4,957 research outputs found
Ground state phase diagram of the half-filled bilayer Hubbard model
Employing a combination of functional renormalization group calculations and
projective determinantal quantum Monte Carlo simulations, we examine the
Hubbard model on the square lattice bilayer at half filling. From this combined
analysis, we obtain a comprehensive account on the ground state phase diagram
with respect to the extent of the system's metallic and (antiferromagnetically
ordered) Mott-insulating as well as band-insulating regions. By means of an
unbiased functional renormalization group approach, we exhibit the
antiferromagnetic Mott-insulating state as the relevant instability of the free
metallic state, induced by any weak finite onsite repulsion. Upon performing a
careful analysis of the quantum Monte Carlo data, we resolve the difficulty of
identifying this antiferromagnetic ground state for finite interlayer hopping
in the weak-coupling regime, where nonmonotonous finite-size corrections are
shown to relate to the two-sheeted Fermi surface structure of the metallic
phase. On the other hand, quantum Monte Carlo simulations are well suited to
identify the transition between the Mott-insulating phase and the band
insulator in the intermediate-to-strong coupling regime. Here, we compare our
numerical findings to indications for the transition region obtained from the
functional renormalization group procedure.Comment: 12 pages, 15 figure
'More Than Meets the Eye': cryptic diversity and contrasting patterns of host-specificity in feather mites inhabiting seabirds
Feather mites are useful models for studying speciation due to their high diversity and strong degree of host specialization. However, studies to date have focused on the evolution of higher-level mite taxa while much hidden diversity likely occurs at the level of host genera and species. In this study, we examined the diversity and evolution of feather mites infesting six sympatric seabird species from six genera, breeding in the Cape Verde archipelago. We report 32 feather mite morphospecies categorized into 10 genera and three families, of which nine correspond to new, undescribed species. Molecular data corroborated morphological species descriptions, except for two morphologically-cryptic, but genetically distinct mite lineages related to Zachvatkinia oceanodromae and Laminalloptes simplex. Using these communities, we then applied a co-structure approach to test the contribution of ectosymbiont and host factors in driving feather mite evolution. Most seabird species hosted specific and unique feather mite species, even under sympatric conditions, and in general, feather mite species exhibited strong host-driven genetic structure. However, patterns of genetic differentiation were variable. That is, some mite species are more generalist than others and mite lineages/haplotypes can be shared by related seabird species. Interestingly, host-specific mites (e.g., Zachvatkinia spp.) tend to display much higher intra-specific diversity compared to more generalist mites (e.g., Microspalax and Plicatalloptes spp.). We discuss ectosymbiont and host life-history traits that might generate these patterns, such as host dispersal and breeding behavior and/or mite spatial and trophic specialization. Our findings highlight both the vast and largely unrecognized diversity of avian feather mites on seabirds, and the intrinsic complexity of the ecological processes underlying the evolution of these ectosymbionts
Mask-based dual-axes tomoholography using soft x-rays
We explore tomographic mask-based Fourier transform x-ray holography with respect to the use of a thin slit as a reference wave source. This imaging technique exclusively uses the interference between the waves scattered by the object and the slit simplifying the experimental realization and ensuring high data quality. Furthermore, we introduce a second reference slit to rotate the sample around a second axis and to record a dual-axes tomogram. Compared to a single-axis tomogram, the reconstruction artifacts are decreased in accordance with the reduced missing data wedge. Two demonstration experiments are performed where test structures are imaged with a lateral resolution below 100 nm
Diversity and structure of feather mite communities on seabirds from the north–east Atlantic and Mediterranean Sea
The richness and structure of symbiont assemblages are shaped by many factors acting at different
spatial and temporal scales. Among them, host phylogeny and geographic distance play essential
roles. To explore drivers of richness and structure of symbiont assemblages, feather mites and seabirds
are an attractive model due to their peculiar traits. Feather mites are permanent ectosymbionts and
considered highly host-specific with limited dispersal abilities. Seabirds harbour species-rich feather
mite communities and their colonial breeding provides opportunities for symbionts to exploit several
host species. To unravel the richness and test the influence of host phylogeny and geographic distance
on mite communities, we collected feather mites from 11 seabird species breeding across the Atlantic
Ocean and Mediterranean Sea. Using morphological criteria, we identified 33 mite species, of which 17
were new or recently described species. Based on community similarity analyses, mite communities
were clearly structured by host genera, while the effect of geography within host genera or species
was weak and sometimes negligible. We found a weak but significant effect of geographic distance
on similarity patterns in mite communities for Cory’s shearwaters Calonectris borealis. Feather mite
specificity mainly occurred at the host-genus rather than at host-species level, suggesting that
previously inferred host species-specificity may have resulted from poorly sampling closely related
host species. Overall, our results show that host phylogeny plays a greater role than geography in
determining the composition and structure of mite assemblages and pinpoints the importance of
sampling mites from closely-related host species before describing mite specificity patterns.APIF postgraduate project from the University of BarcelonaRomanian Ministry of Research, Innovation and Digitization, CNCS/CCCDI-UEFISCDIproject number PNIII-
P1-1.1-PD-2019-0611PNCDI III and by an Institutional Performance Project for Excellence Financing
in RDIContract no. 2PFE/2021 for L.M.S. Financial support was also provided by REN2002-01164/GLOCGL2006-01315/BOS, CGL2009-11278/BOS and CGL2013-42585-P from the Spanish GovernmentFondos
FEDER and BIOCON04/099 from Fundación Banco Bilbao Vizcaya Argentari
‘teen Mental Health First Aid’: a description of the program and an initial evaluation
Additional file 1. Sociodemographic characteristics of the four schools in 2013
Non-FG mediated transport of the large pre-ribosomal subunit through the nuclear pore complex by the mRNA export factor Gle2
Multiple export receptors passage bound pre-ribosomes through nuclear pore complexes (NPCs) by transiently interacting with the Phe-Gly (FG) meshwork of their transport channels. Here, we reveal how the non-FG interacting yeast mRNA export factor Gly-Leu-FG lethal 2 (Gle2) functions in the export of the large pre-ribosomal subunit (pre-60S). Structure-guided studies uncovered conserved platforms used by Gle2 to export pre-60S: an uncharacterized basic patch required to bind pre-60S, and a second surface that makes non-FG contacts with the nucleoporin Nup116. A basic patch mutant of Gle2 is able to function in mRNA export, but not pre-60S export. Thus, Gle2 provides a distinct interaction platform to transport pre-60S to the cytoplasm. Notably, Gle2's interaction platforms become crucial for pre-60S export when FG-interacting receptors are either not recruited to pre-60S or are impaired. We propose that large complex cargos rely on non-FG as well as FG-interactions for their efficient translocation through the nuclear pore complex channe
The Role of Packing, Dispersion, Electrostatics, and Solvation in High‐Affinity Complexes of Cucurbit[ n ]urils with Uncharged Polar Guests
The rationalization of non-covalent binding trends is both of fundamental interest and provides new design concepts for biomimetic molecular systems. Cucurbit[n]urils (CBn) are known for a long time as the strongest synthetic binders for a wide range of (bio)organic compounds in water. However, their host-guest binding mechanism remains ambiguous despite their symmetric and simple macrocyclic structure and the wealth of literature reports. We herein report experimental thermodynamic binding parameters (ΔG, ΔH, TΔS) for CB7 and CB8 with a set of hydroxylated adamantanes, di-, and triamantanes as uncharged, rigid, and spherical/ellipsoidal guests. Binding geometries and binding energy decomposition were obtained from high-level theory computations. This study reveals that neither London dispersion interactions, nor electronic energies or entropic factors are decisive, selectivity-controlling factors for CBn complexes. In contrast, peculiar host-related solvation effects were identified as the major factor for rationalizing the unique behavior and record-affinity characteristics of cucurbit[n]urils
Response of protists to nitrogen addition, arbuscular mycorrhizal fungi manipulation, and mesofauna reduction in a tropical montane rainforest in southern Ecuador
The tropical Andes are a species-rich and nitrogen-limited system, susceptible to increased nitrogen (N) inputs from the atmosphere. However, our understanding of the impacts of increased N input on belowground systems, in particular on protists and their role in nutrient cycling, remains limited. We explored how increased N affects protists in tropical montane rainforests in Ecuador using high-throughput sequencing (HTS) of environmental DNA from two litter layers. In addition, we manipulated the amount of arbuscular mycorrhizal fungi (AMF) and mesofauna, both playing a significant role in N cycling and interacting in complex ways with protist communities. We found that N strongly affected protist community composition in both layers, while mesofauna reduction had a stronger effect on the lower layer. Changes in concentration of the AMF marker lipid had little effect on protists. In both layers, the addition of N increased phagotrophs and animal parasites and decreased plant parasites, while mixotrophs decreased in the upper layer but increased in the lower layer. In the upper layer with higher AMF concentration, mixotrophs decreased, while in the lower layer, photoautotrophs increased and plant parasites decreased. With reduced mesofauna, phagotrophs increased and animal parasites decreased in both layers, while plant parasites increased only in the upper layer. The findings indicate that to understand the intricate response of protist communities to environmental changes, it is critical to thoroughly analyze these communities across litter and soil layers, and to include HTS
Do Disease Stories Need a Hero? Effects of Human Protagonists on a Narrative Visualization about Cerebral Small Vessel Disease
Authors use various media formats to convey disease information to a broad audience, from articles and videos to interviews or documentaries. These media often include human characters, such as patients or treating physicians, who are involved with the disease. While artistic media, such as hand-crafted illustrations and animations are used for health communication in many cases, our goal is to focus on data-driven visualizations. Over the last decade, narrative visualization has experienced increasing prominence, employing storytelling techniques to present data in an understandable way. Similar to classic storytelling formats, narrative medical visualizations may also take a human character-centered design approach. However, the impact of this form of data communication on the user is largely unexplored. This study investigates the protagonist's influence on user experience in terms of engagement, identification, self-referencing, emotional response, perceived credibility, and time spent in the story. Our experimental setup utilizes a character-driven story structure for disease stories derived from Joseph Campbell's Hero's Journey. Using this structure, we generated three conditions for a cerebral small vessel disease story that vary by their protagonist: (1) a patient, (2) a physician, and (3) a base condition with no human protagonist. These story variants formed the basis for our hypotheses on the effect of a human protagonist in disease stories, which we evaluated in an online study with 30 participants. Our findings indicate that a human protagonist exerts various influences on the story perception and that these also vary depending on the type of protagonist.publishedVersio
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