5,696 research outputs found
Quadratic Word Equations with Length Constraints, Counter Systems, and Presburger Arithmetic with Divisibility
Word equations are a crucial element in the theoretical foundation of
constraint solving over strings, which have received a lot of attention in
recent years. A word equation relates two words over string variables and
constants. Its solution amounts to a function mapping variables to constant
strings that equate the left and right hand sides of the equation. While the
problem of solving word equations is decidable, the decidability of the problem
of solving a word equation with a length constraint (i.e., a constraint
relating the lengths of words in the word equation) has remained a
long-standing open problem. In this paper, we focus on the subclass of
quadratic word equations, i.e., in which each variable occurs at most twice. We
first show that the length abstractions of solutions to quadratic word
equations are in general not Presburger-definable. We then describe a class of
counter systems with Presburger transition relations which capture the length
abstraction of a quadratic word equation with regular constraints. We provide
an encoding of the effect of a simple loop of the counter systems in the theory
of existential Presburger Arithmetic with divisibility (PAD). Since PAD is
decidable, we get a decision procedure for quadratic words equations with
length constraints for which the associated counter system is \emph{flat}
(i.e., all nodes belong to at most one cycle). We show a decidability result
(in fact, also an NP algorithm with a PAD oracle) for a recently proposed
NP-complete fragment of word equations called regular-oriented word equations,
together with length constraints. Decidability holds when the constraints are
additionally extended with regular constraints with a 1-weak control structure.Comment: 18 page
Work-related helping and family functioning: a work-home resources perspective
Using the work–home resources (W-HR) model as an overarching framework, our study seeks to examine the interplay between employees’ provision and receipt of interpersonal organizational citizenship behaviours (OCB-I; i.e. helping behaviours), and its spillover effects on two family outcomes (family performance and marital withdrawal behaviours). Further, we simultaneously test resource depletion (emotional exhaustion) and resource generation (personal accomplishment) mechanisms linking OCB-Is and the family domain. Based on a time-lagged, dual-source study of 320 employees, we found that OCB-I enactment is positively related to both exhaustion (only for those who receive low OCB-Is from colleagues) and personal accomplishment at work (regardless of OCB-I receipt), which interferes with and enriches employees’ family lives, respectively. We discuss the theoretical contributions of these findings to OCB research and the W-HR model
Coffee consumption and prostate cancer risk: further evidence for inverse relationship
<p>Abstract</p> <p>Background</p> <p>Higher consumption of coffee intake has recently been linked with reduced risk of aggressive prostate cancer (PC) incidence, although meta-analysis of other studies that examine the association between coffee consumption and overall PC risk remains inconclusive. Only one recent study investigated the association between coffee intake and grade-specific incidence of PC, further evidence is required to understand the aetiology of aggressive PCs. Therefore, we conducted a prospective study to examine the relationship between coffee intake and overall as well as grade-specific PC risk.</p> <p>Methods</p> <p>We conducted a prospective cohort study of 6017 men who were enrolled in the Collaborative cohort study in the UK between 1970 and 1973 and followed up to 31st December 2007. Cox Proportional Hazards Models were used to evaluate the association between coffee consumption and overall, as well as Gleason grade-specific, PC incidence.</p> <p>Results</p> <p>Higher coffee consumption was inversely associated with risk of high grade but not with overall risk of PC. Men consuming 3 or more cups of coffee per day experienced 55% lower risk of high Gleason grade disease compared with non-coffee drinkers in analysis adjusted for age and social class (HR 0.45, 95% CI 0.23-0.90, p value for trend 0.01). This association changed a little after additional adjustment for Body Mass Index, smoking, cholesterol level, systolic blood pressure, tea intake and alcohol consumption.</p> <p>Conclusion</p> <p>Coffee consumption reduces the risk of aggressive PC but not the overall risk.</p
Strategies to Suppress Hydrogen-Consuming Microorganisms Affect Macro and Micro Scale Structure and Microbiology of Granular Sludge
Treatment of anaerobic granules with heat and
two chemical treatments, contacting with 2-bromoethanesulfonate
(BES) and with BESþChloroform, were applied
to suppress hydrogen-consuming microorganisms. Three
mesophilic expanded granular sludge bed (EGSB) reactors—
RHeat, RBES, and RBESþChlo—were inoculated with
the treated sludges and fed with synthetic sugar-based
wastewater (5 gCOD L 1, HRT 20–12 h). Morphological
integrity of granules and bacterial communities were
assessed by quantitative image analysis and 16S rRNA gene
based techniques, respectively. Hydrogen production
in RHeat was under 300mLH2 L 1 day 1, with a transient
peak of 1,000 mLH2 L 1 day 1 after decreasing HRT.
In RBESþChlo hydrogen production rate did not exceed
300mLH2 L 1 day 1 and there was granule fragmentation,
release of free filaments from aggregates, and decrease of
granule density. In RBES, there was an initial period with
unstable hydrogen production, but a pulse of BES triggered
its production rate to 700 200mLH2 L 1 day 1. This
strategy did not affect granules structure significantly. Bacteria
branching within Clostridiaceae and Ruminococcaceae
were present in this sludge. This work demonstrates that,
methods applied to suppress H2-consuming microorganisms
can cause changes in the macro- and microstructure of
granular sludge, which can be incompatible with the operation
of high-rate reactors.European Community fund FEDER
Contract grant number: FCOMP-01-0124-FEDER-007087; PTDC/BIO/69745/2006; SFRH/
BD/29823/2006; SFRH/BD/48965/2008Fundação para a Ciência e a Tecnologia (FCT
Room temperature plasmon laser by total internal reflection
Plasmon lasers create and sustain intense and coherent optical fields below
light's diffraction limit with the unique ability to drastically enhance
light-matter interactions bringing fundamentally new capabilities to
bio-sensing, data storage, photolithography and optical communications.
However, these important applications require room temperature operation, which
remains a major hurdle. Here, we report a room temperature semiconductor
plasmon laser with both strong cavity feedback and optical confinement to
1/20th of the wavelength. The strong feedback arises from total internal
reflection of surface plasmons, while the confinement enhances the spontaneous
emission rate by up to 20 times.Comment: 8 Page, 2 Figure
Reporting on covariate adjustment in randomised controlled trials before and after revision of the 2001 CONSORT statement: a literature review
<p>Abstract</p> <p>Objectives</p> <p>To evaluate the use and reporting of adjusted analysis in randomised controlled trials (RCTs) and compare the quality of reporting before and after the revision of the CONSORT Statement in 2001.</p> <p>Design</p> <p>Comparison of two cross sectional samples of published articles.</p> <p>Data Sources</p> <p>Journal articles indexed on PubMed in December 2000 and December 2006.</p> <p>Study Selection</p> <p>Parallel group RCTs with a full publication carried out in humans and published in English</p> <p>Main outcome measures</p> <p>Proportion of articles reported adjusted analysis; use of adjusted analysis; the reason for adjustment; the method of adjustment and the reporting of adjusted analysis results in the main text and abstract.</p> <p>Results</p> <p>In both cohorts, 25% of studies reported adjusted analysis (84/355 in 2000 vs 113/422 in 2006). Compared with articles reporting only unadjusted analyses, articles that reported adjusted analyses were more likely to specify primary outcomes, involve multiple centers, perform stratified randomization, be published in general medical journals, and recruit larger sample sizes. In both years a minority of articles explained why and how covariates were selected for adjustment (20% to 30%). Almost all articles specified the statistical methods used for adjustment (99% in 2000 vs 100% in 2006) but only 5% and 10%, respectively, reported both adjusted and unadjusted results as recommended in the CONSORT guidelines.</p> <p>Conclusion</p> <p>There was no evidence of change in the reporting of adjusted analysis results five years after the revision of the CONSORT Statement and only a few articles adhered fully to the CONSORT recommendations.</p
AutoHAS: Efficient Hyperparameter and Architecture Search
Efficient hyperparameter or architecture search methods have shown remarkable
results, but each of them is only applicable to searching for either
hyperparameters (HPs) or architectures. In this work, we propose a unified
pipeline, AutoHAS, to efficiently search for both architectures and
hyperparameters. AutoHAS learns to alternately update the shared network
weights and a reinforcement learning (RL) controller, which learns the
probability distribution for the architecture candidates and HP candidates. A
temporary weight is introduced to store the updated weight from the selected
HPs (by the controller), and a validation accuracy based on this temporary
weight serves as a reward to update the controller. In experiments, we show
AutoHAS is efficient and generalizable to different search spaces, baselines
and datasets. In particular, AutoHAS can improve the accuracy over popular
network architectures, such as ResNet and EfficientNet, on CIFAR-10/100,
ImageNet, and four more other datasets
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