Longitudinal and shear mechanical relaxation data are reported for a hydration of 20% of synthetic diethylamine melanin. The longitudinal attenuations per wavelength αλ at frequencies between 1 and 5 MHz show an enormously large amount of absorption above room temperature. The amount αλ/2π=0.55–0.95 at a temperature of 60 °C in the frequency of 1 MHz has never been found in usual polymeric substances where αλ/2π∼0.1. The longitudinal data are interpreted in terms of a combined relaxation and resonance process. Measurements of the shear impedance in the temperature range from −10 to +60 °C, with frequencies ranging from 5.2 to 362 MHz, indicate a distribution of relaxation times, represented by the Davidson-Cole spectrum. Temperature dependency of limiting shear modulus is found to obey the Hirai-Eyring equation.

Assuming the initial population in the hydrogenic 50s state, we simulate Rydberg-state redistribution and photoionization by a nonresonant opticalfrequency pulse versus the number of different n manifolds included. The inclusion of additional n manifolds, around the n = 50 manifold distinguished by the initial-state choice, is shown to invalidate the photoionization predictions based on the single-n manifold approximation. The calculations are performed assuming a linearly polarized, 620 nm pulse, turned on and off suddenly, of ten-optical-period duration and peak intensity 10 9 W cm −2 ensuring effective transient mixing of both-parity Rydberg states around n = 50.

Shear mechanical relaxation data are reported for series of polystyrene and polybutene. Shear measurements in the temperature range from 65 to 150 °C, with frequencies ranging from 0.5 to 100 MHz, indicate a relatively wide distribution of relaxation times, represented by the Davidson-Cole spectrum. The spectrum shows an essentially greater width as the molecular weight increases. This behavior is related to the non-Arrhenius character of melt viscosity. Limiting shear modulus is precisely determined and found to obey the Hirai-Eyring equation G∞= (RT/V0)  exp(Eh/RT), where Eh is the energy required to create one mole of holes and V0 represents molar volume of a monomer unit. The only exceptional case is the lower-molecular-weight polystyrene in which G∞ follows the equation of Barlow, Dickie, and Lamb. The values of Eh/RT at the glass transition temperature for polystyrenes and very low-molecular-weight polybutenes are within the universal constant 3.68±0.13. The origin of the hysteresis loss is discussed in terms of Eh.

Articles you may be interested inAnisotropy in the dielectric spectrum of hydration water and its relation to water dynamics Shear mechanical relaxation and resonance data are reported for 20 wt % hydration of diethylamine melanins with difTerentpH values ranging from 2 to 7. Shear impedance measurements in the temperature range from 60 to -80 o e, with frequencies from I to 362 MHz, indicate a Davidson-Cole spectrum in the primary relaxation and a single relaxation with a characteristic frequency of f = 4 MHz at 6O·C referred to the molecular motions of a group composed of an average molecular weight M. "" 1.4 X 10'. A resonance at 250 MHz is found in the specific melanin called No. I. associated with stacking of indole monomer units. and a single relaxation at f = 270 MHz at 60 ·C is found in the hydrate of melanin No.2. The nature of the stacking is surveyed on account of Fitzgerald's theory. The limiting shear modulus in the primary relaxation related to the molecular motion of backbone chains obeys the modified Hirai-Eyring equation. All the hydrations have an amorphous phase composed of a three-dimensional network structure.

The Ariel 3 satellite (orbital inclination 80°, mean altitude 550 km) was launched from Vandenberg, California on 5 May 1967. One of the five experiments carried by the spacecraft was a synoptic study of v.1.f. phenomena above the ionosphere using a v.1.f. receiver with loop aerial. The peak, mean and minimum signals at 3.2, 9.6 and 16 kHz are measured in each 28 second period around the orbit. At 16 kHz wide (Af= 1 kHz) and narrow (hf = 100 Hz) band channels are used to distinguish C.W. transmissions from GBR (Rugby) from natural noise-like signals such as hiss. The measurements are stored on the satellite tape recorder and telemetered to ground at an appropriate Stadan station. The factors governing the choice of receiver parameters are discussed. The equipment and technical problems encountered are described.