Low-energy boron implants into silicon: A molecular dynamics simulation study of implants into a stepped surface

Molecular dynamics simulations have been conducted to study implantation of boron with a low kinetic energy (E _k in the range 5 eV) into the silicon surface. The bombarded surface has a realistic stepped structure and the geometry of the step edge is taken from the theory of Chadi (1987, Phys. Rev. Lett., 59, 1691). It is found that reflection is the more common event. However subsurface implants and adatom formations are also observed. The effect of the step morphology is important and different trajectories are observed if the ions hit steps of different shapes.     

Simulation of surface effects on the intrinsic dissipation of nanooscillators

The rapid increase of surface area-volume ratio (SVR) with shrinking structure size has a great impact on surface-related intrinsic dissipation, which usually leads to low quality factors for the devices composed of nanoelectromechanical systems. In the present study, the flexural oscillations of nanocantilevers with varying thicknesses and lengths were simulated using the molecular dynamics method, in which the surface effects on the energy dissipation was evaluated when SVR was increased to extremely large values (between 0.4 and 2.0 nm^?1). And, it is also interesting to note that the prediction of the size-dependent Young's modulus by means of resonant frequency of the underdamped oscillation showed good agreement with previous findings.     

Arsenic adsorption onto silicon stepped surfaces: a study at semiempirical level

As adsorption onto Si surfaces vicinal to (100) has been studied using the Hartree–Fock method at a semiempirical level and a cluster model of the surface steps. The simulation conditions apply to the dilute limit of the adsorbate concentration. Accordingly, one As atom is placed on the step in a substitutional or interstitial location, either above or below the surface. The optimal configuration of the system is evaluated from a steepest-descent energy minimization. The central finding is that As is preferably adsorbed in the interstitial location and the physical explanation is that this location allows both a stronger electrostatic coupling with the surface and a lower stress than in the case of the substitutional impurity. This result represents a significant divergence with respect to the known properties of the bulk impurity. It can, however, consistently account for known features of heteroepitaxial growth of As on Si(100).     

Effects of surface pre-presentation on symmetry detection on a 3-D bumpy surface

Abstract:  The aim of this study was to investigate the visual detection mechanism of mirror symmetrical dot patterns drawn on a 3-D bumpy surface (i.e., 3-D noisy curved surface). The focus of this investigation was whether symmetry detection on the bumpy surface is associated with structure recovery of the surface. In Experiment 1, we confirmed that the human visual system can distinguish the bumpy surface from a distorted dot pattern on a transparent bumpy surface. In Experiment 2, we required participants to discriminate between a symmetrical pattern on a transparent (non-visible) bumpy surface and an opaque (visible) bumpy surface for the same stimuli as in Experiment 1. Finally, in Experiment 3, we examined the effect of pre-presentation of the opaque bumpy surface on pattern discrimination. The results showed that pre-presentation of the opaque surface facilitated the detection of a diagonal symmetry, but not in the case of the detection of a cardinal symmetry. These results suggested that diagonal symmetry involves the process of surface recovery, whereas cardinal symmetry does not.     

Ellipses on the surface of a picture

Shapes on the surface of a perspective picture may be misperceived. Subjects picked a match for an ellipse depicting the circular top of a cylinder. The top was depicted as tilted forward from 5 degrees to 85 degrees, generating a series of ellipses on the picture surface. The matches were biased towards a circle over a wide range of midrange tilts, which suggests that, influenced by features of perspective, they were seen as in-between the shape on the surface and the shape they depicted.     

Note on ultrametric hierarchical clustering algorithms

Milligan presented the conditions that are required for a hierarchical clustering strategy to be monotonic, based on a formula by Lance and Williams. In the present paper, the statement of the conditions is improved and shown to provide necessary and sufficient conditions.This work was supported in part by the Boris Kidri Fund, Yugoslavia.     

Semantic clustering as a neuropsychological predictor for amnestic-MCI

ABSTRACT

Recent research has demonstrated that patients with Alzheimer's disease (AD) show deficits in semantic processing when compared to cognitively healthy individuals. This difference is thought to be attributed to losses in higher cortical systems that are predominantly associated with executive functioning. The first aim of the study will be to determine if differences in semantic clustering can accurately differentiate patients with amnestic mild cognitive impairment (aMCI) from cognitively normal (CN) individuals. The second aim will be to determine the extent to which semantic processing might be associated with executive functions. Data from 202 (134 CN, 68 aMCI) participants were analyzed to quantify differences in semantic clustering ratios on the HVLT-R. Study participants ages ranged from 51 to 87 with education ranging from 6 to 20 years. ANCOVA revealed statistically significant differences on semantic clustering ratios (p < .001). Moderate correlations between semantic clustering Category Fluency Test (r = .45) were also found. Statistically significant group differences were also present on Trails-B and WAIS-R Digit Symbol performance (p < .001). Overall, these data indicate that deficits in semantic clustering are present in aMCI patients.     

Semantic clustering as a neuropsychological predictor for amnestic-MCI

Recent research has demonstrated that patients with Alzheimer's disease (AD) show deficits in semantic processing when compared to cognitively healthy individuals. This difference is thought to be attributed to losses in higher cortical systems that are predominantly associated with executive functioning. The first aim of the study will be to determine if differences in semantic clustering can accurately differentiate patients with amnestic mild cognitive impairment (aMCI) from cognitively normal (CN) individuals. The second aim will be to determine the extent to which semantic processing might be associated with executive functions. Data from 202 (134 CN, 68 aMCI) participants were analyzed to quantify differences in semantic clustering ratios on the HVLT-R. Study participants ages ranged from 51 to 87 with education ranging from 6 to 20 years. ANCOVA revealed statistically significant differences on semantic clustering ratios (p < .001). Moderate correlations between semantic clustering Category Fluency Test (r = .45) were also found. Statistically significant group differences were also present on Trails-B and WAIS-R Digit Symbol performance (p < .001). Overall, these data indicate that deficits in semantic clustering are present in aMCI patients.     

Identifying predictor variables of weight loss outcome: Implications for a stepped program and weight management

Abstract

Four variables were identified that predicted outcome for the minimal and moderate intensity weight control programs presented in sequence. Predictive models for pounds lost and percentage overweight lost were computed for both programs and follow-up and accounted for 33% to 62% of the variance. The predictor variable that contributed to the two programs and follow-up was success in losing weight previously. Greater rate of weight loss in the first five weeks contributed to the model for the minimal intensity program and for follow-up and total number of calories expended in nonroutine physical activity added to the model for the minimal intensity program. Marital dissatisfaction of subjects was a predictor for the moderate intensity program and follow-up. The findings have utility for a stepped program for weight and provide confirmation of variables noted as predictors in prior research. This study may help in the quest to identify consistent predictors of weight loss success.     

Effect of semantic clustering on the memory of spatial locations

The effect of altering the labels attached to points was examined in three experiments. The first experiment measured the extent of clustering that occurs based on the labels alone. This experiment also established norms for the remainder of the study. In the second and third experiments, subjects were required to learn the locations of points. The points were labeled in such a way as to suggest certain spatial clusterings. It was shown that subjects cluster points with regard to the labels attached to the points and these clusters may be based solely on the labels attached to the points. Furthermore, an alteration of the learning sequence to induce an alternate clustering showed no noticeable effect.     

Influence of a stereo surface on the perceived tilt of a monocular line

This study addressed the issue of how a stereo-specified surface influences the perceived twodimensional orientation of a monocularly viewed line. In a series of three experiments, it was found that, in general, when a monocular line was embedded in a disparity field specifying a planar surface slanted about the horizontal axis, the tilt of the line depended on the slant of the surface in which it was embedded and on whether the line was presented in the left or in the right visual field. These results, predicted by perspective geometry, are compatible with the hypothesis that the monocular line is perceived as part of the stereo surface. Moreover, it was found that timing is a crucial factor in determining the strength of the effect. The effect was at a maximum when the monocular line and the stereo surface were presented together, with no prior presentation of the surface. The influence of the stereo surface on the monocular line was substantially reduced, however, when the surface alone preceded the combined presentation of the line and the surface.     

Reversible plasticity under nanoindentation of atomically flat and stepped surfaces of fcc metals

Using atomistic simulation, the indentation of single-crystalline Cu is investigated for both an ideal and a stepped (111) surface. Both systems exhibit an intermediate regime of reversible plasticity, characterized by the formation of extended stacking faults, which heal entirely upon withdrawal of the indenter. This regime can be employed to clarify the role of pure stacking fault generation and cross-slip in plasticity. Its existence reveals that, on the atomistic scale, plastic deformation is characterized by material transport rather than by the nucleation of stacking faults. Finally, we establish a criterion–based on the total displacement of particles–to determine after which indentation depth plasticity is generated irreversibly in the material.     

Profiling local optima in K-means clustering: developing a diagnostic technique

Using the cluster generation procedure proposed by D. Steinley and R. Henson (2005), the author investigated the performance of K-means clustering under the following scenarios: (a) different probabilities of cluster overlap; (b) different types of cluster overlap; (c) varying samples sizes, clusters, and dimensions; (d) different multivariate distributions of clusters; and (e) various multidimensional data structures. The results are evaluated in terms of the Hubert-Arabie adjusted Rand index, and several observations concerning the performance of K-means clustering are made. Finally, the article concludes with the proposal of a diagnostic technique indicating when the partitioning given by a K-means cluster analysis can be trusted. By combining the information from several observable characteristics of the data (number of clusters, number of variables, sample size, etc.) with the prevalence of unique local optima in several thousand implementations of the K-means algorithm, the author provides a method capable of guiding key data-analysis decisions.     

Testing a modified cognitive interview with category clustering recall in Iran

The cognitive interview (CI) has been an effective method for interviewing eyewitnesses often leading to changes in legislation and practice in many countries. This study was the first to employ the CI in Iran and test whether category clustering recall (CCR) was superior to a free recall when incorporated within an investigative interview. A between‐subjects design assigned 66 participants to one of three interview conditions after they watched a mock robbery. The participants were interviewed 48 hr later using either a structured interview (SI), the CI, or a modified cognitive interview (MCI) that replaced free recall with CCR at the first retrieval attempt. Analysis of variance suggests CCR was more effective than free recall and the CI group recalled more information than the SI group, replicating the CI superiority effect. This has implications for law enforcement in Iran and worldwide by suggesting these techniques can be used to enhance recall.     

The Effect of a Prejudice-Reduction Simulation on Attitude Change1

The effectiveness of a well-known prejudice-reduction simulation, “Blue Eyes-Brown Eyes,” was assessed as a tool for changing the attitudes of nonblack teacher education students toward blacks. The three outcomes were (a) virtually all of the subjects reported that the experience was meaningful for them; (b) the statistical evidence supporting the effectiveness of the activity for prejudice reduction was moderate; and (c) virtually all of the participants, as well as the simulation facilitator, reported stress from the simulation.