In standardization NAA, it is necessary to characterize the neutron spectrum parameters such as epithermal neutron flux shape factor (α), thermal to epithermal neutron flux ratio (f), thermal neutron flux (φth) and epithermal neutron flux (φepi) in the irradiation facility to determine the concentration of an element in the sample using absolute and k0 standardization methods. The α and f were determined using Cd-ratio multi monitor method using experimental data obtained in PUSPATI TRIGA Mark II research reactor at four irradiation positions (10, 20, 30 and 40) of the rotary rack. The calculated values of α and f ranged from 0.006 to 0.0281 and 18.56 to 19.12 respectively. The average values of φth and φepi were found as 2.33 × 1012 and 1.23 × 1011 n cm?2 s?1 respectively. Moreover, a comparison of the neutron flux parameters in the present study shows an acceptable level of consistency with those of previous studies. 相似文献
A clean-up procedure based on a solid-phase extraction column was optimized for determination of polycyclic aromatic hydrocarbons (PAHs) in lichen extracts to remove co-extracted compounds from the matrix in the final extract. Several kinds of solid phases were evaluated: normal phase (-NH2 and alumina), strong anion exchange and reversed phase. The -NH2 columns were the most effective by using a packed solid bed of 500?mg. The lichen raw extract was loaded on the column previously conditioned with dichloromethane and hexane. Hexane (0.5?mL) was used as rinsing solvent, and PAHs were quantitatively eluted (80–97%) using 2?mL of hexane–dichloromethane (65–35) as eluting solvent. In these conditions, even the heaviest PAHs were quantitatively eluted. The optimized SPE method provides a short time and low-solvent-consumption sample clean-up compared with other conventional methods based on column chromatography. The analytical procedure, dynamic sonication-assisted extraction, followed by the optimized solid-phase extraction clean-up, was used to determine the 16 EPA priority PAHs from native lichens collected from the Aragon valley in central Pyrenees. The PAH concentrations in lichen samples ranged from 352 to 1654?ng?g?1, and the minimum concentration value was established as the regional reference PAH levels in the area. 相似文献
Fine powder of Typha latifolia L. root was used for adsorption of copper and zinc ions from buffered and nonbuffered aqueous solutions. The adsorption reached equilibrium in 60 min. During this time, more than 90 % of the adsorption process was completed. The effect of initial pH, initial concentration of metal ion, and contact time was investigated in a batch system at room temperature. The optimum adsorption performance was observed at pH 5.00 and 4.25 for nonbuffered solutions of Cu(II) and Zn(II), respectively, while for buffered solutions it occurred at pH 6.00. The total metal uptake decreased on application of ammonium acetate buffer, from 37.35 to 17.00 mg g?1 and 28.80 to 9.90 mg g?1 for Cu(II) and Zn(II) solutions, respectively, with 100 mg L?1 initial concentration. The pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich models were used to describe the adsorption kinetics. The experimental data followed the pseudo-second-order kinetic model. The biosorption equilibrium was well described by Langmuir and Freundlich isotherm models. 相似文献
Nanoparticles of ferrites (Fe3O4, NiFe2O4, CuFe2O4, and MnFe2O4) were prepared by a reverse (water/oil) microemulsion method. The microemulsion system consisted of cetyltrimethylammonium bromide, 1-butanol, cyclohexane, and a metal salt solution. The procedure was carried out using aqueous ammonia as the coprecipitating agent. Nanosized particles were characterized by thermal analysis, X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and pyridine adsorption. The NiFe2O4 sample exhibited narrow mesoporous pore size distribution and high surface area ≈233 m2/g. It achieved good adsorption activity towards the dibenzothiophene (DBT) compound (166.3 μmol/g of DBT adsorbent). The structural properties obtained were very interesting for potential applications in the desulfurization process in petroleum refining. 相似文献
Hierarchical semicrystalline block copolymer nanoparticles are produced in a segmented gas‐liquid microfluidic reactor with top‐down control of multiscale structural features, including nanoparticle morphologies, sizes, and internal crystallinities. Control of multiscale structure on disparate length scales by a single control variable (flow rate) enables tailoring of drug delivery nanoparticle function including release rates.
Heterogeneous photocatalysis has been extensively investigated for the degradation of organic pollutants from wastewater. The remarkable advantages of the heterogeneous photocatalysis process depend upon its ability to produce reactive oxygen species under visible/UV/solar light irradiation. However, the long-term stability and reuse potential of these catalysts are of great concern these days, yet understudied. This review aims to systematically present a state of the art understanding of such catalysts' reuse potential. Various important surface characteristics of the photocatalysts for improving the photostability and activity of the catalyst are discussed. Besides, the synergistic effect of different surface modified materials, composite materials and their surface characteristics for their enhanced activity are also covered. Finally, a discussion on various regeneration processes used for such catalysts is also presented, identifying some vital research needs in this field. 相似文献
Marine feed ingredients derived from cephalopods (e.g., squid) and crustaceans (e.g., krill) are commercially used to improve the palatability of shrimp diets. Increase in global demand for shrimps has resulted in overfishing of these marine organisms and is a matter of concern. Insect protein hydrolysate could be a sustainable alternative for the possible replacement of these marine feed ingredients. During this study, four formulations: diet A (control: not containing any palatability enhancer), diet B (containing squid meal and krill oil), diet C (containing 1% insect protein hydrolysate), and diet D (containing 2% insect protein hydrolysate) were tested for (1) time required by first subject to begin feeding (time to strike) and (2) palatability in Litopenaeus vannamei. Additionally, the chemical composition of all four diet formulations was also analyzed. Results indicate that all diets had similar crude composition. The major essential amino acids in all diets were leucine and lysine, whereas eicosapentaenoic acid was the major omega-3 fatty acid in all diets. There were no significant differences between the mean time to strike for all the tested formulations. Palatability of tested formulations was found in the following order: diet D > diet C > diet B = diet A (p < 0.05), indicating that addition of squid meal and krill oil has no effect on palatability in comparison to control, whereas inclusion of insect protein hydrolysates significantly improves the palatability of formulations. Palatability enhancement potential of insect protein hydrolysate could be attributed to the high free amino acid content and water solubility in comparison to squid meal. 相似文献
In the present study, chromatic coordinates, phenolic acids, flavonoids and antioxidant capacity assessed by 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonate (ABTS) and lipid peroxidation inhibition capacity (LPIC) essays and their relative IC50 were investigated in 25 fig cultivars growing in Morocco. The aims of this study were to determine (i) the variation in these compounds among light and dark-colored cultivars, (ii) their partitioning between fruit peel and pulp and (iii) to display network connections among these variables. Twelve phenolic compounds (PCs) were isolated in peel extract versus eight in pulp samples. Anthocyanins, mainly cyanidin-3,5-diglucoside and cyanidin-3-O-rutinoside, were the predominant compounds in peels, where the mean concentrations were 75.90 ± 18.76 and 77.97 ± 18.95 µg/g dw, respectively. On the other hand, (−)-epicatechin and cyanidin-3-O-rutinoside were the major compounds in the pulp extracts, where the mean values were 5.23 ± 4.03 and 9.01 ± 5.67 µg/g dw, respectively. A two-dimensional hierarchically clustered heatmap was applied to the dataset to explore correlations in the dataset and similarities between cultivars, without dimensionality reduction. Results showed that anthocyanins, particularly pelargonidin-3-O-rutinoside, cyanidin-3,5-diglucoside and cyanidin-3-O-rutinoside, were the main contributors to the peels’ free radical scavenging capacity. This capacity was particularly higher in the peel of dark-colored figs compared to the fruit pulp. The local cultivar “INRA 1301” showed the most promising phenolic profile due to its very high levels of almost all detected PCs, especially (−)-epicatechin, quercetin-3-O-rutinoside, quercetin-3-O-glucoside, cyanidine-3,5-diglucoside, cyanidine-3-O-rutinoside and pelargonidin-3-O-rutinoside (54.66, 141.08, 35.48, 494.08, 478.66, 12.56 µg/g dw, respectively). Having the darkest figs in the collection (L* = 25.72, c* = 22.09 and h° = 20.99), this cultivar has also combined promising IC50 values, which were of 19.85, 40.58 and 124.78 µg/mL for DPPH, ABTS and LPIC essays, respectively. 相似文献
We report on a detailed textural analysis of mechanochemically synthesized MOF-199 including N2 adsorption-desorption and CO2 adsorption isotherms data at 77 K and 273 K (up to atmospheric pressure), respectively, and CH4 adsorption data at 298 K (up to 35 bar). We used the isotherm adsorption data to determine the micropore volume of the MOF-199 structures, to establish their methane uptake capacity and to understand how these properties depended on the Ethanol/BTC ratio used during the synthesis. The maximum methane uptake capacity for our specimens was recorded at 130 v/v at 35 bars. These results open an avenue for a better understanding of alternative manufacturing processes of MOF structures for gas storage applications. 相似文献