Remarks on the anisotropic Calder\'{o}n problem

We show uniqueness results for the anisotropic Calder\'{o}n problem stated on transversally anisotropic manifolds. Moreover, we give a convexity result for the range of Dirichlet-to-Neumann maps on general Riemannian manifolds near the zero potential. Finally, we present results for Calder\'{o}n type inverse problems associated to semilinear elliptic equations on general Riemannian manifolds

Magnetic nanocomposites at microwave frequencies

Most conventional magnetic materials used in the electronic devices are ferrites, which are composed of micrometer-size grains. But ferrites have small saturation magnetization, therefore the performance at GHz frequencies is rather poor. That is why functionalized nanocomposites comprising magnetic nanoparticles (e.g. Fe, Co) with dimensions ranging from a few nm to 100 nm, and embedded in dielectric matrices (e.g. silicon oxide, aluminium oxide) have a significant potential for the electronics industry. When the size of the nanoparticles is smaller than the critical size for multidomain formation, these nanocomposites can be regarded as an ensemble of particles in single-domain states and the losses (due for example to eddy currents) are expected to be relatively small. Here we review the theory of magnetism in such materials, and we present a novel measurement method used for the characterization of the electromagnetic properties of composites with nanomagnetic insertions. We also present a few experimental results obtained on composites consisting of iron nanoparticles in a dielectric matrix.Comment: 20 pages, 10 figures, 5 table

Sähköautojen akkujen kiertotalouden liiketoimintamallit

Tiivistelmä. Liikenteen sähköistyessä, sähköautoissa käytettävien litiumioniakkujen määrä on lisääntynyt. Litiumioniakkuihin liittyy kuitenkin haasteita, kuten ympäristövaikutukset ja epävarmuustekijät raaka-aineisiin liittyen. Näiden haasteiden lisäksi tulevaisuudessa huomattava määrä litiumioniakkuja poistuu sähköautokäytöstä. Kiertotalous pyrkii vastaamaan näihin litiumioniakkujen haasteisiin hyödyntämällä akkuja uudelleen alkuperäisen käyttötarkoituksen jälkeen. Työn tavoitteena on kirjallisuuskatsauksen avulla selvittää, mitkä ovat kiertotalouden vaihtoehdot käytetyille litiumioniakuille ja etenkin, miten näiden avulla voidaan tehdä liiketoimintaa. Lisäksi työssä muodostetaan kuvaus litiumioniakkujen kiertotalouden nykytilanteesta Suomessa. Tutkimuksessa selvisi, että liiketoimintamallit litiumioniakkujen kiertotaloudelle ovat: akkujen uudelleenkäyttö sähköautoissa kunnostamisen tai uudelleenvalmistamisen kautta, akkujen uudelleenkäyttö muissa sovelluksissa kunnostamisen tai muuntamisen kautta, ja materiaalien talteenotto kierrättämisen kautta. Lisäksi työssä tunnistettiin kahdeksan suomalaista yritystä ja organisaatiota, joiden toiminnassa korostuu litiumioniakkujen kiertotalous. Työ tarjoaa kattavan kuvauksen litiumioniakkujen kiertotalouden nykytilanteesta sekä yleisellä tasolla että Suomessa liiketoiminnan näkökulmaa painottaen.Circular business models for electric vehicle batteries. Abstract. As traffic has electrified, the number of lithium-ion batteries used in electric cars has increased. However, lithium-ion batteries are subject to challenges such as environmental concerns and uncertainties regarding raw materials. In addition to these challenges, a significant number of lithium-ion batteries of electric vehicles will reach the end of first life in the future. The circular economy seeks to address these challenges of lithium-ion batteries by reusing the batteries after initial use. The aim of the work is through a literature review to find out from the business perspective what are the circular options for used lithium-ion batteries. In addition, the work provides a description of the current situation of the circular economy of lithium-ion batteries in Finland. The study found out that business models for the circular economy of lithium-ion batteries are reuse in electric cars through refurbishing or remanufacturing, reuse in other applications through refurbishing or upgrading, and recovery of materials through recycling. In addition, eight Finnish companies and organizations were identified in the work, whose activities are closely related to the circular economy of lithium-ion batteries. The work provides a comprehensive description of the current situation of the circular economy of lithium-ion batteries both at a general level and in Finland, with an emphasis on the business perspective

Sound mining in the North : a guide to environmental regulation and best practices supporting social sustainability

Julkaistu versi

Ferromagnetic resonance in ϵ\epsilon-Co magnetic composites

We investigate the electromagnetic properties of assemblies of nanoscale $\epsilon$-cobalt crystals with size range between 5 nm to 35 nm, embedded in a polystyrene (PS) matrix, at microwave (1-12 GHz) frequencies. We investigate the samples by transmission electron microscopy (TEM) imaging, demonstrating that the particles aggregate and form chains and clusters. By using a broadband coaxial-line method, we extract the magnetic permeability in the frequency range from 1 to 12 GHz, and we study the shift of the ferromagnetic resonance with respect to an externally applied magnetic field. We find that the zero-magnetic field ferromagnetic resonant peak shifts towards higher frequencies at finite magnetic fields, and the magnitude of complex permeability is reduced. At fields larger than 2.5 kOe the resonant frequency changes linearly with the applied magnetic field, demonstrating the transition to a state in which the nanoparticles become dynamically decoupled. In this regime, the particles inside clusters can be treated as non-interacting, and the peak position can be predicted from Kittel's ferromagnetic resonance theory for non-interacting uniaxial spherical particles combined with the Landau-Lifshitz-Gilbert (LLG) equation. In contrast, at low magnetic fields this magnetic order breaks down and the resonant frequency in zero magnetic field reaches a saturation value reflecting the interparticle interactions as resulting from aggregation. Our results show that the electromagnetic properties of these composite materials can be tuned by external magnetic fields and by changes in the aggregation structure.Comment: 14 pages, 13 figure

Health-Related Quality of Life after Restorative Proctocolectomy : A Cross-Sectional Study

Background and Aims: Patients undergoing restorative proctocolectomy have often suffered from active ulcerative colitis which should be remembered when assessing quality of life after operation. The aim of this study was to explore health-related quality of life after restorative proctocolectomy in those with poor or good pouch function and to compare that to patients with active or inactive ulcerative colitis and to the general population. Material and Methods: Altogether, 282 restorative proctocolectomy patients were investigated. The control group comprised 408 ulcerative colitis patients from the local register. Generic 15D and disease-specific inflammatory bowel disease questionnaire health-related quality of life instruments were used. Population-based data were available for 15D. Pouch function was evaluated with oresland score and colitis activity with simple clinical colitis activity index. Results: 15D results showed that patients with good pouch function had health-related quality of life similar to that of the general population. Health-related quality of life with inflammatory bowel disease questionnaire was equally good in patients with good pouch function (n = 131; 70%) and inactive colitis (n = 95; 63%), and equally impaired in patients with poor pouch function (n = 56; 30%) and active colitis (n = 18; 12%). Conclusion: The majority of patients had health-related quality of life comparable to that in general population. Most patients with active ulcerative colitis are likely to improve their health-related quality of life after successful surgery. These findings are important when informing colitis patients about life after surgery.Peer reviewe

Impacts of winter feeding of reindeer on vegetation and soil in the sub-Arctic: insights from a feeding experiment

The overall impacts of winter feeding, including the effects of both forage and reindeer (Rangifer tarandus), were studied in an experiment in the Hammastunturi herding cooperative (68°N), Finland, with 300 reindeer in a sub-xeric heath forest (35 ha) during March/April 2009 and 2010. The feeding practices on the 50 plots were: (1) feeding with grass silage+hay with leftovers cleared in the spring; (2) feeding with grass silage+hay with leftovers not cleared; and (3) feeding with pellets. In addition, (4) unfenced and (5) fenced control plots were included, on which the reindeer were not fed. No invasive plant species introduced through grass silage+hay were observed on the plots. The coverage of Deschampsia flexuosa increased on grass silage+hay plots after the first winter, and both coverage and height of the grass increased after the second winter. The coverage of Dicranum sp. and Pleurozium schreberi was lower on plots where reindeer were fed with grass silage (leftover silage not cleared) vs. controls. Some dwarf shrubs, e.g., Calluna vulgaris, showed a similar response after the second winter. The N content of Empetrum nigrum was higher on grass silage plots (leftover silage not cleared) after the first winter vs. controls. After two winters, the N content of both E. nigrum and Vaccinium myrtillus was increased. Of the soil variables studied, C/N decreased on grass silage+hay plots vs. fenced controls. We conclude that even a moderate level of feeding may cause changes that can lead to a gradual shift from nutrient-poor heath forest towards a more nutrient-rich type

Longitudinal perspective on cryptocurrency trading and increased gambling problems : a 3 wave national survey study

Objectives: Cryptocurrency trading has gained popularity over the last few years. Trading is facilitated by online platforms that enable 24/7 trading. Cryptocurrency trading is potentially attractive to gamblers, and it may increase their gambling problems. Furthermore, cryptocurrency trading might be a particularly harmful activity for those gambling offshore. We investigated whether cryptocurrency trading predicts excessive gambling over time. We also analyzed how cryptocurrency trading combined with offshore gambling is associated with excessive gambling. Study design: This was a population-based longitudinal survey study. Methods: We surveyed a sample of Finnish people aged 18–75 years (N = 1022, 51.27% male) at three time points in 6-month intervals: April 2021 (T1), October to November 2021 (T2), and April to May 2022 (T3). Of the original T1 respondents, 66.80% took part in T2 and T3. Outcome measure was excessive gambling using the Problem Gambling Severity Index, and the predictor was cryptocurrency trading. We adjusted models for onshore and offshore gambling online, excessive gaming (Internet Gaming Disorder Test), excessive internet use (Compulsive Internet Use Scale), excessive alcohol use (Alcohol Use Disorders Identification Test), and sociodemographic background factors. We used multilevel regression models to investigate within-person and between-person effects. Results: Cryptocurrency trading has increased in popularity over time. Within-person changes in cryptocurrency trading predicted increased excessive gambling. Excessive gambling was also generally more common among cryptocurrency traders. The full model that was adjusted for the number of confounding factors showed that cryptocurrency trading had a within-person effect on excessive gambling. Of the confounding factors, offshore online gambling, excessive gaming, and excessive internet use had within-person effects on excessive gambling. Offshore and onshore online gamblers and excessive gamers showed more excessive gambling than others. Those participants who were both cryptocurrency traders and offshore gamblers showed significantly higher rate of excessive gambling than others. Conclusions: Cryptocurrency trading is a risky activity and associated with a higher rate of excessive gambling over time. Such activity is especially risky among offshore online gamblers, who could view cryptocurrency trading as another form of gambling or as a way to make money for gambling. Policymakers and counselors should be aware of the risks of cryptocurrency trading.publishedVersionPeer reviewe