The ground-state rotational band in 159Tb

162 MeV ⁴⁰Ca ions have been used to Coulomb excite the ground-state band of ¹⁵⁹Tb up to spin $\text{25}\text{2}$. Lifetimes for levels up to spin $\text{25}\text{2}$ have been determined with DSA and recoil distance methods. Multipole mixing ratios for several cascade transitions were extracted from an analysis of γ-ray angular correlation data. Reduced transition probabilities thus deduced in a model-independent way were found to be in agreement with the rotational model with Q₀ = 7.41 ± 0.06 e · b and g_K?g_R = 1.377 ± 0.010.     

Chromatography in the ancient world?

Indications that already in the Ancient World, methods based on chromatographic principles were utilized, are discussed. As pointed out, they had little to do with chromatography.     

Film drainage between two surfactant-coated drops colliding at constant approach velocity

The drainage of the intervening continuous phase film between two drops approaching each other at constant velocity under the influence of insoluble surfactant is investigated. The mathematical model to be solved is a coupled pair of fourth-order nonlinear partial differential equations which arise from the relationships governing the evolution of the film thickness and the surfactant interfacial concentration in the lubrication approximation. We adopt a simplified approach which uses lubrication theory to describe the flow within the drop, marking a departure from the conventional framework in which Stokes flow is assumed. When the model is solved numerically together with the relevant initial and boundary conditions, the results obtained are compared with those found in the literature using the "boundary integral" method to solve for the flow in the drop phase. The close agreement between the results inspires confidence in the predictions of the simplified approach adopted. The analysis on the effect of insoluble surfactant indicates that its presence retards the drainage of the film: The fully immobile interface limit is recovered even in the presence of a small amount of surfactant above a critical concentration; film rupture is either prolonged or prevented. The retardation of the film was attributed to gradients of interfacial tension which gave rise to the Marangoni effect. A study of the influence of various system parameters on the drainage dynamics was conducted and three regimes of drainage and possible rupture were identified depending on the relative magnitudes of the drop approach velocity and the van der Waals interaction force: Nose rupture, rim rupture, and film immobilization and flattening. Finally, the possibility of forming secondary droplets by encapsulating the continuous phase film into the coalesced drop at rupture was examined and quantified in light of these regimes.     

Contribution to the phase diagram of the system PbCl2-AgCI

The side parts of the phase diagram of the binary system PbCl₂-AgCl were studied by using DTA. The only miscibility was found on the silver chloride side up to a concentration of 1.5±0.5 mole% PbCl₂. No solid solution of AgCl in PbCl₂ was observed on the lead chloride side.

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Zusammenfassung Mittels DTA wurden die Randzonen des Phasendiagrammes des binären Systemes PbCl₂-AgCl untersucht. Mischbarkeit konnte lediglich auf der Silberchloridseite bis zu einer Konzentration von 1.5±0.5 mol% mol% PbCl₂ festgestellt werden. Auf der Bleichloridseite konnten keinerlei Mischkristalle zwischen AgCl und PbCl₂ beobachtet werden.

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PbCl₂-AgCl. 1,5±0,5 %. .

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We are very grateful to our colleagues Dr E. Krová and Dr Z. Pokorná for the preparation of the single-crystals and for the chemical analysis.     

Assembly of triple-stranded beta-sheet peptides at interfaces

A 30-residue peptide, BS30, which incorporates two proline residues to induce reverse turns, was designed to form a triple-stranded beta-sheet monolayer at the air-water interface. To discern the structural role of proline, a second peptide, BS30G, identical to BS30 but with glycine residues replacing proline, was prepared and examined in parallel fashion. Surface pressure-molecular area isotherms indicated a limiting area per molecule (ca. 460 A(2)) for BS30 that corresponds well to that estimated from the known dimensions of crystalline beta-sheet monolayers (492 A(2)). Comparable measurements on BS30G yielded a smaller molecular area (380 A(2)). Grazing incidence X-ray diffraction measurements performed on the BS30 monolayer at nominal area per molecule of 500 A(2), exhibited two Bragg peaks corresponding to 4.79 and 34.9 A spacings, consistent with formation of triple-stranded beta-sheet structures that assemble into two-dimensional crystallites at the air-water interface. Visualized by Brewster angle microscopy, BS30 monolayers displayed uniform, solidlike domains, whereas BS30G appeared to be disordered.     

Biosynthesis of 3-(3'-isocyanocyclopent-2-enylidene) propionic acid by trichoderma hamatum (bon.) bain. aggr.

L-Tyrosine is degraded by $\text{Trichoderma}$$\text{hamatum}$ to 3-(3'-isocy-anocyclopent-2-enylidene) propionic acid having Z-configuration about the exocyclic double bond, by fission of the aromatic ring and cyclization of the side chain of the amino acid.     

Imaging thin films of nanoporous low-k dielectrics: comparison between ultramicrotomy and focused ion beam preparations for transmission electron microscopy.

Ultramicrotomy, the technique of cutting nanometers-thin slices of material using a diamond knife, was applied to prepare transmission electron microscope (TEM) specimens of nanoporous poly(methylsilsesquioxane) (PMSSQ) thin films. This technique was compared to focused ion beam (FIB) cross-section preparation to address possible artifacts resulting from deformation of nanoporous microstructure during the sample preparation. It was found that ultramicrotomy is a successful TEM specimen preparation method for nanoporous PMSSQ thin films when combined with low-energy ion milling as a final step. A thick, sacrificial carbon coating was identified as a method of reducing defects from the FIB process which included film shrinkage and pore deformation.     

Structure of plumbazeylanone: a novel trimer of plumbagin from plumbago zeylanica

Plumbazeylanone, a quinone from Plumbago zeylanica is probably 5b,11a,12,12a-tetrahydro-1,7-dihydroxy-5b-(8-hydroxy-3-methyl-1,4-naphthoquinon-2-yl)-5a,12a-dimethyl-5a$\text{H}$-dibenzo[$\text{b}$,$\text{h}$]fluorene-5,13:6,11-diquinone, a novel trimer of plumbagin with an additional methyl group.     

具有中孔结构的SO2-4/Zr-HMS型固体超强酸的合成和结构表征

用TEOS-Zr-HAD-H2O-Ethanol体系合成了Zr-HMS的中孔分子筛, 脱除模板剂后用0.5 mol/L硫酸处理和550 ℃高温焙烧3 h, 制得一种中孔SO2-4/Zr-HMS超强酸催化剂. 采用XRD对其结构进行表征. 用指示剂法、 TG和NH3-TPD对其酸性进行了表征. 结果表明, 经过一系列处理后制得的SO2-4/Zr-HMS催化剂具备HMS中孔分子筛的结构特征, 其酸强度可达H0=-13.75. 在锆及SO2-4含量远远低于SO2-4/ZrO2的条件下, SO2-4/Zr-HMS催化剂对于苯酐和正丁醇酯化反应的活性仍高于SO2-4/ZrO2催化剂.