Greater Coefficient Of Variation Research Articles

Study on the Effect and Enhancement of Near-Natural Integrated Plant Positioning Configuration in the Hilly Gully Region, China

The establishment of protective forests plays a crucial role in mitigating soil erosion on slopes within hilly and gully regions. However, in practical applications, the configuration of protective forests on slopes is intricate and diverse, and the suitability and rationality of different configuration patterns for various slope sections have not been thoroughly investigated. This study focuses on a 40-year-old artificial protective forest, examining 16 different configuration patterns on the top, middle, and lower slopes. It compares the growth conditions, community structure stability, and characteristics of the saturated soil’s hydraulic conductivity. The findings indicate that the top slope should be identified as a critical area for slope protection. The optimal configuration for this area is the “tree + grass” pattern with a spacing of 5 m × 5 m, which promotes the optimal growth of tree species and effectively reduces the surface runoff of gravel particles ranging from 1 cm to 3 cm in diameter. On the middle slope, the “tree + shrub + grass” structure proves effective in slowing down the erosive force of slope runoff. The recommended spacing for trees is 5 m × 6 m, and for understory shrubs, it is 1 m × 6 m. This configuration pattern results in the most stable structure for the plant community and maximizes the water conservation potential of forest litter. By analyzing the characteristics of the saturated soil’s hydraulic conductivity, we find that the complexity of the plant configuration on the lower slopes is correlated with a greater coefficient of variation in the saturated soil’s hydraulic conductivity. Nevertheless, there is no significant difference in the average soil saturated hydraulic conductivity per unit area between the different configuration patterns. Consequently, the lower slope can rely on the natural recovery of herbaceous plants. The results of this research contribute valuable scientific and technical insights to the management of soil erosion in hilly and gully areas, both in China and around the world.

Prognostic Significance of Baseline Blood Glucose Levels and Glucose Variability in Severe Acute Kidney Injury: A Secondary Analysis from the RENAL Study.

Aim: To study the associations between baseline blood glucose levels (BGL), glycemic variability and clinical outcomes in patients with severe acute kidney injury (AKI) receiving continuous renal replacement therapy (CRRT). Methods: We performed a secondary analysis of the Randomized Evaluation of Normal versus Augmented Level of RRT (RENAL) study. A multivariate Cox regression model was used to assess the association between baseline BGL, glycemic variability and clinical outcomes. The primary outcome was all-cause mortality, and secondary outcomes were duration of hospital and intensive care unit (ICU) stay. Results: Baseline BGL data were available in 1404 out of 1508 patients from the RENAL study. Among them, 627 patients died within 90 days of randomization. Compared to patients in the second quartile (BGL 5.8−7.2 mmol/L), patients in the first quartile (BGL < 5.8 mmol/L) had increased mortality rate (90-day HR 1.48; p = 0.001; 28-day HR 1.47; p = 0.042). However, there were no significant differences in ICU and hospital length of stay (LOS) (p = 0.82 and p = 0.33, respectively). Glycemic variability data were from 1345 out of 1404 patients who had data for BG values within 28 days. Higher coefficient of variation (CV) (HR 1.02; P trend = 0.002) and standard deviation value (SD) (HR 1.29; P trend = 0.027) were associated with higher risk of death at day 90. Conclusions: We identified a low BGL within the normal physiological range at baseline and greater CV and SD values as significant modifiable risk factors for mortality in severe AKI patients in ICU, which may be a target for intervention.

Reproducibility of SD-OCT inner macular layer thickness measurements in children with primary congenital glaucoma

To examine the reproducibility of spectral domain optical coherence tomography (SD-OCT) segmented ganglion cell complex and circumpapillary retinal nerve fiber layer (cpRNFL) measurements in children with primary congenital glaucoma (PCG) in comparison with healthy children. 12 children with PCG (G1) and 24 healthy children (G2) were recruited. The following SD-OCT measurements (Spectralis, Heidelberg Engineering) were made in one eye per child: total macular thickness (MT), thicknesses in several subfields and volumes of the three inner macular layers, macular retinal nerve fiber layer (mRNFL), ganglion cell layer (GCL), and inner plexiform layer (IPL) and cpRNFL thickness. In a single day, an expert operator obtained 3 circumpapillary and 3 macular measurements in each participant to determine intraoperator variability. Intraoperator repeatability was defined by the coefficient of variation (CoV) and intraclass correlation (ICC). ICC was excellent in both groups for cpRNFL measurements (G1 ICC=0.950 and G2 ICC=0.995) and for MT was excellent in G1 (ICC=0.957) and moderate in G2 (ICC=552). For the inner macular layer measurements, all ICCs were better in PCG group (mRNFL-ICC: 0.915 vs. 0.765; ICC-GCL: 0.584 vs. 0.263 and ICC-IPL: 0.979 vs. 0.742; G1 and G2 respectively). Greater CoV were recorded for macular measurements (from 0.71% to 9.82%) compared to cpRNFL measurements (from 0.52% to 1.50%). In children with PCG, Spectralis SD-OCT showed excellent intrasession repeatability for cpRNFL, MT, mRNFL and IPL measurements and moderated for GCL measurements. For all macular measurements, ICC were higher in children with PCG than healthy children.

The Influence of Environmental Conditions on Intake Behavior and Activity by Feedlot Steers Fed Corn or Barley-Based Diets.

Simple SummaryCattle wintered at northern latitudes are often exposed to periods of severe cold. Cattle likely alter feed intake and behavior to combat environmental challenges. This study evaluated the influence of diet and environmental changes on intake behavior and activity (lying time) of feedlot steers. Short-term temperature changes impacted both beef feedlot cattle intake behavior and activity. The steers’ diet, whether they were fed corn or barley, interacted with short term environmental changes to influence animal feeding behavior, but diet had limited impact on cattle lying behavior. Lying behavior was influenced by short-term temperature changes in which cattle spent more time lying down on relatively cold days. Overall, environmental shifts and cold temperature conditions could result in greater energetic needs and ultimately impact feedlot steer intake behavior and activity. By providing information related to beef cattle feedlot behavior, we can more effectively manage cattle feeding systems at northern latitudes to improve feed efficiency.This study evaluated the influence of diet and environmental conditions on intake behavior and activity of feedlot steers. Feedlot rations used were comprised of a main concentrate: (1) corn or (2) barley. A GrowSafe system measured individual animal intake and behavior and HOBO accelerometers measured steer standing time. An Onset weather station collected on site weather data. Steer daily intake displayed a diet by temperature class interaction (p ≤ 0.05). Relative temperature change had no effect on variation in intake (p = 0.60); however, diet influenced variation of intake (p < 0.01), where corn-fed steers had a greater coefficient of variation (CV) than barley-fed steers (21.89 ± 1.46 vs. 18.72 ± 1.46%). Time spent eating (min d−1) and eating rate (g min−1) both displayed a diet by temperature class interaction (p ≤ 0.05). Diet did not affect steer lying activity (p ≥ 0.12), however, time spent lying (min d−1) and frequency of lying bouts (bouts d−1) increased on relatively cold days while the duration of lying bouts (min bout−1; p < 0.01) decreased. Short-term environmental temperature changes interacted with diet influencing feedlot beef cattle intake behavior; however, they did not interact with basal diet in respect to steer activity.

Undrained stability analysis of strip footings lying on circular voids with spatially random soil

Random adaptive finite element limit analysis (RAFELA) is introduced to investigate the stability of the footing-voids system with random soils. The emphasis of this study is, for the footing-void system, on quantifying the influence of spatial variability on its bearing capacity and the failure probability. Of particular interest is that random field theory is utilized to characterize the spatial variability of soil, and at the same time, failure probability is calculated by imposing Monte-Carlo simulations on independent cases. Strict close bearing capacity could be obtained within the scope embraced by upper bound (UB) results and lower bound (LB) results. By imposing the proposed modelling, comprehensive parametric studies were carried out, especially for the soil spatial correlation parameters and geometry parameters. The results indicated that the failure probability would increase with the farther distance between the void and the footing, the greater coefficient of variation (COV) and the smaller vertical correlation length. Detailed design tables were presented to assess potential failure probability under different conditions. Typical failure patterns are also summarized, revealing a positive correlation between the failure probability and the diffusion degree of failure curves.

Between-day reliability of IMU-derived spine control metrics in patients with low back pain

Inertial measurement units (IMUs) are a potentially useful tool for clinicians and researchers in assessing spine movement biomechanics and neuromuscular control patterns. This study assessed the between-day reliability of the HIKOB FOX IMU in measuring local dynamic stability (LDS) and variability of trunk movements in patients with chronic low back pain (LBP). The local divergence exponent (λmax) was used to quantify LDS and the mean standard deviation (MeanSD) between cycles was used to quantify variability during 30 repetitive cycles of flexion/extension, rotation, and complex movement tasks. For λmax the average coefficient of variation (CV) was ~10% in the flexion/extension and rotation tasks, and all CV values were <20% when also including the complex task. ICC values for λmax ranged from 0.28 to 0.81. Reliability of λmax was similar between the pelvis and thorax segments (CV: ~10%, ICC: 0.48–0.78) and worse for the lumbar spine (CV: ~15%, ICC: 0.28–0.59). The CV for MeanSD was typically in the range of 20–30%, with even greater CV in the non-primary axes during each task (30–52%). Similarly, ICC values were lowest about the anterior-posterior axis in the flexion/extension task (ICC: 0.15–0.29) and largest about the longitudinal axis in the rotation task (ICC: 0.76–0.88). The moderate between-day reliability of λmax in the sagittal and transverse planes offers improvement over manual and subjective tests with poor reliability that are currently used in clinics. The minimal detectable differences presented give a threshold for change in research and rehabilitation in patients with LBP.

Importance of Maximal Strength and Muscle-Tendon Mechanics for Improving Force Steadiness in Persons with Parkinson's Disease.

Although plantar flexion force steadiness (FS) is reduced in persons with Parkinson’s disease (PD), the underlying causes are unknown. The aim of this exploratory design study was to ascertain the influence of maximal voluntary contraction (MVC) force and gastrocnemius-Achilles muscle-tendon unit behaviour on FS in persons with PD. Nine persons with PD and nine age- and sex-matched non-PD controls (~70 years, 6 females per group) performed plantar flexion MVCs and sub-maximal tracking tasks at 5, 10, 25, 50 and 75% MVC. Achilles tendon elongation and medial gastrocnemius fascicle lengths were recorded via ultrasound during contraction. FS was quantified using the coefficient of variation (CV) of force. Contributions of MVC and tendon mechanics to FS were determined using multiple regression analyses. Persons with PD were 35% weaker during MVC (p = 0.04) and had 97% greater CV (p = 0.01) with 47% less fascicle shortening (p = 0.004) and 38% less tendon elongation (p = 0.002) than controls. Reduced strength was a direct contributor to lower FS in PD (ß = 0.631), and an indirect factor through limiting optimal muscle-tendon unit interaction. Interestingly, our findings indicate an uncoupling between fascicle shortening and tendon elongation in persons with PD. To better understand limitations in FS and muscle-tendon unit behavior, it is imperative to identify the origins of MVC decrements in persons with PD.

Regional-scale investigation of salt ions distribution characteristics in bauxite residue: A case study in a disposal area

Revegetation on bauxite residue disposal areas is the most promising strategy to reduce its potential ecological risk during stacking or disposing. Migration of salt ions in bauxite residue is one of the major issues to stimulate soil formation to support plant growth. 21 residue samples were collected and the related parameters including exchangeable cations, soluble ions, total salt, pH, electrical conductivity (EC) and exchangeable sodium percentage (ESP) were selected to evaluate alkalization and salinization of bauxite residue. High levels of ions, cation exchange capacity (TOC), total salt, exchangeable sodium percentage (ESP) and cation exchange capacity (CEC) in bauxite residue were detected with greater coefficient of variation (CV), which indicated that distribution characteristics of salt ions varied significantly. The percentage of sulfate-chloride-soda type in the residues accounted for 71.43%. The mean value of pH was 10.10, whilst mean value of ESP was 52.05%. It indicated that the residues in this case study belonged to sulfate-chloride-soda saline and alkaline soil. The research results could provide theoretical basis for soil formation in bauxite residue.

Sedation Variability Increases Incidence of Delirium in Adult Medical Intensive Care Unit Patients at a Tertiary Academic Medical Center.

Variability in sedation may increase the incidence of delirium and mortality, as well as increased intensive care unit (ICU) and hospital lengths of stay (LOS), despite mean Richmond Agitation Sedation Scale (RASS) scores at goal. Coefficient of variation (CV) can be used to represent variability with a higher ratio indicating increased variability. Do patients with an increased variability in sedation, as evaluated by CV in RASS, have an increased incidence of delirium? We conducted a retrospective chart review of adult medical ICU patients requiring mechanical ventilation (MV) for ≥24 hours between January and April 2013. Patients were excluded if intubated at an outside hospital, neuromuscularly blocked, suffering from anoxic brain injury, or had a goal RASS of -4 or -5. Outcomes assessed included the presence of delirium, as evaluated by the Confusion Assessment Method, RASS, CV in RASS, duration of MV, ICU, and hospital LOS, and survival. Of 45 included patients, 32 experienced delirium during their ICU admission and 13 did not. The groups were similar at baseline. There was no difference in mean RASS when comparing the delirium and nondelirium groups (-1.6 ± 1.3 vs. -1.8 ± 0.8, respectively; P = 0.61). Patients with delirium had a greater CV in RASS (0.3 ± 0.135 vs. 0.2 ± 0.105; P = 0.02), a longer MV duration [4 (2-8) vs. 3 (2-3) days; P = 0.045], and a trend toward increased ICU LOS [8 (5-12.25) vs. 4 (3-8) days; P = 0.096], but no difference in hospital LOS [13 (10-25) vs. 18 (9-39) days; P = 0.83] and survival (71.9% vs. 69.2%; P = 1.0). Medical ICU patients with delirium had a higher CV in RASS compared with patients without delirium, suggesting that greater variability in sedation may increase the incidence of delirium. Patients with delirium also had a greater duration of MV and a trend toward longer ICU LOS.

Gait Variability Among Breast Cancer Survivors During Forward And Backward Walking

Increase in gait variability measured using instrumented techniques has been associated with increased risk of falls in persons with Parkinson’s disease, decreased functional performance and increased fall-risk in older adults. Recently research on breast cancer survivors (BCS) has focused on estimating fall-risk in this population attributed to gait performance. However, little is known about gait variability characteristics among BCS. PURPOSE: To assess the differences in gait variability among BCS compared to healthy controls during forward, backward, and accelerated forward walking. METHODS: 13 postmenopausal BCS (mean age: 58.5 ± 8.5 years) and 8 healthy controls (mean age: 60.8 ± 6.1 years) participated. Participants completed 5 trials each of forward, backward, and accelerated forward walking conditions on a 16x4’ Zeno walkway with a lead and follow-up distance of 1 m to capture steady-state gait. Coefficient of variation (CV) was calculated as % of standard deviation over mean of 5 trials. CV of stride length, stance time, and stride width were used as dependent variables. A Group (BCS vs healthy controls) X Condition (forward, backward, accelerated forward walking) ANOVA was performed. RESULTS: Significant interaction for stance time showed that BCS had greater CV during forward (4.89 ± 0.63%) and accelerated forward (6.49 ± 0.78%) but lesser CV during backward walking (6.28 ± 1.09%) compared to healthy controls (forward: 3.81 ± 0.80%; accelerated forward: 4.23 ± 1.00%; backward: 9.20 ± 1.38%; P = 0.018). Significant group main effect indicated that BCS (7.09 ± 3.59%) had greater stride length variability compared to healthy controls (3.59 ± 1.32%) across all conditions (P = 0.05). Significant condition main effect was observed for stride length and stance time CV (both P = 0.02) but not stride width (P = 0.063). During forward walking, stride length (by 5%) and stance time (by 3.3%) CV were significantly less compared to backward walking (both P = 0.004). There were no other significant differences. CONCLUSION: Increased stance time variability during backward walking and overall greater stride length variability may be indicative of increased fall-risk among BCS. Future studies need to examine other balance tests in conjunction with these measures to determine the level of fall-risk among BCS.

Reliability analysis of shallow tunnel with surface settlement

Based on the reliability theory and limit analysis method, the roof stability of a shallow tunnel is investigated under the condition of surface settlement. Nonlinear Hoek-Brown failure criterion is adopted in the present analysis. With the consideration of surface settlement, the internal energy and external work are calculated. Equating the rate of energy dissipation to the external rate of work, the expression of support pressure is derived. With the help of variational approach, a performance function is proposed to reliability analysis. Improved response surface method is used to calculate the Hasofer-Lind reliability index and the failure probability. In order to assess the validity of the present results, Monte-Carlo simulation is performed to examine the correctness. Sensitivity analysis is used to estimate the influence of different variables on reliability index. Among random variables, the unit weight significantly affects the reliability index. It is found that the greater coefficient of variation of variables lead to the higher failure probability. On the basis of the discussions, the reliability-based design is achieved to calculate the required tunnel support pressure under different situations when the target reliability index is obtained.

Increased absorbed liver dose in Selective Internal Radiation Therapy (SIRT) correlates with increased sphere-cluster frequency and absorbed dose inhomogeneity.

BackgroundThe higher tolerated mean absorbed dose for selective internal radiation therapy (SIRT) with intra-arterially infused 90Y microspheres compared to external beam therapy is speculated to be caused by absorbed dose inhomogeneity, which allows for liver regeneration. However, the complex liver microanatomy and rheology makes modelling less valuable if the tolerance doses are not based on the actual microsphere distribution. The present study demonstrates the sphere distribution and small-scale absorbed dose inhomogeneity and its correlation with the mean absorbed dose in liver tissue resected after SIRT.MethodsA patient with marginally resectable cholangiocarcinoma underwent SIRT 9 days prior to resection including adjacent normal liver tissue. The resected specimen was formalin-fixed and sliced into 1 to 2-mm sections. Forty-one normal liver biopsies 6-8 mm in diameter were punched from these sections and the radioactivity measured. Sixteen biopsies were further processed for detailed analyses by consecutive serial sectioning of 15 30-μm sections per biopsy, mounted and stained with haematoxylin-eosin. All sections were scrutinised for isolated or conglomerate spheres. Small-scale dose distributions were obtained by applying a 90Y-dose point kernel to the microsphere distributions.ResultsA total of 3888 spheres were found in the 240 sections. Clusters were frequently found as strings in the arterioles and as conglomerates in small arteries, with the largest cluster comprising 453 spheres. An increased mean absorbed dose in the punch biopsies correlated with large clusters and a greater coefficient of variation. In simulations the absorbed dose was 5–1240 Gy; 90% were 10-97 Gy and 45% were <30 Gy, the assumed tolerance in external beam therapy.ConclusionsSphere clusters were located in both arterioles and small arteries and increased in size with increasing sphere concentration, resulting in increased absorbed dose inhomogeneity, which contradicts earlier modelling studies.

Prognostic impact of the sleep-time relative blood pressure decline for predicting the risk of developing diabetes

SBP and a 10 mmHg increase in SBP. Meta-regression and subgroup analyses were used to quantify the relative prognostic value of women versus men. Patients were from Europe, Brazil, and Japan (10 cohorts, N1⁄417,312, CVEs1⁄41,892). One cohort lacked gender-specific HRs from 24 hour and clinic SBP but otherwise had gender-specific information. There was a tendency for women to have a greater 1 SD of SBP and a greater coefficient of variation as compared to men. For women relative to men, a 1 SD increase in nighttime, daytime, 24 hour, and clinic SBP, gave RRs (95% confidence intervals) of 1.18 (1.05-1.31), 1.23 (1.09-1.40), 1.21 (1.07-1.37), and 0.94 (0.83-1.06), respectively. (See Figures.) For a 10 mmHg increase in SBP, the corresponding RRs were 1.06 (0.99-1.14), 1.13 (1.03-1.23), 1.10 (1.01-1.21), and 0.96 (0.89-1.03), respectively. In conclusion, in patients with hypertension, ambulatory SBPs better predict CVEs in women than in men.

Prognostic impact of clinic, daytime, and nighttime systolic blood pressure in 9 cohorts of 13,843 patients with hypertension: systematic review and meta-analysis

SBP and a 10 mmHg increase in SBP. Meta-regression and subgroup analyses were used to quantify the relative prognostic value of women versus men. Patients were from Europe, Brazil, and Japan (10 cohorts, N1⁄417,312, CVEs1⁄41,892). One cohort lacked gender-specific HRs from 24 hour and clinic SBP but otherwise had gender-specific information. There was a tendency for women to have a greater 1 SD of SBP and a greater coefficient of variation as compared to men. For women relative to men, a 1 SD increase in nighttime, daytime, 24 hour, and clinic SBP, gave RRs (95% confidence intervals) of 1.18 (1.05-1.31), 1.23 (1.09-1.40), 1.21 (1.07-1.37), and 0.94 (0.83-1.06), respectively. (See Figures.) For a 10 mmHg increase in SBP, the corresponding RRs were 1.06 (0.99-1.14), 1.13 (1.03-1.23), 1.10 (1.01-1.21), and 0.96 (0.89-1.03), respectively. In conclusion, in patients with hypertension, ambulatory SBPs better predict CVEs in women than in men.

Comparison of reliability of lateral cephalogram and computed tomography for assessment of airway space

The oropharyngeal (OP) and nasopharyngeal structures seems to play roles in the development of the dentofacial complex. Soft palate as a part of nasopharyngeal and OP apparatus has an important role in phonation, deglutition and respiration. The aim of this study was to find whether any correlation exists between the three types of malocclusion and airway space using lateral cephalogram and computed tomography (CT) and to compare its reliability. To obtain important information on the morphology of the soft palate on lateral cephalogram and to determine its etiopathogenesis in obstructive sleep apnea (OSA). Lateral cephalogram of 45 subjects were used to measure the pharyngeal airway. The subjects were divided into three groups (each group included 15 subjects) according to ANB angle: Class I (ANB angle 2-4°), Class II (ANB angle > 4°), Class III (ANB angle ≤ 2°). The result showed a significant reduction in pharyngeal airway in ANB Class II. Type I soft palate, leaf-shape was found in maximum subjects. The volume of airway size showed higher statistical significance with the greater coefficient of variation on CT in relation to corresponding cephalometric airway area. The sagittal skeletal pattern is a contributory factor in variations in the upper airway dimensions. The measurements acquired from both the modalities are reliable and reproducible, but CT gives the better assessment of cross-sectional dimensions of airway space. Morphology of the soft palate can be used as references for etiological research of OSA.

Spatial variation of local stand structure in an Abies forest, 45 years after a large disturbance by the Isewan typhoon

Heterogeneity of forest stand structure often results from repeated small disturbances, but structural variation also arises in a stand that has regenerated after a single large stand-replacing disturbance. We explored the structural variation within a subalpine Abies forest in Japan that regenerated after a large typhoon in 1959. In 2004, four 50 × 50 m plots were established at two sites in the regenerated forest. To characterize local stand structure within each plot, we determined the stem density, stand basal area, mean diameter at breast height (DBH), and coefficient of variation (CV) of DBH in 10 × 10 m subplots. We analyzed the spatial distribution pattern of the trees in each subplot using the L(t) function and categorized the distributions as clumped or non-clumped. The analysis revealed marked variation among subplots in the stand's structural characteristics. Although the spatial distribution patterns of the trees in all plots were clumped, 11 of 50 subplots at one site and 39 of 50 subplots at the other site were non-clumped. Subplots with a clumped distribution pattern generally had a smaller basal area, smaller mean DBH, and greater CV of DBH than subplots with the same density but a non-clumped pattern. These results illustrated the spatial heterogeneity of forest structure that can arise in Abies forest that has experienced a large disturbance, probably because of the different densities and distribution of saplings surviving the disturbance and the different forest growth dynamics that result.

Ultra-performance liquid chromatography tandem mass-spectrometry (UPLC–MS/MS) for the rapid, simultaneous analysis of thiamin, riboflavin, flavin adenine dinucleotide, nicotinamide and pyridoxal in human milk

A novel, rapid and sensitive ultra-performance liquid-chromatography tandem mass spectrometry (UPLC–MS/MS) method for the simultaneous determination of several B-vitamins in human milk was developed. Resolution by retention time or multiple reaction monitoring (MRM) for thiamin, riboflavin, flavin adenine dinucleotide (FAD), nicotinamide and pyridoxal (PL) has been optimized within 2min using a gradient of 10mM ammonium formate (aq) and acetonitrile. Thiamin-(4-methyl-13C-thiazol-5-yl-13C3) hydrochloride, riboflavin-dioxo-pyrimidine-13C4,15N2, and pyridoxal-methyl-d3 hydrochloride were used as internal standards. A sample-like matrix was found to be mandatory for the external standard curve preparation. 13C3-caffeine was added for direct assessment of analyte recovery. Intra- and inter-assay variability for all analytes ranged from 0.4 to 7.9% and from 2.2 to 5.2%, respectively. Samples were subjected to protein precipitation and removal of non-polar constituents by diethyl ether prior to analysis. Quantification was done by ratio response to the stable isotope labeled internal standards. The standard addition method determined recovery rates for each vitamin (73.0–100.2%). The limit of quantitation for all vitamins was between 0.05 and 5ppb depending on the vitamin. Alternative approaches for sample preparation such as protein removal by centrifugal filter units, acetonitrile or trichloroacetic acid revealed low recovery and a greater coefficient of variation. Matrix effect studies indicated a significant influence by matrix constituents, showing the importance of stable isotope labeled internal standards for analyte quantitation in complex matrices.

SU-E-I-18: Variability of Physiological Parameters Estimated by AATH and MTK Models in DCE-MRI.

To assess the accuracy and precision of physiological parameters estimated by the modified Tofts and Kermode (mTK) model and the adiabatic approximation to the tissue homogeneity (AATH) model in dynamic contrast enhanced (DCE) MRI. Computer simulations were performed using the arterial input function (AIF) from Parker et al., and the multiple indicator, multiple path, indicator dilution 4 region (MMID4) model for simulating the tissue concentration time curve. A set of physiological parameters, simulating a breast tumor, was selected as the input to the MMID4. The output was then converted to signal time curve using SPGR signal equation. Four levels of Gaussian noise, corresponding to SNRs of 100, 50, 20 and 10, were added to the signal time curves, with 1000 iterations each. These curves were then transferred back to concentration time curves on which mTK and AATH models were applied for fitting. For AATH model the mean transit time (tau) was held as a fixed parameter ranged from 2 to 10 s, and the final solution was selected based on minimizing the root mean square error. For common parameters obtained by both models (Ktrans, Ve, Vp), AATH provided better accuracy, which agreed with the literatures, whereas mTK resulted in superior precision. As expected, greater coefficient of variation (CV) was found with smaller SNR in all cases. For the parameters that could only be obtained with the AATH model, the CVs were less than 10% for F, E and PS, and around 20% for tau, at the SNR level of 20. Using the MMID4 model for data simulation, this work found that AATH model was more accurate but less precise for estimating physiological parameters as compared with mTK model. The AATH model was able to separate blood flow and permeability estimates with reasonable errors and variations.

Speech-associated labiomandibular movement in Mandarin-speaking children with quadriplegic cerebral palsy: A kinematic study

The purpose of this study was to investigate the speech-associated labiomandibular movement during articulation production in Mandarin-speaking children with spastic quadriplegic (SQ) cerebral palsy (CP). Twelve children with SQ CP (aged 7-11 years) and 12 age-matched healthy children as controls were enrolled for the study. All children underwent analysis of percentage of consonants correct (PCC) and kinematic analysis of speech tasks using the Vicon Motion 370 system. Kinematic parameters included utterance duration, displacement and velocity of the lip and jaw, coefficient of variation (CV) of lip utterance duration, and spatial and temporal coupling of labiomandibular movement of speech produced in mono-syllable (MS) and poly-syllable (PS) tasks. Children with CP showed lower temporal coupling (MS, p = 0.015; PS, p = 0.007), but not spatial coupling, of labiomandibular movement than healthy children. Children with CP had greater CVs (MS, p = 0.003; PS, p = 0.010) and the peak opening displacement and velocity of lower lip and jaw (p < 0.05) and lower PCC (p < 0.001) than healthy children. Children with SQ CP displayed labiomandibular coupling movement impairment, especially in the aspect of temporal coupling. These children also had high temporal oromotor variability and needed to make more effort to coordinate the labiomandibular movement for speech production.

The Effect of Amantadine on Corneal Endothelium in Subjects with Parkinson's Disease

To evaluate the effect of amantadine on corneal endothelial cells in subjects with Parkinson's disease. Cross-sectional study. A total of 169 subjects (169 eyes) taking amantadine orally for Parkinson's disease and the same number of age- and gender-matched controls. Endothelial indices were compared between the amantadine-treated and age-matched control groups. The amantadine-treated group was divided into 3 subgroups according to the cumulative dose and duration of treatment. Endothelial changes were compared between the amantadine group and the normal control group, and among subgroups. Slit-lamp biomicroscopy, central corneal thickness (CCT), endothelial cell density (ECD), coefficient of variation, and hexagonality. The amantadine group had significantly lower ECD (mean +/- standard error; 2662.47+/-29.06 vs. 2784.72+/-25.89, P = 0.002), lower hexagonality (56.94+/-1.07 vs. 60.97+/-0.87, P = 0.004), and greater coefficient of variation (35.59+/-0.57 vs. 32.66+/-0.52, P = 0.000) compared with the age-matched control group. Longer duration and higher cumulative dose amantadine therapy led to a greater reduction in ECD (P<0.05) compared with the normal age-matched control group. Amantadine is more likely to have an effect on corneal endothelial cells in a dose-dependent manner when used long-term.