Conformation of the glycosidic linkage in a disaccharide investigated by double-quantum solid-state NMR.

Double-quantum heteronuclear local field NMR is performed on a sample of a 13C2-labeled disaccharide, in which the two 13C spins are located on opposite sides of the glycosidic linkage. The evolution of the double-quantum coherences is found to be consistent with the solid-state conformation of the molecule, as previously determined by X-ray diffraction. The dependence of the double-quantum evolution on the glycosidic torsional angles is examined by using a graphical molecular manipulation program interfaced to a numerical spin simulation module.     

Enhanced rigidity of recycled polypropylene from packaging waste by compounding with talc and high‐ crystallinity polypropylene

Polypropylene (PP) constituted 30% of the collected material in a Swedish collection system for rigid plastic packaging waste. The PP fraction was however a complex mixture of grades with widely different properties. In order to enhance the rigidity of the recycled PP, modified grades were prepared by compounding with talc and/or a virgin high‐crystallinity PP grade. Adding 20–40% of high‐crystallinity PP enhanced the stiffness and yield strength without impairing the impact resistance. A composite material consisting of 20% of this grade, 20% talc and 60% recycled PP gave mechanical properties similar to those of a commercial talc‐filled PP compound used for demanding engineering applications. The present study demonstrates that recycled PP derived from post‐consumer packaging waste can also be made useful for demanding engineering applications. Copyright © 2001 John Wiley & Sons, Ltd.     

Evaluation of methods aimed at complete removal of template from molecularly imprinted polymers.

Polymers imprinted with clenbuterol were used to study the influence of various post-polymerization treatments [e.g., thermal annealing, microwave assisted extraction (MAE), Soxhlet extraction and supercritical fluid template desorption] on the bleeding of residual template. The aim of the study was to reduce the bleeding to levels that would allow the use of the materials as affinity phases for extraction of clenbuterol from bovine urine at concentrations below 1 ng ml-1. After treatment, the clenbuterol imprinted polymers were packed into solid-phase extraction columns and the bleeding was estimated by quantifying the amount of template released in 10 ml of methanol-acetic acid (9 + 1 v/v). This was followed by an assessment of selectivity and recovery in comparison with non-treated material. The lowest bleeding level was found after MAE using 100% trifluoroacetic acid for 3 x 20 min at 100 degrees C. The collected eluate contained in this case 3 ng ml-1 of clenbuterol. The same material was subsequently used for the extraction of clenbuterol from spiked bovine urine. The resulting selectivity and recovery were lower compared with those obtained using the untreated material. A milder but still efficient method to reduce the bleeding level was found to be MAE with formic acid. In this case a bleeding level of 14 ng ml-1 was found after only a 1 h extraction time. In a second model system, using a polymer imprinted with L-phenylalanine anilide, the bleeding was reduced to a similar level by extensive on-line washing in good swelling solvents containing acid or base additives and after thermal annealing of the polymers in the dry state.     

Rapid Method to Screen Unopened Bottles to Detect Concealed Drugs

A bottle screening method to detect smuggling drugs was developed based on a series of rapid and automated magnetic resonance measurements. Liquid alteration is detected by evaluating chemical and physical properties of the liquid, scanning the bottle with a compact, non-contact magnetic resonance probe. Chemical and molecular diffusion changes are detected by means of the magnetic resonance relaxation time. The inspection device automatically detects the presence of concealed powders dissolved in liquids in a second timescale. The non-ionizing, non-contact method effectively screens bottles, regardless of their shape, size, and color. The proposed system configuration does not require a large magnet generating uniform magnetic fields; rather it inspects the liquid using a compact probe positioned on the wall of the bottle. For a variety of samples tested, the screening does not require detailed information on the expected content of the bottle.     

Crystal field effects on the magnetic fluctuations in RAl2 and RNi2

Zero-field μSR spectra have been recorded for some ferromagnetic Laves phase compounds. A comparison of the temperature dependence of the exponential damping rate, λ(T), for our samples shows that λ(T) is strongly influenced by crystal field effects.     

Interpretation of neutron scattering and μSR data on paramagnetic Gd in terms of magnetic clusters and coherent dissipative structures

Fullyc-axis oriented thin films of YBa₂(Cu_1−x ⁵⁷Fe _x )₃O_7−y were studied by varying the Fe- and O-content and the substrate. For the two substrates MgO and SrTiO₃ no difference in the CEMS spectra was observed. Measurements for differentx andy values and their comparison with results from powder samples proved that the solubility of iron is the same in the films and powders. The substitution of Cu(2) by Fe in the films is the highest ever reported. The CEMS spectrum of a reduced film shows that the direction of the magnetic hyperfine field for doubletC is perpendicular to thec-axis.     

Transverse field μ+SR study of V3Si

We have studied by transverse field positive muon spectroscopy μ+SR, the muon diffusion in V₃Si. We found that the muon is static and localized at tetrahedral interstitial sites below 200 K. Above 200 K the muons diffuse with an activiation energy 2550 (220) K. The nature of this diffusion process is discussed.     

Study of the molecular absorption spectrometric determination of phosphorus in steel, nickel base alloys and zircaloy using the yellow phosphovanadomolybdate complex

Summary The molecular absorption spectrometric method using the yellow phosphovanadomolybdate complex,adopted as ISO-standard for determination of phosphorus in steel, has been optimized.High and varying blank values often reported in literature were found to be due to silicon interference. The silicon is released from the glass beaker during fuming with perchloric acid and the problem is avoided by either using teflon beakers or by adding hydrofluoric and boric acid after fuming.Interferences from elements present in the metal (arsenic, chromium, silicon and the refractory elements) were quantified and procedures are described for masking these interferences in order to make the method applicable to high-alloy steels, tool steels, nickel-base alloys and Zircaloys. Arsenic, hafnium, niobium, tantalum and tungsten cause the most severe interferences. Chromium, titanium and zirconium were found to have weak interferences whereas molybdenum and silicon did not interfere at all despite large amounts of precipitated oxides.Results reported by other authors that many old certified reference materials of low-and high-alloy steels have too high certified phosphorus values were confirmed with the described method as well as with the ICP-OES technique. However, the lower values were only found for alloys without Hf, Nb, Ta or W. Alloys containing these elements were often found to have higher phosphorus values, which reflects interferences not completely removed in the previous analyses of these alloys.

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Untersuchung der molekularabsorptions-spektrometrischen Phosphorbestimmung auf Grund des gelben Phosphovanadomolybdat-Komplex in Stahl, Nickellegierungen und ZircaloyPhosphorbestimmung in Referenzmaterialien