Numerical relativity simulations of binary neutron stars

We present a new numerical relativity code designed for simulations of compact binaries involving matter. The code is an upgrade of the BAM code to include general relativistic hydrodynamics and implements state-of-the-art high-resolution-shock-capturing schemes on a hierarchy of mesh refined Cartesian grids with moving boxes. We test and validate the code in a series of standard experiments involving single neutron star spacetimes. We present test evolutions of quasi-equilibrium equal-mass irrotational binary neutron star configurations in quasi-circular orbits which describe the late inspiral to merger phases. Neutron star matter is modeled as a zero-temperature fluid; thermal effects can be included by means of a simple ideal-gas prescription. We analyze the impact that the use of different values of damping parameter in the Gamma-driver shift condition has on the dynamics of the system. The use of different reconstruction schemes and their impact in the post-merger dynamics is investigated. We compute and characterize the gravitational radiation emitted by the system. Self-convergence of the waves is tested, and we consistently estimate error-bars on the numerically generated waveforms in the inspiral phase

Open Photoacoustic Cell for Blood Sugar Measurement: Numerical Calculation of Frequency Response

A new approach for continuous and non-invasive monitoring of the glucose concentration in human epidermis has been suggested recently. This method is based on photoacoustic (PA) analysis of human interstitial fluid. The measurement can be performed in vitro and in vivo and, therefore, may form the basis for a non-invasive monitoring of the blood sugar level for diabetes patients. It requires a windowless PA cell with an additional opening that is pressed onto the human skin. Since signals are weak, advantage is taken of acoustic resonances of the cell. Recently, a numerical approach based on the Finite Element (FE) Method has been successfully used for the calculation of the frequency response function of closed PA cells. This method has now been adapted to obtain the frequency response of the open cell. Despite the fact that loss due to sound radiation at the opening is not included, fairly good accordance with measurement is achieved

Metrics for Measuring Data Quality - Foundations for an Economic Oriented Management of Data Quality

The article develops metrics for an economic oriented management of data quality. Two data quality dimensions are focussed: consistency and timeliness. For deriving adequate metrics several requirements are stated (e. g. normalisation, cardinality, adaptivity, interpretability). Then the authors discuss existing approaches for measuring data quality and illustrate their weaknesses. Based upon these considerations, new metrics are developed for the data quality dimensions consistency and timeliness. These metrics are applied in practice and the results are illustrated in the case of a major German mobile services provider

“Faking” is Neither Good Nor Bad, It Is a Misleading Concept: A Reply to Tett and Simonet (2021)

This paper comments on Tett and Simonet’s (2021) outline of two contradictory positions on job applicants’ self-presentation on personality tests labelled “faking is bad” (FIB) versus “faking is good” (FIG). Based on self-presentation theory (Marcus, 2009) Tett and Simonet assigned to their FIG camp, I develop the ideas of (a) understanding self-presentation from the applicant’s rather than the employer’s perspective, (b) avoiding premature moral judgment on this behavior, and (c) examining consequences for the validity of applicant responses with a focus on the intended use for, and the competitive context of, selection. Conclusions include (a) that self-presentation is motivationally and morally more complex than assumed by proponents of the FIB view; (b) that its consequences for validity are ambivalent, which implies that simple credos like “FIB” or “FIG” are equally unjustified; and (c) that the label “faking” shall be abandoned from the scientific inquiry on the phenomena at hand, as it contributes to prejudiced and often erroneous conclusions

First-principles analysis of a homo-chiral cycloidal magnetic structure in a monolayer Cr on W(110)

The magnetic structure of a Cr monolayer on a W(110) substrate is investigated by means of first-principles calculations based on the noncollinear spin density functional theory (DFT). As magnetic ground state we find a long-period homochiral left-rotating spin spiral on-top of an atomic-scale anti-ferromagnetic order of nearest neighbor atoms. The rotation angle of the magnetic moment changes inhomogeneously from atom to atom across the spiral. We predict a propagation direction along the crystallographic [001] direction with a period length of 14.3 nm, which is in excellent agreement with a modulation of the local anti-ferromagnetic contrast observed in spin-polarized scanning tunneling microscope experiments by Santos et al. [New J. Phys. 10, 013005 (2008)]. We identify the Dzyaloshinskii-Moriya interaction (DMI) as origin of the homochiral magnetic structure, competing with the Heisenberg-type exchange interaction and magneto-crystalline anisotropy energy. From DFT calculations we extract parameters for a micromagnetic model and thereby determine a considerable inhomogeneity of the spin spiral, increasing the period length by 6% compared to homogeneous spin spirals. The results are compared to the behavior of a Mn and Fe monolayer and Fe doublelayer on a W(110) substrate

Photoacoustics Modelling using Amplitude Mode Expansion Method in a Multiscale T-cell Resonator

The photoacoustic (PA) effect consisting of the generation of an acoustic signal based on the absorption of light has already demonstrated its potential for various spectroscopic applications for both gaseous and solid samples. The signal produced during photoacoustic spectroscopy (PAS) measurement is, however, usually weak and needs to be amplified. This is achieved by using a photoacoustic cell resonator where acoustic resonances are utilized to significantly boost the signal. Therefore, a PA resonator has a significant role in PAS measurement set-ups. When designing or optimizing a new PA resonator, numerical methods are generally used to simulate the photoacoustic signal generation. In this paper, the amplitude mode expansion (AME) method is presented as a quick and accurate simulation tool. The method is used to simulate the photoacoustic signal in a multi-scale T-cell resonator over a wide frequency range. The AME method is based on eigenmode expansion and introduction of losses by quality factors. The AME simulation results are compared and analyzed against the results from the viscothermal method. Reasonably good agreement is obtained between the two methods. However, small frequency shifts in the resonances of the AME method are noted. The shifts are attributed to the location of the dominant mode within the T-cell. The viscothermal method is considered the most accurate method for simulating the photoacoustic signal in small resonators. However, it is computationally very demanding. The AME method provides a much faster simulation alternative. This is particularly useful in the design and optimization of photoacoustic resonators where numerical methods are preferred over experimental measurements due to their speed and low cost.Comment: Comsol Conference 201

Backcoupling of acoustic streaming on the temperature field inside high-intensity discharge lamps

Operating high-intensity discharge lamps in the high frequency range (20-300 kHz) provides energy-saving and cost reduction potentials. However, commercially available lamp drivers do not make use of this operating strategy because light intensity fluctuations and even lamp destruction are possible. The reason for the fluctuating discharge arc are acoustic resonances in this frequency range that are excited in the arc tube. The acoustic resonances in turn generate a fluid flow that is caused by the acoustic streaming effect. Here, we present a 3D multiphysics model to determine the influence of acoustic streaming on the temperature field in the vicinity of an acoustic eigenfrequency. In that case a transition from stable to instable behavior occurs. The model is able to predict when light flicker can be expected. The results are in very good accordance with accompanying experiments

Role of Dzyaloshinskii-Moriya interaction for magnetism in transition-metal chains at Pt step-edges

We explore the emergence of chiral magnetism in one-dimensional monatomic Mn, Fe, and Co chains deposited at the Pt(664) step-edge carrying out an ab-initio study based on density functional theory (DFT). The results are analyzed employing several models: (i) a micromagnetic model, which takes into account the Dzyaloshinskii-Moriya interaction (DMI) besides the spin stiffness and the magnetic anisotropy energy, and (ii) the Fert-Levy model of the DMI for diluted magnetic impurities in metals. Due to the step-edge geometry, the direction of the Dzyaloshinskii vector (D-vector) is not predetermined by symmetry and points in an off-symmetry direction. For the Mn chain we predict a long-period cycloidal spin-spiral ground state of unique rotational sense on top of an otherwise atomic-scale antiferromagnetic phase. The spins rotate in a plane that is tilted relative to the Pt surface by $62^\circ$ towards the upper step of the surface. The Fe and Co chains show a ferromagnetic ground state since the DMI is too weak to overcome their respective magnetic anisotropy barriers. Beyond the discussion of the monatomic chains we provide general expressions relating ab-initio results to realistic model parameters that occur in a spin-lattice or in a micromagnetic model. We prove that a planar homogeneous spiral of classical spins with a given wave vector rotating in a plane whose normal is parallel to the D-vector is an exact stationary state solution of a spin-lattice model for a periodic solid that includes Heisenberg exchange and DMI. The validity of the Fert-Levy model for the evaluation of micromagnetic DMI parameters and for the analysis of ab-initio calculations is explored for chains. The results suggest that some care has to be taken when applying the model to infinite periodic one-dimensional systems.Comment: 21 pages, 9 figure

Interkulturelle Verständigung im multimedialen Zeitalter : ein japanisch-deutsches Symposion an der Nihon-Universität in Tokio ; [Beitrag Symposion an der Nihon-Universität in Tokio, 2001]

Es mag sein, dass sich die japanische Kultur – ganz abgesehen von der Schrift – nicht leicht lesen lässt. Aber warum denn nicht? Warum soll uns die reizvolle Erfahrung erspart bleiben, dass ein wirtschaftlich und technologisch ebenbürtiger Partner der Weltgesellschaft sein Niveau auf einem andern Weg, aufgrund einer verschiedenen sozialen Kultur erreicht hat? Dass sich vermeintliche Universalien – Natur, Liebe, Religion, Familie, Individualität, Bindung, Freiheit – auch ganz anders buchstabieren und in stark abweichender Besetzung bis in 21. Jahrhundert mit Erfolg halten lassen? Warum eigentlich sollen wir nicht besser lesen lernen