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Introduction: In recent years, we witnessed increasing numbers of migrants worldwide owing to famine, poverty, regional conflicts, etc. Efforts by the United Nations and various organizations to help these migrants are hampered by rising anti-migrant sentiments and xenophobic rhetoric in many parts of the world. To arrive at win-win solutions that benefit both natives and migrants, we must discuss the migration problem objectively and scientifically. To do this, we must first resolve the paradox in our understanding of human migration (widely touted as good) vis-a-vis biological invasion (generally regarded as bad).Method: Suspecting that the two similar phenomena are more complex than we think, we reviewed and synthesized the disjoint literatures on human migration and biological invasion in recent times, and that on the human diaspora and human-aided dispersal of plants and animals in our pre-historic past. We then developed models of niche-niche interactions to simulate isolated ecosystems and communities, as well as those experiencing invasions from non-native populations.Results: In this paper, we simulated four invasion mechanisms on a star network: the direct introduction of a non-native population into existing periphery or core niches, or the non-native population first creating its own niche, which is thereafter attached to the periphery or core of the community. We found that periphery invasions can fail, i.e., the non-native population eventually disappears. When periphery invasion is successful, we found that there is little or no harm to the ecosystem or community. On the other hand, core invasion is always catastrophic, where the non-native population establishes itself at the expense of most or all of the native populations. For niche attachments, whether to the periphery or to the core, we found native and non-native populations coexisting in the end, sometimes with increased diversities.Discussion: Our results provide promising new insights and theoretical grounds for policymakers to discuss the ethics of immigration issues scientifically, and to ultimately discover win-win solutions for natives and migrants. The theoretical framework outlined in this paper can also be applied to the problem of introducing non-native biological species for economic gains, at acceptable ecological costs.

Nowadays, patenting activities are essential in converting applied science to technology in the prevailing innovation model. To gain strategic advantages in the technological competitions between regions, nations need to leverage the investments of public and private funds to diversify over all technologies or specialize in a small number of technologies. In this paper, we investigated who the leaders are at the regional and assignee levels, how they attained their leadership positions, and whether they adopted diversification or specialization strategies, using a dataset of 176,193 patent records on graphene between 1986 and 2017 downloaded from Derwent Innovation. By applying a co-clustering method to the IPC subclasses in the patents and using a z-score method to extract keywords from their titles and abstracts, we identified seven graphene technology areas emerging in the sequence synthesis - composites - sensors - devices - catalyst - batteries - water treatment. We then examined the top regions in their investment preferences and their changes in rankings over time and found that they invested in all seven technology areas. In contrast, at the assignee level, some were diversified while others were specialized. We found that large entities diversified their portfolios across multiple technology areas, while small entities specialized around their core competencies. In addition, we found that universities had higher entropy values than corporations on average, leading us to the hypothesis that corporations file, buy, or sell patents to enable product development. In contrast, universities focus only on licensing their patents. We validated this hypothesis through an aggregate analysis of reassignment and licensing and a more detailed analysis of three case studies - SAMSUNG, RICE UNIVERSITY, and DYSON., Comment: 48 pages, 22 figures, 22 appendix figures

As a part of science of science (SciSci) research, the evolution of scientific disciplines has been attracting a great deal of attention recently. This kind of discipline level analysis not only give insights of one particular field but also shed light on general principles of scientific enterprise. In this paper we focus on graphene research, a fast growing field covers both theoretical and applied study. Using co-clustering method, we split graphene literature into two groups and confirm that one group is about theoretical research (T) and another corresponds to applied research (A). We analyze the proportion of T/A and found applied research becomes more and more popular after 2007. Geographical analysis demonstrated that countries have different preference in terms of T/A and they reacted differently to research trend. The interaction between two groups has been analyzed and shows that T extremely relies on T and A heavily relies on A, however the situation is very stable for T but changed markedly for A. No geographic difference is found for the interaction dynamics. Our results give a comprehensive picture of graphene research evolution and also provide a general framework which is able to analyze other disciplines., Comment: 26 pages, 8 figures

Assessing the impact of environmental fluctuations on species coexistence is critical for understanding biodiversity loss and the ecological impacts of climate change. Yet, determining how properties like the intensity, frequency or duration of environmental fluctuations influence species coexistence remains challenging, presumably because previous studies have focused on indefinite coexistence. Here, we model the impact of environmental fluctuations at different temporal scales on species coexistence over a finite time period by employing the concepts of time windowed averaging and performance curves to incorporate temporal niche differences within a stochastic Lotka–Volterra model. We discover that short- and long-term environmental variability has contrasting effects on transient species coexistence, such that short-term variation favours species coexistence, whereas long-term variation promotes competitive exclusion. This dichotomy occurs because small samples (e.g. environmental changes over long time periods) are more likely to show large deviations from the expected mean and are more difficult to predict than large samples (e.g. environmental changes over short time periods), as described in the central limit theorem. Consequently, we show the complex set of relationships among environmental fluctuations and species coexistence found in previous studies can all be synthesized within a general framework by explicitly considering both long- and short-term environmental variation.

We present Coronavirus disease 2019 (COVID-19) statistics in China dataset: daily statistics of the COVID-19 outbreak in China at the city/county level. For each city/country, we include the six most important numbers for epidemic research: daily new infections, accumulated infections, daily new recoveries, accumulated recoveries, daily new deaths, and accumulated deaths. We cross validate the dataset and the estimate error rate is about 0.04%. We then give several examples to show how to trace the spreading in particular cities or provinces, and also contrast the development of COVID-19 in all cities in China at the early, middle and late stages. We hope this dataset can help researchers around the world better understand the spreading dynamics of COVID-19 at a regional level, to inform intervention and mitigation strategies for policymakers., Comment: 11 pages, 7 figures

In this work we study the influence of an electric field on stripes and compare our results with experimental findings from scanning tunneling microscope measurements. By introducing a negative-bias electric field into a time-dependent Ginzburg-Landau equation with stable stripe solutions, we show that hole(electron)-like stripes widen (narrow) compared to the field free case. When a magnetic field is introduced instead, stripe formation is found to be suppressed., Comment: 4 pages, 9 figures