scholarly journals Optimizing Model Calibrations for Natural Product Chemical Compositions with Absorbance-Transmittance Excitation-Emission (A-TEEM) Spectroscopy

2021 ◽  
Vol 120 (3) ◽  
pp. 264a
Author(s):  
Adam M. Gilmore
Author(s):  
D.I. Potter ◽  
M. Ahmed ◽  
K. Ruffing

Ion implantation, used extensively for the past decade in fabricating semiconductor devices, now provides a unique means for altering the near-surface chemical compositions and microstructures of metals. These alterations often significantly improve physical properties that depend on the surface of the material; for example, catalysis, corrosion, oxidation, hardness, friction and wear. Frequently the mechanisms causing these beneficial alterations and property changes remain obscure and much of the current research in the area of ion implantation metallurgy is aimed at identifying such mechanisms. Investigators thus confront two immediate questions: To what extent is the chemical composition changed by implantation? What is the resulting microstructure? These two questions can be investigated very fruitfully with analytical electron microscopy (AEM), as described below.


Author(s):  
Gejing Li ◽  
D. R. Peacor ◽  
D. S. Coombs ◽  
Y. Kawachi

Recent advances in transmission electron microscopy (TEM) and analytical electron microscopy (AEM) have led to many new insights into the structural and chemical characteristics of very finegrained, optically homogeneous mineral aggregates in sedimentary and very low-grade metamorphic rocks. Chemical compositions obtained by electron microprobe analysis (EMPA) on such materials have been shown by TEM/AEM to result from beam overlap on contaminant phases on a scale below resolution of EMPA, which in turn can lead to errors in interpretation and determination of formation conditions. Here we present an in-depth analysis of the relation between AEM and EMPA data, which leads also to the definition of new mineral phases, and demonstrate the resolution power of AEM relative to EMPA in investigations of very fine-grained mineral aggregates in sedimentary and very low-grade metamorphic rocks.Celadonite, having end-member composition KMgFe3+Si4O10(OH)2, and with minor substitution of Fe2+ for Mg and Al for Fe3+ on octahedral sites, is a fine-grained mica widespread in volcanic rocks and volcaniclastic sediments which have undergone low-temperature alteration in the oceanic crust and in burial metamorphic sequences.


Author(s):  
Ardalan A. Nabi ◽  
Lydia M. Scott ◽  
Daniel P. Furkert ◽  
Jonathan Sperry

The rare benzoxazepine ring in the alkaloid inducamide C is unstable and prone to rearrangement, indicating that structural revision of the natural product may be necessary.


Planta Medica ◽  
2008 ◽  
Vol 74 (09) ◽  
Author(s):  
V Myrianthopoulos ◽  
P Magiatis ◽  
AL Skaltsounis ◽  
L Meijer ◽  
E Mikros

Planta Medica ◽  
2011 ◽  
Vol 77 (12) ◽  
Author(s):  
C Chanchao ◽  
S Umthong ◽  
P Phuwapraisirisan ◽  
S Puthong

Planta Medica ◽  
2012 ◽  
Vol 78 (05) ◽  
Author(s):  
SK Jain ◽  
R Sahu ◽  
J Zhang ◽  
MR Jacob ◽  
XC Li ◽  
...  

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