320 research outputs found

    Through a router darkly: how new American copyright enforcement initiatives may hinder economic development, net neutrality and creativity

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    On November 1, 2012, Russia enacted a law putatively aiming to protect Russian children from pedophiles. This law authorizes deep packet inspection (DPI), a method used for monitoring, filtering and shaping internet traffic, which has heightened concerns among many leading privacy groups. These groups are concerned with how the government will use such an intrusive method in prosecuting child predators. Central to this concern is DPI’s capability to allow the Russian government to peer into any citizens’ unencrypted internet traffic and monitor, copy, or even alter the traffic as it moves to its destination. The unresolved question is whether the government’s use of DPI will be restrained and utilized primarily to thwart child predators, or whether it will be expanded to lay the groundwork for a new era of national censorship. Although the United States has not yet adopted similar tactics in regulating its citizens’ internet use, Russia’s implementation of the new DPI monitoring and filtering system will provide an educational opportunity for both privacy advocates and policymakers

    Measuring idiosyncratic risks in leveraged buyout transactions

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    The authors use a contingent claims analysis model to calculate the idiosyncratic risks in Leveraged Buyout transactions.Idiosyncratic Risk; LBO; Private Equity; Benchmarking; CCA

    The Opportunity Cost of Capital of US Buyouts

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    This paper measures the risk-adjusted performance of US buyouts. It draws on a unique and proprietary set of data on 133 US buyouts between 1984 and 2004. For each of them we determine a public market equivalent that matches it with respect to its timing and its systematic risk. After a correction for selection bias in our data, the regression of the buyout internal rates of return on the internal rates of return of the mimicking portfolio yields a positive and statistically significant alpha. Our sensitivity analyses highlight the necessity of a comprehensive risk-adjustment that considers both operating risk and leverage risk for an accurate assessment of buyout performance. This finding is particularly important as existing literature on that topic tends to rely on performance measures without a proper risk-adjustment.

    Demonstration of quantum brachistochrones between distant states of an atom

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    Transforming an initial quantum state into a target state through the fastest possible route---a quantum brachistochrone---is a fundamental challenge for many technologies based on quantum mechanics. Here, we demonstrate fast coherent transport of an atomic wave packet over a distance of 15 times its size---a paradigmatic case of quantum processes where the target state cannot be reached through a local transformation. Our measurements of the transport fidelity reveal the existence of a minimum duration---a quantum speed limit---for the coherent splitting and recombination of matter waves. We obtain physical insight into this limit by relying on a geometric interpretation of quantum state dynamics. These results shed light upon a fundamental limit of quantum state dynamics and are expected to find relevant applications in quantum sensing and quantum computing.Comment: 6 pages, 3 figures, and supplemental materia

    Adenovirus vector delivery stimulates natural killer cell recognition

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    We report that delivery of first-generation replication-deficient adenovirus (RDAd) vectors into primary human fibroblasts is associated with the induction of natural killer (NK) cell-mediated cytolysis in vitro. RDAd vector delivery induced cytolysis by a range of NK cell populations including the NK cell clone NKL, primary polyclonal NK lines and a proportion of NK clones (36 %) in autologous HLA-matched assays. Adenovirus-induced cytolysis was inhibited by antibody blocking of the NK-activating receptor NKG2D, implicating this receptor in this function. NKG2D is ubiquitously expressed on NK cells and CD8+ T cells. Significantly, γ-irradiation of the vector eliminated the effect, suggesting that breakthrough expression from the vector induces at least some of the pro-inflammatory responses of unknown aetiology following the application of RDAd vectors during in vivo gene delivery

    Massive stars in the giant molecular cloud G23.3−0.3 and W41

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    Context. Young massive stars and stellar clusters continuously form in the Galactic disk, generating new Hii regions within their natal giant molecular clouds and subsequently enriching the interstellar medium via their winds and supernovae.Aims. Massive stars are among the brightest infrared stars in such regions; their identification permits the characterisation of the star formation history of the associated cloud as well as constraining the location of stellar aggregates and hence their occurrence as a function of global environment.Methods. We present a stellar spectroscopic survey in the direction of the giant molecular cloud G23.3−0.3. This complex is located at a distance of ~4–5 kpc, and consists of several Hii regions and supernova remnants.Results. We discovered 11 OfK+ stars, one candidate luminous blue variable, several OB stars, and candidate red supergiants. Stars with K-band extinction from ~1.3–1.9 mag appear to be associated with the GMC G23.3−0.3; O and B-types satisfying this criterion have spectrophotometric distances consistent with that of the giant molecular cloud. Combining near-IR spectroscopic and photometric data allowed us to characterize the multiple sites of star formation within it. The O-type stars have masses from ~25–45 M⊙, and ages of 5–8 Myr. Two new red supergiants were detected with interstellar extinction typical of the cloud; along with the two RSGs within the cluster GLIMPSE9, they trace an older burst with an age of 20–30 Myr. Massive stars were also detected in the core of three supernova remnants – W41, G22.7−0.2, and G22.7583−0.4917.Conclusions. A large population of massive stars appears associated with the GMC G23.3−0.3, with the properties inferred for them indicative of an extended history of stars formation

    Spectropolarimetry of the Type Ib Supernova iPTF 13bvn: revealing the complex explosion geometry of a stripped-envelope core-collapse supernova

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    We present six epochs of spectropolarimetric observations and one epoch of spectroscopy of the Type Ib SN iPTF 13bvn. The epochs of these observations correspond to −10 to +61 d with respect to the r-band light-curve maximum. The continuum is intrinsically polarized to the 0.2–0.4 per cent level throughout the observations, implying asphericities of ∼10 per cent in the shape of the photosphere. We observe significant line polarization associated with the spectral features of Ca II IR3, He I/Na I D, He I λλ6678, 7065, Fe II λ4924 and O I λ7774. We propose that an absorption feature at ∼6200 Å, usually identified as Si II λ6355, is most likely to be high-velocity H α at −16 400 km s−1. Two distinctly polarized components, separated in velocity, are detected for both He I/Na I D and Ca II IR3 , indicating the presence of two discrete line-forming regions in the ejecta in both radial velocity space and in the plane of the sky. We use the polarization of He I λ5876 as a tracer of sources of non-thermal excitation in the ejecta; finding that the bulk of the radioactive nickel was constrained to lie interior to ∼50–65 per cent of the ejecta radius. The observed polarization is also discussed in the context of the possible progenitor system of iPTF 13bvn, with our observations favouring the explosion of a star with an extended, distorted envelope rather than a compact Wolf–Rayet star

    Cytosolic PLA2 is required for CTL-mediated immunopathology of celiac disease via NKG2D and IL-15

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    IL-15 and NKG2D promote autoimmunity and celiac disease by arming cytotoxic T lymphocytes (CTLs) to cause tissue destruction. However, the downstream signaling events underlying these functional properties remain unclear. Here, we identify cytosolic phospholipase A2 (cPLA2) as a central molecule in NKG2D-mediated cytolysis in CTLs. Furthermore, we report that NKG2D induces, upon recognition of MIC+ target cells, the release of arachidonic acid (AA) by CTLs to promote tissue inflammation in association with target killing. Interestingly, IL-15, which licenses NKG2D-mediated lymphokine killer activity in CTLs, cooperates with NKG2D to induce cPLA2 activation and AA release. Finally, cPLA2 activation in intraepithelial CTLs of celiac patients provides an in vivo pathophysiological dimension to cPLA2 activation in CTLs. These results reveal an unrecognized link between NKG2D and tissue inflammation, which may underlie the emerging role of NKG2D in various immunopathological conditions and define new therapeutic targets
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