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  1. Hohlfeld, O ; Moura, G ; Pelsser, C. (Ed.)
    While the DNS protocol encompasses both UDP and TCP as its underlying transport, UDP is commonly used in practice. At the same time, increasingly large DNS responses and concerns over amplification denial of service attacks have heightened interest in conducting DNS interactions over TCP. This paper surveys the support for DNS-over-TCP in the deployed DNS infrastructure from several angles. First, we assess resolvers responsible for over 66.2% of the external DNS queries that arrive at a major content delivery network (CDN). We find that 2.7% to 4.8% of the resolvers, contributing around 1.1% to 4.4% of all queries arriving at the CDN from the resolvers we study, do not properly fallback to TCP when instructed by authoritative DNS servers. Should a content provider decide to employ TCP-fallback as the means of switching to DNS-over-TCP, it faces the corresponding loss of its customers. Second, we assess authoritative DNS servers (ADNS) for over 10M domains and many CDNs and find some ADNS, serving some popular websites and a number of CDNs, that do not support DNS-over-TCP. These ADNS would deny service to (RFC-compliant) resolvers that choose to switch to TCP-only interactions. Third, we study the TCP connection reuse behavior of DNS actors and describe a race condition in TCP connection reuse by DNS actors that may become a significant issue should DNS-over-TCP and other TCP-based DNS protocols, such as DNS-over-TLS, become widely used. 
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  2. Abstract

    We review comprehensive observations of electromagnetic ion cyclotron (EMIC) wave-driven energetic electron precipitation using data collected by the energetic electron detector on the Electron Losses and Fields InvestigatioN (ELFIN) mission, two polar-orbiting low-altitude spinning CubeSats, measuring 50-5000 keV electrons with good pitch-angle and energy resolution. EMIC wave-driven precipitation exhibits a distinct signature in energy-spectrograms of the precipitating-to-trapped flux ratio: peaks at >0.5 MeV which are abrupt (bursty) (lasting ∼17 s, or$\Delta L\sim 0.56$ΔL0.56) with significant substructure (occasionally down to sub-second timescale). We attribute the bursty nature of the precipitation to the spatial extent and structuredness of the wave field at the equator. Multiple ELFIN passes over the same MLT sector allow us to study the spatial and temporal evolution of the EMIC wave - electron interaction region. Case studies employing conjugate ground-based or equatorial observations of the EMIC waves reveal that the energy of moderate and strong precipitation at ELFIN approximately agrees with theoretical expectations for cyclotron resonant interactions in a cold plasma. Using multiple years of ELFIN data uniformly distributed in local time, we assemble a statistical database of ∼50 events of strong EMIC wave-driven precipitation. Most reside at$L\sim 5-7$L57at dusk, while a smaller subset exists at$L\sim 8-12$L812at post-midnight. The energies of the peak-precipitation ratio and of the half-peak precipitation ratio (our proxy for the minimum resonance energy) exhibit an$L$L-shell dependence in good agreement with theoretical estimates based on prior statistical observations of EMIC wave power spectra. The precipitation ratio’s spectral shape for the most intense events has an exponential falloff away from the peak (i.e., on either side of$\sim 1.45$1.45MeV). It too agrees well with quasi-linear diffusion theory based on prior statistics of wave spectra. It should be noted though that this diffusive treatment likely includes effects from nonlinear resonant interactions (especially at high energies) and nonresonant effects from sharp wave packet edges (at low energies). Sub-MeV electron precipitation observed concurrently with strong EMIC wave-driven >1 MeV precipitation has a spectral shape that is consistent with efficient pitch-angle scattering down to ∼ 200-300 keV by much less intense higher frequency EMIC waves at dusk (where such waves are most frequent). At ∼100 keV, whistler-mode chorus may be implicated in concurrent precipitation. These results confirm the critical role of EMIC waves in driving relativistic electron losses. Nonlinear effects may abound and require further investigation.

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  3. null (Ed.)
  4. Motivated by settings in which predictive models may be required to be non-discriminatory with respect to certain attributes (such as race), but even collecting the sensitive attribute may be forbidden or restricted, we initiate the study of fair learning under the constraint of differential privacy. Our first algorithm is a private implementation of the equalized odds post-processing approach of (Hardt et al., 2016). This algorithm is appealingly simple, but must be able to use protected group membership explicitly at test time, which can be viewed as a form of “disparate treatment”. Our second algorithm is a differentially private version of the oracle-efficient in-processing approach of (Agarwal et al., 2018) which is more complex but need not have access to protected group membership at test time. We identify new tradeoffs between fairness, accuracy, and privacy that emerge only when requiring all three properties, and show that these tradeoffs can be milder if group membership may be used at test time. We conclude with a brief experimental evaluation. 
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  5. Free, publicly-accessible full text available November 1, 2024
  6. Free, publicly-accessible full text available November 1, 2024
  7. Free, publicly-accessible full text available November 1, 2024
  8. A<sc>bstract</sc>

    A search for new physics in final states consisting of at least one photon, multiple jets, and large missing transverse momentum is presented, using proton-proton collision events at a center-of-mass energy of 13 TeV. The data correspond to an integrated luminosity of 137 fb1, recorded by the CMS experiment at the CERN LHC from 2016 to 2018. The events are divided into mutually exclusive bins characterized by the missing transverse momentum, the number of jets, the number of b-tagged jets, and jets consistent with the presence of hadronically decaying W, Z, or Higgs bosons. The observed data are found to be consistent with the prediction from standard model processes. The results are interpreted in the context of simplified models of pair production of supersymmetric particles via strong and electroweak interactions. Depending on the details of the signal models, gluinos and squarks of masses up to 2.35 and 1.43 TeV, respectively, and electroweakinos of masses up to 1.23 TeV are excluded at 95% confidence level.

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    Free, publicly-accessible full text available October 1, 2024