b1Σ+ and a1Δ emissions from group VI-VI diatomic molecules: b0+ → X10+, x21 emissions of TeO and TeS

Near infrared emissions of the b0⁺→X₁0⁺, X₂1 band systems of TeO and TeS have been observed by chemiluminescence studies in a fast flow system. In both cases the b → X₁ and b → X₂ subtransitions were found to occur with similar intensities. Analysis of the spectra yielded values of the b0⁺ energies T_e of 9966 ^± 10 cm^?1 and 8457 ^± 10 cm^?1 for TeO and TeS, respectively, and vibrational separations ω_e in these states of 726 ^± 10 cm^?1 and 436 ^± 5 cm^?1. The energy splittings of the X₁0⁺ and X₂1 ground state levels were determined to be 789 ^± 10 cm^?1 and 829 ^± 5 cm^?1.     

Novel cellulose fibre reinforced thermoplastic materials

Spun cellulose fibres from the viscose, lyocell and carbamate processes have been used to reinforce thermoplastic commodity polymers, such as polypropylene (PP), polyethylene (PE) and (high impact) polystyrene (HIPS) as well as poly(lactic acid) (PLA) and a thermoplastic elastomer (TPE) for injection moulding applications. A specially developed double pultrusion technique has been employed for compounding. Fibres were analysed in single fibre tensile tests. Strength, stiffness, impact strength, and heat distortion temperature (HDT) were determined for injection-moulded standard test specimen and structural features were revealed by scanning electron microscopy. A strong reinforcing effect was observed in all cases. In particular, high tenacity tyre cord rayon gives excellent composite strength and impact strength, often doubling or tripling the pristine matrix values. In the case of PP, Lyocell type fibres provide enhanced stiffness and HDT, and thus the combination of both fibre types leads to a balanced composite property profile. The PE case is very similar to PP. For HIPS mainly strength and stiffness is increased, while for TPE the property profile is changed completely. With PLA, a biogenic and biodegradable composite with excellent mechanical properties is presented.     

Beitrüge zur Chemie der Si-N-Bindung,XXII N,N′-Tetrakis(trimethylsilyl)methylendiamin

N.N′-Tetrakis-Tetrakis(trimethylsilyl)methylenediamine is prepared by the reaction of lithium-bis(trimethylsilyl)amide with tris(chloromethyl)amine.     

Sample preparation for the determination of radiocalcium by accelerator mass spectrometry

An accelerator mass spectrometric (AMS) technique has been developed for determining ⁴¹Ca/⁴⁰Ca ratios at terrestrial levels of 10^?16?10^?14. Calcium is extracted as calcium oxide from bone and rock samples. The calcium oxide is converted into calcium metal and subsequently into calcium hydride in a two-step reduction process. From these calcium hydride samples 5–10 μA of a negative-ion beam of CaH^?₃ is produced. A new gas-ionization detector and a high-resolution velocity detector allow discrimination against ⁴¹K and the stable isotopes of Ca, resulting in background levels of less than 6 × 10^?16. Hence it is possible (for the first time without pre-enrichment) to study the distribution of ⁴¹Ca in the terrestrial environment. The AMS method for ⁴¹Ca determination is applicable to samples of less than 1 g.     

Evaluation of new organosolv dissolving pulps. Part I: Preparation, analytical characterization and viscose processability

New acidic organosolv pulping processes, such as Acetosolv, Formacell and Milox, promise to have superior potential in terms of purification selectivity and specific investment costs. Consequently, a thorough investigation of these new acidic pulping processes in comparison to state-of-the-art acidic magnesium sulfite technology was conducted. The impact of pulping and bleaching parameters on the physical and chemical characteristics was studied to compare process efficiency and selectivity for each type of pulp made from Eucalypt wood. In addition to a detailed analysis of the chemical composition and physical properties on a molecular and supramolecular level, the TCF-bleached dissolving pulps were tested for their applicability in viscose fiber production. The influence of pulp properties as determined by standard and advanced analytical methods on process performance and selected fiber properties is emphasized.     

A Strategy for the Regional Characterization of Potential Energy Surfaces

The problem of characterization of a region of an n-dimensional potential energy surface with maximization of the quality of representation for a given amount of computational effort is examined with the aid of well known theorems from numerical analysis. A choice of nonlinear grid and a representation of the potential expanded in Chebyshev polynomials is shown to be efficient. The strategy was applied to a two-dimensional analytical representation of a transition state and to the ground-state equilibrium geometry region of the Hartree-Fock potential energy surface obtained with split-valence basis sets for H₂O, H₂S, and H₂Se. Results are reported for the equilibrium geometries and force constants for these molecules. Results are comparable to those obtained by others for H₂O and H₂S. A full set of values is reported for H₂Se.