Use of informal mobile telephony in low income households in Colombia

Access to mobile telephony in Colombia exhibits rather interesting features compared to other countries. Colombia witnessed the beginning of a new alternative for communication consisting in the use of informal resale of minutes on the streets and small stores during the first years of this century. In this paper we are interested in analyzing the main factors that determine the utilization of this kind of service. We use a probabilistic model to explain the characteristics of the people that use `informal resale´ on the streets and we find that people in the modality of prepayment and people from small cities has a higher probability of using this alternative. It is also found that people in the firm-leader use more often this service. These results seem indicate that price differentials among on-net and off-net and between prepaid and postpaid are the causes of the rise of this economic activity.***El acceso a la telefonía móvil en Colombia evidencia ciertas particularidades con respecto a otros países. En Colombia surgió una nueva alternativa de comunicación que consistía en la venta de minutos de celular en las calles y en pequeños negocios durante los primeros años de ésta década. En este documento se analizan las principales características de quienes usan esta modalidad de comunicación con base en una encuesta dirigida a usuarios y no usuarios de bajos ingresos. Se usa un modelo probabilístico para explicar las características de las personas que lo usan y se encuentra que las personas que están en la modalidad de contrato prepago y que viven en ciudades pequeñas tienen una mayor probabilidad de usar esta alternativa de comunicación. De otro lado se encuentra que quienes están con el operador dominante tienden a usar este servicio también de una forma más notoria. Estos resultados parecen indicar que los diferenciales de precios entre las llamadas off-net y on-net así como entre prepago y postpago son los que alimentaron el surgimiento de esta actividad.Mobile telephony, ICT, gender gap, Resale

The determinants of two-dimensional service quality in the drinking water sector - Evidence from Colombia

Quality of drinking water service is considered in two dimensions: Tangibles (measured by sediment, taste, smell, and color) and reliability (measured by service continuity). Using a large and unique household-level dataset, we study important factors that are related to these dimensions in the Colombian drinking water sector. Based on the network design of pumping, purification, and delivery, our main findings are: (1) compared to users who do not receive a subsidy for water consumption, users who receive a subsidy report less reliable service while tangibles of water quality do not show significant difference between the reports of these two types of users; and (2) compared to water supplied by public providers, water supplied by community providers shows worse tangibles, while service reliability does not show significant difference between these two types of providers. These results suggest that Colombia water reform should not only aim to expand service and prompt water usage for the poor, but also strengthen quality control in multiple dimensions. © IWA Publishing 2016

Oroantral communications : a retrospective analysis

Objetive. To analyze characteristics, clinical evolution and surgical techniques of oroantral communication (OAC). Study Design. We included all patients operated at the University Central Hospital (Oviedo, Spain) between 1996 and 2007. The variables assessed were age, sex, medical history, OAC size, sinus disease, surgical technique, duration of hospitalization and post-surgical evolution. Results. We analyzed 12 patients (7 men and 5 women) with an average age of 47.5 years. The most frequent cause of oroantral communication was the extraction of the first upper molar. The average size of fistula was 0.9 cm. Buccal flap repair was used in 7 patients, palatal rotation-advancement flap in 4 patients and buccal fat pad in only one patient. Suture dehiscence was observed in one patient treated with a palatal flap, but no additional surgery was required. Three OAC recurred; all of them following a buccal flap procedure. All recurrences spontaneously closed between one and four months following the procedure. Conclusion. OACs are rare complications and treatment should be individualized to avoid further complication

Optimization of the feeding ports location in a fluidized bed combustor based on Monte Carlo simulations of fuel particles motion

A Monte Carlo model was proposed to characterize the fuel particles motion in a large-scale fluidized bed. The model describes the global motion of a fuel particle with a proper circulation throughout the bed, analyzing its behavior both in the freeboard and inside the bed. The model was validated with experimental results of the lateral mixing of fuel particles in a large-scale fluidized bed reported in the literature. The lateral displacement of the fuel particles and the residence time, both in the freeboard and inside the bed, were obtained from the model. From those data the lateral dispersion coefficient of the fuel particle was determined. The influence of the operational conditions on the lateral dispersion coefficient and on the maximum lateral distance reached by a fuel particle for different residence times in the bed was also analyzed. Finally, an optimal distance between feeding ports to ensure suitable fuel dispersion was obtained.This work has been partially supported by the National Energy Program of Spanish Government (DPI2009-10518 MICINN) and CARDENER-CM (S2009ENE-1660).Publicad

The performance of three ordination methods

The performance of robust principal component analysis (RPCA), detrended correspondence analysis (DCA) and non-metric multidimensional scaling (NMDS) with two demersal fish data sets were assessed in terms of their stability to bootstrap-generated sample variation and the method’s ability to reflect a well-known depth gradient. Stability was assessed for both species and site orderings and configurations, using scaled rank variance (SRV) and Spearman (q) and Procrustes correlations (t0). The NMDS site and species orderings showed the highest stability. DCA performed best in terms of site ordination stability, but NMDS performed best in terms of species ordination stability. In terms of matching the expected ecological variation, NMDS was the most sensitive method for the wider-depth gradient data and DCA was the most sensitive for the narrower-depth gradient data. According to the sensitivity and informative power criteria associated with the stability assessment, t0 was the best methodological approach for site ordinations, and SRV for species ordinations

Circuit FPGA for active rules selection in a transition P system region

P systems or Membrane Computing are a type of a distributed, massively parallel and non deterministic system based on biological membranes. These systems perform a computation through transition between two consecutive configurations. As it is well known in membrane computing, a configuration consists in a m-tuple of multisets present at any moment in the existing m regions of the system at that moment time. Transitions between two configurations are performed by using evolution rules which are in each region of the system in a non-deterministic maximally parallel manner. This article shows the development of a hardware circuit of selection of active rules in a membrane of a transition P-system. This development has been researched by using the Quartus II tool of Altera Semiconductors. In the first place, the initial specifications are defined in orfer to outline the synthesis of the circuit of active rules selection. Later on the design and synthesis of the circuit will be shown, as well as, the operation tests required to present the obtained results

The use of pedicled buccal fat pad combined with sequestrectomy in bisphosphonate-related osteonecrosis of the maxilla

The use of pedicled buccal fat pad flap (BFP) has proved of value for the closure of oroantral and oronasal communications and is a well-established tool in oral and maxillofacial surgery. Otherwise, the perceived limitations of surgical therapy for bisphosphonate-related osteonecrosis of the jaws (BRONJ) have been widely discussed, and recommendations have largely been made to offer aggressive surgery only to stage 3 patients refractary to conservative management. Oroantral communication may be a common complication after sequestrectomy and bone debridement in upper maxillary BRONJ. We report a case series of stage 3 recalcitrant maxillary BRONJ surgically treated with extensive sequestrectomy and first reconstruction using pedicled BFP. All the cases presented an uneventful postoperative healing was uneventful without dehiscence, infection, necrosis or oroantral communication. We postulate that managing initially the site with BFP and primary closure may ensure a sufficient blood supply and adequate protection for an effective bone-healing response to occur. This technique may represent a mechanic protection and an abundant source of adipose-derived adult stem cells after debridement in upper maxillary BRONJ. We evaluate in this work results, advantages and indications of this technique. © Medicina Oral S. L

Evaluating the accuracy of the Distributed Activation Energy Model for biomass devolatilization curves obtained at high heating rates

The characteristic parameters of devolatilization, the activation energy and the frequency factor, can be obtained following different experimental approaches. In the Distributed Activation Energy Model (DAEM), these parameters are derived from several TGA curves that are typically obtained for constant, low heating rate experiments. Then, the results are used to model high heating rate processes typical of industrial combustors. In this work, a wide range of heating rates were employed to obtain different TGA curves of the biomass pyrolysis, in order to analyse the validity of DAEM when extrapolating the kinetic parameters obtained for low heating rate curves used in the laboratory to higher heating rates present in industrial applications. The TGA curves of the biomass pyrolysis employed in DAEM were varied from low heating rates (around 10 K/min, values typically found in the literature on DAEM), to high heating rates (up to 200 K/min). The differences in the activation energy and the frequency factor obtained for different heating rates, were evaluated and the validity of the model was discussed. The results show differences between the activation energy and the frequency factor obtained using low and high heating rates during the TGA tests. Therefore, if an accurate approximation is required when extrapolating the data to high heating rates, the tests should be carried out at high heating rates.The authors would like to express appreciation to the BIOLAB experimental facilities and for the financial support from Projects DPI2009-10518 (MICINN) and CARDENER-CM (S2009ENE-1660).Publicad

Pyrolysis of sewage sludge in a fixed and a bubbling fluidized bed - Estimation and experimental validation of the pyrolysis time

Pyrolysis of sewage sludge was studied experimentally in a stainless-steel reactor operated as a fixed or fluidized bed. A novel measuring technique, consisting of measuring the mass of the whole reactor and the sample on a scale, was applied. The scale was capable of measuring the whole mass of the reactor with enough accuracy to detect the mass released by the sewage sludge sample during its pyrolysis. This original measuring technique permitted the measurement of the evolution over time of the mass of sewage sludge supplied to the bed in batch during its pyrolysis while moving freely in the bed. From the measurement of the mass of the solid residue remaining in the reactor, the pyrolysis time of the sewage sludge sample can be obtained accurately for each operating condition. Different operating conditions were selected to analyze the evolution with time of the sample mass during the pyrolysis process, including the bed temperature and the velocity of the Nitrogen used as inert gas. An increase of the velocity of Nitrogen from that of a fixed bed (0.8U(m)) to that of a low velocity bubbling fluidized bed (2.5U(mf)) accelerates remarkably the pyrolysis process, i.e. reduces the pyrolysis time, however increasing the Nitrogen velocity further has a slight effect on the characteristic velocity of the pyrolysis process. The pyrolysis process of sewage sludge can also be accelerated by increasing the bed temperature, even though the effect of the temperature is lower than that of the Nitrogen velocity. Furthermore, a mathematical model based on a first order apparent kinetics for the pyrolysis of sewage sludge was proposed. The model was employed to estimate the pyrolysis time for each operating condition, obtaining a proper agreement with the experimental measurements.The authors gratefully acknowledge the financial support provided by Fundación Iberdrola under the program "Programa de Ayudas a la Investigación en Energía y Medioambiente"

Modeling the thin-layer drying process of Granny Smith apples: Application in an indirect solar dryer

The thin-layer drying kinetics of Granny Smith apples is determined by thermogravimetric analysis of the drying process at constant temperatures ranging from 20 degrees C to 50 degrees C, using intervals of 5 degrees C. The experimental drying curves obtained in the TGA were fitted to the Wang-Singh equation, which was found to describe precisely the drying process occurring at constant drying temperature. A novel model, capable of predicting the evolution of the moisture ratio of Granny Smith apples during the drying process with variable drying temperatures, was proposed. The model was validated with experimental TGA measurements of the drying of apples at variable temperatures, typical of solar drying, obtaining maximum deviations for the drying time less than 1.5%. Once validated, the model proposed was also applied to the drying of Granny Smith apples in an indirect solar dryer. The comparison of the model prediction with the experimental measurements of the drying of apples at variable drying conditions conducted in a lab-scale solar dryer showed a proper agreement, with low deviations (less than 10%) associated to the thermal inertia of the samples. (C) 2016 Elsevier Ltd. All rights reserved.The thermogravimetric analyses were conducted in the BIOLAB experimental facility (madrimasd.org, lab # 202), a laboratory financed under the infrastructures and lab network of the Madrid (Spain) Regional Governmen