Continuous counter-current extraction of rhenium from roasting dust leach liquor was carried out using a mixer-settler extractor. Tributylphosphate was used as the extractant diluted in kerosene. The effects of the flow rates and extraction stages were investigated. The extraction efficiency was affected by the flow rates of the aqueous and organic phases, and its mechanism was qualitatively discussed on the basis of the stoichiometric relations of the extraction. Rhenium extraction mass balance and simulation in the mixer-settler was also studied. A high rhenium extraction percentage (95.43%) in the phase ratio 1:1 was achieved using a counter-current four-stage extraction process. The continuous counter-current extraction technique was used in this research work showed to be effective for rhenium extraction from the leach solutions of the dust of the molybdenite roasting furnaces.
در فرایند استحصال طلا به روش هیدرومتالورژی، آب بهعنوان پرمصرفیترین ماده اولیه کاربرد دارد که کیفیت آن میتواند نقش مؤثری بر عملکرد فرایند داشته باشد. بنابراین، هدف از این مقاله شناخت اثر کیفیت آب و حضور اکسیدان فرات سدیم در فرایند لیچینگ سیانیدی کانی طلا سولفیددار است. به همین منظور، فرایند لیچینگ سیانیدی ترکیبی از کانسنگهای حاوی طلا معادن سنجده و چاهخاتون با عیار تقریبی معادل mg/kg 2/1 توسط دستگاه بطری چرخان بهمدت 24 ساعت در دمای محیط انجام شد. جهت تهیه محلول لیچینگ از آب (با کیفیتهای متفاوت)، مواد بازی مختلف (آهک هیدارته و سدیم کربنات) و سیانید سدیم با خلوص بالا استفاده شد. جهت مشخصهیابی خاک از آنالیز صفحهای و مشخصه اشعه ایکس دستگاه میکروسکپ الکترونی روبشی استفاده شد. بهمنظور ارزیابی کیفیت آب از آزمونهای مختلف جهت شناسایی یونهای موجود استفاده شد. مقدار سیانید آزاد و طلای محلول بهترتیب از روش تیتراسیون و طیفسنجی جذب اتمی تعیین شد. نتایج نشان داد که استفاده از آب با سختی پایین حاوی اکسیدان فرات سدیم در لیچینگ سیانیدی طلای حاوی سولفید، مقدار طلای محلول از mg/l 0/1 به 1/1 و سیانید آزاد محلول از mg/l 475 به 510 افزایش یافت. همچنین جهت انجام مقایسه استفاده از اکسیدان فرات سدیم بر کاهش اثر حضور ترکیبات سولفیدی موجود در خاک، فرایند تشویه در دمای 700 درجه سانتیگراد بهمدت 60 دقیقه انجام شده است. مشاهده شد که افزودن اکسیدان فرات سدیم به آب علاوه بر اینکه منجر به افزایش سرعت لچینگ شد، تقریبا نتایج مشابهی با تشویهنمودن کانسنگ طلا حاوی سولفید دارد.
Sjögren's syndrome (SS) is a chronic autoimmune disease with a genetic component. Among the genetic factors, the role of HLA class II genes has been suggested and a positive association with DRB1*03 allele has been described. However, there is no consensus on a unique HLA locus for this disease nor on the role of the HLA gene product in the disease. The aim of this study was to analyse prospectively MHC region involvement in the genetic susceptibility to SS by studying DRB1, DQB1, DPB1, TAP1, TAP2 genes and TNF microsatellites in a population of 45 primary SS patients.All the polymorphisms studied were analysed at the genomic level using PCR-based methodologies.Concerning HLA class II alleles, the highest relative risk to develop the disease was associated with the DRB1*15-DRB1*0301 heterozygous genotype (17.8% vs 3.5% in controls - pc < 0.005, OR = 5.96). Analysing other genes located on the same region allowed us to further determine the DRB1 haplotypes at risk. For instance, the DRB1*0301 haplotype involved in the genetic susceptibility to SS was more often associated with the DPB1* 0201 and TNF-a2 alleles in SS patients than in controls. Moreover, all the DRB1*15-DRB1*0301 SS patients were TAP1-0101, TAP2-0101 homozygous, allowing us to deduce the extended genotype at risk as DRB1*15, TAP1-0101, TAP2-0101/DRB1*0301, TAP1-0101, TAP2-0101 which was carried by only 3 controls out of the 130 tested (p < 0.01, OR = 6.68).This study confirmed the role of the MHC region in the susceptibility to Sjögren's disease, and for the first time suggests a synergistic interaction between two HLA-DRB1 extended haplotypes in the genetic mechanisms controlling the disease.
Thermal expansion coefficient Perovskite oxide lattice parameter A B S T R A C T In this study, Thermal expansion coefficient variation of Ln 0.6 Sr 0.4 Co 0.2 M 0.8 O 3 − δ (Ln=La,Nd,Sm and M= Fe,Ni,Mn) perovskite oxide were evalouated. Different compounds were prepared and thermal expansion coefficient were meseaured in different temperature by means of dilatomete r analysis. Structural parameters of compounds were determined by X - ray diffraction and Field Emission Scanning Electron Microscopy (FE - SEM) was used for the morphological study. Using Nd 3+ instead of La 3+ led to tilting of the BO 6 octahedra, phase tran sition from rhombohedral to the orthorhombic. Experimental results showed TEC decreases favorably with substitution of Nd 3+ and Mn 3+ ions in the lattice .
Green chemistry - also called sustainable chemistry - as the cost-effective and environmentally friendly techniques have been gaining more attention recent years. Here, we introduced a fast, non-toxic and sustainable method to synthesize Ag nanoparticles. Various parameters are involved in the bio-synthesis of Ag nanoparticles/multi-walled carbon nanotubes (Ag/MWf-CNT) composites, including silver nitrate concentration, initial pH, temperature, CNT concentration, agitation time, biomass and stirring rate. The Plackett–Burman Design (PBD) approach indicated that the initial pH, the carbon nanotube concentration and the weight of biomass are the major effects of the Ag/MWf-CNT biosynthesis. A quadratic polynomial model was developed using Central Composite Design (CCD) to statistically evaluate the effect of the initial pH (3.5-7), the carbon nanotubes concentration (0.2-1 g/L) and the weight of wet biomass (6-16 g) on the response- reduction percentage of Ag ions. The significant factors and their interactions in the biosynthesis process were examined by means of analysis of variance (ANOVA). The results showed that the wet biomass weight has the most significant effect on the response compared to the other variables. Additionally, the model predicted that up to 89% of Ag+ reduction to Ag nanoparticles were obtained at the optimum range conditions– weight of biomass 13 g, the initial pH range 5.5-6.2 and concentration of carbon nanotubes 0.6 g/L.
Many studies suggest the implication of genetic factors in inflammatory bowel diseases. Despite some associations with HLA genes, the lack of definite data may be due to ethnic variations, clinical heterogeneity, or the involvement of additional susceptibility genes beside or within the major histocompatibility complex (MHC), such as TAP genes. The aim of this study was to analyze in patients with ulcerative colitis (UC) or Crohn's disease (CD) the polymorphism of TAP genes that encode the proteins necessary for the transfer of antigenic peptides through the endoplasmic reticulum membrane.One hundred and one UC and 148 CD patients were compared with 173 unrelated healthy controls. Dimorphisms within the TAP1 and TAP2 alleles were analyzed by sequence-specific oligonucleotide typing.No difference was found between patient groups and controls. However, when CD patients were classified on the basis of their responsiveness to steroid therapy, a significant decrease of TAP2 AA (*0101/*0101) genotype was found in CD patients who did not respond to steroid therapy (22.9% versus 43.7% in steroid responder group; Pc < 0.05; odds ratio = 2.6; 95% confidence limits (CL) = 1.2-5.9). These data appear independent of the distribution of HLA DRB1*01 or DRB1*03 alleles despite a significant linkage disequilibrium between these alleles and TAP2A.This result suggests, despite the absence of arguments favoring a genetic susceptibility to CD, that the TAP2 gene or other genes located on chromosome 6 may be involved in the genetic heterogeneity of CD.
This study investigates the influence of precipitation on the microstructure, texture, and mechanical properties of the deformed and annealed FeNi1.5CrCu0.5 high-entropy alloy produced by vacuum induction melting. For this purpose, the as-cast samples were homogenized at 1080 °C for 12 h followed by two different annealing regimes: one was rapidly quenched in water, while the other was cooled slowly in the furnace to reach 800 °C. This was held for 48 h at this temperature and quenched in water. The homogenized and precipitated samples were then cold-rolled with an 80 % thickness reduction to be heat-treated at 900 °C and 1000 °C. Annealing the cold-rolled specimens at 1000 °C resulted in significant grain refinement in the precipitated sample compared to the homogenized one. The increase in hardness of the precipitated samples can be attributed to the precipitation hardening process. Conversely, recrystallization during cold rolling leads to a slight decrease in hardness and an increase in formability in the precipitated samples. Following recrystallization, the microstructure of the precipitated sample consists of finer grains, with hardness identical to that of the homogenized sample. The shear punch test, as a unique technique for materials' characterization when there is a limitation in the materials' availability, was utilized and showed the variation of strength and formability due to rolling and annealing processes. Also, texture analysis revealed distinct differences between textural components such as Goss and Brass for the homogenized and precipitated samples upon annealing, confirming variations in recrystallization mechanisms.
In this study, the steel grade transition during the ladle change in a continuous casting process is simulated by presenting a new mathematical model. First, the mixing process in a non-isotherm tundish is investigated by a water modeling system. Then, heat transfer mechanisms and solidification process are simulated for a continuous casting machine and the geometric shape of the liquid pool is predicted considering different conditions. The mixing process in the liquid pool of strand is also investigated by a mixing model. Finally, when the solidification process in the strand is completed, the variations of chemical composition in the final product are calculated. To verify the results of the intermix model, several samples are taken from the different positions of the slab and chemical composition of several elements are measured using a spectrometry technique. The model results show that the weight of mixed grade steel are affected by parameters such as molten steel volume in the tundish at the time of new ladle opening, slab dimensions, rate of casting and non-isothermal effect on the tundish. The obtained results also show that the effect of mixing process on the extent of mixing regions in the liquid pool of strand is more significant than the mixing in the tundish.
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