Pathological element-based active device models and their application to symbolic analysis

This paper proposes new pathological element-based active device models which can be used in analysis tasks of linear(ized) analog circuits. Nullators and norators along with the voltage mirror-current mirror (VM-CM) pair (collectively known as pathological elements) are used to model the behavior of active devices in voltage-, current-, and mixed-mode, also considering parasitic elements. Since analog circuits are transformed to nullor-based equivalent circuits or VM-CM pairs or as a combination of both, standard nodal analysis can be used to formulate the admittance matrix. We present a formulation method in order to build the nodal admittance (NA) matrix of nullor-equivalent circuits, where the order of the matrix is given by the number of nodes minus the number of nullors. Since pathological elements are used to model the behavior of active devices, we introduce a more efficient formulation method in order to compute small-signal characteristics of pathological element-based equivalent circuits, where the order of the NA matrix is given by the number of nodes minus the number of pathological elements. Examples are discussed in order to illustrate the potential of the proposed pathological element-based active device models and the new formulation method in performing symbolic analysis of analog circuits. The improved formulation method is compared with traditional formulation methods, showing that the NA matrix is more compact and the generation of nonzero coefficients is reduced. As a consequence, the proposed formulation method is the most efficient one reported so far, since the CPU time and memory consumption is reduced when recursive determinant-expansion techniques are used to solve the NA matrix.Promep-Mexico UATLX-PTC-088Junta de Andalucía TIC-2532Ministerio de Educación y Ciencia TEC2007-67247, TEC2010-14825UC-MEXUS-CONACyT CN-09-31

On the Systematic Synthesis of OTA-Based KHN Filters

According to the nullor-mirror descriptions of OTA, the NAM expansion method for three different types of KHN filters employing OTAs is considered. The type-A filters employing five OTAs have 32 different forms, the type-B filters employing four OTAs have 32 different forms, and the type-C filters employing three OTAs have eight different forms. At last a total of 72 circuits are received. Having used canonic number of components, the circuits are easy to be integrated and both pole frequency and Q-factor can be tuned electronically through tuning bias currents of the OTAs. The MULTISIM simulation results have been included to verify the workability of the derived circuit

Behavioral Modeling of Mixed-Mode Integrated Circuits

Open Access.-- et al.This work is partially supported by CONACyT through the grant for the sabbatical stay of the first author at University of California at Riverside, during 2009-2010. The authors acknowledge the support from UC-MEXUS-CONACYT collaboration grant CN-09-310; by Promep México under the project UATLX-PTC-088, and by Consejeria de Innovacion Ciencia y Empresa, Junta de Andalucia, Spain, under the project number TIC-2532. The third author thanks the support of the JAE-Doc program of CSIC, co-funded by FSE.Peer Reviewe

TrauMAP - Integrating Anatomical and Physiological Simulation (Dissertation Proposal)

In trauma, many injuries impact anatomical structures, which may in turn affect physiological processes - not only those processes within the structure, but also ones occurring in physical proximity to them. Our goal with this research is to model mechanical interactions of different body systems and their impingement on underlying physiological processes. We are particularly concerned with pathological situations in which body system functions that normally do not interact become dependent as a result of mechanical behavior. Towards that end, the proposed TRAUMAP system (Trauma Modeling of Anatomy and Physiology) consists of three modules: (1) a hypothesis generator for suggesting possible structural changes that result from the direct injuries sustained; (2) an information source for responding to operator querying about anatomical structures, physiological processes, and pathophysiological processes; and (3) a continuous system simulator for simulating and illustrating anatomical and physiological changes in three dimensions. Models that can capture such changes may serve as an infrastructure for more detailed modeling and benefit surgical planning, surgical training, and general medical education, enabling students to visualize better, in an interactive environment, certain basic anatomical and physiological dependencies

Parameterization of a Next Generation In-Vivo Forward Solution Physiological Model of the Human Lower Limb to Simulate and Predict Demographic and Pathology Specific Knee Mechanics

The human knee from a mechanical perspective is arguably one of the more complex of the joints of the human body and for this very reason there are a number of pathological factors that can adversely affect knee function, leading to pain, stiffness and an overall reduced quality of life. To rectify these disease conditions, a variety of intervention techniques exist, all of which are predicated on a thorough understanding of the forces and motions that occur at the knee.Various techniques have been developed to further the understanding of how the knee functions; however, many of these strategies involve time and cost consuming processes in order to assess functionality of the knee. Mathematical modeling is a methodology that uses mathematical equations of motion to solve for forces, or in the case of forward modeling, motions given a known set of forces. Such a model is capable of replicating the functionality of the knee in vivo.One application of such a model is in the context of total knee arthroplasty design. Intended for the restoration of functionality after late stage osteoarthritis, total knee arthroplasty devices are highly dependent on their associated design features and the use of a theoretical model affords the opportunity to test the performance of a device without ever needing to manufacture or implant it.In addition, there are also surgical applications where a mathematical model can test joints that otherwise cannot be evaluated under conventional means. This includes modeling of the healthy knee, as well as various functionality-limiting pathological conditions. Perhaps more importantly is the ability to evaluate different intervention techniques to determine the effectiveness in doing so identify which technique most effectively resolves the pathological issues.Advances to the model have focused on parameterization while contributing to a validated normal knee model, an enhancement on the efficiency of the muscles that drive flexion, facilitated methods to evaluate articular geometries and enhancements providing more realistic physiological motions. The model has also been enhanced to account for demographics, as well as abnormal pathology with additional parameters added to better understand gait mechanics at the knee

Dissociation and interpersonal autonomic physiology in psychotherapy research: an integrative view encompassing psychodynamic and neuroscience theoretical frameworks

Interpersonal autonomic physiology is an interdisciplinary research field, assessing the relational interdependence of two (or more) interacting individual both at the behavioral and psychophysiological levels. Despite its quite long tradition, only eight studies since 1955 have focused on the interaction of psychotherapy dyads, and none of them have focused on the shared processual level, assessing dynamic phenomena such as dissociation. We longitudinally observed two brief psychodynamic psychotherapies, entirely audio and video-recorded (16 sessions, weekly frequency, 45 min.). Autonomic nervous system measures were continuously collected during each session. Personality, empathy, dissociative features and clinical progress measures were collected prior and post therapy, and after each clinical session. Two-independent judges, trained psychotherapist, codified the interactions\u2019 micro-processes. Time-series based analyses were performed to assess interpersonal synchronization and de-synchronization in patient\u2019s and therapist\u2019s physiological activity. Psychophysiological synchrony revealed a clear association with empathic attunement, while desynchronization phases (range of length 30-150 sec.) showed a linkage with dissociative processes, usually associated to the patient\u2019s narrative core relational trauma. Our findings are discussed under the perspective of psychodynamic models of Stern (\u201cpresent moment\u201d), Sander, Beebe and Lachmann (dyad system model of interaction), Lanius (Trauma model), and the neuroscientific frameworks proposed by Thayer (neurovisceral integration model), and Porges (polyvagal theory). The collected data allows to attempt an integration of these theoretical approaches under the light of Complex Dynamic Systems. The rich theoretical work and the encouraging clinical results might represents a new fascinating frontier of research in psychotherapy

Towards an epistemology of medical imaging

Tese de doutoramento (co-tutela), História e Filosofia das Ciências (Filosofia), Faculdade de Ciências da Universidade de Lisboa, Università degli Studi di Milano, 201