bluuebunny/crossref_metadata_2025 huggingface dataset:
Heme oxygenase‐1 induction by endogenous nitric oxide: influence of intracellular glutathione
Authors: André Muriel , Felley-Bosco Emanuela
Published: June 2003

To investigate the influence of glutathione (GSH) on cellular effects of nitric oxide (NO) formation, human colon adenocarcinoma cells were transfected with a vector allowing controlled expression of inducible nitric oxide synthase (iNOS). Protein levels of oxidative stress‐sensitive heme oxygenase‐1 (HO‐1) were analyzed in the presence or absence of GSH depletion using L‐buthionine‐[S,R]‐sulfoximine and iNOS induction. While no effect was observed in the presence of iNOS activity alone, a synergistic effect on HO‐1 expression was observed in the presence of iNOS expression and GSH depletion. This effect was prevented by addition of N‐methyl‐L‐arginine. Therefore, targeting of endogenous NO may be modulated by intracellular GSH.
Neutrophil elastase up‐regulates human β‐defensin‐2 expression in human bronchial epithelial cells
Authors: Griffin Siobhan , Taggart Clifford C. , Greene Catherine M. , O'Neill Shane , McElvaney Noel G.
Published: June 2003

Human β‐defensin‐2 (HBD‐2) gene expression is induced by tumour necrosis factor‐α, interleukin‐1β and lipopolysaccharide. The objective of this study was to investigate the effect of neutrophil elastase (NE), a major pro‐inflammatory protease, on HBD‐2 expression. HBD‐2 gene expression was assessed by reverse transcription polymerase chain reaction in the human bronchial epithelial cell line 16HBE14o− and primary normal human bronchial epithelial (NHBE) cells. Optimal HBD‐2 expression was induced with 100 nM NE. Using a HBD‐2‐luciferase reporter construct, luciferase activity increased significantly in 16HBE14o− cells following incubation with NE. An increase in HBD‐2 protein expression was observed in primary NHBE cells after incubation with NE as assessed by laser scanning cytometry. In conclusion, NE up‐regulates HBD‐2 expression in bronchial epithelial cells.
Hepatic expression of PPARα, a molecular target of fibrates, is regulated during inflammation in a gender‐specific manner
Authors: Tai E.Shyong , bin Ali Azhar , Zhang Qian , Loh Lih Ming , Tan Chee Eng , Retnam Leslie , El Oakley Reida Menshawe , Lim Sai-Kiang
Published: June 2003

Dyslipidemia, inflammation and gender are major risk factors in cardiovascular disease. Here we show that hepatic expression of Peroxisome proliferator‐activated receptor α (PPARα), a nuclear receptor that regulates lipid metabolism and inflammation, is regulated in a gender‐specific manner during lipopolysaccharide (LPS)‐induced systemic inflammation. Immediately following LPS‐induced systemic inflammation, hepatic PPARα mRNA level decreased dramatically in mice. It was restored to baseline within 24 h in females but remained below baseline for >72 h in male mice. In gonadectomized mice of both sexes, PPARα mRNA level was restored to baseline within 48 h after the initial decrease.
Identification of hepatic peroxisomal phospholipase A2and characterization of arachidonic acid‐containing choline glycerophospholipids in hepatic peroxisomes
Authors: Yang Jingyue , Han Xianlin , Gross Richard W
Published: June 2003

Recently, a sequence encoding a novel mammalian calcium‐independent phospholipase A2(iPLA2γ) was identified in the human genome and subsequently cloned and expressed in Sf9 insect cells. Unexpectedly, expression studies in recombinant systems demonstrated the usage of multiple translation initiation codons resulting in different polypeptides. Herein, we demonstrate that hepatic iPLA2γ is localized to rat liver peroxisomes, possesses a molecular mass of 63 kDa and that peroxisomal membranes are highly enriched in arachidonic acid‐containing phospholipids. Collectively, these results provide the first demonstration of iPLA2γ in mammalian tissue and suggest the possibility that iPLA2γ can contribute to lipid second messenger generation by hydrolysis of peroxisomal arachidonic acid‐containing phospholipids.
Role of the proteasome in protein oxidation and neural viability following low‐level oxidative stress
Authors: Ding Qunxing , Reinacker Kristi , Dimayuga Edgardo , Nukala Vidya , Drake Jennifer , Butterfield D.Allan , Dunn Jay C. , Martin Sarah , Bruce-Keller Annadora J. , Keller Jeffrey N.
Published: June 2003

Numerous studies suggest that proteasome inhibition may play a causal role in mediating the increased levels of protein oxidation and neuron death observed in conditions associated with oxidative stress. In the present study we demonstrate that administration of non‐toxic levels of oxidative stress does not result in impairment of 20S/26S proteasome activity, and actually increases the expression of specific proteasome subunits. Non‐toxic levels of oxidative stress were observed to elevate the amount of protein oxidation in the presence of preserved proteasomal function, suggesting that proteasome inhibition may not mediate increases in protein oxidation following low‐level oxidative stress. Preserving basal proteasome function appears to be critical to preventing the neurotoxicity of low‐level oxidative stress, based on the ability of proteasome inhibitor treatment to exacerbate oxidative stress toxicity. Taken together, these data indicate that maintaining neural proteasome function may be critical to preventing neurotoxicity, but not the increase in protein oxidation, following low‐level oxidative stress.
An epizootic of highly virulent feline calicivirus disease in a hospital setting in New England
Authors: Schorr-Evans E.M , Poland A , Johnson WE , Pedersen N.C
Published: June 2003

This article reports an outbreak of 24 cases of an unusually virulent feline calicivirus (FCV) infection in a small animal hospital. The circumstances and disease signs were very similar to those recently described in an outbreak of FCV hemorrhagic disease in Northern California (Vet. Microbiol. 73 (2000) 281). The virus entered the facility through shelter cats showing upper respiratory signs. Affected cats manifested high fever, anorexia, labored respirations, oral ulceration, facial and limb edema, icterus, and pancreatitis. The infection spread rapidly among the patients by contaminated animal caretakers and hospital equipment. One case of fomite transmission from an employee to a housecat was documented. Prior vaccination, even with multiple doses of FCV-F9-based live calicivirus vaccine, was not protective. Affected cats often required extensive supportive care for 7–10 days, and the overall mortality from death and euthanasia was 32%. The strain of FCV responsible for this outbreak was genetically and serologically distinct from the FCV strain responsible for a similar epizootic and the FCV-F9 strain contained in most vaccines. Outbreaks of this type are being reported with increasing frequency, and are often associated with the practice of treating sick shelter cats in private practices. Similar to the present epizootic, outbreaks of FCV hemorrhagic disease have been self-limiting, but require prompt application of strict quarantine, isolation, personnel sanitation, and disinfection procedures.
Acute cardiac failure in neuroleptic malignant syndrome☆
Authors: Sparrow Patrick , Murnaghan Dermot , Kearney Peter , Hogan John , Sheppard Mary N.
Published: June 2003

We present a case of rapid onset acute cardiac failure developing as part of Neuroleptic malignant syndrome in a 35‐year‐old woman following treatment with Thioridazine and Lithium. Post mortem histology of cardiac and skeletal muscle showed similar changes of focal cellular necrosis and vacuolation suggesting a common disease process.
Comparing methodological quality and consistency of international guidelines for the management of patients with chronic heart failure
Authors: Kulig Michael , Erika Schulte , Norbert Willich Stefan
Published: June 2003

Background:

Guidelines (GLs) for the management of heart failure (HF) are of great importance in order to define and disseminate therapeutic recommendations based on scientific evidence. The aim was to analyse and to compare the methodological quality of HF GLs as well as to evaluate the consistency of therapeutic recommendations.

Methods:

Eleven international GLs for the management of chronic HF were identified by search of the internet, electronic databases and references of published literature. Their methodological quality was assessed by two different appraisal instruments: (1) according to the US National Guideline Clearinghouse (NGC) on a scale from 0 to 17 points, (2) according to the German Guideline Clearinghouse (Agency for Quality in Medicine, AQUMED) on a scale from 0 to 44 points. Clinical criteria for assessment of the consistency of the recommendations included diagnostic testing, pharmacological and non‐pharmacological treatment.

Results:

The quality scores of the GLs varied substantially with a range of 1.5–15.5 points (NGC) and 8–30 points (AQUMED). The greatest variation was found in the dimensions ‘development’ and ‘evidence’. Only 3 of the 11 GLs (≈30%) were rated as methodologically well prepared. The recommendations on diagnostic procedures and medical management were rather consistent among the different GLs.

Conclusions:

Published international GL recommendations on medical management of patients with chronic HF are broadly consistent. The methodological quality of the GLs, however, varies to a great extent. Improvement is needed in most methodological aspects, especially in the dimensions ‘evidence’ and ‘applicability’.
Differences between general practitioners and cardiologists in diagnosis and management of heart failure: a survey in every‐day practice
Authors: Rutten Frans H. , Grobbee Diederick E. , Hoes Arno W.
Published: June 2003

Background:

Data on diagnosis and management of heart failure in every‐day care are scarce.

Aims:

To compare general practitioners’ and cardiologists’ diagnostic work‐up and management of patients with (suspected) heart failure.

Methods:

In a cross‐sectional survey we studied a sample of 103 files of patients coded as heart failure in primary care (31 general practices), and 99 files of out‐patients coded as heart failure from 9 hospitals in the Netherlands. We defined patients as heart failure ‘GP patients’, when they were managed by a general practitioner without co‐treatment of a cardiologist.

Results:

Patients managed in general practice were older (mean age 79 years (S.D. 8.5) and more often female than ‘cardiology patients’ (mean age 64 years (S.D. 11.7)). Ischaemic heart disease (31 vs. 57%) was more prevalent in ‘cardiology patients’. Additional investigations such as chest radiography (51% vs. 84%), electrocardiography (39% vs. 100%), and (Doppler‐) echocardiography (12% vs. 97%) were performed more often in ‘cardiology patients’. Most patients received diuretics (85% vs.79%). Angiotensin converting enzyme inhibitors (40% vs. 76%), beta‐blockers (9% vs. 30%), spironolactone (11% vs. 32%), and angiotensin‐II‐antagonists (6% vs. 13%) were prescribed much more often to ‘cardiology patients’.

Conclusion:

General practitioners more often treat elderly, female patients with heart failure than cardiologists. General practitioners use less additional investigations and prescribe less potentially beneficial medication, compared to cardiologists. Population characteristics only partly explain these differences, suggesting that the physician's attitude has an important bearing on the uptake of treatment.
Statistical analysis of rockfall volume distributions: Implications for rockfall dynamics
Authors: Dussauge Carine , Grasso Jean‐Robert , Helmstetter Agnès
Published: June 2003

We analyze the volume distribution of natural rockfalls on different geological settings (i.e., calcareous cliffs in the French Alps, Grenoble area, and granite Yosemite cliffs, California Sierra) and different volume ranges (i.e., regional and worldwide catalogs). Contrary to previous studies that included several types of landslides, we restrict our analysis to rockfall sources which originated on subvertical cliffs. For the three data sets, we find that the rockfall volumes follow a power law distribution with a similar exponent value, within error bars. This power law distribution was also proposed for rockfall volumes that occurred along road cuts. All these results argue for a recurrent power law distribution of rockfall volumes on subvertical cliffs, for a large range of rockfall sizes (102–1010 m3), regardless of the geological settings and of the preexisting geometry of fracture patterns that are drastically different on the three studied areas. The power law distribution for rockfall volumes could emerge from two types of processes. First, the observed power law distribution of rockfall volumes is similar to the one reported for both fragmentation experiments and fragmentation models. This argues for the geometry of rock mass fragment sizes to possibly control the rockfall volumes. This way neither cascade nor avalanche processes would influence the rockfall volume distribution. Second, without any requirement of scale‐invariant quenched heterogeneity patterns, the rock mass dynamics can arise from avalanche processes driven by fluctuations of the rock mass properties, e.g., cohesion or friction angle. This model may also explain the power law distribution reported for landslides involving unconsolidated materials. We find that the exponent values of rockfall volume on subvertical cliffs, 0.5 ± 0.2, is significantly smaller than the 1.2 ± 0.3 value reported for mixed landslide types. This change of exponents can be driven by the material strength, which controls the in situ topographic slope values, as simulated in numerical models of landslides [Densmore et al., 1998; Champel et al., 2002].
Reconstruction of the deformed collision zone Between India and Asia by backward motion of lithospheric blocks
Authors: Replumaz A. , Tapponnier P.
Published: June 2003

On the basis of a synthesis of tectonic data available on the India‐Asia collision, we present a first attempt to reconstruct the evolution of the collision zone. Assuming that the deformation of the lithosphere is localized along narrow shear zones and that the interiors of mantle blocks in between remain relatively undeformed, we define block contours from the fault pattern and move back the blocks along their boundary faults. Along convergent or extensional boundaries, the crust is assumed to shorten or stretch coherently. Step‐by‐step, we go backward in time to finally reach the collision onset. For each time step, we find a solution compatible with the data set available and the position of the adjacent blocks for each block. The search for compatibility at the scale of the entire collision zone allows for solving the kinematics of regions with fewer data and suggests plausible scenarios for regions where data is lacking. For each step, we calculate large‐scale displacement maps, and determine Euler poles for each block. For the most recent time step, the map proposed is compared to GPS motions. The deformation budget implies that extrusion absorbed ∼30% of the convergence between India and Siberia during the entire collision span, but varied with time, accounting for as little as 3% or as much as 60% of this convergence at different epochs.
Near‐inertial and tidal currents detected with a vessel‐mounted acoustic Doppler current profiler in the western Mediterranean Sea
Authors: Garcia‐Gorriz E. , Candela J. , Font J.
Published: June 2003

The objective of this study is to separate the subinertial, inertial, and tidal fields from vessel‐mounted acoustic Doppler current profiler (VM‐ADCP) observations acquired during six cruises in the Catalan and Alboran Seas (western Mediterranean Sea). To fulfill this objective we use a method that successfully detects and filters out the main high frequencies that are present in the VM‐ADCP data. The resulting near‐inertial component has frequencies below the Coriolis frequency f in the Catalan Sea, and above f in the Alboran Sea. The tidal component is consistent with observed and modeled tides in the Catalan and Alboran Seas. The steady component is highly correlated with the geostrophic field. There is also a nonfitted (or residual) component, which represents the misfit between the VM‐ADCP data and the model proposed.
Adjoint sensitivity of episodic ozone in the Paris area to emissions on the continental scale
Authors: Schmidt Hauke , Martin Daniel
Published: June 2003

This study presents results of sensitivity calculations with the adjoint of the continental‐scale Eulerian chemistry transport model CHIMERE. In the framework of the Atmospheric Pollution Over the Paris Area (ESQUIF) project, which was designed to improve the understanding of photochemical pollution events in the Paris region, a large number of aircraft and surface observations was performed in order to study the chemical composition around the agglomeration. Here the adjoint CHIMERE model is used to calculate sensitivities of ozone concentrations, in particular of air masses entering the Paris region, with respect to emissions on the continental scale. For 13 case studies the influence of ozone precursors, differentiated with respect to their source type, their geographical origin, and their time of emission, is quantified with the aim of facilitating the interpretation of the observations and to demonstrate the usefulness of adjoint models for such types of studies. It is shown that for all cases the regional peak ozone concentrations are more sensitive to emissions of NOx than to emissions of volatile organic compounds (VOCs). However, the influence of VOCs is extended over a longer time span than for NOx, which is reflected in the more distant source regions of highly influential VOC emissions. On average the sensitivity to biogenic VOCs is significantly smaller than to anthropogenic VOCs. The same is true for NOx emissions. However, as different uncertainties have to be associated with these four emission groups, the uncertainty of the modeled ozone concentration caused by the groups is of the same order of magnitude.
Latitude variation of the subsurface lunar temperature: Lunar Prospector thermal neutrons
Authors: Little R. C. , Feldman W. C. , Maurice S. , Genetay I. , Lawrence D. J. , Lawson S. L. , Gasnault O. , Barraclough B. L. , Elphic R. C. , Prettyman T. H. , Binder A. B.
Published: June 2003

Planetary thermal neutron fluxes provide a sensitive proxy for mafic and feldspathic terranes and are also necessary for translating measured gamma‐ray line strengths to elemental abundances. Both functions require a model for near‐surface temperatures and a knowledge of the dependence of thermal neutron flux on temperature. We have explored this dependence for a representative sample of lunar soil compositions and surface temperatures using the Monte Carlo N‐Particle Code (MCNP™)(MNCP is a trademark of the Regents of the University of California, Los Alamos National Laboratory). For all soil samples, the neutron density is found to be independent of temperature, in accord with neutron moderation theory. The thermal neutron flux, however, does vary with temperature in a way that depends on Δ, the ratio of macroscopic absorption to energy‐loss cross sections of soil compositions. The weakest dependence is for the largest Δ (which corresponds to the Apollo 17 high‐Ti basalt in our soil selection), and the largest dependence is for the lowest Δ (which corresponds to ferroan anorthosite, [FAN] in our selection). For the lunar model simulated, the depth at which the thermal neutron population is most sensitive to temperature is ∼30 g cm−2. These simulations were compared with the flux of thermal neutrons measured using the Lunar Prospector neutron spectrometer over the lunar highlands using a subsurface temperature profile that varies with latitude, λ, as Cos1/4λ. Model results assuming equatorial temperatures of 200 and 250 K are in reasonable agreement with measured data. This range of equatorial temperatures is not inconsistent with the average temperature measured below the diurnal thermal wave at the equator, Tmeas = 252 ± 3 K [Langseth and Keihm, 1977].
Sea surface salinity from space: Science goals and measurement approach
Authors: Koblinsky C. J. , Hildebrand P. , LeVine D. , Pellerano F. , Chao Y. , Wilson W. , Yueh S. , Lagerloef G.
Published: June 2003

Aquarius is a NASA/Earth System Science Pathfinder (ESSP) mission that proposes to make the first‐ever global measurements of sea surface salinity. These measurements will enable improved understanding of oceanic thermohaline circulation and of the changes in oceanic circulation that are related to seasonal to interannual climate variability. Aquarius science goals also address tropical ocean‐climate feedbacks and freshwater budget components of the coupled ocean‐atmosphere system. These oceanographic science requirements for Aquarius dictate measurements of global sea surface salinity that are accurate to 0.2–0.3 psu, as averaged monthly and over 100–200 km areas. Key aspects of the Aquarius salinity mission design include the instrument with its high‐stability L‐band radiometers, the precise calibration of the measurements, and the salinity retrieval algorithm. The Aquarius mission will meet the science needs by providing complete global coverage of ocean surface salinity, with an 8 day cycle of observations using a three beam, L‐band radiometer/scatterometer flying in a 6 am/6 pm polar orbit. This conceptual design has been verified using observations from aircraft flight instruments. The radiometer design for the instrument and the needed precise calibration is based on proven, temperature‐stabilized radiometer designs with internal references, plus vicarious calibration approaches developed in the course of previous space missions.
Cretaceous deformation, Chegitun River area, Chukotka Peninsula, Russia: Implications for the tectonic evolution of the Bering Strait region
Authors: Toro Jaime , Amato Jeffrey M. , Natal'in Boris
Published: June 2003

The Koolen metamorphic dome of Chukotka Peninsula has been interpreted as a mid‐Cretaceous extensional core complex. On the NW flank of the dome, three lithotectonic units are exposed: (1) High‐Grade unit, composed of sillimanite‐grade rocks; (2) Tanatap unit, composed of polydeformed greenschist‐grade phyllites and marbles; (3) Chegitun unit composed of unmetamorphosed early Paleozoic limestones. Four Early Cretaceous to Tertiary deformational events are documented. D1 is attributed to the collisional closure of the South Anyui suture. The 40Ar/39Ar ages from the Tanatap unit constrain this event at 117–124 Ma. Relict kyanite‐bearing assemblages in the High‐Grade unit probably formed during this event under moderately high pressure conditions. D2 is related to extensional deformation in the Koolen dome. In the High‐Grade unit, sillimanite‐grade metamorphism was followed by rapid cooling and exhumation at 109–104 Ma. In the Tanatap unit, early fabrics underwent isoclinal folding, and a new cleavage (S2t) was developed. The kinematics of the High‐Grade unit indicates ductile deformation by top‐to‐the‐south shear, as is the case in the dome core. This suggests that the Koolen dome is a unidirectional core complex formed by south directed extension. We believe collapse of overthickened crust caused extension in the Koolen dome. The crust was thickened during Early Cretaceous collision and during subsequent oroclinal bending of the structures in the Bering Strait region. The youngest structures in the Chegitun Valley are NW striking normal faults kinematically linked to NE striking right‐lateral strike‐slip faults. They are probably the continuation of structures found offshore in the Hope Basin.
High‐pressure metamorphism in the Aegean, eastern Mediterranean: Underplating and exhumation from the Late Cretaceous until the Miocene to Recent above the retreating Hellenic subduction zone
Authors: Ring Uwe , Layer Paul W.
Published: June 2003

We report 40Ar/39Ar ages from various tectonic units in the Aegean and westernmost Turkey. On the basis of published geochronologic data and our 40Ar/39Ar ages we propose that the Aegean is made up of several high‐pressure units, which were successively underplated from the Late Cretaceous until the Miocene. Ages for high‐pressure metamorphism range from 80–83 Ma in parts of the Vardar‐Izmir‐Ankara suture zone in the north to 21–24 Ma for the Basal unit in the Cyclades and the external high‐pressure belt on Crete in the south. Published seismic data suggest that high‐pressure metamorphism is currently occurring underneath Crete. Younging of high‐pressure metamorphism in a southerly direction mimics the southward retreat of the Hellenic subduction zone. We propose that distinct stages of high‐pressure metamorphism were controlled by the underthrusting of fragments of mainly thinned continental crust and that these punctuated events were superposed on progressive slab retreat. By far most of the exhumation of the high‐pressure units occurred early during the orogenic history in a forearc position.
The contribution of ocean‐leaving DMS to the global atmospheric burdens of DMS, MSA, SO2, and NSS SO4=
Authors: Gondwe M. , Krol M. , Gieskes W. , Klaassen W. , de Baar H.
Published: June 2003

The contribution of ocean‐derived DMS to the atmospheric burdens of a variety of sulphur compounds (DMS, MSA, SO2, and nss SO4=) is quantified from season to season. Such quantification, especially for nss SO4= (the climate‐relevant product of DMS oxidation), is essential for the quantification of the radiative forcing of climate that may be attributable to marine phytoplankton under possible future climate conditions. Three‐dimensional chemical transport modeling up to the stratosphere is used as a tool in realizing this aim. Global data sets on oceanic and terrestrial sulphur sources are used as input. We find that the contribution of ocean‐leaving DMS to the global annually averaged column burdens of the modeled compounds is considerable: 11.9 μmol m−2 (98% of total global burden) for DMS; 0.95 μmol m−2 (94% of total global burden) for MSA; 2.8 μmol m−2 (32% of total global burden) for SO2 and 2.5 μmol m−2 (18% of total global burden) for nss SO4=. The mean annual contribution of DMS to the climate‐relevant nss SO4= column burden is greatest in the relatively pristine Southern Hemisphere, where it is estimated at 43%. This contribution is only 9% in the Northern Hemisphere, where anthropogenic sulphur sources are overwhelming. The marine algal‐derived input of the other modeled sulphur compounds (DMS, MSA, and SO2) is also greatest in the Southern Hemisphere where a lower oxidative capacity of the atmosphere, a larger sea‐to‐air transfer of DMS and a larger emission surface area lead to an elevation of the atmospheric DMS burden.
Biological degradation of methyl chloride in coastal seawater
Authors: Tokarczyk Ryszard , Saltzman Eric S. , Moore Robert M. , Yvon‐Lewis Shari A.
Published: June 2003

Methyl chloride (CH3Cl) is the most abundant halocarbon in the atmosphere, and constitutes a significant fraction of the total atmospheric halogen burden. Chemical reactions of CH3Cl in seawater are slow, and it has been believed that the oceans are not an important sink for this compound. However, direct measurements of CH3Cl degradation rates in coastal seawater (Bedford Basin, Nova Scotia), using a stable isotope incubation technique, indicate rapid loss attributed to microbial activity. A series of weekly measurements from March 2000 to May 2001 yielded degradation rates ranging from 0–30% d−1, with an annual mean of 7.4% d−1. If biological uptake of CH3Cl occurs throughout the oceans at similar rates, the mean partial atmospheric lifetime of CH3Cl with respect to oceanic removal could be a few years, rather than several decades as previously thought. This rapid removal would make the oceans a major sink for CH3Cl and lower the overall atmospheric lifetime of CH3Cl from the current estimate of 1.3 to about 1.0 years. Measurements of the degradation rate of CH3Cl in open ocean waters are needed in order to quantify the oceanic uptake rate.
Interpretation of the nitrogen isotopic signal variations in the Mauritanian upwelling with a 2D physical‐biogeochemical model
Authors: Giraud Xavier , Bertrand Philippe , Garçon Véronique , Dadou Isabelle
Published: June 2003

A physical‐biogeochemical model is used to simulate the evolution of the δ15N signal during the last glacial‐interglacial transition in sedimentary cores offshore from the Mauritanian upwelling. The biological model is a classical nitrogen‐based trophic chain model, which also computes the nitrogen isotope fractionation. The 2D physical primitive equation model simulates the coastal upwelling circulation and is applied for different sea level scenarios. The effect of the sea level rise, inducing the shelf immersion, seems to be a main factor explaining the organic nitrogen flux and isotopic signal variations along the last deglaciation. This effect is modulated by an upwelling seasonality that may have been much longer at the Last Glacial Maximum, around 10–11 months instead of 4–5 months at present. Between 15 and 5.5 kyr ago, 60% of the sedimentary δ15N variations could be explained by this local shelf immersion effect. This reconstruction also reproduces the strong isotopic fall occurring between 5.5 kyr and the present.
MAX‐DOAS measurements of BrO and NO2 in the marine boundary layer
Authors: Leser H. , Hönninger G. , Platt U.
Published: June 2003

During a cruise of the German research vessel Polarstern from Bremerhaven, Germany to Capetown, South Africa in October 2000 mid latitude tropospheric bromine oxide (BrO) and nitrogen dioxide (NO2) abundances were investigated by ground‐based MAX‐DOAS (scattered light Multi Axis Differential Optical Absorption Spectroscopy). By comparing the slant column densities of absorbers measured at different elevation angles above the horizon (5° to 90°) it is possible to draw conclusions regarding the vertical distribution of the investigated absorbers (i.e., BrO and NO2). During a period of 2 days in the region north of the Canary Islands (around 35°N, 13°W) significant boundary layer BrO in the 1 ppt range was found. For the remaining time all data points ranged below the detection limit. Boundary layer NO2 was found near Europe and the Canary Islands with mixing ratios in the range of several ppb. In the remote marine air south west of Africa upper limits were derived.
North Atlantic decadal variability and the formation of tropical storms and hurricanes
Authors: Molinari Robert L. , Mestas‐Nuñez Alberto M.
Published: June 2003

Both the annual number of Atlantic tropical storms forming south of 23.5°N and of Atlantic major hurricanes increased between the 1970's/1980's and 1995–2000. These increases are coincident with a multi‐decadal warming in North Atlantic SST suggesting that the high activity of 1995–2000 may persist for the next ∼10 to 40 years. However, during 1950–2000 strong decadal oscillations are superimposed on the multi‐decadal changes in both SST and tropical storms (positive SST anomalies, increased storm activity). We appear to be entering a negative phase of the decadal SST signal implying that tropical storm, and most likely major hurricane, activity may be reduced in the next several years rather than remain at the very high 1995–2000 level when both signals were in their positive phase. Tropical storm activity during 2001 and 2002 is less than the expected only from the multi‐decadal signal but for 2002 the main cause may be El Niño.
Abrupt thermal transition reveals hydrothermal boundary and role of seamounts within the Cocos Plate
Authors: Fisher A. T. , Stein C. A. , Harris R. N. , Wang K. , Silver E. A. , Pfender M. , Hutnak M. , Cherkaoui A. , Bodzin R. , Villinger H.
Published: June 2003

New thermal data from 18–24 Ma lithosphere on the Cocos Plate delineate contrasting subsurface thermal conditions in adjacent sections of crust. Heat flow through seafloor created at the East Pacific Rise is generally suppressed by ∼70% relative to conductive lithospheric cooling models, whereas heat flow through adjacent, similarly‐aged lithosphere generated at the Cocos‐Nazca Spreading Center is consistent with these models. The transition between thermal regimes is remarkably abrupt, only 2–5 km wide, indicating a shallow hydrothermal origin. The transition is more closely associated with differences in the distribution of basement outcrops than with tectonic boundaries, demonstrating the importance of the former in extracting heat from the lithosphere on a regional basis.
The unusual summer of 1994 in East Asia: IOD teleconnections
Authors: Guan Zhaoyong , Yamagata Toshio
Published: June 2003

An extremely hot and dry summer of 1994 was reported in East Asian countries. Using observational data, we have demonstrated that the Indian Ocean Dipole (IOD) is at least one possible cause of the abnormal East Asian summer climate. An anomalous cyclonic circulation over the western Pacific and the southern China weakened the monsoonal northward flow in the lower troposphere. An anomalous anticyclonic circulation with the equivalent barotropic structure around Japan, Korea and the northeastern part of China caused the hot and dry summer of 1994. This accumulation of the lower potential vorticity in the Far East is related to the wave activity from the Mediterranean/Sahara region. The monsoon‐desert mechanism connects a Rossby wave source with the IOD‐induced diabatic heating around the Bay of Bengal. Another Rossby wave‐train pattern was generated in the upper troposphere and propagates northeastward from the southern China. Both the Rossby wave patterns influenced the circulation changes over East Asia.
Evidence for upper crustal anisotropy in the Songpan‐Ganze (northeastern Tibet) terrane
Authors: Vergne Jérôme , Wittlinger Gérard , Farra Véronique , Su Heping
Published: June 2003

The radial and transverse receiver functions obtained at several stations located on the Songpan‐Ganze terrane (Tibetan plateau) are characterized by strong P to S conversions in the first 4 s after the direct P wave. We show that the amplitude variations of these phases with back‐azimuth can be well explained by a simple model with one or two anisotropic layers. The anisotropy we obtained is quite strong (about 15%) and might be related to the presence of highly deformed flyschs and schists in the first 25 km of the crust. This study shows that anisotropy in the crust could be locally high and has to be taken into account when analyzing teleseismic data.
Mountaintop and radar measurements of anthropogenic aerosol effects on snow growth and snowfall rate
Authors: Borys Randolph D. , Lowenthal Douglas H. , Cohn Stephen A. , Brown William O. J.
Published: June 2003

A field campaign designed to investigate the second indirect aerosol effect (reduction of precipitation by anthropogenic aerosols which produce more numerous and smaller cloud droplets) was conducted during winter in the northern Rocky Mountains of Colorado. Combining remote sensing and in‐situ mountain‐top measurements it was possible to show higher concentrations of anthropogenic aerosols (∼1 μg m−3) altered the microphysics of the lower orographic feeder cloud to the extent that the snow particle rime growth process was inhibited, or completely shut off, resulting in lower snow water equivalent precipitation rates.
Multipoint observations of equatorial plasma bubbles
Authors: Burke W. J. , Huang C. Y. , Valladares C. E. , Machuzak J. S. , Gentile L. C. , Sultan P. J.
Published: June 2003

This paper compares evening sector measurements by the Jicamarca unattended long‐term studies of the ionosphere and atmosphere (JULIA) radar, the Ancon scintillation monitor, and plasma density sensors on Defense Meteorological Satellite Program (DMSP) satellites. During more than half of the 110 nights of JULIA operations in 1998 and 1999, backscatter was observed from plumes extending above the layer of bottomside spread F. On 98% of the nights with no plumes, the S4 index measured at Ancon was <0.8. On ∼90% nights with plumes, S4 > 0.8. DMSP F14 crossed the magnetic equator within 7.5° longitude of Ancon near the 2100 local time (LT) meridian on 61 nights. During 32 overpasses, DMSP detected no equatorial plasma bubbles (EPBs), and JULIA detected no plumes. DMSP encountered EPBs on only 9 of the remaining 29 nights when JULIA observed plumes. Two plumes detected by JULIA on 15 April 1999 did not coincide with nearby EPBs crossed by the two satellites on the same evening. We also compared the seasonally averaged percent of nights with S4 ≥ 0.8 at Ancon with the percent of orbits in which a DMSP satellite detected EPBs. Data were accumulated between May 1994 and the first quarter of 2001. On a global scale at solar minimum, DMSP encountered very few EPBs. In years near solar maximum the two data sets were well correlated. However, there were more nights with S4 ≥ 0.8 at Ancon than EPB encounters by DMSP satellites. This discrepancy reflects the effects of different sampling intervals and the fact that about a third of the plumes fail to reach the DMSP altitude. Still, a correlation coefficient of 0.88 indicates that EPB detection at 840 km is a good indicator that scintillation activity is occurring near the spacecraft's longitude at the Earth's surface. The data also suggest that bubbles are often generated in bursts rather than at nearly uniform intervals.
Multipoint measurements of field‐aligned current density in the auroral zone
Authors: Zheng Yihua , Lynch Kristina A. , Boehm Manfred , Goldstein Raymond , Javadi Hamid , Schuck Peter , Arnoldy Roger L. , Kintner Paul M.
Published: June 2003

In this paper we present the analysis and interpretation of a multipoint observation of magnetic field structures at the poleward edge of a premidnight auroral arc by the Enstrophy sounding rocket mission. Four Free‐Flying Magnetometers (FFMs) employing autonomous nanospacecraft technology were deployed from the main payload during the flight, and multipoint magnetic field measurements were made. Signatures consistent with both spatial and temporal interpretations were found to be present when large fluctuations in B were seen at the edge of an arc as the rocket flew into the polar cap. Reasons for the interpretation of spatial or temporal features are given and supported by a simple model of multiple payloads crossing through several moving current sheets and a study of the fine structure of this auroral event using multipoint, correlative wavelet analysis to find velocities of structures at different scale sizes. We show that the direct measurement method of current density using multipoint measurement of magnetic fields gives us a different current density than what would be inferred from a single‐point measurement and that the multipoint measurement also provides an inherent check on the validity of the measurement through a calculation of the divergence of the measured B.
Toroidal‐shaped interplanetary disturbance associated with the halo coronal mass ejection event on 14 July 2000
Authors: Tokumaru Munetoshi , Kojima Masayoshi , Fujiki Ken'ichi , Yamashita Masahiro , Yokobe Atsushi
Published: June 2003

Interplanetary scintillation (IPS) measurements made with the 327 MHz radio telescopes of the Solar–Terrestrial Environment Laboratory, Nagoya University, have been used to study a three‐dimensional structure of the interplanetary (IP) disturbance associated with the halo coronal mass ejection (CME) event on 14 July 2000 (the so‐called “Bastille Day event”). The IPS observations indicated that the Bastille Day IP disturbance was between 0.3 and 0.7 AU at 17 ± 3 hours after the flare occurrence. A model fitting analysis has been applied here to the IPS observations to reconstruct a global structure of the Bastille Day IP disturbance. As a result, the IP disturbance is found to form a loop‐shaped structure that is significantly longer in the longitudinal (east–west) direction than in latitude. This toroidal‐shaped IP disturbance is found to cross the large‐scale magnetic neutral line almost perpendicularly at its center. Our IPS data also show a nonuniform expansion of the IP disturbance, and the fastest direction is found to lie near above the flare site. Using the best‐fit model determined here and information on the ambient solar wind density from in situ measurements, the mass contained by the IP disturbance has been estimated to be ∼ 5.3 × 1016 g. The result obtained from the present analysis is consistent with independent observations that suggest the Bastille Day interplanetary CME has decelerated significantly in the solar wind. The radial evolution of the apparent feature of the IP disturbance has been revealed from a model calculation using the best‐fit parameters, and this evolution is consistent with IPS measurements made at Ooty, India, slightly later in time. While an origin of the toroidal‐shaped disturbance is an open question, the compressed plasma between the coronal ejecta and the ambient solar wind or the ejecta itself are considered as a possible one.
Multipoint observations of a Pi2 pulsation on morningside: The 20 September 1995 event
Authors: Nosé M. , Takahashi K. , Uozumi T. , Yumoto K. , Miyoshi Y. , Morioka A. , Milling D. K. , Sutcliffe P. R. , Matsumoto H. , Goka T. , Nakata H.
Published: June 2003

We investigated a Pi2 pulsation that occurred at 0538 UT on 20 September 1995, using data from ground stations and the ETS‐VI and EXOS‐D satellites. Since ground stations at L = 1.45 − 12.6 and the two satellites were located at 7–10 hours of magnetic local time (MLT), we could investigate characteristics of the morning side Pi2 pulsation in detail. We also examined geomagnetic field data from equatorial and low‐latitude (L ≤ 1.5) stations at 0200 MLT and 1500 MLT. Our findings include the following: (1) Pi2 pulsations on the morning side were observed over a wide range of L (L < 6.1) with almost identical period (T ∼ 70 s) and waveforms; (2) the ETS‐VI satellite located above the geomagnetic equator at L = 6.3 observed a Pi2 pulsation that had nearly the same period and waveforms as the ground Pi2 pulsation; (3) the Pi2 pulsation observed by ETS‐VI appeared in the compressional and radial components; (4) phase lag between the compressional and radial components was ∼180° (5) the ground‐to‐satellite phase lag was ∼180° (∼0°) for the X component and the compressional (radial) component; (6) the EXOS‐D observation placed the plasmapause location at L = 6.8, across which ground Pi2 pulsations changed their characteristics; and (7) no phase delay was found between low‐latitude Pi2 pulsations observed around 0700 MLT, 0200 MLT, and 1500 MLT. From these results we concluded that the morning side Pi2 pulsation was caused by the plasmaspheric cavity mode resonance and that its longitudinal structure was rather uniform.
Paleomagnetism of the Newcastle Range, northern Queensland: Eastern Gondwana in the Late Paleozoic
Authors: Anderson Kari L. , Lackie Mark A. , Clark David A. , Schmidt Phil W.
Published: June 2003

The Newcastle Range is an extensive (2500 km2) and well‐exposed caldera system erupted on the trailing edge of Eastern Gondwana between 325 and 295 Ma. Paleomagnetic samples were collected from ignimbrites and associated microgranitoid intrusions from the central, northern and southern calderas from which three components of magnetization are recognized. Component 1 is considered to be a viscous magnetization acquired during the Brunhes Chron. A presumed Permian component, C2, is found in seven paleomagnetic sites with a mean pole at 30.9°S, 139.7°E (K = 13.9, A95 = 16.8°, ASD = 21.7°), agreeing with previously reported Permian data from Australia. Carboniferous units have a well‐defined characteristic component, C3, distinguished by dual polarity (predominantly reversed) and moderate to steep inclination directions. Paleomagnetic polarities in the Newcastle Range Volcanics are formation dependent and new constraints on the timing of Carboniferous volcanism (∼325–317 Ma) are consistent with recent reanalysis of the base of the Permo‐Carboniferous Reversed Superchron (PCRS). A mean paleomagnetic pole, calculated from 15 VGPs, lies at 63.4°S, 125°E (K = 26.22, A95 = 7.6°, ASD = 15.8°), suggesting that Australia remained at midlatitudes into the Middle Carboniferous. This paleomagnetic pole is consistent with similarly aged poles from Western Gondwana, the conformity of which indicates contributions from nondipole components of the Earth's paleofield were probably not significant in the time immediately preceding the PCRS.
High‐temperature magnetic stability of small magnetite particles
Authors: Muxworthy Adrian R. , Dunlop David J. , Williams Wyn
Published: June 2003

The stability of magnetic domain structures of small grains of magnetite were examined between room temperature and the Curie temperature using a high‐resolution three‐dimensional micromagnetic algorithm. At all times the minimum resolution used was determined by calculating the exchange length. Using an unconstrained model, the single domain (SD) to multidomain (MD) threshold grain size d0 was found to be nearly independent of temperature up to ∼450°C. Above this temperature, d0 was observed to rise sharply. Energy barriers between metastable domain states trapped in local energy minimums (LEM) were determined using a constrained algorithm. Three types of domain structure were considered: SD, vortex, and double vortex (effectively three domain), in a range of grain sizes with side length between 30 and 300 nm. In addition, the effect of varying shape was also considered by examining asymmetric grains with aspect ratios up to 1.4. From the numerical solutions energy barriers between LEM states were determined. It was found that MD grains 300 nm in size display higher stability than smaller SD grains (∼50 nm). Double vortex states were found to be less stable than single vortex states at nearly all temperatures. Blocking temperatures as function of grain size for both symmetric and asymmetric grains were determined and agree well with experimental results. Transdomain thermoremanence analysis indicated that there are a limited number of grain sizes and shapes which will nucleate domain wall‐type structures during cooling. Such nucleation events would cause the total measured remanence to decrease with cooling in conflict with Néel's analytical theory for remanence cooling behavior but in agreement with experimental observations.
Seasonal and interannual variations in geostrophic velocity in the Middle Atlantic Bight
Authors: Dong Shenfu , Kelly Kathryn A.
Published: June 2003

More than 6 years of measurements from the TOPEX/POSEIDON (T/P) altimeter are used to study the seasonal and interannual variations of the geostrophic velocity anomalies in the Middle Atlantic Bight region. Geostrophic velocities from T/P data are compared with the simultaneous low‐pass filtered current meter data. The correlations are all above 95% significance for the three current meter observations at the 1000‐m, 2210‐m, and 2990‐m isobaths. The seasonal mean geostrophic currents from 63°–75°W show coherent variations along isobaths, with seasonal reversals: toward the southwest during the winter and toward the northeast during the summer. The EOF analysis indicates that the seasonal reversals disappeared during 1996. This disruption is part of the intensification of the slope sea gyre and is related to the southward shift of the Gulf Stream, which acts as the boundary between the subpolar and subtropical gyres. The Gulf Stream moved farther south during 1996–1998. The variations in the Gulf Stream position may be caused by the wind stress/wind stress curl change.