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Novel aromatic poly(etheraroylhydrazides), PEHZ, incorporating a methylenic sequence (with number of &bond;CH2&bond; units m = 2, 4, 6, 8, 10, 12) in the main chain, have been obtained by solution polycondensation and characterized with several techniques. In particular, Differential Scanning Calorimetry (DSC) and Wide Angle X-ray Scattering (WAXS) gave interesting results. The complex thermal behavior and the lattice parameters of these linear polyhydrazides are a function of the number of methylene units present in the flexible segment. The relationships we found suggest a model: a polymer with disorder in aliphatic segment layers while preserving chain periodicity, that is the classical model of “conformationally disordered crystalline” polymer. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1687–1701, 1999

A digital coherent-downconverter configuration is described whose operation principle is based on the theory of subharmonic sampling for narrowband waveforms. This configuration uses a fast sampler, operating at microwave frequencies, for directly demodulating the in-phase and quadrature components of a complex input waveform, yielding a sampled sequence in a suitable format for subsequent analogue-to-digital conversion. Unlike the conventional double-conversion coherent-superheterodine architecture, the proposed configuration offers attractive features in terms of cost and complexity and appears particularly suitable for the implementation of the front-end unit in a coherent receiver. An experimental prototype, based on a very fast GaAs MMIC sample-and-hold (SH) circuit, has been implemented for validating the operation principle. Complex demodulation of a 1 GHz input waveform is demonstrated, with 6-bit equivalent accuracy.

N,N′-diphenyl-N,N′-diethylurea (C17H20N2O) crystallizes in the space group P21/c. The unit cell constants are: a= 10.42 ± 0.01 Å, b= 16.86 ± 0.02 Å, c= 10.66 ± 0.001 Å, β = 125°16′ ± 5′; Z= 4, Dx= 1.16 g·cm-3, Dmeas= 1.16 ± 0.01 g·cm-3. Data for 1392 reflections were collected at room temperature on a Picker automated diffractometer. The crystal structure was solved by direct methods and refined by bloc-diagonalized matrix least-squares calculations. The molecule is characterized by a pseudo C2symmetry; both phenyl groups are transwith respect to the oxygen atom. The hybridization of the two nitrogen atoms is intermediate between trigonal and tetrahedral; the nonplanar distortion of the amide groups is about 30°. The amide C-N bond lengths are 1.37 Å.

A configuration for a slotted patch antenna is introduced which allows two separate operating frequencies. Both of these frequencies are associated with a radiating mode almost identical to that of a standard patch. The two resonances are related to the patch width and the slot/patch length, respectively.

Some new structures for neural based A/D conversion are presented. Experimental results on the proposed topologies are reported. The described structures are particularly suitable for the realisation of a low-cost, easily expandable voltmeter for consumer application.