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At least 793 records · Page 44Linked to original sources
PubMed2000

Crystallization of a Large-Pore Three-Dimensional Gallium Fluorophosphate under Mild Conditions This work was supported by EPSRC and the Novartis Trust Fund. The EPSRC provided access to Daresbury Laboratory. We are grateful to L. M. D. Cranswick of Daresbury Laboratory for valuable discussions, Dr. S. O'Leary (Oxford) for performing the thermogravimetric analysis (TGA) measurements, and Professor K. Kuroda (Waseda University) for performing the gas adsorption measurements. The authors acknowledge the EPSRC-funded Collaborative Computational Project Number 14 (http://www.ccp14.ac.uk) for software resources applied in data analysis.

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Journal Article↗
PubMed1984

Multiexponential, multicompartmental, and noncompartmental modeling. II. Data analysis and statistical considerations.

Sums-of-exponentials models are widely used in biomedical research, chiefly as models of data, despite a sizable folklore criticizing their usefulness. Problems in multiexponential model fitting are addressed here, along with an exposition of how to quantify them and critically assess their quality with available statistical methods and computer programs. This class of models also is reconciled with two classes of models of systems: multicompartmental and noncompartmental models. Key issues include the importance of choosing a correct data error model, the necessity for computing model precision estimates, and the distinction between problems due to experiment design or overparameterization and purported difficulties with multiexponential models. Methods for obtaining statistical estimates of model precision, for checking goodness of fit of competing models, and for improving sampling designs are presented. Also the classic Lanczos problem is revisited, and some difficulties are resolved with a more efficient experiment design.

Models, Biological↗
PubMed1987

[Characteristics of the frequency component of EEG alpha rhythm of patients with neurosis-like schizophrenia (based on spectral analysis data)].

In 20 patients with neurosis-like schizophrenia and in 10 healthy subjects the authors, using the spectral analysis, assessed the composition of the alpha-range of the baseline EEG and studied the peculiarities of the frequency components of alpha-rhythm in various states. The patients were characterized by multimodality of the baseline EEG. The patients (versus the normal subjects) presented significantly different types of response of the main frequency components of EEG alpha-rhythm to the hyperventilation test.

Adolescent↗
PubMed2002

A copula-based model for multivariate non-normal longitudinal data: analysis of a dose titration safety study on a new antidepressant.

A new model for multivariate non-normal longitudinal data is proposed. In a first step, each longitudinal series of data corresponding to a given response is modelled separately using a copula to relate the marginal distributions of the response at each time of observation. In a second step, at each observation time, the conditional (on the past) distributions of each response are related using another copula describing the relationship between the corresponding variables. Note that there is no need to consider the same family of distributions for these response variables. The technique is illustrated in a dose titration safety study on a new antidepressant. The haemodynamic effect on diastolic blood pressure, systolic blood pressure and heart rate is studied. These three responses are measured repeatedly over time on ten healthy volunteers during the dose escalation. The available covariates are sex and the concentration of drug in the plasma at time of measurement.

Antidepressive Agents↗
PubMed2005

Statistical evaluation of FRAM gamma-ray isotopic analysis data.

High-purity germanium (HPGe) detector gamma-ray spectra were analyzed using the FRAM (fixed energy, response function analysis with multiple efficiencies) gamma-ray isotopic analysis software. The analyses are based on multiple measurements of samples having well-documented isotopic composition from mass spectrometry measurements. Statistical analyses of the FRAM results are reported, the errors in FRAM analyses arising from the choice of detector type and the energy region are discussed, and the errors that resulted from sample-dependent and analysis-dependent effects are quantified.

Journal Article↗
PubMed2001

Missed appointments in general practice: retrospective data analysis from four practices.

Little is known about which patients miss appointments or why they do so. Using routinely collected data from four practices, we aimed to determine whether patients who missed appointments differed in terms of their age, sex, and deprivation scores from those who did not, and to examine differences between the practices with respect to missed appointments. The likelihood of someone missing at least one appointment was independently associated with being female, living in a deprived area, and being a young adult. Living in a deprived area was associated with a threefold increase in the likelihood of missing an appointment, and the extent of this association was the same across all four practices. Interventions aimed at reducing missed appointments need to be based upon these findings.

Adolescent↗
PubMed1981

Data analysis of two-parameter flow cytometric measurements.

A new procedure was developed to evaluate two-parameter flow cytometric data. These data usually show overlapping distributions of different subpopulations. To calculate the fractions of cells in the various subpopulations, the maximum likelihood method was used, which assumes a superimposition of Gaussian distributions in the histogram. The resolution quality was tested for both one-parameter and two-parameter data using simulated histograms with two superimposed subpopulations. Comparison of this procedure to existing one-parameter evaluations methods, using the same original histograms, yielded satisfactory results. For the case of one parameter as well as for two parameters, the subpopulations were well separated if the distance between the mean values exceeded 2 sigma ; the total count and the proportions of the subpopulations were of minor influence. The evaluation procedure also worked well when applied to simulated two-parameter histograms, similar to DNA protein measurements of cultured cells.

Cell Cycle↗
PubMed2003

Accuracy and reliability of observational gait analysis data: judgments of push-off in gait after stroke.

BACKGROUND AND PURPOSE: Physical therapists routinely observe gait in clinical practice. The purpose of this study was to determine the accuracy and reliability of observational assessments of push-off in gait after stroke. SUBJECTS: Eighteen physical therapists and 11 subjects with hemiplegia following a stroke participated in the study. METHODS: Measurements of ankle power generation were obtained from subjects following stroke using a gait analysis system. Concurrent videotaped gait performances were observed by the physical therapists on 2 occasions. Ankle power generation at push-off was scored as either normal or abnormal using two 11-point rating scales. These observational ratings were correlated with the measurements of peak ankle power generation. RESULTS: A high correlation was obtained between the observational ratings and the measurements of ankle power generation (mean Pearson r=.84). Interobserver reliability was moderately high (mean intraclass correlation coefficient [ICC (2,1)]=.76). Intraobserver reliability also was high, with a mean ICC (2,1) of.89 obtained. DISCUSSION AND CONCLUSION: Physical therapists were able to make accurate and reliable judgments of push-off in videotaped gait of subjects following stroke using observational assessment. Further research is indicated to explore the accuracy and reliability of data obtained with observational gait analysis as it occurs in clinical practice.

Adult↗
PubMedDate not supplied

Origin attribution of polychlorinated dibenzo-p-dioxins and dibenzofurans in sediment and soil from a Japanese freshwater lake area through congener-specific data analysis.

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/PCDFs) in sediment and soil from a freshwater lake area were congener-specifically determined. The obtained data were examined to estimate the major origins of these compounds, with the aid of principal component analysis (PCA). Four major principal components (PCs) were obtained, and three of them were attributed to PCDDs/PCDFs in the atmosphere, in a diphenyl ether herbicide and in pentachlorophenol, based on congener-specific comparisons with references. One PC remained unattributed. These four were interpreted as the major origins of PCDDs/PCDFs in the area. The relative influence of the origins was also investigated.

Agriculture↗
PubMed2001

Multiple-probe thermography for estimating the postmortem interval: I. Continuous monitoring and data analysis of brain, liver, rectal and environmental temperatures in 117 forensic cases.

One hundred seventeen forensic postmortem cases have been studied under controlled conditions. In each case, temperatures of the brain, liver, rectum, and the environment were monitored over a period beginning shortly after death and ending up to 60 h postmortem. The four temperature measurements were recorded every 5 to 10 min using the Microwave Thermography System. Rectal and environmental temperatures were measured by electrical thermocouples while brain and liver temperatures were measured using microwave probes. Data acquisition, analogue-to-digital conversion (ADC), and data processing were provided by a microcomputer. The ADC technique is described and its problems are discussed. The data were then transferred to a mainframe computer for extensive curve-fitting and statistical analysis. The microcomputer-based ADC and data logging and acquisition were found to be accurate, fast, easy to implement, and useful for the field. The postmortem rate of human body cooling was found to be adequately represented by triple-exponential equations.

Adult↗
PubMed1995

A new method for estimating dermal absorption from chemical exposure. 3. Compared with steady-state methods for prediction and data analysis.

PURPOSE: This paper compares unsteady-state and steady-state methods for estimating dermal absorption or analyzing dermal absorption data. The unsteady-state method accounts for the larger absorption rates during short exposure times as well as the hydrophilic barrier which the viable epidermis presents to lipophilic chemicals. METHODS: Example calculations for dermal absorption from aqueous solutions are presented for five environmentally relevant chemicals with molecular weights between 50 and 410 and log10Kow between 0.91 and 6.8: chloromethane, chloroform, chlordane, 2,3,7,8-TCDD, and dibenz(a,h)anthracene. Also, the new method is used to evaluate experimental procedures and data analyses of in vivo and in vitro permeation measurements. RESULTS: In the five example cases, we show that the steady-state approach significantly underestimated the dermal absorption. Also, calculating permeability values from cumulative absorption data measured for exposure periods less than 18 times the stratum corneum lag time will overestimate the actual permeability. CONCLUSIONS: In general, steady-state predictions of dermal absorption will underestimate dermal absorption predictions which consider unsteady-state conditions. Permeability values calculated from data sets which include unsteady-state data will be incorrect. Strategies for analyzing in vitro diffusion cell experiments and confirming steady state are described.

Animals↗