Calibrated single-plunge bipolar electrode array for mapping myocardial vector fields in three dimensions during high-voltage transthoracic defibrillation

Mapping of the myocardial scalar electric potential during defibrillation is normally performed with unipolar electrodes connected to voltage dividers and a global potential reference. Unfortunately, vector potential gradients that are calculated from these data tend to exhibit a high sensitivity to measurement errors. This paper presents a calibrated single-plunge bipolar electrode array (EA) that avoids the error sensitivity of unipolar electrodes. The EA is triaxial, uses a local potential reference, and simultaneously measures all three components of the myocardial electric field vector. An electrode spacing of approximately 500 microm allows the EA to be direct-coupled to high-input-impedance, isolated, differential amplifiers and eliminates the need for voltage dividers. Calibration is performed with an electrolytic tank in which an accurately measured, uniform electric field is produced. For each EA, unique calibration matrices are determined which transform potential difference readings from the EA to orthogonal components of the electric field vector. Elements of the matrices are evaluated by least squares multiple regression analysis of data recorded during rotation of the electric field. The design of the electrolytic tank and electrode holder allows the electric field vector to be rotated globally with respect to the electrode axes. The calibration technique corrects for both field perturbation by the plunge electrode body and deviations from orthogonality of the electrode axes. A unique feature of this technique is that it eliminates the need for mechanical measurement of the electrode spacing. During calibration, only angular settings and voltages are recorded. For this study, ten EAs were calibrated and their root-mean-square (rms) errors evaluated. The mean of the vector magnitude rms errors over the set of ten EAs was 0.40% and the standard deviation 0.07%. Calibrated EAs were also tested for multisite mapping in four dogs during high-voltage transthoracic shocks.     

The SSD graph: a tool for project scheduling and visualization

A graphic tool, the SSD (structure, states and deviation) graph, is proposed for three important phases of project management; planning and scheduling, control, and evaluation. The SSD graph represents the structure, states (scheduled and actual states), and deviation of a system. A project management system using the SSD graph is developed, and it visualizes the actual state of a project and keeps the historical record of the project performance. This system allows a project manager to see the overall status and to review the project performance. Several applications have shown its usefulness for scheduling and control of project systems     

Simplified calibration of single-plunge bipolar electrode array for field measurement during defibrillation

In an earlier study, the authors presented a calibration technique for a triaxial bipolar electrode array (EA) that used 72 data points collected during a global sweep of the electric field vector relative to the EA axes. Although necessary for the initial characterization of the EAs, this data requirement has to be significantly reduced for the technique to become a practical tool. Therefore, in the present study, an analysis is performed to determine the relation between the number of data points used in the calibration and the mean root-mean-square error. The analysis shows that 18 data points can produce results nearly identical to those obtained with the 72-point calibration, thus reducing the required amount of data fourfold.     

Effect of electrode surface area on thresholds for AC stimulation and ventricular fibrillation

Unintended, weak AC stimulation (leakage currents) from medical devices can cause blood pressure collapse and ventricular fibrillation (VF), potentially even death. Yet, little is understood about AC cardiac stimulation. The objective of this paper is to establish the relationship between the stimulation and VF thresholds for electrode size and stimulation frequency. Twenty-four retired male breeder guinea pigs were anesthetized with isoflurane, a tracheotomy and thoracotomy were performed, and vitals were monitored using the lead II ECG and an optical plethysmograph. The circular flat ends of eleven stainless steel rods were used as electrodes with areas ranging from 0.1 to 26.79 mm2. In the first study, 60-Hz AC stimuli of 5 s duration were delivered with strengths from 25-3000 microA or until VF was induced. In the second group, the current thresholds at 20, 40, 80, and 160 Hz were determined at electrode areas of 0.2, 2.01, and 16.4 mm2. Reactions were categorized as having no effect, having some effect (EFFECT, typically blood pressure collapse), and inducing VF. On a log-log scale, electrode radii had a piecewise-linear relationship with the current thresholds for EFFECT (p < 0.005) and VF (p < 0.01). The liminal area determined by the piecewise-linear fit was 2.0 and 2.84 mm2 for EFFECT and VF, respectively. Above the liminal area, the threshold increased proportional to r(1.25) and r(0.95) (r = radius of electrode), for EFFECT and VF, respectively. Based on these experimental results, we present a theoretical framework to explain the electrode size-stimulation threshold variation for both low strength AC stimulation and VF initiation.     

Rapid assessment of electrode characteristics for impedance imaging

Electrical impedance imaging is the technique for producing images of the resistivity of internal body structures based on measurements of voltage and current from electrodes applied to the body's surface. When a multiplicity of electrodes are applied in one or more rows around a body structure such as the thorax or limb, it is useful to be able to rapidly assess the general status of the electrode-body interface to determine if the skin has been suitably prepared, and that electrode and skin impedance are suitably low. In addition, assessment of the impedance of individual electrodes should precede acquisition of data for image formation. This communication presents techniques for assessing the overall skin and electrode impedances relative to the impedance of the body interior, and for assessing the integrity of each electrode's contact impedance.     

A method for designing control parameters of a 3-DOF parallel tool head

The mechatronic system of a parallel tool head consists of the mechanical subsystem and the control subsystem, and appropriate control parameters have a significant effect on the performance of the parallel tool head. Thus, it is a core issue of how to make the right choice of the control parameters. However, due to the time-varying and coupling dynamic characteristics, there is still not an effective control parameters design method during industrial machining process. In this paper, by taking a 3-DOF parallel tool head with proportional control and velocity feedforward compensation as an object of study, a complete method for designing control parameters is investigated. First, a coupling variable is specified to reflect the dynamic properties between the mechanical subsystem and the control subsystem. Next, a novel dynamic index is proposed to evaluate the dynamic load of each driving shaft in the workspace, and the shaft with maximum dynamic load should be mainly pay attention. Then, based on the typical movement experiments, two design indices are proposed to ensure that the coupling variable has appropriate properties during the motion process. Finally, a parameters design experiment and a cutting experiment of an S-shaped test piece are performed, the results show that compared with the original control parameters used in industry, the tracking error of the driving shaft is much better when using the optimized control parameters, and the test piece meets the accuracy requirement. This design thought can also be applied to other parallel manipulators in industry.     

Kalman filter with hypothesis testing: A tool for estimating uncertain parameters

In this paper we present a simple and practical algorithm for the estimation of uncertain parameters of linear systems. The uncertainty is twofold, involving random observation noise, and possible jumps in the parameter values. The jumps may occur at unknown points in time, and are of unknown magnitudes and directions. The algorithm is based on the Kalman filter, with a single-sample hypothesis test, which is used to employ a three-state decision rule (yes, no, maybe). The maybe choice invokes a fading memory Kalman filter. The overall algorithm contains the constant parameter filter, fading memory filter, and the set of tests and rules that enable it to switch back and forth between the two filters. Application examples are presented.     

Molecular visualization: a microcosm of the e-revolution

Molecular visualization software programs display a 3D arrangement of molecules in an interactive format, allowing researchers to examine known molecules as well as theoretical molecules in drug development. In the last two decades, biochemistry has shifted its emphasis from bonds and connectivity to surfaces and interactions. Molecular visualization, at the intersection of computer graphics and chemistry, accelerated this transition with interactive displays of 3D molecular models on personal computers. The free access to both molecular databases and visualization programs has enhanced our understanding of basic biological concepts. Molecular visualization also encompasses a thriving Internet community that is constantly honing and dynamically revising software implementations in response to user feedback. There's no question that computer technology has revolutionized biomedical fields such as biochemistry, genetic engineering, and molecular biology. We can now study critical biomolecules in their folded form rather than as a string of amino acids.     

High-pressure freezing is a powerful tool for visualization of Schizosaccharomyces pombe cells: ultra-low temperature and low-voltage scanning electron microscopy and immunoelectron microscopy

Yeast cells have a thick cell wall composed of an inner network of glucans and an outer layer of mannoproteins, which is difficult to penetrate with osmium tetroxide. We previously developed the sandwich technique to overcome this problem. Although the freeze-etching method allows the fracturing of cryofixed yeast cells, it has been difficult to fracture cryofixed yeast cells for examination by cryo-scanning electron microscopy (SEM). The development of an alternative method of cryofixation, namely, high-pressure freezing, began in the 1960s and is now available for the electron microscopic analysis of yeast. We show here that when high-pressure freezing is combined with ultra-low temperature and low-voltage SEM using the new cryo-system, the Gatan Alto 2500 Cryo Transfer System, fractured and coated yeast samples could be quickly prepared. These samples yielded a fine fracture plane and revealed the ultrastructure of both external and internal cell components. We used this method to analyze the process of septum formation, one of the final and most important events of mitosis, and cell separation. The images we obtained provide a three-dimensional view of these processes for the first time. We also showed that high-pressure freezing in combination with immunoelectron microscopy made it possible to preserve the antigenicity, in situ localization, and behavior of the cell wall component alpha-1,3-glucan and its synthase during septum formation in Schizosaccharomyces pombe.     

Condition assessment for automatic tool changer based on sparsity-enabled signal decomposition method

Automatic tool changer (ATC) is one of the key basic parts in CNC machining centers, and the globoidal indexing cam and the groove cam are the functional units for tool changing. Thus the condition monitoring is important for highly efficient and precision machining. In this paper, a condition monitoring system is constructed for the ATC, especially for the globoidal indexing cam, including vibration signal acquisition, fault feature extraction and localization, and condition assessment. In the constructed system, sparsity-enabled signal decomposition method is introduced to extract transient component and reduce noises in the complex vibration signals, and the transient component is always a key feature for fault localization. Simulation study shows that the sparsity-enabled signal decomposition method is effective in transient feature extraction. The experimental application in condition assessment for the ATC demonstrates that the constructed condition monitoring system has the potential to assess the working condition of the ATC in practical application.     

PLANET: a tool for telecommunication network

PLANET is an integrated software package aiding several steps of the transmission network planning, as well as the traffic simulation. The database of PLANET consists of the structural and the cost models of the transmission systems, the topological alternatives, the circuit routing and grouping rules, etc. The topological and transmission plans of the networks are obtained based on the traffic planning results checked by simulation and they are stored systematically with the input data in the database of plans. The results describe the network topology, the circuit routes meeting different kinds of routing conditions, the grouping solutions and the equipment assignments to the circuit demands of different services. The users of PLANET are provided with lists and graphical documentation that can be directly used in the development of the network. The global structure of the software package as well as the algorithms of specific phases are discussed and the results obtained by the application of PLANET are demonstrated     

FIFA: A fault-injection–fault-analysis-based tool for reliability assessment at RTL level

This paper presents an efficient platform for fault robustness estimation of digital circuits. The proposed platform, named FIFA, was designed as a hardware IP to accelerate the Fault Injection and Fault masking Analysis approach. It supports several fault models as well as single and multiple faults. Synthesis results have shown that the proposed platform can exceed those existent in the literature in terms of area efficiency and performance. In addition, the FIFA platform allows the designer to control complexity and completeness of the analysis process.     

激光工艺参数对PCD刀具材料去除量的影响

为了提高聚晶金刚石(PCD)刀具断屑槽激光去除的效率,选取激光功率、频率、扫描速度和重复次数作为实验因素,以PCD刀具材料去除量为响应指标。通过实验设计,利用Minitab软件建立了聚晶金刚石材料去除量与激光工艺参数之间的回归方程,并对工艺参数进行了优化。实验结果表明,功率对材料去除量的影响最大,频率次之,重复次数影响最小,工艺参数之间的交互作用也影响着材料去除量。所建立的回归方程能够较好地反映聚晶金刚石材料去除量与激光工艺参数之间的关系。     

TOPNET: a tool for the visual simulation of communication networks

TOPNET is a software package for the simulation of communication networks that is being developed with the aim of exploiting as much as possible the visual aspects of a simulation experiment. The communication network topology and architecture are described by drawings, the system dynamics are represented with a class of timed Petri nets, the simulation experiment is controlled through menus and buttons activated with a mouse, and results are graphically displayed on the screen. With the help of an example, the main characteristics of the user interface and the internal architecture of TOPNET are described     

Effect of a bath on the epicardial transmembrane potential during internal defibrillation shocks

Using a three-dimensional model of cardiac tissue, we consider a rectangular slab of tissue. We examine the effect of a defibrillating shock from an intracavitary electrode upon the epicardial transmembrane potential (Vm) for two cases: one in which the epicardium is bounded by air and another in which it is bounded by a conductive bath. We find that the inclusion of the bath changes the polarity of the steady-state Vm in the epicardial region that is closest to the shock electrode. In addition, the magnitude of Vm is increased dramatically if the bath is present; the degree of hyperpolarization increases twenty-fivefold, while the degree of depolarization increases elevenfold. The remaining bulk of the cardiac tissue is relatively unaffected by the inclusion of the bath.     

A quasi-static tool for the EMI/EMC analysis of analog circuits:parasitic extractor tool and simulator of EMI parameters (PET+SEP)

A quasi-static approach for evaluating inductive and capacitive coupling and radiated noise in the standard electromagnetic compatibility (EMC) measurement conditions has been developed. Multilayer structures are analyzed considering a quasi-static Green's function formulation. Variational approaches have been followed to compute inductive and capacitive parasitics. Electric and magnetic multipolar expansions are used for a fast computation of near- and far-field radiated noise in a large broad band. The approach has been validated by considering different cases ranging from simple circuits to realistic switched-mode power supplies and some of the validation cases are presented. The main advantages of this method is the short central processing unit (CPU) time it requires to provide reliable results for EMC analysis and design purposes     

SYSIM: a simulation tool for systolic processors

A simulation tool for systolic processor design has been built. The tool is implemented using synchronous communicating processes. The simulation language allows for hierarchical definition of processor cells. Both high-level and low-level operations can be defined in the system for ease of simulation. Off-line and interactive simulation are possible.     

MEADEP: a dependability evaluation tool for engineers

MEADEP (measure dependability) is a user-friendly dependability-evaluation tool for measurement-based analysis of critical systems. MEADEP consists of 4 software modules: a data preprocessor for converting data in various formats to the MEADEP format, a data analyzer for graphical data-presentation and parameter estimation, a graphical modeling interface for building block diagrams (including the exponential block, Weibull block, and k-out-of-n block) and Markov reward chains, and a model-solution module for availability/reliability calculations with graphical parametric analysis. Use of the tool on failure data, from measurements provides quantitative evaluations of dependability for the target system, while greatly reducing requirements for specialized skills in data-analysis and system-modeling from the user. MEADEP has been applied to evaluate availability for two air-traffic control systems based on operational failure data; the results have provided valuable feedback to the project management of these critical systems. MEADEP has been used to analyze a nuclear power-plant safety model, based on the Eagle 21 architecture and its early field-failure data. The study identified the most sensitive parameter and its most sensitive value segment to the plant mean time between hazards     

Effect of paddle placement and size on defibrillation currentdistribution: a three-dimensional finite element model

A realistic three-dimensional finite-element model (FEM) of the conductive anatomy of a canine thorax was constructed for use in the study of transthoracic electrical defibrillation. The model was constructed from a series of 21 cross-sectional computed tomography (CT) scans of a 14.5 kg beagle, each separated by 0.82 cm. The electrical conductive properties of eight distinct tissues were incorporated, including the anisotropic properties of skeletal muscle. Current density distributions were obtained for six paddle pairings and two paddle sizes. A quantitative basis for comparing the resulting distributions was formulated. The results suggest that placing one or both of the paddles near the heart delivers a higher fraction of current to the heart. However, such placements also produce a less uniform myocardial current density distribution and thus have a higher potential for causing damage. Some paddle positions produced myocardial current densities close to the threshold for damage in successful defibrillations. The results indicate that 12 cm paddles may offer modest advantages over 8 cm paddles in clinical defibrillation