bluuebunny/crossref_metadata_2025_split huggingface dataset:
ON THE SET-THEORETIC STRENGTH OF ELLIS’ THEOREM AND THE EXISTENCE OF FREE IDEMPOTENT ULTRAFILTERS ON ω
Authors: TACHTSIS ELEFTHERIOS 
Published: August 2018

AbstractEllis’ Theorem (i.e., “every compact Hausdorff right topological semigroup has an idempotent element”) is known to be proved only under the assumption of the full Axiom of Choice (AC); AC is used in the proof in the disguise of Zorn’s Lemma.In this article, we prove that in ZF, Ellis’ Theorem follows from the Boolean Prime Ideal Theorem (BPI), and hence is strictly weaker than AC in ZF. In fact, we establish that BPI implies the formally stronger (than Ellis’ Theorem) statement “for every family ${\cal A} = \{ ({S_i},{ \cdot _i},{{\cal T}_i}):i \in I\}$ of nontrivial compact Hausdorff right topological semigroups, there exists a function f with domain I such that $f\left( i \right)$ is an idempotent of ${S_i}$, for all $i \in I$”, which in turn implies ACfin (i.e., AC for sets of nonempty finite sets).Furthermore, we prove that in ZFA, the Axiom of Multiple Choice (MC) implies Ellis’ Theorem for abelian semigroups (i.e., “every compact Hausdorff right topological abelian semigroup has an idempotent element”) and that the strictly weaker than MC (in ZFA) principle LW (i.e., “every linearly ordered set can be well-ordered”) implies Ellis’ Theorem for linearly orderable semigroups (i.e., “every compact Hausdorff right topological linearly orderable semigroup has an idempotent element”); thus the latter formally weaker versions of Ellis’ Theorem are strictly weaker than BPI in ZFA. Yet, it is shown that no choice is required in order to prove Ellis’ Theorem for well-orderable semigroups.We also show that each one of the (strictly weaker than AC) statements “the Tychonoff product $2^{\Cal R} $ is compact and Loeb” and $BPI_{\Cal R}$ (BPI for filters on ${\Cal R}$) implies “there exists a free idempotent ultrafilter on ω” (which in turn is not provable in ZF). Moreover, we prove that the latter statement does not imply $BP{I_\omega }$ (BPI for filters on ω) in ZF, hence it does not imply any of $AC_{\Cal R} $ (AC for sets of nonempty sets of reals) and $BPI_{\Cal R} $ in ZF, either.In addition, we prove that the statements “there exists a free ultrafilter on ω”, “there exists a free ultrafilter on ω which is not idempotent”, and “for every IP set $A \subseteq \omega$, there exists a free ultrafilter ${\cal F}$ on ω such that $A \in {\cal F}$” are pairwise equivalent in ZF.
The Land–Labour Hypothesis in a Settler Economy: Wealth, Labour and Household Composition on the South African Frontier
Authors: Cilliers Jeanne , Green Erik 
Published: August 2018

AbstractTraditional frontier literature identifies a positive correlation between land availability and fertility. A common explanation is that the demand for child labour is higher in newly established frontier regions compared to older, more densely populated farming regions. In this paper, we contribute to the debate by analysing the relationship between household composition and land availability in a closing frontier region, i.e. the Graaff-Reinet district in South Africa’s Cape Colony from 1798–1828. We show that the number of children in farming households increased with frontier closure, while the presence of non-family labourers decreased over time. Contrasting with the classic interpretation, we explain this by acknowledging that the demand for family labour was not a function of its marginal productivity and that farmers reacted differently to diminishing land availability depending on their wealth. Poorer households, which made up the majority of this frontier population, responded to shrinking land availability by employing relatively more family labour, while the wealthiest group invested in strengthening market access.TRANSLATED ABSTRACTS FRENCH – GERMAN – SPANISHJeanne Cilliers et Erik Green.L’hypothèse sur la disponibilité de terres et la main d’œuvre dans une économie de colons: richesse, main d’œuvre et composition du ménage à la frontière sud-africaine.La littérature traditionnelle de la frontière identifie une corrélation positive entre la disponibilité de terres et la fertilité. Une explication courante est que la demande de travail des enfants est supérieure dans les régions frontalières nouvellement établies, par comparaison avec d’anciennes régions agricoles plus densément peuplées. Dans cet article, nous contribuons au débat en analysant la relation entre la composition du ménage et la disponibilité de terres dans une région frontalière en train de fermer, le district de Graaff-Reinert dans la Colonie du Cap en Afrique du Sud, entre 1798 et 1828. Les auteurs montrent que le nombre des enfants dans les ménages agricoles augmenta avec la fermeture des frontières, tandis que la présence d’ouvriers agricoles non familiaux déclina au fil des ans. Contrairement à l’interprétation classique, nous expliquons ce phénomène en reconnaissant que la demande de travailleurs familiaux ne dépendit pas de sa productivité marginale, et que les exploitants agricoles réagirent différemment selon leur richesse à la disponibilité de terres diminuante. Les foyers plus pauvres, qui constituaient la majorité de cette population frontalière, répondirent à la disponibilité de terres déclinante en employant relativement plus de main d’œuvre familiale, tandis que le groupe le plus riche investit dans le renforcement de l’accès au marché.Traduction:Christine Plard
Two case studies from a virtual reality intervention for delusions: feasibility and preliminary evidence
Authors: Dietrichkeit Mona , Flint Kristina , Krieger Eva , Grzella Karsten , Nagel Matthias , Moritz Steffen 
Published: August 2018

AbstractThe use of virtual reality (VR) interventions for psychosis is on the rise. As information-processing biases such as overconfidence in memory are likely to be involved in the formation and maintenance of delusions, VR could also be used to correct cognitive distortions and in turn ameliorate delusions. The present study illustrates two case studies in which a VR intervention was employed to reduce delusions by means of correcting experiences. Participants navigated four virtual environments via a head-mounted display (HMD) and computer and were asked to recollect previously seen faces and objects and to rate their response confidence. The scenarios were created to elicit false memories. Immediately after each response, they received feedback to correct possible overconfidence in false memories. We present two case studies to illustrate individual differences. Both participants benefited from the intervention: delusions were reduced from pre- to post-assessment (after 3 weeks) as measured with the Positive and Negative Syndrome Scale and Psychotic Symptom Scale. This was corroborated by results on the Paranoia Checklist and the Community Assessment of Psychic Experiences collected immediately after the session. Immediate effects also showed a reduction in delusion conviction rate. The present study provides preliminary evidence that delusions may be ameliorated by a VR paradigm designed to correct memory overconfidence. Cybersickness emerged as a problem in one of the patients.
New Techniques and Data for Understanding the Global Soil Respiration Flux
Authors: Bond‐Lamberty Ben 
Published: August 2018

AbstractSoil respiration (Rs; the soil surface‐to‐atmosphere CO2 flux) has been measured in the field for decades, but only recently have we begun to assemble and leverage these small‐scale but extensive data. Recently, Zhao et al. (2017, https://doi.org/10.1002/2016ef000480) applied a novel artificial neural network model to the problem of estimating the global Rs flux and understanding its variations between regions and biomes. Their results point to a convergence in estimates of global Rs, and the power of leveraging the long record of observed Rs in global ecosystems, but also to uncertainties about soils' response to climate change. It will take a combination of long‐term studies, data syntheses, modeling intercomparisons, and probably a new generation of sampling networks and experiments to fully resolve these questions.
Stability and Reactions of CaCO3 Polymorphs in the Earth's Deep Mantle
Authors: Zhang Zhigang , Mao Zhu , Liu Xi , Zhang Yigang , Brodholt John 
Published: August 2018

AbstractAs an important component of carbonates in the mantle, CaCO3 is a major carrier of carbon from the surface to the deep interiors. In recent years, new varieties of CaCO3 polymorphs have been continuously predicted by first principles simulations and verified by experiments. The findings of these polymorphs open the possibility of stabilizing CaCO3 component in the lowermost mantle. Here, through extensive first principles simulations, we inspect the stability and reactions of high‐pressure CaCO3 polymorphs at high temperatures. Systematic errors from approximations to the exchange‐correlation functional in density functional theory have been essentially eliminated with a generalized rescaling method to increase the predictability of the simulations. We find temperature has important effects on the stabilities and the reactions of CaCO3 polymorphs with mantle minerals. In particular, the tetrahedrally structured CaCO3‐polymorph (space group P21/c) is found to be sensitive to temperature with a positive Clapeyron slope of 15.81(6) MPa/K. Reacting with MgSiO3, CaCO3 is shown to be less stable than MgCO3 over the whole mantle pressures (to ~136 GPa) above ~1500 K. And CaCO3 is demonstrated to readily react with SiO2 even in the cold subduction slabs. Thus, high temperature greatly increases the tendency of partitioning calcium into the silicates, and CaCO3 is not likely to be the major host of carbon in the Earth's deep mantle.
Lateral Mixing Processes in the Hadean
Authors: O'Neill C. J. , Zhang S. 
Published: August 2018

AbstractSamples of ancient Eoarchean volcanism suggest the existence of isotopically distinct mantle domains. 142Nd evidence suggests that these domains formed within the first several hundred million years of Earth's history and were preserved until circa 3.7 Ga—a span of almost 800 Myr. Here we explore evolving mantle convection models under Hadean conditions to constrain mantle mixing dynamics and in particular focus on the generation, or preservation, of upper mantle hemispheric compositional anomalies. We find that initially radially homogenous models fail to produce hemispheric anomalies spontaneously due to mixing processes and that rheological and buoyancy effects, or asymmetric processes such as plate tectonics or meteorite impacts, do not generate long‐lived heterogeneities in upper mantle composition from homogenous initial conditions. In contrast, models initiated with compositional variations can preserve these hemispheric differences of periods >800 Myr despite vigorous internal convection, as a function of the proclivity of these models to exhibit stagnant‐lid behavior, resulting in isolated convection cells with restricted lateral transport.
Sensitivity of Seismic Noise Correlation Functions to Global Noise Sources
Authors: Sager Korbinian , Boehm Christian , Ermert Laura , Krischer Lion , Fichtner Andreas 
Published: August 2018

AbstractSurface waves in seismic noise correlation functions are routinely exploited for tomographic studies. However, the observation and proper interpretation of body waves is considerably more difficult. To understand body wave generation in particular and the emergence of noise correlation signals in general, we investigate the sensitivity of correlation functions with respect to global noise sources. Treating noise correlation functions as self‐consistent observables, without the enforcement of Green function retrieval, enables us to investigate the quantitative contribution of different noise sources in space to a signal in a specific time window. The source sensitivity kernel for a surface wave reveals the expected dominant and broad region of stationary phase and thereby confirms the robustness of noise tomography in its current state. In contrast, kernels for potential body waves are highly oscillatory and indicate significant contributions from cross terms, for example, from body wave‐surface wave interactions. While the short‐wavelength nature of the body wave kernel may in the future allow us to infer noise sources with great detail, the importance of cross terms combined with the natural heterogeneity of noise sources renders an interpretation of such an arrival as a pure body wave almost impossible. Furthermore, we show that even long‐wavelength Earth structure significantly distorts sensitivity kernels. It is therefore essential to incorporate 3‐D heterogeneities into high‐resolution imaging of ambient noise sources, especially at higher frequencies.
Circulating insulin-like growth factor I modulates mood and is a biomarker of vulnerability to stress: from mouse to man
Authors: Santi A. , Bot M. , Aleman A. , Penninx B. W. J. H. , Aleman I. Torres 
Published: August 2018

AbstractIndividual susceptibility to anxiety disorders after maladaptive responses to stress is not well understood. We now report that while exploring stress responses in mice after traumatic brain injury (TBI), a condition associated to stress susceptibility, we observed that the anxiogenic effects of either TBI or exposure to life-threatening experiences (predator) were blocked when both stressors were combined. Because TBI increases the entrance into the brain of serum insulin-like growth factor I (IGF-I), a known modulator of anxiety with a wide range of concentrations in the human population, we then determined whether circulating IGF-I is related to anxiety measures. In mice, anxiety-like responses to predator were inversely related to circulating IGF-I levels. Other indicators of mood regulation such as sensitivity to dexamethasone suppression and expression levels of blood and brain FK506 binding protein 5 (FKBP5), a co-chaperone of the glucocorticoid receptor that regulates its activity, were also associated to circulating IGF-I. Indeed, brain FKBP5 expression in mice was stimulated by IGF-I. In addition, we observed in a large human cohort (n = 2686) a significant relationship between plasma IGF-I and exposure to recent stressful life events, while FKBP5 expression in blood cells was significantly associated to plasma IGF-I levels. Collectively, these data indicate that circulating IGF-I appears to be involved in mood homeostasis across different species. Furthermore, the data in mice allow us to indicate that IGF-I may be acting at least in part by modulating FKBP5 expression.
Endogenous transcripts control miRNA levels and activity in mammalian cells by target-directed miRNA degradation
Authors: Ghini Francesco , Rubolino Carmela , Climent Montserrat , Simeone Ines , Marzi Matteo J. , Nicassio Francesco 
Published: August 2018

AbstractLittle is known about miRNA decay. A target-directed miRNA degradation mechanism (TDMD) has been suggested, but further investigation on endogenous targets is necessary. Here, we identify hundreds of targets eligible for TDMD and show that an endogenous RNA (Serpine1) controls the degradation of two miRNAs (miR-30b-5p and miR-30c-5p) in mouse fibroblasts. In our study, TDMD occurs when the target is expressed at relatively low levels, similar in range to those of its miRNAs (100–200 copies per cell), and becomes more effective at high target:miRNA ratios (>10:1). We employ CRISPR/Cas9 to delete the miR-30 responsive element within Serpine1 3'UTR and interfere with TDMD. TDMD suppression increases miR-30b/c levels and boosts their activity towards other targets, modulating gene expression and cellular phenotypes (i.e., cell cycle re-entry and apoptosis). In conclusion, a sophisticated regulatory layer of miRNA and gene expression mediated by specific endogenous targets exists in mammalian cells.
Structural basis of cell wall anchoring by SLH domains in Paenibacillus alvei
Authors: Blackler Ryan J. , López-Guzmán Arturo , Hager Fiona F. , Janesch Bettina , Martinz Gudrun , Gagnon Susannah M. L. , Haji-Ghassemi Omid , Kosma Paul , Messner Paul , Schäffer Christina , Evans Stephen V. 
Published: August 2018

AbstractSelf-assembling protein surface (S-) layers are common cell envelope structures of prokaryotes and have critical roles from structural maintenance to virulence. S-layers of Gram-positive bacteria are often attached through the interaction of S-layer homology (SLH) domain trimers with peptidoglycan-linked secondary cell wall polymers (SCWPs). Here we present an in-depth characterization of this interaction, with co-crystal structures of the three consecutive SLH domains from the Paenibacillus alvei S-layer protein SpaA with defined SCWP ligands. The most highly conserved SLH domain residue SLH-Gly29 is shown to enable a peptide backbone flip essential for SCWP binding in both biophysical and cellular experiments. Furthermore, we find that a significant domain movement mediates binding by two different sites in the SLH domain trimer, which may allow anchoring readjustment to relieve S-layer strain caused by cell growth and division.
A highly reactive precursor in the iron sulfide system
Authors: Matamoros-Veloza Adriana , Cespedes Oscar , Johnson Benjamin R. G. , Stawski Tomasz M. , Terranova Umberto , de Leeuw Nora H. , Benning Liane G. 
Published: August 2018

AbstractIron sulfur (Fe–S) phases have been implicated in the emergence of life on early Earth due to their catalytic role in the synthesis of prebiotic molecules. Similarly, Fe–S phases are currently of high interest in the development of green catalysts and energy storage. Here we report the synthesis and structure of a nanoparticulate phase (FeSnano) that is a necessary solid-phase precursor to the conventionally assumed initial precipitate in the iron sulfide system, mackinawite. The structure of FeSnano contains tetrahedral iron, which is compensated by monosulfide and polysulfide sulfur species. These together dramatically affect the stability and enhance the reactivity of FeSnano.
Ultra-narrow-band near-infrared thermal exciton radiation in intrinsic one-dimensional semiconductors
Authors: Nishihara Taishi , Takakura Akira , Miyauchi Yuhei , Itami Kenichiro 
Published: August 2018

AbstractThermal radiation is the most primitive light emission phenomenon of materials. Broadband radiation from red-hot materials is well known as the kick-starter phenomenon of modern quantum physics in the early twentieth century; even nowadays, its artificial control plays a central role in modern science and technology. Herein, we report the fundamental thermal radiation properties of intrinsic one-dimensional semiconductors and metals, which have not been elucidated because of significant technical challenges. We observed narrow-band near-infrared radiation from semiconducting single-walled carbon nanotubes at 1000–2000 K in contrast to its broadband metallic counterpart. We confirm that the ultra-narrow-band radiation is enabled by the thermal generation of excitons that are hydrogen-like neutral exotic atoms comprising mutually bound electrons and holes. Our findings uncover the robust quantum correlations in intrinsic one-dimensional semiconductors even at 2000 K; additionally, the findings provide an opportunity for excitonic optothermal engineering toward the realization of efficient thermophotovoltaic energy harvesting.
Neural correlates of video game empathy training in adolescents: a randomized trial
Authors: Kral Tammi R. A. , Stodola Diane E. , Birn Rasmus M. , Mumford Jeanette A. , Solis Enrique , Flook Lisa , Patsenko Elena G. , Anderson Craig G. , Steinkuehler Constance , Davidson Richard J. 
Published: August 2018

AbstractThe ability to understand emotional experiences of others, empathy, is a valuable skill for effective social interactions. Various types of training increase empathy in adolescents, but their impact on brain circuits underlying empathy has not been examined. Video games provide a unique medium familiar and engaging to adolescents and can be used to deliver training at scale. We developed an empathy training video game, Crystals of Kaydor (Crystals), and investigated whether playing Crystals increases empathic accuracy (EA) and related brain activation in adolescents (N = 74; 27 female; mean age(sd) = 12.8(0.7) years; age range 11–14 years). Participants completed a resting state functional MRI (rs-fMRI) scan and an EA task during an fMRI scan before and after 2 weeks of daily gameplay with either the empathy training game, Crystals (N = 34), or the commercial video game Bastion (N = 40), an active control condition. There were no group differences in EA improvement following gameplay, however, engagement with training aspects of Crystals was associated with a higher increase in EA-related activation in right temporoparietal junction following gameplay. Moreover, rs-fMRI connectivity in empathy-related brain circuits (posterior cingulate–medial prefrontal cortex; MPFC) was stronger after Crystals gameplay compared to Bastion. The more individuals’ EA increased following Crystals versus Bastion, the stronger their rs-fMRI connectivity in brain circuits relevant for emotion regulation (amygdala-MPFC). These findings suggest that a video game designed to increase empathic accuracy produces behaviorally-relevant, functional neural changes in fewer than 6 h of gameplay in adolescents.
Downstream Products are Potent Inhibitors of the Heparan Sulfate 2-O-Sulfotransferase
Authors: Thieker David F. , Xu Yongmei , Chapla Digantkumar , Nora Chelsea , Qiu Hong , Felix Thomas , Wang Lianchun , Moremen Kelley W. , Liu Jian , Esko Jeffrey D. , Woods Robert J. 
Published: August 2018

AbstractHeparan Sulfate (HS) is a cell signaling molecule linked to pathological processes ranging from cancer to viral entry, yet fundamental aspects of its biosynthesis remain incompletely understood. Here, the binding preferences of the uronyl 2-O-sulfotransferase (HS2ST) are examined with variably-sulfated hexasaccharides. Surprisingly, heavily sulfated oligosaccharides formed by later-acting sulfotransferases bind more tightly to HS2ST than those corresponding to its natural substrate or product. Inhibition assays also indicate that the IC50 values correlate simply with degree of oligosaccharide sulfation. Structural analysis predicts a mode of inhibition in which 6-O-sulfate groups located on glucosamine residues present in highly-sulfated oligosaccharides occupy the canonical binding site of the nucleotide cofactor. The unexpected finding that oligosaccharides associated with later stages in HS biosynthesis inhibit HS2ST indicates that the enzyme must be separated temporally and/or spatially from downstream products during biosynthesis in vivo, and highlights a challenge for the enzymatic synthesis of lengthy HS chains in vitro.