This thesis investigates the behavior of platinum-group elements (PGE) and the mineralogical evolution of platinum-group minerals (PGM) from hypogene to supergene environments, with particular emphasis on whether PGM can form in-situ during lateritization. The origin of PGM in supergene environments remains debated, with contrasting models involving i) the inheritance and mechanical liberation of hypogene PGM during weathering, versus ii) their in-situ formation following PGE mobilization and reprecipitation. At the Falcondo Ni-laterite deposit (Dominican Republic), Pt-Ir-Fe-Ni grains found in a highly weathered chromitite hosted in limonite and characterized by a positive Pt anomaly in chondrite-normalized PGE patterns have previously been interpreted as possible products of neoformation in the lateritic soil. These grains show complex porous textures and occur as accumulations of Pt-Ir-Fe-Ni nanoparticles within Fe-oxyhydroxides. Their occurrence in the upper part of the lateritic profile and their textural relationships with Fe-oxyhydroxides have been used to support PGE mobilization and in-situ PGM growth during lateritization. However, alternative interpretations involving alteration of pre-existing PGM, dissolution, short-distance remobilization, and reprecipitation have also been proposed. Hence, the origin of the Pt-Ir-Fe-Ni alloys remains unresolved.

To investigate this problem, three case studies representing different stages in the evolution of PGM from hypogene to supergene environments were examined: the PGE-rich chromitites of the Herbeira Massif in the Cabo Ortegal Complex (Spain), the Santa Cruz Ni-laterite deposit in Acoje (Philippines), and the Falcondo Ni-laterite deposit. The Herbeira chromitites provide a hypogene reference for the study of primary magmatic PGE concentration in ultramafic rocks and subsequent PGM modification by hydrothermal-related processes, whereas investigation of the Ni-laterites from Santa Cruz and Falcondo allows the study of the behavior of PGE and PGM during intense tropical weathering of ultramafic rocks.

At Herbeira, the PGE-rich chromitites are characterized by enrichment in Pd-group PGE (PPGE: Rh, Pt, and Pd) relative to Ir-group PGE (IPGE: Os, Ir, and Ru) and abundant PGM dominated by Rh-Ir-Pt-bearing arsenides and sulfarsenides, Pt-Ir-Pd-base-metal-bearing alloys, and Pt-Pd-bearing sulfides, commonly associated with base-metal sulfides. Their formation is related to magmatic processes, whereas subsequent post-magmatic processes related to the circulation of hydrated fluids during amphibolite-facies metamorphism that affected these rocks, promoted local PGE mobilization and the alteration of primary PGM into secondary PGM phases. This modification produced porous Pt-bearing alloys and complex PGM textures composed of PGE- and base-metal-bearing nanoparticles, interpreted to result from the mobilization, precipitation, and reorganization of PGE during interaction with hydrothermal fluids. These observations show that porous and complex PGM textures can also develop through hypogene processes. 

In the Santa Cruz Ni-laterite, the PGE and PGM assemblages found in chromitites record the progressive effects of magmatic, serpentinization-related, and lateritic processes. The primary PGM assemblage reflects a magmatic history broadly comparable to that recorded by the Herbeira chromitites. However, during lateritization, resistant PGM phases were preserved and residually concentrated at the upper part of the lateritic profile. This is accompanied by redistribution of PGE within the lateritic profile, including a positive Pt anomaly in chondrite-normalized PGE patterns observed in a limonite-hosted chromitite, interpreted mainly as the result of residual Pt enrichment rather than direct evidence of supergene PGM neoformation. However, the occurrence of a porous Ir-Fe-Ni-Pt grain enclosed in Fe-oxyhydroxides and characterized by the accumulations of PGE-bearing nanoparticles, show textural similarities to the Pt-Ir-Fe-Ni grains from Falcondo, suggesting that comparable processes, including neoformation (?), may have been involved in the genesis of these grains.

High-resolution observations of the Pt-Ir-Fe-Ni alloys from Falcondo reveal porous textures characterized by aligned nanostructures within a goethite/hematite matrix. These nanostructures occur in bundles with different orientations and form previously undescribed stitching textures, defining parallel and triangular patterns. The alloys exhibit a preferential stoichiometry of (Pt, Ir)_0.26Ni_0.29Fe_0.45 and are absent in pristine chromitites. The grains also contain elongated voids and Pt- and Ir-rich patches. Nanoscale observations show that the grains are compositionally heterogeneous polycrystalline aggregates composed of distinct Fe-Ni-rich, Ir-rich, and Pt-Ir-rich alloy domains, with d-spacings similar to cubic phases. Pt nanoparticles occur within goethite and hematite filling pores, suggesting late-stage Pt mobilization and precipitation in the lateritic environment. To evaluate the different possibilities for their genetic history, these observations were compared with PGM described in the literature from magmatic, hydrothermal-related, and supergene environments. Moreover, the unusual textures of the Pt-Ir-Fe-Ni alloys show textural similarities with Widmannstätten patterns found in Fe-Ni meteorites, without implying any genetic relationship. High-resolution textural and compositional observations of the Pt-Ir-Fe-Ni grains do not provide a definitive conclusion on their genesis but show that they cannot be readily explained by a single genetic process and instead suggest a complex, potentially multistage history involving hypogene precursors and subsequent supergene modification leading to PGM (trans-)formation. High-resolution isotopic and trace-element analyses may provide further constraints on the origin of the Pt-Ir-Fe-Ni alloys and help identify possible biogeochemical fingerprints associated with their formation.

Background: Neck pain is one of the most common musculoskeletal disorders worldwide and is frequently associated with impairments in sensorimotor control. Identifying such impairments may be important for guiding targeted rehabilitation and evaluating treatment outcomes. However, objective assessment of cervical sensorimotor functions often requires specialized equipment, highlighting the need for accessible, valid, and reliable assessment methods. Recent advances in virtual reality (VR) provide new opportunities for both assessment and rehabilitation of cervical sensorimotor functions, potentially in remote or home-based settings.

Aim: To evaluate the measurement properties of newly developed VR-based assessments of cervical sensorimotor functions in individuals with and without neck pain, and to investigate the feasibility of a home-based VR sensorimotor intervention for individuals with chronic neck pain.

Methods: This thesis comprises five quantitative studies: four cross-sectional studies of measurement properties and a feasibility randomized controlled trial. Studies I and II evaluated the concurrent validity of VR-based assessments of joint position sense (JPS), cervical reaction acuity (CRA), range of motion (ROM), and fast cervical rotation in 20 participants with and without neck pain. Agreement between the VR-based measures and a reference measurement system was evaluated using Bland–Altman analysis and intraclass correlation coefficients (ICCs). Study III investigated the test–retest reliability and discriminant validity of the CRA test in individuals with chronic traumatic neck pain (CTNP; n = 42) and asymptomatic controls (CON; n = 38). Reliability was assessed using ICCs and the standard error of measurement (SEM), while group differences were examined using analysis of covariance. Study IV used orthogonal projections to latent structures (OPLS) to evaluate the ability of a VR-based test battery comprising assessments of movement sense, JPS, CRA, ROM, and postural sway, to discriminate between participants with CTNP (n = 55) and CON (n = 48). In Studies III and IV, construct validity was assessed by examining associations between VR-based test outcomes and patient-reported outcome measures using correlation analyses and OPLS regression models. Study V evaluated the feasibility of home-based VR sensorimotor training compared with conventional neuromuscular endurance training in individuals with chronic neck pain, and explored physiotherapists’ experiences of delivering the interventions.

Results: The VR-based tests demonstrated acceptable concurrent validity, with generally small measurement biases and moderate to excellent agreement with the reference system for cervical ROM, movement velocity, and the CRA test. Agreement was poorer for JPS and at very high movement velocities. The CRA test demonstrated acceptable test–retest reliability and discriminant validity, except for the variable reaction time which showed weaker measurement properties. From the CRA outcome measures, peak velocity had the strongest ability to discriminate between groups. The multivariate test battery differentiated participants with CTNP from asymptomatic controls and explained approximately 34% of the variation in group membership. Compared with controls, participants with CTNP demonstrated impaired movement sense, reduced movement smoothness and velocity, longer task-completion times, reduced ROM, and greater postural sway. Associations between VR outcomes and patient-reported outcomes were generally low. In Study V, prolonged recruitment was identified. The intervention completion rate was 92% in the VR group and met the predefined feasibility criterion. Adherence and outcome-measure completion rates were high in both groups. Dizziness was reported more frequently in the VR group, whereas neck pain was reported more frequently in the NET group; symptoms of simulator sickness were generally mild. Physiotherapists viewed the delivery of the intervention positively but identified the need for technical support, cost, and required technical skills as potential barriers.

Conclusions: VR-based assessment shows promise as an objective and accessible approach to identifying impairments in cervical sensorimotor function. A future full-scale RCT appears feasible in most respects, provided that challenges related to recruitment and technical support are addressed. Further research should explore patients’ experiences and identify barriers and facilitators to clinical implementation.

Railway infrastructure is a critical component of sustainable transportation systems. However, the linear and rigid nature of railway networks makes them highly vulnerable to climate hazards. Moreover, the growing frequency and intensity of climate hazards driven by climate change increase the risks of climate-related failure modes (CRFMs). Despite this growing concern, understanding of CRFMs, their associated risks, and effective adaptation strategies remains limited. This thesis aims to bridge these gaps by conducting extensive analyses of Swedish railway maintenance dataset, supported by a comprehensive literature review. 

To achieve the thesis objectives, a systematic literature review was first conducted to identify climate hazards and associated CRFMs, irrespective of their intensity, likelihood, or geographical variation. The review provides a comprehensive inventory of climate hazards and CRFMs, offers a structured classification framework, and highlights hazard–failure relationships as well as cascading and compound effects of failures. Furthermore, the proposed adaptation measures were reviewed and categorized into physical, operational, ecological, institutional, and behavioural strategies. Key implementation challenges and potential risks of maladaptation were also discussed. In this context, quantitative risk assessment and the use of predictive models were identified as key institutional and operational strategies, respectively, for effective climate adaptation planning.

Building on these insights, the empirical core of this thesis focuses on assessing the risk of CRFMs and developing predictive tools for the Swedish railway infrastructure. To this end, CRFMs were identified through text mining of historical corrective maintenance data covering all five maintenance regions in Sweden. A probabilistic model was developed to quantify the risk of identified CRFMs, considering both maintenance-related and operational consequences. Risk distributions were subsequently estimated using Monte Carlo simulation. The results enable the prioritization of CRFMs at the national scale and a comparative assessment of regional vulnerability across Sweden. 

Finally, a machine learning framework was developed to distinguish between climate-related and non-climatic failure modes by integrating the failure records with meteorological data. The performance of several machine learning algorithms was evaluated across different time horizons prior to failure events. In addition, the analysis identified key climatic variables that significantly influence model performance and failure classification.

Overall, this thesis provides a fundamental basis and practical evidence to support planning for climate-resilient railway infrastructure. Although the empirical analyses focus on the Swedish railway network, the proposed approaches are transferable and can be applied to other railway systems.