Limit Of Deviation Research Articles

Quality control optimization part II: A method to optimize the accuracy of laboratory quality control

BackgroundQuality control (QC) can be viewed as a diagnostic test that is used to determine whether an assay is in statistical control. Using this framework, QC performance can be evaluated using familiar metrics associated with diagnostic tests. QC plan parameters can be adjusted to optimize performance metrics. MethodsWe developed a simple dichotomous model based on classification of assay errors. Errors are classified as important or unimportant based on a critical shift size, defined as Sc. Using this scheme, we show how QC policies can be analyzed using common accuracy metrics such as sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV). We conducted computer experiments to determine the QC plan that optimizes QC accuracy under a wide range of scenarios. ResultsIn general, traditional QC plans (based on2 or 3 standard deviation limits) are approximately 90% as accurate as optimized QC limits in the scenarios that were tested. There are special circumstances when traditional QC plans do not perform well. ConclusionQC performance can be optimized for specific contexts.

The Uncertainty of Measurements as a Tool for Evaluating the Adequacy of the Mathematical Measurement Model

The article offers a new way of estima-ting the influence of random and methodical errors to the result of measurement for the measurement uncertainty index. The ratio of the difference between theo-retical and experimental data is proposed from the average error of their determination for the quantitative indicator of the influence of methodical error. The ratio of the uncertainty in the measurement of experimental data to the uncertainty in measuring theoretical data for a quantitative measure of the effect of a random error is proposed. These indicators are based on the assumption that the theoretical and experimental data are normally distributed. The theoretical distribution va-ries within the total uncertainty of measurement of type B of the parameter under study. The physical essence of the indicator of the influence of the metho-dical error is the probability with which the results of measuring the average value of the indicator (determined experimentally) are within the li-mits of a possible deviation of the theoretical value of this indicator. Figure — 3. Table 1. References — 14.

Utility of transesophageal echocardiography for intra-operatively assessing pulmonary artery pressure across an isolated ventricular septal defect in children.

The magnitude of pulmonary hypertension (PH) is extremely important with respect to the intra-operative management of children and infants with an isolated ventricular septal defect (VSD). This study aimed to assess the feasibility and accuracy of transesophageal echocardiography for estimating pulmonary arterial systolic pressure (PASP) across isolated VSD. We compared the results of transesophageal echocardiography vs invasive PASP measured simultaneously. This study included 40 patients (age: 6months to 6years; weight: >5kg) who were undergoing elective surgery for isolated VSDs. Flow signals across the VSDs were identified as high velocity turbulent signals in systole via continuous wave Doppler at 0-120° at the mid-esophageal level. Peak velocities were recorded. Radial artery systolic pressures were assessed invasively, and PASPs were obtained after exposing the pulmonary artery intra-operatively. After excluding five patients because of unusable measurements, invasive PASP measurements were obtained in 35 patients (87.5%). There were no significant biases between echocardiographic and catheterization measurements of PASP, with a tight confidence interval measuring, on average, up to 2.6mmHg. However, the±2 standard deviation limits of agreement for mean PASP were -3.8 and 10.6mmHg. PASP measurements via transesophageal echocardiography in cardiac surgical patients under general anesthesia are recommended for use as a screening and monitoring tool for PH in children and infants, but cannot be used as a diagnostic tool.

Synthesis of highly fluorescent carbon dots from lemon and onion juices for determination of riboflavin in multivitamin/mineral supplements

In this work, lemon and onion biomasses commonly found in street markets are for the first time used to develop a facile, fast and low-cost one-step microwave-assisted carbonization method for synthesis of highly fluorescent carbon dots (CDs). The structure and optical properties of CDs were investigated by TEM, XRD, XRF, UV–Vis, FTIR, and fluorescence spectroscopy. CDs displayed satisfactory optical proprieties, a high quantum yield of 23.6%, and excellent water solubility, and the particle size was 4.23–8.22 nm with an average diameter of 6.15 nm. An efficient fluorescent resonance energy transfer (FRET) between the CDs and riboflavin was achieved with CDs acting as donor and riboflavin as acceptor. A linear relationship between FRET and the riboflavin concentration from 0.10 to 3.0 μg/mL was observed, allowing the development of an accurate and fast analytical method to determine this vitamin in multivitamin/mineral supplements. Despite the potential interferences in these supplements, CDs were selective for riboflavin under optimized conditions. A paired t-test at a 95% confidence level indicated no statistically significant difference between the proposed and the reference methods. Recovery test presented values ranged from 96.0% to 101.4%. The limit of detection and relative standard deviation were estimated at 1.0 ng/mL and <2.6% (n = 3), respectively. CDs were successfully synthesized in a domestic microwave oven (1450 W, 6 min), presenting satisfactory parameters when compared with results of other studies reported in the literature, suggesting that the proposed method is a potentially useful method for the synthesis of CDs and determination of riboflavin.

Magnetic hybrid support for ultrasound-assisted magnetic solid-phase extraction of polycyclic aromatic hydrocarbons from produced water

This work describes the synthesis of two hybrid organic-inorganic supports with magnetic properties, using water with a high content of natural organic matter (NOM) as solvent and to compose the organic phase. The materials were used in the ultrasound-assisted magnetic solid-phase extraction (UAMSPE) and magnetic dispersive solid-phase extraction (MdSPE) of five polycyclic aromatic hydrocarbons (PAHs) from produced water (PW). The best extraction conditions were achieved using UAMSPE with 20.0 mg of the adsorbent, total extraction time of 5 min, and 10 mL of ethyl acetate as extractant. The linear range, limit of detection (LOD), limit of quantification (LOQ), correlation coefficient (r), and relative standard deviation (RSD) could reach 0.500–100 μg L−1, 0.010–0.020 μg L−1 (based on S/N = 3), 0.03–0,060 (based on S/N = 3), 0.9943, and 6.7% (50 μg L−1) respectively. Upon optimization, the analysis of two PW samples from different wells found PAHs concentrations in the ranges 0.6–1.7 μg L−1 (sample APP1) and 0.5–1.6 μg L−1 (sample APP2). The method was successfully applied to the determination of PAHs in produced water.

Synthesis of graphene oxide-based poly(p-aminophenol) composite and its application in solid phase extraction of trace amount of Ni(II) from aquatic samples

The results of investigations about the polymerization of p-aminophenol in neutral-weak alkaline medium (pH = 7-8) in our lab showed that the produced polymer which was insoluble in water and soluble in methanol has high tendency to form selectively a blue complex with Ni(II). Investigations into the chemical structure of polymer showed that polymer has a special structure, similar to polyamine in which the aromatic rings are connected through O-bridges. Based on these data, it was decided to polymerize p-aminophenol in situ on graphene oxide (GO) and use as a new sorbent for selective separation and preconcentration of trace amount of Ni(II) from water samples. By this, the rate of sorption of Ni(II) will also be increased considerably with respect to GO alone. Resulting composite (GO-Pp-AP) was characterized by FT-IR, XRD, FE-SEM, and EDS. The obtained data confirmed the uniform growth of the polymer on the GO and the absence of granular particles. The composite shows high tendency and high rate of sorption of Ni(II) and consequently was utilized for solid phase extraction (SPE) of Ni(II) ions before its determination by flame atomic absorption (FAAS). The effects of important parameters on the recovery of Ni(II) were investigated. The presence of foreign ions has no meaningful effect on the recovery percentage of Ni(II). Under the optimum conditions, limit of detection and relative standard deviation were found to be 0.70μgL-1 and 1.8% (for n = 6; at 20μgL-1 of Ni(II)), respectively. Testing the standard reference material and analyzing the spiked real samples exhibit that the procedure can be successfully employed for determination of Ni(II) in natural water and wastewater samples. Graphical abstract ᅟ.

Technical accuracy of ten self-monitoring blood glucose devices commonly used in Dhaka City of Bangladesh

Due to inadequate regulatory mechanisms, the accuracy of the self-monitoring blood glucose (SMBG) devices is not ensured leading to potentially serious clinical consequences in Bangladesh. The present study was undertaken to evaluate the technical accuracy of ten most commonly used SMBG devices marketed in Dhaka City of Bangladesh. Top ten SMBG devices sold in Dhaka City were studied on a group of 100 type 2 diabetes mellitus subjects. Blood glucose values estimated (at fasting and 2 h after breakfast) by SMBG devices, using a blinding technique, were compared with the corresponding laboratory values by enzymatic method using the Dimension RXLMax automated chemistry analyzer. Hematocrit was measured using the Sysmex XT 2000 hematology autoanalyzer. The mean absolute relative error (MARE, %) was used as an indicator of accuracy and precision together. A highly significant correlation was observed between the device and laboratory values. However, none of the devices showed an acceptable accuracy at 5–10% deviation from the corresponding laboratory values either at fasting or postprandial states. On pooling together data from two prandial states, even at 15% deviation limits, 70% of the devices failed to show accurate results. On calculation of MARE, 60% devices were found to be beyond 15% error limit at 95% accuracy level. Corresponding analysis with 90% accuracy level showed 30% beyond the limit. Blood glucose results from around 30% of the top ten SMBG devices sold in Dhaka City do not have even minimum level of technical accuracy, and many others are not optimum in their accuracy levels.

Large deviations of the long term distribution of a non Markov process

We prove that the long term distribution of the queue length process in an ergodic generalised Jackson network obeys the Large Deviation Principle with a deviation function given by the quasipotential. The latter is related to the unique long term idempotent distribution, which is also a stationary idempotent distribution, of the large deviation limit of the queue length process. The proof draws on developments in queueing network stability and idempotent probability.

Parasitic &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$RC$ &lt;/tex-math&gt; &lt;/inline-formula&gt; Aware Delay Corner Model for Sub-10-nm Logic Circuit Design

In this paper, we propose a new statistical corner model for the precise variation analysis of CMOS logic gate delay. The conventional corner model includes pessimism in its prediction of delay variation as a result of inadequate statistical consideration of device characteristics. Therefore, to develop an accurate delay corner model, we analytically derive corner modeling targets for device characteristics, which are statistically shrunk when considering the variation and the correlation of transistor and parasitic resistance and capacitance ( RC ). Then, the derived targets are obtained by multiplying the conventional corner parameters using the newly proposed corner scaling factors. Simulation results verify that the corner model fitted to the proposed targets accurately predicts the three standard deviation limits of delay variation. To implement the parasitic RC aware delay corner in compact models of the process design kit, an artificial neural network is used to model the complex relationship between the parasitic RC and the delay corner model. The delay variations predicted by the proposed model match well with the Monte Carlo simulation results at various simulation conditions, unlike the conventional corner model, which introduces pessimism.

Statistical process control (SPC) for short production run with Cauchy distribution, a case study with corrected numbers approach

Controlling damages in a short production run is very subtle. Because the samples for each part are small, the control charts for each part can be obscure therefore the deviation of the actual from the nominal size of each part in a unique control chart will be applied. Differences between the control limits of various deviations can generate a heavy-tailed distribution. We will discuss it with an example of Cauchy distribution as a member of this family. From Phase (I) we will propose the Corrected Numbers and these numbers will be applied in Phase (II).

Device of instalation of columns on vertical

Problem statement. The introduction of scientific and technological progress in modern construction is a major lever for increasing the efficiency of construction production. Its development is based on the principles of industrialization, which is based on the mechanization and automation of the main and auxiliary processes, as well as the introduction of flexible robotic systems and the use of modern computer systems. One of the main installations of the working equipment is the exhibition of verticality on the foundations and supports of various types of technological equipment and constructions. Particular attention is devoted to it with the industrial method of installation, the essence of which is the mechanized installation of buildings and structures from prefabricated structures of factory production. The exhibition can be visual or instrumental, which is executed using the ruler, theodolites, levelers, etc. The quality of the assembly and the laboriousness of the installation work depend on the method of exhibition. Laser theodolites have been widely used, of which theodolites with the visual system are more common, which are used for application in exhibitionof building structures. Ensuring the accuracy of the installation in the project position within the limits of permissible deviations in height, horizontal or vertical plane depends not only on the accuracy of the equipment, but also on the quality of work to determine their spatial orientation. The durability of equipment depends on many factors, for example, on the accuracy of exhibition the structures, the rate of wear of individual units and parts, the level of oscillations in the joints and fasteners. Purpose. To solve the technical problem of improving the accuracy of exhibition of building structures in a vertical position, a device based on accelerometers is proposed. Conclusion. It is proposed to use the device on the basis of two uniaxial accelerometers for installing the column in a vertical position. The offered device is a universal means that helps to shorten the time of exhibition of building constructions, and also allows to receive measurement information about the spatial position of constructions during the process of installation works and the operation of construction objects.

An energy exchange efficiency prediction approach based on multivariate polynomial regression for membrane-based air-to-air energy recovery ventilator core

Air-to-air energy recovery ventilators (AERVs) are widely applied in building heating, ventilation, and air conditioning (HVAC) systems to reduce energy consumption by reducing heating and cooling loads caused by ventilation. Its energy exchange efficiency data are typically acquired experimentally and are time consuming to be applied to engineering fields when the number of working scenarios to be tested is large. Instead of manual labor and time, detailed numerical calculation methods require the characteristic information of the membrane material, which is difficult for manufacturers to provide. Hence, an energy exchange efficiency prediction approach based on a multivariate polynomial regression model is proposed herein to predict the energy exchange efficiency of the membrane-based AERV (MERV) core. In the proposed approach, a simplified numerical efficiency calculation model of a cross-flow air-to-air enthalpy exchanger is trained with a small sample of experimentally measured efficiency data. Subsequently, the trained model is adopted to predict the energy exchange efficiency of the MERV core made of the same membrane, under other flowrates and structures. As verified by the experimental data, the proposed approach can predict the energy exchange efficiency with absolute deviation limits within ±8.0%. Compared to detailed numerical calculation methods, the proposed approach requires less membrane characteristic information and calculations; thus, the proposed approach is practical for engineering applications to simulate the equipment performance over different conditions and help sizing the equipment with less requirements.

Detection of free core nutation resonance variation in Earth tide from global superconducting gravimeter observations

In order to verify the time variability of free core nutation (FCN) period, global superconducting gravimeter (SG) observations were analyzed based on synthetic test data. The gravity data series were synthesized to check the detectability of resonance variation caused by FCN period change. The tests indicate that the discrepancy between the FCN periods determined by SG and VLBI observations is caused by the high correlation between the FCN parameter and the amplitude factor of the ψ1 wave. The K1 wave is more sensitive to the FCN period change than other diurnal waves. The limit of the standard deviation of the K1 wave is found for more precisely observing the FCN period change. Tidal parameters of diurnal waves estimated from long series of 20 global SG stations were analyzed. A common variation trend is found in the amplitude factor of both K1 and ψ1 waves in all 8 stations above the limit, which indicates the FCN period may be not so stable in time. Furthermore, the variation in the K1 and ψ1 waves constrains the FCN period change to between 2.5 and 4 sidereal days, which also agrees with the possible variation from the current VLBI and SG observations.

Thermodynamic consistency test for data of aqueous solutions of univalent electrolytes at 25 °C: Application to the LiCl + H2O

A thermodynamic consistency test (TCT) was developed for data of aqueous unsaturated electrolyte solutions at 25 °C by using the Gibbs-Duhem equation (GDE), standard referential data and estimates of error propagation. The consistency criteria include a randomness analysis of the errors and maximum deviation limits calculated with discrete forms of the GDE, where the zero equality of the theoretical equation was replaced by a free variable that represents the deviation from this equation. The results of the application of this TCT to 3 groups of data reported in the scientific literature for the LiCl + H2O system at 25 °C showed that two of them are "mostly consistent" and one of them is "totally consistent", according to the criteria of thermodynamic consistency presented in this work.

A sensitive and selective deep eutectic solvent-based ultrasound-assisted liquid phase microextraction procedure for separation-preconcentration and determination of copper in olive oil and water samples

ABSTRACTA green and simple deep eutectic solvent-based ultrasound-assisted liquid phase microextraction method has been developed for the preconcentration of copper as 2-(5-bromo-2-pyridylazo)-5-(diethylamino) phenol chelates. The effects of pH, ligand concentration, DES volume, sample volume, and tetrahydrofuran volume were investigated. Analytical performance parameters like limit of detection, limit of quantification, preconcentration factor, and relative standard deviation were determined as 6.6 μg L−1, 21.8 μg L−1, 15, and <5%, respectively. Validation of the developed method was checked by the analysis of certificated reference materials. The procedure was successfully applied to determination of copper in olive oil and water samples.

Simultaneous determination of dihydroxybenzene isomers at nitrogen-doped graphene surface using fast Fourier transform square wave voltammetry and multivariate calibration

In this paper, a highly sensitive electrochemical method, which is based on the combination of fast Fourier transform square wave voltammetry and multivariate calibration techniques, was developed for simultaneous determination of dihydroxybenzene positional isomers, including catechol, hydroquinone, and resorcinol, in environmental samples. An electrochemical sensor was constructed by the deposition of nitrogen-doped graphene on a glassy carbon electrode to apply as a new approach for the multicomponent analysis. Partial least squares was applied, as a multivariate calibration method, to deconvolute the highly overlapping electrochemical signals from the analytes. Using the simplex experimental design with the degree of 4, 19 ternary mixture solutions of the cited analytes were prepared in the established linear ranges of the analytes. The developed multivariate model was validated by predicting the concentration of 8 independent solutions. The root mean square error values of validation values were between 0.04230 and 0.06549 μM, respectively. The applicability of the proposed method was checked using water samples (collected from both the surface and waste water) and human urine, and the obtained recovery values were between 89.3 and 107.1%. The limits of detection and relative standard deviations for catechol, hydroquinone, and resorcinol were 0.046, 0.046, and 0.045 μM, and 3.6, 3.4 and 3% (N = 5), respectively.

Еталон лісових насаджень на заповідних територіях Національного природного парку «Сколівські Бескиди»

Облік лісових масивів природоохоронних об’єктів є первинним етапом оцінення їх потенціалу. Об’єктом дослідження є лісові насадження заповідної зони Національного природного парку «Сколівські Бескиди». Метою дослідження передбачено відібрати еталон, тобто лісові насадження із максимальним біорізноманіттям та продуктивністю, складною вертикальною структурою. Методику вибіркової лісової інвентаризації вважають найбільш адекватною для отримання репрезентативних даних. Для таких об’єктів лісівничо-таксаційна характеристика доповнюється аналізом просторової структури насаджень та оцінкою біорізноманіття.&#x0D; На території Майданського лісництва виявлено еталон лісових насаджень. Еталон представлений триярусними деревостанами. Після розроблення моделей залежності середнього приросту деревостану від середнього віку, а також запасу деревостану від середнього діаметра дерев першого ярусу, усі об’єкти розділено на дві групи. До першої групи відібрано об’єкти, котрі за величиною запасу (приросту) потрапляють до верхньої частини довірчої зони моделі з одностороннім обмеженням 1-2 стандартні відхилення.&#x0D; Відібрано шість еталонів у віковому діапазоні 55-136 років. Яруси лісового насадження складаються із бука лісового, ялиці білої та ялини європейської. Один еталон характеризує деревостан з модрини європейської, явора, ялини та ялиці. Частка дерев в першому ярусі змінюється в межах 43-63%, у другому – 4-32%, у третьому – 24-31%.&#x0D; Високопродуктивні структурно складні еталони є типовими природними утвореннями, на котрі повинна орієнтуватися господарська діяльність підприємства.

A new portable switchable hydrophilicity microextraction method for determination of vanadium in microsampling micropipette tip syringe system couple with ETAAS

First time we launch an innovative and simple portable in a closed micropipette tip switchable hydrophilicity microextraction syringe system (µS-SHS) couple with electrothermal atomic absorption spectroscopy (ETAAS) was developed for preconcentration and determination of vanadium using 2-(5-Bromo-2-pyridylazo)-5-diethylaminophenol (5- Br-PADAP), as complexing. In the proposed method decanoic acid was used as a switchable hydrophilicity extraction solvent and their polarity was switched on and off (water miscible/immiscible) by simply changing their pH. The phase separation was induced by simply adding sulfuric acid that switch off hydrophilicity (nondispersed/immiscible) of decanoic acid. The metal complex enriched phase (V-(5-Br-PADAP-SHS) was separated by simply removing the aqueous phase through manually dispensed syringe system. Then finally acidic ethanol drawn into the syringe contains metal complex enriched SHS phase to reduce viscosity and directly injected into the ETAAS by using an enclosed micropipette tip syringe system. The multivariate strategy was applied to screen out and optimized the variables. Limit of detection (LOD), enhancement factor (EF) and relative standard deviation (RSD) were found 0.0075 µg L−1, 120 and 2.91%, respectively. Certified reference material of riverine water (SLRS-4), Apple leaves (NIST SRM 1515) and a standard addition method was used to validate the present method. Developed method was applied to water and food samples. We successfully applied the proposed method to analyze vanadium in different real food and water samples.

Modification of magnetized MCM-41 by pyridine groups for ultrasonic-assisted dispersive micro-solid-phase extraction of nickel ions

Nickel is one of the heavy metals, which is discharged to ecosystem by normal process and human actions. Nickel is regarded as crucial ion in the living creature and is a component of protein structure at very low level. Dispersive micro-solid-phase extraction assisted by ultrasonic waves with a new magnetic material using pyridine-functionalized magnetic nanoporous sorbent was utilized for detection of nickel ions at trace levels in real matrices. Magnetized nanoporous silica (MCM-41) was modified with pyridine groups, and the structure of prepared magnetic nanoporous sorbent was confirmed by instrumental techniques. The applied techniques were Fourier-transformed infrared spectroscopy, X-ray powder diffraction, transmission electron microscopy and thermogravimetry–differential thermal analysis. Preconcentrated nickel using the mentioned sample preparation procedure was monitored by GFAAS at ng L−1 concentrations. To optimize the effect of significant parameters on sorption and desorption of nickel ions using the applied sample preparation procedure, Box–Behnken design was utilized. The influencing parameters in the sorption step are: sorption amount (mg), pH of solution and sonication time (min), and these parameters for desorption step are: volume of eluent (mL), concentration of eluent (mol L−1) and sonication time (min). Optimized data for parameters that obtained by Box–Behnken design were: sample’s pH: 7.5, sonication time for sorption: 8 min, sorbent amount: 24 mg, desorption solvent: HCl 1.2 mol L−1, eluent volume: 420 μL and time of sonication for desorption, 8 min. Relative standard deviation and method detection limit for nickel monitoring under optimized conditions by UA-d-μSPE were observed to be < 6% and 0.008 μg L−1, respectively.

Comparison of plication and resection in large-angle exotropia

Plication of the rectus muscles is used sparingly as a tightening procedure compared to resection, however, the relative efficacy of these procedures is difficult to assess because the sparse literature comparing the two is further limited by a lack of imaging. This case series attempts to compare the techniques in cases of exotropia along with quantitative assessment of ultrasound biomicroscopy (UBM). Patients with exotropia of 30Δ-50Δ who had undergone first-time horizontal strabismus surgery were recruited and prospectively underwent UBM evaluation 1year after surgery. Plication was performed by folding the anterior part of the medial rectus muscle posteriorly and tying it at the insertion to the sclera. Resection was performed in a routine manner. Deviation and motility were assessed postoperatively, when UBM was performed. Only patients with basic comitant exotropia without any vertical pattern were included. During the study period, 15 patients underwent resection of the medial rectus and 13 underwent plication. The two groups were age and deviation matched preoperatively. The patients undergoing plication and resection fared equally in terms of postoperative deviation (P=0.81) and abduction limitation (P=0.169). UBM could identify and quantify plication in all cases with excellent agreement with the operative data (intraclass correlation coefficient=0.886; P=0.000). Medial rectus plication or resection performed for similar angles of exotropia produced quantitatively similar results. Plication offered the advantage of being characteristically identifiable and measurable on UBM.