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Hierarchical analyses of community biogeography in the Afromontane highlands
Get PDFThe Afromontane mountains are a complex series of highlands that have intermittently been connected by habitat corridors during climatic cycles, resulting in a mosaic of range disjunctions and allospecies complexes in the present day. Patterns of community relatedness between geographic regions are often determined through single-species analyses or spatial analyses of diversity and nestedness at the species level. To understand patterns of Afromontane community evolution and to assess the effects of taxonomy on our understanding of biogeographic patterns, I concatenated three different lists of Afromontane bird taxa divided into five different taxonomic hierarchies. These lists were converted into a presence-absence matrix across 42 different montane regions, and analyzed using multiple different clustering techniques using a replicable coding pipeline. I use these lists and methods to determine patterns of relatedness between montane blocks, to assess the consistency with which biogeographic regions are recovered, and to shed more light on patterns of connectivity within the Afromontane region. Results reaffirm the distinctiveness of many different biogeographic regions (i.e., the Cameroon Highlands) while also clarifying regional relationships and the presence of ‘transition zones’ between regions. Differences between lists illustrate how our understanding of taxonomy and distribution in the Afromontane highlands can also change our understanding of Afromontane biogeography. Most notably, I find evidence for an Expanded Eastern Arc that includes the Eastern Arc Mountains and highlands in Malawi, Mozambique, and Zimbabwe. This study presents a rigorous yet easily adjustable pipeline for studying regional biogeography from multiple perspectives with classical and novel approaches
The ultimate cost of carbon
Get PDFWe estimate the potential ultimate cost of fossil-fuel carbon to a long-lived human population over a one million–year time scale. We assume that this hypothetical population is technologically stationary and agriculturally based, and estimate climate impacts as fractional decreases in economic activity, potentially amplified by a human population response to a diminished human carrying capacity. Monetary costs are converted to units of present-day dollars by multiplying the future damage fractions by the present-day global world production, and integrated through time with no loss due from time-preference discounting. Ultimate costs of C range from 10k USD to 750k USD per ton for various assumptions about the magnitude and longevity of economic impacts, with a best-estimate value of about 100k USD per ton of C. Most of the uncertainty arises from the economic parameters of the model and, among the geophysical parameters, from the climate sensitivity. We argue that the ultimate cost of carbon is a first approximation of our potential culpability to future generations for our fossil energy use, expressed in units that are relevant to us
Catalytic growth in a shared enzyme pool ensures robust control of centrosome size
Get PDFAccurate regulation of centrosome size is essential for ensuring error-free cell division, and dysregulation of centrosome size has been linked to various pathologies, including developmental defects and cancer. While a universally accepted model for centrosome size regulation is lacking, prior theoretical and experimental works suggest a centrosome growth model involving autocatalytic assembly of the pericentriolar material. Here, we show that the autocatalytic assembly model fails to explain the attainment of equal centrosome sizes, which is crucial for error-free cell division. Incorporating latest experimental findings into the molecular mechanisms governing centrosome assembly, we introduce a new quantitative theory for centrosome growth involving catalytic assembly within a shared pool of enzymes. Our model successfully achieves robust size equality between maturing centrosome pairs, mirroring cooperative growth dynamics observed in experiments. To validate our theoretical predictions, we compare them with available experimental data and demonstrate the broad applicability of the catalytic growth model across different organisms, which exhibit distinct growth dynamics and size scaling characteristics
Comet of the Cellular Cosmos
No full textThis image captures the expression of a GFP-fused calcium sensor in U2OS cell, offering insights into the intricate relationship between calcium bursts and the dynamic behavior of filopodia, driven by MyoX protein expression (not visible here). The fluorescent microscopy image was taken as part of an optimization process for gene transfection, where the sensor was used to track real-time calcium signaling events. The comet-like dotted traces observed here are likely a peculiar result of the staining process, revealing not just a technical artifact but an unexpected visualization of cellular debris. This project, conducted in Ronald Rock's lab, may help elucidate the dependencies between calcium fluxes within the cell and MyoX protein activity, providing a deeper understanding of how calcium dynamics and filopodia extension interplay to regulate cell movement—process that, in worst-case scenarios, contributes to metastasis
Political Economy
Get PDFThis chapter situates Montesquieu’s economic writing within broader political and economic developments that favored the emergence, in France and all over Europe, of political economy. For Montesquieu, the rise of international trade; the increasing dominance of mobile forms of wealth; and transformed expectations for material well-being in modern societies undermined traditional social structures and the forms of political authority that went with them. In this context, Montesquieu’s political thought can be read as a kind of political economy insofar as it employed a moral psychology of other-directedness and self-interest that was better adapted to an emerging commercial society than traditional models of duty and virtue. But Montesquieu, unlike the more straightforwardly economic writers of his time, did not organize his inquiry around questions of plenty so much as he sought, through his comparative method, to explore the diverse ways in which statecraft in the age of commerce could contribute to his ideal of moderate government
Temperature, humidity, and ionisation effect of iodine oxoacid nucleation
Get PDFIodine oxoacids are recognised for their significant contribution to the formation of new particles in marine and polar atmospheres. Nevertheless, to incorporate the iodine oxoacid nucleation mechanism into global simulations, it is essential to comprehend how this mechanism varies under various atmospheric conditions. In this study, we combined measurements from the CLOUD (Cosmic Leaving OUtdoor Droplets) chamber at CERN and simulations with a kinetic model to investigate the impact of temperature, ionisation, and humidity on iodine oxoacid nucleation. Our findings reveal that ion-induced particle formation rates remain largely unaffected by changes in temperature. However, neutral particle formation rates experience a significant increase when the temperature drops from +10 °C to −10 °C. Running the kinetic model with varying ionisation rates demonstrates that the particle formation rate only increases with a higher ionisation rate when the iodic acid concentration exceeds 1.5 × 107 cm−3, a concentration rarely reached in pristine marine atmospheres. Consequently, our simulations suggest that, despite higher ionisation rates, the charged cluster nucleation pathway of iodic acid is unlikely to be enhanced in the upper troposphere by higher ionisation rates. Instead, the neutral nucleation channel is likely to be the dominant channel in that region. Notably, the iodine oxoacid nucleation mechanism remains unaffected by changes in relative humidity from 2% to 80%. However, under unrealistically dry conditions (below 0.008% RH at +10 °C), iodine oxides (I2O4 and I2O5) significantly enhance formation rates. Therefore, we conclude that iodine oxoacid nucleation is the dominant nucleation mechanism for iodine nucleation in the marine and polar boundary layer atmosphere
Practical rare event sampling for extreme mesoscale weather
Get PDFExtreme mesoscale weather, including tropical cyclones, squall lines, and floods, can be enormously damaging and yet challenging to simulate; hence, there is a pressing need for more efficient simulation strategies. Here, we present a new rare event sampling algorithm called quantile diffusion Monte Carlo (quantile DMC). Quantile DMC is a simple-to-use algorithm that can sample extreme tail behavior for a wide class of processes. We demonstrate the advantages of quantile DMC compared to other sampling methods and discuss practical aspects of implementing quantile DMC. To test the feasibility of quantile DMC for extreme mesoscale weather, we sample extremely intense realizations of two historical tropical cyclones, 2010 Hurricane Earl and 2015 Hurricane Joaquin. Our results demonstrate quantile DMC’s potential to provide low-variance extreme weather statistics while highlighting the work that is necessary for quantile DMC to attain greater efficiency in future applications
Advancing geothermal energy: A review of technological developments and environmental impacts
Get PDFThe global demand for sustainable and clean energy sources has driven significant advancements in the field of geothermal energy. This paper provides a comprehensive review of the latest technological developments and environmental impacts associated with the advancement of geothermal energy. Technological developments in geothermal energy have focused on enhancing efficiency, scalability, and cost-effectiveness. Innovations in drilling techniques, such as enhanced geothermal systems (EGS), have expanded the potential for harnessing geothermal resources in previously untapped regions. Furthermore, advancements in materials science and reservoir management techniques have contributed to increased energy extraction and prolonged reservoir life. This review also delves into the environmental impacts of geothermal energy, addressing both the positive and negative aspects. Geothermal power generation produces minimal greenhouse gas emissions compared to traditional fossil fuels, contributing to a cleaner and more sustainable energy landscape. However, concerns about induced seismicity, subsurface fluid management, and the potential release of trace gases during geothermal operations require careful consideration. The integration of geothermal energy into the broader energy mix is explored, emphasizing its role in reducing reliance on fossil fuels and mitigating climate change. Additionally, the review discusses the importance of regulatory frameworks and community engagement in ensuring responsible geothermal development. This paper highlights the dynamic landscape of geothermal energy, showcasing the progress made in technology and the environmental considerations that accompany its expansion. As the world seeks alternative energy sources to address climate change and energy security, understanding the evolving nature of geothermal energy is crucial for informed decision-making and sustainable energy transitions
The role of natural gas as a primary fuel in the near future, including comparisons of acquisition, transmission and waste handling costs of as with competitive alternatives
Get PDFNatural gas comprises about a quarter of the United States’ energy use. It is more environmentally friendly than oil and coal due to lower carbon dioxide (CO2) emissions per unit, less costly per unit of energy and more readily available domestically in abundant supply. However, due to a number of barriers in the political, infrastructural, pricing and other arenas, the use of natural gas as a significant energy source in the United States has been limited. In our paper, we highlight the favorable qualities of natural gas and its benefits for the consumer, producer, and environment, having compared the costs of the various components of the natural gas business such as drilling and transport to that of coal and oil. Moreover, we touch upon the major issues that have prevented a more prevalent use of the gas, such as the fact that the infrastructure of natural gas is more costly since it is transported though pipelines whereas other energy sources such as oil and coal have flexible systems that use trains, trucks and ships. In addition, the powerful lobbies of the coal and oil businesses, along with the inertia in the congress to pass a national climate change bill further dampens incentives for these industries to invest in natural gas, despite its various attractive qualities. We also include discussions of policy proposals to incentive greater use of natural gas in the future
Information versus Knowledge in Climate Change Prediction
Get PDFThis presentation aims to dispel misinformation about climate change through a discussion of relevant scientific studies