scholarly journals Modeling of Photosynthesis Process and Assessing Of Phytoplankton Dynamics Based On Droop Model

2021 ◽  
Vol 16 (2) ◽  
pp. 380-393
Author(s):  
A.I. Abakumov ◽  
S.Ya. Pak
Keyword(s):  
Water Temperature ◽  
Biomass Production ◽  
Decisive Role ◽  
Equilibrium Solutions ◽  
Daily Cycle ◽  
Droop Model ◽  
Cell Quota ◽  
Short Period ◽  
Existence And Stability ◽  
Biomass Dynamics

Droop's well-known model simulates phytoplankton biomass dynamics based on nutrient limitation. The defining parameter is the nutrient concentration in phytoplankton cells (cell quota). This model is modified to description of the photosynthesis processes. The effects of photosynthetically active radiation must be taken into account. At the same time, the nutritional factor remains the main one. Water temperature is considered as a controlling factor. The influence of light during photosynthesis plays a decisive role. The decisive factor is the presence of photosynthetic substances. We conventionally combine them under the name "chlorophyll". Sufficient variability in the proportion of chlorophyll in phytoplankton (chlorophyll quota) directly affects biomass production. The equation for the dynamics of chlorophyll quota is added to the Droop model. The parameters of the model depend on the concentration of nutrients, illumination and water temperature. The properties of the solutions in the model are investigated, the conditions for the existence and stability of equilibrium solutions are clarified. Complex dynamic regimes are revealed in the case of unstable equilibria. It was found that the most sensitive parameter for biomass dynamics is the minimum value of the cell quota. The dynamics of indicators for the daily cycle and the annual cycle of seasonal changes are calculated. The influence of nutrition, illumination and temperature on biomass production has been clarified. During the day, the chlorophyll quota fluctuates insignificantly due to a short period of time. The changes are noticeable at longer times for example during the season.

Qualitative Analysis of Three-Dimensional Single Food-Chain Model with Variable Consumption Rate in Chemostat

2014 ◽  
Vol 955-959 ◽  
pp. 463-470
Author(s):  
Jing Liu ◽  
Hong Wei Jiang ◽  
Chao Liu
Keyword(s):  
Food Chain ◽  
Consumption Rate ◽  
Three Dimensional ◽  
Quadratic Function ◽  
Positive Equilibrium ◽  
Chain Model ◽  
Equilibrium Solutions ◽  
Existence And Stability ◽  
Variable Consumption ◽  
Food Chain Model

The paper studies three-dimensional food-chain model with variable consumption rate in Chemostat. Assume the prey population's consumption rate of the nutrients is quadratic function, and the predator's consumption rate of the prey population is linear function. Use qualitative theory of ordinary differential equation to analyze the equilibrium solution of the model, especially the existence and stability of positive equilibrium solutions and Hopf bifurcation solutions. Finally,several numerical simulations illustrating the theoretical analysis are also given.

scholarly journals Mathematical modelling for malaria under resistance and population movement

2020 ◽  
Vol 38 (2) ◽  
pp. 133-163
Author(s):  
Cristhian Montoya ◽  
Jhoana P. Romero Leiton
Keyword(s):  
Human Population ◽  
Control Strategies ◽  
Basic Reproductive Number ◽  
Reproductive Number ◽  
Transmission Dynamic ◽  
Equilibrium Solutions ◽  
Population Movements ◽  
Existence And Stability ◽  
Theoretical Results ◽  
Disease Free

In this work, two mathematical models for malaria under resistance are presented. More precisely, the first model shows the interaction between humans and mosquitoes inside a patch under infection of malaria when the human population is resistant to antimalarial drug and mosquitoes population is resistant to insecticides. For the second model, human–mosquitoes population movements in two patches is analyzed under the same malaria transmission dynamic established in a patch. For a single patch, existence and stability conditions for the equilibrium solutions in terms of the local basic reproductive number are developed. These results reveal the existence of a forward bifurcation and the global stability of disease–free equilibrium. In the case of two patches, a theoretical and numerical framework on sensitivity analysis of parameters is presented. After that, the use of antimalarial drugs and insecticides are incorporated as control strategies and an optimal control problem is formulated. Numerical experiments are carried out in both models to show the feasibility of our theoretical results.

Long-term effects of hydrometeorological and water quality conditions on algal dynamics in the Paldang dam watershed, Korea

2014 ◽  
Vol 14 (4) ◽  
pp. 601-608
Author(s):  
D.-W. Kim ◽  
J.-H. Min ◽  
M. Yoo ◽  
M. Kang ◽  
K. Kim
Keyword(s):  
Water Quality ◽  
Water Temperature ◽  
Chlorophyll A ◽  
Algal Bloom ◽  
Temporal Variations ◽  
Regulated River ◽  
Han River ◽  
Nutrient Levels ◽  
Short Period

The primary goal of this study is to shed light on some important factors that control algal bloom in a large-scale regulated river system. Long-term impacts of environmental conditions on algal dynamics were investigated in the Paldang dam watershed, Korea. Dam inflow, water temperature, chlorophyll-a, TN, PO4-P and TP data collected at five major dams located on the North Han River (NHR) and at four water quality monitoring sites on the South Han River were analyzed for 21 years (1992 to 2012) to examine spatio-temporal variations in each. A pattern of slightly increasing chlorophyll-a and nutrient levels in the NHR since 2001 indicates that algal dynamics were affected by the increased nutrient levels as well as the reduced flow conditions (−10% to −37%). The temporal variations in monthly averaged data collected during summer monsoon seasons (mainly July) over the two decades show that high chlorophyll-a levels observed in both rivers corresponded to the relatively lower flow condition, which means a reduced amount of dam water release due to low or no rainfall over a short period of time, and abnormally high water temperature. This study shows that flow control is most critical for effectively managing algal level in the rivers in the short term, and nutrient management in the watershed is the key to reducing the potential for algal bloom in the long term.

scholarly journals Jupiter’s decisive role in the inner Solar System’s early evolution

2015 ◽  
Vol 112 (14) ◽  
pp. 4214-4217 ◽  
Author(s):  
Konstantin Batygin ◽  
Greg Laughlin
Keyword(s):  
Solar System ◽  
Dynamical Evolution ◽  
Decisive Role ◽  
Terrestrial Planets ◽  
The Sun ◽  
Mean Motion Resonances ◽  
The Earth ◽  
Short Period ◽  
Orbital Periods ◽  
Gas Drag

The statistics of extrasolar planetary systems indicate that the default mode of planet formation generates planets with orbital periods shorter than 100 days and masses substantially exceeding that of the Earth. When viewed in this context, the Solar System is unusual. Here, we present simulations which show that a popular formation scenario for Jupiter and Saturn, in which Jupiter migrates inward from a > 5 astronomical units (AU) to a ≈ 1.5 AU before reversing direction, can explain the low overall mass of the Solar System’s terrestrial planets, as well as the absence of planets with a < 0.4 AU. Jupiter’s inward migration entrained s ≳ 10−100 km planetesimals into low-order mean motion resonances, shepherding and exciting their orbits. The resulting collisional cascade generated a planetesimal disk that, evolving under gas drag, would have driven any preexisting short-period planets into the Sun. In this scenario, the Solar System’s terrestrial planets formed from gas-starved mass-depleted debris that remained after the primary period of dynamical evolution.

scholarly journals Theory of quasi-stationary kinetic dynamos in magnetized accretion discs

2010 ◽  
Vol 6 (S274) ◽  
pp. 228-231 ◽  
Author(s):  
Claudio Cremaschini ◽  
John C. Miller ◽  
Massimo Tessarotto
Keyword(s):  
Magnetic Fields ◽  
Decisive Role ◽  
Accretion Disc ◽  
Compact Objects ◽  
Accretion Discs ◽  
Larmor Radius ◽  
Equilibrium Solutions ◽  
Temperature Anisotropy ◽  
Starting Point ◽  
Dynamo Effect

AbstractMagnetic fields are a distinctive feature of accretion disc plasmas around compact objects (i.e., black holes and neutron stars) and they play a decisive role in their dynamical evolution. A fundamental theoretical question related with this concerns investigation of the so-called gravitational MHD dynamo effect, responsible for the self-generation of magnetic fields in these systems. Experimental observations and theoretical models, based on fluid MHD descriptions of various types support the conjecture that accretion discs should be characterized by coherent and slowly time-varying magnetic fields with both poloidal and toroidal components. However, the precise origin of these magnetic structures and their interaction with the disc plasmas is currently unclear. The aim of this paper is to address this problem in the context of kinetic theory. The starting point is the investigation of a general class of Vlasov-Maxwell kinetic equilibria for axi-symmetric collisionless magnetized plasmas characterized by temperature anisotropy and mainly toroidal flow velocity. Retaining finite Larmor-radius effects in the calculation of the fluid fields, we show how these configurations are capable of sustaining both toroidal and poloidal current densities. As a result, we suggest the possible existence of a kinetic dynamo effect, which can generate a stationary toroidal magnetic field in the disc even without any net radial accretion flow. The results presented may have important implications for equilibrium solutions and stability analysis of accretion disc dynamics.

MOSAIC SOLUTIONS AND SPATIAL ENTROPY FOR A CLASS OF NEURAL NETWORK MODELS

2000 ◽  
Vol 10 (07) ◽  
pp. 1661-1675 ◽  
Author(s):  
BARBARA JENNINGS ◽  
ERIK S. VAN VLECK
Keyword(s):  
Network Models ◽  
Equation Model ◽  
Equilibrium Solutions ◽  
Neural Network Models ◽  
Differential Equation Model ◽  
Spatial Coupling ◽  
Spatial Entropy ◽  
Stability Theorems ◽  
Existence And Stability ◽  
Regions Of Stability

In this article, we present a lattice differential equation model for a class of neural networks. A subset of the equilibrium solutions called mosaic equilibrium solutions is defined. Existence and stability theorems are proved for mosaic equilibrium solutions. Regions of stability are defined and spatial entropy calculations, as a measure of the complexity of the system, are presented that give insights into the effects of spatial coupling.

scholarly journals The response of small and shallow lakes to climate change: new insights from hindcast modelling

2020 ◽  
Author(s):  
Francesco Piccioni ◽  
Céline Casenave ◽  
Bruno Jacques Lemaire ◽  
Patrick Le Moigne ◽  
Philippe Dubois ◽  
...  
Keyword(s):  
Climate Change ◽  
Water Temperature ◽  
Biomass Production ◽  
Thermal Regime ◽  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Meteorological Data ◽  
Thermal Response ◽  
Production Model ◽  
Ecological Value

Abstract. Small and shallow water bodies are a dominant portion of inland freshwaters. However, the effects of climate change on such ecosystems have rarely been quantitatively adressed. We propose a methodology to evaluate the thermal response of a small and shallow lake to long-term changes in the meteorological conditions, through model simulations. To do so, a 3D hydrodynamic model is forced with meteorological data and used to hindcast the evolution of a urban lake in the Paris region between 1960 and 2017. Its thermal response is analyzed through the definition of a series of indices describing its thermal regime in terms of water temperature, thermal stratification and tendency to biomass production. Model results and meteorological forcing are analyzed over time to test the presence of monotonic trends and 3D simulations are exploited to highlight spatial patterns in the dynamics of stratification. The thermal regime of the study site underwent significant changes. Its response was highly correlated with three meteorological variables: air temperature, solar radiation and wind speed. Mean annual water temperature showed a considerable warming trend of 0.6 °C/dec, accompanied by longer stratification and by an increase of thermal energy available for biomass production. Water warming was significant during all four seasons, with maxima in Spring and Summer, while stratification and energy for phytoplankton growth increased especially during Spring and Autumn. Stratification only established in the deeper areas of the water body, possibly inducing heterogeneity in the release of nutrient from the sediment and in the development of harmful algal blooms. Numerous similar ecosystems might be experiencing analogous changes, and appropriate management policies are needed to preserve their ecological value.

scholarly journals Production efficiency of corn for forage at different growing densities and harvesting times

2019 ◽  
Vol 40 (5Supl1) ◽  
pp. 2407
Author(s):  
Mikael Neumann ◽  
Julio Cezar Heker Junior ◽  
Murilo Klosovski Carneiro ◽  
Lucas Ghedin Ghizzi ◽  
Edelmir Silvio Stadler Junior ◽  
...  
Keyword(s):  
Biomass Production ◽  
Food Production ◽  
Dry Matter ◽  
Nutritional Value ◽  
Statistical Difference ◽  
Production Efficiency ◽  
Production Plant ◽  
Structural Components ◽  
Short Period ◽  
Dry Biomass

The experiment was conducted at the Animal Production Center (Núcleo de Produção Animal – NUPRAN) of the Center for Agrarian and Environmental Sciences of the Universidade Estadual do Centro-Oeste - UNICENTRO - CEDETEG Campus, Guarapuava, State of Paraná. This study aimed to evaluate biomass production, plant physical composition, chemical composition and dry matter contents of the plant and structural components of forage corn. The experiment was carried out in 5x5 factorial with five planting densities (80, 160, 240, 320 and 400 thousand plants ha-1), harvested in 5 times (40, 50, 60, 70 and 80 days after planting). The harvesting time caused a statistical difference for all parameters, and the planting densities factor only caused statistical difference in leaf participation and dry biomass production. There was no interaction for any of the parameters evaluated. Forage corn, harvested in the vegetative stage, can be a great ally of the rural producer, since it presents high potential for food production with high nutritional value in a short period of time, and in significant amount with production of up to 14,720 kg ha-1 dry biomass reached at 80 days of cycle with 320 thousand ha-1, freeing the soil for the production of another crop.

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