bluuebunny/crossref_metadata_2025 huggingface dataset:
Decision Support System for Predicting Traffic Diversion Impact across Transportation Networks Using Support Vector Regression
Authors: Bhavsar Parth , Chowdhury Mashrur , Sadek Adel , Sarasua Wayne , Ogle Jennifer
Published: January 2008

This paper describes follow-up research to a previous study by the authors that used case-based reasoning (CBR) and support vector regression (SVR) to evaluate the likely impacts of implementing diversion strategies in response to incidents on highway networks. In the previous study, the training and testing of the CBR and SVR tools were performed on a single transportation network from South Carolina, which limited the applicability of the developed tool to the specific network for which it was developed. To address this limitation, the current study investigates the feasibility of developing a generic decision support system (DSS) capable of predicting traffic diversion impacts for new transportation networks that the tool has not previously seen. In such cases, users need only to input the geometric and traffic variables, via a graphical user interface, and the tool, which uses a SVR model, will predict the benefits of diverting traffic for a specific incident on the new site. To illustrate the feasibility of developing such a tool, two different highway networks covering portions of I-85 and I-385 in South Carolina were used to train the SVR model, which was then tested on a third network covering portions of I-89 in Vermont. The study found only a 15% difference between the predictions of the SVR model and those of a detailed simulation counterpart, demonstrating the feasibility of developing a generic DSS. Adding more sites and parameters to train the software is also expected to improve the prediction accuracy of the DSS.
Forensic Examination of Severe Heaving of Embankment Constructed with Fluidized Bed Combustion Ash
Authors: Yoon Sungmin , Balunaini Umashankar , Prezzi Monica
Published: January 2008

Coal combustion by-products (CCB) are widely used as structural fill materials in embankment construction works. Fluidized bed combustion (FBC) units, which are used to burn coal, have an advantage over the conventionally used pulverized coal units because they can be used to burn even low-grade or high-sulfur content coal. FBC technology emerged from efforts to reduce the emission of pollutants. A roadway embankment was constructed in 1995 with 60% FBC ash, 35% stoker ash, and 5% Class-F fly ash as part of the South Russell Road extension work at Purdue University, West Lafayette, Indiana. The embankment length, maximum height, and crest width are approximately 200 m, 10 m, and 20 m, respectively. The side slopes are 3:1 (H:V). Heaving of the embankment was observed during and after construction, and the pavement exhibited severe damage at several locations. A forensic investigation of the possible causes and mechanisms for this swelling behavior was undertaken. X-ray diffraction and scanning electron microscopic studies were performed to compare the mineralogical phase composition of fresh samples and samples collected from the heaved embankment. The test results indicated that the formation of ettringite led to the swelling of the embankment, which caused cracking of the pavement. In addition, one-dimensional swelling tests on fresh FBC ash samples, as well as on samples collected from the embankment that underwent heaving, were conducted in a consolidometer to quantify the expansive behavior of this material.
Fiber Reinforcement for Rapid Stabilization of Soft Clay Soils
Authors: Rafalko Susan D. , Brandon Thomas L. , Filz George M. , Mitchell James K.
Published: January 2008

Since World War II, the military has sought methods for rapid stabilization of weak soils for support of its missions worldwide. Over the past 60 years, cement and lime have been the most effective stabilizers for road and airfield applications, although recent developments show promise from nontraditional stabilizers, such as reinforcing fibers. The benefits derived from fibers may depend on whether they are used alone or in combination with chemical stabilizers. The ability of stabilizers to increase the strength of two soft clay soils within 72 h to support C-17 and C-130 aircraft traffic on contingency airfields was investigated. Laboratory test results showed that longer fibers increased the strength and toughness the most for a clay treated only with fibers. For a clay treated with fibers in addition to a chemical stabilizer, shorter fibers increased toughness the most, but the fibers had little effect on strength. Higher dosage rates of fibers had increasing effectiveness, but mixing became difficult for fiber contents above 1%. Poly(vinyl) alcohol fibers were anticipated to perform better than other inert fibers because of hydrogen bonding between the fibers and clay minerals, but these fibers performed similarly to other fibers.
Rapid Alternative for Laboratory Determination of Resilient Modulus Input Values on Stabilized Materials for AASHTO Mechanistic-Empirical Design Guide
Authors: Hilbrich Stacy L. , Scullion Tom
Published: January 2008

NCHRP is in the final stages of developing and implementing a new mechanistic-empirical pavement design guide (MEPDG) to be used by all state highway agencies for layer thickness design. Once adopted, it will become the national procedure required on all federally aided projects. A key material property to be used in the design will be the resilient modulus value, which either can be obtained from laboratory testing or can be backcalculated from deflection data collected with falling weight deflectometers. It is important that realistic design moduli values be used. The standard test method for resilient modulus of subgrade soils and untreated base and subbase materials is AASHTO T307-99. However, the setup for this procedure is both difficult and time-consuming, and the equipment required to run this test is expensive. With the low strain levels used, it is likely that accurate instrumentation will be problematic for most state departments of transportation. The free-free resonant column test is a simple, nondestructive laboratory test method for determining the seismic modulus of pavement materials; it takes approximately 5 min to setup and complete. The equipment costs less than $4,000. For the tests conducted, it appears that the seismic modulus device is a better and more repeatable test for estimating the resilient modulus of stabilized materials, and it shows great potential for acquiring reasonable resilient modulus input values for the new AASHTO MEPDG.
Modeling Traffic Signal Operations with Precedence Graphs
Authors: Head Larry , Gettman Douglas , Bullock Darcy M. , Urbanik Thomas
Published: January 2008

A series of examples of traffic signal operations with the precedence graph model is presented to illustrate the interactions among phases, intervals, and overlaps. The examples are built up from the simple operation of a T-intersection by adding more complex behaviors, including advance “Walk,” delayed overlap termination indications, and advance flashing warning signals. In each of these extensions the required signal timing behavior is illustrated through the appropriate precedence graph model. The precedence graph approach provides a structured conceptual representation to support the analysis of operational behaviors of controller timing features such as added lost time and required fixed timing intervals that are induced when certain overlap features are enabled. It is believed that the precedence graph modeling approach may provide a mechanism to formalize the often ad hoc interaction between traffic signal controller software development, logic design, and field operations. This improved understanding may ultimately result in a better understood and more robust deployment of innovative signal control logic by utilizing a structure-modeling approach similar to that found in project management techniques such as the critical path method and the program evaluation and review technique.
Advance Preempt with Gate-Down Confirmation
Authors: Yohe Jacob R. , Urbanik Thomas
Published: January 2008

The preempt trap, a safety issue at some traffic signals near railroad grade crossings with advance preempt, can be addressed in several ways if the operating authority is aware of the potential problem. However, some solutions, such as not using advance preemption, result in other problems, including potentially unsafe clearance intervals during preemption. A simple solution, available from railroads under the standards of the American Railway Engineering and Maintenance-of-Way Association, that provides both safe and efficient operation is evaluated. The evaluation demonstrates the potential value of the use of advance preempt with gate-down confirmation.
Effectiveness of Alternative Detector Configurations for Option Zone Protection on High-Speed Approaches to Traffic Signals
Authors: Si Jianwen , Urbanik Thomas , Han Lee D.
Published: January 2008

Safety and efficiency are both prime issues of concern at high-speed isolated signalized intersections. However, although safety problems at such intersections can be mitigated by the application of detector configurations with option zone (also called decision zone) protection, such configurations can themselves create problems. Although option zones are often called dilemma zones, the term “dilemma” is reserved for issues associated with yellow and red clearance intervals. In this study, four detector configurations for option zone protection features—the single-detector configuration, the Southern District Institute of Traffic Engineers configuration, the Beirele configuration, and the Bonneson configuration—are compared through computer simulation for their effects relative to the number of vehicles in the option zone, max-out occurrences, and average vehicle delay. The comparison suggests that although each configuration has its own advantages and disadvantages, the Bonneson detector configuration, in most circumstances, yields the lower number of vehicles in the option zone per cycle and less average delay.
Empirical Observations of Dynamic Dilemma Zones at Signalized Intersections
Authors: Liu Yue , Chang Gang-Len , Tao Ruihua , Hicks Thomas , Tabacek Eric
Published: January 2008

The results are presented from an empirical study on the distribution of dilemma zones for different groups of drivers at signalized intersections. With a specially designed video-based system, this study conducted extensive field observations of the responses of 1,123 drivers to a yellow phase at six intersections with high accident frequency, including all critical data such as the speed evolution during the yellow phase, the acceleration and deceleration rates, and the approximate reaction time to an encountered yellow phase. These empirical results revealed that the dilemma zone is dynamic in nature, with its location varying with the driving population, and that the recommended and commonly used practice of extending the yellow phase duration may not eliminate all the dilemma zones. Two types of strategies that can effectively eliminate the dynamic dilemma zones are also designed to improve intersection safety.
Evaluation of Adaptive Maximum Feature in Actuated Traffic Controller
Authors: Yun Ilsoo , Best Matthew , Park Byungkyu (Brian)
Published: January 2008

Several actuated traffic controllers contain the adaptive maximum feature, with which controllers can adjust the maximum green intervals for actuated phases within specified upper and lower limits according to fluctuating traffic demand. It has been difficult, however, to evaluate the merits of this and other features available in modern traffic controllers. Recent developments in traffic signal control system hardware and software technologies have now made it possible to evaluate controller features in a realistic and risk-free environment with hardware-in-the-loop simulation (HILS). HILS is a method of simulation in which one or more actual traffic signal controllers are physically linked with a microscopic traffic simulator. The performance of the adaptive maximum feature is demonstrated with HILS, which consists of an EPAC300 traffic controller and the VisSim microscopic simulation model. The demonstration was conducted at an isolated, fully actuated intersection in Richmond, Virginia. In a feasibility test, the HILS results indicated that the adaptive maximum feature was able to provide traffic signal control operations as efficiently as normal maximum green intervals optimized by Synchro. However, in a robustness test, where 15% changes in traffic volumes were considered, the adaptive maximum feature outperformed the normal settings for maximum green intervals.
Short or Long—Which is Better?
Authors: Han Lee D. , Li Jan-Mou
Published: January 2008

Traffic signal timing would be a trivial undertaking if demand were constant and uniform. Once stochastic factors and demand fluctuation are taken into consideration, however, the optimization of signal timing becomes challenging, if not impossible, even for an isolated, fixed-time signal. To answer the question of whether a longer cycle—more than 150 s, for example—or a shorter one—less than 60 s, for example—is better under fluctuating demand conditions, a probabilistic approach is employed to study minimal average delay by the use of mathematical formulations and Monte Carlo simulations. The idea is to select a cycle length that is small enough to ensure low delay, and hence level of service, but can provide adequate capacity to handle most of the fluctuating demand conditions. A five-step framework is presented for carrying out the analyses, which are demonstrated with a hypothetical example. Subsequent sensitivity analyses, level-of-service assessment, and cycle failure rate estimation were conducted on the basis of random demand and are presented here. Conclusions of the study include the following: (a) introduction of a fluctuating demand level increases the average delay in general, (b) longer cycle lengths do not yield optimal delay results, and (c) with extremely short cycle lengths, delay is usually high because of a lack of capacity and hence frequent cycle failures are guaranteed. A major contribution of this study is a proposed framework for optimizing cycle length under stochastic inter- and intracycle demand levels based on the expectation function of delay. When deployed, this framework can aid traffic engineers in choosing the desirable cycle length for minimal delay or for any reasonable level-of-service requirements.
Methodology to Assess Traffic Signal Transition Strategies for Exit Preemption Control
Authors: Obenberger Jon , Collura John
Published: January 2008

Enabling vehicles to preempt the normal operation of traffic signals has the potential to improve the safety and efficiency of both the requesting vehicle and all other vehicles. Little is known about which strategy is the most effective to exit from preemption control and transition back to the normal traffic signal timing plan. This research evaluates the commonly available transition strategies: best-way, long, short, and hold strategies. The major contribution of this research is to enhance the methodology to evaluate the impacts of using these alternative transition strategies with the software-in-the-loop simulation tool. The research concludes that a statistically significant interaction exists between traffic volume levels and traffic signal transition strategies; this eliminates the ability to determine the isolated effects of either the transition strategies on average travel delay and average travel time or the effects of changes in traffic volume levels on average travel delay and average travel time. Conclusions, however, could be drawn on the performance of different transition strategies for specific traffic volume levels. The research also concludes that for the base traffic volume and a 40% increase in traffic volume, the most effective transition strategies are the best-way and long or hold alternatives. The best way was the most effective transition strategy for a 20% increase in traffic volume. The least effective strategy is the short transition strategy for both the base and 40% increase in traffic volume and the long and short for a 20% increase in traffic volume. Further research needs to be conducted to assess the performance of different transition strategies in returning to coordinated operation under higher levels of traffic volume with varying cycle lengths and different signal timing plans and when different roadway geometric configurations are present.
Opening the New Woodrow Wilson Memorial Bridge
Authors: Douglass Robert D. , Nicholson Ronaldo T. , Crumley Scott C.
Published: January 2008

The challenges of maintaining traffic throughout the construction of a multibillion-dollar transportation improvement are immense. Managers are tasked with leading major construction efforts and implementing crucial traffic switches predominately during summer months when Interstate traffic volumes are typically higher than average. Traffic switches have many potential negative outcomes, including extensive vehicle queues and delays, safety concerns, and negative public perception. High expectations were rooted in the $2.4 billion Woodrow Wilson Bridge (WWB) project well before the record of decision. Input by elected officials and the public began over 10 years ago and continues today as project managers handle nearly 200,000 vehicles daily along Interstate 95 through the work zone near Washington, D.C. The new WWB was designed as a signature bridge near historic Alexandria, Virginia, and was the focus of high expectations from stakeholders. Keeping elected officials abreast of upcoming construction and traffic impacts, staying in touch with the affected communities, and maintaining positive public perception are vital to maintaining the on-time and on-budget status of this megaproject. The high point in meeting these expectations was best demonstrated during the traffic switch to open the new bridge during the summer of 2006. The switch involved the coordination of several government agencies, management of multiple contractors across jurisdictional lines, traffic analyses before and after the switch, extensive public outreach coordination, and traffic switch monitoring. Management of these efforts provided accurate expectations to project staff, media, and motorists before, during, and after the traffic switch.
Inferring relationships between native plant diversity and Lonicera japonica in upland forests in north Mississippi, USA
Authors: Surrette Sherry. B. , Brewer J. Stephen
Published: January 2008

Question: Do anthropogenic disturbances interact with local environmental factors to increase the abundance and frequency of invasive species, which in turn exerts a negative effect on native biodiversity?

Location: Mature Quercus‐Carya and Quercus‐Carya‐Pinus (oak‐hickory‐pine) forests in north Mississippi, USA.

Methods: We used partial correlation and factor analysis to investigate relationships between native ground cover plant species richness and composition, percent cover of Lonicera japonica, and local and landscape‐level environmental variables and disturbance patterns in mature upland forests. We directly measured vegetation and environmental variables within 34 sampling subplots and quantified the amount of tree cover surrounding our plots using digital color aerial photography.

Results: Simple bivariate correlations revealed that high species richness and a high proportion of herbs were associated with low Lonicera japonica cover, moist and sandy uncompacted soils, low disturbance in the surrounding landscape, and periodic prescribed burning. Partial correlations and factor analysis showed that once we accounted for the environmental factors, L japonica cover was the least important predictor of composition and among the least important predictors of species richness. Hence, much of the negative correlation between native species diversity and this invasive species was explained by soil texture and local and landscape‐level land‐use practices.

Conclusions: We conclude that negative correlations between the abundance of invasive species and native plant diversity can occur in landscapes with a gradient of human disturbance, regardless of whether there is any negative effect of invasive species on native species.
Autism spectrum conditons in myotonic dystrophy type 1: A study on 57 individuals with congenital and childhood forms
Authors: Ekström Anne‐Berit , Hakenäs‐Plate Louise , Samuelsson Lena , Tulinius Már , Wentz Elisabet
Published: January 2008

Myotonic dystrophy type 1 (DM1) is an autosomal dominant disorder, caused by an expansion of a CTG triplet repeat in the DMPK gene. The aims of the present study were to classify a cohort of children with DM1, to describe their neuropsychiatric problems and cognitive level, to estimate the size of the CTG expansion, and to correlate the molecular findings with the neuropsychiatric problems. Fifty‐seven children and adolescents (26 females; 31 males) with DM1 (CTG repeats > 40) were included in the study. The following instruments were used: Autism Diagnostic Interview‐Revised (ADI‐R), 5–15, Griffiths Mental Development Scales, and the Wechsler Scales. Based on age at onset and presenting symptoms, the children were divided into four DM1 groups; severe congenital (n = 19), mild congenital (n = 18), childhood (n = 18), and classical DM1 (n = 2). Forty‐nine percent had an autism spectrum disorder (ASD) and autistic disorder was the most common diagnosis present in 35% of the subjects. Eighty‐six percent of the individuals with DM1 had mental retardation (MR), most of them moderate or severe MR. ASD was significantly correlated with the DM1 form; the more severe the form of DM1, the higher the frequency of ASD. The frequency of ASD increased with increasing CTG repeat expansions. ASD and/or other neuropsychiatric disorders such as attention deficit hyperactivity disorder, and Tourette's disorder were found in 54% of the total DM1 group. In conclusion, awareness of ASD comorbidity in DM1 is essential. Further studies are warranted to elucidate the molecular etiology causing neurodevelopmental symptoms such as ASD and MR in DM1. © 2008 Wiley‐Liss, Inc.
Dendrimer adsorption on charged particulate surfaces
Authors: Barnes Timothy J. , Ametov Igor , Prestidge Clive A.
Published: January 2008

The adsorption of a negatively charged poly‐L‐lysine dendrimer SPL‐7013 on alumina particle surfaces was investigated as a function of solution ionic strength and pH. The Langmuir model satisfactorily describes experimental adsorption isotherms; the free energies of adsorption ΔGads, surface affinity constants, maximum adsorbed amounts, and areas per adsorbed dendrimer molecule were calculated. ΔGads for various solution conditions were in the range of − 46 to − 59 kJ mol−1; these are significantly greater in magnitude than for small molecules and reflect the multivalent nature and strong adsorption affinity of dendrimer to oppositely charged surfaces, thus confirming electrostatic attraction as a major driving force. The adsorption affinity and interfacial packing of the dendrimer increase with increased solution salt concentration due to the screening of the electrostatic forces and increased surface charge density of the adsorbent. Similarly, increased adsorption at low pH is ascribed to a greater adsorption site density on alumina. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
Improved dewaterability of iron oxide dispersions: the role of polymeric flocculant type, pH and shear
Authors: McGuire Melanie J. , Addai‐Mensah Jonas , Bremmell Kristen E.
Published: January 2008

Substantial amounts of recyclable water are trapped in mineral waste tailings dams annually due to less than effective dewatering processes. To address this, a study has been conducted of the flocculation performance of four high molecular weight (>5 × 106 Da) polyacrylamides, non‐ionic homopolymer (PAM N), anionic carboxylate substituted copolymer (PAM A), anionic sulfonate substituted copolymer (PAM S), and cationic trimethyl amino ethyl substituted copolymer (PAM C), on the dewaterability of iron oxide suspensions as a function of pH. Significant polymer structure‐mediated and pH‐dependent trends were observed.

Upon flocculation with up to 500 g polymer/t solid, settling rates in the range of 3–100 m/h were observed, along with sediment solid loading in the range 35–40 wt%. Settling rates varied depending on polymeric flocculant type, and were higher for anionic and cationic polymers than for non‐ionic polymers. Settling was most efficient at and below the iso‐electric point (iep, pH 8.5). Polymer structure type did not have any noticeable impact on the extent of pulp consolidation. Moderate shear significantly improved the consolidation (55 wt% solid) of pre‐sedimented pulps. For the selection of a flocculant, a polymer that displayed an opposite charge to that of the particles appeared to provide improved flocculation and dewatering performance. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd.
Polymerization of methyl methacrylate with Nickel(II)α‐benzoinoxime complex
Authors: Harrar‐Ferfera Hafida , Amrani Farouk
Published: January 2008

Polymerizations of methyl methacrylate (MMA) monomer initiated by a novel Ni(II)α‐benzoinoxime complex have been achieved under homogeneous conditions in the 25–60°C temperature range. The activity for polymerization increases with reaction temperature and by carrying out the polymerization in solution of low‐polarity solvents without any induction time. The obtained polymers have weight‐average molecular weights about 105 and slight broad polydispersity indexes (2.2 ≤ Mw/Mn ≤ 3.3). Dependence of rate constants polymerization and decomposition of initiator (kapp and kd, respectively) on temperature was investigated and activation parameters were computed from Arrhenius plot. 1H‐NMR analysis of PMMA revealed a syndio‐rich atactic microstructure in agreement with conventional radical process. Radical scavenger TEMPO effect together with microstructure and molecular weight distributions data supported that the polymerization proceed via free radical mechanism. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
The influence of acrylic acid groups on the microstructure of HDPE/BT system studied by positron annihilation
Authors: Wang Hongmei , Chen Zhe , Fang Pengfei , Wang Shaojie , Xu Yuzhen , Fang Zhengping
Published: January 2008

Two types of composites, high‐density polyethylene (HDPE)/Bentonite (BT) and high‐density polyethylene grafted with acrylic acid (HDPE‐g‐AA)/(BT), are prepared by melt compounding. The microstructure of the composite has been studied by the means of positron annihilation lifetime spectroscopy (PALS). It has been found that the mean free volume size is nearly the same in composites and HDPE matrices with different BT concentration. While the ortho‐positronium (o‐Ps) intensity decreased for HDPE‐g‐AA and its lifetime distribution is narrower than that for pure HDPE. With the increasing of BT content, the o‐Ps intensity increases for HDPE‐g‐AA/BT composites and the o‐Ps intensity decreases for HDPE/BT composites. It is found that the carboxyl group of Acrylic acid plays a significant chemical inhibition on positronium formation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Effects of crosslinking agents and inert diluents on the characteristics of crosslinked polystyrene copolymers
Authors: Tank R. , Beldar A. , Saxena A. , Gupta D. C.
Published: January 2008

The suspension copolymerization of styrene with various vinyl crosslinking monomers, that is, dimethacrylates and divinylbenzene, was carried out with poly (vinyl alcohol) as the suspending agent. The effect of the crosslinking monomers on the characteristics of the styrene copolymers was also studied, and the styrene–divinylbenzene copolymers were found to be the most thermally stable. Inert diluents were added during styrene and divinylbenzene copolymerization to achieve porous, crosslinked polystyrene. Furthermore, the influence of the diluents on the formation of porous styrene–divinylbenzene copolymers was investigated by surface area, pore volume, pore diameter, apparent density, swelling percentage, and compressive strength measurements and the surface morphology. It was observed that among the inert diluents studied, cyclohexanol was the most effective diluent, leading to the styrene–divinylbenzene copolymer beads with maximum porosity. A surface morphology study of the polystyrene copolymer beads supported the porosity in these copolymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Deacetylation of konjac glucomannan by mechanochemical treatment
Authors: Pan Zhidong , He Ke , Wang Yanmin
Published: January 2008

This article presents the experimental results on deacetylation of a konjac glucomannan (KGM) powder with alkali in mechanochemical (MC) treatment by a dry vibrating mill. It is indicated that the acetyl group of the KGM powder could be removed by means of the MC method. In addition, some characteristics, such as gel rheology, particle size/conformation, water absorbency, and thermal behavior, of the deacetylated KGM are analyzed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Flame retardant finishing of cotton fleece fabric. II. Inorganic phosphorus‐containing compounds
Authors: Wu Xialing , Yang Charles Q.
Published: January 2008

Cotton fleece is not able to meet the federal flammability standard for general apparels (CFR 1610) without flame retardant treatment. Consequently, cotton fleece is not available in the market in spite of high demands. In our previous research, we studied the application of a hydroxyl‐functional organophosphorus oligomer as a flame retardant finishing agent for cotton fleece. In this research, we investigated the use of aluminum hydroxyphosphate (AHP) formed in situ on cotton by the reaction of aluminum sulfate and sodium phosphates to reduce the flammability of cotton fleece. We found that the AHP formed on cotton is effective in reducing the cotton fleece's flammability from “Class 3” to “Class 1.” Elemental analysis of aluminum and phosphorus in the AHP shows that the mole ratio of Al/P changes as the pH value of the sodium phosphates solution changes. The pH of the sodium phosphate solutions also affect the quantity of AHP formed on the cotton fleece. The treated cotton fleece retains “Class 1” flammability after one home laundering or the combination of dry‐cleaning and hand washing procedures. The treatment increases the whiteness of the cotton fleece whereas it reduces its bursting strength. The cotton fleece thus treated is also investigated using differential scanning calorimetry and scanning electron microscopy. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Biocomposites composed of epoxidized soybean oil cured with terpene‐based acid anhydride and cellulose fibers
Authors: Takahashi Tsutomu , Hirayama Ken‐ichi , Teramoto Naozumi , Shibata Mitsuhiro
Published: January 2008

Epoxidized soybean oil (ESO) was cured with a terpene‐based acid anhydride (TPAn) at 150°C, and the thermal and mechanical properties of the cured product were compared with ESO cured with hexahydrophthalic anhydride (HPAn), maleinated linseed oil (LOAn), or thermally latent cationic polymerization catalyst (CPI). The ESO‐TPAn showed a higher glass transition temperature (67.2°C) measured by dynamic mechanical analysis than ESO‐HPAn (59.0°C), ESO‐LOAn (−41.0°C), and ESO‐CPI (10.0°C). The storage modulus at 20°C of ESO‐TPAn was higher than those of ESO‐LOAn and ESO‐CPI. Also, ESO‐TPAn showed higher tensile strength and modulus than the other cured ESOs. Regarding the biodegradability measured by biochemical oxygen demand in an activated sludge, ESO‐TPAn possessed some biodegradability, which was lower than that of ESO‐LOAn. Next, biocomposites composed of ESO‐TPAn and regenerated cellulose (lyocell) fabric were prepared by compression molding method. The tensile strength of ESO‐TPAn/lyocell composites increased with increasing fiber content. The tensile strength and modulus of ESO‐TPAn/lyocell composite with fiber content 75 wt % were 65 MPa and 2.3 GPa, which were three times higher than those of ESO‐TPAn. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Bifurcation Model for Characterization of Pulmonary Architecture
Authors: Lee Dongyoub , Park Seong S. , Ban‐Weiss George A. , Fanucchi Michelle V. , Plopper Charles G. , Wexler Anthony S.
Published: January 2008

A flexible mathematical model of an asymmetric bronchial airway bifurcation is presented. The bifurcation structure is automatically determined after the user specifies geometric parameters: radius of parent airway, radii of daughter airways, radii of curvature of the daughter branch toroids, bifurcation angles, and radius of curvature of carina ridge. Detailed shape in the region where the three airways merge is defined by several explicit functions and can be changed with ease in accordance with observed lung structure. These functions take into account the blunt shape of the carina, the smooth transition from the outer transition zone to the inner one, and the shift in carinal ridge starting position as a function of bifurcation asymmetry. We validated the bifurcation model by comparing it to a computed tomography image of a rat lung cast. Three‐dimensional representations of the bifurcation geometry can be viewed at http://mae.ucdavis.edu/wexler/lungs/bifurc.htm. Anat Rec, 291:379–389, 2008. © 2008 Wiley‐Liss, Inc.
Anatomic Geometry of Sound Transmission and Reception in Cuvier's Beaked Whale (Ziphius cavirostris)
Authors: Cranford Ted W. , Mckenna Megan F. , Soldevilla Melissa S. , Wiggins Sean M. , Goldbogen Jeremy A. , Shadwick Robert E. , Krysl Petr , St. Leger Judy A. , Hildebrand John A.
Published: January 2008

This study uses remote imaging technology to quantify, compare, and contrast the cephalic anatomy between a neonate female and a young adult male Cuvier's beaked whale. Primary results reveal details of anatomic geometry with implications for acoustic function and diving. Specifically, we describe the juxtaposition of the large pterygoid sinuses, a fibrous venous plexus, and a lipid‐rich pathway that connects the acoustic environment to the bony ear complex. We surmise that the large pterygoid air sinuses are essential adaptations for maintaining acoustic isolation and auditory acuity of the ears at depth. In the adult male, an acoustic waveguide lined with pachyosteosclerotic bones is apparently part of a novel transmission pathway for outgoing biosonar signals. Substitution of dense tissue boundaries where we normally find air sacs in delphinoids appears to be a recurring theme in deep‐diving beaked whales and sperm whales. The anatomic configuration of the adult male Ziphius forehead resembles an upside‐down sperm whale nose and may be its functional equivalent, but the homologous relationships between forehead structures are equivocal. Anat Rec, 291:353–378, 2008. © 2008 Wiley‐Liss, Inc.
Visualization and experimental analysis of blood vessel formation using transgenic zebrafish
Authors: Cha Young Ryun , Weinstein Brant M.
Published: January 2008

The mechanisms of blood vessel formation have become a subject of enormous scientific and clinical interest. However, it is difficult to visualize the developing vasculature in most living animals due to the ubiquitous and deep localization of vessels within other tissues. The establishment of vascular‐specific transgenic zebrafish with fluorescently “tagged” blood vessels has facilitated high‐resolution imaging studies of developing blood and lymphatic vessels in vivo. Use of these transgenic lines for genetic and chemical screening, experimental manipulations, and time‐lapse imaging has extended our knowledge of how complex networks of vessels assemble in vivo. Birth Defects Research (Part C) 81:286–296, 2007. Published 2008 Wiley‐Liss, Inc.
Agent‐based modeling of multicell morphogenic processes during development
Authors: Thorne Bryan C. , Bailey Alexander M. , DeSimone Douglas W. , Peirce Shayn M.
Published: January 2008

A central challenge in the field of developmental biology is to understand how mechanisms at one level of biological scale (i.e., cell‐level) interact to produce higher‐level (i.e., tissue‐level) phenomena. This challenge is particularly relevant to the study of tissue morphogenesis, the process that generates newly formed, remodeled, or regenerated tissue structures. Morphogenesis arises from the spatially‐ and temporally‐dynamic interactions of individual cells with each other and their local environment. Computational models have been combined with experimental efforts to accelerate the discovery processes. Agent‐based modeling (ABM) is a computational technique that can be used to model collections of individual biological cells and compute their interactions, which generate emergent tissue‐level results. Recently, ABM has been applied to the study of various developmental morphogenic processes, and the purpose of this review is to summarize these studies in order to demonstrate the types of advances that can be expected from pursuing a multicell ABM approach. We also highlight some challenges associated with ABM and suggest strategies for overcoming them. While ABM's application to the study of ecology, epidemiology, and social sciences has a much longer history, we suggest that the application of ABM to the study of morphogenesis has great utility, and when paired with benchtop experimentation, ABM can provide new insights and direct future experimentation. Birth Defects Research (Part C) 81:344–353, 2007. © 2008 Wiley‐Liss, Inc.
Mechanisms controlling human endothelial lumen formation and tube assembly in three‐dimensional extracellular matrices
Authors: Davis George E. , Koh Wonshill , Stratman Amber N.
Published: January 2008

Recent data have revealed new mechanisms that underlie endothelial cell (EC) lumen formation during vascular morphogenic events in development, wound repair, and other disease states. It is apparent that EC interactions with extracellular matrices (ECMs) establish signaling cascades downstream of integrin ligation leading to activation of the Rho GTPases, Cdc42 and Rac1, which are required for lumen formation. In large part, this process is driven by intracellular vacuole formation and coalescence, which rapidly leads to the creation of fluid‐filled matrix‐free spaces that are then interconnected via EC–EC interactions to create multicellular tube structures. EC vacuoles markedly accumulate in a polarized fashion directly adjacent to the centrosome in a region that strongly accumulates Cdc42 protein as indicated by green fluorescent protein (GFP)‐Cdc42 during the lumen formation process. Downstream of Cdc42‐mediated signaling, key molecules that have been identified to be required for EC lumen formation include Pak2, Pak4, Par3, Par6, and the protein kinase C (PKC) isoforms ζ and ε. Together, these molecules coordinately regulate the critical EC lumen formation process in three‐dimensional (3D) collagen matrices. These events also require cell surface proteolysis mediated through membrane type 1 matrix metalloproteinase (MT1‐MMP), which is necessary to create vascular guidance tunnels within the 3D matrix environment. These tunnels represent physical spaces within the ECM that are necessary to regulate vascular morphogenic events, including the establishment of interconnected vascular tube networks as well as the recruitment of pericytes to initiate vascular tube maturation (via basement membrane matrix assembly) and stabilization. Current research continues to analyze how specific molecules integrate signaling information in concert to catalyze EC lumen formation, pericyte recruitment, and stabilization processes to control vascular morphogenesis in 3D extracellular matrices. Birth Defects Research (Part C) 81:270–285, 2007. © 2008 Wiley‐Liss, Inc.
Variation and robustness of the mechanics of gastrulation: The role of tissue mechanical properties during morphogenesis
Authors: von Dassow Michelangelo , Davidson Lance A.
Published: January 2008

Diverse mechanisms of morphogenesis generate a wide variety of animal forms. In this work, we discuss two ways that the mechanical properties of embryonic tissues could guide one of the earliest morphogenetic movements in animals, gastrulation. First, morphogenetic movements are a function of both the forces generated by cells and the mechanical properties of the tissues. Second, cells could change their behavior in response to their mechanical environment. Theoretical studies of gastrulation indicate that different morphogenetic mechanisms differ in their inherent sensitivity to tissue mechanical properties. Those few empirical studies that have investigated the mechanical properties of amphibian and echinoderm gastrula‐stage embryos indicate that there could be high embryo‐to‐embryo variability in tissue stiffness. Such high embryo‐to‐embryo variability would imply that gastrulation is fairly robust to variation in tissue stiffness. Cell culture studies demonstrate a wide variety of cellular responses to the mechanical properties of their microenvironment. These responses are likely to be developmentally regulated, and could either increase or decrease the robustness of gastrulation movements depending on which cells express which responses. Hence both passive physical and mechanoregulatory processes will determine how sensitive gastrulation is to tissue mechanics. Addressing these questions is important for understanding the significance of diverse programs of early development, and how genetic or environmental perturbations influence development. We discuss methods for measuring embryo‐to‐embryo variability in tissue mechanics, and for experimentally perturbing those mechanical properties to determine the sensitivity of gastrulation to tissue mechanics. Birth Defects Research (Part C) 81:253–269, 2007. © 2008 Wiley‐Liss, Inc.
Cellular mechanobiology and cancer metastasis
Authors: Makale Milan
Published: January 2008

The primary cause of cancer treatment failure is invasion and metastasis, and invading tumor cells utilize many of the motility patterns that have been documented for normal morphogenesis. Recently, the role of mechanical forces in guiding various tissue and cell movements in embryonic development has been systematically analyzed with new experimental and computational methods. The tissue and cellular mechanobiology approach also holds promise for increasing the understanding of tumor invasion. In fact, the mechanical stiffness of tumors has correlated with invasiveness, and manipulation of extracellular matrix (ECM) stiffness in vitro has suppressed the cancer phenotype. Several important signaling molecules reside on the cytoskeleton, which is affected by external stress imparted by the ECM, and deformation of the nucleus can trigger the activation of certain genes. All these observations suggest that a synthesis of the biology of cancer cell invasion and cellular mechanobiology may offer new targets for the treatment of malignant disease. Accordingly, sensitive and relevant in vivo models and methods to study cancer mechanobiology are needed. Birth Defects Research (Part C) 81:329–343, 2007. © 2008 Wiley‐Liss, Inc.
New insights into elastic fiber assembly
Authors: Wagenseil Jessica E. , Mecham Robert P.
Published: January 2008

Elastic fibers provide recoil to tissues that undergo repeated stretch, such as the large arteries and lung. These large extracellular matrix (ECM) structures contain numerous components, and our understanding of elastic fiber assembly is changing as we learn more about the various molecules associated with the assembly process. The main components of elastic fibers are elastin and microfibrils. Elastin makes up the bulk of the mature fiber and is encoded by a single gene. Microfibrils consist mainly of fibrillin, but also contain or associate with proteins such as microfibril associated glycoproteins (MAGPs), fibulins, and EMILIN‐1. Microfibrils were thought to facilitate alignment of elastin monomers prior to cross‐linking by lysyl oxidase (LOX). We now know that their role, as well as the overall assembly process, is more complex. Elastic fiber formation involves elaborate spatial and temporal regulation of all of the involved proteins and is difficult to recapitulate in adult tissues. This report summarizes the known interactions between elastin and the microfibrillar proteins and their role in elastic fiber assembly based on in vitro studies and evidence from knockout mice. We also propose a model of elastic fiber assembly based on the current data that incorporates interactions between elastin, LOXs, fibulins and the microfibril, as well as the pivotal role played by cells in structuring the final functional fiber. Birth Defects Research (Part C) 81:229–240, 2007. © 2008 Wiley‐Liss, Inc.
Activator‐inhibitor dynamics of vertebrate limb pattern formation
Authors: Newman Stuart A. , Bhat Ramray
Published: January 2008

The development of the vertebrate limb depends on an interplay of cellular differentiation, pattern formation, and tissue morphogenesis on multiple spatial and temporal scales. While numerous gene products have been described that participate in, and influence, the generation of the limb skeletal pattern, an understanding of the most salient feature of the developing limb—its quasiperiodic arrangement of bones, requires additional organizational principles. We review several such principles, drawing on concepts of physics and chemical dynamics along with molecular genetics and cell biology. First, a “core mechanism” for precartilage mesenchymal condensation is described, based on positive autoregulation of the morphogen transforming growth factor (TGF)‐β, induction of the extracellular matrix (ECM) protein fibronectin, and focal accumulation of cells via haptotaxis. This core mechanism is shown to be part of a local autoactivation‐lateral inhibition (LALI) system that ensures that the condensations will be regularly spaced. Next, a “bare‐bones” model for limb development is described in which the LALI‐core mechanism is placed in a growing geometric framework with predifferentiated “apical,” differentiating “active,” and irreversibly differentiated “frozen” zones defined by distance from an apical source of a fibroblast growth factor (FGF)‐type morphogen. This model is shown to account for classic features of the developing limb, including the proximodistal (PD) emergence over time of increasing numbers of bones. We review earlier and recent work suggesting that the inhibitory component of the LALI system for condensation may not be a diffusible morphogen, and propose an alternative mechanism for lateral inhibition, based on synchronization of oscillations of a Hes mediator of the Notch signaling pathway. Finally, we discuss how viewing development as an interplay between molecular‐genetic and dynamic physical processes can provide new insight into the origin of congenital anomalies. Birth Defects Research (Part C) 81:305–319, 2007. © 2008 Wiley‐Liss, Inc.