Multiple host shifts by the emerging honeybee parasite, Varroa jacobsoni.

Host shifts are a key mechanism of parasite evolution and responsible for the emergence of many economically important pathogens. Varroa destructor has been a major factor in global honeybee (Apis mellifera) declines since shifting hosts from the Asian honeybee (Apis cerana) > 50 years ago. Until recently, only two haplotypes of V. destructor (Korea and Japan) had successfully host shifted to A. mellifera. In 2008, the sister species V. jacobsoni was found for the first time parasitizing A. mellifera in Papua New Guinea (PNG). This recent host shift presents a serious threat to world apiculture but also provides the opportunity to examine host shifting in this system. We used 12 microsatellites to compare genetic variation of V. jacobsoni on A. mellifera in PNG with mites on A. cerana in both PNG and surrounding regions. We identified two distinct lineages of V. jacobsoni reproducing on A. mellifera in PNG. Our analysis indicated independent host shift events have occurred through small numbers of mites shifting from local A. cerana populations. Additional lineages were found in the neighbouring Papua and Solomon Islands that had partially host shifted to A. mellifera, that is producing immature offspring on drone brood only. These mites were likely in transition to full colonization of A. mellifera. Significant population structure between mites on the different hosts suggested host shifted V. jacobsoni populations may not still reproduce on A. cerana, although limited gene flow may exist. Our studies provide further insight into parasite host shift evolution and help characterize this new Varroa mite threat to A. mellifera worldwide.

A novel strain of sacbrood virus of interest to world apiculture.

This study has characterised a novel serotype of Sacbrood virus (SBV) infecting Apis mellifera in New Guinea that has emerged in the presence of the introduced European and Asian serotypes, which infect A. mellifera and Apis cerana, respectively. The New Guinea serotype appears to have evolved through mutation of the European serotype with no evidence of recombination between known strains, although recombination was detected in other SBV isolates from Asia. SBV was also confirmed for the first time causing disease in Apis dorsata (giant Asian honeybee) in Indonesia and found to be infected by the Asian serotype.

Projecting Climate Dependent Coastal Flood Risk With a Hybrid Statistical Dynamical Model.

Numerical models for tides, storm surge, and wave runup have demonstrated ability to accurately define spatially varying flood surfaces. However these models are typically too computationally expensive to dynamically simulate the full parameter space of future oceanographic, atmospheric, and hydrologic conditions that will constructively compound in the nearshore to cause both extreme event and nuisance flooding during the 21st century. A surrogate modeling framework of waves, winds, and tides is developed in this study to efficiently predict spatially varying nearshore and estuarine water levels contingent on any combination of offshore forcing conditions. The surrogate models are coupled with a time-dependent stochastic climate emulator that provides efficient downscaling for hypothetical iterations of offshore conditions. Together, the hybrid statistical-dynamical framework can assess present day and future coastal flood risk, including the chronological characteristics of individual flood and wave-induced dune overtopping events and their changes into the future. The framework is demonstrated at Naval Base Coronado in San Diego, CA, utilizing the regional Coastal Storm Modeling System (CoSMoS; composed of Delft3D and XBeach) as the dynamic simulator and Gaussian process regression as the surrogate modeling tool. Validation of the framework uses both in-situ tide gauge observations within San Diego Bay, and a nearshore cross-shore array deployment of pressure sensors in the open beach surf zone. The framework reveals the relative influence of large-scale climate variability on future coastal flood resilience metrics relevant to the management of an open coast artificial berm, as well as the stochastic nature of future total water levels.

Accelerated plate tectonics.

The concept of a stressed elastic lithospheric plate riding on a viscous asthenosphere is used to calculate the recurrence interval of great earthquakes at convergent plate boundaries, the separation of decoupling and lithospheric earthquakes, and the migration pattern of large earthquakes along an arc. It is proposed that plate motions accelerate after great decoupling earthquakes and that most of the observed plate motions occur during short periods of time, separated by periods of relative quiescence.

Earthquakes and the rotation of the Earth.

A correlation exists between long-term variations in the length of the day, Chandler wobble amplitudes, and global seismic activity. These variations may be partially due to climatic changes and ultimately to explosive volcanic activity.

Helium-3 from the mantle: primordial signal or cosmic dust?

Helium-3 in hotspot magmas has been used as unambiguous evidence for the existence of a primordial, undegassed reservoir deep in the Earth's mantle. However, a large amount of helium-3 is delivered to the Earth's surface by interplanetary dust particles (IDPs). Recycling of deep-sea sediments containing these particles to the mantle, and eventual incorporation in magma, can explain the high helium-3/helium-4 ratios of hotspot magmas. Basafts with high helium-3/helium-4 ratios may represent degassing of helium introduced by ancient (probably 1.5 to 2.0 billion years old) pelagic sediments rather than degassing of primordial lower mantle material brought to the surface in plumes. Influx of IDPs can also explain the neon and siderophile compositions of mantle samples.

Phase changes in the upper mantle.

The C-region of the upper mantle has two transition regions 75 to 90 kilometers thick. In western North America these start at depths of 365 kilometers and 620 kilometers and involve velocity increases of about 9 to 10 percent. The locations of these transition regions, their general shape, and their thicknesses are consistent with, first, the transformation of magnesium-rich olivine to a spinel structure and, then, a further collapse of a material having approximately the properties of the component oxides. The velocity increases associated with each transition region are slightly less than predicted for the appropriate phase change. This can be interpreted in terms of an increasing fayalite content with depth. The location of the transition regions and the seismic velocities in their vicinity supply new information regarding the composition and temperature of the upper mantle. The depths of the transition regions are consistent with temperatures near 1500 degrees C at 365 kilometers and 1900 degrees C at 620 kilometers.

Composition of the Earth.

New estimates of solar composition, compared to earlier measurements, are enriched in Fe and Ca relative to Mg, Al, and Si. The Fe/Si and Ca/Al atomic ratios are 30 to 40 percent higher than chondritic values. These changes necessitate a revision in the cosmic abundances and in the composition of the nebula from which the planets accreted (which have been based on chondritic values). These new values imply that the mantle could contain about 15 weight percent FeO and more CaMgSi(2)O(6) than has been supposed. Geophysical data are consistent with a dense, FeO-rich lower mantle and a CaMgSi(2)O(6) (diopside)-rich transition region. FeO contents of 13 to 18 weight percent appear to be typical of the mantles of bodies in the inner solar system. The oldest komatiites (high-temperature MgO-rich magmas) have a similar chemistry to the derived mantle. These results favor a chemically zoned mantle.

Earth's Viscosity.

Seismic methods are now being used to determine not only Earth's elastic properties, but also by how much it departs from a perfectlyelastic body. The seismic anelasticity (Q) varies by several orders of magnitude throughout the mantle, the main feature being an extremely dissipative zone in the upper mantle above 400 kilometers. Recent determinations of viscosity by McConnell show a similar trend. The two sets of data indicate that the ratio of viscosity to Q is roughly a constant, at least in the upper mantle of Earth. On the assumption that this relation is valid for the rest of Earth, viscosities are estimated in regions that are inaccessible for direct measurement. The implied presence of a low-viscosity zone in the upper mantle, overlying a more viscous, less deformable, lower mantle, reconciles viscosites calculated from the shape of Earth and from postglacial uplift. The mismatch of the deformational characteristics at various levels in Earth, coupled with the changing rate of rotation, may be pertinent to the rate of release of seismic energy as a function of depth.

The Earth as a planet: paradigms and paradoxes.

The independent growth of the various branches of the earth sciences in the past two decades has led to a divergence of geophysical, geochemical, geological, and planetological models for the composition and evolution of a terrestrial planet. Evidence for differentiation and volcanism on small planets and a magma ocean on the moon contrasts with hypotheses for a mostly primitive, still undifferentiated, and homogeneous terrestrial mantle. In comparison with the moon, the earth has an extraordinarily thin crust. The geoid, which should reflect convection in the mantle, is apparently unrelated to the current distribution of continents and oceanic ridges. If the earth is deformable, the whole mantle should wander relative to the axis of rotation, but the implications of this are seldom discussed. The proposal of a mantle rich in olivine violates expectations based on evidence from extraterrestrial sources. These and other paradoxes force a reexamination of some long-held assumptions.

Hotspots, basalts, and the evolution of the mantle.

The trace element concentration patterns of continental and ocean island basalts and of mid-ocean ridge basalts are complementary. The relative sizes of the source regions for these fundamentally different basalt types can be estimated from the trace element enrichment-depletion patterns. Their combined volume occupies most of the mantle above the 670 kilometer discontinuity. The source regions separated as a result of early mantle differentiation and crystal fractionation from the resulting melt. The mid-ocean ridge basalts source evolved from an eclogite cumulate that lost its late-stage enriched fluids at various times to the shallower mantle and continental crust. The mid-ocean ridge basalts source is rich in garnet and clinopyroxene, whereas the continental and ocean island basalt source is a garnet peridotite that has experienced secondary enrichment. These relationships are consistent with the evolution of a terrestrial magma ocean.

Plate tectonics and hotspots: the third dimension.

High-resolution seismic tomographic models of the upper mantle provide powerful new constraints on theories of plate tectonics and hotspots. Midocean ridges have extremely low seismic velocities to a depth of 100 kilometers. These low velocities imply partial melting. At greater depths, low-velocity and high-velocity anomalies record, respectively, previous positions of migrating ridges and trenches. Extensional, rifting, and hotspot regions have deep (> 200 kilometers) low-velocity anomalies. The upper mantle is characterized by vast domains of high temperature rather than small regions surrounding hotspots; the asthenosphere is not homogeneous or isothermal. Extensive magmatism requires a combination of hot upper mantle and suitable lithospheric conditions. High-velocity regions of the upper 200 kilometers of the mantle correlate with Archean cratons.

Earthquake Prediction: Variation of Seismic Velocities before the San Francisco Earthquake.

A large precursory change in seismic body-wave velocities occurred before the earthquake in San Fernando, California. The discovery that this change is mainly in the P-wave velocity clearly relates the effect to the phenomenon of dilatancy in fluid-filled rocks. This interpretation is supported by the time-volume relation obtained by combining the present data with the data from previous studies. The duration of the precursor period is proportional to the square of an effective fault dimension, which indicates that a diffusive or fluid-flow phenomenon controls the time interval between the initiation of dilatancy and the return to a fully saturated condition which is required for rupture.

The Earth as a seismic absorption band.

Attenuation of seismic waves indicates that the earth is not perfectly elastic. Dispersion accompanying absorption gives frequency-dependent "elastic" moduli, a fact that must be taken into account when inverting seismic data. Normal mode data are reinverted after correcting for absorption. The correction removes the discrepancy between body wave and free oscillation interpretations of earth structure.

Circular forms of DNA synthesized by Rous sarcoma virus in vitro.

Electron microscopic analysis of the DNA product synthesized by detergent-disrupted preparations of Rous sarcoma virus in vitro revealed the presence of several interesting molecular forms including covalently closed circular DNA. The identification of such circular DNA indicates that virions of retroviruses contain all the components necessary to facilitate the complete synthesis of mature forms of viral DNA and therefore provide a useful system to delineate the molecular mechanisms involved in their synthesis.

Trace element composition of the mount st. Helens plume: stratospheric samples from the 18 may eruption.

Atmospheric particulate material collected from the stratosphere in the plume of the 18 May 1980 eruption of the Mount St. Helens volcano was quite similar in composition to that of ash that fell to the ground in western Washington. However, there were small but significant differences in concentrations of some elements with altitude, indicating that the stratospheric material was primarily produced from fresh magma, not fragments of the mountain.

Forecasting southern california earthquakes.

Since 1978 and 1979, California has had a significantly higher frequency of moderate to large earthquakes than in the preceding 25 years. In the past such periods have also been associated with major destructive earthquakes, of magnitude 7 or greater, and the annual probability of occurrence of such an event is now 13 percent in California. The increase in seismicity is associated with a marked deviation in the pattern of strain accumulation, a correlation that is physically plausible. Although great earthquakes (magnitude greater than 7.5) are too infrequent to have clear associations with any pattern of seismicity that is now observed, the San Andreas fault in southern California has accumulated sufficient potential displacement since the last rupture in 1857 to generate a great earthquake along part or all of its length.

The viking seismic experiment.

A three-axis short-period seismometer is now operating on Mars in the Utopia Planitia region. The noise background correlates well with wind gusts. Although no quakes have been detected in the first 60 days of observation, it is premature to draw any conclusions about the seismicity of Mars. The instrument is expected to return data for at least 2 years.

Results from the Mars Global Surveyor Thermal Emission Spectrometer.

The Thermal Emission Spectrometer spectra of low albedo surface materials suggests that a four to one mixture of pyroxene to plagioclase, together with about a 35 percent dust component provides the best fit to the spectrum. Qualitative upper limits can be placed on the concentration of carbonates (<10 percent), olivine (<10 percent), clay minerals (<20 percent), and quartz (<5 percent) in the limited regions observed. Limb observations in the northern hemisphere reveal low-lying dust hazes and detached water-ice clouds at altitudes up to 55 kilometers. At an aerocentric longitude of 224 degrees a major dust storm developed in the Noachis Terra region. The south polar cap retreat was similar to that observed by Viking.

Predicting QT prolongation in humans during early drug development using hERG inhibition and an anaesthetized guinea-pig model.

BACKGROUND AND PURPOSE: Drug-induced prolongation of the QT interval can lead to torsade de pointes, a life-threatening ventricular arrhythmia. Finding appropriate assays from among the plethora of options available to predict reliably this serious adverse effect in humans remains a challenging issue for the discovery and development of drugs. The purpose of the present study was to develop and verify a reliable and relatively simple approach for assessing, during preclinical development, the propensity of drugs to prolong the QT interval in humans. EXPERIMENTAL APPROACH: Sixteen marketed drugs from various pharmacological classes with a known incidence -- or lack thereof -- of QT prolongation in humans were examined in hERG (human ether a-go-go-related gene) patch-clamp assay and an anaesthetized guinea-pig assay for QT prolongation using specific protocols. Drug concentrations in perfusates from hERG assays and plasma samples from guinea-pigs were determined using liquid chromatography-mass spectrometry. KEY RESULTS: Various pharmacological agents that inhibit hERG currents prolong the QT interval in anaesthetized guinea-pigs in a manner similar to that seen in humans and at comparable drug exposures. Several compounds not associated with QT prolongation in humans failed to prolong the QT interval in this model. CONCLUSIONS AND IMPLICATIONS: Analysis of hERG inhibitory potency in conjunction with drug exposures and QT interval measurements in anaesthetized guinea-pigs can reliably predict, during preclinical drug development, the risk of human QT prolongation. A strategy is proposed for mitigating the risk of QT prolongation of new chemical entities during early lead optimization.