Evidence for the widespread occurrence of ancient forests on cliffs

2000 ◽  
Vol 27 (2) ◽  
pp. 319-331 ◽  
Author(s):  
D. W. Larson ◽  
U. Matthes ◽  
J. A. Gerrath ◽  
N. W. K. Larson ◽  
J. M. Gerrath ◽  
...  
Author(s):  
D.F. Blake ◽  
LJ. Allamandola ◽  
G. Palmer ◽  
A. Pohorille

The natural history of the biogenic elements H, C, N, O, P and S in the cosmos is of great interest because it is these elements which comprise all life. Material ejected from stars (or pre-existing in the interstellar medium) is thought to condense into diffuse bodies of gravitationally bound gas and dust called cold interstellar molecular clouds. Current theories predict that within these clouds, at temperatures of 10-100° K, gases (primarily H2O, but including CO, CO2, CH3OH, NH3, and others) condense onto submicron silicate grains to form icy grain mantles. This interstellar ice represents the earliest and most primitive association of the biogenic elements. Within these multicomponent icy mantles, pre-biotic organic compounds are formed during exposure to UV radiation. It is thought that icy planetesimals (such as comets) within our solar system contain some pristine interstellar material, including ices, and may have (during the early bombardment of the solar system, ∼4 Ga) carried this material to Earth.Despite the widespread occurrence of astrophysical ices and their importance to pre-biotic organic evolution, few experimental data exist which address the relevant phase equilibria and possible structural states. A knowledge of the petrology of astrophysical ice analogs will allow scientists to more confidently interpret astronomical IR observations. Furthermore, the development and refinement of procedures for analyzing ices and other materials at cryogenic temperatures is critical to the study of materials returned from the proposed Rosetta comet nucleus and Mars sample return missions.


2017 ◽  
Vol 8 (2) ◽  
pp. 166-168
Author(s):  
Verka Maratilova ◽  
Keyword(s):  

2020 ◽  
Author(s):  
Ilya V. Buynevich ◽  
◽  
Albertas Bitinas ◽  
Donatas Pupienis ◽  
Aldona Damušytė ◽  
...  
Keyword(s):  

2021 ◽  
Author(s):  
Eryn Nelson ◽  
Jeffrey S. S. K. Formen ◽  
Christian Wolf

The widespread occurrence and significance of chiral compounds does not only require new methods for their enantioselective synthesis but also efficient tools that allow rapid determination of the absolute configuration,...


Toxins ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 406
Author(s):  
Mauro C. P. Vilar ◽  
Thiago F. C. P. Rodrigues ◽  
Luan O. Silva ◽  
Ana Beatriz F. Pacheco ◽  
Aloysio S. Ferrão-Filho ◽  
...  

Cyanobacteria stand out among phytoplankton when they form massive blooms and produce toxins. Because cyanotoxin genes date to the origin of metazoans, the hypothesis that cyanotoxins function as a defense against herbivory is still debated. Although their primary cellular function might vary, these metabolites could have evolved as an anti-predator response. Here we evaluated the physiological and molecular responses of a saxitoxin-producing Raphidiopsis raciborskii to infochemicals released by the grazer Daphnia gessneri. Induced chemical defenses were evidenced in R. raciborskii as a significant increase in the transcription level of sxt genes, followed by an increase in saxitoxin content when exposed to predator cues. Moreover, cyanobacterial growth decreased, and no significant effects on photosynthesis or morphology were observed. Overall, the induced defense response was accompanied by a trade-off between toxin production and growth. These results shed light on the mechanisms underlying zooplankton–cyanobacteria interactions in aquatic food webs. The widespread occurrence of the cyanobacterium R. raciborskii in freshwater bodies has been attributed to its phenotypic plasticity. Assessing the potential of this species to thrive over interaction filters such as zooplankton grazing pressure can enhance our understanding of its adaptive success.


Author(s):  
Judith Riedo ◽  
Felix E. Wettstein ◽  
Andrea Rösch ◽  
Chantal Herzog ◽  
Samiran Banerjee ◽  
...  

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