124712220
Injection locking of a long-pulse relativistic magnetron
The authors report the injection locking results of a long-pulse (200-400 ns) high power (20-30 MW) relativistic magnetron at 3.3 GHz. Phase-locking with reproducible locked angle was achieved with an injection power ratio as low as 1:200. The locked states were phase stable to within +or-30 degrees during the pulse. Phase locking physics was studied and important effects due to frequency pushing were identified. The locking bandwidth and the dependence of the final locked phase on injection parameters were measured and found to agree well with theory. >
22810790
Detective quantum efficiency of electron area detectors in electron microscopy
Recent progress in detector design has created the need for a careful side-by-side comparison of the modulation transfer function (MTF) and resolution-dependent detective quantum efficiency (DQE) of existing electron detectors with those of detectors based on new technology. We present MTF and DQE measurements for four types of detector: Kodak SO-163 film, TVIPS 224 charge coupled device (CCD) detector, the Medipix2 hybrid pixel detector, and an experimental direct electron monolithic active pixel sensor (MAPS) detector. Film and CCD performance was measured at 120 and 300 keV, while results are presented for the Medipix2 at 120 keV and for the MAPS detector at 300 keV. In the case of film, the effects of electron backscattering from both the holder and the plastic support have been investigated. We also show that part of the response of the emulsion in film comes from light generated in the plastic support. Computer simulations of film and the MAPS detector have been carried out and show good agreement with experiment. The agreement enables us to conclude that the DQE of a backthinned direct electron MAPS detector is likely to be equal to, or better than, that of film at 300 keV.
2001409
Molecular organization of Gram-negative peptidoglycan
The stress-bearing component of the bacterial cell wall—a multi-gigadalton bag-like molecule called the sacculus—is synthesized from peptidoglycan. Whereas the chemical composition and the 3-dimensional structure of the peptidoglycan subunit (in at least one conformation) are known, the architecture of the assembled sacculus is not. Four decades' worth of biochemical and electron microscopy experiments have resulted in two leading 3-D peptidoglycan models: “Layered” and “Scaffold”, in which the glycan strands are parallel and perpendicular to the cell surface, respectively. Here we resolved the basic architecture of purified, frozen-hydrated sacculi through electron cryotomography. In the Gram-negative sacculus, a single layer of glycans lie parallel to the cell surface, roughly perpendicular to the long axis of the cell, encircling the cell in a disorganized hoop-like fashion.
119287588
Holographic superconductors in the Born-Infeld electrodynamics
Abstract We study the effects of the Born–Infeld electrodynamics on the holographic superconductors in the background of a Schwarzschild–AdS black hole spacetime. We find that the presence of Born–Infeld scale parameter decreases the critical temperature and the ratio of the gap frequency in conductivity to the critical temperature for the condensates. Our results mean that it is harder for the scalar condensation to form in the Born–Infeld electrodynamics.
118527348
Holographic superconductor/insulator transition with logarithmic electromagnetic field in Gauss–Bonnet gravity
Abstract The behaviors of the holographic superconductors/insulator transition are studied by introducing a charged scalar field coupled with a logarithmic electromagnetic field in both the Einstein–Gauss–Bonnet AdS black hole and soliton. For the Einstein–Gauss–Bonnet AdS black hole, we find that: i) the larger coupling parameter of logarithmic electrodynamic field b makes it easier for the scalar hair to be condensed; ii) the ratio of the gap frequency in conductivity ω g to the critical temperature T c depends on both b and the Gauss–Bonnet constant α; and iii) the critical exponents are independent of the b and α. For the Einstein–Gauss–Bonnet AdS soliton, we show that the system is the insulator phase when the chemical potential μ is small, but there is a phase transition and the AdS soliton reaches the superconductor (or superfluid) phase when μ is larger than critical chemical potential. A special property should be noted is that the critical chemical potential is not changed by the coupling parameter b but depends on α.
37077901
Asymptotic quasinormal modes of a coupled scalar field in the Gibbons-Maeda dilaton spacetime
Adopting the monodromy technique devised by Motl and Neitzke, we investigate analytically the asymptotic quasinormal frequencies of a coupled scalar field in the Gibbons–Maeda dilaton spacetime. We find that it is described by , which depends on the structure parameters of the background spacetime and on the coupling between the scalar and gravitational fields. As the parameters ξ and βI tend to zero, the real parts of the asymptotic quasinormal frequencies become THln 3, which is consistent with Hod's conjecture. When , the formula becomes that of the Reissner–Nordstrom spacetime.
118397512
Dynamical evolution of scalar perturbation in Hořava-Lifshitz black-hole spacetimes
We study the dynamical evolution of a massless scalar perturbation in the Ho\ifmmode \check{r}\else \v{r}\fi{}ava-Lifshitz black-hole spacetimes with the coupling constants $\ensuremath{\lambda}=\frac{1}{3}$, $\ensuremath{\lambda}=\frac{1}{2}$ and $\ensuremath{\lambda}=3$, respectively. Our calculation shows that, for the three cases, the scalar perturbations decay without any oscillation in which the decay rate imprints the parameter of the Ho\ifmmode \check{r}\else \v{r}\fi{}ava-Lifshitz black hole. The results are quite different from those in the Schwarzschild AdS black hole and can help us understand more about the Ho\ifmmode \check{r}\else \v{r}\fi{}ava-Lifshitz gravity.
121404599
Is Hawking temperature modified by the quantum tunneling beyond semiclassical approximation
Hawking temperature of a static and spherically symmetric black hole beyond semiclassical approximation is studied. The calculations show us that different definition of the particle’s energy gives different Hawking temperature. However, we argue that the result obtained using the standard definition of the particle energy is reasonable because it keeps the validity of the first law of the thermodynamics, i.e., both the Hawking temperature and entropy are not modified by the quantum tunneling beyond semiclassical approximation. The result shows us that any hypothetical $${\hbar}$$ corrections to the tunneling rate are to be interpreted not as quantum corrections to the Hawking temperature but as fluctuations about a thermal background.