Flow-Path: An AllPath flow-based protocol

The work at: The 37th IEEE Conference on Local Computer Networks (LCN). Clearwater, Florida, USA. Date: 22-25 October 2012This paper describes Flow-Path, an AllPath flowbased switching protocol that features improved load adaptive properties. Upon arrival of a new flow to the network, it explores every possible path reaching from source to destination host and selects the lowest latency path at the moment. It is based on the same basic principle than ARPPath, that is, snooping the ARP protocol dialog (request and reply messages) to explore all available paths at the same time that address resolution takes place, but it is flow-based instead of source address-based. While preserving the main advantages of ARP-Path: shortest path bridging exploiting the full network topology, Flow-Path has the advantages of full independence of flows at the time of path creation and guarantees path symmetry (congruency) and increased path diversity. Flow-Path thus improves load distribution, at the expense of increased address table size in each bridge.This work was supported in part by grants from Comunidad de Madrid and Comunidad de Castilla-La Mancha through Projects MEDIANET-CM (S-2009/TIC- 1468) and EMARECE (PII1I09-0204-4319).Publicad

ARP-Path: ARP-based Shortest Path Bridges

This letter is a summary proposal for an evolution of the Ethernet transparent bridge paradigm that provides simple, shortest path bridging in campus networks. ARP-Path Ethernet Switches set up an on-demand path between two hosts just reusing and flooding the standard ARP request frame through all links and confirming the path reaching to the destination host with the ARP reply frame. ARP-Path uses the standard Ethernet frame format, is fully transparent to hosts and does not require spanning tree or link state protocol. Simulation results show superior performance to spanning tree and similar to shortest path routing, with lower complexity. Our implementations confirm backward compatibility, robustness and performance.This work was supported in part by grants from Comunidad de Madrid and Comunidad de Castilla la Mancha through Projects MEDIANET-CM (S- 2009/TIC-1468) and EMARECE (PII1I09-0204-4319).Publicad

Scale Mixture of Rayleigh Distribution

In this paper, the scale mixture of Rayleigh (SMR) distribution is introduced. It is proven that this new model, initially defined as the quotient of two independent random variables, can be expressed as a scale mixture of a Rayleigh and a particular Generalized Gamma distribution. Closed expressions are obtained for its pdf, cdf, moments, asymmetry and kurtosis coefficients. Its lifetime analysis, properties and Rényi entropy are studied. Inference based on moments and maximum likelihood (ML) is proposed. An Expectation-Maximization (EM) algorithm is implemented to estimate the parameters via ML. This algorithm is also used in a simulation study, which illustrates the good performance of our proposal. Two real datasets are considered in which it is shown that the SMR model provides a good fit and it is more flexible, especially as for kurtosis, than other competitor models, such as the slashed Rayleigh distribution

Conformational analysis of a TADDOL-based phosphoramidite P,N ligand in a palladium(II) η3-π-allyl complex

Highlights Two lowest energy conformers differ in allyl conformation, conformer with exo allyl having lower energy. Lowest energy conformer has “chair” conformation of 7-membered ring and “edge-on/face-on/face-on/edge-on” array of pH groups. Next lowest energy conformer with exo allyl has alternating “edge-on/face-on” arrangement and “twist” 7-membered ring. Changes in “chair/twist” conformations with different substrates is possible due to 2.4 kcal/mol energy difference. These results explain stereochemical outcome of the reaction, and will guide design of new catalysts. Abstract The most stable conformations of a TADDOL-based phosphoramidite P,N ligand coordinated to a palladium(II) η3-π-allyl fragment have been investigated using molecular mechanical and quantum mechanical calculations. The conformational analysis initially generated 53 unique structures within 5 kcal/mol and subsequent geometry optimization narrowed the number of low-energy conformers down to 13. The two lowest energy conformers differ mainly in the conformation of the allyl group. The conformer with an endo allyl group has a slightly higher relative energy than the conformer with an exo allyl group. Comparison of the main geometric parameters around the Pd(II) metal center in the two lowest energy conformers with the available X-ray single crystal structures of Pd(II) η3-π-allyl complexes of P,N ligands shows a good agreement in both the bond lengths and angles. The lowest energy structure has a “chair” conformation of the seven-membered phospha-dioxa-cycloheptane ring and “edge-on/face-on/face-on/edge-on” arrangement of the phenyl rings. The next lowest energy conformer with an exo allyl group has a “twist” conformation of the seven-membered ring and alternating “edge-on” and “face-on” arrangement of the phenyl rings as anticipated from the Knowles “edge-on/face-on” concept. The results of this study support published hypotheses regarding the origin of the chiral induction in the enantioselective Pd(0) catalyzed intramolecular allylic alkylation reaction by the repulsive interactions between one of the phenyl groups in the seven-membered ring in the lowest energy conformer of the ligand with the substrate. As such, the results of this research can be used to guide the synthesis of new and improved variants of this important catalyst family

Atypical colororation in the yellow-striped poisonous frog, <i>Dendrobates truncatus</i> (Cope, 1861), in the Colombian Magdalena river valley

Herein we report an atypical coloration in one individual of the yellow-striped poisonous frog, Dendrobates truncatus, in Colombian Magdalena middle valley. The adult individual presented leucism, a rare phenomenon occurs in nature or at very low frequenciesAsociación Herpetológica Argentina (AHA

Effect of water application on wine quality and yield in ‘Carménère’ under the presence of a shallow water table in central Chile

Chile is the world’s leading producer of ‘Carménère’ (Vitis vinifera L.), which in turn is an important variety in Chile, where vineyards are typically grown under irrigated conditions and a large percentage are located in valleys with similar water table levels to those of the study area. Different irrigation management strategies have been used to improve wine quality, such as water stress and deficit irrigations, but the presence of a water table has not been considered in extant literature. This study analyzes the effects of the irrigation regime on grape yield and wine quality when a shallow water table is located between 1.5 to 2.2 m depth during the irrigation season. Five applied water treatments: 0%, 20%, 40%, 75%, and 100% of estimated vineyard evapotranspiration (ETc) were applied in an own-rooted ‘Carménère’ vineyard located in the Peumo Valley (Chile) during three consecutive seasons (2004-2005 to 2006-2007). Applying 1400 to 9400 m3 ha-1 per season (100% ETc) had no substantial effect on the measured quality parameters, although grape production in the treatment without irrigation (0% ETc) was significantly reduced. Applying water at 20% to 40% ETc produced high yield (13 to 16 t ha-1), double the historical mean production, and high quality wine with the presence of a water table close to the bottom of the root zone.Universidad de Concepción, ChileBMBF/CONICYT 231-2010Water Resources Center for Agriculture and MiningCONICYT/FONDAP/1513001

Estudio de las propiedades térmicas de harinas de maíz producidas por tratamiento termico-alcalino

A design of a controlled cooking system (CCS) for corn flours production is presented. The system allows reproducibility in the samples preparation withcontrol of the time and the temperature. The treatment of corn was performed with a cooking time of 120 minutes at 92.5◦C, by adding calcium hydroxide (Ca(OH)2) in concentration between 0 and 0.5% compared to the corn weight.The cooking process was monitored via measures of moisture absorbed by the corn kernels and pH of the solution. The samples were manufactured by operation steps like wet milling, dehydration, dry milling and sieving. The samples were analyzed using modulated differential scanning calorimetry (MDSC)and thermogravimetric analysis (TGA) techniques, which were focused in the thermal stability of the flours and their physical variables: gelatinization range (∆T), enthalpy (∆H), change in heat capacity (∆Cp), temperature decomposition of maximum decomposition rate (Tmd) and residue after decomposition (Rs). The adding of Ca(OH)2 moves the peak gelatinization and the maximum peak of decomposition towards higher temperature. The TGA analysis showed that the addition of calcium hydroxide improves the thermal stability of the flour, since the degradation temperature shifts to higher temperatures as the amount of calcium hydroxide increases. The results were compared with the same analysis performed on raw corn. This study proposes an experimental method, including a controlled cooking system for the production of flour enriched with calcium, which could have a major impact in the field of nutrition. PACS: 64.60.-i, 61.25.hk, 61.25.hp, 83.10.TvSe presenta el diseño de un sistema de cocción controlado (SCC) para la producción de harinas de maíz trillado. El sistema permite la reproducibilidad enla elaboración de las muestras a través del control de tiempo y temperatura. El tratamiento del maíz se realizó con un tiempo de cocción de 120 minutos a 92.5oC, adicionando concentraciones de hidróxido de calcio (Ca(OH)2) entre 0 y 0.5% con relación a la masa de maíz. El proceso de cocción fue monitoreado con medidas de humedad en el grano y pH de la solución. Las harinas fueron fabricadas adicionando operaciones de molienda húmeda, deshidratación, molienda seca y tamizado. Las muestras obtenidas fueron analizadas usandola técnica de calorimetría diferencial de barrido modulada (MDSC) y análisis termogravimétrico (TGA) para estudiar tanto la estabilidad térmica de la harina como sus variables físicas: intervalo de gelatinización (ΔT), entalpía degelatinización (ΔH), cambio en la capacidad calorífica (ΔCp), temperatura de máxima rata de descomposición (Tmd) y residuo después de la descomposición(Rs). Los análisis TGA muestran que la adición de hidróxido de calcio mejora la estabilidad térmica de la harina, puesto que la temperatura de degradación se desplaza a mayores temperaturas a medida que la cantidad de hidróxido de calcio aumenta. MDSC y TGA permitieron observar que la adición Ca(OH)2 produce un desplazamiento de gelatinización y de la máxima rata de descomposición hacia mayores temperaturas. Los resultados fueron comparados con los mismos análisis realizados sobre maíz sin procesar. Con este estudio se propone un método experimental, incluyendo un sistema de cocción controlada para la producción de harinas enriquecidas con calcio, las cuales podrían tener un alto impacto en el campo de la nutrición. PACS: 64.60.-i, 61.25.hk, 61.25.hp, 83.10.T

Path planning for quadrotors in 3D dynamic environments

Un tema de interés sobre los vehículos aéreos no tripulados es la determinación de trayectorias apropiadas que le permitan moverse de una posición inicial a una posición objetivo, garantizando que la trayectoria sea segura, es decir, que no existan riesgos de colisión. En este artículo se presentan dos técnicas de planificación de trayectorias y una estrategia de evasión de obstáculos para cuadricópteros, ambas técnicas funcionales sobre ambientes tridimensionales con obstáculos estáticos o dinámicos restringidos a velocidades constantes. Las técnicas funcionan sobre un ambiente modelado con planos que generan un campo de potencial artificial. La primera técnica está basada en puntos móviles que interconectan la posición inicial con la meta, posteriormente cada punto se mueve hacia zonas libres de la influencia de los obstáculos siguiendo el campo potencial, lo que hace que se encuentren caminos libres de obstáculos. La segunda técnica usa el concepto de zonas seguras, el cual se utiliza como criterio para actualizar la posición de los puntos. Adicionalmente, se propone una metodología de evasión de obstáculos dinámicos, que consiste en transformar el problema de planeación de trayectorias con obstáculos dinámicos al caso de planeación de trayectorias con obstáculos estáticos mediante un proceso de análisis de las posibilidades de colisión. Los resultados muestran que estas técnicas superan los inconvenientes de los algoritmos basados en gradiente descendente como mínimos locales y oscilaciones inestables.A topic of interest on unmanned aerial vehicles is determining appropriate paths that allow them to move from an initial position to a target position, ensuring that the path is safe, in other words, that there is no risk of collision. In this article, two techniques of path planning and an obstacle avoidance strategy for quadricopters are presented. Both techniques are functional on three-dimensional environments with static or dynamic obstacles restricted to constant speeds. The techniques work on an environment modeling with planes which generate an artificial potential field. The first technique is based on moving points that connect the initial position to the goal, and then every point moves towards free zones of influence of obstacles along the potential field, which makes unobstructed paths. The second technique uses the concept of safe areas, which is used as a criterion for updating the position of the points. Additionally, a methodology of dynamic obstacles avoidance is proposed, which is to transform the problem of trajectory planning with dynamic obstacles to the case of path planning with static obstacles through a process of analyzing the possibility of a collision. The results show that these techniques overcome the drawbacks of the gradient descent-based algorithms as local minima and unstable oscillations problems