Properties of the Broad-Range Nematic Phase of a Laterally Linked H-Shaped Liquid Crystal Dimer

In search for novel nematic materials, a laterally linked H-shaped liquid crystal dimer have been synthesized and characterized. The distinct feature of the material is a very broad temperature range (about 50 oC) of the nematic phase, which is in contrast with other reported H-dimers that show predominantly smectic phases. The material exhibits interesting textural features at the scale of nanometers (presence of smectic clusters) and at the macroscopic scales. Namely, at a certain temperature, the flat samples of the material show occurrence of domain walls. These domain walls are caused by the surface anchoring transition and separate regions with differently tilted director. Both above and below this transition temperature the material represents a uniaxial nematic, as confirmed by the studies of defects in flat samples and samples with colloidal inclusions, freely suspended drops, X-ray diffraction and transmission electron microscopy.Comment: 30 pages (including Supplementary Information), 7 Figure

Formation of a Silicate L 3 Phase with Continuously Adjustable Pore Sizes

the magnitude of the gain. Thus, the delay time of ϳ0.5 s observed in REFERENCES AND NOTES ___________________________ Since the demonstration that surfactants could be used in the fabrication of silica mesophases (1), amphiphiles have been used to produce inorganic materials with a variety of mesomorphic structures, including lamellar, hexagonally packed tubular, and cubic forms (2-12). Surfactant-induced assembly of inorganic structures is now recognized as a way to make novel nanoporous materials with larger pore sizes than was previously possible. However, techniques developed thus far have limited capability to produce very large pores of a predetermined size. Here we describe the synthesis and characterization of a new, random, bicontinuous silicate mesomorph for which predetermined pore sizes, over a very large size range, may be obtained. Most procedures for forming mesoporous silicates rely on the micelle-forming properties of a surfactant, typically at a low surfactant concentration. The addition of an inorganic precursor, such as an alkoxysilane, leads to association and coassembly into a mesophase precipitant whose structural dimensions are controlled by the surfactant length. Polymerization of the inorganic precursor and removal of the surfactant results in a rigid silica shell conforming to the structural shape of the mesophase. However, the use of dilute surfactant solutions limits the ability to predict the topology of the mesophase. Also, the typical product of the process is a powder of micrometer-sized particles, thereby limiting uses in filtration, optical, or electronic applications, where large-area thin films or large uniform monoliths of material are required. Finally, the pore volume is filled with surfactant; that is, the surfactant must be removed before the pores can be accessed. These difficulties may be partially avoided by the use of high-concentration surfactant systems in which either the inorganic precursors minimally perturb a preexisting surfactant-water liquid crystalline (LC) structure or the LC nature of the system may be recovered under appropriate experimental conditions, as shown by Attard et al. (6). Also, because the inorganic precursor does not precipitate out of solution, the resultant material conforms to the shape of the container in which it forms, thereby allowing fabrication of large monoliths of a desired size and shape. However, even in these cases, the pore size is limited by the surfactant and the limited range of compositions on the phase diagram for a given mesomorphic structure. Applications of silicate mesophases as filtration media, optical materials, and nanocomposites would be facilitated if th

Host preferences and differential contributions of deciduous tree species shape mycorrhizal species richness in a mixed Central European forest

Mycorrhizal species richness and host ranges were investigated in mixed deciduous stands composed of Fagus sylvatica, Tilia spp., Carpinus betulus, Acer spp., and Fraxinus excelsior. Acer and Fraxinus were colonized by arbuscular mycorrhizas and contributed 5% to total stand mycorrhizal fungal species richness. Tilia hosted similar and Carpinus half the number of ectomycorrhizal (EM) fungal taxa compared with Fagus (75 putative taxa). The relative abundance of the host tree the EM fungal richness decreased in the order Fagus > Tilia >> Carpinus. After correction for similar sampling intensities, EM fungal species richness of Carpinus was still about 30–40% lower than that of Fagus and Tilia. About 10% of the mycorrhizal species were shared among the EM forming trees; 29% were associated with two host tree species and 61% with only one of the hosts. The latter group consisted mainly of rare EM fungal species colonizing about 20% of the root tips and included known specialists but also putative non-host associations such as conifer or shrub mycorrhizas. Our data indicate that EM fungal species richness was associated with tree identity and suggest that Fagus secures EM fungal diversity in an ecosystem since it shared more common EM fungi with Tilia and Carpinus than the latter two among each other

A meta-analysis of functional group responses to forest recovery outside of the tropics

© 2015, Society for Conservation Biology. Both active and passive forest restoration schemes are used in degraded landscapes across the world to enhance biodiversity and ecosystem service provision. Restoration is increasingly also being implemented in biodiversity offset schemes as compensation for loss of natural habitat to anthropogenic development. This has raised concerns about the value of replacing old-growth forest with plantations, motivating research on biodiversity recovery as forest stands age. Functional diversity is now advocated as a key metric for restoration success, yet it has received little analytical attention to date. We conducted a meta-analysis of 90 studies that measured differences in species richness for functional groups of fungi, lichens, and beetles between old-growth control and planted or secondary treatment forests in temperate, boreal, and Mediterranean regions. We identified functional-group-specific relationships in the response of species richness to stand age after forest disturbance. Ectomycorrhizal fungi averaged 90 years for recovery to old-growth values (between 45 years and unrecoverable at 95% prediction limits), and epiphytic lichens took 180 years to reach 90% of old-growth values (between 140 years and never for recovery to old-growth values at 95% prediction limits). Non-saproxylic beetle richness, in contrast, decreased as stand age of broadleaved forests increased. The slow recovery by some functional groups essential to ecosystem functioning makes old-growth forest an effectively irreplaceable biodiversity resource that should be exempt from biodiversity offsetting initiatives