Electron exchange capacity of pyrogenic dissolved organic matter (pyDOM): complementarity of square-wave voltammetry in DMSO and mediated chronoamperometry in water.

Pyrogenic dissolved organic matter (pyDOM) is derived from black carbon, which is important in the global carbon cycle and other biogeochemical redox processes. The electron-exchange capacity (EEC) of pyDOM has been characterized in water using mediated chronoamperometry (MCA), which gives precise results under specific operational conditions, but the broader significance of these EECs is less clear. In this study, we described a novel but complementary electrochemical approach to quantify EECs of pyDOM without mediation using square-wave voltammetry (SWV) in dimethyl sulfoxide (DMSO). Using both the SWV and MCA methods, we determined EECs for 10 pyDOMs, 6 natural organic matter (NOM) samples, and 2 model quinones. The two methods gave similar EECs for model quinones, but SWV gave larger EECs than MCA for NOM and pyDOM (by several-fold and 1-2 orders of magnitude, respectively). The differences in the EECs obtained by SWV and MCA likely are due to multiple factors, including the potential range of electrons sampled, kinetics of electron transfer from (macro)molecular structures, and coupling of electron and proton transfer steps. Comparison of the results obtained by these two methods should provide new insights into important environmental processes such as carbon-cycling, wildfire recovery, and contaminant mitigation using carbon-based amendments.

Influence of Organic Ligands on the Redox Properties of Fe(II) as Determined by Mediated Electrochemical Oxidation.

Fe(II) has been extensively studied due to its importance as a reductant in biogeochemical processes and contaminant attenuation. Previous studies have shown that ligands can alter aqueous Fe(II) redox reactivity but their data interpretation is constrained by the use of probe compounds. Here, we employed mediated electrochemical oxidation (MEO) as an approach to directly quantify the extent of Fe(II) oxidation in the absence and presence of three model organic ligands (citrate, nitrilotriacetic acid, and ferrozine) across a range of potentials (EH) and pH, thereby manipulating oxidation over a broad range of fixed thermodynamic conditions. Fe(III)-stabilizing ligands enhanced Fe(II) reactivity in thermodynamically unfavorable regions (i.e., low pH and EH) while an Fe(II) stabilizing ligand (ferrozine) prevented oxidation across all thermodynamic regions. We experimentally derived apparent standard redox potentials, EHϕ, for these and other (oxalate, oxalate2, NTA2, EDTA, and OH2) Fe-ligand redox couples via oxidative current integration. Preferential stabilization of Fe(III) over Fe(II) decreased EHϕ values, and a Nernstian correlation between EHϕ and log(KFe(III)/KFe(II)) exists across a wide range of potentials and stability constants. We used this correlation to estimate log(KFe(III)/KFe(II)) for a natural organic matter isolate, demonstrating that MEO can be used to measure iron stability constant ratios for unknown ligands.

Spatial distribution and biogeochemistry of redox active species in arctic sedimentary porewaters and seeps.

Redox active species in Arctic lacustrine sediments play an important, regulatory role in the carbon cycle, yet there is little information on their spatial distribution, abundance, and oxidation states. Here, we use voltammetric microelectrodes to quantify the in situ concentrations of redox-active species at high vertical resolution (mm to cm) in the benthic porewaters of an oligotrophic Arctic lake (Toolik Lake, AK, USA). Mn(II), Fe(II), O2, and Fe(III)-organic complexes were detected as the major redox-active species in these porewaters, indicating both Fe(II) oxidation and reductive dissolution of Fe(III) and Mn(IV) minerals. We observed significant spatial heterogeneity in their abundance and distribution as a function of both location within the lake and depth. Microbiological analyses and solid phase Fe(III) measurements were performed in one of the Toolik Lake cores to determine the relationship between biogeochemical redox gradients and microbial communities. Our data reveal iron cycling involving both oxidizing (FeOB) and reducing (FeRB) bacteria. Additionally, we profiled a large microbial iron mat in a tundra seep adjacent to an Arctic stream (Oksrukuyik Creek) where we observed Fe(II) and soluble Fe(III) in a highly reducing environment. The variable distribution of redox-active substances at all the sites yields insights into the nature and distribution of the important terminal electron acceptors in both lacustrine and tundra environments capable of exerting significant influences on the carbon cycle.

A three-dimensional parametric adult head model with representation of scalp shape variability under hair.

Modeling the shape of the scalp and face is essential for the design of protective helmets and other head-borne equipment. However, head anthropometry studies using optical scanning rarely capture scalp shape because of hair interference. Data on scalp shape is available from bald men, but female data are generally not available. To address this issue, scalp shape was digitized in an ethnically diverse sample of 100 adult women, age 18-59, under a protocol that included whole head surface scanning and scalp measurement using a three-dimensional (3D) coordinate digitizer. A combined male and female sample was created by adding 3D surface scans of a similarly diverse sample of 80 bald men. A statistical head shape model was created by standardizing the head scan data. A total of 58 anatomical head landmarks and 12 head dimensions were obtained from each scan and processed along with the scans. A parametric model accounting for the variability of the head shape under the hair as a function of selected head dimensions was developed. The full-variable model has a mean shape error of 3.8 mm; the 95th percentile error was 7.4 mm, which were measured at the vertices. The model will be particularly useful for generating a series of representing a target population as well as for generating subject-specific head shapes along with predicted landmarks and dimensions. The model is publicly available online at http://humanshape.org/head/.

Comparison of univariate and multivariate anthropometric design requirements methods for flight deck design application.

Designing aircraft cockpits to accommodate the wide range of body sizes and shapes existing in the world population has always been a difficult problem for crew station engineers. There is no consensus on the best method for obtaining measurements for body forms that statistically represent the variation within a population. The aim of this research is to compare the two most commonly used anthropometric approaches for dimension specification and flight deck design: the boundary cases multivariate and the percentile univariate. The multivariate approach captured more subjects than the percentile approach (p < .05) for all accommodation assessments using Brazilian Air Force pilots' anthropometry, but was not as effective as had been suggested in the literature. This study showed that the Boundary Cases Multivariate Method was better at evaluating design criteria for cockpit accommodation than the Percentile Univariate Method for accommodation of the central 90% envelope for the Brazilian Air Force crew application. Practitioner summary: The findings show that the Multivariate Boundary Cases approach can better provide anthropometric limits for the desired accommodation level when multiple body dimensions need to be simultaneously considered in a design. It will help researchers, designers, and engineers to solve complex design situations, make improved judgement and take right decisions. Abbreviations: FAR: federal aviation regulation; CS: certification specification; FAA: federal aviation administration; EASA: European union aviation safety agency; EMB: embraer; FAB: Brazilian Air Force; CAD: computer-aided design; MAM: multivariate anthropometric method; USAF: United States Air Force; PCA: principal component analysis; PC: principal component; JSF: joint strike fighter; NATO: North atlantic treaty organization; ISO: International Organization for Standardization; BPAD: Brazilian pilots anthropometric database; RD: radial distance; Error = A-E: error = achieved - expected; SPSS: statistical package for the social sciences; IBM Corp.: International business machines corporation; Acr. Ht, st: acromion height, sitting; But-kn lgt: buttock-knee length; Eye Ht, sit: eye height, sitting; Knee Ht, sit: knee height, sitting; Sitting Ht: sitting height; Thumbtip rch: thumbtip reach; Accom %: accommodated percentage; Af, Am, …, Zf, Zm: cases A-D and W-Z ("f" for female subjects and "m" for male subjects); T: trainer; A: atack; KC: anker and cargo; F: fighter; NG-BR: new generation - Brasil; PPE: personal protective equipment.

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.

Morphology of Modern Arrowhead Tips on Human Skin Analog.

Archery has experienced a recent resurgence in participation and has seen increases in archery range attendance and in children and young adults seeking archery lessons. Popular literature and movies prominently feature protagonists well versed in this form of weaponry. Periodic homicide cases in the United States involving bows are reported, and despite this and the current interest in the field, there are no manuscripts published on a large series of arrow wounds. This experiment utilizes a broad selection of modern arrowheads to create wounds for comparison. While general appearances mimicked the arrowhead shape, details such as the presence of abrasions were greatly influenced by the design of the arrowhead tip. Additionally, in the absence of projectiles or available history, arrowhead injuries can mimic other instruments causing penetrating wounds. A published resource on arrowhead injuries would allow differentiation of causes of injury by forensic scientists.

Current and Future Challenges in Group Therapy.

This article reviews changes and considers challenges in group therapy since AGPA's 50th anniversary 25 years ago. The authors acknowledge the many important changes that have occurred in research, theory, and practice in the last two and a half decades, but focus on four topics: treating trauma with cultural sensitivity; the impact of technology on groups; challenges for LGBTQ clients in group; and the future for psychodynamic groups. The authors review the literature and provide recommendations on how to address the challenges.

Achieving synergy between chemical oxidation and stabilization in a contaminated soil.

Eight in situ solidification/stabilization (ISS) amendments were tested to promote in situ chemical oxidation (ISCO) with activated persulfate (PS) in a contaminated soil. A 3% (by weight) dose of all ISS amendments selected for this study completely activated a 1.5% dose of PS within 3 h by raising temperatures above 30 °C (heat activation) and/or increasing pH above 10.5 (alkaline activation). Heat is released by the reaction of CaO with water, and pH increases because this reaction produces Ca(OH)2. Heat activation is preferred because it generates 2 mol of oxidizing radicals per mole of PS, whereas alkaline activation releases only 1. The relative contribution of heat vs. alkaline activation increased with CaO content of the ISS amendment, which was reflected by enhanced contaminant oxidation with increasing CaO content, and was confirmed by comparing to controls promoting purely heat or alkaline (NaOH) activation. The test soil was contaminated with benzene, toluene, ethylbenzene, and xylenes (BTEX) and polycyclic aromatic hydrocarbons (PAH), particularly naphthalene (NAP). ISS-activated PS oxidized between 47% and 84% of the BTEX & NAP, and between 13% and 33% of the higher molecular weight PAH. ISS-activated PS reduced the leachability of BTEX & NAP by 76%-91% and of the 17 PAH by 83%-96%. Combined ISCO/ISS reduced contaminant leachability far than ISCO or ISS treatments alone, demonstrating the synergy that is possible with combined remedies.

The effects of oral contraceptive use on muscle stiffness across the menstrual cycle.

OBJECTIVE: To determine the effect of oral contraceptives (OC) on hamstring neuromechanics and lower extremity stiffness across the menstrual cycle (MC). DESIGN: Causal comparative. SETTING: Research laboratory. PARTICIPANTS: Thirty, healthy, normally menstruating female volunteers who were using OC (OC group, n = 15) or not (non-OC group, n = 15). ASSESSMENT OF RISK FACTORS: Stiffness and hamstring neuromechanics were assessed at 2 points of the MC corresponding to low (menses) and high (ovulation) hormone concentrations. Menses testing took place 3 to 5 days after the onset of menses (or pills 3-5 for the OC group). Ovulation test session occurred 2 to 4 days after ovulation identified using a commercial ovulation kit (or pills 15-17 in the OC group). MAIN OUTCOME MEASURES: Lower extremity stiffness and hamstring neuromechanics [stiffness, electromechanical delay, rate of force production (RFP), time to 50% peak force (T50%)] and blood plasma concentrations of estradiol-ß-17, free testosterone, and progesterone. RESULTS: Estradiol-ß-17, free testosterone, and progesterone increased at ovulation in the non-OC group and remained constant in the OC group. No changes were observed across the MC or between the groups in other variables (P > 0.05). CONCLUSIONS: Although previous literature suggests a prophylactic effect of OC use with respect to musculoskeletal injury risk, our results indicate that OC use does not affect muscle properties in manners thought to reduce ACL injury risk.

Posttraumatic exogenous Nocardia endophthalmitis.

PURPOSE: To report a case of posttraumatic exogenous Nocardia endophthalmitis. DESIGN: Interventional case report. METHOD: A 46-year-old man presented with counting fingers vision, severe eye pain, hypopyon, and an iris mass consistent with endophthalmitis following a penetrating injury to the left eye. RESULTS: Despite oral fluconazole and repeated intravitreal injections of vancomycin, gentamicin, and amphotericin B, the eye remained painful with a persistent hypopyon and recurrent iris masses. Cultures of the vitreous and iris masses remained negative for organisms. Despite vitrectomy and sector iridectomy of the iris mass with repeat injections of intravitreal antibiotics, the patient continued to have severe pain, poor vision, and developed new iris masses. Enucleation cultures confirmed Nocardia asteroides. CONCLUSIONS: Posttraumatic exogenous Nocardia endophthalmitis is extremely rare, and its clinical signs can mimic a fungal infection.

Perturbations of plasma cortisol and DHEA-S following discontinuation of cocaine use in cocaine addicts.

Changes in plasma levels of cortisol and dehydroepiandrosterone sulfate (DHEA-S) following cocaine discontinuation were assessed in hospitalized chronic cocaine users. Measurements were performed after 6, 9, 18 and 21 days of abstinence. Repeated measures ANOVAs revealed significant time effects for cortisol (P<0.02) and DHEA-S (P<0.001). Changes in the two hormones did not follow the same course. Levels of cortisol were highest on day 6 and then subsequently decreased, whereas DHEA-S levels were low on day 6 and highest on day 18. Repeated measures ANCOVAs were used to test the overall effects of total duration of cocaine use, daily or weekly cocaine amounts consumed, or frequency of use on cortisol secretion. Analyses revealed a significant effect of frequency of use only (P<0.04). More sustained cocaine use was associated with higher cortisol levels and less pronounced cortisol decline after discontinuation of cocaine use, but drug intake variables had no influence on DHEA-S. The effects of presence or absence of life-long histories of aggression were also assessed. Repeated measures ANOVAs revealed a near significant group x time interaction for cortisol, which declined more dramatically in aggressive addicts than in non-aggressive addicts after day 6. DHEA-S was consistently higher in aggressive cocaine addicts, although this effect did not reach statistical significance. There was a noticeable difference in the dynamics of normalization of adrenal hormones between the two groups, with DHEA-S/cortisol ratios rising more dramatically during cocaine abstinence in aggressive than in non-aggressive addicts. In conclusion, lingering neuroendocrine perturbations persist after discontinuation of cocaine use in addicts. Some of these changes could be associated with an increased relapse risk.