bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure and variability of the Denmark Strait Overflow: Model and observations
Authors: Käse R. H. , Girton J. B. , Sanford T. B.
Published: June 2003

We report on a combined modeling and observational effort to understand the Denmark Strait Overflow (DSO). Four cruises over the course of 3 years mapped hydrographic properties and velocity fields with high spatial resolution. The observations reveal the mean path of the dense water, as well as the presence of strong barotropic flows, energetic variability, and strong bottom friction and entrainment. A regional sigma coordinate numerical model of interbasin exchange using realistic bottom topography and an overflow forced only by an upstream reservoir of dense fluid is compared with the observations and used to further investigate these processes. The model successfully reproduces the volume transport of dense water at the sill, as well as the 1000‐m descent of the dense water in the first 200 km from the sill and the intense eddies generated at 1–3 day intervals. Hydraulic control of the mean flow is indicated by a region supercritical to long gravity waves in the dense layer located approximately 100 km downstream of the sill in both model and observations. In addition, despite the differences in surface forcing, both model and observations exhibit similar transitions from mostly barotropic flow at the sill to a bottom‐trapped baroclinic flow downstream, indicating the dominant role of the overflow in determining the full water column dynamics.
A reexamination of evanescent acoustic‐gravity waves: Special properties and aeronomical significance
Authors: Walterscheid R. L. , Hecht J. H.
Published: June 2003

Acoustic‐gravity wave relations indicate that when wave frequency and horizontal wave number approach the characteristic curve‐delineating gravity and acoustic solutions, the horizontal group velocity and Eckart's characteristic impedance become infinite and wave energy E vanishes. It is shown that this behavior is equivalent to assuming incorrectly that wave energy is the same function of vertical wave number for internal and evanescent waves. When the correct form of E for evanescent waves is used, the energy flow velocity U defined in terms of the energy flux Fx = EU is bounded by the sound speed, impedance is bounded by values near unity, and E does not vanish. For waves near the Lamb‐wave solution, the dominant dynamical control of the vertically integrated airglow response is the horizontal divergence. The only significant long‐lived evanescent response following an excitation event should be near the Lamb curve, and here the horizontal divergence is largest for small‐scale high‐frequency waves. The transient response is strongest for those waves that disperse least: waves with long‐horizontal wavelengths and waves not too far from the Lamb and Brunt‐Vaisala (BV) curves. Wave properties are well behaved near the characteristic curve and solutions are linked at the common intersection of the Lamb and BV curves implying that waves should be able to transfer energy from one regime to the other in response to background variations. Nonisothermal calculations show that when lapse rates are large enough waves that are at least partially internal can exist at all frequencies.
Ice cloud microphysics retrievals from millimeter radar and visible optical depth using an estimation theory approach
Authors: Benedetti A. , Stephens G. L. , Haynes J. M.
Published: June 2003

This paper introduces a new, robust, and reliable method to estimate ice cloud microphysical properties from cloud radar reflectivities and visible optical depth. The retrieval is formulated in an estimation theory framework that permits the introduction of optimal combinations of different measurements and a complete characterization of retrieval errors. The sensitivity of the retrieval to the assumed error statistics is assessed performing experiments with variable a priori, optical depth, and forward model uncertainties. Quantitative estimates of the uncertainties show that the average ice water content is retrieved with errors varying between 20 and 30%. The relative error on ice water path is of the same order of magnitude. The retrieval is applied to synthetic and real observations. Retrieved products are checked against other retrieval methods and in situ observations when available. The results compare well with results from other methods. In particular, the method described here is robust and can be applied successfully to a variety of cirrus clouds without suffering from the problems often encountered when using empirically based methods.
Mass balance of free tropospheric aerosol at the Puy de Dôme (France) in winter
Authors: Sellegri K. , Laj P. , Peron F. , Dupuy R. , Legrand M. , Preunkert S. , Putaud J.‐P. , Cachier H. , Ghermandi G.
Published: June 2003

The size‐segregated chemical composition of aerosols was investigated during winters 2000 and 2001 at Puy de Dôme (1465 m above sea level, France), a site most of the time located in the free troposphere. Aerosols have been sampled using low‐pressure cascade impactors (Electrical Low Pressure Impactor (ELPI) and Small Deposition Impactor (SDI) 13 and 12 stages) and analyzed for inorganic (Na+, NH4+, K+, Mg2+, Ca2+, Cl−, NO3−, and SO42−) and organic (HCOO−, CH3COO−, and C2O42−) ions, organic and elemental carbon (OC and EC), insoluble dust, and total mass. Under cloudy conditions, the sampling includes interstitial aerosol as well as the residue of evaporated cloud droplets. Aerosols (and residues of cloud droplets) were sampled in different air masses, which can be classified into three different categories according to their aerosol load and composition: background (BG), anthropogenic (ANT), and specific events (EV) that include advection of Saharan dust and upward transport from the polluted boundary layer to the site. On the basis of the presence or absence of coarse sea‐salt particles, a further classification permits us to distinguish air masses that have or have not been exposed to the ocean. A closed mass balance is achieved on submicron ranges (mean departure of 18.5%) for the three main air mass categories, providing a reliable description of main aerosol types in the west European free troposphere. The total aerosol mass at 50% relative humidity is close to 2.7 ± 0.6 μg m−3 in BG, 5.3 ± 1.0 μg m−3 in ANT, and 15 to 22 μg m−3 in EV air masses. The aerosol mass distribution generally exhibits two submicron modes (Acc1 at 0.2 ± 0.1 μm and Acc2 at 0.5 ± 0.2 μm geometric mean diameter (calculated for every impactor stage) and a supermicron mode (2 ± 1 μm). Aerosols exhibit a high degree of external mixing with carbonaceous (EC and OC) and ionic species associated with Acc1 and Acc2. Concentrations of light carboxylates and mineral dust never exceed 4% of the total content of analyzed compounds, except for a Saharan dust event during which the contribution of insoluble dust reaches 26% of the total aerosol mass. Depending on the sampled air mass, bulk water‐soluble inorganic species and carbonaceous material account for 25–70% and 15–60% of the total mass, respectively. The OC fraction is higher in air masses with low aerosol load (53%, 32%, and 22% for BG, ANT, and EV, respectively). Conversely, the EC fraction is enhanced from 4% in BG to 10% in ANT and 14% in EV. The inorganic fraction is more abundant in EV (55%) and ANT (60%) than in BG (40%) air masses as a result of enhanced nit .
One‐dimensional variational (1‐D Var) retrieval of temperature, water vapor, and a reference pressure from radio occultation measurements: A sensitivity analysis
Authors: von Engeln Axel , Nedoluha Gerald , Kirchengast Gottfried , Bühler Stefan
Published: June 2003

A 1‐D Var retrieval study of simulated radio occultation measurements is presented. Temperature and a water vapor profile are retrieved along with a reference pressure to generate the pressure profile by applying the hydrostatic equation. High‐resolution European Center for Medium‐Range Weather Forecasts (ECMWF) atmospheric fields are used by a ray tracing tool to calculate the exact positions of the tangent point. The 1‐D atmospheric profiles following the calculated tangent point trajectory in the 3‐D ECMWF fields are used to simulate bending angle measurements with a 1‐D forward model. Assimilation of these bending angles in a 1‐D Var tool employing the same 1‐D forward model is performed. We analyze the sensitivity of the retrieval to changes in vertical resolution, horizontal smearing of the tangent point trajectory, and the assumption of hydrostatic equilibrium for a nonvertical atmospheric scan. We find that retrievals calculated without adequate vertical resolution can have significant errors in temperature and water vapor. Errors in the retrieval by assuming hydrostatic equilibrium for a nonvertical scan generally cause only minor errors in the retrieved profiles. A study into the occurrence of rays curving down toward the Earth surface indicates that about 5–10% of the profiles could experience so‐called critical refraction at altitudes between 0.5 km and 2 km in case of the applied high‐resolution ECMWF data.
Organic nitrogen in rain and aerosol at Cape Grim, Tasmania, Australia
Authors: Mace Kimberly A. , Duce Robert A. , Tindale Neil W.
Published: June 2003

During the Southern Hemispheric spring of 2000 (during the months of November and early December), rain, bulk and size‐separated aerosol samples were collected at the Cape Grim Baseline Air Pollution Station located on the island of Tasmania, Australia and analyzed for total organic nitrogen (N), urea, and dissolved free amino acids. Rain and bulk aerosol samples contained organic N at concentrations representing, on average, between 19 and 25% of total N. Urea was not detected in the six rain samples analyzed. However, urea represented ∼24% of the organic N contained in nonbaseline aerosol samples, and ∼2% of the organic N contained within baseline samples. Trajectory analysis combined with meteorological data indicated that high concentrations of urea within aerosols were mainly due to Tasmanian sources, likely animal emissions, although the application of urea fertilizers cannot be dismissed as a source. In nonbaseline samples the highest concentrations of urea were associated with the coarse mode aerosol (>1 μm), although urea was also found in the fine mode aerosol (<1 μm), potentially indicating gas‐to‐particle conversion of urea. Aerosol samples collected in marine air masses contained urea within an intermediate fraction centered at ∼1 μm suggesting the sea surface microlayer as a source. Dissolved free amino acids contributed ∼53% of the organic N in rain, but were not a significant proportion of the total organic N fraction in either nonbaseline or baseline aerosol samples. Due to their presence in rain, amino acids likely exist in aerosols as unhydrolyzed proteins. In cascade impactor samples highly influenced by marine sources, profiles for amino N were inversely related to urea N, possibly indicating live species and the sea surface microlayer as a source for organic N.
Clues to the lithospheric structure of Mars from wrinkle ridge sets and localization instability
Authors: Montési Laurent G. J. , Zuber Maria T.
Published: June 2003

Wrinkle ridges are a manifestation of horizontal shortening in planetary lithospheres, for which deformation is localized on faults that underlie individual ridges. In ridged plains of Mars, such as Solis Planum or Lunae Planum, wrinkle ridges are spaced ∼40 km apart, whereas in the Martian northern lowlands, where ridges are identified only in Mars Observed Laser Altimeter (MOLA) altimetric data, the ridge spacing is at least ∼80 km. We attribute ridge spacing to an instability of the lithosphere under horizontal compression. The localization instability, which results in periodically spaced faults [Montési and Zuber, 2003a], links the difference of ridge spacing in the northern lowlands and in the highland ridged plains to the difference of crustal thickness via the depth of the brittle‐ductile transition (BDT). In Solis and Lunae Plana, where the crust is 50 to 60 km thick, the crust may be ductile at depth, limiting faulting to the BDT of crustal rocks. In the lowlands, the crust is only about 30 km thick and may be brittle throughout. Thus the depth of faulting may be controlled by the BDT of mantle rocks, which is roughly a factor of two deeper than that of crustal rocks. The geotherm can be identical in both regions, at 12 ± 3 K.km−1, although differences of a few K.km−1 can be accommodated within this model. The heat flux implied by this geotherm is similar to the heat produced by radiogenic decay 3 Gyr ago. Our analysis provides a rheological explanation for the difference in spacing between ridges in the highlands and the lowlands, in contrast to the suggestion of Head et al. [2002], who proposed that alternating lowlands ridges are buried by sediments. In addition, finite element models that use the lithospheric structure deduced from ridge spacing show that modest gradients of crustal thickness or heat flux across a ridged plains favor the formation of faults dipping toward high‐elevation areas, as may be the case in Solis Planum [Golombek et al., 2001].
Paleomagnetic record of Martian meteorite ALH84001
Authors: Antretter Maria , Fuller Mike , Scott Edward , Jackson Mike , Moskowitz Bruce , Solheid Peter
Published: June 2003

The natural remanent magnetization (NRM) of the Martian meteorite ALH84001 is predominantly carried by fine magnetite, which is found in association with carbonate. The magnetite is in epitaxial and topotactic relation with the carbonate and formed from the carbonate in the major impact event at 4.0 Ga. The NRM will therefore record this field. The local preferential crystallographic and shape alignment of the magnetite defines local easy directions of magnetization may account for the observed inhomogeneity of the NRM on a microscopic scale. Normalizing the intensity of the NRM by the saturation isothermal remanence (IRMs) then gives an estimate for the 4.0 Ga Martian field one order smaller than the present geomagnetic field. Such a field is unlikely to be strong enough to generate the high‐intensity Martian magnetic anomalies. ALH 84001 in its pristine state as an orthopyroxenite is not a plausible source rock for the Martian anomalies because its magnetite was not formed until the 4.0 Ga event.
A radiative transfer model function for 85.5 GHz Special Sensor Microwave Imager ocean brightness temperatures
Authors: Meissner Thomas , Wentz Frank J.
Published: June 2003

We analyze vertically and horizontally polarized brightness temperatures at 85.5 GHz that were measured by F5 Special Sensor Microwave Imager (SSM/I) over the world oceans. The columnar liquid cloud water content is restricted to below 0.04 mm. We develop a radiative transfer model function in this frequency region that provides a functional relationship between the measured microwave brightness temperatures and the essential geophysical parameters, which are the atmospheric temperature, ocean surface temperature, and wind speed. This will provide the basis for including the higher SSM/I, Tropical Rainfall Measurement Mission Microwave Imager (TMI), and Advanced Microwave Scanning Radiometer frequency channels into oceanic and atmospheric retrieval algorithms, which rely on an accurate forward model.
Retrieval of atmospheric and ocean surface parameters from ADEOS‐II Advanced Microwave Scanning Radiometer (AMSR) data: Comparison of errors of global and regional algorithms
Authors: Mitnik Leonid M. , Mitnik Maia L.
Published: June 2003

Retrieval of the sea surface temperature ts, wind speed W, total atmospheric water vapor content V, and total cloud liquid water content Q over the ocean from the simulated ADEOS‐II AMSR data in the absence of precipitation is considered. The brightness temperatures (TB) with the vertical (V) and horizontal (H) polarizations at the AMSR frequencies ν = 6.9, 10.7, 18.7, 23.8, and 36.5 GHz were computed for the radiosonde and relevant data collected by research vessels. V and Q were retrieved from TB(23.8V) and TB(36.5V) with the physically based “global” (−1.6 < ts ≤ 31°C), “polar” (ts ≤ 15°C), and “tropical” (ts ≥ 24°C) algorithms under the assumption that ts values were derived from the measurements at 6.9 and 10.7 GHz with an error σts. The errors σV and σQ were estimated at several combinations of the difference ΔT36 = TB(36.5V) ‐ TB(36.5H), radiometer noises ΔT and σts. At ΔT36 = 35 K, ΔT = 0.3 K, and σts = 1°C, σV = 1.5 kg/m2 and σQ = 0.029 kg/m2 for a global algorithm. Standard regression techniques were applied to retrieve ts and W from the simulated brightness temperatures for the cases TB(10.7V) ≤ 185 K. For a global data base, three‐channel algorithm (6.9V, 6.9H, 10.7V or 10.7V) yields the ts and W errors equal to 0.40 and 0.58°C and 0.66 and 0.85 m/s as radiometer noises increase from 0.1 to 0.2 K at ν = 6.9 GHz and from 0.13 to 0.27 K at ν = 10.7 GHz.
Radiation properties of leaky modes near the spectral gap region for semi‐infinite printed‐circuit lines
Authors: Villegas Frank J. , Jackson David R. , Williams Jeffery T. , Oliner Arthur A.
Published: June 2003

The radiation field from a leaky mode on a semi‐infinite printed‐circuit line is investigated. Asymptotic formulas for the radiation field are presented for a mode that is either in the physical region (a fast wave with respect to the substrate mode into which leakage occurs), or in the spectral‐gap region (a slow wave). These formulas, as well as a numerically exact representation of the leaky‐mode radiation field, are used to examine the nature of the radiation field and to study how it changes as the leaky mode transitions from the physical region to the spectral‐gap region. A comparison is made between the field radiated by the leaky‐mode current and that radiated by a practical probe feed that launches the semi‐infinite leaky mode current. Another comparison is made between the field radiated by the leaky‐mode current and the exact field radiated by the total current that is excited by a practical gap voltage source on an infinite line.
Simulation of off‐great circle HF propagation effects due to the presence of patches and arcs of enhanced electron density within the polar cap ionosphere
Authors: Zaalov N. Y. , Warrington E. M. , Stocker A. J.
Published: June 2003

Observations over recent years have established that large‐scale electron density structures are a common feature of the polar cap F region ionosphere. These structures take the form of convecting patches and arcs of enhanced electron density which form tilted reflection surfaces for HF radiowaves, allowing off‐great circle propagation paths to be established. Numerical ray tracing has been employed to simulate the effects of these structures on the ray paths of the radiowaves. The simulations have reproduced the precise character of experimental observations of the direction of arrival over a propagation path within the polar cap and of oblique ionograms obtained over the same path.
Arsenic in groundwater in Bangladesh: A geostatistical and epidemiological framework for evaluating health effects and potential remedies
Authors: Yu Winston H. , Harvey Charles M. , Harvey Charles F.
Published: June 2003

This paper examines the health crisis in Bangladesh due to dissolved arsenic in groundwater. First, we use geostatistical methods to construct a map of arsenic concentrations that divides Bangladesh into regions and estimate vertical concentration trends in these regions. Then, we use census data to estimate exposure distributions in the regions; we use epidemiological data from West Bengal and Taiwan to estimate dose response functions for arsenicosis and arsenic‐induced cancers; and we combine the regional exposure distributions and the dose response models to estimate the health effects of groundwater arsenic in Bangladesh. We predict that long‐term exposure to present arsenic concentrations will result in approximately 1,200,000 cases of hyperpigmentation, 600,000 cases of keratosis, 125,000 cases of skin cancer, and 3000 fatalities per year from internal cancers. Although these estimates are very uncertain, the method provides a framework for incorporating better data as it becomes available. Moreover, we examine the remedy of drilling deeper wells in selected regions of Bangladesh. By replacing 31% of the wells in the country with deeper wells the health effects of drinking groundwater arsenic could be reduced by approximately 70% provided that arsenic concentrations in deep wells remain relatively low.
The role of physical, chemical, and microbial heterogeneity on the field‐scale transport and attachment of bacteria
Authors: Mailloux Brian J. , Fuller Mark E. , Onstott Tullis C. , Hall James , Dong Hailiang , DeFlaun Mary F. , Streger Sheryl H. , Rothmel Randi K. , Green Maria , Swift Donald J. P. , Radke Jon
Published: June 2003

A field‐scale bacterial transport experiment was conducted at the Narrow Channel Focus Area of the South Oyster field site located in Oyster, Virginia. The goal of the field experiment was to determine the relative influence of subsurface heterogeneity and microbial population parameters on flow direction, velocity, and attachment of bacteria at the field scale. The field results were compared with results from laboratory‐scale column experiments to develop a method for predicting field‐scale bacterial transport. The field site is a shallow, sandy, unconfined, aerobic aquifer that has been characterized by geophysical, sedimentological, and hydrogeological methods. Comamonas sp. strain DA001 and a conservative tracer, bromide (Br), were injected into an area of high permeability for 12 hours. The Br and bacterial concentrations in the groundwater were monitored for 1 week at 192 sampling ports spaced over a 2‐m vertical zone located from 0.5 to 7 m down‐gradient of the injection well. The bacterial and Br plume was observed to move past 95 sampling ports. The densely characterized field site enabled the comparison of variations in DA001 transport to the aquifer properties. The velocity of the injected plume was correlated with geophysical estimates of hydraulic conductivity. The bacterial and Br plume appeared to follow flow paths not coincident with the hydraulic gradient but through a zone of higher permeability located off the flow axis. The amount of breakthrough of the bacteria was similar in both the high and low permeability layers with only a weak correlation between the observed hydraulic conductivity and amount of bacterial breakthrough. The uniformity in the observed attachment rates across varying grain sizes could be explained by heterogeneity of microbial properties within the single strain of injected bacteria. Application of colloid filtration theory to the field data indicated that variations in the microbial population were described by a lognormal distribution of the collision efficiency (α). Core‐scale studies were used to predict the α distribution and field‐scale transport distances of DA001. In sandy aquifers, physical heterogeneity may play a secondary role in controlling field‐scale bacterial transport, and future research should focus on the microbial factors affecting transport.
Flow, dissolution, and precipitation in dolomite
Authors: Singurindy Olga , Berkowitz Brian
Published: June 2003

The evolution of hydraulic conductivity and porosity during the process of dedolomitization was examined in a series of laboratory experiments by analyzing the effects of concurrent dolomite dissolution and calcium carbonate precipitation. Linear flow experiments were performed in columns of crushed sucrosic dolomite by injecting different concentrations of HCl at various flow rates. Temporal changes in head gradient were used to calculate overall hydraulic conductivities of each column, while chemical analyses of the effluent acid enabled estimation of porosity changes during the experiments. After each experiment, the rock samples were retrieved and sectioned in order to study the pore space geometry, micromorphology, and mineral concentrations. A range of injected HCl concentrations and flow rates was identified which leads to oscillations in the effective hydraulic conductivity and porosity of the evolving rock samples; in all cases, however, the porous medium ultimately clogged. Short‐term experiments were also used to study the formation of dissolution and precipitation bands along the columns. Under the experimental conditions, dolomite dissolution is a reaction rate controlled process; experiments indicated that, as such, the flow rate and the pH of the injected fluid affect dissolution only during the initial stages, when calcium carbonate is dissolved. On the other hand, both the flow rate and the pH of the injected fluid strongly influence the precipitation process throughout the duration of the experiments because higher flow rates retard nucleation. These findings are in qualitative accordance with field observations of dolomite formations.
Glacial‐age deep sea carbonate ion concentrations
Authors: Broecker W. S. , Clark Elizabeth
Published: June 2003

A second stab is taken at the reconstruction of the distribution of carbonate ion concentration in the deep tropical Pacific and Atlantic Oceans. It takes into account glacial to Holocene changes in size‐normalized initial shell weights; it adopts a more rigorous relationship between measured core‐top shell weights and pressure‐normalized CO3= concentrations; and it employs an expanded glacial data set. While the conclusion that the effective glacial CO3= ion concentration decreased with water depth, when greater initial shell weights for glacial‐age shells are adopted, the conclusion is that dissolution during glacial time exceeded that during the late Holocene. This conclusion is seemingly at odds with previous studies of deep Pacific sediments, all of which suggest that more extensive dissolution occurred during periods of interglaciation than during periods of glaciation.
Melt redistribution during the bending of a porous, partially melted layer
Authors: Simakin A. G. , Petford N.
Published: June 2003

A numerical, poro‐viscoelastic finite element flow model has been developed to simulate the redistribution of melt during the folding of a horizontal layer. Important mechanical properties governing the overall rheology of the buckling layer, including porosity, matrix viscosity, melt pressure and changes in deviatoric stress are tracked simultaneously with deformation. Melt migrates down gradients in melt pressure to the outer hinge zone of the folds, away from sites of compression to regions of local tension. For a matrix with dynamic power law rheology, deformation results in the formation of low viscosity, strain weakening zones that coincide with zones of enhanced deviatoric stress that are potential sites for plastic deformation. During fast deformation of layers with large width to height ratios, the more rapidly bending material splits into domains of higher viscosity separated by lower viscosity zones. Porosity (melt fraction) distribution patterns do not appear to be controlled by the matrix rheology. The numerical results and predictions of melt distribution and geometry during deformation correspond well with data from some physical (analogue) laboratory experiments and field observations. The quantitative nature of our results should help refine more qualitative models for the rates and mechanisms of melt extraction and transport in folded crustal migmatite terranes.
Simulation of magnetopause oscillations observed January 9, 1996
Authors: Slinker S. P. , Fedder J. A. , Sibeck D. G. , Lyon J. G. , Frank L. A. , Mukai T.
Published: June 2003

On January 9, 1996, the Geotail spacecraft was near the dusk flank of the magnetopause at 18 MLT. From 0100–0300 UT several short excursions out of the magnetosphere were observed. This time interval was simulated with a 3D MHD magnetosphere model using measured solar wind and IMF data. The simulation produced oscillations resembling those recorded in terms of amplitude and frequency. We describe the details and global nature of the oscillations from the simulation and discuss the most likely source: the Kelvin‐Helmholtz instability.
The effect of ‘noise’ on estimates of the elastic thickness of the continental lithosphere by the coherence method
Authors: Swain C. J. , Kirby J. F.
Published: June 2003

We model the lithosphere as a uniform elastic plate overlying an inviscid fluid and loaded with both surface and subsurface fractal loads to generate synthetic topography and gravity data. To simulate data having low (topographic) signal to (gravity) noise ratio we use an algebraically larger exponent for the subsurface load in the spectral synthesis fractal algorithm.The gravity power spectrum then decays less rapidly than that of topography, the spectra resembling those for central Australia. We find that the coherence method using multitaper spectral estimation yields significant underestimates of plate thickness for both low and normal signal‐to‐noise ratio data, unless the data window is larger than several times the true flexural wavelength. We quantify this bias for the parameters used here and apply it as a correction to an effective elastic thickness estimate for central Australia, obtaining a value of 115 ± 25 km.
The attenuation of fast atmospheric CH4 variations recorded in polar ice cores
Authors: Spahni R. , Schwander J. , Flückiger J. , Stauffer B. , Chappellaz J. , Raynaud D.
Published: June 2003

To reconstruct fast atmospheric trace gas variations from polar ice cores it has to be considered that their amplitudes are attenuated during the enclosure process in the ice. Relevant processes for the attenuation are the molecular diffusion in the open pores of the firn column and the gradual bubble close off in the depth of the transition from firn to ice. These processes depend mainly on temperature and accumulation rate and lead e.g. to a strong attenuation for cold sites with low accumulation rates. With a diffusion and enclosure model it is possible to calculate the attenuation for a single event and to compare ice core records from different sites. We investigate the atmospheric methane (CH4) variation during the cold event 8200 years ago and calculate that its amplitude as recorded in the EPICA Dome C ice core is attenuated to a magnitude between 34% and 59%.
How many paleointensity determinations are required from a single lava flow to constitute a reliable average?
Authors: Biggin A. J. , Böhnel H. N. , Zúñiga F. R.
Published: June 2003

Statistical analysis has been undertaken to investigate the minimum number of paleointensity estimates required to allow certainty (at the 95% confidence limit) that the mean is within 10% of the implied true mean for an entire lava flow. The data used for the analysis was provided by previous, paleointensity studies which used three different methods (Thellier‐Coe, Shaw, and microwave Thellier) on 19 or more samples from three different basalt lava flows. The results strongly suggest that future paleointensity studies need to produce many more estimates per lava flow than is currently the norm in order to ensure that the calculated mean paleointensity does not differ significantly from the true flow mean. Furthermore, they indicate that a low measured dispersion for a small number of estimates is not a safeguard against misrepresentation of the flow mean paleointensity. Finally, we provide quantitative evidence that paleointensity studies should always attempt to maximise vertical coverage of lava flows to avoid biasing of the mean.
Affective disorders in neurological diseases: a case register‐based study
Authors: Nilsson F. M. , Kessing L. V. , Sørensen T. M. , Andersen P. K. , Bolwig T. G.
Published: June 2003

Objective: To investigate the temporal relationships between a range of neurological diseases and affective disorders.

Method: Data derived from linkage of the Danish Psychiatric Central Register and the Danish National Hospital Register. Seven cohorts with neurological index diagnoses and two control group diagnoses were followed for up to 21 years. The incidences of affective disorders in the different groups were compared with the control groups, using competing risks to consider the risk of affective disorder and the risk of death in the same analysis.

Results: We found an increased incidence of affective disorders in dementia, Parkinson's disease, epilepsy, stroke and intracerebral haemorrhage compared with control groups. The association was found to be the strongest for dementia and Parkinson's disease. In hospitalized patients, with incident multiple sclerosis, the incidence of affective disorder was lower than the incidence in the control groups.

Conclusion: In neurological diseases there seems to be an increased incidence of affective disorders. The elevated incidence was found to be particularly high for dementia and Parkinson's disease (neurodegenerative diseases).
Effects of therapeutic doses of 131I in thyroid papillary carcinoma patients with elevated thyroglobulin level and negative 131I whole‐body scan: comparative study
Authors: Koh Jung‐Min , Kim Eun Sook , Ryu Jin Sook , Hong Suck Joon , Kim Won Bae , Shong Young Kee
Published: June 2003

objective Previous studies have shown a high rate of visualization of uptake and a decrease in serum thyroglobulin (Tg) after therapeutic doses of 131I in well‐differentiated thyroid cancer patients with elevated thyroglobulinaemia but negative diagnostic 131I whole‐body scan (DxWBS), but its therapeutic effect remains controversial. We evaluate the effect of therapeutic doses of 131I in patients with elevated thyroglobulin level but negative DxWBS.

design Among papillary thyroid carcinoma patients who underwent total or near‐total thyroidectomy and remnant ablation with radioiodine during 1996 to 2000 in our hospital, the patients who showed elevated serum Tg levels and no abnormal uptake in DxWBS were selected. The selection for treatment or no treatment was decided according to the preference of the patients, considering side‐effects of therapeutic doses of 131I, and the patients were thereafter studied retrospectively.

patients Sixty papillary thyroid carcinoma patients with elevated thyroglobulinaemia but negative DxWBS were included. Twenty‐eight patients were treated, and 32 were untreated.

measurements We compared serum Tg levels measured at less than 3 months before the administration of therapeutic doses of 131I or DxWBS with the levels at 6–12 months after administration between two groups. Comparable data on changes in serum Tg levels during TSH suppression (Tg‐on) and those in hypothyroid phase (Tg‐off) were available in 25 and 49 patients, respectively.

results Percentage decreases in both Tg‐on and Tg‐off levels of the treated group [41·2 (10·1–94·1)% and 37·0 (−176·6–88·4)%, respectively] were significantly higher than those of the untreated group [−43·6 (−180·1–7·3)% and −66·6 (−10644·2–39·1)%, respectively] (P < 0·001). The treated patients were followed‐up for 23·8 ± 19·6 months after the administration of therapeutic doses of 131I. In four cases, serum Tg levels converted to negative (< 1·0 ng/ml) both on and off T4 15–22 months after the administration of therapeutic doses of 131I, and negative serum Tg levels persisted for 24–70 months. However, negative conversion of elevated serum Tg levels was not observed in any of the untreated group. Post‐treatment WBS revealed pathologic uptake in 12 of 28 cases (42·9%).

conclusions This study revealed that the administration of therapeutic doses of 131I has a therapeutic effect, at least for palliation in short‐term observation, considering the serum Tg level as an index of tumour burden, and that it can disclose previously undiagnosed lesion in some patients with differentiated thyroid cancer who show elevated thyroglobulin level but negative diagnostic 131I whole‐body scan.
Scanning electron microscopic study of the cleaning ability of chlorhexidine as a root‐canal irrigant
Authors: Yamashita J. C. , Tanomaru Filho M. , Leonardo M. R. , Rossi M. A. , Silva L. A. B.
Published: June 2003

Aim  To evaluate in vitro the cleaning of root‐canal walls after irrigation with different irrigants.

Methodology  A total of 36 recently extracted human teeth were divided into four experimental groups according to the irrigating solution used: saline; 2% chlorhexidine; 2.5% sodium hypochlorite; and 2.5% sodium hypochlorite + EDTA. The cleaning of the apical, middle and coronal thirds of the root canals was evaluated by scanning electron microscope examination using a 4‐point scoring system.

Results  The best cleaning was obtained using 2.5% sodium hypochlorite and EDTA, followed by 2.5% sodium hypochlorite only (P < 0.05), whose cleaning was similar to chlorhexidine only in the cervical third. Cleaning by saline and 2% chlorhexidine was worse than the other two groups and was similar in all thirds. Better cleaning was found in the cervical and middle thirds for all groups with the worst results in the apical third.

Conclusions  The apical third of the root canals was not cleaned as well as the middle and coronal thirds. Cleaning by chlorhexidine and saline was inferior compared to the cleaning by sodium hypochlorite with and without EDTA.
Technical quality of root canal treatment in Taiwan
Authors: Chueh L.‐H. , Chen S.‐C. , Lee C.‐M. , Hsu Y.‐Y. , Pai S.‐F. , Kuo M.‐L. , Chen C.‐S. , Duh B.‐R. , Yang S.‐F. , Tung Y.‐L. , Hsiao C. K.
Published: June 2003

Aim  To evaluate the current technical quality of root canal treatment (RCT) in Taiwan.

Methodology  A total of 1085 RCT cases, randomly selected from a large sample and representative of the Taiwanese population from April to September 2000, were evaluated by eight endodontic specialists. The qualitative evaluation of RCT cases was based on two variables: length of the root filling and density of the obturation. A root canal with both adequate filling length (the apical termination of the root filling within 2 mm of the radiographic apex) and complete obturation (no lateral or apical canal lumen visible in the apical one‐third of the root canal) was defined as having good‐quality endodontic work (GQEW). A tooth was defined as having a GQEW when all its canals were categorized as GQEW.

Results  From a total of 1867 root canals, overfilling occurred in 235 (12.6%), adequate filling length in 1152 (61.7%), underfilling in 466 (25.0%) and no filling in 12 (0.6%). Of the 1867 root canals, 710 (38.0%) demonstrated complete obturation and 1157 (62%) demonstrated incomplete obturation. GQEW was found in 650 (34.8%) root canals and 329 (30.3%) teeth. The percentage of teeth with GQEW in hospital cases (38.1%) was significantly greater (P < 0.001) than that in private clinic cases (24.3%). In addition, the frequency of teeth with GQEW in the anterior teeth (40.4%) or in the premolars (33%) was significantly greater (P < 0.001) than that in the molars (18.4%).

Conclusions  Approximately 70% of the teeth receiving RCT in Taiwan were either of inadequate filling length or sealing density.
Orascopic visualization technique for conventional and surgical endodontics
Authors: Bahcall J. , Barss J.
Published: June 2003

Aim  To present a technique of integrating fibre optic orascope and rod‐lens endoscope for visualization in conventional and surgical endodontic treatments.

Summary  Innovative advancements in fibre optic and rod‐lens endoscope technology have allowed for the development and evolution of orascopic endodontics. The use of orascopy in conventional and surgical endodontic treatments has enabled the endodontist to become more discerning about the endodontic aetiology and the treatment procedures.

Key learning points

Orascopy is a procedure that uses an orascope or a rod‐lens endoscope for visualization in the oral cavity.

An orascope is made up of fibre optics and an endoscope is made up of glass rods.

Orascopic endodontics is the use of orascopy for visualization in conventional or surgical endodontic treatment.

A 0.8 mm lens diameter, 0°, 10K fibre optic orascope and a 4 mm lens diameter, 30°, 4 cm rod‐lens endoscope are used for visualization in conventional endodontics.

The 2.7 mm lens diameter, 70°, 3 cm long rod‐lens endoscope is used for visualization in surgical endodontics.
The acute phase protein haptoglobin is locally expressed in arthritic and oncological tissues
Authors: Smeets Mirjam B. , Fontijn Jolanda , Kavelaars Annemieke , Pasterkamp Gerard , De Kleijn Dominique P.V.
Published: June 2003

Summary.  Haptoglobin is an acute phase protein known to be highly expressed in the liver. Recently, we showed increased local arterial haptoglobin expression after flow‐induced arterial remodelling and found that haptoglobin is involved in cell migration and arterial restructuring probably through accumulation of a temporary gelatin matrix. Since cell migration and matrix turnover are important features in the pathology of arthritis and cancer, we hypothesized that haptoglobin is also locally expressed in arthritic and oncological tissues. In this study, we investigated local haptoglobin expression in arthritic rats (n = 12) using semi‐quantitative PCR and Western blotting, and we studied haptoglobin mRNA localization in human kidney tumours (n = 3) using in situ hybridization. The arthritic rats demonstrated an increase of haptoglobin mRNA (2.5‐fold, P < 0.001) and protein (2.6‐fold, P < 0.001) in the arthritic Achilles tendon. Haptoglobin protein was also increased in the arthritic ankle (2.6‐fold, P < 0.001) but not in the non‐arthritic knee. In human kidney tumours, tumour and stromal cells produced haptoglobin mRNA. This study shows that the liver protein haptoglobin is, in addition to the artery, also expressed in arthritic and oncological tissues that are recognized for enhanced cell migration and matrix turnover.
Chronic treatment with the thiazolidinedione, MCC‐555, is associated with reductions in nitric oxide synthase activity and β‐cell apoptosis in the pancreas of the Zucker Diabetic Fatty rat
Authors: Pickavance Lucy C. , Widdowson Peter S. , Foster John R. , Williams Gareth , Wilding John P. H.
Published: June 2003

Summary.  The Zucker Diabetic Fatty (ZDF) rat is a model of impaired insulin sensitivity arising from hyperphagia owing to a mutation in the leptin receptor. In time, young ZDF rats, which are not initially diabetic, develop impaired pancreatic β‐cell function leading to apoptotic cell death. This results in an inability to fully compensate for the reduction in insulin sensitivity with hypersecretion of insulin. Young, pre‐diabetic ZDF rats were treated, over a 4‐week period, with the thiazolidinedione compound MCC‐555, and the islet morphology studied in comparison to ZDF rats not given MCC‐555. In particular, changes in the apoptotic incidence, as measured using TUNEL staining to localize apoptotic cells, were studied over the 4‐week period. Changes in the induction of nitric oxide synthase and in the accumulation of nitrate/nitrite within the pancreas were also studied during the time course of administration of MCC‐555. The study has demonstrated that the administration of MCC‐555 significantly decreases the apoptotic incidence in the islets of Langerhans of pre‐diabetic ZDF rats given the compound, as compared to those not given MCC‐555, as well as decreasing the accumulation of nitrate/nitrite within the pancreas.
Defining boundaries during joint cavity formation: going out on a limb
Authors: Lamb K. J. , Lewthwaite J. C. , Bastow E. R. , Pitsillides A. A.
Published: June 2003

Summary.  Whilst factors controlling the site at which joints form within the developing limb are recognised, the mechanisms by which articular element separation occurs during the formation of the joint cavity have not been determined. Herein, we review the relationships between early limb patterning, embryonic movement, extracellular matrix composition, local signalling events and the process of joint cavity formation. We speculate that a pivotal event in this process involves the demarcation of signalling boundaries, established by local mechano‐dependent modifications in glycosaminoglycan synthesis. In our opinion, studies that examine early patterning and also focus on local developmental alterations in tissue architecture are required in order to help elucidate the fundamental principals regulating joint formation.
Older men's experiences of living with severe visual impairment
Authors: Weaver Moore Linda , Miller Margaret
Published: June 2003

Background. Little is known about how men react to their health and illness experiences. Lack of information about the lives of older men is unfortunate considering the anticipated growth of the older male sector of society and the fact that older men age differently than older women. One health‐related experience common to many older men is severe visual impairment caused by macular degeneration, a chronic eye disease that affects central vision. Understanding the health experiences of older men is imperative if nurses are to provide quality care to this growing segment of society.

Aim. The purpose of this study was to gain an understanding of the experience of severe visual impairment from the perspective of older men with macular degeneration.

Method. A phenomenological approach was used to investigate the experience of severe visual impairment in eight older men with macular degeneration. Data were gathered through audiotaped interviews and analysed using a modified Giorgi method.

Findings. The resultant general structural description revealed six central themes: (1) older men's lives were circumscribed by what they could and could not see and could and could not do, (2) cherishing of independence, (3) creation of strategies, (4) acknowledgment of the progression of visual impairment, (5) confrontation of uncertainties, scepticisms, and fears about their diagnosis and treatment, and (6) persistence with hope and optimism.

Conclusions. A thorough nursing history and assessment must be completed, including information about the progression of the visual impairment, strategies used for living with visual loss, and presence of other health problems that may complicate life with visual impairment. Nurses must be aware that older men with macular degeneration are often sceptical about their diagnosis and treatment. Therefore, careful education and clear communication are essential.
Exploring the beliefs and experiences of potential egg share donors
Authors: Rapport Frances
Published: June 2003

Background.  To date there are few attitudinal studies of women's experiences of egg donation, motivation to donate or their thoughts about eggs donated. Studies are predominantly discussed in terms of a specific treatment option and the ethical implications of different treatments. These studies are mainly designed by professionals working in assisted reproductive technology in line with a clinical agenda.

Aim.  This study aimed to explore the beliefs and experiences of potential egg share donors using an interpretative phenomenological methodology to equip health care practitioners to deal better with patients’ needs and desires.

Method.  Open‐ended interviews were conducted immediately following introductory consultations with 11 potential egg share donors from one fertility centre in the United Kingdom (UK). The sample was opportunistic. Data collection took 8 months and van Manen's interpretative phenomenological method was used.

Findings.  Analysis revealed six themes of egg sharing: motherhood (the predominant theme within which all other themes could be subsumed), context, doubt, coping, exchange and empathy. Themes illustrated women's continuation with the scheme despite fears about giving away eggs, the parenting skills of recipient couples and future repercussions of positive outcomes for donor and recipient.

Conclusions.  Egg sharing could be seen as a marker of hope. Buoyed up by the possibility of a successful outcome, women are prepared to undertake repetitive treatment attempts despite continued failure to conceive and knowledge of a slim chance of a positive outcome. Implications for practice, policy and ethics result in recommendations for more in‐depth interview work by independent researchers to gain a clearer picture of women's responses to reproductive technologies and the development of services in line with patient need and individual expectation.