A Systematic Review of the State of Neurosurgical Disparities Research: Past, Present, and Future.

BACKGROUND: The social determinants of health, which influence healthcare access, patient outcomes, and population-level burden of disease, contribute to health disparities experienced by marginalized patient populations. In the present study, we sought to evaluate the landscape of health disparities research within neurosurgery. METHODS: Embase, Ovid-MEDLINE, Scopus, Web of Science, Cochrane Library, and ProQuest Dissertations databases were queried for original research on health disparities regarding access to, outcomes of, and/or postoperative management after neurosurgical procedures in the United States. RESULTS: Of 883 studies screened, 196 were included, of which 144 had a neurosurgery-affiliated author. We found a significant increase in the number of neurosurgical disparities reports beginning in 2010, with only 10 studies reported before 2010. Of the included studies, 3.1% used prospective methods and 63.8% used data from national registries. The disparities analyzed were racial/ethnic (79.6%), economic/socioeconomic (53.6%), gender (18.9%), and disabled populations (0.5%), with 40.1% analyzing multiple or intersecting disparities. Of the included reports, 96.9% were in phase 1 (detecting phase of disparities research), with a few studies in phase 2 (understanding phase), and none in phase 3 (reducing phase). The spine was the most prevalent subspecialty evaluated (34.2%), followed by neuro-oncology (19.9%), cerebrovascular (16.3%), pediatrics (10.7%), functional (9.2%), general neurosurgery (5.1%), and trauma (4.1%). Senior authors with a neurosurgical affiliation accounted for 79.2% of the reports, 93% of whom were academically affiliated. CONCLUSIONS: Although a recent increase has occurred in neurosurgical disparities research within the past decade, most studies were limited to the detection of disparities without understanding or evaluating any interventions for a reduction in disparities. Future research in neurosurgical disparities should incorporate the latter 2 factors to reduce disparities and improve outcomes for all patients.

Gender concordance and publication productivity within Neurosurgical Focus: a 10-year review (2013-2022).

OBJECTIVE: The "leaky academic pipeline" describes how female representation in leadership positions has remained stagnant despite an increase in the number of female trainees. Female mentorship to female mentees, and female role models at higher academic positions have been shown to positively influence academic productivity. To the authors' knowledge, the impact of female editorial board representation on authorship trends in neurosurgical journals remains undescribed. This study aimed to analyze trends in the representation of female topic editors and its impact on female authorship within Neurosurgical Focus over a 10-year period. METHODS: Publicly available data were collected from the journal's website, inclusive from January 2013 to December 2022. The articles were grouped into technical and nontechnical themes based on their relevance to specific technical details regarding surgical techniques. Female gender-concordant publications were defined as publications having a female first author (or co-first author) and a female senior author. Linear regression analysis determined trends in publishing. Odds ratios and 95% CIs were calculated using logistic regression analysis. Pearson correlation and cross-correlation analyses were used to examine each pairwise comparison of time series. The statistical significance of associations was evaluated using t-tests and chi-square and Fisher's exact tests. RESULTS: The number of female topic editors and gender-concordant authors increased over time (p < 0.05). Women accounted for ≥ 50% of the topic editors on nontechnical themes relevant to education and gender diversity. Having a female senior author was associated with higher publication productivity for original research and review articles among female authors (OR 13.73, 95% CI 1.75-394.31; p < 0.05). Female authors had higher odds of publishing editorials with a female topic editor (OR 3.81, 95% CI 1.37-11.02; p < 0.01). Publications with female first and senior authors were significantly more likely to have female topic editors (OR 4.05, 95% CI 1.38-12.92; p < 0.01). A positive association was observed between female senior authors and female topic editors at lag -8, with a correlation coefficient of 0.19 (p = 0.03). CONCLUSIONS: Female attending-to-female trainee mentorship and female representation among editorial boards play a crucial role in enhancing academic productivity among women. Efforts to sustain academic productivity during the early-career period would presumably help increase female representation in neurosurgery.

Preclinical and clinical pharmacology of brexanolone (allopregnanolone) for postpartum depression: a landmark journey from concept to clinic in neurosteroid replacement therapy.

This article describes the critical role of neurosteroids in postpartum depression (PPD) and outlines the landmark pharmacological journey of brexanolone as a first-in-class neurosteroid antidepressant with significant advantages over traditional antidepressants. PPD is a neuroendocrine disorder that affects about 20% of mothers after childbirth and is characterized by symptoms including persistent sadness, fatigue, dysphoria, as well as disturbances in cognition, emotion, appetite, and sleep. The main pathology behind PPD is the postpartum reduction of neurosteroids, referred to as neurosteroid withdrawal, a concept pioneered by our preclinical studies. We developed neurosteroid replacement therapy (NRT) as a rational approach for treating PPD and other conditions related to neurosteroid deficiency, unveiling the power of neurosteroids as novel anxiolytic-antidepressants. The neurosteroid, brexanolone (BX), is a progesterone-derived allopregnanolone that rapidly relieves anxiety and mood deficits by activating GABA-A receptors, making it a transformational treatment for PPD. In 2019, the FDA approved BX, an intravenous formulation of allopregnanolone, as an NRT to treat PPD. In clinical studies, BX significantly improved PPD symptoms within hours of administration, with tolerable side effects including headache, dizziness, and somnolence. We identified the molecular mechanism of BX in a neuronal PPD-like milieu. The mechanism of BX involves activation of both synaptic and extrasynaptic GABA-A receptors, which promote tonic inhibition and serve as a key target for PPD and related conditions. Neurosteroids offer several advantages over traditional antidepressants, including rapid onset, unique mechanism, and lack of tolerance upon repeated use. Some limitations of BX therapy include lack of aqueous solubility, limited accessibility, hospitalization for treatment, lack of oral product, and serious adverse events at high doses. However, the unmet need for synthetic neurosteroids to address this critical condition supersedes these limitations. Recently, we developed novel hydrophilic neurosteroids with a superior profile and improved drug delivery. Overall, approval of BX is a major milestone in the field of neurotherapeutics, paving the way for the development of novel synthetic neurosteroids to treat depression, epilepsy, and status epilepticus.

Baseline frailty status, not advanced patient age, predicts epilepsy surgery outcomes: An analysis of 696 patients from the NSQIP database.

OBJECTIVE: Preoperative risk stratification of patients undergoing epilepsy surgery remains challenging. Recently, the efforts to look beyond age alone as an outcomes predictor has resulted in the development of measures of physiological reserve, or 'frailty indices.' The most frequently cited index in neurosurgery is the 11-item or 5-item modified frailty index (mFI11 or mFI-5). The present study aimed to use a large national registry to evaluate the effect of frailty (as measured by mFI-5 versus age on postoperative outcomes of patients undergoing epilepsy surgery. METHODS: The National Surgical Quality Improvement Program (NSQIP) database, overseen by the American College of Surgeons (ACS), was used to extract data for patients undergoing epilepsy surgery from 2015 to 2019. Univariate and multivariate analyses for age and mFI-5 were performed for the following 30-day outcomes of extended length of hospital stay (eLOS) and non-home discharge (NHD). The effect sizes were summarized by odds ratio and associated 95 % confidence intervals. Receiver operating characteristic (ROC) curve analysis, including area under the curve (AUC), was used to quantify the discrimination. RESULTS: Univariate and multivariate analyses demonstrated that frailty statuses from mFI-5, not age, were significantly predictive of eLOS and NHD. On ROC curve analysis, mFI-5 was a stronger predictor of eLOS (C = 0.59, 95 % CI 0.54-0.64, p < 0.001) and NHD (C = 0.69, 95 % CI 0.64-0.76, p < 0.001) than age (C = 0.53, 95 % CI 0.48-0.58, p = 0.21 and C = 0.53, 95 % CI 0.46-0.59, p = 0.44, respectively). CONCLUSION: Frailty, not age, is an independent risk factor for poor postoperative outcomes, particularly eLOS and NHD, in patients undergoing epilepsy surgery. Usage of mFI-5 for preoperative risk stratification of epilepsy surgery patients can help in prognostication.

Preoperative Frailty Predicts Worse Outcomes after Microvascular Decompression for Trigeminal Neuralgia, Hemifacial Spasm, and Glossopharyngeal Neuralgia: A Multicenter Analysis of 1,473 Patients from a Prospective Surgical Registry.

INTRODUCTION: Microvascular decompression (MVD) is an efficacious neurosurgical intervention for patients with medically intractable neurovascular compression syndromes. However, MVD may occasionally cause life-threatening or altering complications, particularly in patients unfit for surgical operations. Recent literature suggests a lack of association between chronological age and surgical outcomes for MVD. The Risk Analysis Index (RAI) is a validated frailty tool for surgical populations (both clinical and large database). The present study sought to evaluate the prognostic ability of frailty, as measured by RAI, to predict outcomes for patients undergoing MVD from a large multicenter surgical registry. METHODS: The American College of Surgeons-National Surgical Quality Improvement Program (ACS-NSQIP) database (2011-2020) was queried using diagnosis/procedure codes for patients undergoing MVD procedures for trigeminal neuralgia (n = 1,211), hemifacial spasm (n = 236), or glossopharyngeal neuralgia (n = 26). The relationship between preoperative frailty (measured by RAI and 5-factor modified frailty index [mFI-5]) for primary endpoint of adverse discharge outcome (AD) was analyzed. AD was defined as discharge to a facility which was not home, hospice, or death within 30 days. Discriminatory accuracy for prediction of AD was assessed by computation of C-statistics (with 95% confidence interval) from receiver operating characteristic (ROC) curve analysis. RESULTS: Patients undergoing MVD (N = 1,473) were stratified by RAI frailty bins: 71% with RAI 0-20, 28% with RAI 21-30, and 1.2% with RAI 31+. Compared to RAI score 19 and below, RAI 20 and above had significantly higher rates of postoperative major complications (2.8% vs. 1.1%, p = 0.01), Clavien-Dindo grade IV complications (2.8% vs. 0.7%, p = 0.001), and AD (6.1% vs. 1.0%, p < 0.001). The rate of primary endpoint was 2.4% (N = 36) and was positively associated with increasing frailty tier: 1.5% in 0-20, 5.8% in 21-30, and 11.8% in 31+. RAI score demonstrated excellent discriminatory accuracy for primary endpoint in ROC analysis (C-statistic: 0.77, 95% CI: 0.74-0.79) and demonstrated superior discrimination compared to mFI-5 (C-statistic: 0.64, 95% CI: 0.61-0.66) (DeLong pairwise test, p = 0.003). CONCLUSIONS: This was the first study to link preoperative frailty to worse surgical outcomes after MVD surgery. RAI frailty score predicts AD after MVD with excellent discrimination and holds promise for preoperative counseling and risk stratification of surgical candidates. A risk assessment tool was developed and deployed with a user-friendly calculator: https://nsgyfrailtyoutcomeslab.shinyapps.io/microvascularDecompression.

Thirty-day outcomes for suboccipital decompression in adults with Chiari malformation type I: a frailty-driven perspective from the American College of Surgeons National Surgical Quality Improvement Program.

OBJECTIVE: When indicated, patients with symptomatic Chiari malformation type I (CM-I) may benefit from suboccipital decompression (SOD). Although SOD is considered a lower-risk neurosurgical procedure, preoperative risk assessment and careful surgical patient selection remain critical. The objectives of the present study were twofold: 1) describe 30-day SOD outcomes for CM patients with attention to the impact of preoperative frailty and 2) design a predictive model for the primary endpoint of nonhome discharge (NHD). METHODS: There were 1015 CM-I patients who underwent SOD in the 2011-2020 American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) database, as specified by diagnostic and procedural codes (Current Procedural Terminology code 61343). Descriptive statistics were used to analyze total cohort baseline demographics, preoperative comorbidities, and postoperative outcomes within 30 days of surgery. Univariate cross-tabulation was used to compare baseline demographics and preoperative characteristics across the NHD and home discharge (HD) cohorts. Receiver operating characteristic (ROC) curve analysis was used to assess the discriminative ability of the revised Risk Analysis Index (RAI-rev) on NHD. RESULTS: The study cohort had a median age of 36 years, and 80.6% of patients were female. Race distribution was categorized as White (69.9%), Black (16.6%), and other groups (13.6%). The most common preoperative comorbidities were active smoking (24.4%), hypertension (19.2%), and diabetes mellitus (4.7%). The primary outcome of NHD occurred in 4.6% of patients (n = 47). Increasing frailty (measured by the RAI-rev) was associated with a stepwise increase in the rate of NHD: 2.3% for RAI-rev scores 0-10, 5.8% for RAI-rev scores 11-15, 7.6% for RAI-rev scores 16-20, 18.2% for RAI-rev scores 21-25, and 77.8% for RAI-rev scores ≥ 26 (p < 0.001). Other preoperative factors associated with NHD included older age, nonelective surgery, diabetes, hypertension, and elevated creatinine (all p < 0.01). The other most common 30-day complications included unplanned readmission (9.3%), unplanned reoperation (5.3%), return to the operating room (5.8%), Clavien-Dindo grade IV (life-threatening) (1.5%), organ space surgical site infection (SSI) (1.5%), superficial SSI (1.4%), and reoperation for a CSF leak (1.1%). Surgical mortality (within 30 days) was extremely rare (1/1015, 0.1%). ROC curve analysis demonstrated that RAI-rev predicted NHD with significant discriminatory accuracy among CM-I patients who received SOD treatment (C-statistic 0.731, 95% CI 0.648-0.814). CONCLUSIONS: This decade-long analysis of a multicenter surgical registry provides internationally representative, modern rates of 30-day outcomes after suboccipital decompression (with or without duraplasty) for adult CM-I patients. Preoperative frailty assessment with the RAI-rev may help identify higher-risk surgical candidates.

Frailty Measured by the Risk Analysis Index Predicts Nonhome Discharge and Mortality After Resection in Refractory Epilepsy: Analysis of 1236 Patients From a Prospective Surgical Registry, 2012 to 2020.

BACKGROUND: Risk stratification of epilepsy surgery patients remains difficult. The Risk Analysis Index (RAI) is a frailty measurement that augments preoperative risk stratification. OBJECTIVE: To evaluate RAI's discriminative threshold for nonhome discharge disposition (NHD) and mortality (or discharge to hospice within 30 days of operation) in epilepsy surgery patients. METHODS: Patients were queried from the American College of Surgeons-National Surgical Quality Improvement Program database (2012-2020) using diagnosis/procedure codes. Linear-by-linear trend tests assessed RAI's relationship with NHD and mortality. Discriminatory accuracy was assessed by C-statistics (95% CI) in receiver operating characteristic curve analysis. RESULTS: Epilepsy resections (N = 1236) were grouped into temporal lobe (60.4%, N = 747) and nontemporal lobe (39.6%, N = 489) procedures. Patients were stratified by RAI tier: 76.5% robust (RAI 0-20), 16.2% normal (RAI 21-30), 6.6% frail (RAI 31-40), and 0.8% severely frail (RAI 41 and above). The NHD rate was 18.0% (N = 222) and positively associated with increasing RAI tier: 12.5% robust, 34.0% normal, 38.3% frail, and 50.0% severely frail ( P < .001). RAI had robust predictive discrimination for NHD in overall cohort (C-statistic 0.71), temporal lobe (C-statistic 0.70), and nontemporal lobe (C-statistic 0.71) cohorts. The mortality rate was 2.7% (N = 33) and significantly associated with RAI frailty: 1.1% robust, 8.0% normal, 6.2% frail, and 20.0% severely frail ( P < .001). RAI had excellent predictive discrimination for mortality in overall cohort (C-statistic 0.78), temporal lobe (C-statistic 0.80), and nontemporal lobe (C-statistic 0.74) cohorts. CONCLUSION: The RAI frailty score predicts mortality and NHD after epilepsy surgery. This is accomplished with a user-friendly calculator: https://nsgyfrailtyoutcomeslab.shinyapps.io/epilepsy/ .

Clinical efficacy and safety of cannabidiol for pediatric refractory epilepsy indications: A systematic review and meta-analysis.

Antiseizure medications (ASMs) are the mainstay for the treatment of seizure disorders. However, about one-third of people with epilepsy remain refractory to current ASMs. Cannabidiol (CBD) has recently been approved as ASM for three refractory epilepsy syndrome indications in children and adults. In this study, we evaluated the overall clinical potential of an oral CBD to treat refractory epilepsy in patients with Dravet syndrome (DS), Lennox-Gastaut syndrome (LGS), and tuberous sclerosis complex (TSC) through a systematic review and meta-analysis. A comprehensive search of databases was conducted, including randomized controlled trials (RCTs) assessing the effect of CBD in epilepsy patients. The review was conducted as per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The review focused on RCTs involving patients receiving highly purified oral CBD (Epidiolex, 10 to 50 mg/kg/day) for up to 16 weeks. A subgroup analysis by syndrome and CBD with or without concomitant clobazam was conducted. The key outcomes were reduction in seizure frequency, differences in 50% responder rates, adverse events, and interactions with clobazam as co-therapy. Odds ratio (OR) with 95% confidence interval (CI) were estimated. Of 1183 articles screened, we included 6 RCTs meeting our eligibility criteria. All studies were considered to have a low risk of bias. In the pooled analysis, CBD treatment was found to be more efficacious compared to placebo (OR = 2.45, 95% CI =1.81-3.32, p < 0.01). Subgroup analysis by syndrome demonstrated the odds of ≥50% reduction in seizures with CBD treatment in patients with DS (OR = 2.26, 95% CI:1.38-3.70), LGS (OR = 2.98, 95% CI:1.83-4.85) and TSC (OR = 1.99, 95% CI = 1.06-3.76). Compared with placebo, CBD was associated with increased adverse events (OR = 1.81, 95% CI = 1.33-2.46) such as diarrhea, somnolence, and sedation, and any serious adverse events (OR = 2.86, 95% CI = 1.63-5.05). Other factors, including dosage and clobazam co-therapy, were significantly associated with a greater effect on seizure control and side effects of CBD. In conclusion, the study shows that CBD is highly efficacious both as standalone and adjunct therapy with clobazam for controlling seizures in DS, LGS, and TSC conditions while limiting side effects. Further pharmacodynamic investigation of CBD actions, drug interaction assessments, and therapeutic management guidelines are warranted.

The effects of placental transfusion on mothers.

OBJECTIVE: While there is ample evidence supporting delayed cord clamping (DCC) in neonates, the data on the maternal outcomes related to DCC are relatively sparse. Moreover, the outcomes, such as postpartum hemorrhage (PPH), were mostly reported for uncomplicated term vaginal deliveries. The objective of this study was to present the two primary maternal outcomes, incidence of PPH and change in hematocrit pre- and post-delivery in complex situations of preterm deliveries and term cesarean sections. STUDY DESIGN: Maternal data were collected prospectively since the placental transfusion process was implemented in a step-wise fashion in our delivery hospitals, starting August, 2013. These data on very preterm singleton, moderate preterm, very preterm twin gestation, late preterm deliveries and term cesarean sections with DCC or umbilical cord milking (UCM) were compared with respective retrospective cohorts of deliveries in which immediate cord clamping (ICC) was performed. RESULTS: Comparing very preterm singleton deliveries, the incidence of PPH was similar between the ICC and DCC groups (2.3% vs. 1.7%). There was no significant difference in mean hematocrit change pre- and postdelivery (3.06 ± 1.32 vs. 3.47 ± 1.52). When 45 s DCC cohort was compared with 60 s DCC cohort, there were no significant differences in the incidence of PPH (1.7% vs. 4.8%) or the hematocrit change pre- and postdelivery (3.47 ± 1.52 vs. 4.32 ± 1.88). PPH was not observed in either group when comparing retrospective ICC cohort with prospective DCC cohort with 60 s delay in very preterm twin gestation deliveries. There was no significant difference between the mean hematocrit change pre- and postdelivery (5.5 ± 3.3 vs. 5.8 ± 3.9). When moderate and early late preterm deliveries between 32° to 346 weeks of gestation were compared, there were no differences between the incidence of PPH (0.9% vs. 0%) or hematocrit change pre- and postdelivery (4.2 ± 2.3 vs. 4.8 ± 2.9). Comparing late preterm deliveries between 35° and 366 weeks of gestation, there was no significant difference in the incidence of PPH (13% vs. 11.4%) or the mean hematocrit change pre- and postdelivery (5.0 ± 3.0 vs. 5.1 ± 2.8). In term cesarean deliveries, the incidence of PPH was 2.2% in the retrospective ICC group and 1.4% in the prospective UCM group. There was no difference in mean hematocrit change pre- and postdelivery (5.9 ± 3.7 vs. 6.2 ± 2.8). CONCLUSION: DCC or UCM was not associated with the increased risk for PPH or significant change in maternal hematocrit pre- and postdelivery in very preterm singleton, moderate preterm, very preterm twin gestation, late preterm deliveries and term cesarean sections.

Abiotic synthesis of graphite in hydrothermal vents.

Deciphering the origin, age, and composition of deep marine organic carbon remains a challenge in understanding the dynamics of the marine carbon cycle. In particular, the composition of aged organic carbon and what allows its persistence in the deep ocean and in sediment is unresolved. Here, we observe that both high and low temperature hydrothermal vents at the 9° 50' N; 104° 17.5 W East Pacific Rise (EPR) vent field are a source for (sub)micron-sized graphite particles. We demonstrate that commonly applied analytical techniques for quantification of organic carbon detect graphite. These analyses thereby classify graphite as either dissolved or particulate organic carbon, depending on the particle size and filtration method, and overlook its relevance as a carbon source to the deep ocean. Settling velocity calculations indicate the potential for these (sub)micron particles to become entrained in the buoyant plume and distributed far from the vent fields. Thus, our observations provide direct evidence for hydrothermal vents acting as a source of old carbon to the deep ocean.

Archaea dominate oxic subseafloor communities over multimillion-year time scales.

Ammonia-oxidizing archaea (AOA) dominate microbial communities throughout oxic subseafloor sediment deposited over millions of years in the North Atlantic Ocean. Rates of nitrification correlated with the abundance of these dominant AOA populations, whose metabolism is characterized by ammonia oxidation, mixotrophic utilization of organic nitrogen, deamination, and the energetically efficient chemolithoautotrophic hydroxypropionate/hydroxybutyrate carbon fixation cycle. These AOA thus have the potential to couple mixotrophic and chemolithoautotrophic metabolism via mixotrophic deamination of organic nitrogen, followed by oxidation of the regenerated ammonia for additional energy to fuel carbon fixation. This metabolic feature likely reduces energy loss and improves AOA fitness under energy-starved, oxic conditions, thereby allowing them to outcompete other taxa for millions of years.

Iron and sulfide nanoparticle formation and transport in nascent hydrothermal vent plumes.

Deep-sea hydrothermal vents are a significant source of dissolved metals to the global oceans, producing midwater plumes enriched in metals that are transported thousands of kilometers from the vent source. Particle precipitation upon emission of hydrothermal fluids controls metal speciation and the magnitude of metal export. Here, we document metal sulfide particles, including pyrite nanoparticles, within the first meter of buoyant plumes from three high-temperature vents at the East Pacific Rise. We observe a zone of particle settling 10-20 cm from the orifice, indicated by stable sulfur isotopes; however, we also demonstrate that nanoparticulate pyrite (FeS2) is not removed from the plume and can account for over half of the filtered Fe (≤0.2 µm) up to one meter from the vent orifice. The persistence of nanoparticulate pyrite demonstrates that it is an important mechanism for near-vent Fe stabilisation and highlights the potential role of nanoparticles in element transport.

A durable and inexpensive pump profiler to monitor stratified water columns with high vertical resolution.

A pump profiling system for real time sample collection has been constructed for a cost of <$1000 (USD) and mated with a ship's rosette that has conductivity, temperature, depth (CTD) and other sensors. The system permits the collection of ~15 L of water in one minute without exposure to O2 from air for discrete sampling of chemical, microbial and other constituents as well as for real time analyses using sensors. We also coupled a shipboard voltammetry system with solid-state microelectrodes to detect dissolved O2 and H2S. Electrode O2 detection limits (DL) are ~3 µM and compare well with in situ Clark electrode O2 data (DL ~2 µM) from the ship's CTD rosette system. H2S measurements also were reliable, based on previously compared methods. Best resolution of the profiling system can be as small as its orifice of 2.54 cm (0.0254 m) in a quiet sea state, which is an improvement over the maximum resolution achievable using 10 L Niskin bottles that are 1 m in length.

Chromium(iii) oxidation by biogenic manganese oxides with varying structural ripening.

Manganese (Mn) oxides, which are generally considered biogenic in origin within natural systems, are the only oxidants of Cr(iii) under typical environmental conditions. Yet the influence of Mn biooxide mineral structural evolution on Cr(iii) oxidation under varying geochemical conditions is unknown. In this study we examined the role of light, organic carbon, pH, and the structure of biogenic Mn oxides on Cr(iii) oxidation. Aging of Mn oxides produced by a marine bacterium within the widespread Roseobacter clade resulted in structural ripening from a colloidal hexagonal to a particulate triclinic birnessite phase. The structurally diverse Mn oxides were then reacted with aqueous Cr(iii) within artificial seawater in the presence or absence of carbon and light. Here we found that Cr(iii) oxidation capacity was highest at near neutral pH and in the combined presence of carbon and light. Mn oxide ripening from a hexagonal to a triclinic birnessite phase led to decreased Cr(iii) oxidation in the presence of carbon and light, whereas no change in reactivity was observed in the absence of carbon and/or in the dark. As only minimal Cr(iii) oxidation was observed in the absence of Mn oxides, these results strongly point to coupled Mn oxide- and photo-induced generation of organic and/or oxygen radicals involved in Cr(iii) oxidation. Based on Mn oxide concentration and structural trends, we postulate that Mn(ii) produced from the oxidation of Cr(iii) by the primary Mn oxide is recycled in the presence of organics and light conditions, (re)generating secondary hexagonal birnessite and thereby allowing for continuous oxidation of Cr(iii). In the absence of this Mn oxide regeneration, Cr(iii) induced structural ripening of the hexagonal birnessite precludes further Cr(iii) oxidation. These results highlight the complexity of reactions involved in Mn oxide mediated Cr(iii) oxidation and suggest that photochemical carbon reactions are requisite for sustained Cr(iii) oxidation and persistence of reactive Mn oxides.

Sources and fates of heavy metals in a mining-impacted stream: temporal variability and the role of iron oxides.

Heavy metal contamination of surface waters at mining sites often involves complex interactions of multiple sources and varying biogeochemical conditions. We compared surface and subsurface metal loading from mine waste pile runoff and mine drainage discharge and characterized the influence of iron oxides on metal fate along a 0.9-km stretch of Tar Creek (Oklahoma, USA), which drains an abandoned Zn/Pb mining area. The importance of each source varied by metal; mine waste pile runoff contributed 70% of Cd, while mine drainage contributed 90% of Pb, and both sources contributed similarly to Zn loading. Subsurface inputs accounted for 40% of flow and 40-70% of metal loading along this stretch. Streambed iron oxide aggregate material contained highly elevated Zn (up to 27,000 µg g(-1)), Pb (up to 550 µg g(-1)) and Cd (up to 200 µg g(-1)) and was characterized as a heterogeneous mixture of iron oxides, fine-grain mine waste, and organic material. Sequential extractions confirmed preferential sequestration of Pb by iron oxides, as well as substantial concentrations of Zn and Cd in iron oxide fractions, with additional accumulation of Zn, Pb, and Cd during downstream transport. Comparisons with historical data show that while metal concentrations in mine drainage have decreased by more than an order of magnitude in recent decades, the chemical composition of mine waste pile runoff has remained relatively constant, indicating less attenuation and increased relative importance of pile runoff. These results highlight the importance of monitoring temporal changes at contaminated sites associated with evolving speciation and simultaneously addressing surface and subsurface contamination from both mine waste piles and mine drainage.

The EXCITE Trial: analysis of "noncompleted" Wolf Motor Function Test items.

OBJECTIVE: This is the first study to examine Wolf Motor Function Test (WMFT) tasks among EXCITE Trial participants that could not be completed at baseline or 2 weeks later. METHODS: Data were collected from participants who received constraint-induced movement therapy (CIMT) immediately at the time of randomization (CIMT-I, n = 106) and from those for whom there was a delay of 1 year in receiving this intervention (CIMT-D, n = 116). Data were collected at baseline and at a 2-week time point, during which the CIMT-I group received the CIMT intervention and the CIMT-D group did not. Generalized estimating equation (GEE) analyses were used to examine repeated binary data and count values. Group and visit interactions were assessed, adjusting for functional level, affected side, dominant side, age, and gender covariates. RESULTS: In CIMT-I participants, there was an increase in the proportion of completed tasks at posttest compared with CIMT-D participants, particularly with respect to those tasks requiring dexterity with small objects and total incompletes (P < .0033). Compared with baseline, 120 tasks governing distal limb use for CIMT-I and 58 tasks dispersed across the WMFT for CIMT-D could be completed after 2 weeks. Common movement components that may have contributed to incomplete tasks include shoulder stabilization and flexion, elbow flexion and extension, wrist pronation, supination and ulnar deviation, and pincer grip. CONCLUSION: CIMT training should emphasize therapy for those specific movement components in patients who meet the EXCITE criteria for baseline motor control.