Reduction In Coefficient Of Variation Research Articles

Reduction of hypoglycaemia, lifestyle modifications and psychological distress during lockdown following SARS-CoV-2 outbreak in type 1 diabetes.

To assess changes in glucose metrics and their association with psychological distress and lifestyle changes in patients with type 1 diabetes (T1D) using flash glucose monitoring (FGM) during lockdown following severe acute respiratory syndrome coronavirus 2 outbreak. Single-centre, observational, retrospective study enrolling T1D patients who attended a remote visit on April 2020 at the Endocrinology division of the University Hospital Policlinico Consorziale, Bari, Italy. Lockdown-related changes in physical activity level and dietary habits were assessed on a semi-quantitative basis. Changes in general well-being were assessed by the General Health Questionnaire-12 items with a binary scoring system. Glucose metrics were obtained from the Libreview platform for the first 2 weeks of February 2020 (T0) and the last 2 weeks before the phone visit (T1). Out of 84 patients assessed for eligibility, 48 had sufficient FGM data to be included in the analysis. FGM data analysis revealed significant reductions in coefficient of variation, number of hypoglycaemic events, and time below range, while no changes were found in time in range, time above range, mean sensor glucose, and glucose management indicator. Moreover, the frequency of sweets consumption was inversely related to the occurrence of hypoglycaemic events during lockdown. Lockdown-related lifestyle changes, albeit unhealthy, may lead to reduction in FGM-derived measures of hypoglycaemia and glycaemic variability in patients with T1D.

Efficacy and Safety of Glimepiride With or Without Linagliptin Treatment in Patients With HNF1A Diabetes (Maturity-Onset Diabetes of the Young Type 3): A Randomized, Double-Blinded, Placebo-Controlled, Crossover Trial (GLIMLINA).

OBJECTIVESulfonylureas are first-line treatment of hepatocyte nuclear factor 1-α (HNF1A) diabetes (maturity-onset diabetes of the young type 3), but many patients do not achieve optimal glycemic control without episodes of hypoglycemia. We investigated the combination of the sulfonylurea glimepiride and the dipeptidyl peptidase 4 inhibitor linagliptin versus glimepiride monotherapy with respect to glycemic variability, glycemic control, and risk of hypoglycemia.RESEARCH DESIGN AND METHODSIn a randomized, double-blinded, crossover trial, patients with HNF1A diabetes (n = 19; mean ± SD age 43 ± 14 years, BMI 24.8 ± 2.8 kg/m2, and glycated hemoglobin [HbA1c] 7.4 ± 0.2% [57.1 ± 7.3 mmol/mol]) were randomly assigned to treatment with glimepiride + linagliptin 5 mg (16 weeks), washout (4 weeks), and glimepiride + placebo (16 weeks) (or vice versa). Glimepiride was titrated targeting a fasting plasma glucose of 4.5–6.0 mmol/L without hypoglycemia. Treatments were evaluated by continuous glucose monitoring (CGM), HbA1c, and meal test.RESULTSCompared with glimepiride + placebo, glimepiride + linagliptin did not significantly improve the primary end point, mean amplitude of glycemic excursions (MAGE) (mean difference −0.7 mmol/L, P = 0.1540), but displayed significant reductions in coefficient of variation on CGM (−3.6%, P = 0.0401), HbA1c (−0.5%, P = 0.0048), and glimepiride dose (−0.7 mg/day, P = 0.0099). β-cell glucose sensitivity (assessed as C-peptide–to–glucose ratio) during meal test improved with glimepiride + linagliptin. Incidences of hypoglycemia were similar with both treatments.CONCLUSIONSLinagliptin as add-on treatment to glimepiride improved glycemic variability and control without increasing risk of hypoglycemia in patients with HNF1A diabetes.

Landscape Conditions’ Influence on Soil Properties of Arable Land on a Smooth Slope in a Glaciolacustrine Plain

To establish a landscape-focused experiment, the soil cover of an agricultural land unit was studied on a smooth slope of a glaciolacustrine plane, and the factors and parameters of spatial differentiation were determined for several physical, physicochemical, and agrichemical properties. Various degrees of differentiation for certain properties associated with the characteristics of parent rocks were revealed along with the geochemical regimes and the nature of human impact. A significant heterogeneity was recorded in thickness of eluvial horizons, in degree of gleying, soil structure, and organic matter and nitrogen content; moderate heterogeneity was observed in terms of soil texture, physical and chemical properties, and nutritional regime. The main cause for variation of soil properties in the agricultural landscape was the heterogeneity of moraine parent rock: its physical, chemical, and agrochemical properties varied by 19–59%. Natural and human-induced processes in soil formation led to a 2.6-times reduction in the average coefficient of variation for these properties in the arable layer (from 36 to 14%). A number of agrochemical properties became 1.3–1.9 times more heterogeneous due to sheetflood erosion in the transitional eluvial facies, and they became three times more heterogeneous in the eluvial facies as a result of uneven application of organic fertilizers.

Reliability of quadriceps surface electromyography measurements is improved by two vs. single site recordings

PurposeThe reliability of surface electromyography (sEMG) is typically modest even with rigorous methods, and therefore further improvements in sEMG reliability are desirable. This study compared the between-session reliability (both within participant absolute reliability and between-participant relative reliability) of sEMG amplitude from single vs. average of two distinct recording sites, for individual muscle (IM) and whole quadriceps (WQ) measures during voluntary and evoked contractions.MethodsHealthy males (n = 20) performed unilateral isometric knee extension contractions: voluntary maximum and submaximum (60%), as well as evoked twitch contractions on two separate days. sEMG was recorded from two distinct sites on each superficial quadriceps muscle.ResultsAveraging two recording sites vs. using single site measures improved reliability for IM and WQ measurements during voluntary (16–26% reduction in within-participant coefficient of variation, CVW) and evoked contractions (40–56% reduction in CVW).ConclusionsFor sEMG measurements from large muscles, averaging the recording of two distinct sites is recommended as it improves within-participant reliability. This improved sensitivity has application to clinical and research measurement of sEMG amplitude.

A New Statistical Approach to Characterize Chemical-Elicited Behavioral Effects in High-Throughput Studies Using Zebrafish

Zebrafish have become an important alternative model for characterizing chemical bioactivity, partly due to the efficiency at which systematic, high-dimensional data can be generated. However, these new data present analytical challenges associated with scale and diversity. We developed a novel, robust statistical approach to characterize chemical-elicited effects in behavioral data from high-throughput screening (HTS) of all 1,060 Toxicity Forecaster (ToxCast™) chemicals across 5 concentrations at 120 hours post-fertilization (hpf). Taking advantage of the immense scale of data for a global view, we show that this new approach reduces bias introduced by extreme values yet allows for diverse response patterns that confound the application of traditional statistics. We have also shown that, as a summary measure of response for local tests of chemical-associated behavioral effects, it achieves a significant reduction in coefficient of variation compared to many traditional statistical modeling methods. This effective increase in signal-to-noise ratio augments statistical power and is observed across experimental periods (light/dark conditions) that display varied distributional response patterns. Finally, we integrated results with data from concomitant developmental endpoint measurements to show that appropriate statistical handling of HTS behavioral data can add important biological context that informs mechanistic hypotheses.

Identifying abrupt changes and detecting gradual trends of annual rainfall in an Indian arid region under heightened rainfall rise regime

ABSTRACTThis study aimed at identification of abrupt change points (CPs) and detection of gradual trends in 34‐year (1980–2013) annual rainfall at nine stations of an Indian arid region. TheCPswere determined by five tests and their significance was examined by two tests. Furthermore, trends were tested by three tests and their magnitudes were quantified by two tests. Novelty of the study lies in investigating significance of trends sequentially over years by applying Mann–Kendall (M–K) test. The identifiedCPswere similar for standard normal homogeneity test and cumulative deviations test at most stations. In contrast, Pettitt and Bayesian tests detectedCPin years 2002 and 2005 at six and three stations, respectively, and their significance was verified. Results of sequential M–K test did not match with other tests' results. The mean annual rainfall afterCP(350–627 mm) increased by 14–80% of the amount beforeCP(306–444 mm) with 7–42% reduction in coefficient of variation. The box–whisker plots supported these findings. Results of trend tests indicated statistically significant trends at Anjar, Bhachau, Mandvi and Rapar. Trend magnitudes by linear regression prior toCP(−6.2 to 7.1 mm year−1) showed an overall increase afterCP(4.7–40.8 mm year−1) with negative trend at one station. Sen's slope test, showing good harmony with linear regression, revealed that trend magnitudes afterCPwere 2–10 times higher than that for 34‐year period at six stations. Results of M–K test applied for sequential periods emphasized that rainfall trends are becoming stronger over time. This finding suggests that significance level of increasing rainfall trends may further increase in future. Finally, findings of this study are useful for planners and decision makers for developing policies to meet the challenges of the heightened rainfall in study area. Also, the approach used here may be adopted in other parts of the globe.

Improving the logistics of a constant order-cycle kanban system

Kanban systems are simple, effective means of improving production that are widely applied in practice. Based on the logistic process involved, kanban systems can be divided into constant order-quantity and constant order-cycle systems. The former has received much research attention, but the latter, also known as a milk run, has been relatively neglected. Further, most prior work has been based on deterministic data, which is an assumption often violated in practice. We present the case of a manufacturer of domestic water heating equipment where a constant order-cycle kanban implementation initially failed. A structured Define–Measure–Analyse–Improve–Control approach is adopted to improve the process. It was revealed that the failure was due to high variability in the logistic processes involved. Decreasing this variability resulted in a reduction of tardy replenishment routes from 50 to 3%; a reduction in the route time coefficient of variation from 40 to 16%; and a reduction in the mean route time from 31 to 25 min. These improvements allowed one of three existing routes to be eliminated without any negative impact on replenishment. This led to financial savings through the elimination of two operators. The logistic process appears to have a significant impact on kanban performance. Consequently, kanban implementations should not only focus on the kanban system itself but also on the other processes involved. Future research should therefore explore how resources can best be allocated between the different aspects required for a successful kanban implementation.

Some observations on ISO2394:2015 Annex D (Reliability of Geotechnical Structures)

ISO2394:2015 contains a new informative Annex D on “Reliability of Geotechnical Structures”. The emphasis in Annex D is to identify and characterize critical elements of the geotechnical reliability-based design (RBD) process, while respecting the diversity of geotechnical engineering practice arising from the influence of site-specific conditions. Annex D should pave the way for future code revisions to inject greater realism into geotechnical RBD. The most important element is the characterization of geotechnical variability. There are some noteworthy features: (1) the coefficient of variation (COV) of a geotechnical design parameter does not fall within a narrow range of values, (2) the multivariate nature of geotechnical data can be exploited to reduce the COV, (3) spatial variability affects the limit state beyond reduction in COV due to spatial averaging, and (4) statistical uncertainty may be significant, because the volume of soil sampled is a minute fraction of the volume of interest. Another important element is the characterization of model uncertainty. Geotechnical design codes, be it reliability-based or otherwise, must cater to diverse local site conditions and diverse local practices that grew and evolved over the years to suit these conditions. One obvious example is that the COVs of geotechnical parameters can vary over a wide range, because diverse property evaluation methodologies exist to cater to these diverse practice and site conditions. Another example is that deep foundations are typically installed in layered soil profiles that vary from site to site. These diverse site specific design scenarios do not surface in structural engineering. Section D.5.2 notes that reliability calibration for geotechnical RBD is more challenging for this reason.

Cycle-to-cycle variation analysis of early flame propagation in engine cylinder using proper orthogonal decomposition

Experimental investigations on the cycle-to-cycle variations of early flame propagation were conducted at two intake air swirl ratio of 0.55 and 5.68 in a single-cylinder spark-ignition direct-injection (SIDI) optical engine. Both the crank-angle resolved flame images through the quartz insert in the piston and the in-cylinder pressure were simultaneously recorded for 250 consecutive cycles. An algorithm based on the cross-correlation of flame pattern was implemented to compute the two-dimensional velocity fields representing an early flame propagation. Afterwards, the proper orthogonal decomposition (POD) was performed to access the cycle-to-cycle variations of flame propagation. During early flame formation, the uncertainty of velocity was evaluated to be less than 5%. The velocity fields of early flame propagation were significantly affected by in-cylinder air flow. Increasing the swirl ratio from 0.55 to 5.68 augmented the average early flame propagation speed from 2.1m/s to 3.2m/s, and the COV of flame speed was reduced from 49.7% to 25.1%. Good correlations were identified between early flame speed and the pressure-derived results. Similar magnitude of reduction in COV (coefficient of variation) of IMEP (indicated mean efficient pressure) & PP was also found. The coefficients of POD mode 1 were found to represent the flame speed, and the remaining higher POD modes were related to the fluctuation in kinetic energy. The POD coefficients showed good correlations with the pressure-derived results such as CA05 (5% of total heat release) & PP (peak pressure). The weak spiral flow pattern, observed within the flame, was only found in higher POD modes. In summary, using the coefficients and modes of POD, the average and fluctuating parts of early flame propagation can be resolved, thereby providing more quantitative information of the cycle-to-cycle variation during the early combustion process in an engine cylinder.

DESIGN OF A NEW INSTRUMENT FOR MEASURING FRICTIONAL PROPERTIES OF WOVEN FABRICS

Friction measurem ent is one of the important and interesting problems in the study of handle properties of fabrics. Different methods have been developed for measuring friction, such as sliding, Kawabata Evaluation System (KES) and cyclic testing. In this research, considering the possibilities of varying conditions in measuring friction, a new instrument is used in which the bottom surface of fabric can be moved and the top slider is kept fixed in order to prevent slider vibrations. In this method, the force inserted by an extensible yarn connected to the trolley standing on four very smooth bearings was measured. The result of experiments confirmed 7.6% increase in correlation coefficient in the dynamic friction region for nine different test samples and about 4.6% reduction in coefficient of variation compared to the sliding type.

Small area estimation of poverty indicators

AbstractThe authors propose to estimate nonlinear small area population parameters by using the empirical Bayes (best) method, based on a nested error model. They focus on poverty indicators as particular nonlinear parameters of interest, but the proposed methodology is applicable to general nonlinear parameters. They use a parametric bootstrap method to estimate the mean squared error of the empirical best estimators. They also study small sample properties of these estimators by model‐based and design‐based simulation studies. Results show large reductions in mean squared error relative to direct area‐specific estimators and other estimators obtained by “simulated” censuses. The authors also apply the proposed method to estimate poverty incidences and poverty gaps in Spanish provinces by gender with mean squared errors estimated by the mentioned parametric bootstrap method. For the Spanish data, results show a significant reduction in coefficient of variation of the proposed empirical best estimators over direct estimators for practically all domains. The Canadian Journal of Statistics 38: 369–385; 2010 © 2010 Statistical Society of Canada

Introducing a true internal standard for the Comet assay to minimize intra- and inter-experiment variability in measures of DNA damage and repair

The Comet assay (CA) is a sensitive/simple measure of genotoxicity. However, many features of CA contribute variability. To minimize these, we have introduced internal standard materials consisting of ‘reference’ cells which have their DNA substituted with BrdU. Using a fluorescent anti-BrdU antibody, plus an additional barrier filter, comets derived from these cells could be readily distinguished from the ‘test’-cell comets, present in the same gel. In experiments to evaluate the reference cell comets as external and internal standards, the reference and test cells were present in separate gels on the same slide or mixed together in the same gel, respectively, before their co-exposure to X-irradiation. Using the reference cell comets as internal standards led to substantial reductions in the coefficient of variation (CoV) for intra- and inter-experimental measures of comet formation and DNA damage repair; only minor reductions in CoV were noted when the reference and test cell comets were in separate gels. These studies indicate that differences between individual gels appreciably contribute to CA variation. Further studies using the reference cells as internal standards allowed greater significance to be obtained between groups of replicate samples. Ultimately, we anticipate that development will deliver robust quality assurance materials for CA.

Crystal size distribution (CSD) of batch salting-out crystallization process for sodium sulfate

The crystal size distribution (CSD) of sodium sulfate from the batch crystallization of sodium sulfate from concentrated sulfuric acid (spent acid) by salting-out with methanol was analyzed. The effects of amount of methanol added, the agitation rate, temperature and residence time (sampling time) on CSD were investigated. The mean crystal size and the coefficient of variation (c.v.) were the criteria used and the Rosin–Rammler distribution model was assumed. The mean crystal size varied from 0.03 to 0.07 mm while the range of c.v. was 5–45%, though most of the runs gave a c.v. of 20% or less, thus a size independent growth rate could be assumed. Larger mean crystal sizes were obtained for the following conditions: small amount of added methanol (low level of supersaturation), low temperature, low agitation rates and longer residence time. Reduction in coefficient of variation was enhanced by the same factors. A 2 4 factorial design analysis confirmed these findings.

Efficiency of including first-generation information in second-generation ranking and selection: results of computer simulation

Using computer simulation, we evaluated the impact of using first-generation information to increase selection efficiency in a second-generation breeding program. Selection efficiency was compared in terms of increase in rank correlation between estimated and true breeding values (i.e., ranking accuracy), reduction in coefficient of variation of correlation coefficients (i.e., ranking reliability), and increase in realized gain, with best linear unbiased prediction (BLUP). The test populations were generated with varying parameters: selection strategy (forward vs backward selection of parents); number of parents (24∼96); number of crosses per parent (1∼8); heritability (0.05∼0.35); ratio of dominance to additive variance (0∼3); ratio of additive-by-site to additive variance (0∼3); and ratio of dominance-by-site to additive variance (0∼3). The two selection strategies gave distinct results. When parents of the second-generation crosses had been selected via backward selection, adding first-generation information markedly increased selection efficiency. Conversely, when parents had been selected via forward selection, first-generation information provided little increase in efficiency. The amount of increase depended more on heritabilities in both generations and less on dominance and genotype–by–environment effects. Including first-generation information helped more when there were many parents and few crosses per parent in the second generation. Only in the case of extremely low first-generation heritabilities was there no benefit to adding first-generation information in terms of improved ranking reliability and accuracy.

An Efficient Sampling Survey Design to Estimate Pink Shrimp Population Abundance in Biscayne Bay, Florida

We developed an efficient sampling design-based approach using fishery-independent surveys to estimate population abundance of pink shrimp Penaeus duorarum over time in Biscayne Bay, Florida. We initially implemented quarterly stratified random sampling (StRS) using nine habitat strata and determined that average pink shrimp density (numbers/m2) was highest in late fall and lowest in spring and late summer. Coefficient of variation of the quarterly surveys, expressed as percent standard error/mean density, ranged from 5.8% to 14.3%. We found StRS to be more efficient (i.e., with lower variance) than simple random sampling (SRS) in most seasons. Statistical analyses suggested that pink shrimp densities were dependent on the biophysical habitat variables of bottom substrate, depth, and salinity. We also noted ontogenetic shifts in these relationships that were particularly pronounced at the onset of sexual maturation. Poststratification analysis was used to further evaluate several alternative habitat-based sampling schemes. Results showed that a five-strata composite design that used all three habitat variables was similar in performance, but less complex, than the original nine-strata design. In addition, the composite design outperformed both SRS and all other StRS designs indexed on single habitat variables. The new five-strata composite design was implemented in late summer 1997 and achieved a significant reduction in coefficient of variation compared with the late summer 1996 survey. This new design did not perform as well as expected in late fall 1997, which we attribute to a mismatch between our seasonal sample allocation strategy and the timing of pink shrimp recruitment into Biscayne Bay in 1997. Finally, we show how statistical sampling designs that use stratifications based on relevant habitat covariates can yield high-precision abundance estimates at low costs and provide a robust quantitative methodology for identifying habitat essential to fisheries production.

Local Calibration of International Normalised Ratio Improves between Laboratory Agreement: Results from the UK National External Quality Assessment Scheme

In the present study we have performed local calibration of International Normalised Ratio (INR) measurement systems in a large series of laboratories. We assigned INRs to five lyophilised plasma calibrants, one prepared from normal plasma and four using plasma from warfarinised patients, using different International Reference Preparations for Thromboplastin. These five calibrants, and two lyophilised test plasmas were analysed by 349 centres using 60 different thromboplastin instrument combinations. Plasma calibrants were assigned INRs using the WHO reference thromboplastin RBT-90 or the European reference thromboplastin CRM 149R. Each participating centre determined PTs of the calibrants with their local system. These PTs were then used to construct a local calibration graph relating PT to INR. The PTs of test plasmas were converted directly into INR using the local calibration model and into INR using the conventional method. The overall medians of conventionally derived INRs of two test plasmas analysed in 349 centres were 2.50 and 3.10, compared to 2.47 and 3.04 after local calibration where RBT-90 was employed to assign INRs to calibrants. Use of CRM 149R to assign INRs to calibrants led to a significant (p<0.0001) increase in INR to 2.7 and 3.36 respectively. When results were grouped according to the thromboplastin employed, agreement between results with different reagents was improved by local calibration. There was a significant reduction (p<0.01) in the spread of results in different centres as indicated by a reduction in coefficient of variation.

An electromyogram study on mandibular movement in unilateral cleft lip and palate patients before and after orthodontic treatment.

The purpose of this study is to investigate masticatory muscle function in subjects with unilateral cleft lip and palate compared with normal occlusion and the extents of improvement before and after orthodontic treatment. Subjects were twenty pretreatment patients, thirty posttreatment patients and ten controls. Electromyograms were recorded from their masticatory muscles during masticatory movement and tapping movement. Reduction of duration/stroke ratio (D/S) was observed in electromyograms obtained during masticatory movement after orthodontic treatment. The reduction was especially notable in the masseter muscle. In spite of a significant reduction in coefficient of variation (CV) values, a significant difference between the posttreatment group and the control group indicated some persisting irregularity in masticatory movement. Electromyograms taken during tapping movement showed no change in latency in the posttreatment group, but duration of the silent period (SP) was shortened and SP appearance increased. The findings outlined above reveal electromyographically clear improvements in masticatory muscle functions and jaw reflex mechanisms after orthodontic treatment. Nevertheless, parameters for subjects with cleft lip and palate still differed from those for controls with normal occlusion. The influence of plastic surgery in subjects with the defects discussed here causes maxillary retrusion, which in turn results in skeletal malocclusion. Orthodontic treatment should be designed to compensate this dentally and alveolarly. This design and the need to improve masticatory functions would contribute to eliminate the extreme difficulty of the therapeutic process.