Zones lateral flow

Development of the Environmental Policy Integrated Climate (EPIC) model and its predecessor, the Erosion Productivity Impact Calculator, began in the early 1980s.69 70 The first version of EPIC was intended to evaluate the effects of wind and water erosion on plant growth and food production. More recent versions also evaluate factors important to other environmental issues. EPIC is a onedimensional model however, it can estimate lateral flow in soil layers at depth. All versions of EPIC estimate surface runoff, PET, AET, soil-water storage, and PRK below the root zone—these complete the hydrologic water balance for an ET landfill cover. 

Fig. 2.13 A second basic experiment in water flow an aquarium filled and heaped with sand is exposed to rain. At steady state the rain infiltrates along vertical downflow paths (free flow) until a zone of lateral flow (overflow) is reached. The water at the deeper part is stagnant. Eddies create a thin transition or mixing zone.

Fig. 2.14 An entire groundwater system, from the water divide to the terminal base of drainage, built of permeable rocks. The following patterns of water motion are recognizable (1) a through-flow zone with vertical flow paths that join a lateral flow path toward the terminal base of drainage (2) a transition (mixing) zone and (3) a zone of stagnation occurring beneath the level of the terminal base of drainage (zero hydraulic potential).

The vertical downflow paths and the lateral flow zone take the shape of the letter L, hence the name zone of L-shape through-flow paths, which differs from the U-shape flow paths model discussed in section 2.15. 

A closer look at the zone of vertical downflow paths. Local recharge flows vertically down until the zone of lateral flow is reached. In coastal plains the vertical flow zone is fairly thin, on the order of a few meters to a few tens of meters, and it clearly coincides with the aerated zone, and the water table signifies the zone of lateral base flow. In mountainous regions the vertical flow paths are longer, and usually the higher the topographic relief is, the thicker is the zone of vertical downflow. The following observations testify to the existence of vertical downflow paths ... 

Flow of water from fractures is often encountered in mines at different depths. Significant variations in the water properties suggest locations in the downflow zone. In contrast, in mines located in the lateral flow zone or in stagnant systems, uniform water properties are expected. 

Mountain slopes and escarpments are often with no springs, although they are recharged by precipitation. This is a clear indication that in such regions the recharge water flows vertically down until it meets a lateral flow zone at greater depth (Fig. 2.15). 

Hydraulic connectivity in the vertical and lateral flow zones. Hydraulic connectivity is poor in the vertical downflow zone and significantly higher in a lateral base flow zone. 

The hydraulic connectivity is much better along the flow paths of the lateral flow zone. This is best demonstrated on coastal plains groundwater flows from the mountain foothills toward the sea, and along these flow paths local recharge water is added and intermixed. 

The through-flow zone has so far been described in a simplified mode, assuming all the hosting rocks are homogeneously permeable. Deviations from the simplified L-shape of the flow path are caused by the presence of hydraulic barriers, such as clay and shale, that may in certain places block the downflow and create local perched water systems and springs (Fig. 2.16) or cause steps in the path of the lateral flow zone. But the overall L-shape is generally preserved, as the water of perched systems finds pathways to resume the vertical downflow direction. 

Particulate catalyst can be arranged in arrays of any geometric configuration. In such arrays, three levels of porosity (TLP) can be distinguished. The fraction of the reaction zone that is free to the gas flow is the first level of porosity. The void fraction within arrays is the second level of porosity. The fraction of pores within the catalyst pellets is referred as the third level of porosity. Parallel-passage and lateral-flow reactors... 

Deep geopressured subsystem of burial-induced groundwater flow Lateral flow of groundwater Is restricted vertical upward now of groundwater is focuss along faults and through hydrofractured zones... 

Fig. 1. The lateral flow strip structure (A) Schematic representation of the lateral flow strip. A lateral flow strip typically consists of four zones of a sample pad, a conjugate pad, a membrane containing the test and control lines, and an absorbent pad on a backing plate. (B) Lateral (toft and over (bottorft views of a lateral flow strip. The outmost layers of the ends of the strip are plastic cover films.

If a TLC or similar applicator is not available, the capture probe/ streptavidin solution may be applied manually to the lateral flow membranes. Here, a round spot for the capture and control zones would result, vs. the line seen in Fig. 1 generated using the Lino-mat for probe application. This procedure is useful for optimization purposes, but is more laborious than the TLC applicator procedure due to the need to apply probe and tape individual membranes. 

Fig. 1. Lateral flow tests are often constructed from a series of materials that sequentially overlap. The goal is to imbed all reagents so that a flowing sample rehydrates and moves all materials up a test strip. Analytes and reagents then interact in zones placed on the strip. The result is a rapid test that provides information easily visible to the eye.

There are numerous companies that supply materials and components necessary to construct lateral flow tests, and unfortunately, there may be considerable variability in the quality and performance of these materials and components. The most crucial material is the nitrocellulose membrane, which supports the capture zones that are interrogated when the test is read. 

Figure 3. Schematic design of a lateral flow test (According to [69]) (a) sample pad (sample inlet and filtering), conjugate pad (reactive agents and detection molecules), incubation and detection zone with test and control lines (analyte detection and functionality test) and final absorbent pad (liquid actuation), (b) Start of assay by adding liquid sample, (c) Antibodies conjugated to colored nanoparticles bind the antigen, (d) Particles with antigens bind to test line (positive result), particles w/o antigens bind to the control line (proof of vahdity).

Stagnation point produced by the collision of liquid flow against the outlet weir wall forces liquid laterally toward the column wall. Upon collision with the column wall, this lateral flow generates backward flow in the stagnant zone. If the forward flow component is very slow, the backward component will dominate, causing recirculation. 

In prospective study, more innovative devices need to be developed for multiplex analysis. Furthermore, even though lateral flow in 2-D paper sheet has been mostly elucidated based on fiber structure and surface energy, there are still limited study on vertical flow in a 3-D paper device. It was reported that a 3-D paper device coupled with electrochemical electrodes fabricated on two filter paper sheets for detection of multiple cancer markers based on chemiluminescence, which prevents cross-talk between adjacent detection zones. Therefore, 3-D paper sensors with versatile structure need to be further explored to realize multiple anal5d e detection using multiple techniques. 

Enzyme immunoassays, in a card-test format, are also used for screening carcasses by testing of urine for specific antimicrobial residues such as sulfadimidine and chloramphenicol. The sol particle immunoassay uses adsorption of specific antibodies to dyed colloidal particles (e.g., carbon) as a mechanism for making directly visible the presence of residues (i.e., antigen) in the sample. A lateral flow membrane device is used to identify residue-positive samples through the absence of color formation at the test capture zone (Figure 5). 

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