Teorías sobre la figura del emprendedor

Este artículo tiene por objetivo exponer el mapa conceptual de una investigación en que nos interrogamos acerca de los factores que han contribuido históricamente a que en España predomine una estructura empresarial dominada cuantitativamente por la pequeña y mediana empresa, en detrimento de una estructura de tamaño superior, considerando que esta situación empresarial ha sido contemplada como una desventaja competitiva, por limitar la productividad, dificultar la presencia en mercados exteriores, la financiación ajena, y repercutir negativamente en las inversiones en investigación y desarrollo. Dado este contexto, nos planteamos cómo y por medio de qué recursos, determinados empresarios han logrado desarrollar proyectos empresariales innovadores. Por otra parte, podemos considerar que en el estudio de la función empresarial hay dos perspectivas o ejes teóricos. El primero, que llamamos «perspectiva individual», caracteriza al empresario, ya sea por lo que hace o por unos determinados rasgos psicológicos específicos. El segundo, que denominamos «perspectiva estructural», caracteriza al empresario por factores del entorno, de carácter institucional, social, sectorial, cultural e ideológico-político. Sin embargo, consideramos que el estudio de la función emprendedora y la creación de empresas es deficiente si únicamente se toman en cuenta los rasgos de personalidad y de comportamiento de los empresarios individuales, así como exclusivamente los factores estructurales.This paper explains the conceptual frameworek of a research where we were looking at the factors that have favoured a entrepreneurial experience dominated by small and medium enterprise instead of a bigger structure, considering the fact that this structure has been seen as a competitive disadvantage that limits productivity, makes more difficult the transfer to external markets, the financing, and has a negative impact on Research and Development. Therefore, we were looking at how certain entrepreneurs have managed to develop innovative projects. On the other hand, we consider two perspectives on management studies. The first one characterises the businessman according to specific psychological traits. The second one, known as structural perspective, describes factors as derived from environment, from institutional, social, cultural, or ideologically based factors. We conclude that the study of the entrepreneurial function and the creation of companies is deficient if only structural or individual factors are taken into account

Quasinormal modes of massive charged flavor branes

We present an analysis and classification of vector and scalar fluctuations in a D3/D7 brane setup at finite termperature and baryon density. The system is dual to an N=2 supersymmetric Yang-Mills theory with SU(N_c) gauge group and N_f hypermultiplets in the fundamental representation in the quenched approximation. We improve significantly over previous results on the quasinormal mode spectrum of D7 branes and stress their novel physical interpretation. Amongst our findings is a new purely imaginary scalar mode that becomes tachyonic at sufficiently low temperature and baryon density. We establish the existence of a critical density above which the scalar mode stays in the stable regime for all temperatures. In the vector sector we study the crossover from the hydrodynamic to the quasiparticle regime and find that it moves to shorter wavelengths for lower temperatures. At zero baryon density the quasinormal modes move toward distinct discrete attractor frequencies that depend on the momentum as we increase the temperature. At finite baryon density, however, the trajectories show a turning behavior such that for low temperature the quasinormal mode spectrum approaches the spectrum of the supersymmetric zero temperature normal modes. We interpret this as resolution of the singular quasinormal mode spectrum that appears at the limiting D7 brane embedding at vanishing baryon density.Comment: 56 pages, 40 figure

Multi-Channel Inverse Scattering Problem on the Line: Thresholds and Bound States

We consider the multi-channel inverse scattering problem in one-dimension in the presence of thresholds and bound states for a potential of finite support. Utilizing the Levin representation, we derive the general Marchenko integral equation for N-coupled channels and show that, unlike to the case of the radial inverse scattering problem, the information on the bound state energies and asymptotic normalization constants can be inferred from the reflection coefficient matrix alone. Thus, given this matrix, the Marchenko inverse scattering procedure can provide us with a unique multi-channel potential. The relationship to supersymmetric partner potentials as well as possible applications are discussed. The integral equation has been implemented numerically and applied to several schematic examples showing the characteristic features of multi-channel systems. A possible application of the formalism to technological problems is briefly discussed.Comment: 19 pages, 5 figure

Spectroscopic characterisation of CARMENES target candidates from FEROS, CAFE and HRS high-resolution spectra

CARMENES (Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Echelle Spectrographs) started a new planet survey on M-dwarfs in January this year. The new high-resolution spectrographs are operating in the visible and near-infrared at Calar Alto Observatory. They will perform high-accuracy radial-velocity measurements (goal 1 m s-1) of about 300 M-dwarfs with the aim to detect low-mass planets within habitable zones. We characterised the candidate sample for CARMENES and provide fundamental parameters for these stars in order to constrain planetary properties and understand star-planet systems. Using state-of-the-art model atmospheres (PHOENIX-ACES) and chi2-minimization with a downhill-simplex method we determine effective temperature, surface gravity and metallicity [Fe/H] for high-resolution spectra of around 480 stars of spectral types M0.0-6.5V taken with FEROS, CAFE and HRS. We find good agreement between the models and our observed high-resolution spectra. We show the performance of the algorithm, as well as results, parameter and spectral type distributions for the CARMENES candidate sample, which is used to define the CARMENES target sample. We also present first preliminary results obtained from CARMENES spectra

CARMENES input catalogue of M dwarfs. I. Low-resolution spectroscopy with CAFOS

Context. CARMENES is a stabilised, high-resolution, double-channel spectrograph at the 3.5 m Calar Alto telescope. It is optimally designed for radial-velocity surveys of M dwarfs with potentially habitable Earth-mass planets. Aims. We prepare a list of the brightest, single M dwarfs in each spectral subtype observable from the northern hemisphere, from which we will select the best planet-hunting targets for CARMENES. Methods. In this first paper on the preparation of our input catalogue, we compiled a large amount of public data and collected low-resolution optical spectroscopy with CAFOS at the 2.2 m Calar Alto telescope for 753 stars. We derived accurate spectral types using a dense grid of standard stars, a double least-squares minimisation technique, and 31 spectral indices previously defined by other authors. Additionally, we quantified surface gravity, metallicity, and chromospheric activity for all the stars in our sample. Results. We calculated spectral types for all 753 stars, of which 305 are new and 448 are revised. We measured pseudo-equivalent widths of Halpha for all the stars in our sample, concluded that chromospheric activity does not affect spectral typing from our indices, and tabulated 49 stars that had been reported to be young stars in open clusters, moving groups, and stellar associations. Of the 753 stars, two are new subdwarf candidates, three are T Tauri stars, 25 are giants, 44 are K dwarfs, and 679 are M dwarfs. Many of the 261 investigated dwarfs in the range M4.0-8.0 V are among the brightest stars known in their spectral subtype. Conclusions. This collection of low-resolution spectroscopic data serves as a candidate target list for the CARMENES survey and can be highly valuable for other radial-velocity surveys of M dwarfs and for studies of cool dwarfs in the solar neighbourhood.Comment: A&A, in pres

Raising awareness of the accessibility challenges in mathematics MOOCs

MOOCs provide learning environments that make it easier for learners to study from anywhere, at their own pace and with open access to content. This has revolutionised the field of eLearning, but accessibility continues to be a problem, even more so if we include the complexity of the STEM disciplines which have their own specific characteristics. This work presents an analysis of the accessibility of several MOOC platforms which provide courses in mathematics. We attempt to visualise the main web accessibility problems and challenges that disabled learners could face in taking these types of courses, both in general and specifically in the context of the subject of mathematics

C-ERB-2, P53, Ki67 proteins and receptors of estrogen and progesterone on the prognosis of epithelial ovarian cancer

Ovarian cancer is the seventh most common cancer diagnosed in women worldwide. To date, many studies in epithelial ovarian cancer (EOC) have reported on the association HER-2/neu, p53 proteins and steroid hormones and their respective receptors with prognosis and/or the carcinogenesis process, but no definitive conclusion has been reached. Objectives: To assess the proteins c-erbB-2, p53, Ki67 and receptors of estrogen (ER) and progesterone (PR) of EOC, with regard to clinical stage findings and its effect on survival. Methods: 125 patients with a diagnosis of EOC treated by primary surgery and chemotherapy have participated. A surgical stage was noted and analyzed the correlation with c-erbB-2, p53, Ki67, ER and PR. Immunohistochemical analysis, using the anti-c-erbB-2, p53, Ki67 monoclonal antibodies, the antibody cod PR clone PgR and code ER-6-F11 Anti human estrogen. The c-erbB-2 study was complemented by genetic amplification and was reported univariate and multivariate analysis. Results: Age 55.7 ± 16; 50.2% with residual disease (< 2 cm); initial (54.6%) and advanced (45.4%) stage. Univariate analysis showed positive staining for c-erbB-2, p-53, Ki67, PR and ER. The patients with negative receptors had a significantly shortened survival time (p = 0.01) than patients with positive receptors. Multivariable analysis revealed only clinical FIGO stage as an independent prognostic of overall survival (p = 0.002). Other variables like c-erbB-2, p53, Ki67, and ER were not significantly related to survival. Conclusions: We concluded that patients with negative PR had a significantly shortened survival time than patients with positive receptors. The overexpression of markers c-erbB-2, p53, Ki67, and ER, were not significantly related to survival in EOC. Only the FIGO stage was achieved to be an independent predictor of overall survival. They should be evaluated together with the patient’s clinical status and other prognostic factors.info:eu-repo/semantics/publishedVersio