HRTEM study of the {252}γ austenite–martensite interface in an Fe—8Cr–1C alloy

Abstract

High-resolution transmission electron microscopy has been used to image the atomic structure of the (2S2)_γ austenite-martensite interface. By imaging along [101]_γ ∥[111]_α, the interface was viewed edge-on and seen to consist of facets on the close-packed (111)_γ, planes. From the correspondence of atoms in the close-packed planes across the austenite-martensite interface, the magnitude of the shear can be analysed as (a/24)<112> on every close-packed plane in the plane of projection. Comparison with theory indicates that this is an (a/12)<112> Burgers vector out of the plane of projection. Hence, each atomic facet can be viewed as a structural ledge containing an (a/12)<112> transformation dislocation.     

Core structure of a〈100〉 superdislocations in a single-crystal superalloy during high-temperature and low-stress creep

A thorough TEM analysis has been carried out to study the dislocations cutting into γ′ phase in a single-crystal superalloy during uniaxial tensile creep under high-temperature and low-stress conditions. It is proved that the a〈100〉 edge superdislocation originates from the interfacial a〈100〉 dislocations and moves into the γ′ phase by pure climbing. And the dissociation of the a〈100〉 superdislocation core into two a/2〈101〉 superpartial dislocations during uniaxial tensile creep has been identified by HRTEM method for the first time.     

Dynamic properties of edge dislocations decorated by interstitial loops in α-iron and copper

Clusters of self-interstitial atoms (SIAs) in the form of parallel crowdions are created directly in high-energy displacement cascades produced in metals by neutron irradiation. They are equivalent to small perfect dislocation loops and, in isolation in pure metals, undergo fast thermally-activated glide in the direction of their Burgers vector. Their strain field and ability to glide allows long-range interaction with other extended defects. Indeed, dislocations decorated by dislocation loops are commonly observed after neutron irradiation. Dislocations gliding under applied stress also encounter these mobile defects. These effects influence mechanical properties and require further investigation. This paper presents results from an atomic-scale study of copper and α-iron at either 0?K or 300?K. Loop drag and breakaway effects are investigated for an edge dislocation under applied stress interacting with a row of SIA loops below its glide plane. The maximum speed at which a loop is dragged is lower in copper than iron, and the applied stress at which this occurs is also lower. These differences in the dynamics of cluster-dislocation interaction are determined by the atomic structure of the defects and cannot be investigated by continuum treatment.     

Atomic-scale study of {1 1 2} twin boundary structure in a β-Ti alloy

The atomic structure of {1?1?2} twin boundary in a specialty β-Ti alloy, gum metal, has been studied by means of conventional transmission electron microscopy, bright-field and high-angle annular dark field scanning transmission electron microscopy imaging. The observations provide direct evidence that the {1?1?2} twin boundary has a complex, multiple-layer structure, which is composed of various structural units. These structural units are formed as a result of different degrees of inner atomic-column shifting. The complex structure of the {1?1?2} twin boundary is different to the atomic structure of the previously reported ω phase.     

Stress anomaly in Al-rich Ti-Al single crystals deformed by the motion of 1/2«110] ordinary dislocations

The microstructure and plastic deformation behaviour of Al-rich Ti-Al single crystals containing 54.7 and 58.0 at.% Al have been examined, focusing on the effect of chemical ordering of a Al5Ti3 superstructure on anomalous strengthening. Fine precipitates with the Al5Ti3 superstructure were developed in the L10 matrix of the Ti-58.0 at.% Al alloy. The size and volume fraction of the precipitates varied depending on temperature. An anomalous increase in the yield stress of the two alloys appeared at around 800oC. This strengthening mechanism is discussed on the basis of the difference in antiphase-boundary energies on (111), (110) and (001) planes in the Al5Ti3 phase.     

Tailoring of interfaces in amorphous silicon–germanium multilayers on the atomic scale by ultra-high gravity

Amorphous Si/Ge multilayers containing diffuse interfaces have been prepared, heated in an ultra-centrifuge and subsequent interface structure modifications observed by X-ray reflectivity. The thickness of the Si/Ge and Ge/Si interface zones became asymmetrical owing to various effects occurring on the different atoms parallel to the direction of gravity-induced diffusion. The technique could prove useful for tuning physical (electronic, magnetic or optical) properties of layered structures.     

A new type of defect on {1120} planes in ß-Si3N4 produced by neutron irradiation

Measurements of static permittivity, refractive index and density have been carried out to study possible H-bonded complexes in solutions of anisole diluted by benzene together with high-static-permittivity alcohols, i.e. cyclohexanol, n-butanol, tert-butanol, isopropyl alcohol and 1-hexanol. The experiments were performed at 303 K. Dipole moments of the mixtures are calculated from the experimental data and these are used to obtain dipolar increments. The concentration ratio of proton donor to proton acceptor is plotted against a parameter, Ω_B, which is determined from experimental data. From the plot, the dipole moment of the mixture and that of the component B are determined. The order of the complex can be obtained from the nature of the graph. The investigation shows that the interaction between the two components arises solely from a polarization effect.     

Atomic structure and solute segregation of a Σ = 3, [110]/{111} grain boundary in an yttria-stabilized cubic zirconia bicrystal

The atomic structure and chemical composition of a =3, [110]/{111} symmetric tilt grain boundary in an yttria-stabilized cubic zirconia bicrystal has been investigated by high-resolution transmission electron microscopy (HRTEM) and nanoprobe energy-dispersive X-ray spectroscopy. The experimental HRTEM images are compared with simulated images for a model obtained by lattice statics calculations. It is found that the grain boundary has two individual mirror symmetrical planes in cation and anion sublattices. In this case, the cations are forced to form sevenfold coordination in the vicinity of the boundary owing to the restraint of the boundary structure, while the cations in the cubic fluorite structure have eightfold coordination. The segregation of yttrium ions was experimentally detected at the = 3 boundary, a finding that is considered to be closely related to the change in the local coordination at the boundary.     

A model of amygdala–hippocampal–prefrontal interaction in fear conditioning and extinction in animals

Empirical research has shown that the amygdala, hippocampus, and ventromedial prefrontal cortex (vmPFC) are involved in fear conditioning. However, the functional contribution of each brain area and the nature of their interactions are not clearly understood. Here, we extend existing neural network models of the functional roles of the hippocampus in classical conditioning to include interactions with the amygdala and prefrontal cortex. We apply the model to fear conditioning, in which animals learn physiological (e.g. heart rate) and behavioral (e.g. freezing) responses to stimuli that have been paired with a highly aversive event (e.g. electrical shock). The key feature of our model is that learning of these conditioned responses in the central nucleus of the amygdala is modulated by two separate processes, one from basolateral amygdala and signaling a positive prediction error, and one from the vmPFC, via the intercalated cells of the amygdala, and signaling a negative prediction error. In addition, we propose that hippocampal input to both vmPFC and basolateral amygdala is essential for contextual modulation of fear acquisition and extinction. The model is sufficient to account for a body of data from various animal fear conditioning paradigms, including acquisition, extinction, reacquisition, and context specificity effects. Consistent with studies on lesioned animals, our model shows that damage to the vmPFC impairs extinction, while damage to the hippocampus impairs extinction in a different context (e.g., a different conditioning chamber from that used in initial training in animal experiments). We also discuss model limitations and predictions, including the effects of number of training trials on fear conditioning.     

Additive and synergistic relations of early mother–child and caregiver–child interactions and socioeconomic outcomes in adulthood

Prior theoretical and empirical studies have linked the first 3 years of children's life with later life outcomes. One primary explanation is the critical role these experiences play in children's early brain development (including their early language and cognitive abilities) and subsequent schooling achievement. The current study is a registered report with two complementary research objectives: (1) examine to what extent stimulating and responsive interactions with mothers and nonparental caregivers during the first 3 years of life show additive or synergistic associations with key socioeconomic outcomes in adulthood (i.e., educational attainment, salary, and employment status), and (2) examine to what extent academic skills (i.e., mathematics, vocabulary, and literacy) during childhood and adolescence mediate these associations. The sample included 1364 individuals from a birth cohort study who were followed until age 26. Mother–child interactions had positive associations with educational attainment and negative associations with full-time employment, though no synergistic associations were found for the socioeconomic outcomes. In addition, the indirect effects of mother–child interactions on educational attainment through mathematics were strongest for children with less stimulating and responsive caregiver–child interactions. Potential implications of these findings for developmental theory are discussed.     

Coexistence of adjacent vacancy-ordered and eutectic phases in Al–Cu–Ni alloys

ABSTRACT

Copper-mould-cast Al–Cu–Ni alloys show adjacent coexistence of in situ grown ordered and eutectic phases. A bimodal microstructure of α–Al and eutectic α-Al+θ-Al₂Cu phases with length-scale hierarchy evolves during solidification. Microstructural analysis through Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM) shows the presence of Vacancy-ordered phases (VOPs) with different morphologies in two different compositions.     

Mother–Stranger Comparisons of Social Attention in Jealousy Context and Attachment in HFASD and Typical Preschoolers

Affective bonding, social attention, and intersubjective capabilities are all conditions for jealousy, and are deficient in autism. Thus, examining jealousy and attachment may elucidate the socioemotional deficit in autism spectrum disorders (ASD). Jealousy was provoked in 30 high-functioning children with ASD (HFASD) and 30 typical children (ages 3–6 years) through two triadic social (storybook-reading) scenarios – mother-child-rival and stranger-child-rival. A control nonsocial scenario included mother/stranger-book. For both groups, higher jealousy expressions emerged for mother than stranger, and for social than nonsocial scenarios. Attachment security (using Attachment Q-Set) was lower for HFASD than typical groups, but attachment correlated negatively with jealous verbalizations for both groups and with jealous eye gazes for HFASD. Implications for understanding jealousy’s developmental complexity and the socioemotional deficit in ASD are discussed.     

Medical explanations and lay conceptions of disease and illness in doctor–patient interaction

Hilary Putnam’s influential analysis of the ‘division of linguistic labour’ has a striking application in the area of doctor–patient interaction: patients typically think of themselves as consumers of technical medical terms in the sense that they normally defer to health professionals’ explanations of meaning. It is at the same time well documented that patients tend to think they are entitled to understand lay health terms like ‘sickness’ and ‘illness’ in ways that do not necessarily correspond to health professionals’ understanding. Drawing on recent philosophical theories of concept possession, the article argues that this disparity between medical and lay vocabulary implies that it is, in an important range of cases, easier for doctors to create a communicative platform of shared concepts by using and explaining special medical expressions than by using common lay expressions. This conclusion is contrasted with the view that doctors and patients typically understand each other when they use lay vocabulary. Obviously, use of expressions like ‘sickness’ or ‘illness’ does not necessarily lead to poor communication, but it is important that doctors have an awareness of how patients interpret such terms.

Comprehension and utilisation of pointing gestures and gazing in dog–human communication in relatively complex situations

The aim of the present investigation was to study the visual communication between humans and dogs in relatively complex situations. In the present research, we have modelled more lifelike situations in contrast to previous studies which often relied on using only two potential hiding locations and direct association between the communicative signal and the signalled object. In Study 1, we have provided the dogs with four potential hiding locations, two on each side of the experimenter to see whether dogs are able to choose the correct location based on the pointing gesture. In Study 2, dogs had to rely on a sequence of pointing gestures displayed by two different experimenters. We have investigated whether dogs are able to recognise an ‘indirect signal’, that is, a pointing toward a pointer. In Study 3, we have examined whether dogs can understand indirect information about a hidden object and direct the owner to the particular location. Study 1 has revealed that dogs are unlikely to rely on extrapolating precise linear vectors along the pointing arm when relying on human pointing gestures. Instead, they rely on a simple rule of following the side of the human gesturing. If there were more targets on the same side of the human, they showed a preference for the targets closer to the human. Study 2 has shown that dogs are able to rely on indirect pointing gestures but the individual performances suggest that this skill may be restricted to a certain level of complexity. In Study 3, we have found that dogs are able to localise the hidden object by utilising indirect human signals, and they are able to convey this information to their owner.     

Correlates of MMPI–A Scales in Acute Psychiatric and Forensic Samples

The purpose of this study was to expand the empirical basis for interpretation of the Minnesota Multiphasic Personality Inventory–Adolescent (MMPI–A; Butcher et al., 1992). Participants were 157 boys from a forensic setting and 197 girls from an acute psychiatric inpatient setting. Criterion variables were identified from sources such as psychiatrist report, parent report, and psychosocial history. Results generally support the construct validity of MMPI–A scales. Scales measuring internalizing problems were more highly correlated with criterion measures of internalizing behaviors than measures of externalizing behaviors, whereas scales measuring externalizing problems were more highly correlated with externalizing variables than with internalizing criteria. Implications of this study include an expanded empirical foundation for interpretation of the MMPI–A, greater understanding of the constructs it measures, and evidence supporting the generalizability of these constructs across settings.     

Biases and regularities of grapheme–colour associations in Japanese nonsynaesthetic population

Associations between graphemes and colours in a nonsynaesthetic Japanese population were investigated. Participants chose the most suitable colour from 11 basic colour terms for each of 40 graphemes from the four categories of graphemes used in the Japanese language (kana characters, English alphabet letters, and Arabic and kanji numerals). This test was repeated after a three-week interval. In their responses, which were not as temporally consistent as those of grapheme–colour synaesthetes, participants showed biases and regularities that were comparable to those of synaesthetes reported in past studies. Although it has been believed that only synaesthetes, and not nonsynaesthetes, tended to associate graphemes with colours based on grapheme frequency, Berlin and Kay's colour typology, and colour word frequency, participants in this study tended in part to associate graphemes with colours based on the above factors. Moreover, participants that were nonsynaesthetes tended to associate different graphemes that shared sounds and/or meanings (e.g., Arabic and kanji numerals representing the same number) with the same colours, which was analogous to the findings in Japanese synaesthetes. These results support the view that grapheme–colour synaesthesia might have its origins in cross-modal association processes that are shared with the general population.     

Formation and analysis of amorphous and nanocrystalline phases in Al–Cu–Mg alloy under friction stir processing

Homogeneous amorphous and nanocrystalline phases formed in the nugget zone of a friction stir-processed Al–Cu–Mg alloy have been studied. X-ray diffraction analysis indicated a diffuse scattering peak with characteristics of an amorphous phase existed in the range 15°–29°. Further, TEM analysis proved the existence of an amorphous structure. Friction stir processing provides special physical conditions, such as high temperature, high hydrostatic pressure and large shear stress, which could induce the amorphization of the alloy.