Certification of 22 elements in a pure copper (99.5%) sample for spark emission and X-ray fluorescence spectrometry (CRM BAM-376)

 The element contents of Ag, Al, As, Be, Bi, Cd, Co, Cr, Fe, Mg, Mn, Ni, P, Pb, S, Sb, Se, Sn, Te, Ti, Zn and Zr in a pure copper (99.5%) sample (CRM BAM-376) for use in spark emission and X-ray fluorescence spectrometry were certified and the certified values are given. For Si, the certification has not yet been completed, the content of this element will be certified later. The sample was produced and certified in collaboration with the Committee of Chemists of the GDMB Gesellschaft für Bergbau, Metallurgie, Rohstoff- und Umwelttechnik. Data of the homogeneity testing and the certification campaign with 14 participating laboratories using different analytical methods are reported. Received: 3 February 1997/Revised: 21 February 1997/Accepted: 5 March 1997     

The effect of the curing agent content on the curing and liquid‐crystalline phase of liquid‐crystalline epoxy resin

The effect of the curing agent content on the curing behavior and liquid‐crystalline (LC) phase of the liquid‐crystalline epoxy (LCE) resin 4,4′‐di(2,3‐epoxypropyloxy)phenyl benzoate was studied. Diaminodiphenylester (DDE) was used as a curing agent. The curing behavior was observed via differential scanning calorimetry, and the LC phase was investigated with a polarized optical microscopy. The LC phase in the LCE/DDE mixture with a high DDE content was developed during curing. The onset time was inversely proportional to the DDE content. The mesophase stability of LCE/DDE was enhanced by the addition of large amounts of DDE. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 374–379, 2001     

Rotaxane Type Complexation Behavior of Cyclodextrins with Zinc (II) Tetraphenylporphyrin-Viologen Linked Compounds

The complexation behavior of zinc (II) tetraphenylporphyrin-viologen covalently linkedcompounds by a polymethylene chain (ZnPC_nV²⁺; n = 4–9) withtri-O-methyl--cyclodextrin (TM--CD) was investigated by meansof ¹H NMR and UV/Vis absorption spectrometry in acetonitrile-water (1:1, v/v).The ¹H NMR spectra indicated that ZnPC_nV²⁺ existed as a mixture ofa dimer and a monomer at high concentration (>1 × 10^-3 M). The dimerwas degraded to the monomer upon complexation with TM--CD involving theformation of 1:1 and 1:2 (ZnPC_nV²⁺: TM--CD) complexes, whichwas observed by UV/Vis spectrometry. Furthermore, ¹H NMR spectra exhibitedthat there are at least two types of structures for these complexes, one is a fastexchanging complex, and another is a slow exchanging one. A slow exchanging complexcould be assigned as a rotaxane type structure in which the methylene chain moiety ofZnPC_nV²⁺ penetrated into the cavity of TM--CD. Discrete formationconstants for these complexes were evaluated. The values were little affected by the spacermethylene chain length (n 7).     

X-ray photoelectron (ESCA) spectra of some fluorine containing aluminas

The binding energies of the F(1s) and Al(2p) electrons in fluorine containing alumina catalysts are reported. The X-ray photoelectron peaks confirm the formation of a bulk phase of AlF₃ at higher fluorine contents, whereas the fluorine signals at lower percentages originate from surface groups which are substituted by fluorine. By comparing X-ray photoelectron spectroscopy with X-ray diffraction we conclude that the combination of these techniques is a potential tool in detecting crystals on a catalyst surface which have a size under the detection limit of X-ray diffraction.

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F(1s) Al(2p) , . AlF₃ , , . , , , .

     

V2O5/TiO2 oxidation catalysts. II. Texture properties

The texture properties (specific surface area and porosity) of V₂O₅/TiO₂ catalysts obtained from VO(acetylacetonate)₂ have been studied. The presence of sodium leads to a marked decrease in the S_BET values, probably as a consequence of the formation of Na-V bronzes, which lead to a rutilization of the support.

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( ) V₂O₅/TiO₂, - VO()₂. S_BET, , Na-V, .

     

Synthesis of novel poly(meth)acrylates containing tetracyanocyclopropyl groups as piezoelectric chromophores and their properties

p‐(2,2,3,3‐Tetracyanocyclopropyl)phenoxyethyl acrylate ( 5a ) and p‐(2,2,3‐tetracyanocyclopropyl)phenoxyethyl methacrylate ( 5b ) were prepared by the reactions of bromomalononitrile with p‐(2‐acryloyloxyethoxy)benzylidenemalononitrile and p‐(2‐methacryloyloxyethoxy)benzylidenemalononitrile, respectively. Monomers 5a and 5b were polymerized with free‐radical initiators to obtain polymers with multicyanocyclopropane functionalities in the pendant group. The resulting polymers were soluble in acetone, and the inherent viscosities were 0.25–0.30 dL/g. Solution‐cast films showed thermal stability up to 300 °C with glass‐transition temperatures of 140–156 °C. The dipole moments of 5a and 5b , calculated by the atom superposition and electron delocalization molecular orbital method, were 7.58–7.30 D. Piezoelectric coefficients (d₃₁) of the poled polymer films were 1.8–1.9 pC/N, acceptable values for piezoelectric device applications. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 379–384, 2002     

Entangling Light in its Spatial Degrees of Freedom with Four‐Wave Mixing in an Atomic Vapor

Nonlinearities in atomic vapors allow the production of “entangled images”—beams of light whose transverse light distributions exhibit localized correlations in their unavoidable quantum fluctuations (see picture). These spatially entangled beams may prove useful to reduce the noise in absorption imaging and beam positioning below the quantum noise level, as well as for quantum information applications.

     

Synthetic analogs of dioncophylline and michellamines by stille coupling

Dioncophielline and Michellamine Analogs S‐5, R‐5, S‐7, R‐7, S,S‐8, R,R‐8 and R,S‐8 were synthesized by using Stille coupling condition (Pd°‐mediated cross coupling) proceeds in low yield when using stannanes 1 or 2 with tetrahydroisoquinolinyl bromide 3 . The addition of tetrahydroisoquinolinyl iodide 4 instead of 3 significantly improves the efficiency of the coupling and providing a variety of Dioncophielline and Michellamine analogs in moderate yields.     

Uncertainty of measurement. Twenty years afterwards

The application of the concept “uncertainty” causes considerable difficulties. In this paper an analysis of the intrinsic contradictions of the concept itself and its relationship with the statements of metrology is given with the aim of establishing possible reasons for these difficulties. As a result of this analysis several examples are presented to demonstrate the conflicts of the concept and its several statements in the general fundamental notions of metrology. Received: 16 February 2001 / Revised: 2 April 2001 / Accepted: 9 April 2001     

A novel reduction of sodium alkyl thiosulfates with InCl3(cat.)/Sm(0) system in aqueous media: Facile synthesis of disulfides

A novel reduction of sodium alkyl thiosulfates with InCl₃(cat.)/Sm(0) system in aqueous media has been developed, which generates the corresponding disulfides in good yields. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:376–379, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20023     

Complexation thermodynamics of imine-type bis(benzocrown ether)s. Part I. Sandwich complexation of K+, Rb+, Cs+ and Tl+ with polymethylene andm-Phenylene bridged carbonylhydrazones of 4′-formylbenzo-15-crown-5

The complexation thermodynamics of polymethylene andm-phenylene bridged carbonylhydrazones of 4-formylbenzo-15-crown-5 with K⁺, Rb⁺, Cs⁺ and Tl⁺ was investigated by spectrophotometric titrations in methanol at 283–313 K. The carbonylhydrazone sequences in the bridge of the bis(benzocrown ether)s are optical sensors for the sandwich complexation of metal ions. Within the homologous series of polymethylene bridged carbonylhydrazones a stability peak was found for the sandwich complexes of the propylene bridged compound with K⁺, Rb⁺ and Tl⁺. The potassium complex of this ligand shows the highest stability constant compared to all other known bis(benzo-15-crown-5) complexes with K⁺ in methanol.In terms of thermodynamics the formation of intramolecular sandwich complexes is driven by a gain of enthalpy. The unusual high gains of enthalpy and losses of entropy on formation of the most stable sandwich complexes allow us to propose an additional stabilization of the sandwich arrangement by intramolecular hydrogen bridge bonds. The H ^o-TS ^o diagram gave an excellent straight line allowing discussion of the enthalpy-entropy compensation effect at these complexation reactions.     

Interface Dissipative Mechanisms in an Elastomeric Matrix Reinforced with MWCNTs

Dissipative mechanisms occurring at the interface between multiwall nanotubes (MWCNT) and an elastomeric matrix are investigated and quantitatively predicted through analytical equations derived from a micromechanical model. The effects of MWCNT aspect ratio on dissipative properties of the reinforced system are investigated at high strains (100–300%). Cyclic tensile tests illustrate that the fraction of dissipated strain energy increases with the amount of MWCNT and varies with their aspect ratio. Lower mean diameter MWCNT are able to dissipate a higher amount of strain energy. The model developed on the basis of the shear lag theory correctly predicts the dissipated strain energy at high strains, taking into account the different contributions to the mechanical behavior of nanotubes' different aspect ratios.

     

Water‐Based Adhesives with Tailored Hydrophobic Association: Dilution Resistance and Improved Setting Behavior

Hydrophobic association and stimuli‐responsiveness is a powerful tool towards water‐based adhesives with strongly improved properties, which is demonstrated based on the example of hydrophobically modified alkali‐soluble latexes (HASE) with modulated association. Their rheological properties are highly tunable due to the hydrophobic domains that act as physical crosslinking sites of adjustable interaction strength. Ethanol, propanol, and butanol are used as water‐soluble model additives with different hydrophobicity in order to specifically target the association sites and impact the viscoelastic properties and stimuli‐responsiveness. The rheological and mechanical property response upon dilution with water can be tailored, and dilution‐resistant or even dilution‐thickening systems are obtained. The investigations are of high importance for water‐based adhesives, as our findings provide insight into general structure–property relationships to improve their setting behavior, especially upon contact with wet substrates.

     

Correlated electron-pair properties of the Li atom in momentum space

On the basis of multiconfiguration Hartree–Fock calculations, correlated electron-pair intracule (relative motion) and extracule (center-of-mass motion) properties are reported for the Li atom in momentum space. The present results are more accurate and consistent than those in the literature. Received: 10 September 2001 / Accepted: 11 December 2001 / Published online: 22 March 2002     

Coupled-cluster calculation of dispersion contributions to interaction energies and polarizabilities

 The induced dipole dispersion-type contributions to the two-body and nonadditive three-body energies and electric dipole polarizabilities are studied for long-range interactions involving the He, Ne, Ar and Kr atoms and the H₂ and N₂ molecules. The coupled-cluster singles and doubles model and large basis sets are used. Comparison of the energy contributions with data derived from experiment shows in most cases the deviations to be less than 1%; therefore, it may be expected that the calculated polarizability increments are accurately determined and can be used to estimate the accuracy of approximate methods. Received: 20 March 2001 / Accepted: 5 April 2001 / Published online: 27 June 2001     

Amphiphilic Cholic‐Acid‐Modified Dextran Sulfate and its Application for the Controlled Delivery of Superoxide Dismutase

A novel amphiphilic and biodegradable polyelectrolyte DS‐CA is prepared by the esterification of DS with CA. DS‐CA can self‐assemble into stable nanoparticles in water. SOD can effectively associate with DS‐CA at pH = 5.0 by virtue of electrostatic and hydrophobic interactions. SOD release from the complex nanoparticles is slow at pH = 1.2. The release at pH = 7.4 PBS shows an extended behavior and is tunable by changing the weight ratio of SOD to DS‐CA as well as the CA substitution degree. Increasing the CA substitution degree of DS‐CA can significantly enhance the cellular uptake of the loaded SOD. This study demonstrates that the amphiphilic DS‐CA provides a promising strategy for oral delivery of protein/peptide drugs.

     

Development of Semiconducting Polymer Nanoparticles for Photoacoustic Imaging

Semiconducting polymer nanoparticles (SPNs) have evolved into a new class of photonic materials with great potential for biomedical applications. Depending on the polymer structures, SPNs can be developed into optical agents for fluorescence and chemiluminescence imaging, photosensitizers for photodynamic therapy, and heat converters for photothermal therapy. In this feature article, recent work is summarized on the development of SPNs for in vivo photoacoustic (PA) imaging, a state‐of‐the‐art imaging modality that converts light energy into mechanical acoustic waves to provide deep tissue penetration. The structure–property relationship and doping approaches are discussed to reveal the importance of promoting nonradiative decay in amplifying the PA brightness of SPNs. Moreover, their imaging applications, including lymph node mapping, tumor imaging, and monitoring of pathological indexes, are highlighted. These studies demonstrate that SPNs can serve as versatile PA agents for advanced molecular imaging applications.

     

Cycloaddition of bis‐1,3‐dipolar reagents to 1,3‐diarylprop‐2‐en‐1‐ones

Bis pyrazolines and isoxazolines were prepared by 1,3‐dipolar cycloaddition of benzene‐1,3/1,4‐dicarboxaldehyde dihydrazones and dioximes to 1,3‐diaryl‐prop‐2‐en‐1‐ones. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:379–383, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10169