Studies of Inelastic Collisions of NaK and NaCs Molecules with Atomic Perturbers

We have investigated collisions of NaK molecules in the first excited state [2(A)1Σ+], with Ar and He collision partners using laser-induced fluorescence spectroscopy (LIF) and polarization-labeling (PL) spectroscopy in a two-step excitation scheme. Additionally, we have investigated collisions of NaCs molecules in the first excited state [2(A)¹Σ+] with Ar and He perturbers using the LIF technique. We use a pump-probe, two-step excitation process. The pump laser prepares the molecule in a particular ro-vibrational (v, J) level in the A state. The probe laser frequency is scanned over transitions to the 3¹Π in NaK or to the 5³Π in NaCs. In addition to observing strong direct lines, we also see weak collisional satellite lines that arise from collisions in the intermediate state that take the molecule from the prepared level (v, J) to level (v, J + ΔJ). The ratio of the intensity of the collisional line to the intensity of the direct line in LIF and PL yield information about population and orientation transfer. Our results show a propensity for ΔJ=even collisions of NaK with Ar and an even stronger propensity for collisions with He. Collisions of NaCs with Ar do not show any such ΔJ=even propensity. Preliminary investigations of collisions of NaCs with He seem to indicate a slight ΔJ=even propensity. In addition, we observe that rotationally inelastic collisions of excited NaK molecules with potassium atoms destroy almost all of the orientation, while collisions with argon destroy about one third to two thirds and collisions with helium destroy only about zero to one third of the initial orientation

Two-Point Focused Laser Differential Interferometry Second-Mode Measurements at Mach 6

A two-point focused laser differential interferometer (FLDI) is used to make measurements of density fluctuations on a 7 degree half-angle cone in a Mach 6 flow. The system was first characterized in the laboratory using laser induced breakdown to provide a well defined density fluctuation. The speed of the shock wave generated by the breakdown is verified using simultaneous high-speed schlieren. The FLDI system is then installed at the NASA Langley 20-Inch Mach 6 air tunnel to make measurements in the boundary layer of the 7 degree half-angle cone model and in the tunnel freestream for a unit Reynolds number range of 3.0 to 8.22 x 10(exp 6)/ft. Second-mode packets are visible in the spectra, with peak frequencies increasing linearly and peak amplitude increasing as a function of unit Reynolds number. The two-point measurement allows for the calculation of the second-mode wavepacket speeds, which propagate between 88% and 92% of the freestream velocity of the tunnel for all Reynolds numbers. The FLDI measurements are compared to surface-mounted fast-response pressure transducer measurements, where second-mode frequencies and wavepacket speeds are in good agreement

Population Growth Characteristics of Incipient Colonies of the Eastern Subterranean Termite, Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae)

Growth of Reticulitermes flavipes (Kollar) incipient colonies during their first year was documented via a monthly destructive sampling census of 15 unique colonies, each headed by an inbred primary pair, for a total of 180 colonies. King and queen biomass greatly decreased during the first 2 months, coinciding with egg production and colony foundation, but their biomass remained relatively constant thereafter. Three cohorts of eggs were produced, with the greatest number of eggs (mean = 14.5) during the first month. Larvae were present at 1 month, and workers were first observed at 2 months. The survival rate of the initial brood was less than 100%, most likely due to cannibalism. A single soldier was first noted in some colonies at 6 months. Offspring biomass was equal to that of the reproductive pair at the 2-month census, double at 3 months, and quadruple at 11 months. One-year-old colonies ranged in size from 20 to 40 individuals, with an average of 28.9 individuals; total colony biomass was 39.8 mg. The growth rate of these R. flavipes colonies was much slower than was reported in other studies, but our observations are consistent with previous models and suggestions regarding colony growth

Geometry Modeling for Unstructured Mesh Adaptation

The quantification and control of discretization error is critical to obtaining reliable simulation results. Adaptive mesh techniques have the potential to automate discretization error control, but have made limited impact on production analysis workflow. Recent progress has matured a number of independent implementations of flow solvers, error estimation methods, and anisotropic mesh adaptation mechanics. However, the poor integration of initial mesh generation and adaptive mesh mechanics to typical sources of geometry has hindered adoption of adaptive mesh techniques, where these geometries are often created in Mechanical Computer- Aided Design (MCAD) systems. The difficulty of this coupling is compounded by two factors: the inherent complexity of the model (e.g., large range of scales, bodies in proximity, details not required for analysis) and unintended geometry construction artifacts (e.g., translation, uneven parameterization, degeneracy, self-intersection, sliver faces, gaps, large tolerances be- tween topological elements, local high curvature to enforce continuity). Manual preparation of geometry is commonly employed to enable fixed-grid and adaptive-grid workflows by reducing the severity and negative impacts of these construction artifacts, but manual process interaction inhibits workflow automation. Techniques to permit the use of complex geometry models and reduce the impact of geometry construction artifacts on unstructured grid workflows are models from the AIAA Sonic Boom and High Lift Prediction are shown to demonstrate the utility of the current approach

Uncovering the components of the Francisella tularensis virulence stealth strategy

Over the last decade, studies on the virulence of the highly pathogenic intracellular bacterial pathogen Francisella tularensis have increased dramatically. The organism produces an inert LPS, a capsule, escapes the phagosome to grow in the cytosol (FPI genes mediate phagosomal escape) of a variety of host cell types that include epithelial, endothelial, dendritic, macrophage, and neutrophil. This review focuses on the work that has identified and characterized individual virulence factors of this organism and we hope to highlight how these factors collectively function to produce the pathogenic strategy of this pathogen. In addition, several recent studies have been published characterizing F. tularensis mutants that induce host immune responses not observed in wild type F. tularensis strains that can induce protection against challenge with virulent F. tularensis. As more detailed studies with attenuated strains are performed, it will be possible to see how host models develop acquired immunity to Francisella. Collectively, detailed insights into the mechanisms of virulence of this pathogen are emerging that will allow the design of anti-infective strategies

Electroanalysis of neutral precursors in protic ionic liquids and synthesis of high-ionicity ionic liquids

Protic ionic liquids (PILs) are ionic liquids that are formed by transferring protons from Brønsted acids to Brønsted bases. While they nominally consist entirely of ions, PILs can often behave as though they contain a significant amount of neutral species (either molecules or ion clusters), and there is currently a lot of interest in determining the degree of “ionicity” of PILs. In this contribution, we describe a simple electroanalytical method for detecting and quantifying residual excess acids in a series of ammonium-based PILs (diethylmethylammonium triflate, [dema][TfO], dimethylethylammonium triflate, [dmea][TfO], triethylammonium trifluoroacetate, [tea][TfAc], and dimethylbutylammonium triflate [dmba][TfO]). Ultramicroelectrode voltammetry reveals that some of the accepted methods for synthesising PILs can readily result in the formation of non-stoichiometric PILs containing up to 230 mM excess acid. In addition, vacuum purification of PILs is of limited use in cases where non-stoichiometric PILs are formed. While excess bases can be readily removed from PILs, even under ambient conditions, excess acids cannot, even under high vacuum. The effects of excess acid on the electrocatalytic oxygen reduction reaction (ORR) in PILs have been studied, and the onset potential of the ORR in [dema][TfO] increases by 0.8 V upon addition of excess acid to PIL. Based on the results of our analyses, we provide some recommendations for the synthesis of highly-ionic PILs

A two-way photonic interface for linking Sr+ transition at 422 nm to the telecommunications C-band

We report a single-stage bi-directional interface capable of linking Sr+ trapped ion qubits in a long-distance quantum network. Our interface converts photons between the Sr+ emission wavelength at 422 nm and the telecoms C-band to enable low-loss transmission over optical fiber. We have achieved both up- and down-conversion at the single photon level with efficiencies of 9.4% and 1.1% respectively. Furthermore we demonstrate noise levels that are low enough to allow for genuine quantum operation in the future.Comment: 5 pages, 4 figure

Associations of Near-Surface Soil Moisture and Annual Plant Community Dynamics

Invasive species have become an increasingly large concern, particularly in already degraded ecosystems, such as sagebrush (Artemisia tridentata)-steppe of the Intermountain West. Much of this ecosystem is already infested with large cheatgrass (Bromus tectorum) stands and is potentially at risk for future invasions depending on biotic and abiotic conditions. In these ecosystems, the existing vegetation, whether native or non-native, may not effectively utilize the soil moisture resources in the upper portion of the soil, termed the growth pool. If the existing vegetation does not effectively utilize moisture in the growth pool, an open resource is left for the establishment of other plants, including invasives. Through a combination of soil moisture modeling and observational studies, we identified three potential invasion pathways, particularly by annual plants, into a cheatgrass-dominated system, all consistent with the fluctuating resource hypothesis, and all resulting from an available water resource in the growth pool. Results suggest these arid and semi-arid systems are likely to be protected from novel invasive species by complete utilization of growth pool soil water resources by any existing vegetation, whether native or non-native. Our results also suggest the same features which make the site more prone to novel annual invaders may also be useful in guiding establishment of desired vegetation during restoration efforts