bluuebunny/crossref_metadata_2025 huggingface dataset:
Paradoxical effects of learning the Morris water maze on adult hippocampal neurogenesis in mice may be explained by a combination of stress and physical activity
Authors: Ehninger D. , Kempermann G.
Published: December 2005

Studies in rats that assessed the relation of hippocampus‐dependent learning and adult hippocampal neurogenesis suggested a direct regulatory effect of learning on neurogenesis, whereas a similar study in mice had not found such causal link. We here report a substantial decrease of BrdU‐positive cells and other measures of adult hippocampal neurogenesis in mice trained in the hidden (HID) or cued version (VIS) of the Morris water maze as compared to untrained animals (CTR). Particularly, cells on advanced stages of neuronal development contributed to this decrease, whereas earlier progenitors (type 2 cells) were not diminished in HID, but were diminished in VIS as compared to CTR. The differential regulation of type 2 cells in HID and VIS may have been caused by a different degree of physical activity, given that a time‐yoked control group did not differ from HID, and type 2 cells reportedly constitute the proliferative dentate gyrus population that primarily responds to physical activity. The decrease of hippocampal neurogenesis by water maze training was reversible by pre‐exposing animals to the water maze prior to training, suggesting that stress associated with training may have caused the acute downregulation of adult neurogenesis. We propose that in mice the Morris water maze does not provide a pure enough learning stimulus to study the presumed effects of ‘learning’ on adult neurogenesis. In addition, however, our data show that physical activity that is intricately linked to many cognitive tasks in rodents might play an important role in explaining effects of learning on cellular hippocampal plasticity.
Identifying interactions between genes and early environment in the mouse
Authors: Carola V. , Frazzetto G. , Gross C.
Published: December 2005

Interactions between genetic and early environmental factors are recognized to play a critical role in modulating susceptibility to disease, particularly mental illness. In order to better understand such mechanisms at the molecular level, we have developed a screening paradigm in mice that allows us to test the ability of targeted mutations in candidate genes to modify susceptibility to the long‐term effects of different maternal environment. Offspring of genetically identical F1 hybrid dams produced by reciprocal breeding of C57BL/6 and BALB/c parents show alterations in anxiety‐related behavior as a consequence of their different maternal environment. Introduction of targeted mutations into these offspring via the father allows for the identification of candidate genes that alter these maternal effects. Our strategy offers several advantages over other methods to study maternal effects, including the use of genetically identical parents, the ability to identify both prenatal and postnatal effects, the straightforward introduction of mutations and its adaptability to high‐throughput screening. In order to test the utility of this paradigm to screen candidate genes, we tested for gene–environment interactions involving loss‐of‐function mutations in the serotonin 1A receptor gene. Our studies demonstrate that early gene–environment interactions can be successfully tested in the mouse. When combined with conditional gene targeting and other molecular genetic techniques available in the mouse, this approach has the potential to identify the molecular mechanisms underlying early gene–environment effects.
Gravitaxis in Drosophila melanogaster: a forward genetic screen
Authors: Armstrong J. D. , Texada M. J. , Munjaal R. , Baker D. A. , Beckingham K. M.
Published: December 2005

Perception of the earth's gravitational force is essential for most forms of animal life. However, little is known of the molecular mechanisms and neuronal circuitry underlying gravitational responses. A forward genetic screen using Drosophila melanogaster that provides insight into these characteristics is described here. Vertical choice mazes combined with additional behavioral assays were used to identify mutants specifically affected in gravitaxic responses. Twenty‐three mutants were selected for molecular analysis. As a result, 18 candidate genes are now implicated in the gravitaxic behavior of flies. Many of these genes have orthologs across the animal kingdom, while some are more specific to Drosophila and invertebrates. One gene (yuri) located close to a known locus for gravitaxis has been the subject of more extensive analysis including confirmation by transgenic rescue.
The genetic contribution to canine personality
Authors: Saetre P. , Strandberg E. , Sundgren P.‐E. , Pettersson U. , Jazin E. , Bergström T. F.
Published: December 2005

The domestic dog may be exceptionally well suited for behavioral genetic studies owing to its population history and the striking behavior differences among breeds. To explore to what extent and how behavioral traits are transmitted between generations, heritabilities and genetic correlations for behavioral traits were estimated in a cohort containing over 10 000 behaviorally tested German shepherd and Rottweiler dogs. In both breeds, the pattern of co‐inheritance was found to be similar for the 16 examined behavioral traits. Furthermore, over 50% of the additive genetic variation of the behavioral traits could be explained by one underlying principal component, indicating a shared genetic component behind most of the examined behavioral traits. Only aggression appears to be inherited independently of the other traits. The results support a genetic basis for a broad personality trait previously named shyness–boldness dimension, and heritability was estimated to be 0.25 in the two breeds. Therefore, breeds of dogs appear to constitute a valuable resource for behavioral genetic research on the normal behavioral differences in broad personality traits.
Maternal behavior deficits in nulliparous oxytocin knockout mice
Authors: Pedersen C. A. , Vadlamudi S. V. , Boccia M. L. , Amico J. A.
Published: December 2005

The first observations of postpartum oxytocin knockout (OTKO) mice found no maternal behavior deficits. However, it is unclear how detailed those observations were. In this study, we compared maternal behavior exhibited by OTKO and wild‐type (WT) nullipara toward six 2–4‐day‐old foster pups during test sessions conducted on 3 successive days. Each day, subjects were placed in a clean cage 30 min prior to introduction of pups which were deposited in a clump adjacent to the middle of a long wall of each test cage. Behavior was measured for 3.5 h after which pups and test subjects were returned to their home cages. On test days 1 and 3, a significantly smaller proportion of OTKO females retrieved pups to a corner of their cage. Also, significantly fewer pups were retrieved to corners by OTKO females. In contrast to most WTs, most OTKO females mothered pups in the center of the cage where they were initially deposited. Pup‐licking frequencies were significantly lower in OTKO females. Their self‐grooming frequencies also trended toward being lower. Latencies to retrieve and lick pups, latencies to and frequencies of still crouching over pups and proportion of time in nest did not differ between groups. Our findings suggest that OT stimulates a significant proportion of pup‐licking in nulliparous mice, a situation similar to lactating rat mothers. Our results also indicate that OT may play a role in the motivation to retrieve pups to a more secure location.
Developing a Set of Health Indicators for People with Intellectual Disabilities: Pomona Project
Authors: Walsh Patricia Noonan , Linehan Christine , Kerr M. P. , Van Schrojenstein Lantman‐de Valk H. M. J. , Buono Serafino , Azema Bernard , Aussilloux Charles , Määttä Tuomo , Salvador‐Carulla Luis , Garrido‐Cumbrera Marco , Van Hove Geert , Björkman Monica , Ceccotto Raymond , Kamper Marion , Weber Germain , Heiss Cecilia , Haveman Meindert , Jørgensen Frank Ulmer , O'Farrell Lisa
Published: December 2005

Abstract  The European Commission's Health Monitoring Programme culminated in the development of a set of European Community Health Indicators (ECHI) for the general population. Despite evidence of marked disparities between the health of people with intellectual disabilities (ID) and their peers in the general population, the ECHI contain no significant reference to people with ID. To address this deficit, a two‐year grant from the Health Monitoring Programme was awarded to the Pomona project (a collection of researchers from 13 European countries). The project comprised exchanges of expertise; a critical review of published evidence about health and ID; and consultative processes in member states. The project's finding was that there was no systematic monitoring of the health of people with ID in EU member states and, as a consequence, a set of health indicators specific to people with ID was proposed that could lead to such systemic monitoring.
Effect of mutations K97A and E128A on RNA binding and self assembly of papaya mosaic potexvirus coat protein
Authors: Tremblay Marie‐Hélène , Majeau Nathalie , Gagné Marie‐Eve Laliberté , Lecours Katia , Morin Hélène , Duvignaud Jean‐Baptiste , Bolduc Marilène , Chouinard Nicolas , Paré Christine , Gagné Stéphane , Denis Leclerc
Published: December 2005

Papaya mosaic potexvirus (PapMV) coat protein (CP) was expressed (CPΔN5) in Escherichia coli and showed to self assemble into nucleocapsid like particles (NLPs). Twenty per cent of the purified protein was found as NLPs of 50 nm in length and 80% was found as a multimer of 450 kDa (20 subunits) arranged in a disk. Two mutants in the RNA binding domain of the PapMV CP, K97A and E128A showed interesting properties. The proteins of both mutants could be easily purified and CD spectra of these proteins showed secondary and tertiary structures similar to the WT protein. The mutant K97A was unable to self assemble and bind RNA. On the contrary, the mutant E128A showed an improved affinity for RNA and self assembled more efficiently in NLPs. E128A NLPs were longer (150 nm) than the recombinant CPΔN5 and 100% percent of the protein was found as NLPs in bacteria. E128A NLPs were more resistant to digestion by trypsin than the CPΔN5 but were more sensitive to denaturation by heat. We discuss the possible role of K97 and E128 in the assembly of PapMV.
The proline‐rich protein palladin is a binding partner for profilin
Authors: Boukhelifa Malika , Moza Monica , Johansson Thomas , Rachlin Andrew , Parast Mana , Huttelmaier Stefan , Roy Partha , Jockusch Brigitte M , Carpen Olli , Karlsson Roger , Otey Carol A
Published: December 2005

Palladin is an actin‐associated protein that has been suggested to play critical roles in establishing cell morphology and maintaining cytoskeletal organization in a wide variety of cell types. Palladin has been shown previously to bind directly to three different actin‐binding proteins vasodilator‐stimulated phosphoprotein (VASP), α‐actinin and ezrin, suggesting that it functions as an organizing unit that recruits actin‐regulatory proteins to specific subcellular sites. Palladin contains sequences resembling a motif known to bind profilin. Here, we demonstrate that palladin is a binding partner for profilin, interacting with profilin via a poly proline‐containing sequence in the amino‐terminal half of palladin. Double‐label immunofluorescence staining shows that palladin and profilin partially colocalize in actin‐rich structures in cultured astrocytes. Our results suggest that palladin may play an important role in recruiting profilin to sites of actin dynamics.
Dissociation/association properties of a dodecameric cyclomaltodextrinase
Authors: Lee Hee‐Seob , Kim Jin‐Soo , Shim Kyuho , Kim Jung‐Woo , Inouye Kuniyo , Oneda Hiroshi , Kim Young‐Wan , Cheong Kyung‐Ah , Cha Hyunju , Woo Eui‐Jeon , Auh Joong Hyuck , Lee Sung‐Joon , Kim Jung‐Wan , Park Kwan‐Hwa
Published: December 2005

As an effort to elucidate the quaternary structure of cyclomaltodextrinase I‐5 (CDase I‐5) as a function of pH and salt concentration, the dissociation/association processes of the enzyme were investigated under various pH and salt conditions. Previous crystallographic analysis of CDase I‐5 indicated that it existed exclusively as a dodecamer at pH 7.0, forming an assembly of six 3D domain‐swapped dimeric subunits. In the present study, analytical ultracentrifugation analysis suggested that CDase I‐5 was present as a dimer in the pH range of 5.0–6.0, while the dodecameric form was predominant at pH values above 6.5. No dissociation of the dodecamer was observed at pH 7.0 and the above. Gel filtration chromatography showed that CDase I‐5 dissociated into dimers at a rate of 8.58 × 10−2 h−1 at pH 6.0. A mutant enzyme with three histidine residues (H49, H89, and H539) substituted with valines dissociated into dimers faster than the wild‐type enzyme at both pH 6.0 and 7.0. The tertiary structure indicated that the effect of pH on dissociation of the oligomer was mainly due to the protonation of H539. Unlike the pH‐dependent process, the dissociation of wild‐type CDase I‐5 proceeded very fast at pH 7.0 in the presence of 0.2–1.0 m of KCl. Stopped‐flow spectrophotometric analysis at various concentrations of KCl showed that the rate constants of dissociation (kd) from dodecamers into dimers were 5.96 s−1 and 7.99 s−1 in the presence of 0.2 m and 1.0 m of KCl, respectively.
DNA mediated disassembly of hRad51 and hRad52 proteins and recruitment of hRad51 to ssDNA by hRad52
Authors: Navadgi Vasundhara M. , Shukla Ashish , Vempati Rahul Kumar , Rao Basuthkar J
Published: December 2005

Purified human Rad51 and Rad52 proteins exhibit multiple oligomeric states, in vitro. Single‐stranded DNA (ssDNA) renders high molecular weight aggregates of both proteins into smaller and soluble forms that include even the monomers. Consequently, these proteins that have a propensity to interact with each other's higher order forms by themselves, start interacting with monomeric forms in the presence of ssDNA, presumably reflecting the steps of protein assembly on DNA. In the same conditions, DNA binding assays reveal hRad52‐mediated recruitment of hRad51 on ssDNA. Put together, these studies hint at DNA‐induced disassembly of higher‐order forms of Rad51 and Rad52 proteins as steps that precede protein assembly during hRad51 presynapsis on DNA, in vitro.
Active site residues governing substrate selectivity and polyketide chain length in aloesone synthase
Authors: Abe Ikuro , Watanabe Tatsuya , Lou Weiwei , Noguchi Hiroshi
Published: December 2005

Aloesone synthase (ALS) and chalcone synthase (CHS) are plant‐specific type III poyketide synthases sharing 62% amino acid sequence identity. ALS selects acetyl‐CoA as a starter and carries out six successive condensations with malonyl‐CoA to produce a heptaketide aloesone, whereas CHS catalyses condensations of 4‐coumaroyl‐CoA with three malonyl‐CoAs to generate chalcone. In ALS, CHS's Thr197, Gly256, and Ser338, the active site residues lining the initiation/elongation cavity, are uniquely replaced with Ala, Leu, and Thr, respectively. A homology model predicted that the active site architecture of ALS combines a ‘horizontally restricting’ G256L substitution with a ‘downward expanding’ T197A replacement relative to CHS. Moreover, ALS has an additional buried pocket that extends into the ‘floor’ of the active site cavity. The steric modulation thus facilitates ALS to utilize the smaller acetyl‐CoA starter while providing adequate volume for the additional polyketide chain extensions. In fact, it was demonstrated that CHS‐like point mutations at these positions (A197T, L256G, and T338S) completely abolished the heptaketide producing activity. Instead, A197T mutant yielded a pentaketide, 2,7‐dihydroxy‐5‐methylchromone, while L256G and T338S just afforded a triketide, triacetic acid lactone. In contrast, L256G accepted 4‐coumaroyl‐CoA as starter to efficiently produce a tetraketide, 4‐coumaroyltriacetic acid lactone. These results suggested that Gly256 determines starter substrate selectivity, while Thr197 located at the entrance of the buried pocket controls polyketide chain length. Finally, Ser338 in proximity of the catalytic Cys164 guides the linear polyketide intermediate to extend into the pocket, thus leading to formation of the hepataketide in Rheum palmatum ALS.
Recombinant hemoglobin βG83C‐F41Y
Authors: Vasseur‐Godbillon Corinne , Sahu Sarata C. , Domingues Elisa , Fablet Christophe , Giovannelli Janel L. , Tam Tsuey Chyi , Ho Nancy T. , Ho Chien , Marden Michael C. , Baudin‐Creuza Véronique
Published: December 2005

We have engineered a stable octameric hemoglobin (Hb) of molecular mass 129 kDa, a dimer of recombinant hemoglobin (rHb βG83C‐F41Y) tetramers joined by disulfide bonds at the β83 position. One of the major problems with oxygen carriers based on acellular hemoglobin solutions is vasoactivity, a limitation which may be overcome by increasing the molecular size of the carrier. The oxygen equilibrium curves showed that the octameric rHb βG83C‐F41Y exhibited an increased oxygen affinity and a decreased cooperativity. The CO rebinding kinetics, auto‐oxidation kinetics, and size exclusion chromatography did not show the usual dependence on protein concentration, indicating that this octamer was stable and did not dissociate easily into tetramers or dimers at low concentration. These results were corroborated by the experiments with haptoglobin showing no interaction between octameric rHb βG83C‐F41Y and haptoglobin, a plasma glycoprotein that binds the Hb dimers and permits their elimination from blood circulation. The lack of dimers could be explained if there are two disulfide bridges per octamer, which would be in agreement with the lack of reactivity of the additional cysteine residues. The kinetics of reduction of the disulfide bridge by reduced glutathione showed a rate of 1000 m−1·h−1 (observed time coefficient of 1 h at 1 mm glutathione) at 25 °C. Under air, the cysteines are oxidized and the disulfide bridge forms spontaneously; the kinetics of the tetramer to octamer reaction displayed a bimolecular reaction of time coefficient of 2 h at 11 µm Hb and 25 °C. In addition, the octameric rHb βG83C‐F41Y was resistant to potential reducing agents present in fresh plasma.
Embedded Sidewall Samplers and Sensors to Monitor the Subsurface
Authors: Murdoch Lawrence C. , Slack William W. , Harrar William , Siegrist Robert L.
Published: December 2005

Subsurface properties such as moisture content, hydraulic head, or chemical composition may vary markedly over short vertical distances in soil and ground water systems, but conventional samplers and sensors placed in vertical boreholes are often unable to resolve these variations. To improve the resolution of subsurface monitoring, we have developed a method for accessing the side‐wall of a vertical or angled borehole at many discrete intervals along the entire length of the borehole. The method uses an access device that embeds sensors or sediment samplers laterally through the borehole sidewall into the undisturbed formation to distances slightly less than the diameter of the borehole. The access device can also obtain a core sample up to 15 cm long and 4 cm in diameter, and then insert a permeable sleeve for extracting fluid samples (water, gas, nonaqueous phase liquids). The system has been used under field conditions in the United States and Denmark to place electrodes capable of measuring water content (using time domain reflectometry [TDR] waveguides), Eh (using platinum electrodes), or electrical resistivity (using a four‐conductor electrode). At one site, as many as 22 water samplers and 19 resistivity electrodes were installed in a single borehole at vertical spacings as close as 7 cm. This approach was used to install horizontally oriented TDR waveguides at depths greater than 10 m, thereby extending the TDR technique to the study of deep vadose zones. Other applications include measurement of in situ Eh at a site where strong chemical oxidants were injected to remediate sediments contaminated by organic chemicals.
Utility of Simple Models for Capture Zone Delineation in Heterogeneous Unconfined Aquifers
Authors: Cole Bryce E. , Silliman Stephen E.
Published: December 2005

Monte Carlo simulation is used to examine the utility of simple (homogeneous/isotropic) models for the delineation of wellhead protection areas (WHPAs) in heterogeneous, statistically anisotropic, unconfined aquifers. Capture zone geometry is investigated under two hydrologic conditions: regional gradient negligible compared to pumping and significant regional gradient compared to the local gradient due to pumping. Variability of capture zone geometry is quantified in terms of simple measurements (maximum transport distance and maximum width of the capture zone) and the probability of inclusion in the capture zone of a series of hypothetical contaminant source locations. These results indicate that substantial uncertainty exists in the delineation of a wellhead capture zone. This uncertainty is related, principally, to flow that occurs along preferential pathways associated with zones of high hydraulic conductivity. It is suggested that these uncertainties can be accommodated in one of three fashions depending on the value of land, the benefit of wellhead protection, and the availability of funds to perform more thorough field assessment. The first option is to modify the estimated capture zone by a factor of safety. In the absence of significant regional flow, a factor of safety of approximately three applied to the calculated fixed radius estimate of the capture zone appears to be sufficient for the conditions simulated in this project. In the case of a capture zone within a significant regional gradient, uncertainty in the location of the real capture zone will require safety factors on the width of the estimated capture zone on the order of 30, with a safety factor of approximately three in the longitudinal direction. The second option reduces these factors of safety by increasing the risk that the estimated capture zone will not cover the entire area of the real capture zone. Work available in the literature provides insight into the trade‐off between the size of the estimated capture zone and the risk endured. The third option is to reduce uncertainty in the vicinity of a wellhead through additional expenditure to allow the application of classic hydrologic techniques involving conditioning or inverse modeling.
Soil Vacuum Extraction of Perchloroethylene from the Borden Aquifer
Authors: Thomson Neil R. , Flynn David J.
Published: December 2005

An assessment of a conventional soil vacuum extraction (SVE) system to remove perchloroethylene (PCE), a dense nonaqueous phase liquid (DNAPL), was conducted in a dewatered 9 × 9 m block of the surficial sand aquifer located at the Canadian Forces Base (CFB), Borden, Ontario. Approximately two years prior to the installation and operation of the SVE system, 1250 kg of PCE were released under saturated conditions into this experimental cell, forming a heterogeneous DNAPL distribution. Using ground penetrating radar and neutron probe data in conjunction with detailed soil core data, it was determined that approximately 600 kg of PCE were available for removal by the SVE system after dewatering. Performance assessment of this SVE system was based on soil core data and monitoring of in situ gas concentration and pressure, soil temperature, and moisture content.

After the first 25 days of operation, the SVE system had removed 230 kg of PCE, during which time the off‐gas concentration decreased by 70% from an initial concentration of close to 3500 ppmY After 432 days of operation, 63% (376 kg) of the estimated available mass was removed from the SVE target zone. In situ pressure measurements and sulphur hexafluoride tracer tests indicated that advective air movement occurred throughout the SVE target zone. Changes to the extraction well configuration and the use of short‐screened extraction drive points did not increase the mass removal performance.

After 250 days of operation, eight soil cores were removed from the test cell, and bulk soil concentration and soil moisture content measurements were performed at 0.05 m increments along the length of each core. These data revealed zones where significant quantities of PCE remained, even though the cumulative mass removal profile for the SVE system was nonzero asymptotic. In general, these zones coincided with higher moisture content zones reflective of the heterogeneous nature of this porous medium.

This investigation provides insight into some of the limitations of conventional SVE technology to clean up a sand aquifer contaminated with a DNAPL, given a reasonably good estimate of the before‐extraction mass conditions. In particular, the findings clearly show that the heterogeneous nature of the porous medium gives rise to a nonuniform moisture content, a heterogeneous pure phase distribution, and the development of preferential gas phase flow pathways. As a consequence, this will in general limit this technology to remove a considerable fraction of the DNAPL mass present. The results also shed light on the use of soil gas and bulk soil concentration data to provide a representative picture of the in situ mass distribution. And finally, an analysis of the system off‐gas data showed that continuous rather than pulsed operation of the extraction system increased mass removal.
On the Estimation of Stream Flow Depletion Parameters by Drawdown Analysis
Authors: Christensen Steen
Published: December 2005

Hunt (1999) derived a model for computation of stream flow depletion caused by pumping from a well near a stream that does not fully penetrate the aquifer. The model input includes the transmissivity (T) and the storativity (S) of the aquifer and the conductance of the stream bed (λ). We study the experimental and hydrogeological conditions for which drawdown analysis can be expected to produce T, S, and λ estimates that can be used in the model of Hunt (1999) to predict depletion with a specified accuracy. The study is conducted by using a combination of sensitivity analysis and uncertainty analysis. The analysis shows that it is always important to have an accurate estimate of λ in order to accurately predict depletion. Recommendations for the design of a pumping test near a stream are given to achieve this. The pumping well should be located close to the stream. Accurate drawdown measurements should be made both near the pumping well and near the stream, and the measurements should be used simultaneously to estimate T, S, and λ. The duration of the pumping test should be relatively long in order to obtain an accurate estimate of λ. A methodology is proposed in which a desired accuracy of either the estimates of T, S, and λ, or the stream flow predicted from these estimates, is used to estimate the duration of the pumping test. Some examples indicate that in many cases the duration of the test should be from an hour to one or two months. However, if S is large (∼10−1) and λ is small (10‐7 m/s) then the duration should be from several months to years. This would be expensive and not practical, so other methods should be used to estimate λ in this situation.
Simulation of Regional Ground Water Flow and Salt Water Intrusion in Hernando County, Florida
Authors: Guvanasen Varut , Wade Shirley C. , Barcelo Mark D.
Published: December 2005

The projected growth of Hernando County, located along the coast of west‐central Florida, has motivated the county and the Southwest Florida Water Management District to assess ground water resources in the area. As part of the Hernando County Water Resources Assessment Project, a computationally efficient modeling approach was developed to simulate regional ground water flow and salt water intrusion in two adjoining ground water basins in which Hernando County is located. In this modeling approach, the regional ground water flow simulation was divided into two stages: fresh water and sharp‐interface simulations. The first stage was performed using a calibrated fresh water model. Following the fresh water simulation, a calibrated sharp‐interface model was used to evaluate the potential extent of migration of the fresh water/salt water interface as a result of implementing ground water management scenarios. Predictive modeling results indicate that projected future ground water withdrawals will cause less than 0.6 m of additional drawdown within Hernando County. Results also suggest that by the year 2050 the fresh water/salt water interface will migrate landward less than 1.6 km from its 1994 position.
Type Curves for Pumping Test Analysis in Coastal Aquifers
Authors: Sakr Sameh Attiya
Published: December 2005

Conventional methods of analyzing pumping test data usually assume a single‐phase fluid condition. In coastal aquifer systems this condition is not valid when salt water underlies the production well screen. A set of type curves is developed for unsteady state flow toward a fresh water pumping well. The solution accounts for the nonlinear boundary conditions on the interface and for different interface geometry. The governing partial differential equations are solved using the finite‐element approximation for confined, homogeneous, and isotropic aquifer situations. The type curves were used to estimate the aquifer fresh water hydraulic conductivity and aquifer specific storage using pumping test data from a pumping well located on the coast of the Red Sea. The measured drawdowns are consistent with the predicted drawdown of the type curves.
The Recharge Mechanisms in an Alluvial Aquifer Zone in Northeast Brazil
Authors: Santiago Marlucia F. , Frischkorn Horst , Neto Porfírio Sales , Filho Josué Mendes
Published: December 2005

The state government of Ceará has initiated a program of releasing water from dams in order to sustain a continual flow of water in the state's naturally intermittent rivers. However, river/ ground water connections in alluvial areas impose heavy losses on regulated discharges. Our study area, the “Ilha de Limoeiro” (Isle of Limoeiro), is located in the Lower Jaguaribe Basin and comprises an area of approximately 120 km2. We used environmental oxygen‐18 and deuterium, together with hydrochemistry, in order to identify the origin of ground water which is heavily exploited for intensive small‐scale irrigation in that part of the flood‐plain of the Jaguaribe River. This paper discusses the mechanisms of recharge for the different hydrogeologic systems: crystalline basement, thick alluvium, and alluvium/Agu.
Identifying Potential Land Use‐Derived Solute Sources to Stream Baseflow Using Ground Water Models and GIS
Authors: Boutt David F. , Hyndman David W. , Pijanowski Bryan C. , Long David T.
Published: December 2005

This paper presents an approach to examine potential relationships between land use‐derived solutes and baseflow surface water quality using regional ground water and solute transport models linked to geographic information systems (GIS). We demonstrate this approach by estimating chloride concentrations in surface water due to road salt transport through ground water in a large coastal watershed in Michigan. The geologically parameterized model for this study provides a good fit to measured hydraulic heads in the watershed and offers a method to estimate spatially and temporally variable solute fluxes via ground water to streams and lakes. The results demonstrate that there is a considerable legacy of land use influencing surface water quality at the study site. The simulated chloride concentrations produced with salted roads as the only chloride source are similar to measured surface water chloride concentrations throughout most of the watershed, except in regions where other sources for chloride (e.g., high‐density septic systems, locations of oil brine fields) likely exist. Impacts of other land use related solutes on baseflow surface water quality could also be explored using this approach. As a result, watershed managers could be provided with quantitative information about the potential impacts of developments and associated surface‐applied solutes on future surface water quality.
Mapping Coastal Aquifers by Joint Inversion of DC and TEM Soundings‐Three Case Histories
Authors: Albouy Yves , Andrieux Pierre , Rakotondrasoa Gérard , Ritz Michel , Descloitres Marc , Join Jean‐Lambert , Rasolomanana Eddy
Published: December 2005

Electrical and electromagnetic methods are well suited for coastal aquifer studies because of the large contrast in resistivity between fresh water‐bearing and salt water‐bearing formations. Interpretation models for these aquifers typically contain four layers: a highly resistive unsaturated zone; a surficial fresh water aquifer of intermediate resistivity; an underlying conductive, salt water saturated aquifer; and resistive substratum. Additional layers may be added to allow for variations in lithology within the fresh water and salt water layers. Two methods are evaluated: direct current resistivity and time domain electromagnetic soundings. Use of each method alone produces nonunique solutions for resistivities and/or thicknesses of the different layers. We show that joint inversion of vertical electric and time domain electromagnetic soundings produces a more tightly constrained interpretation model at three test sites than is produced by inversion methods applied to each data set independently.
Forecasting of Turbid Floods in a Coastal, Chalk Karstic Drain Using an Artificial Neural Network
Authors: Beaudeau P. , Leboulanger T. , Lacroix M. , Hanneton S. , Wang H.Q.
Published: December 2005

Water collected at the Yport (eastern Normandy, France) Drinking Water Supply well, situated on a karst cavity, is affected by surface runoff‐related turbidity spikes that occur mainly in winter. In order to forecast turbidity, precipitation was measured at the center of the catchment basin over two years, while water level and turbidity were monitored at the well site.

Application of the approach of Box and Jenkins (1976) leads to a linear model that can accurately predict major floods about eight hours in advance, providing an estimate of turbidity variation on the basis of precipitation and water level variation over the previous 24 hours. However, this model is intrinsically unable to deal with (1) nonstationary changes in the time process caused by seasonal variations of in ground surface characteristics or tidal influence within the downstream part of the aquifer, and (2) nonlinear phenomena such as the threshold for the onset of runoff. This results in many false‐positive signals of turbidity in summer.

Here we present an alternative composite model combining a conceptual runoff submodel with a feedforward artificial neural network (ANN). This composite model allows us to deal with meaningful variables, the actioneffect of which on turbidity is complex, nonlinear, temporally variable and often poorly described. Predictions are markedly improved, i.e., the variance of the target variable explained by 12‐hour forward predictions increases from 28% to 74% and summer inaccuracies are considerably lowered. The ANN can adjust itself to new hydrological conditions, provided that on‐line learning is maintained.
A Conceptual Model for DNAPL Transport in Karst Ground Water Basins
Authors: Loop Caroline M. , White William B.
Published: December 2005

Dense nonaqueous phase liquids (DNAPLs) such as perchloroethylene, polychlorinated biphenyls, creosote mixtures, and many solvents and degreasers can be released into karst aquifers through sinkholes and sinking streams in quantities up to tanker car volumes. Although DNAPLs are easily injected into karst aquifers, discharge of the contaminants through springs may be significantly delayed depending on transport mechanism, storm water recharge, and storage sites within the karst aquifer. Storage sites include (1) the epikarst; (2) pools and depressions within underground streams; (3) incorporation of DNAPL within clastic sediments that are present in most conduits; (4) adsorption onto organic materials and onto manganese oxides, iron oxides, and other substrates; and (5) migration to depth within the fracture system. Effective transport of DNAPL contaminants during storm flow pulses requires the exceedance of thresholds best defined in terms of the conduit stream power. Movement of pooled DNAPL requires a boundary shear between the liquid and water flowing over it. DNAPL stored in clastic sediment bleeds out slowly or dissolves into surrounding pore water until storm pulses create a stream flow sufficient to flush the pore water, or possibly move the sediment pile itself. Under extreme flow conditions the entire sediment pile, including the DNAPL, can be entrained and ejected from the conduit system.
Three‐Dimensional Modeling of Density‐Dependent Salt Water Intrusion in Multilayered Coastal Aquifers in Jahe River Baisn, Shandong Province, China
Authors: Cheng Jian M. , Chen Chong X.
Published: December 2005

A three‐dimensional variable density flow and transport model has been developed to study salt water intrusion in the Jahe River Basin, Shandong Province, China, A coupled Eulerian‐Lagrangian method is applied to solve the transport equation, in which the advection part is calculated by a hybrid method of characteristics. In using the density‐dependent tidal effect model, the seaward boundary in the confined apuifer is determined according to tidal‐effect information. The aquifer parameters in the Jahe River Basin are estimated by converging long‐term observational data of the hydraulic head and chloride concentration. Through numerical analysis and prediction, it can be concluded that the main reasons for salt water intrusion are excessive ground water exploitation and an improper arrangement of pumping wells in the lower reaches of the Jahe River Basin as well as the tidal‐affected river. After predicting the effect of several remedial schemes, two measures are suggested to prevent salt water intrusion.
Atrazine Retention and Degradation in the Vadose Zone at a Till Plain Site in Central Indiana
Authors: Bayless E. Randall
Published: December 2005

The vadose zone was examined as an environmental compartment where significant quantities of atrazine and its degradation compounds may be stored and transformed. The vadose zone was targeted because regional studies in the White River Basin indicated a large discrepancy between the mass of atrazine applied to fields and the amount of the pesticide and its degradation compounds that are measured in ground and surface water. A study site was established in a rotationally cropped field in the till plain of central Indiana. Data were gathered during the 1994 growing season to characterize the site hydrogeology and the distribution of atrazine, desethylatrazine, deisopropylatrazine, didealkylatrazine and hydroxyatrazine in runoff, pore water, and ground water. The data indicated that atrazine and its degradation compounds were transported from land surface to a depth of 1.5 m within 60 days of application, but were undetected in the saturated zone at nearby monitoring wells. A numerical model was developed, based on the field data, to provide information about processes that could retain and degrade atrazine in the vadose zone. Simulations indicated that evapotranspiration is responsible for surface directed soil‐moisture flow during much of the growing season. This process causes retention and degradation of atrazine in the vadose zone. Increased residence time in the vadose zone leads to nearly complete transformation of atrazine and its degradation products to unquantified degradation compounds. As a result of macropore flow, small quantities of atrazine and its degradation compounds may reach the saturated zone.
Evaluation of Ground Water Monitoring Network by Principal Component Analysis
Authors: Gangopadhyay Subhrendu , Das Gupta Ashim , Nachabe M.H.
Published: December 2005

Principal component analysis is a data reduction technique used to identify the important components or factors that explain most of the variance of a system. This technique was extended to evaluating a ground water monitoring network where the variables are monitoring wells. The objective was to identify monitoring wells that are important in predicting the dynamic variation in potentiometric head at a location. The technique is demonstrated through an application to the monitoring network of the Bangkok area. Principal component analysis was carried out for all the monitoring wells of the aquifer, and a ranking scheme based on the frequency of occurrence of a particular well as principal well was developed. The decision maker with budget constraints can now opt to monitor principal wells which can adequately capture the potentiometric head variation in the aquifer. This was evaluated by comparing the observed potentiometric head distribution using data from all available wells and wells selected using the ranking scheme as a guideline.
Natural Attenuation of Volatile Organic Compounds (VOCs) in the Leachate Plume of a Municipal Landfill: Using Alkylbenzenes as Process Probes
Authors: Eganhouse Robert P. , Cozzarelli Isabelle M. , Scholl Martha A. , Matthews Lara L.
Published: December 2005

More than 70 individual VOCs were identified in the leachate plume of a closed municipal landfill. Concentrations were low when compared with data published for other landfills, and total VOCs accounted for less than 0.1 % of the total dissolved organic carbon. The VOC concentrations in the core of the anoxic leachate plume are variable, but in all cases they were found to be near or below detection limits within 200 m of the landfill. In contrast to the VOCs, the distributions of chloride ion, a conservative tracer, and nonvolatile dissolved organic carbon, indicate little dilution over the same distance. Thus, natural attentuation processes are effectively limiting migration of the VOC plume. The distribution of C2–3‐benzenes, paired on the basis of their octanol‐water partition coefficients and Henry's law constants, were systematically evaluated to assess the relative importance of volatilization, sorption, and biodegradation as attenuation mechanisms. Based on our data, biodegradation appears to be the process primarily responsible for the observed attenuation of VOCs at this site. We believe that the alkylbenzenes are powerful process probes that can and should be exploited in studies of natural attenuation in contaminated ground water systems.
Distribution Functions of Spring Discharges According to Their Lithologies and the Influence of Lower Limit to Flow: An Example from Spain
Authors: Pérez Eugenic Sanz
Published: December 2005

Specific functions of distribution of the number of springs and of their contributions according to flow for each of nine lithological groups are established. These functions confirm the suitability of a general type of distribution (Sanz 1996), which is a borderline case of the lognormal distribution. The statistical methods proposed for the lithological types presented can be applied to any region if data on flow and Ethology of the aquifers drained by springs are available. These methods have been applied to Spain, a representative region with varied geology, climate and topography; 71.2% of spring flow is supplied by limestones, 19.17% by alluvial sediments and marls, 6.7% by conglomerates and sandstones, and 3% by slates, plutonic rocks, quartzites, and other groups. Springs with discharge rates exceeding 2000 L/s exist only in limestones. The majority of springs with low flow occur in marls. If we consider springs with flow greater than 0.5 L/s, alluvial sediments, sandstones, marls, and limestones have the greatest density of springs per surface area, although the average flow varies greatly from one lithology to the next. The cumulative estimated discharge and the estimated number of springs depend upon the definition of the lower limit of flow. For example, total discharge is reduced by 30% if we eliminate all springs with flow lower than 0.5 L/min.
Chemical Erosion of the Lilburn Cave System, Kings Canyon National Park, California
Authors: Abu‐Jaber Nizar , Hess John W. , Howcroft William
Published: December 2005

Multi‐year Instrumental records for input, throughflow and output waters of the Lilburn Cave system provide control on denudation rates as they respond to seasonal and spatial variability. Data suggest that maximum denudation is in the late fall and early winter. This is when non‐snowmelt discharge is at Its maximum. At lower discharge rates the volume of water moving through the cave system Is the limiting control on the volume of denudation. During periods of snowmelt the limiting control is the rate at which the calcite dissolves. This is probably the result of water flowing through wider channels during these times. Based on instrumental measurements, there is considerable variation in terms of where denudation occurs inside the cave. The loci of dissolution change from year to year. This is to be expected in the dynamic environment of the cave where materials shift routinely. This variability should be studied over longer periods of time in order to more fully understand its extent. The relatively small area of carbonate exposure relative to the area of the drainage basin gives rise to relatively high denudation rates. The carbonate Is being removed at a rate of about 5000 metric tons per year, or at about 830 mm/y. This is about five times the rate reported in the humid karst regions of Malaysia. This information indicates that the relative proportion of carbonate in the drainage basin needs to be considered when trying to estimate denudation in other areas.
A Rapid Screening‐Level Method to Optimize Location of Infiltration Ponds
Authors: Fennemore G.G. , Davis Andy , Goss L. , Warrick A.W.
Published: December 2005

A rapid‐screening technique was developed to identify Ethologies that best disperse artificial recharge via surface infiltration and minimize effects on ground water chemistry. The technique prospectively evaluates basin infiltration rates and water chemistry influences by integrating geotechnical, hydraulic, and water quality data with column test data and numerical modeling. The technique was validated using field data collected from surface infiltration basins designed to recharge ground water pumped from the Pipeline pit gold mine in Nevada. Observed recharge rates at these infiltration sites correlated most significantly with depth to groundwater, with basins in coarse‐grained lithologies performing better (0.45 to 0.85 m/day) than those with fine‐grained layers (<0.30 m/day). Observed water quality resulting from leaching of the previously unsaturated vadose zone showed a transitory (< six months) increase in solute concentrations followed by a decrease to baseline conditions, a phenomenon also observed in column tests that leached native soils with local ground water. Leaching of fine‐grained soils with evaporites resulted in greater solute concentrations (TDS > 2000 mg/L) than coarse‐grained soils (<1200 mg/L). The results of HYDRUS_2D simulations using the accumulated data as input were in agreement with observed ground water chemistry downgradient of the infiltration basins for a variety of lithologies. Sites for infiltration basins can be rapidly screened to include areas with greatest depth to groundwater and in coarsest alluvial sediments, and impact to ground water chemistry can be reliably predicted using computer modeling and column test results.