4,897 research outputs found
First Detection of A Sub-kpc Scale Molecular Outflow in the Starburst Galaxy NGC 3628
We successfully detected a molecular outflow with a scale of 370-450 pc in
the central region of the starburst galaxy NGC 3628 through deep CO(1-0)
observations by using the Nobeyama Millimeter Array (NMA). The mass of the
outflowing molecular gas is ~2.8x10^7 M_sun, and the outflow velocity is
~90(+/-10) km s^{-1}. The expansion timescale of the outflow is 3.3-6.8 Myr,
and the molecular gas mass flow rate is 4.1-8.5 M_sun yr^{-1}. It requires
mechanical energy of (1.8-2.8)x10^{54} erg to create this sub-kpc scale
molecular outflow. In order to understand the evolution of the molecular
outflow, we compare the physical properties between the molecular outflow
observed from our NMA CO(1-0) data and the plasma gas from the soft X-ray
emission of the Chandra X-ray Observatory (CXO) archival data. We found that
the distribution between the molecular outflow and the strong plasma outflow
seems to be in a similar region. In this region, the ram pressure and the
thermal pressure of the plasma outflow are 10^{-(8-10)} dyne cm^{-2}, and the
thermal pressure of molecular outflow is 10^{-(11-13)} dyne cm^{-2}. This
implies the molecular outflow is still expanding outward. The molecular gas
consumption timescale is estimated as 17-27 Myr, and the total starburst
timescale is 20-34 Myr. The evolutionary parameter is 0.11-0.25, suggesting
that the starburst activity in NGC 3628 is still in a young stage.Comment: 15 pages, 14 figures, accepted by Ap
Real-time measurement of phloem turgor pressure in Hevea brasiliensis with a modified cell pressure probe
Background: Although the pressure flow theory is widely accepted for the transport of photoassimilates in phloem sieve elements, it still requires strong experimental validation. One reason for that is the lack of a precise method for measuring the real-time phloem turgor pressure from the sink tissues, especially in tree trunks. Results: Taking the merits of Hevea brasiliensis, a novel phloem turgor pressure probe based on the state of the art cell pressure probe was developed. Our field measurements showed that the phloem turgor pressure probe can sensitively measure the real-time variation of phloem turgor pressure in H. brasiliensis but the calculation of phloem turgor pressure with xylem tension, xylem sap osmotic potential and phloem sap osmotic potential will under-estimate it. The measured phloem turgor pressure gradient in H. brasiliensis is contrary to the Münch theory. The phloem turgor pressure of H. brasiliensis varied from 8-12 bar as a consequence of water withdrawal from transpiration. Tapping could result in a sharp decrease of phloem turgor pressure followed by a recovery from 8-45 min after the tapping. The recovery of phloem turgor pressure after tapping and its change with xylem sap flow suggest the importance of phloem water relationship in the phloem turgor pressure regulation. Conclusion: The phloem turgor pressure probe is a reliable technique for measuring the real-time variation of phloem turgor pressures in H. brasiliensis. The technique could probably be extended to the accurate measurement of phloem turgor pressure in other woody plants which is essential to test the Münch theory and to investigate the phloem water relationship and turgor pressure regulation. <br /
Entropy and Its Quantum Thermodynamical Implication for Anomalous Spectral Systems
The state function entropy and its quantum thermodynamical implication for
two typical dissipative systems with anomalous spectral densities are studied
by investigating on their low-temperature quantum behavior. In all cases it is
found that the entropy decays quickly and vanishes as the temperature
approaches zero. This reveals a good conformity with the third law of
thermodynamics and provides another evidence for the validity of fundamental
thermodynamical laws in the quantum dissipative region.Comment: 10 pages, 3 figure
Integrated-EBG Ridge Waveguide and Its Application to an E-Band Waveguide 32 732 Slot Array Antenna
A methodology of designing an E-band waveguide 32
732 slot array antenna with high-efficiency and low-cost manufacturing characteristics is proposed in this article, which is based on an integrated electronic bandgap (EBG) ridge waveguide designed by integrating a cross rectangle-hollow EBG structures in the conventional ridge waveguide. The integrated EBG structure intercepts the leakage from the unconnected gap in between the two metallic plates of the waveguide, and then it decreases the manufacturing cost without using the diffusion bonding technology and multi-layer welding assembly process. The design guideline is discussed, and then the antenna is fabricated. The measured radiation characteristics are in good agreement with predicted ones, which confirms that the proposed cross rectangle-hollow EBG structures is an attractive candidate of high-performance millimeter wave antenna
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