Observation of Pretransitional Divergence of Shear Viscosity near a Smectic-A—Smectic-B Phase Transition

Strong pretransitional divergence of shear viscosity was observed for the first time near a smectic-A—smectic-B phase transition by capillary shear flow with the layer normal perpendicular to both the flow velocity and velocity gradient. The results are inconsistent with a single power-law type of critical exponent and are suggestive of an essential singularity. Possible implications of the results for recently proposed models of the smectic-B phase and mechanisms for smectic-A—smectic-B phase transitions are discussed

Flow Behavior of an Oriented, Reentrant, Nematic Liquid Crystal

Capillary shear flow of a magnetically aligned liquid crystal was studied in the three Miesowicz orientations in the nematic, the smectic-A and, for the first time, in the reentrant nematic phase. These results indicate that the flow behavior of the reentrant nematic phase is essentially identical to that of the nematic phase and can be described by the hydrodynamic theory of the nematic phase

Observation of Newtonian Capillary Shear Flow in an Oriented Cholesteric Liquid Crystal

Newtonian capillary shear flow was observed for the first time in a cholesteric liquid crystal with the helix axis perpendicular to the flow. The effective viscosity in the cholesteric phase had a magnitude comparable to the viscosity of the isotropic liquid extrapolated to the cholesteric temperature. Oscillatory pitch dependence of the viscosity was seen when the pitch length was comparable to the capillary width

Forward projection of transient signals obtained from a fiber-optic pressure sensor

An analytical/experimental approach is presented to reconstruct the space–time pressure field in a plane and forward project the resultant space–time pressure field using tomographic and wave vector time-domain methods. Transient pressure signals from an underwater ultrasonic planar transducer are first measured using a line fiber-optic pressure sensor which is scanned across a plane at a fixed distance z0 from the transducer. The resulting spatial line integrals in the plane are time-dependent signals which are first used to reconstruct the space–time pressure field in the plane via simply implemented tomographic methods. These signals are then used to forward project the space–time pressure field to arbitrary planes employing a wave vector time-domain method. Verification of the method is first presented using synthetic signals and the impulse response approach. An experimental verification of the approach is then presented using an ultrasonic planar transducer. The results of the projected and experimental fields are compared at various distances for synthetic signals and experimental data. Good correlation is found between the calculated, projected, and experimental data

Finding needles in haystacks: linking scientific names, reference specimens and molecular data for Fungi

DNA phylogenetic comparisons have shown that morphology-based species recognition often underestimates fungal diversity. Therefore, the need for accurate DNA sequence data, tied to both correct taxonomic names and clearly annotated specimen data, has never been greater. Furthermore, the growing number of molecular ecology and microbiome projects using high-throughput sequencing require fast and effective methods for en masse species assignments. In this article, we focus on selecting and re-annotating a set of marker reference sequences that represent each currently accepted order of Fungi. The particular focus is on sequences from the internal transcribed spacer region in the nuclear ribosomal cistron, derived from type specimens and/or ex-type cultures. Re-annotated and verified sequences were deposited in a curated public database at the National Center for Biotechnology Information (NCBI), namely the RefSeq Targeted Loci (RTL) database, and will be visible during routine sequence similarity searches with NR_prefixed accession numbers. A set of standards and protocols is proposed to improve the data quality of new sequences, and we suggest how type and other reference sequences can be used to improve identification of Fungi

Genomic Transition to Pathogenicity in Chytrid Fungi

Understanding the molecular mechanisms of pathogen emergence is central to mitigating the impacts of novel infectious disease agents. The chytrid fungus Batrachochytrium dendrobatidis (Bd) is an emerging pathogen of amphibians that has been implicated in amphibian declines worldwide. Bd is the only member of its clade known to attack vertebrates. However, little is known about the molecular determinants of - or evolutionary transition to - pathogenicity in Bd. Here we sequence the genome of Bd's closest known relative - a non-pathogenic chytrid Homolaphlyctis polyrhiza (Hp). We first describe the genome of Hp, which is comparable to other chytrid genomes in size and number of predicted proteins. We then compare the genomes of Hp, Bd, and 19 additional fungal genomes to identify unique or recent evolutionary elements in the Bd genome. We identified 1,974 Bd-specific genes, a gene set that is enriched for protease, lipase, and microbial effector Gene Ontology terms. We describe significant lineage-specific expansions in three Bd protease families (metallo-, serine-type, and aspartyl proteases). We show that these protease gene family expansions occurred after the divergence of Bd and Hp from their common ancestor and thus are localized to the Bd branch. Finally, we demonstrate that the timing of the protease gene family expansions predates the emergence of Bd as a globally important amphibian pathogen