A Test of Possible NICMOS Non-linearity
Observations of standard stars with NICMOS grism (G096), when compared with the same standards taken by STIS (G750L), show a disagreement over the wavelength range 0.8 to 1 micron. Further comparison with ACS F850LP data confirms thisnon-linearity to be due to NICMOS in the sense that fainter stars in NICMOS appear too faint relative to a brighter normalisation. We investigate this over a wide magnitude range by compiling samples of stars (over the range 8 < J < 17) and galaxies (spanning the range 17 < J < 25), with available data with both NICMOS (F110W and F160W) and ground-based JHbands. We find no difference between the NICMOS F160W and ground-based H-band magnitudes. However, in the case of NICMOS F110W and J-band filters, allowing for differences in the filter response functions, we find a trend at the bright-end (J < 17), confirming a non-linearity but smaller than that was seen in Bohlin effect by a factor of 2-3. No significant slope is seen at the faint-end. This non-linearity is interpreted as being due to trapping and the difference in exposure times between the bright and faint objects (Riess 2005). We conclude that most of the observations will not be strongly affected by this effect as the source count rates are sufficiently high so that the fraction of charge lost to traps is negligible. The most affected observations are for faint sources with relatively short exposures.
INSTRUMENT SCIENCE REPORT
This report gives a description of the IDL software developed to generate the latest geometric correction models and describes the process of using the specific routines to generate geometric correction models.
Thorium-induced Anatomical and Histopathological Changes in Liver of Swiss Mice
ObjectivePresent study is aimed to investigate the anatomical and histopathological changes in liver tissues of Swiss albino male mice, one month after intravenous administration of thorium (232Th; 4 and 40 mg/kg).MethodsSynchrotron X-ray micro-CT imaging, CD31 immuno-cytochemistry, hematoxylin & eosin staining and Periodic acid-Schiff staining were performed to study changes in liver anatomy, blood vessels/capillaries, histology and glycogen content of liver, respectively.ResultsSynchrotron X-ray micro-CT imaging of liver showed loss of blood vessels in mice treated with thorium (4 mg/kg), which was more prominent at higher dose of thorium (40 mg/kg). These thorium-induced changes in liver were correlated with the decrease in CD31 positive cells and loss of tissue architecture. A dose-dependent increase in glycogen content was also observed in the liver of thorium-treated mice.ConclusionOur results provide novel insight about the effects of thorium on liver, which may have significant implications in understanding the mechanism of thorium thorium-induced hepatotoxicity.