Processing of china clay by super-conducting high gradient magnetic separation

Super-conducting high gradient magnetic separation tests on a typical china clay from the western part of India showed that the brightness of the clay can be enhanced from 72.8% to 79% ISO by suitably manipulating the process variables. Important variables studied are feed solid content, retention time, production rate (nummber of canister volumes), number of passes etc. keeping the magnetic field srength constant. The secondary magnet (wire wool matrix) and its packing volume were also not changed during these tests. A brightness of 79% was achieved with a two pass operation for 5 canister volume feed slurry having 15% solid content and with retention rime of about 20 secs. The overall clay recovery is 86%(94%_for the first pass and 92% for the second pass). Understandably, the feed solid content of second pass was lower than 15% while the iron (Fe201) could be reduced by about 55% the reduction in TiO2 was about 12% indicating that there still exists scope for removing Ti02 from this clay and enhancing brightness further. All the SC-HGMS tests were conducted at Bhabha Atomic Research Centre, Trombay, Bombay. India

Quantum versus Semiclassical Description of Selftrapping: Anharmonic Effects

Selftrapping has been traditionally studied on the assumption that quasiparticles interact with harmonic phonons and that this interaction is linear in the displacement of the phonon. To complement recent semiclassical studies of anharmonicity and nonlinearity in this context, we present below a fully quantum mechanical analysis of a two-site system, where the oscillator is described by a tunably anharmonic potential, with a square well with infinite walls and the harmonic potential as its extreme limits, and wherein the interaction is nonlinear in the oscillator displacement. We find that even highly anharmonic polarons behave similar to their harmonic counterparts in that selftrapping is preserved for long times in the limit of strong coupling, and that the polaronic tunneling time scale depends exponentially on the polaron binding energy. Further, in agreement, with earlier results related to harmonic polarons, the semiclassical approximation agrees with the full quantum result in the massive oscillator limit of small oscillator frequency and strong quasiparticle-oscillator coupling.Comment: 10 pages, 6 figures, to appear in Phys. Rev.

On the Mass Eigenstate Composition of the 8B Neutrinos from the Sun

The present data of gallium experiments provide indirectly the only experimental limit on the fraction of $\nu_2$ mass eigenstate for the $^8$B neutrinos from the Sun. However, if to use the experimental data alone, the fraction of $\nu_2$ and, consequently, $sin^2\theta_{sol}$ still is allowed to be varied within a rather broad range. The further experimental efforts are needed to clear this point.Comment: 13 pages, 1 figure, 1 table. Corrected version, published in JCAP04(2007)00

SoK: The Ghost Trilemma

Trolls, bots, and sybils distort online discourse and compromise the security of networked platforms. User identity is central to the vectors of attack and manipulation employed in these contexts. However it has long seemed that, try as it might, the security community has been unable to stem the rising tide of such problems. We posit the Ghost Trilemma, that there are three key properties of identity -- sentience, location, and uniqueness -- that cannot be simultaneously verified in a fully-decentralized setting. Many fully-decentralized systems -- whether for communication or social coordination -- grapple with this trilemma in some way, perhaps unknowingly. We examine the design space, use cases, problems with prior approaches, and possible paths forward. We sketch a proof of this trilemma and outline options for practical, incrementally deployable schemes to achieve an acceptable tradeoff of trust in centralized trust anchors, decentralized operation, and an ability to withstand a range of attacks, while protecting user privacy.Comment: 22 pages with 1 figure and 8 table

Possibility of Recoating of Impurities on Product Kaolin during Froth Flotation - HRTEM-EDS Study

Attempts were made to remove the Fe, Ti minerals from Gujarat kaolin by SC-HGMS and ultraflotation to improve the optical properties. The removal of Fe was higher by SC-HGMS, but that of Ti was almost the same by both techni-ques. The Fe content of the products was relatively low, but the brightness was lower than the expected. A drastic improvement in brightness was observed for the SC-HGMS product compared to the ultra flotation product. One of the probable reasons for the low enhancement in brightness by flotation was thought to be recoating of the impurities on the clay surface during flotation. XPS study conducted on the flotation product ruled out the possibility of such a coating. HRTEM-EDS analyses showed that most of the titania is present in the form of anatase particles of very small size. A part of the Fe forms independent parti-cles of goethite /hematite having nano size. Rest of the Fe is found to be closer to anatase or kaolinite particles either as a part of the structure or nano sized independ-ent particles adhering to the surface and hence is not easily separated. The ultra fine grains of Fe stained ana-tase remaining in the kaolinite surface after flotation is found to have a strong pigment effect. During flotation, high shear energy is given for dispersion and conditioning which is possibly reducing the particle size to sub-micron / nano level. The dissatisfying brightness of the flotation product is attributed to the presence of these fine / colloidal impurities. Fe content in the product samples is relatively low and its influence on brightness is probably smaller than that of the Fe stained anatase. The organic matter and ferriferous smectite identified in the sample even at small percentages may also have a pig-ment effect due to their dark color and colloidal distri-bution

A diagrammatic treatment of neutrino oscillations

We present a covariant wave-packet approach to neutrino flavor transitions in vacuum. The approach is based on the technique of macroscopic Feynman diagrams describing the lepton number violating processes of production and absorption of virtual massive neutrinos at the macroscopically separated space-time regions ("source" and "detector"). Accordingly, the flavor transitions are a result of interference of the diagrams with neutrinos of different masses in the intermediate states. The statistically averaged probability of the process is representable as a multidimensional integral of the product of the factors which describe the differential flux density of massless neutrinos from the source, differential cross section of the neutrino interaction with the detector and a dimensionless factor responsible for the flavor transition. The conditions are analyzed under which the last factor can be treated as the flavor transition probability in the usual quantum-mechanical sense.Comment: 27 pages,7 figures, iopart class. Includes minor corrections made in proofs. References update

CCR2, MCP-1, SDF-1α & DC-SIGN gene polymorphisms in HIV-1 infected patients with & without tuberculosis

Background & Objectives: Variability in the clinical outcome of persons exposed to and infected with HIV-1 and tuberculosis (TB) is determined by multiple factors including host genetic variations. The aim of the present study was to find out whether chemokine, chemokine receptor and DC-SIGN gene polymorphisms were associated with susceptibility or resistance to HIV and HIV-TB in south India. Methods: CCR2 V64I (G/A), monocyte chemoattractant protein-1 (MCP-1) -2518 A/G, stromal cell derived factor-1α; (SDF-1α) 3'UTR G/A and DC-SIGN gene polymorphisms were studied by polymerase chain reaction based methods in HIV-1 infected patients without TB (n=151), with pulmonary TB (PTB) (n=81) and extrapulmonary TB (n=31), 155 PTB patients without HIV and 206 healthy controls. Results: The genotype frequencies of CCR2 V64I, MCP-1 -2518 and DC-SIGN polymorphisms did not differ significantly between the study groups. A significantly increased frequency of GG genotype of SDF-1alpha polymorphism was observed among HIV+PTB+ patients compared to healthy controls (P=0.009, Pc=0.027). Interpretation & Conclusions: Our data suggest that GG genotype of SDF-1alpha 3'UTR polymorphism may be associated with susceptibility to PTB in HIV-1 infected patients. A better understanding of genetic factors that are associated with TB could help target preventive strategies to those HIV patients likely to develop tuberculosis