Effects of Prescribed Fire on Dead Woody Material in Upland Xeric Oak Forests of Oklahoma

The Cross Timbers of Oklahoma is a xeric oak forest adapted to frequent, low intensity fire. These forests may include tracts of old-growth stands that have been altered due to changes in fire regimes following European settlement. Dead wood comes from the death or breakage of trees and is important for wildlife habitat, nutrient cycles, energy storage, carbon sequestration, and erosion control. Dead wood depends on many factors such as site productivity, stand age, and disturbance. Fire has the capacity to create and consume dead wood. The purpose of this study was to determine whether prescribed burning affected the quantity of standing and down dead wood. We studied three wildlife management areas (WMAs) in central and eastern Oklahoma where prescribed burning had been used as one of the primary management practices. At each WMA, we measured 30 transects in each of 8 burn units with fire frequencies ranging 0 to 4.6 fires / decade over 22 - 26 years. Down woody debris (DWD) was measured by the planar intersect method on 50-m transects, and snags were measured on 500-m2 plots along the same transects. Volume of DWD 7.5 cm diameter was variable across the burn units and sites (7.2-8.7 m3 ha-1). Volume of DWD > 7.5 cm diameter was highly variable among burn units and sites (6.2-9.1 m3 ha-1). The volume of total DWD (13.5-17.7) was approximately equal to that of snags (14.1-18.0 m3 ha-1). Linear regression analyses with fires per decade and years since fire as explanatory variables were nearly all nonsignificant for all the metrics of DWD and snags. Multiple regression analyses with site and live basal area as explanatory variables were likewise not significant. The high variability of DWD and snag volume among burn units suggested that stand structure and local disturbances such as wind, ice, and disease may determine dead wood volumes.Department of Natural Resource Ecology and Managemen

Thermal Excitation of Broadband and Long-range Surface Waves on SiO 2 Submicron Films

We detect thermally excited surfaces waves on a submicron SiO 2 layer, including Zenneck and guided modes in addition to Surface Phonon Polaritons. The measurements show the existence of these hybrid thermal-electromagnetic waves from near-(2.7 $\mu$m) to far-(11.2 $\mu$m) infrared. Their propagation distances reach values on the order of the millimeter, several orders of magnitude larger than on semi-infinite systems. These two features, spectral broadness and long range propagation, make these waves good candidates for near-field applications both in optics and thermics due to their dual nature.Comment: Applied Physics Letters, American Institute of Physics, 201

Invasive woody plants as foci of tick-borne pathogens: Eastern redcedar in the southern Great Plains

Habitat preference and usage by disease vectors are directly correlated with landscapes often undergoing anthropogenic environmental change. A predominant type of land use change occurring in the United States is the expansion of native and non-native woody plant species in grasslands, but little is known regarding the impact of this expansion on regional vector-borne disease transmission. In this study, we focused on the impact of expanding eastern redcedar (Juniperus virginiana; ERC) and tested two hypotheses involving relationships between habitat preferences of adult tick species in rural habitats in central Oklahoma. Using CO2 traps, we collected ticks from two densities of ERC and grassland and screened adult ticks for the presence of pathogen DNA. We found support for our first hypothesis with significantly more Amblyomma americanum (Linnaeus) and Dermacentor variabilis (Say) collected in ERC habitats than in grassland. Our second hypothesis was also supported, as Ehrlichia-and Rickettsia-infected A. americanum were significantly more likely to be collected from ERC habitats than grassland. As the first evidence that links woody plant encroachment with important tick-borne pathogens in the continental United States, these results have important ramifications involving human and companion animal risk for encountering pathogen-infected ticks in the southern Great Plains.Peer reviewedEntomology and Plant PathologyNatural Resource Ecology and Managemen

The ansamycin antibiotic, rifamycin SV, inhibits BCL6 transcriptional repression and forms a complex with the BCL6-BTB/POZ domain

BCL6 is a transcriptional repressor that is over-expressed due to chromosomal translocations, or other abnormalities, in ~40% of diffuse large B-cell lymphoma. BCL6 interacts with co-repressor, SMRT, and this is essential for its role in lymphomas. Peptide or small molecule inhibitors, which prevent the association of SMRT with BCL6, inhibit transcriptional repression and cause apoptosis of lymphoma cells in vitro and in vivo. In order to discover compounds, which have the potential to be developed into BCL6 inhibitors, we screened a natural product library. The ansamycin antibiotic, rifamycin SV, inhibited BCL6 transcriptional repression and NMR spectroscopy confirmed a direct interaction between rifamycin SV and BCL6. To further determine the characteristics of compounds binding to BCL6-POZ we analyzed four other members of this family and showed that rifabutin, bound most strongly. An X-ray crystal structure of the rifabutin-BCL6 complex revealed that rifabutin occupies a partly non-polar pocket making interactions with tyrosine58, asparagine21 and arginine24 of the BCL6-POZ domain. Importantly these residues are also important for the interaction of BLC6 with SMRT. This work demonstrates a unique approach to developing a structure activity relationship for a compound that will form the basis of a therapeutically useful BCL6 inhibitor

Theory of Dyakonov-Tamm waves at the planar interface of a sculptured nematic thin film and an isotropic dielectric material

In order to ascertain conditions for surface-wave propagation guided by the planar interface of an isotropic dielectric material and a sculptured nematic thin film (SNTF) with periodic nonhomogeneity, we formulated a boundary-value problem, obtained a dispersion equation therefrom, and numerically solved it. The surface waves obtained are Dyakonov-Tamm waves. The angular domain formed by the directions of propagation of the Dyakonov--Tamm waves can be very wide (even as wide as to allow propagation in every direction in the interface plane), because of the periodic nonhomogeneity of the SNTF. A search for Dyakonov-Tamm waves is, at the present time, the most promising route to take for experimental verification of surface-wave propagation guided by the interface of two dielectric materials, at least one of which is anisotropic. That would also assist in realizing the potential of such surface waves for optical sensing of various types of analytes infiltrating one or both of the two dielectric materials.Comment: accepted for publication in J. Opt.