bluuebunny/crossref_metadata_2025 huggingface dataset:
Predominant expression of Sir2α, an NAD‐dependent histone deacetylase, in the embryonic mouse heart and brain1
Authors: Sakamoto Jun , Miura Tetsuji , Shimamoto Kazuaki , Horio Yoshiyuki
Published: December 2003

Sir2 is an NAD‐dependent histone deacetylase that functions in longevity, gene silencing, heterochromatin formation, DNA repair, and suppression of DNA recombination in yeast. The mammalian homolog Sir2α (SIRT1) has been shown to inhibit p53‐dependent apoptosis, but its physiological roles are still not known. We found that the level of Sir2α expression during embryogenesis was high. The highest Sir2α mRNA expression was detected as early as embryonic day (E) 4.5. Although the level was down‐regulated during embryogenesis, a high level of expression was still found in the late embryonic stage (E18.5). In embryos, Sir2α was expressed at high levels in the heart, brain, spinal cord, and dorsal root ganglia. The expression levels in these organs were high on E10.5–E13.5 and low on E16.5. Quantitative reverse transcription polymerase chain reaction showed a 60% reduction in Sir2α mRNA content in the heart between E12.5 and E14.5. After E14.5, the expression level in the heart remained constant up to 27 months of age. The expression pattern of Sir2α protein in embryonic hearts was consistent with that of mRNA. These results suggest new roles of Sir2α not only in early embryogenesis but also in cardiogenesis and neurogenesis with a stage‐specific manner.
Melanocyte‐specific expression of dopachrome tautomerase is dependent on synergistic gene activation by the Sox10 and Mitf transcription factors
Authors: Ludwig Andreas , Rehberg Stephan , Wegner Michael
Published: December 2003

Sox10 regulates melanocyte development at least partly through its stimulatory effect on Mitf gene expression. Here, we characterize the gene for dopachrome tautomerase (Dct/Trp2) as the second direct Sox10 target in melanocytes, arguing for the existence of Sox10 functions in melanocytes that are independent of its epistatic relationship to Mitf. Sox10 responsiveness was mediated by multiple binding sites within the proximal Dct/Trp2 promoter which display varying affinities and bind Sox10 monomers or dimers. Mitf synergistically enhanced Sox10‐dependent activation of the Dct/Trp2 promoter. Synergy appears mechanistically complex and requires both direct binding of Sox10 to the promoter and the protein's transactivation domain.
Microcystin‐LR and okadaic acid‐induced cellular effects: a dualistic response
Authors: Gehringer Michelle M
Published: December 2003

Microcystins, potent heptapeptide hepatotoxins produced by certain bloom‐forming cyanobacteria, are strong protein phosphatase inhibitors. They covalently bind the serine/threonine protein phosphatases 1 and 2A (PP1 and PP2A), thereby influencing regulation of cellular protein phosphorylation. The paralytic shellfish poison, okadaic acid, is also a potent inhibitor of these PPs. Inhibition of PP1 and PP2A has a dualistic effect on cells exposed to okadaic acid or microcystin‐LR, with both apoptosis and increased cellular proliferation being reported. This review summarises the existing data on the molecular effects of microcystin‐LR inhibition of PP1 and PP2A both in vivo and in vitro, and where possible, compares this to the action of okadaic acid.
Alkylation of human hemoglobin A0 by the antimalarial drug artemisinin
Authors: Selmeczi Katalin , Robert Anne , Claparols Catherine , Meunier Bernard
Published: December 2003

In vitro, the heme cofactor of human iron(II) hemoglobin was efficiently and quickly alkylated at meso positions by the peroxide‐based antimalarial drug artemisinin, leading to heme–artemisinin‐derived covalent adducts. This reaction occurred in the absence of any added protease or in the presence of an excess of an extra non‐heme protein, or even when artemisinin was added to hemolysed human blood. This activation of artemisinin by the heme moiety of non‐digested hemoglobin clearly indicates the high affinity of this drug for heme, and its efficient alkylating ability under very mild conditions.
Intrinsisch motiviert und verzichtbereit
Authors: Abele Andrea E. , Krüsken Jan
Published: December 2003

Zusammenfassung: Determinanten einer Promotionsabsicht und des Wunsches, eine wissenschaftliche Karriere anzustreben, werden bei einer Stichprobe von 610 Diplommathematikerinnen und -mathematikern untersucht. 30% der Befragten wollen sicher oder sehr wahrscheinlich promovieren, und von diesen strebt etwas mehr als die Hälfte eine wissenschaftliche Laufbahn an. Bei den Promotionswilligen gibt es keine statistisch gesicherten Geschlechtsunterschiede; bei denjenigen, die nicht promovieren wollen, sind sich die befragten Frauen ihrer fehlenden Promotionsabsicht sicherer. Entsprechend den theoretischen Vorhersagen beeinflussen zeitlich zurückliegende Variablen des Elternhauses und der Unterstützung in Kindheit und Jugend den Promotionswunsch indirekt über die schulische Leistung. Studienleistungsparameter (insbesondere Examensnote), positives Erleben des Studiums, Mentoren während dieser Zeit und eine spezifische Ausprägung beruflicher Ziele (hohe Ausprägung beruflicher Ziele, die auf geistiges Wachstum angelegt sind und niedrige Ausprägung beruflicher Ziele, die auf “Karriere” im engeren Sinn ausgelegt sind) sind direkte Determinanten der Promotionsabsicht. Die Generalisierbarkeit der Befunde auf andere Fachrichtungen und ihre Implikationen für die akademische Berufslaufbahnforschung auch unter geschlechtsvergleichender Perspektive werden diskutiert.
The German Post-Critical Belief Scale: Internal and External Validity
Authors: Duriez Bart , Appel Claudia , Hutsebaut Dirk
Published: December 2003

Abstract: Recently, Duriez, Fontaine and Hutsebaut (2000) and Fontaine, Duriez, Luyten and Hutsebaut (2003) constructed the Post-Critical Belief Scale in order to measure the two religiosity dimensions along which Wulff (1991 , 1997 ) summarized the various possible approaches to religion: Exclusion vs. Inclusion of Transcendence and Literal vs. Symbolic. In the present article, the German version of this scale is presented. Results obtained in a heterogeneous German sample (N = 216) suggest that the internal structure of the German version fits the internal structure of the original Dutch version. Moreover, the observed relation between the Literal vs. Symbolic dimension and racism, which was in line with previous studies ( Duriez, in press ), supports the external validity of the German version.
Mikro- versus Makroperspektive der retributiven Gerechtigkeit, Strafziele und die Forderung nach Strafe
Authors: Oswald Margit E. , Orth Ulrich , Hupfeld Jörg
Published: December 2003

Zusammenfassung: Wie Personen auf Straftaten reagieren und welche Strafziele sie dabei verfolgen, war bisher kaum Gegenstand psychologischer Forschung. In der vorliegenden Arbeit wird die dimensionale Struktur der Präferenz von Strafzielen untersucht. In zwei Befragungen wurden juristischen Laien Fallgeschichten zur Beurteilung vorgelegt (Raubüberfall, Körperverletzung, Betrug, Vergewaltigung). Die multivariaten Auswertungen weisen eine hohe Übereinstimmung auf: Strafziele lassen sich durch die zwei voneinander unabhängigen Dimensionen Strafhärte und Mikro- versus Makroperspektive klassifizieren. Wird eine Makroperspektive eingenommen, so ist dies mit einer stärkeren Gewichtung von Gesellschaftsinteressen verbunden sowie mit der Präferenz für das Strafziel der positiven Generalprävention. Die Mikroperspektive ist hingegen mit der Überzeugung verbunden, dass Gerechtigkeit insbesondere aus der Perspektive der konkret Beteiligten herzustellen ist. Je nach geforderter Strafhärte geht die Mikroperspektive mit einem Bias entweder für das Opfer und das Strafziel der Vergeltung oder aber für den Täter und das Strafziel der Resozialisierung einher.
Direkte und indirekte Effekte der Argumentqualität
Authors: Reimer Torsten
Published: December 2003

Zusammenfassung: In der Persuasionsforschung (z.B. Petty, Cacioppo & Goldman, 1981 ) werden häufig die Angaben zur Expertise eines Kommunikators und die Qualität der Argumente variiert. Gewöhnlich gelingt es dabei jedoch nicht, diese beiden Faktoren unabhängig voneinander zu manipulieren, wodurch die interne Validität der Experimente eingeschränkt wird. In der vorliegenden Untersuchung wurde die Annahme eines indirekten Effektes der Argumentstärke auf die Einstellung getestet, der über die wahrgenommene Expertise vermittelt ist. 100 Studierenden des Bachelor-Studienganges “Psychologie” an der Universität Basel wurde ein Zeitungsartikel zur Neuregelung der Kreditpunktevergabe im Psychologiestudium vorgelegt. Als unabhängige Variablen wurden die Expertise des Autors (hoch/niedrig/keine Angaben) und die Argumentqualität (hoch/niedrig) variiert. Wie erwartet, hatte die Qualität der verwendeten Argumente nicht nur einen Effekt auf die Einstellung gegenüber der vorgeschlagenen Neuregelung, sondern auch einen massiven Einfluss auf die wahrgenommene Expertise des Kommunikators. Mediationsanalysen belegen darüber hinaus, dass der Effekt der Argumentstärke auf die Einstellung partiell über die wahrgenommene Expertise vermittelt ist.
Diskriminante Validität neuropsychologischer Verfahren in der Demenzdiagnostik
Authors: Damian Marinella , Kreis Markus , Krumm Bertram , Syren Magda , Hentschel Frank
Published: December 2003

Zusammenfassung: Aus einer neuropsychologischen Testbatterie sollten die Testverfahren identifiziert werden, die am meisten zur Differenzialdiagnostik der Demenzen beitragen, um für verschiedene Fragestellungen Kurzformen der Testbatterie zusammenzustellen. Durch die Tests wurden u. a. die folgenden Funktionsbereiche erfasst: Gedächtnis, Aufmerksamkeit, Konzentration, verbale Flüssigkeit, konstruktive Praxie, abstrakt-logisches und planendes Denken. 159 Patienten wurden klinisch, neuropsychologisch und neuroradiologisch untersucht. Die neuropsychologische Untersuchung dauerte ca. 90 Minuten pro Patient. Mit Diskriminanzanalysen wurde untersucht, welche Tests bei möglichst geringen Einbußen in der diagnostischen Sicherheit verzichtbar sind. Die Kürzungen ergaben nur geringe Einbußen bzgl. Sensitivität, Spezifität und Treffsicherheit. Somit können in Abhängigkeit von den Diagnosegruppen, die neuropsychologisch differenziert werden sollen, Kurzformen der Testbatterie mit geringen Einbußen in der diagnostischen Sicherheit und mit deutlichem zeitlichen Gewinn verwendet werden.
Specific Computerized Attention Training in Stroke and Traumatic Brain-Injured Patients
Authors: Sturm W. , Fimm B. , Cantagallo A. , Cremel N. , North P. , North P. , Passadori A. , Pizzamiglio L. , Pizzamiglio L. , Rousseaux M. , Zimmermann P. , Deloche G. , Leclercq M.
Published: December 2003

Abstract: In a multicenter European approach, the efficacy of the AIXTENT computerized training programs for intensity aspects (alertness and vigilance) and selectivity aspects (selective and divided attention) of attention was studied in 33 patients with brain damage of vascular and traumatic etiology. Each patient received training in one of two most impaired of the four attention domains. Control tests were performed by means of a standardized computerized attention test battery (TAP) comprising tests for the four attention functions. Assessment was carried out at the beginning and at the end of a four week baseline period and after the training period of 14 one-hour sessions. At the end of the baseline phase, there was only slight but significant improvement for the most complex attention function, divided attention (number of omissions). After the training, there were significant specific training effects for both intensity aspects (alertness and vigilance) and also for the number of omissions in the divided attention task. The application of inferential single case procedures revealed a high number of significant improvements in individual cases after specific training of alertness and vigilance problems. On the other hand, a non specific training addressing selectivity aspects of attention lead either to improvement or deterioration of alertness and vigilance performance. The results corroborate the findings of former studies with the same training instrument but in patients with different lesion etiologies.
Neuropsychologische Grundlagen komplexer prospektiver Gedächtnisleistung
Authors: Kliegel Matthias , Ramuschkat Grit , Martin Mike
Published: December 2003

Zusammenfassung: Zur Erforschung prospektiver Gedächtnisleistungen wurden in Klinik wie Forschung bislang vor allem einfache Aufgaben eingesetzt, die aber kaum Prozesse wie die Planung oder die Koordination von Mehrfach-Intentionen erfassen, die komplexen prospektiven Aufgaben zugrunde liegen. Ziel der vorliegenden Studie war daher, die deutsche Version des von Kliegel, McDaniel und Einstein (2000) vorgeschlagenen komplexen prospektiven Mehrfachaufgaben-Paradigmas vorzustellen sowie deren Ergebnisse anhand einer Stichprobe von 40 jüngeren und 40 älteren Erwachsenen zu replizieren. Zusätzlich wurde untersucht, inwieweit altersbedingte Leistungsunterschiede in der komplexen prospektiven Gedächtnisaufgabe mit Unterschieden in exekutiven Steuerungsprozessen zusammenhängen. Die Ergebnisse bestätigen frühere Befunde und dokumentieren Alterseffekte bezüglich der Plankomplexität, der Reinstantiierung der Intention sowie der selbstinitiierten Ausführung der multiplen Wechselintention, nicht jedoch in der Planerinnerung. Darüber hinaus zeigen die Resultate von Regressionsanalysen, dass die Varianz im Wisconsin Card Sorting Test die altersbedingte Variabilität der Leistung in der komplexen prospektiven Aufgabe teilweise vorhersagen kann. Das chronologische Alter blieb jedoch als signifikante Einflussgröße bestehen. Insgesamt liefert die Studie konsistente Hinweise auf eine hohe Bedeutung exekutiver Funktionen bei Alterseffekten in komplexen prospektiven Gedächtnisaufgaben.
Toward constraining regional‐scale fluxes of CO2 with atmospheric observations over a continent: 1. Observed spatial variability from airborne platforms
Authors: Gerbig C. , Lin J. C. , Wofsy S. C. , Daube B. C. , Andrews A. E. , Stephens B. B. , Bakwin P. S. , Grainger C. A.
Published: December 2003

We analyze the spatial variability of CO2 measurements from aircraft platforms, including extensive observations acquired over North America during the CO2 Budget and Rectification Airborne (COBRA) study in 2000. The COBRA data set is unique in its dense spatial coverage and extensive profiling in the lower atmosphere. Strong signatures of CO2 fluxes at the land surface were observed in the active and relic mixed layers of the atmosphere (up to ∼20 ppm gradients). Free tropospheric CO2 exhibited significantly less variability except in areas affected by convective transport. Statistical analyses of the COBRA data indicate that CO2 mixed‐layer averages can be determined from vertical profiles with an accuracy of approximately ±0.2 ppm, limited by atmospheric variance. Analysis of the associated representation error suggests that models require horizontal resolution smaller than ∼30 km to fully resolve spatial variations of atmospheric CO2 in the boundary layer over the continent. To provide a global context for these data, we analyzed the GLOBALVIEW marine boundary layer (MBL) reference CO2. Comparison of the MBL reference with extensive aircraft data extending over 20 years, covering the whole troposphere over the northern Pacific, shows significant seasonal biases of up to 2 ppm in the free troposphere, indicating that the MBL reference is a suitable boundary condition only for some applications. The spatial variability of CO2 revealed by the COBRA‐2000 calls for a suitable analysis framework to derive regional and continental fluxes, presented in a companion paper. The problem requires boundary conditions constrained by both surface and upper tropospheric observations and constraints on terrestrial fluxes that exploit the information content of the highly variable CO2 distribution over land.
The quasi 2‐day wave observed in the polar mesosphere: Comparison of the characteristics observed at Tromsø and Poker Flat
Authors: Nozawa S. , Iwahashi H. , Brekke A. , Hall C. M. , Meek C. , Manson A. , Oyama S. , Murayama Y. , Fujii R.
Published: December 2003

A comparison of the quasi 2‐day wave (Q2DW) observed at Tromsø (69.6°N, 19.2°E) and Poker Flat (65.2°, 147.6°W) is presented at four heights of 70, 76, 82, and 88 km using wind data taken for ∼4 years, from 1 November 1998 to 7 November 2002. The characteristics of the Q2DW such as seasonal variation, occurrence of period of maximum amplitude, ratio of meridional to zonal amplitudes, shape of altitude profile of phase, and modulation of amplitude at a 4–10 days rate found at Poker Flat are very similar to those found at Tromsø reported by Nozawa et al. [2003]. The activity of the Q2DW is higher in winter than in summer for meridional and zonal components at the two sites. Long‐term variation (i.e., seasonal variation) of the Q2DW is found to be similar between the two sites, while short‐term variations (i.e., over several days) do not synchronize well with each other. The ratio of amplitudes of the Q2DW between the two sites varies mainly between 0.5 and 2, and there is no significant preference toward either site. Phase differences of Q2DWs between the two sites are examined, and it is found that in‐phase‐like events are more frequently seen than out‐of‐phase‐like events at 76, 82, and 88 km in winter and at 88 km in summer. This can be interpreted to mean that the zonal wave number of the Q2DW appears to be 2 or 4 more often than 3 in the polar upper mesosphere. These results suggest that observed Q2DWs have features consistent with the Rossby gravity wave mode, but the amplitude and phase of the Q2DW are affected significantly by local sources. A possibility that the observed Q2DW is an eastward moving wave is also discussed.
FDTD analysis of ELF wave propagation and Schumann resonances for a subionospheric waveguide model
Authors: Otsuyama T. , Sakuma D. , Hayakawa M.
Published: December 2003

The space formed by the ground and ionosphere is known to act as a resonator for extremely low frequency (ELF) waves. Lightning discharges trigger this global resonance, which is known as Schumann resonance. Even though the inhomogeneity (like day‐night asymmetry, local perturbation, etc.) is important for such a subionospheric ELF propagation, the previous analyses have been always made by some approximations because the problem is too complicated to be analyzed by any exact full‐wave analysis. This paper presents the first application of the conventional numerical FDTD method to such a subionospheric ELF wave propagation, in which any kind of inhomogeneity can be included in this analysis. However, the present paper is intended to demonstrate the workability of this method only for a uniform waveguide (without day‐night asymmetry), by comparing the results from this method with those by the corresponding analytical method.
Flow dimensions corresponding to hydrogeologic conditions
Authors: Walker Douglas D. , Roberts Randall M.
Published: December 2003

The generalized radial flow approach to hydraulic test interpretation uses the flow dimension to describe the change in flow area versus radial distance from the borehole. The flow dimension of a hydraulic test may reflect several characteristics of the hydrogeologic system, including heterogeneity, boundaries, and leakage. We show that a radial flow system with a linear, constant‐head boundary asymptotically reaches a flow dimension of four, while the flow dimension of a leaky aquifer is a function of time and the leakage factor. We use numerical techniques to show that a stationary transmissivity field with a modest level of heterogeneity has a flow dimension that stabilizes at two. We also show that the flow dimension for a nonstationary transmissivity field depends on the form and magnitude of the nonstationarity. The flow dimension observed during hydraulic tests helps identify admissible conceptual models for the tested system, and places hydraulic testing in its full hydrogeologic context.
Uncertainty reduction and characterization for complex environmental fate and transport models: An empirical Bayesian framework incorporating the stochastic response surface method
Authors: Balakrishnan Suhrid , Roy Amit , Ierapetritou Marianthi G. , Flach Gregory P. , Georgopoulos Panos G.
Published: December 2003

In this work, a computationally efficient Bayesian framework for the reduction and characterization of parametric uncertainty in computationally demanding environmental 3‐D numerical models has been developed. The framework is based on the combined application of the Stochastic Response Surface Method (SRSM, which generates accurate and computationally efficient statistically equivalent reduced models) and the Markov chain Monte Carlo method. The application selected to demonstrate this framework involves steady state groundwater flow at the U.S. Department of Energy Savannah River Site General Separations Area, modeled using the Subsurface Flow And Contaminant Transport (FACT) code. Input parameter uncertainty, based initially on expert opinion, was found to decrease in all variables of the posterior distribution. The joint posterior distribution obtained was then further used for the final uncertainty analysis of the stream base flows and well location hydraulic head values.
Analytic expressions for output reliability: Verifying automated calibration and confidence calculations of a groundwater flow simulator
Authors: Zaadnoordijk Willem Jan
Published: December 2003

Auxiliary material for this article contains a data set of the analytic formulae for the partial derivatives of the piezometric head with respect to the logarithm (base 10) of the resistance c and the hydraulic conductivity k. Additional file information is provided in the README.txt.

ftp://ftp.agu.org/apend/wr/2002WR001932‐README.txt

ftp://ftp.agu.org/apend/wr/2002WR001932‐derivatives.ps

ftp://ftp.agu.org/apend/wr/2002WR001932‐derivatives.tex

Analytic relations between input parameters, output variables, and statistics for confidence are derived for semiconfined groundwater flow in a circular domain around a well. The statistics of the two calibrated parameters are derived analytically using a least squares target function. The statistics of the piezometric head are approximated using linear variance analysis (LVA, also known as first‐order second moment method (FOSM)) and quadratic variance analysis (QVA). LVA values for the capture zone radius have been calculated based on numerical derivatives. The results are used to verify TrCalCon, the calibration and confidence module of the groundwater flow simulation package TRIWACO. The LVA and Monte Carlo (MC) results of TrCalCon compare well with the analytic LVA and QVA values, respectively. The problem is only weakly nonlinear in the heads, so that the LVA is accurate enough for practical purposes, and QVA or MC analysis would not be needed. The test can be applied as well to other groundwater simulation packages with a module for automatic parameter optimization and reliability analysis. As presented, the problem is quite simple, and the parameter optimization is relatively easy. The analysis can be expanded easily to make the problem more intricate by adding parameters, changing parameter values, and including other measurements.
Interferometry observations of VHF backscatter from plasma irregularities induced by meteor in sporadic E region
Authors: Chu Yen‐Hsyang , Wang Chien‐Ya
Published: December 2003

With the interferometry technique implemented at the Chung‐Li VHF radar, the spatial structures of the meteor‐induced plasma irregularities responsible for the long‐persisting (more than 4 minutes) range spread echoes are reconstructed. We found that the irregularities assemble in a clump structure centered at height 105 km with vertical extent of 3–8 km and horizontal dimension of 2–10 km. We also found that the plasma irregularities are field‐aligned with appreciably narrow aspect angle. On the basis of the enormously narrow spectral width of the echoes and almost indiscernible delay between range spread echoes and meteor head echoes, we speculate that the mechanism involved in the generation of the plasma irregularities responsible for the range spread echoes is attributed to the perturbation of the intense plasma densities by the neutral turbulences excited by the large wind shear.
Resonant absorption of ULF waves near the ion cyclotron frequency: A simulation study
Authors: Kim Eun‐Hwa , Lee Dong‐Hun
Published: December 2003

We present a numerical investigation of Alfven resonances when frequencies are comparable to the ion cyclotron frequency(ωci) and MHD approximations become no longer valid. We have developed a three‐dimensional multi‐fluid wave model, which can fully include the effects of multi‐ions and electron. We use simple box model of an inhomogeneous plasma to examine how wave coupling properties change when the characteristic MHD resonance modes become comparable to ωci. The wave spectra and energy relations are presented for both MHD waves and ion cyclotron waves. Our results show that previous resonant absorption in pure MHD waves is well confirmed in the multi‐fluid model. By adopting a set of new eigenmodes, we show that the resonant absorption persists even for the higher frequency. It is suggested that, near ωci, the left‐handed circularly polarized mode is likely to behave as a shear mode in the MHD limit.
Properties of fast magnetosonic shocklets at the bow shock
Authors: Stasiewicz K. , Longmore M. , Buchert S. , Shukla P. K. , Lavraud B. , Pickett J.
Published: December 2003

We present detailed properties of fast magnetosonic shocklets (1000 km in size and amplitude of 10 times the background B‐field values) observed in natural unbounded collisionless plasma by a fleet of four Cluster spacecraft at the quasi‐parallel bow shock. We provide for the first time details of the internal structure of shocklets which have magnetic pulses shifted in time from the plasma density pulses, have localized regions with ion acoustic turbulence, and are shown to slow down and thermalize the solar wind ions. The shocklets emit weak electron plasma waves which are used to verify the plasma density profiles within the structure. They move with supersonic speeds (∼250 km/s) and appear in the region with mixing of cold solar wind ion beams and thermalized heated plasma. We provide a qualitative explanation for the observed relationship between the magnetic field and plasma density profiles within the structure based on a nonlinear momentum conservation equation of plasma fluid dynamics.
Firehose instability near substorm expansion‐phase onset?
Authors: Ji Shuo , Wolf R. A.
Published: December 2003

The evolution of plasma ejected earthward from a patch of reconnection at ∼25 RE is studied using a double‐adiabatic‐MHD simulation of a thin filament. Firehose instability occurs in the simulation after a compressional shock reflects from the near‐Earth region. The tailward‐propagating compressional wave, which brakes the earthward flow in the filament, is characterized by strong magnetic fluctuations. Within the context of the Near‐Earth‐X‐Line model of substorms, we suggest that firehose instability might cause the intense magnetic‐field fluctuations observed in the inner plasma sheet at substorm onset.
Control of plasmaspheric dynamics by both convection and sub‐auroral polarization stream
Authors: Goldstein J. , Sandel B. R. , Hairston M. R. , Reiff P. H.
Published: December 2003

The long‐standing hypothesis that plasmaspheric dynamics are described by superposition of corotation and solar‐wind‐driven sunward convection is tested via direct comparison between plasmasphere observations and simulation output. The observations consist of global plasmasphere images produced by the IMAGE extreme ultraviolet (EUV) imager during plasmasphere erosion on 2 June 2001. The simulation is a plasmapause evolution model driven by a time‐varying Volland‐Stern (VS) electric potential distribution. On the dawnside and much of the nightside the model matches the EUV plasmapause position to within 0.2–0.5 earth radii (RE). Near dusk the model plasmapause is about 0.7–1.2 RE farther out than the EUV plasmapause, suggesting that an improved model should include the duskside flow enhancement known as the sub‐auroral polarization stream (SAPS). We demonstrate that including a simplified ad‐hoc SAPS potential can correct the model on the duskside.
On the Solar EUV Deposition in the Inner Comae of Comets with Large Gas Production Rates
Authors: Bhardwaj Anil
Published: December 2003

In this letter we have made a comparative study of degradation of solar EUV radiation and EUV‐generated photoelectrons in the inner comae of comets having different gas production rates, Q, with values 1 × 1028, 7 × 1029, 1 × 1031, and 1 × 1032 s−1. We found that in higher‐Q comets the radial profile of H2O+ photo‐production rate depicts a double‐peak structure and that the differences in sunward and anti‐sunward photoionization rates are pronounced. We show that photoelectron impact ionization is an order of magnitude larger than photoionization rate near the lower photoionization peak in comets with Q > ∼1 × 1031 s−1. The present study reveals the importance of photoelectrons relative to solar EUV as the ionization source in the inner coma of high‐Q comets.
Basal melting of snow on early Mars: A possible origin of some valley networks
Authors: Carr Michael H. , Head James W.
Published: December 2003

Valley networks appear to be cut by liquid water, yet simulations suggest that early Mars could not have been warmed enough by a CO2‐H2O greenhouse to permit rainfall. The vulnerability of an early atmosphere to impact erosion, the likely rapid scavenging of CO2 from the atmosphere by weathering, and the lack of detection of weathering products all support a cold early Mars. We explore the hypothesis that valley networks could have formed as a result of basal melting of thick snow and ice deposits. Depending on the heat flow, an early snowpack a few hundred meters to a few kilometers thick could undergo basal melting, providing water to cut valley networks.
Investigating anomalous absorption using surface measurements
Authors: Sengupta M. , Ackerman T. P.
Published: December 2003

Flux measurements from the 415 nm band of the multifilter rotating shadowband radiometer and liquid water path from the microwave radiometer were used to derive effective radii in warm boundary layer clouds at the U.S. Department of Energy Atmospheric Measurement Program Southern Great Plains site. Surface fluxes computed using the effective radii retrieved using 415 nm measurements showed no bias when compared with observed broadband fluxes. It is therefore inferred that there is no excess absorption at solar and near‐infrared wavelengths in the presence of warm boundary layer clouds.
Eastern Asian emissions of anthropogenic halocarbons deduced from aircraft concentration data
Authors: Palmer Paul I. , Jacob Daniel J. , Mickley Loretta J. , Blake Donald R. , Sachse Glen W. , Fuelberg Henry E. , Kiley Christopher M.
Published: December 2003

The Montreal Protocol restricts production of ozone‐depleting halocarbons worldwide. Enforcement of the protocol has relied mainly on annual government statistics of production and consumption of these compounds (bottom‐up approach). We show here that aircraft observations of halocarbon:CO enhancement ratios on regional to continental scales can be used to infer halocarbon emissions, providing independent verification of the bottom‐up approach. We apply this top‐down approach to aircraft observations of Asian outflow from the TRACE‐P mission over the western Pacific (March–April 2001) and derive emissions from eastern Asia (China, Japan, and Korea). We derive an eastern Asian carbon tetrachloride (CCl4) source of 21.5 Gg yr−1, several‐fold larger than previous estimates and amounting to ≃30% of the global budget for this gas. Our emission estimate for CFC‐11 from eastern Asia is 50% higher than inventories derived from manufacturing records. Our emission estimates for methyl chloroform (CH3CCl3) and CFC‐12 are in agreement with existing inventories. For halon 1211 we find only a strong local source originating from the Shanghai area. Our emission estimates for the above gases result in a ≃40% increase in the ozone depletion potential (ODP) of Asian emissions relative to previous estimates, corresponding to a ≃10% global increase in ODP.
An evaluation of CO2 observations with Solar Occultation FTS for Inclined‐Orbit Satellite sensor for surface source inversion
Authors: Patra Prabir K. , Maksyutov Shamil , Sasano Yasuhiro , Nakajima Hideaki , Inoue Gen , Nakazawa Takakiyo
Published: December 2003

An assessment of the utility of CO2 vertical profile measurements by a solar occultation based satellite sensor is made. We have compared the impacts of these possible vertical profile observations and optimal extensions of the present surface measurement network on the estimation of CO2 regional sources by inverse model. Time‐independent inverse models at two spatial resolutions (22 and 53 regions) and a global transport model are employed in this study. A realistic satellite measurement frequency distribution, obstruction of observation due to clouds, an observation error model for natural CO2 variability have been used. The satellite measurements are valuable to constrain the source uncertainties for the tropical lands with no existing observations. The optimal extension of the surface network appears to be the more effective way to reduce average inverse model uncertainty under both low and high inverse model resolutions; however, in high‐resolution inversion the relative merit of the satellite data is higher than that in the low‐resolution case. Our study suggests that the CO2 observation at greater data density can constrain the inverse model fluxes better. We show that the systematic errors in satellite observations can lead to significant shifts in the inverse model‐estimated fluxes.
Measurement of NO2 by the photolysis conversion technique during the Transport and Chemical Evolution Over the Pacific (TRACE‐P) campaign
Authors: Nakamura K. , Kondo Y. , Chen G. , Crawford J. H. , Takegawa N. , Koike M. , Kita K. , Miyazaki Y. , Shetter R. E. , Lefer B. L. , Avery M. , Matsumoto J.
Published: December 2003

An airborne instrument for in situ measurements of tropospheric nitrogen dioxide (NO2) was developed using the photolytic conversion technique followed by chemiluminescence detection of NO. This instrument was used for the measurements of NO2 on board the NASA P‐3B aircraft during the Transport and Chemical Evolution Over the Pacific (TRACE‐P) campaign. Comparison in the laboratory indicated less than 10% difference between our NO2 instrument and two independent laser‐induced fluorescence instruments in the NO2 range of 30 parts per trillion by volume (pptv) to 50 ppbv. The magnitudes of potential errors in airborne tropospheric NO2 measurements were further assessed using the TRACE‐P data set. The systematic errors estimated for the median NO2 mixing ratios, 70 pptv at 0–2 km (30 pptv at 2–8 km), were 19% (39%). The random errors for a 10 s integration time were estimated to be 5–10%, depending on altitude. The observed NO2 mixing ratios were compared to those calculated by a photochemical box model. Overall, the calculated NO2 values correlated very well with those observed (r2 = 0.97), although the calculations were systematically higher than the observations by about 30%, except for the highest flight levels. The calculated/observed NO2 ratio remained nearly constant, having values close to 1.3 at 0–4 km, and decreased with altitude. The difference between the observed and model‐calculated values, however, was within the combined uncertainty in the measurement and model calculation. The underlying causes for this difference are to be determined in future studies.
Seasonal variation and ecosystem dependence of emission factors for selected trace gases and PM2.5 for southern African savanna fires
Authors: Korontzi S. , Ward D. E. , Susott R. A. , Yokelson R. J. , Justice C. O. , Hobbs P. V. , Smithwick E. A. H. , Hao W. M.
Published: December 2003

In this paper we present the first early dry season (early June‐early August) emission factor measurements for carbon dioxide (CO2), carbon monoxide (CO), methane (CH4), nonmethane hydrocarbons (NMHC), and particulates with a diameter less than 2.5 μm (PM2.5) for southern African grassland and woodland fires. Seasonal emission factors for grassland fires correlate linearly with the proportion of green grass, used as a surrogate for the fuel moisture content, and are higher for products of incomplete combustion in the early part of the dry season compared with later in the dry season. Models of emission factors for NMHC and PM2.5 versus modified combustion efficiency (MCE) are statistically different in grassland compared with woodland ecosystems. We compare predictions based on the integration of emissions factors from this study, from the Southern African Fire‐Atmosphere Research Initiative 1992 (SAFARI‐92), and from SAFARI‐2000 with those based on the smaller set of ecosystem‐specific emission factors to estimate the effects of using regional‐average rather than ecosystem‐specific emission factors. We also test the validity of using the SAFARI‐92 models for emission factors versus MCE to predict the early dry season emission factors measured in this study. The comparison indicates that the largest discrepancies occur at the low end (0.907) and high end (0.972) of MCE values measured in this study. Finally, we combine our models of MCE versus proportion of green grass for grassland fires with emission factors versus MCE for selected oxygenated volatile organic compounds measured in the SAFARI‐2000 campaign to derive the first seasonal emission factors for these compounds. The results of this study demonstrate that seasonal variations in savanna fire emissions are important and should be considered in modeling emissions at regional to continental scales.
Cirrus and water vapor in the tropical tropopause layer observed by Upper Atmosphere Research Satellite (UARS)
Authors: Clark H. L. , Harwood R. S. , Billingham A. , Pumphrey H. C.
Published: December 2003

The Microwave Limb Sounder (MLS) on Upper Atmosphere Research Satellite (UARS) is sensitive to water vapor and ozone in the lower stratosphere. The Cryogenic Limb Array Etalon Spectrometer (CLAES), another of the instruments on UARS, has a spatial and temporal coverage similar to that of MLS and can be used to indicate the presence of cirrus. We examine the relationships among water vapor, ozone, and cirrus in the tropical region at 68 and 83 hPa during December–February 1991/1992, an El Niño period. For most longitudes at 68 hPa, three‐dimensional trajectories show that the cirrus form predominately in air which ascends slowly through the tropical tropopause layer. Cirrus form in air which has travelled a long way in the horizontal, in the westerly jet, before heading equatorward in subtropical anticyclones. In the Indonesian region, however, a greater proportion is found in air which is sinking than in air which is ascending. The western Pacific region sees the highest proportion of cirrus which may have been influenced by convection, and the possible contribution from convection is greater at 83 hPa than at 68 hPa. In cloudy regions, the air is likely to have a high relative humidity. Mixing ratios of ozone from MLS have a tendency to be lower, and this may indicate that ozone is destroyed on the ice particles that comprise the clouds.
Evaluating aerosol/cloud/radiation process parameterizations with single‐column models and Second Aerosol Characterization Experiment (ACE‐2) cloudy column observations
Authors: Menon Surabi , Brenguier Jean‐Louis , Boucher Olivier , Davison Paul , Del Genio Anthony D. , Feichter Johann , Ghan Steven , Guibert Sarah , Liu Xiaohong , Lohmann Ulrike , Pawlowska Hanna , Penner Joyce E. , Quaas Johannes , Roberts David L. , Schüller Lothar , Snider Jefferson
Published: December 2003

The Second Aerosol Characterization Experiment (ACE‐2) data set along with ECMWF reanalysis meteorological fields provided the basis for the single column model (SCM) simulations, performed as part of the PACE (Parameterization of the Aerosol Indirect Climatic Effect) project. Six different SCMs were used to simulate ACE‐2 case studies of clean and polluted cloudy boundary layers, with the objective being to identify limitations of the aerosol/cloud/radiation interaction schemes within the range of uncertainty in in situ, reanalysis and satellite retrieved data. The exercise proceeds in three steps. First, SCMs are configured with the same fine vertical resolution as the ACE‐2 in situ data base to evaluate the numerical schemes for prediction of aerosol activation, radiative transfer and precipitation formation. Second, the same test is performed at the coarser vertical resolution of GCMs to evaluate its impact on the performance of the parameterizations. Finally, SCMs are run for a 24–48 hr period to examine predictions of boundary layer clouds when initialized with large‐scale meteorological fields. Several schemes were tested for the prediction of cloud droplet number concentration (N). Physically based activation schemes using vertical velocity show noticeable discrepancies compared to empirical schemes due to biases in the diagnosed cloud base vertical velocity. Prognostic schemes exhibit a larger variability than the diagnostic ones, due to a coupling between aerosol activation and drizzle scavenging in the calculation of N. When SCMs are initialized at a fine vertical resolution with locally observed vertical profiles of liquid water, predicted optical properties are comparable to observations. Predictions however degrade at coarser vertical resolution and are more sensitive to the mean liquid water path than to its spatial heterogeneity. Predicted precipitation fluxes are severely underestimated and improve when accounting for sub‐grid liquid water variability. Results from the 24–48 hr runs suggest that most models have problems in simulating boundary layer cloud morphology, since the large‐scale initialization fields do not accurately reproduce observed meteorological conditions. As a result, models significantly overestimate optical properties. Improved cloud morphologies were obtained for models with subgrid inversions and subgrid cloud thickness schemes. This may be a result of representing subgrid scale effects though we do not rule out the possibility that better large‐forcing data may also improve cloud morphology predictions.
Reanalysis of total ozone measurements at Dombås and Oslo, Norway, from 1940 to 1949
Authors: Svendby Tove M.
Published: December 2003

Total ozone measurements from Dobson spectrometer number 8 at Dombås, Norway (62.1°N, 9.1°E), and Oslo, Norway (59.9°N, 10.7°E), from 1940 to 1949 have been examined and reanalyzed. New sets of Bass‐Paur absorption and Rayleigh scattering coefficients have been created, and total ozone values have been recalculated using the new coefficients. Approximately half of the ozone registrations at Dombås were based on direct Sun observations calculated from the CC′ wavelength pairs. The long C′ pair has provided valuable information about the effect of atmospheric aerosols on the ozone measurements. A method for determining aerosol corrections is presented which demonstrates that the monthly mean aerosol error can reach 4% total ozone, normally with a higher correction in the summer than in the winter. Also, the influence of SO2 on the Oslo ozone measurements is estimated. The D8 ozone series from 1940 to 1949 has been compared to ozone records from other European stations and to the D56 ozone series from Oslo 1978–1998. Studies of old and new Dobson data demonstrate that the annual variation in the ozone layer has changed during the last 50–60 years. The comparison indicates that the ozone decrease is relatively small for the summer months (2.9 ± 1.8%), whereas the average winter and spring values have deceased by 6.1 ± 3.9% from the 1940s to the 1990s. If the postwar increase in tropospheric ozone is taken into account, the depletion of the ozone layer is considerably higher, probably 8–9% for winter/spring. All the reanalyzed total ozone data from D8 for the period 1940 to 1949 are available at the World Ozone and Ultraviolet Radiation Data Center.
Extended methodology for determining wetting properties of porous media
Authors: Bachmann J. , Woche S. K. , Goebel M.‐O. , Kirkham M. B. , Horton R.
Published: December 2003

Because most methods for assessing the wettability of porous materials are restricted in their applicability, we developed two new methods for measuring contact angles and particle surface energy. The proposed methods (the Wilhelmy plate method (WPM) and the modified capillary rise method (MCRM)) were tested on 24 soils. For comparison, the water drop penetration time test (WDPTT) and the sessile drop method (SDM) were also applied. It was found that advancing contact angles, measured either with WPM or MCRM, agreed well in the range of 0° to 142°. Sessile drop contact angles were within the domain enclosed by the range of advancing and receding contact angles as determined with WPM. WDPTT, however, was only sensitive in the narrow range of 85° to 115°. We conclude that both WPM and MCRM are reliable methods for determining contact angles and particle surface energy over a wide range of porous material wettabilities.
Multirate flowing fluid electric conductivity logging method
Authors: Tsang Chin‐Fu , Doughty Christine
Published: December 2003

The flowing fluid electric conductivity logging method involves the replacement of well bore water by deionized or constant‐salinity water, followed by constant pumping with rate Q, during which a series of fluid electric conductivity logs are taken. The logs can be analyzed to identify depth locations of inflow and evaluate the transmissivity and electric conductivity (salinity) of the fluid at each inflow point. The present paper proposes the use of the method with two or more pumping rates. In particular, it is recommended that the method be applied three times with pumping rates Q, Q/2, and 2Q. Then a combined analysis of the multirate data allows an efficient means of determining transmissivity and salinity values of all inflow points along a well with a confidence measure, as well as their ambient or “far‐field” pressure heads. The method is illustrated by a practical example.
Hysteresis in soil water characteristics as a key to interpreting comparisons of laboratory and field measured hydraulic properties
Authors: Basile Angelo , Ciollaro Guido , Coppola Antonio
Published: December 2003

This study is mainly aimed at assessing the adequacy of laboratory‐based soil hydraulic characterization carried out on undisturbed cores for reproducing the in situ soil hydraulic behavior. Assuming that the laboratory sample size is a representative elementary volume (REV) for a single horizon of the soil profiles examined, the analysis of the hysteretic features of the soil water retention function is used to explain the differences observed in the constitutive soil water relationships as obtained from either laboratory or in situ experiments. Because the wetting procedures differ in laboratory and in field experiments, it is argued that the difference in the obtained hydraulic characteristics is the result of different hysteretic paths. From the comparison of measured hydraulic conductivities we deduce that field and laboratory retention curves are a part of the same hysteresis loop. In such a context the field hydraulic functions can be derived from the laboratory functions using the maximum water content (i.e., at zero pressure head) and air entry value measured in the field. It is shown that the field parameters identified from the measurements in the early phases of the field test are sufficient to reliably describe field hydrological behavior.