A large terrestrial source of methyl iodide

We have identified terrestrial sources of methyl iodide (CH3I) and assessed their importance in its atmospheric budget using a synthesis of field observations. Measurements include those from NASA DC-8 research flights over the United States and the North Atlantic, the AIRMAP long-term ground-observing network in New England, and a field campaign at Duke Forest, North Carolina. We found an average CH3I flux of ∼2,700 ng m-2 d-1 to the atmosphere from midlatitude vegetation and soils, a value similar in magnitude to previous estimates of the oceanic source strength. The large-scale aircraft measurements of vertical profiles over the continental U.S. showed CH3I-mixing ratios comparable to and greater than those observed over the North Atlantic. Overall, midlatitude terrestrial biomes appear to contribute 33 Gg yr-1 to the CH3I global budget. Copyright 2007 by the American Geophysical Union

A large terrestrial source of methyl iodide

We have identified terrestrial sources of methyl iodide (CH3I) and assessed their importance in its atmospheric budget using a synthesis of field observations. Measurements include those from NASA DC‐8 research flights over the United States and the North Atlantic, the AIRMAP long‐term ground‐observing network in New England, and a field campaign at Duke Forest, North Carolina. We found an average CH3I flux of ∼2,700 ng m−2 d−1 to the atmosphere from midlatitude vegetation and soils, a value similar in magnitude to previous estimates of the oceanic source strength. The large‐scale aircraft measurements of vertical profiles over the continental U.S. showed CH3I‐mixing ratios comparable to and greater than those observed over the North Atlantic. Overall, midlatitude terrestrial biomes appear to contribute 33 Gg yr−1 to the CH3I global budget

Plant community structure mediates potential methane production and potential iron reduction in wetland mesocosms.

Abstract Wetlands are the largest natural source of methane to the atmosphere, but factors controlling methane emissions from wetlands are a major source of uncertainty in greenhouse gas budgets and projections of future climate change. We conducted a controlled outdoor mesocosm experiment to assess the effects of plant community structure (functional group richness and composition) on potential methane production and potential iron reduction in freshwater emergent marshes. Four plant functional groups (facultative annuals, obligate annuals, reeds, and tussocks) were arranged in a full-factorial design and additional mesocosms were assigned as no-plant controls. Soil samples from the top 10 cm were collected three times during the growing season to determine potential methane production and potential iron reduction (in unamended soils and in soils amended with 200 mM formate). These data were compared to soil organic matter, soil pH, and previously published data on above and belowground plant biomass. We found that functional group richness was less important than the presence of specific functional groups (reeds or tussocks) in mediating potential iron reduction. In our mesocosms, where oxidized iron was abundant and electron donors were limiting, iron reducing bacteria outcompeted methanogens, keeping methane production barely detectable in unamended lab incubations. When the possibility of re-oxidizing iron was eliminated via anaerobic incubations and the electron donor limitation was removed by adding formate, potential methane production increased and followed the same patterns as potential iron reduction. Our findings suggest that in the absence of abundant oxidized iron and/or the presence of abundant electron donors, wetlands dominated by either reeds or tussocks may have increased methane production compared to wetlands dominated by annuals. Depending on functional traits such as plant transport and rhizospheric oxygenation capacities, this could potentially lead to increased methane emissions in some wetlands. Additional research examining the role these plant functional groups play in other aspects of methane dynamics will be useful given the importance of methane as a greenhouse gas

Thermoelastic impact damage on glass

Etched, as-received and abraded float glass, and etched low-expansion borosilicate glass were impacted at a velocity of 5.62 m/s by a spherical steel impactor of 10.3 mm diameter. The temperature of the glass specimens and that of the impactor were varied, and the effect of thermal shock on the resulting impact damage was investigated. The number, density and the radial spread of inner ring cracks that formed inside the primary ring crack, and the probability of cone crack formation were observed to increase significantly with increasing temperature difference between the impacting bodies, and with the abrasion of the glass surfaces prior to impact. Impacts on soda-lime-silica float glass at specimen temperatures of 700 and 750 °C revealed inner ring cracks without cone cracks, suggesting that significant strength degradation may result in glasses under these impact conditions. Borosilicate glass was found to be much more resistant to inner ring crack formation than soda-lime-silica glass

Dynamics of methane ebullition from a peat monolith revealed from a dynamic flux chamber system

Methane (CH4) ebullition in northern peatlands is poorly quantified in part due to its high spatiotemporal variability. In this study, a dynamic flux chamber (DFC) system was used to continuously measure CH4 fluxes from a monolith of near‐surface Sphagnum peat at the laboratory scale to understand the complex behavior of CH4 ebullition. Coincident transmission ground penetrating radar measurements of gas content were also acquired at three depths within the monolith. A graphical method was developed to separate diffusion, steady ebullition, and episodic ebullition fluxes from the total CH4 flux recorded and to identify the timing and CH4 content of individual ebullition events. The results show that the application of the DFC had minimal disturbance on air‐peat CH4 exchange and estimated ebullition fluxes were not sensitive to the uncertainties associated with the graphical model. Steady and episodic ebullition fluxes were estimated to be averagely 36 ± 24% and 38 ± 24% of the total fluxes over the study period, respectively. The coupling between episodic CH4 ebullition and gas content within the three layers supports the existence of a threshold gas content regulating CH4 ebullition. However, the threshold at which active ebullition commenced varied between peat layers with a larger threshold (0.14 m3 m−3) observed in the deeper layers, suggesting that the peat physical structure controls gas bubble dynamics in peat. Temperature variation (23°C to 27°C) was likely only responsible for small episodic ebullition events from the upper peat layer, while large ebullition events from the deeper layers were most likely triggered by drops in atmospheric pressure

Serial salivary estriol to detect an increased risk of preterm birth.

Journal ArticleOBJECTIVE: To evaluate serial measurements of salivary estriol (E3) to detect increased risk of spontaneous preterm labor and preterm birth. METHODS: A masked, prospective, multicenter trial of 956 women with singleton pregnancies was completed at eight United States medical centers. Saliva was collected weekly, beginning at the 22nd week of gestation until birth, and tested for unconjugated E3 by enzyme-linked immunosorbent assay. Women were separated into high-risk and low-risk groups using the Creasy scoring system. RESULTS: A single, positive (at or above 2.1 ng/mL) salivary E3 test predicted an increased risk of spontaneous preterm labor and delivery in the total population (relative risk [RR] 4.0, P <.005), in the low-risk population (RR 4.0, P < or =.05), and in the high-risk population (RR 3.4, P =.05). Two consecutive positive tests significantly increased the RR in all study groups, with a dramatic improvement in test specificity and positive predictive value but only a modest decrease in sensitivity. In women who presented with symptomatic preterm labor, salivary E3 identified 61% of those who delivered within 2 weeks, using a threshold of 1.4 ng/mL. CONCLUSION: Elevated salivary E3 is associated with increased risk of preterm birth in asymptomatic women and symptomatic women who present for evaluation of preterm labo

ARGG-HDL: A High Level Python Based Object-Oriented HDL Framework

We present a High-Level Python-based Hardware Description Language (ARGG-HDL), It uses Python as its source language and converts it to standard VHDL. Compared to other approaches of building converters from a high-level programming language into a hardware description language, this new approach aims to maintain an object-oriented paradigm throughout the entire process. Instead of removing all the high-level features from Python to make it into an HDL, this approach goes the opposite way. It tries to show how certain features from a high-level language can be implemented in an HDL, providing the corresponding benefits of high-level programming for the user

Large perturbation flow field analysis and simulation for supersonic inlets

An analysis technique for simulation of supersonic mixed compression inlets with large flow field perturbations is presented. The approach is based upon a quasi-one-dimensional inviscid unsteady formulation which includes engineering models of unstart/restart, bleed, bypass, and geometry effects. Numerical solution of the governing time dependent equations of motion is accomplished through a shock capturing finite difference algorithm, of which five separate approaches are evaluated. Comparison with experimental supersonic wind tunnel data is presented to verify the present approach for a wide range of transient inlet flow conditions

Yes we can! Improving medical screening for intimate partner violence through self-efficacy

BACKGROUND: Because individual practitioner's commitment to routine screening for IPV is the greatest predictor that women will be screened and referred for services, it is vital that screeners are dedicated, knowledgeable, and confident in their ability to recognize and assist victims of violence. Self-efficacy has been consistently linked in the literature with successful outcomes. Objectives: Intimate partner violence (IPV) constitutes a major public health problem. In the absence of Federal or State regulation, individual hospitals and systems are left to develop their own policies and procedures. This paper describes the policies and procedures developed by an American domestic violence counseling and resource center. Design: Post test surveys were used. Settings: Hospitals, medical offices, and medical schools surrounding an urban area in Pennsylvania participated. Participants: 320 nurses and medical students participated in training provided by a domestic violence center. METHODS: Post test surveys measured self-efficacy, the perceived usefulness of screening the accessibility of victim services, understanding of obstacles faced by victims, and knowledge-level regarding local IPV services. Participants also self-reported their gender, age, race, and position with the hospital system. RESULTS: Nurses and medical interns exhibit a wide range of self-efficacy regarding their ability to screen victims of intimate partner violence. Intimate partner violence (IPV) training yielded participants who were better informed about IPV services and the obstacles faced by victims. CONCLUSIONS: In the absence of uniform screening guidelines, hospitals, systems, and individual practitioners must be vigilant in screening procedures. Partnerships with women's centers may provide valuable resources and training that may ultimately improve patient care

Magnetic states of linear defects in graphene monolayers: effects of strain and interaction

The combined effects of defect-defect interaction and of uniaxial or biaxial strains of up to 10\% on the development of magnetic states on the defect-core-localized quasi-one-dimensional electronic states generated by the so-called 558 linear extended defect in graphene monolayers are investigated by means of {\it ab initio} calculations. Results are analyzed on the basis of the heuristics of the Stoner criterion. We find that conditions for the emergence of magnetic states on the 558 defect can be tuned by uniaxial tensile parallel strains (along the defect direction) at both limits of isolated and interacting 558 defects. Parallel strains are shown to lead to two cooperative effects that favor the emergence of itinerant magnetism: enhancement of the DOS of the resonant defect states in the region of the Fermi level and tuning of the Fermi level to the maximum of the related DOS peak. A perpendicular strain is likewise shown to enhance the DOS of the defect states, but it also effects a detunig of the Fermi level that shifts away from the maximum of the DOS of the defect states, which inhibts the emergence of magnetic states. As a result, under biaxial strains the stabilization of a magnetic state depends on the relative magnitudes of the two components of strain.Comment: 9 pages 8 figure