scholarly journals Theoretical insights from upscaling Michaelis-Menten microbial dynamics in biogeochemical models: a dimensionless approach

2021 ◽  
Author(s):  
Chris H. Wilson ◽  
Stefan Gerber
Keyword(s):  
Abiotic Factors ◽  
Mean Field ◽  
Parameter Estimates ◽  
Co2 Efflux ◽  
Dimensionless Form ◽  
Effective Response ◽  
Earth Systems ◽  
Microbial Kinetics ◽  
Biogeochemical Models

Abstract. Leading an effective response to the accelerating crisis of anthropogenic climate change will require improved understanding of global carbon cycling. A critical source of uncertainty in Earth Systems Models (ESMs) is the role of microbes in mediating both the formation and decomposition of soil organic matter, and hence in determining patterns of CO2 efflux. Traditionally, ESMs model carbon turnover as a first order process impacted primarily by abiotic factors, whereas contemporary biogeochemical models often explicitly represent the microbial biomass and enzyme pools as the active agents of decomposition. However, the combination of non-linear microbial kinetics and ecological heterogeneity across space guarantees that upscaled dyamics will violate mean-field assumptions via Jensen’s Inequality. Violations of mean-field assumptions mean that parameter estimates from models fit to upscaled data (e.g. eddy covariance towers) are likely systematically biased. Here we present a generic mathematical analysis of upscaling michaelis-menten kinetics under heterogeneity, and provide solutions in dimensionless form. We illustrate how our dimensionless form facilitates qualitative insight into the significance of this scale transition, and argue that it will facilitate cross site intercomparisons of flux data. We also identify the critical terms that need to be constrained in order to unbias parameter estimates.

scholarly journals Theoretical insights from upscaling Michaelis–Menten microbial dynamics in biogeochemical models: a dimensionless approach

2021 ◽  
Vol 18 (20) ◽  
pp. 5669-5679
Author(s):  
Chris H. Wilson ◽  
Stefan Gerber
Keyword(s):  
Abiotic Factors ◽  
Mean Field ◽  
Parameter Estimates ◽  
Co2 Efflux ◽  
Dimensionless Form ◽  
Effective Response ◽  
Microbial Kinetics ◽  
Biogeochemical Models ◽  
Earth System Models

Abstract. Leading an effective response to the accelerating crisis of anthropogenic climate change will require improved understanding of global carbon cycling. A critical source of uncertainty in Earth system models (ESMs) is the role of microbes in mediating both the formation and decomposition of soil organic matter, and hence in determining patterns of CO2 efflux. Traditionally, ESMs model carbon turnover as a first-order process impacted primarily by abiotic factors, whereas contemporary biogeochemical models often explicitly represent the microbial biomass and enzyme pools as the active agents of decomposition. However, the combination of non-linear microbial kinetics and ecological heterogeneity across space and time guarantees that upscaled dynamics will violate mean-field assumptions via Jensen's inequality. Violations of mean-field assumptions mean that parameter estimates from models fit to upscaled data (e.g., eddy covariance towers) are likely systematically biased. Likewise, predictions of CO2 efflux from models conditioned on mean-field values will also be biased. Here we present a generic mathematical analysis of upscaling Michaelis–Menten kinetics under heterogeneity and provide solutions in dimensionless form. We illustrate how our dimensionless form facilitates qualitative insight into the significance of this scale transition and argue that it will facilitate cross-site intercomparisons of flux data. We also identify the critical terms that need to be constrained in order to unbias parameter estimates.

scholarly journals Insight into biogeochemical models from Scale Transition Theory: A dimensionless, scale-free approach

2020 ◽  
Author(s):  
Chris H. Wilson ◽  
Stefan Gerber
Keyword(s):  
Abiotic Factors ◽  
Mean Field ◽  
Transition Theory ◽  
Parameter Estimates ◽  
Co2 Efflux ◽  
Effective Response ◽  
Scale Free ◽  
Scale Transition ◽  
Biogeochemical Models ◽  
Insight Into

AbstractLeading an effective response to the accelerating crisis of anthropogenic climate change will require improved understanding of global carbon cycling. A critical source of uncertainty in Earth Systems Models (ESMs) is the role of microbes in mediating both the formation and decomposition of soil organic matter, and hence in determining patterns of CO2 efflux. Traditionally, ESMs model carbon turnover as a first order process impacted primarily by abiotic factors, whereas contemporary biogeochemical models often explicitly represent the microbial biomass and enzyme pools as the active agents of decomposition. However, the combination of non-linear microbial kinetics and ecological heterogeneity across space guarantees that upscaled dyamics will violate mean-field assumptions via Jensen’s Inequality. Violations of mean-field assumptions mean that parameter estimates from models fit to upscaled data (e.g. eddy covariance towers) are likely systematically biased. Here we present a generic mathematical analysis of upscaled michaelis-menten kinetics, grounded in Scale Transition Theory. We advance the framework by providing solutions in dimensionless form, and illustrate how this approach facilitates qualitative insight into the significance of this scale transition, and argue that it will facilitate future cross site intercomparisons of scale transition effects from flux data. We also discuss the critical terms that need to be constrained in order to unbias parameter estimates.

Enhancing Economic Growth and Government Revenue Generation in Nigeria: The Role of Diaspora Remittances

2021 ◽  
pp. 003464462110256
Author(s):  
Dal Didia ◽  
Suleiman Tahir
Keyword(s):  
Economic Growth ◽  
Parameter Estimates ◽  
Gross Domestic Product Growth ◽  
Correction Model ◽  
Vector Error Correction ◽  
Vector Error ◽  
Long Run ◽  
Short Run ◽  
The Empirical Analysis

Even though remittances constitute the second-largest source of foreign exchange for Nigeria, with a $24 billion inflow in 2018, its impact on economic growth remains unclear. This study, therefore, examined the short-run and long-run impact of remittances on the economic growth of Nigeria using the vector error correction model. Utilizing World Bank data covering 1990–2018, the empirical analysis revealed that remittances hurt economic growth in the short run while having no impact on economic growth in the long run. Our parameter estimates indicate that a 1% increase in remittances would result in a 0.9% decrease in the gross domestic product growth rate in the short run. One policy implication of this study is that Nigeria needs to devise policies and interventions that minimize the emigration of skilled professionals rather than depending on remittances that do not offset the losses to the economy due to brain drain.

scholarly journals Filaments and the Solar Dynamo

1998 ◽  
Vol 167 ◽  
pp. 406-414
Author(s):  
N. Seehafer
Keyword(s):  
Mean Field ◽  
Decisive Role ◽  
Dynamo Theory ◽  
Simultaneous Generation ◽  
Alpha Effect ◽  
Generation Region ◽  
The Mean ◽  
Numerical Bifurcation ◽  
Dynamo Effect

AbstractFilaments are a global phenomenon and their formation, structure and dynamics are determined by magnetic fields. So they are an important signature of the solar magnetism. The central mechanism in traditional mean-field dynamo theory is the alpha effect and it is a major result of this theory that the presence of kinetic or magnetic helicities is at least favourable for the effect. Recent studies of the magnetohydrodynamic equations by means of numerical bifurcation-analysis techniques have confirmed the decisive role of helicity for a dynamo effect. The alpha effect corresponds to the simultaneous generation of magnetic helicities in the mean field and in the fluctuations, the generation rates being equal in magnitude and opposite in sign. In the case of statistically stationary and homogeneous fluctuations, in particular, the alpha effect can increase the energy in the mean magnetic field only under the condition that also magnetic helicity is accumulated there. Generally, the two helicities generated by the alpha effect, that in the mean field and that in the fluctuations, have either to be dissipated in the generation region or to be transported out of this region. The latter may lead to the appearance of helicity in the atmosphere, in particular in filaments, and thus provide valuable information on dynamo processes inaccessible to in situ measurements.

scholarly journals Testing the spatial and temporal framework of speciation in an ancient lake species flock: the leech genus <i>Dina</i> (Hirudinea: Erpobdellidae) in Lake Ohrid

2010 ◽  
Vol 7 (11) ◽  
pp. 3387-3402 ◽  
Author(s):  
S. Trajanovski ◽  
C. Albrecht ◽  
K. Schreiber ◽  
R. Schultheiß ◽  
T. Stadler ◽  
...  
Keyword(s):  
Molecular Clock ◽  
Abiotic Factors ◽  
Time Frame ◽  
Recent Common Ancestor ◽  
Species Flock ◽  
Ancient Lake ◽  
Lake Ohrid ◽  
Most Recent Common Ancestor ◽  
Extant Species

Abstract. Ancient Lake Ohrid on the Balkan Peninsula is considered to be the oldest ancient lake in Europe with a suggested Plio-/Pleistocene age. Its exact geological age, however, remains unknown. Therefore, molecular clock data of Lake Ohrid biota may serve as an independent constraint of available geological data, and may thus help to refine age estimates. Such evolutionary data may also help unravel potential biotic and abiotic factors that promote speciation events. Here, mitochondrial sequencing data of one of the largest groups of endemic taxa in the Ohrid watershed, the leech genus Dina, is used to test whether it represents an ancient lake species flock, to study the role of potential horizontal and vertical barriers in the watershed for evolutionary events, to estimate the onset of diversification in this group based on molecular clock analyses, and to compare this data with data from other endemic species for providing an approximate time frame for the origin of Lake Ohrid. Based on the criteria speciosity, monophyly and endemicity, it can be concluded that Dina spp. from the Ohrid watershed, indeed, represents an ancient lake species flock. Lineage sorting of its species, however, does not seem to be complete and/or hybridization may occur. Analyses of population structures of Dina spp. in the Ohrid watershed indicate a horizontal zonation of haplotypes from spring and lake populations, corroborating the role of lake-side springs, particularly the southern feeder springs, for evolutionary processes in endemic Ohrid taxa. Vertical differentiation of lake taxa, however, appears to be limited, though differences between populations from the littoral and the profundal are apparent. Molecular clock analyses indicate that the most recent common ancestor of extant species of this flock is approximately 1.99 ± 0.83 million years (Ma) old, whereas the split of the Ohrid Dina flock from a potential sister taxon outside the lake is estimated at 8.30 ± 3.60 Ma. Comparisons with other groups of endemic Ohrid species indicated that in all cases, diversification within the watershed started ≤2 Ma ago. Thus, this estimate may provide information on a minimum age for the origin of Lake Ohrid. Maximum ages are less consistent and generally less reliable. But cautiously, a maximum age of 3 Ma is suggested. Interestingly, this time frame of approximately 2–3 Ma ago for the origin of Lake Ohrid, generated based on genetic data, well fits the time frame most often used in the literature by geologists.

ROLE OF ABIOTIC FACTORS IN GOVERNING SUSCEPTIBILITY TO INVASION: A TEST WITH ARGENTINE ANTS

Ecology ◽  
2002 ◽  
Vol 83 (6) ◽  
pp. 1610-1619 ◽  
Author(s):  
David A. Holway ◽  
Andrew V. Suarez ◽  
Ted J. Case
Keyword(s):  
Abiotic Factors ◽  
Argentine Ants

The Colorado potato beetle in movement

2003 ◽  
Vol 135 (1) ◽  
pp. 1-22 ◽  
Author(s):  
G. Boiteau ◽  
A. Alyokhin ◽  
D.N. Ferro
Keyword(s):  
Colorado Potato Beetle ◽  
Leptinotarsa Decemlineata ◽  
Recent Literature ◽  
Abiotic Factors ◽  
Orientation Process ◽  
Potato Beetle ◽  
Host Habitat ◽  
Subject Areas ◽  
Refuge Areas

AbstractThe recent introduction of the concept of refuge areas for the management of the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera : Chrysomelidae), on resistant potato highlighted the existence of important gaps in our knowledge and understanding of this pest's movement within and between habitats. The objective of this review is to synthesize the information available for the benefit of crop managers and to identify subject areas in need of additional research. A traditional, somewhat encyclopedic, review of the old and recent literature on research methods, basics of flight and walking, as well as abiotic and biotic conditions for dispersal, revealed a considerable volume of information accumulated since the early 1900s. There is a consensus on the role of abiotic factors on flight and walking, but a better understanding of the biotic factors will be required before the variability of the dispersal response can be fully explained or predicted. Cybernetic models of orientation proposed in the literature were pulled together into a schematic representation of the orientation process in walking L. decemlineata. The model begins the integration of the different conditions and underlying suggested mechanisms responsible for the orientation of the walking beetle. There is remarkably little information on the orientation of potato beetles during flight. Finally, the seasonality of walking and flight dispersal is reviewed in relation to the host habitat and overwintering sites.

The role of healt-hcare supply chain management in the wake of COVID-19 pandemic: hot off the press

foresight ◽  
2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sriyanto Sriyanto ◽  
Muhammad Saeed Lodhi ◽  
Hailan Salamun ◽  
Sardin Sardin ◽  
Chairil Faif Pasani ◽  
...  
Keyword(s):  
Health Care ◽  
Supply Chain ◽  
Supply Chain Management ◽  
Parameter Estimates ◽  
Chain Management ◽  
Content Type ◽  
Health Care Supply ◽  
Health Care Supply Chain ◽  
Ssa Countries

Purpose The study aims to examine the role of health-care supply chain management during the COVID-19 pandemic in a cross-section of 42 selected sub-Saharan African (SSA) countries. Design/methodology/approach The study used cross-sectional robust least square regression for parameter estimates. Findings The results confirmed the N-shaped relationship between the health-care logistics performance index (HLPI) and COVID-19 cases. It implies that initially HLPI increases along with an increase in COVID-19 cases. Later down, it decreases COVID-19 cases by providing continued access to medical devices and personal protective equipment. Again, it increases due to resuming economic activities across countries. Practical implications The continuing health-care supply chain is crucial to minimize COVID-19 cases. The international support from the developed world in providing health-care equipment, debt resettlement and resolving regional conflicts is deemed desirable to escape the SSA countries from the COVID-19 pandemic. Originality/value The importance of the health-care supply chain during the COVID-19 pandemic is evident in the forecasting estimates, which shows that from August 2021 to April 2022, increasing the health-care supply chain at their third-degree level would reduce coronavirus registered cases. The results conclude that SSA countries required more efforts to contain coronavirus cases by thrice increasing their health-care logistics supply chain.

scholarly journals Spatial spread of the West Africa Ebola epidemic

2016 ◽  
Vol 3 (8) ◽  
pp. 160294 ◽  
Author(s):  
Andrew M. Kramer ◽  
J. Tomlin Pulliam ◽  
Laura W. Alexander ◽  
Andrew W. Park ◽  
Pejman Rohani ◽  
...  
Keyword(s):  
West Africa ◽  
Sierra Leone ◽  
Ebola Virus ◽  
Emerging Diseases ◽  
Relative Probability ◽  
Effective Response ◽  
Spatial Spread ◽  
Force Of Infection ◽  
International Border

Controlling Ebola outbreaks and planning an effective response to future emerging diseases are enhanced by understanding the role of geography in transmission. Here we show how epidemic expansion may be predicted by evaluating the relative probability of alternative epidemic paths. We compared multiple candidate models to characterize the spatial network over which the 2013–2015 West Africa epidemic of Ebola virus spread and estimate the effects of geographical covariates on transmission during peak spread. The best model was a generalized gravity model where the probability of transmission between locations depended on distance, population density and international border closures between Guinea, Liberia and Sierra Leone and neighbouring countries. This model out-performed alternative models based on diffusive spread, the force of infection, mobility estimated from cell phone records and other hypothesized patterns of spread. These findings highlight the importance of integrated geography to epidemic expansion and may contribute to identifying both the most vulnerable unaffected areas and locations of maximum intervention value.

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