Pegging

Cambridge Instruments builds the first commercial SEM 1968 Crewe and colleagues introduce the PEG as electron beam source 1968 Crewe and colleagues build the first STEM prototype 1995 Zach proves the concept of a corrected LVSEM... 

Direct measurement of the interaction potential between tethered ligand (biotin) and receptor (streptavidin) have been reported by Wong et al [16] and demonstrate the possibility of controlling range and dynamics of specific biologic interactions via a flexible PEG-tether. 

The adliesion and fiision mechanisms between bilayers have also been studied with the SEA [M, 100]. Kuhl et al [17] found that solutions of short-chained polymers (PEG) could produce a short-range depletion attraction between lipid bilayers, which clearly depends on the polymer concentration (fignre Bl.20.1 It. This depletion attraction was found to mduce a membrane fusion widiin 10 minutes that was observed, in real-time, using PECO fringes. There has been considerable progress in the preparation of fluid membranes to mimic natural conditions in the SEA [ ], which promises even more exciting discoveries in biologically relevant areas. 

Figure Bl.20.11. Force curves of DMPC/DPPE (dimyristoyl phosphatidylcholine and dipalmitoyl phosphatidylethanolainine) bilayers across a solution of PEG at different concentrations. Clearly visible is a concentration-dependent depletion attraction, with pennission from [17],...

Likewise, Grieco, while working with amphiphile-like reactants, observed an enhanced preference for endo-adduct in aqueous solutions, which he attributed to orientational effects within the micelles that were presumed to be present in the reaction mixture ". Although under the conditions used by Grieco, the presence of aggregates cannot be excluded, other studies have clearly demonstrated that micelle formation is not the reason for the improved selectivities . Micellar a peg tes even tend to diminish the preference for endo adduct. ... 

A large number of polymeric compounds have been investigated, but most modem propellants utilize prepolymers that ate hydroxy-functional polybutadienes (HTPB), carboxy-functional polybutadienes (CTPB), or a family of polyethylene oxides (PEGs) to form urethanes. Typical cure reactions... 

Two-Phase Aqueous Extraction. Liquid—Hquid extraction usually involves an aqueous phase and an organic phase, but systems having two or more aqueous phases can also be formed from solutions of mutually incompatible polymers such as poly(ethylene glycol) (PEG) or dextran. A system having as many as 18 aqueous phases in equiHbrium has been demonstrated (93). Two-phase aqueous extraction, particularly useful in purifying biological species such as proteins (qv) and enzymes, can also be carried out in combination with fermentation (qv) so that the fermentation product is extracted as it is formed (94). 

Hg ", Zn ", Cd " ) light emission is shifted to the red (610—615 nm). In vitro a flash of light is produced (< 1 s) that decays rapidly. Glow-type emission is obtained ia the presence of detergents (Triton X-100), polymers (PEG 6000), coen2yme A, inorganic pyrophosphate, and cytidine nucleotides (206,207). 

Fig. 16. Insulator wall designs (a) peg wall (b) conducting bar wall and (c) segmented bar wall. The gas-side materials are tungsten and tungsten—copper composite, the base material, copper, and the insulators, boron nitride. Slagging grooves are shown.

The composition of PPG—PEG blends has been determined using gpc with coupled density and RI detectors. PEG and PPG have different response factors for the density and RI detectors which were exploited (173). An hplc system with CHROMPAC RP-18C2g column at 298°C and acetonitrile—water or methanol—water as the mobile phase has been used to gather information about the functionaUty of PPO (174). 

Mass Spectrometry. Field desorption mass spectrometry has been used to analy2e PPO (179). Average molecular weight parameters (M and could be determined using either protonated (MH + ) or cation attachment (MNa + ) ions. Good agreement was found between fdms and data supphed by the manufacturer, usually less than 5% difference in all cases up to about 3000 amu. Laser desorption Fourier transform mass spectrometry was used to measure PPG ion and it was claimed that ions up to m/2 9700 (PEG) can be analy2ed by this method (180). 

Trade name Ester type Acid Composition PEG POE" Functions Manufacturer... 

Hardboard is available in either 1/8 or j in. (0.32 or 0.63 cm) thicknesses. It is available as peg board with holes punched in it. A significant but declining use has been in interior paneling and exterior siding, and it competes in many appHcations with thinner OSB and plywood. The U.S. market for hardboard was approximately 669 milHon or 455 X 10 (4.9 biUion ft, 1/8 in. basis) in 1989. 

Surfactants and Dispersants. Castor od can be transformed from an od- to a water-soluble surfactant, depending on the moles of ethylene oxide added to its hydroxyl group. A 40 mole ethylene oxide adduct of castor od, known as PEG-40 castor od, is a surfactant that has cosolvent properties and is utilized as a fragrance solubilizer (118). Glycol hydroxystearate emulsifiers are formulated into shampoos to impart finer peadescence and give better stabdity than gylcol stearates (118) (see Hair preparation). 

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