3C 295, a cluster and its cooling flow at z=0.46

We present ROSAT HRI data of the distant and X-ray luminous (L_x(bol)=2.6^ {+0.4}_{-0.2} 10^{45}erg/sec) cluster of galaxies 3C 295. We fit both a one-dimensional and a two-dimensional isothermal beta-model to the data, the latter one taking into account the effects of the point spread function (PSF). For the error analysis of the parameters of the two-dimensional model we introduce a Monte-Carlo technique. Applying a substructure analysis, by subtracting a cluster model from the data, we find no evidence for a merger, but we see a decrement in emission South-East of the center of the cluster, which might be due to absorption. We confirm previous results by Henry & Henriksen(1986) that 3C 295 hosts a cooling flow. The equations for the simple and idealized cooling flow analysis presented here are solely based on the isothermal beta-model, which fits the data very well, including the center of the cluster. We determine a cooling flow radius of 60-120kpc and mass accretion rates of dot{M}=400-900 Msun/y, depending on the applied model and temperature profile. We also investigate the effects of the ROSAT PSF on our estimate of dot{M}, which tends to lead to a small overestimate of this quantity if not taken into account. This increase of dot{M} (10-25%) can be explained by a shallower gravitational potential inferred by the broader overall profile caused by the PSF, which diminishes the efficiency of mass accretion. We also determine the total mass of the cluster using the hydrostatic approach. At a radius of 2.1 Mpc, we estimate the total mass of the cluster (M{tot}) to be (9.2 +/- 2.7) 10^{14}Msun. For the gas to total mass ratio we get M{gas}/M{tot} =0.17-0.31, in very good agreement with the results for other clusters of galaxies, giving strong evidence for a low density universe.Comment: 26 pages, 7 figures, accepted for publication in Ap

X-ray Spectroscopy of Cooling Clusters

We review the X-ray spectra of the cores of clusters of galaxies. Recent high resolution X-ray spectroscopic observations have demonstrated a severe deficit of emission at the lowest X-ray temperatures as compared to that expected from simple radiative cooling models. The same observations have provided compelling evidence that the gas in the cores is cooling below half the maximum temperature. We review these results, discuss physical models of cooling clusters, and describe the X-ray instrumentation and analysis techniques used to make these observations. We discuss several viable mechanisms designed to cancel or distort the expected process of X-ray cluster cooling.Comment: To appear in Physics Reports, 71 pages, 20 figure

What is a Cool-Core Cluster? A Detailed Analysis of the Cores of the X-ray Flux-Limited HIFLUGCS Cluster Sample

We use the largest complete sample of 64 galaxy clusters (HIghest X-ray FLUx Galaxy Cluster Sample) with available high-quality X-ray data from Chandra, and apply 16 cool-core diagnostics to them, some of them new. We also correlate optical properties of brightest cluster galaxies (BCGs) with X-ray properties. To segregate cool core and non-cool-core clusters, we find that central cooling time, t_cool, is the best parameter for low redshift clusters with high quality data, and that cuspiness is the best parameter for high redshift clusters. 72% of clusters in our sample have a cool core (t_cool < 7.7 h_{71}^{-1/2} Gyr) and 44% have strong cool cores (t_cool <1.0 h_{71}^{-1/2} Gyr). For the first time we show quantitatively that the discrepancy in classical and spectroscopic mass deposition rates can not be explained with a recent formation of the cool cores, demonstrating the need for a heating mechanism to explain the cooling flow problem. [Abridged]Comment: 45 pages, 19 figures, 7 tables. Accepted for publication in A&A. Contact Person: Rupal Mittal ([email protected]

Pectic polysaccharides modulate colloidal stability and astringency perception of bottle aged Cabernet Sauvignon wines

Gefördert im Rahmen des Projekts DEA

RELEVANCE OF ETHICAL GUIDELINES FOR ARTIFICIAL INTELLIGENCE – A SURVEY AND EVALUATION

Ethics for artificial intelligence (AI) is a topic of growing practical relevance. Many people seem to believe that AI could render jobs obsolete in the future. Others wonder who is in charge for the actions of AI systems they encounter. Providing and prioritizing ethical guidelines for AI is therefore an important measure for providing safeguards and increasing the acceptance of this technology. The aim of this research is to survey ethical guidelines for the handling of AI in the ICT industry and evaluate them with respect to their relevance. For this goal, first, an overview of AI ethics is derived from the literature, with a focus on classical Western ethical theories. From this, a candidate set of important ethical guidelines is developed. Then, qualitative interviews with experts are conducted for in-depth feedback and ranking of these guidelines. Furthermore, an online survey is performed in order to more representatively weight the ethical guidelines in terms of importance among a broader audience. Combining both studies, a prioritization matrix is created using the weights from the experts and the survey participants in order to synthesize their votes. Based on this, a ranked catalogue of ethical guidelines for AI is created, and novel avenues for research on AI ethics are presented

The science behind the magic?. The relation of the Harry Potter “Sorting Hat Quiz” to personality and human values

The Harry Potter series describes the adventures of a boy and his peers in a fictional world at the “Hogwarts School of Witchcraft and Wizardry”. In the series, pupils get appointed to one of four groups (Houses) at the beginning of their education based on their personality traits. The author of the books has constructed an online questionnaire that allows fans to find out their House affiliation. Crysel, Cook, Schember, and Webster (2015) argued that being sorted into a particular Hogwarts House through the Sorting Hat Quiz is related to empirically established personality traits. We replicated their study while improving on sample size, methods, and analysis. Although our results are similar, effect sizes are small overall, which attenuates the claims by Crysel et al. The effect vanishes when restricting the analysis to participants who desired, but were not sorted into a particular House. On a theoretical level, we extend previous research by also analysing the relation of the Hogwarts Houses to Schwartz’s Basic Human Values but find only moderate or no relation

Radial structure, inflow and central mass of stationary radiative galaxy clusters

We analyse the radial structure of self-gravitating spheres consisting of multiple interpenetrating fluids, such as the X-ray emitting gas and the dark halo of a galaxy cluster. In these dipolytropic models, the adiabatic dark matter sits in equilibrium, while the gas develops a gradual, smooth, quasi-stationary cooling flow. Both affect and respond to the collective gravitational field. We find that all subsonic, radially continuous, steady solutions require a non-zero minimum central point mass. For Mpc-sized haloes with 7–10 effective degrees of freedom (F2), the minimum central mass is compatible with observations of supermassive black holes. Smaller gas mass influxes enable smaller central masses for wider ranges of F2. The halo comprises a sharp spike around the central mass, embedded within a core of nearly constant density (at 101–102.5 kpc scales), with outskirts that attenuate and naturally truncate at finite radius (several Mpc). The gas density resembles a broken power law in radius, but the temperature dips and peaks within the dark core. A finite minimum temperature occurs due to gravitational self-warming, without cold mass dropout nor needing regulatory heating. X-ray emission from the intracluster medium mimics a β-model plus bright compact nucleus. Near-sonic points in the gas flow are bottlenecks to the allowed steady solutions; the outermost are at kpc scales. These sites may preferentially develop cold mass dropout during strong perturbations off equilibrium. Within the sonic point, the profile of gas specific entropy is flatter than s∝r1/2, but this is a shallow ramp and not an isentropic core. When F2 is large, the inner halo spike is only marginally Jeans stable in the central parsec, suggesting that a large non-linear disturbance could trigger local dark collapse on to the central object

Exploring Digital Transformation’s Impact on Organizational Identity with an Archetype Framework

Recently, IS scholars draw attention on the inter-relation between digital transformation and organiza-tional identity. However, little is known about how digital transformation processes affect organizations’ identity change. We assume to grasp this complex phenomenon by distinguishing different manifesta-tions of digital transformation related to organiza-tional structures and modes of value creation, expect-ing each to have distinctive effects on changing or-ganizational identity. We capture these differing ef-fects in an archetype framework as a heuristic for future research

Fabrication of biomimetic antibacterial titanium surfaces by hydrothermal oxidation

Within this paper we demonstrate a novel approach to create antibacterial nanostructures on the implant material titanium grade 23 by a high-pressure oxidation method. Titanium samples were oxidized and resulting nanostructures were characterized using scanning electron microscopy and contact angle measurements. Antibacterial properties were tested using Escherichia coli and Bacillus subtilis as common lab strains. In addition, cytotoxicity was determined according to ISO 10993-5 standards. Results reveal that the fabricated nanostructures have similar antibacterial properties known from different insect wings like dragonflies or cicadas and have no cytotoxic effect

Potential and Limitations of Research Battery Cell Types for Electrochemical Data Acquisition

Developing new electrode materials and/or electrolytes for lithium-ion batteries requires reliable electrochemical testing thereof. For this purpose, in academic research typically hand-made coin-type cells are assembled. Their advantage is a rather cheap and facile assembly, and possibility to prepare full-cells as well as half-cells, meaning cathode-anode or electrode-elemental lithium configurations. Critical parameters for testing data quality and the potential and limitations of cell tests in half-cell configuration are discussed. Further, on the basis of a round robin test, using highly homogenous commercial electrodes, where graphite is used as anode and LiNi0.33Mn0.33Co0.33O2 (NMC111) as the cathode material, it is shown that data acquired is highly influenced by assembling parameters. Besides known variables such as the amount of electrolyte or electrode positioning, the proper height of the cell stack and the steel grade of the housing material are identified as decisive variables. Finally, it is demonstrated that under proper conditions coin cells can show a great cycle stability of >2200 cycles using 1C as dis-/charge rate while retaining a capacity of 80%. This performance is close to pouch-type cells containing the same electrodes and electrolyte, which were used as a benchmark system and showed >3500 cycles of lifetime