Angular vibrations of cryogenically cooled double-crystal monochromators.

The effect of angular vibrations of the crystals in cryogenically cooled monochromators on the beam performance has been studied theoretically and experimentally. A simple relation between amplitude of the vibrations and size of the focused beam is developed. It is shown that the double-crystal monochromator vibrations affect not only the image size but also the image position along the optical axis. Several methods to measure vibrations with the X-ray beam are explained and analyzed. The methods have been applied to systematically study angular crystal vibrations at monochromators installed at the PETRA III light source. Characteristic values of the amplitudes of angular vibrations for different monochromators are presented.

Use of intermediate focus for grazing incidence small and wide angle x-ray scattering experiments at the beamline P03 of PETRA III, DESY.

We describe the new experimental possibilities of the micro- and nanofocus X-ray scattering beamline P03 of the synchrotron source PETRA III at DESY, Hamburg (Germany), which arise from experiments with smaller beam sizes in the micrometer range. This beamline has been upgraded recently to perform new kinds of experiments. The use of an intermediate focus allows for reducing the beam size of microfocused hard X-rays while preserving a large working distance between the focusing elements and the focus position. For the first time, this well-known methodology has been employed to grazing incidence small- and wide-angle X-ray scattering (GISAXS/GIWAXS). As examples, we highlight the applications to in situ studies using microfluidic devices in GISAXS geometry as well as the investigation of the crystallinity of thin films in GIWAXS geometry.

The variable charge of dioctahedral smectites.

One of the most important properties of smectites is the cation exchange capacity resulting both from the structural permanent charge and the pH depending variable charge. The variable charge, in turn, mainly results from the edge aluminol groups (in the case of dioctahedral smectites). The permanent charges can be calculated using the layer charge density; the variable charges, however, were rarely quantified accurately. The present study was conducted to (i) test and compare different methods for the measurement of the variable charge of dioctahedral smectites (mainly montmorillonites), (ii) characterize the range of differences of the variable charge of smectites from different deposits, and (iii) identify the reason for different variable charge values. Considering a 0.1×0.1 µm montmorillonite particle, a variable charge of 8 meq/100 g (about 10% of the CEC) was calculated. Two CEC (Cu(trien)) based methods provided slightly larger values. These values ranged from 2% to 14% between pH 4 and 6 and from approximately 10% to 30% between pH 4 and 9. With the potentiometric titration method, even larger values for the variable charge were determined (15-35%). Interestingly, both the CEC based methods and the titration method provided comparable trends. Accordingly, any of these methods is suitable to distinguish materials with larger or lower variable charge. One of the reasons for the differences of the variable charge of different bentonites is the variable chemical composition of the smectites, particularly the structural Mg content. Further reasons may be the roughness of the edge surface (not considered in the calculation) and the submicron particle size distribution, which are both difficult to determine.

In situ observation of cluster formation during nanoparticle solution casting on a colloidal film.

We present a real-time study of the nanostructuring and cluster formation of gold nanoparticles deposited in aqueous solution on top of a pre-structured polystyrene colloidal thin film. Cluster formation takes place at different length scales, from the agglomerations of the gold nanoparticles to domains of polystyrene colloids. By combining in situ imaging ellipsometry and microbeam grazing incidence small-angle x-ray scattering, we are able to identify different stages of nanocomposite formation, namely diffusion, roughness increase, layer build-up and compaction. The findings can serve as a guideline for nanocomposite tailoring by solution casting.

N(2)-BET specific surface area of bentonites.

The specific surface areas (SSA(N2BET)) of 36 different bentonites had larger values for Ca(2+)/Mg(2+) bentonites than for Na(+) bentonites. This trend could not be explained by the different d(001) values nor by the different microstructures. The investigation of Cu-triene-exchanged smectites, which on drying at 105 degrees C still had a d(001) value accounting for approximately 13A, proved that the SSA(N2BET) of low-charged smectites increased more than that of high-charged smectites. This could be explained by: (i) more space between the permanent charge sites in the case of low-charged smectites and (ii) the fact that the layers of Cu-triene smectites do not collapse at 105 degrees C. In contrast the SSA(N2BET) of Ca(2+)-exchanged bentonites could not be related to the layer charge density (LCD) as in the case of the Cu-triene-exchanged bentonites which is probably due to the varying number of collapsed layers. In conclusion, the SSA(N2BET) of bentonites which is known to be largely variable is probably determined by microporosity resulting from the quasi-crystalline overlap region and accessible areas of the interlayer. The number of layers per stack and the microstructure are supposed to play a subordinate role. The larger SSA(N2BET) of Ca/Mg bentonites compared to Na bentonites probably can be explained by the larger space between the charges in the case of the presence of divalent cations.

Multiple ionization of atom clusters by intense soft X-rays from a free-electron laser.

Intense radiation from lasers has opened up many new areas of research in physics and chemistry, and has revolutionized optical technology. So far, most work in the field of nonlinear processes has been restricted to infrared, visible and ultraviolet light, although progress in the development of X-ray lasers has been made recently. With the advent of a free-electron laser in the soft-X-ray regime below 100 nm wavelength, a new light source is now available for experiments with intense, short-wavelength radiation that could be used to obtain deeper insights into the structure of matter. Other free-electron sources with even shorter wavelengths are planned for the future. Here we present initial results from a study of the interaction of soft X-ray radiation, generated by a free-electron laser, with Xe atoms and clusters. We find that, whereas Xe atoms become only singly ionized by the absorption of single photons, absorption in clusters is strongly enhanced. On average, each atom in large clusters absorbs up to 400 eV, corresponding to 30 photons. We suggest that the clusters are heated up and electrons are emitted after acquiring sufficient energy. The clusters finally disintegrate completely by Coulomb explosion.

Identification of a crystalline cyanide-containing compound in blast furnace sludge deposits.

During blast furnace operation, a cyanide-containing muddy waste referred to as blast furnace sludge is generated in large amounts. In Germany it was and is still common practice to pump this sludge into surface deposits. Depending on species, cyanide has very different toxicity. To this day there is no information about the type of cyanide occurring in blast furnace sludge deposits. In order to identify the type of cyanide we investigated by means of wet chemical and powder X-ray diffraction analyses 37 samples of three blast furnace deposits. Wet chemical results indicate that both the extremely toxic free cyanide (HCN and CN ) and toxic weak metal-cyanide complexes, for example [Zn(CN)4]2-, are not present in the sludge. By powder X-ray diffraction we identified the crystalline cyanide-containing compound potassium zinc hexacyanoferrate(II) nonahydrate, K2Zn3[Fe(CN)6]2 x 9H2O, as the cyanide-bearing compound. Our study is the first that identifies potassium zinc hexacyanoferrate(II) nonahydrate in the environment. As the iron-cyanide complex [Fe(CN)6] is not acutely toxic, any direct hazard comes from cyanide occurring in the investigated wastes. Under the predominant pH milieu of the sludge (pH about 8) the solubility of potassium zinc hexacyanoferrate(II) nonahydrate is low, thus minimizing the mobility of cyanide.

An evaluation of electromyographic biofeedback in the treatment of myofascial pain-dysfunction syndrome.

Electromyographic (EMG) biofeedback was used in a controlled situation to teach patients with myofascial pain-dysfunction syndrome to relax and masseter muscle. Those receiving biofeedback were able to reduce their mean masseter EMG levels significantly. Concurrently, there was a reduction of symptoms. Seventy-five percent of the successfully treated patients required no further therapy during one year of observation.

[Surgical and hospital hygiene (author's transl)]. / Chirurg und Krankenhaushygiene.

The decades-old rules of surgical asepsis and antisepsis are more valid than ever before. The responsibility for hygiene must be clearly established: in his particular area, the surgeon, and he alone, is responsible. Patients with an increased susceptibility to infection as well as human and personnel inadequacies represent the greatest stumbling blocks in efforts to improve the status of hygiene.