Quenching of oscillations via attenuated coupling for dissimilar electrochemical systems.

The coupled dynamics of two similar and disparate electrochemical cells oscillators are analyzed. For the similar case, the cells are intentionally operated at different system parameters such that they exhibit distinct oscillatory dynamics ranging from periodic to chaotic. It is observed that when such systems are subjected to an attenuated coupling, implemented bidirectionally, they undergo a mutual quenching of oscillations. The same holds true for the configuration wherein two entirely different electrochemical cells are coupled via bidirectional attenuated coupling. Therefore, the attenuated coupling protocol seems to be universally efficient in achieving oscillation suppression in coupled oscillators (similar or heterogeneous oscillators). The experimental observations were verified by numerical simulations using appropriate electrodissolution model systems. Our results indicate that quenching of oscillations via attenuated coupling is robust and therefore could be ubiquitous in coupled systems with a large spatial separation prone to transmission losses.

Independent-noise provoked spiking, synchronized via coupling.

We report experimental and numerical evidence of synchronized spiking phenomena provoked by the interaction of two bidirectionally coupled electrochemical systems subjected to independent stochastic input signals. To this end, the anodic potentials of two such systems were diffusively coupled. The corresponding anodic currents of these systems exhibited excitable fixed point behavior in the vicinity of a homoclinic bifurcation. Following this, the anodic potentials were perturbed by independent noise signals. The invoked oscillatory dynamics are analyzed using normalized variance and cross-correlation coefficient. By systematically varying the coupling strength between the systems and the level of external noise, regions exhibiting synchronized spiking behavior were identified.

Entrainment of aperiodic and periodic oscillations in the Mercury Beating Heart system using external periodic forcing.

We report experimental results indicating entrainment of aperiodic and periodic oscillatory dynamics in the Mercury Beating Heart (MBH) system under the influence of superimposed periodic forcing. Aperiodic oscillations in MBH were controlled to generate stable topological modes, namely, circle, ellipse, and triangle, evolving in a periodic fashion at different parameters of the forcing signal. These periodic dynamics show 1:1 entrainment for circular and elliptical modes, and additionally the controlled system exhibits 1:2 entrainment for elliptical and triangular modes at a different set of parameters. The external periodic forcing of the periodic MBH system reveals the existence of domains of entrainment (1:1, 1:2, 1:3, and 1:4) represented in the Arnold tongue structures. Moreover, Devil's staircase is obtained when the amplitude-frequency space of parameters of the applied signal is scanned.

[Pluripotent stem cells on cell therapy]. / Las células troncales pluripotenciales en la terapia celular.

Induced pluripotent stem (iPS) cells are a novel stem cell population derived from human somatic cells through reprogramming using a set of transcription factors. These iPS cells were shown to share the characteristics of embryonic stem cells, including the ability to give rise to differentiated cells of every tissue type of the body. In the shorter term, iPS cells will be useful for creating patient-identical disease model cells in which the pathological process can be studied and drugs can be tested. Despite critical attitudes, accumulating preclinical evidence supports the effectiveness of iPSC-based cell therapy on the selection of appropriate iPSC clones. The production of iPS cells has also spurred the development of other techniques, for example, transdifferentiation by researchers can now convert heart fibroblasts directly in vivo into myocytes by similar methods. This pluripotent cells is indeed of great value in medical research and it is opening new possibilities in cell therapy.

Preoperative levosimendan. A new way for organoprotection.

Preoperative use of levosimendan in cardiac surgery patients is one of the most attractive therapeutic alternatives in subjects with left or right ventricular dysfunction. Our review explores the pharmacological bases and clinical evidence for the use of levosimendan, with the intention of making a series of recommendations regarding its use in preoperative optimization prior to cardiac surgery. We carried out a survey of 102 Spanish anesthesiologists in order to shed light on the grey areas regarding the use of this drug prior to surgery. Our findings suggest that levosimendan is recommended for patients with severe left or right ventricular dysfunction, moderate left ventricular dysfunction in which Intra-aortic Balloon Counterpulsation (IABC) is necessary and severe pulmonary hypertension. Administration of levosimendan prior to surgical cardiac intervention without an initial bolus reduces the likelihood of complications.

Phase-flip transition in coupled electrochemical cells.

Time delay is introduced in the coupling between a pair of electrochemical cells. As coupling parameters are varied, the anodic current in the two cells oscillate in synchrony in regimes of periodic as well as chaotic dynamics. When the time delay is varied a phase-flip transition is observed: the relative phase between the synchronized oscillations changes abruptly by pi . This is accompanied by an experimentally measurable discontinuous change in the frequency of the synchronized oscillators.

Response to budesonide among atopic and non-atopic infants/preschoolers with recurrent wheezing.

BACKGROUND: The treatment in non-atopic young children with recurrent wheezing remains controversial. OBJECTIVE: The aim of the study was to compare the response of inhaled budesonide in atopic versus non-atopic infants/preschoolers with recurrent wheezing (more than three episodes in the last year or one episode per month in the last three months). METHODS: One hundred and seventy three infants/preschoolers (mean age 1.58+/-0.9 yrs) with recurrent wheezing without previous use of inhaled corticosteroids were enrolled and divided into two categories: atopics (eosinophils in peripheral blood > or =4%) and non-atopics (<4%). Both groups were treated with budesonide (200 mcg bid delivered by MDI and spacer) for three months. The primary outcome was the prevalence of wheezing exacerbation episodes at the end of the treatment. RESULTS: Thirty-seven out of 173 (21.4%) were atopics and they were significantly younger, more frequently with a father with asthma, maternal grandparents with asthma and rhinitis, paternal and maternal grandparents with eczema, and higher number of wheezing episodes in the last year than non-atopics. At the end of the study, among those with good compliance (>70% of the weekly doses), the proportion of wheezing episodes were similar among atopics and non-atopics (57.7% vs. 44.1%, p=0.25, respectively); the number of exacerbations requiring emergency department (ED) visits and hospital admission were also similar. CONCLUSION: Regular budesonide therapy may decrease the episodes of wheezing in infants/preschoolers with recurrent wheezing, independently of atopy.

Ulnar variance and scaphoid fracture.

Between 1997 and 2006, radiographs of 66 scaphoid fractures were retrospectively reviewed to evaluate ulnar variance. Twenty-one (31.8%) patients had an 'ulna neutral' wrist, six (9.1%) had an 'ulna plus' and 39 (59.1%) had an 'ulna minus' wrist. The mean ulnar variance was -1.3 (SD 1.8) mm (range -5.5, 2.5). We observed a significant difference in the distribution of ulnar variance (P < 0.00001) and in the proportion of cases with ulna minus (OR = 5.0; 95% CI: 2.7, 9.3) compared to previous publications.

Interaction of noise with excitable dynamics.

In this paper, the interaction of noise with excitable dynamics of a three-electrode electrochemical cell is examined. Different scenarios involving both external and internal noise sources are considered. In the case of external noise, aperiodic stochastic resonance and regulation of the noise-induced spiking behaviour are investigated. In the case of internal noise, the interaction of intrinsic electrochemical noise with autonomous nonlinear dynamics is studied. The amplitude of this internal noise, determined by the concentration of chloride ions, is monotonically increased and the provoked dynamics are analysed. Our results indicate that internal noise, similar to its external counterpart, is able to induce regularity in the system response.

Comparing the coherence resonance curves invoked by different types of forcing.

We study the different coherence resonance (CR) phenomena induced when an excitable FitzHugh-Nagumo-type system is forced using diverse deterministic and/or stochastic time series. The possible implications of this comparative study involving these different CR's are also discussed. The main result of the present work suggests that for appropriate forcing and system parameters the generated CR curves reflect the correlations of the superimposed time series.

Long-term results of tension-free vaginal tape (TVT) for the treatment of female urinary stress incontinence.

OBJECTIVES: Prospective evaluation of outcome and complications over a 5-year period post-treatment of urinary stress incontinence by TVT, and comparison of our results with the reference studies. MATERIALS AND METHODS: About 94 patients were treated for urinary stress incontinence only by one TVT procedure (single surgical procedure), between April 1997 and December 1998; 68% of patients presented pure urinary stress incontinence and 32% mixed incontinence. We found also a 25.5% rate of sphincter deficiency (UCP < 20 cm H(2)O) in this cohort. Patients were evaluated after 5 years: 52 complete evaluations (clinical, flow measurement with measurement of post-mictional residue, 24h PAD-test, quality of life questionnaire), 30 complete telephone interviews, 12 lost to follow-up (2 patients deceased). RESULTS: About 87% of the patients had a 5-year follow-up. The success rate was 79.2% overall (84.5% for the pure urinary stress incontinence and 67% for the mixed incontinence cases), and 72.2% for the cases of associated sphincter deficiency. We had only a 13% rate of patients lost to follow-up. More than half of the urinary urgency cases were treated successfully, however with a less satisfactory outcome in cases of bladder instability. The urodynamic exploration appeared to reveal that TVT caused dysuria: 52% of patients had a maximum flowrate below 15 ml/s, but the quality of life was improved, with a 95% rate of satisfaction without functional problems. We observed no late complications such as vaginal erosion or rejection of the prolene; the de novo syndrome was rare, with 8.5% of urinary frequency, 6% of urinary urgency and only 5.7% of invalidating dysuria. We saw no cases of pelvic floor disease after TVT treatment. DISCUSSION: Our casuistry results are comparable with the reference studies by Scandinavian authors, Rezapour and Ulmsten, confirming the long-term success of the TVT procedure. Concerning the apparently elevated rates of post-TVT dysuria found by urodynamic exploration, a distinction has to be drawn between post-TVT urinary problems (frequent but oligosymptomatic), and true, severe dysuria (rare). However, "dysuria" in the broad sense did not affect the patients' quality of life, and is a reminder of the absolute necessity of meticulous compliance with the correct surgical techniques. CONCLUSION: Treatment of urinary incontinence by TVT is a reliable, mini-invasive, reproducible technique, almost suitable for outpatients, with no serious complications; it is inexpensive and very successful, including in complicated cases such as sphincter deficiency. All the recent data confirms, with this 5-year follow-up, that the TVT procedure is comparable to the previously gold standard, the Burch colposuspension.

Regulating noise-induced spiking using feedback.

We report successful manipulation of the noise provoked spiking behavior using delayed feedback control. Experiments were performed in a three electrode electrochemical cell under potentiostatic conditions. The uncontrolled system exhibited noise invoked oscillations whose regularity was quantified using normalized variance (NV). Superimposing delayed feedback, for appropriate values of delay (t), an enhancement in the regularity of the spike sequence was attained. Numerical simulations corroborated experimental observations.

Parameter space reduction criteria to search for synchronization domains in coupled discrete systems.

Based on analytical considerations, we introduce criteria that enable us to encapsulate the parameter domains for which chaotic synchronization in linearly coupled map systems may be attained. Our aim is to provide means to readily determine parameter regions which preclude synchronization. This results in a significant reduction of parameter space that one needs to explore. Our findings hold for both identical and quasi-identical (small parameter mismatch) maps subjected to unidirectional and bidirectional coupling. As a testing ground we present numerical calculations for the logistic and cubic maps which validate the predictive capability of our approach. Our main contribution relies on the applicability of one of our criteria to experimental situations. Since in real life it is almost impossible to construct two truly identical systems, the results for quasi-identical maps are of particular relevance.

Noise-aided synchronization of coupled chaotic electrochemical oscillators.

We report experimental and numerical results on noise-enhanced synchronization of two coupled chaotic oscillators. Enhanced synchronization is achieved through superimposing small-amplitude Gaussian noise on a common system parameter of the two chaotic oscillators. A resonancelike behavior is found: at an optimum level of noise, maximum synchronization is attained. The simulations show that the resonance behavior occurs with both identical and nonidentical oscillators. Noncommon (asymmetric and independent) noise does not enhance synchronization; common noise seems to enhance synchronization.

Regulation of photosynthesis of C3 plants in response to progressive drought: stomatal conductance as a reference parameter.

We review the photosynthetic responses to drought in field-grown grapevines and other species. As in other plant species, the relationship between photosynthesis and leaf water potential and/or relative water content in field-grown grapevines depends on conditions during plant growth and measurements. However, when light-saturated stomatal conductance was used as the reference parameter to reflect drought intensity, a common response pattern was observed that was much less dependent on the species and conditions. Many photosynthetic parameters (e.g. electron transport rate, carboxylation efficiency, intrinsic water-use efficiency, respiration rate in the light, etc.) were also more strongly correlated with stomatal conductance than with water status itself. Moreover, steady-state chlorophyll fluorescence also showed a high dependency on stomatal conductance. This is discussed in terms of an integrated down-regulation of the whole photosynthetic process by CO2 availability in the mesophyll. A study with six Mediterranean shrubs revealed that, in spite of some marked interspecific differences, all followed the same pattern of dependence of photosynthetic processes on stomatal conductance, and this pattern was quite similar to that of grapevines. Further analysis of the available literature suggests that the above-mentioned pattern is general for C3 plants. Even though the patterns described do not necessarily imply a cause and effect relationship, they can help our understanding of the apparent contradictions concerning stomatal vs. non-stomatal limitations to photosynthesis under drought. The significance of these findings for the improvement of water-use efficiency of crops is discussed.

[The hemangioma-sternum bifidum malformation syndrome. Report of a patient]. / Espectro malformativo de hemangioma-esternón bífido. Reporte de un paciente.

We present a male patient with a facial haemangioma extending from the lower left lid to the malar region and the upper left lip. The patient also presents a 1 cm round cutaneous notch on the upper third of the sternum. There are not other physical anomalies. The characteristics of the clinical picture suggest the diagnosis of sternal cleft-haemangiomas malformative spectrum (OMIM 140850).

Numerical studies on the dynamics of the globally coupled maps with sequential updating

A system of globally coupled logistic maps with sequential updating is analyzed numerically. It is found that deterministic asynchronous updating schemes may have dramatical influences on the dynamical behaviors of globally coupled systems. Transitions from spatiotemporal chaos to spatially organized states are observed as the coupling parameter varies. It is shown that the model system may exhibit a variety of collective properties such as clustering, traveling wave patterns, and spatial bifurcation cascades.

Noise-aided control of chaotic dynamics in a logistic map

Controlling chaos involves employing small perturbations to a control parameter, resulting in the stabilization of the system (naturally chaotic) on one of the infinite unstable periodic orbits embedded in the chaotic attractor. In this Brief Report we study the constructive role of external noise in increasing the efficiency of controlling chaos. Using a logistic map as an example, control of chaotic dynamics is achieved using a linear delayed-feedback strategy. Working in the subthreshold regime of control (where the value of control constant is less than the minimum value required to stabilize the period-1 target state), system dynamics in the presence of superimposed noise (system plus control plus noise) exhibit a resonance effect. Furthermore it is observed that the time required to reach the target state decreases appreciably in the presence of an optimum level of noise.

Alternating chaotic and periodic dynamics in Chern-Simons-Higgs theory with scalar magnetic interaction.

The dynamical behavior of a Chern-Simons-Higgs system is studied for the spatially homogeneous case. The model, described by interacting gauge and scalar fields includes two parity and time violating terms: the Chern-Simons and the scalar magnetic interaction. For the pure Chern-Simons part of the theory the equations of motion are integrable. In general, however, the model system exhibits an interesting pattern of chaos to order transitions as the scalar magnetic moment is varied. The system dynamics are analyzed using a combination of standard techniques, such as phase space portraits, Lyapunov exponents, and Fourier spectra. (c) 2000 American Institute of Physics.