bluuebunny/crossref_metadata_2025 huggingface dataset:
Retrieving cloud information from passive measurements of solar radiation absorbed by molecular oxygen and O2‐O2
Authors: Daniel J. S. , Solomon S. , Miller H. L. , Langford A. O. , Portmann R. W. , Eubank C. S.
Published: August 2003

The ability to retrieve key information about clouds from observations of atmospheric absorption by molecular oxygen along with the O2‐O2 collision complex is examined. Specifically, the fractional absorption of scattered solar radiation in the oxygen A and B bands and the 477 nm O2‐O2 absorption band at moderate resolution (0.5–6.0 nm) is shown to allow estimates to be made not only of cloud optical depth but also of cloud base and top heights from a down‐looking observing platform above cloud level. We first demonstrate through theoretical calculations that these cloud parameters can be accurately retrieved from measurements of fractional absorption at this moderate resolution and with no requirement of absolutely calibrated radiances. Further, it is shown that the addition of B band and O2‐O2 absorption information to A band observations can decrease the uncertainty in these cloud parameter estimates by more than 50% (depending on the cloud's properties) compared to using A band information alone. The theoretical analysis is supported by sample, above‐cloud measurements of the oxygen A band fractional absorption associated with hurricane Michelle over the Gulf of Mexico. The experimental results are in excellent agreement with the cloud base and top heights inferred from cloud photographs and from dropsonde relative humidity data, demonstrating the capability of this approach for improved cloud remote sensing.
Numerical simulation of permafrost thermal regime and talik development under shallow thaw lakes on the Alaskan Arctic Coastal Plain
Authors: Ling Feng , Zhang Tingjun
Published: August 2003

Thaw lakes are one of the most obvious manifestations of the hydrological system at work in the tundra regions of the Alaskan Arctic Coastal Plain, but the extent of the role of thaw lakes in Arctic land‐atmosphere interactions and feedback has yet to be fully understood. This study uses a two‐dimensional heat transfer model with phase change under a cylindrical coordinate system to simulate the long‐term influence of shallow thaw lakes on the thermal regime of permafrost and talik development on the Alaskan Arctic Coastal Plain. On the basis of previous studies of permafrost and thaw lakes at Barrow, Alaska, a series of simulation cases was conducted using different combinations of long‐term mean lake bottom temperature and lake depth. The simulated results indicate that shallow thaw lakes are a significant heat source to permafrost and talik. For a thaw lake with a long‐term mean lake bottom temperature of greater than 0.0°C a talik forms under the thaw lake. The maximum talik thicknesses (vertical distance from the ground surface to the permafrost surface) are 28.0, 43.0, and 53.2 m 3000 years after the formation of a shallow thaw lake with long‐term mean lake bottom temperatures of 1.0°, 2.0°, and 3.0°C, respectively. Talik development rate is very high in the first several years after a thaw lake formation and decreases gradually with time. No talik forms below a thaw lake with a long‐term mean lake bottom temperature equal to or lower than 0.0°C, but the temperature of permafrost below the thaw lake increases with time. Three thousand years after the formation of a thaw lake with a long‐term mean lake bottom temperature of greater than or equal to −2.0°C, ground temperature increases of more than 0.5°C occur as far as 300 m from the lake shore and as deep as about 400 m below the ground surface. It is concluded that variation of long‐term mean lake bottom temperature has a significant influence on permafrost thermal regime and talik development. Continued monitoring for thaw lake bottom temperature and ground temperature under shallow thaw lakes is needed to further improve the simulation.
Influence of relative humidity on aerosol radiative forcing: An ACE‐Asia experiment perspective
Authors: Markowicz Krzysztof M. , Flatau Piotr J. , Quinn P. K. , Carrico Christian M. , Flatau M. K. , Vogelmann A. M. , Bates David , Liu M. , Rood Mark J.
Published: August 2003

We present direct radiometric observations of aerosol radiative forcing during the ACE‐Asia experiment (March and April of 2001). The observational analysis is based on radiometer data obtained from the NOAA ship Ronald H. Brown, and shipboard measurements of the aerosol chemical and scattering properties are used to construct a model of the aerosol optical properties for use in radiative transfer calculations. The model is validated against the radiometric observations and is used to diagnose the aerosol and environmental factors that contribute to the observed forcings. The mean value of aerosol optical thickness observed during the ACE‐Asia cruise over the Sea of Japan was 0.43 (±0.25) at 500 nm, while the single‐scattering albedo was 0.95 (±0.03) at ambient relative humidity. We find a large correlation (r2 = 0.69) between single‐scattering albedo and relative humidity. Aerosols caused a mean decrease in the diurnally averaged solar radiation of 26.1 W m−2 at the surface, while increasing the atmospheric solar absorption and top of atmosphere reflected solar radiation by 13.4 W m−2 and 12.7 W m−2, respectively. The mean surface aerosol forcing efficiency (forcing per unit optical depth) over the Sea of Japan was −60 W m−2 and is influenced by high values of relative humidity. We show that decreasing the relative humidity to 55% enhances the aerosol forcing efficiency by as much as 6–10 W m−2. This dependency on relative humidity has implications for comparisons of aerosol forcing efficiencies between different geographical locations.
Simulating the impact of sea salt on global nss sulphate aerosols
Authors: Gong S. L. , Barrie L. A.
Published: August 2003

The Canadian Aerosol Module coupled with the Canadian third generation Global Climate Model was used to simulate the global distributions of size‐segregated sea salt and sulphate aerosols of both anthropogenic and natural origins in the atmosphere. A sectional model of 12 size bins was used to treat the size distribution of sea salt and sulphate, which is assumed to be internally mixed in each size bin. The spatial and temporal distributions predicted by the model compare reasonably well with observations. The mixed aerosol simulations yield number and volume size distributions in the marine boundary layer (MBL) comparable with observations. Sea salt particles redistribute the mass and number distributions of sulphate aerosols by serving as a quenching agent to nucleation and as an additional surface area for condensation and by changing the cloud properties in the MBL. By differential simulations of global sea salt and sulphate it is found that the presence of sea salt increases the mass mean diameter of sulphate aerosols by up to a factor of 2 over the MBL with high sea salt concentrations and reduces the global sulphate aerosol mass in the surface MBL layer from 5 to 75% depending on the sea salt distributions. The high impacts are in the midlatitudes of both Northern and Southern Hemispheres with a minimum in the equatorial regions. In the polluted anthropogenic regions of North Pacific and Atlantic, sea salt reduces the sulphate concentration from 10 to 30%. The peak reductions of 50–75% occur in the roaring 40s of the Southern Hemisphere in spring and fall. The impact of sea salt on the annual global mass and number loading is estimated to be 9.13 and 0.76%, respectively. A reduction of 20–60% in the marine cloud droplet number concentrations (CDNC) was predicted because of the presence of sea salt, with greatest reductions in the roaring 40s south (40–70%) and in the midlatitude north (20–40%) where the sea salt concentrations were high. Along the equatorial regions some enhancement of total CDNC was simulated because of the presence of sea salt aerosols.
Strategies for measurement of atmospheric column means of carbon dioxide from aircraft using discrete sampling
Authors: Bakwin P. S. , Tans P. P. , Stephens B. B. , Wofsy S. C. , Gerbig C. , Grainger A.
Published: August 2003

Automated flask sampling aboard small charter aircraft has been proposed as a low‐cost, reliable method to greatly increase the density of measurements of CO2 mixing ratios in continental regions in order to provide data for assessment of global and regional CO2 budgets. We use data from the CO2 Budget and Rectification‐Airborne 2000 campaign over North America to study the feasibility of using discrete (flask) sampling to determine column mean CO2 in the lowest 4 km of the atmosphere. To simulate flask sampling, data were selected from profiles of CO2 measured continuously with an onboard (in situ) analyzer. We find that midday column means can be determined without bias relative to true column means measured by the in situ analyzer to within 0.15 and better than 0.10 ppm by using 10 and 20 instantaneously collected flask samples, respectively. More precise results can be obtained by using a flask sampling strategy that linearly integrates over portions of the air column. Using less than 8–10 flasks can lead to significant sampling bias for some common profile shapes. Sampling prior to the breakup of the nocturnal stable layer will generally lead to large sampling bias because of the inability of aircraft to probe large CO2 gradients that often exist very close to the ground at night and during the early morning.
Variational retrieval of rain profiles from spaceborne passive microwave radiance observations
Authors: Moreau Emmanuel , Bauer Peter , Chevallier Frédéric
Published: August 2003

A variational retrieval method has been implemented to evaluate the possibility of assimilating rain‐affected microwave radiances in an operational weather forecasting model. The method employs an efficient multiple scattering radiative transfer code and its tangent‐linear and adjoint versions to simulate model state equivalent radiances and their sensitivities to changes in hydrometeor contents. Profiles of temperature and humidity together with the ECMWF model convection and cloud schemes are used to produce first‐guess hydrometeor profiles. The hydrometeor error covariance matrix is calculated from the operational error covariance matrix of temperature and humidity convolved with both convection and cloud scheme for each profile. A sensitivity study is applied to a tropical cyclone using data from the TRMM Microwave Imager where large differences between the first‐guess and observed precipitation fields occurred. The study shows that the approach results in single‐column retrievals that compare well with an independent algorithm. A strong dependence of the analysis on the microwave frequencies chosen as observations was noted. This was especially the case in areas where some microwave channels lost their sensitivity to modifications of the profiles due to saturation or where ambiguous contributions from either cloud droplet absorption or raindrop absorption and scattering were present. Including all channels at 10.7, 19.35, 21.3, and 37.0 GHz produced the lowest number of minimization failures. The failures are either due to strongly non‐linear sensitivities of radiances to changes in hydrometeor contents for a given profile or due to areas where the channel dependent spatial resolution produces inconsistent observations.
Long‐term erythemal UV doses at Sodankylä estimated using total ozone, sunshine duration, and snow depth
Authors: Lindfors A. V. , Arola A. , Kaurola J. , Taalas P. , Svenøe T.
Published: August 2003

A method for estimating daily erythemal UV doses using total ozone, sunshine duration, and snow depth has been developed. The method consists of three steps: (1) daily clear‐sky UV doses were simulated using the UVSPEC radiative transfer program, with daily values of total ozone as input data, (2) an empirical relationship was sought between the simulated clear‐sky UV doses, the measured UV doses, and the duration of bright sunshine, and (3) daily erythemal UV doses were estimated using this relationship. The method accounts for the varying surface albedo by dividing the period of interest into winter and summer days, depending on the snow depth. Using this method, the daily erythemal UV doses at Sodankylä were estimated for the period 1950–1999. This was done using Tromsø's total ozone together with Sodankylä's own sunshine duration and snow depth as input data. Although the method is fairly simple, the results are in good agreement, even on the daily scale, with the UV radiation measured with the Brewer spectrophotometer at Sodankylä. Over the period 1950–1999 a statistically significant increasing trend of 3.9% per decade in erythemal UV doses was found for March. The fact that this trend is much more pronounced during the latter part of the period, which is also the case for April, suggests a connection to the stratospheric ozone depletion. For July, on the other hand, a significant decreasing trend of 3.3% per decade, supported by the changes in both total ozone and sunshine duration, was found.
Effect of stress fields on magma chamber stability and the formation of collapse calderas
Authors: Bosworth William , Burke Kevin , Strecker Manfred
Published: August 2003

The summits of many of the Earth’s and other planets’ larger volcanoes are occupied by calderas that formed by collapse into an evacuating, underlying magma chamber. These collapse calderas are typically several tens of square kilometers in area and are commonly elliptical in shape. We show that the long axes of late Quaternary collapse calderas in the Kenya rift valley, the western Basin and Range province, the Snake River‐Yellowstone Plateau, and the Iceland rift zone are parallel to the upper crustal minimum horizontal stress direction (Sh) as determined by independent criteria. We suggest that circular magma chambers beneath these volcanoes became elliptical by stress‐induced spalling of their chamber walls, by a mechanism that is analogous to the formation of breakouts in boreholes and tunnels. In breakouts, the hole becomes elongate parallel to the far‐field minimum stress. In the Kenya rift, Late Pleistocene caldera collapse was accompanied by a 45° rotation of Sh and an increase in the magnitude of the maximum horizontal stress (SH). The breakout model predicts increasingly unstable caldera walls under these conditions, a possible explanation for the sudden appearance of so many collapse events in a volcanic setting that had never experienced them before. This mechanism of stress change‐induced collapse may have played a role in other caldera settings.
Oblique back arc rifting of Taupo Volcanic Zone, New Zealand
Authors: Acocella V. , Spinks K. , Cole J. , Nicol A.
Published: August 2003

Taupo Volcanic Zone (TVZ) is a back arc rift in North Island, New Zealand. Its geometry and kinematics are investigated using shaded relief images, field examination of faults and offset stream channels. The results show that TVZ trends NNE, is ∼250 km long by ∼20 km wide and consists of five segments. Extension is principally manifest as steeply dipping (60°–90°) normal faults parallel to TVZ; these, in the last 300 kyr, have experienced a component of dextral shear. TVZ is therefore an oblique back arc rift. The dextral shear is ∼37% of the total displacement, which, for previously estimated spreading rates ∼7 mm/yr, corresponds to ∼2.6 mm/yr. This value is similar to previous estimates of the dextral shear from the back arc to the forearc domains in the North Island. Distributed dextral shear across TVZ thus suggests that strain partitioning across the plate boundary at latitudes of TVZ is less significant than previously thought.
Drawdown and capture zone topology for nonvertical wells
Authors: Steward David R. , Jin Wei
Published: August 2003

An analytic framework is developed to model the three‐dimensional steady flow generated by wells placed at general nonvertical orientations within a horizontal aquifer. This framework uses closed‐form solutions for a distribution of point sinks and point doublets along the centerline of the well and semi‐infinite panel elements, each with piecewise linearly varying strengths. This extends previously published implementations and enables a boundary condition of uniform head along the cylindrical face of the well to be accurately matched. The resulting model is used to examine the drawdown and capture zone topology for wells spanning orientations ranging from vertical to horizontal. Scaling relationships are developed for wells perpendicular to flow that are invariant with respect to drawdown and to the strength of elements. The capture zone geometry for such wells is variant with respect to a dimensionless pumping rate, going through transition from two‐dimensional flow in a plane perpendicular to the well to two‐dimensional flow in a horizontal plane.
Performance of operational radiosonde humidity sensors in direct comparison with a chilled mirror dew‐point hygrometer and its climate implication
Authors: Wang Junhong , Carlson David J. , Parsons David B. , Hock Terrence F. , Lauritsen Dean , Cole Harold L. , Beierle Kathryn , Chamberlain Edward
Published: August 2003

This study evaluates performance of humidity sensors in two widely used operational radiosondes, Vaisala and Sippican (formally VIZ), in comparison with a research quality, and potentially more accurate, chilled mirror dew‐point hygrometer named “Snow White”. A research radiosonde system carrying the Snow White (SW) hygrometer was deployed in the Oklahoma panhandle and at Dodge City, KS during the International H2O Project (IHOP_2002). A total of sixteen sondes were launched with either Vaisala RS80 or Sippican VIZ‐B2 radiosondes on the same balloons. Comparisons of humidity data from the SW with Vaisala and Sippican data show that (a) Vaisala RS80‐H agrees with the SW very well in the middle and lower troposphere, but has dry biases in the upper troposphere (UT), (b) Sippican carbon hygristor (CH) has time‐lag errors throughout the troposphere and fails to respond to humidity changes in the UT, sometimes even in the middle troposphere, and (c) the SW can detect cirrus clouds near the tropopause and possibly estimate their ice water content (IWC). The failure of CH in the UT results in significant and artificial humidity shifts in radiosonde climate records at stations where a transition from VIZ to Vaisala radiosondes has occurred.
Huge rock eruption caused by the 1999 Chi‐Chi earthquake in Taiwan
Authors: Huang Shih‐Wei , Jean Jiin‐Shuh , Hu Jyr‐Ching
Published: August 2003

The 1999 Chi‐Chi earthquake significantly altered the landscape of central Taiwan. The most remarkable and intriguing feature is believed to be the huge rock eruption at Chiu‐Fen‐Erh‐Shan during the earthquake, which consisted of four separate eruptions accompanied by flashes of light as seen by the residents. Here we present our analysis of the rock eruption process. We propose that a little water trapped in the interconnected fractures, which were located in the base of the rock, caused a very large amount of pressure when the water was vaporized due to frictional heat. The high vapor pressure thus generated, either triggered rock failure or enlarged cracks in the rock, which erupted simultaneously during the 1999 Chi‐Chi earthquake. The four different instances of rock eruptions occurred only at Chiu‐Fen‐Erh‐Shan. We suggest that the eruptions resulted not only from the high vapor pressure, but also from the geologic focusing of seismic waves and tectonic thrust forces together, which concentrated the energy in the region to cause the explosions during the 1999 Chi‐Chi earthquake.
Global sprite occurrence locations and rates derived from triangulation of transient Schumann resonance events
Authors: Sato Mitsuteru , Fukunishi Hiroshi
Published: August 2003

We estimated locations and rates of sprite occurrences on a global scale using 1–100 Hz ELF magnetic field waveform data obtained at Syowa station in Antarctica and Onagawa observatory in Japan. From the ELF data obtained in a period between June 19, 2001 and January 20, 2002, we identified 715,500 events of transient Schumann resonances (SRs). The locations and polarizations of these parent cloud‐to‐ground (CG) discharges were determined by a triangulation method. The charge moments of these CG discharges were calculated with a normal mode expansion model of SR waves. From these results and the empirical sprite initiation probability reported by Hu et al. [2002], the global occurrence rate of sprites is estimated to be about 720 events/day on average. It is also found that the active regions of sprite occurrences are located in North and South America, Africa and South‐East Asia.
Multiple planetary flow regimes and the eddy forcing in Northern Hemisphere wintertime variability
Authors: Wu Qigang , Straus David M.
Published: August 2003

A cluster algorithm is applied to the zonal mean zonal wind ([u]) from winter monthly means of the reanalyses of NCEP/NCAR. Four reproducible and robust clusters are found: two regimes represent the opposite phases the Northern Hemisphere Annular mode (NAM), and two regimes represent the opposite phases of a pattern which can be identified with the Cold Ocean‐Warm Land (COWL) pattern. This identification is accomplished by regressing the [u] on the COWL‐index derived from 500 hPa height data by Wu and Straus [2002]. Transformed Eulerian (or Eliassen‐Palm) eddy forcing analysis is used to examine the maintenance of these clusters. The results show that barotropic forcing by the eddy momentum fluxes appears to maintain the wind anomalies in the upper troposphere and balances the Coriolis acceleration associated with the anomalous transformed mean meridional circulation, while the Coriolis acceleration maintains the wind anomalies against friction in the lower troposphere. This mechanism holds for both NAM‐like and COWL‐like regimes.
Pressure balance inconsistency exhibited in a statistical model of magnetospheric plasma
Authors: Garner T. W. , Wolf R. A. , Spiro R. W. , Thomsen M. F. , Korth H.
Published: August 2003

While quantitative theories of plasma flow from the magnetotail to the inner magnetosphere typically assume adiabatic convection, it has long been understood that these convection models tend to overestimate the plasma pressure in the inner magnetosphere. This phenomenon is called the pressure crisis or the pressure balance inconsistency. In order to analyze it in a new and more detailed manner we utilize an empirical model of the proton and electron distribution functions in the near‐Earth plasma sheet (−50RE<X< −10RE), which uses theTsyganenko[1989]magnetic field model and a plasma sheet representation based upon several previously published statistical studies. We compare our results to a statistically derived particle distribution function at geosynchronous orbit. In this analysis the particle distribution function is characterized by the isotropic energy invariant λ =EV2/3, whereEis the particle's kinetic energy andVis the magnetic flux tube volume. The energy invariant is conserved in guiding center drift under the assumption of strong, elastic pitch angle scattering. If, in addition, loss is negligible, the phase space densityf(λ) is also conserved along the same path. The statistical model indicates thatf(λ,) is approximately independent ofXforX≤ −35REbut decreases with increasingXforX≥ −35RE. The tailward gradient off(λ,) might be attributed to gradient/curvature drift for large isotropic energy invariants but not for small invariants. The tailward gradient of the distribution function indicates a violation of the adiabatic drift condition in the plasma sheet. It also confirms the existence of a “number crisis” in addition to the pressure crisis. In addition, plasma sheet pressure gradients, when crossed with the gradient of flux tube volume computed from theTsyganenko[1989]magnetic field model, indicate Region 1 currents on the dawn and dusk sides of the outer plasma sheet.
Solar cycle dependence of interplanetary Lyman α emission and solar wind anisotropies derived from NOZOMI/UVS and SOHO/SWAN observations
Authors: Nakagawa Hiromu , Fukunishi Hiroshi , Takahashi Yukihiro , Watanabe Shigeto , Taguchi Makoto , Bertaux Jean‐Loup , Lallement Rosine , Quémerais Eric
Published: August 2003

We have investigated the distributions of neutral interplanetary hydrogen Lyman α emission and their solar cycle dependence from observations with the ultraviolet imaging spectrometer (UVS) onboard the NOZOMI spacecraft and the solar wind anisotropy instrument (SWAN) onboard the solar and heliospheric observatory (SOHO) spacecraft. The SOHO/SWAN observation covers the period from the solar minimum in 1996 to the solar maximum in 2001, while the NOZOMI/UVS observation covers the period of 1999–2001 near the solar maximum. The most distinct feature of the full sky Lyman α intensity maps near the solar maximum in 2000 is a structure with a single bright region extending across the ecliptic plane on the upwind side of the interstellar wind. This structure is entirely different from the structure observed by SWAN at the solar minimum in 1996, which shows an intensity depression called a “groove” and bright lobes above and below the groove centered near the ecliptic plane. From the fitting of model calculations to the observational data, it is confirmed that the latitudinal distribution of the ionization rate of the interplanetary hydrogen due to the charge exchange with solar wind protons becomes isotropic toward the solar maximum. However, an important result is that the condition for producing anisotropic ionization rate due to the slow, high‐density solar wind around the equator exists by October 1999, although the theoretical model predicts isotropic ionization rate throughout 1999.
Large nitric acid particles at the top of an Arctic stratospheric cloud
Authors: Deshler Terry , Larsen Niels , Weissner Christoph , Schreiner Jochen , Mauersberger Konrad , Cairo Francesco , Adriani Alberto , Di Donfrancesco Guido , Ovarlez Joelle , Ovarlez Henri , Blum Ulrich , Fricke K. H. , Dörnbrack Andreas
Published: August 2003

In early December 2001, balloon‐borne in situ measurements of particle composition, size, number, phase, and backscatter were completed in an Arctic stratospheric cloud composed of three distinct layers between 22 and 26 km. Below 24.5 km, liquid solution droplets of water, nitric acid, and sulfuric acid and a thin ice layer were observed. Above this layer the particles were primarily solid nitric acid trihydrate. Just above 26 km, at cloud top, where temperatures were near or above the equilibrium temperature for nitric acid trihydrate, there was a thin layer of solid particles narrowly distributed around a radius of 2.0 μm at concentrations of <0.001 cm−3. Lidar backscatter and particle phase measurements approximately 200 km upwind of the in situ measurements indicate a similar vertical structure for the cloud. These in situ measurements represent, to our knowledge, the most comprehensive in situ observations of all phases of polar stratospheric cloud particles, while the large particles at cloud top have not been previously observed and may have implications for producing particles large enough to remove reactive nitrogen from the polar stratosphere.
Water‐soluble organic nitrogen in Amazon Basin aerosols during the dry (biomass burning) and wet seasons
Authors: Mace Kimberly A. , Artaxo Paulo , Duce Robert A.
Published: August 2003

As part of the Large‐Scale Biosphere‐Atmosphere Experiment in Amazonia (LBA), PM10aerosol was collected during both the wet and dry (biomass burning) seasons of 1999 and analyzed for total water‐soluble organic nitrogen (WSON), urea, and 17 amino acids. In addition to total WSON the inorganic N species nitrate (NO3−), nitrite (NO2−), and ammonium (NH4+) were also analyzed. WSON was found to represent ∼45% (mean concentration ∼3.5 nmol N/m3) and ∼43% (mean concentration ∼61 nmol N/m3) of the total N in wet and dry season aerosol samples, respectively. Urea and amino N made up ∼19% of the total organic N in dry season aerosols and ∼2.5% of the total organic N in wet season aerosols; the majority of WSON, ∼80% in the dry season and ∼97% in the wet season, remained uncharacterized. The results suggest that biomass burning is a source of WSON, yet poorly understood (since this data set represents the first study of WSON in the context of biomass burning). Future studies aimed at determining the magnitude of WSON released from biomass burning globally, its species composition, and its biogeochemical significance are needed.
Sea surface temperatures in the equatorial and South Atlantic Ocean during the Last Glacial Maximum (23–19 ka)
Authors: Niebler H.‐S. , Arz H. W. , Donner B. , Mulitza S. , Pätzold J. , Wefer G.
Published: August 2003

We used planktic foraminiferal assemblages in 70 sediment cores from the tropical and subtropical South Atlantic Ocean (10°N–37°S) to estimate annual mean sea surface temperatures (SSTs) and seasonality for the Last Glacial Maximum with a modified version of the Imbrie‐Kipp transfer function method (IKTF) that takes into account the abundance of rare but temperature sensitive species. In contrast to CLIMAP Project Members [1981], the reconstructed SSTs indicate cooler glacial SSTs in the entire tropical/subtropical South Atlantic with strongest cooling in the upwelling region off Namibia (7–10°C) and smallest cooling (1–2°C) in the western subtropical gyre. In the western Atlantic, our data support recent temperature estimates from other proxies. In the upwelling regions in the eastern Atlantic, our data conflict with SST reconstructions from alkenones, which may be due to an environmental preference of the alkenone‐producing algae or to an underestimation of foraminiferal SSTs due to anomalous high abundances of N. pachyderma (sinistral).
Geodynamic significance of the Aeolian volcanism (Southern Tyrrhenian Sea, Italy) in light of structural, seismological, and geochemical data
Authors: De Astis Gianfilippo , Ventura Guido , Vilardo Giuseppe
Published: August 2003

The Aeolian volcanoes are located between the Southern Tyrrhenian Sea back arc and the Calabrian Arc forearc region. Structural, geochemical and seismological data indicate that the early phases of volcanic activity (1.3 Myr) developed in the western sector along WNW‐ESE tear faults controlling the southeastward migration of the forearc–back arc system. This magmatism ceased when delamination processes affected the Calabrian Arc. At 0.8 Myr, the volcanism migrated southeastward and concentrated on the “new” formed NNW‐SSE tear faults related to the postsubduction extensional strain. The compressive strain deduced by focal mechanism of earthquakes in the western sector explains the volcanism ending. The still active volcanism in the central and eastern sectors develops on a NNW‐SSE striking lithospheric discontinuity that crosses the ring‐shaped volcanic belt. Moho upwelling occurs in the area of active volcanism. Fault‐slip data and focal mechanisms from M > 5 earthquakes indicate that the NNW‐SSE discontinuity moves in response to an oblique (strike‐slip/normal) stress related to a WNW‐ESE extension. This direction of extension is consistent with that of the forearc region, where thrust‐type events are lacking and the last compressive phases occurred during Pliocene. The later phases of the Aeolian volcanism are related to the melting of shallower source(s) consistent with a continental rift magmatism. The Aeolian Islands represent a postcollisional, rift‐type volcanism emplaced in an older collision zone.
Stream geomorphology, bank vegetation, and three‐dimensional habitat hydraulics for fish in midwestern agricultural streams
Authors: Rhoads Bruce L. , Schwartz John S. , Porter Stacey
Published: August 2003

Past work on physical habitat in streams has not explicitly considered how differences in channel planform and bank vegetation influence the three‐dimensionality of habitat hydraulics. This study statistically compares frequency distributions of bed elevations, a stage‐independent index of variability in flow depth, and three‐dimensional velocity components for four stream reaches in east central Illinois that have different geomorphological conditions and types of bank vegetation. The analysis shows that bed elevations in a straight channelized reach are significantly less variable than bed elevations in the other three reaches. Distributions of downstream velocities do not differ significantly for two reaches with similar bank vegetation but substantially different channel morphologies, whereas distributions of cross‐stream and vertical velocities are sensitive to differences both in channel planform and bank vegetation. Channel curvature enhances the variance of cross‐stream and vertical velocity distributions through the production of large‐scale helical motion. Conditions that result in net cross‐stream flow, such as abrupt changes in curvature or deflection of the flow laterally, systematically influence the mean of cross‐stream velocity distributions. Corresponding fish studies indicate that the straight, channelized reach has the lowest biotic integrity of the four sites. A detailed comparison of fish population characteristics between this reach and an unmodified reach immediately upstream reveals that the unmodified reach has significantly greater species richness, species diversity, and total biomass than the channelized reach. Thus geomorphological complexity, through its influence on the three‐dimensionality of habitat hydraulics, appears to significantly influence fish community characteristics.
Cellular participation in delayed xenograft rejection of hCD55 transgenic pig hearts by baboons
Authors: Ashton‐Chess Joanna , Roussel Jean‐Christian , Manez Rafael , Ruiz Carmen , Moreau Anne , Cozzi Emanuele , Minault David , Soulillou Jean‐Paul , Blancho Gilles
Published: August 2003

Abstract:  Delayed xenograft rejection (DXR) of pig organs by baboons currently represents the major obstacle to successful xenotransplantation. Although antibodies (Abs) are believed to play a fundamental role in this form of rejection, so far little is known concerning the potential cellular component. Biopsies taken during DXR of human CD55 transgenic pig hearts by non‐treated (n = 2), α‐Gal immunoadsorbed (n = 2), or immunosuppressed (n = 9) baboons were studied. The cellular element was explored by determining not only its phenotype by classical immunohistochemical techniques but also its activity in terms of cytokines, cytolytic enzymes and other mediators using quantitative reverse transcription polymerase chain reaction. All porcine xenografts underwent DXR; within 5 days in non‐treated and immunoadsorbed animals but significantly delayed (6 to 29 days) in immunosuppressed animals. Cellular infiltration in non‐immunosuppressed grafts consisted predominantly of monocytes/macrophages, CD8 cells and a few CD4 T‐cells. The predominant baboon transcripts detectable were the proinflammatory cytokines interleukin1‐α and tumor necrosis factor‐α, the lymphokine interferon‐γ and the cytotoxic enzyme granzyme B. However, these cellular components were lacking in the immunosuppressed animals. Despite these differences, strong immunoglobulin M (IgM) and C5b‐9 complement deposition was observed in all animals at rejection. Together our findings suggest that although the humoral response plays a predominant role in DXR through IgM Abs and complement activation, there is a clear cellular infiltrate in DXR in this model that is likely to contribute to rejection through a strong pro‐inflammatory and cytotoxic environment, necessitating substantial immunosuppression for a prolonged graft survival.
Clinical extracorporeal hybrid liver support – phase I study with primary porcine liver cells
Authors: Sauer I. M. , Kardassis D. , Zeillinger K. , Pascher A. , Gruenwald A. , Pless G. , Irgang M. , Kraemer M. , Puhl G. , Frank J. , Müller A. R. , Steinmüller TH. , Denner J. , Neuhaus P. , Gerlach J. C.
Published: August 2003

Abstract: The objective of this study was to evaluate the feasibility and safety of a hybrid liver support system with extracorporeal plasma separation and bioreactor perfusion in patients with acute liver failure (ALF) who had already fulfilled the criteria for high urgency liver transplantation (LTx). Eight patients (one male, seven female) were treated in terms of bridging to transplantation. The mean age was 36.5 yr (range 20 to 58). Etiology of liver failure was drug‐related in two patients, hepatitis B infection in three patients, and unknown for three patients. The bioreactors were charged with primary liver cells from specific pathogen‐free pigs. Cell viability varied between 91 and 98%. Continuous liver support treatment over a period of 8 to 46 h (mean 27.3 h) was safely performed and well‐tolerated by all patients. No complications associated with the therapy were observed during the follow‐up period. Thrombocytopenia was considered to be an effect of the plasma separation. Subsequently, all patients were transplanted successfully and were observed over at least 3 yr with an organ and patient survival rate of 100%. Screening of patient's sera for antibodies specific for porcine endogenous retroviruses (PERVs) showed no reactivity – either prior to application of the system, or after extracorporeal treatment. The results encourage us to continue the development of the technology, and further studies appear to be justified. The bioreactor technology has been integrated into a modular extracorporeal liver support (MELS) system, combining biologic liver support with artificial detoxification technology.
Geographic variation in sexual dimorphism in the barn owlTyto alba: a role for direct selection or genetic correlation?
Authors: Roulin Alexandre
Published: August 2003

Geographic variation in sexually selected traits is commonly attributed to geographic variation in the net benefit accrued from bearing such traits. Although natural and sexual selection are potentially important in shaping geographic variation, genetic constraints may also play a role. Although a genetic correlation between two traits may itself be the outcome of natural or sexual selection, it may indirectly reinforce the establishment and maintenance of cline variation with respect to one particular trait when across the cline different values of other traits are selected. Using the barn owlTyto alba, a species in which the plumage of females is more reddish‐brown and more marked with black spots than that of males, I report results that are consistent with the hypothesis that both direct selection and genetic constraints may help establish and maintain cline variation in sexual dichromatism. In this species, inter‐individual variation in plumage coloration and spottiness has a genetic basis, and these traits are not sensitive to the environment. Data, based on the measurement of skin specimens, is consistent with the hypothesis that the stronger European cline variation in male spottiness than in female spottiness depends on the combined effects of (1) the similar cline variation in male and female plumage coloration and (2) the more intense phenotypic correlation between plumage coloration and spottiness in males (darker birds are more heavily spotted in the two sexes, but especially males) which is a general feature among the globally distributed barn owls. In northern Europe, male and femaleT. a. guttataare reddish‐brown and heavily spotted, and in southern Europe male and femaleT. a. albaare white, but only females display many spots. Here, I discuss the relative importance of direct selection, genetic correlation and the post‐ice age invasion of Europe byT. alba, in generating sex‐specific cline variation in plumage spottiness and non‐sex‐specific cline variation in plumage coloration.
Foraging behaviour of chick‐rearing rhinoceros auklets Cerorhinca monocerata at Teuri Island, Japan, determined by acceleration‐depth recording micro data loggers
Authors: Kato Akiko , Watanuki Yutaka , Naito Yasuhiko
Published: August 2003

Flight and diving activity of rhinoceros auklets Cerorhinca monocerata breeding on Teuri Island, Japan, were monitored during the summers 1999 and 2000 using miniaturized time‐depth and acceleration recorders. Birds made 14.5 dive bouts per day of on average 15.4 min duration, which consisted of on average 16.2 dives of 12.1 m depth and 42.7 s duration. Birds made 13.8±7.3 flight bouts per day, which lasted on average 11.5±4.5 min. Daily total flight duration was 2.7±1.7 h (range 54 s–5.1 h) and the mean potential foraging range was estimated to be 87 km (maximum 164 km). Most birds stayed at the colony or rested on the water surface during the night. Rhinoceros auklets dived more actively in early morning and in late afternoon than during mid‐day. Compared to results from studies of time allocation in other alcids species, rhinoceros auklets spent longer time flying (3.3 hd−1) and resting on water (13.1 hd−1), and less time diving (3.1 hd−1) and staying at the colony (4.4 hd−1). These foraging patterns are probably related to the nest attendance pattern of rhinoceros auklets, i.e. leaving the colony early in the morning, staying at sea all the day and returning to the colony in the evening to provision their chicks.
The subgingival microflora in phenytoin‐induced gingival hyperplasia
Authors: Takada Kazuko , Sugiyama Hitoshi , Umezawa Koji , Mega Junichi , Hirasawa Masatomo
Published: August 2003

Objectives:  Microbial flora and gingival conditions were compared between a group of patients with phenytoin‐induced gingival hyperplasia as a test group, a control group of patients who were administered phenytoin without gingival hyperplasia and a blank group who took no phenytoin and no gingival hyperplasia in mentally retarded patients.

Materials and methods:  Subgingival plaque samples were collected from a PHT‐induced overgrown gingival pocket and microbiological experiments were performed by culture and PCR methods.

Results:  The predominant genera in total cultivable bacteria from subgingival plaque samples were streptococcus and actinomyces with recovery ranges of 37.6–42.1% and 23.4–25.5% of total bacteria, respectively, in all groups. The test group showed a significantly higher level of obligate Gram‐negative rods than the control and blank groups. Black‐pigmented obligate anaerobic Gram‐negative rods were detected in 10.3% of total cultivable bacteria in the test group. The black‐pigmented rods were predominantly Prevotella intermedia in the test group and Prevotella nigrescens in the control and blank groups. Porphyromonas gingivalis and Porphyromonas endodontalis were also detected in the test group with small values.

Conclusions:  These results suggested that black‐pigmented rods, particularly P. intermedia, could be habitable in the environment of gingival hyperplasia.
Induction of cyclooxygenase‐2 mRNA and protein expression in human gingival fibroblasts stimulated with nicotine
Authors: Chang Yu‐Chao , Tsai Chung‐Hung , Yang Shyh‐Hwang , Liu Chia‐Ming , Chou Ming‐Yung
Published: August 2003

Background:  Cigarette smoking is a major risk factor in the development and further progression of periodontal diseases. COX‐2 is an inducible enzyme believed to be responsible for prostaglandin synthesis at site of inflammation. Currently, there is limited information on the regulation of COX‐2 expression in smoking‐associated periodontal disease.

Objectives:  The aim of the present study was to investigate the effects of nicotine on the expression of cyclooxygenase‐2 (COX‐2) mRNA gene and protein in cultured human gingival fibroblasts (HGFs). Furthermore, to elucidate whether induction of COX‐2 may be associated with nicotine‐ induced cytotoxicity, NS‐398 (a selective COX‐2 inhibitor), was added to test its protective effect.

Methods:  The quantitative reverse‐transcriptase polymerase chain reaction and Western blot assays were used to investigate the effects of human HGFs exposed to nicotine. In addition, NS‐398 was added to test how it modulated the effects of nicotine.

Results:  The exposure of quiescent human HGFs to nicotine resulted in the induction of COX‐2 mRNA expression. The levels of the COX‐2 mRNAs increased about 1.5 and 2.5 fold after exposure to 2.5 and 15 mm nicotine for 2 h (P < 0.05), respectively. Moreover, the peak of COX‐2 mRNA levels induced by nicotine was 10 mm at 2 h incubation period. Investigations of the time dependence of COX‐2 mRNA expression in nicotine‐treated HGFs revealed a rapid accumulation of the transcript, a signal first detectable at 30 min and diminished to control level after 8 h. In addition, 10 mm nicotine also induced COX‐2 protein expression in HGFs. The kinetics of this response showed that COX‐2 was detectable at 4 h and diminished nearly to control level after 24 h. NS‐398 at non‐cytotoxic dose is not able to prevent nicotine‐induced cytotoxicity.

Conclusions:  Taken together, the activation of COX‐2 expression by nicotine suggests a potential role for nicotine in the pathogenesis of smoking‐associated periodontal disease. In addition, nicotine‐induced cytotoxicity is not directly via the induction of COX‐2 expression.
Immunohistochemical localization of fibromodulin in the periodontium during cementogenesis and root formation in the rat molar
Authors: Matias M. A. , Li H. , Young W. G. , Bartold P. M.
Published: August 2003

Background:  Cementum is essential for periodontal regeneration, as it provides anchorage between the root surface and the periodontal ligament. A variety of macromolecules present in the extracellular matrix of the periodontium, including proteoglycans, are likely to play a regulatory role in cementogenesis. Recently, the small leucine‐rich proteoglycan, fibromodulin, has been isolated from bovine periodontal ligament and localized in bovine cementum, as well as in human periodontal ligament.

Objective:  The aim of this study was to examine the distribution of fibromodulin during cementogenesis and root formation.

Methods:  A standard indirect immunoperoxidase technique was employed, using an antifibromodulin polyclonal antibody on sections of molar teeth from rats aged 3, 5 and 8 weeks.

Results:  Immunoreactivity to fibromodulin was evident in the periodontal ligament in all sections. An intense positive stain was observed in the extracellular matrix where the periodontal ligament fibers insert into the alveolar bone and where the Sharpey's fibers insert into the cementum. There was no staining evident in the mineralized cellular and acellular cementum. The intensity of immunoreactivity to the antifibromodulin antibody increased proportionally with increasing tissue maturation.

Conclusion:  The results from this study suggest that fibromodulin is a significant component of the extracellular matrix in the periodontal ligament during development, and may play a regulatory role in the mineralization process or maintaining homeostasis at the hard–soft tissue interface during cementogenesis.
Treatment of polymorphic light eruption
Authors: Ling Tsui C. , Gibbs Neil K. , Rhodes Lesley E.
Published: August 2003

Polymorphic light eruption (PLE) is a highly prevalent photosensitivity disorder, estimated to affect 11–21% people in temperate countries. Typically, PLE appears as a recurrent pruritic eruption comprising papules and/or vesicles and/or plaques, which occurs on photo‐exposed skin sites following sun exposure, and which heals without scarring. Commoner in females, the aetiology is uncertain, although there is evidence of an immune basis. We perform a review of the prophylaxis and treatment of this condition. While sun protection, corticosteroids and desensitization phototherapy are the mainstays of management, a range of anti‐inflammatory and immunomodulatory agents are reported.