Effects Of Heterogeneous Environment Research Articles

Reinvestigating the pollution haven hypothesis: the nexus between foreign direct investments and environmental quality in G-20 countries.

One of the most commonly debated concerns regarding foreign direct investment inflows is the associated environmental adversities that accompany the influx of foreign funds. As a result, assessing the environmental impacts of foreign direct investment inflows is necessary for achieving environmentally friendly economic growth in the contemporary era. Accordingly, the global economies including the members of the Group of Twenty (G-20) should focus on attracting clean foreign direct investments. Against this backdrop, controlling for energy consumption and urbanization, this extant study scrutinizes the effects of foreign direct investment inflows on the carbon dioxide emission figures of selected G-20 countries between 1992 and 2018. The econometric analysis conducted in this paper involves recently developed methods that are efficient in handling cross-sectionally dependent heterogeneous panel data sets. Besides, the analysis is also conducted for sub-panels of high-, upper-middle-, and lower-middle-income G-20 countries to evaluate the possible heterogeneous environmental effects across the G-20countries belonging to different income levels. Overall, the results highlight that higher foreign direct investmentinflows surge carbon dioxide emissions whereby the pollution haven hypothesis is evidenced to hold for the G-20 nations of concern. Similarly, both at the aggregated and disaggregated levels, greater consumption of energy is witnessed to boost carbon dioxide emissions in the long run. Moreover, urbanization is found to trigger carbon dioxide emissions for the G-20 nations overall and the lower-middle-income G-20 nations. Further, the causality analysis reveals that carbon dioxide emissions have bidirectional causal relationships with foreign direct investment inflows, energy consumption, and urbanization. In line with these major findings, this study recommends thatthe governments of the G-20 countries inhibit inflows of dirty foreign direct investments, reduce fossil fuel dependency, and adopt green urbanization policies for achieving higher economic growth without marginalizing environmental well-being.

Effects of Heterogeneous Environment After Deforestation on Plant Phenotypic Plasticity of Three Shrubs Based on Leaf Traits and Biomass Allocation

Phenotypic plasticity among natural plant populations is a species-specific ecological phenomenon of paramount importance that depends on their life forms, development stages, as well as environmental factors. While this phenomenon is broadly understood, it has hardly been observed in nature. This study aimed at understanding phenotypic plasticity and ecological adaptability in three shrubs (Salix etosia, Rubus setchuenensis, and Hydrangea aspera) affected by potential environmental variables after deforesting in sparse Larix spp. forest and tall shrub mixed secondary forests. Soil organic carbon content, total nitrogen content, and available nitrogen content were greater outside the forests, contrary to other measured factors whose availability was higher in the forest interiors. In case of leaf traits and stoichiometric indicators, there were significant interactions of leaf area (LA), leaf dry matter (DW), specific leaf area (SLA), and leaf phosphorus content (LPC) between shrub species and heterogeneous environments (P < 0.05) but not for leaf C/N, N/P, and C/P. Principal components analysis (PCA) indicated that soil temperature, pH value, soil carbon content, soil nitrogen content, and MBC and MBN mainly constituted the first component. Summarized results indicated that TB and leaf C/P of S. etosia were significantly correlated with three principal components, but only marginal significant correlations existed between R/S and relevant components. SLA and R/S of R. setchuenensis had marginal significant relationships with independent variables. Both SLA and TB of H. aspera were significantly correlated with three principal components. Based on the pooled values of leaf functional traits and leaf stoichiometric indicators, R. setchuenensis (vining type) had better leaf traits plasticity to adapt to a heterogeneous environment. In descending order, the ranks of biomass allocation plasticity index of three shrubs were H. aspera (bunch type), R. setchuenensis (vining type), and S. etosia (erect type). The highest integrated plasticity values of leaf traits and biomass allocation was observed in H. aspera (bunch type), followed by R. setchuenensis, and by S. etosia with less adaptive plasticity in heterogeneous environments.

Modeling three-dimensional invasive solid tumor growth in heterogeneous microenvironment under chemotherapy.

A systematic understanding of the evolution and growth dynamics of invasive solid tumors in response to different chemotherapy strategies is crucial for the development of individually optimized oncotherapy. Here, we develop a hybrid three-dimensional (3D) computational model that integrates pharmacokinetic model, continuum diffusion-reaction model and discrete cell automaton model to investigate 3D invasive solid tumor growth in heterogeneous microenvironment under chemotherapy. Specifically, we consider the effects of heterogeneous environment on drug diffusion, tumor growth, invasion and the drug-tumor interaction on individual cell level. We employ the hybrid model to investigate the evolution and growth dynamics of avascular invasive solid tumors under different chemotherapy strategies. Our simulations indicate that constant dosing is generally more effective in suppressing primary tumor growth than periodic dosing, due to the resulting continuous high drug concentration. In highly heterogeneous microenvironment, the malignancy of the tumor is significantly enhanced, leading to inefficiency of chemotherapies. The effects of geometrically-confined microenvironment and non-uniform drug dosing are also investigated. Our computational model, when supplemented with sufficient clinical data, could eventually lead to the development of efficient in silico tools for prognosis and treatment strategy optimization.

Spatial heterogeneity, frequency-dependent selection and polymorphism in host-parasite interactions

BackgroundGenomic and pathology analysis has revealed enormous diversity in genes involved in disease, including those encoding host resistance and parasite effectors (also known in plant pathology as avirulence genes). It has been proposed that such variation may persist when an organism exists in a spatially structured metapopulation, following the geographic mosaic of coevolution. Here, we study gene-for-gene relationships governing the outcome of plant-parasite interactions in a spatially structured system and, in particular, investigate the population genetic processes which maintain balanced polymorphism in both species.ResultsFollowing previous theory on the effect of heterogeneous environments on maintenance of polymorphism, we analysed a model with two demes in which the demes have different environments and are coupled by gene flow. Environmental variation is manifested by different coefficients of natural selection, the costs to the host of resistance and to the parasite of virulence, the cost to the host of being diseased and the cost to an avirulent parasite of unsuccessfully attacking a resistant host. We show that migration generates negative direct frequency-dependent selection, a condition for maintenance of stable polymorphism in each deme. Balanced polymorphism occurs preferentially if there is heterogeneity for costs of resistance and virulence alleles among populations and to a lesser extent if there is variation in the cost to the host of being diseased. We show that the four fitness costs control the natural frequency of oscillation of host resistance and parasite avirulence alleles. If demes have different costs, their frequencies of oscillation differ and when coupled by gene flow, there is amplitude death of the oscillations in each deme. Numerical simulations show that for a multiple deme island model, costs of resistance and virulence need not to be present in each deme for stable polymorphism to occur.ConclusionsOur theoretical results confirm the importance of empirical studies for measuring the environmental heterogeneity for genetic costs of resistance and virulence alleles. We suggest that such studies should be developed to investigate the generality of this mechanism for the long-term maintenance of genetic diversity at host and parasite genes.

Invasion and eradication of a competitively superior species in heterogeneous landscapes

The effect of heterogeneous environments upon the dynamics of invasion and the eradication or control of invasive species is poorly understood, although it is a major challenge for biodiversity conservation. Here, we first investigate how the probability and time for invasion are affected by spatial heterogeneity. Then, we study the effect of control program strategies (e.g. species specificity, spatial scale of action, detection and eradication efficiency) on the success and time of eradication. We find that heterogeneity increases both the invasion probability and the time to invasion. Heterogeneity also reduces the probability of eradication but does not change the time taken for successful eradication. We confirm that early detection of invasive species reduces the time until eradication, but we also demonstrate that this is true only if the local control action is sufficiently efficient. The criterion of removal efficiency is even more important for an eradication program than simply ensuring control effort when the invasive species is not abundant.

Spectroscopy of Photoreactive Systems: Implications for Atmospheric Chemistry

This article focuses on the mechanism and molecular dynamics of light-initiated atmospheric reactions. The availability of photons of the correct wavelengths, the response to collisions, and the effect of heterogeneous environments will be considered in this discussion. A new class of light-initiated reactions occurring in the ground electronic state by concerted mechanisms with significant rates are highlighted with examples such as sulfuric acid dehydration and pyruvic acid decarboxylation. The unprecedented mechanism investigated in pyruvic acid initiates reaction by hydrogen atom chattering on very fast time scales. The dynamics suggests significant consequences for this chemistry in photoprocessing acids and alcohols in the atmosphere. An important observation is that water may potentially affect these reactions' energetics, rates, and mechanisms. Examples from our work on light-initiated reactions of atmospheric targets in the gas phase and as affected by water are discussed to point to future areas for physical chemistry research in this field.

Effects of a Degeneracy in the Competition Model: Part I. Classical and Generalized Steady-State Solutions

We study the competition model where the coefficient functions are strictly positive over the underlying spatial region Ω except b(x), which vanishes in a nontrivial subdomain of Ω, and is positive in the rest of Ω. We show that there exists a critical number λ* such that if λ <λ*, then the model behaves similarly to the well-studied classical competition model where all the coefficient functions are positive constants, but when λ>λ*, new phenomena occur. Our results demonstrate the fact that heterogeneous environmental effects on population models are not only quantitative, but can be qualitative as well. In part I here, we mainly study two kinds of steady-state solutions which determine the dynamics of the model: one consists of finite functions while the other consists of generalized functions which satisfy (u, v)=(∞, 0) on the part of the domain that b(x) vanishes, but are positive and finite on the rest of the domain, and are determined by certain boundary blow-up systems. The research is continued in part II, where these two kinds of steady-state solutions will be used to determine the dynamics of the model.

Effects of Egg Size and Density on Metamorphic Traits in Tadpoles of the Natterjack Toad (Bufo calamita)

Effects of Egg Size and Density on Metamorphic Traits in Tadpoles of the Natterjack Toad (Bufo calamita)

The Effect of Heterogeneous Environments and a Competitor on Genetic Variation in Drosophila

Thirty-six homokaryotypic laboratory populations of Drosophila pseudoobscura, all of which originated from the same freshly collected population, were maintained for 2 yr. The populations had zero, one, two, or three of the following factors variable: medium, temperature, and/or presence of a competitor, D. persimilis. Twelve, 18, and 24 mo after the populations started, estimates of levels of heterozygosity of each population were made by measuring the amount of electrophoretically detectable genetic variation at nine polymorphic enzyme loci. In going from zero to one factor varying, all three factors increased the level of heterozygosity observed; i.e., populations experiencing two temperatures maintained more genetic variation than populations held at one temperature; populations which had two types of media present had higher levels of genetic variation than populations with only one medium; populations to which D. persimilis were added maintained more genetic variation than when D. pseudoobscura was alone. In going from one to two or two to three variables, increased genetic variation sometimes could and sometimes could not be detected. Estimates of population sizes were made. From these it was concluded that genetic drift cannot account for the pattern observed. Therefore, it is concluded that selection was operating; at least some of the electrophoretically detectable alleles may themselves be parts of the units of selection. It is argued that such diversifying selection is important in maintaining high levels of genic variation in natural population, especially in organisms such as Drosophila.