Antiphytopathogenic activity of Psoralea glandulosa (Fabaceae) against Botrytis cinerea and Phytophthora cinnamomi

The resinous exudate, three meroterpenes, namely bakuchiol (1), 3-hydroxybakuchiol (2), 12-hydroxyisobakuchiol (3), and one furanocoumarin, psoralen (4), were isolated from the leaves of culen (Psoralea glandulosa). In addition to these, two semi-synthetic derivatives, bakuchiol acetate (5) and bakuchiol methyl eter (6), were obtained from 1, and were subsequently evaluated in vitro for the inhibitory effect of resin and compounds on the mycelial growth of Botrytis cinerea Pers.: Fr. and Phytophthora cinnamomi Rands. The resinous exudate inhibited the mycelial growth of both the pathogens, while bakuchiol (1) exhibited an inhibitory effect on the mycelial growth of B. cinerea up to 94% at a concentration of 150 mg/L and psoralen (4) reduced the mycelial growth of P. cinnamomi up to 80% at a concentration of 150 mg/L. These compounds have the ability of blocking the development of mycelial growth and may be used as a potential biopesticide in the agricultural sector once the in vivo test results have been validated.     

Rate constants for cyclizations of α-hydroxy radical clocks

The 1-hydroxy-1-methyl-6,6-diphenyl-5-hexenyl radical (4a) and the 1-hydroxy-1-methyl-7,7-diphenyl-6-heptenyl radical (4b) were prepared from the corresponding PTOC esters (anhydrides of a carboxylic acid and N-hydroxypyridine-2-thione). The key step in the synthetic method for the precursors was a coupling reaction of the respective carboxylic acids with the thiohydroxamic acid, which was conducted for ca. 5 min and followed rapidly by chromatography. Rate constants for cyclizations of radicals 4a and 4b in acetonitrile and in THF were measured directly between -30 and 60 °C by laser flash photolysis methods. The Arrhenius functions in acetonitrile are log k = 9.9-2.6/2.303RT and log k = 8.9-4.4/2.303RT (kcal mol(-1)) for 4a and 4b, respectively. Rate constants for cyclizations at room temperature of 9 × 10(7) s(-1) and 4 × 10(5) s(-1) are somewhat larger than the rate constants for cyclizations of analogous alkyl radicals. Crude rate constants at room temperature for H-atom trapping of 4a by thiophenol and 4b by t-butylthiol were k(T) = 1.2 × 10(9) M(-1) s(-1) and k(T) = 2 × 10(7) M(-1) s(-1), respectively, which are modestly larger than rate constants for reactions of alkyl radicals with the same trapping agents.     

Investigation into higher-order mode propagation through orifice plates in circular ducts

Most established techniques for analyzing sound transmission in ducts containing orifices plates are only applicable for plane wave propagation. Once the wavelength of the sound approaches the cross section of the duct, higher order mode propagation in the system must be considered in the analysis. This is a numerically intensive activity if fully coupled calculations of the higher order modes are undertaken. This investigation estimates the acoustic fields in a duct with a simple orifice plate installed using an uncoupled model to estimate the higher order mode contribution. The uncoupled model is then used as the basis for a hybrid decomposition approach to estimate the sound field in the regions before and after the orifice plate installed in a circular duct. This approach is applied to a duct, excited by a point source over a wide frequency range, containing a single orifice plate installed a distance inside the duct. Different orifice plates with one, two and multiple openings are investigated. Of particular interest is the location of the point source relative to the duct axis. If the source is located concentric to the duct axis then, without any orifice plate present, only axially symmetric higher order modes may be excited in the duct. Thus, the investigation considers the point source located in the concentric position and in eccentric positions to vary the contribution from the different types of higher order mode. Estimates of the acoustic fields in the duct obtained using the hybrid decomposition approach are compared with measured data and the applicability of using an uncoupled estimate for the acoustic fields is commented on.     

Studien zum Vorgang der Wasserstoffübertragung. 35. Mitt. Aufklärung des Verlaufs der elektrochemischen Reduktion von Diarylsulfonen zu Arylsulfinsäuren mit Hilfe polarographischer und voltametrischer Messungen

Ohne Zusammenfassung     

RPA for the linewidth of the van der Pol Oscillator

The linewidth of then component van der Pol Oxcillator is calculated in random phase approximation. Forn=2 this model describes a single mode laser. This approximation is asymptotically correct for weak and strong pumping and also in the largen limit for all pumping. The result is in good agreement with numerical results forn=2 in the whole range including the threshold. The corresponding vertex renormalized approximation on the other hand yields poor agreement and the wrong asymptotic value in the limit of strong pumping. The reason for this failure is discussed.     

Synthesis and structure of K+ [iPrN=C=P]-, a 1-aza-3lambda3-phospha-3-allenide

2-Isopropyl(trimethylsilyl)amino-1lambda3-phosphaalkyne 1 reacts with potassium tert-butoxide to form potassium 1-isopropyl-1-aza-3lambda3-phospha-3-allenide (2). This compound was structurally characterized as the corresponding 18-crown-6 ether complex 3. The molecular structure of 1 was also determined in order to compare the bonding situation in the anion and the neutral lambda3-phosphaalkyne. Compound 3 contains a nitrogen-carbon-phosphorus group for which the parameters were shown by X-ray structural analysis and quantum chemical calculations to lie between the extrema N-C[triple bond]P and N=C=P, suggesting reactivity typical of an ambident anion. This is indeed the case, as subsequent reaction of 2 with chlorotrimethylsilane at nitrogen regenerates the lambda3-phosphaalkyne 1; with chlorotriphenylsilane the new derivative 4 is formed. In contrast, chlorotrimethylstannane reacts at phosphorus, giving the 1-aza-3lambda3-phosphaallene isopropyliminomethylidene(trimethylstannyl)phosphane 5.     

On the theory of turbulence: A non eulerian renormalized expansion

A non Eulerian framework for a renormalized theory of isotropic homogeneous steady state turbulence at high Reynold's numbers is developed. By construction it is invariant under random Galilei transformations. A direct interaction factorization is free of infrared singularities and yields Kolmogorov scaling for the static as well as for the dynamic correlation and response functions.