664 research outputs found
Preliminary trials with optical fiber dosimeters at TTF
Ionizing radiation leads to a degradation of the light transmitting properties of fiber optic cables. These effects usually place restrictions on where they can be used in a particle accelerator facility. These effects can also be used to our advantage, the losses from a particle beam create wavelength dependant increases of attenuation by absorption and scattering which can be measured using Optical Time Domain Reflectometry (OTDR). From these measurements a measure of the radiation dose received can be inferred
Tricarbonyliron(0) complexes of bio-derived η4 cyclohexadiene ligands: An approach to analogues of oseltamivir
We have prepared novel [η4] and [η5]+ tricarbonyliron complexes from an unusual enantiopure cyclohexadiene ligand that possesses a quaternary stereocentre; this in turn is prepared through biotransformation of an aromatic ring. The cyclohexadiene ligand initially possessed two hydroxyl groups, both of which could be substituted with other functionality by means of an overall [η4] → [η5]+ → [η4] → [η5]+ → [η4] sequence. From six novel tricarbonyliron complexes which have been prepared, three have been characterised by x-ray crystallography. The reaction sequence we describe is potentially of relevance to the synthesis of analogues of the anti-influenza drug oseltamivir. In addition, the failure of an attempted addition of a bulky nitrogen nucleophile to an [η5]+ complex sheds light on the limits of reactivity for such additions. Thus, two bulky nucleophiles which are each known to add successfully to unencumbered [η5]+ complexes seemingly cannot be added sequentially to adjacent positions on the cyclohexadiene ligand
Software that goes with the flow in systems biology
A recent article in BMC Bioinformatics describes new advances in workflow systems for computational modeling in systems biology. Such systems can accelerate, and improve the consistency of, modeling through automation not only at the simulation and results-production stages, but also at the model-generation stage. Their work is a harbinger of the next generation of more powerful software for systems biologists
Validation of GBS plasma turbulence simulation of the TJ-K stellarator
We present a validation of a three-dimensional, two-fluid simulation of
plasma turbulence in the TJ-K stellarator, a low temperature plasma experiment
ideally suited for turbulence measurements. The simulation is carried out by
the GBS code, recently adapted to simulate 3D magnetic fields. The comparison
shows that GBS retrieves the main turbulence properties observed in the device,
namely the fact that transport is dominated by fluctuations with low poloidal
mode number. The poloidal dependence of the radial
turbulent flux is compared on a poloidal plane with elliptical flux surfaces,
where a very good agreement between experiment and simulation is observed, and
on another with triangular flux surfaces, which shows a poorer comparison. The
fluctuation levels in both cases are underestimated in the simulations. The
equilibrium density profile is well retrieved by the simulation, while the
electron temperature and the electrostatic potential profiles, which are very
sensitive to the strength and localization of the sources, do not agree well
with the experimental measurements
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