Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

The concept of user-centred systems design (UCSD) has no agreed upon definition. Consequently, there is a great variety in the ways it is applied, which may lead to poor quality and poor usability in the resulting systems, as well as misconceptions about the effectiveness of UCSD. The purpose of this paper is to propose a definition of UCSD. We have identified 12 key principles for the adoption of a user-centred development process, principles that are based on existing theory, as well as research in and experiences from a large number of software development projects. The initial set of principles were applied and evaluated in a case study and modified accordingly. These principles can be used to communicate the nature of UCSD, evaluate a development process or develop systems development processes that support a user-centred approach. We also suggest activity lists and some tools for applying UCSD.

https://www.it.uu.se/edu/course/homepage/acsd/vt09/Key_principles.pdf

Key Principles for User-Centred Systems Design

We present a technique for evaluating the usability and effectiveness of ambient displays. Ambient displays are abstract and aesthetic peripheral displays portraying non-critical information on the periphery of a user's attention. Although many innovative displays have been published, little existing work has focused on their evaluation, in part because evaluation of ambient displays is difficult and costly. We adapted a low-cost evaluation technique, heuristic evaluation, for use with ambient displays. With the help of ambient display designers, we defined a modified set of heuristics. We compared the performance of Nielsen's heuristics and our heuristics on two ambient displays. Evaluators using our heuristics found more, severe problems than evaluators using Nielsen's heuristics. Additionally, when using our heuristics, 3-5 evaluators were able to identify 40--60% of known usability issues. This implies that heuristic evaluation is an effective technique for identifying usability issues with ambient displays.

/pdf/heuristic-evaluation-of-ambient-displays-59hvfoy6tp.pdf

Heuristic evaluation of ambient displays

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(11)60830-1.pdf

Sertraline or mirtazapine for depression in dementia (HTA-SADD): a randomised, multicentre, double-blind, placebo-controlled trial

http://www.uselab.tu-berlin.de/wiki/images/6/6d/Miaskiewicz_%282011%29.pdf

Personas and user-centered design: How can personas benefit product design processes?

This paper reports the results of a recent survey of user-centered design (UCD) practitioners. The survey involved over a hundred respondents who were CHI'2000 attendees or current UPA members. The paper identifies the most widely used methods and processes, the key factors that predict success, and the critical tradeoffs practitioners must make in applying UCD methods and processes. Results show that cost-benefit tradeoffs are a key consideration in the adoption of UCD methods. Measures of UCD effectiveness are lacking and rarely applied. There is also a major discrepancy between the commonly cited measures and the actually applied ones. These results have implications for the introduction, deployment, and execution of UCD projects

https://www.it.uu.se/grad/courses/qualresearch/teachingplan/p471-vredenburg.pdf

A survey of user-centered design practice

User-Centered Design (UCD) is a multidisciplinary design approach based on the active involvement of users to improve the understanding of user and task requirements, and the iteration of design and evaluation. It is widely considered the key to product usefulness and usability---an effective approach to overcoming the limitations of traditional system-centered design. Much has been written in the research literature about UCD. As further proof of internationally endorsed best practice, UCD processes are also defined in ISO documents, including ISO 13407 and the associated technical report, ISO TR 18529. Increasingly, UCD has become part of the cultural vernacular of the executives and managers who drive technology development in companies of all sizes.

The state of user-centered design practice

Background. We identified the need to develop a scientifically rigorous measure of health-related quality of life (HRQL) in dementia that would be appropriate for use at all stages of dementia severity and would be available in both self- and proxy-report versions.Method. We used standard psychometric methods to eliminate items with poor psychometric properties (item-reduction field test) and to assess the acceptability, reliability and validity of the item-reduced instruments (psychometric evaluation field test). We developed and validated two versions of DEMQOL: a 28-item interviewer-administered questionnaire that is self-reported by the person with dementia (DEMQOL) and a 31-item interviewer-administered questionnaire that is proxy-reported by a caregiver (DEMQOL-Proxy).Results. DEMQOL shows high reliability (internal consistency and test–retest) and moderate validity in people with mild/moderate dementia. DEMQOL-Proxy shows good acceptability and internal consistency and moderate evidence of validity in people with mild/moderate and severe dementia. Test–retest reliability and performance in people with severe dementia need further testing.Conclusions. DEMQOL and DEMQOL-Proxy show psychometric properties that are comparable with the best available dementia-specific measures of HRQL. We recommend that DEMQOL and DEMQOL-Proxy are used together. Reliability and validity need to be confirmed in independent samples and responsiveness needs to be evaluated.

Development of a new measure of health-related quality of life for people with dementia: DEMQOL.

This paper reports the results of a recent survey involving over one hundred leading professionals of user-centered design (UCD). The survey covered a broad range of issues ranging from the profile of a typical UCD project including the percentage of total budget on UCD, organizational impact of UCD, measures of UCD success, and the most widely used methods and techniques. Results show that cost-benefit tradeoffs are a key consideration in the adoption of UCD methods. Measures of UCD effectiveness are lacking and rarely applied. There is a major discrepancy between the commonly cited measures and what were actually applied.

/pdf/user-centered-design-methods-in-practice-a-survey-of-the-19pocvg7cm.pdf

User-centered design methods in practice: a survey of the state of the art

All-atom molecular dynamics simulations have been used to investigate the adsorption of low molecular weight hyaluronic acid to lipid membranes. We have determined the interactions that govern the adsorption of three different molecular weight hyaluronic acid molecules (0.4, 3.8 & 15.2 kDa) to lipid bilayers that are representative of the surface-active phospholipid bilayers found in synovial joints. We have found that both direct hydrogen bonds and water-mediated interactions with the lipid headgroups play a key role in the binding of hyaluronic acid to the lipid bilayer. The water-mediated interactions become increasingly important in stabilising the adsorbed hyaluronic acid molecules as the molecular weight of hyaluronic acid increases. We also observe a redistribution of ions around bound hyaluronic acid molecules and the associated lipid headgroups, and that the degree of redistribution increases with the molecular weight of hyaluronic acid. By comparing this behaviour to that observed in simulations of the charge-neutral polysaccharide dextran (MW ∼ 15 kDa), we show that this charge redistribution leads to an increased alignment of the lipid headgroups with the membrane normal, and therefore to more direct and water-mediated interactions between hyaluronic acid and the lipid membrane. These findings provide a detailed understanding of the general structure of hyaluronic acid–lipid complexes that have recently been presented experimentally, as well as a potential mechanism for their enhanced tribological properties.

Paul Smith

Papers

A survey of user-centered design practice

The state of user-centered design practice

Development of a new measure of health-related quality of life for people with dementia: DEMQOL.

User-centered design methods in practice: a survey of the state of the art

On the interaction of hyaluronic acid with synovial fluid lipid membranes