bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Modeling of Measurement Error in Generalized Linear Models with Rasch Measures as Covariates
Authors: Battauz Michela , Bellio Ruggero
Published: December 2010

This paper proposes a structural analysis for generalized linear models when some explanatory variables are measured with error and the measurement error variance is a function of the true variables. The focus is on latent variables investigated on the basis of questionnaires and estimated using item response theory models. Latent variable estimates are then treated as observed measures of the true variables. This leads to a two-stage estimation procedure which constitutes an alternative to a joint model for the outcome variable and the responses given to the questionnaire. Simulation studies explore the effect of ignoring the true error structure and the performance of the proposed method. Two illustrative examples concern achievement data of university students. Particular attention is given to the Rasch model.
Suicidal Ideation and Suicide Attempt Among Adolescents in Western Jamaica
Authors: Kukoyi Omobolawa Y. , Shuaib Faisal M. , Campbell-Forrester Sheila , Crossman Lisabeth , Jolly Pauline E.
Published: December 2010

Background: Although extensive studies on adolescent suicidal behavior have been conducted in developed countries such as the United States, little data exist on risk factors for suicide among adolescents in culturally and socially disadvantages settings, such as Jamaica. Aims: To conduct a preliminary investigation of risk factors associated with suicide ideation and attempt among youths in Western Jamaica. Methods: We conducted a cross-sectional study of 342 adolescents aged 10–19 years from 19 schools. Results: Multivariate analysis showed that a history of self-violence, violent thoughts toward others, mental health diagnoses other than depression, and a history of sexual abuse were positively associated with suicide attempt. Sexual abuse, mental health diagnoses other than depression, self-violence, and ease of access to lethal substances/weapons were positively associated with suicide ideation. Conclusions: We found a relatively high prevalence of suicide ideation and suicide attempts among adolescents living in Western Jamaica. An accurate understanding of the prevailing risk factors for suicide attempts will promote a more sympathetic approach to victims and facilitate prevention efforts.
Suicide by Pesticide Poisoning
Authors: Kastanaki Anastasia E. , Kraniotis Christos F. , Kranioti Elena F. , Nathena Despoina , Theodorakis Pavlos N. , Michalodimitrakis Manolis
Published: December 2010

Background: The role of pesticides in suicidal acts has not yet received adequate attention in Greece despite an evident rise of 39% in pesticide use over the period 1990–1992 to 2002–2004. Aims: To investigate the epidemiology of pesticide suicide on the Greek island of Crete, a largely rural agricultural area, and by further exploring the victim profiles, as well as patterns and trends of pesticide ingestion, to suggest probable preventive measures. Methods: Self-poisoning suicides between 1999 and 2007 were reviewed and information gathered was entered into a computerized database. Results: The overall incidence of intentional pesticide poisoning was 1.7 per 100,000, representing the second most frequently used suicide method after hanging. The victim profile was composed of the following features: middle aged male, rural habitant, who carried out a suicidal act by consuming primarily methomyl or paraquat (WHO toxicity class Ib and class II, respectively). As to the place of death, the vast majority was found dead in the place of intoxication. Conclusions: Pesticide self-poisoning accounts for a quarter of the suicides in Crete. More detailed research is required to identify aspects of these deaths amenable to prevention, but measures such as bans on the most toxic pesticides and changes in storage practice would appear to be sensible initial approaches.
No-Suicide Contracts, No-Suicide Agreements, and No-Suicide Assurances
Authors: Edwards Stephen J. , Sachmann Mark D.
Published: December 2010

Background: Suicide prevention contracting (SPC) procedures are often afforded clinical practice validity in the absence of evidence attesting to their efficacy and validity. Aims: This study sought to develop a contemporary profile of SPC, identifying factors associated with utilization, perceived effectiveness, and to describe potentially detrimental factors when activating SPC. Methods: A questionnaire was mailed to a sample of mental health practitioners comprising physicians, mental health nurse practitioners, and allied health practitioners to inquire about their practices and experiences with SPC. Results: There were 420 valid responses, a response rate of 31%. Participants confirmed three types of SPC procedures in operation: (1) 355 (85%) having used verbal no-suicide assurances (NSAs); (2) 317 (76%) using verbal no-suicide agreements (NSAg); and, (3) 154 (37%) using written no-suicide contracts (NSC). The profiled procedures and their clinical application indicate that participants perceived differences in the diagnostic, therapeutic, and medico-legal utility of all three SPC procedures. Importantly, SPC procedures were shown to have a multifaceted potential for detrimental outcomes for patients and practitioners. Conclusions: Until now, SPC had represented a poorly understood and remains a questionable clinical practice intervention. Education initiatives are required that alert mental health practitioners to the dangers of SPC for patients and practitioners alike, and to present alternative interventions containing less risk.
Hazard assessment of explosive volcanism at Somma‐Vesuvius
Authors: Mastrolorenzo G. , Pappalardo L.
Published: December 2010

A probabilistic approach based on the available volcanological data on past Somma‐Vesuvius eruptions has been developed to produce hazard‐zone maps for fallout, pyroclastic density currents (PDCs), and secondary mass flows by using numerical simulations. The hazard maps have been incorporated in a GIS, making them accessible to casual and expert users for risk mitigation and education management. The results allowed us to explore the hazard related to different scenarios from all possible eruptions, ranked according to volcanic explosivity index (VEI) class, in the Vesuvius area and its surroundings including Naples. Particularly, eruptions with VEI ≤ 3 would produce a fallout hazard within about 10 km mostly east of the volcano and a PDC hazard within about 2 km from the crater. Large‐scale events (4 ≤ VEI ≤ 5) would produce a fallout hazard up to 80 km from the vent and a PDC hazard at distances exceeding 15 km. Particularly, the territory northwest of Vesuvius, including metropolitan Naples, featuring a low hazard level for fallout accumulation, is exposed to PDCs also consistent with field evidence and archeological findings. Both volcano flanks and surrounding plains, hills, and mountains are exposed to a moderate–high level of hazard for the passage of secondary mass flows. With the present level of uncertainty in forecasting future eruption type and size on the basis of statistical analysis as well as precursory activity, our results indicate that the reference scenario in the emergency plan should carefully match the worst‐case VEI 5 probabilistic scenario.
Validation of Goddard Earth Observing System‐version 5 MERRA planetary boundary layer heights using CALIPSO
Authors: Jordan Nikisa S. , Hoff Raymond M. , Bacmeister Julio T.
Published: December 2010

This study compares the planetary boundary layer (PBL) height produced by the Goddard Earth Observing System‐version 5 (GEOS‐5) model with Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). Part of GEOS‐5 is an Atmosphere Global Circulation Model (GCM) used by National Aeronautics and Space Administration. Model developers are uncertain of the precision of model PBL height predictions since verification by direct observations of the PBL height is sparse. Validation of the PBL height serves as a diagnostic on whether the physics and dynamics packages are correct in the model. In this work, we report the global daytime PBL heights derived from dissertation work by Jordan (2009). We believe that this is the first large‐scale observational study of PBL heights using CALIPSO. In this paper, we compare CALIPSO PBL heights to matched PBL heights from the GEOS‐5 Modern Era Reanalysis for Research and Applications (MERRA) model. Extensive comparisons between the model output and satellite observations in the Western Hemisphere and over Africa gave model‐measurement correlation coefficients (R) of 0.47–0.73. Comparisons have been performed for regions over land and water using clouds, aerosols, and mixed cloud‐aerosol features to detect the PBL. The present study provides insight of regional PBL height variances in the GEOS‐5 model. For much of the study region GEOS‐5 predicts PBL heights within 25% of CALIPSO observations. A case over the Equatorial Pacific indicates that the GEOS‐5/CALIPSO PBL height ratios exceed 1.25. PBL height biases in the Equatorial Pacific may be related to the GCM coupling scheme implemented in GEOS‐5. Also, in some regions, the CALIPSO PBL heights are generally higher than the GEOS‐5 model.
Diagnosing coastal ocean CO2 interannual variability from a 40 year hydrographic time series station off the east coast of Australia
Authors: McNeil Ben I.
Published: December 2010

Advancing our understanding of the ocean's role in modulating atmospheric carbon dioxide interannual variability is important but limited by the lack of temporal ocean CO2 observations throughout most of the world's oceans. In particular, the role of the coastal ocean for interannual variability of CO2 is unknown, but expected to be large given the dynamics of land to ocean CO2 exchanges. Two coastal hydrographic time series stations at Port Hacking off Sydney, Australia, have collected and measured hydrographic properties (temperature, salinity, nitrate, phosphate, and silicate) since 1942. Here I examine the potential to use empirical relationships derived from nearby discrete CO2 measurements to diagnose CO2 interannual variability at the Port Hacking time series station. I test the approach by predicting interannual variability of CO2 at the Bermuda Time Series Station (BATS) in the North Atlantic between 1988 and 2008 and show the method captures 78% of the observed interannual variability found at BATS. I further use oxygen as a tracer to diagnose the length scales of variability in the southwest Pacific to provide insight into the applicability of the method. After applying the approach at Port Hacking, significant CO2 interannual variability was found (up to ± 30 ppm) that was largely driven by local regional variability in nutrients (nitrate) and temperature with little link to larger modes of variability (SAM or ENSO). Oceanic CO2 was diagnosed to be almost always lower than atmospheric CO2 levels (ΔpCO2 ∼ 10–55 μatm), indicating a quasi‐permanent coastal ocean CO2 sink during winter off Sydney. Direct pCO2 measurements taken along the NSW coastline in April and August 2008 confirm the empirical predictions and a wider CO2 sink along Australia's east coast. If extrapolating the Port Hacking CO2 results to the New South Wales coastline, the annual coastal CO2 sink would be about −0.05 Tg C/yr. Both the empirical predictions and direct measurements of CO2 presented here along the Australian east coast support recent reviews suggesting continental shelves act as a significant CO2 sink, at least during autumn and winter.
Crystal fractionation processes at Baru volcano from the deep to shallow crust
Authors: Hidalgo Paulo J. , Rooney Tyrone O.
Published: December 2010

Linking shallow and deep crustal processes at volcanic arcs is an important component in evaluating the growth and evolution of the continental crust. Commonly, deep crustal processes and the nature of subarc lithosphere are studied long after the volcanism has ceased in obducted arc terranes. In active arcs, studies of deep crustal processes focus on cumulates derived from middle‐lower crustal levels. Although uncommon in the erupted magmas, these cumulates are required by crustal differentiation models of arc magmatism. Quaternary magmas at Baru volcano in Panama contain ubiquitous amphibole‐bearing cumulates that provide an opportunity to probe the magma plumbing system of an active arc volcano. We have determined that these cumulates are related to their host magmas by crystal fractionation processes. Pressure and temperature estimates for amphiboles within these cumulates and the host rock are consistent with sampling of mush/magma zones from throughout the arc crust. These mush zones would be localized in deep hot crustal zones where magmatic differentiation of water‐saturated arc magmas takes place by crystallization of amphibole‐rich cumulates. The identification of middle‐lower crustal cumulates is not exclusive to Baru volcano; similar cumulates are common throughout the Panamanian arc and are consistent with a widespread amphibole‐rich layer present within the arc crust of Panama. Our results highlight the importance of amphibole fractionation in the differentiation sequence of island arcs effectively driving the residual magma to the average andesitic composition of the continental crust.
Remotely triggered microearthquakes and tremor in central California following the 2010 Mw 8.8 Chile earthquake
Authors: Peng Zhigang , Hill David P. , Shelly David R. , Aiken Chastity
Published: December 2010

We examine remotely triggered microearthquakes and tectonic tremor in central California following the 2010 Mw 8.8 Chile earthquake. Several microearthquakes near the Coso Geothermal Field were apparently triggered, with the largest earthquake (Ml 3.5) occurring during the large‐amplitude Love surface waves. The Chile mainshock also triggered numerous tremor bursts near the Parkfield‐Cholame section of the San Andreas Fault (SAF). The locally triggered tremor bursts are partially masked at lower frequencies by the regionally triggered earthquake signals from Coso, but can be identified by applying high‐pass or matched filters. Both triggered tremor along the SAF and the Ml 3.5 earthquake in Coso are consistent with frictional failure at different depths on critically‐stressed faults under the Coulomb failure criteria. The triggered tremor, however, appears to be more phase‐correlated with the surface waves than the triggered earthquakes, likely reflecting differences in constitutive properties between the brittle, seismogenic crust and the underlying lower crust.
A global map of uncertainties in satellite‐based precipitation measurements
Authors: Tian Yudong , Peters‐Lidard Christa D.
Published: December 2010

A global map of measurement uncertainties in satellite‐based precipitation estimates has been produced by computing the variance from an ensemble of six different TRMM‐era data sets at daily, 0.25° resolution. This analysis yields a lower‐bound estimate of the uncertainties, and a consistent global view of the error characteristics and their regional and seasonal variations, and reveals many undocumented error features over areas with no validation data available. The uncertainties are relatively small (40–60%) over the oceans, especially in the tropics, and over southern South America. There are large uncertainties (100–140%) over high latitudes (poleward of 40° latitude), especially during the cold season. High relative uncertainties are also evident through the seasons over complex terrain areas, including the Tibetan Plateau, the Rockies and the Andes. Coastlines and water bodies also indicate high measurement uncertainty. The estimated global uncertainties also exhibit systematic seasonal, regional as well as rain‐rate dependencies, with lowest uncertainties over tropical oceanic regions with strong, convective precipitation, and highest ones over wintery, complex land surfaces with light precipitation.
A comprehensive rocket and radar study of midlatitude spread F
Authors: Earle G. D. , Bhaneja P. , Roddy P. A. , Swenson C. M. , Barjatya A. , Bishop R. L. , Bullett T. W. , Crowley G. , Redmon R. , Groves K. , Cosgrove R. , Vadas Sharon L.
Published: December 2010

An instrumented sounding rocket launched from Wallops Island Virginia has flown through a midlatitude spread F (MSF) event in conjunction with simultaneous ionosonde, HF radar, and 244 MHz scintillation observations from the ground. The in situ measurements include the electric field, horizontal neutral wind, and plasma density within the spread F region. The ground‐based HF radar measurements of wave signatures in the bottomside F region ledge reveal the presence of waves propagating to the north and northwest prior to and during the spreading event. The periods of these bottomside waves range from 16 to 60 min, and they are shown to be associated with a strong tropical storm located ∼2000 km southeast of the launch site. Enhancements in the auroral current system occur about an hour before the MSF first appears, but none of the observed waves can be attributed to this source. The new phase‐sensitive ionosonde system operated at Wallops Island during the experiment confirms the long‐standing hypothesis that this particular spread F event arises from multipath echoes distributed over a wide field of view in the bottomside F region. Evidence of vertically displaced plasma that could produce such multipath echoes is observed in the rocket data at and above the F region peak over spatial scales smaller than the wavelengths observed on the bottomside ledge by the HF radar, but similar to the range separation given by the high resolution ionosonde echoes when the scale lengths of the structures are interpreted in magnetic coordinates. No significant plasma density structures smaller than a few kilometers are observed in the rocket data, and no unusual scintillation is observed along a path coincident with the rocket trajectory.
Observations of ion cyclotron waves in the solar wind near 0.3 AU
Authors: Jian L. K. , Russell C. T. , Luhmann J. G. , Anderson B. J. , Boardsen S. A. , Strangeway R. J. , Cowee M. M. , Wennmacher A.
Published: December 2010

Using 2 Hz magnetic field data from the MESSENGER mission, we have investigated more than 300 strong narrowband ion cyclotron wave (ICW) events at a heliocentric distance of about 0.3 AU during 31 May to 9 June 2008. These nearly circularly polarized transverse waves are observed extensively and discretely in the solar wind, with a median duration of 21 s. They are preferentially observed when the magnetic field is more radial than the ambient solar wind. The waves appear both left‐handed and right‐handed in the spacecraft frame. Their wave frequencies in the spacecraft frame are generally larger than the local proton cyclotron frequency (fpc), with a median of 1.44 fpc. The wave power spectra do not cutoff at the local fpc. On the basis of their wave characteristics, we conclude that they are intrinsically left‐handed in the solar wind frame and they are generated closer to the Sun and carried out to the spacecraft by the super Alfvénic solar wind. After removing the Doppler shift, the wave frequencies in the solar wind frame are all below the local fpc, with a median of 0.35 fpc. The ICWs propagate nearly parallel to the magnetic field, and the median wave amplitude is about 0.73 nT, 3% of the background magnetic field. We compare these observations with earlier Helios observations at 0.3 AU in 1976 and contemporary 1 AU observations.
Dual periodicities in the rotational modulation of Saturn narrowband emissions
Authors: Ye S.‐Y. , Gurnett D. A. , Groene J. B. , Wang Z. , Kurth W. S.
Published: December 2010

Using the Cassini Radio and Plasma Wave Science (RPWS) instrument it has recently been shown that the rotational modulation period of Saturn kilometric radiation (SKR) has two components, one with a period of 10.6 h and the other with a period of 10.8 h. The longer period is primarily observed in the southern hemisphere and the shorter period is primarily observed in the northern hemisphere. In this paper, the modulation period of 5 kHz Saturn narrowband radio emissions is examined, restricting the spacecraft location to either the northern or the southern hemisphere of Saturn. It is found that in both hemispheres, the modulation period of 5 kHz narrowband emissions has two components that are equal to the SKR periods. It is known that Saturn narrowband emissions are first generated in the auroral regions as Z‐mode and then mode convert to escaping L‐O modes at density gradients. These Z‐mode waves are trapped in a region close to the planet and can propagate from one hemisphere to another before they mode convert to L‐O modes, thereby leading to dual periods of Saturn narrowband emissions in each hemisphere. The phase shift between the SKR and narrowband emissions is around 90° in the longitude, which means that SKR leads narrowband emissions by 2–3 h.
Temporal modulation of the four‐peaked longitudinal structure of the equatorial ionosphere by the 2 day planetary wave
Authors: Liu Guiping , Immel Thomas J. , England Scott L. , Kumar Karanam K. , Ramkumar Geetha
Published: December 2010

Observations of electron densities by the Constellation Observing System for Meteorology, Ionosphere, and Climate in August to October 2008 have shown a prominent four‐peaked longitudinal structure in the height of the F2 layer (hmF2) in the equatorial ionosphere. The development of this ionospheric structure in daytime is found to be consistent with the forcing by the eastward‐propagating nonmigrating diurnal tide with zonal wave number 3 (DE3). It is believed that tidal winds can modify the E region electric fields and subsequently produce variations in the ionosphere through the dynamo effect. This study reveals that the amplitude of the hmF2 four‐peaked longitudinal structure is subject to a 2 day periodic modulation on certain intervals in the two‐month time period. Simultaneously, wind measurements from the SKiYMET meteor radar at Thumba (8.5°N, 77°E), India indicate corresponding 2 day planetary wave activity in the mesosphere and lower thermosphere (MLT). The 2 day planetary wave has both zonal and meridional wind components, and it is the variability in the zonal component that most closely corresponds to F2 layer changes. The zonal wind observations by the radar also show that the amplitude of the diurnal tide is modulated by the 2 day wave. This study suggests that the identified 2 day variation of the hmF2 four‐peaked longitudinal structure in the equatorial ionosphere is caused by the interaction between the DE3 tide and the 2 day planetary wave.
Mud volcano response to the 4 April 2010 El Mayor‐Cucapah earthquake
Authors: Rudolph M. L. , Manga M.
Published: December 2010

Mud volcanoes sometimes respond to earthquakes, but the mechanisms by which earthquakes trigger changes in ongoing eruptions or initiate new eruptions are not completely understood. We measured gas discharge at a field of mud volcanoes near the Salton Sea, southern California, before and after the 4 April 2010 El Mayor‐Cucapah earthquake and observed an increase in gas flux immediately following the earthquake and a subsequent recovery to pre‐earthquake values. This earthquake‐eruption pair is of particular interest because the earthquake produced large strains, up to 1.2%, near the mud volcano location, allowing us to test two competing triggering mechanisms: (1) shaking‐induced bubble mobilization and (2) permeability enhancement. We measured the rheology of erupted mud from the mud volcanoes to quantify the importance of mechanism 1 and found that this mechanism is unlikely to be important. We therefore favor the explanation that the increased gas flux was caused by a transient increase in permeability.
Deep structure and seismogenesis of the north‐south seismic zone in southwest China
Authors: Wang Zhi , Zhao Dapeng , Wang Jian
Published: December 2010

To understand the deep structure and seismogenesis in the north‐south seismic zone (NSSZ) in southwest China, we collected a large number of P and S wave arrival time data from both local earthquakes and teleseismic events to invert simultaneously for the three‐dimensional P and S wave velocity (Vp, Vs) structures in the crust and upper mantle. The obtained Vp and Vs models are generally coherent with each other from the crust to the mantle transition zone. The NSSZ is characterized by strong structural heterogeneities from the mountainous areas of southeastern Tibet to the Yangtze Platform. Low‐Vp and low‐Vs anomalies are generally imaged in the upper crust under the Sichuan basin, showing good agreement with the surface geological features that the foreland basin contains primarily Mesozoic and Paleozoic sedimentary rocks with a thickness of several kilometers. The deep part of the Yangtze Platform is characterized by a cratonic lithospheric body dipping southwestward down to 400 km depth beneath the southeastern margin of the Tibetan Plateau, in sharp contrast to low‐velocity anomalies in the upper mantle beneath the Songpan‐Ganzi Fold System and the Northwest Qiangtang Block. At depths of the lower crust and uppermost mantle, a layer with low Vp and low Vs (1%–2%) is revealed under a region west of the Yangtze Platform, which may reflect the ductile flow in the lower crust. Our results indicate that the seismotectonics in the NSSZ is affected significantly by the ductile flow in the lower crust and strong heterogeneities in the upper mantle under southwest China in addition to the dominant role of the India‐Asia collision.
Two‐ and three‐dimensional numerical simulations of the stress field at the thrust front of the Northern Apennines, Italy
Authors: Carminati Eugenio , Vadacca Luigi
Published: December 2010

Two‐ and three‐dimensional mechanical models simulating the seismic cycle along thrust faults are devoted to the active front of the Northern Apennines buried under the Plio‐Pleistocene sediments of the eastern Po Plain. The models aim at understanding two peculiar characters of the stress field in the region: (1) analyses of borehole breakouts and other well data, integrated with seismological information and field evidence, show along‐depth variations (from extensional to strike slip to compressional for increasing depth) of the stress style along the active Mirandola anticline and (2) seismic and borehole breakout data suggest strong lateral rotations of the stress axes along the frontal and lateral ramp portions of the Mirandola thrust fault. Modeling results allowed us to understand that the mechanical decoupling along faults strongly affects the stress distribution in their vicinity, under the form of strong rotations of the principal stress axes. As a consequence the slip (either fast or slow) along active blind thrust faults could drive to local stress fields very different from that associated with regional tectonics. This could explain, together with other processes (such as differential compaction), the along‐depth variation of the stress field observed in the Mirandola region and the strong lateral rotations of the principal stress axes observed along the lateral ramp of the Mirandola thrust fault. Finally, the seismic activity along one of the thrust fault ramps along the Apennines front should not interfere with the state of stress along adjacent ramps.
EOF‐based constrained sensor placement and field reconstruction from noisy ocean measurements: Application to Nantucket Sound
Authors: Yang Xiu , Venturi Daniele , Chen Changsheng , Chryssostomidis Chryssostomos , Karniadakis George Em
Published: December 2010

Sensor placement at the extrema of empirical orthogonal functions (EOFs) is efficient and leads to accurate reconstruction of the ocean state from a limited number of measurements. In this paper, we develop important new extensions of this approach that optimize sensor placement to avoid redundant measurements, employ imperfect EOF modes, and take into account measurement errors. We use the simulation outputs of the Finite Volume Community Ocean Model applied to the Nantucket Sound region to evaluate the performances of the new approach and compare it against other similar techniques. Specifically, we find that there exists a critical size of exclusion volume (whose value is unknown a priori) surrounding each sensor that prevents clustering of sensors while minimizing the reconstruction error. In addition, we propose a new algorithm that can be effective in incorporating gappy data in assimilation schemes. We also derive analytical formulas of the uncertainty in the reconstructed field given any inaccuracies in the measurements. Taken together these developments will aid further in the development of truly real‐time adaptive sampling for ocean forecasting.
Deep ocean circulation and transport where the East Pacific Rise at 9–10°N meets the Lamont seamount chain
Authors: Lavelle J. W. , Thurnherr A. M. , Ledwell J. R. , McGillicuddy D. J. , Mullineaux L. S.
Published: December 2010

We report the first 3‐D numerical model study of abyssal ocean circulation and transport over the steep topography of the East Pacific Rise (EPR) and adjoining Lamont seamount chain in the eastern tropical Pacific. We begin by comparing results of hydrodynamical model calculations with observations of currents, hydrography, and SF6 tracer dispersion taken during Larval Dispersal on the Deep East Pacific Rise (LADDER) field expeditions in 2006–2007. Model results are then used to extend observations in time and space. Regional patterns are pronounced in their temporal variability at M2 tidal and subinertial periods. Mean velocities show ridge‐trapped current jets flowing poleward west and equatorward east of the ridge, with time‐varying magnitudes (weekly average maximum of ∼10 cm s−1) that make the jets important features with regard to ridge‐originating particle/larval transport. Isotherms bow upward over the ridge and plunge downward into seamount flanks below ridge crest depth. The passage (P1) between the EPR and the first Lamont seamount to the west is a choke point for northward flux at ridge crest depths and below. Weekly averaged velocities show times of anticyclonic flow around the Lamont seamount chain as a whole and anticyclonic flow around individual seamounts. Results show that during the LADDER tracer experiment SF6 reached P1 from the south in the western flank jet. A short‐lived change in regional flow direction, just at the time of SF6 arrival at P1, started the transport of SF6 to the west on a course south of the seamounts, as field observations suggest. Approximately 20 days later, a longer‐lasting shift in regional flow from west to SSE returned a small fraction of the tracer to the EPR ridge crest.
Spatial structure of assimilated ozone in the upper troposphere and lower stratosphere
Authors: Wargan Krzysztof , Pawson Steven , Stajner Ivanka , Thouret Valérie
Published: December 2010

Ozone distributions display a rich spatial structure in the upper troposphere and lower stratosphere (UTLS). This study uses in situ aircraft observations to examine how accurately such spatial distributions of ozone are represented in an assimilation of NASA's EOS‐Aura ozone data using meteorological fields from the Goddard Earth Observing System, Version 4. Total ozone columns from the Ozone Monitoring Instrument (OMI) and stratospheric profiles from the Microwave Limb Sounder (MLS) are assimilated. The results demonstrate that the dominant large‐scale ozone distribution is well‐constrained (to realistic concentrations) near 250 hPa in the UTLS. Spatial patterns and the spectral power of variations are similar in the model simulations and the assimilation. The spectral power of the analysis increments is concentrated at large scales. Thus transport, rather than direct assimilation of small‐scale features, is responsible for the spatial ozone structure in the UTLS. Consistent with the documented behavior of the Lin‐Rood transport scheme, we demonstrate that the assimilated ozone represents realistic features on spatial scales of about four‐to‐six model grid boxes (500–800 km) and that smaller scales present in the aircraft observations are represented too weakly in the modeled and assimilated ozone fields. For the assimilated ozone, this result is robust over a range of realistic model‐error‐covariance length scales. The results indicate that observations of ozone on spatial scales that constrain the large‐scale gradients are suited to producing global analyses of UTLS ozone that represent features at higher spatial resolution.
A comparison of stratosphere‐troposphere transport in convection‐permitting and convection‐parameterizing simulations of three mesoscale convective systems
Authors: Chagnon Jeffrey M. , Gray Suzanne L.
Published: December 2010

The transport of stratospheric air into the troposphere within deep convection was investigated using the Met Office Unified Model version 6.1. Three cases were simulated in which convective systems formed over the UK in the summer of 2005. For each of these three cases, simulations were performed on a grid having 4 km horizontal grid spacing in which the convection was parameterized and on a grid having 1 km horizontal grid spacing, which permitted explicit representation of the largest energy‐containing scales of deep convection. Cross‐tropopause transport was diagnosed using passive tracers that were initialized above the dynamically defined tropopause (2 potential vorticity unit surface) with a mixing ratio of 1. Although the synoptic‐scale environment and triggering mechanisms varied between the cases, the total simulated transport was similar in all three cases. The total stratosphere‐to‐troposphere transport over the lifetime of the convective systems ranged from 25 to 100 kg/m2 across the simulated convective systems and resolutions, which corresponds to ∼5–20% of the total mass located within a stratospheric column extending 2 km above the tropopause. In all simulations, the transport into the lower troposphere (defined as below 3.5 km elevation) accounted for ∼1% of the total transport across the tropopause. In the 4 km runs most of the transport was due to parameterized convection, whereas in the 1 km runs the transport was due to explicitly resolved convection. The largest difference between the simulations with different resolutions occurred in the one case of midlevel convection considered, in which the total transport in the 1 km grid spacing simulation with explicit convection was 4 times that in the 4 km grid spacing simulation with parameterized convection. Although the total cross‐tropopause transport was similar, stratospheric tracer was deposited more deeply to near‐surface elevations in the convection‐parameterizing simulations than in convection‐permitting simulations.
Infrared absorption spectra, radiative efficiencies, and global warming potentials of perfluorocarbons: Comparison between experiment and theory
Authors: Bravo Iván , Aranda Alfonso , Hurley Michael D. , Marston George , Nutt David R. , Shine Keith P. , Smith Kevin , Wallington Timothy J.
Published: December 2010

Experimentally and theoretically determined infrared spectra are reported for a series of straight‐chain perfluorocarbons: C2F6, C3F8, C4F10, C5F12, C6F14, and C8F18. Theoretical spectra were determined using both density functional (DFT) and ab initio methods. Radiative efficiencies (REs) were determined using the method of Pinnock et al. (1995) and combined with atmospheric lifetimes from the literature to determine global warming potentials (GWPs). Theoretically determined absorption cross sections were within 10% of experimentally determined values. Despite being much less computationally expensive, DFT calculations were generally found to perform better than ab initio methods. There is a strong wavenumber dependence of radiative forcing in the region of the fundamental C‐F vibration, and small differences in wavelength between band positions determined by theory and experiment have a significant impact on the REs. We apply an empirical correction to the theoretical spectra and then test this correction on a number of branched chain and cyclic perfluoroalkanes. We then compute absorption cross sections, REs, and GWPs for an additional set of perfluoroalkenes.
Relationship between synoptic weather disturbances and particulate matter air pollution over the United States
Authors: Thishan Dharshana K. G. , Kravtsov Sergey , Kahl Jonathan D. W.
Published: December 2010

This study establishes connections between day‐to‐day variability of sea level pressure (SLP), surface air temperature (T), and precipitation (PR) and that of fine particulate matter (PM2.5) air pollution. In particular, matrix methods were applied to quantify statistical relationships between the daily anomalies of these fields over the continental US, during the 7 year study period. The anomalies were defined as deviations from nonoverlapping 2 week averages to focus on synoptic scales. The main effect of synoptic weather systems on day‐to‐day variability of PM2.5 air pollution consists of formation of a high‐pollution area behind propagating anticyclones and a low‐pollution region in the wake of cyclones. This property is rationalized by the fact that the regions just west of the eastward‐propagating cyclones (or anticyclones) experience the cyclonic (anticyclonic) conditions detrimental to (favorable for) PM2.5 accumulation for the longest period of time. The advection of climatological PM2.5 concentrations by anomalous winds associated with propagating weather systems may also contribute to the formation of the above PM2.5 anomalies, but does not represent a dominant effect. This “synoptically controlled” PM2.5 variability accounts for as much as 30% of the total high‐pass filtered particulate matter (PM) variance in the midwest region throughout the year (irrespective of season), while it is substantially less pronounced along the coasts and in the southern US. The authors argue that the apparent correlations between PM and T, as well as PM and PR anomalies do not imply causality, but rather show that these quantities are commonly related to the external factors associated with the life cycle of midlatitude synoptic storms.
Rift zone volcanism and associated cinder cone field in Utopia Planitia, Mars
Authors: Lanz Julia K. , Wagner Roland , Wolf Ursula , Kröchert Jörg , Neukum Gerhard
Published: December 2010

We analyzed a small cone field in SW Utopia Planitia that shows striking similarities to volcanic rift zones on Earth. This is of particular interest as the study area lies off any of the volcanic centers of Mars in the northern hemisphere lowlands and is surrounded by material of the Amazonian aged Vastitas Borealis Formation (VBF). We believe that the study area could be the first direct evidence for volcanic activity in Utopia Planitia prior to the resurfacing by VBF material. The most striking characteristics that we observed are (1) a set of broad eruptive fissures showing signs of ongoing extension during cone formation, (2) parallel dike swarms, (3) magmatic intrusions, and (4) a number of lava flows that have erupted from the fissures and pitted cones that surround a larger cone in the center of the study area and that are often associated with, or aligned along, the fissures and dikes. Cratering model ages indicate that the study area is of Late Noachian to Early Hesperian age and is thus distinctly older than the surrounding VBF, falling into the time frame of the main phases of activity in the volcanic centers of Syrtis Major, Elysium Planitia, and the southern highlands.
Possible crippling of the core dynamo of Mars by Borealis impact
Authors: Arkani‐Hamed Jafar
Published: December 2010

Assuming that the northern lowland of Mars is created by a giant Borealis impact, I investigate its consequences on the thermal state of the mantle and the core dynamo for four different impact models using the scaling laws of crater formation, the shock pressure model of Pierazzo et al. (1997), and the “foundering” shock heating model of Watters et al. (2009). The impact heating enhances the temperature of the mantle by 1000–3000 K down to ∼1000 km depth. The superheated upper mantle ascends rapidly as a giant plume and develops a strong convection in the entire mantle of the subimpact hemisphere, while the antipodal hemisphere remains almost undisturbed for the period of 100 Myr considered in this study. The upwelling of the plume rapidly sweeps up the impact‐heated base of the mantle and replaces it with the cold surroundings, reducing the effects of the impact‐heated mantle on the heat loss of the core. However, direct shock heating stratifies the core and effectively suppresses a preexisting thermal convection in the core. This cripples a preexisting thermally driven core dynamo. It takes 35–85 Myr for the stratified core model to exhaust impact heat and resume global convection and possibly regenerate a strong dynamo. Adding the superheated iron content of an impactor on the core does not create an appreciable dynamo but elongates the heat exhaustion time and delays the regeneration of a strong dynamo by an additional ∼40 Myr. It is concluded that Borealis impact, if it occurred, could have crippled the core dynamo of Mars for up to ∼70–120 Myr.
Implementation of computational methods for designing potential inhibitors against human p38α protein
Authors: M Durga Devi , Pradhan Dibyabhaba , Munikumar Manne , Umamaheswari Amineni
Published: December 2010

p38α, a non-receptor serine/threonine kinase, plays an essential role in cell proliferation, cell differentiation, apoptosis, production of cytokines such as IL1β and TNFα, senescence and tumorigenesis. Over expression of p38α enhances the production of cytokines, leading to inflammation causing cancers. Therefore, the protein p38α is selected as a target for the inhibition of progression of inflammatory cancers. SB203580, BIRB796, 2H-quinolizine-2-one, 7-alkyl-1,5-bis–aryl-pyrazolo pyridinones, aML3403, N-pyrimidyl amides, Fused pyrazoles, SD0006, 4-3-(4-fluoro phenyl )-1H-pyrazol-4-yl)pyridine are the nine published inhibitors for the p38α, but they show side effects like liver toxicity and the development of lung tumors, particularly in smokers, some of which are in the preclinical stage. A small molecule library of 3495 structural analogs of the nine published inhibitors was prepared for ligand based virtual screening. Multiple conformations of the ligands were generated and conformations with ADME violations were discarded. The optimized ligand conformations were docked flexibly into the active site of optimized p38α crystal structure. Fourteen lead molecules obtained were ranked based on XP G-score and binding orientation. In comparison with the nine existing inhibitors, lead ‘1’ (N-(3-Benzooxazol-2-yl-4-hydroxy-phenyl) 2ptolyloxyacetamide) had the highest binding affinity among the lead molecules with XP Gscore of -9.38 kcal/mol and formed four hydrogen bonds: one with each of Ala 51, Glu71 and Asp168 and one water bond (position 420) with binding mode which complements well the crystallographic data of human p38α. The docking result shows the potency of lead ‘1’ as a promising inhibitor for regulating the activity of p38α.
In silico identification of potential inhibitors for human aurora kinase b
Authors: G Mahesh Babu , N. Pradeep , Pradhan Dibyabhaba , MuniKumar Manne , Umamaheswari Amineni
Published: December 2010

Cell cycle progression through mitosis and meiosis involves regulation by serine/threonine kinases from the aurora family. Aurora kinase b (Aurkb) is mainly involved in the proper segregation of chromosomes during mitosis as well as meiosis. However, over expression of Aurkb leads to the unequal distribution of genetic information creating aneuploid cells, a hallmark of cancer. Thus, Aurkb can be used as an effective molecular target for computer-aided drug discovery against cancer. Existing Aurkb inhibitors are less efficient, hence an in silico work was carried out to identify novel potent inhibitors. Three published inhibitors azd1152, zm447439 and N-(4-{[6-methoxy-7-(3-morpholin-4-ylpropoxy) quinazolin- 4-yl] amino} phenyl) benzamide were subjected to high throughput virtual screening of over 1 million entries from a ligand info meta database, to generate a 1161 compound library. The crystal structure was optimized and energy was minimized applying an OPLS force field in Maestro v9.0. Molecular docking using Glide was performed to predict the binding orientation of the prepared ligand molecule into a grid of 20*20*20 Å created around the centroid of the optimized human Aurkb protein. Nine lead molecules with good binding affinity with human Aurkb were identified. In silico pharmacokinetics study for these nine lead molecules has shown no ADME violation. Analysis of lead ‘1’- human Aurkb docking complex has revealed a XP Gscore of -10.20 kcal/mol with a highly stabilized hydrogen bond network with Asp218 and Ala157 and good Van der wall interactions. The docking complex coincides well with the native co- crystallized human Aurkb and inhibitor zm447439 complex. Thus, lead 1 would be highly useful for developing potential drug molecules for the treatment of cancer.
Identification of potent inhibitors for p38δ MAPkinase of human through in silico analysis
Authors: M Naga Lakshmi , Munikumar Manne , Pradhan Dibyabhaba , Umamaheswari Amineni
Published: December 2010

P38δ Mitogen activated protein kinase is a serine/threonine protein kinase that participates in signaling cascades, mediating cellular responses to cytokinines, UV radiation, hyperosmotic stress, inducing keratinocyte differentiation and regulating apoptosis. Over expression of p38δ leads to tumor development by impairing the ERK1/2 –AP1 pathway that is critically linked to the control of cell proliferation and tumorigenesis on skin which was experimentally proven in knockout mice. Therefore, herein, a computational approach was undertaken to design novel inhibitors against p38delta for effective cancer therapy. The tertiary structure of p38δ was retrieved from a protein databank and active sites were predicted from CASTP and site finder and were optimized by applying OPLS force field in Maestro v9.0. Four p38δ specific inhibitors 4-(4-(2-(cyclopentylamino)pyrimidin-4-yl)-1H-pyrazol-3-yl)cyclohexanol,(R)-2-(sec-butylamino)-N-(2-methyl-5-(methylcarbamoyl)phenyl)thiazole-5-carboxamide, BIRB796 and ANP were selected from the literature for high throughput screening against one million compounds from the Ligand.Info metadatabase to generate an in-house library of 1515 structural analogs. The ligand library was prepared using LigPrep and compounds with ADME violations were discarded from the dataset. The candidates from the optimized ligand dataset were docked into the active site of p38δ through sequential application of Glide HTVS, SP and XP methods that penalizes more stringently for minor steric classes subsequently. Through comparative analysis of binding orientations and the XP G-score of the protein-ligand docking complexes with published inhibitor data, 4 lead molecules with the lowest docking scores(-12.12,-10.06,-9.47 and-9.36) are proposed to be considered as potential inhibitors of p38δ. The lead molecules would be highly encouraging for future cancer therapy if tested in animal models.