Hysteresis Areas Research Articles

Dynamics of hand preference in 4 year-old children

Hand preference in groups of 4 year-old children towards either end of the skill continuum (as determined by the Movement ABC test) was explored by means of a catching task in which the ‘direction of approach of the ball’ was used as a control parameter within a dynamical systems framework. In Condition 1, the ball direction was systematically scaled in degrees from the right side of the subject to the left and vice versa. In Condition 2, the spatial location of the ball direction was varied randomly, rather than systematically, over the same range as for Condition 1. In both conditions, the two groups of children were shown to switch between hands (from left to right and vice versa) at well-defined positions on the scale. The different scale values obtained when ball direction was scaled from left to right compared with right to left were used to define hysteresis areas. These areas were more extensive and located more to the left of the midline for the group towards the less skilled end of the continuum than for those towards the more skilled end. Additionally, the less-skilled children were shown to use the right hand more to catch the balls delivered to the left side than did the more skilled children. In Condition 3, objects were placed on the table of the ball-delivery apparatus in order to make the catching action more complicated. The less skilled group were shown to use the right hand more than the left hand in all catching positions whereas the more skilled group showed an equal usage of both catching regimes.

Compaction Properties of Powders: The Relationship Between Compression Cycle Hysteresis Areas and Maximally Applied Punch Pressures

The consolidation behaviors of various pharmaceutical solids were characterized by investigating the relationship between the calculated hysteresis areas and the maximally applied punch pressures. An Instron universal testing apparatus and an instrumented die were used to generate compression cycle profiles at various maximally applied punch pressures for the materials studied. Based on the profiles obtained, hysteresis areas were calculated for the materials studied as a function of maximally applied punch pressures. Furthermore, model profiles describing the plastic and brittle fracture processes were utilized to derive mathematical relationships between the calculated hysteresis cycle areas and the maximally applied punch pressures. The mathematical relationships derived indicate that a linear relationship between hysteresis areas and maximally applied punch pressures exists for plastic materials, whereas for brittle materials the hysteresis areas are related to the square of the maximally applied punch pressures. Experimental data obtained support the mathematical relationships derived. The goodness of fit to the models derived is used to rank order the consolidation mechanism of various drugs and pharmaceutical excipients.

Spreading of hydrophobic silica beads at water—air interfaces

Structured monoparticle layers, formed from 3 ± 1 μm diameter silica beads silylated to a greater (sample A) and a lesser (sample B) extent, have been investigated on water and on aqueous 1.0 M NaCl subphases in a Langmuir film balance. Hydrophobicities corresponding to the different extents of silylation were estimated by determining the wettabilities of identically treated 10 ± 1 μm silica beads. The advancing water contact angles of 98 ± 4° and 76 ± 4° have been calculated for samples A and B respectively. Visual observations of spreading and redispersity, and determinations of surface pressure—surface area isotherms, hysteresis and contact cross-sectional areas led to the assessment of the structural strengths of these two sets of silica beads. Appreciably stronger attractive interactions between neighboring silica beads have been found in structured monoparticle layers prepared from sample A than those formed from sample B. The less hydrophobic silica beads (sample B) were postulated to be separated from each other by a layer of water molecules in the structured monoparticle layer. This postulate has been supported by calculating the total interparticle interaction energies by applying the DLVO theory. Introduction of 1.0 M NaCl did not appreciably affect the behavior of structured monoparticle layers prepared from sample A. Significant creasing was observed, however, in the vicinity of the moving barrier upon the compression of structured monoparticle layers prepared from sample B.

Contact angles of surfactants with a potential to alter the body distribution of colloidal drug carriers on poly (methyl methacrylate) surfaces

Advancing and receding contact angles of various aqueous surfactant solutions were measured on poly (methyl methacrylate) surfaces and the hysteresis vs surfactant concentration areas were determined. Plots of adhesion tension, γ LV cos θ, vs surface tension γ lv were also used to determine the affinity of the surfactants to the polymer surface. The surfactants were classified into 4 groups according to the above characteristics. The classification was compared to body distribution data taken from the literature of surfactant-coated nanoparticles after i.v. injection.

Dipalmitoyl lecithin and lung surfactant adsorption at an air-liquid interface by respirable particles

The effects of kaolin and flyash on synthetic dipalmitoyl lecithin and lung surfactant from the lavage of excised rat lungs were studied using a Wilhelmy-type surface balance. After control studies with dipalmitoyl lecithin and rat lung surfactant, particles were sprinkled onto the surface at minimum surface area and the surface tensions vs surface areas were recorded. The results showed increased minimum surface tensions and decreased hysteresis areas when the particles were added. More particles were required to change the hysteresis area of lung surfactant than were required for synthetic dipalmitoyl lecithin. The effects of changes in surface areas of alumina and zinc oxide particles on dipalmitoyl lecithin were also studied. The amount of particles required to reduce surface tension-surface area hysteresis increased as the particles' surface area per gram decreased. This study indicates that respirable dusts may adsorb dipalmitoyl lecithin or lung surfactant in vivo and, therefore, may prevent surface tension from reaching the low values generally thought to occur in vivo.

Volume-pressure cycles from air and liquid-filled intact rabbit lungs

Air-filled and liquid-filled VP loops cycled over 100–300% FRC were measured using rabbit lung preparations. Four different stages of lung confinement were used ranging from intact lungs with the rib cage immobilized (Stage I) to isolated lungs (Stage IV). Stage I preparations showed larger air-filled and liquid-filled hysteresis areas of1338 ± 214units 2 (air) and 849 ± 73 units 2 (liquid), respectively, compared to797 ± 210units 2 (air) and 128 ± 33 units 2 (liquid) for exercised lungs. The average peak pressure for Stage I at 300% FRC was27.3 ± 3.5cm H 2O compared to21.8 ± 4.8cm H 2O for Stage IV. The tissue contribution of the total air-filled hysteresis area was 63.5% for the Stage I lung preparation and decreased to 23.7% for the Stage IV lung preparations. These observations suggest that the tissue contribution to VP hysteresis may be greater in the intact lung preparation than previously assume based upon excised lung studies and that geometric irreversibility may be a contributing factor.

Bonding Mechanisms and Hysteresis Areas in Compression Cycle Plots

It was shown previously that if compression of a powder is treated in an analogous manner to the compression of a nonporous solid, a plot of the transmitted pressure versus the applied pressure should have a hysteresis area that is linear with respect to the maximally applied pressure if plastic deformation occurs. However, if brittle fracture occurs, the area should be quadratically related to the maximally applied pressure. A series of compounds expected to yield by plastic deformation was tested, and they were found to give the quadratic relationship. Thus, it is indicated experimentally that the assumptions made in general in treating compression cycles may be partially invalid.

Surface isotherms of eicosanoic acid (C 20) and sodium eicosylsulfate (C 20) on substrates containing substituted alkanol amines

The force-area (Tr-~) and surface-potentialarea (~XV-~) characteristics of Arachidic acid (eicosanoic acid, C20) and sodium eicosylsulfate (C20) monolayers at the airwater interface have been investigated over 0.1 N solutions of various substituted alkanol amines. This study of the effect of a series of alkanol amines as cations, at constant ionic strength (0.I N), on the surface properties of an aliphatic carboxylate and an aliphatie sulfate (both C20) was undertaken in order to determine the role played by the stereochemistry, and substitution, within the series. An automated Langmuir trough was used to establish reproducible compression and expansion surface isotherms. Since at high pH monolayers become slightly solubilized into the aqueous substrate, the use of an automated Langmuir trough allows one to overcome this difficulty. Compression-expansion surface isotherms allows one to compare the hysteresis areas (work lost following compression-expansion of the monolayers) of the various long-chain salts. The comparison of compression and expansion isotherms appears to be related to foamability and foam stability. The correlation between monolayer surface properties and foaming characteristics (5) will be presented in a subsequent paper. Theories associated with surface potential, based on elementary models, are generally barely applicable. Nevertheless, it was found that our results could be interpreted by using unsophisticated : assumptions. The reason for this development is probably attributable to our choice of substituted alkanol amines.