bluuebunny/crossref_metadata_2025 huggingface dataset:
The influence of cytokines, chemokines and their receptors on HIV‐1 replication in monocytes and macrophages
Authors: Kedzierska Katherine , Crowe Suzanne M. , Turville Stuart , Cunningham Anthony L.
Published: January 2003

Monocytes, macrophages and dendritic cells play an important role in the initial infection and contribute to its pathogenesis throughout the course of infection. Myeloid cells express CD4 and chemokine receptors known for HIV‐1 fusion and entry. The β‐chemokine receptor, CCR5, is the major co‐receptor in conjunction with CD4 for macrophage (M)‐tropic or (R5) isolates of HIV‐1, whereas the α‐chemokine receptor, CXCR4, facilitates entry of T‐tropic or (X4) HIV‐1 strains. Cells of myeloid lineage may be infected predominantly with R5‐ strains, although infection with dual‐tropic isolates of HIV‐1 (exhibiting the capacity to use CCR‐5 and/or CXCR‐4 for entry) or some strains of X4‐ isolates has also been reported. The expression of chemokine receptors, HIV‐1 infectio n and replication is under continuous regulation by a complex cytokine network produced by a variety of cells. The effects of cytokines/chemokines on HIV‐1 replication in cells of myeloid lineage can be inhibitory (IFN‐α, IFN‐β, IFN‐γ, GM‐CSF, IL‐10, IL‐13 and IL‐16 and β‐chemok ines), stimulatory (M‐CSF, TNF‐α, TNF‐β, IL‐1, IL‐6) or bifunction al, that is both inhibitory and stimulatory (IL‐4). This review focuses on the overall expression of chemokine receptors on cells of myeloid lineage and considers the mechanisms of entry of R5‐, X4‐ and dual‐tropic strains of HIV‐1 into these cells. The effects of cytokines/chemokines on viral entry and productive HIV‐1 infection are also reviewed. Copyright © 2003 John Wiley & Sons, Ltd.
Clinical consequences of hepatitis C virus infection
Authors: Zoulim F. , Chevallier M. , Maynard M. , Trepo C.
Published: January 2003

Hepatitis C virus (HCV) is a positive strand RNA virus that belongs to the Hepacivirinae genus within the Flaviviridae family. HCV infection has a wide spectrum of cellular tropism and clinical presentations. This has major impacts in terms of pathogenesis and diagnosis. Consequently, a wide range of clinical consequences characterises this viral infection, including asymptomatic chronic carriage, acute hepatitis, chronic hepatitis, cirrhosis, hepatocellular carcinoma and extrahepatic manifestations. The latter are commonly observed and may represent the first sign of the disease. A better knowledge of the pathobiology of HCV and its clinical consequences will be important for developing better treatment strategies to cure HCV infection and extrahepatic manifestations. Copyright © 2003 John Wiley & Sons, Ltd.
The new cell culture smallpox vaccine should be offered to the general population
Authors: Bicknell William , James Kenneth
Published: January 2003

A series of major factors must be weighed in deciding whether or not, and to what extent, a particular country should consider pre‐exposure vaccination for smallpox. These include the risk of a bioterrorist attack using smallpox, the risk of secondary spread from another country, the risks and benefits of vaccination, the effectivenes s of vaccination pre‐ and post‐exposure, the prevalence of immunocompromised persons, the capacity of the medical care delivery system and the wealth of a nation. We review here the issues and variables relevant for policy making, propose a framework for country‐specific decision making and suggest the World Health Organization has a key role to play, particularly with regard to lower‐income countries. In doing so, we support the proposition. Copyright © 2003 John Wiley & Sons, Ltd.
The new cell culture smallpox vaccine should not be offered to the general population
Authors: Mortimer Philip P.
Published: January 2003

Cell based smallpox vaccines are to be welcomed, but any decision to vaccinate whole populations must await firstly better intelligence about the gravity of the threat from bioterrorists, including their ability to release smallpox in such a way that wide dissemination could take place; secondly evidence that vaccines grown in cell culture are protective and safe; and thirdly that the vaccines would be generally acceptable and their introduction would not compromise the rest of national immunisation programmes. Smallpox vaccination should not be offered to the general population until these uncertainties have been resolved, by which time bioterrorism might possibly have been overcome or the development of antiviral treatment might have made renewed smallpox vaccination unnecessary. Meanwhile, preparations for rapid deployment of the historically well‐tried containment measures at the epicentres of any smallpox release should proceed, their effectiveness should be tested, and their adequacy kept under review. Copyright © 2003 John Wiley & Sons, Ltd.
Strong interplanetary magnetic field By‐related plasma convection in the ionosphere and cusp field‐aligned currents under northward interplanetary magnetic field conditions
Authors: Le G. , Lu G. , Strangeway R. J. , Pfaff R. F.
Published: January 2003

We present in this paper an investigation of interplanetary magnetic field (IMF) By‐related plasma convection and cusp field‐aligned currents using Fast Auroral Snapshot (FAST) data and the assimilative mapping of ionospheric electrodynamics (AMIE) model during a prolonged interval with large positive IMF By and northward Bz conditions (By/Bz ≫ 1). Using the FAST single trajectory observations to validate the global convection patterns at key times and key locations, we have demonstrated that the AMIE procedure provides a reasonably good description of plasma circulations in the ionosphere during this interval. Our results show that the plasma convection in the ionosphere is consistent with the antiparallel merging model. When the IMF has a strongly positive By component under northward conditions, we find that the global plasma convection forms two cells oriented nearly along the Sun‐Earth line in the ionosphere. In the Northern Hemisphere, the dayside cell has clockwise convection, mainly circulating within the polar cap on open field lines. It appears to be the lobe cell convection. A second cell with counterclockwise convection is located in the nightside, circulating across the polar cap boundary. The lobe cell convection is driven by the reconnection along the antiparallel merging lines poleward of the cusp extending toward the duskside when IMF By/Bz ≫ 1. The field‐aligned currents in the cusp region flow downward into the ionosphere. The return field‐aligned currents extend into the polar cap in the center of the dayside lobe convection cell. The field‐aligned currents are closed through the Peterson currents in the ionosphere, which flow poleward from the polar cap boundary along the electric field direction.
Galileo observations of electron beams and thermal ions in Jupiter's magnetosphere and their relationship to the auroras
Authors: Frank L. A. , Paterson W. R.
Published: January 2003

The thermal ion parameters within the energy range 7 V to 53 kV and the electron velocity distributions for the energy range 1 kV to 53 kV are presented for three Galileo spacecraft orbits around Jupiter. The orbital segments extended from perijove at radial distances about 9 RJ out to positions in the plasma sheet at 50 RJ. Inbound segments and outbound segments were positioned in the local morning and premidnight sectors, respectively, in the Jovian equatorial magnetosphere. Because the magnetic equatorial plane is tilted with respect to the spacecraft orbital plane, the plasma sheet is traversed about every 5 hours at System III longitudes about 110° and 290° alternatively. At radial distances extending to about 30 RJ, there is a strong dependence of ion temperatures on System III longitude. The ion temperatures are higher at 290° relative to those at 110°. At perijove of 9 RJ the ion temperatures were about 5 × 106 K and similar to those in the hot Io torus at 7 RJ. Ion temperatures increased over the radial distance range of 10 to 25 RJ to values of about 5 × 107 to 108 K. At 9 to 20 RJ the ion bulk flows were about 60% of rigid corotational values and were well ordered and directed in the corotational direction. At greater distances in the plasma sheet the bulk motions became highly variable with large reductions in the corotational direction but with large radial outflows. This behavior exhibits a significant dependence on the local‐time position of the spacecraft with greater radial flows in the premidnight sector. Intense electron beams which were aligned parallel and antiparallel to the magnetic field were detected at radial distances of about 20 to 30 RJ. For Jupiter's plasma sheet at these radial distances it appears likely that a region of intense plasma heating at low altitudes is responsible for the electron beams. These electron beams are identified with the main auroral ring. The electron energies in the beams span the range of several keV to tens of keV. Their projection into the auroral ionosphere provides for arc widths in the range of 1000 km or less. The energy fluxes at the Jovian auroral ionosphere, after correction for the angular width of the field of view of the electrostatic analyzer, extend up to 100 ergs/cm2‐s and are sufficient to excite maximum far‐ultraviolet emissions in the megarayleigh range as remotely observed with cameras.
Aftershocks and pore fluid diffusion following the 1992 Landers earthquake
Authors: Bosl W. J. , Nur A.
Published: January 2003

We model the evolution of regional stress following the 1992 Landers earthquake in order to test the importance of pore fluid flow in producing aftershocks. Rising fluid pressure due to pore fluid flow and the resulting Coulomb stress changes were found to be strongly correlated with the time and location of aftershock events. Regional aftershock frequencies computed by integrating pore pressure decay rates also agreed quite well with aftershock data. Calculations show that regions of rising postseismic poroelastic Coulomb stress overlap considerably with regions of positive coseismic Coulomb stress. Thus pore fluid flow, which affects pore pressure within faults and causes regional poroelastic stress evolution following earthquakes, gradually evolves the initial coseismic stress changes. Together these changes provide a reasonable physical mechanism for aftershock triggering which agrees with data for the 1992 Landers earthquake.
Upwelling of deep mantle material through a plate window: Evidence from the geochemistry of Italian basaltic volcanics
Authors: Gasperini D. , Blichert‐Toft J. , Bosch D. , Del Moro A. , Macera P. , Albarède F.
Published: January 2003

The isotopic compositions of basaltic lavas from the Quaternary and Plio‐Pleistocene Italian volcanics (Tuscan Magmatic Province, Roman Magmatic Province, Vesuvius, Aeolian Islands, Etna, and Iblean Basin) define binary hyperbolic relationships in the 87Sr/86Sr–206Pb/204Pb–εNd–εHf space. The isotopic compositions of the two end‐members of these mixing arrays are assessed by least‐squares regression. The mantle‐derived component (206Pb/204Pb = 19.8, 87Sr/86Sr = 0.7025, εNd = +8, εHf = +9) is a rather homogeneous mixture of the standard high‐μ (HIMU) and depleted mantle (DM) components. The crust‐derived component (206Pb/204Pb = 18.5, 87Sr/86Sr > 0.715, εNd = −12, εHf = −11) accounts for the enrichment of K and other large‐ion‐lithophile elements in the Italian volcanics. As shown by the relationship in εHf–εNd space and the lower‐than‐chondritic Hf/Sm ratio, this crustal component is dominated by pelagic sediments rather than terrigenous material. The overall scarcity of calc‐alkaline compositions in the Italian volcanics and the presence of a HIMU component, which is the hallmark of hot spot basalts, raise the question of how plume mantle source contributes to volcanism in a subduction environment. At about 13 Ma, the Apennine collision terminated the westward subduction of the Adria plate under the European margin and rotated the direction of convergence to the northwest. The cumulative differential of subduction between the fossil plate under Tuscany and the active plate under Sicily since the opening of the Tyrrhenian Sea amounts to at least 300 km and is large enough to rift the dipping plate and open a plate window beneath the southern part of the peninsula. This model is consistent with recent high‐resolution seismic tomography. We propose that the counterflow of mixed upper and lower mantle passing the trailing edge of the rifted plate is the source of Italian mafic volcanism. Alternatively, material from a so‐far unidentified plume may be channeled through the plate window. The crustal signature is probably acquired by interaction of the mantle advected through the window with the upper part of the subducted plate.
Erroneous fold tests as an artifact of alteration chemical remanent magnetization
Authors: Madsen Karen Nørgaard , Walderhaug Harald , Torsvik Trond
Published: January 2003

Several studies have shown that an alteration chemical remanent magnetization (CRM) may have a direction intermediate between that of the remanence of the parent phase and the field during remagnetization. In a fold a surviving natural remanent magnetization (NRM) is exposed at varying angles to the remagnetizing field, giving rise to varying degree of remanence deflection. A laboratory experiment was carried out to investigate how the CRM deflection varies with angle between parent phase NRM and remagnetizing field, HCRM, and we discuss how this variation would affect the results of a fold test. The experiment was performed on a Silurian lava, with a well‐defined single component NRM carried by deuterically oxidized titanomagnetite (TM). Specimens of the lava were arranged in a fold configuration with NRM at various angles to a 50 μT laboratory field. Heating to 525°C resulted in oxidation of part of the primary TM phase to hematite, leading to the formation of stable remanence components of intermediate direction, as revealed by thermal demagnetization. Stepwise unfolding of the CRM gave a syntectonic fold test result. The variation of remanence deflection with angle between HCRM and initial NRM can be understood in terms of vector addition of fields or remanence components. A model for CRM acquisition derived from the experimental results was employed to explore CRM in other fold configurations. It appears from analysis of synthetic data that it is possible to falsely conclude both synfold and prefold magnetization from fold tests on postfold or synfold CRM.
The effects of metastable olivine(α) wedge in subducted slabs on theoretical seismic waveforms of deep earthquakes
Authors: Yoshioka Shoichi , Murakami Toru
Published: January 2003

Assuming three kinds of materials, 100% olivine ((Mg0.89Fe0.11)2SiO4), pyrolite, and piclogite as composition of the upper mantle, we constructed pressure–temperature dependent seismic velocity structure models in the upper mantle beneath a subduction zone. For this purpose, we employed values of physical properties of composite minerals newly determined by using a genetic algorithm (GA) and obtained the thermal structure beneath the subduction zone as a numerical solution of a two‐dimensional (2‐D) thermal‐fluid coupled problem. Furthermore, we investigated the effects of a metastable olivine(α) wedge in subducted slabs on theoretical seismic waveforms of deep earthquakes, which propagate through the velocity structure by solving the P‐SV problem numerically. The effects of center frequency of the excited waves at hypocenters, focal mechanism, location of hypocenter, upper mantle compositions, values of physical properties, a dip angle of subducting slabs, anelastic attenuation, subducting velocity, and depth of deep earthquakes on seismic waveforms were investigated in detail. Theoretical seismograms at the Earth's surface indicate that coda waves with small amplitudes of duration time of 20–30 s appear following direct P and S waves for models with the metastable olivine(α) wedge inside the slabs. The coda waves can be explained by the excitation by reflections and conversions at a large seismic velocity discontinuity between the metastable olivine(α) wedge and the surrounding slab. For models with center frequency of 0.25 Hz, purer olivine composition, a faster subducting velocity, and focal depth of 500 km, waves with larger amplitudes were excited at the discontinuity. The results of this study may give important clues to detect the existence of the metastable olivine(α) wedge from seismological observations.
Seismicity at the southern East Pacific Rise from recordings of an ocean bottom seismometer array
Authors: Shen Yang
Published: January 2003

Seismic data recorded by ocean bottom seismometers (OBSs) at the southern East Pacific Rise (SEPR) were analyzed to characterize seismicity at fast spreading mid‐ocean ridges. An automated event detection algorithm based on pattern recognition was developed to identify earthquake‐generated T phases. The waveform cross‐correlation and least squares method was found to provide more robust estimates of T phase relative travel times than the method of picking T phase maximum amplitude. The OBSs and subsequent equatorial Pacific hydrophones recorded earthquakes near an earthquake swarm in 1992, which was located ∼300 km west of the ridge axis at about 18°S and 116°W. The process that generated the 1992 swarm either was reactivated 3 years later during the OBS experiment or has been continuously active in the past decade. This long‐term activity suggests renewable stresses, which are consistent with the interpretation that magma injection was the cause of the 1992 swarm. In contrast to the swarm characteristics of earthquakes on the west flank of the ridge axis, earthquakes on the Nazca flank were randomly distributed in time and space. This difference in seismicity may result from the difference in the thermal structure of the Pacific and Nazca plates. The few earthquakes located at or near the ridge axis had very small magnitudes, reflecting the presence of shallow magma chambers and the thin elastic layer of the SEPR. This result suggests that acoustic monitoring of earthquakes associated with dike intrusion is difficult at regional scales at the SEPR. There is no apparent correlation between seismicity and off‐axis seamounts.
Application of k‐ϵ turbulence models to enclosed basins: The role of internal seiches
Authors: Goudsmit G.‐H. , Burchard H. , Peeters F. , Wüest A.
Published: January 2003

A numerical model was developed for the prediction of the density stratification of lakes and reservoirs. It combines a buoyancy‐extended k‐ϵ model with a seiche excitation and damping model to predict the diffusivity below the surface mixed layer. The model was applied to predict the seasonal development of temperature stratification and turbulent diffusivity in two medium‐sized lakes over time periods ranging from 3 weeks to 2 years. Depending on the type of boundary condition for temperature, two or three model parameters were optimized to calibrate the model. The agreement between the simulated and the observed temperature distributions is excellent, in particular, if lake surface temperatures were prescribed as surface boundary condition instead of temperature gradients derived from heat fluxes. Comparison of different model variants revealed that inclusion of horizontal pressure gradients and/or stability functions is not required to provide good agreement between model results and data. With the aid of uncertainty analysis it is shown that the depth of the mixed surface layer during the stratified period could be predicted accurately within ±1 m. The sensitivity of the model to several parameters is discussed.
Characteristics of interleaving in the western equatorial Pacific
Authors: Richards Kelvin , Banks Helene
Published: January 2003

The characteristics of intrusive thermohaline features in the thermocline of the western equatorial Pacific are examined during two different climatic states. The vertical and meridional structure of the features is determined from a total of 12 high‐resolution meridional sections. Although there is considerable variability of the broader structure of the flow and temperature/salinity fields, the spatial scale of the interleaving is found to be persistent over all sections. The Turner angle and correlations between the spice anomaly and density anomaly suggest that double‐diffusive processes may be important in the vertical flux of properties. The characteristics of the interleaving are compared with the results from the theories of double‐diffusive interleaving and inertial instability. It is found that the observations are consistent with both. It is difficult to differentiate between the two theories in explaining the presence of the layers. Indeed, both mechanisms may be playing a role. The magnitude of the cross‐equatorial fluxes of heat and salt due to the features is estimated and shown to be comparable with estimates due to other processes. There is a strong potential for the interleaving to impinge on the large‐scale dynamics of the equatorial Pacific Ocean.
Physically based modeling of QuikSCAT SeaWinds passive microwave measurements for rain detection
Authors: Boukabara Sid‐Ahmed , Hoffman Ross N. , Grassotti Christopher , Leidner S. Mark
Published: January 2003

We present a method for detecting rain‐contaminated wind vector cells in QuikSCAT SeaWinds scatterometer observations. This rain detection method uses passive measurements of microwave brightness temperature obtained as a signal processing by‐product from the standard SeaWinds active scatterometer measurements. The rain flag is developed theoretically first by calibrating the SeaWinds brightness temperatures using Special Sensor Microwave Imager (SSM/I) observations and then by using physically based simulations including the effects of both rain and ice precipitation. Rain retrievals are validated by comparison to SSM/I‐observed rain rates and to other independently produced SeaWinds rain flags and produce rain maps that agree well with the SSM/I estimates. The rain detection method may be used to complement existing rain flags in the current operational QuikSCAT data product. In addition, an atmospheric correction algorithm was developed to dynamically adjust the backscatter coefficient measurements for variations in water vapor and cloud liquid water; results are not significantly different from the climatological correction currently implemented.
LF/VLF and VHF lightning fast‐stepped leader observations
Authors: Heavner Matthew J. , Smith David A. , Jacobson Abram R. , Sheldon Ricki J.
Published: January 2003

This paper reports multiplatform observations of leader radiation preceding initial cloud‐to‐ground lightning return strokes by <6 ms. Specifically, we present multistation ground‐based LF/VLF recordings of events with large‐amplitude leader activity (comparable in amplitude to the return stroke amplitude). The events were selected for their coincidence with VHF observations by the FORTE satellite. Some FORTE VHF leader step observations have obvious direct and ground reflection components. For these steps, which temporally correspond to specific features in the ground LF/VLF field change records, we calculate a source height based on event satellite geometry. We determine source heights between 4.0 and 5.5 km. For FORTE records with multiple reflected events we calculate vertical leader propagation velocities on the order of 106 m/s. The determined vertical leader propagation speeds are an order of magnitude greater than those reported as typical values for stepped leader velocities associated with initial return strokes.
Retrieval and characterization of ozone profiles from solar infrared spectra at the Jungfraujoch
Authors: Barret B. , De Mazière M. , Demoulin P.
Published: January 2003

Vertical distributions of ozone from June 1996 to November 2000 have been retrieved from high‐resolution Fourier transform infrared (FTIR) solar absorption spectra recorded at the primary Network for Detection of Stratospheric Change station of the Jungfraujoch in the Swiss Alps (46.5°N, 8°E, 3580 m above sea level (asl). The retrievals were performed using the Optimal Estimation Method (OEM), both in a narrow spectral interval (1002.567–1003.2 cm−1) and in a broad spectral interval (1000.0–1005.0 cm−1) in the O3 9.6‐μm band. A thorough characterization of the retrievals has been performed following the lines of OEM, including an information content analysis, a study of the correlations between retrieved instrumental parameters and retrieved ozone concentrations, and an evaluation of the O3 profile error budget. It is demonstrated that the information content is significantly higher for spectra in the broad microwindow, resulting in higher vertical resolutions, on the order of 8 km, of the retrieved profiles extending up to 40 km, and less correlations between retrieved parameters. An independent statistical verification of the retrieval results and their characterization has been performed by comparison of the FTIR ozone profiles with independent measurements. These are the ozone profile measurements from balloon soundings at Payerne, from the microwave radiometer at Bern and the lidar at Observatoire de Haute‐Provence (OHP), and the total column data from the Dobson spectrophotometer at Arosa. Applying the optimum retrieval procedure in the broad spectral interval, an excellent agreement has been found between the FTIR O3 profile data and the correlative data. The largest offset of the FTIR data in comparison with the correlative data is found with respect to the lidar data in the 24‐ to 40‐km layer, and is on the order of 5%. No systematic biases have been found in the troposphere, neither in the upper troposphere‐lower stratosphere (UTLS) up to 18 km. The dispersion of the relative differences between the data sets, if any, is never larger than half of the natural ozone variability.
Information entropy to measure temporal and spatial complexity of unsaturated flow in heterogeneous media
Authors: Mays David C. , Faybishenko Boris A. , Finsterle Stefan
Published: January 2003

Geologic heterogeneity, coupled with the nonlinear interplay of gravity, capillarity, and applied pressure gradients, results in a rich variety of flow behaviors in unsaturated fractured rocks and porous media. In this paper, we evaluate the complexity of these behaviors using information entropy. We create an empirical probability distribution function directly from a data set, then apply Shannon's definition of information entropy to quantify the complexity of the data. As an example, we use information entropy to evaluate the temporal and spatial complexity of simulated flow processes invoked by infiltration into heterogeneous porous media. Our analysis shows that the complexity of this unsaturated flow process depends on both geologic heterogeneity and uncertainty arising from the flow dynamics. Finally, we investigate the marginal value of additional data collection using randomly selected “virtual wells.” These calculations demonstrate that computed information entropy increases with additional virtual wells, but the rate of increase declines.
Methyl bromide cycling in a warm‐core eddy of the North Atlantic Ocean
Authors: Yvon‐Lewis Shari A. , Butler James H. , Saltzman Eric S. , Matrai Patricia A. , King Daniel B. , Tokarczyk Ryszard , Moore Robert M. , Zhang Jia‐Zhong
Published: January 2003

We conducted a detailed investigation of the evolution of methyl bromide concentrations, degradation rates, and ventilation rates for 26 days in a naturally contained, warm‐core eddy of the North Atlantic Ocean. This is the first study of the oceanic cycling of methyl bromide in a natural, contained system with a complete suite of supporting measurements of physical and chemical variables. Methyl bromide concentrations in the mixed layer ranged from 2.3 to 4.2 nmol m−3, degradation rates ranged from 0.1 to 0.9 nmol m−3 d−1, net sea‐to‐air exchange rates ranged from 0 to 0.5 nmol m−3 d−1, and net loss rates through the thermocline were less than 0.1 nmol m−3 d−1. From a mass balance for methyl bromide in the mixed layer, we calculated production rates ranging from <0.1 to 1.3 nmol m−3 d−1. The median of this range, 0.48 nmol m−3 d−1, is higher than the ∼0.15 nmol m−3 d−1 necessary to maintain the reported global oceanic emission of 56 Gg yr−1. This is reasonable, because our study area was supersaturated in methyl bromide, whereas the ocean as a whole is undersaturated.
Long‐range atmospheric transport of terrestrial biomarkers to the western North Atlantic
Authors: Conte Maureen H. , Weber J. C.
Published: January 2003

We analyzed terrestrial plant‐derived leaf wax biomarkers in aerosols collected at Bermuda over a 2.5 years time series. Leaf waxes comprised 60–70% of extractable lipids and 0.5–1.0% of total organic carbon. Biomarker concentrations in biweekly integrated samples varied by over an order of magnitude and indicate that long‐range atmospheric transport is highly episodic. Results indicate that North America is the main source of terrestrial organic carbon in the western North Atlantic and that terrestrial carbon advected from Africa originates mainly in tropical C3 forests to the south of Saharan dust‐source regions. Terrestrial biomarker concentrations were poorly correlated with organic carbon concentrations, which suggest significant source differences. Variations in relative abundance of the major wax compound classes and in their carbon isotopic composition indicate that waxes in aerosols are mainly derived from ablation off living vegetation and reveal a large‐scale seasonal cycle in terrestrial biosphere emissions of wax biomarkers.
Fracture intersections as integrators for unsaturated flow
Authors: Wood Thomas R. , Nicholl Michael J. , Glass Robert J.
Published: January 2003

A simple experiment finds that fracture intersections can act to integrate unsaturated flows, such that regular, low flows entering the intersection from above are transformed into large, less frequent pulses below. At low flows, our simple intersection forms two capillary barriers. Water from above pools at the intersection until sufficient pressure builds to breach the barriers and discharge stored fluid. The barriers then reform and the process is repeated. At low flows, the volume discharged from the intersection remains relatively uniform across a range of flow rates. At higher flows, discharge volume is highly variable, and a viscous stabilized non‐pulsating regime occurs at the highest flow rate that we considered.
Linking wind and interannual upwelling variability in a regional model of the southern Benguela
Authors: Blanke Bruno , Roy Claude , Penven Pierrick , Speich Sabrina , McWilliams James , Nelson Greville
Published: January 2003

We quantify the wind contribution to the development of interannual sea surface temperature (SST) anomalies along the shelf of southern Africa. We compare numerical simulations that differ only in the amount of variability kept in the ERS1/2‐derived surface wind forcing. Surprisingly, most of the cold and warm episodes over the Agulhas Bank are strictly related to local fluctuations of the forcing, whereas the shelf of the west coast extending 400 km north of Cape Columbine is equally sensitive to open‐sea wind fluctuations. We diagnose the respective role of mesoscale eddy activity and of low frequency and intra‐monthly wind fluctuations in generating interannual SST variability. The fair degree of correlation obtained at a few locations between the model and concomitant observations confirms the interest of a regional numerical tool to study anomalous events in the Benguela system.
Experiments in the NH3‐H2O system in the [0, 1 GPa] pressure range ‐ implications for the deep liquid layer of large icy satellites
Authors: Mousis Olivier , Pargamin Judith , Grasset Olivier , Sotin Christophe
Published: January 2003

We have experimentally studied the peritectic's melting temperature of a 25 wt% ammonia water solution in the [0, 1 GPa] pressure range by using a high pressure ‐ low temperature membrane sapphire anvil cell with nitrogen cooled cryostat. Our experimental results are in agreement with those presented by Hogenboom et al. [1997] in the [0, 0.4 GPa] pressure domain where the peritectic's melting temperature follows a plateau at 180 K. The present experimental work fills the lack of data between 0.4 and 0.7 GPa. It also suggests that the peritectic's melting temperature is much higher than that between 0 and 0.4 GPa and does not vary very much with pressure at least up to 1 GPa. This implies the existence of two new high pressure phases in the ammonia‐water system. The behaviour of the peritectic's melting curve above 0.5 GPa might play an important role in the evolution of a deep liquid layer in the interiors of the largest icy satellites including Titan, Ganymede and Callisto. We show that the cooling of the deep liquid layer may have involved the crystallization of an ammonia bearing phase at higher temperature than previously expected. If the initial fraction of ammonia relative to ices is greater than 11 weight per cent, taking the partial ammonia depletion into account may lead to a final liquid layer thinner than previously inferred.
Sensitivity of nuclear magnetic resonance relaxation measurements to changing soil redox conditions
Authors: Bryar Traci R. , Knight Rosemary J.
Published: January 2003

Laboratory proton nuclear magnetic resonance (NMR) relaxation measurements were made on fluid‐saturated soil samples under reducing and oxidizing conditions. We used well‐characterized kaolinite and sand samples with known concentrations of Fe(II) and Fe(III) compounds as the representative soils. Changes in dissolved oxygen concentration in the water in the soils caused changes in relaxation time that are too small to be reliably detected by field NMR measurements. In contrast, NMR relaxation measurements were shown to be very sensitive to small changes in the concentration of Fe(III) species in soil, as a consequence of changing redox conditions. Oxidation of as little as 0.030 mg/g of Fe(II) species to Fe(III) oxyhydroxides resulted in a 30–50% decrease in relaxation time. These results have important implications for the potential use of NMR field instruments to monitor changing redox conditions using the Fe(III)‐Fe(II) redox couple as an indicator.
Predicting oceanic methyl bromide saturation from SST
Authors: King Daniel B. , Butler James H. , Yvon‐Lewis Shari A. , Cotton Sara A.
Published: January 2003

Data collected from the North Pacific Ocean during September and October 1999 were combined with data from other cruises to assess seasonal differences in the relationships between sea surface temperature (SST) and methyl bromide (CH3Br) saturation. We now are able to reproduce observed saturation anomalies substantially better with the revised, seasonal CH3Br‐SST equations than with those that were independent of season. The effect is most noticeable in temperate waters where data combined on an annual basis proved insufficient. The estimated, net global air‐sea flux of CH3Br remains negative at −10 to −18 Gg yr−1, which is consistent with extrapolations from observations.
Evidence of periodic (2–3 hour) near‐tail magnetic reconnection and plasmoid formation: Geotail observations
Authors: Huang Chao‐Song
Published: January 2003

During magnetospheric substorms, magnetic reconnection occurs in the near tail and causes the formation of plasmoids. In this paper, we present Geotail observations of periodic magnetic reconnection and plasmoids in the near tail. On April 17–18, 2002, Geotail was located in the northern lobe and detected ten cycles of magnetic field compressions within 24 hours, and southward turnings of the magnetic field Bz component or formations of plasmoids were clearly identified in the first seven cycles. The average period of the plasmoids was ∼2.5 hours. A solar wind pressure impulse appeared to trigger the first magnetic compression (or plasmoid). Plasmoids continued to occur for many cycles after the solar wind pressure and interplanetary magnetic field had become stable. The observations suggest that substorms can be periodic and that the periodic substorms can occur without requirement of continuous external triggering.
First satellite ozone distributions retrieved from nadir high‐resolution infrared spectra
Authors: Turquety Solène , Hadji‐Lazaro Juliette , Clerbaux Cathy
Published: January 2003

The Interferometric Monitor for Greenhouse Gases (IMG) on board the Japanese ADEOS platform provided the first high resolution atmospheric spectra allowing the simultaneous measurement of several IR absorbing species, including ozone. The paper describes the retrieval of total column ozone fields from nadir radiances, using an inversion algorithm developed for the Infrared Atmospheric Sounding Interferometer (IASI). The accuracy and sensitivity of the retrieved concentrations are assessed. The global distributions obtained from the available IMG/ADEOS Level 1C data are shown to be in good agreement with the TOMS/ADEOS (Total Ozone Mapping Spectrometer) Level 2 measurements.
Critical evaluation of emissions of potential new gases for OH estimation
Authors: Huang Jin , Prinn Ronald G.
Published: January 2003

Reactions with OH in the troposphere provide the dominant removal path for a wide variety of greenhouse and ozone‐depleting gases. Accurate determination of global and regional tropospheric OH concentrations is therefore very important and can be achieved by measuring gases that react with OH and whose emissions are well known. CH3CCl3 has been used for this purpose. Prior studies have shown that three of the new chlorofluorocarbon (CFC) substitutes, HFC‐134a (CH2FCF3), HCFC‐141b (CH3CCl2F), and HCFC‐142b (CH3CClF2), could be used potentially to derive accurate global‐average OH concentrations in the future provided that the industrial emissions of these gases can be reliably estimated. As a test of their currently available emission estimates, we optimally determine the monthly emissions for these three gases using global measurements from the NOAA‐CMDL and Advanced Global Atmospheric Gases Experiment (AGAGE) networks. Our study uses two distinct OH scenarios (constant OH, quadratically varying OH) derived from CH3CCl3 observations. We conclude that current published industrial estimates [Alternative Fluorocarbon Environmental Assessment Study (AFEAS), 2002] of HCFC‐142b and HCFC‐141b need to be increased by 18 ± 15% over the 1992–2000 period and 10−13+15% over the 1993–2000 period, respectively, while the emissions of HFC‐134a (from 1993 to 2000) are only 4 ± 10% more than those yielding the best agreement with atmospheric observations. Estimates of global‐average OH concentrations using measurements and AFEAS [2002] emissions differ statistically from the average OH derived from CH3CCl3 for HCFC‐141b and HCFC‐142b but not for HFC‐134a. On the other hand, OH trends deduced from all three HCFC/HFC gases are implausibly large implying problems with the AFEAS [2002] estimates of the temporal variations in their emissions. As the viability of CH3CCl3 for estimating OH declines in the future, additional evaluations of the emissions and OH kinetics of HCFC‐141b, HCFC‐142b, and HFC‐134a therefore have high priority.
Color and genomic ancestry in Brazilians
Authors: Parra Flavia C. , Amado Roberto C. , Lambertucci José R. , Rocha Jorge , Antunes Carlos M. , Pena Sérgio D. J.
Published: January 2003

This work was undertaken to ascertain to what degree the physical appearance of a Brazilian individual was predictive of genomic African ancestry. Using a panel of 10 population-specific alleles, we assigned to each person an African ancestry index (AAI). The procedure was able to tell apart, with no overlaps, 20 males from northern Portugal from 20 males from São Tomé Island on the west coast of Africa. We also tested 10 Brazilian Amerindians and observed that their AAI values fell in the same range as the Europeans. Finally, we studied two different Brazilian population samples. The first consisted of 173 individuals from a rural Southeastern community, clinically classified according to their Color (white, black, or intermediate) with a multivariate evaluation based on skin pigmentation in the medial part of the arm, hair color and texture, and the shape of the nose and lips. In contrast to the clear-cut results with the African and European samples, our results showed large variances and extensive overlaps among the three Color categories. We next embarked on a study of 200 unrelated Brazilian white males who originated from cosmopolitan centers of the four major geographic regions of the country. The results showed AAI values intermediate between Europeans and Africans, even in southern Brazil, a region predominantly peopled by European immigrants. Our data suggest that in Brazil, at an individual level, color, as determined by physical evaluation, is a poor predictor of genomic African ancestry, estimated by molecular markers.
A pervasive mechanism for analgesia: Activation of GIRK2 channels
Authors: Blednov Y. A. , Stoffel M. , Alva H. , Harris R. A.
Published: January 2003

G protein-coupled inwardly rectifying potassium channels (GIRKs) provide a common link between numerous neurotransmitter receptors and the regulation of synaptic transmission. We asked whether GIRKs specify a single behavioral action that is produced by drugs acting on the diverse receptors coupled with GIRKs. By using GIRK2-null mutant mice, we found marked reduction or complete elimination of the antinociceptive (hot plate test) effects of ethanol, oxotremorine, nicotine, baclofen, clonidine, and the cannabinoid receptor agonist WIN 55,212. However, ketamine analgesia remained intact. For most drugs, there was a sex difference in antinociceptive action, and the impact of deletion of the GIRK2 channel was less in female mice. The deletion of the GIRK2 channel blocks the opioid-dependent component of stress-induced analgesia (SIA), whereas nonopioid SIA was not changed. We propose that opioid, α adrenergic, muscarinic cholinergic, γ-aminobutyric acid-B, and cannabinoid receptors are coupled with postsynaptic GIRK2 channels
in vivo
. Furthermore, this pathway accounts for essentially all of the antinociceptive effects in males, although females appear to recruit additional signal transduction mechanisms for some analgesic drugs.
Photoisomerization of a rotaxane hydrogen bonding template: Light-induced acceleration of a large amplitude rotational motion
Authors: Gatti Francesco G. , León Salvador , Wong Jenny K. Y. , Bottari Giovanni , Altieri Andrea , Morales M. Angeles Farran , Teat Simon J. , Frochot Céline , Leigh David A. , Brouwer Albert M. , Zerbetto Francesco
Published: January 2003

Establishing methods for controlling aspects of large amplitude submolecular movements is a prerequisite for the development of artificial devices that function through rotary motion at the molecular level. Here we demonstrate that the rate of rotation of the interlocked components of fumaramide-derived [2]rotaxanes can be accelerated, by >6 orders of magnitude, by isomerizing them to the corresponding maleamide [2]rotaxanes by using light.
Functional connectivity in the resting brain: A network analysis of the default mode hypothesis
Authors: Greicius Michael D. , Krasnow Ben , Reiss Allan L. , Menon Vinod
Published: January 2003

Functional imaging studies have shown that certain brain regions, including posterior cingulate cortex (PCC) and ventral anterior cingulate cortex (vACC), consistently show greater activity during resting states than during cognitive tasks. This finding led to the hypothesis that these regions constitute a network supporting a default mode of brain function. In this study, we investigate three questions pertaining to this hypothesis: Does such a resting-state network exist in the human brain? Is it modulated during simple sensory processing? How is it modulated during cognitive processing? To address these questions, we defined PCC and vACC regions that showed decreased activity during a cognitive (working memory) task, then examined their functional connectivity during rest. PCC was strongly coupled with vACC and several other brain regions implicated in the default mode network. Next, we examined the functional connectivity of PCC and vACC during a visual processing task and show that the resultant connectivity maps are virtually identical to those obtained during rest. Last, we defined three lateral prefrontal regions showing increased activity during the cognitive task and examined their resting-state connectivity. We report significant inverse correlations among all three lateral prefrontal regions and PCC, suggesting a mechanism for attenuation of default mode network activity during cognitive processing. This study constitutes, to our knowledge, the first resting-state connectivity analysis of the default mode and provides the most compelling evidence to date for the existence of a cohesive default mode network. Our findings also provide insight into how this network is modulated by task demands and what functions it might subserve.
A macromolecular complex of β
2
adrenergic receptor, CFTR, and ezrin/radixin/moesin-binding phosphoprotein 50 is regulated by PKA
Authors: Naren Anjaparavanda P. , Cobb Bryan , Li Chunying , Roy Koushik , Nelson David , Heda Ghanshyam D. , Liao Jie , Kirk Kevin L. , Sorscher Eric J. , Hanrahan John , Clancy John P.
Published: January 2003

It has been demonstrated previously that both the cystic fibrosis transmembrane conductance regulator (CFTR) and β
2
adrenergic receptor (β
2
AR) can bind ezrin/radixin/moesin-binding phosphoprotein 50 (EBP50, also referred to as NHERF) through their PDZ motifs. Here, we show that β
2
is the major adrenergic receptor isoform expressed in airway epithelia and that it colocalizes with CFTR at the apical membrane. β
2
AR stimulation increases CFTR activity, in airway epithelial cells, that is glybenclamide sensitive. Deletion of the PDZ motif from CFTR uncouples the channel from the receptor both physically and functionally. This uncoupling is specific to the β
2
AR receptor and does not affect CFTR coupling to other receptors (e.g., adenosine receptor pathway). Biochemical studies demonstrate the existence of a macromolecular complex involving CFTR-EBP50-β
2
AR through PDZ-based interactions. Assembly of the complex is regulated by PKA-dependent phosphorylation. Deleting the regulatory domain of CFTR abolishes PKA regulation of complex assembly. This report summarizes a macromolecular signaling complex involving CFTR, the implications of which may be relevant to CFTR-dysfunction diseases.
Absence of p16
INK4a
and truncation of ARF tumor suppressors in chickens
Authors: Kim Soo-Hyun , Mitchell Michael , Fujii Hideta , Llanos Susana , Peters Gordon
Published: January 2003

The
INK4b
-
ARF
-
INK4a
locus on human chromosome 9p21 (Human Genome Organization designation
CDKN2B
-
CDKN2A
), and the corresponding locus on mouse chromosome 4, encodes three distinct products: two members of the INK4 cyclin-dependent kinase inhibitor family and a completely unrelated protein, ARF, whose carboxyl-terminal half is specified by the second exon of
INK4a
but in an alternative reading frame. As INK4 proteins block the phosphorylation of the retinoblastoma gene product and ARF protects p53 from degradation, the locus plays a key role in tumor suppression and the control of cell proliferation. To gain further insights into the relative importance of INK4a and ARF in different settings, we have isolated and characterized the equivalent locus in chickens. Surprisingly, although we identified orthologues of INK4b and ARF, chickens do not encode an equivalent of INK4a. Moreover, the reading frame for chicken ARF does not extend into exon 2, because splicing occurs in a different register to that used in mammals. The resultant 60-aa product nevertheless shares functional attributes with its mammalian counterparts. As well as indicating that the locus has been subject to dynamic evolutionary pressures, these unexpected findings suggest that in chickens, the tumor-suppressor functions of INK4a have been compensated for by other genes.