Chemical Relaxation Spectra: Calculation of Relaxation Times for Complex Mechanisms1

1966 ◽  
Vol 70 (7) ◽  
pp. 2319-2324 ◽  
Author(s):  
Gordon G. Hammes ◽  
Paul R. Schimmel
Keyword(s):  
Relaxation Times ◽  
Relaxation Spectra ◽  
Chemical Relaxation

Effect of deformation history on the stress relaxation behaviour of Colombian Caribbean coastal cheese from goat milk

2018 ◽  
Vol 24 (6) ◽  
pp. 487-496 ◽  
Author(s):  
Diego F Tirado ◽  
Diofanor Acevedo ◽  
Ramiro Torres-Gallo
Keyword(s):  
Stress Relaxation ◽  
Profile Analysis ◽  
Relaxation Times ◽  
Goat Milk ◽  
Texture Profile Analysis ◽  
Relaxation Behaviour ◽  
Deformation History ◽  
Relaxation Spectra ◽  
Texture Profile ◽  
Textural Attributes

Textural attributes are a manifestation of the rheological properties and physical structure of foods, cheeses among these. In order to describe these physical properties, the objective of this work was to analyse the effect of deformation history on the stress relaxation behaviour of Colombian Caribbean coastal cheese made from goat milk with 3.75% (F1), 4.00% (F2) and 4.25% (F3) fat content, through prediction made by a four-term Prony series based on Chen's model. For this, stress relaxation data and stress relaxation spectra were analysed. Moreover, textural attributes by texture profile analysis were measured. Physicochemical results were similar to those published by other authors, and all samples meet national and international standards. Results from this work showed that Chen's model could be successfully used to describe the effect of deformation history on the stress relaxation behaviour of Colombian Caribbean coastal cheese made from goat milk. F1 had the highest elastic response, with the most significant residual modules ( P0) and relaxation times (τ1, τ2 and τ3). On the other hand, residual modules and relaxation times (τ1, τ2 and τ3) for cheeses F2 and F3 did not present statistically significant differences (p > 0.05). Besides, by interpretation of the stress relaxation spectra, F1 presented the firmest structure (greatest distribution function and relaxation time) which was characterised by the highest elastic behaviour. Finally, according to texture profile analysis test, F1 had the highest hardness, cohesiveness and chewiness, whereas F2 and F3 did not present statistically significant differences (p > 0.05) between them.

An emerging technology: Nuclear magnetic resonance microscopy

1988 ◽  
Vol 46 ◽  
pp. 1000-1001
Author(s):  
M.J. Hennessy ◽  
E. Kwok
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Relaxation Times ◽  
Basic Research ◽  
Local Environment ◽  
Magnetic Resonance Images ◽  
Nmr Microscopy ◽  
Mri Scans ◽  
Temperature Relaxation ◽  
Nuclear Magnetic

Much progress in nuclear magnetic resonance microscope has been made in the last few years as a result of improved instrumentation and techniques being made available through basic research in magnetic resonance imaging (MRI) technologies for medicine. Nuclear magnetic resonance (NMR) was first observed in the hydrogen nucleus in water by Bloch, Purcell and Pound over 40 years ago. Today, in medicine, virtually all commercial MRI scans are made of water bound in tissue. This is also true for NMR microscopy, which has focussed mainly on biological applications. The reason water is the favored molecule for NMR is because water is,the most abundant molecule in biology. It is also the most NMR sensitive having the largest nuclear magnetic moment and having reasonable room temperature relaxation times (from 10 ms to 3 sec). The contrast seen in magnetic resonance images is due mostly to distribution of water relaxation times in sample which are extremely sensitive to the local environment.

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