Relationship of Latitude-of-Origin to Winter Survival and to Forage and Seed Yields of Wheatgrass (Agropyron species) in Subarctic Alaska

Five field experiments evaluating and comparing numerous grasses were conducted over seven years at the Matanuska Research Farm (61.6°N) near Palmer in southcentral Alaska. Grasses were 34 strains within 14 species of wheatgrass (Agropyron) derived from various geographic areas spanning 32 degrees of latitude; also included were the intergeneric hybrid Agroelymus palmerensis Lepage, Siberian wildrye (Elymus sibiricus L.), two bromegrass (Bromus) cultivars, and one timothy (Phleum pratense L.) cultivar. They were grown in broadcast-seeded plots for forage (two cuts per year), in drilled rows for seed production, and as individual plants in rows for winter-survival determinations

Bromegrass in Alaska. I.Winter Survival and Forage Productivity of Bromus Species, Types, and Cultivars as Related to Latitudinal Adaptation

This report summarizes seven separate field experiments, conducted over more than two decades at the University of Alaska’s Matanuska Research Farm, that compared strains within three bromegrass (Bromus) species for winter hardiness and forage production. Species were (a) smooth bromegrass (B. inermis Leyss.), (b) native Alaskan pumpelly bromegrass (B. pumpellianus Scribn.), and (c) meadow bromegrass (B. biebersteinii Roem. and Schult.), a species native to southwestern Asia

Studies on Emission Processes in Optically Pumped Mercury Vapor

Electron transitions in optically pumped mercury vapor emissio

Pseudoelastic Behavior of Shape Memory Alloys: Constitutive Theory and Identification of the Material Parameters Using Neural Networks

In shape memory alloys, some exceptional effects, like the one- and two-way shape memory effect, are observable. In a certain temperature range, the so-called pseudoelastic effect due to stress induced martensitic phase transitions is additionally observed in NiTi and other shape memory alloys. To identify the pseudoelastic material behavior of NiTi shape memory alloys, tension tests with different strain-rates are discussed. The observed phenomena are modeled within the framework of continuum thermomechanics regarding a geometric linear theory. The proposed model consists of a free energy function in order to represent the occurring energy storage and release effects. Additionally, evolution equations for internal variables, like the inelastic strain tensor and the fraction of martensite, are introduced. The developed system of constitutive equations represents the observed historydependent material behavior. For the identification of the material parameters, the theory of neural networks is applied. Finally, the numerical simulations show a good agreement between the experimental observations and the predictions of the phenomenological model

Field Dependence of the Josephson Plasma Resonance in Layered Superconductors with Alternating Junctions

The Josephson plasma resonance in layered superconductors with alternating critical current densities is investigated in a low perpendicular magnetic field. In the vortex solid phase the current densities and the squared bare plasma frequencies decrease linearly with the magnetic field. Taking into account the coupling due to charge fluctuations on the layers, we extract from recent optical data for SmLa_{1-x} Sr_x CuO_{4-delta} the Josephson penetration length lambda_{ab} approximately 1100 A parallel to the layers at T=10 K.Comment: 5 pages, 6 eps-figures, final version with minor misprints correcte

Optical Properties of Crystals with Spatial Dispersion: Josephson Plasma Resonance in Layered Superconductors

We derive the transmission coefficient, $T(\omega)$, for grazing incidence of crystals with spatial dispersion accounting for the excitation of multiple modes with different wave vectors ${\bf k}$ for a given frequency $\omega$. The generalization of the Fresnel formulas contains the refraction indices of these modes as determined by the dielectric function $\epsilon(\omega,{\bf k})$. Near frequencies $\omega_e$, where the group velocity vanishes, $T(\omega)$ depends also on an additional parameter determined by the crystal microstructure. The transmission $T$ is significantly suppressed, if one of the excited modes is decaying into the crystal. We derive these features microscopically for the Josephson plasma resonance in layered superconductors.Comment: 4 pages, 2 figures, epl.cls style file, minor change

Rapid enzymatic test for phenotypic HIV protease drug resistance

A phenotypic resistance test based on recombinant expression of the active HIV protease in E. coli from patient blood samples was developed. The protease is purified in a rapid onestep procedure as active enzyme and tested for inhibition by five selected synthetic inhibitors (amprenavir, indinavir, nelfinavir, ritonavir, and saquinavir) used presently for chemotherapy of HIVinfected patients. The HPLC system used in a previous approach was replaced by a continuous fluorogenic assay suitable for highthroughput screening on microtiter plates. This reduces significantly the total assay time and allows the determination of inhibition constants (K-i). The Michaelis constant (K-m) and the inhibition constant (K-i) of recombinant wildtype protease agree well with published data for cloned HIV protease. The enzymatic test was evaluated with recombinant HIV protease derived from eight HIVpositive patients scored from sensitive to highly resistant according to mutations detected by genotypic analysis. The measured K-i values correlate well with the genotypic resistance scores, but allow a higher degree of differentiation. The noninfectious assay enables a more rapid yet sensitive detection of HIV protease resistance than other phenotypic assays