Surfactant-like material

For the treatment of lung surfactant deficiency in premature human infants suffering from respiratory distress syndrome, limited clinical trials were performed showing that liposomes in the lung-instilled intratracheally either as an aerosolized mist (Ivey et al., 1977) or as a suspension via an endotracheal tube (Fujiwara et al., 1980)—rapidly improved lung function. No adverse effects were observed as a result of the supplementation with surfactant-like material. It appears, therefore, that liposomes are a suitable system for the delivery of major phospholipid components of endogenous lung surfactant. 

In the lungs of rats instilled with 0.5 ml of a suspension of 1 mg NiO -1-0.1 mg CdO one week before, the alveolar macrophages appeared smaller than those of control, with numerous lamellar bodies of different sizes. The lamellar bodies consisted of membranous whorls, disintegrating structures, as well as accumulation of surfactant-like material (Murthy and Holovack 1991). In addition, the cytoplasm was filled with multivesicular bodies, degenerating mitochondria, as well as primary and secondary lysosomes. 

Pulmonary alveolar proteinosis (PAP) is a rare disorder characterized by the accumulation of surfactant-like material in the alveolar spaces, with resultant impairment in gas exchange (1-8). Since the sentinel description of PAP by Rosen and colleagues in 1958 (9), fewer than 500 cases have been reported in the literature (5). 

Accumulation of surfactant-like material in alveolar spaces Insidious onset of dyspnea and cough Hypoxemia and intrapulmonary shunting... 

The idea of obtaining surfactant-like material from compost has been explored by the group of Montoneri at the University of Torino [43-45]. This group based their studies on the fact that humic acids (HAs) and related compounds in alkaline solutions are capable of reducing the surface tension of water, forming micelles and solubilizing hydrophobic compounds [46]. Most of the applications for HA-like surfactants are currently... 

With respect to our process of extraction of surfactant-like material from wastewater biomass, we considered analytical methods (cation exchange resin (CER) extraction) and more conventional alkaline extractions currently used in the food industry [63],... 

Higher molecular primary unbranched or low-branched alcohols are used not only for the synthesis of nonionic but also of anionic surfactants, like fatty alcohol sulfates or ether sulfates. These alcohols are produced by catalytic high-pressure hydrogenation of the methyl esters of fatty acids, obtained by a transesterification reaction of fats or fatty oils with methanol or by different procedures, like hydroformylation or the Alfol process, starting from petroleum chemical raw materials. 

The most widely studied member of the M41S family is hexagonal MCM-41, which was first prepared by the I S+ liquid-crystal approach (168, 169). A charged surfactant like CTAB produces well-ordered mesoporous materials having ID... 

Synthesis of MCM-41 with Additives. The hydrothermal crystallization procedure as described earlier [10] was modified by adding additional salts like tetraalkylammonium (TAA+) bromide or alkali bromides to the synthesis gel [11]. Sodium silicate solution ( 14% NaOH, 27% Si02) was used as the silicon source. Cetyltrimethylammonium (CTA) bromide was used as the surfactant (Cl6). Other surfactants like octadecylltrimethylammonium (ODA) bromide (C,8), myristyltrimethylammonium (MTA) bromide (C,4) were also used to get MCM-41 structures with different pore diameter. Different tetralkylammonium or alkali halide salts were dissolved in little water and added to the gel before addition of the silica source. The final gel mixture was stirred for 2 h at room temperature and then transferred into polypropylene bottles and statically heated at 100°C for 4 days under autogeneous pressure. The final solid material obtained was washed with plenty of water, dried and calcined (heating rate l°C/min) at 560°C for 6 h. 

Mesostructured aluminophosphate / surfactant composite materials were prepared from aqueous and alcoholic systems. Syntheses in ethanol or methanol, respectively, lead to mixtures of two nanostructured phases. One of these consists of hexagonally arranged rod-like assemblies of the surfactant molecules with the head groups located in the centres, encapsulating the inorganic aluminophosphate the other is lamellar. The syntheses were monitored by in-situ temperature- and time-resolved small angle X-ray scattering (SAXS). 

Figure 3.5 shows the organized mesoporous structure of one of these materials. The wide variety of organic molecules with self-assembling properties allows for the synthesis of a myriad of solids with controlled porosity. Cationic surfactants, like the hexadecyltrimethylammonium used to synthesize MCM-41 [26], or three-block copolymers (hydrophilic-hydrophobic-hydrophilic) are two good examples. 

Furthermore, aggregates of nonionic surfactants like polyoxyethylene alkyl/aryl ethers of the Tergitol, Triton, and Brij series were used as templates for the formation of mesoporous silica materials in neutral or acidic media. The pore diameters of the materials that can be obtained with these surfactants are restricted to around 5.5 nm. The advantages of these surfactants over triblock copolymers are that they are cheap, nontoxic, and biodegradable. An overview of the most commonly used SDAs is compiled in Table 3.1. 

The surface of all inorganic materials exposed to ambient (humid) air is always covered with a thin layer of water adsorbed from the gas phase. The thickness of the adsorbed water layer varies with the humidity and surface chemistry. This water layer has been shown to reduce wear in MEMS operation. However, the high surface tension of the water film can cause an in-use stiction problem. The gas-phase lubrication concept discussed here employs the same equilibrium adsorption principle as the water adsorption in humid environments. The difference is that our approach utilizes a surfactant-like molecule that can provide low adhesion and good lubrication. The entry summarizes the advantages of gas-phase lubrication for MEMS devices and discusses the effect of alcohol adsorption on the adhesion and lubrication of silicon oxide surfaces. 

Stirring systems containing more than 15 wt% surfactant in water produce viscous pastes and gel-like materials which do not settle detectably in months. Dissolving sodium chloride in the aqueous solution can transform a gel-like sample to a low viscosity dispersion. 

The cooperative self-assembly route is the most commonly used synthesis procedure for surfactant templated materials. It uses aqueous solutions at a much lower initial surfactant concentration than for the true liquid templating route, reducing the required amounts of expensive surfactant template. In these solutions, the surfactants are at a high enough concentration to form micelles, which may be spherical, elliptical, rod-like or vesicular, but do not form the ordered aggregates found in the final templated silica-surfactant composites. The solutions are in thermodynamic equilibrium so are stable at a given temperature until the silica precursors are added. Once added, a series of interactions between the inorganic species and the surfactant micelles occur, which involve simultaneous association of all components, hence the name, cooperative self-assembly. The result of the interactions is formation of the silica-surfactant composite, usually a precipitate, with an ordered nanoscale structure similar to those found in concentrated surfactant solutions. 

With only 1 wt% surfactant concentration, the sequence of the three visible peaks in the SAXS spectra shown in Figure 11.16 (l >/3 2) clearly indicates a two-dimensional hexagonal (p6mm) mesostructure. This concentration is lower than those used to obtain S BA-like materials by using nonionic block copolymer... 

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