THE EFFECT OF THE STM TIP ON SI(100) RECONSTRUCTED SURFACES

We present a theoretical study of the effects of the STM tip on the geometry of Si(100) reconstructed surfaces. The energy barrier to switching between different reconstructions is also discussed. We use a molecular dynamics method and self-consistent forces to simulate the time-dependent behaviour of the surface atoms. The molecular orbital calculations are performed at the CNDO level using a cluster model. Our results indicate significant differences for positively and negatively biased tips. The thermally induced rocking of surface dimers is inhibited by the application of a positive bias to the tip and it is promoted by a negative bias. These bias-dependent effects may offer a plausible explanation for the bias dependence of STM images of this surface

EFFECTS OF THE STM TIP ON ADSORBATE IMAGE

Scanning tunnelling microscopy provides atomic scale information about surface topography and electronic structure. However, the way the tip affects the STM image cannot always be neglected. We present a theoretical study of the effect of the non-uniform electric field of the tip on STM image of adsorbed molecules using Bardeen's approach. Self-consistent geometry optimization and wave-function calculations have been carried out within the CNDO approximation in a cluster model. Our results indicate significant effects. Thus for adsorbed CO on metal, the molecules reorient because of the tip, and the image is changed qualitatively as well as quantitatively. This may explain the lack of observation of CO at low coverage by STM. Our results also suggest the STM might be used for molecular modification

Bounds on the satisfiability threshold for power law distributed random SAT

Propositional satisfiability (SAT) is one of the most fundamental problems in computer science. The worst-case hardness of SAT lies at the core of computational complexity theory. The averagecase analysis of SAT has triggered the development of sophisticated rigorous and non-rigorous techniques for analyzing random structures. Despite a long line of research and substantial progress, nearly all theoretical work on random SAT assumes a uniform distribution on the variables. In contrast, real-world instances often exhibit large fluctuations in variable occurrence. This can be modeled by a scale-free distribution of the variables, which results in distributions closer to industrial SAT instances. We study random k-SAT on n variables, m = ϵ(n) clauses, and a power law distribution on the variable occurrences with exponent β. We observe a satisfiability threshold at β≤(2k-1)/(k-1). This threshold is tight in the sense that instances with β ≥ (2k-1)/(k-1)-ϵ for any constant ϵ > 0 are unsatisfiable with high probability (w. h. p.). For β > (2k-1)/(k-1)+ ϵ, the picture is reminiscent of the uniform case: instances are satisfiable w. h. p. for sufficiently small constant clause-variable ratios m/n; they are unsatisfiable above a ratio m/n that depends on β

Considering the role of cognitive control in expert performance

© 2014, Springer Science+Business Media Dordrecht. Dreyfus and Dreyfus’ (1986) influential phenomenological analysis of skill acquisition proposes that expert performance is guided by non-cognitive responses which are fast, effortless and apparently intuitive in nature. Although this model has been criticised (e.g., by Breivik Journal of Philosophy of Sport, 34, 116–134 2007, Journal of the Philosophy of Sport, 40, 85–106 2013; Eriksen 2010; Montero Inquiry:An interdisciplinary Journal of Philosophy, 53, 105–122 2010; Montero and Evans 2011) for over-emphasising the role that intuition plays in facilitating skilled performance, it does recognise that on occasions (e.g., when performance goes awry for some reason) a form of ‘detached deliberative rationality’ may be used by experts to improve their performance. However, Dreyfus and Dreyfus (1986) see no role for calculative problem solving or deliberation (i.e., drawing on rules or mental representations) when performance is going well. In the current paper, we draw on empirical evidence, insights from athletes, and phenomenological description to argue that ‘continuous improvement’ (i.e., the phenomenon whereby certain skilled performers appear to be capable of increasing their proficiency even though they are already experts; Toner and Moran 2014) among experts is mediated by cognitive (or executive) control in three distinct sporting situations (i.e., in training, during pre-performance routines, and while engaged in on-line skill execution). We conclude by arguing that Sutton et al. Journal of the British Society for Phenomenology, 42, 78–103 (2011) ‘applying intelligence to the reflexes’ (AIR) approach may help to elucidate the process by which expert performers achieve continuous improvement through analytical/mindful behaviour during training and competition

Allosteric mechanism of action of the therapeutic anti-IgE antibody omalizumab

Immunoglobulin E and its interactions with receptors FcϵRI and CD23 play a central role in allergic disease. Omalizumab, a clinically approved therapeutic antibody, inhibits the interaction between IgE and FcϵRI, preventing mast cell and basophil activation, and blocks IgE binding to CD23 on B cells and antigen-presenting cells. We solved the crystal structure of the complex between an omalizumab-derived Fab and IgE-Fc, with one Fab bound to each Cϵ3 domain. Free IgE-Fc adopts an acutely bent structure, but in the complex it is only partially bent, with large-scale conformational changes in the Cϵ3 domains that inhibit the interaction with FcϵRI. CD23 binding is inhibited sterically due to overlapping binding sites on each Cϵ3 domain. Studies of omalizumab Fab binding in solution demonstrate the allosteric basis for FcϵRI inhibition and, together with the structure, reveal how omalizumab may accelerate dissociation of receptor-bound IgE from FcϵRI, exploiting the intrinsic flexibility and allosteric potential of IgE

B Cells Regulate Neutrophilia during Mycobacterium tuberculosis Infection and BCG Vaccination by Modulating the Interleukin-17 Response

We have previously demonstrated that B cells can shape the immune response to Mycobacterium tuberculosis, including the level of neutrophil infiltration and granulomatous inflammation at the site of infection. The present study examined the mechanisms by which B cells regulate the host neutrophilic response upon exposure to mycobacteria and how neutrophilia may influence vaccine efficacy. To address these questions, a murine aerosol infection tuberculosis (TB) model and an intradermal (ID) ear BCG immunization mouse model, involving both the μMT strain and B cell-depleted C57BL/6 mice, were used. IL (interleukin)-17 neutralization and neutrophil depletion experiments using these systems provide evidence that B cells can regulate neutrophilia by modulating the IL-17 response during M. tuberculosis infection and BCG immunization. Exuberant neutrophilia at the site of immunization in B cell-deficient mice adversely affects dendritic cell (DC) migration to the draining lymph nodes and attenuates the development of the vaccine-induced Th1 response. The results suggest that B cells are required for the development of optimal protective anti-TB immunity upon BCG vaccination by regulating the IL-17/neutrophilic response. Administration of sera derived from M. tuberculosis-infected C57BL/6 wild-type mice reverses the lung neutrophilia phenotype in tuberculous μMT mice. Together, these observations provide insight into the mechanisms by which B cells and humoral immunity modulate vaccine-induced Th1 response and regulate neutrophila during M. tuberculosis infection and BCG immunization. © 2013 Kozakiewicz et al

Measuring the Effects of Self-Awareness: Construction of the Self-Awareness Outcomes Questionnaire

Dispositional self-awareness is conceptualized in several different ways, including insight, reflection, rumination and mindfulness, with the latter in particular attracting extensive attention in recent research. While self-awareness is generally associated with positive psychological well-being, these different conceptualizations are also each associated with a range of unique outcomes. This two part, mixed methods study aimed to advance understanding of dispositional self-awareness by developing a questionnaire to measure its outcomes. In Study 1, expert focus groups categorized and extended an initial pool of potential items from previous research. In Study 2, these items were reduced to a 38 item self-report questionnaire with four factors representing three beneficial outcomes (reflective self-development, acceptance and proactivity) and one negative outcome (costs). Regression of these outcomes against self-awareness measures revealed that self-reflection and insight predicted beneficial outcomes, rumination predicted reduced benefits and increased costs, and mindfulness predicted both increased proactivity and costs. These studies help to refine the self-awareness concept by identifying the unique outcomes associated with the concepts of self-reflection, insight, reflection, rumination and mindfulness. It can be used in future studies to evaluate and develop awareness-raising techniques to maximize self-awareness benefits while minimizing related costs

But Is It Real? A Review of Research on Enneagram

One of the most common questions I am asked when introducing people to the Enneagram goes something along the lines of: “Yes, but is it real? What scientific evidence is there?” It was exactly that question that prompted me to do my PhD research a few years ago. I could see the Enneagram worked for me but I wanted to know if it could stand up to rigorous psychological research. In this article, I have tried to summarise the published research on the Enneagram so that next time someone asks you that question you can answer confidently, “Yes, there is good evidence of its validity, let me tell you about it…

The clinical features of the piriformis syndrome: a systematic review

Piriformis syndrome, sciatica caused by compression of the sciatic nerve by the piriformis muscle, has been described for over 70 years; yet, it remains controversial. The literature consists mainly of case series and narrative reviews. The objectives of the study were: first, to make the best use of existing evidence to estimate the frequencies of clinical features in patients reported to have PS; second, to identify future research questions. A systematic review was conducted of any study type that reported extractable data relevant to diagnosis. The search included all studies up to 1 March 2008 in four databases: AMED, CINAHL, Embase and Medline. Screening, data extraction and analysis were all performed independently by two reviewers. A total of 55 studies were included: 51 individual and 3 aggregated data studies, and 1 combined study. The most common features found were: buttock pain, external tenderness over the greater sciatic notch, aggravation of the pain through sitting and augmentation of the pain with manoeuvres that increase piriformis muscle tension. Future research could start with comparing the frequencies of these features in sciatica patients with and without disc herniation or spinal stenosis