609 research outputs found
Proving equivalence between imperative and MapReduce implementations using program transformations
Distributed programs are often formulated in popular functional frameworks like MapReduce,
Spark and Thrill, but writing efficient algorithms for such frameworks is usually a non-trivial
task. As the costs of running faulty algorithms at scale can be severe, it is highly desirable
to verify their correctness.
We propose to employ existing imperative reference implementations as specifications
for MapReduce implementations. To this end, we present a novel verification approach in
which equivalence between an imperative and a MapReduce implementation is established
by a series of program transformations.
In this paper, we present how the equivalence framework can be used to prove equivalence
between an imperative implementation of the PageRank algorithm and its MapReduce
variant. The eight individual transformation steps are individually presented and explained
Geometry dominated fluid adsorption on sculptured substrates
Experimental methods allow the shape and chemical composition of solid
surfaces to be controlled at a mesoscopic level. Exposing such structured
substrates to a gas close to coexistence with its liquid can produce quite
distinct adsorption characteristics compared to that occuring for planar
systems, which may well play an important role in developing technologies such
as super-repellent surfaces or micro-fluidics. Recent studies have concentrated
on adsorption of liquids at rough and heterogeneous substrates and the
characterisation of nanoscopic liquid films. However, the fundamental effect of
geometry has hardly been addressed. Here we show that varying the shape of the
substrate can exert a profound influence on the adsorption isotherms allowing
us to smoothly connect wetting and capillary condensation through a number of
novel and distinct examples of fluid interfacial phenomena. This opens the
possibility of tailoring the adsorption properties of solid substrates by
sculpturing their surface shape.Comment: 6 pages, 4 figure
Universality for 2D Wedge Wetting
We study 2D wedge wetting using a continuum interfacial Hamiltonian model
which is solved by transfer-matrix methods. For arbitrary binding potentials,
we are able to exactly calculate the wedge free-energy and interface height
distribution function and, thus, can completely classify all types of critical
behaviour. We show that critical filling is characterized by strongly universal
fluctuation dominated critical exponents, whilst complete filling is determined
by the geometry rather than fluctuation effects. Related phenomena for
interface depinning from defect lines in the bulk are also considered.Comment: 4 pages, 1 figur
Nonperturbative versus perturbative effects in generalized parton distributions
Generalized parton distributions (GPDs) are studied at the hadronic
(nonperturbative) scale within different assumptions based on a relativistic
constituent quark model. In particular, by means of a meson-cloud model we
investigate the role of nonperturbative antiquark degrees of freedom and the
valence quark contribution. A QCD evolution of the obtained GPDs is used to add
perturbative effects and to investigate the GPDs' sensitivity to the
nonperturbative ingredients of the calculation at larger (experimental) scale.Comment: 17 pages, 10 figures; submitted to Phys. Rev.
Ethnic In-Group Favoritism Among Minority and Majority Groups: Testing the Self-Esteem Hypothesis Among Preadolescents
The self-esteem hypothesis in intergroup relations, as proposed by social identity
theory (SIT), states that successful intergroup discrimination enhances momentary
collective self-esteem. This hypothesis is a source of continuing controversy. Furthermore,
although SIT is increasingly used to account for childrenâs group attitudes,
few studies have examined the hypothesis among children. In addition, the
hypothesisâs generality makes it important to study among children from different
ethnic groups. The present study, conducted among Dutch and Turkish preadolescents,
examined momentary collective self-feelings as a consequence of ethnic group
evaluations. The results tended to support the self-esteem hypothesis. In-group
favoritism was found to have a self-enhancing effect among participants high in
ethnic identification. This result was found for ethnic majority (Dutch) and minority
(Turkish) participants.
Spin-Dependent Twist-Four Matrix Elements from g_1 Data in the Resonance Region
Matrix elements of spin-dependent twist-four operators are extracted from
recent data on the spin-dependent g_1 structure function of the proton and
deuteron in the resonance region. We emphasize the need to include the elastic
contributions to the first moments of the structure functions at Q^2 < 2 GeV^2.
The coefficients of the 1/Q^2 corrections to the Ellis-Jaffe sum rules are
found to be 0.04 \pm 0.02 and 0.03 \pm 0.04 GeV^2 for the proton and neutron,
respectively.Comment: 10 pages REVTeX, 4 figure
Development of the bone phenotype and microRNA profile in adults with low-density lipoprotein receptor-related protein 5âhigh bone mass (LRP5-HBM) disease
Pathogenic variants in the Wnt-pathway co-receptor low-density lipoprotein (LDL) receptor-related protein 5 (LRP5) cause high bone mass (LRP5-HBM) due to insensitivity to the endogenous antagonist of Wnt-signaling. Although indicating incessant progression of BMD and biomarkers reflecting bone formation, this has not been confirmed in individuals with LRP5-HBM. We investigated how the LRP5-HBM bone phenotype changes with age in adults and is associated with quantitative changes of bone turnover markers and bone-related microRNAs (miRNAs) in the circulation. Whole body, lumbar spine, total hip, and femoral neck areal BMD (aBMD) and radial and tibial bone microarchitecture and geometry were assessed using DXA and HR-pQCT scans of 15 individuals with LRP5-HBMT253I (11 women; median age 51âyears; range, 19 to 85âyears) with a time interval between scans of 5.8âyears (range, 4.9 to 7.6âyears). Fasting P1NP and CTX were measured in 14 LRP5-HBMT253I individuals and age-, sex-, and body mass index (BMI)-matched controls, and 187 preselected miRNAs were quantified using qPCR in 12 individuals and age-, sex-, and BMI-matched controls. DXA and HR-pQCT scans were assessed in subjects who had reached peak bone mass (agedâ>25âyears, n = 12). Femoral neck aBMD decreased by 0.8%/year (p = 0.01) and total hip by 0.3%/year, and radial volumetric BMD (vBMD) increased 0.3%/year (p = 0.03). Differences in bone turnover markers at follow-up were not observed. Compared to controls, 11 of the 178 detectable miRNAs were downregulated and none upregulated in LRP5-HBM individuals, and five of the downregulated miRNAs are reported to be involved in Wnt-signaling. Bone loss at the hip in LRP5-HBM individuals demonstrates that the bone phenotype does not uniformly progress with age. Differentially expressed miRNAs may reflect changes in the regulation of bone turnover and balance in LRP5-HBM individuals
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