X-ray Photographs of a Solar Active Region with a Multilayer Telescope at Normal Incidence

An astronomical photograph was obtained with a multilayer x-ray telescope. A 4-centimeter tungsten-carbon multilayer mirror was flown as part of an experimental solar rocket payload, and successful images were taken of the sun at normal incidence at a wavelength of 44 angstroms. Coronal Si-XII emission from an active region was recorded on film; as expected, the structure is very similar to that observed at O-VIII wavelengths by the Solar Maximum Mission flat crystal spectrometer at the same time. The small, simple optical system used in this experiment appears to have achieved a resolution of 5 to 10 arc seconds.     

Cloud droplet deposition in subalpine balsam fir forests: hydrological and chemical inputs

Subalpine forests of the northern Appalachians are subject to significant deposition of water and chemicals via cloud droplet impaction. This deposition has been estimated by a method linking micrometeorological measures of turbulent transfer, a detailed representation of canopy structure, and experimentally derived capture efficiencies. Water inputs from clouds are about 46 percent, and chemical inputs range from 150 to 430 percent of the bulk precipitation.     

Sprites, ELF Transients, and Positive Ground Strokes

In two summertime mesoscale convective systems (MCSs), mesospheric optical sprite phenomena were often coincident with both large-amplitude positive cloud-to-ground lightning and transient Schumann resonance excitations of the entire Earth-ionosphere cavity. These observations, together with earlier studies of MCS electrification, suggest that sprites are triggered when the rapid removal of large quantities of positive charge from an areally extensive charge layer stresses the mesosphere to dielectric breakdown.     

Lacticin 481: in vitro reconstitution of lantibiotic synthetase activity

The lantibiotic lacticin 481 is synthesized on ribosomes as a prepeptide (LctA) and posttranslationally modified to its mature form. These modifications include dehydration of serines and threonines, followed by intramolecular addition of cysteines to the unsaturated amino acids, which generates cyclic thioethers. This process breaks eight chemical bonds and forms six newbonds and is catalyzed by one enzyme, LctM. We have characterized the in vitro activity of LctM, which completely processed a series of LctA mutants, displaying a permissive substrate specificity that holds promise for antibiotic engineering.     

Laboratory simulation of charge exchange-produced X-ray emission from comets

In laboratory experiments using the engineering spare microcalorimeter detector from the ASTRO-E satellite mission, we recorded the x-ray emission of highly charged ions of carbon, nitrogen, and oxygen, which simulates charge exchange reactions between heavy ions in the solar wind and neutral gases in cometary comae. The spectra are complex and do not readily match predictions. We developed a charge exchange emission model that successfully reproduces the soft x-ray spectrum of comet Linear C/1999 S4, observed with the Chandra X-ray Observatory.