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101.
Yang Ji-song Liu Jing-shuang Yu Jun-bao Wang Jin-da Qin Sheng-jin Li Xin-hua 《中国地理科学(英文版)》2005,15(3):262-268
Soil respiration is a main dynamic process of carbon cycle in wetland. It is important to contribute to global climate changes.
Water table and nutritious availability are significant impact factors to influence responses of CO2 emission from wetland soil to climate changes. Twenty-four wetland soil monoliths at 4 water-table positions and in 3 nitrogen
status have been incubated to measure rates of CO2 emission from wetland soils in this study. Three static water-table controls and a fluctuant water-table control, with 3
nitrogen additions in every water-table control, were carried out. In no nitrogen addition treatment, high CO2 emissions were found at a static low water table (I) and a fluctuant water table (IV), averaging 306.7mg/(m2·h) and 307.89mg/(m2·h), respectively, which were 51%–57% higher than that at static high water table (II and III). After nitrogen addition, however,
highest CO2 emission was found at II and lowest emission at III. The results suggested that nutritious availability of wetland soil might
be important to influence the effect of water table on the CO2 emission from the wetland soil. Nitrogen addition led to enhancing CO2 emissions from wetland soil, while the highest emission was found in 1N treatments other than in 2N treatments. In 3 nutritious
treatments, low CO2 emissions at high water tables and high CO2 emissions at low water tables were also observed when water table fluctuated. Our results suggested that both water table
changes and nutritious imports would effect the CO2 emission from wetland.
Foundation item: Under the auspices of the National Natural Science Foundation of China (No. 90211003) and the Knowledge Innovation
Program of Chinese Academy of Sciences (No. KACX3-SW-332)
Biography: YANG Ji-song (1978-), male, a native of Chengwu of Shandong Province, Ph.D. candidate, specialized in environmental
ecology and wetland biogeochemistry. E-mail: yangjisong@neigae.ac.cn 相似文献
102.
103.
Low-frequency radio observations offer unique diagnostics of the solar corona and solar wind. After a prolongued hiatus, there is renewed interest in this important frequency regime. Two new ground-based instruments will provide critical new low-frequency observations: the low-frequency array (LOFAR) and the frequency agile solar radiotelescope (FASR). This brief topical review summarizes low-frequency radio phenomena that will be accessible to detailed study by LOFAR and FASR in the coming decade. Energy release, drivers of space weather, and studies of the solar wind are emphasized. Both instruments are expected to play important roles in both basic research problems and national and international space weather capabilities. While FASR is a solar-dedicated instrument, LOFAR is not. Solar observing requirements for LOFAR are briefly discussed. 相似文献
104.
对XPer新发射相连续四年的光学光谱和近红外光度监测结果,XPer近两年的变化不同寻常,主要表现以下两点:(1)尽管它的光学光度V星等只恢复至失去气壳前的亮度,但Ha发射线等值宽度和近红外,J,H和K光度地超过了历史记录的最大值,分别达到了16.34A和5.3^m,5.3^m和5.1^m,表明XPer新发射相气南的密度和尺度较都大,(2)我们首次观测到XPer近红外光度和Hα发射线等值宽度变化趋势 相似文献
105.
Philippe André 《Astrophysics and Space Science》2002,281(1-2):51-66
Detailed studies of nearby cluster-forming molecular clouds can help us understand the physical processes by which most stars
form in galaxies. I review recent advances made on this subject. Submillimeter observations of nearby protoclusters suggest
that stars are generally built from finite, detached reservoirs of mass inside molecular cloud cores, and point to a cloud
fragmentation origin for the IMF. Much progress in this field will come from future large submillimeter instruments such as
Herschel and ALMA.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
106.
1991年3月,我们利用上海25m射电望远镜和欧洲VLBI网联合对几个河外射电源进行了第二历元的327MHzVLBI观测.数据的相关处理先后在上海天文台三台站MK2相关处理机和美国的Caltech/JPL相关处理机进行,以便于比较相关结果。本文给出3C84、3C345和3C380的混合图。与第一历元的观测比较,3C345和3C380的流量密度没有明显的变化,但3C345的结构变化明显。3C84和3C345有喷流的迹象.3C454.3的总流量在不到两年的时间内增加了25%,如果这个变化是内禀的话,那么可能意味着一次新的流量爆发。 相似文献
107.
108.
R. K. Manchanda 《Journal of Astrophysics and Astronomy》2001,22(2-3):145-154
Spectral measurement of Mkn 421 were made in the hard X-ray energy band of 20–200 keV using a high sensitivity, large area
scintillation counter telescope on November 21, 2000 and these coincided with the onset of an active X-ray phase as seen in
the ASM counting rates on board RXTE. The observed spectrum can not be fitted to a single power law similar to the PDS data
of BeppoSAX. The data can be fitted both by a two component power-law function or a combination of an exponential function
with a power law component at the high energies above 80 keV. We identify these components with those arising from the synchrotron
self compton and the high energy power-law tail arising from the upgrading of the thermal photons due to multiple Compton
scattering a la Cyg X-1. A comparison with the earlier data clearly suggests a spectral variability in the hard X-ray spectrum
of the source. We propose a continuously flaring geometry for the source as the underlying mechanism for energy release. 相似文献
109.
C. Tadhunter K. Wills R. Morganti T. Oosterloo R. Dickson 《Monthly notices of the Royal Astronomical Society》2001,327(1):227-232
We present new spectroscopic observations of the southern radio galaxy . Despite the flat-spectrum character of the radio emission from this source, our optical spectra show no sign of the broad permitted lines and non-stellar continuum characteristic of quasar nuclei and broad-line radio galaxies. However, the high-ionization forbidden lines, including [O iii ] λλ 5007, 4959, are unusually broad for a narrow-line radio galaxy , and are blueshifted by 600 km s−1 relative to the low-ionization lines such as [O ii ] λλ 3726,3729. The [O ii ] lines are also considerably narrower than the [O iii ] lines, and have a redshift consistent with that of the recently detected H i 21-cm absorption-line system. Whereas the kinematics of the [O iii ] emission lines are consistent with outflow in an inner narrow-line region, the properties of the [O ii ] emission lines suggest that they are emitted by a more extended and quiescent gaseous component. We argue that, given the radio properties of the source, our line of sight is likely to be lying close to the direction of bulk outflow of the radio jets. In this case it is probable that the quasar nucleus is entirely obscured at optical wavelengths by the material responsible for the H i absorption-line system. The unusually broad [O iii ] emission lines suggest that the radio source is intrinsically compact. Overall, our data are consistent the idea that is a radio source in an early stage of evolution. 相似文献
110.
A very long series of photographic observations of the comet Hale-Bopp has been made during January–April 1997 at the double
astrograph (400/2000) of the Main Astronomical Observatory (Kyiv, Ukraine). Some of the cometary photos were obtained with
two wide-band filter combinations. One of these combinations isolates C2 emission, another — the nearby dust continuum. The images were digitized by means of AMDPH-XY machine and then calibrated
following the standard procedure. After subtraction of the dust continuum the distribution of surface brightness in the C2 emission coma of comet Hale-Bopp was studied. We found an asymmetric brightness distribution both pre- and post-perihelion.
On 21.77 April 1997 a secondary brightness peak is found at the distance of 1.03 × 105 km from the nucleus. It is possible that this peak is related to the extended source of the C2 molecules.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献