Displaying publications 1 - 20 of 1458 in total

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  1. Wan Abas WA, Asseli MR
    Biomed Mater Eng, 1994;4(7):463-71.
    PMID: 7881330
    Local strains acting across an area of skin loaded uniaxially in vivo are converted to stresses using the standard elastic formulae. The stress values are compared to those obtained using the classical Bossinesq and Michell stress functions. The results indicate that these functions are capable of describing the response of the skin, both in the low load and the high load regions.
    Matched MeSH terms: Algorithms
  2. Mohd Idris Jayes
    The discretization of the second-order linear self-adjoint ellliptic partial differential equation problem subject to periodic boundary conditions results in a system of linear equations of the form Mu = s, where M is a block cyclic tridiagonal square matric. In this paper, the relationship between the spectral radius and overrelaxation factor for the problem is derived.
    Pendiskretan masalah persamaan pembeza separa (PPS) eliptik swadampingan linear peringkat kedua menghasilkan satu sistem persamaan linear bentuk Mu = s, dengan M merupakan satu matriks segiempatsama tiga pepenjuru berkitar blok. Dalam kertas ini, hubungan di antara jejari spektrum dan faktor pengenduran berlebihan untuk masalah itu akan dirumuskan.
    Matched MeSH terms: Algorithms
  3. Chaudhuri A, Das P
    The concepts of fuzzy semi-open and semi-closed sets have been utilised to define four types of semi-separation of fuzzy sets corresponding to the notions of separation, Q-separation, weak separation, strong separation and eight types of semi-connectedness viz SiC, SCi-connectedness for i = 1 ,2 ,3 ,4 corresponding to the notions of O-connectedness, connectedness, Oq-connectedness and ci-connectedness of a fuzzy set. Interrelationship between these notions of semi-connectedness of a fuzzy set and their properties have been discussed.
    Konsep set semi-terbuka dan semi-tertutup kabur digunakan untuk mentakrif empat jenis semi-pemisahan bagi set-set kabur sepadan dengan konsep pemisahan, Q-pemisahan, pemisahan lemah, pemisahan kuat dan lapan jenis keberkaitan, iaitu keberkaitan-SiC dan keberkaitan-SCi untuk i=1 ,2 ,3 ,4 sepadan dengan konsep keberkaitan, keberkaitan-Oq dan keberkaitan-Ci bagi set kabur. Hubung kait antara konsep-konsep semi-keberkaitan set kabur ini dan sifat-sifatnya dibincangkan.
    Matched MeSH terms: Algorithms
  4. Gumel AB, Kubota K, Twizell EH
    Math Biosci, 1998 Aug 15;152(1):87-103.
    PMID: 9727298
    A sequential algorithm is developed for the non-linear dual-sorption model developed by Chandrasekaran et al. [1,2] which monitors pharmacokinetic profiles in percutaneous drug absorption. In the experimental study of percutaneous absorption, it is often observed that the lag-time decreases with the increase in the donor concentration when two or more donor concentrations of the same compound are used. The dual-sorption model has sometimes been employed to explain such experimental results. In this paper, it is shown that another feature observed after vehicle removal may also characterize the dual-sorption model. Soon after vehicle removal, the plots of the drug flux versus time become straight lines on a semilogarithmic scale as in the linear model, but the half-life is prolonged thereafter when the dual-sorption model prevails. The initial half-life after vehicle removal with a low donor concentration is longer than that with a higher donor concentration. These features, if observed in experiments, may be used as evidence to confirm that the dual-sorption model gives an explanation to the non-linear kinetic behaviour of a permeant.
    Matched MeSH terms: Algorithms*
  5. Harba MI, Teng LY
    Front Med Biol Eng, 1999;9(1):31-47.
    PMID: 10354908
    Cross-correlating two surface EMG signals detected at two different locations along the path of flow of action potential enables the measurement of the muscle fiber average conduction velocity in those active motor units monitored by the electrodes. The position of the peak of the cross-correlation function is the time delay between the two signals and hence the velocity may be deduced. The estimated velocity using this technique has been observed previously to depend on the location of the electrodes on the muscle surface. Different locations produced different estimates. In this paper we present a measurement system, analyze its inherent inaccuracies and use it for the purpose of investigating the reliability of measurement of conduction velocity from surface EMG. This system utilizes EMG signals detected at a number of locations on the biceps brachii, when under light tension, to look for any pattern of variations of velocity as a function of location and time. It consists of a multi-electrode unit and a set of eight parallel on-line correlators. The electrode unit and the parallel correlators ensure that these measurements are carried out under the same physical and physiological conditions of the muscle. Further, the same detected signals are used in different measurement configurations to try to understand the reasons behind the observed variations in the estimated velocity. The results obtained seem to suggest that there will always be an unpredictable random component superimposed on the estimated velocity, giving rise to differences between estimates at different locations and differences in estimates with time at the same location. Many factors contribute to this random component, such as the non-homogeneous medium between the muscle fibers and the electrodes, the non-parallel geometry and non-uniform conduction velocity of the fibers, and the physical and physiological conditions of the muscle. While it is not possible to remove this random component completely from the measurement, the user must be aware of its presence and how to reduce its effects.
    Matched MeSH terms: Algorithms
  6. Agatonovic-Kustrin S, Alany RG
    Pharm Res, 2001 Jul;18(7):1049-55.
    PMID: 11496944
    PURPOSE: A genetic neural network (GNN) model was developed to predict the phase behavior of microemulsion (ME), lamellar liquid crystal (LC), and coarse emulsion forming systems (W/O EM and O/W EM) depending on the content of separate components in the system and cosurfactant nature.

    METHOD: Eight pseudoternary phase triangles, containing ethyl oleate as the oil component and a mixture of two nonionic surfactants and n-alcohol or 1,2-alkanediol as a cosurfactant, were constructed and used for training, testing, and validation purposes. A total of 21 molecular descriptors were calculated for each cosurfactant. A genetic algorithm was used to select important molecular descriptors, and a supervised artificial neural network with two hidden layers was used to correlate selected descriptors and the weight ratio of components in the system with the observed phase behavior.

    RESULTS: The results proved the dominant role of the chemical composition, hydrophile-lipophile balance, length of hydrocarbon chain, molecular volume, and hydrocarbon volume of cosurfactant. The best GNN model, with 14 inputs and two hidden layers with 14 and 9 neurons, predicted the phase behavior for a new set of cosurfactants with 82.2% accuracy for ME, 87.5% for LC, 83.3% for the O/W EM, and 91.5% for the W/O EM region.

    CONCLUSIONS: This type of methodology can be applied in the evaluation of the cosurfactants for pharmaceutical formulations to minimize experimental effort.

    Matched MeSH terms: Algorithms*
  7. Banjade DP, Tajuddin AA, Shukri A
    Appl Radiat Isot, 2001 Aug;55(2):235-43.
    PMID: 11393765
    Protocols developed for high-energy dosimetry IAEA (Technical Reports Series No. 277, 1997), AAPM (Med. Phys. 10 (1983) 741: Med. Phys. 18 (1991) 73: Med. Phys. 21 (1994) 1251), IPEMB (Phys. Med. Biol. 41 (1996) 2557), and HPA (Phys. Med. Biol. 28 (1983) 1097) have continued to enhance precision in dose measurements and the optimization of radiotherapy procedures. While recent dosimetry protocols, including those due to the IAEA and IPEMB, have made a number of improvements compared with previous protocols, it is further desirable to develop absolute dosimetry methods of dose measurements. Measurements based on careful implementation of procedures contained within the various protocols have been carried out in an effort to determine the extent to which discrepancies exist among the protocols. Dose in water at dmax was measured using cylindrical and parallel-plate ionization chambers for 6 MV photon beams and 5 and 12 MeV electron beams. Results obtained from the use of the AAPM and HPA protocols for 6 MV photon beams were found to be 0.9% larger and 0.1% smaller, respectively, than those measured following the IAEA protocol. Calibration dose measurements for 5 and 12 MeV electron beams in water phantoms were found to agree to within 1%, this being well within recommendations from the ICRU and other sources regarding the accuracy of dose delivery.
    Matched MeSH terms: Algorithms
  8. Agatonovic-Kustrin S, Beresford R, Yusof AP
    J Pharm Biomed Anal, 2001 Sep;26(2):241-54.
    PMID: 11470201
    A quantitative structure-permeability relationship was developed using Artificial Neural Network (ANN) modeling to study penetration across a polydimethylsiloxane membrane. A set of 254 compounds and their experimentally derived maximum steady state flux values used in this study was gathered from the literature. A total of 42 molecular descriptors were calculated for each compound. A genetic algorithm was used to select important molecular descriptors and supervised ANN was used to correlate selected descriptors with the experimentally derived maximum steady-state flux through the polydimethylsiloxane membrane (log J). Calculated molecular descriptors were used as the ANN's inputs and log J as the output. Developed model indicates that molecular shape and size, inter-molecular interactions, hydrogen-bonding capacity of drugs, and conformational stability could be used to predict drug absorption through skin. A 12-descriptor nonlinear computational neural network model has been developed for the estimation of log J values for a data set of 254 drugs. Described model does not require experimental parameters and could potentially provide useful prediction of membrane penetration of new drugs and reduce the need for actual compound synthesis and flux measurements.
    Matched MeSH terms: Algorithms*
  9. Zaridah MZ, Idid SZ, Omar AW, Khozirah S
    J Ethnopharmacol, 2001 Nov;78(1):79-84.
    PMID: 11585692
    Five aqueous extracts from three plant species, i.e., dried husks (HX), dried seeds (SX) and dried leaves (LX) of Xylocarpus granatum (Meliaceae), dried stems (ST) of Tinospora crispa (Menispermaceae) and dried leaves (LA) of Andrographis paniculata (Acanthaceae) were tested in vitro against adult worms of subperiodic Brugia malayi. The relative movability (RM) value of the adult worms over the 24-h observation period was used as a measure of the antifilarial activity of the aqueous extracts. SX extract of X. granatum demonstrated the strongest activity, followed by the LA extract of A. paniculata, ST extract of T. crispa, HX extract and LX extract of X. granatum.
    Matched MeSH terms: Algorithms
  10. Ibrahim S, Green RG, Dutton K, Abdul Rahim R
    ISA Trans, 2002 Jan;41(1):13-8.
    PMID: 12014798
    This paper describes a system using lensed optical fiber sensors that are arranged in the form of two orthogonal projections. The sensors are placed around a process vessel for upstream and downstream measurements. The purpose of the system is for on-line monitoring of particles and droplets being conveyed by a fluid. The lenses were constructed using a custom heating fixture. The fixture enables the lenses to be constructed with similar radii resulting in identical characteristics with minimum differences in transmitted intensity and emission angle. By collimating radiation from two halogen bulbs, radiation can be obtained by the sensors with radiation intensity related to the nature of the media. Each sensor interrogates a finite section of the measurement section. Each sensor provides a view. Parallel sensors provide a projection. Signal processing is carried out on the measured data in the time and frequency domains to investigate the latent information present in the flow signals.
    Matched MeSH terms: Algorithms
  11. Ahmad S, Gromiha MM
    Bioinformatics, 2002 Jun;18(6):819-24.
    PMID: 12075017
    MOTIVATION: Prediction of the tertiary structure of a protein from its amino acid sequence is one of the most important problems in molecular biology. The successful prediction of solvent accessibility will be very helpful to achieve this goal. In the present work, we have implemented a server, NETASA for predicting solvent accessibility of amino acids using our newly optimized neural network algorithm. Several new features in the neural network architecture and training method have been introduced, and the network learns faster to provide accuracy values, which are comparable or better than other methods of ASA prediction.

    RESULTS: Prediction in two and three state classification systems with several thresholds are provided. Our prediction method achieved the accuracy level upto 90% for training and 88% for test data sets. Three state prediction results provide a maximum 65% accuracy for training and 63% for the test data. Applicability of neural networks for ASA prediction has been confirmed with a larger data set and wider range of state thresholds. Salient differences between a linear and exponential network for ASA prediction have been analysed.

    AVAILABILITY: Online predictions are freely available at: http://www.netasa.org. Linux ix86 binaries of the program written for this work may be obtained by email from the corresponding author.

    Matched MeSH terms: Algorithms
  12. Lim CK, Yew KM, Ng KH, Abdullah BJ
    Australas Phys Eng Sci Med, 2002 Sep;25(3):144-50.
    PMID: 12416592 DOI: 10.1007/BF03178776
    Development of computer-based medical inference systems is always confronted with some difficulties. In this paper, difficulties of designing an inference system for the diagnosis of arthritic diseases are described, including variations of disease manifestations under various situations and conditions. Furthermore, the need for a huge knowledge base would result in low efficiency of the inference system. We proposed a hierarchical model of the fuzzy inference system as a possible solution. With such a model, the diagnostic process is divided into two levels. The first level of the diagnosis reduces the scope of diagnosis to be processed by the second level. This will reduce the amount of input and mapping for the whole diagnostic process. Fuzzy relational theory is the core of this system and it is used in both levels to improve the accuracy.
    Matched MeSH terms: Algorithms*
  13. Rohani A, Nasir AA
    MyJurnal
    Four hundred and thirty five (435) cases 0f sexually transmitted infections (STIs) were notified from 20 (twenty) primary care clinics throughout Malaysia from June 1999 till September 2000 using the syndromic approach of STI management, adapted by the Ministry of Health based upon the criteria set by the World Health Organisation (WHO). Gonorrhoea was the most prevalent STI reported (30.34 %), followed by candidiasis (28.05%), syphilis (15.17%) and non-specific urethritis (NSU) — 14.02%) . As seen in most other parts of the world, the younger age groups (those between twenty and thirty nine years old) were found to be more commonly infected with STIs. Initial analysis shows that systematic data collection based on the syndromes and clear—case definitions (algorithms for the syndromic approach} need to be developed and added further to the current manual that is being developed for the health and medical staff at the operational it level. Exploration and expansion of behavioural surveillance research, management information systems of the syndromic approach, and development of new or additional strategies in the manual for the staff too, also need improvement. The Ministry of Health is also concerned about the quantity and quality of the available data based upon syndromic management of STI as compared to laboratory based criteria. Since this programme is very much client centered, the adoption of this approach generally might offer substantial improvements in the quality and effectiveness of STI care, either within the public or the private health care settings in Malaysia.
    Matched MeSH terms: Algorithms
  14. Ibrahimy MI, Ahmed F, Mohd Ali MA, Zahedi E
    IEEE Trans Biomed Eng, 2003 Feb;50(2):258-62.
    PMID: 12665042
    An algorithm based on digital filtering, adaptive thresholding, statistical properties in the time domain, and differencing of local maxima and minima has been developed for the simultaneous measurement of the fetal and maternal heart rates from the maternal abdominal electrocardiogram during pregnancy and labor for ambulatory monitoring. A microcontroller-based system has been used to implement the algorithm in real-time. A Doppler ultrasound fetal monitor was used for statistical comparison on five volunteers with low risk pregnancies, between 35 and 40 weeks of gestation. Results showed an average percent root mean square difference of 5.32% and linear correlation coefficient from 0.84 to 0.93. The fetal heart rate curves remained inside a +/- 5-beats-per-minute limit relative to the reference ultrasound method for 84.1% of the time.
    Matched MeSH terms: Algorithms*
  15. Lim CP, Quek SS, Peh KK
    J Pharm Biomed Anal, 2003 Feb 05;31(1):159-68.
    PMID: 12560060
    This paper investigates the use of a neural-network-based intelligent learning system for the prediction of drug release profiles. An experimental study in transdermal iontophoresis (TI) is employed to evaluate the applicability of a particular neural network (NN) model, i.e. the Gaussian mixture model (GMM), in modeling and predicting drug release profiles. A number of tests are systematically designed using the face-centered central composite design (CCD) approach to examine the effects of various process variables simultaneously during the iontophoresis process. The GMM is then applied to model and predict the drug release profiles based on the data samples collected from the experiments. The GMM results are compared with those from multiple regression models. In addition, the bootstrap method is used to assess the reliability of the network predictions by estimating confidence intervals associated with the results. The results demonstrate that the combination of the face-centered CCD and GMM can be employed as a useful intelligent tool for the prediction of time-series profiles in pharmaceutical and biomedical experiments.
    Matched MeSH terms: Algorithms
  16. Saffor A, bin Ramli AR, Ng KH
    Australas Phys Eng Sci Med, 2003 Jun;26(2):39-44.
    PMID: 12956184
    Wavelet-based image coding algorithms (lossy and lossless) use a fixed perfect reconstruction filter-bank built into the algorithm for coding and decoding of images. However, no systematic study has been performed to evaluate the coding performance of wavelet filters on medical images. We evaluated the best types of filters suitable for medical images in providing low bit rate and low computational complexity. In this study a variety of wavelet filters are used to compress and decompress computed tomography (CT) brain and abdomen images. We applied two-dimensional wavelet decomposition, quantization and reconstruction using several families of filter banks to a set of CT images. Discreet Wavelet Transform (DWT), which provides efficient framework of multi-resolution frequency was used. Compression was accomplished by applying threshold values to the wavelet coefficients. The statistical indices such as mean square error (MSE), maximum absolute error (MAE) and peak signal-to-noise ratio (PSNR) were used to quantify the effect of wavelet compression of selected images. The code was written using the wavelet and image processing toolbox of the MATLAB (version 6.1). This results show that no specific wavelet filter performs uniformly better than others except for the case of Daubechies and bi-orthogonal filters which are the best among all. MAE values achieved by these filters were 5 x 10(-14) to 12 x 10(-14) for both CT brain and abdomen images at different decomposition levels. This indicated that using these filters a very small error (approximately 7 x 10(-14)) can be achieved between original and the filtered image. The PSNR values obtained were higher for the brain than the abdomen images. For both the lossy and lossless compression, the 'most appropriate' wavelet filter should be chosen adaptively depending on the statistical properties of the image being coded to achieve higher compression ratio.
    Matched MeSH terms: Algorithms
  17. Banjade DP, Raj TA, Ng BS, Xavier S, Tajuddin AA, Shukri A
    Med Dosim, 2003;28(2):73-8.
    PMID: 12804703
    Verification of tumor dose for patients undergoing external beam radiotherapy is an important part of quality assurance programs in radiation oncology. Among the various methods available, entrance dose in vivo is one reliable method used to verify the tumor dose delivered to a patient. In this work, entrance dose measurements using LiF:Mg;Ti and LiF:Mg;Cu;P thermoluminescent dosimeters (TLDs) without buildup cap was carried out. The TLDs were calibrated at the surface of a water equivalent phantom against the maximum dose, using 6- and 10-MV photon and 9-MeV electron beams. The calibration geometry was such that the TLDs were placed on the surface of the "solid-water" phantom and a calibrated ionization chamber was positioned inside the phantom at calibration depth. The calibrated TLDs were then utilized to measure the entrance dose during the treatment of actual patients. Measurements were also carried out in the same phantom simultaneously to check the stability of the system. The dose measured in the phantom using the TLDs calibrated for entrance dose to 6-and 10-MV photon beams was found to be close to the dose determined by the treatment planning system (TPS) with discrepancies of not more than 4.1% (mean 1.3%). Consequently, the measured entrance dose during dose delivery to the actual patients with a prescribed geometry was found to be compatible with a maximum discrepancy of 5.7% (mean 2.2%) when comparison was made with the dose determined by the TPS. Likewise, the measured entrance dose for electron beams in the phantom and in actual patients using the calibrated TLDs were also found to be close, with maximum discrepancies of 3.2% (mean 2.0%) and 4.8% (mean 2.3%), respectively. Careful implementation of this technique provides vital information with an ability to confidently accept treatment algorithms derived by the TPS or to re-evaluate the parameters when necessary.
    Matched MeSH terms: Algorithms
  18. Gunasekaran S, Venkatesh B, Sagar BS
    Int J Neural Syst, 2004 Apr;14(2):139-45.
    PMID: 15112371
    Training methodology of the Back Propagation Network (BPN) is well documented. One aspect of BPN that requires investigation is whether or not the BPN would get trained for a given training data set and architecture. In this paper the behavior of the BPN is analyzed during its training phase considering convergent and divergent training data sets. Evolution of the weights during the training phase was monitored for the purpose of analysis. The evolution of weights was plotted as return map and was characterized by means of fractal dimension. This fractal dimensional analysis of the weight evolution trajectories is used to provide a new insight to understand the behavior of BPN and dynamics in the evolution of weights.
    Matched MeSH terms: Algorithms
  19. Huan NJ, Palaniappan R
    J Neural Eng, 2004 Sep;1(3):142-50.
    PMID: 15876633
    In this paper, we have designed a two-state brain-computer interface (BCI) using neural network (NN) classification of autoregressive (AR) features from electroencephalogram (EEG) signals extracted during mental tasks. The main purpose of the study is to use Keirn and Aunon's data to investigate the performance of different mental task combinations and different AR features for BCI design for individual subjects. In the experimental study, EEG signals from five mental tasks were recorded from four subjects. Different combinations of two mental tasks were studied for each subject. Six different feature extraction methods were used to extract the features from the EEG signals: AR coefficients computed with Burg's algorithm, AR coefficients computed with a least-squares (LS) algorithm and adaptive autoregressive (AAR) coefficients computed with a least-mean-square (LMS) algorithm. All the methods used order six applied to 125 data points and these three methods were repeated with the same data but with segmentation into five segments in increments of 25 data points. The multilayer perceptron NN trained by the back-propagation algorithm (MLP-BP) and linear discriminant analysis (LDA) were used to classify the computed features into different categories that represent the mental tasks. We compared the classification performances among the six different feature extraction methods. The results showed that sixth-order AR coefficients with the LS algorithm without segmentation gave the best performance (93.10%) using MLP-BP and (97.00%) using LDA. The results also showed that the segmentation and AAR methods are not suitable for this set of EEG signals. We conclude that, for different subjects, the best mental task combinations are different and proper selection of mental tasks and feature extraction methods are essential for the BCI design.
    Matched MeSH terms: Algorithms*
  20. Gan SH, Ismail R, Wan Adnan WA, Zulmi W, Jelliffe RW
    J Clin Pharm Ther, 2004 Oct;29(5):455-63.
    PMID: 15482390
    Although the kinetic behaviour of tramadol has been described, the present study is the first to our knowledge, to report specifically on the population pharmacokinetic modelling of tramadol hydrochloride.
    Matched MeSH terms: Algorithms*
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