Correction of self-absorption spectral line and ratios of transition probabilities for homogeneous and LTE plasma

Expressions for fundamental spectral line parameters are reported for Gaussian and Lorentzian shape profiles for homogeneous plasma at equilibrium in presence of the self-absorption. These expressions for Lorentzian profiles are applied to the determination of the ratios of transition probabilities and the ratios of optical thicknesses by a new method that we propose in this article. The self-absorption is computed by spectral line profiles with a Simplex algorithm program fitting. Applications to some experimental lines illustrate the appropriate corrections.     

Facile growth of monolayer MoS<Subscript>2</Subscript> film areas on SiO<Subscript>2</Subscript>

Areas of single-layer MoS₂ film can be prepared in a tube furnace without the need for temperature control. The films were characterized by means of Raman spectroscopy, photoluminescence, low-energy electron diffraction and microscopy, and X-ray photoelectron spectroscopy and mapping. Transport measurements show n-doped material with a mobility of 0.26 cm² V^-1 s^-1.     

Propagation of extremely short pulses in a graphene–boron nitride bilayer

In this study we investigate the propagation of extremely short optical pulses in a thin film formed by a graphene grown on a boron nitride substrate. Conduction electrons of the system are described on the basis of the long-wavelength effective Hamiltonian in the case of low temperatures; the electromagnetic field being taken into account within the framework of the classical Maxwell equations. The time evolution of the pulse?s shape for different speeds and maximum amplitudes of an extremely short pulse is analyzed.     

Highly stretched single polymers: atomic-force-microscope experiments versus ab-initio theory

Experimental single-molecule stretching curves for three backbone architectures (single-stranded DNA, various types of peptides, polyvinylamine) are quantitatively compared with corresponding quantum-chemical (zero-temperature) ab-initio calculations in the high-force range of up to two nanonewtons. For high forces, quantitative agreement is obtained with the contour length of the polymers as the only fitting parameter. For smaller forces, the effects of chain fluctuations are accounted for by using recent theoretical results for the stretching response of a freely-rotating-chain model.     

Adsorption of hydrogen and of oxygen on an open metal surface-HREELS investigation at Ni(311)

The adsorption behavior of hydrogen and oxygen on the stepped Ni(311) surface has been investigated by HREELS. A series of metastable phases was found for hydrogen adsorption at low temperatures with a succession of different adsorption sites indicated by the following loss peaks: 55 and 149 meV for the threefold site, shifting with higher coverage to 65 and 155 meV, respectively; 40 and 90 meV for the fourfold site, shifting to 35 and 85 meV with coverage; and 110 and 124 meV for an additional site between close packed rows. Room temperature adsorption of hydrogen leads to the reconstruction of the surface with occupation of three- and fourfold sites, represented by loss peaks at 60 and 145 meV for the threefold site and 74 meV for the fourfold site. This phase is the thermodynamically stable one. Oxygen is most likely initially adsorbed on a bridge site (loss peak at 66 meV). The stepped surface is already oxidized at very low exposures to oxygen, as seen by the characteristic vibration for oxide islands at 55 meV and later by the Fuchs-Kliewer mode of NiO at 68 meV.     

Exploring the performance of spatial stochastic simulation algorithms

Since the publication of Gillespie’s direct method, diverse methods have been developed to improve the performance of stochastic simulation methods and to enter the spatial realm. In this paper we discuss a spatial τ-leaping variant (Sτ) that extends the basic leap method. Sτ takes reaction and both outgoing and incoming diffusion events into account when calculating a leap candidate. A performance analysis shall reveal details on the achieved success in balancing speed and accuracy in comparison to other methods. However, performance analysis of spatial stochastic algorithms requires significant effort — it is crucial to choose suitable (benchmark) models and to carefully define model and simulation setups that take problem and simulation design spaces into account.     

Measurement of the B(+) production cross section in pp collisions at sqrt[s]=7 TeV

Measurements of the total and differential cross sections dσ/dp(T)(B) and dσ/dy(B) for B(+) mesons produced in pp collisions at sqrt[s]=7 TeV are presented. The data correspond to an integrated luminosity of 5.8 pb(-1) collected by the CMS experiment operating at the LHC. The exclusive decay B(+)→J/ψK(+), with J/ψ→μ(+)μ(-), is used to detect B(+) mesons and to measure the production cross section as a function of p(T)(B) and y(B). The total cross section for p(T)(B)>5 GeV and |y(B)|<2.4 is measured to be 28.1±2.4±2.0±3.1 μb, where the first uncertainty is statistical, the second is systematic, and the last is from the luminosity measurement.     

Microswimmers – From Single Particle Motion to Collective Behavior

Locomotion of autonomous microswimmers is a fascinating field at the cutting edge of science. It combines the biophysics of self-propulsion via motor proteins, artificial propulsion mechanisms, swimming strategies at low Reynolds numbers, the hydrodynamic interaction of swimmers, and the collective motion and synchronisation of large numbers of agents. The articles of this Special Issue are based on the lecture notes of an international summer school, which was organized by the DFG Priority Programme 1726 “Microswimmers – From Single Particle Motion to Collective Behaviour” in the fall of 2015. The minireviews provide a broad overview of the field, covering both elementary and advanced material, as well as selected areas from current research.