Widespread evidence for heterogeneous accretion of the terrestrial planets and planetisimals

The abundance and relative proportion of highly siderophile elements (HSEs) in Earth’s mantle deviate from those predicted by low-pressure equilibrium partitioning between metal and silicate during formation of the core. For many elements, high-pressure equilibration in a deep molten silicate layer (or ‘magma ocean’) may account for this discrepancy [1], but some highly siderophile element abundances demand the late addition, a ‘late veneer’, of extraterrestrial material (i.e. heterogeneous accretion) after core formation was complete [2]. Siderophile elements in smaller asteroidal bodies will not be affected by high-pressure metal-silicate equilibration and so, with highly efficient core formation [3] and if a ‘late veneer’ is absent, significant differences in the proportions of HSEs can be anticipated. Here we present new HSE abundance and 187Os/188Os isotope data for basaltic meteorites, the HEDs (howardites, eucrites and diogenites thought to sample the asteroid 4 Vesta), anomalous eucrites (considered to be from distinct Vesta-like parent bodies) angrites and aubrites (from unidentified parent bodies) and SNCs (thought to be from Mars). Our data, taken with those for lunar rocks [4], demonstrate that these igneous meteorites all formed from mantle sources that possessed chondritic (i.e. primitive solar system) elemental and isotope compositions, indicating that late accretion is not unique to Earth, but is a common feature of differentiated planets and asteroidal bodies. Variations in the total HSE abundance suggest that the proportion of ‘late veneer’ added is a simple consequence of the size of each body (cross-section and/or gravitational-attraction), and may account for the volatile element budget, and the oxidationstate of Earth, Mars, the Moon and Vesta

The impact of procurement method on costs of procurement

Collaborative working methods offer the hope of reduced waste, lower tendering costs and improved outputs. The costs of tendering may be influenced by the introduction of different working methods. Transaction cost economics appears to offer an analytical framework for studying the costs of tendering, but it is more to do with providing explanations at the institutional/industry level, not at the level of individual projects. Surveys and interviews were carried out with small samples in UK. The data show that that while tendering costs are not necessarily higher in collaborative working arrangements, there is no correlation between costs of tendering and the way the work is organized. Practitioners perceive that the benefits of working in collaborative procurement routes far outweigh the costs. Tendering practices can be improved to avoid waste, and the suggested improvements include restricting selective tendering lists to 23 bidders, letting bidders know who they are competing with, reimbursing tendering costs for aborted projects and ensuring that timely and comprehensive information is provided to bidders

Generation of internal stress and its effects

Internal stresses may be generated continually in many polycrystalline materials. Their existence is manifested by changes in crystal defect concentration and arrangement, by surface observations, by macroscopic shape changes and particularly by alteration of mechanical properties when external stresses are simultaneously imposed

Atmosphere breathing engines in astronautics

The contents of this note fall into two sections. Part I considers the possibilities and problems involved in using ramjets as a power source for one of the stages of a satellite launching vehicle or similar project. In comparing such a system with rocket powered vehicles, consideration is given to both performance and mass of the various systems. Various trajectories are considered. This work includes a reassessment of projects that have been suggested elsewhere. The second part examines the possibility of using forms of ramjet in the atmosphere of other planets. Because there is insufficient knowledge of these atmospheres, a study has been carried out to determine the approximate performance of a chemical ramjet in atmospheres of Methane, Ammonia, Hydrogen and Carbon Dioxide at Mach 3. The work in Part II is original, there being no previously reported papers on the subject known. These studies, which are necessarily based on several simplifying assumptions, indicate that applications for these engines may be expected to arise in astronautics, and that this is a fruitful field for further studies

The Resonance Peak in Sr2_2RuO4_4: Signature of Spin Triplet Pairing

We study the dynamical spin susceptibility, $\chi({\bf q}, \omega)$, in the normal and superconducting state of Sr$_2$RuO$_4$. In the normal state, we find a peak in the vicinity of ${\bf Q}_i\simeq (0.72\pi,0.72\pi)$ in agreement with recent inelastic neutron scattering (INS) experiments. We predict that for spin triplet pairing in the superconducting state a {\it resonance peak} appears in the out-of-plane component of $\chi$, but is absent in the in-plane component. In contrast, no resonance peak is expected for spin singlet pairing.Comment: 4 pages, 4 figures, final versio

Impact histories of Vesta and Vestoids inferred from howardites, eucrites and diogenites

The parent body of the howardites, eucrites and diogenites (HEDs) is thought to be asteroid (4) Vesta [1]. However, several eucrites have now been recognized, like NWA 011 and Ibitira, with major element compositions and mineralogy like normal eucrites but with different oxygen isotope compositions and minor element concentrations suggesting they are not from the same body [2, 3]. The discoveries of abnormal eucrites and V-type asteroids that are probably not from Vesta [see 4] raise the question whether the HEDs with normal oxygen isotopes are coming from Vesta [3]. To address this issue and understand more about the evolution of Vesta in preparation for the arrival of the Dawn spacecraft, we integrate fresh insights from Ar-Ar dating and oxygen isotope analyses of HEDs, radiometric dating of differentiated meteorites, as well as dynamical and astronomical studies of Vesta, the Vesta asteroid family (i.e., the Vestoids), and other V-type asteroids

The measurement of the winds near the ocean surface with a radiometer-scatterometer on Skylab

The author has identified the following significant results. There were a total of twenty-six passes in the ZLV mode that yielded useful data. Six were in the in-track noncontiguous mode; all others were in the cross-track noncontiguous mode. The wind speed and direction, as effectively determined in a neutral atmosphere at 19.5 m above the sea surface, were found for each cell scanned by S193. It is shown how the passive microwave measurements were used both to compute the attenuation of the radar beam and to determine those cells where the backscatter measurement was suspect. Given the direction of the wind from some independent source, with the typical accuracy of measurement by available meteorological methods, a backscatter measurement at a nadir angle of 50, 43, or 32 deg can be used to compute the speed of the wind averaged over the illuminated area

Seasonal abundance of small cladocerans in Lake Mangakaware, Waikato, New Zealand

The seasonal changes in the dynamics and life histories of the Cladocera in Lake Mangakaware, North Island, New Zealand, were studied over 19 months by sampling at weekly or 2-weekly intervals. Lake Mangakaware is a 13.3 ha polymictic lake with high nutrient status, low Secchi disc transparencies, and an unstable thermal regime. The four planktonic cladoceran species (Bosmina longirostris, B. meridionalis, Ceriodaphnia pulchella, and C. dubia) exhibited disjunct population maxima. Only B. longirostris was perennially present. All species exhibited low fecundities and low lipid content, indicating that food resources were limited and that competitive interactions and resistance to starvation were probably important in determining species success. Increases in body size in cooler seasons were unrelated to clutch size, giving further support for the view that available food was limited. These results are consistent with previous experimental findings that subtle differences in life history can determine seasonal success and the outcome of competition between similar species

Constraint violation stabilization using gradient feedback in constrained dynamics simulation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76126/1/AIAA-11410-903.pd

The Active Traveling Wave in the Cochlea

A sound stimulus entering the inner ear excites a deformation of the basilar membrane which travels along the cochlea towards the apex. It is well established that this wave-like disturbance is amplified by an active system. Recently, it has been proposed that the active system consists of a set of self-tuned critical oscillators which automatically operate at an oscillatory instability. Here, we show how the concepts of a traveling wave and of self-tuned critical oscillators can be combined to describe the nonlinear wave in the cochlea.Comment: 5 pages, 2 figure