A Laboratory Experiment with Relevance to The Survival of Micro-Organisms Entering a Planetary Atmosphere     

S. Al-Mufti  F. Hoyle/snm>  N.C. Wickramasinghe 《Astrophysics and Space Science》1999,268(1-3):51-53

A culture of E. coli was initially subjected to brief exposures to heat for durations of 30–60 s, starting with a temperature of 270 ^°C. A stepwise increase of this temperature from 270 ^°C–750 ^°C and a sequential culturing led to the emergence of a strain of this bacterium with a much higher resistance to flash heating than the original culture possessed. This behaviour would have an important relevance to the survival of micro-organisms upon entering a planetary atmosphere. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Infrared Spectroscopy Over The 2.9–3.9 μm Waveband in Biochemistry and Astronomy     

F. Hoyle  N.C. Wickramasinghe  S. Al-Mufti  A.H. Olavesen  D.T. Wickramasinghe 《Astrophysics and Space Science》1999,268(1-3):161-166

The infrared spectrum of the galactic centre source GC-IRS 7 over the 2.9–3.9 μm waveband is interpreted as strong evidence for bacterial grains. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

The Availability of Phosphorus in The Bacterial Model of The Interstellar Grains     

F. Hoyle  N.C. Wickramasinghe 《Astrophysics and Space Science》1999,268(1-3):191-196

It is shown that phosphorus availability is in close balance with the phosphorus requirement of the bacterial grain model. This correspondence, which would be fortuitous if the interstellar grains were of inorganic origin, points to the correctness of the biological model. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Aromatic Hydrocarbons in Very Small Interstellar Grains     

N.C. Wickramasinghe  F. Hoyle  T. Al-Jubory 《Astrophysics and Space Science》1999,268(1-3):311-316

We show that the recently observed 3.3 μm emission feature in the diffuse radiation from the galactic disk might be due to an ensemble of aromatic molecules distributed within very small interstellar grains. The same particles also provide an explanation of the λ2200 ? interstellar absorption feature. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Diatoms on Earth, Comets, Europa and in Interstellar Space     

Richard B. Hoover  Fred Hoyle  N.C. Wickramasinghe  Miriam J. Hoover  S. Al-Mufti 《Astrophysics and Space Science》1999,268(1-3):197-224

There exists a close correspondence between the measured infrared properties of diatoms and the infrared spectrum of interstellar dust as observed in the Trapezium nebula and toward the galactic center source GC-IRS 7. Diatoms and bacteria also exhibit an absorbance peak near 2200 Å, which is found to agree with the observed ultraviolet absorbance properties of interstellar grains. We review the observational data and consider the known properties of diatoms and bacteria. It is suggested that these characteristics are consistent with the concept of acosmic microbiological system in which these or similar microorganisms might exist on comets, Europa and in interstellar space.  相似文献   

Calculations of Infrared Luxes from Galactic Sources for a Polysaccharide Grain Model     

F. Hoyle/snm>  N.C. Wickramasinghe 《Astrophysics and Space Science》1999,268(1-3):137-154

Using transmittance data appropriate for grain material which is predominantly comprised of polysaccharides we have computed infrared fluxes from several types of galactic infrared source. The model used in these computations involves polysaccharide condensation in material flowing out from O-type stars. With the exception of rather minor discrepancies we show that it is possible to match the2.1–13 μ observations of a wide range of galactic infrared sources. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

A Diatom Model of Dust in the Trapezium Nebula     

Q. Majeed  N.C. Wickramasinghe  F. Hoyle  S. Al-Mufti 《Astrophysics and Space Science》1999,268(1-3):225-227

Measurements are reported of the 5–35 μm infrared spectrum of a mixed diatom culture dispersed in a CsI disc. These data are used to compute the flux from a diatom model of dust in the Trapezium nebula, where dust grain temperatures are assumed to be distributed in the range 230–130 K. Good agreement with the observational data is found for the model. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Syn-sedimentary hydrothermal dolomites in a lacustrine rift basin: Petrographic and geochemical evidence from the lower Cretaceous Erlian Basin,Northern China     

Zhe Yang  Dakang Zhong  Fiona Whitaker  Zhao Lu  Shuo Zhang  Zicheng Tang  Runchao Liu  Zhuang Li 《Sedimentology》2020,67(1):305-329

Dolomites occur extensively in the lower Cretaceous along syn-sedimentary fault zones of the Baiyinchagan Sag, westernmost Erlian Basin, within a predominantly fluvial–lacustrine sedimentary sequence. Four types of dolomite are identified, associated with hydrothermal minerals such as natrolite, analcime and Fe-bearing magnesite. The finely-crystalline dolomites consist of anhedral to subhedral crystals (2 to 10 μm), evenly commixed with terrigenous sediments that occur either as matrix-supporting grains (Fd1) or as massive argillaceous dolostone (Fd2). Medium-crystalline (Md) dolomites are composed of subhedral to euhedral crystals aggregates (50 to 250 μm) and occur in syn-sedimentary deformation laminae/bands. Coarse-crystalline (Cd) dolomites consist of non-planar crystals (mean size >1 mm), and occur as fracture infills cross-cutting the other dolomite types. The Fd1, Md and Cd dolomites have similar values of δ¹⁸O (−20·5 to −11·0‰ Vienna PeeDee Belemnite) and δ¹³C (+1·4 to +4·5‰ Vienna PeeDee Belemnite), but Fd2 dolomites are isotopically distinct (δ¹⁸O −8·5 to −2·3‰ Vienna PeeDee Belemnite; δ¹³C +1·4 to +8·6‰ Vienna PeeDee Belemnite). Samples define three groups which differ in light rare-earth elements versus high rare-earth elements enrichment/depletion and significance of Tb, Yb and Dy anomalies. Medium-crystalline dolomites have signatures that indicate formation from brines at very high temperature, with salinities of 11·8 to 23·2 eq. wt. % NaCl and T_h values of 167 to 283°C. The calculated temperatures of Fd1 and Cd dolomites extend to slightly lower values (141 to 282°C), while Fd2 dolomites are distinctly cooler (81 to 124°C). These results suggest that the dolomites formed from hydrothermal fluid during and/or penecontemporaneous with sediment deposition. Faults and fractures bounding the basin were important conduits through which high-temperature Mg-rich fluids discharged, driven by an abnormally high heat flux associated with local volcanism. It is thought that differing amounts of cooling and degassing of these hydrothermal fluids, and of mixing with lake waters, facilitated the precipitation of dolomite and associated minerals, and resulted in the petrographic and geochemical differences between the dolomites.  相似文献   

First account of apochlorotic diatoms from intertidal sand of a south Florida beach     

Michele V. Blackburn  Fiona Hannah  Andrew Rogerson   《Estuarine, Coastal and Shelf Science》2009,84(4):519-526

During the period January to December 2004, monthly intertidal sand samples were collected from John U. Lloyd State Park beach, Florida. This study is the first to report on spatial and temporal distributions of heterotrophic (apochlorotic) diatoms in a sub-tropical beach, or indeed any sandy beach. Two non-pigmented, apochlorotic diatom morphotypes (strains III and IV) were consistently isolated from two intertidal beach sites and neither conformed to the morphologies of described species. Apochlorotic diatoms were found throughout the year and formed significant peaks in April, attaining total diatom counts of 71.1 and 94.9 cells g⁻¹ wet sand, for the upper tidal zone and lower tidal zone, respectively. Valve morphology is described in detail for the two diatom morphotypes isolated from the beach sites (strains III and IV). Growth responses to changes in salinity (reflecting those of the intertidal zone) were examined in the laboratory for these diatoms. Both morphotypes were euryhaline, tolerating salinities between 10 and 50, and maximum growth rates were achieved at salinities between 20 and 40. Diatoms grew equally well whether grown in the light or the dark and showed no evidence of pigments when viewed by epifluorescence microscopy. The ability of diatoms to burrow into agar and carrageenan at different concentrations was tested. Both morphotypes were observed to develop burrows through non-nutrient agar up to twice the standard concentration (30 g agar l⁻¹). The ease with which these heterotrophic diatoms formed burrows suggests that they were digesting these complex carbohydrates (i.e. phycocolloids) as a nutrient source. Strain IV, however, failed to burrow in a different phycocolloid, carrageenan. Similar degradative actions in the field might have implications for the breakdown of recalcitrant materials or allow diatoms to effectively compete with bacteria for carbon and nutrients.  相似文献