Efficient privacy-preserving group-nearest-neighbor queries with the presence of active adversaries

Location-based services (LBSs) allow users to ask location-dependent queries and receive information based on their location. A group of users can send a group-nearest-neighbor (GNN) query in order to receive a Point Of Interest (POI). This POI in turn shows a point which is the minimum distance from all members of the group. To benefit from these services, it is important to preserve the location privacy of each group user from others in the group (Intragroup location privacy) as well as from anyone outside of the group, including the LBS, (Intergroup location privacy). It may also be necessary to protect the location privacy of the resulting POI from the LBS and other possible attackers. In this paper, we propose two different privacy-preserving protocols for finding the exact answer to a GNN query among a set of returned POIs. The first protocol assumes a semi-honest model while the second one works in a malicious model. The proposed protocols are based on the Anonymous Veto network and Burmester–Desmedt key establishment protocols. The security analysis shows that the proposed protocols provide both Intragroup and Intergroup location privacy; they also protect the location privacy of the resulting POI and are resistant to collusion and multi-point aggregate distance attacks. The performed analyses indicate that they incur a constant computation cost per user and are efficient in terms of computation and communication costs.

     

Cobalt ferrite decoration of molybdenum disulfide nanosheets; development of a nanocomposite-mediated hyperthermia method

Journal of Mechanical Science and Technology - The aims were to characterize MoS2/CoFe2O4 nanocomposite and investigate its thermal therapy efficiency on cancerous (MCF-7) and normal (MCF-10A)...     

Complexes of cobalt nanoparticles and polyfunctional curcumin as antimicrobial agents

Although antimicrobials like penicillin and tetracycline have been documented to be most popular antimicrobials, micro-organisms, especially bacteria, are becoming resistant to more and more antimicrobial agents and hence the main future research in antimicrobial therapy is to develop novel materials which could work as effective antimicrobials. In this context, using direct reduction method, 10 nm Co nanoparticles have been synthesized and further functionalized with curcumin. The characterization showed FCC structured Co nanoparticles to be electrostatically bound to curcumin using the hydroxyl linkage, retaining the magnetic moment of Co as well as the diaryl heptanoid chromophore group of curcumin with the loading percentage of~ 89%. These samples when subjected to Escherichia coli, gram negative bacterium, the antimicrobial activity of Co:curcumin was found to be much enhanced as compared to only Co and only curcumin. The results have been correlated to the mechanism in presence of moisture, which possibly suspends the Co:curcumin complex in the medium, which, due to intimate contact between the biocidal agent and the microorganism, renders the microbial agent ineffective. The synthesized system exhibited a combination of the ability of curcumin to penetrate the cell barrier and render antimicrobial action along with the chelating capacity of Co:curcumin complex. In the same way that strong metal-ligand bonds are vital for the efficiency of metal chelators of toxic metals, these strongly bound metal complexes may prove to be better antimicrobial agents, binding them to the bacterial walls.     

Polymer-embedded stannic oxide nanoparticles as humidity sensors

Stannic oxide (SnO₂) nanoparticles have been suspended in polyvinyl alcohol (PVA) matrix in different PVA:SnO₂ molar ratios ranging from 1:1 to 1:5 using simple chemical route. This suspension was deposited on ceramic substrate and upon drying was carefully detached from the substrate. SnO₂-embedded self-standing, transparent and flexible thin films were hence synthesized. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques show the rutile tetragonal structure of SnO₂ with particle size ~ 5 nm. UV–Visible spectroscopy demonstrates the band gap of 3.9 eV, which does not alter when embedded in polymer. Fourier transform infrared spectroscopy (FTIR) reveals that the properties of SnO₂ do not modify due to incorporation in the PVA matrix. The structures work as excellent humidity sensors at room temperature. For a critical PVA:SnO₂ molar ratio of 1:3, the resistance changes to five times of magnitude in 92% humidity within fraction of second when compared with resistance at 11% humidity. The sample regains its original resistance almost instantaneously after being removed from humid chamber. Nanodimensions of SnO₂ particles and percolation mechanism related to transport through polymer matrix and water molecule as a carrier has been used to understand the mechanism.