Sporadic

Figure 4.6 The growth of disk-shaped crystals, (a) All crystals have been nucleated simultaneously. All crystals have the same radius rt after an elapsed time t. (b) Nucleation is sporadic. Crystal A has had enough time to reach point X, while B has not, although both originate in the same ring a distance r from x.

In terms of spontaneous crystallization, the assumption that N nuclei commence to grow simultaneously at t = 0 is the most unrealistic. We can modify the model to allow for sporadic, spontaneous nucleation by the following... 

A.irbome Basic Chemical Contamination. A critical, and at-first pu22ling problem, was encountered during early manufacturing trials of CA resists. Sporadically, severely distorted resist profiles would be formed in positive-tone CA resists, displaying what seemed to be a cap on the upper surface of the resist image (Fig. 26). In severe cases this cap or T-top would appear as a kin or cmst over the entire wafer surface that prevented development of the pattern. The magnitude of the effect varied dramatically between laboratories and appeared to grow more severe as the time interval between exposure and post-exposure bake was increased. 

The Printing Process. Tme integration of all facets of the printing process is limited, in most cases, to sporadic measurements of the individual elements and processes that contribute to the final product. There is only a limited effort underway as of the mid-1990s to estabUsh close links between electronic prepress and conventional processes such as proofing, plate-making, and printing. 

Styrene is manufactured from ethylbenzene. Ethylbenzene [100-41-4] is produced by alkylation of benzene with ethylene, except for a very small fraction that is recovered from mixed Cg aromatics by superfractionation. Ethylbenzene and styrene units are almost always installed together with matching capacities because nearly all of the ethylbenzene produced commercially is converted to styrene. Alkylation is exothermic and dehydrogenation is endothermic. In a typical ethylbenzene—styrene complex, energy economy is realized by advantageously integrating the energy flows of the two units. A plant intended to produce ethylbenzene exclusively or mostly for the merchant market is also not considered viable because the merchant market is small and sporadic. 

The structure of the first isolated vitamin cyanocobalamin [68-19-9] (la) is known to occur only sporadically, at best, in biological systems. Its isolation... 

Both the adult and the larval cysticerci (bladderworm) of Taenia solium (pork tapeworm) are able to Hve in humans the parasite is found sporadically in uncooked pork. In the stomach, the larva is digested out of the pork flesh it then grows and attaches to the wall of the small intestine. Maturity is reached in 5—12 weeks. The adult is 5 m long, and untreated adult worms may survive for 25 years. 

Commercial arsenic metal is sold at a typical purity of 99% in fragment or lump (5 —7.5 cm) form. Shipments of arsenic metal from China were sporadic, and also temporarily suspended, in 1989. The metal is not sold on a pubhshed price basis and can vary with each shipment. Shipments in early 1990 had leveled to an estimated price of about 2.20/kg. 

Selective gas permeation has been known for generations, and the early use of p adium silver-alloy membranes achieved sporadic industrial use. Gas separation on a massive scale was used to separate from using porous (Knudsen flow) membranes. An upgrade of the membranes at Oak Ridge cost 1.5 billion. Polymeric membranes became economically viable about 1980, introducing the modern era of gas-separation membranes. Hg recoveiy was the first major apphcation, followed quickly by acid gas separation (CO9/CH4) and the production of No from air. 

The site was a drained marsh which received no artificial N inputs, although cattle were present on the site until a couple of weeks before the experiment. NjO emissions were measured by chamber techniques as no instrumental techniques were sensitive enough at that stage to permit micrometeorological measurements. Although spatially very variable, the mean emission rate from the site was 4ng NjO-Nm s h The sporadic measurements made impossible the determination of any response to temperature or water status. 

The seemingly simple question of the relation the characteristics of a mechanically prepared metal surface and adhesion to that surface has sporadically occupied attention for many decades without any very general conclusion being reached [69]. In some recent work, Amada et al. [70,71] grit-blasted a steel substrate, varying the angle between the gun and the specimen surface, and measured the adhesion of a plasma-sprayed alumina coating. They examined profiles of the... 

Shorter status reports that are required with greater frequency tend to be more effective than longer, less frequent reports in helping to maintain continuing momentum. The need to show progress (for example) every month tends to keep PSM installation in focus, while a quarterly submission would permit more sporadic attention to PSM installation. 

The solubility (or insolubility) of different vitamins is of concern in nutrition. Molecules of vitamins B and C contain several —OH groups that can form hydrogen bonds with water (Figure 10.3). As a result, they are water-soluble, readily excreted by the body, and must be consumed daily. In contrast, vitamins A, D, E, and K, whose molecules are relatively nonpolar, are water-insoluble. These vitamins are not so readily excreted they tend to stay behind in fatty tissues. This means that the body can draw on its reservoir of vitamins A, D, E, and K to deal with sporadic deficiencies. Conversely, megadoses of these vitamins can lead to very high, possibly toxic, concentrations in the body. 

Sporadic reports of the 2//-thiopyran transformation are still available. The electrocyclic ring-opening of 2-benzyl-2,4,6-triphenyl-2//-thiopyran (131, X = PhCH2) was detected by laser flash spectroscopy (86MI1). 2-Amino-2//-thiopyran was predicted to be more stable than its valence-bond isomer on the basis of semiempirical MINDO/3 and MNDO calculations (84JPR955). 

Emerging evidence suggests that dysfunction of the ubiquitin-proteasome system may be part of the pathophysiology of sporadic Parkinson s disease, especially... 

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