Coefficient Of Variation Values Research Articles

Repeatability of Corneal Densitometry Measurements using a Scheimpflug Camera in Healthy Normal Corneas.

Purpose:To determine the repeatability of corneal densitometry measured by the Scheimpflug imaging system.Methods:This cross-sectional study was conducted on photorefractive keratectomy candidates. One eye of each participant underwent imaging using Pentacam HR three times, 10 min apart. The repeatability of densitometry measurements was evaluated in four concentric annuli around the corneal apex and in different corneal depths. The repeatability of the measurements was evaluated using the intraclass correlation coefficient (ICC), repeatability coefficient (RC), and coefficient of variation (CV). The difference of repeatability between layers and zones was tested by tolerance index (TI).Results:Sixty eyes of sixty patients with a mean age of 27.76 ± 3.93 years were studied. Half of the participants were female (n = 30, 50%). ICC was above 0.9 in all corneal parts. The posterior layer and central zones showed the least variability of densitometry measurements considering the CV values. The RC was 2.06, 1.17, and 0.92 in anterior, central, and posterior layers, respectively. The RC was 0.88, 0.71, 1.51, and 4.56 in 0–2, 2–6, 6–10, and 10–12 mm circles, respectively. Only the reliability of densitometry in 10–12 mm annulus was statistically lower than the central zone (TI = 0.71).Conclusions:Corneal densitometry measurements provided by the Pentacam had good repeatability. The repeatability of densitometry measurements decreased from the center to the periphery (with an exception for 0–2 mm and 2–6 mm) and from the posterior to the anterior of the cornea. The reliability of the 10–12 mm zone was markedly less than other zones.

Assessment of corneal endothelial cell morphology and anterior segment parameters in COVID-19.

Background:The ocular manifestations of the 2019 novel coronavirus disease (COVID-19) vary from acute follicular, pseudomembranous, and hemorrhagic conjunctivitis to keratoconjunctivitis with subepithelial infiltrates and dendritic lesions. Similar to other respiratory viruses, such as adenoviruses, it is thought that COVID-19 may impact the cornea. However, its impact on the cornea and anterior segment parameters are currently poorly understood.Objective:This study aims to assess the corneal endothelial cell morphology and anterior segment parameters in patients who have recovered from COVID-19.Methods:In this cross-sectional study, the COVID-19 group comprised 34 patients who had been diagnosed with and recovered from COVID-19, while the control group comprised age- and sex-matched individuals without any systemic or ocular diseases. The endothelial cell density (ECD), coefficient of variation (CV) of cell area, hexagonal cell percentage (HEX), anterior chamber depth (ACD), central corneal thickness (CCT), horizontal anterior chamber diameter (HACD), iridocorneal angle (ICA), horizontal visible iris diameter (HVID), pupillary diameter (PD), and keratometry values (K1 and K2) were analyzed for each participant. The differences in each of these between the groups were analyzed using either an independent samples t test or a Mann–Whitney U test based on the normality of the data.Results:Regarding corneal endothelial cell morphology, the ECDs for the COVID-19 and control groups were 2278.50 ± 186.78 cells/mm2 and 2420.15 ± 222.25 cells/mm2, respectively (p = 0.002). A significant increase was noted in CV values in the COVID-19 group compared with the control group (p < 0.001). The HEX values for the COVID-19 and control groups were 56.26 ± 5.75 and 61.50 ± 3.63, respectively (p < 0.001). Regarding the anterior segment parameters, no significant differences were observed between the groups (p > 0.05).Conclusions:It was hypothesized that individuals who had recovered from COVID-19 would demonstrate a reduction in their endothelial functional preserves. A decrease in ECD and HEX and an increase in CV were observed in the individuals during their early post-recovery period from COVID-19.

SPATIOTEMPORAL VARIATION OF THE VEGETATION INDEX BY NORMALIZED DIFFERENCE IN THE HYDROGRAPHIC BASIN OF PERNAMBUCO SEMIARID, BRAZIL

Remote sensing is an important mechanism for spatiotemporal monitoring of vegetation. Vegetation indexes have been widely used in monitoring vegetated areas, to determine and estimate the index of leaf area, biomass, and photosynthetically active radiation, among others. In these indexes, the Normalized Difference Index Vegetation (NDVI) stands out, which indicates the health status of a vegetative canopy. Considering the proven applicability of this index, in addition to the relevant importance of the Caatinga biome, related to the need for monitoring at the expense of desertification processes, the article aimed to analyze temporal variations of the NDVI in a hydrographic basin of the Brazilian semiarid region, in the municipality of Itacuruba/PE, Brazil. The study area covers a hydrographic basin belonging to the São Francisco River. Remote sensing techniques were used to estimate the NDVI in four orbital images provided by NASA/USGS in the year 2020, with less than 10% clouds. Then, the data were subjected to descriptive statistical analysis to obtain minimum, maximum, mean, standard deviation, and coefficient of variation values. The results showed that the NDVI presented values ranging from -0.30 to 0.57. The means found ranged from 0.16 to 0.23 for the months studied, as well as in the standard deviation values, values between 0.06 and 0.09 were found, corroborating other correlated studies in the region. The coefficient of variation data showed average variability, according to the Warrick &amp; Nielsen classification criteria. It is noteworthy that, in addition to the dry climate of the region, the shrubby vegetation presents physiological defense characteristics such as the fall of foliage. It was concluded that the use of remote sensing was effective in evaluating the spatial-temporal dynamics of the vegetation index in the watershed, managing to measure environmental variations at the expense of climate change.

Screening of Soybean Genotypes Based on Root Morphology and Shoot Traits Using the Semi-Hydroponic Phenotyping Platform and Rhizobox Technique

Root-system architecture is vital for improving soybean (Glycine max L.) growth and nutrient uptake. We characterised root-system architecture and shoot traits of 30 soybean genotypes in a semi-hydroponic system 35 days after sowing (DAS) and validated eight genotypes with contrasting root-system architecture in 1.5 m-deep rhizoboxes at the flowering stage. Among them, two genotypes were selected for evaluation through to maturity. Abundant variation (coefficient of variation values ≥ 0.25) was observed in 11 of 13 measured roots and shoot traits during the early growth stage. After late growth stages, strong positive correlations were found between root traits and shoot traits, except for specific root length and diameter. Seed yield and yield traits at final harvest significantly differed between two contrasting soybean genotypes. The large-rooted genotype had a higher harvest index than the small-rooted genotype. Soybean genotypes with larger root systems had a long time to flowering than those with smaller root systems. Genotypes with large-root systems had 106% more leaf area, and 245% more shoot dry weight than those with small systems, presumably due to high canopy photosynthesis to supply the demand for carbon assimilates to roots. Total root length, and root: shoot ratio-traits data collected in the rhizobox study, strongly correlated with the same traits in the semi-hydroponic phenotyping system. We found genetic variation and phenotypic plasticity in other root and shoot traits such as taproot depth, root dry weight, specific root length, and average root diameter among the tested genotypes. Phenology, particularly time to flowering, was associated with root system size. Some root and shoot traits in the semi-hydroponic phenotyping system at the seedling stage produced similar rankings at the later phenological (flowering) stage when grown in the soil-filled rhizoboxes. The soybean genotypes characterised by vastly different root traits could be used for further glasshouse and field studies to improve adaptation to drought and other specific environments.

Inter- and Intra-Individual Variation in the Behavior of Feed Intake on Nutrient Availability in Early Lactating Dairy Cows.

Simple SummaryThe problem of nutrient and energy deficiency and the associated risk of disease in fresh dairy cows has been known for many years. Previous approaches to reducing the risk have been almost exclusively on a herd basis approach but have so far not been sufficiently effective. The present study revealed large variation between individual animals during the first weeks after calving, particularly with respect to dry matter intake (DMI). In addition to the large variation in intake behavior, feed intake and nutrient digestibility, interactions between parameters refute the traditional feeding regimes, based on the mean requirement values at herd level. Inter-individual variation indicates that each animal follows an individual strategy in optimizing DMI. Only if constant access to the feed bunk and balanced diets are made possible, all animals can follow their individual strategy, maximize individual DMI and come closer to the goal of an adequate supply. As there is only a low risk for excessive DMI during early lactation, feeding regimes should not be oriented towards the assumed average level of feed intake but towards the animals with a low level of dry matter intake. Otherwise, it will not be possible to improve the nutrient supply for all animals.Since energetic deficits in dairy cows can only be reduced at an animal level, the objective of the present study was to determine the extent of variation in intake behavior within and between animals during early lactation, to explore the magnitude of interactions between feed intake, intake behavior and nutrient digestibility, and to identify levers for maximizing feed intake at the individual animal level. Feeding behavior, intake and nutrient digestibility of 28 German Holstein dairy cows, fed TMR with 7.0 MJ NEL, were studied between the 2nd and 15th week after calving. Dry matter intake was assessed daily and nutrient digestibility weekly, with iNDF240 as an intrinsic marker. Results showed high intra- and inter-individual variation in intake behavior parameters with coefficients of variation (CV) up to 0.58 in meal frequency. Nutrient digestibility varied only slightly with CV values up to 0.10 in crude protein. Milk yield, meal frequency, feeding time, feeding rate and meal size had significant positive effects on DMI (p < 0.01). To achieve long-term improvements in feed intake, it is important to optimize feed intake and feeding behavior of individual animals by improving feeding conditions and develop technical tools to identify animals with insufficient feed intake.

Spatial Ventilation Inhomogeneity Determined by Electrical Impedance Tomography in Patients With Chronic Obstructive Lung Disease.

The aim of this study was to examine whether electrical impedance tomography (EIT) could determine the presence of ventilation inhomogeneity in patients with chronic obstructive lung disease (COPD) from measurements carried out not only during conventional forced full expiration maneuvers but also from forced inspiration maneuvers and quiet tidal breathing and whether the inhomogeneity levels were comparable among the phases and higher than in healthy subjects. EIT data were acquired in 52 patients with exacerbated COPD (11 women, 41 men, 68 ± 11 years) and 14 healthy subjects (6 women, 8 men, 38 ± 8 years). Regional lung function parameters of forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), forced inspiratory vital capacity (FIVC), forced inspiratory volume in 1 s (FIV1), and tidal volume (VT) were determined in 912 image pixels. The spatial inhomogeneity of the pixel parameters was characterized by the coefficients of variation (CV) and the global inhomogeneity (GI) index. CV and GI values of pixel FVC, FEV1, FIVC, FIV1, and VT were significantly higher in patients than in healthy subjects (p ≤ 0.0001). The ventilation distribution was affected by the analyzed lung function parameter in patients (CV: p = 0.0024, GI: p = 0.006) but not in healthy subjects. Receiver operating characteristic curves showed that CV and GI discriminated patients from healthy subjects with an area under the curve (AUC) of 0.835 and 0.852 (FVC), 0.845 and 0.867 (FEV1), 0.903 and 0.903 (FIVC), 0.891 and 0.882 (FIV1), and 0.821 and 0.843 (VT), respectively. These findings confirm the ability of EIT to identify increased ventilation inhomogeneity in patients with COPD.

Assessment of morpho-genetic diversity of guava (Psidium guajava) hybrids and genotypes

A total of 20 diverse guava genotypes, including the newly bred hybrids were characterized using the morphological, physio-biochemical parameters and microsatellite markers at ICAR-IARI, New Delhi during 2018-19. Most of the qualitative morphological and physio-biochemical parameters had a coefficient of variation value &gt;20%, which indicated substantial diversity. The longest leaves (14.87 cm) were recorded in Lalit, which was statistically at par with Pant Prabhat (14.67 cm), while amongst the hybrids, it is in GH 2018-10 (13.93 cm). The maximum leaf area was recorded in Pant Prabhat (60.33 cm2) while amongst hybrids it was in GH 2018-2 (53.40 cm2). The highest stomatal conductance and net photosynthetic rate was recorded in guava genotype Shweta (9.63 μmol/m2/s) (0.25 mol/m2/sec) while amongst the hybrids it was in GH 2018-8 (8.73μmol/m2/s) (0.26 mol/m2/sec), respectively. The mean genetic diversity indices, viz. major allelic frequency, number of alleles, gene diversity, heterozygosity and polymorphic information content of eight SSRs were 0.497, 3.75, 0.599, 0.071 and 0.542, respectively among the guava genotypes. Furthermore, the eight SSRs based Neighbour-joining (N-J) tree separated the newly bred guava hybrids into different clusters, clades and out-groups.

Inter‐ and intra‐scanner variability of icobrain DM automated brain volumetry software on three different MRI systems

AbstractBackgroundMagnetic Resonance Imaging (MRI) has become part of clinical routine for diagnosis of neurodegenerative brain disorders. Acquisitions are performed at multiple centers, using multiple imaging systems and is therefore subjected to intra‐ and inter‐scanner variability. Detailed analysis of brain volumetry differences between MRI systems and scan‐rescan acquisitions can provide useful information to correct for different MRI scanner effects in future multi‐center longitudinal studies.MethodThe study population (n=10) consisted of five cognitively healthy controls and five patients belonging to different stages of the AD continuum. Subjects underwent brain MRI acquisitions on three different MRI systems with harmonized scan parameters: Philips Achieva dStream 1.5T, Philips Ingenia 3T and GE Discovery MR750w 3T. Sequences were harmonized by keeping acquisition parameters similar (Table 1). To test intra‐scanner variability, each participant underwent two subsequent MRI scans (between‐scan repositioning time 3‐5 minutes) per imaging system, repeated on three different MRI systems within two hours to test inter‐scanner variability. A total of 60 MRI scans were acquired for downstream comparative analysis. Brain volumes, including whole brain, (cortical) gray matter, hippocampal volumes, lateral ventricles, frontal, temporal and parietal cortices were computed with icobrain dm (v5.0). Coefficients of variation (CV), absolute volume differences (AVD), Dice similarity coefficients (DSC) and intraclass correlation coefficients (ICC) were computed to assess within‐ and between‐scanner agreement.ResultThe intra‐scanner CVs over all volumes were 0.948% for Discovery MR750w, 1.050% for Achieva and 1.152% for Ingenia. The inter‐scanner CVs were 3.016% for all‐scanner comparisons, 2.044% for Ingenia vs. Achieva, 3.191% for Achieva vs. GE and 3.326% for Ingenia vs. GE. The AVDs and ICCs were in line with the CV values. The intra‐scanner DSCs (mean±SD) over all volumes were 0.917±0.011 for Discovery MR750w, 0.917±0.010 for Achieva and 0.917±0.015 for Ingenia. The inter‐scanner DSCs were 0.898±0.017 for all‐scanner comparisons, 0.912±0.012 for Ingenia vs. Achieva, 0.888±0.013 for Achieva vs. Discovery MR750w and 0.893±0.015 for Ingenia vs. Discovery MR750w (Table 2, 3, Figure 1).ConclusionThe variability results show an excellent agreement (CV&lt;2%) for within‐scanner and a good agreement (CV&lt;5%) for between‐scanner comparisons in terms of clinical relevance, indicating that MRI acquisition harmonization is beneficial for automated MRI volumetry software.

The impact of aging and reaching movements on grip stability control during manual precision tasks

BackgroundOperating an object by generating stable hand-grip force during static or dynamic posture control of the upper extremities simultaneously is an important daily activity. Older adults require different attentional resources during grip strength control and arm movements. However, the impact of aging and reaching movements on precise grip strength and stability control among older adults is not well understood. This study investigated the impact of aging and reaching movements on grip strength and stability control in both hands of the upper extremities.MethodsFifty healthy young adults (age: 28.8 ± 14.0 years) and 54 healthy older adults (73.6 ± 6.3 years) were recruited to perform isometric grip strength test at 20% maximal voluntary contraction as the target force during three manual precision tasks simultaneously: stationary task (without arm movements), forward-reach task, and backward-reach task. The average grip force (in kg) and coefficient of variation values (expressed as a percentage) during manual precision tasks were calculated to determine the quality of participants’ grip strength. The deviation error, absolute error, and force-stability index values were calculated to determine the strength control relative to the target force.ResultsFor both the young and older groups, the force-stability index values in both hands were significantly higher during forward- and backward-reaching movements than in the stationary condition (p < 0.05). The older group exhibited a significantly lower hand-grip strength and stability of strength control in both hands than the young group (p < 0.05).ConclusionsAging and reaching task performance reduced the grip strength of participants and increased the variations in strength control of both hands relative to the target force, indicating that older adults exhibit poor grip strength and stability control when performing arm-reaching movements. These findings may help clinical therapists in establishing objective indexes for poor grip-stability control screening and developing appropriate rehabilitation programs or health-promotion exercises that can improve grip strength and stability control in older people.

The technical reliability and stability of ATN quantification using the Fujirebio Lumipulse G1200 fully‐automated immunoassay instrument in cerebrospinal fluid

AbstractBackgroundFujirebio’s Lumipulse G1200 is designed to perform fully‐automated, rapid, random access immunoassays for biomarker quantification in biofluids. The Lumipulse instrument was used for quantification of the core Alzheimer’s Disease (AD) cerebrospinal fluid (CSF) biomarkers for Amyloid, Tau, and neurodegeneration (ATN): amyloid β 1–40 (Aβ40), amyloid β 1–42 (Aβ42), phosphorylated Tau 181 (pTau181), and total Tau (tTau). This study evaluated the reliability of the Lumipulse assays by measuring intra‐ and inter‐batch coefficients of variation (CV), and the correlation between Lumipulse values and the clinically used Athena ADmark Aβ42, pTau181 and tTau assays.Method423 CSF samples collected from diagnostic lumbar punctures between 2015 and 2020 were obtained from the MIND biorepository. Aβ40, Aβ42, tTau, and pTau were measured using the Lumipulse G1200 instrument in batches of 50‐60 samples. We tested 60 samples in duplicate to compare the intrabatch stability using the CVs between each pair. Each batch was run with a new set of calibrator controls at the start of each assay to ensure stability for each biomarker run. Finally, we correlated values from the Lumipulse with results from the clinical evaluation using the Athena ADmark test.ResultWe observed low variability in calibrator and control signals between batches with an overall calibrator signal CV of &lt;5% for Aβ40 and tTau, and &lt;10% for Aβ42 and pTau. Control signal CV values for all analytes were &lt;5%. The mean duplicate CV across all batches was similarly stable at &lt;10% for Aβ40, Aβ42, and tTau, and &lt;5% for pTau. Subjects with CV &gt;20% were seen &lt;5% of the time. The correlations between Lumipulse and clinical ADmark results were high for pTau and tTau (R2&gt;0.8 for both analytes), but lower for Aβ42 (R2∼0.5).ConclusionOur results demonstrated that the Lumipulse G1200 is a reliable, easy to use platform for ATN quantification with low sample to sample variability, and generally high correlation to established clinical standards. Inconsistent preanalytical sample handling of clinical send‐outs for Athena ADmark Aβ42 likely resulted in a poor correlation with Lumipulse G1200. The performance of the calibrators and controls proved that the standardization in each batch was consistent.

Effectiveness of Insole Colour on Impact Loading and Lower-Limb Kinematics When Running at Preferred and Nonpreferred Speeds.

While colour of red can play a significant role in altering human perception and performances, little is known about its perceptual-motor effect on running mechanics. This study examined the effects of variations in insole colours on impact forces, ankle kinematics, and trial-to-trial reliability at various running speeds. Sixteen male recreational runners ran on instrumented treadmill at slow (90%), preferred (100%), and fast (110%) running speeds when wearing insoles in red, blue, and white colours. We used synchronized force platform and motion capturing system to measure ground reaction force, ankle sagittal and frontal kinematics, and movement variability. A two-way (colour x speed) ANOVA with repeated measures was performed with Bonferroni adjusted post hoc comparisons, with alpha set at 0.05. Data analyses indicated that participants demonstrated higher impact and maximum loading rate of ground reaction force, longer stride length, shorter contact time, and smaller touchdown ankle inversion as well as larger ankle sagittal range of motion (RoM), but smaller frontal RoM in fast speed as compared with preferred (P < 0.05) and slow speeds (P < 0.001). Although insole colour had minimal effect on mean values of any tested variables (P > 0.05), participants wearing red-coloured orthoses showed higher coefficient of variation values for maximum loading rate than wearing blue insoles (P=0.009). These results suggest that running at faster speed would lead to higher impact loading and altered lower-limb mechanics and that colour used on the tops of insoles influences the wearers' movement repeatability, with implications for use of foot insole in running.

Evaluation of corneal endothelial cell morphology by specular microscopy in patients with acute anterior uveitis.

To determine the structure and morphology of corneal endothelial cell layer in patients with acute anterior uveitis. Thirty-four eyes of 34 acute anterior uveitis patients and 34 eyes of 34 healthy subjects were included. Mean cell density, coefficient of variation, maximum cell area, minimum cell area, average cell area and hexagonality ratio values were evaluated by non-contact specular microscopy. Parameters recorded in both groups were compared. The mean maximum cell area was 1054,44 ± 251,14 µm2, minimum cell area was 152.29 ± 53.65 µm2 and average cell area was 386.91 ± 41.73 µm2 in acute anterior uveitis group and the mean maximum cell area was 1057.65 ± 261.23 µm2, minimum cell area was 147.26 ± 20.45 µm2 and average cell area was 383.53 ± 43.12 µm2 in the control group. There were no significant differences between the two groups in terms of maximum, minimum and average cell area (respectively, p = 0.080, p = 0.72, p = 0.62, p = 0.67). The mean cell density was 2607.74 ± 277.63 cells/ µm2 in acute anterior uveitis group and 2669.35 ± 265.22 cells/µm2 in the control group. (p = 0.358). In acute anterior uveitis group the mean coefficient of variation was 31.68 ± 8.16, hexagonality ratio was 63.85 ± 11.14 and mean central corneal thickness was 571.47 ± 55.99µm; in control group the mean coefficient of variation was 25.29 ± 3.00, mean hexagonality ratio was 72.6 ± 4.80% and mean central corneal thickness was 534.82 ± 33.84µm. Statistically significant differences were seen between the two groups (respectively, P = 0,00, P = 0,00, P = 0.02). The mean central corneal thickness and coefficient of variation values were found higher, and the hexagonality ratio was found lower in acute anterior uveitis group. Our findings suggest that intraocular inflammation in anterior chamber negatively affects the endothelial function in patients with acute anterior uveitis.

Repeatability of Bruch’s Membrane Opening-minimum Rim Width in Age-related Macular Degeneration and Diabetic Macular Edema

Purpose: To evaluate the repeatability of retinal nerve fiber layer (RNFL) thickness and Bruch’s membrane opening-minimum rim width (BMO-MRW) measurements by spectral-domain optical coherence tomography (SD-OCT) in wet age-related macular degeneration (wAMD) and diabetic macular edema (DME).Methods: This was a prospective study. The RNFL thickness and BMO-MRW parameters for each sector and global average were measured twice by SD-OCT. Repeatability was evaluated using the intraclass correlation coefficient (ICC) and coefficient of variation (CV). If the optic disc membrane was confirmed, it was analyzed by dividing it into three groups based on severity.Results: A total of 99 eyes (48 with wAMD, 51 with DME) were included in the analysis. The ICCs of the global RNFL thickness and global BMO-MRW measurements were 0.996 and 0.997, respectively, in wAMD and 0.994 and 0.996, respectively, in DME eyes. The CV values of global RNFL thickness and BMO-MRW were 0.60% and 0.73%, respectively, in wAMD eyes and 1.10% and 1.21%, respectively, in DME eyes. The disc membrane on the optic nerve head significantly affected global BMO-MRW repeatability (B = 0.814, &lt;i&gt;p&lt;/i&gt; &lt; 0.001).Conclusions: Both RNFL thickness and BMO-MRW measurements showed good repeatability in eyes with wAMD and DME. The severity of the optic disc membrane significantly affected the repeatability of BMO-MRW measurements in eyes with wAMD and DME. Therefore, physicians should examine the BMO-MRW in eyes with severe optic disc membrane.

The role of venous pressure variability during hemodialysis in the prediction of impending arteriovenous graft occlusion.

Elevated venous pressure during hemodialysis (VPHD) is associated with arteriovenous graft (AVG) stenosis. This study investigated the role of VPHD variations in the prediction of impending AVG occlusion. Data were retrieved from 118 operations to treat AVG occlusion (occlusion group) and 149 operations to treat significant AVG stenosis (stenosis group). In addition to analyzing the VPHD values for the three hemodialysis (HD) sessions prior to the intervention, VPHD values were normalized to mean blood pressure (MBP), blood flow rate (BFR), BFR × MBP, and BFR2 × MBP to yield ratios for analysis. The coefficient of variation (CV) was used to measure relative variations. The within-group comparisons for both groups revealed no significant differences in the VPHD mean and CV values among the three HD sessions prior to intervention. However, the CVs for VPHD/MBP, VPHD/(BFR × MBP), and VPHD/(BFR2 × MBP) exhibited significant elevation in the occlusion group during the last HD session prior to intervention compared with both the penultimate and antepenultimate within-group HD data (p < 0.05). In the receiver operating characteristic curve analysis, the CV for VPHD/(BFR2 × MBP) was the only parameter able to discriminate between the last and the penultimate HD outcomes (p < 0.001). According to a multivariate analysis, after controlling for covariates, CV for VPHD/(BFR2 × MBP) >8.76% was associated with a higher risk of AVG thrombosis (odds ratio: 3.17, p < 0.001). Increasing the variation in VPHD/(BFR2 × MBP) may increase the probability of AVG occlusion.

Visit-to-Visit Blood PressureVariations and Hemodynamic Deterioration in Atherosclerotic Major Cerebral ArteryDisease

ObjectiveVisit-to-visit variations in blood pressure (BP) in patients with atherosclerotic major cerebral artery disease could impair the function of cerebral collaterals, leading to hemodynamic deterioration at follow-up. However, few studies have investigated the relationship between visit-to-visit BP variability and changes in hemodynamic parameters at follow-up. Materials and methodsWe evaluated 35 medically treated patients with atherosclerotic internal carotid artery or middle cerebral artery disease with no ischemic episodes during follow-up (mean: 35 ± 20 months); these patients had a three-time visit for positron emission tomography examinations with 15O-gas. Differences in the mean hemispheric values of hemodynamic parameters in the cortical territory of the diseased artery between the first and third examinations (changes at follow-up) were correlated with the coefficient of variation (CoV) in three systolic BP (SBP) values at the three examinations (BP variability during follow-up). ResultsCoV values were negatively correlated with changes in oxygen metabolism or cerebral blood flow/cerebral blood volume (CBF/CBV) ratio. In 17 patients with higher CoV values (> group median, 0.072), decreases in CBF, cerebral metabolic rate of oxygen, and CBF/CBV ratio were observed at follow-up; CBV decreased in 18 patients without elevated CoV. A higher CoV was associated with a lack of statin use. ConclusionIn patients with atherosclerotic major cerebral artery disease, high visit-to-visit SBP variations during follow-up may be associated with deterioration in cerebral hemodynamics and metabolism.

Reliability and Repeatability of the Footwork Plantar Pressure Plate System.

Plantar pressure plate instruments are commonly used in clinical practice and biomechanical analysis and are useful to establish a relationship between gait disorders and foot pressure. The aim of this study was to verify the reliability and repeatability of the Footwork pressure plate system for static and dynamic conditions. Forty healthy adults, without apparent gait pathology, were recruited. For the static condition, participants were asked to stand static on the Footwork pressure plate for 5 sec in natural position (arms on either side of the body, feet shoulder-width apart in a comfortable angle, and looking ahead). For the dynamic condition, subjects were told to step five times with each foot on the plate following the three-step protocol. Both conditions were performed in two testing sessions spaced by 1 week. Intrasession and intersession reliability for both conditions showed substantial to almost perfect intraclass correlation coefficient (ICC) values, and low coefficient of variation, low standard error measure, and low percentage error. Intrasession ICCs were 0.724 to 0.993 for static condition evaluation and 0.639 to 0.986 for dynamic condition evaluation. Intersession reliability ICCs ranged from 0.850 to 0.987 for the static condition and from 0.781 to 0.996 for the dynamic condition. Coefficient of variation values were below 8% in both cases and percentage error calculated from standard error measure were less than 10%. The present work demonstrates that the Footwork plantar pressure plate system is a reliable instrument for collecting plantar pressures in static and dynamic conditions. Reliability data were higher for the static trials, probably because of the individual physiologic fluctuations, which are larger during dynamic gait. Reliability for intersession and average intrasession trials were higher than single-test reliability. The results from the present work can be used as a starting point for future research and to establish a basis for sample sizes for investigations that would use the Footwork platform.

On the vocal repertoire of the monkey frog Phyllomedusa venusta: distress call and the presumed non-existing advertisement call

ABSTRACT The anuran advertisement call has been widely used in taxonomic and evolutionary studies due to its essential role in species-specific recognition. For a long time, it has been presumed that P. venusta did not emit mating calls. Here, we observed the entire vocal activity period of P. venusta over the night and recorded male calls and a female distress call. We recognized and described a single male call type, identified as the advertisement call. This call has an extremely low timbre, and it is composed of a single or a sequence of pulsed notes. The multi-noted calls were usually emitted in intrasexual agonistic contexts. Although both call duration and note number have a high coefficient of variation values, they are linearly correlated, so they should be acting as a single independent variable in the P. venusta calls. As expected, the distress call is longer and with a higher timbre than the advertisement call. Interspecific comparisons were made based on the ratio between advertisement call dominant frequency (DF) and body size. This ratio is similar to those of the species of the P. tarsius group.

Tree Diversity and Soil Characteristics in a Tea–Forest Interface in Southwest Sri Lanka

Fragmented and degraded ecosystems should be restored to ensure the biological connectivity among fragmented forest landscapes. The tropical rainforests of Southwestern Sri Lanka are highly degraded and fragmented due to plantation agriculture and human settlements. However, the high spatial variation in environmental factors and ecosystem functions challenge the success rate of restoration interventions. The aim of this study was to assess the vegetation composition and stand structure in relation to the spatial variation in key soil physicochemical parameters in the Endane Biodiversity Corridor that links peripheral forest reserve to the Sinharaja Rainforest Complex (SRC). The site that extends over 24 ha was classified into five land-use categories (productive tea lands, marginal tea lands, scrub—abandoned three years ago, and two woodlands—abandoned 15 years ago) in which the vegetation composition, stand structure, and physicochemical parameters of soil were assessed and mapped. Results revealed that the Shannon diversity index in the scrub and the woodlands were higher than in the tea lands. The diversity among the secondary forest patches was similar. However, with a mean record of 14 species, the species richness was high in sites close to the SRC. In comparison to the SRC (358 Mg ha−1), there was a substantial potential to sequester more carbon in the restoration sites (12–108 Mg ha−1). While explaining 31% of abundance and species distribution, the ordination results revealed a close relationship of the soil parameters to vegetation composition and species abundance. The calculated coefficient variation values for soil parameters (TN, EC, Av.P, Ex.K, OC, and BD) were beyond 12%, indicating high or moderate soil spatial variability among the land use categories. Coefficient of variation for soil pH was estimated to be 9%, revealing low soil spatial variability among the land use categories. The maps of these soil parameters corresponded with the type of land use and fertilizer application to tea fields. The highest and the lowest total N contents were observed in the scrub and woodlands, respectively, which appears to be mediated by the relative composition of N-fixing trees between the two groups. Our results facilitate effective matching of sites to species for restoration of the Endane Biodiversity Corridor that may be replicated in similar restoration contexts in tropical Asia.

Insufficient sampling frequencies skew heart rate variability estimates: Implications for extracting heart rate metrics from neuroimaging and physiological data

BackgroundWhile cardiac pulsations are widely present within physiological and neuroimaging data, it is unknown the extent this information can provide valid and reliable heart rate and heart rate variability (HRV) estimates. The objective of this study was to demonstrate how a slight temporal shift due to an insufficient sampling frequency can impact the validity/accuracy of deriving cardiac metrics. MethodsTwenty-two participants were instrumented with valid/reliable industry-standard or open-source electrocardiograms. Five-minute lead II recordings were collected at 1000 Hz in an upright orthostatic position. Following artifact removal, the 1000 Hz recording for each participant was downsampled to frequencies ranging 2–500 Hz. The validity of each participant’s downsampled recording was compared against their 1000 Hz recording (“reference-standard”) using Bland-Altman plots with 95 % limits of agreement (LOA), coefficient of variation (CoV), intraclass correlation coefficients, and adjusted r-squared values. ResultsDownsampled frequencies of ≥ 50 and ≥ 90 Hz produced highly robust measures with narrow log-transformed 95 % LOA (<±0.01) and low CoV values (≤3.5 %) for heart rate and HRV metrics, respectively. Below these thresholds, the log-transformed 95 % LOA became wider (LOA range: ±0.1–1.9) and more variable (CoV range: 1.5–111.6 %). ConclusionThese results provide an important consideration for obtaining cardiac information from physiological data. Compared to the “reference-standard” ECG, a seemingly negligible temporal shift of the systolic contraction (R wave) greater than 11-milliseconds (90 Hz) away from its true value, lessened the validity of the HRV. Further research is warranted to determine the minimum sampling frequency required to obtain valid heart rate/HRV metrics from pulsatile waveforms.

Exploration of Machine Learning Approaches for Paddy Yield Prediction in Eastern Part of Tamilnadu

Agriculture is the principal basis of livelihood that acts as a mainstay of any country. There are several changes faced by the farmers due to various factors such as water shortage, undefined price owing to demand–supply, weather uncertainties, and inaccurate crop prediction. The prediction of crop yield, notably paddy yield, is an intricate assignment owing to its dependency on several factors such as crop genotype, environmental factors, management practices, and their interactions. Researchers are used to predicting the paddy yield using statistical approaches, but they failed to attain higher accuracy due to several factors. Therefore, machine learning methods such as support vector regression (SVR), general regression neural networks (GRNNs), radial basis functional neural networks (RBFNNs), and back-propagation neural networks (BPNNs) are demonstrated to predict the paddy yield accurately for the Cauvery Delta Zone (CDZ), which lies in the eastern part of Tamil Nadu, South India. The performance of each developed model is examined using assessment metrics such as coefficient of determination (R2), root mean square error (RMSE), mean absolute error (MAE), mean squared error (MSE), mean absolute percentage error (MAPE), coefficient of variance (CV), and normalized mean squared error (NMSE). The observed results show that the GRNN algorithm delivers superior evaluation metrics such as R2, RMSE, MAE, MSE, MAPE, CV, and NSME values about 0.9863, 0.2295 and 0.1290, 0.0526, 1.3439, 0.0255, and 0.0136, respectively, which ensures accurate crop yield prediction compared with other methods. Finally, the performance of the GRNN model is compared with other available models from several studies in the literature, and it is found to be high while comparing the prediction accuracy using evaluation metrics.