The Effect of Carrier Phase Error on the Performance of a Duobinary Shaped QPSK Signal

An analysis is presented showing the effect of carrier phase error on the error-rate of a duobinary shaped, quaternary, phaseshift keying digital radio system. A simple upper bound on the probability of error as a function of phase error is derived and the results are compared to those obtained by computer simulation. The conclusion is reached that such a system exhibits approximately 1.0 dB degradation for a carrier phase error of 3° at an error-rate of 10^-5and a 10 dB degradation at a phase error of 15°.     

Intracellular distribution of lipolytic activity in the female gametophyte of germinating Douglas fir seeds

Acid (pH 5.2) and neutral (pH 7.1) lipase activity was studied in order to localize the sites of lipolysis in cellular fractions of catabolic organ of Douglas fir seed. Cellular particles were separated by differential centrifugation of the tissue homogenate and identified by electron microscopy. Emulsified native neutral lipids were provided as a substrate to protein body, mitochondrial, microsomal and soluble fractions, and endogenous lipids were used as a substrate for light and heavy fat body fractions. Little difference was observed in average specific activity of the two enzyme systems in dry seeds, but acid lipase activity increased sevenfold and neutral lipase activity fourfold during germination. Highest specific activity of both enzyme systems was found to be associated with the heavy fat bodies and the soluble fraction. Heavy fat bodies contained an ample quantity of endogenous substrate while the soluble fraction consisted of little substrate. Experimental data indicated that the soluble fraction was the source of lipases, and the heavy fat bodies were the site of in situ lipolysis.     

The Gradient Projection Algorithm for Multiple Routing in Message-Switched Networks

Various algorithms have been proposed for determining the routing paths designed to minimize the average overall message time delay in message-switched networks. In this paper we describe the application of the gradient projection algorithm to this problem. This algorithm is a gradient-type search procedure designed to handle constrained optimization problems, into which category the routing problem falls. Calculations of the computational complexity of this algorithm indicate that it is particularly well-suited to networks with a limited number of commodities or source-destination pairs. The algorithm is applied to a representative group of distributed-type networks, of varying complexity. Execution times for this algorithm are compared with those obtained using the flow deviation routing algorithm. These agree roughly with the results of the computational requirement calculations; i.e., this algorithm generally requires less execution time for networks with a relatively small number of commodities than does the flow deviation method. (The actual running time depends significantly on the choice of the initial flows or routing paths, however.) For those networks in which all network nodes may be expected to communicate with all other nodes, however, the flow deviation method would be expected to be superior.     

The magnetic field dependence of luminescence in plasma-deposited amorphous silicon

A magnetic field dependent increase in luminescence intensity, which saturates at 30G, is observed at temperatures up to 150K in plasma-deposited amorphous silicon. The effect is explained by a coupling between spin states below 30G caused by low frequency magnetic fluctuations which originate from the photogeneration of carriers. The coupling changes the recombination kinetics when the spin-lattice relaxation time is larger than the recombination time. The effect is related to the anomalous spin dependent photoconductivity and spin dependent luminescence, and is thought to originate from the competing non-radiative transition, which is the tunnelling of a carrier into a singly occupied defect state.     

Fullerenoid lipids: first synthesis of structured triacylglycerols containing an Aza-[60]fullerene unit

Some 1,2- and 1,3-diacyl glycerols (with acyl groups as stearyl, oleyl, linoleyl, or stearolyl) were synthesized by conventional methods. The diacyl glycerols were esterified with 6-bromo-hexanoic acid to give the corresponding bromotriacylglycerols (of the type AAB and ABA containing a bromo group at the distal part of the hexanoate chain). The bromo function was transformed to an azide group by reaction of the bromotriacylglycerols with sodium azide. The resulting azido-triacylglycerols were then reacted with [60]fullerence to give the requisite aza-fullerenoid triacylglycerol of the type ABA or AAB (45–62% yield based on the amount of [60]fullerence reacted). The nitrogen atom attached to the carbon cage formed a “[5,6]-open” type aza substructure, which was confirmed by the appearance of 31–32 signals in the region of δ_C 133–148 (carbon shifts of sp ² carbons of the cage) in the ¹³C nuclear magnetic resonance spectra. The spectroscopic and mass spectrometric properties of these novel fullerenoid triacylglycerols are reported.     

Study on barium titanate ceramics prepared by various methods

Barium titanate (BaTiO₃) ceramics have been fabricated using powders prepared by sol-gel, coprecipitation and mixed oxide methods. The powders prepared by sol-gel and coprecipitation have average crystallite diameters of 100 nm and 300 nm, respectively while the diameter of the mixed oxide powder is 1–3 m. When sintered at the same temperature of 1320°C, the three BaTiO₃ ceramics have very different grain size, with the one prepared by the mixed oxide method having the largest grain size of 20 m. The dielectric permitivity increases as the grain size of the ceramic becomes smaller. The room temperature (25°C) dielectric permittivity, pyroelectric and piezoelectric properties of these ceramics have been measured as functions of the poling field. The BaTiO₃ ceramic fabricated from nanosized powder derived from the coprecipitation method is found to have the smallest grain size and better properties than prepared from the sol-gel route, and is thus a good candidate for use in devices that required thick (10 to 20 m) ferroelectric films.