Existence of an 16O-rich gaseous reservoir in the solar nebula.
(9/95)
Carbonaceous chondrite condensate olivine grains from two distinct petrographic settings, calcium-aluminum-rich inclusion (CAI) accretionary rims and amoeboid olivine aggregates (AOAs), are oxygen-16 (16O) enriched at the level previously observed inside CAIs. This requires that the gas in the nebular region where these grains condensed was 16O-rich. This contrasts with an 16O-poor gas present during the formation of chondrules, suggesting that CAIs and AOAs formed in a spatially restricted region of the solar nebula containing 16O-rich gas. The 16O-rich gas composition may have resulted either from mass-independent isotopic chemistry or from evaporation of regions with enhanced dust/gas ratios, possibly in an X-wind environment near the young Sun. (+info)
The sun compass of the sandhopper Talitrus saltator: the speed of the chronometric mechanism depends on the hours of light.
(10/95)
Experiments on solar orientation were conducted with adult amphipods (Talitrus saltator) subjected to a reduction and/or phase shift of the hours of light (L) or dark (D) with respect to the natural photoperiod: 15 h:9 h L:D (controls), 15 h:9 h inverted (i.e. phase-shifted by 12 h and tested with the sun during the subjective night), 4 h:20 h, 20 h:4 h inverted. The sandhoppers were released in a confined environment, and individual orientation angles were recorded. The results confirm the continuous operation, through the entire 24-h period, of a chronometric mechanism of compensation for apparent solar motion. They show excellent agreement with a recently proposed model of compensation for the sun at constant (not differential) speed and they demonstrate a dependence of the speed of the chronometric mechanism on the L:D ratio in the 24-h period. (+info)
Intake of alcohol and alcoholic beverages and the risk of basal cell carcinoma of the skin.
(11/95)
We prospectively examined the intake of alcoholic beverages in relation to the risk of basal cell carcinoma BCC in two large cohorts of men and women. Alcohol intake was assessed with food frequency questionnaires every 2-4 years, and BCC was ascertained by self-report. We used a pooled logistic regression to model the association between alcohol intake and BCC adjusting for various health, sun exposure, and sun-sensitivity factors. During 8 years of follow-up in women (1986-1994) we recorded 3060 cases of BCC, and during 10 years (1986-1996), we recorded 3028 cases in men. Significant positive associations were observed between total alcohol intake (P for trend <0.0001), alcohol from liquor (P for trend = 0.003), and white wine (P for trend = 0.01) intake and risk of BCC. Compared with those who abstained, those who drank 0.1-4.9 g, 5.0-14.9 g, 15.0-14.9 g, and 30 g or more alcohol a day had multivariate relative risks of 1.11 [95% confidence interval (CI), 1.03, 1.19], 1.26 (95% CI, 1.12, 1.41), 1.29 (95% CI, 1.18, 1.42), and 1.12 (95% CI, 1.01, 1.26), respectively. Alcohol from beer had no association with BCC in either cohort, and red wine appeared to have an inverse association in women (P for trend = 0.004) but not in men. These associations remained unchanged after adjustment for individual vitamins, multivitamin use, outdoor walking, and exclusion of follow-up time after last physical examination among those who never had BCC. Alcohol intake was associated with BCC, but the association appeared to be different for each type of alcoholic beverage. Other studies are needed to confirm these results. (+info)
Samples of stars beyond the solar system: silicate grains in interplanetary dust.
(12/95)
We have identified six circumstellar silicate grains within interplanetary dust particles (IDPs). Their extrasolar origins are demonstrated by their extremely anomalous oxygen isotopic compositions. Three 17O-rich grains appear to originate from red giant or asymptotic giant branch stars. One 16O-rich grain may be from a metal-poor star. Two 16O-poor grains have unknown stellar sources. One of the grains is forsterite, and two are amorphous silicate "GEMS" (glass with embedded metal and sulfides), which is consistent with astronomical identifications of crystalline and amorphous silicates in the outflows of evolved stars. These observations suggest cometary origins of these IDPs and underscore the perplexing absence of silicates among circumstellar dust grains from meteorites. (+info)
Illuminating the circadian clock in monarch butterfly migration.
(13/95)
Migratory monarch butterflies use a time-compensated Sun compass to navigate to their overwintering grounds in Mexico. Here, we report that constant light, which disrupts circadian clock function at both the behavioral and molecular levels in monarchs, also disrupts the time-compensated component of flight navigation. We further show that ultraviolet light is important for flight navigation but is not required for photic entrainment of circadian rhythms. Tracing these distinct light-input pathways into the brain should aid our understanding of the clock-compass mechanisms necessary for successful migration. (+info)
Chondrules with peculiar REE patterns: implications for solar nebular condensation at high C/O.
(14/95)
Rare earth element (REE) data from two ordinary chondrite chondrules show distinct negative chondrite-normalized concentration anomalies of samarium, europium, and ytterbium. The peculiar patterns may be the result of REE gas/solid fractionation at an oxygen fugacity lower than has been assumed for the canonical solar nebula. We suggest that the two ordinary chondrite chondrules acquired the fractionated REE patterns by incorporation of highly reduced, ultrarefractory condensates in their precursors. This interpretation implies that high-temperature condensation processes occurred in nebular environments with a strong deficit in oxygen, such as regions with an enhanced carbon/oxygen ratio. (+info)
Migrating songbirds recalibrate their magnetic compass daily from twilight cues.
(15/95)
Night migratory songbirds can use stars, sun, geomagnetic field, and polarized light for orientation when tested in captivity. We studied the interaction of magnetic, stellar, and twilight orientation cues in free-flying songbirds. We exposed Catharus thrushes to eastward-turned magnetic fields during the twilight period before takeoff and then followed them for up to 1100 kilometers. Instead of heading north, experimental birds flew westward. On subsequent nights, the same individuals migrated northward again. We suggest that birds orient with a magnetic compass calibrated daily from twilight cues. This could explain how birds cross the magnetic equator and deal with declination. (+info)
Pancam multispectral imaging results from the Spirit Rover at Gusev Crater.
(16/95)
Panoramic Camera images at Gusev crater reveal a rock-strewn surface interspersed with high- to moderate-albedo fine-grained deposits occurring in part as drifts or in small circular swales or hollows. Optically thick coatings of fine-grained ferric iron-rich dust dominate most bright soil and rock surfaces. Spectra of some darker rock surfaces and rock regions exposed by brushing or grinding show near-infrared spectral signatures consistent with the presence of mafic silicates such as pyroxene or olivine. Atmospheric observations show a steady decline in dust opacity during the mission, and astronomical observations captured solar transits by the martian moons, Phobos and Deimos, as well as a view of Earth from the martian surface. (+info)