Channel capacity in time sharing multiple-access flat fadingchannels employing variable rate M-QAM transmitter

An approach for obtaining channel capacity when rate adaptive transmitters with co-ordination among all users are time sharing flat fading channels for transmission is presented. This channel capacity is obtained when only the mobile that observes the best channel condition is assigned to transmit at any time. Channel capacity in general gamma fading channels is computed     

Atomic force microscopic imaging of seeded fibril formation and fibril branching by the Alzheimer's disease amyloid-beta protein

BACKGROUND: Amyloid plaques composed of the fibrillar form of the amyloid-beta protein (Abeta) are the defining neuropathological feature of Alzheimer's disease (AD). A detailed understanding of the time course of amyloid formation could define steps in disease progression and provide targets for therapeutic intervention. Amyloid fibrils, indistinguishable from those derived from an AD brain, can be produced in vitro using a seeded polymerization mechanism. In its simplest form, this mechanism involves a cooperative transition from monomeric Abeta to the amyloid fibril without the buildup of intermediates. Recently, however, a transient species, the Abeta amyloid protofibril, has been identified. Here, we report studies of Abeta amyloid protofibril and its seeded transition into amyloid fibrils using atomic force microscopy. RESULTS: Seeding of the protofibril-to-fibril transition was observed. Preformed fibrils, but not protofibrils, effectively seeded this transition. The assembly state of Abeta influenced the rate of seeded growth, indicating that protofibrils are fibril assembly precursors. The handedness of the helical surface morphology of fibrils depended on the chirality of Abeta. Finally, branched and partially wound fibrils were observed. CONCLUSIONS: The temporal evolution of morphologies suggests that the protofibril-to-fibril transition is nucleation-dependent and that protofibril winding is involved in that transition. Fibril unwinding and branching may be essential for the post-nucleation growth process. The protofibrillar assembly intermediate is a potential target for AD therapeutics aimed at inhibiting amyloid formation and AD diagnostics aimed at detecting presymptomatic disease.     

Characterization to species level of Mycobacterium avium complex strains from human immunodeficiency virus-positive and -negative patients

Forty human clinical Mycobacterium avium-M. intracellulare complex strains isolated in Greece were characterized to the species level by PCR with three sets of primers specific for one or both species. M. avium predominated in both human immunodeficiency virus-positive and -negative patients, but the frequency of M. intracellulare isolation appeared to be higher in the latter.     

Catechol O-methyltransferase inhibitor tolcapone has minor influence on performance in experimental memory models in rats

DNA-based immunization is a promising new technique for generating antibodies in laboratory animals for diagnostic purposes in biological science. The main advantages are the elimination of time and labor and the technically demanding steps of antigen purification. The DNA sequence of the protein of interest, cloned in a suitable in vivo expression vector that is administered intramuscularly or intradermally, is sufficient to induce an immune response in animals. We report the induction of antibodies to tobacco mosaic virus (TMV) coat protein (CP) as a highly immunogenic structural protein and potato virus Y (PVY) P1 protein (P1) as a nonstructural protein. The appropriate nucleotide sequences were introduced in a mammalian expression vector (pSG5) and injected intramuscularly into New Zealand White rabbits (Oryctolagus cuniculus). By 10 days post-injection (dpi) a specific immune response was detected against TMV-CP, while it took about 5 weeks for a response to PVY P1. In both cases the antibody titers were significantly above the corresponding pre-immune serum, however, they were considerably below the titer of the matching conventionally produced antiserum. To our knowledge, this is the first report of DNA-based immunization in order to generate antibodies to plant viral proteins, but further improvements are necessary to increase antibody titers before this promising new technique can be introduced broadly in plant science for diagnostic purposes.     

An iterative solution of the two-dimensional electromagnetic inverse scattering problem

A new method, based on an iterative procedure, for solving the two-dimensional inverse scattering problem is presented. This method employs an equivalent Neumann series solution in each iteration step. The purpose of the algorithm is to provide a general method to solve the two-dimensional imaging problem when the Born and the Rytov approximations break down. Numerical simulations were calculated for several cases where the conditions for the first order Born approximation were not satisfied. The results show that in both high and low frequency cases, good reconstructed profiles and smoothed versions of the original profiles can be obtained for smoothly varying permittivity profiles (lossless) and discontinuous profiles (lossless), respectively. A limited number of measurements around the object at a single frequency with four to eight plane incident waves from different directions are used. The method proposed in this article could easily be applied to the three-dimensional inverse scattering problem, if computational resources are available.     

Automated targeting for inter-plant water integration

Apart from in-plant water recovery, inter-plant water integration (IPWI) offers another promising mean for the reduction of fresh water and wastewater flowrates for process plants. This paper extends the automated targeting technique that was developed for single water network into IPWI. This optimisation-based technique is based on the concept of pinch analysis, which enables the setting of various network targets prior to detailed design. The automated targeting technique is formulated as a linear programming model for which global optimum is guaranteed. The proposed technique is demonstrated using several industrial and literature examples.     

A novel implementation of multilevel fast multipole algorithm for higher order Galerkin's method

A new approach is proposed to reduce the memory requirements of the multilevel fast multipole algorithm (MLFMA) when applied to the higher order Galerkin's method. This approach represents higher order basis functions by a set of point sources such that a matrix-vector multiply is equivalent to calculating the fields at a number of points from given current sources at these points. The MLFMA is then applied to calculate the point-to-point interactions. This permits the use of more levels in MLFMA than applying MLFMA to basis-to-basis interactions directly and, thus, reduces the memory requirements significantly.     

Limited-Angle inverse scattering problems and their applications for geophysical explorations

The effect of the limited-angle measurements on the nonlinear inverse scattering problem is investigated. Because of incomplete information obtained in the limited-angle inverse problem, the linearized system matrix in the inversion procedure becomes more ill-conditioned compared to that of the conventional inverse scattering problem where the receivers are placed in a circle that completely surrounds the object. Consequently, the quality of the reconstruction is considerably reduced, and sometimes it is almost impossible to reconstruct the profile because of the sparsity of the measurement data. To overcome the above difficulty, a boosting procedure, which will help us to obtain the maximum amount of information for an arbitrary predefined experimental setup, has been proposed based on a physical viewpoint. The results of the computer simulations for well-to-well tomography demonstrate that by applying the boosting procedure the quality of the reconstruction and the speed of the convergence are improved significantly. Furthermore, for subsurface detection where both the transmitters and receivers are confined to the ground, the reconstruction becomes possible after applying the boosting procedure.     

Mechanism of nitrogen-enhanced negative bias temperature instability in pMOSFET

From the detailed analysis of the dependence of threshold voltage shift and positive fixed charge/interface state generation on the stress time/temperature of negative bias temperature instability (NBTI) for various nitrogen concentrations at the oxide/Si interface, the mechanism of nitrogen-enhanced NBTI effect has been studied experimentally. The experimental results can be understood in terms of the reaction energies of the hydrogen trapping reactions at the interface, which are obtained from first-principles calculations. The calculations show that the nitrogen's lone-pair electrons can trap dissociated hydrogen species more easily than oxygen. From the experimental and theoretical studies, one can conclude that the roles of nitrogen in the NBTI are two folds, i.e., it provides more reaction sites, and it can also enhance the NBTI reaction by reducing the reaction energy.