bluuebunny/crossref_metadata_2025 huggingface dataset:
Memória operacional fonológica e consciência fonológica em escolares ao final do ciclo I do ensino fundamental
Authors: Soares Aparecido José Couto , Jacinto Laís Alves , Cárnio Maria Silvia
Published: January 2013

OBJETIVO: Investigar o desempenho de crianças ao final do Ciclo I do Ensino Fundamental em memória operacional fonológica e consciência fonológica, bem como a possível relação entre essas habilidades nesta faixa de escolaridade. MÉTODOS: O grupo de pesquisa foi composto por 29 sujeitos de ambos os gêneros, com média de idade de 10 anos, todos regularmente matriculados no 5º ano do Ensino Fundamental com ausência de alterações de linguagem oral e/ou escrita. Foi realizada a avaliação da memória operacional fonológica com a utilização do Teste de Repetição de Pseudopalavras e, posteriormente, utilizou-se o Instrumento de Avaliação Sequencial - CONFIAS para avaliar a consciência fonológica. RESULTADOS: Os escolares apresentaram desempenho adequado na memória operacional fonológica independente da similaridade da pseudopalavra. Para a consciência fonológica, observou-se desempenho melhor no nível silábico e inferior ao esperado para o nível fonêmico. Apesar de muitos estudos afirmarem a correlação entre a memória operacional fonológica e a consciência fonológica, esta não foi observada nesta amostra. CONCLUSÃO: A ausência de correlação encontrada entre essas habilidades traz reflexões quanto a possíveis fatores extrínsecos que podem influenciar o desempenho em consciência fonológica.
Aquisição dos gestos na comunicação pré-linguística: uma abordagem teórica
Authors: Lima Etelvina do Rosário Silva , Cruz-Santos Anabela
Published: January 2013

Com o objetivo de compreender as relações entre o gesto e a linguagem e a relevância do gesto no desenvolvimento de competências comunicativo-linguísticas foi realizada uma pesquisa da literatura nacional e internacional. A análise dos dados de múltiplas áreas científicas indica influências transversais do gesto natural na evolução da competência comunicativo-linguística do Homem. Assim, a identificação do sistema de neurónios-espelho promoveu o emergir de vários trabalhos que levantaram hipóteses sobre o paralelismo entre a evolução do gesto versus a evolução da linguagem. A literatura aponta que os gestos naturais possuem uma força preditiva no desenvolvimento da linguagem e ao longo de diferentes períodos influencia diversas componentes: pragmática, semântica e morfossintaxe. A influência do gesto natural para a competência comunicativa continua ao longo da vida, visto que o uso de gestos naturais simultâneos ao discurso possuem a função de desambiguar o conteúdo da mensagem para o interlocutor e de organizar o discurso ao emissor. O uso dos gestos naturais na promoção de competências comunicativo-linguísticas em crianças com perturbações da comunicação pré-linguística torna-se incontornável mas requer um aprofundamento de conhecimentos dado que os estudos relacionados com as competências pragmáticas iniciais direcionam-se sobretudo com o gesto de apontar. Outros estudos analisaram os gestos naturais na compreensão das relações com as componentes da semântica e morfossintaxe em idades mais tardias.
Desarrollo de un instrumento para evaluar la dieta en niños y adolescentes colombianos
Authors: Ardila María Fernanda , Herrán Oscar Fernando
Published: January 2013

OBJETIVOS: desarrollar un cuestionario de frecuencia de consumo, útil en la investigación epidemiológica de las relaciones dieta-cáncer, dieta-enfermedad cardiovascular y dieta-estado de nutrición, en niños y adolescentes. MÉTODOS: sesenta y dos sujetos entre 10 y 20 años de edad, respondieron un recordatorio del consumo de las últimas 24 horas, utilizando el método Max_r se seleccionaron alimentos con poder discriminante para estimar el consumo de 12 nutrientes relacionados con las enfermedades crónicas. RESULTADOS: el cuestionario tiene dos secciones en ellas se indaga por la frecuencia de consumo con nueve categorías. Un total de 22 alimentos hacen parte de la lista de chequeo de la primera sección. Un total de 43 ítems hacen parte de la segunda sección donde se indaga por prácticas y hábitos alimentarios de interés para la salud pública. Todos los coeficientes r alcanzados para los nutrientes de interés estuvieron por encima de 0,90 - mínimo 0,94, máximo 1,0. El mínimo fue para el ácido fólico, el máximo para la grasa total, la grasa poli insaturada y la vitamina A (UI). CONCLUSIONS: el diseño de este cuestionario permitirá la realización de estudios epidemiológicos para explorar las relaciones dieta-cáncer, dieta-enfermedad cardiovascular y dieta-estado de nutrición. Además, facilitará el diseño, ejecución y evaluación de intervenciones individuales y poblacionales.
Seasonal characterization of antioxidant responses in plants of Ipomoea nil cv. Scarlet O'Hara
Authors: Ferreira ML. , Domingos M.
Published: January 2013

Reactive oxygen species can be produced in leaf cells during normal aerobic metabolism or in a variety of exogenous factors, which may cause oxidative damage to plants, unless they have an efficient antioxidant defense system, consisting of enzymatic and non-enzymatic substances. This work raised the hypothesis that plants of Ipomoea nil cv. Scarlet O'Hara, a native species and ornamental vine of the tropics, might tolerate oxidative stress factors imposed by natural fluctuations in weather conditions through changes in the antioxidant profile.The objective of this study was to determine the variations in three leaf antioxidants in plants growing inside a greenhouse without air pollutants and exposed to varying meteorological conditions throughout the four seasons of the year and to observe if such variations are related to the oscillations in meteorological factors. Four experimental campaigns were carried out, one in each season of 2006. Each campaign lasted 28 days and started with 45 plants. Ascorbic acid (AA) concentrations and superoxide dismutase (SOD) and peroxidase (POD) activities were determined in leaves of five plants in nine sampling days of each campaign. The antioxidant responses oscillated throughout the year. The highest values were found during the spring. This seasonal antioxidant profile was associated to variations in temperature, relative humidity and global radiation. Plants of this cultivar may then tolerate oxidative stress naturally imposed by meteorological conditions.
Phenology and frugivory by birds on Miconia ligustroides (MELASTOMATACEAE) in a fragment of cerrado, southeastern Brazil
Authors: Allenspach N. , Telles M. , Dias MM.
Published: January 2013

We identified the avian assembly that consumes Miconia ligustroides (Melastomataceae) fruit and described its phenophases in a fragment of cerrado vegetation located in southeastern Brazil. The fruiting period occurred between March and June, a period of food shortage. In 2005 and 2008, we registered eighteen bird species consuming fruits, during 156 hours of observations. Species of the families Thraupidae and Tyrannidae were the most representative in the number of visits and fruit consumption. Short visits (less than three minutes) and low incidence of defecation apparently indicate that seeds may be released far from the parent-plant, suggesting dispersal efficiency by the studied assembly. Owing to its characteristics, we believe Miconia ligustroides may be useful in the restoration of degraded areas.
Use of habitats by non-volant small mammals in Cerrado in Central Brazil
Authors: Santos-Filho M. , Frieiro-Costa F. , Ignácio ÁRA. , Silva MNF.
Published: January 2013

Non-volant small mammals are organisms capable of yielding precise information on richness, abundance and species composition variations related to the use of habitats. The aim of this research was to compare these variations in Cerrado sensu stricto, Palm Forest, Gallery Forest and Rocky Field. From May 1999 to February 2000, we surveyed non-volant small mammals (hence small mammals) in Serra das Araras Ecological Station. We captured 218 individuals and recaptured 62 individuals, belonging to 21 taxa, 13 rodents and eight marsupials, in a total of 13200 trap-nights. Capture success was 1.7%. We observed higher richness of small mammals in forested areas (Gallery Forest and Palm Forest) than in open areas (Rocky Field and Cerrado sensu stricto). The Palm Forest had the highest richness of marsupials, possibly due to the quality of a specific niche. The Rocky Field had the smallest richness, but with very high abundance of few species, mainly Thrichomys pachyurus and Monodelphis domestica. Forest habitats had similar species composition. The open habitats, Cerrado sensu stricto and Rocky Field, had a distinct species composition between them, and also when compared to forested areas. Different species are exclusive or showed preference for specific habitats. The protection of horizontally heterogeneous biomes, such as Cerrado, has a fundamental importance to the maintenance of the regional diversity of the small mammal community of Central Brazil.
Helminth communities in three sympatric rodents from the Brazilian Atlantic Forest: contrasting biomass and numerical abundance
Authors: Simões RO. , Maldonado-Júnior A. , Luque JL.
Published: January 2013

The study of parasite body size is an important approach to understand the different patterns of helminth community structure, once it is usually analysed using only numerical descriptors which do not capture size heterogeneity among parasite species. In the present study, we compared the pattern in the helminth community of three sympatric wild rodent species Akodon cursor, A. montensis and Oligoryzomys nigripes using numerical abundance and biomass approaches. The cestode Rodentolepis akodontis was the worm with highest biomass in the three rodents. The trichostrongylid Stilestrongylus lanfrediae presented highest biomass in O. nigripes and represented 70% of the total numeric abundance of parasites. Interestingly, for Akodon spp. the species with more biomass represented less than 10% of the total numerical abundance. Parasites with the higher numeric abundance do not have the largest body size. Although the biomass pattern is different from numeric abundance, this difference does not influence in the helminth distribution community among the three sympatric hosts. The status change of a helminth species within the community due to its volumetric dominance might justify a new approach since parasites belonging to different taxa obtain resources from the host in different ways.
Description of the male Hymenoepimecis japi Sobczak et al. 2009 (Hymenoptera, Ichneumonidae) parasitoid of Leucauge roseosignata Mello-Leitão 1943 (Araneae: Tetragnathidae)
Authors: Sobczak JF.
Published: January 2013

The male of Hymenoepimecis japi (Hymenoptera, Ichneumonidae, Pimplinae) is described and illustrated. The specimen was collected in a modified web (cocoon web) of Leucauge roseosignata (Araneae, Tetragnathidae) made in a laboratory. Both, host and parasitoid were collected in Reserva Biológica Serra do Japi, located in Jundiaí, São Paulo, Brazil.
Recovery of Trichostrongylus colubriformis infective larvae from three grass species contaminated in the autumn
Authors: Rocha Raquel Abdallah da , Bricarello Patrizia Ana , Rocha Gilberto Pedroso da , Amarante Alessandro Francisco Talamini do
Published: January 2013

This experiment aimed to assess the recovery of infective larvae (L3) of Trichostrongylus colubriformis from Brachiaria decumbens cv. Australiana, Cynodon dactylon cv. Coast-cross and Panicum maximum cv. Aruana. The experimental module comprised six plots, with two plots per herbage species. Larval survival was assessed from autumn to winter, under the effect of two herbage-paring heights (5 and 30 cm). TThe paring was carried out immediately before contamination with faces containing T. colubriformis eggs. The feces and herbage were collected at one, two, four, eight, 12 and 16 weeks after feces had been deposited in the experimental plots. In general, larvae were recovered from both herbage and feces until the 16th week. The longer persistence of these larvae in the environment was probably due to warmer temperatures. The number of L3 recovered from the pasture was not influenced by the height of plants, except for Brachiaria and Aruana herbage in the fourth week. Regarding the concentrations of larvae per kg of dry matter (L3/kg DM), recovery was higher from low pasture in all three herbage species. During the autumn, the development and survival of the T. colubriformis free-living stages were not affected by the different herbage species.
Epidemiology of Oestrus ovis (Diptera: Oestridae) in sheep in Botucatu, State of São Paulo
Authors: Silva Bruna Fernanda da , Bassetto César Cristiano , Amarante Alessandro Francisco Talamini do
Published: January 2013

The seasonal factors that influence Oestrus ovis infestation in sheep were determined in Botucatu, State of São Paulo, Southwestern Brazil, from April 2008 to March 2011. Two tracer lambs were monthly exposed to natural infestation by O. ovis larvae for 28 consecutive days, by grazing with a sheep flock. Tracer animals were then euthanized and the larvae of O. ovis recovered from nasal and sinus cavities. Of the 72 tracer lambs, 50% were infested with O. ovis larvae and the mean intensity of infestation per head infested was 16.8 larvae, with an average of 7.8 L1, 5.3 L2 and 3.7 L3. O. ovis larvae were present during the four seasons of the year, but the mean larval burden was significantly higher during the spring and summer months, compared to winter (P < 0.05). The highest rate of larvae recovery coincided with mean temperatures between 20 °C and 25 °C and air relative humidity around 70%. Results suggest that evolution and development of O. ovis practically occurs throughout the entire year, with larval infestation especially frequent during the spring and summer months.
Parasites of economically important bivalves from the southern coast of Bahia State, Brazil
Authors: Zeidan Gabriela Calvi , Luz Mariane dos Santos Aguiar , Boehs Guisla
Published: January 2013

This study investigated the parasites of three commercially important bivalve species (Crassostrea rhizophorae, Mytella guyanensis and Lucina pectinata) from the southern coast of Bahia, Brazil. A total of 540 specimens were collected in August 2009 and February 2010, at three localities. The bivalve specimens were measured on their longest axis, opened, and macroscopically examined for the presence of parasites or signs of disease. They were then fixed in Davidson' solution and subjected to routine histological processing, with paraffin embedding and H&E staining; next, the specimens were examined under a light microscope. No parasites were observed associated with L. pectinata. Rickettsia-like organisms (RLOs), Sphenophrya sp. (Ciliophora), Nematopsis sp. (Apicomplexa), Urastoma sp. (Turbellaria) and Bucephalus sp. (Digenea) were observed in both C. rhizophorae and M. guyanensis, as well as Ancistrocoma sp. (Ciliophora) and Tylocephalum sp. (Cestoda) in the former. A high prevalence of Nematopsis sp. was seen, but caused no apparent damage to the host. Bucephalus sp. caused the destruction of tissues, with castration, but showed low prevalence. The other parasites occurred in low prevalence and intensity, without causing significant damage.
Chemical identification of Tagetes minuta Linnaeus (Asteraceae) essential oil and its acaricidal effect on ticks
Authors: Garcia Marcos Valério , Matias Jaqueline , Barros Jacqueline Cavalcante , Lima Dênis Pires de , Lopes Rosângela da Silva , Andreotti Renato
Published: January 2013

The control of tick species that affect animal production is vital for the economic welfare of the cattle industry. This study focused on testing the acaricidal activity of the essential oil from the leaves and stems of Tagetes minuta against several Brazilian tick species, including Rhipicephalus (Boophilus) microplus, Rhipicephalus sanguineus, Amblyomma cajennense and Argas miniatus. The chemical composition of the essential oil was determined by chromatography and spectroscopy analyses, which revealed the presence of monoterpenes. The adult immersion test (AIT) and the larval packet test (LPT) were used to evaluate the efficacy of T. minuta essential oil in tick management at concentrations of 2.5, 5, 10, 20 and 40%. The results demonstrated that the T. minuta essential oil had over 95% efficacy against four species of ticks at a concentration of 20%. These results suggest that the essential oil of T. minuta could be used as an environmentally friendly acaricide.
Estimating fire interval bounds using vital attributes: implications of uncertainty and among‐population variability
Authors: Gosper Carl R. , Prober Suzanne M. , Yates Colin J.
Published: January 2013

Identifying the range of appropriate fire return intervals is crucial for ecosystem management in fire‐prone environments. Plant vital attributes and changes in their associated trait values with time since fire are important indicators of suitable fire interval bounds to conserve biodiversity. However, using vital attributes to derive prescriptions for acceptable fire intervals remains challenging due to (1) uncertainty regarding how traits are best measured, (2) uncertainty in the acceptable ranges of trait values to avoid local extinctions, and (3) potential for variability among populations in the time taken postfire to reach trait threshold values. Using a time‐since‐fire gradient in contrasting mallee and mallee‐heath vegetation types of southwestern Australia, we calculate, compare, and aggregate fire interval bound predictions from nine serotinous non‐resprouters and seven serotinous resprouters across these three sources of uncertainty or variation. Relationships between time since fire and both trait measures reflecting minimum fire interval (mean number of closed fruit per plant or proportion of plants with closed fruit) were typically significant, had reasonable goodness of fit, and showed similar patterns of change with time since fire. Significant relationships reflecting maximum fire interval were less frequent but were more commonly detected using direct measures of mortality than using evidence for decline in reproductive potential. Of the two sources of uncertainty, trait value threshold selection caused more substantial differences in estimated interval bounds than trait measurement method. Variation between populations increased with greater estimated minimum interval length and, in some species, rendered interval estimates of limited practical value. On balance, we conclude that measures of vital attribute traits offer a transparent approach for estimating fire interval bounds at the plant community level, but selection of trait value thresholds is in need of stronger biological justification in their application. Further, variation between populations should be explicitly sampled if fire interval estimates are to be applied across the landscape.
A directed network analysis of heterospecific pollen transfer in a biodiverse community
Authors: Fang Qiang , Huang Shuang-Quan
Published: January 2013

Community studies have shown that plant species are often pollinated by multiple pollinators; however, networks of heterospecific pollen transfer (HPT) in natural communities remain largely unexplored. We analyzed pollen deposition on stigmas of 57 flowering species to build a picture of plant–plant interactions via HPT in a biodiverse alpine meadow in southwest China. Plant species were categorized as pollen donors or recipients by their link numbers and link qualities. We identified 3609 heterospecific pollen grains, representing 410 links among 69 pollen species. Each plant species received on average 7.2 pollen species and donated its pollen to 5.5 species; only a few species donated or received large amounts of pollen or pollen from a large number of species. Compared to specialized plants, generalized plants tended to receive more heterospecific pollen but exported no more pollen to other species. Plant position in the network was related to both floral traits (stigma position) and pollinator generalization level. When different species share the same pollinator, bidirectional HPT may occur, but this was rarely observed in the species‐rich community, indicating that interspecific pollen interference was largely unidirectional. Our study highlights the importance of understanding how sympatric flowering plants reduce deleterious effects of HPT, for example via stigma position. This study is the first to present a pollen transfer network for an entire community and to unravel its properties using directed network analysis.
Research Discontinuity and the Development of Hyper-Short Chronology in Middle Atlantic Archaeology, 1920–1950
Authors: Truncer James
Published: January 2013

Research discontinuity is problematic for many disciplines, but has posed severe challenges for archaeology practically from its inception. The Middle Atlantic region provides good examples of how archaeologists working for different institutions in the area have either met or failed to meet the omnipresent challenge of research discontinuity in the discipline. Once a line of research inquiry is dropped, it can be very difficult to revive. Even if this is the case, the earlier research conclusions can be disarticulated, reinterpreted, or treated as insignificant within new research frameworks. New archaeological approaches or findings are not necessarily undesirable in and of themselves, but scientific frameworks require continuity to build cumulative knowledge and can be easily broken and replaced by substituting alternative and competing non-scientific explanatory frameworks. New York archaeology in the early 20th century maintained scientific research continuity; archaeology in New Jersey and the Chesapeake area did not.
Exploring Tribal Settlement Ecology in the Southeast: A Case Study from the North Carolina Piedmont, 800–1600 Ce
Authors: Jones Eric E. , Gattis Madison , Morrison Thomas C. , Wardner Andrew , Frantz Sara
Published: January 2013

Ecological studies of pre-contact tribal groups tend to focus on the environmental aspects of ecology; far less research has explored the social, economic, and political interactions that influence interactions between a group and its environment and landscape. In this research, we present a comprehensive approach to studying tribal ecology through the use of archaeological settlement patterns. We use a combination of ceramic analysis, GIS-based landscape reconstruction, and discriminant function analysis to explore the relationships between settlement location, size, and various environmental and cultural features of the landscape. Our work focuses on Piedmont Village Tradition (PVT) peoples of the upper Yadkin River Valley in the North Carolina Piedmont during 800-1600 CE. Studies of tribal cultures in the Southeast during this time period are rare. Our results indicate that intergroup relations strongly influenced settlement patterns, suggesting that we take a more inclusive approach to studying their role on the settlement ecology of tribal cultures.
Gifts from an Archaeologist's Bookcase: John L. Cotter's Library
Authors: Boldurian Anthony T. , Mckeel Justin D. , Pickel Mason G.
Published: January 2013

Upon the death of John L. Cotter (1911-1999), renowned archaeologist, University of Pennsylvania, a portion of his library passed to the Clovis Archives. The ca. 3,500 holdings include books, monographs, abundant journals, and letter correspondence. The tomes are peppered by marginalia and book-marked notes, thus preserving insights into the scholar's mind over a 65-year career in both prehistoric and historical archaeology. Due to the collection's size and fragile state, organizing and conserving it have been works-in-progress. In sorting through Cotter's papers on Paleoindian research, two Clovis fluted points—carefully wrapped and bagged—were discovered wedged in a file holder. In this article we describe these artifacts, document their intriguing history, and speculate on their presence within Cotter's library.
Transcript Expression Patterns Illuminate the Mechanistic Background of Hormesis in Caenorhabditis Elegans Maupas
Authors: Steinberg Christian E.W. , Pietsch Kerstin , Saul Nadine , Menzel Stefanie , Swain Suresh C. , Stürzenbaum Stephen R. , Menzel Ralph
Published: January 2013

The animal model Caenorhabditis elegans was employed to study polyphenol- and humic substances-induced hormetic changes in lifespan. A detailed insight into the underlying mechanism of hormesis was uncovered by applying whole genome DNA microarray experimentation over a range of quercetin (Q), tannic acid (TA), and humic substances (HuminFeed®, HF) concentrations. The transcriptional response to all exposures followed a non-linear mode which highlighted differential signaling and metabolic pathways. While low Q concentrations regulated processes improving the health of the nematodes, higher concentrations extended lifespan and modulated substantially the global transcriptional response. Over-represented transcripts were notably part of the biotransformation process: enhanced catabolism of toxic intermediates possibly contributes to the lifespan extension. The regulation of transcription, Dauer entry, and nucleosome suggests the presence of distinct exposure dependent differences in transcription and signaling pathways. TA- and HF-mediated transcript expression patterns were overall similar to each other, but changed across the concentration range indicating that their transcriptional dynamics are complex and cannot be attributed to a simple adaptive response. In contrast, Q-mediated hormesis was well aligned to fit the definition of an adaptive response. Simple molecules are more likely to induce an adaptive response than more complex molecules.
A Real-World Business Approach to Teaching M.B.A. Managerial Accounting: Motivation, Design, and Implementation
Authors: Tan John , Satin Diane C. , Lubwama Christopher W. K.
Published: January 2013

This article explains the motivation, design, and implementation of a real-world business approach to teaching managerial accounting in an M.B.A. program to facilitate a shift in student learning from traditional passive listening to active participation. A teaching methodology requiring students to work through the evolution of a potentially viable business contributes to a long-standing effort in the profession to link practice and theory. The course immerses students in the life of an evolving business in four ways: working assignments based on lectures, discussing costing concepts individually with the instructor, summarizing existing research papers, and most importantly participating in mutual interest groups to develop a realistic business plan based on personal research. This approach integrates learning of cost concepts with developing critical thinking skills. It differs from other student projects because students may choose a business based on interest in any industry, and the instructor provides no cost or industry data. Anecdotal evidence indicates that this approach works to stimulate student learning. This paper also addresses some limitations of this approach.
Speededness and Adaptive Testing
Authors: van der Linden Wim J. , Xiong Xinhui
Published: January 2013

Two simple constraints on the item parameters in a response–time model are proposed to control the speededness of an adaptive test. As the constraints are additive, they can easily be included in the constraint set for a shadow-test approach (STA) to adaptive testing. Alternatively, a simple heuristic is presented to control speededness in plain adaptive testing without any constraints. Both types of control are easy to implement and do not require any other real-time parameter estimation during the test than the regular update of the test taker’s ability estimate. Evaluation of the two approaches using simulated adaptive testing showed that the STA was especially effective. It guaranteed testing times that differed less than 10 seconds from a reference test across a variety of conditions.
Construction of Dynamic Modulus Master Curves with Resilient Modulus and Creep Test Data
Authors: Lee Hyung Suk , Kim Sungho , Choubane Bouzid , Upshaw Patrick
Published: January 2013

For the past few decades, the stiffness of materials used for roadway design and construction has been commonly characterized by the resilient modulus, defined as the ratio of the applied stress to the recoverable strain. However, the resilient modulus is not a fundamental material property of a viscoelastic material. Therefore, the concept of resilient modulus has been subsequently diminished in the latest Mechanistic–Empirical Pavement Design Guide. Although that design guide could not endorse the use of the resilient modulus test protocol as the primary means of characterizing the asphalt concrete modulus in the design of flexible pavements, that protocol has been a primary mixture test, and much laboratory testing has been completed to date. Analysis methodologies are introduced for backcalculating the dynamic modulus from the resilient modulus test data. To assess the usefulness of the proposed algorithm, laboratory experiments in both the uniaxial compression and indirect tensile test modes were carried out on asphalt specimens compacted with the Superpave® gyratory compactor. The backcalculated dynamic modulus was used to generate the master curve, and the creep test data were used to enhance the accuracy of the master curve. The advantage of such a methodology is that the existing resilient modulus and creep test data can be leveraged for estimating the dynamic modulus. The approach would significantly save time and effort in reevaluating the dynamic modulus of an asphalt mixture when the resilient modulus and creep test data are available.
Development of Autonomous Setup for Evaluating Self-Healing Capability of Asphalt Mixtures
Authors: Qiu Jian , Molenaar A. A. A. , Van De Ven Martin F. C. , Wu Shaopeng
Published: January 2013

Asphalt mixtures have self-healing capabilities, yet most self-healing investigations are carried out with complex and time-consuming fatigue tests. To investigate the self-healing capability in a simple, efficient manner, a beam-on-elastic-foundation (BOEF) test setup was proposed. With a notched asphalt concrete beam fully glued to a low modulus rubber foundation, the BOEF setup was able to control the self-healing process autonomously, including crack closure and healing at different rest periods and temperatures. A load crack opening displacement curve was used for characterizing the self-healing capability of the monotonic response with a loading–healing–reloading procedure. In addition, small numbers of dynamic loads were also applied to the BOEF setup under different cracking and healing conditions. An apparent modulus of the BOEF asphalt beam was obtained on the basis of the dynamic response of the load crack opening displacement. The results indicate that the self-healing capability obtained in the monotonic tests depends on the healing time and healing temperature. The healing temperature has the larger effect of the two. Most of the apparent modulus of the BOEF asphalt beam recovers at the beginning of the self-healing process. The influences of healing time and temperature are limited. As a result, the BOEF setup is proved as a potential tool for the self-healing investigation of asphalt mixtures.
Incremental Model for Prediction of Permanent Deformation of Asphalt Concrete in Compression
Authors: Choi Yeong-Tae , Subramanian Vijay , Guddati Murthy N. , Kim Y. Richard
Published: January 2013

Permanent deformation (rutting) is one of the major distresses in asphalt pavement. To predict permanent deformation of asphalt concrete, repeated creep and recovery (or flow number) tests are typically used in the laboratory. However, models for the prediction of permanent deformation that incorporate flow number testing cannot represent the primary region because they concentrate on the secondary region. A new simple permanent deformation model called the incremental model is proposed. The proposed model is derived from the rate model, which is a rigorous mechanical model based on viscoplasticity. Four parameters of the new model provide an understanding of the permanent deformation. Parameter A is related to the initial permanent strain level, and Parameter C provides information about where the secondary region starts. That is, Parameters A and C govern the primary region, where α (alpha) is the slope of the secondary region, and B represents the permanent deformation level of the secondary region. Two mixtures are selected to investigate the deformation characteristics, and repeated creep and recovery tests are performed in compression. The incremental model is verified by applying it to various loading conditions for two mixtures. Furthermore, it is found that α is the material constant and the time-temperature superposition principle is applicable to each parameter. All parameters, except a, depend on both deviatoric stress and reduced load time, which is the product of load time and temperature. The incremental model describes ways to apply the time-temperature supposition principle to permanent deformation.
Simplified Viscoelastic Continuum Damage Model as Platform for Asphalt Concrete Fatigue Analysis
Authors: Underwood B. Shane , Baek Cheolmin , Kim Y. Richard
Published: January 2013

Cracking in asphalt concrete pavements is a major form of pavement distress in the United States. Because the cracking phenomenon is complex and cracking is often affected by both material and structural factors, field engineers have no quick and effective test and analysis protocols. A suite of fatigue analysis tools—as well as applications built around the simplified viscoelastic continuum damage (S-VECD) model—is presented. The S-VECD formulation is presented in a summarized form. Next, the characterization protocols, which are consistent with the capabilities of the asphalt mixture performance tester, are shown. Considerable attention is then given to S-VECD–based analysis tools for assessment of material- and pavement-level fatigue performance. Results show that the S-VECD model can be used to predict the number of cycles until fatigue failure for both constant stress and constant strain loading. The S-VECD model's sensitivity to mixture composition and external factors is shown through predictions of the endurance limit. Finally, pavement performance predictions are used to show how the S-VECD model can predict the field performance results of full-scale accelerated pavement tests, quantify the expected performance of pavement design alternatives, and identify factors that affect top-down cracking.
Hot-Mix Asphalt Permanent Deformation Evaluated by Hamburg Wheel Tracking, Dynamic Modulus, and Repeated Load Tests
Authors: Walubita Lubinda F. , Zhang Jun , Das Gautam , Hu Xiaodi , Mushota Charles , Alvarez Allex E. , Scullion Thomas
Published: January 2013

Permanent deformation (or rutting) is a common distress in hot-mix asphalt (HMA) pavements. As part of the HMA mix and structural design processes to optimize field performance, the Hamburg wheel-tracking, dynamic modulus, and uniaxial repeated load permanent deformation tests have been developed to characterize the HMA rutting resistance potential. The primary objective of this study was to compare the three laboratory rutting tests of HMA mixes and to relate their rutting predictive potential to actual field performance. The research methodology incorporated a two-phase approach: laboratory testing and field performance monitoring of selected mixes under both conventional traffic loading and accelerated pavement testing. For the HMA mixes evaluated, a good correlation was observed in the three laboratory tests and in comparison with actual in situ field performance. Overall, the findings indicated that the Hamburg wheel-tracking test was the most feasible test for daily routine HMA mix design and screening, while both the dynamic modulus and repeated load permanent deformation tests exhibited greater potential for comprehensive characterization of HMA material property (e.g., modulus) and applications for pavement structural design as research-level test tools.
Calibrating and Validating Overlay Tester–Based Fatigue Cracking Model with Data from National Center for Asphalt Technology
Authors: Hu Sheng , Zhou Fujie , Scullion Thomas , Leidy Joe
Published: January 2013

There is a national movement to develop mechanistic–empirical methods for the design of flexible pavements, for which fatigue cracking is a major distress mode. Fatigue cracking has been studied for several decades. Different types of fatigue cracking models have been proposed. After a review of existing fatigue cracking models in the literature, it was found that the overlay tester–based fatigue cracking model was a rational choice for predicting the development of fatigue cracking and for incorporation into the mechanistic–empirical design system. The main features of the overlay tester–based fatigue cracking model include incorporation of both crack initiation and crack propagation stages; involvement of fracture properties (i.e., A and n) of every asphalt layer, if the flexible pavement has multiple asphalt layers and each layer material is different; and use of the simple overlay tester for determining the fracture properties required for predicting both crack propagation and crack initiation. The proposed fatigue cracking model was preliminarily calibrated with material properties and fatigue cracking performance data from seven test sections evaluated in the 2006 test cycle at the National Center for Asphalt Technology's Pavement Test Track. Validation of the calibrated model was performed with performance data from the 2003 test sections at the National Center for Asphalt Technology Pavement Test Track. Thus far, satisfactory results have been obtained. However, further model validation and calibration with more field data, varied traffic load spectra, different environmental conditions, and different materials are still required.
Evaluation of Asphalt Mixture Performance Tester
Authors: Roberts Levi , Romero Pedro , VanFrank Kevin , Ferrin Ryan
Published: January 2013

For more than 5 years, the Utah Department of Transportation collected field material and tested it with the asphalt mixture performance tester (AMPT). Thirty-four field mixtures were evaluated as part of this study. The mixtures were produced according to Utah DOT standard volumetric specifications with two binder grades, Performance Grade (PG) 64-34 and PG 70-28, from three suppliers. The results of these tests showed that the AMPT produced data with a coefficient of variation below 15%, which indicates good repeatability. Mixtures prepared with different binder grades were easily separated. The dynamic modulus master curves of mixtures prepared with the same binder grade were essentially the same regardless of the aggregate source. The same type of mixture was used. These results show that it is possible to obtain input parameters for the Level 1 asphalt mixture from the Mechanistic–Empirical Pavement Design Guide on the basis of historical data, knowledge of the binder grade used, and testing at only one temperature. The single-temperature test can be used for quality control and to verify that the mixture is of the same kind as the historical data available. This approach can significantly reduce the time and effort required to obtain AMPT data without any loss in the capacity of performance prediction and thus make adoption of this device more appealing to state departments of transportation.
Effects of Oxidative Aging on Asphalt Mixture Properties
Authors: Baek Cheolmin , Underwood B. Shane , Kim Y. Richard
Published: January 2013

Aging has long been recognized as a contributing factor to fatigue distress of asphalt concrete pavement. Several research studies have been undertaken to gain fundamental understanding of the aging phenomenon at the asphalt binder level. However, relatively little effort has been made to understand and to quantify the effects of aging on fundamental characteristics of asphalt mixtures. The effects of oxidative aging on the dynamic modulus and the fatigue performance of asphalt mixtures is examined. For this purpose, an asphalt mixture is aged in the laboratory at four aging levels. Mechanical tests for the four aged mixtures are performed to characterize the linear viscoelastic and damage properties. Such characterization is investigated to incorporate the aging effects into a more comprehensive analytical framework for predicting the performance of asphalt concrete pavements. Finally, this framework is used to evaluate the aging effects on an example asphalt concrete pavement. It is found that aging can significantly change the performance of an asphalt concrete pavement, depending on the location evaluated within the pavement structure as well as climate conditions.
Method to Quantify Healing in Asphalt Composites by Continuum Damage Approach
Authors: Palvadi Sundeep , Bhasin Amit , Little Dallas N.
Published: January 2013

The importance of healing and its impact on the fatigue cracking performance of asphalt mixtures are well recognized. Microdamage healing in an asphalt mixture is a function of several factors, such as the physical and chemical properties of the binder, the properties of the mixture, the level of damage before the rest period during which healing occurs, the duration of the rest period, temperature, and pressure. An experimental and analytical method characterizes the healing in an asphalt composite (fine aggregate matrix) as a function of the level of damage before the rest period and the duration of the rest period. The proposed method builds on the viscoelastic continuum damage theory that has been used successfully by other researchers to characterize fatigue cracking in asphalt mixtures. The method is applied to evaluate the healing characteristics of four fine aggregate matrix mixes and is able to quantify the influence of the duration of the rest period and the level of damage preceding the rest period on overall healing. Two verification tests were used to demonstrate that the amount of healing measured by the proposed method was independent of the sequence of loading or rest periods. Results from the initial tests support the hypothesis that the healing characteristics determined with the proposed test method at isothermal conditions can be treated as a characteristic material property.
Asphalt Pavement Analyzer Used to Assess Rutting Susceptibility of Hot-Mix Asphalt Designed for High Tire Pressure Aircraft
Authors: Rushing John F. , Little Dallas N. , Garg Navneet
Published: January 2013

Hot-mix asphalt (HMA) laboratory mix design is intended to determine the proportion of aggregate and binder that, when mixed and compacted under a specified effort, will withstand anticipated loading conditions. Current mix design procedures that use the Superpave® gyratory compactor rely on the engineering properties and volumetrics of the compacted mixture to ensure reliable performance; however, a definitive performance test does not exist. The asphalt pavement analyzer (APA) was evaluated as a tool for assessing HMA mixtures designed to perform under high tire pressure aircraft following FAA specifications. The APA used in this study was specially designed to test simulated high tire pressures of 250 psi, which are becoming more common for aircraft. Thirty-three HMA mixtures were included in the study. Each was designed with the Superpave gyratory compactor, according to preliminary criteria being developed by FAA. The study included some mixtures that contain excessive percentages of natural sand and that do not meet FAA criteria. These mixtures were included to provide relative performance for mixtures expected to exhibit premature rutting. APA testing with the high tire pressure APA resulted in rapid failure of HMA specimens compared with traditional APA testing at lower pressures. Data were analyzed, with a focus on the provision of acceptance recommendations for mixtures to support high tire pressures. A preliminary 10-mm rut depth criterion after 4,000 load cycles is recommended.
Modeling Thermal Stress in Asphalt Mixtures Undergoing Glass Transition and Physical Hardening
Authors: Tabatabaee Hassan A. , Velasquez Raul , Bahia Hussain U.
Published: January 2013

Asphalt binders have been shown to undergo significant time-dependent stiffening when stored at low temperatures. This physical hardening has a significant effect on the laboratory performance of asphalt binders. However, the importance of isothermal conditioning for asphalt mixtures and its effect on thermal cracking performance have been a subject of significant debate. A theoretical approach accounting for the glass transition and physical hardening in the thermal stress buildup in mixtures was derived from relaxation modulus master curves, the William–Landel–Ferry equation, Boltzmann's superposition principle, and a model describing the isothermal contraction of asphalt as a continuous function of conditioning time and temperature. With the model predictions, it is shown that thermal stress relaxation and stress buildup induced by physical hardening can continuously affect thermal stress throughout the cooling process. The cooling rate also affected the amount of delayed stress buildup that occurred after the temperature had stabilized at isothermal conditions as a result of physical hardening. A relatively simple device was developed and used for verification and support of the thermal stress model. Mixture measurements performed at different cooling rates and isothermal conditions supported the theoretical predictions. The findings clearly show that the effect of physical hardening on stress buildup in mixtures is measurable and important. Therefore, the glass transition of asphalts and their behavior under isothermal conditioning needs to be measured to better predict thermal cracking.
Characterization of Fracture Properties of Asphalt Mixtures as Measured by Semicircular Bend Test and Indirect Tension Test
Authors: Kim Minkyum , Mohammad Louay N. , Elseifi Mostafa A.
Published: January 2013

The objective of this study was to investigate the intermediate temperature fracture resistance of various asphalt mixtures, as measured by the semicircular bending (SCB) and indirect tension (IDT) test methods, and to correlate these fracture properties to the cracking performance of Louisiana asphalt pavements. Effects of design and process-based factors such as mixture-producing technologies (e.g., hot mix versus warm mix), asphalt binder grades, aging of test specimens, and reclaimed asphalt pavement (RAP) content on the fracture properties were investigated. Results indicated that the SCB-measured critical strain energy release rate (Jc) values showed good correlation with the IDT-measured toughness index values, especially when laboratory-produced mixtures were compared. In addition, the asphalt binder grade and aging condition of specimens influenced the fracture properties of asphalt mixtures. Asphalt mixtures with polymer-modified asphalt binders exhibited greater fracture resistance than did those with unmodified asphalt binders. The aging of specimens decreased the fracture energy of asphalt mixtures while increasing their strengths. Warm-mix asphalt (WMA) technologies used to produce asphalt mixtures at reduced mixing and compaction temperatures did not negatively affect the fracture resistance of the produced mixtures. Further, incorporating high RAP contents of up to 30% in the WMA production did not seem to reduce the fracture resistance of the produced mixtures. The SCB-measured Jc values demonstrated a good correlation with field cracking performance data. These results demonstrate the suitability of the SCB test method for predicting the cracking performance of asphalt pavements at intermediate service temperatures.