Sample size and the interpretation of census data

This article is directed toward the validity of sampling techniques. The adequacy of a 1/1000 sample is tested by comparing data based on it with similar data based on a proportionately larger sample. Mitra's 1966 data on the prevalence of childlessness among American women, based on a 1/1000 sampling of the 1960 U.S. census, was reformulated based on a sample 50 times larger. The reformulation is tabulated according to race and age of the women. Differences for white women over age 20 were not great; differences for smaller samples. e.g., nonwhites or women under 20, were substantial. Thus, the data was more reliable when the sampling base was very large; it was much less reliable when the sampling base was divided by 10.     

Sources of variability and effect of experimental approach on expression profiling data interpretation

Background  

We provide a systematic study of the sources of variability in expression profiling data using 56 RNAs isolated from human muscle biopsies (34 Affymetrix MuscleChip arrays), and 36 murine cell culture and tissue RNAs (42 Affymetrix U74Av2 arrays).     

Constraints on body size distributions: an experimental approach using a small-scale system

Holling’s (1992) proposition that discontinuities in biotic and abiotic processes generate structure in ecological systems is examined experimentally by imposing size-specific perturbations on marine sediment assemblages. Two kinds of perturbations were applied: organic enrichment and predation, each at two levels. Perturbations significantly affected the densities and relative abundance of the main invertebrate taxa and these effects were consistent with the known effects of enrichment and predation. However, there was little evidence of significant treatment effects on the overall benthic biomass or abundance size spectrum, supporting the contention that the spectrum is conservative and is probably constrained by habitat architecture. Received: 28 June 1999 / Accepted: 24 September 1999     

Effects of normalization errors on size distributions obtained from dynamic light scattering data.

This paper presents a study of the influence of normalization errors on size distributions obtained from the analysis of intensity fluctuations by photon correlation spectroscopy. The effects of these errors are demonstrated by means of computer-generated autocorrelation functions simulating light scattered from a monomodal Schulz distribution of small, spherical, unilamellar lipid vesicles. The calculations show that even small errors in the baseline, modifying the data upon normalization systematically, will cause serious errors in the estimated size distribution. As it turns out this is due to the peculiar characteristics of normalization errors in data of the first order autocorrelation function. The errors introduced there are described in parts by functions of the delay time having positive exponents. Such components are not considered in the integral equations commonly used to analyze the measured data. The error's property to be a function of delay time in turn enables us to obtain the relative baseline error from the inversion of the data. The new method for its determination is described in some detail. Here, it has been realized with a modified version of the size distribution algorithm CONTIN.     

Effect of maturation on the relationship between physical performance and body size

The purpose of the study was to explore the effect of maturation on the body size-physical performance relationship. Based on our previous study that evaluated only muscle strength, we hypothesized that the physical performance tested on pubescent subjects would be related to body size at a higher rate than predicted by standard scaling theory applied on pre- and postpubescent subjects. Six age groups of highly selected and trained junior soccer players (N = 478; age 12-17 years) presumably including prepubescent, pubescent, and postpubescent subjects were evaluated. They were tested using various standard tests of maximum physical performance including muscle strength of 3 leg muscle groups, 2 jumps, sit-ups, hand and foot tapping, and agility. The results revealed a steeper increase of the tested performance with an increase in body size for the pubescent age than for the pre- and postpubescent age. The observed phenomenon was interpreted by different level of maturation of the subjects tested within the same pubescent age group. We conclude that maturation alters the effect of body size on various physical performances and, therefore, this phenomenon needs to be taken into account when interpreting the data from the physical performance tests applied on pubescent subjects.     

Effect of pellet size and pellet quality on pig performance

An experiment involving 1360 growing finishing pigs was undertaken to examine the effect of pellet size and pellet quality, as measured by the Holmen pellet durability test, on pig performance. A barley and soya bean meal diet was used and pellets were of two sizes, 5 and 10 mm diameter. Pellet quality was varied to give two types of pellet by steam conditioning and screening procedure during the pelleting process. The mean difference obtained in pellet durability was 11%.

Pig performance between 30 and 80 kg liveweight was not affected by either pellet size or pellet quality. There were small non-significant trends in favour of both the smaller pellets and the lower quality pellets. These trends, of the order of 1% or less, followed the same pattern as the dry matter content of the diets. The smaller diameter pellets were dried more efficiently in the cooling process and the low durability pellets had less steam added during the manufacturing process, which was reflected in the dry matter content of the finished diets.     

Effect of lidocaine and pyromecaine on the size of an experimental myocardial infarct

The experiments on rats with a 3-day myocardial infarction caused by the left coronary artery ligation have shown that multiple lidocaine and pyromecaine injections according to a given scheme decrease the size of the necrosis area. Drug effects were not related to their action on the blood supply of the ischemic area.     

Design and performance characteristics of a continuous multistage tower fermentor

The design of a continuous multistage tower fermentor is described. The fermentor consists of five stages separated by perforated plates. Each stage includes mechanical mixing provided by two disc turbine impellers and has its own impeller shaft with bearing assembly and flexible coupling that enables the operation of an arbitrary number of stages. The normal operation of this system enables the co-current flow of gas and liquid, but the system can function countercurrently as well. The purpose of this study was to examine the hydrodynamic performance, i.e., the pressure gradient along the tower, the mixing time, gas holdup, the residence lime distribution of the continuous phase, the value of the backflow coefficient, and the oxygen transfer rate under conditions usually used during fermentations. From the interrelations between parameters influencing the proper performance of this system, an optimal design of plate geometry for processes requiring high oxygen transfer rate was formulated.     

Comparison of theoretical and experimental particle diffusion data within human airway casts

The dose delivered to airway cells is a critical factor whether one is addressing the therapeutic (i.e., positive) effects of inhaled pharmacologic agents or the toxic (i.e., negative) effects of pollutants. In this study, theoretical models describing particle deposition have been compared with experimental data from the literature. In the simulations, airways can be either roughor smooth-walled to be consistent with human lungs which can be either lined by cartilaginous rings (i.e., rough) or muscle (i.e., smooth). Particle motion for rough-walled airways within generations I=1–6 is calculated using the formula proposed by Martonen et al. (1). For smooth-walled airways within generations I=7–10, particle motion is calculated using the formula proposed by Martonen et al. (2). Theoretical predictions of particle deposition efficiencies are not only in agreement with the overall best fit empirical correlation presented by Cohen and Asgharian (3) over a wide range of dimensionless diffusion parameters, but also match individual experimental measurements (only available in I=1–6) with regard to effects of the parameters of particle size, flow rate, and airway dimensions. The mean difference in the ratio of experimental-to-theoretical particle diffusion values is 0.9 for a flow rate of 18 L/min and 1.1 for a flow rate of 34 L/min (i.e., the difference is only about 10%) within the upper airways of the casts (airway generations I=1–6), the mean difference for the whole casts was much greater. This may be attributed to the uncertainty of flow conditions in the peripheral airways as a result of the trimmmed nature of the casts. Overall, the findings suggest that the model can be a valuable component of aerosol therapy and risk assessment protocols, especially to address effects of enhanced deposition of pharmacologic drugs and radionuclides at sites within the human tracheobronchial tree.     

A mathematical and empirical model of the performance of a membrane-coupled anaerobic fermentor

A mathematical model was developed to describe the performance of a membrane-coupled anaerobic fermentor (MCAF)-based process. In our experimental results, higher volatile fatty acid (VFA) recovery ratios were obtained at greater filtration ratios. The VFA recovery ratio peaked at an HRT of 12 h and a membrane filtration ratio of 0.95 at a constant SRT. Based on our simulation, the HRT and filtration ratio should be maintained at less than 1 day and above 0.9, respectively, to exceed an organic materials recovery ratio of 35% at a constant SRT of 10 days. Our empirical model, which predicts the effluent VFA concentration (C _o ), described the performance of the MCAF adequately. The model demonstrated that the outlet VFA concentration was a function of three independent parameters—HLR, input organic concentration (C _i ), and membrane filtration ratio (ϕ). Multiple regression analyses were conducted using 50 measurements of the MCAF, yielding the following relationship: C _o  = 0.278ϕ^1.13 C _i ^1.93 HLR^0.11. The correlation coefficient (R ²) was 0.90. The simulation results were consistent with the observed data; therefore, due to its simplicity, this model predicts the effluent VFA concentration of an MCAF adequately.     

Effect of fodder beet cube size on ethanol production via diffusion fermentation

Summary The size of fodder beet cubes used to produce fuel ethanol via diffusion fermentation was varied to see how this affected various fermentation parameters. The highest yeast populations, shortest fermentation times, and highest ethanol yields and fermentation efficiencies were observed when 2.54 cm square cubes (or smaller) were utilized. Ethanol concentrations here averaged 4.21% (v/v) while the highest concentration reached was 4.83%. To minimize energy for slicing beets and still optimize yields, cubes of 1.91–2.54 cm should be used.     

Investigation on the causes of stoichiometric error in genome size estimation using heat experiments: consequences on data interpretation

BACKGROUND AND AIMS: In microdensitometry and flow cytometry, estimation of nuclear DNA content in a sample requires a standard with a known nuclear DNA content. It is assumed that dye accessibility to DNA is the same in the sample and standard nuclei. Stoichiometric error arises when dye accessibility is not proportional between the sample and standard. The aim of the present study was to compare the effects of standardization (external-internal) on nuclear fluorescence of two Coffea species and petunia when temperature increases, and the consequences on genome size estimation. METHODS: Two coffee tree taxa, C. liberica subsp dewevrei (DEW) and C. pseudozanguebarieae (PSE), and Petunia hybrida were grown in a glasshouse in Montpellier, France. Nuclei were extracted by leaf chopping and at least 2 h after nuclei extraction they were stained with propidium iodide for approx. 3 min just before cytometer processing. In the first experiment, effects of heat treatment were observed in mixed (DEW + petunia) and unmixed extracts (petunia and DEW in separate extracts). Nine temperature treatments were carried out (21, 45, 55, 60, 65, 70, 75, 80 and 85 degrees C). In a second experiment, effects of heating on within-species genome size variations were investigated in DEW and PSE. Two temperatures (21 and 70 degrees C) were selected as representative of the maximal range of chromatin decondensation. KEY RESULTS AND CONCLUSIONS: In coffee trees, sample and standard nuclei reacted differently to temperature according to the type of standardization (pseudo-internal vs. external). Cytosolic compounds released in the filtrate would modify chromatin sensitivity to decondensation. Consequently, the 'genome size' estimate depended on the temperature. Similarly, intraspecific variations in genome size changed between estimations at 21 degrees C and 70 degrees C. Consequences are discussed and stoichiometric error detection methods are proposed, along with proposals for minimizing them.