bluuebunny/crossref_metadata_2025 huggingface dataset:
Inhibition of Response Mode in Task Switching
Authors: Koch Iring , Gade Miriam , Philipp Andrea M.
Published: January 2004

Abstract. Task inhibition was explored in two experiments that employed a paradigm in which participants switched among three tasks. Two tasks required manual choice responses based on numerical judgment (parity or magnitude), whereas a third task required an unconditional double-press of both response keys. Both experiments showed that switching to a just-abandoned task (n-2 task repetition) generally leads to a performance cost relative to switching to another task. Specifically, this task inhibition effect also occurred for the double-press task, suggesting inhibition of response mode. Prolonging the task-cuing interval showed that advance task preparation reduced only inhibition of the double-press task but not of the choice tasks (Experiment 1). Prolonging the response-cue interval led to a decrease of the inhibition effect in all tasks (Experiment 2), suggesting a time-based release of task inhibition. Together, the experiments support the notion of a response-related component of task inhibition.
The On-Line Resolution of the Sentence Complement/Relative Clause Ambiguity: Evidence from Spanish
Authors: Demestre Josep , García-Albea José E.
Published: January 2004

Abstract. Two self-paced reading experiments investigated syntactic ambiguity resolution in Spanish. The experiments examined the way in which Spanish subjects initially interpret sentences that are temporarily ambiguous between a sentence complement and a relative clause interpretation. Experiment 1 examined whether the sentence complement preference found in English is observed in Spanish speaking subjects. In Experiment 2, verbal mood was manipulated in order to study the influence of verb-specific information on sentence processing. Since subcategorization for a subjunctive complement clause is generally assumed to be a lexical property of some verbs, the manipulation of the mood of the embedded verb affords us an interesting and novel way to examine the influence of lexical information on syntactic ambiguity resolution. Experiment 1 showed that Spanish speakers initially interpret the ambiguous that-clause as a sentence complement. Experiment 2 showed that verb-specific information, in particular, the information that specifies that a verb subcategorizes for a subjunctive complement, is accessed and used rapidly and affects the ambiguity resolution process. The results are discussed in relation to current models of sentence processing.
On the Perceptual Generality of the Unit-Decade Compatibility Effect
Authors: Nuerk Hans-Christoph , Weger Ulrich , Willmes Klaus
Published: January 2004

Abstract. Number magnitude is assumed to be holistically represented along a single mental number line. Recently, we have observed a unit-decade-compatibility effect which is inconsistent with that assumption (Nuerk, Weger, & Willmes, 2001) . In two-digit Arabic number comparison, we have demonstrated that compatible comparisons in which separate decade and unit comparisons lead to the same decision (32_47, 3 < 4 and 2 < 7) were faster than incompatible trials (37_52, 3 < 5, but 7 > 2). Because overall distance was matched, a holistic model could not account for the compatibility effect. However, one could argue that the compatibility effect was due to the specific vertical perceptual arrangement of the two-digit numbers in Nuerk et al.’s (2001) experiment where the decade digits and unit digits were presented column-wise above each other. To examine this objection, we studied the perceptual generality of the compatibility effect with diagonal presentation. We replicated the compatibility effect with diagonal presentation. It is concluded that the compatibility effect is not due to encoding characteristics imposed by the perceptual setting of the original experiment. In particular, the assumption of an overall analog magnitude representation for two-digit numbers is not consistent with these data.
River transport effects on compressional belts: First results from an integrated analogue‐numerical model
Authors: Persson Katarina S. , Garcia‐Castellanos Daniel , Sokoutis Dimitrios
Published: January 2004

Erosion, deposition, and tectonic processes interact to define the style of deformation in compressional belts. This paper introduces a method of integrating a numerical model for surface transport with analogue sandbox models of compressional belts to further improve our understanding of this interplay. The analogue model provides the numerical model with the rising topography, whereas the numerical model calculates the river network and the resulting amount of erosion and sediment transport. Compared to previous analogue models with uniform (two‐dimensional) erosion this method provides a tool to incorporate process‐based rates of erosion and deposition with spatial distributions that depend on the river network developed on the evolving topography. Rivers running parallel to the evolving mountain belt induce along‐strike changes in erosion and deposition that in turn result in asymmetric tectonic deformation. The additional load of sediments controls the propagation of thrust as well as the direction of vergence of the main thrust. High erosion rates do not always lead to fewer thrusts within the compressional belts but generally steepen and lengthen the lifetime of the affected faults.
Loading rate dependence of permeability evolution in porous aeolian sandstones
Authors: Ojala Ira O. , Ngwenya Bryne T. , Main Ian G.
Published: January 2004

Mechanical properties of rocks are characterized by their notable dependence on the applied deformation rate. However, little is known about the strain rate dependence of fluid flow properties since most laboratory tests are conducted using a single, high strain rate. We have investigated the effect of loading rate on the permeability of porous sandstones by carrying out triaxial compression tests at four different temperatures and strain rates with continuous monitoring of permeability, acoustic emission (AE), and pore fluid chemistry. All tests are characterized by an initial permeability decrease due to inferred compaction of favorably oriented cracks. The amount of initial permeability reduction increases with decreasing strain rate, thus implying a more efficient initial compaction at slower strain rates. At a later stage of loading, permeability correlates with stress, ion concentration, or AE damage depending on the strain rate used. High strain rate tests are characterized by a positive power law or logarithmic correlation between permeability and AE damage. At slow strain rates, permeabilities decrease exponentially with mean effective stress and axial strain for the Locharbriggs sandstone. The Clashach sandstone exhibits a linear correlation between permeability and exit pore fluid concentrations (Si, Mg, Fe, Al) if a slow strain rate is used. These observations have important implications for the applicability of room temperature, high strain rate laboratory data to the conditions that prevail in the Earth's crust.
Posteruption suspended sediment transport at Mount St. Helens: Decadal‐scale relationships with landscape adjustments and river discharges
Authors: Major Jon J.
Published: January 2004

Widespread landscape disturbance by the cataclysmic 1980 eruption of Mount St. Helens abruptly increased sediment supply in surrounding watersheds. The magnitude and duration of the redistribution of sediment deposited by the eruption as well as decades‐ to centuries‐old sediment remobilized from storage have varied chiefly with the style of disturbance. Posteruption suspended sediment transport has been greater and more persistent from zones of channel disturbance than from zones of hillslope disturbance. Despite the severe landscape disturbances caused by the eruption, relationships between discharge magnitudes and frequencies and suspended sediment transport have been remarkably consistent. Discharges smaller than mean annual flows generally have transported <5%, but locally ∼15%, of the annual suspended sediment loads, and infrequent (p < 0.01), large floods have transported as much as 50% of the annual suspended sediment loads in a single day. However, moderate‐magnitude discharges (those greater than mean annual flows but less than 2‐year floods) have transported the greatest amounts of sediment from all disturbance zones. Such discharges have transported, on average, 60% to ∼95% of the annual suspended sediment loads, usually within cumulative periods of 1–3 weeks each year. Although small‐magnitude and large‐magnitude discharges have locally and episodically transported considerable amounts of suspended sediment, there has not been any notable change in the overall nature of the effective discharges; moderate‐magnitude flows have been the predominant discharges responsible for transporting the majority of suspended sediment during 20 years of posteruption landscape adjustment.
The Cretaceous‐Tertiary extinction: Modeling carbon flux and ecological response
Authors: Adams J. Brad , Mann Michael E. , D'Hondt Steven
Published: January 2004

It is widely recognized that a significant negative excursion in carbon isotopic (δ13C) differences between planktic and benthic foraminiferal tests occurred at the Cretaceous‐Tertiary (K‐T) boundary. We applied parametric and nonparametric breakpoint tests and statistical comparisons of different recovery models to assess the timing and pattern of recovery from this negative excursion at South Atlantic Deep Sea Drilling Project (DSDP) Site 528 and equatorial Pacific DSDP Site 577. Our results indicate a two‐stage recovery with an initial recovery to an intermediate state of planktic‐to‐benthic δ13C differences followed by a discontinuous shift to a final state with planktic‐to‐benthic δ13C differences similar to preextinction values. The final discontinuous shift in both the Pacific and Atlantic Ocean sites occurred several million years after the K‐T collapse of planktic‐to‐benthic δ13C differences. Both the first and second stages of recovery are best described by damped exponential relaxations. The pattern and timing of this carbon cycle recovery may have been contingent on the occurrence of key biological events.
Electron density height profiles from GPS receiver data
Authors: Reilly Michael H. , Singh Malkiat
Published: January 2004

A successful ionospheric electron density model assimilates relevant data for determination of its driving parameters. We process about two hours worth of two‐frequency GPS ground‐receiver data from five satellites in order to separate the least squares solution of up to four driving parameters of the electron density profile (EDP) model from the solution of four relative (between satellites) differential hardware biases. The EDP model we use is part of the Ionosphere and Troposphere Raytrace Model (ITRAY), which is our upgrade of the Raytrace/Ionospheric Conductivity and Electron Density model (ICED)‐Bent‐Gallagher (RIBG) model. We use the Westford GPS receiver in Massachusetts to update the EDP model, which we then use to predict EDP distributions at nearby Millstone Hill for comparison with ground truth incoherent‐scatter radar and Digisonde data. We find that a simple procedure often works well when the model time dependence is correct, but we find that forcing the ionospheric model to more closely fit GPS data actually degrades ionospheric specification in the F layer region. We suggest a data diversification remedy.
Surface uplift, tectonics, and erosion of eastern Tibet from large‐scale drainage patterns
Authors: Clark M. K. , Schoenbohm L. M. , Royden L. H. , Whipple K. X. , Burchfiel B. C. , Zhang X. , Tang W. , Wang E. , Chen L.
Published: January 2004

A new regional compilation of the drainage history in southeastern Tibet suggests that the modern rivers draining the plateau margin were once tributaries to a single, southward flowing system which drained into the South China Sea. Disruption of the paleo‐drainage occurred by river capture and reversal prior to or coeval with the initiation of Miocene (?) uplift in eastern Tibet, including ∼2000 m of surface uplift of the lower plateau margin since reversal of the flow direction of the Yangtze River. Despite lateral changes in course due to capture and reversal, the superposition of eastward and southward draining rivers that cross the southeastern plateau margin suggests that uplift has occurred over long wavelengths (>1000 km), mimicking the present low‐gradient topographic slope. Thus reorganization of drainage lines by capture and reversal events explains most of the peculiar patterns of the eastern plateau rivers, without having to appeal to large‐magnitude tectonic shear.
Evidence for an extensive hydrothermal plume in the Tonga‐Fiji region of the South Pacific
Authors: Lupton John E. , Pyle Douglas G. , Jenkins William J. , Greene Ronald , Evans Leigh
Published: January 2004

Several hydrographic stations in the vicinity of the Samoa Islands have 3He/4He above the regional background in the depth range of 1500–1800 m, indicating injection of mantle helium from a local hydrothermal source. The highest δ(3He) = 43.4% was detected at 1726‐m depth at 15.0°S, 173.1°W in the bathymetric gap between the Samoa Islands and the northern end of the Tonga‐Kermadec Arc. The δ(3He) profile at this station decreases to δ(3He) = 26% at 2500‐m depth. The relatively shallow depth of the maximum hydrothermal signal suggests a source different from the conventional Pacific basin helium plume centered at 2500 m that is carried westward from the East Pacific Rise. Stations to the west of this locality show a progressive decrease in the maximum δ(3He) values in the depth range of 1480–1790 m out to 169°E. Stations east of the Tonga‐Fiji region show lower 3He values (<26%) at 1700 m and the profiles are dominated by a deeper maximum at 2500 m, presumably the distal traces of hydrothermal input from East Pacific Rise. This pattern in the 3He distribution suggests that the 1700‐m deep helium plume is carried in a northwesterly direction some 2000 km from its source near the northern end of the Tonga‐Kermadec Arc. At this time very little is known about the source of this hydrothermal plume or the details of its areal extent. Numerous seamounts and rift zones in the region are possible hydrothermal sources for the plume. The summit crater of Vailulu'u, a young seamount at the eastern end of the Samoa chain, was recently discovered to be hydrothermally active at ∼600 m depth [Hart et al., 2000]. However this shallow hydrothermal field on Vailulu'u is an unlikely source for the deeper 1700‐m signal. The most likely source would appear to be the extensional zones of the northern Lau Basin system, such as the Mangatolo Triple Junction. Just as the helium plume emanating from Lo'ihi has helped our understanding of the circulation near the Hawaiian Islands [Lupton, 1996], this helium plume in the Tonga‐Fiji region has great potential for delineating circulation in this area of the south Pacific.
Quantitative bedrock geology of east and Southeast Asia (Brunei, Cambodia, eastern and southeastern China, East Timor, Indonesia, Japan, Laos, Malaysia, Myanmar, North Korea, Papua New Guinea, Philippines, far‐eastern Russia, Singapore, South Korea, Taiwan, Thailand, Vietnam)
Authors: Peucker‐Ehrenbrink Bernhard , Miller Mark W.
Published: January 2004

We quantitatively analyze the area‐age distribution of sedimentary, igneous and metamorphic bedrock based on data from the most recent digital geologic maps of East and Southeast Asia (Coordinating Committee for Coastal and Offshore Geosciences Programmes in East and Southeast Asia (CCOP) and the Geologic Survey of Japan, 1997; 1:2,000,000), published as Digital Geoscience Map G‐2 by the Geological Survey of Japan. Sedimentary rocks, volcanic rocks, plutonic rocks, ultramafic rocks and metamorphic rocks cover 73.3%, 8.5%, 8.8%, 0.9%, and 8.6% of the surface area, respectively. The average ages of major lithologic units, weighted according to bedrock area, are as follows: sedimentary rocks (average stratigraphic age of 123 Myr/median age of 26 Myr), volcanic rocks (84 Myr/20 Myr), intrusive rocks (278 Myr/195 Myr), ultramafic rocks (unknown) and metamorphic rocks (1465 Myr/1118 Myr). The variability in lithologic composition and age structure of individual countries reflects the complex tectonic makeup of this region that ranges from Precambrian cratons (e.g., northeast China and North Korea) to Mesozoic‐Cenozoic active margins (e.g., Japan, the Philippines, Indonesia and New Guinea). The spatial resolution of the data varies from 44 km2 per polygon (Japan) to 1659 km2 per polygon (Taiwan) and is, on average (490 km2/polygon), similar to our previous analyses of the United States of America and Canada. The temporal and spatial resolution is sufficiently high to perform age‐area analyses of individual river basins larger than ∼10,000 km2 and to quantitatively evaluate the relationship between bedrock geology and river chemistry. As many rivers draining tropical, mountainous islands of East and Southeast Asia have a disproportionate effect on the dissolved and particulate load delivered to the world oceans, bedrock geology in such river drainage basins disproportionately affect ocean chemistry.
Morlet wavelet analysis of tropical convection over space and time: Study of poleward propagations of Intertropical Convergence Zone (ITCZ)
Authors: Piyush Shanker A. , Nanjundiah Ravi S.
Published: January 2004

A methodology to use continuous Morlet wavelet transform over space and time has been developed. By means of this method, the power spectra in 4‐dimensional space (viz. space, the spatial‐scale, time and the temporal‐scale) can been estimated. This is applied to study the spatial and temporal scales associated with the poleward propagations of the ITCZ (InterTropical Convergence Zone) over the Indian and West Pacific longitudes. The method has an added advantage that we can obtain the predominant spatial scales over a particular region, the temporal scales associated with them and their time of occurrence. We find that poleward propagations of ITCZ have a predominant spatial scale of about 30°. However the predominant temporal scale varies from year to year. Other regions which do not have significant poleward propagations do not show these (spatial and temporal) characteristics.
Impact of air pollution on wet deposition of mineral dust aerosols
Authors: Fan Song‐Miao , Horowitz Larry W. , Levy Hiram , Moxim Walter J.
Published: January 2004

Mineral dust aerosols originating from arid regions are simulated in an atmospheric global chemical transport model. Based on model results and observations of dust concentration, we hypothesize that air pollution increases the scavenging of dust by producing high levels of readily soluble materials on the dust surface, which makes dust aerosols effective cloud condensation nuclei (CCN). This implies that air pollution could have caused an increase of dust deposition to the coastal oceans of East Asia and a decrease by as much as 50% in the eastern North Pacific.
Deformation and in situ stress in the Nankai Accretionary Prism from resistivity‐at‐bit images, ODP Leg 196
Authors: McNeill L. C. , Ienaga M. , Tobin H. , Saito S. , Goldberg D. , Moore J. C. , Mikada H.
Published: January 2004

Borehole resistivity images from ODP Leg 196 allow rapid and complete qualitative assessment of deformation within the toe of the Nankai prism, Japan. Borehole breakouts were common within the prism but prominent in the trench‐wedge unit around the frontal thrust, suggesting reduced sediment strength. Breakouts indicate consistent σ2 orientations (∼050°), compatible with northwesterly convergence. Deformation is dominated by discrete zones, including the frontal thrust and décollement zone. Prism fractures trend ∼NE–SW, consistent with convergence. The décollement shows minimal deformation and the dominant structural trend is ∼N–S. Prism deformation zones are characterized by high resistivity (compaction), whereas the décollement is apparently dilated, both with conductive fractures. Distribution of fracture orientations varies between log units confirming lithologic and rheologic influence. Pore pressure is elevated within the décollement and the misalignment of conductive fractures may reduce permeability.
An isotopic model for basal freeze‐on associated with subglacial upward flow of pore water
Authors: Souchez R. , Samyn D. , Lorrain R. , Pattyn F. , Fitzsimons S.
Published: January 2004

Subglacial freezing in polar glaciers can have a significant dynamical effect. Recent studies have shown that freezing of pore water flowing upward through subglacial fine‐grained sediments at the freezing interface and progression of this freezing front downward are responsible for fast ice flow stoppage in ice streams. The upward pore water flow leads to the formation of debris‐bearing basal ice layers. A model for stable isotope composition, both in δD and δ18O, is developed for predicting the isotopic composition of the ice segregated by such a mechanism. The development of this isotopic model for water films present along the grains of the subglacial sediment predicts the absence of apparent fractionation for the ice formed. This prediction is tested against two East Antarctic outlet glaciers by studying the δD‐δ18O relationships in the basal ice layers of these glaciers.
Conjugate comparison of Super Dual Auroral Radar Network and Cluster electron drift instrument measurements of E × B plasma drift
Authors: Baker J. B. H. , Greenwald R. A. , Ruohoniemi J. M. , Förster M. , Paschmann G. , Donovan E. F. , Tsyganenko N. A. , Quinn J. M. , Balogh A.
Published: January 2004

Much of our current understanding of magnetospheric electrodynamics is based on the assumption that magnetic field lines often behave as electrostatic equipotentials. This assumption has allowed hemispheric patterns of ionospheric convection to be interpreted in terms of the large‐scale circulation of plasma in the magnetosphere. However, the extent to which the equipotential field‐line assumption is justified for different regions of the magnetosphere has not been adequately explored, largely because of the sparseness of magnetospheric measurements. In this paper, a mathematical formalism is developed that allows conjugate magnetospheric and ionospheric measurements to be compared with each other using a model magnetic field. The technique is demonstrated during an event interval in which Super Dual Auroral Radar Network measurements of ionospheric plasma drift are mapped to the magnetosphere using the Tsyganenko T01 magnetic field model and compared with conjugate measurements from the Cluster spacecraft electron drift instrument. The degree of consistency between the conjugate measurements is discussed in terms of (1) the accuracy of the magnetic field model, (2) the validity of the assumption of equipotential magnetic field lines, and (3) the presence of inductive electric fields in the magnetosphere. It is also shown how conjugate plasma drift measurements can be used to identify small inaccuracies in the location of ionospheric foot points specified by the magnetic model.
Middle and upper thermospheric odd nitrogen: 1. A new analysis of rocket data
Authors: Siskind David E. , Picone J. M. , Stevens M. H. , Minschwaner K.
Published: January 2004

We evaluate the NRLMSISE‐00 model for calculations of odd nitrogen (NO, N(4S)) in the middle to upper thermosphere (z = 140–250 km). NRLMSISE‐00 incorporates new data on O2 that improves the agreement between odd nitrogen models and data significantly. In particular, the photochemical calculation that uses NRLMSISE‐00 predicts a NO solar cycle variation that is significantly less than previous calculations and that agrees well with the NO observations. This agreement is consistent with the inference from FUV solar occultation data that the O2 abundance above 140 km varies weakly with solar activity and that the O2 vertical profile at solar maximum is sensitive to other factors besides molecular diffusion. Residual discrepancies remain with the comparison of calculated to observed N(4S), which may be due to a combination of theoretical deficiencies and uncertainties in the observations.
Kinetic and space charge control of current flow and voltage drops along magnetic flux tubes: 2. Space charge effects
Authors: Boström Rolf
Published: January 2004

The distribution of current‐driven electrostatic potentials along auroral magnetospheric flux tubes is studied analytically, based on the principles of quasi‐neutrality and kinetic orbital motion of electrons and ions governed by inertia, electric forces, and magnetic mirror forces. When certain particle accessibility conditions are fulfilled, the kinetics determines the electron and ion number densities as unique functions of position along the flux tube and local potential. These functions are used to define potential profiles for which electron and ion number densities everywhere match, or alternatively positions where potential jumps (double layers) may occur. Magnetospheric and ionospheric particle sources in the form of Maxwellians with loss cones depending on the total voltage drop are considered, as well as trapped particles. The potential profile generally comprises a potential jump that accounts for a sizeable fraction of the total voltage drop (only by assuming unrealistic velocity distributions of the magnetospheric electron source can solutions without a jump be found). The jump may typically occur around an altitude of 1 RE, an altitude that increases with density of the ionospheric source and that decreases with increasing density of trapped, secondary, and backscattered particles and total voltage drop along the flux tube. Below the potential jump, only small potential variations occur. Above the potential jump, the potential falls off gradually, asymptotically linear in magnetic field intensity. Only a small percentage of the potential drop occurs above an altitude of a few RE, but the weak field extending to higher altitudes is essential for quasi‐neutrality and for the current‐voltage relationship (discussed in a previous paper). Above the potential jump, the number density of particles is reduced as compared to regions without current flow and potential drops. Depending on the density of the ionospheric source, solutions are possible for total potential drops much larger than the temperature of the magnetospheric electron source. While full accessibility for the mirroring electrons tends to be locally violated, accessibility for all particles within the source cone is fulfilled in these solutions, so the current‐voltage relationship does not depend on the shape of the potential profile. Some comments are also made on transient conditions when there is no time for transport of neutralizing ions from the ionosphere.
PandSwave velocity andVP/VSin the wake of the Yellowstone hot spot
Authors: Schutt Derek L. , Humphreys Eugene D.
Published: January 2004

SeismicVP,VS, andVP/VSstructure is imaged across the Yellowstone hot spot swell, including the hot spot track where magmatism occurred at the eastern Snake River Plain ∼6–10 m.y. B.P. Data are teleseismicPandStravel time delays that have been corrected for the well‐understood upper mantle anisotropy and crustal structure. Amplitude variations in the imaged structures are 6.2%, 11.2%, and 8% forVP,VS, andVP/VS, respectively. The dominant structure is a zone which extends beneath the Snake River Plain to a depth of ∼190 km that is high inVP/VSand low inVPandVS. The physical state of the upper mantle is inferred by assuming isostasy, using the volume of melt segregated from the mantle that is inferred from estimates of magma addition to the crust, and using relations that scale changes in temperature, partial melt fraction and composition to density. Specifically, we infer that the low‐velocity mantle beneath the Snake River Plain is partially molten up to 1.0%, and the high‐velocity Yellowstone swell mantle away from the Snake River Plain is ∼80° K cooler and ∼5% depleted in basaltic component. The imaged large seismic velocity variations occur under near isothermal conditions.
North Brazil Current retroflection and transports
Authors: Garzoli Silvia L. , Ffield Amy , Johns William E. , Yao Qi
Published: January 2004

A subset of data collected as a part of a larger program, the North Brazil Current Rings (NBCR) Experiment, is analyzed to study the variability of the transport of the North Brazil Current (NBC) and its relation with the shedding of rings. It is concluded that there is a direct relation between the latitude of penetration, the number of rings shed, and the intensity of the NBC. The data set consists of dynamic height time series derived from three inverted echo sounders and a shallow pressure gauge deployed along a section perpendicular to the South American coast between the continent and 7°N, and between 48° and 45°W. Velocity and hydrographic data collected during the NBCR cruises are also analyzed and used to validate the results. The 15‐month mean transport of the NBC is 16 ± 2 Sv. The 18‐month mean of the retroflected southeastward flow is 22 ± 2 Sv. Both flows display considerable variability. The retroflected southeast flow reaches its maximum value during September 1999, near the time when the climatological North Equatorial Countercurrent (NECC) reaches its maximum strength and it is minimum when the climatological NECC reverses or is not present in the basin. The mean difference between the NBC flow and the retroflected flow during August–December 1999 when the NECC is fully established is −7 Sv. The excess in the retroflected flow is due to North Atlantic water joining the retroflected flow from the South Atlantic. The combination of both flows constitutes the NECC.
Tidally modulated occurrence of megaripples in a saturated surf zone
Authors: Clarke L. B. , Werner B. T.
Published: January 2004

An abstracted model for saturated surf zone megaripple occurrence, based on the hypothesis that megaripples form and persist unless flow conditions change too rapidly or the bed passes through the swash zone, correctly predicts the bed state (presence or absence of megaripples) for 73% of measurements over 1 year at Scripps Beach, more than seven standard deviations above the agreement between a random model and the measurements. Transitions between bed states are predicted within 1.5 hours for 54% of measurements, compared with 6% agreement for a random model. The model is forced with a record of water depth over the beach, H (from offshore tide measurements and inferred changes in bed elevation), assuming that changes in flow conditions and depth are determined by tide level alone in a saturated surf zone. Model parameter values are estimated independent of model results: megaripple formation time, T = 2.5 hours; maximum RMS depth change over time T, ΔHRMS* = 0.1 m; and minimum depth (averaged over time T) below which megaripples are smoothed, Hsw = 0.3 m. Allowing model parameters to vary increases agreement between measurements and model predictions to a maximum 82% for parameter values T = 3 hours, ΔHRMS* = 0.05 m, and Hsw = 0.1 m. Neither bed state nor bed state transitions are correlated with offshore wave conditions.
Retrievals of thin cloud optical depth from a multifilter rotating shadowband radiometer
Authors: Min Qilong , Joseph Everette , Duan Minzheng
Published: January 2004

A method is developed for accurate retrieval of thin cloud optical depth from measurements of a multifilter rotating shadowband radiometer (MFRSR). A key feature of this technique is correction of strong forward scattering of solar radiation into the instrument's field of view, which causes underestimation of retrieved cloud optical depth. To develop the correction method, measurements from the MFRSR under various atmospheric conditions are simulated by using a modified DISORT code that can accurately compute radiative intensity for strong forward scattering by thin clouds. These simulations are used to develop a polynomial fitting technique that corrects forward scattering into direct beam component. The correction is then applied to real MFRSR measurements. First, temporal and spectral variations in direct beam observations are used to discriminate between aerosol and thin cloud conditions. The true thin cloud optical depth, then, is inferred by removing background aerosol optical depth and by applying the polynomial fitting technique to correct the forward scattering contribution. An analysis of uncertainties associated with this method is also conducted and the results show that the retrievals are accurate to better than 5% or 0.05 when optical depth is less than 1.
Cenozoic vertical motions of the Catalan Coastal Ranges (NE Spain): The role of tectonics, isostasy, and surface transport
Authors: Gaspar‐Escribano J. M. , Garcia‐Castellanos D. , Roca E. , Cloetingh S.
Published: January 2004

We analyze the Cenozoic topographic evolution of the Catalan Coastal Ranges (NE Spain) and the role of fault activity, erosion, sedimentation, and isostasy in controlling uplift and subsidence. A forward numerical model constrained by an extensive geological and geophysical data set is used to examine the temporal and spatial record of Cenozoic vertical motions. We show that the effect of isostasy, erosion, and sedimentation is as important as the contribution of fault deformation to the topography of the Catalan Coastal Ranges. The model predicts that Paleogene topography generation by thrusting was compensated by erosion (up to 1.3 km) and isostatic subsidence (up to 1.2 km), resulting in a 1.2–1.9 km high mountain range by the end of compression (29 Ma). During the Neogene, strong tectonic subsidence related to normal faulting and the consequent flexural uplift (of 0.7–1.2 km), surface erosion (as much as 1.6–2.3 km), and sedimentation (up to 4.5 km) led to the present landscape configuration. Extension rates along the Barcelona fault controlled flexural uplift and, in combination with erosion and sedimentation processes, led to the migration of the topographic maximum of the Prelitoral Range toward the easternmost Ebro Basin.
Water cycling in a Bornean tropical rain forest under current and projected precipitation scenarios
Authors: Kumagai Tomo`omi , Katul Gabriel G. , Saitoh Taku M. , Sato Yoshinobu , Manfroi Odair J. , Morooka Toshiyuki , Ichie Tomoaki , Kuraji Koichiro , Suzuki Masakazu , Porporato Amilcare
Published: January 2004

Southeastern Asian tropical rain forests are among the most important biomes in terms of annual productivity and water cycling. How their hydrologic budgets are altered by projected shifts in precipitation is examined using a combination of field measurements, global climate model (GCM) simulation output, and a simplified hydrologic model. The simplified hydrologic model is developed with its primary forcing term being rainfall statistics. A main novelty in this analysis is that the effects of increased (or decreased) precipitation on increased (or decreased) cloud cover and hence evapotranspiration is explicitly considered. The model is validated against field measurements conducted in a tropical rain forest in Sarawak, Malaysia. It is demonstrated that the model reproduces the probability density function of soil moisture content (s), transpiration (Tr), interception (Ic), and leakage loss (Q). On the basis of this model and projected shifts in precipitation statistics by GCM the probability distribution of Ic, Q and, to a lesser extent, s varied appreciably at seasonal timescales. The probability distribution of Tr was least impacted by projected shifts in precipitation.
Dual homogenization of immiscible steady two‐phase flows in random porous media
Authors: Fadili Ali , Ababou Rachid
Published: January 2004

We develop a dual conductivity‐resistivity homogenization for immiscible steady two‐phase flow in heterogeneous, spatially correlated, random porous media. The objective is to obtain macroscale equations for an equivalent homogeneous medium. We assume that the flow is governed locally by the generalized Darcy equations. Two formulations are developed, one in terms of capillary pressure pc and the other in terms of saturation s. In each case the perturbation approach is used to express average and fluctuation equations, and the closure problems are solved using the Wiener‐Kinchine spectral theory. The macroscale permeability Kea and resistivity Rea tensors are determined for each fluid a, which also yield the relative permeabilities. These dual results provide a physically consistent correction of the perturbation‐based tensors. The corrected macroscale tensors are then always positive, symmetric, and reciprocal to each other. We also develop, similarly, the homogenization of the capillary pressure curve pc(x, θ) and of its reciprocal θ(x, pc), where θ is the wetting fluid content. Finally, these general analytical results are applied to the special case where 〈∇pc〉 ≈ 0 and/or 〈∇θ〉 ≈ 0, which can be interpreted as a mean capillary equilibrium.
The use of non‐prescribed medication in the first 3 months of life in rural South Africa
Authors: Bland Ruth M. , Rollins Nigel C. , Broeck Jan Van den , Coovadia Hoosen M. ,   Child Health Group
Published: January 2004

Objective  This paper describes the use of non‐prescribed medications given to a cohort of infants in the first 3 months of life in a rural South African district, and discusses some of the implications for primary health care.

Methods  As part of an ongoing study on breastfeeding, a cohort of 110 infants were visited at home at 6 and 12 weeks of age. Any medications given to the infant since the last visit, the reasons for their administration, and any visits made to traditional healers were recorded via a semi‐structured questionnaire. Determinants of administration of non‐prescribed medication were analysed, including maternal age, education, infant gender and socio‐economic factors.

Results  A total of 107 (97%) infants received non‐prescribed medications in the first 3 months of life: 98 (89%) rectally and 64 (58%) orally. The most common enema contained traditional Zulu medicine made from herbs, given more than once weekly, usually for perceived constipation; the most common oral medication was gripe water, given once daily, mainly for ‘colic’ or ‘wind’. Twenty‐nine (26%) mothers had consulted a traditional healer, most commonly because of concerns about a capillary naevus, thought to cause pain. Mothers with a ‘clean’ water supply were more likely to give non‐prescribed oral medications than those without (OR = 2.7 and P = 0.0223), whilst those who had no education were less likely to administer them than those who had completed school (OR = 0.19 and P = 0.0326).

Conclusions  Non‐prescribed medications are given almost universally to young infants in our area, irrespective of socio‐economic class. Health professionals need to be aware of the extent of, and reasons for, administration of non‐prescribed medications to young infants, so that effective health messages can be targeted at mothers and caregivers.
Epilepsy prevalence in rural Zambia: a door‐to‐door survey
Authors: Birbeck Gretchen L. , Kalichi Ellie M. N.
Published: January 2004

Objectives To identify people with epilepsy (PWE) in our Zambian catchment area of 55 000 people.

Methods A nine‐item, previously validated screening instrument for detecting epilepsy in developing countries was forward‐and‐back translated into Chitonga. Early piloting indicated poor specificity among children, so three questions were added. Local census data were used to estimate the population at risk. Community health workers conducted screening interviews with household heads. All positive screens were referred for physician assessment. A blinded neurologist assessed a randomly selected subset (100 positives, 50 negatives) to determine screening instrument characteristics.

Results We identified 799 people with possible epilepsy (unadjusted prevalence 14.5/1000). The adapted instrument exhibited 86% specificity (adjusted prevalence 12.5/1000). False positives occurred primarily among children who had experienced multiple malaria‐associated seizures. Age‐specific rates were highest for children aged 5–15 years (26.2/1000) and for people over 65 years (15.9/1000). Males were disproportionately represented (55.8%vs.44.2%,P < 0.05), although this trend reversed after childbearing age.

Conclusion Even using a relatively conservative definition, we identified almost 700 PWE. Use of the recommended epidemiological definitions would likely have yielded higher prevalence rates. The age‐specific prevalence did not follow patterns described where neurocysticercosis is the commonest cause of epilepsy. Trends in age‐ and gender‐specific prevalence may offer a clue to the aetiology of epilepsy in this region.
The cost and cost‐effectiveness of malaria vector control by residual insecticide house‐spraying in southern Mozambique: a rural and urban analysis
Authors: Conteh Lesong , Sharp Brian L , Streat Elisebeth , Barreto Avertino , Konar Sundragasen
Published: January 2004

Objectives  To compare two separately funded, but operationally similar, residual household‐spraying (RHS) initiatives; one rural and one peri‐urban in southern Mozambique.

Methods  The rural programme is a regional project involving the participation and co‐ordination of organizations across three countries in southern Africa and is focussed on control in an area in Mozambique of 7552 km2. The second programme focusses on spraying a peri‐urban community within a 10‐km radius around MOZAL, an aluminium smelter plant of area 410 km2. An ingredients approach was used to derive unit costs for both the rural and peri‐urban spraying programmes using detail retrospective cost data and effectiveness indicators.

Results  The economic cost per person covered per year using Carbamates for indoor residual spraying (IRS) in the rural area, excluding the costs of project management and monitoring and surveillance was $3.48 and in the peri‐urban area, $2.16. The financial costs per person covered in the rural area and peri‐urban area per year were $3.86 and $2.41, respectively. The economic costs per person covered were respectively increased by 39% and 31% when project management and monitoring and surveillance were included. The main driving forces behind the costs of delivering RHS are twofold: the population covered and insecticide used. Computed economic and financial costs are presented for all four insecticide families available for use in RHS.

Conclusions  The results from both these initiatives, especially the rural area, should be interpreted as conservative cost estimates as they exclude the additional health gains that the newly introduced programmes have had on malaria rates in the neighbouring areas of South Africa and Swaziland. Both these initiatives show that introducing an IRS programme can deliver a reduction in malaria‐related suffering providing financial support, political will, collaborative management and training and community involvement are in place.
In situ measured elimination of Vibrio cholerae from brackish water
Authors: Pérez María Elena Martínez , Macek Miroslav , Galván María Teresa Castro
Published: January 2004

In situ elimination of fluorescently labelled Vibrio cholerae (FLB) was measured in two saline water bodies in Mexico: in a brackish water lagoon, Mecoacán (Gulf of Mexico; State of Tabasco) and an athalassohaline lake, Alchichica (State of Puebla). Disappearance rates of fluorescently labelled V. cholera O1 showed that they were eliminated from the environment at an average rate of 32% and 63 %/day, respectively (based on the bacterial standing stocks). The indirect immunofluorescence method confirmed the presence of V. cholerae O1 in the lagoon. However, the elimination of FLB was not directly related either to the presence or absence of the bacterium in the water body or to the phytoplankton concentration.
Measuring schistosomiasis case management of the health services in Ghana and Mali
Authors: van der Werf Marieke J. , de Vlas Sake J. , Landouré Aly , Bosompem Kwabena M. , Habbema J. D. F.
Published: January 2004

The World Health Organization recommends passive case detection by regular health services as a minimum strategy for schistosomiasis morbidity control. To evaluate preparedness of the health systems in Ghana and Mali, we presented four clinical scenarios, two with blood in urine (main early symptom of Schistosoma haematobium) and two with (bloody) diarrhoea (main early symptom of S. mansoni), to health workers. We requested the health personnel for an initial diagnosis and case management strategy without providing information about our primary interest in schistosomiasis. The information was used to determine the chance that a person reporting with symptoms that might have been caused by schistosomiasis would receive praziquantel. All selected health workers participated. Their initial diagnosis was frequently S. haematobium for both scenarios with blood in urine. For the two scenarios with (bloody) diarrhoea, only few mentioned S. mansoni. At health centre level, case management in Mali mainly consisted of direct prescription of medication, whereas in Ghana health workers often referred to a hospital or requested a diagnostic test. The ultimate probability of prescribing praziquantel was relatively high for the scenarios with blood in urine, 60% in Ghana and 75% in Mali, but very low for both scenarios with (bloody) diarrhoea (<20%). Of those health care facilities that would prescribe praziquantel, 60% (Ghana) and 80% (Mali) had it in stock. In conclusion, the clinical scenario study showed that patients reporting with blood in urine will be treated with praziquantel at approximately half of the health care facilities, whereas of those presenting with (bloody) diarrhoea only few would receive treatment with praziquantel. Considering these facts, it is questionable if passive case detection is a sufficient basis for effective schistosomiasis morbidity control, especially for S. mansoni infection.
Megazol combined with suramin improves a new diagnosis index of the early meningo‐encephalitic phase of experimental African trypanosomiasis
Authors: Darsaud Annabelle , Chevrier Céline , Bourdon Lionel , Dumas Michel , Buguet Alain , Bouteille Bernard
Published: January 2004

In human African trypanosomiasis (HAT), the parasites invade the central nervous system (CNS), leading to the development of meningo‐encephalitis and an irreversible demyelinating process, which kills the patient unless specific treatment is undertaken. Among the experimental trypanocides, the nitroimidazole derivative megazol alone at optimal doses does not cure late‐stage disease tested in mouse models, however the combination of suramin and megazol is able to cure infected mice without CNS involvement. We recently developed an experimental model of HAT with a sharp decrease in both the food intake and the body weight which may constitute an effective index of the early meningo‐encephalitic phase. Using this model, we tested this hypothesis by the exclusive effectiveness of a megazol and suramin combination treatment to eliminate CNS trypanosomes. Sprague–Dawley rats were infected with Trypanosoma brucei brucei AnTat 1.1E. Food intake and body weight were measured daily from the day of infection to death. Haematocrite was measured twice a week. Treatment consisted of 20 mg suramin per kg body weight administered intraperitoneally (i.p.) alone, or three daily doses (80 mg/kg) of megazol given per os, or suramin (20 mg/kg, i.p.) followed 24 h later by three daily doses (80 mg/kg) of megazol given per os. Treatment was followed by an increase in daily body weight and food intake similar to those of the control animals, 2 weeks after treatment. The anaemia developed after infection is also cleared as shown by the haematocrite measurements. The rats treated with megazol alone died about 29 days after treatment and those treated with suramin, after about 26 days. Seven months later, no signs of relapse were seen in 10 of 12 rats treated with the therapeutic combination, indicating that this chemotherapy regimen was curative. The results support our previous finding, i.e. the decrease in body weight may constitute a diagnosis index of the early meningo‐encephalitic phase.