Papers by Leonardo Espinoza
American Journal of Human Biology, 1995
A sample of 113 boys and 101 girls of the Caracas Mixed-Longitudinal Study was grouped into early... more A sample of 113 boys and 101 girls of the Caracas Mixed-Longitudinal Study was grouped into early, average, and late maturers according to selected cut-off points of the 10th and 90th centiles for age at peak height velocity (APHV). Individual curves were fitted with the cubic spline function, in which height velocity corresponds to the first derivative. Age at menarche (AM) was estimated by recall in a longitudinal context. Differences between groups were assessed with F and t-tests. Girls were approximately 2 years earlier than boys in APHV and thus significantly shorter; their estimated PHV was also significantly lower. APHV in boys and girls occurred 0.4–0.6 years earlier than in European children, which is consistent with a faster tempo of growth of Venezuelan youth. The three maturity groups differed significantly in timing, stature, and AM. Early maturers were taller than average maturers, and the latter were taller than late maturers with maximal differences between the extreme groups at ages 13–14 in boys and 11–12 in girls. Early maturers grew at a faster rate than average maturers, and the latter grew at a faster rate than late maturers up to 13 years in boys and 10–11 years in girls. Despite difficulties encountered in the analysis of mixed-linked longitudinal data, meaningful growth differences were found between maturity groups of urban Venezuelan children. © 1995 Wiley-Liss, Inc.
Nephrology, 2009
Aim: To evaluate the effect of nutritional counselling on nutritional status in peritoneal dialy... more Aim: To evaluate the effect of nutritional counselling on nutritional status in peritoneal dialysis patients.Methods: Twenty-nine peritoneal dialysis patients were randomly selected to receive conventional nutritional counselling during 6 months of follow up. All patients had monthly clinical and biochemical evaluations, and assessments of dialysis adequacy, inflammation and nutritional status at 0, 3 and 6 months.Results: Moderate-severe malnutrition decreased 28% whereas normal nutrition increased 23% at final evaluation (non-significant). Calorie and protein intake remained stable throughout the study (baseline vs final, calorie: 24 ± 8 vs 23 ± 5 Kcal/kg; protein: 1.1 ± 0.5 vs 1.0 ± 0.3 g/Kg, respectively). On the other hand, triceps (16 ± 6 vs 18 ± 8 mm) and subscapular (17 ± 8 vs 20 ± 5 mm) skinfold thicknesses, and mid-arm circumference (27 ± 3 vs 28 ± 3 mm) significantly increased; mid-arm muscle area displayed a non-significant trend to increase (30 ± 9 vs 31 ± 9 cm2) whereas serum albumin significantly increased at the end of study (2.67 ± 0.46 vs 2.94 ± 0.48 g/dL). At final evaluation, median renal creatinine clearance decreased (6.3 (0.8–15.3) vs 2.0 (0.1–6.3) L/week per 1.73 m2) whereas interleukin-6 increased (2.33 (1.9–7.0) vs 4.02 (2.1–8.4) pg/mL).Conclusion: Even though conventional nutritional counselling, as an isolated measure, did not significantly improve all nutritional parameters, it prevented a greater deterioration during 6 months. Nutritional counselling maintained the nutritional status in spite of a decrease in residual renal function and higher systemic inflammation.
This paper shows that the proper connection of single-phase-input/single-phase-output power cells... more This paper shows that the proper connection of single-phase-input/single-phase-output power cells to a multi-pulse transformer to form a 7-levels voltage waveform has an important impact on the overall performance of the topology. Particularly, if the topology is used in systems that are connected to an unbalanced AC network and/or feeds an unbalanced load. The topology in combination with the proposed arrange of the power cells and the multi-pulse transformer becomes best suitable for applications where the quality of the voltage and current waveforms are of main concern. In fact, the topology minimizes the problems produced by unbalanced loads even though the single-phase nature of both the input and output of the power cells. Moreover, the proposed arrange acts as a buffer for the AC mains voltage unbalances as they do not have any effect on the load voltages. The paper includes the comparison between a reported alternative to arrange the cells with the proposed approach. Particularly, the voltages and currents are shown for both an unbalanced AC mains and an unbalanced load. Unbalance and distortion factors are included to quantify the advantages of the proposed arrange.
International Journal of Infectious Diseases, 2008
Abstracts 55 zation and are focused on balancing the demands of the system with the patients' ind... more Abstracts 55 zation and are focused on balancing the demands of the system with the patients' individual needs. Findings from this study suggest that in spite of the lack of resources and the many challenges associated with managing in a complex health care system, F-LNMs are constantly strategizing to facilitate safe patient transitions.
Journal of Geophysical Research, 2005
1] In November 2004, a regional climate change workshop was held in Guatemala with the goal of an... more 1] In November 2004, a regional climate change workshop was held in Guatemala with the goal of analyzing how climate extremes had changed in the region. Scientists from Central America and northern South America brought long-term daily temperature and precipitation time series from meteorological stations in their countries to the workshop. After undergoing careful quality control procedures and a homogeneity assessment, the data were used to calculate a suite of climate change indices over the 1961-2003 period. Analysis of these indices reveals a general warming trend in the region. The occurrence of extreme warm maximum and minimum temperatures has increased while extremely cold temperature events have decreased. Precipitation indices, despite the large and expected spatial variability, indicate that although no significant increases in the total amount are found, rainfall events are intensifying and the contribution of wet and very wet days are enlarging. Temperature and precipitation indices were correlated with northern and equatorial Atlantic and Pacific Ocean sea surface temperatures. However, those indices having the largest significant trends (percentage of warm days, precipitation intensity, and contribution from very wet days) have low correlations to El Niño-Southern Oscillation. Additionally, precipitation indices show a higher correlation with tropical Atlantic sea surface temperatures.
This work of investigation comprises of a project ampler than it must by objective identify and t... more This work of investigation comprises of a project ampler than it must by objective identify and take advantage of the real possibilities to combine the resources by remittances, own income of producers and the governmental contributions to generate more organization and major investment in the municipality of Hidalgo Durango . One includes how antecedent some characteristics of the government programs
Development of technologies based on localized states depends on our ability to manipulate and co... more Development of technologies based on localized states depends on our ability to manipulate and control these nonlinear structures. In order to achieve this, the interactions between localized states and control tools should be well modelled and understood. We present a theoretical and experimental study for handling non-propagating hydrodynamic solitons in a vertically driven rectangular water basin, based on the inclination of the system. Experiments have shown that tilting the basin induces non-propagating solitons to drift towards an equilibrium position through a relaxation process. Our theoretical approach is derived from the parametrically driven damped nonlinear Schrödinger equation which models the system. The basin tilting effect is incorporated as a spatially inhomogeneous linear correction on dissipation. A motion law for hydrodynamic solitons can be deduced from these assumptions. The model equation, which includes a constant speed and a linear relaxation term, nicely reproduces the motion observed in our experiment.
Tetrahedron Letters, 2009
An alternative synthetic approach for the introduction of chirality in b-carboline moiety through... more An alternative synthetic approach for the introduction of chirality in b-carboline moiety through in situ reduction of N-acyliminium ion intermediates generated from imine 2 and chloroformate of 8-phenylmenthyl as chiral auxiliary was achieved. The method applied microwave-assisted irradiation and used PdCl 2 /Et 3 SiH protocol as a mild reducing agent, which decreased reaction times to minutes when compared to the conventional thermal reactions. The diastereoselectivity (4-12:1) of the reduction produced R-amines, which were assigned after chiral auxiliary removal and spectroscopic data compared to products obtained from Noyori asymmetric hydrogenation catalyst.
Tetrahedron-asymmetry, 2009
The first enantioselective synthesis of chichimol ketone (4-methyl-1-hepten-3-one) is described a... more The first enantioselective synthesis of chichimol ketone (4-methyl-1-hepten-3-one) is described and the absolute configuration of the main semiochemical compound is determined as having an (S)-configuration. The synthesis features the use of a ruthenium catalytic asymmetric hydrogenation reaction to introduce chirality into acid 2. The synthetic chichimol ketone (S)-1 displayed a specific rotation that was in accordance with that of the natural product, thereby supporting the (S) configuration for natural chichimol ketone. To assure the correct stereochemical assignment, (S)-1 was converted in the known ketone (S)-5: the main alarm pheromone of the ant Atta texana that is 400 times more active than its (R)enantiomers.
The present work details the experience on designing a multiagent system devoted to a dynamic Job... more The present work details the experience on designing a multiagent system devoted to a dynamic Job Shop setting using the PASSI methodology. The agent system is in charge of the planning and scheduling of jobs and their operations on a set of available machines, while considering the materials assigned to each operation. Dynamicity concerns job orders scheduling on-the-fly and the re-schedule caused by changes to the original plan due to clients, machines and material stocks. The system has been modeled with the PASSI Toolkit (PTK) and implemented over the Jade agent platform.
ii DEDICATORIA A mis padres, Piedad y Gustavo, por su amor, esfuerzo y apoyo incondicional que me... more ii DEDICATORIA A mis padres, Piedad y Gustavo, por su amor, esfuerzo y apoyo incondicional que me han brindado toda la vida, son mi ejemplo de superación y lucha para cumplir con mis metas, gracias por todas sus bendiciones.
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Papers by Leonardo Espinoza