The Development of Solid Spectral Filters for the Regulation of Plant Growth

Phthalocyanine derivatives have been prepared and incorporated into polymer films for use as spectral filters for the modification of plant growth. The unusual absorption characteristics of phthalocyanines, notably the narrow absorption band in the visible region of the electromagnetic spectrum, allows the selective filtering of wavelengths necessary for excitation of either of the two isomeric phytochrome species. The resulting change in the photostationary state for the phytochrome is shown to have a marked effect on the growth characteristics of both chrysanthemums and antirrhinums. Chrysanthemums (short-day plants) grown under a far-red-absorbing film showed a reduction in height (∼14%) and internodal length compared to those grown under a red-absorbing film or a control with no absorption in the visible part of the spectrum; both leaf number and time to flowering were not affected by the presence of the spectral filter. For antirrhinums (long-day plants) both a reduction in height and a substantial increase in leaf area (70%) of the plants grown under the far-red-absorbing film were observed, although flowering was delayed. The potential of these filters as replacements for chemical plant growth regulators is discussed.     

Production and decay of F+(2030) observed in νμ interactions in emulsion

An event representing the production and decay of the charmed F⁺ meson has been identified by means of a 3-constraint fit to decay hypothesis F⁺ → π⁺π⁺π^?π⁰, in which both γ-rays from the π⁰ converted. The event was produced by a charged current ν_μ interaction in an emulsion stack located inside the Fermilab 15-foot bubble chamber. The F⁺ traveled 50 μm, corresponding to a proper time of 1.4 × 10^?13 seconds, before decaying in flight. Its mass was determined to be 2017 ± 25MeV.     

Near-field blockage of an ultralow sidelobe antenna

An analytical model is presented which describes the farfield radiation pattern of an array antenna blocked by a vertical or horizontal metallic cylinder in the near field of the aperture. The implementation of this model as a generalized computer program has been completed, and the computed radiation patterns have been verified by extensive measurements on a low sidelobeX-band slotted waveguide array. The effects of the blockage are summarized graphically for a wide range of obstacle sizes and distances, and for aperture illuminations ranging from conventional reflector-type distributions to ultralow sidelobe distributions. Using dielectric or absorptive coatings to improve the radiation pattern in the presence of cylindrical obstacles is proposed as a logical extension to the existing model.     

Rates of reaction of atomic oxygen with C2H3F,C2H3Cl,C2H3Br, 1,1-C2H2F2, and 1,2-C2H2F2

Rate constants for the reactions of atomic oxygen (O³P) with C₂H₃F, C₂H₃Cl, C₂H₃Br, 1,1-C₂H₂F₂, and 1,2-C₂H₂F₂ have been measured at 307°K using a discharge-flow system coupled to a mass spectrometer. The rate constants for these reactions are (in units of 10¹¹ cm³ mole^?1 s^?1) 2.63 ± 0.38, 5.22 ± 0.24, 4.90 ± 0.34, 2.19 ± 0.18, and 2.70 ± 0.34, respectively. For some of these reactions, the product carbonyl halides were identified.     

EPR of atomic hydrogen 1H and 2H in α-quartz

Detailed EPR measurements of the spin-Hamiltonian parameters for the hydrogen atom H⁰ in its principal low-temperature trapping site in X-irradiated α-quartz have been made at several temperatures in the range 40–100 K. Besides the Zeeman splitting matrix ? and the proton hyperfine matrix $\text{A}$_H, the parameters include the super-hyperfine ²⁹Si matrix describing interaction between these cavity wall atoms and H⁰. The measured spin-Hamiltonian parameters for the isotopes ¹H⁰ and ²H⁰ are compared. The trapping site has been identified and is discussed. The hydrogen atom is mobile within this complex cavity comprised of various silicon and oxygen ions.     

On Bifurcating Periodic Solutions at Low Frequency

A study is made of differential equations which have low-frequency periodic bifurcating solutions. It is shown that the classical Poincaré-Hopf technique for constructing periodic solutions encounters difficulties in the low-frequency limit, and that the branches are determined by nonlinear, rather than linear, balances. Two types of models are investigated: one is autonomous and the other non-autonomous, with a forcing term of small, fixed frequency. The latter model is relevant to several fluid-dynamical situations.     

Selenium-sulfur analogs. 4. Synthesis and characterization of (±)-β-(2-amino-1,3-selenazol-4-yl)alanine

The novel amino acid (±)-β-(2-amino-1,3-selenazol-4-yl)alanine 4a was prepared from selenourea and 1,3-dichloropropan-2-one via a four-step synthetic sequence. Nuclear magnetic resonance analysis indicated a downfield chemical shift of δ 0.29 to 0.30 and δ 0.57 for the C₅-proton of the protonated 2-amino-and 2-acetamido-1,3-selenazoles respectively compared with the analogous thiazoles. The infrared spectra of the selenazole and corresponding thiazole compounds were virtually identical.     

Finiteness, 1/N expansion and supersymmetry breaking

The possibility of spontaneous supersymmetry breaking in the limit of large N, in models with an internal O(N) symmetry, is demonstrated by constructing an explicit example in two dimensions. The model is finite and this is shown to be important for the supersymmetry breaking. A general criterion for finiteness of scalar superfield theories in two dimensions is given. Finally, the generalization of our results to three dimensions, and their relevance to four-dimensional models, is discussed.