Algebraic Integrability of Foliations of the Plane

We give an algorithm to decide whether an algebraic plane foliation F has a rational first integral and to compute it in the affirmative case. The algorithm runs whenever we assume the polyhedrality of the cone of curves of the surface obtained after blowing-up the set B_F of infinitely near points needed to get the dicritical exceptional divisors of a minimal resolution of the singularities of F. This condition can be detected in several ways, one of them from the proximity relations in B_F and, as a particular case, it holds when the cardinality of B_F is less than 9

Dissociation of high-pressure solid molecular hydrogen: Quantum Monte Carlo and anharmonic vibrational study

A theoretical study is reported of the molecular-to-atomic transition in solid hydrogen at high pressure. We use the diffusion quantum Monte Carlo method to calculate the static lattice energies of the competing phases and a density-functional-theory-based vibrational self-consistent field method to calculate anharmonic vibrational properties. We find a small but significant contribution to the vibrational energy from anharmonicity. A transition from the molecular Cmca-12 direct to the atomic I4_1/amd phase is found at 374 GPa. The vibrational contribution lowers the transition pressure by 91 GPa. The dissociation pressure is not very sensitive to the isotopic composition. Our results suggest that quantum melting occurs at finite temperature.Comment: Accepted for publication by Phys. Rev. Let

Theory of phonon-assisted luminescence in solids: Application to hexagonal boron nitride

International audienceIn this manuscript we study luminescence of hexagonal boron nitride (hBN) by means of non-equilibrium Green's functions plus time-dependent perturbation theory. We derive a formula for light emission in solids in the limit of a weak excitation that includes perturbatively the contribution of electron-phonon coupling at the first order. This formula is applied to study luminescence in bulk hBN. This material has attracted interest due to its strong luminescence in the ultraviolet [Watanabe et al., Nature Mat. 3, 404(2004)]. The origin of this luminescence has been widely discussed, but only recently has a clear signature of phonon mediated light emission emerged in the experiments [Cassabois et al., Nature Phot. 10, 262(2016)]. By means of our new theoretical approach we provide a clear and full explanation of light emission in hBN

Automatic supervision of gestures to guide novice surgeons during training

The final publication is available at Springer via http://dx.doi.org/10.1007/s00464-013-3285-9Background Virtual surgery simulators enable surgeons to learn by themselves, shortening their learning curves. Virtual simulators offer an objective evaluation of the surgeon’s skills at the end of each training session. The considered evaluation parameters are based on the analysis of the surgeon’s gestures performed throughout the training session. Currently, this information is usually known by surgeons only at the end of the training session, but very limited during the training performance. In this paper, we present a novel method for automatic and interactive evaluation of the surgeon’s skills that is able to supervise inexperienced surgeons during their training session with surgical simulators. Methods The method is based on the assumption that the sequence of gestures carried out by an expert surgeon in the simulator can be translated into a sequence (a character string) that should be reproduced by a novice surgeon during a training session. In this work, a string-matching algorithm has been modified to calculate the alignment and distance between the sequences of both expert and novice during the training performance. Results The results have shown that it is possible to distinguish between different skill levels at all times during the surgical training session. Conclusions The main contribution of this paper is a method where the difference between an expert’s sequence of gestures and a novice’s ongoing sequence is used to guide inexperienced surgeons. This is possible by indicating to novices the gesture corrections to be applied during surgical training as continuous expert supervision would do.Monserrat, C.; Lucas, A.; Hernández Orallo, J.; Rupérez Moreno, MJ. (2014). Automatic supervision of gestures to guide novice surgeons during training. Surgical Endoscopy. 28(4):1360-1370. doi:10.1007/s00464-013-3285-9S13601370284Ericsson KA (ed) (2009) Development of professional expertise: toward measurement of expert performance and design of optimal learning environments. Cambridge University Press, New YorkMcGaghie WC (2008) Research opportunities in simulation-based medical education using deliberate practice. Acad Emerg Med 15:995–1001Ericsson KA (2008) Deliberate practice and acquisition of expert performance: a general overview. Acad Emerg Med 15:988–994Issenberg SB, McGaghie WC, Petrusa ER et al (2005) Features and uses of high-fidelity medical simulations that lead to effective learning: a BEME systematic review. Med Teach 27:10–28Porte MC, Xeoulis G, Reznick RK, Dubrowski A (2007) Verbal feedback from an expert is more effective than self-accessed feedback about motion efficiency in learning new surgical skills. 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In: IEEE international conference on robotics and biomimetics (ROBIO), Tianjin, pp 247–252. doi: 10.1109/ROBIO.2010.5723335Chmarra MK, Klein S, Winter JCF, Jansen FW, Dankelman J (2010) Objective classification of residents based on their psychomotor laparoscopic skills. Surg Endosc 24(5):1031–1039. doi: 10.1007/s00464-009-0721-yLin HC, Shafran I, Yuh D, Hager GD (2006) Towards automatic skill evaluation: detection and segmentation of robot-assisted surgical motions. Comput Aided Surg 11(5):220–230. doi: 10.3109/10929080600989189Rosen J, Brown JD, Chang L, Sinanan MN, Hannaford B (2006) Generalized approach for modeling minimally invasive surgery as a stochastic process using a discrete Markov model. IEEE Trans Biomed Eng 53(3):399–413. doi: 10.1109/TBME.2005.869771Lahanas V, Loukas C, Nikiteas N, Dimitroulis D, Georgiou E (2011) Psychomotor skills assessment in laparoscopic surgery using augmented reality scenarios. 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Formulación de estrategias de marketing mix a partir del estudio del comportamiento del consumidor de leche en la ciudad de Riobamba/Formulation of marketing mix strategies based on the study of milk consumer behavior in the city of Riobamba

El estudio económico de la conducta del consumidor supone teorías de enfoque positivista y normativo. En este contexto las decisiones de consumo se basan no siempre en un modelo racional, considerando además factores de tipo emocional, experiencias que determinan la decisión de compra. El objetivo de este artículo fue formular estrategias de marketing mix a partir del estudio del comportamiento del consumidor de leche en la ciudad de Riobamba. La metodología utilizada se fundamentó en un estudio cuasi experimental que tomó como base un modelo predeterminado que sirvió para diseñar una encuesta que permitiese identificar y evaluar variables determinantes en la conducta de los consumidores. La investigación permitió determinar las preferencias de marcas de leche, nivel de aceptación del precio, tipo de empaque, medios de comunicación y frecuencia de consumo. Los resultados de la investigación permitieron formular estrategias que contribuyen a incentivar el consumo de leche en la población local. The economic study of consumer behavior supposes theories of positivist and normative approach. In this context, consumer decisions are not always based on a rational model, considering factors of an emotional nature, experiences that determine the purchase decision. The objective of this article was to formulate marketing mix strategies based on the study of milk consumer behavior in the city of Riobamba. The methodology used was based on a quasi-experimental study that took as a basis a predetermined model that served to design a survey that would identify and evaluate determinant variables in the behavior of consumers. The investigation allowed to determine the preferences of milk brands, level of acceptance of the price, type of packaging, means of communication and frequency of consumption. The results of the research allowed to formulate strategies that contribute to encourage the consumption of milk in the local population. Palabras clave: comportamiento del consumidor, neuroeconomía, marketing mix. Keywords: consumer behavior, neuroeconomics, marketing mix