@article{HochleitnerJuengstBrownetal.2015, author = {Hochleitner, Gernot and J{\"u}ngst, Tomasz and Brown, Toby D and Hahn, Kathrin and Moseke, Claus and Jakob, Franz and Dalton, Paul D and Groll, J{\"u}rgen}, title = {Additive manufacturing of scaffolds with sub-micron filaments via melt electrospinning writing}, series = {Biofabrication}, volume = {7}, journal = {Biofabrication}, number = {3}, doi = {10.1088/1758-5090/7/3/035002}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-254053}, year = {2015}, abstract = {The aim of this study was to explore the lower resolution limits of an electrohydrodynamic process combined with direct writing technology of polymer melts. Termed melt electrospinning writing, filaments are deposited layer-by-layer to produce discrete three-dimensional scaffolds for in vitro research. Through optimization of the parameters (flow rate, spinneret diameter, voltage, collector distance) for poly-ϵ-caprolactone, we could direct-write coherent scaffolds with ultrafine filaments, the smallest being 817 ± 165 nm. These low diameter filaments were deposited to form box-structures with a periodicity of 100.6 ± 5.1 μm and a height of 80 μm (50 stacked filaments; 100 overlap at intersections). We also observed oriented crystalline regions within such ultrafine filaments after annealing at 55 °C. The scaffolds were printed upon NCO-sP(EO-stat-PO)-coated glass slide surfaces and withstood frequent liquid exchanges with negligible scaffold detachment for at least 10 days in vitro.}, language = {en} } @article{BrixnerPawłowskaGoetzetal.2014, author = {Brixner, Tobias and Pawłowska, Monika and Goetz, Sebastian and Dreher, Christian and Wurdack, Matthias and Krauss, Enno and Razinskas, Gary and Geisler, Peter and Hecht, Bert}, title = {Shaping and spatiotemporal characterization of sub-10-fs pulses focused by a high-NA objective}, doi = {10.1364/OE.22.031496}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-111120}, year = {2014}, abstract = {We describe a setup consisting of a 4 f pulse shaper and a microscope with a high-NA objective lens and discuss the spects most relevant for an undistorted spatiotemporal profile of the focused beam. We demonstrate shaper-assisted pulse compression in focus to a sub-10-fs duration using phase-resolved interferometric spectral modulation (PRISM). We introduce a nanostructure-based method for sub-diffraction spatiotemporal characterization of strongly focused pulses. The distortions caused by optical aberrations and space-time coupling from the shaper can be reduced by careful setup design and alignment to about 10 nm in space and 1 fs in time.}, language = {en} } @article{OjhaForsterKumaretal.2013, author = {Ojha, Animesh K. and Forster, Stefan and Kumar, Sumeet and Vats, Siddharth and Negi, Segeeta and Fischer, Ingo}, title = {Synthesis of well-dispersed silver nanorods of different aspect ratios and their antimicrobial properties against gram positive and negative bacterial strains}, series = {Journal of Nanobiotechnology}, volume = {11}, journal = {Journal of Nanobiotechnology}, number = {42}, issn = {1477-3155}, doi = {10.1186/1477-3155-11-42}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-122837}, year = {2013}, abstract = {In the present contribution, we describe the synthesis of highly dispersed silver nanorods (NRs) of different aspect ratios using a chemical route. The shape and size of the synthesized NRs were characterized by Transmission Electron Microscopy (TEM) and UV-visible spectroscopy. Longitudinal and transverse absorptions bands confirm the rod type structure. The experimentally recorded UV-visible spectra of NRs solutions were fitted by using an expression of the extinction coefficient for rod like nano structures under the dipole approximation. Simulated and experimentally observed UV-visible spectra were compared to determine the aspect ratios (R) of NRs. The average values of R for NR1, NR2 and NR3 solutions are estimated to be 3.0 +/- 0.1, 1.8 +/- 0.1 and 1.2 +/- 0.1, respectively. These values are in good agreement with those obtained by TEM micrographs. The silver NRs of known aspect ratios are used to study antimicrobial activities against B. subtilis (gram positive) and E. coli (gram negative) microbes. We observed that the NRs of intermediate aspect ratio (R = 1.8) have greater antimicrobial effect against both, B. subtilis (gram positive) and E. coli (gram negative). The NRs of aspect ratio, R = 3.0 has better antimicrobial activities against gram positive than on the gram negative.}, language = {en} } @article{KoenigBaenningerGarciaetal.2013, author = {K{\"o}nig, Markus and Baenninger, Matthias and Garcia, Andrei G. F. and Harjee, Nahid and Pruitt, Beth L. and Ames, C. and Leubner, Philipp and Br{\"u}ne, Christoph and Buhmann, Hartmut and Molenkamp, Laurens W. and Goldhaber-Gordon, David}, title = {Spatially Resolved Study of Backscattering in the Quantum Spin Hall State}, series = {Physical Review X}, volume = {3}, journal = {Physical Review X}, number = {2}, issn = {2160-3308}, doi = {10.1103/PhysRevX.3.021003}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-127225}, pages = {21003}, year = {2013}, abstract = {The discovery of the quantum spin Hall (QSH) state, and topological insulators in general, has sparked strong experimental efforts. Transport studies of the quantum spin Hall state have confirmed the presence of edge states, showed ballistic edge transport in micron-sized samples, and demonstrated the spin polarization of the helical edge states. While these experiments have confirmed the broad theoretical model, the properties of the QSH edge states have not yet been investigated on a local scale. Using scanning gate microscopy to perturb the QSH edge states on a submicron scale, we identify well-localized scattering sites which likely limit the expected nondissipative transport in the helical edge channels. In the micron-sized regions between the scattering sites, the edge states appear to propagate unperturbed, as expected for an ideal QSH system, and are found to be robust against weak induced potential fluctuations.}, language = {en} }