Label-Free Fiber Optic Biosensors With Enhanced Sensitivity

A sensitivity-enhanced long-period grating in-fiber Michelson interferometer with diameter-reduced cladding was proposed for the first time, and was also demonstrated as a label-free biosensor based on refractive index measurement. The cladding structure dependence of the sensitivity for antibody-antigen immuno-sensing was studied experimentally. The proposed biosensor has shown an 8.5-fold sensitivity enhancement as compared to sensors without cladding reduction.     

Reduced integration for improved accuracy of finite element approximations

For completeness the finite element bases which are used for approximate solutions of elliptic problems of order 2p by the Ritz method must include the functions corresponding to the constant value of the pth derivative. In actual usage, to ensure a positive definite system of algebraic equations, additional interpolating functions are introduced. This leads to “multiple covering” of some of the system modes and results in overestimation of stiffness. Reduced integration techniques eliminate some of this multiple covering and thereby give improved accuracy. Selective reduced integration has been found useful in the analysis of flexural problems. In this paper we suggest the use of only the minimal covering that is sufficient for convergence. A technique for solution of the discretized system is given. Numerical performance data show remarkable improvement over conventional procedures. The proposed scheme yields good approximation even for very coarse meshes. This indicates the possibility of considerable economy in the cost of obtaining finite element solutions to complex problems, e.g. coupled field problems, three-dimensional problems, stress concentration etc.     

Antenna selection for spatial multiplexing systems with linearreceivers

Future cellular systems will employ spatial multiplexing with multiple antennas at both the transmitter and receiver to take advantage of large capacity gains. In such systems it will be desirable to select a subset of available transmit antennas for link initialization, maintenance or handoff. We present a criterion for selecting the optimal antenna subset when linear, coherent receivers are used over a slowly varying channel. We propose use of the post-processing SNRs (signal to noise ratios) of the multiplexed streams whereby the antenna subset that induces the largest minimum SNR is chosen. Simulations demonstrate that our selection algorithm also provides diversity advantage thus making linear receivers useful over fading channels     

Roles in information security – A survey and classification of the research area

The concept of roles has been prevalent in the area of Information Security for more than 15 years already. It promises simplified and flexible user management, reduced administrative costs, improved security, as well as the integration of employees’ business functions into the IT administration. A comprehensive scientific literature collection revealed more than 1300 publications dealing with the application of sociological role theory in the context of Information Security up to now. Although there is an ANSI/NIST standard and an ISO standard proposal, a variety of competing models and interpretations of the role concept have developed. The major contribution of this survey is a categorization of the complete underlying set of publications into different classes. The main part of the work is investigating 32 identified research directions, evaluating their importance and analyzing research tendencies. An electronic bibliography including all surveyed publications together with the classification information is provided additionally. As a final contribution potential future developments in the area of role-research are considered.     

Multiferroic properties of Ba(FexTi1 − x)O3 nanorods

Multiferroic Ba(Fe_xTi_1 ? x)O₃ (BFT) nanorods were prepared by a chemical route using polyvinyl alcohol as surfactant. The presence of PVA in excess is responsible to convert cubic or spherical shaped nanoparticles into rodlike structure. Tetragonal phase and nano dimensions in the form of rods of BFT specimens are identified. These BFT nanorods show improvement in the coexistence of ferroelectricity and ferromagnetism of multiferroic properties than their nanoparticles. The effect of low dimensions of BFT rods to control dielectric constant with low loss up to higher frequency region has been observed. With 1% of Fe-doping BFT shows higher value of spontaneous polarization, saturation magnetization and dielectric constant than with other dopants.     

Hybrid AlGaN/GaN-ZnO-nanowire gas sensors

The potential of AIGaN/GaN heterostructures integrated with zinc oxide (ZnO) nanowires for gas sensing applications is demonstrated. Single crystal ZnO nanowires, serving as sensing probes, were selectively grown between two ohmic electrodes of AIGaN/GaN two dimensional electron gas heterostructures by thermal oxidation of sputtered zinc films in air. Electron diffraction and transmission electron microscopy showed the ZnO-nanowires to be crystalline structures oriented in the [001] direction. The fabricated structures were used to detect ethanol, acetone and methanol in a nitrogen background. The results indicate that the hybrid AIGaN/GaN-ZnO nanowires gas sensors are operable over a broad range of temperatures and could potentially be integrated with devices for wireless environmental monitoring.