Calculated carbon-13 NMR relaxation parameters for a restricted internal diffusion model. Application to methionine relaxation in dihydrofolate reductase

1978 ◽  
Vol 100 (23) ◽  
pp. 7159-7165 ◽  
Author(s):  
Robert E. London ◽  
John Avitabile
Keyword(s):  
Diffusion Model ◽  
Dihydrofolate Reductase ◽  
Nmr Relaxation ◽  
Internal Diffusion ◽  
Model Application ◽  
Relaxation Parameters

scholarly journals Same model, different conclusions: An identifiability issue in the linear ballistic accumulator model of decision-making

2020 ◽  
Author(s):  
Nathan J. Evans
Keyword(s):  
Decision Making ◽  
Diffusion Model ◽  
Large Scale ◽  
Drift Rate ◽  
Decision Time ◽  
Measurement Properties ◽  
Decision Threshold ◽  
Experimental Conditions ◽  
Model Application ◽  
Linear Ballistic Accumulator

Evidence accumulation models (EAMs) – the dominant modelling framework for speeded decision-making – have become an important tool for model application. Model application involves using specific model to estimate parameter values that relate to different components of the cognitive process, and how these values differ over experimental conditions and/or between groups of participants. In this context, researchers are often agnostic to the specific theoretical assumptions made by different EAM variants, and simply desire a model that will provide them with an accurate measurement of the parameters that they are interested in. However, recent research has suggested that the two most commonly applied EAMs – the diffusion model and the linear ballistic accumulator (LBA) – come to fundamentally different conclusions when applied to the same empirical data. The current study provides an in-depth assessment of the measurement properties of the two models, as well as the mapping between, using two large scale simulation studies and a reanalysis of Evans (2020a). Importantly, the findings indicate that there is a major identifiability issue within the standard LBA, where differences in decision threshold between conditions are practically unidentifiable, which appears to be caused by a tradeoff between the threshold parameter and the overall drift rate across the different accumulators. While this issue can be remedied by placing some constraint on the overall drift rate across the different accumulators – such as constraining the average drift rate or the drift rate of one accumulator to have the same value in each condition – these constraints can qualitatively change the conclusions of the LBA regarding other constructs, such as non-decision time. Furthermore, all LBA variants considered in the current study still provide qualitatively different conclusions to the diffusion model. Importantly, the current findings suggest that researchers should not use the unconstrained version of the LBA for model application, and bring into question the conclusions of previous studies using the unconstrained LBA.

scholarly journals How Much Entropy Is Contained in NMR Relaxation Parameters?

2021 ◽  
Author(s):  
Falk Hoffmann ◽  
Frans A. A. Mulder ◽  
Lars V. Schäfer
Keyword(s):  
Nmr Relaxation ◽  
Relaxation Parameters

Hydrodynamic effects on the overall adsorption rate of phenol on activated carbon cloth through the advection-diffusion model application

2021 ◽  
Vol 93 ◽  
pp. 267-278
Author(s):  
E. García-Hernández ◽  
C.G. Aguilar-Madera ◽  
E.C. Herrera-Hernández ◽  
R. Ocampo-Pérez ◽  
E. Bailón-García ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Diffusion Model ◽  
Adsorption Rate ◽  
Carbon Cloth ◽  
Activated Carbon Cloth ◽  
Model Application ◽  
Advection Diffusion ◽  
Hydrodynamic Effects

Influence of depyritization on NMR relaxation parameters of Aleksinac oil shale kerogen

Fuel ◽  
1998 ◽  
Vol 77 (9-10) ◽  
pp. 1001-1003 ◽  
Author(s):  
Zoran Ẑujović ◽  
Radivoje Srejić ◽  
Dušan Vučelić ◽  
Branimir Jovančićević ◽  
Dragomir Vitorović
Keyword(s):  
Oil Shale ◽  
Nmr Relaxation ◽  
Relaxation Parameters

scholarly journals Determination of hydrogen exchange and relaxation parameters in PHIP complexes at micromolar concentrations

2021 ◽  
Author(s):  
Lisanne Sellies ◽  
Ruud L. E. G. Aspers ◽  
Marco Tessari
Keyword(s):  
Small Molecules ◽  
Hydrogen Exchange ◽  
Nmr Relaxation ◽  
Para Hydrogen ◽  
Natural Extracts ◽  
Relaxation Parameters ◽  
Selective Inversion ◽  
High Concentrations ◽  
Nmr Signals

Abstract. Non-hydrogenative Para-Hydrogen Induced Polarization (PHIP) is a fast, efficient and relatively inexpensive approach to enhance Nuclear Magnetic Resonance (NMR) signals of small molecules in solution. The efficiency of this technique depends on the interplay of NMR relaxation and kinetic processes, which, at high concentrations, can be characterized by selective inversion experiments. However, in the case of dilute solutions this approach is clearly not viable. Here, we present alternative PHIP-based NMR experiments to determine hydrogen and hydrides’ relaxation parameters as well as the rate constants for p-H2 association and dissociation from asymmetric PHIP complexes at micromolar concentrations. Access to these parameters is necessary to understand and improve the PHIP enhancements of (dilute) substrates present in, for instance, biofluids and natural extracts.

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