Microprocessor-based data acquisition system for respiratory signals

Microprocessors are having an increasing role in online measurements in the medical field instead of large computers because of their compactness, low cost and ease of operation. This paper describes a microprocessor-based data acquisition system representing the primary stage in designing a larger online acquisition and processing system for measurement and correlation of respiratory signals. The system designed has the features of easy communication, flexibility of operation and system's software and hardware. The system uses a mass storage unit for permanent data storage. A detailed discussion of the hardware and software is presented.     

DNA cleavage, antiviral and cytotoxic reactions photosensitized by simple enediyne compounds

Very potent antibiotic antitumor natural products contain a enediyne moiety which, upon thermal activation, is capable of abstracting hydrogens from DNA. 1,6-Diphenyl-3-hexene-1,5-diyne was selected as a candidate for inducing DNA strand breaks photochemically. Easily interconverted with light, both geometric isomers 1 and 2 were expected to be phototoxic. As anticipated, they photosensitized the production of strand breaks in double-stranded supercoiled pBR322, and in single-stranded M13 DNA. The DNA cleavage reactions were favored by the presence of oxygen and were inhibited by ethanol. Preliminary experiments with the (Z)-isomer indicated moderate light-dependent antiviral activity against human immunodeficiency virus (HIV), Sindbis virus, and mouse cytomegalovirus. The enediynes were cytotoxic to Escherichia coli, a gram-negative organism, to Streptococcus faecalis, a gram-positive organism, to Daphnia magna and to fish (Pimephales promelas), but only in the presence of light. The production of o-terphenyl, the expected product of Bergman cyclization of 1, could not be confirmed. However, both 1 and 2 photosensitized the formation of singlet oxygen and of superoxide anion radical, and photodynamic reactions could have been responsible for some of the phototoxic reactions observed.     

Gallager?s Exponent for MIMO Channels: A Reliability-Rate Tradeoff

In this paper, we derive Gallager's random coding error exponent for multiple-input multiple-output (MIMO) Rayleigh block-fading channels, assuming no channel-state information (CSI) at the transmitter and perfect CSI at the receiver. This measure gives insight into a fundamental tradeoff between the communication reliability and information rate of MIMO channels, enabling to determine the required codeword length to achieve a prescribed error probability at a given rate below the channel capacity. We quantify the effects of the number of antennas, channel coherence time, and spatial fading correlation on the MIMO exponent. In addition, the general formulae for the ergodic capacity and the cutoff rate in the presence of spatial correlation are deduced from the exponent expressions. These formulae are applicable to arbitrary structures of transmit and receive correlation, encompassing all the previously known results as special cases of our expressions.     

Feedforward Controller of Ill-Conditioned Hysteresis Using Singularity-Free Prandtl–Ishlinskii Model

Piezoelectric, magnetostrictive, and shape memory alloy actuators are gaining importance in high-frequency precision applications constrained by space. Their intrinsic hysteretic behavior makes control difficult. The Prandtl-Ishlinskii (PI) operator can model hysteresis well, albeit a major inadequacy: the inverse operator does not exist when the hysteretic curve gradient is not positive definite, i.e., ill condition occurs when slope is negative. An inevitable tradeoff between modeling accuracy and inversion stability exists. The hysteretic modeling improves with increasing number of play operators. But as the piecewise continuous interval of each operator reduces, the model tends to be ill-conditioned, especially at the turning points. Similar ill-conditioned situation arises when these actuators move heavy loads or operate at high frequency. This paper proposes an extended PI operator to map hysteresis to a domain where inversion is well behaved. The inverse weights are then evaluated to determine the inverse hysteresis model for the feedforward controller. For illustration purpose, a piezoelectric actuator is used.     

Threshold-Based Time-of-Arrival Estimators in UWB Dense Multipath Channels

The need for accurate positioning has gained significant interest recently, especially in cluttered environments where signals from satellite navigation systems are not reliable. Positioning systems based on ultrawide bandwidth (UWB) technology have been considered for these environments because UWB signals are able to resolve multipath and penetrate obstacles. These systems usually obtain range measurements from timeof- arrival (TOA) estimation of the first path, which can be a challenge in dense multipath environments. In this paper, we analyze and compare the performance of matched filter (MF) and energy detector (ED) TOA estimators based on thresholding in UWB dense multipath channels. The main advantage of threshold-based estimators is that they have the potential for complete analog implementation and hence they are particularly attractive for applications that require low cost battery-powered devices. Closed-form expressions for the estimator bias and mean square error (MSE) are derived as a function of the signalto- noise ratio. A comparison with results obtained from Monte Carlo simulation confirms the validity of our analytical approach. This analysis enables us to determine the threshold value that minimizes the MSE, a critical parameter for optimal estimator design. A simple criteria to determine the threshold value is also presented. It is shown that the estimation accuracy is mainly affected by the ambiguity in the selection of the correct peak at the output of the MF or ED, caused by the fading characteristics of the first path. We also evaluate the performance loss of ED estimators with respect to MF estimators. Finally, results based on experimental measurements in an indoor residential environment are presented in order to compare the performance of TOA estimators in realistic environments.     

Frequency offset estimation for MB-OFDM-based UWB systems

We address low-complexity, highly-accurate frequency offset estimation for multi-band orthogonal frequency division multiplexing (MB-OFDM) based ultra-wide band systems in time-invariant as well as time-variant channels. We investigate the unique characteristics of MB-OFDM systems, namely, different frequency offsets, channel responses, received energies, and preamble structures in different frequency bands. Utilizing them, we develop frequency offset estimators based on the best linear unbiased estimation principle. If compared to the reference estimators, our proposed methods achieve significantly better estimation performance (4 to 6.4 dB (5 to 20 dB) estimation mean-square error advantage in the time-invariant (time-variant) channels) for all preamble patterns of the MB-OFDM system in [8].     

A method for determining the flow front velocity of a plastic melt in an injection molding process

During the filling phase of an injection molding process, the flow front velocity of the plastics melt has a decisive influence on the form part quality. It has been believed that a constant flow front velocity of the melt leads to distortion‐free and residual stress‐free form parts. A process control strategy based on a constant flow front velocity of the melt, however, requires the full understanding of the flow front position as a function of the screw position of the injection molding machine. With current methods, this can only be achieved by direct measurements using a number of sensors inside the mold, which leads to complicated structure, great efforts, and high cost for the tooling equipment. This article proposes, designs, and develops an innovative method for determining the flow front velocity of a plastic melt in an injection molding using only one pressure sensor at the front of the screw and based on the idea of mapping a simulated filling process to a real injection molding process. The mapping ensues that the characteristic event points are identified and matched for both the simulated and real filling process. The results of the simulation analysis and experimental evaluation show that the proposed method can be used to determine the flow front position and the resulting flow front velocity of the melt within the cavity of the mold and provide evidence that the new method offers great potential to process control strategies based on machine independent parameters. POLYM. ENG. SCI., 59:1132–1145 2019. © 2019 Society of Plastics Engineers     

Interaction between triiodothyronine and ovarian steroid hormones on the regulation of the release of thyrotropin and thyrotropin-releasing hormone in vitro

Laparoscopic access to the retroperitoneum without abdominal insufflation has recently been made possible by devices designed to create a dilated laparoscopic cavity maintained by a fixed retraction system. This technique was applied in 10 patients undergoing laparoscopic ligation of the internal spermatic vein via extraperitoneal and intraperitoneal approaches. Gasless laparoscopic varicocelectomy was completed in 7 of 8 men by the extraperitoneal route and in neither of the 2 men approached intraperitoneally. The mean operative time was 170+/-55 min and postoperative pain exceeded the norm for standard insufflative laparoscopic varicocelectomy. Whereas certain theoretical advantages are offered by the gasless extraperitoneal approach to varicocele ligation, exposure through the gasless technique is currently suboptimal. Further development of "retraction" technology is required, prior to its routine application for varicocele ligation.     

Electrostatic enhancement of diffusion-controlled protein-protein association: comparison of theory and experiment on barnase and barstar

The electrostatic enhancement of the association rate of barnase and barstar is calculated using a transition-state theory like expression and atomic-detail modeling of the protein molecules. This expression predicts that the rate enhancement is simply the average Boltzmann factor in the region of configurational space where association occurs instantaneously in the diffusion-controlled limit. Based on experimental evidence, this "transition state" is defined by configurations in which, relative to the stereospecifically bound complex, the two proteins are shifted apart by approximately 8 A (so a layer of water can be accommodated in the interface) and the two binding surfaces are rotated away by 0 degrees to 3 degrees. The values of the average Boltzmann factor, calculated by solving the Poisson-Boltzmann equation, for the wild-type complex and 16 complexes with single mutations are found to correlate well with experimental results for the electrostatic rate enhancement. The predicted rate enhancement is found to be somewhat insensitive to the precise definition of the transition state, due to the long-range nature of electrostatic interactions. The experimental ionic strength dependence of the rate enhancement is also reasonably reproduced.