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1.
BMC Med Educ ; 24(1): 534, 2024 May 14.
Artículo en Inglés | MEDLINE | ID: mdl-38745243

RESUMEN

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.


Asunto(s)
Estudios de Factibilidad , Partería , Humanos , Partería/educación , Kenia , Nigeria , Femenino , Adulto , Evaluación de Programas y Proyectos de Salud , Competencia Clínica , Masculino
2.
Nutrients ; 16(7)2024 Apr 03.
Artículo en Inglés | MEDLINE | ID: mdl-38613083

RESUMEN

The aim of this systematic review is to comprehensively assess the weight loss (WL) practices in different combat sports (CS). The review protocol was preregistered with PROSPERO [CRD42023487196]. Three databases were searched (Web of Science, EBSCOhost, and PubMed) until 8 December 2023. Eligible studies had to meet five criteria: they must have been (a) written in English, (b) published in a peer-reviewed journal, (c) used a survey design to investigate the WL practices of CS athletes, and (d) reported the WL methods used by athletes using a five-point scale. Twenty-six studies (3994 participants from 14 CS) were included. This review found that (1) WL is highly prevalent in CS athletes; (2) many CS athletes started losing weight for competition as teenagers two to three times a year; (3) CS athletes usually lose <5% body weight in 7-14 days before competition; (4) increasing exercise and gradually dieting are the most commonly used WL methods; and (5) the influence of scientific practitioners on athletes is negligible. The habitual practices of CS athletes may be relatively harmless, but in some special cases, CS athletes also perform extreme WL practices. Scientific practitioners have little influence on their WL practices, which may form a vicious cycle of non-qualified influence.


Asunto(s)
Atletas , Deportes , Adolescente , Humanos , Triptófano Oxigenasa , Bases de Datos Factuales , Pérdida de Peso
3.
Behav Brain Sci ; : 1-53, 2024 Mar 14.
Artículo en Inglés | MEDLINE | ID: mdl-38482669

RESUMEN

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.

4.
PLoS One ; 18(8): e0289679, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-37603572

RESUMEN

Allometric equations are often used to estimate plant biomass allocation to different tissue types from easier-to-measure quantities. Biomass allocation, and thus allometric equations, often differs by species and sometimes varies with nutrient availability. We measured biomass components for five nitrogen-fixing tree species (Robinia pseudoacacia, Gliricidia sepium, Casuarina equisetifolia, Acacia koa, Morella faya) and three non-fixing tree species (Betula nigra, Psidium cattleianum, Dodonaea viscosa) grown in field sites in New York and Hawaii for 4-5 years and subjected to four fertilization treatments. We measured total aboveground, foliar, main stem, secondary stem, and twig biomass in all species, and belowground biomass in Robinia pseudoacacia and Betula nigra, along with basal diameter, height, and canopy dimensions. The individuals spanned a wide size range (<1-16 cm basal diameter; 0.24-8.8 m height). For each biomass component, aboveground biomass, belowground biomass, and total biomass, we determined the following four allometric equations: the most parsimonious (lowest AIC) overall, the most parsimonious without a fertilization effect, the most parsimonious without canopy dimensions, and an equation with basal diameter only. For some species, the most parsimonious overall equation included fertilization effects, but fertilization effects were inconsistent across fertilization treatments. We therefore concluded that fertilization does not clearly affect allometric relationships in these species, size classes, and growth conditions. Our best-fit allometric equations without fertilization effects had the following R2 values: 0.91-0.99 for aboveground biomass (the range is across species), 0.95 for belowground biomass, 0.80-0.96 for foliar biomass, 0.94-0.99 for main stem biomass, 0.77-0.98 for secondary stem biomass, and 0.88-0.99 for twig biomass. Our equations can be used to estimate overall biomass and biomass of tissue components for these size classes in these species, and our results indicate that soil fertility does not need to be considered when using allometric relationships for these size classes in these species.


Asunto(s)
Acacia , Árboles , Humanos , Preescolar , Betula , Biomasa , Nitrógeno
5.
Environ Entomol ; 52(4): 618-626, 2023 08 18.
Artículo en Inglés | MEDLINE | ID: mdl-37417547

RESUMEN

Nitrogen (N) is a key nutrient required by all living organisms for growth and development, but is a limiting resource for many organisms. Organisms that feed on material with low N content, such as wood, might be particularly prone to N limitation. In this study, we investigated the degree to which the xylophagous larvae of the stag beetle Ceruchus piceus (Weber) use associations with N-fixing bacteria to acquire N. We paired acetylene reduction assays by cavity ring-down absorption spectroscopy (ARACAS) with 15N2 incubations to characterize rates of N fixation within C. piceus. Not only did we detect significant N fixation activity within C. piceus larvae, but we calculated a rate that was substantially higher than most previous reports for N fixation in insects. While taking these measurements, we discovered that N fixation within C. piceus can decline rapidly in a lab setting. Consequently, our results demonstrate that previous studies, which commonly keep insects in the lab for long periods of time prior to and during measurement, may have systematically under-reported rates of N fixation in insects. This suggests that within-insect N fixation may contribute more to insect nutrition and ecosystem-scale N budgets than previously thought.


Asunto(s)
Escarabajos , Animales , Ecosistema , Fijación del Nitrógeno , Nitrógeno , Insectos , Larva
6.
Commun Chem ; 6(1): 92, 2023 May 11.
Artículo en Inglés | MEDLINE | ID: mdl-37169838

RESUMEN

Intentionally disordered metal-organic frameworks (MOFs) display rich functional behaviour. However, the characterisation of their atomic structures remains incredibly challenging. X-ray pair distribution function techniques have been pivotal in determining their average local structure but are largely insensitive to spatial variations in the structure. Fe-BTC (BTC = 1,3,5-benzenetricarboxylate) is a nanocomposite MOF, known for its catalytic properties, comprising crystalline nanoparticles and an amorphous matrix. Here, we use scanning electron diffraction to first map the crystalline and amorphous components to evaluate domain size and then to carry out electron pair distribution function analysis to probe the spatially separated atomic structure of the amorphous matrix. Further Bragg scattering analysis reveals systematic orientational disorder within Fe-BTC's nanocrystallites, showing over 10° of continuous lattice rotation across single particles. Finally, we identify candidate unit cells for the crystalline component. These independent structural analyses quantify disorder in Fe-BTC at the critical length scale for engineering composite MOF materials.

7.
Oecologia ; 201(3): 827-840, 2023 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-36877257

RESUMEN

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.


Asunto(s)
Ecosistema , Árboles , Fijación del Nitrógeno , Suelo , Monoéster Fosfórico Hidrolasas , Nitrógeno
8.
Sports (Basel) ; 11(1)2023 Jan 05.
Artículo en Inglés | MEDLINE | ID: mdl-36668717

RESUMEN

To examine relationships between Brazilian Jiu Jitsu (BJJ) descriptors (belt rank, experience, gi preference, and fighting style), resistance training (RT) experience, and measures of body composition, strength (maximal handgrip, 3-5-repetition maximum [RM] in barbell glute bridge [GB], prone bench row [PBR], and bench press [BP]), and velocity (GB, PBR, and BP at 7 kg and 30−60% 1-RM), 13 experienced (4.3 ± 3.4 years) BJJ athletes were recruited for this cross-sectional, pilot study. Significant (p < 0.05) Kendall's tau and Bayesian relationships were seen between belt rank and body fat percentage (τ = −0.53, BF10 = 6.5), BJJ experience and body fat percentage (τ = −0.44 to −0.66, BF10 = 2.6−30.8) and GB velocity (τ = −0.45 to −0.46, BF10 = 2.8−3.1), RT experience and strength (τ = 0.44 to 0.73, BF10 = 2.6−75.1) and velocity (τ = −0.44 to 0.47, BF10 = 2.6−3.3), gi preference-training and relative PBR strength (τ = 0.70, BF10 = 51.9), gi preference-competition and height and lean mass (τ = −0.57 to 0.67, BF10 = 5.3−12.4) and BP velocity (τ = −0.52 to 0.67, BF10 = 3.5−14.0). The relevance of body composition and performance measures to sport-specific training and research interpretation are differentially affected by a BJJ athlete's experience (BJJ, belt rank, RT), gi preferences, and fighting style.

9.
ESMO Open ; 8(1): 100743, 2023 02.
Artículo en Inglés | MEDLINE | ID: mdl-36542904

RESUMEN

BACKGROUND: The risk of toxicity-related dose delays, with cancer treatment, should be included as part of pretreatment education and be considered by clinicians upon prescribing chemotherapy. An objective measure of individual risk could influence clinical decisions, such as escalation of standard supportive care and stratification of some patients, to receive proactive toxicity monitoring. PATIENTS AND METHODS: We developed a logistic regression prediction model (Delay-7) to assess the overall risk of a chemotherapy dose delay of 7 days for patients receiving first-line treatments for breast, colorectal and diffuse large B-cell lymphoma. Delay-7 included hospital treated, age at the start of chemotherapy, gender, ethnicity, body mass index, cancer diagnosis, chemotherapy regimen, colony stimulating factor use, first cycle dose modifications and baseline blood values. Baseline blood values included neutrophils, platelets, haemoglobin, creatinine and bilirubin. Shrinkage was used to adjust for overoptimism of predictor effects. For internal validation (of the full models in the development data) we computed the ability of the models to discriminate between those with and without poor outcomes (c-statistic), and the agreement between predicted and observed risk (calibration slope). Net benefit was used to understand the risk thresholds where the model would perform better than the 'treat all' or 'treat none' strategies. RESULTS: A total of 4604 patients were included in our study of whom 628 (13.6%) incurred a 7-day delay to the second cycle of chemotherapy. Delay-7 showed good discrimination and calibration, with c-statistic of 0.68 (95% confidence interval 0.66-0.7), following internal validation and calibration-in-the-large of -0.006. CONCLUSIONS: Delay-7 predicts a patient's individualised risk of a treatment-related delay at cycle two of treatment. The score can be used to stratify interventions to reduce the occurrence of treatment-related toxicity.


Asunto(s)
Linfoma de Células B Grandes Difuso , Tiempo de Tratamiento , Humanos , Factores de Riesgo , Modelos Logísticos
10.
Ambio ; 52(3): 598-615, 2023 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-36583831

RESUMEN

Conservationists speculated on potential benefits to wildlife of lockdown restrictions because of the COVID-19 pandemic but voiced concern that restrictions impeded nature conservation. We assessed the effects of lockdown restrictions on biodiversity conservation in South Africa, a biodiverse country with economic inequality and reliance on wildlife resources. We solicited expert opinion using the IUCN's Threats Classification Scheme to structure a questionnaire and illustrated responses with individual case studies from government parastatal and non-governmental conservation organisations. The most highly reported threats were biological resource use, residential/commercial developments, invasive species, and human intrusions. The trends reported by 90 survey respondents were supported by case studies using environmental compliance data from parastatal conservation organisations. Lack of tourism revenue and funding were cited as hindrances to conservation. Mechanisms to prevent environmental degradation in the face of global emergencies must be implemented and 'ring-fenced' to ensure conservation is not a casualty during future global crises.


Asunto(s)
COVID-19 , Conservación de los Recursos Naturales , Animales , Humanos , Animales Salvajes , Control de Enfermedades Transmisibles/legislación & jurisprudencia , COVID-19/prevención & control , Sudáfrica , Encuestas y Cuestionarios
11.
Sci Total Environ ; 857(Pt 1): 159255, 2023 Jan 20.
Artículo en Inglés | MEDLINE | ID: mdl-36216052

RESUMEN

Perennial grains, such as the intermediate wheatgrass (Thinopyrum intermedium) (IWG), may reduce negative environmental effects compared to annual grain crops. Their permanent, and generally larger, root systems are likely to retain nitrogen (N) better, decreasing harmful losses of N and improving fertilizer N use efficiency, but there have been no comprehensive N fertilizer recovery studies in IWG to date. We measured fertilizer N recovery with stable isotope tracers in crop biomass and soil, soil N mineralization and nitrification, and nitrate leaching in IWG and annual wheat in a replicated block field experiment. Nitrate leaching was drastically reduced in IWG (0.1 and 3.1 kg N ha-1 yr-1) in its third and fourth year since establishment, compared with 5.6 kg N ha-1 yr-1 in annual wheat and 41.0 kg N ha-1 yr-1 in fallow respectively. There were no differences in net N mineralization or nitrification between IWG and annual wheat, though there was generally more inorganic N in the soil profile of annual wheat. More 15N fertilizer was recovered in the straw and all depths of the roots and soils in IWG than annual wheat. However, annual wheat recovered much more 15N fertilizer in the seeds compared to IWG, which had lower grain yields. 15N-labeled fertilizer contributed little (<3 %) to nitrate-N in leachate, highlighting the role of soil microbes in regulating loss of current year fertilizer N. The large reduction in nitrate leaching demonstrates that perennial grains can reduce harmful nitrogen losses and offer a more sustainable alternative to annual grains.


Asunto(s)
Fertilizantes , Nitratos , Fertilizantes/análisis , Nitratos/análisis , Triticum , Agricultura , Suelo , Nitrógeno/análisis , Óxidos de Nitrógeno
12.
BMC Med Educ ; 22(1): 749, 2022 Oct 31.
Artículo en Inglés | MEDLINE | ID: mdl-36316670

RESUMEN

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.


Asunto(s)
Partería , Obstetricia , Masculino , Recién Nacido , Embarazo , Femenino , Humanos , Partería/educación , Universidades , Kenia , Competencia Clínica , Obstetricia/educación , Curriculum
13.
Nanoscale ; 14(44): 16524-16535, 2022 Nov 17.
Artículo en Inglés | MEDLINE | ID: mdl-36285652

RESUMEN

Characterization of nanoscale changes in the atomic structure of amorphous materials is a profound challenge. Established X-ray and neutron total scattering methods typically provide sufficient signal quality only over macroscopic volumes. Pair distribution function analysis using electron scattering (ePDF) in the scanning transmission electron microscope (STEM) has emerged as a method of probing nanovolumes of these materials, but inorganic glasses as well as metal-organic frameworks (MOFs) and many other materials containing organic components are characteristically prone to irreversible changes after limited electron beam exposures. This beam sensitivity requires 'low-dose' data acquisition to probe inorganic glasses, amorphous and glassy MOFs, and MOF composites. Here, we use STEM-ePDF applied at low electron fluences (10 e- Å-2) combined with unsupervised machine learning methods to map changes in the short-range order with ca. 5 nm spatial resolution in a composite material consisting of a zeolitic imidazolate framework glass agZIF-62 and a 0.67([Na2O]0.9[P2O5])-0.33([AlO3/2][AlF3]1.5) inorganic glass. STEM-ePDF enables separation of MOF and inorganic glass domains from atomic structure differences alone, showing abrupt changes in atomic structure at interfaces with interatomic correlation distances seen in X-ray PDF preserved at the nanoscale. These findings underline that the average bulk amorphous structure is retained at the nanoscale in the growing family of MOF glasses and composites, a previously untested assumption in PDF analyses crucial for future non-crystalline nanostructure engineering.

14.
R Soc Open Sci ; 9(6): 210875, 2022 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-35774134

RESUMEN

SARS-CoV-2 emerged in late 2019 as a zoonotic infection of humans, and proceeded to cause a worldwide pandemic of historic magnitude. Here, we use a simple epidemiological model and consider the full range of initial estimates from published studies for infection and recovery rates, seasonality, changes in mobility, the effectiveness of masks and the fraction of people wearing them. Monte Carlo simulations are used to simulate the progression of possible pandemics and we show a match for the real progression of the pandemic during 2020 with an R 2 of 0.91. The results show that the combination of masks and changes in mobility avoided approximately 248.3 million (σ = 31.2 million) infections in the US before vaccinations became available.

15.
BMC Health Serv Res ; 22(1): 872, 2022 Jul 06.
Artículo en Inglés | MEDLINE | ID: mdl-35794569

RESUMEN

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.


Asunto(s)
Personal de Salud , Muerte Materna , Obstetricia , Reorganización del Personal , Estudios Transversales , Femenino , Humanos , Recién Nacido , Kenia , Mortalidad Materna , Embarazo
16.
Chem Sci ; 13(18): 5277-5288, 2022 May 11.
Artículo en Inglés | MEDLINE | ID: mdl-35655549

RESUMEN

We report the crystal structure of a new polymorph of l-tyrosine (denoted the ß polymorph), prepared by crystallization from the gas phase following vacuum sublimation. Structure determination was carried out by combined analysis of three-dimensional electron diffraction (3D-ED) data and powder X-ray diffraction (XRD) data. Specifically, 3D-ED data were required for reliable unit cell determination and space group assignment, with structure solution carried out independently from both 3D-ED data and powder XRD data, using the direct-space strategy for structure solution implemented using a genetic algorithm. Structure refinement was carried out both from powder XRD data, using the Rietveld profile refinement technique, and from 3D-ED data. The final refined structure was validated both by periodic DFT-D calculations, which confirm that the structure corresponds to an energy minimum on the energy landscape, and by the fact that the values of isotropic 13C NMR chemical shifts calculated for the crystal structure using DFT-D methodology are in good agreement with the experimental high-resolution solid-state 13C NMR spectrum. Based on DFT-D calculations using the PBE0-MBD method, the ß polymorph is meta-stable with respect to the previously reported crystal structure of l-tyrosine (now denoted the α polymorph). Crystal structure prediction calculations using the AIRSS approach suggest that there are three other plausible crystalline polymorphs of l-tyrosine, with higher energy than the α and ß polymorphs.

17.
Nature ; 607(7918): 294-300, 2022 07.
Artículo en Inglés | MEDLINE | ID: mdl-35609624

RESUMEN

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.

18.
BMC Pregnancy Childbirth ; 22(1): 410, 2022 May 16.
Artículo en Inglés | MEDLINE | ID: mdl-35578320

RESUMEN

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.


Asunto(s)
Cesárea , Mortalidad Infantil , Niño , Femenino , Instituciones de Salud , Humanos , Recién Nacido , Embarazo , Prevalencia , Rwanda/epidemiología
19.
PLoS One ; 17(4): e0248795, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-35482714

RESUMEN

In east and southern Africa some private ranch owners are corralling (hereafter kraaling) cattle overnight for short periods (for example, seven days) in natural rangelands to create nutrient enriched hotspots which are attractive to large herbivores. However, the effect of season and time after kraal use (alt. age of nutrient enriched hotspots) on large herbivore use of these sites has not been examined. We collated the number of large herbivore sightings per day from camera traps during wet, early and late dry season in nutrient enriched hotspots of varying ages (1, 2, 3 and 4 years) and surrounding vegetation. In addition, above ground grass biomass and height in nutrient enriched hotspots was compared to that of the surrounding vegetation. Furthermore, we tested if repeated grazing in nutrient enriched hotspots stimulated grass compensatory growth. Large herbivore use of nutrient enriched hotspots was similar during wet, early and late dry season. Time after kraal use had a significant effect on mixed feeders (impala and African savanna elephant) utilization of nutrient enriched hotspots but not grazers (zebra and warthog) and browsers (giraffe and greater kudu). Both impala and African savanna elephants mostly used nutrient enriched hotspots one year after kraal use. Aboveground grass biomass and height were higher in surrounding vegetation than in nutrient enriched hotspots. Repeated clipping (proxy for grazing) resulted in compensatory aboveground grass biomass in nutrient enriched hotspots, which declined with time after kraal use. We concluded that nutrient enriched hotspots created through short duration overnight kraaling were important foraging sites for large herbivores.


Asunto(s)
Animales Salvajes , Elefantes , Animales , Biomasa , Bovinos , Herbivoria , Poaceae , Porcinos , Factores de Tiempo
20.
Sci Rep ; 12(1): 5301, 2022 03 29.
Artículo en Inglés | MEDLINE | ID: mdl-35351938

RESUMEN

Meagre (Argyrosomus regius), is a benthopelagic species rapidly emerging in aquaculture, due to its low food to biomass conversion rate, good fillet yield and ease of production. Tracing a species genomic background along with describing the genetic basis of important traits can greatly influence both conservation strategies and production perspectives. In this study, we employed ddRAD sequencing of 266 fish from six F1 meagre families, to construct a high-density genetic map comprising 4529 polymorphic SNP markers. The QTL mapping analysis provided a genomic appreciation for the weight trait identifying a statistically significant QTL on linkage group 15 (LG15). The comparative genomics analysis with six teleost species revealed an evolutionarily conserved karyotype structure. The synteny observed, verified the already well-known fusion events of the three-spine stickleback genome, reinforced the evidence of reduced evolutionary distance of Sciaenids with the Sparidae family, reflected the evolutionary proximity with Dicentrarchus labrax, traced several putative chromosomal rearrangements and a prominent putative fusion event in meagre's LG17. This study presents novel elements concerning the genome evolutionary history of a non-model teleost species recently adopted in aquaculture, starts to unravel the genetic basis of the species growth-related traits, and provides a high-density genetic map as a tool that can help to further establish meagre as a valuable resource for research and production.


Asunto(s)
Lubina , Genoma , Animales , Lubina/genética , Evolución Biológica , Mapeo Cromosómico , Ligamiento Genético , Genoma/genética , Humanos
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