Holed up in a natural crystal

Nature ◽  
2007 ◽  
Vol 446 (7131) ◽  
pp. 35-36 ◽  
Author(s):  
Felix A. Rey
Keyword(s):  
Natural Crystal

scholarly journals Significant artefactual noise in 90Y TOF-PET imaging of low specific activity phantoms arises despite increased acquisition time

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Michel Hesse ◽  
Stephan Walrand
Keyword(s):  
Pet Imaging ◽  
Specific Activity ◽  
Whole Body ◽  
Acquisition Time ◽  
Random Coincidence ◽  
Natural Crystal ◽  
Phantom Studies ◽  
Pet Reconstruction ◽  
Very High ◽  
Tof Pet

AbstractVolumes of usual PET phantoms are about four to sixfold that of a human liver. In order to avoid count rate saturation and handling of very high 90Y activity, reported TOF-PET phantom studies are performed using specific activities lower than those observed in liver radioembolization.However, due to the constant random coincidence rate induced by the natural crystal radioactivity, reduction of 90Y specific activity in TOF-PET imaging cannot be counterbalanced by increasing the acquisition time. As a result, most 90Y phantom studies reported images noisier than those obtained in whole-body 18F-FDG, and thus advised to use dedicated noise control in TOF-PET imaging post 90Y liver radioembolization.We performed acquisitions of the Jaszczak Deluxe phantom in which the hot rod insert was only partially filled with 2.6 GBq of 90Y. Standard reconstruction parameters recommended by the manufacturer for whole-body 18F-FDG PET were used.Low specific activity setups, although exactly compensated by increasing the acquisition time in order to get the same number of detected true coincidences per millilitre, were impacted by significant noise. On the other hand, specific activity and acquisition time setup similar to that used in post 90Y liver radioembolization provided image quality very close to that of whole-body 18F-FDG.This result clearly discards the use of low specific activity phantoms intended to TOF-PET reconstruction parameter optimization. Volume reduction of large phantoms can be achieved by vertically setting the phantoms or by adding Styrofoam inserts.

scholarly journals How Does Bacillus thuringiensis Crystallize Such a Large Diversity of Toxins?

Toxins ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 443
Author(s):  
Guillaume Tetreau
Keyword(s):  
Bacillus Thuringiensis ◽  
Structural Biology ◽  
Structural Information ◽  
Future Evolution ◽  
Mechanisms Of Toxicity ◽  
Bt Toxin ◽  
Natural Crystal ◽  
Biological Insecticide ◽  
Key Drivers

Bacillus thuringiensis (Bt) is a natural crystal-making bacterium. Bt diversified into many subspecies that have evolved to produce crystals of hundreds of pesticidal proteins with radically different structures. Their crystalline form ensures stability and controlled release of these major virulence factors. They are responsible for the toxicity and host specificity of Bt, explaining its worldwide use as a biological insecticide. Most research has been devoted to understanding the mechanisms of toxicity of these toxins while the features driving their crystallization have long remained elusive, essentially due to technical limitations. The evolution of methods in structural biology, pushing back the limits of the resolution attainable, now allows access to be gained to structural information hidden within natural crystals of such toxins. In this review, I present the main parameters that have been identified as key drivers of toxin crystallization in Bt, notably in the light of recent discoveries driven by structural biology studies. Then, I develop how the future evolution of structural biology will hopefully unveil new mechanisms of Bt toxin crystallization, opening the door to their hijacking with the aim of developing a versatile in vivo crystallization platform of high academic and industrial interest.

Natural Crystal Habit and Preferential Growth Directions during PVT of Silicon Carbide

2004 ◽  
Vol 457-460 ◽  
pp. 111-114 ◽  
Author(s):  
Z.G. Herro ◽  
Boris M. Epelbaum ◽  
Matthias Bickermann ◽  
Pierre M. Masri ◽  
Christoph Seitz ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Crystal Habit ◽  
Preferential Growth ◽  
Natural Crystal

Temperature related structural variation of the hydrous components in gypsum

2000 ◽  
Vol 215 (12) ◽  
Author(s):  
P.F. Schofield ◽  
C.C. Wilson ◽  
K.S. Knight ◽  
I.C. Stretton
Keyword(s):  
Neutron Diffraction ◽  
Single Crystal ◽  
Structural Variation ◽  
Natural Crystal

Single crystal neutron diffraction studies have been carried out on a natural crystal of gypsum (CaSO

A scattered ring in a natural crystal of tourmaline

1990 ◽  
Vol 21 (1) ◽  
pp. 41-43 ◽  
Author(s):  
Y H Ja
Keyword(s):  
Natural Crystal

Polarization and Electromagnetic Emissions of Natural Crystalline Structures upon Acoustic Excitation

2019 ◽  
Vol 970 ◽  
pp. 153-166
Author(s):  
Anatoly Bespal’ko ◽  
Anatoly P. Surzhikov ◽  
Pavel Fedotov ◽  
Evgeniy Pomishin ◽  
Oldrich Stary
Keyword(s):  
Density Distribution ◽  
Charge Density ◽  
Surface Charge ◽  
Surface Charge Density ◽  
Signal Amplitude ◽  
Electromagnetic Signal ◽  
Acoustic Excitation ◽  
Charge Density Distribution ◽  
Natural Crystal ◽  
Electromagnetic Emissions

A surface charge density distribution on natural crystal samples is investigated in the paper. Here are revealed regularities of electromagnetic signal amplitude changes upon acoustic excitation of electrified calcite samples depending on the size of the crystals.

Spectroscopic Methods Used for Structural Analysis of Natural Crystals

2013 ◽  
Vol 448-453 ◽  
pp. 3728-3731
Author(s):  
Jian Hua Zhao ◽  
Jia Jun Ma
Keyword(s):  
Crystal Growth ◽  
Structural Analysis ◽  
Detection Methods ◽  
Manual Control ◽  
Spectroscopic Methods ◽  
Color Distribution ◽  
Natural Crystal

Most of the natural crystal color distribution are more uniform, different shades, pastel colors, while in manual control is relatively stable under the conditions of the synthesis of crystal growth, its internal characteristics exhibited excessive uniformity, color uniform, uniform, gaudy, dull, colorant concentration is too high or too low, make crystal color appears too deep or too shallow phenomenon. This paper studies the characteristics of natural crystal detection methods.

Natural Crystal Greenockite (Cadmium Sulfide) as an X‐Ray Detector

1950 ◽  
Vol 21 (11) ◽  
pp. 1196-1196 ◽  
Author(s):  
E. L. Criscuolo ◽  
D. T. O'Connor
Keyword(s):  
Cadmium Sulfide ◽  
X Ray ◽  
Natural Crystal
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