Thermodynamic Analysis of the Selectivity Enhancement Obtained by Using Smart Hydrogels That Are Zwitterionic When Detecting Glucose With Boronic Acid Moieties

Because the boronic acid moiety reversibly binds to sugar molecules and has low cytotoxicity, boronic acid-containing hydrogels are being used in a variety of implantable glucose sensors under development, including sensors based on optical, fluorescence, and swelling pressure measurements. However, some method of glucose selectivity enhancement is often necessary, because isolated boronic acid molecules have a binding constant with glucose that is some forty times smaller than their binding constant with fructose, the second most abundant sugar in the human body. In many cases, glucose selectivity enhancement is obtained by incorporating pendant tertiary amines into the hydrogel network, thereby giving rise to a hydrogel that is zwitterionic at physiological pH. However, the mechanism by which incorporation of tertiary amines confers selectivity enhancement is poorly understood. In order to clarify this mechanism, we use the osmotic deswelling technique to compare the thermodynamic interactions of glucose and fructose with a zwitterionic smart hydrogel containing boronic acid moieties. We also investigate the change in the structure of the hydrogel that occurs when it binds to glucose or to fructose using the technique of small angle neutron scattering.     

Formation and growth of complex precipitates in 316L austenitic steel during long-term annealing experiments

Transmission electron microscopy as well as corresponding analytical techniques, such as energy dispersive X-ray analysis, electron energy loss spectroscopy, and elemental mapping via Gatan imaging filter, have been used to study the growth sequence of complex precipitates with a TiN core formed in a commercial 316L(N) austenitic steel after creep experiments at 600 °C. It was found that the TiN precipitates, which originally exist in the as-delivered steel, serve as nucleation sites for intermetallic and Cr-containing carbide precipitates. The evolution of precipitate formation and growth was analyzed based on undeformed sample screw heads after 84, 164, 5,481, 41,000, and 85,000 h annealing.     

Wiki-Based Stakeholder Participation in Requirements Engineering

Requirements elicitation and documentation are complex activities. So, not only the requirements themselves but also the people involved and the means for managing the requirements will evolve during the project. For example, it might be necessary to add RE personnel, to document templates, or to change the requirements classification scheme. In summary, especially in participative RE, the underlying platform as well the RE approach must be flexible. As the well-known Wikipedia shows, wikis provide a flexible platform for asynchronous collaboration to create content in general. In this article, we investigate how to adapt this approach to support active stakeholder participation in RE. We include a document structure for wiki-based RE and discuss potential problems and solutions based on our experience     

Growth and characterization of TiO2 nanotubes from sputtered Ti film on Si substrate

In this paper, we present the synthesis of self-organized TiO₂ nanotube arrays formed by anodization of thin Ti film deposited on Si wafers by direct current (D.C.) sputtering. Organic electrolyte was used to demonstrate the growth of stable nanotubes at room temperature with voltages varying from 10 to 60 V (D.C.). The tubes were about 1.4 times longer than the thickness of the sputtered Ti film, showing little undesired dissolution of the metal in the electrolyte during anodization. By varying the thickness of the deposited Ti film, the length of the nanotubes could be controlled precisely irrespective of longer anodization time and/or anodization voltage. Scanning electron microscopy, atomic force microscopy, diffuse-reflectance UV–vis spectroscopy, and X-ray diffraction were used to characterize the thin film nanotubes. The tubes exhibited good adhesion to the wafer and did not peel off after annealing in air at 350 °C to form anatase TiO₂. With TiO₂ nanotubes on planar/stable Si substrates, one can envision their integration with the current micro-fabrication technique large-scale fabrication of TiO₂ nanotube-based devices.     

M?glichkeiten und Ergebnisse der Kombination von Messungen der Verh?ltnisse stabiler Wasserstoff-und Kohlenstoff-Isotope mit Resultaten konventioneller Analysen (RSK-Werte) zum Nachweis des Zuckerzusatzes zu Fruchts?ften

Zusammenfassung Die D- und die ¹³C-Werte der Zuk-ker und die ¹³C-Werte fester Bestandteile (Pulpe; bei Citrussäften) aus einer größeren Anzahl von naturbelassenen Apfel-, Grapefruit-, Orangen- und Zitronen-Säften sowie die D- und ₁₃C-Werte von Glucose aus Maisund Kartoffelstärkehydrolysaten sowie von Rübenzuk-ker wurden bestimmt. Die Resultate zeigen pflanzen- und klimatypische Bereiche, die trotz einiger Überschneidungen Verfälschungen (Zuckerung) in unbekannten Proben zu erkennen erlauben. Ein Vergleich der Ergebnisse mit Resultaten konventioneller Analysen (Bestimmung der RSK-Parameter) führt zu sehr guten Übereinstimmungen, so daß aus der Kombination dieser konventionellen Untersuchungsmethoden mit der Isotopen-Verhältnismessung ein zuverlässiger Nachweis des unerlaubten Zuckerzusatzes von Zucker aus C₃- oder C₄-Pflanzen zu Säften resultiert. Als weiterer Ausbau des Verfahrens wird der Einbezug von ¹⁸O-Bestimmungen empfohlen.

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Possibilities and results of the combination of hydrogen and carbon stable isotope ratio determination with results of conventional analyses (RSK-values) for the proof of sugar addition to fruit juices

Summary The D and ¹³C values of the sugars and the ¹³C values of the solid ingredients (pulp; in citrus juices) of a larger number of natural apple, grapefruit, orange and lemon juices, as well as the D and ¹³C values of glucose from corn and potato starch hydrolysates and from beet sugar, have been determined. The values cover plant and climate typical areas which permit, in spite of some overlap, the recognition of the addition of sugar to the juices. A comparison of the results with those of conventional analyses (determination of RSK parameters) agree satisfactorily, thus demonstrating that a combination of these classical criteria together with the isotope ratio determination prove that sugars form C₃-or C₄-plants are illegally added to the juices. With respect to further development of the method future integration of ¹⁸O measurements is recommended.

     

Characterization of a-SiC(x):H thin films as an encapsulation material for integrated silicon based neural interface devices

A fully integrated, wireless neural interface device is being developed to free patients from the restriction and risk of infection associated with a transcutaneous wired connection. This device requires a hermetic, biocompatible encapsulation layer at the interface between the device and the neural tissue to maintain long-term recording/stimulating performance of the device. Hydrogenated amorphous silicon carbide (a-SiC_x:H) films deposited by a plasma enhanced chemical vapor deposition using SiH₄, CH₄, and H₂ precursors were investigated as the encapsulation layer for such device. Si-C bond density, measured by Fourier transform infrared absorption spectrometer, suggests that deposition conditions with increased hydrogen dilution, increased temperature, and low silane flow typically result in increase of Si-C bond density. From the variable angle spectroscopic ellipsometry measurement, no dissolution of a-SiC_x:H was observed during soaking tests in 90 °C phosphate buffered saline. Conformal coating of the a-SiC_x:H in Utah electrode array was observed by scanning electron microscope. Electrical properties were studied by impedance spectroscopy to investigate the performance of a-SiC_x:H as an encapsulation layer, and the results showed long term stability of the material.     

Optimization and limitations of known DEMO divertor concepts

In this work we will introduce and discuss improvements for two types of DEMO divertors based on known designs: (i) gas cooled designs and (ii) liquid coolant concepts. In a first step, the advantages and disadvantages of gas cooling as well as the necessity of a jet impingement to increase the heat transfer coefficients will be discussed. Further discussion deals with the pros and cons of liquid coolant concepts, like for example, liquid metal or water cooling.Thereafter, we will present two rather contrary DEMO divertor concepts which are based on today's knowledge on refractory materials science, fabrication and joining technology. The first improved concept uses water flowing through steel pipes, typically made of Eurofer steel. It is well known that using Eurofer at low temperatures is critical due to its severe embrittlement under neutron irradiation. Here we make a proposal how it could be possible to use the Eurofer steel anyway: the solution could consist in a limited operation period followed by an annealing cycle at 550 °C for a few hours during any maintenance shut down phases. The second design is based on the known helium cooling concept using jet impingement. Drawbacks of the actual He-cooled divertor design are small scale parts as well as the necessary high helium inlet temperature of about 600–800 °C which leads to the question: How can we deal with such high helium temperatures? This paper shows a solution for large scale components as well as a new thermal management for the helium outlet gas that we call ‘cooling of the coolant’.Both concepts are discussed in terms of materials selection due to material limits and joining technology with a special focus on the material issue using already existing and available materials.     

Dehnwechselverhalten eines niedriglegierten warmfesten Schmiedestahles unter betriebsähnlichen Beanspruchungszyklen

Nachbildung der betrieblichen Langzeit-Dehnwechselbeanspruchung an der beheizten Oberfläche massiver Bauteile im Fahrplanbetrieb durch anisotherme Dehnwechselversuche mit betriebsähnlichem Temperatur- und Dehnungsverlauf, ferner durch vergleichbare isotherme Versuche bei der höchsten Zyklustemperatur sowie durch Versuche mit paketweise zusammengefaßten Dehnwechsel- und Kriechbeanspruchungsabschnitten. Versuche bis rd. 3000 h Dauer an einem 1%-CrMoNiV-Turbinenwellenstahl. Auswertung der Ergebnisse nach der verallgemeinerten Schadensakkumulationsregel.     

Fe-Cr-V ferritic steels for possible nuclear applications

Basic mechanical and metallurgical properties of specific ferritic Fe-Cr-V alloys and steels with 5, 10, and 15 wt.% vanadium were investigated. Vanadium is an effective carbide former and can also form a brittle sigma phase with chromium. Therefore, the microstructural investigations focused on the determination and analysis of possible precipitations. The present study showed that sigma phase precipitates increase significantly in alloys with 10 wt.% Cr and 10 wt.% V. The addition of carbon led to grain refinement due to the stabilizing effect of VC. In this way, precipitation hardening as well as fine grain strengthening could be quantified for this class of material. However, compared to typical martensitic steels, the strength of the considered ternary Fe-Cr-V alloys and steels is still lower.     

Precipitation in AISI 316L(N) during creep tests at 550 and 600 °C up to 10 years

The precipitation behaviour in the gauge lengths and in the heads of initially solution annealed type 316L(N) austenitic stainless steel specimens tested in creep at 550 and 600 °C for periods of up to 85 000 h has been studied using several metallographic techniques. Three phases were detected: M₂₃C₆, Laves, and sigma phase. The volume fraction of the precipitated sigma phase was significantly higher than that of carbides and the Laves phase. M₂₃C₆ carbide precipitation occurred very rapidly and was followed by the sigma and Laves phases formation in the delta ferrite islands. Sigma and Laves phases precipitated at grain boundaries after longer times. Two different mechanisms of sigma phase precipitation have been proposed, one for delta ferrite decomposition and another for grain boundary precipitation. Small quantities of the Laves phase were detected in delta ferrite, at grain boundaries and inside the grains.