Stochastic Generation of Particle Structures with Controlled Degree of Heterogeneity

The recently developed void expansion method (VEM) allows for an efficient generation of porous packings of spherical particles over a wide range of volume fractions. The method is based on a random placement of the structural particles under addition of much smaller "void-particles" whose radii are repeatedly increased during the void expansion. Thereby, they rearrange the structural particles until formation of a dense particle packing and introduce local heterogeneities in the structure. In this paper, microstructures with volume fractions between 0.4 and 0.6 produced by VEM are analyzed with respect to their degree of heterogeneity (DOH). In particular, the influence of the void- to structural particle number ratio, which constitutes a principal VEM-parameter, on the DOH is studied. The DOH is quantified using the pore size distribution, the Voronoi volume distribution and the density-fluctuation method in conjunction with fit functions or integral measures. This analysis has revealed that for volume fractions between 0.4 and 0.55 the void-particle number allows for a quasi-continuous adjustment of the DOH. Additionally, the DOH-range of VEM-generated microstructures with a volume fraction of 0.4 is compared to the range covered by microstructures generated using previous Brownian dynamics simulations, which represent the structure of coagulated colloidal suspensions. Both sets of microstructures cover similarly broad and overlapping DOH-ranges, which allows concluding that VEM is an efficient method to stochastically reproduce colloidal microstructures with varying DOH.Comment: 10 pages, 7 figure

Scale Models

Introduction: Without being informed of the expected product, the students will make a Play-doh model of the Earth-Moon system, scaled to size and distance. The facilitator will reveal the true identity of the system at the conclusion of the activity. During the construction phase, students try to guess what members of the solar system their model represents. Each group receives different amounts of Play-doh, with each group assigned a color (red, blue, yellow, white). At the end, groups set up their models and inspect the models of other groups. They report patterns of scale that they notice; as the amount of Play-doh increases, for example, so do the size and distance of the model.McDonald Observator

Avoiding, acknowledging and fixing mistakes: investigation of a complaint about the Australian Community Pharmacy Authority

This investigation into the approval process for pharmaceuticals produced findings with broader lessons for Commonwealth agencies about the importance of proper program design, sharing information necessary to ensure proper outcomes and about service recovery arrangements when things go wrong. Foreword This is a report on the Ombudsman’s investigation of a complaint from a pharmacist about the Department of Health (DoH) and the Department of Human Services (DHS). The complainant contacted our office because he believed that a neighbouring pharmacy had been incorrectly approved to dispense medications under the Pharmaceutical Benefits Scheme (PBS). He told us the neighbouring pharmacy had relocated from its original site to one closer to his pharmacy than the rules allowed and this affected the viability of his business. He had unsuccessfully attempted to find out from DoH and DHS how this had happened, and was frustrated in his attempts to obtain a resolution. The approval process, jointly administered by DoH and DHS, relies upon the pharmacist applying for approval to provide evidence of the distances between their new location, old location and any other nearby pharmacies. There was an error in the measurement of the distances between the pharmacies. This error had come to the attention of the DoH before the approval was finalised, but the information was not relayed to DHS, which granted the approval without knowing that the application did not meet the location requirements. We found problems in the design of the pharmacy approval program, which focussed primarily on the interests of the applicant pharmacist without considering how to protect the interests of other pharmacies in the area. The program was delivered by two separate agencies, without sufficient regard to the need to share information in a timely way to ensure the integrity of the scheme. When it became apparent to DoH that DHS had made a decision based on wrong information, it initially failed to consult with DHS about how to put things right. In our view, DoH responded to the mistake in an inappropriately defensive way. Finally, when someone affected by the error complained about it, they were met by an unwillingness to explain or admit fault, and told their only option was to go to court. We were unable to obtain a remedy for the complainant. However, DoH agreed that, if the complainant makes a claim for compensation including evidence of loss, it will refer that claim to its Minister for consideration. We note that DoH has already implemented changes to its administrative procedures to address some of the problems that this complaint revealed. At the conclusion of this report we make four recommendations that we believe will further strengthen those arrangements, and provide a more open and responsive complaint process. While this complaint is about a very particular set of factual circumstances, we believe it holds broader lessons for Commonwealth agencies about the importance of proper program design, sharing information necessary to ensure proper outcomes and about service recovery arrangements when things go wrong

Transitions of care from child and adolescent mental health services to adult mental health services (TRACK Study) : a study of protocols in Greater London

Background: Although young people's transition from Child and Adolescent Mental Health Services (CAMHS) to Adult Mental Health Services (AMHS) in England is a significant health issue for service users, commissioners and providers, there is little evidence available to guide service development. The TRACK study aims to identify factors which facilitate or impede effective transition from CAHMS to AMHS. This paper presents findings from a survey of transition protocols in Greater London. Methods: A questionnaire survey (Jan-April 2005) of Greater London CAMHS to identify transition protocols and collect data on team size, structure, transition protocols, population served and referral rates to AMHS. Identified transition protocols were subjected to content analysis. Results: Forty two of the 65 teams contacted (65%) responded to the survey. Teams varied in type (generic/targeted/in-patient), catchment area (locality-based, wider or national) and transition boundaries with AMHS. Estimated annual average number of cases considered suitable for transfer to AMHS, per CAMHS team (mean 12.3, range 0–70, SD 14.5, n = 37) was greater than the annual average number of cases actually accepted by AMHS (mean 8.3, range 0–50, SD 9.5, n = 33). In April 2005, there were 13 active and 2 draft protocols in Greater London. Protocols were largely similar in stated aims and policies, but differed in key procedural details, such as joint working between CAHMS and AMHS and whether protocols were shared at Trust or locality level. While the centrality of service users' involvement in the transition process was identified, no protocol specified how users should be prepared for transition. A major omission from protocols was procedures to ensure continuity of care for patients not accepted by AMHS. Conclusion: At least 13 transition protocols were in operation in Greater London in April 2005. Not all protocols meet all requirements set by government policy. Variation in protocol-sharing organisational units and transition process suggest that practice may vary. There is discontinuity of care provision for some patients who 'graduate' from CAMHS services but are not accepted by adult services

DOH: A Content Delivery Peer-to-Peer Network

Many SMEs and non-pro¯t organizations su®er when their Web servers become unavailable due to °ash crowd e®ects when their web site becomes popular. One of the solutions to the °ash-crowd problem is to place the web site on a scalable CDN (Content Delivery Network) that replicates the content and distributes the load in order to improve its response time. In this paper, we present our approach to building a scalable Web Hosting environment as a CDN on top of a structured peer-to-peer system of collaborative web-servers integrated to share the load and to improve the overall system performance, scalability, availability and robustness. Unlike clusterbased solutions, it can run on heterogeneous hardware, over geographically dispersed areas. To validate and evaluate our approach, we have developed a system prototype called DOH (DKS Organized Hosting) that is a CDN implemented on top of the DKS (Distributed K-nary Search) structured P2P system with DHT (Distributed Hash table) functionality [9]. The prototype is implemented in Java, using the DKS middleware, the Jetty web-server, and a modi¯ed JavaFTP server. The proposed design of CDN has been evaluated by simulation and by evaluation experiments on the prototype

Yield curve in an estimated nonlinear macro model

What moves the yield curve? This paper specifies and estimates a dynamic stochastic general equilibrium (DSGE) model solved using a second order approximation to equilibrium conditions to answer this question. From the empirical analysis of U.S. data from 1983:Q1 to 2007:Q4, I find that the monetary policy response to the inflation gap defined by the difference between expected inflation and the inflation target of the central bank is a key channel transmitting macro shocks to the yield curve and that the degree of nominal rigidity determines which macro shocks are more important determinants of the yield curve. With the low degree of nominal rigidity, the inflation target of the central bank drives persistent movements of inflation and the yield curve while fluctuations of markups do so with the high degree of nominal rigidity. Although the estimated linear model puts nearly zero probability on the low degree of nominal rigidity, there is a positive probability mass in the nonlinear model. The analysis in this paper suggests caution on interpreting estimation results in which nonlinear terms of the DSGE model solution are ignored.

Stochastic generation of particle structures with controlled degree of heterogeneity

The recently developed void expansion method (VEM) allows for an efficient generation of porous packings of spherical particles over a wide range of volume fractions. The method is based on a random placement of the structural particles under addition of much smaller "void-particles” whose radii are repeatedly increased during the void expansion. Thereby, they rearrange the structural particles until formation of a dense particle packing and introduce local heterogeneities in the structure. In this paper, microstructures with volume fractions between 0.4 and 0.6 produced by VEM are analyzed with respect to their degree of heterogeneity (DOH). In particular, the influence of the void- to structural particle number ratio, which constitutes a principal VEM-parameter, on the DOH is studied. The DOH is quantified using the pore size distribution, the Voronoi volume distribution and the density-fluctuation method in conjunction with fit functions or integral measures. This analysis has revealed that for volume fractions between 0.4 and 0.55 the void-particle number allows for a quasi-continuous adjustment of the DOH. Additionally, the DOH-range of VEM-generated microstructures with a volume fraction of 0.4 is compared to the range covered by microstructures generated using previous Brownian dynamics simulations, which represent the structure of coagulated colloidal suspensions. Both sets of microstructures cover similarly broad and overlapping DOH-ranges, which allows concluding that VEM is an efficient method to stochastically reproduce colloidal microstructures with varying DO