scholarly journals CO<sub>3</sub><sup>2−</sup> concentration and pCO<sub>2</sub> thresholds for calcification and dissolution on the Molokai reef flat, Hawaii

2006 ◽  
Vol 3 (3) ◽  
pp. 357-369 ◽  
Author(s):  
K. K. Yates ◽  
R. B. Halley
Keyword(s):  
Reef Flat ◽  
Threshold Value ◽  
Published Data ◽  
Carbonate Sediments ◽  
Threshold Values ◽  
Coral Rubble ◽  
The Impact ◽  
Substrate Types ◽  
Atmospheric Pco2

Abstract. The severity of the impact of elevated atmospheric pCO2 to coral reef ecosystems depends, in part, on how seawater pCO2 affects the balance between calcification and dissolution of carbonate sediments. Presently, there are insufficient published data that relate concentrations of pCO2 and CO32− to in situ rates of reef calcification in natural settings to accurately predict the impact of elevated atmospheric pCO2 on calcification and dissolution processes. Rates of net calcification and dissolution, CO32− concentrations, and pCO2 were measured, in situ, on patch reefs, bare sand, and coral rubble on the Molokai reef flat in Hawaii. Rates of calcification ranged from 0.03 to 2.30 mmol CaCO3 m−2 h−1 and dissolution ranged from –0.05 to –3.3 mmol CaCO3 m−2 h−1. Calcification and dissolution varied diurnally with net calcification primarily occurring during the day and net dissolution occurring at night. These data were used to calculate threshold values for pCO2 and CO32− at which rates of calcification and dissolution are equivalent. Results indicate that calcification and dissolution are linearly correlated with both CO32− and pCO2. Threshold pCO2 and CO32− values for individual substrate types showed considerable variation. The average pCO2 threshold value for all substrate types was 654±195 μatm and ranged from 467 to 1003 μatm. The average CO32− threshold value was 152±24 μmol kg−1, ranging from 113 to 184 μmol kg−1. Ambient seawater measurements of pCO2 and CO32− indicate that CO32− and pCO2 threshold values for all substrate types were both exceeded, simultaneously, 13% of the time at present day atmospheric pCO2 concentrations. It is predicted that atmospheric pCO2 will exceed the average pCO2 threshold value for calcification and dissolution on the Molokai reef flat by the year 2100.

scholarly journals CO<sup>2−</sup><sub>3</sub> concentration and pCO<sub>2</sub> thresholds for calcification and dissolution on the Molokai reef flat, Hawaii

2006 ◽  
Vol 3 (1) ◽  
pp. 123-154 ◽  
Author(s):  
K. K. Yates ◽  
R. B. Halley
Keyword(s):  
Reef Flat ◽  
Threshold Value ◽  
Published Data ◽  
Carbonate Sediments ◽  
Threshold Values ◽  
Coral Rubble ◽  
The Impact ◽  
Substrate Types ◽  
Atmospheric Pco2

Abstract. The severity of the impact of elevated atmospheric pCO2 to coral reef ecosystems depends, in part, on how seawater pCO2 affects the balance between calcification and dissolution of carbonate sediments. Presently, there are insufficient published data that relate concentrations of pCO2 and CO32− to in situ rates of reef calcification in natural settings to accurately predict the impact of elevated atmospheric pCO2 on calcification and dissolution processes. Rates of net calcification and dissolution, CO32− concentrations, and pCO2 were measured, in situ, on patch reefs, bare sand, and coral rubble on the Molokai reef flat in Hawaii. Rates of calcification ranged from 0.003 to 0.23 g CaCO3 m−2 h−1 and dissolution ranged from −0.005 to −0.33 g CaCO3 m−2 h−1. Calcification and dissolution varied diurnally with net calcification primarily occurring during the day and net dissolution occurring at night. These data were used to calculate threshold values for pCO2 and CO32− at which rates of calcification and dissolution are equivalent. Results indicate that calcification and dissolution are linearly correlated with both CO32− and pCO2. Threshold pCO2 and CO32− values for individual substrate types showed considerable variation. The average pCO2 threshold value for all substrate types was 654±195 µatm and ranged from 467 to 1003 µatm. The average CO3−- threshold value was 152±24 µmol kg-1, ranging from 113 to 184 µmol kg−1. Ambient seawater measurements of pCO2 and CO32− indicate that CO32− and pCO2 threshold values for all substrate types were both exceeded, simultaneously, 13% of the time at present day atmospheric pCO2 concentrations. It is predicted that atmospheric pCO2 will exceed the average pCO2 threshold value for calcification and dissolution on the Molokai reef flat by the year 2100.

The Organic carbon content of gravel bed herring spawning grounds and the impact of herring spawn deposition

1993 ◽  
Vol 73 (4) ◽  
pp. 863-870 ◽  
Author(s):  
Ian R. Napier
Keyword(s):  
Organic Carbon ◽  
Carbon Content ◽  
Dry Weight ◽  
Published Data ◽  
Organic Carbon Content ◽  
Spawning Grounds ◽  
The Past ◽  
Benthic Food ◽  
The Impact

The dry weight and organic carbon content of eggs and components of Clyde spring herring eggs were measured at intervals during their development. Comparison with previously published data suggests that an increase has occurred in the weight of these eggs over the past thirty years. It is clear that only a small proportion of the material deposited in the form of herring spawn actually remains attached to the substratum when the larvae hatch and so is available for potential integration into the benthic food web. This was confirmed by the determination at intervals over two years of the organic carbon content of the gravel sediments on spawning grounds of the Clyde spring herring. Although the deposition of herring spawn resulted in an immediate marked increase in the carbon content of the spawning ground sediments, carbon levels quickly returned to pre-spawning levels and there was no evidence of any permanent or long lasting increase. This held true when the spawn died and decayed in situ and even when it was mixed into the sediment by wave action. The rapid decrease in carbon levels is attributed to the strong water movements which frequently occur over the spawning grounds.

scholarly journals Threshold Effects of Environmental Regulation on Total Factor Energy Efficiency in China

2015 ◽  
Vol 8 (1) ◽  
pp. 33-37
Author(s):  
Ling Yun Huang ◽  
Hui Qiang Xie
Keyword(s):  
Energy Efficiency ◽  
Environmental Regulation ◽  
Technological Innovation ◽  
Industrial Structure ◽  
Threshold Value ◽  
Threshold Effects ◽  
Threshold Values ◽  
Positive Effects ◽  
Negative Effect ◽  
The Impact

This paper examines the threshold effects of environmental regulation on China’s total factor energy efficiency (TFEE) using technological innovation (as measured by patents) as a threshold variable. Using the Slacksbased measure-undesirable (SBM-undesirable) output model, we first estimate TFEEs in 30 Chinese provinces from 2000 to 2011 under the constraints of energy conservation and emissions reduction. We then analyze the impact of environmental regulation on TFEE based on the panel threshold regression model. The results show that the average TFEE in China from 2000 to 2011 is 0.503, indicating that this measure can be significantly improved. However, environmental regulation has threshold effects on TFEE. Stringent environmental regulation can only improve TFEEs in provinces with technological innovation levels between the first and second threshold values. When technological innovation levels are below the first or above the second threshold value, tighter environmental regulation would lower TFEE. The results suggest that environmental regulation does not always enhance TFEE and that the positive effect of environmental regulation on TFEE must fall within a range of threshold values. In addition, improving the technological innovation level and adjusting the industrial structure have positive effects on TFEE, while the irrational energy consumption structure has a negative effect on TFEE.

scholarly journals Trade Openness and Economic Growth: A Study on Asean-6

Economies ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 113
Author(s):  
My-Linh Thi Nguyen ◽  
Toan Ngoc Bui
Keyword(s):  
Economic Growth ◽  
High Efficiency ◽  
Trade Openness ◽  
Threshold Value ◽  
Research Model ◽  
Domestic Investment ◽  
Threshold Values ◽  
High Level ◽  
The Impact ◽  
Threshold Approach

This paper focuses on examining the nonlinear impact of trade openness (TO) on economic growth (EG) in the Asean-6 countries (Indonesia, Malaysia, Thailand, Singapore, Philippines, and Vietnam). In order to achieve the set research objectives, the authors estimate the research model through the fixed-effect panel threshold approach. Unlike previous studies, this paper finds that there is a nonlinear impact of TO on EG, whereby TO has two threshold values. Specifically, before the first threshold value, TO plays an important role in boosting EG. However, this impact level decreases gradually when TO exceeds this threshold value. In particular, when exceeding the second threshold value, the impact of TO on EG is still positive but has a relatively low value. The research results show that if TO increases to a high level (beyond the threshold value) without combining with other complementary policies, this does not encourage high-efficiency EG. In addition, this study also shows that EG is positively affected by domestic investment and negatively affected by financial crisis. The findings in this paper are of great importance for the Asean-6 countries as well as researchers.

scholarly journals Midregional Pro–Atrial Natriuretic Peptide for the Diagnosis of Cardiac-Related Dyspnea according to Renal Function in the Emergency Department: A Comparison with B-Type Natriuretic Peptide (BNP) and N-Terminal ProBNP

2010 ◽  
Vol 56 (11) ◽  
pp. 1708-1717 ◽  
Author(s):  
Camille Chenevier-Gobeaux ◽  
Sylvie Guerin ◽  
Stéphanie André ◽  
Patrick Ray ◽  
Luc Cynober ◽  
...  
Keyword(s):  
Emergency Department ◽  
Renal Function ◽  
Atrial Natriuretic Peptide ◽  
Natriuretic Peptide ◽  
Impaired Renal Function ◽  
Threshold Value ◽  
Threshold Values ◽  
Emergency Department Patients ◽  
The Impact ◽  
Atrial Natriuretic

BACKGROUND Although renal dysfunction influences the threshold values of B-type natriuretic peptide (BNP) and N-terminal proBNP (NT-proBNP) in diagnosis of cardiac-related dyspnea (CRD), its effects on midregional pro–atrial natriuretic peptide (MR-proANP) threshold values are unknown. We evaluated the impact of renal function on MR-proANP concentrations and compared our results to those of BNP and NT-proBNP. METHODS MR-proANP, BNP, and NT-proBNP concentrations were measured in blood samples collected routinely from dyspneic patients admitted to the emergency department. Patients were subdivided into tertiles based on their estimated glomerular filtration rate [eGFR, in mL · min−1 · (1.73 m2)−1]: tertiles 1 (&lt;44.3), 2 (44.3–58.5), and 3 (≥58.6). RESULTS Of 378 patients studied, 69% (n = 260) had impaired renal function [&lt;60 mL · min−1 · (1.73 m2)−1] and 30% (n = 114) had CRD. MR-proANP, BNP, and NT-proBNP concentrations were significantly increased in patients with impaired renal function. In each tertile, all peptides remained significantly increased in CRD patients by comparison with non-CRD patients. By ROC analysis, MR-proANP, BNP, and NT-proBNP threshold values for the diagnosis of CRD increased as eGFR decreased from tertile 3 to tertile 1. Areas under the ROC curve for all peptides were significantly lower in tertile 1. Using adapted thresholds, MR-proANP, BNP, and NT-proBNP remained independently predictive of CRD, even in tertile 1 patients. CONCLUSIONS Renal function influences optimum cutoff points of MR-proANP for the diagnosis of CRD. With use of an optimum threshold value adapted to the eGFR category, MR-proANP remains as effective as BNP and NT-proBNP in independently predicting a diagnosis of CRD in the emergency department.

scholarly journals Did high Neo-Tethys subduction rates contribute to early Cenozoic warming?

2015 ◽  
Vol 11 (12) ◽  
pp. 1751-1767 ◽  
Author(s):  
G. Hoareau ◽  
B. Bomou ◽  
D. J. J. van Hinsbergen ◽  
N. Carry ◽  
D. Marquer ◽  
...  
Keyword(s):  
Climate Modeling ◽  
Co2 Production ◽  
Carbonate Sediments ◽  
Co2 Fluxes ◽  
Carbon Cycle Model ◽  
Surface Warming ◽  
The Impact ◽  
Early Cenozoic ◽  
Atmospheric Pco2

Abstract. The 58–51 Ma interval was characterized by a long-term increase of global temperatures (+4 to +6 °C) up to the Early Eocene Climate Optimum (EECO, 52.9–50.7 Ma), the warmest interval of the Cenozoic. It was recently suggested that sustained high atmospheric pCO2, controlling warm early Cenozoic climate, may have been released during Neo-Tethys closure through the subduction of large amounts of pelagic carbonates and their recycling as CO2 at arc volcanoes. To analyze the impact of Neo-Tethys closure on early Cenozoic warming, we have modeled the volume of subducted sediments and the amount of CO2 emitted along the northern Tethys margin. The impact of calculated CO2 fluxes on global temperature during the early Cenozoic have then been tested using a climate carbon cycle model (GEOCLIM). We show that CO2 production may have reached up to 1.55 × 1018 mol Ma−1 specifically during the EECO, ~ 4 to 37 % higher that the modern global volcanic CO2 output, owing to a dramatic India-Asia plate convergence increase. The subduction of thick Greater Indian continental margin carbonate sediments at ~ 55–50 Ma may also have led to additional CO2 production of 3.35 × 1018 mol Ma−1 during the EECO, making a total of 85 % of the global volcanic CO2 outgassed. However, climate modeling demonstrates that timing of maximum CO2 release only partially fits with the EECO, and that corresponding maximum pCO2 values (750 ppm) and surface warming (+2 °C) do not reach values inferred from geochemical proxies, a result consistent with conclusions arising from modeling based on other published CO2 fluxes. These results demonstrate that CO2 derived from decarbonation of Neo-Tethyan lithosphere may have possibly contributed to, but certainly cannot account alone for early Cenozoic warming. Other commonly cited sources of excess CO2 such as enhanced igneous province volcanism also appear to be up to 1 order of magnitude below fluxes required by the model to fit with proxy data of pCO2 and temperature at that time. An alternate explanation may be that CO2 consumption, a key parameter of the long-term atmospheric pCO2 balance, may have been lower than suggested by modeling. These results call for a better calibration of early Cenozoic weathering rates.

scholarly journals Establishment of Geochemical Thresholds for Vanadium Throughout Korea and at Potential Development Sites Using Geochemical Map Data

2021 ◽  
Author(s):  
Joo Sung Ahn ◽  
Seung-Jun Youm ◽  
Yong-Chan Cho ◽  
Gil-Jae Yim ◽  
Sang-Woo Ji
Keyword(s):  
Large Scale ◽  
Threshold Value ◽  
Geochemical Data ◽  
Threshold Values ◽  
Order Stream ◽  
Absolute Deviation ◽  
Geochemical Evaluation ◽  
Before And After ◽  
Map Data ◽  
The Impact

Abstract Geochemical maps can be used for a variety of purposes, one of which is to establish regional or local geochemical thresholds for the analyzed elements. In the case of vanadium, as industrial demand and use increases, it is necessary to expand the development of vanadium in Korea. However, the environmental management standards are insufficient. Therefore, in this study, using geochemical data, we derived geochemical threshold values for the entire country and areas with potential for the development of vanadium deposits. The regional (country-wide) threshold value was derived using logarithmic transformation of raw data (N = 23,548) of the first- and second-order stream sediments collected across the country in the late 1990s and the early 2000s. The median + 2 median absolute deviation (MAD) and Tukey inner fence (TIF) values were 116 mg/kg and 200 mg/kg, respectively. Of these, the TIF standard, which showed 0.6% of data exceeding the threshold, was judged to be appropriate for distinguishing clear enrichment or contamination of vanadium. In the case of the Geumsan and Pocheon, areas with potential for vanadium development, the TIF and median + 2 MAD values of 259 mg/kg and 218 mg/kg, respectively, can be used as the criteria for evaluating the impact of environmental pollution before and after deposit development. Likewise, by deriving threshold values of the target elements using geochemical map data, it is possible to provide basic environmental information for geochemical evaluation and follow-up management in advance during large-scale site development.

In situ irradiation effects studies in medium- and high-voltage TEM

1995 ◽  
Vol 53 ◽  
pp. 234-235
Author(s):  
Charles W. Allen
Keyword(s):  
Cross Section ◽  
Particle Flux ◽  
Threshold Value ◽  
High Energy ◽  
Irradiation Damage ◽  
Defect Complexes ◽  
Lattice Position ◽  
Electrons And Ions ◽  
The Masses

With respect to structural consequences within a material, energetic electrons, above a threshold value of energy characteristic of a particular material, produce vacancy-interstial pairs (Frenkel pairs) by displacement of individual atoms, as illustrated for several materials in Table 1. Ion projectiles produce cascades of Frenkel pairs. Such displacement cascades result from high energy primary knock-on atoms which produce many secondary defects. These defects rearrange to form a variety of defect complexes on the time scale of tens of picoseconds following the primary displacement. A convenient measure of the extent of irradiation damage, both for electrons and ions, is the number of displacements per atom (dpa). 1 dpa means, on average, each atom in the irradiated region of material has been displaced once from its original lattice position. Displacement rate (dpa/s) is proportional to particle flux (cm-2s-1), the proportionality factor being the “displacement cross-section” σD (cm2). The cross-section σD depends mainly on the masses of target and projectile and on the kinetic energy of the projectile particle.

In situ Quantification of the Impact of Episodic Enhanced Turbulent Events in Large Phytoplankton

2011 ◽  
Author(s):  
Percy L. Donaghay ◽  
Jan Rines ◽  
James Sullivan
Keyword(s):  
The Impact

Bayesian analysis reveals the impact of load partitioning on microstructural evolution in Ti-6Al-4V during in-situ tensile loading

Materialia ◽  
2021 ◽  
Vol 15 ◽  
pp. 100993
Author(s):  
N. Armstrong ◽  
P.A. Lynch ◽  
P. Cizek ◽  
S.R. Kada ◽  
S. Slater ◽  
...  
Keyword(s):  
Bayesian Analysis ◽  
Microstructural Evolution ◽  
Tensile Loading ◽  
The Impact
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