In situ Raman spectroelectrochemistry as a tool for the differentiation of inner tubes of double-wall carbon nanotubes and thin single-wall carbon nanotubes

In situ Raman spectroelectrochemistry has been used to distinguish between thin single-wall carbon nanotubes (SWCNT) and the inner tubes of double-wall carbon nanotubes (DWCNT). The spectroelectrochemical method is based on the different change of the electronic structure of the inner tube in DWCNT and that of SWCNT during electrochemical charging, which is reflected in the Raman spectra. During electrochemical charging the inner tubes of DWCNT exhibit a delayed attenuation of the intensities of their Raman modes as referred to the behavior of SWCNT of similar diameter. The changes are pronounced for the radial breathing mode (RBM), and thus, these modes are diagnostic for the distinction of inner tubes of DWCNT from the thin SWCNT. The different sensitivities of inner and outer tubes to the applied electrochemical charging is a simple analytical tool for differentiation of SWCNT and DWCNT in a mixture. The significance of the proposed method is demonstrated on a commercial DWCNT sample.     

Introduction of a New Coupling Agent for Selective Coupling of Hydroxy and Amino Group‐Containing Polymers

A new bifunctional coupling agent with an oxazinone and a lactamate group is synthesized. It is shown by means of model reactions that in the presence of aliphatic hydroxy compounds the reaction of the coupling agent is highly selective. At 220 °C, a conversion of the lactamate group of about 90% is observed under elimination of lactam. In a second reaction the oxazinone group is converted with an aliphatic amino compound. This high selectivity is utilized in the synthesis of segmented polyester/polyamide block copolymers by sequential conversion of the coupling agent with hydroxy‐terminated polyesters [poly(butylene terephthalate) (PBT) and polycaprolactone (PCL)] and amino‐terminated polyamide 12 (PA12) under the conditions of reactive extrusion. In the case of the PA12/PBT block copolymer, ductile behavior is observed, whereas the PA12/PCL block copolymer shows elastic properties. Both polymers are phase separated on the nanometer‐scale, as evidenced by AFM and SEM. The thermal behavior of the polymers is affected by the influence of the individual blocks.

     

Metal nitride cluster fullerenes: their current state and future prospects

The world of endohedral fullerenes was significantly enlarged over the past seven years by the cluster fullerenes, which contain structures such as the M(2)C(2) carbides and the M(3)N nitrides. While the carbide clusters are generated under the standard arc-burning conditions according to stabilization conditions, the nitride cluster fullerenes (NCFs) are formed by varying the composition of the cooling gas atmosphere in the arc-burning process. The special conditions for NCF synthesis is described in detail and the optimum conditions for the production of NCFs as the main product in fullerene syntheses are given. A general review of all NCFs reported to date consists of the structures, properties, and stability of the NCFs as well as the abundance of the NCFs in the fullerene soot. It is shown that all cages with even carbon atoms from C(68) to C(98) are available as endohedral nitride cluster structures (with the exception of C(72), C(74), and C(76)). Specifically, the NCFs form the largest number of structures that violate the isolated pentagon rule (IPR). Finally some practical applications of these cluster fullerenes are illustrated and an outlook is given, taking the superior stability of these endohedral fullerenes into account.     

Carbene Rearrangements, 60.‡ Supramolecular Structure‐Reactivity Relationships: Photolysis of a Series of Aziadamantane@Cyclodextrin Inclusion Complexes in the Solid State

Photolyses of the α‐, β‐ and γ‐cyclodextrin complexes of 2‐aziadamantane ( 1 ) in the solid state afforded markedly different product distributions, as determined by quantitative GC and HPLC analyses. The results are discussed with respect to the structures of the inclusion complexes.     

Die Mantelreibung – leistungsbestimmender Parameter bei verrohrten Großlochbohrungen im Lockergestein

Skin friction – a dominant performance parameter for casing rotary drilling piles in cohesive soils. The paper deals with basic treatment of the problem of the skin friction at casing tube while setting up casing rotary drilling piles. A practical forecast algorithm will be presented to determine the necessary torsional moment from the calculated mean skin friction and so to realize a good performance and economic selection of drilling rigs.     

Synergism in the wetting properties of ternary surfactant mixtures

It has been shown that ternary surfactant synergism can be predicted on the basis of nonideality parameters of binary subsystems derived from advancing contact angles. Studies with appropriate surfactant mixtures of glucamides, ether sulfates, secondary alkane sulfonates, and alkylamidopropyl betaines were performed on substrates of different polarity.     

Biological degradation of EDTA: Reaction kinetics and technical approach

The microbial mineralization of EDTA in waste water by a mixed culture was studied with suspended and immobilized cells. Efficient degradation of EDTA could be achieved, though the chelator is stated not to be biodegradable. A complete set of kinetic parameters was determined that enables the modelling of EDTA degradation and, related to this, bacterial growth, ammonium release, maintenance requirement as well as oxygen uptake. In order to obtain important technical scale-up parameters, the microorganisms were immobilized on different carrier particles and employed in continuously operated three-phase airlift-loop reactors. The reactors could be operated at a dilution rate up to D=1·2 h⁻¹ (D≪μ_max) that, at an EDTA concentration of 450 mg dm⁻³, led to EDTA degradation rates up to 12·8 kg m⁻³ day⁻¹. The extent of EDTA deg-radation remained constant at 95–99% with increasing values of D. Achieved kinetic parameters of the biofilm systems were compared with those which were obtained from experiments with suspended cells. © 1998 Society of Chemical Industry     

How background noise shifts eigenvectors and increases eigenvalues in DTI

Indroduction  The signal-to-noise ratio of in vivo diffusion tensor imaging (DTI) is usually very limited, especially if high resolution data is acquired. In a variety of settings, the signal of diffusion weighted images can drop below the background noise level yielding an underestimated diffusion constant. In this work, we report two new artefacts in DTI that are important in this regime. Methods  Both artifacts are described analytically and numerically and are demonstrated in DTI phantoms and in subjects in vivo. Results  First, eigenvectors are systematically shifted towards distinct ‘attractive’ orientations of the gradient scheme. Second, certain eigenvalues can be overestimated due to the underestimation of the measured diffusion, which can result in the misordering of eigenvalues Discussion  We show that these effects are relevant for current clinical settings of DTI.     

Influence of α-dicarbonyl compounds to the molecular weight distribution of melanoidins in sucrose solutions: part 1

The correlations between formation of melanoidins and the content of α-dicarbonyl compounds and colour formation were studied in Maillard reaction model sucrose solutions at high treating temperatures (130 °C) corresponding to the industrial sucrose processing. Molecular weight distribution was determined by gel permeation chromatography (GPC) and α-dicarbonyls as high reactive intermediates of the Maillard reaction were detected by RP-HPLC and GC/MS. Referring to formation of melanoidins, new knowledge could be gained. The investigations clearly point out, that individual α-dicarbonyls are involved in formation of specific molecular weight fractions. 3-Deoxyhexosulose (3-DH) and methylglyoxal are the important α-dicarbonyl compounds in thermal-treated sucrose solutions. A low molecular weight fraction with a molecular weight range of <5,800 g/mol preferably occurs when 3-DH is formed in high concentrations. The high increase in intensity of a low molecular weight fraction is combined with a strong colour formation. In contrast to 3-DH, methylglyoxal promotes the formation of high molecular weight fractions between 6,600 g/mol and approximately 17,000 g/mol. Furthermore, model solutions with a high intensity of high molecular weight fractions show an early colour formation during the starting period of the reaction. Indeed, this early browning is not as intensive as the colour formation caused by the low molecular weight fraction during the later stage of the browning reaction. Out of this, 3-DH can be regarded as the most important intermediate for an intensive colour formation in sucrose solutions.