Context. The chemically peculiar (CP) stars of the upper main sequence are well suited for investigating the impact of magnetic fields and diffusion on the surface layers of slowly rotating stars. They can even be traced in the Magellanic Clouds and are important to the understanding of the stellar formation and evolution. Aims. A systematic investigation of the near-infrared (NIR), 2MASS JHK s , photometry for the group of CP stars has never been performed. Nowadays, there is a great deal of data available in the NIR that reach very large distances. It is therefore very important for CP stars to be unambiguously detected in the NIR region and for these detections to be used to derive astrophysical parameters (age and mass) by applying isochrone fitting. Furthermore, we investigated whether the CP stars behave in a different way to normal-type stars in the various photometric diagrams. Methods. For our analysis, we carefully compiled a sample of CP and apparently normal (non-peculiar) type stars. Only stars for which high-quality (i.e. with low error levels), astrometric, and photometric data are available were chosen. In total, 639 normal and 622 CP stars were selected and further analysed. All stars were dereddened and calibrated in terms of the effective temperature and absolute magnitude (luminosity). Finally, isochrone fitting was applied. Results. No differences in the astrophysical parameters derived from 2MASS and Johnson UBV photometry were found. Furthermore, no statistical significant deviations from the normal type stars within several colour-colour and colour-magnitude diagrams were discovered. Therefore, it is not possible to detect new CP stars with the help of the photometric 2MASS colours only. A new effective temperature calibration, valid for all CP stars, using the (V − K S ) 0 colour was derived.

Electrical efficiency is an important factor for most of the owners of gas engines. To reach a high electrical efficiency, engine manufacturers use four valve cylinder head technology on new designed engines. The change from two valve to four valve technology, in combination with optimized charge motion, can achieve an increase of electrical efficiency up to 2.5%. A significant number of engines in the market are only equipped with two valve cylinder heads, thus leaving potential to reduce carbon emissions and fuel consumption. The scope of the paper applies to the modernization of an already well established gas engine series available on the market with a power range of 500–1100kW [1]. In the first step, the potentials were considered purely in the context of a change in configuration of the spark plug, to pre-chamber spark plug. As second step an optimization of the ports was examined. Due to the pre-existing high level of development of the combustion stage, combined with an adaption of the boost charging system, an improvement of almost 2.5% was achieved. According to data sheets, modern gas engines within this power range have efficiencies in the range of ηe ∼ 44%. The project team therefore proceeded to develop a new cylinder head along with new design leading to a better combustion. Minimizing changes around the periphery of the engine was a prerequisite in order to complete these on site as part of the 30.000-hour service. Intake- as well as exhaustport geometries were optimized with the aid of CFD tools, such that swirl and flow capacity values achieved their specified objectives. The geometries of the water jacket and valve train were also optimized through a similar methodology. These changes led to a 7% reduction in gas exchange work, which directly reflect within improved efficiency levels. Altogether, the various measures (including combustion optimization) resulted in an efficiency improvement of about 2.5% leading to an electric efficiency of 42.9%. The first endurance run shows that the mechanics match the expected technical requirements. Very low wear rates despite the increased masses of the valve train could be reached due to higher qualities in terms of materials. The paper focuses particularly on the flow optimization in conjunction with the variables surrounding the mechanic design. Finally, the test results of the pilot engines are presented alongside an economic analysis.

In some δ Scuti stars, only one or two radial modes are excited (usually the fundamental mode and/or first overtone mode) and the observed peak-to-peak amplitudes exceed 0.3 mag (V ). These stars are known as High Amplitude Delta Scuti (HADS) variables.We here present a detailed photometric and spectroscopic analysis of the HADS star TYC 3637-1152-1. We have derived a metallicity close to solar, a spectral type of F4 V and an age of log t = 9.1. Employing archival time series data from different sources, two frequencies f 0 = 10.034 c/d and f 1 = 12.681 c/d and their harmonics and linear combinations were identified. The period ratio of f 0 /f 1 = 0.791 puts this star into a peculiar position in the Petersen diagram, from which we conclude that TYC 3637-1152-1 is a unique object with peculiar pulsational properties that indicate a transitional state between HADS stars pulsating in the fundamental and first overtone modes and stars pulsating in higher overtones.

About 50 years ago, one thousand ring-like structures (called stellar-rings) were discovered by Isserstedt (1968). They were believed to be groups of young stars formed by shell-like triggered star formation, which would make them excellent tracers of spiral arms, for example. Neglected for 40 years, we used highly accurate kinematic, astrometric, and photometric data to investigate the four most prominent stellar rings. The aim is to investigate if those structures are indeed physically related groups of stars. We used proper motions and parallaxes from the Gaia DR2 to calculate distances and to search for common properties. Color-magnitude diagrams using BVJHK s measurements were investigated and isochrones fitted. None of the four stellar rings consists of a physically related group of young stars. The location of stars in the line-of-sight mimics a ring-like structure on the sky. The color-magnitude diagrams are typical for an integrated field population and not for a young star cluster, for example. The currently available data are sufficient to analyze ring-like structures with a high statistical significance. This allows a new search for such structures in the Milky Way. KEYWORD galaxy: structure -ISM: bubbles -open clusters and associations: general -stars: early-type