Effects of steaming, drying, storage and loading rate on the stress relaxation time constant of parboiled rice

2004 ◽  
Author(s):  
Saifullah M. H. Saif ◽  
Dwyane A. Suter ◽  
Yubin Lan
Keyword(s):  
Relaxation Time ◽  
Stress Relaxation ◽  
Time Constant ◽  
Loading Rate ◽  
Parboiled Rice ◽  
Relaxation Time Constant

scholarly journals Stress relaxation amplitude of hydrogels determines migration, proliferation, and morphology of cells in 3-D

2021 ◽  
Author(s):  
Jonas Hazur ◽  
Nadine Endrizzi ◽  
Dirk W. Schubert ◽  
Aldo R. Boccaccini ◽  
Ben Fabry
Keyword(s):  
Relaxation Time ◽  
Stress Relaxation ◽  
Time Constant ◽  
3D Culture ◽  
Viscoelastic Behavior ◽  
Model Systems ◽  
Cell Behavior ◽  
Relaxation Time Constant ◽  
Young’S Moduli ◽  
The Matrix

The viscoelastic behavior of hydrogel matrices sensitively influences the cell behavior in 3D culture and biofabricated tissue model systems. Previous reports have demonstrated that cells tend to adhere, spread, migrate and proliferate better in hydrogels with pronounced stress relaxation. However, it is currently unknown if cells respond more sensitively to the amplitude of stress relaxation, or to the relaxation time constant. To test this, we compare the behavior of fibroblasts cultured for up to 10 days in alginate and oxidized alginate hydrogels with similar Young's moduli but diverging stress relaxation behavior. We find that fibroblasts elongate, migrate and proliferate better in hydrogels that display a higher stress relaxation amplitude. By contrast, the cells' response to the relaxation time constant was less pronounced and less consistent. Together, these data suggest that it is foremost the stress relaxation amplitude of the matrix that determines the ability of cells to locally penetrate and remodel the matrix, which subsequently leads to better spreading, faster migration, and higher cell proliferation. We conclude that the stress relaxation amplitude is a central design parameter for optimizing cell behavior in 3-D hydrogels.

Regarding the Néel relaxation time constant in magnetorelaxometry

2014 ◽  
Vol 116 (16) ◽  
pp. 163914 ◽  
Author(s):  
J. Leliaert ◽  
A. Coene ◽  
G. Crevecoeur ◽  
A. Vansteenkiste ◽  
D. Eberbeck ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Time Constant ◽  
Relaxation Time Constant ◽  
Néel Relaxation

scholarly journals A Distinguishable Role of eDNA in the Viscoelastic Relaxation of Biofilms

mBio ◽  
2013 ◽  
Vol 4 (5) ◽  
Author(s):  
Brandon W. Peterson ◽  
Henny C. van der Mei ◽  
Jelmer Sjollema ◽  
Henk J. Busscher ◽  
Prashant K. Sharma
Keyword(s):  
Relaxation Time ◽  
Stress Relaxation ◽  
Time Constant ◽  
Extracellular Polymeric Substances ◽  
Principal Component ◽  
Mechanical Stresses ◽  
Extracellular Dna ◽  
Viscoelastic Relaxation ◽  
Content Type ◽  
Relaxation Time Constants

ABSTRACTBacteria in the biofilm mode of growth are protected against chemical and mechanical stresses. Biofilms are composed, for the most part, of extracellular polymeric substances (EPSs). The extracellular matrix is composed of different chemical constituents, such as proteins, polysaccharides, and extracellular DNA (eDNA). Here we aimed to identify the roles of different matrix constituents in the viscoelastic response of biofilms.Staphylococcus aureus,Staphylococcus epidermidis,Streptococcus mutans, andPseudomonas aeruginosabiofilms were grown under different conditions yielding distinct matrix chemistries. Next, biofilms were subjected to mechanical deformation and stress relaxation was monitored over time. A Maxwell model possessing an average of four elements for an individual biofilm was used to fit the data. Maxwell elements were defined by a relaxation time constant and their relative importance. Relaxation time constants varied widely over the 104 biofilms included and were divided into seven ranges (<1, 1 to 5, 5 to 10, 10 to 50, 50 to 100, 100 to 500, and >500 s). Principal-component analysis was carried out to eliminate related time constant ranges, yielding three principal components that could be related to the known matrix chemistries. The fastest relaxation component (<3 s) was due to the presence of water and soluble polysaccharides, combined with the absence of bacteria, i.e., the heaviest masses in a biofilm. An intermediate component (3 to 70 s) was related to other EPSs, while a distinguishable role was assigned to intact eDNA, which possesses a unique principal component with a time constant range (10 to 25 s) between those of EPS constituents. This implies that eDNA modulates its interaction with other matrix constituents to control its contribution to viscoelastic relaxation under mechanical stress.IMPORTANCEThe protection offered by biofilms to organisms that inhabit it against chemical and mechanical stresses is due in part to its matrix of extracellular polymeric substances (EPSs) in which biofilm organisms embed themselves. Mechanical stresses lead to deformation and possible detachment of biofilm organisms, and hence, rearrangement processes occur in a biofilm to relieve it from these stresses. Maxwell analysis of stress relaxation allows the determination of characteristic relaxation time constants, but the biofilm components and matrix constituents associated with different stress relaxation processes have never been identified. Here we grew biofilms with different matrix constituents and used principal-component analysis to reveal that the presence of water and soluble polysaccharides, together with the absence of bacteria, is associated with the fastest relaxation, while other EPSs control a second, slower relaxation. Extracellular DNA, as a matrix constituent, had a distinguishable role with its own unique principal component in stress relaxation with a time constant range between those of other EPSs.

scholarly journals Calculation of Left Ventricular Relaxation Time Constant-Tau in Patients With Aortic Regurgitation by Continuous-Wave Doppler

2008 ◽  
Vol 2 (1) ◽  
pp. 28-30 ◽  
Author(s):  
Bai Xufang
Keyword(s):  
Relaxation Time ◽  
Aortic Regurgitation ◽  
Time Constant ◽  
Continuous Wave ◽  
Left Ventricular ◽  
Simple Method ◽  
Relaxation Time Constant ◽  
Left Ventricular Relaxation ◽  
Ventricular Relaxation ◽  
Continuous Wave Doppler

Left ventricular relaxation time constant, Tau, is the best index to evaluate left ventricular diastolic function. The measurement is only available traditionally in catheter lab. In Echo lab, several methods of non-invasive measurement of Tau have been tried since 1992, however almost all the methods are still utilizing the same formula to calculate Tau as in catheter lab, which makes them inconvenient, time-consuming and sometimes not very accurate. A simple method to calculate Tau in patients with mitral regurgitation has been developed just based on Weiss’ formula and simplified Bernoulli’s equation. Similarly, formulas are developed here by pure mathematical derivative to calculate Tau by continuous-wave Doppler in patients with aortic regurgitation.

scholarly journals Calculation of Left Ventricular Relaxation Time Constant-Tau in Humans by Continuous-Wave Doppler

2008 ◽  
Vol 2 (1) ◽  
pp. 9-11 ◽  
Author(s):  
Xufang Bai
Keyword(s):  
Relaxation Time ◽  
Time Constant ◽  
Continuous Wave ◽  
Left Ventricular Diastolic Function ◽  
Left Ventricular ◽  
Simple Method ◽  
Relaxation Time Constant ◽  
Left Ventricular Relaxation ◽  
Ventricular Relaxation ◽  
Continuous Wave Doppler

Left ventricular relaxation time constant, Tau, is the best index to evaluate left ventricular diastolic function, but the measurement is only available traditionally in catheter lab. In Echo lab, several methods of non-invasive measurement of Tau have been tried since 1992, however almost all the methods are still utilizing the same formula to calculate Tau as in catheter lab, which makes them inconvenient, time-consuming and sometimes not very accurate. Based on Weiss’ formula and simplified Bernoulli’s equation, a simple method is developed by pure mathematical derivative to calculate Tau by continuous-wave Doppler in patients with mitral regurgitation.

Load-sensitive diastolic relaxation in hypertrophied left ventricles

1998 ◽  
Vol 274 (2) ◽  
pp. H609-H615 ◽  
Author(s):  
Wataru Hayashida ◽  
Julian Donckier ◽  
Henri Van Mechelen ◽  
André A. Charlier ◽  
Hubert Pouleur
Keyword(s):  
Relaxation Time ◽  
Angiotensin Ii ◽  
Time Constant ◽  
Left Ventricular ◽  
Control Group ◽  
Relaxation Time Constant ◽  
Significant Prolongation ◽  
Wide Range ◽  
Diastolic Relaxation

We studied effects of enalaprilat and L-158,809, an angiotensin II type-1 receptor antagonist, on left ventricular (LV) diastolic relaxation in 11 normal control dogs and 16 LV hypertrophied (LVH) dogs with perinephritic hypertension. At baseline, LV systolic and end-diastolic pressures and end-systolic elastance were increased in the LVH group (all P < 0.01 vs. the control group). LV relaxation time constant was also prolonged ( P < 0.01), suggesting impaired LV diastolic relaxation in this model of LVH. Before and after the administration of enalaprilat (0.25 mg/kg) and L-158,809 (0.30 mg/kg), LV relaxation was assessed over a wide range of LV loading conditions during vena caval occlusion. LV relaxation time constant was insensitive to load reduction in the control group, which was not affected by enalaprilat or L-158,809. In contrast, LV unloading caused a significant prolongation of the relaxation time constant in the LVH group. This load-sensitive LV relaxation abnormality was significantly improved by enalaprilat or L-158,809. These results support the concept that angiotensin II is involved in the pathogenesis of diastolic dysfunction in pressure-overloaded LVH and also suggest that angiotensin-converting enzyme inhibitors and angiotensin II type-1 receptor antagonists are potentially beneficial in the treatment of the hypertrophied heart.

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