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Notes: Continuous wave difference frequency mixing of a single mode Nd:YAG laser at 1.06 μm and a scanning, single mode ring dye laser (R6G) in a LiNbO3 crystal generates a novel source of widely tunable near infrared radiation in the 1.2–2.2 μm region. In conjunction with the high sensitivity of a pulsed slit nozzle expansion with multipass optics (0.48 m path length), this narrow band source of tunable ir light allows the high resolution study of overtone (v=2←0) spectra for a wide variety of molecular complexes with H stretching vibrations. In this paper, we report the first rotationally resolved spectra of (HF)2 in the first HF stretching overtone region. In particular, we observe Ka=1←0 and 0←0 subbands for a vibrational state from one member of the v=2 overtone triad in (HF)2 with a band center of 7682.8228(5) cm−1. We tentatively assign this state as the hydrogen bond acceptor (i.e., free) HF stretching overtone 2νacc based on predissociation line widths and excellent agreement with predictions based on an anharmonic local mode description of (HF)2. Splittings of 0.2119(5) cm−1 (K'a = 0) and 0.0942(3) cm−1 (K'a = 1) due to interconversion tunneling are found.From the observed intensity alternation due to nuclear spin statistical weights, the overall vibrational symmetry for K'a = 0 and 1 is unambiguously determined to be Γvib=A+ and B+ for the lower and upper tunneling levels, respectively. These A+ and B+ symmetry designations correspond to irreducible representations of the MS4 molecular symmetry group, which allows for large amplitude motion and exchange of the identical HF subunits. Predissociation line broadening is observed in each of the four upper vibrational levels which varies between 56(20) and 175(25) MHz and depends sensitively on both K'a and the tunneling symmetry. This tunneling symmetry dependence, together with the unusual K'a dependence of the tunneling splitting and the anomalously large intensity ratio between the parallel and perpendicular transitions, indicates the presence of vibrational resonances in the overtone region not clearly evidenced in the analysis of the corresponding fundamental HF stretch region. Our results are discussed in the context of earlier static cell FTIR spectra and recent ab initio predictions for this overtone state. The data suggest that the overtone dynamics in (HF)2 can not be satisfactorily described as an oscillator pair connected by a 1D interconversion pathway, and may instead involve substantial coupling to other intermolecular vibrational degrees of freedom.

Notes: . We have characterized a novel, temperature-sensitive mutation affecting motility in Tetrahymena thermophila. Mutants grew and divided normally at the restrictive temperature (38°C), but became nonmotile. Scanning electron microscopic analysis indicated that nonmotile mutants contained the normal number of cilia and that the cilia were of normal length. Transmission electron microscopic analysis indicated that axonemes isolated from nonmotile mutants lacked outer dynein arms, so the mutation was named oad I (outer arm defficient). Motile mutants shifted to 38° C under conditions that prevent cell growth and division (starvation) remained motile suggesting that once assembled into axonemes at the permissive temperature (28° C) the outer arm dyneins remain functional at 38° C. Starved, deciliated mutants regenerated a full complement of functional cilia at 38° C, indicating that the mechanism that incorporates the outer arm dynein into developing axonemes is not affected by the oad I mutation. Starved, nonmotile mutants regained motility when shifted back to 28° C, but not when incubated with cycloheximide. We interpret these results to rule out the hypothesis that the oad I mutation affects the site on the microtubules to which the outer arm dyneins bind. Axonemes isolated from mutants grown for one generation at 38° C had a mean of 6.0 outer arm dyneins, and axonemes isolated from mutants grown for two generations at 38° C had a mean of 3.2 outer arm dyneins. Taken together, these results indicate that the oad I mutation affects the synthesis of outer arm dyneins in Tetrahymena.

Notes: A variable pulse-length electron-beam source capable of 100's μs pulse is reported. Long-pulse electron-beam generation was based on the hollow cathode discharge mode of operation of the back-lighted thyratron and achieved by the modification of circuit parameters that control the discharge. With 75 mTorr Ar and 20 kV applied voltage, the electron beam went through a transient phase before reaching a steady-state long-pulse generation. During the transient phase, a fast-decaying voltage (20–2 kV) and a pulse of 2.5 A and 130 ns FWHM electron beam were observed. The self-extracted long-pulse electron beam has a duration ∼100 μs, energy ∼2 keV, and current density ∼10 A/cm2. The results demonstrate the feasibility of controlling the electron-beam pulse length. The device is simple, robust, and compatible with a plasma environment.

Notes: The reaction of tritordeum and its Hordeum chilense and Triticum spp. parents to Septoria tritici was studied in field and seedling experiments. All H. chilense lines were highly resistant to all the isolates and did not allow pycnidia development. The ‘durum wheat isolate’ developed pycnidia only on durum wheats. The ‘breed wheat isolate’ was very virulent on bread wheat but also on the wild tetra-ploid wheats. The other two isolates were compatible with durum and bread wheat. All hexaploid tritordeums were highly resistant both in the field and the seedling experiments. Some octoploid tritordeums allowed pycnidial development, but at much lower levels than their wheat parent. Resistance in tritordeum was not associated with plant stature and only in octoploid tritordeum was association of resistance with late maturity detected.

Notes: The genome of Tritordeum, AABBHchHch, was substituted into the cytoplasms of Triticum aestivum, T. turgidum and Hordeum chilense by repeated back-crossing to produce alloplasmic lines. This substitution did not greatly affect the characters studied, except yield per plot and fertile ears per plant, which were lower on T. turgidum cytoplasm. Cytoplasm from either H. chilense or T. aestivum could be used for breeding tritordeum.