scholarly journals Nitrogen Reduction by the Fe Sites of Synthetic [Mo3S4Fe] Cubes

2021 ◽  
Author(s):  
Yasuhiro Ohki ◽  
Kenichiro Munakata ◽  
Ryota Hara ◽  
Mami Kachi ◽  
Keisuke Uchida ◽  
...  
Keyword(s):  
Transition Metal ◽  
Active Site ◽  
N2 Fixation ◽  
Carbon Cluster ◽  
Sulfur Compounds ◽  
Sulfur Cluster ◽  
History Of Research ◽  
History Of ◽  
Fe Sites ◽  
Synthetic Metal

Abstract N2 fixation by Nature, which is a crucial process to supply bio-available forms of nitrogen, is performed by nitrogenase. This enzyme employs a unique transition metal-sulfur-carbon cluster as its active-site cofactor ([(R-homocitrate)MoFe7S9C], FeMoco), and the sulfur-surrounded Fe atoms have been postulated to capture and reduce N2. Whereas synthetic counterparts of FeMoco, metal-sulfur clusters, have displayed binding of N2 in a few examples, the reduction of N2 by any synthetic metal-sulfur clusters or even by the extracted form of FeMoco have remained elusive despite a near-50-year history of research. Here we show that the Fe atoms in our synthetic [Mo3S4Fe] cubes capture an N2 molecule and catalyze N2 silylation to form N(SiMe3)3 under treatment with excess Na and Me3SiCl. These results exemplify the first catalytic N2 reduction by a synthetic metal-sulfur cluster with an Fe center supported only by S ligands. This work demonstrates the N2-reducing capability of Fe atoms in a S-rich environment, which Nature has selected to accomplish a similar purpose. This work also suggests some critical features for successful by metal-sulfur compounds, which serve as clues to understand the origin of N2 fixation on Earth.

History of Research on Marine N2 Fixation

2021 ◽  
pp. 31-41
Author(s):  
Jonathan P. Zehr ◽  
Douglas G. Capone
Keyword(s):  
N2 Fixation ◽  
History Of Research ◽  
History Of

History of Research in Mammalian Sexual Behavior

1983 ◽  
Vol 28 (7) ◽  
pp. 545-546
Author(s):  
Rae Silver
Keyword(s):  
Sexual Behavior ◽  
History Of Research ◽  
History Of

Review of early developmental stages of trilobites and agnostids from the Barrandian area (Czech Republic)

2017 ◽  
Vol 186 (1) ◽  
pp. 103-112
Author(s):  
Lukáš Laibl ◽  
Oldřich Fatka
Keyword(s):  
Czech Republic ◽  
Developmental Stages ◽  
History Of Research ◽  
Early Developmental Stages ◽  
History Of ◽  
Barrandian Area ◽  
Early Developmental

This contribution briefly summarizes the history of research, modes of preservation and stratigraphic distribution of 51 trilobite and five agnostid taxa from the Barrandian area, for which the early developmental stages have been described.

Bayesian Inference in Human Time Perception

2017 ◽  
Author(s):  
Darren Rhodes
Keyword(s):  
Time Perception ◽  
Likelihood Function ◽  
Human Perception ◽  
Future Research ◽  
Temporal Properties ◽  
History Of Research ◽  
Psychophysical Testing ◽  
History Of ◽  
Fundamental Dimension ◽  
Perception Of Time

Time is a fundamental dimension of human perception, cognition and action, as the perception and cognition of temporal information is essential for everyday activities and survival. Innumerable studies have investigated the perception of time over the last 100 years, but the neural and computational bases for the processing of time remains unknown. First, we present a brief history of research and the methods used in time perception and then discuss the psychophysical approach to time, extant models of time perception, and advancing inconsistencies between each account that this review aims to bridge the gap between. Recent work has advocated a Bayesian approach to time perception. This framework has been applied to both duration and perceived timing, where prior expectations about when a stimulus might occur in the future (prior distribution) are combined with current sensory evidence (likelihood function) in order to generate the perception of temporal properties (posterior distribution). In general, these models predict that the brain uses temporal expectations to bias perception in a way that stimuli are ‘regularized’ i.e. stimuli look more like what has been seen before. Evidence for this framework has been found using human psychophysical testing (experimental methods to quantify behaviour in the perceptual system). Finally, an outlook for how these models can advance future research in temporal perception is discussed.

Perfektives und Imperfektives Partizip

2020 ◽  
Vol 28 ◽  
pp. 27-79
Author(s):  
Marc Brose
Keyword(s):  
Tense And Aspect ◽  
History Of Research ◽  
New Concepts ◽  
History Of ◽  
Basic Semantic

“Perfective and Imperfective Participle”: This article deals with the basic semantic opposition of the two types of Egyptian participles, jri̯ and jrr. After an extended overview of the history of research presenting the classical approaches of K. Sethe and A. H. Gardiner, who both used established terms of models of tense and aspect, and also the advanced approaches of W. Schenkel, J. P. Allen, K. Jansen-Winkeln and E. Oreál, who introduced new concepts and terminolgy and so tried to overcome the classical approaches, it is nevertheless shown that the classification of the opposition as “perfective–imperfective”, with modernized definitions in contrast to Gardiner’s, suffices to explain the entire functional range of the two types and that the advanced approaches are not necessary.

Angkor Wat: A transcultural history of heritages

2021 ◽  
pp. 1-8
Author(s):  
Chanratana Chen
Keyword(s):  
Architectural History ◽  
World Heritage Site ◽  
Heritage Preservation ◽  
Black And White ◽  
History Of Research ◽  
South And Southeast Asia ◽  
Heritage Site ◽  
History Of ◽  
Historical Photographs ◽  
The University

In December 2019, Michael Falser, of the University of Heidelberg, a specialist on heritage preservation and the art and architectural history of South and Southeast Asia, published his two-volume study, Angkor Wat: A transcultural history of heritages, which he had spent almost ten years researching. The volumes cover the history of research of the most famous monument in Cambodia, Angkor Wat, the world's largest religious monument, listed by UNESCO as a World Heritage Site in 1992. The two volumes include more than 1,400 black-and-white and colour illustrations, including historical photographs and the author's own photographs, architectural plans and samples of tourist brochures and media clips about Angkor Wat, which has been represented as a national and international icon for almost 150 years, since the 1860s.

Active site engineering of atomically dispersed transition metal-heteroatom-carbon catalysts for oxygen reduction

2021 ◽  
Author(s):  
Jiawei Zhu ◽  
Shichun Mu
Keyword(s):  
Transition Metal ◽  
Oxygen Reduction ◽  
Active Site ◽  
Catalytic Reactions ◽  
Single Atom ◽  
Carbon Catalysts

Owing to the advantage of atomic utilization, the single-atom catalyst has attracted much attention and been employed in multifarious catalytic reactions. Their definite site configuration is favorable for exploring the...

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