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Ozdemir Olgun FA, Demirata Ozturk B, Apak R. Determination of Synthetic Food Colorants in Powder Beverage Samples by On-line HPLC–Cupric Reducing Antioxidant Capacity (CUPRAC) Assay with Post-Column Detection. Chromatographia 2016. [DOI: 10.1007/s10337-015-3018-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Yalçın S, Filik H, Apak R. Speciation analysis of manganese in tea samples using flame atomic absorption spectrometry after cloud point extraction. J Anal Chem 2011. [DOI: 10.1134/s1061934812010194] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Balkis N, Müftüoğlu E, Aksu A, Sur HI, Apak R. The chemical oceanographic consequences of environmental restoration projects in the Golden Horn estuary (Marmara Sea, Turkey). Environ Monit Assess 2010; 164:67-79. [PMID: 19353286 DOI: 10.1007/s10661-009-0875-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2008] [Accepted: 03/10/2009] [Indexed: 05/27/2023]
Abstract
The input of industrial and domestic waste to the horizontal circulation in the Golden Horn Estuary of Marmara Sea has resulted in one of the most polluted estuaries in the past. Consequently, the dissolved oxygen concentrations in both the surface and bottom waters decreased toward to the estuary head during 1998-2005. In contrast, the total suspended solids content of the surface water decreased toward to the estuary mouth. However, construction of the operational collector system surrounding the estuary during the process of rehabilitation projects, combined with the opening of the middle pontoons of the Valide Sultan Bridge, resulted in gradually improved water quality of the estuary with a concomitant decrease in pollution. However, phytoplankton blooms and eutrophication persist especially in the innermost part of the Golden Horn in 2005. The region from the estuary mouth up to Camialti has a dynamic structure, and sufficient circulation seemingly occurs in this part of the Golden Horn.
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Affiliation(s)
- N Balkis
- Department of Chemical Oceanography, Institute of Marine Science and Management, Istanbul University, Vefa, 34116, Istanbul, Turkey.
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Ozdemir FA, Demirata B, Apak R. Adsorptive removal of methylene blue from simulated dyeing wastewater with melamine-formaldehyde-urea resin. J Appl Polym Sci 2009. [DOI: 10.1002/app.29835] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Chakrabarti S, Dutta BK, Apak R. Active manganese oxide: a novel adsorbent for treatment of wastewater containing azo dye. Water Sci Technol 2009; 60:3017-3024. [PMID: 19955624 DOI: 10.2166/wst.2009.758] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A new variety of active manganese oxide was prepared, characterized, and tested for its potential of adsorbing Congo Red, a dis-azo dye, from aqueous solutions. Both equilibrium and kinetics were investigated over different values of process parameters such as temperature (25-45 degrees C), adsorbent loading (0.4-0.6%), initial dye concentration (50-500 mg/L), presence of salts (sodium sulphate, 500 mg/L) and the oxygen content (MnO(x), x=1.2, 1.33 and 2) of the adsorbent. The equilibrium adsorption data were fitted to Langmuir and Freundlich isotherms. Langmuir adsorption capacity of the sorbent (x=1.33) for Congo Red was 38.6 mg/g at room temperature which is substantially higher than those for commercial manganese dioxide, red mud, coir pith, activated carbon, and fly ash. The kinetic data were best interpreted using a pseudo-second order model. The results show that the active manganese oxide used in this work removes the dye by reversible adsorption and has the potential for practical use for remediation of textile industry effluents.
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Affiliation(s)
- S Chakrabarti
- Department of Chemical Engineering, University of Calcutta, 92, Acharya P. C. Road, Kolkata 700 009, India.
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Üzer A, Erçağ E, Apak R. Spectrophotometric determination of cyclotrimethylenetrinitramine (RDX) in explosive mixtures and residues with the Berthelot reaction. Anal Chim Acta 2008; 612:53-64. [DOI: 10.1016/j.aca.2008.02.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2007] [Revised: 02/03/2008] [Accepted: 02/07/2008] [Indexed: 10/22/2022]
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Çelik S, Özyürek M, Güçlü K, Apak R. CUPRAC total antioxidant capacity assay of lipophilic antioxidants in combination with hydrophilic antioxidants using the macrocyclic oligosaccharide methyl β-cyclodextrin as the solubility enhancer. REACT FUNCT POLYM 2007. [DOI: 10.1016/j.reactfunctpolym.2007.07.045] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Özyürek M, Çelik S, Berker K, Güçlü K, Tor İ, Apak R. Sensitivity enhancement of CUPRAC and iron(III)-phenanthroline antioxidant assays by preconcentration of colored reaction products on a weakly acidic cation exchanger. REACT FUNCT POLYM 2007. [DOI: 10.1016/j.reactfunctpolym.2007.07.030] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Uzer A, Ercag E, Parlar H, Apak R, Filik H. Spectrophotometric determination of 4,6-dinitro-o-cresol (DNOC) in soil and lemon juice. Anal Chim Acta 2006; 580:83-90. [PMID: 17723759 DOI: 10.1016/j.aca.2006.07.047] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2006] [Revised: 06/19/2006] [Accepted: 07/21/2006] [Indexed: 11/24/2022]
Abstract
Although the use of once widely applied selective herbicide, 4,6-dinitro-o-cresol (DNOC), was cancelled by US-EPA in 1987, it is still found in soil and water due to its slow degradation in the environment. Since solid phase extraction-spectrophotometry combinations are much simpler and cheaper than chromatography/MS based methods and most routine laboratories lack such sophisticated instrumentation, it is desirable to establish novel sensitive, well-established, and field-applicable spectrophotometric methods for the rapid assay of DNOC in water and soil. For this purpose, two distinct spectrophotometric methods utilizing the periodate and copper(II)-neocuproine (Nc) reagents have been developed following Zn/HCl reduction of the pesticide in a microwave oven for 15s, and validated for DNOC determination at mg L(-1) level. The LOD values were 1.6 and 0.2 mg L(-1) for periodate and Cu(II)-Nc methods, respectively. Statistical comparison of the developed methods was made with the aid of high performance liquid chromatography (HPLC) equipped with a C18 (5 microm), 250 mm x 4.6 mm ID reversed phase column in conjunction with a UV (264 nm) detector, and a methanol (HPLC grade) +0.1% glacial acetic acid mixture mobile phase. Both spectrophotometric methods were directly applicable to soil since they were not interfered with common soil cations and anions, together with some pesticides. These methods were applied to real samples such as synthetically contaminated montmorillonite and lemon juice, and overall recovery efficiencies at the order of 95% or greater were achieved in the devised adsorption/elution procedures. An 8-hydroxyquinoline (oxine)-impregnated XAD copolymer resin stabilized with Fe(III) salt was used to preconcentrate DNOC at a concentration factor of 20 from lemon juice contaminated with 1 mg L(-1) DNOC, and the analyte retained at pH 2.5 was eluted with 0.025 M methanolic NaOH. Both the devised spectrophotometric methods and the proposed preconcentration column with optimized sorption and desorption conditions are novel for DNOC assay in the natural environment.
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Affiliation(s)
- A Uzer
- Department of Chemistry, Faculty of Engineering, Istanbul University, Avcilar 34320, Istanbul, Turkey
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Gümüş G, Demirata B, Apak R. Simultaneous spectrophotometric determination of cyanide and thiocyanate after separation on a melamine-formaldehyde resin. Talanta 2000; 53:305-315. [PMID: 18968116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2000] [Revised: 05/26/2000] [Accepted: 05/26/2000] [Indexed: 05/27/2023]
Abstract
A simple indirect spectrophotometric method for the determination of cyanide, based on the oxidation of the cyanide with chlorine (Cl(2)) is described. The residual chlorine is determined by the color reaction with o-tolidine (3,3'-dimethylbenzidine). The maximum absorbance for Cl(2) is at 437 nm. A linear calibration graph (0-4.0x10(-5) M CN(-)) is obtained under optimal reaction conditions at room temperature and pH 11-12. The stoichiometric mole ratio of chlorine to cyanide is 1:1. The effective molar absorptivity for cyanide is 5.87x10(4) l mol(-1) cm(-1) at pH 1.6. The limit of quantification (LOQ) is 3.6x10(-7) M or 9.4 ppb. Effects of pH, excess reagent, sensitivity, reaction time and tolerance limits of interferent ions are reported. The method was applied to the determination of cyanide in a real sample. The basic interferent usually accompanying CN(-), i.e. thiocyanate, is separated from cyanide by sorption on a melamine-formaldehyde resin at pH 9 while cyanide is not retained. Thiocyanate is eluted with 0.4 M NaOH from the column and determined spectrophotometrically using the acidic FeCl(3) reagent. The initial column effluent containing cyanide was analyzed by both the developed chlorine-o-tolidine method and the conventional barbituric acid-pyridine (Spectroquant 14800) procedure, and the results were statistically compared. The developed method is relatively inexpensive and less laborious than the standard (Spectroquant) procedure, and insensitive to the common interferent, cyanate (CNO(-)).
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Affiliation(s)
- G Gümüş
- Department of Chemistry, Faculty of Science and Letters, Istanbul Technical University, Maslak, 80626 Istanbul, Turkey
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Abstract
The decomposition of a number of chlorophenols (CPs), namely 2-CP, 2, 4-dichlorophenol and 2,4,6-trichlorophenol, has been studied in aqueous solution by UV-catalyzed oxidation with H(2)O(2) under UV radiation emitted by a 125-W medium pressure Hg lamp in an immersion well-type quartz photoreactor, and the organic-bound chlorine has been converted into the environmentally harmless inorganic chloride. For oxidant/CP mole ratios between 1:1 and 16:1, the reaction kinetics were modeled and the corresponding rate constants found by periodically measuring the remaining CP, hydrogen peroxide and converted chloride in solution. A theoretical model for the degradation pathway is proposed expressing the rate as a linear function of the concentrations of CP and oxidant. The rate constants for the pseudo-first order approximation of the CP degradation were compared. H(2)O(2), when combined with UV, is an effective photoactivated oxidant. The photodegradation order in terms of the initial rate of CPs destruction was: Cl(3).Ph>/=Cl(2).Ph>Cl.Ph.
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Affiliation(s)
- M Hugül
- Department of Chemistry, Faculty of Engineering, Istanbul University, Avcilar, 34850, Istanbul, Turkey
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Oztürk BD, Filik H, Tütem E, Apak R. Simultaneous derivative spectrophotometric determination of cobalt(II) and nickel(II) by dithizone without extraction. Talanta 2000; 53:263-269. [PMID: 18968111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/1999] [Revised: 02/29/2000] [Accepted: 03/03/2000] [Indexed: 05/27/2023]
Abstract
Dithizone (Dz), a common extractive-photometric ligand for Co(II) and Ni(II), has been dissolved in the water-miscible solvent tetrahydrofurane (THF) so as to constitute a reagent for both metals in aqueous phase without extraction. Complex formation was complete for both metals at pH 12.0 (adjusted by aqueous NH(3)) within 30 min, and the complexes were stable for at least 2 h. First-derivative spectra of the metal dithizonates (singly or as binary mixtures) were preferred to ordinary spectra, because working wavelength determination was more precise and spectral overlap was less. Two wavelengths at which the spectral overlap was minimum were selected as analytical wavelengths, i.e. 620 nm for Co and 740 nm for Ni, and the calibration curves drawn with zero-to-peak values as a function of concentration were linear for these wavelengths. Thus, the total (1)D values at 620 and 740 nm of the mixtures were used to determine Co and Ni concentrations. The relative standard deviation (R.S.D.) for the analysis of Co (3.0 mg l(-1)) individually was 3.5%, and for its admixture with Ni (3.5 mg l(-1)) was 2.5%. The R.S.D. for the analysis of Ni (5.9 mg l(-1)) individually and for its admixture with Co (1.8 mg l(-1)) were 5.5 and 5.8%, respectively. The linear range in (1)D evaluation was between 5.0x10(-6) and 1.0x10(-4) M for Co and 2.0x10(-5)-2.0x10(-4) M for Ni. Interference analysis was performed for individual metal (Co or Ni) determinations. Finally, the method has been applied to a Ni-Cr-based dental alloy (Wiron 99) successfully.
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Affiliation(s)
- B D Oztürk
- Department of Chemistry, Faculty of Science and Letters, Istanbul Technical University, Maslak, Istanbul, Turkey
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Güçlü K, Apak R. Modeling of Copper(II), Cadmium(II), and Lead(II) Adsorption on Red Mud from Metal-EDTA Mixture Solutions. J Colloid Interface Sci 2000; 228:238-252. [PMID: 10926462 DOI: 10.1006/jcis.2000.6974] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The adsorption of toxic heavy metal cations, i.e., Cu(II), Cd(II), and Pb(II), from metal-EDTA mixture solutions on a composite adsorbent having a heterogeneous surface, i.e., bauxite waste red mud, has been investigated and modeled with the aid of a modified surface complexation approach in respect to pH and complexant dependency of heavy metal adsorption. EDTA was selected as the modeling ligand in view of its wide usage as an anthropogenic chelating agent and abundance in natural waters. The adsorption experiments were conducted for metal salts (nitrates), metal-EDTA complexes alone, or in mixtures containing (metal+metal-EDTA). The adsorption equilibrium constants for the metal ions and metal-EDTA complexes were calculated. For all studied cases, the solid adsorbent phase concentrations of the adsorbed metal and metal-EDTA complexes were found by using the derived model equations with excellent compatibility of experimental and theoretically generated adsorption isotherms. The model was useful for metal and metal-EDTA mixture solutions either at their natural pH of equilibration with the sorbent, or after pH elevation with NaOH titration up to a certain pH. Thus adsorption of every single species (M(2+) or MY(2-)) or of possible mixtures (M(2+)+MY(2-)) at natural pH or after NaOH titration could be calculated by the use of simple quadratic model equations, once the initial concentrations of the corresponding species, i.e., [M(2+)](0) or [MY(2-)](0), were known. The compatibility of theoretical and experimental data pairs of adsorbed species concentrations was verified by means of nonlinear regression analysis. The findings of this study can be further developed so as to serve environmental risk assessment concerning the expansion of a heavy metal contaminant plume with groundwater move ment in soil consisting of hydrated-oxide type minerals. Copyright 2000 Academic Press.
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Affiliation(s)
- K Güçlü
- Department of Chemistry, Faculty of Engineering, Istanbul University, Avciotalar, Istanbul, 34850, Turkey
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Abstract
As an alternative to species distribution diagrams (pM vs pH curves in aqueous solution) drawn for a fixed total metal concentration, this work has developed simple linear models for correlating the limiting pH of metal ion solubility-in equilibrium with the least soluble amorphous metal hydroxide solid phase-to the total metal concentration. Thus adsorptive metal removal processes in complex systems can be better designed once the limiting pH of heavy metal solubility (i.e., pH*) in such a complex environment can be envisaged by simple linear equations. pH* vs pMt (Mt = total metal concentration that can exist in aqueous solution in equilibrium with M(OH)2(s)) linear curves for uranyl-hydroxide, uranyl-carbonate-hydroxide, and mercuric-chloride-hydroxide simple and mixed-ligand systems and cupric-carbonate-hydroxide complexes in equilibrium with mixed hydroxide solid phases may enable the experimental chemist to distinguish true adsorption (e.g., onto hydrous oxide sorbents) from bulk precipitation removal of the metal and to interpret some anomalous metal fixation data-usually attributed to pure adsorption in the literature-with precipitation if the pMt at the studied pH is lower than that tolerated by pH* vs pMt curves. This easily predictable pH* corresponding to a given pMt may aid the design of desorptive mobilization experiments for certain metals as well as their adsorptive removal with the purpose of simulating metal adsorption and desorption cycles in real complex environments with changing groundwater pH. Copyright 1999 Academic Press.
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Affiliation(s)
- R Apak
- Faculty of Engineering, Istanbul University, Avcilar, Istanbul, 34850, Turkey
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Abstract
4-Chlorophenol in the presence of catalysts was decomposed in aqueous solution by a 125 W medium pressure mercury lamp in a thermostated quartz batch photoreactor, and the organic bound chlorine was catalytically converted into the environmentally less harmful inorganic chloride. Differences in the concentration of 4-chlorophenol and of the intermediates, such as hydroquinone and quinone, are followed by HPLC. The best catalyst among a homolog series for the photo-decomposition of 4-chlorophenol was selected as finely dispersed platinum oxide on a TiO2 semiconductor support, and kinetic parameters of the Langmuir-Hinshelwood type decomposition reaction were reported for the selected catalyst. A simple mechanism of substrate degradation in accord with the chosen kinetic model was postulated. The developed process may serve photooxidative removal of chlorophenols in wastewater without using costly oxidants.
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Affiliation(s)
- M Hügül
- University of Istanbul, Faculty of Engineering, Department of Chemistry, Turkey
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Filik H, Apak R. A Chelating Ion Exchanger for Gallium Recovery from Alkaline Solution Using 5-Palmitoyl-8- hydroxyquinoline Immobilized on a Nonpolar Adsorbent. SEP SCI TECHNOL 1998. [DOI: 10.1080/01496399808545244] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Tütem E, Apak R, Sözgen K. The interaction of antitumor-active anthraquinones with biologically important redox couples: I. Spectrophotometric investigation of the interaction of carminic acid and mitoxantrone with the iron (II, III) and copper (I, II) redox couples. J Inorg Biochem 1996; 61:79-96. [PMID: 8576709 DOI: 10.1016/0162-0134(95)00023-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Studying the interaction of antitumor-active anthraquinones with biologically important redox couples is important in understanding the possible reductive or oxidative mode of metabolism of these antineoplastic agents coupled with the formation of free radicals. The interactions of such anthraquinones, i.e., carminic acid (CA) and mitoxantrone (Mx) with iron(II, III) and copper(I, II) redox couples in oxygenated and deaerated solutions, were investigated by UV-Visible and IR-spectroscopy. The superoxide radical reagent, nitroblue tetrazolium (NBT), was added to the metal and anthraquinone solutions and their binary mixtures at varying pH. Formazan, the reduction product of NBT, was produced mainly as a result of Fe(II)-NBT and Fe(II)-Mx-NBT interactions. The ternary mixtures of the lower valencies of iron and copper with CA and NBT exhibited intensive charge-transfer bands in the visible region, while metal-Mx-NBT combinations did not produce such bands, possibly due to the blockage of the redox-active aminoethanolamine side-chains of Mx through coordination with the metals. Copper-Mx combinations showed an oxygen sensitivity as spectral evidence was obtained for the oxidative transformation of Mx to the cyclic primary metabolite. The results were evaluated in regard to the possible oxidative activation of the studied anthracenediones with iron and copper systems.
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Affiliation(s)
- E Tütem
- Department of Chemistry, Faculty of Engineering, Istanbul University, Turkey
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