bluuebunny/crossref_metadata_2025 huggingface dataset:
Epidemiology and risk factors for hepatitis C in Alaska Natives
Authors: McMahon Brian J. , Hennessy Thomas W. , Christensen Carol , Bruden Dana , Sullivan Daniel G. , Homan Chriss , Deubner Heike , Bruce Michael G. , Livingston Stephen , Williams James , Gretch David R.
Published: February 2004

Large cohorts of persons infected with hepatitis C virus (HCV) that include patients with multiple risk exposures and behaviors have been rarely reported. We herein describe a population-based cohort of 759 Alaska Natives (AN) with HCV who were recruited into a long-term follow-up study. History of injection drug use (IDU) was reported by 60.1% and blood transfusion by 14.0%. The most common genotype was 1a (42.0%), followed by 1b (20.3%), 2b (14.7%), 3a (14.3%), and 2a (7.8%). By multivariable analysis, risk exposures (blood transfusion vs. other; P < 0.01; odds ratio [OR], 2.87; 95% confidence interval [CI], 1.51-5.45) and year of infection (P < 0.01; OR, 3.47; 95% CI, 1.34-8.96) were significantly associated with HCV RNA-positivity. Having an RNA concentration ≥2 million copies/mL was associated with male gender (OR, 1.94) and genotype (P < 0.01 overall; 1a vs. 3a: OR, 1.92; 2b vs. 3a: OR, 3.17) by multivariable analysis. In conclusion, the two principal risk exposures for AN infected with HCV (IDU and blood transfusion) are the same as the overall U.S. population. Persons with a history of blood transfusion were more likely to be HCV RNA positive than those without such history. Higher RNA levels found in males may explain the more severe disease previously reported in this group. (Hepatology 2004;39:325-332.)
Altered gene expression in acute systemic inflammation detected by complete coverage of the human liver transcriptome
Authors: Coulouarn Cédric , Lefebvre Grégory , Derambure Céline , Lequerre Thierry , Scotte Michel , Francois Arnaud , Cellier Dominique , Daveau Maryvonne , Salier Jean-Philippe
Published: February 2004

The goal of the current study was to provide complete coverage of the liver transcriptome with human probes corresponding to every gene expressed in embryonic, adult, and/or cancerous liver. We developed dedicated tools, namely, the Liverpool nylon array of complementary DNA (cDNA) probes for approximately 10,000 nonredundant genes and the LiverTools database. Inflammation-induced transcriptome changes were studied in liver tissue samples from patients with an acute systemic inflammation and from control subjects. One hundred and fifty-four messenger RNAs (mRNA) correlated statistically with the extent of inflammation. Of these, 134 mRNA samples were not associated previously with an acute-phase (AP) response. The hepatocyte origin and proinflammatory cytokine responsiveness of these mRNAs were confirmed by quantitative reverse-transcription polymerase chain reaction (Q-RT-PCR) in cytokine-challenged hepatoma cells. The corresponding gene promoters were enriched in potential binding sites for inflammation-driven transcription factors in the liver. Some of the corresponding proteins may provide novel blood markers of clinical relevance. The mRNAs whose level is most correlated with the AP extent (P < .05) were enriched in intracellular signaling molecules, transcription factors, glycosylation enzymes, and up-regulated plasma proteins. In conclusion, the hepatocyte responded to the AP extent by fine tuning some mRNA levels, controlling most, if not all, intracellular events from early signaling to the final secretion of proteins involved in innate immunity. Supplementary material for this article can be found on the Hepatology website (http://interscience.wiley.com/jpages/0270-9139/suppmat/index.html). (Hepatology 2004;39:353-364.)
PAR1 antagonism protects against experimental liver fibrosis. Role of proteinase receptors in stellate cell activation
Authors: Fiorucci Stefano , Antonelli Elisabetta , Distrutti Eleonora , Severino Beatrice , Fiorentina Roviezzo , Baldoni Monia , Caliendo Giuseppe , Santagada Vincenzo , Morelli Antonio , Cirino Giuseppe
Published: February 2004

In fibroblasts, thrombin induces collagen deposition through activation of a G-protein-coupled receptor, proteinase-activated receptor 1 (PAR1). In the current study, we examined whether PAR1 antagonism inhibits hepatic stellate cell (HSC) activation in vitro and whether it protects against fibrosis development in a rodent model of cirrhosis. A rat HSC line was used for in vitro studies whereas cirrhosis was induced by bile duct ligation (BDL). The current results demonstrated that HSCs express PAR1, as well as proteinase-activated receptors 2 (PAR2) and 4 (PAR4), and that all three PARs were up-regulated in response to exposure to growth factor in vitro. Exposure to thrombin and to SFLLRN-(SF)-NH2, a PAR1 agonist, and GYPGKF (GY)-NH2, a PAR4 agonist, triggered HSC proliferation and contraction, as well as monocyte chemotactic protein-1 (MCP-1) production and collagen I synthesis and release. These effects were inhibited by the PAR1 antagonist. Administration of this antagonist, 1.5 mg/kg/d, to BDL rats reduced liver type I collagen messenger RNA (mRNA) expression and surface collagen by 63%, as measured by quantitative morphometric analysis. Similarly, hepatic and urinary excretion of hydroxyproline was reduced significantly by the PAR1 antagonist. In conclusion, PARs regulates HSC activity; development of PAR antagonists might be a feasible therapeutic strategy for protecting against fibrosis in patients with chronic liver diseases. (Hepatology 2004;39:365-375.)
Detection and identification of tumor-associated protein variants in human hepatocellular carcinomas
Authors: Zeindl-Eberhart Evelyn , Haraida Sibylle , Liebmann Sibylle , Jungblut Peter Roman , Lamer Stephanie , Mayer Doris , Jäger Gundula , Chung Stephen , Rabes Hartmut Manfred
Published: February 2004

The proteomic approach is a valuable tool to detect and identify proteins that are associated with cancer. In previous investigations on experimentally induced rat hepatomas, we detected aldose reductase-like protein (ARLP) as a highly significant marker protein. Our present study was intended to look for the presence of similar tumor-associated marker proteins on human hepatocellular carcinomas (HCC). We found several novel tumor-associated protein variants that represent members of the aldo-keto reductase (AKR) superfamily. Human aldose reductase-like protein-1 (hARLP-1) was the most prominent tumor-associated AKR member detected in HCC by 2-dimensional electrophoresis (2-DE) and identified by mass spectrometric fingerprinting. The enzyme was found in 4 distinct forms (hARLP-1, 36/7.4 (kd/pI); hARLP-2, 36/7.2; hARLP-3, 36/6.4; and hARLP-4, 33/7.35). In addition, a human aldose reductase-like protein (hARLP-5, 36/7.6) was identified that differed from hARLP-1 by 1 amino acid (D313N), indicating 2 allelic forms of the human aldose reductase-like gene. A novel antibody directed against common parts of the hARLPs revealed hARLP reactivity in human HCC by immunohistochemistry. Furthermore, aldose reductase (AR) was identified and characterized as a tumor-associated variant. In conclusion, in all investigated human HCCs at least one of the various types of the described tumor-associated proteins of the AKR superfamily was clearly present. Of these HCC samples, 95% were positive for hARLPs as proven by 2-DE analysis and/or by use of the antibody directed against hARLP. Thus, hARLP is a strong candidate for use as an immunohistochemical diagnostic marker of human HCC. (Hepatology 2004;39:540-549.)
Determinants of survival and the effect of portosystemic shunting in patients with Budd-Chiari syndrome
Authors: Murad Sarwa Darwish , Valla Dominique-Charles , de Groen Piet C. , Zeitoun Guy , Hopmans Judith A.M. , Haagsma Elizabeth B. , van Hoek Bart , Hansen Bettina E. , Rosendaal Frits R. , Janssen Harry L.A.
Published: February 2004

Budd-Chiari syndrome (BCS) is a rare disorder that is characterized by hepatic venous outflow obstruction. The aim of this study was to assess determinants of survival and to evaluate the effect of portosystemic shunting. In this international multicenter study, 237 patients with BCS, diagnosed between 1984 and 2001, were investigated. Univariate, multivariate, and time-dependent Cox regression analyses were performed. Overall survival at 1, 5, and 10 years was 82% (95% CI, 77%-87%), 69% (95% CI, 62%-76%), and 62% (95% CI, 54%-70%), respectively. Encephalopathy, ascites, prothrombin time, and bilirubin were independent determinants of survival. A prognostic classification combining these factors could identify three classes of patients (classes I-III). The 5-year survival rate was 89% (95% CI, 79%-99%) for class I, 74% (95% CI, 65%-83%) for class II, and 42% (95% CI, 28%-56%) for class III. Anticoagulants were administered to 72%; only for patients in class I was this associated with a trend toward improved survival (relative risk [RR], 0.14; 95% CI, 0.02-1.21). Portosystemic shunting was performed in 49% of the patients (n = 117); only for patients in class II, time-dependent analyses suggested an improved survival (RR, 0.63; 95% CI, 0.26-1.49). In conclusion, at the time of diagnosis, patients with BCS can be classified into good (I), intermediate (II), and poor (III) prognostic classes, according to simple baseline clinical and laboratory parameters. Our results suggest an improved survival after surgical portosystemic shunting for patients with an intermediate prognosis (class II). (Hepatology 2004;39:500-508.)
Effect of peginterferon alfa-2a on liver histology in chronic hepatitis C: A meta-analysis of individual patient data
Authors: Cammà Calogero , Di Bona Danilo , Schepis Filippo , Heathcote Jenny E. , Zeuzem Stefan , Pockros Paul J. , Marcellin Patrick , Balart Luis , Alberti Alfredo , Craxì Antonio
Published: February 2004

Multicenter randomized trials have shown that once-weekly pegylated interferon (peginterferon) alfa-2a is more efficacious than conventional interferon alfa-2a (IFN) in patients with chronic hepatitis C. We performed a meta-analysis of 1,013 previously untreated patients (from 3 randomized trials) with pretreatment and post-treatment liver biopsies to assess the differences between peginterferon alfa-2a and IFN in terms of their effects on liver histology. Reported values were standardized mean differences (SMD) between patients receiving peginterferon alfa-2a and those receiving IFN (post-treatment value minus baseline value for each group). We used a random-effects model to quantify the average effect of peginterferon alfa-2a on liver histology. Peginterferon alfa-2a significantly reduced fibrosis compared with IFN (SMD, −0.14; 95% CI: −0.27, −0.01; P = .04). A reduction in fibrosis was observed among sustained virologic responders (SMD, −0.59; 95% CI: −0.89, −0.30; P < .0001) and patients with recurrent disease (SMD, −0.34; 95% CI: −0.54, −0.14; P = .0007), whereas no significant reduction was observed among nonresponders (SMD, −0.13; 95% CI: −0.32, 0.05; P = .15). Logistic regression analysis indicated that patients with sustained virologic responses (SVRs) had an odds ratio (OR) of 1.61 (95% CI: 1.14, 2.29) for reduction in fibrosis compared with patients without SVRs, whereas obese patients (body mass index [BMI] > 30 kg/m2) had an OR of 0.56 (95% CI: 0.35, 0.90) compared with normal-weight (BMI < 25 kg/m2) and overweight patients (BMI, 25-30 kg/m2). In conclusion, in patients with chronic hepatitis C with or without cirrhosis, peginterferon alfa-2a (relative to IFN) significantly reduced fibrosis. The beneficial effects of peginterferon on liver histology are closely related to virologic response. (Hepatology 2004;39:333-342.)
Structured treatment interruption in patients with alveolar echinococcosis
Authors: Reuter Stefan , Buck Andreas , Manfras Burkhard , Kratzer Wolfgang , Seitz Hanns Martin , Darge Kassa , Reske Sven Norbert , Kern Peter
Published: February 2004

In human alveolar echinococcosis (AE), benzimidazoles are given throughout life because they are only parasitostatic. It has been a longstanding goal to limit treatment, and recent reports suggest that, in selected cases, benzimidazoles may be parasitocidal. Previously, we showed that positron -emission tomography (PET) using [18F]fluoro-deoxyglucose discriminates active from inactive lesions in AE. We have now performed a 3-year prospective study in 23 patients and conducted a structured treatment interruption in those without signs of PET activity. Disease progression was further assessed by ultrasound, computerized tomography, laboratory parameters, and clinical examination.We found PET-negative lesions in 15 of 23 patients and benzimidazoles were discontinued in these patients. After 18 months, patients were reevaluated, and, of the 15 initially PET-negative patients, 8 showed either new activity on PET (n = 6) or signs of clinical progression (n = 2). Reinitiation of benzimidazoles halted parasite growth again. No further progression was detected after 36 months. PET had a sensitivity of 91% for the detection of active lesions. In conclusion, despite successful suppression of metabolic activity, in most cases benzimidazoles do not kill the parasite. PET is a reliable tool for assessing metabolic activity and for timely detection of relapses. Neither duration of treatment, kind of treatment, lesion size, calcifications, or regressive changes reliably indicate parasite death. We discourage the discontinuation of benzimidazoles in inoperable AE even after many years of treatment. However, patients with a poor compliance of benzimidazole intake or patients suffering from side effects to benzimidazoles might be assessed for PET negativity. If permanent discontinuation of benzimidazoles is attempted, the course of disease should be followed by PET. (Hepatology 2004;39:509-517.)
How fairness perceptions make innovative behavior more or less stressful
Authors: Janssen Onne
Published: February 2004

The purpose of this study was to examine how perceptions of distributive and procedural fairness moderate the relationship between innovative behavior and stress. The results of a survey carried out among 118 first‐line managers from six organizations in the public health domain demonstrated that innovative behavior was positively related to the stress reactions of job‐related anxiety and burnout only when levels of both distributive fairness and procedural fairness were low. Copyright © 2004 John Wiley & Sons, Ltd.
The relationship between individual creativity and team creativity: aggregating across people and time
Authors: Pirola‐Merlo Andrew , Mann Leon
Published: February 2004

This paper investigates how the creativity of individual team members is related to team creativity, and the influence of climate for creativity in the workplace on individual and team creativity. A multilevel theoretical model is proposed, and the authors report a study which tests the model using a sample of 54 research and development teams. The results showed that team creativity scores could be explained statistically by aggregation processes across both people and time. Team creativity at a particular point in time could be explained as either the average or a weighted average of team member creativity; the creativity of project outcomes was explained by either the maximum of or average of team creativity across time‐points. According to the model, failure to account for aggregation across time as well as across individuals can result in misleading empirical results, and can result in the erroneous conclusion that team climate influences team creativity directly rather than indirectly via individuals. Copyright © 2004 John Wiley & Sons, Ltd.
Intra‐seasonal variability of wintertime temperature over East Asia
Authors: Gong Dao‐Yi , Ho Chang‐Hoi
Published: February 2004

There has been a profound warming over East Asia during the winter months (November through to March) over the past few decades. The goal of this study is to address the question of whether the daily temperature has become more variable in conjunction with this warming by using observed temperature data obtained from 155 Chinese and Korean stations. Prior to the analysis, the annual cycle is removed to obtain daily temperature anomalies for each winter for each station. Results show that the intra‐seasonal variance generally decreases, implying that the daily temperatures are becoming less variable. Considering all stations as a whole, the rate of change is −0.49°C2 per decade (equivalent to −3.59% per decade). The changes are more robust in the northeastern portion of China. In contrast, there are no dominant trends for the skewness coefficients, except for clear negatively skewed trends in northeastern China. These results are consistent with an increase in the number of extremely cold events. Over the region, the frequency of low‐temperature extremes (as low as below minus two standard deviations) increases at a rate of change of 0.26 days per decade, significant at the 95% confidence level. Both the Siberian high and Arctic oscillation (AO) exert a notable influence on the temperature variance. Intra‐seasonal variance of the Siberian high and AO are significantly correlated with the temperature variance, whereas the seasonal mean state of the AO affects the temperature variance by modulating the high‐frequency components of the Siberian high. The intra‐seasonal variance of the Siberian high tends to decline at a rate of change of −10.7% per decade, significant at the 99% level; meanwhile, the mean wintertime AOs have strengthened in the last few decades. These two climate features together make a considerable contribution to the changes in intra‐seasonal temperature variance in East Asia. Copyright © 2004 Royal Meteorological Society
Impact of sea‐surface temperature anomalies in the equatorial Indian Ocean and western Pacific on the Asian summer monsoon in three general circulation models
Authors: Tschuck P. , Chauvin F. , Dong B. , Arpe K.
Published: February 2004

The sensitivities of the Asian summer monsoon to sea‐surface temperature (SST) anomalies in the equatorial Indian Ocean and the western Pacific are compared in three different general circulation models (ARPÈGE, ECHAM, UGAMP). The impacts to idealized anomalies of 1 K show common features, notably a weaker monsoon for warm equatorial Indian Ocean SSTs. For a warm western Pacific, the impact over India shows a dipole structure with increases in the southern part and decreases in the northern part for the ECHAM and UGAMP models, with ARPÈGE showing a different response. The models also disagree on the linearity of the impact. The response to cold anomalies is nearly the same, with opposite sign, as for warm anomalies in the ECHAM model but is non‐linear in the ARPÈGE and UGAMP models. The study underlines the need for accurate measurements of the regional SSTs, which are as equally important for local rainfall as the remote large‐scale impact from the El Niño–Southern Ocean oscillation. Copyright © 2004 Royal Meteorological Society
Pitch angle dispersion of ion injections
Authors: Anderson B. J. , Takahashi K.
Published: February 2004

Substorm‐injected particles are time dispersed with pitch angle such that low pitch angle particles arrive earliest on the dayside at geosynchronous orbit, opposite the sense predicted by drift in a dipole field. In contrast to energy dispersion which is well understood, pitch angle dispersion of particle injections has not been quantitatively explained. We present a statistical analysis of energetic ion injections observed by the Active Magnetospheric Particle Tracer Explorers/Charge Composition Explorer (AMPTE/CCE) satellite, and we compare the results with model calculations of single‐particle drift in realistic model magnetospheric electric and magnetic fields. The data analysis is based on observations made from August 1984 to February 1986, which cover all local times, radial distances between 5.5 and 8.8 RE, and dipole latitudes between −16° and 16° and includes over 400 events mostly beyond 8 RE. Using events observed between L = 8 and L = 9, where the effects of the satellite radial motion are minimal, we study the local time dependence of the injection delay time between different energies and pitch angles. We find that high pitch angle injection is delayed from low pitch angle injection and that the delay increases westward from the evening sector reaching ∼2 min (67° versus 23° pitch angles) at 1200 magnetic local time (MLT) at 120–220 keV. The observations are compared to proton drift calculations in static magnetic (T89c) and electric (Volland‐Stern) field models. The calculations reproduce the observed drift times, pitch angle dispersion, and local time dependences, showing for the first time that sufficiently realistic magnetospheric magnetic field models can account for reverse pitch angle dispersion. Detailed examination of the curvature and gradient drift terms shows that the pitch angle dispersion is due principally to compression of the dayside magnetosphere, which preferentially suppresses the gradient and curvature drifts of near equatorially mirroring particles.
Kinetic properties of solar wind minor ions and protons measured with SOHO/CELIAS
Authors: Hefti S. , Grünwaldt H. , Ipavich F. M. , Bochsler P. , Hovestadt D. , Aellig M. R. , Hilchenbach M. , Kallenbach R. , Galvin A. B. , Geiss J. , Gliem F. , Gloeckler G. , Klecker B. , Marsch E. , Möbius E. , Neugebauer M. , Wurz P.
Published: February 2004

Using observations of the Charge Time‐of‐Flight(CTOF) charge and mass spectrometer of the Charge, Element and Isotope Analysis System (CELIAS), and of CELIAS/proton monitor on board the Solar and Heliospheric Observatory (SOHO), we present an overview of speeds and kinetic temperatures of minor ions and protons in the solar wind near solar minimum, covering the Carrington Rotations 1908 to 1912. In the case of a collision‐dominated solar wind the speed of minor ions is expected to be lower or equal to the speed of the protons, and all species are expected to have equal temperatures. On the other hand, minor ions can be accelerated and heated by wave‐particle interaction. In this case, equal thermal speeds of all species are expected. CTOF data allow the determination of the kinetic parameters of various ions with high accuracy and with high time resolution. The mean O6+ speed of the observed period is 390 km s−1. The speeds of Si7+ and Fe9+ correlate well with O6+, the linear correlation coefficient being 0.96 or higher. Our results also indicate that silicon and iron tend to lag behind oxygen with a speed difference of ∼20 km s−1 at 500 km s−1. At the same time, the kinetic temperature of the ions under investigation exhibit the well‐known mass proportionality, which is attributed to wave‐particle interactions. During the period of low solar activity in consideration, many cases are observed where the kinetic temperature is extraordinarily low (104 K for O6+).
Kinetic theory of the drift kink instability in a current sheet
Authors: Daughton William
Published: February 2004

The linear stability of a current sheet is of interest in connection with the dynamics of the magnetotail and in particular as a triggering mechanism for substorms. Until recently, most theoretical work in this area has concentrated on the collisionless tearing mode. Recent simulations suggest that for thin current sheets another long wavelength electromagnetic mode, the so‐called drift kink instability, may also be of importance. The linear stability analysis for a Harris‐type equilibrium is formulated using a kinetic description for both ions and electrons. The orbit integrals are treated numerically using the exact unperturbed particle orbits and including the global structure of the perturbation inside the integral. It is found that the drift kink has a significant electrostatic component which strongly alters the mode structure and real frequency relative to the case of a purely electromagnetic mode. The resulting growth rates, mode structure and parametric dependences are presented and compared with previous results. The effect of finite parallel wavelength is considered, and the relevance of the drift kink mode to the magnetotail is discussed.
Multistation measurements of Pc5 geomagnetic power amplitudes at high latitudes
Authors: Ballatore Paola , Lanzerotti Louis J. , Maclennan Carol G.
Published: February 2004

Geomagnetic data from four Antarctic stations, located at −80 corrected geomagnetic (CGM) latitude, have been analyzed. The magnetic local time (MLT) occurrence distributions and seasonal dependence of geomagnetic power levels in the Pc5 frequency band are studied. It is found that the pulsation power can be significantly influenced by the MLT location of the station at the specific UT time considered, regardless of interplanetary conditions or geomagnetic activity. A shift of power amplitudes toward higher values is found during local summer, likely in association with the increased ionospheric conductance. The local dayside summer increase of power relative to the winter condition is higher than on the nightside. This finding is explained by the magnetospheric cusp influence on the production of geomagnetic power.
Seafloor geomagnetic vector anomaly of the intersection of the Mid‐Atlantic Ridge and the Kane Transform Fault: Implications for magnetization of the oceanic crust
Authors: Fujiwara Toshiya , Fujimoto Hiromi
Published: February 2004

We investigated the fine‐scale magnetic structure of the oceanic crust and upper mantle around the western intersection of the Mid‐Alantic Ridge and the Kane Transform Fault, using the geomagnetic vector field measured at the seafloor. The strikes of magnetic boundaries were found to reflect of the local tectonics represented by fault strikes and dips. The ridge‐transform intersection is characterized by magnetic boundary strikes rotated eastward. The strike directions reflect the direction of recent magmatic activity. These indicate that a few traces of faults extending obliquely from the ridge axis to the transform fault are associated with neovolcanism. Magnetic boundary strikes in the lower part of the transform valley wall and near a linear trace of the transform fault indicate deformation or tilting of the crust associated with transform faulting. It is also indicated that the crustal block around the median ridge is tilted by uplift, accompanied by injection or emplacement and serpentinization of peridotites. The nodal basin consists of extrusive basalts in the E–W direction and N–S trending magnetic strikes. Submersible observation of in situ magnetization of oceanic crust shows that extrusive basalts are typically strongly magnetized. The most recent neovolcanic ridge has a mean magnetization of 50 A/m. The mean magnetization of the ridge axis is 20 A/m. The magnetization of the 3 Ma ridge flank in the inside corner high is about 10 A/m. The gabbroic layer in the transform valley has a magnetization less than 2 A/m. The serpentinized peridotites in the median ridge have magnetization less than 1 A/m. This magnetization records a reversal in polarity, which is important because the serpentinized peridotites contribute to the marine geomagnetic anomaly pattern.
Thermal and dynamic modeling of deep subduction of a spreading center: Implications for the fate of the subducted Chile Rise, southern Chile
Authors: Daniel Andy J. , Kusznir Nick J. , Styles Peter
Published: February 2004

Our objective is to determine whether the Chile Rise spreading center, currently subducting south of the Chile Triple Junction in southern Chile, continues or ceases to separate after subduction. A two‐dimensional kinematic thermal model is used to predict the temperature history of the subduction zone during spreading center subduction. Density anomalies, calculated from the temperature fields of the thermal model, are then used to define body forces that drive the motion of a dynamic viscous fluid model of spreading center subduction. Viscous models that include only local inplane driving forces predict that the Chile Rise spreading center ceases to separate after ridge subduction. If global in‐plane plate forces are also included in the viscous model, continuing separation of the subducted Chile Rise is predicted, but at a greatly diminished rate. Fully continuing separation of the subducted Chile Rise only occurs if the subducted Nazca and Antarctic plates remain rigid, allowing the lateral transmission of global plate forces from along strike; however, this situation is unlikely as young subducted plates are believed to fragment. Continuing separation but at a greatly diminished rate is believed to be the most plausible hypothesis for spreading center subduction in southern Chile. Dynamic viscous modeling of subduction in the central Andes suggests a viscosity of 2.5×1020 Pa s for upper mantle above the 400 km phase transition.
Saturated heat conduction and Joule heating in the Venus ionosphere by 100 Hz fields
Authors: Cole K. D.
Published: February 2004

The ratio of the Joule heating and conduction cooling terms in the macroscopic energy equation of electrons in an ionized gas is examined under conditions which may include saturation of the heat flux. The saturation flux may be represented in an approximation, sufficient for our purposes, by a quantity αnkT(kT/m)0.5, where n, T, and m are, respectively, the electron density, temperature, and mass, and α may be of the order of 0.1. Consequences of this assumption are developed for application to the question of Joule heating of electrons by 100 Hz electric fields in the Venus ionosphere. When saturation exists, there can be large overestimates of the conduction cooling, and corresponding underestimates of the temperature, if the classical Spitzer‐Harm formula is employed. A minimal reduction factor to apply to this cooling rate is presented. Taking into account both the existence of saturation and the burst nature of the 100 Hz fields, it is shown that Joule heating by observed fields may balance conduction cooling in parts of the Venus ionosphere. In particular, this occurs at, and somewhat below, high Venus ionopauses. It is suggested that more research on these regions may add to our knowledge of saturation.
Reconsidering the inverted‐V particle signature: Relative frequency of large‐scale electron acceleration events
Authors: Newell Patrick T.
Published: February 2004

The shape of auroral zone large‐scale electron acceleration events is widely described as an inverted V, with the spectral peak gradually rising to and falling from the spatially central peak. We investigated the relative frequency of all sharp (≥3) electron energy flux enhancement events which are large‐scale enough to be resolvable in the DMSP F7 particle data set. The first three days of each month of 1984 were studied, amounting to 355 passes through the nightside oval (restricted to the range 2000–2300 magnetic local time (MLT)) with a total of 1049 such events. Only 42 of these 1049 events actually fit the inverted‐V morphology, with another 76 cases fitting an extremely loose definition of an inverted V. Thus, between 4.0 and 11% of all sharp energy flux enhancements are inverted Vs, depending on the strictness of the criteria. In that subset of events for which electrostatic acceleration is likely, namely those which have monoenergetic peaks and which extend over 20 km or more, inverted Vs are still just 10–29% of the total. More common are events which have relatively constant “monoenergetic peaks” (accelerating potentials). A crucial feature common to all non‐V forms with monoenergetic peaks is that the maximum accelerating potential (spectral peak) is observed near one edge or both. Thus very large gradients in the potential exist near the edges of large‐scale auroral forms, implying much larger electric fields than does an inverted V. The present study thus supports earlier evidence that the important physics of auroral arcs is associated with the edge of the arcs, rather than the central portion of the acceleration region. The most common type of energy flux enhancement event is a broad spectral enhancement (suprathermal burst). Contrary to popular perception, suprathermal bursts are not always narrowly confined in latitude. All categories of sharp electron energy flux enhancement events studied here exhibited a sharp high‐energy drop off near the spectral peak, suggesting acceleration of one type or another (either wave‐particle or electrostatic).
Effect of magnetic discontinuities on the propagation of energetic particles: Ulysses observations of the onset of the March 1991 solar particle event
Authors: Sanderson T. R. , Erdös G. , Balogh A. , Forsyth R. J. , Marsden R. G. , Gosling J. T. , Phillips J. L. , Tranquille C.
Published: February 2004

We present observations of energetic ions from the Cosmic Ray and Solar Particle Investigation (COSPIN) and Heliosphere Instrument for Spectra Composition and Anisotropy at Low Energy (HISCALE) instruments on board the Ulysses spacecraft. We examine in detail the onset of energetic ions observed during the March 1991 series of solar events. Active region 6555, at E28 at 2247 UT on March 22, 1991 (day 81), was most likely responsible for the high‐energy protons subsequently seen at Ulysses. A slow increase in the high‐energy (∼50 MeV) proton intensity, made up of many small but rapid intensity increases, began around 9 hours after the onset of the event, taking 1.5 days to reach maximum intensity. On the flank, and in front of a coronal mass ejection (CME), coming from a previous event, we observed a region with a drop in the magnetic field strength. This region was populated with hot shocked plasma and, owing to the low magnetic field pressure, had an ion plasma beta >1. Mirror mode waves, with discontinuities appearing at the edges of the waves, produced a larger‐than‐average number of magnetic field discontinuities, a large fraction of the discontinuities being aligned with their normals oriented along the radial direction, suggesting that they were being convected outward by the CME. These discontinuities acted as a series of barriers to the propagation of the energetic solar particles coming from the solar event, delaying substantially the onset of the particle event at Ulysses.
“Blob” analysis of auroral substorm dynamics
Authors: Carbary J. F. , Liou K. , Lui A. T. Y. , Newell P. T. , Meng C. I.
Published: February 2004

One month's worth of Polar ultraviolet imager (UVI) data were subjected to a “blob” analysis to determine the statistical dynamics of substorm features observed in the Lyman‐Birge‐Hopfield long (LBHL) band (152–188 nm). Adapted from similar DoD analyses of target images, the analysis consists of finding, on a frame‐by‐frame basis beginning at substorm onset, the following aspects of an individual auroral feature: peak power (i.e., power of precipitating electrons), total power, centroid location (magnetic local time (MLT) and magnetic latitude (MLAT), and speed of centroid. Over 120 individual auroral features were successfully acquired at onset and tracked until dissipation during January 1997. The power in the peak pixel and total power were random in time but displayed transient spikes that lasted 5–10 min. Over the course of a substorm, the total energy of blobs averaged ∼2.0 − 104 GJ. A histogram of these energies suggests no preferred energy but that lower energies were more common than higher energies. Analysis of the blob positional dynamics generally supports a poleward and westward movement. During the course of a substorm, 90% of the blobs moved poleward, while over 60% moved westward. However, these movements were not steady and displayed random components. Furthermore, a sizable minority (∼35%) of the blobs moved eastward, which does not agree with the conventional picture of auroral surges. Blob speeds varied from essentially zero up to several kilometers per second. However, during the January substorms the blobs did appear to have a preferred speed of 0.84 ± 0.34 km s−1.
Global core plasma model
Authors: Gallagher D. L. , Craven P. D. , Comfort R. H.
Published: February 2004

The global core plasma model (GCPM) provides empirically derived core plasma density as a function of geomagnetic and solar conditions throughout the inner magnetosphere. It is continuous in value and gradient and is composed of separate models for the ionosphere, plasmasphere, plasmapause, trough, and polar cap. The relative composition of plasmaspheric H+, He+, and O+ is included in the GCPM. A blunt plasmaspheric bulge and rotation of the bulge with changing geomagnetic conditions is included. The GCPM is an amalgam of density models intended to serve as a framework for continued improvement as new measurements become available and are used to characterize core plasma density, composition, and temperature.
The dc electrical coupling of flow vortices and flow channels in the magnetosphere to the resistive ionosphere
Authors: Borovsky Joseph E. , Bonnell John
Published: February 2004

The dc electrical coupling of magnetospheric flow vortices and magnetospheric flow channels to the ionosphere is numerically calculated. The equations governing the coupling are derived from current continuity plus Ohm's laws taken for the regions of field‐aligned current between the ionosphere and magnetosphere and for the Pedersen layer of the ionosphere. For vortices the strength of the coupling (as measured by fractional penetration of the magnetospheric electric fields down to the ionosphere and by the amount of power dissipation) varies, as expected, with the size of the vortex footprint in the ionosphere. However, because of the diode‐like nature of the field‐aligned currents, the coupling also varies with sign of the vorticity: Positive center vortices (vorticity antiparallel to
) couple much more strongly than do negative center vortices (vorticity parallel to
). Negative center vortices tend to dissipate most of their energy in parallel currents, whereas positive center vortices dissipate most of their energy in Pedersen currents. The electric fields of positive center vortices spread across
as they connect to the ionosphere, whereas the electric fields of negative center vortices stay confined to their magnetic footprints. Consequently, positive center vortices in the magnetosphere produce quasi‐circular vortices of flow in the ionosphere whereas negative center vortices in the magnetosphere produce narrow east‐west‐elongated vortices of flow in the ionosphere. Negative center vortices in the magnetosphere could produce east‐west‐aligned bright arclike features, and positive center vortices could produce east‐west‐aligned black‐arc features imbedded in large circular patches of aurora. Flow channels in the magnetosphere drive field‐aligned currents into the ionosphere: The upward field‐aligned current on the negative‐charged edge of the channel tends to spread across
, whereas downward current on the positive charge edge tends to stay confined. In the magnetosphere the current spreading results in a back emf that produces a backward flow outside the flow channel on the negative‐charged edge.
Observations of plasmas in the Io torus with the Galileo spacecraft
Authors: Frank L. A. , Paterson W. R.
Published: February 2004

On December 7, 1995, the Galileo spacecraft passed through the Io torus near the magnetic equatorial plane of Jupiter. High– resolution measurements of positive ions and electrons in the energy/charge (E/Q) range of 0.9 V to 52 kV were acquired over the jovicentric radial distances of 5.6 to 7.8 Rj. At radial distances beyond Io's orbit at 5.9 Rj the plasma instrument (PLS) observed intense magnetically field‐aligned beams of electrons with average energies of hundreds of eV to several keV. The directional energy fluxes at the spacecraft position ranged from ∼1.5 to 90 erg cm−2S−1sr−1 in directions parallel and antiparallel to the magnetic field. The corresponding range of energy fluxes into Jupiter's ionosphere was ∼9 to 560 erg Cm−2s−1, sufficient for the production of auroral emissions at far‐ultraviolet wavelengths with brightnesses in the range of 0.06 to 3 mega‐Rayleighs. The largest energy fluxes were observed at ∼7.8 Rj and were comparable to those observed during the close flyby of Io. The torus plasmas were observed to rigidly corotate with Jupiter out to a radial distance of ∼7 Rj and are slower at greater radial distances. Fluctuations of the bulk ion speeds and densities were found to be superposed upon the general pattern of corotation and are suggestive of interchange of magnetic flux tubes in the plasma torus. For an isolated field‐aligned electron beam, the radial component of plasma flow was directed toward Jupiter at a speed of ∼4 km s−1. The other electron beams also occurred coincidentally with the fluctuations in the radial component of flow. The observations of these low‐energy electron beams are consistent with the absence of magnetically field‐aligned acceleration of electrons into Jupiter's ionosphere. The electron acceleration appears to be due to intense heating of the ionospheric plasmas associated with large currents driven by the interchange motions in the torus plasmas.
Anomalous cosmic ray argon and other rare elements at 1‐4 MeV/nucleon trapped within the Earth's magnetosphere
Authors: Mazur J. E. , Mason G. M. , Blake J. B. , Klecker B. , Leske R. A. , Looper M. D. , Mewaldt R. A.
Published: February 2004

We summarize over 6 years of observations of ∼1–4 MeV/nucleon heavy ions trapped in the Earth's magnetosphere on L shells of 1.7–3. We obtained these new results in low Earth orbit with the SAMPEX spacecraft; they extend the observations of trapped heavy ions in this L range to much lower energies than had previously been examined in detail. At 1–4 MeV/nucleon we observed a trapped population with a peak intensity near L∼2.3 that includes the anomalous cosmic ray species O, Ne, and Ar also observed in interplanetary space at 1 AU. We also found elements with low first ionization potential (C, Mg‐S, and Fe) trapped with the same spatial distribution. The low‐energy trapped population increased in intensity between 1996 and 1997, roughly during solar minimum and minimum geomagnetic activity. It is possible that the 1–4 MeV/nucleon trapped population originates from a number of sources, including high‐energy trapped anomalous cosmic rays that have lost energy in the residual atmosphere in the case of O and Ne, and directly incident, singly charged anomalous cosmic rays that have become stripped and subsequently trapped in the case of Ar. The group of trapped elements with low first ionization potential (C, Mg‐S, and Fe) have roughly solar wind abundances relative to one another, suggesting a possible link between this trapped component and recently discovered solar wind pickup ions released from dust grains within the inner heliosphere.
On the evolution of outward and inward Alfvénic fluctuations in the polar wind
Authors: Bavassano B. , Pietropaolo E. , Bruno R.
Published: February 2004

Plasma and magnetic field measurements by Ulysses are used to investigate the radial evolution of hourly‐scale Alfvénic fluctuations in the polar wind. The data span from 1.4 to 4.3 AU in heliocentric distance. Different radial regimes at different distances emerge. Inside about 2.5 AU the large outward traveling fluctuations decrease faster, in terms of energy per unit mass, than the small inward ones. This is in agreement with previous low‐latitude observations inside 1 AU within the trailing edge of fast streams. As a result of this different gradient the ratio of inward to outward fluctuation energy rises to about 0.5 near 2.5 AU. Beyond this distance the radial gradient of the inward fluctuations becomes increasingly steeper, while that of the outward ones does not vary appreciably. A state is quickly reached where both populations decline at almost the same rate. These results on the behavior of outward and inward Alfvénic fluctuations are new and represent a constraint for models of turbulence evolution in steadily expanding flows like the polar wind. Finally, an extrapolation to regions near the Sun would suggest that Alfvénic fluctuations at hourly scale should not play a relevant role in solar wind heating and acceleration. Obviously, this last conclusion may be invalidated by non‐WKB effects and by compressive and dissipative processess close to the Sun.
A conjugate study of Pc3–4 pulsations at cusp latitudes: Is there a clock angle effect?
Authors: Engebretson M. J. , Cobian R. K. , Posch J. L. , Arnoldy R. L.
Published: February 2004

Pc3–4 (15–50 mHz) pulsations are often observed during daytime hours in the Earth's magnetosphere and on the ground. The ion foreshock region of the solar wind upstream of Earth is now understood to be a major source of these waves, and the general dependence of their occurrence in the magnetosphere on the cone angle of the interplanetary magnetic field (IMF) is well attested. However, there have also been suggestions that the IMF clock angle should introduce latitudinal or local time asymmetries in wave occurrence, and in particular, that Pc3–4 pulsations might preferentially reach northern versus southern high‐latitude regions. In order to test this latter suggestion, we have compared a full year's (1997) data from two cusp‐latitude stations, Sondrestromfjord, Greenland, and South Pole, Antarctica, both near 74° corrected geomagnetic latitude. Our data show the usual strong IMF cone angle control of Pc3–4 wave occurrence/amplitude but also indicate that occurrence and relative amplitude are essentially identical near both cusps; any clock angle control is at most a second‐order effect, not detectable in our analysis. We further find little seasonal dependence in the ratio of power in the two cusp regions other than that attributable to differences in solar illumination. These observations, in conjunction with the well‐known sharp cutoff in wave activity for cone angles above 45°, indicate that only those perturbations occurring at the subsolar bow shock can reach the magnetopause and propagate to any location in the dayside magnetosphere. In addition, the absence of a clock angle effect supports earlier suggestions that Pc3–4 signals in the magnetosheath do not cross streamlines and thus do not propagate as waves, but are rather convected as spatial structures in the highly turbulent, high‐beta downstream magnetosheath plasma.
Model study of ionospheric dynamics during a substorm
Authors: Zhu L. , Schunk R. W. , Sojka J. J. , David M.
Published: February 2004

A global substorm electrodynamic model and a global ionospheric model were coupled in order to study ionospheric dynamics during substorms, with the focus on small‐scale substorm electrodynamic and plasma structures. The simulation results show that in the expansion phase, structured precipitation and channeled field‐aligned currents quickly develop in the substorm onset region. The Hall and Pedersen conductance ratio in the region increases significantly, and the magnetospheric field‐aligned currents are mainly closed by highly structured Hall currents. Correspondingly, the plasma in the ionosphere also undergoes significant changes during a substorm and is highly structured in both the horizontal and vertical directions. In the substorm onset region, there are spatially separated small‐scale Ti and Te hot spots, downward ExB drifts, decreased total electron contents, and a lowered ionosphere. Also, there is a significant O+ → NO+ conversion, leading to a great increase of NO+ and a lowering of the O+ peak height. These small‐scale electrodynamic and plasma structures are very important for more realistically simulating the ionospheric dynamics during substorms. These results not only help to elucidate the multiscale ionospheric responses to substorms but also provide a theoretical guidance and cautions for the interpretation of various substorm observational data.