Private Data Transfer over a Broadcast Channel

We study the following private data transfer problem: Alice has a database of files. Bob and Cathy want to access a file each from this database (which may or may not be the same file), but each of them wants to ensure that their choices of file do not get revealed even if Alice colludes with the other user. Alice, on the other hand, wants to make sure that each of Bob and Cathy does not learn any more information from the database than the files they demand (the identities of which will be unknown to her). Moreover, they should not learn any information about the other files even if they collude. It turns out that it is impossible to accomplish this if Alice, Bob, and Cathy have access only to private randomness and noiseless communication links. We consider this problem when a binary erasure broadcast channel with independent erasures is available from Alice to Bob and Cathy in addition to a noiseless public discussion channel. We study the file-length-per-broadcast-channel-use rate in the honest-but-curious model. We focus on the case when the database consists of two files, and obtain the optimal rate. We then extend to the case of larger databases, and give upper and lower bounds on the optimal rate.Comment: To be presented at IEEE International Symposium on Information Theory (ISIT 2015), Hong Kon

Mechanochemical synthesis, characterization and photocatalytic Properties of M2O3/TiO2 (M = Fe, Mn) nano-composite under visible light

Nano-particles of homogeneous solution between TiO2 and M2O3 (M = Fe, Mn; upto 10 wt %) have been prepared by mechanochemical milling of TiO2 and yellow/Red Fe2O3 and Mn2O3 using a planetary ball mill. Photocatalytic activities of TiO2 / M2O3 powders were investigated by photooxidation of different dyes like Rhodamine B (RB), Methyl orange (MO), thymol blue (TB) and Bromocresol green (BG) under visible light (300-W Xe lamp; λ > 420 nm). The results show that the alloy of TiO2 with 5 wt % of Fe2O3 (YFT1) exhibit photocatalytic activity 3-5 times higher than that of P25 TiO2 and 5 wt % of Mn2O3 /TiO2 (MNT1). Therefore, we have mainly discussed on Fe2O3/TiO2 alloy. XRD of powders show that it has anatase structure with no peak of any of Fe2O3/Mn2O3. EDX spectra show that Fe/Mn is uniformly distributed in TiO2. The average particle size and crystallite size of YFT1, MNT1 were found to be 30±5 nm (TEM), 100±5 nm (SEM) and 12 nm (XRD) respectively. Optical adsorption edge of YFT1 is found to be 2.26 eV. EPR and magnetic susceptibility show that Fe3+ is in low spin state corresponding to µB = 1.8 BM. As the band edge is lower than TiO2, which means that Fe3+ is situated in between conduction band and valence band. The optical absorption causes the formation of hole on Fe3+ and liberated electron goes to conduction band. This charge separation is facilitated by visible light rather than UV or near UV light due to lesser energy gap between Fe3+ and bottom of conduction band. The oxidation state of iron has been found to be +3 from redox titration and XPS

Motion Artifact removal in Ambulatory ECG Signal using ICA

No Abstrac

On the Detection of Magnetic Helicity

Magnetic fields in various astrophysical settings may be helical and, in the cosmological context, may provide a measure of primordial CP violation during baryogenesis. Yet it is difficult, even in principle, to devise a scheme by which magnetic helicity may be detected, except in some very special systems. We propose that charged cosmic rays originating from known sources may be useful for this purpose. We show that the correlator of the arrival momenta of the cosmic rays is sensitive to the helicity of an intervening magnetic field. If the sources themselves are not known, the method may still be useful provided we have some knowledge of their spatial distribution.Comment: 5 pages, 1 figure, discussions and references added, submited to Phys. Rev.