Daily dietary molybdenum intake in Belgium using duplicate portion sampling

 For the first time daily dietary molybdenum intake in Belgium has been evaluated by duplicate portion sampling, heating in a microwave oven for destruction and atomic absorption spectrometric determination of this element. The mean intake value (87±11 μg/day) is lower than levels found for most other countries and is situated at the lower end of the recommended range for a safe and adequate daily dietary intake. Received: 14 October 1996     

The crystal structure of LiMgAlD6 from combined neutron and synchrotron X-ray powder diffraction

LiMgAlH₆ is the intermediate phase when LiMg(AlH₄)₃ is heated. It contains 9.4 wt.% hydrogen, of which 4.8 wt.% is released during the decomposition step to MgH₂ and LiH. Deuterated LiMgAlD₆ was prepared by heat-treating LiMg(AlD₄)₃ at 130 °C. Powder neutron and synchrotron X-ray diffraction patterns were measured and the structure was refined using the Rietveld technique on both patterns simultaneously. LiMgAlD₆ crystallizes in the trigonal space group P321 with a = 7.9856(4) Å and c = 4.3789(3) Å. The structure consists of isolated AlD₆ octahedra connected through octahedrally coordinated Mg- and Li-atoms.     

Stress–strain properties of polyurethane–polyacrylate interpenetrating polymer networks

Two-component interpenetrating polymer networks (IPN) of the SIN type (simultaneous interpenetrating networks) were prepared from two different polyurethanes (a polyester type and a polyether type) and a polyacrylate of two different crosslink densities. The linear polymers and prepolymers were combined in solution, together with crosslinking agents and catalysts, films cast, and subsequently chain extended and crosslinked in situ. In all cases, maxima in tensile strengths significantly higher than the tensile strengths of component networks occurred. This was explained by an increase in crosslink density due to interpenetration.     

Tribomechanische und -chemische Vorgänge an dem Wälzlagerstahl 100 Cr 6

Tribological Processes of the Ball Bearing Steel 100 Cr 6 . Tribomechanical and tribochemical processes of the ball bearing steel 100 Cr 6 were investigated under the influence of ultra high vacuum and different gases by the pin/ring method. The conditions for adhesive wear indicated by prow formation were optimal in ultra high vacuum. Pressures of oxygen, nitrogen and air greater than 10^?6 Pa increase the lubrication by formation of thin films, measured by ellipsometry. Increasing nitrogen pressure produces a surface hardening, which can be observed by nitrided wear particles. The presence of pure oxygen creates permanently oxide films with a thickness of 10 nm. This causes abrasive wear.     

Real-time measurements of semiconductor laser spectra

A technique for measuring the instantaneous spectrum of a semiconductor laser is described. Spectral fluctuations of several different devices, including three different length channel-substrate buried-crescent lasers emitting at 1.52 μm were examined. The shortest (100-μm) device showed a trend towaxds single-mode operation, and it is believed that devices of up to 70-μm length should emit predominantly in one longitudinal mode. Mode selection effects, thought to be due to reflections from the monitor diode, were observed in a 1.3-μm packaged laster. The technique has also been used to measure correlations between successive pulses, and between spectral width and mean position.     

Testicular cancer risk and maternal parity: a population-based cohort study

The aim was to study, in a population-based cohort design, whether first-born sons run a higher risk of testicular cancer than later born sons; to investigate whether this difference in risk was affected by birth cohort, age of the son, maternal age, interval to previous delivery and other reproductive factors; and, finally, to evaluate to what extent changes in women's parity over time might explain the increasing incidence of testicular cancer. By using data from the Civil Registration System, a database was established of all women born in Denmark since 1935 and all their children alive in 1968 or born later. Sons with testicular cancer were identified in the Danish Cancer Registry. Among 1015994 sons followed for 15981 967 person-years, 626 developed testicular cancer (443 non-seminomas, 183 seminomas). Later born sons had a decreased risk of testicular cancer (RR = 0.80, 95% CI = 0.67-0.95) compared with first-born sons. The RR was 0.79 (95% CI = 0.64-0.98) for non-seminomas and 0.81 (95% CI = 0.58-1.13) for seminomas. There was no association between testicular cancer risk and overall parity of the mother, maternal or paternal age at the birth of the son, or maternal age at first birth. The decreased risk of testicular cancer among later born sons was not modified by age, birth cohort, interval to the previous birth, sex of the first-born child, or maternal age at birth of the son or at first birth. The increased proportion of first-borns from birth cohort 1946 to birth cohort 1969 only explained around 3% of an approximated two-fold increase in incidence between the cohorts. Our data document a distinctly higher risk of testicular cancer in first-born compared with later born sons and suggest that the most likely explanation should be sought among exposures in utero. The increase in the proportion of first-borns in the population has only contributed marginally to the increase in testicular cancer incidence.     

Surface modification of polymers and practical adhesion

The, nature of polymer surfaces has received increasing attention as the use of these materials, in a variety of forms, increases yearly. Modifications of polymer surfaces for adhesion, friction, and diffusion oriented appiications have necessitated a careful analysis of the surfade region morphology (surface physics) and chemical properties of the surface layer (surface chemistry). The behavior of composite structures has involved the discipline of classical fracture mechanics. The orientation of polymeric species or additives which migrate to the interface may modify the wetting characteristics and, most certainly, the frictional properties in addition to the diffusion of penetrant species beyond the boundary layer. The above topics are discussed within the framework of recent analytical and theoretical developments in surface science. The findings of these recent studies have facilitated many exciting technological advances.