CL Method Research Articles

Laccase immobilisation on Poly(ethylene) terephthalate grafted with maleic anhydride (PET-g-MAH) nanofiber mat

A comparative study was carried out on three different enzyme immobilisation methods which were physical adsorptions (PA), covalent bonding (CV) and covalent bonding of cross-linked enzyme aggregates (CL) for laccase immobilisation on Poly(ethylene) Terephthalate (PET) grafted with Maleic Anhydride (MAH) nanofiber mats. The chemically inert PET was successfully grafted with MAH at temperature between 40 – 45 °C and used as the carrier to immobilised laccase in the form of electrospun nanofiber mats. The peaks from carbonyl (C=O) and alkene (C=C) groups appeared on the spectral subtraction between PET and PET-g-MAH nanofiber mats. These groups might be the potential group to form covalent bond between the amine groups of laccase enzyme. Laccase immobilised on the PET-g-MAH nanofiber mats using CL methods using glutaraldehyde as crosslinker gave the best performance with the highest enzyme loading and immobilisation yield which were 40.88 μg/mg and 48.37 %. On top of that, the immobilised laccase on PET-g-MAH nanofiber mats also managed to retain 69.01 % of its initial activity after 10 repeated cycles of 2, 2-azino-bis 3-ethylbenzothiazoline-6-sulfonic acid (ABTS) oxidations. These results demonstrate that PET-g-MAH nanofiber is a good material to be considered as laccase carrier.

ВИЗНАЧЕННЯ ОРТОФОСФАТУ У ВОДАХ МЕТОДОМ ТВЕРДОФАЗНОЇ ХЕМІЛЮМІНЕСЦЕНЦІЇ

Phosphorus is one of the most important nutrients. Excessive content of its compounds in water objects leads to eutrophication, as well as reduces water quality. Methods based on the formation of molybdophosphate heteropolyacid (HPA) in an acidic medium with its subsequent reduction and spectrophotometric detection of the formed reduced "blue" HPA are most often used to determine phosphorus compounds. These methods are unsuitable for the analysis of waters with a phosphorus content <40 μg /L. The use of the chemiluminescent method (CL) makes it possible to increase the sensitivity of the determination, but CL detection in an acidic medium under the conditions of formation of HPA is limited by the existing indicator systems. To increase the selectivity of the method for determining the microquantities of phosphate relative to metal ions, we used an approach based on the adsorption removal of analyte with next determination using the CL method. Previous removal of phosphate from an aqueous solution in the form of reduced molybdostibiumphosphate HPA was released using batch technique in optimal conditions of its formation in the solution. Silica modified with cetyltrimethylammonium bromide was used as anion exchange adsorbent. Then the concentrate was processed with alkaline lucigenin solution and registration of the CL glow resulting from the reaction. Under optimal conditions of phosphate determination, the calibration curve is linear in the range from 3.7 to 147 μg PO43–/L with a detection limit of 0.8 μg PO43–/L. Cations K+, Na+, Fe(III), Mo(VI), NH4+ and anions Cl–, F–, HCO3–, С4Н4О62–, Asc–, NO2–, SO42–, as well as EDTA, do not interfere. Silicates (SiO32–) do not interfere with the determination of phosphate, even in 100-fold excess. Nitrates at concentrations below the average content in drinking water do not interfere with the determination. The developed technique was tested on a sample of pump room water. The technique is characterized by high sensitivity and a wide range of detectable concentrations. It is not inferior in sensitivity to flow methods using fluorescent or chemiluminescent detection.

A Green Analytical Method for the Multielemental Determination of Halogens and Sulfur in Pet Food

A suitable and green analytical method using microwave-induced combustion and ion chromatography with conductivity detection (IC-CD) and mass spectrometry detection (IC-MS) was proposed for the halogens and sulfur determination in pet food using a single analysis. Samples (up to 500 mg) were efficiently digested in a closed system under oxygen pressure (20 bar). Ultrapure water and 50 mmol L−1 or 100 mmol L−1 (NH4)2CO3 were evaluated as absorbing solutions. Trueness was evaluated by recovery tests using standard solution and certified reference materials. In both tests, mean recoveries ranging from 91 to 108% for all analytes were obtained using 50 mmol L−1 (NH4)2CO3 as absorbing solution. AOAC International recommended official methods for Cl and F determination in animal feed were also performed. Results for Cl using proposed method were in agreement with those obtained using AOAC official method, while the results for F were not compared between them because the concentration in the samples using AOAC official method was not detected. Precision was evaluated in terms of repeatability and the relative standard deviations (RSDs) using the proposed method were always lower than 8%. The proposed method presents several advantages when compared with AOAC International official methods such as the multielemental determination capability, lower waste generation, lower limits of detection, lower RSDs, and higher sample throughput. Sixteen samples destined to cats or dogs from different manufacturers were analyzed and the results showed a wide variation. These results indicate that an efficient quality control should be performed, and the proposed method is an excellent alternative as a new analytical tool for routine analysis of pet food.

EFL Learners’ Reflections on Cooperative Learning: Issues of Implementation

This study has described and identified the opinions and experiences of the EFL learners who participated in CL English lessons. The participants in this study were 10 tenth-grade male students, aged 14-15 years in four boys’ secondary schools in Al-Baha city. Two English teachers were asked to implement cooperative learning in their classrooms for 12 weeks. The researcher interviewed ten randomly selected students from the cooperative learning classes at the end of the study.The results and findings of this study showed that most students found that CL enabled them to improve their English skills, make new relationships with others classmates, perform different roles, improve their oral presentation skills, build their self confidence, take on responsibility, respect different opinions and offer their different views, increase their motivation, and develop their friendships with their classmates.However, there were few drawbacks and obstacles to using the CL method. These included: low achiever EFL learners depending on high achiever learners, classmates not giving group members a chance to state their opinions, and poor group member distribution and supervision by the teacher. In the following chapter, the researcher presents a general discussion of the results in this study.

Prospects for using a new sequential chemiluminescence strategy for monitoring the caffeine content in soft and energy drinks via the catalytic activities of different nano-metal oxides.

This article suggests a new sequential injection analysis chemiluminescence (SIA-CL) strategy for monitoring the caffeine (CAF) content in soft and energy drinks using the catalytic activities of different nano-metal oxides. The present study describes three different SIA-CL systems (luminol-ferricyanide (III) coupled with Fe2 O3 or ZnO nanoparticles (NPs), and luminol-H2 O2 coupled with CuONPs. All experimental conditions were optimized and the linear concentration ranges of pure CAF were evaluated using the calibration graphs. The selectivity of the developed SIA-CL systems was studied under the influence of various interfering species that may be present in soft or energy drinks such as sodium ions, sucrose, glucose, sodium benzoate, sodium citrate, riboflavin, niacin, citric, phosphoric and ascorbic acids. International Council for Harmonization (ICH) guidelines were obeyed for the validation of the suggested CL methods. The developed SIA-CL systems displayed linear relationships over the concentration ranges 1.0-350, 5.0-400 and 10.0-400μgml-1 with Fe2 O3 NPs, ZnO NPs and CuO NPs, respectively. The recorded lower limits of detection and quantification were 0.7, 2.7 and 7.8μgml-1 , and 1.0, 5.0 and 10.0μgml-1 for the previously mentioned SIA-CL systems. The results revealed high selectivity for CAF determination and were in good agreement with those obtained by other reported methods.

Integral concurrent learning: Adaptive control with parameter convergence using finite excitation

SummaryConcurrent learning (CL) is a recently developed adaptive update scheme that can be used to guarantee parameter convergence without requiring persistent excitation. However, this technique requires knowledge of state derivatives, which are usually not directly sensed and therefore must be estimated. A novel integral CL method is developed in this paper that removes the need to estimate state derivatives while maintaining parameter convergence properties. Data recorded online is exploited in the adaptive update law, and numerical integration is used to circumvent the need for state derivatives. The novel adaptive update law results in negative definite parameter error terms in the Lyapunov analysis, provided an online‐verifiable finite excitation condition is satisfied. A Monte Carlo simulation illustrates improved robustness to noise compared to the traditional derivative formulation. The result is also extended to Euler‐Lagrange systems, and simulations on a two‐link planar robot demonstrate the improved performance compared to gradient‐based adaptation laws.

β-Cyclodextrin functionalization of metal-organic framework MOF-235 with excellent chemiluminescence activity for sensitive glucose biosensing

Herein, we developed a new CL method for the detection of glucose, exhibiting high sensitivity, low limit of detection, good stability and reliability for analysis of real biological samples. The MOF-235/β-cyclodextrin (β-CD) hybrids were facilely prepared by a simple method, and characterized by XRD, TGA, FT-IR and SEM. The as-prepared hybrids exhibited highly catalytic activity for the hydrogen peroxide-luminol system, and gave more than 30-fold enhancement in CL response as compared with that of hydrogen peroxide-luminol system, thus could be used for sensitive detection of H2O2 and glucose. The excellent catalytic performance of the MOF-235/β-CD hybrids is ascribed to the large surface area of MOF-235 as well as the synergistic effect between β-CD and MOF-235. The proposed sensing strategy coupled with CL detection method showed low detection limits of 5 nM and 10 nM for H2O2 and glucose, respectively. Successful application of the MOF-235/β-CD hybrid in CL assay of glucose in real human serum samples is demonstrated as an efficient catalyst for sensitive chemiluminescence-based analyses. The success of this work favors to facilitate the future development in CL catalysts via MOF functionalization.

Quantitative Monitoring of Cefradine in Human Urine Using a Luminol/Sulfobutylether–β-Cyclodextrin Chemiluminescence System

In this paper, a sensitive, rapid, and simple flow-injection chemiluminescence (FI-CL) technique is described for determining cefradine in human urine and capsule samples at the picogram level. The results show that cefradine within 0.1–100.0 nmol/L quantitatively quenches the CL intensity of the luminol/sulfo butylether–β-cyclodextrin (SBE–β-CD) system, with a relative correlation coefficient r of 0.9931. Subsequently, the possible mechanism for the quenching phenomenon is discussed in detail using the FI-CL and molecular docking methods. The proposed CL method, with a detection limit of 0.03 nmol/L (3σ) and relative standard deviations <3.0% (N = 7), is then implemented to monitor the excretion of cefradine in human urine. After orally administration, the cefradine reaches a maximum value of 1.37 ± 0.02 mg/mL at 2.0 h in urine, and the total excretion is 4.41 ± 0.03 mg/mL within 8.0 h. The absorption rate constant ka, the elimination rate constant ke, and the half-life t1/2 are 0.670 ± 0.008 h−1, 0.744 ± 0.005 h−1, and 0.93 ± 0.05 h, respectively.

Seismic behavior comparison of reinforced concrete interior beam-column joints based on different loading methods

Due to the difference in loading point, experimental researches on seismic behavior of beam-column joint can be generally divided into two types, namely loading at beam ends (BL method) and loading at column top end (CL method). This paper presents an experimental investigation aimed at comparing the cyclic behavior of interior beam-column joints with different loading methods. Four groups of full-scale interior beam-column subassemblages were tested under reversed cyclic loading. Two identical specimens were tested under two different loading methods in each group. On the basis of the experimental results, the paper discusses the distinctions of cyclic behaviors under different loading methods in terms of crack pattern, joint shear strength, joint shear transfer mechanism, joint shear deformation, longitudinal bar-slip, energy dissipation, and stiffness degradation. In addition, a numerical simulation of these four groups of specimens is shown and discussed. The experimental results and numerical analyses confirm that the loading method can have certain influence on the cyclic behavior of the beam-column joints. The joint shear strength, joint shear deformation and longitudinal beam bar slip of beam-ends loading specimens (BL specimens) are considerably larger than that of column-end loading specimens (CL specimens), although the loading protocol used for CL method is more severe than BL method in terms of number of loading cycles. In consequence, the influence of loading method should be considered when the seismic behavior of the beam-column joint is evaluated according to a great number of existing beam-column joint tests.

Facile synthesis of upconversion nanoparticles with high purity using lanthanide oleate compounds

A novel strategy for preparing highly pure NaYF4-based upconversion nanoparticles (UCNPs) was developed using lanthanide oleate compounds [Ln(OA)3] as the precursor, denoted as the Ln–OA preparation method. Compared to the conventional solvothermal method for synthesizing UCNPs using lanthanide chloride compounds (LnCl3) as the precursor (denoted as the Ln–Cl method), the Ln–OA strategy exhibited the merits of high purity, reduced purification process and a uniform size in preparing core and core–shell UCNPs excited by a 980 or 808 nm near infrared (NIR) laser. This work sheds new insight on the preparation of UCNPs and promotes their application in biomedical fields.

Measurement of Cl− : Br−Ratios in the Porewater of Clay-Rich Rocks—A Comparison of the Crush-and-Leach and the Paper-Absorption Methods

Characterization of porewater chemistry in low-permeability, clay-rich rocks provides insights into solute transport mechanisms and the origin and residence time of porewater. Extraction of porewater for chemical quantification is challenging, and several methods have been applied including squeezing, advective displacement, crush and leach, and a relatively new technique that extracts porewater by absorption into a cellulosic paper by capillary action. Here we compare porewater Cl−and Br−mass ratios from samples using the paper-absorption and crush-and-leach techniques. Samples were obtained from Upper Ordovician shales in the Michigan Basin in Ontario, the Opalinus Clay at the Mont Terri Rock Laboratory in Switzerland, and the Upper Ordovician Lorraine Group shale in southern Quebec. The data display consistent and reproducible differences among methods for Cl−and Br−mass ratios, with the paper-absorption method producing systematically lower Cl− : Br−ratios. The observed differences in Cl− : Br−ratios are attributed primarily to anion exclusion effects which are stronger for Br−than for Cl−, resulting in higher Br−concentrations in the largest pores that are preferentially sampled by the paper-absorption technique. In addition, calculations suggest that Cl−is more effective than Br−in forming ion pairs and clusters with neutral or positive charge which can enter the diffuse double layer. This causes a further decrease in the Cl− : Br−ratios for the mobile water. One important message from this work is that different extraction methods should not be expected to converge on a unique porewater Cl− : Br−ratio because each method reflects different proportions of the interlayer, diffuse double layer, and mobile fractions of porewater.

PP.27.02] PERFORMANCE OF FULLY AUTOMATED CHEMILUMINESCENCE ALDOSTERONE IMMUNOASSAY IN A POPULATION OF HYPERTENSIVE PATIENTS

Objective: Verify, retrospectively the ARR threshold in a population of hypertensive patients investigated for PA, and to attest the precision of the new method in intra venous salt loading (ivSLT) as confirmatory test. Design and method: We compared aldosterone results obtained with the CL method and RIA in stored blood samples from hypertensive patients investigated for PA (102 baseline and 85 after ivSLT). Results: A very good correlation between RIA and CL aldosterone assays was found in the all population for both aldosterone (r 0.922) and ARR (r 0.977). For the ARR, Deming regression demonstrated a good accordance between methods, and according to the fit model, considering our institutional cut-off of 32 pg/ml/pg/ml, the corresponding ARR cut off with CL aldosterone assay is 20 pg/ml/mUL. However, the correlation was was lower in the low end of aldosterone concentrations (r 0.676 for aldosterone <100 pg/ml by RIA). Accordingly, results of ivSLT with both assays were concordant in only 66% of patients. Conclusions: CL assay displays an accuracy similar to RIA for ARR screening, but its diagnostic accuracy remains suboptimal in the low end of aldosterone concentrations, which characterizes the setting of confirmatory tests such as ivSLT.

Determination of urea in milk based on N-bromosuccinimide–dichlorofluorescein postchemiluminescence method

A new postchemiluminescence (PCL) reaction was observed when urea was injected into the reaction mixture after the CL reaction of N-bromosuccinimide and dichlorofluorescein. A possible reaction mechanism was proposed based on the studies of the CL kinetic characteristics, CL spectra, fluorescence spectra, and other experiments. A new flow injection CL method for the determination of urea was established based on the PCL reaction. The relative standard deviation for the determination of urea was 1.3% (n = 11, c = 5.0 × 10−8 g/mL). The CL intensity responded linearly to the concentration of urea in the range 2.0 × 10−9–1.0 × 10−6 g/mL (r = 0.9992). The detection limit was 7 × 10−10 g/mL. The method had been applied to the determination of urea in milk with satisfactory results.

Trace Analysis of Sinomenine Hydrochloride Using CdTe/CdS Quantum Dots-enhanced Chemiluminescence.

A novel flow-injection chemiluminescence (FI-CL) method was described for the determination of sinomenine hydrochloride (SIN). The method was based on the inhibitory effect of SIN on the CL reaction of luminol and K3Fe(CN)6 in an alkaline solution, which was sensitized by CdTe/CdS quantum dots (QDs). Under the optimized conditions, the linear range for the determination of SIN was 1.0 × 10(-8) to 1.4 × 10(-6) mol/L. The detection limit was 7.5 × 10(-9) mol/L, and the relative standard deviation was 2.47% (n = 11). The current CL method was applied to determine SIN in pharmaceutical formulations and biological fluids with satisfactory results. The possible CL reaction mechanism was discussed briefly.

Feasibility of halogen determination in noncombustible inorganic matrices by ion chromatography after a novel volatilization method using microwave-induced combustion

A microwave-induced combustion (MIC) system based on the volatilization process was applied for subsequent halogen determination from noncombustible inorganic matrices. Portland cement samples were selected to demonstrate the feasibility of the proposed method, allowing the subsequent determination of Cl and F by ion chromatography (IC). Samples were mixed with high-purity microcrystalline cellulose, wrapped with a polyethylene film and combusted in quartz closed vessels pressurized with oxygen (20bar). Water and NH4OH (10, 25 or 50mmolL−1) were evaluated for Cl and F absorption, but water was selected, using 5min of reflux after volatilization. Final solutions were also suitable for analysis by pontentiometry with ion-selective electrode (ISE) for both analytes, and no difference was found when comparing the results with IC. The accuracy of the proposed method for Cl was evaluated by analysis of certified reference materials (CRMs), and agreement with certified values ranged from 98% to 103%. Results were also compared to those using the procedure recommended by the American Society of Testing and Materials (ASTM) for the determination of total chlorides (C114-13), and no difference was found. Volatilization by MIC using a mixture of cement, cellulose and a biological CRM was carried out in order to evaluate the accuracy for F, and recovery was about 96%. The proposed method allowed suitable limits of detection for Cl and F by IC (99 and 18mgkg−1, respectively) for routine analysis of cement. Using the proposed method, a relatively low standard deviation (<7%), high throughput (up to eight samples can be processed in less than 30min) and lower generation of laboratory effluents, when compared to the ASTM method, were obtained. Therefore, the method for volatilization of Cl and F by MIC and subsequent determination by IC can be proposed as a suitable alternative for cement analysis.

Parameterization of the DFTB3 method for Br, Ca, Cl, F, I, K, and Na in organic and biological systems.

We present an extension to the recent 3OB parametrization of the Density Functional Tight Binding Model DFTB31,2 for biological and organic systems. Parameters for the halogens F, Cl, Br, and I have been developed for use in covalently bound systems and benchmarked on a test set of 106 molecules (the ‘OrgX’ set), using bonding distances, bonding angles, atomization energies, and vibrational frequencies to assess the performance of the parameters. Additional testing has been done with the X40 set of 40 supramolecular systems containing halogens,3 adding a simple correction for the halogen bonds that are strongly overbound in DFTB3. Furthermore, parameters for Ca, K, and Na as counterions in biological systems have been created. To benchmark geometries as well as ligand binding energies a test set ‘BioMe’ of 210 molecules has been created that cover coordination to various functional groups frequently occurring in biological systems. The new DFTB3/3OB parameter set outperforms DFT calculations with a double-ζ basis set in terms of energies and can reproduce DFT geometries, with some minor deviations in bond distances and angles due to the use of a minimal basis set.

Skeletal muscle water and electrolytes following prolonged dehydrating exercise.

We studied if dehydrating exercise would reduce muscle water (H2Omuscle ) and affect muscle electrolyte concentrations. Vastus lateralis muscle biopsies were collected prior, immediately after, and 1 and 4 h after prolonged dehydrating exercise (150 min at 33 ± 1 °C, 25% ± 2% humidity) on nine endurance-trained cyclists (VO2max = 54.4 ± 1.05 mL/kg/min). Plasma volume (PV) changes and fluid shifts between compartments (Cl(-) method) were measured. Exercise dehydrated subjects 4.7% ± 0.3% of body mass by losing 2.75 ± 0.15 L of water and reducing PV 18.4% ± 1% below pre-exercise values (P < 0.05). Right after exercise H2Omuscle remained at pre-exercise values (i.e., 398 ± 6 mL/100 g dw muscle(-1)) but declined 13% ± 2% (342 ± 12 mL/100 g dw muscle(-1); P < 0.05) after 1 h of supine rest. At that time, PV recovered toward pre-exercise levels. The Cl(-) method corroborated the shift of fluid between extracellular and intracellular compartments. After 4 h of recovery, PV returned to pre-exercise values; however, H2Omuscle remained reduced at the same level. Muscle Na(+) and K(+) increased (P < 0.05) in response to the H2Omuscle reductions. Our findings suggest that active skeletal muscle does not show a net loss of H2O during prolonged dehydrating exercise. However, during the first hour of recovery H2Omuscle decreases seemly to restore PV and thus cardiovascular stability.

Development of a novel method for detection ofClostridium difficileusingHS‐SPME‐GC‐MS

A novel method has been developed that allows successful differentiation between Clostridium difficile culture-positive and culture-negative stool samples based on volatile organic compound (VOC) evolution and detection by headspace solid-phase microextraction coupled with gas chromatography mass spectrometry (HS-SPME-GC-MS). The method is based on the activation of p-hydroxyphenylacetate decarboxylase produced by Cl. difficile and the detection of a specific VOC, that is 2-fluoro-4-methylphenol from an enzyme substrate. In addition, other VOCs were good indicators for Cl. difficile, that is isocaproic acid and p-cresol, although they could not be used alone for identification purposes. One hundred stool samples were tested, of which 77 were positive by culture. Detection using HS-SPME-GC-MS allowed confirmation of the presence of Cl. difficile within 18 h with a sensitivity and specificity of 83·1 and 100%, respectively. It is recommended that this new approach could be used alongside conventional methods for Cl. difficile detection, including toxin detection methods, which would allow any false-negative results to be eliminated. The ability to identify Cl. difficile-positive stool samples by the analysis of VOCs could allow the development of a VOC detection device which could allow rapid diagnosis of disease and hence prompt treatment with appropriate antibiotics.

Cosmological parameter estimation with large scale structure observations

We estimate the sensitivity of future galaxy surveys to cosmological parameters, using the redshift dependent angular power spectra of galaxy number counts, Cℓ(z1,z2), calculated with all relativistic corrections at first order in perturbation theory.We pay special attention to the redshift dependence of the non-linearity scale and present Fisher matrix forecasts for Euclid-like and DES-like galaxy surveys. We compare the standard P(k) analysis with the new Cℓ(z1,z2) method. We show that for surveys with photometric redshifts the new analysis performs significantly better than the P(k) analysis. For spectroscopic redshifts, however, thelarge number of redshift bins which would beneeded to fully profit from the redshift information, is severely limited by shot noise.We also identify surveys which can measure the lensing contribution and we study the monopole, C0(z1,z2).

Preliminary Results of Double-Bundle Anterior Cruciate Ligament Reconstruction and Technique-Specific Problems

Background: In this study, we determined the efficiency of anterior cruciate ligament (ACL) reconstruction using the double-bundle technique and addressed technique-specific problems. Patients and Methods: Twenty-nine patients who underwent ACL reconstruction due to ACL rupture with the arthroscopic double-bundle ENDOBUTTON CL method using autogenous hamstring tendons were evaluated. All patients were males and the mean age was 24.3 years (range 20 - 41 years). The mean follow-up period was 36.4 months (minimum 16 and maximum 53 months). Diagnosis was based on medical history and physical examination. Lachman, anterior drawer and pivot shift tests were performed. The patient diagnosis was verified with X-ray roentgenogram and magnetic resonance imaging (MRI). Tunnel mergence and graft hanging problems were discussed. Results: Pre- and postoperative clinical assessments of the patients showed the mean Lysholm score increased from 60.2 (48 - 72) preoperatively to 91.5 (85 - 98) at the final visit, whereas the mean Tegner score increased from 5.58 (3 - 9) preoperatively to 6.03 (4 - 9) at the final visit. According to the International Knee Documentation Committee (IKDC) knee ligament standard evaluation system, five patients were classified as B (17%); 11 patients were classified as C (38%); and 13 patients were classified as D (45%) before the surgery. At the postoperative evaluation, 17 (59%) patients were classified as A; 11 (38%) patients were classified as B; and 1 (3%) patient was classified as C. Conclusion: The double-bundle technique using hamstring tendons and femoral braces is an efficient and satisfactory method for ACL reconstruction.