Real-Time Misbehavior Detection in IEEE 802.11e Based WLANs

The Enhanced Distributed Channel Access (EDCA) specification in the IEEE 802.11e standard supports heterogeneous backoff parameters and arbitration inter-frame space (AIFS), which makes a selfish node easy to manipulate these parameters and misbehave. In this case, the network-wide fairness cannot be achieved any longer. Many existing misbehavior detectors, primarily designed for legacy IEEE 802.11 networks, become inapplicable in such a heterogeneous network configuration. In this paper, we propose a novel real-time hybrid-share (HS) misbehavior detector for IEEE 802.11e based wireless local area networks (WLANs). The detector keeps updating its state based on every successful transmission and makes detection decisions by comparing its state with a threshold. We develop mathematical analysis of the detector performance in terms of both false positive rate and average detection rate. Numerical results show that the proposed detector can effectively detect both contention window based and AIFS based misbehavior with only a short detection window.Comment: Accepted to IEEE Globecom 201

Gravity wave characteristics in the mesopause region revealed from OH airglow imager observations over Northern Colorado

Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Space Physics 119 (2014): 630-645, doi:10.1002/2013JA018955.Using 5 years of all-sky OH airglow imager data over Yucca Ridge Field Station, CO (40.7°N, 104.9°W), from September 2003 to September 2008, we extract and deduce quasi-monochromatic gravity wave (GW) characteristics in the mesopause region. The intrinsic periods are clustered between approximately 4 and 10 min, and many of them are unstable and evanescent. GW occurrence frequency exhibits a clear semiannual variation with equinoctial minima, which is likely related to the seasonal variation of background wind. The anomalous propagation direction in January 2006, with strong southward before major warming starting in 21 January and weak southward propagation afterward, was most likely affected by stratospheric sudden warming. The momentum fluxes show strongly anticorrelated with the tides, with ~180° out of phase in the zonal component. While in the meridional component, the easterly maximum occurred approximately 2–6 h after maximum easterly tidal wind. However, the anticorrelations are both weakest during the summer. The dissipating and breaking of small-scale and high-frequency GW's components could have a potential impact on the general circulation in the mesopause region.This work was carried out at the University of Science and Technology of China, with support from the National Natural Science Foundation of China grants (41025016, 41127901, 41225017, 41074108, and 41121003), the National Basic Research Program of China grant 2012CB825605, the Chinese Academy of Sciences Key Research Program KZZD-EW-01, and the Fundamental Research Funds for the Central Universities.2014-07-3

Constructing a Thin Disordered Self‐Protective Layer on the LiNiO₂ Primary Particles Against Oxygen Release

One of the major challenges facing the application of layered LiNiO2 (LNO) cathode materials is the oxygen release upon electrochemical cycling. Here it is shown that tailoring the provided lithium content during synthesis process can create a disordered layered Li1-xNi1+xO2 phase at the primary particle surface. The disordered surface, which serves as a self-protective layer to alleviate the oxygen loss, possesses the same layered rhombohedral structure (R m) as the inner core of primary particles of the Li1-xNi1+xO2 (x ≈ 0). With advanced synchrotron-based x-ray 3D imaging and spectroscopic techniques, a macroporous architecture within the agglomerates of LNO with ordered surface (LNO-OS) is revealed after only 40 cycles, concomitant with the reduction of nickel on the primary particle surface throughout the whole secondary particles. Such chemomechanical degradation accelerates the deterioration of LNO-OS cathodes. Comparably, there are only slight changes in the nickel valence state and interior architecture of LNO with a thin disordered surface layer (LNO-DS) after cycling, mainly arising from an improved robustness of the oxygen framework on the surface. More importantly, the disordered surface can suppress the detrimental H2 ⇋ H3 phase transition upon cycling compared to the ordered one

Correction:Structural and Functional Insights into an Archaeal Lipid Synthase

(Cell Reports 33, 108294-1–9.e1–e4; October 20, 2020) In the originally published version of this article, the supplemental information file containing Figures S1–S7 and Table S1 was inadvertently removed. The complete supplemental information file is now included with the paper online. The production team regrets this error

Structural and Functional Insights into an Archaeal Lipid Synthase

The UbiA superfamily of intramembrane prenyltransferases catalyzes an isoprenyl transfer reaction in the biosynthesis of lipophilic compounds involved in cellular physiological processes. Digeranylgeranylglyceryl phosphate (DGGGP) synthase (DGGGPase) generates unique membrane core lipids for the formation of the ether bond between the glycerol moiety and the alkyl chains in archaea and has been confirmed to be a member of the UbiA superfamily. Here, the crystal structure is reported to exhibit nine transmembrane helices along with a large lateral opening covered by a cytosolic cap domain and a unique substrate-binding central cavity. Notably, the lipid-bound states of this enzyme demonstrate that the putative substrate-binding pocket is occupied by the lipidic molecules used for crystallization, indicating the binding mode of hydrophobic substrates. Collectively, these structural and functional studies provide not only an understanding of lipid biosynthesis by substrate-specific lipid-modifying enzymes but also insights into the mechanisms of lipid membrane remodeling and adaptation

Generation of Trophoblast Stem Cells from Rabbit Embryonic Stem Cells with BMP4

Trophoblast stem (TS) cells are ideal models to investigate trophectoderm differentiation and placental development. Herein, we describe the derivation of rabbit trophoblast stem cells from embryonic stem (ES) cells. Rabbit ES cells generated in our laboratory were induced to differentiate in the presence of BMP4 and TS-like cell colonies were isolated and expanded. These cells expressed the molecular markers of mouse TS cells, were able to invade, give rise to derivatives of TS cells, and chimerize placental tissues when injected into blastocysts. The rabbit TS-like cells maintained self-renewal in culture medium with serum but without growth factors or feeder cells, whilst their proliferation and identity were compromised by inhibitors of FGFs and TGF-β receptors. Taken together, our study demonstrated the derivation of rabbit TS cells and suggested the essential roles of FGF and TGF-β signalings in maintenance of rabbit TS cell self-renewal

Potential of Core-Collapse Supernova Neutrino Detection at JUNO

JUNO is an underground neutrino observatory under construction in Jiangmen, China. It uses 20kton liquid scintillator as target, which enables it to detect supernova burst neutrinos of a large statistics for the next galactic core-collapse supernova (CCSN) and also pre-supernova neutrinos from the nearby CCSN progenitors. All flavors of supernova burst neutrinos can be detected by JUNO via several interaction channels, including inverse beta decay, elastic scattering on electron and proton, interactions on C12 nuclei, etc. This retains the possibility for JUNO to reconstruct the energy spectra of supernova burst neutrinos of all flavors. The real time monitoring systems based on FPGA and DAQ are under development in JUNO, which allow prompt alert and trigger-less data acquisition of CCSN events. The alert performances of both monitoring systems have been thoroughly studied using simulations. Moreover, once a CCSN is tagged, the system can give fast characterizations, such as directionality and light curve

Detection of the Diffuse Supernova Neutrino Background with JUNO

As an underground multi-purpose neutrino detector with 20 kton liquid scintillator, Jiangmen Underground Neutrino Observatory (JUNO) is competitive with and complementary to the water-Cherenkov detectors on the search for the diffuse supernova neutrino background (DSNB). Typical supernova models predict 2-4 events per year within the optimal observation window in the JUNO detector. The dominant background is from the neutral-current (NC) interaction of atmospheric neutrinos with 12C nuclei, which surpasses the DSNB by more than one order of magnitude. We evaluated the systematic uncertainty of NC background from the spread of a variety of data-driven models and further developed a method to determine NC background within 15\% with {\it{in}} {\it{situ}} measurements after ten years of running. Besides, the NC-like backgrounds can be effectively suppressed by the intrinsic pulse-shape discrimination (PSD) capabilities of liquid scintillators. In this talk, I will present in detail the improvements on NC background uncertainty evaluation, PSD discriminator development, and finally, the potential of DSNB sensitivity in JUNO

Real-time Monitoring for the Next Core-Collapse Supernova in JUNO

Core-collapse supernova (CCSN) is one of the most energetic astrophysical events in the Universe. The early and prompt detection of neutrinos before (pre-SN) and during the SN burst is a unique opportunity to realize the multi-messenger observation of the CCSN events. In this work, we describe the monitoring concept and present the sensitivity of the system to the pre-SN and SN neutrinos at the Jiangmen Underground Neutrino Observatory (JUNO), which is a 20 kton liquid scintillator detector under construction in South China. The real-time monitoring system is designed with both the prompt monitors on the electronic board and online monitors at the data acquisition stage, in order to ensure both the alert speed and alert coverage of progenitor stars. By assuming a false alert rate of 1 per year, this monitoring system can be sensitive to the pre-SN neutrinos up to the distance of about 1.6 (0.9) kpc and SN neutrinos up to about 370 (360) kpc for a progenitor mass of 30$M_{\odot}$ for the case of normal (inverted) mass ordering. The pointing ability of the CCSN is evaluated by using the accumulated event anisotropy of the inverse beta decay interactions from pre-SN or SN neutrinos, which, along with the early alert, can play important roles for the followup multi-messenger observations of the next Galactic or nearby extragalactic CCSN.Comment: 24 pages, 9 figure