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PubMed2006

Corpus callosum morphometrics in young children with autism spectrum disorder.

This study assessed midsagittal corpus callosum cross sectional areas in 3-4 year olds with autism spectrum disorder (ASD) compared to typically developing (TD) and developmentally delayed (DD) children. Though not different in absolute size compared to TD, ASD callosums were disproportionately small adjusted for increased ASD cerebral volume. ASD clinical subgroup analysis revealed greater proportional callosum reduction in the more severely affected autistic disorder (AD) than in pervasive developmental disorder-not otherwise specified (PDD-NOS) children. DD children had smaller absolute callosums than ASD and TD. Subregion analysis revealed widely distributed callosum differences between ASD and TD children. Results could reflect decreased inter-hemispheric connectivity or cerebral enlargement due to increase in tissues less represented in the corpus callosum in ASD.

Analysis of Variance↗

PubMed1991

Experimental and theoretical studies of rate constant evaluation for the solute-matrix interaction in affinity chromatography.

In an investigation of the problem of determining kinetic parameters for the interaction of a solute with immobilized ligand sites on an affinity matrix, a combination of experimental studies and numerical simulations of frontal chromatography of methyl orange on Sephadex G-25 has yielded a simpler method than existing procedures for characterizing solute-matrix kinetics. A significant change in approach has entailed the direct evaluation of the kinetic contribution to boundary spreading from the flow-rate dependence of boundary variance under conditions of concentration-independent chromatographic migration (linear kinetics). This kinetic contribution is then interpreted in terms of an experimentally more appropriate form of a quantitative relationship for diffusion-free chromatographic migration (H. W. Hethcote and C. DeLisi, 1982, J. Chromatogr. 240, 269-281). Finally, the results of numerical simulations of concentration-dependent chromatographic migration (Langmuir kinetics) have indicated that rate constants should also be determinable under these conditions by extrapolation of their apparent values obtained by the above procedure to infinite dilution.

Alcohol Dehydrogenase↗

PubMed1990

Predicting 1-year outcome following acute myocardial infarction: physicians versus computers.

Whether decision rules derived statistically from patient data can produce better decisions than an expert clinician or a model of the expert clinician (expert system) is controversial. We examined this issue in the context of predicting cardiac death by 1 year for patients discharged from the hospital following acute myocardial infarction. Decision rules were derived from a base sample of 781 patients. These decision rules and three experienced cardiologists then estimated probability of death by 1 year for each patient in a separate test sample (n = 400). In our evaluation of the performance of the decision rules and physicians, we detected no differences, although the decision rules and physicians tended to classify the patients somewhat differently. Further multivariate analyses on the physicians' predictions showed that two of the physicians paid attention to somewhat different variables than the third physician. Lack of agreement among expert cardiologists would complicate modeling of a consensual decision-making process within the framework of an expert system.

Aged↗

PubMed1990

Use of a Lotus 1-2-3 spreadsheet to plot the confidence and the prediction intervals in linear regression analysis.

Computer-derived spreadsheet programs such as Lotus 1-2-3 are being used by many investigators for individualized statistical calculations. Spreadsheet templates have been described for the performance of simple statistical tests by non-statisticians with relatively limited computer experience. This paper describes a template for use with Lotus 1-2-3 for automatic graphic display of confidence and prediction intervals of simple linear regression analysis. The graph can be printed using the Lotus printgraph program. The program also allows comparison of the slope and the intercept of two regression lines.

Computer Graphics↗

PubMed1994

DATALOAD: a user-friendly program to prepare binding data for the "LIGAND" software.

This paper presents a program for the preparation of binding data to be used with the LIGAND software. This program will analyze saturation and competition/displacement binding data, and prepare all the necessary files that provide the input values for the final processing by the LIGAND package. Features include choices of different units for specific activity of the labeled tracer, and screen editing of the data, and results are provided as an average of replicates or as individual points. The program creates a graphic file to observe the raw data as a B/T vs T graph, prior to the analysis with the LIGAND program. The program saves all the information in a session file. Calculation of the bound/free values for the raw data is also provided.

Computer Graphics↗

PubMedDate not supplied

Pulmonary gas mixing during spontaneous breathing and at high-frequency ventilation.

This work is intended to estimate the contribution of either laminar or turbulent dispersion during spontaneous breathing on one hand, and at high-frequency pulmonary ventilation on the other. For that purpose, we performed a computer simulation of a mathematical model of gas transport in the human airways governed by a combination of axial convection and longitudinal dispersion. Calculations were carried out by incorporating two dispersion coefficients, proposed by Taylor and Scherer respectively, into the mathematical model. Moreover, computations were performed with five constant flow rates and two inert heavy (SF6) and light (He) gases to enhance the effect of mixing. It is concluded that Taylor laminar dispersion cannot play a significant role in the human airways; however, it seems that convective gas mixing with disturbed dispersion--corresponding to a regime of quasi-steady state--can account for most gas transport during spontaneous respiration and high-frequency ventilation.

Models, Biological↗

PubMed1989

A least squares algorithm to determine the mechanical time constant distribution of the lung during forced expiration.

A method to determine the mechanical time-constant distribution of the lung during a forced expiration manoeuvre is proposed. The method is based on a least squares algorithm constrained to give reasonably smooth non-negative solutions. The smoothing constraint was imposed by minimizing the second derivative of the distribution function in accordance with the physiological meaning of the time-constant distribution. Nevertheless, the obtained solution depends greatly on the relative weights of the two terms in the objective function to be minimized i.e., the error on the fit of the volume signal and the smoothness of the distribution function. To select the optimum smoothing weight, a criterion based on the stability of the reconstructed distribution shape was defined. The performance of the algorithm and that of the defined criterion were evaluated by using simulated signals of forced expired volume. The error of reconstructed distributions was quantified by means of the area enclosed between this distribution and the original one used to generate the simulated volume signal. The results obtained showed that for all the analyzed signals: (1) There is a value of the weight of the smoothing constraint which gives rise to a solution that is optimum in a least squares sense. (2) The proposed stabilization criterion enables us to approach this optimum solution from experimental signals.

Algorithms↗

PubMedDate not supplied

An operator approach to interactive data processing. II. Some applications of scalars and vectors.

A modular software system for interactive data processing is described in part I of this series. Flexibility and portability are stressed. The system works as an interpreter and new functions may be introduced instantly. A simple graphical user interface controls performance. Arbitrary data types are supported. In the current work, the system has been implemented for numerical data (scalars and one-dimensional arrays). Some commonly used parametric and non-parametric statistical procedures (such as Students t-test, linear regression, Mann-Whitney and Wilcoxon tests) illustrate the use of scalars. Arrays can indicate complex quantities, used in signal analysis. The fast Fourier transform is a basic building block. It is included into other functions such as convolution, cross-correlation and digital filter design. The benefit of such constructions is illustrated by adaptive filtering of evoked potentials.

Computers↗

PubMedDate not supplied

Microcomputer BASIC program to calculate the probability of graft and patient survival in renal transplantation.

A BASIC program was written for the estimation of the probability of graft and patient survival in renal transplantation on a microcomputer. The program was developed for single-centre statistics in renal transplant units and uses the life table and logrank test method for calculation of survival rates. The program structure is described in detail to make rewriting easy. It is hoped that this report will help transplant centres without access to main-frame computers to develop user-friendly software running on their own computer.

Actuarial Analysis↗

PubMed1990

A computer program for the statistical analysis of cancer inhibition/promotion experiments.

The computer program discussed and presented in this paper is designed for the statistical analysis of data from cancer inhibition/promotion experiments that involve Type I censoring. The theoretical derivation of the method is described in Biometrics 43 (1987) 525-534 and Appl. Math. Lett. 1 (1988) 197-201. Turbo Pascal is used to compute maximum likelihood estimates of the parameters of interest: the mean number of induced tumors per animal, and the mean time to tumor detection. The program conducts a likelihood ratio test to determine if there is an overall experiment effect, and allows the user to select options to isolate the pair(s) of groups contributing to the experiments effect, to isolate group differences in terms of tumor number and growth rate, and to graph 95% confidence regions for the vector parameter of interest.

Animals↗

PubMed1990

Self-organising learning control and its application to muscle relaxant anaesthesia.

The concept of a self-organising control system is attractive in biomedicine because of the imprecise nature of available physiological models. In this paper a particular strategy called a self-organising controller (SOC) originating from the work of Barron on aerospace systems is applied to the control of muscle relaxant anaesthesia. The SOC algorithm, which requires no prior knowledge of system dynamics, is described, both in single variable and multivariable format. Simulation results are presented for SOC performance on a well-established pancuronium model. Three implementations are described, being the use of a general purpose language, a SUN workstation approach, and a parallel computer transputer solution. The latter approach becomes important for multivariable control because of the computing-intensive nature of SOC. The transputer is shown to be a suitable vehicle for implementation in terms of speed and parallelism for SOC.

Algorithms↗

PubMed1994

Analysis of anisotropy decays in terms of correlation time distributions, measured by frequency-domain fluorometry.

We describe the theory and practical aspects of analyzing fluorescence anisotropy decays in terms of correlation times distributions. In our model the rotational motions of the fluorophores were described using Gaussian or Lorentzian distributions of the correlation times. The theory is presented both for time and frequency-domain measurements, although the simulations and measurements are focused on the frequency-domain measurements of the anisotropy decays. Analysis of simulated data is presented to illustrate the nature of the data and the resolution which can be expected with presently available frequency-domain measurements. Additionally, we describe experimental data for samples where one can reasonably expect a single exponential and/or discrete multi-exponential correlation time distributions, and for samples where the anisotropy decay might be expected to display a distribution of correlation times. These samples include small single tryptophan peptides in propylene glycol, the single tryptophan residue in S. Nuclease, and the single tryptophan residue in the native and partially unfolded states of ribonuclease T1.

Amino Acid Sequence↗

PubMed1995

Simulation of fractograms of fat emulsions in power-programmed sedimentation field-flow fractionation (SdFFF).

A quasi-empirical approach to the simulation of fractograms was examined to verify that the elution behavior of emulsions in power-based field programmed sedimentation field-flow fractionation (SdFFF) is consistent and predictable. The approach was applied to Intralipid, a commercial soybean emulsion and to an investigational medium chain triglyceride emulsion. The simulations predicted the fractograms that were obtained under various conditions of field strength, field decay and velocity of the suspending fluid, using distribution parameters obtained from one preliminary measurement of size distribution profile. Predicted fractograms were compared to experimental ones, under various fractionating powers. Good agreement was observed in most cases, in which interference of the secondary relaxation effects was not effective. The agreement confirmed the applicability of the approach to emulsions and that the simulations can be used instead of actual experiments for the optimization of their characterization by power-programmed SdFFF.

Chemical Fractionation↗

PubMed1996

NMR of residual protons in partly deuterated anisotropic materials with phase-alternated decoupling of deuterium spins.

A new method is presented for decoupling spins with S = 1 like deuterium in anisotropic media while observing other spins such as residual protons in partly deuterated samples. The carrier frequency of a weak radiofrequency (RF) field is applied near the center of the doublet arising from the quadrupolar interaction of the S = 1 spins. The phase of the RF field is periodically reversed with intervals matching the reciprocal of the magnitude of the quadrupolar splitting. It is shown by theory and experiment that, even when the irradiating field is quite weak, the efficiency of this phase-alternated decoupling scheme is much better than for simple continuous-wave irradiation at the center of the doublet, an established technique which is usually referred to as double quantum decoupling. The phase-alternated experiment makes it possible to decouple large quadrupolar interactions with a weak RF field. A theoretical analysis and numerical simulations are presented to demonstrate the decoupling performance. Proton spectra of partly deuterated dibromobutane in a liquid crystalline solvent have been recorded to illustrate the efficiency of phase-alternated deuterium decoupling.

Chemical Phenomena↗

PubMed2005

Comparison of left ventricular volumes and ejection fractions measured by three-dimensional echocardiography versus by two-dimensional echocardiography and cardiac magnetic resonance in patients with various cardiomyopathies.

End-diastolic volume and end-systolic volume were measured in 35 consecutive patients with cardiomyopathy using 2-dimensional (2-D) and 3-dimensional (3-D) echocardiography (2, 4, and 8 planes) and cardiac magnetic resonance imaging. Three-dimensional echocardiography correlates better with magnetic resonance imaging than does 2-D echocardiography. Its accuracy improves with the increase in the number of planes used. Two-dimensional echocardiography underestimates volumes, mainly in the subgroup with an ejection fraction of <50%, whereas 3-D echocardiography does not, if enough planes are used. However, in patients with an end-diastolic volume > or =150 ml, the underestimation of 3-D echocardiography is statistically significant. Increasing the number of planes to 8 reduces this bias. Conversely, patients with an end-diastolic volume <150 ml are accurately studied with just 4 planes.

Adult↗

PubMed2006

A new method for quantifying residue conservation and its applications to the protein folding nucleus.

The conservation of residues in columns of a multiple sequence alignment (MSA) reflects the importance of these residues for maintaining the structure and function of a protein. To date, many scores have been suggested for quantifying residue conservation, but none has achieved the full rigor both in biology and statistics. In this paper, we present a new approach for measuring the evolutionary conservation at aligned positions. Our conservation measure is related to the logarithmic probabilities for aligned positions, and combines the physicochemical properties and the frequencies of amino acids. Such a measure is both biologically and statistically meaningful. For testing the relationship between an amino acid's evolutionary conservation and its role in the Phi-value defined protein folding kinetics, our results indicate that the folding nucleus residues may not be significantly more conserved than other residues by using the biological-relevance weighted statistical scoring method suggested in this paper as an alternative to entropy-based procedures.

Amino Acid Sequence↗

PubMed2004

Pituitary volumes in pediatric maltreatment-related posttraumatic stress disorder.

BACKGROUND: Previous findings suggest that corticotrophin-releasing hormone (CRH) is elevated in adults with posttraumatic stress disorder (PTSD), maltreated children, and children with maltreatment-related PTSD. METHODS: Magnetic resonance imaging was used to measure pituitary volumes in 61 medication-naïve maltreated subjects with PTSD (31 male and 30 female subjects) and 121 nontraumatized healthy comparison subjects (62 male and 59 female subjects). RESULTS: Overall, no differences were seen between PTSD and control subjects in pituitary volumes. There was a significant age-by-group effect for PTSD subjects to have greater differences in pituitary volume with age than control subjects. Post hoc analyses revealed that pituitary volumes were significantly larger in pubertal and postpubertal maltreated subjects with PTSD than control subjects but were similar in prepubertal maltreated subjects with PTSD and control subjects. Pituitary volumes were larger in the PTSD subjects with history of suicidal ideation. CONCLUSIONS: These findings may suggest developmental alterations in pituitary volume in maltreatment-related pediatric PTSD. This finding may be associated with stress-related differences in CRH and may be more pronounced in pediatric patients with PTSD comorbid with suicidal ideation.

Adolescent↗

PubMed2004

Impaired hippocampal function during the detection of novel words in schizophrenia.

BACKGROUND: Patients with schizophrenia have smaller hippocampal volumes and perform abnormally on most declarative memory tasks. Although these findings are likely related, the impact of hippocampal pathology on cognitive performance in schizophrenia remains unclear. This study examined this relationship by measuring the volume of the hippocampus and its activation during memory task performance. METHODS: Participants included 15 patients with schizophrenia and 16 age-matched control subjects. Hippocampal volume was determined via three-dimensional volumetric analysis of high-resolution magnetic resonance images. Hippocampal activity was assessed by measuring changes in blood oxygen level-dependent signal during a recognition memory task. RESULTS: Patients with schizophrenia had smaller hippocampal volumes bilaterally and demonstrated poorer performance on the recognition memory task, largely because of a heightened rate of false alarms to novel stimuli. Both groups showed robust hippocampal activity to old and new items when compared with a low-level baseline task; however, direct comparison of hippocampal activity during recognition task performance revealed that healthy control, but not the schizophrenia, subjects showed significant right anterior hippocampal activation during the evaluation of novel items. CONCLUSIONS: The impaired ability to classify new items as previously not experienced is associated with decreased recruitment and smaller volume of the hippocampus in schizophrenia.

Adult↗