Absolute dimensions of eclipsing binaries. XXIV, The Be star system DW Carinae, a member of the open cluster Collinder 228

Context. The study of detached eclipsing binaries which are members of stellar clusters is is a powerful way of determining the properties of the cluster and of constraining the physical ingredients of theoretical stellar evolutionary models. Aims. DWCarinae is a close but detached early B-type eclipsing binary in the young open cluster Collinder 228. We have measured accurate physical properties of the components of DWCar (masses and radii to 1%, effective temperatures to 0.02 dex) and used these to derive the age, metallicity and distance of Collinder 228. Methods. The rotational velocities of both components of DWCar are high, so we have investigated the performance of double-Gaussian fitting, one- and two-dimensional cross-correlation and spectral disentangling for deriving spectroscopic radial velocites in the presence of strong line blending. Gaussian and cross-correlation analyses require substantial corrections for the effects of line blending, which are only partially successful for cross-correlation. Spectral disentangling is to be preferred because it does not assume anything about the shapes of spectral lines, and is not significantly affected by blending. However, it suffers from a proliferation of local minima in the least-squares fit. We show that the most reliable radial velocities are obtained using spectral disentangling constrained by the results of Gaussian fitting. Complete Strömgren uvby light curves have been obtained and accurate radii have been measured from them by modelling the light curves using the Wilson-Devinney program. This procedure also suffers from the presence of many local minima in parameter space, so we have constrained the solution using an accurate spectroscopic light ratio. The effective temperatures and reddening of the system have been found from Strömgren photometric calibrations. Results. The mass and radius of DWCarA are MA = 11.34 ± 0.12 M and RA = 4.558 ± 0.045 R. The values for DWCar B are MB =10.63 ± 0.14 M and RB = 4.297 ± 0.055 R. Strömgren photometric calibrations give effective temperatures of TeffA = 27 900 ±1000 K and TeffB = 26 500 ± 1000 K, and a reddening of Eb−y = 0.18 ± 0.02, where the quoted uncertainties include a contribution from the intrinsic uncertainty of the calibrations. The membership of DWCar in Cr 228 allows us to measure the distance, age and chemical composition of the cluster. We have used empirical bolometric corrections to calculate a distance modulus of 12.24 ±0.12 mag for DWCar, which is in agreement with, and more accurate than, literature values. A comparison between the properties of DWCar and the predictions of recent theoretical evolutionary models is undertaken in the mass-radius and mass-Teff diagrams. The model predictions match the measured properties of DWCar for an age of about 6 Myr and a fractional metal abundance of Z ≈ 0.01

Conditional quantum state engineering in repeated 2-photon down conversion

The U(1,1) and U(2) transformations realized by three-mode interaction in the respective parametric approximations are studied in conditional measurement, and the corresponding non-unitary transformation operators are derived. As an application, the preparation of single-mode quantum states using an optical feedback loop is discussed, with special emphasis of Fock state preparation. For that example, the influence of non-perfect detection and feedback is also considered.Comment: 17 pages, 4 figures, using a4.st

Researchers’ opinions about ethically sound dissemination of BCI research to the public media

BCI research and (future) applications raise ethical questions. A websurvey among 144 BCI researchers identified disseminating BCI research to the public media as a central topic. Most researchers felt that BCI scientists must responsibly communicate with the media and that general ethical guidelines on BCI research and application are needed within the next 5 years. We recommend further debate on ethical aspects related to BCI and the development of guidelines

An Investigation in Oxidative Cation Formation: The Total Synthesis of Lactodehydrothyrsiferol and Synthetic Application for a Bimolecular Carbon–Carbon Bond Forming Reaction

The first total synthesis of lactodehydrothyrsiferol, a selective inhibitor of protein phosphatase 2A, was accomplished through the application of our electron-transfer-initiated cyclization reaction. Other highlights of our synthetic strategy include a novel method for the formation of 1,1-disubstuted vinyl iodides from a terminal alkyne, a Suzuki-Miyaura cross coupling reaction on a iodinated allylic carbonate, a one pot diepoxidation of a diene to generate two epoxides with opposite stereochemical identities, an asymmetric Nozaki-Hiyama-Kishi reaction, and the selective deoxygenation of a triol. This document will focus on the key epoxide cascade and completion of the synthesis. An oxidative method to form Carbon–Carbon bonds through Carbon–Hydrogen bond cleavage is described herein. Chromene and isochromene both form aromatically stabilized oxocarbenium ions in the presence of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The reactivity of these cations was explored with a variety of nucleophiles. In addition, the electronic properties were altered on the benzopyran ring system to elucidate the substrate scope for this transformation