Schallabsorbierende Doppelböden

Sound‐absorbing raised floors. Concrete core cooling is increasingly used as a temperature control method for office buildings. Concrete core cooling systems are integrated in slabs and preclude the installation of sound‐absorbing suspended ceilings, which would reduce the performance of such systems to uneconomical levels. Sound‐absorbing raised floors offer an alternative to sound‐absorbing ceilings. More than 60 sound absorption coefficient measurements were carried out in a reverberation chamber for different fitted carpets, sound‐absorbing raised floors and combinations thereof. This paper describes the different floor configurations and the corresponding sound absorption coefficients.     

Deutsche Nationalbibliothek 4. Erweiterungsbau in Leipzig – Besonderheiten bei der Unterfangung und der Bestandssicherung

Derzeit entsteht der 4. Erweiterungsbau der Deutschen Nationalbibliothek in Leipzig. Der neue Baukörper grenzt bereichsweise an die Bestandsgebäude und wurde 6 bis 8 m unterhalb der bestehenden Fundamente gegründet. Der setzungsempfindliche Baugrund infolge eines 4 m mächtigen Kohleflözes musste in der Planung besonders berücksichtigt werden. Um die Bestandsgebäude gegen Setzungen, Rissbildungen und Schiefstellungen zu schützen, wurden außergewöhnliche Sicherungsmaßnahmen realisiert: –·Zusammenspannen der Gebäude mittels Anordnung von Zugstäben –·Auskreuzung gefährdeter Bereiche durch Holz‐Fachwerkverbände –·Anwendung einer besonderen Technologie der HDI‐Unterfangung. Mit diesen Maßnahmen konnten ungleichmäßige Setzungen und Rissbildungen weitestgehend vermieden werden. The German National Library in Leipzig – 4^th extension – Special features of the underpinning and safety measures of inventory. At present the 4^th extension of the German National Library in Leipzig is under construction. The new building is near the existing buildings and was founded in 6 to 8 m below the existing foundations. The ground is liable to subsidence due to a 4 m thick coal seam. This had to be specially considered in the planning. To protect the existing buildings against settlements, cracking and misalignment extraordinary safety measures were implemented: –·tensioning arrangement of buildings by means of tension bars –·strengthening of vulnerable areas by timber trussed bond –·using a special technology of grouted underpinning With these measures, non‐uniform settlements and cracks could be largely avoided.     

Tunable photoemission from an excitonic antitrap

We study the influence of lithographically defined, electrostatic trap configurations on the photon emission from dipolar excitons in coupled quantum wells. The emission is surprisingly enhanced for an excitonic antitrap compared to a trap configuration, an effect more pronounced for a trap with smaller diameter. We explain the observations by the interplay between the exciton formation process, the lateral charge-carrier dynamics, and the dipole-dipole interactions between the excitons. Exploiting this interplay allows us to efficiently tune the excitonic emission energy with very small intensity variation.     

A small-window moving average-based fully automated baseline estimation method for Raman spectra

A fully automated and model-free baseline-correction method for vibrational spectra is presented. It iteratively applies a small, but increasing, moving average window in conjunction with peak stripping to estimate spectral baselines. Peak stripping causes the area stripped from the spectrum to initially increase and then diminish as peak stripping proceeds to completion; a subsequent increase is generally indicative of the commencement of baseline stripping. Consequently, this local minimum is used as a stopping criterion. A backup is provided by a second stopping criterion based on the area under a third-order polynomial fitted to the first derivative of the current estimate of the baseline-free spectrum and also indicates whether baseline is being stripped. When the second stopping criterion is triggered instead of the first one, a proportionally scaled simulated Gaussian baseline is added to the current estimate of the baseline-free spectrum to act as an internal standard to facilitate subsequent processing and termination via the first stopping criterion. The method is conceptually simple, easy to implement, and fully automated. Good and consistent results were obtained on simulated and real Raman spectra, making it suitable for the fully automated baseline correction of large numbers of spectra.     

Intrinsic Surface Dipoles Control the Energy Levels of Conjugated Polymers

Conjugated polymers are an important class of materials for organic electronics applications. There, the relative alignment of the electronic energy levels at ubiquitous organic/(in)organic interfaces is known to crucially impact device performance. On the prototypical example of poly(3‐hexylthiophene) and a fluorinated derivative, the energies of the ionization and affinity levels of π‐conjugated polymers are revealed to critically depend on the orientation of the polymer backbones with respect to such interfaces. Based on extensive first‐principles calculations, an intuitive electrostatic model is developed that quantitatively traces these observations back to intrinsic intramolecular surface dipoles arising from the π‐electron system and intramolecular polar bonds. The results shed new light on the working principles of organic electronic devices and suggest novel strategies for materials design.     

Pyrolytic acrylamide formation from purified wheat gluten and gluten-supplemented wheat bread rolls

Recent studies have revealed different acrylamide formation mechanisms, e. g. from carnosine (N-beta-alanyl-L-histidine) and aminopropionamide as additional precursors. The occurrence of acrylamide in food matrices devoid of common precursors such as meat supports an additional formation pathway. Gluten was recovered from wheat flour by water extraction. Starch, reducing sugars and amino acids were removed using alpha-amylase and NaCl solution and were completely absent in the purified gluten fraction. The gluten was dry heated at temperatures ranging from 160 to 240 degrees C for 8 to 12 min and analyzed for acrylamide and cinnamic amide using liquid chromatography-tandem mass spectrometry. Acrylamide could be detected up to 3997 microg/kg gluten dry weight. Cinnamic amide was detected and unambiguously identified in the gluten samples, thus confirming the proposed formation of acrylamide from proteins. After gluten addition to bread roll dough, protein pyrolysis to form acrylamide in the complex food matrix was assessed. Contents of asparagine and reducing sugars were diminished due to the addition of the gluten. In contrast to the expectation with respect to the well-established common formation mechanism of acrylamide, it increased from 53.4 to 63.9 microg/kg (+20%), which was in good correlation with the higher proportion of gluten. As demonstrated by the t-test, the increase in acrylamide was significant when comparing 0 and 15% gluten addition. Additionally, cinnamic amide could be found in crusts of bread rolls. Thus, evidence for pyrolytic formation of acrylamide from wheat gluten was provided.     

The Influence of Excess Coupling Agent on the Microdeformation Processes and Mechanical Properties of Poly(propylene)/Wood‐Flour Composites

Summary: It is well known that coupling agents improve the adhesion between poly(propylene) and wood fillers leading to an increase of the composite mechanical properties. Above a certain concentration limit of the coupling agent, however, deterioration of the mechanical properties often occurs, and little attention has been directed so far towards finding out the reasons for that behavior. Transmission electron microscopy and high‐voltage electron microscopy were used in this work to study the morphology and microdeformation behavior of PP/wood‐flour composites modified with high amounts of maleated poly(propylene) as a coupling agent. It was found that the coupling agent containing a higher concentration of grafted maleic anhydride forms a separate phase in the poly(propylene) matrix, influencing the mechanical properties of the composites.

HVEM micrograph of the deformation structure of wood‐filled poly(propylene) composite showing fibrils stretching between the coupling agent domains and the PP matrix.     

RebG- and RebM-catalyzed indolocarbazole diversification

Rebeccamycin and staurosporine represent two broad classes of indolocarbazole glycoside natural products with antitumor properties. Based upon previous sequence annotation and in vivo studies, rebG encodes for the rebeccamycin N-glucosyltransferase, and rebM for the requisite 4'-O-methyltransferase. In the current study, an efficient in vivo biotransformation system for RebG was established in both Streptomyces lividans and Escherichia coli. Bioconversion experiments revealed RebG to glucosylate a set of indolocarbazole surrogates, the products of which could be further modified by in vitro RebM-catalyzed 4'-O-methylation. Both RebG and RebM displayed substrate promiscuity, and evidence for a remarkable lack of RebG regioselectivity in the presence of asymmetric substrates is also provided. In the context of the created indolocarbazole analogues, cytotoxicity assays also highlight the importance of 4'-O-methylation for their biological activity.