The measurement of a diffuse astrophysical neutrino flux using starting track events marks the first time IceCube has observed and subsequently measured the astrophysical diffuse flux using a dataset composed primarily of starting track events. Starting tracks combine an excellent angular and energy resolution. This enables us to take advantage of the self-veto effect in the southern sky reducing the atmospheric neutrino rate allowing us to detect astrophysical neutrinos to energies well below 100 TeV. We measure the astrophysical flux as $\phi^{per-flavor}_{Astro}=1.68^{+0.19}_{-0.22}$(at 100 TeV) and $\gamma_{Astro} = 2.58^{+0.10}_{-0.09}$ assuming a single power law flux. The astrophysical flux 90% sensitive energy range is 3 TeV to 500 TeV, extending IceCube's reach to the low energy astrophysical flux by an order of magnitude. A brief summary of tests performed to search for neutrinos from the galactic plane using this dataset is also provided. With this sample, we did not find statistically significant evidence for emission from the galactic plane. We then tested the impact of these galactic plane neutrinos on the isotropic diffuse flux, with at most 10% effect on the overall normalization and negligible impact to the spectral index.
Daniels Collins, R. Guerraoui, J. Komatovic
et al.
We address the problem of online payments, where users can transfer funds among themselves. We introduce Astro, a system solving this problem efficiently in a decentralized, deterministic, and completely asynchronous manner. Astro builds on the insight that consensus is unnecessary to prevent double-spending. Instead of consensus, Astro relies on a weaker primitive---Byzantine reliable broadcast---enabling a simpler and more efficient implementation than consensus-based payment systems. In terms of efficiency, Astro executes a payment by merely broadcasting a message. The distinguishing feature of Astro is that it can maintain performance robustly, i.e., remain unaffected by a fraction of replicas being compromised or slowed down by an adversary. Our experiments on a public cloud network show that Astro can achieve near-linear scalability in a sharded setup, going from 10K payments/sec (2 shards) to 20K payments/sec (4 shards). In a nutshell, Astro can match VISA-level average payment throughput, and achieves a 5× improvement over a state-of-the-art consensus-based solution, while exhibiting sub-second 95^th percentile latency.
The IceCube Neutrino Observatory measured a flux of high-energy astrophysical neutrinos in several detection channels. The energy spectrum is fitted as unbroken power-law, but different best-fit parameters were obtained in the various analyses covering different energy ranges between few TeV to 10 PeV. Here, we present an update to the analysis of through-going muon-neutrinos from the Northern Hemisphere. It was extended to almost ten years of data and an improved treatment of systematic uncertainties on the atmospheric fluxes was implemented. The updated best-fit parameters for the astrophysical flux assuming a power-law energy spectrum are $\phi_{astro}=1.44$ and $\gamma_{astro}=2.28$. We will present the results of the spectral fit and discuss how the measured flux compares to other IceCube results.
Oligodendrocyte precursor cells (OPCs) in the adult brain contribute to white matter homeostasis. After white matter damage, OPCs compensate for oligodendrocyte loss by differentiating into mature oligodendrocytes. However, the underlying mechanisms remain to be fully defined. Here, we test the hypothesis that, during endogenous recovery from white matter ischemic injury, astrocytes support the maturation of OPCs by secreting brain-derived neurotrophic factor (BDNF). For in vitro experiments, cultured primary OPCs and astrocytes were prepared from postnatal day 2 rat cortex. When OPCs were subjected to chemical hypoxic stress by exposing them to sublethal CoCl2 for 7 d, in vitro OPC differentiation into oligodendrocytes was significantly suppressed. Conditioned medium from astrocytes (astro-medium) restored the process of OPC maturation even under the stressed conditions. When astro-medium was filtered with TrkB-Fc to remove BDNF, the BDNF-deficient astro-medium no longer supported OPC maturation. For in vivo experiments, we analyzed a transgenic mouse line (GFAPcre/BDNFwt/fl) in which BDNF expression is downregulated specifically in GFAP+ astrocytes. Both wild-type (GFAPwt/BDNFwt/fl mice) and transgenic mice were subjected to prolonged cerebral hypoperfusion by bilateral common carotid artery stenosis. As expected, compared with wild-type mice, the transgenic mice exhibited a lower number of newly generated oligodendrocytes and larger white matter damage. Together, these findings demonstrate that, during endogenous recovery from white matter damage, astrocytes may promote oligodendrogenesis by secreting BDNF. SIGNIFICANCE STATEMENT The repair of white matter after brain injury and neurodegeneration remains a tremendous hurdle for a wide spectrum of CNS disorders. One potentially important opportunity may reside in the response of residual oligodendrocyte precursor cells (OPCs). OPCs may serve as a back-up for generating mature oligodendrocytes in damaged white matter. However, the underlying mechanisms are still mostly unknown. Here, we use a combination of cell biology and an animal model to report a new pathway in which astrocyte-derived BDNF supports oligodendrogenesis and regeneration after white matter damage. These findings provide new mechanistic insight into white matter physiology and pathophysiology, which would be broadly and clinically applicable to CNS disease.
We introduce a new space VLBI project, the Second VLBI Space Observatory Program (VSOP2), following the success of the VLBI Space Observatory Program (VSOP1). VSOP2 has 10 times higher angular resolution, up to about 40 micro arcseconds, 10 times higher frequency up to 43 GHz, and 10 times higher sensitivity compared to VSOP1. Then VSOP2 should become a most powerful tool to observe innermost regions of AGN and astronomical masers. ASTRO-G is a spacecraft for VSOP2 project constructing in ISAS/JAXA since July 2007. ASTRO-G will be launched by JAXA H-IIA rocket in fiscal year 2012. ASTRO-G and ground-based facilities are combined as VSOP2. To achieve the good observation performances, we must realize new technologies. They are large precision antenna, fast-position switching capability, new LNAs, and ultra wide-band down link, etc.. VSOP2 is a huge observation system involving ASTRO-G, ground radio telescopes, tracking stations, and correlators, one institute can not prepare a whole system of VSOP2. Then we must need close international collaboration to get sufficient quality of resultant maps and to give a sufficient quantity of observation time for astronomical community. We formed a new international council to provide guidance on scientific aspects related of VSOP2, currently called the VSOP2 International Science Council (VISC2).