Stiff tissue

The variation of contrast with defocus can be illustrated by a series of snapshots from the examination of another caries lesion, this time one that had occurred naturally in a tooth (Peck and Briggs 1987). The sequence in Fig. 9.11 shows what would be seen over the shoulder of the microscopist as he 

In order to illustrate this, Fig. 9.12 shows three pictures of a specimen of enamel that was specially prepared so that the left half was slightly demineralized and the right half was sound. V(z) curves were measured over each half of the specimen, and these are shown as a continuous curve for the sound enamel and a broken curve for the demineralized enamel. At focus (and indeed for a fair range of z either side of focus, especially positive defocus) the two V z) curves lie almost on top of each other. This implies that at focus the two halves of the specimen will give almost identical contrast, and this is what is seen in the top picture. By a defocus of z = -10 pm, the two curves have separated, with the sound enamel curve lying above the demineralized curve. This corresponds to the demineralized enamel appearing darker than 

Rayleigh angle, and hence the Rayleigh velocity, by the formulae given in eqns (7.7) and (7.8). 

The way the V(z) curves change over enamel containing a white spot lesion is illustrated in Fig. 9.13 (Peck et al. 1989). At each of the points labelled by letters along the line across the centre of the picture in Fig. 9.13(i), measurements of V(z) were made. Four of these are presented in Fig. 9.13(ii) the letters correspond to the points in Fig. 9.13(i). Curve (a) comes from the intact surface zone. There are three well pronounced maxima apart from the focal maximum, with a fourth trying to appear. The period of the oscillations is about 13 pm. Curve (f) comes from the core of the lesion. The attenuation is much more severe here, and so the heights of the maxima fall off much more rapidly away from focus. The period is also smaller it is reduced to about 

The measurements on tooth enamel described above were analysed on the assumption that the enamel is, over the scale of each measurement, an 

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Chokalingam, K., N. Juncosa-Melvin, S. A. Hunter et al. 2009. Tensile stimulation of murine stem ceU-collagen sponge constructs increases collagen type I gene expression and linear stiffness. Tissue Eng Part A 15 2561-70. 

Uses. The use of titanium alloys for cast partial dentures offers light weight, low cost, good ductihty, adequate stiffness, chemical passivity toward foods and oral fluids, and biocompatibiHty with the oral tissues. 

Juvenile dermatomyositis (JDM) is perhaps the most uniform, in terms of clinical and histopathological features, of the whole PM/DM disease complex. Presentation may be before 5 years of age with peak incidence between 8 and 12 years. The disease may remit and recur until well into young adult life. The skin lesions include a facial rash in butterfly distribution across nose and cheeks. Erythematous skin changes are seen over extensor surfaces of joints, especially knees, knuckles and elbows. Muscle involvement is generally evident some time later and takes the form of weakness and stiffness, particularly affecting shoulder and pelvic musculature. Proximal muscles are often worse affected than distal muscles and extensors worse than flexors. In the absence of prompt and effective treatment contractures may occur at elbows, ankles, knees, and hips. Subcutaneous calcification and skin ulceration may be found calcification of deeper-lying connective tissue may be apparent on X-ray. 

In order to develop a tissue-engineered heart valve, a group at Children s Hospital in Boston evaluated several synthetic absorbable polyesters as potential scaffolding materials for heart valves. Unfoitu-nately, the most synthetic polyesters proved to be too stiff to be function as flexible leaflets inside a tri-leaflet valve. " In the late 1990s, a much more flexible PHAs called poly-3-hydroxyoctanoate-co-3-hydroxyhexanoate (PHO) was used as the scaffold material for the valve leaflet, and then the entire heart valve. ... 

Fibrobiasts, ieukocytes, tissues, amniotic fiuid ceiis, or serum can be used for the assay of many of the above enzymes. Patients with these disorders exhibit a variety of ciinicai findings that may inciude cioudy corneas, mentai retardation, stiff joints, cardiac ab-normaiities, hepatospienomegaiy, and short stature, depending on the specific disease and its severity. 

In contrast, the COX-2 enzyme is not produced normally in most tissues, but its production is increased rapidly in the presence of inflammation and local tissue injury. This leads to the synthesis of prostaglandins involved in pain and inflammation. Consequently, blocking the COX-2 enzyme results in analgesic and anti-inflammatory effects. The beneficial effects of NSAIDs in reducing pain, decreasing joint stiffness, and improving function in patients with OA are thought to be due to inhibition of the COX-2 isoenzyme. 

Why does the amount of acid in paper make such a difference Acids are corrosive chemicals. Corrosive chemicals can destroy material or living tissue on contact. Paper does not contain enough acid to burn skin, but over time the paper becomes stiff and brittle and eventually falls apart. As a result, precious personal memories or important historical documents that were written on acidic paper can be lost. Acid-containing paper can also transfer the acid to other objects in a process called acid migration. The acid can weaken or destroy the fibers in fabrics. It can also ruin photographs. Therefore, to preserve those irreplaceable memories, be sure to use paper that is acid-free. 

Hou FJ, Lang SM, Hoshaw SJ, et al. (1998) Human vertebral body apparent and hard tissue stiffness. J Biomech 31 1009-1015... 

Fan the tissue-covered thermometer bulb with a piece of cardboard or other stiff paper. After one minute, read and record the final temperature in the data table. Remove the tissue and wipe the bulb dry. 

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