Chironomid-based water depth reconstructions: an independent evaluation of site-specific and local inference models

Water depth is an important environmental variable that explains a significant portion of the variation in the chironomid fauna of shallow lakes. We developed site-specific and local chironomid-water depth inference models using 26 and 104 surface-sediment samples, respectively, from seven kettlehole lakes in the Plymouth Aquifer, southeast Massachusetts, USA. Our site-specific model spans a depth gradient of 5.6 m, has an r2jack of 0.90, root mean square error of prediction (RMSEP) of 0.5 m and maximum bias of 0.7 m. Our local model has a depth gradient of 11.7 m, an r2 jack of 0.71,RMSEP of 1.6 m and maximum bias of 2.9 m. Principal coordinates of neighbourhood matrices (PCNM) analysis showed that there is no influence of spatial autocorrelation on the site-specific model, but PCNM variables explained a significant amount of variance (4.8%) in the local model. This variance, however, is unique from the variance explained by water depth. We applied the inference models to a Holocene chironomid record from Crooked Pond, a site for which multiple, independent palaeohydrological reconstructions are available. The chironomid-based reconstructions are remarkably similar and show stable water depths of ~5 m, interrupted by a 2-m decrease between 4,200 and 3,200 cal a BP. Sedimentological evidence of water level fluctuations at Crooked Pond, obtained using the so-called Digerfeldt approach, also shows a drop in water depths around that time. The period of reconstructed lower water levels coincides with the abrupt decline in moisture-dependent hemlock in this region, providing further evidence for this major palaeohydrological event. The site-specific model has the best performance statistics, but the high percent abundance of fossil taxa from the long core that are absent or rare in the training set makes the site-specific reconstruction unreliable for the period before 4,400 cal a BP. The fossil taxa are well represented in the local model, making it the preferred inference model. The strong similarity between the chironomid-based reconstructions and the independent palaeohydrological records highlights the potential for using chironomid-based inference models to determine past lake depths at sites where temperature was not an influencing factor

Rescue therapy for vasospasm following aneurysmal subarachnoid hemorrhage: a propensity score-matched analysis with machine learning

OBJECTIVE: Rescue therapies have been recommended for patients with angiographic vasospasm (aVSP) and delayed cerebral ischemia (DCI) following subarachnoid hemorrhage (SAH). However, there is little evidence from randomized clinical trials that these therapies are safe and effective. The primary aim of this study was to apply game theory-based methods in explainable machine learning (ML) and propensity score matching to determine if rescue therapy was associated with better 3-month outcomes following post-SAH aVSP and DCI. The authors also sought to use these explainable ML methods to identify patient populations that were more likely to receive rescue therapy and factors associated with better outcomes after rescue therapy. METHODS: Data for patients with aVSP or DCI after SAH were obtained from 8 clinical trials and 1 observational study in the Subarachnoid Hemorrhage International Trialists repository. Gradient boosting ML models were constructed for each patient to predict the probability of receiving rescue therapy and the 3-month Glasgow Outcome Scale (GOS) score. Favorable outcome was defined as a 3-month GOS score of 4 or 5. Shapley Additive Explanation (SHAP) values were calculated for each patient-derived model to quantify feature importance and interaction effects. Variables with high SHAP importance in predicting rescue therapy administration were used in a propensity score-matched analysis of rescue therapy and 3-month GOS scores. RESULTS: The authors identified 1532 patients with aVSP or DCI. Predictive, explainable ML models revealed that aneurysm characteristics and neurological complications, but not admission neurological scores, carried the highest relative importance rankings in predicting whether rescue therapy was administered. Younger age and absence of cerebral ischemia/infarction were invariably linked to better rescue outcomes, whereas the other important predictors of outcome varied by rescue type (interventional or noninterventional). In a propensity score-matched analysis guided by SHAP-based variable selection, rescue therapy was associated with higher odds of 3-month GOS scores of 4-5 (OR 1.63, 95% CI 1.22-2.17). CONCLUSIONS: Rescue therapy may increase the odds of good outcome in patients with aVSP or DCI after SAH. Given the strong association between cerebral ischemia/infarction and poor outcome, trials focusing on preventative or therapeutic interventions in these patients may be most able to demonstrate improvements in clinical outcomes. Insights developed from these models may be helpful for improving patient selection and trial design

Extrações sequenciais de chumbo e zinco em solos de área de mineração e metalurgia de metais pesados

A extração sequencial permite obter informações mais detalhadas sobre origem, modo de ocorrência, disponibilidade biológica e físico-química, mobilização e transporte dos metais pesados em ambientes naturais. Com o objetivo de estudar as formas de Pb e Zn foram selecionados oito perfis de solos de diferentes locais dentro de área de mineração e metalurgia de Pb, no município de Adrianópolis (PR), Vale do Rio Ribeira. As amostras foram coletadas nas profundidades de 0 a 10, 10 a 20 e 20 a 40 cm. Foram determinados os teores totais de Pb e Zn e sua especiação nas formas: solúvel; trocável; ligada a carbonatos; ligada à matéria orgânica; ligada aos óxidos de Fe de Al de baixa cristalinidade; ligada aos óxidos de Al cristalinos e filossilicatos 1:1 e 2:1; e residual. Com base nos valores percentuais de participação de cada fração nos teores totais, procedeu-se ao agrupamento das amostras similares por meio da análise de componentes principais (PCA). Houve basicamente duas formas de contaminação dos perfis de solo, sendo uma em decorrência das partículas das chaminés e a outra em função do acúmulo de rejeitos sólidos sobre os solos. A primeira foi mais prejudicial ao ambiente em razão dos maiores teores totais e de formas mais disponíveis no solo (solução mais trocável). De modo geral, houve maior associação de Pb aos carbonatos, seguida das frações residual e óxidos de Fe e Al de baixa cristalinidade. O Zn apresentou-se em formas mais insolúveis, aumentando a participação da fração residual nos teores totais. A PCA foi sensível às diferentes formas de Pb nos solos, pois promoveu o agrupamento das amostras, principalmente, em função da participação das formas trocáveis, ligadas aos óxidos de Fe e Al e ligadas aos carbonatos, em relação aos teores totais