ABSTRACT
Mixtures of the two non-ionic surfactants hexaoxyethylene dodecyl ether (C(12)E(6)) and n-dodecyl-beta-D-maltoside (beta-C(12)G(2)) were studied with regard to surface properties, bulk properties, foam films, and foams. The reason for studying a mixture of an ethylene oxide (C(i)E(j)) and a sugar (C(n)G(m)) based surfactant is that despite being non-ionic, these two surfactants behave quite differently. Firstly, the physico-chemical properties of aqueous solutions of C(n)G(m) surfactants are less temperature-sensitive than those of C(i)E(j) solutions. Secondly, the surface charge density q(0) of foam films stabilized by C(n)G(m) surfactants is pH insensitive down to the so-called isoelectric point, while that of foam films stabilized by C(i)E(j) surfactants changes linearly with the pH. The third difference is related to interaction forces between solid surfaces. Under equilibrium conditions very high forces are needed to expel beta-C(12)G(2) from between thiolated gold surfaces, while for C(12)E(6) low loads are sufficient. Fourthly, the adsorption of C(12)E(6) and beta-C(12)G(2) on hydrophilic silica and titania, respectively, is inverted. While the surface excess of C(12)E(6) is large on silica and negligible on titania, beta-C(12)G(2) adsorbs very little on silica but has a large surface excess on titania. What is the reason for this different behaviour? Under similar conditions and for comparable head group sizes, it was found that the hydration of C(i)E(j) surfactants is one order of magnitude higher but on average much weaker than that of C(n)G(m) surfactants. Moreover, C(n)G(m) surfactants possess a rigid maltoside unit, while C(i)E(j) surfactants have a very flexible hydrophilic part. Indeed, most of the different properties mentioned above can be explained by the different hydration and the head group flexibilities. The intriguing question of how mixtures of C(i)E(j) and C(n)G(m) surfactants would behave arises organically. Thus various properties of C(12)E(6)+beta-C(12)G(2) mixtures in aqueous solution have been studied with a focus on the 1:1 mixture. The results are compared with those of the single surfactants and are discussed accordingly.
ABSTRACT
Bimonthly recordings of ultra-low-frequency acceleration ballistocardiograms overa 2 to 7 year period in 73 patients with ischemic heart disease and 50 matched control subjects within the framework of a clinical follow-up were subjected to measurement of IJ amplitude (reflecting force of contraction), IJ velocity (reflecting contractility), and IJ velocity variation coefficient. These repeated measurements were correlated with 24-hour vanillylmandelic acid (VMA) excretion in the urine, arthythemia incidence, heart rate, and clinical outcome in each subject. Moth-to-month variability of the IJ velocity was highly significantly correlated with 24-hour VMA excretionas well as with the likelihood of subsequent myocardial infartion or sudden death. Data on 24 of the patients with ischemic heart disease were available during a two-year period prior to their death from documented myocardial infarction or presumed fatal arrhythmia without a fresh infarction at autopsy. Their records were compared with those made during the same time period on individually matched control subjects and on patients with documented ischemic heart disease who survived the period of study. The mean force of cardiac contraction (IJ amplitude) was consistently lower in the group destined todie early than in the other two groups during the first 18 months. During the 6 monthsprior to death, however, their tracings show a relatively increased force of cardiac contraction and an increased product of force x pulse rate (referred to as the "drive index"), as well as an increase in the incidence of cardiac arrhythmias. None of these late increases was observed during comparable periods of time among surviving patients orcontrol subjuects.
