Magnetoconductivity and magnetoluminescence studies in bipolar and almost hole-only sandwich devices made from films of a π-conjugated molecule

We present magnetoconductivity and magnetoluminescence measurements in sandwich devices made from films of a π-conjugated molecule and demonstrate effects of more than 30 and 50% magnitude, respectively, in fields of 100 mT at room-temperature. It has previously been recognized that the effect is caused by hyperfine coupling, and that it is phenomenologically similar to other magnetic field effects that act on electron–hole pairs, which are well-known in spin-chemistry. However, we show that the very large magnitude of the effect contradicts present knowledge of the electron–hole pair recombination processes in electroluminescent π-conjugated molecules, and that the effect persists even in almost hole-only devices. Therefore, this effect is likely caused by the interaction of radical pairs of equal charge.     

Polynomial perceptrons and their applications to fading channelequalization and co-channel interference suppression

This paper investigates the behaviors of polynomial perceptrons and introduces a fractionally spaced recursive polynomial perceptron with low complexity and fast convergence rate. The nonlinear mapping ability of the polynomial perceptron is analyzed. It is shown that a polynomial perceptron with degree L(⩾4) satisfies the Stone-Weierstrass theorem and can approximate any continuous function to within a specified accuracy. Moreover, the nonlinear mapping ability of a polynomial perceptron with degree L is similar to that of the three-layer perceptron with one hidden layer for time same number of neurons in the input layer. The nonlinear mapping ability of the fractionally spaced recursive polynomial perceptron is also presented. Applications of polynomial perceptrons for fading channel equalization and co-channel interference suppression in a 16-level quadrature amplitude modulation receiver system are considered. Computer simulations are used to evaluate and compare the performance of polynomial perceptron (PP) and fractionally spaced bilinear perceptron (FSBLP) with that of the synchronous decision feedback multilayer perceptron (SDFMLP), fractionally spaced decision feedback multilayer perceptron (FSDFMLP), and the conventional decision feedback equalizer (DFE). The results show that the performance of the fractionally spaced bilinear perceptron is clearly superior to that of the other structures     

Performance of IJF-OQPSK and Partial Response (PR) IJF-OQPSK Modems in a Nonlinearly Amplified and Adjacent-Channel Interference Satellite Environment

The performance of intersymbol-interference and jitterfree offset-QPSK (IJF-OQPSK) and partial-response (PR) IJFOQPSK modems in a nonlinearly amplified multichannel environment is studied and compared to that of conventional QPSK and OQPSK modems. Power efficiency is maximized by operating the high-power amplifier (HPA) in full saturation. The effect of adjacent-channel interference and flat fade on the performance of illustrative nonlinear satellite systems is investigated. Simulation and measurement results are reported. It is shown that both IJF-OQPSK and PR-IJF-OQPSK modems exhibit a significant performance improvement compared to QPSK and OQPSK modems, in illustrative SCPC and on-board regenerative satellite systems, they provide an improvement of more than 4 dB compared to QPSK.     

Electrochemical oxidation of organyl-2,2-dichlorovinyl sulfides and 1,2-bis(organylchalcogeno)-1,2-dichloroethylenes

Two steps were observed in the electrochemical oxidation of organyl-2,2-dichlorovinyl sulfides RSCHCCl₂. Macroscale electrolyses gives, respectively the sulfoxides (at the first step) and the sulfones (at the second step). This method offers advantage over the chemical oxidation. With 1,2-bis(organylchalcogeno)-1,2-dichloroethylenes RYCClCClYR (Y=S, Se, Te) selectivity was not so high, the main product being the bis-sulf(selen)oxide.     

A Digital Approach to Symbol Timing Recovery Systems

An analysis of a symbol timing recovery (STR) technique using digital processing is presented. The ratio of the discrete spectral power at the symbol rate frequency to the nearby continuous spectral power is used as a criterion of STR performance. It is shown that this power ratio equals the quality factor of the narrow bandpass filter and that it does not depend on the value of the delay element. The performance of the STR subsystem is consequently determined by the quality factor of the bandpass filter rather than by the specific delay. In addition to this, some experimental evidence that the additive channel noise has little effect on the power ratio is given. A modified phase-locked loop with anLCprefiiter is proposed to extract the symbol timing clock. This prefilter improves the acquisition and synchronization performance of the PLL. The STR technique presented here has the advantages of lower cost and simpler hardware implementation over other serial STR techniques.     

An empirical formula for calculation of range of charged particles with Z from 2 to 103 and energy from 2.5 MeV/nucleon to 500 MeV/nucleon in beryllium

A new empirical formula for quick estimation of range in beryllium material of charged particles with the charge number from 2 to 103 and with energy in the range from 2.5 to 500 MeV/nucleon has been given. This formula was found based on a table of ranges measured experimentally and calculated up to 1990. It is shown that the differences between the values calculated by our formula and the values tabulated in the table is less than about 2% for all ions in the whole energy range.     

An analytical model for performance evaluation of parallelinterference cancellers in CDMA systems

In multistage parallel interference cancellation, the tentative decisions for different users at each stage are mutually correlated, and they are also correlated with Gaussian noise. By taking the correlations into consideration and employing Price's theorem, an analytical model is proposed to refine the variance evaluation of the final decision variable. It is shown that the refined variance is very close to that obtained by simulation and can improve the accuracy in bit error rate evaluation     

An Adaptive Combined DFE/RSSE Structure for Unknown Channel with Severe ISI

This paper presents an adaptive combinedDFE/RSSE structure for transmission using a largeconstellation size over a slowly time-varying channelwith severe ISI. This structure combines theconventional decision-feedback equalization (DFE) withthe reduced state sequence estimation (RSSE).Analytical and simulation results carried out for 8PSKsignals indicate that the proposed scheme outperformsboth the conventional DFE and RSSE techniques.     

Soldier defense secretions of the genusHospitalitermes in Peninsular Malaysia

Soldier defense secretions of the genusHospitalitermes (Isoptera, Termitidae, Nasutitermitinae) were chemically analyzed by GC-MS and were found to contain volatile monoterpenes and polyoxygenated diterpenes. Interspecific and intraspecific chemical variations forH. umbrinus, H. hospitalis, H. flaviventris, andH. bicolor are described. Interspecific variations in monoterpene and diterpene structures and compositions were evident. A remarkable example of large intraspecific variation from a single species was observed inH. umbrinus, indicating that colonies of this species can be separable into two chemically distinct groups. The diterpenes found in one of these groups have unusually high molecular weights.     

Chemical defense secretions of some species of Malaysian rhinotermitidae (Isoptera,Rhinotermitidae)

The defense secretions of the soldiers of the Malaysian rhinotermitid,Parrhinotermes aequalis (Havilandi) andP. pygmaeus (John),Termitogeton planus (Havilandi) andSchedorhinotermes malaccensis (Holmgren) consist mainly of vinyl ketones, whereas that ofProrhinotermes flavus (Bugnion & Popoff) gives (E)-1-nitropentadecene. The chemistry of the defense secretions ofParrhinotermes andTermitogeton is documented and based on their chemical relationships;Termitogeton shows a closer affinity to the Rhinotermitinae than Heterotermitinae.