bluuebunny/crossref_metadata_2025 huggingface dataset:
Differential expression of specific FGF ligand and receptor isoforms during angiogenesis associated with prostate cancer progression
Authors: Huss Wendy J. , Barrios Roberto J. , Foster Barbara A. , Greenberg Norman M.
Published: December 2002

BACKGROUND

The aim of this study was to elucidate how changes in temporal and spatial expression patterns of individual components of the fibroblast growth factor (FGF) signaling axis correlate with prostate cancer‐associated angiogenesis to contribute to the progression of this disease.

METHODS

The temporal and spatial expression patterns of specific FGF ligands and receptors were characterized by immunoblot, in situ hybridization, and immunohistochemical analyses in the transgenic adenocarcinoma of the mouse prostate (TRAMP) model.

RESULTS

We detected expression of high molecular weight isoform of FGF‐2 in PIN lesions and detected both high and low molecular weight isoforms of FGF‐2 in advanced tumors. Expression of the mRNA encoding the FGFR1iiib isoform was found to be specifically and differentially expressed in tumor vasculature in TRAMP but was not detected in prostate‐associated vasculature in nontransgenic mice. Expression of the FGFR2iiic isoform was observed to be elevated in the epithelial component of PIN lesions in TRAMP mice.

CONCLUSION

By using the TRAMP model, the expression of FGFR1iiib in intraductal vasculature and expression of FGF‐2 protein were found to be concomitant with the emergence of PIN. These observations implicate specific changes in the FGF axis with the initiation and progression of prostate cancer and underscore the utility of animal models to identify specific molecular changes in early disease. Prostate 54: 8–16, 2003. © 2002 Wiley‐Liss, Inc.
Inhibition of the enzymatic activity of prostate‐specific antigen by boric acid and 3‐nitrophenyl boronic acid
Authors: Gallardo‐Williams Maria T. , Maronpot Robert R. , Wine Robert N. , Brunssen Susan H. , Chapin Robert E.
Published: December 2002

BACKGROUND

Prostate specific antigen (PSA) is a well‐established marker of prostate cancer, but it can also degrade extracellular matrix proteins such as fibronectin and could be involved in tumor progression and metastasis. In this study, we have addressed the use of boric acid and 3‐nitrophenyl boronic acid (NPBA) as PSA inhibitors in vitro.

METHODS

The inhibition of PSA by boric acid was studied by using specific fluorogenic substrates. Fibronectin, a biologically relevant substrate for PSA, was used as a substrate in a zymographic assay, and the degradation of fibronectin by PSA in the presence of boric acid and NPBA was followed by Western Blot.

RESULTS

Low concentrations of boric acid partially inhibited the proteolytic activity of PSA toward a synthetic fluorogenic substrate. Also, by Western blot, we have found significant inhibition in the proteolysis of fibronectin by PSA in the presence of boric acid as well as NPBA. Results indicate that the boronated compounds used in this study can be used for the modulation of PSA activity.

CONCLUSION

PSA activity is inhibited in vitro by boric acid and NPBA. If degradation of fibronectin by PSA were, in fact, an important step in the progression of prostate cancer, then borate‐induced inhibition of PSA activity should help reduce the development and proliferation of prostate carcinomas. Prostate 54: 44–49, 2003. © 2002 Wiley‐Liss, Inc.
Will succession planning increase shareholder wealth? evidence from investor reactions to relay CEO successions
Authors: Shen Wei , Cannella, Albert A.
Published: December 2002

Our study examines investor reactions to a specific form of succession planning—relay succession. Theory predicts that both the initiation and the outcome of a relay CEO succession process will influence shareholder wealth. Our results show that investors generally do not react to the initiation of the process as indicated by heir apparent appointment; but react negatively when the process ends in heir apparent exit from the firm and react positively when the process ends in heir apparent promotion to the CEO position. We also found a strong positive investor reaction to outside CEO promotion and a negative investor reaction to nonheir inside CEO promotion. Further, firm performance exerts an important influence on the wealth effect of heir apparent promotion and exit. Copyright © 2002 John Wiley & Sons, Ltd.
Cointegration of firm strategies within groups: a long‐run analysis of firm behavior in the Japanese steel industry
Authors: Nair Anil , Filer Larry
Published: December 2002

This paper uses cointegration analysis to study the competitive interaction among firms within the integrated and minimill groups in the Japanese steel industry. The use of cointegration analysis overcomes some of the limitations associated with prior attempts at modeling firm behavior within groups, and allows us to model strategies that take considerable time to adjust. Results indicate that several strategies displayed slow adjustment characteristics. All of the strategies that displayed these properties were cointegrated within the group. Finally, over the long run, the rate of strategic response to ‘shocks’ in the system varied across members and strategies: some converged, while others diverged from the group relationship. We conclude by discussing the relevance of our findings to research on strategic groups and competitive dynamics among firms. Thus the paper contributes to the literature on strategic groups and competitive dynamics, and illustrates the use of cointegration analyses to study the competitive behavior of firms. Copyright © 2002 John Wiley & Sons, Ltd.
Qualification initiative surface technology: offer, need, networks
Authors: Baron Waldemar
Published: December 2002

Auf die Überwindung von Innovationsbarrieren nicht‐technischer Art im Bereich moderner Oberflächentechnik insbesondere bei (kleinen und mittleren) Unternehmen zielt das laufende Projekt “Wissenstransfer Oberflächentechnik”, das im Auftrag des Bundesministeriums für Bildung und Forschung (BMBF) vom VDI‐Technologiezentrum Düsseldorf durchgeführt wird. Teil des Projektes ist eine Qualifizierungsinitiative zur Oberflächentechnik. Dabei geht es zunächst darum, die fachspezifischen Bildungsangebote besser zugänglich zu machen, den Qualifizierungsbedarf zu ermitteln sowie Qualifizierungsnetze zu konzipieren und entsprechende Anregungen zu geben. Ergebnisse werden im Rahmen von Fachtagungen, über ein Internetportal sowie mittels intensiver Pressearbeit und einer Schriftenreihe Wissenstransfer Oberflächentechnik an interessierte Stellen transportiert und verbreitet. Im Sinne strategischer Allianzen werden zahlreiche Partner und Institute mit einschlägiger Kompetenz in die Aktivitäten einbezogen, mit Teilanalysen beauftragt sowie für Fachveranstaltungen gewonnen.
Otto von Guericke and the Founding of the Science of Air Pressure
Authors: Streitenberger Peter , Schneider Ditmar
Published: December 2002

Aus Anlass des 400. Geburtstages von Otto von Guericke würdigt der vorliegende Beitrag die überragende Bedeutung Guerickes für die Herausbildung der auf der experimentellen Methode basierenden neuen Naturwissenschaft im 17. Jahrhundert. Guericke gilt unbestritten als Erfinder der Vakuumluftpumpe und hervorragender Experimentator, der durch seine publikumswirksamen Experimente eindrucksvoll die Wirkungen des atmosphärischen Luftdrucks demonstrierte. Weniger bekannt sind dagegen seine physikalisch‐interpretatorischen Leistungen, ohne die er nicht unabhängig zur Lehre vom Luftdruck gelangt wäre. Im folgenden Beitrag wird daher gezeigt, dass Guericke durch eine Reihe subtiler Vakuumexperimente und deren physikalische Deutung sowie durch die Übertragung der Prinzipien der Hydrostatik von Flüssigkeiten auf Gase auch wichtige Beiträge zur Begriffsentwicklung der Physik geleistet hat.
Observed variations of upper ocean zonal currents in the western equatorial Pacific and their relation to the local wind
Authors: Matsuura Hiroshi
Published: December 2002

Observed variations of upper‐ocean zonal currents on the equator at 142°E and 147°E from November 1994 through October 1996, when the surface warm water layer was well developed, are described in relation to the wind forcing and the stratification. The variations of zonal currents were strongly correlated with the variations of local zonal wind stress in two distinct frequency bands separated by very low coherence for periods exceeding 10 days. One band encompasses the annual period, and the other band brackets approximately the 30‐ to 80‐day period. At annual period, high coherence with almost zero phase was limited to a region of very shallow depth, with high coherence at almost 180° phase seen at about 100 m. An eastward current above the Equatorial Undercurrent (EUC), which developed only during boreal summer with the seasonal upward displacement of the upper thermohaline, was responsible for this subsurface coherence maximum. At the 30‐ to 80‐day period, a high positive cross correlation between zonal current speed and zonal wind stress was seen from the shallowest observation depth to about the zero‐crossing depth between the South Equatorial Current and the EUC (ZCD), and a high negative correlation was seen below. The ZCD was located near the 29°C isotherm, and the vertical extent of high positive cross correlation in this band was found to vary together with the interannual and annual variations of the ZCD. There were temperature variations in this band, possibly caused by meridional or vertical advection, which were coherent with those of the zonal current.
Soil CO2 production and surface flux at four climate observatories in eastern Canada
Authors: Risk David , Kellman Lisa , Beltrami Hugo
Published: December 2002

Soils constitute the largest terrestrial source of carbon dioxide to the atmosphere, and in the context of changing global temperature and moisture patterns, it is critical that we understand the climatic controls on soil respiration. We use subsurface CO2 concentrations, surface CO2 flux and detailed physical monitoring of the subsurface regime to examine physical controls on soil CO2 production. Results indicate that subsurface CO2 production is very sensitive to the subsurface thermal regime, where relationships were robust and also stable across all land use types studied. In contrast, the thermal dependence of surface CO2 flux was much weaker. We found that soil heat content, rather than soil temperature, was the most descriptive index of the biological processes contributing to soil profile CO2 production at our study sites. Soil moisture was also found to have an important influence on subsurface CO2 production, particularly because of the relationship between moisture and soil profile diffusivity. Nondiffusive profile CO2 transport also appears to be important at these sites where the subsurface controls on transport change regularly and markedly.
Arc parallel extension and localization of volcanic complexes in Guadeloupe, Lesser Antilles
Authors: Feuillet N. , Manighetti I. , Tapponnier P. , Jacques E.
Published: December 2002

Subduction of Atlantic seafloor under the Caribbean plate causes shallow earthquakes within the Lesser Antilles volcanic arc. Such earthquakes, above the subduction interface, show strike‐slip or normal fault plane solutions, the latter with ∼E‐W striking nodal planes. To better assess seismic hazard and the coupling between volcanism and tectonics, we investigated faulting related to overriding‐plate deformation in the Guadeloupe archipelago. Using aerial photographs, satellite SPOT images, and topographic maps (1/25000 scale), we mapped active and middle to late Pleistocene fissures and normal fault systems that cut the uplifted coral platforms Grande‐Terre and Marie‐Galante and the volcanic rocks of Basse‐Terre. The available marine geophysical data show that the faults extend offshore to bound submarine rifts. The E‐W striking, 1500 m deep, V‐shaped Marie‐Galante rift separates the two islands of Marie‐Galante and Grande‐Terre. Normal faults in the north of Grande‐Terre appear to mark the similarly V‐shaped, western termination of the 5000 m deep, N°50E to N130°E striking Desirade graben. Three shallow, M ∼ 5.5 earthquakes (6 May 1851, 29 April 1897, 3 August 1992) appear to have ruptured segments of the Marie‐Galante rift boundary faults. The young “La Grande Découverte” volcanic complex of Basse‐Terre, including the 1440 A.D. Soufrière dome, lies within the western termination of the Marie‐Galante rift. The ancient volcanic shoulders of the rift buttress the active dome to the north and south, which may explain why major prehistoric sector collapses and pyroclastic avalanches have been directed southwestward into the Caribbean Sea, or southeastward into the Atlantic Ocean. The Marie‐Galante rift is typical of other troughs transverse to the northeastern edge of the Caribbean plate. We interpret such troughs, which are roughly orthogonal to the arc, to result from slip‐partitioning and extension perpendicular to plate convergence. That they disappear southward implies that they result from interaction between the Caribbean and North American plates.
Imaging the mantle beneath Iceland using integrated seismological techniques
Authors: Allen Richard M. , Nolet Guust , Morgan W. Jason , Vogfjörd Kristín , Bergsson Bergur H. , Erlendsson Pálmi , Foulger G. R. , Jakobsdóttir Steinunn , Julian Bruce R. , Pritchard Matt , Ragnarsson Sturla , Stefánsson Ragnar
Published: December 2002

Using a combination of body wave and surface wave data sets to reveal the mantle plume and plume head, this study presents a tomographic image of the mantle structure beneath Iceland to 400 km depth. Data comes primarily from the PASSCAL‐HOTSPOT deployment of 30 broadband instruments over a period of 2 years, and is supplemented by data from the SIL and ICEMELT networks. Three sets of relative teleseismic body wave arrival times are generated through cross correlation: S and SKS arrivals at 0.03–0.1 Hz, and P and PKIKP arrivals at 0.03–0.1 and 0.8–2.0 Hz. Prior to inversion the crustal portion of the travel time anomalies is removed using the crustal model ICECRTb. This step has a significant effect on the mantle velocity variations imaged down to a depth of ∼250 km. Inversion of relative arrival times only provides information on lateral velocity variations. Surface waves are therefore used to provide absolute velocity information for the uppermost mantle beneath Iceland. The average wave number for the Love wave fundamental mode at 0.020 and 0.024 Hz is measured and used to invert for the average S velocity. Combination of the body wave and surface wave information reveals a predominantly horizontal low‐velocity anomaly extending from the Moho down to ∼250 km depth, interpreted as a plume head. Below the plume head a near‐cylindrical low‐velocity anomaly with a radius of ∼100 km and peak VP and VS anomalies of −2% and −4%, respectively, extends down to the maximum depth of resolution at 400 km. Within the plume head, in the uppermost mantle above the core of the plume, there is a relatively high velocity with a maximum VP and VS anomaly of +2%. This high‐velocity anomaly may be the result of the extreme degree of melt extraction necessary to generate the thick (46 km) crust in central Iceland. Comparison of the plume volumetric flux implied by our images, the crustal generation rate, and the degree of melting suggested by rare earth element inversions, suggests that (1) mantle material must be flowing horizontally away from the plume core faster than the overlying lithosphere and (2) the bulk of the plume material does not participate in melting beneath Iceland.
Talc under tension and compression: Spinodal instability, elasticity, and structure
Authors: Stixrude Lars
Published: December 2002

Talc occurs as a product of alteration of ultramafic rocks and may be a significant constituent of oceanic lithosphere and the arc mantle wedge. We explore the physical properties and structure of talc over a wide pressure range with density functional theory using the variable cell shape plane wave pseudopotential method in the local density (LDA) and generalized gradient (GGA) approximations. For LDA, the theoretical equation of state agrees with room temperature experimental measurements of the volume to within 2% when estimated effects of lattice vibrations are accounted for. We predict a spinodal mechanical instability (vanishing bulk modulus) at a volume 4% larger than the experimental volume at ambient conditions. Results for compression and tension are well represented by a fourth‐order Birch‐Murnaghan finite strain expansion withK0= 37.8,K0′ = 13. 6,K0K0″ = −153, whereKis the bulk modulus, primes indicate pressure derivatives and subscript 0 refers to zero pressure. The estimated theoretical value ofK0at 300 K (29 GPa) is considerably less than that determined from the experimental equation of state, a difference we attribute to the constraints of strain compatibility in the polycrystalline laboratory sample. Thec* =csin β axis is found to be a factor of 7 more compressible than thebaxis, consistent with experimental data. Compression in thea–bplane is accommodated primarily by the Mg‐octahedra. The polyhedral bulk modulus of the Mg‐octahedra is considerably greater than one‐third the linear modulus of theaaxis. The difference is attributed to the increasing regularity of the Mg‐octahedra on compression as measured by the octahedral tilt angle. The t sheet maintains registry with the o sheet by rotation of the Si‐tetrahedra; the tetrahedral rotation angle rises from a value of 3° at the experimental volume to a theoretically predicted value of 22° at a volume of 170 Å3where the pressure is 26 GPa. Tetrahedral rotation leads to small Si‐O‐Si angles at the highest pressures investigated (<122° at 26 GPa), which leads us to speculate that talc may undergo pressure‐induced amorphization under low‐temperature compression.
Adjustment of the marine atmospheric boundary layer to the large‐scale bend in the California coast
Authors: Edwards Kathleen A. , Rogers David P. , Dorman Clive E.
Published: December 2002

Observations of the surface wind field off the U.S. West Coast were made from satellite by the Sea Surface Microwave/Imager (SSM/I) during June 1994 and June 1996. The coast bends inward 28° at 40° N latitude. Northerly wind speeds are high within a region that extends far south and offshore of this bend, bounded on the east by the California coast. On average, the high‐speed wind zone extends ∼250 km from shore and 800 km alongcoast. Long coast‐perpendicular aircraft transects show that moving onshore, the depth of the MABL decreases, the northerly wind speed increases, and the Froude number increases. A network of oceanographic buoys records the surface wind speed, direction, and pressure. From six buoy pressure measurements, the geostrophic wind vector was computed to represent the synoptic flow over the Oregon‐northern California coastal waters. The satellite surface wind fields were composited by the direction of the buoy geostrophic background wind. The predominant direction is 210°–180°. A high‐speed region extends south of the bend for directions in the 0°–180° range (moving counterclockwise), which corresponds to a downcoast component of the pressure gradient. For directions between 180° and 0°, flow splits at the bend and the region of highest winds is found to its north and offshore. A high‐speed region south of the bend was present in 65% of the satellite wind maps as well as in the June averages. The flow's response to coastal promontories such as Point Arena is nested within this broad zone of fast, thin, likely supercritical flow.
Emissions of carbon dioxide, carbon monoxide, and methane from boreal forest fires in 1998
Authors: Kasischke Eric S. , Bruhwiler Lori P.
Published: December 2002

The global boreal forest region experienced some 17.9 million ha of fire in 1998, which could be the highest level of the decade. Through the analysis of fire statistics from North America and satellite data from Russia, semimonthly estimates of area burned for five different regions in the boreal forest were generated and used to estimate total carbon release and CO2, CO, and CH4emissions. Different levels of biomass, as well as different biomass categories, were considered for each of the five different regions (including peatlands in the Russian Far East and steppes in Siberia), as were different levels of fraction of biomass (carbon) consumed during fires. Finally, two levels of flaming versus smoldering combustion were considered in the model. Boreal forest fire emissions for 1998 were estimated to be 290–383 Tg of total carbon, 828–1103 Tg of CO2, 88–128 Tg of CO, and 2.9–4.7 Tg of CH4. The higher estimate represents 8.9% of total global carbon emissions from biomass burning, 13.8% of global fire CO emissions, and 12.4% of global fire CH4emissions. Russian fires accounted for 71% of the total emissions, with the remainder (29%) from fires in North America. Assumptions regarding the level of smoldering versus flaming generally resulted in small (<4%) variations into the emissions estimates, although in two cases, these variations were higher (6% and 12%). We estimated that peatland fires in the Russian Far East contributed up to 40 Tg of carbon to the atmosphere in the fall of 1998. The combined seasonal CO emissions from forest and peatland fires in Russia are consistent with anomalously high atmospheric CO measurements collected at Point Barrow, Alaska.
Processes controlling water vapor in the winter Arctic tropopause region
Authors: Pfister Leonhard , Selkirk Henry B. , Jensen Eric J. , Podolske James , Sachse Glen , Avery Melody , Schoeberl Mark R. , Mahoney Michael J. , Richard Erik
Published: December 2002

This work describes transport and thermodynamic processes that control water vapor near the tropopause during the SAGE III—Ozone Loss and Validation Experiment (SOLVE), held during the Arctic 1999/2000 winter season. Aircraft‐based water vapor, carbon monoxide, and ozone measurements are analyzed so as to establish how deeply tropospheric air mixes into the Arctic lowermost stratosphere and what the implications are for cloud formation and water vapor removal in this region of the atmosphere. There are three major findings. First, troposphere‐to‐stratosphere exchange extends into the Arctic stratosphere to about 13 km. Penetration is to similar levels throughout the winter; however, because ozone increases with altitude most rapidly in the early spring, tropospheric air mixes with the highest values of ozone in that season. The effect of this upward mixing is to elevate water vapor mixing ratios significantly above their prevailing stratospheric values of about 5 ppmv. Second, the potential for cloud formation in the stratosphere is highest during early spring, with about 20% of the parcels which have ozone values of 300–350 ppbv experiencing ice saturation in a given 10 day period. Third, during early spring, temperatures at the tropopause are cold enough so that 5–10% of parcels experience relative humidities above 100%, even if the water content is as low as 5 ppmv. The implication is that during this period, dynamical processes near the Arctic tropopause can dehydrate air and keep the Arctic tropopause region very dry during early spring.
Satellite surveillance of evaporative depletion across the Indus Basin
Authors: Bastiaanssen Wim G. M. , Ahmad Mobin‐ud‐Din , Chemin Yann
Published: December 2002

The irrigated Indus Basin in Pakistan has insufficient water resources to supply all its stakeholders. Information on evaporative depletion across the Basin is an important requirement if the water resources are to be managed efficiently. This paper presents the Surface Energy Balance Algorithm for Land (SEBAL) method used to compute actual evapotranspiration for large areas based on public domain National Oceanic and Atmospheric Administration (NOAA) satellite data. Computational procedures for retrieving actual evapotranspiration from satellites have been developed over the last 20 years. The current work is among the first applications used to estimate actual evapotranspiration on an annual scale across a vast river basin system with a minimum of ground data. Only sunshine duration and wind speed are required as input data for the remote sensing flux algorithm. The results were validated in the Indus Basin by comparing results from a field‐scale transient moisture flow model, in situ Bowen ratio measurements, and residual water balance analyses for an area of 3 million ha. The accuracy of assessing time‐integrated actual annual evapotranspiration varied from 0% to 10% on a field scale to 5% at the regional level. Spatiotemporal information on actual evapotranspiration helps to evaluate water distribution and water use between large irrigation project areas. Wide variations in evaporative depletion between project areas and crop types were found. Satellite‐based measurements can provide such information and avoid the need to rely on field databases.
Nonpoint source groundwater pollution and endogenous regulatory policies
Authors: Lee Donna J. , Kim C. S.
Published: December 2002

Theory suggests that in the absence of transaction costs, pollution externalities can be mitigated efficiently by charging polluters a tax equal to the marginal social cost of pollution. All other regulatory mechanisms therefore may be no more efficient than a marginal cost pollution tax. We developed a stylized model of dynamic groundwater pollution without transaction costs to examine alternate policies. Using mitigation cost, tax burden, and excess burden we compared the relative efficiency of each tax policy under competitive market conditions. For groundwater nitrate pollution in a Midwestern farming region, results show that the least cost policy is a constant tax on the polluting input, followed by a variable tax on the polluting input and a pollution tax.
A theoretical analysis of carbon isotope evolution of decomposing plant litters and soil organic matter
Authors: Feng Xiahong
Published: December 2002

Systematic variations in the carbon isotopes of soil organic matter (SOM) have been observed in a variety of ecosystems. Such variations may provide important insights into physical and biological processes that mediate carbon storage, nutrient availability, and trace gas emissions. To study carbon cycles using carbon isotopes, it is important to link carbon isotope systematics with carbon dynamics models, so that carbon isotope variations can be interpreted in the context of rates and fluxes of carbon transport in ecosystems. This paper presents a theoretical analysis, in which carbon isotopic evolution of decaying organic matter is modeled for a system in which the rate of litter or soil organic matter decomposition is controlled by substrate quality and microbial growth rate. The model examines two mechanisms controlling the isotopic evolution of carbon in a system with a one‐time input: kinetic isotopic fractionation by soil microbes and differential decomposition. The model produces several important characteristics of a SOM decomposing system: (1) for a system with a single population of organic matter, the carbon‐13/carbon‐12 ratio in SOM increases with increasing carbon loss as a result of kinetic isotope fractionation of respiration; (2) for a given isotopic fractionation factor, the isotopic enrichment relative to the original organic material increases with the decomposition rate; and (3) for a system containing multiple organic matter components having different qualities and isotopic compositions (e.g., cellulose and lignin), the temporal evolution of the SOM isotope ratio reflects the competing dominance of isotopic fractionation and preferential reservation of one or more organic components.
Terrestrial ecosystems and the global biogeochemical silica cycle
Authors: Conley Daniel J.
Published: December 2002

Most research on the global Si cycle has focused nearly exclusively on weathering or the oceanic Si cycle and has not explored the complexity of the terrestrial biogeochemical cycle. The global biogeochemical Si cycle is of great interest because of its impact on global CO2 concentrations through the combined processes of weathering of silicate minerals and transfer of CO2 from the atmosphere to the lithosphere. A sizable pool of Si is contained as accumulations of amorphous silica, or biogenic silica (BSi), in living tissues of growing plants, known as phytoliths, and, after decomposition of organic material, as remains in the soil. The annual fixation of phytolith silica ranges from 60–200 Tmol yr−1 and rivals that fixed in the oceanic biogeochemical cycle (240 Tmol yr−1). Internal recycling of the phytolith pool is intense with riverine fluxes of dissolved silicate to the oceans buffered by the terrestrial biogeochemical Si cycle, challenging the ability of weathering models to predict rates of weathering and consequently, changes in global climate. Consideration must be given to the influence of the terrestrial BSi pool on variations in the global biogeochemical Si cycle over geologic time and the influence man has had on modifying both the terrestrial and aquatic biogeochemical cycles.
Phytoplankton influences on tropical climate
Authors: Timmermann Axel , Jin Fei‐Fei
Published: December 2002

We study the effect of ocean biology on tropical surface temperatures using a simplified coupled atmosphere‐ocean model. It is shown that moderate phytoplankton blooms, occuring e.g. during La Niña conditions, lead to a vertical redistribution of heat in the surface layers and an associated surface layer warming of about 20 W/m2. The positive air‐sea coupling in the eastern equatorial Pacific plays an important role in amplyfying this signal, thereby damping La Niña conditions. This temperature‐regulating feedback acts as a biological thermostat within the surface ocean and influences also the amplitude and asymmetry of the El Niño‐Southern Oscillation.
Estimating tidally driven mixing in the deep ocean
Authors: St. Laurent L. C. , Simmons H. L. , Jayne S. R.
Published: December 2002

Using a parameterization for internal wave energy flux in a hydrodynamic model for the tides, we estimate the global distribution of tidal energy available for enhanced turbulent mixing. A relation for the diffusivity of vertical mixing is formulated for regions where internal tides dissipate their energy as turbulence. We assume that 30 ± 10% of the internal tide energy flux dissipates as turbulence near the site of generation, consistent with an estimate based on microstructure observations from a mid‐ocean ridge site. Enhanced levels of mixing are modeled to decay away from topography, in a manner consistent with these observations. Parameterized diffusivities are shown to resemble observed abyssal mixing rates, with estimated uncertainties comparable to standard errors associated with budget and microstructure methods.
A new look at possible connections between solar activity, clouds and climate
Authors: Kristjánsson J. E. , Staple A. , Kristiansen J. , Kaas E.
Published: December 2002

We present a re‐evaluation of the hypothesis of a coupling between galactic cosmic rays, clouds and climate. We have used two independent estimates of low cloud cover from the International Satellite Cloud Climatology Project, covering 16.5 years of data. The cloud cover data are used in conjunction with estimates of galactic cosmic ray flux and measurements of solar irradiance. It is found that solar irradiance correlates better and more consistently with low cloud cover than cosmic ray flux does. The correlations are considerably lower when multichannel retrievals during daytime are used than retrievals using IR‐channels only. Due to large autocorrelations, the statistical significance of the results is marginal. A mechanism is suggested whereby solar irradiance variations are amplified by interacting with sea surface temperature (SST), and subsequently low cloud cover. The feasibility of such a mechanism is supported by negative correlations between SSTs and low cloud cover in subtropical regions.
Anomalous diffusion of multiple impurity species: Predicted implications for the ice core climate records
Authors: Rempel Alan W. , Wettlaufer J. S. , Waddington Edwin D.
Published: December 2002

We investigate the transport of impurities that are interpreted as climate proxies and are soluble in the premelted liquid that separates ice grains in the polar ice sheets even at subfreezing temperatures. Spatial variations in the relative abundances of multiple impurity species lead to gradients in their intergranular concentrations, defined as the ratio of the mass of dissolved impurity to the mass of premelted liquid. We show how diffusion down these intergranular concentration gradients affects anomalies in the bulk concentrations, defined as the ratio of the impurity mass to the mass of a polycrystalline sample, which are measured in polar ice cores. To illustrate these processes, we show that two initially asynchronous, periodic signals evolve to become in‐phase after a short time: similar behavior is evident in coastal Antarctica, where there is a migration of methane sulfonate (MSA−) from summer to winter peaks, and it becomes in‐phase with the primary deposition of sea salt. Moreover, the approach allows us to examine how an initially constant bulk concentration profile is influenced by an abrupt change to the bulk concentration of a second component. The resulting profiles share features with those observed in the Eemian compositional record from the Greenland Ice Core Project (GRIP) ice core.
The sulfur cycle at high‐southern latitudes in the LMD‐ZT General Circulation Model
Authors: Cosme E. , Genthon C. , Martinerie P. , Boucher O. , Pham M.
Published: December 2002

This modeling study was motivated by the recent publication of year‐round records of dimethylsulfide (DMS) and dimethylsulfoxide (DMSO) in Antarctica, completing the available series of sulfate and methanesulfonic acid (MSA). Sulfur chemistry has been incorporated in the Laboratoire de Météorologie Dynamique‐Zoom Tracers (LMD‐ZT) Atmospheric General Circulation Model (AGCM), with high‐resolution and improved physics at high‐southern latitudes. The model predicts the concentration of six major sulfur species through emissions, transport, wet and dry deposition, and chemistry in both gas and aqueous phases. Model results are broadly realistic when compared with measurements in air and snow or ice, as well as to results of other modeling studies, at high‐ and middle‐southern latitudes. Atmospheric MSA concentrations are underestimated and DMSO concentrations are overestimated in summer, reflecting the lack of a DMSO heterogeneous sink leading to MSA. Experiments with various recently published estimates of the rate of this sink are reported. Although not corrected in this work, other defects are identified and discussed: DMS concentrations are underestimated in winter, MSA and non‐sea‐salt (nss) sulfate concentrations may be underestimated at the South Pole, the deposition scheme used in the model may not be adapted to polar regions, and the model does not adequately reproduces interannual variability. Oceanic DMS sources have a major contribution to the variability of sulfur in these regions. The model results suggest that in a large part of central Antarctica ground‐level atmospheric DMS concentrations are larger in winter than in summer. At high‐southern latitudes, high loads of DMS and DMSO are found and the main chemical sink of sulfur dioxide (SO2) is aqueous oxidation by ozone (O3), whereas oxidation by hydrogen peroxide (H2O2) dominates at the global scale. A comprehensive modeled sulfur budget of Antarctica is provided.
Seasonal, intraseasonal, and interannual variability of global land fires and their effects on atmospheric aerosol distribution
Authors: Ji Yimin , Stocker Erich
Published: December 2002

In order to understand the variability of global land fires and their effects on the distribution of atmospheric aerosols, statistical methods were applied to the Tropical Rainfall Measuring Mission (TRMM) fire products as well as the Total Ozone Mapping Spectrometer (TOMS) aerosol index products for a period of 4 years from January 1998 to December 2001. The fire data in this period manifested a strong annual cycle of land fires in Southeast Asia with a peak in March and in Africa and North and South America with a peak in August. The data also indicated interannual variations in Indonesia and Central America associated with the 1998–1999 El Niño‐Southern Oscillation cycle. The variability of global atmospheric aerosol is consistent with the fire variations over these regions. However, in southwestern Australia, intense fires were recorded in TRMM fire data, but no smoke was observed in the TOMS aerosol product. Excluding the Australian region, the correlation between fire count and TOMS aerosol index is about 0.55 for fire pixels. Empirical orthogonal function analysis (EOF) and singular spectrum analysis methods were used to analyze the TRMM Science Data and Information System pentad fire composite data and TOMS pentad aerosol index data for this 4 year period. The EOF analyses showed contrast between the Northern and Southern Hemispheres and also intercontinental transitions in Africa and America. These analyses also identified 25–60 day intraseasonal oscillations that were superimposed on the annual cycles of both fire and aerosol data. The intraseasonal variability of fires showed a similarity of Madden‐Julian oscillation mode.
The need of polarization modeling for ozone profile retrieval from backscattered sunlight
Authors: Hasekamp Otto P. , Landgraf Jochen , van Oss Roeland
Published: December 2002

In the ultraviolet and visible part of the spectrum, measurements of space‐borne grating spectrometers are in general sensitive to the state of polarization of the observed light. The correction for this polarization sensitivity is based on broadband polarization measurements. In parts of the spectrum where the state of polarization is varying rapidly with wavelength this correction is not sufficient and severely limits the accuracy of the atmospheric parameters retrieved from the polarization corrected measurements. In this paper we demonstrate that the problems due to instrument polarization sensitivity can be solved in a natural way by the use of polarization modeling. For the forward model of a retrieval algorithm we propose the combination of a vector radiative transfer model to simulate the transport of radiation in the probed atmosphere and a straightforward simulation of the instrument polarization sensitivity by use of the Mueller matrix formalism. The use of a vector radiative transfer model also overcomes another common bias in retrieval algorithms, caused by the widely used scalar approximation of atmospheric radiative transfer. The capability and need of the proposed approach are demonstrated for ozone profile retrieval from measurements of the Global Ozone Monitoring Experiment (GOME). A comparison of retrieved profiles with 123 ozonesonde profiles shows that the use of a polarization forward model yields a significant improvement in root‐mean square difference of about a factor 1.5 in the stratosphere as well as in the troposphere. Also, a solar zenith angle dependence in the differences is reduced significantly.
Knudsen diffusion, gas permeability, and water content in an unconsolidated porous medium
Authors: Reinecke Stefan A. , Sleep Brent E.
Published: December 2002

The Knudsen diffusion coefficient was measured at different levels of water saturation for an unconsolidated porous medium consisting of silt‐sized particles. The Knudsen diffusion coefficient was found to increase from 4.4 × 10−3 cm2/s to 1.0 × 10−1 cm2/s as water saturation decreased from 82% to 54%. A comparison between the experimental Knudsen diffusion coefficients and predicted values of the corresponding effective binary diffusion coefficients indicated that diffusion at high saturations (>64%) were in the transition regime between Knudsen diffusion and molecular diffusion. The results suggest that Knudsen diffusion has significant implications for the prediction of organic vapor transport in partially saturated silts and in less permeable soils. An expression was developed for the influence of water saturation on Knudsen diffusion coefficients, using the Brooks‐Corey capillary pressure saturation relationship. Data from previous studies were also combined with results from this study to develop a correlation between the gas phase permeability and the Knudsen diffusion coefficient for variably saturated porous media. For permeabilities less than 10−10 cm2, the new correlation begins to deviate significantly from an existing correlation for dry porous media.
Piezometric response in shallow bedrock at CB1: Implications for runoff generation and landsliding
Authors: Montgomery David R. , Dietrich William E. , Heffner John T.
Published: December 2002

Experimental observations comparing two steep unchanneled valleys in the Oregon Coast Range, one intensively instrumented (CB1) and the other monitored for runoff but which produced a debris flow (CB2), shed light on the mechanisms of shallow flow in bedrock, its interaction with the vadose zone, and its role in generating landslides. Previous work at CB1 led to the proposal that during storms pulses of rainfall transmit pressure waves through the vadose zone and down to the saturated zone to create rapid pore pressure response and runoff [Torres et al., 1998]. Here, we document the associated rapid pore pressure response in the shallow fractured bedrock that underlies these colluvium‐mantled sites and examine its influence on the generation of storm flow, seasonal variations in base flow, and slope stability in the overlying colluvial soil. Our observations document rapid piezometric response in the shallow bedrock and a substantial contribution of shallow fracture flow to both storm flow and seasonal variations in base flow. Saturated hydraulic conductivity in the colluvial soil decreases with depth below the ground surface, but the conductivity of the near‐surface bedrock displays no depth dependence and varies over five orders of magnitude. Analysis of runoff intensity and duration in a series of storms that did and did not trigger debris flows in the surrounding area shows that the landslide inducing storms had the greatest intensity over durations similar to those predicted by a simple model of piezometric response. During a monitored storm in February 1992, the channel head at the base of the neighboring CB2 site failed as a debris flow. Automated piezometric measurements document that the CB2 debris flow initiated several hours after peak discharge, coincident with localized development of upward spikes of pressure head from near‐surface bedrock into the overlying colluvial soil in CB1. Artesian flow observed exfiltrating from bedrock fractures on the failure surfaces at CB2 further implicates bedrock fracture flow in both runoff generation by subsurface storm flow and suggests a connection to landslide initiation. Our observations show that the timing of shallow landslide initiation can be delayed relative to both peak rainfall and peak runoff and support the argument that the influence of fracture flow on shallow landsliding helps explain the wide variability in the occurrence of slope instability in topographically analogous locations.
A Three‐Pathway Pore Model Describes Extensive Transport Data from Mammalian Microvascular Beds and Frog Microvessels
Authors: WOLF MATTHEW B.
Published: December 2002

Objective: To show that a three‐pathway pore model can describe extensive transport data in cat and rat skeletal muscle microvascular beds and in frog mesenteric microvessels.

Methods: A three‐pathway pore model was used to predict transport data measured in various microcirculatory preparations. The pathways consist of 4‐ and 24‐nm radii pore systems with a 2.5:1 ratio of hydraulic conductivities and a water‐only pathway of variable conductivity. The pore sizes and relative hydraulic conductivities of the small‐ and large‐pore systems were derived from a model fit to reflection coefficient (σ) data in the cat hindlimb. The fraction (αw) of total hydraulic conductivity (Lp) or hydraulic capacity (LpS) contributed by the water‐only pathway was uniquely determined for each preparation by a fit of the three‐pathway model (parameters fixed as above) to σ data measured in that preparation. These parameter values were unchanged when the model was used to predict diffusion capacity (permeability‐surface area product, PdS) data in the cat or rat preparations or diffusional permeability (Pd) data in frog microvessels. The values for Lp or LpS used to predict diffusional data in each preparation were taken from the literature. Predictions of Pd ratios for solute pairs were also compared with experimental data.

Results: The three‐pathway model closely predicted the trend of PdS or Pd experimental data in all three preparations; in general, predicted Pd ratios for paired solutes were quite similar to experimental data. For these comparisons, the only parameter varied between these preparations was αw.It varied considerably, from 7 to 16 to 41% of total in frog, rat, and cat preparations. Individual PdS or Pd experimental data were closely predicted in the cat but somewhat overestimated in the frog and rat. This result could be due the use of Lp or LpS values in the model that were affected by methodological problems. Calculated hydraulic conductivities of the water‐only pathway in the three preparations were quite similar.

Conclusions: These results support the hypothesis of a common structure of the transmembrane pathways in these three, very different, microcirculatory preparations. What varies considerably between them is the total number of soluteconducting pathways, but not their dimensions, nor the hydraulic conductivities of their water‐only pathways. Because of the wide variation of αw among these preparations, the ratio of Pd to Lp for any solute is not constant, but the deviation from constancy may not be detectable because of errors in the experimental data.
ZM323881, a Novel Inhibitor of Vascular Endothelial Growth Factor‐Receptor‐2 Tyrosine Kinase Activity
Authors: WHITTLES C.E. , POCOCK T.M. , WEDGE S.R. , KENDREW J. , HENNEQUIN L.F. , HARPER S.J. , BATES D.O.
Published: December 2002

Objective: Vascular endothelial growth factor (VEGF) increases vascular permeability and angiogenesis in many pathological conditions including cancer, arthritis, and diabetes. VEGF activates VEGF‐Receptor 1(VEGF‐R1) and VEGF‐Receptor 2 (VEGF‐R2), which autophosphorylate to initiate a signaling cascade resulting in angiogenesis and increased microvascular permeability. Here we describe a novel VEGF‐R2 selective inhibitor, ZM323881 (5‐{[7‐(benzyloxy) quinazolin‐4‐yl]amino}‐4‐fluoro‐2‐methylphenol), that is a potent and selective inhibitor of VEGF‐R2 tyrosine kinase in vitro (IC50 < 2 nM), compared with other receptor tyrosine kinases, including VEGF‐R1 (IC50 > 50 µM).

Methods: Endothelial cell proliferation was assayed by 3H‐thymidine incorporation in response to VEGF‐A ± ZM323881. The effect of ZM323881 on VEGF‐mediated permeability was measured in frog microvessels using the Landis Michel technique. To ensure that ZM323881 was effective in frogs, western analysis was performed on protein extracted from frog lungs incubated in the presence or absence of VEGF‐A or VEGF‐A with ZM323881.

Results: ZM323881 inhibits VEGF‐A‐induced endothelial cell proliferation (IC50 = 8 nM) and VEGF‐R2 tyrosine phosphorylation in vitro. VEGF‐A‐mediated increases in vascular permeability in perfused mesenteric microvessels in vivo were reversibly abolished by both ZM323881 and the class III receptor tyrosine kinase inhibitor PTK787/ZK222584.

Conclusions: These data suggest that VEGF‐R2 phosphorylation is necessary for VEGF‐A‐mediated increases in microvascular permeability in vivo.