5,098 research outputs found
The Directed Dominating Set Problem: Generalized Leaf Removal and Belief Propagation
A minimum dominating set for a digraph (directed graph) is a smallest set of
vertices such that each vertex either belongs to this set or has at least one
parent vertex in this set. We solve this hard combinatorial optimization
problem approximately by a local algorithm of generalized leaf removal and by a
message-passing algorithm of belief propagation. These algorithms can construct
near-optimal dominating sets or even exact minimum dominating sets for random
digraphs and also for real-world digraph instances. We further develop a core
percolation theory and a replica-symmetric spin glass theory for this problem.
Our algorithmic and theoretical results may facilitate applications of
dominating sets to various network problems involving directed interactions.Comment: 11 pages, 3 figures in EPS forma
Should We Learn Probabilistic Models for Model Checking? A New Approach and An Empirical Study
Many automated system analysis techniques (e.g., model checking, model-based
testing) rely on first obtaining a model of the system under analysis. System
modeling is often done manually, which is often considered as a hindrance to
adopt model-based system analysis and development techniques. To overcome this
problem, researchers have proposed to automatically "learn" models based on
sample system executions and shown that the learned models can be useful
sometimes. There are however many questions to be answered. For instance, how
much shall we generalize from the observed samples and how fast would learning
converge? Or, would the analysis result based on the learned model be more
accurate than the estimation we could have obtained by sampling many system
executions within the same amount of time? In this work, we investigate
existing algorithms for learning probabilistic models for model checking,
propose an evolution-based approach for better controlling the degree of
generalization and conduct an empirical study in order to answer the questions.
One of our findings is that the effectiveness of learning may sometimes be
limited.Comment: 15 pages, plus 2 reference pages, accepted by FASE 2017 in ETAP
A topological classification of convex bodies
The shape of homogeneous, generic, smooth convex bodies as described by the
Euclidean distance with nondegenerate critical points, measured from the center
of mass represents a rather restricted class M_C of Morse-Smale functions on
S^2. Here we show that even M_C exhibits the complexity known for general
Morse-Smale functions on S^2 by exhausting all combinatorial possibilities:
every 2-colored quadrangulation of the sphere is isomorphic to a suitably
represented Morse-Smale complex associated with a function in M_C (and vice
versa). We prove our claim by an inductive algorithm, starting from the path
graph P_2 and generating convex bodies corresponding to quadrangulations with
increasing number of vertices by performing each combinatorially possible
vertex splitting by a convexity-preserving local manipulation of the surface.
Since convex bodies carrying Morse-Smale complexes isomorphic to P_2 exist,
this algorithm not only proves our claim but also generalizes the known
classification scheme in [36]. Our expansion algorithm is essentially the dual
procedure to the algorithm presented by Edelsbrunner et al. in [21], producing
a hierarchy of increasingly coarse Morse-Smale complexes. We point out
applications to pebble shapes.Comment: 25 pages, 10 figure
Analysis of High Dimensional Data from Intensive Care Medicine
As high dimensional data occur as a rule rather than an exception in critical care today, it is of utmost importance to improve acquisition, storage, modelling, and analysis of medical data, which appears feasable only with the help of bedside computers. The use of clinical information systems offers new perspectives of data recording and also causes a new challenge for statistical methodology. A graphical approach for analysing patterns in statistical time series from online monitoring systems in intensive care is proposed here as an example of a simple univariate method, which contains the possibility of a multivariate extension and which can be combined with procedures for dimension reduction
Explaining the t tbar forward-backward asymmetry without dijet or flavor anomalies
We consider new physics explanations of the anomaly in the top quark
forward-backward asymmetry measured at the Tevatron, in the context of flavor
conserving models. The recently measured LHC dijet distributions strongly
constrain many otherwise viable models. A new scalar particle in the
antitriplet representation of flavor and color can fit the t tbar asymmetry and
cross section data at the Tevatron and avoid both low- and high-energy bounds
from flavor physics and the LHC. An s-channel resonance in uc to uc scattering
at the LHC is predicted to be not far from the current sensitivity. This model
also predicts rich top quark physics for the early LHC from decays of the new
scalar particles. Single production gives t tbar j signatures with high
transverse momentum jet, pair production leads to t tbar j j and 4 jet final
states.Comment: 7 pages, 6 figures; v2: notation clarified, references adde
Colored Resonant Signals at the LHC: Largest Rate and Simplest Topology
We study the colored resonance production at the LHC in a most general
approach. We classify the possible colored resonances based on group theory
decomposition, and construct their effective interactions with light partons.
The production cross section from annihilation of valence quarks or gluons may
be on the order of 400 - 1000 pb at LHC energies for a mass of 1 TeV with
nominal couplings, leading to the largest production rates for new physics at
the TeV scale, and simplest event topology with dijet final states. We apply
the new dijet data from the LHC experiments to put bounds on various possible
colored resonant states. The current bounds range from 0.9 to 2.7 TeV. The
formulation is readily applicable for future searches including other decay
modes.Comment: 29 pages, 9 figures. References updated and additional K-factors
include
Structure and mechanism of human DNA polymerase η
The variant form of the human syndrome xeroderma pigmentosum (XPV) is caused by a deficiency in DNA polymerase eta (Pol eta), a DNA polymerase that enables replication through ultraviolet-induced pyrimidine dimers. Here we report high-resolution crystal structures of human Pol eta at four consecutive steps during DNA synthesis through cis-syn cyclobutane thymine dimers. Pol eta acts like a 'molecular splint' to stabilize damaged DNA in a normal B-form conformation. An enlarged active site accommodates the thymine dimer with excellent stereochemistry for two-metal ion catalysis. Two residues conserved among Pol eta orthologues form specific hydrogen bonds with the lesion and the incoming nucleotide to assist translesion synthesis. On the basis of the structures, eight Pol eta missense mutations causing XPV can be rationalized as undermining the molecular splint or perturbing the active-site alignment. The structures also provide an insight into the role of Pol eta in replicating through D loop and DNA fragile sites
Persistent work-life conflict and health satisfaction - A representative longitudinal study in Switzerland
Background: The objectives of the present study were (1) to track work-life conflict in Switzerland during the years 2002 to 2008 and (2) to analyse the relationship between work-life conflict and health satisfaction, examining whether long-term work-life conflict leads to poor health satisfaction.
Methods: The study is based on a representative longitudinal database (Swiss Household Panel), covering a six-year period containing seven waves of data collection. The sample includes 1261 persons, with 636 men and 625 women. Data was analysed by multi-level mixed models and analysis of variance with repeated measures.
Results: In the overall sample, there was no linear increase or decrease of work-life conflict detected, in either its time-based or strain-based form. People with higher education were more often found to have a strong work-life conflict (time- and strain-based), and more men demonstrated a strong time-based work-life conflict than women (12.2% vs. 5%). A negative relationship between work-life conflict and health satisfaction over time was found. People reporting strong work-life conflict at every wave reported lower health satisfaction than people with consistently weak work-life conflict. However, the health satisfaction of those with a continuously strong work-life conflict did not decrease during the study period.
Conclusions: Both time-based and strain-based work-life conflict are strongly correlated to health satisfaction. However, no evidence was found for a persistent work-life conflict leading to poor health satisfaction
Contact Manifolds, Contact Instantons, and Twistor Geometry
Recently, Kallen and Zabzine computed the partition function of a twisted
supersymmetric Yang-Mills theory on the five-dimensional sphere using
localisation techniques. Key to their construction is a five-dimensional
generalisation of the instanton equation to which they refer as the contact
instanton equation. Subject of this article is the twistor construction of this
equation when formulated on K-contact manifolds and the discussion of its
integrability properties. We also present certain extensions to higher
dimensions and supersymmetric generalisations.Comment: v3: 28 pages, clarifications and references added, version to appear
in JHE
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