Zur Berechnung der statischen Auslenkung elastisch gelagerter Rohre

Zusammenfassung In den bisherigen Arbeiten über Schwingungen von Rohren mit einem freien und einem eingespannten Ende nahm man an, da? das feste Ende starr eingespannt sei. Es wird gezeigt, da? diese ungenaue Annahme (die zu auff?lligen Unterschieden zwischen berechneten und gemessenen Werten führt) unn?tig ist und ersetzt werden kann durch die Annahme einer “linearen” Einspannung (verallgemeinerten elastischen Einspannung), deren Koeffizienten aus gemessenen Frequenzen der freien Schwingungen des Rohrs bestimmt werden k?nnen. Herrn Prof. Dr. rer. nat.F. Weidenhammer zur Vollendung des 60. Lebensjahres in Verehrung und Dankbarkeit gewidmet     

A Noise Thermometer for Practical Thermometry at Low Temperatures

The application of a magnetic-field-fluctuation thermometer (MFFT) is described for practical thermometry in the low-temperature range. The MFFT inductively measures the magnetic noise generated by Johnson noise currents in a metallic temperature sensor. The temperature of the sensor is deduced from its thermal magnetic noise spectrum by applying the Nyquist theorem, making the thermometer in principle linear over a wide range of temperatures. In this setup, a niobium-based dc SQUID gradiometer detects the magnetic field fluctuations. The gradiometer design optimizes the inductive coupling to the metallic temperature sensor, yet equally ensures sufficient insensitivity to external magnetic interference. In order to obtain a highly sensitive and fast thermometer, the SQUID chip is placed directly onto the surface of the temperature sensor. The compact setup of the gradiometer/temperature sensor unit ensures good conditions for thermal equilibration of the sensor with the temperature to be measured, a factor that becomes increasingly important in the temperature range below 1 K. The first direct comparison measurements of the MFFT with a high-accuracy realization of the Provisional Low Temperature Scale of 2000 (PLTS-2000) are presented. Special emphasis is given to the investigation of the linearity, speed, and accuracy of the MFFT.     

Immunogold FIB‐SEM: Combining Volumetric Ultrastructure Visualization with 3D Biomolecular Analysis to Dissect Cell–Environment Interactions

Volumetric imaging techniques capable of correlating structural and functional information with nanoscale resolution are necessary to broaden the insight into cellular processes within complex biological systems. The recent emergence of focused ion beam scanning electron microscopy (FIB‐SEM) has provided unparalleled insight through the volumetric investigation of ultrastructure; however, it does not provide biomolecular information at equivalent resolution. Here, immunogold FIB‐SEM, which combines antigen labeling with in situ FIB‐SEM imaging, is developed in order to spatially map ultrastructural and biomolecular information simultaneously. This method is applied to investigate two different cell–material systems: the localization of histone epigenetic modifications in neural stem cells cultured on microstructured substrates and the distribution of nuclear pore complexes in myoblasts differentiated on a soft hydrogel surface. Immunogold FIB‐SEM offers the potential for broad applicability to correlate structure and function with nanoscale resolution when addressing questions across cell biology, biomaterials, and regenerative medicine.     

Early performances of cement paste in the presence of triethanolamine: Rheology,setting and microstructural development

The effect of triethanolamine (TEA) at various dosages on the early performance of cement paste was systematically evaluated through the techniques of rheological measurements, penetration tests, and ultrasonic pulse velocity. The correlation of early performance to the chemical hydration process was analyzed by calorimetry, zeta potential, in situ XRD, and pore solution analysis. It is found that the effect of TEA on the early performance of cement paste is strongly dependent on its dosage. With the TEA dosage below 0.1 wt%, the setting and microstructural development of cement paste are retarded. Meanwhile, the yield stress of fresh paste is decreased due to the increasing zeta potential of cement grains. The promoted formation of ettringite (AFt) and monosulfate (AFm) caused by TEA decreases the rheological retention ability. At dosages ≥0.2 wt%, the reaction of aluminate-containing phases is greatly accelerated and a flash setting is observed. Besides, the importance of ferric phase on the reaction of cement with TEA is highlighted. At a low dosage, TEA prefers to accelerate the dissolution of tetracalcium aluminoferrite (C₄AF) first and increases the [Fe] in the pore solution of cement paste. In cement without C₄AF, the retardation of TEA on silicate phase hydration is significantly alleviated.     

Three component terpolymer and IPN hydrogels with response to stimuli

Two different types of multi-stimuli-shrinking hydrogels were synthesized (IPNs and terpolymeric hydrogels) by properly polymerizing N-isopropylacrylamide, 2-hydroxyethyl methacrylate and 2-acrylamido-2-methylpropanesulfonic acid in various mutual ratios and different synthetic orders. Both classical (CP) and frontal (FP) polymerizations were used and the resulting material properties compared. The best compositions and synthetic routes were found and the swelling, morphological and thermal material properties were studied. The results show that some IPNs exhibit marked stimuli-shrinking properties while some terpolymers present an opposite behavior. IPNs swell more than terpolymers and show a sharper stimuli-response, with a larger swelling ratio variation. In addition, FP allowed obtaining samples with the same characteristic of CP materials, but with significant preparation advantages. It has been demonstrated that by varying monomer mutual ratio, synthetic technique (FP or CP) and structural architecture (terpolymers or IPNs), different materials having peculiar properties and characteristics can be obtained.     

Mapping bacterial surface layers affinity to polyelectrolytes through the building of hybrid macromolecular structures

A novel hybrid sandwich-like supramolecular structure (polyelectrolyte multilayer/S-layer/ polyelectrolyte multilayer/S-layer) has been built by combining polyelectrolyte multilayer deposition and self-assembly of isolated SbpA proteins from Bacillus sphaericus CCM2177. Neutron reflectometry measurements were used to confirm the formation of an S-layer on negative poly(styrene sulphonate) (PSS) terminated multilayers, further adsorption of cationic poly(allylamine hydrochloride) polyelectrolyte on the exposed S-layer surface, and final polyelectrolyte multilayer deposition. Surface topography investigations with atomic force microscopy showed that: (i) the two dimensional structure of the S-layer is similar to those found in bacteria, (ii) cationic poly(allylamine hydrochloride) adsorbs on the bacterial protein side that faces the aqueous media, and (iii) anionic poly(styrene sulphonate) does not adsorb on the S-layer surface. Mechanical stability studies on recrystallized S-layers on anionic negative poly(styrene sulphonate) reveal that loads of 20 nN are able to unfold the S-layer protein. A second adsorption of SbpA monomers on top of a structure composed of polyelectrolyte multilayer/S-layer/polyelectrolyte multilayer led to the formation of S-layers patches mechanically stable for loads up to 9 nN. This hybrid polymer-protein supramolecular complex has permitted to elucidate the nature of the affinity of the bacterial cell surface protein to polyelectrolytes.     

Residue analysis of the pharmaceutical diclofenac in different water types using ELISA and GC-MS

A highly sensitive and specific indirect competitive enzyme-linked immunosorbent assay (ELISA) for the determination of diclofenac in water samples was developed. With pure water, the limit of detection (LOD, S/N = 3) and IC50 were found to be 6 ng/L and 60 ng/L, respectively. The analytical working range was about 20-400 ng/L. Highest cross-reactivity (CR) of 26 tested pharmaceuticals, metabolites, and pesticides was found for 5-hydroxydiclofenac (100%). Other estimated values were well below 4% and, therefore, are negligible. The assay was applied for the determination of diclofenac in tap and surface water samples as well as wastewater collected at 20 sewage treatment plants (STPs) in Austria and Germany. Humic substances were identified as main interference in surface water. Wastewater samples which were only submitted to filtration and dilution yielded about 25% higher diclofenac concentrations using the ELISA compared to GC-MS. However, the ELISA turned out to be a simple, inexpensive, and accurate method for the determination of diclofenac both in influent and effluent wastewater after rather simple sample preparation, i.e., filtration, acidification, and readjustment to neutral pH-value, and at least 10-fold dilution with pure water.     

Round robin test on ring shear testers

In 2008 a round robin project on ring shear testers was initiated in order to determine a range of results for a defined bulk solid (limestone powder CRM-116), similar to a round robin project with Jenike shear testers carried out in the 1980s. All users of automatic ring shear testers RST-XS or RST-01.pc were invited to take part. Twenty-seven labs supplied results. Finally, per stress level up to 60 yield loci (21 labs) measured with the RST-XS, and up to 19 yield loci (10 labs) measured with the RST-01.pc have been received.Compared to the above mentioned tests on Jenike-type shear testers, both ring shear testers provide clearly smaller standard deviations. Thus, despite different ambient conditions, the range of results is quite narrow.With the mean values and standard deviations calculated from the ring shear tester results a kind of “reference range” is defined. This range should be matched with a certain probability with the results of future tests with the standard powder if the instructions regarding stresses and ambient conditions are followed. Thus, the results provide orientation to all users of ring shear testers RST-XS and RST-01.pc.     

Derivation of the propagation equations for higher order aberrations of local wavefronts

From the literature the analytical calculation of local power and astigmatism of a wavefront after refraction and propagation is well known; it is, e.g., performed by the Coddington equation for refraction and the classical vertex correction formula for propagation. Recently the authors succeeded in extending the Coddington equation to higher order aberrations (HOA). However, equivalent analytical propagation equations for HOA do not exist. Since HOA play an increasingly important role in many fields of optics, e.g., ophthalmic optics, it is the purpose of this study to extend the propagation equations of power and astigmatism to the case of HOA (e.g., coma and spherical aberration). This is achieved by local power series expansions. In summary, with the results presented here, it is now possible to calculate analytically the aberrations of a propagated wavefront directly from the aberrations of the original wavefront containing both low-order and high-order aberrations.