bluuebunny/crossref_metadata_2025 huggingface dataset:
Velocity‐porosity relationships for slope apron and accreted sediments in the Nankai Trough Seismogenic Zone Experiment, Integrated Ocean Drilling Program Expedition 315 Site C0001
Authors: Hashimoto Y. , Tobin H. J. , Knuth M.
Published: December 2010

In this study, we focused on the porosity and compressional wave velocity of marine sediments to examine the physical properties of the slope apron and the accreted sediments. This approach allows us to identify characteristic variations between sediments being deposited onto the active prism and those deposited on the oceanic plate and then carried into the prism during subduction. For this purpose we conducted ultrasonic compressional wave velocity measurements on the obtained core samples with pore pressure control. Site C0001 in the Nankai Trough Seismogenic Zone Experiment transect of the Integrated Ocean Drilling Program is located in the hanging wall of the midslope megasplay thrust fault in the Nankai subduction zone offshore of the Kii peninsula (SW Japan), penetrating an unconformity at ∼200 m depth between slope apron sediments and the underlying accreted sediments. We used samples from Site C0001. Compressional wave velocity from laboratory measurements ranges from ∼1.6 to ∼2.0 km/s at hydrostatic pore pressure conditions estimated from sample depth. The compressional wave velocity‐porosity relationship for the slope apron sediments shows a slope almost parallel to the slope for global empirical relationships. In contrast, the velocity‐porosity relationship for the accreted sediments shows a slightly steeper slope than that of the slope apron sediments at 0.55 of porosity. This higher slope in the velocity‐porosity relationship is found to be characteristic of the accreted sediments. Textural analysis was also conducted to examine the relationship between microstructural texture and acoustic properties. Images from micro‐X‐ray CT indicated a homogeneous and well‐sorted distribution of small pores both in shallow and in deeper sections. Other mechanisms such as lithology, clay fraction, and abnormal fluid pressure were found to be insufficient to explain the higher velocity for accreted sediments. The higher slope in velocity‐porosity relationship for accreted sediments can be explained by weak cementation, critical porosity or differences in loading history.
STEREO and Wind observations of a fast ICME flank triggering a prolonged geomagnetic storm on 5–7 April 2010
Authors: Möstl C. , Temmer M. , Rollett T. , Farrugia C. J. , Liu Y. , Veronig A. M. , Leitner M. , Galvin A. B. , Biernat H. K.
Published: December 2010

On 5 April 2010 an interplanetary (IP) shock was detected by the Wind spacecraft ahead of Earth, followed by a fast (average speed 650 km/s) IP coronal mass ejection (ICME). During the subsequent moderate geomagnetic storm (minimum Dst = −72 nT, maximum Kp = 8−), communication with the Galaxy 15 satellite was lost. We link images from STEREO/ SECCHI to the near–Earth in situ observations and show that the ICME did not decelerate much between Sun and Earth. The ICME flank was responsible for a long storm growth phase. This type of glancing collision was for the first time directly observed with the STEREO Heliospheric Imagers. The magnetic cloud (MC) inside the ICME cannot be modeled with approaches assuming an invariant direction. These observations confirm the hypotheses that parts of ICMEs classified as (1) long–duration MCs or (2) magnetic–cloud–like (MCL) structures can be a consequence of a spacecraft trajectory through the ICME flank.
Chemical processing does not always impair heterogeneous ice nucleation of mineral dust particles
Authors: Sullivan Ryan C. , Miñambres Lorena , DeMott Paul J. , Prenni Anthony J. , Carrico Christian M. , Levin Ezra J. T. , Kreidenweis Sonia M.
Published: December 2010

Exposing Arizona Test Dust (ATD) particles to nitric acid vapor in an aerosol flow tube impaired subsequent deposition ice nucleation below water‐saturation, but promoted condensation/immersion‐freezing on approach to water saturation and had no apparent impact on freezing of activated droplets above water saturation. The fraction of particles capable of nucleating ice at −30°C was determined using a continuous flow diffusion chamber. Exposure to HNO3 at 26% relative humidity with respect to water (RHw) reduced the fraction of particles subsequently nucleating ice to below our quantification limit in the deposition nucleation regime below 97% RHw, while leading to a sharper step‐wise increase in ice nucleation between 97–100% RHw compared to unreacted dust. These observations contrast with the effect of concentrated sulfuric acid condensation, which in most cases has been reported to reduce ice nucleation of ATD and other dusts both below and above water saturation.
Heterogeneous water table response to climate revealed by 60 years of ground water data
Authors: Weider Kaitlyn , Boutt David F.
Published: December 2010

Recent findings suggest that climate change will lead to modifications in the timing and nature of precipitation, giving rise to an altered hydrologic cycle. The response of subsurface hydrology to decadal climate and longer‐term climate change to date has been investigated via site specific analyses, modeling studies, and proxy analysis. Here we present the first instrumental long‐term regional compilation and analysis of the water table response to the last 60 years of climate in New England. Ground water trends are calculated as normalized anomalies and analyzed with respect to regional compiled precipitation, temperature, and streamflow. The time‐series display decadal patterns with ground water levels being more variable and lagging that of precipitation and streamflow pointing to site specific and non‐linear response to changes in climate. Recent trends (i.e., last 10 years) suggest statistically significant increasing water tables, which could lead to a higher risk for flooding in New England.
Dawn‐dusk oscillation of Saturn's conjugate auroral ovals
Authors: Nichols J. D. , Cowley S. W. H. , Lamy L.
Published: December 2010

We present observations of the oscillation of the dawn‐dusk locations of Saturn's northern and southern UV auroral ovals obtained using the Hubble Space Telescope during the 2009 equinoctial campaign. We determine the dawn‐dusk locations of the centers of the southern and northern auroral ovals from the mean of the dawnward and duskward extents of the emission, and order the computed locations by the phases of the respective SKR oscillations for each hemisphere. We show that statistically significant ∼1–2° oscillations of the dawn‐dusk location of the auroral ovals are evident, with the duskward displacement being in lagging quadrature with the SKR power. These results, the first to indicate that the location of the northern auroral oval oscillates, show that the cause of the oscillation is an external magnetospheric current system, and the sense of the oscillations is consistent with the expected displacement caused by magnetic perturbations observed throughout Saturn's magnetosphere.
Interaction of Saturn's magnetosphere and its moons: 3. Time variation of the Enceladus plume
Authors: Jia Y.‐D. , Russell C. T. , Khurana K. K. , Ma Y. J. , Kurth W. , Gombosi T. I.
Published: December 2010

The major momentum‐loading source in Saturn's magnetosphere, Enceladus, has been studied with seven Cassini flybys between 2005 and 2008. In this paper, we first use parameter tests with our 3‐D magnetohydrodynamic simulation to demonstrate and determine the sensitivity of the interaction to both electron impact rates and charge‐exchange rates. We also investigate the reasons behind our previous discovery that in the plume, within about two Enceladus radii of the plume's source, the momentum‐loading rates per unit ion and neutral density are orders of magnitude lower than at greater distances. We find that depletion of hot electrons and variations in charge‐exchange rates are two possible explanations for such a reduction of the momentum‐loading rates. Assisted by the Cassini observations, we use our understanding of the plasma interaction to determine the temporal variation of Enceladus' neutral plume, which is important in understanding its origin, as well as the geological evolution of this icy moon. We base our study on magnetometer observations during all seven flybys to present the first comparative analysis to all flybys in 2005 and 2008. It is found that the maximum variation in gas production rates is one third the largest rate. The plasma momentum‐loading rate ranges from 0.8 to 1.9 kg/s, which is consistent with previous studies.
Unique observations of a geomagnetic SI+ − SI− pair: Solar sources and associated solar wind fluctuations
Authors: Rastogi R. G. , Janardhan P. , Ahmed K. , Das A. C. , Bisoi Susanta K.
Published: December 2010

This paper describes the occurrence of a pair of oppositely directed sudden impulses (SI) in the geomagnetic field (ΔX) at ground stations, called SI+ − SI− pairs, that occurred between 1835 UT and 2300 UT on 23 April 1998. The SI+ − SI− pair was closely correlated with corresponding variations in the solar wind density, while solar wind velocity and the southward component of the interplanetary magnetic field (Bz) did not show any correspondence. Further, this event had no source on the visible solar disk. However, a rear‐side partial halo coronal mass ejection (CME) and an M1.4 class solar flare behind the west limb took place on 20 April 1998, the date corresponding to the traceback location of the solar wind flows. This event presents empirical evidence, which to our knowledge is the most convincing evidence for the association of specific solar events to the observations of an SI+ − SI− pair. In addition, it shows that it is possible for a rear‐side solar flare to propagate a shock toward the Earth.
In situ measurement of a newly created polar cap patch
Authors: Lorentzen D. A. , Moen J. , Oksavik K. , Sigernes F. , Saito Y. , Johnsen M. G.
Published: December 2010

The Investigation of Cusp Irregularities 2 sounding rocket was launched 5 December 2008 at 1035 UT. We present an overview of the associated solar wind and auroral conditions, and we look in detail at the relationship between poleward moving auroral forms (PMAFs) and the creation of polar cap patches using ground‐based optical and radar data as well as in situ data from the rocket payload. The solar wind was found to be dominated by a stable interplanetary magnetic field (IMF) Bz < 0 and by an IMF By > 0 situation. The aurora was characterized by a series of PMAFs throughout the period of interest. Associated with each PMAF were polar cap patches seen to emerge from the most poleward location of the PMAFs. On the basis of the available data, we present a conceptual model explaining the creation of the polar cap patches under the given solar wind and ionospheric conditions.
Self‐consistent particle simulation of whistler mode triggered emissions
Authors: Hikishima Mitsuru , Omura Yoshiharu , Summers Danny
Published: December 2010

Self‐consistent electromagnetic particle simulations were performed to analyze whistler mode triggered emissions in the magnetosphere. Triggering whistler mode waves injected at the magnetic equator induces a nonlinear absolute instability that results in rising tone emissions similar to natural whistler mode chorus emissions. The triggering wave causes a depletion of resonant electrons at the resonance velocity. The phase‐organized resonant electrons released by the triggering waves generate coherent waves that undergo nonlinear growth with increasing frequencies. The essential mechanism is the same as that for the generation of chorus emissions. Saturation of the nonlinear wave growth is caused by enhancement of resonant electrons at high pitch angles that have been trapped and guided along the resonance velocity by the triggered emissions. Because of the decreasing resonance velocity resulting from the increasing frequency, trapped electrons are accelerated to higher pitch angles. Saturation of the nonlinear wave growth thereby results in electron acceleration.
Electromagnetic pulses generated by meteoroid impacts on spacecraft
Authors: Close S. , Colestock P. , Cox L. , Kelley M. , Lee N.
Published: December 2010

Meteoroid impacts on spacecraft are known to cause mechanical damage, but their electrical effect on spacecraft systems are not well characterized. Several reported spacecraft anomalies are suggestive of an electrical failure associated with meteoroid impact. We present a theory to explain plasma production and subsequent electric fields occurring when a meteoroid strikes a spacecraft, ionizing itself and part of the spacecraft. This plasma, with a charge separation commensurate with different specie mobilities, can produce a strong electromagnetic pulse (EMP) at broad frequency spectra, potentially causing catastrophic damage if the impact is relatively near an area with low shielding or an open umbilical. Anomalies such as gyrostability loss can be caused by an EMP without any detectable momentum transfer due to small (<1 μg) particle mass. Subsequent plasma oscillations can also emit significant power and may be responsible for many reported satellite anomalies. The presented theory discusses both a dust‐free plasma expansion with coherent electron oscillation and a dusty plasma expansion with macroscopic charge separation.
Multipoint observation of fast mode waves trapped in the dayside plasmasphere
Authors: Takahashi Kazue , Bonnell John , Glassmeier Karl‐Heinz , Angelopoulos Vassilis , Singer Howard J. , Chi Peter J. , Denton Richard E. , Nishimura Yukitoshi , Lee Dong‐Hun , Nosé Masahito , Liu Wenlong
Published: December 2010

Multipoint observations of a dayside Pc4 pulsation event provide evidence of fast mode waves trapped in the plasmasphere (plasmaspheric cavity mode or virtual resonance). Time History of Events and Macroscale Interactions during Substorms (THEMIS)‐A, the primary source of data for the present study, was moving outward near noon and detected poloidal oscillations, characterized by the azimuthal electric field component Ey and the radial and compressional magnetic field components Bx and Bz. The structure of the plasmasphere was constructed from the mass density radial profile estimated from the frequency of toroidal standing Alfvén waves observed at this spacecraft. The outer edge of the plasmapause (the maximum of the equatorial Alfvén velocity VAeq) was located at L ∼ 7, and the minimum of VAeq was located at L ∼ 4, forming a potential well structure required for mode trapping. Relative to the ground magnetic pulsations observed in the H component at a low‐latitude station (L = 1.5), the Ey component exhibited a broad amplitude maximum around L ∼ 3.5 and maintained a nearly constant phase from L = 2 to L = 5. In contrast, the Bz component exhibited an amplitude minimum and switched its phase by 180° at L = 3.8. This radial mode structure is consistent with theoretical models of mode trapping. Also, the Ey and Bz components oscillated ±90° out of phase, as is expected for radially standing waves.
Structural architecture of the Colima Volcanic Complex
Authors: Norini G. , Capra L. , Groppelli G. , Agliardi F. , Pola A. , Cortes A.
Published: December 2010

The Colima Volcanic Complex (CVC) is currently the most active Mexican volcano and is located in the western sector of the Trans–Mexican Volcanic Belt, inside the active Colima Rift, a regional N‐S‐striking extensional structure. The Colima Rift is filled by a ∼1 km‐thick sequence of quaternary lacustrine sediments, alluvium, and colluvium, mostly underling the about 3000‐m‐thick volcanic pile of the CVC. In this work we present the results of a detailed morphostructural and field study of Quaternary faults and fractures in the CVC and the surrounding area, including the regional structures of the Colima Rift. We also present a geometrical modeling of the faults inside the volcano and a numerical model of the gravity‐induced stress and strain fields of the CVC. The study attempts to characterize the geometry, kinematics, and dynamics of the deformation features of the CVC and relate it with the volcano structure, the geology of the substratum, and the geodynamic setting of the region. Our model considers that the observed deformation of the CVC and the surroundings results from the interplay between the active N‐S‐trending regional extensional tectonics and the southward spreading of the volcano over its basement forming an E‐W‐oriented volcanotectonic graben. The interaction between regional tectonics and previously unrecognized volcanic spreading can control magma migration and flank instability, in an area where eruptions and sector failures represent a potential high risk for more than 500,000 people.
Acoustic resonant oscillations between the atmosphere and the solid earth during the 1991 Mt. Pinatubo eruption
Authors: Watada Shingo , Kanamori Hiroo
Published: December 2010

Long‐period harmonic Rayleigh waves were observed on seismometers during the 1991 Mt. Pinatubo eruption in the Philippines. The amplitude spectrum of the Rayleigh waves shows two distinct peaks at periods of about 230 and 270 s. In the Earth's atmosphere, long‐wavelength standing acoustic waves are bounded in a low‐sound‐velocity channel between the thermosphere and the ground. The Rayleigh waves and the fundamental and first overtone of atmospheric acoustic waves trapped in the low‐sound‐velocity channels have approximately the same horizontal wavelength and frequency at periods of 230 and 270 s, respectively, i.e., the atmosphere and the solid earth satisfy the condition for acoustic resonant oscillations. The standing atmospheric long‐wavelength acoustic waves set off by the eruption selectively excited seismic spheroidal modes near the resonant period through acoustic resonant coupling and resulted in harmonic Rayleigh waves. In contrast, gravity waves and Lamb waves (atmospheric boundary waves) do not couple to the ground efficiently and are not easily observed as ground disturbance on seismograms during volcanic eruptions.
What induced the exceptional 2005 convection event in the northwestern Mediterranean basin? Answers from a modeling study
Authors: Herrmann Marine , Sevault Florence , Beuvier Jonathan , Somot Samuel
Published: December 2010

Open‐sea convection occurring in the northwestern Mediterranean basin (NWMED) is at the origin of the formation of Western Mediterranean Deep Water (WMDW), one of the main Mediterranean water masses. During winter 2004–2005, a spectacular convection event occurred, observed by several experimental oceanographers. It was associated with an exceptionally large convection area and unusually warm and salty WMDW. Explanations were proposed tentatively, relating the unusual characteristics of this event to the Eastern Mediterranean Transient (EMT) or to the atmospheric conditions during winter 2004–2005 in the NWMED. They could, however, not be supported until now. Here we used numerical modeling to understand what drove this convection event. The control simulation performed for the period 1961–2006 reproduces correctly the long‐term evolution of the Mediterranean Sea circulation, the EMT, and the NWMED convection event of 2004–2005. Sensitivity simulations are then performed to assess the respective contributions of atmospheric and oceanic conditions to this event. The weakness of the winter buoyancy loss since 1988 in the NWMED prevented strong convection to occur during the 1990s, enabling heat and salt contents to increase in this region. This resulted in the change of WMDW characteristics observed in 2005. The strong buoyancy loss of winter 2004–2005 was responsible for the intensity of the convection observed this winter in terms of depth and volume of newly formed WMDW. The EMT did not fundamentally modify the convection process but potentially doubled this volume by inducing a deepening of the heat and salt maximum that weakened the preconvection stratification.
High anthropogenic carbon content in the eastern Mediterranean
Authors: Schneider A. , Tanhua T. , Körtzinger A. , Wallace D. W. R.
Published: December 2010

This work presents data of dichlorodifluoromethane (CFC‐12), dissolved inorganic carbon and total alkalinity from a cruise to the Mediterranean Sea during October–November 2001, with the main focus on the CFC‐12 data and on the eastern basin. Using the transit time distribution method, the anthropogenic carbon concentrations in the basin were estimated. Results were cross‐checked with a back‐calculation technique. The entire water column of the Mediterranean Sea contains anthropogenic CO2, with minimum concentrations of 20.5 μmol kg−1 (error range: 16.9–27.1 μmol kg−1) in the most eastern part of the basin at intermediate depths, where the waters' mean age is >130 yr. Column inventories of up to 154 mol m−2 (132–179 mol m−2) are found and a total inventory of 1.7 Pg (1.3–2.1 Pg) of anthropogenic carbon in the Mediterranean Sea was estimated. There is a net flux of 38 Tg yr−1 (30–47 Tg yr−1) of dissolved inorganic carbon through the Strait of Gibraltar into the Atlantic Ocean and an opposite net flux of 3.5 Tg yr−1 (−1.8–9.2 Tg yr−1) of anthropogenic carbon into the Mediterranean Sea.
Data assimilation and bathymetric inversion in a two‐dimensional horizontal surf zone model
Authors: Wilson G. W. , Özkan‐Haller H. T. , Holman R. A.
Published: December 2010

A methodology is described for assimilating observations in a steady state two‐dimensional horizontal (2‐DH) model of nearshore hydrodynamics (waves and currents), using an ensemble‐based statistical estimator. In this application, we treat bathymetry as a model parameter, which is subject to a specified prior uncertainty. The statistical estimator uses state augmentation to produce posterior (inverse, updated) estimates of bathymetry, wave height, and currents, as well as their posterior uncertainties. A case study is presented, using data from a 2‐D array of in situ sensors on a natural beach (Duck, NC). The prior bathymetry is obtained by interpolation from recent bathymetric surveys; however, the resulting prior circulation is not in agreement with measurements. After assimilating data (significant wave height and alongshore current), the accuracy of modeled fields is improved, and this is quantified by comparing with observations (both assimilated and unassimilated). Hence, for the present data, 2‐DH bathymetric uncertainty is an important source of error in the model and can be quantified and corrected using data assimilation. Here the bathymetric uncertainty is ascribed to inadequate temporal sampling; bathymetric surveys were conducted on a daily basis, but bathymetric change occurred on hourly timescales during storms, such that hydrodynamic model skill was significantly degraded. Further tests are performed to analyze the model sensitivities used in the assimilation and to determine the influence of different observation types and sampling schemes.
Advection‐condensation paradigm for stratospheric water vapor
Authors: Liu Y. S. , Fueglistaler S. , Haynes P. H.
Published: December 2010

The advection‐condensation (A‐C) paradigm is a starting point for a theoretical framework for analysis of atmospheric water vapor distributions and changes therein in a changing climate. It postulates that water vapor concentrations are governed to leading order by the transport through the full four‐dimensional temperature (and hence saturation mixing ratio) field. Brewer's (1949) qualitative deduction of the stratospheric circulation based on water vapor measurements was a first and prominently successful application of this paradigm. Here we examine the quantitative validity of the A‐C paradigm by predicting stratospheric water vapor based on the saturation mixing ratio at the Lagrangian dry point of trajectories calculated using data from the European Centre for Medium‐range Weather Forecasts. Using different data sets for the calculation, we show that results are sensitive to seemingly small differences in temperatures and wind fields and that interpretation of results (in terms of identification of effects of processes deliberately neglected by the advection‐condensation paradigm) requires a careful error calculation. We introduce a semiempirical approach to analyze errors in the Lagrangian predictions of water vapor. We show that persistent (in time and space) errors in the temperature fields lead to similar errors in the Lagrangian model predictions. Conversely, biases in the variance of the temperature fields introduces a systematic bias in the model prediction. Further, model predictions are affected by dispersion and the time scale of troposphere‐to‐stratosphere transport. Our conclusion is that water vapor predictions for the stratospheric overworld based on the A‐C paradigm have a dry bias of −40% ± 10% and −50% ± 10% when small‐space‐scale and short‐time‐scale temperature fluctuations not resolved by the ECMWF reanalyses are taken into account. We suggest that the correction to the A‐C paradigm most likely to remove this dry bias is the inclusion of cloud microphysical processes (such as incomplete sedimentation of particles allowing reevaporation), which relax the assumption of instantaneous dehydration to the saturation mixing ratio. Interestingly, the bias attributed to the A‐C paradigm in terms of water vapor concentration is found to be proportional to the measured water concentration, and a constant offset in terms of frost point temperature can account for much of the bias and its variability in water vapor mixing ratios.
Multimodel assessment of the factors driving stratospheric ozone evolution over the 21st century
Authors: Oman L. D. , Plummer D. A. , Waugh D. W. , Austin J. , Scinocca J. F. , Douglass A. R. , Salawitch R. J. , Canty T. , Akiyoshi H. , Bekki S. , Braesicke P. , Butchart N. , Chipperfield M. P. , Cugnet D. , Dhomse S. , Eyring V. , Frith S. , Hardiman S. C. , Kinnison D. E. , Lamarque J.‐F. , Mancini E. , Marchand M. , Michou M. , Morgenstern O. , Nakamura T. , Nielsen J. E. , Olivié D. , Pitari G. , Pyle J. , Rozanov E. , Shepherd T. G. , Shibata K. , Stolarski R. S. , Teyssèdre H. , Tian W. , Yamashita Y. , Ziemke J. R.
Published: December 2010

The evolution of stratospheric ozone from 1960 to 2100 is examined in simulations from 14 chemistry‐climate models, driven by prescribed levels of halogens and greenhouse gases. There is general agreement among the models that total column ozone reached a minimum around year 2000 at all latitudes, projected to be followed by an increase over the first half of the 21st century. In the second half of the 21st century, ozone is projected to continue increasing, level off, or even decrease depending on the latitude. Separation into partial columns above and below 20 hPa reveals that these latitudinal differences are almost completely caused by differences in the model projections of ozone in the lower stratosphere. At all latitudes, upper stratospheric ozone increases throughout the 21st century and is projected to return to 1960 levels well before the end of the century, although there is a spread among models in the dates that ozone returns to specific historical values. We find decreasing halogens and declining upper atmospheric temperatures, driven by increasing greenhouse gases, contribute almost equally to increases in upper stratospheric ozone. In the tropical lower stratosphere, an increase in upwelling causes a steady decrease in ozone through the 21st century, and total column ozone does not return to 1960 levels in most of the models. In contrast, lower stratospheric and total column ozone in middle and high latitudes increases during the 21st century, returning to 1960 levels well before the end of the century in most models.
Isotopic composition of water in the tropical tropopause layer in cloud‐resolving simulations of an idealized tropical circulation
Authors: Blossey Peter N. , Kuang Zhiming , Romps David M.
Published: December 2010

The processes that fix the fractionation of the stable isotopologues of water in the tropical tropopause layer (TTL) are studied using cloud‐resolving model simulations of an idealized equatorial Walker circulation with an imposed Brewer‐Dobson circulation. This simulation framework allows the explicit representation of the convective and microphysical processes at work in the TTL. In this model, the microphysical transfer of the isotopologues (here, HD16O and H218O) among water vapor and condensed phase hydrometeors is explicitly represented along with those of the standard isotopologue (H216O) during all microphysical interactions. The simulated isotopic ratios of HD16O in water vapor are consistent with observations in both magnitude and the vertical structure in the TTL. When a seasonal cycle is included in the Brewer‐Dobson circulation, both the water vapor mixing ratio and the isotopic ratios of water vapor display a seasonal cycle as well. The amplitude and phase of the seasonal cycle in HD16O are comparable to those observed. The results suggest that both the sublimation of relatively enriched ice associated with deep convection and fractionation by cirrus cloud formation affect the isotopic composition of water vapor in the TTL and its seasonal cycle.
Morphological equilibrium of short channels dissecting the tidal flats of coastal lagoons
Authors: Toffolon Marco , Lanzoni Stefano
Published: December 2010

The equilibrium bed profile of tidal channels dissecting the tidal flats of coastal lagoons is studied within a rational one‐dimensional framework. A general analytical solution is obtained which expresses the bed profile in terms of a modified longitudinal coordinate, accounting implicitly for channel convergence and adjacent shoals. For values of the relevant parameters typical of costal lagoons, inertia and friction effects as well as overtides are shown to provide minor corrections to the equilibrium bed profile. The overall shape of the profile is also shown to be slightly affected by the equilibrium condition used in its derivation, consisting in a requirement on either residual erosion/deposition fluxes or maximum velocity. In particular, the asymptotic form of the analytical solution is common to both the equilibrium requirements, thus suggesting the existence of general morphological relationships relating the depth at the channel mouth or, alternatively, the length of the channel to the tidal amplitude, to the degree of channel convergence, to the critical velocity for erosion/deposition and to the extent of intertidal storage areas. The profile shape is affected as well; for instance, nearly constant‐depth channels tend to form when convergence is strong. The equilibrium configuration also implies that a power law relationship of the type proposed by O'Brien‐Jarret‐Marchi for tidal inlets, relating the channel cross section to the tidal prism, holds throughout the entire channel. Finally, the theoretical profile is shown to reasonably reproduce the bed configurations observed in a number of tidal channels surveyed within the Lagoon of Venice (Italy).
Growth and fluctuations of suncups on alpine snowpacks
Authors: Mitchell Kevin A. , Tiedje T.
Published: December 2010

A mathematical model for suncups on glacier and alpine snow during the summer melting season is compared with time‐lapse field observations. The model consists of a nonlinear partial differential equation whose solution spontaneously forms quasi‐periodic patterns similar to suncups when started from a random initial condition. The suncup patterns are found to fully develop in 5 days in the field under full sun. The patterns fluctuate chaotically in time, both in the observations and in the model. The fluctuations can be described mathematically in terms of diffusion of individual suncups. According to the model, the rate at which the suncups diffuse contains information about the effect of the suncups on the albedo of the snow.
A potential vorticity theory for the formation of elongate channels in river deltas and lakes
Authors: Falcini Federico , Jerolmack Douglas J.
Published: December 2010

Rivers empty into oceans and lakes as turbulent sediment‐laden jets, which can be characterized by a Gaussian horizontal velocity profile that spreads and decays downstream because of shearing and lateral mixing at the jet margins. Recent experiments demonstrate that this velocity field controls river‐mouth sedimentation patterns. In nature, diffuse jets are associated with mouth bar deposition forming bifurcating distributary networks, while focused jets are associated with levee deposition and the growth of elongate channels that do not bifurcate. River outflows from elongate channels are similar in structure to cold filaments observed in ocean currents, where high potential vorticity helps to preserve coherent structure over large distances. Motivated by these observations, we propose a hydrodynamic theory that seeks to predict the conditions under which elongate channels form. Our approach models jet velocity patterns using the flow vorticity. Both shearing and lateral spreading are directly related to the vertical component of vorticity. We introduce a new kind of potential vorticity that incorporates sediment concentration and thus allows study of jet sedimentation patterns. The potential vorticity equation reduces the number of fluid momentum equations to one without losing generality. This results in a compact analytical solution capable of describing the streamwise evolution of the potential vorticity of a sediment‐laden jet from initial conditions at the river mouth. Our theory predicts that high potential vorticity is a necessary condition for focused levee deposition and the creation of elongate channels. Comparison to numerical, laboratory, and field studies indicates that potential vorticity is a primary control on channel morphology. Our results may be useful for designing river delta restoration schemes such as the proposed Mississippi Delta diversion.
Mechanisms of cadmium toxicity and tolerance in Populus
Authors: Induri Brahma Reddy , DiFazio Stephen , Ellis Danielle , Slavov Gancho , Yin Tong-Ming , Tuskan Gerald
Published: December 2010

Background and Methods:

Cadmium (Cd), ranked the 7th most hazardous substance, is one of the most widespread pollutants of soil and water in industrialized nations. Its increased movement in soil-plant systems is posing a serious threat to human health. Cd, without any known functions in plants, was found to be toxic even at minute concentrations, leading to the development of symptoms such as leaf roll, chlorosis and root and shoot growth reduction. Phytoremediation is an emerging cost-effective and environment friendly technology that utilizes high biomass producing plants including Populus plants to remove, transform or stabilize contaminants in soils. The objectives of our study were to record phenotypic variation in a Populus pedigree to Cd exposure, to identify Cd tolerant and susceptible genotypes of Populus, to map QTLs (Quantitative Trait Loci - genomic regions responsible) for Cd tolerance and accumulation in Populus and to predict a mechanism for Cd toxicity and tolerance in susceptible and tolerant Populus genotypes.QTL mapping was accomplished by conducting a greenhouse hydroponic study in which 252 genotypes of a Populus pseudo-backcross progeny were grown for 40 days and treated with 25 µM Cd. Phenotypic variation in total dry weight was recorded on these genotypes and was used for identifying QTL for Cd tolerance. We identified genotypes with contrasting responses to the Cd treatment and conducted a microarray study to identify potential Cd tolerance mechanisms based on gene expression patterns.

Results/Conclusions:

Significant variation was observed among genotypes in response to Cd treatment based on changes in total dry weight. Cd tolerant and susceptible genotypes were identified based on the least square mean differences (Control-Cd treated for each genotype) among all the genotypes. Three QTLs were identified for Cd tolerance and they accounted for approximately 25% of the phenotypic variation in Cd tolerance measured as total dry weights.In the microarray study, the Cd-susceptible genotype had higher expression of Fe-transporters compared to the tolerant genotypes, and Cd and Fe levels were significantly different in foliage. Even the susceptible genotype controls had higher, though not significant, Fe levels than tolerant genotype controls. We therefore hypothesize that part of the mechanism for Cd tolerance is determined by the differences in the activity of Fe transporters in genotypes with differential Fe homeostasis.
Benchmarking triple stores with biological data
Authors: Mironov Vladimir
Published: December 2010

We have compared the performance of five non-commercial triple stores, Virtuoso-open source, Jena SDB, Jena TDB, SWIFT-OWLIM and 4Store. We examined three performance aspects: the query execution time, scalability and run-to-run reproducibility. The queries we chose addressed different ontological or biological topics, and we obtained evidence that individual store performance was quite query specific. We identified three groups of queries displaying similar behavior across the different stores: 1) relatively short response time, 2) moderate response time and 3) relatively long response time. OWLIM proved to be a winner in the first group, 4Store in the second, and Virtuoso in the third. Our benchmarking showed Virtuoso to be a very balanced performer – its response time was better than average for all the 24 queries; it showed a very good scalability and a reasonable run-to-run reproducibility.
Populous: A Tool For Populating OWL Ontologies From Templates
Authors: Jupp Simon
Published: December 2010

We present Populous, a tool for gathering content with which to populate an ontology. Domain experts need to add content, that is often repetitive in its form, but without having to tackle the underlying ontological representation. Populous presents users with a table based form in which columns are constrained to take values from particular ontologies; the user can select a concept from an ontology via its meaningful label to give a value for a given entity attribute.Populated tables are mapped to patterns that can then be used to automatically generate the ontology's content. Populous's contribution is in the knowledge gathering stage of ontology development. It separates knowledge gathering from the conceptualisation and also separates the user from the standard ontology authoring environments. As a result, Populous can allow knowledge to be gathered in a straight-forward manner that can then be used to do mass production of ontology content.
Thermal conductivity of polyethylene glycol nanofluids containing carbon coated metal nanoparticles
Authors: Zhang Haiyan , Wu Qiguang , Lin Jin , Chen Jin , Xu Zhuowen
Published: December 2010

Polyethylene glycol nanofluids containing carbon coated Cu (Al, Fe) nanoparticles with core-shell structure are prepared in this paper. High efficiency on heat transfer is achieved by collaborative effect between nanocarbon and metal nanoparticles. The results show that the thermal conductivity of nanofluid is relevant to the type of filler and increases with the increasing of filler loading. An 27% enhancement in thermal conductivity is observed by adding only 0.5 wt % of carbon coated Cu nanoparticles in polyethylene glycol, and 49%, 40%, and 30% enhancement in thermal conductivity for carbon coated Cu, Al, and Fe nanoparticles loading of 1.5 wt %, respectively. The carbon coated metal nanofluid exhibit better stability after 14 days and no obvious sedimentation is observed. Compared with carbon coated Al and Fe nanoparticles, carbon coated Cu nanoparticles nanofluids have the best stability and dispersibility and can efficiently enhance the thermal conductivity of base fluid. Moreover, nanofluids stabilities are different when nanofluids were dispersed by three ways. Nanofluids dispersed by ball milling way possess the best stability, followed by nanofluids dispersed by ultrasonic dispersion way and magnetic stirring way.
Sum-frequency generation of acetate adsorption on Au and Pt surfaces: Molecular structure effects
Authors: Braunschweig Björn , Mukherjee Prabuddha , Kutz Robert B. , Wieckowski Andrzej , Dlott Dana D.
Published: December 2010

The reversible adsorption of acetate on polycrystalline Au and Pt surfaces was investigated with broadband sum-frequency generation (SFG) and cyclic voltammetry. Specifically adsorbed acetate as well as coadsorbed sulfuric acid anions are observed for the first time with SFG and give rise to dramatically different SFG intensities on Au and Pt surfaces. While similar coverages of acetate adlayers on Au and Pt surfaces are well established by previous studies, an identification of the interfacial molecular structure has been elusive. However, we have applied the high sensitivity of SFG for interfacial polar ordering to identify different acetate structures at Au and Pt surfaces in contact with HClO4 and H2SO4 electrolytes. Acetate competes with the formation of surface oxides and shifts the oxidation threshold of both Au and Pt electrodes anodically. Effects of the supporting electrolyte on the formation of acetate adlayers are revealed by comparing SFG spectra in HClO4 and H2SO4 solutions: Sulfuric acid anions modify the potential-dependent acetate adsorption, compete with adsorbed acetate on Au and coadsorb with acetate on Pt surfaces.
Temperature-stable parallel-plate dielectric cell for broadband liquid impedance measurements
Authors: Mazzeo Brian A. , Chandra Satyan , Mellor Brett L. , Arellano Jesus
Published: December 2010

A liquid impedance cell for broadband impedance measurements up to 110 MHz is presented. The design incorporates temperature control and minimizes parasitic capacitance and inductance. The cell is simple to fabricate and uses chemically resistant materials, stainless steel, and Teflon. This dielectric cell can be used in a variety of liquid measurements, particularly those related to impedance measurements of biological objects in solution. Temperature control is illustrated in measurements of the permittivity of deionized water from 5 to 55 ºC. Numerical fitting procedures employed on the relaxation curves indicate good agreement with previous studies on beta-lactoglobulin and hen lysozyme. Titration capability is demonstrated through dielectric titration of hen lysozyme and beta-lactoglobulin.
A numerical method for determining highly precise electron energy distribution functions from Langmuir probe characteristics
Authors: Bang Jin-Young , Chung Chin-Wook
Published: December 2010

Electron energy distribution functions (EEDFs) were determined from probe characteristics using a numerical ac superimposed method with a distortion correction of high derivative terms by varying amplitude of a sinusoidal perturbation voltage superimposed onto the dc sweep voltage, depending on the related electron energy. Low amplitude perturbation applied around the plasma potential represented the low energy peak of the EEDF exactly, and high amplitude perturbation applied around the floating potential was effective to suppress noise or distortion of the probe characteristic, which is fatal to the tail electron distribution. When a small random noise was imposed over the stabilized prove characteristic, the numerical differentiation method was not suitable to determine the EEDF, while the numerical ac superimposed method was able to obtain a highly precise EEDF.
Hard x-ray correlation analysis as a diagnostic tool for the measurement of magnetic turbulence in tokamaks
Authors: Saha S. K. , Hui A. K. , Chowdhury S. , Raychaudhuri Santwana , Banik D.
Published: December 2010

A diagnostic has been developed for the measurement and characterization of the magnetic turbulence occurring in the core region of a tokamak. A specially shielded detector looking in the tangential direction has been employed to measure the thin target bremsstrahlung from the core plasma. The thick target bremsstrahlung from the limiter is also recorded at the same time. Auto- and cross-correlation analyses have been shown to yield, respectively, the stochasticity of the magnetic fluctuations in the core region and the consequent diffusion coefficient of the nonthermal electrons. The measured stochasticity bears a relationship with the diffusion coefficient. Data obtained from internal magnetic probes corroborate the above trend but the hard x-ray measurement data are shown to be more reliable than those obtained from magnetic probes.
Algorithmic differentiation and the calculation of forces by quantum Monte Carlo
Authors: Sorella Sandro , Capriotti Luca
Published: December 2010

We describe an efficient algorithm to compute forces in quantum Monte Carlo using adjoint algorithmic differentiation. This allows us to apply the space warp coordinate transformation in differential form, and compute all the 3M force components of a system with M atoms with a computational effort comparable with the one to obtain the total energy. Few examples illustrating the method for an electronic system containing several water molecules are presented. With the present technique, the calculation of finite-temperature thermodynamic properties of materials with quantum Monte Carlo will be feasible in the near future.
Effects of strain on defect structure in II-VI green color converters
Authors: Zhu Y. , McKernan S. , Xie J. , Miller T. J. , Haase M. A. , Sun X. , Smith T. L. , Leatherdale C. A.
Published: December 2010

State-of-the-art green emission efficiency has been achieved with light-emitting diodes incorporating CdMgZnSe color-converting quantum well heterostructures, although dark line defects (DLDs) limit the device reliability. We have determined that misfit strain plays an important role in the formation of extended stacking faults (SFs) and DLDs in II-VI green converters. Even small strain causes SFs to extend to accommodate misfit strain and extended SFs further give rise to DLDs when they intersect active regions. Detailed strain relaxation mechanisms for both tensile and compressive strain have been investigated, which may apply for other semiconductor heterostructures with an fcc lattice. Careful control of the layer strain via close lattice matching prevents the extension of SFs and leads to DLD-free converters.
Spectroscopic studies of the origin of radiation-induced degradation in phosphorus-doped optical fibers and preforms
Authors: Origlio G. , Messina F. , Girard S. , Cannas M. , Boukenter A. , Ouerdane Y.
Published: December 2010

In this paper, we study the radiation-induced point defects related to the phosphorus element that is commonly used to improve the optical properties of silica-based glasses but is responsible of a dramatic increase in their radiation sensitivity. To this aim, the influence of x-ray irradiation on prototype phosphorus-doped canonical fibers and their related preforms was investigated by in situ radiation induced attenuation (RIA), optical absorption, and electron spin resonance (ESR) spectroscopy. The RIA spectra in the (1.5–5 eV) range, can be explained by the presence of at least three absorption bands induced by radiation exposure. Additionally the X-dose dependence of such bands was studied. The main responsible defect for these absorption peaks was the phosphorus oxygen hole center (POHC) center, whose presence was also detected by ESR measurements both in irradiated fibers and preforms, together with the lineshape of the so called P2 defect. Correlations between the RIA bands and the ESR results allow us to assign the 2.3 and 3.0 eV bands to POHCs and to propose a scheme for the simultaneous creation of POHC and P2 defects after x-ray exposure.