Selective filters

Filter Selection. A variety of product- and process-related factors govern filter selection. Considerations include the characteristics of the fluid to be filtered, ie, its chemical composition and compatibiHty with the filtration system (inclusive of the membrane, filter hardware, piping, etc), the level of bioburden present, specifications on effluent quaHty, the volume of product to be filtered, flow rate, and temperature. 

Filter selection, based on the feed capacity, m /h, to be handled, varies from 1 to 45 m /h in the many sizes available. A permanent magnetic filter is shown in Figure 11. 

Instruments for the measurement of fluorescence are known as fluorimeters or spectrofluorimeters. The essential parts of a simple fluorimeter are shown in Fig. 18.1. The light from a mercury-vapour lamp (or other source of ultraviolet light) is passed through a condensing lens, a primary filter (to permit the light band required for excitation to pass), a sample container, a secondary filter (selected to absorb the primary radiant energy but transmit the fluorescent... 

The overriding factor will be the filtration characteristics of the slurry whether it is fast filtering (low specific cake resistance) or slow filtering (high specific cake resistance). The filtration characteristics can be determined by laboratory or pilot plant tests. A guide to filter selection by the slurry characteristics is given in Table 10.3 which is based on a similar selection chart given by Porter et al. (1971). 

Because on CCD setups excitation for D, S, and A images is usually filter-selected from a single white light source the relative intensity of excitation is approximately fixed. Confocal microscopes use separate laser lines, often from distinct lasers, that can (and for optimal imaging should) be independently adjusted. Thus, on CCD setups y (Eq. (7.6)) is constant for a given set of filters whereas on the confocal, it varies from image to image (also, see Sect. 7.4.2). 

In addition to the ability to react nonspecifically with hydrocarbons, active nitrogen can readily participate in energy transfer reactions with volatile organometal-lic compounds, leading to atomic emission from the metal atom. By use of appropriate optical filters, selective detection of elements such as aluminum, lead, tin, and mercury has been achieved in the presence of large excesses of organics [58],... 

Excitation filter selects wavelengths of light from a light source that fall in the maximum absorption region of a specific fluorophore. 

K+ channels selectively transport K+ across membranes, hyperpolarize cells, set membrane potentials and control the duration of action potentials, among a myriad of other functions. They use diverse forms of gating, but they all have very similar ion permeabilities. All K+ channels show a selectivity sequence of K+ Rb+ > Cs+, whereas the transport of the smallest alkali metal ions Na+ and Li+ is very slow—typically the permeability for K+ is at least 104 that of Na+. The determination of the X-ray structure of the K+-ion channel has allowed us to understand how it selectively filters completely dehydrated K+ ions, but not the smaller Na+ ions. Not only does this molecular filter select the ions to be transported, but also the electrostatic repulsion between K+ ions, which pass through this molecular filter in Indian file, provides the force to drive the K+ ions rapidly through the channel at a rate of 107-108 per second. (Reviewed in Doyle et al., 1998 MacKinnon, 2004.)... 

The most important factors in filter selection are the specific resistance of the filter cake, the quantity to be filtered, and the solids concentration. For free-filtering materials, a rotary vacuum filter is generally the most satisfactory since it has a very high capacity for its size and does not require any significant manual attention. If the cake has to be washed, the rotary drum is to be preferred to the rotary leaf. If a high degree of washing is required, however, it is usually desirable to repulp the filter cake and to filter a second time. 

Hydrophobie filters do not come directly into contact with the product, and therefore the standard baeterial retention test alone is generally sufficient validation. However, as hydrophilie filters are in direet contact with the product, additional validation is necessary for eaeh produet type to demonstrate that the filters selected for product sterilization do not affeet the safety, identity, strength, quality, or purity of the drug produet. Qualifieation of hydrophilie filters is also neeessary to demonstrate that the speeifie produet type in eonjunetion with a baeterial ehallenge does not affect the filter effieaey. Validation of filters by means of baeterial retention tests requires special equipment and is often arranged between the filter manufacturer and the BPS operator. 

Phenol- and chloroform-extract and ethanol precipitate the recovered RNA (see Subheading 3.7). The RNA is reverse transcribed, purified, and precipitated as detailed in Subheadings 3.6 (25) and 3.7, and then RNA is used for the nitrocellulose filter selection step and cocaine displacement of nAChR-bound RNA molecules (Fig. 2). 

Inlet filter. In air compressors filter selection is an important factor in preventing fouling. Most high-efficiency air filters have a triple-stage filtration system. Also these filters often have rain shades to prevent water from entering the filters. Site conditions play a very important part in the selection of the filters. 

Filter selection depends on the dye system. Incorrect fdter selection leads to poor images. The appropriate fluorescent light wavelength for this mix of Nile Red and Nile Blue is 488... 

One optical filter for the measurement of water vapor is installed in the filter wheel as the standard. In this way, the water vapor is measured in each sample, enabling the instrument to subtract the absorption signal coming from water vapor from the measured signal for a gas of interest, giving a more correct measurement. Similarly, by measuring the same air sample with more optical filters, one filter selected for each gas in the sample, it is possible to compensate for the interference of one gas on another. 

Transverse relaxation filter/selective longitudinal relaxation Slow Rapid Increased 75, 76... 

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