Methane Emission from a Tropical Wetland in Ka‘au Crater, O‘ahu, Hawai‘i.

v. ill. 23 cm.QuarterlyNatural tropical wetlands constitute an important but still poorly studied source of atmospheric methane, a powerful greenhouse gas. We measured net methane emission, soil profiles of methane generation and oxidation, and related environmental parameters in a tropical wetland occupying the Ka‘au extinct volcanic crater on the Hawaiian island of O‘ahu. The wetland has a fluctuating water table with dynamics that can be reproduced using precipitation data and a simple model. Median net methane flux was 117 mg m_2 day_1 and is consistent with measurements at other tropical sites. Net methane flux in the Commelina diffusa–dominated vegetation pattern (honohono) was significantly higher than that of the invasive Psidium cattleianum–dominated pattern (strawberry guava). Net methane emission in the honohono vegetation pattern was also significantly higher during the ‘‘wet’’ season compared with the ‘‘dry’’ season, although we did not find a clear correlation between net methane emission, water table level, or precipitation. We show that the measured fluxes are consistent with the integrated potential methane generation over the uppermost 30 cm of soil and consumption of @50% of that methane in the soil. Absence of a correlation between net methane emission and water table level may be due to suppression of the activity of strictly anaerobic methanogens by dynamic redox conditions in the upper layers of soil and varying rates of methane oxidation by facultive methanotrophs

Handwritten Digits Recognition

My work of diploma consisted in developing a Windows application for the recognition of the handwritten digits. The source images come from a pen-scanner. The user can also draw the digits directly with the mouse and do the recognition of it. In this software, I integrated the SVM Light reconizer

Shear-Wave Splitting and Mantle Flow Beneath the Colorado Plateau and its Boundary with the Great Basin

Shear-wave splitting measurements from SKS and SKKS phases show fast polarization azimuths that are subparallel to North American absolute plate motion within the central Rio Grande Rift (RGR) and Colorado Plateau (CP) through to the western rim of the CP, with anisotropy beneath the CP and central RGR showing a remarkably consistent pattern with a mean fast azimuth of 4 degrees +/- degrees 6 E of N. Approaching the rim from the southeast, fast anisotropic directions become north-northeast-south-southwest (NNE-SSW), rotate counter clockwise to north-south in the CP-GB transition, and then to NNW-SSE in the western Great Basin ( GB). This change is coincident with uppermost mantle S-wave velocity perturbations that vary from +4% beneath the western CP and the eastern edge of the Marysvale volcanic field to about -8% beneath the GB. Corresponding delay times average 1.5 sec beneath the central CP, decrease to approximately 0.8 sec near the CP-GB transition, and increase to about 1.2 sec beneath the GB. For the central CP, we suggest anisotropy predominantly controlled by North American plate motion above the asthenosphere. The observed pattern of westward-rotating anisotropy from the western CP through the CP-GB transition may be influenced to asthenospheric flow around a CP lithospheric keel and/or by vertical flow arising from edge-driven small-scale convection. The anisotropic transition from the CP to the GB thus marks a first-order change from absolute plate motion dominated lithosphere-asthenosphere shear to a new regime controlled by regional flow processes. The NNW-SSE anisotropic fast directions of split SKS waves in the eastern GB area are part of a broad circular pattern of seismic anisotropic fast direction in the central GB that has recently been hypothesized to be due to toroidal flow around the sinking Juan de Fuca-Gorda slab.National Science Foundation EAR 9706094, 9707188, 9707190, 0207812Los Alamos National Laboratory Institute of Geophysics and Planetary PhysicsNational Science Foundation Cooperative EAR-000430Department of Energy National Nuclear Security AdministrationGeological Science

Evidence linking calcium to increased organo-mineral association in soils

Geochemical indicators are emerging as important predictors of soil organic carbon (SOC) dynamics, but evidence concerning the role of calcium (Ca) is scarce. This study investigates the role of Ca prevalence in SOC accumulation by comparing otherwise similar sites with (CaCO$_{3}$-bearing) or without carbonates (CaCO$_{3}$-free). We measured the SOC content and indicators of organic matter quality (C stable isotope composition, expressed as δ$^{13}$C values, and thermal stability) in bulk soil samples. We then used sequential sonication and density fractionation (DF) to separate two occluded pools from free and mineral-associated SOC. The SOC content, mass, and δ$^{13}$C values were determined in all the fractions. X-ray photoelectron spectroscopy was used to investigate the surface chemistry of selected fractions. Our hypothesis was that occlusion would be more prevalent at the CaCO$_{3}$-bearing site due to the influence of Ca on aggregation, inhibiting oxidative transformation, and preserving lower δ$^{13}$C values. Bulk SOC content was twice as high in the CaCO$_{3}$-bearing profiles, which also had lower bulk δ$^{13}$C values, and more occluded SOC. Yet, contrary to our hypothesis, occlusion only accounted for a small proportion of total SOC (< 10%). Instead, it was the heavy fraction (HF), containing mineral-associated organic C, which accounted for the majority of total SOC and for the lower bulk δ$^{13}$C values. Overall, an increased Ca prevalence was associated with a near-doubling of mineral-associated SOC content. Future investigations should now aim to isolate Ca-mediated complexation processes that increase organo-mineral association and preserve organic matter with lower δ$^{13}$C values

NPY Y1 receptor is not involved in the hemodynamic response to an acute cold pressor test in mice

The vasoconstrictor neuropeptide Y (NPY) has been shown to down-regulate tyrosine hydroxylase expression in cultured adrenal chromaffin cells, which probably accounts for the higher plasma resting norepinephrine (NE) and epinephrine (E) concentrations observed in Y1 knock-out mice (Y1-/-) than in wild-type mice (Y1+/+). The aim of this work was to study the hemodynamic response of Y1-/- mice to an acute stimulation of the sympathetic nervous system (cold pressor test, CPT). Plasma catecholamine concentrations were higher in Y1-/- mice than in wild-type animals at the end of the CPT. The CPT-induced increase in mean arterial blood pressure (MAP) and heart rate (HR) was similar in both genotypes. Independently of the genotype, females had significantly slower HR than males throughout the 15 min duration of the CPT. There was no difference in the sensitivity of the baroreceptor reflex, as reflected by the change in HR divided by the concurrent change in MBP between Y1-/- and Y1+/+ mice. In conclusion, mice lacking the Y1 receptor can maintain normal hemodynamic response to an acute activation of the sympathetic system, albeit at the expense of increased catecholamine discharge.http://www.sciencedirect.com/science/article/B6T0M-4MT54Y4-3/1/f346666c9ec021eeffb80529f17474d

Blood sampling methodology is crucial for precise measurement of plasma catecholamines concentrations in mice

Epinephrine (E) and norepinephrine (NE) play a major role in regulating metabolism and cardiovascular physiology. Both are secreted in response to stress and their measurement in plasma allows the study of sympathoadrenal function. Several studies investigating sympathoadrenal physiology are conducted using mice. Review of the literature revealed that basal mouse NE and E plasma concentrations range within 4-140nM depending on the blood sampling method. Such variability doesn't allow study comparison and may conceal catecholamine variations in response to stress. Therefore, our aim was to determine a reliable sampling method to measure mouse plasma catecholamine concentrations. Results showed that arterial catheterization is the most accurate sampling method: E and NE basal levels were similar to those found in humans (1.1±0.3nM and 4.1±0.5nM, respectively). Retro-orbital bleeding led to analogous results. On the contrary, decapitation was stressful for mice and consequently NE and E concentrations were high (24.6±2.7nM and 27.3±3.8nM, respectively). These different bleeding methods were compared in terms of their ability to detect sympathoadrenal system stimulation (cold-pressure test). With catheter and retro-orbital samplings the expected increase in NE and E levels was easily perceived. In contrast, with decapitation no significant change in E was detected. In conclusion, arterial-catheter and retro-orbital blood sampling methods appear to be the most accurate procedures for studying the sympathetic nervous system in mice in both unstressed and stressed condition

Are soil carbon credits empty promises? Shortcomings of current soil carbon quantification methodologies and improvement avenues

As the consequences of climate change are looming large, agricultural soil carbon credits have emerged as an increasingly advocated lever to incentivize the reduction of greenhouse gas emissions and promote carbon storing farming practices. These credits are exchanged on self-regulated voluntary carbon markets, each of them using distinct protocols to assess the changes in soil carbon stocks and convert them into carbon credits. Although serious discrepancies between protocols have already been noted regarding general carbon credit accounting principles, an in-depth evaluation of how changes in soil organic carbon stocks are calculated is still lacking. In this context, the primary objective of our study was to investigate how changes in soil organic carbon stock are estimated by the major carbon credit protocols worldwide. We evaluated the requirements of each protocol regarding the estimation of the initial SOC stock as well as the modelling and/or measurement of changes in stock with time. We found that existing protocols vary greatly in their scientific rigour. We showed in particular that some protocols do not require in situ soil analyses to estimate initial soil carbon stocks but rely on regional values, leading them to potentially overestimate these stocks by up to 2.5 times. Our study also found that the protocols relying on models require different farming practices and different levels of information for each practice to estimate SOC stock changes. The protocols relying, at least partly, on soil sampling also displayed different requirements for the sampling design, sampling tools, SOC analysis methods and SOC stock calculation methods. On this basis, we suggest reforms designed to improve and standardize the quantification of carbon stock changes in soils and to improve the reliability of soil carbon credits

Re-think It Conference Proceedings

Essays contributed by participants in Re-think it: Libraries for a New Age, a conference on library design, services, values, and visions, which was held in the Mary Idema Pew Library Learning and Information Commons at Grand Valley State University, August 10 - 12, 2015.https://scholarworks.gvsu.edu/rethinkit_proceedings/1000/thumbnail.jp

FAME : A new beamline for X-ray absorption investigations of very-diluted systems of environmental, material and biological interests

International audienceFAME is the French Absorption spectroscopy beamline in Material and Environmental sciences at the ESRF (France), operational since September 2002. Technically speaking, the source is a 0.85 T bending magnet and the main optical element is a two-crystals monochromator using either Si(111) or Si(220) monocrystals so that the available energy ranges from 4 to 40 keV. The first crystal is liquid nitrogen cooled in order to avoid a thermal bump and thus preserve the energy resolution. The second crystal is dynamically bent during the energy scan in order to focus the beam in the horizontal plane. Two bendable mirrors are located before and after the monochromator, for beam-collimation (to optimize the energy resolution) and vertical focalization, respectively. During scans, the beam on the sample is kept constant in position and size (around 150 × 200 μm2, V × H). The high flux on the sample combined with the sensitivity of our 30-elements fluorescence detector allow to decrease the detection limit down to 10 ppm or around less than a monolayer. Moreover, quick-EXAFS acquisition is operational: the acquisition time may be reduced down to 30s