Nominal gel

Figure 15.5 gives a wealth of information. It is important to understand that each series of three separate results at each nominal gel content represents an adjustment in DCP concentration to give the nominal gel content in the presence of 0, 0.5 and 2.0 phr TAC (increasing TAC concentration produces progressive increase in melt modulus and foam density). Result positively indicates that gel content is not a suitable indicator to predict foam density (as previously suggested). However, if all... 

Airway cross-sections have the nominal anatomy shown in Fig. 5.16. Airway surface liquid (AST), primarily composed of mucus gel and water, surrounds the airway lumen with a thickness thought to vary from 5 to 10 mm. AST lies on the apical surface of airway epithelial cells (mostly columnar ciliated epithelium). This layer of cells, roughly two to three cells thick in proximal airways and eventually thinning to a single cell thickness in distal airways, rests along a basement membrane on its basal surface. Connective tissue (collagen fibers, basement membranes, elastin, and water) lies between the basement membrane and airway smooth muscle. Edema occurs when the volume of water within the connective tissue increases considerably. Interspersed within the smooth muscle are respiratory supply vessels (capillaries, arteriovenous anastomoses), nerves, and lymphatic vessels. 

As a practical result, the amount of gel to be prepared for a preparative column must exceed the nominal volume of the final column by 10%. For the packing of production-scale columns the maximum pressure rate of the column has to be considered. The large columns consist mostly of borosilicate glass tubes with similar pressure stabilities. For example, a Superformance column with dimensions of 1000 mm in length and 50 mm in width is pressure stable up to 14 bar. Therefore, Fractogel EMD BioSEC should be packed with a... 

Gel permeation chromatography was performed in tetrahydrofuran using a Waters pump system and a Model 410 differential refractive index detector for the eluant. Five Ultrastyragel columns with nominal porosities ranging from 500 to 105 angstroms were used for all the samples and the polystyrene standards. 

The two key points of Figure 3.4 are the height of the volume differential ( diff. ) and percentage of particles below 40 pm (one gel has a mean of 90% of the particles in the nominal range in comparison with 80% for the others). The blue curve has a much higher... 

On-line size exclusion chromatographic (SEC) analyses were performed with a Waters Model 401 differential refractometer (DR), a Waters Model 480 ultraviolet (UV) variable wavelength spectrophotometer and a Foxboro Miran lA infrared (IR) photometer, equipped with a zinc selenide ultramicro flowcell of 1.5 mm nominal pathlength and 4.5 /xl volume, purchased from the same supplier. A set of ten Mycrostyra-gel (Waters Associates) columns, regenerated by Analytical Sciences Inc. (ASI) and of nominal porosities 100, 500 (two) 10 (two), 10 (three), 10 and lO X, in the order given and a mobile phase flow rate of 1 ml/min was used. The column set had a specific resolution of 19.7 in 1,4-dioxane, as determined by the method of Yau(2). 

The upper curve, which is the result of a curve fitting procedure to the points shown, is the HETP curve. The column was 25 cm long, 9 mm in diameter and packed with 8.5 micron (nominal 10 micron) Partisil silica gel. The mobile phase was a solution of 4.8 Sw/v ethyl acetate in n-decane. The minimum of the curve is clearly indicated and it is seen that the fit of the points to the curve is fairly good. As a result of the curve fitting procedure the values of the Van Deemter constants could be determined and the separate contributions to the curve from the multipath dispersion, longitudinal dispersion and the resistance to mass transfer calculated. 

Gel Permeation Chromatography. Polymer Laboratories narrow distribution polystyrene standards with nominal molecular weights of 1250, 2150, 3250, 5000, 9000, 34500, 68000 and 170000 g/mole were dissolved in HPLC... 

Different grades of Methocel and Metolose are supplied, with nominal viscosities of 4000 mPa s (measured with a Brookfield viscometer on a 2% w/v solution). Methocel 4M types E and are different in their hydration rates, type being the quickest. Metoloses SH4000 differ in their gel temperature. Grades 60 and 90 were used. Another polymer of 4000 mPa s viscosity was used hydroxyethylcellulose, in order to observe effects on the dissolution rate. 

This work has demonstrated that sorbent tubes are viable samplers for inorganic acid mists existing as vapors and aerosols. A silica gel sampling tube was developed which will collect at least a 4-hour sample of inorganic acid at a nominal flow rate of 0.2 Lpm. The optimum sampler geometry was determined to be a 7-mm O.D./4.8-mm I.D. glass tube packed with 20-40 mesh washed silica gel, 700 mg in the primary section and 200 mg in the backup. 

The strong points of this technique are its absence of interaction with the stationary phase, rapid dilution and the potential to recover all of the analytes. Because the technique permits the separation of nominal masses ranging from 200 to 107 Da, its main applications are in the analyses of synthetic and natural polymers. The choice of stationary phase for a given separation is made by examination of the calibration curve of various columns. The column of choice is that which provides a linear range over the masses of the compounds found in the sample. The calibration has to be conducted with the same type of polymers because macromolecules can have various forms ranging from pellet-like to thread-like. The data presented in Table 7.1 show the domains of application of the three gels shown in Fig. 7.3, depending on the standards that are used. 

Gel Permeation Chromatography. A Water Associates model 200 gel permeation chromatograph fitted with five Styragel columns having nominal porosity designations 107, 107,106, 1.5 X 105, and 1.5 X 104 A was used for the analysis of molecular weight distribution in TFE at a temperature of 50.0 0.5°C and a flow rate of 1.00 =t 0.05 ml/min. Further details concerning instrumental and operational parameters, sample preparation and injection, and data acquisition and reduction have been reported elsewhere (I). 

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