Heat transport by laminar boundary layer flow with polymers

Motivated by recent experimental observations, we consider a steady-state Prandtl-Blasius boundary layer flow with polymers above a slightly heated horizontal plate and study how the heat transport might be affected by the polymers. We discuss how a set of equations can be derived for the problem and how these equations can be solved numerically by an iterative scheme. By carrying out such a scheme, we find that the effect of the polymers is equivalent to producing a space-dependent effective viscosity that first increases from the zero-shear value at the plate then decreases rapidly back to the zero-shear value far from the plate. We further show that such an effective viscosity leads to an enhancement in the drag, which in turn leads to a reduction in heat transport.Comment: 7 pages, 8 figures, 1 tabl

Growth of the White-Mouse Gastrocnemius Muscle I. In Terrestrial Gravity

The gastrocnemius muscle from white mice (Swiss Webster, female; NLW, male and female; varying in age from 6 to 13 weeks and in body mass from 8 to 36 gm) were analyzed by means of Huxley\u27s Equation for Heterauxic Growth where double logarithmic plots were performed of muscle size as a function of body mass. These mice had been grown in normal gravity. Relative wet mass, relative dry mass, and percent dry mass did not display significant changes with body mass. Percent noncollagen nitrogen [NCN] in the dry muscle, however, did show an effect which was not significantly different from that anticipated from Galileo\u27s Principle of Similitude: [NCN] ∝ (Body Mass)1/3

Growth of the White-Mouse Gastrocnemius Muscle II. In Non-Terrestrial Gravity

Exposure of white mice (Swiss Webster, female; NLW, male and female) to 1.5 to 7.0 G\u27s of chronic centrifugation from the age of 5 weeks for durations of 1 to 8 weeks is known to cause some reduction in body growth. However, the retardation of muscular development was not as drastic. When corrections were made for differences between experimental and control body mass by means of Huxley\u27s Equation for Heterauxic Growth, the muscles of experimental mice were seen to be larger than those of control animals of the same size. The measurements of muscle size, in order of increasing high-G response were: wet mass, dry mass, and noncollagen nitrogen (NCN) content. These data were examined in terms of the Huxley Heterauxic Equation, as modified from a consideration of Galileo\u27s Principle of Similitude: muscle size ∝(inertial field) (body mass)4/3. Although all experimental muscle measurements (relative to constant body size) increased with centrifugation, any single detected compensation was much less than the total compensation predicted by this equation. The best empirical relationship found for high-G data was a linear one between the logarithm of effect upon muscles size and logarithm of effect upon body size

Continuum description of finite-size particles advected by external flows. The effect of collisions

The equation of the density field of an assembly of macroscopic particles advected by a hydrodynamic flow is derived from the microscopic description of the system. This equation allows to recognize the role and the relative importance of the different microscopic processes implicit in the model: the driving of the external flow, the inertia of the particles, and the collisions among them. The validity of the density description is confirmed by comparisons of numerical studies of the continuum equation with Direct Simulation Monte Carlo (DSMC) simulations of hard disks advected by a chaotic flow. We show that the collisions have two competing roles: a dispersing-like effect and a clustering effect (even for elastic collisions). An unexpected feature is also observed in the system: the presence of collisions can reverse the effect of inertia, so that grains with lower inertia are more clusterized.Comment: Final (strongly modified) version accepted in PRE; 6 pages, 3 figure

The preparation of a Non-Desiccated Sodium Caseinate Sol and its use in ice cream

1. The body and texture of ice cream are improved by the replacement of dry skimmilk by sodium caseinate sols. This improvement was shown up to 2.5 to 5.0 percent replacement, depending on the composition of the mix. 2. The flavor of ice cream was progressively improved by the replacement of dry skimmilk by sodium caseinate sols up to 3 to 4 percent replacement, depending on the composition of the mix. 3. This flavor improvement was due to the careful pH control used in the preparation of the sodium caseinate sols. 4. The type of melting of the ice cream was altered by the replacement of dry skimmilk by sodium caseinate sols. 5. The use of sodium caseinate sols increased the initial and maximum overrun and decreased the whipping time of the ice creams produced. 6. The curves for whipping time show that from 1.5 to 3.0 percent replacement of dry skimmilk by the sodium caseinate sols is necessary to effect sufficient improvement in whip to warrant their use. A 3 percent replacement would be necessary with a mix containing 14 percent fat and 10 percent serum solids. 7. The use of sodium caseinate preparations as additional solids, i.e., in addition to the amounts of serum solids (8 to 10 percent) commonly used by the trade, has been suggested. The amounts of milk protein that would be required to yield sufficient improvement in whip and in body and texture score would, in the light of the figures presented, be large enough to make their use questionable

Rouse Chains with Excluded Volume Interactions: Linear Viscoelasticity

Linear viscoelastic properties for a dilute polymer solution are predicted by modeling the solution as a suspension of non-interacting bead-spring chains. The present model, unlike the Rouse model, can describe the solution's rheological behavior even when the solvent quality is good, since excluded volume effects are explicitly taken into account through a narrow Gaussian repulsive potential between pairs of beads in a bead-spring chain. The use of the narrow Gaussian potential, which tends to the more commonly used delta-function repulsive potential in the limit of a width parameter "d" going to zero, enables the performance of Brownian dynamics simulations. The simulations results, which describe the exact behavior of the model, indicate that for chains of arbitrary but finite length, a delta-function potential leads to equilibrium and zero shear rate properties which are identical to the predictions of the Rouse model. On the other hand, a non-zero value of "d" gives rise to a prediction of swelling at equilibrium, and an increase in zero shear rate properties relative to their Rouse model values. The use of a delta-function potential appears to be justified in the limit of infinite chain length. The exact simulation results are compared with those obtained with an approximate solution which is based on the assumption that the non-equilibrium configurational distribution function is Gaussian. The Gaussian approximation is shown to be exact to first order in the strength of excluded volume interaction, and is found to be accurate above a threshold value of "d", for given values of chain length and strength of excluded volume interaction.Comment: Revised version. Long chain limit analysis has been deleted. An improved and corrected examination of the long chain limit will appear as a separate posting. 32 pages, 9 postscript figures, LaTe

Risk Assessment Matrices for Workplace Hazards: Design for Usability

In occupational safety and health (OSH), the process of assessing risks of identified hazards considers both the (i) foreseeable events and exposures that can cause harm and (ii) the likelihood or probability of occurrence. To account for both, a table format known as a risk assessment matrix uses rows and columns for ordered categories of the foreseeable severity of harm and likelihood/ probability of that occurrence. The cells within the table indicate level of risk. Each category has a text description separate from the matrix as well as a word or phrase heading each row and column. Ideally, these header terms will help the risk assessment team distinguish among the categories. A previous project provided recommended sets of header terms for common matrices based on findings from a survey of undergraduate OSH students. This paper provides background on risk assessment matrices, discusses usability issues, and presents findings from a survey of people with OSH-related experience. The aim of the survey was to confirm or improve the prior recommended sets of terms. The prior recommendations for severity, likelihood, and extent of exposure were confirmed with minor modifications. Improvements in the probability terms were recommended