1,958 research outputs found
Nabootsing N.S. baansignaleringssysteem: Deel I : Ontvanger schakeling
No full textBij de N.S. bestaat behoefte om te beschikken over een nabootser van het transmissie systeem voor de overdracht van signaleringen en commando's (het N.S. Quiktrol-systeem). Dit verslag beschrijft de realisering van een dergelijke nabootser, m.b.v. een M6800 microprocessor en dan vooral de ontvanger schakeling.Applied SciencesElectrotechniekLaboratorium voor automatische verkeerssysteme
Workshop on transformation products of emerging pollutants in the aquatic environment (TREMEPOL project)
No full text
β-Glucosidase and β-Galactosidase-Mediated Transglycosylation of Steviol Glycosides Utilizing Industrial Byproducts
No full textStevia rebaudiana Bertoni is a plant cultivated worldwide due to its use as a sweetener. The sweet taste of stevia is attributed to its numerous steviol glycosides, however, their use is still limited, due to their bitter aftertaste. The transglycosylation of steviol glycosides, aiming at the improvement of their taste, has been reported for many enzymes, however, glycosyl hydrolases are not extensively studied in this respect. In the present study, a β-glucosidase, MtBgl3a, and a β-galactosidase, TtbGal1, have been applied in the transglycosylation of two steviol glycosides, stevioside and rebaudioside A. The maximum conversion yields were 34.6 and 33.1% for stevioside, while 25.6 and 37.6% were obtained for rebaudioside A conversion by MtBgl3a and TtbGal1, respectively. Low-cost industrial byproducts were employed as sugar donors, such as cellulose hydrolyzate and acid whey for TtbGal1- and MtBgl3a- mediated bioconversion, respectively. LC-HRMS analysis identified the formation of mono- and di- glycosylated products from stevioside and rebaudioside A. Overall, the results of the present work indicate that both biocatalysts can be exploited for the design of a cost-effective process for the modification of steviol glycosides. © Copyright © 2021 Zerva, Chorozian, Kritikou, Thomaidis and Topakas
LITERARY TEXTBY N.S. LESKOV AS A SYSTEM OF LANGUAGE MEANS
No full textThe article gives a linguistic and stylistic analysis of N.S. Leskov’s fiction. One of the main ambitions of the author is to reveal the possible correlation between the language features of N.S. Leskov’s heroes and the Russian cultural tradition of the past. Some original and vivid examples of the speech of representatives of specific Russian professions and estates are analyzed as well as linguistic parallels between complicated church language and the writer’s system of stylistic devices are defined. We show new interlinks between historic, linguistic and literary aspects of the text and especially N.S. Leskov’s unusual world as a form of culturally-historically determined consciousness. We pay special attention to Old Slavonic «experiment» in Leskov’s texts and skaz , polyphony of names of his heroes and writers’ examples of folk etymology. We came to the conclusion that in The Notes of the Unknown different stylistic and linguistic devices are combined
Effect of chemical modifiers on the kinetic parameters characterizing the electrothermal atomization of chromium
No full textThe mechanism of atomization of chromium, in the absence and in the presence of chemical modifiers, in electrothermal graphite atomizers was investigated. This has been accomplished by the determination of the kinetic parameters (atomization energy, Ea, and order of release, x) characterizing its atomization. The tested chemical modifiers are Na2WO4, Mg(NO3)2, Ca(NO3)2, Rh and Pt. The dissipation process of the atomic vapor was also studied. The diffusion parameters are calculated in the absence and in the presence of chemical modifiers. In the absence of chemical modifiers, Cr atoms are produced in the gas phase by thermal desorption of adsorbed atoms, a first-order process. Pyrolysis temperatures (Tpyr) ≥ 1300°C probably promote the formation of chromium carbide (Cr3C2) and therefore the atomization mechanism includes two steps: (i) the thermal decomposition of Cr3C2 and (ii) the thermal desorption of adsorbed Cr(ads). In the presence of Mg(NO3)2 and Ca(NO3)2 modifiers, atomization of Cr proceeds through a two-precursor mechanism, wherein the first step must include the thermal decomposition of its oxide. In the presence of Na2WO4, Rh and Pt, a single-precursor mechanism is observed. This should be a diffusion process through the bulk of the modifier. Platinum and Rh probably trap Cr atoms and interaction of Cr atoms with graphite must be precluded
Bisphenol A, 4-t-octylphenol, and 4-nonylphenol determination in serum by Hybrid Solid Phase Extraction-Precipitation Technology technique tailored to liquid chromatography-tandem mass spectrometry
No full textA rapid liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and optimized for the simultaneous determination of bisphenol A, 4-t-octylphenol and 4-nonylphenol in human blood serum. For the first time, the electrospray ionization (ESI) parameters of probe position, voltage potential, sheath gas flow rate, auxiliary gas flow rate, and ion transfer tube temperature were thoroughly studied and optimized for each phenol by a univariate approach. As a consequence, low instrumental limits of detection were reported, demonstrating at 0.2. ng/mL (in solvent matrix) excellent injection repeatability (RSD. <. 14.5%) and a confirmation peak for all target phenols. Extraction and purification of serum was performed by the novel Hybrid Solid Phase Extraction-Precipitation Technology technique (Hybrid SPE-PPT). The limits of detection in human blood serum were 0.80, 1.3 and 1.4. ng/mL for BPA, 4-t-OP and 4-NP, respectively. © 2015 Elsevier B.V
Determination of eight artificial sweeteners in wastewater by hydrophilic interaction liquid chromatography-tandem mass spectrometry
No full textThe development of a method for the simultaneous determination of eight artificial sweeteners, namely aspartame (ASP), alitame (ALI), neotame (NEO), acesulfame (ACS), saccharin (SAC), cyclamate (CYC), sucralose (SCL) and neohesperidin dihydrochalcone (NHDC), under hydrophilic interaction liquid chromatography (HILIC) conditions is presented herein. The ionization of all the compounds was achieved by negative electrospray. Two silica-based columns, a fully porous (XBridge HILIC) and a fused-core one (Kinetex HILIC), were compared. For HILIC optimization, the effect of the following parameters was studied: the mobile phase, column temperature, pH and ionic strength of the ammonium formate buffer. The optimized mobile phase was 5 mM ammonium formate buffer pH 3.5-methanol-acetonitrile (15/10/75 v/v), with a flow rate of 100 μL min-1 at 50°C. The asymmetry factor of the peaks was lower on the Kinetex HILIC column than that on the XBridge HILIC. The predominant retention mechanism of all the analytes on silica columns seems to be partition to the aqueous layer. The method was validated in tap water and wastewater samples using Kinetex HILIC. Three deuterated internal standards were used, one for each category of sweeteners (dipeptides, sulfamates and sugars). The instrumental limits of detection ranged from 0.24 (SAC) to 4.4 (SCL) μg L-1. The recoveries in influent samples ranged from 39% (CYC) to 97% (NEO), while recoveries were better for the other two matrices. Inter-day precision (%RSD, n = 6) ranged from 4.2% (SAC) to 20% (ALI) in influent samples. The method was applied to influents and effluents from the wastewater treatment plant of Athens for seven consecutive days and high levels of sucralose and sulfamates were found. © 2013 The Royal Society of Chemistry
Multi-residue methodology for the determination of 16 coccidiostats in animal tissues and eggs by hydrophilic interaction liquid chromatography – Tandem mass spectrometry
No full textA simple, sensitive and efficient confirmatory method was developed and validated for the determination of 16 coccidiostats in animal tissues and eggs using hydrophilic interaction liquid chromatography–tandem mass spectrometry (HILIC-MS/MS). The sample preparation consisted of a solid-liquid extraction with ACN and dispersive SPE cleanup with MgSO 4 and C 18 . Analysis was realized in an Acquity BEH HILIC silica column, in SRM mode. Both positive and negative ionization was performed, using polarity switching. Isocratic elution was used with a mobile phase of ACN: aqueous ammonium formate 1 mM with 0.1% formic acid (80:20, v/v). Method validation was performed in eggs, poultry, bovine, ovine, porcine and rabbit tissue and exceptionally low LODs were achieved, varying from 0.004 μg kg −1 (decoquinate in porcine tissue) to 0.560 μg kg −1 (halofuginone in eggs). The developed methodology was applied in 82 muscle and egg samples through the Greek National Residue Control Plan for coccidiostats. © 2018 Elsevier Lt
Characterization of the retention of artificial sweeteners by hydrophilic interaction liquid chromatography
No full textThe aim of this work was to study the chromatographic behavior of polar artificial sweeteners on three hydrophilic interaction liquid chromatography (HILIC) columns: Kinetex HILIC (unbounded silica, core shell), ZIC HILIC (sulfoalkylbetain) and TSKgel Amide-80 (amide). The studied analytes were dipeptides (aspartame, neotame, advantame, alitame), sulfamates (acesulfame, saccharin, cyclamate), and sugars (sucralose, neohesperidin dihydrochalcone). Critical parameters such as the mobile phase pH, buffer concentration, column temperature, and organic modifier were studied for the investigation of the retention mechanism. Partition and adsorption models were also used. The retention mechanism of dipeptides seems to be partition for the aqueous layer and weak electrostatic interactions or hydrogen bonds. For the sulfamates, on Kinetex and ZIC HILIC columns, it is likely that partitioning to the aqueous layer is combined with the ERLIC phenomena at pH 5.5. For the TSKgel Amide, the partition and the hydrogen bonds formed between the analytes and carbamoyl groups of the stationary phase play an important role in the retention mechanism. For sucralose, partition seems to be the predominant mechanism in every column, while, for neohesperidin dihydrochalcone, both partition to aqueous layer and hydrogen bonding seems to contribute to the retention. This is also the first report of a method for the chromatographic determination of advantame, a new sweetener. © 2018 Taylor & Francis
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