Ultrahigh-Energy Photons as a Probe of Nearby Transient Ultrahigh-Energy Cosmic-Ray Sources and Possible Lorentz-Invariance Violation

Detecting neutrinos and photons is crucial to identifying the sources of ultrahigh-energy cosmic rays (UHECRs), especially for transient sources. We focus on ultrahigh-energy gamma-ray emission from transient sources such as gamma-ray bursts, since >EeV gamma rays can be more direct evidence of UHECRs than PeV neutrinos and GeV-TeV gamma rays. We demonstrate that coincident detections of about 1-100 events can be expected by current and future UHECR detectors such as Auger and JEM-EUSO, and the detection probability can be higher than that of neutrinos for nearby transient sources at <50-100 Mpc. They may be useful for constraining the uncertain cosmic radio background as well as knowing the source properties and maximum energy of UHECRs. They can also give us more than 10^4 times stronger limits on the Lorentz-invariance violation than current constraints.Comment: 4 pages, 3 figures, replaced to match the published version (PRL, 103, 081102

Prompt high-energy neutrinos from gamma-ray bursts in photospheric and synchrotron self-Compton scenarios

We investigate neutrino emission from gamma-ray bursts (GRBs) under alternative scenarios for prompt emission (the photospheric and synchrotron self-Compton scenarios) rather than the classical optically thin synchrotron scenario. In the former scenario, we find that neutrinos from the pp reaction can be very important at energies around 10-100 TeV. They may be detected by IceCube/KM3Net and useful as a probe of baryon acceleration around/below the photosphere. In the latter scenario, we may expect about EeV pgamma neutrinos produced by soft photons. Predicted spectra are different from that in the classical scenario, and neutrinos would be useful as one of the clues to the nature of GRBs (the jet composition, emission radius, magnetic field and so on).Comment: 5 pages, 3 figures, replaced to match the final version published as PRD Rapid Communication, 78, 101302. Minor typos fixe

Successful islet allotransplantation in diabetic rats immunosuppressed with FK506: A functional and immunological study

The effect of a novel immunosuppressive agent, FK506, on fresh islet allografts was evaluated in diabetic rats across major histocompatibility complex (MHC) barriers with respect to the transplantation (TR) site, islet source, treatment regimen, and antidonor antibody (Ab) titers of the recipients after TR. The functional periods of Wistar (Wi) islets transplanted under kidney capsule (KC) or intraportally (IPo) and of a mixture of Wi and Lewis (Le) islets under KC or IPo in nonimmunosuppressed ACI rat recipients were 6.9 ± 0.4 (n = 7), 6.4 ± 0.5 (n = 7), 5.6 ± 0.4 (n = 7), and 6.2 ± 0.4 (n = 5) days, respectively. FK506 treatment at 1 mg/kg/d intramuscularly (IM) for 2 weeks (protocol I) following islet TR under KC and IPo significantly prolonged the allograft function to more than 71.8 ± 11.3 (n = 10) and 161.7 ± 18.6 (n = 11) days, respectively. Additional treatment with FK506 at 1 mg/kg/wk (protocol II) further increased the islet survival under KC to more than 212.6 ± 22.3 (n = 8) days. With this FK506 treatment protocol, the Wi + Le mixed-islet allograft function was extended to more than 106.1 ± 10.5 (n = 7) and 167.9 ± 28.6 (n = 7) days under KC and IPo, respectively. Nephrectomy in 8 8 ACI rats with long-term-functioning Wi (n = 6) and Wi + Le (n = 2) islet allografts resulted in their return to hyperglycemia. Immunohistochemical staining showed abundant insulin-positive cells at the graft site, with small numbers of CD4- and CD8-positive cells present in the vicinity of the normal-appearing islets. Macrophages were not detected. The immunosuppressive effect of FK506 was further tested in ACI rats presensitized by a previous Wi islet TR. When the duration between the first and second TR under KC was 114.3 ± 20.5 days, protocol II treatment significantly prolonged the graft function to more than 152.9 ± 28.7 (n = 8) days. However, with a short duration of about 2 weeks between the two TRs, the same FK506 protocol achieved islet graft function of 14.0 ± 3.8 days (n = 7). Additional immunosuppression with cyclophosphamide did not further improve the survival time. Antidonor Abs detected in ACI recipients of Wi islet allografts were significantly lower in the FK506-treated animals compared with the nontreatment group. Wi and Le skin grafts performed in three ACI rats with long-term-functioning Wi islets IPo caused the rejection of the islet allografts. Skin grafts were also rejected in the first-set fashion. Six ACI recipients with long-term-functioning IPo Wi islet allografts were rendered hyperglycemic by streptozocin (STZ) injection. Long-term normoglycemia without further FK506 immunosuppression was achieved following retransplantation with fresh Wi islets IPo (n = 2), but not under KC (n = 2). The results of the present study indicate that FK506 was an effective immunosuppressant for islet allotransplantation in diabetic ACI rats across MHC barriers with islets from two donor strains, as well as in sensitized recipients whose antidonor activities had subsided. The efficacy of the immunosuppression was influenced by the FK506 treatment protocol and the site of the islet transplant. The results suggest that FK506 could be useful in clinical islet TR. © 1994

Effect in supralethally irradiated rats of granulocyte colony- stimulating factor and lisofylline on hematopoietic reconstitution by syngeneic bone marrow or whole organ passenger leukocytes

We have previously shown the existence of migratory hematopoietic stem cells in adult solid organs. This study demonstrates that granulocyte colony- stimulating factor (G-CSF) and lisofylline, a phosphatidic acid inhibitor that suppresses hematopoiesis-inhibiting cytokines, can enhance the engraftment of organ-based hematopoietic stem cells. When syngeneic heart grafts or liver nonparenchymal cells were transplanted into lethally irradiated (9.5 Gy) Lewis rats, complete hematopoietic reconstitution and animal survival were significantly improved by treating the recipient with G- CSF or, to a lesser extent, with lisofylline. Pretreatment of hepatic nonparenchymal cell donors with G-CSF, but not lisofylline, also resulted in striking improvement of recipient survival which was associated with an augmented subpopulation of donor stem cells. The results suggest that these drugs can be used to enhance the chimerism that we postulate to be the basis of organ allograft acceptance

Very-High-Energy Gamma-Ray Signal from Nuclear Photodisintegration as a Probe of Extragalactic Sources of Ultrahigh-Energy Nuclei

It is crucial to identify the ultrahigh-energy cosmic-ray (UHECR) sources and probe their unknown properties. Recent results from the Pierre Auger Observatory favor a heavy nuclear composition for the UHECRs. Under the requirement that heavy nuclei survive in these sources, using gamma-ray bursts as an example, we predict a diagnostic gamma-ray signal, unique to nuclei - the emission of de-excitation gamma rays following photodisintegration. These gamma rays, boosted from MeV to TeV-PeV energies, may be detectable by gamma-ray telescopes such as VERITAS, HESS, and MAGIC, and especially the next-generation CTA and AGIS. They are a promising messenger to identify and study individual UHE nuclei accelerators.Comment: 7 pages, 4 figures, accepted for publication in PRD, with extended descriptions. Conclusions unchange

Weighted Radon transforms for which the Chang approximate inversion formula is precise

We describe all weighted Radon transforms on the plane for which the Chang approximate inversion formula is precise. Some subsequent results, including the Cormack type inversion for these transforms, are also given