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

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

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

Melatonin Induces Follicle Maturation in Danio rerio

Most organisms modulate their reproductive activity responding to day length by the nocturnal release of melatonin by the pineal gland. This hormone is also responsible for synchronizing reproduction with specific external environment stimuli in order to optimize reproductive success

70% efficiency of bistate molecular machines explained by information theory, high dimensional geometry and evolutionary convergence

The relationship between information and energy is key to understanding biological systems. We can display the information in DNA sequences specifically bound by proteins by using sequence logos, and we can measure the corresponding binding energy. These can be compared by noting that one of the forms of the second law of thermodynamics defines the minimum energy dissipation required to gain one bit of information. Under the isothermal conditions that molecular machines function this is joules per bit ( is Boltzmann's constant and T is the absolute temperature). Then an efficiency of binding can be computed by dividing the information in a logo by the free energy of binding after it has been converted to bits. The isothermal efficiencies of not only genetic control systems, but also visual pigments are near 70%. From information and coding theory, the theoretical efficiency limit for bistate molecular machines is ln 2 = 0.6931. Evolutionary convergence to maximum efficiency is limited by the constraint that molecular states must be distinct from each other. The result indicates that natural molecular machines operate close to their information processing maximum (the channel capacity), and implies that nanotechnology can attain this goal