Flow-through systems

Groundwater environments can be represented as a simple flow-through system. For the situation where chemical weathering of mineral grains is transport controlled, the weathering rate of a mineral should be directly dependent on the rate of throughput of water. For the situation where rates are controlled by surface... 

Recent advances and further improvements have led to a broad variety of applications for single-mode microwave instruments, offering flow-through systems as well as special features such as solid-phase peptide synthesis or in situ on-line analy-... 

Solid-supported technologies are already well established methods in medicinal chemistry and automated synthesis. Over the last couple of years new trends have evolved in this field which are of utmost importance as they have the potential to revolutionize the way chemical synthesis especially for library production is performed. Microchip-based synthesis technologies and multistep sequences with solid-supported catalysts or reagents in flow-through systems are only two spectacular examples. A new approach is the use of solid-supported systems for the scale-up of chemical reactions thereby enabling the rapid and smooth transition from discovery to development units. 

In general, only valid studies were used to derive predicted no effect concentrations (PNECs). Because in some cases only a few valid data were available, studies valid with restrictions have been used based on expert judgement. Invalid or non-assignable studies have not been used. In instances of volatile compounds, valid studies were generally those using closed, flow-through systems, preferably with analytical measurements. 

Figure 6 Different cell types for dissolution testing using the flow-through system. Type (a) tablet cell (12 mm), (b) tablet cell (22.6 mm), (c) cell for powders and granulates, (d) cell for implants, (e) cell for suppositories and soft gelatin capsules, (f) cell for ointments and creams.

In vitro dissolution data can be collected in closed systems (e.g., in compendial dissolution vessels) or by using open (flow-through) systems (1). 

The purchaser will specify the characteristics of the barrier or buffer fluid. Where the required flow, pressure, and temperature are factors, they shall be jointly established by the vendor and the seal manufacturer and shall be noted on the data sheets. When dual seals (as in Items b and c above) are provided, the barrier or buffer fluid shall be circulated by means of a circulating device such as a pumping ring or a flow-through system from an external source (see Appendix D). 

LC50 (96-h static flow-through system) for Oncorhynchus mykiss 7.36 mg/L (Hodson et al., 1984), 4.7 mg/L (Dalich et ah, 1982), Cyprinodon variegatus 10 ppm using natural seawater (Heitmuller et al., 1981). 

Fig. 5.4. Various positions of ISE s in a simple flow-through system [105 J.

Titration techniques can be appUed both to continuous monitoring and to analyses of discrete samples in flow-through systems. Generally it holds that the equivalence point for the reaction... 

Type 1 industrial systems represent an initial stage requiring a high throughput of energy and materials to function, and exhibit little or no resource recovery. It is a once flow-through system with rudimentary end-of-pipe pollution controls. 

Nanduri, V., Kim, G., Morgan, M., Ess, D., Flahm, B. K., Kothapalli, A., Valadez, A., Geng, T., and Bhunia, A. K. (2006). Antibody immobilization on waveguides using a flow-through system shows improved Listeria monocytogenes detection in an automated fiber optic biosensor RAPTOR. Sensors 6, 808-822. 

Larsen T, Kjeldsen P, Christensen TH. 1992. Sorption of hydrophobic hydrocarbons on three aquifer materials in a flow through system. Chemosphere 24 439-451. 

Buffers can be irrigated by industrial and municipal effluent to remove inorganic and organic compounds. In this application, the buffer is operated as a flow-through system that absorbs, sequesters, and metabolizes priority pollutants from the wastewater sources. It is often installed as the final filter at stream edges or around site perimeters. The buffer provides additional benefits as a visual barrier and it reduces noise, intercepts dust, and creates a wind break for operators. In addition, it can provide an aesthetic landscape for the neighborhood. 

Wastewater flows through system under hydrostatic heads. 

Purging requires either a continuous flow of water through the system or the recirculation of water through filters. The large amounts of "clean" water required by flow-through systems is expensive and may not be widely available (73). Recirculating systems use much less water than flow-through systems. However, the filters used to purify the water may become a source of off-flavors (74). 

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