Wess-Zumino-Witten model off criticality

We study the renormalization group flow properties of the Wess-Zumino-Witten model in the region of couplings between $g^2=0$ and $g^2=4\pi/k$, by evaluating the two-loop Zamolodchikov's $c$-function. We also discuss the region of negative couplings.Comment: 8 page

Human-Computer Interaction for BCI Games: Usability and User Experience

Brain-computer interfaces (BCI) come with a lot of issues, such as delays, bad recognition, long training times, and cumbersome hardware. Gamers are a large potential target group for this new interaction modality, but why would healthy subjects want to use it? BCI provides a combination of information and features that no other input modality can offer. But for general acceptance of this technology, usability and user experience will need to be taken into account when designing such systems. This paper discusses the consequences of applying knowledge from Human-Computer Interaction (HCI) to the design of BCI for games. The integration of HCI with BCI is illustrated by research examples and showcases, intended to take this promising technology out of the lab. Future research needs to move beyond feasibility tests, to prove that BCI is also applicable in realistic, real-world settings

Diagnostic performance of transthyretin measurement in fat tissue of patients with ATTR amyloidosis

In this article, the diagnostic performance of a transthyretin (TTR) ELISA for detection and characterization of transthyretin-derived (ATTR) amyloid in abdominal subcutaneous fat tissue was studied. Fat tissue specimens were analyzed of 38 patients with ATTR amyloidosis, 70 controls, and 17 carriers of a TTR mutation. Amyloid amount was graded semi-quantitatively in Congo red-stained specimens (0-4+). Amyloid was extracted from tissue in guanidine, and the TTR concentration was measured using a sandwich TTR-ELISA. The TTR concentration of patients with ATTR amyloidosis (mean 0.84 ng/mg fat tissue) was significantly higher than controls (p<0.001). With a TTR concentration of 0.13 ng/mg fat tissue as cut-off value, 32 of the 38 ATTR patients were identified resulting in a sensitivity of 84%. Sixty-seven of the 70 controls had values below the cut-off value resulting in a specificity of 96%. Thus, measuring TTR in fat tissue is useful for detecting ATTR amyloidosis and for characterizing amyloid as ATTR type

Lagrangian dynamics and statistical geometric structure of turbulence

The local statistical and geometric structure of three-dimensional turbulent flow can be described by properties of the velocity gradient tensor. A stochastic model is developed for the Lagrangian time evolution of this tensor, in which the exact nonlinear self-stretching term accounts for the development of well-known non-Gaussian statistics and geometric alignment trends. The non-local pressure and viscous effects are accounted for by a closure that models the material deformation history of fluid elements. The resulting stochastic system reproduces many statistical and geometric trends observed in numerical and experimental 3D turbulent flows, including anomalous relative scaling.Comment: 5 pages, 5 figures, final version, publishe

Single crystal growth and physical properties of the layered arsenide BaRh_2As_2

Single crystals of BaRh_2As_2 have been synthesized from a Pb flux. We present the room temperature crystal structure, single crystal x-ray diffraction measurements as a function of temperature T, anisotropic magnetic susceptibility \chi versus T, electrical resistivity in the ab-plane \rho versus T, Hall coefficient versus T and magnetic field H, and heat capacity C versus T measurements on the crystals. The single crystal structure determination confirms that BaRh_2As_2 forms in the tetragonal ThCr_2Si_2 type structure (space group I4/mmm) with lattice parameters a = b = 4.0564(6)\AA and c = 12.797(4) \AA. Band structure calculations show that BaRh_2As_2 should be metallic with a small density of states at the Fermi energy N(E_ F) = 3.49 states/eV f.u. (where f.u. \equiv formula unit) for both spin directions. \rho(T) data in the ab-plane confirm that the material is indeed metallic with a residual resistivity \rho(2K) = 29 \mu \Omega cm, and with a residual resistivity ratio \rho(310K)/\rho(2K) = 5.3. The observed \chi(T) is small (\sim 10^{-5} cm^3/mol) and weakly anisotropic with \chi_{ab}/\chi_ c \approx 2. The C(T) data indicate a small density of states at the Fermi energy with the low temperature Sommerfeld coefficient \gamma = 4.7(9) mJ/mol K^2. There are no indications of superconductivity, spin density wave, or structural transitions between 2K and 300K. We compare the calculated density of states versus energy of BaRh_2As_2 with that of BaFe_2As_2.Comment: Accepted for publication in Phys. Rev.

Ancient Yersinia pestis genomes from across Western Europe reveal early diversification during the First Pandemic (541–750)

The first historically documented pandemic caused by Yersinia pestis began as the Justinianic Plague in 541 within the Roman Empire and continued as the so-called First Pandemic until 750. Although paleogenomic studies have previously identified the causative agent as Y. pestis, little is known about the bacterium’s spread, diversity, and genetic history over the course of the pandemic. To elucidate the microevolution of the bacterium during this time period, we screened human remains from 21 sites in Austria, Britain, Germany, France, and Spain for Y. pestis DNA and reconstructed eight genomes. We present a methodological approach assessing single-nucleotide polymorphisms (SNPs) in ancient bacterial genomes, facilitating qualitative analyses of low coverage genomes from a metagenomic background. Phylogenetic analysis on the eight reconstructed genomes reveals the existence of previously undocumented Y. pestis diversity during the sixth to eighth centuries, and provides evidence for the presence of multiple distinct Y. pestis strains in Europe. We offer genetic evidence for the presence of the Justinianic Plague in the British Isles, previously only hypothesized from ambiguous documentary accounts, as well as the parallel occurrence of multiple derived strains in central and southern France, Spain, and southern Germany. Four of the reported strains form a polytomy similar to others seen across the Y. pestis phylogeny, associated with the Second and Third Pandemics. We identified a deletion of a 45-kb genomic region in the most recent First Pandemic strains affecting two virulence factors, intriguingly overlapping with a deletion found in 17th- to 18th-century genomes of the Second Pandemic. © 2019 National Academy of Sciences. All rights reserved

Direct Observation of Martensitic Phase-Transformation Dynamics in Iron by 4D Single-Pulse Electron Microscopy

The in situ martensitic phase transformation of iron, a complex solid-state transition involving collective atomic displacement and interface movement, is studied in real time by means of four-dimensional (4D) electron microscopy. The iron nanofilm specimen is heated at a maximum rate of ∼10^(11) K/s by a single heating pulse, and the evolution of the phase transformation from body-centered cubic to face-centered cubic crystal structure is followed by means of single-pulse, selected-area diffraction and real-space imaging. Two distinct components are revealed in the evolution of the crystal structure. The first, on the nanosecond time scale, is a direct martensitic transformation, which proceeds in regions heated into the temperature range of stability of the fcc phase, 1185−1667 K. The second, on the microsecond time scale, represents an indirect process for the hottest central zone of laser heating, where the temperature is initially above 1667 K and cooling is the rate-determining step. The mechanism of the direct transformation involves two steps, that of (barrier-crossing) nucleation on the reported nanosecond time scale, followed by a rapid grain growth typically in ∼100 ps for 10 nm crystallites

The Lie Algebraic Significance of Symmetric Informationally Complete Measurements

Examples of symmetric informationally complete positive operator valued measures (SIC-POVMs) have been constructed in every dimension less than or equal to 67. However, it remains an open question whether they exist in all finite dimensions. A SIC-POVM is usually thought of as a highly symmetric structure in quantum state space. However, its elements can equally well be regarded as a basis for the Lie algebra gl(d,C). In this paper we examine the resulting structure constants, which are calculated from the traces of the triple products of the SIC-POVM elements and which, it turns out, characterize the SIC-POVM up to unitary equivalence. We show that the structure constants have numerous remarkable properties. In particular we show that the existence of a SIC-POVM in dimension d is equivalent to the existence of a certain structure in the adjoint representation of gl(d,C). We hope that transforming the problem in this way, from a question about quantum state space to a question about Lie algebras, may help to make the existence problem tractable.Comment: 56 page