Iron speciation is one of the most widely applied proxies used to reconstruct oxygen levels and redox conditions in past aqueous environments. The iron speciation proxy estimates proportions of ...different reactive iron species in fine‐grained sedimentary rocks, which are mapped to redox conditions based on empirical calibrations from modern sediments. It is based on a standardized extraction technique of sequentially applying acetate, hydroxlamine‐HCl, dithionite, and oxalate solutions to a powdered sample in order to dissolve iron phases and quantify the amount of iron carried by carbonates, “easily reducible” oxyhydroxides, ferric iron (oxyhydr)oxides, and magnetite, respectively. Although tested on pure minerals and mixtures, assessments of whether this sequential extraction process accurately dissolves the targeted minerals in natural sediments and sedimentary rocks are lacking. In our study, residues from each sequential extraction step were analyzed using rock magnetic and X‐ray diffraction experiments to identify and quantify the iron‐bearing minerals that were dissolved. The dithionite extraction robustly removes the targeted mineralogy as magnetic data show it to solubilize nearly all of the goethite. However, magnetic quantification of magnetite was orders of magnitude less than the iron measured in the oxalate extraction; X‐ray diffraction data suggest that dissolution of iron‐bearing clays, specifically berthierine/chamosite, could explain this disparity. Our data compilation shows higher values of iron from the oxalate extraction in Precambrian sedimentary rock samples, suggesting a significant temporal shift in iron cycling. Recognition of heterogeneity in chemical extraction efficiency and targeting is vital for holistic multiproxy interpretation of past oxygen levels and communication between disciplines.
Plain Language Summary
Sequential chemical extractions, where a series of solutions are applied to a powdered rock sample to selectively dissolve certain phases, are heavily utilized throughout Earth Science research. These methodologies provide a tool for estimating different reactive forms of an element; understanding how these pools change over time in a given environment allows us to better understand cycling of the element by biological, chemical, and geologic processes on the Earth's surface. In this study, we focus on a sequential chemical extraction method that measures the element iron, the most abundant transition metal in Earth's crust. Although heavily utilized for understanding nutrient cycling and ancient oxygen levels, the method is largely untested using actual rock samples that contain a mixture of minerals of different shapes and sizes. Such tests are needed to evaluate whether the extractions are accurately and completely dissolving the targeted minerals. We utilized magnetic and X‐ray diffraction methods that can sensitively measure iron minerals within natural samples. We found that some of the extractions worked as expected, but others did not, dissolving additional unexpected mineral types and/or slowly dissolving minerals across multiple extractions.
Key Points
Magnetic and X‐ray diffraction analyses on natural samples corroborate the efficiency of certain chemical extractions, such as dithionite
The majority of iron in the oxalate extraction is not dissolved from magnetite, but instead comes from iron‐bearing clays
Recognition of the heterogeneity in chemical extraction efficiency and targeting is vital for studies of past and present iron cycling
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
In 1992, the National Institute of Mental Health and 6 teams of investigators began a multisite clinical trial, the Multimodal Treatment of Attention-Deficit Hyperactivity Disorder (MTA) study. Five ...hundred seventy-nine children were randomly assigned to either routine community care (CC) or one of three study-delivered treatments, all lasting 14 months. The three MTA treatments-monthly medication management (usually methylphenidate) following weekly titration (MedMgt), intensive behavioral treatment (Beh), and the combination (Comb)-were designed to reflect known best practices within each treatment approach. Children were assessed at four time points in multiple outcome. Results indicated that Comb and MedMgt interventions were substantially superior to Beh and CC interventions for attention-deficit hyperactivity disorder symptoms. For other functioning domains (social skills, academics, parent-child relations, oppositional behavior, anxiety/depression), results suggested slight advantages of Comb over single treatments (MedMgt, Beh) and community care. High quality medication treatment characterized by careful yet adequate dosing, three times daily methylphenidate administration, monthly follow-up visits, and communication with schools conveyed substantial benefits to those children that received it. In contrast to the overall study findings that showed the largest benefits for high quality medication management (regardless of whether given in the MedMgt or Comb group), secondary analyses revealed that Comb had a significant incremental effect over MedMgt (with a small effect size for this comparison) when categorical indicators of excellent response and when composite outcome measures were used. In addition, children with parent-defined comorbid anxiety disorders, particularly those with overlapping disruptive disorder comorbidities, showed preferential benefits to the Beh and Comb interventions. Parental attitudes and disciplinary practices appeared to mediate improved response to the Beh and Comb interventions.
Pulse pile-up in pulse-height energy analyzers increases when the incident rate of pulses increases relative to the inverse of the dead time per pulse of the detection system. Changes in the observed ...energy distributions with incident rate and detector-electronics-formed pulse shape then occur. We focus on weak high energy tails in X-ray spectra, important for measurements on partially ionized, warm (50–500 eV average electron energy), pure hydrogen plasma. A first-principles two-photon pulse-pile-up model is derived specific to trapezoidal-shaped pulses; quantitative agreement is found between the measurements and the model’s predictions. The model is then used to diagnose pulse-pile-up tail artifacts and mitigate them in relatively low count-rate spectra.
Swanson et al discuss the diagnosis, epidemiology, treatment, prognosis and pathophysiology of attention-deficit hyperactivity disorder and hyperkinetic disorder.
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DOBA, GEOZS, IJS, IMTLJ, IZUM, KILJ, KISLJ, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SIK, UILJ, UKNU, UL, UM, UPCLJ, UPUK, VSZLJ
Previous research has been inconclusive whether attention-deficit/hyperactivity disorder (ADHD), when comorbid with disruptive disorders (oppositional defiant disorder ODD or conduct disorder CD), ...with the internalizing disorders (anxiety and/or depression), or with both, should constitute separate clinical entities. Determination of the clinical significance of potential ADHD + internalizing disorder or ADHD + ODD/CD syndromes could yield better diagnostic decision-making, treatment planning, and treatment outcomes.
Drawing upon cross-sectional and longitudinal information from 579 children (aged 7-9.9 years) with ADHD participating in the NIMH Collaborative Multisite Multimodal Treatment Study of Children With Attention-Deficit/Hyperactivity Disorder (MTA), investigators applied validational criteria to compare ADHD subjects with and without comorbid internalizing disorders and ODD/CD.
Substantial evidence of main effects of internalizing and externalizing comorbid disorders was found. Moderate evidence of interactions of parent-reported anxiety and ODD/CD status were noted on response to treatment, indicating that children with ADHD and anxiety disorders (but no ODD/CD) were likely to respond equally well to the MTA behavioral and medication treatments. Children with ADHD-only or ADHD with ODD/CD (but without anxiety disorders) responded best to MTA medication treatments (with or without behavioral treatments), while children with multiple comorbid disorders (anxiety and ODD/CD) responded optimally to combined (medication and behavioral) treatments.
Findings indicate that three clinical profiles, ADHD co-occurring with internalizing disorders (principally parent-reported anxiety disorders) absent any concurrent disruptive disorder (ADHD + ANX), ADHD co-occurring with ODD/CD but no anxiety (ADHD + ODD/CD), and ADHD with both anxiety and ODD/CD (ADHD + ANX + ODD/CD) may be sufficiently distinct to warrant classification as ADHD subtypes different from "pure" ADHD with neither comorbidity. Future clinical, etiological, and genetics research should explore the merits of these three ADHD classification options.
3-Year Follow-up of the NIMH MTA Study Jensen, Peter S; Arnold, L. Eugene; Swanson, James M ...
Journal of the American Academy of Child and Adolescent Psychiatry,
08/2007, Volume:
46, Issue:
8
Journal Article
Peer reviewed
Objective: In the intent-to-treat analysis of the Multimodal Treatment Study of Children With ADHD (MTA), the effects of medication management (MedMgt), behavior therapy (Beh), their combination ...(Comb), and usual community care (CC) differed at 14 and 24 months due to superiority of treatments that used the MTA medication algorithm (Comb+MedMgt) over those that did not (Beh+CC). This report examines 36-month outcomes, 2 years after treatment by the study ended. Method: For primary outcome measures (attention-deficit/hyperactivity disorder ADHD and oppositional defiant disorder ODD symptoms, social skills, reading scores, impairment, and diagnostic status), mixed-effects regression models and orthogonal contrasts examined 36-month outcomes. Results: At 3 years, 485 of the original 579 subjects (83.8%) participated in the follow-up, now at ages 10 to 13 years, (mean 11.9 years). In contrast to the significant advantage of MedMgt+Comb over Beh+CC for ADHD symptoms at 14 and 24 months, treatment groups did not differ significantly on any measure at 36 months. The percentage of children taking medication greater than 50% of the time changed between 14 and 36 months across the initial treatment groups: Beh significantly increased (14% to 45%), MedMed+Comb significantly decreased (91% to 71%), and CC remained constant (60%-62%). Regardless of their treatment use changes, all of the groups showed symptom improvement over baseline. Notably, initial symptom severity, sex (male), comorbidity, public assistance, and parental psychopathology (ADHD) did not moderate children's 36-month treatment responses, but these factors predicted worse outcomes over 36 months, regardless of original treatment assignment. Conclusions: By 36 months, the earlier advantage of having had 14 months of the medication algorithm was no longer apparent, possibly due to age-related decline in ADHD symptoms, changes in medication management intensity, starting or stopping medications altogether, or other factors not yet evaluated. (Contains 2 tables and 4 figures.)
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