The dinoflagellate species originally described as Pfiesteria shumwayae Glasgow et Burkholder, recently transferred to a new genus, Pseudopfiesteria Litaker et al., is reclassified into the redefined genus Pfiesteria Steidinger et Burkholder, as Pfiesteria shumwayae within the order Peridiniales. This change is based upon consideration of a compilation of previous and new morphological analyses and molecular phylogenetic analyses. Morphological analysis with scanning and transmission electron microscopy supports previous findings except in the sulcal area. In the cells examined, the sulcus is partly concealed by the peduncle cover plate (p.c.), which originates at the right side of the sulcus along the left side of the 6c and 5 000 plates. The fine structure of the p.c. appears similar to that of other thecal plates. The 1 00 plate can also extend slightly over the sulcus. Transmission electron microscopy revealed that Pfiesteria shumwayae can have at least six sulcal plates; the number remains uncertain and may vary. The sulcal plates of this small, delicately thecate species have not been clearly discerned by scanning electron microscopy of membranestripped and/or suture-swollen cells. The Kofoidian thecal plate formula for the genus Pfiesteria is Po, cp, X, 4 0 , la, 5-6 00 , 6c, p.c., ?s, 5 000 , 0p, 2 0000 . The monophyletic grouping of ''pfiesteria-like'' taxa within the order Peridiniales, as well as the grouping of Pfiesteria piscicida and Pfiesteria shumwayae within the same genus, is also supported by the preponderance of previous molecular evidence, and by the phylogenetic trees contributed in the present analysis. Pfiesteria appears to be closely related to as-yet informally www.elsevier.com/locate/hal Harmful Algae 5 (2006) 481-496 described cryptoperidiniopsoids and calcareous dinoflagellates such as Thoracosphaera; thus, the family classification requires revision that is beyond the scope of this study. #
The increased emphasis on nano-structured materials is placing an ever increasing demand on sample preparation techniques to unveil such fine structure. Nano-structured fibers are even more difficult because of the ease with which these materials can smear even when prepared under liquid nitrogen (LN2) as shown (Figure 1). This is especially true for the islandin- the-sea structures where it is rather hard to reveal the island structures due to smearing. In the search for a possible solution, a sample preparation technique that has shown great results in other composite structures of different polymer blends was applied to these structures.
Gels constitute a fascinating class of materials which exhibit a variety of unusual properties due to the presence of a highly connected, rigidifying 3-D network [ 11. Many organic gels consist of a polymeric network within a liquid matrix and exhibit solid-like properties, as discerned from rheology [2]. Hydrogels, in particular, have received considerable attention due to their applicability as delivery vehicles in aqueous media [3]. Since bulk gel properties depend on network morphology (e.g., pore size and fibril diameter), the network must be isolated from the matrix liquid for microscopical analysis so that structure-property-processing relationships can be identified for material design and fabrication purposes. Network isolation in aqueous gels can be readily accomplished through freeze drying [4,5], although care must be exercised to avoid crystalinduced artifacts. If the sublimation boundary of the matrix liquid is experimentally accessible, this technique can also be utilized to prepare nonaqueous gels for SEM or TEM investigation [6]. In a new generation of gels, a disordered amphiphilic block copolymer [7] comprises the matrix, while a self-association molecule, dibenzylidene sorbitol (DB S), induces physical gelation. This communication reports on the extraction of the copolymer matrix from a DBS gel, leaving behind an intact percolation network that is responsible for intriguing thermoreversible properties.A 29,000 g/mol polydimethylsiloxane (PDMS), polyethylene oxide (PEO), and polypropylene oxide (PPO) copolymer was provided by OSi Specialties. Its composition was 20/32/48 (wt%) PDMS/PEO/PPO. The DBS was supplied by Milliken. Gels were formulated by adding DBS ( I 2 wt%) to the copolymer continuously stirred in a 50 ml glass beaker held at 190°C. After 5 min of mixing, the beaker was cooled slowly to ambient temperature. Gelation occurred over the course of up to 4 hrs, depending on concentration. Since freeze drying was impractical due to the low copolymer vapor pressure, critical point drying (CPD) was selected to remove the copolymer. This approach has proven valuable in extracting small organic molecules from aerogels [8]. Dissolution of polymers in a supercritical fluid is identical to dissolution in a liquid solvent and is governed by solvent quality, i.e., enthalpic interactions between polymer segments and solvent molecules. To discern if CPD solvents such as C0.L or monochlorotrifluoromethane (Freon 13) could be used, the solubility parameters (6) of the copolymer blocks were first determined. According to regular solution theory [9], these 6 can be used to discern the solution behavior of component i, through ZnypAh2, where yi is the activity coefficient of component i. The solubility parameter difference (Ah) is equal to h-xja $9, where +j is the volume fraction of component j in the mixture. In an ideal solution (with infiiite miscibility), the enthalpy of mixing vanishes so that yi+l and A h a .Solubility parameters were obtained from tabulated data or calculated from group-contribu...
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