886 research outputs found
Influence of variation of etching conditions on the sensitivity of PADC detectors with a new evaluation method
At the Paul Scherrer Institut, a personal neutron dosimetry system based on chemically etched poly allyl diglycol carbonate (PADC) detectors and an automatic track counting (Autoscan 60) for neutron dose evaluations has been in routine use since 1998. Today, the hardware and the software of the Autoscan 60 are out of date, no spare components are available anymore and more sophisticated image-analysis systems are already developed. Therefore, a new evaluation system, the ‘TASLIMAGE', was tested thoroughly in 2009 for linearity, reproducibility, influence of etching conditions and so forth, with the intention of replacing the Autoscan 60 in routine evaluations. The TASLIMAGE system is based on a microscope (high-quality Nikon optics) and an ultra-fast three-axis motorised control for scanning the detectors. In this paper, the TASLIMAGE system and its possibilities for neutron dose calculation are explained in more detail and the study of the influence of the variation of etching conditions on the sensitivity and background of the PADC detectors is described. The etching temperature and etching duration were varied, which showed that the etching conditions do not have a significant influence on the results of non-irradiated detectors. However, the sensitivity of irradiated detectors decreases by 5 % per 1°C when increasing the etching temperature. For the variation of the etching duration, the influence on the sensitivity of irradiated detectors is less pronounce
50 Jahre D-Mark
Im Laufe des letzten halben Jahrhunderts ist die Deutsche Mark zu einem Symbol für Stabilität geworden. Was läßt sich aus ihrer Geschichte für ihren Nachfolger, den Euro, lernen? Welche Chancen und Risiken sind mit der Ablösung der D-Mark verbunden? Welche Voraussetzungen müssen für eine stabile Entwicklung des Euro erfüllt sein? --
Fiber transport of spatially entangled photons
Entanglement in the spatial degrees of freedom of photons is an interesting
resource for quantum information. For practical distribution of such entangled
photons it is desireable to use an optical fiber, which in this case has to
support multiple transverse modes. Here we report the use of a hollow-core
photonic crystal fiber to transport spatially entangled qubits.Comment: 4 pages, 4 figure
Spatiotemporal control of active topological defects
Topological defects play a central role in the physics of many materials,
including magnets, superconductors and liquid crystals. In active fluids,
defects become autonomous particles that spontaneously propel from internal
active stresses and drive chaotic flows stirring the fluid. The intimate
connection between defect textures and active flow suggests that properties of
active materials can be engineered by controlling defects, but design
principles for their spatiotemporal control remain elusive. Here we provide a
symmetry-based additive strategy for using elementary activity patterns, as
active topological tweezers, to create, move and braid such defects. By
combining theory and simulations, we demonstrate how, at the collective level,
spatial activity gradients act like electric fields which, when strong enough,
induce an inverted topological polarization of defects, akin to an exotic
negative susceptibility dielectric. We harness this feature in a dynamic
setting to collectively pattern and transport interacting active defects. Our
work establishes an additive framework to sculpt flows and manipulate active
defects in both space and time, paving the way to design programmable active
and living materials for transport, memory and logic.Comment: 37 pages (including Methods), 5 figures + 4 extended data figures.
Corrected some previous errors without change in result
A new technique for transumbilical insertion of central venous silicone catheters in newborn infants
Aim: A new technique allowing placement of umbilical silicone venous catheters (USVC) is described and compared with percutaneous silicone venous catheters (PSVC)
Lasing oscillation in a three-dimensional photonic crystal nanocavity with a complete bandgap
We demonstrate lasing oscillation in a three-dimensional photonic crystal
nanocavity. The laser is realized by coupling a cavity mode, which is localized
in a complete photonic bandgap and exhibits the highest quality factor of
~38,500, with high-quality semiconductor quantum dots. We show a systematic
change in the laser characteristics, including the threshold and the
spontaneous emission coupling factor by controlling the crystal size, which
consequently changes the strength of photon confinement in the third dimension.
This opens up many interesting possibilities for realizing future ultimate
light sources and three-dimensional integrated photonic circuits and for more
fundamental studies of physics in the field of cavity quantum electrodynamics.Comment: 14 pages, 4 figure
- …