2,3-Dimethylbiphenyl: Kinetics of its cyclisation reaction and effects of maturation upon its relative concentration in sediments

The rate constants of the cyclisation reaction of 2,3-dimethylbiphenyl to give 1-methylfluorene under non-catalytic conditions have been obtained at five temperatures between 460 and 500°C. The activation energy, activation entropy and frequency factor for the reaction have been determined from the experimental data. These kinetic parameters were then used to calculate the temperature ranges where the reaction occurs under natural conditions in sedimentary sequences which have experienced different heating rates. The coincidence of the measured and calculated values has been taken as evidence that the cyclisation reaction occurs in sediments under non-catalytic conditions.     

IGU Commission on Geographic Information Systems

The International Geographical Union Reports

IGU Commission on Geographic Information SystemsGoegraphic information systems in higher education — A workshop — Columbus, Ohio, June 10–11, 1989     

Magnetic field at the core boundary in the nearly symmetric hydromagnetic dynamo z

Summary The behaviour of the poloidal and toroidal magnetic field at the core-mantle boundary is analysed in more detail, assuming that the conductive layer in the lowest mantle is thin. We can conclude that, in the case of the Z-model of the nearly symmetric hydromagnetic dynamo, the poloidal field may be considered potential everywhere in the mantle and that the azimuthal field depends on the geostrophic azimuthal velocity in the same manner as derived in[1] and[3].

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aau ¶rt;-amu n¶rt;nuu m n¶rt; amuu aauum n¶rt;u nu¶rt;a u mu¶rt;a n. am ¶rt;, m Z-¶rt;u nmu umuu¶rt;aum ¶rt;ua aum nu¶rt;a n umam nmua ¶rt; amuu a n¶rt;u . ¶rt;m¶rt;am na [1] u [3] auum auma aum n m auma mu.

     

A Waste Treatment/Disposal Site Evaluation Process for Areas Underlain by Carbonate Aquifers

Fractured carbonate or karst aquifers are highly susceptible to contamination. In Minnesota, the areas underlain by karst aquifers are often characterized by thin soil cover, poorly cased wells and/or collapse features. When coupled with improper land use decisions these aquifers have become extensively contaminated.
Evaluation of existing or potentially contaminated sites has required development of unique site evaluation techniques or combinations of techniques. Shallow geophysics have been used successfully to determine subsurface karst features, pinpoint locations for additional investigations and evaluate pump-test data. Soil texture, density and relative moisture content have been closely examined and criteria established to evaluate subsurface erosion susceptibility. Percent rock core recovery, mechanical response of drilling and drilling fluid loss have been used to characterize the secondary porosity and potential contamination susceptibility of the carbonate rock. Dye tracing via surface sinks and well injection have determined primary flow paths and have been useful in estimating flow times.
These techniques used solely or in conjunction have been very useful in evaluating contamination existing in the aquifers and as a predictive tool to evaluate the proposed land uses impacts.     

Heating rate effects on aromatic maturity indicators

Aromatic maturity indicators based upon dimethylnaphthalenes, trimethylnaphthalenes and methylphenanthrenes have been determined for two sedimentary sequences from northwest Western Australia. The rate of change of these indicators with depth has been modelled using a kinetic expression which accounts for the effects of continuously varying time and temperature. Activation energies and entropies of activation have been measured. Maturity indicators with similar and with very different kinetic parameters have been used to construct plots to illustrate their behaviours under a variety of thermal regimes. Maturity indicators with similar activation energies behave almost identically over a wide range of heating rates while those with substantial differences display more diverse behaviour. The former may be used to relate kerogen-based maturity indicators with those determined from crude oils, whereas the latter can provide information about the maximum palaeotemperatures and heating rates of sedimentary hydrocarbons. It was also observed that the kinetic parameters for particular aromatic maturity indicators differed between the two sedimentary sequences, suggesting that source and mineral matrix effects can influence their behaviour.     

Acid catalysis of alkyl hydrogen exchange and configurational isomerisation reactions: acyclic isoprenoid acids

Acid-catalysed alkyl hydrogen exchange and configurational isomerisation has been studied in a series of acyclic isoprenoid acids when they were heated at 160°C in the presence of a montmorillonite. Hydrogen exchange occurred between the adsorbed water of the clay surface and the a position of the isoprenoid acids. In cases where this position was chiral, exchange was accompanied by configurational isomerisation. Configurational isomerisation occurred more slowly in experiments conducted without a clay matrix in the presence of water. These results have been rationalized in terms of a reaction mechanism involving protonation of the carbonyl oxygen causing enolization and consequent hydrogen exchange at the a position of the acids. This mechanism was used to account for the relatively fast rate of isomerisation of C-2 chiral centres in sedimentary acyclic isoprenoid acids during maturation.     

Identification of some diterpenoid hydrocarbons in petroleum

19-Norisopimarane and isopimarane have been synthesized from isopimara-9(11), 15-diene-3β, 19-diol. Analysis of the alkane fractions of an Australian crude oil by GC-MS showed the presence of nine diterpenoid hydrocarbons (diterpanes), of which one was bicyclic two were tricyclic and six were tetracyclic.19-Norisopimarane and isopimarane were identified by comparison of their mass spectra and GC retention times with those of the synthetic standards. ent-Beyerane, 16a(H)-phyllocladane, 16)β(H)-phyllocladane, ent-16α(H)-kaurane and labdane were also identified by comparison with authentic reference compounds. The remaining two compounds were tentatively identified as rimuane and as a 17-nortetracyclic diterpane on the basis of mass spectral evidence. The diterpanes are probably derived from conifer resins.     

Impact of carbonaceous aerosol emissions on regional climate change

The past and future evolution of atmospheric composition and climate has been simulated with a version of the Max Planck Institute Earth System Model (MPI-ESM). The system consists of the atmosphere, including a detailed representation of tropospheric aerosols, the land surface, and the ocean, including a model of the marine biogeochemistry which interacts with the atmosphere via the dust and sulfur cycles. In addition to the prescribed concentrations of carbon dioxide, ozone and other greenhouse gases, the model is driven by natural forcings (solar irradiance and volcanic aerosol), and by emissions of mineral dust, sea salt, sulfur, black carbon (BC) and particulate organic matter (POM). Transient climate simulations were performed for the twentieth century and extended into the twenty-first century, according to SRES scenario A1B, with two different assumptions on future emissions of carbonaceous aerosols (BC, POM). In the first experiment, BC and POM emissions decrease over Europe and China but increase at lower latitudes (central and South America, Africa, Middle East, India, Southeast Asia). In the second experiment, the BC and POM emissions are frozen at their levels of year 2000. According to these experiments the impact of projected changes in carbonaceaous aerosols on the global mean temperature is negligible, but significant changes are found at low latitudes. This includes a cooling of the surface, enhanced precipitation and runoff, and a wetter surface. These regional changes in surface climate are caused primarily by the atmospheric absorption of sunlight by increasing BC levels and, subsequently, by thermally driven circulations which favour the transport of moisture from the adjacent oceans. The vertical redistribution of solar energy is particularly large during the dry season in central Africa when the anomalous atmospheric heating of up to 60 W m⁻² and a corresponding decrease in surface solar radiation leads to a marked surface cooling, reduced evaporation and a higher level of soil moisture, which persists throughout the year and contributes to the enhancement of precipitation during the wet season.     

Analysis of landslide susceptibility in the Suusamyr region, Tien Shan: statistical and geotechnical approach

The Suusamyr region is located in the northern part of the Tien Shan Range in Central Asia. In 1992, this region was hit by the Ms = 7.3 Suusamyr earthquake triggering several large landslides along the Suusamyr Valley and on the southern slopes of the adjacent Suusamyr Range. One of these landslides had been investigated by geophysical and geotechnical methods in order to determine local trigger factors. The present paper focuses on the influence of geological and morphological factors upon landslide occurrence on a regional scale. The analysis is based on a digital data set including landslides triggered in 1992 and several older landslides as well as various types of digital elevation models (DEMs), ASTER image data, and geological and active fault maps. These data were combined to compute landslide susceptibility (LS) maps using statistical methods, Landslide Factor and Conditional Analyses (LFA, CA), as well as a geotechnical one, the Newmark's Method (NM). The landslide data set was also analyzed with respect to the size–frequency relationship. An erratum to this article can be found at