140 research outputs found
Time-resolved fast-neutron imaging with a pulse-counting image intensifier
A new imaging method that combines high-efficiency fast-neutron detection with sub-ns time resolution is presented. This is achieved by exploiting the high neutron detection efficiency of a thick scintillator and the fast timing capability and flexibility of light-pulse detection with a dedicated image intensifier. The neutron converter is a plastic scintillator slab or, alternatively, a scintillating fibre screen. The scintillator is optically coupled to a pulse counting image intensifier which measures the 2-dimensional position coordinates and the Time-Of-Flight (TOF) of each detected neutron with an intrinsic time resolution of less than 1 ns. Large-area imaging devices with high count rate capability can be obtained by lateral segmentation of the optical readout channels
Phantomschmerz nach Extremitätenamputation : Diagnostik und Biofeedback-Behandlung
Phantomschmerz ist ein multifaktoriell bedingtes Schmerzsyndrom, für das kaum wirksame Behandlungsmöglichkeiten vorhanden sind. In Teil 1 der vorliegenden Arbeit wurde ein diagnostisches Interview zur Erfassung von Phantom- und Stumpfempfindungen validiert. Dabei konnte beim Phantom- und Stumpfschmerz - wie auch bei anderen Schmerzsyndromen - zwischen einer affektiven und einer sensorischen Schmerzkomponente unterschieden werden. In Teilstudie 2 wurde ein Vergleich zwischen arm- und beinamputierten Patienten mit Phantomschmerz angestellt. Bei beinamputierten Patienten trat ebenso wie bei Armamputierten eine Verschiebung der Repräsentationsgebiete im primären somatosensorischen Kortex auf, diese war jedoch bei den Beinamputierten variabler ausgeprägt. Zugleich nutzten die beinamputierten gegenüber den armamputierten Patienten signifikant häufiger eine Prothese. In Teilstudie 3 wurde mit fünf arm- bzw. beinamputierten Patienten ein zehnstündiges Biofeedback-Training durchgeführt, das zu einer signifikanten Reduktion des Phantomschmerzes führte. Besonders gut profitierten Patienten, die zusätzlich an Stumpfschmerz litten, eine hohe Reagibilität der Stumpfmuskulatur sowie attackenförmige Schmerzen zeigten
The ORFEUS II Echelle Spectrum of HD 93521: A reference for interstellar molecular hydrogen
During the second flight of the ORFEUS-SPAS mission in November/December
1996, the Echelle spectrometer was used extensively by the Principal and Guest
Investigator teams as one of the two focal plane instruments of the ORFEUS
telescope. The spectrum of HD 93521 was obtained during this mission with a
total integration time of 1740 s. This spectrum shows numerous sharp
interstellar absorption lines. We identified 198 lines of molecular hydrogen
including at least 7 lines with a high velocity component. Also most of the 67
identified interstellar metal lines are visible with a high velocity component.
We present plots of the complete ORFEUS Echelle spectrum together with tables
of all identified interstellar absorption lines including all 14 detectable HI
lines. In addition several identified stellar lines, partially with narrow
absorption components, and stellar wind lines are given in a separate table.Comment: 18 pages, 33 figure
ORFEUS-II Far-Ultraviolet Observations of 3C273: 1. Interstellar and Intergalactic Absorption Lines
We present the first intermediate-resolution (lambda / 3000) spectrum of the
bright quasi-stellar object 3C273 at wavelengths between 900 and 1200 A.
Observations were performed with the Berkeley spectrograph aboard the
ORFEUS-SPAS II mission. We detect Lyman beta counterparts to
previously-identified intergalactic Lyman-alpha features at cz = 19900, 1600,
and 1000 km/s; counterparts to other putative Lyman-alpha clouds along the
sight line are below our detection limit. The strengths of the two very low
redshift Lyman-beta features, which are believed to arise in Virgo intracluster
gas, exceed preflight expectations, suggesting that the previous determination
of the cloud parameters may underestimate the true column densities. A
curve-of-growth analysis sets a minimum H I column density of 4 E14/cm^2 for
the 1600 km/s cloud. We find marginally significant evidence for Galactic H_2
along the sight line, with a total column density of about 1 E15/cm^2. We
detect the stronger interstellar O VI doublet member unambiguously; the weaker
member is blended with other features. If the Doppler b value for O VI is
comparable to that determined for N V then the O VI column density is 7 +/- 2
E14/cm^2, significantly above the only previous estimate. The O VI / N V ratio
is about 10, consistent with the low end of the range observed in the disk.
Additional interstellar species detected for the first time toward 3C273 (at
modest statistical significance) include P II, Fe III, Ar I, and S III.Comment: LaTeX file, 11 pages, 4 encapsulated PostScript figures. Uses
aaspp4.sty and astrobib.sty. (Astrobib is available from
http://www.stsci.edu/software/TeX.html .) The ORFEUS telescope is described
at http://sag-www.ssl.berkeley.edu/orfeus/ . To appear in ApJ (Letters
Memory-Relevant Mushroom Body Output Synapses Are Cholinergic
Memories are stored in the fan-out fan-in neural architectures of the mammalian cerebellum and hippocampus and the insect mushroom bodies. However, whereas key plasticity occurs at glutamatergic synapses in mammals, the neurochemistry of the memory-storing mushroom body Kenyon cell output synapses is unknown. Here we demonstrate a role for acetylcholine (ACh) in Drosophila. Kenyon cells express the ACh-processing proteins ChAT and VAChT, and reducing their expression impairs learned olfactory-driven behavior. Local ACh application, or direct Kenyon cell activation, evokes activity in mushroom body output neurons (MBONs). MBON activation depends on VAChT expression in Kenyon cells and is blocked by ACh receptor antagonism. Furthermore, reducing nicotinic ACh receptor subunit expression in MBONs compromises odor-evoked activation and redirects odor-driven behavior. Lastly, peptidergic corelease enhances ACh-evoked responses in MBONs, suggesting an interaction between the fast- and slow-acting transmitters. Therefore, olfactory memories in Drosophila are likely stored as plasticity of cholinergic synapses
Spectral Energy Distributions of starburst galaxies in the 900-1200 A range
We present the 970-1175 A spectral energy distributions (SEDs) of 12
starburst galaxies observed with the Far Ultraviolet Spectroscopic Explorer
FUSE. We take benefit of the high spectral resolution of FUSE to estimate a
continuum as much as possible unaffected by the interstellar lines. The
continuum is rather flat with, in few cases, a decrease at lambda <~1050 A, the
amplitude of which being correlated with various indicators of the dust
extinction. The far-UV SEDs are compared with synthetic population models. The
galaxies with almost no extinction have a SED consistent with an on-going star
formation over some Myrs. We derive a mean dust attenuation law in the
wavelength range 965-1140 A by comparing the SED of obscured galaxies to an
empirical dust-free SED. The extinction is nearly constant longward of 1040 A
but rises at shorter wavelengths. We compare our results with other studies of
the extinction for galaxies and stars in this wavelength range.Comment: 11 pages, 6 postscript figures, accepted for publication in Astronomy
& Astrophysic
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