308 research outputs found
A computationally efficacious free-energy functional for studies of inhomogeneous liquid water
We present an accurate equation of state for water based on a simple
microscopic Hamiltonian, with only four parameters that are well-constrained by
bulk experimental data. With one additional parameter for the range of
interaction, this model yields a computationally efficient free-energy
functional for inhomogeneous water which captures short-ranged correlations,
cavitation energies and, with suitable long-range corrections, the non-linear
dielectric response of water, making it an excellent candidate for studies of
mesoscale water and for use in ab initio solvation methods.Comment: 6 pages, 5 figure
Evaluation of classical precipitation descriptions for Îłâ˛â˛(Ni3NbâD022) in Ni-base superalloys
The growth/coarsening kinetics of Îłâ˛â˛(Ni3NbâD022) precipitates have been found by numerous researchers to show an apparent correspondence with the classical (Ostwald ripening) equation outlined by Lifshitz, Slyozov and (separately) Wagner for a diffusion controlled regime. Nevertheless, a significant disparity between the actual precipitate size distribution shape and that predicted by LSW is frequently observed in the interpretation of these results, the origin of which is unclear. Analysis of the literature indicates one likely cause for this deviation from LSW for Îłâ˛â˛ precipitates is the âencounterâ phenomenon described by Davies et al. (Acta Metall 28(2):179â189, 1980) that is associated with secondary phases comprising a high volume fraction. Consequently, the distributions of both Îłâ˛â˛ precipitates described in the literature (Alloy 718) and measured in this research in Alloy 625 are analysed through employing the LifshitzâSlyozov-Encounter-Modified (LSEM) formulation (created by Davies et al.). The results of the LSEM analysis show good far better agreement than LSW with experimental distributions after the application of a necessary correction for what is termed in this research as âdirectional encounterâ. Moreover, the activation energy for Îłâ˛â˛ coarsening in Alloy 625 shows conformity with literature data once the effect of heterogeneous (on dislocations) precipitate nucleation at higher temperatures is accounted for
Community health workers and accountability: reflections from an international âthink-inâ
Community health workers (CHWs) are frequently put forward as a remedy for lack of health system capacity, including challenges associated with health service coverage and with low community engagement in the health system, and expected to enhance or embody health system accountability. During a âthink inâ, held in June of 2017, a diverse group of practitioners and researchers discussed the topic of CHWs and their possible roles in a larger âaccountability ecosystem.â This jointly authored commentary resulted from our deliberations. While CHWs are often conceptualized as cogs in a mechanistic health delivery system, at the end of the day, CHWs are people embedded in families, communities, and the health system. CHWsâ social position and professional role influence how they are treated and trusted by the health sector and by community members, as well as when, where, and how they can exercise agency and promote accountability. To that end, we put forward several propositions for further conceptual development and research related to the question of CHWs and accountability
Modelling Clock Synchronization in the Chess gMAC WSN Protocol
We present a detailled timed automata model of the clock synchronization
algorithm that is currently being used in a wireless sensor network (WSN) that
has been developed by the Dutch company Chess. Using the Uppaal model checker,
we establish that in certain cases a static, fully synchronized network may
eventually become unsynchronized if the current algorithm is used, even in a
setting with infinitesimal clock drifts
Topological Metal MoP Nanowire for Interconnect
The increasing resistance of Cu interconnects for decreasing dimensions is a
major challenge in continued downscaling of integrated circuits beyond the 7-nm
technology node as it leads to unacceptable signal delays and power consumption
in computing. The resistivity of Cu increases due to electron scattering at
surfaces and grain boundaries of the interconnects at the nanoscale.
Topological semimetals, owing to their topologically protected surface states
and suppressed electron backscattering, are promising material candidates to
potentially replace current Cu interconnects as low-resistance interconnects.
Here, we report the attractive resistivity scaling of topological metal MoP
nanowires and show that the resistivity values are comparable to those of Cu
interconnects below 500 nm cross-section areas. More importantly, we
demonstrate that the dimensional scaling of MoP nanowires, in terms of line
resistance versus total cross-sectional area, is superior to those of effective
Cu and barrier-less Ru interconnects, suggesting MoP is an attractive solution
to the current scaling challenge of Cu interconnects.Comment: 4 figure
1D-confined crystallization routes for tungsten phosphides
Topological materials confined in one-dimension (1D) can transform computing
technologies, such as 1D topological semimetals for nanoscale interconnects and
1D topological superconductors for fault-tolerant quantum computing. As such,
understanding crystallization of 1D-confined topological materials is critical.
Here, we demonstrate 1D-confined crystallization routes during
template-assisted nanowire synthesis where we observe diameter-dependent phase
selectivity for topological metal tungsten phosphides. A phase bifurcation
occurs to produce tungsten monophosphide and tungsten diphosphide at the
cross-over nanowire diameter of ~ 35 nm. Four-dimensional scanning transmission
electron microscopy was used to identify the two phases and to map
crystallographic orientations of grains at a few nm resolution. The 1D-confined
phase selectivity is attributed to the minimization of the total surface
energy, which depends on the nanowire diameter and chemical potentials of
precursors. Theoretical calculations were carried out to construct the
diameter-dependent phase diagram, which agrees with experimental observations.
Our find-ings suggest a new crystallization route to stabilize topological
materials confined in 1D.Comment: 5 figure
Robust transcriptome-wide discovery of RNA-binding protein binding sites with enhanced CLIP (eCLIP)
As RNA-binding proteins (RBPs) play essential roles in cellular physiology by interacting with target RNA molecules, binding site identification by UV crosslinking and immunoprecipitation (CLIP) of ribonucleoprotein complexes is critical to understanding RBP function. However, current CLIP protocols are technically demanding and yield low-complexity libraries with high experimental failure rates. We have developed an enhanced CLIP (eCLIP) protocol that decreases requisite amplification by ~1,000-fold, decreasing discarded PCR duplicate reads by ~60% while maintaining single-nucleotide binding resolution. By simplifying the generation of paired IgG and size-matched input controls, eCLIP improves specificity in the discovery of authentic binding sites. We generated 102 eCLIP experiments for 73 diverse RBPs in HepG2 and K562 cells (available at https://www.encodeproject.org), demonstrating that eCLIP enables large-scale and robust profiling, with amplification and sample requirements similar to those of ChIP-seq. eCLIP enables integrative analysis of diverse RBPs to reveal factor-specific profiles, common artifacts for CLIP and RNA-centric perspectives on RBP activity
Illustrating the impact of commercial determinants of health on the global COVID-19 pandemic: Thematic analysis of 16 country case studies
Previous research on commercial determinants of health has primarily focused on their impact on noncommunicable diseases. However, they also impact on infectious diseases and on the broader preconditions for health. We describe, through case studies in 16 countries, how commercial determinants of health were visible during the COVID-19 pandemic, and how they may have influenced national responses and health outcomes. We use a comparative qualitative case study design in selected low- middle- and high-income countries that performed differently in COVID-19 health outcomes, and for which we had country experts to lead local analysis. We created a data collection framework and developed detailed case studies, including extensive grey and peer-reviewed literature. Themes were identified and explored using iterative rapid literature reviews. We found evidence of the influence of commercial determinants of health in the spread of COVID-19. This occurred through working conditions that exacerbated spread, including precarious, low-paid employment, use of migrant workers, procurement practices that limited the availability of protective goods and services such as personal protective equipment, and commercial actors lobbying against public health measures. Commercial determinants also influenced health outcomes by influencing vaccine availability and the health system response to COVID-19. Our findings contribute to determining the appropriate role of governments in governing for health, wellbeing, and equity, and regulating and addressing negative commercial determinants of health.Toby Freeman ... Fran Baum ... Connie Musolino ... Joanne Flavel ... et al
Optimal Design of a Trickle Bed Reactor for Light Fuel Oxidative Desulfurization based on Experiments and Modelling
YesIn this work, the performance of oxidative desulfurization (ODS) of dibenzothiophene (DBT) in light gas oil (LGO) is evaluated with a homemade manganese oxide (MnO2/Îł-Al2O3) catalyst. The catalyst is prepared by Incipient Wetness Impregnation (IWI) method with air under moderate operating conditions. The effect of different reaction parameters such as reaction temperature, liquid hour space velocity and initial concentration of DBT are also investigated experimentally. Developing a detailed and a validated trickle bed reactor (TBR) process model that can be employed for design and optimization of the ODS process, it is important to develop kinetic models for the relevant reactions with high accuracy. Best kinetic model for the ODS process taking into account hydrodynamic factors (mainly, catalyst effectiveness factor, catalyst wetting efficiency and internal diffusion) and the physical properties affecting the oxidation process is developed utilizing data from pilot plant experiments. An optimization technique based upon the minimization of the sum of the squared error between the experimental and predicted composition of oxidation process is used to determine the best parameters of the kinetic models. The predicted product conversion showed very good agreement with the experimental data for a wide range of the operating condition with absolute average errors less than 5%
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