Helium resonance lines in the flare of 15 June, 1973

Time sequences of He i and He ii resonance line intensities at several sites within the flare of 15 June, 1973 are derived from observations obtained with the Naval Research Laboratory's Slitless Spectroheliograph on Skylab. The data are compared with predictions in six model flare atmospheres based on two values for the heating rate and three for the flux of photoionizing coronal X-rays and EUV. A peak ionizing flux more than 10³ times that in the quiet Sun is indicated. For most conditions in flare kernels the He ii L and L lines are found to be formed by collisional excitation, thereby contributing to the local cooling of the plasma at temperatures above 6 × 10⁴ K. Emission in the higher Lyman lines is generally the result of a mixture of collisional excitation at these temperatures and photoionization and recombination at temperatures near 2.5 × 10⁴ K. We discuss implications for the common practice of deriving stellar coronal fluxes from He ii 1640 Å fluxes assuming dominance of the recombination mechanism.Chief, Quantum Physics Division, National Institute of Standards and Technology.Operated jointly by the National Institute of Standards and Technology and the University of Colorado.Operated by the National Optical Astronomy Observatories of the Association of Universities for Research in Astronomy, Inc. under contract with the National Science Foundation.     

Tidal current observation in the southern Yellow Sea in the summers of 2001 and 2003

Direct current observations in the Yellow Sea interior are very scarce due to intense fishing and trawling activities. Most previous studies on tides in the area were based on coastal measurements or satellite altimeter sea levels and have not been rigorously compared with direct measurements. In this paper, tidal currents are studied with current profiles from three bottom-moored Sontek Acoustic Doppler Profilers （ADPs） deployed in the southern Yellow Sea in summer of 2001 and 2003. The measured current series were dominated by tidal currents. Maximum velocities are between 40-80 cm/s at the mooring stations. M2 current is the most dominant primary tidal constituent, while MS4 and M4 are the most significant shallow water tides with much smaller amplitudes than the primary tides.     

UV-radiation in galaxies

I review the origin of UV-radiation in galaxies of different morphological types. UV-excess in spectra of massive elliptical galaxies which have predominantly old stellar populations is traditionally explained by the contribution of low-mass stars at very late, poorly known stages of evolution—by so called ‘AGB-manqué’ stars or by the population of extended horizontal branch. However recent results from the GALEX survey of a large sample of nearby ellipticals have also demonstrated probable traces of recent star formation in a third of all ellipticals observed. In spiral galaxies extended UV-disks have been discovered by the GALEX; they are certainly illuminated by the current star formation, but what has provoked star formation in the areas of very low gas density, beyond the distribution of older stars, is a puzzle yet. The UV-spectra of starburst galaxies or starforming galactic nuclei are characterized by weak emission lines, if any, quite dissimilar to their optical spectra.     

Holocene paleohydrological reconstruction of Lake Strzeszyńskie (western Poland) and its implications for the central European climatic transition zone

Western Poland is located in the central European climatic transition zone, which separates the mild and humid Atlantic climate of Western Europe and the East European continental climate. This region is sensitive to lateral shifts of the European climate zones and is particularly suitable for reconstructing Holocene climate variability. This paper presents detailed analyses of the sedimentary record from Lake Strzeszyńskie since the Late Pleistocene. These include smear-slide and thin-section observations, X-ray fluorescence core scanning, magnetic susceptibility measurements, pollen analyses, and radiocarbon dating. The sediment record reveals three distinct sedimentary units consisting of: (1) an alternation of sand layers and laminated silt and clay deposits accumulated prior to 14,600 cal yr BP; (2) faintly laminated calcareous sediments intercalated with organic matter-rich layers deposited between 14,600 and 10,200 cal yr BP; and (3) massive calcareous mud deposited after 10,200 cal yr BP. The Holocene period is marked by nine phases of organic-rich sedimentation and enhanced Fe deposition, which occurred at ca. 10.1, 9.3, 6.4–6.1, 5.5–5.1, 4.7–4.5, 2.7–2.4, 1.3–1.2, 0.8–0.6, 0.4–0.2 kyr cal BP. These phases are associated with high lake levels and correspond with wet periods recognized in several other records from Poland and central Europe. These phases partly coincide with North Atlantic cold periods, which may suggest that high lake levels are triggered by an ocean-continent linking mechanism.     

Effects of long-term medieval agriculture on soil properties: A case study from the Kislovodsk basin,Northern Caucasus,Russia

The chemical properties and biological activities of soils were studied in the vicinity of the medieval settlement Podkumskoe-3 in the Kislovodsk basin (Northern Caucasus, Russia). Between the 5th and 8th centuries this area was ploughed regularly, but it was then abandoned up to the present day. It has been established that past human activity leads to soil undergoing significant transformations in terms of microbial communities and enzyme activity, and that such changes are maintained over long periods. Long-term manuring in the middle of the first millennium AD led to an increase in organic carbon content and the accumulation of nitrate nitrogen. Soils of ancient abandoned fields are associated with increases in microbial biomass, number of saprotrophic bacteria, urease activity, and fungal mycelium biomass. The observed changes in the microbiological and biochemical properties of soil were conditioned by secondary anthropogenically induced succession after the abandonment of arable lands.     

Geophysical Signature of the Shallow Water Flow in the Deepwater Basin of the Northern South China Sea

Shallow water flow (SWF), a disastrous geohazard in the continental margin, has threatened deepwater drilling operations. Under overpressure conditions, continual flow delivering unconsolidated sands upward in the shallow layer below the seafloor may cause large and long-lasting uncontrolled flows; these flows may lead to control problems and cause well damage and foundation failure. Eruptions from over-pressured sands may result in seafloor craters, mounds, and cracks. Detailed studies of 2D/3D seismic data from a slope basin of the South China Sea (SCS) indicated the potential presence of SWF. It is commonly characterized by lower elastic impedance, a higher Vp/Vs ratio, and a higher Poisson’s ratio than that for the surrounding sediments. Analysis of geological data indicated the SWF zone originated from a deepwater channel system with gas bearing over-pressured fluid flow and a high sedimentation rate. We proposed a fluid flow model for SWF that clearly identifies its stress and pressure changes. The rupture of previous SWF zones caused the fluid flow that occurred in the Baiyun Sag of the northern SCS.     

Libration of arguments of circumbinary-planet orbits at resonance

The paper refers to fictitious resonant orbits of planet type that surround both components of a binary system. In case of 16 studied examples a suitable choice of the starting values leads to a process of libration of special angular arguments and to an evolution with an at least temporary stay of the planet in the resonant orbit. The ratio of the periods of revolution of the binary and a planet is equal to 1:5. Eight orbits depend on the ratio 1:5 of the masses of the binary components, but two other ratios appear as well. The basis of this study is the planar, elliptic or circular restricted problem of three bodies, but remarks at the end of the text refer to a four-body problem.     

Simulation of double cold cores of the 35°N section in the Yellow Sea with a wave-tide-circulation coupled model

Based on the MASNUM wave-tide-circulation coupled numerical model, the temperature structure along 35°N in the Yellow Sea was simulated and compared with the observations. One of the notable features of the temperature structure along 35°N section is the double cold cores phenomena during spring and summer. The double cold cores refer to the two cold water centers located near 122°E and 125°E from the depth of 30m to bottom. The formation, maintenance and disappearance of the double cold cores are discussed. At least two reasons make the temperature in the center (near 123°E) of the section higher than that near the west and east shores in winter. One reason is that the water there is deeper than the west and east sides so its heat content is higher. The other is invasion of the warm water brought by the Yellow Sea Warm Current (YSWC) during winter. This temperature pattern of the lower layer (from 30m to bottom) is maintained through spring and summer when the upper layer (0 to 30m) is heated and strong thermocline is formed. Large zonal span of the 35°N section (about 600 km) makes the cold cores have more opportunity to survive. The double cold cores phenomena disappears in early autumn when the west cold core vanishes first with the dropping of the thermocline position. Supported by the National Basic Research Program of China (No. G1999043809) and the National Science Foundation of China (No. 49736190).     

Resource allocation for regional earthquake risk mitigation: a case study of Tehran,Iran

This paper presents a new optimization model to help cities in seismically active developing countries decide (1) How much to spend on pre-earthquake mitigation versus waiting until after an event and paying for reconstruction or simply not rebuilding damaged buildings? (2) Which buildings to mitigate and how? and (3) Which buildings to reconstruct and how? It extends previously developed optimization models to consider the particular issues that arise in such countries. First, the model allows for the possibility that some damaged buildings will not be reconstructed immediately and keeps track of any lost building inventory. Second, buildings can be mitigated to, or when damaged, reconstructed to, any appropriate structural type and seismic design level. Finally, the model objectives include minimizing the chance of an extremely high death toll in any one earthquake and minimizing the average annual death toll across earthquakes. The model is illustrated through a case study analysis for Tehran, Iran.     

Spatial Variability of Mass Movements in the Satluj Valley,Himachal Pradesh during 1990～2006

Satluj Valley is known to have a history of landslides and related mass movement activities since the geological times. Geological and geomorphological settings combined with anthropogenic activities constitute a propensity towards slope failure. During the last two decades,the area witnessed substantial increase in athropogenic pressure,mainly due to the exploitation of hydropower potential,changing landuse pattern and population growth. In addition,a shift of the climatic patterns in the form of larger area falling under the influence of rains was observed. These natural as well as anthropogenic changes in the area have resulted in increased spatial coverage of landslide in the area. This paper documents these changes during 1990～2006.