Structure and stability of helices in square-well homopolymers

Recently, it has been demonstrated [Magee et al., Phys. Rev. Lett. 96, 207802 (2006)] that isolated, square-well homopolymers can spontaneously break chiral symmetry and freeze into helical structures at sufficiently low temperatures. This behavior is interesting because the square-well homopolymer is itself achiral. In this work, we use event-driven molecular dynamics, combined with an optimized parallel tempering scheme, to study this polymer model over a wide range of parameters. We examine the conditions where the helix structure is stable and determine how the interaction parameters of the polymer govern the details of the helix structure. The width of the square well (proportional to lambda) is found to control the radius of the helix, which decreases with increasing well width until the polymer forms a coiled sphere for sufficiently large wells. The helices are found to be stable for only a window of molecular weights. If the polymer is too short, the helix will not form. If the polymer is too long, the helix is no longer the minimum energy structure, and other folded structures will form. The size of this window is governed by the chain stiffness, which in this model is a function of the ratio of the monomer size to the bond length. Outside this window, the polymer still freezes into a locked structure at low temperature, however, unless the chain is sufficiently stiff, this structure will not be unique and is similar to a glassy state.Comment: Submitted to Physical Review

Summary report: A preliminary investigation into the use of fuzzy logic for the control of redundant manipulators

The Rice University Department of Mechanical Engineering and Materials Sciences' Robotics Group designed and built an eight degree of freedom redundant manipulator. Fuzzy logic was proposed as a control scheme for tasks not directly controlled by a human operator. In preliminary work, fuzzy logic control was implemented for a camera tracking system and a six degree of freedom manipulator. Both preliminary systems use real time vision data as input to fuzzy controllers. Related projects include integration of tactile sensing and fuzzy control of a redundant snake-like arm that is under construction

Web Mediators for Accessible Browsing

We present a highly accurate method for classifying web pages based on link percentage, which is the percentage of text characters that are parts of links normalized by the number of all text characters on a web page. K-means clustering is used to create unique thresholds to differentiate index pages and article pages on individual web sites. Index pages contain mostly links to articles and other indices, while article pages contain mostly text. We also present a novel link grouping algorithm using agglomerative hierarchical clustering that groups links in the same spatial neighborhood together while preserving link structure. Grouping allows users with severe disabilities to use a scan-based mechanism to tab through a web page and select items. In experiments, we saw up to a 40-fold reduction in the number of commands needed to click on a link with a scan-based interface, which shows that we can vastly improve the rate of communication for users with disabilities. We used web page classification and link grouping to alter web page display on an accessible web browser that we developed to make a usable browsing interface for users with disabilities. Our classification method consistently outperformed a baseline classifier even when using minimal data to generate article and index clusters, and achieved classification accuracy of 94.0% on web sites with well-formed or slightly malformed HTML, compared with 80.1% accuracy for the baseline classifier.National Science Foundation (IIS-0308213, IIS-039009, IIS-0093367, P200A01031, EIA-0202067

Clients\u27 Perceptions of Their Counseling Experiences for Trauma Related to Anesthesia Awareness (AA)

Each year in the United States, approximately 81 million individuals receive surgeries in which .1% to .2% (20,000 to 40,000/20 million) experience Anesthesia Awareness (AA). More than 50% of the AA cases result in mental distress or Posttraumatic Stress Disorder (PTSD). Because the percentage of AA cases among surgeries makes it appear to be a rare occurrence, and because it has received rather limited research attention, I decided to undertake an interpretative phenomenological analysis to discover AA clients’ perceptions of their counseling experience, and encourage development of therapeutic interventions to meet their needs. The broad research question for my study was how do clients perceive their experience of counseling for trauma related to AA? The context was provided by a review of the literature which focused on trauma and PTSD, AA, clients’ perceptions of counseling, counseling for trauma, and counseling for PTSD. Semi-structured interviews were used to collect data which then was coded to identify emerging themes which were then clustered. The clustered themes were used to answer the broad and specific research questions. Based on the findings of my study, the theme of relational factors of counselors most often emerged as helpful to counseling (e.g., Rogerian- congruence, unconditional positive regard, accurate empathic understanding), whereas, the therapy process, external barriers, and PTSD symptoms most often emerged as hindering to counseling. Implications for counselors and counselor educators include increased understanding and insight regarding AA survivors and the role of relationship when counseling this population which may lead to more effective interventions and expanded professional roles to work with this population