Definición e implementación de métricas objetivas para la evaluación funcional del miembro superior: aplicación a población con lesión medular cervical

En personas que padecen una Lesión Medular cervical, la función de los miembros superiores se ve afectada en mayor o menor medida, dependiendo fundamentalmente del nivel de la lesión y de la severidad de la misma. El déficit en la función del miembro superior hace que la autonomía e independencia de las personas se vea reducida en la ejecución de Actividades de la Vida Diaria. En el entorno clínico, la valoración de la función del miembro superior se realiza principalmente con escalas clínicas. Algunas de ellas valoran el nivel de dependencia o independencia en la ejecución de Actividades de la Vida Diaria, como, por ejemplo, el índice de Barthel y la escala FIM (Medida de la Independencia Funcional). Otras escalas, como Jebsen-Taylor Hand Function, miden la función del miembro superior valorando la destreza y la habilidad en la ejecución de determinadas tareas funcionales. Estas escalas son generales, es decir, se pueden aplicar a distintas poblaciones de sujetos y a la presencia de distintas patologías. Sin embargo, existen otras escalas desarrolladas específicamente para valorar una patología concreta, con el objetivo de hacer las evaluaciones funcionales más sensibles a cambios. Un ejemplo es la escala Spinal Cord Independence Measure (SCIM), desarrollada para valorar Lesión Medular. Las escalas clínicas son instrumentos de medida estandarizados, válidos para su uso en el entorno clínico porque se han validado en muestras grandes de pacientes. No obstante, suelen poseer una elevada componente de subjetividad que depende principalmente de la persona que puntúa el test. Otro aspecto a tener en cuenta, es que la sensibilidad de las escalas es alta, fundamentalmente, a cambios groseros en el estado de salud o en la función del miembro superior, de forma que cambios sutiles en el sujeto pueden no ser detectados. Además, en ocasiones, poseen saturaciones en el sistema de puntuación, de forma que mejorías que se puedan producir por encima de un determinado umbral no son detectadas. En definitiva, estas limitaciones hacen que las escalas clínicas no sean suficientes, por sí mismas, para evaluar estrategias motoras del miembro superior durante la ejecución de movimientos funcionales, siendo necesaria la búsqueda de instrumentos de medida que aporten objetividad, complementen las valoraciones y, al mismo tiempo, intenten solventar las limitaciones que poseen las escalas. Los estudios biomecánicos son ejemplos de métodos objetivos, en los que diversas tecnologías se pueden utilizar para recoger información de los sujetos. Una concreción de estos estudios son los estudios cinemáticos. Mediante tecnología optoelectrónica, inercial o electromagnética, estos estudios proporcionan información objetiva acerca del movimiento realizado por los sujetos, durante la ejecución de tareas concretas. Estos sistemas de medida proporcionan grandes cantidades de datos que carecen de una interpretación inmediata. Estos datos necesariamente deben ser tratados y reducidos a un conjunto de variables que, a priori, posean una interpretación más sencilla para ser utilizados en la práctica clínica. Estas han sido las principales motivaciones de esta investigación. El objetivo principal fue proponer un conjunto de índices cinemáticos que, de forma objetiva, valoren la función del miembro superior; y validar los índices propuestos en poblaciones con Lesión Medular, para su uso como instrumentos de valoración en el entorno clínico. Esta tesis se enmarca dentro de un proyecto de investigación: HYPER (Hybrid Neuroprosthetic and Neurorobotic Devices for Functional Compensation and Rehabilitation of Motor Disorders, referencia CSD2009-00067 CONSOLIDER INGENIO 2010). Dentro de este proyecto se lleva a cabo investigación en el desarrollo de modelos, para determinar los requisitos biomecánicos y los patrones de movimiento de los miembros superiores en sujetos sanos y personas con lesión medular. Además, se realiza investigación en la propuesta de nuevos instrumentos de evaluación funcional en el campo de la rehabilitación de los miembros superiores. ABSTRACT In people who have suffered a cervical Spinal Cord Injury, upper limbs function is affected to a greater or lesser extent, depending primarily on the level of the injury and the severity of it. The deficit in the upper limb function reduces the autonomy and independence of persons in the execution of Activities of Daily Living. In the clinical setting, assessment of upper limb function is mainly performed based on clinical scales. Some value the level of dependence or independence in performing activities of daily living, such as the Barthel Index and the FIM scale (Functional Independence Measure). Other scales, such as the Jebsen-Taylor Hand Function, measure upper limb function in terms of the skill and ability to perform specific functional tasks. These scales are general, so can be applied to different populations of subjects and the presence of different pathologies. However, there are other scales developed for a specific injury, in order to make the functional assessments more sensitive to changes. An example is the Spinal Cord Independence Measure (SCIM), developed for people with Spinal Cord Injury. The clinical scales are standardized instruments measure, valid for use in the clinical setting because they have been validated in large patient samples. However, they usually have a high level of subjectivity which mainly depends on the person who scores the test. Another aspect to take into account is the high sensitivity of the scales mainly to gross changes in the health status or upper limb function, so that subtle changes in the subject may not be detected. Moreover, sometimes, have saturations in the scoring system, so that improvements which may occur above a certain threshold are not detected. For these reasons, clinical scales are not enough, by themselves, to assess motor strategies used during movements. So, it’s necessary to find measure instruments that provide objectivity, supplement the assessments and, at the same time, solving the limitations that scales have. Biomechanical studies are examples of objective methods, in which several technologies can be used to collect information from the subjects. One kind of these studies is the kinematic movement analysis. By means of optoelectronics, inertial and electromagnetic technology, these studies provide objective information about the movement performed by the subjects during the execution of specific tasks. These systems provide large quantities of data without easy and intuitive interpretation. These data must necessarily be treated and reduced to a set of variables that, a priori, having a simpler interpretation for their use in the clinical practice. These were the main motivations of this research. The main objective was to propose a set of kinematic indices, or metrics that, objectively, assess the upper limb function and validate the proposed rates in populations with Spinal Cord Injury, for use as assessment tools in the clinical setting. This dissertation is framed within a research project: HYPER (Neurorobotic Devices for Functional Compensation and Rehabilitation of Motor Disorders, grant CSD2009- 00067 CONSOLIDER INGENIO 2010). Within this research project, research is conducted in relation to the biomechanical models development for determining the biomechanical requirements and movement patterns of the upper limb in healthy and people with Spinal Cord Injury. Moreover, research is conducted with respect to the proposed of new functional assessment instruments in the field of upper limb rehabilitation.

A combined measure for quantifying and qualifying the topology preservation of growing self-organizing maps

The Self-OrganizingMap (SOM) is a neural network model that performs an ordered projection of a high dimensional input space in a low-dimensional topological structure. The process in which such mapping is formed is defined by the SOM algorithm, which is a competitive, unsupervised and nonparametric method, since it does not make any assumption about the input data distribution. The feature maps provided by this algorithm have been successfully applied for vector quantization, clustering and high dimensional data visualization processes. However, the initialization of the network topology and the selection of the SOM training parameters are two difficult tasks caused by the unknown distribution of the input signals. A misconfiguration of these parameters can generate a feature map of low-quality, so it is necessary to have some measure of the degree of adaptation of the SOM network to the input data model. The topologypreservation is the most common concept used to implement this measure. Several qualitative and quantitative methods have been proposed for measuring the degree of SOM topologypreservation, particularly using Kohonen's model. In this work, two methods for measuring the topologypreservation of the Growing Cell Structures (GCSs) model are proposed: the topographic function and the topology preserving map

Computing the Hessenberg matrix associated with a self-similar measure

We introduce in this paper a method to calculate the Hessenberg matrix of a sum of measures from the Hessenberg matrices of the component measures. Our method extends the spectral techniques used by G. Mantica to calculate the Jacobi matrix associated with a sum of measures from the Jacobi matrices of each of the measures. We apply this method to approximate the Hessenberg matrix associated with a self-similar measure and compare it with the result obtained by a former method for self-similar measures which uses a fixed point theorem for moment matrices. Results are given for a series of classical examples of self-similar measures. Finally, we also apply the method introduced in this paper to some examples of sums of (not self-similar) measures obtaining the exact value of the sections of the Hessenberg matrix.

Independence in CLP Languages

Studying independence of goals has proven very useful in the context of logic programming. In particular, it has provided a formal basis for powerful automatic parallelization tools, since independence ensures that two goals may be evaluated in parallel while preserving correctness and eciency. We extend the concept of independence to constraint logic programs (CLP) and prove that it also ensures the correctness and eciency of the parallel evaluation of independent goals. Independence for CLP languages is more complex than for logic programming as search space preservation is necessary but no longer sucient for ensuring correctness and eciency. Two additional issues arise. The rst is that the cost of constraint solving may depend upon the order constraints are encountered. The second is the need to handle dynamic scheduling. We clarify these issues by proposing various types of search independence and constraint solver independence, and show how they can be combined to allow dierent optimizations, from parallelism to intelligent backtracking. Sucient conditions for independence which can be evaluated \a priori" at run-time are also proposed. Our study also yields new insights into independence in logic programming languages. In particular, we show that search space preservation is not only a sucient but also a necessary condition for ensuring correctness and eciency of parallel execution.

Exploiting goal independence in the analysis of logic programs

This paper illustrates the use of a top-down framework to obtain goal independent analyses of logic programs, a task which is usually associated with the bottom-up approach. While it is well known that the bottomup approach can be used, through the magic set transformation, for goal dependent analysis, it is less known that the top-down approach can be used for goal independent analysis. The paper describes two ways of doing the latter. We show how the results of a goal independent analysis can be used to speed up subsequent goal dependent analyses. However this speed-up may result in a loss of precisión. The influence of domain characteristics on this precisión is discussed and an experimental evaluation using a generic top-down analyzer is described.

Effectiveness of global analysis in strict independence-based automatic program parallelization

This paper presents a study of the effectiveness of global analysis in the parallelization of logic programs using strict independence. A number of well-known approximation domains are selected and tlieir usefulness for the application in hand is explained. Also, methods for using the information provided by such domains to improve parallelization are proposed. Local and global analyses are built using these domains and such analyses are embedded in a complete parallelizing compiler. Then, the performance of the domains (and the system in general) is assessed for this application through a number of experiments. We argüe that the results offer significant insight into the characteristics of these domains, the demands of the application, and the tradeoffs involved.

Independence in constraint logic programs

Studying independence of literals, variables, and substitutions has proven very useful in the context of logic programming (LP). Here we study independence in the broader context of constraint logic programming (CLP). We show that a naive extrapolation of the LP definitions of independence to CLP is unsatisfactory (in fact, wrong) for two reasons. First, because interaction between variables through constraints is more complex than in the case of logic programming. Second, in order to ensure the efUciency of several optimizations not only must independence of the search space be considered, but also an orthogonal issue - "independence of constraint solving." We clarify these issues by proposing various types of search independence and constraint solver independence, and show how they can be combined to allow different independence-related optimizations, from parallelism to intelligent backtracking. Sufficient conditions for independence which can be evaluated "a-priori" at run-time are also proposed. Our results suggest that independence, provided a suitable definition is chosen, is even more useful in CLP than in LP.

Conditional parallelization of nonStrict independence. Procedures and assessmen

This paper presents a conditional parallelization process for and-parallelism based on the notion of non-strict independence, a more relaxed notion than the traditional of strict independence. By using this notion, a parallelism annotator can extract more parallelism from programs. On the other hand, the intrinsic complexity of non-strict independence poses new challenges to this task. We report here on the implementation we have accomplished of an annotator for non-strict independence, capable of producing both static and dynamic execution graphs. This implementation, along with the also implemented independence checker and their integration in our system, have resulted what is, to the best of our knowledge, the first parallelizing compiler based on nonstrict independence which produces dynamic execution graphs. The paper also presents a preliminary assessment of the implemented tools, comparing them with the existing ones for strict independence, which shows encouraging results.

Independence and search space preservation in dynamically scheduled constraint logic languages

This paper performs a further generalization of the notion of independence in constraint logic programs to the context of constraint logic programs with dynamic scheduling. The complexity of this new environment made necessary to first formally define the relationship between independence and search space preservation in the context of CLP languages. In particular, we show that search space preservation is, in the context of CLP languages, not only a sufficient but also a necessary condition for ensuring that both the intended solutions and the number of transitions performed do not change. These results are then extended to dynamically scheduled languages and used as the basis for the extension of the concepts of independence. We also propose several a priori sufficient conditions for independence and also give correctness and efficiency results for parallel execution of constraint logic programs based on the proposed notions of independence.

A collaborative filtering similarity measure based on singularities.

Recommender systems play an important role in reducing the negative impact of informa- tion overload on those websites where users have the possibility of voting for their prefer- ences on items. The most normal technique for dealing with the recommendation mechanism is to use collaborative filtering, in which it is essential to discover the most similar users to whom you desire to make recommendations. The hypothesis of this paper is that the results obtained by applying traditional similarities measures can be improved by taking contextual information, drawn from the entire body of users, and using it to cal- culate the singularity which exists, for each item, in the votes cast by each pair of users that you wish to compare. As such, the greater the measure of singularity result between the votes cast by two given users, the greater the impact this will have on the similarity. The results, tested on the Movielens, Netflix and FilmAffinity databases, corroborate the excellent behaviour of the singularity measure proposed.

A Balanced Memory-Based Collaborative Filtering Similarity Measure.

Collaborative filtering recommender systems contribute to alleviating the problem of information overload that exists on the Internet as a result of the mass use of Web 2.0 applications. The use of an adequate similarity measure becomes a determining factor in the quality of the prediction and recommendation results of the recommender system, as well as in its performance. In this paper, we present a memory-based collaborative filtering similarity measure that provides extremely high-quality and balanced results; these results are complemented with a low processing time (high performance), similar to the one required to execute traditional similarity metrics. The experiments have been carried out on the MovieLens and Netflix databases, using a representative set of information retrieval quality measures.

Obtaining contradiction measure on intuitionistic fuzzy sets from fuzzy connectives

In a previous paper, we proposed an axiomatic model for measuring self-contradiction in the framework of Atanassov fuzzy sets. This way, contradiction measures that are semicontinuous and completely semicontinuous, from both below and above, were defined. Although some examples were given, the problem of finding families of functions satisfying the different axioms remained open. The purpose of this paper is to construct some families of contradiction measures firstly using continuous t-norms and t-conorms, and secondly by means of strong negations. In both cases, we study the properties that they satisfy. These families are then classified according the different kinds of measures presented in the above paper.

A methodology to measure the interface shear strength by means of the fiber push-in test

A methodology is presented to measure the fiber/matrix interface shear strength in composites. The strategy is based on performing a fiber push-in test at the central fiber of highly-packed fiber clusters with hexagonal symmetry which are often found in unidirectional composites with a high volume fraction of fibers. The mechanics of this test was analyzed in detail by means of three-dimensional finite element simulations. In particular, the influence of different parameters (interface shear strength, toughness and friction as well as fiber longitudinal elastic modulus and curing stresses) on the critical load at the onset of debonding was established. From the results of the numerical simulations, a simple relationship between the critical load and the interface shear strength is proposed. The methodology was validated in an unidirectional C/epoxy composite and the advantages and limitations of the proposed methodology are indicated.

Topological measure locating the effective crossover between segregation and integration in a modular network

We introduce an easily computable topological measure which locates the effective crossover between segregation and integration in a modular network. Segregation corresponds to the degree of network modularity, while integration is expressed in terms of the algebraic connectivity of an associated hypergraph. The rigorous treatment of the simplified case of cliques of equal size that are gradually rewired until they become completely merged, allows us to show that this topological crossover can be made to coincide with a dynamical crossover from cluster to global synchronization of a system of coupled phase oscillators. The dynamical crossover is signaled by a peak in the product of the measures of intracluster and global synchronization, which we propose as a dynamical measure of complexity. This quantity is much easier to compute than the entropy (of the average frequencies of the oscillators), and displays a behavior which closely mimics that of the dynamical complexity index based on the latter. The proposed topological measure simultaneously provides information on the dynamical behavior, sheds light on the interplay between modularity and total integration, and shows how this affects the capability of the network to perform both local and distributed dynamical tasks.

Independence, Global analysis, and parallelism, in dinamically scheduled constraint logic programming.

El punto de vista de muchas otras aplicaciones que modifican las reglas de computación. En segundo lugar, y una vez generalizado el concepto de independencia, es necesario realizar un estudio exhaustivo de la efectividad de las herramientas de análisis en la tarea de la paralelizacion automática. Los resultados obtenidos de dicha evaluación permiten asegurar de forma empírica que la utilización de analizadores globales en la tarea de la paralelizacion automática es vital para la consecución de una paralelizarían efectiva. Por último, a la luz de los buenos resultados obtenidos sobre la efectividad de los analizadores de flujo globales basados en la interpretación abstracta, se presenta la generalización de las herramientas de análisis al contexto de los lenguajes lógicos restricciones y planificación dinámica.