Analysis Of Population Dynamics Research Articles

Impact of Organic Loading Rate in Volatile Fatty Acids Production and Population Dynamics Using Microalgae Biomass as Substrate

Volatile fatty acids (VFAs) are regarded as building blocks with a wide range of applications, including biofuel production. The traditional anaerobic digestion used for biogas production can be alternatively employed for VFAs production. The present study aimed at maximizing VFAs productions from Chlorella vulgaris through anaerobic digestion by assessing the effect of stepwise organic loading rates (OLR) increases (3, 6, 9, 12 and 15 g COD L−1 d−1). The biological system was proven to be robust as organic matter conversion efficiency into VFAs increased from 0.30 ± 0.02 COD-VFAs/CODin at 3 g COD L−1 d−1 to 0.37 ± 0.02 COD-VFAs/CODin at 12 g COD L−1d−1. Even though, the hydrolytic step was similar for all studied scenario sCOD/tCOD = 0.52–0.58), the highest OLR (15 g COD L−1 d−1) did not show any further increase in VFAs conversion (0.29 ± 0.01 COD-VFAs/CODin). This fact suggested acidogenesis inhibition at 15 g COD L−1d−1. Butyric (23–32%), acetic (19–26%) and propionic acids (11–17%) were the most abundant bioproducts. Population dynamics analysis revealed microbial specialization, with a high presence of Firmicutes followed by Bacteroidetes. In addition, this investigation showed the microbial adaptation of Euryarchaeota species at the highest OLR (15 g COD L−1d−1), evidencing one of the main challenges in VFAs production (out-competition of archaea community to avoid product consumption). Stepwise OLR increase can be regarded as a tool to promote VFAs productions. However, acidogenic inhibition was reported at the highest OLR instead of the traditional hydrolytic barriers. The operational conditions imposed together with the high VFAs and ammonium concentrations might have affected the system yields. The relative abundance of Firmicutes (74%) and Bacteroidetes (20%), as main phyla, together with the reduction of Euryarchaeota phylum (0.5%) were found the best combination to promote organic matter conversion into VFAs.

Knowledge based analysis of continental population and migration dynamics

Continental migration studies range from elaborate recording of periodic migration data to regression analysis to statistical models that may combine several sources of quantitative and qualitative data. It is the writer's observation that continuous mathematical modeling has not been attempted to estimate continental migration because of the complexity of the governing mathematical models. In this study the writer proposes a continuous mathematical model to estimate continental population and migration trends. The proposed model is based on knowledge-based population dynamics model developed earlier which was used to estimate global population levels and stability of world population under various stress scenarios. In this study one of these models are extended to include continental population and continental migration concepts. Resulting mathematical model is calibrated using historical continental population data which is a reliable data source. If historical continental migration is a zero-sum process, the outcome of the calibrated model yields continental population growth and intercontinental migration estimates. Results obtained are in line with global projections that are made in other studies. The proposed model is also used for future projections.

Invasion dynamics of the white piranha (Serrasalmus brandtii) in a Neotropical river basin

Clarifying the intricate history of unrecorded fish invasions represents an important step in understanding the invasion process. Here, we elucidate the invasion of a Neotropical river basin in Southeastern Brazil by a very efficient predator, the white piranha (Serrasalmus brandtii). We used a temporal series of population dynamics data (2008–2016) and analyses of mitochondrial DNA sequences (COI, 16S, and control region) of specimens from the entire native (Sao Francisco River Basin, Southeastern Brazil) and invaded (Jequitinhonha River Basin, JRB) ranges. We detected low genetic diversity (h = 0.5835) and strong genetic structure in the invasive range (Fst = 0.9141), despite high genetic diversity (h = 0.8900) and low genetic structure (Fst from 0.0740 to 0.1348) in the native range. High genetic structure in the invaded range was associated with a hydroelectric dam that prevented the admixture of two independent introductory acts into the JRB (downstream and upstream of the Irape Dam). The rapid invasion capability of Serrasalmus brandtii, with few propagules, indicates that the species should be included in ecological risk assessments for restocking efforts of other commercially or ecologically important fish species and dam construction in Brazil. The combination of genetic and population dynamic datasets enabled the reconstruction of a top predator fish invasion in the Neotropics and shed light on ecological factors that influenced its invasion success.

Stochastic Modelling for Dynamics of Interacting Populations

Abstract The paper deals with a mathematical model for two interacting populations. Under the assumption of fast stochastic contacting of populations, we derive stochastic Poisson-type differential equations with a small parameter and propose an approximative algorithm for quantitative analysis of population dynamics that consists of two steps. First, we derive an ordinary differential equation for mean value of each population growth and analyse the average asymptotic population behaviour. Then, applying diffusion approximation procedure, we derive a stochastic Ito differential equation for small random deviations on the average motion in a form of a linear non-homogeneous Ito stochastic differential equation and analyse the probabilistic characteristics of the Gaussian process given by this equation.

TRENDS IN THE DEVELOPMENT OF MODERN GEODEMOGRAPHIC SITUATION IN THE KARGAPOL DISTRICT OF THE KURGAN REGION

The study of geodemographic processes is the most important element of the tasks of socio-economic development of territories of different levels and the country as a whole. The article is devoted to identifying the development trends of the geodemographic situation of the administrative unit of the region - Kargapol district of the Kurgan region. They remain largely negative despite the measures taken to support the population by the authorities at all levels. The trends were determined on the basis of an analysis of population dynamics, fertility rates - general, special and age-specific birth rates, mortality rates - total and infant mortality rates, values of the natural and mechanical movement of the population. These indicators are interconnected with each other and with the age and sex structure of the population and the structure of the population as a productive force, i.e. labor resources. To analyze the age structure of labor resources, we used the coefficient of the total demographic load of the able-bodied population, and the coefficient of labor replacement. The conclusion is made about the deepening of crisis phenomena in the geodemographic situation, which requires additional measures by influencing precisely those processes that have the most negative consequences.

Long transients in ecology: Theory and applications.

This paper discusses the recent progress in understanding the properties of transient dynamics in complex ecological systems. Predicting long-term trends as well as sudden changes and regime shifts in ecosystems dynamics is a major issue for ecology as such changes often result in population collapse and extinctions. Analysis of population dynamics has traditionally been focused on their long-term, asymptotic behavior whilst largely disregarding the effect of transients. However, there is a growing understanding that in ecosystems the asymptotic behavior is rarely seen. A big new challenge for theoretical and empirical ecology is to understand the implications of long transients. It is believed that the identification of the corresponding mechanisms along with the knowledge of scaling laws of the transient's lifetime should substantially improve the quality of long-term forecasting and crisis anticipation. Although transient dynamics have received considerable attention in physical literature, research into ecological transients is in its infancy and systematic studies are lacking. This text aims to partially bridge this gap and facilitate further progress in quantitative analysis of long transients in ecology. By revisiting and critically examining a broad variety of mathematical models used in ecological applications as well as empirical facts, we reveal several main mechanisms leading to the emergence of long transients and hence lays the basis for a unifying theory.

The Exergy Footprint as a Sustainability Indicator: An Application to the Neanderthal–Sapiens Competition in the Late Pleistocene

A thermodynamic analysis of population dynamics and of sustainability provides rigor to many important issues. In this work, the “system society” is analysed in connection with the “system environment” using an exergy metric, and the method includes an internalization of the externalities (capital, labour, environmental effects) conducted on the basis of a “system + environment” balance. In this perspective, this study investigates the Late Pleistocene extinction of the Homo neanderthalensis, which took place in a geologically short time and in the presence of a competing species, the Homo sapiens. The case in study is not trivial, and its choice not casual: in those times, the only factor that could lead to an advantage of one group over the other was their respective resource use intensity. A specific indicator, the exergy footprint (EF), is here applied to measure the total amount of primary resources required to produce a certain (material or immaterial) commodity, including the resources needed for the physical survival of the individuals. On the basis of the available data, the results of a steady-state analysis show that the EF of the Neanderthal was higher than that of the Sapiens, and that with both species sharing the same ecological niche in a time of dwindling resources, the less frugal of the two was also more fragile in an evolutionary sense.

Flip bifurcation and stability analysis of a fractional-order population dynamics with Allee effect

In this paper, we established a fractional-order logistic model for a monoclonal brain tumor growth known as Glioblastoma (GB). We show at first that the model possesses non-negative solutions. Furthermore, we studied the stability, existence, and uniqueness of the constructed model. To investigate the case for the extinction of the tumor population, we consider the Allee threshold. By using the center manifold theorem and bifurcation theory, we show that the model undergoes flip bifurcation. The numerical results support the theoretical study.

Bubble behaviors and CO2 absorption characteristics in nanoabsorbents

The objectives of this study are to present a comprehensive analysis of the CO2 bubble population dynamics and to investigate their effects on the CO2 absorption characteristics in nanoabsorbents (methanol with various concentrations of Al2O3 nanoparticles) with a rectangular bubble column. The population balance model (PBM) as a well-established method based on the Euler-Euler model is employed to compute the size distribution of bubbles and to account for the bubbles coalescence and breakage in multiphase flow. The coupled volume-of-fluid (VOF) method is selected to clearly capture the coalescence and breakup processes of successively rising bubbles. The results show that there is a significant influence of the leading bubble on the following one, including the increment of the velocity, the deformation of the bubble shape and the flow instability. It is also found that the critical distance at which the influences can be exerted is related to the bubble wake trailed by the leading bubble. Accordingly, five types of bubble wakes and their effects on the bubble behaviors such as the coalescence and breakup are categorized. Finally, by further analyzing the bubble behaviors in methanol with different volume fraction of Al2O3, it is found that the coalescence and breakup of bubbles are dominated by the bubble wake and enhanced by the eddy in local liquid. It is concluded that the higher concentration of nanoparticles is favorable to the bubble coalescence and breakup, which enhance the mass transfer performance by increasing the interfacial area.

Phylogeography of Dendrolimus punctatus (Lepidoptera: Lasiocampidae): Population differentiation and last glacial maximum survival.

Although the Masson pine moth, Dendrolimus punctatus, is one of the most destructive forest pest insects and is an endemic condition in China, we still do not fully understand the patterns of how its distribution range varies in response to Quaternary climatic oscillations. Here, we sequenced one maternally inherited mitochondrial gene (COI) and biparentally inherited nuclear data (ITS1 and ITS2) among 23 natural populations across the entire range of the species in China. A total of 51 mitotypes and 38 ribotypes were separately obtained using mtDNA and ITS1 data. Furthermore, significant phylogeographical structure (N ST > G ST, p < 0.01) were detected. The spatial distribution of mitotypes implied that two distinct groups existed in the species: one in the southwest distribution, including 10 locations, and the other located in the northeast region of China. It is suggested, therefore, that each group was derived from ancestors that occupied different isolated refugia during previous periods, possibly last glacial maximum. Mismatch distribution and Bayesian population dynamics analysis suggested the population size underwent sudden expansion, which is consistent with the results of ecological niche modeling. As a typical phytophagous insect, the history of population expansion was in accordance with the host plants, providing abundant food resources and habitat. Intraspecific success rate of barcoding identification was lower than interspecific ones, indicating a level of difficulty in barcoding individuals from different populations. However, it still provides an early insight into the pattern of genetic diversity within a species.OPEN RESEARCH BADGES This article has been awarded an Open Data and Open Materials. All materials and data are publicly accessible via the Open Science Framework at https://doi.org/10.5061/dryad.2df87g2. Learn more about the Open Practices badges from the Center for Open Science: https://osf.io/tvyxz/wiki.

Weak electric fields promote resonance in neuronal spiking activity: Analytical results from two-compartment cell and network models.

Transcranial brain stimulation and evidence of ephaptic coupling have sparked strong interests in understanding the effects of weak electric fields on the dynamics of neuronal populations. While their influence on the subthreshold membrane voltage can be biophysically well explained using spatially extended neuron models, mechanistic analyses of neuronal spiking and network activity have remained a methodological challenge. More generally, this challenge applies to phenomena for which single-compartment (point) neuron models are oversimplified. Here we employ a pyramidal neuron model that comprises two compartments, allowing to distinguish basal-somatic from apical dendritic inputs and accounting for an extracellular field in a biophysically minimalistic way. Using an analytical approach we fit its parameters to reproduce the response properties of a canonical, spatial model neuron and dissect the stochastic spiking dynamics of single cells and large networks. We show that oscillatory weak fields effectively mimic anti-correlated inputs at the soma and dendrite and strongly modulate neuronal spiking activity in a rather narrow frequency band. This effect carries over to coupled populations of pyramidal cells and inhibitory interneurons, boosting network-induced resonance in the beta and gamma frequency bands. Our work contributes a useful theoretical framework for mechanistic analyses of population dynamics going beyond point neuron models, and provides insights on modulation effects of extracellular fields due to the morphology of pyramidal cells.

Optical control, selection and analysis of population dynamics in ultrafast protein X-ray crystallography.

Ultrafast pump-probe X-ray crystallography has now been established at X-ray free electron lasers that operate at hard X-ray energies. We discuss the performance and development of current applications in terms of the available data quality and sensitivity to detect and analyse structural dynamics. A discussion of technical capabilities expected at future high repetition rate applications as well as future non-collinear multi-pulse schemes focuses on the possibility to advance the technique to the practical application of the X-ray crystallographic equivalent of an impulse time-domain Raman measurement of vibrational coherence. Furthermore, we present calculations of the magnitude of population differences and distributions prepared with ultrafast optical pumping of single crystals in the typical serial femtosecond crystallography geometry, which are developed for the general uniaxial and biaxial cases. The results present opportunities for polarization resolved anisotropic X-ray diffraction analysis of photochemical populations for the ultrafast time domain. This article is part of the theme issue 'Measurement of ultrafast electronic and structural dynamics with X-rays'.

Population genetics of the capybara, Hydrochoerus hydrochaeris, in the Chaco-pampean region

Hydrochoerus hydrochaeris is an herbivorous rodent that inhabits most wetlands of South America. It is a well-known species, but studies about their population genetics are scarce. The aim of this study was to analyze the genetic diversity, population genetic structure and historical population dynamics of the species in the Chaco-pampean region, using mitochondrial DNA control region sequences and a non-invasive sampling design. Our results showed the existence of four haplogroups in the study area. Haplogroup I is composed by individuals from most of the study area, while the remaining include individuals from some sites in Paraguay (haplogroups III and IV) or Argentina (haplogroup II). The genetic diversity was low in haplogroups I, III and IV. Our results suggest that the Paraná and Paraguay rivers would be acting as a migration corridor for the species. Historical population dynamics analyses and haplotype network showed past population expansions and secondary contact between haplogroups I–II and I–IV, which could be related to past climatic events such as the Iberá Wetlands formation. These results must be taken as working hypotheses for future studies about the population genetics of capybara and related species inhabiting the region.

Global phylodynamics of Echovirus 30 revealed differential behavior among viral lineages

Echovirus 30 (E30) is an important causative agent of aseptic meningitis worldwide. Despite this, the global and regional dispersion patterns, especially in South America, are still largely unknown. We performed an in-depth analysis of global E30 population dynamics, by using the VP1 sequences of 79 strains isolated in Argentina, between 1998 and 2012, and 856 sequences from GenBank. Furthermore, the 3Dpol regions of 329 sequences were analyzed to study potential recombination events. E30 evolution was characterized by co-circulation and continuous replacement of lineages over time, where four lineages appear to circulate at present and another four lineages appear to have stopped circulating. Five lineages showed a global distribution, whereas three other lineages had a more restricted circulation pattern. Strains isolated in South America belong to lineages E and F. Analysis of the 3Dpol region of Argentinean strains indicated that recombination events occurred in both lineages.

Geographical analysis of Russian population dynamics in Baltic republics, Belarus, Ukraine and Moldova in the second half of the 20th century

Geographical analysis of Russian population dynamics in Baltic republics, Belarus, Ukraine and Moldova in the second half of the 20th century

ОПЫТ ДЕНДРО-ЗООЛОГИЧЕСКОГО МОНИТОРИНГА ЛЕСОВ ЮГО-ЗАПАДНОЙ ЧАСТИ РЕСПУБЛИКИ САХА (ЯКУТИЯ)

In Lensky district of the Republic Sakha (Yakutia) an attempt to monitor invertebrates living on trees was made. As a result of the work, 172 species of dendrobiont insects were identified, among which dangerous pests of foliage (Deporousbetulae, Chrysomelapopuli), physiological and technical pests of wood (Hylobiusabietis, Hylobiusalbosparsus, Monochamusssovi, Monochamussutor, Phaenopsguttulata, Phaenopscyanea), species included in the list of quarantine insects pests (Monochamusurussovi, Monochamussutor). For the above species the analysis of population dynamics was carried out. For each identified species, phenology features, trophic and biotopic preferences were studied and refined. The results obtained in the course of the work can be a basis for the development of principles of environmental management and protection.

Modeling and Analysis of Population Dynamics of Human Cells Pertaining to HIV/AIDS with Treatment

In this paper, a mathematical model has been formulated to describe the population dynamics of human cells pertaining to the HIV/AIDS disease with ART as treatment and is analyzed. The human cells have been divided into four compartments Susceptible – Asymptomatic – Symptomatic – AIDS (SAIV). The well posedness of the four dimensional dynamical system is proved and the steady states of the model are identified. Additionally, parametric expression for the basic reproduction number is constructed following next generation matrix method and analyzed its stability using Routh Hurwitz criterion. From the analytical and numerical simulation studies it is observed that if the basic reproduction is less than one unit then the solution converges to the disease free steady state i.e., disease will wipe out and thus the treatment is said to be successful. On the other hand, if the basic reproduction number is greater than one then the solution converges to endemic equilibrium point and thus the infectious cells continue to replicate i.e., disease will persist and thus the treatment is said to be unsuccessful. Sensitivity analysis of the model parameters is conducted and their impact on the reproduction number is analyzed. Finally, the model of the present study simulated using MATLAB. The results and observations have been included in the text of this paper lucidly.

Surviving background extinction: Inferences from historic and current dynamics in the contrasting population structures of two endemic Mexican cycads

AbstractEcological and microevolutionary perspectives were used to investigate signs of background extinction in two endemic species. We studied relict populations of the cycad Dioon caputoi, contrasting its population structure and neighborhood size with those of Dioon planifolium as a demographically healthier reference population. Population dynamics analysis was performed on two populations of D. caputoi through Integral Projection Models and genetic neighborhoods compared between species through 172 Inter Simple Sequence Repeat loci performed in one population of each of the two study species. The D. caputoi populations mostly comprised adult plants, while D. planifolium presented mainly juvenile individuals. Dioon caputoi showed equilibrium in population growth (i.e., λ ≈ 1), with low recruitment, and its genetic neighborhood revealed highly related individuals in a unique distance class (rij = 0.407, 33 m). A contrasting pattern was found in D. planifolium, which showed higher relatedness in the first distance class (rij = 0.543, 5 m), gradually decreasing to 20 m. The discrepancies between the two species reflect different strategies of persistence. Dioon caputoi conserves a relict dynamics with signs of a multigenerational, attritional loss of reproductive fitness, while D. planifolium does not. This study furthers our understanding of the background extinction process and the information will thus contribute to the management and conservation of this endangered species.

Enhancement of biocontrol efficacy of Cryptococcus laurentii by cinnamic acid against Penicillium italicum in citrus fruit

Cinnamic acid was effective to control blue mold caused by Penicillium italicum in ‘Orah’ mandarins. The inhibition of fruit decay was positively correlated with cinnamic acid concentration. Cinnamic acid at 1.5 mM, in combination with the biocontrol yeast Cryptococcus laurentii at 1 × 107 cells/mL, provided synergistic effects against P. italicum. Population dynamic analysis demonstrated that the growth of C. laurentii in fruit rind wounds was not significantly influenced by cinnamic acid. C. laurentii multiplied rapidly, regardless of whether the yeast was used alone or combined with cinnamic acid. By contrast, spore germination and mycelial growth of P. italicum in the culture medium were markedly inhibited by cinnamic acid. By using propidium iodide fluorescent staining, loss of membrane integrity in P. italicum was observed after cinnamic acid treatment. Furthermore, cinnamic acid led to the leakage of cellular constituents including soluble proteins and carbohydrates from hyphae of P. italicum. These results indicated that the fungal pathogen P. italicum is more sensitive to cinnamic acid than the biocontrol yeast C. laurentii. Taken together, our data suggest that the enhancement in biocontrol efficacy of C. laurentii might be associated with the differential influence of cinnamic acid on the antagonistic yeast and the fungal pathogen.

Population genetics of benzimidazole-resistant Haemonchus contortus and Haemonchus placei from buffalo and cattle: implications for the emergence and spread of resistance mutations

The population genetics of nematode parasites are poorly understood with practical reference to the selection and spread of anthelmintic resistance mutations. Haemonchus species are important to study the nematode population genetics due to their clinical importance in ruminant livestock, and the availability of genomic resources. In the present study, it has been examined that Haemonchus contortus and Haemonchus placei populations from three buffalo and nine cattle hosts. Seventy-three individual adult worms of H. contortus and 148 of H. placei were analysed using a panel of seven microsatellite markers. The number of alleles per locus in H. contortus and H. placei indicated that all populations were polymorphic for the microsatellites used in the present study. Genetic diversity parameters included high levels of allelic richness and heterozygosity, indicating effective population sizes, high mutation rates and high transmission frequencies in the area. Genetic structure parameters revealed low genetic differentiation between and high levels of genetic variation within H. contortus and H. placei populations. Population dynamic analyses showed an absence of heterozygosity excess in both species, suggesting that there was no deviation from genetic drift equilibrium. Our results provide a proof of concept for better understanding of the consequences of specific control strategies, climatic change or management strategies on the population genetics of anthelmintic resistance alleles in Haemonchus spp. infecting co-managed buffalo and cattle.