First transformations of pyrano[3,4-b]indol-3-ones to salvadoricine and 2,3-diacylindoles

The readily available methylated pyrano[3,4-b]indol-3-ones 1a and 1b were hydrolyzed to furnish the 2-acetylindol-3-alkanoic acids 2 and 4 . Compound 2 was easily transformed selectively to 2-acetyl-3-methylindole ( 3 , salvadoricine). Substrate 1b reacts with molecular oxygen from the air only in the presence of a catalyst to give 2,3-diacetylindole ( 5 ) while 1a reacts with nitrosobenzene via a proposed Diels-Alder step to yield 2-acetylindole-3-carbaldehyde ( 6 ). The latter product can also be obtained in low yield from the reaction of 1a with molecular oxygen from the air.     

Preparation of calcium alginate nanoparticles using water-in-oil (W/O) nanoemulsions

A procedure for the preparation of calcium alginate nanoparticles in the aqueous phase of water-in-oil (W/O) nanoemulsions was developed. The emulsions were produced from mixtures of the nonionic surfactant tetraethylene glycol monododecyl ether (C(12)E(4)), decane, and aqueous solutions of up to 2 wt % sodium alginate by means of the phase inversion temperature (PIT) emulsification method. This method allows the preparation of finely dispersed emulsions without a large input of mechanical energy. With alginate concentrations of 1-2 wt % in the aqueous phase, emulsions showed good stability against Ostwald ripening and narrow, monomodal distributions of droplets with radii <100 nm. Gelation of the alginate was induced by the addition of aqueous CaCl(2) to the emulsions under stirring, and particles formed were collected using a simple procedure based on extraction of the surfactant on addition of excess oil. The final particles were characterized using cryo-transmission electron microscopy (cryo-TEM) and dynamic light scattering (DLS). They were found to be essentially spherical with a homogeneous interior, and their size was similar to that of the initial emulsion droplets. The herein presented "low-energy" method for preparation of biocompatible nanoparticles has the potential to be used in various applications, e.g., for the encapsulation of sensitive biomacromolecules.     

Determination of aromatic hydrocarbons in asphalt release agents using headspace solid-phase microextraction and gas chromatography-mass spectrometry

The possibility of quantitative analysis of aromatic hydrocarbons in oil-based asphalt release agents was investigated using headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS). The target analytes studied were benzene, toluene, ethylbenzene, p-, m-, and o-xylene (BTEX) and 1,3,5-trimethylbenzene and 1,2,4-trimethylbenzene. Experimental parameters influencing HS-SPME efficiency were studied (equilibration time between sample and headspace and between headspace and SPME fiber, sample amount and sample matrice effects). A HS-SPME method using hexadecane as a surrogate matrice was developed. The detection limit was estimated as 0.03-0.08 ppm (w/w) for the target analytes investigated. Good linearity was observed (R2 > 0.999) for all calibration curves at high, medium and low concentration level. The repeatability of the method (RSD, relative standard deviation) was found to be less than 10% (generally less than 5%) in triplicate samples and approximately 2% at eight consecutive tests on one and the same sample. The accuracy of the method given by recovery of spiked samples was between 85 and 106% (generally between 95 and 105%). The HS-SPME method developed was applied to four commercially available asphalt release agents. External calibration and standard addition approaches were investigated regarding accuracy. The results showed that standard addition generates higher accuracy than external calibration. The contents of target aromatic hydrocarbons in the asphalt release agents studied varied greatly from approximately 0.1-700 ppm. The method described looks promising, and could be a valuable tool for determination of aromatic hydrocarbons in different types of organic matrices.     

Darstellung,struktur und eigenschaften on bis(cyclopentadienyl)oxalatotitan(IV) und bis(cyclopentadienyl)bis(hydrogenmaleinato)titan(IV)

The reaction of (π-C₅H₅)₂TiCl₂ with oxalic acid or maleic acid in aqueous solution yields dicyclopentadienyloxalatotitanium(IV) or dicyclopentadienylbis(hydrogenmaleato)titanium(IV), respectively. X-ray analyses show that both compounds are monomeric. The oxalate group acts as bidentate chelating ligand and each of the hydrogenmaleate groups is bonded via one oxygen atom to the titanium atom.     

二维传声器阵列测量技术及其对飞机进场着陆过程噪声的实验研究

发展了一种由111个传声器组成的M维平面传声器阵列测量技术,111个传声器在平面阵列中的位置应用随机优化的方法确定,从而保证平面传声器阵列在感兴趣的测量频率范围内具有理想的性能,并应用数值模拟的方法检验了平面传声器阵列的频谱特性.应用此平面传声器阵列对当前流行的民用客机进场着陆过程中飞机噪声源进行了测量分析,实验结果表明应用此项技术可以辨别出在飞机表面上所有重要的噪声源,并可获得全尺寸飞机机体重要噪声源的详细的频谱特性、指向特性和声级变化.     

Ionization of clusters in strong x-ray laser pulses

The effect of intense x-ray laser interaction on argon clusters is studied theoretically with a mixed quantum/classical approach. In comparison to a single atom we find that ionization of the cluster is suppressed, which is in striking contrast to the observed behavior of rare-gas clusters in intense optical laser pulses. We have identified two effects responsible for this phenomenon: A high space charge of the cluster in combination with a small quiver amplitude and delocalization of electrons in the cluster. We elucidate their impact for different field strengths and cluster sizes.     

Small-Molecule Diffusion in Semicrystalline Polymers as Revealed by Experimental and Simulation Studies

Summary: Diffusion of n-hexane in poly(ethylene-co-1-hexene)s with 15–75 wt.% crystallinity was studied by desorption experiments analyzing data using the Fickian equations with a concentration dependent diffusivity. The effect of the impenetrable crystalline phase on the penetrant diffusivity (D) is described by D = D_a/(τβ), where D_a is the diffusivity of the amorphous polymer, τ is the geometrical impedance factor and β is a factor describing the constraining effect of the crystals on the non-crystalline phase. For a polymer with 75 wt.% crystallinity, τβ varied markedly with penetrant concentration (v_1a) in the penetrable phase: 1000 (v_1a = 0) and 10 (v_1a = 0.15). This penetrant-uptake had no effect on the gross crystal morphology, i.e. β must be strongly dependent on v_1a. Samples saturated in n-hexane exhibited a penetrant-induced loosening of the interfacial structure, as revealed by an increase in crystal density that require an increased mobility in the interfacial component and by a decrease in the intensity of the asymmetric X-ray scattering associated with the interfacial component. The geometrical impedance factor has been modelled by mimicking spherulite growth and τ was obtained as the ratio of the diffusivities of the fully amorphous and semicrystalline systems. The maximum τ obtained from these simulations is ca. ten, which suggests that β in the systems with v_1a = 0.15 takes values close to unity. The simulations showed that the geometrical impedance factor is insensitive to the ratio of the crystal width and the crystal thickness. A free path length scaling parameter characteristic of the amorphous phase correlated with τ.