Teeth, shearing

Today, stainless steels find their primary use in wrought form for temporary appHcations such as orthodontic wires, brackets, and temporary crowns. The temporary crowns are obtained in preformed sizes/shapes and then are trimmed by the dentist with shears to fit over prepared teeth that are awaiting the fabrication of permanent cast crowns. 

The two legs of each fusehead were then bonded together with Mipolan (jnixt of polyvinyl chloride, tricresylphosphate butyleneglycolphthal ate), the tips of the teeth suitably bent and the bridge wire soldered into position. After dipping the bridge wires into fusehead compns. the back of the comb was sheared off (Ref 2,p Ger... 

With the advent of stable isotope paleoaltimetry towards the turn of the millennium the stable isotope and tectonics communities have witnessed an increasing number of isotopic mineral proxies developed to address the long-term topographic histories of orogenic belts and continental plateaus. These proxies include calcite from paleosols (see for example Quade et al. 2007, this volume and references therein), fluvial and lacustrine rocks the phosphate and carbonate component of mammal teeth (Kohn and Dettman 2007, this volume and references therein), smectite and kaolinite from paleosols, weathered sediments and volcanic ashes (e.g., Chamberlain et al. 1999 Takeuchi and Larson 2005 Mulch et al. 2006a) as well as white mica from extensional shear zones and fluid inclusions in hydrothermal veins (e.g., Mulch et al. 

The characteristic length of the contacting chamber, e.g. the slot width between rotor and stator in teeth-rimed emulsifiers or the nozzle diameter in high pressure homogenizers (utilizing the shear of the high-speed liquid jet) will be denoted as d. 

The basic high-speed dispersing impeller blade is a flat disk with teeth or similar serration around the diameter, as shown in Fig. 17.1. On some models, disks may be without teeth, or several may be stacked up with small gaps between disks so that material between the disks is sheared as the impeller turns. Sometimes two shafts are used in the same mixing chamber their disks may interlock and counterrotate, thereby enhancing shear. 

The toothpaste is like a solid, but liquid when sheared. It stays on a toothbrush as a little white sausage. It contains a large fraction of fine solid particles, as you find out by diluting with water and vinegar, and letting the mixture settle. The particles (which are mildly abrasive) are smaller than 30 pm. How could you get toothpaste to be effective in the crevices between the teeth where it really is necessary ... 

Figure 7.9 Shear-stress dependence of the relative viscosity for dispersions in white spirit of acrylic copolymer particles of radius a = 157 nm at a volume fraction of p =0.40 for differing concentrations of nonadsorbing polyisobutylene polymer of molecular weight 411,000. The particles had been stabilized by addition of a comb-graft copolymer of PMMA backbone (which adsorbed to the particles) with non-adsorbing poly(12-hydroxystearic acid) teeth. The con-centrations (in weight per unit volume) of polyisobutylene are 1.0% ( ), 0.85%(B), 0.6%(D), 0.5%(V), 0.4%( ), and 0.1 %(0)- (From Bus-call et al. 1993, with permission from the Journal of Rheology.)...

For the toothed rotor/stator mills, there are localized areas of high shear where the most energy is imparted to the particles, and breakage is believed to occur, through a combination of shear and collision. Therefore, useful parameters that quantify mill performance will reflect these effects. Three typical parameters used in rotor-stator mill scale up are tip speed (rotation rate of rotor x rotor circumference), shear rate (tip speed/distance between rotor and stator), and shear frequency (rotation rate x number of slots on rotor x number of slots on stator).Rotor-stator types typically differ in the number of rows of teeth and the number of teeth in each row of rotor and stator, though other geometric differences are possible. When rotor-stators of different design are available for study, shear frequency appears to have... 

Fig. 5. TEM images of the 2-hour pellicle layer formed in situ on the surface (left) or within slots (right) of enamel specimens exposed to the oral environment on the buccal (top) or palatal site (bottom) of the upper first molar teeth. Comparison of the pellicle layers formed on the surface or within slots (i.e. shielded from shearing forces) does not reveal differences in thickness and ultrastructure of the adsorbed protein coatings. However, clear differences are evident between the pellicles formed within 2 h on buccally and palatally exposed enamel slabs. On the palatally carried enamel specimens - even within the slots - an outer globular pellicle layer cannot be detected. Bar = 200 nm. 

The rotary pick mineral sizer has been used as a secondary crusher for soft to moderately hard limestone. The construction is similar to that of the rolls crusher, but the rotors are fitted with alloy steel teeth, which break the rock by a combination of compression, tension and shear. 

The role of theory is to determine the conditions of h, c, tool geometry (rake angle), and work material thermo-physical-mechanical properties that give rise to serrated rather than continuous or other classifications of chips and, in the conditions of serrated chip formation, to predict such measurable features of the serration as the maximum and minimum chip thickness hi and h2, the angle 0 at which the saw teeth are inclined to the back face of the chip, the teeth face separation L, and the shear-band width . If such quantities are predicted, then the cycles of temperature and stress in the tool will also be known. 

Roll crushers are size reduction devices that shear (or compress) the material that is to be reduced in size. The surfaces used can take the form of a rotating roll and a stationary anvil, or two equal-speed rolls rotating in opposite directions. The surfaces of the rolls can be smooth, corrugated, or toothed. The particular design of the teeth and corrugations is critical in keeping the production of lines and dust to a minimum (Roman, 1967). 

Carter, J.M., Sorensen, S.E., Johnson, R.R., Teitelbaum, R.L. and Levine, M.S. (1983) Punch Shear Testing of Extracted Vital and Endodontically Treated Teeth. J. Biomechanics 16(10), 841-848. 

Utilized a miniature punch shear apparatus to determine shear strength and toughness perpendicular to the direction of dentinal tubules. Dentin harvested from the cemento-enamel junction to one-third the distance to the root apex. Strengths novel measurements, precise measurements, defined specimen location, defined orientation of testing. Limitations tooth type not defined for constrained tests, teeth stored in mineral oil prior to testing. 

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