Kiran Natarajan

Microbially-induced flocculation and flotation for pyrite separation from oxide gangue minerals

Selective separation of pyrite from quartz and calcite was achieved through microbiologically induced flotation and flocculation in presence of Bacillus polymyxa. Adsorption behavior of bacterial cells onto pyrite, calcite and quartz was established. Surface chemical changes on various minerals brought about by bacterial interaction were established through zeta-potential measurements as a function of pH. It has been shown that pyrite can be separated from quartz and calcite through either selective flocculation or flotation after interaction with cells of B. polymyxa or bioproteins separated from the bacterial metabolite. The results of this study are significant from the viewpoint of desulphurisation of flotation tailings with respect to environmental control.

Electrobioleaching of polymetallic ocean nodules

Abstract In this paper, a novel electrobioleaching process for recovering valuable non-ferrous metals from ocean nodules is described. The key for successful and efficient dissolution of copper, nickel and cobalt from ocean nodules depends on prior reduction of the manganese and ferric oxides with which the above valuable non-ferrous metals are interlocked. We have shown that through the application of negative reduction potential or DC current, significant reduction of manganic and iron oxides in the ocean nodules can be achieved, thus liberating the occluded copper, nickel and cobalt for easy dissolution in an acid medium. Polarization studies using a slurry electrode system indicated that maximum dissolution of iron and manganese due to electrochemical reduction occurred at negative DC potentials of −600 and −1400 mV(SCE). Electroleaching and electrobioleaching of ocean nodules in the presence of Thiobacillus ferrooxidans and T. thiooxidans at the above negative applied DC potentials resulted in significant dissolution of copper, nickel and cobalt in 1 M H 2 SO 4 and in sulphuric acid at pH 0.5 and 2.0. Mechanisms involved in electrobioleaching of ocean nodules are discussed. The effect of bacterial metabolites in the dissolution of copper, nickel and cobalt from the ocean nodules is also examined as a function of pH, time and applied potentials. Various electrochemical and biochemical parameters were optimized and the electrobioleaching process so developed is shown to yield almost complete dissolution of all metal values.

Development of a clean bioelectrochemical process for leaching of ocean manganese nodules

Through the application of negative reduction potential significant reduction of manganic and iron oxides in the ocean manganese nodules can be achieved, liberating the occluded copper, nickel and cobalt for easy dissolution in an acid medium. Electroleaching and electrobioleaching of ocean manganese nodules in the presence of Thiobacillus ferrooxidans and Thiobacillus thiooxidans at the above negative applied dc potentials resulted in significant dissolution of copper, nickel and cobalt in 1 M H2SO4. The role of galvanic interactions in the bioleaching of ocean manganese nodules in the presence of T thiooxidans is also discussed, (C) 2002 Published by Elsevier Science Ltd.

Strategies for efficient start-up of continuous biooxidation process for refractory gold ores

Strategies for efficient start-up of a continuous process for biooxidation of refractory gold ore and concentrate obtained from Hutti Gold Mines Limited (HGML), India are discussed in this work. The biooxidation of the concentrate at high pulp density (10%) with wild strain of Thiobacillus ferrooxidans isolated from HGML mines is characterized by significant lag phase (20 days) and incomplete oxidation (35%) even after prolonged operation (60 days). Two strategies, biooxidation with concentrate adapted cells and a step leaching strategy, in which the pulp density is progressively increased from 2% to 10% were considered and the latter resulted in efficient biooxidation of concentrate. Conversion of such a process from batch to continuous operation is shown to result in complete biooxidation of the concentrate and gold extraction efficiency in excess of 90%.

Totally implantable hearing aid surgical technique and the first Indian experience with Envoy esteem

Hearing aids are the principal means of auditory rehabilitation for patients with moderate to severe sensorineural hearing loss. Although technical improvements and modifications have improved the fidelity of conventional aids, hearing aids still have many limitations. Implantable hearing aids offer patients with hearing loss several potential advantages over conventional hearing aids. This presentation will highlight our first experience, the indications, the procedure, the advantages and the current status of totally implantable hearing aids.

Public Health Implications of Obstructive Sleep Apnea Burden

ObjectiveTo assess the implications of obstructive sleep apnea (OSA) burden among Indian children.MethodsMonteCarlo simulations were performed in order to estimate the number of OSA related obesity cases among Indian children (1–14 y of age) and the number of cases of stroke, coronary heart disease (CHD) and type 2 diabetes, considered as main adverse outcomes of OSA related childhood obesity, according to untreated and treated [adenotonsillectomy (AT) alone and AT associated to continuous positive airway pressure (CPAP)] pediatric OSA. Data used to perform MonteCarlo simulations were derived from a review about current literature exploring OSA related obesity.ResultsThe analysis on the number of adverse outcomes according to treated and untreated obesity related to OSA showed that treatments reduce the number of obesity cases, resulting in a great reduction of the amount of stroke, CHD and type 2 diabetes cases. However, the cost for treating adverse outcome was higher in patients treated for obesity related to OSA compared to those not receiving any treatment.ConclusionsThe reduction in the number of adverse outcomes due to treatment of obesity related OSA implicates the urgent need for public health policies in providing screening for OSA among children population: an early detection and a consequently prompt reaction to pediatric OSA could improve the burden of OSA related obesity.

Clinical audit of outcomes in Cochlear Implantation an Indian experience.

This retrospective study is based on the assessment of outcomes of Cochlear Implantation taking into account various scoring systems like Category of Auditory Performance (CAP) and Speech Intelligibility Rating (SIR). 100 candidates who were implanted between June 1997-June 2005 at Madras ENT Research Foundation (MERF), a tertiary referral center for cochlear implantation were included in the study. The results were analyzed using the above scoring systems to assess the performance levels of each implantee and to arrive at a cumulative result on the outcome of the implantation. Practical issues of concern to Cochlear Implantation in the Indian subcontinent were also analyzed.

Cathodic reductive dissolution and surface adsorption behavior of ocean manganese nodules

Cathodic slurry reductive dissolution of ocean manganese nodules in 1 M H2SO4 at 600 and 1000 mA resulted in significant dissolution of copper and nickel, while the dissolved copper was simultaneously deposited at the cathode. Dissolved manganese could be anodically converted to MnO2. Ocean manganese nodules exhibited good adsorption capacities for copper and nickel from acl dic solutions. Adsorption behavior and mechanisms for uptake of various metal ions such as copper, nickel, cobalt and iron are discussed.

Long term outcome of cochlear implantation in five children with common cavity deformity.

INTRODUCTION A common cavity (CC) deformity is a deformed inner ear in which the cochlea and vestibule are confluent forming a common rudimentary cystic cavity. The outcome of cochlear implantation (CI) in this deformity is not expected as good as in other cochlear deformity. Categories of Auditory Performance (CAP) score, Speech Intelligibility Rating (SIR) scale, Meaningful Auditory-Integration Scale (MAIS) and Meaningful Use of Speech Scale (MUSS) are scales designed to assess benefit of functional device (hearing aid, Cochlear implant, ABI) in young children. The aim of the study was to observe and report the long-term audiological progress and speech development of children with CC deformity after CI by means of CAP, SIR, MAIS, MUSS scores and CI aided threshold. METHODS AND MATERIALS The retrospective and prospective study was carried out in five Indian children with CC deformity who underwent CI from 2004 to 2010. Demographic data of onset and/or duration of deafness, age at implantation, time with hearing aids before implantation, duration with CI and co-morbidity were retrieved from a local data base. Their outcome score in audition and speech development on the basis of their CAP and SIR score at the end of 1 year of habilitation were collected. All the patients were called to follow up to obtain latest CI aided audiogram, CAP, SIR, MAIS and MUSS scores. RESULTS One male and four female children were detected with common cavity deformity among 258 deaf children of age below 6 years operated during study period. The CAP and SIR Scores increased from average of 0.4 and 1 to 3.4 and 2.4, respectively, over one year of habilitation. The CAP score improved in subsequent follow up to average of 5.0 after more than 3 years of follow up but the SIR score hardly improved. We assessed the MAIS and MUSS at last visit after 3 years. The mean of MAIS and MUSS was 32.4 and 26.4, respectively. CONCLUSION Though the habilitation outcome was not up to the mark in children with CC deformity, CI provides excellent awareness of environment sound and development of few words.

Does cerebellar flocculus size affect subjective outcomes in pediatric auditory brainstem implantation

OBJECTIVES The objectives of study was to 1) Describe relevant surgical anatomy in defining and accessing the lateral recess for placement of electrode, 2) Propose a working classification for grades of Flocculus; 3) To determine if different grades of cerebellar flocculus effects placement of ABI electrode and subjective outcomes in implantees. METHODS Our study was a prospective study, and comprised of cohort of 12 patients who underwent ABI surgery via retrosigmoid approach between 1 Jan 2012 to 31 Dec 2014. All children with congenital profound sensorineural hearing loss with either absent cochlea or cochlear nerve were included in the study. Relevant anatomy was noted. We also noted down the difficulty encountered during the placement of ABI electrode. Auditory perception and speech intelligibility was scored post operatively for 1 year. RESULTS Cerebellar flocculus was divided into 4 grades depending on the morphology of cerebellar flocculus. It was noted that Grade 3 & 4 flocculus (Group B) had difficult ABI electrode placement in comparison to Grade 1 & 2 flocculus (Group A). The subjective outcomes of Group A was better than Group B. However the p value was not statistically significant. CONCLUSION Cerebellar flocculus can be graded depending on morphology and size. Flocculus of higher grades can make the placement of ABI electrodes difficult and adversely effects the postoperative subjective outcomes.