750 research outputs found
Reproducibility in Management Science
With the help of more than 700 reviewers we assess the reproducibility of nearly 500 articles published in the journal Management Science before and after the introduction of a new Data and Code Disclosure policy in 2019. When considering only articles for which data accessibility and hard- and software requirements were not an obstacle for reviewers, the results of more than 95%of articles under the new disclosure policy could be fully or largely computationally reproduced.However, for 29% of articles at least part of the dataset was not accessible to the reviewer. Considering all articles in our sample reduces the share of reproduced articles to 68%. These figures represent a significant increase compared to the period before the introduction of the disclosure policy, where only 12% of articles voluntarily provided replication materials, out of which 55% couldbe (largely) reproduced. Substantial heterogeneity in reproducibility rates across different fields is mainly driven by differences in dataset accessibility. Other reasons for unsuccessful reproduction attempts include missing code, unresolvable code errors, weak or missing documentation, but also soft- and hardware requirements and code complexity. Our findings highlight the importance of journal code and data disclosure policies, and suggest potential avenues for enhancing their effectiveness.<br/
Ab initio simulations of liquid NaSn alloys: Zintl anions and network formation
Using the Car-Parrinello technique, ab initio molecular dynamics simulations
are performed for liquid NaSn alloys in five different compositions (20, 40,
50, 57 and 80 % sodium). The obtained structure factors agree well with the
data from neutron scattering experiments. The measured prepeak in the structure
factor is reproduced qualitatively for most compositions. The calculated and
measured positions of all peaks show the same trend as function of the
composition.\\ The dynamic simulations also yield information about the
formation and stability of Sn clusters (Zintl anions) in the liquid. In our
simulations of compositions with 50 and 57 % sodium we observe the formation of
networks of tin atoms. Thus, isolated tin clusters are not stable in such
liquids. For the composition with 20 % tin only isolated atoms or dimers of tin
appear, ``octet compounds'' of one Sn atom surrounded by 4 Na atoms are not
observed.Comment: 12 pages, Latex, 3 Figures on reques
An improved observable for the forward-backward asymmetry in B -> K* l+ l- and Bs -> phi l+ l-
We study the decay B -> K* l+ l- in the QCD factorization approach and
propose a new integrated observable whose dependence on the form factors is
almost negligible, consequently the non--perturbative error is significantly
reduced and indeed its overall theoretical error is dominated by perturbative
scale uncertainties. The new observable we propose is the ratio between the
integrated forward--backward asymmetry in the [4,6] GeV^2 and [1,4] GeV^2
dilepton invariant mass bins. This new observable is particularly interesting
because, when compared to the location of the zero of the FBA spectrum, it is
experimentally easier to measure and its theoretical uncertainties are almost
as small; moreover it displays a very strong dependence on the phase of the
Wilson coefficient C_10 that is otherwise only accessible through complicated
CP violating asymmetries. We illustrate the new physics sensitivity of this
observable within the context of few extensions of the Standard Model, namely
the SM with four generations, an MSSM with non--vanishing source of flavor
changing neutral currents in the down squark sector and a Z' model with tree
level flavor changing couplings.Comment: 19 pages, 7 figure
Aharonov-Bohm interference in topological insulator nanoribbons
Topological insulators represent novel phases of quantum matter with an
insulating bulk gap and gapless edges or surface states. The two-dimensional
topological insulator phase was predicted in HgTe quantum wells and confirmed
by transport measurements. Recently, Bi2Se3 and related materials have been
proposed as three-dimensional topological insulators with a single Dirac cone
on the surface and verified by angle-resolved photoemission spectroscopy
experiments. Here, we show unambiguous transport evidence of topological
surface states through periodic quantum interference effects in layered
single-crystalline Bi2Se3 nanoribbons. Pronounced Aharonov-Bohm oscillations in
the magnetoresistance clearly demonstrate the coverage of two-dimensional
electrons on the entire surface, as expected from the topological nature of the
surface states. The dominance of the primary h/e oscillation and its
temperature dependence demonstrate the robustness of these electronic states.
Our results suggest that topological insulator nanoribbons afford novel
promising materials for future spintronic devices at room temperature.Comment: 5 pages, 4 figures, RevTex forma
Model-independent constraints on new physics in b --> s transitions
We provide a comprehensive model-independent analysis of rare decays
involving the b --> s transition to put constraints on dimension-six Delta(F)=1
effective operators. The constraints are derived from all the available
up-to-date experimental data from the B-factories, CDF and LHCb. The
implications and future prospects for observables in b --> s l+l- and b --> s
nu nu transitions in view of improved measurements are also investigated. The
present work updates and generalises previous studies providing, at the same
time, a useful tool to test the flavour structure of any theory beyond the SM.Comment: 1+39 pages, 12 figures, 3 tables. v2: minor modifications, typos
corrected, references added, version to be published in JHE
Analyzing ChIP-chip Data Using Bioconductor
Analyzing ChIP-chip Data Using Bioconducto
TMS-Induced Cortical Potentiation during Wakefulness Locally Increases Slow Wave Activity during Sleep
BACKGROUND: Sleep slow wave activity (SWA) is thought to reflect sleep need, increasing in proportion to the length of prior wakefulness and decreasing during sleep. However, the process responsible for SWA regulation is not known. We showed recently that SWA increases locally after a learning task involving a circumscribed brain region, suggesting that SWA may reflect plastic changes triggered by learning. METHODOLOGY/PRINCIPAL FINDINGS: To test this hypothesis directly, we used transcranial magnetic stimulation (TMS) in conjunction with high-density EEG in humans. We show that 5-Hz TMS applied to motor cortex induces a localized potentiation of TMS-evoked cortical EEG responses. We then show that, in the sleep episode following 5-Hz TMS, SWA increases markedly (+39.1±17.4%, p<0.01, n = 10). Electrode coregistration with magnetic resonance images localized the increase in SWA to the same premotor site as the maximum TMS-induced potentiation during wakefulness. Moreover, the magnitude of potentiation during wakefulness predicts the local increase in SWA during sleep. CONCLUSIONS/SIGNIFICANCE: These results provide direct evidence for a link between plastic changes and the local regulation of sleep need
Adsorption of CO on a Platinum (111) surface - a study within a four-component relativistic density functional approach
We report on results of a theoretical study of the adsorption process of a
single carbon oxide molecule on a Platinum (111) surface. A four-component
relativistic density functional method was applied to account for a proper
description of the strong relativistic effects. A limited number of atoms in
the framework of a cluster approach is used to describe the surface. Different
adsorption sites are investigated. We found that CO is preferably adsorbed at
the top position.Comment: 23 Pages with 4 figure
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