A tabu search heuristic for the Equitable Coloring Problem

The Equitable Coloring Problem is a variant of the Graph Coloring Problem where the sizes of two arbitrary color classes differ in at most one unit. This additional condition, called equity constraints, arises naturally in several applications. Due to the hardness of the problem, current exact algorithms can not solve large-sized instances. Such instances must be addressed only via heuristic methods. In this paper we present a tabu search heuristic for the Equitable Coloring Problem. This algorithm is an adaptation of the dynamic TabuCol version of Galinier and Hao. In order to satisfy equity constraints, new local search criteria are given. Computational experiments are carried out in order to find the best combination of parameters involved in the dynamic tenure of the heuristic. Finally, we show the good performance of our heuristic over known benchmark instances

Combinatorial Assortment Optimization

Assortment optimization refers to the problem of designing a slate of products to offer potential customers, such as stocking the shelves in a convenience store. The price of each product is fixed in advance, and a probabilistic choice function describes which product a customer will choose from any given subset. We introduce the combinatorial assortment problem, where each customer may select a bundle of products. We consider a model of consumer choice where the relative value of different bundles is described by a valuation function, while individual customers may differ in their absolute willingness to pay, and study the complexity of the resulting optimization problem. We show that any sub-polynomial approximation to the problem requires exponentially many demand queries when the valuation function is XOS, and that no FPTAS exists even for succinctly-representable submodular valuations. On the positive side, we show how to obtain constant approximations under a "well-priced" condition, where each product's price is sufficiently high. We also provide an exact algorithm for $k$-additive valuations, and show how to extend our results to a learning setting where the seller must infer the customers' preferences from their purchasing behavior

The influence of copolymer composition on PLGA/nHA scaffolds´ cytotoxicity and in vitro degradation

The influence of copolymer composition on Poly(Lactide-co-Glycolide)/ nanohydroxyapatite (PLGA/nHA) composite scaffolds is studied in the context of bone tissue engineering and regenerative medicine. The composite scaffolds are fabricated by thermally-induced phase separation and the effect of bioactive nanoparticles on their in vitro degradation in phosphate-buffered solution at 37 °C is analyzed over eight weeks. The indirect cytotoxicity evaluation of the samples followed an adaptation of the ISO 10993-5 standard test method. Based on the measurement of their molecular weight, molar mass, pH, water absorption and dimensions, the porous scaffolds of PLGA with a lower lactide/glycolide (LA/GA) molar ratio degraded faster due to their higher hydrophilicity. All of the samples without and with HA are not cytotoxic, demonstrating their potential for tissue engineering applications.SGIker (UPV/EHU, MICINN, GV/EJ, ERDF and ESF) is really appreciated. This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013 and Grant SFRH/BD/111478/2015 (S.R). The authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (Agencia Estatal de Investigación(AEI)/FEDER, Unión Europea(UE))info:eu-repo/semantics/publishedVersio

Influence of Li doping on the morphology and luminescence of Ga_2O_3 microrods grown by a vapor-solid method

Gallium oxide microrods have been grown by an evaporation-deposition method by using a precursor containing lithium in order to check the influence of such dopant on the morphology and physical properties of the obtained ß-Ga_2O_3 structures. SEM studies show that the morphology is modified with respect to undoped gallium oxide, promoting the growth of micropyramids transversal to the microwire axis. Raman analysis reveals good crystal quality and an additional Raman peak centred at around 270 cm^(-1), characteristic of these samples and not present in undoped monoclinic gallium oxide. The presence of the Li^(+) ions also influences the luminescence emission by inducing a red-shift of the characteristic UV-blue defect band of gallium oxide. In addition, an intense sharp peak centred around 717 nm observed both by cathodoluminescence (CL) and photoluminescence (PL) is also attributed to the presence of these ions. The Li related luminescence features have also been investigated by PL excitation (PLE) spectra and by the temperature dependence of the luminescence

Two-loop renormalization group analysis of hadronic decays of a charged Higgs boson

We calculate next-to-leading QCD corrections to the decay $H^+ \to u\bar d$ for generic up and down quarks in the final state. A recently developed algorithm for evaluation of massive two-loop Feynman diagrams is employed to calculate renormalization constants of the charged Higgs boson. The origin and summation of large logarithmic corrections to the decay rate of the top quark into a lighter charged Higgs boson is also explained.Comment: 10 pages + 4 figures, PostScript

β-Ga₂O₃ nanowires for an ultraviolet light selective frequency photodetector

The behaviour of ß-Ga₂O₃ nanowires as photoconductive material in deep ultraviolet photodetectors to operate in the energy range 3.0-6.2 eV has been investigated. The nanowires were grown by a catalyst-free thermal evaporation method on gallium oxide substrates. Photocurrent measurements have been carried out on both undoped and Sn-doped Ga₂O₃ nanowires to evidence the influence of the dopant on the photodetector performances. The responsivity spectrum of single nanowires show maxima in the energy range 4.8-5.4 eV and a strong dependence on the pulse frequency of the excitation light has been observed for undoped nanowires. Our results show that the responsivity of beta- Ga₂O₃ nanowires can be controlled by tuning the chopper frequency of the excitation light and/ or by doping of the nanowires. Non-linear behavior in characteristic current-voltage curves has been observed for Ga₂O₃ : Sn nanowires. The mechanism leading to this behaviour has been discussed and related to space-charged-limited current effects. In addition, the responsivity achieved by doped nanowires at lower bias is higher than for undoped ones

Observation of spontaneous self-channelling of light in air below the collapse threshold

We report the observation of the self-guided propagation of 120 fs, 0.56 mJ infrared radiation in air for distances greater than one meter. In contrast to the known case of filamentation, in the present experiment the laser power is lower than the collapse threshold. Therefore the counter balance between Kerr self focussing and ionization induced defocussing as the stabilizing mechanism is ruled out. Instead, we find evidences of a process in which the transversal beam distribution reshapes into a form similar to a Townes soliton. We include numerical support for this conclusion

Apoyos para la interacción comunicativa con un estudiante sordo bilingüe durante su formación como Ingeniero Mecánico en una Universidad del Suroccidente Colombiano.

El presente trabajo investigativo tuvo como propósito conocer los apoyos implementados para favorecer la interacción comunicativa entre un estudiante Sordo bilingüe y la población oyente, durante su formación como Ingeniero Mecánico en una Universidad del Suroccidente Colombiano. Considerando que el lenguaje, la comunicación humana y la diversidad comunicacional son objetos de estudio de la Fonoaudiología, fue de gran pertinencia conocer los apoyos implementados, para así aportar al crecimiento de la profesión desde una mirada centrada en los procesos lingüístico-sociales; y a su vez, aportar en la construcción de condiciones normativas en la institución donde se llevó a cabo, de forma que se garantice el derecho a la educación de la población Sorda en igualdad de condiciones, desde el reconocimiento de las particularidades lingüísticas, acorde con lineamientos y políticas nacionalesPregradoFONOAUDIOLOGO(A

BioDR : semantic indexing networks for biomedical document retrieval

In Biomedical research, retrieving documents that match an interesting query is a task performed quite frequently. Typically, the set of obtained results is extensive containing many non-interesting documents and consists in a flat list, i.e., not organized or indexed in any way. This work proposes BioDR, a novel approach that allows the semantic indexing of the results of a query, by identifying relevant terms in the documents. These terms emerge from a process of Named Entity Recognition that annotates occurrences of biological terms (e.g. genes or proteins) in abstracts or full-texts. The system is based on a learning process that builds an Enhanced Instance Retrieval Network (EIRN) from a set of manually classified documents, regarding their relevance to a given problem. The resulting EIRN implements the semantic indexing of documents and terms, allowing for enhanced navigation and visualization tools, as well as the assessment of relevance for new documents.Fundação para a Ciência e a Tecnologia (FCT)Maria Barbeito” contract XuntaHUELLA financed by the Consellería de Sanidade (Xunta de Galicia de Galicia