Boltzmann, Gibbs and the Concept of Equilibrium

The Boltzmann and Gibbs approaches to statistical mechanics have very different definitions of equilibrium and entropy. The problems associated with this are discussed and it is suggested that they can be resolved, to produce a version of statistical mechanics incorporating both approaches, by redefining equilibrium not as a binary property (being/not being in equilibrium) but as a continuous property (degrees of equilibrium) measured by the Boltzmann entropy and by introducing the idea of thermodynamic-like behaviour for the Boltzmann entropy. The Kac ring model is used as an example to test the proposals

The spin-echo system reconsidered

Simple models have played an important role in the discussion of foundational issues in statistical mechanics. Among them the spin--echo system is of particular interest since it can be realized experimentally. This has led to inferences being drawn about approaches to the foundations of statistical mechanics, particularly with respect to the use of coarse-graining. We examine these claims with the help of computer simulations

Evaluating deliberative dialogues focussed on healthy public policy

Background: Deliberative dialogues have recently captured attention in the public health policy arena because they have the potential to address several key factors that influence the use of research evidence in policymaking. We conducted an evaluation of three deliberative dialogues convened in Canada by the National Collaborating Centre for Healthy Public Policy in order to learn more about deliberative dialogues focussed on healthy public policy. Methods: The evaluation included a formative assessment of participants’ views about and experiences with ten key design features of the dialogues, and a summative assessment of participants’ intention to use research evidence of the type that was discussed at the dialogue. We surveyed participants immediately after each dialogue was completed and again six months later. We analyzed the ratings using descriptive statistics and the written comments by conducting a thematic analysis. Results: A total of 31 individuals participated in the three deliberative dialogues that we evaluated. The response rate was 94% (N = 29; policymakers (n = 9), stakeholders (n = 18), researchers (n = 2)) for the initial survey and 56% (n = 14) for the follow-up. All 10 of the design features that we examined as part of the formative evaluation were rated favourably by all participant groups. The findings of the summative evaluation demonstrated a mean behavioural intention score of 5.8 on a scale from 1 (strongly disagree) to 7 (strongly agree). Conclusion: Our findings reinforce the promise of deliberative dialogues as a strategy for supporting evidence-informed public health policies. Additional work is needed to understand more about which design elements work in which situations and for different issues, and whether intention to use research evidence is a suitable substitute for measuring actual behaviour change

Lattice Model for water-solute mixtures

A lattice model for the study of mixtures of associating liquids is proposed. Solvent and solute are modeled by adapting the associating lattice gas (ALG) model. The nature of interaction solute/solvent is controlled by tuning the energy interactions between the patches of ALG model. We have studied three set of parameters, resulting on, hydrophilic, inert and hydrophobic interactions. Extensive Monte Carlo simulations were carried out and the behavior of pure components and the excess properties of the mixtures have been studied. The pure components: water (solvent) and solute, have quite similar phase diagrams, presenting: gas, low density liquid, and high density liquid phases. In the case of solute, the regions of coexistence are substantially reduced when compared with both the water and the standard ALG models. A numerical procedure has been developed in order to attain series of results at constant pressure from simulations of the lattice gas model in the grand canonical ensemble. The excess properties of the mixtures: volume and enthalpy as the function of the solute fraction have been studied for different interaction parameters of the model. Our model is able to reproduce qualitatively well the excess volume and enthalpy for different aqueous solutions. For the hydrophilic case, we show that the model is able to reproduce the excess volume and enthalpy of mixtures of small alcohols and amines. The inert case reproduces the behavior of large alcohols such as, propanol, butanol and pentanol. For last case (hydrophobic), the excess properties reproduce the behavior of ionic liquids in aqueous solution.Comment: 28 pages, 13 figure

Towards a better understanding of the nomenclature used in information-packaging efforts to support evidence-informed policymaking in low- and middle-income countries

Background: The growing recognition of the importance of concisely communicating research evidence and other policy-relevant information to policymakers has underpinned the development of several information-packaging efforts over the past decade. This has led to a wide variability in the types of documents produced, which is at best confusing and at worst discouraging for those they intend to reach. This paper has two main objectives: to develop a better understanding of the range of documents and document names used by the organizations preparing them; and to assess whether there are any consistencies in the characteristics of sampled documents across the names employed to label (in the title) or describe (in the document or website) them. Methods: We undertook a documentary analysis of web-published document series that are prepared by a variety of organizations with the primary intention of providing information to health systems policymakers and stakeholders, and addressing questions related to health policy and health systems with a focus on low- and middle-income countries. No time limit was set. Results: In total, 109 individual documents from 24 series produced by 16 different organizations were included. The name ‘policy brief/briefing’ was the most frequently used (39%) to label or describe a document, and was used in all eight broad content areas that we identified, even though they did not have obviously common traits among them. In terms of document characteristics, most documents (90%) used skimmable formats that are easy to read, with understandable, jargon-free, language (80%). Availability of information on the methods (47%) or the quality of the presented evidence (27%) was less common. One-third (32%) chose the topic based on an explicit process to assess the demand for information from policy makers and even fewer (19%) engaged with policymakers to discuss the content of these documents such as through merit review. Conclusions: This study highlights the need for organizations embarking on future information-packaging efforts to be more thoughtful when deciding how to name these documents and the need for greater transparency in describing their content, purpose and intended audience

Anomalous latent heat in non-equilibrium phase transitions

We study first-order phase transitions in a two-temperature system, where due to the time-scale separation all the basic thermodynamical quantities (free energy, entropy, etc) are well-defined. The sign of the latent heat is found to be counterintuitive: it is positive when going from the phase where the temperatures and the entropy are higher to the one where these quantities are lower. The effect exists only out of equilibrium and requires conflicting interactions. It is displayed on a lattice gas model of ferromagnetically interacting spin-1/2 particles.Comment: 4 pages, 2 figure

The global stock of research evidence relevant to health systems policymaking

Background: Policymakers and stakeholders need immediate access to many types of research evidence to make informed decisions about the full range of questions that may arise regarding health systems. Methods: We examined all types of research evidence about governance, financial and delivery arrangements, and implementation strategies within health systems contained in Health Systems Evidence (HSE) (http://www.healthsystemsevidence.org). The research evidence types include evidence briefs for policy, overviews of systematic reviews, systematic reviews of effects, systematic reviews addressing other questions, systematic reviews in progress, systematic reviews being planned, economic evaluations, and health reform and health system descriptions. Specifically, we describe their distribution across health system topics and domains, trends in their production over time, availability of supplemental content in various languages, and the extent to which they focus on low- and middle-income countries (LMICs), as well as (for systematic reviews) their methodological quality and the availability of user-friendly summaries. Results: As of July 2013, HSE contained 2,629 systematic reviews of effects (of which 501 are Cochrane reviews), 614 systematic reviews addressing other questions, 283 systematic reviews in progress, 186 systematic reviews being planned, 140 review-derived products (evidence briefs and overviews of systematic reviews), 1,669 economic evaluations, 1,092 health reform descriptions, and 209 health system descriptions. Most systematic reviews address topics related to delivery arrangements (n = 2,663) or implementation strategies (n = 1,653) with far fewer addressing financial (n = 241) or governance arrangements (n = 231). In addition, 2,928 systematic reviews have been quality appraised with moderate AMSTAR ratings found for reviews addressing governance (5.6/11), financial (5.9/11), and delivery (6.3/11) arrangements and implementation strategies (6.5/11); 1,075 systematic reviews have no independently produced user-friendly summary and only 737 systematic reviews have an LMIC focus. Literature searches for half of the systematic reviews (n = 1,584, 49%) were conducted within the last five years. Conclusions: Greater effort needs to focus on assessing whether the current distribution of systematic reviews corresponds to policymakers’ and stakeholders’ priorities, updating systematic reviews, increasing the quality of systematic reviews, and focusing on LMICs

Two-dimensional lattice-fluid model with water-like anomalies

We investigate a lattice-fluid model defined on a two-dimensional triangular lattice, with the aim of reproducing qualitatively some anomalous properties of water. Model molecules are of the "Mercedes Benz" type, i.e., they possess a D3 (equilateral triangle) symmetry, with three bonding arms. Bond formation depends both on orientation and local density. We work out phase diagrams, response functions, and stability limits for the liquid phase, making use of a generalized first order approximation on a triangle cluster, whose accuracy is verified, in some cases, by Monte Carlo simulations. The phase diagram displays one ordered (solid) phase which is less dense than the liquid one. At fixed pressure the liquid phase response functions show the typical anomalous behavior observed in liquid water, while, in the supercooled region, a reentrant spinodal is observed.Comment: 9 pages, 1 table, 7 figure

Monte Carlo Study of an Extended 3-State Potts Model on the Triangular Lattice

By introducing a chiral term into the Hamiltonian of the 3-state Potts model on a triangular lattice additional symmetries are achieved between the clockwise and anticlockwise states and the ferromagnetic state. This model is investigated using Monte Carlo methods. We investigate the full phase diagram and find evidence for a line tricritical points separating the ferromagnetic and antiferromagnetic phases.Comment: 6 pages, 10 figure