Coefficient Of Variation In Diameter Research Articles

High-Speed Generation of Microbubbles with Constant Cumulative Production in a Glass Capillary Microfluidic Bubble Generator.

This work reports a simple bubble generator for the high-speed generation of microbubbles with constant cumulative production. To achieve this, a gas-liquid co-flowing microfluidic device with a tiny capillary orifice as small as 5 μm is fabricated to produce monodisperse microbubbles. The diameter of the microbubbles can be adjusted precisely by tuning the input gas pressure and flow rate of the continuous liquid phase. The co-flowing structure ensures the uniformity of the generated microbubbles, and the surfactant in the liquid phase prevents coalescence of the collected microbubbles. The diameter coefficient of variation (CV) of the generated microbubbles can reach a minimum of 1.3%. Additionally, the relationship between microbubble diameter and the gas channel orifice is studied using the low Capillary number (Ca) and Weber number (We) of the liquid phase. Moreover, by maintaining a consistent gas input pressure, the CV of the cumulative microbubble volume can reach 3.6% regardless of the flow rate of the liquid phase. This method not only facilitates the generation of microbubbles with morphologic stability under variable flow conditions, but also ensures that the cumulative microbubble production over a certain period of time remains constant, which is important for the volume-dominated application of chromatographic analysis and the component analysis of natural gas.

GENERALIZED LINEAR MODELS FOR TREE SURVIVAL IN LOBLOLLY PINE PLANTATIONS

ABSTRACT To quantify the surviving trees in a forest stand and estimate the probability of an individual tree to survival are a fundamental task in forest management planning. Therefore, the main goal of this paper was to estimate the tree survival probability in loblolly pine (Pinus taeda L.) plantations based on generalized linear models (GLM). The data set was obtained from forest inventories carried out in the Midwest of Santa Catarina State, Brazil. The data analysis combined strategies for selecting covariates and different specifications of link functions in a Bernoulli GLM. We performed strategies for covariate selection at plot-level along with the standard stepwise procedure, where we considered the elastic net approach, as well as its special cases the lasso and ridge penalization. Our analyses showed that the stepwise procedure combined with the complementary log-log link function provide the best fit. The variables that most contributed to assess tree survival were basal area, number of individuals, maximum diameter, diameter of the average cross-sectional area and the diameter coefficient of variation per plots. This model presents 81.5% of accuracy given by ROC curve. Finally, we evaluated the fitted model by means of the half-Normal plots and randomized quantile residuals, whose results showed evidence of a suitable fit. We suggest the stepwise procedure for selecting covariates for a tree survival probability model, besides a complementary log-log link function.

Rapid Production and Recovery of Cell Spheroids by Automated Droplet Microfluidics.

The future of the life sciences is linked to automation and microfluidics. As robots start working side by side with scientists, robotic automation of microfluidics in general, and droplet microfluidics in particular, will significantly extend and accelerate the life sciences. Here, we demonstrate the automation of droplet microfluidics using an inexpensive liquid-handling robot to produce human scaffold-free cell spheroids at high throughput. We use pipette actuation and interface the pipetting tip with a droplet-generating microfluidic device. In this device, we produce highly monodisperse droplets with a diameter coefficient of variation (CV) lower than 2%. By encapsulating cells in these droplets, we produce cell spheroids in droplets and recover them to standard labware containers at a throughput of 85,000 spheroids per microfluidic circuit per hour. The viability of the cells in spheroids remains high throughout the process and decreases by >10% (depending on the cell line used) after a 16 h incubation period in nanoliter droplets and automated recovery. Scaffold-free cell spheroids and 3D tissue constructs recapitulate many aspects of functional human tissue more accurately than 2D or single-cell cultures, but assembly methods for spheroids (e.g., hanging drop microplates) have limited throughput. The increased throughput and decreased cost of our method enable spheroid production at the scale needed for lead discovery drug screening, and approach the cost at which these microtissues could be used as building blocks for organ-scale regenerative medicine.

Research on contribution rate of plant community characteristics and stand spatial structure to landscape aesthetics quality of forest parks and its influencing factors

The composition and evaluation of the plant community characteristics and stand spatial structure are the keys to the forest park landscape, and are of great significance to the optimization and promotion of forest park landscape. The research took Jinsiwan Forest Park in Fujian Province as the research object, and selected 40 typical samples and 24 factors to reflect the community characteristics and stand spatial structure. The scenic beauty estimation value of each sample was calculated by using scenic beauty estimation (SBE) method to construct a multiple regression linear model and landscape evaluation and prediction between SBE and various influencing factors categories, and analyze contributions of plant community characteristics and stand spatial structure to landscape aesthetics quality of forest parks. The findings indicated that the main factors affecting SBE included litter, uniformity of ground plants, abundance of conifer, crown density, variation coefficient of diameter at breast height (DBH), competition index, under branch height and uniform angle index, accounting for 20.809 per cent, 20.424 per cent, 14.547 per cent, 14.162 per cent, 10.790 per cent, 8.189 per cent, 6.455 per cent and 4.624 per cent respectively. The contribution rates of community characteristics and stand special structure were 87.187 per cent and 12.813 per cent. The research further explained the important roles of plant community characteristics and stand spatial structure in the scenic beauty estimation of forest parks.

Diversity and production in an Afromontane Forest

This contribution evaluates the effect of forest structure and tree species diversity on plot productivity and individual tree growth in the unique Knysna forests in Southern Africa using mapped tree data from an observational study that has been re-measured over a period of 40 years. The effects of tree species diversity and forest structure on tree growth and forest production are evaluated on three levels of resolution: a) the forest community (canopy, sub-canopy species), b) the subplots (number of trees per ha, skewness of the diameter distribution, diameter coefficient of variation) and c) the immediate neighborhood of selected reference trees (“Mingling”, “Dominance”, Aggregation” and “Size Variation”). An analysis of the community level identified two distinct clusters, one including dominant/canopy species with the highest growth rates and a greater variation of growth, and another cluster which includes the remaining subcanopy species which have a smaller maximum size and lower rates of growth. The area-based structure variables on plot level have a highly significant effect on total basal area growth. However, the effects of forest density and species richness on productivity were not straight forward. Maximum basal area production of about 0.75 m2/ha/year is achieved at medium levels of richness (around 20 species per ha) and medium levels of density (around 30 m2/ha basal area) using percentile regression estimates. The relative “Dominance” of a selected reference tree had a highly significant effect on individual tree growth on all investigated species. Other neighbourhood structure variables were only occasionally significant or not significant at all. This contribution presents a new theoretical framework for analysing natural forests that includes community, plot and neighborhood variables of forest structure and diversity, and a first specific analysis of the structure and dynamics of the Knysna Afromontane Forest, based on a unique set of longterm observations. The species-area (SAR) model developed in this study, represents a new general approach that can be used to derive a common standard of tree species diversity for different plot sizes, the species richness per hectare.

Contribution of objective and subjective attributes to the variation in the whiteness and brightness of commercial mohair sale lots

Colour properties are measured prior to the sale of merino wool as they are of commercial importance when greasy wool is sold and when wool is dyed. With the paucity of knowledge of the colour properties of commercial mohair, this study aimed to identify and quantify the factors affecting the brightness (Y) and yellowness (Y-Z) values of commercial lots of Australian mohair. The research database comprised 520 sale lots (>500,000 kg mohair), which had tristimulus tests, and was sold during the period 2001–2009. Mohair was subjectively classed and sale lots objectively tested using international standard methods for mean fibre diameter (MFD, μm), fibre diameter coefficient of variation (%), International Wool Testing Organization (IWTO) clean wool base (IWTO yield, %w/w), vegetable matter (VM, %w/w) and the tristimulus values X, Y and Z (T units). The tristimulus values of Australian mohair were affected by the objective measurements of MFD, VM%, the subjective classing of stain, cotting, kemp and length and by the year and selling season. Variation in Y was more easily predicted with 90.5% of variance explained by the best model compared with variation in Y-Z, where the best model explained 51.6% of the total variance. Visually assessed properties of the mohair were very important in separating mohair of different Y properties, accounting for almost 80% of the total variance, but were far less important in accounting for the variance in Y-Z, accounting for about 9–10% of the total variance. The most important effects on the Y of mohair were associated with subjectively determined fault categories determined before the sale of mohair. In particular, stain fault explained about two-thirds of the variance in brightness of mohair sale lots. Stained mohair had much lower brightness than mohair free of stain but stain fault explained very little of the variation in yellowness of mohair sale lots. The extent of the differences in tristimulus values between seasons and years were not large for Y but were more important for yellowness (Y-Z), and these effects are likely to be of commercial importance. Generally, brightness decreased and yellowness increased as MFD increased up to about 30 μm. Both cotting and kemp fault were associated with reduced brightness and increased yellowness. The effects of VM% on tristimulus values were small. IWTO yield was associated with changes in tristimulus values, but in the best model, IWTO yield was not a significant determinant. This study indicates that commercial Australian fleece (nonfaulted) mohair was essentially white. Faulted mohair on the other hand exhibited poorer colour characteristics. The mohair subjectively identified as stained prior to sale comprised all the mohair which would be regarded as not white, and this investigation indicates that the effect of staining is on the brightness of mohair rather than the Y-Z measurement. Unlike the situation with merino wool, there was little relationship between the naturally occurring contaminants, as measured by the IWTO washing yield, and either Y or Y-Z.

Effect of Spirulina (Arthrospira plantensis) Supplementation on Wool Quality in Purebred and Crossbred Merino Lambs Fed Pasture and Lucerne Hay Basal Diets

This study investigated the effects of Spirulina (Arthrospira plantensis) supplementation level, basal diet, sire breed, and sex on wool quality parameters in purebred and crossbred Merino lambs. A total of 48 lambs, over two consecutive years (n=24 per year), was randomly allocated into Spirulina supplementation level (CONTROL, LOW, MEDIUM, HIGH) groups and balanced by sire breed (Black Suffolk, Dorset, Merino, White Suffolk) and sex (ewes, wethers). Lambs had ad libitum access to a basal diet of pasture and Lucerne hay, and had Spirulina supplement daily throughout the 42-day feeding trial, after a 21-day adjustment phase. Mid-side wool samples were removed from each lamb at the beginning and end of the feeding trial and commercially analysed for quality. The wool quality data were transformed into ‘wool trait change over the feeding trial period’ by the difference between the wool measurements at the beginning and end of the experiment prior to statistical analysis. Wool clean fleece weight (CFW) was significantly influenced by level of supplementation, basal diet and sex (P<0.05). Spirulina-supplemented lambs on Lucerne hay basal diet elicited higher CFW responses which increased with supplementation level. CONTROL lambs had the lightest CFW regardless of basal diet. Sire breed and sex variations were significant (P<0.05) as wool from Suffolk-sired lambs and ewes had the highest fibre diameter coefficient of variation (CV) and CFW, respectively. CV and fibre diameter standard deviation were the most affected wool traits by significant interactions between Spirulina supplementation level, sire breed and sex. It was concluded that Spirulina supplementation with Lucerne hay basal diet improves wool CFW without compromising wool fibre diameter, comfort factor and spinning fineness in dual-purpose prime lambs.

Effects of site of assessment and variation in wool quality traits on the tactile assessment of textural greasy wool handle

Variation in textural greasy wool handle across the fleece of Merino sheep was explored. Results demonstrate that there were significant differences across nine sites on the fleece. The inclusion of the covariates fibre diameter, fibre diameter co-efficient of variation, staple length, dust penetration, staple structure, greasy wool colour and resistance to compression, helped to explain some of the variation in textural greasy wool handle between sites such that site of assessment was no longer a significant factor (P = 0.065). However, in practice, those involved with clip preparation or sheep selection based on textural greasy wool handle assessment are unlikely to have these measurements available. The results highlight the importance of nominating a site of assessment when recording textural greasy wool handle.

Genetic parameters for bodyweight, wool, and disease resistance and reproduction traits in Merino sheep. 4. Genetic relationships between and within wool traits

The aim of this paper was to describe the genetic relationship among expressions at different ages of seven wool traits: greasy and clean fleece weights, fibre diameter, coefficient of variation of fibre diameter, staple length and strength, and mean fibre curvature. Genetic correlations among measurements at different ages for the same trait were moderate to high, and ranged from ~0.6 for both fleece weights to 0.9 and higher for mean fibre diameter and curvature. Generally, low to moderate genetic correlations (0.3–0.4) were estimated between fleece weights and fibre diameter, clean fleece weight and staple length, and fibre diameter and staple strength. Small positive genetic correlations (0.2) were estimated between greasy and clean fleece weight with fibre diameter coefficient of variation, and between fibre diameter and staple length. Mean fibre curvature had a negative genetic correlation (approximately –0.4) with most other wool traits, the exceptions were staple strength (~0.0) and coefficient of variation of fibre diameter (approximately –0.1). Fibre diameter, staple length and staple strength had negative genetic correlations with coefficient of variation of fibre diameter (–0.15, –0.10, and –0.61, respectively). The results indicate that for most wool traits only one measurement across ages is required to make accurate selection decisions. The relationships between traits are generally moderate to low suggesting that simultaneous genetic improvement is possible.

Ultrasound recorded axillary artery blood flow during elbow-flexion exercise.

To characterize and evaluate the repeatability of ultrasound recorded blood flow in the axillary artery during one-arm dynamic elbow flexion. 11 healthy women (23 +/- 0.9 yr, 168 +/- 1.7 cm, 63 +/- 1.1 kg) performed 90 degrees elbow flexion in supine position. Mean maximum blood velocity was recorded by ultrasound during and after two submaximal loads, representing 16 and 24% of maximal voluntary contraction, and after exhaustion (.VO(2peak))Axillary artery diameter was measured after each workload. Each subject was examined two times 8 wk apart. Oxygen uptake was measured during exercise. Values are mean +/- SE. Flow was not different in the two tests. Flow was 25% higher immediately after than during exercise at the submaximal workloads. Flow immediately after .VO(2peak) was 1420 +/- 79 mL.min(-1). Axillary artery diameter after .VO(2peak) was 8% larger than at rest. Coefficient of variation ranged from 11 to 23%, coefficient of repeatability ranged from 230 mL.min(-1) at rest to 940 mL.min(-1) after exercise. Coefficient of repeatability for artery diameter was 0.09 cm; coefficient of variation for diameter was about 4% at all recording times. The present study showed that ultrasound recordings of blood flow during dynamic elbow-flexion exercise were reproducible. The method can be used to study training-induced flow changes and can detect differences of about 130 mL.min(-1). Artery diameter seemed to increase as flow and load increased.

Seasonal variation in fibre diameter and length in wool of grazing Merino sheep with low or high staple strength

The associations between fibre growth characteristics and wool staple strength were investigated in groups (n = 10) of Merino wethers with either low or high staple strength. Sheep grazed together on pastures based on subterranean clover and annual rye grass for about 13 months. The sheep were weighed and injected intradermally with [35 S]-cysteine at about 14-day intervals. Mid-side patches were harvested and dye bands placed in the wool at about 28-day intervals. Patch clean wool growth, pasture digestible dry matter/ha and pasture crude protein/ha had similar seasonal amplitudes of production (287, 286 and 267% of respective minimum). These were significantly higher than the seasonal amplitude in liveweight (24.5%). The seasonal amplitude in fibre diameter was significantly greater than that for rate of fibre elongation (71.4 and 41.4% respectively). This seasonality in fibre length and diameter resulted in statistically significant seasonal fluctuations in the ratio of fibre length growth to fibre diameter. Fortnightly variability in fibre diameter was not significantly related to variability in fibre length growth rate between sheep for individual time periods. However, for the pooled data over the experimental period a statistically significant relationship (R2 = 0.13, P&lt;0.01) was improved with the addition of parameters for sampling time and staple strength group. Staple strengths for the low and high staple strength groups were 25.6 and 32.8 N/ktex respectively (P = 0.057). There were no significant differences between the staple strength groups in seasonal change in liveweight, wool production or fibre parameters measured in this study but the low staple strength group had longer fibres. Staple strength was most highly correlated with mid-side fibre diameter coefficient of variation (R2 = 0.50) followed by seasonal amplitude in liveweight.

Estimation of the mean caliper: a new simple approach.

Morphometric measurements are commonly carried out on structures the shape of which approximates that of a sphere. We calculated some stereological data of eosinophil granules by using digitized planimetry, performed on transmission electronmicrographs. By using a new approach for mean caliper (D) estimation and extrapolating an approximate granule axial ratio, we were able to calculate the granule density size. We deduced from a numerical analysis for various sphere sizes distributions from which an underestimation of not more than 4% may be contributed to D in most cases, assuming that the diameter coefficient of variation is less than 35%. The methodology we propose for mean ellipsoid caliper estimation seems to be useful in cases in which the disector method is not suitable.

Single-valued strength of ‘‘perfect’’ silica fibers

An analysis has been made of the tensile strength statistics of two silica fibers with quite different degrees of diameter uniformity. It has been found that the coefficient of variation in diameter (νd) is equal to that in minimum diameter (νd,min) and that the measured coefficient of variation in breaking load (νL) and breaking stress (calculated assuming constant d) are twice this value. Since νL =νσ =2νd =2νd,min it is clear the apparent variability in strength is the result of the variability in diameter and therefore the real strength is essentially single valued. Because of this lack of statistical variation in breaking strength, it is suggested that these fibers are flaw-free as drawn.

A Study of Hairiness and Diameter of Open-End Yarn Processed Through Single- and Double-Cylinder Carding Machines and Its Comparison with Ring Yarn

An investigation was made on the hairiness and diameter of ring and open-end (OE) yarns processed through single- and double-cylinder carding machines. Yarn hairiness was measured with a photoelectric tester designed by the East China College of Textile Technology. When the length and the number of frequency distributions of hairs of both yarns were measured, three conclusions were reached: 1) the total and average length of hairs and the percentage of extremely short and long hairs of OE yarns are both greater than those of ring yarns; 2) Hairiness of OE yarns processed through single- or double-cylinder carding machines is of nearly the same value in both total and average length but differs significantly in coefficient of variation; 3) the between-bobbin coefficient of variation of the hairiness of OE yarn is greater than that of ring yarn, but there is no great difference in the within-bobbin coefficients of variation of the hairiness of these two yarns. The diameter of OE yarn processed through the double-cylinder carding machine is about 2% smaller than that of yarn processed with the single-cylinder carding machine, which is not very significant. OE yarn has a lower coefficient of variation in diameter than ring yarn. The within-bobbin coefficient of variation in diameter of either OE yarn or ring yarn is higher than its between-bobbin coefficient of variation.