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Variation in the pollen diet of managed bee species across European agroecosystems
No full textBee-mediated pollination plays a crucial role in sustaining global food production. However, while the demand for these pollination services is increasing, many bee species are in decline. To address this discrepancy, farmers use managed bee species to improve crop pollination. One key factor affecting pollination efficiency is the affinity for the crop of interest (i.e., the extent to which a bee integrates floral resources of a crop into its diet). In this study, we characterised and compared the pollen foraging preferences of three managed bee species: Apis mellifera, Bombus terrestris, and Osmia bicornis, across European agricultural landscapes and across biogeographic regions. Managed populations of each bee species were experimentally established at 128 agricultural sites growing either apple or rapeseed, in landscapes representing gradients in terms of the proportion of cropland, in eight European countries. We conducted pollen store sampling and employed palynological analyses to describe the foraging preferences of these species and to extrapolate their suitability as pollinators for both crops. Our findings reveal that A. mellifera and B. terrestris exhibited a more generalised pollen diet compared to O. bicornis, which showed stronger preference to certain pollen forage plants, but these were mainly non-crop rather than crop plants. These results question the relevance of using O. bicornis in apple orchards and rapeseed crops given their poor affinity with these crops. Overall, A. mellifera collected the highest proportion of rapeseed pollen in its diet, and A. mellifera and B. terrestris collected higher proportions of apple pollen than O. bicornis. Our findings also highlight substantial variation in the percentage of focal crop pollen in the diet across biogeographic regions, while landscape composition had virtually no impact. These results provide valuable insights for selecting the most suitable managed bee species to enhance the pollination of two key crops in Europe
IDH-mutant astrocytomas with primitive neuronal component have a distinct methylation profile and a higher risk of leptomeningeal spread
No full textIDH-mutant astrocytomas are diffuse gliomas that are defined by characteristic mutations in IDH1 or IDH2 and do not have complete 1p/19q co-deletion. The established grading criteria include histological features of brisk mitotic activity (grade 3) and necrosis and/or microvascular proliferation (grade 4). In addition, homozygous deletion of the CDKN2A/B locus has recently been implemented as a molecular marker for grade 4 IDH-mutant astrocytomas. Here, we describe a subgroup of high-grade IDH-mutant astrocytomas characterised by a primitive neuronal component based on histology and a distinct DNA methylation profile (n = 51, ASTRO PNC). Misinterpretation as carcinoma metastasis was common, since GFAP expression was absent in the primitive neuronal component, whereas TTF-1 expression was detected in 15/19 cases (79%) based on immunohistochemistry. Apart from mutations in IDH1, TP53, and ATRX, we observed enrichment for alterations in RB1 (n = 19/51, 37%) and MYCN (n = 14/51, 27%). Homozygous CDKN2A/B deletion (n = 1/51, 2%) and CDK4 amplification (n = 3/51, 6%) were relatively rare events. Clinical (n = 31 patients) and survival data (n = 23 patients) indicate a clinical behaviour similar to other CNS WHO grade 4 IDH-mutant astrocytomas, however with an increased risk for leptomeningeal (n = 7) and extra-axial (n = 2) spread. Taken together, ASTRO PNC is defined by a distinct molecular and histological appearance that can mimic metastatic disease and typically follows an aggressive clinical course
Conjugate Bayesian analysis of the Wald model: on an exact drift-rate posterior
No full textIn cognitive psychology, simple response times are often modeled as the time required by a one-dimensional Wiener process with drift to first reach a given threshold. This stochastic process’s first-passage time follows a Wald distribution, which is a specific parameterization of the inverse-Gaussian distribution. It can be shown that the Gaussian-Gamma distribution is a conjugate prior with respect to an inverse-Gaussian likelihood, albeit under a parameterization different from that of the Wald distribution. This leads to a posterior distribution that does not directly correspond to the core parameters of the Wiener process; that is, the drift-rate and the threshold parameter. While the marginal threshold posterior under a Gaussian-Gamma prior is relatively easy to derive and turns out to be a known distribution, this is not the case for the marginal drift-rate posterior. The present work addresses this issue by providing the exact marginal posterior distributions of the drift-rate parameter under a Gaussian-Gamma prior—something that has not yet been done in the literature. Unfortunately, the probability density function of this distribution cannot be expressed in terms of elementary functions. Thus, different methods of approximation are discussed as an expedient for time-critical applications
An analytic invariant of G2 manifolds
No full textWe prove that the moduli space of holonomy G2-metrics on a closed 7-manifold canbe disconnected by presenting a number of explicit examples. We detect differentconnected components of the G2-moduli space by defining an analytic refinement¯ν(M,g) ∈ Z of the defect invariant ν(M,φ) ∈ Z/48 of G2-structures φ on a closed7-manifold M introduced by the first and third authors. The ¯ν-invariant is definedusing η-invariants and Mathai-Quillen currents on M and we compute it for twistedconnected sums à la Kovalev, Corti-Haskins-Nordström-Pacini and extra-twisted connectedsums as constructed by the second and third authors. In particular, we find examplesof G2-holonomy metrics in different components of the moduli space wherethe associated G2-structures are homotopic and other examples where they are not
Native fold delay and its implications for co-translational chaperone binding and protein aggregation
No full textBecause of vectorial protein translation, residues that interact in the native protein structure but are distantly separated in the primary sequence are unavailable simultaneously. Instead, there is a temporal delay during which the N-terminal interaction partner is unsatisfied and potentially vulnerable to non-native interactions. We introduce “Native Fold Delay” (NFD), a metric that integrates protein topology with translation kinetics to quantify such delays. We found that many proteins exhibit residues with NFDs in the range of tens of seconds. These residues, predominantly in well-structured, buried regions, often coincide with aggregation-prone regions. NFD correlates with co-translational engagement by the yeast Hsp70 chaperone Ssb, suggesting that native fold-delayed regions have a propensity to misfold. Supporting this, we show that proteins with long NFDs are more frequently co-translationally ubiquitinated and prone to aggregate upon Ssb deletion
Biomimetic freestanding microfractals for flexible electronics
No full textThe microfractals of leaf skeletons can be effective substrates for flexible electronics due to their high surface-to-volume ratio, transparency, breathability and flexibility. The challenge lies in replicating these fractal surfaces at the microscale in a way that is scalable, freestanding, and integrable with various materials. In this study, we present a novel method for the biomimetic microfabrication of leaf-skeleton-based fractal surfaces. We utilized a modified electrospinning method, replacing the fiber collector with a metalized biotic collector to replicate the microstructures. The biomimetic microfractals demonstrated ~90% replication accuracy, >80% transparency, good stretchability, and breathability, and were freestanding. The method is versatile, allowing for the use of a wide range of polymers in biomimetic microfabrication. For application in flexible electronics, biomimetic conductive fractal patterns (BCFP) were fabricated by immobilizing Ag Nanowires (AgNW) using a simple spray-based method. The BCFP exhibited high conductivity with sheet resistances <20 Ω sq–1 while maintaining good transparencies. The BCFP adheres conformally to human skin, acting as an electronic skin (e-skin). To demonstrate the application, the BCFP was used to fabricate a tactile pressure sensor. In addition to their excellent transparency at low sheet resistances, stretchability, moisture resistance, and tight conformal bonding with the target surface, the BCFP also allows the evaporation of perspiration, making them suitable for long-term use as epidermal sensors. The application of BCFP in advanced bionic skin was demonstrated through gesture monitoring experiments
Non-native plants in road verges attract pollinators despite associated declines in native flowers
No full textMarginal habitats are increasingly recognized for their potential value in pollinator conservation. Road verges, which cover extensive areas, provide abundant floral resources and contribute to habitat heterogeneity and connectivity in homogeneous landscapes. However, road verges are also hotspots for the establishment and dispersal of non-native plants, raising doubts on their suitability to support diverse pollinator populations. We sampled flowering plants and visiting insects in roadsides of southeastern Manitoba, Canada, and leveraged datasets of bee communities from surrounding areas and Wildlife Management Areas (WMAs) to compare pollinator communities across habitats. Plant communities in road verges were dominated by a subset of abundant non-native species and were disproportionately visited by generalist pollinators. Non-native plant abundance was negatively correlated with native plant richness and abundance in the verges but positively associated with bee richness and abundance. Landscape context and scale also influenced pollinators. We found strong differences in pollinator richness, abundance, and community composition at larger (ecozone) scales, with local landscape composition and configuration also contributing significantly, albeit to a lesser extent. Road verge bee communities were distinct and less even than those in surrounding areas and WMAs, and exhibited a markedly higher proportion of polylectic to oligolectic individuals. These findings suggest that road verges can support generalist pollinators but are less suitable for specialists, highlighting their potential to maintain pollination services in heavily disturbed or densely-forested landscapes while also revealing limitations in harboring representatively diverse and even communities
Selective peptide bond formation via side chain reactivity and self-assembly of abiotic phosphates
No full textIn the realm of biology, peptide bonds are formed via reactive phosphate-containing intermediates, facilitated by compartmentalized environments that ensure precise coupling and folding. Herein, we use aminoacyl phosphate esters, synthetic counterparts of biological aminoacyl adenylates, that drive selective peptide bond formation through side chain-controlled reactivity and self-assembly. This strategy results in the preferential incorporation of positively charged amino acids from mixtures containing natural and non-natural amino acids during the spontaneous formation of amide bonds in water. Conversely, aminoacyl phosphate esters that lack assembly and exhibit fast reactivity result in random peptide coupling. By introducing structural modifications to the phosphate esters (ethyl vs. phenyl) while retaining aggregation, we are able to tune the selectivity by incorporating aromatic amino acid residues. This approach enables the synthesis of sequences tailored to the specific phosphate esters, overcoming limitations posed by certain amino acid combinations. Furthermore, we demonstrate that a balance between electrostatic and aromatic stacking interactions facilitates covalent self-sorting or co-assembly during oligomerization reactions using unprotected N-terminus aminoacyl phosphate esters. These findings suggest that self-assembly of abiotic aminoacyl phosphate esters can activate a selection mechanism enabling the departure from randomness during the autonomous formation of amide bonds in water