Formation of decagonal and approximant phases in the Al-Ni-Ru system

Al-Ni-Ru alloys with a wide composition range have been synthesized and examined by X-ray and electron diffraction experiments. In this system, two types of decagonal (d) phases are formed, namely basic-type and superlattice-type d phases. Annealing experiments have shown that the basic-type d phase is stable at high temperatures and that its single-phase region is located in a small composition range around Al 75 Ni 15 Ru 10 . On the other hand, the superlattice-type d phase is metastable and has been found to form only in the samples before annealing. Besides the d phases, a high-order crystal approximant phase with lattice parameters a = 99.5 Å and b = 84.6 Å has been found. The structural relation between the approximant phase and the d phase is discussed in terms of a phason tensor.     

Thermal expansion of icosahedral Al-Pd-Mn and decagonal Al-Cu-Co quasicrystals

Thermal expansion measurements have been performed by X-ray diffractometry on icosahedral Al-Pd-Mn (i-(Al-Pd-Mn)) in the temperature range between 10 and 700K and on decagonal Al-Cu-Co (d-(Al-Cu-Co)) in the range between 100 and 750K. The linear thermal expansion coefficient alpha(T) of i-(Al-Pd-Mn) is about half of that for the pure aluminium phase at room temperature and does not show a negative thermal expansion at low temperatures. The degree of anisotropy in the thermal expansion of d-(Al-Cu-Co) is small; the ratio of the average alpha between the tenfold periodic direction and a quasiperiodic direction perpendicular to it is 0:93 +/- 0:05. The Gruneisen parameter gamma(T) has been evaluated from the measured alpha(T). gamma for d-(Al-CuCo) is almost isotropic, similar to alpha. The gamma values for the two phases lie in the range between 1.5 and 1.8, which are comparable with those for conventional metallic crystals. They are almost constant over the temperature range studied.     

Topological instability and electronegativity effects on the glass-forming ability of metallic alloys

The glass-forming ability (GFA) of metallic alloys is associated with a topological instability criterion combined with a new parameter based on the average electronegativity difference of an element and its surrounding neighbours. In this model, we assume that during solidification the glassy phase competes directly with the supersaturated solid solution having the lowest topological instability factor for a given composition. This criterion is combined with the average electronegativity difference among the elements in the alloy, which reflects the strength of the liquid. The GFA is successfully correlated with this combined criterion in several binary glass-forming systems.     

Some effects of epistemological structure on memory

Graph theoretical models of the epistemological structure imposed upon a set of mathematical concepts by Ss’ definitions of them were constructed. Three graphical characteristics of the models were manipulated in a series of experiments to assess their effects on recall. Experiment I showed that recall and confidence of recall were highest for concept pairs connected by short paths, next highest for those connected by long paths, and lowest for those not connected by paths. Experiment II replicated the result of Experiment I that recall and confidence of recall were greater for concept pairs connected by paths than for those not connected by paths and revealed no differences in recall between concept pairs connected by many paths and those connected by a few paths. Experiment III found no differences in recall of abstract and concrete concepts, The abstractness of a concept was quantified by the mean path length from the concept to primitive (undefined) concepts. The approach of building a model of each S’s epistemological structure was supported by the finding that, while a given. S’s definitions of the concepts remained relatively constant, there were considerable differences in definitions of the concepts between Ss.     

Key distance effects on perceived harmonic structure in music

Two experiments provide convergent evidence for the hypothesis that listeners interpret chords in terms of their harmonic functions in a system of interrelated keys. The perceived associations between chords undergo significant changes depending on the broader tonal framework in which they are embedded. Three independent context effects are identified, and their magnitude is found to be a systematic function of the distance between the context key and the key lot keys) of which the chords are members. In the first experiment, listeners rate how musically related one chord is to a second chord; the chords are those that function within two maximally distant major keys (C major and F# major). All possible chord pairs from this set are presented in each of three context keys: G major which is close to C major and distant from F# major), A major (which is moderately distant from both C major and F# major), and B major (which is close to F# major and distant from C major). The second experiment measures recognition memory for the same chords embedded in tonal sequences in C, G, A, or B major keys, or random sequences. In the two experiments, the distance between the context key and the key of the chords on the circle-of-fifths affects: (1) the probability that a repeated chord is correctly recognized, (2) the strength of association between chords from the same key measured in terms of both confusion errors and direct relatedness judgments, and (3) asymmetries in confusion errors and relatedness judgments when the chords are in different keys. Perceived harmonic relations are thus found to be strongly context dependent, but the context effects are lawful functions of interkey distance. We conclude that listeners possess a highly articulated system of knowledge about the harmonic functions of chords in musical keys and an appreciation of musical structure at the level of abstract tonal centers.     

The effects of stimulus structure and familiarity on same-different comparison

It was hypothesized that performance in the same-different comparison task is based on two modes of processing: (1) structural processes that organize the detailed parts of a stimulus into a well-formed whole, and (2)analytic processes that decompose the stimulus into features. This hypothesis was supported, but with the unexpected finding of individual differences in the mode of processing underlying “same” responses. Those Ss in the “same” condition whose reaction times were faster for symmetrical than for asymmetrical patterns supported the hypothesis for structural processes. The remaining Ss in the “same” condition, as well as all the Ss in the “different” condition, were unaffected by symmetry. These Ss supported the hypothesis for analytic processes. Although familiarity effects were obtained for both structural and analytic Ss, the rotation of the familiar patterns into an unfamiliar orientation virtually eliminated familiarity effects for the structural Ss, but left them intact for analytic Ss.     

The effects of relational structure on analogical learning

Relational structure is important for various cognitive tasks, such as analogical transfer, but its role in learning of new relational concepts is poorly understood. This article reports two experiments testing people’s ability to learn new relational categories as a function of their relational structure. In Experiment 1, each stimulus consisted of 4 objects varying on 2 dimensions. Each category was defined by two binary relations between pairs of objects. The manner in which the relations were linked (i.e., by operating on shared objects) varied between subjects, producing 3 logically different conditions. In Experiment 2, each stimulus consisted of 4 objects varying on 3 dimensions. Categories were defined by three binary relations, leading to six logically different conditions. Various learning models were compared to the behavioral data, based on the theory of schema refinement. The results highlight several shortcomings of schema refinement as a model of relational learning: (1) it can make unreasonable demands on working memory, (2) it does not allow schemas to grow in complexity, and (3) it incorrectly predicts learning is insensitive to relational structure. We propose schema elaboration as an additional mechanism that provides a more complete account, and we relate this mechanism to previous proposals regarding interactions between analogy and representation construction. The current findings may advance understanding of the cognitive mechanisms involved in learning and representing relational concepts.     

The effects of preschool on educationally advantaged children: First phases of a longitudinal study

This study is concerned with the preschool and kindergarten phases of a ten-year longitudinal research project designed to investigate the immediate and long-term effects of preschool on educationally advantaged children. Preschool data dealing with IQ, social competency, and school readiness, as well as physical abilities and self-concept were collected on two waves of subjects. Wave I(N = 129) consisted of 87 experimental and 42 control subjects, and in Wave II(N = 85) there were 54 experimental and 31 control subjects. Follow-up data on school readiness and social competency data were obtained from Wave I subjects in kindergarten. Analysis of data indicated that social competency, was enhanced through preschool participation and although there were no significant group differences in kindergarten test results, substantial social competency gains were observed for both groups. Findings will have greater meaning as the longitudinal study continues.     

Social structure and the effects of conformity

Conformity is an often criticized feature of human belief formation. Although generally regarded as a negative influence on reliability, it has not been widely studied. This paper attempts to determine the epistemic effects of conformity by analyzing a mathematical model of this behavior. In addition to investigating the effect of conformity on the reliability of individuals and groups, this paper attempts to determine the optimal structure for conformity. That is, supposing that conformity is inevitable, what is the best way for conformity effects to occur? The paper finds that in some contexts conformity effects are reliability inducing and, more surprisingly even when it is counterproductive, not all methods for reducing its effect are helpful. These conclusions contribute to a larger discussion in social epistemology regarding the effect of social behavior on individual reliability.     

Some effects of time-pressure on vertical structure and decision-making accuracy in small groups

Eighteen four-person groups were given a decision-making task to perform in one of three time-pressure conditions—3 min, 5 min, and 15 min (high, moderate, and low time-pressure, respectively). Observers recorded the number of times each group member communicated to other group members and to the group as a whole. As predicted, there were significant and strong effects of time-pressure on vertical structuring within the groups. Specifically, groups in the high time-pressure condition shared air-time less equally than did groups in the low time-pressure condition. Furthermore, group members in the high time-pressure condition reported more salient leadership than did group members in the low time-pressure condition. Finally, consistent with contingency theory, there was some evidence to indicate that unequal sharing of air-time was associated with low intermember attraction in the low time-pressure groups, but there was no such relationship for the high time-pressure groups. The decision-accuracy data showed some significant quadratic trends, but no effects of time-pressure on indices of efficiency. The vertical structuring findings were interpreted in terms of social expectations about how to behave under time-pressure, whereas the decision-accuracy findings were interpreted within a performance-arousal perspective.     

The effects of classification structure on organized free recall in children

A sorting presentation procedure was used to study the effects of three classification schemes (self-generated, thematic, or taxonomic) on the organized free recall of second and fifth graders. Recall and clustering were significantly higher for subjects who used self-generated organizations than for subjects given the experimenter-prescribed taxonomic classification. The results indicated that memory performance benefitted when the organization of stimulus materials was consonant with children's personal classification structures.     

Elaboration structure and list length effects on verbal elaboration phenomena

The effects of elaboration structure (Sentence, Semantic paragraph, Syntactic paragraph) and list length (8, 12, 16 pairs) on paired-associate learning were investigated in a 3 × 3 factorial design. Seventy-five educable retardates were tested on acquisition (S-R) and reversal (R-S) tasks. Significant acquisition differences were found in the 8-pair list, where Semantic paragraph Ss performed better than Sentence Ss. In the longer lists, all structures were equally effective in facilitating acquisition (mean first trial correct = 60%), as well as reversal (mean correct = 95%). Sentence form (declarative, imperative, interrogative) was controlled in each elaboration structure. Analyses indicated that significantly fewer acquisition errors were made on pairs presented in declarative and imperative, as opposed to interrogative, elaborations. Tests of recall for the elaborations revealed that Ss in all conditions generally recalled them as declarative sentences. Further observations at 24 pairs confirmed the 12- and 16-pair findings.     

Stability and strain of decagonal Al-Ni-Co quasicrystal under high pressure up to 70GPa

The stability of high-quality decagonal Al72Ni20Co8 single quasicrystals has been investigated under high pressure up to 67 GPa by means of an in situ angular-dispersive X-ray powder diffraction method using synchrotron radiation and a diamond anvil cell. It is found that the compression behaviour is almost isotropic. On the other hand, the strain behaviour on compression is found to be fairly anisotropic. This means that the quasiperiodic structure in the decagonal Al72Ni20Co8 quasicrystal is much more easily distorted than is the periodic structure.     

Robust effects of syntactic structure on visual word processing

A series of experiments explored the effect of the syntactic structure of a sentence fragment on the processing of a subsequent target word. In both a naming and a lexical decision task, modal verb contexts followed by main verb targets and preposition contexts followed by noun targets produced faster response times than did the opposite pairings (i.e., modal/noun and preposition/ verb). This syntactic context effect occurred across several different variations in the method of context presentation. Also, unlike some previous findings on syntactic priming, the present effects did not disappear when a naming task was employed. The magnitude of the syntactic priming effect was similar in the naming and lexical decision tasks when the response times were slow, but was larger in the lexical decision task when the response times were faster. The implications of these results for recent discussions of the relationship between task structure and the locus of observed contextual effects are discussed.     

The effects of family structure on institutionalized children's self-concepts

This study examined the effects of family structure (intact, stepparent, and single parent) on children's self-concepts, using Parish and Taylor's Personal Attribute Inventory for Children. One hundred sixty-six institutionalized children in Grades 5 through 12 participated in the study. Although a trend was noted for students from single-parent families to check fewer positive adjectives, they did not differ significantly (.05 level) from children from intact families or stepfamilies.     

Pattern perception in infants: effects of structure and transformation

Four experiments on pattern perception in 4-month-old infants are reported. The first two experiments examined the perception of pattern structure as defined by Garner (1974). Although the infants did not show an immediate preference for well-structured patterns (Experiment 1), during habituation they showed a reliable decrement in looking only to well-structured patterns (Experiment 2). On recovery trials in Experiment 2 infants were presented with two types of pattern change: a new configuration of the habituation pattern and a change in the orientation of the habituation pattern. The infants recovered looking to the orientation change, but generally not to the changes in configuration. It is argued that the results of Experiment 2 highlight the role of symmetry, especially vertical symmetry, in infant pattern perception. Recovery of looking to changes in the orientation, size, and position of the habituation pattern was examined in Experiments 3 and 4 where it was demonstrated that such changes are salient to the infant, arguably because of the presence of a surrounding, external frame.     

Fitting index of predominance based on periodicity of strengths of pattern and suppression in binocular rivalry

The predominance of the strength of pattern over the strength of suppression during binocular rivalry has generally been defined as the percentage of total time of appearance. Is this fit for an index of the predominance? Theoretically, the strengths of pattern and suppression periodically oscillate throughout the observation period. From this assumption, the best fitting indices of predominance were examined. The simplest model of the visual system was one in which the periodicity of the two originates was expressed by a differential equation. Various indices were examined by the solution of its equation so that a power function of the ratio of the time of appearance to that of disappearance was obtained as the most suitable index of the predominance.     

The self in autobiographical memory: effects of self-salience on narrative content and structure

Contemporary models of autobiographical memory attribute a prominent role to the conceptualisation of the self. In an attempt to better understand the impact of the self as an organising feature of autobiographical memory, narratives of personal episodes were elicited, either after a questionnaire about the self (self-prime condition) or after a distractor task (control condition). Participants also wrote a narrative of a turning-point memory, which is by definition a self-focused narrative. Narratives were divided into propositions and analysed for the types of statements used. As predicted, when writing self-focused turning-point narratives participants included more statements relating to the meaning of an event and connecting it to the self, and fewer statements focusing on the who, what, where, and when of the narrative. Narratives written after the self-prime also demonstrated characteristics that were similar to turning-point narratives, although not on all measures. This shift in narrative focus in turning-point and self-primed memory narratives indicates an increased attempt to fulfil goals of coherence rather than correspondence (Conway, 2005). These findings lend insight into the nature of the relationship between the semantic conceptualisation of the self, and the process of retrieving event-specific knowledge in episodic memory.