Direct spectroscopic evidence for ionized polycyclic aromatic hydrocarbons in the interstellar medium.

Long-slit 8-13 micrometers spectroscopy of the nebula around NGC 1333 SVS 3 reveals spatial variations in the strength and shape of emission features that are probably produced by polycyclic aromatic hydrocarbons (PAHs). Close to SVS 3, the 11.2 micrometers feature develops an excess at approximately 10.8-11.0 micrometers and a feature appears at approximately 10 micrometers. These features disappear with increasing distance from the central source, and they show striking similarities to recent laboratory data of PAH cations, providing the first identification of emission features arising specifically from ionized PAHs in the interstellar medium.

Ototoxicity resulting from intracochlear perfusion of Streptococcus pneumoniae in the guinea pig is modified by cefotaxime or amoxycillin pretreatment.

Acute changes in the electrophysiology and ultrastructure of the organ of Corti were studied after microperfusion of c. 5 x 10(6) CFU of serotype 2 Streptococcus pneumoniae D39 or Escherichia coli K-12 directly into the scala tympani of guinea pigs. Hearing loss was assessed by recording the auditory nerve compound action potential response to a 10 kHz tone pip. Mean hearing loss 3 h after pneumococcal perfusion (n = 4) was 44 dB, compared to 6 dB after E. coli perfusion (n = 4) (P<0.001). After pneumococcal perfusion, scanning electron microscopy revealed damage to hair cell stereocilia and cratering of the apical surface of supporting cells. Intraperitoneal injection of 100 mg/kg cefotaxime (n = 4) or 100 mg/kg amoxycillin (n = 4) 30 min before perfusion of pneumococci significantly reduced mean hearing loss to 23 dB (P=0.01) or 20 dB (P=0.01), respectively, and diminished ultrastructural damage. The data suggest that if pneumococci invade the inner ear during meningitis, cochlear deafness may rapidly ensue.

Ground-based thermal infrared observations of comet Hale-Bopp (C/1995 O1) during 1996.

Thermal infrared (IR) imaging and spectroscopy of comet Hale-Bopp (C/1995 O1) during June, August, and September 1996 traced the development of the dust coma several months before perihelion. Images revealed nightly variations in the brightness of the inner coma from 1 to 12 June that were correlated with the appearance of a northward-pointing jet. The central IR flux increased by a factor of 8 between 1 June and 30 September, and the September data showed IR jets that corresponded to similar structures that were visible in reflected sunlight at shorter wavelengths. At all epochs, 8- to 13-micrometer spectra of the central coma revealed a strong silicate emission feature, including an 11.2-micrometer feature indicative of crystalline olivine, even when the comet was at a heliocentric distance of 4.1 astronomical units.

Pacific Ocean climate change: atmospheric forcing, ocean circulation and ecosystem response.

A major climate change event that affected atmospheric forcing, ocean circulation and ecosystem structure of the Pacific Ocean began in the mid-1970s. Changes in biomass, and presumably productivity, of the lower trophic levels (phytoplankton and Zooplankton) were directly attributed to this event. It also appears that some individual species at higher trophic levels were influenced, but cause-and-effect relationships are more difficult to document at the species level. Recent work shows that at least five major pelagic ecosystems responded to this event, but in different ways, and both increases and decreases in biomass were seen. Changes of this magnitude are well documented in the paleo-oceanographic record. However, it remains to be determined to what extent the changes were caused by natural cycles versus anthropogenic change (global warming).

Cytotoxic effects on hair cells of guinea pig cochlea produced by pneumolysin, the thiol activated toxin of Streptococcus pneumoniae.

The cytolytic toxin, pneumolysin, from the gram positive bacterium, Streptococcus pneumoniae, when perfused through the scala tympani of the guinea pig cochlea reduced the amplitude of both the compound action potential and the cochlear microphonic potential. When the surface of the organ of Corti was examined by scanning electron microscopy, both inner and outer hair cells and supporting cells were found to be damaged. Inner hair cells and outer hair cells of row 3 were the most susceptible to damage by pneumolysin, followed by row 2 and then by row 1 of the outer hair cells. Damage to hair cells included disruption and splaying of stereocilia, loss of stereocilia and complete dissolution of hair bundles. Apical surfaces of hair cells and supporting cells were torn, pitted and cratered with shrinkage and tearing of cell boundaries. Within the dose range perfused (0.05-1 micrograms/microliters in a 10 microliters aliquot), the magnitude of the physiological and anatomical lesions was concentration dependent. The cytotoxic effects of pneumolysin reported here may be clinically significant factors in deafness caused by meningitis and otitis media in humans.

Primary production in the North Pacific Central Gyre: A controversy with important implications.

Photosynthesis in the ocean is measured by (14)C-CO(2) uptake in bottle incubations. It can also be estimated from the distribution of biogeochemical properties. In the subtropical gyres, the biogeochemical method yields a rate that is apparently greater than that measured by the (14)C technique. This led to the controversial suggestion that oceanic primary production has been substantially underestimated. If correct, this suggestion also requires that there be a larger input of nitrogen and phosphorus, and it would make it difficult to explain the observed steady-state vertical distribution of properties. Resolution of the controversy is likely to be of broad interest to oceanographers because it may also lead to new insights into oceanic mixing and the cycling of carbon and nitrogen.

The infrared spectrum of comet Bradfield (1987s) and the silicate emission feature.

Infrared (1-20 micrometers) observations of comet Bradfield (1987s) from three observatories are reported. Silicate emission is prominent in all the data, from heliocentric distance r=0.87 to 1.45 AU. A CVF spectrum at r=1.45 AU shows a peak at 11.3 micrometers identified as crystalline olivine; the spectral shape is similar to that in Halley. Dust optical properties are similar to those of the grains in Halley's jets. Dust production rate near perihelion was approximately 10(6) g s-1 and varied in proportion to (r-2). We suggest that some differences in grain properties among comets could result from differences in the thermal history of the nuclear surface and the relative fraction of the dust particles originating in the subsurface icy layer versus the devolatilized mantle.

Climate and Chlorophyll a: Long-Term Trends in the Central North Pacific Ocean.

Since 1968 a significant increase in total chlorophyll a in the water column during the summer in the central North Pacific Ocean has been observed. A concomitant increase in winter winds and a decrease in sea surface temperature suggest that long-period fluctuations in atmospheric characteristics have changed the carrying capacity of the central Pacific epipelagic ecosystem.