Multi-epoch, multi-frequency VLBI study of the parsec-scale jet in the blazar 3C 66A

We present the observational results of the Gamma-ray blazar, 3C 66A, at 2.3, 8.4, and 22 GHz at 4 epochs during 2004-05 with the VLBA. The resulting images show an overall core-jet structure extending roughly to the south with two intermediate breaks occurring in the region near the core. By model-fitting to the visibility data, the northmost component, which is also the brightest, is identified as the core according to its relatively flat spectrum and its compactness. As combined with some previous results to investigate the proper motions of the jet components, it is found the kinematics of 3C 66A is quite complicated with components of inward and outward, subluminal and superluminal motions all detected in the radio structure. The superluminal motions indicate strong Doppler boosting exists in the jet. The apparent inward motions of the innermost components last for at least 10 years and could not be caused by new-born components. The possible reason could be non-stationarity of the core due to opacity change.Comment: 24 pages, 4 figure

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

Hydrogen Generation from Al-NiCl2/NaBH4 Mixture Affected by Lanthanum Metal

The effect of La on Al/NaBH4 hydrolysis was elaborated in the present paper. Hydrogen generation amount increases but hydrogen generation rate decreases with La content increasing. There is an optimized composition that Al-15 wt% La-5 wt% NiCl2/NaBH4 mixture (Al-15 wt% La-5 wt% NiCl2/NaBH4 weight ratio, 1 : 3) has 126 mL g−1 min−1 maximum hydrogen generation rate and 1764 mL g−1 hydrogen generation amount within 60 min. The efficiency is 88%. Combined with NiCl2, La has great effect on NaBH4 hydrolysis but has little effect on Al hydrolysis. Increasing La content is helpful to decrease the particle size of Al-La-NiCl2 in the milling process, which induces that the hydrolysis byproduct Ni2B is highly distributed into Al(OH)3 and the catalytic reactivity of Ni2B/Al(OH)3 is increased therefore. But hydrolysis byproduct La(OH)3 deposits on Al surface and leads to some side effect. The Al-La-NiCl2/NaBH4 mixture has good stability in low temperature and its hydrolytic performance can be improved with increasing global temperature. Therefore, the mixture has good safety and can be applied as on board hydrogen generation material

Ultrahigh Sensitivity Temperature Sensor Based on Harmonic Vernier Effect

A high-sensitivity and miniature open cavity Fabry–Perot interferometer (OCFPI) encapsulated with the polydimethylsiloxane (PDMS) film based on high-order harmonic Vernier effect is designed and experimentally investigated. To the best of our knowledge, PDMS is applied for the first time to fill the open cavity of Fabry–Perot interferometer to obtain high-temperature sensitivity. The resonant dip (peak) wavelength of the designed temperature sensor monotonically moves toward the shortwave direction as the temperature increases from 40°C to 60°C due to the effects of expansion and thermo–optic property of PDMS. The proposed OCFPI encapsulated with PDMS film provides the following excellent performance advantages. (1) Compared with traditional all-fiber air-cavity OCFPIs with temperature sensitivity of approximately 10 pm/°C, the proposed OCFPI sensor has a much higher temperature sensitivity of -3.4 nm/°C at the temperature range of 40°C–60°C with a magnification factor ( M -factor) of approximately 11 when order of harmonic Vernier effect i = 4. (2) The proposed OCFPI exhibits good reversibility during the heating and cooling processes, and the measured M -factor matches well with the theoretically calculated M -factor. (3) The proposed OCFPI shows excellent stability with maximum wavelength deviation of 0.567 nm (internal envelope based on a fourth-order harmonic Vernier effect) and 0.042 nm (upper envelope) within 450 min. (4) The proposed OCFPI is inexpensive, robust, easy to fabricate, and compact, which can be used in harsh environments. Therefore, it provides excellent potential in dynamic temperature measurement

Aqua­(2-hydr­oxy-5-sulfonatobenzoato-κO 1)bis­(2-phenyl-1H-1,3,7,8-tetra­aza­cyclo­penta­[l]phenanthrene-κ2 N 7,N 8)zinc(II)

In the title compound, [Zn(C7H4O6S)(C19H12N4)2(H2O)], the ZnII ion is coordinated by two N,N′-bidentate 2-phenyl-1H-1,3,7,8-tetra­azacyclo­penta­[l]phenanthrene ligands, one O-monodentate 5-sulfosalicylate dianion and a water mol­ecule. This results in a distorted cis-ZnO2N4 octa­hedral coordination geometry for the metal ion. In the crystal, mol­ecules are expanded into a three-dimensional supra­molecular motif via O—H⋯O, O—H⋯N and N—H⋯(O,S) hydrogen bonds. In addition, π–π stacking inter­actions between the aromatic rings of the polycyclic ligands consolidate the sturcture [shortest centroid–centroid distance = 3.501 (2) Å]