A new highly ordered Al-Ni-Ru decagonal quasicrystal with 1.6 nm periodicity

A new decagonal quasicrystal (the D phase) with a period of about 1.6 nm was found to form in conventionally solidified and heat-treated Al₇₅Ni₁₅Ru₁₀ alloys. The electron diffraction patterns of the Al-Ni-Ru D phase exhibit a large number of quite sharp diffraction spots located at precise decagonal symmetry positions, indicating a highly ordered decagonal quasicrystal with a long-range quasiperiodic correlation. The D phase is formed with a composition close to Al₇₄Ni₁₅Ru₁₁, as determined by energy-dispersive X-ray analysis. By means of high-resolution electron microscopy, the structural features of the Al-Ni-Ru D phase, which are obviously different from that of the Al-Pd D phase (a typical decagonal quasicrystal with 1.6 nm periodicity reported previously), have been revealed.     

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.     

A new stable icosahedral quasicrystal in the Cd-Mg-Dy system

A new stable icosahedral quasicrystal has been found in annealed Cd-Mg-Dy alloys. The composition of the icosahedral phase was determined to be approximately Cd₆₆Mg₂₁Dy₁₃. Powder X-ray and electron diffraction patterns revealed that the phase has a primitive icosahedral lattice with a quasilattice parameter a_R = 0.5634 nm. The electron diffraction study confirmed that the phase has a well ordered primitive icosahedral structure.     

From the decagonal phase to a related crystalline one

Abstract

We present here a rotation matrix in five-dimensional space which connects the decagonal phase to a tetragonal crystalline related phase through a one-dimensional quasicrystals range by means of a phason-phonon coupling. Phason and phonon fields are determined in a general way and, from this result, a simple linear approximation is given. Continuous evolution density-wave patterns are shown.     

An ordered arrangement of atom columnar clusters in a pentagonal quasiperiodic lattice of an Al-Ni-Co decagonal quasicrystal

The structure of an Al-Ni-Co decagonal quasicrystal (called the S1-type superstructure), which shows diffraction patterns with superlattice reflections, has been studied by atomic-scale observations of electron microscopy. The structure of the decagonal quasicrystal can be characterized as an ordered arrangement of two kinds of atom columnar cluster with different directions of pentagonal symmetry. A fundamental lattice, which is constructed by connecting all the atom clusters, shows a pentagonal quasiperiodic lattice with a bond length of about 2 nm. The pentagonal lattice is divided into two superlattices, which are constructed by connecting atom clusters with the same directions of pentagonal symmetry, with a bond length of 2     

Structural study of a superlattice Al-Ni-Ru decagonal quasicrystal using high-resolution electron microscopy and a high-angle annular dark-field technique

A high-quality superlattice Al-Ni-Ru decagonal quasicrystal with 0.4nm periodicity, formed in the conventionally solidified Al₇₀Ni₂₀Ru₁₀ alloy, has been studied by high-resolution electron microscopy and a high-angle annular dark-field (Z-contrast) technique. It has been clearly revealed that its structure is characterized as an aperiodically ordered arrangement of decagon-shaped atomic columnar clusters which have a diameter of 2nm and show pentagonal symmetry. On the basis of high-resolution electron microscopy structure images, and the atom-resolution Z-contrast observations which highlight the transition-metal sites, the arrangement of atoms in the superlattice decagonal quasicrystal are proposed.     

A constitutive model for quasicrystal plasticity

High-pressure X-ray diffraction studies on gadolinium sesquioxide (Gd₂O₃) have been carried out up to a pressure of ～25 GPa in a diamond-anvil cell at room temperature. Gadolinium oxide, which has a cubic or bixbyite structure under ambient conditions, undergoes an irreversible structural phase at around 12 GPa. The high-pressure phase has been identified as a hexagonal La₂O₃-type structure. The bulk modulus and its pressure derivative of this phase have been calculated.     

A new stacking motif in the decagonal approximant Mn3Ga5

The structure of the decagonal approximant Mn₃Ga₅     

How to see the Burgers vector of a quasicrystal dislocation

Abstract

We derive, in a density-wave framework, the ‘invisibility condition’ for dislocations in quasicrystals. Our results should be essential for a correct analysis of dislocations in these systems, in particular for measuring their six-dimensional Burgers vectors.     

A direct comparison between climb and glide dislocation velocities in an icosahedral Al-Pd-Mn quasicrystal

The formation and evolution of a dislocation dipole has been recorded during an in-situ heating experiment in a transmission electron microscope (TEM) at 740°C. The formation took place by pure climb in parallel planes but no subsequent annihilation was observed. Since annihilation was only possible by glide, this situation indicates that glide in two-fold planes is a considerably more difficult process than climb, at least at high temperature.     

A neural correlate of consciousness related to repression

In previous research Libet (1966) discovered that a critical time period for neural activation is necessary in order for a stimulus to become conscious. This necessary time period varies from subject to subject. In this current study, six subjects for whom the time for neural activation of consciousness had been previously determined were administered a battery of psychological tests on the basis of which ratings were made of degree of repressiveness. As hypothesized, repressive subjects had a longer critical time period for neural activation of consciousness, suggesting the possibility that this neurophysiological time factor is a necessary condition for the development of repression.     

Transformation of the decagonal quasicrystalline phase to a B2 crystalline phase in the Al-Cu-Co system by high-energy ball milling

Samples of a decagonal quasicrystalline phase, located in the Al-Cu-Co system and synthesized by a slow cooling technique, have been mechanically milled in a high-energy planetary ball mill for 10, 20 and 30h. The milled powders, as well as powders that had been annealed (after milling) for times ranging from 30 to 150min at 600C, were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. A phase transformation from the decagonal phase to a B2 crystalline phase during highenergy ball milling is reported here for the first time. Powders milled for more than 10h contained predominantly the B2-type crystalline phase with a lattice parameter of 0.29nm. This crystalline phase was found to be quite stable after milling for 30h and also on subsequent annealing at 600C. These experimental results lend support to an earlier suggestion that the decagonal phase in Al-Cu-Co is actually less stable than the B2 phase at low temperatures.     

Psychophysiological arousal related to Type A components in adolescent boys

The association between psychophysiological responses (heart rate, skin conductance and blood volume) and Type A behavior was studied in adolescent boys (n = 48) in computer-controlled experiments. Although psychophysiological arousal was related to the type of stress-evoking element, task-specificity did not result in significant psychophysiological differences between Type As and Nontype As. The indication is that physiological arousal may be a constitutional characteristic of Type A behavior. The multidimensionality of type A behavior must be considered in any investigation examining the psychophysiological Type A-Nontype A differences. Different Type A dimensions, together with previously found psychological differences, were related to specific psychophysiological reactions.     

A sufficient condition for conditional expectation to be monotonically related to distribution parameters

In this paper we give a sufficient condition for conditional expectation to be a monotonic function of a parameter of the joint probability distribution. A second sufficient condition is given for the case where varying the parameter of the joint distribution leaves the shape of that distribution unchanged. Finally, an application of the condition is illustrated on the counter models for choice reaction time of LaBerge (1962) and Nickerson (1969).     

Loneliness related to self-concept

The Differential Loneliness Scale and the UCLA Loneliness Scale were given to 30 persons attending a mental growth group (test group) and 36 adult students of psychology (the control group). Ages of the subjects ranged from 19 to 45 years. Self-concept was measured by Fitts' Tennessee Self-concept Scale and scored using both Clinical and Counselling forms. The first group showed greater loneliness, lower scores on physical self, and higher scores on moral-ethical self than the controls, and also had significantly lower scores on the neurosis scale and the defensive positive scale. A trend towards social maladjustment and personality disordered behavior was observed. Shyness and the typical introverted character for many Finns are discussed in connection with loneliness, social maladjustment, and lack of social skills.     

A review of psychological factors related to bullying victimization in schools

School bullying is a serious problem affecting the victims, their daily life, and society in general. An increasing amount of research on school bullying has recently been published which calls for an updated review on the literature. The objective of this article is to review psychological variables which may explain individual reactions to bullying victimization in school-aged children. The selected psychological variables are coping, social support, attachment, negative affectivity/neuroticism, and somatization. The strengths and limitations of the reviewed research are discussed, and future research directions focusing on a more dynamic understanding of personal factors are suggested.     

Majority reaction to shifting and stable attitudinal deviates

Female undergraduates, in groups of four, voted several times on appropriate treatment for a delinquent, using an electrical signalling device. Two simulatedgroup members consistently agreed with subjects' initial position. A third simulated member (target) exhibited one of nine response patterns. In six movement conditions (which formed a 2 × 3 design), the target (a) gradually moved a short distance toward or away from modal group opinion and (b) manifested high, medium, or low net agreement with the majority position. In three stable conditions, the target consistently (a) agreed with modal opinion, (b) disagreed, or (c) took a neutralposition. In movement conditions, the target was evaluated significantly more favourably in the toward than in the away condition and in the high agreement than in the medium and low agreement conditions. In stable conditions, the agreeing target was liked significantly better than the neutral and disagreeing targets. The target's response pattern also affected subjects' attributions about the target's motives, communication to the target (in notes interspersed between votes), and opinion change. Results were discussed in terms of previous research dealing with majority reaction to moving and stable attitudinal deviates.