Atomic carbon chains as spin-transmitters: an \textit{Ab initio} transport study

An atomic carbon chain joining two graphene flakes was recently realized in a ground-breaking experiment by Jin {\it et al.}, Phys. Rev. Lett. {\bf 102}, 205501 (2009). We present {\it ab initio} results for the electron transport properties of such chains and demonstrate complete spin-polarization of the transmission in large energy ranges. The effect is due to the spin-polarized zig-zag edge terminating each graphene flake causing a spin-splitting of the graphene $\pi_z$ bands, and the chain states. Transmission occurs when the graphene $\pi$-states resonate with similar states in the strongly hybridized edges and chain. This effect should in general hold for any $\pi$-conjugated molecules bridging the zig-zag edges of graphene electrodes. The polarization of the transmission can be controlled by chemically or mechanically modifying the molecule, or by applying an electrical gate

A low-luminosity soft state in the short period black hole X-ray binary Swift J1753.5-0127

We present results from the spectral fitting of the candidate black hole X-ray binary Swift J1753.5-0127 in an accretion state previously unseen in this source. We fit the 0.7-78 keV spectrum with a number of models, however the preferred model is one of a multi-temperature disk with an inner disk temperature $\mathrm{k}T_\mathrm{in}=0.252\pm0.003$ keV scattered into a steep power-law with photon index $\Gamma=6.39^{+0.08}_{-0.02}$ and an additional hard power law tail ($\Gamma=1.79\pm0.02$). We report on the emergence of a strong disk-dominated component in the X-ray spectrum and we conclude that the source has entered the soft state for the first time in its ~10 year prolonged outburst. Using reasonable estimates for the distance to the source ($3$ kpc) and black hole mass ($5M_{\odot}$), we find the unabsorbed luminosity (0.1-100 keV) to be $\approx0.60$% of the Eddington luminosity, making this one of the lowest luminosity soft states recorded in X-ray binaries. We also find that the accretion disk extended towards the compact object during its transition from hard to soft, with the inner radius estimated to be $R_{\mathrm{in}}=28.0^{+0.7}_{-0.4} R_g$ or ~$12R_g$, dependent on the boundary condition chosen, assuming the above distance and mass, a spectral hardening factor $f=1.7$ and a binary inclination $i=55^{\circ}$.Comment: 10 pages, 5 figures, accepted for publication in MNRA

Innovative methods in European road freight transport statistics: A pilot study

By using innovative methods, such as the automated transfer of corporate electronic data to National Statistical Institutions, official transport data can be significantly improved in terms of reliability, costs and the burden on respondents. In this paper, we show that the automated compilation of statistical reports is possible and feasible. Based on previous findings, a new method and tool were developed in cooperation with two business partners from the logistics sector in Austria. The results show that the prototype could successfully be implemented at the partner companies. Improved data quality can lead to more reliable analyses in various fields. Compared to actual volumes of investments into transport, the costs of transport statistics are limited. By using the new and innovative data collection techniques, these costs can even be reduced in the long run; at the same time, the risk of bad investments and wrong decisions caused by analyses relying on poor data quality can be reduced. This results in a substantial value for business, research, the economy and the society

Distorted cyclotron line profile in Cep X-4 as observed by NuSTAR

We present spectral analysis of NuSTAR and Swift observations of Cep X-4 during its outburst in 2014. We observed the source once during the peak of the outburst and once during the decay, finding good agreement in the spectral shape between the observations. We describe the continuum using a powerlaw with a Fermi-Dirac cutoff at high energies. Cep X-4 has a very strong cyclotron resonant scattering feature (CRSF) around 30 keV. A simple absorption-like line with a Gaussian optical depth or a pseudo-Lorentzian profile both fail to describe the shape of the CRSF accurately, leaving significant deviations at the red side of the line. We characterize this asymmetry with a second absorption feature around 19 keV. The line energy of the CRSF, which is not influenced by the addition of this feature, shows a small but significant positive luminosity dependence. With luminosities between (1-6)e36 erg/s, Cep X-4 is below the theoretical limit where such a correlation is expected. This behavior is similar to Vela X-1 and we discuss parallels between the two systems.Comment: 6 pages, 4 figure, accepted for publication in ApJ letter

Localized Edge Vibrations and Edge Reconstruction by Joule Heating in Graphene Nanostructures

Under the terms of the Creative Commons Attribution License 3.0 (CC-BY).Control of the edge topology of graphene nanostructures is critical to graphene-based electronics. A means of producing atomically smooth zigzag edges using electronic current has recently been demonstrated in experiments [Jia et al., Science 323, 1701 (2009)]. We develop a microscopic theory for current-induced edge reconstruction using density functional theory. Our calculations provide evidence for localized vibrations at edge interfaces involving unpassivated armchair edges. We demonstrate that these vibrations couple to the current, estimate their excitation by Joule heating, and argue that they are the likely cause of the reconstructions observed in the experiments.A. P. J. is grateful to the FiDiPro program of the Finnish Academy. Computational resources were provided by the Danish Center for Scientific Computing (DCSC).Peer reviewe

Quality prescribing in general practice

To implement continuous improvement of prescribing in general practice with a model closely linking the work of general practitioner and a clinical pharmacist aiming to improve the safety and efficiency of treatment with medicine. Emphasise is on polypharmacy (multiple medications) which is increasing across countries and although appropriate especially in patients with multiple comorbidities it can cause serious problems to patients and is a major challenge for the health care systems. Problems include adverse drug reactions and harmful drug interactions with reduced quality of life, increased overall morbidity, mortality and increased costs to health care systems

Cyclotron lines in highly magnetized neutron stars

Cyclotron lines, also called cyclotron resonant scattering features (CRSF) are spectral features, generally appearing in absorption, in the X-ray spectra of objects containing highly magnetized neutron stars, allowing the direct measurement of the magnetic field strength in these objects. Cyclotron features are thought to be due to resonant scattering of photons by electrons in the strong magnetic fields. The main content of this contribution focusses on electron cyclotron lines as found in accreting X-ray binary pulsars (XRBP) with magnetic fields on the order of several 1012 Gauss. Also, possible proton cyclotron lines from single neutron stars with even stronger magnetic fields are briefly discussed.With regard to electron cyclotron lines, we present an updated list of XRBPs that show evidence of such absorption lines. The first such line was discovered in a 1976 balloon observation of the accreting binary pulsar Hercules X-1, it is considered to be the first direct measurement of the magnetic field of a neutron star. As of today (mid 2018), we list 36 XRBPs showing evidence of one ore more electron cyclotron absorption line(s). A few have been measured only once and must be confirmed (several more objects are listed as candidates). In addition to the Tables of objects, we summarize the evidence of variability of the cyclotron line as a function of various parameters (especially pulse phase, luminosity and time), and add a discussion of the different observed phenomena and associated attempts of theoretical modeling. We also discuss our understanding of the underlying physics of accretion onto highly magnetized neutron stars. For proton cyclotron lines, we present tables with seven neutron stars and discuss their nature and the physics in these objects.Comment: 32 pages, 15 figures, 8 Tables, accepted by A&A 201

A Soft X-Ray Spectral Episode for the Clocked Burster, GS 1826-24 as Measured by Swift and NuSTAR

We report on NuSTAR and Swift observations of a soft state of the neutron star low-mass X-ray binary GS 1826-24, commonly known as the "clocked" burster. The transition to the soft state was recorded in 2014 June through an increase of the 2-20 keV source intensity measured by MAXI, simultaneous with a decrease of the 15-50 keV intensity measured by Swift/BAT. The episode lasted approximately two months, after which the source returned to its usual hard state. We analyze the broad-band spectrum measured by Swift/XRT and NuSTAR, and estimate the accretion rate during the soft episode to be about 13% of Eddington, within the range of previous observations. However, the best fit spectral model, adopting the double Comptonization used previously, exhibits significantly softer components. We detect seven type-I X-ray bursts, all significantly weaker (and with shorter rise and decay times) than observed previously. The burst profiles and recurrence times vary significantly, ruling out the regular bursts that are typical for this source. One burst exhibited photospheric radius expansion, and we estimate the source distance at about (5.7 / xi_b^1/2) kpc, where xi_b parameterizes the possible anisotropy of the burst emission. Interpreting the soft state as a transition from an optically thin inner flow to an optically thick flow passing through a boundary layer, as is commonly observed in similar systems, is contradicted by the lower optical depth measured for the double Comptonization model we find for this soft state. The effect of a change in disk geometry on the burst behavior remains unclear.Comment: 40 pages (single-column, doubled spaced format), 9 figures, 3 tables; submitted to Ap