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.

Vega is a rapidly rotating star.

Vega, the second brightest star in the northern hemisphere, serves as a primary spectral type standard. Although its spectrum is dominated by broad hydrogen lines, the narrower lines of the heavy elements suggested slow to moderate rotation, giving confidence that the ground-based calibration of its visible spectrum could be safely extrapolated into the ultraviolet and near-infrared (through atmosphere models), where it also serves as the primary photometric calibrator. But there have been problems: the star is too bright compared to its peers and it has unusually shaped absorption line profiles, leading some to suggest that it is a distorted, rapidly rotating star seen pole-on. Here we report optical interferometric observations that show that Vega has the asymmetric brightness distribution of the bright, slightly offset polar axis of a star rotating at 93 per cent of its breakup speed. In addition to explaining the unusual brightness and line shape peculiarities, this result leads to the prediction of an excess of near-infrared emission compared to the visible, in agreement with observations. The large temperature differences predicted across its surface call into question composition determinations, adding uncertainty to Vega's age and opening the possibility that its debris disk could be substantially older than previously thought.

Objective measures of dysphagia complexity in children related to suckle feeding histories, gestational ages, and classification of their cerebral palsy.

Data collected during the routine assessment of 117 dysphagic children with cerebral palsy have been related to both suckle feeding histories and gestational ages and to the classification of cerebral palsy. In addition, a concurrent survey involving 281 children with cerebral palsy in special schools was undertaken which revealed that the sample of referred children appeared to be a true representation of a wider population of dysphagic children with cerebral palsy. A Feeding Difficulty Symptom Score (FDSS) describes the severity of swallowing symptoms reported. A numerical Dysphagia Complexity Index (DCI) quantifies numerically the neurological complexity of the swallowing difficulty. The FDSS correlates closely with the DCI. Twenty-seven percent of mothers of the children who were referred for advice on their present swallowing difficulties stated that they recalled no suckle feeding problems. However, there was no difference in the severity of present swallowing difficulties between those infants who suckle fed well and those who experienced severe difficulties. Those referred children with cerebral palsy born at term exhibited more complex later swallowing problems and were more likely to be classified as athetoid than those born preterm.

Non-invasive technique for assessment and management planning of oral-pharyngeal dysphagia in children with cerebral palsy.

The non-invasive Exeter Dysphagia Assessment Technique (EDAT) was evaluated as a method of assessing the aetiology of dysphagia in children with cerebral palsy (CP). Data were collected from a group of 20 typically developing children (nine girls, 11 boys; age range 7 to 14 years) for comparison with 125 dysphagic children with CP (81 boys, 44 girls; age range 1 to 18 years). The swallowing mechanism has been separated into physiological phases: anticipatory, delivery, oral transit, and oral-pharyngeal. Normal or abnormal function in each phase was recorded and the common causes of any impaired phase were considered, starting with generalized possibilities before focusing on specific parts of swallowing physiology. Data from 125 dysphagic children with CP show marked differences from the data for the typically developing children. Interpreting individual results was valuable in assisting the assessment team to formulate management strategies; two examples are presented. The technique appears to provide a cost-effective, non-invasive, and valuable clinical tool.

Interferometric seeing measurements on Mt. Wilson: power spectra and outer scales.

We have measured power spectra of atmospheric phase fluctuations with the Mark III stellar interferometer on Mt. Wilson under a wide variety of seeing conditions. On almost all nights, the high-frequency portions of the temporal power spectra closely follow the form predicted by the standard Kolmogorov-Tatarski model. At lower frequencies, a variety of behavior is observed. On a few nights, the spectra clearly exhibit the low-frequency flattening characteristic of turbulence with an outer-scale length of the order of 30 m. On other nights, examination of individual spectra yields no strong evidence of an outer scale less than a few kilometers in size, but comparison of the spectra on different interferometer baselines shows a saturation of the spatial structure function on long baselines. This saturation is consistent with the assumption of an outer-scale length similar to that derived for the nights when low-frequency flattening of the spectra is clearly seen. We discuss possible explanations of this behavior and conclude that power spectra from a single interferometer baseline are a poor diagnostic for the effective outer scale compared with multiple-baseline spectra.

Ultraviolet radiation-induced connective tissue changes in the skin of hairless mice.

Hairless mice (Skh/ hr1 ) were exposed to ultraviolet A (UVA; peak irradiance at 365 nm), or to ultraviolet B (UVB; peak irradiance at 313 nm) radiation. The animals received 12 treatments on alternate days. Connective tissue changes in the skin were monitored by assaying hydroxyproline and desmosine as an indication of collagen and elastin concentrations, respectively. The activities of prolyl hydroxylase and collagen glucosyl-transferase, enzymes participating in the biosynthesis of collagen, were also assayed. The concentration of elastin was significantly increased in mice treated with UVA or UVB. The concentration of collagen was unaffected by the treatments, but the activity of prolyl hydroxylase, reflecting collagen synthetic capacity, was decreased in UVA-treated mice. The collagen glucosyl-transferase activity was unchanged. Irradiation of purified human prolyl hydroxylase with UVA in vitro decreased the enzyme activity at higher doses, but UVB had no effect. The results indicate that definitive changes in the biochemistry of dermal connective tissues can be induced by exposure of mice to UV irradiation.

Wound healing: biological effects of Nd:YAG laser on collagen metabolism in pig skin in comparison to thermal burn.

Pig skin was treated with the Nd:YAG laser at 1,060 nm or electrocautery, at energy densities of 649 +/- 20 J/cm2 and 612 J/cm2, respectively. Biopsies of treated areas and of normal skin were performed at 7, 14, and 60 days after treatment and processed for histology, electron microscopy and biochemical assays. Wound healing, as shown histologically, was similar in both treated groups. Depth of injury appeared to reach reticular dermis at day 7 in each treated group. However, thermal burn was more destructive of regular collagen, whereas the laser appeared to damage deep dermal blood vessels without destroying surrounding connective tissue. Biochemical assays revealed increased collagen production and increased collagenolytic activity 7 days after laser injury. However, by day 60, there was a reduction in total collagen content in laser treated skin below that of normal skin, which correlated with decreased collagen synthesis and unchanged collagenolytic activity. In burn specimens there was an initial decrease in total collagen content which reverted to normal by day 60. Active collagen degradation occurred at all 3 time points, but a marked increase in synthetic activity occurred as the burn scar was laid down. Laser treatment resulted in reduction of the amount of collagen below that in burn scarred or normal skin, suggesting that classical scar formation may be inhibited. These results indicate that the Nd:YAG laser may be useful for the treatment of keloids and hypertrophic scars.

A simultaneous-coupling azo dye method for the quantitative assay of esterase using alpha-naphthyl acetate as substrate.

This paper describes a simultaneous-coupling azo dye method for the measurement of esterase activity using the histochemical substrate, alpha-naphthyl acetate. By the choice of two diazonium salts with optimal coupling characteristics, the reaction can be carried out at any pH between 3.0 and 9.5. The azo dye is maintained in solution for spectrophotometric measurements with bovine serum albumin. The simultaneous-coupling method is compared with an assay based on the direct measurement of released alpha-naphthol by its ultra-violet absorbance in a pH study of hog liver esterase. There is good agreement between the data obtained by both methods.