共查询到20条相似文献,搜索用时 31 毫秒
1.
J. Trümper 《Die Naturwissenschaften》1979,66(6):286-293
Unlike single neutron stars which appear as radio pulsars, neutron stars in close binary systems emit intense X-radiation. These superdense objects are of interest not only as the end stages of stellar evolution but also as physical laboratories which are dominated by superstrong gravitational and magnetic fields and in which matter densities and temperatures attain extreme values. 相似文献
2.
W. Reich 《Die Naturwissenschaften》1983,70(1):1-6
A new all-sky radio continuum survey at 408 MHz has recently been completed, which up to now represents the most accurate map of radio emission from the whole sky. This map forms a new standard for comparison with other astronomical observations. To study the physical nature of the radio emission from different areas in our Galaxy, further observations at higher frequencies are required. A companion 1420 MHz survey will cover the whole sky too, while at 2700 MHz high-resolution observations concentrate on complex radio sources along the galactic plane. 相似文献
3.
The impact of extraterrestrial matter onto Earth is a continuous process. On average, some 50,000 tons of dust are delivered to our planet every year. While objects smaller than about 30 m mainly disintegrate in the Earth’s atmosphere, larger ones can penetrate through it and cause damage on the ground. When an object of hundreds of meters in diameter impacts an ocean, a tsunami is created that can devastate coastal cities. Further, if a km-sized object hit the Earth it would cause a global catastrophe due to the transport of enormous amounts of dust and vapour into the atmosphere resulting in a change in the Earth’s climate. This article gives an overview of the near-Earth asteroid and comet (near-Earth object-NEO) impact hazard and the NEO search programmes which are gathering important data on these objects. It also points out options for impact hazard mitigation by using deflection systems. It further discusses the critical constraints for NEO deflection strategies and systems as well as mitigation and evacuation costs and benefits. Recommendations are given for future activities to solve the NEO impact hazard problem. 相似文献
4.
Although turbidite deposits are classically considered to be good reservoir rocks for oil and gas, there are no reports concerning
their source rock potential in the literature. The sediments from the Vallfogona Formation in the South-Eastern Pyrenees present
numerous organic matter-rich levels interbedded in sandstones and coarse turbidite deposits. Two types of organic matter deposits
were differentiated on the basis of organic geochemistry and petrography: type A and type B. Type A was deposited in a carbonate
marine environment under hypersaline conditions as indicated mainly by even/odd n-alkane predominance, pristane and phytane ratio (Pr/Ph) < 1, presence of gammacerane, and trisnorneohopane over trisnorhopane
ratio (Ts/Tm) > 1. Type B was deposited in a more mud-rich marine environment evidenced by the predominance of odd n-alkane, Pr/Ph ≥ 1, Ts/Tm < 1, the absence of gammacerane, similar concentrations of the C27 and C29 regular steranes, and the greater abundance of C27 diasteranes. Turbidite facies can be regarded as an environment where organic matter sedimentation is heterogeneous in type
and amount. This study suggests that turbidite deposits with interbedded organic matter-rich levels may act as a combined
source–reservoir system. 相似文献
5.
L. V. Mukhortova I. N. Bezkorovainaya 《Mitigation and Adaptation Strategies for Global Change》2006,11(1):191-202
The evaluation of biospheric role of the boreal forests in the accumulation of carbon is connected with the evaluation of
organic matter (OM) pool in soils. The research sites were larch forests, they are situated on Nizhne-Tungusskoe Plateau.
Larch forests of feather-moss and lichen types (110 and 380 years old) were formed on 'ochric podbur' soils. Litter stocks
are 3.5–4.5 kg m− 2 with thickness 10–25 cm. Cryomezomorphic northern taiga soils contains 38–73 t (carbon) ha− 1. Pool of fast mineralized OM has average value 38.1 t (carbon) ha− 1, including 20.5 and 6.4 t (Carbon) ha− 1 of labile compounds on surface and in the soil, and 11.2 t (carbon) ha− 1 of mobile OM. Microbial mass reaches 1.78–3.47 t (carbon) ha− 1, its proportion is 3.6–4.9% of the total OM carbon. Zoomass of feather-moss larch forest is 0.20–0.61 * 10− 2, in lichen larch forest −0.01–0.07 * 10− 2 t (carbon) ha− 1. A pool of resistant to biological decomposition and bonded to mineral soil matrix OM is 17.7 t (carbon) ha− 1 and it varies from 18.6 to 29.0 in feather-moss larch forest, and from 6.4 to 17.0 t (carbon) ha− 1 in lichen larch forest. Two-years field experiment has been performed to determine transformation rates of various plant
litter fractions and to clarify the role of soil biota in these processes. The results showed participation of all biota groups
in the decomposition of plant residues caused weight loss of larch-needles and root mortmass. Isolation of organic matter
from all-size invertebrate groups leads to some decrease of decomposition activity. 相似文献
6.
Cairney JW 《Die Naturwissenschaften》2000,87(11):467-475
Most terrestrial plants live in mutualistic symbiosis with root-infecting mycorrhizal fungi. Fossil records and molecular
clock dating suggest that all extant land plants have arisen from an ancestral arbuscular mycorrhizal condition. Arbuscular
mycorrhizas evolved concurrently with the first colonisation of land by plants some 450–500 million years ago and persist
in most extant plant taxa. Ectomycorrhizas (about 200 million years ago) and ericoid mycorrhizas (about 100 million years
ago) evolved subsequently as the organic matter content of some ancient soils increased and sclerophyllous vegetation arose
as a response to nutrient-poor soils respectively. Mycorrhizal associations appear to be the result of relatively diffuse
coevolutionary processes. While early events in the evolution of mycorrhizal symbioses may have involved reciprocal genetic
changes in ancestral plants and free-living fungi, available evidence points largely to ongoing parallel evolution of the
partners in response to environmental change. 相似文献
7.
B. J. Smallwood G. A. Wolff B. J. Bett C. R. Smith D. Hoover J. D. Gage A. Patience 《Die Naturwissenschaften》1999,86(7):320-324
On the highly productive Oman Margin of the Arabian Sea, where an intense permanent oxygen minimum impinges on the continental
slope, there is no relationship between oxygen concentration and sedimentary organic-carbon content. However, we provide photographic
and molecular evidence that benthic invertebrates play a significant role in the redistribution of organic matter. High densities
of spider crabs and brittle stars characterize a narrow band near the base of the oxygen minimum zone, where sediments have
depleted organic carbon contents and a remarkable lipid composition that is indicative of metabolic alteration of phytoplankton-derived
sterols by invertebrate detritivores. The distributions of sedimentary sterols and the high abundances of epifaunal crabs
and brittle stars suggest that the metabolism of the megabenthos profoundly influences the quality of organic matter in underlying
sediments.
Received: 12 June 1998 / Accepted in revised form: 26 January 1999 相似文献
8.
Wolfgang Kundt 《Die Naturwissenschaften》1981,68(2):63-75
There are 109±0.5 neutron stars in the Galaxy. They are born in supernova explosions. Isolated neutron stars are observed as (radio-)pulsars, in some cases also as γ-ray pulsars and as IR-, optical and X-ray pulsars. Binary neutron stars, when accreting mass from their companion, become flickering, periodic and/or bursting X-ray sources, and probably also γ-ray bursters. They may all derive from binary star systems. The masses of population-I-neutron stars are compatible with (1.4 ±0.2)M ⊙; their surface magnetic fields fall almost exclusively within 1012.2 and 1013.2 Gauss (at birth). The radii of population-II-neutron stars are (10 -3 +6 )km. Even in exotic sources like SS 433 and Cyg X-1, the compact core may well be a neutron star. 相似文献
9.
Jianhua GAO Guishan YANG Weixin OU 《Frontiers of Environmental Science & Engineering in China》2008,2(1):81-88
In order to explore the effect of different ecological zones and their above plants in the organic matter cycling of the whole
tidal salt marsh, indicators such as total organic carbon (TOC), total nitrogen (TN), C/N ratio, δ13C and δ15N of surface, core sediments, and plants of tidal salt marshes in North Jiangsu Province are analyzed. Subsequently, distribution
regularities of these measurement indicators are discussed, and the biogeochemistry processes between sediments and plants
are also analyzed. Lastly, the organic matter sources of different ecologic zones in tidal salt marsh are evaluated, and the
organic matter accumulations in different ecologic zones induced by their plants are also compared. These results indicate
that TOC, TN, C/N ratio and δ13C showed obvious zonal distribution. The organic matter sources are dominated by marine input in the silt flat, artemisia schrenkiana flat, and the transition zone between silt and spartina alterniflora flat, and are controlled by terrigenous input in spartina alterniflora flat. Spartina alterniflora plays an important role in the accumulation of organic matter in the whole tidal salt marshes ecosystem. In the study area,
the annually increased TOC, organic matter and TN in the spartina alterniflora, artemisia schrenkiana and reed flats reach 6,451, 12,043 and 536 t, respectively. The amount of TOC, organic matter and TN accumulated in the spartina alterniflora flat is more than that in other ecological zones, which shows that the spartina alterniflora flat exert a non-replaceable effect on the material cycle and exchange in the whole tidal salt marshes ecosystem.
__________
Translated from Environmental Science, 2005, 26(6): 51–56 [译自: 环境科学] 相似文献
10.
北运河沙河水库沉积物营养盐分布特征及其溯源分析 总被引:3,自引:0,他引:3
通过采集沙河水库表层(0~20 cm)沉积物样品,分析了沉积物中氮、磷、有机质的分布特征,并结合排污口附近和水库典型区域沉积物中有机质(Organic Matter, OM)和溶解性有机物(Dissolved Organic Matter, DOM)的荧光光谱特征、分子量分布特征(Molecular Weight Distribution, MWD),研究了点源污染对沙河水库沉积物营养盐分布的潜在影响.结果表明,表层沉积物间隙水中氨氮(NH~+_4-N)、磷酸盐(PO■-P)平均浓度及沉积物中总氮(TN)、总磷(TP)的平均含量依次为(52.13±40.32)、(1.75±1.88) mg·L~(-1)与(2853.81±1501.93)、(1496.00±454.06) mg·kg~(-1).库区沉积物中TN、TP含量由库上游((1898.00±1047.54)、(1264.00±104.61) mg·kg~(-1))经库心区((2996.67±1405.13)、(1340.00±332.47) mg·kg~(-1))至库下游((4500.00±920.00)、(1750.00±10.00) mg·kg~(-1))依次增高.沉积物C/N比分析表明,点源污染区与库区沉积物中有机质来源于陆源与自生生物源的混合源.而三维荧光光谱和分子量分布的分析表明,点源污染区与库区沉积物中DOM的组成特性具有一致性,且主要来源于自生生物源.Pearson相关性分析表明,沉积物中营养盐(TN、TP)与有机质具有显著相关关系(p0.01).这些结果清楚地表明,点源污染区沉积物中高的营养盐、有机质含量是库区污染物累积的潜在重要来源. 相似文献
11.
Wang Yayi Wang Shuying Peng Yongzhen Zhu Guibing Ling Yunfang 《Frontiers of Environmental Science & Engineering in China》2007,1(2):226-232
To supply the valuable operating parameters for the popular usage of the new denitrifying phosphors removal process, it is
essential to study the dominant biochemical reactions and the characteristics of denitrifying phosphorus removing bacteria
(DPB). Thus, parallel batch experiments using DPB sludge were carried out to assess the effect of substrates (sewage, HAc,
and endogenous carbon source) on denitrifying dephosphorus removal efficiency in this study. The results showed that the initial
specific phosphorus release rate increased with the high concentration of the short-chain volatile fatty acids ratio in the
influent, and sufficient phosphorus was released by DPB. This improved the subsequent denitrification and phosphorus uptake
efficiency. The specific endogenous denitrification mainly relies on the internal carbon source (PHB) stored by poly-P bacteria.
Denitrifying phosphorus removing bacteria were very hungry when the internal PHB was consumed. Consequently, the specific
endogenous denitrification rate was low and the phosphorus uptake did not happen. On the other hand, in the experiment, the
denitrifying phosphorus removal performance under two temperature conditions (8–10°C and 25–26°C) was also investigated and
analyzed. It was found that the lower temperature decreased the specific phosphorus release and uptake rate, but did not inhibit
the denitrifying phosphorus removal completely. Therefore, the negative influence of the low temperature on the overall phosphorus
removal was not significant.
Translated from Acta Scientiae Circumstantiae, 2006, 26 (2): 186–192 [译自: 环境科学学报] 相似文献
12.
Cao ZH Ding JL Hu ZY Knicker H Kögel-Knabner I Yang LZ Yin R Lin XG Dong YH 《Die Naturwissenschaften》2006,93(5):232-236
Identifying prehistoric irrigated rice fields and characterizing the beginning of paddy soil development are important for a better understanding of human development and agricultural history. In 2003, paddy soils and irrigated rice fields buried at a depth of 100–130 cm were excavated at Chuo-dun-shan in the Yangtze River Delta, close to Suzhou, China. The fields of sizes between 1.4 and 16 m2 were surrounded with ridges that were connected to ditches/ponds via outlets to control the water level within the fields. Many carbonized and partly carbonized rice grains with an age of 3,903 B.C.(measured 14C age 5,129±45 a BP) were recovered. The surface layers of these buried paddy fields showed a high content of soil organic matter and a considerable high density of rice opals. The latter were identified to derive from Oryza spp. Solid-state 13C nuclear magnetic resonance spectroscopy revealed aromatic carbon (C) as the predominant organic C form in the fossil surface layer. This is expected, if the major source represents burnt rice and straw. In summary, our data are in agreement with new evidences indicating that in China, paddy soils and irrigated rice cultivation were initiated and developed more than 6,000 years ago. 相似文献
13.
Xiaoliang Wang Curtis Robbins S. Kent Hoekman Judith C. Chow John G. Watson Dennis Schuetzle 《Frontiers of Environmental Science & Engineering in China》2011,5(3):320-330
Thermochemical biomass gasification, followed by conversion of the produced syngas to fuels and electrical power, is a promising
energy alternative. Real-world characterization of particulate matter (PM) and other contaminants in the syngas is important
to minimize damage and ensure efficient operation of the engines it powers and the fuels created from it. A dilution sampling
system is demonstrated to quantify PM in syngas generated from two gasification plants utilizing different biomass feedstocks:
a BioMax?15 Biopower System that uses raw and torrefied woodchips as feedstocks, and an integrated biorefinery (IBR) that
uses rice hulls and woodchips as feedstocks. PM2.5 mass concentrations in syngas from the IBR downstream of the purification system were 12.8–13.7 μg·m−3, which were significantly lower than the maximum level for catalyst protection (500 μg·m−3) and were 2–3 orders of magnitude lower than those in BioMax?15 syngas (2247–4835 μg·m−3). Ultrafine particle number concentration and PM2.5 chemical constituents were also much lower in the IBR syngas than in the BioMax?15. The dilution sampling system enabled
reliable measurements over a wide range of concentrations: the use of high sensitivity instruments allowed measurement at
very low concentrations (∼1 μg·m−3), while the flexibility of dilution minimized sampling problems that are commonly encountered due to high levels of tars
in raw syngas (∼1 g·m−3). 相似文献
14.
Guo Jin Ma Jun Shi Xuehua 《Frontiers of Environmental Science & Engineering in China》2007,1(2):251-256
To understand the water purification mechanism of potassium permanganate as a coagulation-aid during the preoxidation process,
the microtopography of its reductive products, the newly formed hydrous manganese dioxide and the aged hydrous manganese dioxide,
was investigated. The morphology of natural organic matter (NOM) adsorbed by the newly formed hydrous manganese dioxide was
also compared with that of NOM alone. By using the tapping mode atomic force microscopy (AFM), the observation results show
that the newly formed hydrous manganese dioxide possess a perforated sheet (with a thickness of 0–1.75 nm) as well as some
spherical particle structures compared with the hydrous manganese dioxide with 2 h aging time, which demonstrated that the
newly formed hydrous manganese dioxide had a large surface area and adsorption capacity. When 1 mmol/L newly formed hydrous
manganese dioxide was added, the microtopography of NOM molecules shifted from a loosely dispersed pancake shape (with adsorption
height of 5–8.5 nm) to a densely dispersed and uniform spherical structure. These results provide a valid proof that it is
the perfect adsorption capability of the newly formed hydrous manganese dioxide that might result in the coagulation aid effect
of potassium permanganate preoxidation.
Translated from Environmental Science, 2006, 27(5): 945–949 [译自: 环境科学] 相似文献
15.
Since the announcement by Fleischmann and Pons that the excess enthalpy generated in the negatively polarized Pd–D-D2O system was attributable to nuclear reactions occurring inside the Pd lattice, there have been reports of other manifestations
of nuclear activities in this system. In particular, there have been reports of tritium and helium-4 production; emission
of energetic particles, gamma or X-rays, and neutrons; as well as the transmutation of elements. In this communication, the
results of Pd–D co-deposition experiments conducted with the cathode in close contact with CR-39, a solid-state nuclear etch
detector, are reported. Among the solitary tracks due to individual energetic particles, triple tracks are observed. Microscopic
examination of the bottom of the triple track pit shows that the three lobes of the track are splitting apart from a center
point. The presence of three α-particle tracks outgoing from a single point is diagnostic of the 12C(n,n′)3α carbon breakup reaction and suggests that DT reactions that produce ≥9.6 MeV neutrons are occurring inside the Pd
lattice. To our knowledge, this is the first report of the production of energetic (≥9.6 MeV) neutrons in the Pd–D system.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
16.
Yubo CUI Hongbo LIU Chunxue BAI 《Frontiers of Environmental Science & Engineering in China》2008,2(3):349-353
A new biological nitrogen removal process, which is named herein “The circulating fluidized bed bioreactor (CFBBR)”, was developed
for simultaneous removal of nitrogen and organic matter. This process was composed of an anaerobic bed (Riser), aerobic bed
(Downer) and connecting device. Influent and nitrified liquid from the aerobic bed enters the anaerobic bed from the bottom
of the anaerobic bed, completing the removal of nitrogen and organic matter. The system performance under the conditions of
different inflow loadings and nitrified liquid recirculation rates ranging from 200% to 600% was examined. From a technical
and economic point of view, the optimum nitrified liquid recirculation ratewas 400%. With a shortest total retention time
of 2.5 h (0.8 h in the anaerobic bed and 1.5 h in the aerobic bed) and a nitrified liquid recirculation rate of 400% based
on the influent flow rate, the average removal efficiencies of total nitrogen (TN) and soluble chemical oxygen demand (SCOD)
were found to be 88% and 95%, respectively. The average effluent concentrations of TN and SCOD were 3.5 mg/L and 16 mg/L,
respectively. The volatile suspended solid (VSS) concentration, nitrification rate and denitrification rate in the system
were less than 1.0 g/L, 0.026-0.1 g NH4
+-N/g VSS·d, and 0.016–0.074 g NOx
−-N/g VSS·d, respectively.
__________
Translated from Environmental Engineering, 2007, 25(6): 2, 7–10 [译自: 环境工程] 相似文献
17.
Laura Domingo Stephen T. Grimes M. Soledad Domingo M. Teresa Alberdi 《Die Naturwissenschaften》2009,96(4):503-511
Expansion of C4 grasses during Late Miocene and Early Pliocene constitutes one of the most remarkable biotic events of the Cenozoic era.
The Teruel–Alfambra region (northeastern Spain) contains one of the most complete Miocene–Pliocene sequences of mammalian
fossil sites in the world. In this study, stable isotope (δ
13C and δ
18O) analyses have been performed on the tooth enamel from the equid Hipparion from 19 localities spanning a time interval from approximately 10.9 to 2.7 Ma. This time range starts with the first appearance
of this genus in Spain and ends at its extinction. An increase in δ
13C at about 4.2 Ma has been observed, indicative of a shift toward a more open habitat. This shift may be related to a large
scale vegetation change which occurred across the Miocene–Pliocene boundary when C4 grasses expanded. This expansion might in turn be linked to global tectonic events such as the uplift of the Himalaya and/or
the closure of the Panama Isthmus. However, other more regional factors may have ultimately enhanced the trend toward more
open habitats in the Western Mediterranean Basin. The Messinian Salinity Crisis was a major environmental event that may have
been responsible for the isotopic changes seen in the equid Hipparion from the Iberian Peninsula along with an increase in the aridity detected ~4.6 Ma ago in the Sahara. Even though the exact
factor triggering the isotopic change observed in the Hipparion enamel remains mostly unknown, this study demonstrates that the global environmental changes detected across the Miocene–Pliocene
boundary are also recorded in the realm of the Iberian Peninsula.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
18.
传统北京烤鸭烤制过程中大气污染物的排放特征 总被引:6,自引:5,他引:1
烤鸭是具有北京特色的传统美食之一,制作过程采用果木炭火烤制方式,与其它食物烹饪过程存在明显的差异,国内还未对这类餐饮源的排放特征进行过系统研究,为掌握这类餐饮源排放特征,从而为污染控制提供技术依据,选取北京市具有代表性的烤鸭店,研究了其烤鸭烤制过程中大气污染物的排放特征.结果表明,传统烤鸭烤制过程中排放的油烟、颗粒物、挥发性有机物(VOCs)和醛酮类化合物的基准排放浓度分别为(0.74±0.45)、(15.32±7.93)、(7.60±3.41)和(1.22±0.59)mg·m~(-3);颗粒物排放浓度要远高于油烟排放浓度,VOCs组分构成相对复杂,既包括烷烃、烯烃、芳香烃等VOCs也包括醛酮类、醇类、酯类等含氧VOCs和卤代烃,其中3-甲基呋喃、乙醇和乙酸甲酯的浓度最高;醛酮类化合物的主要组分有乙醛、甲醛和丙烯醛等,其中C1~C3物质占72.27%. 相似文献
19.
For 25 years the conception has been well established that the overwhelming majority of chemical elements and their isotopes have been synthesized in stars during the course of stellar evolution, in particular during the advanced stages and in supernova explosions. Until now this general idea has not led to major difficulties or inconsistencies. On the contrary, the theoretical models have been very successful in explaining the observed abundances in meteorites, planets (including the earth), stars (including the sun) and galactic cosmic rays. Our present understanding of nucleosynthesis will be reviewed with special attention given to nucleosynthetic processes in primordial stars and supernovae. We will concentrate primarily on predictions which can be made for relative abundances rather than for absolute abundances, because the latter problem requires evolutionary models of the galaxy which are beyond the scope of this article. 相似文献