Band 35, Heft 2

We report I-Xe ages and other relevant xenon data for seven ordinary chondrites from H and L-groups of petrologic types 4-6, which were selected on the basis of minimum weathering and shock effects. Nevertheless, no chronological order with respect to the I-Xe ages exists among the different petrologic types. We demonstrate, however, that the degree to which the 1-Xe record is preserved in these chondrites, but not necessarily the age, is dependent on the thermal metamorphic history. In order to explain the lack of chronological order among the chondrites, spatiotemporal variations in the condensation-accretion process or inhomogeneities in the isotopic composition of iodine in the solar nebula is required.

The Oklo natural nuclear reactors have been studied mainly by isotopic and chemical analyses of uranium and fission products. Interpretation of these analyses allows parameters which characterize these reactions (flux, fluence,...), and also the age and duration of the nuclear reactions to be evaluated. The mechanisms and extent of fission-product migration can also be discussed. The behaviour of various elements formed in the Oklo uraninite and in oxyde fuels of pressurized water reactors is compared and found to be similar. Therefore, experience gained from the study of the Oklo phenomenon can provide valuable information on the long-term storage of radioactive wastes in geological media.

We describe three lithic fragments from the Lancé carbonaceous chondrite which apparently are of igneous origin and of basaltic parentage. They consist of large enstatite grains (pheno-crysts ?) which poikilitically include some olivine and abundant Fe-Ni metal and Fe sulfide blebs. These enstatites are set into a matrix of partly ophitic and partly porphyritic plagioclase (~ an71) and interstitial clinopyroxene and clinopyroxene plus plagioclase intergrowths. Mineral compositions are highly variable and reflect a complex genesis. Olivine compositions range from fo5 to fo60 and sometimes exhibit compositional zoning. Enstatites are mostly of en 98 com-position with some Fe-enrichment towards grain surfaces and cracks. Plagioclases have about an71 but mostly are altered to nonstoichiometric high-alkali compositions (with original Al/Si ratios corresponding to ~ an 70) or are partly replaced by K-free nepheline. Generally two clinopyroxenes are present within the plagiophyric portions of the fragments: One low Fe/Mg augite (~ en53 wo44) rich in Ti, Al, Cr, and Mn (Fe/Mn ≦ 2) and a ferrosalite (~ en15 wo47) poor in Ti, Cr, and Mn (Fe/Mn ~ 100). One fragment also contains spinel (hercynite) which apparently is xenocrystic in nature. Our investigation indicates: (1) The fragments are of igneous origin. (2) The original melt was of basaltic composition, crystallizing the primary mineral association ol + en + plag + low-Fe augite. (3) During crystallization the melt suffered strong reduction which led to segregation of Fe-Ni droplets from the melt and which continuously lowered the Fe/Mn ratio of successively crystallizing silicates from nearly chondritic (~ 100) to 0.6. (4) Probably after incorporation into the Lancé breccia the fragments suffered to different degrees metasomatic alterations which were caused by the addition of Na, K, and Fe to the system. The origin of the pre-Lancé basaltic melt cannot yet be established.

We report data for volatile/mobile Ag, As. Au, Bi, Cd, Co, Cs, Cu, Ga, In, Rb, Sb, Se, Te, TI and Zn in exterior and/or interior samples of four Antarctic meteorites from the Allan Hills (ALH) : A77005 (unique achondrite) ; A77257 (ureilite) ; A77278 (L3) ; A77299 (113). Exterior samples reflect contamination and/or leaching by weathering but trace element (ppm-ppt) contents in interior samples seem reasonable for representatives of these rare meteoritic types. The A77005 achondrite seems related to shergottites; other samples extend compositional ranges previously known for their groups or types. With suitable precautions, Antarctic meteorite finds yield trace element data as reliable as those obtained from previously - known falls.

Two impact melt samples from the Lappajärvi crater (Scandinavia) are highly enriched in siderophile elements, such as Ir, Re, and Os. This indicates the presence of a meteoritic component. The simultaneous enrichments of Ni, Co, Cr, and Se suggest a chondritic projectile. Because of the relatively large indigenous contributions to Ni, Co, and Cr, it is not possible to distinguish between a normal and a carbonaceous chondrite. The high concentrations of relatively volatile elements could point towards a volatile-rich projectile. The two melt samples have high Re/Ir ratios compared to chondritic ratios. Enrichment of Re relative to Ir is very unusual in terrestrial impact melts. Loss of Re, because of volatilisation under oxidizing conditions or by weathering is frequently observed. The high Re/Ir ratios and the high abundances of relatively volatile elements either indicate the presence of a volatile rich phase or they characterize a type of meteorite, which has not been sampled. Some lunar highland rocks have a pattern of meteoritic elements rather similar to that observed for the Lappajärvi meteorite. The Lappajärvi crater is, after Rocheehouart, the second European crater where a significant amount of meteoritic component has been found. A melt sample from the Lake St. Martin crater (Manitoba), did not show any enrichment in meteoritic elements.

It is shown that howardites fit extraordinary well into a binary mixing diagram for both their major and trace element compositions. Eucrites and diogenites would be suitable endmembers. In the mixing diagram computed from the elemental compositions of howardites, we find at a certain position a composition with very special features. This composition designated PR* contains all refractory incompatible elements in almost C 1, i.e. primitive, abundances. If 43% olivine is added to PR* in order to match the C 1 value for the Mg/Si ratio, a composition is obtained which has almost exact C 1 abundance values for all lithophile elements of non-volatile character. Because of its probable genetic relation we have used an olivine composition equal to that of pallasites. An eucrite parent body (EPB) with eucrites, diogenites and pallasites as the major building blocks has been previously suggested by various authors. The bulk composition of the EPB, resulting from our computations is found to be almost chondritic, but with a considerable depletion of volatile and moderately volatile elements. A comparison of the bulk composition of the EPB with that of Earth and Moon reveals a number of remarkable differences. Thus, the similarity of the composition of the silicate phases of Earth and Moon becomes even more remarkable and must be taken as strong indication for the genetic relationship of Earth and Moon.

Human immunoglobulin (IgG), bovine fibrinogen and bovine serum albumin were irradiated at room temperature with short pulses (50 ns to 2 μs) of 16 MeV electrons in 0.2 M NaClO 4 solution containing phosphate buffer (pH 7.5). In the presence of N 2 O the intensity of light (LSI) scattered by the protein solutions increased after the pulse indicating aggregation. The latter process originates from the attack of protein molecules by OH radicals (aggregation is impeded by t-butanol and augmented by N 2 O). Upon plotting the relative increase of LSI vs. log time (after the pulse) sigmoidally shaped curves were obtained. From these findings and results of optical absorption measurements the following is inferred: Aggregation occurs as a consequence of chemical alterations of the protein molecules induced by the attack by OH radicals. The transient species formed during and a few pis after the pulse are reacting within a period of several ms. At the end of this period the formation of aggregates starts. It is concluded that the primary radiation chemical process consists (among others) in the generation of nuclcation sites. The latter subsequently initiate aggregation processes.

Tetrahedrally coordinated copper(I) complexes CuL 4 X have been synthesized, L being P(OR) 3 , PR 3 or P(R) n (OR) 3-n , and X being a non-coordinating anion such as perchlorate or tetrafluoroborate. Depending on the nature of the bound phosphorus ligand the Cu(I) complexes give well resolved 63 Cu NMR spectra including a quintet signal due to spin-spin coupling between 63 Cu and 31 P. The 63 Cu NMR spectra have been analyzed with reference to the chemical shift δ, the shielding constant σ* (given on an absolute atomic scale), the linewidth ⊿v, and the coupling constant J( 63 Cu- 31 P). Generally, the relative magnitude of these NMR parameters are in satisfactory agreement with results reported for isoelectronic Ni(O) complexes with the phosphorus ligands mentioned above. Furthermore, the NMR properties of the Cu(I) compounds are discussed in terms of σ-donor or π-acceptor capacities of the ligands coordinated, and stereochemical properties of the complexes.

NMR investigations of 17 O, 33 S, 95 Mo, and 97 Mo have been used to elucidate the existence and the behaviour of the oxothiomolybdate species, MoO 4-n Sn 2- (n = 0, 1, 2, 3, 4) in aqueous solution. Very large chemical shifts and surprisingly narrow lines have been found for these nuclei in the different species.

The frequency-wave vector dispersion relations, the frequency spectrum, the Debye temperature, the temperature dependence of the Debye-Waller factor and the mean square displacements of the atoms molybdenum and chromium, the metals for which long range forces are also important, have been computed on the basis of the extended improved Fielek model for BCC transition metals. The model considers, for the first time the d shell-d shell central interactions upto next-nearest-neighbours. The calculated results show a satisfactory agreement with the available experimental data.

Mixed CT-crystals of composition anthracene c phenanthrene 1-c -tetracyanobenzene (Anth c Phen 1-c -TCNB, 0 ≦ c ≦ 1) have been investigated using ESR, optical and Raman spectroscopy. The data yield information on structural features and exciton transport as well as on the interrelation between these properties. With respect to their structural properties the mixed crystals can be prepared into two classes: orientations and lacking molecular motion as well as a phase transitions. b) Crystals with excess anthracene (c < 0.5) are comparable to Anth-TCNB: they also undergo a first order phase transition though at a lower transitions temperature T t (T t = 155 K for c = 0.75, whereas T t = 206 K for c = 1). Mini-triplet-excitons confined to the anthracene moiety were found. Their diffusion takes place quasi-onedimensionally and independently of temperature, i.e. especially without being affected by the phase transition. This result holds for the fast component of the diffusion tensor as well as for the slow one.

The change of the prefactor exponent for restricted valence percolation in 3 and 4 dimensions is shown to occur between valences 2 and 3 as in 2 dimensions. For valence 2 the exponent is SAW-like and after the change it assumes the normal percolative value for each dimension.

The magnetic behaviour of the normal-temperature form of CsYbO 2 has been studied in the temperature range between 2.8 and 251.3 K. Besides at temperatures below about 12 K the magnetic data are well interpreted by means of a model in which the influence of the crystal field is theoretically described by the angular overlap model and the influence of magnetic interaction by the molecular field model. By this the transferability of the angular overlap parameters from one compound to another is tested. The energy values of the crystal-field levels of the 2 F 7/2 ground state are calculated.

A wave equation of a kind proposed by Pais in 1953 describes a particle with an infinite sequence of quantum states, which belong to the symmetrical representations (λ, 0) of the group SU 3. Particles composed of such single ones are connected with the whole set of representations (λ, μ) of SU 3. The wave equation is compatible with an exclusion principle. Assuming that only particles with zero triality occur, all quarks and quarklike particles are excluded. Neither coulours, nor bags are needed, as we do not need repulsive forces to exclude Li-atoms with symmetrical wave functions.

Electrophilic substitution in aromatic substrates by iodine monochloride is about 10 5 times faster than by iodine in potassium iodide. This is due to the permanent dipole in the iodine monochloride, with iodine as the positive end, which greatly facilitates electrophilic attack.