Significant Difference In Coefficient Of Variation Research Articles

Using optimized monochromatic energy dispersive X-ray fluorescence to determine the cadmium concentration in cacao and soil samples

Following the implementation of food safety limits on cadmium (Cd) in cacao products, there has been a growing demand for monitoring Cd in cacao tissues and soils. Traditional methods like acid digestion followed by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) are time-consuming and costly. X-ray Fluorescence is an alternative technique that offers advantages in terms of speed, cost, ease of use and less environmental impact. However, to date, relatively high detection limits have impeded its application for food safety limits. This study examines a Monochromatic Energy Dispersive X-ray Fluorescence (MEDXRF) method optimized for Cd analysis as an alternative to ICP-MS. Using a measurement time of 200 s, the average limit of quantification (LOQ) was 0.178 mg Cd kg−1 for biological samples and 0.205 mg Cd kg−1 for soil samples. A strong correlation (y = 1.013 x + 0.003, R2 = 0.984) with ICP-MS results was found for 95 bean, 16 cacao liquor, 75 leaf, and 91 soil samples. The coefficient of variation (CV) among three replicates was below the threshold value of 15 % for most samples with Cd concentrations above the reported LOQ values. Additionally, a significant difference in CV was obtained between soils sieved over 500 μm (median 8.2 %) or 2 mm (median 9.8 %). However, no significant difference in CV was observed between 500 μm unpeeled beans and cocoa liquor with particle size of 20 μm. Based on our data, the proposed procedure is to analyze three replicates for 200 s with a sample size of 500 μm. The optimized MEDXRF technique offers important advantages in terms of cost-effectiveness and efficiency of routine Cd monitoring in the cacao supply chain, large-scale screening, and scientific research, and could be extended to other crops and heavy metals that are subject to food safety regulation at low concentrations.

Evaluation of a Web-Based Surgical Training Approach and Insights from Distal Bypass Competition 2021 Using a Simulator Kit

ObjectiveThe study aimed to assess a novel web-based surgical training approach among young vascular surgeons and validate web-based evaluation methods for assessing anastomosis skills through the online Distal Bypass Competition (DBC). MethodsThe Objective Structured Assessment of Technical Skill (OSATS) was utilized to assess anastomosis proficiency using a simulator among 42 participants (17 junior and 25 senior surgeons) in the DBC 2021. Initial evaluation of basic anastomosis skills was conducted via recorded videos, comparing OSATS scores with instructor-derived impression-based scores (Comprehensive Evaluation Score: CES) during the nomination round. Real-time evaluations conducted over Zoom focused on assessing technical and composition scores of the anastomoses to determine finalists. The ice-skating method addresses potential variability among judges by excluding the highest and lowest scores for each procedural element from the final evaluation. This method, demonstrated in real-time, provides trainees with valuable feedback on which movements are highly rated, enhancing the educational impact. Evaluation criteria included precision in needlework, external appearance, handling of the intima, and internal morphology of the anastomosis. Furthermore, voluntary survey questionnaires were administered to gather participant feedback on their experience with DBC 2021. ResultsThe OSATS was associated with a lower coefficient of variation (CV) than was the CES (0.19 ± 0.07 vs. 0.24 ± 0.09, P=0.01) with regard to the evaluation of basic anastomotic skills in the nomination round. Interestingly, there was no significant difference in CV between PES based on OSATS and CES in the senior class (0.16 ± 0.06 vs. 0.22 ± 0.09, P=0.13), but a significant difference was particularly evident in the junior class (0.12 ± 0.07 vs. 0.27 ± 09, P=0.03). Lower scores were associated with higher CVs in both classes, but the OSATS improved the CV among participants who had inadequate anastomosis skills. In real-time evaluation, composition scores exhibited higher CVs compared to technical scores, even among high-scoring participants. Notably, the internal morphology of the anastomosis had the largest CV in the composition scores. The ice-skating method reduced the CV as compared to the original data evaluated using the OSATS (0.15 ± 0.04 vs. 0.09 ± 0.02 for the technical score, P<0.01 and 0.18 ± 1.00 vs. 0.07 ± 0.05 for the composition score, P=0.03); accordingly, the ice-skating method was more conducive to objective, real-time evaluation. The results of the post-DBC survey indicated that 89% of participants reported increased training time, and half of these participants indicated that their confidence in their clinical skills related to this procedure increased due to the process of training for the DBC. ConclusionsThe OSATS yielded more detailed evaluations of anastomosis skill with lower variability compared to the instructor’s impression-based evaluation in this web-based training. Real-time evaluation methods, such as the ice-skating method, have proven to be valuable tools for standardized assessment of web-based surgical education.

Intrasubject variability of sustained attention is associated with elevated self-reported attention deficits in women with a fragile X premutation allele.

Women with a fragile X premutation (PM) self-report higher rates of attention difficulties than women without a PM; however, results of studies using objective measures of attention are inconsistent. The present study assessed whether intrasubject variability during a sustained attention task better predicted functional outcomes in women with a PM than the previously published standard reaction time and accuracy variables. We analyzed continuous performance test, a computerized measure of sustained attention, and the Conners' Adult Attention-Deficit/Hyperactivity Disorder Rating Scale Report (CAARS) data from 273 women with a PM and 175 women without a PM aged 18-50 years. Separate analyses using Pearson correlations and independent t tests were performed on the full range of coefficient of variation (CV) of reaction time scores and the subset of scores that showed higher variability. Performance variability of sustained attention measured by the continuous performance test was associated with functional outcomes measured by the CAARS in women with a PM but not women without a PM. Specifically, the CV in those with higher variability was correlated with two CAARS subscale scores (p = .006). Independent t tests showed significant differences in CV between CAARS scores dichotomized for the presence of subclinical symptoms for two subscales (p ≤ .001-.007). Correlation between the full range of CV scores and the CAARS Inattention/Memory Problems subscale approached significance (p = .012). Findings highlight the importance of including intrasubject variability in analyzing attention in clinical populations as a more sensitive objective measure associated with reported symptoms and to assist in predicting functional outcomes. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Diverse water management in a preceding wheat crop does not affect maize yield but increases inter-annual variability: A six-year field study

As maize-based crop rotation systems are essential to ensure global food security, understanding the effect of the preceding crops and the associated management on the subsequent maize is crucial. Here we address this view with a 6-year field experiment in the North China Plain's annual winter wheat and summer maize rotation system. Effects of preceding wheat with three water management (conventional irrigation, Con.W/M; optimized irrigation, Opt.W/M; minimum irrigation, Min.W/M) on maize yield and water consumption are investigated. We find that water management in the preceding wheat crop does not affect the subsequent maize yield but increases the interannual yield variability. Over the six years, an average yield of > 10.7 Mg ha-1 is achieved for maize in the three treatments. The highest coefficient of variation (CV) of yield is observed in Min.W/M (12.0%), while there is no significant difference in CV between Con.W/M and Opt.W/M. The annual water consumption follows a decreasing trend in the order of Con.W/M (357 mm), Opt.W/M (332 mm), and Min.W/M (290 mm), which primarily attribute to variations in initial water storage in the deeper soil profile (below 80 cm). The variation in water storage would be eliminated during the following maize growing stages due to ample rainfall in the temperate continental monsoon climate. The findings show that kernel weight (KW) is the primary determinant (accounting for 55–86%) to the observed variations in maize yield. In the Min.W/M treatment, the interactive effect of killing degree days, growing degree days, maximum temperature, and solar radiation accounts for 85% of the variation observed in KW. This study provides insights into the effect of the preceding wheat on the subsequent maize for grain yield and water consumption in the rotation system.

Deep progressive learning achieves whole-body low-dose 18F-FDG PET imaging

ObjectivesTo validate a total-body PET-guided deep progressive learning reconstruction method (DPR) for low-dose 18F-FDG PET imaging.MethodsList-mode data from the retrospective study (n = 26) were rebinned into short-duration scans and reconstructed with DPR. The standard uptake value (SUV) and tumor-to-liver ratio (TLR) in lesions and coefficient of variation (COV) in the liver in the DPR images were compared to the reference (OSEM images with full-duration data). In the prospective study, another 41 patients were injected with 1/3 of the activity based on the retrospective results. The DPR images (DPR_1/3(p)) were generated and compared with the reference (OSEM images with extended acquisition time). The SUV and COV were evaluated in three selected organs: liver, blood pool and muscle. Quantitative analyses were performed with lesion SUV and TLR, furthermore on small lesions (≤ 10 mm in diameter). Additionally, a 5-point Likert scale visual analysis was performed on the following perspectives: contrast, noise and diagnostic confidence.ResultsIn the retrospective study, the DPR with one-third duration can maintain the image quality as the reference. In the prospective study, good agreement among the SUVs was observed in all selected organs. The quantitative results showed that there was no significant difference in COV between the DPR_1/3(p) group and the reference, while the visual analysis showed no significant differences in image contrast, noise and diagnostic confidence. The lesion SUVs and TLRs in the DPR_1/3(p) group were significantly enhanced compared with the reference, even for small lesions.ConclusionsThe proposed DPR method can reduce the administered activity of 18F-FDG by up to 2/3 in a real-world deployment while maintaining image quality.

Reproducibility of sequential ambulatory blood pressure and pulse wave velocity measurements in normotensive and hypertensive individuals.

Errors in blood pressure (BP) measurement account for a large proportion of misclassified hypertension diagnoses. Ambulatory blood pressure monitoring (ABPM) is often considered to be the gold standard for measurement of BP, but uncertainty remains regarding the degree of measurement error. The aim of this study was to determine reproducibility of sequential ABPM in a population of normotensive and well controlled hypertensive individuals. Individual participant data from three randomized controlled trials, which had recorded ABPM and carotid-femoral pulse wave velocity (PWV) at least twice were combined ( n = 501). We calculated within-individual variability of daytime and night-time BP and compared the variability between normotensive ( n = 324) and hypertensive ( n = 177) individuals. As a secondary analysis, variability of PWV measurements was also calculated, and multivariable linear regression was used to assess characteristics associated with blood pressure variability (BPV). Within-individual coefficient of variation (CoV) for systolic BP was 5.4% (day) and 7.0% (night). Equivalent values for diastolic BP were 6.1% and 8.4%, respectively. No statistically significant difference in CoV was demonstrated between measurements for normotensive and hypertensive individuals. Within-individual CoV for PWV exceeded that of BP measurements (10.7%). BPV was associated with mean pressures, and BMI for night-time measurements. PWV was not independently associated with BPV. The variability of single ABPM measurements will still yield considerable uncertainty regarding true average pressures, potentially resulting in misclassification of hypertensive status and incorrect treatment regimes. Repeated ABPM may be necessary to refine antihypertensive therapy.

Low-Cost, Smartphone-Based Specular Imaging and Automated Analysis of the Corneal Endothelium.

PurposeSpecular and confocal microscopes are important tools to monitor the health of the corneal endothelium (CE), but their high costs significantly limit accessibility in low-resource environments. We developed and validated a low-cost, fully automated method to quantitatively evaluate the CE using smartphone-based specular microscopy.MethodsA OnePlus 7 Pro smartphone attached to a Topcon SL-D701 slit-lamp was used to image the central corneal endothelium of 30 eyes using the specular reflection technique. A novel on-device image processing algorithm automatically computed endothelial cell density (ECD), percentage of hexagonal cells (HEX), and coefficient of variation (CV) values. These values were compared with the ECD, HEX, and CV generated by a Tomey EM-4000 specular microscope used to image the same set of eyes.ResultsNo significant differences were found in ECD (2799 ± 156 cells/mm2 vs. 2779 ± 166 cells/mm2; P = 0.28) and HEX (52 ± 6% vs. 53 ± 6%; P = 0.50) computed by smartphone-based specular imaging and specular microscope, respectively. A statistically significant difference in CV (34 ± 3% vs. 30 ± 3%; P < 0.01) was found between the two methods. The concordance achieved between the smartphone-based method and the Tomey specular microscope is very similar to the concordance between two specular microscopes reported in the literature.ConclusionsSmartphone-based specular imaging and automated analysis is a low-cost method to quantitatively evaluate the CE with accuracy comparable to the clinical standard.Translational RelevanceThis tool can be used to screen the CE in low-resource regions and prompt investigation of suspected corneal endotheliopathies.

Intraindividual variability in driving simulator parameters of healthy drivers of different ages

Intraindividual variability is a fundamental behavioural characteristic of aging but has been examined to a very limited extent in driving. This study investigated intraindividual variability in driving simulator measures in healthy drivers of different ages using the coefficient of variation (COV) as a variability measure. Participants were healthy volunteers who were regular drivers, who were divided into a “young” group, a “middle-aged” group, and an “old” group. They drove in two environments (rural, 72 drivers; urban, 60 drivers), under conditions of moderate and high traffic load, without and with distraction (conversation). Significant differences in COV were observed in the rural condition for headway distance and lateral position as a function of traffic load, with high traffic (without and with distraction) resulting in increased COV of headway and decreased COV of lateral position. Significant differences in COV were observed in the urban condition for headway distance only, with high traffic (without and with distraction) resulting in increased COV of headway. No age effects were found for any of the driving conditions. The results indicate that traffic load affected headway distance and lateral position in opposite directions in all three age groups: high traffic resulted in increased variability of headway in both rural and urban conditions but in decreased variability of lateral position in the rural conditions compared to moderate traffic irrespective of distraction. The study indicates that driving conditions affect the intraindividual variability of driving measures in selective ways, which may be linked to the extent of automatization of the driving variables and to adaptive changes to traffic condition challenges.

Quantifying the uncertainty introduced by internal climate variability in projections of Canadian crop production

Internal climate variability (ICV) is one of the major sources of uncertainty in climate projections, yet it is seldom quantified for projections of crop production. Our study focuses on quantifying the uncertainty due to ICV in projections of crop productions in Canada. We utilize climate scenarios from two large ensembles (LEs, CanESM2-LE and CanRCM4-LE with 25 members each) as inputs to the crop models in the Decision Support System for Agrotechnology Transfer. We simulate crop yields for canola, maize and spring wheat under the future climates of four global warming levels. The coefficient of variation (CV) of the projected crop production across the LE members is used to quantify the uncertainty related to ICV and this is compared with the CVs generated using the 20 GCMs in the Coupled Model Intercomparison Project Phase 5 (CMIP5). Crop production in Canada could increase with global warming, e.g. spring wheat production could increase by up to 21% at the warming level of 3.0 °C. The projections often produce larger uncertainty associated with the GCMs than from ICV at all warming levels above 2.0 °C. The results from an asymptotic test for the equality of CVs show a significant difference in CVs of projections of canola production between CanESM2-LE/CanRCM4-LE and CMIP5 for the warming level of 3.0 °C. However, the test results do not indicate a significant difference among the ensembles at all four warming levels for maize and spring wheat. The uncertainty due to ICV is often comparable to that associated with GCMs at the warming level of 1.5 °C, e.g. a CV of 6.0 and 6.4% for CanESM2-LE and CanRCM4-LE and 6.6% for CMIP5 in the projections of spring wheat production. We conclude there is a need to account for uncertainty related to ICV in projections of Canadian crop production, especially at lower warming levels.

Transient analysis of advancing contact angle measurements on polished rock surfaces

Abstract Contact angle measurements for gas-liquid-rock systems are important for modeling multi-phase flow and transport in the subsurface. These data are needed in applications such as the extraction of oil and gas resources, geologic sequestration of carbon dioxide, contaminant fate and transport, and aquifer recharge through the vadose zone. Contact angles are frequently measured with the sessile drop method. Previous research has largely ignored the dynamic behavior of sessile droplets on geologic materials. This study investigates the dynamic behavior of sessile water droplets on prepared rock surfaces in the presence of air. Droplet diameter and advancing contact angle were determined at 0.5 s intervals for ∼ 90 s on flat polished disks of Burlington limestone, Crossville sandstone, Mancos shale, Sierra White granite, Vermilion Bay granite, and Westerly granite using a Kruss DSA 30 Drop Shape Analyzer. The droplet diameter and advancing contact angle data sets were nonlinearly regressed against time using two different two-parameter models. The median coefficients of determination for the fits were 0.85 and 0.96, respectively. The resulting parameter estimates were used to compute the apparent equilibrium contact angle, θe, for each disk following droplet diameter stabilization. Estimates of θe ranged from 37.2° for Mancos shale to 75.6° for Burlington limestone. Analysis of variance indicated statistically significant differences in θe between the rock types at the 95% confidence level. The variability of θe on the polished rock surfaces, as quantified by the coefficient of variation (CV) for θe, varied between ∼ 3 and ∼ 9%; there were no significant differences in CV between the rock types. Neutron radiography indicated changes droplet morphology over time were due to the spontaneous imbibition of water into the rock matrix. The transient analysis employed in this study permits a more meaningful estimate of the equilibrium contact angle for rocks than taking the initial value or averaging over time as is frequently done.

Endothelial alterations in 712 keratoconus patients.

To investigate the effect of the severity of keratoconus on the corneal endothelium using specular microscopy. Seven hundred and twelve eyes from the Homburg Keratoconus Center (HKC) database were included in this retrospective study. Corneal endothelium was evaluated using the Tomey EM-3000 specular microscope. Keratoconus-related topographic and tomographic data were obtained from Scheimpflug-based tomography (Oculus Pentacam® HR). Eyes were classified into stages 0 (healthy) to 4 (severe keratoconus) according to the Topographic Keratoconus Classification (TKC). Subgroups were analysed based on contact lens (CL) type (none/rigid/soft). The frequencies of keratoconus stages 0/1/2/3/4 according to TKC were 169/94/206/166/77. The endothelial cell density (ECD) for the endothelial cell area for TKC 0/1/2/3/4 was 2611/2624/2557/2487/2401 cells per mm² and the coefficient of variation (CV) was 40.9/40.0/41.6/46.2/49.0%, respectively. The more severe the keratoconus stage, the lower the endothelial cell count (p<0.001) and the higher the CV (p<0.001). No contact lens wearing was noted in 207 eyes (NoCL), rigid CL in 200 (RCL) and soft CL in 54 (SCL). CD for NoCL/RCL/SCL was 2523/2533/2644 per mm² and CV was 41.8/54.1/43.1%, respectively. A significant difference in CV was found between NoCL and RCL (p=0.02), and no significant difference in CV was found between NoCL and SCL (p=0.07). Endothelial cell density (ECD) did not differ significantly between NoCL and RCL or SCL. Endothelial cell density (ECD) decreases and CV increases significantly with increasing tomographic severity of keratoconus. In patients with RCL compared to eyes without CL wear, we found a statistically significantly higher CV in the endothelial cell size.

Corneal Endothelial Characteristics, Central Corneal Thickness, and Intraocular Pressure in a Population of Chinese Age-Related Cataract Patients.

Purpose To describe corneal endothelial characteristics, central corneal thickness, and intraocular pressure in a population of Chinese age-related cataract patients and to determine the effects of age, gender, hypertension, and body mass index (BMI). Methods 1551 eyes were examined preoperatively. The parameters measured were endothelial cell density (CD), average cell area (CA), coefficient of variation (CV), cell hexagonality (HEX), central corneal thickness (CCT), intraocular pressure (IOP), and axial length (AL). Results There were significant differences in CV and BMI between genders. There was a significant decrease in CD, CCT, and IOP and, conversely, an increase in CA and BMI with increasing age. The patients who suffered from hypertension had bigger CA, less CD, and lower HEX than the patients who did not suffer from hypertension. CD has a negative correlation with age and CV and a positive correlation with CCT, CCT has a positive association with CD and IOP, and IOP had a negative relationship with age and a positive relationship with CCT, CA, and HEX. Conclusions Normative data for the corneal endothelium, central corneal thickness, and intraocular pressure in the normal age-related cataract patients are reported which will serve as a baseline for comparative studies about cataract.

Effects of feeding frequency and density on growth, energy budget and physiological performance of sea cucumber Apostichopus japonicus (Selenka)

Feeding frequency and density are two of the most important factors that directly affect the growth and physiology of sea cucumber Apostichopus japonicus. In the present study, a 60-day experiment was conducted to evaluate the effects of feeding frequency (1 time, 2 times and 3 times per day) and stocking density (D10, D20, D40 and D60) on growth performance, feed utilization, endocrine response and energy budget of sea cucumber. The results revealed that there was no significant interaction between feeding frequency and stocking density on final weight and specific growth rate (SGR). The maximum SGR occurred at treatment of stocking density D10 with feeding thrice per day. Stepwise multiple regression analysis showed that SGRW and SGRE increased with increasing feeding frequency, and decreased with the increase of stocking density. Density had significant influence on coefficient of variation (CV) for the sea cucumber body weight. For D10 and D20, no significant difference in CV was found between different feeding frequencies. Feed intake, energy intake and feces production rate were significantly affected by feeding frequency, stocking density and their interaction. Density also had significant influence on food conversion efficiency and protein efficiency ratio. Apparent digestibility coefficients of crude protein and crude lipid exhibited remarkable descending trends as stocking density increased. The energy for growth decreased and energy required for metabolism increased with the increase of stocking density, suggesting that crowding stress modified their energy allocation by inhibiting the accumulation of growth energy and accelerating energy consumption of sea cucumber. Cortisol level in coelomic fluid of sea cucumber significantly increased with the increase of stocking density, which could generate energy to satisfy the increasing demand of stress-related energy. Lactate level significantly elevated, and glucose level in coelomic fluid and glycogen in muscle showed remarkable descending trends from D10 to D60, implying long-term energy consumption under high stocking density. Feeding frequency had significant influence on glucose, glycogen and cortisol levels. To some extent, increasing feeding frequency could effectively reduce coefficient of variation of sea cucumber, especially under high stocking density. Statement of relevance•In the present study, a 60-day experiment was conducted to evaluate the effects of feeding frequency (1 time, 2 times and 3 times per day) and stocking density (D10, D20, D40 and D60) on growth performance, feed utilization, endocrine response and energy budget of sea cucumber.•Increasing feeding frequency could effectively reduce coefficient of variation of sea cucumber.•The present study provided valuable information for the intensive culture of A. japonicus.

Reproducibility of (18)F-FDG PET uptake measurements in head and neck squamous cell carcinoma on both PET/CT and PET/MR.

To investigate reproducibility of fluorine-18 fludeoxyglucose ((18)F-FDG) uptake on (18)F-FDG positron emission tomography (PET)/CT and (18)F-FDG PET/MR scans in patients with head and neck squamous cell carcinoma (HNSCC). 30 patients with HNSCC were included in this prospective study. The patients were scanned twice before radiotherapy treatment with both PET/CT and PET/MR. Patients were scanned on the same scanners, 3 days apart and according to the same protocol. Metabolic tumour activity was measured by the maximum and peak standardized uptake value (SUVmax and SUVpeak, respectively), and total lesion glycolysis from the metabolic tumour volume defined from ≥50% SUVmax. Bland-Altman analysis with limits of agreement, coefficient of variation (CV) from the two modalities were performed in order to test the reproducibility. Furthermore, CVs from SUVmax and SUVpeak were compared. The area under the curve from cumulative SUV-volume histograms were measured and tested for reproducibility of the distribution of (18)F-FDG uptake. 24 patients had two pre-treatment PET/CT scans and 21 patients had two pre-treatment PET/MR scans available for further analyses. Mean difference for SUVmax, peak and mean was approximately 4% for PET/CT and 3% for PET/MR, with 95% limits of agreement less than ±20%. CV was small (5-7%) for both modalities. There was no significant difference in CVs between PET/CT and PET/MR (p = 0.31). SUVmax was not more reproducible than SUVpeak (p = 0.09). (18)F-FDG uptake in PET/CT and PET/MR is highly reproducible and we found no difference in reproducibility between PET/CT and PET/MR. This is the first report to test reproducibility of PET/CT and PET/MR.

Variability, frequency composition, and complexity of submaximal isometric knee extension force from subacute to chronic stroke

We examined changes in the variability, frequency composition, and complexity of force signal from subacute to chronic stage of stroke during maintenance of isometric knee extension and compared these parameters between chronic stroke and healthy subjects. The sample included 15 healthy (65±8years) and 23 chronic stroke subjects (65±14years, 6–112months post-stroke) of whom 10 (64±15years) were also examined 11–22days post-stroke (subacute stage). The subjects performed isometric knee extension at 10%, 20%, 30%, and 50% of peak torque for 10s (two trials each). Coefficient of variation (CV) was used as a measure of force variability. The median frequency and relative power in the 0–3, 4–6, and 8–12Hz bands were obtained through a power spectrum analysis of the force signal. The signal complexity was quantified using the sample entropy (SampEn). The longitudinal analysis revealed a significant decrease in CV from subacute to chronic stage across all contraction levels (P<0.001) but no significant changes in the frequency and entropy parameters. Comparison between the chronic stroke and control subjects revealed no significant difference in CV across the force levels (P>0.05) but significantly decreased median frequency (P<0.01), with the relative power increased in 0–3Hz band and decreased in 4–6 and 8–12Hz bands in both paretic and non-paretic legs (P<0.001). SampEn was also significantly decreased in chronic stroke, bilaterally (P<0.001). These results indicate a shift toward lower frequencies and a less complex physiological process underlying force control in chronic stroke. The overall results suggest the improvement in force variability from subacute to chronic stroke but without normalization in the frequency composition and complexity of the force signal. Thus, disordered structure of the force signal remains a marker of impaired motor control long after stroke occurrence despite apparent recovery in force variability.

Corneal endothelial cell density and morphology in low and moderate myopic Chinese eyes.

To describe and compare the corneal endothelial cell density and morphology in young, low and moderate myopic Chinese adults in Malaysian Chinese population. Non-contact specular microscopy (Topcon SP3000P, Tokyo, Japan) was performed in low (n=78; 21.22±1.51 years) and moderate (n=78; 21.82±1.40 years) myopic subjects. The mean of three consecutive measurements of endothelial cell density (MCD), coefficient of variation (CV) in the cell size, and hexagonal appearance of the cell were obtained. In low myopic eyes the MCD was 3 063.0±176.2/mm(2), the mean CV was 33.4±4.0% and the mean hexagonal appearance of the cell was 57.9±2.7%. In moderate myopic eyes the MCD was 2961.6±159.0/mm(2), the mean CV was 33.9±3.6% and mean hexagonal appearance of the cell was 56.2±4.7%. There were statistically significant differences in MCD (P<0.000) and hexagonal appearance of the cell (P<0.005) between low and moderate myopic eyes. The corneal endothelial cell layer in more myopic eyes tends to have less MCD and cell hexagonality compared to lower myopic eyes. Nevertheless, there is no significant difference in CV between low and moderate myopic eyes.

페달링 시 웨지의 삽입 유무에 따른 족저압의 영역별 비교 연구

The purpose of this study was to study effects of inserted wedge on foot pressure during pedaling. Seven cyclists (age: 34.4±4.6year, height: 174.0±4.2cm, weight: 84.6±6.2kg) participated in 10 second maximal tests with and without wedges by their condition of varus or valgus. Movement of the knee joint was obtained through 3D motion analysis system (Motion analysis Corps., USA), and foot pressure were measured by F-scan System (Tekscan Inc., Boston, USA). Foot pressure was analyzed by contact area, contact pressure, peak contact pressure, contact force and peak contact force of 4 regions such as toe, forefoot, midfoot and rear-foot. CV(coefficient of variation) of mediolateral trajectory of the knee and CV of mediolateral COP(center of pressure) of foot pressure, which is closely related with lower limb vertical alignment, were analyzed. Results showed that CV of mediolateral trajectory of the knee and CV of COP at forefoot were significantly decreased with inserted wedge (p.05). There were no significant differences in CV of COP at toe, midfoot and rearfoot. Contact pressure, peak contact pressure, contact force, and peak contact force at the forefoot were signifi-cantly increased after inserting wedges (p.05) and there was no significant difference in contact area at the forefoot after inserting wedges. Contact area and contact force at the midfoot were significantly decreased with wedge(p.05). However, there was no significant differences in contact pressure and peak contact pres-sure at the midfoot. There were no significant differences in foot pressure at toe and rearfoot with wedges. It could be concluded that inserted wedges made increasing effects of contact pressure, peak contact pressure, contact force, peak contact force of the forefoot by decreasing the variability of the knee and COP of foot pressure. Inserting wedges by considering rider`s physical characteristics will help vertical alignment of lower limb and the resulting vertical alignment will do positive effects on the prevention of injuries and efficiency of force transmission to the pedal.

Horses, hormones and habits

Feeding frequency and density are two of the most important factors that directly affect the growth and physiology of sea cucumber Apostichopus japonicus. In the present study, a 60-day experiment was conducted to evaluate the effects of feeding frequency (1 time, 2 times and 3 times per day) and stocking density (D10, D20, D40 and D60) on growth performance, feed utilization, endocrine response and energy budget of sea cucumber. The results revealed that there was no significant interaction between feeding frequency and stocking density on final weight and specific growth rate (SGR). The maximum SGR occurred at treatment of stocking density D10 with feeding thrice per day. Stepwise multiple regression analysis showed that SGRW and SGRE increased with increasing feeding frequency, and decreased with the increase of stocking density. Density had significant influence on coefficient of variation (CV) for the sea cucumber body weight. For D10 and D20, no significant difference in CV was found between different feeding frequencies. Feed intake, energy intake and feces production rate were significantly affected by feeding frequency, stocking density and their interaction. Density also had significant influence on food conversion efficiency and protein efficiency ratio. Apparent digestibility coefficients of crude protein and crude lipid exhibited remarkable descending trends as stocking density increased. The energy for growth decreased and energy required for metabolism increased with the increase of stocking density, suggesting that crowding stress modified their energy allocation by inhibiting the accumulation of growth energy and accelerating energy consumption of sea cucumber. Cortisol level in coelomic fluid of sea cucumber significantly increased with the increase of stocking density, which could generate energy to satisfy the increasing demand of stress-related energy. Lactate level significantly elevated, and glucose level in coelomic fluid and glycogen in muscle showed remarkable descending trends from D10 to D60, implying long-term energy consumption under high stocking density. Feeding frequency had significant influence on glucose, glycogen and cortisol levels. To some extent, increasing feeding frequency could effectively reduce coefficient of variation of sea cucumber, especially under high stocking density.•In the present study, a 60-day experiment was conducted to evaluate the effects of feeding frequency (1 time, 2 times and 3 times per day) and stocking density (D10, D20, D40 and D60) on growth performance, feed utilization, endocrine response and energy budget of sea cucumber.•Increasing feeding frequency could effectively reduce coefficient of variation of sea cucumber.•The present study provided valuable information for the intensive culture of A. japonicus.

Could the coefficient of variation (COV) of the corneal endothelium be overestimated when a centre‐dot method is used?

Background: Little has been published on the reliability of estimates of the coefficient of variation (COV) in cell area for human corneal endothelia. The present study compares two methods.Methods: A non‐contact specular micrograph (Topcon SP‐2000P) was obtained from the central region of the corneal endothelium of 20 healthy myopic white European subjects, aged from 32 to 53 years, half of whom were successful long‐term soft contact lens wearers. The captured image file was either assessed using a machine‐based algorithm, in which 25 cells in the middle of the image were marked and their areas reported (designated as ‘centre‐dot’ method) or by a manual method, by which all the cells in the image were outlined on very high magnification prints of the endothelia and the cell areas measured by a manual digitiser in stream mode. The average cell area was used to calculate the endothelial cell density (ECD), while the COV was calculated from the standard deviation (SD) of the cell area measures.Results: Identical mean cell area values were found (392 µm2) with the two methods, a marginally higher ECD estimate (2,594 versus 2,569) with the centre‐dot method (p = NS) but a much higher COV with the centre‐dot method (43.8 versus 29.0 per cent). This highly statistically significant difference in COV (p < 0.001) was seen in both contact lens wearers and non‐contact lens wearers. A Bland‐Altman analysis reveals a bias in the centre‐dot method, especially for the COV estimates, that appears to be linked to erroneous definition of a single large cell domain on any individual image.Conclusions: A centre‐dot method can be reliably used to generate useful data on cell area and ECD but it should be used cautiously for estimates of polymegethism (COV).

Development of size hierarchies prior to the onset of density-dependent mortality in irrigated and fertilized loblolly pine stands

Nine years of growth and stand development were investigated in a 2 × 2 nutrient and water factorial experiment with four replications. The study was located on an infertile, excessively drained sandy site in Scotland County, North Carolina, U.S.A. The hypothesis tested was that increased growth following irrigation and fertilization would increase the rate at which size hierarchies develop. The hypothesis was investigated by comparing the coefficient of variation (CV) of stem volume over time and examining the stem volume relative growth rate (RGR) of trees of different initial size in control and irrigated + fertilized stands. Even though there were no statistically significant differences in CV among treatments, there was a tendency for increased CV over time in the control stands, whereas CV initially increased, then decreased, and became constant in the irrigated + fertilized plots. The lack of increase in CV in the irrigated + fertilized plots was explained by unusually low variation in RGR across tree size classes and negative relation of RGR and size. Therefore, the hypothesis that increased growth resulted in a more rapid development of size hierarchies was rejected. The high RGR of small trees in the irrigated + fertilized treatment could not be explained by differences in vertical distribution of needles compared with the control treatment. Small trees in the irrigated + fertilized plots were overtopped by neighboring trees to the same degree as small trees in the control plots.