bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Considerations for modeling doses from radionuclides transported through groundwater
Authors: Waters Robert D. , Gruebel Marilyn M.
Published: February 2004

Analysts typically incorporate into groundwater pathway models for low‐level radioactive waste a simplified approach for the buildup and decay of radioactive progeny during environmental transport. The inventory is transported to the exposure point, with doses calculated there for the parent and progeny based on predicted concentrations of the parent radionuclides. This approach generally provides conservative values because maximum combined doses are larger than they would be if transport of parent and progeny were based on differing travel times. For some radionuclides, however, the approach causes underestimation of doses. Because of buildup of radiologically significant progeny, the dose at the exposure point may be higher at later arrival times than at the parent's arrival time. Also, if a parent radionuclide is shorter‐lived and less mobile than one of its progeny, the parent may reach maximum dose before the progeny. We developed an alternate approach that provides conservative doses for these radionuclides.
Use of temporal moments to investigate the effects of nonuniform grain‐size distribution on the transport of sorbing solutes
Authors: Cunningham Jeffrey A. , Roberts Paul V.
Published: February 2004

We use temporal moment analysis to examine the effects of nonuniform grain size on the transport of sorbing solute through porous media. We consider the case of advective‐dispersive transport with sorption nonequilibrium governed by diffusion into spherical grains. For constant grain radius a and diffusion rate Da, the temporal moments for this problem are well known and have been reported elsewhere. In this paper, we consider the more realistic case, where there exists a distribution of diffusional timescales td ≡ a2/Da. The first and second temporal moments are unaffected by this distribution, but the third temporal moment is increased by a factor proportional to the variance of the distribution. This result holds regardless of the particular form of the distribution. Higher‐order temporal moments depend on the higher‐order moments of the distribution of td. Thus, even if the mean diffusion rate is relatively fast, higher‐order temporal moments of the solute transport may exhibit significant nonequilibrium effects; hence it may not be possible to decide the validity of the “local equilibrium assumption” based solely on the second temporal moment. Also, our analysis shows that in simulation of aquifer remediation by pump‐and‐treat, the appropriate choice for the contaminant desorption rate depends upon the remediation goal.
Horizontal infiltration into wet soil
Authors: Witelski T. P.
Published: February 2004

We obtain the long‐time asymptotic similarity solution for the wetting front for water absorption from a constant source into a homogeneous layer of soil with a preexisting moisture distribution. The presence of the initial water distribution in the soil introduces a time shift that advances the position of the wetting front. The time shift can be explicitly calculated for any form of diffusivity. A dynamic time shift is derived to yield a very efficient means for estimating the water content distribution and front position for all times in Brooks‐Corey‐type soil models.
Constitutive relationships and pore structure of undisturbed fracture zone samples with cohesionless fault gouge layers
Authors: Fischer Ulrich , Kulli Beatrice , Flühler Hannes
Published: February 2004

Multiphase flow processes in fractured rocks are of major importance for the remediation of subsurface contamination, for engineering petroleum reservoirs, and for the safety analysis of nuclear waste repositories. We developed procedures for determining the water retention curve, gas permeability function, and pore structure of undisturbed fracture‐zone samples with cohesionless fault gouge layers in the laboratory. Mylonitic samples were taken at Grimsel Test Site (Switzerland). Intrinsic permeabilities of the fault gouge layers were 5 orders of magnitude higher, and significant desaturation occurred at capillary pressure heads about 10 times lower than in the surrounding granodiorite, thus showing that at this site gas flow would take place mainly in the fracture zone. The measured water retention and gas permeability data were well represented by parametric models designed for porous media. Gas flow could only be detected at water saturations below about 0.8, thus showing strong phase interference at high water saturations. To relate these findings to the pore structure of the samples, a qualitative and quantitative description of the pore space was obtained at different scales using fluorescent resin imbibition and image analysis techniques. Results show that the fracture zone consists of a continuous and interconnected fracture network that is filled with a porous medium‐like material, thus explaining the applicability of the above mentioned models and the rather strong phase interference.
Comparison of hydrochemical tracers to estimate source contributions to peak flow in a small, forested, headwater catchment
Authors: Rice Karen C. , Hornberger George M.
Published: February 2004

Three‐component (throughfall, soil water, groundwater) hydrograph separations at peak flow were performed on 10 storms over a 2‐year period in a small forested catchment in north‐central Maryland using an iterative and an exact solution. Seven pairs of tracers (deuterium and oxygen 18, deuterium and chloride, deuterium and sodium, deuterium and silica, chloride and silica, chloride and sodium, and sodium and silica) were used for three‐component hydrograph separation for each storm at peak flow to determine whether or not the assumptions of hydrograph separation routinely can be met, to assess the adequacy of some commonly used tracers, to identify patterns in hydrograph‐separation results, and to develop conceptual models for the patterns observed. Results of the three‐component separations were not always physically meaningful, suggesting that assumptions of hydrograph separation had been violated. Uncertainties in solutions to equations for hydrograph separations were large, partly as a result of violations of assumptions used in deriving the separation equations and partly as a result of improper identification of chemical compositions of end‐members. Results of three‐component separations using commonly used tracers were widely variable. Consistent patterns in the amount of subsurface water contributing to peak flow (45–100%) were observed, no matter which separation method or combination of tracers was used. A general conceptual model for the sequence of contributions from the three end‐members could be developed for 9 of the 10 storms. Overall results indicated that hydrochemical and hydrometric measurements need to be coupled in order to perform meaningful hydrograph separations.
Stream water chemistry in Japanese forested watersheds and its variability on a small regional scale
Authors: Ohrui Kiyokazu , Mitchell Myron J.
Published: February 2004

Stream water chemistry was investigated for 25 forested watersheds located about 100 km northwest of Tokyo, Japan. Stream Ca2+ and NO3− concentrations increased and Na+, HCO3−, and SiO2 concentrations decreased with increases in stream discharge rates due to the increased importance of soil water to stream water and decreased importance of groundwater during periods of high precipitation inputs. Stream chemistry was significantly different from soil water chemistry, especially during low flow, suggesting a large contribution of groundwater to the streams during these periods. There were large differences of stream chemistry among watersheds in NO3− and HCO3− concentrations (44 ± 30 and 114 ± 82 µeq L−1, respectively; average ± standard deviation), and smaller differences in Cl− concentrations (46 ± 8 µeq L−1). Patterns of stream NO3− concentrations were affected by the stand age, which affected the ability of the forest to retain N, and the nitrification potential, which regulated N mobility. Patterns of stream HCO3− concentrations varied concomitantly with Ca2+, Na+, and SiO2 concentrations and pH (6.6 ± 0.5) were important attributes of the stream waters of these watersheds, due to the warm humid climate that enhanced N mineralization, nitrification, and mineral weathering.
Kinematic wave model for water movement in municipal solid waste
Authors: Bendz David , Singh Vijay P. , Rosqvist Håkan , Bengtsson Lars
Published: February 2004

The movement of water in a large (3.5 m3) undisturbed sample of 22‐year‐old municipal solid waste has been modeled using a kinematic wave approximation for unsaturated infiltration and internal drainage. The model employs a two‐parameter power expression as macroscopic flux law. The model parameters were determined and interpreted in terms of the internal geometry of the waste medium by fitting the model to one set of infiltration and drainage data. The model was validated using another set of data from a sequence of water input events. The results of the validation show that the model performs satisfactorily, but further development of the model to incorporate spatial variability would increase its capability.
Analytical solution and timescale for transport of reacting solutes in rivers and streams
Authors: Wörman Anders
Published: February 2004

A number of biogeochemical reactions and lateral hydrodynamic mixing affects the transport of solute elements in streams and rivers. The combination of the various mechanisms gives rise to an accumulation of the solute in temporary storage zones and a retardation of solute migration. A new model framework is proposed from which an analytical solution is derived describing the concentration as a function of distance along the stream, depth into storage zones, and time. The model includes the effects of sorption of solutes to suspended solids and bed sediments, a lateral exchange with the storage zones, first‐order reactions, and dilution. The migration velocity is close to the advection velocity of the stream for a short travel distance, but it continuously decreases as the distance increases. The timescale of the process is linearly related to a modified Damköhler number; a dimensionless form of the lateral exchange coefficient. The analytical solution has been verified for two tracer experiments with both a sorbing and a nonreactive tracer and the Cr transport in the Vistula River, Poland. The lateral diffusion coefficient can be tentatively evaluated from the transport of Chernobyl Cs in several European rivers as a special case of the interpretative model. The lateral mixing coefficient varies with stream conditions in the order of 0.1 × 10−6 < Ds < 10 × 10−6 (m2/s).
On the variability of fracture surfaces in unsaturated chalk
Authors: Weisbrod Noam , Nativ Ronit , Ronen Daniel , Adar Eilon
Published: February 2004

The topographical variations in a fractured chalk surface were studied by laser scanning in laboratory experiments after cycles of immersion in tap water and air drying. The surfaces were found to erode by up to 0.295 and 0.352 mm following wetting for 10 min and 14 hours, respectively. Topographical changes were related to the nonuniform release of particles from the surface under no‐shear flow conditions. The total amount of particles released decreased exponentially with time during a 96‐hour experiment, from 11 mg/L following a wetting period of 10 min (at the beginning of the experiment) to 1 mg/L following a wetting period of 48 hours (at the end of the experiment). These preliminary results suggest that under conditions of variable water content (highly significant in arid and semiarid regions), the aperture, roughness, and flow channels of fractures in soft rocks are transient properties. In the field site, fracture apertures are >1 order of magnitude smaller than expected from the laboratory observations. This discrepancy is related among other possible reasons, to partial wetting and drying cycles and to the development of flow channels within the filling materials rather than along the fracture surfaces.
Hillslope processes, drainage density, and landscape morphology
Authors: Tucker Gregory E. , Bras Rafael L.
Published: February 2004

Catchment morphology and drainage density are strongly influenced by hillslope processes. The consequences of several different hillslope process laws are explored in a series of experiments with a numerical model of drainage basin evolution. Five different models are considered, including a simple diffusive‐advective process transition, a runoff generation threshold, an erosion threshold, and two types of threshold‐activated landsliding. These different hillslope processes alter both the visual appearance of the landscape and the predicted relationship between slope and contributing area. On the basis of the different threshold theories, we derive expressions for the relationships between drainage density and environmental factors such as rainfall, relief, and mean erosion rate. These relationships vary depending on the dominant hillslope threshold. In particular, the sign of the predicted relationship between drainage density and relief is positive in semiarid, low‐relief landscapes and negative in humid landscapes dominated by a saturation threshold and/or in high‐relief landscapes dominated by simple threshold landsliding.
Influence of aperture variability on dissolutional growth of fissures in Karst Formations
Authors: Hanna R. Blair , Rajaram Harihar
Published: February 2004

The influence of aperture variability on dissolutional growth of fissures is investigated on the basis of two‐dimensional numerical simulations. The logarithm of the fissure aperture before dissolution begins is modeled as a Gaussian stationary isotropic random field. The initial phase of dissolutional growth is studied up to the time when turbulent flow first occurs at a point within the fissure (the breakthrough time). The breakthrough time in variable aperture fissures is smaller than that in uniform fissures and decreases as the coefficient of variation of the aperture field (σ/μ) increases. In comparing uniform and variable aperture fissures in limestone, the breakthrough time with σ/μ=0.1 is about a factor of 2 smaller than that in a uniform fissure. The breakthrough time is reduced by about an order of magnitude with σ/μ=2.0. The mechanism leading to reduced breakthrough times is the focusing of flow into preferential flow channels which are enlarged at a faster rate than the surrounding regions of slower flow. Dissolution channels are narrower and more tortuous as σ/μincreases. Investigations of the influence of reaction rate reveal that the influence of aperture variability is more pronounced in rapidly dissolving rock. In uniform fissures in rapidly dissolving minerals, breakthrough times are very long since water becomes saturated with respect to the mineral within a short distance of the entrance to the flow path. However, in variable aperture fissures, breakthrough occurs rapidly because of selective growth along preferential flow channels, which progressively capture larger fractions of the total flow. These results partly explain why conduits develop rapidly in gypsum, although previous one‐dimensional studies suggest that conduit growth will not occur.
The fate of geothermal arsenic in the Madison and Missouri Rivers, Montana and Wyoming
Authors: Nimick David A. , Moore Johnnie N. , Dalby Charles E. , Savka Michael W.
Published: February 2004

Geothermal As from Yellowstone National Park causes high As concentrations (10–370 μg/L) in the Madison and Missouri Rivers in Montana and Wyoming. Arsenic transport is largely conservative in the upper basin as demonstrated by the near equivalence of dissolved and total‐recoverable As concentrations, the constancy of As loads, and consistent ratios of concentrations of As to conservative geothermal tracers. Diurnal cycling of As between aqueous and solid phases in response to pH‐induced changes in sorption equilibria causes small variations of about 10–20% in dissolved As concentrations. HCl‐extractable As concentrations in river and lake sediment in the upper basin are variable depending on position relative to the As‐rich headwaters and geochemical and physical processes associated with lakes. In the lower Missouri River, large quantities of suspended sediment from tributaries provide sufficient sorption sites for substantial conversion of As from the aqueous phase to the solid phase.
On field‐scale dispersion of strongly sorbing solutes in soils
Authors: Streck Thilo , Piehler Hans
Published: February 2004

The practical application of parallel soil column (or stream tube) models is hindered by the difficulty to assess the probability density function of the pore water velocity, which at present requires extensive measurements. However, many environmentally relevant chemicals are strongly sorbed to the soil matrix. In this case, solute transport can be modeled to a good approximation on the basis of the pdf of infiltration and a constant water content. The exact value of the water content and its variability are not important. This follows from analysis of the travel time moments of a generalized multicompartment model and is shown to hold true for kinetic sorption to an arbitrary number of arbitrarily connected sorbent compartments with different equilibrium partitioning coefficients.
Influx and efflux of moisture in a desert soil during a 1 year period
Authors: Athavale R. N. , Rangarajan R. , Muralidharan D.
Published: February 2004

Spatial and temporal variation of moisture flux in soil over a 1 year period was studied in the Thar desert of India. Tritium was injected at a depth of 0.8 m at 18 sites distributed over an area of 50 km2 and at 20 adjacent points at a single site over a sand dune, before the 1994 monsoon. Vertical soil profiles were collected from the 18 sites after the end of monsoon and at the end of the year and from the multiple‐injections site at different time intervals throughout the year. Moisture flux values, computed from tritium and moisture distribution in soil profiles, show that the moisture influx at a site depends upon the grain size of the top 20 cm layer and that about 68% of the total influx of water below the injection depth is lost during the summer months. The data for the multiple‐injections site show that the tritium spike was displaced to a depth of 4 m by the end of the monsoon, and it remained stationary during the postmonsoön period of 8 months, although about 64% of the soil moisture was lost. The spiked layer showed enrichment in the specific activity of tritium during summer months. These observations suggest that vapor diffusion is the dominant process for moisture loss from the Thar desert soil. The net input (natural recharge) to groundwater due to 1994 precipitation was 62 mm.
Analysis of steady state chloride transport through two heterogeneous field soils
Authors: Jacques Diederik , Kim Dong‐Ju , Diels Jan , Vanderborght Jan , Vereecken Harry , Feyen Jan
Published: February 2004

Chloride transport was investigated in a loamy soil and a silty‐loam soil at the field scale under steady state flow conditions using a water flux of 2.84 cm d−1 for the loamy and 1.5 cm d−1 for the silty‐loam soil. The solute plume movement was recorded by means of horizontally installed time domain reflectrometry (TDR) probes at 5 depths up to 90 cm below the soil surface and 24 locations along a transect of 8 m. The measurements consisted of solute resident concentrations every 2 hours in the loamy soil for a total period of 42 days and every 4 hours for the silty‐loam soil for a period of 65 days. Parameters of the convective‐dispersive equation (CDE) and the lognormal stochastic‐convective transport model (CLT) were determined using time‐normalized resident concentration breakthrough curves Crt*(z, t). In addition, temporal moments of Crt*(z, t) were related to travel time moments and transport parameters for the two transport processes. At both sites the breakthrough curves at different depths were better described by the CLT than by the CDE. However, early solute breakthrough was underestimated at most depths. Mean travel time and dispersivity were estimated using the temporal moments of Crt*(z, t) with the assumption of a stochastic‐convective transport process. In the loamy soil, solute was traveling from a heterogeneous, macroporous top soil toward a subsoil containing significantly fewer macropores. The flow of solutes through the macropores is not detected by the TDR probes, resulting in a larger observed mean travel time compared with the expected mean travel time based on the piston flow model and no increase in dispersivity. In contrast, in the subsoil the observed and expected mean travel times were in good agreement, and dispersivity increased with depth. In the silty‐loam soil, mean travel times derived from concentration measurements were larger than the expected mean travel times based on the piston flow model, implying temporal storage of solutes in stagnant water zones. Dispersivity also showed deviations from the expected linear increase with depth, probably because of changing soil properties with depth.
Application of time domain reflectometry to determination of volumetric water content in rock
Authors: Sakaki Toshihiro , Sugihara Kozo , Adachi Tetsuya , Nishida Kaoru , Lin Wei‐ren
Published: February 2004

Time domain reflectometry (TDR) is a widely used technique for measuring soil water content. To examine its applicability to rock, the authors applied TDR to a variety of rocks in the laboratory. The obtained relationships between the apparent dielectric constant and the volumetric water content showed a behavior that can be partly explained by the effect of gaps between the TDR probe and rock. For rocks with an effective porosity smaller than that of soil, the well‐known model presented by Topp et al. [1980] for soil tended to overestimate the water content. For such rocks it was determined that an individual calibration was needed for accurate determination of water content. If no experimental calibration is possible, frequently used mixing models may be used to establish the calibration function. Our investigations suggest that TDR showed the potential for measuring the apparent dielectric constant of rock and, further, for determining water content in rock.
Soil water and the persistence of floods and droughts in the Mississippi River Basin
Authors: Bonan Gordon B. , Stillwell‐Soller Lana M.
Published: February 2004

In six independent multiyear simulations of the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM3) coupled to the NCAR Land Surface Model (LSM 1.0), the Mississippi River Basin stands out as a region in which surface air temperature is, during summer months, negatively correlated with soil water and precipitation. To determine if these correlations represent, in part, a land surface feedback in which wet soils caused by high rates of precipitation lead to higher latent heat fluxes, creating a cooler, moister atmosphere, and vice versa, several experiments in which soil water was initialized to either wet (saturated) or dry (wilting point) were performed. In an ensemble of five wet and five dry 60‐day simulations for summer conditions, initially wet soils resulted in cold surface air temperature compared to initially dry soils. Latent heat flux increased and sensible heat flux decreased in the wet experiment compared to the dry experiment only for the first 30 days even though the surface was colder and wetter than the dry experiment throughout the full 60 days. Precipitation increased for the initially wet soils compared to the dry soils over much of the Mississippi River Basin, but only during the first 30 days. This increase was small, and most of the increased flux of water into the atmosphere was advected out of the region. The magnitude of the wet‐dry signal depended on the manner in which soil water limited evapotranspiration. A step‐function response, in which soil water did not limit evapotranspiration until near wilting point, produced a stronger signal than a linear ramping function scaled between field capacity and wilting point. These results suggest that soil moisture feedbacks amplify the severity and persistence of floods and droughts and that the manner in which soil water limits evapotranspiration, which is poorly understood, is a key control of this response.
Uncertainty of monthly rainfall estimates from rain gauges in the Global Precipitation Climatology Project
Authors: McCollum Jeffrey R. , Krajewski Witold F.
Published: February 2004

The Global Precipitation Climatology Project (GPCP), initiated by the World Climate Research Program, has as a main objective the production of monthly global rainfall estimates on a 2.5° × 2.5° longitude/latitude grid by combining different sources of information such as satellite remote sensing and rain gauges. It is important to understand the accuracy of the rain gauge estimates of mean area rainfall because these are considered the most reliable estimates for regions with high numbers of gauges. Methods to model the error resulting from using rain gauge data to estimate the spatially averaged rainfall accumulation have been developed previously. Three of these methods are investigated in this study: an empirical equation derived from rain gauge data, an analytical equation derived from statistical concepts, and an empirical equation derived from theory with parameters determined from calibration. Simulations are performed to determine the utility of these three approaches in estimating the error of the rain gauge mean in the context of the GPCP.
The regional persistence and variability of annual streamflow in the United States
Authors: Vogel Richard M. , Tsai Yushiou , Limbrunner James F.
Published: February 2004

Inference from individual streamflow records can be extremely misleading, even for large samples. One is often tempted to trust information available from a streamflow record rather than to exploit regional average statistics of those records. This study documents that regional average streamflow statistics usually contain much more information about the variability and persistence of streamflow at a particular site than does the individual streamflow record for that site. Experiments are performed using time series of annual streamflow at 1544 gauging stations across the continental United States. We document that 18 broad water resource regions of the United States are homogeneous in terms of the year‐to‐year persistence of streamflow, whereas much smaller regions are required to obtain homogeneity in terms of the variability of streamflow. Classical homogeneity measures ignore the serial correlation of streamflow. Instead, homogeneity is quantified using the sampling properties of at‐site estimates of the coefficient of variation Cυ and lag‐one correlation ρ1 of annual streamflows. Additional experiments using the Hurst coefficient reveal that the long‐term persistence structure of historical annual streamflow series is indistinguishable from the long‐term persistence structure of either an AR(1) or ARMA(1,1) process. If historical flow series are generated from either an AR(1) or ARMA(1,1) process, then even given 1544 observed time series, we are unable to distinguish between those two processes.
Reactive transport modeling of redox geochemistry: Approaches to chemical disequilibrium and reaction rate estimation at a site in northern Wisconsin
Authors: Keating Elizabeth Harrison , Bahr Jean M.
Published: February 2004

The purpose of this study is to investigate the hydrology and redox geochemistry of shallow groundwater discharging to a stream in northern Wisconsin. In this organic‐rich aquifer, we observe both oxygen reducing zones and iron reducing zones whose boundaries are roughly constant over time. To investigate the apparent steady state between solute fluxes and redox reaction rates, we develop a reactive transport model of carbon oxidation. We use a “quasi‐kinetic,” “partial‐equilibrium” approach to modeling redox reactions, a hybrid approach between traditional equilibrium approaches and fully kinetic approaches that require large computer resources. Our model suggests that observed trends in redox sensitive elements can only be explained by oxidation rates that are both dependent on the predominant electron acceptor and are spatially variable. Our coupled models provide field‐based estimates of redox kinetics, which are otherwise difficult to obtain in hydrologically complex systems.
Recurrent erysipelas: risk factors
Authors: Pavlotsky Felix , Amrani Shalom , Trau Henry
Published: February 2004

Background: Several systemic and regional risk factors have been described for erysipelas. However, those predisposing for recurrent episodes are not well defined.

Materials and methods: We performed a retrospective analysis of 574 patients hospitalized in our institution during a 3 year period. The analysis included demographic, epidemiologic, and medical chart review data with special attention to background disorders. The patients with single and recurrent episodes of erysipelas were compared.

Results: The recurrent cases occurred mainly in the lower limb with several risk factors that were statistically more common than in the single episode group including overweight, venous insufficiency, lymphedema, tinea pedis, and previous regional surgical intervention or trauma.

Conclusions: Patients with erysipelas, especially when it involves the lower limb, should be instructed to reduce weight, control venous insufficiency and/or lymphedema and to emphasize prevention and treatment of tinea pedis. The role of prophylactic antibiotics requires further study.
Major determinants of optic nerve head topographic characteristics in a normal Turkish population
Authors: Akar Yusuf , Orhan Mehmet , İrkeç Murat , Karaag˘aoglu Ergun
Published: February 2004

Aim: To determine the factors affecting the topographic characteristics of the optic nerve head in a normal Turkish population.

Methods: A cross‐sectional study was performed on the optic nerve head of the right eyes of 613 healthy subjects of both sexes aged 11−77 years using a confocal scanning laser ophthalmoscope. The study population was divided into three groups (<20 years, 20−50 years, and>50 years) to evaluate age‐related changes in the optic nerve head topography. A total of 15 variables were determined. Statistical analysis was performed using Student's t‐test, anova, Tukey HSD test, linear regression analysis and Pearson's correlation coefficient.

Results: Four eyes were excluded from the study due to poor image quality. There were 307 female subjects and 302 male subjects. The mean age of the subjects was 42.1 ± 15.1 years. The mean optic disc areas were 1.99 ± 0.45 mm2 and 1.97 ± 0.41 mm2 for male and female subjects, respectively. The disc area of the subjects ranged between 1.01 and 4.19 mm2. Disc area was found to be associated with all of the optic nerve head variables studied, and was also found to be significantly increased with advancing age (P < 0.05). The only variable that showed a sex‐related difference was neuroretinal rim volume, which was found to be higher in female subjects in all cases.

Conclusion: Optic disc area was found to be the main determinant of the optic nerve head topography in a normal population. Optic disc area was found to be significantly increased with ageing in a normal population. These acquired changes to the optic disc could suggest stretching of the scleral ring, which may highlight the role of advancing age on the pathogenesis of glaucomatous optic neuropathy.
Outcome of consecutive trabeculectomy
Authors: Zalish Miriam , Oron Yoram , Geyer Orna
Published: February 2004

Purpose: To establish a criterion for success of primary phakic trabeculectomy in the second eye of the same patient, using the first operated eye as a predictor for the surgical outcome.

Methods: The outcome of primary phakic trabeculectomy was retrospectively compared in both eyes of 23 patients. Sixteen patients were treated with antimetabolites and seven were not. Postoperative intraocular pressure and number of glaucoma medications in paired eyes of the same patients were compared. Surgical success was defined as postoperative IOP of <20 mmHg without medication. Bleb morphology and the number of glaucoma medications were also compared in both eyes.

Results: There was a positive correlation between the two eyes of a patient in the IOP values at each postoperative time point in both groups (with and without antimeta­bolites) (P > 0.05). At the last follow‐up visit after trabeculectomy, the number of glaucoma medications used in paired eyes were not significantly different (P > 0.83). Surgical failure occurred more often in paired eyes than in single eyes. Bilateral failure occurred in 60% (3/5) of the failed trabeculectomies with antimetabolites and in 100% (3/3) of the failed trabeculectomies without antimetabolites.

Conclusion: Trabeculectomy outcome in paired eyes of patients was similar in both antimetabolites treated and untreated eyes. Thus, trabeculectomy outcome in the first operated eye can predict the surgical result in the second eye of the same patient.
Late reactivation of thyroid orbitopathy
Authors: Selva Dinesh , Chen Celia , King Georgina
Published: February 2004

Background: Thyroid orbitopathy is characterized by spontaneous remissions and exacerbations. Although data on the natural history are scarce, the active phase is usually self‐limited, encompassing an average period of 18−36 months. Late reactivation, defined as active orbitopathy occurring after more than 5 years of quiescent disease, appears to be an uncommon and poorly documented event. The aim of the present study was to assess the incidence and characteristics of late reactivation of thyroid orbitopathy within a tertiary referral orbital clinic.

Methods: A retrospective case review was conducted of patients with thyroid orbitopathy seen at the Royal Adelaide Hospital Orbital Clinic between 1996 and 2001.

Results: From 193 cases of thyroid orbitopathy, eight cases (5%) of late reactivation were identified. The mean age of patients was 51 years (range 32−76 years) with a female to male ratio of 3:1. All cases presented with proptosis and seven demonstrated increased diplopia and gaze restriction. Signs of soft tissue inflammation were seen in three cases. All were euthyroid at presentation with a past history of thyroid orbitopathy and hyperthyroidism. One patient had an association of smoking with reactivation but the remainder had no discernible precipitants. The average interval between the initial orbitopathy and reactivation was 12 years (range 6−30 years). Computed tomography revealed enlarged extraocular muscles in seven cases and two showed partial response to treatment with low dose radiotherapy and steroids. The average length of disease activity was 14 months (range 9−18 months).

Conclusion: Late reactivation of thyroid orbitopathy appears to be an uncommon phenomenon. It may occur under euthyroid conditions with no obvious precipitants and often presents as a reactivation of myopathy.
Arthur Thomas Paterson: the life and times of a New Zealand ophthalmologist
Authors: Hart Richard H , McGhee Charles NJ
Published: February 2004

Arthur Thomas Paterson was a pre‐eminent New Zealand ophthalmologist who settled in the United Kingdom after the First World War and became a leading figure in the development of ophthalmic services in the north‐east of England. This vignette explores his contributions to clinical education and the establishment of comprehensive ophthalmic services in Newcastle upon Tyne. It also highlights the Arthur Thomas Paterson scholarship bequest to enable New Zealand ophthal­mologists to acquire additional specialist training in inter­national centres of excellence.
Clinical Case Notes
Authors: Chou Shih‐Yu , Kao Shu‐Ching , Hsu Wen‐Ming
Published: February 2004

A 43‐year‐old man presented suffering from decreasing vision in both eyes for 3 months. The patient's visual acuity was 6/20 (non‐corrected) in the right eye and 6/10 (−1.75/−1.00 × 91) in the left. Ocular examination of both eyes revealed anterior subcapsular opacities of both lenses with the right eye being more severe than the left. He had been taking finasteride (Propecia; Merck, Sharp and Dohme) at 1 mg/day for 3 years to treat early stage of androgenic alopecia. It was highly suspected that finasteride was associated with the anterior subcapsular opacity on the lens, and the patient therefore discontinued use of finasteride. He underwent uneventful cataract extraction surgery and intraocular lens implantation of the right eye. One month after cataract surgery in the right eye, the best‐corrected visual acuity was right 6/6 (−1.25) and left 6/10 (−2.00/−0.50 × 100). To the best of the authors’ knowledge, this is the first reported case of Propecia‐associated cataract.
Clinical Case Notes
Authors: Sanfilippo Paul , Troutbeck Robyn , Vandeleur Kevin , Lenton Lee
Published: February 2004

Adult‐onset foveomacular vitelliform dystrophy is characterized by a focal, round or oval shaped, subretinal foveal yellow lesion that presents bilaterally and usually symmetrically in the fourth or fifth decade of life. In addition to clinical observation, diagnosis of the disease process has until now been assisted by electrophysiological and fundus fluorescein studies. Two cases are presented that correlate the clinical fundus appearance with optical coherence tomo­graphy findings and describe the location of the yellow vitelliform material.
Evaluating Australia’s National Medicines Policy using geographical mapping
Authors: Roughead E. E. , Monteith G. R. , Harvey K. J. , Tett S. E.
Published: February 2004

Abstract

Background: There has been a proliferation of quality use of medicines activities in Australia since the 1990s. However, knowledge of the nature and extent of these activities was lacking. A mechanism was required to map the activities to enable their coordination.

Aims: To develop a geographical mapping facility as an evaluative tool to assist the planning and implementation of Australia’s policy on the quality use of medicines.

Methods: A web‐based database incorporating geographical mapping software was developed. Quality use of medicines projects implemented across the country was identified from project listings funded by the Quality Use of Medicines Evaluation Program, the National Health and Medical Research Council, Mental Health Strategy, Rural Health Support, Education and Training Program, the Healthy Seniors Initiative, the General Practice Evaluation Program and the Drug Utilisation Evaluation Network. In addition, projects were identified through direct mail to persons working in the field.

Results: The Quality Use of Medicines Mapping Project (QUMMP) was developed, providing a Web‐based database that can be continuously updated. This database showed the distribution of quality use of medicines activities by: (i) geographical region, (ii) project type, (iii) target group, (iv) stakeholder involvement, (v) funding body and (vi) evaluation method. At September 2001, the database included 901 projects. Sixty‐two per cent of projects had been conducted in Australian capital cities, where approximately 63% of the population reside. Distribution of projects varied between States. In Western Australia and Queensland, 36 and 73 projects had been conducted, respectively, representing approximately two projects per 100 000 people. By comparison, in South Australia and Tasmania approximately seven projects per 100 000 people were recorded, with six per 100 000 people in Victoria and three per 100 000 people in New South Wales. Rural and remote areas of the country had more limited project activity.

Conclusions: The mapping of projects by geographical location enabled easy identification of high and low activity areas. Analysis of the types of projects undertaken in each region enabled identification of target groups that had not been involved or services that had not yet been developed. This served as a powerful tool for policy planning and implementation and will be used to support the continued implementation of Australia’s policy on the quality use of medicines. (Intern Med J 2002; 32: 66–71)
Minidose (1 mg) warfarin as prophylaxis for central vein catheter thrombosis
Authors: Heaton D. C. , Han D. Y. , Inder A.
Published: February 2004

Abstract

Background: Central vein catheters, which are used in the treatment of cancer patients, are prone to thrombotic complications of the catheter or adjacent vein. Previous studies suggest that 1 mg warfarin daily (minidose) can significantly reduce that risk.

Aims: This study aims to establish whether minidose warfarin could reduce catheter‐related thrombosis in adult patients with haematological malignancies.

Methods: Patients were randomly selected to receive warfarin or not. The end‐points studied were: (i) occlusion by thrombus, (ii) removal of catheter for other reasons or (iii) 90 days free of thrombus.

Results: There was no significant difference in the incidence of catheter thrombosis or venous thrombosis and no significant variation in catheter survival between the study and control groups.

Conclusions: This study found no benefit of the routine use of minidose warfarin for prophylaxis of central vein catheter thrombosis in patients with haematolog‐ ical malignancies and therefore does not support the routine use of minidose warfarin for prophylaxis in such patients. (Intern Med J 2002; 32: 84–88)
Advanced glycation endproducts and pro‐inflammatory cytokines in transgenic Tg2576 mice with amyloid plaque pathology
Authors: Münch Gerald , Apelt Jenny , Rosemarie‐Kientsch‐Engel  , Stahl Peter , Lüth Hans Joachim , Schliebs Reinhard
Published: February 2004

Increased expression and altered processing of the amyloid precursor protein (APP) and generation of β‐amyloid peptides is important in the pathogenesis of amyloid plaques in Alzheimer's disease (AD). Transgenic Tg2576 mice overexpressing the Swedish mutation of human APP exhibit β‐amyloid deposition in the neocortex and limbic areas, accompanied by gliosis and dystrophic neurites. However, murine plaques appear to be less cross‐linked and the mice show a lower degree of inflammation and neurodegeneration than AD patients. ‘Advanced glycation endproducts (AGEs)’, formed by reaction of proteins with reactive sugars or dicarbonyl compounds, are able to cross‐link proteins and to activate glial cells, and are thus contributing to plaque stability and plaque‐induced inflammation in AD. In this study, we analyze the tissue distribution of AGEs and the pro‐inflammatory cytokines IL‐1β and TNF‐α in 24‐month‐old Tg2576 mice, and compare the AGE distribution in these mice with a younger age group (13 months old) and a typical Alzheimer's disease patient. Around 70% of the amyloid plaque cores in the 24‐month‐old mice are devoid of AGEs, which might explain their solubility in physiological buffers. Plaque associated glia, which express IL‐1β and TNF‐α, contain a significant amount of AGEs, suggesting that plaques, i.e. Aβ as its major component, can induce intracellular AGE formation and the expression of the cytokines on its own. In the 13‐month‐old transgenic mice, AGEs staining can neither be detected in plaques nor in glial cells. In contrast, AGEs are present in high amounts in both plaques and glia in the human AD patient. The data obtained in this show interesting differences between the transgenic mouse model and AD patients, which should be considered using the transgenic approach to test therapeutical strategies to eliminate plaques or to attenuate the inflammatory response in AD.
Alzheimer's associated variant ubiquitin causes inhibition of the 26S proteasome and chaperone expression
Authors: Hope Andrew D. , De Silva Rohan , Fischer David F. , Hol Elly M. , Van Leeuwen Fred W. , Lees Andrew J.
Published: February 2004

Intracellular protein inclusions in Alzheimer's disease and progressive supranuclear palsy contain UBB+1, a variant ubiquitin. UBB+1 is able block the 26S proteasome in cell lines. Proteasome inhibition by drug action has previously been shown to induce a heat‐shock response and render protection against stress. We investigated UBB+1 by developing a stable, conditional expression model in SH‐SY5Y human neuroblastoma cells. Induction of UBB+1 expression caused proteasome inhibition as was confirmed by reduced ability to process misfolded canavanyl proteins, accumulation of GFPu, a proteasome substrate, and reduced cleavage of a fluorogenic substrate. We show that expression of UBB+1 induces expression of heat‐shock proteins. This priming of the chaperone system in these cells promotes a subsequent resistance to tert‐butyl hydroperoxide‐mediated oxidative stress. We conclude that although UBB+1‐expressing cells have a compromised ubiquitin‐proteasome system, they are protected against oxidative stress conditions.
Differential neurochemical properties of central serotonergic transmission in Roman high‐ and low‐avoidance rats
Authors: Giorgi O. , Piras G. , Lecca D. , Hansson S. , Driscoll P. , Corda M. G.
Published: February 2004

The selective breeding of Roman high‐ (RHA/Verh) and low‐avoidance (RLA/Verh) rats for rapid versus poor acquisition of active avoidant behaviour has produced two behavioural phenotypes with different performances in a variety of animal models of anxiety, in which RLA/Verh rats are consistently more fearful than RHA/Verh rats. In addition, these two lines display different functional properties of brain neurotransmitters like serotonin (5‐HT), known to be involved in the expression of anxiety‐ and depression‐related behaviours. Therefore, we used brain microdialysis and [3H]‐citalopram binding autoradiography to characterize further the neurochemical properties of 5‐HTergic transmission in the two lines. No significant line‐related differences were detected in the basal 5‐HT output in the frontoparietal cortex (FPCx). In contrast, the increase in the cortical 5‐HT output elicited by the systemic administration or the local application, via reverse dialysis, of chlorimipramine and fluoxetine was more robust in RHA/Verh than in RLA/Verh rats. Moreover, the binding signal of [3H]‐citalopram to 5‐HT re‐uptake sites was more intense in the FPCx of RHA/Verh rats than in their RLA/Verh counterparts. These findings suggest that the functional tone of the 5‐HTergic projection to the FPCx is stronger in the RHA/Verh line relative to the RLA/Verh line. It is proposed that RLA/Verh rats may be used as a model with heuristic value for studying the role of 5‐HTergic transmission in anxiety and in the anxiolytic effects of monoamine re‐uptake inhibitors.
Modulation of the histaminergic system and behaviour by α‐fluoromethylhistidine in zebrafish
Authors: Peitsaro Nina , Kaslin Jan , Anichtchik Oleg V. , Panula Pertti
Published: February 2004

The functional role of histamine (HA) in zebrafish brains was studied. Zebrafish did not display a clear circadian variation in brain HA levels. Loading of zebrafish with l‐histidine increased HA concentration in the brain. A single injection of the histidine decarboxylase (HDC) inhibitor, α‐fluoromethylhistidine (α‐FMH), gave rise to a rapid reduction in zebrafish brain HA. Low HDC activity in the brain after injections verified the effect of α‐FMH. A reduction in the number of histaminergic fibres but not neurones and an increased expression of HDC mRNA was evident after α‐FMH. Automated behavioural analysis after α‐FMH injection showed no change in swimming activity, but abnormalities were detected in exploratory behaviour examined in a circular tank. No significant behavioural changes were detected after histidine loading. The time spent for performance in the T‐maze was significantly increased in the first trial 4 days after α‐FMH injections, suggesting that lack of HA may impair long‐term memory. The rostrodorsal telencephalon, considered to correspond to the mammalian amygdala and hippocampus in zebrafish, is densely innervated by histaminergic fibres. These results suggest that low HA decreases anxiety and/or affects learning and memory in zebrafish, possibly through mechanisms that involve the dorsal forebrain.