Patients with profuse hair shedding may reveal anagen hair dystrophy: a diagnostic clue of alopecia areata incognita.

BACKGROUND: Several patients, especially women, seek advice because of hair loss. They may be diagnosed clinically as having telogen effluvium (TE) or androgenetic alopecia (AGA), but histopathology may reveal that a proportion of them have in fact alopecia areata incognita (AAI). OBJECTIVES: To detect dystrophic anagen hairs in such patients. METHODS: We studied 1932 patients with hair loss and no signs of classical alopecia areata. They were submitted to the modified wash test (which counts the total number of telogen hairs lost and the percentage of vellus hairs) and divided into patients having pure TE (403), patients with AGA+TE (1235) and patients with pure AGA (294). Dystrophic hairs were detected with a low magnification microscope. RESULTS: Dystrophic hairs were observed in 13 patients with TE (3.2%), in 54 with AGA+TE (4.4%) and in none with AGA. In addition, 7 patients with TE and 32 with AGA+TE developed small patches of alopecia areata in 6 to 9 weeks. No patches developed in patients with AGA. CONCLUSIONS: The presence of dystrophic hairs and the development of patches of alopecia areata (and their absence in pure AGA) provide a first evidence of the possibility that within the heterogenous condition named TE some patients have in fact AAI.

Darwin--a mission to detect and search for life on extrasolar planets.

The discovery of extrasolar planets is one of the greatest achievements of modern astronomy. The detection of planets that vary widely in mass demonstrates that extrasolar planets of low mass exist. In this paper, we describe a mission, called Darwin, whose primary goal is the search for, and characterization of, terrestrial extrasolar planets and the search for life. Accomplishing the mission objectives will require collaborative science across disciplines, including astrophysics, planetary sciences, chemistry, and microbiology. Darwin is designed to detect rocky planets similar to Earth and perform spectroscopic analysis at mid-infrared wavelengths (6-20 mum), where an advantageous contrast ratio between star and planet occurs. The baseline mission is projected to last 5 years and consists of approximately 200 individual target stars. Among these, 25-50 planetary systems can be studied spectroscopically, which will include the search for gases such as CO(2), H(2)O, CH(4), and O(3). Many of the key technologies required for the construction of Darwin have already been demonstrated, and the remainder are estimated to be mature in the near future. Darwin is a mission that will ignite intense interest in both the research community and the wider public.

Fiber optic interferometry: statistics of visibility and closure phase.

Interferometric observations with three telescopes or more provide two observables: closure phase information and visibility measurements. When single-mode interferometers are used, both observables have to be redefined in the light of the coupling phenomenon between the incoming wave front and the fiber. We introduce the estimator of both the so-called modal visibility and the modal closure phase. Then we compute the statistics of the two observables in the presence of partial correction by adaptive optics, paying attention to the correlation between the measurements. We find that the correlation coefficients are mostly zero and in any case are never greater than 1/2 for the visibilities and 1/3 for the closure phases. From this theoretical analysis, a data-reduction process using classic least-squares minimization is investigated. In the framework of the AMBER instrument, the three-beam recombiner of the Very Large Telescope Interferometer (VLTI), we simulate the observation of a single Gaussian source and study the performances of the interferometer in terms of diameter measurements. We show that the observation is optimized, i.e., that the signal-to-noise ratio (SNR) of the diameter is maximal when the FWHM of the source is roughly 1/2 of the mean resolution of the interferometer. We finally point out that, in the case of an observation with three telescopes, neglecting the correlation between the measurements leads to overestimating the SNR by a factor of square root of 2. We infer that in any case this value is an upper limit.