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- 2011 (6) (entfernen)
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- Beitrag zu einem Tagungsband (3)
- Vortrag (2)
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- Backlight (1)
- Computed tomography (1)
- Computer-Tomographie (1)
- Detektor (1)
- Dicondylia (1)
- Fluorescence screen (1)
- Fluoreszenzschirm (1)
- Grylloblattodea (1)
- Hinterleuchten (1)
- Long period grating (LPG) (1)
Eingeladener Vortrag
- nein (2)
External and internal head structures of adults of Galloisiana yuasai (Grylloblattodea) are described. The results are compared with conditions found in representatives of other lower neopteran lineages, notably in Austrophasma and Karoophasma (both Mantophasmatodea). Sutures and ridges of the head capsule are discussed. A new nomenclature for head muscles is presented for the entire Dicondylia (= Zygentoma + Pterygota). Galloisiana (like its sister taxon Grylloblatta) is mostly characterized by plesiomorphic features, such as the largely unspecialized orthopteroid mouthparts, the multisegmented filiform antennae, the presence of trabeculae tentorii, the absence of muscles associated with the antennal ampullae, the presence of musculus stipitalis transversalis (0mx11) and the presence of musculus tentoriofrontalis anterior (0te2). Autapomorphies of Grylloblattodea are: (i) compound eyes composed of only 60 ommatidia or less; (ii) a lacinia with a proximal tooth; (iii) a rounded submentum; (iv) loss of musculus craniohypopharyngealis (0hy3); and (v) loss of musculus labroepipharyngealis (0lb5). The phylogenetic evaluation of 104 characters of the head yields a branching pattern with Grylloblattodea as a sister group of Mantophasmatodea in clade Xenonomia. Putative synapomorphies of both taxa are: (i) a distinct angle (more than 60°) between the submentum and the mentum; (ii) posteriorly oriented labial palpi; (iii) a flat and lobe-like hypopharynx with a suspensorium far ventrad of the anatomical mouth opening; (iv) loss of musculus tentorioparaglossalis (0la6); and (v) a connection between the antennal ampulla and the supraoesophageal ganglion containing nuclei. Xenonomia is placed in a clade with the two dictyopteran terminals. Another monophyletic group is Embioptera + Phasmatodea. Most branches of the single tree obtained in our analysis are weakly supported. The results clearly show that more data and a much broader taxon sampling are required to clarify the phylogenetic interrelationships of the lower neopteran orders. However, our results narrow down the spectrum of possible solutions, and represent a starting point for future phylogenetic analyses, with an extensive concatenated dataset.
We investigated to our knowledge for the first time the capabilities of long period gratings (LPG) in single-mode microstructured polymer optical fibre (mPOF) as real-time gamma dosimeter. The fibre is made from polymethyl methacrylate (PMMA) with a polycarbonate jacket. We measured the radiation-induced wavelength shift of the mPOF LPG loss feature wavelength and the radiation-induced attenuation of a mPOF for
different wavelength between 600 nm and 800 nm for gamma radiation with an energy distribution between 6 keV and 18 keV.
A novel approach to strongly suppress artifacts in radiography and computed tomography caused by the effect of diffuse background Signals (backlight) of 2D X-ray detectors is suggested. Depending on the detector geometry the mechanism may be different, either based on the optical scattering of the fluorescent screen materials into optical detection devices or Compton or X-ray fluorescence scattering by the detector components. Consequently, these erroneous intensity portions result in locally different violations of Lambert Beers law in single projections (radiographs).
When used as input data for computed tomography these violations are directly observed via modulation of the projected mass as a function of the rotation Phase and the samples aspect ratio (dynamics). The magnitude of the diffuse Background signal depends on the detector area covered by the projected sample. They are more pronounced the smaller the shaded area and the stronger the total attenuation.
Moreover, the local intensity mismatch depends on the attenuation of the sample.
We present very basic reference data measured with multiple metal foils at a synchrotron radiation source. Beam hardening artifacts can be excluded due to the monochromatic radiation. The proposed correction procedure assumes a constant (non-local) scattering mechanism.
In den unterschiedlichsten Methoden der Computertomographie tritt häufig ein diffuses Untergrundsignal in den Einzelprojektionen auf: im Falle der Parallelstrahl-CT mit Synchrotronstrahlung handelt es sich um ein Hinterleuchten durch den Fluoreszenzschirm, der vor der CCD-Kamera angeordnet ist. Dieses Hinterleuchten unterscheidet sich von dem bekannten Nachleuchten (Phosphoreszenz) durch zeitliche Konstanz.
Hier äußert sich das Hinterleuchten als Modulation der projizierten Masse und somit als Funktion der Phase (Projektionswinkel) und des Aspektverhältnisses des Objektes. Der Einfluss des Hinterleuchtens ist abhängig von der Größe des von der Probe abgeschatteten Detektorbereiches und des Objektumfangs (Dynamik). Dies hat u.a. zur Folge, dass Abweichungen vom Absorptionsgesetz auftreten, die umso
stärker ausgeprägt sind, je weniger Detektorfläche das Objekt abdeckt und je stärker das Objekt schwächt. Dabei können Aufhärtungseffekte wegen der monochromatischen Strahlung ausgeschlossen werden.
Mit Referenzmessungen und einem isotropen, homogenen Ansatz, der diese Abweichung als Hinterleuchten beschreibt, lassen sich die auftretenden Fehler deutlich verringern.