Local nanoscale phase impurities are degradation sites in halide perovskites.

Understanding the nanoscopic chemical and structural changes that drive instabilities in emerging energy materials is essential for mitigating device degradation. The power conversion efficiency of halide perovskite photovoltaic devices has reached 25.7 per cent in single-junction and 29.8 per cent in tandem perovskite/silicon cells1,2, yet retaining such performance under continuous operation has remained elusive3. Here we develop a multimodal microscopy toolkit to reveal that in leading formamidinium-rich perovskite absorbers, nanoscale phase impurities, including hexagonal polytype and lead iodide inclusions, are not only traps for photoexcited carriers, which themselves reduce performance4,5, but also, through the same trapping process, are sites at which photochemical degradation of the absorber layer is seeded. We visualize illumination-induced structural changes at phase impurities associated with trap clusters, revealing that even trace amounts of these phases, otherwise undetected with bulk measurements, compromise device longevity. The type and distribution of these unwanted phase inclusions depends on the film composition and processing, with the presence of polytypes being most detrimental for film photo-stability. Importantly, we reveal that both performance losses and intrinsic degradation processes can be mitigated by modulating these defective phase impurities, and demonstrate that this requires careful tuning of local structural and chemical properties. This multimodal workflow to correlate the nanoscopic landscape of beam-sensitive energy materials will be applicable to a wide range of semiconductors for which a local picture of performance and operational stability has yet to be established.

Performance-limiting nanoscale trap clusters at grain junctions in halide perovskites.

Halide perovskite materials have promising performance characteristics for low-cost optoelectronic applications. Photovoltaic devices fabricated from perovskite absorbers have reached power conversion efficiencies above 25 per cent in single-junction devices and 28 per cent in tandem devices1,2. This strong performance (albeit below the practical limits of about 30 per cent and 35 per cent, respectively3) is surprising in thin films processed from solution at low-temperature, a method that generally produces abundant crystalline defects4. Although point defects often induce only shallow electronic states in the perovskite bandgap that do not affect performance5, perovskite devices still have many states deep within the bandgap that trap charge carriers and cause them to recombine non-radiatively. These deep trap states thus induce local variations in photoluminescence and limit the device performance6. The origin and distribution of these trap states are unknown, but they have been associated with light-induced halide segregation in mixed-halide perovskite compositions7 and with local strain8, both of which make devices less stable9. Here we use photoemission electron microscopy to image the trap distribution in state-of-the-art halide perovskite films. Instead of a relatively uniform distribution within regions of poor photoluminescence efficiency, we observe discrete, nanoscale trap clusters. By correlating microscopy measurements with scanning electron analytical techniques, we find that these trap clusters appear at the interfaces between crystallographically and compositionally distinct entities. Finally, by generating time-resolved photoemission sequences of the photo-excited carrier trapping process10,11, we reveal a hole-trapping character with the kinetics limited by diffusion of holes to the local trap clusters. Our approach shows that managing structure and composition on the nanoscale will be essential for optimal performance of halide perovskite devices.

Evaluation of the feasibility of a midwifery educator continuous professional development (CPD) programme in Kenya and Nigeria: a mixed methods study.

BACKGROUND: Midwifery education is under-invested in developing countries with limited opportunities for midwifery educators to improve/maintain their core professional competencies. To improve the quality of midwifery education and capacity for educators to update their competencies, a blended midwifery educator-specific continuous professional development (CPD) programme was designed with key stakeholders. This study evaluated the feasibility of this programme in Kenya and Nigeria. METHODS: This was a mixed methods intervention study using a concurrent nested design. 120 randomly selected midwifery educators from 81 pre-service training institutions were recruited. Educators completed four self-directed online learning (SDL) modules and three-day practical training of the blended CPD programme on teaching methods (theory and clinical skills), assessments, effective feedback and digital innovations in teaching and learning. Pre- and post-training knowledge using multiple choice questions in SDL; confidence (on a 0-4 Likert scale) and practical skills in preparing a teaching a plan and microteaching (against a checklist) were measured. Differences in knowledge, confidence and skills were analysed. Participants' reaction to the programme (relevance and satisfaction assessed on a 0-4 Likert scale, what they liked and challenges) were collected. Key informant interviews with nursing and midwifery councils and institutions' managers were conducted. Thematic framework analysis was conducted for qualitative data. RESULTS: 116 (96.7%) and 108 (90%) educators completed the SDL and practical components respectively. Mean knowledge scores in SDL modules improved from 52.4% (± 10.4) to 80.4% (± 8.1), preparing teaching plan median scores improved from 63.6% (IQR 45.5) to 81.8% (IQR 27.3), and confidence in applying selected pedagogy skills improved from 2.7 to 3.7, p < 0.001. Participants rated the SDL and practical components of the programme high for relevance and satisfaction (median, 4 out of 4 for both). After training, 51.4% and 57.9% of the participants scored 75% or higher in preparing teaching plans and microteaching assessments. Country, training institution type or educator characteristics had no significant associations with overall competence in preparing teaching plans and microteaching (p > 0.05). Qualitatively, educators found the programme educative, flexible, convenient, motivating, and interactive for learning. Internet connectivity, computer technology, costs and time constraints were potential challenges to completing the programme. CONCLUSION: The programme was feasible and effective in improving the knowledge and skills of educators for effective teaching/learning. For successful roll-out, policy framework for mandatory midwifery educator specific CPD programme is needed.

Experiences, barriers and perspectives of midwifery educators, mentors and students implementing the updated emergency obstetric and newborn care-enhanced pre-service midwifery curriculum in Kenya: a nested qualitative study.

INTRODUCTION: To achieve quality midwifery education, understanding the experiences of midwifery educators and students in implementing a competency-based pre-service curriculum is critical. This study explored the experiences of and barriers to implementing a pre-service curriculum updated with emergency obstetric and newborn care (EmONC) skills by midwifery educators, students and mentors in Kenya. METHODS: This was a nested qualitative study within the cluster randomised controlled trial investigating the effectiveness of an EmONC enhanced midwifery curriculum delivered by trained and mentored midwifery educators on the quality of education and student performance in 20 colleges in Kenya. Following the pre-service midwifery curriculum EmONC update, capacity strengthening of educators through training (in both study arms) and additional mentoring of intervention-arm educators was undertaken. Focus group discussions were used to explore the experiences of and barriers to implementing the EmONC-enhanced curriculum by 20 educators and eight mentors. Debrief/feedback sessions with 6-9 students from each of the 20 colleges were conducted and field notes were taken. Data were analysed thematically using Braun and Clarke's six step criteria. RESULTS: Themes identified related to experiences were: (i) relevancy of updated EmONC-enhanced curriculum to improve practice, (ii) training and mentoring valued as continuous professional development opportunities for midwifery educators, (iii) effective teaching and learning strategies acquired - peer teaching (teacher-teacher and student-student), simulation/scenario teaching and effective feedback techniques for effective learning and, (iv) effective collaborations between school/academic institution and hospital/clinical staff promoted effective training/learning. Barriers identified were (i) midwifery faculty shortage and heavy workload vs. high student population, (ii) infrastructure gaps in simulation teaching - inadequate space for simulation and lack of equipment inventory audits for replenishment (iii) inadequate clinical support for students due to inadequate clinical sites for experience, ineffective supervision and mentoring support, lack/shortage of clinical mentors and untrained hospital/clinical staff in EmONC and (iv) limited resources to support effective learning. CONCLUSION: Findings reveal an overwhelmed midwifery faculty and an urgent demand for students support in clinical settings to acquire EmONC competencies for enhanced practice. For quality midwifery education, adequate resources and regulatory/policy directives are needed in midwifery faculty staffing and development. A continuous professional development specific for educators is needed for effective student teaching and learning of a competency-based pre-service curriculum.

Reconsidering the link between past material culture and cognition in light of contemporary hunter-gatherer material use.

Many have interpreted symbolic material culture in the deep past as evidencing the origins sophisticated, modern cognition. Scholars from across the behavioural and cognitive sciences, including linguists, psychologists, philosophers, neuroscientists, primatologists, archaeologists and paleoanthropologists have used such artefacts to assess the capacities of extinct human species, and to set benchmarks, milestones or otherwise chart the course of human cognitive evolution. To better calibrate our expectations, the present paper instead explores the material culture of three contemporary African forager groups. Results show that, while these groups are unequivocally behaviourally modern, they would leave scant long-lasting evidence of symbolic behaviour. Artefact-sets are typically small, perhaps as consequence of residential mobility. When excluding traded materials, few artefacts have components with moderate-strong taphonomic signatures. Present analyses show that artefact function influences preservation probability, such that utilitarian tools for the processing of materials and the preparation of food are disproportionately likely to contain archaeologically traceable components. There are substantial differences in material-use between populations, which create important population-level variation preservation probability independent of cognitive differences. I discuss the factors - cultural, ecological and practical - that influence material choice. In so doing, I highlight the difficulties of using past material culture as an evolutionary or cognitive yardstick.

Using Plasmodium knowlesi as a model for screening Plasmodium vivax blood-stage malaria vaccine targets reveals new candidates.

Plasmodium vivax is responsible for the majority of malaria cases outside Africa. Unlike P. falciparum, the P. vivax life-cycle includes a dormant liver stage, the hypnozoite, which can cause infection in the absence of mosquito transmission. An effective vaccine against P. vivax blood stages would limit symptoms and pathology from such recurrent infections, and therefore could play a critical role in the control of this species. Vaccine development in P. vivax, however, lags considerably behind P. falciparum, which has many identified targets with several having transitioned to Phase II testing. By contrast only one P. vivax blood-stage vaccine candidate based on the Duffy Binding Protein (PvDBP), has reached Phase Ia, in large part because the lack of a continuous in vitro culture system for P. vivax limits systematic screening of new candidates. We used the close phylogenetic relationship between P. vivax and P. knowlesi, for which an in vitro culture system in human erythrocytes exists, to test the scalability of systematic reverse vaccinology to identify and prioritise P. vivax blood-stage targets. A panel of P. vivax proteins predicted to function in erythrocyte invasion were expressed as full-length recombinant ectodomains in a mammalian expression system. Eight of these antigens were used to generate polyclonal antibodies, which were screened for their ability to recognize orthologous proteins in P. knowlesi. These antibodies were then tested for inhibition of growth and invasion of both wild type P. knowlesi and chimeric P. knowlesi lines modified using CRISPR/Cas9 to exchange P. knowlesi genes with their P. vivax orthologues. Candidates that induced antibodies that inhibited invasion to a similar level as PvDBP were identified, confirming the utility of P. knowlesi as a model for P. vivax vaccine development and prioritizing antigens for further follow up.

Symbiotic nitrogen fixation does not stimulate soil phosphatase activity under temperate and tropical trees.

Symbiotic nitrogen (N)-fixing plants can enrich ecosystems with N, which can alter the cycling and demand for other nutrients. Researchers have hypothesized that fixed N could be used by plants and soil microbes to produce extracellular phosphatase enzymes, which release P from organic matter. Consistent with this speculation, the presence of N-fixing plants is often associated with high phosphatase activity, either in the soil or on root surfaces, although other studies have not found this association, and the connection between phosphatase and rates of N fixation-the mechanistic part of the argument-is tenuous. Here, we measured soil phosphatase activity under N-fixing trees and non-fixing trees transplanted and grown in tropical and temperate sites in the USA: two sites in Hawaii, and one each in New York and Oregon. This provides a rare example of phosphatase activity measured in a multi-site field experiment with rigorously quantified rates of N fixation. We found no difference in soil phosphatase activity under N-fixing vs. non-fixing trees nor across rates of N fixation, though we note that no sites were P limited and only one was N limited. Our results add to the literature showing no connection between N fixation rates and phosphatase activity.

Prevalence and factors associated with caesarean section in Rwanda: a trend analysis of Rwanda demographic and health survey 2000 to 2019-20.

BACKGROUND: Caesarean section (CS) is an important medical intervention for reducing the risk of poor perinatal outcomes. However, CS trends in sub-Saharan Africa (SSA) continue to increase yet maternal and neonatal mortality and morbidity remain high. Rwanda, like many other countries in SSA, has shown an increasing trend in the use of CS. This study assessed the trends and factors associated with CS delivery in Rwanda over the past two decades. METHODS: We used nationally representative child datasets from the Rwanda Demographic and Health Survey 2000 to 2019-20. All births in the preceding 3 years to the survey were assessed for the mode of delivery. The participants' characteristics, trends and the prevalence of CS were analysed using frequencies and percentages. Unadjusted and adjusted logistic regression analyses were used to assess the factors associated with population and hospital-based CS in Rwanda for each of the surveys. RESULTS: The population-based rate of CS in Rwanda significantly increased from 2.2% (95% CI 1.8-2.6) in 2000 to 15.6% (95% CI 13.9-16.5) in 2019-20. Despite increasing in all health facilities over time, the rate of CS was about four times higher in private (60.6%) compared to public health facilities (15.4%) in 2019-20. The rates and odds of CS were disproportionately high among women of high socioeconomic groups, those who resided in Kigali city, had multiple pregnancies, and attended at least four antenatal care visits while the odds of CS were significantly lower among multiparous women and those who had female babies. CONCLUSION: Over the past two decades, the rate of CS use in Rwanda increased significantly at health facility and population level with high regional and socio-economic disparities. There is a need to examine the disparities in CS trends and developing tailored policy guidelines to ensure proper use of CS in Rwanda.

The determinants of staff retention after Emergency Obstetrics and Newborn Care training in Kenya: a cross-sectional study.

INTRODUCTION: Kenya's maternal mortality ratio is relatively high at 342/100,000 live births. Confidential enquiry into maternal deaths showed that 90% of the maternal deaths received substandard care with health workforce related factors identified in 75% of 2015/2016 maternal deaths. Competent Skilled Health Personnel (SHP) providing emergency obstetric and newborn care (EmONC) in an enabling environment reduces the risk of adverse maternal and newborn outcomes. The study objective was to identify factors that determine the retention of SHP 1 - 5 years after EmONC training in Kenya. METHODS: A cross-sectional review of EmONC SHP in five counties (Kilifi, Taita Taveta, Garissa, Vihiga and Uasin Gishu) was conducted between January-February 2020. Data was extracted from a training database. Verification of current health facilities where trained SHP were deployed and reasons for non-retention were collected. Descriptive data analysis, transfer rate by county and logistic regression for SHP retention determinants was performed. RESULTS: A total of 927 SHP were trained from 2014-2019. Most SHP trained were nurse/midwives (677, 73%) followed by clinical officers (151, 16%) and doctors (99, 11%). Half (500, 54%) of trained SHP were retained in the same facility. Average trained staff transfer rate was 43%, with Uasin Gishu lowest at 24% and Garissa highest at 50%. Considering a subset of trained staff from level 4/5 facilities with distinct hospital departments, only a third (36%) of them are still working in relevant maternity/newborn/gynaecology departments. There was a statistically significant difference in transfer rate by gender in Garissa, Vihiga and the combined 5 counties (p < 0.05). Interval from training in years (1 year, AOR = 4.2 (2.1-8.4); cadre (nurse/midwives, AOR = 2.5 (1.4-4.5); and county (Uasin Gishu AOR = 9.5 (4.6- 19.5), Kilifi AOR = 4.0 (2.1-7.7) and Taita Taveta AOR = 1.9 (1.1-3.5), p < 0.05, were significant determinants of staff retention in the maternity departments. CONCLUSION: Retention of EmONC trained SHP in the relevant maternity departments was low at 36 percent. SHP were more likely to be retained by 1-year after training compared to the subsequent years and this varied from county to county. County policies and guidelines on SHP deployment, transfers and retention should be strengthened to optimise the benefits of EmONC training.

Improving midwifery educators' capacity to teach emergency obstetrics and newborn care in Kenya universities: a pre-post study.

BACKGROUND: International Confederation of Midwives and World Health Organization recommend core competencies for midwifery educators for effective theory and practical teaching and practice. Deficient curricula and lack of skilled midwifery educators are important factors affecting the quality of graduates from midwifery programmes. The objective of the study was to assess the capacity of university midwifery educators to deliver the updated competency-based curriculum after the capacity strengthening workshop in Kenya. METHODS: The study used a quasi-experimental (pre-post) design. A four-day training to strengthen the capacity of educators to deliver emergency obstetrics and newborn care (EmONC) within the updated curriculum was conducted for 30 midwifery educators from 27 universities in Kenya. Before-after training assessments in knowledge, two EmONC skills and self-perceived confidence in using different teaching methodologies to deliver the competency-based curricula were conducted. Wilcoxon signed-rank test was used to compare the before-after knowledge and skills mean scores. McNemar test was used to compare differences in the proportion of educators' self-reported confidence in applying the different teaching pedagogies. P-values < 0.05 were considered statistically significant. FINDINGS: Thirty educators (7 males and 23 females) participated, of whom only 11 (37%) had participated in a previous hands-on basic EmONC training - with 10 (91%) having had the training over two years beforehand. Performance mean scores increased significantly for knowledge (60.3% - 88. %), shoulder dystocia management (51.4 - 88.3%), newborn resuscitation (37.9 - 89.1%), and overall skill score (44.7 - 88.7%), p < 0.0001. The proportion of educators with confidence in using different stimulatory participatory teaching methods increased significantly for simulation (36.7 - 70%, p = 0.006), scenarios (53.3 - 80%, p = 0.039) and peer teaching and support (33.3 - 63.3%, p = 0.022). There was improvement in use of lecture method (80 - 90%, p = 0.289), small group discussions (73.3 - 86.7%, p = 0.344) and giving effective feedback (60 - 80%, p = 0.146), although this was not statistically significant. CONCLUSION: Training improved midwifery educators' knowledge, skills and confidence to deliver the updated EmONC-enhanced curriculum. To ensure that midwifery educators maintain their competence, there is need for structured regular mentoring and continuous professional development. Besides, there is need to cascade the capacity strengthening to reach more midwifery educators for a competent midwifery workforce.

Divergent Pathways of Nitrogen-Fixing Trees through Succession Depend on Starting Nitrogen Supply and Priority Effects.

AbstractNitrogen-fixing trees are a major potential source of nitrogen in terrestrial ecosystems. The degree to which they persist in older forests has considerable implications for forest nitrogen budgets. We characterized nitrogen-fixing tree abundance across stand age in the contiguous United States and analyzed a theoretical model to help understand competitive outcomes and successional trajectories of nitrogen-fixing and nonfixing trees. Nitrogen-fixing tree abundance is bimodal in all regions except the northeastern United States, even in older forests, suggesting that competitive exclusion (including priority effects) is more common than coexistence at the spatial scale of our analysis. Our model analysis suggests conditions under which alternative competitive outcomes are possible and when they are transient (lasting decades or centuries) versus persistent (millennia). Critically, the timescale of the feedbacks between nitrogen fixation and soil nitrogen supply, which is thought to drive the exclusion of nitrogen-fixing trees through succession, can be long. Therefore, the long transient outcomes of competition are more relevant for real forests than the long-term equilibrium. Within these long-term transients, the background soil nitrogen supply is a major determinant of competitive outcomes. Consistent with the expectations of resource ratio theory, competitive exclusion is more likely at high and low nitrogen supply, while intermediate nitrogen supply makes coexistence or priority effects possible. However, these outcomes are modified by the nitrogen fixation strategy: obligate nitrogen fixation makes coexistence more likely than priority effects, compared with perfectly facultative fixation. These results advance our understanding of the successional trajectories of nitrogen-fixing trees and their effects on ecosystem development in secondary succession.

Light, nitrogen supply, and neighboring plants dictate costs and benefits of nitrogen fixation for seedlings of a tropical nitrogen-fixing tree.

The ability to fix nitrogen may confer a competitive advantage or disadvantage to symbiotic nitrogen-fixing plants depending on the availability of soil nitrogen and energy to fuel fixation. Understanding these costs and benefits of nitrogen fixation is critical to predicting ecosystem dynamics and nutrient cycling. We grew inoculated (with symbiotic bacteria) and uninoculated seedlings of Pentaclethra macroloba (a nitrogen-fixing tree species) both in isolation and with Virola koschnyi (a nonfixing species) under gradients of light and soil nitrogen to assess how the ability to fix nitrogen and fixation activity affect growth, biomass allocation, and responses to neighboring plants. Inoculation itself did not provide a growth advantage to nitrogen fixers, regardless of nitrogen limitation status. Higher nitrogen fixation rates increased biomass growth similarly for nitrogen-limited and nitrogen-saturated fixers. Nodule production was offset by reduced fine-root biomass for inoculated nitrogen fixers, resulting in no change in total belowground allocation associated with nitrogen fixation. Under nitrogen-limited conditions, inoculated nitrogen fixers partially downregulated fixation in the presence of a nonfixing neighbor. These results suggest that nitrogen fixation can provide a growth advantage, even under nitrogen-saturated conditions, and that nitrogen fixers may reduce fixation rates to minimize facilitation of neighbors.

Selective Chemical Modulation of Interlayer Excitons in Atomically Thin Heterostructures.

Strongly bound interlayer excitons (XIs) in atomically thin transition metal dichalcogenide (TMDC) heterostructures such as MoS2/WSe2 show promising optoelectronic properties for spin-valleytronics and excitonic devices. The ability to probe and control XIs is critical for the development of such applications. This Letter introduces a versatile chemical method for selectively tailoring interlayer excitons in TMDC heterostructures. We show that two organic layers form uniform layers on a WSe2/MoS2 heterostructure and that the XI photoluminescence may be either preserved or quenched. The interlayer emission can also be modulated differently by the formation of the organic layer on either side of the TMDC/TMDC heterostructure. We find that the resulting interlayer emission is dominated by selective photoinduced charge transfer over dark-state p-doping effects. These results shed critical insights on interlayer excitons at the TMDC/TMDC heterointerfaces and provide a versatile approach for selectively tailoring them for optoelectronic applications.

Is it possible to store spotted wolffish (Anarhichas minor) sperm by refrigeration?

Spotted wolffish Anarhichas minor reproduction in captivity is dependent on in vitro fertilization. However, it is often challenging to acquire sufficient fresh sperm to fertilize the eggs that are obtained. In this study, we evaluate the possibility to store spotted wolffish sperm by refrigeration. Spotted wolffish sperm has the particularity that is already motile on stripping, and currently it is not possible to immobilize and reactivate. Thus, sperm refrigeration protocols should focus in extending this motility period that usually lasts up to 2 days. In a first experiment, we evaluated the possibility that the motility period of the sperm was limited by contamination with urine. The urea concentration in the sperm obtained both by stripping (17.10 ± 1.98 mg/dL) and directly from the testis (12.59 ± 2.37 mg/dL) was similar (p > 0.05), which indicate that the sperm collection method used avoid contamination with urine. Afterwards, we tested the possibility that the sperm motility period was limited by energy stores. The ATP concentration (initial value 5.65 ± 0.86 nmol/109 cells) remained stable (p = 0.099) during 30 h after sperm collection, and similar values (p = 0.329) were recorded at end of sperm storage in both diluted (3.88 ± 1.35 nmol/109 cells) and undiluted samples (4.76 ± 1.08 nmol/109). This indicates that the low intracellular ATP consumption, derived from the slow sperm motility, can probably be compensated rapidly enough by mitochondrial synthesis of ATP in the spotted wolffish sperm. In both experiments, diluted sperm kept higher percentage of motile cells during the storage time.

Early indirect impact of COVID-19 pandemic on utilisation and outcomes of reproductive, maternal, newborn, child and adolescent health services in Kenya: A cross-sectional study.

The paper determined the initial impact of COVID-19 pandemic on reproductive, maternal, newborn, child and adolescent health (RMNCAH) services in Kenya. Hospital data for the first four months (March-June 2020) of the pandemic and the equivalent period in 2019 were compared using two-sample test of proportions. Despite the global projections for worse indicators, there were no differences in monthly mean ( SD) attendance between March-June 2019 vs 2020 for antenatal care (400,191.2 12,700.0 vs 384,697.3 20,838.6), hospital births (98,713.0 4,117.0 vs 99,634.5 3,215.5), family planning attendance (431,930.5 19,059.9 vs 448,168.3 31,559.8), post-abortion care (3,206.5 111.7 vs 448,168.3 31,559.8) and pentavalent 1 immunisation (114,701.0 3,701.1 vs 110,915.8 7,209.4), p>0.05. However, there were significant increases in FP utilisation among young people (25.7% to 27.0%), injectable (short-term) FP method uptake (58.2% to 62.3%), caesarean section rate (14.6% to 15.8%), adolescent maternal deaths (6.2% to 10.9%) and fresh stillbirths (0.9% to 1.0%) with a reduction in implants (long-term) uptake (16.5% to 13.0%) (p <0.05). With uncertainty around the duration of the pandemic, strategies to mitigate against catastrophic indirect maternal health outcomes are urgently needed.

Direct Imaging of Correlated Defect Nanodomains in a Metal-Organic Framework.

Defect engineering can enhance key properties of metal-organic frameworks (MOFs). Tailoring the distribution of defects, for example in correlated nanodomains, requires characterization across length scales. However, a critical nanoscale characterization gap has emerged between the bulk diffraction techniques used to detect defect nanodomains and the subnanometer imaging used to observe individual defects. Here, we demonstrate that the emerging technique of scanning electron diffraction (SED) can bridge this gap uniquely enabling both nanoscale crystallographic analysis and the low-dose formation of multiple diffraction contrast images for defect analysis in MOFs. We directly image defect nanodomains in the MOF UiO-66(Hf) over an area of ca. 1000 nm and with a spatial resolution ca. 5 nm to reveal domain morphology and distribution. Based on these observations, we suggest possible crystal growth processes underpinning synthetic control of defect nanodomains. We also identify likely dislocations and small angle grain boundaries, illustrating that SED could be a key technique in developing the potential for engineering the distribution of defects, or "microstructure", in functional MOF design.

Effects of two centuries of global environmental variation on phenology and physiology of Arabidopsis thaliana.

Intraspecific trait variation is caused by genetic and plastic responses to environment. This intraspecific diversity is captured in immense natural history collections, giving us a window into trait variation across continents and through centuries of environmental shifts. Here we tested if hypotheses based on life history and the leaf economics spectrum explain intraspecific trait changes across global spatiotemporal environmental gradients. We measured phenotypes on a 216-year time series of Arabidopsis thaliana accessions from across its native range and applied spatially varying coefficient models to quantify region-specific trends in trait coordination and trait responses to climate gradients. All traits exhibited significant change across space or through time. For example, δ15 N decreased over time across much of the range and leaf C:N increased, consistent with predictions based on anthropogenic changes in land use and atmosphere. Plants were collected later in the growing season in more recent years in many regions, possibly because populations shifted toward more spring germination and summer flowering as opposed to fall germination and spring flowering. When climate variables were considered, collection dates were earlier in warmer years, while summer rainfall had opposing associations with collection date depending on regions. There was only a modest correlation among traits, indicating a lack of a single life history/physiology axis. Nevertheless, leaf C:N was low for summer- versus spring-collected plants, consistent with a life history-physiology axis from slow-growing winter annuals to fast-growing spring/summer annuals. Regional heterogeneity in phenotype trends indicates complex responses to spatiotemporal environmental gradients potentially due to geographic genetic variation and climate interactions with other aspects of environment. Our study demonstrates how natural history collections can be used to broadly characterize trait responses to environment, revealing heterogeneity in response to anthropogenic change.

Meta-analysis on the potential for increasing nitrogen losses from intensifying tropical agriculture.

Fertilized temperate croplands export large amounts of reactive nitrogen (N), which degrades water and air quality and contributes to climate change. Fertilizer use is poised to increase in the tropics, where widespread food insecurity persists and increased agricultural productivity will be needed, but much less is known about the potential consequences of increased tropical N fertilizer application. We conducted a meta-analysis of tropical field studies of nitrate leaching, nitrous oxide emissions, nitric oxide emissions, and ammonia volatilization totaling more than 1,000 observations. We found that the relationship between N inputs and losses differed little between temperate and tropical croplands, although total nitric oxide losses were higher in the tropics. Among the potential drivers we studied, the N input rate controlled all N losses, but soil texture and water inputs also controlled hydrological N losses. Irrigated systems had significantly higher losses of ammonia, and pasture agroecosystems had higher nitric oxide losses. Tripling of fertilizer N inputs to tropical croplands from 50 to 150 kg N ha-1  year-1 would have substantial environmental implications and would lead to increases in nitrate leaching (+30%), nitrous oxide emissions (+30%), nitric oxide (+66%) emissions, and ammonia volatilization (+74%), bringing tropical agricultural nitrate, nitrous oxide, and ammonia losses in line with temperate losses and raising nitric oxide losses above them.

A mechanism of expansion: Arctic deciduous shrubs capitalize on warming-induced nutrient availability.

Warming-induced nutrient enrichment in the Arctic may lead to shifts in leaf-level physiological properties and processes with potential consequences for plant community dynamics and ecosystem function. To explore the physiological responses of Arctic tundra vegetation to increasing nutrient availability, we examined how a set of leaf nutrient and physiological characteristics of eight plant species (representing four plant functional groups) respond to a gradient of experimental nitrogen (N) and phosphorus (P) enrichment. Specifically, we examined a set of chlorophyll fluorescence measures related to photosynthetic efficiency, performance and stress, and two leaf nutrient traits (leaf %C and %N), across an experimental nutrient gradient at the Arctic Long Term Ecological Research site, located in the northern foothills of the Brooks Range, Alaska. In addition, we explicitly assessed the direct relationships between chlorophyll fluorescence and leaf %N. We found significant differences in physiological and nutrient traits between species and plant functional groups, and we found that species within one functional group (deciduous shrubs) have significantly greater leaf %N at high levels of nutrient addition. In addition, we found positive, saturating relationships between leaf %N and chlorophyll fluorescence measures across all species. Our results highlight species-specific differences in leaf nutrient traits and physiology in this ecosystem. In particular, the effects of a gradient of nutrient enrichment were most prominent in deciduous plant species, the plant functional group known to be increasing in relative abundance with warming in this ecosystem.

To the hunter go the spoils? No evidence of nutritional benefit to being or marrying a well-reputed Hadza hunter.

OBJECTIVES: The incentives underlying men's hunting acquisition patterns among foragers are much debated. Some argue that hunters preferentially channel foods to their households, others maintain that foods are widely redistributed. Debates have focused on the redistribution of foods brought to camp, though the proper interpretation of results is contested. Here we instead address this question using two nutritional variables, employed as proxies for longer-term food access. We also report on broader patterns in nutritional status. MATERIALS AND METHODS: We measured male hunting success, hemoglobin concentration and body fatness among bush-living Hadza. Hunting success was measured using an aggregated reputation score. Hemoglobin concentration, a proxy for dietary red meat, was measured from fingerprick capillary blood. Body fatness, a proxy for energy balance, was measured using BMI and bioelectrical impedance. RESULTS: We find no statistically significant relationship between a hunter's success and any measure of his nutritional status or that of his spouse. We further find that: women are, as elsewhere, at greater risk of iron-deficiency anemia than men; men had slightly lower BMIs than women; men but not women had significantly lower hemoglobin levels than in the 1960s. DISCUSSION: The absence of an association between hunting reputation and nutritional status is consistent with generalized food sharing. Null results are difficult to interpret and findings could potentially be a consequence of insufficient signal in the study measures or some confounding effect. In any event, our results add to a substantial corpus of existing research that identifies few nutritional advantages to being or marrying a well-reputed Hadza hunter.