Material removal

Why are acid-soluble materials removed before the dehydrated residue is treated with HF ... 

In terms of membrane area used and doUar value of the membrane produced, artificial kidneys are the single largest appHcation of membranes. Similar hoUow-fiber devices are being explored for other medical uses, including an artificial pancreas, in which islets of Langerhans supply insulin to diabetic patients, or an artificial Uver, in which adsorbent materials remove bUinibin and other toxins. 

The hulls are the first material removed from the process to merit concern in respect to safeguards. These represent a possible route for special nuclear material (SNM) to be clandestinely removed from the system. Special instmmentation is used to assay the hulls containers for residual SNM. This step not only monitors the dissolver for proper functioning, but also serves an accountancy function as a material access area portal and enables the satisfaction of contractual requirements regarding process losses (40). 

The distribution of impurities over a flat sihcon surface can be measured by autoradiography or by scanning the surface using any of the methods appropriate for trace impurity detection (see Trace and residue analysis). Depth measurements can be made by combining any of the above measurements with the repeated removal of thin layers of sihcon, either by wet etching, plasma etching, or sputtering. Care must be taken, however, to ensure that the material removal method does not contaminate the sihcon surface. 

Disclosing waxes or pressure indicating pastes, are used in fitting a dental appHance to estabhsh the location and extent of high spots or pressure areas, as on impressions and complete dentures. They are very soft, salve-like compositions that are painted onto the tissue side of an impression or denture. When the wax-coated denture is seated in the mouth, the soft paste is forced out of the areas showing hard contact between the denture and the mucous membrane. These areas on the denture can be easily marked and material removed from the denture to reheve the premature or hard contact. 

Cavitation has three negative side effects in valves—noise and vibration, material removal, and reduced flow. The bubble-collapse process is a violent asymmetrical implosion that forms a high-speed microjet and induces pressure waves in the fluid. This hydrodynamic noise and the mechanical vibration that it can produce are far stronger than other noise-generation sources in liquid flows. If implosions occur adjacent to a solid component, minute pieces of material can be removed, which, over time, will leave a rough, cinderlike surface. 

Pluggage of cooling water return lines had occurred repeatedly. The material removed from internal surfaces contained large amounts of grease, oil, and rust (Fig. 5.18). 

Clostridia frequently are found where sulfate-reducing bacteria are present, often in high numbers inside tubercles. A typical microbiological analysis of tubercular material removed from a troubled service water system main is given in Table 6.4. Clostridia counts above 10 /g of material are high enough to cause concern. When acid producers... 

Microbiological analysis of material removed from corroded areas showed high aerobic and relatively high anaerobic counts (Table 6.7). Fungi counts were also elevated, indicating relatively high die-off of aerobic bacteria that is, the coolant was approaching its useful life. 

TABLE 6.7 Microbiological Evaluation of Material Removed from Corroded Areas in Case History 6.7 ... 

Secondary and tertiary processing normally infers material removal processes, e.g. turning, grinding, honing. Adequate machining allowances must be provided for at the primary/secondary processing stage when a secondary/tertiary process is used respectively. 

Usually nondestructive sample preparation may involve material removal... 

Another consideration in the application of absorption as a control technique is the treatment or disposal of the material removed from the absorber. In most cases, the scrubbing liquid containing the VOC is regenerated in an operation known as stripping, in which the VOC is desorbed from the absorbent liquid, typically at elevated temperatures and/or under vacuum. The VOC is then recovered as a liquid by a condenser. 

Porosity constitutes a important criterion in a description based on straining. Porosity is determined by the formula V /Vc, in which V c is the total or apparent volume limitated by the filter wall and is the free volume between the particles. The porosity of a filter layer changes as a function of the operation time of the filters. The grains become thicker because of the adherence of material removed from the water, whether by straining or by some other fixative mechanism of particles on the filtering sand. Simultaneously the interstices between the grains diminish in size. This effect assists the filtration process, in particular for slow sand filters, where a deposit is formed as a skin or layer of slime that has settled on the... 

Holden et al. [27] reported the first Raman results on nanotubes produced from a Co-catalyzed carbon arc. Thread-like material removed from the chamber was encapsulated in a Pyrex ampoule in -500 Torr of He gas for Raman scattering measurements. Sharp first-order lines were observed at 1566 and 1592 cm and second-order lines al 2681 and 3180 cm , but only when cobalt was present in the core of the anode. These sharp lines had not been observed previously in... 

Selection of the off-take position is important from the standpoint of the amount of material removed. Locating the off-take in the proximity of the material stream or at points of splash will result in greater removal of materials. This positioning may be desirable as a means to control splash effects provided that the off-take velocity is kept low. 

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