Adsorption on carbon nanotubes: quantum spin tubes, magnetization plateaus, and conformal symmetry

We formulate the problem of adsorption onto the surface of a carbon nanotube as a lattice gas on a triangular lattice wrapped around a cylinder. This model is equivalent to an XXZ Heisenberg quantum spin tube. The geometric frustration due to wrapping leads generically to four magnetization plateaus, in contrast to the two on a flat graphite sheet. We obtain analytical and numerical results for the magnetizations and transition fields for armchair, zig-zag and chiral nanotubes. The zig-zags are exceptional in that one of the plateaus has extensive zero temperature entropy in the classical limit. Quantum effects lift up the degeneracy, leaving gapless excitations which are described by a $c=1$ conformal field theory with compactification radius quantized by the tube circumference.Comment: 5 pages, 6 figure

Ablative Thermal Protection System (TPS) Margin Study

Predicting the reliability of the heat shield for crewed space vehicles has been a topic of continuing interest within NASA for many years. The design of a thermal protection system (TPS) is subject to numerous large sources of uncertainty and reliability assessments of such TPS are rare. The proposed talk discusses both the application of Design Of Experiments (DOE) to developing a new arc jet testing campaign for a given TPS and the reliability assessment conducted for the same TPS for a crewed space capsule (similar to Apollo capsules) to withstand re-entry to earth from space. The objectives of the study were to 1) provide recommendations for a planned arc jet testing campaign, 2) determine the design reliability of a proposed TPS, and 3) conduct a sensitivity analysis to determine the effect of input parameters and user choices on the TPS thermal design reliability. The development of a recommended arc jet test matrix employed a combination of techniques based on the analysis of variance (ANOVA) statistical methodology. The techniques employed include DOE, response surface (RS) methodology and uncertainty quantification (UQ). The recommended test matrix consisted of 30 test cases and includes four replicated condition pairs. Randomization was used to establish the test order, the testing facility, and the test sample cut pattern from three lots of material. The resulting arc jet test matrix was a compromise between one derived from statistical DOE techniques and the existing capabilities of arc jet test facilities located at NASA JSC and ARC. Statistical metrics were employed to objectively compare the assessment-derived matrix to an existing testing proposal. Five of the six metrics examined favored the new proposed test plan over the existing proposed test plan; one of the metrics (and, perhaps, the most important) strongly favored the new test plan proposal over the existing test plan. The reliability assessment investigated the sensitivity of reliability estimates to various input parameters, which included multiple studies to examine the total bond line temperature reliability based on 7 body point locations for 2 proposed trajectories. Each body point and trajectory combination was subjected to 5 different combinations of trajectory and aerothermal environment assumptions. The reliability was assessed based on a composite material failure criterion, which associated a greater probability of system failure proportional with the exceedance of an assumed safe bond line temperature limit. The study also investigated the sensitivity of reliability predictions to various input and problem formulation parameters. A large, statistically significant difference was found in the estimated TPS reliability when considering various formulations of the reliability problem, including the use of different failure conditions. The proposed talk will summarize the work performed in these areas and highlight some of the findings and recommendations that emerged from the work

Cryo-EM model of the bullet-shaped vesicular stomatitis virus.

Vesicular stomatitis virus (VSV) is a bullet-shaped rhabdovirus and a model system of negative-strand RNA viruses. Through direct visualization by means of cryo-electron microscopy, we show that each virion contains two nested, left-handed helices: an outer helix of matrix protein M and an inner helix of nucleoprotein N and RNA. M has a hub domain with four contact sites that link to neighboring M and N subunits, providing rigidity by clamping adjacent turns of the nucleocapsid. Side-by-side interactions between neighboring N subunits are critical for the nucleocapsid to form a bullet shape, and structure-based mutagenesis results support this description. Together, our data suggest a mechanism of VSV assembly in which the nucleocapsid spirals from the tip to become the helical trunk, both subsequently framed and rigidified by the M layer

National HPCC Software Exchange

This report describes an effort to construct a National HPCC Software Exchange (NHSE). This system shows how the evolving National Information Infrastructure (NII) can be used to facilitate sharing of software and information among members of the High Performance Computing and Communications (HPCC) community. To access the system use the URL: http://www.netlib.org/nse/

CIAS-DM: A Model-Based, Human-Centered Architectural Modeling Method + Tool

A recent trend in architecture is for the built environment pro-actively contributes to enhancing human health, well-being, performance, and social interactions in measurable, predictable, and adaptable ways. Buildings are becoming interfaces and digital machines and their roles and capabilities are expanding. Accommodating this trend will require architectural design methods and tools to evolve. Sensing, monitoring, actuation, intelligence, and communication subsystems are now integral components of environmental designers’ vocabularies and considerations when designing space and form. At present, the theories, methods, and tools for representing and incorporating these elements during design do not exist. Developing these artifacts is an active area of research. This dissertation focuses on representing the affordances of complex, interactive, architectural systems (CIAS) and proposes, evaluates, and refines the Complex, Interactive, Architectural Systems Design Methodology (CIAS-DM). The purpose of CIAS-DM is to aid designers in making sure they understand the design challenge well at the start of the project. The Validation Square Research Design is used to evaluate CIAS-DM. Results are preliminary, but indicate that using a method similar to CIAS-DM may be useful for helping designers manage the scope of complex,interactive design challenges

Day Centres for Homeless People in South London: Early Learning Points from Operating During the First COVID-19 Lockdown in England

Context: Many day centres for homeless people remained open during the first national lockdown in England following the COVID-19 pandemic. Lacking any official guidance on how to adapt, day centres for homeless people had to navigate risks of infection and changes in the situation of homeless people during this time. Objective: This small study aimed to discover how some day centres for homeless people approached and experienced the implications of lockdown. The objective was to draw early learning points to inform further research on the future trajectory of day centre provision for homeless people during the pandemic and beyond. Methods: This rapid qualitative study included semi-structured phone interviews with day centre managers (n = 5) and a systematic search of public facing websites of day centres (n = 10) across four South London boroughs. Data were analysed inductively, using the framework method. Findings: Findings indicate three learning points 1: the importance of strong networks between day centres with local authorities and other organisations for homeless people to enable services to provide humanitarian assistance, 2: the significance of day centres in their role as humanitarian assistants as a first point of contact for newly homeless people 3: the value of a central information hub. Limitations: The regional focus on South London and the sample size, which reflects ethical imperatives involved in avoiding undue pressure on day centre staff during the COVID-19 pandemic, limit this study. The findings are to be considered as a springboard for in-depth research into day centres’ support for homeless people during and after the COVID-19 pandemic. Implications: Findings are valuable as a snapshot of this largely under-researched group of services and service users during the first lockdown. Further research based on the findings could lead to good practice examples to inform the future trajectory of social care provision for homeless people

Fryer control strategy improvement:towards acrylamide reduction in crisp manufacture

This paper describes research efforts to improve the operation of industrial scale crisp fryers to ensure that product quality targets are exceeded. The work described was undertaken within a project whose aim is to minimise the acrylamide formation arising during processing operations. The existing fryer temperature control scheme was found to be sub-optimal from an acrylamide perspective and involved considerable operator intervention, particularly at fryer start-up. A new temperature control system was designed and implemented to overcome the shortcomings of the existing strategy. Fryer temperature and crisp moisture were regulated effectively through gas flow and dwell time modifications. Interactions between loops were compensated for and start-up was automated to reduce the impact of operator-to-operator variation. The resulting scheme was found to deliver much-improved temperature control which will lead to a resultant decrease in acrylamide formation

Polyelectrolyte Complex Nanoparticles for Protection and Delayed Release of Enzymes in Alkaline pH and at Elevated Temperature during Hydraulic Fracturing of Oil Wells

Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive version is available at www3.interscience.wiley.comPolyethylenimine-dextran sulfate polyelectrolyte complexes (PEC) were used to entrap two enzymes used to degrade polymer gels following hydraulic fracturing of oil wells in order to obtain delayed release and to protect the enzyme from harsh conditions. Degradation, as revealed by reduction in viscoelastic moduli, of borate-crosslinked hydroxypropyl guar gel by commercial enzyme loaded in polyelectrolyte nanoparticles was delayed up to 11 hours, compared to about three hours for equivalent systems where the enzyme mixture was not entrapped. PEC nanoparticles also protected both enzymes from denaturation at elevated temperature and pH

TRY plant trait database - enhanced coverage and open access

Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives