Mechanical stresses, influencing

From Eq. (11), it is clear that mechanical stress influences the fluctuation spectrum of membranes and, in particular, one expects a contribution to the... 

Ristic, R.L and Sherwood, J.N., 2001. The influence of mechanical stress on the growth and dissolution of crystals. Chemical Engineering Science, 56, 2267-2280. 

The use of stress terminology has been discussed in Chapter 1, where it was pointed out that the value of the term stress in indicating some adverse force or influence lies in its extreme generality, without the need for a precise quantification. Nevertheless it is appropriate that a scientific discipline should be concerned with definable quantities. This will be the starting point for this paper, which will follow the example of Levitt (1972) who applied the concepts and terminology of mechanical stress (force per unit area) and strain (a definable dimension change) to the study of plant responses to the environment. This approach will be developed here in an attempt to incorporate the philosophies behind stress effects into a general treatment of the responses of ecosystems to adverse environmental conditions. 

In this volume not all stress types are treated. Various aspects have been reviewed recently by various authors e.g. The effects of oxygen on recombinant protein expression by Konz et al. [2]. The Mechanisms by which bacterial cells respond to pH was considered in a Symposium in 1999 [3] and solvent effects were reviewed by de Bont in the article Solvent-tolerant bacteria in biocatalysis [4]. Therefore, these aspects are not considered in this volume. Influence of fluid dynamical stresses on micro-organism, animal and plant cells are in center of interest in this volume. In chapter 2, H.-J. Henzler discusses the quantitative evaluation of fluid dynamical stresses in various type of reactors with different methods based on investigations performed on laboratory an pilot plant scales. S. S. Yim and A. Shamlou give a general review on the effects of fluid dynamical and mechanical stresses on micro-organisms and bio-polymers in chapter 3. G. Ketzmer describes the effects of shear stress on adherent cells in chapter 4. Finally, in chapter 5, P. Kieran considers the influence of stress on plant cells. 

The deformation of the analyte, under the influence of an externally applied mechanical stress, is followed as a function of temperature. When the deformation of the sample is followed in the absence of an external load, the technique is identified as thermodilatometry. 

The polymorphs of FeOOH and also ferrihydrite can be dehydrated to those of Fe203 under the influence of either heat or mechanical stress,... 

An edible film should have good water vapor barrier properties (low or no water permeation and diffusion through film), which should not increase or increase very little with increasing relative vapor pressure (Lawton, 1996). Films should withstand mechanical stress and strain to such an extent that they do not break easily under a decent mechanical force (Talja et al, 2008). Thus, composition of starch-based films is an important factor influencing its barrier and mechanical properties. Also, starch-based edible films may have an impact on the sensory and textural characteristics of the food. 

Mechanical syntheses are, of course, generally affected by the presence of radical acceptors (20,29). The yield on copolymers also increases with duration of mechanical stress. However, if the milling time is too long, the properties of the graft or block copolymers can be deteriorated by degradation of initial product. The nature of the balls and mill material can also influence the reaction (37) the mechanical activation of inorganic materials. The production of graft and block copolymers on freshly formed surfaces has been established in the lierature. 

Polarization of a ferroelectric material varies nonlinearly with the applied electric field. The P-E behaviour is characterized by a hysteresis loop and observation of the hysteresis loop is the best evidence for the existence of ferroelectrcity in a material. The hysteresis loop has its origin in the rearrangement of domains under the influence of an applied elecric field. Generally, the domains are randomly distributed, giving a net zero polarization. Under an applied field or mechanical stress, favourably oriented domains... 

The weak physical forces that hold together self-assembled nanoparticles are, of course, susceptible to disruption under the influence of thermodynamic and/or mechanical stresses. Hence some workers have investigated ways to reinforce nanoscale structures via covalent bonding. For instance, improved stability of protein nanoparticles, in particular, casein micelles, can be achieved by enzymatic cross-linking with the enzyme transglutaminase, which forms bonds between protein-bound glutamine and lysine residues. By this means native casein micelles can be converted from semi-reversible association colloids into permanent nanogel particles (Huppertz and de Kruif, 2008). 

A purely hydrophilic matrix of hypromellose prolongs the release of tramadol from Tramal long (Fig. 3) developed by Gruenenthal. The tablets have the same dimensions, resulting in an identical release profile for all dosages (100, 150, 200 mg, see Fig. 4). For a titrated effect linear pharmacokinetics on increasing doses produce dose-proportional blood levels at any time. External influences, such as pH value, mechanical stress, surface-active... 

This chapter is concerned with the influence of mechanical stress upon the chemical processes in solids. The most important properties to consider are elasticity and plasticity. We wish, for example, to understand how reaction kinetics and transport in crystalline systems respond to homogeneous or inhomogeneous elastic and plastic deformations [A.P. Chupakhin, et al. (1987)]. An example of such a process influenced by stress is the photoisomerization of a [Co(NH3)5N02]C12 crystal set under a (uniaxial) chemical load [E.V. Boldyreva, A. A. Sidelnikov (1987)]. The kinetics of the isomerization of the N02 group is noticeably different when the crystal is not stressed. An example of the influence of an inhomogeneous stress field on transport is the redistribution of solute atoms or point defects around dislocations created by plastic deformation. 

Stability of an enzyme is usually understood to mean temperature stability, although inhibitors, oxygen, an unsuitable pH value, or other factors such as mechanical stress or shear can decisively influence stability (Chapter 17). The thermal stability of a protein, often employed in protein biochemistry, is characterized by the melting temperature Tm, the temperature at which a protein in equilibrium between native (N) and unfolded (U) species, N U, is half unfolded (Chapter 17, Section 17.2). The melting temperature of a protein is influenced on one hand by its amino acid sequence and the number of disulfide bridges and salt pairs, and on the other hand by solvent, added salt type, and added salt concentration. Protein structural stability was found to correlate also with the Hofmeister series (Chapter 3, Section 3.4 Hofmeister, 1888 von Hippel, 1964 Kaushik, 1999) [Eq. (2.18)]. 

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