Nitric acid leaching of polymetallic middlings of concentration

Investigations into the nitric acid leaching of polymetallic middlings with the purpose of the maximal recovery of copper and zinc into the solution are performed. Using methods of mathematical planning of the experiment, the optimal process parameters are determined: ratio L: S = 5, the consumption of nitric acid is 80 cm3 per 20 g of the charge, and the process duration is 120 min. © 2013 Allerton Press, Inc

Academic stress and its effect on medical students’ mental health status

This review aimed to analyze the data on features of a medical students’ mental status and its dynamics in the course of study. The analysis was applied to the scientific publications (mainly over the past 5 years) on the issue of academic stress and medical students’ mental status in different countries from computer databases: PubMed, Medical-Science, eLibrary, Web of Science, and Scopu

Electroextraction of lead from a lead trilonate solution

Laboratory studies of the cathode process of the electroextraction of zinc from the trilonate electrolyte obtained after the purification of solutions after leaching lead cakes of zinc production are performed. The potential scan rate is determined by recording potentiodynamic curves; the optimal electrolyte acidity, the composition, and the temperature are established. Values of activation energy confirming the concentration nature of process polarization are found. © 2013 Allerton Press, Inc

DNA polymorphism and selection at the bindin locus in three Strongylocentrotus sp. (Echinoidea)

Text S1. PCR reactions. Text S2. GenBank bindin sequences. (DOC 68 kb

Optimization of Nanostructuring Burnishing Technological Parameters by Taguchi Method

On the basis of application of Taguchi optimization method, an approach for researching influence of nanostructuring burnishing technological parameters, considering the surface layer microhardness criterion, is developed. Optimal values of burnishing force, feed and number of tool passes for hardened steel AISI 420 hardening treatment are defined

PERSONALIZED (LOCAL) UV-CROSSLINKING AS A TREATMENT OF KERATOCONUS AND CORNEAL ECTASIA

There is no doubts that problem of keratoconus treatment is high relevant. The number of diagnosed ectasia, including iatrogenic ectasia, increased — in recent years. The amount of post-LASIK and ectasia after RK in late postoperative period multiplies significantly. It is associated not only with inception of new ways of treatment into practice, but also with the upgrade of diagnostic methods and equipment. A new method of local personalized crosslinking (LCXL) was integrated into clinical practice using Laplace’s equation, pachymetry and topography maps data, It exceeds usual Dresden protocol on several parameters. This article shows the reaction of patients’ eyes on the treatment and the effectiveness of technique is provided. Materials and methods: topographic indications were evaluated (Orbscan II (B+L)) of 28 patients (40 eyes) aged 18 — 44 with keratoconus stages I-IV (12 eyes — I stage; 16 eyes — II stage; 9 eyes — III stage; 3 eyes — IV stage classified by Abugova T.D.), as well as UCVA, BCVA for 12 months after surgery. Normal values were estimated by characteristics of 30 eyes without any refractive errors. Results: LCXL is an effective way of treatment of corneal ectasia; it’s more effective in early stages. This technique has a strong controlled refractive impact and allows to reduce inflammatory after procedure

Studying the Impact of Alkaline Sulfide Leaching Parameters Upon the Efficiency of Arsenic Recovery from Copper Skimmings of Lead Production

The article is concerned with the problem of arsenic circulation as copper skimmings of lead production — the product of the lead bullion decopperization process at a metallurgical complex, uniting copper and lead plants. A brief overview of the methods of processing arsenic-containing middling products for the purpose of arsenic removal is given; the main advantages and disadvantages are indicated. The possibility of processing copper skimmings by the method of alkaline sulfide leaching with separation into arsenic-containing solution and lead-copper precipitate is studied. The results of the researches into the influence of temperature, process duration, solids content in the pulp, particle size, and the ratio of sodium hydroxide to elemental sulfur in the alkaline sulfide reagent on the process of alkaline sulfide leaching of copper skimmings af lead production are provided. Within the studied range of varied factors, the highest indexes of arsenic extraction into solution (85.04%) were achieved under the following conditions: temperature — 85oC, duration — 4 hours, solids content in the pulp — 350 g/dm3, frac-tion (–0.08 mm), NaOH/S ratio = 100 g/100 g in 1 dm3 of the solution. The proposed method for processing copper skimmings will allow one to selectively isolate arsenic into the dump waste product during subsequent precipitation and separate contaminant from lead-copper cake, into which precious metals also pass. Such an approach provides the reduction of arsenic circulation between the lead and copper manufacturing facilities. © 2020, Ore and Metals Publishing house. All rights reserved