Basin entropy as an indicator of a bifurcation in a time-delayed system.

The basin entropy is a measure that quantifies, in a system that has two or more attractors, the predictability of a final state, as a function of the initial conditions. While the basin entropy has been demonstrated on a variety of multistable dynamical systems, to the best of our knowledge, it has not yet been tested in systems with a time delay, whose phase space is infinite dimensional because the initial conditions are functions defined in a time interval [-τ,0], where τ is the delay time. Here, we consider a simple time-delayed system consisting of a bistable system with a linear delayed feedback term. We show that the basin entropy captures relevant properties of the basins of attraction of the two coexisting attractors. Moreover, we show that the basin entropy can give an indication of the proximity of a Hopf bifurcation, but fails to capture the proximity of a pitchfork bifurcation. The Hopf bifurcation is detected because before the fixed points become unstable, a oscillatory, limit-cycle behavior appears that coexists with the fixed points. The new limit cycle modifies the structure of the basins of attraction, and this change is captured by basin entropy that reaches a maximum before the Hopf bifurcation. In contrast, the pitchfork bifurcation is not detected because the basins of attraction do not change as the bifurcation is approached. Our results suggest that the basin entropy can yield useful insights into the long-term predictability of time-delayed systems, which often have coexisting attractors.

Bifurcations, relaxation time, and critical exponents in a dissipative or conservative Fermi model.

We investigated the time evolution for the stationary state at different bifurcations of a dissipative version of the Fermi-Ulam accelerator model. For local bifurcations, as period-doubling bifurcations, the convergence to the inactive state is made using a homogeneous and generalized function at the bifurcation parameter. It leads to a set of three critical exponents that are universal for such bifurcation. Near bifurcation, an exponential decay describes convergence whose relaxation time is characterized by a power law. For global bifurcation, as noticed for a boundary crisis, where a chaotic transient suddenly replaces a chaotic attractor after a tiny change of control parameters, the survival probability is described by an exponential decay whose transient time is given by a power law.

Development and decay of vortex flows in viscoelastic fluids between concentric cylinders.

We study the development and decay of vortex in viscoelastic fluids between coaxial cylinders by means of experiments with solutions of polyacrylamide and glycerin and numerical simulations. The transient process is triggered when the inner cylinder is either abruptly started or stopped while the outer is kept fixed. The azimuthal velocity, obtained by means of digital particle velocimetry, exhibits oscillations before reaching the stationary state. The development of the vortex is characterized by means of the overshoot, i.e. the difference between the maximum and the stationary velocity. Analogously, in the decay of the vortex, the azimuthal velocity changes its direction and the relevant parameter is the undershoot defined as the maximum reversed transient velocity. To get a deeper insight into this phenomenon, the experimental results are supplemented with numerical simulations of rheological models as the Oldroyd-B and White-Metzer. The results obtained with the first model reveal the dependence of the overshoot and undershoot with the elasticity number of the fluid. Using the White-Metzer model we explain the increase of the overshoot produced by the reduction of the solvent viscosity in terms of the shear-thinning effects.

Small-worldness favours network inference in synthetic neural networks.

A main goal in the analysis of a complex system is to infer its underlying network structure from time-series observations of its behaviour. The inference process is often done by using bi-variate similarity measures, such as the cross-correlation (CC) or mutual information (MI), however, the main factors favouring or hindering its success are still puzzling. Here, we use synthetic neuron models in order to reveal the main topological properties that frustrate or facilitate inferring the underlying network from CC measurements. Specifically, we use pulse-coupled Izhikevich neurons connected as in the Caenorhabditis elegans neural networks as well as in networks with similar randomness and small-worldness. We analyse the effectiveness and robustness of the inference process under different observations and collective dynamics, contrasting the results obtained from using membrane potentials and inter-spike interval time-series. We find that overall, small-worldness favours network inference and degree heterogeneity hinders it. In particular, success rates in C. elegans networks - that combine small-world properties with degree heterogeneity - are closer to success rates in Erdös-Rényi network models rather than those in Watts-Strogatz network models. These results are relevant to understand better the relationship between topological properties and function in different neural networks.

Identification of biomedical journals in Spain and Latin America.

OBJECTIVES: Journals in languages other than English that publish original clinical research are often not well covered in the main biomedical databases and therefore often not included in systematic reviews. This study aimed to identify Spanish language biomedical journals from Spain and Latin America and to describe their main features. METHODS: Journals were identified in electronic databases, publishers' catalogues and local registries. Eligibility was determined by assessing data from these sources or the journals' websites, when available. FINDINGS: A total of 2457 journals were initially identified; 1498 met inclusion criteria. Spain (27.3%), Mexico (16.0%), Argentina (15.1%) and Chile (11.9%) had the highest number of journals. Most (85.8%) are currently active; 87.8% have an ISSN. The median and mean length of publication were 22 and 29 years, respectively. A total of 66.0% were indexed in at least one database; 3.0% had an impact factor in 2012. A total of 845 journals had websites (56.4%), of which 700 (82.8%) were searchable and 681 (80.6%) free of charge. CONCLUSIONS: Most of the identified journals have no impact factor or are not indexed in any of the major databases. The list of identified biomedical journals can be a useful resource when conducting hand searching activities and identifying clinical trials that otherwise would not be retrieved.

Organization and identification of solutions in the time-delayed Mackey-Glass model.

Multistability in the long term dynamics of the Mackey-Glass (MG) delayed model is analyzed by using an electronic circuit capable of controlling the initial conditions. The system's phase-space is explored by varying the parameter values of two families of initial functions. The evolution equation of the electronic circuit is derived and it is shown that, in the continuous limit, it exactly corresponds to the MG model. In practice, when using a finite set of capacitors, an excellent agreement between the experimental observations and the numerical simulations is manifested. As the delay is increased, different periodic or aperiodic solutions appear. We observe abundant periodic solutions that have the same period but a different alternation of peaks of dissimilar amplitudes and propose a novel symbolic method to classify these solutions.

Antiperiodic oscillations.

The investigation of regular and irregular patterns in nonlinear oscillators is an outstanding problem in physics and in all natural sciences. In general, regularity is understood as tantamount to periodicity. However, there is now a flurry of works proving the existence of "antiperiodicity", an unfamiliar type of regularity. Here we report the experimental observation and numerical corroboration of antiperiodic oscillations. In contrast to the isolated solutions presently known, we report infinite hierarchies of antiperiodic waveforms that can be tuned continuously and that form wide spiral-shaped stability phases in the control parameter plane. The waveform complexity increases towards the focal point common to all spirals, a key hub interconnecting them all.

Inferring long memory processes in the climate network via ordinal pattern analysis.

We use ordinal patterns and symbolic analysis to construct global climate networks and uncover long- and short-term memory processes. Data analyzed are the monthly averaged surface air temperature (SAT field), and the results suggest that the time variability of the SAT field is determined by patterns of oscillatory behavior that repeat from time to time, with a periodicity related to intraseasonal oscillations and to El Niño on seasonal-to-interannual time scales.

Experimental results on synchronization times and stable states in locally coupled light-controlled oscillators.

Recently, a new kind of optically coupled oscillators that behave as relaxation oscillators has been studied experimentally in the case of local coupling. Even though numerical results exist, there are no references about experimental studies concerning the synchronization times with local coupling. In this paper, we study both experimentally and numerically a system of coupled oscillators in different configurations, including local coupling. Synchronization times are quantified as a function of the initial conditions and the coupling strength. For each configuration, the number of stable states is determined varying the different parameters that characterize each oscillator. Experimental results are compared with numerical simulations.

Asociación entre prematuridad y embarazadas en edad avanzada / Asociation between prematurity and old age pregnant women

Determinar la asociación entre la prematuridad y embarazadas con edad mayor o igual a 35 años. La muestra fue de 1 863 embarazadas (Casos: 620, Controles: 1 243). La variable de exposición fue edad > 35 años y lade resultado prematuridad ( gestación < 37 semanas, según la OMS):Para determinar el modelo parsimonioso se utilizó la prueba de máxima de verosimilitud. Ciudad Hospitalaria "Dr Enrique Tejera" y Maternidad del Sur, valencia. Resultados: La evaluación cruda de la asoción mostro un odds ratio (OR) de 2,07 (IC95 por ciento = 1,6 a 2,6 P = 0,0001). La multiparidad condicionó modificación del efecto. la embarazada añosa nulípara tiene incremento de riesgo de prematuridad (OR = 4,5; IC95 por ciento = 1,3 a 15,5 P = 0,01). Por el contrario, en la añosa multípara, la asociasión noi es estadísticamente significativa (OR = 1,3; IC95 por ciento = 0,8 a 2,1 P = 0,1). El embarazo en las mujeres añosas aumenta el riesgo de parto prematuro y este riesgo se incrementa si la mujer es primigesta

Bajo peso al nacer: importancia / Low birth weight: importance

Conocer las características maternas y perinatales del recién nacido de bajo peso y hacer sugerencias para una mejor atención. Departamento de Obstetricia y ginecología, Hospital "Dr. Adolfo Prince Lara", Puerto Cabello. Estudio descriptivo, retrospectivo, epidemiológico de 365 recién nacidos de bajo peso (menor de 2500 g), sucedidos durante los años 2003-2005. De un total de 7940 nacidos vivos, durante el trienio la incidencia fue 4,59 por ciento. Las pacientes son 90,48 por ciento no casadas, 23,81 por ciento de 19 años o menos, 50,71 por ciento no controló el embarazo. En antecedentes familiares: hipertensión 40,89 por ciento y diabetes 26,11 por ciento personales: aborto 37,41 por ciento y cesárea previa 31,71 por ciento. Diagnóstico de ingreso: trabajo de parto 47,9 por ciento, cesárea previa 14,6 por ciento (52/357), la rotura prematura de membrana 13,72 por ciento. El 58.98 por ciento son multigestas, el 50.42 por ciento preterminó, parto vaginal 61,9 por ciento fueron neonatos femeninos 59,08 por ciento, el peso entre 2000 y 2500 g 61,92 por ciento y la talla de 45-49 cm 46.02 por ciento (168/356); globalmente tuvieron índice Apgar 6 o menos el 78,03 por ciento. La morbilidad global fue 29,31 por ciento; la mortalidad perinatal global fue 26,3 por ciento, la fetal 14,79 por ciento y neonatal 11,5 por ciento. El síndrome de dificultad respiratoria y la sepsis fueron las patologías preponderantes. Los neonatos de bajo peso presentan una elevada morbimortalidad perinatal, representada principalmente por problemática respiratoria y la sepsis. Debemos insistir en una atención prenatal y perinatal intensiva

Amenaza de parto prematuro e infección urinaria / Urinary infection and premature birth threat

Estudiar la incidencia de infecciones urinarias en las amenazas de parto prematuro. Investigación descriptiva, epidemiológica, en 497 amenazas de parto prematuro, a 428 se realizó examen de orina, de estas 294 (68,69 por ciento) reportaron infección urinaria, grupo estudio, periodo diciembre 2001 - diciembre 2004. Departamento de Obstetricia y Ginecología. Hospital "Dr. Adolfo Prince Lara", Puerto Cabello, Estado Carabobo. Incidencia de infección urinaria en la amenaza de parto prematuro fue 68,69 por ciento (294/298). Aspectos clínicos predominantes: embarazos entre 29 y 36 semanas 68,37 por ciento (201/294), antecedente de infección urinaria 64,63 por ciento (190/294) y sintomatología urinaria presente 82,31 por ciento (242/294). Urocultivo a 206 casos del grupo estudio 70,06 por ciento (206/294), resultado positivo 66,99 por ciento (138/206). Germen frecuente escherichia coli 79,71 por ciento (110/138), sensibilidad a la ampicilina 34,41 por ciento (53/138) y cefalosporina 31,88 por ciento (44/138). Las amenazas de parto prematuro tienen estrecha relación con las infecciones urinarias, tratarlas adecuadamente permite disminuir sus consecuencias

Chaos-induced coherence in two independent food chains.

Coherence evolution of two food web models can be obtained under the stirring effect of chaotic advection. Each food web model sustains a three-level trophic system composed of interacting predators, consumers, and vegetation. These populations compete for a common limiting resource in open flows with chaotic advection dynamics. Here we show that two species (the top predators) of different colonies chaotically advected by a jetlike flow can synchronize their evolution even without migration interaction. The evolution is characterized as a phase synchronization. The phase differences (determined through the Hilbert transform) of the variables representing those species show a coherent evolution.

La Revisión sistemática en hematología / Systematic reviews in hematology

La revisión sistemática es un diseño epidemiológico observacional de carácter retrospectivo que se encarga de seleccionar, analizar y resumir estudios primarios para responder una pregunta de investigación. La revisión sistemática estrecha los vínculos entre la mejor evidencia científica y la gestión sanitaria óptima. En la era de la medicina basada en la evidencia, la revisión sistemática es la fuente para el incremento de la eficiencia de la práctica clínica. a través de una revisión sistemática Cochrane, se esbozan las diferentes etapas que conducen a su desarrollo.

Steady-state stabilization due to random delays in maps with self-feedback loops and in globally delayed-coupled maps.

We study the stability of the fixed-point solution of an array of mutually coupled logistic maps, focusing on the influence of the delay times, , of the interaction between the and maps. Two of us recently reported [Phys. Rev. Lett. 94, 134102 (2005)] that if are random enough, the array synchronizes in a spatially homogeneous steady state. Here we study this behavior by comparing the dynamics of a map of an array of delayed-coupled maps with the dynamics of a map with self-feedback delayed loops. If is sufficiently large, the dynamics of a map of the array is similar to the dynamics of a map with self-feedback loops with the same delay times. Several delayed loops stabilize the fixed point, when the delays are not the same; however, the distribution of delays plays a key role; if the delays are all odd a periodic orbit (and not the fixed point) is stabilized. We present a linear stability analysis and apply some mathematical theorems that explain the numerical results.

Association between prematury and maternal anemia in Venezuelan pregnant women during third trimester at labor

El objetivo de este estudio fue determinar la asociación y su magnitud entre prematuridad y anemia materna al final del tercer trimestre del embarazo (en el momento del trabajo de parto). Estudio de Casos de Controles (2 controles por caso). Entre mayo y diciembre de 1996 fueron estudiadas 543 embarazadas al final del tercer trimestre gestacional y en trabajo de parto. Los casos fueron 181. La anemia fue definida como la presencia de Hb< de 11g/dL(OMS). Los datos fueron analizados mediante regresión logística. Para evaluar la significancia de los modelos reducidos se utilizó la prueba de razón verosimilitud. Se determinó que la prematuridad está asociada significativamente con anemia materna (OR: 1.70 IC95 por ciento = 1,18 a 2,57,p = 001), después de ajustar por desprendimiento placentario, ruptura prematura de membranas-RPM-partos prematuros previos, menos de 5 visitas prenatales y sangramiento uterino en más de un trimestre. La anemia materna al final del tercer trimestre está asociada con un mayor riesgo de prematuridad

Consecuencias de un reporte sobre interacciones medicamentosas en una emergencia hospitalaria / Consequences of a report on drug interactions in an emergency departament

En 1991 reportamos las interaciones medicamentosas encontradas en las historias clínicas de una Emergencia Hospitalaria. Dos años después evaluamos nuevamente las indicaciones hechas en esa misma Emergencia. No hubo diferencias con el grupo anterior en relación a sexo, edad y número de drogas administradas por pacientes. Hubo en cambio, disminución significativa en el porcentaje de interaciones importantes, así como en el promedio de interacciones por paciente y el de interacciones importantes por paciente. Entre los medicamentos más usados los antiácidos ocuparon un segundo lugar con 36 por ciento y la Ranitidina el noveno con 16 por ciento . La cimetidina desapareció entre los diez más usados. En los casos en que se indicó antiácidos o Ranitidina hubo interaciones en el 54 y 25 por ciento respectivamente, pero estas no fueron significativas. Los resultados de este nuevo análisis señalan una disminución significativa de las interacciones medicamentosas mostrando así que la educación continua permite indicar la terapia más adecuada a cada paciente

Controlled release of theophylline from inert matrices: effect of channeling material on release rate

Sustained release theophylline tablets containing stearic acid wax and lactose fast flo as chanelling agent were prepared and evaluated. The fusion technique was used for dispersing the drug in the different levels of stearic acid. The release rate of theophylline from the prepared tablets increased with the increase of the level of the channeling material in the formula. The drug release from tablets containing high level of wax (30 and 60 per cent ) and low level of channeling material (59 per cent and 29 per cent ) followed the diffusion controlled model for inert porous matrix. The drug release increased significantly with the increase of lactose fast flow level in the formula. After 2 hours of testing dissolution, the tablets start to erode and the mechanism of drug release deviate from the diffusion controlled model. The mechanism of drug release was dependent on the level of the channeling material in the matrix

Principales interacciones medicamentosas en una emergencia hospitalaria: análisis de 100 casos / Main drug interactions at hospital: emergency department analysis of 100 cases

Revisamos prospectivamente las historias clínicas de 100 pacientes consecutivos que ingresaron por emergencia de un hospital general el primer tremestre de 1991, para determinar fármacos más frecuentemente usados y sus interacciones utilizando un programa computarizado (Drug Interaction Program) haciendo énfasis en medicamentos antiulcerosos. El número de drogas indicada por pacientes fue 4.29 ñ 1.39. Los antiácidos (39%) y la cimetidina (35%) ocuparon el tercero y cuarto lugar. Hubo interaciones en 79 pacientes y en 66 (84%) fueron importantes, promediandose 2.44 ñ 2.13 interacciones por paciente. Los antiácidos y la cimetidina fueron igualmente indicados, de 35 pacientes que recibieron cimetidina 3 (8.5%) tenían indicación primaria de su uso (Hemorragia Digestiva). La interacción clínica de la cimetidina con otros medicamentos es analizada. Nuestros resultados indican que las interacciones medicamentosas son un riesgo permanente en nuestros hospitales. Sugerimos la utilización de un programa computarizado de interacciones medicamentosas o una tabla actualizada de medicamentos en las emergencias de nuestros hospitales