bluuebunny/crossref_metadata_2025 huggingface dataset:
The origin of osteoprogenitor cells responsible for heterotopic ossification following hip surgery: An animal model in the rabbit
Authors: Rumi Mustasim N. , Deol Gurvinder S. , Singapuri Kishor P. , Pellegrini Vincent D.
Published: August 2004

Purpose. To investigate the source of osteoprogenitor cells responsible for heterotopic ossification (HO) following total hip arthroplasty in an animal model.

Methods. New Zealand White (NZW) rabbits (n = 20) received a radiation treatment 24 h preoperatively to the hip joint of one hindquarter and to the femoral shaft of the contralateral side. Subjects underwent bilateral hip surgery 24 h after treatment. Subjects were euthanized and radiographed 4 months postoperatively. Heterotopic ossification was graded according to a modified Brooker scale. Mean grade, intra‐observer reliability, and statistical significance (p < 0.05) were evaluated to compare the severity of heterotopic ossification between hindquarters treated with hip irradiation versus those treated with femoral shaft irradiation.

Results. The Fleiss Weighted Kappa Statistic indicated “almost perfect” (0.872) intra‐rater reliability of radiographic heterotopic ossification grading. The average heterotopic ossification grade for the group receiving radiation to the hip was significantly greater than that for the group receiving radiation to the femoral shaft (2.575 versus 2.0, p < 0.02).

Conclusion. Although both have some beneficial effect, our results demonstrate that irradiation of the femoral canal is significantly more effective than irradiation of the hip joint and abductor musculature for heterotopic ossification prophylaxis. This suggests that osteoprogenitor cells responsible for heterotopic ossification originate from both the hip abductors and the femoral canal, but the data provide indirect evidence that the femoral canal may be a more dominant source of these cells in the rabbit model. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.
Wave slope and wave age effects in measurements of electromagnetic bias
Authors: Melville W. Kendall , Felizardo Francis C. , Matusov Peter
Published: July 2004

We present measurements of Ku band electromagnetic (EM) bias made for 2 months from a platform in Bass Strait off the southeast coast of Australia during the austral winter of 1992. EM bias, ε, the difference between the electromagnetic and true mean sea levels, was measured using Doppler scatterometers. Linear wave theory was used to relate the Doppler signal to the surface displacement, giving simultaneous coincident backscatter and wave measurements, including significant wave height, Hs. On the basis of dimensional reasoning, we suggest that the usual inhomogeneous correlations of the normalized bias β = ε/Hs with the 10 m wind speed, U10, and Hs may be improved by correlating the data with nondimensional variables, including a characteristic wave slope, s, and wave age, c/U10, where c is a characteristic phase speed of the surface waves. Using both polynomial correlations and optimal estimation techniques to fit the data, we find that the standard error of the fit is reduced by ∼50% when the dimensionless variables are used. We find that the dependence of the EM bias on the wave slope is consistent with earlier tower‐based measurements and the theory of short‐wave modulation by longer waves. We discuss the implications of these results for operational implementation of EM bias algorithms based on wave slope and wave age.
Modeling dimethylsulphide production in the upper ocean
Authors: Cropp Roger A. , Norbury John , Gabric Albert J. , Braddock Roger D.
Published: July 2004

Dimethylsulphide (DMS) is produced by upper ocean ecosystems and emitted to the atmosphere, where it may have an important role in climate regulation. Several attempts to quantify the role of DMS in climate change have been undertaken in modeling studies. We examine a model of biogenic DMS production and describe its endogenous dynamics and sensitivities. We extend the model to develop a one‐dimensional version that more accurately resolves the important processes of the mixed layer in determining the ecosystem dynamics. Comparisons of the results of the one‐dimensional model with an empirical relationship that describes the global distribution of DMS, and also with vertical profiles of DMS in the upper ocean measured at the Bermuda Atlantic Time Series, suggest that the model represents the interaction between the biological and physical processes well on local and global scales. Our analysis of the model confirms its veracity and provides insights into the important processes determining DMS concentration in the oceans.
Paleomagnetic results from the Snake River Plain: Contribution to the time‐averaged field global database
Authors: Tauxe Lisa , Luskin Casey , Selkin Peter , Gans Phillip , Calvert Andy
Published: August 2004

This study presents paleomagnetic results from the Snake River Plain (SRP) in southern Idaho as a contribution to the time‐averaged field global database. Paleomagnetic samples were measured from 26 sites, 23 of which (13 normal, 10 reverse) yielded site mean directions meeting our criteria for acceptable paleomagnetic data. Flow ages (on 21 sites) range from 5 ka to 5.6 Ma on the basis of 40Ar/39Ar dating methods. The age and polarity for the 21 dated sites are consistent with the Geomagnetic Reversal Time Scale except for a single reversely magnetized site dated at 0.39 Ma. This is apparently the first documented excursion associated with a period of low paleointensity detected in both sedimentary and igneous records. Combining the new data from the SRP with data published from the northwest United States between the latitudes of 40° and 50°N, there are 183 sites in all that meet minimum acceptability criteria for legacy and new data. The overall mean direction of 173 normally magnetized sites has a declination of 2.3°, inclination of 61.4°, a Fisher concentration parameter (κ) of 58, and a radius of 95% confidence (α95) of 1.4°. Reverse sites have a mean direction of 182.4° declination, −58.6° inclination, κ of 50, and α95 of 6.9°. Normal and reversed mean directions are antipodal and indistinguishable from a geocentric axial dipole field at the 95% confidence level. Virtual geomagnetic pole dispersion was found to be circularly symmetric, while the directional data were elongate north‐south. An updated and corrected database for the northwestern U.S. region has been contributed to the Magnetics Information Consortium (MagIC) database at http://earthref.org.
Observations of cosmic ray electrons and positrons during the early stages of the A‐ magnetic polarity epoch
Authors: Clem John , Evenson Paul
Published: July 2004

As part of our ongoing investigation of the charge sign dependence in solar modulation, we measured the cosmic ray positron abundance (0.8 GeV to 4.5 GeV) and electron flux (20 MeV to 4.5 GeV) on balloon flights from Lynn Lake, Manitoba during August 2002. We find that the decrease in the positron abundance observed in 2000 persists in 2002. The low‐energy electron flux observed on a very high altitude flight (48.8 km) reconfirms the negative slope in the spectrum. We compared our data with published data from the Ulysses spacecraft. Although other explanations are possible, we propose that finite heliospheric latitude gradients in electron fluxes have appeared in the A‐ polarity epoch, whereas no latitude gradients in electrons were observed in the A+ epoch.
Ocean wave spectrum and dissipation rate derived from CMOD4 model function
Authors: Lyzenga David R.
Published: July 2004

A simplified version of the energy balance equation is solved to obtain an expression for the ocean wave equilibrium spectrum, which is then used with a two‐scale electromagnetic scattering model to calculate the radar cross section of the ocean surface. Two parameters in the energy balance equation are adjusted to minimize the difference between the calculated radar cross‐section values and those given by the CMOD4 model function over a range of incidence angles and look directions, and for a series of wind speeds. The RMS difference between the CMOD4 and two‐scale radar cross‐section values using this model is 0.16 dB for incidence angles from 25° to 45° and wind speeds from 5 to 15 m/s. The slope variances computed from this model also agree fairly well with those measured by Cox and Munk. However, since the largest wave number influencing the C‐band backscatter is approximately 200 rad/m, the spectrum is probably not valid beyond this wave number. Finally, since the spectrum is determined by the relative magnitudes of the wave growth and dissipation rates, some inferences about these parameters can be drawn. Assuming the exponential growth rate parameter to be equal to previous measurements, the dissipation rate implied by this model is more than an order of magnitude larger than that due to molecular viscosity for wind speeds greater than 7 m/s. This conclusion is consistent with observations by Jähne and Riemer, which also indicated a dissipation rate much larger than the viscous dissipation rate at high wind speeds.
Transpacific and regional atmospheric transport of anthropogenic semivolatile organic compounds to Cheeka Peak Observatory during the spring of 2002
Authors: Killin Robert K. , Simonich Staci L. , Jaffe Daniel A. , DeForest Cindy L. , Wilson Glenn R.
Published: July 2004

Ambient high‐volume (hi‐vol) air samples were collected between 15 March and 30 May 2002, at Cheeka Peak Observatory (CPO), located on the tip of the Olympic Peninsula, Washington State. This sampling campaign was in conjunction with the Intercontinental Transport and Chemical Transformation 2002 (ITCT 2K2) campaign and the Photochemical Ozone Budget of the Eastern North Pacific Atmosphere 2 (PHOEBA2) experiment. The anthropogenic semivolatile organic compounds (SOCs) measured during this time period included polycyclic aromatic hydrocarbons (PAHs) and various U.S. current‐use and historical‐use pesticides. The total PAH concentration ranged from 0.480 to 4.49 ng/m3, which is comparable to other remote sites throughout the globe. Ten pesticides (hexachlorobenzene, dacthal, chlorothalonil, heptachlor, trans‐nonachlor, cis‐nonachlor, endosulfan I, triallate, trifluralin, and mirex) were also measured, and their concentrations (0.104–57.0 pg/m3) were comparable to other remote sites and less than agricultural areas. Gas‐phase/particle‐phase partitioning was explored, with significant correlation to temperature found with endosulfan I and retene and the possible relationship at CPO of low TSP concentration and the concentration of nonexchangeable compounds in the particle phase. Principal component analysis, as well as a t‐test, showed that there were elevated concentrations of anthropogenic SOCs measured during possible transpacific events on 15–16 March, 27–28 March, and 22–23 April 2002 that were identified using the GEOS‐CHEM model. The potential sources of these compounds at CPO were determined using diagnostic ratios of their concentrations, back trajectories calculated using Hybrid Single‐Particle Lagrangian Integrated Trajectory (HYSPLIT4), local meteorological conditions, and U.S. pesticide use data. Additional data are needed to confirm the sources of anthropogenic SOCs at CPO during regional and transpacific atmospheric transport events.
Present‐day sea level change: Observations and causes
Authors: Cazenave A. , Nerem R. S.
Published: July 2004

The determination of the present‐day rate of sea level change is important for a variety of scientific and socioeconomic reasons. With over a decade of precision sea level measurements from satellite altimetry in hand and with the recent launch of new satellite missions addressing different aspects of sea level change, observationally, we have more information on sea level change than ever before. In fact, the geocentric rate of global mean sea level rise over the last decade (1993–2003) is now known to be very accurate, +2.8 ± 0.4 mm/yr, as determined from TOPEX/Poseidon and Jason altimeter measurements, 3.1 mm/yr if the effects of postglacial rebound are removed. This rate is significantly larger than the historical rate of sea level change measured by tide gauges during the past decades (in the range of 1–2 mm/yr). However, the altimetric rate could still be influenced by decadal variations of sea level unrelated to long‐term climate change, such as the Pacific Decadal Oscillation, and thus a longer time series is needed to rule this out. There is evidence that the sea level rise observed over the last decade is largely due to thermal expansion, as opposed to the influx of freshwater mass from the continents. However, estimates of thermal expansion are still sufficiently uncertain to exclude some contribution of other sources, such as the melting of mountain glaciers and polar ice. Moreover, independent measurements of total ice melting during the 1990s suggest up to 0.8 mm/yr sea level rise, an amount that could eventually be canceled by change in land water storage caused by anthropogenic activities. Another important result of satellite altimetry concerns the nonuniform geographical distribution of sea level change, with some regions exhibiting trends about 10 times the global mean. Thermal expansion appears responsible for the observed regional variability. For the past 50 years, sea level trends caused by change in ocean heat storage also show high regional variability. The latter observation has led to questions about whether the rate of 20th century sea level rise, based on poorly distributed historical tide gauges, is really representative of the true global mean. Such a possibility has been the object of an active debate, and the discussion is far from being closed.
Spatial and temporal variability of water productivity in the Syr Darya Basin, central Asia
Authors: Abdullaev Iskandar , Molden David
Published: July 2004

Application of water productivity analysis can provide clues in the search for solutions to solve water management problems of central Asia. It is in this context that this paper provides an analysis of water productivity both spatially and temporally in the cotton and rice production areas of Syr Darya Basin of central Asia. The spatial analysis includes different farm types and basin segments, and the temporal analysis includes 3 hydrological years during 1999–2001. The analysis of temporal data showed that in water‐deficient years, water productivity, both in terms of supply and evapotranspiration, is higher than the same in water‐abundant years. The data also show that type and size of farms have an impact on water productivity in the case of both cotton and rice. This study concludes by suggesting strategies and options for enhancing the average water productivity both in the cotton‐ and rice‐growing areas of the Syr Darya Basin.
Radiocarbon as a thermocline proxy for the eastern equatorial Pacific
Authors: Rodgers Keith B. , Aumont Olivier , Madec Gurvan , Menkes Christophe , Blanke Bruno , Monfray Patrick , Orr James C. , Schrag Daniel P.
Published: July 2004

An ocean model is used to test the idea that sea surface Δ14C behaves as a thermocline proxy in the eastern equatorial Pacific. The ORCA2 model, which includes Δ14C as a passive tracer, has been forced with reanalysis fluxes over 1948–1999, and the output is compared with a previously reported Galapagos Δ14C record. The model reproduces the abrupt increase in the seasonally minimum Δ14C in 1976/77 found in the data. This increase is associated with neither a shift of thermocline depth over the NINO3 region, nor a change in the relative proportion of Northern/Southern source waters. Rather, it is due to a decrease in the Sub‐Antarctic Mode Water (SAMW) component of the upwelling water, thereby representing a decrease in entrainment of water from below the base of the directly ventilated thermocline.
Combining a receptor‐oriented framework for tracer distributions with a cloud‐resolving model to study transport in deep convective clouds: Application to the NASA CRYSTAL‐FACE campaign
Authors: Xueref I. , Gerbig C. , Fridlind A. , Lin J. C. , Wofsy S. C. , Daube B. C. , Ackerman A. S. , Smith J. E. , Sayres D. , Vellovic J. , Baumgardner D. G. , Wang D. , Weinstock E. , Andrews A. E. , Gottlieb E. W. , Anderson J. G.
Published: July 2004

Quantitative models of deep convection play a central role to improve understanding of weather, trace gas distributions, and radiative regime of the upper troposphere. Cloud‐resolving models of deep convection are useful tools to simulate relevant processes. Observations of tracers such as CO2 can provide critical constraints on mass transport within these models. However, such measurements do not span the entire four‐dimensional domain in space and time. We introduce a new method to improve tracer constraints on such models, combining a Receptor‐Oriented Atmospheric Modeling (ROAM) framework with airborne and ground‐based CO2 data. We illustrate the application of ROAM in generating initial and boundary conditions of CO2 for cloud‐resolving model simulations, for a case study in the CRYSTAL‐FACE campaign. Observations and model results were compared for CO2 profiles from the surface up to 16 km, inside and outside of a deep convective cloud. ROAM generated concentration fields that agreed within 0.5 ppm (1σ) of observations outside the cloud. When ROAM‐derived initial and boundary CO2 concentrations were fed to a state‐of‐the‐art cloud‐resolving model (DHARMA), the combined modeling system successfully reproduced observed concentration differences, 0.2–0.8 ppm, between in‐cloud and out‐of‐cloud air at 9 ∼ 14 km. Results suggest that ∼25% of air at 14 km was lifted through the convective system from the PBL. This study demonstrates the potential of the receptor‐oriented framework to constrain redistribution of air within convective systems using CO2, and it points to the need for better coordinated tracer measurements in future field missions.
Causes of exceptional atmospheric circulation changes in the Southern Hemisphere
Authors: Marshall Gareth J. , Stott Peter A. , Turner John , Connolley William M. , King John C. , Lachlan‐Cope Thomas A.
Published: July 2004

We demonstrate that recent observed trends in the annual and austral summer Southern Hemisphere Annular Mode (SAM) are unlikely to be due to internal climate variability, since they exceed any equivalent‐length trends in a millennial General Circulation Model (GCM) control run with constant forcings. In contrast we show that observed trends in the SAM are consistent with the combined effects of anthropogenic and natural forcings in GCM simulations. As these trends begin prior to stratospheric ozone depletion we challenge the assertion that this process is primarily responsible for changes in the SAM. Moreover, anthropogenic forcings have a larger effect on the austral summer SAM in combination with natural forcings than when acting in isolation.
Influence of a simple fracture intersection on density‐driven immiscible flow: Wetting vs. nonwetting flows
Authors: Ji Sung‐Hoon , Nicholl Michael J. , Glass Robert J. , Lee Kang‐Kun
Published: July 2004

The influence of a single fracture intersection on density‐driven immiscible flow is compared between wetting (water into air) and nonwetting (Trichloroethylene into water) flows. At low supply rates, the intersection acted as a hysteretic gate to pulsed flow of the wetting phase, but had minimal influence on nonwetting phase flow. For both cases, increasing the supply rate led to the formation of continuous fluid tendrils that crossed the intersection without interruption. The wetting experiment returned to pulsed flow as the supply rate was decreased, while the nonwetting experiment maintained a continuous flow structure. Results suggest a fundamental difference between wetting and nonwetting phase flows in fracture networks.
Heat flow in the Nipigon arm of the Keweenawan rift, northwestern Ontario, Canada
Authors: Perry H. K. C. , Jaupart C. , Mareschal J.‐C. , Rolandone F. , Bienfait G.
Published: August 2004

In the Archean Superior Province, the Nipigon Embayment, in the area of Lake Nipigon north of Lake Superior, is covered by MidProterozoic sediments intruded by Keweenawan diabase sills. It has been interpreted as a failed arm of the ca. 1100 Ma Keweenawan rift. Six new heat flow values in this area show that the region of low heat flow associated with the Keweenawan rift in Lake Superior extends northwards along the western margin of the Nipigon Embayment. The average heat flow in the Nipigon area (39 ± 5 mWm−2) is only slightly lower than that of the adjacent western Superior Province (42 ± 8 mWm−2), indicating that the volume of Keweenawan mafic intrusives in the Nipigon crust is small.
Effect of aluminium on the compressibility of silicate perovskite
Authors: Daniel Isabelle , Bass Jay D. , Fiquet Guillaume , Cardon Hervé , Zhang Jianzhong , Hanfland Michael
Published: August 2004

Volume measurements for aluminous MgSiO3 perovskite containing 5 mol% Al2O3 were carried out up to pressures of 40 GPa at ambient temperature, using monochromatic synchrotron X‐ray diffraction. A least‐squares refinement of the data to the Birch‐Murnaghan equation of state yields the following parameters V0 = 163.234(8) Å3, KT0 = 251.5(13) GPa, K′0 = 4. Within uncertainties, the presence of 5 mol% Al2O3 in MgSiO3 perovskite induces a decrease of the bulk modulus in the range of 0% to 1.8%. Thus, KT of perovskite is affected little if at all by the presence of Al3+. This result is in excellent agreement with the values deduced from sound velocity measurements on the same sample [Jackson et al., 2004]. We discuss the possible origin of discrepancies among the different bulk moduli reported to date for aluminous perovskite. In light of recent calculations, our results are consistent with aluminium being dissolved in MgSiO3 perovskite through a coupled substitution mechanism involving the replacement of both Mg2+ and Si4+ in the dodecahedral and octahedral sites by 2 Al3+. Moreover, any slight reduction in the bulk modulus of MgSiO3 perovskite induced by the dissolution of 5 mol% Al2O3, indicates that the relative proportions of the minerals characteristic of the lower mantle, as inferred from seismological models, should not be significantly altered by the introduction of Al in the system.
Broadband calibration of R/V Ewing seismic sources
Authors: Tolstoy M. , Diebold J. B. , Webb S. C. , Bohnenstiehl D. R. , Chapp E. , Holmes R. C. , Rawson M.
Published: July 2004

The effects of anthropogenic sound sources on marine mammals are of increasing interest and controversy [e.g., Malakoff, 2001]. To understand and mitigate better the possible impacts of specific sound sources, well‐calibrated broadband measurements of acoustic received levels must be made in a variety of environments. In late spring 2003 an acoustic calibration study was conducted in the northern Gulf of Mexico to obtain broad frequency band measurements of seismic sources used by the R/V MauriceEwing. Received levels in deep water were lower than anticipated based on modeling, and in shallow water they were higher. For the marine mammals of greatest concern (beaked whales) the 1–20 kHz frequency range is considered particularly significant [National Oceanic Atmospheric Administration and U. S. Navy, 2001; Frantzis et al., 2002]. 1/3‐octave measurements show received levels at 1 kHz are ∼20–33 dB (re: 1 μPa) lower than peak levels at 5–100 Hz, and decrease an additional ∼20–33 dB in the 10–20 kHz range.
The effect of hydrate content on seismic attenuation: A case study for Mallik 2L‐38 well data, Mackenzie delta, Canada
Authors: Chand Shyam , Minshull Tim A.
Published: July 2004

Observations of velocities in sediments containing gas hydrates show that the strength of sediments increases with hydrate saturation. Hence it is expected that the attenuation of these sediments will decrease with increasing hydrate saturation. However, sonic log measurements in the Mallik 2L‐38 well and cross hole tomography measurements in the Mallik field have shown that attenuation increases with hydrate saturation. We studied a range of mechanisms by which increasing hydrate saturation could cause increased attenuation. We found that a difference in permeability between the host sediment and the newly formed hydrate can produce the observed effect. We modelled attenuation in terms of Biot and squirt flow mechanisms in composite media. We have used our model to predict observed attenuations in the Mallik 2L‐38 well, Mackenzie Delta, Canada.
Timely detection of anthropogenic change in the Atlantic meridional overturning circulation
Authors: Vellinga M. , Wood R. A.
Published: July 2004

Detection of anthropogenic weakening of the Atlantic meridional overturning circulation (‘MOC’) may be improved by monitoring a limited number of key oceanic variables. We have identified a set of potentially useful ocean hydrographic observations in the climate general circulation model HadCM3. When the model is forced by an anthropogenic climate forcing scenario for the 21st century, a pattern is found that captures co‐variability of these variables and strength of the MOC. Fingerprints of this pattern emerge clearly on time scales of 10 years from background noise caused by internal variability. If similar results are found in other climate models this will provide useful information for the design of an MOC observing system.
Atmospheric response to observed intraseasonal tropical sea surface temperature anomalies
Authors: Matthews Adrian J.
Published: July 2004

The major tropical convective and circulation features of the intraseasonal or Madden–Julian oscillation (MJO) are simulated as a passive response to observed MJO sea surface temperature (SST) anomalies in an atmospheric general circulation model (AGCM), strengthening the case for ocean–atmosphere interactions being central to MJO dynamics. However, the magnitude of the surface fluxes diagnosed from the MJO cycle in the AGCM, that would feed back onto the ocean in a coupled system, are much weaker than in observations. The phasing of the convective–dynamical model response to the MJO SST anomalies and the associated surface flux anomalies is too fast compared to observations of the (potentially) coupled system, and would act to damp the SST anomalies.
A statistical study of subauroral E‐region coherent backscatter observed near 100 MHz with passive radar
Authors: Meyer Melissa G. , Sahr John D. , Morabito Andrew
Published: July 2004

We provide a statistical summary of the Doppler features extracted from 21,000 independent E‐region irregularity observations made during 2002 and 2003. These data were acquired using the Manastash Ridge Radar, which detects the scatter of commercial FM broadcasts near 100 MHz and observes at subauroral latitude. In particular, we present histograms of Doppler velocity and spectral width of the observations and discuss trends in these data with respect to local time and the geomagnetic Kp index. We find an asymmetric velocity distribution composed entirely of type 1 Doppler spectra; these waves are associated with the modified two‐stream instability. Type 2 echoes are completely absent, suggesting a strong latitude and/or wave number dependence in the conditions for secondary wave instability. We compare our observations with HF and VHF coherent scatter results reported by others. Because the radar is completely passive, it is well suited for extended, unattended observations; in this 2‐year period of nearly continuous operation, we find pronounced seasonal variation in our observations. The method of radar operation provides excellent data for statistical summary, as it is completely free of range and Doppler aliasing, while also providing fine time and frequency resolution.
Wave‐formed sediment ripples: Transient analysis of ripple spectral development
Authors: Davis Joseph P. , Walker David J. , Townsend Murray , Young Ian R.
Published: July 2004

A new method has been developed that models the changes a wave‐formed rippled sediment bed undergoes as it is actively evolving between two given equilibrium states due to a change in surface wave conditions. The transient analysis of rippled beds has received very little attention within the literature. Dynamic changes within ripple parameters have implications for the estimation of flow dissipation and sediment transport by changing the bottom roughness height. The method uses the spectral density function of the rippled bed and is based on a series of ripple growth and ripple transition experimental tests. The ripple evolution model was developed from the well‐known Logistic Growth Law. Fitting the general solution of the logistic nonlinear differential equation to the experimental data enabled the evolution rate of the bed to be determined for each experimental test. It was concluded that there was no difference between the evolution rate determined from the ripple growth tests and the ripple transition tests. This indicated that the two types of growth are special cases of the same evolution processes, which is adequately modeled by the logistic growth equation. A functional dependence was established between the ripple evolution rate and the Shields parameter. This allows the evolution rate to be estimated from flow and sediment properties. The estimation of the rate at which rippled sediment beds evolve under a variable sea state has the potential to lead to significant improvements to the way ripple transition and hence bottom roughness is approximated in coastal wave models.
A multivariate empirical‐orthogonal‐function‐based measure of climate model performance
Authors: Mu Qiaozhen , Jackson Charles S. , Stoffa Paul L.
Published: August 2004

A measure of the average distance between climate model predictions of multiple fields and observations has been developed that is based on the use of empirical orthogonal functions (EOFs). The application of EOFs provides a means to use information about spatial correlations in natural variability to provide a more balanced view of the significance of changes in model predictions across multiple fields, seasons, and regions. A comparison is made between the EOF‐based measure and measures that are normalized by grid point variance and spatial variance for changes in the National Center for Atmospheric Research Community Climate Model, Version 3.10 (CCM3.10), parameter controlling initial cloud downdraft mass flux (ALFA), an important parameter within the Zhang and McFarlane [1995] convection scheme. All measures present consistent views that increasing ALFA from its default value creates significant improvements in precipitation, shortwave radiation reaching the surface, and surface latent heat fluxes at the expense of degrading predictions of total cloud cover, near‐surface air temperature, net shortwave radiation at the top of the atmosphere, and relative humidity. However, the relative importance of each of these changes, and therefore the average view of the change in model performance, is significantly impacted by the details of how each measure of model performance handles regions with little or no internal variability. In general, the EOF‐based measure emphasizes regions where modeled‐observational differences are large, excluding those regions where internal variability is small.
Measuring fluxes of trace gases at regional scales by Lagrangian observations: Application to the CO2 Budget and Rectification Airborne (COBRA) study
Authors: Lin J. C. , Gerbig C. , Wofsy S. C. , Andrews A. E. , Daube B. C. , Grainger C. A. , Stephens B. B. , Bakwin P. S. , Hollinger D. Y.
Published: August 2004

We present a general framework for designing and analyzing Lagrangian‐type aircraft observations in order to measure surface fluxes of trace gases on regional scales. Lagrangian experiments minimize uncertainties due to advection by measuring tracer concentrations upstream and downstream of the study region, assuring that observed concentration changes represent fluxes within the region. The framework includes (1) a receptor‐oriented model of atmospheric transport, including turbulent dispersion, (2) an upstream tracer boundary condition, (3) a surface flux model that predicts the distribution of tracer fluxes in time and space, and (4) a Bayesian inverse analysis that combines a priori information with observations to yield optimal estimates of tracer fluxes by the flux model. We use a receptor‐oriented transport model, the Stochastic Time‐Inverted Lagrangian Transport (STILT) model, to simulate ensembles of particles representing air parcels transported backward in time from an observation point (receptor), linking receptor concentrations with upstream locations and surface inputs. STILT provides the capability to forecast flight tracks for Lagrangian experiments in the presence of atmospheric shear and dispersion. STILT may be used to forecast flight tracks that sample the upstream tracer boundary condition, or to analyze the data and provide optimized parameters in the surface flux model. We present a case study of regional scale surface CO2 fluxes using data over the United States obtained in August 2000 in the CO2 Budget and Rectification Airborne (COBRA‐2000) study. STILT forecasts were obtained using the National Centers for Environmental Prediction Eta model to plan the flight tracks. Results from the Bayesian inversion showed large reductions in a priori errors for estimates of daytime ecosystem uptake of CO2, but constraints on nighttime respiration fluxes were weaker, due to few observations of CO2 in the nocturnal boundary layer. Derived CO2 fluxes from the influence‐following analysis differed notably from estimates using a conventional one‐dimensional budget (“Boundary Layer Budget”) on a typical day, due to time‐variable contributions from forests and croplands. A critical examination of uncertainties in the Lagrangian analyses revealed that the largest uncertainties were associated with errors in forecasting the upstream sampling locations and with aggregation of heterogeneous fluxes at the surface. Suggestions for improvements in future experiments are presented.
Clustering within rootless cone groups on Iceland and Mars: Effect of nonrandom processes
Authors: Bruno B. C. , Fagents S. A. , Thordarson T. , Baloga S. M. , Pilger E.
Published: July 2004

This study aims at quantifying the spatial distribution of cones within rootless cone groups (RCGs). Our data set consists of (1) seven Icelandic RCGs (identified through field investigations), (2) seven candidate RCGs on Mars (identified through Mars Orbiter Camera (MOC) and Thermal Emission Imaging System (THEMIS) images), and (3) four groups of impact craters on Mars (also identified through MOC and THEMIS images) to determine if they can be remotely distinguished from the RCGs purely on the basis of their spatial distribution. Several independent statistical techniques are used, including nearest neighbor analysis, analysis of variance (ANOVA), and linear alignment detection analysis. Our results indicate that the spatial distribution of each RCG is not random: Within a cone group, cones preferentially form near existing cones. The presence of at least one significant linear cone alignment in each RCG (and strong linear alignments in some groups) suggests that rootless cones form as the surface signature of preferred lava pathways. An ANOVA on mean nearest neighbor distances reveals the Martian cone groups to be statistically indistinguishable from the Icelandic RCGs, supporting existing interpretations that they represent rootless cone groups. A similar ANOVA showed that the Martian cone groups do not resemble the Martian impact crater clusters studied: The impact craters have significantly greater nearest neighbor distances and show no evidence of aggregation within a crater group.
Neonatal Hepatic Drug Elimination
Authors: Gow Paul J. , Ghabrial Hany , Smallwood Richard A. , Morgan Denis J. , Ching Michael S.
Published: July 2004

After the transition from in utero to newborn life, the neonate becomes solely reliant upon its own drug clearance processes to metabolise xenobiotics. Whilst most studies of neonatal hepatic drug elimination have focussed upon in vitro expression and activities of drug‐metabolising enzymes, the rapid physiological changes in the early neonatal period of life also need to be considered. There are dramatic changes in neonatal liver blood flow and hepatic oxygenation due to the loss of the umbilical blood supply, the increasing portal vein blood flow, and the gradual closure of the ductus venosus shunt during the first week of life. These changes which may well affect the capacity of neonatal hepatic drug metabolism. The hepatic expression of cytochromes P450 1A2, 2C, 2D6, 2E1 and 3A4 develop at different rates in the postnatal period, whilst 3A7 expression diminishes. Hepatic glucuronidation in the human neonate is relatively immature at birth, which contrasts with the considerably more mature neonatal hepatic sulfation activity. Limited in vivo studies show that the human neonate can significantly metabolise xenobiotics but clearance is considerably less compared with the older infant and adult. The neonatal population included in pharmacological studies is highly heterogeneous with respect to age, body weight, ductus venosus closure and disease processes, making it difficult to interpret data arising from human neonatal studies. Studies in the perfused foetal and neonatal sheep liver have demonstrated how the oxidative and conjugative hepatic elimination of drugs by the intact organ is significantly increased during the first week of life, highlighting that future studies will need to consider the profound physiological changes that may influence neonatal hepatic drug elimination shortly after birth.
Role of Soy Diet and L‐Arginine in Cyclosporin‐A‐Induced Osteopenia in Rats
Authors: Clementi Giuseppe , Fiore Carmelo Erio , Mangano Nunzio Guido , Cutuli Vincenza Maria Catena , Pennisi Piera , Caruso Antonina , Prato Agatina , Matera Mario , Amico‐Roxas Matilde
Published: July 2004

Our previous studies show that chronic administration of L‐arginine decreases cyclosporin‐A‐induced bone loss. The present study was designed to investigate whether a soy diet could prevent cyclosporin A‐induced osteopenia and eventually improve the protective effect of L‐arginine. Rats on soy diet were treated with cyclosporin‐A, L‐arginine, cyclosporin‐A+L‐arginine or saline. Control groups received a normal diet and the same pharmacological treatment. Our results show that a soy diet prevents osteopenia only in the spinal cord (+30%) and confirm the protective effect of L‐arginine in cyclosporin‐A‐induced osteopenia in whole body, pelvis and spine of rats on a normal diet (+31%, +55%, +55%, respectively). Moreover these data show that the osteoprotective effect of L‐arginine in the whole body, pelvis and spine improves in the case of soy diet (+60%, +72%, +89%, respectively). The results suggest that a soy diet exerts a positive effect in cyclosporin‐A‐induced osteopenia only in sites with high turn‐over and improves the osteoprotective effect of L‐arginine.
Novel Effects of 5,8,11‐Eicosatriynoic Acid, a Lipoxygenase Inhibitor, on Ca2+ Mobilization in Madin Darby Canine Kidney Cells
Authors: Lee Kam‐Chung , Chou Kang‐Ju , Cheng Jin‐Shiung , Wang Jue‐Long , Tang Kwong‐Yui , Tseng Li‐Ling , Jan Chung‐Ren
Published: July 2004

The effect of 5,8,11‐eicosatriynoic acid, a widely used lipoxygenase inhibitor, on Ca2+ fate in Madin Darby canine kidney cells was examined by using fura‐2 as a Ca2+ probe. At concentrations between 2–100 μM 5,8,11‐eicosatriynoic acid increased [Ca2+]i concentration‐dependently with an EC50 of 20 μM . Extracellular Ca2+ removal decreased the Ca2+ signals, indicating that 5,8,11‐eicosatriynoic acid triggered Ca2+ release and Ca2+ influx. 5,8,11‐Eicosatriynoic acid (30 μM) induced a [Ca2+]i increase in Ca2+‐free medium after pretreatment with carbonylcyanide m‐chlorophenylhydrazone (2 μM), a mitochondrial uncoupler, and thapsigargin (1 μM), an endoplasmic reticulum Ca2+ pump inhibitor for 20 min. Conversely, 5,8,11‐eicosatriynoic acid pretreatment almost abolished the Ca2+ release induced by carbonylcyanide m‐chlorophenylhydrazone and thapsigargin. These results suggest that 30 μM 5,8,11‐eicosatriynoic acid released Ca2+ from the endoplasmic reticulum, mitochondria and other stores. Addition of 3 mM Ca2+ increased [Ca2+]i after preincubation with 2–50 μM 5,8,11‐eicosatriynoic acid for 10 min. in Ca2+‐free medium concentration‐dependently. Pretreatment with 10 μM La3+ abolished 30 μM 5,8,11‐eicosatriynoic acid ‐induced [Ca2+]i increases, but adding La3+ during the decay phase had no effect. 5,8,11‐Eicosatriynoic acid‐induced Ca2+ release was not altered by inhibiting phospholipase C with 2 μM 1‐(6‐((17β‐3‐methoxyestra‐1,3,5(10)‐trien‐17‐yl)amino)hexyl)‐1H‐pyrrole‐2,5‐dione (U73122), but was decreased by 60% by 40 μM aristolochic acid. Several other lipoxygenase inhibitors such as baicalein (50 μM), 5.8.11.14‐eicosatetraynoic acid (ETYA; 0.1–0.2 mM), caffeic acid (5–50 μM), esculetin (5–50 μM), α‐pentyl‐3‐(2‐quinolinylmethoxy)‐benzenemethanol (REV‐5901; 0.1–0.2 mM) and α‐pentyl‐4‐(2‐quinolinylmethoxy)‐benzenemethanol (L‐655238; 80–100 μM) had no effect on [Ca2+]i. Collectively, the data suggest that the lipoxygenase inhibitor 5,8,11‐eicosatriynoic acid induced a [Ca2+]i increase in renal tubular cells concentration‐dependently, by releasing intracellular Ca2+ from multiple stores in an inositol 1,4,5‐trisphosphate‐independent manner, and by inducing extracellular Ca2+ influx in a La3+‐sensitive manner.
The Phagocytosis of Rod Outer Segments is Inhibited by Selected Drugs in Retinal Pigment Epithelial Cell Cultures
Authors: Mannerström Marika , Mäenpää Hanna , Toimela Tarja , Salminen Lotta , Tähti Hanna
Published: July 2004

The effects of tamoxifen, toremifene and chloroquine on the phagocytosis of rod outer segments by retinal pigment epithelium were evaluated in human retinal pigment epithelial cell line D407 and pig retinal pigment epithelial cell culture. Retinal pigment epithelial cells were exposed to different concentrations of tamoxifen (1–20 μM), toremifene (1–20 μM) and chloroquine (1–1000 μM), and challenged with FITC‐labeled rod outer segments for 24 hr. The phagocytized (bound and ingested) rod outer segments were measured fluorometrically, and the effect of the drugs on the phagocytosis was determined. The cytotoxicity of the drugs was evaluated by measuring their effects on mitochondrial enzyme activities (WST‐1‐test). The results showed that the test compounds inhibited the phagocytosis of rod outer segments in both D407 and pig retinal pigment epithelial cells. The phagocytic activity was more sensitive to tamoxifen (EC50 7.2 μM for D407 cells and 3.6 μM for pig retinal pigment epithelial cells) and toremifene (EC50 6.2 μM and 3.1 μM respectively) than to chloroquine (EC50 77.2 μM for D407 cells). The inhibition of rod outer segment phagocytosis in both cell cultures started at lower dose levels of test compounds than the cytotoxicity indicated by the WST‐1‐test. The experiments were carried out both in serum‐free medium and serum‐containing medium. Serum seemed to be a critical factor in the medium and caused difficulties in the interpretation of the results.
Developmental Toxicity in the Pregnant Rabbit by theClass III Antiarrhythmic Drug Sotalol
Authors: Sköld Anna‐Carin , Danielsson Bengt R.
Published: July 2004

The purpose of this study was to investigate the potential of sotalol to cause developmental toxicity in the pregnant rabbit. Sotalol is a β‐adrenoceptor blocking drug which also has class III antiarrhythmic properties via Ikr channel blockade. Experiment 1: Nine pregnant New Zealand White rabbits were given doses of either 300, 225, or 150 mg/kg of sotalol during gestational days, called Days, 13–16 which resulted in total litter loss. Experiment 2: A single dose of sotalol, 100 or 150 mg/kg was administered during Days 8–17 to 15 rabbits. Dosing on Day 8, 9, or 10 resulted in a slightly higher incidence of embryonic death compared to historical controls. There was marked increased embryonic death of 55–90% (four does with total litter loss), decreased number of live foetuses per litter, and elevated mean foetal weight after dosing during Days 12–16. Experiment 3: 16 pregnant rabbits were administered single doses of sotalol of either 100, 85, 75, 60 or 50 mg/kg on Day 14. The main finding was increased embryonic death, which ranged from total litter loss to ∼30% at 50 mg/kg. At 50 mg/kg, the maternal Cmax, AUC1–24 hr, and t1/2 were approximately 45 μM, 340 μmol×hr/l, and 6 hr, respectively. In conclusion, sotalol treatment resulted in embryonic death in the rabbit in early pregnancy in the same way as has been seen for other drugs with Ikr blocking properties (class III antiarrhythmics) in rodents. The observed developmental toxicity in the rabbit is most likely secondary to embryonic arrhythmia as has been shown in rodent studies. The results may indicate that Ikr blocking agents are developmental toxicants across species including man.
Altered Expression of Lung Cytochrome P450 3A1 in Rat after Exposure to Sulfur Mustard
Authors: Pons Françoise , Calvet Jean‐Henri , Haag Muriel , Raeppel Véronique , Keravis Thérèse , Frossard Nelly
Published: July 2004

Expression of cytochromes P450 (CYP) and glutathione S‐transferases in the lung may be affected by inhaled pollutants. We have investigated the effect of sulfur mustard on the expression of CYP 1A1, 2B1, 2E1 and 3A1, as well as of α‐, μ‐ and π‐glutathione S‐transferases in rat lung. Sulfur mustard (0.025, 0.05 or 0.1 mg/kg) or its vehicle was administered to anaesthetized animals by intratracheal injection. Expression of CYP and glutathione S‐transferases was analysed 24 hr after administration of the vesicant warfare using western blotting. Preservation of airway epithelium integrity after animal exposure to sulfur mustard was confirmed by histological examination of tracheal and lung tissues from control and treated animals. Constitutive levels of CYP 2B1 and 3A1 proteins were found in lung tissue from control rats, whereas CYP 1A1 and 2E1 proteins were not detected. Animal exposure to sulfur mustard enhanced CYP 3A1 protein levels by 80 to 103%. In contrast, exposure to sulfur mustard neither modified CYP 2B1 expression, nor led to detectable expression of CYP 1A1 or 2E1. Constitutive levels of α‐, μ‐ and π‐glutathione S‐transferase proteins were found in lung tissue from control rats. Exposure to sulfur mustard had no effect on expression of either of the glutathione S‐transferases. Our results show that intratracheal exposure to sulfur mustard selectively increases CYP 3A1 expression in rat lung. Taking into account the major role of CYP of the 3A family in the metabolism of drugs, up‐regulation of CYP 3A1 by sulfur mustard might have important therapeutic consequences.
Pharmacological Antagonism of the Slow‐Activating Delayed Rectifying Potassium Channel (IKs) Has No Effect on Cochlear Structure and Function in vivo
Authors: Whitworth Craig A. , Rybak Leonard P. , Kemp Ramon , Spence Stan
Published: July 2004

The experimental class III antiarrhythmic drug, L‐768673, prolongs the refractory period of cardiac myocytes by selectively blocking the slow‐activating delayed rectifying potassium (IKs) channel. The IKs channel has also been identified in vestibular dark cells and in the marginal cells of the stria vascularis. In the stria vascularis, the IKs channel plays an important role in cochlear homeostasis. Genetic null deletion of the IKs channel in mice and man results in profound hearing loss and cochlear pathology. Therefore, the purpose of the present study was to investigate the effect of L‐768673 on the auditory function and cochlear morphology in rats using auditory brainstem‐evoked response and light microscopy. Auditory testing was performed one week prior to dosing, following 14 days of administration and 28 days after the completion of dosing. L‐768673 (50 or 250 mg/kg/day for 14 days), had no significant effects on auditory function or cochlear morphology. The results of this study suggest that high doses of L‐768673 are not toxic to the inner ear of adult rats treated for 14 consecutive days, and that the ototoxic potential of orally administered L‐768673 and similar IKs‐selective compounds is unlikely at doses within the therapeutic range.