A high-precision contrast injector for small animal x-ray digital subtraction angiography

The availability of genetically altered animal models of human disease for basic research has generated great interest in new imaging methodologies. Digital subtraction angiography (DSA) offers an appealing approach to functional imaging in small animals because of the high spatial and temporal resolution, and the ability to visualize and measure blood flow. The micro-injector described here meets crucial performance parameters to ensure optimal vessel enhancement without significantly increasing the total blood volume or producing overlap of enhanced structures. The micro-injector can inject small, reproducible volumes of contrast agent at high flow rates with computer-controlled timing synchronized to cardiopulmonary activity. Iterative bench-top and live animal experiments with both rat and mouse have been conducted to evaluate the performance of this computer-controlled micro-injector, a first demonstration of a new device designed explicitly for the unique requirements of DSA in small animals. Injection protocols were optimized and screened for potential physiological impact. For the optimized protocols, we found that changes in the time-density curves for representative regions of interest in the thorax were due primarily to physiological changes, independent of micro-injector parameters.     

Accuracy of drug infusion pumps under computer control

Prototype systems implementing algorithms for automated drug infusions are typically constructed by coupling a microcomputer to a drug infusion pump through a serial communications interface. Infusion rates demanded of the infusion pump in many computed-controlled drug delivery applications are made to change at intervals much shorter than those encountered under routine clinical use. Because the ability of infusion pumps to maintain accurate flow rates during high frequency rate changes has not been documented, the purpose of this study was to validate the volumetric accuracy of three commercially available infusion pumps operating in a demanding computer-controlled application. In independent 2-h evaluations, the infusion rate demanded of each pump changed as often as every 5, 10, or 15 s using an algorithm for computer-controlled pharmacokinetic model-driven intravenous infusion. Accuracy of the infusion devices was determined gravimetrically. At all measurement times, each of the infusion pumps was accurate to within approximately +/- 5% of the expected volumetric output under each of the infusion rate intervals tested. Flow rate accuracy of +/- 5% is equal to the nominal expected accuracy of these infusion pumps in conventional clinical use.     

Automatic Focusing of a Computer-Controlled Microscope

An on-line focusing procedure for a computer-controlled microscope employed in the measurement of human chromosome images is discussed. The method is based on an algorithm proposed by Mendelsohn and Mayall. A focusing accuracy of standard deviation less than 1/20th micron in the slide-objective distance has been achieved. Changes of the focus position with time, and for individual chromosomes within a metaphase, have been investigated. The method has proved insensitive to imperfections in the scanner photocathode. The method has also been used to determine the autofocusing accuracy of an analog metaphase-finding apparatus.     

A flexible blood flow phantom capable of independently producingconstant and pulsatile flow with a predictable spatial flow profile forultrasound flow measurement validations

The validation of the ultrasound time-domain correlation method of measuring blood flow has required the development of a flexible blood flow phantom capable of generating predictable flow profiles under a wide variety of conditions. The purpose of the phantom is to generate flow with well-known flow properties and not to mimic actual in vivo vessels. This paper describes a flow phantom which can independently generate both constant and pulsatile flow over a wide range of flow rates with a spatially fully developed laminar flow profile. It incorporates a computer-controlled pulsatile pump, which can produce different temporal pulsatile waveforms. The flow phantom also supports multiple vessels, different vessel sizes, as well as different attenuating media. The fluid most commonly used in the phantom is Sephadex mixed with water, and the probability density function of ultrasound reflected from Sephadex is experimentally determined and compared with that of blood. Examples of different constant and pulsatile flow experiments using the phantom are presented.     

An automated stand for express-diagnostics of magnetoresistive structures

The design of an automated measuring stand for express-diagnostics of magnetoresistive structures are presented. This computer-controlled stand allows measurements of the magnetoresistances of film structures with high accuracy in a low alternating magnetic field. The stand has been tested on single- and multiple-layer magnetoresistive structures.     

Substitution Method for Swept-Frequency Measurements of Dielectric Properties at Microwave Frequencies

A solid-state computer-controlled system has been used to make swept-frequency measurements of the insertion loss and reflectance of biological specimens and other media. A substitution procedure was used for direct comparison of samples to allow determination of small differences (on the order of 0.1 dB) in insertion loss and reflectance.     

Electrocutaneous Tracking: A Methodology for Evaluating Sensory Feedback Codes

An objective and relevant methodology for evaluating sensory feedback codes has been developed using electrocutaneous tracking. This methodology involves dynamic (or continuous) interpretation and response by a subject to electrically produced cutaneous sensations. Results from the comparison of ten codes are briefly presented here to show the usefulness of this methodology. A general purpose computer-controlled electrocutaneous stimulation facility being developed is expected to expedite the examination of many other sensory feedback codes.     

Experimental investigation of an adaptive feedback algorithm forhot spot reduction in radio-frequency phased-array hyperthermia

A computer-controlled adaptive phased array radiofrequency hyperthermia system for improved therapeutic tumor heating is experimentally investigated. Adaptive array feedback techniques are used to modify the electric-field in hyperthermia experiments with a homogeneous saline phantom target. A hyperthermia phased-array antenna system has been modified to implement adaptive nulling and adaptive focusing algorithms. The hyperthermia system is a ring phased-array antenna applicator with four independently controlled RF transmitter channels operating at a CW frequency of 100 MHz. The hyperthermia phased array is made adaptive by software modifications which invoke a gradient-search feedback algorithm that controls the amplitude and phase of each transmitter channel. The gradient-search algorithm implements the method of steepest descent for adaptive nulling (power minimization) and the method of steepest ascent for adaptive focusing (power maximization). The feedback signals are measured by electric-field short-dipole probe antennas. The measured data indicate that with an adaptive hyperthermia array it may be possible to maximize the applied electric field at a tumor position in a complex scattering target body and simultaneously minimize or reduce the electric field at target positions where undesired high-temperature regions (hot spots) occur     

Identification and control for automated regulation of hemodynamic variables during hemodialysis

This paper proposes a novel model-based control methodology for a computer-controlled hemodialysis system, designed to maintain the hemodynamic stability of end-stage renal failure patients undergoing fluid removal during hemodialysis. The first objective of this paper is to introduce a linear parameter varying system to model the hemodynamic response of patients during hemodialysis. Ultrafiltration rate (UFR) and dialysate sodium concentration (DSC) are imposed as the inputs, and the model computes the relative blood volume (RBV), percentage change in heart rate ( ?HR), and systolic blood pressure (SBP) during the course of hemodialysis. The model parameters were estimated based on data collected from 12 patients undergoing 4 profiled hemodialysis sessions. The modeling results demonstrated that the proposed model could be useful for estimating the individual patient's hemodynamic behavior during hemodialysis. Based on the model, the second objective is to implement a computer-controlled hemodialysis system for the regulation of RBV and HR during hemodialysis while maintaining SBP within stable range. The proposed controller is based on a model predictive control approach utilizing pre-defined constraints on the control inputs (UFR and DSC) as well as the output (SBP). The designed control system was experimentally verified on four patients. The results demonstrated that the proposed computer-controlled hemodialysis system regulated the RBV and HR of the patients according to individual reference profiles with an average mean square error of 0.24% and 2.6%, respectively, and thus can be potentially useful for ensuring the stability of patients undergoing hemodialysis by avoiding sudden changes in hemodynamic variables.     

Structure of GaAs-Ga1?xAlxAs superlattices grown by metal-organic chemical vapour deposition

A computer-controlled metal-organic chemical vapour deposition system employing a fast-switching gas manifold has been used to prepare GaAs-Ga1?xAlxAs superlattice structures. A combination of cross-sectional transmission electron microscopy and Auger and secondary ion mass spectrometry sputter profiling have allowed accurate measurements to be made of layer thickness and GaAs-Ga1?xAlxAs interface widths. Layers as thin as 15 ? have been observed and interface widths less than 20 ? measured.     

Automated steady-state admittance spectroscopy for surface studies with application to solar cells

A new technique for automated admittance measurements as a function of frequency and bias has been developed and applied to characterize the insulator-base semiconductor interface of ITO semiconductor-insulator-semiconductor (SIS) solar cells. The system utilizes a computer-controlled automatic network analyzer and represents a significant improvement over impedance bridge and/or lock-in amplifier measurements arising from significantly higher speed with comparable accuracy. The results ofC-VandG-Vmeasurements of small indium tin oxide-SiOx-polycrystalline silicon solar cells, which have been used to optimize the fabrication of large-area high-efficiency solar cells are presented and discussed.     

平锁缝纫机运动控制卡设计

针对平扣眼锁眼缝纫机结构复杂,电器器件多,控制复杂的特点,在对平扣眼锁眼锁眼机的功能特征、系统结构、人机操作界面等问题的深入分析的基础上,提出了一种基于DSP和FPGA的平扣眼锁眼缝纫机运动控制卡的设计方案,该方案集成了运动控制、交流伺服控制、步进驱动控制、接口控制等功能,具有通用性好软件易于修改升级调试方便等特点。经现场应用结果表明,各项指标完全满足设计要求,得到了很好的实际应用。     

A computer-controlled research ventilator for small animals: designand evaluation

The understanding of the mechanical properties of the mammalian respiratory system and how they change under the influence of drugs and in disease are frequently pursued in small animals, since they can be easily obtained in large numbers as pure-bred strains. However, conventional experimental set-ups for studying small animals are generally limited in their ability to measure gas flow into the lungs. Here, the authors present a computer-controlled research ventilator for small animals which can provide conventional mechanical ventilation as well as arbitrary flow perturbations with a bandwidth from 0-55 Hz. Respiratory impedance is estimated from the displacement of the piston and the pressure it generates, thereby obviating the need for a direct flow measurement. The performance of the device was tested on mechanical loads whose impedances were calculated theoretically. The measured and predicted loads agreed within less than 5% up to 30 Hz. Furthermore, the measured impedance of two mechanical loads in series precisely matched the sum of their individual impedances     

LSI and VLSI research in Japan

The author reviews recent advancements in LSI and VLSI research in Japan, especially concerning the basic technology useful for microfabrication. The first computer-controlled vector scan electron-beam exposure system in Japan was reported in 1967. Recently, the variable area rectangular technique has been experimentally pursued. Another group is working on probe forming by quadrupole lenses. A raster scan electron system enabling high charge density electron-beam exposure and use of PMMA resist has been designed and constructed. In the processing field, a high-frequency plasma system, a plasma transport system, and a high-pressure oxidation system are under development. Various self-aligning devices, such as diffusion self-alignment, multiple-wall self-alignment, and those which work near punch-through regions are described.     

A simple analytical solution to the three-compartmentpharmacokinetic model suitable for computer-controlled infusion pumps

The disposition of many drugs following an intravenous bolus injection can be described by a biexponential or triexponential equation. Computer-controlled infusion pumps have been developed which dose intravenous drugs based on models of drug disposition. These pumps can maintain steady plasma drug concentrations and facilitate controlled increases and decreases in drug concentration, enhancing titration of intravenous drugs. Several investigators have proposed analytical solutions to the biexponential and triexponential disposition functions for use in computer-controlled infusion pumps. Because of the complexity of these analytical solutions, other investigators have used numerical techniques to approximate the analytical solution. We have derived an extremely simple analytical solution to polyexponential disposition functions. This solution simplifies both the prediction of the plasma drug concentration by a computer-controlled infusion pump and the stepwise calculation of the infusion rate required to maintain constant plasma drug concentrations.     

Applications of a computer-controlled terminal to mobile-telephone communication systems

A computer-controlled terminal offers numerous advantages in efficiency and versatility when applied to a mobile-telephone communications system. A particular computer-controlled terminal is described and an example is used to show how complex systems requirements can be satisfied by using this terminal.     

Pulsed measurements and circuit modeling of weak and strong avalanche effects in GaAs MESFETs and HEMTs

An extensive characterization of the on-state breakdown characteristics of GaAs based MESFETs and HEMTs has been carried out by means of DC and pulsed measurements and of circuit simulations. A computer-controlled, three-terminal Transmission Line Pulse (TLP) system with 50-100 ns pulse width and sub-ns risetime has been developed, which allows automated pulsed measurements of device I-V characteristics. The TLP system has been adopted for nondestructive measurements of the on-state breakdown characteristics of GaAs MESFETs and HEMTs up to unprecedented values of gate current density (I/sub G//W=30 mA/mm has been reached), in strong avalanche conditions. The device behavior in strong avalanche conditions is dominated by a parasitic bipolar effect (PBE) similarly to SOI and bulk Si MOSFETs. By taking into account this and other parasitic effects, an equivalent circuit model, suitable for SPICE simulations has been developed. The proposed model is capable of predicting the exact behavior of the gate and drain currents in both weak and strong avalanche conditions.     

A physiologic regurgitant cardiac valve phantom for magneticresonance imaging or color Doppler ultrasound study

Noninvasive imaging has proven successful in the evaluation of valvular heart disease; primarily with magnetic resonance imaging (MRI) and color Doppler ultrasound (CFM). However, the relationship between the morphology of regurgitant flow in MRI and CFM, as a function of hemodynamic parameters (chamber pressure difference, lesion size, compliance, etc.) is not understood. The goals for this work were: 1) to develop a computer-controlled regurgitant cardiac valve phantom, compatible with artifact-free CFM and MR imaging, 2) to create regurgitant lesions in the phantom which appear similar to those detected clinically, 3) to produce and measure physiologic pressure differences between chambers, compliances, and regurgitant fractions as seen in mild, moderate, and severe regurgitation. Mean chamber pressure differences ranged from 43-142 mmHg over the range of diseases simulated. Similarly, regurgitant flow rates ranged from approximately 0.54-18.6 L/min. Compliance values ranged from 0.83 to 21.95 cc/mmHg. No coherent or incoherent artifacts were observed in MRI or CFM images. Images show a high degree of similarity to regurgitant lesions detected with each modality, confirming that all design goals were met. The system should allow extensive comparative analysis of Doppler ultrasound and MRI flow jets under a wide range of controllable hemodynamic conditions in future experiments.     

Computer-controlled resist exposure in the scanning electron microscope

In modern microelectronics, complicated structures with very small dimensions must be fabricated on active-device materials. This task has been traditionally accomplished by photolithographic techniques, but electron-beam exposure of resist materials has recently been explored [1]-[3]. Submicron electron devices have been fabricated in several laboratories, often featuring a flying-spot scanner to generate the pattern being exposed [4]-[7]. Paper tape drives have been used for repetitive patterns [8], and computer control of the electron beam has been reported also [1], [9]. The electron resist that has shown the highest resolution to date appears to be poly-(methyl methacrylate) (PMM). We have used this material in a resist form for microelectronic device fabrication, and in bulk form to determine energy dissipation profiles. The exposure is performed with a computer-controlled scanning electron microscope (CCSEM). In this paper, we describe the electron beam system briefly, discuss the processes involved in resist exposure and development, describe our exposure procedures using the CCSEM, and show results of fabricated devices and energy dissipation studies.     

Zugsicherungstechnik bei der Wiener U-Bahn

For the second building stage of the Vienna subway with the lines U3 and U6 whose first plants went in operation in September 1988, the conceptions for the signal installations and the train protection were to be determined on time. Numerous innovations are to be recorded although one could not yet then decide for computer-controlled interlocking systems nevertheless compared to the plants in the subway ground net, as the modular interlocking system (MSU) developed especially for the Vienna subway, the electronic LZB devices LZB 513, simulation with the system TRANSIT, remote control of the interlocking stations with the computer-controlled system Command 900 as well as integration of the proved computer-controlled train guidance system BLW. The report consequently contains the outfit state of the last decade on the sector train control system plants at the Vienna subway with view onto the outfit of the new lines.