromine on the Ag(100) and Au(100) surfaces results in different bonding configurations.Comment: 10 pages, 4 figure, 5 tables, Phys. Rev. B, in pres

Negative incentive steering in a policy network

In this article the process of developing a policy for the recent comprehensive retrenchment operation in the Dutch university system is analysed from a theoretical point of view on decisionmaking. The article especially addresses the question whether some empirical evidence can be found for the rationalist view of collective decision-making, which states that a process of social communication should eventually lead to a unanimous and rational consensus concerning the selection of the optimal policy.\ud \ud The actual analysis concerns the way a retrenchment policy has been developed in a process of social communication between the most important actors: the Minister of Education and Science and the thirteen Dutch universities. It is assumed that the various communicative linkages between these actors can be interpreted as a policy network in which both governmental and non-governmental actors operate.\ud \ud The article concludes that in the Dutch university policy-network a complicated balance of interdependencies exists and that several sub-networks can be distinguished. It is also concluded that the Minister, while recognizing the interdependencies in the network, was able to use a special kind of (negative) incentive, inducing the universities to act as he wished.\ud \ud This negative incentive steering, however, also persuaded the universities to go to the utmost in their consultation efforts, thus trying to reach the rationalist ideal of collective decision-making. The final conclusion therefore is that the rationalist view of collective decision-making does not appear to be unrealistic. The article ends with a warning against a common mistake made regarding the normative appearance of the rationalist perspective