Thermal melting of density waves on the square lattice

We present the theory of the effect of thermal fluctuations on commensurate "p x p" density wave ordering on the square lattice (p >= 3, integer). For the case in which this order is lost by a second order transition, we argue that the adjacent state is generically an incommensurate striped state, with commensurate p-periodic long range order along one direction, and incommensurate quasi-long-range order along the orthogonal direction. We also present the routes by which the fully disordered high temperature state can be reached. For p=4, and at special commensurate densities, the "4 x 4" commensurate state can melt directly into the disordered state via a self-dual critical point with non-universal exponents.Comment: 12 pages, 5 figure

Polychronicity in top management teams: The impact on strategic decision processes and performance of new technology ventures

This study focuses on polychronicity as a cultural dimension of top management teams (TMTs). TMT polychronicity is the extent to which team members mutually prefer and tend to engage in multiple tasks simultaneously or intermittently instead of one at a time and believe that this is the best way of doing things. We explore the impact of TMT polychronicity on strategic decision speed and comprehensiveness and, subsequently, its effect on new venture financial performance. Contrary to popular time-management principles advocating task prioritization and focused sequential execution, we found that TMT polychronicity has a positive effect on firm performance in the context of dynamic unanalyzable environments. This effect is partially mediated by strategic decision speed and comprehensiveness. Our study contributes to research on strategic leadership by focusing on a novel value-based characteristic of the TMT (polychronicity) and by untangling the decision-making processes that relate TMT characteristics and firm performance. It also contributes to the attention-based view of the firm by positioning polychronicity as a new type of attention structure

3C a multi-wavelength database for the future GTC cosmological surveys

The 3C Database aims to provide complete multi-wavelength information over different cosmological fields, such as GOODS, Groth or Sa68 allowing detailed studies on wide samples of galaxies

Actividades de ocio-tiempo libre y paseo fuera del hogar en ancianos de la provincia de Guadalajara

ObjetivoConocer cuáles son las actividades de ocio-tiempo libre y paseo diario en ancianos de la provincia de Guadalajara, en la hipótesis que éstas son susceptibles de mejorarse.DiseñoSe trata de un estudio descriptivo, transversal, de base poblacional.EmplazamientoEfectuado en el ámbito comunitario, en el marco de la atención primaria.ParticipantesPersonas mayores de 65 años, sin deterioro cognitivo y residentes en la comunidad, seleccionados de modo aleatorio a partir de bases de datos poblacionales. La muestra finalmente estudiada está compuesta en el medio rural por 192 varones y 196 mujeres. En el medio urbano por 172 varones y 220 mujeres.IntervencionesCada persona era entrevistada en su domicilio o en el centro de salud según sus preferencias mediante cuestionario, previamente sometido a estudio de estabilidad en las respuestas mediante coeficiente kappa test-retest. Efectuamos cribado de deterioro cognitivo mediante test de Pfeiffer.Resultados principalesCaminan menos de media hora al día en el medio rural un 43,6% (IC, 38,6-48,7) de los ancianos y el 34,4% (IC, 29,8-39,4) en el medio urbano. En el caso de los varones, un 24,7% (IC, 20,4-29,6) y en las mujeres el 51,4% (IC, 46,5-56,3). Las diferencias son significativas en ambos casos. No tienen aficiones en el medio rural un 12,1% (IC, 9,1-15,9) de los ancianos y el 9,4% (IC, 6,8-12,9) en el urbano. En el caso de los varones, un 11,3% (8,3-15,1) y el 10,1% (IC, 7,5-13,5) en las mujeres. No existen diferencias significativas.ConclusionesEs necesario fomentar las actividades de ocio-tiempo libre, pero sobre todo el paseo diario superior a media hora en las personas mayores de 65 años de la provincia de Guadalajara.ObjectiveTo find out what elderly people in the province of Guadalajara do in their leisure/free time and daily walking, in the supposition that these can be improved.DesignThis was a descriptive, crossover study based on a population-group.SettingAt community level, in the primary care context.ParticipantsPeople over 65 without cognitive deterioration and resident in the community, selected at random on the basis of population data bases. The sample finally studied was made up of 192 men and 196 women from the country-side, and 172 men and 220 women from an urban background.InterventionsEveryone was interviewed at home or the health centre according to their preferences through a questionnaire, which had undergone a stability study of the replies beforehand through the kappa test-retest coefficient. We screened cognitive deterioration through the Pfeiffer test.Main resultsIn the country, 43.6% of elderly people (CI: 38.6-48.7) walked under half an hour a day; in the urban context, 34.4% (CI: 29.8-39.4) did so. 24.7% of men (CI: 20.4-29.6) did so; and 51.4% of women (CI: 46.5-56.3). The differences were significant in the two cases. 12.1% (CI: 9.1-15.9) of elderly people in the country had no hobbies, and 9.4% (CI: 6.8-12.9) in the town. Among men and women, this broke down as 11.3% (CI: 8.3-15.1) and 10.1% (CI: 7.5-13.5), respectively. There were no significant differences.ConclusionsLeisure and free time activities among people over 65 in the province of Guadalajara must be fostered; but above all a daily walk for over half an hour must be encouraged

Pair-breaking quantum phase transition in superconducting nanowires

A quantum phase transition (QPT) between distinct ground states of matter is a wide-spread phenomenon in nature, yet there are only a few experimentally accessible systems where the microscopic mechanism of the transition can be tested and understood. These cases are unique and form the experimentally established foundation for our understanding of quantum critical phenomena. Here we report the discovery that a magnetic-field-driven QPT in superconducting nanowires - a prototypical 1d-system - can be fully explained by the critical theory of pair-breaking transitions characterized by a correlation length exponent $\nu \approx 1$ and dynamic critical exponent $z \approx 2$. We find that in the quantum critical regime, the electrical conductivity is in agreement with a theoretically predicted scaling function and, moreover, that the theory quantitatively describes the dependence of conductivity on the critical temperature, field magnitude and orientation, nanowire cross sectional area, and microscopic parameters of the nanowire material. At the critical field, the conductivity follows a $T^{(d-2)/z}$ dependence predicted by phenomenological scaling theories and more recently obtained within a holographic framework. Our work uncovers the microscopic processes governing the transition: The pair-breaking effect of the magnetic field on interacting Cooper pairs overdamped by their coupling to electronic degrees of freedom. It also reveals the universal character of continuous quantum phase transitions.Comment: 22 pages, 5 figure

Arresting bubble coarsening: A two-bubble experiment to investigate grain growth in presence of surface elasticity

Many two-phase materials suffer from grain-growth due to the energy cost which is associated with the interface that separates both phases. While our understanding of the driving forces and the dynamics of grain growth in different materials is well advanced by now, current research efforts address the question of how this process may be slowed down, or, ideally, arrested. We use a model system of two bubbles to explore how the presence of a finite surface elasticity may interfere with the coarsening process and the final grain size distribution. Combining experiments and modelling in the analysis of the evolution of two bubbles, we show that clear relationships can be predicted between the surface tension, the surface elasticity and the initial/final size ratio of the bubbles. We rationalise these relationships by the introduction of a modified Gibbs criterion. Besides their general interest, the present results have direct implications for our understanding of foam stability

Tonic-clonic seizures as a possible complication for cerebrospinal fluid leakage after intradural spinal surgery, a case report

Abstract Background Cerebrospinal fluid leakage is a well-known spinal surgery complication, especially in adults population. Pseudomeningocele is its most common manifestation and it can bring to some conditions, such as intracranial hypotension, infections and wound healing complication. Epilepsy is not classically associated to CSF leakage. We described a case of a female patient who developed tonic-clonic seizures associated with a pseudomeningocele after a detethering surgery. Case description A 16 year old female was admitted to our department for surgical treatment of a tethered cord for a sacral lipoma. Her medical history was remarkable mental retardation with psychiatric disturbs and hypothyroidism. She underwent a surgical intervention for the detethering of conus and dura was closed by a suture and fibrin glue. During third postoperative day she started to suffer a severe occipital headache, followed by tonic-clonic seizures. During suture removal, a collection suspected for a pseudomeningocele was found and chemical and radiological exams confirmed the dubious. Despite a continuous bed rest, collection continued to form. So, we decided to perform a surgical revision and to close dural defect. After intervention, patient did not suffer postural headache anymore and after 3 and 6 months she was found in good health. Conclusion We described the importance of significant morbidity, i.e. that of tonic clonic seizures as a sign of an occult CSF leakage after spinal surgery. Here, hydrocephalus as a condition was present, the change in pressure of CSF can determine seizures as well as promote this complication. A pseudomeningocele is not a trivial complication

Optical Interferometry of early-type stars with PAVO@CHARA. I. Fundamental stellar properties

We present interferometric observations of 7 main-sequence and 3 giant stars with spectral types from B2 to F6 using the PAVO beam combiner at the CHARA array. We have directly determined the angular diameters for these objects with an average precision of 2.3%. We have also computed bolometric fluxes using available photometry in the visible and infrared wavelengths, as well as space-based ultraviolet spectroscopy. Combined with precise \textit{Hipparcos} parallaxes, we have derived a set of fundamental stellar properties including linear radius, luminosity and effective temperature. Fitting the latter to computed isochrone models, we have inferred masses and ages of the stars. The effective temperatures obtained are in good agreement (at a 3% level) with nearly-independent temperature estimations from spectroscopy. They validate recent sixth-order polynomial (B-V)-$T_\mathrm{eff}$ empirical relations \citep{Boyajian2012a}, but suggest that a more conservative third-order solution \citep{vanBelle2009} could adequately describe the (V-K)-$T_\mathrm{eff}$ relation for main-sequence stars of spectral type A0 and later. Finally, we have compared mass values obtained combining surface gravity with inferred stellar radius (\textit{gravity mass}) and as a result of the comparison of computed luminosity and temperature values with stellar evolutionary models (\textit{isochrone mass}). The strong discrepancy between isochrone and gravity mass obtained for one of the observed stars, $\gamma$\,Lyr, suggests that determination of the stellar atmosphere parameters should be revised.Comment: 13 pages, 9 figures, accepted for publication in MNRA