bluuebunny/crossref_metadata_2025_split huggingface dataset:
Frequency‐Dependent P Wave Anisotropy Due to Wave‐Induced Fluid Flow and Elastic Scattering in a Fluid‐Saturated Porous Medium With Aligned Fractures
Authors: Guo Junxin , Gurevich Boris 
Published: August 2020

AbstractSeismic anisotropy is an important attribute for fracture detection and characterization. If fracture size is comparable to the wavelength or fluid diffusion length, the P wave anisotropy is frequency dependent. By solving the Biot's equations of dynamic poroelasticity and using the Foldy approximation, we investigate the frequency‐dependent P wave anisotropy in a fluid‐saturated porous rock with a set of aligned penny‐shaped fractures. This approach includes the effects of both wave‐induced fluid flow (WIFF) and elastic scattering on P wave anisotropy. The results show that the velocity and attenuation anisotropy in the WIFF and elastic scattering regimes have quite different features and are affected by various factors. In particular, the background permeability and fluid viscosity primarily affect the frequency‐dependent anisotropy caused by WIFF. The fracture geometry (radius and thickness) and fracture density have significant effects on both WIFF and elastic scattering‐induced frequency‐dependent anisotropy. The fluid bulk modulus also affects the frequency‐dependent anisotropy. With the vanishing fluid bulk modulus, the frequency dependency vanishes in the WIFF regime but is the largest in the elastic scattering regime. Predictions of the model agree with previous models in all known limiting cases. Comparison with experimental data shows that WIFF and elastic scattering are important causes for frequency‐dependent P wave anisotropy, and our model is capable to account for these effects.
Modeling of the Influence of Sea Ice Cycle and Langmuir Circulation on the Upper Ocean Mixed Layer Depth and Freshwater Distribution at the West Antarctic Peninsula
Authors: Schultz C. , Doney S. C. , Zhang W. G. , Regan H. , Holland P. , Meredith M. P. , Stammerjohn S. 
Published: August 2020

AbstractThe Southern Ocean is chronically undersampled due to its remoteness, harsh environment, and sea ice cover. Ocean circulation models yield significant insight into key processes and to some extent obviate the dearth of data; however, they often underestimate surface mixed layer depth (MLD), with consequences for surface water‐column temperature, salinity, and nutrient concentration. In this study, a coupled circulation and sea ice model was implemented for the region adjacent to the West Antarctic Peninsula, a climatically sensitive region which has exhibited decadal trends towards higher ocean temperature, shorter sea ice season, and increasing glacial freshwater input, overlain by strong interannual variability. Hindcast simulations were conducted with different air‐ice drag coefficients and Langmuir circulation parameterizations to determine the impact of these factors on MLD. Including Langmuir circulation deepened the surface mixed layer, with the deepening being more pronounced in the shelf and slope regions. Optimal selection of an air‐ice drag coefficient also increased modeled MLD by similar amounts and had a larger impact in improving the reliability of the simulated MLD interannual variability. This study highlights the importance of sea ice volume and redistribution to correctly reproduce the physics of the underlying ocean, and the potential of appropriately parameterizing Langmuir circulation to help correct for biases towards shallow MLD in the Southern Ocean. The model also reproduces observed freshwater patterns in the West Antarctic Peninsula during late summer and suggests that areas of intense summertime sea ice melt can still show net annual freezing due to high sea ice formation during the winter.
Effects of Typhoons on Surface Seawater pCO2 and Air‐Sea CO2 Fluxes in the Northern South China Sea
Authors: Yu Peisong , Wang Zhaohui Aleck , Churchill James , Zheng Minhui , Pan Jianming , Bai Yan , Liang Chujin 
Published: August 2020

AbstractThis study assessed the effects of typhoons on sea surface pCO2 and CO2 flux in the northern South China Sea (SCS). During the passage of three major typhoons from May to August 2013, sea surface pCO2, surface seawater temperature (SST), and other meteorological parameters were continuously measured on a moored buoy. Surface water in the region was a source of CO2 to the atmosphere with large variations ranging from hours to months. SST was the primary factor controlling the variation of surface pCO2 through most of the time period. Typhoons are seen to impact surface pCO2 in three steps: first by cooling, thus decreasing surface pCO2, and then by causing vertical mixing that brings up deep, high‐CO2 water, and lastly triggering net uptake of CO2 due to the nutrients brought up in this deep water. The typhoons of this study primarily impacted air‐sea CO2 flux via increasing wind speeds. The mean CO2 flux during a typhoon ranged from 3.6 to 5.4 times the pretyphoon mean flux. The magnitude of the CO2 flux during typhoons was strongly inversely correlated with the typhoon center distance. The effect of typhoons accounted for 22% of the total CO2 flux in the study period, during which typhoons occurred only 9% of the time. It was estimated that typhoons enhanced annual CO2 efflux by 23–56% in the northern SCS during the last decade. As such, tropical cyclones may play a large and increasingly important role in controlling CO2 fluxes in a warmer and stormier ocean of the future.
Influence of the Pacific‐South American Modes on the Global Spectral Wind‐Wave Climate
Authors: Echevarria E. R. , Hemer M. A. , Holbrook N. J. , Marshall A. G. 
Published: August 2020

AbstractIn this study, we analyze the influence of the Pacific‐South American modes (PSA‐1 and PSA‐2) on the global wind‐wave climate using wave data derived from a WAVEWATCH III global wave hindcast. We apply an empirical orthogonal function analysis to daily‐averaged directional wave spectra to extract the two main patterns of interannual wave spectral variability. These are related to changes in the wave spectral density levels (variability in the wave heights) and to rotations of the wave signal (variability in wave direction). The PSA‐1 mode is positively correlated with the wave height variability in the southeast Pacific and negatively correlated in the Indian Ocean sector of the Southern Ocean. The PSA‐2 mode presents a strong negative correlation with wave heights in the central South Pacific. Moreover, the PSA modes are significantly correlated with changes in modeled wave direction in the South Pacific region. Composite maps of wind anomalies during positive stages of PSA‐1 and PSA‐2 provide a compelling explanation for the observed correlation patterns. The methodology applied in this study is also used to assess the influence of other climate modes on the global wind‐wave climate (namely, the Southern Annular Mode, Arctic Oscillation, North Atlantic Oscillation, El Niño/Southern Oscillation, and the Pacific North American mode). While our results are consistent with previous studies, we provide more clarity as to how different atmospheric modes influence the variability of specific components of the wave spectrum. Importantly, we assess how these climate modes would modulate the interannual variability of wave direction.
Lichen-like association of Chlamydomonas reinhardtii and Aspergillus nidulans protects algal cells from bacteria
Authors: Krespach Mario K C , García-Altares María , Flak Michal , Schoeler Hanno , Scherlach Kirstin , Netzker Tina , Schmalzl Anica , Mattern Derek J , Schroeckh Volker , Komor Anna , Mittag Maria , Hertweck Christian , Brakhage Axel A 
Published: August 2020

Abstract
Organismal interactions within microbial consortia and their responses to harmful intruders remain largely understudied. An important step toward the goal of understanding functional ecological interactions and their evolutionary selection is the study of increasingly complex microbial interaction systems. Here, we discovered a tripartite biosystem consisting of the fungus Aspergillus nidulans, the unicellular green alga Chlamydomonas reinhardtii, and the algicidal bacterium Streptomyces iranensis. Genetic analyses and MALDI-IMS demonstrate that the bacterium secretes the algicidal compound azalomycin F upon contact with C. reinhardtii. In co-culture, A. nidulans attracts the motile alga C. reinhardtii, which becomes embedded and surrounded by fungal mycelium and is shielded from the algicide. The filamentous fungus Sordaria macrospora was susceptible to azalomycin F and failed to protect C. reinhardtii despite chemotactically attracting the alga. Because S. macrospora was susceptible to azalomycin F, this data imply that for protection the fungus needs to be resistant. Formation of the lichen-like association between C. reinhardtii and A. nidulans increased algal growth. The protection depends on the increased amounts of membrane lipids provided by resistant fungi, thereby generating a protective shelter against the bacterial toxin. Our findings reveal a strategy whereby algae survive lethal environmental algicides through cooperation with fungi.
The influence of a priori grouping on inference of genetic clusters: simulation study and literature review of the DAPC method
Authors: Miller Joshua M. , Cullingham Catherine I. , Peery Rhiannon M. 
Published: August 2020

AbstractInference of genetic clusters is a key aim of population genetics, sparking development of numerous analytical methods. Within these, there is a conceptual divide between finding de novo structure versus assessment of a priori groups. Recently developed, Discriminant Analysis of Principal Components (DAPC), combines discriminant analysis (DA) with principal component (PC) analysis. When applying DAPC, the groups used in the DA (specified a priori or described de novo) need to be carefully assessed. While DAPC has rapidly become a core technique, the sensitivity of the method to misspecification of groups and how it is being empirically applied, are unknown. To address this, we conducted a simulation study examining the influence of a priori versus de novo group designations, and a literature review of how DAPC is being applied. We found that with a priori groupings, distance between genetic clusters reflected underlying FST. However, when migration rates were high and groups were described de novo there was considerable inaccuracy, both in terms of the number of genetic clusters suggested and placement of individuals into those clusters. Nearly all (90.1%) of 224 studies surveyed used DAPC to find de novo clusters, and for the majority (62.5%) the stated goal matched the results. However, most studies (52.3%) omit key run parameters, preventing repeatability and transparency. Therefore, we present recommendations for standard reporting of parameters used in DAPC analyses. The influence of groupings in genetic clustering is not unique to DAPC, and researchers need to consider their goal and which methods will be most appropriate.
Recycled arc mantle recovered from the Mid-Atlantic Ridge
Authors: Urann B. M. , Dick H. J. B. , Parnell-Turner R. , Casey J. F. 
Published: August 2020

AbstractPlate tectonics and mantle dynamics necessitate mantle recycling throughout Earth’s history, yet direct geochemical evidence for mantle reprocessing remains elusive. Here we present evidence of recycled supra-subduction zone mantle wedge peridotite dredged from the Mid-Atlantic Ridge near 16°30′N. Peridotite trace-element characteristics are inconsistent with fractional anhydrous melting typically associated with a mid-ocean ridge setting. Instead, the samples are best explained by hydrous flux melting which changed the melting reactions such that clinopyroxene was not exhausted at high degrees of melting and was retained in the residuum. Based on along-axis ridge depth variations, this buoyant refractory arc mantle is likely compensated at depth by denser, likely garnet-rich, lithologies within the mantle column. Our results suggest that highly refractory arc mantle relicts are entrained in the upper mantle and may constitute >60% of the upper mantle by volume. These highly refractory mantle domains, which contribute little to mantle melting, are under-represented in compilations of mantle composition that rely on inverted basalt compositions alone.
Lipo-chitooligosaccharides as regulatory signals of fungal growth and development
Authors: Rush Tomás Allen , Puech-Pagès Virginie , Bascaules Adeline , Jargeat Patricia , Maillet Fabienne , Haouy Alexandra , Maës Arthur QuyManh , Carriel Cristobal Carrera , Khokhani Devanshi , Keller-Pearson Michelle , Tannous Joanna , Cope Kevin R. , Garcia Kevin , Maeda Junko , Johnson Chad , Kleven Bailey , Choudhury Quanita J. , Labbé Jessy , Swift Candice , O’Malley Michelle A. , Bok Jin Woo , Cottaz Sylvain , Fort Sébastien , Poinsot Verena , Sussman Michael R. , Lefort Corinne , Nett Jeniel , Keller Nancy P. , Bécard Guillaume , Ané Jean-Michel 
Published: August 2020

AbstractLipo-chitooligosaccharides (LCOs) are signaling molecules produced by rhizobial bacteria that trigger the nodulation process in legumes, and by some fungi that also establish symbiotic relationships with plants, notably the arbuscular and ecto mycorrhizal fungi. Here, we show that many other fungi also produce LCOs. We tested 59 species representing most fungal phyla, and found that 53 species produce LCOs that can be detected by functional assays and/or by mass spectroscopy. LCO treatment affects spore germination, branching of hyphae, pseudohyphal growth, and transcription in non-symbiotic fungi from the Ascomycete and Basidiomycete phyla. Our findings suggest that LCO production is common among fungi, and LCOs may function as signals regulating fungal growth and development.
Identifying the nature of the active sites in methanol synthesis over Cu/ZnO/Al2O3 catalysts
Authors: Laudenschleger Daniel , Ruland Holger , Muhler Martin 
Published: August 2020

AbstractThe heterogeneously catalysed reaction of hydrogen with carbon monoxide and carbon dioxide (syngas) to methanol is nearly 100 years old, and the standard methanol catalyst Cu/ZnO/Al2O3 has been applied for more than 50 years. Still, the nature of the Zn species on the metallic Cu0 particles (interface sites) is heavily debated. Here, we show that these Zn species are not metallic, but have a positively charged nature under industrial methanol synthesis conditions. Our kinetic results are based on a self-built high-pressure pulse unit, which allows us to inject selective reversible poisons into the syngas feed passing through a fixed-bed reactor containing an industrial Cu/ZnO/Al2O3 catalyst under high-pressure conditions. This method allows us to perform surface-sensitive operando investigations as a function of the reaction conditions, demonstrating that the rate of methanol formation is only decreased in CO2-containing syngas mixtures when pulsing NH3 or methylamines as basic probe molecules.
A hybrid achromatic metalens
Authors: Balli F. , Sultan M. , Lami Sarah K. , Hastings J. T. 
Published: August 2020

AbstractMetalenses, ultra-thin optical elements that focus light using subwavelength structures, have been the subject of a number of recent investigations. Compared to their refractive counterparts, metalenses offer reduced size and weight, and new functionality such as polarization control. However, metalenses that correct chromatic aberration also suffer from markedly reduced focusing efficiency. Here we introduce a Hybrid Achromatic Metalens (HAML) that overcomes this trade-off and offers improved focusing efficiency over a broad wavelength range from 1000–1800 nm. HAMLs can be designed by combining recursive ray-tracing and simulated phase libraries rather than computationally intensive global search algorithms. Moreover, HAMLs can be fabricated in low-refractive index materials using multi-photon lithography for customization or using molding for mass production. HAMLs demonstrated diffraction limited performance for numerical apertures of 0.27, 0.11, and 0.06, with average focusing efficiencies greater than 60% and maximum efficiencies up to 80%. A more complex design, the air-spaced HAML, introduces a gap between elements to enable even larger diameters and numerical apertures.
Single-site pyrrolic-nitrogen-doped sp2-hybridized carbon materials and their pseudocapacitance
Authors: Tian Kesong , Wang Junyan , Cao Ling , Yang Wei , Guo Wanchun , Liu Shuhu , Li Wei , Wang Fengyan , Li Xueai , Xu Zhaopeng , Wang Zhenbo , Wang Haiyan , Hou Yanglong 
Published: August 2020

AbstractIntegrating nitrogen species into sp2-hybridized carbon materials has proved an efficient means to improve their electrochemical performance. Nevertheless, an inevitable mixture of nitrogen species in carbon materials, due to the uncontrolled conversion among different nitrogen configurations involved in synthesizing nitrogen-doped carbon materials, largely retards the precise identification of electrochemically active nitrogen configurations for specific reactions. Here, we report the preparation of single pyrrolic N-doped carbon materials (SPNCMs) with a tunable nitrogen content from 0 to 4.22 at.% based on a strategy of low-temperature dehalogenation-induced and subsequent alkaline-activated pyrolysis of 3-halogenated phenol-3-aminophenol-formaldehyde (X-APF) co-condensed resins. Additionally, considering that the pseudocapacitance of SPNCMs is positively dependent on the pyrrolic nitrogen content, it could be inferred that pyrrolic nitrogen species are highly active pseudocapacitive sites for nitrogen-doped carbon materials. This work gives an ideal model for understanding the contribution of pyrrolic nitrogen species in N-doped carbon materials.
Evolving cooperation in multichannel games
Authors: Donahue Kate , Hauser Oliver P. , Nowak Martin A. , Hilbe Christian 
Published: August 2020

AbstractHumans routinely engage in many distinct interactions in parallel. Team members collaborate on several concurrent projects, and even whole nations interact with each other across a variety of issues, including trade, climate change and security. Yet the existing theory of direct reciprocity studies isolated repeated games. Such models cannot account for strategic attempts to use the vested interests in one game as a leverage to enforce cooperation in another. Here we introduce a general framework of multichannel games. Individuals interact with each other over multiple channels; each channel is a repeated game. Strategic choices in one channel can affect decisions in another. With analytical equilibrium calculations for the donation game and evolutionary simulations for several other games we show that such linkage facilitates cooperation. Our results suggest that previous studies tend to underestimate the human potential for reciprocity. When several interactions occur in parallel, people often learn to coordinate their behavior across games to maximize cooperation in each of them.
X-ray microtomography is a novel method for accurate evaluation of small-bowel mucosal morphology and surface area
Authors: Virta Johannes , Hannula Markus , Tamminen Ilmari , Lindfors Katri , Kaukinen Katri , Popp Alina , Taavela Juha , Saavalainen Päivi , Hiltunen Pauliina , Hyttinen Jari , Kurppa Kalle 
Published: August 2020

AbstractThe often poorly orientated small-bowel mucosal biopsies taken for the diagnostics of celiac disease and other intestinal disorders are prone to misinterpretation. Furthermore, conventional histopathology has suboptimal sensitivity for early histopathological changes observed in short-term challenge studies. X-ray microtomography (micro-CT) is a promising new method for accurate imaging of human-derived biological samples. Here, we report that micro-CT could be utilized to create virtual reconstructions of endoscopically obtained intestinal biopsies. The formed digital 3D images enabled selection of always optimal cutting angles for accurate measurement of the mucosal damage and revealed diagnostic lesions in cases interpreted as normal with conventional histomorphometry. We also demonstrate that computer-assisted point cloud analysis can be used to calculate biologically meaningful surface areas of the biopsies in different stages of mucosal damage with excellent replicability and correlation with other disease parameters. We expect the improved diagnostic accuracy and capability to measure the surface areas to provide a powerful tool for the diagnostics of intestinal diseases and for future clinical and pharmaceutical trials.
Decisions and disease: a mechanism for the evolution of cooperation
Authors: Karlsson Carl-Joar , Rowlett Julie 
Published: August 2020

AbstractIn numerous contexts, individuals may decide whether they take actions to mitigate the spread of disease, or not. Mitigating the spread of disease requires an individual to change their routine behaviours to benefit others, resulting in a ‘disease dilemma’ similar to the seminal prisoner’s dilemma. In the classical prisoner’s dilemma, evolutionary game dynamics predict that all individuals evolve to ‘defect.’ We have discovered that when the rate of cooperation within a population is directly linked to the rate of spread of the disease, cooperation evolves under certain conditions. For diseases which do not confer immunity to recovered individuals, if the time scale at which individuals receive accurate information regarding the disease is sufficiently rapid compared to the time scale at which the disease spreads, then cooperation emerges. Moreover, in the limit as mitigation measures become increasingly effective, the disease can be controlled; the number of infections tends to zero. It has been suggested that disease spreading models may also describe social and group dynamics, indicating that this mechanism for the evolution of cooperation may also apply in those contexts.
The prostaglandin synthases, COX-2 and L-PGDS, mediate prostate hyperplasia induced by low-dose bisphenol A
Authors: Wu Shuangshuang , Huang Dongyan , Su Xin , Yan Han , Ma Aicui , Li Lei , Wu Jianhui , Sun Zuyue 
Published: August 2020

AbstractThis study aimed to identify prostaglandin synthases (PGS) that mediate bisphenol A (BPA)-induced prostatic hyperplasia and explore their underlying mechanisms. In an in vivo study, male adult Sprague–Dawley rats were treated with different concentrations of BPA (10, 30, 90, or 270 μg/kg, i.g., daily), or with vehicle for 4 weeks. Results revealed that low-dose BPA induced prostatic hyperplasia with increased PCNA/TUNEL ratio. It significantly upregulated the expression of cyclooxygenase-2 (COX-2) and NF-κB in the dorsolateral prostate (P < 0.05) and the expression of lipocalin-type prostaglandin D synthase (L-PGDS) in ventral prostate (P < 0.05). The level of estradiol (E2)/testosterone (T) and expression of androgen receptor (AR) and estrogen receptor α (ERα) were also altered. In vitro studies showed that low-dose BPA (0.1–10 nM) promoted the proliferation of human prostate fibroblasts and epithelial cells, and significantly upregulated the expression of COX-2 and L-PGDS in the cells. The two types of cell proliferation induced by BPA were inhibited by COX-2 inhibitor (NS398) and L-PGDS inhibitor (AT56), with increased apoptosis level. These findings suggested that COX-2 and L-PGDS could mediate low-dose BPA-induced prostatic hyperplasia through pathways involved in cell proliferation and apoptosis, which might be related to the functions of ERα and AR. The role of COX-2/NF-κB pathway in dorsolateral prostate requires further research.