Mechanical and structural studies of low density polyethylene

This paper is one of a series concerned with the complete characterisation of the creep behaviour of oriented polymers, the correlation of creep behaviour with other mechanical properties and the interpretation of such data in the light of present structural knowledge. Sheets of oriented low-density polyethylene were prepared from initially isotropic sheets by cold-drawing, cold-drawing followed by heat-treatment at 55° C, drawing at a temperature of 55° C and hot-drawing at temperatures in the range 90 to 100° C. At each draw ratio, specimens were cut at angles of 0°, 45° and 90° to the draw direction. For each specimen, the variation of longitudinal and lateral strain with time, during uniaxial tensile creep at 20° C, was measured simultaneously by direct extensometer methods, for a wide range of applied stresses. All the materials exhibited complex anisotropic non-linear viscoelastic behaviour. The methods of presenting such data are discussed and the results are presented in some detail. Many similarities in the creep behaviour of the cold- and hot-drawn materials are noted. However, marked differences are apparent in the non-linearity and creep rate of the 45° specimens from these two materials at high draw ratio. These, and other effects found at high draw ratio, are discussed with reference to the structural studies reported in part 1. At low draw ratio, it is shown that the anomalous behaviour of the modulus in the draw direction, reported previously for cold-drawn material, may also be found in the hot-drawn material, although at a different creep time. On the basis of obvious differences in wide-angle X-ray patterns other workers had previously predicted that the anomalous mechanical behaviour of cold-drawn LDPE was probably unique. The anomalous behaviour of the hot-drawn material is also explained in terms of the structures discussed in part 1.     

Hypnotic blindness and the relevance of cognitive style.

Real, hypnotized and simulating, unhypnotized subjects were instructed to use either a constructive or a concentrative cognitive style when attempting to respond to a suggestion for hypnotic blindness; also, some subjects were administered the suggestion without any instructions about cognitive style. More reals who received the constructive rather than the concentrative instructions reported complete blindness; a similar number of simulators who received the different instructions reported complete blindness. Moreover, reals who received the constructive instructions reported a more rapidly developed belief in their blindness. The findings are discussed in terms of the relevance of cognitive style to subjects' reports of hypnotic blindness, and the possibility is considered that both reports of and belief in hypnotic blindness are determined in part by cognitive style. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reports of real and false memories: The relevance of hypnosis, hypnotizability, and context of memory test.

30 high- and 30 low-hypnotizable Ss saw slides of a purse snatching and then imagined seeing the slides in hypnosis or waking conditions. The experimenter suggested the offender had a moustache (true), wore a scarf (false), and picked up flowers (false). Memory was tested by the experimenter after the suggestion, by another experimenter during an inquiry session, and again by the 2nd experimenter after the experimenter appeared to end the session. Hypnotizability, but not hypnosis, was associated with false memory reports; more high- than low-hypnotizable Ss reported false memories. The context of testing influenced true and false memory reports; fewer reports occurred in an informal rather than a formal test context. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Trance logic in hypnosis and imagination.

Investigated, in 2 experiments, trance logic, or the tolerance of logical incongruity, in age regression and hallucination. Exp 1 tested 21 hypnotizable and 19 unhypnotizable Ss in an application of the real-simulating model of hypnosis. Exp 2 tested 26 high and 19 low imagery ability Ss in an adaptation of the model to the imagination context. Ss' experiences were investigated through the experimenal analysis technique. More real than simulating Ss displayed trance logic during age regression, but they did not differ on the major measures of trance logic during hallucination. This pattern of responding occurred in both the hypnosis and the imagination contexts. Ss' comments suggested that completeness of and belief in age regression or hallucination may play some role in trance logic. The importance of understanding trance logic from the S's point of view is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Experiential analysis of hypnosis: Some new observations on hypnotic phenomena.

10 Ss who were assessed on the Harvard Group Scale of Hypnotic Susceptibility as being highly susceptible to hypnosis were shown videotaped versions of their previous hypnotic sessions in the presence of an independent inquirer who attempted to foster Ss' personal comments on their own experiences. A special method of inquiry called the "experiential analysis technique" was constructed to study Ss' recall, which was examined for fantasy involvement, rapport, and individual modes of cognition. Data from the application of the method indicate the idiosyncratic ways in which Ss interpret routine suggestions, the degree to which they become personally involved with the hypnotist, and 3 distinct modes of cognizing, which were labeled "concentrative-cooperative," "cognitive-independent," and "cognitive-constructive." (9 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The impact of videotape playback of hypnotic events on posthypnotic amnesia.

Examined the breakdown of amnesia by showing 48 hypnotic and nonhypnotic undergraduates (Harvard Group Scale of Hypnotic Susceptibility) a videotape of the hypnotic events they had experienced. The extent of the amnesia for these events was defined precisely, and simulating procedures were employed to analyze the cues in the overall test situation. Videotape display of the hypnotic events was presented via the Experiential Analysis Technique and served to optimize conditions for breakdown. Some hypnotic Ss' amnesia could not be broken down even though they were exposed via videotape playback to the events to be recalled and when suggestions for the period of amnesia were quite explicit. Simulators showed breaching of amnesia but attributed their recall to the videotape rather than to the hypnotic session. Hypnotic Ss were distinctive in their inability to recall experiential aspects of their performance even though they could recall behavioral aspects. The data are discussed in relation to the hypothesis that dissociative cognitive mechanisms underlie posthypnotic amnesia. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual conversion disorder: A case analysis of the influence of visual information.

We examined the influence of visual information on a decision task that was administered to an individual with monocular visual conversion disorder. Findings indicated that his performance was influenced by the visual information and by motivation instructions. The findings are discussed in terms of a model of hysterical blindness that recognizes the interplay of cognitive and motivational processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)