Calibration Relationship Research Articles

Tetra-detector size exclusion chromatography characterization of molecular and solution properties of soluble microbial polysaccharides from an anaerobic membrane bioreactor

Characterization of the molecular properties of soluble microbial products (SMP) is critical for understanding the membrane filtration and fouling mechanisms in anaerobic and aerobic membrane bioreactors (AnMBR & MBR). In this study, the distributions of the absolute molecular weight and intrinsic viscosity of SMP polysaccharides from an AnMBR were effectively determined by a high performance size exclusion chromatography (HPSEC) that was coupled with the refractive index (RI), diode array UV (DAUV), right and low angle light scattering (LS), and viscometer (Vis) detectors. Based on the tetra-detector HPSEC determined absolute molecular weights and intrinsic viscosity, a universal calibration relationship for the SMP polysaccharides was developed and the molecular conformations, average molecular weights, and hydrodynamic sizes of the SMP polysaccharides were also explored. Two factors which can be derived from the tetra-detector HPSEC analysis were proposed for the characterization of the viscous and osmotic pressure properties of the SMP polysaccharides. In addition, it was also extrapolated how to analyze the resistance characteristics of the concentration polarization layers formed in membrane filtration based on the molecular properties determined by the tetra-detector HPSEC analysis.

Speckle characterization of surface roughness obtained by laser texturing

In this work, results obtained from roughness characterization ofmicro-textured USIBOR steel samples are shown. Laser texturing is used for creating specific periodic microstructures with positive topographies by molten metal displacement technique. Three different methods based on speckle technique (contrast intensity, binary image analysis, spot size measurement) are testedfor a contactless inspection and determination of surface roughness. Characterization and calibration relationship are based on the correlation between measured roughness (with conventional methods) and results from speckle techniques.

Vascular risk factors are associated with retinal arteriolar narrowing and venular widening in children and adolescents with type 1 diabetes.

The aim of the study was to describe the relationship of retinal arteriolar and venular calibre with vascular risk factors in children and adolescents with type 1 diabetes. In this hospital-based cross-sectional study, the medical files of 483 children and adolescents with type 1 diabetes were audited to collect retinal images and relevant clinical data. Retinal vascular calibre was measured using standardised protocols. After multivariable adjustments, a vascular risk profile that included: older age, higher serum creatinine, higher systolic blood pressure (SBP), higher body mass index (BMI), abnormal estimated glomerular filtration rate (eGFR), lower high-density lipoproteins (HDL) cholesterol, longer duration of diabetes and higher serum sodium was associated with narrower central retinal artery equivalent (CRAE) (95% CI=-4.10/-0.76, p=0.004). A specific risk profile, including higher total cholesterol level, higher BMI, lower physical activity level, higher HbA1c, higher triglyceride levels, female gender and lower socio-economic status, was associated with wider central retinal vein equivalent (CRVE) (95% CI=1.14/5.62, p=0.003). In summary, these findings support evidence that cardiovascular disease may have its origins early in life. Prospective and/or intervention studies are required to confirm whether the observed associations are involved in the causal pathway for retinal vascular calibre.

A monitoring technique for disbond area in carbon fiber–reinforced polymer bonded joints using embedded fiber Bragg grating sensors: Development and experimental validation

This study evaluated fatigue-induced disbond areas in carbon fiber–reinforced polymer double-lap joints using embedded fiber Bragg grating sensors. When the disbond grew by cyclic loading, the embedded fiber Bragg grating sensors yielded reflection spectra having two peaks representing a step-like strain distribution generated by the disbond; the peak at the shorter wavelength corresponded to the unloaded disbond region. The ratio of the peak intensity at the shorter wavelength to that at the longer wavelength increased gradually with increasing disbond length. The relationship between the peak intensity ratio and the disbond length was analyzed by coupled structural–optical analysis and was validated by comparing analytical peak intensity ratio with the experiment results. The disbond length was then estimated from the measured spectra based on this analytical calibration relationship, but the estimated disbond area exceeded that observed using the ultrasonic C-scan technique. Additional experiments including destructive observation of the adhesive suggested that an embedded fiber Bragg grating sensor could detect a moving disbond tip earlier than conventional nondestructive techniques.

Determination of carnosic acid and carnosol in Rosmarinus officinalis L. by high-performance capillary electrophoresis

ABSTRACTCarnosol and carnosic acid in Rosmarinus officinalis L. were separated by high-performance capillary electrophoresis using a 50 cm capillary, a 12 mmol/L 80:20 pH 9.9 borax:methanol buffer using 25 kV of applied voltage at 30°C with detection at 280 nm. Rosmarinus officinalis L. was extracted with methanol with ultrasound at 170 W and 50 kHz for 20 min. The precision, repeatability, and recovery of the method were evaluated. The calibration relationships for carnosol and carnosic acid were y = 2.331x + 5.92 from 0.01 to 0.160 mg/mL and y = 7.980x + 4.32 from 0.005 to 0.080 mg/mL, respectively. The established method allows the separation and quantification of carnosic acid and carnosol in R. officinalis from various locations in China.

Determination of Polyphenols in Lycium barbarum Leaves by High-Performance Liquid Chromatography–Tandem Mass Spectrometry

ABSTRACTHigh-performance liquid chromatography coupled with high-resolution mass spectrometry was used for the determination of polyphenols in Lycium barbarum leaves. Twenty compounds extracted by methanol–water were tentatively identified that included chlorogenic acids, flavonoids, and phenolic acids. Neochlorogenic acid, chlorogenic acid, cryptochlorogenic acid, isochlorogenic acid B, isochlorogenic acid A, and isochlorogenic acid C were identified in Chinese cultivated L. barbarum leaves for the first time. Caffeic acid and isoquercitrin were also present. The concentrations of these compounds in L. barbarum leaves were determined. The results showed that all analytes had linear calibration relationships with limits of detection from 0.318 to 3.35 ng mL−1. The polyphenols and flavonoids in L. barbarum leaves provided strong 2,2-diphenyl-1-picrylhydrazyl radical-scavenging capacity (IC50 of 23.1 ± 0.4 to 26.0 ± 0.4 µg mL−1). This method is suitable for the determination of polyphenols in L. barbarum leaves, which provide polyphenols with suitable antioxidant activity.

Parametrization of Chain Molecules in Dissipative Particle Dynamics.

This paper presents a consistent strategy for parametrization of coarse-grained models of chain molecules in dissipative particle dynamics (DPD), where the soft-core DPD interaction parameters are fitted to the activities in solutions of reference compounds that represent different fragments of target molecules. The intercomponent parameters are matched either to the infinite dilution activity coefficients in binary solutions or to the solvent activity in polymer solutions. The respective calibration relationships between activity and intercomponent interaction parameter are constructed from the results of Monte Carlo simulation of the coarse-grained solutions of reference compounds. The chain conformation is controlled by the near neighbor and second neighbor bond potentials, which are parametrized by fitting the intramolecular radial distribution functions of the coarse-grained chains to the respective atomistic molecular dynamics simulations. The consistency, accuracy, and transferability of the proposed parametrization strategy is demonstrated drawing on the example of nonionic surfactants of the poly(ethylene oxide) alkyl ether (CnEm) family. The lengths of tail and head sequences are varied (n = 8-12 and m = 3-9), so that the critical micelle concentration ranges from 10 to 0.1 mM. The surfactants are modeled at different coarse-graining levels using DPD beads of different diameters. We found consistent agreement with experimental data for the critical micelle concentration and aggregation number, especially for surfactants with relatively long hydrophilic segments. Depending on the system, we observed surfactant aggregation into spheroidal, elongated, or core-shell micelles, as well as into irregular agglomerates. Using the models at different coarse-graining levels for the same molecules, we found that the smaller the bead size the better is agreement with experimental data.

Calibration of soil moisture sensing with subsurface heated fiber optics using numerical simulation

AbstractThe heat pulse probe method can be implemented with actively heated fiber optics (AHFO) to obtain distributed measurements of soil water content (θ) by using reported soil thermal responses measured by Distributed Temperature Sensing (DTS) and with a soil‐specific calibration relationship. However, most reported applications have been calibrated to homogeneous soils in a laboratory, while inexpensive efficient in situ calibration procedures useful in heterogeneous soils are lacking. Here we employed the Hydrus 2‐D/3‐D code to define a soil‐specific calibration curve. We define a 2‐D geometry of the fiber optic cable and the surrounding soil media, and simulate heat pulses to capture the soil thermal response at different soil water contents. The model was validated in an irrigated field using DTS data from two locations along the FO deployment in which reference moisture sensors were installed. Results indicate that θ was measured with the model‐based calibration with accuracy better than 0.022 m3 m−3.

Measuring the sedimentation rate in a magnetorheological fluid column via thermal conductivity monitoring

Measuring sedimentation rate of magnetorheological fluids (MRFs) is of great importance when designing and synthesizing MRFs for engineering applications. A method of characterizing sedimentation rate in an MRF column is proposed utilizing thermal conductivity correlated with particle concentration. A series of MRF samples composed of carbonyl iron particles suspended in silicone oil were prepared, and their concentrations (measured as volume fraction, ∅) and thermal conductivities, k, were tested. A calibration curve was developed to relate particle concentration, ∅, to thermal conductivity, k, using this set of MRF samples with known concentration. The particle concentration, ∅, in the MRF column was then monitored by measuring thermal conductivities (k) at a fixed location and using this calibration relationship. Finally, sedimentation rate in the MRF column was determined by examining how particle concentration varied with time. The sedimentation rate measured in the MRF column was validated using visual observation of mudline (boundary between the topmost clarified fluid zone and MRF below).

Dynamics of Oxine-Copper in Pears and Soil by High-Performance Liquid Chromatography

ABSTRACTOxine-copper, which is used as a disinfectant for vegetables, was determined by high-pressure liquid chromatography (HPLC) with an ultraviolet detector. The calibration relationship was linear from 0.025 µg mL−1 to 20 µg mL−1 and good precision was obtained. The recovery was between 72.8 and 113.8%. The limits of quantification were 0.1 mg kg−1 in soil and 0.05 mg kg−1 in pears. The half-lives of oxine-copper in pears in 2011 and 2012 were 7.1 days and 7.8 days in Hebei, 10.1 days and 10.4 days in Shandong, and 4 days and 8.9 days in Henan. The half-lives of oxine-copper in soil in 2011 and 2012 were 8.1 days and 9.1 days in Hebei, 6.8 days and 8.6 days in Shandong, and 9.7 days and 8.9 days in Henan. The maximum residue of oxine-copper in pears was 1.64 mg kg−1.

Relationship of retinal vascular calibre and diabetic retinopathy in Chinese patients with type 2 diabetes mellitus: the Desheng Diabetic Eye Study.

To describe the relationship of retinal arteriolar and venular calibre with diabetic retinopathy (DR) and related risk factors, including glucose levels and other biomarkers in a Chinese population with type 2 diabetes mellitus (T2DM). A cross-sectional study. Patients with T2DM were recruited from a local community in urban Beijing. Seven fields 30° colour fundus photographs were taken and examined for the presence and severity of DR using a standardised grading system. Retinal vascular calibres were measured and expressed as average central retinal arteriolar and venular equivalent using a computer-based program. A total of 1340 patients with T2DM were included for analysis. Of these, 472 (35.22%) had DR. Wider retinal venular calibre, but not arteriolar calibre, was associated with increasing glucose and glycosylated haemoglobin A1c levels (p<0.006) and dyslipidaemia (p for trend <0.05). After adjusting for possible covariates, the higher quartile of retinal venular calibre was associated with higher prevalence of any DR (OR 2, 95% CI 1.36 to 2.95). Venular calibre increased from 224.33 μm in those without retinopathy to 231.21 μm in those with mild, 241.01 μm in those with moderate and 235.65 μm in those with severe retinopathy (p for trend <0.001). Arteriolar calibre was not associated with DR. In the current study, wider venular calibre, but not arteriolar calibre, was shown to be associated with development and increased severity of DR independently from other risk factors in a Chinese diabetic population.

Determination of Eriodictyol by a Modified Multi-Walled Carbon Nanotube Glassy Carbon Electrode

ABSTRACTA modified multi-walled carbon nanotube glassy carbon electrode was fabricated, and the electrochemical behavior of eriodictyol on the surface of the multi-walled carbon nanotubes was investigated in detail. The cyclic voltammetry of eriodictyol showed a significant enhancement of the anodic peak current and a negative shift of the anodic peak potential at the modified glassy carbon electrode compared to a bare glassy carbon electrode. These results indicated that the multi-walled carbon nanotubes catalyzed the oxidation of eriodictyol. A method for the electrochemical determination of eriodictyol was developed using differential pulse voltammetry. Under the optimized conditions, the calibration relationship between the anodic peak current and eriodictyol concentration was linear from 1.0 to 1.0 × 103 ng mL−1 with a detection limit of 0.33 ng mL−1. The device was validated for precision and accuracy and used to determine eriodictyol in peanut shells with satisfactory results.

Characterization of Paraoxon-ethyl and Parathion-ethyl Complexes with β-Cyclodextrin Modified Zirconium Oxide Thin Films by Infrared Spectroscopy

ABSTRACTThe detection of organophosphate compounds was demonstrated using sol–gel materials made of zirconia composite films. The detection was performed via inclusion complexes of the organophosphates of paraoxon-ethyl and parathion-ethyl with the zirconium dioxide-β-cyclodextrin composite film. The formation of sol–gel thin film process was investigated and optimized. The morphology of zirconium dioxide with β-cyclodextrin gel was characterized by scanning electron microscopy and energy-dispersive spectroscopy. Attenuated total reflectance Fourier transform infrared spectroscopy was used for the characterization of the inclusion complexes of paraoxon-ethyl and parathion-ethyl on zirconium dioxide with β-cyclodextrin film. The hydrolysis of paraoxon-ethyl by zirconium dioxide with the β-cyclodextrin gel thin film caused peak shifts in the attenuated total reflectance Fourier transform infrared spectra. The increase in absorption intensity correlated with increasing paraoxon-ethyl concentration, but this trend was not observed for parathion-ethyl. The hydroxyl vibration band of the intermolecular and intramolecular hydrogen bonds was observed to decline with increasing paraoxon-ethyl concentration. Quantitative analysis of paraoxon-ethyl using attenuated total reflectance Fourier transform infrared spectra provided a linear calibration relationship from 1 to 7 µM with a limit of detection as low as 30 nM.

Determination of iron in zeolite catalysts by a smartphone camera-based colorimetric analyzer

ABSTRACTA colorimetric analyzer was improved to determine iron in zeolites prepared by incipient wetness impregnation. Software was installed in an Android smartphone for measuring red, green, and blue light intensities. The blue color was suitable for creating a calibration relationship for iron. The optimum distance from the smartphone camera to the sample holder was 5 cm. The brightness was controlled by a table lamp with a 7 W light emitting diode located at 25 cm above the sample holder. Under these conditions, there was no influence from ambient light. A calibration equation was created from 0–1.2% (w/w) iron and stored in the program for analysis. The results agreed well with flame atomic absorption spectrophotometric measurements with a sample throughput exceeding 40 h−1. The relative standard deviation and the relative error were less than 1%. This method was convenient, rapid, simple, inexpensive, and easy with little chemical waste produced.

Validity of treadmill- and track-based individual calibration methods for estimating free-living walking speed and VO2 using the Actigraph accelerometer.

BackgroundFor many patients clinical prescription of walking will be beneficial to health and accelerometers can be used to monitor their walking intensity, frequency and duration over many days. Walking intensity should include establishment of individual specific accelerometer count, walking speed and energy expenditure (VO2) relationships and this can be achieved using a walking protocol on a treadmill or overground. However, differences in gait mechanics during treadmill compared to overground walking may result in inaccurate estimations of free-living walking speed and VO2. The aims of this study were to compare the validity of track- and treadmill-based calibration methods for estimating free-living level walking speed and VO2 and to explain between-method differences in accuracy of estimation.MethodsFifty healthy adults [32 women and 18 men; mean (SD): 40 (13) years] walked at four pre-determined speeds on an outdoor track and a treadmill, and completed three 1-km self-paced level walks while wearing an Actigraph monitor and a mobile oxygen analyser. Speed- and VO2-to-Actigraph count individual calibration equations were computed for each calibration method. Between-method differences in calibration equation parameters, prediction errors, and relationships of walking speed with VO2 and Actigraph counts were assessed.ResultsThe treadmill-calibration equation overestimated free-living walking speed (on average, by 0.7 km · h−1) and VO2 (by 4.99 ml · kg−1 · min−1), while the track-calibration equation did not. This was because treadmill walking, from which the calibration equation was derived, produced lower Actigraph counts and higher VO2 for a given walking speed compared to walking on a track. The prediction error associated with the use of the treadmill-calibration method increased with free-living walking speed. This issue was not observed when using the track-calibration method.ConclusionsThe proposed track-based individual accelerometer calibration method can provide accurate and unbiased estimates of free-living walking speed and VO2 from walking. The treadmill-based calibration produces calibration equations that tend to substantially overestimate both VO2 and speed.

A probability of benefit (AUC) approach to phase II cancer trials

For modern cytostatic but non-cytotoxic agents that result in stable disease without tumour shrinkage, traditional RECIST-defined measures of tumour response used in phase II trials may be less suitable than quantitative measures such as Ki67 proliferation index, change in tumour mass, or fluorothymidine (FLT) uptake. Dichotomising such measures is statistically inefficient. A better approach is to use the Mann-Whitney test. For this, assumptions are few, the sample size formula is simple, and it has an intuitive interpretation in terms of Probability of Benefit (ie the chance of a superior outcome on the new intervention). For phase II trials, discrimination between promising and unpromising treatments is more relevant than assessment of definitive outcomes and the common measure of discrimination offered by a test variable (the area under the receiver operating characteristic curve - AUC) is another interpretation of the Mann-Whitney statistic. Standard values of the AUC from diagnostic testing offer a ready-made calibration, and approximate but useful relationships to other common measures exist, including the hazard ratio, Cohen's standardised difference, the odds ratio, Pearson's correlation, and Number needed to Treat. Values of these measures corresponding to AUCs considered useful for diagnosis show that effects need to be much larger than typically used. This may not be a bad thing: sample sizes are smaller, yet if combined with a sensible likelihood ratio criterion for “strong” evidence, the risk of a misleading positive signal is small and the chance of failure in phase III is reduced.

Determination of Isomaltooligosaccharides in Milk Powder by Ultra-High Performance Liquid Chromatography–Tandem Mass Spectrometry

ABSTRACTIsomaltooligosaccharides are widely used in food with health benefits. A sensitive and selective method for the determination of three isomaltooligosaccharides is reported using ultra-high performance liquid chromatography–tandem mass spectrometry. The method was validated by characterization of the linearity, accuracy, precision, and the limits of detection and quantification. Under the optimized conditions, the calibration relationships were linear for the analytes with correlation coefficients exceeding 0.998. The recoveries were from 91.5% to 107.6% with coefficients of variation below 9.0%. The limits of detection and quantification were 1.20 µg mL−1 and 3.60 µg mL−1 for isomaltose, 0.15 µg mL−1 and 0.50 µg mL−1 for panose, and 0.55 µg mL−1 and 1.80 µg mL−1 for isomaltotriose. The validated method was employed for the determination of isomaltooligosaccharides in milk powder.

Refinement of major- and minor-element PIXE analysis of rocks and minerals

An attempt has been made to assess the accuracy of the particle-induced X-ray emission (PIXE) fundamental parameters with standards approach to quantifying major- and minor-element constituents of silicate glasses and minerals. A deviation from linearity at low energies in the channel-energy calibration relationship was identified as a source of undesired residues in GUPIX-fitting. A correction for this effect was developed using a general-purpose spectrum fitting program and was incorporated in GUPIX. The PIXE spectra of sixteen well-characterized electron microprobe standards were then processed. Complementary electron probe micro-analysis (EPMA) measurements were used to support the comparison of the PIXE results with previous characterizations. Major element concentrations were found to differ on average from literature values as follows: SiO2 (−0.28±0.12%), Al2O3 (0.72±0.74%), MgO (0.11±0.63%), Na2O (−2.6±1.2%), K2O (1.1±0.7%), CaO (−0.35±0.37%), TiO2 (2.5±1.9%), MnO (0.8±4.7%), FeO (0.98±0.93%). These results indicate that major and minor elemental analysis can be achieved with high accuracy using the present Guelph micro-PIXE setup.

Calibration of Water Content Reflectometer Sensors with a Large Soil Sample

In situ measurement of soil water content is of fundamental importance in vadose zone processes. While time domain reflectometry (TDR) is a universally accepted technique, having been developed since the 1980s, water content reflectometer (WCR) is still a relatively new technique and does not hold a similar background. The main goal of this study was to establish an accurate calibration curve for WCR sensors to be installed in an artificial hillslope designed to study the triggering of shallow landslides. Therefore, high accuracy calibration at the high end of the water content range and for large soil volumes was necessary. An experimental device was specifically designed to provide a calibration procedure for a soil control volume commensurate with the application scale of the probes in the hillslope. A large box container (60 by 50 by 60 cm) was used, inside which three WCR probes and three tensiometers were arranged. A drip emitter produced assigned flow rates, while a load cell at the base measured the time evolution of the infiltrated water mass. Water content was evaluated at approximately steady-state flow conditions for infiltration and drainage experiments, performed with varying degrees of compaction to detect the effect of the porosity on the calibration curve. The experimental results suggest a calibration relationship linearly depending not only on the WCR output signal but also on the porosity. In addition, the calibration curve provided by the manufacturer significantly underestimates the soil water content, with a range of predicted volumetric water content values between 3 and 35%, compared with actual values varying between 19 and 61%.

Nitroprusside as a Novel Reagent for Flow Injection Spectrophotometric Determination of Captopril

ABSTRACTA novel flow injection system for the determination of captopril in pharmaceutical formulations is described. Nitroprusside was employed as a new, nontoxic reagent. Captopril reacted with nitroprusside in basic solution to yield a red chromophore with maximum absorbance at 521 nm. The calibration relationship was linear for concentrations from 3.0 × 10−6 to 1.0 × 10−3 mol L−1 with a limit of detection of 1.0 × 10−6 mol L−1. The recoveries from captopril tablets were between 99.7 and 102.3%. The sampling frequency was 50 h−1 and the relative standard deviation was estimated to be 1.0% for 5.0 × 10−4 mol L−1 captopril. A paired t-test showed that analysis of tablets by the flow procedure and a potentiometry provided similar results at the 95% confidence level.