bluuebunny/crossref_metadata_2025 huggingface dataset:
Seasonality of spectral albedo and transmittance as observed in the Arctic Transpolar Drift in 2007
Authors: Nicolaus Marcel , Gerland Sebastian , Hudson Stephen R. , Hanson Susanne , Haapala Jari , Perovich Donald K.
Published: May 2011

The first continuous and high temporal resolution record of spectral albedo and transmittance of snow and sea ice in the Arctic Ocean over an entire summer season is presented. Measurements were performed at a manned station on multiyear sea ice in the Transpolar Drift during the drift of the schooner Tara from April to September 2007. Concurrent autonomous measurements of ice mass balance and weekly observations of snow and sea‐ice properties complement the data set. The seasonality of physical and biological processes of snow and sea ice is characterized, including quantification of melt onset (10 June), melt season duration, and freeze onset (15 August). Over one year, approximately two thirds of the transmitted energy reached the ocean during the 66‐day‐long melt season. During the second half of July, transmitted irradiance decreased by 90% and absorption in and directly under the ice increased, significantly affecting the vertical partitioning of irradiance. The spectral radiation time series suggests that high biomass abundance in or below the sea ice caused this decrease. Comparing the spectral data set with broadband albedo data measured at the same location shows that 90% of the temporal variability of broadband albedo can be explained by variability in spectral albedo integrated over the limited wavelength range. The combination of spectral radiation and ice mass balance measurements allows a comprehensive description, and quantification, of snow and sea‐ice processes, even with minimal additional in situ observations, suggesting such data sets can be collected autonomously to provide insight into the physical and biological processes on sea ice.
Noah land surface model modifications to improve snowpack prediction in the Colorado Rocky Mountains
Authors: Barlage Michael , Chen Fei , Tewari Mukul , Ikeda Kyoko , Gochis David , Dudhia Jimy , Rasmussen Roy , Livneh Ben , Ek Mike , Mitchell Ken
Published: May 2011

Simulated snowpack by the Noah land surface model (LSM) shows an early depletion due to excessive sublimation and too early onset of snowmelt. To mitigate these deficiencies, five model modifications are tested to improve snowpack performance: (1) time‐varying snow albedo, (2) solar radiation adjustment for terrain slope and orientation, (3) reducing the surface exchange coefficient for stable boundary layers, (4) increase of fresh snow albedo, and (5) adjusting surface roughness length when snow is present. The Noah LSM is executed from 1 November 2007 to 1 August 2008 for the headwater region in the Colorado Rocky Mountains with complex terrain, and its results are evaluated against 1 km Snow Data Assimilation System (SNODAS) output and individual Natural Resources Conservation Service Snowpack Telemetry (SNOTEL) sites. The most effective way to improve magnitude and timing of seasonal maximum snow water equivalent (SWE) is the introduction of the time‐varying albedo formulation and the increase in fresh snow albedo. Minor improvement is obtained by reducing nighttime sublimation through adjusting the stable boundary layer surface exchange coefficient. Modifying the surface roughness length over snow surfaces and adding a terrain slope and orientation adjustment for radiation has little effect on average SWE conditions for the entire modeling domain, though it can have a significant effect in certain regions. The net effect of all changes is to improve the magnitude and timing of seasonal maximum SWE, but the snow period end is now somewhat too long. Adding the terrain slope and orientation effects does have an effect on local surface energy flux components depending on the cell slope and orientation.
Importance of structure and its measurement in quantifying function of forest ecosystems
Authors: Shugart H. H. , Saatchi S. , Hall F. G.
Published: May 2011

The structure of forests, the three‐dimensional arrangement of individual trees, has a profound effect on how ecosystems function and cycle carbon, water, and nutrients. The increased need to understand local to global dynamics of ecosystems, a prerequisite to understand the coupling of the biosphere to other components of Earth systems, has created a demand for extensive ecosystem structure data. Repeated satellite observations of vegetation patterns in two dimensions have made significant contributions to our understanding of the state and dynamics of the global biosphere. Recent advances in remote sensing technology allow us to view the biosphere in three dimensions and provide us with refined measurements of horizontal, as well as vertical, structure of forests. This paper provides an introductory review of the importance of the three‐dimensional characterization of terrestrial ecosystem structure of forests and woodlands and its potential measurement from space. We discuss the relevance of these measurements for reducing the uncertainties of terrestrial carbon cycle and the response of ecosystems to future climate. By relating the 3‐D structure to forest biomass, carbon content, disturbance characteristics, and habitat diversity, we examine the requirements for future satellite sensors in terms of precision and spatial and temporal resolutions. In particular, we focus this review on measurements from lidar and radar sensors that provide vertical and horizontal characterization of vegetation and are currently recommended for next generation of NASA's Earth observing and European Earth Explorer systems.
An examination of direct ground wave soil moisture monitoring over an annual cycle of soil conditions
Authors: Steelman Colby M. , Endres Anthony L.
Published: May 2011

Direct ground wave (DGW) measurements obtained with ground‐penetrating radar have been used in a number of previous studies to estimate volumetric water content in the shallow soil zone; however, these studies have generally involved controlled field experiments or measurements collected across limited natural ranges of soil moisture conditions. To further investigate the capacity of this method, we have undertaken an extensive field study using multifrequency (i.e., 225, 450, and 900 MHz) DGW measurements to monitor a complete annual cycle of soil water content variations typical of midlatitude climates at three sites with different soil textures. The use of common‐midpoint surveys allowed us to understand the nature and evolution of the near‐surface electromagnetic wavefields and their impact on DGW moisture predictions. We present the novel characterization of a wide‐range of seasonal moisture dynamics including soil freezing and thawing process using multifrequency DGW measurements for a range of soil textures. These data showed significant temporal variations in both the near‐surface wavefield and multifrequency DGW velocities corresponding to both seasonal and shorter‐term variations in soil conditions. Although all of the measurement sites displayed similar temporal responses, the rate and magnitude of these velocity variations corresponded to varying soil water contents, which were controlled by the soil textural properties. Although there were no observed systematic differences in DGW velocities due to frequency dispersion for the 225–900 MHz range, the DGW measurements obtained using higher‐frequency antennas was less impacted by near‐surface wavefield interference due to their shorter signal pulse duration. DGW velocity measurements combined with an appropriate dielectric mixing formula provided quantitative predictions of soil water content that accurately replicated the soil sample data over the annual cycle of moisture conditions.
Porosity and grain size controls on compaction band formation in Jurassic Navajo Sandstone
Authors: Schultz Richard A. , Okubo Chris H. , Fossen Haakon
Published: May 2011

Determining the rock properties that permit or impede the growth of compaction bands in sedimentary sequences is a critical problem of importance to studies of strain localization and characterization of subsurface geologic reservoirs. We determine the porosity and average grain size of a sequence of stratigraphic layers of Navajo Sandstone that are then used in a critical state model to infer plastic yield envelopes for the layers. Pure compaction bands are formed in layers having the largest average grain sizes (0.42–0.45 mm) and porosities (28%), and correspondingly the smallest values of critical pressure (∼22 MPa) in the sequence. The results suggest that compaction bands formed in these layers after burial to ∼1.5 km depth in association with thrust faulting beneath the nearby East Kaibab monocline, and that hardening of the yield caps accompanied compactional deformation of the layers.
Extremely low long‐term erosion rates around the Gamburtsev Mountains in interior East Antarctica
Authors: Cox S. E. , Thomson S. N. , Reiners P. W. , Hemming S. R. , van de Flierdt T.
Published: May 2011

The high elevation and rugged relief (>3 km) of the Gamburtsev Subglacial Mountains (GSM) have long been considered enigmatic. Orogenesis normally occurs near plate boundaries, not cratonic interiors, and large‐scale tectonic activity last occurred in East Antarctica during the Pan‐African (480–600 Ma). We sampled detrital apatite from Eocene sands in Prydz Bay at the terminus of the Lambert Graben, which drained a large pre‐glacial basin including the northern Gamburtsev Mountains. Apatite fission‐track and (U‐Th)/He cooling ages constrain bedrock erosion rates throughout the catchment. We double‐dated apatites to resolve individual cooling histories. Erosion was very slow, averaging 0.01–0.02 km/Myr for >250 Myr, supporting the preservation of high elevation in interior East Antarctica since at least the cessation of Permian rifting. Long‐term topographic preservation lends credence to postulated high‐elevation mountain ice caps in East Antarctica since at least the Cretaceous and to the idea that cold‐based glaciation can preserve tectonically inactive topography.
Gravity wave variations during the 2009 stratospheric sudden warming as revealed by ECMWF‐T799 and observations
Authors: Yamashita Chihoko , Liu Han‐Li , Chu Xinzhao
Published: May 2011

ECMWF‐T799 is used to study gravity wave (GW) variations during the 2009 stratospheric sudden warming (SSW) in the Arctic. The magnitude and occurrence of GWs correlate with the location and strength of the polar vortex that is strongly disturbed by planetary wave (PW) growth. This location dependence on PW phase explains the observed GW variability during SSWs. During the development and the onset of SSW, the zonal‐mean GW potential energy density (GW‐Ep) increases on January 5 and 15–22 in association with the growth of PW wavenumber 1 and wavenumber 2, respectively. As the initial prominent PW magnitude in the lower mesosphere progresses downward, GW‐Ep enhancement also seems to show a corresponding descent from January 5–22. GW‐Ep peaks before the wind reversal occurrence and significantly weakens after the SSW. These variations are confirmed by COSMIC/GPS observations. Lidar data from Antarctica are also used to validate GWs as derived in ECMWF.
Stochastic modeling of the AE index and its relation to fluctuations in Bz of the IMF on time scales shorter than substorm duration
Authors: Rypdal M. , Rypdal K.
Published: May 2011

We perform a detailed analysis of the auroral electrojet (AE) index on the typical substorm time scales from one minute up to a few hours. Through a systematic test against a model for selfsimilar motion in the form of fractional Lévy flights, and against a model for fractional Brownian motion in multifractal time, it is demonstrated that the AE index is better approximated by a multifractal model than by a fractional Lévy flight. Standard structure function analysis of the z‐component Bz of the interplanetary magnetic field indicates that it is neither selfsimilar nor multifractal, but approximately satisfies a version of extended selfsimilarity. A method to discern an underlying multifractality also in Bz is pointed out.
Total electron content in the Mars ionosphere: Temporal studies and dependence on solar EUV flux
Authors: Lillis Robert J. , Brain David A. , England Scott L. , Withers Paul , Fillingim Matthew O. , Safaeinili Ali
Published: May 2011

Total electron content (TEC) derived from radar signal distortions is a useful tool in probing the ionosphere of Mars. We consider 26 months of data from the subsurface mode of the Mars Express MARSIS instrument and confirm that the TEC dependence on solar zenith angle (SZA) approximately matches Chapman theory. After detrending this dependence, we find no clear trend with Martian season or dust activity but find that disturbed solar and space weather conditions can produce prolonged higher TEC values and that isolated solar energetic particle events are coincident with short‐lived increases in TEC of ∼1015 m−2 at all SZAs. We present the first comparison between TEC and directly measured solar EUV flux in the 30.4 nm He‐II line. We find that the relationship between TEC and both He‐II line irradiance and F10.7 solar radio flux (a long‐used EUV proxy) can be expressed as power laws with exponents of 0.54 and 0.44, respectively, in approximate agreement with Chapman theory.
Reconstructing drought variability for Mongolia based on a large‐scale tree ring network: 1520–1993
Authors: Davi N. , Jacoby G. , Fang K. , Li J. , D'Arrigo R. , Baatarbileg N. , Robinson D.
Published: May 2011

Previous tree ring based hydrologic studies in Mongolia have been regional in scale. Here, we present a large‐scale summer drought reconstruction for Mongolia that reveals the main summer moisture patterns of the past. This reconstruction is based on a network of tree ring chronologies that span the country. The resulting drought model explains 61% of the variance and is extended to cover 1520–1993 by using a nested approach to modeling. Severe droughts and harsh winter conditions occurred in Mongolia from ∼1999–2002 and contributed to massive livestock mortality and economic loss. These droughts were extreme in the context of the past several hundred years. Significant periodicities are found at 40 (90%), 19.3–25 (99%), 11.6 (95%), 6.4–7.2 (95%), and 2.8 years (99%). This high‐resolution drought reconstruction and associated tree ring chronologies supplement and extend the sparse meteorological data in Mongolia and can be used to better understand climate variability and potential forcings of climate.
On the uncertainty of radio occultation inversions in the lower troposphere
Authors: Sokolovskiy S. , Rocken C. , Schreiner W. , Hunt D.
Published: May 2011

Development of radio‐holographic inversion methods that solve for multipath propagation of radio occultation signals in the moist lower troposphere resulted in significant reduction of inversion errors of the bending angle and refractivity. Still, inversion errors depend on the length of recorded radio occultation signals, additive noise, and some tunable inversion parameters. These errors have components with nonzero mean (biases) and thus must be understood and quantified for weather and climate applications. In this study a physical explanation of the above mentioned inversion biases is given and their magnitude is evaluated (about 1% in the tropical lower troposphere). Assuming data with 50 Hz sampling rate and a noise level that is typical for the COSMIC GPS radio occultation observations, this magnitude can be considered as the measure of uncertainty of radio holographic inversions below ∼5 km in the moist tropical troposphere.
Understanding climate change–induced variations in daily temperature distributions over Italy
Authors: Simolo C. , Brunetti M. , Maugeri M. , Nanni T. , Speranza A.
Published: May 2011

We investigate changes in the probability density functions and the probability of moderate extremes for maximum and minimum daily temperature anomalies in Italy from 1951 up to 2008. Evaluation of trends in time‐varying percentiles and higher‐moment analysis of empirical density functions give no evidence of long‐term changes in scale or shape of daily anomaly distributions, their temporal evolution being essentially driven by a forward, nonuniform shift in the mean. In this context, on the basis of an appropriate theoretical model for daily anomalies, we provide a realistic representation of the temporal evolution of moderate warm and cold extremes by explicitly considering the inherent nonlinearity between changes in the mean and those in exceedance probabilities. Consistency between expected and observed exceedance probabilities suggests that changes in moderate extremes can be well understood with a simple, rigid shift of the density functions alone, without invoking any change in shape.
Desert dust aerosol age characterized by mass‐age tracking of tracers
Authors: Han Qin , Zender Charles S.
Published: May 2011

We introduce and apply to dust aerosols an efficient method to track tracer age (time since emission) as a function of space and time in large‐scale geophysical models. Our mass‐age tracking (MAT) method follows the full tracer lifecycles directly and does not depend on proxy, ensemble, or Green's function techniques. MAT sends a mass‐age tracer through the same algorithms that the host models use to predict tracer mass processes and then estimates age as the ratio of mass‐age to mass. We apply MAT to size‐resolved dust aerosol tracers to study the age of dust that remains in the atmosphere and the age of dust at deposition. The results include the first global distribution maps of aerosol age. Dust age varies with location, time, and particle size and is strongly sensitive to climate, wind and precipitation in particular. The global average age of dust at deposition agrees with residence time at ∼2.7 days, while dust in the atmosphere is, on average, twice as old. As expected, older dust prevails far from sources, at higher altitudes and in smaller sizes. Dust age exhibits a seasonal cycle, stronger for larger dust particles, that peaks in April–June, the period of maximum Asian and North African emissions. The oldest dust at deposition falls in the Antarctic and South Pacific Convergence Zone about 1 month after emission. The mass‐weighted ages provided by MAT are useful for investigating and parameterizing the evolution of aerosol physical and chemical properties.
Chemical characterization of aerosols over the Atlantic Ocean and the Pacific Ocean during two cruises in 2007 and 2008
Authors: Zhang M. , Chen J. M. , Wang T. , Cheng T. T. , Lin L. , Bhatia R. S. , Hanvey M.
Published: May 2011

To help understand the chemical properties of marine aerosols and the long‐distance transport of continental aerosols to remote oceanic regions, total suspended particulates (TSP) samples were collected over the Atlantic Ocean and the Pacific Ocean during two cruises in September–December 2007 (cruise I) and March–April 2008 (cruise II) aboard the M/V Oceanic II. Data were analyzed and interpreted with the aid of back trajectory, principal component, and multiple linear regression analyses. Compared with the results over the South Pacific from 2 decades ago, the non‐sea‐salt sulfate (NSS‐SO42−) concentrations over the South Pacific have increased by a factor of ∼1.5, while the NO3− concentration has remained constant. On average, NSS‐SO42− accounted for 30–52% of the total SO42− during the two cruises. Chloride deficit was observed in all samples, with NSS‐SO42− being the preferred species for acid displacement over the South Pacific and the Mediterranean Sea. Persistent clean marine air masses were only observed over the northern Atlantic and South Pacific during cruise I, while more frequent impacts of continental air (dust, biomass burning, and industrial plumes) were observed during cruise II. Combined with the NAAPS aerosol maps, these results indicate that during cruise II, (1) southern Atlantic was influenced by Southern Africa and the interhemisphere transport of biomass burning plumes in Central Africa, (2) northern Atlantic was under the combined pollution plumes of Sahara dust intrusion and biomass burning, and (3) the Mediterranean Sea was affected by the mixed pollution from biomass burning and industrial contamination, as well as Saharan dust.
Cloud and the corresponding precipitation chemistry in south China: Water‐soluble components and pollution transport
Authors: Sun Minghu , Wang Yan , Wang Tao , Fan Shaojia , Wang Wenxing , Li Penghui , Guo Jia , Li Yuhua
Published: May 2011

To investigate the transport and deposition of pollutants in south China, the chemical composition of cloud water and rainwater was studied at Mount Heng, which is located in the heart of China's acid rain affected region. A total of 194 cloud samples and 38 event‐based precipitation samples from March to May 2009 were analyzed for a wide variety of water‐soluble compounds. The volume‐weighted mean (VWM) pH of cloud water was 3.80, indicating an acidic nature. Compared with cloud water, precipitation was much less acidic with a VWM pH value of 4.35. The concentration results show that in cloud water, SO42− was the dominant anion, followed by NO3−, controlling the acidity, while NH4+ accounted for 69.8% of the total cations, dominating the cloud water neutralization. In rainwater, a similar situation appeared, but with a slightly higher Ca2+concentration. In both cloud water and precipitation the acidities were found to be mainly due to sulfuric acid, followed by nitric acid. The calculation of neutralization factors and the application of multiple linear regression analysis showed the higher NH4+ contribution to the neutralization process in both types of samples. The very weak correlations of ions in rain with the ones in cloud water on the event basis suggested that cloud and precipitation events may be associated with different air masses. With relatively high ionic concentrations and higher frequency, air masses from the east and south directions were associated with the high cloud deposition of the major species at our site.
Surface radiative fluxes over the pan‐Arctic land region: Variability and trends
Authors: Shi Xiaogang , Wild Martin , Lettenmaier Dennis P.
Published: May 2011

Surface radiative fluxes are a key driver of the land surface hydrological cycle, but because in situ measurements are sparse, relatively little attention has been focused on their space‐time variations. Recent satellite data and atmospheric model reanalysis products have resulted in data sets that predict most or all terms in the surface energy budget and offer the opportunity to investigate variations in surface radiative fluxes. This study contributes the NASA Energy and Water Cycle Study (NEWS), which is intended to improve estimates of the terrestrial energy budget components for the hydrologic and ecological communities. We analyzed surface downward shortwave (DSW) and longwave radiation (DLW) and albedo over the pan‐Arctic domain from (1) the European Centre for Medium‐Range Weather Forecast (ECMWF) 40‐Year Reanalysis (ERA‐40), (2) the ECMWF Interim Reanalysis (ERA‐Interim), (3) the International Satellite Cloud Climatology Project‐Flux Data (ISCCP‐FD), and (4) a Temperature Index (TIND) scheme for the period from 1984 to 2006. As compared with in situ measurements, the reanalysis products provide better estimates of the DSW diurnal cycle than do the satellite product and temperature index scheme simulation. At the regional scale, all data sets have similar temporal patterns except for DLW in ISCCP and snow season albedo. In terms of dominant spatial variability, all data sets show large variability in the pan‐Arctic. In addition, DSW and DLW show a similar latitudinal gradient. However, the difference in albedo suggests a need of improvement for the reanalysis products. For a small number of stations with relatively long records, we analyzed long‐term trends in DSW and found a turning point between 1985 and 1990. Before that, a dimming period exists, whereas brightening occurred thereafter.
Apollo lunar heat flow experiment revisited: A critical reassessment of the in situ thermal conductivity determination
Authors: Grott M. , Knollenberg J. , Krause C.
Published: May 2011

Lunar heat flow was determined in situ during the Apollo 15 and 17 missions, but some uncertainty is connected to the value of the regolith's thermal conductivity, which enters as a linear factor into the heat flow calculation. Different approaches to determine the conductivity yielded discordant results, which led to a downward correction of the obtained heat flow values by 30%–50% subsequent to the publication of the first results. We have reinvestigated likely causes for the observed discrepancies and find that neither poor coupling between the probe and regolith nor axial heat loss can explain the obtained results. Rather, regolith compaction and compression likely caused a local increase of the regolith's thermal conductivity by a factor of 2–3 in a region which extends at least 2–5 cm from the borehole wall. We conclude that the corrected lunar heat flow values, which are based on thermal diffusivity estimates sampling a large portion of undisturbed regolith, represent robust results. Future in situ measurements of regolith thermal conductivity using active heating methods should take care to both minimize regolith disturbance during probe emplacement and maximize heating time to obtain reliable results. We find that for the Apollo measurements, heating times should have exceeded at least 100 h, and ideally 200 h.
Geology of the Martian crustal dichotomy boundary: Age, modifications, and implications for modeling efforts
Authors: Irwin Rossman P. , Watters Thomas R.
Published: May 2011

The contrast in crustal thickness, surface age, elevation, and morphology between the southern cratered highlands and northern lowland plains of Mars is termed the crustal dichotomy. The oldest exposed sections of the crustal dichotomy boundary are ancient cratered slopes, which influenced post‐Noachian fresh crater morphometry, Late Noachian valley network planform, and the degradation patterns of Middle to Late Noachian (∼3.92–3.7 Ga) impact craters. Noachian visible and topographically defined impact craters at the top of the cratered slope show no evidence of flexure‐induced normal faulting. These observations and published geophysical data collectively require an Early to Pre‐Noachian age for the crustal dichotomy, prior to the largest recognized impact basins. Late Noachian plateau deposits and more prolonged Tharsis volcanism appear to have buried parts of the old cratered slope, and fretted terrain developed in this transition zone during the Early Hesperian Epoch (∼3.7–3.6 Ga). Fretted/knobby terrains, lowland plains, and most visible structures (wrinkle ridges, fractures, and normal faults) postdate Noachian crater modification and are several hundred million years younger than the cratered slope of the crustal dichotomy, so they provide no valid basis or constraint for models of its formation. Long‐wavelength topography in cratered terrain dates to Early to Pre‐Noachian time and provides a useful model constraint. Geological and geophysical observations are thus reconciled around an early age and relatively rapid development of the Martian crustal dichotomy.
Observed ENSO teleconnections to Southern Ocean SST anomalies diagnosed from a surface mixed layer heat budget
Authors: Ciasto Laura M. , England Matthew H.
Published: May 2011

This study examines the mechanisms that govern the El Niño Southern Oscillation (ENSO) teleconnections to variability in extratropical Southern Hemisphere sea surface temperature (SST) anomalies using several observational and reanalysis products. During the warm season, turbulent heat fluxes and heat advection by Ekman currents contribute equally to ENSO‐related SST variability throughout the Southern Ocean, while shortwave radiation has a larger contribution in the subtropics. A comparison of the ocean mixed layer heat budget between multiple re‐analysis products reveals that the relative contributions of the turbulent, radiative and Ekman heat fluxes to ENSO‐related SST anomalies is consistent between the NCEP, ERA‐40 and OAFlux/ISCCP products, but discrepancies exist with regard to the structure and amplitude of the turbulent heat fluxes and, to a lesser extent, the shortwave radiation. However, a comparison between the tendencies in SST and flux‐derived temperatures reveals minimal residuals, suggesting that the ENSO‐signal in the SST field can be resolved by turbulent, Ekman, and radiative heat fluxes, particularly in the ERA‐40 products.
Stability field of the hcp‐structure for Fe, Fe‐Ni, and Fe‐Ni‐Si alloys up to 3 Mbar
Authors: Sakai Takeshi , Ohtani Eiji , Hirao Naohisa , Ohishi Yasuo
Published: May 2011

The phase relations of Fe, Fe90Ni10 and Fe87.9Ni4.4Si7.7 were investigated up to 273(6) GPa and 4490(560) K, 250(19) GPa and 2730(110) K and 304(3) GPa and 2780(210) K, respectively, and the hexagonal close‐packed structure was found to be stable in all of these compounds under the pressure and temperature conditions studied. We did not observe other phases such as a body‐centered cubic structure. The axial ratio (c/a) of Fe87.9Ni4.4Si7.7 at 300 GPa showed an almost constant value of 1.593–1.596 against temperature. The weak temperature dependency of the axial ratio of hcp‐Fe‐Ni‐Si alloy indicates that the c‐axis is still harder than the a‐axis at high temperature condition. Therefore the alignment of hcp‐Fe–Ni–Si alloy with the c‐axis parallel to the Earth's rotation axis could account for the observation of the seismic wave anisotropy of the inner core.
Donald Eric Weiss 1924 - 2008
Authors: Spurling Thomas H.
Published: May 2011

Don Weiss was born in the Melbourne suburb of St Kilda on 4 October 1924 and died in Melbourne on 30 July 2008. He was educated in South Australia, at Scotch College, the South Australian School of Mines and Industry, and the University of Adelaide. He joined the Council for Scientific and Industrial Research (CSIR) in 1948 and worked for CSIR and its successor organization, CSIRO, until his retirement in 1984. He was the Chief of the CSIRO Division of Chemical Technology from 1974 to 1979 and Director of CSIRO's Planning and Evaluation Advisory Unit from 1979 to 1984. He was a highly imaginative and creative scientist whose work was always driven by his clear understanding of its application. He made important contributions to separation science but is best known for his contributions to technology for water and waste water treatment. His enduring legacy is the more than twenty MIEX plants that have been installed around the world.
John Henry Carver 1926 - 2004
Authors: Crompton R. W. , Dracoulis G. D. , Lewis B. R. , McCracken K. G. , Williams J. S.
Published: May 2011

John Henry Carver made distinguished contributions to national and international physics, not only through his research in nuclear physics, atomic and molecular physics, and planetary atmospheric physics, but also as a scientific administrator. His years as the Elder Professor of Physics at the University of Adelaide saw him enter the field of rocket-based atmospheric physics by forging strong links with the nearby Weapons Research Establishment through which he had access to rockets to fly equipment developed in his laboratory and, eventually, to launch a small satellite developed and built by his team. This led to his appointment to the Scientific and Technical Subcommittee of the United Nations Committee on the Peaceful Uses of Outer Space, which he chaired for the record term of twenty-five years. As an academic administrator he was equally distinguished, serving on numerous boards and committees of the University of Adelaide before moving to Canberra as Director of the Australian National University's Research School of Physical Sciences, a position he held for fifteen years. In addition, he served with distinction on numerous national and international scientific advisory bodies. He was a passionate advocate for his School and his leadership will be long remembered.
'It is not so!' Otto Finsch, Expectations and Encounters in the Pacific, 1865 - 85
Authors: Howes Hilary S.
Published: May 2011

This article focuses on the Pacific experiences of the German ornithologist and ethnologist Otto Finsch (1839?1917). Between 1879 and 1882, Finsch voyaged extensively in the Pacific, visiting Hawai?i, parts of Micronesia and island Melanesia, New Zealand, New Guinea and the Torres Strait Islands. In 1884, he returned to New Guinea and was instrumental in the acquisition of Kaiser-Wilhelmsland and the Bismarck Archipelago as German protectorates.While his numerous publications on the indigenous inhabitants of these areas naturally reflect the prevailing scientific and colonial discourses of the late nineteenth century, I argue that they were also significantly shaped by his personal encounters with Pacific peoples. Through close comparisons of texts produced before, during and after his Pacific voyages, I discuss the ways in which these encounters challenged Finsch's pre-voyage assumptions about ?race' and human difference: the breadth of individual variation within supposedly homogeneous races, the extent of overlap between such races, and the reliability of particular cultural practices as diagnostics of savagery or civilization. I also emphasize links between Finsch's story and broader issues in the history of science, including the influence of observers' trajectories of travel on the
constitution of regional topographies of difference, the standardization and mobilization of travellers' observations for metropolitan audiences, the human interface between discovery and communication, and the policing of scientific knowledge and interpretation of field observations by metropolitan authorities.
The Search for a Solution to Australian Locust Outbreaks: How Developments in Ecology and Government Responses Influenced Scientific Research
Authors: Deveson E. D.
Published: May 2011

A national research approach to the ?grasshopper problem' began following a plague of the Australian plague locust (Chortoicetes terminifera Walker) in inland south-eastern Australia in the 1930s. After the plague of the 1950s, the role of arid inland areas as a source of migrations into agricultural areas received greater attention. In the 1960s and 1970s, international collaborative experimental research with the CSIRO advanced the knowledge of locust lifecycles and population ecology. Studies of nocturnal mass migration on upper-level winds brought a new understanding of Australian locust population dynamics. This paper traces Australian research into locust ecology within the contexts of locust infestations and government responses to them. Investigations on Australian locusts reflected many contemporary ideas and methods in entomological research and contributed to the development of international ecological theory during the twentieth century. International locust research based on the phase change and outbreak area model of Uvarov particularly influenced work carried out in Australia.
Follicle-stimulating hormone receptor (FSHR)-derived peptide vaccine induced infertility in mice without pathological effect on reproductive organs
Authors: Yang Li-Hua , Li Jin-Tao , Yan Ping , Liu Hong-Li , Zeng Su-Yun , Wu Yu-Zhang , Liang Zhi-Qing , He Wei
Published: May 2011

In a previous study it was found that priming with recombinant human follicle-stimulating hormone receptor (rhFSHR) protein (F140) and boosting with a peptide containing amino acids 32–44 from FSHR showed a specific immune response and fertility inhibition in adult male mice. However, this priming and boosting led to damage of the reproductive organs. Therefore, to eliminate this damage, the peptide prime–boost strategy was explored as a possible means of avoiding the pathological change while maintaining infertility. Immunisation with the peptide prime–boost strategy led to decreased fertility 10 weeks after vaccination, which is consistent with Balb/C mice treated with the protein prime–peptide boost regime. In contrast to the cellular swelling and spotty necrosis in spermatogonia observed in the protein-primed mice, the mice receiving peptide priming did not display pathological damage in seminiferous tubules and interstitial cells. Thus, the prime–boost immune regime with the FSHR-derived peptide potentially provides a much safer candidate for a contraceptive vaccine.
Gene expression analysis of bovine blastocysts produced by parthenogenic activation or fertilisation
Authors: Labrecque Rémi , Sirard Marc-André
Published: May 2011

The processes underlying the very first moments of embryonic development are still not well characterised in mammals. To better define the kinetics of events taking place following fertilisation, it would be best to have perfect synchronisation of sperm entry. With fertilisation occurring during a time interval of 6 to 12 h in the same group of fertilised oocytes, this causes a major variation in the time of activation of embryonic development. Bovine parthenogenesis could potentially result in better synchronisation and, if so, would offer a better model for studying developmental competence. In the present study, bovine oocytes were either parthenogenetically activated or fertilised and cultured in vitro for 7 days. Gene expression analysis for those two groups of embryos at early and expanded stages was performed with BlueChip, a customised 2000-cDNA array developed in our laboratory and enriched in clones from various stages of bovine embryo development. The microarray data analysis revealed that only a few genes were differentially expressed, showing the relative similarity between those two kinds of embryos. Nevertheless, the fact that we obtained a similar diversity of developmental stages with parthenotes suggests that synchronisation is more oocyte-specific than sperm entry-time related. We then analysed our data with Ingenuity pathway analysis. Networks of genes involved in blastocyst implantation but also previous stages of embryo development, like maternal-to-embryonic transition, were identified. This new information allows us to better understand the regulatory mechanisms of embryonic development associated with embryo status.
Sperm motility activation, sperm heterogeneity and sperm–female tract interactions in Bennett's wallaby (Macropus rufogriseus rufogriseus)
Authors: Boere Janneke , Díaz Daniela Esteban , Holt William V.
Published: May 2011

Sperm–oviduct interactions in Bennett’s wallaby (Macropus rufogriseus rufogriseus) were investigated using in vitro cocultures of cauda epididymal spermatozoa and oviducal epithelial cells. Kidney epithelial cells were used as non-reproductive control tissues. Spermatozoa attached to epithelial cells of both origins, but sperm survival and activity was higher when cocultured with oviducal cells. New findings during live sperm–epithelial interactions included: (1) a high frequency of reversible head movements, from linear (streamlined configuration) to T shape (thumbtack configuration) in swimming spermatozoa immediately after the start of coculture; (2) the loss of sperm tails (tail shedding) increasing with time; and (3) interrupted swimming patterns, where periods of fast movement were interspersed with slower swimming while the spermatozoa interacted with the epithelial cell surface. Sperm motility activation responses were characterised after diluting the epididymal samples in phosphate-buffered saline, medium M199 and Tyrode’s medium. The results confirmed that the marsupial oviduct is able to support the viability and motility of a sperm subpopulation for at least 20 h in vitro and suggest that some spermatozoa shed their tails after binding, possibly as a result of a selective process.
Differential developmental requirements for individual histone H3K9 methyltransferases in cleavage-stage porcine embryos
Authors: Park Ki-Eun , Johnson Christine M. , Wang Xin , Cabot Ryan A.
Published: May 2011

Dimethylated H3K9 is a heritable epigenetic mark that is closely linked with transcriptional silencing and known to undergo global remodelling during cleavage development. Five mammalian histone methyltransferases (HMTases), namely Suv39H1, Suv39H2, SetDB1, EHMT1 and EHMT2, have been shown to mediate the methylation of H3K9. The aim of the present study was to determine the developmental requirements of these HMTases during cleavage development in porcine embryos. We hypothesised that knockdown of the abovementioned HMTases would differentially affect porcine cleavage development. To test this hypothesis, IVM and IVF porcine oocytes were divided into one of three treatment groups, including non-injected controls, oocytes injected with a double-stranded interfering RNA molecule specific for one of the HMTases and oocytes injected with a corresponding mutated (control) double-stranded RNA molecule. Nuclei were counted in all embryos 6 days after fertilisation. Although no significant difference in total cell number was detected in embryos injected with EHMT1 and EHMT2 interfering RNAs (compared with their respective control groups), embryos injected with interfering RNAs that targeted Suv39H1, Suv39H2 and SetDB1 had significantly lower cell numbers than their respective control groups (P < 0.05). This suggests that individual HMTases differentially affect in vitro developmental potential.
Temporal effects of exogenous oocyte-secreted factors on bovine oocyte developmental competence during IVM
Authors: Hussein Tamer S. , Sutton-McDowall Melanie L. , Gilchrist Robert B. , Thompson Jeremy G.
Published: May 2011

We investigated whether paracrine signalling between the bovine oocyte and cumulus cells is altered during the course of in vitro maturation (IVM). Bovine COCs were cocultured with denuded oocytes or treated with specific oocyte-secreted factors, namely recombinant bone morphogenetic protein (BMP)-15 or growth differentiation factor (GDF)-9, beginning from 0 or 9 h IVM. To generate a 9-h denuded oocyte (DO) group, COCs were cultured intact for the first 9 h of IVM and then denuded. Coculturing intact COCs with DOs denuded immediately after collection or following 9 h of maturation did not affect cleavage rate, but improved blastocyst yield (P < 0.05) on Day 8 (51 and 61%, respectively; P < 0.05) and cell number compared with COCs cultured alone (41%). Significantly, we observed higher levels of endogenous GDF-9 and BMP-15 protein in oocytes of COCs matured for 9 h compared with no incubation. The addition of 175 ng mL–1 GDF-9 or 10% v/v BMP-15 from partially purified transfected 293H cell supernatant for 24 h IVM significantly enhanced development to the blastocyst stage from 40% (control) to 51 and 47%, respectively (P < 0.05). However, treatment of COCs with GDF-9 or BMP-15 between 9 and 24 h of IVM did not increase blastocyst yield. These results provide evidence of quantitative and possibly qualitative temporal changes in oocyte paracrine factor production during IVM.
Two distinct conformations of helix 6 observed in antagonist-bound structures of a
β
1
-adrenergic receptor
Authors: Moukhametzianov Rouslan , Warne Tony , Edwards Patricia C. , Serrano-Vega Maria J. , Leslie Andrew G. W. , Tate Christopher G. , Schertler Gebhard F. X.
Published: May 2011

The
β
1
-adrenergic receptor (
β
1
AR) is a G-protein-coupled receptor whose inactive state structure was determined using a thermostabilized mutant (
β
1
AR–M23). However, it was not thought to be in a fully inactivated state because there was no salt bridge between Arg139 and Glu285 linking the cytoplasmic ends of transmembrane helices 3 and 6 (the R
3.50
 - D/E
6.30
“ionic lock”). Here we compare eight new structures of
β
1
AR–M23, determined from crystallographically independent molecules in four different crystals with three different antagonists bound. These structures are all in the inactive R state and show clear electron density for cytoplasmic loop 3 linking transmembrane helices 5 and 6 that had not been seen previously. Despite significantly different crystal packing interactions, there are only two distinct conformations of the cytoplasmic end of helix 6, bent and straight. In the bent conformation, the Arg139-Glu285 salt bridge is present, as in the crystal structure of dark-state rhodopsin. The straight conformation, observed in previously solved structures of β-receptors, results in the ends of helices 3 and 6 being too far apart for the ionic lock to form. In the bent conformation, the R
3.50
 - E
6.30
distance is significantly longer than in rhodopsin, suggesting that the interaction is also weaker, which could explain the high basal activity in
β
1
AR compared to rhodopsin. Many mutations that increase the constitutive activity of G-protein-coupled receptors are found in the bent region at the cytoplasmic end of helix 6, supporting the idea that this region plays an important role in receptor activation.
Effect of biaxial strain on half-metallicity of transition metal alloyed zinc-blende ZnO and GaAs: a first-principles study
Authors: Chen Li-Juan , Tian Ren-Yu , Yang Xiao-Bao , Zhao Yu-Jun
Published: May 2011

The electronic structure, magnetic and half-metallic properties of transitional metal (TM)-alloyed zinc-blende ZnO and GaAs (TM = Cr, Mn, Fe, Co, Ni) thin films with biaxial strains on the (0 0 1) plane are studied by density functional theory and beyond. Here, we focus on two simple layer-by-layer delta doping structures with the TM substituting along the (1 0 0) planes (type-I) and (0 0 1) planes (type-II). We find that the Fe-, Co- and Ni-alloyed GaAs, Mn- and Fe-alloyed ZnO, and Co-alloyed ZnO(II) show antiferromagnetic (AFM) states, while Ni-alloyed ZnO(I) and Cr-alloyed GaAs show ferromagnetic (FM) coupling independent of the biaxial strain within 25% along the (0 0 1) plane. For the systems of Cr-alloyed ZnO, Co-alloyed ZnO(I), Ni-alloyed ZnO(II) and Mn-alloyed GaAs(I, II), the strain from the substrate will induce a phase transition from AFM to FM states. The Co-alloyed ZnO(I), Ni-alloyed ZnO(I, II) and Cr-alloyed GaAs(I, II) systems are demonstrated to be half-metallic from the generalized gradient approximation (GGA) calculations. The Cr-alloyed ZnO and Mn-alloyed GaAs systems also show robust half-metallicity with a large spin-flip gap by a GGA + U description, although their half-metallicity disappears with the standard GGA description.
Tuning of electron g factors by electric fields in asymmetric InAs quantum dot molecules
Authors: Shang Deshuang , Wang Jiqing , Mao Huibing , Zhao Qiang , Yang Pingxiong , Zhu Ziqiang , Chu Junhao
Published: May 2011

Most self-assembled quantum dot molecules (QDMs) are composed of dots of different sizes stemming from imperfect control of crystal growth. In this paper we use the intrinsic structural asymmetry to tune spin-polarized states by reversing electric fields. We calculate electron g factors of InAs/GaAs QDMs with inequivalent dots under external electric fields. The g factor in the asymmetric system exhibits remarkable tunability under the forward applied field. In contrast, it is not very sensitive to the backward electric field within the resonant region. Hence, different spin-polarized states can be switched by reversing an applied field. Furthermore, g factors for both bonding and anti-bonding states can be tuned to zero under the same positive field (6.6 mV nm−1) in the asymmetric QDM.
Tribological properties of oleic acid-modified graphene as lubricant oil additives
Authors: Zhang Wei , Zhou Ming , Zhu Hongwei , Tian Yu , Wang Kunlin , Wei Jinquan , Ji Fei , Li Xiao , Li Zhen , Zhang Peng , Wu Dehai
Published: May 2011

Liquid phase exfoliated graphene sheets were modified by oleic acid and dispersed in lubricant oils as additives. The tribological behaviours of graphene-contained oils were investigated using a four-ball tribometer. The lubricant with optimized graphene concentrations of 0.02–0.06 wt% showed enhanced friction and anti-wear performance, with friction coefficient and wear scar diameter reduced by 17% and 14%, respectively.