A comparison between calculated and observed elastically induced precipitate shape transitions in a Cu-2 At. Pct Co alloy

Elastic and interfacial energy calculations have been performed for misfitting spherical-, cuboidal-, octahedral-, and tetrakaidecahal-shaped precipitates in a face-centered cubic (fcc) matrix ac- counting to first order for the difference in elastic constants between precipitate and matrix phases. The energy calculations predict a number of possible precipitate shape transitions with increasing particle size, depending upon the material parameters and anisotropy of the interfacial energy. Predicted shape transitions were compared with experimentally observed transitions of coherent, Co-rich precipitates in a low volume fraction Cu-2 at. pct Co alloy. The predicted octahedron-to-tetrakaidecahedron transition was not observed. Rather, the corners of the octa- hedra were observed to become progressively more rounded with increasing particle size. Pos- sible sources of disagreement between calculations and experiment are discussed. formerly with the Department of Materials Science and Engineering, Carnegie Mellon University.     

A comparison of the crystallographic structures of two catalytic antibodies with esterase activity

The crystallographic structure of the Fab fragment of the catalytic antibody, 29G11, complexed with an (S)-norleucine phenyl phosphonate transition state analog was determined at 2.2 A resolution. The antibody catalyzes the hydrolysis of norleucine phenyl ester with (S)-enantioselectivity. The shape and charge complementarity of the binding pocket for the hapten account for the preferential binding of the (S)-enantiomer of the substrate. The structure is compared to that of the more catalytically efficient antibody, 17E8, induced by the same hapten transition state analog. 29G11 has different residues from 17E8 at eight positions in the heavy chain, including four substitutions in the hapten-binding pocket: A33V, S95G, S99R and Y100AN, and four substitutions at positions remote from the catalytic site, I28T, R40K, V65G and F91L. The two antibodies show large differences in the orientations of their variable and constant domains, reflected by a 32 degrees difference in their elbow angles. The VL and VH domains in the two antibodies differ by a rotation of 8.8 degrees. The hapten binds in similar orientations and locations in 29G11 and 17E8, which appear to have catalytic groups in common, though the changes in the association of the variable domains affect the precise positioning of residues in the hapten-binding pocket.     

A comparison of three W170 protocols

This study compared the W170 scores of 9 male subjects in kgm/kg X min resultant from the following protocols: 2 X 6 min workloads (3 min rest between each bout), 3 X 4 min workloads (1 1/2 min rest between each bout), and 4 X 3 min workloads (1 min rest between each bout). Each subject experienced 2 preliminary rides in order to overcome the problems of learning and habituation and the order of the 3 experimental treatments was randomly assigned to each subject. An analysis of variance repeated measures design revealed that there was no statistically significant difference between the 3 protocols at the 0.05 level. The scores for the three W170 protocols correlated -0.084, 0.040, and -0.142 with VO2 max in ml/kg X min. The correlation coefficient between actual VO2 max in ml/kg X min and that predicted from the Astrand-Ryhming nomogram was 0.723.     

Influence of precipitate morphology on the high temperature fatigue properties of SRR99

Fatigue crack growth (FCG) tests have been conducted in air at 650°C and 850°C on 〈001〉 oriented single crystals of SRR99 having the γ′ particles in the form of: (A) 0.3 μm cuboids; (B) 0.2 μm ogdoadical cuboids; and (C) a coarse, rafted γ′ structure. In general, reducing the frequency and increasing the temperature enhances crack-tip shielding at low ΔKs due to increasing oxide induced crack closure. In material A at 650°C the crack path changes from one of γ′ precipitate cutting on {001} to propagation within the matrix as ΔK increases. Enhanced crack branching at 850°C improves the Paris regime behaviour compared with that seen at 650°C. In material B at 650°C, greater cross slip at lower frequency reduces slip reversibility, thus enhancing the fatigue crack growth rate (FCGR). At 850°C crack tip blunting and meandering, associated with γ′ cutting, improves the high ΔK FCG response and on a strength/modulus normalized basis is comparable with that seen for material A. Material C shows a similar FCG resistance to A at 650°C, but there is an acceleration in FCGR at 850°C, which can be accounted for in terms of the lower proof stress and modulus of this microstructure.     

The influence of precipitate morphology on microvoid growth and coalescence in tensile fractures

A study of the fine-scale topography of tensile fractures in selected aluminum alloys was made to provide information on the influence of second-phase microconstituents on microvoid initiation, growth, and coalescence. The test materials included three commercial aluminum alloys and three high-purity Al-Cu binary alloys heat-treated to provide a wide range of precipitate morphology. The fracture surfaces of notched-tensile specimens were examined, and the fine-scale topographic features compared with microstructural parameters. The principal observations made were: 1) for a dual precipitate morphology, void initiation first occurs at the larger precipitates, 2) fracture may occur by growth and coalescence of voids initiated at only a small fraction of precipitate sites, 3) void initiation can occur independent of precipitate particles, and 4) intergranular fracture may occur by growth and coalescence of microvoids within the grain-boundary zone. These observations established that the detailed aspects of fracture by microvoid coalescence are intimately related to precipitate morphology, but no simple, uniform correlation of fracture surface topography with precipitate size and distribution was evident.     

Organochlorines in Pleuronectidae: comparison between three tissues of three species inhabiting the Northwest Atlantic

The authors evaluated signal changes in the human primary visual cortex during visual stimulation using functional magnetic resonance imaging (MRI) scanner at 1.5 Tesla. Experiments were performed on 10 normal volunteers and 2 patients with homonymous hemianopsia. In the normal volunteers, a signal increase was observed on the bilateral primary visual cortex during hemifield stimulation. In one patient with homonymous hemianopsia after cerebral infarction, the signal change was clearly decreased on the affected side. In the other patient, who was recovering from multiple sclerosis to an almost normal visual field, the fMRI results were within normal limits. These results suggest that it is possible to map noninvasively the activation of the visual stimulation with a clinical MRI system, and that this test might be useful as an objective method of visual field examination.     

Accommodation of angular incompatibilities between interfacial facets during precipitate growth

Precipitate growth in a duplex stainless steel and a titanium aluminide alloy has been studied using transmission electron microscopy. Particles with similar crystallography and acicular form arise in both cases, and are bounded by two principal facets. One facet, designated C, is based on a commensurate singular interface structure, and the coherency strains are accommodated by interfacial defects. The other facet, designated I, is based on a singular configuration that is incommensurate in one dimension. The orientation relationship (OR) between the particle and the matrix for the singular C structure is Kurdjumov-Sachs (K-S), whereas that for the I facet is Pitsch. The angular incompatibility between these two types of facets must be accommodated to minimize the displacement field as particles grow. The present observations suggest that this is accomplished through the generation of crystal dislocations at facet junctions and their subsequent climb along the facets. The total density of defects needed to accommodate the angular discrepancy is fixed, but the partitioning of these dislocations between C and I facets is not. The actual partitioning determines the observed OR for a particle, and is determined by the kinetics of climb, which is likely to be different in the two facets. In the stainless steel, the observations are consistent with climb occurring in both the C and I facets, but faster in the I facet, leading to a distribution of observed ORs that is skewed away from Pitsch toward K-S. In the titanium aluminide alloy, no climb into the C facets was found, so a unique OR close to K-S arises. This article is based on a presentation made in the “Hume-Rothery Symposium on Structure and Diffusional Growth Mechanisms of Irrational Interphase Boundaries,” which occurred during the TMS Winter meeting, March 15–17, 2004, in Charlotte, NC, under the auspices of the TMS Alloy Phases Committee and the co-sponsorship of the TMS-ASM Phase Transformations Committee.     

Accommodation of angular incompatibilities between interfacial facets during precipitate growth

Precipitate growth in a duplex stainless steel and a titanium aluminide alloy has been studied using transmission electron microscopy. Particles with similar crystallography and acicular form arise in both cases, and are bounded by two principal facets. One facet, designated C, is based on a commensurate singular interface structure, and the coherency strains are accommodated by interfacial defects. The other facet, designated I, is based on a singular configuration that is incommensurate in one dimension. The orientation relationship (OR) between the particle and the matrix for the singular C structure is Kurdjumov-Sachs (K-S), whereas that for the I facet is Pitsch. The angular incompatibility between these two types of facets must be accommodated to minimize the displacement field as particles grow. The present observations suggest that this is accomplished through the generation of crystal dislocations at facet junctions and their subsequent climb along the facets. The total density of defects needed to accommodate the angular discrepancy is fixed, but the partitioning of these dislocations between C and I facets is not. The actual partitioning determines the observed OR for a particle, and is determined by the kinetics of climb, which is likely to be different in the two facets. In the stainless steel, the observations are consistent with climb occurring in both the C and I facets, but faster in the I facet, leading to a distribution of observed ORs that is skewed away from Pitsch toward K-S. In the titanium aluminide alloy, no climb into the C facets was found, so a unique OR close to K-S arises. This article is based on a presentation made in the “Hume-Rothery Symposium on Structure and Diffusional Growth Mechanisms of Irrational Interphase Boundaries,” which occurred during the TMS Winter meeting, March 15–17, 2004, in Charlotte, NC, under the auspices of the TMS alloy Phases Committee and the co-sponsorship of the TMS-ASM Phase Transformations Committee.     

Influence of precipitate morphology on intermediate temperature creep properties of a nickel-base superalloy single crystal

The influence of γ’ precipitate morphology on the-creep behavior of the single crystal nickel-base superalloy NASAIR 100 at 760-°C was investigtated. As-heat treated crystals with cuboidal γ’ particles and crystals given an additional pre-rafting treatment to form a continuous lamellar structure were creep tested at stress levels which produced rupture lives ranging from 40 to 2500 hours. At high applied stresses, the crystals with cuboidal γ’ had both lower minimum creep rates and longer rupture lives than the crystals with lamellar γ. At lower stress levels, the initially cubic γ’ material maintained a lower crep rate, but exhibited a similar rupture life compared to the pre-rafted crystals. Examination of the microstructures which developed during creep indicated that dislocations could shear the semi-coherent γ’ rafts relatively easily compared to the coherent cuboidal γ’. In tests at lower applied stresses, slow directional coarsening of the initially cuboidal γ’ resulted in the development of a lamellar structure similar to that in the pre-rafted material, such that the rupture lives of the two materials were similar.     

A comparison of three procedures for classifying addicts.

2 prevalent techniques plus a 3rd technique which compared individual to group profiles were employed to analyze the profiles of 2,179 narcotic addicts, using the Sixteen Personality Factor Questionnaire. It is concluded that inferences from classification studies can be related to the techniques used. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of three approaches to criterion measurement.

3 different criterion measures were used to assess comparative job competency of 1711 workers in 16 occupations. These were used in conjunction with the General Aptitude Test Battery (GATB) aptitude scores to establish prediction patterns of occupational success. Rating A was job oriented, Rating B was behavior oriented, and Rating C was trait oriented. The 3 scales are described and the distribution of highest r's with GATB aptitudes is given as an empirical means of determining the relative effectiveness of the 3 approaches to criterion measurement. Conclusions are: (a) Ratings A and C are generally more useful than Rating B; (b) use of Rating A may well be justified, despite the time and expense involved if the occupations under consideration are "white-collar" and predictor aptitudes are already identified; and (c) the more economical Rating C appears to be most useful for "blue-collar" occupations and for exploratory studies to identify predictor batteries. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of temperature measurements using three ear thermometers

Following anecdotal and research-based reports of inaccuracies encountered with the use of ear thermometers in patient care settings, this two-phase study was designed to compare the accuracy of three ear thermometers when used in a multioperator environment. The within-subject variation (limits of agreement) in ear temperature measurements obtained with the three ear thermometers in a multioperator condition by using an oral temperature reference standard ranged from +/- 1.25 degrees F to 1.85 degrees F. In multioperator, multisubject patient care environments using a pulmonary artery catheter core temperature as the reference standard, the limits of agreement for ear temperature measurements obtained with the three different ear thermometers ranged from +/- 2.19 degrees F to 2.85 degrees F. These results suggest that there is substantial variation in ear measurements and raise questions about the use of ear thermometers when there are multiple personnel taking temperatures, as occurs in hospital-based clinical practice environments. Handedness of the operator, position of the patient, and the ear used for measurement did not produce clinically significant variability in ear temperature measurements.     

Accommodation of angular incompatibilities between interfacial facets during precipitate growth

Precipitate growth in a duplex stainless steel and a titanium aluminide alloy has been studied using transmission electron microscopy. Particles with similar crystallography and acicular form arise in both cases, and are bounded by two principal facets. One facet, designated C, is based on a commensurate singular interface structure, and the coherency strains are accommodated by interfacial defects. The other facet, designated I, is based on a singular configuration that is incommensurate in one dimension. The orientation relationship (OR) between the particle and the matrix for the singular C structure is Kurdjumov-Sachs (K-S), whereas that for the I facet is Pitsch. The angular incompatibility between these two types of facets must be accommodated to minimize the displacement field as particles grow. The present observations suggest that this is accomplished through the generation of crystal dislocations at facet junctions and their subsequent climb along the facets. The total density of defects needed to accommodate the angular discrepancy is fixed, but the partitioning of these dislocations between C and I facets is not. The actual partitioning determines the observed OR for a particle, and is determined by the kinetics of climb, which is likely to be different in the two facets. In the stainless steel, the observations are consistent with climb occurring in both the C and I facets, but faster in the I facet, leading to a distribution of observed ORs that is skewed away from Pitsch toward K-S. In the titanium aluminide alloy, no climb into the C facets was found, so a unique OR close to K-S arises. This article is based on a presentation made in the “Hume-Rothery Symposium on Structure and Diffusional Growth Mechanisms of Irrational Interphase Boundaries,” which occurred during the TMS Winter meeting, March 15–17, 2004, in Charlotte, NC, under the auspices of the TMS alloy Phases Committee and the co-sponsorship of the TMS-ASM Phase Transformations Committee.     

A simple costing of three methods used to prepare endoscopy equipment

The paper describes a DRIM-1 X-ray monitor which directly measures and records the product of an absorbed (exposure) dose and the actual area of X-ray beam onto the outside surface of the depth diaphragm (cGy.cm2). The principle of action of the device is based on the measurement of the charge coming from the detecting unit--a preamplifier ionization chamber. The device may be used to control the time-stability of a radiation signal in the X-ray apparatus.     

A comparison of three methods of group vocational counseling.

Superimposed a group discussion process over a typical vocational counseling process in which the primary focus was on test information, and over 2 atypical vocational counseling processes, one in which occupational information was primary and the other in which test information and occupational information were optional and randomly presented upon a group member's request. All Ss selected goals in the initial stages of counseling. 57 undergraduates were studied in 6 single-sex experimental groups and 2 control groups. Data from a levels-of-decision-making scale, the Edwards Personal Preference Schedule, and the Kuder Occupational Preference Inventory show that the atypical groups learned significantly more and retained longer than did both the typical and control groups. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of three groups of vocationally indecisive students.

Three groups of college students with vocational problems (19 who sought professional counseling at a university counseling center, 52 who enrolled in a class in career planning, and 32 who sought no professional help) were compared on 5 measures: an attitudes toward counselors and counseling scale, a perceived usefulness of counseling item, an alternate sources of help question, the Career Decision Scale, and Rotter's Internal–External Locus of Control Scale. A discriminant analysis, followed by comparison of the 3 groups on each of the 5 measures, indicated that those who used the services of a counseling center had a significantly more positive attitude toward counseling and counselors. The higher scores on levels of career indecision, which were found among the nonseekers in comparison to the class takers, were ascribed to experimental conditions. Results suggest that some previous findings that indicate attitudes may not be important in predicting help-seeking behavior may not apply to those who have vocational problems. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A comparison of the efficiency of three anesthesia circle systems

To assess the sensitivity of standard echocardiography in detecting ventricular motion abnormalities in patients with coronary artery disease (CAD) without prior myocardial infarction, 56 consecutive patients with a history of angina pectoris were studied during an angina-free period. In the 48 patients with adequate echocardiograms, the amplitude of septal and posterior wall motion in the high, mid, and low left ventricle was determined and used to predict prospectively in a blinded fashion the sites of angiographically-determined CAD. Twenty-eight of 35 patients (80%) with disease of the left anterior descending artery (LAD) had diminished interventricular septal motion (P less than 0.001) and 14 of 27 patients (52%) with disease of posterior vessels had diminished posterior wall motion on echocardiogram. When abnormalties of echocardiographic wall motion were compared with left ventriculography, the results were similar. Echocardiography may aid in predicting the presence and distribution of CAD, especially LAD disease.