Membranes nucleopore

Invasiveness of the chemiluminescence (CL) lines was measured by in vitro and in vivo methods. The in vitro monitoring process comprised the movement of cells across a membrane of defined pore size within a specially designed growth chamber or MlCS (membrane invasion culture system). A 10-p diameter Nucleopore membrane was coated with a mixture of laminin (to promote invasion), collagen, and gelatin. Cells were added to the top side of the chamber in media and the extent of cell movement into the bottom of the chamber (invasion) through the membrane determined. 

Figure 2. Membrane-separated culture apparatus, modified for anaerobic operation, M, nucleopore membrane O, overflow S, magnetic stirrers E, extension tubes F, millipore filters.

The template-assisted synthetic strategies outlined above produce micro- or mesoporous stmetures in which amorphous or crystalline polymers can form around the organic template ligands (174). Another approach is the use of restricted spaces (eg, pores of membranes, cavities in zeolites, etc.) which direct the formation of functional nanomaterials within thek cavities, resulting in the production of ultrasmaU particles (or dots) and one-dimensional stmetures (or wkes) (178). For example, in the case of polypyrrole and poly(3-methylthiophene), a solution of monomer is separated from a ferric salt polymerization agent by a Nucleopore membrane (linear cylindrical pores with diameter as small as 30 nm) (179—181). Nascent polymer chains adsorb on the pore walls, yielding a thin polymer film which thickens with time to eventually yield a completely filled pore. De-encapsulation by dissolving the membrane in yields wkes wherein the polymer chains in the narrowest fibrils are preferentially oriented parallel to the cjlinder axes of the fibrils. 

The nucleopore membrane filters are more recent developments, being available since 1965 [35-37]. Nucleopore membrane filters are prepared by means of a nuclear physical process neutron irradiation in a nuclear reactor followed by chemical etching. The structure of the resulting filters is geometrically regular. The capillary filter model fits a nuclear membrane filter well [38]. 

Both classic membrane filters and nucleopore membrane filters are made of organic materials soluble in many nonaqueous solvents. Types of metallic membrane filters are also available, for example, silver metal membrane filters. These filters are made by means of a powder metallurgy process. They are useful for organic microanalysis of aerosol samples [39]. 

Prepare lysing syringes by inserting a folded Nucleopore membrane between a 1-ml syringe and the needle. One syringe/ time point is required. 

Syringes for cell lysis. For each, fold a Nucleopore membrane in half and place it between the needle and barrel of a 1-mL disposable syringe. 

This approach involves determination of the extent to which spermatozoa can migrate through a membrane (e.g., a Nucleopore membrane with 5 xm pore size). This extent correlates primarily with the fraction of fast and straight-swimming cells in the sperm sample and with the sperm progressive velocity [68]. 

The photoinitiator may be loaded on the membrane surface by adsorption or may be dissolved in the monomer solution. For example, PET nucleopore membranes were modified using BP dissolved in the monomer solution following UV irradiation of the solution and the immersed membrane (Yang and Yang 2003). It was shown that photografting occurred mainly on the top membrane surface rather than in the membrane pores. This approach is relatively simple however, its main drawback is a low local concentration of BP on the membrane surface because BP moves to the membrane surface only by diffusion. This results in a low grafting efficiency. High bulk BP concentration may cause a side reaction, such as homopolymerization. In addition, the use of monomers that do not have a common solvent with BP is limited BP is almost insoluble in water. 

Yang, B. and Yang, W. 2003. Photografting modification of PET nucleopore membranes. ... 

Extremely simple fluids are used for the aqueous, alkaline, and organic phases. Deaerated distilled water purified by a Milli-Q nucleopore membrane and CP reagent grade chemicals were used for the preparation of alkaline and saline solutions. A... 

Isolation of predominant species Water samples from each source were membrane-flitered through 0.45-micron Gelman nucleopore membranes to count the colony-forming units (CFU) per ml of sample. The following dilution series was filtered in triplicate 100 ml of sample, 10 ml of sample, 10 ml of 1 10 dilution, 10 ml of 1 100 dilution, and 10 ml of a 1 1,000 dilution. One membrane of each dilution was then placed on each of the following nutrient media ... 

Fig. 5.26 SEM micrographs of several membrane surfaces reveal a range of pore structures that in turn result in a range of separation applications. An experimental, microporous, polyethylene membrane is shown (A) with elongated, stretched porous regions of various sizes, separated by fibrils, in the draw direction, and unstretched lamellae normal to the draw direction. This surface structure is quite different from three commercial membranes (B-D). One membrane (B) consists of a low density network of rounded pores, many of which are larger than 1 /im across. A nucleopore membrane (C) has more defined pore structure with rounded pores bored through from one side to the other. The morphology in (D) is an open network structure with the polymer in the form of strings of particles.

Artificial membranes had been constructed that contain a parallel layer-type assembly of gold nano-tubules that span the complete thickness of a natural or artificial membrane. These nano-tube-doped membranes are e.g. prepared via a template method depositing gold within the pores of a template membrane. The inside diameters of the Au nano-tubules can be adjusted by controlling the metal deposition time from fully open to completely closed. Based on the template (e.g. Nucleopore membranes) the nano-tubules have inside diameters down to molecular dimensions. Thus, these nano-filtcrs can be used to cleanly separate small molecules on the basis of molecular size. 

The deuteron NMR work of Crawford et al. [210-212] on 5CB-d2 confined into cylindrical submicrometer channels of organic (Nucleopore) membranes, provided the first insight into the order and dynamics of liquid crystals in cylindrical micro-cavities. The NMR pattern directly reflects the distribution of molecular directors in the cavity. According to theoretical predictions [213, 214] the nematic director field can be here either ... 

Filterability This test mimics the entrance of the polymer solution in the porous medium by passing the diluted solution through a filter with circular pores. It is an indicator of the solution injectivity. Method filtration at 2 bar on a 5 microns nucleopore membrane. 

In this case, the polymer particles are separated from the aqueous phase by a membrane through which the particles cannot permeate. Suitable membranes include dialysis tubes (molecular weight cut-off 10000-15 000 g mol ) or, for example, Nucleopore membranes, which are available with pore diameters from 15 nm to several micrometers. 

In the diafiltration method [23], which uses the Nucleopore membranes, the dispersion is filtered under pressure through the membrane. Like the dialysis method, diafiltration can be used not only to separate the aqueous phase, but also to purify a polymer dispersion, that is to separate all the water-soluble components. When used for the latter purpose, the dispersion is continuously rinsed with water during the diafiltration process. Filter cake formation is prevented by adopting a cross-flow filtration arrangement in which, for example, a stirrer is used to create a convective current parallel to the surface of the membrane. 

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