Transport of water in frozen soil IV. Analysis of experimental results on the effects of ice content

Effects of ice content on the transport of water in frozen soil are studied experimentally and theoretically under isothermal conditions. A physical law, that the flux of water in unsaturated frozen soil is proportional to the gradient of total water content is proposed. Theoretical justification is made by the use of the two-phase flow theory. The experimental results are shown to support the proposed physical law. The results of this study are presented in two parts and this is the second paper describing the theoretical aspects of the study.     

Three components of 3–4 μm absorption bands

We present 2–4 μm spectra of six infrared sources for which the extinction is not purely interstellar, but is dominated by circumstellar or molecular cloud dust. In all cases the absorption bands differ from the interstellar case, though a component of the interstellar absorption is often present. We also present an improved absorption spectrum for the galactic centre source IRS 7, correcting spurious features in our previous spectrum. Three independent components can be identified: (i) The interstellar component, probably of organic origin, and itself not necessarily invariant; (ii) The symmetrical water ice feature at 3.06 μm, found most commonly in molecular clouds; (iii) A component at 3.53 μm possibly identified with solid formaldehyde grains, and seen only in molecular clouds because of its weakness. Other absorption components appear to be unrelated to those in the 3–4 μm region, most notably the 10 μm absorption found in oxygen-rich giants and the interstellar medium, and presumable inorganic in nature. Our observations include the first detection of water ice absorption in a source in the ρ Oph dark cloud. Biological materials provide the best fit to the interstellar case, but do not presently account for the distinct 3.53 μm component. We stress the need for further laboratory experiments using simpler organic materials.     

Determination of earthquake early warning parameters, τc and Pd, for southern California

We explore a practical approach to earthquake early warning in southern California by determining a ground-motion period parameter  τ _c   and a high-pass filtered displacement amplitude parameter Pd from the initial 3 s of the P waveforms recorded at the Southern California Seismic Network stations for earthquakes with M > 4.0. At a given site, we estimate the magnitude of an event from  τ _c   and the peak ground-motion velocity ( PGV ) from Pd . The incoming three-component signals are recursively converted to ground acceleration, velocity and displacement. The displacements are recursively filtered with a one-way Butterworth high-pass filter with a cut-off frequency of 0.075 Hz, and a P -wave trigger is constantly monitored. When a trigger occurs,  τ _c   and Pd are computed. We found the relationship between  τ _c   and magnitude ( M ) for southern California, and between Pd and PGV for both southern California and Taiwan. These two relationships can be used to detect the occurrence of a major earthquake and provide onsite warning in the area around the station where onset of strong ground motion is expected within seconds after the arrival of the P wave. When the station density is high, the methods can be applied to multistation data to increase the robustness of onsite early warning and to add the regional warning approach. In an ideal situation, such warnings would be available within 10 s of the origin time of a large earthquake whose subsequent ground motion may last for tens of seconds.     

Chaoborus (Diptera: Chaoboridae) mandibles—paleolimnological indicators of the historical status of fish populations in acid-sensitive lakes

Paleolimnological analyses of Chaoborus mandibles were used to assess the status of fish populations over the previous 150 to 300 years in five lakes from the Adirondack region of New York State. Windfall Pond (pH 6.5) has not acidified and currently has viable fish populations. Big Moose Lake (pH 5.0) has acidified in recent years, and the number of fish populations declined from 14 in the 1930's to seven in the early 1980's. The occurrence of only migratory Chaoborus (subgenus Sayomyia) in the cores indicated the long term presence of fish populations in Windfall Pond and Big Moose Lake. Brooktrout Lake (pH 5.0), Deep Lake (pH 4.7) and Upper Wallface Pond (pH 4.8) have all acidified in recent years, and all three are currently fishless. Chaoborus (Sayomyia) was present throughout the Brooktrout Lake core, but the entirely limnetic species, C. americanus, appeared in the topmost interval in the core. The appearance of C. americanus in the top of the core indicated a recent elimination of fish from Brooktrout Lake, probably during the 1970's. Elimination of fish by the 1940's was inferred for Deep Lake because C. americanus appeared above the 1930 level and replaced C. trivittatus as the dominant. Dominance of C. americanus throughout the Upper Wallface Pond core indicated that planktivorous fish were never present. These results strongly suggest that stratigraphic analyses of Chaoborus mandibles provide a useful assessment of the general status of historical fish populations in Adirondack lakes. The technique should be useful in other regions, as well as for applications other than those concerning lake acidification.This is the eleventh of a series of papers to be published by this journal which is a contribution of the Paleoecological Investigation of Recent Lake Acidification (PIRLA) project. Drs. D.F. Charles and D.R. Whitehead are guest editors for this series.     

Multistage Variscan magmatism in the central Tauern Window (Austria) unveiled by U/Pb SHRIMP zircon data

U/Pb SHRIMP ages of nine Variscan leucocratic orthogneisses from the central Tauern Window (Austria) reveal three distinct pulses of magmatism in Early Carboniferous (Visean), Late Carboniferous (Stephanian) and Early Permian, each involving granitoid intrusions and a contemporaneous opening of volcano-sedimentary basins. A similar relationship has been reported for the Carboniferous parts of the basement of the Alps further to the west, e.g. the “External massifs” in Switzerland. After the intrusion of subduction-related, volcanic-arc granitoids (374?±?10?Ma; Zwölferkogel gneiss), collisional intrusive-granitic, anatectic and extrusive-rhyolitic/dacitic rocks were produced over a short interval at ca. 340?Ma (Augengneiss of Felbertauern: 340?±?4?Ma, Hochweißenfeld gneiss: 342?± 5?Ma, Falkenbachlappen gneiss: 343?±?6?Ma). This Early Carboniferous magmatism, which produced relatively small volumes of melt, can be attributed to the amalgamation of the Gondwana-derived “Tauern Window” terrane with Laurussia–Avalonia. Probably due to the oblique nature of the collision, transtensional phenomena (i.e. volcano-sedimentary troughs and high-level intrusives) and transpressional regimes (i.e. regional metamorphism and stacked nappes with anatexis next to thrust planes) evolved contemporaneously. The magmas are mainly of the high-K I-type and may have been generated during a short phase of decompressional melting of lithospheric mantle and lower crustal sources. In the Late Carboniferous, a second pulse of magmatism occurred, producing batholiths of calc-alkaline I-type granitoids (e.g. Venediger tonalite: 296?±?4?Ma) and minor coeval bodies of felsic and intermediate volcanics (Heuschartenkopf gneiss: 299?±?4?Ma, Peitingalm gneiss: 300?±?5?Ma). Prior to this magmatism, several kilometres of upper crust must have been eroded, because volcano-sedimentary sequences hosting the Heu- schartenkopf and Peitingalm gneisses rest unconformably on 340-Ma-old granitoids. The youngest (Permian) period of magma generation contains the intrusion of the S-type Granatspitz Central Gneiss at 271?±?4?Ma and the extrusion of the rhyolitic Schönbachwald gneiss protolith at 279?±?9?Ma. These magmatic rocks may have been associated with local extension along continental wrench zones through the Variscan orogenic crust or with a Permian rifting event. The Permian and the above-mentioned Late Carboniferous volcano-sedimentary sequences were probably deposited in intra-continental graben structures, which survived post-Variscan uplift and Alpine compressional tectonics.     

The impact of cooling flows on the TX–LBol relation for the most luminous clusters

We examine the effects of cooling flows on the T _X– L _Bol relation for a sample of the most X-ray luminous ( L _Bol > 10⁴⁵ erg s⁻¹) clusters of galaxies known. Using high-quality ASCA X-ray spectra and ROSAT images we explicitly account for the effects of cooling flows on the X-ray properties of the clusters and show that this reduces the previously noted dispersion in the T _X– L _Bol relationship. More importantly, the slope of the relationship is flattened from L _Bol ∝  T ³_X to approximately L _Bol ∝  T ²_X, in agreement with recent theoretical models which include the effects of shocks and pre-heating on the X-ray gas. We find no evidence for evolution in the T _X– L _Bol relation within z  ∼ 0.3. Our results demonstrate that the effects of cooling flows must be accounted for before cosmological parameters can be determined from X-ray observations of clusters. The results presented here should provide a reliable basis for modelling the T _X– L _Bol relation at high X-ray luminosities.