Quantum materials with strong spin-orbit coupling : challenges and opportunities for materials chemists

ASG acknowledges funding through an EPSRC Early Career Fellowship EP/T011130/1.Spin-orbit coupling is a quantum effect that can give rise to exotic electronic and magnetic states in the compounds of the 4d and 5d transition metals. Exploratory synthesis, chemical tuning and structure-property characterisation of such compounds is an increasingly active area of research with both fundamental and application-related outlooks, but requires great care with regards to the chemistry of these materials that has not always been considered. This Perspective will give an accessible introduction to topical materials with strong spin-orbit coupling, their crystal chemistry, and their structure-property relationships, which overlaps with the contemporary investigation of some of the same materials within different communities. It will also outline some of the challenges faced in their synthesis and characterisation, and the contributions that materials chemists can make to overcoming these.Publisher PDFPeer reviewe

Occurrence of Pharmaceuticals and Personal Care Products (PPCP) & Artificial Sweeteners (AS) in Surface Waters of Maryland's Chesapeake Bay Western Shore

In the United States, nutrient, personal care products (PPCP) and artificial sweeteners (AS) pollution in lakes, rivers, and estuaries is a problem that has been recognized for decades and is of special concern for many in coastal Maryland. PPCP are used on a daily basis, and include prescription analgesics, antibiotics, over-the-counter medications, fragrances, and cleansers. AS are synthetic sugar substitutes, ubiquitous in everyday food and drink, including soft drinks, baked food and dairy products. The widespread use of PPCP and AS by human populations results in their sustained contribution to surface waters via wastewater treatment. This study used 13 PPCP and 2 AS to describe their sources and temporospatial patterns in Maryland’s Western Shore. Sampling was conducted over three seasons in 2021 at 79 sites, including headwater streams, groundwater, and rivers feeding into the Chesapeake Bay. Sites were influenced by a mix of wastewater treatment plants (WWTP) and onsite wastewater treatment systems (OWTS). The detection frequency of the study compounds ranged from 2% to 100% in large catchments and 31% to 100% in headwater catchments. Six PPCP and AS were measurable at 80% or more of the sites, illustrating their ubiquitous presence throughout the study area. During the study, individual PPCP and AS concentrations were highly variable temporally, ranging from non-detectable to 6.58 μg/L. Major factors controlling concentrations were proximity to wastewater treatment, discharge and season. Four compounds—Ace-K, carbamazepine, sucralose and caffeine—were used as tracers to identify wastewater sources as they have distinct removal efficiencies during wastewater treatment and have anthropogenic origins. Caffeine to sucralose/Ace-K/carbamazepine ratios were used to identify discharges of untreated wastewater. Finally, PPCP and AS concentrations were explored in one headwater stream during storm events. Stormflow discharge was shown to impact the water quality of the receiving waters. The combination of discharge data, OWTS distribution data, an extensive suite of PPCP and AS and varied catchment types used in this thesis contributes to the understanding of human sourced wastewater pollution in coastal communities

Intermultiplet transitions and magnetic long-range order in Sm-based pyrochlores

We present bulk and neutron scattering measurements performed on the isotopically enriched $^{154}\mathrm{Sm_2Ti_2O_7}$ and $^{154}\mathrm{Sm_2Sn_2O_7}$ samples. Both compounds display sharp heat capacity anomalies, at 350 mK and 440 mK, respectively. Inelastic neutron scattering measurements are employed to determine the crystalline electric field (CEF) level scheme, which includes transitions between the ground-state and first excited $J$ multiplets of the $\mathrm{Sm}^{3+}$ ion. To further validate those results, the single-ion magnetic susceptibility of the compounds is calculated and compared with the experimental DC-susceptibility measured in low applied magnetic fields. It is demonstrated that the inclusion of intermultiplet transitions in the CEF analysis is fundamental to the understanding of the intermediate and, more importantly, low temperature magnetic behaviour of the Sm-based pyrochlores. Finally, the heat capacity anomaly is shown to correspond to the onset of an all-in-all-out long-range order in the stannate sample, while in the titanate a dipolar long-range order can be only indirectly inferred.Comment: 13 pages, 10 Figure

Spin dynamics of coupled spin ladders near quantum criticality in Ba2CuTeO6

We report inelastic neutron scattering measurements of the magnetic excitations in Ba2CuTeO6, proposed by ab initio calculations to magnetically realize weakly coupled antiferromagnetic two-leg spin-1/2 ladders. Isolated ladders are expected to have a singlet ground state protected by a spin gap. Ba2CuTeO6 orders magnetically, but with a small Neel temperature relative to the exchange strength, suggesting that the interladder couplings are relatively small and only just able to stabilize magnetic order, placing Ba2CuTeO6 close in parameter space to the critical point separating the gapped phase and Neel order. Through comparison of the observed spin dynamics with linear spin wave theory and quantum Monte Carlo calculations, we propose values for all relevant intra- and interladder exchange parameters, which place the system on the ordered side of the phase diagram in proximity to the critical point. We also compare high field magnetization data with quantum Monte Carlo predictions for the proposed model of coupled ladders.Comment: 14 pages, 12 figure

Themes and variations: An exploratory international investigation into resuscitation decision-making

AbstractBackgroundDo Not Attempt Cardiopulmonary Resuscitation (DNACPR) decisions are made in hospitals throughout the globe. International variation in clinicians' perception of DNACPR decision-making and implementation and the factors influencing such variation has not previously been explored.MethodsA questionnaire asking how DNACPR decisions are made, communicated and perceived in their country was composed: it consisted of seven closed-answer and four open-answer questions. It was distributed to 143 medical professionals with prior published material relating to DNACPR decisions. Under-represented geographical areas were identified and an additional 34 physicians were contacted through medical colleagues and students at the university hospital from which this study was based. The respondents had 4 weeks to answer the questionnaire.Results78 responses (44%) were received from 43 countries. All continents were represented. 88% of respondents reported a method for implementing DNACPR decisions, 90% of which discussed resuscitation wishes with the patient at least half of the time. 94% of respondents thought that national guidance for DNACPR order implementation should exist; 53% of countries surveyed reported existence of such guidance. Cultural attitudes towards death, medical education and culture, health economics and the societal role of family were commonly identified as factors influencing perception of DNACPR decisions.ConclusionsThe majority of countries surveyed make some form of DNACPR decision but differing cultures and economic status contribute towards a heterogeneity of approaches to resuscitation decision-making. Adequacy of relevant medical education and national policy are two areas that were regularly identified as impacting upon the processes of DNACPR decision-making and implementation

Carbonate : an alternative dopant to stabilize new perovskite phases ; synthesis and structure of Ba3Yb2O5CO3 and related isostructural phases Ba3Ln2O5CO3 (Ln = Y, Dy, Ho, Er, Tm and Lu)

In this paper we report the synthesis of the new layered perovskite oxide carbonate, Ba3Yb2O5CO3. This phase is formed when 3BaCO(3):1Yb(2)O(3) mixtures are heated in air at temperatures 1000 degrees C, while above this temperature the carbonate is lost and the simple oxide phase Ba3Yb4O9 is observed. The structure of Ba3Yb2O5CO3 was determined from neutron diffraction studies and consists of a tripled perovskite with double Yb-O layers separated by carbonate layers, the first example of a material with such a structure. Further studies showed that analogous Ba(3)Ln(2)O(5)CO(3) phases could be formed for other rare earths (Ln = Y, Dy, Ho, Er, Tm and Lu). The results highlight the ability of the perovskite structure to accommodate carbonate groups, and emphasise the need to consider their potential presence particularly for perovskite systems prepared in lower temperature synthesis routes

Prevalence of liver fluke (Fasciola hepatica) in wild Red Deer (Cervus elaphus): coproantigen ELISA is a practicable alternative to faecal egg counting for surveillance in remote populations

Red deer (Cervus elaphus) are hosts of liver fluke (Fasciola hepatica); yet, prevalence is rarely quantified in wild populations. Testing fresh samples from remote regions by faecal examination (FE) can be logistically challenging; hence, we appraise frozen storage and the use of a coproantigen ELISA (cELISA) for F. hepatica surveillance. We also present cELISA surveillance data for red deer from the Highlands of Scotland. Diagnoses in faecal samples (207 frozen, 146 fresh) were compared using a cELISA and by FE. For each storage method (frozen or fresh), agreement between the two diagnostics was estimated at individual and population levels, where population prevalence was stratified into cohorts (e.g., by sampling location). To approximate sensitivity and specificity, 65 post-slaughter whole liver examinations were used as a reference. At the individual level, FE and cELISA diagnoses agreed moderately (κfrozen = 0.46; κfresh = 0.51), a likely reflection of their underlying principles. At the population level, FE and cELISA cohort prevalence correlated strongly (Pearson’s R = 0.89, p < 0.0001), reflecting good agreement on relative differences between cohort prevalence. In frozen samples, prevalence by cELISA exceeded FE overall (42.8% vs. 25.8%) and in 9/12 cohorts, alluding to differences in sensitivity; though, in fresh samples, no significant difference was found. In 959 deer tested by cELISA across the Scottish Highlands, infection prevalence ranged from 9.6% to 53% by sampling location. We highlight two key advantages of cELISA over FE: i) the ability to store samples long term (frozen) without apparent loss in diagnostic power; and ii) reduced labour and the ability to process large batches. Further evaluation of cELISA sensitivity in red deer, where a range of fluke burdens can be obtained, is desirable. In the interim, the cELISA is a practicable diagnostic for F. hepatica surveillance in red deer, and its application here has revealed considerable geographic, temporal, sex and age related differences in F. hepatica prevalence in wild Scottish Highland red deer

Application of deep learning for the analysis of stomata: A review of current methods and future directions

Plant physiology and metabolism relies on the function of stomata, structures on the surface of above ground organs, which facilitate the exchange of gases with the atmosphere. The morphology of the guard cells and corresponding pore which make up the stomata, as well as the density (number per unit area) are critical in determining overall gas exchange capacity. These characteristics can be quantified visually from images captured using microscopes, traditionally relying on time-consuming manual analysis. However, deep learning (DL) models provide a promising route to increase the throughput and accuracy of plant phenotyping tasks, including stomatal analysis. Here we review the published literature on the application of DL for stomatal analysis. We discuss the variation in pipelines used; from data acquisition, pre-processing, DL architecture and output evaluation to post processing. We introduce the most common network structures, the plant species that have been studied, and the measurements that have been performed. Through this review, we hope to promote the use of DL methods for plant phenotyping tasks and highlight future requirements to optimise uptake; predominantly focusing on the sharing of datasets and generalisation of models as well as the caveats associated with utilising image data to infer physiological function

Magnetic frustration and spontaneous rotational symmetry breaking in PdCrO2

In the triangular layered magnet PdCrO2 the intralayer magnetic interactions are strong, however the lattice structure frustrates interlayer interactions. In spite of this, long-range, 120$^\circ$ antiferromagnetic order condenses at $T_N = 38$~K. We show here through neutron scattering measurements under in-plane uniaxial stress and in-plane magnetic field that this occurs through a spontaneous lifting of the three-fold rotational symmetry of the nonmagnetic lattice, which relieves the interlayer frustration. We also show through resistivity measurements that uniaxial stress can suppress thermal magnetic disorder within the antiferromagnetic phase.Comment: 9 pages, 9 figure