Bioclimatic envelope models use associations between aspects of climate and species' occurrences to estimate the conditions that are suitable to maintain viable populations. Once bioclimatic ...envelopes are characterized, they can be applied to a variety of questions in ecology, evolution, and conservation. However, some have questioned the usefulness of these models, because they may be based on implausible assumptions or may be contradicted by empirical evidence. We review these areas of contention, and suggest that criticism has often been misplaced, resulting from confusion between what the models actually deliver and what users wish that they would express. Although improvements in data and methods will have some effect, the usefulness of these models is contingent on their appropriate use, and they will improve mainly via better awareness of their conceptual basis, strengths, and limitations.
Ecological niche modeling is a set of analytical tools with applications in diverse disciplines, yet creating these models rigorously is now a challenging task. The calibration phase of these models ...is critical, but despite recent attempts at providing tools for performing this step, adequate detail is still missing. Here, we present the kuenm R package, a new set of tools for performing detailed development of ecological niche models using the platform Maxent in a reproducible way.
This package takes advantage of the versatility of R and Maxent to enable detailed model calibration and selection, final model creation and evaluation, and extrapolation risk analysis. Best parameters for modeling are selected considering (1) statistical significance, (2) predictive power, and (3) model complexity. For final models, we enable multiple parameter sets and model transfers, making processing simpler. Users can also evaluate extrapolation risk in model transfers via mobility-oriented parity (MOP) metric.
Use of this package allows robust processes of model calibration, facilitating creation of final models based on model significance, performance, and simplicity. Model transfers to multiple scenarios, also facilitated in this package, significantly reduce time invested in performing these tasks. Finally, efficient assessments of strict-extrapolation risks in model transfers via the MOP and MESS metrics help to prevent overinterpretation in model outcomes.
The activity of many heterogeneous catalysts is limited by strong correlations between activation energies and adsorption energies of reaction intermediates. Although the reaction is ...thermodynamically favourable at ambient temperature and pressure, the catalytic synthesis of ammonia (NH
), a fertilizer and chemical fuel, from N
and H
requires some of the most extreme conditions of the chemical industry. We demonstrate how ammonia can be produced at ambient pressure from air, water, and concentrated sunlight as renewable source of process heat
nitrogen reduction with a looped metal nitride, followed by separate hydrogenation of the lattice nitrogen into ammonia. Separating ammonia synthesis into two reaction steps introduces an additional degree of freedom when designing catalysts with desirable activation and adsorption energies. We discuss the hydrogenation of alkali and alkaline earth metal nitrides and the reduction of transition metal nitrides to outline a promoting role of lattice hydrogen in ammonia evolution. This is rationalized
electronic structure calculations with the activity of nitrogen vacancies controlling the redox-intercalation of hydrogen and the formation and hydrogenation of adsorbed nitrogen species. The predicted trends are confirmed experimentally with evolution of 56.3, 80.7, and 128 μmol NH
per mol metal per min at 1 bar and above 550 °C
reduction of Mn
N
to Mn
N and hydrogenation of Ca
N
and Sr
N to Ca
NH and SrH
, respectively.
Species’ invasions have long been regarded as enormously complex processes, so complex as to defy predictivity. Phases of this process, however, are emerging as highly predictable: the potential ...geographic course of an invasion can be anticipated with high precision based on the ecological niche characteristics of a species in its native geographic distributional area. This predictivity depends on the premise that ecological niches constitute long‐term stable constraints on the potential geographic distributions of species, for which a sizeable body of evidence is accumulating. Hence, although the entire invasion process is indeed complex, the geographic course that invasions are able to take can be anticipated with considerable confidence.
Aim To evaluate the evolutionary conservatism of coarse-resolution Grinnellian (or scenopoetic) ecological niches. Location Global. Methods I review a broad swathe of literature relevant to the topic ...of niche conservatism or differentiation, and illustrate some of the resulting insights with examplar analyses. Results Ecological niche characteristics are highly conserved over short-to-moderate time spans (i.e. from individual life spans up to tens or hundreds of thousands of years); little or no ecological niche differentiation is discernible as part of the processes of invasion or speciation. Main conclusions Although niche conservatism is widespread, many methodological complications obscure this point. In particular, niche models are frequently over-interpreted: too often, they are based on limited occurrence data in high-dimensional environmental spaces, and cannot be interpreted robustly to indicate niche differentiation.
A. Townsend Peterson, one of the pioneers of ecological niche modeling, presents a synthesis that illuminates new and more effective infectious disease mapping methods. His work—the culmination of ...twelve years of refinement—breaks new ground by integrating biogeographic and ecological factors with spatial models. Aimed at seasoned epidemiologists and public health experts, this interdisciplinary book explains the conceptual and technical underpinnings of Peterson’s approach while simultaneously describing the potentially enormous benefits of his modeling method.
Peterson treats disease transmission areas for what they are—distributions of species. The book argues that complex, fragmented, and highly irregular disease patterns can only be understood when underlying environmental drivers are considered. The result is an elegant modeling approach that challenges static spatial models and provides a framework for recasting disease mapping. Anyone working in the area of disease transmission, particularly those employing predictive maps, will find Peterson’s book both inspiring and indispensable.
Platinum is a nearly perfect catalyst for the hydrogen evolution reaction, and its high activity has conventionally been explained by its close-to-thermoneutral hydrogen binding energy (G ∼ 0). ...However, many candidate nonprecious metal catalysts bind hydrogen with similar strengths but exhibit orders-of-magnitude lower activity for this reaction. In this study, we employ electronic structure methods that allow fully potential-dependent reaction barriers to be calculated, in order to develop a complete working picture of hydrogen evolution on platinum. Through the resulting ab initio microkinetic models, we assess the mechanistic origins of Pt’s high activity. Surprisingly, we find that the G ∼ 0 hydrogen atoms are inert in the kinetically relevant region and that the active hydrogen atoms have ΔG’s much weaker, similar to that of gold. These on-top hydrogens have particularly low barriers, which we compare to those of gold, explaining the high reaction rates, and the exponential variations in coverage lead directly to Pt’s strong kinetic response to the applied potential. This explains the unique reactivity of Pt that is missed by conventional Sabatier analyses and suggests true design criteria for nonprecious alternatives.
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