bluuebunny/crossref_metadata_2025 huggingface dataset:
ONLINE PRONOUN RESOLUTION IN L2 DISCOURSE: L1 Influence and General Learner Effects
Authors: Roberts Leah , Gullberg Marianne , Indefrey Peter
Published: July 2008

This study investigates whether advanced second language (L2) learners of a nonnull subject language (Dutch) are influenced by their null subject first language (L1) (Turkish) in their offline and online resolution of subject pronouns in L2 discourse. To tease apart potential L1 effects from possible general L2 processing effects, we also tested a group of German L2 learners of Dutch who were predicted to perform like the native Dutch speakers. The two L2 groups differed in their offline interpretations of subject pronouns. The Turkish L2 learners exhibited a L1 influence, because approximately half the time they interpreted Dutch subject pronouns as they would overt pronouns in Turkish, whereas the German L2 learners performed like the Dutch controls, interpreting pronouns as coreferential with the current discourse topic. This L1 effect was not in evidence in eye-tracking data, however. Instead, the L2 learners patterned together, showing an online processing disadvantage when two potential antecedents for the pronoun were grammatically available in the discourse. This processing disadvantage was in evidence irrespective of the properties of the learners' L1 or their final interpretation of the pronoun. Therefore, the results of this study indicate both an effect of the L1 on the L2 in offline resolution and a general L2 processing effect in online subject pronoun resolution.
Interrelated laboratory and space plasma experiments
Authors: Koepke M. E.
Published: July 2008

Many advances in understanding space plasma phenomena have been linked to insight derived from theoretical modeling and/or laboratory experiments. Advances for which laboratory experiments played an important role are reviewed here. How the interpretation of the space plasma data was influenced by one or more laboratory experiments is described. The space physics motivation of laboratory investigations and the scaling of laboratory plasma parameters to space plasma conditions are discussed. Examples demonstrating how laboratory experiments develop physical insight, validate or invalidate theoretical models, discover unexpected behavior, establish observational signatures, and pioneer diagnostic methods for the space community are presented. The various device configurations found in space‐related laboratory investigations are outlined. A primary objective of this review is to articulate the overlapping scientific issues that are addressable in space and laboratory experiments. A secondary objective is to convey the wide range of laboratory and space plasma experiments involved in this interdisciplinary alliance. Over time the degree to which the interrelated experiments can be compared has increased, thanks to improved diagnostic techniques in space and closer attention to matching dimensionless space parameters in the laboratory.
Forbush decreases of cosmic rays: Energy dependence of the recovery phase
Authors: Usoskin I. G. , Braun I. , Gladysheva O. G. , Hörandel J. R. , Jämsén T. , Kovaltsov G. A. , Starodubtsev S. A.
Published: July 2008

Cause and general shape of Forbush decreases of cosmic rays are relatively well understood, however, the knowledge of their recovery times remains rather poor. Earlier results of theoretical and fragmentary statistical studies are in disagreement whether the recovery time does or does not depend on the energy of cosmic rays. A thorough empirical study of the recovery phase of strong isolated Forbush decreases is presented here, based on the ground based data from the World Neutron Monitor Network since 1964 and three ground based muon telescopes since 1973. In total 39 strong Forbush decreases, suitable for the analysis, have been identified for the period 1964–2006, 24 of them depicting a clear energy dependence of the recovery time and 15 consistent with no energy dependence. All analyzed Forbush decreases with magnitudes exceeding 10% demonstrate an energy dependence of the recovery time, while smaller events can be of either type. No apparent relation between the occurrence of energy dependent/independent recovery and the IMF polarity has been found. This result provides an observational constraint for more detailed modeling of the propagation of interplanetary transients and their dynamic effects on cosmic ray transport.
Probabilistic tephra hazard maps for the Neapolitan area: Quantitative volcanological study of Campi Flegrei eruptions
Authors: Mastrolorenzo G. , Pappalardo L. , Troise C. , Panizza A. , De Natale G.
Published: July 2008

Tephra fall is a relevant hazard of Campi Flegrei caldera (Southern Italy), due to the high vulnerability of Naples metropolitan area to such an event. Here, tephra derive from magmatic as well as phreatomagmatic activity. On the basis of both new and literature data on known, past eruptions (Volcanic Explosivity Index (VEI), grain size parameters, velocity at the vent, column heights and erupted mass), and factors controlling tephra dispersion (wind velocity and direction), 2D numerical simulations of fallout dispersion and deposition have been performed for a large number of case events. A bayesian inversion has been applied to retrieve the best values of critical parameters (e.g., vertical mass distribution, diffusion coefficients, velocity at the vent), not directly inferable by volcanological study. Simulations are run in parallel on multiple processors to allow a fully probabilistic analysis, on a very large catalogue preserving the statistical proprieties of past eruptive history. Using simulation results, hazard maps have been computed for different scenarios: upper limit scenario (worst‐expected scenario), eruption‐range scenario, and whole‐eruption scenario. Results indicate that although high hazard characterizes the Campi Flegrei caldera, the territory to the east of the caldera center, including the whole district of Naples, is exposed to high hazard values due to the dominant westerly winds. Consistently with the stratigraphic evidence of nature of past eruptions, our numerical simulations reveal that even in the case of a subplinian eruption (VEI = 3), Naples is exposed to tephra fall thicknesses of some decimeters, thereby exceeding the critical limit for roof collapse. Because of the total number of people living in Campi Flegrei and the city of Naples (ca. two million of inhabitants), the tephra fallout risk related to a plinian eruption of Campi Flegrei largely matches or exceeds the risk related to a similar eruption at Vesuvius.
Evidence for and implications of a Bering plate based on geodetic measurements from the Aleutians and western Alaska
Authors: Cross Ryan S. , Freymueller Jeffrey T.
Published: July 2008

Global Positioning System (GPS) measurements are used to examine the hypothesis of a clockwise rotating Bering plate. Originally proposed on the basis of seismicity, the Bering plate encompasses the Bering Sea, western Alaska, and the Aleutian Islands. GPS measurements from the Bering plate's interior show south to southwest motions of 3–5 mm/a (where a is years). We construct elastic dislocation models to determine the spatial distribution and intensity of locked patches on the Aleutian subduction interface. We use these to remove interseismic strain from the GPS observation and determine an arc translation velocity for each region of the Aleutians, revealing south and southwest motions of 4–8 mm/a. We combine the arc translation rates with measurements from the Bering plate's interior sites and estimate the Euler pole for the Bering plate relative to North America to be located at 42.5°N, 121.3°E with an angular speed of 6.0°/Ma. The clockwise rotation of the Bering plate may cause left lateral faulting in interior Alaska. The Bering plate's interaction with south‐central Alaska may be responsible for the decreased slip rate on the western Denali fault and for contraction across the central Alaska Range. We analyze slip partitioning along the Aleutian arc on the basis of both GPS measurements and slip azimuths of thrust earthquakes and find a systematic discrepancy between plate convergence direction and slip azimuths. We conclude that slip partitioning in the back arc only develops west of Amchitka Pass, whereas slip partitioning in the fore arc is present throughout the arc.
Upper lithospheric structure of the subduction zone offshore of southern Arauco peninsula, Chile, at ∼38°S
Authors: Contreras‐Reyes Eduardo , Grevemeyer Ingo , Flueh Ernst R. , Reichert Christian
Published: July 2008

A joint interpretation of swath bathymetric, seismic refraction, wide‐angle reflection, and multichannel seismic data was used to derive a detailed tomographic image of the Nazca–South America subduction zone system offshore southern Arauco peninsula, Chile at ∼38°S. Here, the trench basin is filled with up to 2.2 km of sediments, and the Mocha Fracture Zone (FZ) is obliquely subducting underneath the South American plate. The velocity model derived from the tomographic inversion consists of a ∼7‐km‐thick oceanic crust and shows P wave velocities typical for mature fast spreading crust in the seaward section of the profile, with uppermost mantle velocities >8.4 km s−1. In the trench–outer rise area, the top of incoming oceanic plate is pervasively fractured and likely hydrated as shown by extensional faults, horst‐and‐graben structures, and a reduction of both crustal and mantle velocities. These slow velocities are interpreted in terms of extensional bending‐related faulting leading to fracturing and hydration in the upper part of the oceanic lithosphere. The incoming Mocha FZ coincides with an area of even slower velocities and thinning of the oceanic crust (10–15% thinning), suggesting that the incoming fracture zone may enhance the flux of chemically bound water into the subduction zone. Slow mantle velocities occur down to a maximum depth of 6–8 km into the upper mantle, where mantle temperatures are estimated to be 400–430°C. In the overriding plate, the tomographic model reveals two prominent velocity transition zones characterized by steep lateral velocity gradients, resulting in a seismic segmentation of the marine fore arc. The margin is composed of three main domains: (1) a ∼20 km wide frontal prism below the continental slope with Vp ≤ 3.5 km s−1, (2) a ∼50 km area with Vp = 4.5–5.5 km s−1, interpreted as a paleoaccretionary complex, and (3) the seaward edge of the Paleozoic continental framework with Vp ≥ 6.0 km s−1. Frontal prism velocities are noticeably lower than those found in the northern erosional Chile margin, confirming recent accretionary processes in south central Chile.
Cross‐shelf transport of freshwater on the New Jersey shelf
Authors: Castelao Renato , Schofield Oscar , Glenn Scott , Chant Robert , Kohut Josh
Published: July 2008

Repeated hydrographic surveys off New Jersey about 100 km south of the Hudson River mouth were conducted during spring and summer 2006. Glider observations reveal a strong seasonal variation in the surface salinity. Buoyant water is restricted to an area close to the coast during spring, but spans the entire shelf width during summer. During late July and August, freshwater lenses with large density anomaly are found up to 100 km from the coast. Surface velocity maps, satellite imagery and drifters' trajectories revealed the existence of a jet directed offshore and to the south, from near the river mouth toward the study region. This provides a direct pathway for transporting freshwater and any biogeochemical material it contains, including phytoplankton, dissolved organic and nonalgal particulate matter, across the shelf. The highest frequency of observation of the freshwater lenses offshore occurs when the jet transport is large, and the river discharge is relatively high. The transport in the jet is correlated with upwelling winds on scales of a few days.
Uniform particle‐droplet partitioning of 18 organic and elemental components measured in and below DYCOMS‐II stratocumulus clouds
Authors: Hawkins L. N. , Russell L. M. , Twohy C. H. , Anderson J. R.
Published: July 2008

Microphysical and chemical aerosol measurements collected during DYCOMS‐II research flights in marine stratocumulus clouds near San Diego in 2001 were used to evaluate the partitioning of 18 organic and elemental components between droplet residuals and unactivated particles. Bulk submicron particle (between 0.2 and 1.3 μm dry diameter) and droplet residual (above 9 μm ambient diameter) filter samples analyzed by Fourier Transform Infrared (FTIR) spectroscopy and X‐ray Fluorescence (XRF) were dominated by sea salt, ammonium, sulfate, and organic compounds. For the four nighttime and two daytime flights studied, the mass concentration of unactivated particles and droplet residuals were correlated (R2 > 0.8) with consistent linear relationships for mass scavenging of all 18 components on each flight, meaning that the measured particle population partitions between droplet residuals and unactivated particles as if the particles contain internal mixtures of the measured components. Scanning electron microscopy (SEM) for flights 3, 5, and 7 support some degree of internal mixing since more than 90% of measured submicron particles larger than 0.26 μm included sea salt‐derived components. The observed range of 0.26 to 0.40 of mass scavenging coefficients for the four nighttime flights results from the small variations in temperature profile, updraft velocity, and mixed layer depth among the flights. The uniformity of scavenging coefficients for multiple chemical components is consistent with the aged or processed internal mixtures of sea salt, sulfate, and organic compounds expected at long distances downwind from major particle sources.
Intermediate‐scale tropical inertia gravity waves observed during the TWP‐ICE campaign
Authors: Evan S. , Alexander M. J.
Published: July 2008

We describe a 2‐day wave event observed in high‐resolution radiosonde soundings of horizontal wind and temperature taken during the TWP‐ICE experiment in Darwin area. The vertical profiles of temperature, zonal and meridional wind speeds are analyzed using the S‐transform wavelet analysis. Results of the analysis reveal the presence of 2‐day inertia gravity waves in the stratosphere between 20 and 27 km. The wave presents vertical and horizontal wavelengths of around 6 km and 7220 km respectively. The wave was observed to propagate southeastward during the end of the easterly phase of the QBO. The total vertical momentum flux associated with the waves is estimated to be 1 to 2.2 × 10−3 m2s−2. This is of the same order of magnitude as previous observations of 4–10 day Kelvin waves in the lower stratosphere.
Molecular distributions and stable carbon isotopic compositions of dicarboxylic acids and related compounds in aerosols from Sapporo, Japan: Implications for photochemical aging during long‐range atmospheric transport
Authors: Aggarwal Shankar G. , Kawamura Kimitaka
Published: July 2008

Molecular and stable carbon isotopic (δ13C value) compositions of dicarboxylic acids, ketoacids, and dicarbonyls in aerosol samples (i.e., total suspended particles) collected in Sapporo, northern Japan during spring and summer were determined to better understand the photochemical aging of organic aerosols during long‐range transport from East Asia and Siberia. Their molecular distributions were characterized by the predominance of oxalic acid (C2) followed by malonic (C3) or occasionally succinic (C4) acids. Concentrations of total diacids ranged from 106–787 ng m−3 with ketoacids (13–81 ng m−3) and dicarbonyls (2.6–28 ng m−3) being less abundant. Water‐soluble organic carbon (WSOC) comprised 23–69% of aerosol organic carbon (OC). OC to elemental carbon (EC) ratios were high (3.6–19, mean: 8.7). The ratios of C3/C4 and WSOC/OC did not show significant diurnal changes, suggesting that the Sapporo aerosols were not seriously affected by local photochemical processes and instead they were already aged. δ13C values of the dominant diacids (C2 − C4) ranged from −14.0 to −25.3‰. Largest δ13C values (−14.0 to −22.4‰, mean: −18.8‰) were obtained for C2, whereas smallest values (−25.1 to −31.4‰, mean: −28.1‰) were for azelaic acid (C9). In general, δ13C values of C2 − C4 diacids became less negative with aerosol aging (i.e., WSOC/OC), presumably due to isotopic fractionation during photochemical degradation of diacids. By comparing the δ13C values of diacids in the Sapporo aerosols with different air mass source regions, we suggest that although initial δ13C values of diacids depend on their precursor sources, the enrichment in 13C can be ascribed to aerosol photochemical aging.
Study on lightning activity and precipitation characteristics before and after the onset of the South China Sea summer monsoon
Authors: Yuan Tie , Qie Xiushu
Published: July 2008

The data from the lightning imaging sensor (LIS), precipitation radar (PR), and passive microwave imaging (TMI) onboard the Tropical Rainfall Measuring Mission (TRMM) satellite from 1998 to 2005 have been used to investigate the lightning activity and precipitation characteristics before and after the onset of the South China Sea (SCS) summer monsoon. The results show that the lightning activity over the SCS begin to enhance in April, peak in May, and decrease after June. Compared to the premonsoon season, mean cell‐level flash rate decreased 13% and mean flash optical radiance increased 15% during the monsoon season, respectively. The mean flash rate is higher during the premonsoon season. On the basis of the observations of PR and TMI, it can be found that vertical development of precipitation systems in the premonsoon season was stronger than that in the monsoon season, so frequent lightning activity were observed. Further research indicates that when maximum radar reflectivity at 7 km asl reached 36 dBZ, the probability of lightning occurrence was 50% in the premonsoon season, and it increased to 38 dBZ in the monsoon season. The flash rate of precipitation systems can be expressed as functions of maximum storm top height, maximum snow depth and minimum polarization corrected temperatures (PCTs), respectively. Among those, the most stable one is the relationship between flash rate and maximum snow depth.
An evaluation of operational GOES‐derived single‐layer cloud top heights with ARSCL data over the ARM Southern Great Plains Site
Authors: Smith William L. , Minnis Patrick , Finney Heather , Palikonda Rabindra , Khaiyer Mandana M.
Published: July 2008

Cloud top heights retrieved from Geostationary Operational Environmental Satellite (GOES) data are evaluated using comparisons to 5 years of surface‐based cloud radar and lidar data taken at the Atmospheric Radiation Measurement (ARM) program's site near Lamont, Oklahoma. Separate daytime and nighttime algorithms developed at NASA Langley Research Center (LaRC) applied to GOES imager data and an operational CO2‐slicing technique applied to GOES sounder data are tested. Comparisons between the daytime, nighttime and CO2‐slicing cloud top heights and the surface retrievals yield mean differences of −0.84 ± 1.48 km, −0.56 ± 1.31 km, and −1.30 ± 2.30 km, respectively, for all clouds. The errors generally increase with increasing cloud altitude and decreasing optical thickness. These results, which highlight some of the challenges associated with passive satellite cloud height retrievals, are being used to guide development of a blended LaRC/CO2‐slicing cloud top height product with accuracies suitable for assimilation into weather forecast models.
Multipoint observations of magnetospheric compression‐related EMIC Pc1 waves by THEMIS and CARISMA
Authors: Usanova M. E. , Mann I. R. , Rae I. J. , Kale Z. C. , Angelopoulos V. , Bonnell J. W. , Glassmeier K.‐H. , Auster H. U. , Singer H. J.
Published: July 2008

Following a long interval (many days) of sustained very quiet geomagnetic conditions, electromagnetic ion cyclotron (EMIC) wave activity was seen by the CARISMA array (www.carisma.ca) on the ground for several hours simultaneously with enhanced solar wind density and related magnetic compression seen at GOES 12 on 29th June 2007. The THEMIS C, D, and E satellites were outbound in a “string‐of‐pearls” configuration and each observed EMIC waves on L‐shells ranging from 5 to 6.5. THEMIS resolved some of the spatial‐temporal ambiguity and defined the radial extent of EMIC activity to be ∼1.3 Re. The band‐limited EMIC waves were seen slightly further out in radial distance by each subsequent THEMIS satellite, but in each case were bounded at high‐L by a decrease in density as monitored by spacecraft potential. The EMIC wave activity appears to be confined to a region of higher plasma density in the vicinity of the plasmapause, as verified by ground‐based cross‐phase analysis. The structured EMIC waves seen at THEMIS E and on the ground have the same repetition period, in contradiction to expectations from the bouncing wave packet hypothesis. Compression‐related EMIC waves are usually thought to be preferentially confined to higher L's than observed here. Our observations suggest solar wind density enhancements may also play a role in the excitation of radially localised EMIC waves near the plasmapause.
ASTER Land Surface Emissivity Database of California and Nevada
Authors: Hulley G. C. , Hook S. J. , Baldridge A. M.
Published: July 2008

Land surface temperature and emissivity (LST&E) are essential parameters for a wide range of studies undertaken at a variety of spatial scales. LST&E products are generated by a number of spaceborne sensors such as ASTER, MODIS, and AIRS at varying spatial, spectral and temporal resolutions. We have developed an approach for producing gridded, mean, seasonal ASTER LST&E Datasets at a spatial resolution of 100 m at nadir. This paper shows a mean wintertime and summertime emissivity dataset for California and Nevada, USA using all available data since mission launch (2000). Comparison of the two seasonal datasets indicates the greatest variability occurs in areas affected by snow such as the Sierra Nevada Mountains, and in agricultural regions. Comparisons of the new emissivity dataset with laboratory measurements of geologic samples show emissivity differences of less than 0.5%, while 1–3% differences were found for water and vegetation using spectra from the MODIS UCSB library.
Temporal and spatial characteristics of Pc1 waves observed by ST5
Authors: Engebretson M. J. , Posch J. L. , Westerman A. M. , Otto N. J. , Slavin J. A. , Le G. , Strangeway R. J. , Lessard M. R.
Published: July 2008

We present the results of a study of Pc1 waves (0.2–5 Hz) recorded by the three spacecraft of NASA's Space Technology 5 (ST5) mission, which operated in a dawn‐dusk, 300 × 4500 km Sun‐synchronous orbit in a “string‐of‐pearls” configuration from 26 March through 23 June 2006. Regions with Pc1 wave activity are not only localized to rather narrow L shells but can appear and disappear on the time scales of ∼10 s to 10 min as examined by ST5. Only half of the 48 identified events were observed by all three spacecraft, and five events were observed by only one spacecraft. Only seven events were observed below L = 4, and only one was observed below L = 3.6, consistent with the relatively quiet geomagnetic conditions during this interval. The temporal occurrence distribution of Pc1 events was similar to that recorded at Halley, Antarctica (L = 4.56), during this same interval in that the number and intensity of events increased during magnetospheric compressions and during the recovery phase of magnetic storms, but they were reduced or absent during main phase and early recovery phase. This agreement suggests that if Pc1 events occur during main phase, their nearly universal absence in ground records cannot be ascribed to ionospheric screening effects or obscuration by irregular ULF noise generated in the ionosphere. These findings also suggest that although electromagnetic ion cyclotron waves might theoretically cause rapid depletion of radiation belt electrons during the main phase of storms, such waves cannot be assumed to occur during the main phase of all storms.
Nonlinear effects of temperature, fluid pressure, and inelastic porosity on dynamic fault slip and fault tip propagation: Emergence of slip strengthening and pulse‐like fault slip
Authors: Suzuki Takehito , Yamashita Teruo
Published: July 2008

We theoretically study dynamic faulting, taking account of thermoporoelastic effects including inelastic porosity change; the porosity is assumed to increase with increasing fault slip. We first derive the analytical solutions for the changes of fluid pressure, temperature, and fault slip, assuming 1‐D fault model. As found in our previous study, the evolution of these quantities is controlled by a single nondimensional parameter Su, a quantity proportional to the rate of increase in inelastic porosity multiplied by the thickness of shear heating zone. If we assume that temperature elevation remains below the melting temperature of fault rocks, Su is found be close to zero or greater than unity. Our 2‐D simulation shows that pulse‐like slip appears when Su is greater than unity, which is a necessary consequence of the emergence of slip strengthening, while slip weakening caused by thermal pressurization arises when Su is close to zero. The applied shear stress is entirely released when Su is close to zero, while it is released only partially when Su is greater than unity, so that the latter will be more reasonable according to seismological observations. The fault tip stress increases significantly with the fault extension in classical singular fault model. In contrast, the fault tip stress is only weakly dependent on the size of extending fault in our model when Su is greater than unity, so that the fault growth is more vulnerable to spatial perturbation of model parameters. Our present study indicates the importance of slip strengthening for the understanding of dynamic faulting.
Probabilistic prediction of hydroclimatic variables with nonparametric quantification of uncertainty
Authors: Maity Rajib , Nagesh Kumar D.
Published: July 2008

A semiparametric, copula‐based approach is proposed to capture the dependence between teleconnected hydroclimatic variables for the prediction of response variable using the information of climate precursors. The copulas have an excellent property to study the scale‐free dependence structure while preserving such dependence during simulation. This property is utilized in the proposed approach. The usefulness of the proposed method can be recognized in three distinct aspects: (1) It captures the dependence pattern preserving scale‐free or rank‐based “measure of association” between the variables. (2) The proposed method is able to quantify the uncertainty associated with the relationship between teleconnected variables due to various factors; thus, the probabilistic predictions are available along with information of uncertainty. (3) Instead of parametric probability distribution, nonparametrically estimated probability densities for data sets can be handled by the proposed approach. Thus, the proposed method can be applied to capture the relationship between teleconnected hydroclimatic variables having some linear and/or nonlinear cause‐effect relationship. The proposed method is illustrated by an example of the most discussed problem of Indian summer monsoon rainfall (ISMR) and two different large‐scale climate precursors, namely, El Niño–Southern Oscillation (ENSO) and Equatorial Indian Ocean Oscillation (EQUINOO). The dependence between them is captured and investigated for its potential use to predict the monthly variation of ISMR using the proposed method. Predicted rainfall is shown to correspond well with the observed rainfall with a correlation coefficient of 0.81 for the summer monsoon months, i.e., June through September. Moreover, the uncertainty associated with the predicted values is also made available through boxplots. The method, being general, can be applied to similar analysis to assess the dependence between teleconnected hydroclimatic variables for other regions of the world and for different temporal scales such as seasonal.
Simulating nonsorted circle development in arctic tundra ecosystems
Authors: Daanen Ronald P. , Misra Debasmita , Epstein Howard , Walker Donald , Romanovsky Vladimir
Published: July 2008

Nonsorted circles, ubiquitous to the Arctic Tundra region, are patterned ground features with circular semibarren areas surrounded by vegetation. These circles are formed and persist as an ecosystem due to complex soil‐water‐energy‐ice‐plant relationships and dynamics in the Arctic. In this paper, we present the first model that captures the dynamics of the physical and biological components of the nonsorted circle ecosystem in order to understand its formation and persistence, especially in a changing climatic environment. We have applied a coupled model describing (1) vegetation dynamics (ArcVeg) and (2) coupled heat and moisture transport with phase change (WIT) in the active layer of the soil where such circles are initiated and developed. We simulated the system behavior during the formation process starting with a random vegetation development. The vegetation provided heterogeneous insulation to the soil surface. During freezing, the noninsulated areas froze first, resulting in preferential ice accumulation in those areas. The ice prevented the vegetation from developing further in those areas and thus developed and stabilized the nonsorted circle pattern. The model produced a nonsorted circle pattern that was well compared to those observed in the field. The model also illustrated that the availability of water was critical for the sustenance and stability of the nonsorted circle. The effect of climatic variations on the freezing process on the other hand did not seem to affect the formation and sustenance of nonsorted circles.
Centennial‐scale evolution of Dansgaard‐Oeschger events in the northeast Atlantic Ocean between 39.5 and 56.5 ka B.P.
Authors: Dickson Alexander J. , Austin William E. N. , Hall Ian R. , Maslin Mark A. , Kucera Michal
Published: July 2008

There is much uncertainty surrounding the mechanisms that forced the abrupt climate fluctuations found in many palaeoclimate records during Marine Isotope Stage (MIS)‐3. One of the processes thought to be involved in these events is the Atlantic Meridional Overturning Circulation (MOC), which exhibited large changes in its dominant mode throughout the last glacial period. Giant piston core MD95‐2006 from the northeast Atlantic Ocean records a suite of palaeoceanographic proxies related to the activity of both surface and deep water masses through a period of MIS‐3 when abrupt climate fluctuations were extremely pronounced. A two‐stage progression of surface water warming during interstadial warm events is proposed, with initial warming related to the northward advection of a thin warm surface layer within the North Atlantic Current, which only extended into deeper surface layers as the interstadial progressed. Benthic foraminifera isotope data also show millennial‐scale oscillations but of a different structure to the abrupt surface water changes. These changes are argued to partly be related to the influence of low‐salinity deepwater brines. The influence of deepwater brines over the site of MD95‐2006 reached a maximum at times of rapid warming of surface waters. This observation supports the suggestion that brine formation may have helped to destabilize the accumulation of warm, saline surface waters at low latitudes, helping to force the MOC into a warm mode of operation. The contribution of deepwater brines relative to other mechanisms proposed to alter the state of the MOC needs to be examined further in future studies.
Progesterone and its Metabolite Allopregnanolone Differentially Regulate Hemostatic Proteins after Traumatic Brain Injury
Authors: VanLandingham Jacob W , Cekic Milos , Cutler Sarah M , Hoffman Stuart W , Washington Ebony R , Johnson Sarah J , Miller Darren , Stein Donald G
Published: July 2008

Our laboratory has shown in numerous experiments that the neurosteroids progesterone (PROG) and allopregnanolone (ALLO) improve molecular and functional outcomes after traumatic brain injury (TBI). As coagulopathy is an important contributor to the secondary destruction of nervous tissue, we hypothesized that PROG and ALLO administration may also have a beneficial effect on coagulation protein expression after TBI. Adult male Sprague—Dawley rats were given bilateral contusions of the medial frontal cortex followed by treatments with PROG (16 mg/kg), ALLO (8 mg/kg), or vehicle (22.5% hydroxypropyl-β-cyclodextrin). Controls received no injury or injections. Progesterone generally maintained procoagulant (thrombin, fibrinogen, and coagulation factor XIII), whereas ALLO increased anticoagulant protein expression (tissue-type plasminogen activator, tPA). In addition, PROG significantly increased the ratio of tPA bound to neuroserpin, a serine protease inhibitor that can reduce the activity of tPA. Our findings suggest that in a model of TBI, where blood loss may exacerbate injury, it may be preferable to treat patients with PROG, whereas it might be more appropriate to use ALLO as a treatment for thrombotic stroke, where a reduction in coagulation would be more beneficial.
Microthrombosis after Aneurysmal Subarachnoid Hemorrhage: An Additional Explanation for Delayed Cerebral Ischemia
Authors: Vergouwen Mervyn DI , Vermeulen Marinus , Coert Bert A , Stroes Erik SG , Roos Yvo BWEM
Published: July 2008

Patients with aneurysmal subarachnoid hemorrhage (SAH) who experience delayed cerebral ischemia (DCI) have an increased risk of poor outcome. Delayed cerebral ischemia is considered to be caused by vasospasm. However, not all patients with DCI have vasospasm. Inversely, not all patients with vasospasm develop clinical symptoms and signs of DCI. In the past, treatments aiming at vasospasm were not successful in preventing ischemia. The purpose of this review is to give an overview of clinical data showing that DCI cannot always be attributed to vasospasm, and to present an in-depth analysis of clinical and autopsy studies on the role of microthrombosis in the pathogenesis of DCI. Clinical studies show that DCI is associated with an activation of the coagulation cascade within a few days after SAH, preceding the time window during which vasospasm occurs. Furthermore, impaired fibrinolytic activity, and inflammatory and endothelium-related processes, lead to the formation of microthrombi, which ultimately result in DCI. The presence of microthrombi is confirmed by autopsy studies. Insight in the pathophysiology of DCI is crucial for the development of effective therapies against this complication. Because multiple pathways are involved, future research should focus on drugs with pleiotropic effects.
Chronic Riluzole Treatment Increases Glucose Metabolism in Rat Prefrontal Cortex and Hippocampus
Authors: Chowdhury Golam MI , Banasr Mounira , de Graaf Robin A , Rothman Douglas L , Behar Kevin L , Sanacora Gerard
Published: July 2008

Riluzole is believed to modulate glutamatergic function by reducing glutamate release and facilitating astroglial uptake. We measured13C labeling in metabolites in prefrontal cortex and hippocampus during a 10 mins infusion of [1-13C]glucose in urethane anesthetized rats treated with riluzole (21 days, 4 mg/kg per day, i.p.) or saline. Total and13C concentrations of metabolites were determined in extracts using1H-[13C] NMR spectroscopy. In prefrontal cortex ( P < 0.05) and hippocampus ( P < 0.05) riluzole increased13C labeling over saline in glutamate-C4 (to 112% and 130%), GABA-C2 (to 142% and 171%), and glutamine-C4 (to 118% and 233%) without affecting total metabolite levels ( P > 0.2). Our findings indicate that contrary to expectation chronic riluzole enhanced glucose oxidative metabolism and glutamate/glutamine cycling.
The Role of Akt Signaling in Oxidative Stress Mediates NF-κB Activation in Mild Transient Focal Cerebral Ischemia
Authors: Song Yun Seon , Narasimhan Purnima , Kim Gab Seok , Jung Joo Eun , Park Eun-Hee , Chan Pak H
Published: July 2008

Reactive oxygen species, derived from hypoxia and reoxygenation during transient focal cerebral ischemia (tFCI), are associated with the signaling pathway that leads to neuronal survival or death, depending on the severity and duration of the ischemic insult. The Akt survival signaling pathway is regulated by oxidative stress and is implicated in activation of nuclear factor-κB(NF-κB). Mild cerebral ischemia in mice was used to induce increased levels of Akt phosphorylation in the cortex and striatum. To clarify the role of Akt activation by NF-κB after tFCI, we injected the specific Akt inhibitor IV that inhibits Akt phosphorylation/activation. Inhibition of Akt phosphorylation induced decreases in sequential NF-κB signaling after 30 mins of tFCI at 1 h. Furthermore, the downstream survival signals of the Akt pathway were also decreased. Akt inhibitor IV increased ischemic infarct volume and apoptotic-related DNA fragmentation. Superoxide production in the ischemic brains of mice pretreated with the Akt inhibitor was higher than in vehicle-treated mice. In addition, those pretreated mice showed a reduction of approximately 33% in copper/zinc-superoxide dismutase expression. We propose that Akt signaling exerts its neuroprotective role by NF-κB activation in oxidative cerebral ischemia in mice.
Multiple Linear Analysis Methods for the Quantification of Irreversibly Binding Radiotracers
Authors: Kim Su Jin , Lee Jae Sung , Kim Yu Kyeong , Frost James , Wand Gary , McCaul Mary E , Lee Dong Soo
Published: July 2008

Gjedde—Patlak graphical analysis (GPGA) has commonly been used to quantify the net accumulations (Kin) of radioligands that bind or are taken up irreversibly. We suggest an alternative approach (MLAIR: multiple linear analysis for irreversible radiotracers) for the quantification of these types of tracers. Two multiple linear regression model equations were derived from differential equations of the two-tissue compartment model with irreversible binding. Multiple linear analysis for irreversible radiotracer 1 has a desirable feature for ordinary least square estimations because only the dependent variable CT( t) is noisy. Multiple linear analysis for irreversible radiotracer 2 provides Kin from direct estimates of the coefficients of independent variables without the mediation of a division operation. During computer simulations, MLAIR1 provided less biased Kin estimates than the other linear methods, but showed a high uncertainty level for noisy data, whereas MLAIR2 increased the robustness of estimation in terms of variability, but at the expense of increased bias. For real [11C]MeNTI positron emission tomography data, both methods showed good correlations, with parameters estimated using the standard nonlinear least squares method. Multiple linear analysis for irreversible radiotracer 2 parametric images showed remarkable image quality as compared with GPGA images. It also showed markedly improved statistical power for voxelwise comparisons than GPGA. The two MLAIR approaches examined were found to have several advantages over the conventional GPGA method.
Universal Features in the Genome-level Evolution of Protein Domains
Authors: Cosentino Lagomarsino Marco , Sellerio Alessandro , Heijning Philip , Bassetti Bruno
Published: July 2008

Protein domains are found on genomes with notable statistical distributions, which bear a high degree of similarity. Previous work has shown how these distributions can be accounted for by simple models, where the main ingredients are probabilities of duplication, innovation, and loss of domains. However, no one so far has addressed the issue that these distributions follow definite trends depending on protein-coding genome size only. We present a stochastic duplication/innovation model, falling in the class of so-called Chinese Restaurant Processes, able to explain this feature of the data. Using only two universal parameters, related to a minimal number of domains and to the relative weight of innovation to duplication, the model reproduces two important aspects: (a) the populations of domain classes (the sets, related to homology classes, containing realizations of the same domain in different proteins) follow common power-laws whose cutoff is dictated by genome size, and (b) the number of domain families is universal and markedly sublinear in genome size. An important ingredient of the model is that the innovation probability decreases with genome size. We propose the possibility to interpret this as a global constraint given by the cost of expanding an increasingly complex interactome. Finally, we introduce a variant of the model where the choice of a new domain relates to its occurrence in genomic data, and thus accounts for fold specificity. Both models have general quantitative agreement with data from hundreds of genomes, which indicates the coexistence of the well-known specificity of proteomes with robust self-organizing phenomena related to the basic evolutionary ``moves'' of duplication and innovation.
A Genome‐wide Scan of Loci Linked to Serum Adiponectin in Two Populations of African Descent
Authors: Hicks Chindo , Zhu Xiaofeng , Luke Amy , Kan Donghui , Adeyemo Adebowale , Wu Xiaodong , Cooper Richard S.
Published: July 2008

Objective: The objectives were to identify quantitative trait loci linked to serum adiponectin concentration and to estimate heritability in two populations of African descent.

Research Methods and Procedures: We conducted a genome scan for serum adiponectin concentration in two populations of African descent. Genome‐wide microsatelitte markers were typed in an African‐American population consisting of 203 families from the Chicago area and in a Nigerian Yoruba population consisting of 146 families. Linkage analysis was performed to identify loci. Variance component model was used to estimate heritability.

Results: Estimates of heritability adjusted for age, gender, and BMI were 0.45 and 0.70 for the African‐American and Nigerian families, respectively. In both populations, adiponectin was significantly negatively correlated with BMI, height, and weight. After adjusting for age, gender, and BMI, we found evidence of genetic linkage to adiponectin on chromosomes 11 [limit of detection (LOD) score = 2.89] and 17 (LOD score = 1.35) in the Nigerian sample. Among the African‐Americans, we found genetic linkage on chromosomes 2 (LOD score = 1.82), 4 (LOD score = 2.12), and 11 (LOD score = 2.33). Analysis based on combined data yielded a maximum LOD score of 3.21 on chromosome 11.

Discussion: Consistency of the finding on chromosome 11 suggests that this region is likely to be involved in regulation of adiponectin, either through a primary influence on hormone levels or through pathways influencing body composition. These results suggest that adiponectin could be a potential therapeutic target for obesity.
Effects of Acute and Chronic Protein Intake on Metabolism, Appetite, and Ghrelin During Weight Loss
Authors: Leidy Heather J. , Mattes Richard D. , Campbell Wayne W.
Published: July 2008

Objective: This study evaluated the effects of acute and chronic consumption of higher dietary protein on energy expenditure, macronutrient use, appetite, and appetite‐regulating hormones during weight loss in women.

Research Methods and Procedures: Thirty‐eight women chronically consuming a 750 kcal/d energy‐deficit diet with a protein content of 30% (higher protein‐chronic diet, HP‐CD, n = 21) or 18% (normal protein‐chronic diet, NP‐CD, n = 17) for 9 weeks were tested. On separate days, metabolic, appetite, and hormonal responses were measured over 4 hours when the women consumed a higher protein‐acute meal (HP‐AM) (30% of energy as protein) or a normal protein‐acute meal (NP‐AM) (18% of energy as protein).

Results: With chronic diet groups combined, HP‐AM led to lower respiratory exchange ratio (0.829 ± 0.005 vs. 0.843 ± 0.008; p < 0.05), lower carbohydrate oxidation (p < 0.05), and higher fat oxidation (p < 0.05) compared with NP‐AM. HP‐AM also led to reduced self‐reported postprandial hunger (p < 0.001) and desire to eat (p < 0.001) and lower postprandial ghrelin (252 ± 16 vs. 274 ± 18 ng/mL · 240 minutes, p < 0.05) compared with NP‐AM. No differences in postprandial energy expenditure (PPEE) occurred between meals. When combining acute meals, respiratory exchange ratio was lower (p < 0.05) and protein oxidation (p < 0.001) was higher in the HP‐CD vs. NP‐CD. An acute meal‐by‐chronic diet interaction was observed with PPEE such that HP‐AM led to greater PPEE in the HP‐CD vs. NP‐CD (28.7 ± 2.7 vs. 19.9 ± 2.7 kcal/min for 195 minutes; p < 0.05).

Conclusions: During weight loss, thermogenesis and protein use appear to be influenced by chronic protein intake, while appetite and ghrelin are more responsive to acute protein intake.
Triaxial Accelerometry for Assessment of Physical Activity in Young Children
Authors: Tanaka Chiaki , Tanaka Shigeho , Kawahara Junko , Midorikawa Taishi
Published: July 2008

Objective: The purpose of the present study was to derive linear and non‐linear regression equations that estimate energy expenditure (EE) from triaxial accelerometer counts that can be used to quantitate activity in young children. We are unaware of any data regarding the validity of triaxial accelerometry for assessment of physical activity intensity in this age group.

Research Methods and Procedures: EE for 27 girls and boys (6.0 ± 0.3 years) was assessed for nine activities (lying down, watching a video while sitting and standing, line drawing for coloring‐in, playing blocks, walking, stair climbing, ball toss, and running) using indirect calorimetry and was then estimated using a triaxial accelerometer (ActivTracer, GMS).

Results: Significant correlations were observed between synthetic (synthesized tri‐axes as the vector), vertical, and horizontal accelerometer counts and EE for all activities (0.878 to 0.932 for EE). However, linear and non‐linear regression equations underestimated EE by >30% for stair climbing (up and down) and performing a ball toss. Therefore, linear and non‐linear regression equations were calculated for all activities except these two activities, and then evaluated for all activities. Linear and non‐linear regression equations using combined vertical and horizontal acceleration counts, synthetic counts, and horizontal counts demonstrated a better relationship between accelerometer counts and EE than did regression equations using vertical acceleration counts. Adjustment of the predicted value by the regression equations using the vertical/horizontal counts ratio improved the overestimation of EE for performing a ball toss.

Discussion: The results suggest that triaxial accelerometry is a good tool for assessing daily EE in young children.