We quantified placoid scale morphology and flexibility in the shortfin mako Isurus oxyrinchus and the blacktip shark Carcharhinus limbatus. The shortfin mako shark has shorter scales than the blacktip shark. The majority of the shortfin mako shark scales have three longitudinal riblets with narrow spacing and shallow grooves. In comparison, the blacktip shark scales have five to seven longitudinal riblets with wider spacing and deeper grooves. Manual manipulation of the scales at 16 regions on the body and fins revealed a range of scale flexibility, from regions of nonerectable scales such as on the leading edge of the fins to highly erectable scales along the flank of the shortfin mako shark body. The flank scales of the shortfin mako shark can be erected to a greater angle than the flank scales of the blacktip shark. The shortfin mako shark has a region of highly flexible scales on the lateral flank that can be erected to at least 50°. The scales of the two species are anchored in the stratum laxum of the dermis. The attachment fibers of the scales in both species appear to be almost exclusively collagen, with elastin fibers visible in the stratum laxum of both species. The most erectable scales of the shortfin mako shark have long crowns and relatively short bases that are wider than long. The combination of a long crown length to short base length facilitates pivoting of the scales. Erection of flank scales and resulting drag reduction is hypothesized to be passively driven by localized flow patterns over the skin. J. Morphol. 2012. © 2012 Wiley Periodicals, Inc.
The huge chemical space potential of synthetic polymers means that in many studies only a small parameter range can be realistically synthesized in a short time and hence the “best” formulations may not be optimum. Throughput is traditionally limited by the need for deoxygenation in radical polymerizations, but advances in photopolymerization now provide opportunities for “in-air” polymerizations. Here, we have developed a protocol using liquid handling robots (or multichannel pipettes) with blue light photolysis of reversible addition fragmentation chain transfer agents and tertiary amine deoxygenation to enable the synthesis of polymer libraries in industry-standard 96-well plates with no specialized infrastructure and no degassing step. The roles of solvents and amine deoxygenators are explored to optimize the polymerization, particularly to look at alternatives to dimethyl sulfoxide (DMSO) for hydrophobic monomer (co)polymerization. DMSO is shown to aid the degassing process but is not easy to remove and hence prevents isolation of pure polymers. In contrast, using dioxane in-plate evaporation or precipitation of the tertiary amine allowed isolation of polymers in-plate. This removed all reaction components yielding pure polymers, which is not easily achieved with systems using metal catalysts and secondary reductants, such as ascorbic acid. As an example of the throughput, in just under 40 h, 392 polymers were synthesized and subsequently analyzed direct from plates by a 96-well plate sampling size exclusion chromatography system to demonstrate reproducibility. Due to less efficient degassing in dioxane (compared to DMSO), the molecular weight and dispersity control were limited in some cases (with acrylates giving the lowest dispersities), but the key aim of this system is to access hundreds of polymers quickly and in a format needed to enable testing. This method enables easy exploration of chemical space and development of screening libraries to identify hits for further study using precision polymerization methods.
Oxidative assembly of metal chalcogenide nanocrystals (NCs) enables the formation of 2-D (dense) and 3-D porous structures without the presence of intervening ligands between particles that can moderate transport properties. This route has been demonstrated to be successful for a range of single-component structures including CdQ, PbQ, and ZnQ (Q = S, Se, Te). En route to the controllable assembly of multicomponent nanostructures, the roles of Q redox properties (2Q2− → Q22− + 2e) responsible for particle cross-linking and the native structure (cubic zinc blende vs hexagonal wurtzite) in the kinetics of assembly in single-component CdQ NCs are evaluated using time-resolved dynamic light scattering (TR-DLS). For wurtzite CdQ, the rates follow the ease of oxidation, with telluride as the fastest, followed by selenide and sulfide. However, when comparing CdS wurtzite (w) and zinc blende (zb), the cubic NCs exhibit surprisingly slow kinetics. NMR studies reveal the zb structure to have lower ligand coverage (by a factor of 4) relative to that of w, and the formation of free disulfide (the product of ligand oxidation) is slow. This is attributed to differences in the surface energies of w and zb facets, with w having polar (0001) facets of high energy compared to the neutral facets of the zb structure. The zb-CdS NCs prepared by low-temperature synthesis methods are likely to suffer from surface defects that may moderate reactivity. EPR studies suggest that zb-CdS has paramagnetic sulfur vacancies not present in w-CdS. These data suggest that structure plays an unexpectedly large role in the kinetics of CdQ NC oxidative assembly, providing a useful lever to moderate activities in multicomponent assemblies.
Our relationships with the mass media are at least partly determined by the perceived utility of the information we gather from them. We look to the media to fulfill certain functions-surveillance, correlation, socialization, and entertainment (Wright, 1986). We develop mechanisms through which we understand our environment and the forces at play therein. These are often enacted through cognitive shortcuts, or heuristics. These cognitive schema are influenced by who we are (our background), what we do (our direct, personal experiences), and what we see, hear, and learn through our exposure to mass media. Media representations play an important role in informing the ways in which we understand social, cultural, ethnic, and racial differences. Racial identity may play an especially powerful role in shaping our responses to mass media.Racial identity and racial group orientation are at the heart of research programs that are exploring the unique character of African American belief systems and their influence on the behavioral choices made by African Americans. This article examines the nature of racial group identity in an effort to determine its role in the formation of African American media orientations. The framework governing our analysis treats racial identity as one of many forms of individual identity that, in combination, help to shape our relations with others. Racial identity, as an organizing mechanism, is
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