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The viscosities of dimethyl ether (DME, [C.sub.2][H.sub.6]O) and of the fluorinated propene isomers 2,3,3,3-tetrafluoroprop-1-ene (R1234yf, [C.sub.3][H.sub.2][F.sub.4]) and trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) were measured in a combined temperature range from 242 K to [...]

Quartz crystal impedance analysis has been developed as a technique to assess whether room-temperature ionic liquids are Newtonian fluids and as a small-volume method for determining the values of their viscosity-density product, p[eta]. Changes in the impedance spectrum of a 5-MHz fundamental frequency quartz corstal induced by a water-miscible room-temperature ionic liquid, 1-butyl-3-methylimiclazolium trifluoromethylsulfonate ([C4mim][OTf]), were measured. From coupled frequency shift and bandwidth changes as the concentration was varied from 0 to 100% ionic liquid, it was determined that this liquid provided a Newtonian response. A second water-immiscible ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [[C.sub.4]mim][NT[f.sub.2]], with concentration varied using methanol, was tested and also found to provide a Newtonian response. In both cases, the values of the square root of the viscosity--density product deduced from the small-volume quariz crystal technique were consistent with those measured using a viscometer and density meter. The third harmonic of the crystal was found to provide the closest agreement between the two measurement methods; the pure ionic liquids had the largest difference of ~10%. In addition, 18 pure ionic liquids were tested, and for 11 of these, good-quality frequency shift and bandwidth data were obtained; these 12 all had a Newtonian response. The frequency shift of the third harmonic was found to vary linearly with square root of viscosity-density product of the pure ionic liquids up to a value of [check]([rho][eta]) [approximately or equal to] 18 kg [m.sup.-2] [s.sup.-1/2], but with a slope 10% smaller than that predicted by the Kanazawa and Gordon equation. It is envisaged that the quartz costal technique could be used in a high-throughput microfluidic system for characterizing ionic liquids.

We show the theoretical and experimental combination of acoustic and optical methods for the in situ quantitative evaluation of the density, the viscosity, and the thickness of soft layers adsorbed on chemically tailored metal surfaces. For the highest sensitivity and an operation in liquids, a Love mode surface acoustic wave (SAW) sensor with a hydrophobized gold-coated sensing area is the acoustic method, while surface plasmon resonance (SPR) on the same gold surface as the optical method is monitored simultaneously in a single setup for the real-time and label-free measurement of the parameters of adsorbed soft layers, which means for layers with a predominant viscous behavior. A general mathematical modeling in equivalent viscoelastic transmission lines is presented to determine the correlation between experimental SAW signal shifts and the wavegnide structure including the presence of the adsorbed layer and the supporting liquid from which it segregates. A methodology is presented to identify from SAW and SPR simulations the parameters representatives of the soft layer. During the absorption of a soft layer, thickness or viscosity changes are observed in the experimental ratio of the SAW signal attenuation to the SAW signal phase and are correlated with the theoretical model. As application example, the simulation method is applied to study the thermal behavior of physisorbed PNIPAAm, a polymer whose conformation is sensitive to temperature, under a cycling variation of temperature between 20 and 40[degrees]C. Under the assumption of the bulk density and the bulk refractive index of PNIPAAm, thickness and viscosity of the film are obtained from simulations; the viscosity is correlated to the solvent content of the physisorbed layer.

A novel, experimentally simple, and highly sensitive method for measuring the loading of a quartz crystal resonator was developed. The method is based on the use of double-sideband suppressed-carrier modulated high-frequency signal, which is swept through the resonance range of the resonator. Induced current in the resonator is passed through a capacitor, and the voltage over the capacitor is demodulated on an analog multiplier. The phase and amplitude information is carded to the frequency-doubled modulation signal and measured on a conventional low-frequency two-phase lock-in amplifier. A complex dimensionless loading parameter is obtained from the experimental data by nonlinear model fitting. The real and complex parts of this loading parameter have a simple relationship with other parameters commonly used for characterizing the resonator loading. The performance of the method was demonstrated by measuring a series of different glycerol--water mixtures ranging from 0 up to 100% glycerol. The results were close to the shear acoustic impedance of these mixtures measured and calculated from their viscosities and densities.

Intrinsic viscosity provides insight to molecular structure and interactions in solution. A new microchip method is described for fast and accurate measurements of viscosity and intrinsic viscosity of polymer and biopolymer solutions. Polymer samples are diluted with solvent in the microfluidic chip by imposing pressure gradients across the channel network. The concentration and flow dilutions of the polymer sample are calculated from the fluorescent signals recorded over a range of dilutions. The viscosities at various polymer dilutions are evaluated using mass and momentum balances in the pressure-driven microchannel flow. The technique is particularly important to many chemical, biological, and medical applications where sample is available in very small quantities. The intrinsic viscosity experiments were performed for three classes of polymer solutions: (a) poly(ethylene glycol), polymers with linear hydrocarbon chains; (b) bovine serum albumin, biopolymer chains with hydrophobic and hydrophilic amino acids, and (c) DNA fragments, biological macromolecules with double-stranded polymeric chains. The measured values of intrinsic viscosity agree remarkably well with the available data obtained using different methods. The data exhibit power law behavior for molecular weight as described by the Mark--Houwink--Sakurada equation. Experiments were performed to understand the effect of solvent quality and salt concentration on molecular conformations and the intrinsic viscosity of the polymers. This method offers a new way to study the conformational changes in proteins and DNA solutions in various buffer conditions such as pH, ionic strength, and surfactants. The effects of shear rate in the micro-channel and mixing time on the accuracy and limitation of the measurement method are discussed.

The advantages of representing experimental plate height data as a plot of [K.sub.v]/[u.sub.o.sup.2] or [H.sup.2]/[K.sub.v] versus [K.sub.v]/(H[u.sub.o]) instead of as H versus [u.sub.0] are discussed ([K.sub.v]=column permeability). Multiplying the values on both axes by the ratio of a reference pressure drop and mobile-phase viscosity, the obtained plots directly yield the kinetic performance limits of the tested support structure, without any need for further numerical optimization. Directly showing the range of plate numbers or analysis times wherein the tested support geometry can yield faster separations or produce more plates than another support type, such kinetic plots are ideally suited to compare the performance of differently shaped or sized LC supports. The approach hence obviates the need for a common reference length, which is a clear problem if it is attempted to compare differently shaped supports on the basis of their flow resistance [empty set] and reduced plate height h. It is also shown how an MS Excel template file, only requiring the user to paste the column permeability [K.sub.v] and a series of experimental ([u.sub.0], H) data, can be used to automatically establish a series of so-called kinetic performance (KP) numbers, which can be used to completely describe the performance characteristics of the considered support. The advantages of the proposed data representation methods are demonstrated by applying them to several recent literature plate height data sets, showing that the obtained kinetic plots directly visualize the range of plate numbers where new approaches such as ultra-high-pressure HPLC or the use of open-porous silica monoliths can be expected to provide a substantial gain and where not. The data analysis also showed that the most generally relevant KP numbers are [N.sub.opt] (the plate number for which the support achieves its best analysis time/pressure cost ratio), [t.sub.opt] (the time needed to obtain [N.sub.opt] plates), and [t.sub.1K] (the time needed to generate 1000 or 1 kilo of theoretical plates). These KP numbers are much more informative than the [H.sub.min], [u.sub.0,opt,] and [K.sub.v] data traditionally employed to quantify the performance of LC supports.

The vibrational dephasing of the CO stretching mode of hemoglobin-CO (HbCO) inside living human erythrocytes in liquid solutions and in a glassy matrix is measured using the ultrafast spectrally resolved stimulated vibrational echo experiments. It is demonstrated that the dynamics of the protein are same inside erythrocytes and in aqueous solution and are independent of the viscosity.

The electron-exchange luminescence from a bicyclic dioxetane was studied.

Oxidation yields decrease upon increasing the viscosity of the solvent when peroxynitrite reacts with an excess of CO2 in the presence of a variety of reactants. This rules out the involvement of a competition between glycerol and ABTS/ferrocyanide for the oxidizing radicals in the decrease in the oxidation yields. It is concluded that the decomposition of peroxynitrite in the presence of CO2 occurs through the formation of CO(sub 3)(super *-) and *NO2 in a solvent cage.

A numerical code is developed to study the effect of ion density and temperature (as well as ion pressure and temperature gradients) on the amplitude of the local maxima of the poloidal viscosity with respect to the poloidal Mach number using the model developed by Shaing [1]. The sum of the poloidal viscosity and ion-neutral collisions is determined from the dependence of the plasma radial current on the radial electric field in a biased electrode experiment. The experimental results in the interchangeable module stellarator agree qualitatively with the predictions of the numerical calculation regarding the effects of variation of ion density and temperature on viscosity. Index Terms - Biased electrode experiments, L-H transition, stellarators, viscosity.

Lowering the viscosity of an HPLC mobile phase using liquid C[O.sub.2]/organic solvent mixtures has proven to be an effective means of increasing chromatographic efficiency, shortening analysis time, and lowering the pressure drop under ambient conditions. Such mixtures easily retain the high solvating power of common organic solvents but have low viscosities that are similar to those of supercritical fluids. To overcome the disadvantages of C[O.sub.2] such as acidity in aqueous solution and reactivity toward some basic analytes, liquid mixtures of CH[F.sub.3]/methanol/[H.sub.2]O are investigated in HPLC separations. Triazine herbicides were used as the test solutes for reversed-phase HPLC. While either C[O.sub.2-] or CH[F.sub.3]-containing (20 mol %) enhanced-fluidity mobile phase provided better efficiency, shorter analysis time, and lower pressure drop than the methanol/[H.sub.2]O mobile phase, the mobile phase containing CH[F.sub.3] was superior to that with C[O.sub.2] in chromatographic performance. C[O.sub.2] also influences the pH of the water-containing mobile phase, which results in resolution loss for some analytes with high p[K.sub.a]s. The addition of a 10 mM phosphate buffer improved the efficiency for all the mobile phases, either with or without C[O.sub.2] or CH[F.sub.3], which affirms the importance of maintaining pH for ionizable analytes in reversed-phase HPLC using either common or enhanced-fluidity liquid mobile phase. The strongest enhancement in chromatographic performance was provided by the CH[F.sub.3]-containing mobile phase with buffer.

Numerical calculations based on Shaing's L-H transition theory in stellarators and performed by Dahi et al. determine viscosity as a function of ion flow speed in the interchangeable module stellarator (IMS). The calculations predict local maximums in viscosity at flows corresponding to Mach numbers -2 and -10, but not elsewhere. The local peaks manifest themselves as jumps in flow speed, and as regions of high radial electric field ([E.sub.r]) shear. By inducting flows swept between Mach numbers [+ or -]5, an electron injection biasing probe revealed a jump at -2, but none at +2, in agreement with the numerical results. A series of flow profiles at constant bias confirmed this result. Altogether, these data agree well with the numerical calculations and provide support for Shaing's L-H transition model as applied to stellarators.

A viscosity test was carried out on peroxynitrite to determine the validity of the free radical theory that the rate of unimolecular decomposition is slower in high-viscosity solvents. The biological oxidant, which is a product of superoxide and nitric oxide, was not found to undergo single-bond homolysis to form free radical formation as the rate of rearrangements were not affected by changes in viscosity.

Seven sulfonated polystyrene standards (18 000-3 000 000 g/mol), taken as model substances for macromolecular polyelectrolytes, were dissolved in aqueous 0.1 M sodium nitrate solution and characterized by multiangle laser light scattering coupled on-line to flow field-flow fractionation. The distributions of molar mass and root mean square radius and the diffusion coefficients were obtained for each sample using a constant field of force for separation. Relationships between molar mass and root mean square radius [[[.sub.z].sup.0.5] = (2.71 x [10.sup.-2])[[M.sub.w].sup.0.56]] or diffusion coefficient [D = (7.10 x [10.sup.-8])[[M.sub.w].sup.-0.68]] were calculated. To investigate the static analytical range of this novel hyphenated technique a mixture of all seven samples was fractionated applying a programmed field. The relationship obtained between root mean square radius and molar mass was used to calculate a Mark-Houwink equation [[[Eta]]calcd = (2.99 x [10.sup.-2])[[M.sub.w].sup.0.68]]. To verify this result, the intrinsic viscosities for all samples were measured at low shear rate and found to be in good agreement [[[Eta]]calcd = (2.77 x [10.sup.-2])[[M.sub.w].sup.0.67]].

A study was conducted to verify if membrane enzymes are controlled by the viscosity of the surrounding lipids. Results showed that n values for bilayers in the liquid-crystalline phase would have to be significantly larger than those for gel phases if a basis for viscosity-dependent regulation of mebrane enzymes is desired. Results also showed that membrane enzymes are easily affected by the viscosity of the aqueous phase.

Predicting IM Part Toughness From Melt Viscosity Designers of structural plastics products frequently face a common but tough question - how to correctly utilize the resin supplier's data in their [...]

The effects of solvent viscosity on ([k.sub.cat]) and [k.sub.cat]/[K.sub.M] for the orotidine 5'-monophosphate decarboxylase (OMPDC) from Methanothermobacter thermautotrophicus (MtOMPDC) and Saccharomyces cerevisiae (ScOMPDC) are determined to understand the mechanism and the structural basis for the large rate acceleration and proficiency. The values of [k.sub.cat] and [k.sub.cat]/[K.sub.M] which are influenced by solvent viscosity indicated the similarities between rates of substrate binding, decarboxylation, and product dissociation and the ability of the 5-fluoro substituent to stabilize the anionic intermediate.

The concept of protein dynamic states is described, where the protein dynamics is being organized hierarchically with respect to solvent slaving. The results support a model for allostery in human adult hemoglobin (HbA) in which the ligand-binding-induced transition from the deoxy T state to the high -affinity R state proceeds through a progression of T state intermediates.

The spontaneous liquid crystal phase separation of single-walled carbon nanotubes (SWNTs) dispersed in biological hyaluronic acid solutions is being described. The analysis reveals that such a phase separation leads to an increase in the dispersion viscosity of the solution.

Gas-expanded liquids (GXLs) are a new and benign class of liquid solvents, which might offer many advantages for separations, reactions, and advanced materials. A study focuses on the synergism of experimental techniques with theoretical modeling resulting in a powerful combination for exploring chemical structure and transport in the cybotactic region of GXLs at the nanometer lengthscale.

The interconversion dynamics of the ligand in the primary docking site (PDS) of myoglobin (Mb) and hemoglobin (Hb) in viscous solvents are studied to elucidate the extent of the coupling between the functionally important protein internal dynamics and the solvent-coupled large-scale protein motion. The interconversion rates in the PDS of Hb in water solution are slower than those of Mb in trehalose, which shows that the interconversion barrier in Hb is intrinsically higher than that in Mb and is not modified by the solvent viscosity.

The study deals with a photoresponsive viscosity system, which is based on report on viscosity control using a ferrocenyl surfactant. The system is fundamentally different in utilizing a dynamic change in the aggregated state of the photoresponsive surfactants.

The observation that rapid-state folding can deviate from a Kramerslike dependence on solvent viscosity is presented. Although the speed of chain diffusion through solvent is often viewed as the physical 'speed limit' for folding, nanosecond dynamics that are independent of solvent friction contribute significantly to the folding time when folding becomes sufficiently rapid, which implies that internal friction may impose a rather stringent limit on folding rates.

The situations in which sets of (x,y) data obey linear relationships with a common intercept are analyzed. This revealed that intercepts in each fit are not identical.

A method for calculating microwave propagation through magnetoactive, low-pressure plasma under conditions of electron-cyclotron resonance (ECR) is presented. The influence of electron gas viscosity on the microwave propagation is investigated. The numerical calculations show the importance of the viscosity effects on microwave propagation through the high-concentrated, magnetoactive plasma, especially for strong ECR interaction. Index Terms--Electron-cyclotron resonance, electron viscosity, magnetoactive plasma, microwave propagation.

The melt viscosity of the dendritic polyether macromolecules based on 3,5-dihydroxybenzyl alcohol depends on the molecular weight regardless of other factors. A profile obtained for the changes in the melt viscosity with the molecular weight fails to indicate a critical molecular weight even for molecules with molecular weights about 85,000 amu. The complex viscosity and the steady-shear viscosity are identical. Ball-bearing-like molecules are generated due to branching and surface congestion of dendritic macromolecules preventing links between molecules.