Attenuation of vehicle noise over short grass

Field experiments to investigate the attenuation of noise from single vehicles over short grass indicate that for a microphone height of 1·2 m and a source/receiver distance <30 m, the rate of attenuation is 4·8 dB(A) per doubling of distance. Some evidence is presented to suggest that for source/receiver distances >30 m the rate of attenuation increases with distance.     

The vibrational transition moment for the ν2 bands of 14ND3 and 15ND3

Intensities were measured at high pressure (200 Torr) for blended K-multiplets in the P and R branches of the s0 → aν₂ and a0 → sν₂ bands of ¹⁴ND₃. Intensities of 55 individual lines at 10 Torr of ¹⁵ND₃ were also measured by deconvolution of the true line shape from the observed vibration-rotation spectrum and the instrumental line shape. From these results we estimate a transition moment of 0.179 ± 0.010 D for both ¹⁴ND₃ and ¹⁵ND₃. These lead to a derivative of the dipole moment, $\text{|}\text{?μ}\text{?Q}{}_2\text{| = 93}\text{cm}{}^{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}\text{sec}{}^{\mathrm{?1}}$.     

Helium emission spectra—I. intermediate pressure studies

The apparent cross sections of the n¹P(n = 3,4,5,6) and n^1,3D(n = 4,5,6,7) levels have been measured as a function of pressure between 5 and 200 mTorr at 1·5KeV electron impact excitation energy. The 4¹S apparent cross section was measured under the same conditions to observe secondary electron effects. A detailed analysis is made on the mechanisms of excitation transfer out of the n¹P levels in terms of radiative and collision processes. Collisional n¹P?nF transfer cross sections are calculated for the n = 4 and n = 5 levels and the results are in agreement with the principle of detailed balance. An analysis of the 6¹P apparent cross section indicates that collision processes other than n¹P?nF become important at n = 6 level in determining collisional transfer out of n¹P. Evaluation of n^1,3D apparent cross sections show that direct collisional gain and loss become more important as n increases.     

Different adsorption behaviors of methane and carbon dioxide in the isotypic nanoporous metal terephthalates MIL-53 and MIL-47

A distinct step in the isotherm occurs during the adsorption of CO2 on MIL-53 at 304 K. Such behavior is neither observed during the adsorption of CH4 on MIL-53 nor during the adsorption on the isostructural MIL-47. This phenomenon seems to be due to a different mechanism than that of previous adsorption steps on MOF samples. It is suggested that a breathing behavior is induced in MIL-53 during CO2 adsorption.     

A lower bound on heavy-lepton production by neutrinos

A lower bound on σ(νA→M…) is given, in terms of the structure functions which can most easily be measured in ν+A→μ+… reactions, for heavy leptons (m) of the type required by renormalizable models of weak interactions.     

The ν4 fundamental of three isotopic species of CF4

The vibration-rotation spectra of the ν₄ fundamental of ¹²CF₄, ¹³CF₄, and ¹⁴CF₄ have been observed with 0.06 cm^?1 resolution. A least squares fit of the data has been used to evaluate the pertinent molecular constants. The band centers are 631.199, 629.285, and 627.348 cm^?1 for ¹²CF₄, ¹³CF₄, and ¹⁴CF₄, respectively. The Coriolis constant ζ₄ has been estimated for the three isotopes.     

B(C6F5)3 adducts of transition metal acyl compounds

The transition metal acyl compounds [Co(L)(CO)3(COMe)] (L = PMe3, PPhMe2, P(4-Me-C6H4)3, PPh3 and P(4-F-C6H4)3), [Mn(CO)5(COMe)] and [Mo(PPh3)(eta(5)-C5H5)(CO)2(COMe)] react with B(C6F5)3 to form the adducts [Co(L)(CO)3(C{OB(C6F5)3}Me)] (L = PMe3, 1, PPhMe2, 2, P(4-Me-C6H4)3, 3, PPh3, 4, P(4-F-C6H4)3), 5, [Mn(CO)5(C{OB(C6F5)3}Me)] 6 and [Mo(eta(5)-C5H5)(PPh3)(CO)2(C{OB(C6F5)3}Me)], 7. Addition of B(C6F5)3 to a cooled solution of [Mo(eta(5)-C5H5)(CO)3(Me)], under an atmosphere of CO gave [Mo(eta(5)-C5H5)(CO)3(C{OB(C6F5)3}Me)] 8. In the presence of adventitious water, the compound [Co{HOB(C6F5)3}2{OP(4-F-C6H4)3}2] 9, was formed from [Co(P(4-F-C6H4)3)(CO)3(C{OB(C6F5)3}Me)]. The compounds 4 and 9 have been structurally characterised. The use of B(C6F5)3 as a catalyst for the CO-induced migratory-insertion reaction in the transition metal alkyl compounds [Co(PPh3)(CO)3(Me)], [Mn(CO)5(Me)], [Mo(eta(5)-C5H5)(CO)3(Me)] and [Fe(eta(5)-C5H5)(CO)2(Me)] has been investigated.     

Generalized Contour Dynamics: A Review

Contour dynamics is a computational technique to solve for the motion of vortices in incompressible inviscid flow. It is a Lagrangian technique in which the motion of contours is followed, and the velocity field moving the contours can be computed as integrals along the contours. Its best-known examples are in two dimensions, for which the vorticity between contours is taken to be constant and the vortices are vortex patches, and in axisymmetric flow for which the vorticity varies linearly with distance from the axis of symmetry. This review discusses generalizations that incorporate additional physics, in particular, buoyancy effects and magnetic fields, that take specific forms inside the vortices and preserve the contour dynamics structure. The extra physics can lead to time-dependent vortex sheets on the boundaries, whose evolution must be computed as part of the problem. The non-Boussinesq case, in which density differences can be important, leads to a coupled system for the evolution of both mean interfacial velocity and vortex sheet strength. Helical geometry is also discussed, in which two quantities are materially conserved and whose evolution governs the flow.