bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of constitutive model parameters on the predicted migration of DNAPL in heterogeneous porous media
Authors: Gerhard J. I. , Kueper B. H.
Published: October 2003

This study examines the influence of constitutive models and their parameters on predictions of the spatial and temporal distribution of a finite release of a dense, nonaqueous phase liquid (DNAPL) into a two‐dimensional, spatially correlated random permeability field. The base case simulation employed a comprehensive constitutive model that was validated against relevant one‐dimensional laboratory experiments. The base case was perturbed in the course of nine individual simulations, where each simulation examined the consequences of simplifying a single model characteristic. None of the nine subsequent simulations was able to reproduce, within ±10%, the spatial and temporal migration characteristics of the nonwetting fluid body at late time predicted by the base case. Capillary pressure‐saturation relationships that do not incorporate specific displacement and terminal pressures are demonstrated to severely overpredict the spatial extent of nonwetting fluid advancement. This suggests that van Genuchten‐based models may not be suitable for predicting DNAPL migration in saturated porous media. Not accounting for any one of hysteresis, nonwetting phase trapping, or the proper curvature or end‐point values of the nonwetting phase imbibition relative permeability curve profoundly influenced the time predicted for all nonwetting fluid movement to cease. The practical implication of this study is that an appropriate, comprehensive constitutive model, characterized with suitable parameter values, is necessary to accurately simulate a complete DNAPL release below the water table in both space and time.
Comparative evaluation of urban storm water quality models
Authors: Vaze J. , Chiew Francis H. S.
Published: October 2003

The estimation of urban storm water pollutant loads is required for the development of mitigation and management strategies to minimize impacts to receiving environments. Event pollutant loads are typically estimated using either regression equations or “process‐based” water quality models. The relative merit of using regression models compared to process‐based models is not clear. A modeling study is carried out here to evaluate the comparative ability of the regression equations and process‐based water quality models to estimate event diffuse pollutant loads from impervious surfaces. The results indicate that, once calibrated, both the regression equations and the process‐based model can estimate event pollutant loads satisfactorily. In fact, the loads estimated using the regression equation as a function of rainfall intensity and runoff rate are better than the loads estimated using the process‐based model. Therefore, if only estimates of event loads are required, regression models should be used because they are simpler and require less data compared to process‐based models.
Periodic mid‐Cretaceous oceanic anoxic events linked by oscillations of the phosphorus and oxygen biogeochemical cycles
Authors: Handoh Itsuki C. , Lenton Timothy M.
Published: October 2003

A series of oceanic anoxic events (OAEs) occurred in the mid‐Cretaceous warm period (120–80 Ma) that have been linked with high rates of organic carbon burial, warm high‐ and low‐ latitude temperatures, and sea‐level changes. OAEs have been studied individually, but a causal mechanism that connects them has been lacking. We show that peaks in phosphorus accumulation in marine sediments broadly coincide with OAEs 1a, 1b, 1d, 2, and 3, and exhibit a 5–6 Myr periodicity, which for reactive‐P is prominent over 100–80 Ma. Oxic‐anoxic oscillations of this frequency are also found in a model of the coupled N, P, C, and O2 biogeochemical cycles. These oscillations are maintained by positive feedbacks between phosphate concentration, biological productivity, and anoxia in the global ocean and counteracting, but slower, negative feedbacks involving changes in atmospheric oxygen. An increase in phosphorus weathering rate above a critical threshold can shift the system into self‐sustaining oscillation. This could have been caused by tectonic and volcanic forcing increasing atmospheric CO2 and global warmth 120–80 Ma, augmented by the rise of flowering plants around 100 Ma. With a plausible forcing scenario, we are able to reproduce the approximate timing of OAEs 1a, 1b, 1d, 2, and 3 in the model.
Aircraft observations of a lightning channel in STEPS
Authors: Warner Tom A. , Helsdon John H. , Detwiler Andrew G.
Published: October 2003

We analyze a portion of an intracloud lightning channel that was captured on video by an instrumented aircraft and mapped three‐dimensionally by a ground‐based lightning mapping array (LMA). By comparing the electric fields measured on the aircraft with a model which simulates the electrostatic field present after charge was effectively deposited by this flash, we estimate that the channel formed ∼80 m in front of and passed ∼30 m below the aircraft, in agreement with the average LMA locations, and that it deposited on the order of 0.02 mC/m of negative charge.
Geometrical approach to surface wave finite frequency effects
Authors: Tanimoto T.
Published: October 2003

A simple geometrical result for the finite frequency effects of surface waves is derived by examining a normal mode formula in its asymptotic limit. An ellipse, determined by wavelength and locations of source and receiver, is shown to give the spread due to finite frequency effects in an analytically continued latitude coordinate. This spread has the form of the Gaussian distribution and its width is determined by the ellipse. Since this Gaussian distribution function is normalized at each distance, in the direction perpendicular to the ray path, peak values along ray path change from source to receiver, making a contrast to ray theoretical results which put equal weights along ray path. The result is valid only for laterally homogeneous earth models, but since finite frequency effects are important for low frequency waves for which lateral heterogeneity effects are less severe, this geometrical relation may be useful for tomographic studies.
Gravity/topography admittance inversion on Venus using niching genetic algorithms
Authors: Lawrence Kristin P. , Phillips Roger J.
Published: October 2003

We used niching genetic algorithms (NGAs) to invert localized Venus gravity/topography admittance over lowland regions Atalanta and Lavinia Planitiae, as well as volcanic rise Atla Regio for comparison. Assuming both top (topography) and bottom (mantle density anomalies) loads, we calculated theoretical admittance using thin elastic shell models. We inverted admittance for crustal thickness, elastic lithosphere thickness, mantle density anomaly thickness, and ratio (pz) of mantle density anomaly to topographic load. NGA inversion provides an efficient means of finding globally optimal and sub‐optimal solutions. Error analyses of all three regions show that pz is a robust estimate; there is significant trade‐off between elastic lithosphere and mantle anomaly thicknesses, while crustal thickness is ill‐constrained. Optimal models suggest that mantle density anomalies are ∼+1 to 2% underlying lowland regions and ∼−3 to −4% underlying Atla Regio.
Inverse projection method for determination of distribution of real CME latitudes applied to the 1997–1998 SOHO LASCO observations
Authors: Skirgiello Marta
Published: October 2003

Coronograph observations of coronal mass ejections (CMEs) do not provide the real latitude of their origin. The registered apparent latitude is the projection of the CME trajectory on the plane of the sky, and it may considerably differ from their original location. We show in this paper, how the projection effects can be eliminated from CME latitude distribution. The proposed method is based on the assumption that events move radially, their longitudinal distribution is uniform, and they are all detected. This tool has been applied to SOHO LASCO data, for which detection efficiency was near 100%. The obtained distributions of real latitudes have cut off at ∼20° in 1997 (minimum solar activity) and ∼50° in 1998 (rise phase). The events observed at higher latitudes proved to be only apparent projections of events really originated at lower latitudes.
Secondary organic aerosol formation in the atmosphere via heterogeneous reaction of gaseous isoprene on acidic particles
Authors: Limbeck Andreas , Kulmala Markku , Puxbaum Hans
Published: October 2003

Water‐soluble macromolecular substances with spectral properties of “humic‐like substances” (HULIS) were recently found to form the major identified fraction of the organic aerosol at urban and rural sites in Europe. With primary sources identified so far (e.g., biomass combustion) it is not possible to explain the observed HULIS levels in Europe, therefore there is an ongoing search for other sources ‐ which form HULIS in situ in the atmosphere. Here we show that secondary aerosol formation of atmospheric polymers occurs by heterogeneous reaction of isoprenoid or terpenoid emissions in the presence of a sulfuric acid aerosol catalyst. Competing oxidants such as ozone or the presence of humidity decreased the reaction yield, but the formation of humic–like substances was not disabled. Calculations indicate that the presented reaction pathway could be an additional source for HULIS in the continental aerosol.
Modeling of the first indirect effect: Analysis of measurement requirements
Authors: Feingold Graham
Published: October 2003

We investigate the extent to which aerosol extinction is a suitable proxy for the aerosol affecting drop formation. First we use multiple realizations of a cloud model to investigate the sensitivity of cloud drop effective radius re to aerosol parameters (size distribution and composition) and dynamical parameters (updraft and liquid water content). In general, re is most sensitive to cloud liquid water, a parameter often ignored in indirect effect analyses. The relative importance of the other parameters varies for different conditions but aerosol concentration Na is consistently important. Updraft plays an increasingly important role under high aerosol loadings. A breakdown of the individual aerosol terms contributing to drop size change shows that use of aerosol extinction as a proxy for size distribution and composition tends to underestimate the magnitude of the first indirect effect. This may influence interpretation of current satellite and surface remote measurements of the indirect effect.
Observations of the effect of wind on the cooling of active lava flows
Authors: Keszthelyi Laszlo , Harris Andrew J. L. , Dehn Jonathan
Published: October 2003

We present the first direct observations of the cooling of active lava flows by the wind. We confirm that atmospheric convective cooling processes (i.e., the wind) dominate heat loss over the lifetime of a typical pahoehoe lava flow. In fact, the heat extracted by convection is greater than predicted, especially at wind speeds less than 5 m/s and surface temperatures less than 400°C. We currently estimate that the atmospheric heat transfer coefficient is about 45–50 W m−2 K−1 for a 10 m/s wind and a surface temperature ∼500°C. Further field experiments and theoretical studies should expand these results to a broader range of surface temperatures and wind speeds.
When is the strain in the meter the same as the strain in the rock?
Authors: Segall Paul , Jónsson Sigurjón , Ágústsson Kristján
Published: October 2003

Borehole dilatometers are emplaced in porous fluid saturated rock. Pore‐fluid flow induces strain, however there is no fluid exchange with the dilatometer. Thus, the strainmeter response is the same as the strain in the rock only when the rock remains undrained. Otherwise the instrumental strain Δinst is given by Δinst = C1 (Δ∞ − C2p∞), where Δ∞ and p∞ are strain and pore pressure far from the borehole, and C1 and C2 depend on poroelastic rock properties. Postseismic strain in the rock is expected to increase as the induced pore pressure gradients relax. However, a dilatometer ∼3 km from a Mw 6.5 earthquake in south Iceland shows a postseismic strain change opposite in sign to the coseismic response. The theory developed here for a homogeneous, isotropic medium can only partly explain this discrepancy. Fracture dominated poroelastic response may yield an improved fit to the data.
Integrated parameterization of irrigation in the land surface model ORCHIDEE. Validation over Indian Peninsula
Authors: de Rosnay P. , Polcher J. , Laval K. , Sabre M.
Published: October 2003

The work presented here describes a new modeling infrastructure of irrigation which is integrated in a land surface model and which will make this model a suitable tool for studies of interactions between irrigation water use and climate change. The model is presented and validated off‐line over the Indian Peninsula. Numerical experiments are conducted with a 1 degree spatial resolution land surface model. Two 2‐year simulations, forced by the ISLSCP (1987–88) data sets, are conducted with and without irrigation. The analysis focuses on irrigation modeling validation and briefly presents first results on irrigation's impact on the surface fluxes.
Application of Meteosat thermal data to map soil infiltrability in the central part of the Lake Chad basin, Africa.
Authors: Leblanc Marc , Razack Moumtaz , Dagorne Dominique , Mofor Linus , Jones Chris
Published: October 2003

In the central part of the Lake Chad Basin, Africa, the superficial Quaternary aquifer (500,000 km2) forms the main water resource. Little is known about the aquifer recharge processes. Large piezometric depressions affect the aquifer and are still unexplained. Meteosat thermal composite data were used to infer qualitative information about time‐space variations of soil moisture. Over the aquifer, Meteosat data reveal that after heavy rainfall, the piezometric depressions (Kadzell, Chari‐Baguirmi) appear cooler than the surrounding areas (Manga and Harr). The interpretation is that above the depressions, rainwater accumulates at the surface and does not infiltrate deep into the ground, leading to the observed cooler ground. Accordingly, the depressions are characterized by low rainwater infiltrability, which presumably results in a small rainfall recharge. As far as we know, this is the first time that an observed surface phenomenon is directly related to the origin of some piezometric depressions.
Surface‐water transport of suspended matter through wetland vegetation of the Florida everglades
Authors: Saiers James E. , Harvey Judson W. , Mylon Steven E.
Published: October 2003

The mobility of waterborne particulate matter plays an important role in the water quality, landscape evolution, and ecology of freshwater wetlands. In this work, we measured the surface‐water transport of inorganic particles in a tracer experiment at a wetland in the Florida Everglades. Comparison of the results of this experiment to calculations of a three‐dimensional transport model shows that dispersive mixing was small and that rate‐limited mass‐transfer reactions with emergent vegetation and periphyton substantially reduced water‐column concentrations of particles.
Ulysses Observations at Solar Maximum: Introduction
Authors: Smith Edward J. , Marsden Richard G.
Published: October 2003

Observations during Ulysses' second solar orbit reveal basic changes between solar minimum and maximum. Fast high latitude wind disappeared in the southern hemisphere allowing slow wind to expand to all latitudes. In the north polar cap, both fast wind and a polar coronal hole were present. The magnetic field polarity reversal was detected in the north polar cap. The source dipole of the heliospheric magnetic field had a nearly equatorial, rather than an axial, orientation. Coronal mass ejections occurred at all latitudes including fast wind from the polar cap. Analysis of magnetic clouds confirmed their close association with solar filaments. The electron‐proton ratio of galactic cosmic rays changed at the magnetic polarity reversal. Solar Energetic Particles were present at all latitudes including the formation of particle “reservoirs” that require access to all latitudes and longitudes. Reservoir particles are also present at solar minimum at low flux levels.
Satellite observation of internal solitary waves converting polarity
Authors: Zhao Zhongxiang , Klemas Victor V. , Zheng Quanan , Yan Xiao‐Hai
Published: October 2003

On a SPOT‐3 visible image over the South China Sea continental shelf, two contrasting signatures of internal solitary waves (ISWs) are observed: darker stripes leading brighter stripes in the lower part, and brighter stripes leading darker stripes in the upper part. The authors suggest that the contrasting patterns are caused by ISWs of different polarities. A packet of ISWs is observed in the process of converting polarity due to bottom shoaling, both in the propagation direction and in the transect direction. The evolution process can be obtained by transferring information from the spatial domain to the temporal domain. The conversion process starts with the original depression ISWs passing the 160 m isobath. The evolution process can be divided into two phases: the first is the broadening of the original depression waves and the second is the appearance of the new‐born elevation waves. These two phases are verified using numerical simulation.
Glaciochemical investigation of an ice core from Belukha glacier, Siberian Altai
Authors: Olivier Susanne , Schwikowski Margit , Brütsch Sabina , Eyrikh Stella , Gäggeler Heinz W. , Lüthi Martin , Papina Tatyana , Saurer Matthias , Schotterer Ulrich , Tobler Leonhard , Vogel Edith
Published: October 2003

During summer 2001, a 140 m long ice core was recovered from the Belukha glacier (49°48′26″N, 86°34′43″E, 4062 m a.s.l.) in the Siberian Altai. The englacial temperature of −17°C indicates that this unique glaciochemical record is well preserved and suitable for the reconstruction of air pollution levels in this previously unexplored region. The upper 86 m were dated by 210Pb and cover the period 1862–2001. A lack of strong winter minima was observed in the δ18O record and attributed to the small amount of precipitation during that season and to wind erosion. The ion concentrations are comparable to those observed in Swiss glaciers, except for ammonium and formate, where enhanced concentrations indicate biogenic emissions from Siberian forests. Sulfate, ammonium and nitrate records all show anthropogenic impacts despite the remoteness of this site.
Seismicity and tectonics of the South Shetland Islands and Bransfield Strait from a regional broadband seismograph deployment
Authors: Robertson Maurice Stacey D. , Wiens Douglas A. , Shore Patrick J. , Vera Emilio , Dorman LeRoy M.
Published: October 2003

We investigate the tectonics of the South Shetland Trench and Bransfield Strait by performing a detailed study of local seismicity. During 1997–1999 we deployed seven land seismometers and 14 ocean bottom seismometers in the South Shetland Island region. The data we obtained indicate a high level of local seismicity (mb 2–5), and we accurately located ∼150 earthquakes. Many of the earthquakes occur at locations and depths indicative of ongoing subduction in the South Shetland trench. A focal mechanism for the largest event in the forearc indicates shallow angle thrusting. The maximum depth of seismicity is ∼65 km, but the majority of the events are shallower than 30 km. These seismic results are consistent with recent magnetic, GPS, and multichannel seismic reflection data that suggest continued subduction at a very slow rate. The South Shetland trench thus represents an extreme end‐member of hot subduction resulting from slow convergence of young lithosphere, and the absence of intermediate depth earthquakes is consistent with thermal assimilation of the slab at shallow depths. We have located many earthquakes associated with volcanism and rifting in Bransfield Strait. A swarm of events near a submarine volcano suggests current magmatic activity. A normal faulting focal mechanism in the northeastern part of the strait gives evidence of extension. Earthquakes associated with rifting in the northeastern portion of the strait are clustered along well‐established rifts, but the seismicity is much more diffuse to the southwest. This observation is consistent with other evidence that extension has propagated from northeast to southwest.
First‐principles prediction of the P‐V‐T equation of state of gold and the 660‐km discontinuity in Earth's mantle
Authors: Tsuchiya Taku
Published: October 2003

The P‐V‐T equation of state (EOS) of gold is the most frequently used pressure calibration standard in high‐P‐T in situ experiments. Empirically proposed EOS models, however, severely scatter under high‐P‐T conditions, which is a serious problem for studies of the deep Earth. In this study, the EOS of gold is predicted using a first‐principles electronic structure calculation method without any empirical parameters. The calculated thermoelastic properties of gold compare favorably to experimental data at ambient conditions so that BT0 and B′T0 are 166.7 GPa and 6.12, respectively. Up to V/Va = 0.7, the calculated Grüneisen parameter of gold depends on volume according to the function γ/γa = (V/Va)ζ with γa of 3.16 and ζ of 2.15. On the basis of these data, the validity of previous EOS models is discussed. It is found that the present ab initio EOS provides a 1.3 GPa higher pressure than Anderson's scale at 23 GPa and 1800 K and largely reduces the discrepancy observed between conditions at the transition of Mg2SiO4 and the 660‐km seismic discontinuity. However, a discrepancy of about 0.7 GPa still remains between the 660‐km discontinuity and the postspinel transition.
Distribution and intraseasonal variability of rain over Indian Oceanic region from Indian Remote Sensing Satellite IRS‐P4 Multifrequency Scanning Microwave Radiometer
Authors: Pokhrel Samir , Varma A. K. , Gairola R. M. , Agarwal Vijay K.
Published: October 2003

Multifrequency Scanning Microwave Radiometer (MSMR) onboard Indian Remote Sensing Satellite (IRS‐P4) has been utilized for measurement of precipitation over Indian Oceanic region. MSMR‐derived monthly rain rates for the month of August for three consecutive years are compared with that from TMI and PR. A reasonably good agreement is found. Rain distributions are presented for three seasons, namely, premonsoon (February–May), monsoon (June–September), and postmonsoon (October–January) for the entire period of MSMR from June 1999 to September 2001. The year‐to‐year difference in the three seasons is found in agreement with the weather reports. Latitudinal distribution of the MSMR‐derived rain rate for the Arabian Sea and the Bay of Bengal and for the entire study area are analyzed and are found to be in good agreement with climatology. Furthermore, starting from 60°E longitude up to 95°E, at every 5° interval, latitudinal distribution of rain rate is plotted for the three monsoon seasons. It is found that the vigor of monsoon rain begins building up between 65° and 70°E and goes beyond 95°E. A time series and wavelet analysis of daily rain rate is presented for monsoon seasons of three consecutive years. Wavelet analysis clearly shows the presence of long waves of 30–60 and 10–20 day oscillations and also of synoptic scale of 3–6 day oscillations in the monsoon rain. Furthermore, Hovmoller diagrams of daily rain over the northern Bay of Bengal are analyzed for monsoon seasons of three years, and some northward propagation of rain is reported.
Effects of changes in environmental conditions on atmospheric mercury exchange: Comparative analysis from a rice paddy field during the two spring periods of 2001 and 2002
Authors: Kim Ki‐Hyun , Kim Min‐Young , Kim Joon , Lee Gangwoong
Published: October 2003

The environmental mobilization characteristics of Hg were investigated in a rice paddy field in the Hari district of Kang Hwa Island, Korea during two field campaigns held in late March 2001 and late April 2002. In the course of these two field campaigns, we measured the concentration, concentration gradients (between two different heights of 1 and 5 m), and fluxes of Hg with the aid of micrometeorological approaches. The results of our experiments consistently indicate that the study area behaved as both source and sink of Hg, yielding a net emission rate of 183 (1st) to 28 ng m−2 h−1 (2nd campaign). It was however found that the soil‐air exchange patterns of Hg during the two study periods, although investigated in similar seasonal cycles, contrast to a large extent. Upward emission prevailed in both the frequency and magnitude during the 1st study period, but dry deposition was seen more dominantly in terms of frequency during the 2nd study period. In light of the fact that the occurrence patterns of Asian Dust events differed greatly between the two study periods, the possible role of long‐range transport of airborne pollutants (LRTAP) as sources of Hg into the study area has also been examined using information on air mass movement patterns. Because observed differences in Hg flux patterns generally reflect changes in environmental conditions across study periods, the bi‐directional exchange patterns of Hg during the two field campaigns were explained in relation to highly diverse environmental conditions that persisted in each study period.
Modeling aerosols on the mesoscale‐γ: Treatment of soot aerosol and its radiative effects
Authors: Riemer N. , Vogel H. , Vogel B. , Fiedler F.
Published: October 2003

Aerosol particles modify the transfer of solar radiation in the atmosphere. To quantify this impact, the composition and the size distribution of the aerosol have to be known. In this study, simulations with a comprehensive model system including meteorological processes, gas phase chemistry, and aerosol dynamics and chemistry were carried out to investigate the impact of aerosol particles on global radiation. The model system is applied to a summer situation in the southwestern part of Germany. The aerosol model represents the aerosol population by several overlapping modes. It originally accounted for the species sulfate, nitrate, ammonium, and water and now has been extended to treat soot. Since the optical properties of soot particles depend critically on their mixing state, the transfer of soot from the external into the internal mixture is parameterized. On the basis of the simulated aerosol distributions the optical properties of the aerosol were derived using Mie calculations. These results serve as input data for the radiative transfer calculations, where we considered the wavelength interval from 280 nm to 700 nm. The results of the radiative transfer calculations show that for the summer situation presented, the aerosol in the boundary layer reduces the downward flux of the solar radiation by up to 25 W m−1. Sensitivity studies showed that up to 50% of this effect can be attributed to the impact of soot.
High‐latitude mesospheric mean winds: A comparison between Tromsø (69°N) and Svalbard (78°N)
Authors: Hall C. M. , Aso T. , Manson A. H. , Meek C. E. , Nozawa S. , Tsutsumi M.
Published: October 2003

Daily mean winds in the upper mesosphere regions above Tromsø (69°N, 19°E) and Svalbard (78°N, 16°E) are presented; these having been obtained from 6 years' operation of the middle frequency radar at Tromsø and almost 2 years' operation of the Svalbard meteor radar. The findings depart somewhat from the predictions of current modeling, particularly in that outflow from the pole occurs almost all year‐round. This picture is in accordance with a Ferrell cell circulation in summer but not in winter. Gravity‐wave drag, parameterized by the Rayleigh drag coefficient, is suggested as a likely cause of the widespread ageostrophic motion characterizing the winter dynamics.
Indo‐Asian pollution during INDOEX: Microphysical particle properties and single‐scattering albedo inferred from multiwavelength lidar observations
Authors: Müller Detlef , Franke Kathleen , Ansmann Albert , Althausen Dietrich , Wagner Frank
Published: October 2003

We present for the first time a comprehensive data set of vertically resolved physical particle properties, and the single‐scattering albedo at 532 nm, derived from multiwavelength lidar observations of pollution plumes advected from India and Southeast Asia out over the tropical Indian Ocean during the northeast monsoon. The parameters follow from the inversion of optical data that were obtained from six‐wavelength aerosol lidar observations at Hulhule Island (4.1°N, 73.3°E), Maldives, in the framework of the Indian Ocean Experiment (INDOEX) (February/March 1999) and three follow‐up campaigns in July and October 1999 and in March 2000. Effective particle radii were 0.20 ± 0.08 μm for pollution plumes above 1‐km height, advected during the northeast monsoon. Volume concentrations ranged from 6 to 44 μm3 cm−3, and surface‐area concentrations were 95–774 μm2 cm−3. The particles showed substantial absorption when advected from northern India. The imaginary part of the wavelength‐independent complex refractive index was as large as 0.045i. The respective mean value was 0.022i ± 0.014i for observations during the northeast monsoon. The mean real part was 1.54 ± 0.11. The mean single‐scattering albedo at 532 nm was 0.90 ± 0.06. Values were as low as 0.8 during advection of air from northern India. On average, less absorbing particles were advected from southern India and Southeast Asia. The numbers indicate that the major contributor to the observed pollution from northern India is absorbing soot‐like material from, e.g., fossil fuel and firewood burning. The effective radius was well correlated with the Ångström exponents of the underlying extinction spectra. Strong correlation of the single‐scattering albedo was found not only with respect to the imaginary part of the complex refractive index but also with respect to the particle extinction‐to‐backscatter ratio. A comparison to Ångström exponents and single‐scattering albedo obtained from Sun photometer and satellite observations showed good representativity of the lidar‐derived quantities. Comparison with results from airborne in situ observations showed substantial deviations of Ångström exponents and single‐scattering albedo.
Measurements of ambient atmospheric C2H5Cl and other ethyl and methyl halides at coastal California sites and over the Pacific Ocean
Authors: Low Jason C. , Wang Nun Yii , Williams Jody , Cicerone Ralph J.
Published: October 2003

Spatial and temporal distributions of atmospheric CH3Cl, CH3Br, C2H5Cl, and C2H5Br were determined by gas chromatography/mass spectrometry measurements at coastal California and inland sites from 1996 through 1999. The median concentrations observed at a clean coastal site were 585, 13.1, 3.3, and 0.3 ppt (parts per trillion) for CH3Cl, CH3Br, C2H5Cl, and C2H5Br, respectively. To our knowledge, these represent the first quantitative measurements of atmospheric C2H5Cl. High variation was seen in CH3Br and C2H5Cl measurements from the other two California sites, a rural inland site and a coastal site with urban influence. When compared to the California stationary sites, the median Northern Hemispheric results from measurements taken along Pacific Ocean transects between California and New Zealand from 1996 through 1999 were similar for CH3Cl (594 ppt) and C2H5Br (0.3 ppt) but lower for CH3Br (10.4 ppt) and C2H5Cl (2.6 ppt). Median concentrations of Southern Hemispheric CH3Br (9.4 ppt), C2H5Cl (1.6 ppt), and C2H5Br (less than 0.2 ppt) were lower than the Northern Hemispheric results. No significant correlation was found between the atmospheric concentrations of the methyl halides with the ethyl halides.
Intercomparison of peroxy radical measurements at a rural site using laser‐induced fluorescence and Peroxy Radical Chemical Ionization Mass Spectrometer (PerCIMS) techniques
Authors: Ren Xinrong , Edwards Gavin D. , Cantrell Christopher A. , Lesher Robert L. , Metcalf Andrew R. , Shirley Terry , Brune William H.
Published: October 2003

Two different instruments were deployed to measure hydroperoxy radical (HO2) and total peroxy radicals during May and June 2002 at a rural site located at Rock Springs near State College, Pennsylvania. One instrument was the Penn State Ground‐Based Tropospheric Hydrogen Oxides Sensor (GTHOS), which measured HO2 by laser‐induced fluorescence (LIF) of OH following the chemical conversion of HO2 to OH by adding NO. The other was the Peroxy Radical Chemical Ionization Mass Spectrometer (PerCIMS) instrument that provided HO2 (HO2 mode) or total peroxy radicals (HOxROx mode) measurements. The two instruments were compared by exchanging calibration sources and by side‐by‐side ambient measurements. Excellent agreement was obtained in the calibration comparisons with the slope of a correlation plot close to 1.0 and a small intercept. Daily HO2 measurements from GTHOS and PerCIMS (in HO2 mode) on 4 days show that diurnal variations normally agreed to within about 40%. A comparison of HO2 measured by GTHOS and HOxROx measured by PerCIMS shows good correlation for both average diurnal variation and individual diurnal cycles. On average, HO2 from GTHOS was about 0.66 times the HOxROx from PerCIMS, meaning that organic peroxy radicals account for about one third of the total peroxy radicals in this environment.
Effects of host shading on consumption and growth of the geometrid Epirrita autumnata: interactive roles of water, primary and secondary compounds
Authors: Henriksson J. , Haukioja E. , Ossipov V. , Ossipova S. , Sillanpää S. , Kapari L. , Pihlaja K.
Published: October 2003

Shading is assumed to reduce allocation to plant phenolics and to defense in general. We here report the results of experimental shading of individual branches or whole canopies in mountain birch on foliar chemistry and on the growth and consumption of a geometrid, Epirritaautumnata. Branch‐wide shading tended to have at least as strong effects on both leaf chemistry and herbivore performance as canopy‐wide shading, indicating local responses of the host to shading. Responses to shading varied among the key leaf traits. Leaf water content was higher and toughness lower in shaded than in non‐shaded leaves. Leaf sugars were lower and protein‐bound and free amino acids higher in shaded than in control leaves. Sucrose and galactose were at high levels in unshaded branches adjacent to shaded ones, suggesting that partial shading enhanced translocation of sugars within canopies. Total phenolics and soluble proanthocyanidins were low in both shading treatments. Of the other phenolic groups, concentrations of gallotannins and cell‐wall‐bound proanthocyanidins did not differ between shaded and non‐shaded leaves. Epirrita larvae grew better in both types of shading treatments compared to either unshaded control trees or to unshaded branches in the branch‐shading trees. By far the most important correlate of larval growth was the amount of water consumed with leaf mass (r=0.94). When variance in water intake was standardized (also largely eliminating parallel variation in proteins), fructose and glucose still had significant positive correlations and proanthocyanidins negative with larval growth on control but not on shade leaves. Concentrations of several phenolic compounds correlated negatively with intake of dry matter and especially water, and different phenolics were important in shaded (gallotannins) and in control (flavonoids) leaves. Our findings strongly suggest that the effects of putatively defensive leaf traits on insect consumption and growth interact with nutritive leaf traits, particularly with water.
Metamorphic synchrony and aggregation as antipredator responses in American toads
Authors: DeVito Jill
Published: October 2003

Safety in numbers serves as an antipredator defense strategy in many organisms, as aggregation can reduce the probability of predation for individual group members. It has long been suggested that some organisms are under selective pressure to synchronize vulnerable life stages with conspecifics, but there have been very few experimental tests of this hypothesis. Furthermore, the role of aggregation of conspecific animals within cohorts during vulnerable life stages is poorly understood.

Previous studies indicate that predation pressure may select for synchronous metamorphosis and the subsequent formation of metamorphic aggregations in North American toad species. In a series of laboratory experiments, I demonstrated that 1) Bufo americanus tadpoles in the presence of a predator exhibit higher levels of aggregation than tadpoles maintained in the absence of predator stimuli, and 2) B. americanus exposed to predator chemical cues metamorphose more synchronously than control tadpoles. I also found that toads at the climax of metamorphosis exhibit higher levels of aggregation than pre‐metamorphic individuals. These results support the hypothesis that predation pressure has played a role in selection for life stage synchrony, and that aggregation serves as an antipredator defense in animals with synchronous transitions.
Digging deep – structure–function relationships in the melatonin receptor family
Authors: Barrett Perry , Conway Shaun , Morgan Peter J.
Published: October 2003

Abstract: The melatonin receptor family is a small group of receptors within the G protein‐coupled receptor (GPCR) superfamily. The group comprises of three subtypes which bind melatonin and one member, the melatonin related receptor (MRR), that shares >40% sequence identity with the other melatonin receptors but does not bind melatonin. Identification of two subtypes expressed in the mouse suprachiasmatic nucleus, one of which (MT1) inhibits neuronal firing and the other (MT2) mediating the phase advancing properties of melatonin has given renewed interest to the development of subtype specific compounds for each of the mammalian melatonin receptors. Towards this goal site‐directed and chimaeric receptor mutagenesis studies have been performed which have provided some insight into the structure–function relationships of the melatonin receptors. Furthermore, these studies may lead to the identification of the ligand for the orphan MRR.
Genital Mycoplasmosis in Rats: A Model for Intrauterine Infection1
Authors: BROWN MARY B. , PELTIER MORGAN , HILLIER MARGARET , CRENSHAW BARBARA , REYES LETICIA
Published: October 2003

PROBLEM: Microbial infections of the chorioamnion and amniotic fluid have devastating effects on pregnancy outcome and neonatal morbidity and mortality. The mechanisms by which bacterial pathogens cause adverse effects are best addressed by an animal model of the disease with a naturally‐occurring pathogen.  METHOD OF STUDY: Intrauterine infection in humans as well as genital mycoplasmosis in humans and rodents is reviewed. We describe a genital infection in rats, which provides a model for the role of infection in pregnancy, pregnancy wastage, low birth weight, and fetal infection.  RESULTS: Infection of Sprague‐Dawley rats with Mycoplasma pulmonis either vaginally or intravenously resulted in decreased litter size, increased adverse pregnancy outcome, and in utero transmission of the microorganism to the fetus. CONCLUSION: Mycoplasma pulmonis is an ideal model to study maternal genital infection during pregnancy, the impact of infections on pregnancy outcome, fetal infection, and maternal‐fetal immune interactions.
Designer blood vessels and therapeutic revascularization
Authors: Berglund Joseph D , Galis Zorina S
Published: October 2003

Inadequate vascular perfusion leads to fatal heart attacks, chronic ulcers, and other serious clinical conditions. The body's capacity to restore vascular perfusion through angiogenesis and arteriogenesis is often impaired by pre‐existing disease, and availability of native replacements for nonfunctional arteries is limited in many patients. Thus, recreating blood vessels of various calibres through novel engineering technologies has emerged as a radical option among therapeutic strategies for revascularization. Ranging from artificial, recycled or reassembled natural conduits to sophisticated microdevices, we refer to these as ‘designer blood vessels’. Our common efforts to continuously improve vascular replacement design have provided many clues about our own blood vessels, but nature's ability to create nonthrombogenic, immunocompatible, strong, yet biologically responsive blood vessels remains unparalleled. Just as art reproductions never equal the original masterpiece, designer blood vessels may never attain nature's perfection. Nevertheless, they will provide a valuable option as long as they come close enough and are available to many.

British Journal of Pharmacology (2003) 140, 627–636. doi:10.1038/sj.bjp.0705457
Paracrine control of vascularization and neurogenesis by neurotrophins
Authors: Emanueli Costanza , Schratzberger Peter , Kirchmair Rudolf , Madeddu Paolo
Published: October 2003

The neuronal system plays a fundamental role in the maturation of primitive embryonic vascular network by providing a paracrine template for blood vessel branching and arterial differentiation. Furthermore, postnatal vascular and neural regeneration cooperate in the healing of damaged tissue.

Neurogenesis continues in adulthood although confined to specific brain regions. Following ischaemic insult, neural staminal cells contribute towards the healing process through the stimulation of neurogenesis and vasculogenesis.

Evidence indicates that nerves and blood vessels exert a reciprocal control of their own growth by paracrine mechanisms. For instance, guidance factors, including vascular endothelial growth factor A (VEGF‐A) and semaphorins, which share the ability of binding neuropilin receptors, play a pivotal role in the tridimensional growth pattern of arterial vessels and nerves.

Animal models and clinical studies have demonstrated a role of VEGF‐A in the pathogenesis of ischaemic and diabetic neuropathies. Further, supplementation with VEGF‐A ameliorates neuronal recovery by exerting protective effects on nerves and stimulating reparative neovascularization. Human tissue kallikrein, a recently discovered angiogenic and arteriogenic factor, accelerates neuronal recovery by stimulating the growth of vasa nervorum.

Conversely, the neurotrophin nerve growth factor, known to regulate neuronal survival and differentiation, is now regarded as a stimulator of angiogenesis and arteriogenesis.

These results indicate that angiogenesis and neurogenesis are paracrinally regulated by growth factors released by endothelial cells and neurons. Supplementation of these growth factors, alone or in combination, could benefit the treatment of ischaemic diseases and neuropathies.

British Journal of Pharmacology (2003) 140, 614–619. doi:10.1038/sj.bjp.0705458
Submucosal microinfusion of endothelin and adrenaline mobilizes ECL‐cell histamine in rat stomach, and causes mucosal damage: a microdialysis study
Authors: Bernsand M , Ericsson P , Björkqvist M , Zhao C ‐M , Håkanson R , Norlén P
Published: October 2003

Rat stomach ECL cells release histamine in response to gastrin. Submucosal microinfusion of endothelin or adrenaline, known to cause vasoconstriction and gastric lesions, mobilized striking amounts of histamine. While the histamine response to gastrin is sustainable for hours, that to endothelin and adrenaline was characteristically short‐lasting (1–2 h).

The aims of this study were to identify the cellular source of histamine mobilized by endothelin and adrenaline, and examine the differences between the histamine‐mobilizing effects of gastrin, and of endothelin and adrenaline.

Endothelin, adrenaline or gastrin were administered by submucosal microinfusion. Gastric histamine mobilization was monitored by microdialysis.

Local pretreatment with the H1‐receptor antagonist mepyramine and the H2‐receptor antagonist ranitidine did not prevent endothelin‐ or adrenaline‐induced mucosal damage. Submucosal microinfusion of histamine did not cause damage. Acid blockade by ranitidine or omeprazole prevented the damage, suggesting that acid back diffusion contributes.

Gastrin raised histidine decarboxylase (HDC) activity close to the probe, without affecting the histamine concentration. Endothelin and adrenaline lowered histamine by 50–70%, without activating HDC. Histamine mobilization declined upon repeated administration. Endothelin reduced the number of histamine‐immunoreactive ECL cells locally, and reduced the number of secretory vesicles. Thus, unlike gastrin, endothelin (and adrenaline) is capable of exhausting ECL‐cell histamine.

Microinfusion of α‐fluoromethylhistidine (known to deplete ECL cells but not mast cells of histamine) reduced the histamine‐mobilizing effect of endothelin by 80%, while 1‐week pretreatment with omeprazole enhanced it, supporting the involvement of ECL cells.

Somatostatin or the prostanoid misoprostol inhibited gastrin‐, but not endothelin‐stimulated histamine release, suggesting that endothelin and gastrin mobilize histamine via different mechanisms.

While gastrin effectively mobilized histamine from ECL cells in primary culture, endothelin had no effect, and adrenaline, a modest effect. Hence, the striking effects of endothelin and adrenaline on ECL cells in situ are probably indirect, possibly a consequence of ischemia.

British Journal of Pharmacology (2003) 140, 707–717. doi:10.1038/sj.bjp.0705473
Roles of KATP channels in delayed cardioprotection and intracellular Ca2+ in the rat heart as revealed by κ‐opioid receptor stimulation with U50,488H
Authors: Chen Mai , Zhou Jing‐Jun , Kam Kenneth Wan‐Lung , Qi Jian‐Song , Yan Wing‐Yi , Wu Song , Wong Tak‐Ming
Published: October 2003

The effect of preconditioning with U50,488 H (UP), a selective kappa‐opioid receptor (κ‐OR) agonist, on infarct size and intracellular Ca2+ ([Ca2+]i) in the heart subjected to ischaemic insults were studied and evaluated. U50,488 H administered intravenously reduced the infarct size 18–48 h after administration in isolated hearts subjected to regional ischaemia/reperfusion (I/R). The effect was dose dependent. A peak effect was reached at 10 mg kg−1 U50,488 H and at 24 h after administration. The effect of 10 mg kg−1 U50,488 H at 24 h after administration was abolished by nor‐binaltorphimine (nor‐BNI), a selective κ‐OR antagonist, indicating the effect was κ‐OR mediated.

The infarct reducing effect of U50,488 H was attenuated when a selective blocker of mitochondrial (5‐hydroxydecanoic acid, 5‐HD) or sarcolemmal (HRM‐1098) ATP‐sensitive potassium channel (KATP) was coadministered with U50,488 H 24 h before ischaemia or when 5‐HD was administered just before ischaemia.

U50,488 H also attenuated the elevation in [Ca2+]i and reduction in electrically induced [Ca2+]i transient in cardiomyocytes subjected to ischaemic insults. The effects were reversed by blockade of KATP channel, which abolished the protective effect of preconditioning with U50,488 H.

The results indicated that mitochondrial KATP channel serves as both a trigger and a mediator, while sarcolemmal KATP channel as a trigger only, of delayed cardioprotection of κ‐OR stimulation. The effects of these channels may result from prevention/attenuation of [Ca2+]i overload induced by ischaemic insults.

British Journal of Pharmacology (2003) 140, 750–758. doi:10.1038/sj.bjp.0705475