Metastability in pressure-induced structural transformations of CdSe/ZnS core/shell nanocrystals

The kinetics and thermodynamics of structural transformations under pressure depend strongly on particle size due to the influence of surface free energy. By suitable design of surface structure, composition, and passivation it is possible, in principle, to prepare nanocrystals in structures inaccessible to bulk materials. However, few realizations of such extreme size-dependent behavior exist. Here we show with molecular dynamics computer simulation that in a model of CdSe/ZnS core/shell nanocrystals the core high pressure structure can be made metastable under ambient conditions by tuning the thickness of the shell. In nanocrystals with thick shells, we furthermore observe a wurtzite to NiAs transformation, which does not occur in the pure bulk materials. These phenomena are linked to a fundamental change in the atomistic transformation mechanism from heterogenous nucleation at the surface to homogenous nucleation in the crystal core. Our results suggest a new route towards expanding the range of available nanoscale materials

Off-target effects of bacillus Calmette–Guérin vaccination on immune responses to SARS-CoV-2: implications for protection against severe COVID-19

Background and objectives: Because of its beneficial off-target effects against non-mycobacterial infectious diseases, bacillus Calmette–Guérin (BCG) vaccination might be an accessible early intervention to boost protection against novel pathogens. Multiple epidemiological studies and randomised controlled trials (RCTs) are investigating the protective effect of BCG against coronavirus disease 2019 (COVID-19). Using samples from participants in a placebo-controlled RCT aiming to determine whether BCG vaccination reduces the incidence and severity of COVID-19, we investigated the immunomodulatory effects of BCG on in vitro immune responses to SARS-CoV-2. Methods: This study used peripheral blood taken from participants in the multicentre RCT and BCG vaccination to reduce the impact of COVID-19 on healthcare workers (BRACE trial). The whole blood taken from BRACE trial participants was stimulated with γ-irradiated SARS-CoV-2-infected or mock-infected Vero cell supernatant. Cytokine responses were measured by multiplex cytokine analysis, and single-cell immunophenotyping was made by flow cytometry. Results: BCG vaccination, but not placebo vaccination, reduced SARS-CoV-2-induced secretion of cytokines known to be associated with severe COVID-19, including IL-6, TNF-α and IL-10. In addition, BCG vaccination promoted an effector memory phenotype in both CD4+ and CD8+ T cells, and an activation of eosinophils in response to SARS-CoV-2. Conclusions: The immunomodulatory signature of BCG’s off-target effects on SARS-CoV-2 is consistent with a protective immune response against severe COVID-19

Optimizing the Day to Day Operation of Utility Systems

At the 2002 IETC, Linnhoff March presented an overview of spreadsheet-based software packages to rigorously model site utility systems. Such models allow the user to plan future scenarios that might impact upon the system operation (energy saving projects, production changes, new equipment, future energy tariffs, etc). Indeed, since last year, the DOE has made utility system template models freely available to industrial users as reported elsewhere at the 2003 IETC. Until last year, most industrial applications of this utility system software were set up for planning purposes, largely off-line. More recently, these applications have become more sophisticated and can operate on-line in real time. They include complex optimization routines to ensure that the utility system is always being operated in the best possible way under any prevailing conditions of production, energy tariffs and other variables. These optimizer models typically reduce day-to-day utility system operating costs by between 2 and 5%

Bathymetric and terminus evolution as determined by remote-sensing techniques: Tasman Glacier, New Zealand

Global glacier recession is increasing the number of glaciers that terminate in proglacial lakes, yet knowledge about the processes that drive ice-berg calving are still poorly understood. This knowledge-gap is in part due to the challenge of obtaining good data sets in a highly dynamic and dangerous environment. We are using emerging remote technologies, in the form of a remote controlled jet boat to survey bathymetry, and Structure from Motion (SfM) to characterise terminus morphology, to better understand relationships between lake growth and terminus evolution. Comparison of results between the jet boat mounted dual-frequency Garmin fish-finder with an Odom Echotrac DF3200 MKII with 200/38 kHz dual-frequency transducer, showed that after a sound velocity adjustment, the remote survey obtained depth data within ± 1 m of the higher grade survey equipment. A maximum water depth of 240 m was recorded 250 m away from the terminus, and the sub-aerial cliff height ranged from 5-44 m. However in some regions, water depth was 180 m only 20 m away from the calving face. Here the sub-aerial cliff height was around 20-25 m, meaning portions of the terminus were, or very close to, buoyancy. A sub-aqueous ice-ramp, 30 m below the water, extended out into the lake from the terminus for approximately 80 m in the central-eastern region. Despite a lake expansion of nearly 1 km since the survey of Dykes et al. (2011), the spatial similarity of the sub-aqueous ramp may indicate that other processes, for example, subglacial hydrology, have influence on the evolving terminus morphology

The Steam System Assessment Tool (SSAT): Estimating Steam System Energy, Cost, and Emission Savings

The U. S. Department of Energy's (DOE) Industrial Technology Program BestPractices Steam effort is developing a number of software tools to assist industrial energy users to improve the efficiency of their steam system. A major new BestPractices Steam software tool- the Steam System Assessment Tool (SSAT) -was released in December 2002 for public use. The SSAT can be applied to steam systems to quantify the magnitude- energy, cost, and emission savings- of key potential steam system improvement opportunities. This paper describes the key attributes of the SSAT, how the tool was developed, and the major benefits that can be gained from using the tool

Glacier retreat: Feedbacks and implications for glacier tourism

Since the culmination of the most recent advance period in 2008/09, the Fox and Franz Josef Glaciers situated on the West Coast of New Zealand, have lost around 500 m in length and experienced significant ice thinning in their lower regions. But even as the glaciers rapidly retreat, they remain some of New Zealand’s most popular tourist attractions, with over 300,000 international tourists visiting the glacier region each year. In this research we take a multidisciplinary approach combining cutting-edge technology (unmanned aerial surveys and structure from motion modelling) to measure and monitor the rapidly changing physical characteristics of the glaciers, along with face-to-face semi-structured interviews with local tourism stakeholders (n=13) and visitor interviews (n=500), to explore the impact of these changes on the visitor experience. It was found that in addition to shortening and thinning, the region of the Fox Glacier that is heavily utilised for tourism is becoming increasingly debris-covered. This is due to melt-out of englacial debris and increased rockfall from the surrounding recently exposed valley slopes. With thinning the previously convex glacier cross-profile has flattened and modelling has demonstrated that falling rocks can now travel up to 50 m further out onto the glacier surface than was the case in 2008/09 – potentially into regions utilised for guided glacier walks. Overwhelmingly, the majority of the visitors surveyed expected the glaciers to get smaller in the future, and a number identified the importance of seeing the glaciers before they disappeared due to climate-related change. Interestingly, some stakeholder interviews revealed local optimism in that the glacier will readvance in the future, and that the tourists will continue to visit. When visitors were asked if they would still visit the glaciers even if the only way to see them was by helicopter, over one-half of respondents indicated they would still visit. By integrating physical and social perspectives we gain greater understanding of the impacts that climate change will have on glacier tourism in New Zealand