Visible Breakdown Research Articles

Subhuman Remainders: The Unbuilt Subject in Francis Bacon’s “Study of a Baboon”, Jan Švankmajer’s <em>Darkness, Light, Darkness</em>, and Patricia Piccinini’s “The Young Family”

Subhuman Remainders: The Unbuilt Subject in Francis Bacon’s “Study of a Baboon”, Jan Švankmajer’s <em>Darkness, Light, Darkness</em>, and Patricia Piccinini’s “The Young Family”

A study of enteric-coated liquid-filled hard gelatin capsules with biphasic release characteristics

Studies were carried out using enteric-coated, liquid-filled hard gelatin capsules with biphasic rapid and sustained release characteristics, containing 80 mg of propranolol in a novel HALO ™ drug delivery formulation designed to avoid hepatic first-pass metabolism. The disintegration at pH 1.0 of HALO ™-propranolol capsules, coated with different levels (3–12 mg/cm 2) of enteric polymer (methacrylic acid copolymer, type A USP/NF) was visually assessed using the disintegration test for enteric-coated capsules described in the BP 1988. Quantification of propranolol release, at pH 1.0, from enteric-coated capsules was carried out using a dissolution procedure based on the USP XXII method. The results of the study showed that significant release of propranolol (> 10%) could take place at low coating levels (3 mg/cm 2) without visible breakdown of the enteric coat. In a further study, enteric-coated HALO ™-propranolol capsules coated with 4 mg/cm 2 of enteric polymer were stored under a variety of conditions for up to 18 months. Dissolution and disintegration studies showed that under conditions of low temperature storage (4°C) HALO ™-propranolol capsules released significant amounts ( > 10%) of propranolol at pH 1.0 without visible breakdown of the enteric coat. Dissolution studies carried out at pH 6.8 following acid challenge demonstrated that inadequate enteric protection greatly affected the subsequent sustained-release dissolution profile of HALO ™-propranolol capsules. The present investigation demonstrates the importance of ensuring a sufficient enteric-coating level for oral dosage vehicles to maintain post gastric dissolution characteristics and illustrates the need for a reliable means of assessing enteric coat performance in vitro.

Some characteristics of Co2-laser-induced multiple spark breakdown at pressures up to 11 atm

A study has been made of the visible breakdown plasma produced by focusing single TEA CO2 laser pulses 200 nsec wide with salt lenses of 16- and 22-cm focal lengths in argon, helium, neon-helium, and nitrogen at pressures up to 11 atm. Pulse energies ranged from 0.9 to 11 J, with a maximum intensity at the 1-mm focal diameter of 6.6×109 W/cm2. At this incident intensity, well above the breakdown threshold, the main breakdown plasma in argon occurred well upstream of the focus and its multiple structure extended over 5–9 cm. In the focal region only a few isolated sparks were seen. At incident powers closer to threshold, the breakdown occurred closer to, or at, the focus, and migrated upstream toward the laser as the pressure was increased. The spatial structure of the breakdown plasma as seen by time-integrated photography, and the temporal development, monitored by photon drag observations of the transmitted power pulse, were studied with various gases, pressures, and incident pulse energies. A description of the breakdown process is offered which accounts for many of its features, especially the absence of breakdown in the focal region.

Electrical Breakdown Caused by Dust Motion in Low-Pressure Atmospheres: Considerations for Mars

Electrification of agitated dust can cause visible breakdown in a carbon dioxide atmosphere at low pressure in a laboratory experiment. Dust storms on earth become electrified, with accompanying breakdown phenomena. Martian dust storms may reduce the atmospheric conductivity by capturing fast ions on particles, and, by electrifying, may cause discharges in the relatively low pressure atmosphere.

Mechanism for Laser Surface Damage of Glasses

A visible breakdown is produced on glass surfaces by high-intensity laser light. The mechanism believed to be responsible for this breakdown is discussed. The successive steps of the mechanism are: optical absorption, fluorescence, chemical reaction by quenching the fluorescence, and breakdown. The theory of this mechanism is in good agreement with our experimental data obtained with different glasses at wavelengths of 10 600, 6943, and 5300 Å.

Collagenolytic activity in regenerating forelimbs of the adult newt ( Triturus viridescens)

Summary A collagenolytic enzyme capable of degrading reconstituted collagen fibrils at neutral pH and physiological temperature, not demonstrable in the intact forelimb of the adult newt ( Triturus viridescens ) appears in cultures of healing and regenerating tissues of the amputation stump. Tissues proximal to the regenerating region are inactive. The amount of enzyme produced, measured by visible breakdown of thermally reconstituted mammalian collagen gels, and confirmed by release of radioactivty from 14 C-glycine-labeled collagen gels, rises to a peak at 15 days and remains at a high level during the phases of dedifferentiation of the stump and blastema formation, but gradually falls after 20 days as early digital differentiation occurs. Living cells are required for collagenase production since freezing and thawing inactivates the explants.

Laser-Induced Prebreakdown and Breakdown Phenomena Observed in Cloud Chamber

Direct observation of initiating electrons below the threshold for visible breakdown discharge is reported. With the cloud-chamber techniques used, minimum detectable ionization is estimated at 5000 ion pairs/${\mathrm{cm}}^{3}$. Production of initial electrons is ascribed to photoionization, in a manner which is consistent with Phelp's model. Above the visible breakdown threshold, thermal-gradient effects overcome all other sources of droplet formation in the cloud chamber.

SOME EFFECTS OF RAINFALL, RADIANT DRYING, AND SOIL FACTORS ON INFILTRATION UNDER RAINFALL INTO SOILS

SummaryThe effect of the structural condition of a soil on infiltration under laboratory simulated rainfall was investigated. Infiltration was greater with better structural condition for both undisturbed and disturbed samples. The infiltration rate of a soil surface damaged by intense rainfall decreases as rainfall continues. After equal periods of exposure there was little difference, for any of three soils examined, between total infiltration of rainfall at a rate of 6 in. per hour and at 4 in. per hour. The application of a pressure less than atmospheric to the underside of 2‐in.‐deep samples, simulating the moisture tension observed in the transmission zone on infiltration into deep soil columns, did not increase infiltration under rainfall as would be expected. For a clay soil previously exposed to rainfall, infiltration rate after radiant drying for 24 hr. and rewetting was only half that of replicates which were dried in shade.The nature of the cation with which a soil may be saturated markedly affects the permeability of the soil to water; and this effect persisted when water was applied with the added mechanical action of falling drops. Artificial crumbs of pure clays and a clay mixture were brought to moisture equilibrium with saturated water vapour, and their stability under rainfall examined. Calcium‐saturated kaolin crumbs were rapidly broken down and dispersed under rainfall, in marked contrast to their stability on immersion in water without the mechanical effect of falling drops. Calcium‐saturated illite and montmorillonite experienced no visible breakdown of the crumbs and no dispersion for the same rainfall exposure.