bluuebunny/crossref_metadata_2025 huggingface dataset:
A new diffusion matrix for whistler mode chorus waves
Authors: Horne Richard B. , Kersten Tobias , Glauert Sarah A. , Meredith Nigel P. , Boscher Daniel , Sicard‐Piet Angelica , Thorne Richard M. , Li Wen
Published: October 2013

Global models of the Van Allen radiation belts usually include resonant wave‐particle interactions as a diffusion process, but there is a large uncertainty over the diffusion rates. Here we present a new diffusion matrix for whistler mode chorus waves that can be used in such models. Data from seven satellites are used to construct 3536 power spectra for upper and lower band chorus for 1.5≤L∗≤10 MLT, magnetic latitude 0°≤|λm|≤60° and five levels of Kp. Five density models are also constructed from the data. Gaussian functions are fitted to the spectra and capture typically 90% of the wave power. The frequency maxima of the power spectra vary with L∗ and are typically lower than that used previously. Lower band chorus diffusion increases with geomagnetic activity and is largest between 21:00 and 12:00 MLT. Energy diffusion extends to a few megaelectron volts at large pitch angles >60° and at high energies exceeds pitch angle diffusion at the loss cone. Most electron diffusion occurs close to the geomagnetic equator (<12°). Pitch angle diffusion rates for lower band chorus increase with L∗ and are significant at L∗=8 even for low levels of geomagnetic activity, while upper band chorus is restricted to mainly L∗<6. The combined drift and bounce averaged diffusion rates for upper and lower band chorus extend from a few kiloelectron volts near the loss cone up to several megaelectron volts at large pitch angles indicating loss at low energies and net acceleration at high energies.
Three‐dimensional simulation of dust charging and dusty plasma using SPIS
Authors: Anuar A. K. , Honary F. , Hapgood M. , Roussel J.‐F.
Published: October 2013

This paper presents new observations of the behavior of simulated dust particles in space plasma based on a 3‐D particle in cell code. Multistep Monte Carlo collision is employed to simulate the dust charging process, which is validated for the cases of charging of isolated dust particle and ensemble dust particles, where results indicate good agreement between simulation and theories. The code is then used to investigate plasma properties near a charged surface in a vicinity of a cloud of dust particles. The simulation reveals that a cloud of dust particle close to a spacecraft surface affects plasma densities around the spacecraft as well as the spacecraft's surface potential. It is suggested that dust cloud causes the surface to charge to higher negative potential. The simulation also suggests that the combination of surface potential and dust cloud potential produces a region of trapped low‐energy electrons.
The evolution of flux pileup regions in the plasma sheet: Cluster observations
Authors: Hamrin M. , Norqvist P. , Karlsson T. , Nilsson H. , Fu H. S. , Buchert S. , André M. , Marghitu O. , Pitkänen T. , Klecker B. , Kistler L. M. , Dandouras I.
Published: October 2013

Bursty bulk flows (BBFs) play an important role for the mass, energy, and magnetic flux transport in the plasma sheet, and the flow pattern in and around a BBF has important consequences for the localized energy conversion between the electromagnetic and plasma mechanical energy forms. The plasma flow signature in and around BBFs is often rather complicated. Return flows and plasma vortices are expected to exist at the flanks of the main flow channel, especially near the inner plasma sheet boundary, but also farther down‐tail. A dipolarization front (DF) is often observed at the leading edge of a BBF, and a flux pileup region (FPR) behind the DF. Here we present Cluster data of three FPRs associated with vortex flows observed in the midtail plasma sheet on 15 August 2001. According to the principles of Fu et al. (2011, 2012c), two of the FPRs are considered to be in an early stage of evolution (growing FPRs). The third FPR is in a later stage of evolution (decaying FPR). For the first time, the detailed energy conversion properties during various stages of the FPR evolution have been measured. We show that the later stage FPR has a more complex vortex pattern than the two earlier stage FPRs. The two early stage FPR correspond to generators, E·J<0, while the later stage FPR only shows weak generator characteristics and is instead dominated by load signatures at the DF, E·J>0. Moreover, to our knowledge, this is one of the first times BBF‐related plasma vortices have been observed to propagate over the spacecraft in the midtail plasma sheet at geocentric distances of about 18RE. Our observations are compared to recent simulation results and previous observations.
Very long period conduit oscillations induced by rockfalls at Kilauea Volcano, Hawaii
Authors: Chouet Bernard , Dawson Phillip
Published: October 2013

Eruptive activity at the summit of Kilauea Volcano, Hawaii, beginning in 2010 and continuing to the present time is characterized by transient outgassing bursts accompanied by very long period (VLP) seismic signals triggered by rockfalls from the vent walls impacting a lava lake in a pit within the Halemaumau pit crater. We use raw data recorded with an 11‐station broadband network to model the source mechanism of signals accompanying two large rockfalls on 29 August 2012 and two smaller average rockfalls obtained by stacking over all events with similar waveforms to improve the signal‐to‐noise ratio. To determine the source centroid location and source mechanism, we minimize the residual error between data and synthetics calculated by the finite difference method for a point source embedded in a homogeneous medium that takes topography into account. We apply a new waveform inversion method that accounts for the contributions from both translation and tilt in horizontal seismograms through the use of Green's functions representing the seismometer response to translation and tilt ground motions. This method enables a robust description of the source mechanism over the period range 1–1000 s. The VLP signals associated with the rockfalls originate in a source region ∼1 km below the eastern perimeter of the Halemaumau pit crater. The observed waveforms are well explained by a simple volumetric source with geometry composed of two intersecting cracks including an east striking crack (dike) dipping 80° to the north, intersecting a north striking crack (another dike) dipping 65° to the east. Each rockfall is marked by a similar step‐like inflation trailed by decaying oscillations of the volumetric source, attributed to the efficient coupling at the source centroid location of the pressure and momentum changes induced by the rock mass impacting the top of the lava column. Assuming a simple lumped parameter representation of the shallow magmatic system, the observed pressure and volume variations can be modeled with the following attributes: rockfall volume (200–4500 m3), length of magma column (120–210 m), diameter of pipe connecting the Halemaumau pit crater to the subjacent dike system (6 m), average thickness of the two underlying dikes (3–6 m), and effective magma viscosity (30–210 Pa s). Most rockfalls occur during episodes of sustained deflation of the Kilauea summit. The mass loss rate in the shallow magmatic system is estimated to be 1400–15,000 kg s−1 based on measurements of the temporal variation of VLP period in the two large rockfalls that occurred on 29 August 2012.
The 5 September 2012 Nicoya, Costa Rica Mw 7.6 earthquake rupture process from joint inversion of high‐rate GPS, strong‐motion, and teleseismic P wave data and its relationship to adjacent plate boundary interface properties
Authors: Yue Han , Lay Thorne , Schwartz Susan Y. , Rivera Luis , Protti Marino , Dixon Timothy H. , Owen Susan , Newman Andrew V.
Published: October 2013

On 5 September 2012, a large thrust earthquake (Mw 7.6) ruptured a densely instrumented seismic gap on the shallow‐dipping plate boundary beneath the Nicoya Peninsula, Costa Rica. Ground motion recordings directly above the rupture zone provide a unique opportunity to study the detailed source process of a large shallow megathrust earthquake using very nearby land observations. Hypocenter relocation using local seismic network data indicates that the event initiated with small emergent seismic waves from a hypocenter ~10 km offshore, 13 km deep on the megathrust. A joint finite‐fault inversion using high‐rate GPS, strong‐motion ground velocity recordings, GPS static offsets, and teleseismic P waves reveals that the primary slip zone (slip > 1 m) is located beneath the peninsula. The rupture propagated downdip from the hypocenter with a rupture velocity of ~3.0 km/s. The primary slip zone extends ~70 km along strike and ~30 km along dip, with an average slip of ~2 m. The associated static stress drop is ~3 MPa. The seismic moment is 3.5 × 1020 Nm, giving Mw = 7.6. The coseismic large‐slip patch directly overlaps an onshore interseismic locked region indicated by geodetic observations and extends downdip to the intersection with the upper plate Moho. At deeper depths, below the upper plate Moho, seismic tremor and low‐frequency earthquakes have been observed. Most tremor locates in adjacent areas of the megathrust that have little coseismic slip; a region of prior slow slip deformation to the southeast also has no significant coseismic slip or aftershocks. An offshore locked patch indicated by geodetic observations does not appear to have experienced coseismic slip, and aftershocks do not overlap this region, allowing the potential for a comparable size rupture offshore in the future.
Silver and Chan revisited
Authors: Walsh E. , Arnold R. , Savage M. K.
Published: October 2013

Seismic shear waves emitted by earthquakes can be modeled as plane (transverse) waves. When entering an anisotropic medium, they can be split into two orthogonal components moving at different speeds. This splitting occurs along an axis, the fast polarization, that is determined by geologic conditions. We present here a comprehensive analysis of the Silver and Chan (1991) method, used to obtain shear wave splitting parameters, comprising theoretical derivations and statistical tests of the assumptions used to construct the standard errors. We find discrepancies in the derivations of equations in their article, with the most important being a mistake in how the standard errors are calculated. Our simulations suggest that the degrees of freedom are being overestimated by this method, and consequently, the standard errors are too small. Using a set of S waveforms from very similar shallow earthquakes on Reunion Island, we perform a statistical analysis on the noise of these replicates and find that the assumption of Gaussian noise does not hold. Further, the properties of background noise differ substantially from the noise obtained from the shear wave splitting analysis. However, we find that the estimated standard errors for the fast polarization are comparable to the spread in the fast polarization parameters between events. Delay time errors appear to be comparable to delay time estimates once cycle skipping is accounted for. Future work using synthetic seismograms with simulated noise should be conducted to confirm this is the case for earthquakes in general.
Downdip landward limit of Cascadia great earthquake rupture
Authors: Hyndman R. D.
Published: October 2013

This paper examines the constraints to the downdip landward limit of rupture for the Cascadia great earthquakes off western North America. This limit is a primary control for ground motion hazard at near‐coastal cities. The studies also provide information on the physical controls of subduction thrust rupture globally. The constraints are (1) “locked/transition” zones from geodetic deformation (GPS, repeated leveling, tide gauges); (2) rupture zone from paleoseismic coastal marsh subsidence, “paleogeodesy”; (3) temperature on the thrust for the seismic‐aseismic transition; (4) change in thrust seismic reflection character downdip from thin seismic to thick ductile; (5) fore‐arc mantle corner aseismic serpentinite and talc overlying the thrust; (6) updip limit of episodic tremor and slip (ETS) slow slip; (7) rupture area associations with shelf‐slope basins; (8) depth limit for small events on the thrust; and (9) landward limit of earthquakes on the Nootka transform fault zone. The most reliable constraints for the limit of large rupture displacement, >10 m, are generally just offshore in agreement with thermal control for this hot subduction zone, but well‐offshore central Oregon and near the coast of northern Washington. The limit for 1–2 m rupture that can still provide strong shaking is less well estimated 25–50 km farther landward. The fore‐arc mantle corner and the updip extent of ETS slow slip are significantly landward from the other constraints. Surprisingly, there is a downdip gap between the best other estimates for the great earthquake rupture zone and the ETS slow slip. In this gap, plate convergence may occur as continuous slow creep.
Poleward propagating subinertial alongshore surface currents off the U.S. West Coast
Authors: Kim Sung Yong , Cornuelle Bruce D. , Terrill Eric J. , Jones Burt , Washburn Libe , Moline Mark A. , Paduan Jeffrey D. , Garfield Newell , Largier John L. , Crawford Greg , Michael Kosro P.
Published: October 2013

The network comprising 61 high‐frequency radar systems along the U.S. West Coast (USWC) provides a unique, high resolution, and broad scale view of ocean surface circulation. Subinertial alongshore surface currents show poleward propagating signals with phase speeds of O(10) and O(100–300)
that are consistent with historical in situ observations off the USWC and that can be possibly interpreted as coastally trapped waves (CTWs). The propagating signals in the slow mode are partly observed in southern California, which may result from scattering and reflection of higher‐mode CTWs due to curvature of shoreline and bathymetry near Point Conception, California. On the other hand, considering the order of the phase speed in the slow mode, the poleward propagating signals may be attributed to alongshore advection or pressure‐driven flows. A statistical regression of coastal winds at National Data Buoy Center buoys on the observed surface currents partitions locally and remotely wind‐forced components, isolates footprints of the equatorward propagating storm events in winter off the USWC, and shows the poleward propagating signals year round.
Tropospheric SF6: Age of air from the Northern Hemisphere midlatitude surface
Authors: Waugh D. W. , Crotwell A. M. , Dlugokencky E. J. , Dutton G. S. , Elkins J. W. , Hall B. D. , Hintsa E. J. , Hurst D. F. , Montzka S. A. , Mondeel D. J. , Moore F. L. , Nance J. D. , Ray E. A. , Steenrod S. D. , Strahan S. E. , Sweeney C.
Published: October 2013

Observations of SF6 are used to quantify the mean time since air was in (“mean age” from) the Northern Hemisphere (NH) midlatitude surface layer. The mean age is a fundamental property of tropospheric transport that can be used in theoretical studies and used to evaluate transport in comprehensive models. Comparisons of simulated SF6 and an idealized clock tracer confirm that the time lag between the SF6 mixing ratio at a given location and the NH midlatitude surface provides an accurate estimate of the mean age. The ages calculated from surface SF6 measurements show large meridional gradients in the tropics but weak gradients in the extratropics, with near‐zero ages at the surface north of 30°N and ages around 1.4 years south of 30°S. Aircraft measurements show weak vertical age gradients in the lower and middle troposphere, with only slight increases of age with height in the NH and slight decreases with height in the Southern Hemisphere. There are large seasonal variations in the age at tropical stations (annual amplitudes around 0.5–1.0 year), with younger ages during northern winter, but only weak seasonal variations at higher latitudes. The seasonality and interannual variations in the tropics and Southern Hemisphere are related to changes in locations of tropical convection. There is qualitative agreement, in both spatial and temporal variations, between the simulated ages and observations. The model ages tend to be older than observed, with differences of ~0.2 year in the Northern Hemisphere upper troposphere and throughout the Southern Hemisphere troposphere.
Diurnal variation in Sahara desert sand emissivity during the dry season from IASI observations
Authors: Masiello Guido , Serio Carmine , Venafra Sara , DeFeis Italia , Borbas Eva E.
Published: October 2013

The problem of diurnal variation in surface emissivity over the Sahara Desert during non‐raining days is studied and assessed with observations from the Infrared Atmospheric Sounding Interferometer (IASI). The analysis has been performed over a Sahara Desert dune target area during July 2010. Spinning Enhanced Visible and Infrared Imager observations from the European geostationary platform Meteosat‐9 (Meteorological Satellite 9) have been also used to characterize the target area. Although the amplitude of this daily cycle has been shown to be very small, we argue that suitable nighttime meteorological conditions and the strong contrast of the reststrahlen absorption bands of quartz (8–14 μm) can amplify its effect over the surface spectral emissivity. The retrieval of atmospheric parameters show that, at nighttime, an atmospheric temperature inversion occurs close to the surface yielding a thin boundary layer which acts like a lid, keeping normal convective overturning of the atmosphere from penetrating through the inversion. This mechanism traps water vapor close to the land and drives the direct adsorption of water vapor at the surface during the night. The diurnal variation in emissivity at 8.7 μm has been found to be as large as 0.03 with high values at night and low values during the day. At 10.8 μm and 12 μm, the variation has the same sign as that at 8.7 μm, but with a smaller amplitude, 0.019 and 0.014, respectively. The impact of these diurnal variations on the retrieval of surface temperature and atmospheric parameters has been analyzed.
Comparison of GEOS‐Chem aerosol optical depth with AERONET and MISR data over the contiguous United States
Authors: Li Shenshen , Garay Michael J. , Chen Liangfu , Rees Erika , Liu Yang
Published: October 2013

Aerosol optical properties simulated by the global 3‐D tropospheric chemistry and transport model Goddard Earth Observing System (GEOS)‐Chem (GC) from 2008 to 2010 over the contiguous United States were evaluated with ground observations from Aerosol Robotic Network (AERONET) sites and aerosol products reported by the Multiangle Imaging Spectroradiometer (MISR). Overall, the correlation coefficient (r) and regression slope between AERONET and GC2° × 2.5° (2° latitude × 2.5° longitude) daily total column aerosol optical depth (AOD) were 0.6 and 0.51, respectively. After using the nested GC0.5° × 0.667° model to control for spatial variability, removing several outliers, and averaging over a monthly timescale, the agreement was significantly improved to an r of 0.84 and a slope of 0.75. Seasonal, hourly, and geographical statistics for GC0.5° × 0.667° and AERONET AODs show a similar data range and variation, with higher mean values in the summer, the evening, and in the eastern U.S. Smaller correlation coefficients are seen in the summer and winter, in the evening, and in the western U.S. To investigate the optical properties of major GC tracers, MISR level 2 aerosol products were used to calculate inorganic aerosol, dust, and absorbing non‐dust AOD. Both GC and MISR suggest that on average, inorganic aerosol has the highest AOD (GC: 0.071, MISR: 0.089) nationally, followed by absorbing non‐dust species (GC: 0.025, MISR: 0.041), and dust (GC: 0.013, MISR: 0.014). The large discrepancies in our intercomparison are due to GC underestimation of inorganic aerosol levels during all four seasons in the western U.S. and dust during summer in the eastern U.S., along with overestimation of summertime‐absorbing non‐dust species over the northwestern U.S. These uncertainties are attributed to underestimation of inorganic aerosol emissions in more polluted western regions, the transport of Sahara dust in the summer, misuse of the fire files, MISR retrieval uncertainties in the surface, and choice of aerosol models.
The hydrological impact of geoengineering in the Geoengineering Model Intercomparison Project (GeoMIP)
Authors: Tilmes Simone , Fasullo John , Lamarque Jean‐Francois , Marsh Daniel R. , Mills Michael , Alterskjær Kari , Muri Helene , Kristjánsson Jón E. , Boucher Olivier , Schulz Michael , Cole Jason N. S. , Curry Charles L. , Jones Andy , Haywood Jim , Irvine Peter J. , Ji Duoying , Moore John C. , Karam Diana B. , Kravitz Ben , Rasch Philip J. , Singh Balwinder , Yoon Jin‐Ho , Niemeier Ulrike , Schmidt Hauke , Robock Alan , Yang Shuting , Watanabe Shingo
Published: October 2013

The hydrological impact of enhancing Earth's albedo by solar radiation management is investigated using simulations from 12 Earth System models contributing to the Geoengineering Model Intercomparison Project (GeoMIP). We contrast an idealized experiment, G1, where the global mean radiative forcing is kept at preindustrial conditions by reducing insolation while the CO2 concentration is quadrupled to a 4×CO2 experiment. The reduction of evapotranspiration over land with instantaneously increasing CO2 concentrations in both experiments largely contributes to an initial reduction in evaporation. A warming surface associated with the transient adjustment in 4×CO2 generates an increase of global precipitation by around 6.9% with large zonal and regional changes in both directions, including a precipitation increase of 10% over Asia and a reduction of 7% for the North American summer monsoon. Reduced global evaporation persists in G1 with temperatures close to preindustrial conditions. Global precipitation is reduced by around 4.5%, and significant reductions occur over monsoonal land regions: East Asia (6%), South Africa (5%), North America (7%), and South America (6%). The general precipitation performance in models is discussed in comparison to observations. In contrast to the 4×CO2 experiment, where the frequency of months with heavy precipitation intensity is increased by over 50% in comparison to the control, a reduction of up to 20% is simulated in G1. These changes in precipitation in both total amount and frequency of extremes point to a considerable weakening of the hydrological cycle in a geoengineered world.
Global observations of gravity wave intermittency and its impact on the observed momentum flux morphology
Authors: Wright C. J. , Osprey S. M. , Gille J. C.
Published: October 2013

Three years of gravity wave observations from the High Resolution Dynamics Limb Sounder instrument on NASA's Aura satellite are examined. We produce estimates of the global distribution of gravity wave momentum flux as a function of individual observed wave packets. The observed distribution at the 25 km altitude level is dominated by the small proportion of wave packets with momentum fluxes greater than ∼0.5 mPa. Depending on latitude and season, these wave packets only comprise ∼7–25% of observations, but are shown to be almost entirely responsible for the morphology of the observed global momentum flux distribution. Large‐amplitude wave packets are found to be more important over orographic regions than over flat ocean regions, and to be especially high in regions poleward of 40°S during austral winter. The momentum flux carried by the largest packets relative to the distribution mean is observed to decrease with height over orographic wave generation regions, but to increase with height at tropical latitudes; the mesospheric intermittency resulting is broadly equivalent in both cases. Consistent with previous studies, waves in the top 10% of the extratropical distribution are observed to carry momentum fluxes more than twice the mean and waves in the top 1% more than 10× the mean, and the Gini coefficient is found to characterize the observed distributions well. These results have significant implications for gravity wave modeling.
A global model of meteoric sodium
Authors: Marsh Daniel R. , Janches Diego , Feng Wuhu , Plane John M. C.
Published: October 2013

A global model of sodium in the mesosphere and lower thermosphere has been developed within the framework of the National Center for Atmospheric Research's Whole Atmosphere Community Climate Model (WACCM). The standard fully interactive WACCM chemistry module has been augmented with a chemistry scheme that includes nine neutral and ionized sodium species. Meteoric ablation provides the source of sodium in the model and is represented as a combination of a meteoroid input function (MIF) and a parameterized ablation model. The MIF provides the seasonally and latitudinally varying meteoric flux which is modeled taking into consideration the astronomical origins of sporadic meteors and considers variations in particle entry angle, velocity, mass, and the differential ablation of the chemical constituents. WACCM simulations show large variations in the sodium constituents over time scales from days to months. Seasonality of sodium constituents is strongly affected by variations in the MIF and transport via the mean meridional wind. In particular, the summer to winter hemisphere flow leads to the highest sodium species concentrations and loss rates occurring over the winter pole. In the Northern Hemisphere, this winter maximum can be dramatically affected by stratospheric sudden warmings. Simulations of the January 2009 major warming event show that it caused a short‐term decrease in the sodium column over the polar cap that was followed by a factor of 3 increase in the following weeks. Overall, the modeled distribution of atomic sodium in WACCM agrees well with both ground‐based and satellite observations. Given the strong sensitivity of the sodium layer to dynamical motions, reproducing its variability provides a stringent test of global models and should help to constrain key atmospheric variables in this poorly sampled region of the atmosphere.
Characterizing sampling biases in the trace gas climatologies of the SPARC Data Initiative
Authors: Toohey M. , Hegglin M. I. , Tegtmeier S. , Anderson J. , Añel J. A. , Bourassa A. , Brohede S. , Degenstein D. , Froidevaux L. , Fuller R. , Funke B. , Gille J. , Jones A. , Kasai Y. , Krüger K. , Kyrölä E. , Neu J. L. , Rozanov A. , Smith L. , Urban J. , von Clarmann T. , Walker K. A. , Wang R. H. J.
Published: October 2013

Monthly zonal mean climatologies of atmospheric measurements from satellite instruments can have biases due to the nonuniform sampling of the atmosphere by the instruments. We characterize potential sampling biases in stratospheric trace gas climatologies of the Stratospheric Processes and Their Role in Climate (SPARC) Data Initiative using chemical fields from a chemistry climate model simulation and sampling patterns from 16 satellite‐borne instruments. The exercise is performed for the long‐lived stratospheric trace gases O3 and H2O. Monthly sampling biases for O3 exceed 10% for many instruments in the high‐latitude stratosphere and in the upper troposphere/lower stratosphere, while annual mean sampling biases reach values of up to 20% in the same regions for some instruments. Sampling biases for H2O are generally smaller than for O3, although still notable in the upper troposphere/lower stratosphere and Southern Hemisphere high latitudes. The most important mechanism leading to monthly sampling bias is nonuniform temporal sampling, i.e., the fact that for many instruments, monthly means are produced from measurements which span less than the full month in question. Similarly, annual mean sampling biases are well explained by nonuniformity in the month‐to‐month sampling by different instruments. Nonuniform sampling in latitude and longitude are shown to also lead to nonnegligible sampling biases, which are most relevant for climatologies which are otherwise free of biases due to nonuniform temporal sampling.
Velocities in the plume of the 2010 Eyjafjallajökull eruption
Authors: Bjornsson H. , Magnusson S. , Arason P. , Petersen G. N.
Published: October 2013

The eruption of the Icelandic volcano Eyjafjallajökull in the spring of 2010 lasted for 39 days with an explosive phase (14–18 April), an effusive phase (18 April to 4 May) and a phase with renewed explosive activity (5–17 May). Images every 5 s from a camera mounted 34 km from the volcano are available for most of the eruption. Applying the maximum cross‐correlation method (MCC) on these images, the velocity structure of the eruption cloud has been mapped in detail for four time intervals covering the three phases of the eruption. The results show that on average there are updrafts in one part of the cloud and lateral motion or downdrafts in another. Even within the updraft part, there are alternating motions of strong updrafts, weak updrafts, and downward motion. These results show a highly variable plume driven by intermittent explosions. The results are discussed in the context of integral plume models and in terms of elementary parcel theory.
Entrainment rates and microphysics in POST stratocumulus
Authors: Gerber H. , Frick G. , Malinowski Szymon P. , Jonsson H. , Khelif D. , Krueger Steven K.
Published: October 2013

An aircraft field study (POST; Physics of Stratocumulus Top) was conducted off the central California coast in July and August 2008 to deal with the known difficulty of measuring entrainment rates in the radiatively important stratocumulus (Sc) prevalent in that area. The Center for Interdisciplinary Remotely‐Piloted Aircraft Studies Twin Otter research aircraft flew 15 quasi‐Lagrangian flights in unbroken Sc and carried a full complement of probes including three high‐data‐rate probes: ultrafast temperature probe, particulate volume monitor probe, and gust probe. The probes' colocation near the nose of the Twin Otter permitted estimation of entrainment fluxes and rates with an in‐cloud resolution of 1 m. Results include the following: Application of the conditional sampling variation of classical mixed layer theory for calculating the entrainment rate into cloud top for POST flights is shown to be inadequate for most of the Sc. Estimated rates resemble previous results after theory is modified to take into account both entrainment and evaporation at cloud top given the strong wind shear and mixing at cloud top. Entrainment rates show a tendency to decrease for large shear values, and the largest rates are for the smallest temperature jumps across the inversion. Measurements indirectly suggest that entrained parcels are primarily cooled by infrared flux divergence rather than cooling from droplet evaporation, while detrainment at cloud top causes droplet evaporation and cooling in the entrainment interface layer above cloud top.
Wave heating and Jeans escape in the Martian upper atmosphere
Authors: Walterscheid R. L. , Hickey M. P. , Schubert G.
Published: October 2013

Gusty flow over rough terrain is likely to be a significant source of fast gravity waves and acoustic waves in the atmosphere of Mars, as it is in Earth's atmosphere. Accordingly, we have used a numerical model to study the dissipation in the thermosphere and exosphere of Mars of upward‐propagating fast gravity waves and acoustic waves. Model simulations are performed for a range of wave periods and horizontal wavelengths. Wave amplitudes are constrained by the Mars Global Surveyor and Mars Odyssey aerobraking data, and gravity wave phase velocities are limited by occultation data. Dissipating gravity waves heat some regions of the thermosphere and cool others through the effects of sensible heat flux divergence, while acoustic waves mainly heat the Mars thermosphere. Heating rates can be on the order of several hundred Kelvin per day. The cycle‐integrated effects on the Jeans escape flux are also investigated and found to be on the order of background values and even greater and might be a significant source of loss of the Martian atmosphere to space.
Characterization of the spatial and temporal variability of surface water in the Soudan‐Sahel region of Africa
Authors: Kaptué Armel T. , Hanan Niall P. , Prihodko Lara
Published: October 2013

Water is a precious resource since the lives and livelihoods of human societies depend on their ability to access this resource. This is particularly true in arid and semiarid regions like the Sahel where permanent surface waters are rare and hydrological solutions (e.g., accessing deep aquifers) are often not feasible. This work is devoted to the determination of the spatial and temporal variations of surface water extent at 250 m over 9 years (2003–2011) for the Soudan‐Sahel region using visible and infrared imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS) from both Terra and Aqua platforms. The methodology is automatic and could be applied to other regions and sensors. We utilized a combination of two MODIS spectral indices: the Normalized Difference Vegetation Index and the Modified Normalized Difference Water Index. Accuracy assessments carried out on 743 lakes across 37 Landsat images selected in Sahelian Africa on the basis of a stratified sampling show that the new product is (i) reliably able to detect surface water bodies of approximately 50 ha and larger, (ii) improves on existing surface water body products, and (iii) can be used to monitor the seasonal distribution of surface water in semiarid regions.
Effect of nutrient enrichment on δ13CH4 and the methane production pathway in the Florida Everglades
Authors: Holmes M. Elizabeth , Chanton Jeffrey P. , Bae Hee‐Sung , Ogram Andrew
Published: October 2013

Water Conservation Area 2A in the Florida Everglades is characterized by a nutrient gradient with high levels in the north from agricultural runoff and more oligotrophic conditions in the southern interior. Based on laboratory incubations and field studies, we found that the relative importance of methane (CH4) production mechanisms shifted along this gradient, with a greater contribution due to hydrogenotrophic methanogenesis at higher nutrient levels. The relative contributions of hydrogenotrophic and acetoclastic methanogenesis were determined from laboratory experiments and verified with field results. In the lab the relative contributions of the two pathways were determined from the differences in CH4 production rates in soil collected from sites along the nutrient gradient that was incubated with and without an inhibitor of acetoclastic methanogenesis (methyl fluoride, CH3F). In the nutrient‐poor soil, most of the CH4 was formed via acetate fermentation and only 25% came from hydrogenotrophic methanogenesis. At the nutrient‐impacted site CH4 was produced at fourfold higher rates and the proportion of CH4 produced via hydrogenotrophic methanogenesis increased to 50%. Isotopic fractionation factors for hydrogenotrophic and acetoclastic methanogenesis were calculated from the soil incubations and applied to δ13C‐CO2 and δ13C‐CH4 measured in pore water from the same transect. The trend of increased hydrogenotrophic relative to acetoclastic CH4 production along the nutrient‐impacted gradient was mirrored in the field data, which produced similar results to the lab incubation work, with up to 23% of the CH4 produced from hydrogenotrophic methanogenesis at the nutrient‐poor site and nearly half at the nutrient‐impacted site.
Cholecystectomy by using a surgical robotic system
Authors: Romero‐Talamás Héctor , Kroh Matthew
Published: October 2013

Because of their frequency, hepato‐biliary procedures have been the gateway for innovation to permeate into the realm of general surgery. Robotics and single‐incision techniques are the latest manifestation in the evolution of minimally invasive surgery. Enthusiasm for the latter has increased due to its inarguably superior cosmetic result. Nevertheless, there are several technical disadvantages associated with this approach that have raised several concerns. The robotic platform may provide a solution to these issues. We analyze the strengths and weaknesses of the robotic system for cholecystectomy and its relation to single site technology. We review all available literature addressing robotic single site cholecystectomy. Due to the advent of specific robotic single site technology, many of the challenges commonly associated with single site cholecystectomy have been alleviated. Although this novel approach has not yet been extensively tested, the available evidence suggests that it is at least equivalent to LC in selected patients. Robotic single site cholecystectomy is safe and feasible and adequately compensates for many of the challenges commonly associated with conventional single site cholecystectomy. Large, high‐quality studies are needed to further clarify the role of this procedure and its value as part of the surgeon's armamentarium.
New technologies for single‐site robotic surgery in hepato‐biliary‐pancreatic surgery
Authors: Diana Michele , Pessaux Patrick , Marescaux Jacques
Published: October 2013

Laparoendoscopic single‐site surgery (LESS) aims to reduce incision‐related complications by using a single surgical access through which multiple instruments are inserted simultaneously. First descriptions of LESS procedures date back to the early 90s, but the approach initially failed to gain popularity because of technical challenges that markedly impair the principles of laparoscopic ergonomics. In recent years LESS has been increasingly applied to hepatobiliary procedures including cholecystectomies and liver resections. However, the uptake of LESS in hepatobiliary is limited. The surgical robotic platform might play a fundamental role in facilitating the uptake of LESS by the surgical community since robotic science made it possible to develop adequate technology to deal with some of the LESS issues such as restoring surgical triangulation. In this paper the current state‐of‐the‐art for robotic LESS applied to the hepatobiliary system and emerging technologies enabling safer LESS procedures have been reviewed and future perspectives commented on the light of our experience.
Female donor to male recipient gender discordance results in inferior graft survival: a prospective study of 1,042 liver transplants
Authors: Croome Kristopher P. , Segal Dan , Hernandez‐Alejandro Roberto , Adams Paul C. , Thomson Alan , Chandok Natasha
Published: October 2013

Background

The influence of donor‐recipient gender mismatch on outcomes after liver transplantation (LT) is controversial. The aim of this study was to evaluate the effect of donor and recipient gender discordance on graft survival.

Methods

All patients who underwent primary LT from 1994–2012 at a single‐center were identified prospectively. Clinico‐demographic data were collected at the time of LT and last follow‐up. Gender match included both male donor to male recipient (MM) and female donor to female recipient (FF), while gender mismatch included female donor to male recipient (FM) and male donor to female recipient (MF). Survival curves for graft survival were generated using Kaplan–Meier method and compared by log‐rank test. Unadjusted and multivariate adjusted COX regression analyzing graft survival at up to 10 years post‐transplant was performed.

Results

A total of 1,042 subjects fulfilled the criteria. Graft survival in patients receiving a donor‐recipient gender match was better than those receiving a gender mismatch (P = 0.047). Female‐to‐male transplants had the worst graft survival of all combinations (P < 0.001); this difference was maintained in multivariate regression after adjustment for recipient and donor variables (hazards ratio 2.09, P = 0.013).

Conclusion

Female‐to‐male liver transplants are associated with a statistically significant poorer graft survival as compared with other donor‐recipient gender groups.
Technique of endoscopic ultrasonography‐guided pancreatic duct intervention (with videos)
Authors: Itoi Takao , Yasuda Ichiro , Kurihara Toshio , Itokawa Fumihide , Kasuya Kazuhiko
Published: October 2013

To date, several endoscopic ultrasonography (EUS)‐guided interventions have been reported. Of these interventions, EUS‐guided pancreatic duct (PD) intervention seems to be the most difficult and challenging procedure to accomplish. We provide suggestions for EUS‐guided PD intervention, which includes PD stenting and the rendezvous technique following EUS‐guided pancreatography. PD stenting is performed between the PD and the gastrointestinal tract (stomach, duodenum, or jejunum). The rendezvous technique is performed using a guidewire across the papilla or anastomotic site for retrograde stent insertion. EUS‐guided PD intervention is still challenging because it is not established yet. Thus, although EUS‐guided PD intervention seems to be promising, it should be performed in selected patients such as those of failed standard endoscopic retrograde cholangiopancreatography.
On the Reaction Products of 4‐Substituted 3‐Pyridinesulfonamides with Some Benzenesulfonyl Chloride Derivatives
Authors: Brzozowski Zdzisław , Sławiński Jarosław , Szafrański Krzysztof
Published: October 2013

The reactions of 4‐substituted 3‐pyridinesulfonamides 1a, 1b, 1c, 1d, 1e with benzenesulfonyl chlorides 2a, 2b, 2c, 2d, 2e, 2f in acetonitrile were investigated. Depending on the structure of arylsulfonyl chlorides and the reaction conditions the following four types of products were obtained in good yields: 3‐sulfamoyl‐4‐R‐1‐arylpyridinium chlorides 3, 4, 5, 6, 7, 8; 1,10‐bis(3‐nitrobenzenesulfonylimino)deca‐2,4,6,8‐tetraene‐2,9‐disulfonamides 9, 10, 11, 12; 1‐substituted 1,4‐dihydro‐4‐oxo‐3‐pyridinesulfonamides 13, 14; and 4‐methoxy‐3‐[N‐(2,5‐dichlorophenyl)sulfonyl] sulfonamidates 15 and 16. The mechanisms of these reactions were discussed.
A Novel Synthetic Protocol for the Heteroannulation of Oxocarbazole and Oxoazacarbazole Derivatives through Corresponding Oxoketene Dithioacetals
Authors: Tyagi Ruchi , Kaur Navjeet , Singh Bhawani , Kishore Dharma
Published: October 2013

An efficient novel strategy for the heteroannulation of 6,7‐dihydropyrazolo[3,4‐b]carbazol‐8(1H,5H,9H)‐one 4 and 5‐N‐benzyl‐6,7‐dihydropyrazolo[3,4‐b]carbazol‐8(1H,9H)‐one 5 has been developed to allow the incorporation of pyrazole, isoxazole, pyrimidine, benzodiazepine, and benzothiazepine rings through their corresponding oxoketene dithioacetal derivatives 6 and 7, respectively.
Synthesis of 1H‐Imidazoles Catalyzed by Cu‐Nanoparticle and Its Physicochemical Properties
Authors: Pagadala Ramakanth , Gandhare Nilesh V. , Kusampally Uppalaiah , Jetti Venkateshwarlu , Meshram Jyotsna S. , Juneja H. D.
Published: October 2013

Series of 1‐arylmethyl‐4, 5‐dihydro‐2‐aryl‐1H‐imidazole were synthesized expeditiously in good yields from 1,2‐diaminoethane and aromatic aldehydes in the presence of Cu nanoparticle under microwave irradiation in solvent‐free method. Monodisperse spherical Cu nanoparticles with a diameter range of 45 ± 8 nm were synthesized by polyol process. The particle size and elemental structure of copper nanoparticles were confirmed by XRD data and was found to be having a face‐centered cubic structure. The resulting substituted imidazoles have been studied in the achievement of degree of drug absorption enhancement as well as the potential associated toxicity on the basis of hypothetical antibacterial pharmacophores and structures that were designed to interact with both of gram‐positive and gram‐negative bacteria. All the synthesized molecules were characterized on the basis of 1H NMR, 13C NMR, mass spectrometry, and elemental data.
New Synthesis of Diazepino[3,2,1‐ij]quinoline and Pyrido[1,2,3‐de]quinoxalines via Addition–Elimination Followed by Cycloacylation
Authors: Baraldi Pier Giovanni , Ruggiero Emanuela , Tabrizi Mojgan Aghazadeh
Published: October 2013

This paper describes a convenient and efficient synthesis of new fused tricyclic diazepino[3,2,1‐ij]quinolines and substituted pyrido[1,2,3‐de]quinoxalines. o‐Phenylenediamines are transformed in the tricycle nucleus in only a few‐step synthetic sequence to produce ethyl 2,8‐dioxo‐1,2,3,4‐tetrahydro‐8H [1,4]diazepino[3,2,1‐ij]quinoline‐7‐carboxylate, ethyl 8‐oxo‐1,2,3,4‐tetrahydro‐8H‐[1,4]diazepino[3,2,1‐ij]quinoline‐7‐carboxylate and ethyl 2,7‐dioxo‐2,3‐dihydro‐1H,7H‐pyrido[1,2,3‐de]quinoxaline‐6‐carboxylate. The method is economical and simple to perform.
Synthesis and Herbicidal Activity of Muti‐Substituted Pyrido[4,3‐d]pyrimidin‐4‐ones
Authors: Zhai Yue‐E , Shi De‐Qing
Published: October 2013

A series of novel muti‐substituted pyrido[4,3‐d]pyrimidin‐4‐one derivatives5a,5b,5c,5d,5e,5f,5g,5h,5i,5j,5k,5lwere designed and synthesized by the muti‐step reaction.N,S‐acetal1reacted with acetyl acetamide in the presence of zinc nitrate to obtain muti‐substituted pyridine2, which reacted with triethyl orthoformate to give 8‐cyano‐5‐methyl‐7‐methylthio‐pyrido[4,3‐d]pyrimidin‐4‐one3; the target compounds5were obtained in good yields by the oxidation of3with H2O2in a catalytic amount of sodium tungstate then by the substitution with various substituted phenols. Their structures were confirmed by IR,1H NMR, EI‐MS, and elemental analyses. The preliminary bioassay indicated that some of them displayed moderate herbicidal activity against dicotyledonous weedBrassica campestrisL. at the concentration of 100 mg/L. For example, compounds5a,5f, and5gpossessed 76.0%, 62.7%, and 60.2% inhibition againstB.campestrisat the concentration of 100 mg/L. Moreover,5aexhibited 58.2% inhibition againstB.campestrisat the concentration of 10 mg/L.
CONTRIBUTION DENSITIES, TRANSITIONS AND PENSION RIGHTS: THE CASE OF JORDAN
Authors: Forteza Alvaro , Mussio Irene
Published: October 2013

Using micro‐data from the Social Security Corporation (SSC), we analyse the dynamics of social security coverage in the Jordanian labour force. We characterise patterns of contribution densities and transition rates and fit survival models for transitions. We also simulate pension rights. We compare patterns in the Jordanian SSC and in social security programmes in three Latin American countries for which a similar analysis has been conducted. We find comparatively low contribution densities and transition rates in Jordan, which is consistent with low coverage and low turnover rates. Copyright © 2013 John Wiley & Sons, Ltd.
Determinants of Household Vulnerability to Food Insecurity: A Case Study of Semi‐Arid Districts in Malawi
Authors: Kakota Tasokwa , Nyariki Dickson , Mkwambisi David , Kogi‐Makau Wambui
Published: October 2013

This paper looks at household vulnerability to food insecurity and its determinants in two semi‐arid districts in Malawi. A randomly selected sample of 200 households was interviewed. The descriptive statistics revealed that female‐headed households were more vulnerable to food insecurity than male‐headed households because of low access to resources for food production and purchases. A two‐stage least squares regression analysis showed that amongst the main determinants of household vulnerability were income, household size, land size and access to climate information. The findings imply that policies should promote diversification of livelihoods and equal opportunities and rights to access resources. Copyright © 2013 John Wiley & Sons, Ltd.