Smooth profiles from τ (p) and X(p) data

Summary. We reduce the problem of constructing a smooth, 1-D, monotoni-cally increasing velocity profile consistent with discrete, inexact τ ( p ) and X( p ) data to a quadratic programming problem with linear inequality constraints. For a finite-dimensional realization of the problem it is possible to find a smooth velocity profile consistent with the data whenever such a profile exists. We introduce an unusual functional measure of roughness equivalent to the second central moment or 'Variance' of the derivative of depth with respect to velocity for smooth profiles, and we prove that its minimal value is unique. In our experience, solutions minimizing this functional are very smooth in the sense of the two-norm of the second derivative and can be constructed inexpensively by solving one quadratic programming problem. Still smoother models (in more traditional measures) may be generated iteratively with additional quadratic programs. All the resulting models satisfy the τ ( p ) and X( p ) data and reproduce travel-time data remarkably well, although sometimes τ ( p ) data alone are insufficient to ensure arrivals at large X; then an X( p ) datum must be included.     

The Changing Incidence of Extremes in Worldwide and Central England Temperatures to the End of the Twentieth Century

Annual and seasonal gridded ocean surface temperature anomalies show an increase in warm extremes and a decrease in cold extremes since the late 19th century attributable entirely to the overall warming trend. Over land, however, a reduction in the total incidence of extremes may reflect improved instrumental exposures. Our estimates of extremes are made by deriving percentiles from fits of anomalies on 5° latitude ×5° longitude resolution to modified 2-parameter gamma distributions. A non-parametric method is used to check the validity of the results. Fields of percentiles created using this technique can be used to map the distribution of unusual temperature anomalies across the globe on any time scale from a month to about a decade, from 1870 onwards. We apply a similar technique to assess changes in the incidence of extreme daily Central England temperature anomalies. The incidence of these extremes, relative to individual monthly average temperatures, has declined.     

Leaching of sodium from skeletal parts during fossilization

Sodium content of bone and dentine of modern Bison bison is more (0.68-0.83 wt. %) than that of the enamel (0.50-0.56 wt. %). In fossil bone and dentine the sodium content is much lower (0.15-0.41 wt.%) than in corresponding modern samples while there appears to be no significant difference between modern and fossil enamel in most instances. The lowered sodium content in fossil material appears to be attributable to diagenetic removal. The physical properties of the bone have a strong influence on the amount of sodium removed.     

Extragalactic cosmic rays and the galactic magnetic field

The origin and behavior of cosmic rays in the Galaxy depends crucially upon whether the galactic magnetic field has a closed topology, as does the field of Earth, or whether a major fraction of the lines of force connect into extragalactic space. If the latter, then cosmic rays could be of extragalactic origin, or they could be of galactic origin, detained in the Galaxy by the scattering offered by hydromagnetic waves, etc. If, on the other hand, the field is largely closed, then cosmic rays cannot be of extragalactic origin (at least below 10¹⁶ eV). They must be of galactic origin and escape because their collective pressure inflates the galactic field and they push their way out.This paper examines the structure of a galactic field that opens initially into intergalactic space and, with the inclusion of turbulent diffusion, finds no possibility for maintaining a significant magnetic connection with an extragalactic field. Unless some mechanism can be found, we are forced to the conclusion that the field is closed, that cosmic rays are of galactic origin, and that cosmic rays escape from the Galaxy only by pushing their way out.     

Solar-cycle dependence of galactic cosmic ray flux

The coronal green line intensity is inappropriate for correlation studies of galactic cosmic ray variations. Being a non-monotonic function of coronal temperature, the green line intensity is a good index of neither coronal temperature nor solar wind speed. A more appropriate measure of coronal activity is the intensity of the electron corona. Two-dimensional observations of the K-corona trace changes in coronal morphology during the solar cycle. An index based on four years of K-coronal measurements made in Hawaii shows that activity in the lower corona is not better correlated than sunspot number with long-term modulation. Correlation analysis defines the time lag of modulation much too poorly to permit its use in estimating the size of the heliosphere.     

The Fréchet derivative for the one-dimensional electromagnetic induction problem

Summary. From consideration of the higher order terms, it is shown that the magneto-telluric response is Fréchet differentiable with respect to conductivity; this result remains valid for discontinuous profiles, which is not so in the case of the corresponding free-oscdlation problem for the elastic earth. The remainder term in the Fréchet formula is shown to be O|δσ|² and a numerical estimate is made of the bounding constant for a restricted class of conductivity models.     

Probable causes of late twentieth century tropospheric temperature trends

We assess the most probable causes of late twentieth century (1960–1994) tropospheric temperature changes. Optimal detection techniques are used to compare observed spatio-temporal patterns of near-surface and tropospheric temperature change with results from experiments performed with two different versions of the Hadley Centre climate model. We detect anthropogenic forcings, particularly well-mixed greenhouse-gases, with a less certain sulfate aerosol cooling influence. More limited evidence exists for a detectable volcanic influence. Our principal results do not depend upon the choice of model. Both models, but particularly HadCM3, appear to overestimate the simulated climate response to greenhouse gases (especially at the surface) and volcanoes. This result may arise, at least in part, due to errors in the forcings (especially sulfate) and technical details of our approach, which differs from previous studies. We use corrected and uncorrected versions of the radiosonde record to assess sensitivity of our detection results to observational uncertainties. We find that previous corrections applied to the radiosonde temperature record are likely to have been sub-optimal in only taking into account temporal consistency. However, the choice of corrected or uncorrected version has no systematic effect upon our main conclusions. We show that both models are potentially internally consistent explanations of observed tropospheric temperatures.     

Manganese(III) binding to a pyoverdine siderophore produced by a manganese(II)-oxidizing bacterium

The possible roles of siderophores (high affinity chelators of iron(III)) in the biogeochemistry of manganese remain unknown. Here we investigate the interaction of Mn(III) with a pyoverdine-type siderophore (PVD_MnB1) produced by the model Mn(II)-oxidizing bacterium Pseudomonas putida strain MnB1. PVD_MnB1 confirmed typical pyoverdine behavior with respect to: (a) its absorption spectrum at 350-600 nm, both in the absence and presence of Fe(III), (b) the quenching of its fluorescence by Fe(III), (c) the formation of a 1:1 complex with Fe(III), and (d) the thermodynamic stability constant of its Fe(III) complex. The Mn(III) complex of PVD_MnB1 had a 1:1 Mn:pvd molar ratio, showed fluorescence quenching, and exhibited a light absorption spectrum (A_max = 408-410 nm) different from that of either PVD_MnB1-Fe(III) or uncomplexed PVD_MnB1. Mn(III) competed strongly with Fe(III) for binding by PVD_MnB1 in culture filtrates (pH 8, 4°C). Equilibration with citrate, a metal-binding ligand, did not detectably release Mn from its PVD_MnB1 complex at a citrate/PVD_MnB1 molar ratio of 830 (pH 8, 4°C), whereas pyrophosphate under the same conditions removed 55% of the Mn from its PVD_MnB1 complex. Most of the PVD_MnB1-complexed Mn was released by reaction with ascorbate, a reducing agent, or with EDTA, a ligand that is also oxidized by Mn(III). Data on the competition for binding to PVD_MnB1 by Fe(III) vs. Mn(III) were used to determine a thermodynamic stability constant (nominally at 4°C) for the neutral species MnHPVD_MnB1 (log K = 47.5 ± 0.5, infinite dilution reference state). This value was larger than that determined for FeHPVD_MnB1 (log K = 44.6 ± 0.5). This result has important implications for the metabolism, solubility, speciation, and redox cycling of manganese, as well as for the biologic uptake of iron.     

Crystal morphology and surface structures of orthorhombic MgSiO3 in the presence of divalent impurity ions

Many rheological and transport properties of rocks are determined by the grain boundary structures of their constituent minerals. These grain boundaries often also hold a high concentration of dopant ions. Here, as a first step towards modelling the transport and rheological behaviour of the lower mantle, we report the results of lattice static simulations on the surface structures of Fe²⁺ and Ca²⁺-doped orthorhombic MgSiO₃-perovskite. For all the surfaces we studied, the energies of the doped structures are lowered, sometimes by more than 1 J/m², with respect to the pure surfaces. From our calculated crystal morphologies, we predict that the grains become more tabular as the concentration of Fe²⁺ ions increases, while under equilibrium conditions the grains are cubic. By calculating the replacement energies of Mg²⁺ by Fe²⁺ and Ca²⁺ ions in the six outermost surface layers, we conclude that these divalent ions would tend to segregate onto the crystal surfaces. We suggest, therefore, that the grain boundary structure and rheology of MgSiO₃-perovskite dominated rocks will be strongly affected by the presence of minor elements in the lower mantle.