49,314 research outputs found
Bounds on Worst-Case Responsiveness for Agreement Algorithms
No full textWe study the worst-case time complexity of solving two agreement problems, consensus and broadcast, in systems with n processes subject to no more than t process failures. In both problems, correct processes must decide on a common value; in the consensus problem, each process has an input and if the inputs of correct processes are all the same, then that must be the common decision, whereas in the broadcast problem, only one process (the sender) has an input and if the sender is correct, then its input must be the common decision. We focus on systems where there is an upper bound Δ on the message delivery time but it is expected that typically, messages arrive much faster, say within some time d. While Δ may or may not be known in advance, d is inherently unknown and specific to each execution. The goal is to design deterministic algorithms whose running times have minimal to no dependence on Δ, a property called responsiveness.
We present a generic algorithm transformation that, when applied to appropriate eventually-synchronous consensus (or broadcast) algorithms, results in consensus (or broadcast) algorithms for send omission failures, authenticated Byzantine failures, and unauthenticated Byzantine failures whose running times have no dependence on Δ; their worst-case time complexities are all O(td), which is asymptotically optimal. The algorithm for send omission failures requires n > 2t, while those for Byzantine failures, both authenticated and unauthenticated, require n > 3t. The failure-resilience of the unauthenticated Byzantine algorithm is optimal.
For authenticated Byzantine failures, existing agreement algorithms provide worst-case time complexity O(t Δ) when n is at most 3t. (When n ≤ 2t, broadcast is solvable while consensus is not.) We prove a lower bound on the worst-case time complexity of ⌊(3t-n)/2⌋ d + Δ when n is at most 3t. Although lower bounds of Δ and (t+1)d were already known, our new lower bound indicates that, at least when n ≤ 2t, it is impossible for an algorithm to pay these bounds in parallel
Sulfur reduction and oxidation processes, from wetland scale to micro scale, in an inland acid sulfate soil of the lower Murray-Darling River floodplains, Australia
No full textAlso published as: Geological Survey of Finland, 2012; Guide 56:110-112Wallace, L., McPhail, D.C., Fitzpatrick, R.W., Welch, S., Kirste, D., Beavis, S. & Lamontagne, S.http://projects.gtk.fi/7iassc/conference/programme/presentation.htm
Gender and export behaviour: Evidence from women-owned enterprises
No full textThe original publication can be found at www.springerlink.comThis article draws on the results of a qualitative, exploratory study of 20 Australian women business owners to demonstrate how using a ‹gender as social identity’ lens provides new insights into the influence of gender on exporting and entrepreneurial behaviour. Interview data reveal perceptions of gender identity and gender relations varied and influenced the interpretations which women business owners placed on their exporting activities. Women in the study used different terms to describe exporter and entrepreneurial characteristics to those found in extant literature. A strong theme was exporting as a life-changing experience that allowed the women to grow personally as well as grow the business and succeed as exporters.Catherine L. Welch, Denice E. Welch and Lisa Hewerdin
Life of occam-Pi
No full textThis paper considers some questions prompted by a brief review of the history of computing. Why is programming so hard? Why is concurrency considered an “advanced” subject? What’s the matter with Objects? Where did all the Maths go? In searching for answers, the paper looks at some concerns over fundamental ideas within object orientation (as represented by modern programming languages), before focussing on the concurrency model of communicating processes and its particular expression in the occam family of languages. In that focus, it looks at the history of occam, its underlying philosophy (Ockham’s Razor), its semantic foundation on Hoare’s CSP, its principles of process oriented design and its development over almost three decades into occam-? (which blends in the concurrency dynamics of Milner’s ?-calculus). Also presented will be an urgent need for rationalisation – occam-? is an experiment that has demonstrated significant results, but now needs time to be spent on careful review and implementing the conclusions of that review. Finally, the future is considered. In particular, is there a future
Measurement of the branching fractions for B--> D(*)+pi(-)l(-)(nu)over-bar(l) and (B)over-bar(0)-> D-(*)0 pi(+)l(-)(nu)over-bar(l)
No full textWe report on a measurement of the branching fractions for B- --> D(*)+ pi(-)l(-)(nu) over bar (l) and (B) over bar (0) --> D-(*)0 pi(+)l(-)(nu) over bar (l) with 275 x 10(6) B (B) over bar events collected at the Y(4S) resonance with the Belle detector at KEKB. Events are tagged by fully reconstructing one of the B mesons in hadronic modes. We obtain B(B- --> D(+)pi(-)l(-)(nu) over bar (l)) = (0.54 +/- 0.07 (stat) +/- 0.07(syst) +/- 0.06(BR)) x 10(-2), B(B- --> D*+pi(-) l(-) (nu) over bar (l)) (0.67 +/- 0.11 (stat) +/- 0.09(syst) +/- 0.03(BR)) x 10(-2), B((B) over bar (0) --> D(0)pi(+)l(-) (nu) over bar (l)) = (0.33 +/- 0.06(stat) +/- 0.06(syst) +/- 0.03(BR)) x 10(-2), B((B) over bar (0) -->D(*0)pi(+)l(-)(nu) over bar (l)) = (0.65 +/- 0.12(stat) +/- 0.08(syst) +/- 0.05(BR)) x 10(-2), where the third error comes from the error on (B) over bar --> D((*))l(-)(nu) over bar (l) decays. Contributions from B-0 --> D(*+)l(-)(nu) over bar (l) decays are excluded in the measurement of (B) over bar (0) --> D(0)pi(+)l-(nu) over bar (l).Astronomy & AstrophysicsPhysics, Particles & FieldsSCI(E)0ARTICLE5null7
Vitamin D deficiency in slipped upper femoral epiphysis: time to physeal fusion
No full textBackground: slipped upper femoral epiphysis (SUFE) has an incidence of 1-7 per 100,000 adolescents in the UK and its link with obesity well established. With a rising number of paediatric orthopaedic patients presenting with vitamin D deficiency, the aim of our study was to establish the prevalence of vitamin D deficiency in SUFE patients presenting to an orthopaedic department in the UK and whether a low vitamin D level increases the time to proximal femoral physeal fusion, post-surgical fixation.Methods: a total of 27 paediatric patients, with a female to male ratio of 17:10 and a mean age of 11.5 years (SD 1.99), range 8 to 16 years, presented with a SUFE and had their vitamin D level assessed during the study period, June 2007 to July 2012 (inclusive). The majority of these patients (85.2%) were assessed as vitamin D deficient, with a serum 25-(OH)D <52 nmols/L . The time taken for >50% physeal fusion on anteroposterior radiography post-surgical fixation quoted in the literature is 9.6 months with no reported vitamin D deficiency or insufficiency. Results: in our study the median time to physeal fusion in the vitamin D deficient and insufficient patients was 25 months, interquartile range 17-43 (mean of 29 months, SD 16.8). A negative correlation was also observed between vitamin D level and the time taken for physeal fusion following surgical fixation.Conclusion: we conclude that a high prevalence of vitamin D deficiency has been observed in our SUFE patients. Comparing the time taken for physeal closure as 9.6 months in the literature with vitamin D deficient patients, this is prolonged. Indeed a negative correlation between vitamin D level and time to physeal fusion has been demonstrated. This study highlights the need for regular vitamin D status assessment in SUFE patients in order to allow early implementation of treatment with vitamin D supplementation. The impact of vitamin D screening and supplementation on SUFE outcomes should be investigated further.<br/
Immunotherapy
No full textA chapter covering metastasis immunotherapy in multi-author volume devoted to all aspects of cancer metastasis
Thigh muscle and subcutaneous tissue thickness measured using ultrasound imaging in older females living in extended care: a preliminary study
No full textAssociations between muscle strength and physical function in older females in extended care homes: a preliminary study
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