The HERMES high-resolution spectrograph project aims at exploiting the specific potential of small but flexible telescopes in observational astrophysics. The optimised optical design of the spectrograph is based on the well-proven concept of white-pupil beam folding for high-resolution spectroscopy. In this contribution we present the complete project, including the spectrograph design and procurement details, the telescope adaptor and calibration unit, the detector system, as well as the optimised data-reduction pipeline. We present a detailed performance analysis to show that the spectrograph performs as specified both in optical quality and in total efficiency. With a spectral resolution of 85 000 (63 000 for the low-resolution fibre), a spectral coverage from 377 to 900 nm in a single exposure and a peak efficiency of 28%, HERMES proves to be an ideal instrument for building up time series of high-quality data of variable (stellar) phenomena.

Context. The influence of binarity on the late stages of stellar evolution remains an open issue. Aims. While the first binary post-AGB stars were serendipitously discovered, the distinct characteristics of their spectral energy distribution (SED) allowed us to launch a more systematic search for binaries. We selected post-AGB objects, which exhibit a broad dust excess starting either at H or K, pointing to the presence of a gravitationally bound dusty disc in the system. We initiated an extensive multiwavelength study of those systems and here report on our radial velocity and photometric monitoring results for six stars of early F type, which are pulsators of small amplitude. Methods. To determine the radial velocity of low signal-to-noise ratio time-series data, we constructed dedicated autocorrelation masks based on high signal-to-noise ratio spectra, used in our published chemical studies. The radial velocity variations were analysed in detail to differentiate between pulsational variability and variability caused by orbital motion. When available, the photometric monitoring data were used to complement the time series of radial velocity data and to establish the nature of the pulsation. Finally, orbital minimalisation was performed to constrain the orbital elements. Results. All of the six objects are binaries with orbital periods ranging from 120 to 1800 days. Five systems have non-circular orbits. The mass functions range from 0.004 to 0.57 M and the companions are probably unevolved objects of (very) low initial mass. We argue that these binaries must have evolved through a phase of strong binary interaction when the primary was a cool supergiant. Although the origin of the circumstellar disc is not well understood, the disc is generally believed to have formed during this strong interaction phase. The eccentric orbits of these highly evolved objects remain poorly understood. In one object, the line-of-sight grazes the edge of the puffed-up inner rim of the disc. Conclusions. These results corroborate our earlier statement that evolved objects in binary stars create a Keplerian dusty circumbinary disc. With the measured orbits and mass functions, we conclude that the circumbinary discs seem to have a major impact on the evolution of a significant fraction of binary systems. Tables 4-6 are only available in electronic form at

Gamma Doradus stars (hereafter γ Dor stars) are gravity-mode pulsators of spectral type A or F. Such modes probe the deep stellar interior, offering a detailed fingerprint of their structure. Four-year high-precision space-based Kepler photometry of γ Dor stars has become available, allowing us to study these stars with unprecedented detail. We selected, analyzed, and characterized a sample of 67 γ Dor stars for which we have Kepler observations available. For all the targets in the sample we assembled high-resolution spectroscopy to confirm their F-type nature. We found fourteen binaries, among which are four single-lined binaries, five double-lined binaries, two triple systems, and three binaries with no detected radial velocity variations. We estimated the orbital parameters whenever possible. For the single stars and the single-lined binaries, fundamental parameter values were determined from spectroscopy. We searched for period spacing patterns in the photometric data and identified this diagnostic for 50 of the stars in the sample, 46 of which are single stars or single-lined binaries. We found a strong correlation between the spectroscopic v i sin and the period spacing values, confirming the influence of rotation on γ Dor-type pulsations as predicted by theory. We also found relations between the dominant g-mode frequency, the longest pulsation period detected in series of prograde modes, v i sin , and T log eff .

The asteroseismic and planetary studies, like all research related to stars, need precise and accurate stellar atmospheric parameters as input. We aim at deriving the effective temperature (T eff ), the surface gravity (log g), the metallicity ([Fe/H]), the projected rotational velocity (v sin i) and the MK type for 169 F, G, K, and M-type Kepler targets which were observed spectroscopically from the ground with five different instruments. We use two different spectroscopic methods to analyse 189 high-resolution, high-signalto-noise spectra acquired for the 169 stars. For 67 stars, the spectroscopic atmospheric parameters are derived for the first time. KIC 9693187 and 11179629 are discovered to be double-lined spectroscopic binary systems. The results obtained for those stars for which independent determinations of the atmospheric parameters are available in the literature are used for a comparative analysis. As a result, we show that for solar-type stars the accuracy of present determinations of atmospheric parameters is ± 150 K in T eff , ± 0.15 dex in [Fe/H], and ± 0.3 dex in log g. Finally, we confirm that the curveof-growth analysis and the method of spectral synthesis yield systematically different atmospheric parameters when they are applied to stars hotter than 6,000 K.

Most mammalian cell types, including endothelial cells, respond to cell swelling by activating a Cl ؊ current termed I Cl,swell , but it is not known how the physical stimulus of cell swelling is transferred to the channels underlying I Cl,swell . We have investigated the precise relation between cell volume and I Cl,swell in endothelial cells by performing whole-cell current recordings while continuously monitoring cell thickness (T c ) as a measure for cell volume. The time course of T c was accurately predicted by a theoretical model that describes volume changes of patch-clamped cells in response to changes in the extracellular osmolality (OSM o ). This model also predicts significant changes in intracellular ionic strength (⌫ i ) when OSM o is altered. Under all experimental conditions I Cl,swell closely followed the changes in ⌫ i , whereas I Cl,swell and cell volume were often found to change independently. These results do not support the hypothesis that ⌫ i regulates the volume set point for activation of I Cl,swell . Instead, they are in complete agreement with a model in which a decrease of ⌫ i rather than an increase in cell volume is the initial trigger for activation of I Cl,swell .All living cells are programmed to activate a series of cellular processes to counter the harmful effects of cell swelling. One of the first detectable effects of cell swelling in most vertebrate cells is an increase in the plasma membrane permeability to anions, through the opening of anion channels (1). Although different types of swelling-activated anion currents have been functionally described, one phenotype seems to be predominant. This outwardly rectifying current, which under normal conditions is mainly carried by Cl Ϫ , has been termed I Cl,swell for swelling-activated Cl Ϫ current, and the underlying channel has been termed VRAC for volume-regulated anion channel. The biophysical and pharmacological properties of I Cl,swell ͞VRAC have been extensively studied (for recent reviews, see refs. 2-4), but the precise activation mechanism of I Cl,swell is still not resolved. Particularly, it remains unclear how the cell ''senses'' changes in its volume and translates this physical stimulus into the opening of VRAC.Hypotonicity-induced cell swelling is accompanied by a dilution of the intracellular medium, resulting in a decrease of ⌫ i , the intracellular ionic strength. Interestingly, it was recently shown that ⌫ i modulates I Cl,swell , independent of the molecular nature of the intracellular ions. A model was proposed in which ⌫ i regulates the volume set point for activation of VRAC, by modulating a putative ''volume sensor '' (5-7).In the present study we tested this model by investigating the relation between cell volume, ⌫ i , and I Cl,swell in endothelial cells. To this end, we set up a combined system that enables the simultaneous measurement of whole-cell currents and cell thickness (T c ). A theoretical model was developed that accurately predicts the osmotically induced volume changes and the conco...