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排序方式: 共有49条查询结果,搜索用时 31 毫秒
21.
Nadine v. Blohn Karoline Diehl Anke Nölscher Alexander Jost Subir K. Mitra Stephan Borrmann 《Journal of Atmospheric Chemistry》2013,70(2):131-150
Laboratory experiments were carried out in the Mainz vertical wind tunnel to determine the retention of the trace gases ammonia and sulfur dioxide dissolved in supercooled cloud droplets during riming. The conditions during riming were similar to the ones in atmospheric mixed phase clouds: temperatures from ?18 °C to ?5 °C, liquid water contents between 1 and 1.5 g m?3, liquid drop radii between 10 and 20 μm, liquid phase concentrations from 1 to 22 mg/l. As collectors, floating ice particles and snow flakes with diameters between 6 mm and 1.5 cm were used. After riming the retention coefficients, i.e. the fractions of the species which remained in the ice phase after freezing were determined. Retention coefficients lying between 0.1 and 1.0 were measured depending on the solubility and dissociation of the trace gas, liquid phase concentration, ambient air temperature, and shape of rimed collector. This can be explained from the chemists’ point of view by the effective Henry’s law constant of the species and physically with the rate of latent heat removal from the rimed collector during freezing. Parameterizations derived from the different experimental cases describe the retention coefficients as a function of temperature. In general, an average retention of ammonia of 92?±?21 % was determined independently of liquid phase concentration while mean values for sulfur dioxide were 53?±?10 % at low liquid phase concentrations and 29?±?7 % at high liquid phase concentrations. 相似文献
22.
Groundwater-dependent, spring-fed ecosystems of the Cuatrociénegas Basin, Coahuila, Mexico, host >70 endemic species. These
desert springs occur primarily aligned along the base of an anticline that bisects the Cuatrociénegas Basin, but the hydrogeologic
controls of the springs are poorly understood. The hypothesis that spring locations are controlled by subsurface geology,
such as buried anticlines or faulting, versus stratigraphic controls is tested by evaluating: (1) regional structural styles;
(2) fracture models of analogous structures; (3) hydrogeologic data; and (4) geophysical surveys. Jurassic and Cretaceous
siliciclastic and carbonate rocks deposited on the Coahuila Block west of the Cuatrociénegas Basin have dips <10° and lack
faults because of a structurally rigid granodiorite basement. To the east of the Coahuila Block and around the Cuatrociénegas
Basin, the Coahuila Folded Belt has anticlines associated with basement-involved faults, 10–25° backlimb dips, and forelimb
dips up to vertical or slightly overturned. Springs in the western sub-basin that represent 85% of total basin discharge are
located on zones of highest anticipated fracture density predicted by fracture models of analogous anticlines. Spring waters
reveal elevated temperature (32–35°C) and low tritium (<1 tritium unit). Gravimetry and time-domain electromagnetic surveys
correspond with a best-fit Cuatrociénegas Basin hydrogeologic model of fractures associated with reverse faulting controlling
spring locations in the western Cuatrociénegas Basin. Springs in the eastern sub-basin are located where ephemeral streams
have eroded through confining beds along the base of alluvial fans and lack faulting. Regional variations in structural style
are an important control on the location of springs in the Cuatrociénegas Basin. 相似文献
23.
Roland Diehl Dieter H. Hartmann Nikos Prantzos 《Meteoritics & planetary science》2007,42(7-8):1145-1157
Abstract— Gamma rays from radioactive byproducts of cosmic nucleosynthesis are direct messengers from nuclear processes taking place in various cosmic sites, and can be measured with telescopes operated in space. Due to low detector sensitivity, up until now, only a handful of sources have been detected in that electromagnetic window. Cobalt lines from SN1987A and 44Ti lines from the Cassiopeia A (Cas A) supernova remnant offer unique constraints on the properties of the innermost regions of core collapse supernovae. Diffuse gamma‐ray lines from the decay of radioactive 26Al and the annihilation of positrons are bright enough for mapping the Milky Way in the MeV regime, and are both measured by recent spaceborne spectrometers with unprecedented precision. This constrains the sources of Al production and the state of interstellar gas in the vicinity of these sites: the total mass of 26Al produced by stellar sources throughout the Galaxy is estimated to be ~3 M⊙ per Myr, and the interstellar medium near those sources appears to be characterized by velocities of ~100 km s?1. Positron annihilation must occur in a modestly ionized, warm phase of the interstellar medium, but at present the major positron production site(s) remain unknown. The spatial distribution of the annihilation gamma‐ray emission constrains positron production sites and positron propagation in the Galaxy. 60Fe radioactivity has been clearly detected recently; the flux ratio relative to 26Al of about 15% is on the lower side of predictions from massive star and supernova nucleosynthesis models. Those views at nuclear and astrophysical processes in and around cosmic sources by space‐based gamma‐ray telescopes offer invaluable information on cosmic nucleosynthesis. 相似文献
24.
25.
Roland Diehl 《Experimental Astronomy》1995,6(4):103-108
The imaging telescope COMPTEL aboard the NASA Compton Observatory satellite has been demonstrated to be capable of imaging diffuse emission along the Galactic plane. Here we describe details of the imaging data spaces and methods to model the background. Different methods of imaging analysis are compared. Verification of consistency among these methods is a key factor in overall assessment of diffuse emission results. Source simulations and statistical analysis through the bootstrap method are applied to verify the significances of image structures. 相似文献
26.
Numerical sensitivity studies were carried out to investigate the influence of shape variations of colliding ice particles on the collisional behavior. Therefore, two general ice particle shapes were considered: ice plates and ice columns. The changing of the shape of the ice particles was described by the changing of the axis ratio of the particles. Numerical growth calculations with a cloud model were carried out to show the impact of the axis ratio variations on the collectional growth in comparison to calculations with a constant axis ratio. Ice plates show significant differences between the two cases, whereas for ice columns the effect of the axis ratio variations is less important. 相似文献
27.
A first-order, semi-analytical method for the long-term motion of resonant satellites is introduced. The method provides long-term solutions, valid for nearly all eccentricities and inclinations, and for all commensurability ratios. The method allows the inclusion of all zonal and tesseral harmonics of a nonspherical planet.We present here an application of the method to a synchronous satellite includingonly theJ
2 andJ
22 harmonics. Global, long-term solutions for this problem are given for arbitrary values of eccentricity, argument of perigee and inclination. 相似文献
28.
Tobias Diehl John Clinton Nicolas Deichmann Carlo Cauzzi Philipp Kästli Toni Kraft Irene Molinari Maren Böse Clotaire Michel Manuel Hobiger Florian Haslinger Donat Fäh Stefan Wiemer 《Swiss Journal of Geoscience》2018,111(1-2):221-244
This report summarizes the seismicity in Switzerland and surrounding regions in the years 2015 and 2016. In 2015, the Swiss Seismological Service detected and located 735 earthquakes in the region under consideration. With a total of 20 earthquakes of magnitude ML ≥ 2.5, the seismic activity of potentially felt events in 2015 was close to the average of 23 earthquakes over the previous 40 years. Seismic activity was above average in 2016 with 872 located earthquakes of which 31 events had ML ≥ 2.5. The strongest event in the analyzed period was the ML 4.1 Salgesch earthquake, which occurred northeast of Sierre (VS) in October 2016. The event was felt in large parts of Switzerland and had a maximum intensity of V. Derived focal mechanisms and relative hypocenter relocations of aftershocks image a SSE dipping reverse fault, which likely also hosted an ML 3.9 earthquake in 2003. Another remarkable earthquake sequence in the Valais occurred close to Sion with four felt events (ML 2.7–3.2) in 2015/16. We associate this sequence with a system of WNW-ESE striking fault segments north of the Rhône valley. Similarities with a sequence in 2011, which was located about 10 km to the NE, suggest the existence of an en-echelon system of basement faults accommodating dextral slip along the Rhône-Simplon line in this area. Another exceptional earthquake sequence occurred close to Singen (Germany) in November 2016. Relocated hypocenters and focal mechanisms image a SW dipping transtensional fault segment, which is likely associated with a branch of the Hegau-Bodensee Graben. On the western boundary of this graben, micro-earthquakes close to Schlattingen (TG) in 2015/16 are possibly related to a NE dipping branch of the Neuhausen Fault. Other cases of earthquakes felt by the public during 2015/16 include earthquakes in the region of Biel, Vallorcine, Solothurn, and Savognin. 相似文献
29.
Lee H. Spangler Laura M. Dobeck Kevin S. Repasky Amin R. Nehrir Seth D. Humphries Jamie L. Barr Charlie J. Keith Joseph A. Shaw Joshua H. Rouse Alfred B. Cunningham Sally M. Benson Curtis M. Oldenburg Jennifer L. Lewicki Arthur W. Wells J. Rodney Diehl Brian R. Strazisar Julianna E. Fessenden Thom A. Rahn James E. Amonette Jon L. Barr William L. Pickles James D. Jacobson Eli A. Silver Erin J. Male Henry W. Rauch Kadie S. Gullickson Robert Trautz Yousif Kharaka Jens Birkholzer Lucien Wielopolski 《Environmental Earth Sciences》2010,60(2):227-239
A controlled field pilot has been developed in Bozeman, Montana, USA, to study near surface CO2 transport and detection technologies. A slotted horizontal well divided into six zones was installed in the shallow subsurface. The scale and CO2 release rates were chosen to be relevant to developing monitoring strategies for geological carbon storage. The field site was characterized before injection, and CO2 transport and concentrations in saturated soil and the vadose zone were modeled. Controlled releases of CO2 from the horizontal well were performed in the summers of 2007 and 2008, and collaborators from six national labs, three universities, and the U.S. Geological Survey investigated movement of CO2 through the soil, water, plants, and air with a wide range of near surface detection techniques. An overview of these results will be presented. 相似文献
30.