Comparación de métodos de reducción de dimensión basados en análisis por localidades

En este trabajo se realiza una comparación de las principales técnicas de reducción de dimensión no lineal basadas en análisis por localidades, tales como: Locally linear embedding, Isometric feature mapping y Maximum variance unfolding. El estudio pretende determinar, bajo criterios objetivos, cuál de las técnicas consideradas conserva de mejor manera las propiedades locales de la variedad, y la estructura global de los datos de entrada al realizar un mapeo a un espacio de menor dimensión. Los métodos son especialmente analizados en aplicaciones de visualización. Las inmersiones obtenidas son evaluadas por medio de dos criterios: Error de Conservación de Vecindarios y Promedio de Vecinos Conservados. Para la validación experimental se utilizan bases de datos artificiales y reales que permiten confirmar visualmente la calidad de las inmersiones obtenidas. Con base en los resultados se observa que la técnica Maximum variance unfolding presenta inmersiones de mejor calidad, debido a que la técnica de optimización de este algoritmo preserva exactamente las distancias entre puntos cercanos en el espacio de baja dimensión, conservando la estructura global de la variedad analizada.In this paper, a comparison of methods for nonlinear dimensionality reduction is proposed in order to determine which technique preserves better the local properties, without losing the overall structure of the original data. We seek to establish which of these methods is the most appropriate for visualization tasks. The embeddings obtained with each technique are evaluated by two criteria Preservation Neighborhood Error and Preserved Neighbors Average. The methodologies were tested on artificial and real-world data sets which allow us to visually confirm the quality of the embedding. The results obtained show that Maximum variance unfolding computes high quality embeddings, because the optimization problem pretends to preserve exactly the local pair-wise distance between neighbors and conserve the global manifold structure

Metodología para evaluar el difeomorfismo de un atractor caótico usando el filtro de kalman en señales fisiológicas

Para la caracterización de señales fisiológicas, las cuales contienen estructuras fuertemente no lineales, es común usar procedimientos derivados de técnicas fractales que hacen parte del análisis de complejidad. En este trabajo se propone una función de evaluación basada en el filtro de Kalman para predecir puntos de un atractor reconstruido en el espacio de estados y medir la capacidad de esos puntos para reconstruir la señal en el tiempo, y así, evaluar la calidad de ese atractor a partir de una señal unidimensional. Se propone el uso de medidas estadísticas como Kullback–Leibler, Kolmogorov–Smirnov y Hellinger para determinar a diferencia entre la estructura estadística embebida en los puntos que fueron resultado de la predicción usando el atractor reconstruido y los puntos correspondientes de la señal original.Los resultados fueron obtenidos sobre la reconstrucción de atractores provenientes de señales ECG usando la base de datos del MIT-BIH y señales EEG obtenidas en la Clínica para Epilepsia de la Universidad de Bonn. Así, fue posible evaluar la capacidad depredicción correspondiente a los atractores reconstruidos a partir de los registros, con lo que se puede concluir que un atractor con alta capacidad de predicción en el tiempo implica buenas propiedades de embebimiento en el espacio de estados.In order to characterize physiological signals, which may have highly nonlinear structures, it’s common to use methodologies derived from fractal techniques that make part of complexity analysis. This work proposes is proposed an evaluation function based on measuring the capacity of prediction of a neural network trained with Kalman filter to predict points in a reconstructed state space attractor, so measuring the quality of the attractor from a onedimensional signal. We propose use of statistic measures such as Kullback –Leibler, Kolmogorov-Smirnov and Hellinger to determine difference between the embedded statistic structure in the predicted points and the original signal points. Results were obtained on attractor reconstruction from ECG signals of MIT-BIH database and EEG signals obtained from Clinic for Epileptologie Epileptologie Bonn University database. In this way, it was possible to evaluate the prediction capacity corresponding to reconstruct attractors from records, from which we concluded that an attractor with high capacity of time series prediction implies good embedding properties in state space

Systemic lupus erythematosus and diffuse alveolar hemorrhage, etiology and novel treatment strategies.

Diffuse alveolar hemorrhage is a severe respiratory complication of systemic lupus erythematosus. The illness develops over hours to a few days and is the systemic lupus erythematosus-associated syndrome with highest mortality. Although no specific symptoms have been identified, a number of features are associated with diffuse alveolar hemorrhage, with a drop in blood hemoglobin the most prominent. Dyspnea, blood-stained sputum, diffuse infiltrates identified by chest imaging, elevated single breath-diffusing capacity for monoxide, thrombocytopenia and C3 hypocomplementemia are other commonly reported signs of diffuse alveolar hemorrhage. The etiology is not completely understood but many patients develop diffuse alveolar hemorrhage concomitant with lupus nephritis, suggesting immune complex-driven pathology. Biopsy studies have identified both cases with capillaritis and a bland non-inflammatory phenotype. An animal model of diffuse alveolar hemorrhage has indicated requirement of B lymphocytes and complement receptor-mediated apoptotic body phagocytosis by monocytes as part of the pathogenesis. This review will discuss considerations when diagnosing the condition and available therapies. Infections and other causes of hemorrhage have to be excluded as these require different treatment strategies. Methylprednisolone and cyclophosphamide remain the most commonly used therapies. Plasmapheresis and rituximab are other beneficial treatment options. A few studies have also considered intrapulmonary Factor VII therapy, extracorporeal membrane oxygenation and mesenchymal stem cell therapy. There is an unmet need of better definition of diffuse alveolar hemorrhages etiology and pathology for development of improved treatment strategies

Prevalence of beta hemolytic Streptococcus in patients with acute pharyngoamigdalitis in a Chachapoyas, Amazonas hospital

Introducción: En Chachapoyas hay numerosos pacientes con faringoamigdalitis aguda y cuadros clínicos con las complicaciones no supurativas que causa el Streptococcus pyogenes. Diseño: Estudio transversal. Lugar: Hospital I Higos Urco, EsSalud, Chachapoyas, Amazonas, e Instituto de Medicina Tropical Daniel A. Carrión, Universidad Nacional Mayor de San Marcos. Participantes: Pacientes con faringoamigdalitis aguda. Intervenciones: A 148 pacientes, seleccionados aleatoriamente, que acudieron al consultorio externo de otorrinolaringología por presentar cuadros clínicos compatibles con faringoamigdalitis aguda, se les tomó muestras de secreción faringoamigdaliana con hisopos y, usando el medio de transporte Amies con carbón (Difco), fueron enviados al Instituto de Medicina Tropical Daniel A. Carrión, en donde fueron procesados. Principales medidas de resultados: Presencia de Streptococcus beta hemolítico y otras bacterias cultivables. Resultados: Las enterobacterias fueron las más aisladas (49,1%) de los cultivos positivos. Solo 5 Streptococcus beta hemolíticos fueron aislados: un Streptococcus pyogenes, tres Streptococcus agalactiae y un Streptococcus del grupo G, los cuales fueron sensibles a los betalactámicos, macrólidos y lincosamidas. Conclusiones: Se sugiere realizar estudios complementarios con el dosaje de antiestreptolisina O.Introduction: There are numerous Chachapoyas patients with acute pharyngoamigdalitis and clinical non suppurative complications caused by Streptococcus pyogenes. Design: Transversal study. Setting: Hospital I Higos Urco, EsSalud, Chachapoyas, Amazonas, and Instituto de Medicina Tropical Daniel A. Carrion, Universidad Nacional Mayor de San Marcos. Participants: Patients with acute pharyngoamigdalitis. Interventions: One hundred and forty-eight randomized outpatient subjects attending an ear, nose and throat office for clinical symptoms compatible with acute pharyngoamigdalitis had a sample of pharynx and tonsils taken with a cotton swab and sent in Amies with carbon medium (Difco) to the Instituto de Medicina Tropical Daniel A. Carrion to be processed. Main outcome measures: Presence of beta hemolytic Streptococcus and other bacteriae. Results: Positive cultures revealed mainly Enterobacteriae (49,1%). Only 5 beta hemolytic Streptococcus were isolated: one Streptococcus pyogenes, three Streptococcus agalactiae and one group G Streptococcus, all sensitive to betalactamics, macrolides and lincosamides. Conclusions: We suggest to do complementary studies with antiestreptolysin O determination

Masses, radii, and orbits of small Kepler planets : The transition from gaseous to rocky planets

We report on the masses, sizes, and orbits of the planets orbiting 22 Kepler stars. There are 49 planet candidates around these stars, including 42 detected through transits and 7 revealed by precise Doppler measurements of the host stars. Based on an analysis of the Kepler brightness measurements, along with high-resolution imaging and spectroscopy, Doppler spectroscopy, and (for 11 stars) asteroseismology, we establish low false-positive probabilities (FPPs) for all of the transiting planets (41 of 42 have an FPP under 1%), and we constrain their sizes and masses. Most of the transiting planets are smaller than three times the size of Earth. For 16 planets, the Doppler signal was securely detected, providing a direct measurement of the planet's mass. For the other 26 planets we provide either marginal mass measurements or upper limits to their masses and densities; in many cases we can rule out a rocky composition. We identify six planets with densities above 5 g cm-3, suggesting a mostly rocky interior for them. Indeed, the only planets that are compatible with a purely rocky composition are smaller than 2 R ⊕. Larger planets evidently contain a larger fraction of low-density material (H, He, and H2O).Peer reviewedFinal Accepted Versio

How formation time-scales affect the period dependence of the transition between rocky super-Earths and gaseous sub-Neptunesand implications for η⊕

One of the most significant advances by NASA's ${\mathit Kepler}$ Mission was the discovery of an abundant new population of highly irradiated planets with sizes between the Earth and Neptune. Subsequent analysis showed that at ~1.5 Earth radii there is a transition from a population of predominantly rocky super-Earths to non-rocky sub-Neptunes, which must have substantial volatile envelopes. Determining the origin of these highly irradiated rocky planets will be critical to our understanding of low-mass planet formation and the frequency of potentially habitable Earth-like planets. These short-period rocky super-Earths could simply be the stripped cores of sub-Neptunes, which have lost their envelopes due to atmospheric photo-evaporation or other processes, or they might instead be a separate population of inherently rocky planets, which never had significant envelopes. Using models of atmospheric photo-evaporation, we show that if most bare rocky planets are the evaporated cores of sub-Neptunes then the transition radius should decrease as surveys push to longer orbital periods, since on wider orbits only planets with smaller less massive cores can be stripped. On the other hand, if most rocky planets formed after their disks dissipate then these planets will have formed without initial gaseous envelopes. In this case, we use N-body simulations of planet formation to show that the transition radius should increase with orbital period, due to the increasing solid mass available in their disks. Moreover, we show that distinguishing between these two scenarios should be possible in coming years with radial velocity follow-up of planets found by TESS. Finally, we discuss the broader implications of this work for current efforts to measure $\eta_{\mathrm{\oplus}}$, which may yield significant overestimates if most rocky planets form as evaporated cores.Comment: 8 pages, 4 figures, accepted for publication in the Monthly Notices of the Royal Astronomical Societ

The PLATO 2.0 mission

PLATO 2.0 has recently been selected for ESA's M3 launch opportunity (2022/24). Providing accurate key planet parameters (radius, mass, density and age) in statistical numbers, it addresses fundamental questions such as: How do planetary systems form and evolve? Are there other systems with planets like ours, including potentially habitable planets? The PLATO 2.0 instrument consists of 34 small aperture telescopes (32 with 25 s readout cadence and 2 with 2.5 s candence) providing a wide field-of-view (2232 deg 2) and a large photometric magnitude range (4-16 mag). It focusses on bright (4-11 mag) stars in wide fields to detect and characterize planets down to Earth-size by photometric transits, whose masses can then be determined by ground-based radial-velocity follow-up measurements. Asteroseismology will be performed for these bright stars to obtain highly accurate stellar parameters, including masses and ages. The combination of bright targets and asteroseismology results in high accuracy for the bulk planet parameters: 2 %, 4-10 % and 10 % for planet radii, masses and ages, respectively. The planned baseline observing strategy includes two long pointings (2-3 years) to detect and bulk characterize planets reaching into the habitable zone (HZ) of solar-like stars and an additional step-and-stare phase to cover in total about 50 % of the sky. PLATO 2.0 will observe up to 1,000,000 stars and detect and characterize hundreds of small planets, and thousands of planets in the Neptune to gas giant regime out to the HZ. It will therefore provide the first large-scale catalogue of bulk characterized planets with accurate radii, masses, mean densities and ages. This catalogue will include terrestrial planets at intermediate orbital distances, where surface temperatures are moderate. Coverage of this parameter range with statistical numbers of bulk characterized planets is unique to PLATO 2.0. The PLATO 2.0 catalogue allows us to e.g.: - complete our knowledge of planet diversity for low-mass objects, - correlate the planet mean density-orbital distance distribution with predictions from planet formation theories,- constrain the influence of planet migration and scattering on the architecture of multiple systems, and - specify how planet and system parameters change with host star characteristics, such as type, metallicity and age. The catalogue will allow us to study planets and planetary systems at different evolutionary phases. It will further provide a census for small, low-mass planets. This will serve to identify objects which retained their primordial hydrogen atmosphere and in general the typical characteristics of planets in such low-mass, low-density range. Planets detected by PLATO 2.0 will orbit bright stars and many of them will be targets for future atmosphere spectroscopy exploring their atmosphere. Furthermore, the mission has the potential to detect exomoons, planetary rings, binary and Trojan planets. The planetary science possible with PLATO 2.0 is complemented by its impact on stellar and galactic science via asteroseismology as well as light curves of all kinds of variable stars, together with observations of stellar clusters of different ages. This will allow us to improve stellar models and study stellar activity. A large number of well-known ages from red giant stars will probe the structure and evolution of our Galaxy. Asteroseismic ages of bright stars for different phases of stellar evolution allow calibrating stellar age-rotation relationships. Together with the results of ESA's Gaia mission, the results of PLATO 2.0 will provide a huge legacy to planetary, stellar and galactic science

Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

Background Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide.Methods A multimethods analysis was performed as part of the GlobalSurg 3 study-a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital.Findings Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3.85 [95% CI 2.58-5.75]; p<0.0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63.0% vs 82.7%; OR 0.35 [0.23-0.53]; p<0.0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer.Interpretation Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised

Outcomes from elective colorectal cancer surgery during the SARS-CoV-2 pandemic

This study aimed to describe the change in surgical practice and the impact of SARS-CoV-2 on mortality after surgical resection of colorectal cancer during the initial phases of the SARS-CoV-2 pandemic