Upper and lower bounds of buckling loads

Upper and lower bounds of buckling load for a nonuniform elastic column under conservative loading are considered. Compatible admissible moment and displacement functions are expressed in terms of a compatible coordinate system. The generalized Timoshenko Quotient and the modified Schreyer and Shih formula are the proposed upper and lower bounds. Both bounds when iterated converge to the exact buckling load. The method described here is simple and convenient and applies to all self-adjoint problems without exception.     

Ethanol reforming processes over ZnO-supported palladium catalysts: Effect of alloy formation

ZnO- and SiO₂-supported palladium catalysts were evaluated in the ethanol steam-reforming and oxidative ethanol steam-reforming reactions in the temperature range 548–723 K. The catalysts were characterized before and after reaction by X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy and infrared spectroscopy using CO as a probe molecule. On silica-supported Pd catalyst, ethanol decomposes into H₂, CO and CH₄ in both steam-reforming and oxidative steam-reforming reactions. In contrast, ZnO-supported catalysts containing the PdZn phase exhibit a better catalytic performance for hydrogen production through dehydrogenation of ethanol into acetaldehyde and ulterior reforming.     

Macromolecular assembly of Helicobacter pylori urease investigated by mass spectrometry

The supramolecular assembly of Helicobacter pylori urease was studied by nanoflow electrospray ionization orthogonal time-of-flight mass spectrometry. The measured molecular mass of the urease complex of 1.06 MDa corresponds to a dodecameric (alphabeta)(12) assembly of urease alpha (26 kDa) and beta (61 kDa) subunits. The dodecamer disassembles readily into (alphabeta)(3) subunits in solution and under controlled collisional-induced dissociation in the gas phase. This is in strong support of an ((alphabeta)(3))(4) architecture consistent with the recently published x-ray structure. In vitro, the alpha and beta subunits are capable of re-assembling to (alphabeta)(3), but not further to the dodecameric complex.     

Aufbau der Ligandsysteme des C,D-Tetradehydrocorrins und Isobakteriochlorins durch Sulfidkontraktion. Kurzmitteilung

Synthesis of C, D-Tetradehydrocorrins and Isobacteriochlorins via Sulfide Contraction The reaction sequences shown in Schemes 4 and 5 illustrate the use of the sulfide contraction method for the synthesis of isobacteriochlorins and (metal free) C, D-tetradehydrocorrins. The tetradehydrocorrin synthesis fills a gap in a spectrum of corrinoid (A → D) ring closures that ranges from A.W. Johnson's oxidative (A → D)-cyclizations to octadehydrocorrinoids on the one side to the photochemical 1, 19-secocorrin → corrincycloisomerization on the other (Scheme 7). Such a multiplicity of reaction paths towards corrinoids is of interest in connection with the problem of the origin of the corrin structure.     

Modification of ISFETs by covalent anchoring of poly(hyroxyethyl methacrylate) hydrogel. Introduction of a thermodynamically defined semiconductor-sensing membrane interface

Silicon dioxide ion-sensitive field effect transistors were modified by silylation with methacryloxypropyltrimethoxysilane (MPTS) and with in situ photopolymerized poly(hydroxyethyl methacrylate). Subsequently, the covalently linked methacrylate was swollen with a buffered potassium chloride solution, prior to the introduction of a hydrophobic sensing membrane. The introduced hydrogel layer effects a significant reduction in the peak-to-peak noise levels and eliminates completely interference from carbon dioxide. The method is compatible with integrated circuit photolithographic techniques and improves the development of potentiometric biosensors and chemical sensors.     

A half-century of nonclassical organometallic chemistry: a personal perspective

A review of some developments in transition metal (nonclassical) organometallic chemistry is presented, with emphasis on areas to which the author himself has made major and/or seminal contributions: especially fluxional organometallics, fluxional metal carbonyls, and the discovery and full explanation of agostic hydrogen atoms. An effort has been made to present these topics from the perspective of today rather than in strictly chronological order, with a sufficient number of specific examples to be concrete, but by no means encyclopedic. Particular topics covered are "ring whizzers", concerted shifts of two or more CO ligands, twirling M(CO)(3) groups, and merry-go-rounds. In addition, the following topics are discussed: the unfinished business of mu(2),eta(2),eta(2)-ethene complexes and arene complexes of the lanthanides and actinides.     

Preparation and properties of starch-based colloidal microgels

Novel starch microgels were prepared by emulsion cross-linking and characterized with respect to shape, volume, and mass density. Starch microgels appear to be negatively charged ( approximately -50 mV), with a particle size varying as a function of the type of cross-linker (ca. 0.25-10 microm). Environmental scanning electron microscopy observations show a dependence of the particle swelling on the cross-linking density. Viscosimetry reveals that starch microgels behave as charged polymers, where the reduced viscosity increases with dilution (anomalous viscosity behavior) for sufficiently low kappaalpha (ca. kappaalpha <3), the ratio of the particle radius (a), and the Debye length (kappa(-1)). Analogous results are obtained for reference-charged rigid silica spheres, which approach the hard sphere limit for increasing ionic strengths. The shape of the microgels appears to play a minor role in the anomalous viscosity behavior, which is more likely dominated by electrostatic effects.     

Pedicelloside,nouveau phtalide isole de gentiana pedicellata wall.

The title compound, isolated from $\text{Gentiana pedicellata}$ leaves, is a new alkyl-3-phthalide characterized by an acylated side chain. It has been identified by spectral analysis as [3-(1-β-D-glucosyloxy)-2-hydroxy]benzoyl 3-(3-phthalidyl)-propyl ester.