Temperature dependence of the stacking fault energy of glide set-dissociated dislocations in Si

Recently, it was found that the dissociation distance of glide set dislocations introduced in Si just below the melting temperature by laser shock peening (LSP) is unusually wide (Iwata et al. J. Jpn Inst. Met. Materi.,79(2015),308–314). In order to distinguish whether or not this is to be attributed to uncorrelated motions of leading and trailing Shockley partials or the intrinsic temperature dependence of the stacking fault energy (SFE), dislocations introduced by LSP were annealed at 1350 °C, which should be high enough for the uncorrelated partials to assume the equilibrium correlated configuration. It was found that this unusual widening of a dissociated dislocation introduced by LSP is attributed to uncorrelated motions of Shockley partials. Following this conclusion, the temperature dependence of the intrinsic SFE of Si was determined on correlated dissociated dislocations up to near the melting temperature. The intrinsic SFE of Si shows only negligibly small temperature dependence from 400 °C up to near the melting temperature.     

The arms of the chimeras

This article seeks to compare the approach developed in 1974 by Michel de M'Uzan to the concept of the ‘chimera’ with Thomas Ogden's ( 1995 , 2005 ) reflections on ‘the analytic third’. This comparison shows that in spite of the different theoretical approaches, unconscious to unconscious communication – a subject of interest in contemporary psychoanalytic research – makes it possible to grasp the intersubjective data deployed in the field of the session. After reviewing M. de M'Uzan's conception of the ‘chimera’ – a product of the unconsciouses of patient and analyst alike, and which emerges during a process of depersonalization in the analyst – the author proposes her hypothesis of the chimera as a particular intersubjective third whose creation, in a hallucinatory state, makes it possible to gain access to the bodily and emotional basis of the trauma. The author describes the chimera as a mental ‘squiggle’ between the two members of the pair which finds expression in different forms; further, she considers that the chimera that seizes the analyst is underpinned by the unconscious affinities of traumatic zones in both protagonists, which permit the grounding, configuration and sharing of the territories of suffering, as apprehended in this paper.     

ASSESSING THE ROLE OF EFFORT REDUCTION IN THE REINFORCING EFFICACY OF TIMEOUT FROM AVOIDANCE

Rats responded on concurrent schedules of shock‐postponement or deletion (avoidance) and timeout from avoidance. In Experiment 1, 3 rats' responses on one lever postponed shocks for 20 s and responses on a second lever produced a 1‐min timeout according to a variable‐interval 45‐s schedule. Across conditions, a warning signal (white noise) was presented 19.5 s, 16 s, 12 s, 8 s, or 4 s before an impending shock. Raising the duration of the warning signal increased both avoidance and timeout response rates. Timeout responding, although positively correlated with avoidance responding, was not correlated with the prevailing shock rate. In Experiment 2, 3 rats' responses on one lever deleted scheduled shocks according to a variable‐cycle 30‐s schedule and responses on a second lever produced a 2‐min timeout as described above. After this baseline condition, the avoidance lever was removed and noncontingent shocks were delivered at intervals yoked to the receipt of shocks in the baseline sessions. Timeout responding decreased when the avoidance lever was removed, even though the shock‐frequency reduction afforded by the timeout remained constant. These results suggest that a key factor in the reinforcing efficacy of timeout is suspension of the requirement to work to avoid shock, rather than the reduction in shock frequency associated with timeout.     

Withdrawal,matching, withdrawal-matching,and variable-matching strategies in reducing attack-instigated aggression

Several studies have investigated strategies that a participant in dyadic aggression may use to reduce the aggression of the other participant. In one set of these studies the subject is instigated to aggression by an opponent who sets maximum shocks for the subject to receive during the first block of six trials. Following attack-instigation, opponents shift to withdrawal and matching strategies for 18 trials. The withdrawal strategy is an abrupt shift to the lowest levels of shock possible. The matching strategy is the exact matching by an opponent of the shock set by the subject on the previous trial. With these procedures the withdrawal strategy has been the most effective method to reduce aggression. These results led to the suggestion that the effectiveness of the withdrawal strategy may be due to immediate, unambiguous communication by the opponent of his willingness to reduce attack. This hypothesis was tested in the present study by creating a matching condition modified to include immediate, unambiguous communication of willingness to reduce attack. In this withdrawal-matching condition the opponent followed attack with two trials of the lowest levels of shock before shifting to a matching strategy. Although the withdrawal-matching strategy did not lead to shock settings that were significantly lower than the matching strategy, there was evidence that subjects interacting with withdrawal-matching opponents did reduce their shock settings from block 1 to block 4 more rapidly than subjects interacting with matching opponents. A variable matching strategy was also used to provide a more realistic analogy of matching in the mundane world. While subjects with variable-matching opponents also did not set shock levels during blocks 2, 3, and 4 that were significantly lower than the matching strategy, there was evidence that subjects in this condition reduced their shock levels more rapidly than subjects with matching opponents. Although the effects were not as strong as expected, the results do provide some support for the interpretation that the effectiveness of the withdrawal strategy may be due to unambiguous communication of willingness by the opponent to reduce his or her aggression. The effectiveness of the variable-matching strategy was attributed to interrupting the tendency of the subject and his or her opponent to match each other's responses. Consistent with earlier attack-instigated aggression studies, the withdrawal strategy in the present study led to a rapid reduction in aggression.     

Within-session changes in responding during several simple schedules

Pigeons' key pecking was reinforced by food delivered by several fixed-interval, variable-ratio, and differential-reinforcement-of-low-rate schedules. Rate of responding, number of responses per reinforcer, length of postreinforcement pause, running response rate, and the time required to collect an available reinforcer changed systematically within sessions when the schedules provided high rates of reinforcement, but usually not when they provided low rates. These results suggest that the factors that produce within-session changes in responding are generally similar for different schedules of reinforcement. However, a separate factor may also contribute during variable-ratio schedules. The results question explanations for within-session changes that are related solely to the passage of time, to responding, and to one interpretation of attention. They support the idea that one or more factors related to reinforcement play a role.     

Temporal control in fixed-interval schedules

The peak procedure was used to study temporal control in pigeons exposed to seven fixed-interval schedules ranging from 7.5 to 480 s. The focus was on behavior in individual intervals. Quantitative properties of temporal control depended on whether the aspect of behavior considered was initial pause duration, the point of maximum acceleration in responding, the point of maximum deceleration, the point at which responding stopped, or several different statistical derivations of a point of maximum responding. Each aspect produced different conclusions about the nature of temporal control, and none conformed to what was known previously about the way ongoing responding was controlled by time under conditions of differential reinforcement. Existing theory does not explain why Weber's law so rarely fit the results or why each type of behavior seemed unique. These data fit with others suggesting that principles of temporal control may depend on the role played by the particular aspect of behavior in particular situations.     

Preference for signaled over unsignaled shock schedules: Ruling out asymmetry and response fixation as factors

Experiment 1 tested whether a “symmetrical” choice procedure yields results different from those previously reported using the “unidirectional” standard changeover procedure (e.g., Badia & Culbertson, 1972). Subjects could change at any time from unsignaled to signaled shock by pressing a lever and from signaled to unsignaled shock by pressing a second lever. Results were identical to those of the standard procedure and showed that the standard procedure is fully adequate. Experiment 2 tested whether choice of high density signaled shock over low-density unsignaled shock (Badia, Coker, & Harsh, 1973) resulted from initial training with equal-density schedules. Subjects were trained and tested with signaled shock twice as dense as unsignaled shock. Three of four subjects strongly preferred the signaled condition, thus ruling out carry-over and “response fixation” as alternative explanations.     

Choice between fixed-interval schedules: Graded versus step-like choice functions

Pigeons chose between two fixed-interval schedules of food reinforcement. A single peck on one of two lighted keys started the fixed-interval schedule correlated with that key. The schedule had to be completed before the next choice opportunity. The durations of the fixed intervals were varied over conditions from 15 s to 40 s. To maximize the rate of reinforcement, the pigeons had to choose exclusively the shorter of the two schedules. Nevertheless, choice was not all-or-none. Instead, relative choice, and the rates of producing the fixed intervals, varied in a graded fashion with the disparity between the two schedules. Choice ratios under this procedure (single response to choose) were highly sensitive to the ratios of the fixed-interval schedules.     

Effects of reinforcer duration on responding in two-link chained interval schedules

Each of five pigeons was exposed to two or more durations of access to mixed grains on two-link, chained, interval schedules in which both links were identical fixed-interval or variable-interval schedules. Response rates were an increasing function of reinforcer duration for both initial and terminal links. For both types of interval schedules, initial-link response rates were more sensitive to reinforcer duration than were terminal-link response rates. The present results, together with prior ones, suggest that chaining and choice procedures are each sufficient for demonstrating substantial sensitivity of responding to changes in reinforcer duration.     

Intractable properties of responding under a fixed-interval schedule

The behavior engendered by the fixed-interval schedule is characterized by its variability within and across intervals. The present experiment was designed to assess further the magnitude of interval-to-interval dynamics and to explore conditions which might enhance control by response number for subsequent output. Pigeons were exposed to three experimental manipulations after responding had stabilized under a fixed-interval five-minute schedule. First, a discrete five-stimulus counter was added so that the key color changed after a fixed number of responses. Then additional grain presentations were made at the end of the interval so that high response output was differentially reinforced in the presence of the counter stimuli. Finally, the counter stimuli were presented as an irregular clock (i.e., independently of responding), but the durations were yoked to performance under the counter condition. The data show that response number can exert influence from one interval to the next, but this source of control is weak and not influenced by the experimental manipulations. Results from the clock arrangement indicate that behavior is controlled largely by the stimulus conditions prevailing at the time of interval onset.