Imaging performance of telescope mirrors for far-ultraviolet astronomy.

We describe image testing, surface metrology, and modeling of telescope mirrors (0.5 m in diameter, f/4.3) for the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite.

The interstellar N2 abundance towards HD 124314 from far-ultraviolet observations.

The abundance of interstellar molecular nitrogen (N2) is of considerable importance: models of steady-state gas-phase interstellar chemistry, together with millimetre-wavelength observations of interstellar N2H+ in dense molecular clouds predict that N2 should be the most abundant nitrogen-bearing molecule in the interstellar medium. Previous attempts to detect N2 absorption in the far-ultraviolet or infrared (ice features) have hitherto been unsuccessful. Here we report the detection of interstellar N2 at far-ultraviolet wavelengths towards the moderately reddened star HD 124314 in the constellation of Centaurus.

Observations of the vacuum ultraviolet and x-ray brightness profiles of Fe, Ni, and Ge in magnetically confined fusion plasmas.

The spatial brightness profiles of emission lines for the K-like through He-like ionization states of Fe, Ge, and Ni have been measured during a set of experiments in which Fe and Ge were introduced into FTU tokamak plasmas by using the laser blowoff technique. Nickel was an intrinsic impurity observed during these experiments that was sputtered from the inconel limiter. The brightness profiles were measured by spatially scanable, photometrically calibrated vaccum ultraviolet and x-ray spectrometers that covered the 1 to 1700 A region.

Deficiency of molecular hydrogen in the disk of beta Pictoris.

Molecular hydrogen (H2) is by far the most abundant material from which stars, protoplanetary disks and giant planets form, but it is difficult to detect directly. Infrared emission lines from H2 have recently been reported towards beta Pictoris, a star harbouring a young planetary system. This star is surrounded by a dusty 'debris disk' that is continuously replenished either by collisions between asteroidal objects or by evaporation of ices on Chiron-like objects.

Resolving the structure of ionized helium in the intergalactic medium with the far ultraviolet spectroscopic explorer.

The neutral hydrogen (H I) and ionized helium (He II) absorption in the spectra of quasars are unique probes of structure in the early universe. We present Far-Ultraviolet Spectroscopic Explorer observations of the line of sight to the quasar HE2347-4342 in the 1000 to 1187 angstrom band at a resolving power of 15,000. We resolve the He II Lyman alpha (Lyalpha) absorption as a discrete forest of absorption lines in the redshift range 2.

Far-ultraviolet imaging spectroscopy of Io's atmosphere with HST/STIS.

Well-resolved far-ultraviolet spectroscopic images of O I, S I, and previously undetected H ILyman-alpha emission from Io were obtained with the Hubble space telescope imaging spectrograph (STIS). Detected O I and S I lines (1250 to 1500 angstroms) have bright equatorial spots (up to 2.5 kilorayleighs) that shift position with jovian magnetic field orientation; limb glow that is brighter on the hemisphere facing the jovian magnetic equator; and faint diffuse emission extending to approximately 20 Io radii.

Reinforcement without awareness: II. Word class.

In a previous study of reinforcement without awareness by Lieberman, Sunnucks, & Kirk (this issue), subjects were told that the experiment was on ESP; two words were presented on every trial, and their task was to choose the word the experimenter was thinking of. In fact, reinforcement was contingent on the loudness of the subjects' voices when responding. They found stronger evidence for reinforcement without awareness than in many previous studies, and they attributed their success in part to the reinforcement of a response to which subjects were unlikely to attend.

A comparison of pulpectomy alone versus pulpectomy with trephination for the relief of pain.

Patients who when initially seen have pain of endodontic origin have a higher incidence of posttreatment pain than those who are pain-free pretreatment. The purpose of this study was to compare two methods of treatment--pulpectomy alone or pulpectomy with trephination--for the reduction of posttreatment pain in patients presenting with acute periradicular pain of pulpal origin. Seventeen patients with pretreatment pain were studied.

Measurements of the photocurrent enhancement of reverse-biased silicon photodiodes in the 0.05-1.5-keV photon-energy range.

The measured photocurrents from two different p-n-junction silicon photodiodes at 170-Å (73-eV) and at 8.34-Å (1480-eV) light are presented. One is a standard extreme-UV photodiode fabricated on low resistivity silicon (70-100 Ω cm), and the other is fabricated on high-resistivity silicon (> 2 × 10(4) Ω cm).

Measured conversion efficiencies of P45, paraterphenyl, tetraphenyl butadiene, and sodium salicylate phosphors in the soft-x-ray wavelength range.

The measured conversion efficiencies at 9.89, 23.6, 44.

Peak reflectivity measurements of W/C, Mo/Si, and Mo/B(4)C multilayer mirrors in the 8-190-A range using both Kalpha line and synchrotron radiation.

Peak reflectivity measurements of W/C, Mo/Si, and Mo/B(4)C multilayer mirrors have been performed using line and synchrotron radiation in the 8-190 A wavelength range. Short wavelength measurements using a line source were corrected for nonmonochromatic and divergent incident radiation. Reflectivities of Mo/Si mirrors, measured with synchrotron radiation, ranged from 25 to 44% but decreased significantly around the Si absorption edge.

Near normal incidence spectroscopy of a Penning ionization discharge in the 110-180 A range with flat multilayer mirrors.

Al III to Al v spectra emitted from a Penning ionization discharge have been recorded in the 110-180 i range using two flat multilayer mirrors (Mo/Si and Mo/B(4)C) as dispersive elements in a near normal incidence configuration.

Ultraviolet spectrometer observations of neptune and triton.

Results from the occultation of the sun by Neptune imply a temperature of 750 +/- 150 kelvins in the upper levels of the atmosphere (composed mostly of atomic and molecular hydrogen) and define the distributions of methane, acetylene, and ethane at lower levels. The ultraviolet spectrum of the sunlit atmosphere of Neptune resembles the spectra of the Jupiter, Saturn, and Uranus atmospheres in that it is dominated by the emissions of H Lyman alpha (340 +/- 20 rayleighs) and molecular hydrogen. The extreme ultraviolet emissions in the range from 800 to 1100 angstroms at the four planets visited by Voyager scale approximately as the inverse square of their heliocentric distances.