bluuebunny/crossref_metadata_2025 huggingface dataset:
Chikotsa—Secrets, Silence, and Hiding: Social Risk and Reproductive Vulnerability in Central Mozambique
Authors: Chapman Rachel R.
Published: November 2006

In this article, I examine pregnancy narratives and patterns of reproductive health seeking among women of fertile age in central Mozambique. I map the interplay between gendered economic marginalization, maternal risk perceptions, and pregnancy management strategies. By interpreting my data in light of Shona illness theories, I illuminate the ways that embodied experiences of reproductive vulnerability, risk perceptions, and social inequalities are linked: women attribute the most serious maternal complications to human‐ or spirit‐induced reproductive threats of witchcraft and sorcery. This construction of reproductive vulnerability as social threats related to material and social competition significantly influences prenatal health seeking. Data reveal the structural and cognitive gap between biomedical constructions of risk and lay social threat perceptions. Plural health care systems are strategically utilized by women seeking to minimize both social and biological harm. On‐the‐ground ethnography shows that maternal health initiatives must take this plurality into full and accommodative account to achieve viable improvements in reproductive care and outcomes.
Childhood Sexual Abuse and HIV Risk among Crack‐Using Commercial Sex Workers in San Salvador, El Salvador: A Qualitative Analysis
Authors: Dickson‐Gómez Julia , Bodnar Gloria , Gueverra Aradenia , Rodriguez Karla , Gaborit Mauricio
Published: November 2006

This article explores the relationship between childhood sexual abuse (CSA) and later HIV risk. It draws on qualitative, in‐depth interviews with 40 women who either used crack or engaged in commercial sex work in the greater metropolitan area of San Salvador, El Salvador, 28 of whom experienced CSA. Although the relationship between CSA and later HIV risk has been clearly demonstrated, the processes that lead women who have experienced CSA to experience HIV risk are unclear. The theoretical model presented here incorporates the psychological effects of CSA, particularly stigmatization, as well as its social consequences and the larger context of poverty in which these women live. The meanings women draw from past abuse experiences and their rationale for choices made help explain the association between CSA and later risk as mediated through sex work and crack addiction. Self‐report data gathered in this study indicate that HIV prevalence may be considerably higher in this high‐risk population than Salvadoran national rates.
Development of a Micro Swimming Robot Using Optimised Giant Magnetostrictive Thin Films
Authors: Zhang Y. , Liu G. , Li H.
Published: November 2006

A fish‐like swimming micro robot is developed using an optimised fin actuator made of giant magnetostrictive films (GMFs). The force oscillation dynamic model of a GMF cantilever with variable cross‐section area is derived, and the propulsive model of the fish robot in liquid is established. A discrete variate method for optimising caudal fin configuration is proposed to optimise its propulsive force and drive efficiency under the constraints of fixed surface area and sufficient fin end strength. Both theoretical analysis and experimental results have confirmed that the optimised caudal fin configuration can generate more powerful propulsion and improved efficiency.
A Multi‐Agent Control Architecture for a Robotic Wheelchair
Authors: Galindo C. , Cruz-Martin A. , Blanco J. L. , Fernńndez-Madrigal J. A. , Gonzalez J.
Published: November 2006

Assistant robots like robotic wheelchairs can perform an effective and valuable work in our daily lives. However, they eventually may need external help from humans in the robot environment (particularly, the driver in the case of a wheelchair) to accomplish safely and efficiently some tricky tasks for the current technology, i.e. opening a locked door, traversing a crowded area, etc. This article proposes a control architecture for assistant robots designed under a multi‐agent perspective that facilitates the participation of humans into the robotic system and improves the overall performance of the robot as well as its dependability. Within our design, agents have their own intentions and beliefs, have different abilities (that include algorithmic behaviours and human skills) and also learn autonomously the most convenient method to carry out their actions through reinforcement learning. The proposed architecture is illustrated with a real assistant robot: a robotic wheelchair that provides mobility to impaired or elderly people.
Optimal Design of a Bio‐Inspired Anthropocentric Shoulder Rehabilitator
Authors: Mustafa S. K. , Yang G. , Yeo S. H. , Lin W.
Published: November 2006

This paper presents the design of a bio‐inspired anthropocentric 7‐DOF wearable robotic arm for the purpose of stroke rehabilitation. The proposed arm rehabilitator synergistically utilizes the human arm structure with non‐invasive kinematically under‐deterministic cable‐driven mechanisms to form a completely deterministic structure. It offers the advantages of being lightweight and having high dexterity. Adopting an anthropocentric design concept also allows it to conform to the human anatomical structure. The focus of this paper is on the analysis and design of the 3‐DOF‐shoulder module, called the shoulder rehabilitator. The design methodology is divided into three main steps: (1) performance evaluation of the cable‐driven shoulder rehabilitator, (2) performance requirements of the shoulder joint based on its physiological characteristics and (3) design optimization of the shoulder rehabilitator based on shoulder joint physiological limitations. The aim is to determine a suitable configuration for the development of a shoulder rehabilitator prototype.
Design and Implementation of NTU Wearable Exoskeleton as an Enhancement and Assistive Device
Authors: Low K. H. , Liu X. , Yu H.
Published: November 2006

This article presents a wearable lower extremity exoskeleton (LEE) developed to enhance the ability of a human’s walking while carrying heavy loads. The ultimate goal of the current research work is to design and control a power assist system that integrates a human’s intellect for feedback and sensory purposes. The exoskeleton system in this work consists of an inner exoskeleton and an outer exoskeleton. The inner exoskeleton measures the movements of the wearer and provides these measurements to the outer exoskeleton, which supports the whole exoskeleton system to walk following the wearer. A special footpad, which is designed and attached to the outer exoskeleton, can measure the zero moment point (ZMP) of the human as well as that of the exoskeleton in time. Using the measured human ZMP as the reference, the exoskeleton’s ZMP is controlled by trunk compensation so that the exoskeleton can walk stably. A simulation platform has first been developed to examine the gait coordination through inner and outer exoskeletons. A commercially available software, xPC Target, together with other toolboxes from MATLAB, has then been used to provide a real‐time operating system for controlling the exoskeleton. Real‐time locomotion control of the exoskeleton is implemented in the developed environment. Finally, some experiments on different objects showed that the stable walking can be achieved in the real environment.
Pivoting a Large Object: Whole‐Body Manipulation by a Humanoid Robot
Authors: Yoshida E. , Blazevic P. , Hugel V. , Yokoi K. , Harada K.
Published: November 2006

In this article, we present a method of whole‐body manipulation of large objects by a humanoid robot using a pivoting motion. Pivoting manipulation can be an alternative to pushing or lifting for more dexterous and stable operation, which is often used by humans to move large and bulky furniture. This article describes a method and control techniques for a humanoid robot to perform the manipulation of a large object through whole‐body motion by applying this pivoting motion. For this purpose, first the object is manipulated by two arms of a humanoid robot using impedance control for grasping, together with body balancing control while the robot stays at the same place. Next, the movement of the humanoid robot itself is performed by stepping motion with the help of resolved momentum control to guarantee the robot stability. The proposed manipulation is validated through dynamic simulation and real hardware experiment of the humanoid robot HRP‐2 performing the pivoting task.
Using a Gyro as a Tool for Continuously Variable Lateral Stabilisation of Dynamic Bipeds
Authors: Mayer N. M. , Masui K. , Browne M. , Asada M. , Ogino M.
Published: November 2006

We present simulations of different types of biped walking machines that are stabilized in the lateral direction by adding a gyro. The simulations show that, in principle, it is indeed possible to stabilise biped walking machines. Examples presented in this work include a three‐dimensional version of the simplest walking model, which is based on earlier investigations, and an actuated biped robot. Here, the gyro is used as a reaction wheel. Finally, a rotor–brake combination is outlined that was used in an artistic biped robot at the Aichi World Exhibition.
Development of Underwater Microrobot with Biomimetic Locomotion
Authors: Zhang W. , Guo S. , Asaka K.
Published: November 2006

Microrobots have powerful applications in biomedical and naval fields. They should have a compact structure, be easy to manufacture, have efficient locomotion, be driven by low voltage and have a simple control system. To meet these purposes, inspired by the leg of stick insects, we designed a novel type of microrobot with biomimetic locomotion with 1‐DOF (degree of freedom) legs. The locomotion includes two ionic conducting polymer film (ICPF) actuators to realize the 2‐DOF motion. We developed several microrobots with this locomotion. Firstly, we review a microrobot, named Walker‐1, with 1‐DOF motion. And then a new microrobot, named Walker‐2, utilizing six ICPF actuators, with 3‐DOF motion is introduced. It is 47 mm in diameter and 8 mm in height (in static state). It has 0.61 g of dried weight. We compared the two microrobot prototypes, and the result shows that Walker‐2 has some advantages, such as more flexible moving motion, good balance, less water resistance, more load‐carrying ability and so on. We also compared it with some insect‐inspired microrobots and some microrobots with 1‐DOF legs, and the result shows that a microrobot with this novel type of locomotion has some advantages. Its structure has fewer actuators and joints, a simpler control system and is compact. The ICPF actuator decides that it can be driven by low voltage (less than 5 V) and move in water. A microrobot with this locomotion has powerful applications in biomedical and naval fields.
The Development of a Hybrid Underwater Micro Biped Robot
Authors: Guo S. , Okuda Y. , Zhang W. , Ye X. , Asaka K.
Published: November 2006

There has been a great demand, in the medical field and in industrial applications, for a novel micro biped robot with multiple degrees of freedom that can swim smoothly in water or in aqueous medium. The fish‐like micro‐robot studied is a type of miniature device that is installed with sensing and actuating elements. This article describes the new structure and motion mechanism of a hybrid type of underwater micro‐robot using an ion‐conducting polymer film (ICPF) actuator, and discusses the swimming and floating characteristics of the micro‐robot in water, measured by changing the voltage frequency and the amplitude of the input voltage. Results indicate that the swimming speed of the proposed underwater micro‐robot can be controlled by changing the frequency of the input voltage, and the direction (upward or downward) can be manipulated by changing the frequency of the electric current applied and the amplitude of the voltage.
Impact of Prenatal Chlorpyrifos Exposure on Neurodevelopment in the First 3 Years of Life Among Inner-City Children
Authors: Rauh Virginia A. , Garfinkel Robin , Perera Frederica P. , Andrews Howard F. , Hoepner Lori , Barr Dana B. , Whitehead Ralph , Tang Deliang , Whyatt Robin W.
Published: November 2006

OBJECTIVE. The purpose of this study was to investigate the impact of prenatal exposure to chlorpyrifos on 3-year neurodevelopment and behavior in a sample of inner-city minority children.

METHODS. As part of an ongoing prospective cohort study in an inner-city minority population, neurotoxicant effects of prenatal exposure to chlorpyrifos were evaluated in 254 children through the first 3 years of life. This report examined cognitive and motor development at 12, 24, and 36 months (measured with the Bayley Scales of Infant Development II) and child behavior at 36 months (measured with the Child Behavior Checklist) as a function of chlorpyrifos levels in umbilical cord plasma.

RESULTS. Highly exposed children (chlorpyrifos levels of >6.17 pg/g plasma) scored, on average, 6.5 points lower on the Bayley Psychomotor Development Index and 3.3 points lower on the Bayley Mental Development Index at 3 years of age compared with those with lower levels of exposure. Children exposed to higher, compared with lower, chlorpyrifos levels were also significantly more likely to experience Psychomotor Development Index and Mental Development Index delays, attention problems, attention-deficit/hyperactivity disorder problems, and pervasive developmental disorder problems at 3 years of age.

CONCLUSIONS. The adjusted mean 36-month Psychomotor Development Index and Mental Development Index scores of the highly and lower exposed groups differed by only 7.1 and 3.0 points, respectively, but the proportion of delayed children in the high-exposure group, compared with the low-exposure group, was 5 times greater for the Psychomotor Development Index and 2.4 times greater for the Mental Development Index, increasing the number of children possibly needing early intervention services.
Effect of Opening Midlevel Neonatal Intensive Care Units on the Location of Low Birth Weight Births in California
Authors: Haberland Corinna A. , Phibbs Ciaran S. , Baker Laurence C.
Published: November 2006

OBJECTIVE. Despite evidence and recommendations encouraging the delivery of high-risk newborns in hospitals with subspecialty or high-level NICUs, increasing numbers are being delivered in other facilities. Causes for this are unknown. We sought to explore the impact of diffusion of specialty or midlevel NICUs on the types of hospitals in which low birth weight newborns are born.

DESIGN. We used birth certificate, death certificate, and hospital discharge data for essentially all low birth weight, singleton California newborns born between 1993 and 2000. We identified areas likely to have been affected by the opening of a new nearby midlevel unit, analyzed changes over time in the share of births that took place in midlevel NICU hospitals, and compared patterns in areas that were and were not likely affected by the opening of a new midlevel unit. We also tracked the corresponding changes in the share of births in high-level hospitals and in those without NICU facilities (low-level).

RESULTS. The probability of a 500- to 1499-g infant being born in a midlevel unit increased by 17 percentage points after the opening of a new nearby unit. More than three quarters of this increase was accounted for by reductions in the probability of birth in a hospital with a high-level unit (−15 points), and the other portion was resulting from reductions in the share of newborns delivered in hospitals with low-level centers (−2 points). Similar patterns were observed in 1500- to 2499-g newborns.

CONCLUSIONS. The introduction of new midlevel units was associated with significant shifts of births from both high-level and low-level hospitals to midlevel hospitals. In areas in which new midlevel units opened, the majority of the increase in midlevel deliveries was attributable to shifts from high-level unit births. Continued proliferation of midlevel units should be carefully assessed.
Limited Value of Plain Radiographs in Infant Torticollis
Authors: Snyder Emma M. , Coley Brian D.
Published: November 2006

OBJECTIVE. The purpose of this work was to assess the frequency of clinically relevant findings from plain films of infants evaluated for torticollis.

PATIENTS AND METHODS. After institutional review board approval, radiology records were searched for infants 0 to 12 months of age who underwent plain film study for torticollis or “head tilt.” Infants evaluated for trauma or Down syndrome were excluded. All of the studies were reviewed, demographic data was recorded, and any additional imaging studies were examined.

RESULTS. A total of 502 patients (189 girls and 313 boys) were identified with an average age of 0.37 ± 0.2 years. Head tilt was to the left in two thirds of patients. Ten patients had abnormal findings reported. Six of these proved normal on subsequent studies (3 suspected occipital-C1 fusions, 2 suspected cervical fusions, and 1 suspected hemivertebra). Four patients had true bony vertebral abnormalities including absent left C7 pedicle, multiple fusion anomalies from C4 to T2, C3 hemivertebra and thoracic spine anomalies, and C4 hypoplasia. This last patient had abnormal kyphosis on physical examination and demonstrated instability with dynamic testing. Twenty-five additional patients with normal plain films underwent spine computed tomography or magnetic resonance imaging; all were normal.

CONCLUSIONS. The true-positive yield of plain films in nontraumatic infant torticollis was low (4 of 502). There were more false-positive than true-positive results. A common rationale for imaging is to exclude craniocervical or other unstable abnormalities that might contraindicate physical therapy, seen in only 1 of the 502 cases. Close physical examination could safely eliminate most patients sent for radiography.
Field Performance of Three Compacted Clay Landfill Covers
Authors: Albright William H. , Benson Craig H. , Gee Glendon W. , Abichou Tarek , Tyler Scott W. , Rock Steven A.
Published: November 2006

A study was conducted at sites in subtropical Georgia, seasonal and humid Iowa, and arid southeastern California to evaluate the field hydrology of compacted clay covers for final closure of landfills. Water balance of the covers was monitored with large (10 by 20 m), instrumented drainage lysimeters for 2 to 4 yr. Initial drainage at the Iowa and California sites was <32 mm yr−1 (i.e., unit gradient flow for a hydraulic conductivity of 10−7 cm s−1, the regulatory standard for the clay barriers in this study); initial drainage rate at the Georgia site was about 80 mm yr−1 The drainage rate at all sites increased by factors ranging from 100 to 750 during the monitoring periods and in each case the drainage rate exceeded 32 mm yr−1 by the end of the monitoring period. The drainage rates developed a rapid response to precipitation events, suggesting that increases in drainage rate were the result of preferential flow. Although no direct observations of preferential flow paths were made, field measurements of water content and temperature at all three sites suggested that desiccation or freeze–thaw cycling probably resulted in formation of preferential flow paths through the barrier layers. Data from all three sites showed the effectiveness of all three covers as hydraulic barriers diminished during the 2 to 4 yr monitoring period, which was short compared with the required design life (often 30 yr) of most waste containment facilities.
Gas Transport Parameters in the Vadose Zone: Development and Tests of Power‐Law Models for Air Permeability
Authors: Kawamoto Ken , Moldrup Per , Schjønning Per , Iversen Bo V. , Komatsu Toshiko , Rolston Dennis E.
Published: November 2006

The soil‐air permeability (ka) and its dependency on air‐filled porosity (ε) govern convective air and gas transport in soil. For example, accurate prediction of ka(ε) is a prerequisite for optimizing soil vapor extraction systems for cleanup of soils polluted with volatile organic chemicals. In this study, we measured ka at different soil‐water matric potentials down to 5.6‐m depth, totaling 25 differently textured soil layers. Comparing ka and soil‐gas diffusivity (Dp/D0) measurements on the same soil samples suggested an analogy between how the two soil‐gas transport parameters depend on ε. The exponent in a power‐law model for ka(ε) was typically smaller than for Dp(ε)/D0, however, probably due to the influence of soil structure and large‐pore network being more pronounced for ka than for Dp/D0 In analogy to recent gas diffusivity models and in line with capillary tube models for unsaturated hydraulic conductivity, two power‐law ka(ε) models were suggested. One ka(ε) model is based on the Campbell pore‐size distribution parameter b and the other on the content of larger pores (ε100, corresponding to the air‐filled porosity at −100 cm H2O of soil‐water matric potential). Both new models require measured ka at −100 cm H2O (ka,100) as a reference point to obtain reasonably accurate predictions. If ka,100 is not known, two expressions for predicting ka,100 from ε100 were proposed but will cause at least one order of magnitude uncertainty in predicted ka The ka(ε) model based on only ε100 performed well in the model tests and is recommended together with a similar model for gas diffusivity for predicting variations in soil‐gas transport parameters in the vadose zone.
Modeling Dynamic Sorption of Cadmium in Cropland Soils
Authors: Chen Weiping , Chang Andrew C. , Wu Laosheng , Page Albert L.
Published: November 2006

In sorption experiments, Cd in the solution phase may be surface adsorbed or immobilized and precipitated into mineral phases. The reaction kinetics can be described by a two‐site model combining a linear instantaneous model for the surface adsorption and a first‐order reaction kinetic model with forward and backward reaction constants for the immobilization and precipitation of the mineral phase. A simplified sequential procedure was developed to study the contribution of these two processes. Results of batch Cd adsorption experiments with two California soils were used to illustrate the model validity. When the Cd sorption was obtained by varying the initial Cd solution concentration and maintaining constant equilibration time, the amounts of Cd in the solid phase as well as the adsorbed and mineral phases increase linearly with the initial Cd solution concentrations. As much as 90% of the sorbed Cd may be in the mineral phase. When the Cd sorption was examined at varying equilibration time and a constant Cd initial solution concentration, the sorbed Cd in the mineral phase increased exponentially to approach a maximum with time. The forward and backward reaction constants were obtained by fitting the sorption data to the model equations. It showed that the forward reaction was five times faster than the backward reaction for both soils and the reaction rates were two times faster in the heavier textured Holtville clay loam soil than the Arlington sandy loam soil.
Root Water Extraction and Limiting Soil Hydraulic Conditions Estimated by Numerical Simulation
Authors: van Lier Quirijn de Jong , Metselaar Klaas , van Dam Jos C.
Published: November 2006

Root density, soil hydraulic functions, and hydraulic head gradients play an important role in the determination of transpiration‐rate‐limiting soil water contents. We developed an implicit numerical root water extraction model to solve the Richards equation for the modeling of radial root water extraction. The average soil water content at the moment root water potential dropped below a defined critical value was then estimated. The dependence of average water content at the onset of plant water stress on potential transpiration and root density was compared with an analytical solution for hydraulic conditions in the root sphere. The critical value was a function of potential transpiration rate, soil hydraulic properties, and root density. Matric flux potential appears to be a convenient hydraulic property to determine the onset of limiting hydraulic conditions, as numerical simulations showed that, at onset, matric flux potential vs. distance from the root surface is independent of soil type. This was also determined analytically under the constant‐rate assumption. Mean water content occurs at about 0.53 times the half‐distance between roots. This allows calculation of the mean limiting soil water content and pressure head from the matric flux potential at this distance, which is a function of transpiration rate and root density only. A nomogram was developed that—given the transpiration rate, the root density, and the soil hydraulic functions—allows determination of the values of mean water content and mean pressure head that occur at the onset of transpiration reduction.
Nitrous Oxide and Ammonia Emissions from Urine‐Treated Soils: Texture Effect
Authors: Singurindy Olga , Richards Brian K. , Molodovskaya Marina , Steenhuis Tammo S.
Published: November 2006

Urine‐treated soils have been implicated as an important source of gaseous N losses to the atmosphere. The goal of our research was to quantify NH3 and N2O emissions from urine under different simplified and controlled soil conditions and to relate these results to urinary‐N transformation processes in soil. We studied the influence of soil texture (coarse vs. fine sand), moisture distribution with depth, air‐filled pore space, and rate of air movement, which affected both soil drying processes and emission rates. Laboratory experiments were performed with synthetic urine in both aerobic and anaerobic conditions. Texture was the most important factor controlling NH3 volatilization and N2O emission factors in urine‐treated sands. Generally, the finer the sand texture, the higher the input of denitrification to the total N2O emissions; however, the air‐filled pore space threshold, below which denitrification became dominant, was greater in coarse sand. In addition, the evaporation rate of the urine water component was found to be an important parameter in total NH3 and N2O emissions. Ammonia volatilization occurred during the first day of the treatments, with volatilization rates closely related to evaporation rates in both sand textures. Finer sand texture caused reductions in the urine evaporation rate and therefore in NH3 volatilization rates. Urine evaporation increased air‐filled pore space, thereby improving aeration conditions in the sand that contribute to nitrification dominance of N2O production. Moreover, evaporation of urine, enriched with dissolved N2O, increased total N2O emission. Results from these simplified experiments need confirmation under field soil conditions.
The Dual Gravimetric Hot‐Air Method for Measuring Soil Water Diffusivity
Authors: Tyner J. S. , Arya L. M. , Wright W. C.
Published: November 2006

The hot‐air method provides rapid measurement of a soil's unsaturated hydraulic diffusivity function. The original method consists of blowing hot air across one end of a soil column for a short period, and then quickly extruding, dissecting, and oven drying the soil to provide the soil water content profile, which is used to calculate the soil's unsaturated hydraulic diffusivity. This research presents a novel approach to measuring the soil water content profile during a hot‐air test. During the drying process, a soil column is suspended in a horizontal position by a load cell attached at each end. The measured change in force from the two load cells enables calculation of the soil water content profile, without soil extrusion, dissection, and oven drying. Because the test is nondestructive, it permits estimation of the water content profile and calculation of the unsaturated hydraulic diffusivity function at multiple times. Similarity of the diffusivity functions at various times during the drying process provides evidence of proper testing conditions, a utility not available with the destructive approach. We applied the method to a silt loam and a clay loam and both soils achieved a RMSE of 0.012 compared with the traditionally measured water content profile. We also modeled the performance of the new method on previously published hot‐air water content profiles and achieved similar results.
Treatability of Nonylphenol Ethoxylate Surfactants in On‐Site Wastewater Disposal Systems
Authors: Huntsman Brent E. , Staples Charles A. , Naylor Carter G. , Williams Jim‐Bob
Published: November 2006

The fate of nine‐mole nonylphenol ethoxylate (NPE9) discharged to an on‐site wastewater disposal (septic) system was the focus of a 2‐year investigation. Known amounts of NPE9‐based detergent were metered daily into the plumbing at a single‐family household. The ethoxylate‐containing wastewater was discharged to the highly anoxic environment of a 4500‐L septic tank before distribution to the oxic subsurface via 100 m of leach line. After 180 days of injecting detergent to the septic system, periodic soil pore water and/or groundwater samples were collected and analyzed for nonylphenol ethoxylates (NPEs), nonylphenol ether carboxylates, and nonylphenol. The NPE9 and degradation intermediates that were measured were reduced by 99.99% on a molar basis. An 18% reduction in molar concentration within the septic tank was observed. This was followed by a further 96.7% reduction of molar concentration within the leach lines. As the pore water migrated through the vadose zone, an additional 99.69% reduction in molar concentration was measured between the bottom of the leach lines (leach line effluent) and the lowest vadose zone monitoring location. The results obtained from these analyses indicate that degradation of the surfactant occurs within the anoxic portion of the disposal system with continued rapid biodegradation in the oxic unsaturated zone. Only trace amounts of degradation residuals were detected in soil pore water. The concentration and distribution of various degradation intermediates with respect to location, time, and ambient physical conditions were evaluated. Rapid and systematic degradation of NPE in on‐site wastewater disposal systems was documented.
Extended Acid Digestion for Inactivation of Fecal Coliforms
Authors: Puchajda Bartek , Oleszkiewicz Jan
Published: November 2006

The objective of this research was to establish a correlation between inactivation of fecal coliforms caused by organic acids in their un‐ionized form in batch acid digesters and semicontinuously fed acid digesters at both mesophilic (38°C) and low‐mesophilic (24°C) temperatures. Batch acid digesters achieved a U.S. Environmental Protection Agency Class A level of fecal coliforms within 6 to 7 days of digestion at both temperatures. Semicontinuously fed, staged, acid‐digestion systems achieved Class A standards on average only at mesophilic temperature at a solids retention time of 11 days. Systems operated at low‐mesophilic temperatures did not achieve Class A standards.
Effects of Organisms on the Release of Phosphorus at the Interface Between Sediment and Water
Authors: Jin Xiangcan , Jiang Xia , Yao Yang , Li Lihe , Wu Fengchang
Published: November 2006

Organisms at the interface between sediment and water play a significant role in the cycling of phosphorus. This study reports experimental results of the influence of organisms on phosphorus release. Results show that benthic organisms controlled the low level of phosphate in overlying water with light. The maximum phosphorus release rate can reach 7.31 mg m −2 d −1 without organisms, nearly twice that in a similar system with organisms. However, significant decreases in the concentrations of sodium‐hydroxide‐extractable phosphorus and hydrochloric‐acid‐extractable phosphorus were observed in the experimental system with organisms, while no significant changes were observed without organisms. In addition, the dissolved oxygen concentration in the system was higher with organisms than without organisms with light. This study is significant to the understanding of phosphorus cycling at the interface between sediment and water in lakes.
Fate Estimation of Estrogenic Substances in an Urban River by Flux Calculation
Authors: Yamashita Naoyuki , Tanaka Hiroaki , Miyajima Kiyoshi , Tamamoto Hiroyuki , Miyamoto Norihiro , Yasojima Makoto , Komori Koya , Suzuki Yutaka
Published: November 2006

This study investigated the fate of estrogenic substances in an urban river receiving discharge from wastewater treatment plants (WTPs) by flux calculation, focusing on the middle reaches of the Tama River in Tokyo, which is one of the most urbanized rivers in Japan. The level of estrogenic activity flux was almost negligibly small at the upstream station. The level was considerably raised after inflows from the WTPs and then the level declined in the lower reaches of the river. When contributions of estrogenic substances to estrogenic activity were estimated, estrone (E1) was the primary contributor to the total estrogenic activity in all the sampling stations, followed by estradiol (E2). The contribution of nonylphenol to estrogenic activity was small. The E1 and E2 accounted for approximately 90% or more of estrogenic activity in the Tama River. As for the total fluxes of the estrogenic substances in the study area in the Tama River, the proportion of flux associated with WTP discharge was approximately 100% of the total fluxes, and the effects of the tributaries flowing into the river were almost negligible. When the reduction ratios of estrogenic activity were calculated by the flux, the ratios were found to increase toward the lower reaches of the river. Similar changes were observed for E1. Meanwhile, the change of reduction ratios for E2 was different from that observed for estrogenic activity.
Characteristics of Highway Stormwater Runoff
Authors: Han Younghan , Lau Sim‐Lin , Kayhanian Masoud , Stenstrom Michael K.
Published: November 2006

Highway stormwater runoff was monitored at three highway sites in Los Angeles, California, during the 2000 to 2003 wet seasons. Event mean concentrations (EMCs), partial event mean concentrations (PEMCs), and mass first flush (MFF) factors were calculated for more than 20 water quality parameters for samples from 20 storm events from each site. The early runoff had higher concentrations, as indicated by the PEMCs at 30 and 60 minutes into the storm, which were 1.9 to 7.4 times higher than the EMCs. A strong first flush was observed for chemical oxygen demand (COD) and other organic pollutants, with 40% of the pollutant mass being discharged in the first 20% of the runoff. A weak first flush was observed for ionic pollutants, such as nitrate and nitrite. Pearson correlation analyses of the EMCs, PEMCs, and MFFs showed strong correlations among dissolved organic carbon, COD, total Kjeldahl nitrogen, oil and grease, and ammonia‐nitrogen. Contrary to generally held beliefs, poor correlation between total suspended solids and most other conventional pollutants was observed. In addition, poor correlation between most monitored pollutants and storm characteristics, except for antecedent dry days, was observed.
Performance of a Constructed Wetland‐Pond System for Treatment and Reuse of Wastewater from Campus Buildings
Authors: Ou Wen‐Sheng , Lin Ying‐Feng , Jing Shuh‐Ren , Lin Hsien‐Te
Published: November 2006

A constructed wetland‐pond system consisting of two free‐water‐surface‐flow (FWS) wetland cells, a scenic pond, and a slag filter in series was used for reclamation of septic tank effluent from a campus building. The results show that FWS wetlands effectively removed major pollutants under a hydraulic loading rate between 2.1 and 4.2 cm/d, with average efficiencies ranging from 74 to 78% for total suspended solids, 73 to 88% for 5‐day biochemical oxygen demand, 42 to 49% for total nitrogen, 34 to 70% for total phosphorous, 64 to 79% for total coliforms, and 90 to 99.9% for Escherichia coli. After passing through the scenic pond and slag filter, the reclaimed water was used for landscape irrigation. There were a variety of ornamental plants and aquatic animals established in the second FWS cell and scenic pond with good water quality, thus enhancing landscape and ecology amenity in campuses.
The Role of Wealth Transformations: An Application to Estimating the Effect of Tax Incentives on Saving
Authors: Pence Karen M.
Published: November 2006

Researchers may want to estimate the percentage change of a variable, such as household wealth or corporate profits, that takes on economically significant nonpositive values. Using the logarithmic transformation, however, requires discarding observations with nonpositive values. This paper describes a possible solution to this problem-the inverse hyperbolic sine transformation-and shows how to implement this transformation optimally in the case of median regression. As an illustration of the usefulness of this transformation, I revisit a specification sometimes used to estimate the effect of tax incentives on household saving.
Does Integrating Economic and Biological Systems Matter for Public Policy? The Case of Yellowstone Lake
Authors: Settle Chad , Shogren Jason F
Published: November 2006

Integrated economic and ecologic modeling systems can yield more precise predictions about the underlying physical system and the risks imposed to humans and the environment. But do more accurate risk assessments matter for environmental policy that is in part influenced by the consumers of this physical system? Herein we discuss a situation within the crown jewel of the US national park system in which the answer is no. For endangered cutthroat trout populations threatened by the invasion of exotic lake trout in Yellowstone Lake, if one accounts for the preferences of the average visitor, the optimal policy can be bluntly summarized as "fix the roads, forget the fish." To reverse this outcome, the typical visitor to the Park would have to be more forward-thinking and more generous toward a species that she would never see.
New Wet Flue Gas Desulfurization Process Using Granular Limestone and Organic Acid Additives
Authors: Liu Shengyu , Xiao Wende
Published: November 2006

A new wet FGD process in which sulfur dioxide was absorbed in the bubble reactor using granular limestone simultaneously adding acetic acid had been proposed. The main difference compared to conventional wet FGD process was the ability of the new process to utilize granular limestone directly as a desulphurization reagent simultaneously adding acetic acid. Thus, the pulverizing of limestone, which causes power consumption, can be saved. Only using granular limestone directly as absorbent without acetic acid, SO2 removal efficiency and limestone utilization were too low. Adding some concentration of acetic acid, the performance of the new wet FGD process was confirmed to be equal to or higher than that of a conventional process in various tests. Various parameters of the new FGD process which would affect the sulfur dioxide removal efficiency and limestone utilization were studied.
Cluster-Based Modeling of Fluidized Catalytic Oxidation of n-Butane to Maleic Anhydride
Authors: Hakimelahi Hamid Reza , Sotudeh-Gharebagh Rahmat , Mostoufi Navid
Published: November 2006

A mathematical model is proposed for the partial oxidation on n-butane to maleic anhydride (MAN) in a gas-solid fluidized bed reactor. The reactor consists of two regions, i.e., a lower dense region and an upper dilute region. The dynamic two-phase structure was used for modeling the lower dense bed hydrodynamics. The upper region hydrodynamics was modeled by a cluster based approach. This allows the porosity distribution to be calculated for plug flow reactor model assumed for the gas phase in this region. The basic assumption in the cluster based approach is that the solid particles move only as clusters and the amount of single particles in the upper region is negligible. The mathematical model was obtained from coupling the kinetic sub-model, obtained from the literature, with this hydrodynamics sub-model. Comparing the results of the model with the experimental data available in the literature showed close agreement. Two other methods (i.e., particle based approach and short-cut) were also tested in this work. However, it was found that the cluster based approach modeling is quite suitable for the fluidized bed reactor used in this study. The short-cut method seems reasonably applicable for the prediction of the overall conversion but does not provide any local information (such as concentration profiles, yield, etc.) within the fluidized bed reactor.
Lipid Extraction from Olea Europea L. by Supercritical Carbon Dioxide for Analytical Use
Authors: Perretti Giuseppe , Montanari Luigi , Fantozzi Paolo
Published: November 2006

The aim of this work is to determine the feasibility of applying SFE technique by supercritical CO2, to the gravimetric measurement of lipids in olives by verifying the feasibility of extractions, studying the analytes solubility in SC-CO2, optimizing the preparation of sample, appraising the repeatability of the data obtainable with the adopted method. The olive cultivar "Moraiolo and two different supercritical fluid laboratory instruments were used. Initial trials were performed to verify the extractability of the oil from matrix. The degree of solubility was determined by the quantitative amount of extracted and collected solute, reported for the quantity of solvent used (CO2). Once the feasibility was established and the solubility was studied, it was necessary carry out specific trials to find a better formula for the sample preparation. This involved type of matrix (humidity, structure, oil content, density, etc.) and equipment commonly available in laboratories deals in food product analysis.
Adverse Selection in Health Insurance
Authors: Cutler David M. , Zeckhauser Richard J.
Published: November 2006

Individual choice among health insurance policies may result in risk-based sorting across plans. Such adverse selection induces three types of losses: efficiency losses from individuals' being allocated to the wrong plans; risk-sharing losses, because premium variability is increased; and losses from insurers' distorting their policies to improve their mix of insureds. We discuss the potential for these losses and present empirical evidence on adverse selection in two groups of employees: Harvard University and the Group Insurance Commission of Massachusetts (serving state and local employees). In both groups, adverse selection is a signiacant concern. Harvards decision to contribute an equal amount to all insurance plans led to the disappearance of the most generous policy within three years. The Group Insurance Commission has contained adverse selection by subsidizing premiums proportionally and managing the most generous policy very tightly. A combination of prospective or retrospective risk adjustment, coupled with reinsurance for high-cost cases, seems promising as a way to provide appropriate incentives for enrollees and to reduce losses from adverse selection.
Is Price Inflation Different for the Elderly? An Empirical Analysis of Prescription Drugs
Authors: Berndt Ernst R. , Cockburn Iain M. , Cocks Douglas L. , Epstein Arnold M. , Griliches Zvi
Published: November 2006

Recently controversy has surrounded the issue of whether Social Security payments to the elderly should continue to be adjusted automatically according to changes in the Consumer Price Index (CPI). One issue in the public policy debate concerns whether price inflation is different for the elderly, particularly because the official Bureau of Labor Statistics price indexes for medical care have been growing more rapidly than the overall CPI, and medical care expenditures constitute a larger proportion of the elderlys budget than of the youngs.Using annual IMS data from 1990 to 1996, we examine empirically whether elderly-nonelderly price inflation differentials exist for prescription pharmaceuticals. We assess prices for prescription drugs destined for ultimate use by the elderly versus the nonelderly at three points in the distribution chain: initial sales from manufacturers, intermediate purchases by retail pharmacies, and final sales from retail pharmacies to patients or payors. We find that at the initial point in the distribution chain, no differences in price inflation exist for the aggregate of drugs destined for use by the elderly versus those for the nonelderly. At the intermediate sell-in point to pharmacy distribution, we examine antibiotics (ABs), antidepressants (ADs), and calcium channel blockers (CCBs). For ABs, since 1992 price inflation has been somewhat greater for the elderly than for the young, reflecting in part the elderlys more intensive use of newer branded products having fewer side effects, adverse drug interactions and more convenient dosingattributes of particular importance to the elderly. For ADs, price inoation is considerably less for the elderly than for the young, due in large part to the elderlys greater use of older generic products. For CCBs, elderly-nonelderly differentials are negligible. None of these differentials adjust for variations in quality.At the final retail sell-out point, we examine only ADs. We find that because retailers obtain larger gross margins on generic than on branded products, and because the elderly are disproportionately large users of generic ADs, the elderly-nonelderly price inflation differential benefiting the elderly at the intermediate point is reduced considerably at final sale.
Managed Care and Health Care Expenditures: Evidence from Medicare, 1990-1994
Authors: Baker Laurence C. , Shankarkumar Sharmila
Published: November 2006

Increases in the activity of managed care organizations may have "spillover effects," influencing the entire health care delivery system's performance, so that care for both managed-care and nonmanaged-care patients is affected. Some proposals for Medicare reform have incorporated spillover effects as a way that increasing Medicare HMO enrollment could contribute to savings for Medicare.This paper investigates the relationship between HMO market share and expenditures for the care of beneficiaries enrolled in traditional fee-for-service Medicare. We find that increases in systemwide HMO market share (which includes both Medicare and non-Medicare enrollment) are associated with declines in both Part A and Part B fee-for-service expenditures. The fact that managed care can influence expenditures for this population, which should be well insulated from the direct effects of managed care, suggests that managed-care activity can have broad effects on the entire health care market. Increases in Medicare HMO market share alone are associated with increases in Part A expenditures and with small decreases in Part B expenditures. This suggests that any spillovers directly associated with Medicare HMO enrollment are small.For general health care policy discussions, these results suggest that assessment of new policies that would influence managed care should account not only for its effects on enrollees but also for its systemwide effects. For Medicare policy discussions, these findings imply that previous results that seemed to show large spillover effects associated with increases in Medicare HMO market share, but inadequately accounted for systemwide managed-care activity and relied on older data, overstated the magnitude of actual Medicare spillovers.
Quadratic transformations: a model for population growth. I
Authors: Kesten Harry
Published: November 2006

A reasonably general but greatly simplified model for a finite sexually reproducing population is considered. We restrict ourselves to the case where there are distinct, non-overlapping generations, but there is hope that the techniques will also be applicable to some very simple minded continuous time models with overlapping generations (see also Section 5, Example 3). There aret∞< ∞ different types of females andt1< ∞ types of males and our main concern is the asymptotic behavior of the variablesand