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  • Salonen, J Sakari (Helsingin yliopisto, 2012)
    Palaeoclimatic reconstructions from fossil proxies have provided important insights into the natural variability of climate in the late Quaternary. However, major challenges remain in ensuring the robustness of these reconstructions. Multiple factors may introduce variability and biases into the palaeoclimatic estimates. For example, quantitative reconstructions use diverse modern calibration data-sets, and a wide variety of numerical calibration methods. While the choice of calibration data-set and calibration method may significantly influence the reconstructions, the comparison and analysis of these data-sets and methods have received relatively little attention. Further challenges are presented by the validation of the prepared reconstructions and the identification of climatic variables which can be robustly reconstructed from a given proxy. In this work, summer temperature reconstructions are prepared based on late-Quaternary pollen sequences from northern Finland and northern Russia, covering the Holocene and the early part of the last glacial period (Marine Isotope Stages 5d c). The major aim of this work is to validate these reconstructions and to identify sources of bias in them. Reconstructions are prepared using a number of different calibration methods and calibration sets, to analyse the between-reconstruction variability introduced by the choice of calibration method and calibration set. In addition, novel regression tree methods are used to test the ecological significance of different climatic factors, with the aim of identifying parameters which could feasibly be reconstructed. In the results, it is found that the choice of calibration method, calibration data-set, and fossil pollen sequence can all significantly affect the reconstruction. The problems in choosing calibration data are especially acute in pre-Holocene reconstructions, as it is difficult to find representative calibration data for reconstructions from non-analogue palaeoclimates which become increasingly common in the more distant past. First-order trends in the reconstructed palaeoclimates are found to be relatively robust. However, the degree of between-reconstruction variability stresses the importance of independent validation, and suggests that ensemble reconstructions using different methods and proxies should be increasingly relied on. The analysis of climatic response in northern European modern pollen samples by regression trees suggests secondary climatic determinants such as winter temperature and continentality to have major ecological influence, in addition to summer temperature which has been the most commonly reconstructed variable in palaeoclimatic studies. This suggests the potential to reconstruct the secondary parameters from fossil pollen. However, validating the robustness of secondary-parameter reconstructions remains a major challenge for future studies.
  • Schulman, Nina (Helsingin yliopisto, 2007)
    Knowing the chromosomal areas or actual genes affecting the traits under selection would add more information to be used in the selection decisions which would potentially lead to higher genetic response. The first objective of this study was to map quantitative trait loci (QTL) affecting economically important traits in the Finnish Ayrshire population. The second objective was to investigate the effects of using QTL information in marker-assisted selection (MAS) on the genetic response and the linkage disequilibrium between the different parts of the genome. Whole genome scans were carried out on a grand-daughter design with 12 half-sib families and a total of 493 sons. Twelve different traits were studied: milk yield, protein yield, protein content, fat yield, fat content, somatic cell score (SCS), mastitis treatments, other veterinary treatments, days open, fertility treatments, non-return rate, and calf mortality. The average spacing of the typed markers was 20 cM with 2 to 14 markers per chromosome. Associations between markers and traits were analyzed with multiple marker regression. Significance was determined by permutation and genome-wise P-values obtained by Bonferroni correction. The benefits from MAS were investigated by simulation: a conventional progeny testing scheme was compared to a scheme where QTL information was used within families to select among full-sibs in the male path. Two QTL on different chromosomes were modelled. The effects of different starting frequencies of the favourable alleles and different size of the QTL effects were evaluated. A large number of QTL, 48 in total, were detected at 5% or higher chromosome-wise significance. QTL for milk production were found on 8 chromosomes, for SCS on 6, for mastitis treatments on 1, for other veterinary treatments on 5, for days open on 7, for fertility treatments on 7, for calf mortality on 6, and for non-return rate on 2 chromosomes. In the simulation study the total genetic response was faster with MAS than with conventional selection and the advantage of MAS persisted over the studied generations. The rate of response and the difference between the selection schemes reflected clearly the changes in allele frequencies of the favourable QTL. The disequilibrium between the polygenes and QTL was always negative and it was larger with larger QTL size. The disequilibrium between the two QTL was larger with QTL of large effect and it was somewhat larger with MAS for scenarios with starting frequencies below 0.5 for QTL of moderate size and below 0.3 for large QTL. In conclusion, several QTL affecting economically important traits of dairy cattle were detected. Further studies are needed to verify these QTL, check their presence in the present breeding population, look for pleiotropy and fine map the most interesting QTL regions. The results of the simulation studies show that using MAS together with embryo transfer to pre-select young bulls within families is a useful approach to increase the genetic merit of the AI-bulls compared to conventional selection.
  • Wang, Cong (Helsingin yliopisto, 2010)
    This thesis studies the intermolecular interactions in (i) boron-nitrogen based systems for hydrogen splitting and storage, (ii) endohedral complexes, A@C60, and (iii) aurophilic dimers. We first present an introduction of intermolecular interactions. The theoretical background is then described. The research results are summarized in the following sections. In the boron-nitrogen systems, the electrostatic interaction is found to be the leading contribution, as 'Coulomb Pays for Heitler and London' (CHL). For the endohedral complex, the intermolecular interaction is formulated by a one-center expansion of the Coulomb operator 1/rab. For the aurophilic attraction between two C2v monomers, a London-type formula was derived by fully accounting for the anisotropy and point-group symmetry of the monomers.
  • Kurtén, Theo (Helsingin yliopisto, 2007)
    Nucleation is the first step of the process by which gas molecules in the atmosphere condense to form liquid or solid particles. Despite the importance of atmospheric new-particle formation for both climate and health-related issues, little information exists on its precise molecular-level mechanisms. In this thesis, potential nucleation mechanisms involving sulfuric acid together with either water and ammonia or reactive biogenic molecules are studied using quantum chemical methods. Quantum chemistry calculations are based on the numerical solution of Schrödinger's equation for a system of atoms and electrons subject to various sets of approximations, the precise details of which give rise to a large number of model chemistries. A comparison of several different model chemistries indicates that the computational method must be chosen with care if accurate results for sulfuric acid - water - ammonia clusters are desired. Specifically, binding energies are incorrectly predicted by some popular density functionals, and vibrational anharmonicity must be accounted for if quantitatively reliable formation free energies are desired. The calculations reported in this thesis show that a combination of different high-level energy corrections and advanced thermochemical analysis can quantitatively replicate experimental results concerning the hydration of sulfuric acid. The role of ammonia in sulfuric acid - water nucleation was revealed by a series of calculations on molecular clusters of increasing size with respect to all three co-ordinates; sulfuric acid, water and ammonia. As indicated by experimental measurements, ammonia significantly assists the growth of clusters in the sulfuric acid - co-ordinate. The calculations presented in this thesis predict that in atmospheric conditions, this effect becomes important as the number of acid molecules increases from two to three. On the other hand, small molecular clusters are unlikely to contain more than one ammonia molecule per sulfuric acid. This implies that the average NH3:H2SO4 mole ratio of small molecular clusters in atmospheric conditions is likely to be between 1:3 and 1:1. Calculations on charged clusters confirm the experimental result that the HSO4- ion is much more strongly hydrated than neutral sulfuric acid. Preliminary calculations on HSO4- NH3 clusters indicate that ammonia is likely to play at most a minor role in ion-induced nucleation in the sulfuric acid - water system. Calculations of thermodynamic and kinetic parameters for the reaction of stabilized Criegee Intermediates with sulfuric acid demonstrate that quantum chemistry is a powerful tool for investigating chemically complicated nucleation mechanisms. The calculations indicate that if the biogenic Criegee Intermediates have sufficiently long lifetimes in atmospheric conditions, the studied reaction may be an important source of nucleation precursors.
  • Calsamiglia, John (Helsingin yliopisto, 2001)
  • Havukainen, Martti (Helsingin yliopisto, 1999)
  • Saxell, Sami (Helsingin yliopisto, 2009)
    Arguments arising from quantum mechanics and gravitation theory as well as from string theory, indicate that the description of space-time as a continuous manifold is not adequate at very short distances. An important candidate for the description of space-time at such scales is provided by noncommutative space-time where the coordinates are promoted to noncommuting operators. Thus, the study of quantum field theory in noncommutative space-time provides an interesting interface where ordinary field theoretic tools can be used to study the properties of quantum spacetime. The three original publications in this thesis encompass various aspects in the still developing area of noncommutative quantum field theory, ranging from fundamental concepts to model building. One of the key features of noncommutative space-time is the apparent loss of Lorentz invariance that has been addressed in different ways in the literature. One recently developed approach is to eliminate the Lorentz violating effects by integrating over the parameter of noncommutativity. Fundamental properties of such theories are investigated in this thesis. Another issue addressed is model building, which is difficult in the noncommutative setting due to severe restrictions on the possible gauge symmetries imposed by the noncommutativity of the space-time. Possible ways to relieve these restrictions are investigated and applied and a noncommutative version of the Minimal Supersymmetric Standard Model is presented. While putting the results obtained in the three original publications into their proper context, the introductory part of this thesis aims to provide an overview of the present situation in the field.
  • Vehmas-Lehto (nykyinen Vehmas-Thesslund), Inkeri (Helsingin yliopisto, 1989)
    This is a study in the field of translation criticism: it assesses the quality of certain translations, finds reasons for their inadequacy, and suggests methods for their improvement. The leading principle is that adequacy, that is to say the compliance of a translation with the norms of the target language, and, to a certain extent, with those of the target culture as well, is an inherent part of translation quality. The study is based on the hypothesis that, in order to be adequate, Finnish translations of Russian journalistic texts should resemble the corresponding Finnish functional style, i.e. Finnish journalistic language. The text corpus used in the study consists of (1) Russian journalistic texts, (2) their published translations (PTrs), (3) alternative translations serving as suggestions for improvement, and (4) authentic Finnish journalistic texts used as material for comparison. The assessment of the quality of the PTrs is based both on the intuition of the researcher and on a series of experiments. According to experiment (1), the PTrs are usually identifiable as translations, primarily because of the general impression they make of clumsiness and obscurity. Experiment (2) shows that the PTrs are experienced as unpleasant, uninteresting, and apt to arouse suspicion. Experiment (3) reveals an abundance of emotive elements in the vocabulary. Experiment (4) corroborates the difficulty of comprehending the PTtrs. The reasons for the inadequacy of the translations are investigated using textual comparisons. These reveal a number of covert errors, i.e. deviations from the usage and recommendable norms of Finnish journalistic language. Covert errors are basically due to interference from the source texts. They are mostly quantitative: e.g. an abundance of coordinated constructions, emotive words, and clichés, a high average length of sentences, clauses, and noun phrases, a high frequency of nouns and adjectives, and a low frequency of connectives. Covert errors are due to translation interference, i.e. the influence of source language features on the translation. Interference reduces the comprehensibility of translations. The gravest covert error in the PTrs is their nominal style. Verbal nouns give rise to a great amount of long, left-branching noun phrases, which overload the short-time memory of the reader. In the source texts, long noun phrases constitute no big problem, because Russian modifiers stand after the noun.
  • Kornak, Jacek (Helsingin yliopisto, 2015)
    The subject of this study is the term: queer which I analyse as a political concept. In many English-speaking countries queer has been a common abusive term for homosexuals and other sexually non-normative individuals. From around the end of the 1980s the term was picked up by many activists and academics as a tool for political engagement. Initially queer was politicized in the context of the AIDS crisis but soon afterwards, the term was used to address political, social and cultural marginalization of sexual minorities. Queer has ever since remained one of the most significant concepts in contemporary sexual minority politics. I examine how queer became a powerful political signifier and I study political messages that the term carried. My study focuses on multiple uses of queer , rising from various forms of direct political activism to numerous academic publications. I argue that the term often functioned as a type of alternative identity, a basis of community, an incitement for political action and even a philosophical category. Rather than trying to establish common elements between the uses of queer , I present the multiplicity of routes by which queer was mobilized politically. The research here described investigates an underexplored topic in the academic literature, as most publications to this day offer analyses of queer theories or activism, while the very concept queer has often been overlooked. By discussing the political uses of the term, my study therefore goes beyond the scope of so-called queer theory. Instead, I analyse these theories from a novel standpoint, reflecting on the conceptual politics that queer performs in various texts. This thesis traces the conceptual change that queer underwent to become an umbrella term for various political claims. At the end of the 1980s, queer was used by ACT UP activists and, subsequently, by other groups and individuals to express disagreement with mainstream U.S. sexual politics. From about 1991 queer enters academia. I study texts by Teresa de Lauretis, Michael Warner, Judith Butler, Eve Kosofsky Sedgwick, Lee Edelman and several others. I offer conceptual analyses of their use of queer as a political concept. I also engage in discussion about the consequences of certain political claims for sexual minorities. My findings indicate that queer was one of the central concepts used in academic debates concerning sexual minorities in the 1990s. For instance, Teresa de Lauretis used the term to criticize the previous lesbian and gay discourse and to incite development of a new language that would accommodate the multiplicity of experiences of lesbian and gay people. Judith Butler used the term to address intersections of sex, class and race. For Eve Kosofsky Sedgwick queer is a specific deconstructive term, whereas for Jack (Judith) Halberstam it is an anarchic term that opens a horizon of an alternative politics. Over the past recent decades there have been countless uses of queer as a political concept. My thesis analyses the most influential ones. I present a variety of political purposes the concept serves and point out the importance of this concept within contemporary sexual minority movement and thought.
  • Sjöblom, Solveig (Helsingin yliopisto, 2009)
    Erwinia carotovora subsp. carotovora (Ecc) is a Gram-negative enterobacterium that causes soft-rot in potato and other crops. The main virulence determinants, the extracellular plant cell wall -degrading enzymes (PCWDEs), lead to plant tissue maceration. In order to establish a successful infection the production of PCWDEs are controlled by a complex regulatory network, including both specific and global activators and repressors. One of the most important virulence regulation systems in Ecc is mediated by quorum sensing (QS), which is a population density -dependent cell-to-cell communication mechanism used by many Gram-negative bacteria. In these bacteria N-acylhomoserine lactones (AHSL), act as diffusible signaling molecules enabling communication between bacterial cells. The AHSLs are structurally diverse and differ in their acyl chain length. This gives the bacteria signaling specificity and enables the recognition and communication within its own species. In order to detect and respond to the AHSLs the bacteria use QS regulators, LuxR-type proteins. The aim of this study was to get a deeper understanding of the Ecc QS system. In the first part of the study we showed that even different strains of Ecc use different dialects and of physiological concentrations, only the cognate AHSL with the correct acyl chain is recognized as a signal that can switch on virulence genes. The molecular basis of the substrate specificity of the AHSL synthase ExpI was investigated in order to recognize the acyl chain length specificity determinants of distinct AHSL synthases. Several critical residues that define the size of the substrate-binding pocket were identified. We demonstrated that in the ExpISCC1 mutations M127T and F69L are sufficient to change the N-3-oxohexanoyl-L-homoserine lactone producing ExpISCC1 to an N-3-oxooctanoyl-L-homoserine lactone (3-oxo-C8-HSL) producing enzyme. In the second study the means of sensing specificity and response to the AHSL signaling molecule were investigated. We demonstrated that the AHSL receptor ExpR1 of Ecc strain SCC3193 has strict specificity for the cognate AHSL 3-oxo-C8-HSL. In addition we identified a second AHSL receptor ExpR2 with a novel property to sense AHSLs with different acyl chain lengths. In the absence of AHSLs ExpR1 and ExpR2 were found to act synergistically to repress the virulence gene expression. This repression was shown to be released by addition of AHSLs and appears to be largely mediated by the global negative regulator RsmA. In the third study random transposon mutagenesis was used to widen the knowledge of the Ecc QS regulon. Two new QS-controlled target genes, encoding a DNA-binding regulator Hor and a plant ferredoxin-like protein FerE, were identified. The QS control of the identified genes was executed by the QS regulators ExpR1 and ExpR2 and as expression of PCWDE genes mediated by the RsmA repressor. Hor was shown to contribute to bacterial virulence at least partly through its control of PCWDE production, while FerE was shown to contribute to oxidative stress tolerance and in planta fitness of the bacteria. In addition our results suggest that QS is central to the control of oxidative stress tolerance in Ecc. In conclusion, these results indicate that Ecc strain SCC3193 is able to react and respond both to the cognate AHSL signal and the signals produced by other bacterial species, in order to control a wide variety of functions in the plant pathogen Ecc.
  • Hattula, Katarina (Helsingin yliopisto, 2007)
    Rab8 and its interacting proteins as regulators of cell polarization During the development of a multi-cellular organism, progenitor cells have to divide and migrate appropriately as well as organize their differentiation with one another, in order to produce a viable embryo. To divide, differentiate and migrate cells have to undergo polarization, a process where internal and external components such as actin, microtubules and adhesion receptors are reorganized to produce a cell that is asymmetric, with functionally different surfaces. Also in the adult organism there is a continuous need for these processes, as cells need to migrate in response to tissue damage and to fight infection. Improper regulation of cell proliferation and migration can conversely lead to disease such as cancer. GTP-binding proteins function as molecular switches by cycling between a GTP-bound (active) conformation and a GDP-bound (inactive) conformation. The Ras super-family of small GTPases are found in all eukaryotic cells. They can be functionally divided into five subfamilies. The Ras family members mainly regulate gene expression, controlling cell proliferation and differentiation. Ras was in fact the first human oncogene to be characterized, and as much as 30% of all human tumors may be directly or indirectly caused by mutations of Ras molecules The Rho family members mainly regulate cytoskeletal reorganization. Arf proteins are known to regulate vesicle budding and Rab proteins regulate vesicular transport. Ran regulates nuclear transport as well as microtubule organization during mitosis. The focus of the thesis of Katarina Hattula, is on Rab8, a small GTPase of the Rab family. Activated Rab8 has previously been shown to induce the formation of new surface extensions, reorganizing both actin and microtubules, and to have a role in directed membrane transport to cell surfaces. However, the exact membrane route it regulates has remained elusive. In the thesis three novel interactors of Rab8 are presented. Rabin8 is a Rab8-specific GEF that localizes to vesicles where it presumably recruits and activates its target Rab8. Its expression in cells leads to remodelling of actin and the formation of polarized cell surface domains. Optineurin, known to be associated with a leading cause of blindness in humans (open-angle glaucoma), is shown to interact specifically with GTP-bound Rab8. Rab8 binds to an amino-terminal region and interestingly, the Huntingtin protein binds a carboxy-terminal region of optineurin. (Aberrant Huntingtin protein is known to be the cause Huntington s disease in humans.) Co-expression of Huntingtin and optineurin enhanced the recruitment of Huntingtin to Rab8-positive vesicular structures. Furthermore, optineurin promoted cell polarization in a similar way to Rab8. A third novel interactor of Rab8 presented in this thesis is JFC1, a member of the synaptogamin-like protein (Slp) family. JFC1 interacts with Rab8 specifically in its GTP-bound form, co-localizes with endogenous Rab8 on tubular and vesicular structures, and is probably involved in controlling Rab8 membrane dynamics. Rab8 is in this thesis work clearly shown to have a strong effect on cell shape. Blocking Rab8 activity by expression of Rab8 RNAi, or by expressing the dominant negative Rab8 (T22N) mutant leads to loss of cell polarity. Conversely, cells expressing the constitutively active Rab8 (Q67L) mutant exhibit a strongly polarized phenotype. Experiments in live cells show that Rab8 is associated with macropinosomes generated at ruffling areas of the membrane. These macropinosomes fuse with or transform into tubules that move toward the cell centre, from where they are recycled back to the leading edge to participate in protrusion formation. The biogenesis of these tubules is shown to be dependent on both actin and microtubule dynamics. The Rab8-specific membrane route studied contained several markers known to be internalized and recycled (1 integrin, transferrin, transferrin receptor, cholera toxin B subunit (CTxB), and major histocompatibility complex class I protein (MHCI)). Co-expression studies revealed that Rab8 localization overlaps with that of Rab11 and Arf6. Rab8 is furthermore clearly functionally linked to Arf6. The data presented in this thesis strongly suggests a role for Rab8 as a regulator for a recycling compartment, which is involved in providing structural and regulatory components to the leading edge to participate in protrusion formation.
  • Furuhjelm, Johanna (Helsingin yliopisto, 2004)
  • Holmström, Eero (Helsingin yliopisto, 2012)
    Understanding radiation effects in silicon (Si) is of great technological importance. The material, being the basis of modern semiconductor electronics and photonics, is subjected to radiation already at the processing stage, and in many applications throughout the lifetime of the manufactured component. Despite decades of research, many fundamental questions on the subject are still not satisfactorily answered, and new ones arise constantly as device fabrication shifts towards the nanoscale. In this study, methods of computational physics are harnessed to tackle basic questions on the radiation response of bulk and nanostructured Si systems, as well as to explain atomic-scale phenomena underlying existing experimental results. Empirical potentials and quantum mechanical models are coupled with molecular dynamics simulations to model the response of Si to irradiation and to characterize the created crystal damage. The threshold displacement energy, i.e., the smallest recoil energy required to create a lattice defect, is determined in Si bulk and nanowires, in the latter system also as a function of mechanical strain. It is found that commonly used values for this quantity are drastically underestimated. Strain on the nanowire causes the threshold energy to drop, with an effect on defect production that is significantly higher than in an another nanostructure with similar dimensions, the carbon nanotube. Simulating ion irradiation of Si nanowires reveals that the large surface area to volume ratio of the nanostructure causes up to a three-fold enhancement in defect production as compared to bulk Si. Amorphous defect clusters created by energetic neutron bombardment are predicted, on the basis of their electronic structure and abundance, to cause a deleterious phenomenon called type inversion in Si strip detectors in high-energy physics experiments. The thinning of Si lamellae using a focused ion beam is studied in conjunction with experiment to unravel the cause for the failure of the thinning method for very thin samples. Simulations predict a mechanism of erosion of the structure which is observed as catastrophic shrinkage of the sample in experiment. The results of the thesis contribute to the understanding of fundamental questions of radiation effects in Si as well as provide explanations to known experimental conundrums. At the same time, the results unambiguously indicate that further experimental testing is needed in order to ultimately evaluate the accuracy of the theoretical predictions.
  • Järvi, Tommi (Helsingin yliopisto, 2009)
    Nanotechnology applications are entering the market in increasing numbers, nanoparticles being among the main classes of materials used. Particles can be used, e.g., for catalysing chemical reactions, such as is done in car exhaust catalysts today. They can also modify the optical and electronic properties of materials or be used as building blocks for thin film coatings on a variety of surfaces. To develop materials for specific applications, an intricate control of the particle properties, structure, size and shape is required. All these depend on a multitude of factors from methods of synthesis and deposition to post-processing. This thesis addresses the control of nanoparticle structure by low-energy cluster beam deposition and post-synthesis ion irradiation. Cluster deposition in high vacuum offers a method for obtaining precisely controlled cluster-assembled materials with minimal contamination. Due to the clusters small size, however, the cluster-surface interaction may drastically change the cluster properties on deposition. In this thesis, the deposition process of metal and alloy clusters on metallic surfaces is modelled using molecular dynamics simulations, and the mechanisms influencing cluster structure are identified. Two mechanisms, mechanical melting upon deposition and thermally activated dislocation motion, are shown to determine whether a deposited cluster will align epitaxially with its support. The semiconductor industry has used ion irradiation as a tool to modify material properties for decades. Irradiation can be used for doping, patterning surfaces, and inducing chemical ordering in alloys, just to give a few examples. The irradiation response of nanoparticles has, however, remained an almost uncharted territory. Although irradiation effects in nanoparticles embedded inside solid matrices have been studied, almost no work has been done on supported particles. In this thesis, the response of supported nanoparticles is studied systematically for heavy and light ion irradiation. The processes leading to damage production are identified and models are developed for both types of irradiation. In recent experiments, helium irradiation has been shown to induce a phase transformation from multiply twinned to single-crystalline nanoparticles in bimetallic alloys, but the nature of the transition has remained unknown. The alloys for which the effect has been observed are CuAu and FePt. It is shown in this thesis that transient amorphization leads to the observed transition and that while CuAu and FePt do not amorphize upon irradiation in bulk or as thin films, they readily do so as nanoparticles. This is the first time such an effect is demonstrated with supported particles, not embedded in a matrix where mixing is always an issue. An understanding of the above physical processes is essential, if nanoparticles are to be used in applications in an optimal way. This thesis clarifies the mechanisms which control particle morphology, and paves way for the synthesis of nanostructured materials tailored for specific applications.
  • Jansson, Ville (Helsingin yliopisto, 2013)
    Neutron irradiation induces structural nano-scale changes in steels that in the long term cause degradation of the mechanical properties of the materials. These processes are important to understand to e.g. ensure the integrity of the steel wall of the reactor pressure vessel during the operational life-time of a nuclear power plant. In this thesis, some of the irradiation defects have been studied by using as a model alloy the iron-carbon (Fe-C) system, as iron and carbon are the basic elements in any steel. The interactions between C and vacancy (V) clusters and between C and self-interstitial atom (SIA) clusters have been studied using Molecular Dynamics simulation techniques. This way C-V clusters, such as C2V and CV2, able to trap large SIA clusters, have been identified and characterized. Using Object Kinetic Monte Carlo (OKMC), an model for the radiation-induced nanostructure evolution in Fe-C has been constructed. The model was validated by reproducing experimental data in terms of V and SIA cluster densities and mean sizes from irradiation experiments at low (340 K) and high operational temperature of light water reactors (560 K), as well as reproducing data from post-irradiation annealing up to 780 K. The new model has allowed a deeper understanding of the effect of carbon on the irradiation defect evolution. It was found that the effect of the immobile C-V complexes can be introduced using generic traps for SIA and vacancy clusters. These generic traps have a binding energy that depends on the size of the trapped cluster, which is supported by previously performed atomistic studies. Different trap regimes need to be used at low and high temperatures to account for the different populations of 1/2 <111> and <100> SIA loops at different temperatures, as observed in previous TEM studies. The traps are found to have an important function as nucleation points that promote the growth of larger clusters. The nanostructure evolution model, which is the main result of this thesis, is fully based on physical considerations and only uses a few parameters for calibration. The model is found to be capable of reproducing the experimental trends both at 340 K, 560 K and for annealing up to 700 K; thereby providing insight into the physical mechanisms of importance to determine the type of nanostructural evolution undergone by Fe alloys during irradiation.