Hollow shells

PM Control - An impingement-plate scrubber is a vertical chamber with plates mounted horizontally inside a hollow shell. Impingement-plate scrubbers operate as eountercurrent PM collection devices. The scrubbing liquid flows down the tower while the gas stream flows upward. Contact between the liquid and the particle-laden gas occurs on the plates. The plates are equipped with openings that allow the gas to pass through. Some plates are perforated or slotted, while more complex plates have valve-like openings. 

Drawing Tantalum has a tendency to gall and is normally anodised to provide a surface which will carry a drawing lubricant. Seamless tube is produced by cupping followed by drawing or by hollow shells. 

Organoclay materials with higher-order organization can also be prepared by template-directed methods involving self-assembled supramolecular structures. In this approach, preformed organic architectures in the form of tubes, fibers, hollow shells, gyroids, helicoids, and so on are transferred into hybrid materials exhibiting structural hierarchy, complex form and ordered mesoporosity [47-55]. For example,... 

The lube oil cooler consists of a hollow shell with several tubes running through it. Cooling water flows inside the shell of the cooler and around the outside of the tubes. Lube oil flows inside the tubes. The water and lube oil never make physical contact. 

Ferritin is composed by the arrangement of 24 protein subunits, which results in a hollow shell of 8 nm inner diameter and 13 nm outer diameter (Fig. 13). Ferritin from vertebrates have two types of subunits heavy (H) and light (L). The subunit composition of human ferritins depends on the origin of the protein H2L22 for liver ferritin, H20L4 for muscle ferritin, etc. Access channels are formed by the intersection of subunits. The 8 channels located at the intersection of three subunits are hydrophilic while the 6 channels located at the intersection of 4 subunits are hydrophobic. The empty protein is called apoferritin (30). 

We may wonder what effect these gigantic explosions and accompanying radiation may have on the galactic environment of the hypernova. Such an energy release could only produce holes, hollow shells in the distribution of interstellar matter. After 1 million years, these cavities reach a radius of 150 to 500 light-years, according to calculation. The initial excesses are followed by a calmer expansion at speeds below 10 km s ... 

Caruso F, Schuler C, Kurth DG. Coreshell particles and hollow shells containing metallo-supramolecular components. Chem Mater 1999 11 3394-3399. 

Accdg to Colver (Ref 12, p 497), early hollow shells were used by Chinese. They were made of earthenware. They were filled... 

Carbon, of course, is the ideal element for simple-minded chemists. Obey a few elementary valency rules, and almost any organic structure you can doodle would exist, if you could make it. And this is perhaps the justification for my own simple-minded contribution to the story of C60. For many years I have maintained a scientific alter ego, Daedalus, whose musings used to appear in New Scientist but now appear in Nature. Daedalus launches scientific proposals which are intended to fall in that uneasy no-man s-land between the clearly feasible and the clearly fantastic. His aim is inevitably rather erratic, and many of the attempts land on one side or the other. An account of some of Daedalus s chemical proposals has appeared in Chemistry in Britain (Jones 1987). His greatest moment came late in 1966, when he proposed the hollow-shell graphite molecule (Jones 1966). 

Similar attempts to minimize surface energy are also seen throughout the natural world, from water drops to cells, and in the chemical world where fullerenes and boranes, capsular compounds formed of boron hydride networks, both form hollow shells. 

II.C. van der Waals Attraction. The van der Waals attraction between the hollow shells of the ferritin can be easily computed in the pairwise summation approximation. Let us consider a large sphere B made up of a small sphere b and a spherical shell S. The interaction free energy Fbb between two large spheres can be written (assuming pairwise interactions) as... 

While the outer radius of the apoferritin molecule (a = 63.5 A) can be accurately determined, for example by dynamic light scattering,21 the inner radius (of the hollow shell) is more difficult to estimate. The iron cores of the ferritin have a maximum diameter of the order of 80 A, while the six hydrophobic channels have a length of about 12 A.27 In what follows the value 20 A will be employed for the average thickness of the shell. The Hamaker... 

The form of microcapsules is frequently expressed by an ellipsoidal hollow shell of revolution rather than a spherical shell. In the case of a thin oblate ellipsoidal shell, the form factor is represented by... 

Chemical vapor condensation (CVC) was applied by Lee for the production of Ti02 nanoparticles by decomposition of Ti(0)(acac)2. In the temperature range of 800-1000 °C hollow-shell nanoparticles (10-40 nm diameter, 4-5 nm thick) of anatase-rutile mixed phases were obtained. The formation of the hollow structure is a result of the competition... 

Fig. 8.3. Autocatalytic methods (a) active material is disposed in a hollow shell (b) boron bubble scheme.

Fig. 8.4. Three possibilities of autocatalytic schemes (i) hollow shell, (ii) two pieces, (iii) four pieces.

The simplest scheme which might be autocatalytic is indicated in the sketch where the active material is disposed in a hollow shell as indicated in Fig. 8.3a. Suppose that when the firing plug is in place one has just the critical mass for this configuration. If as the reaction proceeds the expansion were to proceed only inward it is easy to see from diffusion theory that v would increase. Of course in actual fact it will proceed outward (tending to decrease v ) as well as inward and the outward expansion would in reality give the dominant effect. However, even if the outward expansion were very small compared to the inward expansion, it has been calculated that this method gives very low efficiency with 12 an efficiency of only about 10 was calculated. 

Other well-established methods of analysis include modeling the experimental data using geometrical solid-body representations of the scattering species. This method allows for the construction of many kinds of geometrical models (e.g., hollow shells, core-shell particles, lamellar structures, etc. and provides for the interactive least-squares refinement of the dimensions of the models to fit the data. This approach has been widely used to analyze SANS data obtained from colloidal and polymeric systems. ... 

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