Seaweed structure

The growth of crystallization phenomenon sometimes forms nontrivial and beautiful stmctures. Some of the crystals are associated with polyhedral stmcture, but more complex dendrite/fractal and seaweed structures can also appear [105, 106]. Dendrites are anisotropic ramihed structures with nearly paraboloidal growing... 

Isol. from Eucheuma spinosum and Agardhiella tenera red seaweeds. Structure... 

The adsorption of semicrystalline polymers at the polymer melt-solid interface is another interesting question to be answered. When a monolayer of semicrystalline polymer molecules is prepared on a solid surface, nucleation and crystal growth can be very different from that found in the bulk due to confinement effects [72-78]. Polymer chains in the vicinity of the solid surface tend to crystallize into lamellar crystals with either flat-on or edge-on orientations, depending on specific interactions with solids [79-81]. Among a variety of morphologies reported in the literature, the formation of dendrites or seaweed structures via the so-called diffusion-limited aggregation (DLA) process was the most commonly observed in semicrystalline polymer monolayers [76, 82]. 

Napolitano and coworkers studied the cold crystallization of poly(ethylene terephthalate) (PET) and poly(L-lactide) (PLEA) films confined between two Al layers (i.e., sandwiched films) [50, 53]. They reported that, after thermal annealing at a temperature where the maximum crystallization rate in the bulk was achieved, crystallization was inhibited when the thickness of the films was less than 20 nm for PET or less than 10 nm for PLEA. Such a threshold corresponds to the thickness of the adsorbed layers (i.e., a great reduction in the molecular mobility compared to the bulk) formed between the two solid substrates. Judging from the ratio between the thicknesses of the adsorbed layers and corresponding Rg of the polymers, their adsorbed layers are considered as the interfacial sublayer in our classifications. Hence, the discrepancy is noticed between the uncapped PE and PEO interfacial sublayers, where we can clearly see the seaweed structures (Fig. 6.5a), and the sandwiched PET and PLEA interfacial sublayer. This contrast... 

FIG. 6 Morphology diagram. Plotted is the dimensionless supercooling A versus the crystalline anisotropy e. Compact dendritic (CD) and compact seaweed (CS) structure comprise most of the diagram, under the influence of noise, fractal seaweed (FS) and fractal dendrites (FD) are encountered. For details see text and Ref. 108. 

Compact dendritic (CD) structures formally exist at arbitrarily small anisotropy e but their velocity goes to zero with e 0. It was only recently discovered that there is another structure, compact seaweed (CS), which is favorable for smaller e and larger A [94]. 

FIG. 8 Compact seaweed originating from the simulation of an isotropic phase by a phase-field model [120]. A doublon structure is just about to emerge from the chaotic background. 

A serious point is the neglect of surface tension and anisotropy in these derivations. In the experiments analyzed so far the relation VX const, seems to hold approximately, but what happens when the capillary anisotropy e goes to zero Numerically, tip-splitting occurs at lower velocities for smaller e. Most likely in a system with anisotropy e = 0 (and zero kinetic coefficient) the structures show seaweed patterns at velocities where the diffusion length is smaller than the short wavelength hmit of the neutral stability curve, as discussed in Sec. V B. 

Xylans as true homopolymers occur in seaweeds of the Palmariales and Nemaliales, however, their backbone consists of Xylp residues linked by -(1 3) (Type X3, Fig. la) or mixed -(1 3, 1 -> 4)-glycosidic linkages (Type Xmy Fig. lb). They are assumed mainly to have a structural function in the cell-wall architecture, but a reserve function cannot be ruled out [4]. From the microfibrils of green algae (Siphonales) such as Caulerpa and Bryop-sis sp., X3 was isolated and the structure confirmed by methylation analysis, C-NMR spectroscopy [7], as well as by mass spectrometry of enzymically released linear oligosaccharides up to a degree of polymerization (DP) of... 

Figure 4 Stabilized bromine antimicrobials are produced by eosinophils, a type of mammalian white blood cell. Bacteria are captured by phagocytosis and contained intracellularly within vesicles called phagosomes. Granules release cationic surfactants, lytic enzymes, and eosinophil peroxidase into the phagosome in a process known as degranulation. Eosinophil peroxidase, an enzyme that is structurally similar to the bromoperoxidases found in seaweed (Figure I), selectively catalyzes oxidation of bromide to hypobromite by reducing hydrogen peroxide to water. The hypobromite immediately reacts with nitrogenous stabilizers such as aminoethanesulfonic acid (taurine) to form more effective and less toxic antimicrobial agents.

In 1992, Paul and Van Alstyne reported on the processes that occur after tissue disruption in different species of the calcified green seaweed Halimeda [56]. After wounding, these algae transform their major secondary metabolite, the his-enoylacetate diterpene halimedatetraacetate (48), into halimedatrial (50) and epihalimedatrial (51). The structural relationship between the educt and the reaction products suggests that the transformation occurs by a combination of solvolysis and hydrolysis reactions as indicated in Scheme 14 [108]. 

The known anthelmintic properties of the seaweed Digenea simplex Agardh were traced back to a-kainic acid (75) after several decades of intense work by Japanese workers (117, 118). A structure was rapidly proposed for this relatively small molecule (C10H15NO4) on the basis of chemical (119) and X-ray evidence (120). a-Allokainic acid was isolated soon after from the same source, and its structure was established as 76 (121, 122). 

Van der Strate H, Van de Zande L, Stam WT, Olsen JL (2002) The contribution of haploids, diploids and clones to fine-scale population structure in the seaweed Cladophoropsis membranacea (Chlorophyta). Mol Ecol 11 329-345 Verlaque M, Boudouresque CF, Meinesz A, Gravez V (2000) The Caulerpa racemosa complex (Caulerpales, Ulvophyceae) in the Mediterranean sea. Bot Mar 43 49-68 Vinueza LR, Branch GM, Branch ML, Bustamante RH (2006) Top-down herbivory and bottom-up El Nino effects on Galapagos rocky-shore communities. Ecol Monogr 76 111-131 Wahl M and Hay ME (1995) Associational resistance and shared doom effects of epibiosis on herbivory. Oecologia 102 329-340... 

Fischer G, Wiencke C (1992) Stable carbon isotope composition, depth distribution and fate of macroalgae from the Antarctic Peninsula region. Polar Biol 12 341-348 Foster MS (1992) How important is grazing to seaweed evolution and assemblage structure in the north-east Pacific In John DM, Hawkins SJ, Price JH (eds) Plant-animal interactions in the marine benthos. Clarendon, Oxford, pp 61-85... 

Proposed aquaculture applications of degradable polymers include seaweed culture nets, fishing nets and lines, and temporary structures used for restoration of wet lands, beaches or other marsh areas [11-14], Weathering and hydrolysis are the most common degradation mechanisms encountered in aquatic applications. Continually submerged articles pose special challenges since temperatures are low and photodegradation and oxidation effects are limited. 

Carlucci MJ, Pujol CA, Ciancia M, Noseda MD, Matulewicz MC, Damonte EB, Cerezo AS (1997) Antiherpetic and anticoagulant properties of carrageenans from the red seaweed Gigartina skottsbergii and their cyclized derivatives correlation between structure and biological activity. Int J Biol Macromol 20 97-105... 

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