bluuebunny/crossref_metadata_2025 huggingface dataset:
Economic Conditions Early in Life and Individual Mortality
Authors: van den Berg Gerard J , Lindeboom Maarten , Portrait France
Published: March 2006

We analyze the effect of economic conditions early in life on individual mortality rate later in life, using business cycle conditions early in life as an exogenous indicator. Individual records from Dutch registers of birth, marriage, and death, covering a window of unprecedented size (1912–2000) are merged with historical data on macroeconomic and health indicators. We correct for secular changes over time and other mortality determinants. We nonparametrically compare those born in a recession to those born in the preceding boom, and we estimate duration models where the individual's mortality rate depends on current conditions, conditions early in life, age individual characteristics, including individual socioeconomic indicators, and interaction terms. The results indicate a significant negative effect of economic conditions early in life on individual mortality rates at all ages.
Money in a Theory of Banking
Authors: Diamond Douglas W , Rajan Raghuram G
Published: March 2006

We examine the role of banks in the transmission of monetary policy. In economies where banks use real demand deposits to finance their lending, fluctuations in the timing of production can force banks to scramble for real liquidity, or even fail, which can greatly affect lending and aggregate output. The adverse effect on output can be reduced if banks finance with nominal deposits. Nominal deposits also open a “financial liquidity” channel for monetary policy to affect real activity. The banking system may be better off, however, issuing real deposits (e.g., foreign exchange denominated) under some circumstances.
Putting Risk in Its Proper Place
Authors: Eeckhoudt Louis , Schlesinger Harris
Published: March 2006

This paper examines preferences toward particular classes of lottery pairs. We show how such concepts as prudence and temperance can be fully characterized by a preference relation over these lotteries. If preferences are defined in an expectedutility framework with differentiable utility, the direction of preference for a particular class of lottery pairs is equivalent to signing the nth derivative of the utility function. What makes our characterization appealing is its simplicity, which seems particularly amenable to experimentation.
The Big Push Déjà Vu: A Review of Jeffrey Sachs's The End of Poverty: Economic Possibilities for Our Time
Authors: Easterly William
Published: March 2006

Jeffrey Sachs's new book (The End of Poverty: Economic Possibilities for Our Time, Penguin Press: New York, 2005) advocates a “Big Push” featuring large increases in aid to finance a package of complementary investments in order to end world poverty. These recommendations are remarkably similar to those first made in the 1950s and 1960s in development economics. Today, as then, the Big Push recommendation overlooks the unsolvable information and incentive problems facing any large-scale planning exercise. A more promising approach would be to design incentives for aid agents to implement interventions piecemeal whenever they deliver large benefits for the poor relative to costs.
What Determines Cartel Success?
Authors: Levenstein Margaret C , Suslow Valerie Y
Published: March 2006

Following George Stigler (1964), many economists assume that incentive problems undermine attempts b firms to collude to raise prices and restrict output. But the potential profits from collusion can create a powerful incentive as well. Theory cannot tell us, a priori, which effect will dominate: whether or when cartels succeed is thus an empirical question. We examine a wide variety of empirical studies of cartels to answer the following questions: (1) Can cartels succeed? (2) If so, for how long? (3) What impact do cartels have? (4) What causes cartels to break up? We conclude that many cartels do survive, and that the distribution of duration is bimodal. While the average duration of cartels across a range of studies is about five years, many cartels break up very quickly (i.e., in less than a year). But there are many others that last between five and ten years, and some that last decades. Limited evidence suggests that cartels are able to increase prices and profits, to varying degrees. Cartels can also affect other non-price variables, including advertising, innovation, investment, barriers to entry, and concentration. Cartels break up occasionally because of cheating or lack of effective monitoring, but the biggest challenges cartels face are entry and adjustment of the collusive agreement in response to changing economic conditions. Cartels that develop organizational structures that allow them the flexibility to respond to these changing conditions are more likely to survive. Price wars that erupt are often the result of bargaining issues that arise in such circumstances. Sophisticated cartel organizations are also able to develop multipronged strategies to monitor one another to deter cheating and a variety of interventions to increase barriers to entry.
The International Monetary Fund in a Time of Crisis: A Review of Stanley Fischer'sIMF Essays from a Time of Crisis: The International Financial System, Stabilization, and Development
Authors: Conway Patrick
Published: March 2006

Stanley Fischer was deputy managing director of the IMF from 1994 to 2001 and, perhaps more than any other individual, he personifies the international “rapid response” to financial crises in the 1990s. This book is a collection of essays written during his tenure at the IMF; taken together, the essays represent the strongest and most logical defense of IMF initiatives in the 1990s in print. My review essay comprises six parts. In parts 2 through 4, I provide an overview of Fischer's arguments in three central areas of contention: stabilization policy, the impact of IMF programs on poverty, and the IMF's anticipation of and response to international financial crisis. I then compare Fischer's arguments to those raised by the IMF's critics during that period. The controversial issues of these parts can be resolved only through empirical investigation but, on the issues of greatest importance from the financial crises of the 1990s, both Fischer and the IMF's critics make logically consistent arguments with little empirical support. In part 5, I review the recent empirical literature to illuminate what evidence has been found in support of—or counter to—the assertions of Fischer and the IMF's critics. Part 6 provides conclusions and suggestions for follow-on empirical research.
Childhood Fears and Phobias: Advances in Assessment and Treatment
Authors: King Neville J. , Muris Peter , Ollendick Thomas H. , Gullone Eleonora
Published: March 2006

The specific phobias in children, such as night-time fears and animal phobias, should not be underestimated since they cause personal distress to the child and also much interference with daily activities. Intervention plans should be informed by multimethod assessment, using tools that are empirically sound and developmentally sensitive. This article selectively reviews a number of assessment tools including structured diagnostic interview schedules, standardised instruments such as anxiety or fear self-report questionnaires, and behavioural tasks. An overview is given of the main intervention approaches, from a behavioural perspective, including traditional behavioural intervention procedures such as systematic desensitisation and its variants, cognitive–behavioural therapy, and behavioural family therapy. The authors also present recent developments in psychodynamic treatment for phobic and anxious children. Finally, we present conclusions on the empirical standing of the various treatment approaches and also examine the important issue of treatment outcome prediction.
The Origins of Blood–Injection Fear/Phobia in Cancer Patients Undergoing Intravenous Chemotherapy
Authors: Carey Catherine L. , Harris Lynne M.
Published: March 2006

In the present study, responses of 197 people who were receiving chemotherapy at two outpatient clinics and who completed a questionnaire about the presence and origin of blood-injection-injury (BII) fear were examined. From this sample, 36 participants (18.9%) reported ‘strong feelings of fear, disgust or discomfort’ towards the sight of blood, receiving injections or both. Of the 36, 7 participants (19.4%) had first noticed these concerns while they were receiving chemotherapy, and a further 19 (52.8%) reported noticing them during a traumatic experience unrelated to treatment. A subgroup of 22 participants completed the Origins Questionnaire (Menzies & Clarke, 1993). Of these participants, 7 (31.8%) were classified as having an associative onset, and 6 (27.7%) were classified as nonassociative. Only 1 participant with an associative onset attributed the fear to trauma related to chemotherapy. From these data, it appears that while a large minority of the chemotherapy patients who completed the questionnaire experienced distress associated with blood and injections, in the majority of cases the onset of these fears was not attributable to trauma associated with chemotherapy.
Community Trial of an Evidence-Based Anxiety Intervention for Children and Adolescents (the FRIENDS Program): A Pilot Study
Authors: Farrell Lara J. , Barrett Paula M. , Claassens Susanne
Published: March 2006

The aim of the current pilot study was to examine the effectiveness of the FRIENDS program (a cognitive–behavioural intervention for children and adolescents with anxiety) within a community-based clinic in Brisbane, Australia. A total of 18 children participated in the study and completed the FRIENDS program at Pathways Health and Research Centre, an innovative research-based psychology clinic for children, adolescents and families. All participants either met criteria for an anxiety disorder (N = 11) or were experiencing subclinical symptoms of anxiety (N = 7) before commencing the intervention. Before and following treatment, participants were assessed using a diagnostic interview and completed a number of self-report questionnaires. Results indicated that 73% of the participants who met criteria for an anxiety disorder before the intervention were diagnosis-free following treatment. Positive treatment effects were also found for questionnaire data, indicating that there were significant reductions on self-report levels of anxiety and depression following treatment. The outcome of this research suggests that the FRIENDS program is an effective treatment for children with anxiety, and results from this community trial replicate findings from controlled treatment trials.
On the Decline ofn= 1 Research inBehaviour Change: A Comment and Some Questions
Authors: Sharpley Christopher F.
Published: March 2006

Then= 1 research design and the ethos underpinning it have importantly contributed to applied behaviour analysis since its inception. Many papers inBehaviour Change(BC) using this methodology have been of value to practitioners in the field, as well as to researchers and teachers. However, the rate of publication ofn= 1 papers in BC has decreased during the last decade. The present article first documents that decline in rate of publication, then raises some issues for discussion about why this has occurred. Comments from the wider readership are invited in an effort to resurrect this valuable and informative clinical research tradition.
The CB1 Cannabinoid Receptor Is the Major Cannabinoid Receptor at Excitatory Presynaptic Sites in the Hippocampus and Cerebellum
Authors: Kawamura Yoshinobu , Fukaya Masahiro , Maejima Takashi , Yoshida Takayuki , Miura Eriko , Watanabe Masahiko , Ohno-Shosaku Takako , Kano Masanobu
Published: March 2006

Endocannabinoids work as retrograde messengers and contribute to short-term and long-term modulation of synaptic transmission via presynaptic cannabinoid receptors. It is generally accepted that the CB1 cannabinoid receptor (CB1) mediates the effects of endocannabinoid in inhibitory synapses. For excitatory synapses, however, contributions of CB1, “CB3,” and some other unidentified receptors have been suggested. In the present study we used electrophysiological and immunohistochemical techniques and examined the type(s) of cannabinoid receptor functioning at hippocampal and cerebellar excitatory synapses. Our electrophysiological data clearly demonstrate the predominant contribution of CB1. At hippocampal excitatory synapses on pyramidal neurons the cannabinoid-induced synaptic suppression was reversed by a CB1-specific antagonist,N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (AM251), and was absent in CB1 knock-out mice. At climbing fiber (CF) and parallel fiber (PF) synapses on cerebellar Purkinje cells the cannabinoid-dependent suppression was absent in CB1 knock-out mice. The presence of CB1 at presynaptic terminals was confirmed by immunohistochemical experiments with specific antibodies against CB1. In immunoelectron microscopy the densities of CB1-positive signals in hippocampal excitatory terminals and cerebellar PF terminals were much lower than in inhibitory terminals but were clearly higher than the background. Along the long axis of PFs, the CB1 was localized at a much higher density on the perisynaptic membrane than on the extrasynaptic and synaptic regions. In contrast, CB1 density was low in CF terminals and was not significantly higher than the background. Despite the discrepancy between the electrophysiological and morphological data for CB1 expression on CFs, these results collectively indicate that CB1 is responsible for cannabinoid-dependent suppression of excitatory transmission in the hippocampus and cerebellum.
Speech Outcome and Velopharyngeal Function in Cleft Palate: Comparison of Le Fort I Maxillary Osteotomy and Distraction Osteogenesis—Early Results
Authors: Chanchareonsook Nattharee , Whitehill Tara L. , Samman Nabil
Published: March 2006

Objective:

To compare speech outcome and velopharyngeal (VP) status of subjects with repaired cleft palate who underwent either conventional Le Fort I osteotomy or maxillary distraction osteogenesis to correct maxillary hypoplasia.

Design:

Prospective randomized study with blind assessment of speech outcome and VP status.

Subjects:

Twenty-two subjects were randomized into conventional Le Fort I osteotomy and Le Fort I distraction groups. All were native Chinese (Cantonese) speakers.

Method:

Perceptual judgment of resonance and nasal emission, study of VP structures by nasoendoscopy, and instrumental measurement by nasometry. Assessments were performed preoperatively and at 3 months postoperatively.

Main Outcome Measures:

Assessment of VP closure, perceptual rating of hypernasality and nasal emission, nasalance, and amount of maxillary advancement.

Results:

There was no statistical difference in any of the outcome measures between the 10 subjects with conventional Le Fort I osteotomy and the 12 subjects with maxillary distraction: hypernasality (chi-square = 3.850, p = 0.221), nasal emission (chi-square = 0.687, p = 0.774), VP gap size (chi-square = 1.527, p = 0.635, and nasalance (t = −0.145, p = 0.886). There was no correlation between amount of maxillary advancement and any of the outcome measures (p = .05 for all). Changes in VP gap size and resonance are described.

Conclusion:

Results need to be interpreted with caution because of the small sample size and early follow-up. However, this study utilized an assessment protocol involving a variety of outcome measures and careful consideration of reliability factors, which can be a model for further and follow-up studies.
Tongue-Palate Contact during Bilabials in Normal Speech
Authors: Gibbon Fiona E. , Lee Alice , Yuen Ivan
Published: March 2006

Objective:

Previous research using electropalatography (EPG) identified a compensatory articulation called bilabial-lingual double articulations. These double articulations were produced for bilabials by some speakers with cleft palate and involved closure at the lips occurring simultaneously with complete tongue-palate constriction. However, no normative English EPG data exist to confirm the abnormal status of these double articulations.

Design:

This study reports normative data for EPG contact during bilabial closure. Acoustic and EPG data were recorded for bilabials in different vowel contexts.

Participants:

Eight normal English-speaking adults.

Measures:

One measure identified complete tongue-palate constriction, and a second measure calculated percent contact.

Results:

There were no instances of complete tongue-palate constriction, though some EPG contact occurred in the lateral regions of the palate. The vowel context significantly affected the amount of contact present, with /i/ having the most and /a/ having the least amount of contact.

Conclusion:

Complete tongue-palate constriction during bilabials of the type found in bilabial-lingual double articulations is not a feature of normal English speech and can therefore be considered an abnormal articulation pattern. Speech-language pathologists who use EPG in their clinical work should be aware that some lateral contact during bilabial closure is normal.
Influence of cross-section on the strength of timber beams
Authors: Bahadori-Jahromi A. , Kermani A. , Zhang B. , Harte A. M. , Bayne K. , Turner J. , Walford B.
Published: March 2006

This paper investigates the strength and deformation characteristics of lightweight timber composite beams manufactured with six different cross-sectional profiles in comparison with readily available laminated veneer lumber (LVL) and glued-laminated (Glulam) beams. All engineered profiles comprised solid timber or LVL flanges and three-ply plywood webs. The number of webs varied from one to four. The beams had an overall depth of 290 mm and were either 88 mm or 106 mm wide. A study was conducted to provide a comparison of the beam designs and to determine possible effects of cross-sectional configuration and connection details on the structural properties of the beams. To enable a realistic analysis, 12 beams were replicated for each design. The individual components of the beams were tested prior to assembly to obtain the modulus of elasticity and shear modulus and were grouped to provide an even distribution of the material properties. The addition of extra webs to the I-beam profile significantly enhanced the bending and shear capacity of the beam while maintaining a high strength to weight ratio. The boxed I-beam proved to be the most efficient to manufacture and displayed superior structural performance compared with the rest of the profiles in terms of flexural stiffness and bending and shear capacity. The experimental results confirmed the significant contribution of the shear deflection to the total deflection of the I-beams, box beams and even solid section beams.
Effects of beam bar anchorage on beam–column joint behaviour
Authors: Kuang J. S. , Wong H. F.
Published: March 2006

Reversed cyclic-load tests are carried out on full-scale reinforced concrete (RC) exterior beam–column joints, which are fabricated to simulate those in as-built RC framed buildings designed to BS 8110. Emphasis of the study is placed on the effects of the types of beam bar anchorage and location of laps in column reinforcement on the seismic behaviour and shear strength of RC exterior joints subjected to simulated earthquake load. The behaviour is investigated with different types of anchorage in beam reinforcement and laps in column bars at the lower zone of the column. It has been shown from the experiment that all the specimens have low ductility capacity and poor energy dissipation ability. The test results are compared with two preseismic design codes (BS 8110 and EC 2) and two seismic design codes (ACI-318 and NZS 3101). It is shown that the types of reinforcement anchorage in beams have significant effects on the shear capacity and hysteretic behaviour of exterior beam–column joints. Present codes of practice do not accurately predict the shear strength of the non-seismically detailed joints. It is indicated that ignoring the design of beam–column joints may lead to potential damage of RC framed buildings in an unexpected low to moderate earthquake.
Structural analysis of CFRP-plated pultruded GRP beams
Authors: Turvey G. J.
Published: March 2006

Within the context of small deflection beam theory, an exact analysis is presented for a pultruded glass reinforced plastic (GRP) beam stiffened by carbon fibre reinforced plastic (CFRP) plating, which is adhesively bonded to the inner and outer faces of the top and bottom flanges and extends over the central part of the span. The analysis assumes full composite action between the GRP and CFRP and takes account of shear deformation as well as the effects of the rotational stiffness of the connections at the ends of the beam. Exact expressions for the mid-span deflection, the end rotations and the required end rotation capacity for a prescribed mid-span deflection–span limit are presented for the two practical load cases of a point load at mid-span and a uniform load extending over the whole span. The deflection–load–span relationships for these two load cases are recast into three structural performance indices, λδ, λQ and λL, which quantify the benefits of the partial CFRP plating and the stiffness of the end connections in reducing the mid-span deflection, increasing the load capacity and the span relative to an otherwise identical unplated simply supported beam. The analysis requires the increase in cross-sectional area and second moment of area, due to the bonded CFRP plating to be specified. Closed-form expressions are presented for the determination of both of these quantities. Two examples of the use of the equations are presented, which show the structural performance benefits of CFRP plating for pultruded GRP wide flange beams with idealised and practical (bolted cleat) end connections. An important result arising from one of the examples is that there is little point in plating more than 60% of the beam's span.
Simplified FE model for RC structures under earthquakes
Authors: Cotsovos D. M. , Pavlović M. N.
Published: March 2006

This paper presents work that is an extension of a nonlinear finite-element model with proved capacity for yielding realistic predictions of the response of reinforced-concrete (RC) structures under static monotonic and cyclic loading. 1 , 2 The material model adopted is simpler than most models in current use, and it relies essentially on three key properties: triaxiality, brittleness and independency of both loading rate and load path. 3 The existing nonlinear finite-element program for static loads is presently modified to extend its use for the solution of nonlinear dynamic problems, and the resulting package is employed to investigate the behaviour of RC structures under earthquake loading. The aim of the presented case studies is to illustrate the numerical stability of the nonlinear scheme and its ability to provide realistic predictions through a comparative study between numerical and experimental data.
Characterization of Unsaturated Zone Hydrogeologic Units using Matrix Properties and Depositional History in a Complex Volcanic Environment
Authors: Flint Lorraine E. , Buesch David C. , Flint Alan L.
Published: March 2006

Characterization of the physical and unsaturated hydrologic properties of subsurface materials is necessary to calculate flow and transport for land use practices and to evaluate subsurface processes such as perched water or lateral diversion of water, which are influenced by features such as faults, fractures, and abrupt changes in lithology. Input for numerical flow models typically includes parameters that describe hydrologic properties and the initial and boundary conditions for all materials in the unsaturated zone, such as bulk density, porosity, and particle density, saturated hydraulic conductivity, moisture‐retention characteristics, and field water content. We describe an approach for systematically evaluating the site features that contribute to water flow, using physical and hydraulic data collected at the laboratory scale, to provide a representative set of physical and hydraulic parameters for numerically calculating flow of water through the materials at a site. An example case study from analyses done for the heterogeneous, layered, volcanic rocks at Yucca Mountain is presented, but the general approach for parameterization could be applied at any site where depositional processes follow deterministic patterns. Hydrogeologic units at this site were defined using (i) a database developed from 5320 rock samples collected from the coring of 23 shallow (<100 m) and 10 deep (500–1000 m) boreholes, (ii) lithostratigraphic boundaries and corresponding relations to porosity, (iii) transition zones with pronounced changes in properties over short vertical distances, (iv) characterization of the influence of mineral alteration on hydrologic properties such as permeability and moisture‐retention characteristics, and (v) a statistical analysis to evaluate where boundaries should be adjusted to minimize the variance within layers. Model parameters developed in this study, and the relation of flow properties to porosity, can be used to produce detailed and accurate representations of the core‐scale hydrologic processes ongoing at Yucca Mountain.
Evaluating Nitrogen and Water Management in a Double‐Cropping System Using RZWQM
Authors: Hu C. , Saseendran S. A. , Green T. R. , Ma L. , Li X. , Ahuja L. R.
Published: March 2006

Simulation of water and nutrient processes can enhance intensive agriculture to help feed the world's population in a sustainable manner. Due to excessive N application, environmental protection and agricultural sustainability have become major issues in agriculture. In this study, we calibrated and tested the RZWQM model to assess N management in a double‐cropping system comprised of winter wheat (Triticum aestivum L.) and corn (Zea mays L.) at Luancheng, in the North China Plain. Data, including biomass, grain yield, soil water, and soil and crop N, were used from 2001–2003 field trials applying 200 to 800 kg N ha−1 yr−1 for five cropping seasons. In general, soil water, biomass, and grain yields were predicted better than plant N uptake or soil residual N. Once it had been tested and used to improve the understanding of N processes in this cropping system, the model was further used to evaluate the effects of alternative water and N management scenarios on N leaching. Typical application rates of both water and N could be reduced by about half based on these results, which would have high economic, social, and environmental impacts in China. The results also demonstrate the potential of RZWQM for evaluating N and water management practices in other regions and climates of the world with intensive agriculture.
Desperately Seeking a Cause for Hotspots in Regional‐Scale Groundwater Plumes Resulting from Non‐Point Source Pesticide Applications
Authors: Loague Keith , Soutter Leigh A.
Published: March 2006

The source of high concentration pesticide hotspots within groundwater is of considerable concern. This paper reports on a simulation intensive study designed to examine if and how nonpoint source (NPS) pesticide applications can result in regional‐scale groundwater contamination with local high‐concentration hotspots. For this study, a hotspot is defined to have a concentration of at least one order of magnitude greater than the maximum contaminate level for the pesticide of interest. To address the hotspot question synthetic data were prepared for a generalized regional‐scale saturated NPS system. The synthetic data were constructed by generating 1, 2‐dibromo‐3‐chloropropane (DBCP) water‐table loading scenarios that vary in space and time, creating alternative porous media realizations for different large‐scale features, and designing well networks to simulate pumping. Fluid flow and solute transport simulations were conducted in a straightforward concept‐development mode, for the individual boundary‐value problems that result from the different synthetic data combinations. The simulations were conducted hierarchically, with only the data combinations that result in high concentrations being used at the next simulation level. The results from the more than 11 000 NPS simulations scenarios considered in this study yielded only 15 DBCP hotspots. Generating hotspots for label recommended NPS applications, within contaminated regional‐scale groundwater systems, required the combination of elevated water‐table loading concentrations and high pumping rates. The effort reported here provides a foundation for future work focused on the sources of pesticide hotspots in regional‐scale groundwater systems.
Spatial Analysis of Model Error, Illustrated by Soil Carbon Dioxide Emissions
Authors: Pringle M. J. , Lark R. M.
Published: March 2006

A spatial analysis of model error is required when the observations and model predictions are made at locations in space. This is because: (i) a model may reproduce observed variations better at some spatial scales than others, (ii) the model may be more or less successful at reproducing the relative variability of a process at different spatial scales, and (iii) the spatial pattern of model error may contain information about its possible sources. A geostatistical analysis can address these issues. We developed a model of carbon dioxide (CO2) emissions from soil. The soil (Dystric and Typic Eutrudepts) was sampled on a 1024‐m transect at Silsoe, UK. Observed CO2emissions were compared with model predictions at 156 random locations on the transect. A spatial analysis of the model's error, using a (cross‐validated) linear model of coregionalization, revealed details not apparent with a nonspatial analysis. The model could not predict high‐frequency fluctuations in CO2emissions, but could accurately predict lower‐frequency fluctuations. Factorial cokriging analysis allowed us to estimate and visualize the low‐frequency components. We interpolated model error to unsampled locations, and found bias on soil with relatively large clay contents. Volumetric water content had a weak scale‐dependent correlation with model error. We propose the inter‐block correlation to quantify the effect of a change of support on the correlation of observations and model predictions; the best pixel size for the prediction of soil CO2emissions on the transect was 10 to 20 m.
On the Value of Local Measurements for Prediction of Pesticide Transport at the Field Scale
Authors: Beven Keith , Zhang Danrong , Mermoud André
Published: March 2006

Pesticide transport through the soil profile at the field scale is notoriously difficult to predict because of a lack of appropriate field‐scale models and model parameters that take adequate account of heterogeneity in local flow rates and parameters. It is generally impossible to measure all the parameters required to describe that heterogeneity. A way of approximating pesticide transport at the field scale, given uncertainty in the representation of both local characteristics and field‐scale distributions, is presented. The methodology allows prior estimates of field‐scale distribution parameters to be conditioned on uncertain column‐scale measurements. It is shown how this conditioning can drastically constrain steady‐state flow predictions of atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐1,3,5‐triazine) transport to groundwater for a site in the Rhone Valley, Switzerland. Some of the simplifying assumptions of the current analysis, in particular, to allow for transient simulations, can be relaxed in the future as more computer power becomes available. The methodology, however, should remain valid.
Long‐Term Solute Transport under Semi‐Arid Conditions: Pedon to Field Scale
Authors: Woods S. A. , Kachanoski R. G. , Dyck M. F.
Published: March 2006

Knowledge of factors controlling the spatial and temporal variability of transport in the vadose zone is limited. The objective of this study was to quantify the transport of a tracer at the field scale after 34 yr of low transient flow under semiarid conditions. A Cl− tracer was surface applied to plots (a Chernozemic soil) near Saskatoon, Canada. Thirty‐four years later, soil cores (6‐m depth) were taken along a 90‐m transect (1‐m spacing) and two embedded 10‐m transects (0.2‐m spacing) along one of the plots. The cores were sectioned (0.1‐m intervals) and analyzed for Cl−, bulk density, and soil water content. Although the site is level, slight differences in surface slope had a great effect on surface water redistribution, soil profile development, and the movement of water and solute. After 34 yr, the mean travel depth of the Cl− on a slight knoll was 1.70 m below the surface, compared with 2.76 m in a very slight depression 20 m away. The grade between knoll and depression was 1.8%. After a 19‐mo fallow period, considerably more redistributed surface water was stored in the soil in the slight depression than on the nearby level area. The spatial pattern of the increase in soil water storage (19 mo) was significantly correlated to Cl− transport (34 yr) suggesting that the measured pattern of increase in soil water storage was typical of long‐term patterns. The measurements suggested that 10% of redistributed water ended up as increased deep drainage.
Stochastic Continuum Transport Equations for Field‐Scale Solute Transport: Overview of Theoretical and Experimental Results
Authors: Vanderborght Jan , Kasteel Roy , Vereecken Harry
Published: March 2006

One‐dimensional transport models that predict field‐scale averaged solute fluxes are often used to estimate the risk of nonpoint source groundwater contamination by widespread surface‐applied chemicals. However, within‐field variability of soil hydraulic properties leads to lateral variation in local solute fluxes. When this smaller scale variability is characterized in a geostatistical sense, stochastic three‐dimensional flow and transport equations can be used to predict field‐scale averaged transport in terms of geostatistical parameters. We discuss the use of stochastic equations for the parameterization of equivalent one‐dimensional models predicting averaged solute fluxes. First, we consider the equivalent one‐dimensional convection dispersion model and the equivalent dispersivity, which characterizes the spreading of laterally averaged concentrations or solute fluxes. Second, we discuss the parameterization of a stream tube model to predict local transport variables (i.e., distributions of local concentrations and local arrival times) These local transport variables are shown to be important for predicting nonlinear local transport processes and useful for inversely inferring the spatial structure of soil properties. Stochastic flow and transport equations reveal a dependency of equivalent model parameters on transport distance and flow rate, which reflects the importance of smaller scale heterogeneities on field‐scale transport. Approximate solutions of stochastic flow and transport equations are obtained for steady‐state and uniform flow. The effect of transient flow conditions on transport is discussed. Throughout the paper we refer to experimental and numerical data that confirm or contradict results from stochastic flow and transport equations.
Automatic Calibration and Predictive Uncertainty Analysis of a Semidistributed Watershed Model
Authors: Lin Zhulu , Radcliffe David E.
Published: March 2006

Semidistributed models are commonly calibrated manually, but software for automatic calibration is now available. We present a two‐stage routine for automatic calibration of the semidistributed watershed model Soil and Water Assessment Tool (SWAT) that finds the best values for the model parameters, preserves spatial variability in essential parameters, and leads to a measure of the model prediction uncertainty. In the first stage, a modified global Shuffled Complex Evolution (SCE‐UA) method was employed to find the “best” values for the lumped model parameters. In the second stage, the spatial variability of the original model parameters was restored and a local search method (a variant of Levenberg–Marquart method) was used to find a more distributed set of parameters using the results of the previous stage as starting values. A method called “regularization” was adopted to prevent the parameters from taking extreme values. In addition, we applied a nonlinear calibration‐constrained method to develop confidence intervals for annual and 7‐d average flow predictions. We calibrated stream flow in the Etowah River measured at Canton, GA (a watershed area of 1580 km2) for the years 1983 to 1992 and used the years 1993 to 2001 for validation. The Parameter Estimator (PEST) software was used to conduct the two‐stage automatic calibration and prediction uncertainty analysis. Calibration for daily and monthly flow produced a very good fit to the measured data. Nash‐Sutcliffe coefficients for daily and monthly flow over the calibration period were 0.60 and 0.86, respectively. They were 0.61 and 0.87, respectively, for the validation period. The nonlinear prediction uncertainty analysis worked well for long‐term (annual) flow in that our prediction confidence intervals included or were very near to the observed flow for most years. It did not work well for short‐term (7‐d average) flows in that the prediction confidence intervals did not include the observed flow, especially for low and high flow conditions.
Seasonal Dynamics of Preferential Flow in a Water Repellent Soil
Authors: Täumer K. , Stoffregen H. , Wessolek G.
Published: March 2006

The temporal dynamic of water repellency in soils has a strong influence on water flow and the appearance of preferential flow paths at potentially water repellent sites. To quantify this effect, field investigations were conducted at a sandy site near Berlin, Germany. A large number of soil samples were collected at 32 different times during a 3‐yr period. Additionally, a time domain reflectometry (TDR) array with 63 probes measured water contents hourly along a transect of 130 by 60 cm. On the basis of these sampling campaigns the area share of water repellent soil regions was measured. Water content changes were observed with the TDRs at high spatial and temporal resolution after several rainfall events. Heterogeneities in water content changes were analyzed. To quantify the heterogeneity (i.e., the degree of preferential flow) we propose the use of the effective cross section, ECS, for water flow. This parameter was calculated by fitting the β function to the cumulative values of the water content change over a horizontal cross section at a depth of 25 cm. Sampling and TDR measurements showed similar seasonal dynamics of preferential flow, with the highest occurrence in summer and early autumn and a maximum accessible soil volume in the spring. Preferential flow in the winter month was enhanced not only by water repellency, but also by freezing and melting. We also tried to calculate the ECS from climatic data. It was possible to calculate the ECS using a linear relationship with the initial soil moisture at the 10‐cm depth, the duration and amount of precipitation, and the potential evapotranspiration rate.
Effects of Shallow Groundwater Management on the Spatial and Temporal Variability of Boron and Salinity in an Irrigated Field
Authors: Shouse P. J. , Goldberg S. , Skaggs T. H. , Soppe R. W. O. , Ayars J. E.
Published: March 2006

In some irrigated regions, the disposal of agricultural drainage waters poses significant environmental challenges. Efforts are underway to develop irrigation water management practices that reduce the volume of drainage generated. One such management strategy involves restricting flow in subsurface drains in an effort to raise the water table and induce the consumption of groundwater by crops. A potential complication with this management approach is that upward groundwater flow may salinize the soil and increase concentrations of phytotoxic elements such as B. In this study, salinity and B concentrations were monitored for 3 yr in a 60‐ha agricultural field located in San Joaquin Valley, California. The irrigated field was managed according to a restricted drainage, shallow groundwater management technique. Salinity and B measurements were made biannually at approximately 75 sites within the field. Soil salinity and B concentrations were found to be highly correlated in the field. The observed spatial and temporal variability in B and salinity was largely a product of soil textural variations within the field and the associated variations in salt leaching. During the 3‐yr study, the field changed very little from one year to the next, although within a given year there were fluctuations related to cropping and irrigation practices and to environmental conditions. However, any changes arising during the growing season were erased in the fallow season by winter rainfall and preplant irrigations that uniformly leached salts from approximately the top 1 m of the field. Overall, it appears that the shallow groundwater management program used in this study could be continued and sustained in this field without increasing soil salinity or B concentrations, and without decreases in yield.
Root Zone Soil Moisture Assessment Using Remote Sensing and Vadose Zone Modeling
Authors: Das Narendra N. , Mohanty Binayak P.
Published: March 2006

Soil moisture is an important hydrologic state variable critical to successful hydroclimatic and environmental predictions. Soil moisture varies both in space and time because of spatio‐temporal variations in precipitation, soil properties, topographic features, and vegetation characteristics. In recent years, air‐ and space‐borne remote sensing campaigns have successfully demonstrated the use of passive microwave remote sensing to map soil moisture status near the soil surface (≈0–0.05 m below the ground) at various spatial scales. In this study root zone (e.g., ≈0–0.6 m below the ground) soil moisture distributions were estimated across the Little Washita watershed (Oklahoma) by assimilating near‐surface soil moisture data from remote sensing measurements using the Electronically Scanned Thinned Array Radiometer (ESTAR) with an ensemble Kalman filter (EnKF) technique coupled with a numerical one‐dimensional vadose zone flow model (HYDRUS‐ET). The resulting distributed root zone soil moisture assessment tool (SMAT) is based on the concept of having parallel noninteracting streamtubes (hydrologic units) within a geographic information system (GIS) platform. The simulated soil moisture distribution at various depths and locations within the watershed were compared with measured profile soil moisture data using time domain reflectometry (TDR). A reasonable agreement was found under favorable conditions between footprint‐scale model estimations and point‐scale field soil moisture measurements in the root zone. However, uncertainties introduced by precipitation and soil hydraulic properties caused suboptimal performance of the integrated model. The SMAT holds great promise and offers flexibility to incorporate various data assimilation techniques, scaling, and other hydrological complexities across large landscapes. The integrated model can be useful for simulating profile soil moisture estimation and for predicting transient soil moisture behavior for a range of hydrological and environmental applications.
On the Effective Averaging Schemes of Hydraulic Properties at the Landscape Scale
Authors: Zhu Jianting , Mohanty Binayak P. , Das Narendra N.
Published: March 2006

Hydraulic parameters of the vadose zone at a spatial resolution typically larger than 1 km2 are a key input for land–atmosphere feedback schemes in soil–vegetation–atmosphere transfer (SVAT) models. Previous studies investigated the significance of first‐ and second‐order moments of soil hydraulic parameters on “effective” parameter estimation in heterogeneous soils at the landscape or remote‐sensing footprint/pixel scale. In this study, we examined the impact of the skewness (third‐order moment) of hydraulic parameter distributions on “effective” soil hydraulic parameter averaging schemes for steady‐state vertical flow in heterogeneous soils in a flat landscape. The effective soil hydraulic parameter of the heterogeneous soil formation is obtained by conceptualizing the soil as an equivalent homogeneous medium. The averaging scheme requires that the effective homogeneous soil will discharge the same ensemble moisture flux across the soil surface. Using three widely used unsaturated hydraulic conductivity functions and various types of probability distribution functions to represent spatial variability for the nonlinear shape factor in the hydraulic conductivity function, we derive the effective parameter values. Numerical and field experimental results show that distribution skewness is also important in determining the upscaled effective parameters in addition to the mean and variance. Negative skewness enhances heterogeneity effects, which make the “effective” α parameter deviate more significantly from the arithmetic mean. In the case of negative skewness, a few small α values make the heterogeneous soil more permeable (with larger flux), which hence causes the “effective” heterogeneous system to deviate more from the homogeneous formation with arithmetic mean parameters.
Vadose Zone Flow and Transport of Dissolved Organic Carbon at Multiple Scales in Humid Regimes
Authors: Jardine P. M. , Mayes M. A. , Mulholland P. J. , Hanson P. J. , Tarver J. R. , Luxmoore R. J. , McCarthy J. F. , Wilson G. V.
Published: March 2006

Scientists must embrace the necessity to offset global CO2 emissions regardless of politics. Efforts to enhance terrestrial organic carbon sequestration have traditionally focused on aboveground biomass and surface soils. An unexplored potential exists in thick lower horizons of widespread, mature soils such as Alfisols, Ultisols, and Oxisols. We present a case study of fate and transport of dissolved organic carbon (DOC) in a highly weathered Ultisol, involving spatial scales from the laboratory to the landscape. Our objectives were to interpret processes observed at various scales and provide an improved understanding of coupled hydrogeochemical mechanisms that control DOC mobility and sequestration in deep subsoils within humid climatic regimes. Our approach is multiscale, using laboratory‐scale batch and soil columns (0.2 by 1.0 m), an in situ pedon (2 by 2 by 3 m), a well‐instrumented subsurface facility on a subwatershed (0.47 ha), and ephemeral and perennial stream discharge at the landscape scale (38.4 ha). Laboratory‐scale experiments confirmed that lower horizons have the propensity to accumulate DOC, but that preferential fracture flow tends to limit sequestration. Intermediate‐scale experiments demonstrated the beneficial effects of C diffusion into soil micropores. Field‐ and landscape‐scale studies demonstrated coupled hydrological, geochemical, and microbiological mechanisms that limit DOC sequestration, and their sensitivity to local environmental conditions. Our results suggest a multi‐scale approach is necessary to assess the propensity of deep subsoils to sequester organic C in situ. By unraveling fundamental organic C sequestration mechanisms, we improve the conceptual and quantitative understanding needed to predict and alter organic C budgets in soil systems.