The Evidence for a Binary origin of the Young Planetary Nebula HB 12

The young planetary nebulae play an important role in stellar evolution when intermediate- to low-mass stars (0.8 $\sim$ 8 M$_\odot$) evolve from the proto-planetary nebulae phase to the planetary nebulae phase. Many young planetary nebulae display distinct bipolar structures as they evolve away from the proto-planetary nebulae phase. One possible cause of their bipolarity could be due to a binary origin of its energy source. Here we report our detailed investigation of the young planetary nebula, Hubble 12, which is well-known for its extended hourglass-like envelope. We present evidence with time-series photometric observations the existence of an eclipsing binary at the center of Hubble 12. Low-resolution spectra of the central source show, on the other hand, absorption features such as CN, G-band & Mg b{\arcsec}, which can be suggestive of a low-mass nature of the secondary component.Comment: 9 pages, 11 figures, Accepted for publication in A

Optimal relaying in heterogeneous delay tolerant networks

In Delay Tolerant Networks (DTNs), there exists only intermittent connectivity between communication sources and destinations. In order to provide successful communication services for these challenged networks, a variety of relaying and routing algorithms have been proposed with the assumption that nodes are homogeneous in terms of contact rates and delivery costs. However, various applications of DTN have shown that mobile nodes should be divided into different classes in terms of their energy requirements and communication ability, and real application data have revealed the heterogeneous contact rates between node pairs. In this paper, we design an optimal relaying scheme for DTNs, which takes into account nodes’ heterogeneous contact rates and delivery costs when selecting relays to minimise the delivery cost while satisfying the required message delivery probability. Extensive results based on real traces demonstrate that our relaying scheme requires the least delivery cost and achieves the largest maximum delivery probability, compared with the schemes that neglect nodes’ heterogeneity

A readily accessible multifunctional probe: simultaneous recognition of the cation ZN²⁺ and the anion F⁻ via distinguishable wavelengths

The probe 1 was readily prepared via condensation of 8-formyl-7-hydroxy-coumarin and carbonic dihydrazide in a one-step procedure. Probe 1 exhibited high sensitivity and selectivity towards Zn²⁺ and F⁻ through a “turn-on” fluorescence response and/or ratiometric colorimetric response with low detection limits of the order of 10-8 M. The complex behaviour was fully investigated by spectral titration, isothermal titration calorimetry, 1H NMR spectroscopic titration and mass spectrometry. Interestingly, probe 1 not only recognizes the cation Zn²⁺ and the anion F⁻, but can also distinguish between these two ions via the max wavelength in their UV-vis spectra (360 nm for 1-Zn²⁺ versus 400 nm for 1-F⁻ complex) or their fluorescent spectra (λₑₓ / λₑm = 360 nm/ 454 nm for 1-Zn²⁺ versus λₑₓ / λₑm = 400 nm/ 475 nm for 1-F⁻ complex) due to their differing red-shifts. Additionally, probe 1 has been further explored in the detection of Zn²⁺ in living cells