Distribution of molecular weight in glyceride polymerizates or aggregates of them after contact with lunar grains     

S. K. Asunmaa  R. Haack 《Earth, Moon, and Planets》1977,16(3):325-334

Increase in the statistical average molecular weight up to 1200–1300 in different fractions of glycerides from 250–300 starting value was determined by gel permeation chromatography for fractions kept in thin layer contact with lunar grains for two years at 25 °C. An additional shoulder maximum was present atM = 2000. This highest distribution fraction mean value indicates degrees of polymerization of 8, if the 250–300 non-aggregated fraction is a monoglyceride and the 800–810 fraction its trimer. Assuming that the 800–810 refers to a triglyceride, only aDP = 3 is characteristic of theM = 2000. Spectrographic analysis was used for further elucidation of the distribution data; and reaction mechanisms are discussed. The main conclusion is that the lunar grain surfaces have exerted a catalytic action for production of the high molecular weight species. Information of this kind is of profound importance in evaluations of formation i.e. synthesis of more complicated and especially CH-radicals containing molecules that have been spectroscopically identified in interplanetary and interstellar space and extensively discussed in recent literature. If heterogeneous nucleation and growth on catalytically active solid surfaces is found to be one feasible reaction mechanism for syntheses in space, the reaction yields will not necessarily depend on collision encounter reactions exclusively. Since the latter have low reaction cross sections even in resonating filaments of space molecular and ionic aggregates, the solid substrate anchored reactions might make an essential contribution to the final yield. This mechanism will undoubtedly act also as a selector system so far that it via lattice isomorfism, epitaxy, and via a set of discrete surface energies will favor synthesis of preferred molecular bonds and aggregates and by this way guide the molecular ‘evolution’ along selected paths only.  相似文献   

Influence Of Advection Differencing Error Upon Large-Eddy Simulation Accuracy     

John W. Glendening  Tracy Haack 《Boundary-Layer Meteorology》2001,98(1):127-153

Accurate prediction of turbulent features by alarge-eddy simulation (LES) model requires accuratenumerical evaluation of the nonlinear advective terms. In the presence of a mean wind, use of second-order orfourth-order finite differencing produces large lossesof turbulent energy at high wavenumbers, an inaccuracyconsistent with idealized numerical properties ofthese schemes. The discrete differencing inaccuraciesalso affect the small wavenumber ``large eddy'structure and the horizontally-averaged turbulentquantities. With a high accuracy pseudospectraltechnique, this energy loss does not occur andspectral behaviour corresponds to filtered Kolmogorovtheory predictions out to the de-aliasing cutoffwavenumber. The inaccuracy of the finite differenceschemes is greatly ameliorated through a Galileantransformation of the advective term.  相似文献   

Oxidation of Elemental Mercury in the Atmosphere; Constraints Imposed by Global Scale Modelling   总被引：1，自引：0，他引：1  

Torbjörn Bergan  Henning Rodhe 《Journal of Atmospheric Chemistry》2001,40(2):191-212

We use the global mercury model published by Bergan et al. (1999) to evaluate the potential role of ozone and the hydroxyl radical as gas phase oxidants for the oxidation of elemental mercury in the atmosphere. The magnitude of natural and man-made mercury emissions are taken from recent literature estimates. We consider only two mercury reservoirs, elemental mercury, Hg⁰, and the more soluble divalent form, HgII. Wet and dry deposition of HgII is explicitly treated.Applying monthly mean fields of ozone for the oxidation of gas phase Hg⁰ and using the reaction rate by Hall (1995) yields a global transformation of Hg⁰ to HgII which is too slow to keep the simulated concentration of Hg⁰ near observed values. This shows that there must be additional important removal processes for Hg⁰ or that the reaction rate proposed by Hall (1995) is too slow. A simulation in which the oxidation rate was artificially increased, so that the global turn-over time of Hg⁰ is one year and the simulated average concentration of Hg⁰ realistic, produces latitudinal and seasonal variations in Hg⁰ that do not support the hypothesis that gas phase reaction with O₃ is the major oxidation process for Hg⁰.Recent studies indicate that OH may be an important gas phase oxidant for Hg⁰ (Sommar et al., 2001). Using OH as the sole oxidantand applying the oxidation rate by Sommar et al., we calculate aconcentration of Hg⁰ well below (about a factor of three) the observations. By prescribing a slower rate, corresponding to a turn-over time of Hg⁰ of one year, we calculate concentrations of both Hg⁰ in surface air and HgII in precipitation which correspond reasonably well, both in magnitude and temporal variation, with seasonal observations in Europe and North America. This result supports the suggestion that the oxidation by OH is an important pathway for the removal of Hg⁰. In view of the uncertainties associated with our calculations, this conclusion should still be regarded as tentative.  相似文献   

Isotopic composition of lead in moss and soil of the European Arctic     

U Haack  B Kienholz  J Schneider 《Geochimica et cosmochimica acta》2004,68(12):2613-2622

Moss, O and C horizons of podzols, mainly forming complementary sample triplets, as well as filter residues of molten snow from northern Norway, northern Finland and NW Russia have been analyzed by TIMS for their Pb isotopic composition in order to study the impacts of local geogenic/anthropogenic sources and long range atmospheric transport on the Pb balance in the European Arctic. Samples were taken along two N-S transects covering an area of ∼188.000 km², including both pristine environments in the W and certain regions towards the E severely contaminated by heavy metal emissions originating from large nickel smelters and processing plants in NW Russia.The lead in moss and O horizon samples clearly reflects atmospheric deposition, as it displays overall uniform isotope ratios and is decoupled from the geogenic background, i.e. the underlying mineral soils in the C horizon. Moss and O horizon samples from the eastern N-S transect are isotopically indistinguishable from those taken along the western transect but their Pb concentrations tend to be ∼2 times higher. This points to considerable contamination originating from the nearby Russian industrial and urban centers. However, isotopic signals of emissions from individual industrial point sources cannot be unambiguously identified because they lack characteristic isotope signatures. Pb derived from gasoline additives is swamped by Pb from other sources and can also be excluded as a major contributor to the environmental Pb in the European Arctic.Overall, the Pb isotopic signatures of moss and O horizon overlap values recorded in atmospheric lead all over central and southern Europe, more than 2000 km south of the study area. This may be taken as indicating continent-wide mixing of Pb derived from similar sources in the atmosphere or as reflecting economic globalization, or both. O horizon samples, which accumulate lead over 20-30 yr, conform to a distinct Pb isotope reference line in ²⁰⁷Pb/²⁰⁶Pb vs. ²⁰⁸Pb/²⁰⁶Pb space (“European Standard Pollution,” ESP) defined by atmospheric Pb considered to be representative for the technical civilization in Europe. Conversely, the Arctic moss samples with a lifetime of <3 yr display a deviating linear trend reflecting a recent change of atmospheric input towards significantly more radiogenic Pb derived from Mississippi Valley-type ores in the U.S., fully compatible with signatures found in epiphytic lichens from Canada, but also in Pb from urban waste incinerators in central Europe. Considering the elevated Pb concentrations in moss collected along the eastern N-S transect, this congruence indicates that the Pb in moss of the European Arctic most probably originates from the nearby Russian centers of urbanization and not from transatlantic transport. We therefore suspect imported industrial goods and their subsequent attrition to be a more plausible explanation for the appearance of MVT lead in Europe.  相似文献   

Spurenelemente in Biotiten aus Graniten und Gneisen     

Udo K. Haack 《Contributions to Mineralogy and Petrology》1969,22(2):83-126

91 biotites (53 from granites, 35 from highly metamorphic gneisses, 3 from redwitzites) were separated and analyzed for Fe, Mn, Zn, Cl, Sn, Ni, Co, Or, Cu, V, Mo, Pb. Biotites from gneisses contain much more Ni, Co, Cr, V but less Fe, Mn, Zn than those from granites. However, the distinction between biotites from gneisses and from granites on the basis of these elements is not certain. If a gneiss undergoes anatexis, the contents of Ni, Co, Cr, V, Zn and Sn of the preexistent biotite fractionate: Zn, Sn and Pe enter the anatectic melt readily while Ni, Co, Cr and V concentrate in the remaining matter (restite). Ni, Co, Cr and V are strongly positively correlated with one another but negatively with Fe and Zn, the latter being positively correlated with Pe. The chemical composition of biotites from granites depends not only on a potential degree of secondary decomposition into chlorite and muscovite but much more on the percentage of biotite in the rock: The more biotite, the higher the content of Ni, Co, Cr, V and the lower Fe, Zn and Sn in the biotite. Thus, it is possible to distinguish between normal and abnormal concentrations of an element in a biotite and in a rock. This might be useful in geochemical prospecting. Abnormal high concentrations of Sn and Zn were found in biotites from some granites which are connected with mineralizations of these elements. It is impossible hitherto to gain informations about the history and the parental material of a granitic magma from the minor elements in the rock or the biotite because their concentrations depend on how much biotite could be incorporated by the melt. The distribution coefficient of Cl between the lattice of 4 biotites and their fluid inclusions was determined to be 0,08.  相似文献   

THE NEED FOR PROFESSIONALISM AND ITS ATTRIBUTES IN HYDROGEOLOGY     

Roger J. Henning 《Ground water》1978,16(6):451-452

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The stability of fission tracks in epidote and vesuvianite     

Udo Haack 《Earth and Planetary Science Letters》1976,30(1):129-134

The stability of fission tracks in epidote and vesuvianite (idiocrase) was studied at different temperatures for several periods of time. The tracks in epidote are almost as heat-resistant as those in garnet; in vesuvianite they are much less stable. These results are in line with the rule that tracks in minerals with high lattice energies need higher activation energies to fade than in minerals with low lattice energies.  相似文献   

Klimatologische Wasserbilanz von Nordamerika     

Dr. Ingrid Henning  Dr. D. Henning 《Theoretical and Applied Climatology》1977,25(1):51-66

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Rb/Sr ages of granitic rocks along the middle reaches of the Omaruru River and the timing of orogenetic events in the Damara Belt (Namibia)     

U. Haack  E. Gohn  J. A. Klein 《Contributions to Mineralogy and Petrology》1980,74(4):349-360

Six new Rb/Sr whole rock age determinations from the central zone of the Damara Orogenic Belt, in combination with a structural analysis of the planar frabics in granitic rocks to establish the age of granite deformation in a relative time-scale, made it possible to determine an approximate absolute age for three phases of deformation. A minimal age for F₁ is 553 ±22 MA, F₂ took place shortly after 514±22 MA and F₃ has an age of 459–479 MA. The F₂ age verges on the time of the peak in the metamorphic temperature curve.These and other data fit an interpretation based on the model of a single long-lasting (> 80 MA) thermal event throughout the central zone of the Damara Orogen, wherein the age of F₃ would coincide with cooling to 300° C and indicate uplifting of the mountain chain.  相似文献   

A new engineering-geological rock durability classification     

Henning J. Olivier 《Engineering Geology》1979,14(4):255-279

The construction of the 5.3-m diameter, 82-km long Orange—Fish Tunnel in the Republic of South Africa, in sensibly horizontal beds of mudrocks, siltstones and sandstones of the Karoo Supergroup (Upper Carboniferous to Triassic age), revealed the paramount importance of rock durability. The presence of non-durable rock types was found to be one of the causes of the rock distress problems encountered in some tunnel sections during construction.

Geomechanical tests conducted on representative samples of potentially difficult rock types from the Orange—Fish Tunnel, indicated important limitations of international rock material classifications, such as the Deere—Miller Modulus—Strength and the Deere—Gamble Durability—Plasticity systems. The inadequacy of these classifications in the case of the Karoo sedimentary rocks, underlined the need for a new rock durability classification which could be used for the timely indication of the presence of non-durable rock material sections at tunnel level.

An account is given of the lithology, mineralogy and the postulated weathering mechanics of the Karoo rocks encountered, as well as the application of these parameters to the numerical methods used for the quantitative assessment of rock durability. It is considered that a reliable appraisal of this time-dependent parameter can be provided by the measurement of the strength and free swelling properties of the intact rock material.

A new rock durability classification, styled the Geodurability Classification, is discussed. This empirical system appears to be practical and simple as it depends on the minimum number of index rock properties, which can be measured fairly rapidly in a field laboratory by means of simple test apparatus and semi-skilled labour. It is based on different ranges of ratios of the uniaxial compressive strength, σ_c, and the “Duncan” free swelling coefficient, ε_D, as index parameters. The intact rock material is classified according to a rating system which varies from “excellent” (Class A) to “very poor” (Class F).

The extensive use of the Geodurability Classification indicated such a system to be particularly relevant to compacted and weakly cemented rocks, where the tendency of the rock material to deteriorate with time (and not the presence of rock discontinuities such as joints and bedding planes) dominates the time-dependent behaviour of tunnel rock masses.  相似文献