The cyclodimerisation of 3-methyl-2-butenenitrile

3-Methyl-2-butenenitrile (1) cyclodimerised on treatment with lithium diisopropylamide in dimethoxyethane at temperatures between ?78°C and 0°C to 3-amino-4-cyano-1,5,5-trimethyl-1,3-cyclohexadiene (2) the structure of which was established by acid hydrolysis to the known 4-cyano-1,5,5-trimethyl-1-cyclohexene-3-one (3).     

Noise nuisance caused by road traffic in residential areas: Part III

The results of a social survey of 2933 respondents at 53 sites in Greater London have already been reported in Parts I and II of this series of papers, which were concerned largely with prediction of noise nuisance over a wide range of traffic conditions. The present paper is devoted to closer examination of a number of factors which mediate individual responses to noise, notably individual differences in noise sensitivity. This is influenced by differences in age, sex and occupational class, and appears to extend beyond attitudes to noise. The data from the total sample has been submitted to canonical correlation and automatic interaction detector analysis and the results of these procedures confirm the conclusions presented in Parts I and II.     

Conical parametric scattering of a single extraordinary beam in BaTiO3 crystal

In this paper, the parametric scattering of a single extraordinary polarized beam of laser in BaTiO₃ photorefractive crystal has been investigated experimentally and theoretically. The resulting pattern consists of beam fanning, isotropic ring, and anisotropic one. Among all parts of scattering pattern, isotropic ring has not been studied as much as beam fanning and anisotropic ring, and there still are some differences in reports about it. Therefore, the study has mainly focused on this part. In this experimental configuration, isotropic ring is just visible in positive angles although the other parts of parametric scattering pattern can be visible from behind and in front of the crystal. In addition to steady state pattern in forward and backward directions, its transient behavior with the rotation of crystal has been studied. The results of experiments have been analyzed carefully, and their theoretical explanations have been presented based on the standard theory of parametric scattering in photorefractive crystals. It has been shown that this configuration corresponds to the so called parametric B-process scattering.     

Scaffold diversity of exemplified medicinal chemistry space

The scaffold diversity of 7 representative commercial and proprietary compound libraries is explored for the first time using both Murcko frameworks and Scaffold Trees. We show that Level 1 of the Scaffold Tree is useful for the characterization of scaffold diversity in compound libraries and offers advantages over the use of Murcko frameworks. This analysis also demonstrates that the majority of compounds in the libraries we analyzed contain only a small number of well represented scaffolds and that a high percentage of singleton scaffolds represent the remaining compounds. We use Tree Maps to clearly visualize the scaffold space of representative compound libraries, for example, to display highly populated scaffolds and clusters of structurally similar scaffolds. This study further highlights the need for diversification of compound libraries used in hit discovery by focusing library enrichment on the synthesis of compounds with novel or underrepresented scaffolds.     

Noise from neighbours and the sound insulation of party walls in houses

Nine-hundred-and-seventeen residents in a sample of attached houses constructed since 1970 were interviewed in the course of a national survey dealing with nuisance occasioned by noise from neighbours. The airborne sound insulation of the party walls, measured prior to occupation, ranged from zero to 120 dB AAD. Two-thirds of the respondents heard noise from their neighbours and even at performance levels meeting or exceeding the minimum requirements of the Building Regulations nearly 50% did so. Of the total sample, some 18% were seriously bothered by neighbours' noise. Highly significant relationships were found between physical performance rated in dB AAD (Aggregate Adverse Deviation) and a variety of subjective responses. These include reports of hearing neighbours' noise, of being bothered by it, hearing neighbours' conversation, and, in particular, the direct rating of sound insulation quality by respondents, which last appears to provide the most reliable and consistent indication of the likelihood of experiencing nuisance from neighbours' noise. These results provide, for the first time, empirical validation of the U.K. performance rating procedure. In addition, the survey findings emphasize the importance of impact noises, not included in the standardized performance measurements, but which contribute substantially to nuisance, particularly between houses where airborne sound insulation is comparatively good. Other findings indicate that occupants were very satisfied with their general environment and only slightly less so with their homes. Poor sound insulation was a prominent criticism of the dwellings, being ranked third among spontaneous adverse comments and first in a ranking of nine commonly encountered building defects. These results indicate the importance of sound insulation to occupants of recently built houses, placing this aspect of design and construction within a wider context. The overall results of the survey provide a practical guide to estimating the consequences, in terms of occupants' attitudes to noise from neighbours, of raising or lowering standards of sound insulation performance between houses.     

Evidence for a transition in deformation mechanism in nanocrystalline pure titanium processed by high-pressure torsion

Nanocrystalline titanium with an average grain size of about 60–70 nm was prepared by high-pressure torsion. The results of hardness and structural evolutions indicate that a strain-induced hardening–softening–hardening–softening behaviour occurs. For coarse-grained titanium, 〈a〉-type dislocation multiplication, twinning and a high pressure-induced α-to-ω phase transformation play major roles to accommodate deformation, leading to a significant strain hardening. As deformation proceeds, dynamic recrystallisation leads to a decrease in dislocation density, especially for 〈a〉-type dislocations, leading to a slight strain softening. The 〈c〉-component dislocation multiplication dominates the deformation when the grain size decreases to 100 nm and 〈c〉-component dislocation multiplication, grain refinement and the α-to-ω phase transformation contribute to the second strain hardening. The following strain softening is attributed to dynamic recovery.