1,959 research outputs found
On a game of chance in Marc Elsberg’s thriller “GREED”
A (possibly illegal) game of chance, which is described in Chap. 14 of Marc Elsberg’s thriller “GREED”, seems to offer an excellent chance of winning. However, as the gambling starts and evolves over several rounds, the actual experience of the vast majority of the gamblers in a pub is strikingly different. We provide an analysis of this specific game and several of its variants by elementary tools of probability. Thus we also encounter an interesting threshold phenomenon, which is related to the transition from a profit zone to a loss area. Our arguments are motivated and illustrated by numerical calculations with Python
Operation characteristics of piezoelectric quartz tuning forks in high magnetic fields at liquid helium temperatures
Piezoelectric quartz tuning forks are investigated in view of their use as
force sensors in dynamic mode scanning probe microscopy at temperatures down to
1.5 K and in magnetic fields up to 8 T. The mechanical properties of the forks
are extracted from the frequency dependent admittance and simultaneous
interferometric measurements. The performance of the forks in a cryogenic
environment is investigated. Force-distance studies performed with these
sensors at low temperatures are presented
Role of anion exchangers in Cl- and HCO3- secretion by the human airway epithelial cell line Calu-3
Despite the importance of airway surface liquid pH in the lung's defenses against infection, the mechanism of airway HCO3- secretion remains unclear. Our aim was to assess the contribution of apical and basolateral Cl-/HCO3- exchangers to Cl- and HCO3- transport in the Calu-3 cell line, derived from human airway submucosal glands. Changes in intracellular pH (pH(i)) were measured following substitution of Cl- with gluconate. Apical Cl- substitution led to an alkalinization in forskolin-stimulated cells, indicative of Cl-/HCO3- exchange. This was unaffected by the anion exchange inhibitor DIDS but inhibited by the CFTR blocker CFTRinh-172, suggesting that the HCO3- influx might occur via CFTR, rather than a solute carrier family 26 (SLC26) exchanger, as recently proposed. The anion selectivity of the recovery process more closely resembled that of CFTR than an SLC26 exchanger, and quantitative RT-PCR showed only low levels of SLC26 exchanger transcripts relative to CFTR and anion exchanger 2 (AE2). For pHi to rise to observed values (similar to 7.8) through HCO3- entry via CFTR, the apical membrane potential must reverse to at least + 20 mV following Cl- substitution; this was confirmed by perforated-patch recordings. Substitution of basolateral Cl- evoked a DIDS-sensitive alkalinization, attributed to Cl-/HCO3- exchange via AE2. This appeared to be abolished in forskolin-stimulated cells but was unmasked by blocking apical efflux of HCO3- via CFTR. We conclude that Calu-3 cells secrete HCO3- predominantly via CFTR, and, contrary to previous reports, the basolateral anion exchanger AE2 remains active during stimulation, providing an important pathway for basolateral Cl- uptake
Triaxiality in galaxy clusters: Mass versus Potential reconstructions
Accounting for the triaxial shapes of galaxy clusters will become important
in the context of upcoming cosmological surveys. We show that, compared to the
gas density distribution, the cluster gravitational potential can be better
characterised by a simple 3D model and is more robust against fluctuations.
Perturbations in the gas density distribution can have a substantial influence
on the derived thermodynamic properties, while cluster potentials are smooth
and well-approximated by a spheroidal model. We use a statistical sample of 85
galaxy clusters from a large cosmological hydrodynamical simulation to
investigate cluster shapes as a function of radius. In particular, we examine
the shape of isodensity and isopotential shells and analyze how it is affected
by the choice of component (gas vs. potential), substructure removal (for the
gas density) and the definition of the computation domain (interior vs.
shells). We find that the orientation and axis ratios of gas isodensity
contours are degenerate with the presence of substructures and unstable against
fluctuations. We observe that, as the derived cluster shape depends on the
method used for removing the substructures, thermodynamic properties extracted
from e.g. X-ray emissivity profiles suffer from this additional, often
underestimated bias. In contrast, the shape reconstruction of the potential is
largely unaffected by these factors and converges towards simple geometric
models for both relaxed and dynamically active clusters. The observation that
cluster potentials are better represented by simple geometrical models and
reconstructed with a low level of systematics for both dynamically active and
relaxed clusters suggests that by characterising galaxy clusters by their
potential rather than by their mass, dynamically active and relaxed clusters
could be combined in cosmological studies, improving statistics and lowering
scatter.Comment: Updated with referee's comments, revised version submitted to A&A, 16
pages, 14 figure
Characterizing galaxy clusters by their gravitational potential: systematics of cluster potential reconstruction
Context. Biases in mass measurements of galaxy clusters are one of the major
limiting systematics in constraining cosmology with clusters. Aims. We aim to
demonstrate that the systematics associated with cluster gravitational
potentials are smaller than the hydrostatic mass bias and that cluster
potentials could therefore be a good alternative to cluster masses in
cosmological studies. Methods. Using cosmological simulations of galaxy
clusters, we compute the biases in the hydrostatic mass (HE mass) and those in
the gravitational potential, reconstructed from measurements at X-ray and
millimeter wavelengths. In particular, we investigate the effects of the
presence of substructures and of non-thermal pressure support on both the HE
mass and the reconstructed potential. Results. We find that the bias in the
reconstructed potential (6%) is less than that of the HE mass (13%), and that
the scatter in the reconstructed potential decreases by about 35% with respect
to that in the HE mass. Conclusions. This study shows that characterizing
galaxy clusters by their gravitational potential is a promising alternative to
using cluster masses in cluster cosmology.Comment: submitted to the journal A&A, 16 pages, 26 figure
Dualisation of the General Scalar Coset in Supergravity Theories
The dualised formulation of the symmetric space sigma model is peformed for a
general scalar coset G/K where G is a maximally non-compact group and K is it's
maximal compact subgroup.By using the twisted self-duality condition the
general form of the first-order equations are obtained.The results are applied
to the example of SL(2,R)/SO(2) scalar manifold of the IIB supergravity.Comment: 22 page
Experimental measurement of stress at a four-domain junction in lead zirconate titanate
A junction between two lamellar bands of ferroelectric domains in a lead zirconate titanate (PZT) ceramic is analysed using Kikuchi diffraction patterns in the transmission electron microscope. Indexing of the diffraction patterns allowed the determination of the 3D relative orientation of the 4 different domains at the junction and thus the characterisation of the domain boundaries. The local c/a ratio could also be determined from the misorientations at the domain boundaries. Analysis of the data showed that large stresses were concentrated at the junction, and that this is inevitable at such band junctions. Such stress concentrations could act as nuclei for cracking of the ceramic under additional loading in service, perhaps particularly as a consequence of extended electromechanical cycling. Moreover, the stresses would increase with increasing c/a making the issues all the more serious for Ti-rich compositions having larger c/a ratios
Diamond detector preparation for high intensity beam monitoring and high precision T0 determination
Growth and texture of Spark Plasma Sintered Al2O3 ceramics: a combined analysis of X-rays and Electron Back Scatter Diffraction
Textured alumina ceramics were obtained by Spark Plasma Sintering (SPS) of
undoped commercial a-Al2O3 powders. Various parameters (density, grain growth,
grain size distribution) of the alumina ceramics, sintered at two typical
temperatures 1400{\deg}C and 1700{\deg}C, are investigated. Quantitative
textural and structural analysis, carried out using a combination of Electron
Back Scattering Diffraction (EBSD) and X-ray diffraction (XRD), are represented
in the form of mapping, and pole figures. The mechanical properties of these
textured alumina ceramics include high elastic modulus and hardness value with
high anisotropic nature, opening the door for a large range of applicationsComment: 16 pages, 6 figures, submitted to J. Appl. Phy
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