Snail shells

Each element of an array detector is essentially a small electron multiplier, as with the point ion collector, but much smaller and often shaped either as a narrow linear tube or as somewhat like a snail shell. 

The human cochlea, which derives its name from the Greek word koch-lias, consists of approximately three turns of a circular duct, wound in a manner similar to that of a snail shell (Figure 9.4). The ahihty to resolve different tones is determined hy the pattern of vibration of the flexible cochlear partition. This partition has three main components (Figure 9.5). When... 

From the atomic to the macroscopic level chirality is a characteristic feature of biological systems and plays an important role in the interplay of structure and function. Originating from small chiral precursors complex macromolecules such as proteins or DNA have developed during evolution. On a supramolecular level chirality is expressed in molecular organization, e.g. in the secondary and tertiary structure of proteins, in membranes, cells or tissues. On a macroscopic level, it appears in the chirality of our hands or in the asymmetric arrangement of our organs, or in the helicity of snail shells. Nature usually displays a preference for one sense of chirality over the other. This leads to specific interactions called chiral recognition. 

Homochirality is the choice in Nature for one handedness or another. Macroscopic homochirality can be observed in the winding of some species of snail shell... 

Figure 8.12 Homochiral snail shell. (Reproduced by permission of Steve Crompton)...

In the present-day ocean, about half of the PIC exported to oceanic sediments consists of the remains of foraminiferans. These microorganisms are protozoans. They are widespread in the marine environment with some species having a pelagic lifestyle and others benthic. As shown in Figure 15.1a, their calcareous structures have the appearance of a chambered snail shell and are composed of the mineral calcite. Since this hard part is covered by tissue, it is technically a type of skeleton. These detrital remains are referred to as tests or forams. Among the present-day and extinct species of foraminiferans, considerable variation exists in the size, shape, and density of their tests. 

Ruch5 revived Lord Kelvin s idea and extended it in order to allow sorting of objects, e.g., snail shells, by helicity. Accordingly, in relation to chiral similarity, (M)j(M) and (M) (P) hexahelieene/heptahelieene molecule pairs would be regarded as homochirally and heterochirally similar, respectively. 

You turn back to Sally. Zollner devised three rests for Slade to see if Slade could use the fourth dimension to perform miracles. One He gave Slade two oak rings that were to be interlocked without breaking them. Two He gave Slade a snail shell and watched to see if a right spiral could be turned into a left spiral, and vice versa. Three He gave Slade a rubber band and asked him to place a knot in one strand of the band. Actually it was band made from dried gut, but you get the idea. ... 

In the case of bivalves, only one organic sheet is formed at the front, whereas many sheets are formed in snail shells. As a result, unlike bivalves, snail shells grow as a tower-like pyramidal stacking structure, as illustrated in Fig. 14.4(b). 

Mathematical symmetry is a little more restrictive than is the meaning of the word in everyday usage. For example, some might say tliat flowers, diamonds, butterflies, snail shells, and paisley ties (Fig. 3.1) are all Itighly symmetrical because of (lie harmony and attractiveness of their forms and proportions, but the pattern of a paisley tie is not balanced in mathematical language, it lacks symmetry elements. A (lower, crystal, or molecule is said to liave symmetry if it has two or more orientations in space that are indistinguishable, and the criteria forjudging these are based on symmetry elements and symmetry operations. 

Fig. 3.1 The shapes and patterns of some pleasing designs found in nature or constructed as artifacts (a) the flower of the black-eyed Susan. RmJbetkia hirin, lb) the flower, stem, and leaves of the black-eyed Susan (c) a red eft, Notophtluilrrws vintlescens (d) a cut diamond (c) a paisley tie (f) a snail shell. Cepea ne/noralis (g) a monarch butterfly, Daniws plexippiix (h) a suspension bridge. Which are truly symmetrical ...

The two chromatids in Fig. 26-13G are said to be coiled with opposite handedness. Can you draw this conclusion from Fig. 26 alone What are the biological implications for mitosis 280 Does the DNA have a differing chirality at the molecular level Compare this observation with the existence of snail shells or flowers497 with both right and left handedness within the same species. 

Goodfriend GA (1992) The use of land snail shells in paleoenvironmental reconstruction. Quat Sci Rev 11 665-685... 

Shells have been used as tools, sometimes in their original form and sometimes with modifications. Large bivalves or snail shells are useful as scoops,... 

Sound waves are detected inside the cochlea of the inner ear. The cochlea is a fluid-filled, membranous sac that is coiled like a snail shell. The primary detection is accomplished hy specialized neurons inside the cochlea called hair cells (Figure 32.30). Each cochlea contains approximately 16,000 hair cells, and each hair cell contains a hexagonally shaped bundle of 20 to 300 hairlike projections called stereocilia (Figure 32.31). These stereocilia are graded in length across the bundle. Mechanical deflection of the hair bundle, as occurs when a sound wave arrives at the ear, creates a change in the membrane potential of the hair cell. 

Odum H. T. (1951) Notes on the strontium content of seawater, celestite radiolaria and strontianite snail shells. Science 114, 211-213. 

Goodfriend, G. A., 1991, Holocene trends in in land snail shells from the Negev Desert and their implications for changes in rainfall source areas, Quat. Res., 35 417-426. 

At the end of the 3 long burrow the soil is moist and cool, often littered with webbing, bones and insect parts. The entrance is covered by a silken cap, made with snail shells and other hard pieces, to keep the burrow humid and fire-proof. A low silk-covered mound around the entrance traps dew and raindrops for drinking and helps prevent flooding of the burrow. If the burrow does flood, air is trapped by the spider s hairy body, sustaining the spider until the water soaks away. 

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