An hourglass model for the flare of HST-1 in M87

To explain the multi-wavelength light curves (from radio to X-ray) of HST-1 in the M87 jet, we propose an hourglass model that is a modified two-zone system of Tavecchio & Ghisellini (hereafter TG08): a slow hourglass-shaped or Laval nozzle-shaped layer connected by two revolving exponential surfaces surrounding a fast spine, through which plasma blobs flow. Based on the conservation of magnetic flux, the magnetic field changes along the axis of the hourglass. We adopt the result of TG08---the high-energy emission from GeV to TeV can be produced through inverse Compton by the two-zone system, and the photons from radio to X-ray are mainly radiated by the fast inner zone system. Here, we only discuss the light curves of the fast inner blob from radio to X-ray. When a compressible blob travels down the axis of the first bulb in the hourglass, because of magnetic flux conservation, its cross section experiences an adiabatic compression process, which results in particle acceleration and the brightening of HST-1. When the blob moves into the second bulb of the hourglass, because of magnetic flux conservation, the dimming of the knot occurs along with an adiabatic expansion of its cross section. A similar broken exponential function could fit the TeV peaks in M87, which may imply a correlation between the TeV flares of M87 and the light curves from radio to X-ray in HST-1. The Very Large Array (VLA) 22 GHz radio light curve of HST-1 verifies our prediction based on the model fit to the main peak of the VLA 15 GHz radio light curve.Comment: 14 pages, 2 figures, accepted for publication in A

The ant-parasitizing genus Pseudacteon Coquillett (Diptera: Phoridae) from China with description of three new species

The ant-parasitizing genus Pseudacteon Coquillett is reported for the first time in China. Three new species, P. quadrisetalis Liu & Cai, sp. n., P. obtusatus Liu & Cai, sp. n. and P. hexosetalis Liu & Wang, sp. n., are described and illustrated

6-Formyl-2-naphthyl cis-1,5,7-trimethyl-2,4-dioxo-3-aza­bicyclo­[3.3.1]nonane-7-carboxyl­ate

In the title compound, C23H23NO5, the C5N ring adopts an envelope conformation with a C atom as the flap, whilst the saturated C6 ring fused to it adopts a chair conformation. In the crystal, inversion dimers linked by pairs of N—H⋯O hydrogen bonds generate R 2 2(8) loops

On the Security of an Improved Password Authentication Scheme Based on ECC

The design of secure remote user authentication schemes for mobile applications is still an open and quite challenging problem, though many schemes have been published lately. Recently, Islam and Biswas pointed out that Lin and Hwang et al.\u27s password-based authentication scheme is vulnerable to various attacks, and then presented an improved scheme based on elliptic curve cryptography (ECC) to overcome the drawbacks. Based on heuristic security analysis, Islam and Biswas claimed that their scheme is secure and can withstand all related attacks. In this paper, however, we show that Islam and Biswas\u27s scheme cannot achieve the claimed security goals and report its flaws: (1) It is vulnerable to offline password guessing attack, stolen verifier attack and denial of service (DoS) attack; (2) It fails to preserve user anonymity. The cryptanalysis demonstrates that the scheme under study is unfit for practical use

Measurement-device-independent QKD with Modified Coherent State

The measurement-device-independent quantum key distribution (MDI-QKD) protocol has been proposed for the purpose of removing the detector side channel attacks. Due to the multi-photon events of coherent states sources, real-life implementations of MDI-QKD protocol must employ decoy states to beat the photon-number-splitting attack. Decoy states for MDI-QKD based on the weak coherent states have been studied recently. In this paper, we propose to perform MDI-QKD protocol with modified coherent states (MCS) sources. We simulate the performance of MDI-QKD with the decoy states based on MCS sources. And our simulation indicates that both the secure-key rate and transmission distance can be improved evidently with MCS sources.The physics behind this improvement is that the probability of multi-photon events of the MCS is lower than that of weak coherent states while at the same time the probability of single-photon is higher