bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantification of Effect of Polymer-Modified Asphalt on Flexible Pavement Performance
Authors: Von Quintus Harold L. , Mallela Jagannath , Buncher Mark
Published: January 2008

Polymer-modified asphalt (PMA) mixtures are routinely used today in flexible pavement structures or overlays carrying high volumes of traffic. Although there have been numerous laboratory and field studies comparing the performance of PMA and conventional hot-mix asphalt (HMA) mixtures, for example, Superpave® and Marshall, there has not been a concerted effort to quantify the benefits of using PMA mixtures or to develop guidance on when the use of PMA mixtures is cost-effective. An investigation of nearly three dozen real-world pavement sections in North America was conducted to quantify the benefits of using PMA mixtures. The test sections used in performance comparisons included both roadway and accelerated pavement test sections. Performance data for the test sections were derived from published literature or other public sources such as the Long-Term Pavement Performance or the National Center for Asphalt Technology databases. On the basis of the performance comparisons made between PMA and conventional sections, it was found that PMA mixtures significantly enhance not only the rutting performance of flexible pavements but also their fatigue and fracture performance. The examples used in this study show an extended service life for deep-strength HMA pavements of 5 to 10 years through the use of PMA mixtures, on the basis of the performance observations from the companion test sections, which were constructed mostly with older Marshall or Hveem mixtures. A definite bias exists between the predicted and measured distress values for the sections with PMA mixtures when using current mechanistic-empirical distress prediction models. This finding suggests a need for different calibration factors in PMA mixtures for use in rutting and fatigue cracking prediction equations.
How Many Steps Do you Have in Reserve?
Authors: Morency Catherine , Demers Marie , Lapierre Lucie
Published: January 2008

The aim of this study was to estimate the benefits that people could achieve by trading their car for a nonmotorized mode of travel, such as walking, to make their short daily trips. For this purpose, detailed information on travel behavior gathered through large-scale travel surveys conducted in the greater Montreal, Quebec, Canada, area was used. The travel behavior observed in recent travel surveys was analyzed to estimate the number of short trips for various population segments. These surveys gathered travel and sociodemographic information for approximately 5% of the population. Data from the 2003 survey revealed that more than 7 million motorized trips were made during a typical weekday; 862,000 (11.7%) were shorter than 1.6 km (1 mi). With the appropriate speed and stride for each population segment, these motorized kilometers were converted into numbers of steps to appraise the potential physical activity benefits of making these short trips by foot instead of by a motorized mode. The results show that about 837,000 motorized kilometers could be converted into almost 1,156 million steps every day. Overall, 12.5% of the population had steps in reserve, an average of 2,660 steps per person. Such a shift in mode choice could help some people meet their required physical activity volumes through their daily travel patterns while helping to save energy, reduce pollution, and mitigate traffic congestion.
Overall Level of Service of Urban Walking Environment and Its Influence on Pedestrian Route Choice Behavior
Authors: Muraleetharan Thambiah , Hagiwara Toru
Published: January 2008

The objective of this study was to understand and quantify better the influence of the overall level of service (LOS) of the urban walking environment on pedestrian route choice behavior. A methodology for estimating the overall LOS of pedestrian walkways and crosswalks was developed on the basis of the concept of total utility value, which comes from a stated preference survey. Each sidewalk and crosswalk link was assigned an overall LOS according to its operational and geometric characteristics determined from field measurements. For analysis of pedestrian behavior, this study used data from a revealed preference survey on individual route choice behavior. A geographic information system network database was used to store the characteristics of the routes that pedestrians used. Network analysis with the ArcGIS program was used to analyze the routes, which included determination of the shortest-path routes and the optimized-LOS-path routes between origin-destination pairs. A comparative analysis of the actual routes and the estimated alternative routes was performed. On the basis of the results, a multinomial logit model was developed to express the route choice behaviors of pedestrians quantitatively. The model results indicate that pedestrians choose routes not only for distance but also for the overall LOS of sidewalks and crosswalks. On longer travel paths, pedestrians divert from the shortest-path route and are found to use sidewalks and crosswalks with high LOS. On shorter routes, pedestrians tend not to avoid sidewalks or crosswalks with low LOS. This analysis suggests that efforts to accommodate pedestrians in urban areas should focus on improving the walking environment of the road network.
Effects of Various Minimum Green Times on Percentage of Pedestrians Waiting for Midblock “Walk” Signal
Authors: Van Houten Ron , Ellis Ralph , Kim Jin-Lee
Published: January 2008

Pedestrians often do not wait for the “Walk” sign at signal-controlled midblock crossings. Many factors may contribute to this phenomenon, but one variable could be the waiting time. One study has shown that as the waiting time for an elevator in university buildings was systematically increased, more people took the stairs rather than the elevators. It is likely that the major reason why people try to cross against the signal at midblock signal-controlled crosswalks when there are gaps in traffic in the first half of the roadway is the length of the average waiting time. It is common to have minimum green times of 1 min or more on a main line with a signal-controlled midblock crosswalk. Arriving early in a cycle, a pedestrian may become frustrated and attempt to cross a street with fast, heavy traffic. The purpose of this study was to determine the effect of waiting time on pedestrian signal compliance at two midblock crosswalks in Miami-Dade County, Florida. One crosswalk traversed an arterial multilane road with two-way traffic, and the second crosswalk traversed a multilane road with one-way traffic. At both crosswalks the minimum green time varied between 30 and 120 s. The results indicated that the rate of pedestrian compliance decreased as the minimum green time was increased and that the rate of compliance dropped more rapidly as the minimum green time was increased at the location with the lower average daily traffic and one-way traffic. The data also showed that the percentage of pedestrians trapped at the centerline increased with an increased minimum green time.
Review of Lightweight Deflectometer for Routine in Situ Assessment of Pavement Material Stiffness
Authors: Fleming Paul R. , Frost Matthew W. , Lambert John P.
Published: January 2008

The use of a portable lightweight deflectometer (LWD) for construction quality control or material investigation for earthworks and road construction is increasing around the world. LWD is reviewed as a field evaluation tool, the test variables and data quality are discussed, and the usefulness and limitations for a variety of earthwork and road assessment scenarios are described. A state-of-the-art reference document is provided for LWD users, consultants, material specifiers, contractors, and clients. Data from road foundations (subgrades, granular capping, and subbase) and fully constructed in-service (thinly surfaced) roads were reviewed to demonstrate the flexibility of the LWD and to show that its determination of stiffness modulus may differ from that of the conventional falling weight deflectometer to a varying extent. A series of laboratory investigations was undertaken to demonstrate the sensitivity to uniformity of plate-surface contact and the limitations in the interpretation of peak displacement from the device. A good understanding of the device workings and careful specification of the test variables are required both to analyze the data correctly and to permit comparison between data sets. It is concluded that the device is a useful and versatile field quality control and pavement investigation tool if an understanding of the device issues is considered by data users.
Advanced Approaches to Characterizing Nonlinear Pavement System Responses
Authors: Ceylan Halil , Gopalakrishnan Kasthurirangan , Guclu Alper
Published: January 2008

The use of falling weight deflectometer–based backcalculation techniques to determine pavement layer moduli is a cost-effective and widely used method for the structural evaluation of an existing pavement. The nonlinear stress-sensitive response of pavement geomaterials has been well established, and mechanistic-based pavement design can be improved by inclusion of these nonlinear material properties. To further the science of nonlinear backcalculation, the TRB Strength and Deformation Characteristics of Pavement Sections Committee has assembled four data sets that can be used to demonstrate the ability to derive stress-dependent moduli for pavement layers. In this study, validated artificial neural network (ANN)–based backcalculation-type flexible pavement analysis models were used to evaluate the TRB Nonlinear Pavement Analysis Project data sets. The Illi-Pave finite element (FE) model, considering nonlinear stress-dependent geomaterials characterization, was utilized to generate a solution database for developing the ANN-based structural models. Such use of ANN models enables the incorporation of needed sophistication in structural analysis, such as FE modeling with proper materials characterization, into routine practical design. This study illustrated the complexities associated with interpreting the backcalculated modulus values. In general, the predicted strains agreed reasonably well with the measured strain values, whereas the predicted stresses did not.
Consideration of Finite Slab Size in Backcalculation Analysis of Jointed Concrete Pavements
Authors: Setiadji B. H. , Fwa T. F.
Published: January 2008

The effects of finite slab size and load transfer across joints usually are ignored in the backcalculation analysis of jointed concrete pavements when the test load is applied on an interior point of the slab concerned. Although correction factors have been proposed to take these effects into consideration, the benefits of doing so have yet to be established, and their use has not been accepted in routine backcalculation tests. A study was conducted to assess whether significant improvements in the accuracy of backcalculation analysis could be achieved by considering finite slab size and load transfer at joints in the backcalculation analysis of jointed concrete pavement systems. Five backcalculation methods were evaluated with measured deflection data extracted from the Long-Term Pavement Performance database, and comparisons were made with the measured pavement properties. The analysis based on the measured field data offered affirmative evidence of the theoretical lower- and upper-bound estimates provided by backcalculation solutions based on the infinite slab model and one-slab model, respectively. An error analysis was presented to show that the infinite slab model gave superior solutions as compared with the one-slab model. A nine-slab model that considered finite slab size and joint load transfer effects resulted in only marginal improvements in the backcalculation results. Two finite slab size models that applied correction factors to infinite-slab solutions were found to produce the largest errors among the five backcalculation models studied.
Development of Transfer Functions for Spectral Compatibility of Inertial Profilers Used in Long-Term Pavement Performance Program
Authors: Kutay M. Emin , Weaver Eric , Wiser Larry
Published: January 2008

A quantification of the difference in the wavelength content produced by K. J. Law Engineers and International Cybernetics Corporation (ICC) profilers is presented. Transfer functions were developed to modify the power spectral density (PSD) of profiles recorded by the ICC profilers to produce a pseudo–K. J. Law PSD so that it is compatible with the spectral content of the profiles recorded by the K. J. Law profiler. Comparison of PSDs of the original K. J. Law and pseudo–K. J. Law profilers exhibited an excellent match in most pavements. Furthermore, a transfer function was developed and used to reconstruct a pseudo–K. J. Law pavement profile from the ICC profile, whose spectral content is similar to that of the K. J. Law profile, by using the inverse fast Fourier transform technique. The international roughness indexes (IRIs) of pseudo–K. J. Law profiles were in general closer to the IRIs of K. J. profiles than those of the ICC profiles. The technique presented here has the potential to be applied to inertial profile equipment types other than those considered in this study, therefore allowing comparisons of data sets.
Wavelet Analysis of Energy Content in Pavement Roughness and Truck Dynamic Axle Loads
Authors: Papagiannakis A. T. , Zelelew H. M. , Muhunthan B.
Published: January 2008

A wavelet approach is used to study the interaction between pavement roughness profile and heavy-truck axle dynamics. Profile and load variation are quantified in terms of their sum of squares or energy, in units of millimeters squared per meter and kilonewtons squared per meter, respectively. The dynamic axle load and pavement roughness profile data are decomposed into distinct frequency subbands and relative or percent energy is computed. The results are presented in the form of three-dimensional plots of relative dynamic load energy, pavement roughness energy, and pavement roughness frequency. They demonstrate the drastically different response of two types of suspensions to roughness excitation. Energy also was normalized by dividing by the length traveled, resulting in units of millimeters squared per meter and kilonewtons squared per meter for the profile and the dynamic load, respectively. The normalized energy results show a much higher dynamic load activity for the rubber suspension than for the air suspension. The normalized energy of load shows a high correlation with the normalized energy of the pavement roughness. The normalized energy of the pavement roughness profile shows a high correlation with the conventional international roughness index.
Los Angeles, California, Metro Green Line
Authors: Mieger David , Chu Chaushie
Published: January 2008

The Los Angeles, California, Metro Green Line opened for service in 1995 and was immediately branded by critics as the “line to nowhere” because it did not directly serve the central business district or any other major activity center. It was located close to the Los Angeles International Airport but did not quite reach it. The line was located close to the principal Amtrak north–south rail corridor between Los Angeles and San Diego, California, but did not quite reach that. In fact, the line was so controversial in 1995 that the television program 60 Minutes did an exposé of the Los Angeles Metro System and specifically identified the project as an example of poor planning and management. Despite these criticisms, the Metro Green Line has been surprisingly successful in attracting relatively high ridership during its first decade of operation. Average weekday boardings on the Green Line have grown from 13,600 to more than 37,000 per day. Many Green Line riders use the line as a feeder route to the heavily used Metro Blue Line, which directly serves downtown Los Angeles and Long Beach, California. This connection seems to have benefited both lines, and during the past decade, Blue Line ridership has more than doubled from 39,600 to 80,400. Further extensions of the Green Line are now being considered as a part of Los Angeles transit plans. Perceived failures of the original project are reviewed and some of the reasons for the relatively high levels of ridership growth on the line are explored. The overall theme of the paper concerns light rail transit projects that serve nontraditional markets.
Owner-Controlled Accelerated Project
Authors: Venturato Tony , Schroeder Jim
Published: January 2008

There is much discussion these days about project delivery methods. Owners want to consider ways of fast-tracking mass transit projects. Design–build, which overlaps design and construction, gets a lot of attention, but owners should consider other alternatives to avoid unintended consequences on light rail projects through an urban area. Design–build shifts the risk and the control to the construction contractor, and in an environment where third parties are ubiquitous and interactions can be intense, owners should think about the consequences of loss of control. In Houston, Texas, the starter line light rail project, MetroRail, used a unique, fast-track project delivery method called the owner-controlled accelerated project (OCAP), which overlapped design and construction but kept the risk and control with the owner. With OCAP, the owner chooses to be placed in the middle of the frenzy and chaos of a highly visible public works project, becoming the arbiter for and brunt of all controversy. But the control that is inextricably coupled to the risk makes it all worthwhile. MetroRail was done in record-breaking time (4 years from start of design to revenue service) and stayed within budget. Its reliability is evidenced by ridership that exceeds Year 2020 projections and by a 99.3% on-time performance.
Transforming a Bus Station into a Transit-Oriented Development
Authors: Cottrell Wayne D.
Published: January 2008

While most transit-oriented development (TOD) is oriented toward rail, bus stations can also serve as centers of TODs. The El Monte, California, bus station (EMBS), around which a transit village has been proposed, is examined. The village would have little impact on the surrounding community, though, without improvements in access to the EMBS. With a 1-km ring as the potential sphere of influence, theoretically no one can walk, bicycle, or ride a shuttle bus to the station, given impedances such as major street crossings and lengthy feeder shuttle headways. With construction of two pedestrian bridges and signing and lighting improvements along an adjacent bicycle path, the number of residents in the SOI would rise to potentially 40,800, with two-thirds of them within a 5-km bicycle ride of the EMBS. The proposed improvements might cost about $5 million. To connect the EMBS to a business park and Metrolink rail station located just outside the ring, an automated people mover (APM) is proposed. The APM would serve the roughly 5,000 employees of the business park, and it would facilitate transfers between the EMBS, Metrolink, and the proposed Silver Line (light rail to terminate at the Metrolink station). The APM would cost more than $30 million, but it could enhance transit use, local development, and real estate values. For areas within the ring not affected by the improvements, shuttle bus services need reorientation. The importance of pedestrian connectivity is emphasized, as are the cost-effectiveness of bicycling improvements, ideal setting for an APM, need for streamlined shuttle bus service, and importance of multiple access modes.
Logit Models for Forecasting Nationwide Intercity Travel Demand in the United States
Authors: Ashiabor Senanu , Baik Hojong , Trani Antonio
Published: January 2008

Nested and mixed logit models were developed to study national-level intercity transportation in the United States. The models were used to estimate the market share of automobile and commercial air transportation of 3,091 counties and 443 commercial service airports in the United States. Models were calibrated with the use of the 1995 American Travel Survey. Separate models were developed for business and nonbusiness trip purposes. The explanatory variables used in the utility functions of the models were travel time, travel cost, and traveler's household income. Given an input county-to-county trip demand table, the models were used to estimate county-to-county travel demand by automobile and commercial airline between all counties and commercial-service airports in the United States. The model has been integrated into a computer software framework called the transportation systems analysis model that estimates nationwide intercity travel demand in the United States.
Passenger Market Equilibrium for Competing Airports in Multiple Airport Region
Authors: Tien Shin-Lai , Schonfeld Paul
Published: January 2008

Major metropolitan areas are often served by two or three air carrier airports. Researchers have developed airport choice models that focus on the decision structures and attributes of the passengers’ choice of departure airport. A study extended the scope of airport choice models in a multiple airport system region and tried to estimate from the viewpoint of airport authorities how many flights a competing airport should seek and the resulting passenger shares when market equilibrium is reached. Each airport aims to maximize its own payoff in this game in an air travel oligopolistic market by determining its own strategies while being affected by those of its opponents. The payoff function is formulated to reflect the airlines’ and the passengers’ responses. The prices charged by airports to airlines are assumed to influence flight frequencies and, hence, the passengers’ preferences among airports. The passenger market shares equilibrium is then determined when no airport has incentives to deviate from its own pricing strategies. The structure of the model can help analyze the impact of airports’ strategies and those of their competitors. To demonstrate the model's potential as a policy analysis tool, a simple numerical example is designed and solved.
Air Traffic Control Complexity and Safety
Authors: Majumdar Arnab , Ochieng Washington Yotto
Published: January 2008

“Air traffic control (ATC) complexity” can be defined as the interaction between air traffic and the sector characteristics through which this air traffic flies. Research indicates that complexity is the prime determinant of the air traffic controller's workload. Research has attempted to define and classify complexity variables that have been used to assess the capacity of en route airspace in Europe and North America. Such variables can also be used to assist in ATC sector design by highlighting those complexity factors that can lead to high workload and potentially risky scenarios for the controller. With the use of a structured interview technique, a study analyzed these ATC complexity variables for their impact on controller workload and safety. Seventy-nine air traffic controllers were interviewed about the factors that affected their workload. These controllers were based in 14 area control centers in Europe, including those of high complexity, such as Maastricht, Netherlands, as well as in nine centers in Asia, one in Africa, and Mumbai, India, a region with major traffic growth in recent years. On the basis of these interviews, a taxonomy of more than 50 complexity variables subdivided into 11 major groupings, such as traffic mix and entry and exit points, has been developed. In addition to rating of the impact of the individual complexity factors to assess their effect on airspace, interactions between complexity variables were deduced from the interviews. These interactions enable assessment of the factors that add to layers of complexity for controllers. Such a taxonomy can assist airspace planners in designing sectors that avoid complex ATC situations. How the impact of such complexity factors can be investigated in sector design is outlined.
Aircraft-Based Pavement Surface Roughness Assessment
Authors: Cardoso Samuel Hautequest
Published: January 2008

It has long been recognized that each aircraft responds differently to a pavement surface roughness pattern. On the basis of that observation, the development of two aircraft-based roughness assessment criteria is discussed. Both allow the analysis of pavement surface profiles obtained from surveys carried out at 1-m intervals. The single wavelength roughness criterion looks for acceptable and excessive single double amplitudes in the profiles of runways and taxiways. The overall roughness criterion considers the template and the root-mean-square (RMS) approaches. Both work as a function of the critical wavelengths (Lc) and double amplitudes (2A). These parameters are estimated for each aircraft as a function of its velocity at the takeoff rotational point and the aircraft response frequency. For the template approach, windows are constructed with Lc and 2A for each particular aircraft for identifying the acceptable and excessive roughness areas in the profiles. The RMS approach initially estimates RMS limit values for acceptable and excessive roughness for each aircraft on the basis of its critical wavelength. Values of RMS are estimated for runway segments with the same lengths of the critical wavelengths and then compared with the RMS limit values. Excellent agreement was observed between the single wavelength roughness criterion and the FAA and International Civil Aviation Organization criteria. In addition, excessive bump deformations obtained by other authors for Georgia's Hartsfield–Jackson Atlanta International Airport Runway 8L-26R were found to be above the same criterion's excessive roughness curve.
Analyzing Effects of Spring Highway Load Restrictions on North Dakota's Agricultural Freight Flows
Authors: Mitra Subhro , Tolliver Denver , Varma Amiy , Dybing Alan
Published: January 2008

This paper describes a statewide agricultural freight transportation model that is used to estimate the benefits of improving North Dakota's state highway system by removing spring load restrictions. The transportation model measures changes in freight flows caused by truck weight regulations during the spring thaw cycle. The primary focus is on grain transportation. A geographic information system (GIS) network of federal, state, and county roads is developed to represent flows from fields to elevators and final destinations. The state is divided into 182 production zones on the basis of agricultural land use patterns. The data for the trip generation component of the model are derived from satellite imagery of crop layers in the state, with the use of GIS spatial analysis and algorithms developed for this purpose. The annual demand at elevators is estimated from grain movement reports filed with the State of North Dakota. Agricultural freight movement is modeled separately as two flows: internal-to-internal (i.e., from fields to elevators) and internal-to-external (i.e., from elevators to final destinations). CUBE transportation planning software is used to model the flows. In addition, the onion model concept used in Iowa is applied as a demand planning tool to capture the effects of spring load restrictions, which are dynamic and move from the southern to the northern part of the state during the spring thaw cycle. The costs of spring load limits are quantified as the increased distance and travel time caused by circuitous truck movements or as the reduced payload per trip.
Funding for Pupil Transportation
Authors: McDonald Noreen C. , Howlett Marc Alan
Published: January 2008

School districts spend approximately $17 billion annually on pupil transportation. More than half of all students in the United States are eligible for transportation at public expense. Despite this major financial investment and the large number of daily student trips, relatively little scholarly material is written on funding for pupil transportation. This article provides research background on pupil transportation funding, establishes a comprehensive framework of analysis for evaluating methods of state funding, and presents case studies of six states to highlight institutional differences. The key questions about state pupil transportation policy are (a) whether pupil transportation is mandated by the state, (b) what the eligibility requirements are for state aid, and (c) what formula is used for reimbursement. Funding for pupil transportation varies greatly among states, with differences that include student eligibility for transportation, funding formulas, and state aid as a percentage of transportation costs. The primary method of pupil transportation funding consists of state reimbursement for a portion of a school district's expenditures. The remaining costs must then be covered by local funding sources. Unlike some other areas of school finance, pupil transportation programs receive little funding from the federal government. The research also identifies safety, school siting, and walking to school as areas in which pupil transportation policies have important impacts.
Online Tool for Delivering Research Results
Authors: Monsere Christopher M. , Breakstone Aaron , Bertini Robert L. , Bish Douglas W.
Published: January 2008

Often, the challenge for the practitioner in disseminating research results is to package and present them in a manner that is accessible and easy to use while still providing depth, guidance, and necessary information. In most cases, final research reports are made available in printed form and online; however, for some applications, converting a report to a more interactive online report (tool) can produce results that are easier for the user to access. This is particularly true in this age of information overload and as practitioners find themselves needing to “do more with less.” This paper describes how research results from an update to the Oregon Department of Transportation database of crash reduction factors were incorporated into an online tool. The paper describes the methodology for cataloging a total of 94 crash countermeasures, reviewing the literature, and developing the interactive online tool. The tool allows users to search on the basis of key parameters for the countermeasures most appropriate to a particular highway safety improvement project and to access directly pertinent citations from the literature review database. A case study describes how a traffic safety professional might use this online tool in practice.
Effect of the Built Environment on Motorized and Nonmotorized Trip Making
Authors: Guo Jessica Y. , Bhat Chandra R. , Copperman Rachel B.
Published: January 2008

It has become well recognized that nonmotorized transportation is beneficial to a community's health as well as its transportation system performance. In view of the limited public resources available for improving public health and transportation, the present study aims to ( a) assess the expected impact of built environment improvements on the substitutive, complementary, or synergistic use of motorized and nonmotorized modes and ( b) examine how the effects of built environment improvements differ for different population groups and for different travel purposes. The bivariate ordered probit models estimated in this study suggest that few built environment factors lead to the substitution of motorized mode use by nonmotorized mode use. Instead, factors such as increased bikeway density and street network connectivity have the potential to promote more nonmotorized travel to supplement individuals’ existing motorized trips. Meanwhile, the heterogeneity found in individuals’ responsiveness to built environment factors indicates that built environment improvements need to be sensitive to local residents’ characteristics.
Do Transportation and Communications Tend to be Substitutes, Complements, or Neither?
Authors: Choo Sangho , Lee Taihyeong , Mokhtarian Patricia L.
Published: January 2008

With aggregate data from the U.S. Consumer Expenditure Survey for 19 years, 1984 through 2002, this study analyzes relationships between expenditures on transportation and communications. Several classification schemes for expenditure categories were used, from the most aggregate [two categories (transportation and communications)] to the most disaggregate [nine transportation categories (new vehicle purchases, used vehicle purchases, vehicle finance charges, gasoline and motor oil, vehicle maintenance and repairs, vehicle insurance, public transportation, out-of-town lodging, and other entertainment including bikes and recreational vehicles) and five communications categories (telephone service; miscellaneous household equipment including phones and computers; television, radio, and sound equipment; postage and stationery; and reading)]. Aggregate demand system modeling (in particular, the linear approximate almost ideal demand system) was then used to determine the relationships between expenditures on transportation and those on communications, again for several different classifications. The model results indicate that transportation and communications categories have substitution and complementarity relationships, often not symmetric. However, a dominant effect of complementarity can be found in the influence of communications on transportation.
Augmentation with olanzapine in TCA‐refractory depression with melancholic features: a consecutive case series
Authors: Takahashi Hitoshi , Kamata Mitsuhiro , Yoshida Keizo , Higuchi Hisashi , Ishigooka Jun
Published: January 2008

Using an 8‐week, open label study design, we report the effect of augmentation strategy with olanzapine in hospitalized depressive patients with melancholic features who had insufficient response to a tricyclic antidepressant (TCA), amitriptyline. Subjects were hospitalized patients meeting the criteria of DSM‐IV major depressive disorder with melancholic features who had been suffering from residual symptoms after treatment of amitriptyline. After study entry, olanzapine was added to amitriptyline and the dose was adjusted according to patients' clinical condition. Data were analyzed using an intent‐to‐treat methodology, with last observation carried forward. Paired t‐test was adopted to assess the data from baseline to endpoint. Of 26 patients who enrolled in this study, 23 patients completed the trial and 3 patients dropped out. The mean dose of olanzapine was 6.5 (SD = 2.4) mg/day. The mean score of Montgomery–Asberg Depression Rating Scale (MADRS) was significantly decreased from 33.6 (SD = 3.5) to 20.8 (SD = 9.1) during this study (37.9% from baseline) (p < 0.001). Ten patients (38.5%) were considered as responders (50% or greater reduction in MADRS scores from baseline). These results suggest that augmentation with olanzapine in TCAs‐resistant melancholia may be effective and well tolerated. We cannot draw any conclusion with certainty from the open‐label, uncontrolled clinical trial. Double blind, controlled trial is needed to confirm this preliminary finding. Copyright © 2008 John Wiley & Sons, Ltd.
Contracts for concurrency
Authors: Nienaltowski Piotr , Meyer Bertrand , Ostroff Jonathan S.
Published: January 2008

The SCOOP model extends the Eiffel programming language to provide support for concurrent programming. The model is based on the principles of Design by Contract. The semantics of contracts used in the original proposal (SCOOP_97) is not suitable for concurrent programming because it restricts parallelism and complicates reasoning about program correctness. This article outlines a new contract semantics which applies equally well in concurrent and sequential contexts and permits a flexible use of contracts for specifying the mutual rights and obligations of clients and suppliers while preserving the potential for parallelism. We argue that it is indeed a generalisation of the traditional correctness semantics. We also propose a proof technique for concurrent programs which supports proofs—similar to those for traditional non-concurrent programs—of partial correctness and loop termination in the presence of asynchrony.
High-Resolution TEM and the Application of Direct and Indirect Aberration Correction
Authors: Hetherington Crispin J.D. , Chang Lan-Yun Shery , Haigh Sarah , Nellist Peter D. , Gontard Lionel Cervera , Dunin-Borkowski Rafal E. , Kirkland Angus I.
Published: January 2008

Aberration correction leads to a substantial improvement in the directly interpretable resolution of transmission electron microscopes. Correction of the aberrations has been achieved electron-optically through a hexapole-based corrector and also indirectly by computational analysis of a focal or tilt series of images. These direct and indirect methods are complementary, and a combination of the two offers further advantages. Materials characterization has benefitted from the reduced delocalization and higher resolution in the corrected images. It is now possible, for example, to locate atomic columns at surfaces to higher accuracy and reliability. This article describes the JEM-2200FS in Oxford, which is equipped with correctors for both the image-forming and probe-forming lenses. Examples of the use of this instrument in the characterization of nanocrystalline catalysts are given together with initial results combining direct and indirect methods. The double corrector configuration enables direct imaging of the corrected probe, and a potential confocal imaging mode is described. Finally, modifications to a second generation instrument are outlined.
A vacuum ultraviolet laser photoionization and pulsed field ionization study of nascent S(P2,1,3) and S(D21) formed in the 193.3nm photodissociation of CS2
Authors: Zhou Jingang , Jones Brant , Yang Xueliang , Jackson W. M. , Ng C. Y.
Published: January 2008

The photoionization efficiency (PIE) and pulsed field ionization–photoion (PFI-PI) spectra for sulfur atoms S(P2,1,03) and S(D21) resulting from the 193.3nm photodissociation of CS2 have been measured using tunable vacuum ultraviolet (vuv) laser radiation in the frequency range of 82750–83570cm−1. The PIE spectrum of S(P2,1,03) near their ionization threshold exhibits steplike structures. On the basis of the velocity-mapped ion-imaging measurements, four strong autoionizing peaks observed in the PIE measurement in this frequency range have been identified to originate from vuv excitation of S(D21). The PFI-PI measurement reveals over 120 previously unidentified new Rydberg lines. They have been assigned as Rydberg states [3p3(S∘4)ndD∘3 (n=17–64)] converging to the ground ionic state S+(S∘4) formed by vuv excitations of S(P2,1,03). The converging limits of these Rydberg series have provided more accurate values, 82985.43±0.05, 83162.94±0.05, and 83559.04±0.05cm−1 for the respective ionization energies of S(P03), S(P13), and S(P23) to form S+(S∘4). The relative intensities of the PFI-PI bands for S(P03), S(P13), and S(P23) have been used to determine the branching ratios for these fine structure states, S(P03):S(P13):S(P23)=1.00:1.54:3.55, produced by photodissociation of CS2 at 193.3nm.
Method for nonlinear characterization of radio frequency coils made of high temperature superconducting material in view of magnetic resonance imaging applications
Authors: Girard Olivier , Ginefri Jean-Christophe , Poirier-Quinot Marie , Darrasse Luc
Published: January 2008

A contactless method based on reflectometry to accurately characterize an inductive radio frequency (rf) resonator even in the occurrence of a strong electrical nonlinearity is presented. Nonlinear extraction of the unloaded quality factor and resonance frequency is possible by combining an initial low-level swept-frequency calibration with high-level single-frequency measurements. The extraction protocol relies on a simple intrinsic R, L, C model and does not involve a fitting procedure according to a particular nonlinearity model. It includes a correction for strong coupling conditions between the probe and the rf coil, which allows extending the analysis over a wide range of transmitted power. Electrical modeling based on the extracted intrinsic data allows predicting the coil behavior when loaded by any kind of matching network. The method will have implications in different domains such as Magnetic Resonance (MR) applications with superconducting probe heads or analysis of rf properties in nonlinear materials. The method is demonstrated here by characterizing a high temperature superconducting (HTS) coil dedicated to MR imaging at 64MHz. The coil consists in a multiturn spiral design that is self-resonant close to the MR frequency of interest. The Q factor and the resonance frequency are determined as a function of the actual power dissipated in the HTS coil accounting for losses occurring in the measurement system. Further characteristics of the HTS coil are considered in the present paper. The relation between the transmitted power and the magnetic field generated by the coil, which is the most relevant characteristics for MR applications, is directly accessible. The equivalent impedance of the coil under test is also expressed as a function of the total current flowing in the windings. The method could be extended to assess the fundamental properties of the nonlinear material (e.g., the London penetration depth or the critical current density) by including any pertinent model.
TRIPLET ESR IN l‐TYROSINE
Authors: Maling J. E. , Rosenheck K. , Weissbluth M.
Published: January 2008

Abstract— Triplet state electron spin resonances have been observed from L‐tyrosine in low temperature glasses at 77° K on irradiation by u.v. light in the band between 220 and 300 millimicrons. Two different resonances have been observed. and ESR spectra and optical absorption spectra as a function of degree of ionization show that the resonances are due to the ionized and un‐ionized forms of tyrosine respectively. Solvent composition and temperature affect the ratio of the concentrations of the two forms but not their resonant fields. The resonances have half lives of from two to three seconds at 77° K.
CHEMILUMINESCENCE OF TETRAKIS‐(DIMETHYLAMINO)‐ETHYLENE
Authors: Paris J. P.
Published: January 2008

Abstract— The dependence of the chemiluminescence intensity of tetrakis‐(dimethylamino)‐ethylene (TDE) on the concentration of TDE and methanol activator has been shown to be to the second power for each compound. In addition to being activated by methanol, a quenching rate constant of 9.3 times 108/M/sec for methanol on the excited state of TDE was shown to cause a decrease of chemiluminescence intensity at high concentrations. Chemical reactions of TDE di‐cation in basic solutions indicated that a disproportionation occurs which produces a 50 per cent yield of TDE. On the basis of the kinetics and chemistry of TDE, a mechanism of chemiluminescence is proposed in which the excited state of TDE is produced by a bisdimethylaminocarbene dimerization.
THE AUTOXIDATION OF TETRAKIS‐(DIMETHYLAMINO)‐ETHYLENE
Authors: Urry W. H. , Sheeto J.
Published: January 2008

Abstract— The reaction of tetrakis‐(dimethylamino)‐ethylene (I) with oxygen in non‐hydroxylic solvents gives tetramethylurea (II), tetramethyloxamide (III), tetramethyl‐hydrazine (IV), and bis‐(dimethylamino)‐methane (V) in yields that are virtually independent of solvent and temperature, or whether chemiluminescence occurs. Autoxidation over water solutions, however, first gives octamethyloxamidinium peroxide (VI) which then hydrolyzes to give III and dimethylamine, and undergoes an alternative demethylation reaction to give tetramethyl 2‐(dimethylamino)‐2‐hydroxy‐2‐(methylamino)‐acetamidinium (VIII) and formate (IX) salts. Both courses of autoxidation are observed in solutions containing lithium chloride, in methanol or in water‐dioxane mixtures. A common intermediate is suggested.
ON THE POSSIBILITY OF GENERATION AND TRANSFER OF ELECTRONIC ENERGY IN BIOCHEMICAL SYSTEMS
Authors: Cilento G.
Published: January 2008

Abstract— Generation of electronically excited species is a distinct possibility in biological systems; the most likely ones at present appear to be flavins, metalloporphyrins, oxygen and certain conjugated carbonyl compounds. Thyroxine should be very active in certain cases of electronic energy transfer.
Monte Carlo investigations of megavoltage cone‐beam CT using thick, segmented scintillating detectors for soft tissue visualization
Authors: Wang Yi , Antonuk Larry E. , El‐Mohri Youcef , Zhao Qihua , Sawant Amit , Du Hong
Published: January 2008

Megavoltage cone‐beam computed tomography (MV CBCT) is a highly promising technique for providing volumetric patient position information in the radiation treatment room. Such information has the potential to greatly assist in registering the patient to the planned treatment position, helping to ensure accurate delivery of the high energy therapy beam to the tumor volume while sparing the surrounding normal tissues. Presently, CBCT systems using conventional MV active matrix flat‐panel imagers (AMFPIs), which are commonly used in portal imaging, require a relatively large amount of dose to create images that are clinically useful. This is due to the fact that the phosphor screen detector employed in conventional MV AMFPIs utilizes only of the incident radiation (for a 6 MV x‐ray spectrum). Fortunately, thick segmented scintillating detectors can overcome this limitation, and the first prototype imager has demonstrated highly promising performance for projection imaging at low doses. It is therefore of definite interest to examine the potential performance of such thick, segmented scintillating detectors for MV CBCT. In this study, Monte Carlo simulations of radiation energy deposition were used to examine reconstructed images of cylindrical CT contrast phantoms, embedded with tissue‐equivalent objects. The phantoms were scanned at 6 MV using segmented detectors having various design parameters (i.e., detector thickness as well as scintillator and septal wall materials). Due to constraints imposed by the nature of this study, the size of the phantoms was limited to . For such phantoms, the simulation results suggest that a 40 mm thick, segmented CsI detector with low density septal walls can delineate electron density differences of and at doses of 1.54 and 3.08 cGy, respectively. In addition, it was found that segmented detectors with greater thickness, higher density scintillator material, or lower density septal walls exhibit higher contrast‐to‐noise performance. Finally, the performance of various segmented detectors obtained at a relatively low dose (1.54 cGy) was compared with that of a phosphor screen similar to that employed in conventional MV AMFPIs. This comparison indicates that for a phosphor screen to achieve the same contrast‐to‐noise performance as the segmented detectors to 59 times more dose is required, depending on the configuration of the segmented detectors.
New, and Some Not-so-New, Vaccines for Adolescents and Diseases They Prevent
Authors: Fishbein Daniel B. , Broder Karen R. , Markowitz Lauri , Messonnier Nancy
Published: January 2008

Adolescents in the United States now have the opportunity to receive new vaccines that prevent invasive meningococcal infections, pertussis (whooping cough), and cervical cancer. Except for their potential to cause serious illness, these infections could not be more different. Their incidence ranges from extremely low to quite high. Early clinical manifestations of infection range from none to life-threatening illness. Two of the vaccines are similar to those already in use, whereas 1 is completely new. In conjunction with the 4 vaccines previously recommended for adolescents (the tetanus and diphtheria booster, hepatitis B, measles-mumps-rubella, and varicella), the 3 new vaccines (meningococcal, human papillomavirus, and the tetanus-diphtheria-pertussis booster [which replaced the tetanus-diphtheria booster]) bring the number recommended for adolescents to 6. In this article, we describe key characteristics of the 3 new vaccines and infections they were designed to prevent. We also briefly discuss other vaccines recommended for all adolescents who have not already received them and new vaccines that are still under development.