Giardia lamblia is an intestinal protozoan that inhabits the intestinal tract of man and other mammals by attaching to the mucosal surface via the contractile activity of an attachment organelle called the ventral adhesive disk. We have investigated the presence of other attachment mechanisms in G. lamblia trophozoites by using microfabricated substrates that sterically interfere with formation of the hypothesized "negative pressure" under the ventral adhesive disk that would mediate attachment to a substratum. Pillars measuring 1 microm high and 2 microm in diam. were constructed in microarrays with spacings smaller than the diameter of the ventral adhesive disk. Using high resolution field emission scanning electron microscopy, the attachment of trophozoites to the tops of pillars in the microfabricated substrates was investigated. Firm adhesion of trophozoites was observed to be mediated by direct attachment of the ventrolateral flange membrane to the tops of microfabricated pillars. Attachment to microfabricated surfaces was 16% of that observed for attachment mediated by the ventral adhesive disk (4.4 +/- 1.5 cells/100 micro2 micropillar surface vs. 25.9 +/- 3.1 cells/100 micro2 flat substrate, p < 0.0001) This is the first report of trophozoite adhesion to a substratum by a mechanism other than the direct attachment of the ventral adhesive disk, and provides experimental evidence that the ventrolateral flange may play a role in trophozoite adhesion. A hypothesis is presented describing how the adhesive nature of the ventrolateral flange might be involved in normal attachment of G. lamblia trophozoites to a substratum.

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INTRODUCTIONadjustable parameters, as follows: volume fractions, interaction parameters, and chain lengths. Nauman and He found that the volume fraction of the compoNew polymers are required to fulfill the ever increasing nents was the most important in determining the demand for varied applications. The three main methmorphology of the polymer system. For a ternary sysods for creating new polymers are designing new monotem, a component with a volume fraction of 0.6 or mers, developing new polymerization mechanisms for higher formed a continuous phase, but no continuous old monomers, and synergistically blending existing phase was observed for a volume fraction less than polymers. Due to an extensive and lengthy process, the 0.33. The semicontinuous structure was limited to the development of new commercial polymers is very rare. range of 0.3 -0.5. The dispersed morphologies were The use of new polymerization mechanisms for old confined to volume fractions less than 0.45. However, monomers has been successful but has its limitations. many of the predicted morphologies, including those The utilization of polymer blends is increasing in imporwith commercial importance, need further examinatance from year to year. The technique of polymer tion. blending provides a cost-effective means of fabricating This article focuses on the preparation of new polymaterials with a specific application. Multiphase mers by solution blending and, in particular, composiblends can be made by a variety of methods. The curtional quenching. A combination of solvent dissolution rent techniques include melt blending, reaction techand flash devolatilization is used to achieve the final nologies, and compositional quenching.

INTRODUCTIONadjustable parameters, as follows: volume fractions, interaction parameters, and chain lengths. Nauman and He found that the volume fraction of the compo-New polymers are required to fulfill the ever increasing nents was the most important in determining the demand for varied applications. The three main methmorphology of the polymer system. For a ternary sysods for creating new polymers are designing new monotem, a component with a volume fraction of 0.6 or mers, developing new polymerization mechanisms for higher formed a continuous phase, but no continuous old monomers, and synergistically blending existing phase was observed for a volume fraction less than polymers. Due to an extensive and lengthy process, the 0.33. The semicontinuous structure was limited to the development of new commercial polymers is very rare. range of 0.3 -0.5. The dispersed morphologies were The use of new polymerization mechanisms for old confined to volume fractions less than 0.45. However, monomers has been successful but has its limitations. many of the predicted morphologies, including those The utilization of polymer blends is increasing in imporwith commercial importance, need further examinatance from year to year. The technique of polymer tion. blending provides a cost-effective means of fabricating This article focuses on the preparation of new polymaterials with a specific application. Multiphase mers by solution blending and, in particular, composiblends can be made by a variety of methods. The curtional quenching. A combination of solvent dissolution rent techniques include melt blending, reaction techand flash devolatilization is used to achieve the final nologies, and compositional quenching. 1 blend. The morphology of the blend is governed by The possibilities of blending the major polymers spinodal decomposition. Cavanaugh et al. 3 described a are infinite. Without a model, finding the appropriate methodology for the computer-aided design of polymer system of polymers to produce a desired blend can be blends. In this work, we provide some confirming rearduous and costly, especially when more than two sults from cast films and bulk samples produced by components are involved. Previously, Nauman and compositional quenching. He 2 predicted a wealth of morphologies by solving the component continuity equations, which are fourthorder partial differential equations. Despite the complexity of these equations, they contain only a few EXPERIMENTAL Thin films were made by solvent casting from singleCorrespondence to: E. B. Nauman.phase solutions, with xylene as the solvent, and were

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