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- Accelerator mass spectrometry (2)
- PH (2)
- Acid (1)
- Alloy 2219 (1)
- Aluminium Alloy (1)
- Antioxidant additives (1)
- Anwendungsmöglichkeiten (1)
- Arbeitsanleitung (1)
- Asphalt oxidation (1)
- Binder aging (1)
Organisationseinheit der BAM
- 7 Bauwerkssicherheit (3)
- 1 Analytische Chemie; Referenzmaterialien (1)
- 1.2 Biophotonik (1)
- 4 Material und Umwelt (1)
- 4.1 Biologische Materialschädigung und Referenzorganismen (1)
- 7.1 Baustoffe (1)
- 7.2 Ingenieurbau (1)
- 7.5 Technische Eigenschaften von Polymerwerkstoffen (1)
- 8 Zerstörungsfreie Prüfung (1)
- 8.6 Faseroptische Sensorik (1)
Die Mikro- und Nanotechnologie gehört zu den Schlüsseltechnologien des 21. Jahrhunderts mit hohen Wachstumsprognosen, wie auch die im Auftrag des BMBF durchgeführte Studie “Nanotechnologie als wirtschaftlicher Wachstumsmarkt” von 2004 ausführlich darstellt. Aus diesem Trend resultiert ein steigender Bedarf an Messsystemen, die Nanostrukturen prozessnah bzw. im Fertigungsprozess charakterisieren können. Virtuelle Messgeräte liefern Erkenntnisse zur Entwicklung neuartiger Messsysteme, Analyse und Optimierung bestehender Verfahren sowie die Bestimmung der Messunsicherheit und modellbasierten Korrektur systematischer Fehler. Der virtuelle Messprozess umfasst neben dem Messmittel auch die Probe und die Wechselwirkungen zwischen beiden. In diesem Beitrag werden virtuelle Messgeräte vorgestellt sowie deren Anwendung diskutiert.
Oxidative aging induces significant stiffening of asphalt binders that leads to a pronounced reduction in the overall durability of asphalt pavements. The strategic implementation of antioxidant additives provides a potential solution to alleviate this issue. This work presents results from the second phase of the global consortium for antioxidants research aimed at investigating the effectiveness of potential antioxidants in increasing the durability of asphalt binders. Sixteen laboratories around the world participated in this effort and a total of 28 binders from diverse geographical regions were tested. Two promising antioxidants, namely zinc diethyldithiocarbamate (ZDC) and kraft lignin were evaluated in this phase and blended with the binders at specific proportions. Subsequently, a comprehensive investigation was conducted to assess rheological characteristics and chemical properties of the various blends, utilising Dynamic Shear Rheometer (DSR) measurements and Fourier Transform Infrared (FTIR) Spectroscopy. The findings indicate that additives such as ZDC hold considerable promise as an effective antioxidant, particularly when considering a wide diversity of binders. In general, its incorporation does not compromise the rutting performance of the binders and significantly improves fatigue performance. Therefore, research efforts should be focused on exploring additional facets to assess its practical applicability in field.
The first international round-robin exercise for the measurement of the long-lived radionuclide 10Be has been conducted. Ten participating accelerator mass spectrometry (AMS) facilities have each measured three samples at the 10-12 to 10-14 10Be/9Be level. All results have been made traceable to the NIST SRM 4325 standard to avoid additional discrepancies that arise when different facilities use different calibration materials. Hence, the data concentrates on pure measurement distinctions. Multivariate statistical investigations have been performed to reveal a bias between facilities, i.e. two distinguished groups could be identified. Maximum discrepancies between two single facilities are in the range of 6–31% depending on the absolute 10Be/9Be value. These findings should be considered when comparing 10Be data produced at one AMS facility with that produced at another facility, which is e.g. often the case for in situ 10Be dating studies. Round-robin exercises are a very helpful tool as part of an overall quality assurance scheme to improve the accuracy, and not only the precision, of AMS data.
This paper proposes a novel method to estimate the lateral displacement of high-rise structures under wind loads. The coefficient β(x) is firstly derived, reflecting the relation between the structural lateral dynamic displacement and the inclination angle at the height x of a structure. If the angle is small, it is the ratio between the structural fundamental mode shape and its first-order derivative without influence of external loads. Several dynamic experiments of structures are performed based on a laser remote sensing vibrometer and an inclinometer, which shows that the fundamental mode is dominated in the structural displacement response under different types of excitations. Once the coefficient β(x) is curve-fitted by measuring both the structural lateral dynamic displacement and the inclination angle synchronously, the real-time structural lateral displacement under operational conditions is estimated by multiplying the coefficient β(x) with the inclination angle. The advantage of the proposed method is that the coefficient β(x) can be identified by lateral dynamic displacement measured in high resolution by the remote sensing vibrometer, which is useful to reconstruct the displacement accurately by the inclination angle under operational conditions
The influence of interfacial pH between AISI 4135 steel and seawater under different polarization potentials on the formation of calcareous deposits has been studied. An interfacial pH of 9.61 at −0.9 V vs. SCE using state of the art iridium oxide microelectrode was found to be the critical pH for the precipitation of magnesium hydroxide. Calcareous deposits with a double-layer structure comprising an inner-brucite layer and an outer-aragonite layer were found to form at potentials between −1.0 V and −1.2 V vs. SCE. Furthermore, the facilitation of hydrogen permeation into steel induced by the formation of calcareous deposits was verified using the Devanathan-Stachurski electrochemical test. The mechanism of calcareous deposits facilitates hydrogen permeation into steel is related to its inhibition on hydrogen recombination and escape processes.
Carbon arc-air gouging is a common technology when repairing defects in welded structures. Often this technique is applied in repeated cycles even on the same location of the joint. Due to the multiple heat input by gouging and subsequent re-welding, the residual stresses are strongly influenced. This can become crucial when microstructure and mechanical properties are adversely affected by multiple weld reparations. Knowledge about the relation of gouging and residual stresses is scarce but important when high strength steels, which are sensitive to residual stresses, are processed. The present study shows the effect of repair welding on a high strength steel structural element. The weld and the heat affected zone were subjected to multiple thermal cycles by gouging and subsequent repair welding. The residual stresses were determined by X-ray diffraction at different positions along the joint. The results showed that the residual stress level has increased by the repair cycles. This is most pronounced for the heat affected zone. Adapted welding procedures may prevent detrimental residual stress distributions.
Im vorliegenden Bericht wurde untersucht, Spanndrahtbrüche in einem Brückenträger sowohl mittels Schallemissionsanalyse (SEA) als auch mit (eingebetteter) verteilter faseroptischer akustischer Sensorik (DAS) zu erkennen. Die Ergebnisse zeigen, dass die Bruchsignale anhand beider Messverfahren detektiert werden können. Die jeweils detektierten Drahtbrüche werden miteinander verglichen. Durch eine Gegenüberstellung werden SEA und DAS detailliert dargestellt.
Objective: The utilization of fluorescein-guided biopsies and resection has been recently discussed as a suitable strategy to improve and expedite operative techniques for the resection of central nervous system (CNS) tumors. However, little is known about the optical properties of sodium fluorescein (NaFl) in human tumor tissue and their potential impact on ex vivo analyses involving fluorescence-based methods.
Methods: Tumor tissue was obtained from a study cohort of an observational study on the utilization of fluorescein-guided biopsy and resection (n=5). The optical properties of fluorescein-stained tissue were compared to the optical features of the dye in vitro and in control samples consisting of tumor tissue of high-grade glioma patients (n=3) without intravenous (i.v.) application of NaFl. The dye-exposed tumor tissues were used for optical measurements to confirm the detectability of NaFl emission ex vivo. The tissue samples were fixed in 4%PFA, immersed in 30% sucrose, embedded in Tissue-Tek OCT compound, and cut to 10 mm cryosections. Spatially resolved emission spectra from tumor samples were recorded on representative slides with a Confocal Laser Scanning Microscope FV1000 (Olympus GmbH, Hamburg, Germany) upon excitation with lexc = 488 nm.
Results: Optical measurements of fluorescein in 0.9% sodium chloride (NaCl) under in vitro conditions showed an absorption maximum of lmax abs = 479 nm as detected with spectrophotometer Specord 200 and an emission peak at lmax em = 538 nm recorded with the emCCD detection system of a custom-made microscope-based single particle setup using a 500 nm long-pass filter. Further measurements revealed pH- and concentration-dependent emission spectra of NaFl. Under ex vivo conditions, confocal laser scanning microscopy of fluorescein tumor samples revealed a slight bathochromic shift and a broadening of the emission band.
Conclusion: Tumor uptake of NaFl leads to changes in the optical properties – a bathochromic shift and broadening of the emission band – possibly caused by the dye’s high pH sensitivity and concentration-dependent reabsorption acting as an innerfilter of the dye’s emission, particularly in the short wavelength region of the Emission spectrum where absorption and fluorescence overlap. Understanding the ex vivo optical properties of fluorescein is crucial for testing and validating its further applicability as an optical probe for intravital microscopy, immunofluorescence localization studies, and flow cytometry analysis.
Investigation of the Thermal Stability of Proteinase K for the Melt Processing of Poly(L‑lactide)
(2022)
The enzymatic degradation of aliphatic polyesters offers unique opportunities for various use cases in materials science. Although evidently desirable, the implementation of enzymes in technical applications of polyesters is generally challenging due to the thermal lability of enzymes. To prospectively overcome this intrinsic limitation, we here explored the thermal stability of proteinase K at conditions applicable for polymer melt processing, given that this hydrolytic enzyme is well established for its ability to degrade poly(L-lactide) (PLLA). Using assorted spectroscopic methods and enzymatic assays, we investigated the effects of high temperatures on the structure and specific activity of proteinase K. Whereas in solution, irreversible unfolding occurred at temperatures above 75−80 °C, in the dry, bulk state, proteinase K withstood prolonged incubation at elevated temperatures. Unexpectedly little activity loss occurred during incubation at up to 130 °C, and intermediate levels of catalytic activity were preserved at up to 150 °C. The resistance of bulk proteinase K to thermal treatment was slightly enhanced by absorption into polyacrylamide (PAM) particles. Under these conditions, after 5 min at a temperature of 200 °C, which is required for the melt processing of PLLA, proteinase K was not completely denatured but retained around 2% enzymatic activity. Our findings reveal that the thermal processing of proteinase K in the dry state is principally feasible, but equally, they also identify needs and prospects for improvement. The experimental pipeline we establish for proteinase K analysis stands to benefit efforts directed to this end. More broadly, our work sheds light on enzymatically degradable polymers and the thermal processing of enzymes, which are of increasing economical and societal relevance.