A reformulation strategy for mixed-integer linear bi-level programming problems

Bi-level programming has been used widely to model interactions between hierarchical decision-making problems, and their solution is challenging, especially when the lower-level problem contains discrete decisions. The solution of such mixed-integer linear bi-level problems typically need decomposition, approximation or heuristic-based strategies which either require high computational effort or cannot guarantee a global optimal solution. To overcome these issues, this paper proposes a two-step reformulation strategy in which the first part consists of reformulating the inner mixed-integer problem into a nonlinear one, while in the second step the well-known Karush-Kuhn-Tucker conditions for the nonlinear problem are formulated. This results in a mixed-integer nonlinear problem that can be solved with a global optimiser. The computational and numerical benefits of the proposed reformulation strategy are demonstrated by solving five examples from the literature

Soft leptogenesis in the inverse seesaw model

We consider leptogenesis induced by soft supersymmetry breaking terms ("soft leptogenesis"), in the context of the inverse seesaw mechanism. In this model there are lepton number (L) conserving and L-violating soft supersymmetry-breaking B-terms involving the singlet sneutrinos which, together with the -- generically small-- L-violating parameter responsible of the neutrino mass, give a small mass splitting between the four singlet sneutrino states of a single generation. In combination with the trilinear soft supersymmetry breaking terms they also provide new CP violating phases needed to generate a lepton asymmetry in the singlet sneutrino decays. We obtain that in this scenario the lepton asymmetry is proportional to the L-conserving soft supersymmetry-breaking B-term, and it is not suppressed by the L-violating parameters. Consequently we find that, as in the standard see-saw case, this mechanism can lead to sucessful leptogenesis only for relatively small value of the relevant soft bilinear coupling. The right-handed neutrino masses can be sufficiently low to elude the gravitino problem. Also the corresponding Yukawa couplings involving the lightest of the right-handed neutrinos are constrained to be \sum |Y_{1k}|^2\lesssim 10^{-7} which generically implies that the neutrino mass spectrum has to be strongly hierarchical.Comment: 28 pages, 1 figure; some references added; final version to appear in JHE

Presentación, clasificación y evolución de los pacientes con carcinoma hepatocelular en un centro de Veracruz, México

ResumenAntecedentesLa estadificación en el carcinoma hepatocelular (CHC) otorga pronóstico y orientación terapéutica. La resección y el trasplante hepático son opciones curativas y las terapias de ablación se aplican a pacientes que no reciben tratamiento curativo. La sobrevida tras la resección hepática o terapias de ablación es variada.ObjetivoDescribir la presentación, la estadificación, el manejo y la evolución de los pacientes con CHC en nuestro centro.Pacientes y métodosCuarenta y dos pacientes fueron seguidos prospectivamente durante 7 años. La sobrevida se calculó mediante Kaplan-Meier y log-rank entre los sistemas de estadificación (Okuda, BCLC y CLIP) y tipos de tratamiento (resección hepática, ablación por radiofrecuencia y ningún tratamiento quirúrgico).ResultadosLa edad media ± desviación estándar de los pacientes fue 68,9 ± 9,5 años; el 57% fueron mujeres y el 54% cirróticos. El 31% tenía infección por VHC. El tamaño medio del tumor fue 6.48 ± 2.52cm. Los estadios CLIP 0, Okuda I y BCLC A tuvieron mejor sobrevida que otros estadios (p<0.05). La resección tuvo mejor sobrevida (mediana: 32 meses y sobrevida a 1, 3 y 5 años del 83, el 39 y 19.7%) que ablación por radiofrecuencia (25 meses, y el 90 y el 17.2% a 1 y 3 años) y que ningún tratamiento quirúrgico (1 año<5%) (p<0.05).ConclusiónLos pacientes con CHC en nuestro centro al igual que otra población en México son diagnosticados tardíamente. El pronóstico usando CLIP y BCLC es similar a la literatura. Los mejores resultados se observaron en estadios tempranos y los que tuvieron resección quirúrgica del CHC.AbstractBackgroundHepatocellular carcinoma (HCC) staging provides a basis for calculating disease prognosis and therapeutic guidance. Liver resection and transplantation are curative options, and ablation therapies are applied to patients that are not candidates for curative treatment. Survival after liver resection or ablation therapies varies.AimsTo describe the presentation, staging, management, and outcome in patients with HCC in our center.Patients and methodsForty-two patients had a 7-year prospective follow-up. Survival was calculated with the Kaplan-Meier analysis and the log-rank test was used for its comparison between the staging systems (Okuda, BCLC, and CLIP) and types of treatment (liver resection, radiofrequency ablation, and no surgical treatment).ResultsThe mean age of the patients was 68.9 ± 9.5 years; 57% were women. A total of 54% of the patients presented with cirrhosis and 31% were infected with hepatitis C virus (HCV). The mean tumor size was 6.48 ± 2.52cm. The CLIP 0, Okuda I, and BCLC A stages had better survival rates than the other stages (P<0.05). Survival with resection was superior (median of 32 months and survival at 1, 3, and 5 years of 83, 39, and 19.7%, respectively) to that of both radiofrequency ablation (median of 25 months and survival at 1 and 3 years of 90 and 17.2%, respectively) and no surgical treatment (1 year < 5%) (P<0.05).ConclusionThe patients at our center were diagnosed at late stages of HCC, as is the case in other Mexican populations. Outcome in relation to CLIP and BCLC was similar to the prognoses reported in the literature. The best results were observed in the patients with early stage disease and those that underwent HCC resection surgery

THE HIGH CADENCE TRANSIENT SURVEY (HITS). I. SURVEY DESIGN AND SUPERNOVA SHOCK BREAKOUT CONSTRAINTS

Indexación: Web of Science; Scopus.We present the first results of the High Cadence Transient Survey (HiTS), a survey for which the objective is to detect and follow-up optical transients with characteristic timescales from hours to days, especially the earliest hours of supernova (SN) explosions. HiTS uses the Dark Energy Camera and a custom pipeline for image subtraction, candidate filtering and candidate visualization, which runs in real-time to be able to react rapidly to the new transients. We discuss the survey design, the technical challenges associated with the real-time analysis of these large volumes of data and our first results. In our 2013, 2014, and 2015 campaigns, we detected more than 120 young SN candidates, but we did not find a clear signature from the short-lived SN shock breakouts (SBOs) originating after the core collapse of red supergiant stars, which was the initial science aim of this survey. Using the empirical distribution of limiting magnitudes from our observational campaigns, we measured the expected recovery fraction of randomly injected SN light curves, which included SBO optical peaks produced with models from Tominaga et al. (2011) and Nakar & Sari (2010). From this analysis, we cannot rule out the models from Tominaga et al. (2011) under any reasonable distributions of progenitor masses, but we can marginally rule out the brighter and longer-lived SBO models from Nakar & Sari (2010) under our best-guess distribution of progenitor masses. Finally, we highlight the implications of this work for future massive data sets produced by astronomical observatories, such as LSST.http://iopscience.iop.org/article/10.3847/0004-637X/832/2/155/meta;jsessionid=76BDFFFE378003616F6DBA56A9225673.c4.iopscience.cld.iop.or

On Quantum Effects in Soft Leptogenesis

It has been recently shown that quantum Boltzman equations may be relevant for leptogenesis. Quantum effects, which lead to a time-dependent CP asymmetry, have been shown to be particularly important for resonant leptogenesis when the asymmetry is generated by the decay of two nearly degenerate states. In this work we investigate the impact of the use of quantum Boltzman equations in the framework ``soft leptogenesis'' in which supersymmetry soft-breaking terms give a small mass splitting between the CP-even and CP-odd right-handed sneutrino states of a single generation and provide the CP-violating phase to generate the lepton asymmetry.Comment: 15 pages, 4 figures. Replacement to match published versio

Fatty Acid Methyl Esters as Biosolvents of Epoxy Resins: A Physicochemical Study

The C8 to C18 fatty acid methyl esters (FAME) have been compared as solvents for two epoxy resin pre-polymers, bisphenol A diglycidyl ether (DGEBA) and triglycidyl paminophenol ether (TGPA). It was found that the solubilization limits vary according to the ester and that methyl caprylate is the best solvent of both resins. To explain these solubility performances, physical and chemical properties of FAME were studied, such as the Hansen parameters, viscosity, binary diffusion coefficient and vaporization enthalpy. Determination of the physicochemical parameters of FAME was carried out by laboratory experimentations and by calculation from bibliographic data. The Hansen parameters of FAME and epoxy resins pre-polymers were theoretically and experimentally determined. The FAME chain length showed a long dependence on the binary diffusion parameters and kinematic viscosity, which are mass and momentum transport properties. Moreover, the vaporization enthalpy of these compounds was directly correlated with the solubilization limits

Leptogenesis from Soft Supersymmetry Breaking (Soft Leptogenesis)

Soft leptogenesis is a scenario in which the cosmic baryon asymmetry is produced from a lepton asymmetry generated in the decays of heavy sneutrinos (the partners of the singlet neutrinos of the seesaw) and where the relevant sources of CP violation are the complex phases of soft supersymmetry-breaking terms. We explain the motivations for soft leptogenesis, and review its basic ingredients: the different CP-violating contributions, the crucial role played by thermal corrections, and the enhancement of the efficiency from lepton flavour effects. We also discuss the high temperature regime $T > 10^7$ GeV in which the cosmic baryon asymmetry originates from an initial asymmetry of an anomalous $R$-charge, and soft leptogenesis reembodies in $R$-genesis.Comment: References updated. Some minor corrections to match the published versio

The Little Review on Leptogenesis

This is a brief review on the scenario of baryogenesis through leptogenesis. Leptogenesis is an appealing scenario that may relate the observed baryon asymmetry in the Universe to the low-energy neutrino data. In this review talk, particular emphasis is put on recent developments on the field, such as the flavourdynamics of leptogenesis and resonant leptogenesis near the electroweak phase transition. It is illustrated how these recent developments enable the modelling of phenomenologically predictive scenarios that can directly be tested at the LHC and indirectly in low-energy experiments of lepton-number and lepton-flavour violation.Comment: 15 pages, based on a plenary presentation given at the DISCRETE'08 Symposium, 11-16 December 2008, Valencia, Spai

Visceral fat area and cardiometabolic risk: The Kardiovize study

BACKGROUND: Visceral fat is associated with adiposity-based complications. Bioimpedance measurement allows estimation of visceral fat area (VFA) in an easy manner. However, a validated cut-off value for VFA by bioimpedance associated with cardiometabolic risk is lacking in European population. AIM: To determine cut-off values of VFA measured via bioimpedance associated with cardiometabolic risk. METHODS: Random cross-sectional Czech population-based sample of 25-64 years old subjects. Receiver Operating Characteristic (ROC) curves were used and the area under the curve (AUC), sensitivity, and specificity were calculated. The Cardiometabolic Disease Staging System (CMDS) was used to classify cardiometabolic risk: Stage 1 - 1 or 2 metabolic syndrome (MetS) components, without impaired fasting glucose (IFG); Stage 2 - MetS or IFG; Stage 3 - MetS with IFG; Stage 4 - type 2 diabetes and/or cardiovascular disease. RESULTS: 2052 participants (54.5% females, median age 49 years) were included. Median VFA (inter-quartile range) were 82.2 cm2 (54.8) in men and 89.8 cm2 (55.6) in women. The best VFA cut-offs associated with Stage 1 in men and women were 71 cm2 (sensitivity = 0.654; specificity = 0.427) and 83 cm2 (sensitivity = 0.705; specificity = 0.556) ; Stage 2: 84 cm2 (sensitivity = 0.673; specificity = 0.551) and 98 cm2 (sensitivity = 0.702; specificity = 0.628) ; Stage 3: 90 cm2 (sensitivity = 0.886; specificity = 0.605) and 109 cm2 (sensitivity = 0.755; specificity = 0.704); Stage 4: 91 cm2 (sensitivity = 0.625; specificity = 0.611) and 81 cm2 (sensitivity = 0.695; specificity = 0.448), respectively. CONCLUSION: A cut-off value of VFA of 71 cm2 in men and 83 cm2 in women exhibited the earliest stage of cardiometabolic risk, and 90 cm2 in men and 109 cm2 in women showed the best performance to detect risk