Hydrodynamical simulations of the decay of high-speed molecular turbulence – II. Divergence from isothermality     

Georgi Pavlovski  Michael D. Smith  Mordecai-Mark Mac Low 《Monthly notices of the Royal Astronomical Society》2006,368(2):943-958

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Characteristics of normal fatty acids from sediments as a function of geologic-geochemical factors     

Iordanka Kovacheva  Georgi Kovachev 《Geochimica et cosmochimica acta》1985,49(1):299-305

Forty-nine samples from Mesozoic rocks of Northern Bulgaria and from recent marine muds of the Black Sea have been analyzed for fatty acids (FA), using extraction, treatment with ion exchange resin and gas chromatography. There is a higher concentration of normal (n) FA in the recent marine sediments, as well as in their bitumen extracts than in the rocks as a whole. There is twice as much n-FA in the rocks containing dispersed organic matter (DOM) formed mainly by benthonic organisms as compared to ancient sediments with planktonic DOM. The content of n-FA has decreased nine and five times, respectively in planktonic DOM in the sequence: limestones-marls-argillites and clayey siltstones, while the amount of organic carbon has risen four and two times. The n-FA are chiefly represented by C₁₆ and C₁₈ and in the recent sediments also by C₂₂ molecules. However when the level of maturity of DOM corresponds to the katagenetic degrees of MK₃ and MK₄, maximum is in n-FA with 19 and 20 carbon atoms. A gradual decrease in the amount of the n-FA with even-numbered carbon atoms was noted as maturity of the planktonic DOM increases from early diagenesis in recent marine sediments to the katagenetic degrees of MK₃ and MK₄ in ancient rocks. The ratios $\text{FA}\text{HC}$ and $\text{FA}\text{HC}\text{+ FA}$ have also decreased when the katagenetic maturity of DOM changes from PK₃ degree to MK₄ degree. These geochemical features may be used as an additional criterion in determining the principal phase of oil formation.  相似文献   

Georg von Neumayer (1826 bis 1909) und das 1. Internationale Polarjahr 1882/1883     

Johannes Georgi 《Ocean Dynamics》1964,17(6):249-272

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Gewässerkontaminationen durch Butonat infolge aviochemischer Applikation von Fekama AT 25 auf forstwirtschaftlichen Nutzflächen     

K. Grahl  W. W. v. Tümpling Georgi  W. Dedek  H. Goralczyk 《洁净——土壤、空气、水》1981,9(6):627-637

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Heating rate profiles in galaxy clusters     

Edward C. D. Pope  Georgi Pavlovski  Christian R. Kaiser  Hans Fangohr 《Monthly notices of the Royal Astronomical Society》2006,367(3):1121-1131

In recent years, evidence has accumulated suggesting that the gas in galaxy clusters is heated by non-gravitational processes. Here, we calculate the heating rates required to maintain a physically motivated mass flow rate, in a sample of seven galaxy clusters. We employ the spectroscopic mass deposition rates as an observational input along with temperature and density data for each cluster. On energetic grounds, we find that thermal conduction could provide the necessary heating for A2199, Perseus, A1795 and A478. However, the suppression factor of the classical Spitzer value is a different function of radius for each cluster. Based on the observations of plasma bubbles, we also calculate the duty cycles for each active galactic nucleus (AGN), in the absence of thermal conduction, which can provide the required energy input. With the exception of Hydra-A, it appears that each of the other AGNs in our sample requires duty cycles of roughly 10⁶–10⁷ yr to provide their steady-state heating requirements. If these duty cycles are unrealistic, this may imply that many galaxy clusters must be heated by very powerful Hydra-A type events interspersed between more frequent smaller scale outbursts. The suppression factors for the thermal conductivity required for combined heating by AGN and thermal conduction are generally acceptable. However, these suppression factors still require 'fine-tuning' of the thermal conductivity as a function of radius. As a consequence of this work, we present the AGN duty cycle as a cooling flow diagnostic.  相似文献   

Sorption and Chemical Reactions of PAHs with Dissolved Humic Substances and Related Model Polymers     

Frank‐Dieter Kopinke  Anett Georgi  Katrin Mackenzie 《洁净——土壤、空气、水》2001,28(7):385-399

Sorption coefficients measured for PAHs on dissolved humic substances by SPME and FQT were found to be inevitably different and method‐dependent – SPME provides activity‐based and FQT concentration‐based sorption coefficients. Poly(acrylic acid) esters as well‐defined model polymers were used in sorption experiments, leading to the conclusion that short aliphatic chains are more effective in binding PAHs than aromatic moieties. FQT was inappropriate to measure sorption coefficients for the interaction of pyrene with poly(acrylic acid) esters but the experiments revealed a characteristic shift in the fluorescence spectrum. Using pyrene as a probe for the molecular environment in the sorbed state, the observed spectral shift indicated a highly hydrophobic microenvironment. The empirical relationships between lg K_DOC and lg K_OW were generalized on the basis of a modified Flory‐Huggins concept. Introducing only one sorbent‐specific parameter, the solubility parameter δ_DOM, the calculation of sorption coefficients became possible for a wide range of HOCs using fundamental data readily available from the literature. Long‐term experiments showed that reactive PAHs (such as acenaphthylene and 9‐methylanthracene) are able to react with HAs under strictly abiotic and anoxic conditions, whereas less reactive PAHs (such as naphthalene and dihydroanthracene) do not form bound residues. The HA reveals two functions in the interaction, behaving as a reaction partner and as a protecting ligand.  相似文献   

Spatial distribution of earthquakes in aftershock zones of the Garm region, Soviet Central Asia   总被引：1，自引：0，他引：1  

Mariana Eneva  Michael W. Hamburger  Georgi A. Popandopulo 《Geophysical Journal International》1992,109(1):38-53

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Das neue Absolut-Pyrheliometer von Prof. K. Wegener     

Dr. J. Georgi 《Pure and Applied Geophysics》1951,20(1):77-84

Zusammenfassung Der neuartige pyrheliometrische Messvorgang nach Prof.K. Wegener wird analysiert. Bei ihm sind gewisse Fehlerquellen anderer Strahlungsmesser vermieden. Jedoch bestehen Bedenken, ob das neue Verfahren die kalorische Sonnenenergie inabsolutem Masse liefern kann.

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Summary The new pyrheliometric principle of Prof.K. Wegener has been analyzed. Although some disadvantages of existing radiation meters have been avoided, the measurement of the caloric intensity of solar radiation inabsolute units seems dubious.

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Stochastic heating of cooling flows     

Georgi Pavlovski  Edward C. D. Pope 《Monthly notices of the Royal Astronomical Society》2009,399(4):2195-2200

It is generally accepted that the heating of gas in clusters of galaxies by active galactic nuclei is a form of feedback. Feedback is required to ensure a long-term, sustainable balance between heating and cooling. This work investigates the impact of proportional stochastic feedback on the energy balance in the intracluster medium. Using a generalized analytical model for a cluster atmosphere, it is shown that an energy equilibrium can be reached exponentially quickly. Applying the tools of stochastic calculus, it is demonstrated that the result is robust with regard to the model parameters, even though they affect the amount of variability in the system.  相似文献   

Elektronenproduktion,Rekombination, Elektronendichte und Absorption in der ionosphärischenD-Region und ihre jahreszeitlichen Variationen     

Georgi T. Nestorov 《Pure and Applied Geophysics》1965,62(1):148-160

Zusammenfassung Es wird die Gleichung für die Elektronenproduktionq(z) abgeleitet, die die meteorologischen Elemente der Mesosphäre berücksichtigt. Nach Angaben über die mit Satelliten und Raketen gemessene Röntgenstrahlung mit 8 Å wird das Differentialspektrum des ionisierenden Energieflusses für eine mittlere Sonnenaktivität konstruiert. Auf dieser Grundlage und nach der bekannten Intensität der Strahlung Ly- sowie nach Angaben über dieElektronenproduktion der kosmischen Strahlung werden die Profileq _Rö(z),q _Ly-(z) undq _CR(z) für mittlere geographische Breiten und Standardatmosphäre entwickelt. Nach eingehender Analyse der vollständigen Gleichung für den effektiven Rekombinationskoeffizienten wird für die Verhältnisse in der tiefen Ionosphäre der Beitrag jeder einzelnen Komponente der Gleichung bestimmt. ist eine recht veränderliche Grösse, die von den aeronomischen und meteorologischen Verhältnissen und der Sonnenzenitdistanz abhängt. Aus den fürq(z) und (z) erhaltenen Angaben werden zwei ElektronendichteprofileN(z) für =30° und 75° erhalten. Das ProfilN(z) bei =30° wird mit dem gemittelten Profil einer umfangreichen Gruppe experimentell gefundener VerteilungenN(z) verglichen; das Profil bei =75° wird durch Messung der deviativen und nondeviativen Absorption für eine längere Zeitperiode überprüft. In beiden Fällen hat sich die Richtigkeit der theoretisch erhaltenen Profile bestätigt. Die jahreszeitlichen Variationen der nondeviativen Absorption in derD-Region sind ausschliesslich durch die Variationen der meteorologischen Parameter im Bereich der Mesopause bei konstantem Energiefluss der ionisierenden Strahlung bedingt.

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Summary An equation about the electron production is deduced in which the meteorological elements of the mesosphere are taken into account. The differential spectrum of the ionizing energy flux with 3 Å for average solar activity is constructed on evidence from rocket and satelitc measurements. The profilesq _Rö(z),q _Ly-(z) andq _CR(z) for mean geographical latitudes and standard atmosphere are plotted on that basis as well as on data fot the known intensity of the Ly- emission and the electron production of the cosmic rays. An exhaustive analysis is made of the full equation for the effective recombination coefficient and the contribution of all its components at lower ionosphere conditions is determined. is a rather variable quantity, dependent on the aeronomical and meteorological condition of the area under consideration, as well as on the solar zenith angle. Two profiles for the electron concentrationN(z) at =30° and 75° are drawn on the basis of data forq(z) and (z). The profileN(z) at =30° is compared with the averaged profile of a large group experimentally obtained distributionsN(z); the profile at =75° is checked by measurements of the deviative and nondeviative absorption taken for a lengthy period. Both checks are in good agreement with the theoretically obtained profiles. The seasonal variations of the nondeviative absorption in theD region could be completely explained with the variations of the meteorological parameters in the mesopause area at constant energy flux of the ionizing radiation.

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