A Pseudo-Two-Dimensional (P2D) Model for FeS2 Conversion Cathode Batteries

Conversion cathode materials are gaining interest for secondary batteries due to their high theoretical energy and power density. However, practical application as a secondary battery material is currently limited by practical issues such as poor cyclability. To better understand these materials, we have developed a pseudo-two-dimensional model for conversion cathodes. We apply this model to FeS2 - a material that undergoes intercalation followed by conversion during discharge. The model is derived from the half-cell Doyle-Fuller-Newman model with additional loss terms added to reflect the converted shell resistance as the reaction progresses. We also account for polydisperse active material particles by incorporating a variable active surface area and effective particle radius. Using the model, we show that the leading loss mechanisms for FeS2 are associated with solid-state diffusion and electrical transport limitations through the converted shell material. The polydisperse simulations are also compared to a monodisperse system, and we show that polydispersity has very little effect on the intercalation behavior yet leads to capacity loss during the conversion reaction. We provide the code as an open-source Python Battery Mathematical Modelling (PyBaMM) model that can be used to identify performance limitations for other conversion cathode materials

High Depth-of-Discharge Zinc Rechargeability Enabled by a Self-Assembled Polymeric Coating

Zinc has the potential for widespread use as an environmentally friendly and cost-effective anode material pending the resolution of rechargeability issues caused by active material loss and shape change. Here, a self-assembled Nafion-coated Celgard 3501 (NC-Celgard) separator is shown to enable unprecedented cycle life of a Zn anode in alkaline electrolyte at high depth-of-discharge (DODZn). Using commercially relevant energy-dense electrodes with high areal capacities of 60 mAh cm–2, Zn–Ni cells tested at 20% DODZn cells achieve over 200 cycles while 50% DODZn cells achieve over 100 cycles before failure. The 20% and 50% DOD cells deliver an average of 132 and 180 Wh L–1 per cycle over their lifetime respectively. Rechargeability is attributed to the highly selective diffusion properties of the 300 nm thick negatively charged Nafion coating on the separator which prevents shorting by dendrites and inhibits redistribution of the active material. Crossover experiments show that the NC-Celgard separator is practically impermeable to zincate ([Zn(OH)4]2–), outperforming commercial Celgard, cellophane, Nafion 211 and 212 separators while still allowing hydroxide transport. This work demonstrates the efficacy of selective separators for increasing the cycle life of energy-dense Zn electrodes without adding significant volume or complexity to the system

Metal oxide coating of carbon supports for supercapacitor applications.

The global market for wireless sensor networks in 2010 will be valued close to $10 B, or 200 M units. TPL, Inc. is a small Albuquerque based business that has positioned itself to be a leader in providing uninterruptible power supplies in this growing market with projected revenues expected to exceed$26 M in 5 years. This project focused on improving TPL, Inc.'s patent-pending EnerPak{trademark} device which converts small amounts of energy from the environment (e.g., vibrations, light or temperature differences) into electrical energy that can be used to charge small energy storage devices. A critical component of the EnerPak{trademark} is the supercapacitor that handles high power delivery for wireless communications; however, optimization and miniaturization of this critical component is required. This proposal aimed to produce prototype microsupercapacitors through the integration of novel materials and fabrication processes developed at New Mexico Technology Research Collaborative (NMTRC) member institutions. In particular, we focused on developing novel ruthenium oxide nanomaterials and placed them into carbon supports to significantly increase the energy density of the supercapacitor. These improvements were expected to reduce maintenance costs and expand the utility of the TPL, Inc.'s device, enabling New Mexico to become the leader in the growing global wireless power supply market. By dominating this niche, new customers were expected to be attracted to TPL, Inc. yielding new technical opportunities and increased job opportunities for New Mexico

CSI: Dognapping workshop : an outreach experiment designed to produce students that are hooked on science.

The CSI: Dognapping Workshop is a culmination of the more than 65 Sandian staff and intern volunteers dedication to exciting and encouraging the next generation of scientific leaders. This 2 hour workshop used a 'theatrical play' and 'hands on' activities that was fun, exciting and challenging for 3rd-5th graders while meeting science curriculum standards. In addition, new pedagogical methods were developed in order to introduce nanotechnology to the public. Survey analysis indicated that the workshop had an overall improvement and positive impact on helping the students to understand concepts from materials science and chemistry as well as increased our interaction with the K-5 community. Anecdotal analyses showed that this simple exercise will have far reaching impact with the results necessary to maintain the United States as the scientific leader in the world. This experience led to the initiation of over 100 Official Junior Scientists

Critical Dimensions in Architectural Photography: Contributions to Architectural Knowledge

This paper illustrates and explores three critical dimensions of photography in architecture, each of which informs the production of images, texts, and other artifacts which establish what might be called a building’s media footprint. The paper’s broad goal is to question the extent to which these critical dimensions are relevant to architectural decision-making processes. Acknowledging that such dimensions as the ones examined here rarely predict an architect’s specific design decisions in a transparent manner, the paper discusses not only the decisions made by architects during the process of designing buildings, but the decisions made by critics, visitors, and members of the general public as they engage in activities such as visiting buildings, writing about them and, particularly, photographing them. First, the text discusses the potential of buildings to operate as mechanisms for producing images, in the sense originated by Beatriz Colomina. The question is developed through the analysis of the space of photography – mapping of points of view, directions of view, and fields of view of defined photographic collections. Secondly, it considers photography’s complicity in the canonization of buildings, and specifically, the extent to which photography is responsible for distinguishing between major and minor architectural works. Finally, the essay examines the erosion over time of photography’s historical power to frame when confronted with contemporary technologies of virtual reality and photo realistically rendered digital models. Each of these critical dimensions, or concepts, develops a specific aspect of how photographic information about buildings is organized, structured, and disseminated, and is thus only part of the larger project of architectural epistemology, which inquires into this wider field. This will be done through an examination of the Mies van der Rohe-designed Commons Building at ITT in Chicago and the evolution of its relationship with architectural photography and photographic representation – both on its own terms and through the prism of the Rem Koolhaas-designed McCormick Tribune Student Center, which adds to and incorporates the Commons Building. Until the end of the twentieth century, the Commons Building on the campus of the Illinois Institute of Technology was generally considered one of Mies van der Rohe’s lesser works. Reportedly neglected by its own architect during the design process, and frequently marginalized in academic discussions of the campus, when mentioned at all the building was often cited as an unrefined prototype of Crown Hall. This discourse took a new direction when in 1998, Rem Koolhaas/OMA won a design competition for a student center on the IIT campus: uniquely among the competition entries, Koolhaas’s design incorporated the Commons Building within a new context – what ultimately became the McCormick Tribune Campus Center (MTCC). When critics concluded that the incorporation of the Commons Building into the larger whole could compromise its integrity as an exemplar of Mies’s work, the building became the object of renewed interest and controversy. The two projects considered here show a clear evolution in architecture’s relationship with the photographic image. Specifically, the history of the Commons Building can be traced through photographs: during and shortly following its construction, the building was photographed as part of Mies’s own attention to publicity; it was documented as part of historical analyses; and over time it was visited and photographed by casual and amateur photographers. Following the competition results, photographs of the Commons Building were strategically deployed by both proponents and critics of Koolhaas’s design. Contemporary photographs of the building appear in architectural and campus guidebooks and on websites such as Flickr.com. Examining the ways in which photographs of the Commons Building appear in these various contexts allows discussion of the critical dimensions identified above and permits us to trace the evolution of the mutually reinforcing relationship between architecture and photography

A model for presenting accelerometer paradata in large studies : ISCOLE

Background: We present a model for reporting accelerometer paradata (process-related data produced from survey administration) collected in the International Study of Childhood Obesity Lifestyle and the Environment (ISCOLE), a multi-national investigation of >7000 children (averaging 10.5 years of age) sampled from 12 different developed and developing countries and five continents. Methods: ISCOLE employed a 24-hr waist worn 7-day protocol using the ActiGraph GT3X+. Checklists, flow charts, and systematic data queries documented accelerometer paradata from enrollment to data collection and treatment. Paradata included counts of consented and eligible participants, accelerometers distributed for initial and additional monitoring (site specific decisions in the face of initial monitoring failure), inadequate data (e.g., lost/malfunction, insufficient wear time), and averages for waking wear time, valid days of data, participants with valid data (>= 4 valid days of data, including 1 weekend day), and minutes with implausibly high values (>= 20,000 activity counts/min). Results: Of 7806 consented participants, 7372 were deemed eligible to participate, 7314 accelerometers were distributed for initial monitoring and another 106 for additional monitoring. 414 accelerometer data files were inadequate (primarily due to insufficient wear time). Only 29 accelerometers were lost during the implementation of ISCOLE worldwide. The final locked data file consisted of 6553 participant files (90.0% relative to number of participants who completed monitoring) with valid waking wear time, averaging 6.5 valid days and 888.4 minutes/day (14.8 hours). We documented 4762 minutes with implausibly high activity count values from 695 unique participants (9.4% of eligible participants and Conclusions: Detailed accelerometer paradata is useful for standardizing communication, facilitating study management, improving the representative qualities of surveys, tracking study endpoint attainment, comparing studies, and ultimately anticipating and controlling costs.Peer reviewe

Early warning signals of simulated Amazon rainforest dieback

Copyright © The Author(s) 2013. This article is published with open access at Springerlink.comWe test proposed generic tipping point early warning signals in a complex climate model (HadCM3) which simulates future dieback of the Amazon rainforest. The equation governing tree cover in the model suggests that zero and non-zero stable states of tree cover co-exist, and a transcritical bifurcation is approached as productivity declines. Forest dieback is a non-linear change in the non-zero tree cover state, as productivity declines, which should exhibit critical slowing down. We use an ensemble of versions of HadCM3 to test for the corresponding early warning signals. However, on approaching simulated Amazon dieback, expected early warning signals of critical slowing down are not seen in tree cover, vegetation carbon or net primary productivity. The lack of a convincing trend in autocorrelation appears to be a result of the system being forced rapidly and non-linearly. There is a robust rise in variance with time, but this can be explained by increases in inter-annual temperature and precipitation variability that force the forest. This failure of generic early warning indicators led us to seek more system-specific, observable indicators of changing forest stability in the model. The sensitivity of net ecosystem productivity to temperature anomalies (a negative correlation) generally increases as dieback approaches, which is attributable to a non-linear sensitivity of ecosystem respiration to temperature. As a result, the sensitivity of atmospheric CO2 anomalies to temperature anomalies (a positive correlation) increases as dieback approaches. This stability indicator has the benefit of being readily observable in the real world.NERCJoint DECC/Defra Met Office Hadley Centre Climate ProgrammeUniversity of Exete

Prevention of Hypovolemic Circulatory Collapse by IL-6 Activated Stat3

Half of trauma deaths are attributable to hypovolemic circulatory collapse (HCC). We established a model of HCC in rats involving minor trauma plus severe hemorrhagic shock (HS). HCC in this model was accompanied by a 50% reduction in peak acceleration of aortic blood flow and cardiomyocyte apoptosis. HCC and apoptosis increased with increasing duration of hypotension. Apoptosis required resuscitation, which provided an opportunity to intervene therapeutically. Administration of IL-6 completely reversed HCC, prevented cardiac dysfunction and cardiomyocyte apoptosis, reduced mortality 5-fold and activated intracardiac signal transducer and activator of transcription (STAT) 3. Pre-treatment of rats with a selective inhibitor of Stat3, T40214, reduced the IL-6-mediated increase in cardiac Stat3 activity, blocked successful resuscitation by IL-6 and reversed IL-6-mediated protection from cardiac apoptosis. The hearts of mice deficient in the naturally occurring dominant negative isoform of Stat3, Stat3β, were completely resistant to HS-induced apoptosis. Microarray analysis of hearts focusing on apoptosis related genes revealed that expression of 29% of apoptosis related genes was altered in HS vs. sham rats. IL-6 treatment normalized the expression of these genes, while T40214 pretreatment prevented IL-6-mediated normalization. Thus, cardiac dysfunction, cardiomyocyte apoptosis and induction of apoptosis pathway genes are important components of HCC; IL-6 administration prevented HCC by blocking cardiomyocyte apoptosis and induction of apoptosis pathway genes via Stat3 and warrants further study as a resuscitation adjuvant for prevention of HCC and death in trauma patients

Stellar Archaeology: a Keck Pilot Program on Extremely Metal-Poor Stars from the Hamburg/ESO Survey. II. Abundance Analysis

We present a detailed abundance analysis of 8 stars selected as extremely metal poor candidates from the Hamburg/ESO Survey (HES). For comparison, we have also analysed 3 extremely metal-poor candidates from the HK survey, and 3 additional bright metal-poor stars. With this work, we have doubled the number of extremely metal-poor stars ([Fe/H]$\le 3.0$) with high-precision abundance analyses. Our sample of extremely metal-poor candidates from the HES contains 3 stars with [Fe/H] $\le -3.0$, 3 more with [Fe/H]$\le -2.8$, and 2 stars that are only slightly more metal rich. Thus, the chain of procedures that led to the selection of these stars from the HES successfully provides a high fraction of extremely metal-poor stars. We verify that our stellar parameters, derived in Paper I, lead to acceptable ionization and excitation balances for Fe, ruling out substantial non-LTE effects in Fe. For the $\alpha-$elements Mg, Si, Ca, Ti, the light element Al, the iron-peak elements Sc, Cr, Mn, and the neutron capture elements Sr and Ba, we find trends in abundance ratios [X/Fe] similar to those found by previous studies. However,the scatter in most of these ratios, even at [Fe/H]$\le -3.0$ dex, is surprisingly small. Only Sr and Ba show scatter larger than the expected errors. Future work (the 0Z project) will provide much stronger constraints on the scatter (or lack thereof) in abundances for a greater number of stars. We discuss the implications of these results for the early chemical evolution of the Galaxy, including such issues as the number of contributing SN, and the sizes of typical fragments in which they were born. In addition, we have identified a very metal poor star that appears to be the result of the s-process chain, operating in a very metal-poor environment, with extremely enhanced C, Ba, and Pb, and somewhat enhanced Sr.Comment: 36 pages, 9 tables, 14 figures included; accepted for publication in the July 2002 issue of The Astronomical Journa