Air-ground interaction in long range propagation of low frequency sound and vibration—field tests and model verification

An extensive program of intermediate and long range impulsive sound propagation field tests have been conducted. The test program and the performed measurements are presented. Particular focus is given on the air-ground interaction and its effect on low frequency sound and vibration propagation. It is found that the pressure wave interaction with the viscoelastic Rayleigh wave in the ground may have a significant effect on the ground impedance and the sound and vibration propagation. This introduces an important mechanism not covered in commonly used ground impedance models. Numerical simulation models have been developed and verified against the test data. The ground impedance does not only effect the sound pressure propagation. If either acoustically induced ground vibration, or ground to building transmitted vibration, is to be considered, the acousto-seismic impedance has a dramatic effect on the level of ground vibration induced by a given sound pressure. For a site where Rayleigh wave interaction appears at the dominant frequencies of the sound pressure, the ground vibration may be greater than a factor 100 (40 dB) than at a site with ground conditions not making the interaction happen.     

Appearance of a relativistically rotating disk

The appearance of a rotating disk, as perceived by a corotating observer in accordance with two operational procedures is discussed, and the results compared. It is noted that naive generalizations of operational procedures which correctly represent the disk geometry when stationary lead to mutually contradictory pictures when the disk rotates.     

The interpretation of pressure-dependent very-low-pressure pyrolysis experiments

Unimolecular rate data from systems such as very-low-pressure pyrolysis (steady-state flow) and static experiments where gas-gas collisions compete with gas-wall collisions must be interpreted in terms of reactant inhomogeneity arising from finite diffusion rates, rather than using the usual assumption of a well-stirred reactor. An integrodifferential equation describing this process is derived, and a numerical variational solution applicable to weak gas-gas collisions is presented. This gives a powerful method for obtaining collisional energy transfer probabilities from such experiments. Previously reported data (on cyclobutane and cycloheptatriene reactions) are reinterpreted to give conventional values for average energy transfer, replacing the anomalously low collisional efficiencies proposed previously.     

Homonuclear two-dimensional J-resolved spectroscopy. The examination of resonances due to strong coupling in the two-dimensional J-spectrum of 1,6-diazathianthrene: The role of first order character in the position and intensity of resonances due to strong coupling

Resonances due to strong coupling were observed in the two-dimensional J-resolved (2DJ) ¹H-nmr spectrum of 1,6-diazathianthrene. Complete analysis of the 2DJ spectral responses predicts that the resonances due to strong coupling are shifted outward from F₁ = 0 Hz with a corresponding diminution in intensity as the term v_A- v_B increases in proceeding to successively higher spectrometer operating frequencies.     

Nonexistence of an a priori bound at the center in terms of anL 1 bound on the boundary for solutions of uniformly elliptic equations on a sphere

Summary Positive solutions on the unit sphere of second order uniformly elliptic nonvariational equations are found which exhibit behavior sharply differing from that of positive harmonic functions, despite the fact that the coefficients may be uniformly arbitrarily close (at least for n=2) to those of the Laplacian. A solution is found whose boundary integral on expanding concentric subspheres tends to zero and another is found for which this boundary iutegral tends to infinity. This work was supported by the Air Force Office of Scientific Research and the National Academy of Sciences through a Postdoctoral Research Fellowship for 1964–1965 at the University of Genova.     

Hindman's theorem and groups

We prove a theorem which limits the possible uncountable generalizations of Hindman's theorem.     

Generation and reactions of 2-lithio-2-substituted-1,3-benzodithioles; new,convenient acyl carbanion equivalents

The reaction ofBuⁿLi with 2-substituted-1,3-benzodithioles yields anions which react predictably with organic electrophiles to yield products in which the protected carbonyl group is readily unmasked. The anions constitute useful acyl carbanion equivalents.     

Collisional energy transfer in highly vibrationally excited molecules: A very low-pressure pyrolysis study of acetyl chloride

The average downward energy transfer (〈Δ E_down〉) is obtained for highly vibrationally excited acetyl chloride with Ne and C₂H₄ bath gases at ca. 870 K. Data are obtained by the technique of very low-pressure pyrolysis (VLPP). Fitting these data by solution of the appropriate reaction-diffusion integrodifferential master equation yields the gas/gas collisional energy transfer parameters: 〈Δ E_down〉 values are 220 ± 10 cm^?1 (Ne bath gas) and 330 ± 20 cm^?1 (C₂H₄). These energy transfer quantities are much less than those predicted by statistical theories, or those observed for similar sized molecules such as CH₃CH₂Cl. These results are explained by the qualitative predictions of the biased random walk model wherein the fundamental mechanism of energy transfer is the multiple interactions between the bath gas and the individual atoms of the reactant molecule, during the course of the collision event. The charge distribution of acetyl chloride decreases the number of such interactions, thereby reducing the amount of energy transferred per collision.