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PubMed2001

The Swedish system for quality assessment of agricultural soils.

Soil quality assessment is based on the concept of soil functions. The performances of three soil functions, crop production, biological decomposition and matter exchange with the atmosphere and groundwater, are used as quality criteria. Soil properties that can be used as indicators for the degree of functional performance were identified. Each soil property selected was graded into five classes--from best (class 1) to worst (class 5). Grading was based biological on boundary conditions as well as on statistical distribution. The system outlined can be used to interpret the quality state of agricultural soils, provides for a relative comparison between soils, and may be helpful in an environmental monitoring program to assess trends in data.

Crops, Agricultural↗
PubMed2002

A note on sample size calculation in bioequivalence trials.

Based on fundamental pharmacokinetic relationships, a multiplicative model is commonly used in bioequivalence trials. With regard to the parametric analysis, this implies the assumption of a lognormal distribution. Statistical methods for sample size calculation has been consolidated over the last years. Recently, methods for sample size calculation in the additive model, i.e., under normality assumption, were presented. Hence, these methods are reviewed from a statistical and regulatory point of view.

Models, Biological↗
PubMed1994

Bioequivalence: performance of several measures of rate of absorption.

The highest point of the plasma concentration-time profile, Cmax, is currently used by regulatory agencies to assess the rate of drug absorption after single dose administration of oral products. It is, however, quite insensitive, and a number of new measures of rate have been proposed. Using simulations, several approaches toward measuring rate were tested. A set of model scenarios for drugs with typical mean characteristics and statistical distributions was investigated. Using different kinetic models of disposition, the time course of the concentration in plasma was simulated. Intraindividual and interindividual variability and assay error were modeled using Monte Carlo techniques. The accuracy, precision, and ease of use of the various measures of rate were evaluated by simulating crossover design clinical trials and then determining the probability of declaring bioequivalence as a function of differences in rates of absorption between test and reference formulations. All of the rate measures tested showed a degree of insensitivity to changes in rate and no universally superior measure was found. Indeed, the main conclusion is that the choice of a measure should be based on simulations of the particular situation in a bioequivalence trials.

Computer Simulation↗
PubMed2004

Using the gene ontology for microarray data mining: a comparison of methods and application to age effects in human prefrontal cortex.

One of the challenges in the analysis of gene expression data is placing the results in the context of other data available about genes and their relationships to each other. Here, we approach this problem in the study of gene expression changes associated with age in two areas of the human prefrontal cortex, comparing two computational methods. The first method, "overrepresentation analysis" (ORA), is based on statistically evaluating the fraction of genes in a particular gene ontology class found among the set of genes showing age-related changes in expression. The second method, "functional class scoring" (FCS), examines the statistical distribution of individual gene scores among all genes in the gene ontology class and does not involve an initial gene selection step. We find that FCS yields more consistent results than ORA, and the results of ORA depended strongly on the gene selection threshold. Our findings highlight the utility of functional class scoring for the analysis of complex expression data sets and emphasize the advantage of considering all available genomic information rather than sets of genes that pass a predetermined "threshold of significance."

Adolescent↗
PubMed1996

Confirmatory P-technique analyses of therapist discourse: high-versus low-quality child therapy sessions.

From a sample of 35 child therapy sessions, 3 of the highest and 3 of the lowest quality sessions (HQS and LQS) were identified by independent ratings on the Loyola Child Psychotherapy Process Scales. Each of the 535 therapist-utterances in the HQS and the 372 therapist-utterances in the LQS were rated on 15 language interaction scales. Principal-components P-technique analyses were applied separately to the HQS and LQS, revealing 3 factors, Responsive Informing (RI), Initiatory Questioning (IQ), and Positive Regard (PR), that seemed to correspond across session types. Using confirmatory P-technique, a general measurement model with acceptable goodness-of-fit was determined for HQS. Two factors emerged: RI and IQ but not PR. Using a bootstrap procedure, random halves of the HQS were repeatedly sampled and compared via multigroup confirmatory factor analysis to create a reference distribution of the magnitudes of their difference chi-squares. Random resamples of HQS and LQS were then compared, resulting in a second reference distribution. Statistical tests and effect-size measures revealed replicable and large differences between sessions types.

Child↗
PubMed2002

Macroecological patterns of phytoplankton in the northwestern North Atlantic Ocean.

Many issues in biological oceanography are regional or global in scope; however, there are not many data sets of extensive areal coverage for marine plankton. In microbial ecology, a fruitful approach to large-scale questions is comparative analysis wherein statistical data patterns are sought from different ecosystems, frequently assembled from unrelated studies. A more recent approach termed macroecology characterizes phenomena emerging from large numbers of biological units by emphasizing the shapes and boundaries of statistical distributions, because these reflect the constraints on variation. Here, I use a set of flow cytometric measurements to provide macroecological perspectives on North Atlantic phytoplankton communities. Distinct trends of abundance in picophytoplankton and both small and large nanophytoplankton underlaid two patterns. First, total abundance of the three groups was related to assemblage mean-cell size according to the 3/4 power law of allometric scaling in biology. Second, cytometric diversity (an ataxonomic measure of assemblage entropy) was maximal at intermediate levels of water column stratification. Here, intermediate disturbance shapes diversity through an equitable distribution of cells in size classes, from which arises a high overall biomass. By subsuming local fluctuations, macroecology reveals meaningful patterns of phytoplankton at large scales.

Animals↗
PubMed2003

An off-normal fibre-like texture in thin films on single-crystal substrates.

In the context of materials science, texture describes the statistical distribution of grain orientations. It is an important characteristic of the microstructure of polycrystalline films, determining various electrical, magnetic and mechanical properties. Three types of texture component are usually distinguished in thin films: random texture, when grains have no preferred orientation; fibre texture, for which one crystallographic axis of the film is parallel to the substrate normal, while there is a rotational degree of freedom around the fibre axis; and epitaxial alignment (or in-plane texture) on single-crystal substrates, where an in-plane alignment fixes all three axes of the grain with respect to the substrate. Here we report a fourth type of texture--which we call axiotaxy--identified from complex but symmetrical patterns of lines on diffraction pole figures for thin films formed by solid-state reactions. The texture is characterized by the alignment of planes in the film and substrate that share the same d-spacing. This preferred alignment of planes across the interface manifests itself as a fibre texture lying off-normal to the sample surface, with the fibre axis perpendicular to certain planes in the substrate. This texture forms because it results in an interface, which is periodic in one dimension, preserved independently of interfacial curvature. This new type of preferred orientation may be the dominant type of texture for a wide class of materials and crystal structures.

Journal Article↗
PubMed2000

Changes in the distribution of body mass index of adults and children in the US population.

BACKGROUND: National survey data show increases in mean body mass index (BMI) and in the prevalence of overweight and obesity for adults and children in the United States, indicating a change in the distribution of BMI. OBJECTIVE: To apply graphical methods to describe changes in the distribution of BMI. DESIGN: BMI values from the third National Health and Nutrition Examination Survey (NHANES III: 1988-94) were compared with data from earlier cross-sectional nationally representative surveys for adults 20-74 y of age and for children and adolescents 6-17 y of age. Tukey mean-difference plots were used to investigate the changes in the distributions of BMI within sex-age groups. RESULTS: Mean-difference plots allow qualitative visual comparisons of the distributions of BMI between surveys. For all sex-age groups, there was increasing skewness with a greater shift in the upper part of the distribution so that, within each group, the heaviest subgroup was heavier in NHANES III than in prior surveys. For the youngest children, the lower part of the distribution showed virtually no change. With increasing age the whole distribution tended to shift upward slightly, suggesting an increase in BMI across the entire population. CONCLUSIONS: These changes in the distribution of BMI suggest the combination of both profound environmental determinants and a population with a high degree of susceptibility. The reasons for the increasing prevalence of obesity should be sought in part by seeking to understand the factors causing increases in the population as a whole.

Adolescent↗
PubMed2002

Chronic exposure to the ultraviolet radiation levels from arc welding does not result in obvious damage to the human corneal endothelium.

Occupational exposure of the cornea to ultraviolet radiation (UVR, e.g. in welding) is a well-known cause of 'arc eye' (photo-keratoconjunctivitis), but has also been considered to be a risk for the development of alterations in the size (polymegethism) and shape (pleomorphism) of the deeper-lying human corneal endothelial cells. Human data are however limited and so a further study was undertaken, with a control group. Non-contact specular micrographs of the central region of the corneal endothelium were obtained from 40 white males aged between 32 and 63 years; 20 were arc welders with an average of 25 +/- 7 years job experience, while the others were office workers (n = 20). All the welders reported occupational exposure to UVR (i.e. welders 'flashes') and up to 3 times per year. None of the subjects had a history of contact lens wear, major eye disease or surgery. The endothelial image was scanned, projected onto an overlay and cell border marking carried out in a masked fashion. The overlay was independently analysed, by a customised semi-automated method, providing cell-border-adjusted data on cell areas and cell shape (sides) on 124 to 260 cells per image. The endothelial cell density (ECD) values were also calculated from individual cell area values. All corneas appeared to be healthy, and showed no fluorescein staining indicating damage to the surface epithelium. Central corneal thickness values were normal at 0.531 +/- 0.031 (mean +/- SD) and 0.527 +/- 0.036 mm in the welders and non-welders respectively. All endothelia appeared healthy, with no evidence of cell oedema. The group-mean endothelial cell area was 393 +/- 35 and 392 +/- 21 microm2, ECD values were 2855 +/- 224 cells mm(-2) and 2852 +/- 210 cells mm(-2), while the percentages of 6-sided cells were 60 +/- 5.2 and 59 +/- 4.1% respectively. Cell area distributions were statistically identical (p > or = 0.8), and cell area-side relationships were marginally, but not statistically different. This study does not indicate that chronic ultraviolet radiation exposure, through occupational welding (mainly electrical arc), results in or is associated with endothelial cell polymegethism and pleomorphism. This may indicate that, despite the periodic flash welding exposures, the exposure levels are still below those needed to cause damage to the corneal endothelium. This study outcome can be taken to indicate that despite the occurrence of welders flash episodes, the eye protection habitually used by these workers was adequate to protect their corneal endothelium.

Adult↗
PubMed1988

Cartilage proteoglycans. Assembly with hyaluronate and link protein as studied by electron microscopy.

Aggregates formed by the interaction of cartilage proteoglycan monomers and fragments thereof with hyaluronate were studied by electron microscopy by use of rotary shadowing [Wiedemann, Paulsson, Timpl, Engel & Heinegård (1984) Biochem. J. 224, 331-333]. The differences in shape and packing of the proteins bound along the hyaluronate strand in aggregates formed in the presence and in the absence of link protein were examined in detail. The high resolution of the method allowed examination of the involvement in hyaluronate binding of the globular core-protein domains G1, G2 and G3 [Wiedemann, Paulsson, Timpl, Engel & Heinegård (1984) Biochem. J. 224, 331-333; Paulsson, Mörgelin, Wiedemann, Beardmore-Gray, Dunham, Hardingham, Heinegård, Timpl & Engel (1987) Biochem. J. 245, 763-772]. Fragments comprising the globular hyaluronate-binding region G1 form complexes with hyaluronate with an appearance of necklace-like structures, statistically interspaced by free hyaluronate strands. The closest centre-to-centre distance found between adjacent G1 domains was 12 nm. Another fragment comprising the binding region G1 and the adjacent second globular domain G2 attaches to hyaluronate only by one globule. Also, the core protein obtained by chondroitinase digestion of proteoglycan monomer binds only by domain G1, with domain G3 furthest removed from the hyaluronate. Globule G1 shows a statistical distribution along the hyaluronate strands. In contrast, when link protein is added, binding is no longer random, but instead uninterrupted densely packed aggregates are formed.

Animals↗
PubMed1983

Suggestions for optimizing reliability with the synthetic sentence identification test.

The reliability of the Synthetic Sentence Identification (SSI) test was determined for a group of 33 listeners with mild-to-moderate sensorineural hearing loss. Randomizations of the 10-item test were administered 12 times (six trials on each of two days) under identical listening conditions. Lists were presented monaurally, under earphones, at 90 dB SPL with a cafeteria background noise set at a signal-to-noise ratio (S/N) estimated (by adaptive procedure for each subject) to obtain 50% performance. Average scores ranged from 48.8% for Trial 1 to 67.9% for Trial 9. Reliability of the 12 measurements was determined by Pearson correlation, analyses of variance, and by testing individual differences in scores against a theoretical statistical distribution. Results evidenced large intra-subject variability, especially for the initial trials conducted in each testing session. However, if sufficient practice trials are presented each day under relatively difficult listening conditions, the scores on subsequent lists tend to remain relatively stable. Suggested procedures to optimize reliability are included.

Adolescent↗
PubMed1990

Selected acoustic characteristics of voices before intubation and after extubation.

Effects of endotracheal intubation on acoustic characteristics of voices were investigated for 8 male and 8 female subjects using a miniature neck accelerometer and computerized analysis methods. Variables extracted from sustained vowels were (1) spectral slopes of the average waveforms, (2) harmonics-to-noise ratios (H/N), (3) coefficients of variation for amplitude (CVA), (4) coefficients of variation for fundamental frequency (CVF), (5) amplitude perturbation (shimmer), and (6) fundamental frequency perturbation (jitter). Fundamental frequency (Fo) distributional statistics (mean Fo, Fo standard deviation, and Fo mid-90% range) were also obtained from oral readings. Results for the sustained vowel samples showed that after extubation, (1) spectral slopes were less steep, and (2) both shimmer and jitter were greater than before intubation. Results for the passage reading revealed that the mean Fo was lower and the Fo standard deviation and mid-90% range were smaller after the extubation than before intubation. It was concluded that even short-term endotracheal intubation affects acoustic characteristics of voice and that selected measures of waveform characteristics are sensitive enough to reveal such effects.

Adult↗
PubMed2001

Circannual variation in human semen parameters.

The aim of the present study was to determine whether there were significant monthly variations in the semen parameters (i.e. volume, sperm count, total sperm count, motile and normal sperm count) of men living in a Mediterranean climate area. A total of 10 877 semen analysis results were included. Semen samples were obtained as a part of an initial screening of male partners from couples with infertility problems who were attending our laboratory from 1970 to 2000. Log transformation and cubic root transformation were used to test the sample distribution. Statistical significance was adjusted by year of examination, patient's age and sexual abstinence period by performing covariance analyses. Differences between months were assessed with the Bonferroni post-hoc test. There was an increase in March and a decrease in September in the adjusted mean sperm count (p < 0.0005), total sperm count (p < 0.0005), motile sperm count (p=0.01) and normal sperm count (p=0.002). There were no variations in semen volume in the study period. Monthly changes in semen quality are confirmed in this population.

Adult↗
PubMed1999

Molecular characterisation of a membrane-bound galactosyltransferase of plant cell wall matrix polysaccharide biosynthesis.

Galactomannan biosynthesis in vitro is catalysed by membrane preparations from developing fenugreek seed endosperms. Two enzymes interact: a GDP-mannose dependent (1-->4)-beta-D-mannan synthase and a UDP-galactose dependent (1-->6)-alpha-D-galactosyltransferase. The statistical distribution of galactosyl substituents along the mannan backbone, and the degree of galactose substitution of the primary product of galactomannan biosynthesis appear to be regulated by the specificity of the galactosyltransferase. We now report the detergent solubilisation of the fenugreek galactosyltransferase with retention of activity, the identification on gels of a putative 51 kDa galactosyltransferase protein, and the isolation, cloning and sequencing of the corresponding cDNA. The solubilised galactosyltransferase has an absolute requirement for added acceptor substrates. Beta-(1-->4)-linked D-manno-oligosaccharides with chain lengths greater than or equal to 5 acted as acceptors, as did galactomannans of low to medium galactose-substitution. The putative galactosyltransferase cDNA encodes a 51282 Da protein, with a single transmembrane alpha helix near the N terminus. We have also confirmed the identity of the galactosyltransferase by inserting the cDNA in frame into the genome of the methylotrophic yeast Pichia pastoris under the control of an AOX promoter and the yeast alpha secretion factor and observing the secretion of galactomannan alpha-galactosyltransferase activity. Particularly high activities were observed when a truncated sequence, lacking the membrane-spanning helix, was expressed.

Amino Acid Sequence↗
PubMed2001

Patients with pressure ulcers in Finnish hospitals.

The purpose of this descriptive study was to produce knowledge of the degree of pressure ulcers, pressure ulcer patients' physical and psychological well-being and the association of these factors with pressure ulcers' severity. These patients were treated in Finland's capital area hospitals. The pressure ulcer patients' sampling was gathered during 1 day with two questionnaires, which was completed by nurses. The response rate was 94%, and data analysis was based on percentage distributions. Statistical association was tested with the chi2 test. The measurement identified 164 patients with a total of 257 pressure ulcers. Prevalence was 6.4%. Most of the ulcers (40%) were grade II ulcers. Fifty-six per cent of patients suffered poor general health, 63% of the patients were immobile, but psychological well-being was better with 29% of pressure ulcer patients being adequately motivated to follow treatment for their pressure ulcers. It is essential to identify high-risk patients in order to provide optimal care.

Adult↗
PubMed2003

Relation between stimulus and response in frog olfactory receptor neurons in vivo.

The spiking activity of receptor neurons was recorded extracellularly in the frog olfactory epithelium in response to four odourants applied at precisely controlled concentrations. A set of criteria was formulated to define the spikes in the response. Four variables - latency, duration, number of interspike intervals and frequency - were determined to quantify the responses. They were studied at the single neuron, neuron population and ciliary membrane levels. The dose-response curves were determined using specific functions and their characteristics were evaluated. The characteristic molar concentrations at threshold or at maximum duration and the characteristics of variables, e.g. minimum latency or maximum frequency, have asymmetric histograms with peaks close to the origin and long tails. Dynamic ranges have even more asymmetric histograms, so that a significant fraction of neurons presents a much wider range than their one-decade peak. From these histograms, response properties of the whole neuron population can be inferred. In general, location along the concentration axis (thresholds), width (dynamic ranges) and heights of dose-response curves are independent, which explains the diversity of curves, prevents their global categorization and supports the qualitative coding of odourants. No evidence for odourant-independent types of neurons was found. Finally, receptor activation and ciliary membrane conductance were reconstructed in the framework of a model based on firing data, known mucus biochemical and neuron morpho-electrical characteristics. It is in agreement with independent determinations of Kd of odourant-receptor interaction and of conductance characteristics, and describes their statistical distributions in the neuron population.

Action Potentials↗
PubMed1991

Propranolol in the treatment of acute migraine attacks.

The efficacy of the beta-adrenoceptor antagonist propranolol in the acute treatment of patients in attacks of either classical (migraine with aura) or common migraine (migraine without aura) headache was assessed in a double-blind placebo-controlled crossover trial with fixed doses. The trial was carried out on 25 patients. The treatment period was set at eight weeks, with the provision of shortening or lengthening it if necessary with a maximum period of seventeen weeks. A minimum of three migraine attacks were treated during each treatment period. Patients were assessed according to: the mean duration and mean severity per treatment period of migraine attacks. The secondary efficacy assessment was made on the basis of the percentage of attacks requiring escape medication per treatment period. The study, based on the t-distribution statistical model with a confidence level of 95%, showed that propranolol had no significant effect in aborting acute attacks of migraine when compared with placebo.

Acute Disease↗