Scratch behavior

Honma Y, Futaki N, Nakamura A, Nakaike S Involvement of IL-31 on scratching behavior in NC/Nga mice with atopic-like dermatitis. Exp Dermatol 2006 15 161-167. 

The role of mast cells and histamine inducing itch remains unclear in dry skin. It has been shown that histamine concentrations increase 48 hours following acetone treatment in a dry environment.23 A subsequent study demonstrated an increased number of mast cells and histamine levels in the dermis of hairless mice in response to low environmental humidity.46 The authors did not examine a relationship between scratching behavior with the increase in mast cells and histamine. Miyamoto et al. used the mouse model treated with water followed by 1 1 acetone ether to see if they could demonstrate an increase in mast cell number or degranulation however, they found no difference.24 Furthermore, they performed the same study on mast cell deficient mice and were able to induce a similar scratching behavior, which suggests that mast cells may not play a definite role in the mechanism of itch in dry skin. 

Nojima et al. recently demonstrated an increase of scratching behavior and scaly skin in rats treated with water followed by 1 1 acetone ether. In addition, this report also revealed an increase in Fos-like immunoreactivity within the superficial dorsal horn of these rats. This immunoreactivity serves as a marker of the nerves that are directly stimulated by impairment in barrier function.25 A correlation... 

Thurston CL, Campbell IG, Culhane ES, Carstens E, Watkins LR (1992) Characterization of intrathecal vasopressin-induced antinociception, scratching behavior, and motor suppression. Peptides 13 17-25... 

FIGURE 17.7 Slurry abrasive effect on scratching performance. Ultrahigh-purity (TEOS base) colloidal silica slurry has an excellent oxide scratch behavior. On the contrary, the fumed silica has a tendency to scratch the oxide surface. A step-by-step dilute HF etching reveals smaller and smaller scratches. 

Fig. 17 Effects of TRK-820 on the scratching behavior in mice induced by histamine (a) or substance P (b). Mice (ICR strain) were given a p.o. administration of vehicle (open bars) or TRK-820 (filled bars). Then, 30 min later, phosphate-buffered saline, pH 7.4 (PBS), histamine (a), or substance P (b) was i.d.-injected. Immediately after the injection of PBS, histamine, or substance P, the number of scratching events was recorded and counted over a 30-min period. The numbers of scratching events observed with histamine or substance P injections in the absence of TRK-820 were considered 100% on the vertical axes. Each value represents the mean standard error of the mean (S.E.M.) (n = 8). P < 0.01 compared between the PBS and histamine- or substance P-injected groups (Dunnett s test). Reprinted from [51] with permission from Elsevier. Copyright (2002)...

Iverson et al. [100,101] reported on the relative toxicity of domoic acid following oral or i.p. administration in both mice and rats. These authors used both extracts of contaminated mussels and purified DOM, obtaining similar results with each. Using scratching behavior, seizures, and death as the criteria for DOM toxicity, they reported consistently reproducible toxicity following... 

Carbon-based polymer nano composites represent an interesting type of advanced materials with structural characteristics that allow them to be applied in a variety of fields. Functionalization of carbon nanomaterials provides homogeneous dispersion and strong interfacial interaction when they are incorporated into polymer matrices. These features confer superior properties to the polymer nanocomposites. This chapter focuses on nanodiamonds, carbon nanotubes and graphene due to their importance as reinforcement fillers in polymer nanocomposites. The most common methods of synthesis and functionalization of these carbon nanomaterials are explained and different techniques of nanocomposite preparation are briefly described. The performance achieved in polymers by the introduction of carbon nanofillers in the mechanical and tribological properties is highlighted, and the hardness and scratching behavior of the nanocomposites are also discussed. 

The objective of this article is to highlight the importance of understanding scratch behavior of polymers by giving readers an up-to-date knowledge in this field of research. The theoretical framework concerning interfacial contacts will be introduced, and the experimental aspects in terms of methodology and quantitative measures summarized. Various factors influence the scratch behavior of polymers in different ways which will be discussed. 

To assess the scratch behavior of polsmiers, scratch tests are performed. A compendium of the use of various instruments and methods applied is given in Reference (20). Although different setups have been used for scratch studies, the basic principle relies on the use of a stylus to scratch a surface (2,3,21 3). The stylus can be made of materials ranging from diamond and sapphire, to tool steel, and silicon nitrite for the case of AFM tips. It also comes with a variety of geometries including conical tips with different included angles, spherical tips of different radii, and Berkovich tip. In addition, the observation length scale and controlled experimental parameters are instrument specific. 

Individual scratch is often done with a constant loading rate (which includes constant load) and constant scratch rate. The scale of damage of interest varies from macroscopic features to those of nanometer scale. This renders comparisons between studies difficult. The recent concerted industry-university effort (6,7,44) has led to the development of a scratch test method and universal scratch testing equipment to facilitate good scratch test practices and fimdamental study of scratch behavior of polymers. Figure 4 presents the scratch tester that was developed. It aims to provide reasonable capability to vary experimental conditions for capturing the essential scratch characteristic of the materials with reliable and reproducible results. One unique feature of the tester is its ability to alter scratch load and velocity at a linear rate. This feature is foimd to be useful in understanding scratch behavior of polymers, to be presented in later sections. 

From the equations presented in under Theoretical Backgroimd, it can be derived that materials properties, such as modulus and yield strength, and any modifications that might affect them will influence the scratch behavior of polymers. The unique characteristics of poljnners make research in polymer scratch particularly challenging. First, as mentioned in the previous section, polymers are viscoelastic-viscoplastic in nature. This makes polymer properties very sensitive to test conditions, especially temperature and strain rate (21,34,56,63,64). 

Effect of Scratch Velocity and Temperature. Another frequently investigated experimental parameter on the effect of scratch behavior of materials is the scratching rate or the scanning velocity. Since polymers are viscoelastic-viscoplastic in nature, the importance of scratching rate lies in its ability to change the strain and strain rate at the interface of the sample and the indenter and thus alters the deformation mode. The relationship between velocity and coefficient of fiction will depend on the relaxation state of the surface concerned, especially for nanoscratch (21,56,57,63-65). It was shown that rate and temperature interplay to affect nanotribological behavior of polymer films (57). 

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