Low-viscosity Solutions Research Articles

Capillary viscometer for evaluating low-viscosity solutions at elevated temperatures

A capillary viscometer designed for evaluating low-viscosity (0.2–10 cp) solutions at elevated temperatures [20–150 °C (68–302 °F)] has been built and extensively tested. This viscometer is automated, so that minimum operator effort is needed to obtain the viscosity as a function of temperature for a given solution. This viscometer is normally operated at a constant back pressure of 90 psi to avoid bubble formation. While the viscosities are routinely measured at a shear rate of about 38 s−1, viscosity measurement at other shear rates (10–250 s−1) can also be achieved by changing the set point on the flow controller.

Relationship of Chemical Structure to Corneal Penetration and Influence of Low-Viscosity Solution on Ocular Bioavailability

Current understanding of the mechanism of corneal penetration by organic molecules proposes the epithelial layer as the rate-limiting membrane for water-soluble compounds and the stromal layer as rate limiting for lipid-soluble compounds. This suggests that the relationship between corneal permeability and the logarithm of oil/water partition coefficients, for a series of drugs, should not be the typical, single, continuous, parabolic-shaped curve. Corneal penetration studies have been conducted in unanesthetized albino rabbits using various organic compounds, representing five orders of magnitude in partition coefficient, at a constant concentration of 4 × 10−5 M dispensed in either a 1- or 90-centipoise (cps) solution. It has been shown that for non-ionizable compounds, a pair of bell-shaped curves were generated, one for lipid-soluble and one for water-soluble compounds. Small water-soluble species demonstrate very high apparent permeabilities, which may relate to the presence of aqueous pores or other paracellular drug movement. Penetration of ionizable compounds does not appear to correlate well with the structural relationships invoked for un-ionized compounds. Consistent with the proposed mechanisms of corneal penetration, oil-soluble drug substances show no improvement in drug bioavailability when dosed from a 90-cps solution, and water-soluble drugs show a modest improvement in ocular drug bioavailability. Small water-soluble substances demonstrate no improvement due to their already high bioavailability. The importance of nonproductive absorption and precorneal drainage on bioavailability is addressed.

Telomer Acids: Monocarboxylic acids with long‐chain branching; Their derivatives, properties and potential uses in lubricants

AbstractTelomer acids are synthesized by addition of acetic anhydride to α‐olefins using managenese (III) acetate as a free radical initiator. The telomerization mechanism comprises initiation, propagation and termination steps. The reaction product consists of a mixture of acids having [xn+2] carbon atoms (n: number of carbon atoms of α‐olefin: x:1, 2, 3, 4, …). The “first telomer” (x=1) is a linear fatty acid. Under appropriate conditions, mainly telomer acid (x:2, 3, 4, …) are obtained, being α‐ and γ‐branched monocarboxylic acids, characterized by long‐chain branches. Telomer acids derived from α‐olefins up to n=14 are liquids at room temperature, despite the high molecular weight. Esters of telomer acids show interesting properties in lubricant applications: low pour point, high viscosity index, low viscosity as a function of molecular weight, good thermo‐oxidative stability and a remarkably low elastomer swell. In amino amide derivatives, the telomer acid structure gives low viscosity properties, as is, for instance, found in significant viscosity reductions by using telomer acid as coreactant in polyisobutenyl succinic anhydride—tetraethylene pentamine condensation products. Dispersancy properties of these products are retained. Telomer acid metal salts exhibit quite different solubility characteristics and rheological properties than do fatty acid salts. Calcium salts of telomer acids are readily soluble in mineral oil: the rheology of these low viscosity solutions exhibits Newtonian behavior. Solvent‐free magnesium salts which are liquid can be obtained. Neutral and overbased calcium salts show pour point depressing activity in paraffinic oils. For overbased calcium salts, decrease of coefficient of friction with increasing temperature has been observed.

HYDRODYNAMICS AND MASS TRANSFER IN BUBBLE COLUMNS: EFFECT OF SOLIDS

Abstract The hydrodynamics and mass transfer in a large diameter bubble column (Dc 0.305 m), specifically, the effects of gas velocity and the presence of solids on the gas holdup structure, gas-liquid interfacial area, and volumetric mass transfer coefficients in viscous as well as low viscosity solutions are studied. The sulfite oxidation technique was employed to measure the gas-liquid interfacial area. Volumetric mass transfer coefficients were measured using a chemical method (sulfite oxidation) as well as physical absorption of oxygen from air, and the overall gas holdups were measured using the hydrostatic head technique. The effect of solids on the gas holdup structure was examined using the dynamic gas disengagement method. With the addition of polystyrene particles, the gas-liquid interfacial area decreased for low viscosity systems, whereas it increased for viscous systems. This was shown to be due to the effect of solids on bubble coalescence. The wettability characteristics of solid surfaces ...

Hearing loss induced by viscous fluids in the middle ear.

Dextran solutions of low viscosity (7.5 centipoise) and high viscosity (2.2 poise) were instilled in turn into the middle ears of guinea pigs, using an open bulla preparation. The degree of conductive hearing loss induced was assessed by measurement of the cochlear microphonic. Both solutions produced a comparable degree of hearing loss which was frequency dependent, ranging from 30 dB at 500 Hz to almost zero at 4000 Hz. The results indicate that the degree of conductive hearing loss produced by a serous effusion in otitis media is due solely to an effect on compliance in the middle ear and is independent of the viscosity of the effusion.

Photoluminescence quantum yield and excitation energy migration in low viscosity solutions

An expression for the relative quantum yield is derived for the general case of energy transfer accompanied by diffusion. The migration of excitation energy among donors has been taken into account. Detailed discussion of the case of moderate diffusion is given.

Synthesis of Polyamides by Direct Polycondensation with Picryl Chloride. II. Reaction Conditions and Mechanism

A polycondensation reaction of p-aminobenzoic acid occurred at room temperature in the presence of picryl chloride to give polyamide in a quantitative yield. Reaction conditions, solvents, temperatures, concentrations of the monomer, and amount of picryl chloride were investigated. A combination of picryl chloride and pyridine was found to be satisfactory for the polycondensation. A model reaction suggests that the polycondensation reaction proceeds through the formation of an active ester from picryl chloride and carboxylic acid, followed by aminolysis with amino group. The polyamide with the solution viscosity of 1.0 was obtained in quantitative yield under optimum conditions. Polyamides from aromatic dicarboxylic acids and aromatic diamine had lower solution viscosities than that from p-aminobenzoic acid. The reaction mechanism is discussed.

Synthesis of Polyesters by Direct Polycondensation with Picryl Chloride

The polycondensation reaction of various dicarboxylic acids and diols such as terephthalic acid and ethylene glycol occurred at room temperature in pyridine in the presence of picryl chloride to give polyesters in high yield. Reaction conditions, basic solvents, temperatures, concentrations of monomer, and amount of picryl chloride were investigated. A combination of picryl chloride and pyridine was found to be satisfactory for the polyester synthesis. The polycondensation reaction possibly proceeds through the formation of an active ester from picrylic acid and carboxylic acid, followed by esterification with hydroxyl group. Yields of polyester from 2,5-pyridinedicarboxylic acid and 1,10-decanediol by this direct polycondensation reached up to 89%, and the solution viscosity of the polyester was approximately 1.0 under optimum reaction conditions. The polyester obtained from terephthalic acid and 1,5-pentanediol had a higher solution viscosity than those from various combinations of dicarboxylic acids and diols. Aliphatic dicarboxylic acid such as adipic acid yielded polyester having a lower solution viscosity than aromatic dicarboxylic acid.

The Evolution of an Observed Cold Front. Part I. Numerical Simulation

The 48 h evolution of an observed cold front is simulated by a three-dimensional mesoscale-numerical model for a typical springtime synoptic situation over the southeastern United States. The model used in this study employs anelastic equations of motion on a limited-area domain with locally determined inflow/outflow side boundaries. Both the observed and simulated characteristics of the weather system indicate a mature front which intensifies and then weakens over the 48 h period. Moist convection occurs in the form of intermittent squall lines in the observed case; in the numerical simulation, convection develops above and somewhat ahead of the surface front after 24 h as in ensemble of convective cells. An investigation is made of the mesoscale and subsynoptic-scale features of this solution to determine their sensitivity to the inclusion of moisture and to the magnitude of the eddy viscosity used in the numerical simulation. The primary effect of increased eddy viscosity is to reduce somewhat the propagation speed of the front. The major changes due to moisture inclusion occur when convection develops along the cold front; these convective effects, which are apparent in the subsynoptic as well as the mesoscale features of the solution, include increased low-level convergence, reduced surface pressure due to diabatic heating, and the deflection of winds due to upper-level divergence. In addition, small temperature changes occur in the middle troposphere between the jet stream and the surface front when either viscosity or moisture is varied; these disturbances are a clear manifestation of the effect which changes in the cross-stream circulation intensity have upon the frontal system. A fundamental feature of the mesoscale structure of the front in all cases is the tendency of the line of maximum horizontal convergence at the surface to move ahead of the line of maximum vertical vorticity. This phase shift appears to be related to, the propagation characteristics of the frontal system. Also, the mesoscale moist convection develops a cellular structure throughout the convective zone in the low-viscosity solution; the use of higher viscosity tends to suppress these cells, particularly near the surface.

Isolation of Bloodstream Trypomastigotes of Trypanosoma cruzi by a Gradient of Metrizamide

Several methods have been used to isolate bloodstream forms (trypomastigotes) of trypanosomes from other blood components. Four of them have been widely applied: (1) defibrination of the blood by incubation in a medium containing calcium chloride and shaking with glass beads followed by passage of the parasites through a sintered glass funnel (Fulton and Spooner, 1957, Ann. Trop. Med. Parasitol. 51: 417-421); (2) defribination followed by low speed centrifugation in Krebs-buffered-glucose-saline layered on density gradients of sucrose (Williams and Cover, 1966, Trans. R. Soc. Trop. Med. Hyg. 60: 426-427; Jaffe et al., 1969, Exp. Parasitol. 25: 311-318); (3) separation using a gradient of N-methyl-3-5-diacetamide-2-4-6-triiodobenzoate and Ficoll (Budzko and Kierszenbaum, 1974, J. Parasitol. 60: 1037-1038); (4) separation using a DEAE-cellulose column (Lanham, 1968, Nature 218: 1273-1274; Lanham and Godfrey, 1970, Exp. Parasitol. 28: 521-534; Gutteridge et al., 1978, Parasitology 76: 159-176; Villalta and Leon, 1979, J. Parasitol. 65: 188-189). Electron microscopic observations made on Trypanosoma cruzi isolated by the first three methods indicate variable contamination with platelets (unpubl. observ.). The fourth method, which is being used routinely for isolation of Trypanosoma brucei, presents two problems. First, erythrocytes and bloodstream forms of T. cruzi have a similar surface charge (de Souza et al., 1977, J. Protozool. 24: 411-415). This problem was solved by a preliminary separation of the trypanosomes from the erythrocytes, using low speed centrifugation leaving the DEAE-cellulose column for separation of the trypanosomes from other blood components (Gutteridge et al., 1978, loc. cit.; Villalta and Leon, 1979, loc. cit.). Second, several lines of evidence indicate that passage of trypomastigotes of T. cruzi through DEAE-cellulose column may alter some properties of the parasite such as the transport of amino acids (Goldberg et al., 1976, J. Protozool. 23: 79-186), the surface charge (de Souza et al., 1977, loc. cit.), and infectivity to mice (Villalta and Leon, 1979, loc. cit.). In view of the problems pointed out above we decided to develop a method for separation of bloodstream trypomastigotes of T. cruzi by using a gradient of Metrizamide [2-(3acetoamido-5-N-methylacetamido-2-4-6-triiodobenzamido)-2-deoxy-D-glucose]. This substance has a molecular weight of 789, a density of 2.17 g/cm3, gives solutions of low viscosity and osmolality, dissolves readily in water or dilute solutions of salts, has no ionizable groups, and can be stored indefinitely at -20 C (Rickwood and Bimie, 1975, FEBS Lett. 50: 102-110). It has been applied to isolate several types of cells and subcellular particles. Blood (about 30 ml) obtained by bleeding mice through the retroorbital sinus (1-4.107 trypomastigotes/ml) was collected with medium 199 plus 3.8% sodium citrate as anticoagulant and centrifuged at 500 g for 5 min to pellet most of the erythrocytes, and left at 37 C for 30 min so that some pelleted trypomastigotes could move to the supernatant. The supernatant was centrifuged at 2,800 g for 30 min after which the pellet was resuspended in 3 ml of medium 199 plus 10% fetal bovine serum and left at 37 C for 5 min for aggregation of the platelets. In some experiments, adenosine diphosphate (final concentration of 1 mg/ml) was added slowly with occasional shaking in order to improve agglutination of the platelets. However, this step can be omitted. Pressing the platelet aggregate gently with a Pasteur pipette improved the liberation of some trypanosomes. The suspension containing the parasites plus aggregated platelets and other blood cells was layered on the top

Interconnected fibre masses precipitated from solutions of polymers

IN studies to increase the mechanical strength of polymeric encapsulants for high voltage electronic devices we have formed fibre masses of unusual structure from isotactic polypropylene. The method for producing these three-dimensionally interconnected fibrous structures is described here and involves agitation of a solution of the polymer at sonic frequencies with simultaneous cooling. This process has since been observed for polyethylene and polybutene-1. Furthermore, the process has been extended to other polymers, both crystalline and non-crystalline, through a process we call ‘seeding’. Uniform reinforcement of encapsulating resins through the addition of high strength, short fibres, is not practical because of the complex shapes and numerous small interstices of the devices to be encapsulated. We therefore set out in 1973 to form fibres in situ by precipitation from low viscosity solutions which would readily impregnate a device of complex geometry. As a secondary objective, we hoped to polymerise the solvent to form a matrix around the fibres thereby producing a self-reinforced composite.

Conformation and Hydrolytic Stability of Polysaccharide fromXanthomonas campestris

Abstract Xanthomonas campestris polysaccharide in the solid state is stable to 225°C in air and 250°C in inert atmosphere. In solution, even at moderate temperatures, the polymer undergoes hydrolytic degradation via the glycosidic linkages, and occurrence of main-chain scission results in lower solution viscosity. In solution, the polymer can exist in ordered and disordered conformations. In distilled water at temperatures ≤ 50°C, the polymer exists in the disordered conformation. In the presence of salt, acid, or base the polymer exists in the ordered conformation. In the ordered conformation the polymer exhibits a far greater hydrolytic stability. The higher stability of the ordered conformation is especially demonstrated when the polymer is aged in acid or base solutions. Contrary to the expected lower stability of the glycosidic linkages in acid or base than in water, Xanthomonas campestris polysaccharide shows higher stability in these media.

Magnetic interactions between nitroxide free radicals and lanthanides or Cu2+ in liquids

Heisenberg exchange has been found in all previous work to be the dominant intermolecular magnetic interaction between paramagnetic species in solutions of low viscosity, and this conclusion is confirmed here in analysis of interactions between Cu2+ and a nitroxide free radical. Exchange between a fast relaxing metal ion and a slow relaxing radical contributes equally to the transverse and longitudinal relaxation probabilities, T−12 and T−11, of the radical. A new result that could be of significance in investigations of molecular dynamics in liquids is that dipole–dipole interactions between ions of the lanthanide series and free radicals are dominant in all conditions over Heisenberg exchange. In the liquid phase, Gd3+ is particularly effective in inducing free radical longitudinal relaxation.

Strahlungslose Energieübertragung von angeregten N-Heteroareniumkationen zu Rhodamin B. / Non-Radiative Energy Transfer from Excited N-Heteroarenium Cations to Rhodamin B.

The systems acridizinium- and N-methylacridinium ion, respectively, as energy donors and rhodamin B (tetrafluoroborate) as energy acceptor show in solutions of low viscosity (solvent : methanol) energy transfer by resonance, in which a multi-step mechanism is participating. The experimental results of the detected singlet-singlet transfer are in good agreement with the predictable values of Förster's theory, if the spectroscopic parameters of the donor and the acceptor are corrected by assumption of their dependence upon concentration.

Preparation and properties of low-viscosity cuprammonium spinning solutions

Preparation and properties of low-viscosity cuprammonium spinning solutions

Metrizamide interferes with the determination of protein by the lowry method

Metrizamide, a tri-iodinated benzamido-derivative of glucose, is a density-gradient material which gives dense aqueous solutions of low viscosity and osmolality (1). These advantages, coupled with its nonionic nature, chemical inertness, and low degree of hydration in solution, promise that it will be increasingly used for the separation of biological macromolecules, subcellular components, viruses, and cells by equilibrium density gradient centrifugation (2–4). In the course of our attempts to use Metrizamide to facilitate the fractionation of membranous organelles of pituitary homogenates by equilibrium density centrifugation (5), we have found that Metrizamide, even at concentrations as low as 1%, significantly interferes with protein determination by the Lowry method. We report here that the interference of Metrizamide can be circumvented by the use of appropriate blanks and calibration curves.

Synthesis of Radial Thermoplastic Elastomers

Abstract The combination of anionic polymerization techniques and a subsequent coupling reaction created a versatile process for producing block polymers of not only controlled block length and block sequence but also with a controlled number of branches. This process has been successfully used in commercial production since 1967. Radial styrene-diene block polymers have properties significantly different from linear polymers of the same molecular weight, showing lower melt viscosities as well as lower solution viscosities. This feature is significant in adhesive applications because it allows the use of polymers of higher molecular weights with a corresponding improvement in shear resistance.

Identification of functional tumor vessels by resorcin-crystal violet stain infusion.

A resorcin-crystal violet solution of low viscosity injected into the circulatory plexus supplying a tumor is used to identify and characterize functional tumor vessels. Unstained sections of tumor tissue demonstrate heavily stained vascular endothelium with no leakage of stain to extravascular tissue for intact vessels, and little or no background staining. The method is simple to apply for tumor vessel morphology and morphometry.

New Directions for Starch and Glucose Research

AbstractEnzymes have become a prime commercial tool for modification of starch and glucose. Today we see enzymes used to convert starch to glucose and again to convert glucose to a mixture of glucose and fructose, invert sugar in the terminology of cane and beet sugar manufacturers. We will expect to see greater use of enzymes to modify starch granules to produce a new way of dextrinization of starch. Enzymes may also be used to modify starch molecules to increase the degree of branching producing new properties among which can be those giving solutions of low viscosity, but high solids contents. Starch or glucose derivatives can also be sources of sugar for derivatizing protein to produce glycoproteins a potential new class of water soluble gums or food additives. Low caloric sweetners are possibly by more extensive modification of glucose similar to thio‐glucose or sugar sweetner attached to nondigestible polysaccharides such as cellulose. Isomerization of glucose to fructose can provide crystalline fructose which may find wider use in special diet foods. Appropriate derivatization of starch could produce polymers compatible with pure synthetic plastics in which they could act to modify and improve plastic properties.

Solution and bulk flow properties of linear and branched styrene–butadiene rubbers

AbstractThe solution and bulk flow properties of various styrene‐butadiene rubbers have been investigated. Bulk flow properties were measured with the Instron capillary rheometer, while the Weissenberg rheogoniometer was used to measure to steady‐state and oscillatory flow properties of 15% wt solutions in decalin.A comparison of the rheological information obtained from the solution and bulk behavior with GPC and intrinsic viscosity data makes it possible to distinguish between different forms of branching and between the effects of molecular weight distribution and branching.Branching decreases the hydrodynamic volume of a polymer coil relative to its molecular weight, so that branched polymers have lower solution viscosities at the same molecular weight than linear polymers. This effect is more pronounced for short‐chain and dendritic forms of branching than for star‐shaped long‐chain branching. At higher concentrations and especially for bulk polymers, however, star‐shaped long‐chain branching will give rise to much higher viscosities, which is hardly, if at all, found for short‐chain or dendritic forms of branching.Star‐shaped branching greatly affects the shear sensitivity of the bulk viscosity, whereas it has relatively little effect on polymer fluid elasticity either in bulk or in solution, this elasticity being mostly determined by the width of the molecular weight distribution Mz/Mw.