scholarly journals Precambrian Paleobiology: Precedents, Progress, and Prospects

2021 ◽  
Vol 9 ◽  
Author(s):  
J. William Schopf
Keyword(s):  
Fossil Record ◽  
Analytical Techniques ◽  
Oxygenic Photosynthesis ◽  
Evolutionary Significance ◽  
Definitive Evidence ◽  
Eukaryotic Organisms ◽  
Ediacaran Fauna ◽  
The 19Th Century ◽  
Primordial Soup ◽  
Zone Temperature

In 1859, C. R. Darwin highlighted the “inexplicable” absence of evidence of life prior to the beginning of the Cambrian. Given this lack of evidence and the natural rather than theological unfolding of life’s development Darwin espoused, over the following 50 years his newly minted theory was disputed. At the turn of the 19th century, beginning with the discoveries of C. D. Walcott, glimmerings of the previously “unknown and unknowable” early fossil record came to light – but Walcott’s Precambrian finds were also discounted. It was not until the breakthrough advances of the 1950’s and the identification of modern stromatolites (1956), Precambrian phytoplankton in shales (1950’s), stromatolitic microbes in cherts (1953), and terminal-Precambrian soft-bodied animal fossils (1950’s) that the field was placed on firm footing. Over the following half-century, the development and application of new analytical techniques coupled with the groundbreaking contributions of the Precambrian Paleobiology Research Group spurred the field to its international and distinctly interdisciplinary status. Significant progress has been made worldwide. Among these advances, the known fossil record has been extended sevenfold (from ∼0.5 to ∼3.5 Ga); the fossil record has been shown consistent with rRNA phylogenies (adding credence to both); and the timing and evolutionary significance of an increase of environmental oxygen (∼2.3 Ga), of eukaryotic organisms (∼2.0 Ga), and of evolution-speeding and biota-diversifying eukaryotic sexual reproduction (∼1.2 Ga) have been identified. Nevertheless, much remains to be learned. Such major unsolved problems include the absence of definitive evidence of the widely assumed life-generating “primordial soup”; the timing of the origin of oxygenic photosynthesis; the veracity of postulated changes in global photic-zone temperature from 3.5 Ga to the present; the bases of the advent of eukaryotic sexuality-requiring gametogenesis and syngamy; and the timing of origin and affinities of the small soft-bodied precursors of the Ediacaran Fauna.

scholarly journals Characterization and Identification of Varnishes on Copper Alloys by Means of UV Imaging and FTIR

Coatings ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 298
Author(s):  
Miriam Truffa Giachet ◽  
Julie Schröter ◽  
Laura Brambilla
Keyword(s):  
Copper Alloys ◽  
Analytical Techniques ◽  
Experimental Methodology ◽  
Artificial Ageing ◽  
Non Invasive ◽  
Uv Imaging ◽  
Before And After ◽  
The Comparative Study ◽  
The 19Th Century ◽  
Analytical Tools

The application of varnishes on the surface of metal objects has been a very common practice since antiquity, both for protective and aesthetic purposes. One specific case concerns the use of tinted varnishes on copper alloys in order to mimic gilding. This practice, especially flourishing in the 19th century for scientific instruments, decorative objects, and liturgical items, results in large museum collections of varnished copper alloys that need to be preserved. One of the main challenges for conservators and restorers deals with the identification of the varnishes through non-invasive and affordable analytical techniques. We hereby present the experimental methodology developed in the framework of the LacCA and VERILOR projects at the Haute École ARC of Neuchâtel for the identification of gold varnishes on brass. After extensive documentary research and analytical campaigns on varnished museum objects, various historic shellac-based varnishes were created and applied by different methods on a range of brass substrates with different finishes. The samples were then characterized by UV imaging and infrared spectroscopy before and after artificial ageing. The comparative study of these two techniques was performed for different thicknesses of the same varnish and for different shellac grades in order to implement an identification methodology based on simple non-invasive examination and analytical tools, which are accessible to conservators.

scholarly journals Spectroscopic study of an icon painted on wooden panel

2015 ◽  
Vol 69 (4) ◽  
pp. 387-393
Author(s):  
Sofija Stojanovic ◽  
Maja Gajic-Kvascev ◽  
Ljiljana Damjanovic
Keyword(s):  
Analytical Techniques ◽  
Paint Layer ◽  
Blue Pigment ◽  
Blue Colour ◽  
X Ray ◽  
Micro Raman Spectroscopy ◽  
Green Earth ◽  
Materials Used ◽  
The 19Th Century ◽  
Wooden Panel

Russian icon painted on wooden panel analyzed in this work is interesting for art historians because there is no precise information in which workshops it was made or who the author was. Similar icons are often found in churches and monasteries in our region. In order to obtain information about materials used for creation of investigated icon two micro-analytical techniques were used: Energy-Dispersive X-Ray Fluorescence spectroscopy (EDXRF) and micro-Raman spectroscopy. Obtained results confirmed presence of following materials: lead-white, vermilion, minium, ultramarine, brown and green earth pigments and silver in combination with yellow organic varnish, which served to an iconographer for gilding. Ground layer was made of calcite. Blue pigment ultramarine was probably used for blue colour as well as for obtaining particulars hues in several parts of the paint layer. This can be important information for further research concerning particular workshop in which the icon was made. Identified materials are typical for Russian iconography of the 19th century.

scholarly journals Dihydrolipoamide dehydrogenase from halophilic archaebacteria

1984 ◽  
Vol 218 (3) ◽  
pp. 811-818 ◽  
Author(s):  
M J Danson ◽  
R Eisenthal ◽  
S Hall ◽  
S R Kessell ◽  
D L Williams
Keyword(s):  
Steady State ◽  
Iodoacetic Acid ◽  
Enzymic Activity ◽  
Evolutionary Significance ◽  
Dihydrolipoamide Dehydrogenase ◽  
Kinetic Measurements ◽  
Steady State Kinetic ◽  
Halophilic Archaebacteria ◽  
Eukaryotic Organisms ◽  
State Kinetic

Dihydrolipoamide dehydrogenase has been discovered in the halophilic archaebacteria for the first time. The enzyme from both classical and alkaliphilic halobacteria has been investigated. (1) The enzyme specifically catalysed the stoichiometric oxidation of dihydrolipoamide by NAD+. Enzymic activity was optimal at 2 M-NaCl and was remarkably resistant to thermal denaturation. (2) The relative molecular masses (Mr) of the native enzyme from the various species of halobacteria were determined to be within the range 112000-120000. (3) The enzyme exhibited a hyperbolic dependence of catalytic activity on both dihydrolipoamide and NAD+ concentrations. From these steady-state kinetic measurements the dissociation constant (Ks) of dihydrolipoamide was determined to be 57 (+/- 5) microM. (4) The enzyme was only susceptible to inactivation by iodoacetic acid in the presence of its reducing ligands, dihydrolipoamide or NADH. The rate of inactivation followed a hyperbolic dependence on the concentration of dihydrolipoamide, from which the Ks of this substrate was calculated to be 55 (+/- 7) microM. Together with the steady-state kinetic data, the pattern of inactivations is consistent with the involvement in catalysis of a reversibly reducible disulphide bond, as has been found in dihydrolipoamide dehydrogenase from non-archaebacterial species. In eubacterial and eukaryotic organisms, dihydrolipoamide dehydrogenase functions in the 2-oxo acid dehydrogenase complexes. These multienzyme systems have not been detected in the archaebacteria, and, in the context of this apparent absence, the possible function and evolutionary significance of archaebacterial dihydrolipoamide dehydrogenase are discussed.

scholarly journals Role of thylakoid membranes in oxygenic photosynthesis: A comparative perspective using murburn concept

2020 ◽  
Author(s):  
Kelath Murali Manoj ◽  
Daniel Andrew Gideon ◽  
Abhinav Parashar ◽  
Deepak Haarith ◽  
Afsal Manekkathodi
Keyword(s):  
Lipid Membranes ◽  
Biological Membrane ◽  
Thylakoid Membranes ◽  
Oxygenic Photosynthesis ◽  
Evolutionary Significance ◽  
Reaction Systems ◽  
Membrane Interfaces ◽  
Gradient Based ◽  
Electron Group

Murburn concept is a new redox metabolic paradigm which advocates that several redox enzymes generate/stabilize diffusible reactive (oxygen) species (DRS or DROS) to carry out useful electron/moiety transfer reactions at biological membrane interfaces (Manoj 2020a). Herein, we show that the components and principles of redox reactions within chloroplasts/cyanobacteria share several similarities with soluble and simple extracellular or peroxisomal heme-enzymes that carry out electron/group transfer. We explore the comparison in detail with membrane-embedded and complex systems that catalyze: (i) microsomal xenobiotic metabolism and (ii) mitochondrial oxidative phosphorylation. We point out that the murburn interpretations of catalytic phenomena are consistent through the various reaction systems cited above. Further, we argue that evolutionary constraints and the physiological restrictions of neutral pH ranges discount proton-gradient based explanations for bioenergetic phosphorylations in chloroplasts. Therefore, we propose that the highly packed thylakoid membranes with minute aqueous volumes serve to enhance the lifetimes of oxygen-centered radicals and intermediates. The murburn perspective could also potentially explain protein supercomplexes in chloroplasts, and generation of ATP in mitochondria by photo-activation. Our proposal also highlights the evolutionary significance of lipid membranes and utility of oxygen in diverse life processes.

scholarly journals Diplomasi Politik Kesultanan Palembang Dan Kolonial Belanda Tanggal 23 Mei 1803

2017 ◽  
Vol 13 (2) ◽  
pp. 188-204
Author(s):  
Muhammad Ilham
Keyword(s):  
Analytical Techniques ◽  
Primary Sources ◽  
The Political ◽  
Scientific Journals ◽  
Secondary Sources ◽  
Analysis Technique ◽  
Diplomatic Edition ◽  
Colonial Government ◽  
The 19Th Century ◽  
The Relationship

Abstract   Diplomacy, Politics, Sultanate, Colonial This research was conducted as an effort to find out how the political diplomacy relations used by the Palembang sultan in establishing relations with Western powers, especially the Dutch Company in the archipelago. Political diplomacy is important because diplomacy is one way to foster and establish friendly relations between one person and people from other countries who aim to collaborate in various interests of the sultanate and government interests. To be able to establish relationships with one another, a device or diplomat is needed to establish the relationship. The main problem discussed in this study is to look at the Codicology, Philology, Transliteration, and Types of diplomacy in the Malay letters made by the Palembang authorities for the Dutch colonial government and also this research aims to find out what reasons and objectives to be achieved in fill in the letters. For this purpose, this type of research includes qualitative research, using secondary and primary sources. Primary sources are obtained from original texts and secondary sources in the form of books relating to the Palembang Sultanate, theses, dissertations and scientific journals. The technique of collecting data is to examine and select selectively then displayed and used in accordance with the time limit, namely the 19th century. After that, the data analysis technique uses descriptive-analytical techniques, namely to describe the full text, then analyze the meanings contained in the method and methods used is a single diplomatic edition method. After that, the writing of history to see and describe the findings in the letter with a historical approach.   Keywords: Diplomacy, Politics, Sultanate, Colonial  

Review: Freshwater and Soil Foraminifera – A Story of Long-Forgotten Relatives

2021 ◽  
Vol 51 (4) ◽  
pp. 318-331
Author(s):  
Maria Holzmann ◽  
Andrew J. Gooday ◽  
Ferry Siemensma ◽  
Jan Pawlowski
Keyword(s):  
Fossil Record ◽  
Phylogenetic Analyses ◽  
Molecular Data ◽  
Complex Environments ◽  
Molecular Phylogenetic ◽  
Terrestrial Habitats ◽  
Genomic Studies ◽  
Morphological And Molecular Data ◽  
Fresh Impetus ◽  
The 19Th Century

ABSTRACT Foraminifera are a primarily marine taxon widespread in all oceanic habitats, from shallow, brackish-water settings to deep-seafloor and pelagic realms. Their diversity is remarkable with several thousand species described and a fossil record tracing back to the Cambrian. While foraminifera represent one of the best-studied groups of marine meiofauna, much less is known about their non-marine relatives. The first freshwater foraminifera were described in the 19th century by European and North American protozoologists, but interest in them lapsed during much of the 20th century and was not rekindled until the advent of molecular systematics provided a fresh impetus to their study. Several new species, genera, and families have been described recently based on morphological and molecular data derived from cultured specimens. In parallel, environmental genomic studies revealed that foraminifera are highly diverse and ubiquitous in freshwater and soil environments. Molecular phylogenetic analyses places non-marine foraminifera in a few clades among the large array of single-chambered (monothalamous) lineages, suggesting that several independent colonization events of freshwater and terrestrial habitats occurred. Non-marine foraminifera are turning from obscure curiosities to being recognized as an important part of soil and freshwater microbial communities, a major component of these complex environments.

New approaches to cataloguing and understanding evolutionary diversity: a perspective from Australian herpetology

2014 ◽  
Vol 62 (6) ◽  
pp. 417 ◽  
Author(s):  
Paul Oliver ◽  
J. Scott Keogh ◽  
Craig Moritz
Keyword(s):  
Conservation Planning ◽  
Taxonomic Status ◽  
Analytical Techniques ◽  
Fundamental Unit ◽  
Evolutionary Significance ◽  
New Approaches ◽  
Evolutionary Studies ◽  
Evolutionary Lineages ◽  
Biodiversity Information ◽  
Lineage Diversity

Species are a fundamental unit for all fields of biology but conceptual and practical limitations have hampered the process of identifying and describing species in many organismal groups. One outcome of these challenges is the accumulation of genetically divergent lineages and morphologically distinctive populations that are ‘known’, but remain of uncertain taxonomic status and evolutionary significance. These lineages are also currently not effectively incorporated into evolutionary studies or conservation planning and management. Here we suggest three ways to address this issue. First, there is a need to develop improved frameworks to systematically capture taxonomically unrecognised lineage diversity. Second, increased utilisation of metadata frameworks will allow better recording and dissemination of biodiversity information. Finally, emerging genomic and analytical techniques will provide powerful new tools to improve our identification and understanding of evolutionary lineages.

Shale-hosted biota from the Dismal Lakes Group in Arctic Canada supports an early Mesoproterozoic diversification of eukaryotes

2021 ◽  
pp. 1-25
Author(s):  
Corentin C. Loron ◽  
Galen P. Halverson ◽  
Robert H. Rainbird ◽  
Tom Skulski ◽  
Elizabeth C. Turner ◽  
...  
Keyword(s):  
New Species ◽  
Fossil Record ◽  
Arctic Canada ◽  
Eukaryotic Organisms ◽  
Biological Innovations ◽  
One New Species ◽  
Eukaryotic Microfossils ◽  
High Diversity

Abstract The Mesoproterozoic is an important era for the development of eukaryotic organisms in oceans. The earliest unambiguous eukaryotic microfossils are reported in late Paleoproterozoic shales from China and Australia. During the Mesoproterozoic, eukaryotes diversified in taxonomy, metabolism, and ecology, with the advent of eukaryotic photosynthesis, osmotrophy, multicellularity, and predation. Despite these biological innovations, their fossil record is scarce before the late Mesoproterozoic. Here, we document an assemblage of organic-walled microfossils from the 1590–1270 Ma Dismal Lakes Group in Canada. The assemblage comprises 25 taxa, including 11 morphospecies identified as eukaryotes, a relatively high diversity for this period. We also report one new species, Dictyosphaera smaugi new species, and one unnamed taxon. The diversity of eukaryotic forms in this succession is comparable to slightly older assemblages from China and is higher than worldwide contemporaneous assemblages and supports the hypothesis of an earlier diversification of eukaryotes in the Mesoproterozoic.

scholarly journals The Archean origin of oxygenic photosynthesis and extant cyanobacterial lineages

2021 ◽  
Vol 288 (1959) ◽  
Author(s):  
G. P. Fournier ◽  
K. R. Moore ◽  
L. T. Rangel ◽  
J. G. Payette ◽  
L. Momper ◽  
...  
Keyword(s):  
Fossil Record ◽  
Surface Oxidation ◽  
Oxygenic Photosynthesis ◽  
Evolutionary Models ◽  
Crown Group ◽  
Relative Dating ◽  
Wide Range ◽  
Rapid Diversification ◽  
Oxygenic Phototrophs ◽  
Age Estimates

The record of the coevolution of oxygenic phototrophs and the environment is preserved in three forms: genomes of modern organisms, diverse geochemical signals of surface oxidation and diagnostic Proterozoic microfossils. When calibrated by fossils, genomic data form the basis of molecular clock analyses. However, different interpretations of the geochemical record, fossil calibrations and evolutionary models produce a wide range of age estimates that are often conflicting. Here, we show that multiple interpretations of the cyanobacterial fossil record are consistent with an Archean origin of crown-group Cyanobacteria. We further show that incorporating relative dating information from horizontal gene transfers greatly improves the precision of these age estimates, by both providing a novel empirical criterion for selecting evolutionary models, and increasing the stringency of sampling of posterior age estimates. Independent of any geochemical evidence or hypotheses, these results support oxygenic photosynthesis evolving at least several hundred million years before the Great Oxygenation Event (GOE), a rapid diversification of major cyanobacterial lineages around the time of the GOE, and a post-Cryogenian origin of extant marine picocyanobacterial diversity.

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