scholarly journals Spatiotemporal variations of nitrogen isotopic records in the Arabian Sea

2015 ◽  
Vol 12 (1) ◽  
pp. 1-14 ◽  
Author(s):  
S.-J. Kao ◽  
B.-Y. Wang ◽  
L.-W. Zheng ◽  
K. Selvaraj ◽  
S.-C. Hsu ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Arabian Sea ◽  
Euphotic Zone ◽  
Southeastern Part ◽  
Data Set ◽  
Global Coherence ◽  
One Step ◽  
Isotopic Records ◽  
Bottom Depth ◽  
Reported Data

Abstract. Available reports of dissolved oxygen, δ15N of nitrate (δ 15NNO3) and δ15N of total nitrogen (δ15Nbulk) for trap material and surface/downcore sediments from the Arabian Sea (AS) were synthesized to explore the AS' past nitrogen dynamics. Based on 25 μmol kg−1 dissolved oxygen isopleth at a depth of 150 m, we classified all reported data into northern and southern groups. By using δ15Nbulk of the sediments, we obtained geographically distinctive bottom-depth effects for the northern and southern AS at different climate stages. After eliminating the bias caused by bottom depth, the modern-day sedimentary δ15Nbulk values largely reflect the δ15NNO3 supply from the bottom of the euphotic zone. Additionally to the data set, nitrogen and carbon contents vs. their isotopic compositions of a sediment core (SK177/11) collected from the most southeastern part of the AS were measured for comparison. We found a one-step increase in δ15Nbulk starting at the deglaciation with a corresponding decrease in δ13CTOC similar to reports elsewhere revealing a global coherence. By synthesizing and reanalyzing all reported down core δ15Nbulk, we derived bottom-depth correction factors at different climate stages, respectively, for the northern and southern AS. The diffusive sedimentary δ15Nbulk values in compiled cores became confined after bias correction revealing a more consistent pattern except recent 6 ka. Such high similarity to the global temporal pattern indicates that the nitrogen cycle in the entire AS had responded to open-ocean changes until 6 ka BP. Since 6 ka BP, further enhanced denitrification (i.e., increase in δ15Nbulk) in the northern AS had occurred and was likely driven by monsoon, while, in the southern AS, we observed a synchronous reduction in δ15Nbulk, implying that nitrogen fixation was promoted correspondingly as the intensification of local denitrification at the northern AS basin.

scholarly journals Spatio-temporal variations of nitrogen isotopic records in the Arabian Sea

2014 ◽  
Vol 11 (6) ◽  
pp. 8713-8748
Author(s):  
S.-J. Kao ◽  
B. Wang ◽  
L. Zheng ◽  
K. Selvaraj ◽  
S.-C. Hsu ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Arabian Sea ◽  
Euphotic Zone ◽  
Temporal Variations ◽  
Southeastern Part ◽  
Global Pattern ◽  
Spatio Temporal ◽  
Isotopic Records ◽  
Bottom Depth ◽  
Reported Data

Abstract. Nitrogen and carbon contents vs. their isotopic compositions for past 35 ka for a sediment core (SK177/11) collected from the most southeastern part of the Arabian Sea (AS) were presented. A one-step increase in δ15Nbulk starting at the deglaciation with a corresponding decrease in δ13CTOC was found similar to documentation elsewhere which showed a global coherence in general. We synthesized available reports including dissolved oxygen, δ15N of nitrate (δ15NNO3), as well as δ15N of total nitrogen (δ15Nbulk) for trap material and surface/downcore sediments in the AS in order to explore the past nitrogen dynamics in the Arabian Sea. According to 25 μmol kg−1 dissolved oxygen isopleth at 150 m deep, we classified all reported data into northern and southern groups. We obtained geographically distinctive bottom-depth effects for northern and southern AS at different climate stages. By eliminating the bias caused by bottom depth, the modern day sedimentary δ15Nbulk values largely reflect the δ15NNO3 supply from the bottom of the euphotic zone; meanwhile, the diffusive sedimentary δ15Nbulk in long cores became confined revealing a more consistent pattern except recent 6 ka. The nitrogen cycle in entire AS apparently responded to open-ocean changes until 6 ka, during which further enhanced denitrification in the northern AS was likely local and driven by monsoon; while in the southern AS either nitrogen fixation was enhanced correspondingly to the continuously reduced δ15Nbulk for a compensation or the decreasing trend just followed the global pattern dominated by a longer term coupling of N2 fixation and denitrification.

scholarly journals TNO-MACC_II emission inventory; a multi-year (2003–2009) consistent high-resolution European emission inventory for air quality modelling

2014 ◽  
Vol 14 (20) ◽  
pp. 10963-10976 ◽  
Author(s):  
J. J. P. Kuenen ◽  
A. J. H. Visschedijk ◽  
M. Jozwicka ◽  
H. A. C. Denier van der Gon
Keyword(s):  
Particulate Matter ◽  
Air Quality ◽  
High Resolution ◽  
Emission Inventory ◽  
Point Sources ◽  
Air Quality Modelling ◽  
Emission Data ◽  
Data Set ◽  
Spatially Distributed ◽  
Reported Data

Abstract. Emissions to air are reported by countries to EMEP. The emissions data are used for country compliance checking with EU emission ceilings and associated emission reductions. The emissions data are also necessary as input for air quality modelling. The quality of these "official" emissions varies across Europe. As alternative to these official emissions, a spatially explicit high-resolution emission inventory (7 × 7 km) for UNECE-Europe for all years between 2003 and 2009 for the main air pollutants was made. The primary goal was to supply air quality modellers with the input they need. The inventory was constructed by using the reported emission national totals by sector where the quality is sufficient. The reported data were analysed by sector in detail, and completed with alternative emission estimates as needed. This resulted in a complete emission inventory for all countries. For particulate matter, for each source emissions have been split in coarse and fine particulate matter, and further disaggregated to EC, OC, SO4, Na and other minerals using fractions based on the literature. Doing this at the most detailed sectoral level in the database implies that a consistent set was obtained across Europe. This allows better comparisons with observational data which can, through feedback, help to further identify uncertain sources and/or support emission inventory improvements for this highly uncertain pollutant. The resulting emission data set was spatially distributed consistently across all countries by using proxy parameters. Point sources were spatially distributed using the specific location of the point source. The spatial distribution for the point sources was made year-specific. The TNO-MACC_II is an update of the TNO-MACC emission data set. Major updates included the time extension towards 2009, use of the latest available reported data (including updates and corrections made until early 2012) and updates in distribution maps.

scholarly journals 200-Hundred Year Climate Record From Antarctic Peninsula

1990 ◽  
Vol 14 ◽  
pp. 353-353
Author(s):  
D.A. Peel ◽  
R. Mulvaney
Keyword(s):  
Antarctic Peninsula ◽  
Ice Core ◽  
Weddell Sea ◽  
Average Temperature ◽  
Air Temperatures ◽  
Isotope Record ◽  
James Ross Island ◽  
Weather Stations ◽  
Isotopic Records ◽  
Reported Data

A stable isotope record extending back to 1795 is now available from Dolleman Island (70°35.2′S, 60°55.5′W), a small ice rise on the Weddell Sea coast of Antarctic Peninsula. An accurate chronology has been achieved by combined stratigraphic analysis of clear seasonal cycles in δ18O and excess SO4. Previous work (Peel and others, 1988) has shown that, since 1947, there is generally a satisfactory correlation between interannual variations in δ18O and air temperature (T) as recorded at weather stations in various parts of the region, suggesting that the derived δ18O/T ratio may be used to reconstruct air temperatures for the earlier period.Taken together with previously-reported data (Aristarain and others, 1986) for an ice core from James Ross Island it is now possible to propose a regional climatic signal for the Weddell Sea coastal sector of the region. The most striking feature is a broad maximum in δ18O for the mid-19th century, implying decadal average temperature at least as high as the present. This contrasts with available evidence from elsewhere in the southern hemisphere which suggest that this period was cooler than today. Tentative explanations for the anomaly are proposed based on evidence for a period (1974–80), where climatic shifts are clearly amplified in the isotopic records.

The drivers of economic growth in South Asia: evidence from a dynamic system GMM approach

2019 ◽  
Vol 46 (3) ◽  
pp. 564-577 ◽  
Author(s):  
Mohammad Mafizur Rahman ◽  
Rezwanul Hasan Rana ◽  
Suborna Barua
Keyword(s):  
Economic Growth ◽  
South Asia ◽  
Energy Use ◽  
Government Expenditure ◽  
Data Set ◽  
Content Type ◽  
Dynamic Estimation ◽  
One Step ◽  
Key Variables ◽  
Generalised Method Of Moments

Purpose The purpose of this paper is to explore the drivers of economic growth in South Asia region for the period of 1975–2016 using the World Bank data. Design/methodology/approach Panel corrected standard error (static estimation) approach and one-step system generalised method of moments (dynamic estimation) approach are used. Findings Both the static and dynamic estimations indicate that energy use, gross capital formation and remittances are the main drivers of economic growth in South Asian countries. The effects of all these variables are positive and significant. The extent of the effect of energy use is much higher than that of other two variables on the economic growth. A 1 per cent increase in the growth of energy consumption can expedite the gross domestic product growth by approximately 3 per cent in South Asia. However, the key variables, such as trade, government expenditure and foreign direct investment demonstrate no significant effect. Originality/value The current research is original in the sense that it investigated the issue with a new data set using improved econometric techniques. Moreover, in South Asia as a whole, this kind of study is totally absent, particularly with panel data of a large number of years. Furthermore, this study has taken into account the problem of heterogeneity and the biases created by cross-section dependence, which were mostly absent in previous studies. Therefore, the findings of this research are new contributions to the existing literature.

Timing, cause and consequences of mid-Holocene climate transition in the Arabian Sea

2016 ◽  
Vol 86 (2) ◽  
pp. 162-169 ◽  
Author(s):  
Rajeev Saraswat ◽  
Dinesh Kumar Naik ◽  
Rajiv Nigam ◽  
Anuruddh Singh Gaur
Keyword(s):  
Dissolved Oxygen ◽  
Arabian Sea ◽  
Seawater Temperature ◽  
Subsurface Water ◽  
Water Interface ◽  
Holocene Climate ◽  
Carbon Burial ◽  
Sediment Fraction ◽  
Surface Productivity ◽  
Climate Transition

AbstractWe reconstruct centennial scale quantitative changes in surface seawater temperature (SST), evaporation-precipitation (from Mg/Ca and δ18O of surface dwelling planktic foraminifera), productivity (from relative abundance of Globigerina bulloides), carbon burial (from %CaCO3 and organic carbon [%Corg]) and dissolved oxygen at sediment-water interface, covering the entire Holocene, from a core collected from the eastern Arabian Sea. From the multi-proxy record, we define the timing, consequences and possible causes of the mid-Holocene climate transition (MHCT). A distinct shift in evaporation-precipitation (E-P) is observed at 6.4 ka, accompanied by a net cooling of SST. The shift in SST and E-P is synchronous with a change in surface productivity. A concurrent decrease is also noted in both the planktic foraminiferal abundance and coarse sediment fraction. A shift in carbon burial, as inferred from both the %CaCO3 and %Corg, coincides with a change in surface productivity. A simultaneous decrease in dissolved oxygen at the sediment-water interface, suggests that changes affected both the surface and subsurface water. A similar concomitant change is also observed in other cores from the Arabian Sea as well as terrestrial records, suggesting a widespread regional MHCT. The MHCT coincides with decreasing low-latitude summer insolation, perturbations in total solar intensity and an increase in atmospheric CO2.

The role of shared study space in shaping graduate students’ social networks

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yaoyi Zhou ◽  
Ying Hua
Keyword(s):  
Social Networks ◽  
Graduate Students ◽  
Spatial Proximity ◽  
Quadratic Assignment ◽  
Data Set ◽  
Content Type ◽  
Class Project ◽  
Highly Correlated ◽  
Reported Data

Purpose The purpose of this paper is to study whether the use of a shared study space played a role in shaping graduate students’ social networks by exploring how the copresence in space was related to the structure of friendship and advice networks. The authors first proposed two concepts of spatial copresence: measured spatial-temporal copresence and perceived copresence. The authors then examined the role of copresence through a case study of a shared study space occupied by 27 graduate students in the same department. Design/methodology/approach Copresence relations were first constructed through a six-month room access history data set and self-reported data to examine whether measured spatial-temporal copresence was consistent with perceived copresence. Friendship and advice network relations were then analyzed with copresence, social media connections, class project collaboration relations and social homophily (nationality, gender, cohort) through quadratic assignment procedure (QAP) and MQAP analysis. Findings The authors found that students who used the shared study space more often reported more friendship and advice ties. The perceived copresence and the measured spatial-temporal copresence were highly correlated. Copresence relations, as measured by survey and room access history, were both significantly correlated with advice relation, which was associated with perceived social support. Originality/value This study contributes to the debate about whether “space” continues to play significant roles in graduate students’ social networks in the context of flexible learning environments. The results also reveal new directions for research methods in studying spatial proximity in flexible settings.

scholarly journals Graph-neural-network-based delay estimation for communication networks with heterogeneous scheduling policies

2021 ◽  
Vol 2 (4) ◽  
pp. 1-8
Author(s):  
Martin Happ ◽  
Matthias Herlich ◽  
Christian Maier ◽  
Jia Lei Du ◽  
Peter Dorfinger
Keyword(s):  
Neural Network ◽  
Neural Networks ◽  
Communication Networks ◽  
Delay Estimation ◽  
Percentage Error ◽  
Extended Model ◽  
Data Set ◽  
Scheduling Policies ◽  
One Step ◽  
Graph Neural Networks

Modeling communication networks to predict performance such as delay and jitter is important for evaluating and optimizing them. In recent years, neural networks have been used to do this, which may have advantages over existing models, for example from queueing theory. One of these neural networks is RouteNet, which is based on graph neural networks. However, it is based on simplified assumptions. One key simplification is the restriction to a single scheduling policy, which describes how packets of different flows are prioritized for transmission. In this paper we propose a solution that supports multiple scheduling policies (Strict Priority, Deficit Round Robin, Weighted Fair Queueing) and can handle mixed scheduling policies in a single communication network. Our solution is based on the RouteNet architecture as part of the "Graph Neural Network Challenge". We achieved a mean absolute percentage error under 1% with our extended model on the evaluation data set from the challenge. This takes neural-network-based delay estimation one step closer to practical use.

scholarly journals Properties of cores of the water masses in the Okhotsk Sea

2016 ◽  
Vol 184 (1) ◽  
pp. 204-218
Author(s):  
Vladimir A. Luchin ◽  
Andrey A. Kruts
Keyword(s):  
Spatial Distribution ◽  
Dissolved Oxygen ◽  
Oxygen Content ◽  
Sea Water ◽  
Water Masses ◽  
Okhotsk Sea ◽  
Data Set ◽  
Water Properties ◽  
Oceanographic Data

Spatial distribution of depth and water properties (temperature, salinity, dissolved oxygen content) are considered in detail for cores of the Okhotsk Sea water masses: subsurface, intermediate, and deep, on the base of the most comprehensive oceanographic data set.

scholarly journals Electrochemical Study of Nd and Pr Co-Deposition onto Mo and W from Molten Oxyfluorides

Metals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1494
Author(s):  
Vesna S. Cvetković ◽  
Dominic Feldhaus ◽  
Nataša M. Vukićević ◽  
Tanja S. Barudžija ◽  
Bernd Friedrich ◽  
...  
Keyword(s):  
Electrochemical Techniques ◽  
Earth Metal ◽  
Open Circuit ◽  
X Ray Diffraction ◽  
Step Process ◽  
Wave Voltammetry ◽  
One Step ◽  
Current Densities ◽  
Low Levels ◽  
Reported Data

Electrodeposition processes of neodymium and praseodymium in molten NdF3 + PrF3 + LiF + 1 wt.%Pr6O11 + 1 wt.%Nd2O3 and NdF3 + PrF3 + LiF + 2 wt.%Pr6O11 + 2 wt.%Nd2O3 electrolytes at 1323 K were investigated. Cyclic voltammetry, square wave voltammetry, and open circuit potentiometry were applied to study the electrochemical reduction of Nd(III) and Pr(III) ions on Mo and W cathodes. It was established that a critical condition for Nd and Pr co-deposition in oxyfluoride electrolytes was a constant praseodymium deposition overpotential of ≈−0.100 V, which was shown to result in co-deposition current densities approaching 6 mAcm−2. Analysis of the results obtained by applied electrochemical techniques showed that praseodymium deposition proceeds as a one-step process involving exchange of three electrons (Pr(III)→Pr(0)) and that neodymium deposition is a two-step process: the first involves one electron exchange (Nd(III)→Nd(II)), and the second involves an exchange of two electrons (Nd(II)→Nd(0)). X-ray diffraction analyses confirmed the formation of metallic Nd and Pr on the working substrate. Keeping the anodic potential to the glassy carbon working anode low results in very low levels of carbon oxides, fluorine and fluorocarbon gas emissions, which should qualify the studied system as an environmentally friendly option for rare earth metal deposition. The newly reported data for Nd and Pr metals co-deposition provide valuable information for the recycling of neodymium-iron-boron magnets.

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