Use of mesalime and electric arc furnace (EAF) dust as neutralising agents in biooxidation and their effects on gold recovery in subsequent cyanidation

The cost of lime/limestone for neutralisation is the second largest operating cost in bioleaching. Therefore, these studies have been conducted with the aim to investigate the possibilities for use of by-products such as mesalime and electric arc furnace (EAF) dust for neutralisation during biooxidation of a refractory gold concentrate. Experiments were carried out using a retention time of 57 h in a one-stage reactor and the influence of two industrial by-products on the biooxidation performance was evaluated. The neutralising capacity of EAF dust was lower, while the mesalime was similar to the Ca(OH)₂ reference. The arsenopyrite oxidation in experiments ranged from 85% to 90%, whereas the pyrite oxidation was 63–74%. In subsequent cyanidation, final gold recoveries of 90% were achieved in bioresidues from mesalime and Ca(OH)₂, while the EAF dust bioresidue had a recovery of 85%. A comparatively high elemental sulphur content in EAF dust probably encapsulates part of the gold, which explains the lower recovery for the EAF dust bioresidue despite a longer residence time. Cyanide consumption was relatively high and ranged from 8.1 to 9.2 kg/ton feed after 24 h of cyanidation. Overall, the by-products tested here have proved to be feasible options as neutralising agents in bioleaching operations.     

Parasympathetic neuropathy associated with left ventricular diastolic dysfunction in patients with insulin-dependent diabetes mellitus

BACKGROUND: As extracorporeal shock wave lithotripsy (ESWL) is frequently carried out on an outpatient basis, it is crucial to choose an adequate analgesic with less adverse effect. This study evaluated the use of three different intravenous agents: fentanyl, tramadol HCl and tenoxicam in ESWL. METHODS: One hundred and twenty patients undergoing lithotripsy were randomly assigned to receive either intravenous fentanyl 1 microgram/kg, tramadol HCl 1.5 mg/kg or tenoxicam 0.3 mg/kg before lithotripsy. Pain intensity was recorded using verbal rating pain scales (VRPS). Cases without adequate analgesia (VRPS > 4) or could not tolerate the pain, additional bolus of fentanyl 25 micrograms were given until adequate analgesia was achieved. Side effects were recorded as well. RESULTS: No significant differences were found among groups in demographic data, VRPS, number of total shock waves, cases with supplementary fentanyl, mean dose of supplementary fentanyl or the incidence of dizziness. However, the incidence of nausea or vomiting was significantly higher in fentanyl and tramadol groups comparing with tenoxicam group (15.0% and 25.0% vs. 0.0%). Oxygen saturation in fentanyl group was also significantly lower than the other two groups (p < 0.01). In addition, VRPS had a significant correlation with voltage intensities (p < 0.05). CONCLUSIONS: Lithotripsy can be satisfactorily performed by employing fentanyl, tramadol or tenoxicam for analgesia; tenoxicam apparently offers a better analgesic quality with less side effect. Furthermore, the need for stronger analgesia during larger voltage intensity should be tailored to the needs of the individuals.     

Alcohol abuse exaggerates autonomic dysfunction in chronic liver disease

BACKGROUND: Advanced chronic liver disease is characterized by peripheral arterial vasodilation and increased plasma catecholamine concentrations. These haemodynamic alterations may reflect impaired vascular responsiveness due to autonomic nerve dysfunction. METHODS: Three established non-invasive tests based on the heart reactions to deep breathing (expiratory/inspiratory (E/I) ratio) and to tilt (acceleration and brake indices) were used to evaluate age-related autonomic nerve function in 27 patients with chronic alcoholic and non-alcoholic liver disease. Liver function was estimated by demethylating capacity. The results were compared with a control group consisting of 56 healthy individuals. RESULTS: Overall, 12 patients (52%) had autonomic neuropathy (10 of 13 (77%) patients with alcoholic and 2 of 14 (14%) with non-alcoholic liver disease). Variance analysis showed that the age-corrected E/I ratio, but not the acceleration and brake indices, was significantly decreased compared with controls both in patients with alcoholic and non-alcoholic liver disease, indicating vagal nerve dysfunction (P < 0.0001 and 0.0133, respectively). The decrease in E/I ratio was also significantly more pronounced (-1.77 (0.62) (median (interquartile range)) versus 0.76 (0.70); P = 0.049) in patients with alcoholic compared with non-alcoholic liver disease. Furthermore, in contrast to non-alcoholics, patients with alcoholic liver disease were unable to increase their diastolic blood pressure after return to upright from a tilted position, indicating additional sympathetic neuropathy. CONCLUSIONS: Autonomic, mainly vagal, nerve dysfunction is common in patients with liver diseases and is further exaggerated by alcohol abuse. Autonomic neuropathy may contribute to altered vascular responsiveness in patients with chronic liver diseases.     

A note on class effects in Aptitude?×?Treatment interactions.

Results pertaining to methodological aspects of an Aptitude?×?Treatment interaction study previously conducted by the author (1977) with 271 5th graders are presented. One treatment group in the study was given imagery instructions, the other had no imagery instructions. Among the aptitude variables were 2 versions of a paired-associates learning task. Within-class analyses and analyses in which class effects were allowed to have influence were conducted. In the latter analyses there were several significant Aptitude?×?Treatment interactions with subscores derived from the paired-associates tasks, but this was not the case in the within-class analyses. The interactions found are interpreted as being consequences of class effects with respect to errors of measurement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stability and change in broad and narrow factors of intelligence from ages 12 to 15 years.

A battery of cognitive tests was administered in the 6th grade (12-yr-olds) and again in 9th grade (15-yr-olds) to a sample of 225 boys and 242 girls. In the 8th grade, the same students answered an inventory about reading activities. Hierarchical confirmatory factor models were fitted to the test data from each of the 2 occasions, defining a General Intelligence factor and residual factors representing Crystallized Intelligence and General Visualization. Results indicate high stability for the general factor (.92 to .94) and for the residual of the General Visualization factor. There were strong autoregressive relations among the latent variables but no or weak cross-lagged relations. Few relations were found between reading activities and changes in abilities. R. B. Cattell's investment hypothesis of ability development is discussed in relation to the results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

镍基合金Inconel718可切削加工性的试验研究

Inconel718是一种高强度耐热镍基合金,具有优良的高温强度、高温硬度和耐蚀性,在高温条件下能长期工作,已被广泛地应用于宇航工业、航空工业的涡轮发动机和相关零件的制造。分析Inconel718的机械性能、微观组织结构及其对切削加工性能的影响并进行了相关的试验验证,在试验数据的基础上,研究Inconel718中含碳量对切削过程中刀具磨损的影响。试验结果表明,Inconel718中含碳量在刀具后刀面磨损中起着非常重要的作用,Inconel718合金中含碳量越高,合金中所含的细微硬质夹杂物也越多,在切削过程中使刀具产生严重的后刀面磨粒磨损,从而降低材料的切削加工性。     

A method for identification of geometrical tool changes during machining of titanium alloy Ti6Al4V

There exists an increasing demand for cost and time-efficient cutting tests for describing the performance of different combinations of cutting tools and workpiece materials in the cutting process both in industry and academia. Cutting tools are expected to withstand the heat and the pressure developed during the machining of difficult-to-machine materials such as Ti6Al4V. This article introduces a new test method which may be used in order to analyze both the machinability of a workpiece material as well as the cutting tool behavior. The experiments were performed by using a predefined sequence of feeds, a so-called Stepwise Increased Feed Test. A gradually increased load on the cutting edge was thus applied up to the point where plastic deformation of the cutting edge was obtained. The limit for the initial change in tool geometry was identified through analysis of measured cutting forces.     

Relations between volume flexibility and part cost in assembly lines

This paper presents a strategy for achieving volume flexibility in assembly lines, so that varying production demands can be met. The strategy involves providing assembly lines inherent cycle-time flexibility, through creating the possibility for operators to handle multiple work stations. A basic part-cost model serves as a basis for analyzing the cost effects of different staffing alternatives, its taking account of different performance parameters and numbers of operators. Use of the part-cost model is illustrated by analyzing two specific cases differing in the number of operators assigned to the assembly line, the operators being partly permanent and partly temporary workers. It is shown how the costs are affected by the production performance of the work force in question, temporary operators being expected to display a somewhat lower level of performance than permanent workers.     

EFFECTS OF CUTTING SPEED WHEN TURNING AGE HARDENED INCONEL 718 WITH PCBN TOOLS OF BINDERLESS AND LOW-CBN GRADES

Application of polycrystalline cubic boron nitride (PCBN) tools as an alternative for ceramic and cemented carbide tools in machining superalloys has been frequently identified as a solution for enhancing process efficiency but only a limited number of studies has been done in this area. The current study explores the effect of the cutting speed, which was varied in a wide range (2–14 m/s), on machinability of age hardened Inconel 718 with PCBN tools. Performance of binderless PCBN grade and grade with low-cBN content was evaluated in terms of tool life, tool wear, cutting forces and surface quality. Chip formation and process dynamics were analyzed as well. It was found that low-cBN grade provided 70–90% better surface finish and tool life than the binderless at moderate speeds (5–8 m/s). Performance of both grades at low and high speed ranges was non-satisfactory due to notching and flaking respectively. At low cutting speed adhesive wear plays a major role while as the speed increases a chemical wear becomes dominant.     

Tool wear mechanisms of PcBN in machining Inconel 718: Analysis across multiple length scale

Recently, PcBN tooling have been successfully introduced in machining Ni-based superalloys, yet our knowledge of involved wear mechanisms remains limited. In this study, an in-depth investigation of PcBN tool degradation and related wear mechanisms when machining Inconel 718 was performed. Diffusional dissolution of cBN is an active wear mechanism. At high cutting speed oxidation of cBN becomes equally important. Apart from degradation, tool protection phenomena were also discovered. Oxidation of Inconel 718 resulted in formation of γ-Al₂O₃ and (Al,Cr,Ti)₃O₄ spinel that were deposited on the tool rake. Also on the rake, formation of (Ti,Nb,Cr)N takes place due to cBN-workpiece interaction. This creates a sandwich tool protection layer forming continuously as tool wear progresses. Such in operando protection enabled counterbalancing tool wear mechanisms and achieved high performance of PcBN in machining.