Logic Rating of Electromechanical Relays
Electromechanical relays were the first logic element used in a computer. Today, small compact reed relays are again being extensively used as logic elements. A logic factor, FL, measures the improvement that a logic device can affect if interposed between a logic source and logic detector. A logic figure of merit, TFM, determined when FL = 1.0 can be used for comparison of the logic performance of logic devices. TFM is developed for an arbitrary electromechanical relay. For a miniature reed relay packaged for printed circuit boards, TFM = 1.7 milliseconds. For comparison, solid-state devices have TFM ¿ 1 nanoseconds and COSMOS (complementary symmetry metal oxide semiconductor) devices have TFM ¿ 20 nanoseconds.
On measures of logic performance: logic quantum, factor, and figure of merit
A basic logic operation is considered of transferring a logic decision from one point to another point. A certain energy level, WL, corresponding to decision threshold and a time delay, TL, are encountered in the transfer process. The product, WLTL, is a logic quantum, HL. If the logic transfer takes place through an intermediate device, a logic factor, FL, can be introduced to describe the reduction in logic quanta that the device can produce under optimum conditions. Optimization is carried out, as for instance with ideal transformers, to "match" the logic source to the device and the device to the logic detector. The condition FL = 1 marks a boundary between a useful and a uselessd evice, and a logicf igure of merit, TPH,in units of time corresponds to the fastest source-detector combination such that FL = 1. Logic performance is considered in some detail for a particular linear model of a device. Nonlinear devices and relay devices are considered in less detail, although some numerical calculations are given for a current-switch, two-transistor computer device. The logic figure of merit represents a unique measure of high-speed logic performance and is therefore valuable in comparing devices including associated circuitry on a common basis.
New Sweet-Tasting C21-Pregnane Glycosides from Pericarps of Myriopteron extensum.
Ten novel C21 pregnane glycosides, extensumside C-L (1-10), were isolated as highly sweet-tasting substances from the edible pericarps of Myriopteron extensum (Wight) K. Schum by sensory-guided fractionation and purification. Their structures were determined through 1D and 2D NMR, such as HSQC, HMBC, 1H-1H COSY, HSQC-TOCSY, and ROESY, as well as other spectroscopic analysis combined with chemical evidence. These compounds shared the same aglycone, 3β,16α-dihydroxy-pregn-5-en-20-one, and contained the deoxysugar chain and the glucose chain which were linked to C-3 and C-16 of the aglycone, respectively. The sweetness potency was evaluated by a human sensory panel test and preliminary structure-taste relationship was discussed. The sweetness intensities of these compounds are between 50 and 400 times greater than that of sucrose. Furthermore, quantitation analyses of compounds 1, 3, 4, and 6 in different parts of M. extensum indicated that the concentrations of these sweet components in the pericarps are obviously higher than those in stems and roots.