No abstract

No abstract

Clinical investigations of laser photobioactivation, or biostimulation, might be differently designed and more fruitful if knowledge of basic biochemical mechanisms were better understood. In this investigation, biochemical events identified as responses to 904 nm irradiation included increased ascorbic acid uptake by fibroblasts. These cells also showed increased hydroxyproline formation, and this was increased several-fold by the addition of proline to the medium. Maximum biochemical responses were observed at a pulse frequency of 67 Hz and a pulse width of 150 nsec with an energy density of approximately 7 mJ/cm2 per exposure. Elements in the mitochondrial cytochrome system are proposed as the radiation absorbing chromophore(s). Hypothetically, the energy generated is linked to ascorbic acid uptake, which in turn stimulates collagen synthesis.

Two college students developed symptoms of poisoning following ingestion of a salt solution during a college physiology laboratory exercise. Symptoms included nausea, vomiting, diarrhea, and altered consciousness. The ingested solution was identified as isotonic buffered saline containing sodium azide in a concentration of 1.0 g/L. The solution was commercially prepared for instrumentation use only and was used inadvertently for the exercise instead of freshly preparing sodium chloride in water. One student drank three sips of the solution and survived. The other student drank 700 to 800 mL and over several days became progressively ill, suffering myocardial damage and cardiac dysrhythmias, and, finally, died. Toxicologic studies confirmed the presence of azide in an antemortem urine sample from the deceased. Sodium azide is an uncommon but potent poison which can cause serious illness and death.

A multidimensional dynamic surface tension detector (DSTD) for flowing liquid samples is reported. The DSTD is based on measuring the pressure with time of a repeating drop formed by the flow of liquid out the end of a pointed stainless steel capillary. This pressure-based DSTD provides information on dynamic surface tension at the air-liquid interface and adhesion at the solid-liquid interface on the side of the pointed capillary tip for each drop of surfactant solution, resulting in rapid characterization of complex samples. The signal obtained with the pressure-based DSTD is characterized, and a method is developed for extraction of the desired analytical information from the pressure signal. The DSTD was calibrated with 2-propanol over the range of 0-0.30 in relative surface tension lowering, Δγ/γ. The experimentally obtained Δγ/γ was in agreement with a theoretical model and published data for Δγ/γ over this range. A data analysis method was developed to adapt the DSTD to applications such as liquid chromatography and flow injection analysis, where the concentration of surfactant changes as a function of time. The DSTD signal yields a pressure-based Δγ/γ that is due to surface tension alone and a time-based Δγ/γ that is a combination of both surface tension and adhesion, providing essentially a contact angle measurement on a flowing sample. The data analysis method involves plotting the pressure-based and time-based surface tension measurements against each other at the same surfactant concentration for each pair of measurements, yet over a range of concentrations to establish a slope. This is referred to as a dynamic analysis plot and is applied in the characterization of various surfactants such as dodecyl sulfate ion-paired with tetrabutylammonium, industrial surfactant solutions FC-171 and FC-129, and biological surfactants tetradecyl maltoside, benzyldimethyldodecylammonium bromide, and 3-(N-decyl-N,N-dimethylammonio)-1-propanesulfonate. The slopes of the dynamic analysis plots for these surfactants were found to be unique, generally independent of concentration, and useful for understanding the type and degree of operating surface interactions. The FC-171 solution was found to exhibit considerable adhesion at the capillary tip, while dodecyl sulfate was found to have a small adhesion effect. Adhesion for dodecyl sulfate solutions was significantly enhanced by coating the stainless steel capillary tip with a hydrophobic polymer. Thus, there is potential for tuning the extent of the surface tension and adhesion effects for selective chemical analysis. The detection limit for dodecyl sulfate ion-paired with tetrabutylammonium is 0.9 ppm. Application of the DSTD for liquid chromatography is demonstrated, and the multidimensional data are shown to be useful in identifying and characterizing the poly(ethylene glycol)s separated from 2-propanol.