Displaying publications 201 - 220 of 349 in total

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  1. Fulltext The effect of laser repetition rate on the LASiS synthesis of biocompatible silver nanoparticles in aqueous starch solution
    Zamiri R, Zakaria A, Ahangar HA, Darroudi M, Zamiri G, Rizwan Z, et al.
    Int J Nanomedicine, 2013;8:233-44.
    PMID: 23345971 DOI: 10.2147/IJN.S36036
    Laser ablation-based nanoparticle synthesis in solution is rapidly becoming popular, particularly for potential biomedical and life science applications. This method promises one pot synthesis and concomitant bio-functionalization, is devoid of toxic chemicals, does not require complicated apparatus, can be combined with natural stabilizers, is directly biocompatible, and has high particle size uniformity. Size control and reduction is generally determined by the laser settings; that the size and size distribution scales with laser fluence is well described. Conversely, the effect of the laser repetition rate on the final nanoparticle product in laser ablation is less well-documented, especially in the presence of stabilizers. Here, the influence of the laser repetition rate during laser ablation synthesis of silver nanoparticles in the presence of starch as a stabilizer was investigated. The increment of the repetition rate does not negatively influence the ablation efficiency, but rather shows increased productivity, causes a red-shift in the plasmon resonance peak of the silver-starch nanoparticles, an increase in mean particle size and size distribution, and a distinct lack of agglomerate formation. Optimal results were achieved at 10 Hz repetition rate, with a mean particle size of ~10 nm and a bandwidth of ~6 nm 'full width at half maximum' (FWHM). Stability measurements showed no significant changes in mean particle size or agglomeration or even flocculation. However, zeta potential measurements showed that optimal double layer charge is achieved at 30 Hz. Consequently, Ag-NP synthesis via the laser ablation synthesis in solution (LASiS) method in starch solution seems to be a trade-off between small size and narrow size distributions and inherent and long-term stability.
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  2. Optimization of semi-aerobic stabilized leachate treatment using ozone/Fenton's reagent in the advanced oxidation process
    Abu Amr SS, Aziz HA, Adlan MN, Bashir MJ
    J Environ Sci Health A Tox Hazard Subst Environ Eng, 2013;48(7):720-9.
    PMID: 23445415 DOI: 10.1080/10934529.2013.744611
    The objective of this study was to investigate the performance of employing Fenton's reagent in the advanced oxidation of ozone to treat stabilized landfill leachate in an ozone reactor. A central composite design (CCD) with response surface methodology (RSM) was applied to evaluate the relationships between operating variables, such as ozone and Fenton dosage, pH, and reaction time, to identify the optimum operating conditions. Quadratic models for the following four responses proved to be significant with very low probabilities (<0.0001): chemical oxygen demand (COD), color, NH-N, and ozone consumption (OC). The obtained optimum conditions included a reaction time of 90 min, 30 g/m³ ozone, 0.01 mol/L₂H₂O,0.02 mol/L Fe²⁺, and pH 5. COD, color, and NH₃-N removal rates of 79%, 100%, and 20%, respectively, and 0.18 kg O₃/kg COD OC were obtained. The predictions correspond well with experimental results (COD, color, and NH-N removal rates of 78%, 98.5%, and 19%, respectively, and 0.29 kg O₃/kg COD OC). This method reduces the treatment time and improves the treatment efficiency relative to a previously published method that used Fenton's reagent prior to ozonation.
    Matched MeSH terms: Spectrophotometry
  3. Fulltext Green biosynthesis of silver nanoparticles using Curcuma longa tuber powder
    Shameli K, Ahmad MB, Zamanian A, Sangpour P, Shabanzadeh P, Abdollahi Y, et al.
    Int J Nanomedicine, 2012;7:5603-10.
    PMID: 23341739 DOI: 10.2147/IJN.S36786
    Green synthesis of noble metal nanoparticles is a vastly developing area of research. Metallic nanoparticles have received great attention from chemists, physicists, biologists, and engineers who wish to use them for the development of a new-generation of nanodevices. In this study, silver nanoparticles were biosynthesized from aqueous silver nitrate through a simple and eco-friendly route using Curcuma longa tuber-powder extracts, which acted as a reductant and stabilizer simultaneously. Characterizations of nanoparticles were done using different methods, which included ultraviolet-visible spectroscopy, powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray fluorescence spectrometry, and Fourier-transform infrared spectroscopy. The ultraviolet-visible spectrum of the aqueous medium containing silver nanoparticles showed an absorption peak at around 415 nm. Transmission electron microscopy showed that mean diameter and standard deviation for the formation of silver nanoparticles was 6.30 ± 2.64 nm. Powder X-ray diffraction showed that the particles are crystalline in nature, with a face-centered cubic structure. The most needed outcome of this work will be the development of value-added products from C. longa for biomedical and nanotechnology-based industries.
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  4. Simultaneous determination of preservatives (benzoic acid, sorbic acid, methylparaben and propylparaben) in foodstuffs using high-performance liquid chromatography
    Saad B, Bari MF, Saleh MI, Ahmad K, Talib MK
    J Chromatogr A, 2005 May 06;1073(1-2):393-7.
    PMID: 15909546
    A reversed-phased HPLC method that allows the separation and simultaneous determination of the preservatives benzoic (BA) and sorbic acids (SA), methyl- (MP) and propylparabens (PP) is described. The separations were effected by using an initial mobile phase of methanol-acetate buffer (pH 4.4) (35:65) to elute BA, SA and MP and changing the mobile phase composition to methanol-acetate buffer (pH 4.4) (50:50) thereafter. The detector wavelength was set at 254 nm. Under these conditions, separation of the four components was achieved in less than 23 min. Analytical characteristics of the separation such as limit of detection, limit of quantification, linear range and reproducibility were evaluated. The developed method was applied to the determination of 67 foodstuffs (mainly imported), comprising soft drinks, jams, sauces, canned fruits/vegetables, dried vegetables/fruits and others. The range of preservatives found were from not detected (nd)--1260, nd--1390, nd--44.8 and nd--221 mg kg(-1) for BA, SA, MP and PP, respectively.
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  5. Effect of inorganic salts and glucose additives on dose-response, melting point and mass density of genipin gel dosimeters
    Al-jarrah AM, Abdul Rahman A, Shahrim I, Razak NN, Ababneh B, Tousi ET
    Phys Med, 2016 Jan;32(1):36-41.
    PMID: 26494156 DOI: 10.1016/j.ejmp.2015.09.003
    Genipin gel dosimeters are hydrogels infused with a radiation-sensitive material which yield dosimetric information in three dimensions (3D). The effect of inorganic salts and glucose on the visible absorption dose-response, melting points and mass density of genipin gel dosimeters has been experimentally evaluated using 6-MV LINAC photons. As a result, the addition of glucose with optimum concentration of 10% (w/w) was found to improve the thermal stability of the genipin gel and increase its melting point (Tm) by 6 °C accompanied by a slight decrease of dose-response. Furthermore, glucose helps to adjust the gel mass density to obtain the desired tissue-equivalent properties. A drop of Tm was observed when salts were used as additives. As the salt concentration increased, gel Tm decreased. The mass density and melting point of the genipin gel could be adjusted using different amounts of glucose that improved the genipin gel suitability for 3D dose measurements without introducing additional toxicity to the final gel.
    Matched MeSH terms: Spectrophotometry
  6. Removal of humic and tannic acids by adsorption-coagulation combined systems with activated biochar
    Jung C, Phal N, Oh J, Chu KH, Jang M, Yoon Y
    J Hazard Mater, 2015 Dec 30;300:808-814.
    PMID: 26340547 DOI: 10.1016/j.jhazmat.2015.08.025
    Despite recent interest in transforming biomass into bio-oil and syngas, there is inadequate information on the compatibility of byproducts (e.g., biochar) with agriculture and water purification infrastructures. A pyrolysis at 300°C yields efficient production of biochar, and its physicochemical properties can be improved by chemical activation, resulting in a suitable adsorbent for the removal of natural organic matter (NOM), including hydrophobic and hydrophilic substances, such as humic acids (HA) and tannic acids (TA), respectively. In this study, the adsorption affinities of different HA and TA combinations in NOM solutions were evaluated, and higher adsorption affinity of TA onto activated biochar (AB) produced in the laboratory was observed due to its superior chemisorption tendencies and size-exclusion effects compared with that of HA, whereas hydrophobic interactions between adsorbent and adsorbate were deficient. Assessment of the AB role in an adsorption-coagulation hybrid system as nuclei for coagulation in the presence of aluminum sulfate (alum) showed a synergistic effect in a HA-dominated NOM solution. An AB-alum hybrid system with a high proportion of HA in the NOM solution may be applicable as an end-of-pipe solution.
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  7. Phytoremediation of iron from red soil of tropical region by using Centella asiatica
    Bhat IU, Mauris EN, Khanam Z
    Int J Phytoremediation, 2016 Sep;18(9):918-23.
    PMID: 26940261 DOI: 10.1080/15226514.2016.1156637
    The accumulation and removal efficiency of Fe by Centella asiatica was carried out at various Fe concentrations in soil treatments (0, 50, 100, 150 and 200 mg Fe/kg soil). Iron accumulation in different parts of C. asiatica (leaf, stem and root) was analyzed by atomic absorption spectrophotometer (AAS). Factorial experiment with a completely randomized design and Duncan's test were used for data analyses. The results revealed that C. asiatica have the ability to uptake and accumulate Fe significantly (p 1 and <1, respectively, further supporting its metal hyperaccumulator properties.
    Matched MeSH terms: Spectrophotometry, Atomic
  8. Fulltext Optimisation of the Photonic Efficiency of TiO2 Decorated on MWCNTs for Methylene Blue Photodegradation
    Abdullahi N, Saion E, Shaari AH, Al-Hada NM, Keiteb A
    PLoS One, 2015;10(5):e0125511.
    PMID: 25993127 DOI: 10.1371/journal.pone.0125511
    MWCNTs/TiO2 nanocomposite was prepared by oxidising MWCNT in H2SO4/HNO3 then decorating it with TiO2-p25 nanopowder. The composites were characterised using XRD, TEM, FT-IR PL and UV-vis spectroscopy. The TEM images have shown TiO2 nanoparticles immobilised onto the sidewalls of the MWCNTs. The UV-vis spectrum confirms that the nanocomposites can significantly absorb more light in the visible regions compared with the commercial TiO2 (P25). The catalytic activity of these nanocomposites was determined by photooxidation of MB aqueous solution in the presence of visible light. The MWCNTs/TiO2 (1:3) mass ratio showed maximum degradation efficiency. However, its activity was more favourable in alkaline and a neutral pH than an acidic medium.
    Matched MeSH terms: Spectrophotometry
  9. Iridoids from Rothmannia macrophylla
    Ling SK, Tanaka T, Kouno I
    J Nat Prod, 2001 Jun;64(6):796-8.
    PMID: 11421747
    A new iridoid glucoside with an ether linkage between C-3 and C-10 and a novel nonglycosidic iridoid with an ether linkage between C-3 and C-6 and a lactonic linkage at C-1, named macrophylloside (1) and macrophyllide (2), respectively, were isolated from the leaves of Rothmannia macrophylla, along with six known iridoids. Their structures were established by NMR and MS spectroscopies.
    Matched MeSH terms: Spectrophotometry, Infrared
  10. The concentration of selected minerals and phytate in Malaysian Brachiaria decumbens
    Noordin MM, Zhang SS, Rahman SO, Haron J
    Vet Hum Toxicol, 2000 Oct;42(5):276-9.
    PMID: 11003117
    Samples of Brachiaria decumbens collected from 5 farms representing the Peninsular Malaysia were subjected to selected trace mineral and phytate analyses to explain the pathogenesis of B decumbens intoxication. Concentrations of Cu, Zn, Fe and Mo were comparable to other grasses while that of phytate was low. The molar ratios of Cu:Zn, Cu:Mo, and Cu:Fe warrant that Cu deficiency is involved in the toxicity of B decumbens. This might aggravate the development of photosensitization of unpigmented or lightly pigmented areas of affected animals. The Zn:phytate ratio could predispose to Zn deficiency during intoxication.
    Matched MeSH terms: Spectrophotometry, Atomic
  11. Quaternized wood as sorbent for reactive dyes
    Low KS, Lee CK, Tan BF
    Appl Biochem Biotechnol, 2000 Jun;87(3):233-45.
    PMID: 10982232
    Various species of local wood modified with N-(3-chloro-2-hydroxypropyl)-trimethylammonium chloride showed sorption enhancement for hydrolyzed Reactive Blue 2 (HRB) compared to the untreated samples. The enthalpy of sorption of HRB on Simpoh (Dillenia suffruticosa) was found to be endothermic. Maximum sorption capacity calculated from the Langmuir isotherm was 250.0 mg/g. Under continuous flow conditions HRB could be successfully removed. Dye removal was a function of bed depth and flow rate. However, the bed depth service time model of Bohart and Adams was not applicable in the HRB-quaternized wood system. The modified wood was applied to a sample of industrial textile effluent, and it was found to be able to remove the color successfully under batch conditions.
    Matched MeSH terms: Spectrophotometry
  12. The accumulation and distribution of trace metals in some localized marine species
    Yusof AM, Rahman NA, Wood AK
    Biol Trace Elem Res, 1994;43-45:239-49.
    PMID: 7710833
    Trace elements, such as As, Co, Cr, Hg, Sb, and Zn, were determined by neutron activation analysis (NAA), whereas Cd, Cu, and Pb were determined by graphite furnace atomic absorption spectroscopy (GFAAS) in clam, crab, prawn, swamp cerith, and mussel samples after digestion by microwave heating under controlled conditions before eluting the solutions through a column of a chelating resin, Chelex-100. The standard used in the determination of percentage volatile elements retained by microwave digestion and also in the activation process was Lobster Hepatopancreas TORT-1, whereas known mixed standards were prepared from nitrate salts to determine the efficiency of the separation procedure at a controlled pH. Mercury and lead detected in crabs exceeded the maximum permissible level. Some species also showed a high affinity toward certain elements, and their levels of accumulation in the tissues of these species corresponded with the concentration of these elements in sediments, especially at sites in the vicinity of an industrial zone.
    Matched MeSH terms: Spectrophotometry, Atomic
  13. Effects of salinity and pre-exposure on acute cadmium toxicity to seabass, Lates calcarifer
    Shazili NA
    Bull Environ Contam Toxicol, 1995 Jan;54(1):22-8.
    PMID: 7756781
    Matched MeSH terms: Spectrophotometry, Atomic
  14. Determination of a new antifilarial drug, UMF-058, and mebendazole in whole blood by high-performance liquid chromatography
    Ramanathan S, Nair NK, Mansor SM, Navaratnam V
    J. Chromatogr., 1993 Jun 02;615(2):303-7.
    PMID: 8335708
    A rapid and selective high-performance liquid chromatographic assay for simultaneous quantitative determination of a new antifilarial drug (UMF-058, I) and mebendazole (MBZ) is described. After a simple extraction from whole blood, both compounds were analysed using a C18 Nova Pak reversed-phase column and a mobile phase of methanol-0.05 M ammonium dihydrogenphosphate (50:50, v/v) adjusted to pH 4.0, with ultraviolet detection at 291 nm. The average recoveries of I and MBZ over a concentration range of 25-250 ng/ml were 92.0 +/- 7.7 and 84.4 +/- 4.4%, respectively. The minimum detectable concentrations in whole blood for I and MBZ were 7 and 6 ng/ml, respectively. This method was found to be suitable for pharmacokinetic studies.
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  15. Kinetics and mechanism of the alkaline hydrolysis of securinine
    Lajis NH, Noor HM, Khan MN
    J Pharm Sci, 1995 Jan;84(1):126-30.
    PMID: 7714735
    The hydroxide ion-catalyzed hydrolysis of securinine involves the ring opening of the lactone moiety. The rate of hydrolysis is insensitive to the ionic strength. The observed pseudo-first-order rate constants reveal a decrease of approximately 4-fold due to the increase in the MeCN content from 4 to 50% (v/v) in mixed aqueous solvent. The temperature dependence of the rate of hydrolysis follows the Eyring equation, which yields delta H* and delta S* as 11.0 kcal mol-1 and -34.5 cal deg-1 mol-1, respectively. The hydroxyl carboxylate product of the alkaline hydrolysis of securinine is shown to undergo cyclization in acidic medium to yield securinine. The observed pseudo-first-order rate constants for cyclization increase linearly with an increase in [H+]. The change in the content of MeCN from 3.8 to 47.2% (v/v) in mixed aqueous solvents does not show an effect on the rate of the cyclization reaction. The most plausible mechanisms for alkaline hydrolysis and acid cyclization reactions are also discussed.
    Matched MeSH terms: Spectrophotometry, Ultraviolet
  16. Fulltext Synthesis, Characterization, and Toxicity Assessment of Pluronic F127-Functionalized Graphene Oxide on the Embryonic Development of Zebrafish (Danio rerio)
    Shamsi S, Alagan AA, Sarchio SNE, Md Yasin F
    Int J Nanomedicine, 2020;15:8311-8329.
    PMID: 33149578 DOI: 10.2147/IJN.S271159
    Background: In the current literature, there are ongoing debates on the toxicity of graphene oxide (GO) that demonstrate contradictory findings regarding its toxicity profile. As a potential drug carrier, these findings are very concerning due to the safety concerns in humans, as well as the dramatic rise of GO being excreted into the environment. Therefore, there is an imperative need to mitigate the potential toxicity of GO to allow for a safer application in the future.

    Purpose: The present study aims to address this issue by functionalizing GO with Pluronic F127 (PF) as a means to mitigate toxicity and resolve the biocompatibility of GO. Although results from previous studies generally indicated that Pluronic functionalized GO exhibits relatively low toxicity to living organisms, reports that emphasize on its toxicity, particularly during embryonic developmental stage, are still scarce.

    Methods: In the present study, two different sizes of native GO samples, GO and NanoGO, as well as PF-functionalized GO, GO-PF and NanoGO-PF, were prepared and characterized using DLS, UV-Vis, Raman spectroscopy, FTIR, and FESEM analyses. Toxicological assessment of all GO samples (0-100 µg/mL) on zebrafish embryonic developmental stages (survival, hatching and heart rates, and morphological changes) was recorded daily for up to 96 hours post-fertilization (hpf).

    Results: The toxicity effects of each GO sample were observed to be higher at increasing concentrations and upon prolonged exposure. NanoGO demonstrated lower toxicity effects compared to GO. GO-PF and NanoGO-PF were also found to have lower toxicity effects compared to native GO samples. GO-PF showed the lowest toxicity response on zebrafish embryo.

    Conclusion: These findings highlight that toxicity is dependent on the concentration, size, and exposure period of GO. Functionalization of GO with PF through surface coating could potentially mitigate the toxicity effects of GO in embryonic developmental stages, but further investigation is warranted for broader future applications.

    Matched MeSH terms: Spectrophotometry, Ultraviolet
  17. Effects of Fuller's Earth and activated charcoal on oral absorption of paraquat in rabbits
    Idid SZ, Lee CY
    Clin Exp Pharmacol Physiol, 1996 Aug;23(8):679-81.
    PMID: 8886489
    1. Thirty male rabbits of local strain (weighing 1.5-2 kg) were divided into five groups. Four groups were treated with an oral dose of paraquat, which was followed by either Fuller's Earth or activated charcoal 0.5 or 2.0 h later. The remaining group acted as the control group and was treated only with an oral dose of paraquat. The dose of paraquat was 20.0 mg/kg given in a concentration of 20.0 mg/mL. 2. Both adsorbents were administered in 15 mL normal saline as a 30% slurry. Blood was sampled from the ear vein 0.5, 1, 2, 4, 8 and 24h after the administration of paraquat. 3. Paraquat concentration was determined spectophotometrically at 600 nm by comparing against a standard curve of paraquat obtained by the addition of standard paraquat into normal rabbit serum and extracting interfering substances with ether. 4. The results of the present study show that either adsorbent can bring down the serum paraquat level. There was no significant difference found in the effectiveness of either adsorbent. 5. It is concluded that the administration of an adsorbent as early as possible will help in the reduction of paraquat absorption from the gastrointestinal tract. 6. Activated charcoal is still effective in lowering serum paraquat concentration when given more than 1 h after ingestion of paraquat.
    Matched MeSH terms: Spectrophotometry
  18. A facile water-induced complexation of lycopene and pectin from pink guava byproduct: Extraction, characterization and kinetic studies
    Nagarajan J, Krishnamurthy NP, Nagasundara Ramanan R, Raghunandan ME, Galanakis CM, Ooi CW
    Food Chem, 2019 Oct 30;296:47-55.
    PMID: 31202305 DOI: 10.1016/j.foodchem.2019.05.135
    The redfleshed pulp discarded from pink guava puree industry is a rich source of lycopene and pectin. In this study, we developed a facile extraction process employing water as the primary extraction medium to isolate the lycopene and pectin from pink guava decanter. When the decanter was suspended in water, the complexation of lycopene and pectin formed the cloudy solution, where the colloidal complexes were recovered through centrifugation. The presence of lycopene and pectin in the complex was confirmed by the spectroscopic, microscopic and chromatographic analyses. The lycopene fractionated from the complexes had a purity level of 99% and was in all-trans configuration. The colloidal complexes yielding the highest concentration of lycopene was obtained at pH 7, 1% (w/v) solid loading and 25 °C. The experimental data of time-course extraction of lycopene-pectin complex were best fitted with two-site kinetic model, hinting the fast- and slow-release phases in the extraction process.
    Matched MeSH terms: Spectrophotometry
  19. Verifying measurements of residual calcium content in demineralised cortical bone
    Ariffin AF, Yusof N, Mohd S, Rahman SA, Ramalingam S, Mansor A, et al.
    Cell Tissue Bank, 2019 Dec;20(4):527-534.
    PMID: 31456097 DOI: 10.1007/s10561-019-09785-4
    Calcium contents of demineralised human cortical bone determined by titrimetric assay and atomic absorption spectrophotometry technique were verified by comparing to neutron activation analysis which has high recovery of more than 90%. Conversion factors determined from the comparison is necessary to correct the calcium content for each technique. Femurs from cadaveric donors were cut into cortical rings and demineralised in 0.5 M hydrochloric acid for varying immersion times. Initial calcium content in the cortical bone measured by titration was 4.57%, only 21% of the measurement by neutron activation analysis; while measured by atomic absorption spectrophotometer was 13.4%, only 61% of neutron activation analysis. By comparing more readings with the measurements by neutron activation analysis with 93% recovery, a conversion factor of 4.83 was verified and applied for the readings by titration and 1.45 for atomic absorption spectrophotometer in calculating the correct calcium contents. The residual calcium content started to reduce after the cortical bone was demineralised in hydrochloric acid for 8 h and reduced to 13% after 24 h. Using the linear relationship, the residual calcium content could be reduced to less than 8% after immersion in hydrochloric acid for 40 h. Atomic absorption spectrophotometry technique is the method of choice for calcium content determination as it is more reliable compared to titrimetric assay.
    Matched MeSH terms: Spectrophotometry, Atomic
  20. Fulltext Ultrasound-assisted sequentially precipitated nickel-silica catalysts and its application in the partial hydrogenation of edible oil
    Lim MSW, Yang TC, Tiong TJ, Pan GT, Chong S, Yap YH
    Ultrason Sonochem, 2021 May;73:105490.
    PMID: 33609992 DOI: 10.1016/j.ultsonch.2021.105490
    Sequentially precipitated Mg-promoted nickel-silica catalysts with ageing performed under various ultrasonic intensities were employed to study the catalyst performance in the partial hydrogenation of sunflower oil. Results from various characterisation studies showed that increasing ultrasonic intensity caused a higher degree of hydroxycarbonate erosion and suppressed the formation of Ni silicates and silica support, which improved Ni dispersion, BET surface area and catalyst reducibility. Growth of silica clusters on the catalyst aggregates were observed in the absence of ultrasonication, which explained the higher silica and nickel silicate content on the outer surface of the catalyst particle. Application of ultrasound also altered the electron density of the Ni species, which led to higher activity and enhanced product selectivity for sonicated catalysts. The catalyst synthesised with ultrasonic intensity of 20.78 Wcm-2 achieved 22.6% increase in hydrogenation activity, along with 28.5% decrease in trans-C18:1 yield at IV = 70, thus supporting the feasibility of such technique.
    Matched MeSH terms: Spectrophotometry, Atomic
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