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A combination of non-interactive statistical methods is discussed to analyze multiparametric light-scatter data obtained by means of computer-assisted centrifugal elutriation.
CAD has been used in over 20,000 patients in an Accident and Emergency Department. Structured documentation has replaced normal case notes and a patient record is created which includes investigations and management. A copy of the documentation acts as an immediate communication to the general practitioner. The information is held on a computer and is readily accessed to produce feedback and to allow audit of any number of parameters. The results show that an improvement in diagnostic accuracy and a reduction in admissions and unnecessary laparotomies continues over 15 years. Problems have occurred; some are inherent to the system and some have been minimized as a result of a series of studies. The savings in terms of finance and facilities are considerable and the cost is small in comparison as the programs are available and the cost of hardware has diminished. It is concluded that documentation is essential. This allows the more accurate collection of information, permits analysis, acts as a method of communication and creates a detailed patient record. The use of this part of the CADA system produces a considerable improvement in the parameters used to assess satisfactory patient management. The computer diagnostic program produces a higher level of diagnostic accuracy than that obtained by doctors who are not using the system. It does not normally exceed the accuracy of the doctors who are using the structured documentation and entering the information into the computer. Other mathematical models might lead to an improvement, particularly if they were based on the diagnostic process used by a senior clinician. The method of entry of information could be facilitated by modern technology, including light pens or word sensitive computers. This would reduce the time required for completion of the documents. A number of possible improvements in the CADA system are reported and some have been studied in detail with little evidence of significant change. The computer part of the system has an educational value and presents a stimulating challenge to the junior hospital staff seeing the patient for the first time in the Accident and Emergency Department. Rapid feedback is possible and advantageous. Possibly the greatest value of the computer is in the analysis of the value of clinical features in diagnosis, which has not been easy in the past. It has also allowed precise assessment of the value of investigations in the diagnosis of patients with a suspected disease, which leads to more appropriate management and the saving of facilities.(ABSTRACT TRUNCATED AT 400 WORDS)
The main pathways by which technologically enhanced radioactive materials can impact on human health have been examined. Analytical methods are presented for calculation of the radiation doses for the dominant pathways for external and internal exposure. The application of computer modelling to the assessment of the radiological impact of NORM is also discussed.
The search for novel leads is a critical step in the drug discovery process. Computational approaches to identify new lead molecules have focused on discovering complete ligands by evaluating the binding affinity of a large number of candidates, a task of considerable complexity. A new computational method is introduced in this work based on the premise that the primary molecular recognition event in the protein binding site may be accomplished by small core fragments that serve as molecular anchors, providing a structurally stable platform that can be subsequently tailored into complete ligands. To fulfill its role, we show that an effective molecular anchor must meet both the thermodynamic requirement of relative energetic stability of a single binding mode and its consistent kinetic accessibility, which may be measured by the structural consensus of multiple docking simulations. From a large number of candidates, this technique is able to identify known core fragments responsible for primary recognition by the FK506 binding protein (FKBP-12), along with a diverse repertoire of novel molecular cores. By contrast, absolute energetic criteria for selecting molecular anchors are found to be promiscuous. A relationship between a minimum frustration principle of binding energy landscapes and receptor-specific molecular anchors in their role as "recognition nuclei" is established, thereby unraveling a mechanism of lead discovery and providing a practical route to receptor-biased computational combinatorial chemistry.
Tautomeric transitions of DNA bases are proton transfer reactions, which are important in biology. These reactions are involved in spontaneous point mutations of the genetic material. In the present study, intrinsic reaction coordinates (IRC) analyses through ab initio quantum chemical calculations have been carried out for the individual DNA bases A, T, G, C and also A:T and G:C base pairs to estimate the kinetic and thermodynamic barriers using MP2/6-31G** method for tautomeric transitions. Relatively higher values of kinetic barriers (about 50-60 kcal/mol) have been observed for the single bases, indicating that tautomeric alterations of isolated single bases are quite unlikely. On the other hand, relatively lower values of the kinetic barriers (about 20-25 kcal/mol) for the DNA base pairs A:T and G:C clearly suggest that the tautomeric shifts are much more favorable in DNA base pairs than in isolated single bases. The unusual base pairing A':C, T':G, C':A or G':T in the daughter DNA molecule, resulting from a parent DNA molecule with tautomeric shifts, is found to be stable enough to result in a mutation. The transition rate constants for the single DNA bases in addition to the base pairs are also calculated by computing the free energy differences between the transition states and the reactants.
PURPOSE: This study aimed at the development of a seizure-detection system by training neural networks with quantitative motion information extracted from short video segments of neonatal seizures of the myoclonic and focal clonic types and random infant movements. METHODS: The motion of the infants' body parts was quantified by temporal motion-strength signals extracted from video segments by motion-segmentation methods based on optical flow computation. The area of each frame occupied by the infants' moving body parts was segmented by clustering the motion parameters obtained by fitting an affine model to the pixel velocities. The motion of the infants' body parts also was quantified by temporal motion-trajectory signals extracted from video recordings by robust motion trackers based on block-motion models. These motion trackers were developed to adjust autonomously to illumination and contrast changes that may occur during the video-frame sequence. Video segments were represented by quantitative features obtained by analyzing motion-strength and motion-trajectory signals in both the time and frequency domains. Seizure recognition was performed by conventional feed-forward neural networks, quantum neural networks, and cosine radial basis function neural networks, which were trained to detect neonatal seizures of the myoclonic and focal clonic types and to distinguish them from random infant movements. RESULTS: The computational tools and procedures developed for automated seizure detection were evaluated on a set of 240 video segments of 54 patients exhibiting myoclonic seizures (80 segments), focal clonic seizures (80 segments), and random infant movements (80 segments). Regardless of the decision scheme used for interpreting the responses of the trained neural networks, all the neural network models exhibited sensitivity and specificity>90%. For one of the decision schemes proposed for interpreting the responses of the trained neural networks, the majority of the trained neural-network models exhibited sensitivity>90% and specificity>95%. In particular, cosine radial basis function neural networks achieved the performance targets of this phase of the project (i.e., sensitivity>95% and specificity>95%). CONCLUSIONS: The best among the motion segmentation and tracking methods developed in this study produced quantitative features that constitute a reliable basis for detecting neonatal seizures. The performance targets of this phase of the project were achieved by combining the quantitative features obtained by analyzing motion-strength signals with those produced by analyzing motion-trajectory signals. The computational procedures and tools developed in this study to perform off-line analysis of short video segments will be used in the next phase of this project, which involves the integration of these procedures and tools into a system that can process and analyze long video recordings of infants monitored for seizures in real time.
Statistical adjustment of baseline differences (bias attributable to confounding covariates) in the comparison of rates is often carried out by the stratification approach (e.g. the "direct standardization method"). However, this approach is usually not feasible for simultaneous adjustment of more than one confounding covariates given modest sample size. Also, the stratification approach requires grouping a continuous adjustment variable into broad categories, and consequently, residual confounding of the adjusted rates can still occur. These drawbacks can be overcome by multiple regression. This communication considers a statistical procedure for the comparison of occurrence rate of some event across two or more exposure or treatment groups adjusting for one or more confounding covariates. The procedure is based on the multiple logistic regression model. A detailed numeric example to illustrate the application of the method is presented. A computer program to carry out the statistical procedures is available from the authors.
The paper presents a finite-element model for the analysis of steady flow of a viscous fluid through a connected system of elastic tubes with the aim of simulating the conditions of blood flow through the human arterial system. The governing equations of the model are non-linear in character and are solved through an iterative computational procedure. This model is capable of incorporating the effects of stenosis on flow and pressure. Typical results are presented and discussed. Quantitative results have been obtained on blood flow through a model of the human arterial system corresponding to the sets of prescribed conditions at the terminations. Also computational results on the effect of stenosis in typical arteries of the system are presented.
We have developed a program to facilitate the simultaneous analysis and weighted least-squares curve fitting of families of exponential decay curves, subject to appropriate constraints. The simultaneous analysis of all curves allows one to pool information from several subjects or experiments, and avoids the need for approximations inherent in normalizing or transforming data. Selected parameters of the model can be constrained, i.e. shared among several curves, or set to a constant value. Hypotheses about the system under study can be tested in an objective, statistically valid manner. A BASIC computer program for routine data analysis is presented, with an example of its application to illustrative data.
For a number of reasons, it is desirable to fabricate coils which, for a known current, shall produce predetermined values of the magnetic field intensity at a number of points within a nuclear magnetic resonance imager. The calculation of the magnetic field intensity at a set of points involves the integration of the Biot-Savart equation for all components of the segments of conductor which make up the coil. This process in itself is a rather formidable task. When this process is parameterized in terms of coil diameter, coil spacing, etc. the problem is to determine the values of these parameters to match values of magnetic field intensities which are desired. The problem thereby increases in complexity to the point where, by ordinary methods, the problem becomes intractable. This note describes an algorithm and offers a computer subroutine to calculate magnetic fields for coils of arbitrary shape and complexity for fixed currents.
The hormone-receptor interaction is reconsidered and a minimal kinetic theory for the signal transduction in native cells is proposed. The basic equation for the time evolution of the concentration of the hormone-receptor complex is obtained. It is shown, that the hormone-receptor interaction is regulated by a cycle of G protein, i.e. kinetic parameters associated with the G protein cycle enter this equation. The existence of exponential and oscillatory regimes in kinetics of the G protein cycle, and hormone-receptor interactions are predicted. Experimental kinetic curves for agonist binding are computer-simulated, and numerical values for various kinetic and equilibrium parameters are obtained.
A method is proposed to determine the conformational equilibrium of flexible polypeptides in solution, using the data provided by NMR spectroscopy and theoretical conformational calculations. The algorithm consists of the following three steps: (i) search of the conformational space in order to find conformations with reasonably low energy; (ii) simulation of the NOE spectrum and vicinal coupling constants for each of the low energy conformations; and (iii) determining the statistical weights of the conformations, by means of the maximum-entropy method, in order to obtain the best fit of the averaged NOE intensities and coupling constants to the experimental quantities. The method has been applied to two cyclic enkephalin analogs: DNS1-c-[D-A2bu2,Trp4,Leu5]enkephalin (ENKL) and DNS1-c-[D-A2bu2,Trp4,D-Leu5]enkephalin (ENKD). NMR measurements were carried out in deuterated dimethyl sulfoxide. Two techniques were used in conformational search: the electrostatically driven Monte Carlo method (EDMC), which results in extensive search of the conformational space, but gives only energy minima, and the molecular dynamics method (MD), which results in a more accurate, but also more confined search. In the case of EDMC calculations, conformational energy was evaluated using the ECEPP/3 force field augmented with the SRFOPT solvation-shell model, while in the case of MD the AMBER force field was used with explicit solvent molecules. Both searches and subsequent fitting of conformational weights to NMR data resulted in similar conformations of the cyclic part of the peptides studied. For both ENKL and ENKD a common feature of the low-energy solution conformations is the presence of a type II' or type IV beta-turn at residues 3 and 4; the ECEPP/3 force field also gives a remarkable content of type III beta-turn. These beta-turns are tighter in the case of ENKL, which is reflected in different distributions of the D-A2bu(N gamma H)...D-A2bu(CO) and D-A2bu(N gamma H)...Gly3(CO) hydrogen-bonding distances, indicating that the D-A2bu(N gamma H) amide proton is more shielded from the solvent than in the case of ENKD. This finding conforms with the results of temperature coefficient data of the D-A2bu(N gamma H) proton. It has also been found that direct (MD) or Boltzmann (EDMC) averages of the observables do not exactly conform with the measured values, even when explicit solvent molecules are included. This suggests that improving force-field parameters might be necessary in order to obtain reliable conformational ensembles in computer simulations, without the aid of experimental data.
In the event of weak autoradiographic labelling, the proportion of truly labelled cells or structures can be calculated from the frequency distributions of grains per area or cell structure for i = 0, 1,..., n grains using the results obtained for an experimental group after the application of a radioactively labelled substance and those obtained for a control group without radioactivity. The principle of this computer-aided method is also applicable when the grain counts are related to varying areas in histological sections.
MULCOX is a user-friendly FORTRAN program for the analysis of regression effects when individual study subjects may experience multiple events or failures. Each marginal distribution of the multivariate failure time variable is formulated by a Cox proportional hazards model. The maximum partial likelihood estimators of the regression parameters in these marginal models are approximately jointly normal. The MULCOX program estimates the marginal models as well as the joint covariance matrix. In addition, it implements several multivariate inference procedures. The program runs on both mainframe computers and microcomputers. The running time is quite acceptable even for large samples. A simple example is provided to illustrate the features of the program.
Computation using a coherent system of units demonstrates simply that no significant specific biological and pharmacological effects can be expected from very highly diluted solutions.
Agreement between two methods of computing the fractal dimensions of complex figures was examined. 16 complex figures were scanned and the fractal dimensions were computed under two conditions. There was no significant difference between the two methods.
A model of the neural control of quiet breathing in an anaesthetised and tracheostomised laboratory animal is presented. The loop consisting of the brain generator with its respiratory "master function", the phrenic command, the aerodynamics of the lungs and the volume information carried by the vagus nerves is described in mathematical terms. Computer model experiments are presented and compared with corresponding physiological situations. The stability of the model is demonstrated.
The main purpose of the project was to develop computerized instruments that could be used by nurses and patients to assess their cooperation and mutual contributions to care. This paper presents a part of the project: the reliability and validity testing phase of a process of instrument development. To test the validity and reliability of the instruments, data were collected with questionnaires from nurses (n = 146) and patients (n = 286). The validity evaluated as construct validity and the reliability evaluated as internal consistency of the instruments were quite good. Construct validity was tested by factor analysis, and internal consistency was tested by Cronbach's alpha coefficient, which varied from 0.69 to 0.79. The instruments, which consisted of a software application that can be operated in a www environment, were meant to be used as tools in the psychiatric nursing context for assessing the cooperation between the nurses and patients and the patient's participation in his/her care. Furthermore, the computer programme can be used as a tool for developing and assessing the patient orientation in nursing.