Open Photoacoustic Cell for Blood Sugar Measurement: Numerical Calculation of Frequency Response

A new approach for continuous and non-invasive monitoring of the glucose concentration in human epidermis has been suggested recently. This method is based on photoacoustic (PA) analysis of human interstitial fluid. The measurement can be performed in vitro and in vivo and, therefore, may form the basis for a non-invasive monitoring of the blood sugar level for diabetes patients. It requires a windowless PA cell with an additional opening that is pressed onto the human skin. Since signals are weak, advantage is taken of acoustic resonances of the cell. Recently, a numerical approach based on the Finite Element (FE) Method has been successfully used for the calculation of the frequency response function of closed PA cells. This method has now been adapted to obtain the frequency response of the open cell. Despite the fact that loss due to sound radiation at the opening is not included, fairly good accordance with measurement is achieved

Computational Structural Analysis: Multiple Proteins Bound to DNA

BACKGROUND: With increasing numbers of crystal structures of proteinratioDNA and proteinratioproteinratioDNA complexes publically available, it is now possible to extract sufficient structural, physical-chemical and thermodynamic parameters to make general observations and predictions about their interactions. In particular, the properties of macromolecular assemblies of multiple proteins bound to DNA have not previously been investigated in detail. METHODOLOGY/PRINCIPAL FINDINGS: We have performed computational structural analyses on macromolecular assemblies of multiple proteins bound to DNA using a variety of different computational tools: PISA; PROMOTIF; X3DNA; ReadOut; DDNA and DCOMPLEX. Additionally, we have developed and employed an algorithm for approximate collision detection and overlapping volume estimation of two macromolecules. An implementation of this algorithm is available at http://promoterplot.fmi.ch/Collision1/. The results obtained are compared with structural, physical-chemical and thermodynamic parameters from proteinratioprotein and single proteinratioDNA complexes. Many of interface properties of multiple proteinratioDNA complexes were found to be very similar to those observed in binary proteinratioDNA and proteinratioprotein complexes. However, the conformational change of the DNA upon protein binding is significantly higher when multiple proteins bind to it than is observed when single proteins bind. The water mediated contacts are less important (found in less quantity) between the interfaces of components in ternary (proteinratioproteinratioDNA) complexes than in those of binary complexes (proteinratioprotein and proteinratioDNA).The thermodynamic stability of ternary complexes is also higher than in the binary interactions. Greater specificity and affinity of multiple proteins binding to DNA in comparison with binary protein-DNA interactions were observed. However, protein-protein binding affinities are stronger in complexes without the presence of DNA. CONCLUSIONS/SIGNIFICANCE: Our results indicate that the interface properties: interface area; number of interface residues/atoms and hydrogen bonds; and the distribution of interface residues, hydrogen bonds, van der Walls contacts and secondary structure motifs are independent of whether or not a protein is in a binary or ternary complex with DNA. However, changes in the shape of the DNA reduce the off-rate of the proteins which greatly enhances the stability and specificity of ternary complexes compared to binary ones

Validation eines skalierten Flugzeugrumpfmodells mittels experimenteller und numerischer Modalanalyse

Der Geräuschpegel im Flugzeuginnenraum ist ein wichtiges Qualitätsmerkmal bei der Bewertung einer Flugzeugkabine. Das Ziel jeder akustischen Kabinenauslegung ist deshalb eine Optimierung der Lärmbelastung und eine Minderung von auftretenden Schwingungen. Eine Entwicklung auf Basis von experimentellen Verfahren ist in der Regel zeit- und kostenintensiv. Um diesen Aufwand zu reduzieren kommen vermehrt computergestützte Simulationen zum Einsatz. Vor allem im Bereich von tiefen und mittleren Frequenzen basieren viele Vorhersagemethoden auf der Finite-Elemente-Methode. Mit Blick auf Antriebskonzepte die sich im hinteren Bereich des Flugzeuges befinden und dort im tiefen Frequenzbereich Strukturschwingungen auslösen, stellt sich die Frage, in wie weit die Ausbreitung der Schwingungen vorhersagbar ist. Um dies zu Überprüfen müssen die FE-Modelle mittels experimenteller Untersuchungen validiert werden. In dieser Arbeit wird ein vereinfachtes skaliertes Flugzeugrumpfmodell betrachtet, welches aus einer konischen und einer zylindrischen Sektion besteht. Für weitere Untersuchungen kann dieses Modell um immer mehr Details ergänzt werden, sodass es einem echten Flugzeug immer näher kommt. Um jedoch FE-Modelle für echte Flugzeuge zu validieren, sollten die experimentellen Untersuchungen an Testobjekten in Orginalgröÿe mit einem möglichst hohen Detaillierungsgrad durchgeführt werden. Für erste Untersuchungen des Schwingungsverhaltens sowie zur Überprü- fung der generellen Vorhersagemöglichkeiten durch FE-Modelle, ist es sinnvoll mit dem vereinfachten Modell zu beginnen

The electronic structure of iridium and its oxides

Iridium-based materials are among the most active and stable electrocatalysts for the oxygen evolution reaction. Amorphous iridium oxide structures are found to be more active than their crystalline counterparts. Herein, we combine synchrotron-based Xray photoemission and absorption spectroscopies with theoretical calculations to investigate the electronic structure of Ir metal, rutile-type IrO2, and an amorphous IrOx. Theory and experiment show that while the Ir 4f line shape of Ir metal is well described by a simple Doniach–Šunji´c function, the peculiar line shape of rutile-type IrO2 requires the addition of a shake-up satellite 1 eV above the main line. In the catalytically more active amorphous IrOx, we find that additional intensity appears in the Ir 4f spectrum at higher binding energy when compared with rutile-type IrO2 along with a pre-edge feature in the OK-edge. We identify these additional features as electronic defects in the anionic and cationic frameworks, namely formally OI and IrIII, which may explain the increased activity of amorphous IrOx electrocatalysts. We corroborate our findings by in situ X-ray diffraction as well as in situ X-ray photoemission and absorption spectroscopies