bluuebunny/crossref_metadata_2025 huggingface dataset:
Mouthrinses containing triclosan reduce the incidence of recurrent aphthous ulcers (RAU)
Authors: Skaare Anne B. , Herlofson Bente B. , Barkvoll Pål
Published: December 2005

Abstract Triclosan, an antibacterial agent introduced in toothpastes and mouth‐rinses, has recently been shown to have anti‐inflammatory and analgesic properties. The aim of the present double‐blind cross‐over study was to examine the effect of triclosan on the incidence of recurrent aphthous ulceration (RAU) when administered in mouthrinses. The study included 30 patients with a history of multiple recurrent aphthous ulcers. Three different triclosan‐containing mouth‐rinses, differing only in their solubilizing agents were used and compared with a control rinse. The number of new ulcers, ulcer‐free days and the severity of pain were recorded. The results showed that the patients experienced a significant decrease in the number of oral ulcers during the experimental period when the mouthrinses contained triclosan. It may thus be concluded that triclosan has the potential to reduce the number of aphthous ulcers presumably due to its anti‐inflammatory properties.
Prevalence of furcation involvements in patients referred for periodontal treatment
Authors: Svärdström Gram , Wennström Jan L.
Published: December 2005

Abstract The aim of this study was to evaluate the prevalence of furcation‐involved molars in a patient sample referred for periodontal treatment, A total of 222 patients aged, 14‐73 years (mean age 45 years), and with signs of destructive periodontal disease in at least 2 quadrants of the dentition were included in the study. The clinical examination involved assessments of oral hygiene status, gingival conditions, probing pocket depth and presence/degree of furcation involvement. In addition, a full mouth intraoral radiographic examination was performed. The results revealed that 4% of the patients presented with all 12 molars, while 3% had lost all molars, 52% of the individuals had at least 8 molars; 95% of subjects < 30 years of age and 19% in the age 60 years. In patients aged ≥40 years, every 2nd molar showed advanced periodontal destruction in the furcation area. The prevalence of furcation involved molars was higher in the maxilla than in the mandible. From the age of 30 years, about 50% of the 1st and 2nd molars in the maxilla showed at least 1 furcation site with deep involvement, while in the mandible a similar prevalence was observed first after the age of 40 years. The highest frequency of furcation involvement was found at the distal site of the maxillary 1st molar (53%), and the mesial aspects of the maxillary 2nd molar showed the lowest frequency (20%), Furcation sites with a probeable trunk region were observed at a frequency of 17‐22% at the various tooth sites. It was concluded that tooth morphology may be an important factor that accounts for the variability in prevalence of molar furcation involvement.
A case of localized juvenile periodontitis: treatment and 3 years follow‐up with superimposable radiographs
Authors: Dubrez B. , Baehni P. , Cimasoni G.
Published: December 2005

Abstract A 17‐year‐old male patient with localized juvenile periodontitis was treated by subgingival instrumentation with full thickness flap on the lower molars, combined with a 3‐week course of systemic tetracycline, and a programme of supervised oral hygiene. The treatment was rapidly followed by dramatic clinical and microbiological improvement. However, despite good oral hygiene, gingival inflammation recurred at regular intervals. It was necessary to maintain the clinical results by periodic subgingival instrumentation with an ultrasonic sealer. Healing of alveolar bone was monitored in the lower 1st molar regions over 3 years by using superimposable radiographs. Quantitative analysis of bone density performed with a high‐resolution digitalisation technique showed a considerable improvement 1 year after therapy. However, continuous remodelling, probably related to variations in inflammation, occurred during the 3 postoperative years.
Principles of pharmacologic intervention
Authors: Goodson J. M.
Published: December 2005

Abstract Compared to studies with conventional maintenance, relatively few studies have been conducted that have tested pharmacologic intervention as a means for supportive periodontal care. Despite the scarcity of data, several principles have begun to emerge. First, it is clear that removal of subgingival calcultis is necessary for the highest level of a long–term effectiveness. Hence, pharmacologic intervention appears best suited as an adjunctive therapy directed toward “problem sites” sites that fail to respond adequately to conventional maintenance procedures. Intrapocket drug delivery systems appear to offer particular promise since therapy can be directed to selected sites that appear to be failing. Additional effectiveness may also be obtained by use of chlorhexidine mouth rinses for short periods of time during healing to control re–infection. Eradication of reservoirs of infection throughout the mouth also appears to be an important principle related to long–term stabilization. Studies to date suggest that superior clinical response can be obtained by intrapocket delivery systems. Furthermore, up to 2 years of periodontal stabilization can be achieved by these means and longer disease–free maintenance intervals can be established. Additional clinical trials will be necessary to fully optimize and understand this therapeutic approach, but initial studies have reported promising results.
A logistic regression model for the decision to perform access surgery
Authors: Loesche Walter J. , Taylor George , Giordano James , Hutchinson Rowland , Ran Charles F. , Chen Yin‐Miao , Schork M. Anthony
Published: December 2005

Abstract Access surgery may be recommended to about 80% of patients who present with advanced forms of periodontal disease. In this report, a multivariate logistic regression analysis which incorporated several clinical parameters for each tooth examined, i.e., tooth type, furcation involvement, bleeding on probing, attachment level, probing depth, mobility and BANA test score, was conducted using generalized estimating equations (GEE). This approach identified parameters that were significantly associated at p < 0.05 level with the need for access surgery or extraction for periodontal purposes. The estimated probabilities derived from the GEE model were plotted over the complete spectrum of operating conditions to obtain a receiver‐operator characteristic (ROC) curve. At a probability cutpoint of 0.8, the decision threshold for surgery/extraction at the pre‐treatment examination would have a sensitivity of 76.1% and a specificity of 75.3%. We have taken this 0.8 cut point to look at specific clinical decisions made by our examiners after the patients had received scaling and root planing plus 2 weeks unsupervised usage of systemic antimicrobials. The clinicians' decision was taken as the primary reference standard. The model's estimated decision agreed with the clinicians' decision in 226 of the 284 teeth, for an accuracy of 80%. The specificity was 90% and the sensitivity was 43%.
Loss of molars in periodontally treated patients: a retrospective analysis five years or more after active periodontal treatment
Authors: Dannewitz Bettina , Krieger Jörg K. , Hüsing Johannes , Eickholz Peter
Published: December 2005

Objectives: Evaluation of tooth loss in molars and prognostic factors for molar survival.

Material and Methods: Five hundred and five molars in 71 patients (mean age 46 years; 40 females) were evaluated. The following inclusion criteria were required: periodontal therapy of at least one molar, at least 5 years of supportive periodontal therapy, and baseline assessment of furcation involvement (FI).

Results: At baseline 200 of 505 molars exhibited no FI, 116 degree I, 122 degree II, and 67 degree III FI. Twenty‐seven molars did not receive periodontal treatment; 127 molars were subjected to non‐surgical therapy, and 227 to flap surgery. Tunnel preparation was performed on 14 molars, root resection on 20, regenerative therapy on 57 teeth, and 33 molars were extracted. During the average follow‐up period of 107 months 38 molars were lost additionally. Molars with degree III FI had the highest mortality. A multi‐level proportional hazard model revealed smoking, baseline bone loss, number of molars left, and degree III FI as risk factors influencing the retention time of molars.

Conclusion: Overall periodontal therapy results in a good prognosis of molars. Degree III FI leads to a significant deterioration of prognosis. Beyond FI smoking, baseline bone loss, and number of molars left influence molar survival.
Immediate effect of instrumentation on the subgingival microflora in deep inflamed pockets under strict plaque control
Authors: Rhemrev G. E. , Timmerman M. F. , Veldkamp I. , Van Winkelhoff A. J. , Van der Velden U.
Published: December 2005

Objective: To investigate (1) reduction in the number of microorganisms obtained directly after subgingival instrumentation, (2) rate of bacterial re‐colonization during 2 weeks, under supragingival plaque‐free conditions.

Materials and Methods: Effects of subgingival instrumentation were measured at one deep pocket in 22 patients (11 smokers and 11 non‐smokers). Immediately after initial therapy, experimental sites, under strict plaque control, were instrumented subgingivally. Microbiological evaluation was performed at pre‐instrumentation, immediate post‐instrumentation and 1 and 2 weeks post‐instrumentation.

Results: Mean total anaerobic clolony forming units (CFUs) dropped from 3.9 × 106 before to 0.09 × 106 immediately following instrumentation. Significant reductions were found for Tannerella forsythia, Micromonas micros, Fusobacterium nucleatum and spirochetes. Significant reductions were not observed for Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia and Campylobacter rectus. Except for spirochetes, no reduction in prevalence of specific periodontal bacteria was found immediately after instrumentation. During follow‐up, mean total CFU tended to increase. Prevalence of periodontal bacteria further reduced. No effect of smoking was found.

Conclusion: Results indicate that subgingival mechanical cleaning in itself, has a limited effect, in actually removing bacteria. The subsequent reduction in prevalence of specific periodontal bacteria shows that it is apparently difficult for these species to survive in treated pockets.
Neural cell adhesion molecule (NCAM –/– ) null mice show impaired sensitization of the startle response
Authors: Plappert C. F. , Schachner M. , Pilz P. K. D.
Published: December 2005

The neural cell adhesion molecule (NCAM) plays important roles in development of the nervous system and in synaptic plasticity and memory formation in the adult. The present study sought to further investigate the role of NCAM in learning by testing habituation and footshock sensitization learning of the startle response (SR) in NCAM null mutant (NCAM –/– ) and wildtype littermate (NCAM +/+) mice. Whereas habituation is a form of non‐associative learning, footshock sensitization is induced by rapid contextual fear conditioning. Habituation was tested by repetitive presentation of acoustic and tactile startle stimuli. Although NCAM –/– mice showed differences in sensitivity in both stimulus modalities, habituation learning was intact in NCAM –/– mice, suggesting that NCAM does not play a role in the mechanisms underlying synaptic plasticity in the startle pathway. Footshock sensitization was elicited by presentation of electric footshocks between two series of acoustic stimuli. In contrast to habituation, footshock sensitization learning was attenuated in NCAM –/– mice: the acoustic SR increase after the footshocks was lower in the mutant than in wildtype mice, indicating that NCAM plays an important role in the relevant brain areas, such as amygdala and/or the hippocampus.
Transgenic mice expressing a human mutant β1 thyroid receptor are hyperactive, impulsive, and inattentive
Authors: Siesser W. B. , Zhao J. , Miller L. R. , Cheng S.‐Y. , McDonald M. P.
Published: December 2005

Attention deficit hyperactivity disorder (ADHD) is the most commonly diagnosed childhood psychiatric disorder. We have found that a transgenic mouse bearing a human mutant thyroid receptor (TRβ1) expresses all of the defining symptoms of ADHD—inattention, hyperactivity, and impulsivity—as well as a ‘paradoxical’ response to methylphenidate (MPH). As with ADHD, the behavioral phenotypes expressed by the TRβ transgenic mice are dynamic and sensitive to changes in environmental conditions, stress, and reinforcement. TRβ transgenic mice are euthyroid except for a brief period during postnatal development, but the behavioral phenotypes, elevated dopamine turnover, and paradoxical response to MPH persist into adulthood. Thus, like the vast majority of children with ADHD, the TRβ transgenic mice exhibit the symptoms of ADHD in the complete absence of thyroid abnormalities. This suggests that even transient perturbations in developmental thyroid homeostasis can have long‐lasting behavioral and cognitive consequences, including producing the full spectrum of symptoms of ADHD.
Modern Imaging of Brain Malformations with Particular Reference to Endocrinology
Authors: Griffiths P. D.
Published: December 2005

Advances in neuro‐imaging techniques, such as MR imaging, have allowed the demonstration of a wide range of subtle pathologies not possible with previous methods. This is particularly true in the case of brain malformations. In this review I will discuss the range of imaging methods available and describe a structural approach to classifying the range of brain malformations. The most common variety of pituitary malformations are also included in this review.
Radiative transfer along rays in curved space–times
Authors: Broderick Avery E.
Published: December 2005

Radiative transfer in curved space–times has become increasingly important to understanding high-energy astrophysical phenomena and testing general relativity in the strong field limit. The equations of radiative transfer are physically equivalent to the Boltzmann equation, where the latter has the virtue of being covariant. We show that by a judicious choice of the basis of the phase space, it is generally possible to make the momentum derivatives in the Boltzmann equation vanish along an arbitrary (including non-geodesic) path, thus reducing the problem of radiative transfer along a ray to a path integral in coordinate space.
A Simple Solution for Drawdown Calculation in a Large‐Diameter Well
Authors: Çogo;imen Mesut
Published: December 2005

Large‐diameter wells are used extensively in developing countries, especially in unconsolidated alluvial deposits or fissured rocks of shallow depths. Principally, they have large storage volume ready for exploitation by direct pumping. A simple calculation procedure for drawdown in a large‐diameter wellhas been proposed. This is a new method that involves the use of the independent variable transform. The governing equation can be used easily for the evaluation of drawdowns in both pumping and observation wells. Type curves obtained by the procedure developed in this paper are compared with those already available in ground water literature. The accordance of the derived type curves in this study with that of Papadopulos and Cooper (1967) is obvious. However, in this paper, a simple transient solution is presented that allows one to find the drawdown at the pumping and observation wells in an extensive confined aquifer.
Use of Quantitative Models to Design Microbial Transport Experiments in a Sandy Aquifer
Authors: Scheibe Timothy D. , Chien Yi‐Ju , Radtke Jonathan S.
Published: December 2005

A suite of numerical models was applied to the problem of designing field tracer and bacterial injection experiments in a sandy surficial aquifer near Oyster, Virginia. The models were constructed based on the integration of diverse characterization data including hydrologic, geophysical, geological, geochemical, and biological information. A one‐dimensional particle‐tracking model was used to analyze laboratory transport experiments conducted using intact core samples to prescribe transport parameters describing solute dispersion and bacterial fate. A geostatistical model of three‐dimensional hydraulic conductivity variations was developed, conditioned on in situ measurements of hydraulic conductivity and interpretations of geophysical data, and used to generate alternative aquifer descriptions. A regional‐scale, two‐dimensional flow model was used to design pumping rates of a forced‐gradient hydraulic control system. Information from these various models was then combined into a high‐resolution, three‐dimensional flow and transport model for the prediction of field‐scale solute and bacterial transport. Model predictions were used in an iterative experimental design process to specify. (1) the locations of multilevel samplers for monitoring transport; (2) frequency and timing of sample collection during bromide tracer injection experiments; and (3) frequency and timing of sample collection during a bacterial injection experiment. At each stage of the design, information gained during the previous stage was used to refine the model and target subsequent experimentation.
Noninvasive Determination of the Location and Distribution of DNAPL Using Advanced Seismic Relfection Techniques
Authors: Temples Tom J. , Waddell Michael G. , Domoracki William J. , Eyer Jerome
Published: December 2005

Recent advances in seismic reflection amplitude analysis (e.g., amplitude versus offset‐AVO, bright spot mapping) technology to directly detect the presence of subsurface DNAPL (e.g., CCl4) were applied to 216–Z‐9 crib, 200 West Area, DOE Hanford Site, Washington.

Modeling to determine what type of anomaly might be present was performed. Model results were incorporated in the interpretation of the seismic data to determine the location of any seismic amplitude anomalies associated with the presence of high concentrations of CCl4. Seismic reflection profiles were collected and analyzed for the presence of DNAPL. Structure contour maps of the contact between the Hanford fine unit and the Plio/Pleistocene unit and between the Plio/Pleistocene unit and the caliche layer were interpreted to determine potential DNAPL flow direction.

Models indicate that the contact between the Plio/Pleistocene unit and the caliche should have a positive reflection coefficient. When high concentrations of CCl4 are present, the reflection coefficient of this interface displays a noticeable positive increase in the seismic amplitude (i.e., bright spot).

Amplitude data contoured on the Plio/Pleistocene‐caliche boundary display high values indicating the presence of DNAPL to the north and east of the crib area. The seismic data agree well with the well control in areas of high concentrations of CCl4.
Numerical Inverse Interpretation of Single‐Hole Pneumatic Tests in Unsaturated Fractured Tuff
Authors: Vesselinov Velimir V. , Neuman Shlomo P.
Published: December 2005

A numerical inverse method was used to interpret simultaneously multirate injection and recovery data from single‐hole pneumatic tests in unsaturated fractured tuff at the Apache Leap Research Site near Superior, Arizona. Our model represents faithfully the three‐dimensional geometry of boreholes at the site, and accounts directly for their storage and conductance properties by treating them as high‐permeability and high‐porosity cylinders of finite length and radius. It solves the airflow equations in their original nonlinear form and yields information about air permeability, air‐filled porosity and dimensionless borehole storage coefficient. Some of this is difficult to accomplish with analytical type‐curves. Air permeability values obtained by our inverse method agree well with those obtained by steady‐state and type‐curve analyses.
Quantitative Measurement of Channel‐Block Hydraulic Interactions by Experimental Saturation of a Large, Natural, Fissured Rock Mass
Authors: Guglielmi Yves , Mudry Jacques
Published: December 2005

The hydrodynamic behavior of fissured media relies on the relationships between a few very conductive fractures (channels) and the remaining low‐conductivity fractures and matrix (blocks). We made a quantitative measurement of those relationships and their effect on water drainage and storage in a 19,000 m3 natural reservoir consisting of karstified limestones. This reservoir was artificially saturated with water by closing a water gate on the main outlet during a varying time (Δt) fixed by the operator. The water gate was completely or partly closed until the water pressure reached a particular specified value. If the water gate was left completely closed long enough, the water pressure was fixed by the elevation of temporary outlets at the site boundaries. The water elevation within the reservoir was monitored by means of pressure cells located on single fractures representative of the bedding plane and the two families of fractures of the massif network.

The comparison of pressure variations with the network geometry allows us to identify a typical double permeability characterized by a few very conductive channels along 10 vertical faults. These channels limit blocks consisting of low‐conductivity bedding planes and a rather impervious matrix.

Depending on the closure interval, Δt, of the water gate, the total volume of water stored in the reservoir can vary from 0.8 m3 (Δt = 5 minutes) to 18.6 m3 (Δt = 2 days). Such a variance of storage versus closure time is explained by the reservoir's double permeability that is characterized by blocks that saturate much more slowly than channels. If plotted versus time, this injected volume fits a power relationship, according to the saturation state of the blocks. In less than 34 minutes, storage is close to zero in the blocks and to 1.6 to 2 m3 in the channels. For closing times shorter than 1 hour, only 1% of the volume that flows in the channels is stored into the blocks. Depending on the water pressure and for a given Δt = 3000 minutes, the volume of water stored is controlled by the geometry of the joint network and of the aquifer boundaries.

Such an experiment shows that the flow is concentrated in about 10% of the fractured network (channels). The water storage that takes place in the 90% remaining fractures (blocks) depends mainly on time during which pressure remains high into the 10% channels. The accurate modeling of such typical double‐permeability media needs a careful study of the geometry of the channels whose narrowings modify the flow and induce dam effects that maintain a high pressure gradient with surrounding blocks.
Fracture Wall Cements and Coatings from Two Clayey Till Aquitards
Authors: Corrigan Catherine A. , Jamieson Heather E. , Remenda Victoria H.
Published: December 2005

Secondary minerals occurring at the faces of fractures, the only reliable visual evidence of the presence of hydraulically conductive fractures in clayey unlithified aquitards, have been characterized for two uncontaminated field sites, Dalmeny, Saskatchewan, and Laidlaw, Ontario. Preliminary identification of secondary minerals and their variations with depth was made using a MunsellTM Color Chart. Subsequent microscopic analyses (petrography, electron microprobe analysis, scanning electron microscopy, and X‐ray diffraction) were used to identify iron‐oxide mineralogy. Iron oxides were identified as goethite, ferrihydrite, and hematite at Dalmeny, where they occur to depths of 10 to 15 m, and goethite and ferrihydrite at Laidlaw, observed to depths of 7 m. In both cases, the identification of ferrihydrite was tentative due to the problems of small sample size and peak overlap in X‐ray diffraction. The iron oxides do not form coatings on the surfaces of the fractures as had been previously thought; rather they form cements linking the matrix grains. Thus there is potential for decreased permeability and increased surface reactivity parallel to and inward from the fracture faces. The pattern of iron‐oxide distribution suggests that the youngest deposits, and those with the greatest surface reactivity and potential for contaminant retardation, are found at greatest depths in the fractures. Manganese oxides form in isolated clusters in larger pores and indentations, although the exact manganese minerals could not be firmly identified.
Colloid Mobilization in the Field Using Citrate to Remediate Chromium
Authors: Johnson Carol R. , Hellerich Lucas A. , Nikolaidis Nikolaos P. , Gschwend Philip M.
Published: December 2005

We investigated the feasibility of cleaning aquifer sediments, long contaminated with chromium (Cr) from a metal plating facility, by detaching colloid‐sized sorbents from the immobile aquifer solids and then pumping those colloids to the surface for treatment. In laboratory experiments using aquifer solids from the site, several solutions (water at various pHs, phosphate, oxalate, ascorbate, citrate) were examined for their ability to disperse colloids and Cr. Based on these tests, a 5 mM citrate solution at pH 7 was selected. Subsequently, such a citrate solution was used in the field in two single‐well injection‐withdrawal experiments. Large quantities of colloids were released immediately after injection. The colloidal particles mobilized by citrate in the field had more than 20 times higher Cr concentrations than did the average aquifer sediments, implying success in mobilizing Cr‐associated phases. Further, laboratory and field tests showed that anion exchange of citrate for chromate caused some additional release of Cr from these aquifer solids.
Ground Water Flow Analysis of a Mid‐Atlantic Outer Coastal Plain Watershed, Virginia, U.S.A.
Authors: Robinson Michael A. , Reay William G.
Published: December 2005

Models for ground water flow (MODFLOW) and particle tracking (MODPATH) were used to determine ground water flow patterns, principal ground water discharge and recharge zones, and estimates of ground water travel times in an unconfined ground water system of an outer coastal plain watershed on the Delmarva Peninsula, Virginia. By coupling recharge and discharge zones within the watershed, flowpath analysis can provide a method to locate and implement specific management strategies within a watershed to reduce ground water nitrogen loading to surface water. A monitoring well network was installed in Eyreville Creek watershed, a first‐order creek, to determine hydraulic conductivities and spatial and temporal variations in hydraulic heads for use in model calibration. Ground water flow patterns indicated the convergence of flow along the four surface water features of the watershed; primary discharge areas were in the noontide portions of the watershed. Ground water recharge zones corresponded to the surface water features with minimal development of a regional ground water system. Predicted ground water velocities varied between < 0.01 to 0.24 m/day, with elevated values associated with discharge areas and areas of convergence along surface water features. Some ground water residence times exceeded 100 years, although average residence times ranged between 16 and 21 years; approximately 95% of the ground water resource would reflect land use activities within the last 50 years.
Rapid Evolution of Redox Processes in a Petroleum Hydrocarbon‐Contaminated Aquifer
Authors: Chapelle Francis H. , Bradley Paul M. , Lovley Derek R. , O'Neill Kathleen , Landmeyer James E.
Published: December 2005

Ground water chemistry data collected over a six‐year period show that the distribution of contaminants and redox processes in a shallow petroleum hydrocarbon‐contaminated aquifer has changed rapidly over time. Shortly after a gasoline release occurred in 1990, high concentrations of benzene were present near the contaminant source area. In this contaminated zone, dissolved oxygen in ground water was depleted, and by 1994 Fe(lll) reduction and sulfate reduction were the predominant terminal electron accepting processes. Significantly, dissolved methane was below measurable levels in 1994, indicating the absence of significant methanogenesis. By 1996, however, depletion of solid‐phase Fe(lll)‐oxyhydroxides in aquifer sediments and depletion of dissolved sulfate in ground water resulted in the onset of methanogenesis. Between 1996 and 2000, water‐chemistry data indicated that methanogenic metabolism became increasingly prevalent. Molecular analysis of 16S‐rDNA extracted from sediments shows the presence of a more diverse methanogenic community inside as opposed to outside the plume core, and is consistent with water‐chemistry data indicating a shift toward methanogenesis over time. This rapid evolution of redox processes reflects several factors including the large amounts of contaminants, relatively rapid ground water flow (∼0.3 m/day [∼1 foot/day]), and low concentrations of microbially reducible Fe(lll) oxyhydroxides (∼ 1 umol/g) initially present in aquifer sediments. These results illustrate that, under certain hydrologic conditions, redox conditions in petroleum hydrocarbon‐contaminated aquifers can change rapidly in time and space, and that the availability of solid‐phase Fe(lll)‐oxyhydroxides affects this rate of change.
Measuring the Hydraulic Conductivity of Shallow Submerged Sediments
Authors: Kelly Susan E. , Murdoch Lawrence C.
Published: December 2005

The hydraulic conductivity of submerged sediments influences the interaction between ground water and surface water, but few techniques for measuring K have been described with the conditions of the submerged setting in mind. Two simple, physical methods for measuring the hydraulic conductivity of submerged sediments have been developed, and one of them uses a well and piezometers similar to well tests performed in terrestrial aquifers. This test is based on a theoretical analysis that uses a constant‐head boundary condition for the upper surface of the aquifer to represent the effects of the overlying water body. Existing analyses of tests used to measure the hydraulic conductivity of submerged sediments may contain errors from using the same upper boundary conditions applied to simulate terrestrial aquifers. Field implementation of the technique requires detecting minute drawdowns in the vicinity of the pumping well. Low‐density oil was used in an inverted U‐tube manometer to amplify the head differential so that it could be resolved in the field. Another technique was developed to measure the vertical hydraulic conductivity of sediments at the interface with overlying surface water. This technique uses the pan from a seepage meter with a piezometer fixed along its axis (a piezo‐seep meter). Water is pumped from the pan and the head gradient is measured using the axial piezometer. Results from a sandy streambed indicate that both methods provide consistent and reasonable estimates of K. The pumping test allows skin effects to be considered, and the field data show that omitting the skin effect (e.g., by using a single well test) can produce results that underestimate the hydraulic conductivity of streambeds.
Deep Water Circulation, Residence Time, and Chemistry in a Karst Complex
Authors: Aquilina L , Ladouche B. , Doerfliger N. , Bakalowicz M.
Published: December 2005

We investigated the hydrochemistry of a complex karst hydrosystem made of two carbonate units along a coastal lagoon. Ground water emerges on the lagoon floor from a submarine spring. In addition, thermal waters circulate through the limestone and mix with karst water near the lagoon shore.

A distinction between the water from the two carbonate units is related to marine influences and human activities. In one of the massifs, the data show an incongruent dissolution of dolomite with time. In the other system, a slight contamination by saline fluids from the thermal reservoir has led to high calcium and magnesium concentrations. 36C1, I4C, and 3H data constrain the residence time of the water, and allow for the distinguishing of four circulation types: (1) shallow surface circulation (primarily above sea level) in the karstic units with short residence times (<20 years); (2) shallow subsurface circulation (approximately 0 to ‐50 m) below the karstic units with residence time in the order of 50 years; (3) deep circulation at depth of 700 to 1500 m in the Jurassic limestones below thick sedimentary cover, with residence time of several thousand years for a part of the water; and (4) deep circulation at a depth of ∼2500 m, which represents the thermal reservoir in the Jurassic units with residence time of ∼100,000 years.

An interpretative hydrogeological framework is based on the constraints of the geochemical analyses of the deep thermal system, and by water flow from the surface to the deep parts of the carbonate formations.
A Finite World, Earth Sciences, and Public Trust
Authors: Narasimhan T.N.
Published: December 2005

The beginning of the 21st century has coincided with our recognition that life‐sustaining earth cycles are remarkably fine‐tuned, and that humans have developed technological abilities to perturb these cycles. Also, inspired by the gifts of freedom and democracy, humans have given themselves laws to exploit nature for profit. The upshot is that nature's balance, governed by immutable physical laws, is being confronted by social laws driven by human aspirations. This conflict and its implications to the human relevance of the earth sciences are explored in the context of an extraordinary tradition of European culture known as public trust.
A Statistical Estimator of the Spatial Distribution of the Water‐Table Altitude
Authors: Sepúlveda Nicasio
Published: December 2005

An algorithm was designed to statistically estimate the areal distribution of water‐table altitude. The altitude of the water table was bounded below by the minimum water‐table surface and above by the land surface. Using lake elevations and stream stages, and interpolating between lakes and streams, the minimum water‐table surface was generated. A multiple linear regression among the minimum water‐table altitude, the difference between land‐surface and minimum water‐table altitudes, and the water‐level measurements from surficial aquifer system wells resulted in a consistently high correlation for all groups of physiographic regions in Florida. A simple linear regression between land‐surface and water‐level measurements resulted in a root‐mean‐square residual of 4.23 m, with residuals ranging from — 8.78 to 41.54 m. A simple linear regression between the minimum water table and the water‐level measurements resulted in a root‐mean‐square residual of 1.45 m, with residuals ranging from –7.39 to 4.10 m. The application of the multiple linear regression presented herein resulted in a root‐mean‐square residual of 1.05 m, with residuals ranging from — 5.24 to 5.63 m. Results from complete and partial F tests rejected the hypothesis of eliminating any of the regressors in the multiple linear regression presented in this study.
A Fresh Water Odyssey: Some Observations on the Global Resource
Authors: Wood Warren W.
Published: December 2005

Appreciable increases in the human population are expected to continue in the next 50 to 100 years. This population will require additional water for nonfungible (nonexchangeable) uses such as irrigated agriculture, livestock watering, domestic supply, and ecosystem support. Because most of the world's easily captured water is already identified and allocated, society must improve efficiency, change the present allocations, and/or develop new sources to meet the expected demands. As the global economy expands, apparently unrelated changes in policy or technology may have large, unexpected consequences for water resources. Foreshadowing these changes in stress on these resources will be the result of nonlinear thinking. Whereas policy cannot create new water, it can provide strategies to promote more efficient use of present water and foster an environment in which important technological improvements can be made. This manuscript provides a brief overview of some of the physical and policy considerations relating to fresh water resources.
MODFLOW 2000 Head Uncertainty, a First‐Order Second Moment Method
Authors: Glasgow Harry S. , Fortney Matthew D. , Lee Jejung , Graettinger Andrew J. , Reeves Howard W.
Published: December 2005

A computationally efficient method to estimate the variance and covariance in piezometric head results computed through MODFLOW 2000 using a first‐order second moment (FOSM) approach is presented. This methodology employs a first‐order Taylor series expansion to combine model sensitivity with uncertainty in geologic data. MOD‐FLOW 2000 is used to calculate both the ground water head and the sensitivity of head to changes in input data. From a limited number of samples, geologic data are extrapolated and their associated uncertainties are computed through a conditional probability calculation. Combining the spatially related sensitivity and input uncertainty produces the variance‐covariance matrix, the diagonal of which is used to yield the standard deviation in MODFLOW 2000 head. The variance in piezometric head can be used for calibrating the model, estimating confidence intervals, directing exploration, and evaluating the reliability of a design. A case study illustrates the approach, where aquifer transmis‐sivity is the spatially related uncertain geologic input data. The FOSM methodology is shown to be applicable for calculating output uncertainty for (1) spatially related input and output data, and (2) multiple input parameters (trans‐missivity and recharge).
Sources of Ground Water Salinity on Islands Using 18O,2H, and 34S
Authors: Allen D.M.
Published: December 2005

Stable isotopes of 18O and 2H in water, and 34S and l8O in dissolved SO4 are used to verify the interpretation of the chemical evolution and proposed sources of salinity for two islands that have undergone postglacial rebound. Results for δ18O and δ34S in dissolved SO4 on the Gulf Islands, southwest British Columbia, Canada, suggest a three‐component mixing between (1) atmospheric SO4 derived largely from recharge of meteoric origin, (2) modern marine SO4 associated with either modern‐day salt water intrusion or Pleistocene age sea water, and (3) terrestrial SO4. The age of the marine SO4 is uncertain based on the geochemistry and SO4 isotopes alone. Two options for mixing of saline ground waters are proposed—either between current‐day marine SO4 and atmospheric SO4, or between older (Pleistocene age) marine SO4 and atmospheric SO4. δ18O and δ2H compositions are relatively consistent between both islands, with a few samples showing evidence of mixing with water that is a hybrid mixture of Fraser River water and ocean water. The isotopic composition of this hybrid water is ∼δ18O = 10 %c. δ18O and δ2H values for many saline ground waters plot close to the global meteoric water line, which is distinctly different from the local meteoric water line. This suggests a meteoric origin for ground waters that is different from the current isotopic composition of meteoric waters. It is proposed these waters may be late Pleistocene in age and were recharged when the island was submerged below sea level and prior to rebound at the end of the last glaciation.
Multiple‐Aquifer Characterization from Single Borehole Extensometer Records
Authors: Pope Jason P. , Burbey Thomas J.
Published: December 2005

Measurement and analysis of aquifer‐system compaction have been used to characterize aquifer and confining unit properties when other techniques such as flow modeling have been ineffective at adequately quantifying storage properties or matching historical water levels in environments experiencing land subsidence. In the southeastern coastal plain of Virginia, high‐sensitivity borehole pipe extensometers were used to measure 24.2 mm of total compaction at Franklin from 1979 through 1995 (1.5 mm/year) and 50.2 mm of total compaction at Suffolk from 1982 through 1995 (3.7 mm/year). Analysis of the extensometer data reveals that the small rates of aquifer‐system compaction appear to be correlated with withdrawals of water from confined aquifers. One‐dimensional vertical compaction modeling indicates measured compaction is the result of nonrecoverable hydrodynamic consolidation of the fine‐grained confining units and interbeds, as well as recoverable compaction and expansion of coarse‐grained aquifer units. The calibrated modeling results indicate that nonrecoverable specific storage values decrease with depth and range from 1.5 × 10−5/m for aquifer units to 1.5 × 10−4/m for confining units and interbeds. The aquifer and Potomac system recoverable specific storage values were all estimated to be 4.5 × 10−6/m, while the confining units and interbeds had values of 6.0 × 10−6/m. The calibrated vertical hydraulic conductivity values of the confining units and interbeds ranged from 6.6 × 10−4m/year to 2.0 × 10−3 m/year. These parameter values will be useful in future management and modeling of ground water in the Virginia Coastal Plain.
Geophysical Monitoring and Evaluation of Coastal Plain Aquifers
Authors: Land Lewis A. , Lautier Jeff C. , Wilson Nathaniel C. , Chianese Gabrielle , Webb Steven
Published: December 2005

We use time domain electromagnetic (TDEM) soundings to monitor ground water conditions beneath the coastal plain in eastern North Carolina. The TDEM method measures the earth's response to an induced electromagnetic field. The resulting signal is converted, through a complex inversion process, to apparent resistivity values, which can be directly correlated to borehole resistivity logs. TDEM soundings are used to map the interface between fresh and salt water within coastal aquifers, and estimate depth to basement when siting new monitoring wells. Focused TDEM surveys have identified areas of salt water encroachment caused by high volumes of discharge from local supply wells. Electromagnetic sounding, when used in tandem with the state's network of monitoring wells, is an accurate and inexpensive tool for evaluating fresh water/salt water relationships on both local and regional scales within coastal plain aquifers.
Evaluation of Volatilization as a Natural Attenuation Pathway for MTBE
Authors: Lahvis Matthew A. , Baehr Arthur L , Baker Ronald J.
Published: December 2005

Volatilization and diffusion through the unsaturated zone can be an important pathway for natural attenuation remediation of methyl tert‐butyl ether (MTBE) at gasoline spill sites. The significance of this pathway depends primarily on the distribution of immiscible product within the unsaturated zone and the relative magnitude of aqueous‐phase advection (ground water recharge) to gaseous‐phase diffusion. At a gasoline spill site in Laurel Bay, South Carolina, rates of MTBE volatilization from ground water downgradient from the source are estimated by analyzing the distribution of MTBE in the unsaturated zone above a solute plume. Volatilization rates of MTBE from ground water determined by transport modeling ranged from 0.0020 to 0.0042 g m‐2/year, depending on the assumed rate of ground water recharge. Although diffusive conditions at the Laurel Bay site are favorable for volatilization, mass loss of MTBE is insignificant over the length (230 m) of the solute plume. Based on this analysis, significant volatilization of MTBE from ground water downgradient from source areas at other sites is not likely. In contrast, model results indicate that volatilization coupled with diffusion to the atmosphere could be a significant mass loss pathway for MTBE in source areas where residual product resides above the capillary zone. Although not documented, mass loss of MTBE at the Laurel Bay site due to volatilization and diffusion to the atmosphere are predicted to be two to three times greater than mass loading of MTBE to ground water due to dissolution and recharge. This result would imply that volatilization in the source zone may be the critical natural attenuation pathway for MTBE at gasoline spill sites, especially when considering capillary zone limitations on volatilization of MTBE from ground water and the relative recalcitrance of MTBE to biodegradation.
The Role of Water in Computational and Experimental Derivation of Binding Thermodynamics in SH2 Domains
Authors: Geroult Sebastien , Virdee Satpal , Waksman Gabriel
Published: December 2005

We have studied the role of bound interface water molecules on the prediction of the thermodynamics of SH2 domain binding to tyrosyl phosphopeptides using a method based on accessible surface area buried upon association. We studied three phosphopeptide ligands, which have been shown by Lubman and Waksman (J Mol Biol;328:655, 2003) and Davidson et al. (JACS;124:205, 2002) to have similar binding free energies but very different thermodynamic signatures. The thermodynamic model is semiempirical and applies to the crystal structure of the SH2 domain‐bound forms. We explored all possible combinations of bound interfacial waters. We show that the model does not predict the binding thermodynamics of either ligand. However, we identified the empirical formula describing the heat capacity change as the source of the problem. Indeed, systematic exploration of heat capacity change values between 0 and −300 cal/mol deg results in a sharp distribution of the number of ligand/SH2/water‐subset structures that provide binding thermodynamics similar to experimental values. The heat capacity change values at which the distributions peak are different for each peptide. This prompted us to experimentally determine the heat capacity change for each of the peptides and we found them to coincide with the values of the peaks. The implications of such findings are discussed.