The heat capacity of the restricted primitive model electrolyte

The constant-volume heat capacity, C_V(T, rho), of the restricted primitive model (RPM) electrolyte is considered in the vicinity of its critical point. It is demonstrated that, despite claims, recent simulations for finite systems do not convincingly indicate the absence of a divergence in C_V(T, rho)--which would point to non-Ising-type criticality. The strong qualitative difference between C_V for the RPM and for a Lennard-Jones fluid is shown to result from the low critical density of the former. If one considers the theoretically preferable configurational heat-capacity density, C_V/V, the finite-size results for the two systems display qualitatively similar behavior on near-critical isotherms.Comment: 5 Pages, including 5 EPS figures. Also available as PDF file at http://pallas.umd.edu/~luijten/erikpubs.htm

Screening in Ionic Systems: Simulations for the Lebowitz Length

Simulations of the Lebowitz length, $\xi_{\text{L}}(T,\rho)$, are reported for t he restricted primitive model hard-core (diameter $a$) 1:1 electrolyte for densi ties $\rho\lesssim 4\rho_c$ and $T_c \lesssim T \lesssim 40T_c$. Finite-size eff ects are elucidated for the charge fluctuations in various subdomains that serve to evaluate $\xi_{\text{L}}$. On extrapolation to the bulk limit for $T\gtrsim 10T_c$ the low-density expansions (Bekiranov and Fisher, 1998) are seen to fail badly when $\rho > {1/10}\rho_c$ (with $\rho_c a^3 \simeq 0.08$). At highe r densities $\xi_{\text{L}}$ rises above the Debye length, \xi_{\text{D}} \prop to \sqrt{T/\rho}, by 10-30% (upto $\rho\simeq 1.3\rho_c$); the variation is portrayed fairly well by generalized Debye-H\"{u}ckel theory (Lee and Fisher, 19 96). On approaching criticality at fixed $\rho$ or fixed $T$, $\xi_{\text{L}}(T, \rho)$ remains finite with $\xi_{\text{L}}^c \simeq 0.30 a \simeq 1.3 \xi_{\text {D}}^c$ but displays a weak entropy-like singularity.Comment: 4 pages 5 figure

The Integrative Expert: Moral, Epistemic, and Poietic Virtues in Transformation Research

Over the past 50 years, policy makers have sought to shape new and emerging technologies in light of societal risks, public values, and ethical concerns. While much of this work has taken place during “upstream” research prioritization and “downstream” technology regulation, the actual “midstream” work of engineers and other technical experts has increasingly been seen as a site for governing technology in society. This trend towards “socio-technical integration” is reflected in various governance frameworks such as Sustainable Development (SD), Technology Assessment (TA), and Responsible Innovation (RI) that are at the center of transformation research. Discussions around SD, TA, and RI often focus on meso- and macro-level processes and dynamics, with less attention paid to the qualities of individuals that are needed to support transformation processes. We seek to highlight the importance of micro-level practices by drawing attention to the virtues of technical experts. Drawing on empirical study results from embedding philosophical-reflective dialogues within science and engineering laboratories, we claim that poietic, as well as moral and epistemic, virtues belong to those required of technical experts who foster integrative practices in transformation research

The impact of lead time on truckload transportation rates

Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2008.Includes bibliographical references (leaves 80-81).The objective of this thesis was to analyze truckload shipment transactions in order to determine if rates are impacted by tender lead time, which is the amount of time between when a carrier is offered a load to when the load needs to be picked up. The research specifically focused on how tender rejections by carriers are the ultimate driver of transportation cost variances since most rates are contractually fixed in advance. The data revealed a strong correlation between tender rejections and increased costs. Many factors affect transportation costs. The transportation model in the paper included three key baseline factors: distance, origin, and destination of the load. The model also included tender and pick up day of week activity, economies of scale, carrier size, and tender lead time to quantify how the factors influence the cost of a load. The research suggests that even though the baseline factors dominate the cost of most loads, shippers can create savings by modifying business policy with regard to tender lead time and other factors included in the model.by Erik R. Caldwell and Bryan C. Fisher.M.Eng.in Logistic

Trends and Regional Variation in Hip, Knee and Shoulder Replacement

Analyzes patterns in underuse or overuse of joint replacements among Medicare beneficiaries by geographic regions and race/ethnicity. Explores underlying factors and highlights the need for physician and patient education and shared decision making

From Affect to Action:Choices in Attending to Disconcertment in Interdisciplinary Collaborations

Reports from integrative researchers who have followed calls for sociotechnical integration emphasize that the potential of interdisciplinary collaboration to inflect the social shaping of technoscience is often constrained by their liminal position. Integrative researchers tend to be positioned as either adversarial outsiders or co-opted insiders. In an attempt to navigate these dynamics, we show that attending to affective disturbances can open up possibilities for productive engagements across disciplinary divides. Drawing on the work of Helen Verran, we analyze “disconcertment” in three sociotechnical integration research studies. We develop a heuristic that weaves together disconcertment, affective labor, and responsivity to analyze the role of the body in interdisciplinary collaborations. We draw out how bodies do affective labor when generating responsivity between collaborators in moments of disconcertment. Responsive bodies can function as sensors, sources, and processors of disconcerting experiences of difference. We further show how attending to disconcertment can stimulate methodological choices to recognize, amplify, or minimize the difference between collaborators. Although these choices are context-dependent, each one examined generates responsivity that supports collaborators to readjust the technical in terms of the social. This analysis contributes to science and technology studies scholarship on the role of affect in successes and failures of interdisciplinary collaboration

From Affect to Action: Choices in Attending to Disconcertment in Interdisciplinary Collaborations

Reports from integrative researchers who have followed calls for sociotechnical integration emphasize that the potential of interdisciplinary collaboration to inflect the social shaping of technoscience is often constrained by their liminal position. Integrative researchers tend to be positioned as either adversarial outsiders or co-opted insiders. In an attempt to navigate these dynamics, we show that attending to affective disturbances can open up possibilities for productive engagements across disciplinary divides. Drawing on the work of Helen Verran, we analyze “disconcertment” in three sociotechnical integration research studies. We develop a heuristic that weaves together disconcertment, affective labor, and responsivity to analyze the role of the body in interdisciplinary collaborations. We draw out how bodies do affective labor when generating responsivity between collaborators in moments of disconcertment. Responsive bodies can function as sensors, sources, and processors of disconcerting experiences of difference. We further show how attending to disconcertment can stimulate methodological choices to recognize, amplify, or minimize the difference between collaborators. Although these choices are context-dependent, each one examined generates responsivity that supports collaborators to readjust the technical in terms of the social. This analysis contributes to science and technology studies scholarship on the role of affect in successes and failures of interdisciplinary collaboration