Open arrangements

Solid samples can also be measured in transmission, although reflection or transflection measurements are more common. Open arrangements with the source on one side of the sample and the spectral analyser on the other side are prevalently used, e.g. in industrial process control. For absolute quantitative analysis the thickness of the object must either be constant or be measured. 

The active-site cleft has a less open arrangement in renins than in the other aspartic proteinases. Many loops as well as the helix hc (residues 224-236) belonging to the C-domain (residues 190-302) are significantly closer to the active site in the renin structures compared to those of endothiapepsin-inhibitor complexes. This is partly due to a difference in relative position of the rigid body comprising the C-domain. For instance, there is a domain rotation of 4° and translation of 0.1 A in the human renin complex with respect to the endothiapepsin-difluorostatone complex. 

Fig. 6. The crystal structure of ice (a) the basic unit, showing the tetrahedral arrangement of four oxygen atoms round any one oxygen (b) the open arrangement of these units as they fit together in ordinary ice(Ih) (c) the alternative positions for the hydrogen atoms, which are represented by the small filled circles, two along each hydrogen bond. (The vertical line, marked with 3 in (a), is a threefold symmetry axis all the vertical lines in (b) coincide with trigonal axes of the ice crystal.)...

Until the availability of high-resolution electron microscopy, the structure of silica xerogels remained a matter of conjecture. Now, there is no longer any doubt that the amorphous framework is made up of very small globular units (see Figure 10.6). These primary particles are isotropic and have fairly uniform size of 1-2 nm (with a molar mass 2000 g mol 1). In some xerogels the primary particles are densely packed within secondary particles, whereas in other systems there is a more open arrangement (Barby, 1976). 

This kind of valve is essential when tight shutoff is needed, particularly of gas flow. Multipass plug cocks, butterfly valves, slide valves, check valves, various quick-opening arrangements, etc. have limited and often indispensable applications, but will not be described here. 

The RDC has a moderate throughput typically in the range of 20 to 35 mV(h m ) [500 to 850 gal/(h ft )j, and it can be turned down to 20 to 35 percent of the design rate. However, the relatively open arrangement leads to some bacWixing and results in only moderate mass-transfer performance. As a consequence, some RDC columns are being replaced by more efficient extractor designs. The RDC can be... 

Its Molecular Structure The six-pointed snowflakes reflect the open arrangement of bonds. In order to freeze, molecules of liquid water separate slightly from one another as a result of hydrogen bonding. The volume of cooling liquid increases as the molecules move apart and the density decreases. At 0°C, the liquid water freezes to solid water, ice. The volume rises and the density drops dramatically, from 1.000 g/mL to 0.917 g/mL, as the water molecules assume the open arrangement. ... 

The size- and shape-selective characteristics of zeolites come from their unique framework structures in general they are formed from open arrangements of A104 and 8104 tetrahedra linked by shared oxygen atoms (the Al and Si atoms are therefore often referred to as T-atoms). Strictly speaking, the designa-... 

The surface of a solid material is the place where the material is in contact with the surrounding medium. The term "surface" is used if the medium is vacuum or a gaseous atmosphere. The contact with liquids or other solids is termed an "interface". Surfaces and interfaces are a universal phenomenon of the real structure of solid materials. The open arrangement of surface atoms or molecules compared with those of the bulk leads to special surface properties. Generally, the changes in the physical and chemical properties of surfaces are not limited to their topmost mono-layer but to a more or less extended transition region. 

Icebergs float on water. The open arrangement of water molecules In Ice partially collapses when the substance melts, so that the liquid has a higher density up to about 4°C. 

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