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- XANES (3)
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- Radar (2)
- Bond lengths (1)
- Concrete cover of tendon ducts (1)
- Concrete slabs (1)
The effects of femtosecond laser pulse irradiation on the glass structure of alkaline silicate glasses were investigated by x-ray absorption near edge structure spectroscopy using the beamline of the Physikalisch-Technische Bundesanstalt at the electron synchrotron BESSY II in Berlin (Germany) by analyzing the magnesium Κ-edge absorption peak for different laser fluences. The application of fluences above the material modification threshold (2.1 J/cm²) leads to a characteristic shift of ~1.0 eV in the Κ-edge revealing a reduced (~3%) mean magnesium bond length to the ligated oxygen ions (Mg-O) along with a reduced average coordination number of the Mg ions.
The redeposited material (debris) resulting from ablation of a potassium–magnesium silicate glass upon scanning femtosecond laser pulse irradiation (130 fs, 800 nm) in air environment is investigated by means of three complementary surface analytical methods. Changes in the electronic band structure of the glass constituent Magnesium (Mg) were identified by X-ray Absorption Near Edge Structure spectroscopy (XANES) using synchrotron radiation. An up-shift of ≈0.8 eV of a specific Magnesium Κ-edge absorption peak in the spectrum of the redeposited material along with a significant change in its leading edge position was detected. In contrast, the surface left after laser ablation exhibits a downshift of the peak position by ≈0.9 eV. Both observations may be related to a change of the Mg coordinative state of the laser modified/redeposited glass material. The presence of carbon in the debris is revealed by micro Raman spectroscopy (µ-RS) and was confirmed by energy dispersive X-ray spectroscopy (EDX). These observations are attributed to structural changes and chemical reactions taking place during the ablation process.
Validation of non-destructive testing methods is necessary to create a common basis where different systems can be compared and their applications and limitations be identified. This can be achieved through comparing the measurements taken by several systems used for a common diagnostic purpose under practical but controlled testing conditions. Well-designed small and large laboratory or field specimens promise such conditions.
The special concrete specimen (LCS) at BAM was constructed for validation purposes, in particular, to be used for evaluating the performance of echo methods. The thickness of the specimen is varying and it contains carefully designed built-in faults, such as voids, honeycombs and tendon ducts with various degrees of grouting defects. Since the geometry and condition of the defects are known, it can be used to compare the performance of radar, ultrasonic, impact-echo. The research was conducted within the Research group FOR384, sponsored by the German Research Society DFG.
Spin transition in heptanuclear star-shaped iron(III)-antimony(V) NCS- and CN-bridged compounds
(2009)
The precursor [FeIII(L)Cl] (LH2 = N,N'-bis(2'-hydroxy-benzyliden)-1,6-diamino-3-azahexane) has been prepared and Mössbauer spectroscopy assigned a high-spin (S = 5/2) state at room temperature. The precursor is combined with the bridging units [SbV(X)6]- (X = CN-, NCS-) to yield star-shaped heptanuclear clusters [(LFeIII-X)6SbV]Cl5. The star-shaped compounds are in general high-spin systems at room temperature. On cooling to 20 K some of the iron(III) centers switch to the low-spin state as indicated by Mössbauer spectroscopy, i.e. multiple electronic transitions. While the cyano-bridged complex performs a multiple spin transition the thiocyanate-compound shows no significant population at both temperatures.
In this study, we investigated galacturonic (GalAc)- and mannuronic (ManAc) acids as novel targeting ligands for receptor-mediated gene delivery. GalAc and ManAc were coupled to either polyethyleneimine (PEI) or PEIpolyethyleneglycol (PEG). Furthermore, lactobionic acid (LacAc), which comprises a GalAc-related carbohydrate ring, was coupled to each of the polymers through its open-chain gluconic acid moiety. The molar mass distributions of the polymers were characterized by analytical ultracentrifugation and size exclusion chromatography. PEI-conjugatepDNA complexes were transfected into HepG2-, HeLa-, and 16HBE14o--cells. Gene expression mediated by GalAc- and LacAc-functionalized PEI-conjugates was lower than for PEI. In contrast, gene expression mediated by ManAc-functionalized PEI-conjugates was up to three orders of magnitude higher than for the other tested PEI-conjugates, in particular for negatively charged gene vectors at low N/P ratios, independent of the cell line. Pre-incubation of cells with an excess of ManAc before transfection significantly inhibited transfection rates only for ManAc-functionalized PEI-conjugates. Coupling of methyl-α-D-mannuronic acid to PEI resulted in significantly lower transfection rates than for ManAc-PEI based complexes. Together with fluorescence microscopy images of fluorescein-labelled ManAc-functionalized dextrans and FACS analyses of cells, these results demonstrate that receptor-mediated endocytosis of ManAcPEI-conjugatepDNA complexes via ManAc-specific receptors was involved in gene transfer. In conclusion, ManAc-modification of PEI-polymers represents a novel strategy for receptor-mediated gene delivery which could be promising for in vivo application.
To satisfy the applied compressive stresses of friction welded drive pinion fabricated by using the joint-site structure (JSS) method, three different variants were followed: (A) the initial design with two joints was carried out. Two different burn-off lengths were examined for this variant. (B) The optimum burn-off length was considered for only one weld zone. (C) The weld zone was moved radially from the initial location and two different gap sizes were compared. The smallest gap size for the third variant led to the largest weld length. The lack of structural welding defects for this variant was assessed by ultrasonic testing. Hardness of the material after friction welding (FW) was correlated to the Continuous Cooling Transformation (CCT) diagram of the used materials and revealed the phase/microstructure transformation of the material. The simulated applied stresses on the optimized friction welded design of the drive pinion showed suitable results. The new drive pinion friction welded by the JSS method reduced the weight of the component by approx. 14%.