4,882 research outputs found
On the Computational Complexity of Vertex Integrity and Component Order Connectivity
The Weighted Vertex Integrity (wVI) problem takes as input an -vertex
graph , a weight function , and an integer . The
task is to decide if there exists a set such that the weight
of plus the weight of a heaviest component of is at most . Among
other results, we prove that:
(1) wVI is NP-complete on co-comparability graphs, even if each vertex has
weight ;
(2) wVI can be solved in time;
(3) wVI admits a kernel with at most vertices.
Result (1) refutes a conjecture by Ray and Deogun and answers an open
question by Ray et al. It also complements a result by Kratsch et al., stating
that the unweighted version of the problem can be solved in polynomial time on
co-comparability graphs of bounded dimension, provided that an intersection
model of the input graph is given as part of the input.
An instance of the Weighted Component Order Connectivity (wCOC) problem
consists of an -vertex graph , a weight function ,
and two integers and , and the task is to decide if there exists a set
such that the weight of is at most and the weight of
a heaviest component of is at most . In some sense, the wCOC problem
can be seen as a refined version of the wVI problem. We prove, among other
results, that:
(4) wCOC can be solved in time on interval graphs,
while the unweighted version can be solved in time on this graph
class;
(5) wCOC is W[1]-hard on split graphs when parameterized by or by ;
(6) wCOC can be solved in time;
(7) wCOC admits a kernel with at most vertices.
We also show that result (6) is essentially tight by proving that wCOC cannot
be solved in time, unless the ETH fails.Comment: A preliminary version of this paper already appeared in the
conference proceedings of ISAAC 201
Ultrasonic Measurement of Formability in Thin Ferritic Steel Sheet
The formability of rolled sheet metal is strongly influenced by the texture of the polycrystalline metal. For steel sheet, it is desirable to have high drawability to make automobile body parts, etc. In addition, material homogeneity is desired; that is, material cut from different parts of a rolled sheet should have the same plastic deformation when subjected to deep drawing
One-dimensional quantum magnetism in the S= 1/2 Mo(V) system KMoOP2O7
We present a comprehensive experimental and ab initio study of the S=1/2Mo5+ system, KMoOP2O7, and show that it realizes the S=12 Heisenberg chain antiferromagnet model. Powder neutron diffraction reveals that KMoOP2O7 forms a magnetic network comprised of pairs of Mo5+ chains within its monoclinic P21/n structure. Antiferromagnetic interactions within the Mo5+ chains are identified through magnetometry measurements and confirmed by analysis of the magnetic specific heat. The latter reveals a broad feature centered on TN=0.54 K, which we ascribe to the onset of long-range antiferromagnetic order. No magnetic Bragg scattering is observed in powder neutron-diffraction data collected at 0.05 K, however, which is consistent with a strongly suppressed ordered moment with an upper limit μord<0.15μB. The one-dimensional character of the magnetic correlations in KMoOP2O7 is verified through analysis of inelastic neutron-scattering data, resulting in a model with J2≈34 K and J1≈-2 K for the intrachain and interchain exchange interactions, respectively. The origin of these experimental findings are addressed through density-functional theory calculations
Phase-Diverse Coherent Diffractive Imaging: High Sensitivity with Low Dose
This Letter demonstrates that coherent diffractive imaging (CDI), in combination with phase-diversity methods, provides reliable and artefact free high-resolution images. Here, using x rays, experimental results show a threefold improvement in the available image contrast. Furthermore, in conditions requiring low imaging dose, it is demonstrated that phase-diverse CDI provides a factor of 2 improvement in comparison to previous CDI techniques
Lensing in the Hercules Supercluster
We report Keck LRIS observations of an arc-like background galaxy near the
center of Abell 2152 (z=0.043), one of the three clusters comprising the
Hercules supercluster. The background object has a redshift z=0.1423 and is
situated 25 arcsec north of the primary component of the A2152 brightest
cluster galaxy (BCG). The object is about 15 arcsec in total length and has a
reddening-corrected R-band magnitude of . Its spectrum
shows numerous strong emission lines, as well as absorption features. The
strength of the H-alpha emission would imply a star formation rate \SFR
\approx 3h^{-2} \msun yr in the absence of any lensing. However, the
curved shaped of this object and its tangential orientation along the major
axis of the BCG suggest lensing. We model the A2152 core mass distribution
including the two BCG components and the cluster potential. We present velocity
and velocity dispersion profile measurements for the two BCG components and use
these to help constrain the potential. The lens modeling indicates a likely
magnification factor of for the lensed galaxy, making A2152 the
nearest cluster in which such significant lensing of a background source has
been observed. Finally, we see evidence for a concentration of early-type
galaxies at near the centroid of the X-ray emission previously
attributed to A2152. We suggest that emission from this background
concentration is the cause of the offset of the X-ray center from the A2152
BCG. The background concentration and the dispersed mass of the Hercules
supercluster could add further to the lensing strength of the A2152 cluster.Comment: Accepted for publication in AJ (January 2001). 9 pages; uses
emulateapj.sty. The all-important "Figure 1" is included here in GIF format;
for a version which includes Figure 1 as a high-resolution Postscript image,
see: http://adcam.pha.jhu.edu/~jpb/a2152.ps.g
Tailored elastic surface to body wave Umklapp conversion
Elastic waves guided along surfaces dominate applications in geophysics, ultrasonic inspection, mechanical vibration, and surface acoustic wave devices; precise manipulation of surface Rayleigh waves and their coupling with polarised body waves presents a challenge that offers to unlock the flexibility in wave transport required for efficient energy harvesting and vibration mitigation devices. We design elastic metasurfaces, consisting of a graded array of rod resonators attached to an elastic substrate that, together with critical insight from Umklapp scattering in phonon-electron systems, allow us to leverage the transfer of crystal momentum; we mode-convert Rayleigh surface waves into bulk waves that form tunable beams. Experiments, theory and simulation verify that these tailored Umklapp mechanisms play a key role in coupling surface Rayleigh waves to reversed bulk shear and compressional waves independently, thereby creating passive self-phased arrays allowing for tunable redirection and wave focusing within the bulk medium
Study protocol: A phase III randomised, double-blind, parallel arm, stratified, block randomised, placebo-controlled trial investigating the clinical effect and cost-effectiveness of sertraline for the palliative relief of breathlessness in people with chronic breathlessness
© Published by the BMJ Publishing Group Limited. Introduction: Breathlessness remains a highly prevalent and distressing symptom for many patients with progressive life-limiting illnesses. Evidence-based interventions for chronic breathlessness are limited, and there is an ongoing need for high-quality research into developing management strategies for optimal palliation of this complex symptom. Previous studies have suggested that selective serotonin reuptake inhibitors such as sertraline may have a role in reducing breathlessness. This paper presents the protocol for a large, adequately powered randomised study evaluating the use of sertraline for chronic breathlessness in people with progressive life-limiting illnesses. Methods and analysis: A total of 240 participants with modified Medical Research Council Dyspnoea Scale breathlessness of level 2 or higher will be randomised to receive either sertraline or placebo for 28 days in this multisite, double-blind study. The dose will be titrated up every 3 days to a maximum of 100 mg daily. The primary outcome will be to compare the efficacy of sertraline with placebo in relieving the intensity of worst breathlessness as assessed by a 0-100 mm Visual Analogue Scale. A number of other outcome measures and descriptors of breathlessness as well as caregiver assessments will also be recorded to ensure adequate analysis of participant breathlessness and to allow an economic analysis to be performed. Participants will also be given the option of continuing blinded treatment until either study data collection is complete or net benefit ceases. Appropriate statistical analysis of primary and secondary outcomes will be used to describe the wealth of data obtained. Ethics and dissemination: Ethics approval was obtained at all participating sites. Results of the study will be submitted for publication in peer-reviewed journals and the key findings presented at national and international conferences. Trial registration number ACTRN12610000464066
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