Low temperature age hardening in U-13 at.% Nb: An assessment of chemical redistribution mechanisms

Low temperature aging (<350 °C) of U-13 at.% Nb martensite results in increased strength levels accompanied by significant ductility loss. To determine the decomposition mechanism(s) responsible for these mechanical property changes, atom probe tomography was used to examine the niobium and impurity distributions after aging at 200 or 300 °C for times ranging from 2 h to 70 days. No patterns of niobium or impurity atoms were observed that would indicate segregation to the martensitic twin interfaces, making this hardening mechanism unlikely. Phase separation into roughly equiaxed regions of high and low niobium concentration was clearly observed after aging at 300 °C for 70 days. However, only subtle niobium concentration changes were observed after aging at 200 °C relative to the as-quenched condition, indicating that conventional phase separation is an unlikely explanation for the dramatic mechanical property changes at 200 °C. Therefore, consideration of aging mechanisms other than segregation and phase separation may be warranted.     

STABILITY OF RESINS IN PELLETISED HOPS

The α-acids content and Lead Conductance Value of hop pellets, manufactured from seedless Pride of Ringwood hops grown in Australia and stored at 5°C, 20°C or 30°C, were monitored over a twelve month storage period. No decrease in α-acids content occurred during storage at 5°C, whereas at 20°C the decrease (ca. 7%) was approximately one-third that experienced for baled hops of the same variety. At both 5°C and 20°C the Lead Conductance Value decreased at approximately one-third the rate of that in baled hops. During twelve months storage at 30°C the α-acids content of the hop pellets decreased by approximately 40% and the Lead Conductance Value by 30%. The hop pellets stored at 20°C and 30°C developed rancid odours during the twelve months storage period.     

Output feedback eigenstructure assignment using a new reduced orthogonality condition

This paper presents a new method of output feedback eigenstructure assignment. A new, reduced orthogonality condition is derived which is less restrictive on the design degrees of freedom than others in the literature. From this a novel, general formulation for the gain matrix is admitted which utilizes a two stage design process. In the first stage, a subset of desired eigenvectors is assigned, either left or right. In the second stage, a dual set is assigned which adheres to the necessary and sufficient conditions for output feedback eigenstructure assignment proved earlier in the paper. A numerical example is presented to illustrate the whole procedure.     

Effective components of TORDIA cognitive–behavioral therapy for adolescent depression: Preliminary findings.

In this report, we conducted a secondary analysis of the Treatment of SSRI-Resistant Depression in Adolescents (TORDIA) study to explore the impact of specific cognitive–behavioral therapy (CBT) treatment components on outcome. In TORDIA, 334 youths (ages 12 to 18 years) with major depressive disorder who had failed to respond to an adequate course of selective serotonin reuptake inhibitor (SSRI) medication were randomized to a medication switch (either to an alternative SSRI or venlafaxine) with or without 12 weeks of adjunctive CBT. Participants who had more than 9 CBT sessions were 2.5 times more likely to have adequate treatment response than those who had 9 or fewer sessions. CBT participants who received problem-solving and social skills treatment components, controlling for number of sessions and other confounding variables, were 2.3 and 2.6 times, respectively, more likely to have a positive response. These preliminary findings underscore the importance of receiving an adequate number of sessions to attain an adequate clinical response. Finally, social skills and problem solving may be active elements in CBT for adolescent depression and should be considered in treatment by those working with seriously depressed youths. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The History of ICRP and the Evolution of its Policies

Within 12 months of the discovery of X rays in 1895, papers appeared in the literature reporting adverse effects from high exposure. In 1925, the first International Congress of Radiology, held in London, considered the need for a protection committee, which it established at its second congress in Stockholm in 1928. This paper celebrates the 80^th anniversary of ICRP by tracing the history of the development of its policies, and identifying a few of the personalities involved from its inception up to the modern era. The paper follows the progress from the early controls on worker doses to avoid deterministic effects, through the identification of stochastic effects, to the concerns about public exposure and increasing stochastic risk estimates. The key features of the recommendations made by ICRP from 1928 up to the most recent in 2007 are identified.     

Forum A historical context for theories underpinning the production of the built environment

The quest for ‘theory’ in the Building Research & Information special issue ‘Developing Theories of the Built Environment’ (36(3) 2008) needs to be understood within a larger historical and political context. It would benefit from engaging with a rich vein of work on the production of the built environment over the last 30 years. Theory inherently develops in the political context in which it exists; if it fails to do so, it may be dangerous. This commentary traces the intellectual underpinning concerned with understanding the process of change in the built environment, particularly the result of changes in social relations and the social labour process. The production of the built environment is seen as encompassing all the social processes concerned with producing the built environment, built products, buildings and infrastructure, and out of natural resources, whilst consumption is applied to all the processes involved in consuming these, including the well-being of tenants. And between these are situated the processes of exchange, distribution, and circulation, involving complex webs of relations between developers, builders, and landlords and landowners. The challenge is not only to engage and learn from past work, but also to state explicitly what is currently driving the need for a theory (or set of theories).

La quête de la « théorie » dans ce numéro spécial de Building Research & Information consacré aux théories du développement du milieu bâti (volume 36(3), 2008) doit être comprise dans un contexte historique et politique plus large. Elle aurait intérêt à s'appuyer sur les nombreux travaux concernant la production du cadre bâti publiés au cours de ces 30 dernières années. La théorie se développe, de manière inhérente, dans le contexte politique dans lequel elle existe; dans le cas contraire, la situation pourrait devenir dangereuse. Cet article analyse le raisonnement intellectuel sous-jacent concernant la compréhension du processus de changement dans le milieu bâti, notamment les conséquences des changements dans les relations sociales et dans le processus social du travail. La production du cadre bâti est considérée comme englobant tous les processus sociaux liés à la production du cadre bâti, des produits de construction, des bâtiments et des infrastructures et aux ressources naturelles alors que la consommation s'applique à tous les processus qui entrent en jeu dans la consommation de ceux-ci, y compris le bien-être des occupants. Entre ces deux notions, on trouve les processus d'échange, de distribution et de circulation qui font intervenir des réseaux de relations entre promoteurs, constructeurs, bailleurs et propriétaires fonciers. La difficulté ne vient pas seulement du fait qu'il faut tirer profit des travaux et de l'expérience passés mais qu'il faut également expliquer ce qui motive aujourd'hui la nécessité d'une théorie (ou d'un ensemble de théories).

Mots clés: cadre bâti, cadres conceptuels, consommation, processus de travail, cadre politique, production, relations sociales     

Concurrent software verification with states, events, and deadlocks

We present a framework for model checking concurrent software systems which incorporates both states and events. Contrary to other state/event approaches, our work also integrates two powerful verification techniques, counterexample-guided abstraction refinement and compositional reasoning. Our specification language is a state/event extension of linear temporal logic, and allows us to express many properties of software in a concise and intuitive manner. We show how standard automata-theoretic LTL model checking algorithms can be ported to our framework at no extra cost, enabling us to directly benefit from the large body of research on efficient LTL verification. We also present an algorithm to detect deadlocks in concurrent message-passing programs. Deadlock- freedom is not only an important and desirable property in its own right, but is also a prerequisite for the soundness of our model checking algorithm. Even though deadlock is inherently non-compositional and is not preserved by classical abstractions, our iterative algorithm employs both (non-standard) abstractions and compositional reasoning to alleviate the state-space explosion problem. The resulting framework differs in key respects from other instances of the counterexample-guided abstraction refinement paradigm found in the literature. We have implemented this work in the magic verification tool for concurrent C programs and performed tests on a broad set of benchmarks. Our experiments show that this new approach not only eases the writing of specifications, but also yields important gains both in space and in time during verification. In certain cases, we even encountered specifications that could not be verified using traditional pure event-based or state-based approaches, but became tractable within our state/event framework. We also recorded substantial reductions in time and memory consumption when performing deadlock-freedom checks with our new abstractions. Finally, we report two bugs (including a deadlock) in the source code of Micro-C/OS versions 2.0 and 2.7, which we discovered during our experiments. This research was sponsored by the National Science Foundation (NSF) under grants no. CCR-9803774 and CCR-0121547, the Office of Naval Research (ONR) and the Naval Research Laboratory (NRL) under contract no. N00014-01-1-0796, the Army Research Office (ARO) under contract no. DAAD19-01-1-0485, and was conducted as part of the Predictable Assembly from Certifiable Components (PACC) project at the Software Engineering Institute (SEI). This article combines and builds upon the papers (CCO⁺04) and (CCOS04). Received December 2004 Revised July 2005 Accepted July 2005 by Eerke A. Boiten, John Derrick, Graeme Smith and Ian Hayes     

Testing and evaluating virus detectors for handheld devices

The widespread use of personal digital assistants and smartphones gives securing these devices a high priority. Yet little attention has been placed on protecting handheld devices against viruses. Currently available antivirus software for handhelds is few in number. At this stage, the opportunity exists for the evaluation and improvement of current solutions. By pinpointing weaknesses in the current antivirus software, improvements can be made to properly protect these devices from a future tidal wave of viruses. This research evaluates four currently available antivirus solutions for handheld devices. A formal model of virus transformation that provides transformation traceability is presented. Two sets of ten tests each were administered; nine tests from each set involved the modification of source code of two known viruses for handheld devices. The testing techniques used are well established in PC testing; thus the focus of this research is solely on handheld devices. Statistical analysis of the test results show high false negative production rates for the antivirus software and an overall false negative production rate of 47.5% with a 95% confidence interval between 36.6% and 58.4%. This high rate shows that current solutions poorly identify modified versions of a virus. The virus is left undetected and capable of spreading, infecting and causing damage.     

A method of limited replication for the efficient in vivo delivery of adenovirus to cancer cells

Replication-deficient viral vectors are currently being used in gene transfer strategies to treat cancer cells. Unfortunately, viruses are limited in their ability to diffuse through tissue. This makes it virtually impossible to infect the majority of tumor cells in vivo and results in inadequate gene transfer. This problem can be addressed by allowing limited viral replication. Limited viral replication facilitates greater penetration of virions into tissue and can improve gene transfer. We have developed a strategy of limited viral replication using AdRSVlaclys, a chemically modified E1-deleted adenovirus, to codeliver an exogenous plasmid encoding the adenovirus E1 region. This system allows one round of viral replication. We examined the effect of this limited adenovirus replication in vitro and in vivo. In culture, codelivery of virus and pE1 resulted in a large increase in infected cells when compared with control cells exposed to virus and pUC19. In experiments on nude mice bearing HeLa ascites tumors, intraperitoneal injection of AdRSVlaclys/pE1 resulted in a significantly higher percentage of infected HeLa cells as compared with the PBS controls (p < 0.05) or the AdRSVlaclys/pUC19 controls (p < 0.01). These data demonstrate that the transcomplementation of replication-deficient adenovirus with exogenous E1 DNA leads to limited replication, and this controlled replication enhances gene transfer efficiency of adenovirus in vivo.