6,712 research outputs found

    Archeological Investigations at the Hudnall-Pirtle Site (41RK4) An Early Caddo Mound Center in Northeast Texas

    Get PDF
    The Hudnall-Pirtle site (41RK4) is situated on a large T-1 alluvial terrace of the Sabine River in northern Rusk County in Texas. This area of the state, commonly called Northeast Texas, is part of the Southern Gulf Coastal Plain, a relatively level, sloping plain formed by the pre-Pleistocene embayment of the Gulf of Mexico. From a biogeographical perspective, the site is located in the Oak-Hickory-Pine forest of eastern Texas, otherwise known as the Pineywoods. This area represents the western extension of the southern coniferous forests and is dominated by shortleaf and loblolly pine trees. Hardwood trees, including various oaks, hickory, elm, and gum, are the dominant vegetation in the floodplains of rivers and major creeks in Northeast Texas

    Air and Spray Mixture Temperature Effects on Atomization of Agricultural Sprays

    Get PDF
    spray drift associated with agrochemical operations is highly dependent upon the physical properties of the spray solution with respect to how they influence atomization.  This study examined two spray solutions across a wide range of solution temperatures for two nozzles spraying into two high speed airstreams.  The dynamic surface tension and viscosity of the spray solutions were also measured across the range of temperatures.  Generally as the solution temperature increased, the dynamic surface tension and viscosity both decreased.  This decrease in physical properties was directly related to the decrease in spray droplet size for all nozzles and airspeeds tested.  Monitoring of spray solution temperature throughout the spray system of a typical agricultural aircraft demonstrated that while changes in the spray solutions temperature do occur, the range is much less than the ranges across which this atomization study covered.  During a typical aerial application scenario, the temperature of a spray solution and the associated physical properties and atomization characteristics would not be expected to see significant variation

    Effects of transport on fecal glucocorticoid levels in captive-bred cotton-top tamarins (Saguinus oedipus)

    Get PDF
    The relocation of animals can induce stress when animals are placed in novel environmental conditions. The movement of captive animals among facilities is common, especially for non-human primates used in research. The stress response begins with the activation of the hypothalamic-pituitary-adrenal (HPA) axis which results in the release of glucocorticoid hormones (GC), which at chronic levels could lead to deleterious physiological effects. There is a substantial body of data concerning GC levels affecting reproduction, and rank and aggression in primates. However, the effect of transport has received much less attention. Fecal samples from eight (four male and four female) captive-bred cotton-top tamarins (Saguinus oedipus) were collected at four different time points (two pre-transport and two post-transport). The fecal samples were analyzed using an immunoassay to determine GC levels. A repeated measures analysis of variance (ANOVA) demonstrated that GC levels differed among transport times (p = 0.009), but not between sexes (p = 0.963). Five of the eight tamarins exhibited an increase in GC levels after transport. Seven of the eight tamarins exhibited a decrease in GC levels from three to six days post-transport to three weeks post-transport. Most values returned to pre-transport levels after three weeks. The results indicate that these tamarins experienced elevated GC levels following transport, but these increases were of short duration. This outcome would suggest that the negative effects of elevated GC levels were also of short duration

    Two-channel pseudogap Kondo and Anderson models: Quantum phase transitions and non-Fermi liquids

    Full text link
    We discuss the two-channel Kondo problem with a pseudogap density of states, \rho(\w)\propto|\w|^r, of the bath fermions. Combining both analytical and numerical renormalization group techniques, we characterize the impurity phases and quantum phase transitions of the relevant Kondo and Anderson models. The line of stable points, corresponding to the overscreened non-Fermi liquid behavior of the metallic r=0r=0 case, is replaced by a stable particle-hole symmetric intermediate-coupling fixed point for 0. For r>\rmax, this non-Fermi liquid phase disappears, and instead a critical fixed point with an emergent spin--channel symmetry appears, controlling the quantum phase transition between two phases with stable spin and channel moments, respectively. We propose low-energy field theories to describe the quantum phase transitions, all being formulated in fermionic variables. We employ epsilon expansion techniques to calculate critical properties near the critical dimensions r=0r=0 and r=1r=1, the latter being potentially relevant for two-channel Kondo impurities in neutral graphene. We find the analytical results to be in excellent agreement with those obtained from applying Wilson's numerical renormalization group technique.Comment: Added reference

    Quantum phase transitions in a resonant-level model with dissipation: Renormalization-group studies

    Full text link
    We study a spinless level that hybridizes with a fermionic band and is also coupled via its charge to a dissipative bosonic bath. We consider the general case of a power-law hybridization function \Gamma(\w)\propto |\w|^r with r≥0r\ge 0, and a bosonic bath spectral function B(\w)\propto \w^s with s≥−1s\ge -1. For r<1r<1 and max(0,2r−1)<s<1\mathrm{max}(0,2r-1)<s<1, this Bose-Fermi quantum impurity model features a continuous zero-temperature transition between a delocalized phase, with tunneling between the impurity level and the band, and a localized phase, in which dissipation suppresses tunneling in the low-energy limit. The phase diagram and the critical behavior of the model are elucidated using perturbative and numerical renormalization-group techniques, between which there is excellent agreement in the appropriate regimes. For r=0r=0 this model's critical properties coincide with those of the spin-boson and Ising Bose-Fermi Kondo models, as expected from bosonization.Comment: 14 pages, 14 eps figure

    Energetic particles observed by ISEE-1 and ISEE-2 in a cusp diamagnetic cavity on 29 September 1978

    Get PDF
    International audienceObservations by the ISEE-1 and ISEE-2 spacecraft on 29 September 1978 show large CEP (Cusp Energetic Particle) fluxes while passing through the dayside magnetospheric cusp in near coincident orbits. The event was observed around 11:00 MLT between roughly 12:30 and 13:00 UT by ISEE-1 and 12:00 and 13:00 UT by ISEE-2. During these periods, both electron and ion fluxes increased by more than two orders of magnitude, with the electron flux showing a strong peak at a pitch angle of 90°. The solar wind was ~710 km s?1 and the Dst was ~?200 nT, suggesting the occurrence of a strong geomagnetic storm. The ISEE-1 and ISEE-2 observations, however, show no time-energy dispersion of the CEPs, leading us to believe that these particles could not be the result of substorm processes in the magnetotail. The local magnetic field was depressed and extremely turbulent. Changes in the magnitude of the magnetic field anticorrelate closely to variations of the electron flux. The observations in electron flux peaking at 90° and the close anticorrelation between the local magnetic field strength and electron flux are unique and provide evidence of a potential local source for these energetic particles
    • …
    corecore