Concave surface

Minimum thickness requirements are 11/2 times the indentation diagonal measurement, and there should be no visible marking or bulge visible on the side opposite the indentation.The Vickers test is based on a plane surface however, correction tables are available for both convex and concave surfaces (see ASTM E92) (2). 

Uses. Sound-absorbing materials are frequendy used to reduce reverberation, or the persistence of sound in a space after generation of the sound ceases to reduce focused reflections from concave surfaces to prevent echoes, or delayed sound reflections from distant surfaces and to prevent the buildup of sound by multiple reflections within rooms and other enclosures. Sound-absorbing materials also are used to reduce the transmission of noise from one location to another by multiple reflections from sound-reflecting surfaces. 

The two homologous repeats, each of 88 amino acids, at both ends of the TBP DNA-binding domain form two stmcturally very similar motifs. The two motifs each comprise an antiparallel p sheet of five strands and two helices (Figure 9.4). These two motifs are joined together by a short loop to make a 10-stranded p sheet which forms a saddle-shaped molecule. The loops that connect p strands 2 and 3 of each motif can be visualized as the stirmps of this molecular saddle. The underside of the saddle forms a concave surface built up by the central eight strands of the p sheet (see Figure 9.4a). Side chains from this side of the P sheet, as well as residues from the stirrups, form the DNA-binding site. No a helices are involved in the interaction area, in contrast to the situation in most other eucaryotic transcription factors (see below). 

Concave surfaces are of industrial importance, in relation to the internal surface of bores, holes and pipes, but are not found on typical solid testpieces and have received much less discussion. The stress patterns will tend to be the opposite of those found on convex surfaces for example, an oxide growing by cation diffusion should be in tension at the metal interface. Bruce and Hancock have discussed the oxidation of curved surfaces and show how the time to adhesive failure of the oxide can be predicted if its mechanical properties are known. 

Compressive forces on enamel applied to a convex surface are less than when a concave surface is coated, and it is therefore apparent that the sharper the radius of the metal the weaker the enamel applied to it will be. This fact is also relevant to mechanical damage. 

Johansson21 made his crystals by grinding and then bending. Recent practice seems to be bending to radius R, then grinding the concave surface to R 2.23... 

The capillary tube cases are readily proved directly, for it is evident from Fig. 43 that the pressure just beneath the concave surface is less than that just beneath the plane surface by an amount hjv, whereas the vapour-pressures just above these surfaces differ by h/Y. Hence... 

For a bubble to be formed in a liquid, such as steam in water, for example, it is necessary for a surface of separation to be produced. Kelvin has shown that, as a result of the surface tension between the liquid and vapour, the vapour pressure on the inside of a concave surface will be less than that at a plane surface. As a result, the vapour pressure Pr inside the bubble is less than the saturation vapour pressure P, at a plane surface. The relation between Pr and P, is ... 

The idea to produce a converging objective from a reflecting, concave surface, instead of a refractive lens, was recognised by Galileo himself, and tried by Zucchi in 1616 (Fig. 4). Such arrangement, however, does not deliver acceptable image quality as a spherical surface used off-axis produces strong aberrations, and Zucchi s attempt was doomed for reasons he could not know. 

Chatterjee synthesis of isocomene constituted fraud because of the low probability of hydrogenation occurring from the concave surface of ester 24. The final direct proof was obtained by the synthesis of Chatterjee ketone 30, its hydrogenation to 29, and further conversion to epiisocomene [21],... 

Figure 2 shows FFEM images of Mal3 (Phyt)2/SQDG (9 1 mol/mol) vesicle membranes in the presence (Fig. 2A, B) or in the absence (Fig. 2C, D) of BR. Small particles were observed in Figure 2A, B, whereas no such particles were observed for pure Mai (Phyt)2/SQDG vesicles. In addition, two fracture faces of the bilayer membranes, a convex surface (a hydrophobic face of an inner leaflet, Fig. 2A) and a concave surface (a hydrophobic face of an outer leaflet, Fig. 2B) exhibited intramembraneous particles, suggesting BR was incorporated into vesicles transmembraneously.

Modem gratings may be etched on concave surfaces so that they will serve a dual purpose of diffracting light and also focusing the radiation. This decreases the number of parts in a spectrometer and also decreases losses in intensity by having fewer optical parts. 

Subjected to steady acceleration, a droplet is flattened gradually. When a critical relative velocity is reached, the flattened droplet is blown out into a hollow bag anchored to a nearly circular rim which contains at least 70% of the mass of the original droplet. Surface tension force is sufficient to allow the bag shape to develop. The bag, with a concave surface to the gas flow, is stretched and swept off in the downstream direction. The rupture of the bag produces a cloud of very fine droplets presumably via a perforation mode, and the rim breaks up into relatively larger droplets, although all droplets are at least an order of magnitude smaller than the initial droplet size. This is referred to as bag breakup (Fig. 3.10)T2861... 

Since u] does not change with n, a geometrically plane surface is implied. Strictly, equation 17.10 is not applicable to highly convex or concave surfaces. Equations 17.9 and 17.10 may be combined to give ... 

If the coefficient of the hydrophobic parameter is greater than 0.5 and less than 1.0, then expect a concave surface about substituent X of the ligand. 

These investigations focused for the first time on a new aspect of topicity that takes into account the influence of the shape of a bent structure on its reactivity. The remarkable inertness of the inner surface contrasts with the pronounced reactivity of the outer concave surface of Cjq. Almost unperturbed, atomic species or reactive molecules can be studied at ambient conditions once they are encapsulated by CgQ. Moreover, the wavefunction of the guest atom can be influenced by a permanent distortion of the Cjq cage. This was demonstrated by exohedral derivatization of N Cgo, leading to a lowering of the f symmetry, which influences the ESR spectra of the paramagnetic guest [99-103]. 

Due to the pyramidalization of the C atoms and the rigid cage structure of Cjq the outer convex surface is very reactive towards addition reactions but at the same time the inner concave surface is inert (chemical Faraday cage). This allows the encapsulation, observation and tuning of the wavefimction of extremely reactive species that otherwise would immediately form covalent bonds with the outer surface. 

Start timing when the bottom of the liquid meniscus (the concave surface of the liquid in the tube, see Fig. 17.2) passes the upper timing mark on the viscometer, E. 

The Kelvin effect is not limited to spheres. For example, the neck of liquid between two supports is described by a paraboloid of revolution. In this case the radius of curvature of the concave surface is outside the liquid and therefore introduces a minus sign into Equation (40). In addition, the factor of 2 is not required to describe the Kelvin effect for this geometry. Example 6.2 illustrates a test of the Kelvin equation based on this kind of liquid neck. 

To make a cupel, the cavity is nearly filled with hone-ash, which is first compressed slightly with the hands, and afterwards by means of the plunger, D, which is formed of the same metal as the mould, and has the lower end turned convex, so as exactly to correspond to the concave surface of the cupel, When the plunger Is introduced, it Is struck several times with a mallet till the hone-ash is well consolidated. The plunger is then withdrawn, and hy inserting at the lower and smaller end of the mould a solid wooden cylinder, which exactly fits the aperture, the cupel is F1 2i0-readily forced out, and is then placed to dry on the ledge which surrounds the furnace chimney—Figs. 230 and... 

---