Coding Strategies for Noise-Free Relay Cascades with Half-Duplex Constraint

Two types of noise-free relay cascades are investigated. Networks where a source communicates with a distant receiver via a cascade of half-duplex constrained relays, and networks where not only the source but also a single relay node intends to transmit information to the same destination. We introduce two relay channel models, capturing the half-duplex constraint, and within the framework of these models capacity is determined for the first network type. It turns out that capacity is significantly higher than the rates which are achievable with a straightforward time-sharing approach. A capacity achieving coding strategy is presented based on allocating the transmit and receive time slots of a node in dependence of the node's previously received data. For the networks of the second type, an upper bound to the rate region is derived from the cut-set bound. Further, achievability of the cut-set bound in the single relay case is shown given that the source rate exceeds a certain minimum value.Comment: Proceedings of the 2008 IEEE International Symposium on Information Theory, Toronto, ON, Canada, July 6 - 11, 200

Capacity for Half-Duplex Line Networks with Two Sources

The focus is on noise-free half-duplex line networks with two sources where the first node and either the second node or the second-last node in the cascade act as sources. In both cases, we establish the capacity region of rates at which both sources can transmit independent information to a common sink. The achievability scheme presented for the first case is constructive while the achievability scheme for the second case is based on a random coding argument.Comment: Proceedings of the IEEE International Symposium on Information Theory, Austin, TX, USA, June 12 - 18, 201

Design of diversity-achieving LDPC codes for H-ARQ with cross-packet channel coding

In wireless scenarios an effective protocol to increase the reliability for time-varying channels is the hybrid automatic repeat request (H-ARQ). The H-ARQ scheme with cross-packet channel coding (CPC) is a recently published extension of H-ARQ with several advantages. No full-diversity low-density parity-check (LDPC) code design for the whole range of coding rates yielding full-diversity has been published. In this paper the authors provide a new outage behavior analysis and a new structured LDPC code ensemble achieving full-diversity for H-ARQ with CPC by exploiting the rootcheck principle. Simulation results show that the new code design outperforms the previous approaches, providing full-diversity and good coding gain, also at high coding rates

On the Capacity of the Binary-Symmetric Parallel-Relay Network

We investigate the binary-symmetric parallel-relay network where there is one source, one destination, and multiple relays in parallel. We show that forwarding relays, where the relays merely transmit their received signals, achieve the capacity in two ways: with coded transmission at the source and a finite number of relays, or uncoded transmission at the source and a sufficiently large number of relays. On the other hand, decoding relays, where the relays decode the source message, re-encode, and forward it to the destination, achieve the capacity when the number of relays is small. In addition, we show that any coding scheme that requires decoding at any relay is suboptimal in large parallel-relay networks, where forwarding relays achieve strictly higher rates.Comment: Author's final version (to appear in Transactions on Emerging Telecommunications Technologies

Hyperactive Sleeping Beauty Transposase Enables Persistent Phenotypic Correction in Mice and a Canine Model for Hemophilia B

Sleeping Beauty (SB) transposase enables somatic integration of exogenous DNA in mammalian cells, but potency as a gene transfer vector especially in large mammals has been lacking. Herein, we show that hyperactive transposase system delivered by high-capacity adenoviral vectors (HC-AdVs) can result in somatic integration of a canine factor IX (cFIX) expression-cassette in canine liver, facilitating stabilized transgene expression and persistent haemostatic correction of canine hemophilia B with negligible toxicity. We observed stabilized cFIX expression levels during rapid cell cycling in mice and phenotypic correction of the bleeding diathesis in hemophilia B dogs for up to 960 days. In contrast, systemic administration of an inactive transposase system resulted in rapid loss of transgene expression and transient phenotypic correction. Notably, in dogs a higher viral dose of the active SB transposase system resulted into transient phenotypic correction accompanied by transient increase of liver enzymes. Molecular analysis of liver samples revealed SB-mediated integration and provide evidence that transgene expression was derived mainly from integrated vector forms. Demonstrating that a viral vector system can deliver clinically relevant levels of a therapeutic protein in a large animal model of human disease paves a new path toward the possible cure of genetic diseases

Kinetics of Humoral and Memory B Cell Response Induced by the Plasmodium Falciparum 19-kilodalton Merozoite Surface Protein 1 in mice.

The 19-kDa carboxyl-terminal fragment of the merozoite surface protein-1 (MSP-1(19)) has been shown to regulate antibody (Ab)-mediated protective immunity to blood-stage malaria infection. But the serological memory to this antigen tends to be short-lived, and little is known of the mechanisms that regulate the formation of B cell memory to MSP-1(19) antigen. We studied the formation of B cell memory response after immunization with the recombinant 19-kDa Plasmodium falciparum merozoite surface protein 1 (PfMSP-1(19)). Immunization with PfMSP-1(19) resulted in delayed increase in germinal center (GC) B cell numbers. This poor GC reaction correlated with short-lived PfMSP-1(19)-specific antibodies in serum and the short life of PfMSP-1(19)-specific plasma cells and memory B cells (MBCs) in spleen and bone marrow. PfMSP-1(19)-specific MBCs were capable of producing antigen (Ag)-specific Ab-secreting cell (ASC) responses that were short-lived following challenge immunization of the immune mice with antigen or transgenic Plasmodium berghei parasite expressing PfMSP-1(19) in place of native P. berghei MSP-1(19) at 8 weeks after the last immunization or following adoptive transfer into naive hosts. However, no protection was achieved in PfMSP-1(19) immune mice or recipient mice with PfMSP-1(19)-specific MBCs following challenge with transgenic P. berghei. Our findings suggest that PfMSP-1(19)-specific IgG production by short-lived plasma cells combined with the poor ability of the PfMSP-1(19)-induced MBCs to maintain the anamnestic IgG responses failed to contribute to protection against infection

A sweet taste receptor-dependent mechanism of glucosensing in hypothalamic tanycytes

Hypothalamic tanycytes are glial-like glucosensitive cells that contact the cerebrospinal fluid of the third ventricle, and send processes into the hypothalamic nuclei that control food intake and body weight. The mechanism of tanycyte glucosensing remains undetermined. While tanycytes express the components associated with the glucosensing of the pancreatic β cell, they respond to nonmetabolisable glucose analogues via an ATP receptor-dependent mechanism. Here, we show that tanycytes in rodents respond to non-nutritive sweeteners known to be ligands of the sweet taste (Tas1r2/Tas1r3) receptor. The initial sweet tastant-evoked response, which requires the presence of extracellular Ca2+, leads to release of ATP and a larger propagating Ca2+ response mediated by P2Y1 receptors. In Tas1r2 null mice the proportion of glucose nonresponsive tanycytes was greatly increased in these mice, but a subset of tanycytes retained an undiminished sensitivity to glucose. Our data demonstrate that the sweet taste receptor mediates glucosensing in about 60% of glucosensitive tanycytes while the remaining 40% of glucosensitive tanycytes use some other, as yet unknown mechanism