Materials Literature
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By using 30/70 polyethersulfone/NMP (N-methyl-2-pyrrolidone) solutions as an example, we have determined the role of air-gap distance on nascent fiber morphology, performance, and thermal properties. An increase in air-gap distance results in a hollow fiber with a less layer of fingerlike voids and a significant lower…
Quantitative x-ray diffraction investigations were performed on ultrafine-grained copper samples with various crystallite sizes processed by severe plastic deformation. In the x-ray diffraction patterns, common features such as the relative maximum intensity, considerable broadening, long tails, centroid positions of…
The esterification reaction between wood fibers and maleated polypropylenes was investigated. The reaction was conducted in a reactor in the presence of xylene used as a solvent and sodium hypophosphite as catalyst. The reaction between wood fibers and pure maleic anhydride was also investigated. The appearance of an…
The thermal conductivity of electrochemically etched porous silicon (PS) layers was determined over a wide temperature range (T = 35 - 320 K) using the dynamic technique. Both the doping level of the silicon wafers (p and ) and the porosity P of the porous layers (P = 64 - 89%) were varied. The measured thermal conduc…
We present the results of over 90 tight-binding molecular-dynamics simulations of collisions between three- and five-atom silicon clusters, at a system temperature of 2000K. Much the most likely products are found to be two 'magic' four-atom clusters. We show that previous studies, which focused on the equilibrium bin…
Peltier current lead was proposed to reduce heat leak from the current lead. The temperature of the hot side of semiconductors was kept to be room temperature and the liquid nitrogen was used to cool the system in the experiment. The experiment confirmed the principle of the Peltier current lead, and the reduction of…
BACKGROUND: We previously reported the successful creation of tissue-engineered valve leaflet constructs and the implantation of these autologous tissue leaflets in the pulmonary valve position in a lamb model. The optimal cell origin for creating these valve leaflets remains unclear. This study was designed to compar…
In a self-consistent semi-empirical numerical approach based on ab-initio-calculations for small samples, we evaluate the GMR effect for disordered (001)-(3--Fe/3--V)$_\infty$ multilayers by means of a Kubo formalism. We consider four different types of disorder arrangements: In case (i) and (ii), the disorder consist…
During epitaxial crystal growth a pattern that has initially been imprinted on a surface approximately reproduces itself after the deposition of an integer number of monolayers. Computer simulations of the one-dimensional case show that the quality of reproduction decays exponentially with a characteristic time which…
Ohne ein Oxidans wie O 2 kann Methan an Fe/H‐ZSM‐5‐Katalysatoren selektiv zu Benzol, Toluol und Naphthalin umgesetzt werden. Methan wird dabei an Eisenoxidclustern aktiviert, und das Primärprodukt Ethylen reagiert in Oligomerisierungen und Cyclisierungen an Brønsted‐sauren Zentren zu den aromatischen Produkten.
The incorporation of pyrrole units was the key to stabilizing the largest annulene from Sondheimer et al., [30]annulene. Of the new aromatic [30]porphyrins 1–3, the 16-phenyl derivative 2 is the most stable.
The synthesis and magnetic properties of have been investigated. The formation of is found to depend strongly on annealing temperature. Pure single-phase compound can be synthesized at ambient pressure when . The main phase of the Laves structure can still be observed up to x = 0.8. The study of crystalline parameters…
A nucleophilic rather than a radical mechanism was recently proposed for the McMurry reaction. Quantum chemical density functional calculations support this hypothesis. An intramolecular and an intermolecular pathway for the CC coupling step are discussed, and the pinacolate complexes 1 and 2 are identified as centra…
We present an x-ray absorption spectroscopy study at the Cu K edge on Cu-doped soda-lime and BK7 glass waveguides obtained by ion exchange under various preparation conditions. The total electron yield and x-ray fluorescence yield collection modes were used to evidence the chemical behavior of surfacial and deep Cu io…
Biexciton and triexciton states in CuCl quantum dots were studied by means of time-resolved size-selective pump-and-probe technique. A clear induced absorption band is observed on the high-energy side of the excitation photon energy. The new induced absorption is assigned to the transition from the exciton ground stat…
We have measured the dielectric relaxation of several low-molecular-weight glass-forming materials for temperatures ranging from 25 K to and for values of the loss tangent down to . For the materials under study (salol, glycerol, N-methyl- -caprolactam, 2-methyltetrahydrofuran, 3-methylpentane, and o-terphenyl) a -rel…
The switching transition of polymer stabilized cholesteric texture liquid crystals is studied via confocal microscopy. This noninvasive probe enables the simultaneous imaging of the polymer network and the liquid crystal domain structure. We find that the two-stage switching often occurring in these systems results fr…
We present a technique to control the length of carbon nanotubes. Individual carbon nanotubes can be locally cut by applying a voltage pulse to the tip of a scanning tunneling microscope (STM). Topographic imaging and STM spectroscopy are subsequently used to investigate the result. The electronic properties of a nano…
We study the two pseudo-cubic perovskite ruthenates and , by means of LSDA electronic structure calculations using the LMTO method for both the idealized cubic and the real orthorhombic structures. The LSDA calculations predict that both orthorhombic structures are ferromagnetic, with magnetic moments of 2.0 and respe…
A new hydrogenation catalyst is formed by thermolysis of the anionic carbonyl cluster [Ag3Ru10C2(CO)28Cl]2− anchored to the mesoporous silicate MCM-41. The cluster was isolated and characterized in MCM-41 both before and after thermal treatment. The picture on the right shows a model, based in particular on EXAFS anal…