Atomic data relevant to line formation in strongly magnetized white dwarf stars     

G. Wunner  F. Geyer  H. Ruder 《Astrophysics and Space Science》1987,131(1-2):595-599

The discovery of magnetic field strengths in the range of 500 million Gauss in the objects Grw+70°8247 and PG1031+224 has given enormous impetus to investigations of magnetic white dwarf stars. We have determined intensities of Balmer transitions for B>10⁸ Gauss as a function of field and find strong oscillations of the transitions strengths, which are of importance to the quantitative analysis of the observed spectra and the interpretation of polarimetric measurements in these objects.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.  相似文献   

Travel time based approach for the assessment of vulnerability of karst groundwater: the Transit Time Method     

Karolin Brosig  Tobias Geyer  Ali Subah  Martin Sauter 《Environmental Geology》2008,54(5):905-911

Karst aquifers represent important water resources in many parts of the world. Unfortunately, karst aquifers are characterised by high contamination risks. This paper presents a travel time based method for the estimation of karst groundwater vulnerability. It considers (1) physics-based lateral flow within the uppermost weathered zone (epikarst) in a limestone-dominated region and (2) high velocities of vertical infiltration at discrete infiltration points (e.g. sinkholes) or lines (e.g. dry valleys, faults). Consequently, the Transit Time Method honours the actual flow path within the unsaturated zone of a karst aquifer system. A test site in Northern Jordan was chosen for the demonstration of the assessment technique, i.e. the catchment area of the Qunayyah Spring north of the capital Amman. The results demonstrate that zones of highest vulnerability lie within valleys and nearby main fault zones. It also reveals that regions, categorised as protected areas by other methods due to thick unsaturated zones, contribute to a major degree to the total risk.  相似文献   

Influence of Wind on Dynamics and Flushing of Shallow Estuaries     

W.R. Geyer 《Estuarine, Coastal and Shelf Science》1997,44(6):713-722

Observations of two small estuaries in Cape Cod, U.S.A. indicate large variations in salinity structure that are forced by variations in along-estuary wind stress. During onshore winds, the estuarine circulation is reduced, and the along-estuary salinity gradient increases as freshwater accumulates. During offshore winds, the surface outflow is enhanced, freshwater is flushed out of the estuary, and the along-estuary salinity gradient becomes weak. Constrictions block the wind-induced flushing, resulting in strong salinity fronts across the constrictions. The residence time of one of the estuaries varies by more than a factor of three in response to variations in wind-induced flushing. The other estuary has little variation of flushing associated with winds, due to a constriction at the mouth that inhibits the wind-induced exchange. The strong influence of winds on the flushing of these estuaries is due in part to their shallow depths, which accentuates the influence of wind stress relative to the effects of the horizontal density gradient. In addition, the residence times of the estuaries are comparable to the time scale of wind forcing, allowing large changes in water properties during wind events.  相似文献   

A polarimetric investigation of the eclipsing binary XY ursae majoris     

E. H. Geyer  K. Metz 《Astrophysics and Space Science》1977,52(2):351-356

On three nights in February 1976 we carried out polarimetric measurements, in V, of the short periodic eclipsing binary XY UMa, covering a complete cycle. The results are as follows:

1. Within all phase intervals the linear polarization does not exceed 0.1%.
2. In the phase range 0 ^p .95–1 ^p .35 the scatter of the Stokes parametersQ andU is about twice that within the phase interval 0 ^p .35–0 ^p .95.
3. A periodogram analysis of these data revealed a period of 21000 s, which is equal to half the orbital periodP _o=0^d.47899 within 1.5%.

From these we derive the conclusions that no circumstellar envelope can be made responsible for the observed long-term changes of the light curve and system brightness, supporting the earlier spectroscopic finding. The different scatter of the Stokes parameters at different phase intervals and theP _o/2 periodicity are in favor of the star spot model for XY UMa proposed by one of the authors (E. G.).  相似文献   

Phytoplankton Spatial Variability in the River-Dominated Estuary,Apalachicola Bay,Florida     

Natalie L. Geyer  Markus Huettel  Michael S. Wetz 《Estuaries and Coasts》2018,41(7):2024-2038

In shallow estuaries with strong river influence, the short residence time and pronounced gradients generate an environment for plankton that differs substantially in its dynamics from that of the open ocean, and the question arises “How is phytoplankton biomass affected?” This study assesses the small-scale spatial and temporal distribution of phytoplankton in Apalachicola Bay, a shallow bar-built estuary in the Florida Panhandle. Phytoplankton peaks were characterized to gain insights into the processes affecting spatial heterogeneity in biomass. Chlorophyll a (Chl a) distribution at 50-m spatial resolution was mapped using a flow-through sensor array, Dataflow©, operated from a boat that sampled four transects across the bay every 2 weeks for 16 months. Chl a peaks exceeding background concentrations had an average width of 1.3?±?0.7 km delineated by an average gradient of 3.0?±?6.0 μg Chl a L^?1 km^?1. Magnitude of E-W wind, velocity of N-S wind, tidal stage, and temperature affected peak characteristics. Phytoplankton contained in the peaks contributed 7.7?±?2.7% of the total integrated biomass observed along the transects during the study period. The river plume front was frequently a location of elevated Chl a, which shifted in response to river discharge. The results demonstrate that despite the shallow water column, river flushing, and strong wind and tidal mixing, distinct patchiness develops that should be taken into consideration in ecological studies and when assessing productivity of such ecosystems.  相似文献   

Ionenselektive Elektroden (ISE) — Untersuchungen zur Potentialeinstellung und Anwendung in der Analytik     

U. P. Decker  R. Geyer 《洁净——土壤、空气、水》1984,12(1):19-27

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An Approach for Classification of Groundwaters by Synchronous Fluorescence Spectroscopy and Discriminant Analysis     

W. Geyer  L. Brüggemann  U. Schmitz 《洁净——土壤、空气、水》1996,24(5):206-211

Monitoring and evaluation of groundwater quality in drinking water protectorates is of particular interest if the uncontrolled entry of pollutants, for example by infiltrating river water, cannot be excluded. A fluorescence spectroscopic method is presented as possible alternative to the conventional expensive hydrochemical investigations. This method uses the information yielded by synchronous fluorescence spectra. After a Fourier transformation of the original spectra and a following discriminant analysis, the samples can be classified in different groups corresponding to the different types of groundwater. The method was tested in the drinking water protectorate of a waterworks of a German metropolis (Halle, Sachsen-Anhalt). We found a prediction rate of about 90% in the investigated case.  相似文献   

Present climate and climate change over North America as simulated by the fifth-generation Canadian regional climate model     

Leo Šeparović  Adelina Alexandru  René Laprise  Andrey Martynov  Laxmi Sushama  Katja Winger  Kossivi Tete  Michel Valin 《Climate Dynamics》2013,41(11-12):3167-3201

The fifth-generation Canadian Regional Climate Model (CRCM5) was used to dynamically downscale two Coupled Global Climate Model (CGCM) simulations of the transient climate change for the period 1950–2100, over North America, following the CORDEX protocol. The CRCM5 was driven by data from the CanESM2 and MPI-ESM-LR CGCM simulations, based on the historical (1850–2005) and future (2006–2100) RCP4.5 radiative forcing scenario. The results show that the CRCM5 simulations reproduce relatively well the current-climate North American regional climatic features, such as the temperature and precipitation multiannual means, annual cycles and temporal variability at daily scale. A cold bias was noted during the winter season over western and southern portions of the continent. CRCM5-simulated precipitation accumulations at daily temporal scale are much more realistic when compared with its driving CGCM simulations, especially in summer when small-scale driven convective precipitation has a large contribution over land. The CRCM5 climate projections imply a general warming over the continent in the 21st century, especially over the northern regions in winter. The winter warming is mostly contributed by the lower percentiles of daily temperatures, implying a reduction in the frequency and intensity of cold waves. A precipitation decrease is projected over Central America and an increase over the rest of the continent. For the average precipitation change in summer however there is little consensus between the simulations. Some of these differences can be attributed to the uncertainties in CGCM-projected changes in the position and strength of the Pacific Ocean subtropical high pressure.  相似文献   

Polycyclic aromatic hydrocarbons in the aquatic environment: Jerry M. Neff. Applied Science Publishers Ltd., London, 1979, 262 pp.     

R.A. Geyer 《Marine Chemistry》1981,10(2):167-168

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Identification of a blue object with a newly detected X-ray source     

Geyer  E. H.  Hoffmann  M. 《Astrophysics and Space Science》1983,95(2):291-298

An approximate analytical solution for self-similar flow behind a spherically-symmetric magnetogasdynamic strong shock wave is investigated using the method of Laumbach and Probstein (1969). The total energy of flow is taken to be dependent on the shock radius obeying a power law. The shock is propagating into a perfect gas at rest with non-uniform density and magnetic field.  相似文献