bluuebunny/crossref_metadata_2025 huggingface dataset:
Simultaneous partitioning of silicon and oxygen into the Earth's core during early Earth differentiation
Authors: Tsuno Kyusei , Frost Daniel J. , Rubie David C.
Published: November 2012

Silicon and oxygen are potential light elements in the Earth's core and may be involved in metal‐silicate reactions at the present day core‐mantle boundary. We have performed multianvil experiments at 25 GPa and 2770–3080 K to understand the simultaneous partitioning of these elements between liquid iron–rich metal and silicate melt. The presence of O in liquid Fe at high temperatures influences the partitioning of Si, causing more Si to partition into the metal than would be expected based on lower temperature measurements. Although Si and O are mutually exclusive in Fe metal at <3000 K, the level at which both element concentrations are similar in the liquid metal rises above 1 wt % at >3000 K. We have developed a thermodynamic model based on these experiments that accounts for the interaction between O and Si in the liquid metal. Comparison between this model and the previous results of diamond‐anvil cell experiments up to 71 GPa indicates very little pressure dependence but a strong temperature dependence for O and Si partitioning. Our model predicts that subequal concentrations of Si and O, sufficient to explain the outer core density deficit, would have partitioned into core‐forming metal if equilibration occurred between the metal and a magma ocean with a bulk silicate Earth composition at an average depth of ~1200 km (~50 GPa and ~3300 K). An O‐ and Si‐enriched buoyant layer may have developed at the top of the outer core as a result of subsequent equilibration with the overlying mantle.
Enhanced transfer of terrestrially derived carbon to the atmosphere in a flooding event
Authors: Bianchi Thomas S. , Garcia‐Tigreros Fenix , Yvon‐Lewis Shari A. , Shields Michael , Mills Heath J. , Butman David , Osburn Christopher , Raymond Peter , Shank G. Christopher , DiMarco Steven F. , Walker Nan , Reese Brandi Kiel , Mullins‐Perry Ruth , Quigg Antonietta , Aiken George R. , Grossman Ethan L.
Published: November 2012

Rising CO2concentration in the atmosphere, global climate change, and the sustainability of the Earth's biosphere are great societal concerns for the 21st century. Global climate change has, in part, resulted in a higher frequency of flooding events, which allow for greater exchange between soil/plant litter and aquatic carbon pools. Here we demonstrate that the summer 2011 flood in the Mississippi River basin, caused by extreme precipitation events, resulted in a “flushing” of terrestrially derived dissolved organic carbon (TDOC) to the northern Gulf of Mexico. Data from the lower Atchafalaya and Mississippi rivers showed that the DOC flux to the northern Gulf of Mexico during this flood was significantly higher than in previous years. We also show that consumption of radiocarbon‐modern TDOC by bacteria in floodwaters in the lower Atchafalaya River and along the adjacent shelf contributed to northern Gulf shelf waters changing from a net sink to a net source of CO2to the atmosphere in June and August 2011. This work shows that enhanced flooding, which may or may not be caused by climate change, can result in rapid losses of stored carbon in soils to the atmosphere via processes in aquatic ecosystems.
Revised Eocene‐Oligocene kinematics for the West Antarctic rift system
Authors: Granot R. , Cande S. C. , Stock J. M. , Damaske D.
Published: November 2012

Past plate motion between East and West Antarctica along the West Antarctic rift system had important regional and global implications. Although extensively studied, the kinematics of the rift during Eocene‐Oligocene time still remains elusive. Based on a recent detailed aeromagnetic survey from the Adare and Northern Basins, located in the northwestern Ross Sea, we present the first well‐constrained kinematic model with four rotations for Anomalies 12o, 13o, 16y, and 18o (26.5–40.13 Ma). These rotation poles form a cluster suggesting a stable sense of motion during that period of time. The poles are located close to the central part of the rift implying that the local motion varied from extension in the western Ross Sea sector (Adare Basin, Northern Basin, and Victoria Land Basin) to dextral transcurrent motion in the Ross Ice Shelf and to oblique convergence in the eastern end of the rift zone. The results confirm previous estimates of 95 km of extension in the Victoria Land Basin.
Toward quantifying discrete groundwater discharge from frozen seepage faces using thermal infrared images
Authors: Pandey Priyanka , Gleeson Tom , Baraer Michel
Published: November 2012

Frozen groundwater seeps from discrete features, such as fractures and faults, are common along steep faces of cliffs, mines, quarries, and road cuts in cold environments at high elevations and latitudes. Our objective is to test whether thermal infrared imaging can be used to quantify groundwater discharge from such discrete features in freezing conditions. Discrete seeps and freezing cliff faces were simulated in a cold room laboratory with a systematic series of experiments captured through infrared imaging. Two zones of distinct surface temperatures were observed at the ice surface: a zone of relatively warm and constant surface temperature above a zone with high thermal gradients. Experimental conditions impacted the length of the relative warm zone. A strong correlation is observed between length of the relative warm zone and the discharge rate suggesting that groundwater discharge from discrete features could be quantified using noninvasive infrared imaging.
Seismic anisotropy of subducting oceanic uppermost mantle from fossil spreading
Authors: Audet Pascal
Published: November 2012

Identifying the sources of seismic anisotropy in subduction zone forearcs is key to understanding mantle deformation processes. Current models based on the interpretation of shear‐wave splitting measurements favor the flow‐induced alignment of olivine crystals around down‐going slabs or the presence of foliated serpentine minerals due to subduction‐related processes, thereby neglecting fossil slab fabric as a significant source of anisotropy. We use seismic receiver functions to show evidence for strong anisotropy within anhydrous uppermost mantle of subducting oceanic plates in the forearcs of Nankai, Cascadia, Mexico, and Costa Rica subduction zones. Seismic anisotropy models from the inversion of receiver function waveforms are consistent with fossil fabric generated at spreading ridges.
The vertical structure of Jupiter's equatorial zonal wind above the cloud deck, derived using mesoscale gravity waves
Authors: Watkins C. , Cho J. Y‐K.
Published: November 2012

Data from the Galileo Probe, collected during its descent into Jupiter's atmosphere, is used to obtain a vertical profile of the zonal wind from ~0.5 bar (upper troposphere) to ~0.1 µbar (lower thermosphere) at the probe entry site. This is accomplished by constructing a map of gravity wave Lomb‐Scargle periodograms as a function of altitude. The profile obtained from the map indicates that the wind speed above the visible cloud deck increases with height to ~150 m s‐1 and then levels off at this value over a broad altitude range. The location of the turbopause, as a region of wide wave spectrum, is also identified from the map. In addition, a cross‐equatorial oscillation of a jet, which has previously been linked to the QQO in the stratosphere, is suggested by the profile.
Modeling the impact of reduced sea ice cover in future climate on the Baltic Sea biogeochemistry
Authors: Eilola K. , Mårtensson S. , Meier H. E. M.
Published: November 2012

In a warming future climate, the sea ice cover is expected to decrease, with very likely large consequences for the marine ecosystem. We investigated the impact of future sea ice retreat on the Baltic Sea biogeochemistry at the end of the century, using an ensemble of regionalized global climate simulations. We found that the spring bloom will start by up to one month earlier and winds and wave‐induced resuspension will increase, causing an increased transport of nutrients from the productive coastal zone into the deeper areas. The internal nutrient fluxes do not necessarily increase because they also depend on oxygen and temperature conditions of the bottom water. Winter mixing increases in areas having reduced ice cover and in areas having reduced stratification due to increased freshwater supply. The reduced sea ice cover therefore partly counteracts eutrophication because increased vertical mixing improves oxygen conditions in lower layers.
Evidence of gravity wave ducting in the mesopause region from airglow network observations
Authors: Suzuki S. , Shiokawa K. , Otsuka Y. , Kawamura S. , Murayama Y.
Published: November 2012

We present observational evidence of gravity wave ducting and show, for the first time, that the ducting occurs over large horizontal distances in the mesopause region. An optical network of four all‐sky imagers in Japan identified two‐dimensional patterns of small‐scale gravity wave bands in OH airglow images on 13 June 2004. The wave signatures clearly showed northward propagation of more than 1800 km over a wide range of latitudes. The horizontal wavelength, horizontal phase speed, and wave period were estimated from the airglow data as 33.4 km, 42.8 m s−1, and 13.4 min, respectively. The wave structure lasted for the whole 5‐h airglow observation period. Simultaneous MF radar wind data and TIMED/SABER measurements suggested that the wave was trapped and ducted at the airglow height. The ducting likely contributed to the remarkable coherence of the wave as it propagated northward.
Nature of axial tail instability and bubble‐blob formation in near‐Earth plasma sheet
Authors: Zhu P. , Raeder J. , Hegna C. C. , Sovinec C. R.
Published: November 2012

Previous global magnetohydrodynamic (MHD) simulations of substorm events have identified the dynamic presence of an axial tail instability that is uniform in the dawn‐dusk direction in the near‐Earth plasma sheet. The axial tail instability is found to be a major cause of the initial growing MHD force imbalance on closed field lines prior to the subsequent magnetic reconnection and substorm expansion onset processes. In this work, energy principle analysis indicates that a two‐dimensional thin current sheet configuration in the magnetotail is typically stable to the axial mode within the framework of ideal MHD model. However, linear resistive MHD calculations find axial tail instabilities on closed field lines in the generalized Harris sheet configurations. The properties of these instabilities are similar to the axial tail modes observed in the global MHD simulations. The axial tail mode is unstable in regimes of low Lundquist number and regions with small normal component of magnetic field. Such resistive axial tail instability would by many researchers be considered as tearing instability in a two‐dimensional tail configuration. Unlike the conventional tearing mode of Harris sheet, the linear axial tail instability does not involve any reconnection process. Instead, the nature of the mode is dominantly a slippage process among neighboring flux tubes as facilitated by resistive dissipation. A natural consequence of the axial tail instability is shown to be the formation of bubble‐blob pairs in the pressure and entropy profiles in the near‐Earth plasma sheet.
MHD simulation of the inner‐heliospheric magnetic field
Authors: Wiengarten T. , Kleimann J. , Fichtner H. , Cameron R. , Jiang J. , Kissmann R. , Scherer K.
Published: November 2012

Maps of the radial magnetic field at a heliocentric distance of 10 solar radii are used as boundary conditions in the MHD code CRONOS to simulate a three‐dimensional inner‐heliospheric solar wind emanating from the rotating Sun out to 1 AU. The input data for the magnetic field are the result of solar surface flux transport modeling using observational data of sunspot groups coupled with a current‐sheet source surface model. Among several advancements, this allows for higher angular resolution than that of comparable observational data from synoptic magnetograms. The required initial conditions for the other MHD quantities are obtained following an empirical approach using an inverse relation between flux tube expansion and radial solar wind speed. The computations are performed for representative solar minimum and maximum conditions, and the corresponding state of the solar wind up to the Earth's orbit is obtained. After a successful comparison of the latter with observational data, they can be used to drive outer‐heliospheric models.
The role of transient ion foreshock phenomena in driving Pc5 ULF wave activity
Authors: Hartinger M. D. , Turner D. L. , Plaschke F. , Angelopoulos V. , Singer H.
Published: November 2012

The ion foreshock is a source of energy for magnetospheric ULF waves, but it is usually only considered effective at driving ULF waves with frequencies above the Pc5 (2–7 mHz) range. We present observations for an 8 h high speed solar wind interval on 14 July 2008 during which three distinct types of transient ion foreshock phenomena (TIFP) were observed just upstream of the dayside bow shock. We demonstrate that TIFP generate global magnetospheric Pc5 ULF waves with amplitudes as large as 10 mV/m in the electric field and 10 nT in the magnetic field. We characterize the magnetospheric ULF response to several different TIFP that occur during this interval, including the first report of the ULF response to a foreshock bubble. Using a novel spacecraft configuration, we find that the local time with the highest Pc5 wave amplitude is closely related to the location of the ion foreshock. Statistical studies of Pc5 ULF wave activity, other case studies of ULF waves driven by processes in the ion foreshock, and recent theoretical and simulation work on TIFP place these results in context: TIFP are an important energy source for Pc5 ULF waves in the magnetosphere.
Kinetic analysis of the energy transport of bursty bulk flows in the plasma sheet
Authors: Cao Jinbin , Ma Yuduan , Parks George , Reme Henri , Dandouras Iannis , Zhang Tielong
Published: November 2012

The energy transport of bursty bulk flows (BBFs) is very important to the understanding of substorm energy transport. Previous studies all use the MHD bulk parameters to calculate the energy flux density of BBFs. In this paper, we use the kinetic approach, i.e., ion velocity distribution function, to study the energy transport of an earthward bursty bulk flow observed by Cluster C1 on 30 July 2002. The earthward energy flux density calculated using kinetic approach QKx is obviously larger than that calculated using MHD bulk parameters QMHDx. The mean ratio QKx/QMHDx in the flow velocity range 200–800 km/s is 2.7, implying that the previous energy transport of BBF estimated using MHD approach is much underestimated. The underestimation results from the deviation of ion velocity distribution from ideal Maxwellian distribution. The energy transport of BBF is mainly provided by ions above 10 keV although their number density Nf is much smaller than the total ion number density N. The ratio QKx/QMHDx is basically proportional to the ratio N/Nf. The flow velocity v(E) increases with increasing energy. The ratio Nf/N is perfectly proportional to flow velocity Vx. A double ion component model is proposed to explain the above results. The increase of energy transport capability of BBF is important to understanding substorm energy transport. It is inferred that for a typical substorm, the ratio of the energy transport of BBF to the substorm energy consumption may increase from the previously estimated 5% to 34% or more.
Ab initio investigation on the high‐temperature thermodynamic properties of Fe3+‐bearing MgSiO3 perovskite
Authors: Tsuchiya Taku , Wang Xianlong
Published: November 2012

High‐pressure (P) and high‐temperature (T) thermodynamics and spin transition of Fe3+‐bearing MgSiO3 perovskite (Pv) are investigated by means of the internally consistent LDA + U method combined with the lattice dynamics method. Fe3+ is found to contribute mainly to the low frequency phonons. The spin transition of iron in the B site occurs at 55 GPa at 300 K and from ~75 to ~90 GPa at lower mantle temperatures. Although high‐spin Fe3+ expands the volume of Pv, most of the bulk thermodynamic properties of Pv are insensitive to Fe3+ incorporation at least at XFe2O3 = 0.0625, with the exception of the Grüneisen parameter. The calculated properties are in good agreement with room temperature experimental data, but a significant increase suggested in the isothermal bulk modulus is not predicted. Results clearly demonstrate that Fe3+‐bearing perovskite alone does not reproduce the density and the bulk sound velocity of the Earth's lower mantle simultaneously.
Coordinated investigation of summer time mid‐latitude descending E layer (Es) perturbations using Na lidar, ionosonde, and meteor wind radar observations over Logan, Utah (41.7°N, 111.8°W)
Authors: Yuan Tao , Fish C. , Sojka J. , Rice D. , Taylor M. J. , Mitchell N. J.
Published: November 2012

It is well known that there is a strong correlation between the formation of a descending sporadic E layer (Es) and the occurrence of large upper atmospheric zonal wind shears, most likely driven by solar thermal tides and/or gravity waves. We present new results of Es perturbation events captured between 13 and 17 July 2011 (UT days 194–198) as part of a coordinated campaign using a wind/temperature Na lidar at Utah State University [41.7ºN, 111.8°W], and a Canadian Advanced Digital Ionosonde (CADI; Scientific Instrumentation Ltd., Saskatoon, Saskatchewan, Canada) and SkiYMet meteor wind radar, both located at nearby Bear Lake Observatory [41.9°N, 111.4°W]. During this period, the CADI detected strong descending Es on 2 days (195 and 197) when large modulations of the top‐side mesospheric Na layer occurred in synchronism with strong oscillations in the ionosonde E region echoes. A weakening in the descending E layer echoes was observed on the other 2 days (196 and 198) coincident with a large reduction in the zonal diurnal and semidiurnal amplitudes above 95 km. Both tidal components were found to have comparable contributions to the total zonal wind shear that was critical for Es formation and its downward propagation. Further investigation indicates that the weakening tidal amplitudes and the occurrence of the Es events were also influenced by a strong quasi‐two‐day period modulation, suggesting significant quasi‐two‐day wave (QTDW) interactions with the tides. Indeed, a nonlinear, wave‐wave interaction‐induced 16‐hour period child wave was also detected, with amplitude comparable to that of the prevailing tides. These interaction processes and their associated effects are consistent with earlier Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model studies of nonlinear interactions between the migrating tidal waves and the QTDW and were probably responsible for the observed damping of the tidal amplitudes resulting in the disruption of the Es.
A method for specifying atmospheric gravity wavefields for long‐range infrasound propagation calculations
Authors: Drob D. P. , Broutman D. , Hedlin M. A. , Winslow N. W. , Gibson R. G.
Published: November 2012

Two important challenges in infrasound propagation physics are (1) to explain frequently observed infrasound signals in the classical near‐field shadow zones and (2) to accurately predict observed waveform amplitude and signal duration. For these problems, the role that small‐scale internal atmospheric gravity wave fluctuations play has recently been realized. This paper provides a methodology for representing small‐scale internal gravity wave fluctuations which is suitable for infrasound propagation calculations. Adapted from the numerical weather prediction and climate modeling communities, the resulting stochastic gravity wave noise field model is three‐dimensional, time dependent, and self‐consistent with the atmospheric background state. To illustrate the methodology the resultant gravity wavefields are applied to ray‐trace simulations of observed infrasound travel times for a dense seismic network in the Western United States which recorded infrasound signals from a large surface explosion.
Improving the temporal and spatial distribution of CO2 emissions from global fossil fuel emission data sets
Authors: Nassar Ray , Napier‐Linton Louis , Gurney Kevin R. , Andres Robert J. , Oda Tomohiro , Vogel Felix R. , Deng Feng
Published: November 2012

Through an analysis of multiple global fossil fuel CO2 emission data sets, Vulcan emission data for the United States, Canada's National Inventory Report, and NO2 variability based on satellite observations, we derive scale factors that can be applied to global emission data sets to represent weekly and diurnal CO2 emission variability. This is important for inverse modeling and data assimilation of CO2, which use in situ or satellite measurements subject to variability on these time scales. Model simulations applying the weekly and diurnal scaling show that, although the impacts are minor far away from sources, surface atmospheric CO2 is perturbed by up to 1.5−8 ppm and column‐averaged CO2 is perturbed by 0.1−0.5 ppm over some major cities, suggesting the magnitude of model biases for urban areas when these modes of temporal variability are not represented. In addition, we also derive scale factors to account for the large per capita differences in CO2 emissions between Canadian provinces that arise from differences in per capita energy use and the proportion of energy generated by methods that do not emit CO2, which are not accounted for in population‐based global emission data sets. The resulting products of these analyses are global 0.25° × 0.25° gridded scale factor maps that can be applied to global fossil fuel CO2 emission data sets to represent weekly and diurnal variability and 1° × 1° scale factor maps to redistribute spatially emissions from two common global data sets to account for differences in per capita emissions within Canada.
A global analysis on the view‐angle dependence of plane‐parallel oceanic liquid water cloud optical thickness using data synergy from MISR and MODIS
Authors: Liang Lusheng , Girolamo Larry Di
Published: November 2012

We examine the viewing zenith angle dependent bias (VZA bias) in warm cloud optical thickness (τ) retrieved from a plane‐parallel approach applied to fused Moderate Resolution Imaging Spectroradiometer (MODIS) and Multi‐angle Imaging SpectroRadiometer (MISR) data for the months of January and July between 2001 and 2008. The near‐simultaneous multiple view‐angle observations from MISR offers many advantages over previous τ‐VZA bias studies: 1) The analysis no longer requires seasonal and latitudinal cloud invariant assumptions, 2) consistent cloudy scene identification with VZA, 3) stratification of VZA‐bias with scene characteristics, and 4) a greater range of sun‐view geometries. Contrasting results between previous studies are resolved through careful consideration of the relative azimuth angle (RAZ) between sun and view. Relative to nadir‐retrieved τ, τ increases in both forward‐ and backscatter directions with higher value in backscatter directions for solar zenith angle (SZA) < ~40°. For SZA > ~40°, τ increases with increasing VZA in backscatter directions and strongly decreases in forward‐scatter directions. For the most oblique views, ~40–100% absolute monthly mean differences relative to nadir‐retrieved τ is common. This behavior is strongly tied to the sampled RAZ and explained based on three factors tied to the spatial heterogeneity of clouds. These factors also explain the behavior of the τ‐VZA bias when stratified by nadir‐retrieved τ and spatial heterogeneity, even in the thin‐cloud limit where sun‐glint effects are evident. We also observe an underestimation of τ relative to nadir in the rainbow‐scattering directions and attribute it to an overestimation of the cloud‐drop effective radius retrieved from MODIS due to cloud heterogeneity. There remains a need to quantify the bias in nadir‐retrieved τ as a function of SZA and spatial heterogeneity as a step toward providing bias correction over a wide range of sun‐view geometries.
Identifying tropospheric baseline air masses at Mauna Loa Observatory between 2004 and 2010 using Radon‐222 and back trajectories
Authors: Chambers Scott D. , Zahorowski Wlodek , Williams Alastair G. , Crawford Jagoda , Griffiths Alan D.
Published: November 2012

We use 7 years of hourly radon observations at Mauna Loa Observatory (MLO), together with 10‐day back trajectories, to identify baseline air masses at the station. The amplitude of the annual MLO radon cycle, based on monthly means, was 98 mBq m–3 (39 –137 mBq m–3), with maximum values in February (90th percentile 330 mBq m–3) and minimum values in August (10th percentile 8.1 mBq m–3). The composite diurnal radon cycle (amplitude 49 mBq m–3) is discussed with reference to the influences of local flow features affecting the site, and a 3‐hour diurnal sampling window (0730–1030 HST) is proposed for observing the least terrestrially influenced tropospheric air masses. A set of 763 baseline events is selected, using the proposed sampling window together with trajectory information, and presented along with measured radon concentrations as a supplement. This data set represents a resource for the selection of baseline events at MLO for use with a range of trace species. A reduced set of 196 “deep baseline” events occurring in the July–September window is also presented and discussed. The distribution (10th/50th/90th percentile) of radon in deep‐baseline events (8.7/29.2/66.1 mBq m–3) was considerably lower than that for the overall set of 763 baseline events (12.3/40.8/104.1 mBq m–3). Results from a simple budget calculation, using sonde‐derived mixing depths and literature‐based estimates of oceanic radon flux and radon concentrations in the marine boundary layer, indicate that the main source of residual radon in the lower troposphere under baseline conditions at MLO is downward mixing from aged terrestrial air masses in the upper troposphere.
Variability of extratropical ozone stratosphere–troposphere exchange using microwave limb sounder observations
Authors: Olsen Mark A. , Douglass Anne R. , Kaplan Trevor B.
Published: November 2012

The extratropical stratosphere–troposphere exchange (STE) of ozone from 2005 to 2010 is estimated by combining Microwave Limb Sounder ozone observations and MERRA reanalysis meteorological fields in an established direct diagnostic framework. The multiyear mean ozone STE is 275 Tg yr−1 and 214 Tg yr−1 in the Northern and Southern Hemispheres, respectively. The year‐to‐year variability is greater in the Northern Hemisphere, where the difference between the highest and the lowest annual flux is 15% of the multiyear mean compared with 6% in the Southern Hemisphere. Variability of lower stratospheric ozone and variability of the net mass flux both contribute to interannual variability in the Northern Hemisphere ozone flux. The flux across the extratropical 380 K surface determines the amount of flux across the extratropical tropopause, and the greatest seasonal variability of the 380 K ozone flux occurs in the late winter/early spring, around the time of greatest flux. Both the mass flux and the ozone mixing ratios on the 380 K surface show recurring spatial patterns, but interannual variability of these quantities and their alignment contribute to the ozone flux variability. The spatial and temporal variability are not well represented when zonal and/or monthly mean fields are used to calculate the ozone STE, although this results in a small high bias of the seasonal amplitude and annual magnitude. If the climatological variability over these 6 years is representative, the estimated number of years required to detect a 2 − 3% decade−1 trend in ozone STE using this diagnostic is 35 − 39 years.
A combined laboratory and modeling study of the infrared extinction and visible light scattering properties of mineral dust aerosol
Authors: Alexander Jennifer M. , Laskina Olga , Meland Brian , Young Mark A. , Grassian Vicki H. , Kleiber Paul D.
Published: November 2012

Optical properties, including infrared (IR) extinction and visible light scattering of mineral dust aerosol, are measured experimentally and compared to modeling results using T‐matrix theory. The work includes studies of complex, authentic field samples of Saharan sand, Iowa loess, and Arizona road dust (ARD). Particle size distributions and aerosol optical properties are measured simultaneously. These authentic dust samples are treated as external mixtures of mineral components. The mineral compositions for the Saharan sand and Iowa loess samples have been reported by Laskina et al. [2012], and the mineralogy for ARD is derived here using a similar method. T‐matrix‐based simulations, using measured particle size distributions and a priori particle shape models, are carried out for each mineral component of the authentic samples. The simulated optical properties for the complex dust mixtures are obtained by a weighted average of the properties of the mineral components, based on a given sample mineralogy. T‐matrix simulations are then directly compared with the measured IR extinction spectra and visible light scattering phase function and linear polarization profiles for each sample. Generally good agreement between experiment and theory is obtained. Model simulations that account for differences in particle shape with mineralogy and include a broad range of eccentric spheroid shape parameters offer a significant improvement over more commonly applied models that ignore variations in particle shape with size or mineralogy and include only a moderate range of shape parameters.
Water interactions with micronized lunar surrogates JSC‐1A and albite under ultra‐high vacuum with application to lunar observations
Authors: Poston Michael J. , Grieves Gregory A. , Aleksandrov Alexandr B. , Hibbitts Charles A. , Darby Dyar M. , Orlando Thomas M.
Published: November 2012

Interactions of molecular water with two lunar regolith surrogates (micronized JSC‐1A and albite) were examined using temperature program desorption (TPD) and diffuse reflectance infrared Fourier transform spectroscopy. TPD revealed water desorption during initial heating to 750 K under ultrahigh vacuum and diffuse reflectance infrared Fourier transform spectroscopy indicated possible water formation via recombinative desorption of native hydroxyls above 425 ± 25 K. Dissociative chemisorption of water (i.e., formation of surface hydroxyl sites) was not observed on laboratory time scales after controlled dosing of samples (initially heated above 750 K) with 0.2–500 L exposures of water. However, preheated samples of both types of surrogates were found to have a distribution of molecular water chemisorption sites, with albite having at least twice as many as the JSC‐1A samples by mass. A fit to the TPD data yields a distribution function of desorption activation energies ranging from ~ 0.45 to 1.2 eV. Using the fitted distribution function as an initial condition, the TPD process was simulated on the time scale of a lunation.
Sand transport beneath waves: The role of progressive wave streaming and other free surface effects
Authors: Kranenburg Wouter M. , Ribberink Jan S. , Schretlen Jolanthe J. L. M. , Uittenbogaard Rob E.
Published: November 2012

Recent large‐scale wave flume experiments on sheet‐flow sediment transport beneath Stokes waves show more onshore‐directed sediment transport than earlier sheet‐flow experiments in oscillating flow tunnels. For fine sand, this extends to a reversal from offshore‐ (tunnels) to onshore (flumes)‐directed transport. A remarkable hydrodynamic mechanism present in flumes (with free water surface), but not in tunnels (rigid lid), is the generation of progressive wave streaming, an onshore wave boundary layer current. This article investigates whether this streaming is the full explanation of the observed differences in transport. In this article, we present a numerical model of wave‐induced sand transport that includes the effects of the free surface on the bottom boundary layer. With these effects and turbulence damping by sediment included, our model yields good reproductions of the vertical profile of the horizontal (mean) velocities, as well as transport rates of both fine and medium sized sediment. Similar to the measurements, the model reveals the reversal of transport direction by free surface effects for fine sand. A numerical investigation of the relative importance of the various free surface effects shows that progressive wave streaming indeed contributes substantially to increased onshore transport rates. However, especially for fine sands, horizontal gradients in sediment advection in the horizontally nonuniform flow field also are found to contribute significantly. We therefore conclude that not only streaming, but also inhomogeneous sediment advection should be considered in formulas of wave‐induced sediment transport applied in morphodynamic modeling. We propose a variable time‐scale parameter to account for these effects.
Intrastream variability in solute transport: Hydrologic and geomorphic controls on solute retention
Authors: Patil Sopan , Covino Timothy P. , Packman Aaron I. , McGlynn Brian L. , Drummond Jennifer D. , Payn Robert A. , Schumer Rina
Published: November 2012

Hydrologic fluctuations and geomorphic heterogeneity are expected to produce substantial variability in solute transport within rivers. However, this variability has not been sufficiently explored due to the limited availability of solute injection data in most rivers. Here, we analyzed 81 tracer injection breakthrough curves (BTCs) along Stringer Creek, a 5.5 km2watershed in Montana. BTC measurements were obtained for three baseflow conditions at 27 reaches along a 2600 m stream channel. BTCs in upstream reaches (first 1400 m) had receding tails with shallow slopes, indicating high solute retention. Conversely, BTCs in downstream reaches (1400 to 2600 m) had receding tails with steeper slopes, indicating low solute retention relative to upstream reaches. Difference in BTC tails along the stream channel coincided with changes in channel morphology and bedrock geology. Specifically, channel slope increases from 5–6% (upstream) to 9% (downstream), channel sinuosity decreases from a maximum of 1.32 (upstream) to 1.02 (downstream), and the underlying bedrock changes from sandstone (upstream) to granite‐gneiss (downstream). Importantly, intrastream differences in BTC tails were distinctly observable only during the two lowest baseflow conditions. Spatial variability of BTC tail‐slopes was most sensitive to changes in local discharge at low flow, and to changes in channel sinuosity at high flow. BTC tail‐slopes varied temporally with local discharge and velocity at upstream reaches, but not at downstream reaches. These results suggest that local interactions between channel morphology and solute retention vary with hydrologic conditions, and that solute retention becomes more homogeneous at higher stream discharge.
A comprehensive sounding of the ionospheric HF radio link from Antarctica to Spain
Authors: Ads A. G. , Bergadà P. , Vilella C. , Regué J. R. , Pijoan J. L. , Bardají R. , Mauricio J.
Published: November 2012

Since 2003, our group has been investigating the performance of different transmission techniques for low‐power low‐interference High Frequency (HF) ionospheric communication systems. Specifically, we have focused on the link between the Spanish Antarctic Station (SAS) Juan Carlos I in Livingston Island and Ebro Observatory (OE) in Spain, in order to transmit the data gathered from some geomagnetic sensors. These transmission techniques require a valuable knowledge of the channel behavior, thus a comprehensive narrowband and wideband sounding of the ionospheric channel is needed. Some significant improvements both in the system and in the signal processing have been done to achieve this goal. The analysis time and the frequency band have been extended to 24 hours per day and to the whole HF band (2‐30 MHz). Moreover, new measurements of the absolute propagation time and the Doppler frequency shift are introduced. In this paper, the sounding results obtained using the new system are presented.
Space Weather and Challenges for Modern Society
Authors: Brekke Pål , Steen Roger , Onsager Terry , Wintoft Peter , Olaussen Alf , Pirjola Risto , Stauning Peter , Sundelius Bengt , Ohnstad Trond , Marti Luis
Published: November 2012

Key Points

Meeting summary after the OSLO TIEMS Space Weather Conference
A stochastic reconstruction framework for analysis of water resource system vulnerability to climate‐induced changes in river flow regime
Authors: Nazemi Alireza , Wheater Howard S. , Chun Kwok P. , Elshorbagy Amin
Published: November 2012

Key Points

Climate change causes shifts in flow regime

The shifts can be reconstructed

Canadian prairies is vulnerable to the regime shifts
Has the Time Come for Predictive Computer Modeling in CNS Drug Discovery and Development?
Authors: Geerts H , Spiros A , Roberts P , Carr R
Published: November 2012

We discuss whether a new paradigm, quantitative systems pharmacology (QSP), based on computational neuroscience modeling combined with proper drug target engagement and pharmacology, human pathology, imaging studies, and calibration and validation using clinical studies in human subjects might improve the success rate of central nervous systems research and development (CNS R&D) projects. We suggest that an improved understanding of neuronal circuit interactions using a humanized computer‐based integration of physiology and pharmacology knowledge can substantially de‐risk new CNS projects.

CPT: Pharmacometrics & Systems Pharmacology (2012) 1, e16; doi:10.1038/psp.2012.17; advance online publication 28 November 2012
Epidemiologic Advances in Spasmodic Dysphonia
Authors: Tanner Kristine
Published: November 2012

Recently research offers new insights into the pathogenesis, pathophysiology, and socioemotional implications of spasmodic dysphonia (SD). Among these advances are epidemiologic studies clarifying (1) SD onset and course, (2) SD risk factors, and (3) the relationships among SD course, treatment, and psychosocial impact. In this paper, I will provide a summary of recent epidemiologic and socioemotional research advances involving the onset, course, risk factors, and psychosocial impact of SD.
Behavioral Management of Unilateral Vocal Fold Paralysis and Paresis
Authors: Schneider Sarah L.
Published: November 2012

Purpose: In this article, I will summarize the process of selecting appropriate voice therapy candidates and relevant treatment techniques for patients with unilateral vocal fold paralysis or paresis.

Methods: I will present a review of the literature and pertinent clinical experience while laying out diagnostic tools, considerations for choosing voice therapy candidates, and specific therapy techniques that clinicians may employ. In addition, I highlight how these decisions are guided by a thorough behavioral diagnostic voice evaluation.

Results: There are a number of publications in the literature that discuss the role of voice therapy and the types of voice therapy techniques commonly used in treating vocal fold motion impairment. However, little efficacy data exist about the utility of voice therapy alone in this population.

Conclusions: Behavioral management of patients with vocal fold paralysis and paresis is widely accepted as part of the treatment process. With little efficacy data to support outcomes for specific voice therapy techniques alone with this patient population, we must continue to rely primarily on our clinical experience and outcomes from other populations to guide the therapeutic process.
Updates on Vocal Tremor and its Management
Authors: Barkmeier-Kraemer Julie
Published: November 2012

Vocal tremor is a neurogenic voice disorder characterized by a nearly periodic modulation in pitch and loudness during sustained phonation. This voicing pattern is the result of tremor affecting structures within the speech mechanism, resulting in modulation of lung pressure, phonation, articulation, and resonance during speaking. Speaking patterns in these individuals may be perceived as similar to spasmodic dysphonia or muscle tension dysphonia. The key to determining the presence of vocal tremor and distinguishing it from other voice disorders requires familiarity with the perceptual, acoustic, and physiologic patterns associated with vocal tremor during different voicing and speech contexts. Management of those with vocal tremor can be challenging because of its co-occurrence with other neurological disorders. The two most common methods for managing vocal tremor include pharmaceutical treatment, most commonly applied via injections of Botulinum Toxin Type A (Botox®), and behavioral modification of speaking patterns. The latter approach is in early clinical phases of research and has not yet been subjected to clinical trials. In this paper, I will summarize the clinical characteristics of vocal tremor in comparison to what is known about tremor in general and describe Botox® and behavioral approaches for managing individuals with this voice disorder.
Lumbago – Diagnostik
Authors: Artner Juraj
Published: November 2012

Kaum ein Symptom in der Humanmedizin ist so interdisziplinär vertreten und komplex wie der Rückenschmerz. Daher sind ein breites Fachwissen, interdisziplinäre differenzialdiagnostische Herangehensweise und adäquate strukturierte Abklärung und Patientenführung unumgänglich. Zur adäquaten Abklärung des Rückenschmerzes muss man zwischen akuten und chronischen Verläufen zu unterscheiden: Die Abklärung chronischer Schmerzen ist komplexer und erfolgt interdisziplinär. Unabhängig von seiner Fachrichtung sollte der Untersucher bei jedem Rückenschmerz eine Basisdiagnostik durchführen, bestehend aus Anamnese und Basisuntersuchung. Als Warnsignal („Red Flag“) gilt z.B. ein Sturz aus größerer Höhe, Tumoranamnese, B-Symptomatik, Ruheschmerz und neurologische Ausfälle. Als Provokationstests kommen u.a. der Iliosakral-Dehnugnstest, der Patrick-Fabere-Test und der Lasègue-Test infrage.
Ungewöhnlicher Leberabszess – Eine Mahlzeit mit schwerwiegenden Folgen
Authors: Eisner Friederike , Ladurner Ruth , Heuschmid Martin , Glatzle Jörg
Published: November 2012

Pyogene Leberabszesse äußern sich durch intermittierendes oder kontinuierliches Fieber und gegebenenfalls durch ihre verdrängende Wirkung. In der radiologischen Diagnostik stellen sich Leberabszesse als zystische Raumforderungen dar. Wichtige Ursachen sind z. B. eine aszendierende Cholangitis, septische Streuherde, parasitäre Abszesse oder Penetration. Der Krankheitsverlauf kann schleichend, aber auch akut und dramatisch sein. Prognosebestimmend ist die rasche Diagnose und Therapieeinleitung.
Wo ein Kläger, da ein Richter
Authors: Rojahn Julia
Published: November 2012

Nach einer spät diagnostizierten Appendizitis beschwert sich der Patient über die behandelnde Ärztin. Sie wird vor die Gutachterkommission der Ärztekammer geladen. Und obwohl sie sich nichts vorzuwerfen hat, wird das Verfahren eines ihrer unangenehmsten beruflichen Erlebnisse.
Für Sie gelesen – Buchtipps
Authors: Kainer Franz , Quabach Ralf , Petersen Steffen , Koch Peter , Just Birgit , Preuß Barbara
Published: November 2012

In dieser Rubrik stellen wir Ihnen interessante Neuerscheinungen vor – aus unterschiedlichen Fachgebieten, aber immer relevant für die Weiterbildung. In dieser Ausgabe:
Extremality conditions for generalized channels
Authors: Jenčová Anna
Published: November 2012

A generalized channel is a completely positive map that preserves trace on a given subspace. We find conditions under which a generalized channel with respect to a positively generated subspace J is an extreme point in the set of all such generalized channels. As a special case, this yields extremality conditions for quantum protocols. In particular, we obtain new extremality conditions for quantum 1-testers with 2 outcomes, which correspond to yes/no measurements on the set of quantum channels.
Algebro-geometric solutions to the modified Sawada-Kotera hierarchy
Authors: Wu Lihua , He Guoliang , Geng Xianguo
Published: November 2012

Based on solving the Lenard recursion equation and the zero-curvature equation, we derive the modified Sawada-Kotera (SK) hierarchy associated with a 3 × 3 matrix spectral problem. Resorting to the characteristic polynomial of Lax matrix for the modified SK hierarchy, we introduce a trigonal curve \documentclass[12pt]{minimal}\begin{document}$\mathcal {K}_{m-1}$\end{document}Km−1 and present the corresponding Baker-Akhiezer function and meromorphic function on it. The Abel map is introduced to straighten out the modified SK flows. With the aid of the property of the Baker-Akhiezer function and the meromorphic function and their asymptotic expansions, we arrive at their explicit Riemann theta function representations. Algebro-geometric solutions of the entire modified SK hierarchy are obtained by using asymptotic expansion of the meromorphic function and its Riemann theta function representation. As an application, we give two simple examples.
Joule heating and current-induced domain wall motion
Authors: Curiale J. , Lemaître A. , Niazi T. , Faini G. , Jeudy V.
Published: November 2012

We investigate numerically and experimentally the Joule heating produced by current pulses and its contribution to current-induced domain wall (DW) motion in a (Ga,Mn)As ferromagnetic semiconductor. Different thermal coupling between tracks and substrates are explored. A direct contact leads to a logarithmic transient temperature rise and a stationary state determined by the substrate thickness. The introduction of a low thermal conducting (Ga,In)As interlayer produces an additional temperature rise whose time variation and magnitude are analyzed. Experimentally, the measured temperature rises present a good agreement with predictions over more than four orders of magnitude in time for values of the heat conductivity and of the heat capacity close to those reported in the literature. The Joule heating is shown to produce non-linearities in the domain wall velocity versus current density characteristics. A correction of Joule heating is proposed and permits the identification of the flow regimes from a comparison of domain-wall dynamics in tracks presenting different pinning characteristics.
Global existence and energy decay of solutions for the wave equation with a time varying delay term in the weakly nonlinear internal feedbacks
Authors: Benaissa Abbes , Benaissa Abdelkader , Messaoudi Salim. A.
Published: November 2012

We consider the nonlinear wave equation in a bounded domain with a delay term in the weakly nonlinear internal feedback u″(x, t) − Δxu(x, t) + μ1σ(t)g1(u′(x, t)) + μ2σ(t)g2(u′(x, t − τ(t))) = 0 and prove the global existence of solutions in suitable Sobolev spaces by means of the energy method combined with the Faedo-Galerkin procedure under a certain relation between the weight of the delay term in the feedback, the weight of the term without delay and the speed of the delay. Furthermore, we study the asymptotic behavior of solutions using the multiplier method and some general weighted integral inequalities.