Wettability experiments

To obtain information about the surface structure of the PZLL-PB-PZLL films, solvent-cast samples were investigated by means of XPS, replica electron microscopy and wettability experiments [31]. For the triblock copolymers with the smallest PB content (12mol%), these experiments also confirmed a microphase-separated structure at the surface of the films. The PB content at the surface, however, was found to be about twice as large as the bulk PB content. To account for the enhanced PB content at the film surface, the PB domains were proposed to rise above the PZLL matrix in the form of convex lenses (Fig. 3). The presence of these convex PB domains at the film surface was confirmed by replica electron microscopy experiments. Unordered amino acid sequences form an interfacial zone at the film surface between the PB domains and the PZLL matrix. Since the amide bonds in the peptide sequences in the interfacial zone are not involved in intramolecular hydrogen bonding, they are able to bind water, which explains the low water contact angles that were measured on the PZLL-PB-PZLL films. 

Dynamic vapour phase techniques are interesting tools for the determination of these properties. When compared to standard wettability experiments, they provide two main benefits. They can easily and reproducibly be applied to powders and a wide variety of probe molecules can be selected. In the current study dynamic gravimetric vapour sorption (DVS) and inverse gas chromatography (IGC) have been used to characterise the energetic and acid-base properties of a calcined ruthenium oxide / MCM41 catalyst as well as the corresponding MCM41 support. 

If only Londons forces are present across the interface, the work of adhesion is fiiUy determined because the nondispersive part is equal to zero. Indeed and can be easily determined by wettability experiments (Wu 1982). The only existence of London interactions at the interface between to adherends leads to ... 

In the case of hydrophilic surfaces (Si—NH2, Si—OH), the AFM tip interacts with the water layer adsorbed on the surface and the measured adhesion force results from the adhesion between water adsorbed on the both surfaces (tip and sample) and from the adhesion force due to the van der Waal forces between the NH2 or OH sites existing at the grafted wafer surface. On the contrary, during wettability experiments, the water droplet deposed on the surface does is not sensitive to OH sites existing at the hydroxylated wafer surface but only to water molecules adsorbed on the hydroxylated surface. 

Zarzycki and coworkers [77] studied the influence of temperature on the separation of cholesterol and bile acids using reversed-phase stationary phases. The best chromatographic conditions for the separation of mnlticomponent samples of steroids were chosen. Experiments were performed on wettable plates with RP-18W and at the temperatnres of 5, 10, 20, 30, 40, 50, and 60°C. The studies showed (Figure 9.9) that the degree of separation in the high-temperature region can be increased by an improvement of the efficiency of the chromatographic system. However, a relatively weak retention-temperatnre response for the studied steroids was observed. 

Most suitable for the examination of the surface is x-ray photoelectron spectroscopy, whereas the wettability determination can be established by a detailed interpretation of core flooding experiments and wettability index measurements. The results of such studies show that the organic carbon content in the surface is well correlated with the wetting behavior of the material characterized by petrophysical measurements [1467,1468]. 

Acute Toxicity. The LD50 following oral administration of parathion, either in propylene glycol solutions or in aqueous suspensions of the 15% wettable powder, has been determined for rats, mice, and guinea pigs. The lethal dose was approximated for rabbits and dogs. The results of these experiments are summarized in Table I. Statistical evaluation was by the method of Wilcoxon and Litchfield (11). 

Dermal Absorption. To determine the toxicity of parathion following dermal application, the method of Draize, Woodard, and Calvery (3) was followed. Variables considered in the design of these experiments were concentration as a factor of area, solvent, exposure time, and number of exposures. In some cases the wettable powder was applied in the dry form, while in other cases sufficient water was added to produce a viscid paste. All doses in the table are presented as milligrams per kilogram of parathion, regardless of the concentration or solvent. 

Following oral administration of a lethal dose to a dog (25 mg. per kg. wettable powder) tissues taken immediately after death analyzed as follows no parathion recovered from bladder bile, liver, kidney, abdominal fat, saliva, or intestine small quantities (2 to 7 p.p.m.) of parathion recovered from oxalated blood, spleen, lung, brain, and spinal cord. The urinary bladder was strongly contracted and no urine could be collected. The results of these two experiments indicate a universal distribution of parathion following acutely lethal doses. 

Thus, concerning drug load, only the tablet formulation is shown to be robust. Therefore, in the case of poorly wettable drug, the effect of dose can have direct impact on the decision whether to develop a tablet or a capsule dosage form. Such effects are not uncommon in Trial and Error experiments. Owing to lack of scientiLcally based formulation work, it is often impossible to understand the reasons for the behavior of the capsule versus the tablet formulation. 

Alcohols also promote wettability and penetration of the wood surface. This may easily be shown by the following simple experiment. When equal sized drops of distilled water were placed on the surface of a freshly planed piece of southern yellow pine, the times for the drops to completely soak into the wood were observed. On the early wood it took 65 seconds and on the latewood 179 seconds. When similar drops of 50% ethanol solution were used instead of pure water, it required only six seconds to disappear into the earlywood and 26 seconds into the latewood. However, if a small drop of adhesive syrup, with no hardener added, was placed on the wood surface, no adsorption took place at all. It was surmised that the viscosity prevented its permeation. When the adhesive was diluted with 50% alcohol it was readily absorbed and produced a red stained spot on either earlywood or latewood areas. This showed that the low molecular weight adhesive molecules could readily permeate the wood structure before condensation with the curing agent. 

A number of studies have examined fibril formation in the presence of different solid nonbiological surfaces, as summarized in Table 1. While many of these studies have focused on the formation of fibrils, the wettability and RMS of some surfaces have been characterized. Typical surface contact angles are also presented in Table 1 to aid comparison between these surface-based experiments. 

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