Nitrogen isotopes in the solar system

Measurements of the isotopic composition of nitrogen in the solar system are summarized. We show that the 30% change, during the last 3 to 4 billion years, of ${}^{15}\text{N}{}^{14}\text{N}$ in solar-wind-bearing lunar soils and breccias probably does not reflect changes in this ratio at the solar surface. Such changes, whether by spallation or thermonuclear reactions are ruled out by comparing the yields of ¹⁵N with those of other rare isotopes such as ⁹Be, ¹¹B, ³He or ¹³C, even if an arbitrary degree of solar mixing is introduced. Moreover, we calculate that the solar activity required for producing significant amounts of ¹⁵N by spallation at the solar surface should have resulted in a particle bombardment of the Moon of an intensity that would have produced amounts of spallation isotopes (e.g.¹⁵N, ²¹Ne, ³⁸Ar, ¹³¹Xe) several orders of magnitude in excess of what is actually found in the whole regolith.We argue that accretion of interstellar matter also does not work as a cause for a significant change of the photospheric ${}^{15}\text{N}{}^{14}\text{N}$ ratio. Evidence is presented that the mixing depth at the solar surface on a time scale of ?10⁹ years is (10^?2 ?10^?1) M_⊙ Mixing to this depth renders accretion of interstellar matter as a source of compositional changes at the solar surface inefficient, even if allowance is made for the expected large difference in the accretion rates of condensed and gaseous matter. A quantitative treatment of several alternatives of solar accretion leads to serious contradictions (e.g. with the low Ne abundances in planetary atmospheres or with the amounts of nitrogen that should have been directly accreted by the Moon), and we conclude that accretion during the main sequence life of the Sun is an unlikely source of changes in ${}^{15}\text{N}{}^{14}\text{N}$ at the solar surface.A ratio of ${}^{15}\text{N}{}^{14}\text{N}\text{= (4.0 ± 0.3) × 10}{}^{\mathrm{?3}}$ is our best estimate for average solar system material and for the Sun. We propose that a rare, very light nitrogen component (called LPN) is admixed in varying amounts to planetary matter. Undiluted LPN has not been found in meteorites or planetary atmospheres, but we show that the combined effects of LPN admixture and isotope fractionation can in principle account for the variability of ${}^{15}\text{N}{}^{14}\text{N}$ observed in the planetary system. Determination of the Jovian ${}^{15}\text{N}{}^{14}\text{N}$ ratio with an accuracy of ~10% would crucially test our interpretation of the nitrogen isotope observations.     

The radio frequency dielectric properties of the stratified UG1–UG2 geological unit in the Bushveld Complex

A new measurement technique enables the complex dielectric properties of the geological strata comprising the UG1–UG2 (Upper Group 1–Upper Group 2) unit of the Bushveld Complex in South Africa to be determined with unprecedented detail at radio frequencies (RF). Results of non-destructive laboratory measurements of representative diamond drill core samples from the UG1–UG2 unit are presented at 25 MHz. These data establish that the UG1 and UG2 chromitite layers are embedded in rock strata (norite, pyroxenite and anorthosite) which are translucent in the HF spectral band, whereas the chromitite layers themselves exhibit significant velocity contrast, making them good radar reflectors. The data presented here is useful for calibration of the radar system, and for predicting the range and resolution performance of borehole radars operating in both the hanging and footwalls of the economically important platiniferous UG2 reef.     

Determination of magnitude by use of seismographs recording ground velocity

Summary Two electromagnetic seismographs HSJ-I, which are coupled with short-period galvanometers, record the velocity of the ground motion in the range of periods from 0.3 to 20 s in the seismological station Moxa. In this way the magnitude of an earthquake can be calculated without respect to the period of the ground motion. The results of such a determination of magnitudes are compared with those reached in the usual manner from short and long-period seismographs recording the ground displacement.Publication No. 45 of the Institut für Geodynamik, 69 Jena (DDR), Burgweg 11, der Deutschen Akademie der Wissenschaften zu Berlin, Forschungsgemeinschaft. Presented at the IUGG-Assembly, Zurich 1967.     

Viscous damping of nonlinear magneto-acoustic waves

The motivation for the present work is discussed, and in Section 2 the nonlinear Burger's equation is derived for wave propagation in a compressible unstratified viscous fluid permeated by a magnetic field (initially constant), using the reductive perturbation method of Taniuti and Wei (1968). An analytic solution of the equation is given (after Sakai, 1972) and the angular behaviour is shown for certain parameters describing the nonlinearity and damping of the system, for both fast- and slow-mode disturbances.     

Use of physiological responses in Mytilus trossulus as integrative bioindicators of sewage pollution

Mussels, Mytilus trossulus (average shell length 43+/-0.8 mm), were sampled from a beach in Alaska that received untreated sewage for several years, a second beach adjacent to a secondary wastewater outfall, and two nearby reference beaches. Survival time in air, byssal thread production rate, and prevalence of trematode parasites were determined for each group. Tolerances to aerial exposure was significantly lower (P<0.05) at both sewage outfall sites than at the reference sites. Mussels exposed to untreated sewage produced fewer byssal threads and had a significantly higher prevalence of encysted trematodes than mussels from the other beaches, including the secondary wastewater site. Survival in air, byssal thread production, and trematode prevalence in mussels may be useful indicators in evaluating the longterm health of beaches exposed to sewage.