bluuebunny/crossref_metadata_2025 huggingface dataset:
Conceptual, methodological, and statistical challenges in brain imaging studies of developmentally based psychopathologies
Authors: PETERSON BRADLEY S.
Published: August 2003

Brain imaging studies in developmentally based psychopathologies most often use magnetic resonance imaging (MRI) to study regional volumes, task-related activity, neurometabolite concentrations, or the paths of fiber tracts within the brain. Methodological challenges for the use of MRI in studying these disorders include understanding the ultrastructural correlates of brain structure and function that are below the limits of resolution of this imaging modality and developing better methods for approximating the anatomical boundaries of the cytoarchitectonic units that are defined by those ultrastructural characteristics. Conceptual challenges include distinguishing findings that represent pathophysiologically central causes from compensatory and epiphenomenal effects, a difficulty that stems directly from the inherently correlational nature of imaging data. The promise of functional imaging studies must capitalize on the specificity of the cognitive and behavioral probes that are used to illuminate core features of the pathophysiology of developmental disorders, while recognizing the assumptions and limitations of the subtraction paradigms that are used to isolate the brain functions of interest. Statistical challenges include incorporating adequate statistical models for scaling effects within the brain, as well as modeling important demographic correlates that contribute to the substantial interindividual variability inherent in most imaging data. Statistical analyses need to consider the substantial intercorrelation of measures across the brain and the importance of correcting for multiple statistical comparisons, as well as the need for improved methods for brain warping and for assessing effective connectivity in functional imaging studies.
BACKCOUNTRY POTS
Authors: Kowalewski Stephen A.
Published: August 2003

In Mesoamerica, the pottery made and used in regions peripheral to highly developed core areas is relatively plain; it is not standardized; and it has a narrow range of forms. Such pottery does not represent cultural “backwardness” or a tradition separate from that of core areas. Instead, backcountry pottery is explained by rational economic behavior of producers and consumers whose choices are constrained by location at the distant ends of dendritic or solar market systems. The literature on peasant markets provides a basis for distinguishing core versus peripheral economic behavior. Expectations for peripheral pottery are generated from this and from archaeological studies of pottery specialization. The pre-Hispanic pottery form Peñoles, a mountainous periphery of the Valley of Oaxaca, exhibits the expected characteristics. These results are limited by small sample size; more detailed studies should find a macroregional economy that is more variegated than that portrayed by the core–periphery dichotomy.
Cognitive asymmetries associated with apolipoprotein E genotype
in patients with Alzheimer's disease
Authors: FINTON MICHAEL J. , LUCAS JOHN A. , RIPPETH JULIE D. , BOHAC DARYL L. , SMITH GLENN E. , IVNIK ROBERT J. , PETERSEN RONALD C. , GRAFF-RADFORD NEILL R.
Published: August 2003

The relationship between apolipoprotein E (apoE) genotype and
cognitive performance was examined in 200 patients with probable
Alzheimer's disease (AD). Differences between composite
measures of verbal and nonverbal functioning were used to define
asymmetric patterns of cognition. Patients who were homozygous
for apoE ε4 demonstrated relatively worse nonverbal as compared
to verbal cognitive ability. In contrast, participants who were
heterozygous for apoE ε4 or who possessed no ε4 allele
demonstrated relatively equivalent verbal and nonverbal cognitive
abilities. Although age and dementia severity also contributed
to these patterns, apoE genotype appears to have a significant
unique contribution to cognitive performance in these individuals.
The ε4 allele may thus be associated with a specific
neurocognitive phenotype among patients with AD, with the overall
pattern of cognitive asymmetry dependent upon ε4 dose.
(JINS, 2003, 9, 751–759.)
Automated Three-Dimensional Tracing of Neurons in Confocal and
Brightfield Images
Authors: He Wenyun , Hamilton Thomas A. , Cohen Andrew R. , Holmes Timothy J. , Pace Christopher , Szarowski Donald H. , Turner James N. , Roysam Badrinath
Published: August 2003

Automated three-dimensional (3-D) image analysis methods are
presented for tracing of dye-injected neurons imaged by fluorescence
confocal microscopy and HRP-stained neurons imaged by transmitted-light
brightfield microscopy. An improved algorithm for adaptive 3-D
skeletonization of noisy images enables the tracing. This algorithm
operates by performing connectivity testing over large N × N
× N voxel neighborhoods exploiting the sparseness of the
structures of interest, robust surface detection that improves upon
classical vacant neighbor schemes, improved handling of process ends or
tips based on shape collapse prevention, and thickness-adaptive
thinning. The confocal image stacks were skeletonized directly. The
brightfield stacks required 3-D deconvolution. The results of
skeletonization were analyzed to extract a graph representation.
Topological and metric analyses can be carried out using this
representation. A semiautomatic method was developed for reconnection
of dendritic fragments that are disconnected due to insufficient dye
penetration, an imaging deficiency, or skeletonization errors.
Rethinking the mandatory/discretionary legislation distinction in WTO jurisprudence
Authors: SIM KWAN KIAT
Published: August 2003

A WTO member state whose legislation is alleged to have infringed WTO rules often invokes the mandatory/discretionary distinction, which states that only legislation mandating actions inconsistent with WTO rules can be challenged; legislation merely granting the discretion to do so cannot be challenged. This article highlights the treatment of this distinction by the Panel and the Appellate Body in recent decisions, in particular, United States–Section 211 Omnibus Appropriation Act of 1998 (‘US–Section 211’), and United States – Countervailing Measures Concerning Certain Products from the European Communities (‘US–Countervailing Measures’). The reasoning and analysis in these cases extended beyond the characterization of the form of the legislation to an examination of the effect of the legislation, and may portend a reconsideration of the mandatory/discretionary distinction and a reformulation of the test for reviewing a state's legislation for WTO-compliance.
WTO dispute settlement: the politics of procedure in Appellate Body rulings
Authors: SMITH JAMES McCALL
Published: August 2003

This paper investigates how the Appellate Body has coped with its precarious position in the WTO. It must rely on decentralized enforcement of its rulings; interpret new regulatory rules that are complex and contested; hear and resolve all disputes; and deal with governments litigating issues on which they fail to achieve consensus in negotiations. In this setting, the Appellate Body cannot easily promote both its reputation for coherence and its record of compliance – the dual underpinnings of its perceived authority. In response, it has crafted an activist and politically sophisticated approach to several procedural issues. Despite underlying disagreements among member states, the Appellate Body has seized chances to enact procedural reforms that encourage consensus rulings, improve its access to information, and expand its judicial discretion. While no guarantee of success, these procedures should enhance the Appellate Body's ability to reduce the intrinsic political risks of WTO adjudication.
Evolution and dynamics of equatorial plasma bubbles: Relationships to ExB drift, postsunset total electron content enhancements, and equatorial electrojet strength
Authors: Dabas R. S. , Singh Lakha , Lakshmi D. R. , Subramanyam P. , Chopra P. , Garg S. C.
Published: August 2003

The growth in altitude/latitude of equatorial plasma bubbles was monitored, using simultaneous recordings of VHF scintillations at five locations situated between 3° and 23°N magnetic latitudes along a common meridian (84°E) during February 1980. The onsets of postsunset scintillation were mostly abrupt in character, and their occurrence at higher latitudes was conditional on their prior appearance at lower latitudes, indicating a causal link to irregularities associated with rising equatorial plasma bubbles. The day‐to‐day occurrence and the latitudinal, and effectively altitudinal, growths are examined in relation to the prereversal enhancement in h′F during sunset hours and its rate of rise, the onset of a postsunset secondary maximum (PSSM) in ionospheric electron content (IEC), and equatorial electrojet strength (EEJ) variations. It is observed that the bubble and associated irregularities, after its onset over the magnetic equator, reached the highest altitudes/latitudes only on those days when a prior PSSM in IEC is observed there in addition to high values of h′F, dh′F/dt and bubble rise velocity; otherwise it will be confined to near equatorial latitudes only. Also, the equatorial h′F, dh′F/dt, magnitude of PSSM and intensity of 4 GHz scintillations at low latitude are all showing positive correlation with daytime EEJ strength variations. It is concluded that, after the initial development of a bubble, the ExB drift and the PSSM play an important role in the subsequent growth and evolution, and EEJ is a useful parameter for the prediction of the development.
Organic dye effects on dense nonaqueous phase liquids (DNAPL) entry pressure in water saturated porous media
Authors: Tuck David M. , Iversen Gary M. , Pirkle William A.
Published: August 2003

Visualization of DNAPL behavior in porous media is generally accomplished using three oil‐soluble dyes: SudanIII, SudanIV, or Oil‐Red‐O. The dyes are generally assumed to not influence that behavior. That assumption was tested in the SudanIV‐tetrachloroethene (PCE)‐water‐glass system. The dye significantly changes surface chemistry as a function of concentration and interface age. PCE mobility increases through lower adhesion tension. Increased mobility was demonstrated using entry pressure experiments for undyed and dyed PCE entering water‐saturated glass bead media. Statistically significant entry pressure reduction occurred at a dye concentration of 0.0411 g/L, approximately two orders of magnitude lower than typically used. Dye type, concentration, and surface chemistry are therefore important experimental parameters which should be reported in multiphase flow studies. Dye use increases DNAPL surface chemical complexity, making them reasonable analogs for field DNAPLs. PCE entry pressure was strongly influenced by intrinsic permeability, providing experimental support for Bond number formulations which include permeability.
Control mechanisms for the oceanic distribution of silicon isotopes
Authors: Wischmeyer André G. , De La Rocha Christina L. , Maier‐Reimer Ernst , Wolf‐Gladrow Dieter A.
Published: August 2003

Marine diatoms take up silicic acid for the buildup of their opaline shells and discriminate against the heavier silicon isotope. For the first time, the overall oceanic distribution of silicon isotopes has been estimated by integration of the Hamburg Model of the Ocean Carbon Cycle, version 4 (HAMOCC4). It is shown that the relationship between the silicic acid concentration and its silicon isotope composition is not a simple Rayleigh distillation curve. Only the Southern Ocean and the equatorial Pacific show a clear functional dependency similar to the Rayleigh distillation curve. Model results can be used to predict opal silicon isotope compositions in the sediment and constrain the use of silicon isotopes as a proxy for silicic acid utilization. Owing to the structure of the Pacific current system, it might be valid to apply a relationship between surface silicic acid concentrations and the silicon isotope signal in the equatorial Pacific sediments.
Evaluation of spreading critical exponents from the spatiotemporal evolution of emission regions in the nighttime aurora
Authors: Uritsky Vadim M. , Klimas Alexander J. , Vassiliadis Dimitris
Published: August 2003

Recently, it has been found that the spatiotemporal evolution of auroral emission regions, as depicted by the ultraviolet imager (UVI) onboard the POLAR spacecraft, follows well‐defined power law statistical relations characteristic of complex systems near criticality [Uritsky et al., 2002b]. In this study, we continue our investigation of scaling features in the auroral emissions with emphasis on their dynamical characteristics. Based on an analysis of more than 6,700 emission events, we estimate the so‐called spreading critical exponents that govern the mean field evolution of localized perturbations in nonequilibrium systems with spatially extended degrees of freedom. We show that the auroral emissions display scale‐free spreading behavior that manifests itself through characteristic power‐law auroral emission area dynamics. The spreading exponents so obtained are consistent with scaling relations predicted for self‐organized criticality.
Plasma density enhancements associated with equatorial spread F: ROCSAT‐1 and DMSP observations
Authors: Le G. , Huang C.‐S. , Pfaff R. F. , Su S.‐Y. , Yeh H.‐C. , Heelis R. A. , Rich F. J. , Hairston M.
Published: August 2003

Large‐scale plasma density depletions are typically associated with equatorial spread F (ESF) plasma irregularities in the nightside F region, especially in the postsunset sector. Data gathered on the ROCSAT‐1 spacecraft reveal numerous cases of localized, discrete plasma density enhancements in the nightside low‐latitude region at ∼600 km altitude. In some cases, nearly simultaneous DMSP observations at ∼800 km reveal similar density enhancements in the same local time sector. These density enhancement structures occur in association with ESF plasma depletions, i.e., the density enhancements are observed in the same local time where ESF plasma depletions are also present simultaneously. Within these discrete structures, the plasma density may be enhanced by ∼2–3 times above the background density. The density enhancement regions have sharp, distinct edges with embedded irregularities that appear to have similar scale sizes and density fluctuation spectra as those typically found in plasma depletions. Examples studied here occur at local times about 3 hours after sunset near the equatorial anomaly region, ∼10° to 20° from the magnetic equator. The ion velocity data within the density enhancement regions show upward plasma drifts perpendicular to the magnetic field, similar to those within adjacent plasma depletion regions. The magnetic field‐aligned plasma flows are generally poleward within the density enhancement regions. The observations suggest that density enhancement structures are caused by the polarization electric field which is generated within the equatorial plasma depletions and then maps to the higher latitudes along the magnetic field lines.
Tephra layers in the Siple Dome and Taylor Dome ice cores, Antarctica: Sources and correlations
Authors: Dunbar Nelia W. , Zielinski Gregory A. , Voisins Daniel T.
Published: August 2003

Volcanic ash, or tephra layers, are found in the Taylor Dome, Siple Dome A, and Siple Dome B ice cores. Significant shard concentrations are found at a number of depths in all three cores. Electron and ion microprobe analyses indicate that the geochemical composition of most layers is basaltic, basanitic, or trachytic, and the geochemical signatures of the layers suggest derivation from the Pleiades volcanic center, Mt. Melbourne volcano, or small mafic centers, probably in the Royal Society Range area. Presence of tephra layers suggests an episode of previously unrecognized Antarctic volcanic activity between 1776 and 1805 A.D., from at least two volcanic centers. A strong geochemical correlation (D = 3.49 and 3.97 with a value of 4 considered identical) is observed between tephra layers at depth of 79.2 m in the Taylor Dome ice core, and layers between 97.2 and 97.7 m depth in the Siple B core. This correlation, and the highly accurate depth‐age scale of the Siple B core suggest that the age of this horizon in the Taylor Dome ice core presented by Steig et al. [1998a, 2000] should be revised downward, to the younger age of 675 ± 25 years before 1995. This revised chronology is consistent with vertical strain measurements presented by Hawley et al. [2003].
Distribution and formation of Okhotsk Sea Intermediate Water: An analysis of isopycnal climatological data
Authors: Itoh Motoyo , Ohshima Kay I. , Wakatsuchi Masaaki
Published: August 2003

In order to clarify the distribution and formation of Okhotsk Sea Intermediate Water (OSIW) an isopycnal climatological data set based on all of the available historical observations is developed and examined. The isopycnal maps clearly show that there are two direct ventilation sources for OSIW: Dense Shelf Water (DSW) with cold and fresh properties influenced by sea ice formation in the northwest shelf region and Forerunner of Soya Warm Current Water (FSCW), which has warm and saline properties originating in the Japan Sea. The cold and fresh water extends southward from the northwest shelf to the shelf slope off Sakhalin Island. It suggests that DSW is transported southward by the East Sakhalin Current. The DSW enters the Kuril Basin and mixes with FSCW and Western Subarctic Water (WSAW) originating from the North Pacific to form OSIW. The annual mean production rate of DSW estimated from the total volume of DSW over the shelf in spring and summer is 0.67 Sv (1 Sv = 106 m3/s). The annual mean volume transport of FSCW is estimated to be 0.08 Sv on the basis of its cross‐section area and the current speed. Assumption of isopycnal mixing yields a mixing ratio of 1:1:0.1 among DSW, WSAW, and FSCW to form OSIW. We estimate the annual production rate of OSIW to be 1.4 Sv; the corresponding OSIW's renewal time is 7 years. Continued assumption of isopycnal mixing yields a mixing ratio of 0.6:0.4 between WSAW and OSIW to form Oyashio Intermediate Water (OYIW).
Influence of submicron absorptive aerosol on Sea‐viewing Wide Field‐of‐view Sensor (SeaWiFS)‐derived marine reflectance during Aerosol Characterization Experiment (ACE)‐Asia
Authors: Li LiPing , Fukushima Hajime , Frouin Robert , Mitchell B. Greg , He Ming‐Xia , Uno Itsushi , Takamura Tamio , Ohta Sachio
Published: August 2003

Sea‐viewing Wide Field‐of‐view Sensor observation of the east Asian seas during the March–April 2001 Aerosol Characterization Experiment‐Asia shows large areas of underestimated or even negative water‐leaving radiance in the blue. To investigate the cause of the problem, three cloud‐free matchup stations around Japan were analyzed, where in situ measurements were made onboard R/V Ronald H. Brown at the time of satellite overpass. Using an optimization method, information on the possible composition of aerosols was obtained from sky radiance data collected onboard the ship. An iterative radiative transfer simulation was carried out in an attempt to reproduce the satellite‐measured top‐of‐atmosphere reflectance. The resulting water reflectance and aerosol optical thickness (AOT) agreed well with in situ measurements when the effect of submicron absorbing particles was considered in the radiative transfer simulation. The error in the retrieved water reflectance was much decreased, with average values of about 6% at 412 and 443 nm for the three stations. The effect of the Asian dust was also simulated in comparison with that of small absorptive aerosols. The underestimation could not be solely attributed to Asian dust. It was also found that at one of the stations, where the presence of dust aerosols was anticipated, an aerosol model mixed with both dust and soot improved the accuracy of the estimated AOT compared with the case of soot as the only absorptive aerosol (error of 13% at 865 nm instead of 44%). Submicron absorbing particles, in addition of the Asian dust, should be considered in the optical remote sensing of east Asian waters.
Statistics of Arctic cloud downwelling infrared emissivity
Authors: Neshyba Steven P , Rathke Carsten
Published: August 2003

Time series of optical depth of Arctic stratus clouds are investigated for scaling properties and biases with respect to a plane‐parallel model. The study is based on 3 years of infrared spectrometer and microwave radiometer measurements made at the Atmospheric Radiation Measurement North Slope of Alaska site. Power spectra of radiance and radiance emissivity are found to indicate scaling with a spectral coefficient on the order of 5/3 over 0.5–10 hours, consistent with the Kolmogorov‐Obukhov prediction [Kolmogorov, 1941] for three‐dimensional turbulence. Irradiance emissivities inferred from the data set, using an independent column approximation and 6‐hour time intervals, are further analyzed to find reduction factors for the same mean optical depth in a plane‐parallel representation. These factors are estimated to average 0.82 in March and 0.48 in September but with a high degree of variability: The most inhomogeneous quarters of these data sets exhibit reduction factors of 0.57 (March) and 0.20 (September). Observed reduction factors for radiance and irradiance are found to depend primarily on the ratio of mean optical depth to variance, a result consistent with exact results for a γ distribution of cloud thickness.
Measurements of OH and HO2 concentrations in the Southern Ocean marine boundary layer
Authors: Creasey D. J. , Evans G. E. , Heard D. E. , Lee J. D.
Published: August 2003

Field measurements of hydroxyl (OH) and hydroperoxy (HO2) radicals have been made in the remote Southern Ocean marine boundary layer at the Cape Grim Baseline Air Pollution Station in northwestern Tasmania. Measurements were made with a time resolution of 30 s over a period of 4 weeks during austral summer 1999 in the second Southern Ocean Photochemistry Experiment. Laser‐induced fluorescence at reduced pressure was used to measure [OH] with an average detection limit at noon of (1.4 ± 0.5) × 105 molecule cm−3 (1σ), for a 2.5 min integration period, and HO2 was measured following its conversion to OH via the addition of NO, with an average detection limit of (5.4 ± 1.7) × 105 molecule cm−3 (1σ). Air masses arriving at Cape Grim originated from the Australian continent, Tasmania, and Southern Ocean/Antarctic regions, the latter (“Baseline” air) characterized by extremely low [NO] allowing a study of the chemistry of the unperturbed background atmosphere. In Baseline air, daytime average maxima for OH and HO2 of 3.5 × 106 molecule cm−3 (0.14 parts per trillion by volume (pptv)) and 2 × 108 molecule cm−3 (8 pptv) were observed, and a very high correlation coefficient (r = 0.95) was observed between the OH concentration and the rate of OH production from ozone photolysis. A steady state expression for OH, assuming production only from ozone photolysis and loss only by reaction with CO and CH4, overestimates the observed daytime maximum concentration in Baseline air by 20%. The HO2 concentration was found to depend upon the square root of the rate of O3 photolysis, as expected at very low concentrations of NO.
Microphysics of atmospheric carbon dioxide uptake by a cloud droplet containing a solid nucleus
Authors: Chen Wei‐Hsin , Lu Jau‐Jang
Published: August 2003

Microphysics of atmospheric carbon dioxide absorption by a cloud aerosol containing a spherical solid nucleus at low Reynolds number (Reg = 1) is investigated through numerical simulation. Particular emphasis is placed on the impact of the solid particle on the solute transport process in the aerosol. Simulations indicate that carbon dioxide transported by internal circulation in a pure water droplet is significant. Therefore, during the absorption period the lowest CO2 concentration moves from the droplet center, through the centerline, and then toward the vortex center. When a solid nucleus with rs/rl = 0.5 exists in the droplet, the vortex strength is reduced markedly. Nevertheless, the role played by the internal circulation on mass transport is still obvious. This results in the lowest CO2 concentration being located at the front stagnation point of the nucleus as the exposure time is sufficiently long. Once the nucleus is large to a certain extent, such as rs/rl = 0.8, the internal flow retarded by the solid particle is more remarkable, whereby the radial diffusion becomes very important. Consequently, the entire mass transfer is characterized by one‐dimensional transport. The above investigations clearly reveal that the nature of the solute movement in the droplet is highly relevant to the nucleus size. As a whole, with increasing size of the solid particle, diffusional mass transfer progressively dominates convective mass transfer; however, it simultaneously increases the surface‐to‐volume ratio of the liquid phase. Because the importance of the ratio is beyond that of the diffusion, the absorption rate of the aerosol rises as the nucleus size increases.
Snow water equivalent interpolation for the Colorado River Basin from snow telemetry (SNOTEL) data
Authors: Fassnacht S. R. , Dressler K. A. , Bales R. C.
Published: August 2003

Inverse weighted distance and regression nonexact techniques were evaluated for interpolating methods snow water equivalent (SWE) across the entire Colorado River Basin of the western United States. A 1‐km spacing was used for the gridding of snow telemetry (SNOTEL) measurements for the years 1993, 1998, and 1999, which on average, represented higher than average, average, and lower than average snow years. Because of the terrain effects, the regression techniques (hypsometric elevation and multivariate physiographic parameter) were found to be superior to the weighted distance approaches (inverse distance weighting squared, and optimal power inverse distance weighting). A regression detrended inverse weighted distance method was developed for the hypsometric and multivariate techniques in order to preserve the point SNOTEL data. On the basis of root mean square error analysis and estimates of SWE volumes in different elevation zones for the entire basin and for subbasins the elevation detrended method with a point by point regression was found to be the most appropriate technique. Various search radii and anisotropies of the search ellipse were tested with the hypsometric method, producing only small difference in the root mean square error and SWE volumes.
Volume averaging for determining the effective dispersion tensor: Closure using periodic unit cells and comparison with ensemble averaging
Authors: Wood Brian D. , Cherblanc Fabien , Quintard Michel , Whitaker Stephen
Published: August 2003

In this work, we use the method of volume averaging to determine the effective dispersion tensor for a heterogeneous porous medium; closure for the averaged equation is obtained by solution of a concentration deviation equation over a periodic unit cell. Our purpose is to show how the method of volume averaging with closure can be rectified with the results obtained by other upscaling methods under particular conditions. Although this rectification is something that is generally believed to be true, there has been very little research that explores this issue explicitly. We show that under certain limiting (but mild) assumptions, the closure problem provides a Fourier series solution for the effective dispersion tensor. When second‐order spatial stationarity is imposed on the velocity field, the method yields a simple Fourier series that converges to an integral form in the limit as the period of the unit cell approaches infinity. This limiting result is identical to the quasi‐Fickian forms that have been developed previously via ensemble averaging by Deng et al. [1993] and recently by Fiori and Dagan [2000] except in the definition of the averaging operation. As a second objective we have conducted a numerical study to evaluate the influence of the size of the averaging volume on the effective dispersion tensor and its volume averaged statistics. This second objective is complimentary in many ways to recent research reported by Rubin et al. [1999] (via ensemble averaging) and by Wang and Kitanidis [1999] (via volume averaging) on the block‐averaged effective dispersion tensor. The variability of the effective dispersion tensor from realization to realization is assessed by computing the volume‐averaged effective dispersion tensor for an ensemble of finite fields with the same (ensemble) statistics. Ensembles were generated using three different sizes of unit cells. All three unit cell sizes yield similar results for the value of the mean effective dispersion tensor. However, the coefficient of variation depends strongly upon the size of the unit cell, and our results are consistent with those developed by Fiori [1998] from the ensemble averaging perspective. This implies that in applications the actual value of the effective dispersion tensor may be significantly different than expected on the basis of unconditioned hydraulic conductivity statistics, and this variation should be considered when applying macrodispersion to real‐world systems.
A comparison of modeled, remotely sensed, and measured snow water equivalent in the northern Great Plains
Authors: Mote Thomas L. , Grundstein Andrew J. , Leathers Daniel J. , Robinson David A.
Published: August 2003

Various methods are available to measure or estimate the quantity of water present in a snowpack. Historically, the National Weather Service has relied on direct measurements taken at first order and cooperative weather stations. Because of the great spatial variability in snow cover density, point measurements are often of limited utility in identifying snow water equivalent (SWE) values over a given area or watershed. Increasingly, remote sensing techniques and physical models have been used to supplement point measurements of SWE and to improve areal estimates of snow water equivalent. This paper compares daily first‐order SWE observations from five stations across the northern Great Plains with those estimated from passive microwave remotely sensed data and from an energy and mass balance model (SNTHERM). A commonly utilized SWE algorithm is applied to Special Sensor Microwave/Imager (SSM/I) data across the northern Great Plains during the 1990s. Various filtering algorithms are applied to eliminate those situations in which the SSM/I SWE algorithms are known to be ineffectual. Airborne gamma estimates are also included in the comparison but are limited to only a few observations a year. Although the modeled SWE is generally in good agreement with the observed SWE, there is a tendency for the SNTHERM model to underestimate SWE, but it is typically within the margin of error of the observations. The microwave SWE algorithm apparently overestimates SWE significantly late in the season, compared to in situ observations, likely a result of snow grain growth during snow metamorphism.
Spectral observations of transient features in the FUV Jovian polar aurora
Authors: Gérard J.‐C. , Gustin J. , Grodent D. , Clarke J. T. , Grard A.
Published: August 2003

Images of the Jovian FUV aurora show several morphologically and dynamically different regions. The main oval is usually fairly steady while the high‐latitude emission inside the oval can vary over timescales of <1 min. We describe time and spatially resolved spectral observations of the Jovian aurora made with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. Time‐tagged spectra have been used to determine variations of the amount of hydrocarbon absorption above the auroral source layer. Rapid brightenings are observed in the high‐latitude emission with typical lengths of 50–100 s. They generally are not correlated with enhancements of the main oval in the same longitude sector, indicating decoupled source regions in the magnetosphere. The location of the high‐latitude spots and their variability suggest that, unlike the main auroral oval, the polar cap brightenings are connected to short‐term variations of the solar wind parameters. Results from a two‐stream electron transport model are used to convert observed spectral color ratios into mean electron energies 〈E〉. Electron energies during these brightenings typically range from 40 to 120 keV, close to the values found in the main oval. The time evolution of 〈E〉 generally shows little correlation or anticorrelation with the energy flux precipitated during these transient events. This feature suggests that the mechanism responsible for rapid transient brightenings does not increase the energy of the precipitated electrons, but it enhances their number flux. Pitch angle scattering into the loss cone by magnetic pumping of energy perpendicular to the field lines following magnetic field compression is a possible process.
Formation of cloud droplets by multicomponent organic particles
Authors: Raymond Timothy M. , Pandis Spyros N.
Published: August 2003

Cloud condensation nuclei (CCN) in the atmosphere are usually composed of multiple inorganic and organic chemical species. Determining the ability of these multicomponent particles to activate into cloud droplets is necessary for understanding and quantifying the effect of aerosols on cloud formation and properties. Internally mixed, multicomponent particles as well as particles consisting of a core coated with hexadecane were used in the present study. Laboratory experiments were performed using combinations of sodium chloride, ammonium sulfate, pinonic acid, pinic acid, norpinic acid, glutamic acid, leucine, and hexadecane. Activation diameters were determined combining a Tandem Differential Mobility Analyzer (TDMA) with a thermal diffusion Cloud Condensation Nucleus Counter (CCNC). Studies were performed at supersaturations of 0.3% and 1% with dry particle diameters ranging between 0.02 and 0.2 micrometers. The results were compared to a theory assuming additive behavior of the constituent species. This assumption was sufficient for the prediction of the CCN activation diameter of the mixed particles.
Nitrogen loss from Titan
Authors: Shematovich V. I. , Johnson R. E. , Michael M. , Luhmann J. G.
Published: August 2003

Dissociation and dissociative ionization of molecular nitrogen by solar UV radiation and by photoelectrons and sputtering by the magnetospheric ions and pickup ions are the main sources of translationally excited (hot) nitrogen atoms and molecules in the upper atmosphere of Titan. As Titan does not posses an intrinsic magnetic field, Saturn's magnetospheric ions can penetrate Titan's exobase and sputter atoms and molecules from it. The sputtering of nitrogen from Titan's upper atmosphere by the corotating nitrogen ions and by photodissociation was addressed earlier [Lammer and Bauer, 1993; Shematovich et al., 2001]. Here penetration of slowed and deflected magnetospheric N+ and carbon‐containing pickup ions is described using a Monte Carlo model. The interaction of these ions with the atmospheric neutrals leads to the production of fast neutrals that collide with other atmospheric neutrals producing heating and ejection of atoms and molecules. Results from Brecht et al. [2000] are used to estimate the net flux and energy spectra of the magnetospheric and pickup ions onto the exobase. Sputtering is primarily responsible for any ejected molecular nitrogen, and, for the ion fluxes used, we show that the total sputtering contribution is comparable to or larger than the dissociation contribution giving a total loss rate of ∼3.6 × 1025 nitrogen neutrals per second.
Mars: Dust devil track survey in Argyre Planitia and Hellas Basin
Authors: Balme Matthew R. , Whelley Patrick L. , Greeley Ronald
Published: August 2003

Dust devils and dust devil tracks have been frequently observed in Viking Orbiter and Mars Orbiter Camera (MOC) images, but the parameters that control their distribution have been poorly constrained. Here we investigate the abundance of dust devil tracks in two large study areas, Argyre Planitia and Hellas Basin, using a survey of over 3000 MOC narrow‐angle (NA) images. We report the effect of season, elevation, and surface properties on track distribution using measurements of dust devil track density (the number of dust devil tracks per square kilometer). In both areas, dust devil tracks occur predominantly in summer and are rarely observed in winter. The lifetime of dust devil tracks is inferred to be short (i.e., less than a few months). There is no unambiguous correlation of abundance with elevation; rather the spatial distribution follows albedo patterns, suggesting that dust availability controls the abundance of dust devil tracks. We estimate the total dust lifting potential of dust devils using the average dust devil track density for Argyre and Hellas and conclude that, unless the average dust devil track is greater than 20 m wide, longer than 2 km, and more than 40 μm deep, they cannot account for the estimated global sedimentation rate. In addition, by comparing 2 Mars years of observations, we find no evidence of an increase in dust devil track density prior to the global dust storm that occurred in June 2001. We conclude that dust devils did not trigger this storm.
Low mutation rate of hMSH2 and hMLH1 in Taiwanese hereditary non‐polyposis colorectal cancer
Authors: Wei S‐C , Yu C‐Y , Tsai‐Wu J‐J , Su Y‐N , Sheu J‐C , Wu C‐HH , Wang C‐Y , Wong J‐M
Published: August 2003

Hereditary non‐polyposis colorectal cancer (HNPCC), the most common type of hereditary colorectal cancer, is thought to be a simple Mendelian disease involving DNA mismatch repair genes. The majority of mutations associated with HNPCC occur in the hMSH2 and hMLH1 genes. The reported incidence of mismatch repair gene mutations in HNPCC kindreds varies considerably (from 22 to 86%), and most mutations are unique. This study aimed to determine the genetic basis of Taiwanese HNPCC kindreds, focusing on the two major genes involved in this disease. A total of 15 Taiwanese HNPCC kindreds meeting the Amsterdam criteria, including 72 affected individuals among a total of 266 individuals, were analyzed using both RNA‐ and DNA‐based methods. The mutation rate of hMSH2 and hMLH1 in these 15 kindreds was 0% and 20%, respectively, which is lower than that reported in other countries. Two novel mutations were discovered in hMLH1: one was an allelic loss of a 5.2‐kb genomic fragment causing exon 16 deletion; and the other was a two‐nucleotide deletion that resulted in a frameshift mutation of exon 3. We also identified one hMLH1 exon 4 mutation (a C to T transition in codon 117), which had been reported previously in western countries. This is the first genetic study of HNPCC from Taiwan.
Is maternal age at delivery related to childhood food allergy?
Authors: Dioun Anahita F. , Harris Sion Kim , Hibberd Patricia L.
Published: August 2003

The prevalence of food allergies is increasing. Concurrently, the average maternal age at birth is also increasing. We conducted a preliminary study to evaluate whether maternal age at the time of delivery is associated with a food allergy in children. Case and control patients were identified among consecutive patients seen by one of us (AD) in the Allergy/Immunology program at the Children's Hospital Boston between 11/1/98 and 2/28/00. Case patients were born in Massachusetts and had evidence of clinical sensitivity and IgE to one or more food allergens (n = 58). Control patients were those born in Massachusetts who had a negative skin test and/or RAST to inhalant and/or food allergens (n = 96). A second comparison group consisted of all live births in Massachusetts in 1999 (n = 80,866). Information on maternal age at birth was missing from 3/58 (5%) of patients with a food allergy and 4/96 (4%) of the control patients, so these patients were not included in the analysis. The proportion of children whose mother was aged 30 and over at their birth was significantly higher in children with a food allergy than control patients (78% vs. 55% p = 0.005) and higher than all births in Massachusetts (78% vs. 53% p = 0.0002). Mothers of children with a food allergy had about three times greater odds of being aged 30 or over at the time of delivery than mothers in either of the comparison groups. Further exploration of the data using logistic regression showed that maternal age over 30 at delivery and being first born were independent predictors of the child having a food allergy. In this study, the presence of a food allergy in children was related to older maternal age at delivery. Additional studies are needed to further evaluate this relationship and its potential implication in preventive strategies for food allergies in children.
The canopy arthropods of old and mature pinePinus sylvestrisin Norway
Authors: Thunes Karl H. , Skarveit John , Gjerde Ivar
Published: August 2003

We fogged 24 trees in two pine dominated forests in Norway with a synthetic pyrethroid in order to compare the canopy‐dwelling fauna of arthropods between costal (Kvam) and boreal (Sigdal) sites and between old (250–330 yr) and mature (60–120 yr) trees at Sigdal. Almost 30 000 specimens were assigned to 510 species; only 93 species were present at both sites. Species diversity, as established by rarefaction, was similar in old and mature trees. However, the number of species new to Norway (including nine species new to science) was significantly higher in the old trees. We suggest that the scarcity of old trees, habitat heterogeneity and structural differences between old and mature trees may explain these patterns. Productivity and topographic position at the site of growth explained the between‐tree variation in species occurrence for the more abundant species, which were mainly Collembola and Oribatida. Species diversity was similar at the boreal and coastal sites, but there were clear differences in species composition.
Unique elevational diversity patterns of geometrid moths in an Andean montane rainforest
Authors: Brehm Gunnar , Süssenbach Dirk , Fiedler Konrad
Published: August 2003

Alpha‐diversity of geometrid moths was investigated along an elevational gradient in a tropical montane rainforest in southern Ecuador. Diversity was measured using 1) species number, 2) extrapolated species number (Chao 1 estimator), 3) rarefied species number, and 4) Fisher's alpha. When applied to the empirical data set, 1 and 2 strongly depended on the sample size, whereas 3 and 4 were suitable and reliable measures of local diversity. At single sites, up to 292 species were observed, and extrapolation estimates range from 244 to 445 species. Values for Fisher's alpha are among the highest ever measured for this moth family, and range from 69 to 131 per site. In contrast to theoretical assumptions and empirical studies in other regions of the world, the diversity of geometrid moths remained consistently high along the entire gradient studied. Diversity measures correlated with neither altitude nor ambient temperature. The large subfamily Ennominae has previously been assumed to be a group that occurs mainly at low and medium elevations. However, no decline in diversity was found in the study area. The diversity of the other large subfamily, Larentiinae, even increased from the lowest elevations and was highest at elevations above 1800 m. The roles of a decreasing diversity of potential host‐plants, decreasing structural complexity of the vegetation, increasingly unfavourable climatic conditions and possible physiological adaptations in determining herbivore species richness are discussed. A relatively low predation pressure might be an advantage of high‐altitude habitats. The physiognomy of the Andes (folded mountains, large areas at high altitudes) might also have allowed speciation events and the development of a species‐rich high‐altitude fauna. There is evidence that the species‐richness of other groups of herbivorous insects in the same area declines as altitude increases. This emphasises difficulties that are associated with biodiversity indicator groups, and calls for caution when making generalisations from case studies.
Survival of migrating sea trout (Salmo trutta) and Atlantic salmon (Salmo salar) smolts negotiating weirs in small Danish rivers
Authors: Aarestrup K. , Koed A.
Published: August 2003

Abstract –The survival of brown trout and Atlantic salmon smolts during passage over small weirs was estimated in two small Danish rivers during the spring of 1998. Parallel groups of smolts were released upstream and downstream of the weirs and recaptured in traps further downstream. The results showed a smolt loss varying from 18 to 71% for trout and 53% for salmon. Furthermore, the surviving smolts from the upstream groups were delayed for up to 9 days compared to downstream groups. The study demonstrated that an increased proportion of total river discharge allocated to fish passage increased the smolt survival. Losses may be because of fish penetrating grids erected at fish farm inlets, predation and delays, which may lead to desmoltification. The low survival may seriously threat both the long‐term viability of wild populations of anadromous salmonids and the outcome of the intensive stocking programme in Denmark.
Pleomorphic adenoma of the submandibular salivary glands with marked ossification
Authors: Xu Hui , Shimizu Yoshinaka , Niki Takayuki , Nagasaka Hiroshi , Kawamura Hiroshi , Ooya Kiyoshi
Published: August 2003

This article describes an unusual case of pleomorphic adenoma arising in the submandibular salivary glands that was associated with marked ossification. CT scan showed an irregular high‐density mass in the left submandibular region. Histologic examination of the resected mass revealed a well‐circumscribed pleomorphic adenoma with chondroid tissue intermingled with glandular and trabecular epithelial components. Irregularly formed osseous tissue was present in the chondroid tissue. The osseous tissue showed bone matrix on von Kossa's staining. Alkaline phosphatase expression was restricted to the vicinity of osseous tissue. Tartrate‐resistant acid phosphatase‐positive osteoclasts were observed at the periphery of the osseous tissue. CD34 staining demonstrated many microvascular vessels in both the chondroid and osseous tissues. We conclude the osseous tissue in pleomorphic adenoma was bone in nature, and via the process of endochondral ossification most likely depended on angiogenesis.
Innate immune system is implicated in recurrent aphthous ulcer pathogenesis
Authors: Lewkowicz Natalia , Lewkowicz Przemyslaw , Kurnatowska Anna , Banasik Malgorzata , Glowacka Ewa , Cedzyński Maciej , Świerzko Anna , Lauk‐Puchala Bożena , Tchórzewski Henryk
Published: August 2003

Background:  Recurrent aphthous ulcers (RAU) is a chronic inflammatory disease with evidence of inappropriate immune response. This study presents the status of innate immune system in RAU.

Methods:  Twenty RAU patients and 19 healthy individuals were selected. The status of peripheral blood neutrophils (reactive oxygen intermediates (ROI) production, CD11b, TNF‐RI and TNF‐RII expression), concentration of antioxidants, sTNF‐R, C3c, C4 and haemolytic activity of the complement system, as well as mannose‐binding lectin (MBL), in the serum of RAU patients in active stage and in remission of the disease were determined.

Results:  Peripheral blood neutrophils were primed in RAU, which resulted in increased ROI production by resting and fMLP‐stimulated neutrophils and diminished ROI production after in vitro priming. The increased expression of CD11b on resting and fMLP‐stimulated neutrophils in RAU may also point to their previous in vivo stimulation. The decreased total antioxidant status of serum observed in RAU may be a result of increased ROI production by peripheral blood neutrophils. The levels of C3c, C4 and haemolytic activity of the complement system were higher in RAU than in healthy people. No significant differences between active and remission RAU were noted.

Conclusion:  Presented observations confirm that the innate immune system is involved in RAU pathogenesis.