Kinetic Analysis of Solution-Precipitation During Liquid-Phase Sintering of Alumina

Densification controlled by solution-precipitation during liquid-phase sintering was analyzed for the aluminamagnesium aluminosilicate glass system. As a model system for liquid-phase sintering, narrowly sized alumina powders and up to 20 vol% magnesium aluminosilicate glass samples were isothermally sintered at 1550° to 1650°C. Densification rate increases with increasing liquid content and sintering temperature but decreases with increasing density. For samples with >15% grain growth, the densification rate during the solution-precipitation stage of sintering was proportional to (particle size)⁻² and thus interface reaction-controlled. Activation energies ranged from 270 to 500 kJ/mol over the relative density range of 66% to 96%, respectively. The low activation energy is attributed to densification by particle rearrangement, whereas the higher activation energy is due to densification controlled by interface-reaction-controlled solution-precipitation. Intermediate activation energies are attributed to simultaneous densification by the two mechanisms.     

Preparation of Silicon Carbide/Aluminum Nitride Ceramics Using Organometallic Precursors

Solid solutions of 2H -SiC/AlN can be prepared at temperatures less than 1600°C by rapid pyrolysis ("hot drop") of mixtures of [(Me₃Si)_0.80((CH₂=CH)MeSi)_1.0(MeHSi)_0.35] _n (VPS) or [MeHSiCH₂] _n (MPCS) with [R₂AlNH₂]₃, where R=Et, i -Bu or simply by slow pyrolysis of the precursor mixture in the case of [Et₂AlNH₂]₃. In contrast, slow pyrolysis of mixtures of VPS or MPCS with [ i -Bu₂AlNH₂]₃ yields a composite of 2 H -AlN and 3 C -SiC at 1600°C, which transforms into a single 2 H -SiC/AlN solid solution on heating to 2000°C. The influences of the nature of the precursor and processing conditions on the structure, composition, and purity of the SiC/AlN materials are discussed.     

Silicon Nitride Derived from an Organometallic Polymeric Precursor: Preparation and Characterization

Partially crystalline Si₃N₄, with nanosized crystals and a specific surface area greater than 200 m²/g, is obtained by pyrolysis of a commercially available vinylic polysilane in a stream of anhydrous NH₃ to 1000°C. This polymer does not contain N initially. Crystallization to high-purity α-Si₃N₄ proceeds with additional heating above 1400°C under N₂. The changes in crystallinity, powder morphology, infrared spectra, and elemental compositions, for samples annealed from 1000° to 1600°C under N₂, are consistent with an amorphous-to-crystalline transformation. Although macroscopic consolidation and local densification occur at 1400°C, volatilization and accompanying weight loss limit bulk densification. The effect of temperature on specific surface area is examined and related to the sintering process. These results are applicable to pyrolysis, decomposition, and crystallization studies of ceramics synthesized by polymeric precursor routes.     

A Liquid Silazane Precursor To Silicon Nitride

The reaction of dichlorosilane, H₂SiCl₂, with gaseous NH₃ in dichloromethane or diethyl ether solution results in the formation of a silazane oil containing silicon, hydrogen, and nitrogen in good yield. This ammonolysis product can be pyrolyzed in an N₂ atmosphere (temperature to 1150°C) to give α-Si₃N₄ in ∼70% yield. The ceramic product formed has a relatively porous, fine-grained microstructure with some cracks and blisters.     

Biofeedback and electrodermal self-regulation in psychopathy.

Examined the degree to which psychopaths can learn to modify their spontaneous skin resistance responses (SSRRs) using intructions and biofeedback. Ten clinically defined psychopaths and 12 control Ss were tested, using a within-S design. Ss were required to increase and decrease the frequency of SSRRs, first without feedback, then with biofeedback training, and finally without feedback. During prefeedback with instructions alone, control Ss were able to raise SSRRs relative to resting baselines, but psychopaths showed no SSRR control. After 16 min of biofeedback training, both groups were able to raise and lower their SSRRs to a comparable degree. The results for heart rate, measured at the same time, presented the opposite pattern; during prefeedback with instructions alone, both groups produced comparable increases in heart rate, but in postfeedback the controls maintained heart rate whereas the psychopaths did not. Data suggest that psychopaths are as capable of learning to voluntarily regulate electrodermal activity as are controls, but they still differ in autonomic patterning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

"On the myth of intellectual decline in adulthood": Erratum.

Reports an error in the original article by J. L. Horn and G. Donaldson (American Psychologist, 1976, Vol 31[10], 701–719; see record 1977-07954-001). On page 717 the sentence that begins with the last line of the left-hand measure should read "The effect is shown by comparing (e.g., over 5 years) the first-test and retest average scores for those who do and those who do not survive for a while longer (another 5 years).' (The following abstract of this article originally appeared in PA, Vol 57:7954). Considers that careful review of the logical and empirical bases for the myth argument indicates that there is little to justify it. There is evidence that some of the abilities of intelligence improve throughout substantial parts of adulthood, or at least do not decline as much or as early as other abilities. Perhaps some individuals manage to avoid decrements which affect others. Positive sampling bias and wishful thinking in the conduct and interpretation of research tend to work against finding support for any decrement hypothesis that may be true. Yet the evidence suggests that if one lives long enough, decrement in at least some of the important abilities of intelligence is likely to occur. However, the reasonable interpretations that are possible for existing results are too complex… (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of Assigned and Participative Goal Setting on Performance and Job Satisfaction: Erratum.

Reports an error in the the article "Effects of Assigned and Participative Goal Setting on Performance and Job Satisfaction" by Gary P. Latham and Gary A. Yukl (Journal of Applied Psychology. Vol 61(2) Apr 1976, 166-171). The last paragraph in the Results section subtitled "Manipulation Check and Reliability of Measures" on page 168 was a repetition of the previous paragraph. It should be changed to read as follows: The internal consistency of the satisfaction measure was .83, The stability of the satisfaction scale, as estimated by the correlation between the before and after measures of satisfaction, was .70 (p 1977-30702-001.) Evaluated the job performance of 41 female typists under participative or assigned goal setting conditions over a 10-wk period. Significant productivity improvement occurred in both conditions during the 2nd 5 wks. There was no significant difference between conditions with respect to goal difficulty or frequency of goal attainment. Job satisfaction declined slightly in both conditions. Individual trait measures such as need for independence did not moderate the effects of either type of goal setting. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Death anxiety and care of the terminally-ill: A review of the clinical literature.

Reviews the literature on death anxiety as it relates to psychosocial care of the terminally ill. The literature strongly supports the need for caregivers to understand their own fears and feelings in order to deal with terminal patients. The negative potential consequences of misunderstood feelings about death are discussed as well as several major correlates (sex, socioeconomic status, occupation, general anxiety, and level of consciousness). Some results of groups emphasizing ventilation of fears about death are also reviewed briefly. Their positive effects on treatment suggest the value of gaining more accurate understanding of death anxiety through future research. (French abstract) (44 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Deficient passive and one-way active avoidance acquisition following medial forebrain bundle lesions in rats.

In 3 experiments with 93 Long-Evans male hooded rats, cathodal electrolytic lesions of the medial forebrain bundle (MFB) at posterior hypothalamic levels produced a mild, transient hypodipsia and lowered jump thresholds to footshock. Lesions produced marked deficits in passive avoidance performance in a paradigm that paired discrete, linearly incrementing footshock intensities with contact of a water spout following 48 hrs of water deprivation. Injections of levo-dextro-5-hydroxytryptophan (75 mg g, ip), the immediate metabolic precursor of serotonin, had no effect on the passive avoidance performance of either experimental or operated control Ss. Lesions of the MFB also resulted in deficient acquisition in a 1-trial step-through passive avoidance paradigm not using motivation to drink and caused a severe acquisition deficit in a 1-way active avoidance task. Lesions of the septal nuclei produced lowered jump thresholds but did not affect acquisition in the 1st passive avoidance task. Results are interpreted as indicating a lesion-induced deficiency in fear learning, independent of the serotonergic functions of the MFB. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of instructions and modeling on trainees low in interpersonal-communication skills.

Examined the effects of instructions and modeling in the reflection-of-feeling training of individuals low in interpersonal-communication skills. Participants with low scores on R. Carkhuff's Communication Index (25 males and 25 females) were randomly assigned by sex to 1 of the 5 training groups so that there were 5 males and 5 females in each group. After viewing videotaped training material, each participant conducted a 15-min interview with a volunteer "client" and completed the Communication Index a second time. Interviews were scored for frequency of reflection-of-feeling responses and level of empathic communication displayed. Analysis of the reflection-of-feeling data indicated that instructions and instructions-plus-modeling were facilitative procedures. Ratings of written and verbal empathy demonstrated the effectiveness of the 2 combined conditions: instructions-plus-modeling and modeling-plus-instructions. Calculation of correlations among scores on criterion measures revealed a positive correlation between reflection-of-feeling scores and ratings of empathic communication. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)