5,320 research outputs found
A parallel algorithm for solving the incompressible Navier-Stokes problems
AbstractWe introduce and analyze a parallel algorithm for solving the Navier-Stokes equations based on the splitting of the two main difficulties involved, the presence of nonlinear terms and the zero divergence condition. The numerical results obtained by using the proposed algorithm are quite consistent with those furnished by other known algorithms. Numerical results are discussed, as well as the advantages of this new algorithm
SU(1,1) Coherent States For Position-Dependent Mass Singular Oscillators
The Schroedinger equation for position-dependent mass singular oscillators is
solved by means of the factorization method and point transformations. These
systems share their spectrum with the conventional singular oscillator. Ladder
operators are constructed to close the su(1,1) Lie algebra and the involved
point transformations are shown to preserve the structure of the
Barut-Girardello and Perelomov coherent states.Comment: 11 pages, 5 figures. This shortened version (includes new references)
has been adapted for its publication in International Journal of Theoretical
Physic
Preference incorporation in MOEA/D using an outranking approach with imprecise model parameters
Multi-objective Optimization Evolutionary Algorithms (MOEAs) face numerous challenges when they are used to solve Many-objective Optimization Problems (MaOPs). Decomposition-based strategies, such as MOEA/D, divide an MaOP into multiple single-optimization sub-problems, achieving better diversity and a better approximation of the Pareto front, and dealing with some of the challenges of MaOPs. However, these approaches still require one to solve a multi-criteria selection problem that will allow a Decision-Maker (DM) to choose the final solution. Incorporating preferences may provide results that are closer to the region of interest of a DM. Most of the proposals to integrate preferences in decomposition-based MOEAs prefer progressive articulation over the “a priori” incorporation of preferences. Progressive articulation methods can hardly work without comparable and transitive preferences, and they can significantly increase the cognitive effort required of a DM. On the other hand, the “a priori” strategies do not demand transitive judgements from the DM but require a direct parameter elicitation that usually is subject to imprecision. Outranking approaches have properties that allow them to suitably handle non-transitive preferences, veto conditions, and incomparability, which are typical characteristics of many real DMs. This paper explores how to incorporate DM preferences into MOEA/D using the “a priori” incorporation of preferences, based on interval outranking relations, to handle imprecision when preference parameters are elicited. Several experiments make it possible to analyze the proposal's performance on benchmark problems and to compare the results with the classic MOEA/D without preference incorporation and with a recent, state-of-the-art preference-based decomposition algorithm. In many instances, our results are closer to the Region of Interest, particularly when the number of objectives increases
Interacting holographic tachyon model of dark energy
We propose a holographic tachyon model of dark energy with interaction
between the components of the dark sector. The correspondence between the
tachyon field and the holographic dark energy densities allows the
reconstruction of the potential and the dynamics of the tachyon scalar field in
a flat Friedmann-Robertson-Walker universe. We show that this model can
describe the observed accelerated expansion of our universe with a parameter
space given by the most recent observational results.Comment: 7 pages, 8 figures, accepted for publication in IJMP
An ACO-based Hyper-heuristic for Sequencing Many-objective Evolutionary Algorithms that Consider Different Ways to Incorporate the DM's Preferences
Many-objective optimization is an area of interest common to researchers, professionals, and practitioners because of its real-world implications. Preference incorporation into Multi-Objective Evolutionary Algorithms (MOEAs) is one of the current approaches to treat Many-Objective Optimization Problems (MaOPs). Some recent studies have focused on the advantages of embedding preference models based on interval outranking into MOEAs; several models have been proposed to achieve it. Since there are many factors influencing the choice of the best outranking model, there is no clear notion of which is the best model to incorporate the preferences of the decision maker into a particular problem. This paper proposes a hyper-heuristic algorithm—named HyperACO—that searches for the best combination of several interval outranking models embedded into MOEAs to solve MaOPs. HyperACO is able not only to select the most appropriate model but also to combine the already existing models to solve a specific MaOP correctly. The results obtained on the DTLZ and WFG test suites corroborate that HyperACO can hybridize MOEAs with a combined preference model that is suitable to the problem being solved. Performance comparisons with other state-of-the-art MOEAs and tests for statistical significance validate this conclusion
Ile-1781-Leu and Asp-2078-Gly Mutations in ACCase Gene, Endow Cross-resistance to APP, CHD, and PPZ in Phalaris minor from Mexico
Herbicides that inhibit acetyl coenzyme A carboxylase (ACCase) are commonly
used in Mexico to control weedy grasses such as little seed canarygrass (Phalaris minor).
These herbicides are classified into three major families (ariloxyphenoxypropionates (APP),
cyclohexanodiones (CHD), and, recently, phenylpyrazolines (PPZ)). In this work, the resistance
to ACCase (APP, CHD, and PPZ) inhibiting herbicides was studied in a biotype of
Phalaris minor (P. minor) from Mexico, by carrying out bioassays at the whole-plant level
and investigating the mechanism behind this resistance. Dose-response and ACCase in vitro
activity assays showed cross-resistance to all ACCase herbicides used. There was no
difference in the absorption, translocation, and metabolism of the 14C-diclofop-methyl between
the R and S biotypes. The PCR generated CT domain fragments of ACCase from the R
biotype and an S reference were sequenced and compared. The Ile-1781-Leu and Asp-2078-Gly
point mutations were identified. These mutations could explain the loss of affinity for
ACCase by the ACCase-inhibing herbicides. This is the first report showing that this substitution confers resistance to APP, CHD, and PPZ herbicides in P. minor from Mexico.
The mutations have been described previously only in a few cases; however, this is the first
study reporting on a pattern of cross-resistance with these mutations in P. minor. The findings
could be useful for better management of resistant biotypes carrying similar mutations
Crystallization Process and Site-Selective Excitation of Nd3+ in LaF3/NaLaF4 Sol–Gel-Synthesized Transparent Glass-Ceramics
In this study, transparent oxyfluoride glass-ceramics (GCs) with NaLaF4 nanocrystals (NCs) were prepared by the sol–gel method for the first time. Three different molar ratios of La(CH3COO)3/Na(CH3COO) were used to obtain the GCs, which were sintered at 450, 550 and 650 °C for 1 min. X-ray diffraction (XRD) was employed to follow the evolution of the xerogel during the heat treatments and to study crystal growth for the three temperatures. In all cases, the LaF3 crystalline phase was present, but crystallization of NaLaF4 was only promoted at 650 °C. Thermogravimetric and thermodifferential analysis (TGA-DTA) and Fourier transform infrared spectroscopy (FTIR) were used to analyze the crystallization process. High-resolution transmission electron microscopy (HRTEM) was employed to confirm NaLaF4 crystallization and determine the size distribution. The incorporation of Nd3+ ion into NaLaF4 and LaF3 nanocrystals was confirmed by site-selective emission and excitation spectra. The Nd3+ emission intensities in both phases depend not only on the NaLaF4/LaF3 ratio but also on their emission efficiencies.The authors acknowledge financial support from MINECO under projects MAT2017-87035-C2-1-P/-2-P (AEI/FEDER, UE), and Basque Government PIBA2018-24. This article is a part of the dissemination activities of the project FunGlass, which has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 739566
Phase diagram of the (bosonic) Double-Exchange Model
The phase diagram of the simplest approximation to Double-Exchange systems,
the bosonic Double-Exchange model with antiferromagnetic super-exchange
coupling, is fully worked out by means of Monte Carlo simulations, large-N
expansions and Variational Mean-Field calculations. We find a rich phase
diagram, with no first-order phase transitions. The most surprising finding is
the existence of a segment like ordered phase at low temperature for
intermediate AFM coupling which cannot be detected in neutron-scattering
experiments. This is signaled by a maximum (a cusp) in the specific heat. Below
the phase-transition, only short-range ordering would be found in
neutron-scattering. Researchers looking for a Quantum Critical Point in
manganites should be wary of this possibility. Finite-Size Scaling estimates of
critical exponents are presented, although large scaling corrections are
present in the reachable lattice sizes.Comment: 17 pages, 14 figure
Highly sensitive molecular diagnosis of prostate cancer using surplus material washed off from biopsy needles
INTRODUCTION: Currently, final diagnosis of prostate cancer (PCa) is based on histopathological analysis of needle biopsies, but this process often bears uncertainties due to small sample size, tumour focality and pathologist’s subjective assessment.
METHODS: Prostate cancer diagnostic signatures were generated by applying linear discriminant analysis to microarray and real-time RT–PCR (qRT–PCR) data from normal and tumoural prostate tissue samples. Additionally, after removal of biopsy tissues, material washed off from transrectal biopsy needles was used for molecular profiling and discriminant analysis.
RESULTS: Linear discriminant analysis applied to microarray data for a set of 318 genes differentially expressed between non-tumoural and tumoural prostate samples produced 26 gene signatures, which classified the 84 samples used with 100% accuracy. To identify signatures potentially useful for the diagnosis of prostate biopsies, surplus material washed off from routine biopsy needles from 53 patients was used to generate qRT–PCR data for a subset of 11 genes. This analysis identified a six-gene signature that correctly assigned the biopsies as benign or tumoural in 92.6% of the cases, with 88.8% sensitivity and 96.1% specificity.
CONCLUSION: Surplus material from prostate needle biopsies can be used for minimal-size gene signature analysis for sensitive and accurate discrimination between non-tumoural and tumoural prostates, without interference with current diagnostic procedures. This approach could be a useful adjunct to current procedures in PCa diagnosis.
British Journal of Cancer (2011) 105, 1600–1607. doi:10.1038/bjc.2011.435 www.bjcancer.com
Published online 18 October 2011
& 2011 Cancer Research UKMinisterio de Ciencia e Innovacion (PI080274), Fundación Marato TV3, Ministerio de Educacio´n (GEN2001-4856- C13, GEN2001-4865-C13-10 and SAF2005-05109), Ministerio de Sanidad (PI020231), Red Temática de Cáncer of the Instituto Carlos III (ISCIII-RETIC RD06/0020), Xarxa de Bancs de Tumors de Catalunya-ICO (XBTC) and Fundación Ramón Areces.Peer Reviewe
Simulating spin systems on IANUS, an FPGA-based computer
We describe the hardwired implementation of algorithms for Monte Carlo
simulations of a large class of spin models. We have implemented these
algorithms as VHDL codes and we have mapped them onto a dedicated processor
based on a large FPGA device. The measured performance on one such processor is
comparable to O(100) carefully programmed high-end PCs: it turns out to be even
better for some selected spin models. We describe here codes that we are
currently executing on the IANUS massively parallel FPGA-based system.Comment: 19 pages, 8 figures; submitted to Computer Physics Communication
- …