Umeå University

This paper incorporates corruption in the tax administration in a Mirrleesian model of optimal income taxation. In a multi-type setting with a discrete ability distribution, we show that the marginal tax structure can be designed to fully offset the incentives to evade taxes. The optimal marginal tax rates reflect two key determinants: the welfare weight the government attaches to each ability type, and how the private cost of tax evasion varies across the income distribution. We also extend the analysis by examining how public expenditures on tax enforcement can serve as a complementary instrument.

The Encephaliozoon cuniculi is an obligate intracellular microsporidian parasite with a highly reduced genome, yet it contains several key components of an actin cytoskeleton. In this study, we characterise the α-actinin-like protein from the parasite to gain insight into its role in actin organisation. The protein contains three domains typical of α-actinins: an N-terminal actin-binding domain and a C-terminal calmodulin-like domain, separated by a rod domain. Gel filtration analysis demonstrated that the recombinant protein formed stable dimers, consistent with the canonical antiparallel α-actinin structure. Actin co-sedimentation assays and electron microscopy confirmed that the α-actinin-like protein binds and cross-links actin filaments into tight bundles, whereas the isolated actin-binding domain binds but does not cross-link filaments. AlphaFold modelling predicted an overall structural arrangement compatible with an antiparallel dimer. Our results identify the E. cuniculi α-actinin-like protein as a true α-actinin homologue. The presence of actin-binding proteins in E. cuniculi as well as in other microsporidia with very small genomes implies that an actin-based cytoskeleton is important for their survival.

This work evaluated the protein quality of shiitake mushroom cultivated on low-nitrogen wood substrates that has previously been shown to enhance biorefinery processes through biological pretreatment. The effects of different initial mushroom substrates (IMSs) on amino acid (AA) content in shiitake fruit bodies (FBs) and spent mushroom substrates (SMSs) were studied using alder, birch and aspen wood substrates with varying nitrogen levels by adding whey (0-2%). Twenty-two AAs, including nine essential AAs (EAAs), were detected and analyzed. Total AA (TAA) content reached up to 13% in FBs and 5% in SMSs. The FBs showed good protein quality according to FAO/WHO guidelines, despite a low nitrogen content (∼ 0.6%) in IMS. Whey addition increased TAA and EAA levels in FBs while substrate species had distinct effects. Birch generally enhanced AA levels, alder reduced them, and aspen showed AA-specific but mostly positive responses. In SMS, whey addition also increased TAA, but the effects of wood species on TAA generally showed patterns opposite to that observed in FBs. Using 13 IMS chemical constituents as predictive variables in partial least squares regression, five models for AAs in FBs and 15 for SMS were achieved. The C/N ratio and soluble NO 2 were major predictors, whereas Klason lignin had the least influence. The results suggested that shiitake SMS is a valuable resource for potential protein extraction and biofuel production. • Shiitake has a robust amino acid (AA) profile on different low nitrogen substrates • Spent mushroom substrate (SMS) is a good feedstock to coproduce protein and biofuel • AA content in fruit bodies (FB) and SMS were modeled using 13 substrate variables • 15 AAs in SMS and 5 in FBs were predictable and dependent on substrate components • C/N and soluble NO 2 influenced AAs in FB and SMS the most, Klason lignin the least

Developing effective fractionation methods remains challenging in biorefining. γ-Valerolactone (GVL) is a promising green solvent, yet its application in softwood biorefineries is still underexplored. In this study, GVL pretreatment for softwood biorefining was assessed at laboratory and pilot scales. The effects of temperature (170–210 °C), time (20–60 min), and GVL-to-water ratios (20:80 – 80:20 %) on the biorefining of spruce sawdust were initially investigated through lab-scale experiments using a 1-L reactor. A GVL/water solution at a 40:60 ratio, assisted by 0.4 g of sulfuric acid per 100 g of biomass, enabled the solubilization of up to 81.4 % of lignin and nearly the entire hemicellulosic fraction, while effectively preserving cellulose, which was subsequently saccharified with over 90 % conversion. Lignin was regenerated from the liquors and characterized using pyrolysis-gas chromatography/mass spectrometry, high-performance size-exclusion chromatography, Fourier-transform infrared spectroscopy, and 1 H- 13 C heteronuclear single-quantum coherence nuclear magnetic resonance spectroscopy. The biorefinery concept was successfully scaled up and validated at pilot scale in a 50-L reactor, where enzymatic saccharification of the resulting cellulosic pulp produced hydrolysates that, upon fermentation, yielded 231.4 g of ethanol per kilogram of pulp. Lignin regenerated from the pilot-scale pretreatment liquors (118.9 g per kilogram of raw sawdust) and the lignin-rich saccharification residue (182.7 g/kg) were subjected to hydrothermal liquefaction, and the resulting biocrudes were characterized to assess their potential for biofuel formulation. The study showed the suitability of GVL for spruce biorefining to achieve high recovery of digestible cellulose, lignin and hemicelluloses fractions, that are subsequently valuable for chemicals and fuels production. • γ-Valerolactone (GVL) enabled efficient organosolv pretreatment of spruce sawdust. • High solubilization of lignin and hemicelluloses were achieved. • Enzymatic saccharification of pulps achieved conversions above 90 % at lab scale. • The biorefinery concept was scaled up and validated in a 50-L pilot reactor. • Lignin streams from pilot tests were converted to biocrudes via HTL.

Mutant phenotypes often vary across genetically distinct individuals. To identify the causes of such genetic background effects, we studied differences in gene essentiality across 18 genetically diverse natural yeast strains. We identified 39 genes that were essential in the laboratory reference strain but not in at least one other genetic background, and we mapped and validated the genetic variants that were responsible for the differences in gene essentiality. These variants typically occurred in single modifier genes that tended to differ between genetic backgrounds. The affected genes often indirectly compensated for the loss of the essential gene and identified naturally occurring evolutionary trajectories. Overall, our results highlight the prevalence of changes in gene essentiality in natural populations, as well as the underlying mechanisms. A thorough understanding of the causes of genetic background effects is crucial for the interpretation of genotype-to-phenotype relationships, including those associated with human disease.

Many real-world decisions involve uncertainty, yet some are governed by logical constraints that make certain outcomes objectively more or less probable. Despite this, people often commit reasoning errors such as the conjunction fallacy, i.e. judging a conjunction of events as more likely than a single constituent event. This fallacy has proven robust across populations and contexts, and difficult to fully mitigate. While previous research has shown that reformulating problems or providing explicit instruction can reduce such errors, these approaches often yield limited success and may not generalize to everyday decision-making, where task structures are ambiguous and feedback is sparse. We investigated whether individuals could reduce conjunction fallacies through repeated exposure to decision tasks paired with minimal outcome feedback. Participants (N=56) were randomly assigned to a training group, which completed a series of conjunction judgment tasks with feedback, or a control group. Results showed that the training group improved on both trained and untrained conjunction tasks, including those based on real-world and clinical scenarios, while the control group showed no such improvement. No transfer effects were observed for unrelated base-rate tasks. Performance gains were gradual, suggesting that participants developed judgment strategies over time rather than immediately adopting normative rules. These findings demonstrate that conjunction fallacies can be mitigated through self-guided learning with minimal instruction, offering a promising approach to improving probabilistic reasoning.

Altered ceramide accumulation contributes to skeletal muscle insulin resistance, but mechanisms underlying fibre-type-specific susceptibility remain unclear. We hypothesized that fibre-type-specific ceramide metabolism governs vulnerability to lipid-induced insulin resistance. Lipidomics and quantification of ceramide-pathway enzymes were performed in mouse skeletal muscles with distinct fibre-type composition (oxidative, mixed and glycolytic) from control-diet (n = 12) and high-fat-diet (HFD; n = 12) mice. In humans, lipidomics and enzyme profiling were done in vastus lateralis biopsies from 36 adults stratified into oxidative or glycolytic phenotypes; insulin sensitivity was determined by glucose tolerance testing. siRNA-mediated silencing of SGMS1 and SGMS2 followed by lipidomics probed sphingomyelin-ceramide cycling in human myoblasts. In mouse muscle, ceramide composition rather than total content, differed by fibre type: oxidative muscle was enriched in very-long-chain ceramides, whereas glycolytic and mixed muscles contained higher C18-ceramides, paralleled by fibre-type-specific expression of enzymes involved in de novo synthesis and sphingomyelin-ceramide cycling. HFD induced ceramide remodelling, with C18-ceramides accumulating in oxidative and mixed muscles and very-long-chain species decreasing in glycolytic muscle; among all assessed enzymes, only SGMS2 was significantly downregulated in oxidative muscle. In humans, an oxidative phenotype associated with higher very-long-chain ceramides and insulin sensitivity, whereas a glycolytic phenotype displayed higher C16-18 ceramides, higher SGMS1 and SMPD2 expression, and lower insulin sensitivity. Elastic net regression identified C16-18 ceramides and galactosylceramides as negative predictors of insulin sensitivity. SGMS2 silencing caused broader ceramide accumulation than SGMS1 silencing, supporting a central role for SGMS2-mediated sphingomyelin-ceramide cycling in limiting ceramide burden.

The Court of Justice of the European Union (CJEU) portrays the preliminary ruling procedure (PRP) as a dialogue between itself and national courts in which parties play a secondary role. Under this conception, what duty does national judges have to justify when they decide not to request a preliminary ruling? While both the CJEU and the European Court of Human Rights (ECtHR) have case-law on this matter, the expectations placed on national courts remain unclear. This article clarifies what is expected by outlining the purpose, applicability and extent of the duty to give reasons for non-referral. It shows that the duty arises primarily in party-led initiatives before courts of last instance, and that the required reasoning depends on the diligence of the party’s request. This has constitutional implications: by highlighting the parties, the duty partially transforms the PRP, marking a departure from their traditional exclusion from the procedure. Yet, reliance on party requests leaves gaps in absence of such initiatives. This article argues that the duty should also be understood in the logic of Article 267(3) TFEU – requiring apex courts to justify non-referral on their own motion, in line with their obligation to refer.