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PubMed2002

Algorithmic cooling and scalable NMR quantum computers.

We present here algorithmic cooling (via polarization heat bath)-a powerful method for obtaining a large number of highly polarized spins in liquid nuclear-spin systems at finite temperature. Given that spin-half states represent (quantum) bits, algorithmic cooling cleans dirty bits beyond the Shannon's bound on data compression, by using a set of rapidly thermal-relaxing bits. Such auxiliary bits could be implemented by using spins that rapidly get into thermal equilibrium with the environment, e.g., electron spins. Interestingly, the interaction with the environment, usually a most undesired interaction, is used here to our benefit, allowing a cooling mechanism. Cooling spins to a very low temperature without cooling the environment could lead to a breakthrough in NMR experiments, and our "spin-refrigerating" method suggests that this is possible. The scaling of NMR ensemble computers is currently one of the main obstacles to building larger-scale quantum computing devices, and our spin-refrigerating method suggests that this problem can be resolved.

Journal Article↗

PubMed1982

Increase in apparent compressibility of cytochrome c upon oxidation.

The apparent molal adiabatic compressibilities of ferri- and ferrocytochrome c have been determined from measurements of density and sound velocity. The values found were +2.99 X 10(-8) and -2.40 X 10(-8) cm5 mol-1 dyne-1 for the ferri and ferro forms, respectively. Experiments were performed on identical solutions containing either the oxidized or reduced form of protein. Solutions of ferricytochrome c were found to have significantly greater adiabatic compressibility than equivalent solutions of ferrocytochrome c at 25 degrees C and pH 7.15. The remarkable similarity of the three-dimensional structures of the ferri and ferro proteins [Takano, T. & Dickerson, R.E. (1980) Proc. Natl. Acad. Sci. USA 77, 6371-6375] strongly suggests that this difference in compressibility is due to an increase in volume fluctuations within ferricytochrome c relative to the ferro form rather than a change in equilibrium structure or hydration. Such a difference in the dynamic properties of the structures is consistent with both the crystallographic thermal B factors and the observed increase in amide hydrogen exchange kinetics when ferrocytochrome c is oxidized. The relative magnitude of the root mean square volume fluctuations is approximated from an ideal solution treatment of the compressibility data and yields a ratio of delta Vrms (ferri cyt c)/ delta Vrms (ferro cyt c) = 1.3.

Animals↗

PubMedDate not supplied

Telecardiology for effective healthcare services.

Continuous monitoring of the electrocardiogram (ECG) and other signals related to current heart activity are necessary for patients who are suffering from cardiac diseases. This paper deals with the work that has been carried out to transmit ECGs from remote sites. Software has been developed which enables the uploading of ECG data from a patient so that the physician can monitor the state of the patient from a distance and at the same time may consult other experts for a second opinion. Records can only be examined by the authorized physician after proper registration and diagnosis or prescription may be sent back to the referring site. Further consultation with the patient through a 'chat' facility is also possible. The suitability of the system over transport control protocol (TCP), internet protocol (IP), local area network (LAN), wide area network (WAN) and World Wide Web (WWW) has been assessed. The bandwidth, latency, availability, security and ubiquity have also been discussed. A study has also been undertaken in order to make the system compatible with available bandwidths and to find out which one out of a number of available techniques is most efficient for ECG data compression. The results indicate that the scheme is suitable for telecardiology and can form part of an overall telemedicine system in a health care network.

Computer Security↗

PubMed1999

Experimental comparison of data transformation procedures for analysis of principal components.

Results of principal component analysis depend on data scaling. Recently, based on theoretical considerations, several data transformation procedures have been suggested in order to improve the performance of principal component analysis of image data with respect to the optimum separation of signal and noise. The aim of this study was to test some of those suggestions, and to compare several procedures for data transformation in analysis of principal components experimentally. The experiment was performed with simulated data and the performance of individual procedures was compared using the non-parametric Friedman's test. The optimum scaling found was that which unifies the variance of noise in the observed images. In data with a Poisson distribution, the optimum scaling was the norm used in correspondence analysis. Scaling mainly affected the definition of the signal space. Once the dimension of the signal space was known, the differences in error of data and signal reproduction were small. The choice of data transformation depends on the amount of available prior knowledge (level of noise in individual images, number of components, etc), on the type of noise distribution (Gaussian, uniform, Poisson, other), and on the purpose of analysis (data compression, filtration, feature extraction).

Computer Simulation↗

PubMed2003

Monotony of surprise and large-scale quest for unusual words.

The problem of characterizing and detecting recurrent sequence patterns such as substrings or motifs and related associations or rules is variously pursued in order to compress data, unveil structure, infer succinct descriptions, extract and classify features, etc. In molecular biology, exceptionally frequent or rare words in bio-sequences have been implicated in various facets of biological function and structure. The discovery, particularly on a massive scale, of such patterns poses interesting methodological and algorithmic problems and often exposes scenarios in which tables and synopses grow faster and bigger than the raw sequences they are meant to encapsulate. In previous study, the ability to succinctly compute, store, and display unusual substrings has been linked to a subtle interplay between the combinatorics of the subword of a word and local monotonicities of some scores used to measure the departure from expectation. In this paper, we carry out an extensive analysis of such monotonicities for a broader variety of scores. This supports the construction of data structures and algorithms capable of performing global detection of unusual substrings in time and space linear in the subject sequences, under various probabilistic models.

Algorithms↗

PubMed1995

Short superstrings and the structure of overlapping strings.

Given a collection of strings S = [s1,...,sn] over an alphabet sigma, a superstring alpha of S is a string containing each si as a substring, that is, for each i, 1 < or = i < or = n, alpha contains a block of magnitude of si consecutive characters that match si exactly. The shortest superstring problem is the problem of finding a superstring alpha of minimum length. The shortest superstring problem has applications in both computational biology and data compression. The shortest superstring problem is NP-hard (Gallant et al., 1980); in fact, it was recently shown to be MAX SNP-hard (Blum et al., 1994). Given the importance of the applications, several heuristics and approximation algorithms have been proposed. Constant factor approximation algorithms have been given in Blum et al. (1994) (factor of 3), Teng and Yao (1993) (factor of 2 8/9), Czumaj et al. (1994) (factor of 2 5/6), and Kosaraju et al. (1994) (factor of 2 50/63). Informally, the key to any algorithm for the shortest superstring problem is to identify sets of strings with large amounts of similarity, or overlap. Although the previous algorithms and their analyses have grown increasingly sophisticated, they reveal remarkably little about the structure of strings with large amounts of overlap. In this sense, they are solving a more general problem than the one at hand. In this paper, we study the structure of strings with large amounts of overlap and use our understanding to give an algorithm that finds a superstring whose length is no more than 2 3/4 times that of the optimal superstring. Our algorithm runs in O(magnitude of S + n3) time, which matches that of previous algorithms. We prove several interesting properties about short periodic strings, allowing us to answer questions of the following form: Given a string with some periodic structure, characterize all the possible periodic strings that can have a large amount of overlap with the first string.

Algorithms↗

PubMed1995

Telemammography: implementation issues.

Telemammography has the potential to improve access to centralized expertise for the interpretation of breast imaging studies. Digital mammography has more demanding spatial resolution requirements than other forms of medical imaging because of the need to detect microcalcifications, the fine details of lesion margins, and subtle architectural distortion. The resolution requirements for mammography have important implications for image acquisition and display technologies. The large size of the resulting image data sets places significant demands on local and wide area networks as well as storage media. Image data compression will be particularly important for telemammography to help make systems practical and affordable. This article describes how existing technologies can be adapted to implement telemammography systems in the near future.

Algorithms↗

PubMed1989

Evaluation of routine telephone transmission of nuclear medicine studies.

Rapid and reliable transmission of nuclear medicine studies using conventional telephone lines and commercially available modems and computer systems has been accomplished through use of software developed within the authors' hospital. Original digital images of all-night and weekend studies, acquired on any of the acquisition computers from different manufacturers, are now routinely sent for remote reading at the physician's home. Data, software, and letters are routinely exchanged using modems and standard telephone lines with a sister institution in Haifa, Israel. The software has been designed to achieve no loss data compression and minimal turnaround time loss. Thus, an average lung perfusion image or gallbladder study requires about 1-3 minutes of transmission time. Full analysis and display software is available on the remote computer.

Computer Communication Networks↗

PubMedDate not supplied

Microcomputer-based coronary care unit central station.

A four-bed central station that can be connected to any commercial intensive-care bedside monitor was developed. The system is based on a personal computer (IBM-AT compatible) as a local unit and on a microcontroller Intel 8031 as a remote unit. Four ECG signals are low-pass filtered, multiplexed, sampled at 256-Hz per channel, 8-bit A/D converted, preprocessed, and converted to a serial format RS-232 by the remote unit. The real-time display of the signals is at the standard speed of 25 and 50 mm/sec. Heartrate, alarms, trend plots, and general patient data are shown on an Olivetti M280 and EGA 13'' color monitor as the local unit. The communication speed was set at 57.6 Kbaud full duplex. Additionally, to reach standard monitoring sweep rates using a 13'' screen with 640 x 350 pixels, an ECG data-compression algorithm was implemented in the remote unit. This unit can support up to eight input channels and can work with any personal computer, via RS-232, with the appropriate software. It also allows other signal preprocessing software that could be developed, such as QRS detection or ST segment quantification, to be loaded into its random access memory and to be run under PC command. The development of this system demonstrated the use of a widespread piece of commercial equipment, the PC, in a very specific application, CCU monitoring, assuring low-cost system implementation. This feature is particularly attractive in upgrading existing CCU units in less developed countries.

Biomedical Engineering↗

PubMed2001

Effects of gender and age differences on the distribution of bone content in the third lumbar vertebra.

STUDY DESIGN: A cross-sectional study on the distribution of bone mineral content in the third lumbar vertebrae. OBJECTIVES: To evaluate the effects of age and gender on the distribution of bone mineral content in the third lumbar vertebrae. SUMMARY OF BACKGROUND DATA: Compression fractures occur mainly at the vertebral body. Variations in the distribution of bone mass in a vertebra, if undefined, may bias the ability of the acquired bone mineral density values, which was usually measured posteroanteriorly, to predict the risk of fractures. METHODS: The bone mineral content of the whole L3, including the L3 vertebral body and the posterior segment, was measured using a lateral approach with a dual energy radiograph absorptiometer on 177 healthy Taiwanese adults including 65 men and 55 premenopausal and 57 postmenopausal women. RESULTS: The proportion of bone mineral content in the vertebral body was significantly lower in premenopausal women than in age-matched men (39.1 +/- 0.9% vs. 50.0 +/- 1.7%, P < 0.0001). Furthermore, whereas postmenopausal women showed a decreased proportion of bone mineral content in the vertebral body with increased age (about -0.0022 per year, P = 0.0001), premenopausal women and men showed a sustained proportion. CONCLUSIONS: The proportion of bone mineral content distributed in the body of L3 vertebrae was lower in women than in men. The discrepancy of this parameter between the genders was even larger with increased ages.

Absorptiometry, Photon↗

PubMed2003

Information content in the Nagel-Schreckenberg cellular automaton traffic model.

We estimate the set dimension and find bounds for the set entropy of a cellular automaton model for single lane traffic. Set dimension and set entropy, which are measures of the information content per cell, are related to the fractal nature of the automaton [S. Wolfram, Physica D 10, 1 (1989); Theory and Application of Cellular Automata, edited by S. Wolfram (World Scientific, Philadelphia, 1986)] and have practical implications for data compression. For models with maximum speed v(max), the set dimension is approximately log((v(max)+2))2.5, which is close to one bit per cell regardless of the maximum speed. For a typical maximum speed of five cells per time step, the dimension is approximately 0.47.

Journal Article↗

PubMed2003

Vortex dynamics in evolutive flows: a weakly chaotic phenomenon.

We make use of a wavelet method to extract, from experimental velocity signals obtained in an evolutive flow, the dominating velocity components generated by vortex dynamics. We characterize the resulting time series complexity by means of a joint use of data compression and of an entropy diffusion method. We assess that the time series emerging from the wavelet analysis of the vortex dynamics is a weakly chaotic process with a vanishing Kolmogorov-Sinai entropy and a power-law growth of the information content. To reproduce the Fourier spectrum of the experimental signal, we adopt a harmonic dependence on time with a fluctuating frequency, ruled by an inverse power-law distribution of random events. The complexity of these fluctuations is determined by studying the corresponding artificial sequences. We reproduce satisfactorily both spectral and complex properties of the experimental signal by locating the complexity of the fluctuating process at the border between the stationary and the nonstationary states.

Journal Article↗

PubMed2002

Language trees and zipping.

In this Letter we present a very general method for extracting information from a generic string of characters, e.g., a text, a DNA sequence, or a time series. Based on data-compression techniques, its key point is the computation of a suitable measure of the remoteness of two bodies of knowledge. We present the implementation of the method to linguistic motivated problems, featuring highly accurate results for language recognition, authorship attribution, and language classification.

Algorithms↗

PubMed2001

Multichannel ECG compression using multichannel adaptive vector quantization.

Adaptive vector quantization (AVQ) is a recently proposed approach for electrocardiogram (ECG) compression. The adaptability of the approach can be used to control the quality of reconstructed signals. However, like most of other ECG compression methods, AVQ only deals with the single-channel ECG, and for the multichannel (MC) ECG, coding ECG signals on a channel by channel basis is not efficient, because the correlation across channels is not exploited. To exploit this correlation, an MC version of AVQ is proposed. In the proposed approach, the AVQ index from each channel is collected to form a new input vector. The vector is then vector quantized adaptively using one additional codebook called index codebook. Both the MIT/BIH database and a clinical Holter database are tested. The experimental results show that, for exactly the same quality of reconstructed signals, the MC-AVQ performs better than single-channel AVQ in terms of bit rate. A theoretical analysis supporting this result is also demonstrated in this paper. For the same and relatively good visual quality, the average compressed data rate/channel is reduced from 293.5 b/s using the single-channel AVQ to 238.2 b/s using the MC-AVQ in the MIT/BIH case.

Algorithms↗

PubMed1999

Feature extraction and quantification of the variability of dynamic performance profiles due to the different sagittal lift characteristics.

Investigation of manual material handling (MMH) tasks, such as lifting, requires the quantification of the various kinematic and kinetic parameters of performance for assessment of the functional capacity and/or task demand profiles. Traditional statistical descriptive analyses usually involve computing the summary statistics (maximum, minimum, mean, and/or range) of the resulting performance parameters over the cycle duration (i.e., lifting/lowering cycle). Consequently, the significant information content of the time-varying signals is diminished, limiting the sensitivity of subsequent hypothesis testing procedures. The present study developed a methodology for representing and quantifying performance data variability of the kinematic and kinetic motion profiles due to the different lift characteristics (load, mode, and speed) during MMH tasks while capturing the temporal characteristics. Using a database of motion profiles from a manual lifting experiment, the Karhunen-Loeve Expansion (KLE) feature extraction technique was shown to be quite effective for representing the various motion profiles. The number of basis vectors (eigenvectors) and corresponding coefficients needed for accurate representation were substantially smaller than the original data set, resulting in data compression. Moreover, the effects of lift characteristics were investigated using analysis of variance techniques that recognize the vectorial constitution of the waveforms. The application of these techniques will enable the quantification of highly phasic profiles and enhance the ability to document the effect of intervening measures such as educational or physical training/exercise on the kinematic and kinetic patterns of performance. Additionally, the differential influence of lift characteristics on the variability of performance during different phases of lifting and lowering provides added resolution in the analysis of MMH tasks.

Adult↗

PubMed2004

High-performance computing service over the internet for intraoperative image processing.

This paper presents a framework for a cluster system that is suited for high-resolution image processing over the Internet during surgery. The system realizes high-performance computing (HPC) assisted surgery, which allows surgeons to utilize HPC resources remote from the operating room. One application available in the system is an intraoperative estimator for the range of motion (ROM) adjustment in total hip replacement (THR) surgery. In order to perform this computation-intensive estimation during surgery, we parallelize the ROM estimator on a cluster of 64 PCs, each with two CPUs. Acceleration techniques such as dynamic load balancing and data compression methods are incorporated into the system. The system also provides a remote-access service over the Internet with a secure execution environment. We applied the system to an actual THR surgery performed at Osaka University Hospital and confirmed that it realizes intraoperative ROM estimation without degrading the resolution of images and limiting the area for estimations.

Arthroplasty, Replacement, Hip↗

PubMed1995

A new computer network system for communicating perinatal decision support information via a telephone line.

OBJECTIVE: For fetal monitoring and assessment of high risk mother and fetus at regional hospitals, we developed a new computer network system. METHODS: The system incorporates a notebook-type personal computer (PC-9801nv) at regional hospital for communication in with 3 servers (IBM5580-YOC) connected via 2 Ethernet LANs to 2 host computers (IBM3080, IBM3174) and 5 workstations (IBM5521 V2b), and transmits the compressed data by telephone. When the data arrive, the doctor in perinatal center can immediately display and interpret the data on his workstation and give appropriate advice to the doctor at the regional hospital. RESULTS: The rate of reliable data transmission was 100%. Each 1 hour recording session and characteristic perinatal information was transmitted in less than 2 minutes. Regional medical institutions can easily access the center, and thereby can receive both simplified automatic diagnosis by fetal cardiotocography and pregnancy-risk evaluation. CONCLUSIONS: Because this system uses telephone circuits, it can be accessed from all regions of the country. Thus, our system is useful for perinatal management of high risk mother and fetus.

Adult↗

PubMed1993

Remote control software.

Any of these remote control packages will accomplish the task of controlling another PC from a distant machine. Since all of the programs are easy to use, perform the same functions, and provide excellent security, there is no one clear winner. If your aim is to control Windows programs remotely, then Carbon Copy for Windows is the fastest software. It falls short in running DOS based programs and has greater hardware requirements because it is a Windows application. Norton pcAnywhere is a reliable program that rivals Carbon Copy for Windows' speed, even when controlling a Windows program remotely. Its support for DOS is better. Close-Up is the easiest to install, will run DOS programs without problem, and can run Windows programs as well. Under Windows, DOS programs can be executed in a window or as a full screen application. However, its speed ratings when working in Windows have been among the slowest. Carbon Copy for the Mac brings most of the features of the Windows version of this program to the Macintosh environment. The software allows users to control remote Macintosh computers, and to perform file transfers in the background. It does not permit a PC to control a Mac or a Mac to control a PC. List prices for these programs are $179 to $199 for packages with host and remote software, but street prices range from approximately $100 to $120. A 9600 baud modem with data compression (yielding a net speed of about 14,400 bits/sec) and error correction costs approximately $200 to $300.(ABSTRACT TRUNCATED AT 250 WORDS)

Computer Systems↗