Zener fractional order determination and biomechanical blood flow characterization

El propósito principal de la presente publicación consiste en la determinación adecuada del orden fraccional en el modelo viscoelástico de Zener y el análisis de las implicaciones que se derivan de la precisión en la obtención del mismo. Esto se realiza empleando el método numérico de Levenberg-Marquardt a partir de valores reportados en la literatura. Los parámetros utilizados son obtenidos para un segmento de arteria empleando un experimento de relajación a los esfuerzos. Una vez determinado el orden fraccional se procede a determinar la solución del modelo empleando la función de dos parámetros de Mittag-Leffler y la operación de convolución, con la finalidad de comparar el comportamiento del modelo de orden fraccional con el de orden entero e identificar sus principales diferencias. Se obtienen además las deformaciones que experimenta la arteria bajo el estímulo de un pulso sanguíneo normal y otros disímiles, simulando el efecto provocado en el flujo sanguíneo por una arritmia y el ocasionado por el proceso de ventilación mecánica. Por último se analiza la respuesta dinámica del material bajo una serie de pulsos, utilizando la operación de convolución y el método numérico de Gauss-Kronrod, identificando la precisión en la reproducción de los mismos en el modelo de orden fraccional comparado con el de orden entero.The main purpose of this publication is the proper determination of the fractional order at the Zener viscoelastic models and the analysis of the implications derived from the accuracy in obtaining this. The procedure is performed using the numerical method of Levenberg-Marquardt from values reported in the literature. The parameters used are obtained from an artery segment using a stress relaxation test. After determining the fractional order is proceeded to find the model solution using, the function of Mittag-Leffler with two parameters and the convolution operation in order to compare the behavior of the fractional model vs the integer order and identify their key differences. The displacements present on the artery are obtained, under the stimulus of a normal blood pulse and two dissimilar, simulating the effect in blood flow caused by an arrhythmia and by mechanical ventilation process. Finally the dynamic response from the pulses is analyzed using the convolution operation and Gauss Kronrod numeric method, where the solutions accuracy obtained by the fractional model is observed, an compared with the integer order model.Peer Reviewe

Inter‐ and Intra‐Annual Variability of Nitrogen Concentrations in the Headwaters of the Mero River

This study examines the inter‐ and intra‐annual variability of different forms of N [total nitrogen (TN), nitrate‐nitrogen (N‐NO3) and total Kjeldahl nitrogen (TKN)] in stream waters of a rural headwater catchment in Galicia (NW Spain) during a 5‐year period, covering 2004–2009 water years (October–September). Daily time series were used to verify the temporal variability and to characterize the nitrogen pollution. The TN concentrations were low, although the values constantly exceeded the critical range (0.5–1.0 mg L−1) over which potential risk of eutrophication of water systems exists. Nitrate was the predominant form of nitrogen in the river throughout the study period, accounting for 82–85% of the TN. Significant differences were found for different forms of N between water years and seasons, indicative of wide inter‐ and intra‐annual variability of nitrogen concentrations, mainly related to rainfall and flow oscillations. The seasonal pattern in the concentrations of TN, N‐NO3 and TKN in stream water was similar to many humid and temperate catchments, with higher concentrations in winter, when variability was also the highest in the period, and lower values in summer

Flow injection determination of readily assimilable nitrogen compounds during vinification

A flow injection method for the determination of readily assimilable nitrogen (r.a.n.), i.e. ammonium and aminated nitrogen, is reported. The difference in pH of the sample in the presence and absence of formaldehyde, which blocks the amino function, provides the value of r.a.n. by monitoring the changes in absorbance of bromothymol blue at 616 nm. The detection and quantification limits are 10 and 11.6 mg l-1, respectively; the reproducibility and repeatability are 3.94 mg l-1 and 1.35 mg l-1, respectively; and the sample throughput is 20 samples h-1. The method has been applied to the analysis of 120 samples of must and wine subjected to biological aging. The proposed method also provides good correlation with the reference method used in routine analysis, and it is faster and gives sufficient precision for wineries requirements

Improving the Understanding of N Transport in a Rural Catchment Under Atlantic Climate Conditions From the Analysis of the Concentration–Discharge Relationship Derived From a High-Frequency Data Set

[Abstract] Understanding processes controlling stream nutrient dynamics over time is crucial for implementing effective management strategies to prevent water quality degradation. In this respect, the study of the nutrient concentration–discharge (C–Q) relationship during individual runoff events can be a valuable tool for extrapolating the hydrochemical processes controlling nutrient fluxes in streams. This study investigated nitrogen concentration dynamics during events by analyzing and interpreting the nitrogen C–Q relationship in a small Atlantic (NW Iberian Peninsula) rural catchment. To this end, nitrate (NO3-N) and total Kjeldahl nitrogen (TKN) concentrations were monitored at a high temporal resolution during 102 runoff events over a 6-year period. For each of the selected runoff events, C–Q response was examined visually for the presence and direction of hysteresis loops and classified into three types of responses, namely clockwise, counterclockwise, and no hysteresis. Changes in concentration (ΔC) and the hysteresis direction (ΔR) were used to quantify nitrogen ( and TKN) patterns during the runoff events. The transport mechanisms varied between compounds. The most frequent hysteretic response for was counterclockwise with enrichment. On the contrary, the main TKN dynamic was enrichment with clockwise hysteresis. Event characteristics, such as rainfall amount, peak discharge (i.e., maximum discharge of the runoff event), and event magnitude relative to the initial baseflow (i.e., the difference between the maximum discharge of the runoff event and the initial baseflow divided by initial baseflow) provided a better explanation for hysteresis direction and magnitude for TKN than antecedent conditions (antecedent precipitation and baseflow at the beginning of the event). For hysteresis, the role of hydrometeorological conditions was more complex. The hysteresis magnitude was related to the magnitude of the event relative to the initial baseflow and the time elapsed since a preceding runoff event. These findings could be used as a reference for the development of N mitigation strategy in the region.This research has been supported by the Spanish Ministry of Education and Science (grant no. REN2003-08143) and Xunta of Galicia (grant nos. PGIDIT05RAG10303PR and 10MDS103031PR)Xunta of Galicia; PGIDIT05RAG10303PRXunta of Galicia; 10MDS103031P

PMCTrack: Delivering performance monitoring counter support to the OS scheduler

Hardware performance monitoring counters (PMCs) have proven effective in characterizing application performance. Because PMCs can only be accessed directly at the OS privilege level, kernellevel tools must be developed to enable the end-user and userspace programs to access PMCs. A large body of work has demonstrated that the OS can perform effective runtime optimizations in multicore systems by leveraging performance-counter data. Special attention has been paid to optimizations in the OS scheduler. While existing performance monitoring tools greatly simplify the collection of PMC application data from userspace, they do not provide an architecture-agnostic kernel-level mechanism that is capable of exposing high-level PMC metrics to OS components, such as the scheduler. As a result, the implementation of PMC-based OS scheduling schemes is typically tied to specific processor models. To address this shortcoming we present PMCTrack, a novel tool for the Linux kernel that provides a simple architecture-independent mechanism that makes it possible for the OS scheduler to access per-thread PMC data. Despite being an OSoriented tool, PMCTrack still allows the gathering of monitoring data from userspace, enabling kernel developers to carry out the necessary offline analysis and debugging to assist them during the scheduler design process. In addition, the tool provides both the OS and the user-space PMCTrack components with other insightful metrics available in modern processors and which are not directly exposed as PMCs, such as cache occupancy or energy consumption. This information is also of great value when it comes to analyzing the potential benefits of novel scheduling policies on real systems. In this paper, we analyze different case studies that demonstrate the flexibility, simplicity and powerful features of PMCTrack.Facultad de InformáticaInstituto de Investigación en Informátic