Sound insulation of domestic roofing systems: Part 1

The three parts of this paper are to be published in three issues of Applied Acoustics. The present part discusses the experimental facilities of the measuring laboratory and gives details of tests conducted on ceiling specimens. In Part 2 the work on various types of roof component will be presented. In Part 3 will follow the results of tests carried out on the roof and ceiling components combined. It will also consider the ability of the roofing system to provide sound insulation, as a component of the whole building envelope, from typical external noise spectra. The availability of sound insulation values obtained by laboratory measurements does provide the building industry with guidance in building design, even though values for actual buildings may vary considerably from laboratory-measured values.     

Polymers on disordered hierarchical lattices: A nonlinear combination of random variables

The problem of directed polymers on disordered hierarchical and hypercubic lattices is considered. For the hierarchical lattices the problem can be reduced to the study of the stable laws for combining random variables in a nonlinear way. We present the results of numerical simulations of two hierarchical lattices, finding evidence of a phase transition in one case. For a limiting case we extend the perturbation theory developed by Derrida and Griffiths to nonzero temperature and to higher order and use this approach to calculate thermal and geometrical properties (overlaps) of the model. In this limit we obtain an interpolation formula, allowing one to obtain the noninteger moments of the partition function from the integer moments. We obtain bounds for the transition temperature for hierarchical and hypercubic lattices, and some similarities between the problem on the two different types of lattice are discussed.     

Sound insulation of domestic roofing systems—Part 2

In the first part of this series of papers,² tests carried out on the ceiling component of a roofing system were described. In this second part, the experiments conducted on various types of roof component are outlined. The effect of coupling the ceiling and roof components to form the complete roofing system will be the central theme of the third and final part.     

The thermogravimetry of sulfanilamide and related sulfa drugs

TG curves are shown for 12 sulfa drugs up to a temperature of 800°C. With some minor refinements, the curves can be used for a qualitative identification of the drugs. Currently, there is not a good method for rapidly identifying this type of drug qualitatively. Sample sizes were about 2 mg, and a 2.2-mg sample gave a full scale deflection with the instrument used. Some of the evolved gases were also analyzed with SO₂ found to be the major component of pyrolysis.     

Phosphorus-based combinatorial libraries: Use of amino acid derivatives as synthons

Summary Phosphorus has been used as a scaffold to prepare combinatorial libraries of phosphoramidates in which one of the diversity elements resulted from derivatives of amino acids. A small library was prepared for analytical and characterization purposes, followed by a larger library of approximately 8800 compounds. Libraries were assembled on solid supports using the conventional pool-and-divide method, followed by cleavage from the supports at the end of the synthesis. Mass spectrometry was used to confirm that library synthesis had been successful. Individual compounds were also prepared to study the stability of compounds of this type.     

The “invariance principle” in approximate molecular orbital theories

The widely used invariance “principle” of approximate MO theories is shown to be physically unreasonable and formally unnecessary. The use of ZDO-type schemes in an internally-defined orbital basis is proposed to replace this restrictive principle.     

Some comments on the counterpoise correction for the basis set superposition error at the correlated level

The use of the counterpoise method for the mitigation of basis set superposition error at the correlated level is discussed. Evidence is presented to show that the ghost basis plays a dual role in the counterpoise method: The orbitals of the system are improved by the ghost basis but at the expense of a nonphysical increase in the dimension of the virtual space. This second factor has no effect on application of the counterpoise method at the SCF level but it makes the use of the counterpoise method at the correlated level much less straightforward. © 1993 John Wiley & Sons, Inc.