Search

The fabrication of metal–insulator– metal (MIM) diode using an ultrathin Al2O3 insulator layer, deposited using atomic layer deposition (ALD) is presented. The Al2O3 insulating layer was found to be highly uniform throughout the diode junction, effectively overcoming the main fabrication challenge in MIM diodes. The diodes exhibit strong non-linear current–voltage curves, have a typical zero-bias curvature coefficient of 5.4 V−1 and a zero-bias resistance of approximately 118 kΩ, a value considerably smaller than other MIM diode topologies and that allows more current to be rectified. Other results including current ratio and yield of the diode also competes favorably with the state-of-the-art MIM diodes such as the recently produced metal-octadecyltrichlorosilane (OTS)-metal structure.

Context: The Helmi streams are a kinematic substructure whose progenitor is likely a dwarf galaxy. Although 20 years have passed since their discovery, it is still unclear whether their members are chemically distinguishable from other halo stars in the Milky Way. Aim: We aim to precisely characterize the chemical properties of the Helmi streams. Methods: We analyzed high-resolution, high signal-to-noise ratio spectra for 11 Helmi stream stars through a line-by-line abundance analysis. We compared the derived abundances to homogenized literature abundances of the other halo stars, including those belonging to other kinematic substructures, such as Gaia-Enceladus and Sequoia. Results: Compared to typical halo stars, the Helmi stream members clearly show low values of [X/Fe] in elements produced by massive stars, such as Na and $\alpha$-elements. This tendency is seen down to metallicities of at least [Fe/H]$\sim -2.2$, suggesting type~Ia supernovae already started to contribute to the chemical evolution at this metallicity. We find that the [$\alpha$/Fe] ratio does not evolve significantly with metallicity, making the Helmi stream stars less distinguishable from Gaia-Enceladus stars at [Fe/H]$\gtrsim -1.5$. The almost constant but low value of [$\alpha$/Fe] might be indicative of quiescent star formation with low efficiency at the beginning and bursty star formation at later times. We also find extremely low values of [Y/Fe] at low metallicity, providing further support for the claim that light neutron-capture elements are deficient in Helmi streams. While Zn is deficient at low metallicity, it shows a large spread at high metallicity. The origin of the extremely low Y abundances and Zn variations remains unclear. Conclusion: The Helmi stream stars are distinguishable from the majority of the halo stars if homogeneously derived abundances are compared., Comment: Accepted version

Day-to-day variations in surface air temperature affect society in many ways, but daily surface air temperature measurements are not available everywhere. Therefore, a global daily picture cannot be achieved with measurements made in situ alone and needs to incorporate estimates from satellite retrievals. This article presents the science developed in the EU Horizon 2020–funded EUSTACE project (2015–19, www.eustaceproject.org) to produce global and European multidecadal ensembles of daily analyses of surface air temperature complementary to those from dynamical reanalyses, integrating different ground-based and satellite-borne data types. Relationships between surface air temperature measurements and satellite-based estimates of surface skin temperature over all surfaces of Earth (land, ocean, ice, and lakes) are quantified. Information contained in the satellite retrievals then helps to estimate air temperature and create global fields in the past, using statistical models of how surface air temperature varies in a connected way from place to place; this needs efficient statistical analysis methods to cope with the considerable data volumes. Daily fields are presented as ensembles to enable propagation of uncertainties through applications. Estimated temperatures and their uncertainties are evaluated against independent measurements and other surface temperature datasets. Achievements in the EUSTACE project have also included fundamental preparatory work useful to others, for example, gathering user requirements, identifying inhomogeneities in daily surface air temperature measurement series from weather stations, carefully quantifying uncertainties in satellite skin and air temperature estimates, exploring the interaction between air temperature and lakes, developing statistical models relevant to non-Gaussian variables, and methods for efficient computation.

BackgroundAt Bristol Dental Hospital, we received almost 5000 calls per week, and we were not answering over 60% of these. This led to numerous informal complaints from frustrated patients and families to clinicians and administrative staff, reducing patient experience and affecting staff morale.MethodWe set up a Task and Finish group with clinical and managerial leadership using staff engagement and a clear message to improve our performance. We agreed metrics and feedback to administrative teams about weekly performance.ResultsCalls received fell from nearly 5000 calls per week to under 3000. Calls answered when available; we term ‘when available’ to indicate during standard operating hours when the line is not already occupied. During core hours call answering improved significantly from around 35% to over 75%. Complaints have dropped significantly in the same time period.ReflectionsEffective leadership with staff engagement has improved telephony at a dental hospital in the UK significantly. This initiative has been adopted by other areas in the Trust and helped inform good practice around the Trust.

Context. The local stellar halo of the Milky Way contains the debris from several past accretion events. Aims. Here we study in detail the structure and properties of nearby debris associated with the Helmi streams, which was originally identified as an overdensity in integrals of motion space. Methods. We use 6D phase-space information from Gaia EDR3 combined with spectroscopic surveys, and we analyse the orbits and frequencies of the stars in the streams using various Galactic potentials. We also explore how the Helmi streams constrain the flattening, q, of the Galactic dark matter halo. Results. We find that the streams are split into substructures in integrals of motion space, most notably into two clumps in angular momentum space. The clumps have consistent metallicity distributions and stellar populations, supporting a common progeny. In all the realistic Galactic potentials explored, the Helmi streams’ stars depict a diffuse distribution close to Ωz/ΩR ∼ 0.7. At the same time, the reason for the substructure in angular momentum space appears to be a Ωz : Ωϕ resonance close to 1:1. This resonance is exactly 1:1 in the case where the (density) flattening of the dark halo is q = 1.2. For this halo shape, the substructure in angular momenta is also long-lasting. Conclusions. Our findings suggest that the structure of the Galactic potential leaves a clear imprint on the properties of phase-mixed debris streams.

The debris from past merger events is expected and, to some extent, known to populate the stellar halo near the Sun. We aim to identify and characterise such merger debris using Gaia DR3 data supplemented by metallicity and chemical abundance information from LAMOST LRS and APOGEE for halo stars within 2.5 kpc from the Sun. We utilise a single linkage-based clustering algorithm to identify over-densities in Integrals of Motion space that could be due to merger debris. Combined with metallicity information and chemical abundances, we characterise these statistically significant over-densities. We find that the local stellar halo contains 7 main dynamical groups, some of in-situ and some of accreted origin, most of which are already known. We report the discovery of a new substructure, which we name ED-1. In addition, we find evidence for 11 independent smaller clumps, 5 of which are new: ED-2, 3, 4, 5 and 6 are typically rather tight dynamically, depict a small range of metallicities, and their abundances when available, as well as their location in Integrals of Motion space, suggest an accreted origin. The local halo contains an important amount of substructure, of both in-situ and accreted origin., Comment: 7 pages, 5 figures, submitted to A&A, our catalogue and substructures will be made available online upon acceptance or before upon reasonable request

Archaeological investigations of faunal remains in Australia, particularly Pleistocene sites, have been limited in the specific study of microfauna. This research asked whether isotopes from microfaunal teeth excavated from Carpenter’s Gap 3 could be used as a reliable proxy to determine past climates in Australia. Additionally, the taphonomic processes of cave systems affecting the assemblage were also investigated. Results of isotope studies of !13C indicated a fluctuating past environment. The glacial period and terminal Pleistocene reflected a cooler and drier environment before an increase in !13C values during the Mid-Late Holocene to the present. This has been interpreted as a shift to C4 plants being the main source of murid subsistence. This is supported by palaeoclimate data showing a variable past Australian climate. Additionally, taphonomy studies indicated the use of the cave system by predatory birds and humans intermittently. There was little evidence for human modification on bone, however, further microscopic analysis may reveal additional details. This project has shown how microfaunal remains can be used to develop an understanding of past climate changes and environmental responses. Further, it has provided information about human occupation and subsistence in Australia over the last ~33 000 years.

Despite an increase in heatwaves and rising air temperatures in the Arctic, little research has been conducted into the temperatures of proglacial lakes in the region. An assumption persists that they are cold and uniformly feature a temperature of 1 °C. This is important to test, given the rising air temperatures in the region (reported in this study) and potential to increase water temperatures, thus increasing subaqueous melting and the retreat of glacier termini from where they are in contact with lakes. Through analysis of ASTER surface temperature product data, we report warm (>4 °C) proglacial lake surface water temperatures (LSWT) for both ice-contact and non-ice-contact lakes, as well as substantial spatial heterogeneity. We present in situ validation data (from problematic maritime areas) and a workflow that facilitates the extraction of robust LSWT data from the high-resolution (90 m) ASTER surface temperature product (AST08). This enables spatial patterns to be analysed in conjunction with surrounding thermal influences, such as parent glaciers and topographies. This workflow can be utilised for the analysis of the LSWT data of other small lakes and crucially allows high spatial resolution study of how they have responded to changes in climate. Further study of the LSWT is essential in the Arctic given the amplification of climate change across the region.

Recent collaborations between JPL's Integrated Model Centric Engineering (IMCE) initiative and the Europa Clipper project have produced six distinct applications of MBSE. Most of these collaborations have been successful, and all have been valuable learning experiences. Here we describe all of the applications including technical approach, benefits, challenges, and lessons learned.

Copernicus is a European Union Earth Observation program, dedicated to monitor our planet and its environment, giving free access to remote sensing data and derived Earth Observation products. For proper use in environmental monitoring and scientific applications, it is fundamental to guarantee high quality and consistency of these satellite derived products. One of the possibilities to ensure product quality is to perform quantitative comparisons of satellite derived products with the corresponding in situ observation. Two options can then be considered for ground data sources: through intensive field campaigns or making use of permanent ground stations deployed and maintained on the long term. In the first case, a large variety of variable can be assessed, but logistical challenges and financial resources limit in time and space the products validation. More over meteorological constrains often limit the number of data that can actually be used for Earth Observation products. The second option is from far the most cost effective although it is not yet possible to cover all ground variables with permanent field deployment.To achieve these objectives of systematic and long-term data validation, the Ground-Based Observations for Validation (GBOV) service has been implemented, facilitating the use of observations from operational ground-based monitoring networks and their comparison to EO products. The service is guaranteed through 3 different components:Collection of multi-year ground-based observations (Reference Measurements - RMs) of high relevance for the understanding of land surface processes from more than 50 existing sites. These RMs are then upscaled to generate Land Products (LPs), in order to validate the Copernicus products. In particular, the LPs distributed through the GBOV portal are: Top of Canopy Reflectance (ToC-R), surface albedo, Leaf Area Index (LAI), Fraction of Absorbed Photosynthetically Available Radiation (FAPAR), Fraction of Covered ground (FCover), Surface Soil Moisture (SSM) and Land Surface Temperature (LST). Upgrade of existing sites with new instrumentation or establishing entirely new monitoring sites to close thematic or geographical gaps. In 2019 new instrumentation has been installed in three different sites: Hainich (Germany), Valencia (Spain) and Tumbarumba (Australia). Litchfield (Australia), Dahra (Senegal) and Skukuza (South Africa) will be equipped with new instrumentation in the course of 2020. Implementation and maintenance of a database for the distribution of the Reference Measurements and the corresponding Land Products, available through the website https://land.copernicus.eu/global/gbov. GBOV data access is completely free, after registration and acceptation of the terms of use and the data policy.

Time series of global and regional mean surface air temperature (SAT) anomalies are a common metric used to estimate recent climate change. Various techniques can be used to create these time series from meteorological station data. The degree of difference arising from using five different techniques, based on existing temperature anomaly dataset techniques, to estimate Arctic SAT anomalies over land and sea ice was investigated using reanalysis data as a test bed. Techniques that interpolated anomalies were found to result in smaller errors than noninterpolating techniques relative to the reanalysis reference. Kriging techniques provided the smallest errors in estimates of Arctic anomalies, and simple kriging was often the best kriging method in this study, especially over sea ice. A linear interpolation technique had, on average, root-mean-square errors (RMSEs) up to 0.55 K larger than the two kriging techniques tested. Noninterpolating techniques provided the least representative anomaly estimates. Nonetheless, they serve as useful checks for confirming whether estimates from interpolating techniques are reasonable. The interaction of meteorological station coverage with estimation techniques between 1850 and 2011 was simulated using an ensemble dataset comprising repeated individual years (1979–2011). All techniques were found to have larger RMSEs for earlier station coverages. This supports calls for increased data sharing and data rescue, especially in sparsely observed regions such as the Arctic.

In this article three education and health services professionals, Julia Halpin, Sally Pitt and Emma Dodd, describe and reflect upon the way in which a small group of professionals from health and education services worked in collaboration to meet the need to inform and empower parents of preschool children with a diagnosis of autistic spectrum disorder (ASD). Julia and Sally, both clinical nurse specialists, and Emma, an educational psychologist, outline the background to the project in terms of demographics, epidemiology and service needs, and explain the way in which the interagency project was initiated as a ‘bottom-up’ response, reflecting on the advantages and disadvantages of this way of working. The team piloted an innovative evaluation method which is offered as a tool that could usefully be developed further.

The current concept for a potential Mars Sample Return (MSR) campaign includes a series of missions that could drill, package, and return Mars rock cores to Earth through four sequential flight missions. A combination of structural stability, migration, force, hardware testing and analysis were employed to determine elements within the potential MSR campaign that could alter the mechanical integrity of Mars rock cores during transport to Earth. Therefore, Mars simulant rock cores, such as Bishop Tuff and China Ranch Massive Gypsum, were drilled to create samples for survivability tests to simulate the high frequency vibrations of a Mars Ascent Vehicle (MAV) and high gravity force shock of the Earth Entry Vehicle (EEV) that would be expected during MSR. Prototype hardware was designed and fabricated to accommodate the cores desired for vibration and shock testing. Proto-flight (PF) and flight acceptance (FA) vibration levels were established for both solid and liquid MAV fuel types. Drilling methods were investigated to produce both pristine and fractured cores. Elements such as core orientation, amount of ullage (headspace), and clamshell position were tested to better understand the causes and amount of fracturing throughout these flight-like environments.

Four sealing methods for encapsulating samples in 1 cm diameter thin-walled sample tubes were designed, along with a set of tests for characterization and evaluation of sample preservation capability for the proposed Mars Sample Return (MSR) campaign. The sealing methods include a finned shape memory alloy (SMA) plug, expanding torque plug, contracting SMA ring cap, and expanding SMA ring plug. Mechanical strength and hermeticity of the seal were measured. Robustness of the seal to Mars simulant dust, surface abrasion, and pressure differentials were tested. Survivability tests were run to simulate thermal cycles on Mars, vibration from a Mars Ascent Vehicle (MAV), and shock from Earth Entry Vehicle (EEV) landing. Material compatibility with potential sample minerals and organic molecules were studied to select proper tube and seal materials that would not lead to adverse reactions nor contaminate the sample. Cleaning and sterilization techniques were executed on coupons made from the seal materials to assess compliance with planetary protection and contamination control. Finally, a method to cut a sealed tube for sample removal was designed and tested.

A new study of two open clusters, M16 and M67, and two globular clusters, M3 and M71 is presented, exploring data taken with the WFC/INT and the Hubble Space Tele- scope (HST) in a variety of broad-band filters. A dedicated, fully functioning reduction pipeline was constructed to reduce the data used in this study. Employing SExtractor, photometry is conducted in both g and i band filters to obtain Hertzsprung-Russell (HR) diagrams which are fitted with isochrones to determine the average age, distance, metallicity and extinction of each cluster. We find that M16 is ≈ 2 kpc away, with a high dust extinction of E(B-V)≈ 0.5. For M67 the distance was found to be ≈ 0.7 kpc and the cluster is less affected by extinction, showing E(B-V)≈ 0.2. M3 is consistent with being 13 kpc away and it shows little to no extinction. For M71 the distance was found to be ∼ 3kpc and we estimate a moderate extinction of E(B-V)≈ 0.25. The re- sults of this study highlight the stark contrast between open and globular clusters. We find that M16 and M67 (open clusters) have average ages of < 10 Myrs and 3.5 Gyrs, respectively. Globular clusters are found to be much older with ages of 9.5Gyrs and 11 Gyrs for M3 and M71, respectively. It was found that open clusters contained stars that are on average more metal-poor, with lower metallicities of [Fe/H]≈ −0.8 to [Fe/H]≈ −0.5, compared to [Fe/H]≈ −0.5 and [Fe/H]≈ 0.05 for M16 and M67, re- spectively. Future work could be undertaken to correct for issues found in this study, and investigate/infer the metallicities of the birth clouds.