Controllable electron-momentum filter in a δ-doped magnetically modulated semiconductor nanostructure

ABSTRACT

We have theoretically investigated the control of wave-vector filtering (WVF) by introducing δ-doping into a magnetically modulated nanostructure fabricated by depositing ferromagnetic stripes on top and bottom of a GaAs/Al_xGa_{1 ?x}As heterostructure. With the help of an improved transfer matrix method, the Schrödinger equation for electrons in this semiconductor nanostructure is solved exactly and the transmission efficient calculated numerically. We demonstrate that the WVF efficiency is associated closely with the weight and position of the δ-doping, which may be helpful for designing a controllable electron-momentum filter based on such a magnetically modulated semiconductor nanostructure.     

Amorphization of TiNi induced by high-pressure torsion

Using high-resolution electron microscopy, we investigated the initial stages of high-pressure-torsion-induced crystalline-to-amorphous transformation of TiNi. It is found that the deformation-induced amorphization initiated from dislocation core regions in the interior of grains and from grain boundaries. It is believed that both the energy stored in the dislocations and the energy stored in the grain boundaries contribute significantly to driving the crystalline-to-amorphous transformation.     

Core Knowledge and the Emergence of Symbols: The Case of Maps

Map reading is unique to humans but is present in people of diverse cultures, at ages as young as 4 years old. Here, we explore the nature and sources of this ability and ask both what geometric information young children use in maps and what nonsymbolic systems are associated with their map-reading performance. Four-year-old children were given two tests of map-based navigation (placing an object within a small three-dimensional [3D] surface layout at a position indicated on a two-dimensional [2D] map), one focused on distance relations and the other on angle relations. Children also were given two nonsymbolic tasks, testing their use of geometry for navigation (a reorientation task) and for visual form analysis (a deviant-detection task). Although children successfully performed both map tasks, their performance on the two map tasks was uncorrelated, providing evidence for distinct abilities to represent distance and angle on 2D maps of 3D surface layouts. In contrast, performance on each map task was associated with performance on one of the two nonsymbolic tasks: Map-based navigation by distance correlated with sensitivity to the shape of the environment in the reorientation task, whereas map-based navigation by angle correlated with sensitivity to the shapes of 2D forms and patterns in the deviant-detection task. These findings suggest links between one uniquely human, emerging symbolic ability, geometric map use, and two core systems of geometry.     

The ambiguity of loss affects some,but not all autobiographical memories: redemption and contamination,agency and communion

ABSTRACT

Compared with clear-cut loss by death, ambiguous loss is defined as a loss that is not definite because the person is missing or mentally absent but physically present (e.g., through Alzheimer's disease). We expected the ambiguity of loss to show in psychologically more compromised loss memories and self-defining memories, but not in autobiographical memories in general. Thirty Chinese adults who had lost a parent through death, thirty whose parent had gone missing, and thirty who cared for a demented parent narrated their loss experiences and memories of sad and turning-point events as well as self-defining memories. Individuals with ambiguous loss narrated the loss and a self-defining memory with more contamination and fewer redemption sequences, and only the loss memory with fewer themes of agency and communion than individuals with definite loss, but not in memories of sad and turning point events. Effects of ambiguity of loss were independent of prolonged grief, which in turn independently predicted some of these effects. Thus the ambiguous quality of loss predicts effects on loss memories and self-defining memories independently of psychiatric symptoms.     

Contexts of a person's prior intentions facilitate observational learning in 2.5-year-old children

We examined whether contexts suggesting an actor's prior intentions facilitate observational learning in 2.5-year-olds. In Experiment 1, children observed an experimenter handle one box before proceeding to open a second box. In two prior intention conditions, children either watched the experimenter extract a toy from the first box or saw that the box had already been opened. In two no prior intention conditions, children watched the demonstration with only the second box or paired with irrelevant actions upon the first box. Children successfully opened the second box more often in the two prior intention conditions than in the two no prior intention conditions. Experiment 2 investigated stimulus generalization as another explanation for these results. A functionally different trap-tube task served as the pre-demonstration apparatus. Before watching the experimenter open the box, children either saw her extract a toy from the tube with a stick or observed the toy accidentally fall from the opening. In both cases, children opened the box at similar high rates. We discuss children's use of others’ prior intentions or observable outcomes in observational learning.     

The Young-Laplace equation associated with transverse shear stress within the surface layer of a solid

ABSTRACT

The Young-Laplace equation was firstly established based on a liquid film without shearing resistance. It is not valid for a solid. By taking into account the in-plane shearing and transverse shearing within a surface layer, we reconstruct the Young-Laplace equation for a solid. This new version shows that the equilibrium of a solid surface is determined by the bulk stress, the surface membrane stress and the transverse shear stress acting together. The transverse shear stress depends on the gradient of the Gaussian curvature of the surface and the strain. The intrinsic membrane stress and transverse shear stress cause residual stresses to appear in the interior of the solid. The intrinsic transverse shear stress occurs only in a non-spherical shaped body.     

Character Strengths and Deep Connections Following Hurricanes Katrina and Rita: Spiritual and Secular Pathways to Resistance Among Volunteers

This study investigated a conceptual model with two pathways, altruism and perceived spiritual support, leading to resilience among student volunteers following Hurricanes Katrina and Rita (H‐KR). Both strengths share the sense of deep connections. Parallel pathways with the two major constructs were estimated using structural equation modeling, adjusting for demographics and peritraumatic emotional reactions. The two indicators may have served as a protective mechanism for all volunteers despite differing racial/cultural backgrounds. The potential protection of these strength factors was mediated through optimism and hope. Resilience among minority volunteers was associated more with faith‐related strengths, as indicated in the relevant pathway that also contributed to their altruistic actions. The resilience of white volunteers, however, was directly associated with altruism, a strength that does depend heavily on religious beliefs. Further, the modification index suggested a direct path from race to depression.     

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.     

The effect of university ranking on learning satisfaction: Social identities and self‐identity as the suppressor and mediators

The popularization of higher education has developed into a worldwide trend of ranking universities. In light of the lack of research from the student perspective and the non‐individualism of East Asian society, the goal of the present study was to integrate social identity theory and characteristics of Chinese achievement goals in order to determine the relationships between university rankings and students’ university identity, major identity, self‐identity, and learning satisfaction (LS). The participants included 1052 undergraduates (49.4% male, 50.6% female) from 13 universities in Taiwan. A questionnaire was conducted. The results of hierarchical regression analyses show that university ranking positively correlates with students’ university identity, major identity, and self‐identity but negatively correlates with LS due to the effect of university identity acting as a suppressor. The results of structural equation modelling show that: (1) students’ major identity and self‐identity completely mediate the effect of university identity on LS; and (2) university ranking has a significantly negative effect on LS after adding multiple identities as the suppressor and mediators. Furthermore, as students progress further into their studies, both their university identity and major identity gradually decline, while their self‐identity remains constant. Theoretical and practical implications for higher education are also discussed.