bluuebunny/crossref_metadata_2025 huggingface dataset:
Factors Associated with Parental Acceptance of Dental Sealants
Authors: Selwitz Robert H. , Colley Brenda J. , Rozier R. Gary
Published: April 2007

Whereas a number of surveys have documented oral disease preventive behaviors and associated factors, little is known about public knowledge and beliefs about dental sealants. In this study, factors associated with the presence of sealants were studied in first and second graders residing in Columbia, SC. From a sample of 1,119 children, 88 were found clinically to have sealants; 508 did not have, but needed them. Parents of the sealant children (n=87) and of a random sample of the no‐sealant children (n=289) were interviewed by telephone to obtain information regarding (1) factors related to parents' inclination to obtain sealants for their children, (2) ability of the family to obtain oral disease preventive services, and (3) the influence of others in the family's decision‐making efforts. Analysis of 16 factors thought to be related to sealant presence revealed that parents were more likely to obtain dental sealants for their children if dentists or their staffs recommended them, if the parents were knowledgeable about dental sealants, if the parents were more highly educated, and if the parents had dental insurance coverage. Parents were less likely to obtain dental sealants for their children if they heard about them from mass media. The latter finding is unexpected and may have been influenced by conflicting or negative opinion expressed by some dental practitioners through mass media or other channels of communication. The results of this study suggest that efforts to enhance the utilization of dental sealants should include strategies to (1) encourage dentists to promote them with their patients and the public, (2) educate potential consumers about the benefits of dental sealants, and (3) promote greater insurance coverage for oral health care, including sealants.
A Profile of Black and Hispanic Subgroups' Access to Dental Care: Findings from the National Health Interview Survey
Authors: Aday Lu Ann , Forthofer Ronald N.
Published: April 2007

This study examined which black and Hispanic minority subgroups were least likely to obtain dental care and why, based on logistic regression analyses of the 1986 National Health Interview Survey. Blacks and Hispanics were less apt to have private dental insurance coverage, to be knowledgeable about the purpose of fluoride, to have been to a dentist in the past year, and, when they did go, were more apt to have gone in response to symptoms rather than for preventive reasons, compared to whites. Logistic regression analyses foradults 18 years of age and older and for children and adolescents 2 to 17 years of age showed that the following individuals had the lowest probability of having been to a dentist in the past year: males, members of larger families, adults who were unemployed or in blue‐collar jobs, those who lived in the South or nonmetropolitan areas, people who perceived their health to be fair or poor, and those with no private dental insurance. Mexican‐Americans were least likely to have been to a dentist regardless of their income or education. In general, the findings confirmed the importance of dental insurance, as well as suggesting a need for more school‐based dental programs and public health clinic‐based dental health education and outreach efforts for targeting minority children and adults.
Comparison of Number and Mean Charge Between Dental Sealants and One‐surface Restorations
Authors: Kuthy Raymond A. , Clive Jonathan M.
Published: April 2007

An important concern of the insurer is how sealants, if a covered benefit, will affect the premium. Important factors that may have an influence on determining the premium include the decline in caries rate coupled with the long‐term cost to an insurer for sealants vs one‐surface restorations. In this study of more than 1 million dentally insured children (aged 5–15), the mean charge ($) for sealants and one‐surface restorations was determined, along with the frequency of these procedures, by patient age. For this group of children, 43 percent of one‐surface restorations occurred between ages 12–14, whereas 32 percent of the patients received sealants at either 7 or 8 years of age. States varied substantially in the number of sealants as a percentage of the number of restorations. Only three states had more sealants placed than one‐surface, posterior restorations. Three states had an annual increase in the ratio of sealant to restoration charge, while 13 states had an annual decrease. With the exclusion of a few states with a minimum number of sealants and restorations in 1988, the highest ratio of the cost of sealants to the cost of one‐surface restorations was observed in New York (.60) and New Jersey (.56) and the lowest observed in Kansas and Utah (.37). The ratios for both New York and New Jersey were lower in 1988 than in the previous two years. The ratio of the number of one‐surface, posterior restorations to the population served was approximately the same for each NIDR region in the contiguous United States. Alaska and Hawaii had a higher proportion
A Review of Methods to Forecast Restorative Treatment Needs
Authors: McGuire Sheila M.
Published: April 2007

Decision makers in the areas of health policy, resource allocation, and manpower requirements rely implicitly on estimations of treatment needs on which to base their forecasts. The less specific the treatment‐need estimate, the less precise the forecast. In previous decades, high caries rates were so prevalent that the dental profession could risk having inexact projections because overwhelming need and demand existed. However, rampant decay is no longer a common occurrence. Decay levels are declining in our nation's children and adults have fewer missing teeth. Therefore, restorative treatment needs and patterns in adult populations are transforming at a time when health care costs are spiraling and budget analysts at all levels of government are questioning the priority of continued support of dental care, dental education, and dental research at current levels. The purpose of this review is to present the existing methods of forecasting restorative treatment needs and to postulate the development of a new method based on the collective experiences of practicing dentists nationwide, an empirical method, to convert surface‐specific oral health status data to restorative treatment need information. Need estimations based on empirical data would more accurately reflect the actual distribution of services that practicing dentists provide.
The How and Why of the ADA's Evaluation Program for Dental Therapeutic Products
Authors: Whall Clifford W.
Published: April 2007

Since 1930, the Council on Dental Therapeutics of the American Dental Association has been evaluating dental drug products for safety and efficacy through its Acceptance Program. To date, numerous products have been evaluated, and many hundreds have received the council's seal of acceptance. Acceptance criteria are rigorous, and the council relies on expert consultants to evaluate the supporting data. There are no manufacturer fees involved with the Acceptance Program. When a product has been awarded the seal, it means that adequate data have been submitted, and that the product is safe and does what it says it will do. This paper describes, in detail, how the Acceptance Program works.
Professionally Applied and Prescribed Fluoride Products
Authors: Grodberg Marcus G.
Published: April 2007

The US regulatory process relative to the marketing of sodium fluoride dietary supplements and professionally applied topical fluorides is examined with regard to interactions of ADA, NIH, academia, and the FDA, as well as resultant effects on industry, practitioners, and patients. Restrictions on noncaries use of fluoride limit commercial claims, but not professional practice. Prenatal fluoride supplements are still unapproved. Finally, the effects of generic competition and the regulatory process on costs, sales, quality of professional fluoride products and on new product research are discussed.
FDA and ADA Evaluation of Dental Implants
Authors: Schumann David
Published: April 2007

The FDA classification of endosseous dental implants (EDI) is reviewed. Factors impacting the long‐term efficacy of dental implants and the guidelines for development of EDI are enumerated. The role of the ADA in evaluation of EDIs is also discussed. Recommendations for development of performance criteria and reporting format are made.
A Practitioner's View
Authors: Halpert Lawrence F.
Published: April 2007

A private practitioner expresses his opinions concerning the FDA and ADA evaluatory processes.
What Do Consumers Want?
Authors: Apple William
Published: April 2007

A consumers' advocate discusses the needs of the consumer in evaluating dental products. Although commending the roles of the FDA and ADA in evaluating products, numerous questions are raised and recommendations made concerning advertising claims.
A Researcher's View
Authors: Horowitz Herschel S.
Published: April 2007

The Food and Drug Administration (FDA), by ensuring that the health care products used by Americans are both safe and effective, provides an essential regulatory function. With respect to the regulation of dental drug products, this researcher perceives that the FDA has not changed or modified its position on a number of issues to reflect new scientific information. Reasons for this inflexibility include the size and ponderousness of the agency, inadequate staff with dental expertise, and a failure to keep current with new dental research findings. The FDA must solve these problems if it wishes to regulate intelligently. The acceptance and certification programs of the American Dental Association ensure that products offered to the profession and the public that bear its seal of acceptance are safe and effective. The ADA's Council on Dental Therapeutics has a long history of staying current on issues in dental research and public health and regularly seeks consultation from eminently qualified experts. Overall, it has done an excellent job over the years in conducting an important voluntary regulatory program. Both the FDA and the ADA benefit and help protect the oral health of the public.
The Regulatory Process for Dental Devices: a Researcher's View
Authors: de Rijk Waldemar G.
Published: April 2007

Comments from the three previous speakers ranged from moderate satisfaction to strong dissatisfaction with the regulatory process. Three different types of research are identified that seem to predict the ease of compliance with the 510(k) process. No one expressed satisfaction with the PMA application. It seems that current evaluation procedures inhibit the developing and marketing of new devices, but foster only enhancements to existing de‐vices. The development of new evaluation methods is advocated to provide fast, inexpensive, but rigorous assessment of the clinical safety and treatment value of new devices.
Legal and Regulatory Developments of the 1990s in Oral Care Products: Learning from What Has Come Before
Authors: O'Reilly James T.
Published: April 2007

The development of oral care products has occurred faster than congressional enactments regulating these products. Terms such as “cosmetic, drug, and new drug” are defined. A history of scientific publications and common acceptance by experts is necessary for the FDA to categorize a product as “generally recognized as safe and effective” (GRASE). The FDA classification process of the numerous over‐the‐counter drugs into a few categories, each of which required a three‐part approval process, is not complete. Delays in the FDA's OTC review resulted in an “OTC moratorium”, which allows new products to enter the market at the owners risk. The relative risks and benefits of marketing an oral care product with or without an approved New Drug Application are discussed. Increased resources at the FDA are recommended to expedite fairness to manufacturers and to eliminate inappropriate oral care products from the market.
The best possible child
Authors: Parker Michael
Published: April 2007

Julian Savulescu argues for two principles of reproductive ethics: reproductive autonomy and procreative beneficence, where the principle of procreative beneficence is conceptualised in terms of a duty to have the child, of the possible children that could be had, who will have the best opportunity of the best life. Were it to be accepted, this principle would have significant implications for the ethics of reproductive choice and, in particular, for the use of prenatal testing and other reproductive technologies for the avoidance of disability, and for enhancement. In this paper, it is argued that this principle should be rejected, and it is concluded that while potential parents do have important obligations in relation to the foreseeable lives of their future children, these obligations are not best captured in terms of a duty to have the child with the best opportunity of the best life.
Variable extrafloral nectary expression and its consequences in quaking aspen
Authors: Doak Patricia , Wagner Diane , Watson Adam
Published: April 2007

Extrafloral nectaries (EFNs) are secretory glands most commonly linked to defensive mutualisms. Both a plant’s need for defense and the strength of defense provided by mutualists will vary with plant condition and local insect community. Thus, the benefit of EFNs may vary spatially and temporally. However, little attention has been paid to natural variation in the presence and abundance of EFNs within and among individuals of the same species. Quaking aspen, Populus tremuloides Michx., bear EFNs on a subset of their leaves. Here, we describe patterns of EFN expression on shoots within ramets, among ramets, and among putative clones in interior Alaska. We also examine the relationship between EFN presence and herbivory by both the very abundant aspen leaf miner, Phyllocnistis populiella Chambers, and less common chewing herbivores. The proportion of leaves bearing EFNs varied from 33% to 87% among distinct aspen stands. Within stands, short (1–2 m height) ramets had higher EFN frequency than their taller (>4 m) neighbors. Patterns of herbivory also differed between short and tall ramets. Compared with leaves without EFNs, those with EFNs suffered less mining damage on short ramets but slightly higher damage on tall ramets. Tall ramets suffered more chewing damage than short ramets, but this damage was unrelated to the presence of EFNs. Our results suggest that variable EFN expression may be explained by variation in the benefits of EFNs. Leaves with EFNs on short ramets benefit through reduction in leaf mining, but this benefit does not extend to tall ramets or other forms of herbivory.
Contrasting the abundance, nitrogen, and carbon of epiphytic macrolichen species between host trees and soil types in a sub-boreal forest
Authors: Campbell Jocelyn , Fredeen Arthur L.
Published: April 2007

Differences in lichen diversity and abundance and lichen N and C pools were examined across the two dominant host tree species ( Picea engelmannii Parry ex Engelm. × Picea glauca (Moench) Voss) and Abies lasiocarpa (Hook.) Nutt.)) and two soil types (fine- and coarse-textured soils) in an old-growth sub-boreal forest in central British Columbia, Canada. Forty-four epiphytic macrolichen species were identified across the study area. Hair lichen species, particularly nonsorediate Bryoria species, were more abundant in spruce on coarse-textured soils, while cyanolichens were most commonly observed in subalpine fir on fine-textured soils. Overall macrolichen biomass and C pools were greatest in subalpine fir trees on coarse-textured soils. The tripartite species Lobaria pulmonaria (L.) Hoffm. was the dominant macrolichen, particularly over fine-textured soils where its stand level biomass was greater than that of all other species combined. The N pools of L. pulmonaria in combination with the less abundant N-rich bipartite cyanolichens amounted to 7.5 ± 1.9 kg N·ha–1on fine-textured soils. These results indicate that epiphytic cyanolichens may make substantial contributions to ecosystem N despite their relatively insignificant contributions to overall forest biomass and C stocks.
A new concept for Dictyostelium sphaerocephalum based on morphology and phylogenetic analysis of nuclear ribosomal internal transcribed spacer region sequences
Authors: Romeralo Maria , Fiz-Palacios Omar , Lado Carlos , Cavender James C.
Published: April 2007

Three dictyostelid isolates were found in Spain and Argentina that are morphologically different from known species. These isolates have some features similar to Dictyostelium sphaerocephalum (Oudem.) Sacc., Marchal & É.J. Marchal, but differ in size and sorocarp branching pattern. We sequenced the nuclear ribosomal internal transcribed spacer region to explore phylogenetic relationships among this group of species, including the three new isolates and their closest relatives. In all phylogenetic analyses performed, sequences of all three isolates group together with sequences from “typical” D. sphaerocephalum samples. This result supports previous observations of the morphological plasticity in dictyostelids, especially D. sphaerocephalum, leading us to broaden the classical concept of this species.
Decomposition of oak leaf litter is related to initial litter Mn concentrations
Authors: Davey Matthew P. , Berg Björn , Emmett Bridget A. , Rowland Phil
Published: April 2007

The factors determining the quantity of litter being incorporated into stable organic matter were examined as part of a broader study investigating carbon (C) sequestration in forest ecosystems. Litter was collected from 20 common oak (Quercus robur L.) stands in Wales (UK) and placed in litter-decomposition bags. These bags were installed in an oak stand for 3, 6, 12, 21, and 31 months to study the effect of litter quality on decomposition (mass loss) rates and the limit value for a broad-leaf species. Results indicate that the initial decomposition rate is highly correlated with the manganese content of the litter (P = 0.007, R2 = 0.34). In the final stages of decomposition, limit values ranged between 57% and 95% of initial litter mass. These estimated limit values were not significantly correlated with initial concentrations of other nutrients. However, Ca concentrations gave a significance level of P = 0.067. Estimated rates of C sequestration in soil ranged from 0.93 to 80.22 g C·m–2·year–1.
Density dependence and interspecific interactions between arbuscular mycorrhizal fungi mediated plant growth, glomalin production, and sporulation
Authors: Violi Helen A. , Treseder Kathleen K. , Menge John A. , Wright Sara F. , Lovatt Carol J.
Published: April 2007

Functional differences between the arbuscular mycorrhizal fungi Glomus intraradices Schenk and Smith and Scutellospora heterogama Nicolson and Gerdemann as they affect Persea americana Mill. growth, glomalin, and fungal sporulation were examined by varying the composition and relative density of the two fungi over a gradient of available phosphorus (P). The plant benefit provided by these mycorrhizal fungi together was not a simple sum of the benefits provided by each fungus in monoculture at its respective density. Glomus intraradices and S. heterogama interacted to reduce plant growth rates and uptake of P, zinc (Zn), and iron (Fe) relative to plants inoculated with G. intraradices alone. Thus, for plant growth and nutrition, no evidence for functional complementarity was detected. Instead, interspecific interactions between mycorrhizal fungi resulted in a negative feedback on plants. Under high available P, fungal functional differences were reduced, whereas the overall difference between mycorrhizal and nonmycorrhizal plants was greatest. Overall, S. heterogama produced more glomalin than did G. intraradices. In a mixture, sporulation of the inferior mutualist, S. heterogama, was lower than that of the superior mutualist, G. intraradices, but interspecific fungal interactions increased the sporulation of both fungi. Despite the negative impact of interspecific interactions on plants, supporting multiple arbuscular mycorrhizal fungi was of greater benefit than being nonmycorrhizal.
Stress in western Canada from regional moment tensor analysis
Authors: Ristau John , Rogers Garry C , Cassidy John F
Published: April 2007

More than 180 regional moment tensor (RMT) solutions for moderate-sized earthquakes (M ≥ 4) are used to examine the contemporary stress regime of western Canada and provide valuable information relating to earthquake hazard analysis. The overall regional stress pattern shows mainly NE–SW-oriented P axes for most of western Canada with local variations. In the northern cordillera, the maximum compressive stress direction (σ1) varies from east–west to north–south to NE–SW from south to north. The stress direction σ1 is consistent with the P axis direction for the largest earthquakes, except in the central and northern Mackenzie Mountains where there is a 16° difference. The Yakutat collision zone shows a steady change in σ1 from east–west in the east to north–south in the west. In the Canada – United States border region, RMT solutions suggest a north–south compressional regime may extend through southern British Columbia and northern Washington to the eastern Cordillera. In the Vancouver Island – Puget Sound region, RMT solutions do not show any obvious pattern in faulting style. However, the stress results are consistent with margin-parallel compression in the crust and downdip tension in the subducting slab. Along the Queen Charlotte fault σ1 is oriented ~45° to the strike of the northern section of the fault, which is dominated by strike-slip faulting, and ~60° to the strike of the southern section, which is dominated by high-angle thrust faults. The amount of thrust faulting infers a significant amount of convergence between the Pacific and North America plates in the southern Queen Charlotte Islands region.
Hikorocodium Endo is not an alga but an inozoid sponge
Authors: Senowbari-Daryan Baba , Rigby J Keith
Published: April 2007

The genus Hikorocodium, with the type species Hikorocodium elegantae from the Permian of Japan, was described originally as a codiacean alga by Endo. It is not a codiacean alga but an inozoid sponge of the family Preperonidellidae. Several fossils described later by Endo and other authors as H. elegantae should be assigned to different inozoid sponge taxa. Specimens of H. fertiliz, described by Endo from the Jurassic of Japan, are also sponge fragments. The taxonomic positions of H. transversum Endo and H. kuramotoi Nakamura, as sponges or algae, remain uncertain.
A reappraisal of the allochthonous nature of the Rosenberg slice and Stanbridge Group of southern Quebec and northwestern Vermont
Authors: Schoonmaker Adam , Kidd William SF
Published: April 2007

The Ordovician Stanbridge Group of Quebec has long been considered an allochthonous nappe. It is an internally coherent unit that consists of lower slaty limestone overlain by slate, which is correlated with the Highgate and Morses Line formations, respectively, in Vermont. In Quebec, the basal limestones have been inferred to be thrust over Cambrian dolomites (Gorge Formation in Vermont) of the Rosenberg slice, part of the parauthochthonous shelf, although this contact is not exposed there. In the Missisquoi River gorge of Vermont, a conformable sequence of upper Gorge–Highgate–Morses Line formations is exposed. The map distribution of rock units indicates that this conformable relationship probably extends up to at least the middle unit of the Stanbridge Group. Therefore, the relationships in Vermont require that the Stanbridge Group must be part of the parauthochthonous Taconic foreland rather than a far-traveled nappe. The Rosenberg slice in Quebec forms a large anticline (Highgate anticline) whose western limb is truncated by the Rosenberg thrust. In Vermont, the anticline is internally cut by the Highgate Falls Thrust, which is an out-of-sequence thrust that decreases in displacement northwards to the International Border.
Atypical diagenetic effects on strontium-isotope composition of Early Jurassic belemnites, Queen Charlotte Islands, British Columbia, Canada
Authors: Gröcke Darren R , Hesselbo Stephen P , Findlay Duncan J
Published: April 2007

In this study, strontium-, carbon- and oxygen-isotope data are reported from Early Jurassic belemnites from Yakoun River, Queen Charlotte Islands (QCI), British Columbia. Assuming that the established ammonite correlations between Canada and Europe are accurate, the seawater 87Sr/86Sr curve between Europe and QCI should be similar. However, the Rarenodia planulata and Phymatoceras crassicosta ammonite biozones from Yakoun River record 87Sr/86Sr values that are lower than expected. This shift is interpreted to be a result of diagenetic alteration by later hydrothermal fluid (87Sr-depleted). In general, the diagenetic samples have more negative δ13Cbel and δ18Obel values, and higher Mn concentrations, but show no difference in Fe concentration. A δ13Cbel curve from diagenetically screened samples exhibits only slightly depleted values with respect to a similar curve generated from Europe. A similar curve for δ18Obel shows a striking similarity with that generated from Europe. This study illustrates that diagenetic effects on Sr-isotope composition can lower values from the expected seawater 87Sr/86Sr curve, thus potentially producing erroneous correlations between ammonite biostratigraphic schemes. Traditional screening methods for diagenesis, such as cathodoluminescence and trace-element abundances, were inadequate for evaluating diagenesis in the Yakoun River sections. Other such studies must also consider alternative and (or) a combination of methods in evaluating geochemical data from belemnites.
The innovation process: adoption of information and communication technology for the construction industry
Authors: Rankin J H , Luther R
Published: April 2007

The paper discusses innovation and uses information and communication technology (ICT) as an example. A general framework that is broad in the perspectives it examines is presented for the analysis of innovations and technology adoption in the construction industry. The framework is described in relation to the life cycle of a technological innovation and consists of two primary perspectives: a macroview (top) and a microview (bottom). The analysis models either determine characteristics or measure values. Each analysis model is discussed in some detail and applied to an ICT example. The relevance of the framework is summarized by a discussion of how these interrelated analyses are applicable to the decision-making process within a particular firm and of the mechanisms required by the industry to improve the innovation process. A framework is required that is comprehensive in its ability to look at information and knowledge flows in support of innovation within the industry and at the interrelationships between micro and macro influences. Gaps in current approaches include a lack of quantitative analysis tools, the ability to reflect the dynamic aspect of innovation, and industry knowledge of practical decision-making tools. Key words: innovation, technology adoption, information and communication technology, construction engineering.
Experimental study on the behavior of carbon fiber reinforced polymer sheets bonded to concrete
Authors: Kamel Ayman S , Elwi Alaa E , Cheng Roger J.J
Published: April 2007

This paper presents a study on the interfacial behavior of carbon fiber reinforced polymer (CFRP) sheets when applied to concrete members as external reinforcement. Two bond test methods that are detailed in the paper were used in separate test series to study the bond behavior and failure mechanism of CFRP sheets bonded to concrete. A modified push-apart test method was proposed and tested. It was concluded that there existed an effective length beyond which there will be no increase in the ultimate capacity of the joint. An experimental test method to determine the effective bond length was also proposed and tested. The strains at the edge of the CFRP sheets are consistently higher than those at the center. The anchorage requirements for the CFRP sheets were also investigated in this study. Anchor sheets placed at 90° to the primary test sheets and bonded underneath the tested sheet showed better or equivalent overall bond behavior compared with those bonded on top of the tested sheet. The distance at which the anchor sheet is placed from the crack does not appear to change the bond behavior.Key words: bond, concrete, debonding, failure mechanism, carbon fiber reinforced polymer (CFRP) sheets, anchor sheets.
A hybrid approach for developing special purpose simulation tools
Authors: Mohamed Y , AbouRizk S M
Published: April 2007

The use of simulation techniques is an effective approach for modeling construction operations. Unfortunately, the high level of technical knowledge and development time required for building functional simulation models renders simulation modeling an impractical technology for many in the construction industry. Research in construction simulation tackles this conflict by providing modeling approaches that reduce the knowledge and time usually required for building simulation models of construction operations. Special purpose simulation (SPS) allows construction engineers with only minimal simulation knowledge to build practical simulation models. This paper presents a hybrid approach (HSPS) for effective and time-saving development of SPS tools. The approach utilizes visual, general purpose modeling elements to customize the simulation behaviors of new SPS elements, minimizing the programming effort required for developing these elements. This paper describes the theoretical background to the HSPS approach, its implementation, and a sample application successfully created subsequently. It also shows the results of an experiment quantifying the savings in development time achieved using this approach.Key words: automation, simulation models, computerized simulation, tunnel construction, construction management.
Effect of aggregate type, gradation, and compaction level on thermal properties of hot-mix asphalts
Authors: Mrawira Donath M , Luca Joseph
Published: April 2007

This paper investigates the effects of mix design factors on the thermal properties of Superpave asphalt concrete. The thermal properties were measured using a guarded testing device (k-alpha device) developed recently at the University of New Brunswick. Two aggregate types, three gradations (determined by the material retained on a 4.75 mm sieve), and four compaction levels (at 35, 70, 100, and 160 gyrations) were investigated. The aggregate was 12.5 mm maximum nominal size with PG58-34 asphalt binder used for all mixes. The findings show that the thermal conductivity of the asphalt concrete ranged from 1.7 to 2.1 W/m·K. The specific heat capacity varied with the aggregate source and ranged from 940 to 2000 J/kg·K. The thermal diffusivity was found to vary with aggregate source. The aggregate type was found to have the most significant effect on the thermal properties. The compaction level had an effect but not a statistically significant one. The range of thermal properties determined in this paper is comparable to that found in the literature.Key words: thermal properties, asphalt concrete, pavement temperature prediction, heat conduction, transient state, thermal conductivity, thermal diffusivity, heat capacity.
Integration of field and laboratory testing to determine the causes of a premature pavement failure
Authors: Chen Dar Hao , Chen Tung-Tsan , Scullion Tom , Bilyeu John
Published: April 2007

The main objective of the forensic study was to identify the cause(s) of the pavement failure on a temporary detour of an interstate highway in Austin, Texas. Ground penetrating radar (GPR), falling weight deflectometer (FWD), coring, trenching, and comprehensive laboratory tests were performed. It was found that the main cause of the premature failure was attributed to material and construction practices. The base material used on this project did not meet the Triaxial class 1 requirement; it tested as a class 2.3 material. The base material was found to be highly moisture susceptible; it did not meet the Texas Department of Transportation's (TxDOT's) compressive strength requirements when subjected to capillary soaking. In addition, the repetitive triaxial test results revealed that the stiffness and load-carrying capability and resistance to permanent deformation became inadequate when the base material was exposed to moisture. It is believed that moisture entered this pavement primarily through poorly compacted AC layers and longitudinal joints. Cores taken in March 2004 from the original type B and C layers confirmed that the majority of cores have air voids exceeding 9%. The lower type B layer was also badly segregated and debonded from the upper type C layer at some locations. GPR results also indicated that the joints in the pavement were excessively porous. Further tests on the recovered binder for the type B layer indicated that the binder was prematurely aged, most probably from overheating during production.Key words: pavement failure, forensic, ground penetrating radar (GPR), falling weight deflectometer (FWD), laboratory testing.
Nonlinear cash flow optimization model
Authors: Son Jaeho , Mack Martin , Mattila Kris G
Published: April 2007

During construction, progress payments (cash inflow) are made periodically to contractors based on work performed. Contractors are required to pay the direct costs (cash outflow) during construction. The net difference between the cash inflow and outflow is the overdraft, which contractors must finance either from the bank or from their own resources. To increase profit margin, contractors consider methods to improve their cash flow, which will increase profit. These methods include front end loading (Stark 1974) and shifting of activities (Easa 1992). These two linear procedures could be done sequentially. However, this sequential linear formulation may not produce an optimized solution because of the nonlinear characteristics of the model. This note examines the combination of the two linear procedures into a single nonlinear formulation such that better profit margin can be achieved.Key words: cost analysis, optimization, linear programming, nonlinear programming.
Predicting construction productivity using situation-based simulation models
Authors: Choy Eldon , Ruwanpura Janaka Y
Published: April 2007

Construction site operations are very complex, and they involve complicated relationships among numerous tasks, factors, obstacles, risks, and uncertainties, or triggering situations that affect productivity. To improve the performance of construction operations, one needs to understand the impact these triggering situations have on productivity. The paper discusses a recently developed technique, called situation-based simulation modeling, that is used to model the triggering situations in construction to predict productivity. This tool can model the cause-and-effect relationships among various triggering situations, which previous construction models have ignored. Construction operations that were directly observed and recorded for more than 3500 person-hours served as the data source for the development of the model. The simulation results are not only able to accurately predict productivity relative to the actual productivity observed at the site, but also provide the basis for recommendations to mitigate problematic situations to improve productivity.Key words: construction, productivity, modeling, simulation, situation-modeling.
Characteristics of volcanic ash and natural lime based stabilized clayey soils
Authors: Hossain K M.A , Lachemi M , Easa S
Published: April 2007

Clayey soils are stabilized with various percentages of volcanic ash (VA), finely ground natural lime (NL), Portland cement, and their combinations. The influence of stabilizers and their combinations is evaluated through standard Proctor compaction, unconfined compressive strength, splitting tensile strength, modulus of elasticity, and California bearing ratio (CBR) tests. The durability of stabilized soil mixtures is judged based on drying shrinkage and the influence of water immersion on strength. Correlations between compressive strength, modulus of elasticity, and CBR are also established. Stabilized soil mixtures can be used in various constructions, including road pavements and low-cost housing.Key words: soil stabilization, volcanic ash, natural lime, mechanical properties, durability.
Digital image correlation analysis of crack behavior in a reinforced concrete beam during a load test
Authors: Küntz Michel , Jolin Marc , Bastien Josée , Perez Fabien , Hild François
Published: April 2007

A displacement-measuring technique using digital image cross-correlation was applied to study the in situ behavior of a shear crack in a reinforced concrete beam during a bridge static load test. A numerical approach allowed measurement of the displacement field at the location of the crack on a 110 mm × 130 mm surface with a resolution of the order of 10 µm. Results of the analysis indicate that crack loading varies significantly with load position and sequence of applications to the structure. These results further indicate that damage cannot be attributed to the repetition of a single load cycle, as is often the case. The findings should improve the understanding of the fatigue behavior of reinforced concrete structures under operating conditions.Key words: displacement field, crack opening displacement, digital image correlation, static loading test, fatigue, durability, reinforced concrete, monitoring.
A chronographic method for construction project planning
Authors: Francis Adel , Miresco Edmond
Published: April 2007

Generally, the utilization of traditional scheduling methods represents a complex and cumbersome task for most project managers. Using the existing tools often requires long preparation, and the quality of the graphical output of the planning job is suboptimal. The lack of accuracy in the representation of the execution process diminishes the reliability of the schedule. This article proposes a new planning approach that that can simulate the real conditions of projects. The concepts of graphical scheduling models are analyzed to position the new chronographic approach among other graphical scheduling techniques. The theoretical concept, the mathematical model, and the graphical approach for this new planning method are summarized. Among other features, the proposed chronographic method allows the internal division of activities and relationships as a function of quantities, and new realistic types of floats are proposed. The output may be represented on numerous levels of hierarchical detail or as a combination of these levels. The result is modeling that produces improved visual clarity, increased flexibility, and more adaptability to changes for construction projects.Key words: planning, scheduling, modeling, time-scaled, chronographic method, Gantt, critical path method, precedence.
Assessment of engineering properties of Bangkok clay
Authors: Horpibulsuk Suksun , Shibuya Satoru , Fuenkajorn Kittitep , Katkan Wanchai
Published: April 2007

Due to the effect of structure, Bangkok clay is stable in a metastable state. Its void ratio, e, is the summation of the void ratio sustained by the intrinsic fabric, eR, and the additional void ratio due to the structure, es. The intrinsic state line (eRversus log σ′v, where σ′vis the effective vertical stress) is developed in terms of the void ratio at the liquid limit, eL. At the post-yield state, esis inversely proportional to σ′v. The residual additional void ratio, esr, which cannot be eliminated by the increase in effective vertical stress, is constant at about 0.20 for soft Bangkok clay and 0.12 for medium stiff Bangkok clay. From these findings and the ideal condition of zero compression at the pre-yield state, the field yield stress and field compression curve can be assessed. The undrained shear strength is directly related to the field yield stress, since both reflect the structure. The soil structure does not significantly influence the permeability. The permeability of the clay in structured and destructured states is identical under the same void ratio and can be determined from the generalized state parameter, e/eL. These observations result in a simple and practical method for assessment of the engineering properties of natural Bangkok clay.Key words: Bangkok clay, destructured state, compression, intrinsic state line, permeability, structured state, vane shear strength.
Analysis of piles in a residual soil—The ISC'2 prediction
Authors: Fellenius Bengt H , Santos Jaime A , Fonseca António Viana da
Published: April 2007

The 2nd International Conference on Site Characterization (ISC'2), held in 2004, included a seminar for prediction of pile capacity involving three 6 m embedment length test piles, one 350 mm square driven concrete pile, and two 600 mm diameter, strain-gage instrumented, bored piles. Invited predictors were provided with results of in situ, laboratory tests and dynamic tests. Test layout, soil information, and pile data are presented with calculations of pile capacity and load distribution, submitted predictions, and results of the static loading tests. The CPT-calculated capacities show considerable scatter—total values ranged from 500 to 1400 kN for the driven pile and from 1000 to 1900 kN for the bored piles. The static loading test on the driven pile showed an offset limit load of 1200 kN and a plunging capacity of 1500 kN. Despite pile movements of 100 mm for 1200 kN of applied load, neither of the bored piles showed signs of having reached an ultimate resistance value. Effective stress analysis of strain measurements for the bored piles showed the data to correlate to a β coefficient of 1.0 and a toe coefficient of 16. Most submitted predictions underestimated the capacity of the driven pile and overestimated the capacities of the bored piles.Key words: pile capacity, effective stress analysis, shaft and toe resistances, β coefficient, CPTU, dynamic testing.
Behaviour of sands under generalized drainage boundary conditions
Authors: Sivathayalan Siva , Logeswaran Paramaguru
Published: April 2007

An experimental study of the behaviour of sands under generalized drainage boundary conditions is presented. The influence of partially drained conditions, which generally is a reflection of the loading rate and the permeability of the soil, has been studied by limiting the volumetric deformation between drained and undrained states. The effect of potential pore-pressure variations in situ has been assessed by simulating various levels of volumetric deformation during shear. Conventional drained and undrained tests were also carried out on the same sands to enable a direct evaluation of the effect of drainage. A triaxial device with the ability to control strain-paths was used to carry out the tests, and all tests were performed under compression loading with no change in total lateral stress. A systematic change in the stress–strain response was noted as the drainage conditions gradually change from drained to undrained. The maximum excess pore pressure generated owing to inhibition of drainage is almost linearly related to the amount of drainage blocked. These results support the contention that the undrained state may not represent the most damaging scenario under field loading conditions. Much smaller minimum shear strength values compared with the undrained strength were measured when pore-pressure boundary conditions caused expansive volume changes. The domain of strain-softening response, and hence liquefaction susceptibility, increased owing to such loading.Key words: partial drainage, liquefaction, strain softening, laboratory testing, soil mechanics.
Comparison study of live cells by atomic force microscopy, confocal microscopy, and scanning electrochemical microscopy
Authors: Zhao Xiaocui , Petersen Nils O , Ding Zhifeng
Published: April 2007

In this report, three kinds of scanning probe microscopy techniques, atomic force microscopy (AFM), confocal microscopy (CM), and scanning electrochemical microscopy (SECM), were used to study live cells in the physiological environment. Two model cell lines, CV-1 and COS-7, were studied. Time-lapse images were obtained with both contact and tapping mode AFM techniques. Cells were more easily scratched or moved by contact mode AFM than by tapping mode AFM. Detailed surface structures such as filamentous structures on the cell membrane can be obtained and easily discerned with tapping mode AFM. The toxicity of ferrocenemethanol (Fc) on live cells was studied by CM in reflection mode by recording the time-lapse images of controlled live cells and live cells with different Fc concentrations. No significant change in the morphology of cells was caused by Fc. Cells were imaged by SECM with Fc as the mediator at a biased potential of 0.35 V (vs. Ag/AgCl with a saturated KCl solution). Cells did not change visibly within 1 h, which indicated that SECM was a noninvasive technique and thus has a unique advantage for the study of soft cells, since the electrode scanned above the cells instead of in contact with them. Reactive oxygen species (ROS) generated by the cells were detected and images based on these chemical species were obtained. It is demonstrated that SECM can provide not only the topographical images but also the images related to the chemical or biochemical species released by the live cells.Key words: live cells, atomic force microscopy, confocal microscopy, scanning electrochemical microscopy.
1D and 2D NMR investigations of the micelle-formation process in 8-phenyloctanoate micelles
Authors: Landry Josette M , Marangoni D Gerrard , Lumsden Michael D , Berno Robert
Published: April 2007

The micellization process of sodium 8-phenyloctanoate in a deuterated aqueous solution was studied, using 1H NMR spectroscopy and two-dimensional (2D) nuclear Overhauser enhancement spectroscopy (NOESY). 1H NMR spectra, acquired for the sodium 8-phenyloctanoate before and after the critical micelle concentration (CMC) value, showed that large chemical-shift changes were observed for both the aromatic proton peaks and the peaks for the methylene protons near the terminal phenyl group. The plots for the methylene protons near the headgroup do not show these large chemical-shift changes. These observations support the view that the terminal phenyl ring of the surfactant is primarily located in the micellar interior. The 2D NOESY experiments show significant cross-peaks, between the phenyl protons and the methylene protons of the surfactant, that substantiate the conclusions on those drawn from NMR aromatic solute induced shift (ASIS) experiments on the same and similar systems. All these observations are consistent with the Gruen model of the micelle and previous NMR NOESY experiments for other surfactant systems.Key words: surfactants, micelles, NMR, NOESY.