bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling drifting snow in Antarctica with a regional climate model: 2. Results
Authors: Lenaerts J. T. M. , van den Broeke M. R.
Published: January 2012

This paper presents a model study of the impact of drifting snow on the lower atmosphere, surface snow characteristics, and surface mass balance of Antarctica. We use the regional atmospheric climate model RACMO2.1/ANT with a high horizontal resolution (27 km), equipped with a drifting snow routine and forced by ERA‐Interim (1989–2009) at its lateral and ocean boundaries. Drifting snow sublimation (SUds) is significant in Antarctica, especially in the coastal regions (>150 mm water equivalent yr−1). Integrated over the ice sheet, SUds removes ∼6% of the annually precipitated snow. Drifting snow interacts with the atmosphere, as it increases the lower atmospheric moisture content and reduces surface sublimation (SUs), and leads to increased snowfall in regions where the atmosphere usually is close to saturation. Drifting snow sublimation (SUds) is smallest in summer, when katabatic wind speeds are lower and melting and surface sublimation consolidate the snow surface. Compared to a simulation without drifting snow, total sublimation (SUds + SUs) doubles on the grounded ice sheet if drifting snow is considered. Drifting snow erosion is locally significant, but can be neglected on a continent‐wide scale.
Spherical dynamic models of top‐down tectonics
Authors: Morra G. , Quevedo L. , Müller R. D.
Published: January 2012

We use the Multipole–Boundary Element Method (MP‐BEM) to simulate regional and global geodynamics in a spherical 3‐D setting. We first simulate an isolated subducting rectangular plate with length (Llitho) and width (Wlitho) varying between 0.5 and 2 times the radius of the Earth (REarth) and with viscosity ηlitho varying between 100 and 500 times the upper mantle (ηUM), sinking in a layered mantle characterized by lower‐upper mantle viscosity ratioλ = ηLM/ηUM varying between 1 and 80. In a mantle with small upper/lower viscosity contrast (λ ≅ 1), trench and plate motions are weakly dependent on Wlitho; plate motion is controlled by slab pull if Llitho ≤ REarth, while for longer plates plate speed strongly decreases because of the plate basal friction and flow reorganization. An increasing viscosity ratio λ gradually breaks this pattern, and for λ ≅ 10 combined with Wlitho ≈ REarth(and greater) trench advance and retreat are simultaneously observed. These results offer a first‐order explanation of the origin of the size (Llitho ≈ Wlitho ≈ REarth) of the largest plates observed over the past 150 Myr. Finally, two global plate tectonic simulations are performed from reconstructed plates and slabs at 25 Ma before present and before 100 Ma, respectively. It is shown that MP‐BEM predicts present plate kinematics if plate‐mantle decoupling is adopted for the longest plates (Llitho > REarth). Models for 100 Ma show that the slab‐slab interaction between India and Izanagi plates at 100 Ma can explain the propagation of the plate reorganization from the Indian to the Pacific plate.
Winter sea‐ice melt in the Canada Basin, Arctic Ocean
Authors: Jackson Jennifer M. , Williams William J. , Carmack Eddy C.
Published: January 2012

Recent warming and freshening of the Canada Basin has led to the year‐round storage of solar radiation as the near‐surface temperature maximum (NSTM). Using year‐round ocean (from ice tethered profilers and autonomous ocean flux buoys), sea‐ice (from ice mass balance buoys), and atmosphere (from NCEP/NCAR reanalysis) data from 2005–2010, we find that heat from the NSTM is entrained into the surface mixed layer (SML) during winter. Entrainment can only occur when the base of the SML reaches the top of the NSTM. If this condition is met, the surface forcing and stratification together determine whether the SML deepens into the NSTM. Heat transfer occurs by diffusion or by the erosion of the summer halocline. The average temperature of the SML warmed by as much as 0.06°C during storm events. Solar radiation began warming the SML about 1 month early during the winter of 2007–2008 and this can be explained by thin sea ice.
Diapycnal diffusivities from a tracer release experiment in the deep sea, integrated over 13 years
Authors: Rye Craig D. , Messias Marie‐Jose , Ledwell James R. , Watson Andrew J. , Brousseau Andrew , King Brian A.
Published: January 2012

A section across the Atlantic at 24°S recorded in March 2009, sampled a tracer plume released in the deep Brazil Basin 13 years earlier. The 1‐D diffusion equation was used to model the vertical spread of the tracer, yielding a mean diapycnal diffusivity estimate of approximately 3 × 10−4 m2/s at 4 km depth. This estimate is similar to that found by surveys of the tracer plume made between 1996 and 2000, within four years of the tracer release and therefore provides strong evidence for the long‐term stability of that result.
On the threshold of flow in a tight natural rock
Authors: Meredith P. G. , Main I. G. , Clint O. C. , Li L.
Published: January 2012

The behaviour of hydraulically ‘tight’ barrier rocks is a key determinant of the long‐term integrity of potential underground storage sites for the waste products from low‐carbon emission energy production technologies (including nuclear waste and CO2captured from fossil fuels). Here we isolate the relationship between crack‐induced permeability and porosity using an initially crack‐free natural crystalline material. We vary secondary porosity from an initial value of zero, and demonstrate that the bulk permeabilityK varies with total connected porosity Φ above the percolation threshold Φc as K = K0(Φ − Φc)n, where n = 3.8 ± 0.4, i.e., similar to results obtained for higher porosity rocks, indicating universality of this scaling law. Close to the percolation threshold a modest change in total porosity from 1% to 5% or so results in a massive change in permeability of 7 orders of magnitude or more. The results are consistent with a continuum percolation model that reflects the microstructure of the pore/induced microcrack network in the natural material.
Assimilation of passive and active microwave soil moisture retrievals
Authors: Draper C. S. , Reichle R. H. , De Lannoy G. J. M. , Liu Q.
Published: January 2012

Near‐surface soil moisture observations from the active microwave ASCAT and the passive microwave AMSR‐E satellite instruments are assimilated, both separately and together, into the NASA Catchment land surface model over 3.5 years using an ensemble Kalman filter. The impact of each assimilation is evaluated using in situ soil moisture observations from 85 sites in the US and Australia, in terms of the anomaly time series correlation‐coefficient, R. The skill gained by assimilating either ASCAT or AMSR‐E was very similar, even when separated by land cover type. Over all sites, the mean root‐zone R was significantly increased from 0.45 for an open‐loop, to 0.55, 0.54, and 0.56 by the assimilation of ASCAT, AMSR‐E, and both, respectively. Each assimilation also had a positive impact over each land cover type sampled. For maximum accuracy and coverage it is recommended that active and passive microwave observations be assimilated together.
Urban precipitation extremes: How reliable are regional climate models?
Authors: Mishra Vimal , Dominguez Francina , Lettenmaier Dennis P.
Published: January 2012

We evaluate the ability of regional climate models (RCMs) that participated in the North American Regional Climate Change Assessment Program (NARCCAP) to reproduce the historical season of occurrence, mean, and variability of 3 and 24‐hour precipitation extremes for 100 urban areas across the United States. We show that RCMs with both reanalysis and global climate model (GCM) boundary conditions behave similarly and underestimate 3‐hour precipitation maxima across almost the entire U.S. RCMs with both boundary conditions broadly capture the season of occurrence of precipitation maxima except in the interior of the western U.S. and the southeastern U.S. On the other hand, the RCMs do much better in identifying the season of 24‐hour precipitation maxima. For mean annual precipitation maxima, regardless of the boundary condition, RCMs consistently show high (low) bias for locations in the western (eastern) U.S. Our results indicate that RCM‐simulated 3‐hour precipitation maxima at 100‐year return period could be considered acceptable for stormwater infrastructure design at less than 12% of the 100 urban areas (regardless of boundary conditions). RCM performance for 24‐hour precipitation maxima was slightly better, with performance acceptable for stormwater infrastructure design judged adequate at about 25% of the urban areas.
Neutral thermospheric dynamics observed with two scanning Doppler imagers: 2. Vertical winds
Authors: Anderson C. , Conde M. , McHarg M. G.
Published: January 2012

This article is the second in a series of three papers reporting on observations of the 630.0 nm thermospheric airglow emission by two spatially separated scanning Doppler imagers (SDI’s) in Alaska. In this article, line‐of‐sight wind measurements from these instruments in four common‐volume regions lying along the great circle joining the two observatories have been used to derive estimates of the vertical wind in those common‐volumes. These estimates are combined with the vertical winds measured directly in each of the station zeniths to resolve both the spatial and temporal variations of the vertical wind field. Data from four nights are presented as examples of the wave‐like oscillations and frequently high spatial correlations that are observed. A statistical study of data from the full 19‐night data set showed that the frequency of observing statistically significant correlation between vertical winds measured at separate locations decreased linearly with increasing separation. A linear fit to this trend indicated that for this particular location and orientation the largest separation over which statistically significant correlation would be expected to occur is approximately 540 km.
Polarization of Pc1/EMIC waves and related proton auroras observed at subauroral latitudes
Authors: Nomura R. , Shiokawa K. , Sakaguchi K. , Otsuka Y. , Connors M.
Published: January 2012

We have investigated the polarization of Pc1 geomagnetic pulsations and related proton auroras at subauroral latitudes, using an induction magnetometer and an all‐sky camera at Athabasca, Canada (54.7°N, 246.7°E, magnetic latitude (mlat) 61.7°N). Isolated proton auroras often appear in association with Pc1 pulsations, because of proton scattering by electromagnetic ion cyclotron (EMIC) waves in the magnetosphere. We used the proton aurora as a proxy for the location and size of the Pc1 ionospheric source. For 27 Pc1 events with simultaneously observed proton auroras over 4 years from September 7, 2005 to September 6, 2009, we calculated the distances between the Pc1 ionospheric source and the observation site, normalized by the scale size of the source. We tried three different definitions of the scale size of Pc1 ionospheric source to calculate the normalized distances. We found that the rotation angleθ between the Pc1 polarization ellipse and the direction to the proton aurora changes from 90° to 0° as the normalized distance increases. For the definition of the scale sizes that gives most clear θ‐transition from 90° to 0°, the transition occurs at the normalized distance ∼2.0–4.0, while it was ∼1.0–2.0 by the model calculation of Fujita and Tamao (1988). The averaged major axes tend to point toward the proton aurora at larger distances. The difference of the transition location may imply that the Pc1 ionospheric sources are larger than the isolated proton auroras, or that the inhomogenuity of the ionospheric conductivity by the proton precipitation affects the transition distances.
Serpentinization of oceanic peridotites: 2. Kinetics and processes of San Carlos olivine hydrothermal alteration
Authors: Malvoisin Benjamin , Brunet Fabrice , Carlut Julie , Rouméjon Stéphane , Cannat Mathilde
Published: January 2012

The kinetics of the reaction (Mg,Fe)‐olivine + H2O → serpentine + magnetite + brucite + H2 were investigated at 500 bars in the 250–350°C range using natural olivine (San Carlos; Fo91) with grain sizes between 1 and 150 μm and for run durations up to 514 d. The amount of magnetite produced, which directly relates to reaction progress, was accurately monitored using up to 24 time‐resolved magnetic measurements per experiment. Eighty percent of serpentinization was achieved after 60 d for olivine grain sizes of 5–15μm and after 500 d for grain sizes of 50–63 μm. Serpentinization kinetics were found to be inversely proportional to the geometrical surface area of the starting olivine grains. They were one or two orders of magnitude slower than serpentinization kinetics commonly used for modeling serpentinization‐related processes. The nature of the serpentine mineral product depended on the initial olivine grain size (IGS); for IGS in the 5–150μm range lizardite formed, and olivine dissolution was the rate‐limiting process. At IGS below 5μm, chrysotile crystallized instead of lizardite, and the relationship between olivine surface area and reaction kinetics no longer held. We infer that for such small olivine grain sizes dissolution is no longer the rate‐limiting process. Serpentinization in our experiments was associated with the creation of new reactive surface area according to two cooperative processes: etch pits formation associated with dissolution and grain fracturing for IGS above 20μm. Interestingly, fractures and etch pits with similar geometry and sizes were also observed for residual olivine (with a typical grain size of 50 μm) in serpentinized peridotite samples from the Southwest Indian Ridge. This suggests that the processes governing olivine serpentinization kinetics in our experiments are similar to those prevailing in natural systems. We therefore suggest that the new kinetic data set that we present here, which encompasses a range of olivine grain sizes and reaction temperatures, is relevant to the serpentinization of olivine in the oceanic crust insofar as water is available.
Evaluation of Arctic sea ice thickness simulated by Arctic Ocean Model Intercomparison Project models
Authors: Johnson Mark , Proshutinsky Andrey , Aksenov Yevgeny , Nguyen An T. , Lindsay Ron , Haas Christian , Zhang Jinlun , Diansky Nikolay , Kwok Ron , Maslowski Wieslaw , Häkkinen Sirpa , Ashik Igor , de Cuevas Beverly
Published: January 2012

Six Arctic Ocean Model Intercomparison Project model simulations are compared with estimates of sea ice thickness derived from pan‐Arctic satellite freeboard measurements (2004–2008); airborne electromagnetic measurements (2001–2009); ice draft data from moored instruments in Fram Strait, the Greenland Sea, and the Beaufort Sea (1992–2008) and from submarines (1975–2000); and drill hole data from the Arctic basin, Laptev, and East Siberian marginal seas (1982–1986) and coastal stations (1998–2009). Despite an assessment of six models that differ in numerical methods, resolution, domain, forcing, and boundary conditions, the models generally overestimate the thickness of measured ice thinner than ∼2 m and underestimate the thickness of ice measured thicker than about ∼2 m. In the regions of flat immobile landfast ice (shallow Siberian Seas with depths less than 25–30 m), the models generally overestimate both the total observed sea ice thickness and rates of September and October ice growth from observations by more than 4 times and more than one standard deviation, respectively. The models do not reproduce conditions of fast ice formation and growth. Instead, the modeled fast ice is replaced with pack ice which drifts, generating ridges of increasing ice thickness, in addition to thermodynamic ice growth. Considering all observational data sets, the better correlations and smaller differences from observations are from the Estimating the Circulation and Climate of the Ocean, Phase II and Pan‐Arctic Ice Ocean Modeling and Assimilation System models.
Numerical investigation of the quasi 2 day wave in the mesosphere and lower thermosphere
Authors: Yue Jia , Liu Han‐Li , Chang Loren C.
Published: January 2012

The zonal wave number 3 planetary wave with about a 2 day period is a recurrent wave feature in the mesosphere and lower thermosphere (MLT). The quasi 2 day wave (QTDW) exhibits strong seasonal variability with peak amplitudes after summer solstice. In late January and early February, satellites also discovered two strong enhancements of the QTDW in meridional wind, one peak at summer midlatitudes near 90 km and the other in the tropical lower thermosphere. For the first time, this double‐peak characteristic of the QTDW meridional component is numerically investigated by the National Center for Atmospheric Research (NCAR) thermosphere‐ionosphere‐mesosphere‐electrodynamics general circulation model (TIME‐GCM) with the QTDW forcing prescribed at the lower model boundary and explained by the combined effect of baroclinic‐barotropic instability and Rossby normal mode. Baroclinic‐barotropic instability is capable of amplifying the QTDW, manifesting as Eliassen‐Palm (EP) flux divergence in the summer mesosphere. Without the direct contribution from baroclinic‐barotropic instability, the simulated QTDW response in a lower thermosphere temperature and horizontal wind resembles that of the (3, 0) Rossby‐gravity normal mode. In the summer middle atmosphere, the wave amplitude grows substantially, like an internal wave in the regions of large refractive index. As the wave amplitude growth ceases near the mesopause, where the zonal wind reverses direction, the QTDW reaches its maximum amplitude, displaying an enhanced meridional component in the tropical lower thermosphere. Several new aspects on the QTDWs in the MLT were also revealed. Compared with a prior model run, the propagation of the QTDW can also be prohibited by a self‐generated critical layer in a strong thermospheric easterly wind. In addition, a direct contribution from the migrating diurnal tide to the QTDW amplitude in the MLT is found. This is largely attributed to the change of the background zonal wind caused by the tide, thus leading to the increase of the QTDW refractive index in the summer middle atmosphere.
A new inversion method to calculate emission inventories without a prior at mesoscale: Application to the anthropogenic CO2 emission from Houston, Texas
Authors: Brioude J. , Petron G. , Frost G. J. , Ahmadov R. , Angevine W. M. , Hsie E.‐Y. , Kim S.‐W. , Lee S.‐H. , McKeen S. A. , Trainer M. , Fehsenfeld F. C. , Holloway J. S. , Peischl J. , Ryerson T. B. , Gurney K. R.
Published: January 2012

We developed a new inversion method to calculate an emission inventory for an anthropogenic pollutant without a prior emission estimate at mesoscale. This method employs slopes between mixing ratio enhancements of a given pollutant (CO2, for instance) with other co‐emitted tracers in conjunction with the emission inventories of those tracers (CO, NOy, and SO2 are used in this example). The current application of this method employed in situ measurements onboard the NOAA WP‐3 research aircraft during the 2006 Texas Air Quality Study (TexAQS 2006). We used 3 different transport models to estimate the uncertainties introduced by the transport models in the inversion. We demonstrated the validity of the new inversion method by calculating a 4 × 4 km2 emission inventory of anthropogenic CO2 in the Houston area in Texas, and comparing it to the 10 × 10 km2 Vulcan emission inventory for the same region. The calculated anthropogenic CO2 inventory for the Houston Ship Channel, home to numerous major industrial and port emission sources, showed excellent agreement with Vulcan. The daytime CO2 average flux from the Ship Channel is the largest urban CO2 flux reported in the literature. Compared to Vulcan, the daytime urban area CO2 emissions were higher by 37% ± 6%. Those differences can be explained by uncertainties in emission factors in Vulcan and by increased emissions from point sources and on‐road emitters between 2002, the reference year in Vulcan, and 2006, the year that the TexAQS observations were made.
Regular airborne surveys of Arctic sea ice and atmosphere
Authors: Herber Andreas B. , Haas Christian , Stone Robert S. , Bottenheim Jan W. , Liu Peter , Li Shao‐Meng , Staebler Ralf M. , Strapp J. Walter , Dethloff Klaus
Published: January 2012

The Arctic is undergoing rapid environmental change, manifested most dramatically by reductions in sea ice extent and thickness. The changes are attributed to anthropogenic effects related to greenhouse warming, with secondary contributions from changing ocean and wind currents as well as from pollutants, especially “absorbing” black carbon. The warmer Arctic air temperatures and new patterns of wind and ocean circulation have also contributed to a younger ice cover [Maslanik et al., 2011]. Specific factors that determine the temporal distribution of sea ice are poorly understood because few observations of key variables have been made in the central Arctic. For example, the planetary boundary layer (PBL), the lowest part of the atmosphere governed by interaction with Earth's surface, plays a critical role involving the exchange of momentum, heat, water vapor, trace gases, and aerosol particles. Satellites can provide limited observations of sea ice properties, but so far, accurate measurements of ice thickness or boundary layer properties have not been easily obtained. Although satellite retrievals of geophysical variables might be an essential source of information, their reliability remains questionable owing to inadequate spatial and/or temporal resolution and to a need for further validation.
Dark sky enters the lexicon
Authors: Showstack Randy
Published: January 2012

“Basketbrawl,” “cloud music,” “humblebrag,” and “occupy Wall Street.” These are some of the catchwords and phrases that lexicographer Grant Barrett included in a year‐end newspaper column, “Which words will live on?,” in the New York Times on 31 December 2011. Among the couple dozen examples of new language was “dark sky.” Barrett wrote that it “designates a place free of nighttime light pollution. For example, the island of Sark in the English Channel is a dark‐sky island.”
New global map of forest canopy height
Authors: Balcerak Ernie
Published: January 2012

Just how tall are forests around the world? A new global map shows forest canopy height at 1‐kilometer spatial resolution. Simard et al. used satellite data from the Geoscience Laser Altimeter System aboard the Ice, Cloud, and land Elevation Satellite (ICESat) to create a global map of the height of the forest canopy. They validated their map by comparing it with field measurements of canopy height from sites around the globe. The authors compared their map against another recently published map of canopy height and found that it was better correlated with the field data. They also found canopy height differences across forest disturbance gradients.
Gravity's effect on landslides: A strike against Martian water
Authors: Schultz Colin
Published: January 2012

A pile of sand, gravel, or other granular material takes on a familiar conical shape, with the slope of the pile's walls coming to rest at the static angle of repose. If the material exceeds this angle, it will trigger an avalanche, tumbling down until it comes to rest at the dynamic angle of repose. Static angles of repose for coarse, angular materials tend to be around 40° from the horizontal, while smooth grains are stable at up to 20°. As largely a matter of geometry, grain properties, and internal friction, scientists have assumed these two angles of repose are fixed for a given substance. Observations of the angles of gully walls on Mars, found to be too shallow for the materials involved, have been used to argue that surface water must have played a part, either lubricating landslides or depositing the material directly. However, research by Kleinhans et al., using the parabolic flight of an airplane to test the effect of gravity on angles of repose, demonstrates that water need not have been present.
Reconstructing ocean properties from seismic data
Authors: Balcerak Ernie
Published: January 2012

Ocean temperature, density, and salinity change with depth on fine scales. Some scientists are beginning to use acoustic images to reconstruct these water column properties. In this technique, acoustic waves are generated in the ocean by an active seismic source such as an air gun array, and the reflected waves are recorded at surface. The recorded field is then carefully processed to obtain an acoustic image of the layer's reflectivity. The speed of sound and the amount of energy reflected and transmitted vary depending on the water's temperature and salinity, so these reflected acoustic waves indirectly contain information on the water properties. However, analyzing acoustic data to extract water column properties can be tricky. Kormann et al. show that a mathematical method known as full waveform inversion can be used to reconstruct high‐resolution temperature and salinity profiles from simulated one‐dimensional seismic ocean data. The work is a step toward making the method of using seismic data to retrieve water column properties more widely applicable. (Journal of Geophysical Research‐Oceans, doi:10.1029/2011JC007216, 2011)
Changing Chilean coastal currents could drive aquatic evolution
Authors: Schultz Colin
Published: January 2012

For invertebrate and fish species that spend most of their lives in rich coastal waters rather than migrating freely throughout the open ocean, the formation of island populations and the associated risk of genetic diversity loss are threats to long‐term population health. Many species cope through a spawning mechanism whereby larvae are released en masse into near‐shore ocean currents, like pollen adrift in the wind. The larvae are viable in open waters from days to months, but only those that find their way back to shore can settle and develop. To increase their chances, different species' larvae often use particular swimming behaviors, for example, varying their depth in the water column throughout the day.
When will Antarctic ozone begin to recover?
Authors: Balcerak Ernie
Published: January 2012

Emissions of ozone‐depleting substances have declined over recent decades, but it takes time for the ozone layer to recover. Regular measurements of ozone levels above the South Pole now stretch back 25 years. Hassler et al. analyzed these recorded ozone data to assess changes in ozone loss rates. Consistent with previous studies, they found that ozone loss rates have been stable over the past 15 years, neither increasing nor decreasing. However, they predict that, assuming future atmospheric dynamics are similar to today's, ozone loss rates will begin to decline noticeably between 2017 and 2021. (Journal of Geophysical Research‐Atmospheres, doi:10.1029/2011JD016353, 2011)
Plasmodium falciparum has rare correlation properties
Authors: Shah Kushal
Published: January 2012

A plot of the correlation function of a given DNA sequence has certain characteristic features common to almost all organisms. One common feature is that the correlation values at distances that are multiples of three is higher than correlation values at other distances. Because of this such a correlation plot can be divided into two or three curves with different scalings. P. falciparum has a rare correlation property which is probably unique. I have analyzed genomes of many bacteria, fungi and protozoa and found that P. falciparum is the only organism whose DNA sequence correlation plot can be divided into four curves with different scalings. This property is neither shared by other species of the Plasmodium genus nor by other AT rich genomes. This could be a hint that the DNA sequence of P. falciparum has undergone certain rare mutational events.
Regulation of human microsomal prostaglandin E synthase-1 by IL-1β requires a distal enhancer element with a unique role for C/EBPβ
Authors: Walters Jewell N. , Bickford Justin S. , Newsom Kimberly J. , Beachy Dawn E. , Barilovits Sarah J. , Herlihy John-David , Nick Harry S.
Published: January 2012

The studies of PGE2 (prostaglandin E2) biosynthesis have focused primarily on the role of cyclo-oxygenases. Efforts have shifted towards the specific PGE2 terminal synthases, particularly mPGES-1 (microsomal PGE synthase 1), which has emerged as the crucial inducible synthase with roles in pain, cancer and inflammation. mPGES-1 is induced by pro-inflammatory cytokines with studies focusing on the proximal promoter, mediated specifically through Egr-1 (early growth-response factor 1). Numerous studies demonstrate that the mPGES-1 promoter (PTGES) alone cannot account for the level of IL-1β (interleukin 1β) induction. We identified two DNase I-hypersensitive sites within the proximal promoter near the Egr-1 element and a novel distal site near −8.6 kb. Functional analysis of the distal site revealed two elements that co-operate with basal promoter expression and a stimulus-dependent enhancer. A specific binding site for C/EBPβ (CCAAT/enhancer-binding protein β) in the enhancer was directly responsible for inducible enhancer activity. ChIP (chromatin immunoprecipitation) analysis demonstrated constitutive Egr-1 binding to the promoter and induced RNA polymerase II and C/EBPβ binding to the promoter and enhancer respectively. Knockout/knockdown studies established a functional role for C/EBPβ in mPGES-1 gene regulation and the documented interaction between Egr-1 and C/EBPβ highlights the proximal promoter co-operation with a novel distal enhancer element in regulating inducible mPGES-1 expression.
Model-free nuclear magnetic resonance study of intermolecular free energy landscapes in liquids with paramagnetic Ln3+ spotlights: Theory and application to Arg-Gly-Asp
Authors: Fries Pascal H.
Published: January 2012

We propose an easily applicable method for investigating the pair distribution function of a lanthanide Ln3+ complex LnL (L = ligand) with respect to any solvent or solute molecule A carrying observable nuclear spins. Let r be the distance of Ln3+ to the observed nuclear spin I. We derive a simple expression of the experimental value of the configurational average of 1/r6 in terms of longitudinal paramagnetic relaxation (rate) enhancements (PREs) of the spin I measured on a standard high-resolution NMR spectrometer and due to well-chosen concentrations of LnL complexes in which Ln3+ is a fast-relaxing paramagnetic lanthanide or the slowly-relaxing gadolinium Gd3+. The derivation is justified in the general case of a molecule A which is by turns in a bound state where it follows the complex and a free state where it moves independently. It rests on the expression of the underlying PRE theory in terms of the angle-dependent pair distribution function of LnL and A. The simplifications of this theory in the high-field regime and under the condition of fast exchange between bound and free states are carefully discussed. We also show that original information on the angle dependence of the molecular pair distribution function can be gained from the measured paramagnetic dipolar shifts induced by complexed fast-relaxing Ln3+ ions. The method is illustrated by the case study of the anionic Lnttha3− = [Ln3+(ttha)]3− (ttha6− = triethylene tetraamine hexacetate) complex interacting with the biologically important tripeptide Arg-Gly-Asp (RGD) which carries peripheral ionic groups. The usefulness of an auxiliary reference outer sphere probe solute is emphasized.
Gas-phase photodissociation of CH3COCN at 308 nm by time-resolved Fourier-transform infrared emission spectroscopy
Authors: Yeh Yu-Ying , Chao Meng-Hsuan , Tsai Po-Yu , Chang Yuan-Bin , Tsai Ming-Tsang , Lin King-Chuen
Published: January 2012

By using time-resolved Fourier-transform infrared emission spectroscopy, the fragments of HCN(v = 1, 2) and CO(v = 1–3) are detected in one-photon dissociation of acetyl cyanide (CH3COCN) at 308 nm. The S1(A″), 1(nO, π*CO) state at 308 nm has a radiative lifetime of 0.46 ± 0.01 μs, long enough to allow for Ar collisions that induce internal conversion and enhance the fragment yields. The rate constant of Ar collision-induced internal conversion is estimated to be (1–7) × 10−12 cm3 molecule−1 s−1. The measurements of O2 dependence exclude the production possibility of these fragments via intersystem crossing. The high-resolution spectra of HCN and CO are analyzed to determine the ro-vibrational energy deposition of 81 ± 7 and 32 ± 3 kJ/mol, respectively. With the aid of ab initio calculations, a two-body dissociation on the energetic ground state is favored leading to HCN + CH2CO, in which the CH2CO moiety may further undergo secondary dissociation to release CO. The production of CO2 in the reaction with O2 confirms existence of CH2 and a secondary reaction product of CO. The HNC fragment is identified but cannot be assigned, as restricted to a poor signal-to-noise ratio. Because of insufficient excitation energy at 308 nm, the CN and CH3 fragments that dominate the dissociation products at 193 nm are not detected.
Anti-Stokes bright yellowish emission of NdAlO3 nanocrystals
Authors: Strek Wieslaw , Marciniak Lukasz , Hreniak Dariusz , Lukowiak Anna
Published: January 2012

Infrared laser diode–induced anti-Stokes bright yellowish emission of NdAlO3 nanocrystalline powder was observed at room temperature in ambient atmosphere. The emission intensity was found to be unaltered with lowering temperature and to increase by two orders of magnitude in vacuum. The temperature of bright emission under ambient atmosphere was determined to be 350 °C. It was found that the yellowish emission was accompanied by a giant photocurrent of 0.5 microamperes at relatively low applied voltage. The power dependence of the photocurrent was governed by an avalanche-like mechanism. The origin of the bright emission is discussed in terms of charge transfer luminescence of Nd3+.
Transient reduction of the drag coefficient of charged droplets via the convective reversal of stagnant caps
Authors: Hamlin Brad S. , Ristenpart William D.
Published: January 2012

Droplets are frequently observed to move as if they were solid rather than liquid, i.e., with no slip at the liquid-liquid interface. This behavior is usually explained in terms of the so-called “stagnant cap” model, in which surfactants accumulate at the trailing edge of the droplet, immobilizing the surface and increasing the observed drag coefficient. Here, we show that the drag coefficient for charged droplets is temporarily reduced by reversing the direction of an electric driving force. Using high speed video, we simultaneously track the velocity and relative interfacial velocity of individual aqueous droplets moving electrophoretically through oil. The observed velocity behavior is highly sensitive to the concentration of surfactant. For sufficiently low or sufficiently high concentration, upon reversal of the electric field the droplet rapidly accelerates in the opposite direction but then decelerates, concurrent with a transient rearrangement of tracer particles on the droplet surface. In contrast, droplets with intermediate surfactant concentrations exhibit neither deceleration nor significant tracer particle rearrangement. We interpret the observations in terms of convectively dominated rearrangement of the stagnant cap, and we discuss the implications for precise electrophoretic control of droplet motion in lab-on-a-chip devices and industrial electrocoalescers.
Optically driven method for magnetically levitating diamagnetic material using photothermal effect
Authors: Mizutani Yasuhiro , Tsutsumi Akihiro , Iwata Tetsuo , Otani Yukitoshi
Published: January 2012

Optically driven actuators do not require contact and thus can be used to generate movement remotely. In this paper, we propose a method for optically driving a magnetic levitation system that consists of a diamagnetic material as the moving object, a neodymium magnet, and a temperature-sensitive ferrite for varying the potential energy of the diamagnetic object. The diamagnetic object is levitated by the magnetic force between it and the neodymium magnet. Laser irradiation of the temperature-sensitive ferrite reduces its magnetic susceptibility due to the photothermal effect. In this study, the conditions for levitation are derived using a numerical approach. The results reveal that movement can be controlled in a three-dimensional region.
Spinor representation for loop quantum gravity
Authors: Livine Etera , Tambornino Johannes
Published: January 2012

We perform a quantization of the loop gravity phase space purely in terms of spinorial variables, which have recently been shown to provide a direct link between spin network states and simplicial geometries. The natural Hilbert space to represent these spinors is the Bargmann space of holomorphic square-integrable functions over complex numbers. We show the unitary equivalence between the resulting generalized Bargmann space and the standard loop quantum gravity Hilbert space by explicitly constructing the unitary map. The latter maps SU(2)-holonomies, when written as a function of spinors, to their holomorphic part. We analyze the properties of this map in detail. We show that the subspace of gauge invariant states can be characterized particularly easy in this representation of loop gravity. Furthermore, this map provides a tool to efficiently calculate physical quantities since integrals over the group are exchanged for straightforward integrals over the complex plane.
Pitch angle scattering of relativistic electrons from stationary magnetic waves: Continuous Markov process and quasilinear theory
Authors: Lemons Don S.
Published: January 2012

We develop a Markov process theory of charged particle scattering from stationary, transverse, magnetic waves. We examine approximations that lead to quasilinear theory, in particular the resonant diffusion approximation. We find that, when appropriate, the resonant diffusion approximation simplifies the result of the weak turbulence approximation without significant further restricting the regime of applicability. We also explore a theory generated by expanding drift and diffusion rates in terms of a presumed small correlation time. This small correlation time expansion leads to results valid for relatively small pitch angle and large wave energy density—a regime that may govern pitch angle scattering of high-energy electrons into the geomagnetic loss cone.
The origin of unique initial magnetization curves in Dy-substituted (Nd1−x, Dyx)2Fe14B (x = 0−1) sintered magnets
Authors: Kobayashi K. , Urushibata K. , Matsushita T. , Akiya T.
Published: January 2012

The coercivities (Hc), saturation magnetizations (Js), and anisotropy constants K1 of (Nd1−x, Dyx)2Fe14B sintered magnets (x = 0 to 1.0) are determined using high magnetic field measurements up to about 8 MA/m. The Ha, Js, and K1 values of samples with x < 0.5 are similar to those obtained in previous studies using single crystals; the Hc values for the sintered magnets are reported here for the first time. The magnetization into the single-domain states (SDS) in Dy-substituted sintered magnets is completed in lower fields than with Dy-free magnets (for example, 0.64 MA/m in the x = 1.0 sample and 1.6 MA/m in the x = 0.25 sample). The volume fraction of magnetized SDS grains when applying fields less than the demagnetizing fields of the samples also increases with increasing Dy content, i.e., 22 vol. % for a Dy-free sample and 48 vol. % for a Nd-free sample. A characteristic magnetization behavior of large pinning-like magnetization curves appeared in samples that were initially magnetized in a direction perpendicular to the c-axis and successively magnetized in the parallel direction. The apparent pinning field increased with increasing Dy concentration and reached 2.8 MA/m for the Nd-free samples. The origin of this behavior is the tilting of the c-axis in the crystal grains of sintered magnets and the clear preference for crystal grains in Dy-substituted samples to form SDS grains.
Minimum energy states of the cylindrical plasma pinch in single-fluid and Hall magnetohydrodynamics
Authors: Khalzov I. V. , Ebrahimi F. , Schnack D. D. , Mirnov V. V.
Published: January 2012

Relaxed states of a plasma column are found analytically in single-fluid and Hall magnetohydrodynamics (MHD). We perform complete minimization of the energy with constraints imposed by invariants inherent in the corresponding models. It is shown that the relaxed state in Hall MHD is a force-free magnetic field with uniform axial flow and/or rigid azimuthal rotation. In contrast, the relaxed states in single-fluid MHD are more complex due to the coupling between velocity and magnetic field. Cylindrically and helically symmetric relaxed states are considered for both models. Helical states may be time dependent and analogous to helical waves, propagating on a cylindrically symmetric background. Application of our results to reversed-field pinches (RFP) is discussed. The radial profile of the parallel momentum predicted by the single-fluid MHD relaxation theory is shown to be in reasonable agreement with experimental observation from the Madison symmetric torus RFP experiment.
Modeling of asymmetric pulsed phenomena in dielectric-barrier atmospheric-pressure glow discharges
Authors: Ha Yan , Wang Huijuan , Wang Xiaofei
Published: January 2012

Asymmetric current pulses in dielectric-barrier atmospheric-pressure glow discharges are investigated by a self-consistent, one-dimensional fluid model. It is found that the glow mode and Townsend mode can coexist in the asymmetric discharge even though the gas gap is rather large. The reason for this phenomenon is that the residual space charge plays the role of anode and reduces the gap width, resulting in the formation of a Townsend discharge.
Experimental verification of strong rotational dependence of fluorescence and predissociation yield in the b 1Πu(v = 1) level of 14N2
Authors: Wu C. Y. Robert , Judge D. L. , Tsai M.-H. , Lin Y.-C. , Yih T.-S. , Lo J.-I. , Fung H.-S. , Lee Y.-Y. , Lewis B. R. , Heays A. N. , Gibson S. T.
Published: January 2012

New, rotationally resolved fluorescence-excitation spectra confirm coupled-channel Schrödinger-equation predictions of strong rotational dependence of the fluorescence and predissociation yields in the b(v = 1) level of 14N2.
Evolution of metastable state molecules N2(A3Σu+) in a nanosecond pulsed discharge: A particle-in-cell/Monte Carlo collisions simulation
Authors: Gao Liang , Sun Jizhong , Feng Chunlei , Bai Jing , Ding Hongbin
Published: January 2012

A particle-in-cell plus Monte Carlo collisions method has been employed to investigate the nitrogen discharge driven by a nanosecond pulse power source. To assess whether the production of the metastable state N2(A3Σu+) can be efficiently enhanced in a nanosecond pulsed discharge, the evolutions of metastable state N2(A3Σu+) density and electron energy distribution function have been examined in detail. The simulation results indicate that the ultra short pulse can modulate the electron energy effectively: during the early pulse-on time, high energy electrons give rise to quick electron avalanche and rapid growth of the metastable state N2(A3Σu+) density. It is estimated that for a single pulse with amplitude of −9 kV and pulse width 30 ns, the metastable state N2(A3Σu+) density can achieve a value in the order of 109 cm−3. The N2(A3Σu+) density at such a value could be easily detected by laser-based experimental methods.
Electrostatic shock dynamics in superthermal plasmas
Authors: Sultana S. , Sarri G. , Kourakis I.
Published: January 2012

The propagation of ion acoustic shocks in nonthermal plasmas is investigated, both analytically and numerically. An unmagnetized collisionless electron-ion plasma is considered, featuring a superthermal (non-Maxwellian) electron distribution, which is modeled by a κ-(kappa) distribution function. Adopting a multiscale approach, it is shown that the dynamics of low-amplitude shocks is modeled by a hybrid Korteweg-de Vries–Burgers (KdVB) equation, in which the nonlinear and dispersion coefficients are functions of the κ parameter, while the dissipative coefficient is a linear function of the ion viscosity. All relevant shock parameters are shown to depend on κ: higher deviations from a pure Maxwellian behavior induce shocks which are narrower, faster, and of larger amplitude. The stability profile of the kink-shaped solutions of the KdVB equation against external perturbations is investigated. The spatial profile of the shocks is found to depend upon the dispersion and the dissipation term, and the role of the interplay between dispersion and dissipation is elucidated.
Bremsstrahlung of fast electrons in long air gaps
Authors: Oreshkin E. V. , Barengolts S. A. , Chaikovsky S. A. , Oginov A. V. , Shpakov K. V. , Bogachenkov V. A.
Published: January 2012

The results of an experiment on discharges in long atmospheric pressure air gaps at a pulsed voltage of amplitude up to 800 kV and risetime 150–200 ns have been analyzed. In the experiment, a radiation pulse of photon energy >5 keV and duration 10–20 ns was observed. In analyzing the experimental data it was supposed that a streamer is a plasma protrusion whose surface is equipotential to the cathode surface. It has been shown that the x-ray pulse results from the switch of electrons into the mode of "runaway" from the head of anode-directed streamers. For the electrons injected in the electrode gap from the streamer head, conditions for their switching into the mode of continuous acceleration are realized due to the enhanced electric field at the head. The predicted maximum of the spectrum of the bremsstrahlung generated by the runaway electron beam is around 15 keV. The presence of a maximum in the bremsstrahlung spectrum is due to that the photons emitted by electrons are absorbed by atoms of the gas in which the discharge operate.
A high accuracy femto-/picosecond laser damage test facility dedicated to the study of optical thin films
Authors: Mangote B. , Gallais L. , Zerrad M. , Lemarchand F. , Gao L. H. , Commandré M. , Lequime M.
Published: January 2012

A laser damage test facility delivering pulses from 100 fs to 3 ps and designed to operate at 1030 nm is presented. The different details of its implementation and performances are given. The originality of this system relies the online damage detection system based on Nomarski microscopy and the use of a non-conventional energy detection method based on the utilization of a cooled CCD that offers the possibility to obtain the laser induced damage threshold (LIDT) with high accuracy. Applications of this instrument to study thin films under laser irradiation are presented. Particularly the deterministic behavior of the sub-picosecond damage is investigated in the case of fused silica and oxide films. It is demonstrated that the transition of 0–1 damage probability is very sharp and the LIDT is perfectly deterministic at few hundreds of femtoseconds. The damage process in dielectric materials being the results of electronic processes, specific information such as the material bandgap is needed for the interpretation of results and applications of scaling laws. A review of the different approaches for the estimation of the absorption gap of optical dielectric coatings is conducted and the results given by the different methods are compared and discussed. The LIDT and gap of several oxide materials are then measured with the presented instrument: Al2O3, Nb2O5, HfO2, SiO2, Ta2O5, and ZrO2. The obtained relation between the LIDT and gap at 1030 nm confirms the linear evolution of the threshold with the bandgap that exists at 800 nm, and our work expands the number of tested materials.