Stock preparation

The objective of fiber stock preparation systems is to modify the different ingoing raw materials in such a way that the finished stock finally supplied to the paper machine suits the requirements of the paper machine and of the quality demands put on the produced paper or board. The raw stocks used are the various types of virgin pulps as well as recovered paper grades. They are available in the form of bales, loose material or, in the case of integrated mills, as suspensions. The finished stock is a suspension of defined quality as far as the mixture and characteristics of the fibers, additives, and impurities are concerned. This quality essentially determines paper machine runnability and is the basis for the final paper and board quality. 

A stock preparation system comprises essentially three levels (Fig. 4.1)  

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The unit processes in fiber preparation and their objectives are  

Separation processes are of high importance in recovered paper processing as this 

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Subsequent to stock preparation and proper dilution, the paper furnish usually is fed to the paper machine through one or more screens or other devices to remove dirt and fiber bundles. It then enters a flow spreader which provides a uniform flowing stream and which is the width of the paper machine. The flow spreader, or manifold, discharges the slurry into a headbox, where fiber flocculation is minimised by microturbulence and where the proper pressure head is provided to cause the slurry to flow at the proper velocity through the slice and onto the moving Fourdrinier wire. 

Activation of PE residues with these crosslinkers can proceed by one of two routes the purified PE phospholipid may be modified in organic solvent prior to incorporation into a liposome, or an intact liposome containing PE may be activated while suspended in aqueous solution. Most often, the PE derivative is prepared before the liposome is constructed. In this way, a stable, stock preparation of modified PE may be made and used in a number of different liposomal recipes to determine the best formulation for the intended application. However, it may be desirable to modify PE after formation of the liposomal structures to ensure that only the outer half of the lipid bilayer is altered. This may be particularly important if substances to be entrapped within the liposome are sensitive or react with the PE derivatives. 

As was discussed in Chapter 13, hydrogen does not react directly with some elements, so the hydrides must be prepared in a different way. Alfred Stock prepared silicon hydrides by first making the magnesium compound, then reacting it with water. 

From the 100 ppm Na stock, prepare standards of 1,3, 5, and 7 ppm in 25-mL volumetric flasks. A control sample may also be provided. Dilute to the mark with distilled H20. 

E. coli DH5a (pJF119fsa) strain was conserved at —80°C in glycerol stocks prepared from exponential-phase cultures. 

Stock preparation wash DEAE cellulose three times with H20 on a magnetic stirrer for some minutes. Allow the cellulose to sediment and pour off the supernatant with fine particles. Leave the cellulose for 30 min in 1 M NaOH, then wash with H20 until the pH of the supernatant is neutral DEAE cellulose (OH form). Leave cellulose for 30 min in 1 M HC1, then wash until the pH of supernatant is neutral DEAE cellulose (CL form). Store at 4°C. This solution is stable for 1 year without preservative. 

Costly raw stock preparation and needs shaped performs. Raw stock needs preparation such as pre warming. Screw units masticate as well as heat the stock. 

FIBRE FURNISH. It is well established (9) that when fibres are beaten or refined at a neutral or slightly alkaline pH the efficiency of the process is greater than at the acidic pH of around 4.5 common in alum/rosin systems. (When running an alum/rosin system it is inevitable that much of the stock preparation part of the mill operates at low pH because most of the water used is recycled from the wet-end of the paper machine). 

Alfred Stock prepared silicon hydrides by the means of the following reactions ... 

Bliss, T. (1998). Screening in the stock preparation system. Proc. 1998 TAPPI Stock Preparation Short Course, Apr. 29-May 1, Atlanta, GA, 151-174. TAPPI Press, Norcross, GA. 

There is no sharp line of demarcation between the manufacturing methods described in this chapter. For example, some writers consider "foam-in-place" or "pour-in-place" varieties of molding. The technique of "frothing" may be used in "pour-in-place" methods. Slab stock prepared by continuous slab production is used in lamination (1). 

For each drug concentration, take 5 x 106 cells (for 10 replicates) and infect with 0.5 mL of virus stock prepared from B95-8 cells (see Appendix 3). 

The first operation in the paper mill involves stock preparation the slushing of baled pulp, the refining or beating of chemical pulps, the blending of pulp stocks and additives prior to forming paper. 

Once constructed, the plasmid sequences are introduced into the virus chromosome by co-transfection of the plasmid with naked wild type viral DNA. Recombination occurs at a low but useful frequency between these DNAs at their homologous regions, flanking the polyhedrin gene. The progeny virus from the co-transfection are plaqued, and the plaques are scored for type. Under a dissecting microscope, the recombinants can be selected from the wild types based on their distinctive plaque morphology due to a lack of PIBs. Once selected and a stock prepared, one has a virus which on infection of cells will direct the production of both additional virus and the product of the... 

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