Axioms for grounded truth

We axiomatize Leitgeb’s (2005) theory of truth and show that this theory proves all arithmetical sentences of the system of ramified analysis up to ε0. We also give alternative axiomatizations of Kripke’s (1975) theory of truth (Strong Kleene and supervaluational version) and show that they are at least as strong as the Kripke-Feferman system KF and Cantini’s VF, respectively

Puutüvede metaani- ja naerugaasivood erinevates metsaökosüsteemides

Väitekirja elektrooniline versioon ei sisalda publikatsiooneMetaan (CH4) ja dilämmastikoksiid ehk naerugaas (N2O) on ohtlikud kasvuhoonegaasid (KHG), mille osakaal globaalses kliima soojenemises kasvab. On teada, et maismaaökosüsteemid, eriti metsad reguleerivad nende gaaside emissioone, kuid alles viimasel aastakümnel on seda hakatud neid voogusid lähemalt uurima. Erinevates kliimavööndites, metsaökosüsteemides ja puuliikide tasemel on KHG voogude taga olevate protsesside intensiivsus ja keskkonnatingimuste mõju neile voogudele erinev, mistõttu on oluline nende selgitamine ja kvantifitseerimine. Käesolevas doktoritöös uuriti puutüvede CH4 ja N2O voogude rolli kahes parasvöötme kaldaäärses metsas Eestis ja Doonau jõe vesikonnas (Austrias), troopilises palmisoos Amazonase madalikul Peruus ja troopilises vihmametsas La Reunioni saarel. Lisaks analüüsiti CH4 ja N2O voogude ajalist dünaamikat ja veetaseme mõju nendele voogudele. Uuritud parasvöötme metsamuldade kõrgema veesisalduse korral olid metaani ja naerugaasi emissioonid puutüvedest suuremad, eriti nende madalamates segmentides. Kaldaäärsete metsade puuliikide (hall lepp, harilik saar, paplid) tüveemissioonid sõltusid eeskätt veerežiimist ja temperatuurist, olles kõrgemad märjematel ja jahedatel perioodidel, kusjuures ööpäevaseid voogude muutusi ei täheldatud. Troopikas oli peamiseks teguriks sademete režiim, sest nii aasta- kui ka ööpäevaringselt on õhu- ja mullatemperatuur ühtlaselt kõrge. Seejuures oli tüvevoogude puhul sageli määravaks taimede füsioloogiliste ja morfoloogiliste parameetrite erinevus. Näiteks uuringu tulemused näitavad, et Amazonase soode palmide alumised tüveosad emiteerisid mõlemaid gaase märgatavalt vähem kui ülaosad, mis oli tõenäoliselt tingitud tüvede erinevast morfoloogiast võrreldes puudega. La Reunioni vulkaanilisel saarel täheldatud CH4 ja N2O sidumine puutüvedes oli vähem seotud mullaomadustega, seal mängisid tõenäoliselt olulist rolli tüvesid katvad samblad ja samblikud. Seni tehtud vähesed uuringud näitavad CH4 ja N2O voogude suurt varieeruvust puutüvede ja atmosfääri vahel erinevates metsaökosüsteemides. Mõnes metsas võivad puutüvede ja- võrade gaasivood olla olulisim osa nende gaaside kogubilansis, mis mõnikord muudavad need metsad süsiniku sidujatest selle allikaks. Seetõttu on puude gaasivoogude paremaks mõistmiseks ning metsade globaalse metaani- ja naerugaasibilansi selgitamiseks vajalikud täiendavad interdistsiplinaarsed, eeskätt mikrobioloogilised ja isotoopuuringud.Terrestrial ecosystems like forests play an essential role in the global carbon cycle, regulating climate and climate change by contributing to the methane (CH4) and nitrous oxide (N2O) exchange with the atmosphere. However, the complexity of various climatic zones, forest ecosystem types, tree species and their physiological dynamics cause a challenge to identify and quantify the processes and pathways behind the fluxes. This thesis investigates the specific role of CH4 and N2O fluxes from tree stems in two temperate riparian forests in Estonia and the Danube River basin (Austria), a tropical palm swamp forest in Amazonian Peru, and a tropical rain forest at the volcanic island of La Reunion. Further, their temporal dynamics and the impact of altering water tables on these fluxes are examined. Enhanced CH4 and N2O emissions at higher soil water content were found in temperate forests, especially at the lower segments of the tree stems. The investigated species (grey alder, poplar, ash) demand stable hydrological regimes to form and maintain aerenchyma to exchange gas between the tree above the water and the submerged tissues. Consequently, seasonal adaptations were identified, but diurnal changes of CH4 and N2O fluxes were not found. Observations in the tropics revealed the relevance of specific physiological and morphological parameters in trees' role as a source or sink. Amazonian palm stems formed pseudobark in the lower stem zones, likely inhibiting the radial gas exchange. The observed net uptake of CH4 and N2O by tree stems at La Reunion was less linked to adjunct soils, instead, cryptogamic covers likely play a dominating role. A limited number of studies in different forest ecosystem show high variability of CH4 and N2O exchange between tree stems and atmosphere. In some forests, tree stem fluxes can even dominate in budgets of these gases. Therefore, further complex interdisciplinary investigations are required to better understanding these relationships. Identifying microorganisms and biochemical pathways is evident for reliable estimation and further modelling of the gas exchange dynamics.https://www.ester.ee/record=b545080

Type-free truth

This book is a contribution to the flourishing field of formal and philosophical work on truth and the semantic paradoxes. Our aim is to present several theories of truth, to investigate some of their model-theoretic, recursion-theoretic and proof-theoretic aspects, and to evaluate their philosophical significance. In Part I we first outline some motivations for studying formal theories of truth, fix some terminology, provide some background on Tarski’s and Kripke’s theories of truth, and then discuss the prospects of classical type-free truth. In Chapter 4 we discuss some minimal adequacy conditions on a satisfactory theory of truth based on the function that the truth predicate is intended to fulfil on the deflationist account. We cast doubt on the adequacy of some non-classical theories of truth and argue in favor of classical theories of truth. Part II is devoted to grounded truth. In chapter 5 we introduce a game-theoretic semantics for Kripke’s theory of truth. Strategies in these games can be interpreted as reference-graphs (or dependency-graphs) of the sentences in question. Using that framework, we give a graph-theoretic analysis of the Kripke-paradoxical sentences. In chapter 6 we provide simultaneous axiomatizations of groundedness and truth, and analyze the proof-theoretic strength of the resulting theories. These range from conservative extensions of Peano arithmetic to theories that have the full strength of the impredicative system ID1. Part III investigates the relationship between truth and set-theoretic comprehen- sion. In chapter 7 we canonically associate extensions of the truth predicate with Henkin-models of second-order arithmetic. This relationship will be employed to determine the recursion-theoretic complexity of several theories of grounded truth and to show the consistency of the latter with principles of generalized induction. In chapter 8 it is shown that the sets definable over the standard model of the Tarskian hierarchy are exactly the hyperarithmetical sets. Finally, we try to apply a certain solution to the set-theoretic paradoxes to the case of truth, namely Quine’s idea of stratification. This will yield classical disquotational theories that interpret full second-order arithmetic without set parameters, Z2- (chapter 9). We also indicate a method to recover the parameters. An appendix provides some background on ordinal notations, recursion theory and graph theory