Binding of Water & Organic Liquid Components (Ethyl Alcohol, Methyl Alcohol, Propyl Alcohol, Formic Acid, Acetone, Pyridine & Glycerol) at Interface & the Gibbs Surface Excess

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Salvaging the values from the rejects of a by-product recovery plant

Two samples of table tailings (-147 pm and -74 pm in size) from refrac¬tory linings of the precious metal recovery (PMR) plant of Indian Copper Complex (ICC), Ghatshila were received to study the possbility to re¬cover residual values of precious metals from them. Analyses, as reported by ICC, were 0.021% Au and 0.39% Ag for the -147 pm sample and 0.023% Au and 0.47%Ag for the -74 pm sample. Multi-Gravity Separator (MGS) studies, with varying design and operating variables, showed three fold upgradation - assay of Au improved from 0.023% to 0.076% and assay of Ag improved from 0.47% to 1.53%. The -74 pm sample yielded better results with MGS than the -147 pm sample

Modified hydrocycloning for effective elimination of stubborn slimes

The present paper deals with the skillful exploitation of the extremely high shear fields inside a hydrocyclone to effectively eliminate a sticky slime from a phosphate ore before beneficiating the coarser fraction using con¬ventional mineral processing techniques. Earlier studies on samples of the same ore at NML and abroad established that it was necessary to pass the ore through a series of three stages of desliming, each consisting of a step of rigorous attrition scrubbing followed by hydrocycloning, for effective elimination of the slime. With the new approach,by innovative modifica¬tions on the standard hydrocyclone design, it was possible to eliminate all the stages of attrition scrubbing while minimising the stages of hydrocycloning. It could be established that the modified technique not only yielded concentrate of grade comparable to that obtained by employ¬ing the earlier more complex flowsheet, it also improved the P205 recovery

Gravity separation at variable 'g' for management of mineral wastes and pollution

The treatment of mineral wastes in the form of slimes and its utilisation, for management of pollution and conservation of mineral wealth, have become very important now-a-days. Multi Gravity Separator (MGS) is the latest inclusion to various gravity separation machines developed far the treatment offines and ultrafines. In this paper, results of recent studies carried out at NML with MGS using slimes of chromite ore, iron ore, phosphatic soil etc. are discussed to evaluate the effectiveness of the equipment for the treatment of slimes. In most of the cases, three to four fold upgradations have been achieved even at very fine sizes

Intergranular Corrosion of Deformed SS304

Intergranuular corrosion (IGC) and intergranular stress corrosion cracking (IGSCC) of commercial stainless steels e.g. type 304 and 316 are frequently observed in several process environments. These localized attacks are normally attributed to the carbide precipitation and concomitant depletion of chromium near grain boundary due to alloy exposure to sensitization temperature. Such undesirable microchemistry is expected to be changed further if the material undergoes deformation prior to sensitization

Minerological aspects of lead sintering

A brief overview on lead sinter microstructure is presented. Characteristic micro-structural features of a good and bad sinter are highlighted and these are used in a case study involving use of a low grade and complex concentrate of lead (-40% Pb) in the sintering operation. The plant sinter produced exhibited low strength and its nticrostructural examination revealed non-uniform distribution of porosity along with unsintered galena and low melting lead silicate phase. Part replacement of limestone by lime helped in producing sinter with good physical properties and desirable microstructure. The sinter with modified feed chemistry had more uniform distribution of porosity and presence of primarily a Pb-Fe silicate phase characterised by a (Pb+Fe):Si mole ratio of 3:1. Ca-Pb-Zn-Fe-Al-silicate phase identified as hardysonite and a spine! phase of the type (Fe,Zn)O.(Fe,Al),OJ. Lead nietal/oxide/sulphide occurred in the sinter only rarely. The likely implications of lime addition to the sinter charge mix are discussed Key Words: Lead. Complex and low grade concentrate. Sintering. Process Mineralog

Characterization and its implication on beneficiation of low grade iron ore by gravity separation

Studies were undertaken on low grade iron ore sample from Noamundi iron ore mines. The objective of this study was to examine the possibility of the physical beneficiation of low grade iron ore sample by physical methods for the blast furnace route of iron production. The present investigation relies on petrography and ore mineralogical characterization, ore textures (primary, secondary, metamorphic), liberation characters and its impact on the mineral beneficiation methods to produce quality concentrate. The geological characters, alteration mineralogy, morphometric variation, ore microscopy (using model microscope with transmitted and reflected light) and thereby understanding the genesis has given proper insight into the occurrence of various minerals. In addition to this, representative samples were employed for detailed investigation by using XRD, SEM-EDS and cathodoluminescence (CL) studies for confirmation of major as well as minor ore minerals and associated gangue minerals. Investigations suggest that lateritic iron ore samples obtained from the study area are composed of hematite (two generations), goethite (two generations) and limonitic material (younger generation) in association with major gangue minerals such as clay minerals (kaolinite, illite), bauxitic minerals(gibbsite, boehmite and diaspore), cryptocrystalline silica(japer, chert) and crystalline quartz as well as apatite and collophane. Fair liberation obtained below 74 micron size. It was interesting to find that inspite of the complex mineralogy of iron ore, beneficiation results using gravity separation like multi gravity separator (MGS), particularly in finer size ranges was encouraging. The result of ore-gangue mineralogical studies were found quite useful in evaluating the separation efficacy of gravity separation process. The process mineralogical data corroborated well with beneficiation results

Wettability characteristics of an Al2O3/SiO2-based ceramic modified with CO2, Nd:YAG, excimer and high-power diode lasers

Interaction of CO2, Nd:YAG, excimer and high power diode laser (HPDL) radiation with the surface of an Al2O3/SiO2 based ceramic was found to effect significant changes in the wettability characteristics of the material. It was observed that interaction with CO2, Nd:YAG and HPDL radiation reduced the enamel contact angle from 1180 to 310, 340 and 330 respectively. In contrast, interaction with excimer laser radiation resulted an increase in the contact angle to 1210. Such changes were identified as being due to: (i) the melting and partial vitrification of the Al2O3/SiO2 based ceramic surface as a result of interaction with CO2, Nd:YAG HPDL radiation. (ii) the surface roughness of the Al2O3/SiO2 based ceramic increasing after interaction with excimer laser radiation. (iii) the surface oxygen content of the Al2O3/SiO2 based ceramic increasing after interaction with CO2, Nd:YAG and HPDL radiation. The work has shown that the wettability characteristics of the Al2O3/SiO2 based ceramic could be controlled and/or modified with laser surface treatment. In particular, whether the laser radiation had the propensity to cause surface melting. However, a wavelength dependance of the change of the wetting properties could not be deduced from the findings of this work

Sociobiological Control of Plasmid copy number

Background:
All known mechanisms and genes responsible for the regulation of plasmid replication lie with the plasmid rather than the chromosome. It is possible therefore that there can be copy-up mutants. Copy-up mutants will have within host selective advantage. This would eventually result into instability of bacteria-plasmid association. In spite of this possibility low copy number plasmids appear to exist stably in host populations. We examined this paradox using a computer simulation model.

Model:
Our multilevel selection model assumes a wild type with tightly regulated replication to ensure low copy number. A mutant with slightly relaxed replication regulation can act as a “cheater” or “selfish” plasmid and can enjoy a greater within-host-fitness. However the host of a cheater plasmid has to pay a greater cost. As a result, in host level competition, host cell with low copy number plasmid has a greater fitness. Furthermore, another mutant that has lost the genes required for conjugation was introduced in the model. The non-conjugal mutant was assumed to undergo conjugal transfer in the presence of another conjugal plasmid in the host cell.

Results:
The simulatons showed that if the cost of carrying a plasmid was low, the copy-up mutant could drive the wild type to extinction or very low frequencies. Consequently, another mutant with a higher copy number could invade the first invader. This process could result into an increasing copy number. However above a certain copy number within-host selection was overcompensated by host level selection leading to a rock-paper-scissor (RPS) like situation. The RPS situation allowed the coexistence of high and low copy number plasmids. The non-conjugal “hypercheaters” could further arrest the copy numbers to a substantially lower level.

Conclusions:
These sociobiological interactions might explain the stability of copy numbers better than molecular mechanisms of replication regulation alone

Mechanical Responses and Stress Fluctuations of a Supercooled Liquid in a Sheared Non-Equilibrium State

A steady shear flow can drive supercooled liquids into a non-equilibrium state. Using molecular dynamics simulations under steady shear flow superimposed with oscillatory shear strain for a probe, non-equilibrium mechanical responses are studied for a model supercooled liquid composed of binary soft spheres. We found that even in the strongly sheared situation, the supercooled liquid exhibits surprisingly isotropic responses to oscillating shear strains applied in three different components of the strain tensor. Based on this isotropic feature, we successfully constructed a simple two-mode Maxwell model that can capture the key features of the storage and loss moduli, even for highly non-equilibrium state. Furthermore, we examined the correlation functions of the shear stress fluctuations, which also exhibit isotropic relaxation behaviors in the sheared non-equilibrium situation. In contrast to the isotropic features, the supercooled liquid additionally demonstrates anisotropies in both its responses and its correlations to the shear stress fluctuations. Using the constitutive equation (a two-mode Maxwell model), we demonstrated that the anisotropic responses are caused by the coupling between the oscillating strain and the driving shear flow. We measured the magnitude of this violation in terms of the effective temperature. It was demonstrated that the effective temperature is notably different between different components, which indicates that a simple scalar mapping, such as the concept of an effective temperature, oversimplifies the true nature of supercooled liquids under shear flow. An understanding of the mechanism of isotropies and anisotropies in the responses and fluctuations will lead to a better appreciation of these violations of the FDT, as well as certain consequent modifications to the concept of an effective temperature.Comment: 15pages, 17figure