Molecules in Circumstellar Envelopes of Carbon Stars     

F. Larsen  H. Olofsson  K. Eriksson  B. Gustafsson 《Astrophysics and Space Science》1997,251(1-2):235-238

We have searched for line emission from various transitions of a number of molecules, including CO, HCN, CN, CS and SiO, as well as some of their isotopic variants, towards a sample of 68 bright carbon stars. Part of the data has already been published in Olofsson et al. (1993a,b). The aim of the project is to obtain a better understanding of the carbon star phenomenon and the processes involved. In particular, we would like to obtain reliable mass loss rates and molecular abundances for these objects. This requires careful and detailed modelling, which is currently underway. Our hope is that the study of these bright carbon stars will serve as a guide to the study of higher mass loss rate objects. Some preliminary observational results are presented here. This revised version was published online in September 2006 with corrections to the Cover Date.  相似文献   

Modeling the combined impact of changing climate and changing nutrient loads on the Baltic Sea environment in an ensemble of transient simulations for 1961–2099     

H. E. M. Meier  R. Hordoir  H. C. Andersson  C. Dieterich  K. Eilola  B. G. Gustafsson  A. H?glund  S. Schimanke 《Climate Dynamics》2012,39(9-10):2421-2441

The combined future impacts of climate change and industrial and agricultural practices in the Baltic Sea catchment on the Baltic Sea ecosystem were assessed. For this purpose 16 transient simulations for 1961–2099 using a coupled physical-biogeochemical model of the Baltic Sea were performed. Four climate scenarios were combined with four nutrient load scenarios ranging from a pessimistic business-as-usual to a more optimistic case following the Baltic Sea Action Plan (BSAP). Annual and seasonal mean changes of climate parameters and ecological quality indicators describing the environmental status of the Baltic Sea like bottom oxygen, nutrient and phytoplankton concentrations and Secchi depths were studied. Assuming present-day nutrient concentrations in the rivers, nutrient loads from land increase during the twenty first century in all investigated scenario simulations due to increased volume flows caused by increased net precipitation in the Baltic catchment area. In addition, remineralization rates increase due to increased water temperatures causing enhanced nutrient flows from the sediments. Cause-and-effect studies suggest that both processes may play an important role for the biogeochemistry of eutrophicated seas in future climate partly counteracting nutrient load reduction efforts like the BSAP.  相似文献   

The spectral hardening associated with the westward travelling surge     

Åke Steen  Georg Gustafsson 《Planetary and Space Science》1981,29(9):1011-1017

Photometer recordings of auroral emissions from N⁺₂ and OI have demonstrated that the ratios between the emissions show a characteristic plateau just prior to the passage of a westward travelling surge. The plateau may be interpreted as a temporary (approx. 1 min) cessation in the spectral hardening of the precipitating particles associated with the surge. The characteristic energy of the plateau is about one keV above the level prior to the beginning of the surge. The results have been interpreted in terms of an instability that is switched on during the time of the plateau and then turned off when the electron density is increased above a certain limit.  相似文献   

Spot Satellite Data For Exploration Of Fractured Aquifers In A Semi-Arid Area In Southeastern Botswana     

P. Gustafsson 《Hydrogeology Journal》1994,2(2):9-18

In areas with little primary porosity and low bedrock hydraulic conductivity, hydrogeological properties are mainly determined by secondary factors, such as fracture zones and associated weathering. Fracture zones in areas with limited regolith cover are often detectable on satellite images as linear features originating mainly from pronounced vegatation anomalies, topographic effects or both. SPOT multispectral and panchromatic data of a 2000 km² semi-arid area in southeastern Botswana have, in this study, been merged and interpreted in an image processing system resulting in a detailed lineament map and a delineation of dry season vegetation. The lineament data have been analyzed in a geographical information system and correlation studies of borehole and geophysical data with satellite lineaments have been carried out. The study shows that a digital approach, using satellite data in combination with existing field data, can provide a time- and cost-effective tool for the identification and narrowing of target areas for groundwater exploration in semi-arid areas.  相似文献   

Distribution of silver in massive sulfide ores   总被引：1，自引：0，他引：1  

Örjan Amcoff 《Mineralium Deposita》1984,19(1):63-69

The distribution of silver in connection with the formation of massive sulfide ores is discussed. It is proposed: 1) The affinity between silver and galena-rich ores is only pronounced if antimony and/or bismuth are also present in significant amounts, and 2) The degree of correlation between silver and lead is partly a function of the Ag/Sb+Bi ratio in the ore and increasing with decrease in ratio at least up to Ag/Sb+Bi=1. Observations of correlated Cu/Ag ratios in complex ores indicate that some silver was solved in chalcopyrite at the time of deposition. This is often masked by the much higher silver contents associated with galena. The Bi/Sb ratio is expected to increase downwards stratigraphically in galena-rich ores, due to a larger solubility of silver-bismuth in galena as compared with silver-antimony, at a realistic deposition temperature (200–300 °C). However, such an effect will only rarely be seen, due to incomplete separation of the ore-constituents at the time of deposition, as well as to post-depositional changes.  相似文献   

Spodic Material for In Situ Treatment of Arsenic in Ground Water   总被引：2，自引：0，他引：2  

J. Lindberg  J. Sterneland  P.-O. Johansson  J.P. Gustafsson 《Ground Water Monitoring & Remediation》1997,17(4):125-130

The leaching of chromium-copper-arsenic salts from old wood preservation sites is a threat to ground water at many places in Sweden. The installation of in situ reactive barriers is an attractive "passive' technique to prevent the further spreading of contaminants. The use of peat as a reactive barrier material has been suggested for heavy metals, but this material was expected to be unsatisfactory for arsenic (As). Therefore, the feasibility of using spodic B horizon material for the retention of arsenic was tested in laboratory column experiments. Contaminated soil was taken from an old preservation site and leached under conditions designed to imitate the field conditions. The arsenic load during the three-month duration of the test corresponded to a load at the field site during three years. The B horizon material proved to be efficient for retention of arsenic, despite the observation that As(III) dominated the As speciation. The As(III) concentration was reduced from 1 to 3 mg dm⁻³ to < 0.02 mg dm⁻³. Pure peat was, as expected, not suited as a reactive barrier for As, and a mixed B horizon/peat reactive barrier also proved unsatisfactory for the removal of As. It is therefore important to separate the B horizon material from any peat that is used to sorb heavy metals. Before applying the B horizon reactive barrier technique in the field, the effect of the naturally occurring variability of the reactive compounds should be tested. The inclusion of oxidizing agents in the barrier could possibly improve the lifetime considerably. Furthermore, the influence of the flow rate should be evaluated since the kinetics of the arsenic adsorption is relatively slow.  相似文献   

Spatial and temporal relations between auroral emission and cosmic noise absorption     

Georg Gustafsson 《Planetary and Space Science》1969,17(12):1961-1972

An investigation has been made of the relation between auroral emission at λ5577 Å and the cosmic noise absorption using a new technique. A photometer and the antenna of a riometer were mounted on a 60 m long rotating antenna boom which had a speed of 1 rev per 3 min. The instruments were directed at an elevation angle of 45°. From the analysis of several break-ups of the aurora it has been found that during a period of 15–20 min in the middle of a break-up there may be an increase of the absorption by a factor 2 to 4 which does not correspond to a similar increase of the auroral emission. These changes in the emission-absorption ratio has been interpreted as peaks in the energy spectrum of the incoming particles. The structures of auroral emission and auroral absorption are sometimes very similar over periods of hours and the appearance of the structure is usually in the form of an east-west oriented arc. The cross correlation coefficient may be as high as 0·9 during these events over long periods of time. However, a number of exceptional cases have appeared where little structure was found in the riometer record while the photometer showed structure and vice versa.  相似文献   

Tentative Detection of Circumstellar CO2 from the AGB Star R Crateris     

N. Ryde  K. Eriksson  B. Gustafsson  M. Lindqvist  H. Olofsson 《Astrophysics and Space Science》1997,255(1-2):301-302

We report on and discuss the detection of an emission feature at 14.98 μm from the oxygen-rich, semi-regularly pulsating Asymptotic Giant Branch star R Crateris, a feature which we suggest to be due to the ₀ ¹ Q-branch of circumstellar CO2. We also suggest a reasonable excitation mechanism, which could explain the height, the width and the asymmetry of the feature. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

Cluster探测到磁尾等离子体注入的特征   总被引：1，自引：0，他引：1       下载免费PDF全文

何兆海  刘振兴  沈超  段素平  刘晓  张永存  姚丽  宗秋刚  H.Rème  G.Gustafsson 《地球物理学报》2008,51(2):307-315

利用Cluster卫星2001～2004年磁尾运行期间RAPID仪器的数据,确定了115例磁尾等离子体注入事件,借助时序叠加法统计研究磁尾等离子体注入现象的特征.注入事件主要分布于磁地方时夜晚20时至凌晨04时.与同步轨道区观测到的粒子注入事件类似,可以将磁尾粒子注入事件分成五类：（1）只有离子注入;（2）离子先于电子注入;（3）离子和电子同时注入;（4）电子先于离子注入;（5）只有电子注入.磁尾粒子注入时,质子（能量范围0～40 keV）的温度和数密度同时显著增加,沿地球径向的传播速度也明显增大.统计分析磁尾注入期间同时观测到的晨昏对流电场,发现电场可分为两类：（A）注入后电场突然增大,电场强度为正;（B）注入后电场突然增大,电场强度为负.利用磁层磁场（T89c）和电场（Volland-Stern）模型模拟粒子注入后赤道面的电漂移速度矢量,模拟结果与统计结果基本一致,表明晨昏对流电场引起的电漂移是驱动磁尾（-18R_EE）等离子体沿地球径向注入的机制之一.  相似文献   

Process refinements improve a hydrological model concept applied to the Niger River basin   总被引：1，自引：0，他引：1       下载免费PDF全文

Jafet C.M. Andersson  Berit Arheimer  Farid Traoré  David Gustafsson  Abdou Ali 《水文研究》2017,31(25):4540-4554

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