\u3ci\u3eUrophora Affinis\u3c/i\u3e and \u3ci\u3eU. Quadrifasciata\u3c/i\u3e (Diptera: Tephritidae) Released and Monitored by USDA, APHIS, PPQ as Biological Control Agents of Spotted and Diffuse Knapweed

USDA, APHIS, PPQ has distributed the seedhead gall flies Urophora affinis and U. quadrifasciata (Diptera: Tephritidae) as classical biological agents of the introduced weeds spotted and diffuse knapweed (Centaurea maculosa and C. diffusa, respectively) (Asteraceae) in the United States. From 1987 to 1996, Urophora spp. have been released in 97 counties in 14 midwestern and western states. Established populations of U. affinis and U. quadrifasciata are confirmed in 85 and 95 counties, respectively, among all 14 states. These include the first reports of successful establishment of Urophora spp. in Arizona (two counties), Colorado (eight counties), Michigan (one county), Minnesota (six counties), Nebraska (four counties), Nevada (two counties), North Dakota (one county), South Dakota (four coun­ties), Utah (three counties), and Wisconsin (two counties). The first confirmed establishment of U. quadrifasciata in Indiana and Michigan is also reported

Atomic kinetic energy, momentum distribution and structure of solid neon at zero-temperature

We report on the calculation of the ground-state atomic kinetic energy, $E_{k}$, and momentum distribution of solid Ne by means of the diffusion Monte Carlo method and Aziz HFD-B pair potential. This approach is shown to perform notably for this crystal since we obtain very good agreement with respect to experimental thermodynamic data. Additionally, we study the structural properties of solid Ne at densities near the equilibrium by estimating the radial pair-distribution function, Lindemann's ratio and atomic density profile around the positions of the perfect crystalline lattice. Our value for $E_{k}$ at the equilibrium density is $41.51(6)$ K, which agrees perfectly with the recent prediction made by Timms {\it et al.}, $41(2)$ K, based on their deep-inelastic neutron scattering experiments carried out over the temperature range $4 - 20$ K, and also with previous path integral Monte Carlo results obtained with the Lennard-Jones and Aziz HFD-C2 atomic pairwise interactions. The one-body density function of solid Ne is calculated accurately and found to fit perfectly, within statistical uncertainty, to a Gaussian curve. Furthermore, we analyze the degree of anharmonicity of solid Ne by calculating some of its microscopic ground-state properties within traditional harmonic approaches. We provide insightful comparison to solid $^4$He in terms of the Debye model, in order to size the relevance of anharmonic effects in Ne.Comment: 20 pages, 7 figures. To be published in Physical Review

Modal cut-off and the V-parameter in photonic crystal fibers

We address the long-standing unresolved problem concerning the V-parameter in a photonic crystal fiber (PCF). Formulate the parameter appropriate for a core-defect in a periodic structure we argue that the multi-mode cut-off occurs at a wavelength lambda* which satisfies V_PCF(lambda*)=pi. Comparing to numerics and recent cut-off calculations we confirm this result.Comment: 3 pages including 2 figures. Accepted for Optics Letter

Generation of Lamprey Monoclonal Antibodies (Lampribodies) Using the Phage Display System.

The variable lymphocyte receptors (VLRs) consist of leucine rich repeats (LRRs) and comprise the humoral antibodies produced by lampreys and hagfishes. The diversity of the molecules is generated by stepwise genomic rearrangements of LRR cassettes dispersed throughout the VLRB locus. Previously, target-specific monovalent VLRB antibodies were isolated from sea lamprey larvae after immunization with model antigens. Further, the cloned VLR cDNAs from activated lamprey leukocytes were transfected into human cell lines or yeast to select best binders. Here, we expand on the overall utility of the VLRB technology by introducing it into a filamentous phage display system. We first tested the efficacy of isolating phage into which known VLRB molecules were cloned after a series of dilutions. These experiments showed that targeted VLRB clones could easily be recovered even after extensive dilutions (1 to 109). We further utilized the system to isolate target-specific "lampribodies" from phage display libraries from immunized animals and observed an amplification of binders with relative high affinities by competitive binding. The lampribodies can be individually purified and ostensibly utilized for applications for which conventional monoclonal antibodies are employed

A Ka-band (32 GHz) beacon link experiment (KABLE) with Mars Observer

A proposal for a Ka-Band (32 GHz) Link Experiment (KABLE) with the Mars Observer mission was submitted to NASA. The experiment will rely on the fourth harmonic of the spacecraft X-band transmitter to generate a 33.6 GHz signal. The experiment will rely also on the Deep Space Network (DSN) receiving station equipped to simultaneously receive X- and Ka-band signals. The experiment will accurately measure the spacecraft-to-Earth telecommunication link performance at Ka-band and X-band (8.4 GHz)

Cool White Dwarfs Revisited -- New Spectroscopy and Photometry

In this paper we present new and improved data on 38 cool white dwarfs identified by Oppenheimer et al. 2001 (OHDHS) as candidate dark halo objects. Using the high-res spectra obtained with LRIS, we measure radial velocities for 13 WDs that show an H alpha line. We show that the knowledge of RVs decreases the UV-plane velocities by only 6%. The radial velocity sample has a W-velocity dispersion of sig_W = 59 km/s--in between the values associated with the thick disk and the stellar halo. We also see indications for the presence of two populations by analyzing the velocities in the UV plane. In addition, we present CCD photometry for half of the sample, and with it recalibrate the photographic photometry of the remaining WDs. Using the new photometry in standard bands, and by applying the appropriate color-magnitude relations for H and He atmospheres, we obtain new distance estimates. New distances of the WDs that were not originally selected as halo candidates yield 13 new candidates. On average, new distances produce velocities in the UV plane that are larger by 10%, with already fast objects gaining more. Using the new data, while applying the same UV-velocity cut (94 km/s) as in OHDHS, we find a density of cool WDs of 1.7e-4 pc^-3, confirming the value of OHDHS. In addition, we derive the density as a function of the UV-velocity cutoff. The density (corrected for losses due to higher UV cuts) starts to flatten out at 150 km/s (0.4e-4 pc^-3), and is minimized (thus minimizing a possible non-halo contamination) at 190 km/s (0.3e-4 pc^-3). These densities are in a rough agreement with the estimates for the stellar halo WDs, corresponding to a factor of 1.9 and 1.4 higher values.Comment: Accepted to ApJ. New version contains some additional data. Results unchange

Investigation of Polymer–Plasticizer Blends as SH-SAW Sensor Coatings for Detection of Benzene in Water with High Sensitivity and Long-Term Stability

We report the first-ever direct detection of benzene in water at concentrations below 100 ppb (parts per billion) using acoustic wave (specifically, shear-horizontal surface acoustic wave, SH-SAW) sensors with plasticized polymer coatings. Two polymers and two plasticizers were studied as materials for sensor coatings. For each polymer–plasticizer combination, the influence of the mixing ratio of the blend on the sensitivity to benzene was measured and compared to commercially available polymers that were used for BTEX (benzene, toluene, ethylbenzene, and xylene) detection in previous work. After optimizing the coating parameters, the highest sensitivity and lowest detection limit for benzene were found for a 1.25 μm thick sensor coating of 17.5%-by-weight diisooctyl azelate-polystyrene on the tested acoustic wave device. The calculated detection limit was 45 ppb, with actual sensor responses to concentrations down to 65 ppb measured directly. Among the sensor coatings that showed good sensitivity to benzene, the best long-term stability was found for a 1.0 μm thick coating of 23% diisononyl cyclohexane-1,2-dicarboxylate-polystyrene, which was studied here because it is known to show no detectable leaching in water. The present work demonstrates that, by varying type of plasticizer, mixing ratio, and coating thickness, the mechanical and chemical properties of the coatings can be conveniently tailored to maximize analyte sorption and partial chemical selectivity for a given class of analytes as well as to minimize acoustic-wave attenuation in contact with an aqueous phase at the operating frequency of the sensor device

Design considerations for large space electric power systems

As power levels of spacecraft rise to the 50 to 100 kW range, it becomes apparent that low voltage (28 V) dc power distribution and management systems will not operate efficiently at these higher power levels. The concept of transforming a solar array voltage at 150 V dc into a 1000 V ac distribution system operating at 20 kHz is examined. The transformation is accomplished with series-resonant inverter by using a rotary transformer to isolate the solar array from the spacecraft. The power can then be distributed in any desired method such as three phase delta to delta. The distribution voltage can be easily transformed to any desired load voltage and operating frequency. The reasons for the voltage limitations on the solar array due to plasma interactions and the many advantages of a high voltage, high frequency at distribution system are discussed

A model colloidal fluid with competing interactions: bulk and interfacial properties

Using a simple mean-field density functional theory theory (DFT), we investigate the structure and phase behaviour of a model colloidal fluid composed of particles interacting via a pair potential which has a hard core of diameter $\sigma$, is attractive Yukawa at intermediate separations and repulsive Yukawa at large separations. We analyse the form of the asymptotic decay of the bulk fluid correlation functions, comparing results from our DFT with those from the self consistent Ornstein-Zernike approximation (SCOZA). In both theories we find rich crossover behaviour, whereby the ultimate decay of correlation functions changes from monotonic to long-wavelength damped oscillatory decay on crossing certain lines in the phase diagram, or sometimes from oscillatory to oscillatory with a longer wavelength. For some choices of potential parameters we find, within the DFT, a $\lambda$-line at which the fluid becomes unstable with respect to periodic density fluctuations. SCOZA fails to yield solutions for state points near such a $\lambda$-line. The propensity to clustering of particles, which is reflected by the presence of a long wavelength $\gg \sigma$, slowly decaying oscillatory pair correlation function, and a structure factor that exhibits a very sharp maximum at small but non zero wavenumbers, is enhanced in states near the $\lambda$-line. We present density profiles for the planar liquid-gas interface and for fluids adsorbed at a planar hard wall. The presence of a nearby $\lambda$-transition gives rise to pronounced long-wavelength oscillations in the one-body densities at both types of interface.Comment: 14 pages, 11 figure