Viscosity sensitivity

Special vortex no22le designs which deUver lower flows using a large opening have been used to reduce plugging problems. Also, viscosity-sensitive no22les, where flow is increased as viscosity is increased, are used to control variation in soflds concentrations. 

A different approach to design a self-calibrating dye was proposed [70], in which a viscosity-sensitive molecular rotor (2-cyano-3-(4-dimethylaminophenyl) prop-2-enoic acid) was covalently linked to a reference dye, 7-methoxycoumarin-3-carboxylic acid, which exhibited no viscosity sensitivity (40, Fig. 13). A ratiometric measurement, that is, rotor emission relative to reference emission, was shown to be widely independent of dye concentration [70]. However, the design of such a ratiometric dye poses some challenges because of resonance energy transfer from... 

Fig. 13 Self-calibrating dyes DMA-2,4 and p-A,A-dimethylaminobenzoic acid. Compound 40 is an engineered ratiometric dye composed of a viscosity-sensitive molecular rotor and a nonviscosity-sensitive reference dye [70]...

Fig. 6.7. Viscosity sensitive fluorophores molecular rotors. DCVJ = 9-(dicyanovinyl)-julolidine, CCVJ = 9-(carboxy-2-cyano)vinyl julolidine, CMAM = 2-cyano-3-(p-dimethyl-aminophenyl)acrylic acid, methyl ester.

Variations in viscosity have been also followed with FRET probes. An innovative FRET pair constituted by a viscosity sensitive dye (CMAM) and a viscosity-independent coumarin, which acts as internal reference, demonstrated a high sensitivity for detecting viscosity changes in vitro [52],... 

The reversed dependence of this concerted decarboxylation reaction, as well as the concerted ortho-rearrangement on the polarity of solvents (cf. Tables II and VI), and the competition of decarboxylation to phenol formation in nonpolar solvents, are striking. Lack of information on the influence of substituents, viscosity, sensitization, or possible quenching in direct comparison with the formation of rearranged products and phenol do not yet... 

Aged emulsions containing a substantial portion of large (>200 xm) droplets exhibit a lower temperature-viscosity sensitivity, and this effect must be considered in calculating pressure gradients. Adjustment factors shown are for temperature increases (lower viscosity). The inverse of the factor applies to temperature decreases (higher viscosity). 

PROBES. An excimer-forsing probe, l,3-bis-(l-pyrene)propane (3PP), was obtained from a commercial source and used without further purification. A viscosity-sensitive probe. 1-(4-dimethylaminophenyl)-6-phenyl-l, 3,5-hexatriene (Di IA-BPH), was dissolved in DGEBA by rotating the resin at 45 C for several hours. An internal standard, 9,10-diphenylanthracene (DPA), at a concentration of 2x10" mol/1 was added to the resin-hardener mixture. 

Owing to the lack of sensitivity of the BPP probe at the longer cure times, we have examined the use of other types of viscosity-sensitive probe molecules. Figure 2 gives the excitation and emission spectra of the viscosity sensitive dye DMA-DPH in diglycidyl ether of bisphenol A (DGEBA). The excitation and the emission spectra of the internal standard DPA are similar to the ones published by Berlman(8). 

Separations should initially be attempted with the capillary thermostatted at close to ambient temperature. The capillary temperature can be increased on most commercial CE units to as high as 60 C without substantially increasing current with most buffers. When this is done using the same applied voltage, decreased buffer viscosity leads to an increase in analyte electrophoretic mobility, thus, decreasing separation times. Also, it is important to note that, when sample introduction is hydrostatic (same pressure/vacuum and time), increased capillary temperature will lead to an increase in the injected sample volume as a result of decreased buffer viscosity. " Sensitivity may not necessarily be increased. However, Undesirable effects include concurrent changes in buffer pH, band broadening due to increased diffusion, and possible thermal denaturation of the sample. 

Optimization of processing conditions (curing parameters) in fabrication of UV-cured automotive organic protective coatings fluorescence of a viscosity-sensitive molecular probe monitored during curing of coatings... 

If a process is viscosity sensitive this should be noted and a standard drawn up so products are always used within the prescribed limits. 

Products that have not gelled or solidified and are covered by points test interval, record, viscosity and viscosity sensitivity may be used by a customer for a further period of 6 months. Other pre-defined periods may be used for test intervals. 

Neither oil-based nor synthetic-based fluids exhibited any significant shear viscosity sensitivity to fiber concentration at ambient or elevated temperature. It may be possible for OBM or SBM sweeps to be utilized in the field with no increase in BCD. 

Upon photocatalysis with nanostructured silver, aromatic nitro and amine compounds undergo reductive and, respectively, oxidative coupling yielding specific azo derivatives. 6 -Nitro-l,3,3-trimethylspiro-(indolino-2,2 -benzopyran), to which crown ethers may be attached for size sensitive complexation, is a photochromic systems, used both as photoresponsive self-assembled monolayer on surface " and as a viscosity sensitive material. ... 

If it is assumed that k j (diffusive destruction of the cage pair) is the only solvent (viscosity) sensitive rate constant, then the qualitative implications of the scheme are obvious. The value of F should follow the fluidity (f = 1/vlscoslty). This means that the values of ko for a perester undergoing simple 0-0 bond homolysis should increase with fluidity (viscosity decrease) while kg should decrease with solvent fluidity. The yield of a perester product, from the corresponding hyponltrlte, should increase with fluidity decrease (viscosity Increase). The yields of ethers from either perester or hyponltrlte should likewise Increase with fluidity decrease. All of these qualitative expectation were in fact observed (Table I). 

A second means of obtaining Is from the sum of If k is really the only viscosity sensitive rate constant, then the kQ+ks sum should be constant in all solvents and equal to the value obtained by extrapolation. This was not the case for either the perbenzoate ( ) or the peracetate (3) Figure 2 also shows the Pp values from ko/kg which takes into account the variation of both k and kg with solvent (triangles). The descrepancy the two means of estimating k is very large and negates any conclusions concerning the N2 effect. 

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