Reducing Orbit Covariance for Continuous Thrust Spacecraft Transfers

The calculus of variations is used to develop the necessary theory and derive the optimality conditions for a spacecraft to transfer between a set of initial and final conditions, while minimizing a combination of fuel consumption and a function of the estimation error covariance matrix associated with the spacecraft state. The theory is developed in a general manner that allows for multiple observers, moving observers, covariance associated with an arbitrary frame, a wide variety of observation types, multiple gravity bodies, and uncertainties in the spacecraft equations of motion based on the thrusting status of the engine. A series of example trajectories from low Earth orbit (LEO) to a near geosynchronous Earth orbit (GEO) shows that either the trace of the covariance at the final time or the integral of the trace of the covariance matrix associated with the error in the Cartesian position and velocity can be reduced significantly with a small increase in the fuel consumption. An additional example illustrates the covariance associated with the semimajor axis can be significantly reduced for a transfer from Earth orbit to lunar orbit. This example illustrates multiple, moving observers as well as a transfer in a multi-body gravitational field

Observational epidemiological study to identify the clinical profile of naïve patients starting antiretroviral (ARV) therapy in Spain

Purpose of the study: To identify the proportion of patients starting ARV treatment with NNRTIs or with a PI/r and to explore and compare their clinical profile establishing different factors whereby physicians select the initial ARV treatment in a Spanish clinical setting. Methods: An observational study was conducted in two different phases. In Phase I a cross-sectional registration was conducted for patients who initiated ARV treatment in a 6-month period in 65 Spanish hospitals. In Phase II clinical and social-demographic features were collected retrospectively of patients who visited HIV clinics between August and November 2010 who had started ARV treatment containing an NNRTIs or a PI/r in Phase I. Summary of results: In Phase I, 1,687 subjects who initiated ARV treatment were registered, of which 53% started with an NNRTI-based regimen whereas 42% started with a PI/r-based regimen. Two percent of the treatment initiations occurred in a clinical trial. In Phase II, 642 patients were paired consecutively and retrospectively. The group of patients was composed of predominantly male subjects (81% vs 19%). The median time between diagnosis and the start of ARV treatment was 3.6±5.3 years. At the initiation of treatment, 72% of patients had a CD4 count below 350 cells/µl. Although treatment based on NNRTIs in naïve patients is the most frequent option in Spain, the analysis of clinical profiles shows that PI/r-based therapy is more often used than NNRTIs with statistical significance in patients with high viral load, Fig. A (≥100.000 copies/ml) (58% vs 42%; OR:1,75; 95% CI: 1,26–2,43; p<0,01), with CD4 cell counts <200 cells/µl, Fig. B (68% vs 31%; OR: 2,92; 95% CI: 1,99–4,27; p<0,01), and in patients at CDC stage C (65% vs 35%; OR: 2,05; CI: 1,27–3,31; p<0,01). Conclusions: In Spain, HIV is still diagnosed late (as measured by CD4 count<350 cells/µl). Treatment based on NNRTIs are more frequently used in naïve patients, although PIs/r-based regimens play an important role being the preferred option in patients with high viral load (≥100.000 copies/ml) and low CD4 cell count (<200 cells/µl)

Red Eye: Next Steps for Conducting Research in Knowledge, Attitude and Practice in Ophthalmology

Background: Research in Knowledge, Attitude and Practice (KAP) in health sciences is relevant to health care providers and patients to identify factors to address educational interventions.Methods: A pilot study based on surveys amongst participants in a medical update conference in Cali, Colombia, was conducted to estimate participants’ knowledge on red eye in 2011.Results: The population was composed of medical students and general practitioners, with 72.7% of students being in their final year of their training. The classification of red eye was correct in 47% of respondents and we found errors in the classification of emergency, glaucoma and uveitis.Conclusions: Further research proposals in KAP are required for the recognition of this medical education indicator

Binary Collisions and the Slingshot Effect

We derive the equations for the gravity assist manoeuvre in the general 2D case without the constraints of circular planetary orbits or widely different masses as assumed by Broucke, and obtain the slingshot conditions and maximum energy gain for arbitrary mass ratios of two colliding rigid bodies. Using the geometric view developed in an earlier paper by the authors the possible trajectories are computed for both attractive or repulsive interactions yielding a further insight on the slingshot mechanics and its parametrization. The general slingshot manoeuvre for arbitrary masses is explained as a particular case of the possible outcomes of attractive or repulsive binary collisions, and the correlation between asymptotic information and orbital parameters is obtained in general.Comment: 12 pages, 7 figures, accepted for publication Dec'07, Celestial Mechanics and Dynamical Astronom

A unified and automated approach to attractor reconstruction

We present a fully automated method for the optimal state space reconstruction from univariate and multivariate time series. The proposed methodology generalizes the time delay embedding procedure by unifying two promising ideas in a symbiotic fashion. Using non-uniform delays allows the successful reconstruction of systems inheriting different time scales. In contrast to the established methods, the minimization of an appropriate cost function determines the embedding dimension without using a threshold parameter. Moreover, the method is capable of detecting stochastic time series and, thus, can handle noise contaminated input without adjusting parameters. The superiority of the proposed method is shown on some paradigmatic models and experimental data from chaotic chemical oscillators.Deutsche Forschungsgemeinschafthttps://doi.org/10.13039/501100001659Peer Reviewe

A unified and automated approach to attractor reconstruction

We present a fully automated method for the optimal state space reconstruction from univariate and multivariate time series. The proposed methodology generalizes the time delay embedding procedure by unifying two promising ideas in a symbiotic fashion. Using non-uniform delays allows the successful reconstruction of systems inheriting different time scales. In contrast to the established methods, the minimization of an appropriate cost function determines the embedding dimension without using a threshold parameter. Moreover, the method is capable of detecting stochastic time series and, thus, can handle noise contaminated input without adjusting parameters. The superiority of the proposed method is shown on some paradigmatic models and experimental data from chaotic chemical oscillators

q-Deformed Superalgebras

The article deals with q-analogs of the three- and four-dimensional Euclidean superalgebra and the Poincare superalgebra.Comment: 38 pages, LateX, no figures, corrected typo

In Vitro Alpha-Amylase Inhibition by Paragis (Eleusine Indica (L.) Gaertn) Extract and Its Fractions

Plants are rich sources of potential hypoglycemic agents to control blood glucose. Since the antidiabetic studies on Eleusine Indica has not been widely explored, this study aimed to investigate the effect of crude ethanol extracts as well as acetone, ethyl acetate and aqueous fractions of E. Indica using an in vitro α-amylase assay (iodine method) and to determine the phytochemical profile of the plant sample using colorimetric qualitative tests. Crude ethanol extract of paragis was found to be the most potent α-amylase inhibitor among all plant samples with 96.56 ± 1.60 % inhibition at 100 µg/mL extract concentration, and is significantly higher (p<0.001, Tukey’s post-hoc test) than the acarbose standard with 79.56 ± 0.44 % inhibition at the same concentration. Qualitative tests showed that these samples contain phytochemicals such as glycosides, phenols, saponins, tannins, and terpenoids. Through this finding, it was postulated that synergistic effects of these phytochemicals may contribute to its hypoglycemic activity in vitro. Inhibition of α-amylase suggested that E. Indica has the potential to hinder glucose absorption in the small intestine. Statistical correlation with the 13C nuclear magnetic resonance phytochemical profile and the inhibition activity will be subject for future studies to identify the specific structural features of active compounds

Desempeño de las técnicas de agrupamiento para resolver el problema de ruteo con múltiples depósitos

El problema de ruteo de vehículos considerando múltiples depósitos es clasificado como NP duro, cuya solución busca determinar simultáneamente las rutas de un conjunto de vehículos, atendiendo un conjunto de clientes con una demanda determinada. La función objetivo del problema consiste en minimizar el total de la distancia recorrida por las rutas, teniendo en cuenta que todos los clientes deben ser atendidos cumpliendo restricciones de capacidad de depósitos y vehículos. En este artículo se propone una metodología híbrida que combina las técnicas aglomerativas de clusterización para generar soluciones iniciales con un algoritmo de búsqueda local iterada, iterated location search (ILS) para resolver el problema. Aunque en trabajos previos se proponen los métodos de clusterización como estrategias para generar soluciones de inicio, en este trabajo se potencia la búsqueda sobre el sistema de información obtenido después de aplicar el método de clusterización. Además se realiza un extenso análisis sobre el desempeño de las técnicas de clusterización y su impacto en el valor de la función objetivo. El desempeño de la metodología propuesta es factible y efectivo para resolver el problema en cuanto a la calidad de las respuestas y los tiempos computacionales obtenidos, sobre las instancias de la literatura evaluadas.The vehicle routing problem considering multiple depots is classified as NP-hard. MDVRP determines simultaneously the routes of a set of vehicles and aims to meet a set of clients with a known demand. The objective function of the problem is to minimize the total distance traveled by the routes given that all customers must be served considering capacity constraints in depots and vehicles. This paper presents a hybrid methodology that combines agglomerative clustering techniques to generate initial solutions with an iterated local search algorithm (ILS) to solve the problem. Although previous studies clustering methods have been proposed like strategies to generate initial solutions, in this work the search is intensified on the information generated after applying the clustering technique. Besides an extensive analysis on the performance of techniques, and their effect in the final solution is performed. The operation of the proposed methodology is feasible and effective to solve the problem regarding the quality of the answers and computational times obtained on request evaluated literature