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Journal articles on the topic 'Coupled two-dimensional HPLC systems'

Author: Grafiati

Published: 4 June 2021

Last updated: 20 February 2023

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1

Kirby, Jason, William Maher, Michael Ellwood, and Frank Krikowa. "Arsenic Species Determination in Biological Tissues by HPLC - ICP - MS and HPLC - HG - ICP - MS." Australian Journal of Chemistry 57, no. 10 (2004): 957. http://dx.doi.org/10.1071/ch04094.

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The use of high-pressure liquid chromatography coupled directly or by a hydride generation system to an inductively coupled plasma mass spectrometer for the unambiguous measurement of 13 arsenic species in marine biological extracts is described. The use of two chromatography systems; a Supelcosil LC-SCX cation-exchange column eluted with a 20 mM pyridine mobile phase adjusted to pH 2.2 and 2.6 with formic acid, with a flow rate of 1.5 mL min−1 at 40°C, and a Hamilton PRP-X100 anion-exchange column eluted with 20 mM NH4H2PO4 buffer at pH 5.6, with a flow rate of 1.5 mL min−1 at 40°C, was required to separate and quantify cation and anion arsenic species. Under these conditions, arsenous acid could not be separated from other arsenic species and required the use of an additional hydride generation step. Arsenic species concentrations in a locally available Tasmanian kelp (Durvillea potatorum), a certified reference material (DORM-2), and a range of commercially available macroalgae supplements and sushi seaweeds have been measured and are provided for use as in-house quality control samples to assess the effectiveness of sample preparation, extraction, and measurement techniques.

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2

Pinho, Carina, Zita E. Martins, Catarina Petisca, Agata M. Figurska, Olívia Pinho, and Isabel M. P. L. V. O. Ferreira. "Size exclusion and reversed-phase high-performance liquid chromatography/UV for routine control of thermal processing of cows' and donkey milk major proteins." Journal of Dairy Research 79, no. 2 (March 16, 2012): 224–31. http://dx.doi.org/10.1017/s0022029912000064.

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Cows' and donkey milks (raw and thermally processed) and respective whey were analysed for quantification of major proteins. Two different chromatographic approaches, size exclusion (SE-HPLC) and reversed-phase high performance liquid chromatography (RP-HPLC) both coupled to UV detection were used. Usefulness of these methods for routine control of the effect of thermal processing was evaluated. The external standard method was used to calibrate the SE-HPLC and RP-HPLC systems. Concerning quantification of β-lactoglobulin (β-lg), α-lactalbumin (α-la), lysozyme (lys), and total casein (cn), no significant differences between results obtained by SE-HPLC and by RP-HPLC (t-test, P>0·05) were observed for raw milks and whey. Heating of cows' milk promoted aggregation of denatured proteins as observed by SE-HPLC, whereas α-la and β-lg from donkey milk were stable to thermal processing at 100°C (5 min). Lys was quantified in donkey raw milk and whey however, in thermally processed donkey milk lys was denatured and could not be quantified by HPLC.

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3

Veizerová, L., J. Piešťanský, K. Maráková, J. Galba, D. Rauová, S. Dokupilová, E. Havránek, and P. Mikuš. "Comparison of column-coupled electrophoresis with liquid chromatography methods in food analysis of quinine." Acta Facultatis Pharmaceuticae Universitatis Comenianae 59, no. 1 (January 1, 2012): 67–80. http://dx.doi.org/10.2478/v10219-012-0011-y.

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Comparison of column-coupled electrophoresis with liquid chromatography methods in food analysis of quinineComparison of column-coupled electrophoresis with liquid chromatography methods in food analysis of quinine (QUI) is presented in this work. The capillary isotachophoresis (CITP) on-line coupled with capillary zone electrophoresis (CZE) and hyphenated with fibre-based spectrophotometric diode array detection (DAD) was compared with, (i) high performance liquid chromatography (HPLC) method with DAD detection, and (ii) HPLC method with fluorescence detection (FD). These methods were compared through their performance parameters and determined concentrations of QUI in beverages. The concentrations of QUI in two selected bitter drinks determined by the CITP-CZE-DAD method were in a good accordance with the HPLC-DAD and HPLC-FD methods. In addition, the electrophoretic method, as well as the chromatographic methods, was able to separate potential QUI related impurities from the QUI peak. The CITP-CZE-DAD method provided excellent performance parameters that were comparable (precision, accuracy, LOD, robustness) or even better (separation efficiency) than those ones provided by the chromatographic methods. Moreover, the effectivity of the electrophoresis method was higher when considering cost of analysis (equipment, consumption of separation systems), environmental aspects (organicvs. aqueous solvents), on-line sample pretreatment (CITP preconcentration and sample clean-up suitable also for the more complex matrices). Considering these findings, CITP-CZE-DAD was approved as a routine automatized method for the highly reliable quality food control.

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4

Fang, Lei, Hua Zhang, Jie Zhou, Yanling Geng, and Xiao Wang. "Rapid Screening and Preparative Isolation of Antioxidants fromAlpinia officinarumHance Using HSCCC Coupled with DPPH-HPLC Assay and Evaluation of Their Antioxidant Activities." Journal of Analytical Methods in Chemistry 2018 (2018): 1–6. http://dx.doi.org/10.1155/2018/3158293.

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An efficient method using high-speed counter-current chromatography (HSCCC) coupled with DPPH-HPLC assay has been developed for rapid screening and preparative isolation of antioxidants from ethyl acetate fraction ofAlpinia officinarumHance. Target-guided by DPPH-HPLC assay, two antioxidants, galangin and kaempferide, were targeted and further separated with purities of 99.3% and 98.5% by HSCCC using petroleum ether–ethyl acetate–methanol–water (0.8 : 1 : 1 : 0.8,v/v) as the solvent system. The antioxidant activities of galangin and kaempferide were further evaluated by measuring their inhibiting effects on superoxide anion radical, hydroxyl radical, and hydrogen peroxide in different luminol chemiluminescence (CL) systems. As a result, galangin and kaempferide both showed potent antioxidant activities. Results of the present study indicated that the combinative method by offline coupling DPPH-HPLC and HSCCC could be widely applied for rapid screening and isolation of antioxidants from complex TCM extract.

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5

Pan, Ru, Dejia Shao, Xueyong Qi, Yun Wu, Wenyan Fu, Yanru Ge, and Haizhen Fu. "Extraction of trace tilmicosin in real water samples using ionic liquid-based aqueous two-phase systems." Water Science and Technology 67, no. 8 (April 1, 2013): 1671–77. http://dx.doi.org/10.2166/wst.2013.015.

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The effective method of ionic liquid-based aqueous two-phase extraction, which involves ionic liquid (IL) (1-butyl-3-methyllimidazolium chloride, [C4mim]Cl) and inorganic salt (K2HPO4) coupled with high-performance liquid chromatography (HPLC), has been used to extract trace tilmicosin in real water samples which were passed through a 0.45 μm filter. The effects of the different types of salts, the concentration of K2HPO4 and of ILs, the pH value and temperature of the systems on the extraction efficiencies have all been investigated. Under the optimum conditions, the average extraction efficiency is up to 95.8%. This method was feasible when applied to the analysis of tilmicosin in real water samples within the range 0.5–40 μg mL−1. The limit of detection was found to be 0.05 μg mL−1. The recovery rate of tilmicosin was 92.0–99.0% from the real water samples by the proposed method. This process is suggested to have important applications for the extraction of tilmicosin.

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6

Hafner, Verena, David Czock, Jürgen Burhenne, Klaus-Dieter Riedel, Jürgen Bommer, Gerd Mikus, Christoph Machleidt, Thomas Weinreich, and Walter E. Haefeli. "Pharmacokinetics of Sulfobutylether-Beta-Cyclodextrin and Voriconazole in Patients with End-Stage Renal Failure during Treatment with Two Hemodialysis Systems and Hemodiafiltration." Antimicrobial Agents and Chemotherapy 54, no. 6 (April 5, 2010): 2596–602. http://dx.doi.org/10.1128/aac.01540-09.

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ABSTRACT Sulfobutylether-beta-cyclodextrin (SBECD), a large cyclic oligosaccharide that is used to solubilize voriconazole (VRC) for intravenous administration, is eliminated mainly by renal excretion. The pharmacokinetics of SBECD and voriconazole in patients undergoing extracorporeal renal replacement therapies are not well defined. We performed a three-period randomized crossover study of 15 patients with end-stage renal failure during 6-hour treatment with Genius dialysis, standard hemodialysis, or hemodiafiltration using a high-flux polysulfone membrane. At the start of renal replacement therapy, the patients received a single 2-h infusion of voriconazole (4 mg per kg of body weight) solubilized with SBECD. SBECD, voriconazole, and voriconazole-N-oxide concentrations were quantified in plasma and dialysate samples by high-performance liquid chromatography (HPLC) and by HPLC coupled to tandem mass spectrometry (LC-MS-MS) and analyzed by noncompartmental methods. Nonparametric repeated-measures analysis of variance (ANOVA) was used to analyze differences between treatment phases. SBECD and voriconazole recoveries in dialysate samples were 67% and 10% of the administered doses. SBECD concentrations declined with a half-life ranging from 2.6 ± 0.6 h (Genius dialysis) to 2.4 ± 0.9 h (hemodialysis) and 2.0 ± 0.6 h (hemodiafiltration) (P < 0.01 for Genius dialysis versus hemodiafiltration). Prediction of steady-state conditions indicated that even with daily hemodialysis, SBECD will still exceed SBECD exposure of patients with normal renal function by a factor of 6.2. SBECD was effectively eliminated during 6 h of renal replacement therapy by all methods, using high-flux polysulfone membranes, whereas elimination of voriconazole was quantitatively insignificant. The SBECD half-life during renal replacement therapy was nearly normalized, but the average SBECD exposure during repeated administration is expected to be still increased.

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7

Rugină, Dumitriţa, Zoriţa Diaconeasa, Cristina Coman, Andrea Bunea, Carmen Socaciu, and Adela Pintea. "Chokeberry Anthocyanin Extract as Pancreaticβ-Cell Protectors in Two Models of Induced Oxidative Stress." Oxidative Medicine and Cellular Longevity 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/429075.

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The aim of this study was to investigate the protective effects of a chokeberry anthocyanin extract (CAE) on pancreaticβ-cells (βTC3) exposed to hydrogen peroxide- (H2O2-) and high glucose- (HG-) induced oxidative stress conditions. In order to quantify individual anthocyanins high performance liquid chromatography (HPLC) coupled to photodiode array (PDA) was used. The identification of the fragment ion pattern of anthocyanins was carried out by electrospray ionization mass spectrometry (LC-ESI-MS). The results showed that physiologically achievable concentrations of CAE (1, 5, and 10 μM) protectβTC3 against H2O2- and HG-induced cytotoxicity. Antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were increased in pancreaticβ-cells pretreated with CAE compared to cells exposed to the prooxidant agents. GSH levels initially reduced after exposure to H2O2and HG were restored by pretreatment with CAE. Insulin secretion inβTC3 cells was enhanced by CAE pretreatment. CAE restored the insulin pool and diminished the intracellular reactive oxygen species level in glucose-induced stress condition inβTC3 cells. These results demonstrate that anthocyanins from CAE were biologically active, showing a secretagogue potential and an antioxidative protection of enzymatic systems, conferring protection against H2O2and glucose toxicity inβTC3 cells.

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8

Wu, Zhisheng, Xinyuan Shi, Na Zhao, Yanling Pei, Manfei Xu, Luwei Zhou, Yang Li, and Yanjiang Qiao. "Estimation of multivariate detection limits of four quality parameters in licorice using MEMS–NIR spectrometry coupled with two sampling accessories." Journal of Innovative Optical Health Sciences 08, no. 05 (August 21, 2015): 1550009. http://dx.doi.org/10.1142/s1793545815500091.

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In this work, multivariate detection limits (MDL) estimator was obtained based on the micro-electro-mechanical systems–near infrared (MEMS–NIR) technology coupled with two sampling accessories to assess the detection capability of four quality parameters (glycyrrhizic acid, liquiritin, liquiritigenin and isoliquiritin) in licorice from different geographical regions. 112 licorice samples were divided into two parts (calibration set and prediction set) using Kennard–Stone (KS) method. Four quality parameters were measured using high-performance liquid chromatography (HPLC) method according to Chinese pharmacopoeia and previous studies. The MEMS–NIR spectra were acquired from fiber optic probe (FOP) and integrating sphere, then the partial least squares (PLS) model was obtained using the optimum processing method. Chemometrics indicators have been utilized to assess the PLS model performance. Model assessment using chemometrics indicators is based on relative mean prediction error of all concentration levels, which indicated relatively low sensitivity for low-content analytes (below 1000 parts per million (ppm)). Therefore, MDL estimator was introduced with alpha error and beta error based on good prediction characteristic of low concentration levels. The result suggested that MEMS–NIR technology coupled with fiber optic probe (FOP) and integrating sphere was able to detect minor analytes. The result further demonstrated that integrating sphere mode (i.e., MDL0.05,0.05, 0.22%) was more robust than FOP mode (i.e., MDL0.05,0.05, 0.48%). In conclusion, this research proposed that MDL method was helpful to determine the detection capabilities of low-content analytes using MEMS–NIR technology and successful to compare two sampling accessories.

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9

Katsa, Maria, Natalia Papalouka, Theodora Mavrogianni, Irene Papagiannopoulou, Marios Kostakis, Charalampos Proestos, and Nikolaos S. Thomaidis. "Comparative Study for the Determination of Fat-Soluble Vitamins in Rice Cereal Baby Foods Using HPLC-DAD and UHPLC-APCI-MS/MS." Foods 10, no. 3 (March 18, 2021): 648. http://dx.doi.org/10.3390/foods10030648.

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Two liquid chromatographic systems, one coupled to atmospheric pressure chemical ionization and tandem mass spectrometric methods (UHPLC-APCI-MS/MS) and the other a high-performance liquid chromatographic coupled to diode array detector (HPLC-DAD) were used to develop and validate methods for the simultaneous determination of fat-soluble vitamins A, D3 and E in rice cereal baby foods. The chromatographic separation was performed on C18 columns with a mixture of methanol-acetonitrile as mobile phase for all methods. The extraction of fat-soluble vitamins included enzymatic hydrolysis with α-amylase, saponification, extraction with petroleum ether or n-hexane and purification with silica cartridge (only for vitamin D3). Quantification of vitamin D3 and E through UHPLC-APCI-MS/MS was performed by the use of internal standards (IS) D3-d3 and E-d6, respectively, while IS was not used for vitamin A. The methods were optimized and validated in terms of linearity, precision, trueness, limits of detection and quantification. The recoveries were in the range of 85.0–107% for retinol, 92.0–105% for α-tocopherol and 95.2–106% for cholecalciferol and the %RSD (Relative Standard Deviation) values ranged from 6.4% to 15%. The evaluation of the methods was also conducted through the estimation of uncertainties, the application in commercial samples and the participation in a proficiency test

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10

Carail, Michel, and Catherine Caris-Veyrat. "Carotenoid oxidation products: From villain to saviour?" Pure and Applied Chemistry 78, no. 8 (January 1, 2006): 1493–503. http://dx.doi.org/10.1351/pac200678081493.

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Carotenoid oxidation products have various structures, among which epoxides and apo- or seco-carotenoids are the two main families. Although both these compound types are widely found in the natural world, the sensitivity of carotenoids to oxidation means they can also be an unwanted presence in in vitro assays. On the other hand, carotenoid oxidation products have also provided chemists with useful chemical tools for the structural identification of carotenoids, and in the natural world they are important biological mediators for plants and animals. In vitro, carotenoid oxidation products have been found to exert various effects which are either potentially beneficial or, on the contrary, detrimental to human health. However, to date, few carotenoid oxidation products have been found in humans. In order to isolate and characterize carotenoid oxidation products and identify their mechanism of formation, we set up two chemical oxidation systems. Lycopene was oxidized with potassium permanganate in a biphasic system to produce the fullest possible range of apo-lycopenals and some diapocarotene-dials. Biomimetic chemical systems of a heminic enzyme center were shown to oxidize lycopene and β-carotene into different families of molecules. Analysis by high-performance liquid chromatography coupled with a diode array-UV/vis detector and a mass spectrometry detector (HPLC-DAD-MS) was used to gain insight into the possible mechanisms of formation of the carotenoid oxidation products formed by these biomimetic systems.

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11

Vanek, Martin, Filip Mravec, Martin Szotkowski, Dana Byrtusova, Andrea Haronikova, Milan Certik, Volha Shapaval, and Ivana Marova. "Fluorescence lifetime imaging of red yeast Cystofilobasidium capitatum during growth." EuroBiotech Journal 2, no. 2 (April 1, 2018): 114–20. http://dx.doi.org/10.2478/ebtj-2018-0015.

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AbstractRed yeast Cystofilobasidium capitatum autofluorescence was studied by means of confocal laser scanning microscopy (CLSM) to reveal distribution of carotenoids inside the cells. Yeasts were cultivated in 2L fermentor on glucose medium at permanent light exposure and aeration. Samples were collected at different times for CLSM, gravimetric determination of biomass and HPLC determination of pigments. To compare FLIM (Fluorescence Lifetime Imaging Microscopy) images and coupled data (obtained by CLSM) with model systems, FLIM analysis was performed on micelles of SDS:ergosterol and SDS:coenzyme Q with different content of ergosterol and coenzyme Q, respectively, and with constant addition of beta-carotene. Liposomes lecithin:ergosterol:beta-carotene were investigated too. Two different intracellular forms of carotenoids were observed during most of cultivations, with third form appeared at the beginning of stationary phase. Observed behavior is probably due to formation of some kind of carotenoid protective system in membranes of different compartments of yeast cell, especially cytoplasmic membrane.

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12

Kanda, A., K. Takuwa-Kuroda, E. Iwakoshi-Ukena, Y. Furukawa, O. Matsushima, and H. Minakata. "Cloning of Octopus cephalotocin receptor, a member of the oxytocin/vasopressin superfamily." Journal of Endocrinology 179, no. 2 (November 1, 2003): 281–91. http://dx.doi.org/10.1677/joe.0.1790281.

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We reported that the common octopus, Octopus vulgaris, in common with vertebrates, possesses two members of the oxytocin/vasopressin superfamily: octopressin (OP) and cephalotocin (CT). This was the first observation of its kind in invertebrates. As OP and CT have different biological activities, the presence of specific receptors has been proposed. We cloned the cDNA of an orphan receptor from Octopus brain and found it to encode a polypeptide of 397 amino acids that displays sequences characteristic of G-protein coupled receptors. The orphan receptor showed high homology to receptors of the oxytocin/vasopressin superfamily and seemed to conserve the agonist-binding pocket common to the oxytocin and vasopressin receptors. Xenopus oocytes that express the orphan receptor responded to the application of CT by an induction of membrane Cl(-) currents coupled to the inositol phosphate/Ca(2+) pathway. OP and the other members of the oxytocin/vasopressin superfamily did not activate this receptor. HPLC fractionation of the Octopus brain extract combined with an oocyte assay yielded a single substance that was identical to CT. On the basis of these results, we conclude that the cloned receptor is the CT receptor (CTR). Expression of CTR mRNA in Octopus was detected in the central and the peripheral nervous systems, the pancreas, the oviduct and the ovary. This receptor may mediate physiological functions of CT in Octopus such as neurotransmission, reproduction and metabolism.

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13

Pasqualone, Antonella, Laura Nunzia Delvecchio, Giuseppe Gambacorta, Barbara Laddomada, Valeria Urso, Agata Mazzaglia, Paolo Ruisi, and Giuseppe Di Miceli. "Effect of Supplementation with Wheat Bran Aqueous Extracts Obtained by Ultrasound-Assisted Technologies on the Sensory Properties and the Antioxidant Activity of Dry Pasta." Natural Product Communications 10, no. 10 (October 2015): 1934578X1501001. http://dx.doi.org/10.1177/1934578x1501001026.

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Phenolic compounds have antioxidant properties and activate endogenous detoxification defense systems able to scavenge the reactive species of oxygen. The external layers of wheat caryopsis, largely constituting by-products of the milling industry such as bran and various middlings, contain relevant amounts of phenolic compounds. The aim of the research has been to evaluate the effect of supplementation with wheat bran aqueous extracts, obtained by ultrasound-assisted technologies, on the sensory properties and antioxidant activity of dry pasta. The HPLC-DAD characterization of the extract evidenced the presence of ferulic and p-coumaric acids. The supplemented pasta showed significantly higher antioxidant activity and phenolic content than the control, coupled to good overall sensory judgment. In addition, two different pasta drying diagrams were adopted, and the comparison of the corresponding end-products allowed it to be pointed out that the processing technology has to be carefully set up to prevent possible detrimental effects on the antioxidant activity. The proposed utilization of bran might add value to a milling by-product that, otherwise, is mostly employed in animal feeding.

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14

Grotti, Marco, Francesco Soggia, Cristina Lagomarsino, Walter Goessler, and Kevin A. Francesconi. "Arsenobetaine is a significant arsenical constituent of the red Antarctic alga Phyllophora antarctica." Environmental Chemistry 5, no. 3 (2008): 171. http://dx.doi.org/10.1071/en08025.

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Environmental context. Although arsenic occurs in marine animals at high concentrations, the pathways by which it is biotransformed and accumulated remain largely unknown. The observation that some species of algae can contain significant concentrations of arsenobetaine, a major marine arsenic species, is relevant to explanations of the source of this compound to marine animals and its transport through the marine food web. Abstract. Significant amounts of arsenobetaine (up to 0.80 μg As g–1 dry mass, representing 17% of the extractable arsenic) were found in the extracts of all four samples of the red alga Phyllophora antarctica collected from two sites in Antarctica (Terra Nova Bay and Cape Evans). The assignment was made with high performance liquid chromatography–inductively coupled plasma mass spectrometry (HPLC-ICPMS) based on exact cochromatography with a standard compound with two chromatographic systems (cation-exchange and ion-pairing reversed-phase), each run under two sets of mobile phase conditions. Particular care was taken during sample preparation to ensure that the arsenobetaine was of algal origin and did not result from epiphytes associated with the alga. Another red alga, Iridaea cordata, collected from Terra Nova Bay, did not contain detectable concentrations of arsenobetaine. For both algal species, the majority of the extractable arsenic was present as arsenosugars. Confirmation that marine algae can contain significant amounts of arsenobetaine allows a simpler explanation for the widespread occurrence of this arsenical in marine animals.

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15

Takishita, Yoko, Alfred Souleimanov, Carine Bourguet, Leanne B. Ohlund, Alexandre A. Arnold, Lekha Sleno, and Donald L. Smith. "Pseudomonas entomophila 23S Produces a Novel Antagonistic Compound against Clavibacter michiganensis subsp. michiganensis, a Pathogen of Tomato Bacterial Canker." Applied Microbiology 1, no. 1 (May 18, 2021): 60–73. http://dx.doi.org/10.3390/applmicrobiol1010006.

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Biopesticides, which consist of antagonistic microorganisms, or the bioactive compounds they produce offer attractive alternatives to synthetic agrochemicals as a means of reducing plant diseases in crop production systems. In our previous study, a strain of Pseudomonas entomophila 23S was reported to have a strong antagonistic activity toward Clavibacter michiganensis subsp. michiganensis (Cmm), a pathogen of tomato bacterial canker disease, which causes serious damage to the tomato production industry. This study focused on purification and characterization of the anti-Cmm compound(s) produced by P. entomophila 23S. The cell-free supernatant was first subjected to butanol extraction, fractioned by solid-phase extraction (SPE), and purified by high-performance liquid-chromatography (HPLC). The semi-preparative purified compounds retained anti-Cmm activity. These compounds were then characterized by liquid chromatography coupled with high-resolution tandem mass spectrometry (LC-HRMS/MS) and nuclear magnetic resonance (NMR). Two anti-Cmm compounds, C15H16N2O and C16H18N2O, were isolated by this procedure. From the LC/MS spectra, the compounds were predicted to have an isoquinoline ring, the presence of which was confirmed by NMR. The compounds differed with respect to the presence of a methyl group in a side chain. In addition, P. entomophila 23S grown in different culture media produced the greatest amounts of these anti-Cmm compounds when in Nutrient Broth (NB), where bacterial growth was the slowest. NB composition is more favorable in stimulating P. entomophila 23S to produce higher amounts of these anti-Cmm compounds.

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Sanin, A. L., and E. A. Semyonov. "Quantum coupled oscillators in two-dimensional systems." Optical Memory and Neural Networks 22, no. 1 (March 2013): 28–36. http://dx.doi.org/10.3103/s1060992x13010049.

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Qiu Changdong, 邱昌东, and 卢道明 Lu Daoming. "Entanglement Characteristics in Two-Dimensional Coupled Cavity Systems." Acta Optica Sinica 36, no. 5 (2016): 0527001. http://dx.doi.org/10.3788/aos201636.0527001.

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18

AHN, Y., E. BERTOCCHI, and J. BARBER. "Shakedown of coupled two-dimensional discrete frictional systems." Journal of the Mechanics and Physics of Solids 56, no. 12 (December 2008): 3433–40. http://dx.doi.org/10.1016/j.jmps.2008.09.003.

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19

Ruden, P. Paul, and Zhiqiang Wu. "Exchange effect in coupled two‐dimensional electron gas systems." Applied Physics Letters 59, no. 17 (October 21, 1991): 2165–67. http://dx.doi.org/10.1063/1.106116.

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Suzuki, Yuta, Shun Nakagawa, and Koichi Narahara. "Nonlinear Plasma Waves in Coupled Two-Dimensional Electron Systems." Japanese Journal of Applied Physics 47, no. 12 (December 19, 2008): 8756–60. http://dx.doi.org/10.1143/jjap.47.8756.

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21

Tanaka, Yasuyuki. "Recent Advances in Structural Characterization of Elastomers." Rubber Chemistry and Technology 64, no. 3 (July 1, 1991): 325–85. http://dx.doi.org/10.5254/1.3538561.

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Abstract One of the main targets of the structural characterization of elastomers so far has been the correlation of the polymerization conditions with the properties of the resulting polymers. The first step is the analysis of polymer structure, such as the chemical composition of copolymers, isomeric structure of diene polymers, degree of branching, extent of modification, functionality of end groups, amounts of abnormal groups, tacticity, and so on. Progress in nuclear magnetic resonance spectroscopy (NMR) makes possible the second step, which is the structural characterization of polymer chains, such as the sequence distribution of comonomer units in copolymer, isomeric units in diene polymers, configurational sequences in vinyl polymers, head and tail arrangement of monomer units. Recent development of FT-NMR spectroscopy, high-field spectroscopy from 300 MHz to 600 MHz at 1H-NMR, solid-state 13C-NMR, and two-dimensional NMR has facilitated a more detailed analysis of these structural features. The complexity of the structure of elastomers, which is derived from highly controlled copolymerization processes, leads to the widespread application of modern FT-NMR spectroscopy. It may reasonably be said that a fair number of structural problems in elastomers has been solved by NMR analysis. The high sensitivity of Fourier-transform infrared spectroscopy (FT-IR) has enabled one to determine trace structural changes in elastomers. Coupled on-line techniques such as gas-chromatography-mass-spectrometry combined with pyrolysis, liquid chromatography-NMR, and gel permeation chromatography-FT-IR will be powerful tools for the characterization of elastomers. Progress in analytical instruments has stimulated the development of high-performance elastomers, the synthesis of new speciality elastomers, and the elucidation of mechanisms for property enhancements. The use of modern instruments and a combination of ordinary methods of structural analysis have satisfied needs to some extent. However, a newer method of structural characterization is always desired in order to achieve higher orders of information. for example, the characterization of inhomogeneity along the polymer chain and between the polymer chains has become an important problem, especially in polymer blend systems. As to the former problem, spectroscopic methods provide only limited information. Although the NMR and FT-IR spectroscopies are very powerful tools for the analysis of short sequence distributions, it is difficult to characterize the distribution of long sequences and hybrid systems containing random and blocked sequences along the polymer chain. Gel permeation chromatography (GPC) is one of the most popular techniques for the analysis of molecular-weight distribution. However, it provides complicated information including molecular-weight distribution and chemical-composition distribution in the case of copolymers. Recent progress of high-performance liquid chromatography (HPLC) has provided a new powerful tool for the structural characterization of copolymers. It is appropriate to review the recent advances in structural characterization of elastomers, especially the characterization of microstructure of polymer chains, from the viewpoints of methodology and applicability of new methods. As to the NMR analysis of elastomers, reviews are available. Here, considerable attention is focused on the procedures for the assignment of signals, because the applicability of a NMR method is based on the reliability of the signal assignments. The other topics are selected to provide direct information for polymer synthesis or polymer properties.

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Metzger, S., and Bernd O. Kolbesen. "Application of HPLC for the Analysis of Organic Additives in Cleaning Chemicals and Cleaning Mixtures." Solid State Phenomena 103-104 (April 2005): 221–26. http://dx.doi.org/10.4028/www.scientific.net/ssp.103-104.221.

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The suitability of high performance liquid chromatography (HPLC) for the direct determination of the concentration of complexing agents for single chemistry cleaning is demonstrated. HPLC, coupled to a mass spectrometric detector (HPLC-MS) and two-dimensional mass spectrometry (MS/MS) have been applied for the investigation of the reactions involved in the decomposition of the complexing agents. The techniques described are useful for determining the stability of organic additives in wet chemical cleaning baths.

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23

Vazifehshenas, T., and S. Rostami. "Local field corrections in two-dimensional coupled electron–LO phonon systems." Physica Scripta 84, no. 1 (June 28, 2011): 015706. http://dx.doi.org/10.1088/0031-8949/84/01/015706.

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Sy, H. K., and L. M. Song. "Exchange Potential and Plasma Modes in Coupled Two-Dimensional Electron Systems." physica status solidi (b) 136, no. 1 (July 1, 1986): 201–6. http://dx.doi.org/10.1002/pssb.2221360122.

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25

Wazwaz, Abdul-Majid. "Multiple kink solutions for two coupled integrable (2+1)-dimensional systems." Applied Mathematics Letters 58 (August 2016): 1–6. http://dx.doi.org/10.1016/j.aml.2016.01.019.

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26

Guo, Shuangjian, Qionglin Dai, Hongyan Cheng, Haihong Li, Fagen Xie, and Junzhong Yang. "Spiral wave chimera in two-dimensional nonlocally coupled Fitzhugh–Nagumo systems." Chaos, Solitons & Fractals 114 (September 2018): 394–99. http://dx.doi.org/10.1016/j.chaos.2018.07.029.

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27

Sy, H. K. "Field theoretical treatment of plasma modes in coupled two-dimensional systems." Solid State Communications 61, no. 4 (January 1987): 245–47. http://dx.doi.org/10.1016/0038-1098(87)91011-8.

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28

SOFIANOS, S. A., G. J. RAMPHO, and R. M. ADAM. "TWO-DIMENSIONAL INTEGRODIFFERENTIAL EQUATIONS FOR MULTI-STRANGE HYPERNUCLEI." Modern Physics Letters A 24, no. 11n13 (April 30, 2009): 1027–30. http://dx.doi.org/10.1142/s0217732309000516.

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We present a Faddeev-type coupled integrodifferential equations describing unequal mass A-particle systems. The equations are obtained by assuming an expansion of the A-particle wave function in Faddeev amplitudes which, in turn, are expanded in terms of Potential Harmonics. By projecting the resulting system on rij-space we obtained a system of coupled equations which can be used to study multi-strange hypernuclei.

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29

HU, BEN YU-KUANG. "MANY-BODY EFFECTS IN FRICTIONAL DRAG BETWEEN COUPLED TWO-DIMENSIONAL ELECTRON SYSTEMS." International Journal of Modern Physics B 13, no. 05n06 (March 10, 1999): 469–78. http://dx.doi.org/10.1142/s0217979299000369.

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Independently contacted coupled quantum wells separated by barriers which allow significant interlayer interactions but no tunneling have been fabricated. When current is passed through one layer, the interlayer interactions drag carriers in the second layer, resulting in a voltage response (for open circuits). The magnitude of the response gives a quantitative measure of the effective interlayer interactions and response functions of the system, and hence this is an excellent laboratory for the study of many-body phenomena in two-dimensional electron gases. We review the Boltzmann and Kubo formalisms for the theory of drag effects in coupled quantum wells and discuss three specific cases where many-body effects significantly affect the drag: (1) acoustic phonon-mediated drag, (2) large enhancements due to coupled plasmon modes, and (3) interplay of screening and Landau levels in large magnetic fields.

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30

Rubel, H., A. Fischer, W. Dietsche, C. Jörger, K. von Klitzing, and K. Eberl. "The frictional drag between coupled two-dimensional electronic systems in magnetic fields." Physica B: Condensed Matter 249-251 (June 1998): 859–63. http://dx.doi.org/10.1016/s0921-4526(98)00331-7.

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31

Constantin, P., C. Fefferman, E. S. Titi, and A. Zarnescu. "Regularity of Coupled Two-Dimensional Nonlinear Fokker-Planck and Navier-Stokes Systems." Communications in Mathematical Physics 270, no. 3 (January 9, 2007): 789–811. http://dx.doi.org/10.1007/s00220-006-0183-1.

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32

Chen, Tsung-Wei, Zhi-Yang Huang, and Dah-Wei Chiou. "Dynamical precession of spin in the two-dimensional spin-orbit coupled systems." Physics Letters A 383, no. 21 (July 2019): 2504–14. http://dx.doi.org/10.1016/j.physleta.2019.05.007.

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33

Xiao, Cong, and Dingping Li. "Semiclassical magnetotransport in strongly spin–orbit coupled Rashba two-dimensional electron systems." Journal of Physics: Condensed Matter 28, no. 23 (May 9, 2016): 235801. http://dx.doi.org/10.1088/0953-8984/28/23/235801.

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34

Gennaro, A. M., and P. R. Levstein. "High-temperature dipolar local field correlations in two-dimensional exchange-coupled systems." Journal of Physics: Condensed Matter 3, no. 4 (January 28, 1991): 455–65. http://dx.doi.org/10.1088/0953-8984/3/4/009.

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35

Hwang, T. L., and A. J. Shaka. "Reliable Two-Dimensional Rotating-Frame Cross-Relaxation Measurements in Coupled Spin Systems." Journal of Magnetic Resonance, Series B 102, no. 2 (October 1993): 155–65. http://dx.doi.org/10.1006/jmrb.1993.1078.

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36

Santiago, C. D., C. H. Marchi, and L. F. Souza. "Performance of geometric multigrid method for coupled two-dimensional systems in CFD." Applied Mathematical Modelling 39, no. 9 (May 2015): 2602–16. http://dx.doi.org/10.1016/j.apm.2014.10.067.

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37

Kay, Lewis E., J. N. Scarsdale, D. R. Hare, and J. H. Prestegard. "Simulation of two-dimensional cross-relaxation spectra in strongly coupled spin systems." Journal of Magnetic Resonance (1969) 68, no. 3 (July 1986): 515–25. http://dx.doi.org/10.1016/0022-2364(86)90340-9.

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38

Weitzmann, Peter, Jesper Kragh, Peter Roots, and Svend Svendsen. "Modelling floor heating systems using a validated two-dimensional ground-coupled numerical model." Building and Environment 40, no. 2 (February 2005): 153–63. http://dx.doi.org/10.1016/j.buildenv.2004.07.010.

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39

Failor, B. H., P. L. Coleman, J. S. Levine, Y. Song, H. Sze, P. D. LePell, C. A. Coverdale, C. Deeney, L. Pressley, and R. Schneider. "Charge-coupled device systems for recording two-dimensional multi-mega-amperez-pinch data." Review of Scientific Instruments 72, no. 4 (April 2001): 2023–31. http://dx.doi.org/10.1063/1.1355264.

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40

Shen Chuan-Sheng, Zhang Ji-Qian, and Chen Han-Shuang. "System size selected effects induced by clustering in two-dimensional coupled cell systems." Acta Physica Sinica 56, no. 11 (2007): 6315. http://dx.doi.org/10.7498/aps.56.6315.

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41

Groll, R. "Statistical Eulerian Diffusion Approach of Four-Way-Coupled Multiphase Systems." Defect and Diffusion Forum 297-301 (April 2010): 832–37. http://dx.doi.org/10.4028/www.scientific.net/ddf.297-301.832.

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Volume-fraction weighted and Reynolds averaged momentum transport equations are solved in an Euler/Euler approach to simulate numerically the turbulent, dispersed two- phase °ow in a two-dimensional channel and a three-dimensional conic di®user °ow. Particular attention is given to the modelling of turbulent di®usion and particle wall interaction, assuming local equilibrium but introducing individual terms for particle/°uid drag interaction, particle collisions and trajectory crossings. These in°uences have been quanti¯ed in terms of partial viscosities, a restitution power and a turbulence structure parameter. Boussinesq approxima- tions have been used for each phase and their interaction, whose formulation was provided in the framework of the eddy-viscosity modelling concept.

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42

Oney-Montalvo, Julio Enrique, Ksenia Morozova, Manuel Octavio Ramírez-Sucre, Matteo Scampicchio, and Ingrid Mayanin Rodríguez-Buenfil. "Determination of Peak Purity in HPLC by Coupling Coulometric Array Detection and Two-Dimensional Correlation Analysis." Sensors 22, no. 5 (February 24, 2022): 1794. http://dx.doi.org/10.3390/s22051794.

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This work aims to evaluate the purity of chromatographic peaks by a two-dimensional correlation (2D-corr) analysis. Such an analysis leads to two contour plots: synchronous and asynchronous. The synchronous contour plot provides information on the number of peaks present in the chromatogram. The asynchronous contour plot reveals the presence of overlapping species on each peak. The utility of 2D-corr analysis was demonstrated by the chromatographic analysis of Capsicum chili extracts obtained by HPLC coupled with a coulometric array of sixteen detectors. Thanks to 16 electrochemical sensors, each poised at increasing potentials, the resulting 2D-corr analysis revealed the presence of at least three species on the peak located at a retention time of 0.93 min. Mass spectrometry (MS) analysis was used to analyze the coeluting species, which were identified as: quinic acid (3.593 min), ascorbic acid (3.943 min), and phenylalanine (4.229 min). Overall, this work supports the use of 2D-corr analysis to reveal the presence of overlapping compounds and, thus, verify the signal purity of chromatographic peaks.

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43

Schulze-Halberg, A. "Higher-order Darboux transformations for two-dimensional Dirac systems with diagonal matrix potential." Journal of Physics: Conference Series 2090, no. 1 (November 1, 2021): 012038. http://dx.doi.org/10.1088/1742-6596/2090/1/012038.

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Abstract We construct the explicit form of higher-order Darboux transformations for the two-dimensional Dirac equation with diagonal matrix potential. The matrix potential entries can depend arbitrarily on the two variables. Our construction is based on results for coupled Korteweg-de Vries equations [27].

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44

Myrzakul, Akbota, and Ratbay Myrzakulov. "Integrable motion of two interacting curves, spin systems and the Manakov system." International Journal of Geometric Methods in Modern Physics 14, no. 07 (March 31, 2017): 1750115. http://dx.doi.org/10.1142/s0219887817501158.

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Integrable spin systems are an important subclass of integrable (soliton) nonlinear equations. They play important role in physics and mathematics. At present, many integrable spin systems were found and studied. They are related with the motion of three-dimensional curves. In this paper, we consider a model of two moving interacting curves. Next, we find its integrable reduction related with some integrable coupled spin system. Then, we show that this integrable coupled spin system is equivalent to the famous Manakov system.

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45

Kopietz, Peter. "Vertex Corrections in Gauge Theories for Two-dimensional Condensed Matter Systems." International Journal of Modern Physics B 12, no. 16n17 (July 10, 1998): 1673–92. http://dx.doi.org/10.1142/s0217979298000910.

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We calculate the self-energy of two-dimensional fermions that are coupled to transverse gauge fields, taking two-loop corrections into account. Given a bare gauge field propagator that diverges for small momentum transfers q as 1/qη, 1<η≤ 2, the fermionic self-energy without vertex corrections vanishes for small frequencies ω as Σ(ω)∝ ωγ with γ=2/(1+η)<1. We show that inclusion of the leading radiative correction to the fermion-gauge field vertex leads to Σ(ω)∝ωγ [1-aη ln (ω0/ω)], where aη is a positive numerical constant and ω0 is some finite energy scale. The negative logarithmic correction is consistent with the scenario that higher order vertex corrections push the exponent γ to larger values.

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46

Kosior, M. A., N. Pagano, A. Staropoli, C. De Canditiis, V. Longobardi, G. Zullo, F. Vinale, and B. Gasparrini. "142 Metabolomic analysis of fresh and frozen bovine seminal plasma: A preliminary study." Reproduction, Fertility and Development 32, no. 2 (2020): 197. http://dx.doi.org/10.1071/rdv32n2ab142.

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Sperm cryopreservation is essential for assisted reproduction; however, freezing induces biochemical and physical damage to the sperm membrane structures, negatively affecting sperm fertilising ability (Castro et al. 2006 J. Anim. Sci. Biotechnol. 5, 1-9). Metabolomics is the study of small molecules, commonly known as metabolites, which play essential roles in biological systems. Emerging research in the field of metabolomics showed a potential role in identifying male fertility biomarkers (Bieniek et al. 2016 Asian J. Androl. 18, 426-433). Metabolites present in the seminal plasma play several roles related to sperm motility, sperm membrane protection from oxidative stress, and regulation of metabolic activity (Therien et al. 1995 Biol. Reprod. 52, 1372-1379). However, the extent of metabolite changes in seminal plasma during cryopreservation is still not well known. Therefore, the aim of this study was to evaluate the differences of the seminal plasma metabolites between fresh and frozen bovine sperm. Four ejaculates from eight Holstein (Bos taurus) bulls (4-6 years age) maintained at an authorised national semen collection center (Centro Tori Chiacchierini, Civitella D’Arna, Italy) under uniform management conditions were collected weekly using an artificial vagina (IMV Technologies). Each ejaculate was split into two aliquots (one fresh and one frozen) at −20°C for at least 2h. Seminal plasma from fresh (immediately) and frozen-thawed semen was separated from sperm by centrifugation (1600×g for 10min), and supernatants were then transferred to a 2-mL tube and stored at −80°C until use. After methanol extraction of metabolites, samples were centrifuged at 6400×g for 30min at 4°C, and supernatants were analysed using a liquid chromatography-mass spectrometry (LC-MS; Agilent 1260 HPLC; Agilent Technologies) system with an autosampler and a binary pump coupled to an Agilent Q-TOF 6540 (Agilent Technologies). Univariate analyses of the data were performed using bioinformatics approaches. The differences between fresh and frozen seminal plasma samples were analysed using a paired Student's t-test. Twenty-three metabolites were found in both fresh and frozen seminal plasma samples, out of which eight were significantly different (P<0.05) between the two groups; among these, hypotaurine, ceramide, and isoindoline were identified. In particular, hypotaurine and ceramide were downregulated, whereas isoindoline was upregulated in fresh samples compared with frozen samples. To the best of our knowledge, this is the first study to identify seminal plasma metabolites in fresh and frozen samples by using LC-MS. In order to ensure the reliability and accuracy of results, the validation of the method used in the analysis of biosamples is still in progress, as is the evaluation of the metabolic profile in sperm cells. In conclusion, the results of this study suggest that LC-MS can be a promising screening tool to detect metabolites potentially associated with bull fertility.

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DE SOUSA VIEIRA, M., A. J. LICHTENBERG, and M. A. LIEBERMAN. "NONLINEAR DYNAMICS OF SELF-SYNCHRONIZING SYSTEMS." International Journal of Bifurcation and Chaos 01, no. 03 (September 1991): 691–99. http://dx.doi.org/10.1142/s0218127491000506.

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We investigate the self-synchronization of nonlinear systems. The particular system considered is two-coupled, digital phase-locked loops. It is shown that the overall dynamics is far more complicated than that of a single loop, which is governed by a one-dimensional circle map. In the case of two-coupled loops, we observe that the dynamics is governed by explicit mapping equations only for certain regions of the parameter space. In the regions for which mapping equations can be derived, we find the universality class of the coupled loops. Using such a two loop system as a transmitter of a chaotic signal, it is shown how a third loop can synchronize with this signal. Our results may provide one possible solution to the problem of secure communications.

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48

Rubel, H., A. Fischer, W. Dietsche, K. von Klitzing, and K. Eberl. "Observation of Screening in the Magneto-Coulomb Drag between Coupled Two-Dimensional Electron Systems." Physical Review Letters 78, no. 9 (March 3, 1997): 1763–66. http://dx.doi.org/10.1103/physrevlett.78.1763.

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49

Duan, Hong-Guang, Peter Nalbach, Valentyn I. Prokhorenko, Shaul Mukamel, and Michael Thorwart. "On the origin of oscillations in two-dimensional spectra of excitonically-coupled molecular systems." New Journal of Physics 17, no. 7 (July 31, 2015): 072002. http://dx.doi.org/10.1088/1367-2630/17/7/072002.

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50

Liu, Cheng-Yang. "Electro-optical resonant switching in two-dimensional side-coupled waveguide-cavity photonic crystal systems." Physics Letters A 375, no. 44 (October 2011): 3895–98. http://dx.doi.org/10.1016/j.physleta.2011.09.024.

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