bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic Cancer Risk Assessment and Counseling: Recommendations of the National Society of Genetic Counselors
Authors: Trepanier Angela , Ahrens Mary , McKinnon Wendy , Peters June , Stopfer Jill , Grumet Sherry Campbell , Manley Susan , Culver Julie O. , Acton Ronald , Larsen‐Haidle Joy , Correia Lori Ann , Bennett Robin , Pettersen Barbara , Ferlita Terri Diamond , Costalas Josephine Wagner , Hunt Katherine , Donlon Susan , Skrzynia Cecile , Farrell Carolyn , Callif‐Daley Faith , Vockley Catherine Walsh
Published: March 2004

These cancer genetic counseling recommendations describe the medical, psychosocial, and ethical ramifications of identifying at‐risk individuals through cancer risk assessment with or without genetic testing. They were developed by members of the Practice Issues Subcommittee of the National Society of Genetic Counselors Cancer Genetic Counseling Special Interest Group. The information contained in this document is derived from extensivereview of the current literature on cancer genetic risk assessment and counseling as well as the personal expertise of genetic counselors specializing in cancer genetics. The recommendations are intended to provid information about the process of genetic counseling and risk assessment for hereditary cancer disorders rather than specific information about individual syndromes. Key components include the intake (medical and family histories), psychosocial assessment (assessment of risk perception), cancer risk assessment (determination and communication of risk), molecular testing for hereditary cancer syndromes (regulations, informed consent, and counseling process), and follow‐up considerations. These recommendations should not be construed as dictating an exclusive course of management, nor does use of such recommendations guarantee a particular outcome. These recommendations do not displace a health care provider's professional judgment based on the clinical circumstances of a client.
Short‐ and Long‐Term Impact of Receiving Genetic Mutation Results in Women at Increased Risk for Hereditary Breast Cancer
Authors: Lim Jacqueline , Macluran Mariette , Price Melanie , Bennett Barbara , Butow Phyllis ,   kConFab Psychosocial Group
Published: March 2004

Forty‐seven unaffected women from high‐risk breast cancer families who had received results for hereditary breast/ovarian predisposition genes between 1 month and 5 years ago were interviewed regarding their experiences. Women responded to open‐ended questions. The initial emotional turmoil reported by most was generally short lived. However, the impact of genetic testing went beyond the individual to the extended family and social context, particularly in the short‐term. A common theme was the difficulty associated with divulging a result to family members, who were also adjusting to their own result. The majority of carriers reported advantages that were both physical (options for surveillance programs and prophylactic surgery) and emotional (reduced uncertainty, increased awareness of options and knowledge about risk, preparation time). Most carriers reported no change in lifestyle although some reported discovering their mutation status as a positive life‐changing experience. Implications for genetic counseling and further research are discussed.
Initiation of Reflective Frames in Counseling for Huntingtons Disease Predictive Testing
Authors: Sarangi Srikant , Bennert Kristina , Howell Lucy , Clarke Angus , Harper Peter , Gray Jonathon
Published: March 2004

Genetic professionals and clients are likely to assign different meanings to the extended format of the counseling protocols for predictive testing. In order to facilitate informed, client‐centerd decisions about the possibility of predictive testing, counselors routinely use the question format to initiate what we call “reflective frames” that invite clients to discuss their feelings and encourage them to adopt introspective and self‐reflective stances toward their own experience—spanning the past, the present, and the hypothetical future. We suggest that such initiations of reflective frames constitute a key element of counselors' nondirective stance, although the exact nature of their formulations can be complex and varied. Examining 24 Huntington's Disease (HD) clinic sessions involving 12 families in South Wales with the tools of discourse analysis, our focus in this paper is twofold: (i) to propose a classification of six types of reflective questions (e.g. nonspecific invites, awareness and anxiety, decision about testing, impact of result, dissemination, and other) and to examine their distribution across the various clinic appointments, and (ii) to investigate the scope of these questions in terms of temporal and social axes. We link our analysis to the current debate within the genetic counseling profession about the merits of reflection‐ versus information‐focused counseling styles and the need to abide by professionally warranted and institutionally embedded counseling protocols.
Family Environments of Women Seeking BRCA1/BRCA2 Genetic Mutation Testing: An Exploratory Analysis
Authors: Keenan Lisa A. , Lesniak Karen T. , Guarnaccia Charles A. , Althaus Becky , Ethington Gaby , Blum Joanne L.
Published: March 2004

Although there is some understanding of the shared characteristics and predictors of psychological distress of women participating in hereditary breast and ovarian cancer registries, these same characteristics are only beginning to be identified in research on community women seeking genetic testing for BRCA1/BRCA2 gene mutations. This study provides an initial exploration of characteristics associated with family environments for 51 community women waiting to receive such genetic testing results. Thirty‐four of the 36 women classified on family environment type of the Family Environment Scale (FES) were from Personal Growth‐Oriented families. Comparisons of women with and without personal cancer histories resulted in a trend for women with personal cancer histories to be classified as from Independence‐Oriented families. Reported distress appears to vary for different family emphases based on family and personal cancer history. A moral–religious family emphasis consistently appeared to be associated with decreased psychological distress. Preliminary analyses comparing these community women (who were not part of a hereditary registry but were self‐ or physician‐referred) seeking genetic testing with normal and distressed family means found that increased cohesion and expressiveness may be related to decreased conflict, indicative of potentially supportive family environments for these women. When compared with normative data, a subset consisting of the Ashkenazi Jewish women showed a trend of less cohesion than normal families, but similar cohesion levels as distressed families.
Characterization of Siberian Arctic coastal sediments: Implications for terrestrial organic carbon export
Authors: Guo Laodong , Semiletov Igor , Gustafsson Örjan , Ingri Johan , Andersson Per , Dudarev Oleg , White Daniel
Published: March 2004

Surface sediments were collected during the 2000 TransArctic Expedition along the Siberian Arctic coastline, including the Ob, Yenisey, Khatanga, Lena, and Indigirka estuaries. Sediments were characterized for elemental composition (total organic carbon, TOC, black carbon, BC, and total N, as well as major and trace elements), isotopic signature (δ13C, δ15N, Δ14C, εNd, 87Sr/86Sr), and organic molecular composition to better understand river export variations over the large spatial scale of the Siberian Arctic. On average, 79 ± 9% of the total C in sediments was organic while 21 ± 9% was inorganic. BC made up 9 ± 4% of the TOC pool, with a general increasing trend from west to east along the Siberian coast. The combined Nd‐ and Sr‐isotopes (εNd and 87Sr/86Sr) were used to define two distinct sediment sources between east and west Siberian regions with the Khatanga River as a boundary. Data from pyrolysis‐GC/MS of the sedimentary organic carbon (SOC) indicated an increase in the freshness of the organic matter from west to east on the Siberian Arctic coast, with increasing relative abundance of furfurals (polysaccharides) with respect to nitriles. Values for the δ13C of SOC ranged from −27.1‰ (mostly terrigenous) to −23.8‰, while δ15N increased from east to west (3.1 to 5.2‰) with a significant correlation with C/N ratio. Values for the Δ14C of SOC ranged from −805 to −279‰, with a consistent trend increasing from the east (Indigirka River) to the west (Ob River). These Δ14C values corresponded to a 14C age of 2570 ± 30 yBP in the Ob estuary and 13,050 ± 50 yBP in the Indigirka estuary. Most importantly, Δ14C values were significantly correlated with the ratio of BC/TOC (R2 = 0.91, n = 6), consistent with the distribution pattern of increasing permafrost zone from the west to the east along the Siberian coast. Together, our results suggest that older OC was derived from the release of recalcitrant BC during permafrost thawing and riverbank and coastal erosion, likely enhanced by ongoing environmental changes in the northern ecosystem.
Acidification of forest soil in Russia: From 1893 to present
Authors: Lapenis A. G. , Lawrence G. B. , Andreev A. A. , Bobrov A. A. , Torn M. S. , Harden J. W.
Published: March 2004

It is commonly believed that fine‐textured soils developed on carbonate parent material are well buffered from possible acidification. There are no data, however, that document resistance of such soils to acidic deposition exposure on a timescale longer than 30–40 years. In this paper, we report on directly testing the long‐term buffering capacity of nineteenth century forest soils developed on calcareous silt loam. In a chemical analysis comparing archived soils with modern soils collected from the same locations ∼100 years later, we found varying degrees of forest‐soil acidification in the taiga and forest steppe regions. Land‐use history, increases in precipitation, and acidic deposition were contributing factors in acidification. The acidification of forest soil was documented through decreases in soil pH and changes in concentrations of exchangeable calcium and aluminum, which corresponded with changes in communities of soil microfauna. Although acidification was found at all three analyzed locations, the trends in soil chemistry were most pronounced where the highest loading of acidic deposition had taken place.
Speciation and fluxes of nutrients (N, P, Si) from the upper Yukon River
Authors: Guo Laodong , Zhang Jia‐Zhong , Guéguen Céline
Published: March 2004

Water samples were collected from the Yukon River near the Stevens Village Station from May to September 2002 and analyzed for nutrients (N, P, and Si) in dissolved, particulate, organic, and inorganic forms to examine temporal variations in nutrient concentrations, fluxes, and phase partitioning. Both NO3 and PO4 concentrations in the Yukon River were much lower than those of world rivers, with an average concentration of 2.43 ± 0.63 μM‐N and 0.053 ± 0.040 μM‐P, respectively. Si(OH)4 concentrations were more comparable to those of world rivers, with an average concentration of 82 ± 21 μM‐Si. Integrated annual fluxes were 2.4 × 108 mole‐NO3, 3.4 × 106 mole‐PO4, and 8.7 × 109 mole‐Si(OH)4, respectively. Nutrient discharge during the river ice open season contributed 73 to 95% of the annual flux depending on nutrient species. Within the total N pool transported by the Yukon River, dissolved inorganic N comprised 7 ± 4% and particulate N made up 25 ± 10%, while dissolved organic N (DON) was the dominant N species (with an average of 67 ± 10%). In contrast, P was predominantly partitioned in the particulate phase (with an average of 94 ± 6%), leaving 4 ± 5% of the total P in the dissolved organic phase and ∼2 ± 1% in the dissolved inorganic phase. The partitioning of N and P indicates that the transformation between dissolved and particulate or inorganic and organic phases may play a critical role in controlling the flux of bioavailable nutrients and thus the nutrient dynamics in the Yukon River Basin and its coastal region. Nutrient specific fluxes normalized to drainage area in the Yukon River Basin were 0.57 mmole/m2/yr for NO3, 0.012 mmole/m2/yr for PO4, and ∼19 mmole/m2/yr for Si(OH)4, respectively. The relatively low specific fluxes of NO3 and PO4 in the Yukon River Basin reflect its pristine status or little anthropogenic influence, whereas cold climate in the Arctic/subarctic region may be responsible for its lower Si(OH)4 specific flux, in agreement with a general trend of increasing Si specific flux with decreasing latitude in global river systems. A warming climate and thus deeper permafrost active layer in the Yukon River watershed would likely enhance the export flux of nutrients into the Bering Sea.
F‐region plasma distribution seen from TIMED/GUVI and its relation to the equatorial spread F activity
Authors: Kil Hyosub , DeMajistre Robert , Paxton Larry J.
Published: March 2004

The OI 135.6‐nm nightglow images from GUVI on board the TIMED satellite provide a unique opportunity to investigate the global plasma distribution in the F region. We report that there exist large seasonal‐longitudinal variations in the F‐region plasma density which may explain some aspects of the equatorial spread F (ESF) morphology. We suggest that an occurrence of high plasma density is responsible for the strong ESF activity during equinox periods at most longitudes, whereas an occurrence of low plasma density is responsible for the suppressed ESF activity during northern summer in the American‐Atlantic sector.
Biotic enhancement of weathering, atmospheric oxygen and carbon dioxide in the Neoproterozoic
Authors: Lenton Timothy M. , Watson Andrew J.
Published: March 2004

It has been suggested that biological colonization of the land surface began in the Neoproterozoic 1000–544 million years ago (Ma). We hypothesize that this colonization involved selective weathering of P from rocks, as well as an amplification of overall weathering rates. We show that two recent models, despite differences in the feedback mechanisms represented, predict that an increase in the weathering flux of P to the ocean would have caused a rise in atmospheric O2 in the Neoproterozoic. This in turn may have provided a necessary condition for the evolution of animals with hard skeletons seen in the ‘Cambrian explosion’. Increased weathering of silicate rocks would also have caused a decline in atmospheric CO2, which could have been a causal factor in the Neoproterozoic glaciations.
Lightning charge moment changes in U.S. High Plains thunderstorms
Authors: Cummer Steven A. , Lyons Walter A.
Published: March 2004

We report measurements of impulsive (2 ms) lightning charge moment changes in more than 1000 cloud‐to‐ground (CG) return strokes detected by the National Lightning Detection Network in three United States High Plains storms during the Severe Thunderstorm Electrification and Precipitation Study (STEPS) field program of 2000. The positive CG strokes (+CGs) in a mesoscale convective system exhibit an unusual charge moment distribution with a small median and long tail. Analysis suggests the presence of two different classes of +CGs in this MCS, one with small charge moment changes (≤50 C km) and the other containing larger charge moment changes (50–1400 C km). The distributions of negative cloud‐to‐ground stroke charge moment changes are roughly log‐normal in shape with means varying from 17.7 to 36.8 C km. When combined with past measurements these means vary by a factor of 4 between storms, and there is probably not a single distribution that represents well all storms.
Electrical conductivity of unsaturated porous media: Pore‐scale model and comparison with laboratory data
Authors: Dalla E. , Cassiani G. , Brovelli A. , Pitea D.
Published: March 2004

This paper presents a novel pore‐scale approach for the derivation of electrical properties of porous media. In this approach we create a digital porous medium on the basis of experimental grain‐size distribution data and apply a drainage simulator based on pore‐morphology analysis. Then we simulate via finite difference discretization the electrical charge flow within the two‐fluid and solid pore‐scale distributions, and derive the effective resistivity of the porous medium. Simulation results have been compared with resistivity data from a UK Permo‐Triassic Sandstone (Sherwood S.). Agreement between measured and simulated bulk conductivities at different saturation values is excellent; this confirms the validity of the adopted approach, and its underlying assumptions.
Rupture model of the 1999 Düzce, Turkey, earthquake deduced from high and low frequency strong motion data
Authors: Birgören Gülüm , Sekiguchi H. , Irikura K.
Published: March 2004

We investigated the rupture process of the 1999 Düzce Earthquake by applying the multi time‐window linear waveform inversion method to low‐frequency ground motions (≤0.5 Hz) in the near source area. Then, we performed the forward modelling of higher frequency ground motions (0.3–10.0 Hz) by the Empirical Green's Function (EGF) method to image the strong motion generation area (SMGA). We also examined the source model to check whether the supershear phenomenon occurred inside the asperities or not. Slip distribution model from the inversion suggests 2 asperities. The maximum slip is obtained as 5 m near the hypocenter. The high first time window front propagation velocity (FTWFPV) and consequently, high apparent rupture velocity found from the investigation of rupture progression indicated that eastern propagation partially showed supershear behaviour. The EGF simulation, which identifies an average rupture velocity (Vr) in SMGA, supports this finding.
The Boycott effect in magma chambers
Authors: Blanchette F. , Peacock T. , Bush J. W. M.
Published: March 2004

We investigate the plausibility of the stratified Boycott effect as a source of layering in magma chambers. Crystal settling within the magma chamber will generate buoyant fluid near the sloping sidewalls whose vertical ascent may be limited by the ambient stratification associated with vertical gradients in SiO2. The resulting flow may be marked by a layered structure, each layer taking the form of a convection cell spanning the lateral extent of the magma chamber. Using parameters relevant to magma chambers, we estimate that such convection cells would be established over a timescale of a month and have a depth on the order of 4m, which is roughly consistent with field observations of strata within solidified chambers.
Export of young terrigenous dissolved organic carbon from rivers to the Arctic Ocean
Authors: Benner Ronald , Benitez‐Nelson Bryan , Kaiser Karl , Amon Rainer M. W.
Published: March 2004

Soils in the drainage basins of Arctic rivers are a major global reservoir of aged organic carbon. The fate of this old carbon is of growing concern as the effects of climate change become more evident in the Arctic. We report natural abundance14C data indicating that dissolved organic carbon (DOC) from several Eurasian and North American rivers is predominantly young and largely derived from recently‐fixed C in plant litter and upper soil horizons. Concentrations of dissolved lignin phenols, unique organic tracers of terrestrial plant material, and14C content in DOC were strongly correlated throughout the Arctic Ocean, indicating terrigenous DOC is mostly young and widely distributed in polar surface waters. These young ages of terrigenous DOC in rivers and the ocean indicate little of the old carbon stored in Arctic soils is currently being mobilized in the dissolved component of continental runoff.
Study of the atmospheric pressure loading signal in very long baseline interferometry observations
Authors: Petrov Leonid , Boy Jean‐Paul
Published: March 2004

Redistribution of air masses due to atmospheric circulation causes loading deformation of the Earth's crust, which can be as large as 20 mm for the vertical component and 3 mm for horizontal components. Rigorous computation of site displacements caused by pressure loading requires knowledge of the surface pressure field over the entire Earth surface. A procedure for computing three‐dimensional displacements of geodetic sites of interest using a 6 hourly pressure field from the National Centers for Environmental Prediction numerical weather models and the Ponte and Ray [2002] model of atmospheric tides is presented. We investigated possible error sources and found that the errors of our pressure loading time series are below the 15% level. We validated our model by estimating the admittance factors of the pressure loading time series using a data set of 3.5 million very long baseline interferometry observations from 1980 to 2002. The admittance factors averaged over all sites are 0.95 ± 0.02 for the vertical displacement and 1.00 ± 0.07 for the horizontal displacements. For the first time, horizontal displacements caused by atmospheric pressure loading have been detected. The closeness of these admittance factors to unity allows us to conclude that on average, our model quantitatively agrees with the observations within the error budget of the model. At the same time we found that the model is not accurate for several stations that are near a coast or in mountain regions. We conclude that our model is suitable for routine data reduction of space geodesy observations.
Green's functions, source signatures, and the normalization of teleseismic wave fields
Authors: Bostock M. G.
Published: March 2004

We examine the canonical source/Green's function separation problem in the context of teleseismic P wave scattering from receiver‐side crust and upper mantle structure. Conventional “receiver function” analysis affords a leading order approximation to the S component of the Green's function but provides no information on P‐to‐P scattering. We demonstrate that an improved estimate of the three‐dimensional Earth's Green's function, including scattered P contributions, can be achieved through consideration of its theoretical spectral properties. Under conditions typical of the real Earth the P component of the Green's function is shown to be minimum phase. This behavior is responsible for the success of receiver functions in mantle studies. The minimum‐phase property is used here to normalize the source signature on P wave seismograms, thereby facilitating implementation of multichannel, multicomponent deconvolution of both Green's function and source signature within the log spectral domain. Examples using both synthetic simulations and seismograms recorded on the Canadian National Seismograph Network illustrate the recovery of accurate and reproducible estimates of the P wave Green's function. Our approach can be adapted to a range of source‐receiver configurations. In particular, it may prove useful in the recovery of compressional properties beneath portable, field arrays where calibration is provided by nearby, permanent installations.
High‐resolution analysis of early diagenetic effects on magnetic minerals in post‐middle‐Holocene continental shelf sediments from the Korea Strait
Authors: Liu Jian , Zhu Rixiang , Roberts Andrew P. , Li Shaoquan , Chang Jeong‐Hae
Published: March 2004

Two studied sediment cores from the Korea Strait contain mud sequences (14 m and 32.62 m in thickness) that were deposited during the last 6,000 years. The sediments have uniform lithology and geochemical properties, however, marked down‐core changes in magnetic properties suggest that diagenesis has significantly impacted the magnetic properties. An expanded view of early diagenetic reactions that affect magnetic mineral assemblages is evident in these rapidly deposited continental shelf sediments compared to deep‐sea sediments. The studied sediments are divided into four descending intervals, based on magnetic property variations. Interval 1 is least affected by diagenesis and has the highest concentrations of detrital magnetite and hematite, and the lowest solid‐phase sulfur contents. Interval 2 is characterized by the presence of paramagnetic pyrite and sharply decreasing magnetite and hematite concentrations, which suggest active reductive dissolution of detrital magnetic minerals. Interval 3 is marked by a progressive loss of hematite with depth, and coincides with the minimum magnetite concentration. Interval 4 has an increasing down‐core enhancement of authigenic greigite, which apparently formed at depths of 3–30 m below the sediment‐water interface due to arrested pyritization reactions. These results indicate delays of thousands of years for acquisition of magnetizations carried by greigite, which suggests that studies of geomagnetic field behavior from greigite‐bearing continental shelf sediments should be conducted with care. Also, virtually complete destruction of detrital magnetic minerals at depth suggests that magnetic studies of rapidly deposited shelf sediments are unlikely to provide a meaningful signature associated with syn‐depositional environmental processes.
Efficient Kalman filter techniques for the assimilation of tide gauge data in three‐dimensional modeling of the North Sea and Baltic Sea system
Authors: Sørensen J. V. T. , Madsen H. , Madsen H.
Published: March 2004

Data assimilation in operational forecasting systems is a discipline undergoing rapid development. Despite the ever increasing computational resources, it requires efficient as well as robust assimilation schemes to support online prediction products. The parameter considered for assimilation here is water levels from tide gauge stations. The assimilation approach is Kalman filter based and examines the combination of the Ensemble Kalman Filter with spatial and dynamic regularization techniques. Further, both a Steady Kalman gain approximation and a dynamically evolving Kalman gain are considered. The estimation skill of the various assimilation schemes is assessed in a 4‐week hindcast experiment using a setup of an operational model in the North Sea and Baltic Sea system. The computationally efficient dynamic regularization works very well and is to be encouraged for water level nowcasts. Distance regularization gives much improved results in data sparse areas, while maintaining performance in areas with a denser distribution of tide gauges.
A numerical comparison of approximations to the Stokes equations used in ice sheet and glacier modeling
Authors: Hindmarsh R. C. A.
Published: March 2004

A computational analysis of the accuracy of different approximations to the Stokes equations for momentum balance used in ice sheet modeling is performed by solving a particular tractable form of the equations appropriate for small perturbations of the ice surface, describing the uniform flow of ice with a Glen rheology on an infinitely long and broad section. The approximants comprise the shallow ice approximation and various schemes for incorporating longitudinal stresses and, in one case, the horizontal gradient of the horizontal plane shear stresses. The simplifications lead to a vertically one‐dimensional numerical problem, whose solution can be computed rapidly. The relaxation rate of perturbations as well as other response descriptors for the stable full system and approximants are compared. Compared with the shallow ice approximation, the inclusion of longitudinal stresses increases accuracy at shorter wavelengths, but accuracy is poor at wavelengths around or less than the ice sheet thickness. Even though analysis shows that the horizontal gradients of the horizontal plane shear stresses are of similar magnitude to longitudinal stress effects, computations show, in agreement with glaciological belief, that longitudinal stress effects are more significant and need to be corrected for first in practice. Two schemes, a multilayer scheme and a one‐layer scheme, are particularly good and should be investigated further in cases where perturbations from uniformity are large. Some other apparently plausible approximations introduce nonphysical instabilities. New schemes need to be assessed in the way described in this paper before being used in real ice sheet models.
Deep and bottom water export from the Southern Ocean to the Pacific over the past 38 million years
Authors: van de Flierdt Tina , Frank Martin , Halliday Alex N. , Hein James R. , Hattendorf Bodo , Günther Detlef , Kubik Peter W.
Published: March 2004

The application of radiogenic isotopes to the study of Cenozoic circulation patterns in the South Pacific Ocean has been hampered by the fact that records from only equatorial Pacific deep water have been available. We present new Pb and Nd isotope time series for two ferromanganese crusts that grew from equatorial Pacific bottom water (D137‐01, “Nova,” 7219 m water depth) and southwest Pacific deep water (63KD, “Tasman,” 1700 m water depth). The crusts were dated using10Be/9Be ratios combined with constant Co‐flux dating and yield time series for the past 38 and 23 Myr, respectively. The surface Nd and Pb isotope distributions are consistent with the present‐day circulation pattern, and therefore the new records are considered suitable to reconstruct Eocene through Miocene paleoceanography for the South Pacific. The isotope time series of crusts Nova and Tasman suggest that equatorial Pacific deep water and waters from the Southern Ocean supplied the dissolved trace metals to both sites over the past 38 Myr. Changes in the isotopic composition of crust Nova are interpreted to reflect development of the Antarctic Circumpolar Current and changes in Pacific deep water circulation caused by the build up of the East Antarctic Ice Sheet. The Nd isotopic composition of the shallower water site in the southwest Pacific appears to have been more sensitive to circulation changes resulting from closure of the Indonesian seaway.
A stochastic index flow model of flow duration curves
Authors: Castellarin Attilio , Vogel Richard M. , Brath Armando
Published: March 2004

Annual flow duration curves (AFDCs) are used increasingly because unlike traditional period of record flow duration curves (FDCs), they provide confidence intervals for the median AFDC, they enable one to assign return periods to individual AFDCs, and they offer opportunities for developing a generalized stochastic model of daily streamflow. Previous stochastic models of FDCs and AFDCs were unable to reproduce the variance of AFDCs. We introduce an index flow approach to modeling the relationship between an FDC and AFDCs of daily streamflow series, which is able to reproduce the FDC, as well as the mean, median, and variance of the AFDCs without resorting to assumptions regarding the seasonal or persistence structure of daily streamflow series. Our approach offers additional opportunities for the regionalization of flow duration curves and for the generation of time series of daily streamflows at ungauged sites. Our approach is tested on three river basins in eastern central Italy.
Laboratory evaluation of a hydrodynamic inverse modeling method based on water content data
Authors: Lambot S. , Hupet F. , Javaux M. , Vanclooster M.
Published: March 2004

The inverse modeling method of Lambot et al. [2002] for estimating the hydraulic properties of partially saturated soils, which was numerically validated, is further tested on laboratory‐scale transient flow experiments. The method uses the global multilevel coordinate search algorithm combined sequentially with the local Nelder‐Mead simplex algorithm to obtain the inverse of the one‐dimensional Richards equation using soil moisture time series measured at three different depths during natural infiltration. Flow experiments were conducted on a homogeneous artificial sand column and three undisturbed soil columns collected from agricultural fields. Three models describing the unsaturated soil hydraulic properties were used and compared: the model of Mualem and van Genuchten, the model of Assouline, and the decoupled van Genuchten–Brooks and Corey combination. The performances of all three models were similar, except for Assouline's model, which provided poorer results in two cases. The inversion method provided relatively good estimates for the water retention curves and also for the saturated conductivity when the moisture range explored was not too small. Water content time series were very well reproduced for the artificial soil and a sandy loam soil, but for two silt loam soils, larger errors were observed. The prediction of the water transfer behavior in the soil columns was poor when flow properties were estimated using directly determined hydraulic properties. The main limiting factor for applying the inversion method, particularly for nonsandy soils, was the characterization of the initial conditions in terms of the pressure head profile. Furthermore, the use of only soil moisture data is essential to enable the hydrogeophysical characterization of soils.
First‐order variance of travel time in nonstationary formations
Authors: Cirpka Olaf A. , Nowak Wolfgang
Published: March 2004

Evaluating uncertainty in solute transport under nonstationary flow conditions is a computationally demanding task. This is particularly true for cases with a two‐point covariance function of log conductivity depending on the actual positions of the points rather than their distance vector. These may occur when the geological formation exhibits a trend. Nonstationarity can also be the result of uncertainty in the trend parameters of the mean log conductivity value, or it may originate from conditioning of the log conductivity field to measurements of, for example, head or conductivity. We present an efficient numerical method for evaluating the variance of travel time in such formations. We cover cases in which the nonstationary covariance functions are constructed from stationary counterparts, either by scaling functions or by summation with nonstationary functions resulting from marginalization or conditioning. We apply a matrix‐based first‐order second‐moment (FOSM) method for uncertainty propagation, using the continuous adjoint‐state method for coupled systems to evaluate the sensitivity matrix. The resulting matrix‐matrix multiplications are accelerated by fast Fourier transformation (FFT) techniques after periodic embedding of the covariance matrices referring to the stationary counterparts. The combination of these methods makes it possible to compute the travel time uncertainty in domains discretized by several hundred thousand log conductivity values on standard personal computers within a reasonable time‐frame. For demonstration, we apply the method to a binary medium and a medium exhibiting a continuous trend in the covariance function. In the latter application we also demonstrate the effects of marginalization and conditioning.
Late Quaternary core stratigraphy of the northern New South Wales continental shelf
Authors: Roberts J. J. , Boyd R.
Published: March 2004

On the southeast Australian continental margin, mixed siliciclastic and temperate carbonate sediments are presently forming along the narrow 20–35 km‐wide northern New South Wales shelf over an area of 4960 km2. Here, year‐round, highly energetic waves rework inner and mid‐shelf clastic sediments by northward longshore currents or waning storm flows. The strong East Australian Current flows south, sweeping clastic and outer shelf biogenic sands and gravels. Quaternary siliciclastic inner shelf cores consist of fine to medium, lower shoreface sand and graded storm beds of fine to coarse sand. Physically abraded, disarticulated molluscs such as Donacidae and Glycymeridae form isolated gravel lags. Highstand inner shelf clastics accumulate at 0.53 m/103 y in less than 50 m water depth. Clastic mid‐shelf cores contain well‐sorted, winnowed, medium shoreface sands, with a fine sand component. Fine sand and mud in this area is discharged mainly from New South Wales' largest river, the Clarence. The seaward jutting of Byron Bay results in weakened East Australia Current flows through the mid‐shelf from Ballina to Yamba allowing the fine sediments to accumulate. Quaternary carbonate outer shelf cores have uniform and graded beds forming from the East Australian Current and are also influenced by less frequent storm energy. Modern clastic‐starved outer shelf hardgrounds are cemented by coralline algae and encrusting bryozoans. Clay‐sized particles are dominantly high‐Mg calcite with minor aragonite and smectite/kaolinite. Carbonate sands are rich in bryozoan fragments and sponge spicules. Distinctive (gravel‐sized) molluscs form isolated shells or shell lag deposits comprising Limopsidae and Pectinidae. The upper slope sediments are the only significant accumulation of surficial mud on the margin (18–36 wt%), filling the interstices of poorly sorted, biogenic gravels. Pectinid molluscs form a basal gravel lag. During highstand the outer shelf accumulates sediment at 0.40 m/103 y, with the upper slope accumulating a lower 0.23 m/103 y since transgression. Transgression produced a diachronous (10–14 ka) wave‐ravinement surface in all cores. Relict marine hardgrounds overlie the wave‐ravinement surface and are cemented by inorganic calcite from the shallow and warm East Australian Current. Transgressive estuarine deposits, oxygen isotope Stage 3–5 barriers or shallow bedrock underlie the wave‐ravinement surface on the inner and mid shelf. Northern New South Wales is an example of a low accommodation, wave‐ and oceanic current‐dominated margin that has produced mixed siliciclastic–carbonate facies. Shelf ridge features that characterise many storm‐dominated margins are absent.
Geochronological constraints on the polymetamorphic evolution of the granulite‐hosted Challenger gold deposit: implications for assembly of the northwest Gawler Craton*
Authors: Tomkins A. G. , Dunlap W. J. , Mavrogenes J. A.
Published: March 2004

A temperature–time history for the granulite‐hosted Challenger gold deposit in the Christie Domain of the Gawler Craton, South Australia, has been derived using a range of isotopic decay systems including U–Pb, Sm–Nd, Rb–Sr and40Ar/39Ar. Nd model ages and detrital zircon ages suggest a protolith age of ca2900 Ma for the Challenger Gneiss. Gold mineralisation was probably introduced under greenschist/amphibolite‐facies conditions towards the end of the Archaean, between 2800 and 2550 Ma. However, evidence for the exact age and P–T conditions of this event was almost completely removed by granulite‐facies metamorphism during the Sleafordian Orogeny, which peaked aroundca 2447 Ma. Cooling to 350°C occurred before 2060 Ma. It is possible that the Christie Domain was then subject to further sedimentation and volcanism in the periodca 2000–1800 Ma before reburial and a second period of orogeny aroundca 1710–1615 Ma. During this second orogeny, the eastern Christie Domain experienced heterogeneous fluid‐induced retrograde metamorphism at lower greenschist‐ to amphibolite‐facies conditions, with metamorphic grade varying between structural blocks. At this time, the Challenger deposit was subject to greenschist‐facies conditions (not significantly hotter than 350°C), while at Mt Christie (50 km to the south) lower amphibolite‐facies conditions prevailed and to the west the Ifould Block experienced extensive plutonism. A third very low‐temperature thermal pulse aroundca 1531 Ma, which reached ∼150–200°C, is recorded at the Challenger deposit. It is likely that the global Grenvillian Orogeny (1300–1000 Ma) was a major period of domain exhumation and juxtaposition.
4350–3130 Ma detrital zircons in the Southern Cross Granite–Greenstone Terrane, Western Australia: implications for the early evolution of the Yilgarn Craton
Authors: Wyche S. , Nelson D. R. , Riganti A.
Published: March 2004

SHRIMP U‐Pb zircon analysis indicates that detrital zircons from extensive quartzite units in the Southern Cross Granite–Greenstone Terrane of the central Yilgarn Craton have ages ranging from ca 4350 Ma to ca 3130 Ma. Regional mapping studies indicate that the quartzites lie at the stratigraphic base of the exposed succession. The detrital zircon age profiles of the Southern Cross Granite–Greenstone Terrane quartzites are remarkably similar to those of quartzites in the Narryer and South West Terranes, in the northwest and southwest of the Yilgarn Craton respectively, and are significantly older than any igneous rocks that have been dated anywhere in the Yilgarn Craton other than the Narryer Terrane. Similar detrital‐zircon‐bearing quartzites have not been identified in the Murchison Granite–Greenstone Terrane. These age profiles suggest that the quartzites have a common depositional history. Granites in the central Yilgarn Craton are mainly younger than ca 2750 Ma and contain rare xenocrystic zircons older than 3100 Ma. If the central and western Yilgarn quartzites were all deposited at approximately the same time, the lack of preserved continental crust in the Southern Cross and Murchison Granite–Greenstone Terranes, and the South West Terrane, that is older than 3100 Ma, suggests that pre‐3100 Ma Narryer‐like continental crust may have been rifted or extensively reworked during deposition of greenstone successions between ca 3000 and ca 2700 Ma. If not, then a ca 4350 Ma detrital zircon in the Southern Cross Granite–Greenstone Terrane indicates more widespread, very old, continental crust than has previously been identified.
Spatial distribution and source of heavy metals in reclaimed lands of Homebush Bay: the venue of the 2000 Olympic Games, Sydney, New South Wales
Authors: Suh J‐Y. , Birch G. F. , Hughes K. , Matthai C.
Published: March 2004

A large part of the Sydney 2000 Olympic Site at Homebush Bay was reclaimed over several decades using an estimated 9 Mt of domestic, commercial and industrial waste. Past activities, such as reclamation of wetlands, land clearing, shoreline remodelling and industrial practices, have caused an adverse environmental impact on the Homebush Bay site. Core samples (n = 4513) collected from the reclaimed lands of Homebush Bay show that, prior to remediation, soil contaminated by heavy metals (Cr, Cu, Pb, Zn) may have posed a threat to groundwater in the area. Mean Pb concentrations from the three land types at the Olympic site range from 65 to 374 µg/g in reclaimed areas, 78–167 µg/g in landfill areas and 44–52 µg/g in non‐infilled areas, respectively. Heavy‐metal concentrations in soils from non‐infilled areas indicate that these parts of the site were uncontaminated. The distribution of heavy metals in soil samples revealed a close association between elevated concentrations and the presence of fill materials at the site. Metal concentrations were frequently above Australian and New Zealand Guidelines for Fresh and Marine Water Quality. The Olympic Coordination Authority's remediation strategy to clean up the Homebush Bay site included consolidating contaminated waste into landscaped hills, which were capped with impermeable clay and thermal destruction of scheduled waste on site. The primary aims of the current study were to provide a scientific foundation for the remediation/rehabilitation of natural systems, and to make a contribution to the Olympic Coordination Authority's Development Plan and Environmental Management System for the site.
New records of Late Neoproterozoic Acraman ejecta in the Officer Basin
Authors: Hill A. C. , Grey K. , Gostin V. A. , Webster L. J.
Published: March 2004

New occurrences of the Acraman impact ejecta layer were recently discovered in two drillholes, Giles 1 and Murnaroo 1, in the eastern Officer Basin, South Australia, using acritarch biostratigraphy and lithostratigraphy to predict the position. Fractured crystals were also observed in palynological preparations from drillhole SCYW 1a on the Stuart Shelf. These discoveries improve stratigraphic control of Late Neoproterozoic successions, especially in the eastern Officer Basin and will allow a test of the hypothesis that the Acraman impact event caused a global catastrophe.
Cenozoic volcanism, tectonism and stream derangement in the Snowy Mountains and northern Monaro of New South Wales
Authors: Sharp K. R.
Published: March 2004

Studies of Cenozoic lavas and associated sediments in the Kiandra–Cabramurra and Adaminaby–Cooma areas identify and date tectonic deformations responsible for differential uplift and drainage development of the region. Volcanic activity on the northern Monaro was mainly Eocene–Oligocene but in the extreme north there are Early Miocene sediments and lavas. Volcanic activity and folding began to rearrange the drainage in the Eocene–Oligocene. The headwaters of the Murrumbidgee River originally flowed south into the Eucumbene River but Early Miocene folding and faulting uplifted the Monaro Range and created a large lake near Adaminaby. Lake overtopping rerouted the drainage east and then south along the basalt‐filled valley of an old north‐flowing tributary, the 'Adaminaby River', forming the present‐day Murrumbidgee River. The folding also produced a 300 m height difference between the Berridale and Adaminaby Plateaus and formed a section of the Great Divide. This fold displacement ranks with the largest Cenozoic fault displacements. In the Kiandra area tectonism associated with Early Miocene volcanism rearranged the drainage and tilted the Kiandra area and Kosciuszko Block to the north.
Isotopic constraints on crustal architecture and Permo‐Triassic tectonics in New Guinea: possible links with eastern Australia
Authors: Crowhurst P. V. , Maas R. , Hill K. C. , Foster D. A. , Fanning C. M.
Published: March 2004

New U–Pb zircon ages and Sr–Nd isotopic data for Triassic igneous and metamorphic rocks from northern New Guinea help constrain models of the evolution of Australia's northern and eastern margin. These data provide further evidence for an Early to Late Triassic volcanic arc in northern New Guinea, interpreted to have been part of a continuous magmatic belt along the Gondwana margin, through South America, Antarctica, New Zealand, the New England Fold Belt, New Guinea and into southeast Asia. The Early to Late Triassic volcanic arc in northern New Guinea intrudes high‐grade metamorphic rocks probably resulting from Late Permian to Early Triassic (ca 260–240 Ma) orogenesis, as recorded in the New England Fold Belt. Late Triassic magmatism in New Guinea (ca 220 Ma) is related to coeval extension and rifting as a precursor to Jurassic breakup of the Gondwana margin. In general, mantle‐like Sr–Nd isotopic compositions of mafic Palaeozoic to Tertiary granitoids appear to rule out the presence of a North Australian‐type Proterozoic basement under the New Guinea Mobile Belt. Parts of northern New Guinea may have a continental or transitional basement whereas adjacent areas are underlain by oceanic crust. It is proposed that the post‐breakup margin comprised promontories of extended Proterozoic–Palaeozoic continental crust separated by embayments of oceanic crust, analogous to Australia's North West Shelf. Inferred movement to the south of an accretionary prism through the Triassic is consistent with subduction to the south‐southwest beneath northeast Australia generating arc‐related magmatism in New Guinea and the New England Fold Belt.