178 research outputs found
Glass capillary X-ray lens: fabrication technique and ray tracing calculations
A new method for producing a compound refractive X-ray lens is described. The lens is designed as glass capillary "lled by a set of concave individual lenses. The method is appropriate for the preparation of 10}1000 spherical lenses in a glass capillary with a diameter of 0.1}1 mm. Lens aberrations are considered and simple formulas for spot size are derived. Ray-tracing simulations on the focusing experiments using 18 keV X-rays are reported. ( 2000 Elsevier Science B.V. All rights reserved
Deep-core photoionization of krypton atoms below and above the 1s ionization threshold
Electronic relaxation of atomic Kr below and above the 1s ionization threshold is investigated experimentally using hard x-ray photoelectron spectroscopy. The experimental results are interpreted with the aid of relativistic Dirac-Fock calculations. The 1s orbital core-hole lifetime is extracted and the satellite's structures accompanying the photoelectron main line are assigned. Auger spectra recorded below and above the K edge are also investigated. In particular, the Auger cascade originating from vacancies of different origin in the L shell is analyzed in great detail. Competition between radiative KL versus nonradiative KLL Auger emission is emphasized
Dendritic planarity of Purkinje cells is independent of Reelin signaling
The dendritic planarity of Purkinje cells is critical for cerebellar circuit formation. In the absence of Crk and CrkL, the Reelin pathway does not function resulting in partial Purkinje cell migration and defective dendritogenesis. However, the relationships among Purkinje cell migration, dendritic development and Reelin signaling have not been clearly delineated. Here, we use synchrotron X-ray microscopy to obtain 3-D images of Golgi-stained Purkinje cell dendrites. Purkinje cells that failed to migrate completely exhibited conical dendrites with abnormal 3-D arborization and reduced dendritic complexity. Furthermore, their spines were fewer in number with a distorted morphology. In contrast, Purkinje cells that migrated successfully displayed planar dendritic and spine morphologies similar to normal cells, despite reduced dendritic complexity. These results indicate that, during cerebellar formation, Purkinje cells migrate into an environment that supports development of dendritic planarity and spine formation. While Reelin signaling is important for the migration process, it does not make a direct major contribution to dendrite formation.1111Ysciescopu
The Nature of Ultra-Luminous Compact X-Ray Sources in Nearby Spiral Galaxies
Studies were made of ASCA spectra of seven ultra-luminous compact X-ray
sources (ULXs) in nearby spiral galaxies; M33 X-8 (Takano et al. 1994), M81 X-6
(Fabbiano 1988b; Kohmura et al. 1994; Uno 1997), IC 342 Source 1 (Okada et al.
1998), Dwingeloo 1 X-1 (Reynolds et al. 1997), NGC 1313 Source B (Fabbiano &
Trinchieri 1987; Petre et al. 1994), and two sources in NGC 4565 (Mizuno et al.
1999). With the 0.5--10 keV luminosities in the range 10^{39-40} ergs/s, they
are thought to represent a class of enigmatic X-ray sources often found in
spiral galaxies. For some of them, the ASCA data are newly processed, or the
published spectra are reanalyzed. For others, the published results are quoted.
The ASCA spectra of all these seven sources have been described successfully
with so called multi-color disk blackbody (MCD) emission arising from
optically-thick standard accretion disks around black holes. Except the case of
M33 X-8, the spectra do not exhibit hard tails. For the source luminosities not
to exceed the Eddington limits, the black holes are inferred to have rather
high masses, up to ~100 solar masses. However, the observed innermost disk
temperatures of these objects, Tin = 1.1--1.8 keV, are too high to be
compatible with the required high black-hole masses, as long as the standard
accretion disks around Schwarzschild black holes are assumed. Similarly high
disk temperatures are also observed from two Galactic transients with
superluminal motions, GRO 1655-40 and GRS 1915+105. The issue of unusually high
disk temperature may be explained by the black hole rotation, which makes the
disk get closer to the black hole, and hence hotter.Comment: submitted to ApJ, December 199
Development of a one-dimensional Wolter mirror for achromatic full-field X-ray microscopy
We investigated a one-dimensional Wolter mirror (which consists of an elliptical mirror and a hyperbolic mirror) with the aim of developing an achromatic full-field X-ray microscope with a resolution of better than 50 nm. X-ray mirrors were ultraprecisely fabricated by elastic emission machining to give a figure accuracy of 2 nm (peak-to-valley). A one-dimensional Wolter mirror that had been precisely constructed was evaluated in terms of the point-spread function at the center of the field of view (FOV) and the FOV at an X-ray energy of 11.5 keV at BL29XUL of SPring-8. It was found to have a minimum resolution of 43 nm and a FOV equivalent to 12.1 μm. These results are highly consistent with calculation results. © 2011 SPIE.S. Matsuyama, N. Kidani, H. Mimura, J. Kim, Y. Sano, K. Tamasaku, Y. Kohmura, M. Yabashi, T. Ishikawa, and K. Yamauchi "Development of a one-dimensional Wolter mirror for achromatic full-field x-ray microscopy", Proc. SPIE 8139, Advances in X-Ray/EUV Optics and Components VI, 813905 (28 September 2011); https://doi.org/10.1117/12.892987.SPIE Optical Engineering + Applications, 2011, San Diego, California, United State
Suzaku Observation of AXP 1E 1841-045 in SNR Kes 73
Anomalous X-ray pulsars (AXPs) are thought to be magnetars, which are neutron
stars with ultra strong magnetic field of -- G. Their energy
spectra below 10 keV are modeled well by two components consisting of a
blackbody (BB) (0.4 keV) and rather steep power-law (POW) function
(photon index 2-4). Kuiper et al.(2004) discovered hard X-ray component
above 10 keV from some AXPs. Here, we present the Suzaku observation of
the AXP 1E 1841-045 at the center of supernova remnant Kes 73. By this
observation, we could analyze the spectrum from 0.4 to 50 keV at the same time.
Then, we could test whether the spectral model above was valid or not in this
wide energy range. We found that there were residual in the spectral fits when
fit by the model of BB + POW. Fits were improved by adding another BB or POW
component. But the meaning of each component became ambiguous in the
phase-resolved spectroscopy. Alternatively we found that NPEX model fit well
for both phase-averaged spectrum and phase-resolved spectra. In this case, the
photon indices were constant during all phase, and spectral variation seemed to
be very clear. This fact suggests somewhat fundamental meaning for the emission
from magnetars.Comment: To appear in the proceedings of the "40 Years of Pulsars: Millisecond
Pulsars, Magnetars and More" conference, held 12-17 August 2007, in Montreal
QC (AIP, in press, eds: C. Bassa, Z. Wang, A. Cumming, V. Kaspi
Swift and Suzaku Observations of the X-Ray Afterglow from the GRB 060105
Results are presented of early X-ray afterglow observations of GRB 060105 by
Swift and Suzaku. The bright, long gamma-ray burst GRB 060105 triggered the
Swift Burst Alert Telescope (BAT) at 06:49:28 on 5 January 2006. The Suzaku
team commenced a pre-planned target of opportunity observation at 19 ks (5.3
hr) after the Swift trigger. Following the prompt emission and successive very
steep decay, a shallow decay was observed from T_0+187 s to T_0+1287 s. After
an observation gap during T_0 +(1.5-3) ks, an extremely early steep decay was
observed in T_0+(4-30) ks. The lightcurve flattened again at T_0+30 ks, and
another steep decay followed from T_0+50 ks to the end of observations. Both
steep decays exhibited decay indices of 2.3 - 2.4. This very early break, if it
is a jet break, is the earliest case among X-ray afterglow observations,
suggesting a very narrow jet whose opening angle is well below 1 degree. The
unique Suzaku/XIS data allow us to set very tight upper limits on line emission
or absorption in this GRB. For the reported pseudo-redshift of z=4.0+/-1.3 the
upper limit on the iron line equivalent width is 50 eV.Comment: 8 pages, 5 figures, Accepted for publication in PASJ Suzaku Special
Issue (vol. 58
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