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71.
Marine waters from six sites around Hong Kong with varying levels of sewage pollution were examined for noroviruses (NoVs) by PCR cloning and sequencing of a highly-variable N-terminal region of the VP1 capsid gene, at the ORF1-ORF2 junction of NoV. Phylogenetic analysis of genogroups GI- and GII-specific PCR clones obtained from different marine sites indicated that human NoV GI.1 and GII.4 strains are the most prevalent genotypes circulating in Hong Kong waters. GI- and GII-specific TaqMan-based real-time PCR assays targeting the ORF1-ORF2 junction of NoVs were used to quantify NoV particles in marine water samples in parallel with total Escherichia coli counts which were enumerated on TBX medium. No correlation of any significance between NoV and E. coli counts was observed which highlighted the inadequacy in using E. coli as a fecal indicator to predict the level of NoVs in marine waters to protect public health. 相似文献
72.
The response of saltation to wind speed fluctuations 总被引:2,自引:0,他引:2
The response time of saltation to spatial or temporal wind speed fluctuations constitutes an important control parameter for aeolian sediment transport and deposition. In this paper, we present direct measurements of the response time obtained from several field experiments. The sand transport was studied using six small microphones arranged in a vertical profile and collocated with a sonic anemometer, a webcam and a cup anemometer tower. The webcam was coupled with the sonic anemometer via a personal computer and provides information on creeping and saltating grains with a sampling rate of 10 Hz. Sediment transport measurements were obtained over four periods. The Wiener filter, a signal processing technique, is used to obtain a discrete transfer function that relates the horizontal wind speed and the non‐intermittent sand transport. The transfer function can be established using an exponential function with a time constant or characteristic response time τ without time shift. The response time fluctuated between zero and 1·5 seconds depending on the turbulence intensity, the saltation activity, the measuring height and sampling rates. The Wiener filter coefficients suggest that the response of saltation to wind speed alterations is determined by more than one process. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
73.
Hans G. Machel 《Hydrogeology Journal》1999,7(1):94-107
This article provides a critical synopsis of the effects of groundwater flow on mineral diagenesis. Emphasis is placed on
those aspects and processes that change porosity and permeability in carbonate aquifers, because they are of particular importance
to human societies as sources of supplies of water for human consumption (drinking, irrigation) and of crude oil and natural
gas.
Diagenetic settings in carbonates as well as clastics are generally ill defined. This paper proposes a new comprehensive classification
of diagenetic settings into near-surface, shallow-, intermediate-, and deep-burial diagenetic settings; hydrocarbon-contaminated
plumes; and fractures. These settings are defined on the basis of mineralogy, petroleum, hydrogeochemistry, and hydrogeology.
This classification is applicable to all sedimentary basins.
Diagenesis is governed by various intrinsic and extrinsic factors that include thermodynamic and kinetic constraints, as well
as microstructural factors that may override the others. These factors govern diagenetic processes, such as dissolution, compaction,
recrystallization, replacement, and sulfate–hydrocarbon redox-reactions. Processes such as cementation, dissolution, and dolomitization
require significant flow of groundwater driven by an externally imposed hydraulic gradient. Other processes, such as stylolitization
and thermochemical sulfate reduction, commonly take place without significant groundwater flow in hydrologically nearly or
completely stagnant systems that are geochemically "closed."
Two major effects of groundwater flow on mineral diagenesis are enhancement and reduction of porosity and permeability, although
groundwater flow can also leave these rock properties essentially unchanged. In extreme cases, an aquifer or hydrocarbon reservoir
rock can have highly enhanced porosity and permeability due to extensive mineral dissolution, or it can be plugged up due
to extensive mineral precipitation.
Received, April 1998 · Revised, July 1998 · Accepted, September 1998 相似文献
74.
Zusammenfassung Eine Kurvenvergleichsmethode zur Interpretation räumlicher Induktions-pfeilprofile wird unter der Voraussetzung entwickelt, dass die Verteilung der von den geomagnetischen Variationen im Erdinnern induzierten Ströme linear ist. Sie gründet sich auf die lineare Abhängigkeit der Länge des Induktionspfeils von der vertikalen Komponente des Biot-Savartschen Gesetzes. Die Frequenzabhängigkeit des Induktionspfeiles ermöglicht die Angabe eines für die Leitfähigkeitsstruktur charakteristischen Widerstandes und einer Induktivität. Wird zur Bestimmung von Induktionspfeilen das gesamte Horizontalfeld benutzt, so geht die Linearität der Beziehung zwischen Pfeillänge und Ortsfunktion verloren. Für eine Reihe von Strommodellen werden derartige Ortsfunktionenp
z
berechnet und diskutiert. Sie dienen als Beispiele von Musterkurven für die entwickelte Interpretationsmethode.
Mitteilung aus dem Geomagnetischen Institut der DAW, Potsdam, Nr. 212. 相似文献
Summary One curve-matching method is developed in order to interprete the geomagnetic induction arrow profiles when the distribution of telluric currents in the underground is assumed to be linear. It bases on the linear dependence of the lengths of the induction arrows from the vertical component of the Biot-Savarts Law, which is a function of the radius vector. This is valid when the inducing field has only a horizontal component and the induced horizontal field is zero. In case that the model approximates the current distribution one gets a resistivity and an inductivity from the dependence of frequency of the induction arrows. Some model curves concerning several current distributions are drawn and discussed.
Mitteilung aus dem Geomagnetischen Institut der DAW, Potsdam, Nr. 212. 相似文献
75.
Prof. Dr. Hans Ertel 《Pure and Applied Geophysics》1963,55(1):119-122
Resumen Como aplicación hidrodinámica de un problema más general, tratado al principio, demostraremos el siguiente teorema:El rotacional del campo de la variación unitaria del torbellino de las partículas que se mueven rotacionalmente en líquidos ideales y homogéneos puede representarse por medio de paréntesis deLagrange.
Zusammenfassung Als hydrodynamische Anwendung eines eingangs behandelten allgemeineren Problems wird folgender Satz bewiesen:Der Rotor des Feldes der individuellen Ableitung des Wirbelvektors der sich drehend bewegenden Partikel idealer und homogener inkompressibler Flüssigkeiten läßt sich mittels der Klammersymbole vonLagrange darstellen.相似文献
76.
Summary The compressional angle of isallo stress theory for the case of a cylindrical (circular and elliptic) and spherical subsurface inhomogeneity, assuming that the conjugate fracture surfaces are inclined at a Mohr angle of 30° toward the largest compression, has been calculated. The solution for a spherical and cylindrical inclusion in an infinite medium subject to a uniform stress field (at infinity) were taken as the basis for the stress analysis. The stress angle was then calculated for the mentioned types of inclusions. 相似文献
77.
Ocean Dynamics - Meeresoptische Messungen auf der Forschungsplattform “Nordsee” haben gezeigt, daß dort während schwerer Stürme, hauptsächlich durch den Einfluß... 相似文献
78.
Rainfall-induced landslide event of May 2010 in the eastern part of the Czech Republic 总被引:1,自引:2,他引:1
Tom��? P��nek Rudolf Br��zdil Jan Klime? Veronika Smolkov�� Jan Hradecky Pavel Zahradn��?ek 《Landslides》2011,8(4):507-516
More than 150 landslides originated in the eastern part of the Czech Republic (region of the Flysch Outer Western Carpathians—hereinafter,
OWC) due to soil saturation caused by antecedent precipitation and long lasting and intensive rainfalls on 16–18 May 2010
(>300 mm as measured by some stations). As a consequence, a multitude of small failures originated 88% of which was smaller
than 104 m2. Most landslides are characterised as shallow (<10 m) or middle–deep (10–30 m) incipient (rather short travel) landslides,
debris slides and soil slips spatially clustered to a geological domain underlain by rather weak thin-bedded flysch and unconsolidated
Quaternary deposits. An exception to this is represented by a kilometre-long rockslide (∼2–3 mil m3) affecting tectonically weakened and weathered claystone/mudstone-dominated flysch on the southern slope of Mt. Girová (the
Beskydy Mountains). The rockslide is one of the largest long runout landslides in the territory of the Czech Republic activated
over the past few decades as it reaches the dimensions of the largest documented Holocene long runout landslides in the Czech
part of the OWC. A majority of the May 2010 landslide events developed inside older (Holocene or historic) landslide terrains,
which points to their spatial persistency and recurrent nature. In spite of the fact that the May 2010 landslide event was
not as destructive as some previous landslide activisation in the OWC region (e.g. July 1997 event), it left many slope failures
at the initial stage of their potential future reactivation. 相似文献
79.
Hans J. Lippolt Rolf S. Wernicke Werner Boschmann 《Physics and Chemistry of Minerals》1993,20(6):415-418
In order to test the chronometer qualities of speculante for the (U + Th)/He dating method, 4He release experiments by stepwise heating of two specularites from the Rimbach mineralization locality in the southern Vosgues (France) have been carried out. The diffusion coefficients define linear Arrhenius plots within a temperature interval of 250 to 830 °C, which is suggestive of volume diffusion. Extrapolation of the diffusion behavior to 20° C yields diffusion coefficients (D20 values) smaller than 10?26 [cm2 s?1] for both hematites with activation energies at 116 [kJ/mole]. The results of our study suggest that specularite is a very helium retentive hematite variety which is capable of quantitatively retaining radiogenic helium over geologic periods of time. 相似文献
80.
In this paper it is argued that the re-establishment of a metropolitan government in the Greater Copenhagen Area in 2000 (Greater
Copenhagen Authority) is not to be seen as a return to the kind of regional, coordinative authority (Greater Copenhagen Council)
that was abolished in the Thatcherite climate of the 1980s. Throughout the 1980s and 1990s new forms of urban governance,
entrepreneurialism and a higher national priority to the capital region were introduced, which changed the conditions under
which the new metropolitan government is operating. This `contextualization' of the analysis of the two generations of metropolitan
government points to the fact that typologies of metropolitan government, such as the one put forward by Sharpe (1995), often
lacks analytical cogency.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献