scholarly journals Following Molecular Mobility during Chemical Reactions: No Evidence for Active Propulsion

2021 ◽  
Author(s):  
Lucy L. Fillbrook ◽  
Jan-Philipp Günther ◽  
Günter Majer ◽  
Daniel J. O’Leary ◽  
William S. Price ◽  
...  
Keyword(s):  
Chemical Reactions ◽  
Molecular Mobility

scholarly journals Comment on “Boosted molecular mobility during common chemical reactions”

Science ◽  
2021 ◽  
Vol 371 (6526) ◽  
pp. eabe8322
Author(s):  
Jan-Philipp Günther ◽  
Lucy L. Fillbrook ◽  
Thomas S. C. MacDonald ◽  
Günter Majer ◽  
William S. Price ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Reactions ◽  
Molecular Mobility ◽  
Diffusion Coefficients ◽  
Diffusion Measurement ◽  
Nmr Diffusion ◽  
Signal Intensities ◽  
Nuclear Magnetic

The apparent “boosted mobility” observed by Wang et al. (Reports, 31 July 2020, p. 537) is the result of a known artifact. When signal intensities are changing during a nuclear magnetic resonance (NMR) diffusion measurement for reasons other than diffusion, the use of monotonically increasing gradient amplitudes produces erroneous diffusion coefficients. We show that no boosted molecular mobility is observed when shuffled gradient amplitudes are applied.

scholarly journals Response to Comment on “Boosted Molecular Mobility During Common Chemical Reactions”

2020 ◽  
Author(s):  
huan wang ◽  
Myeonggon Park ◽  
Ruoyu Dong ◽  
junyoung kim ◽  
Yoon-Kyoung Cho ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Gradient ◽  
Chemical Reactions ◽  
Molecular Mobility ◽  
Control Experiment ◽  
Magnetic Field Gradient

<h2>Günther et al. report that their control experiment using randomized magnetic field gradient sequences disagreed with findings we had reported using linear gradients. However, we show that measurements in our laboratory are consistent using both methods.<br></h2>

scholarly journals Response to Comment on “Boosted Molecular Mobility During Common Chemical Reactions”

2020 ◽  
Author(s):  
huan wang ◽  
Myeonggon Park ◽  
Ruoyu Dong ◽  
junyoung kim ◽  
Yoon-Kyoung Cho ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Gradient ◽  
Chemical Reactions ◽  
Molecular Mobility ◽  
Control Experiment ◽  
Magnetic Field Gradient

<h2>Günther et al. report that their control experiment using randomized magnetic field gradient sequences disagreed with findings we had reported using linear gradients. However, we show that measurements in our laboratory are consistent using both methods.<br></h2>

scholarly journals Comment on “Boosted Molecular Mobility During Common Chemical Reactions"

2020 ◽  
Author(s):  
Jan-Philipp Günther ◽  
Lucy Fillbrook ◽  
Thomas MacDonald ◽  
Günter Majer ◽  
William S. Price ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Diffusion Coefficient ◽  
Magnetic Resonance ◽  
Chemical Reactions ◽  
Molecular Mobility ◽  
Diffusion Measurement ◽  
Nmr Diffusion ◽  
Signal Intensities ◽  
Nuclear Magnetic

The apparent “boosted mobility” observed by nuclear magnetic resonance (NMR) diffusion measurements is the result of a known artefact. When signal intensities are changing during an NMR diffusion measurement for reasons other than diffusion, the use of monotonically increasing gradient amplitudes produces erroneous diffusion coefficient values. We show that no boosted molecular mobility is observed when shuffled gradient amplitudes are applied.

scholarly journals Response to Comment on “Boosted molecular mobility during common chemical reactions”

Science ◽  
2021 ◽  
Vol 371 (6526) ◽  
pp. eabe8678
Author(s):  
Huan Wang ◽  
Myeonggon Park ◽  
Ruoyu Dong ◽  
Junyoung Kim ◽  
Yoon-Kyoung Cho ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Gradient ◽  
Chemical Reactions ◽  
Molecular Mobility ◽  
Control Experiment ◽  
Magnetic Field Gradient

Günther et al. report that their control experiment using randomized magnetic field gradient sequences disagreed with findings we had reported using linear gradients. However, we show that measurements in our laboratory are consistent using both methods.

Surface reactions observed by photoemission electron microscopy (PEEM)

1992 ◽  
Vol 50 (1) ◽  
pp. 286-287
Author(s):  
H.H. Rotermund
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Work Function ◽  
Chemical Reactions ◽  
Reaction Diffusion ◽  
Dynamic Processes ◽  
Clean Surface ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces ◽  
Photoemission Electron

Chemical reactions at a surface will in most cases show a measurable influence on the work function of the clean surface. This change of the work function δφ can be used to image the local distributions of the investigated reaction,.if one of the reacting partners is adsorbed at the surface in form of islands of sufficient size (Δ>0.2μm). These can than be visualized via a photoemission electron microscope (PEEM). Changes of φ as low as 2 meV give already a change in the total intensity of a PEEM picture. To achieve reasonable contrast for an image several 10 meV of δφ are needed. Dynamic processes as surface diffusion of CO or O on single crystal surfaces as well as reaction / diffusion fronts have been observed in real time and space.

Microwaves: Application in Electron Microscopy

1990 ◽  
Vol 48 (3) ◽  
pp. 140-141
Author(s):  
Anthony S-Y Leong ◽  
David W Gove
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Chemical Reactions ◽  
Electromagnetic Waves ◽  
Tissue Fixation ◽  
Primary Method ◽  
Dipolar Molecules ◽  
Wide Range ◽  
Time Required ◽  
Cryostat Sections

Microwaves (MW) are electromagnetic waves which are commonly generated at a frequency of 2.45 GHz. When dipolar molecules such as water, the polar side chains of proteins and other molecules with an uneven distribution of electrical charge are exposed to such non-ionizing radiation, they oscillate through 180° at a rate of 2,450 million cycles/s. This rapid kinetic movement results in accelerated chemical reactions and produces instantaneous heat. MWs have recently been applied to a wide range of procedures for light microscopy. MWs generated by domestic ovens have been used as a primary method of tissue fixation, it has been applied to the various stages of tissue processing as well as to a wide variety of staining procedures. This use of MWs has not only resulted in drastic reductions in the time required for tissue fixation, processing and staining, but have also produced better cytologic images in cryostat sections, and more importantly, have resulted in better preservation of cellular antigens.

Fine structure and properties of defects in naturally occurring silicates and oxides

1990 ◽  
Vol 48 (4) ◽  
pp. 460-461
Author(s):  
David R. Veblen
Keyword(s):  
Chemical Reactions ◽  
High Resolution Electron Microscopy ◽  
Extended Defects ◽  
Single Chain ◽  
Naturally Occurring ◽  
Resolution Electron ◽  
Fine Structures ◽  
Image Simulations ◽  
Similar Crystal Structure

Extended defects and interfaces control many processes in rock-forming minerals, from chemical reactions to rock deformation. In many cases, it is not the average structure of a defect or interface that is most important, but rather the structure of defect terminations or offsets in an interface. One of the major thrusts of high-resolution electron microscopy in the earth sciences has been to identify the role of defect fine structures in reactions and to determine the structures of such features. This paper will review studies using HREM and image simulations to determine the structures of defects in silicate and oxide minerals and present several examples of the role of defects in mineral chemical reactions. In some cases, the geological occurrence can be used to constrain the diffusional properties of defects.The simplest reactions in minerals involve exsolution (precipitation) of one mineral from another with a similar crystal structure, and pyroxenes (single-chain silicates) provide a good example. Although conventional TEM studies have led to a basic understanding of this sort of phase separation in pyroxenes via spinodal decomposition or nucleation and growth, HREM has provided a much more detailed appreciation of the processes involved.

Sign in / Sign up

Export Citation Format

Share Document