Strontium Monoxide Measurements in Methane-air Flames

The spectroscopy of alkaline earth metal compounds has been an area of active research for several decades. This is at least in part stimulated by the application of these compounds to practical areas ranging from technology to medicine. The use of these compounds in the field of pyrotechnics was the motivation for a series of flame emission spectroscopy (FES) experiments with strontium containing compounds. Specifically, strontium monoxide (SrO) is studied as a candidate radiator for the diagnostic of methane-air flames. SrO emissions have been observed in flames with temperatures in the range of 1200-1600-K for two compounds: strontium hydroxide and strontium chloride. Comparisons are made of the measured SrO spectra to simulated spectra in the near-infrared region (700-900-nm) and conditions of local thermodynamic equilibrium (LTE) are discussed

Synthesis of Knowledge of Hazardous Fuels Management in Loblolly Pine Forests

This synthesis provides an overview of hazardous fuels management in loblolly pine (Pinus taeda) forests, as well as a reference guide on prescribed burning and alternative fuel management treatments. Available information is presented on treatment feasibility, approximate costs, and effects on soil, water quality, and wildlife. The objectives of fuel management in loblolly pine forests are to reduce the density of some targeted plant vegetation and change the structural condition of the forest, or both. Prescribed burning is the most common tool for managing fuels in the South due to the relatively low cost per acre and the ability to reduce fuel levels rather than rearrange them. Mechanical treatments may be effective in reducing wildfire risk by redistributing the fuels closer to the ground, creating a more compact fuel bed. Mulching (mastication) and chipping are the only common mechanical treatments in the Southern United States and generally are used as precursors to prescribed burning. The limited use of mechanical treatments is due to the rapid redevelopment of live fuels and higher treatment costs than prescribed burning. Herbicide treatments for hazardous fuels management are a realistic option in certain situations. Although herbicides cannot replace prescribed burning or mechanical operations where dead fuels must be removed or repositioned closer to the ground, they are useful as preliminary treatments to kill or suppress live fuels or following a prescribed burn or mechanical operation to kill resprouting woody species. Although livestock grazing is no longer common in southern forests, grazing can be used to reduce certain types of live fuels. For example, sheep grazing has been used in Florida to control saw palmetto (Serenoa repens). Wider impacts of fuel treatments are discussed for several social and ecological factors, such as soil erosion, water quality, wildlife, and public acceptability

Exact asymptotic analysis for metapopulation dynamics on correlated dynamic landscapes

We compute the mean patch occupancy for a stochastic, spatially explicit patch-occupancy metapopulation model on a dynamic, correlated landscape, using a mathematically exact perturbation expansion about a mean-field limit that applies when dispersal range is large. Stochasticity in the metapopulation and landscape dynamics gives negative contributions to patch occupancy, the former being more important at high occupancy and the latter at low occupancy. Positive landscape correlations always benefit the metapopulation, but are only significant when the correlation length is comparable to, or smaller than, the dispersal range. Our analytical results allow us to consider the importance of spatial kernels in all generality. We find that the shape of the landscape correlation function is typically unimportant, and that the variance is overwhelmingly the most important property of the colonisation kernel. However, short-range singularities in either the colonisation kernel or landscape correlations can give rise to qualitatively different behaviour

Tracking system analytic calibration activities for the Mariner Mars 1971 mission

Data covering various planning aspects of Mariner Mars 1971 mission are summarized. Data cover calibrating procedures for tracking stations, radio signal propagation in the troposphere, effects of charged particles on radio transmission, orbit calculation, and data smoothing

Probing complex RNA structures by mechanical force

RNA secondary structures of increasing complexity are probed combining single molecule stretching experiments and stochastic unfolding/refolding simulations. We find that force-induced unfolding pathways cannot usually be interpretated by solely invoking successive openings of native helices. Indeed, typical force-extension responses of complex RNA molecules are largely shaped by stretching-induced, long-lived intermediates including non-native helices. This is first shown for a set of generic structural motifs found in larger RNA structures, and then for Escherichia coli's 1540-base long 16S ribosomal RNA, which exhibits a surprisingly well-structured and reproducible unfolding pathway under mechanical stretching. Using out-of-equilibrium stochastic simulations, we demonstrate that these experimental results reflect the slow relaxation of RNA structural rearrangements. Hence, micromanipulations of single RNA molecules probe both their native structures and long-lived intermediates, so-called "kinetic traps", thereby capturing -at the single molecular level- the hallmark of RNA folding/unfolding dynamics.Comment: 9 pages, 9 figure

Functional insights from the structure of the 30S ribosomal subunit and its interactions with antibiotics

The 30S ribosomal subunit has two primary functions in protein synthesis. It discriminates against aminoacyl transfer RNAs that do not match the codon of messenger RNA, thereby ensuring accuracy in translation of the genetic message in a process called decoding. Also, it works with the 50S subunit to move the tRNAs and associated mRNA by precisely one codon, in a process called translocation. Here we describe the functional implications of the high-resolution 30S crystal structure presented in the accompanying paper, and infer details of the interactions between the 30S subunit and its tRNA and mRNA ligands. We also describe the crystal structure of the 30S subunit complexed with the antibiotics paromomycin, streptomycin and spectinomycin, which interfere with decoding and translocation. This work reveals the structural basis for the action of these antibiotics, and leads to a model for the role of the universally conserved 16S RNA residues A1492 and A1493 in the decoding process

HAS AN INTEGRATED PEST MANAGEMENT APPROACH REDUCED BLACKBIRD DAMAGE TO SUNFLOWER?

Since the mid- 1970s many new and modified damage abatement methods have been used to reduce blackbird damage to ripening sunflower in the northern Great Plains. To assess the overall impact of these techniques, we analyzed the dynamic relationship between breeding blackbird densities and sunflower damage. Breeding density estimates were made at both the regional and county levels, whereas, sunflower damage estimates were made at the county level only. Periodic regional estimates of breeding densities between 1967 and 1998 for red-winged blackbirds (Agelaius phoeniceus), common grackles (Quiscalus quiscula), and yellow-headed blackbirds (Xanthocephalus xanthocephalus) showed no differences among years. To increase our ability to detect changes in breeding density, we started intensive county-level surveys in 1996. These surveys, in four counties in North Dakota and South Dakota, showed that blackbird densities were greater in 1998 and 1999 than during the previous two years. We surveyed sunflower damage in two of these counties from 1994 to 1998 and found no difference in damage (F= 1.8%) among years. In 1997 and 1998, with the two other counties added to the survey, we found that damage was similar between years, averaging 2.2%. Dollar loss per hectare was trending lower in three of the study counties that had a historical database for comparison. This supports the idea that \u27local\u27 breeding densities are not correlated with damage levels. We will continue to use annual estimates of breeding densities and sunflower damage to assess the effects of an evolving Integrated Pest Management program

Atomic Structures of the 30S Subunit and Its Complexes with Ligands and Antibiotics

The two subunits that make up the ribosome have both distinct and cooperative functions. The 30S ribosomal subunit binds messenger RNA (mRNA) and is involved in the selection of cognate transfer RNA (tRNA) by monitoring codon–anticodon base-pairing during the decoding process. The 50S subunit catalyzes peptide-bond formation. Both subunits work in concert to move tRNAs and mRNAs relative to the ribosome in translocation, and both are the target of a large number of naturally occurring antibiotics. Thus, useful information about the mechanism of translation can be gleaned from structures of both individual subunits and the intact ribosome. In this paper, we describe our work on the determination of the atomic structure of the 30S ribosomal subunit and its complexes with RNA ligands, antibiotics, and initiation factor IF1. The results provide structural insights into how the ribosome recognizes cognate tRNA and discriminates against near-cognate tRNA. They also provide a structural basis for understanding the action of various antibiotics that target the 30S subunit