Two-way Circuit Research Articles

A communication network within the cytoplasmic domain of toll-like receptors has remained conserved during evolution

Toll/IL-1R (TIR) domain, that is, the cytoplasmic domain, in toll-like receptors (TLRs) from different species showed high sequence conservation in stretches spread across the surface as well as the core of the domain. To probe the structure–function significance of these residues, especially those coming from the core of TIR domains, we analyzed molecular dynamics trajectories of sequence similarity based models of human TIR domains. This study brought forth that N-terminal of the TIR domain simultaneously interacts with the flanking residues of the BB loop and central β-sheets. At the same time, residues of the central β-strands form favorable contacts with the DD loop and C-terminal, thus forming a two-way circuit between the N- and C-termini. In this work, the array of intradomain interactions is termed as communication network. Importantly, the “hubs” of this communication network were found to be conserved in all human TLRs. Earlier mutagenesis–function correlation work brought forth that certain mutations in the “core” of the TIR domain of TLR4 (e.g. in IFI767–769AAA and L815A) led to almost complete abrogation of signaling and reasoning for this dramatic loss-of-function has remained unclear, since these sites are not surface exposed. Using MD studies, we show here that this communication network gets disrupted in mutants of human TLR4 which were earlier reported to be functionally compromised. Extension of MD studies to heterodimer of TLR1/2 suggested that this evolutionarily conserved communication network senses the interactions formed upon dimerization and relays it to surfaces which are not involved in direct interdomain contacts.

Two-way circuits with inverse transmission properties

An active or passive three-terminal circuit may be modified, as shown here, to operate in both directions in an inverse manner, i.e. if the voltage transfer ratio (VTR) in the forward direction is T, the value in the return direction is 1/T.

Switched diversity with feedback for DPSK mobile radio systems

Switched diversity with feedback for differential phase shift keying (DPSK) mobile radio is discussed. The technique uses multiple transmit antennas at the base station but only one receive antenna at the mobile. The base station transmits with one antenna that is switched when the mobile informs the base station that the received signal has fallen below a fixed level. The implementation of switched diversity with feedback in a digital mobile radio system is first described, and then the bit error rate performance of the system is analyzed with fading as a function of several design parameters. Implementation of the system is shown to be relatively simple, yet the system is shown to reduce substantially the required received E <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</inf> /N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> for a given error rate at the mobile as compared to a system without diversity. For example, with five transmit antennas the required received E <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">b</inf> /N <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> for a 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> bit error rate is 13 dB less. The system capacity and availability assuming 32 kb/s audio and flat fading is then discussed. It is shown that with three-corner base station diversity and four transmit antennas at each base station, 126 two-way circuits per cell can be used in a fully loaded 40-MHz bandwidth system with a ten-percent probability that the error rate exceeds 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> .

Ultra-Short Wave Radio Links for Telephony

IT is now well known that electric waves having a wave-length of less than about 8 metres are of little use for long-distance radio communication, owing to X the apparent inability of the ionosphere to deflect such waves back to the earth's surface. For shorter; distances and particularly over stretches of water,; however, these short waves are being found to have a useful application in providing a radio link in the ordinary land-line telephone system. In this connexion, the radio link is an alternative to the use of a submarine cable, and it has the advantages of lower installation cost and ease of maintenance. An experimental two-way circuit of this type, operating on a wave-length of about five metres, was inaugurated by the Post Office engineers across the Bristol Channel in 1932 (see NATURE, 130, 604, Oct. 22, 1932). This radio circuit operates between Cardiff and eston-super-Mare and links up with the ordinary inland telephone network, thus forming part of the London-Cardiff trunk circuit. The recent opening of a similar radio link, on a much shorter wave-length, across the English Channel for use in connexion with the cross-channel air services was referred to in NATURE of February 3, p. 167.