Echinopsacetylenes A and B, new thiophenes from Echinops transiliensis

Two new polyacetylene thiophenes, echinopsacetylenes A and B (1 and 2), were isolated from the roots of Echinops transiliensis. The structures of 1 and 2 were elucidated on the basis of spectroscopic analyses and chemical transformations. Echinopsacetylenes A (1) is the first natural product possessing an α-terthienyl moiety covalently linked with another thiophene moiety. Echinopsacetylenes B (2) is the first natural thiophene conjugated with a fatty acid moiety. Echinopsacetylene A (1) showed toxicity against the Formosoan subterranean termite (Coptotermes formosanus).     

Fundamental aspects of pulse phase-locked loop technology-based methods for measurement of ultrasonic velocity.

A new instrument based on a constant frequency pulse phase-locked loop concept has been developed to accurately measure the ultrasonic phase velocity in condensed matter. Measurements of the sound velocity in ultrapure water are reported in which both damped and undamped transducers are used with the instrument together with reflectors of various thicknesses placed in the sound propagation path. An analysis of measurements made with the new instrument and similar measurements, taken under identical experimental conditions, using a popular variable frequency pulsed-phase-locked loop instrument is reported. Uncertainties in both measurement systems are analyzed and discussed. A method for measuring inherent phase shifts, not addressed by previous investigators, within the variable frequency pulsed phase-locked loop system and a derivation of the equations that govern the overall use of variable frequency systems using phase-sensitive comparisons are presented. The effects of a finite pulse length on the measurements of phase velocity in dispersive media are addressed in detail.     

REPAIR SYNTHESIS IN HUMAN LYMPHOCYTES PROVOKED BY PHOTOLYSIS OF ETHIDIUM AZIDE

Abstract— The azide analog of ethidium was mixed with human lymphocytes and when photolyzed with visible light provoked repair synthesis as shown by incorporation of tritiated thymidine in the presence of hydroxyurea. The use of photolyzed drug, or incubation of drug-cell mixtures in the dark was without effect. These experiments should prove useful in targeting drug action sites and in studying the details of DNA repair.     

On solutions to coupled multiparameter nonlinear Sturm- Liouville boundary value problems whose state components have a specified nodal structure

In preceding articles ([3] and [5]), we began an examination of the structure of the solution set to the two-parameter system \(\matrix{\qquad\qquad-(p_{1}(x)u^{\prime})^{\prime}+q_1(x)u= \lambda u+f(u,v)u\cr \qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad\qquad in (a,b)\cr \qquad(*)\ \ -(p_{2}(x)v^{\prime})^\prime+ q_{2}(x)v=\mu v+g(u,v)v\cr \qquad\qquad u(a)=u(b)=0=v(a)=v(b).}\) In this article, we treat the case left uncovered in our previous analysis; namely, we assume f (s,0) = 0 and g(0,t) = 0 for all s, t ∈ ?. In this situation, solutions to (*) of the form (λ, μ, u, 0) or (λ, μ,0,v lie in linear subspaces of ?.² dx (C01 [a, b] 2. As such, they are neither locally expressable as functions of (λ, μ) nor are à priori bounded in terms of (λ, μ), as was crucial to the analysis in [3] and [5]. Nevertheless, we demonstrate that solutions to (*) of the form (λ, μ, u, v) with u having n ? 1 simple zeros in (a, b) and v having m ? 1 simple zeros in (a, b), where n and m are positive integers, arise as global secondary bifurcations from solutions of the form (λ,μ,u,0) with u having n ? 1 simple zeros in (a, b) and from solutions of the form (λ, μ, o, v) with v having m ? 1 simple zeros in (a, b). Moreover, we establish that solutions to (*) of the form (λ,μ,u,v) with u having n ? 1 simple zeros in (a, b) and v having m ? 1 simple zeros in (a, b) serve as a link between solutions of the form (λ, μ, u, 0) with u having n ? 1 simple zeros in (a,b) and solutions of the form (λ, μ, 0, v) with v having m ? 1 simple zeros in (a, b). The analysis in this article when combined with that in [3] and [5] provides a fairly comprehensive examination of the structure of the solution set to (*).     

In‐Situ and Ex‐Situ Microscopic Study of Gas Phase Propylene Polymerization over a High Activity TiCl4‐MgCl2 Heterogeneous Ziegler‐Natta Catalyst

In‐situ gas phase poly(propylene) (PP) formation over a high activity TiCl₄‐MgCl₂‐supported Ziegler‐Natta catalyst has been studied by video microscopy combined with ex‐situ light microscopy, SEM, high‐resolution TEM, and STEM/PEELS/EDX for the first time. In‐situ observation revealed rapid formation of poly(propylene) beads 9–10 μm in size (< 1/30 s) as well as growth of significant amounts of polymer within local regions. Catalyst particles containing 2–5 nm‐sized MgCl₂ crystalline domains are subjected to transformations during catalysis that form PP/catalyst aggregated structures of 30–50 μm in size.