The mechanical properties of anisotropic polymers

The work in this period can conveniently be split into two parts which are reported separately. Part I is concerned with experimental work on the stress-strain properties of anisotropic polythene. This work was initiated as a first step in the collection of data on anisotropic polymers. The results provide a very useful, general idea of the properties of a polymer, together with their variation with anisotropy. The experience gained during this work has also been of use when considering apparatus design details for creep measurements. Part II is concerned with the design of an apparatus for creep studies. The design considerations are discussed in Section 1; an outline of several design proposals being given in Section 2. The design project was started in the latter part of the period under review and therefore no comprehensive tests have yet been performed

The mechanical properties of anisotropic polymers: progress report no. 7

Part I General Developments The major part of the period under review was devoted to a study of the tensile creep properties of isotropic and uniaxially oriented Perspex sheets (standard grade) using the three heavy-duty creep rigs mentioned in the previous Progress Report (No. 6. September, 1968). Measurements of lateral contraction were made simultaneously with the tensile strain measurements during most of the creep tests. The creep rupture behaviour and optical anisotropy of the oriented sheets were also studied in an attempt to present a more complete picture of the behaviour of the material. Some of the early results of this work have already been published and copies sent to the Ministry. (Darlington and Saunders; 1969). Details of the complete work will be found in part II of this report. The two types of contraction extensometer described in Progress Report No. 5 were used during the Perspex studies and reasonable agreement was obtained between the results. The techniques required with the contraction devices were considerably improved during the period under review and the absolute validity of the contraction measurements is now more certain. Some comments on the general performance of the apparatus are given in section 2.8.4

The mechanical properties of anisotropic polymers: Progress report no. 6

Part 1 General Developments The basic development work on the tensile creep apparatus was completed by March, 1968. A description of the latest 'heavy-duty' creep rig and two types of contraction extensometer, together with the relevant creep trials, was given in Progress Report No. 5. Since then two further 'heavy-duty' creep rigs have been assembled and tested and are now ready for use with rigid plastics. In addition, further trials of the double transducer contraction extensometer described in Report No. 5 have been carried out. These trials are described in part 2 of this report The trials were considered reasonably satisfactory and each of the three heavy-duty creep rigs has now been fitted with a device of this type in addition to the normal tensile extensometer. The polythene creep rig described in Progress Report No. 3 has been working satisfactorily for over a year and no further modifications have been made in the period under review. At the conclusion of the above-mentioned trials it was considered that the creep apparatus was unlikely to require any further major changes. A detailed report of all the apparatus has therefore been prepared with the intention of submitting it for publication to the Journal of Scientific Instruments. It is at present being examined at the Ministry of Technology. (CoA Memo. No. 158)

The mechanical properties of anisotropic polymers: progress report no. 5

A report of work carried out during the period 1st October, 1967, to 31st March, 1963

Creep studies on oriented thermoplastics

The enhancement of many of the mechanical properties of thermoplastics which may be achieved by orienting the molecules has been known for some time. It has been exploited in the production of textile fibres end oriented films. Molecular orientation also occurs during processes such as extrusion, moulding or forming. Here, unless carefully controlled, it may well cause a deterioration in the properties of the finished article. In view of this a systematic study on the anisotropy of the mechanical properties of thermoplastics, resulting from molecular orientation, is being carried out at present in these laboratories … [cont.]

An apparatus for the measurement of tensile creep and contraction ratios in small non-rigid specimens

An apparatus is described for precise measurement of creep properties in specimens with gauge lengths down to 1.2 cm. An extensometer has been developed which is supported independently of the specimen and exerts a load on the specimen of less than 5 grams. It can thus be used with small non-rigid specimens. The extensometer will detect strains down to 2 x 10-6. The stability is excellent. An adaptation of the system which allows simultaneous measurement of tensile strain and lateral strain during creep is also described. The apparatus was designed for the measurement of anisotropy of creep properties in oriented thermoplastics and reference to such measurements is given. It is however entirely suitable for general application to small specimens

A reappraisal of the rank-and-file versus bureaucracy debate

This paper celebrates some of the considerable strengths of Hyman’s 1970s/early 1980s analysis of unions in general and bureaucracy specifically, and reapplies it to more recent developments within British unions, while at the same time providing a critique of Hyman’s refutation of the ‘rank-and-file’ versus ‘union bureaucracy’ conception of intra-union relations. It argues that the wider set of implications Hyman drew from the accentuated pressures towards the bureaucratisation of workplace unionism that he identified ‘bent the stick’ too far in the opposite direction. In attempting to defend and refine the classical revolutionary Marxist analytical framework, the paper maintains that the conflict of interest that exists between full-time officials and rank-and-file members is a meaningful generalisation of a real contradiction within trade unionism, notwithstanding the variations and complexities involved. It examines the nature and social dynamics of full-time union officialdom, shop stewards and workplace unionism, and the relationship between the two. In the process, the limits and potential of both Hyman’s ‘earlier’ and ‘later’ writings are highlighted and some broader generalisations are drawn with relevance to current dilemmas for trade unionism

Dependence receptor involvement in subtilisin-induced long-term depression and in long-term potentiation

The serine protease subtilisin induces a form of long-term depression (LTD) which is accompanied by a reduced expression of the axo-dendritic guidance molecule Unco-ordinated-5C (Unc-5C). One objective of the present work was to determine whether a loss of Unc-5C function contributed to subtilisin-induced LTD by using Unc-5C antibodies in combination with the pore-forming agents Triton X-100 (0.005%) or streptolysin O in rat hippocampal slices. In addition we have assessed the effect of subtilisin on the related dependence receptor Deleted in Colorectal Cancer (DCC) and used antibodies to this protein for functional studies. Field excitatory postsynaptic potentials (fEPSPs) were analysed in rat hippocampal slices and protein extracts were used for Western blotting. Subtilisin produced a greater loss of DCC than of Unc-5C, but the antibodies had no effect on resting excitability or fEPSPs and did not modify subtilisin-induced LTD. However, antibodies to DCC but not Unc-5C did reduce the amplitude of theta-burst long-term potentiation (LTP). In addition, two inhibitors of endocytosis – dynasore and tat-gluR2(3Y) – were tested and, although the former compound had no effect on neurophysiological responses, tat-gluR2(3Y) did reduce the amplitude of subtilisin-induced LTD without affecting the expression of DCC or Unc-5C but with some loss of PostSynaptic Density Protein-95. The results support the view that the dependence receptor DCC may be involved in LTP and suggest that the endocytotic removal of a membrane protein or proteins may contribute to subtilisin-induced LTD, although it appears that neither Unc-5C nor DCC are involved in this process. (220)

The state of workplace union reps organisation in Britain today

This article provides a brief evaluation of the state of workplace union reps’ organization in Britain as we approach the second decade of the 2000s. It documents the severe weakening of workplace union organization over the last 25 years, which is reflected in the declining number of reps, reduced bargaining power and the problem of bureaucratization. But it also provides evidence of the continuing resilience, and even combativity in certain areas of employment, of workplace union reps organization, and considers the future potential for a revival of fortunes