We present a metric condition $\TTMetric$ which describes the geometry of classical small cancellation groups and applies also to other known classes of groups such as two-dimensional Artin groups. We prove that presentations satisfying condition $\TTMetric$ are diagrammatically reducible in the sense of Sieradski and Gersten. In particular, we deduce that the standard presentation of an Artin group is aspherical if and only if it is diagrammatically reducible. We show that, under some extra hypotheses, $\TTMetric$-groups have quadratic Dehn functions and solvable conjugacy problem. In the spirit of Greendlinger's lemma, we prove that if a presentation P = 〈X| R〉 of group G satisfies conditions $\TTMetric -C'(\frac {1}{2})$, the length of any nontrivial word in the free group generated by X representing the trivial element in G is at least that of the shortest relator. We also introduce a strict metric condition $\TTMetricStrict$, which implies hyperbolicity.

The recent discovery of several late Linearbandkeramik (LBK) sites in Central Europe, including Vráble in south-west Slovakia, has revealed evidence for increasing diversity in Neolithic mortuary practices, which may reflect inter-community war and socio-political crisis at the end of the LBK. Here, the authors combine osteological and radiocarbon analyses of inhumations from Vráble. Rather than a straightforward sign of inter-community conflict and war, this development reflects a culmination of internal conflict and a diversification in the ritual treatment of human bodies. The emerging variability in LBK methods of manipulating and depositing dead bodies can be interpreted as an experimental approach in how to negotiate social conflicts and community boundaries.

Our research at the large LBK settlement site of Vráble, southwest Slovakia, revealed dynamics of social integration and antagonisms unfolding in an agglomerated, early farming community. During its lifespan from 5250 to 4950 bc, it constantly grew until around 5050 bc it was inhabited by about 70 contemporaneous longhouses. We found that Vráble consisted of markedly autonomous farmstead units that were held together by village-wide social institutions including sharing and communality. Nevertheless, from the beginning, a contradiction between particular farmstead and collective village and neighbourhood interests existed and rose. Towards the end of the village's existence, around 5075 bc an elaborate enclosure was constructed around one of the three neigbourhoods, actively blocking contact with the others. Along this enclosure, human bodies were deposited, showing a social categorization that we interpret as relating to social inequality. This rising level of conflict and emerging social inequality was, we argue, not sustainable under the conditions of early farming societies and led to the village's abandonment at 4950 bc.

The flow induced by a disk rotating at the bottom of a cylindrical tank is characterised using numerical techniques – computation of steady solutions or time-averaged two-dimensional and three-dimensional direct simulations – as well as laser-Doppler velocimetry measurements. Axisymmetric steady solutions reveal the structure of the toroidal flow located at the periphery of the central solid body rotation region. When viewed in a meridional plane, this flow cell is found to be bordered by four layers, two at the solid boundaries, one at the free surface and one located at the edge of the central region, which possesses a sinuous shape. The cell intensity and geometry are determined for several fluid-layer aspect ratios; the flow is shown to depend very weakly on Froude number (associated with surface deformation) or on Reynolds number if sufficiently large. The paper then focuses on the high Reynolds number regime for which the flow has become unsteady and three-dimensional while the surface is still almost flat. Direct numerical simulations show that the averaged flow shares many similarities with the above steady axisymmetric solutions. Experimental measurements corroborate most of the numerical results and also allow for the spatio-temporal characterisation of the fluctuations, in particular the azimuthal structure and frequency spectrum. Mean azimuthal velocity profiles obtained in this transitional regime are eventually compared to existing theoretical models.

Understanding the conformational dynamics of CRISPR (clustered regularly interspaced short palindromic repeat)–Cas9 is of the utmost importance for improving its genome editing capability. Here, molecular dynamics simulations performed using Anton-2 – a specialized supercomputer capturing micro-to-millisecond biophysical events in real time and at atomic-level resolution – reveal the activation process of the endonuclease Cas9 toward DNA cleavage. Over the unbiased simulation, we observe that the spontaneous approach of the catalytic domain HNH to the DNA cleavage site is accompanied by a remarkable structural remodeling of the recognition (REC) lobe, which exerts a key role for DNA cleavage. Specifically, the significant conformational changes and the collective conformational dynamics of the REC lobe indicate a mechanism by which the REC1–3 regions ‘sense’ nucleic acids, ‘regulate’ the HNH conformational transition, and ultimately ‘lock’ the HNH domain at the cleavage site, contributing to its catalytic competence. By integrating additional independent simulations and existing experimental data, we provide a solid validation of the activated HNH conformation, which had been so far poorly characterized, and we deliver a comprehensive understanding of the role of REC1–3 in the activation process. Considering the importance of the REC lobe in the specificity of Cas9, this study poses the basis for fully understanding how the REC components control the cleavage of off-target sequences, laying the foundation for future engineering efforts toward improved genome editing.

In our contribution we present and analyze implementation of the resistive switching structures for logic application based on Zadeh fuzzy logic. Resistive switching structures based on HfOx and TaOx were connected in an anti-serial configuration (complementary resistive switch). The complementary resistive switches integrated into logic circuit for Min-Max function implementation were analyzed using quasi-static voltage sweeps. We have shown that the accuracy of the Min/Max function determination depends on the ratio of the high and low resistivity states of the single switches. Determination of the Min/Max values is relevant only above the threshold voltage of the resistive structures. Reproducibility of the Min/Max function constructed from the resistive switching structures is demonstrated.

The Pristine survey uses narrow-band photometry on the region of the Ca II H & K absorption lines to find extremely metal-poor stars. With a spectroscopic follow-up sample of 205 stars in the magnitude range 14 < V < 18, we compute the success rates for finding extremely metal-poor stars and modify the selection criteria used to select stars for follow-up. This reduces the sample to 149 stars, and from these we report success rates of 22% for recovering stars with [Fe/H] < −3.0 and 70% for [Fe/H] < −2.5. When compared to previous works that search for extremely metal-poor stars, the success rates of Pristine show an improvement in efficiency by a factor of ~4 − 5.

The present study explores the effect of a magnetically modified halloysite (mHNT) surface on the structure and properties of biodegradable polymer nanocomposites based on poly ɛ-caprolactone (PCL). Halloysite nanotubes (HNTs) have been modified by a scalable and tunable procedure using magnetic Fe oxide particles prepared by microwave-assisted synthesis fromferrous sulfate at high pH. The HNT content in composites prepared in melt varied from 5 to 30 wt.%. Application of magnetically modified HNT to PCL resulted in the formation of soft magnetic materials. Analyses of the nanocomposite structure revealed that both natural and magnetized HNTs, as well as free magnetite particles are dispersed uniformly in the polymer matrix. Investigation of the mechanical and physical properties confirmed that the reinforcing ability of HNTs was not affected by magnetic modification.

Research within the history of economic thought has focused only little on the development of economics under dictatorship. This paper attempts to show how a country with a relatively large and internationally established community of social scientists in the 1920s, the Soviet Union, was subjected to repression. We tell this story through the case of Isaak Il’ich Rubin, a prominent Russian economist and historian of economic thought, who in the late 1920s was denounced by rival scholars and repressed by the political system. By focusing not only on his life and work, but also on that of his opponents and institutional clashes, we show how the decline of a social science tradition in Russia and the USSR as well as the Stalinization of Soviet social sciences emerged as a process over time. We analyze the complex interplay of ideas, scholars, and their institutional context, and conclude that subsequent repression was arbitrary, suggesting that no clear survival or career strategy existed in the Stalinist system, due to a situation of fundamental uncertainty.

Different from previous triennial reports, this report covers the activities of IAU Commission 36 ‘Theory of Stellar Atmospheres’ over the past six years†, and will be the last report from the ‘old’ Commission 36. After the General Assembly in Honolulu (August 2015), a new Commission ‘Stellar and Planetary Atmospheres’ (C.G5, under Division G, ‘Stars and Stellar Physics’) has come into life, and will continue our work devoted to the outer envelopes of stars, as well as extend it to the atmospheres of planets (see Sect. 4).

The business meeting of IAU Commission 36 took place during the GA in Beijing on August 27th, and its major topic was the re-structuring of the IAU Divisions and consequences for our Commission. The meeting was conducted by the new president, Joachim Puls, since the past president (still in charge during the GA), Martin Asplund, could not participate.

The epiphytic lichen Evernia prunastri is sensitive to air pollution and reacted by total retreat to the worsening of air quality during the peak of SO2 pollution in Central Europe (1950s–1990). Since 1990, after a significant decrease in air pollution, epiphytic lichens recolonized previously polluted areas, including E. prunastri. We investigated the physiological status of E. prunastri, transplanted for six months in 34 sites in the urban area of Bratislava (Slovakia) under current conditions. The content of chlorophylls, cortical and medullar secondary metabolites and soluble proteins were explored. We then examined the relationship of these parameters with the environmental quality status, reflected by the diversity of epiphytic lichens. The results showed that the physiological status of E. prunastri did not change significantly after exposure. Positive correlations were found between lichen diversity in the sampling sites and physiological parameters (photosynthetic pigments and phaeophytinization quotient) in the transplants. Transplants from sampling sites with a greater proportion of nitrophilous lichens displayed a decrease in photosynthetic pigments. Sites where E. prunastri naturally occurred had a lower proportion of nitrophilous species in comparison to sites where E. prunastri was not present. This suggests that the indicator species E. prunastri may also recolonize sites with low eutrophication in urban environments under decreased air pollution, and the information on its presence can help to assess the pressure caused by nitrogen excess.

The following study will present findings on the validity of the adaptation of the Burger and Cooper's Desirability of Control Scale into Spanish. Two samples are present: the first involving 1,999 people to study their psychometric properties. In the second sample, 111 people were included to estimate test/ retest reliability. Cultural adaptation was performed using the translation & back-translation method. Item analysis, internal consistency and test/re-test reliability were assessed, then evidence of the validity of the internal structure was determined by using exploratory and confirmatory factor analysis. Subject recruitment was performed to gather the 1,999 subjects stratified by age, gender quotas as designed in the sampling plan. Of the subjects, 51% were female, average age of 45 years old (SD = 17.5). All items from the original scale were understood correctly, while five items presented ceiling effect. Cronbach's alpha = .736 and a test-retest correlation r = .713 were obtained. The factor structure indicated the presence of four dimensions: forecast, autonomy, power and influence and reactance which were reassured in the confirmatory analysis (x2/df = 4.805, CFI =.932, TLI =.954, RMSEA = .062). The basic dimensions of the scale have shown to be stable and well-defined, though not perfect. The scope, possible applications of the scale and further research are later proposed and discussed.

A rich research history exists for crystalline growth by vapor–liquid–solid (VLS) methods, but not for amorphous growth. Yet VLS growth in the absence of crystallographic influences provides an ideal laboratory for exploring surface energy effects, including the role of line tension. We discuss the growth of amorphous silica nanowires from indium droplets by a modified VLS method. Multiple strands issue from each droplet, each strand having <1% (i.e., < 5 nm) of the radius of the droplet. We analyze the surface forces for this system, including line tension, and combine data in a novel way to estimate the surface energy of silica, the interfacial energy of liquid indium on silica, and the line tension at the three-phase boundary. The results suggest that the growth of these silica strands would be impossible without the presence of a negative line tension that also serves to stabilize the strand radii against perturbation.