| 1. |
- Kamae, Tuneyoshi, et al.
(författare)
-
PoGOLite - A high sensitivity balloon-borne soft gamma-ray polarimeter
- 2008
-
Ingår i: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 30:2, s. 72-84
-
Tidskriftsartikel (refereegranskat)abstract
- We describe a new balloon-borne instrument (PoGOLite) capable of detecting 10% polarisation from 200 mCrab point-like sources between 25 and 80 keV in one 6-h flight. Polarisation measurements in the soft gamma-ray band are expected to provide a powerful probe into high energy emission mechanisms as well as the distribution of magnetic fields, radiation fields and interstellar matter. Synchrotron radiation, inverse Compton scattering and propagation through high magnetic fields are likely to produce high degrees of polarisation in the energy band of the instrument. We demonstrate, through tests at accelerators, with radioactive sources and through computer simulations, that PoGOLite will be able to detect degrees of polarisation as predicted by models for several classes of high energy sources. At present, only exploratory polarisation measurements have been carried out in the soft gamma-ray band. Reduction of the large background produced by cosmic-ray particles while securing a large effective area has been the greatest challenge. PoGOLite uses Compton scattering and photo-absorption in an array of 217 well-type phoswich detector cells made of plastic and BGO scintillators surrounded by a BGO anticoincidence shield and a thick polyethylene neutron shield. The narrow Held of view (FWHM = 1.25 msr, 2.0 deg x 2.0 deg) obtained with detector cells and the use of thick background shields warrant a large effective area for polarisation measurements (similar to 228 cm(2) at E = 40 keV) without sacrificing the signal-to-noise ratio. Simulation studies for an atmospheric overburden of 3-4 g/cm(2) indicate that neutrons and gamma-rays entering the PDC assembly through the shields are dominant backgrounds. Off-line event selection based on recorded phototube waveforms and Compton kinematics reduce the background to that expected for a similar to 100 mCrab source between 25 and 50 keV. A 6-h observation of the Crab pulsar will differentiate between the Polar Cap/Slot Gap, Outer Gap, and Caustic models with greater than 5 sigma significance; and also cleanly identify the Compton reflection component in the Cygnus X-1 hard state. Long-duration flights will measure the dependence of the polarisation across the cyclotron absorption line in Hercules X-1. A scaled-down instrument will be flown as a pathfinder mission from the north of Sweden in 2010. The first science flight is planned to take place shortly thereafter.
|
|
| 2. |
- Navarro-Alvarez, Nalu, et al.
(författare)
-
Intramuscular transplantation of engineered hepatic tissue constructs corrects acute and chronic liver failure in mice
- 2010
-
Ingår i: Journal of Hepatology. - 0168-8278 .- 1600-0641. ; 52:2, s. 211-219
-
Tidskriftsartikel (refereegranskat)abstract
- Background & Aims: Transplantation of isolated hepatocytes holds great promise as ail alternative to whole organ liver transplantation. For treatment of liver failure, access to the portal circulation has significant risks and intrahepatic hepatocyte engraftment is poor. In advanced cirrhosis, transplantation into ail extrahepatic site is necessary and intrasplenic engraftment is short-lived. Strategies that allow repeated extrahepatic infusion of hepatocytes Could improve the efficacy and safety of hepatocyte transplantation for the treatment of liver failure. Methods: A non-immunogenic self-assembling peptide nanofiber (SAPNF) was developed as a three-dimensional scaffold and combined with growth factors derived from a conditionally immortalized human hepatocyte cell line to engineer a hepatic tissue graft that Would allow hepatocyte engraftment outside the liver. Results:The hepatic tissue Constructs maintained hepatocyte-specific gene expression and functionality in vitro. When transplanted into skeletal muscle as ail extrahepatic site for engraftment, the engineered hepatic grafts provided life-saving support in models of acute, fulminant, and chronic liver failure that recapitulates these clinical diseases. Conclusions: SAPNF-engineered hepatic Constructs engrafted and functioned as hepatic tissues within the muscle to provide life-sustaining liver Support. These engineered tissue Constructs contained no animal products that Would limit their development as a therapeutic approach.
|
|
