SOLPS-ITER simulations of a CPS-based liquid metal divertor for the EU DEMO: Li vs. Sn

In this work, we study the effect of installing a liquid metal divertor (LMD) using a capillary-porous structure in the EU DEMO tokamak within the same envelope of the baseline solid divertor. We used the SOLPS-ITER code to model the Scrape-Off Layer (SOL) plasma and neutrals, coupled to a target thermal model to enable the self-consistent calculation of the LM target erosion rate, and adopting a fluid neutral model for the sake of simplicity. First calculations considering only D and Li (or Sn) showed a significant reduction of the steady state target heat load with respect to simulations considering only D, thanks to vapor shielding. Nevertheless, the computed peak target heat flux (~31 MW/m2 and ~44 MW/m2 for Li and Sn, respectively) was still larger than/borderline to the power handling limit of the LMD concepts considered. Moreover, the impurity concentration in the pedestal - a proxy for the core plasma dilution/contamination - was computed to be above/close to tolerability limits suggested by previous COREDIV calculations. These results indicate that the operational window of an LMD for the EU DEMO, without any additional impurity seeding, might be too narrow, if it exists, and that Sn looks more promising than Li. A second set of calculations was then performed simulating Ar seeding in the SOL, to further reduce the target heat load, and consequently the metal erosion rate. It was found that the mitigation of the plasma heat load due to Ar radiation in the SOL effectively replaces the radiation associated to vapor shielding in front of the target, thus allowing to operate the LMD in a regime of low target erosion. The resulting operational window was found to be significantly wider, both in terms of tolerable peak target heat flux and of acceptable core plasma contamination.

Generalizing Boltzmann Configurational Entropy to Surfaces, Point Patterns and Landscape Mosaics

Several methods have been recently proposed to calculate configurational entropy, based on Boltzmann entropy. Some of these methods appear to be fully thermodynamically consistent in their application to landscape patch mosaics, but none have been shown to be fully generalizable to all kinds of landscape patterns, such as point patterns, surfaces, and patch mosaics. The goal of this paper is to evaluate if the direct application of the Boltzmann relation is fully generalizable to surfaces, point patterns, and landscape mosaics. I simulated surfaces and point patterns with a fractal neutral model to control their degree of aggregation. I used spatial permutation analysis to produce distributions of microstates and fit functions to predict the distributions of microstates and the shape of the entropy function. The results confirmed that the direct application of the Boltzmann relation is generalizable across surfaces, point patterns, and landscape mosaics, providing a useful general approach to calculating landscape entropy.

Response to Comment on “Information arms race explains plant-herbivore chemical communication in ecological communities"

Zu et al. 2020 (1) proposed a simple, parameter-free, information-arms-race theory to explain the distributions of plant-herbivore interactions and plant-volatile associations observed in plant-herbivore communities. We received a comment by Bass and Kessler (Oct. 2020) questioning this theory and suggesting that a simpler neutral model can explain the observed distributions. This, with our response, went to peer review and was not published (Oct. 29, 2020). The authors have decided to publish their comment on EcoEvoRxiv (2) and so here, we are posting our reply. In sum, we present arguments to show that the comment from Bass and Kessler is based on an incorrect understanding of our study and furthermore suffers from circular reasoning, and that therefore their conclusions are not supported.

Response to Comment on “Information arms race explains plant-herbivore chemical communication in ecological communities”

Zu et al. 2020 (1) proposed a simple, parameter-free, information-arms-race theory to explain the distributions of plant-herbivore interactions and plant-volatile associations observed in plant-herbivore communities. We received a comment by Bass and Kessler (Oct. 2020) questioning this theory and suggesting that a simpler neutral model can explain the observed distributions. This, with our response, went to peer review and was not published (Oct. 29, 2020). The authors have decided to publish their comment on EcoEvoRxiv (2) and so here, we are posting our reply. In sum, we present arguments to show that the comment from Bass and Kessler is based on an incorrect understanding of our study and furthermore suffers from circular reasoning, and that therefore their conclusions are not supported.

Seeing the Forest for the trees: Assessing genetic offset predictions with Gradient Forest

Gradient Forest (GF) is increasingly being used to forecast climate change impacts, but remains mostly untested for this purpose. We explore its robustness to assumption violations, and relationship to measures of fitness, using SLiM simulations with explicit genome architecture and a spatial metapopulation. We evaluate measures of GF offset in: (1) a neutral model with no environmental adaptation; (2) a monogenic "population genetic" model with a single environmentally adapted locus; and (3) a polygenic "quantitative genetic" model with two adaptive traits, each adapting to a different environment. Although we found GF Offset to be broadly correlated with fitness offsets under both single locus and polygenic architectures. It could also be confounded by neutral demography, genomic architecture, and the nature of the adaptive environment. GF Offset is a promising tool, but it is important to understand its limitations and underlying assumptions, especially when used in the context of forecasting maladaptation.

Simulāciju modelis dzesēšanas paneļiem ar iebūvētu latento siltumenerģijas akumulācijas sistēmu

Promocijas darba mērķis – uz vienādojumiem balstīta simulācijas modeļa izstrāde dzēšanas panelim ar integrētu latento termālās enerģijas akumulatoru, kas ir eksperimentāli validēts un paredzēts izmatošanai gandrīz nulles enerģijas ēkās. Šāda modeļa izstrāde ir nepieciešama, lai šī tehnoloģija būtu gatava izmantošanai būvniecības industrijā. Promocijas darbs ietver literatūras apskatu un eksperimentālu pētījumu. Literatūras apskatā ir iekļauts pārskats par gandrīz nulles enerģijas ēku prasībām Eiropas Savienības dalībvalstīs, iepriekšējiem pētījumiem pasīvās dzesēšanas tehnoloģiju jomā un latento termālās enerģijas akumulatoru tehnoloģijām. Pasīvās dzesēšanas sistēmas, kas ir aplūkotas literatūras apskatā, tiek uzskatītas par potenciāliem dzesēšanas enerģijas avotiem, ko var izmantot kopā ar iepriekš minētajiem dzesēšanas paneļiem. Šo tehnoloģiju kombināciju var lietot, lai reaģētu uz telpu pārkaršanas problēmām gandrīz nulles enerģijas ēkās. Eksperimentālā pētījuma mērķis ir iepriekš minētā paneļa simulācijas modeļa izstrāde un validācija. Pētījumā izmantotais matemātiskais modelis ir izstrādāts, izmantojot dinamisko simulāciju rīku IDA ICE, un ietver apakšmodeļus, kas rakstīti NMF (Neutral Model Format) programmēšanas valodā. Simulāciju modelis ir validēts eksperimentālos mērījumos, kas veikti testa kamerā, kas izstrādāta speciāli šim pētījumam. Eksperimentālajā pētījumā veikta arī salīdzinoša analīze, kurā savstarpēji salīdzināti izstrādātā simulācijas modeļa rezultāti ar rezultātiem, kas iegūti no plūsmas dinamikas simulācijas (CFD), ko iepriekš izstrādājusi cita pētnieku komanda. Izstrādātā simulācijas modeļa precizitāte attiecībā pret eksperimentālajiem mērījumiem testa kamerā: maksimālā novirze ir 2,2 °C, vidējā kvadrātiskā kļūda – 1,01 °C. Rezultāti liecina par to, ka izstrādātā modeļa precizitāte ir līdzvērtīga vai augstāka par precizitāti, kas ziņota citos līdzīgos pētījumos. Līdz ar to var uzskatīt, ka šī modeļa precizitāte ir pietiekama, lai to izmantotu enerģijas patēriņa, termālā komforta un dzesēšanas slodžu simulācijās, kas ietver pilnu ēkas apjomu. Eksperimentālajā pētījumā ir norādīti arī vairāki izstrādātā modeļa ierobežojumi, kas būtu jāņem vērā, lai sasniegtu precizitāti, kas uzrādīta šajā pētījumā.

Reticulate evolution in a neutral model: speciation, extinctions, and hybridizations

Evolution is usually pictured as a tree where ancient species branch into new ones and eventually disappear. In this simplified view, the balance between speciation and extinction fully determines the diversity of life. Hybridization, however, introduces another level of complexity, allowing neighboring branches of the tree to interact, mixing their genetic content. This generates further diversity leading to reticulated phylogenetic trees. In this paper we study processes of speciation, extinction and hybridization using a genetically and spatially explicit neutral model of diversification. Speciation, extinction and hybridization events are tracked throughout the evolutionary process leading to complete and exact phylogenetic trees. We found that genome size played a key role in these processes, increasing the extinction rate and decreasing the hybridization rate. In our simulations, hybridization after one speciation event occurred throughout the evolutionary process but hybridization after two speciation events was only observed during the initial radiation. Most hybridization occurred between relatively abundant species, discarding lack of sexual partners or small population sizes as potential causes. We found that hybridization occurred mostly because of opportunity (genetic similarity and spatial proximity) between recently branched species, when the number of accumulated mutations is not yet too large.