bluuebunny/crossref_metadata_2025 huggingface dataset:
Genome-Wide Linkage and Admixture Mapping of Type 2 Diabetes in African American Families From the American Diabetes Association GENNID (Genetics of NIDDM) Study Cohort
Authors: Elbein Steven C. , Das Swapan K. , Hallman D. Michael , Hanis Craig L. , Hasstedt Sandra J.
Published: October 2008

OBJECTIVE—We used a single nucleotide polymorphism (SNP) map in a large cohort of 580 African American families to identify regions linked to type 2 diabetes, age of type 2 diabetes diagnosis, and BMI.

RESEARCH DESIGN AND METHODS—After removing outliers and problematic samples, we conducted linkage analysis using 5,914 SNPs in 1,344 individuals from 530 families. Linkage analysis was conducted using variance components for type 2 diabetes, age of type 2 diabetes diagnosis, and BMI and nonparametric linkage analyses. Ordered subset analyses were conducted ranking on age of type 2 diabetes diagnosis, BMI, waist circumference, waist-to-hip ratio, and amount of European admixture. Admixture mapping was conducted using 4,486 markers not in linkage disequilibrium.

RESULTS—The strongest signal for type 2 diabetes (logarithm of odds [LOD] 4.53) was a broad peak on chromosome 2, with weaker linkage to age of type 2 diabetes diagnosis (LOD 1.82). Type 2 diabetes and age of type 2 diabetes diagnosis were linked to chromosome 13p (3–22 cM; LOD 2.42 and 2.46, respectively). Age of type 2 diabetes diagnosis was linked to 18p (66 cM; LOD 2.96). We replicated previous reports on chromosome 7p (79 cM; LOD 2.93). Ordered subset analysis did not overlap with linkage of unselected families. The best admixture score was on chromosome 12 (90 cM; P = 0.0003).

CONCLUSIONS—The linkage regions on chromosomes 7 (27–78 cM) and 18p overlap prior reports, whereas regions on 2p and 13p linkage are novel. Among potential candidate genes implicated are TCF7L1, VAMP5, VAMP8, CDK8, INSIG2, IPF1, PAX8, IL18R1, members of the IL1 and IL1 receptor families, and MAP4K4. These studies provide a complementary approach to genome-wide association scans to identify causative genes for African American diabetes.
Follow-Up Analysis of Genome-Wide Association Data Identifies Novel Loci for Type 1 Diabetes
Authors: Grant Struan F.A. , Qu Hui-Qi , Bradfield Jonathan P. , Marchand Luc , Kim Cecilia E. , Glessner Joseph T. , Grabs Rosemarie , Taback Shayne P. , Frackelton Edward C. , Eckert Andrew W. , Annaiah Kiran , Lawson Margaret L. , Otieno F. George , Santa Erin , Shaner Julie L. , Smith Ryan M. , Skraban Robert , Imielinski Marcin , Chiavacci Rosetta M. , Grundmeier Robert W. , Stanley Charles A. , Kirsch Susan E. , Waggott Daryl , Paterson Andrew D. , Monos Dimitri S. ,   the DCCT/EDIC Research Group, Polychronakos Constantin , Hakonarson Hakon
Published: October 2008

OBJECTIVE—Two recent genome-wide association (GWA) studies have revealed novel loci for type 1 diabetes, a common multifactorial disease with a strong genetic component. To fully utilize the GWA data that we had obtained by genotyping 563 type 1 diabetes probands and 1,146 control subjects, as well as 483 case subject–parent trios, using the Illumina HumanHap550 BeadChip, we designed a full stage 2 study to capture other possible association signals.

RESEARCH DESIGN AND METHODS—From our existing datasets, we selected 982 markers with P < 0.05 in both GWA cohorts. Genotyping these in an independent set of 636 nuclear families with 974 affected offspring revealed 75 markers that also had P < 0.05 in this third cohort. Among these, six single nucleotide polymorphisms in five novel loci also had P < 0.05 in the Wellcome Trust Case-Control Consortium dataset and were further tested in 1,303 type 1 diabetes probands from the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) plus 1,673 control subjects.

RESULTS—Two markers (rs9976767 and rs3757247) remained significant after adjusting for the number of tests in this last cohort; they reside in UBASH3A (OR 1.16; combined P = 2.33 × 10−8) and BACH2 (1.13; combined P = 1.25 × 10−6).

CONCLUSIONS—Evaluation of a large number of statistical GWA candidates in several independent cohorts has revealed additional loci that are associated with type 1 diabetes. The two genes at these respective loci, UBASH3A and BACH2, are both biologically relevant to autoimmunity.
Effect of a Successful Intensive Lifestyle Program on Insulin Sensitivity and Glucose Tolerance in Obese Youth
Authors: Shaw Melissa , Savoye Mary , Cali Anna , Dziura James , Tamborlane William V. , Caprio Sonia
Published: October 2008

OBJECTIVE—To evaluate the impact on glucose metabolism of a lifestyle program (the Yale Bright Bodies Program) for obese children.

RESEARCH DESIGN AND METHODS—Thirteen Bright Bodies and ten clinic-care control subjects who were part of a large randomized clinical trial had 75-g oral glucose tolerance tests at the beginning and end of the 12-month study.

RESULTS—Bright Bodies subjects had significantly greater decreases in weight, BMI, and body fat than clinic-care subjects, and the Bright Body subjects’ changes in body composition were accompanied by marked improvements in insulin sensitivity (P = 0.009) and glucose tolerance (P = 0.04).

CONCLUSIONS—An intensive lifestyle program that successfully reduces body weight and body fat can markedly improve insulin sensitivity and glucose metabolism in obese youth.
Serum Levels of the Adipokine FGF21 Depend on Renal Function
Authors: Stein Sebastian , Bachmann Anette , Lössner Ulrike , Kratzsch Jürgen , Blüher Matthias , Stumvoll Michael , Fasshauer Mathias
Published: October 2008

OBJECTIVE—To investigate renal elimination of the adipokine fibroblast growth factor 21 (FGF21) by determining circulating FGF21 levels in patients on chronic hemodialysis (CD) as compared with control subjects with a glomerular filtration rate (GFR) >50 ml/min.

RESEARCH DESIGN AND METHODS—FGF21 was determined by enzyme-linked immunosorbent assay in control (n = 60) and CD (n = 60) patients and correlated to clinical and biochemical measures of renal function, glucose and lipid metabolism, and inflammation in both groups.

RESULTS—Median serum FGF21 levels were >15-fold higher in CD patients (3,710.6 ng/l) than in subjects with a GFR >50 ml/min (201.9 ng/l) (P < 0.001). Furthermore, serum creatinine positively and GFR negatively predicted FGF21 concentrations in multiple regression analyses in control subjects (P < 0.05).

CONCLUSIONS—FGF21 serum levels increase in CD patients and are related to markers of renal function in control subjects.
Correlation between the levels of survivin and survivin promoter-driven gene expression in cancer and non-cancer cells
Authors: Konopka Krystyna , Spain Christopher , Yen Allison , Overlid Nathan , Gebremedhin Senait , Düzgüneş Nejat
Published: October 2008

Survivin, a member of the inhibitor of apoptosis (IAP) protein family, is associated with malignant transformation and is over-expressed in most human tumors. Using lipoplex-mediated transfection, we evaluated the activity of the reporter enzyme, luciferase, expressed from plasmids encoding the enzyme under the control of either the cytomegalovirus (CMV) or survivin promoters, in tumor- and non-tumor-derived human and murine cells. We also examined whether there is a correlation between the survivin promoter-driven expression of luciferase and the level of endogenous survivin. Human cancer cells (HeLa, KB, HSC-3, H357, H376, H413), oral keratinocytes, GMSM-K, and chemically immortalized human mammary cells, 184A-1, were transfected with Metafectene at 2 μl/1 μg DNA. Murine squamous cell carcinoma cells, SCCVII, mouse embryonic fibroblasts, NIH-3T3, and murine immortalized mammary cells, NMuMG, were transfected with Metafectene PRO at 2 μl/1 μg DNA. The expression of luciferase was driven by the CMV promoter (pCMV.Luc), the human survivin promoter (pSRVN.Luc-1430), or the murine survivin promoters (pSRVN.Luc-1342 and pSRVN.Luc-194). Luciferase activity was measured, using the Luciferase Assay System and expressed as relative light units (RLU) per ml of cell lysate or per mg of protein. The level of survivin in the lysates of human cells was determined by ELISA and expressed as ng survivin/mg protein. In all cell lines, significantly higher luciferase activity was driven by the CMV promoter than by survivin promoters. The expression of luciferase driven by the CMV and survivin promoters in murine cells was much higher than that in human cells. The cells displayed very different susceptibilities to transfection; nevertheless, high CMV-driven luciferase activity appeared to correlate with high survivin-promoter driven luciferase expression. The survivin concentration in lysates of cancer cells ranged from 5.8 ± 2.3 to 24.3 ± 2.9 ng/mg protein (mean, 13.7 ng/mg). Surprisingly, elevated survivin protein was determined in lysates of non-tumor-derived cells. Survivin levels for GMSM-K and 184A-1 cells, were 16.7 ± 8.7 and 13.5 ± 6.2 ng/mg protein, respectively. The expression of endogenous survivin did not correlate with the level of survivin promoter-driven transgene activity in the same cells. The expression of survivin by non-tumorigenic, transformed cell lines may be necessary for their proliferative activity. The level of survivin promoter-driven gene expression achieved via liposomal vectors in OSCC cells was too low to be useful in cancer-cell specific gene therapy.
Probable annual floods in a small lowland river estimated with the use of various sets of data
Authors: Banasik Kazimierz , Byczkowski Andrzej
Published: October 2008

Probable annual floods in a small lowland river estimated with the use of various sets of data

The results of estimation of the probable annual flood flows with the use of various sets of data from a small agricultural lowland river are presented. The traditional statistical series are formed from the annual maximum (AM) flows of hydrological years. After examination of the homogeneity of the series, two sets of data were formed (AM1 of 34 elements and AM2 of 40 elements), which differed in the significance level of one of the stationary tests. The other series for flood frequency analysis has been formed by selecting peaks over threshold discharges (POT). A computer program, developed by IMGW (Institute of Hydrology and Water Management), and spreadsheet were applied for frequency analysis with the use of AM series and POT series, respectively. Results of computations with the use of AM1 and AM2 data indicate for nonsignificant differences in probable flood flows, and significant with the probable flood flow estimated with the POT data.
Possible effects of climate change on ecological functioning of shallow lakes, Lake Loenderveen as a case study
Authors: Schep Sebastiaan , Ter Heerdt Gerard , Janse Jan , Ouboter Maarten
Published: October 2008

Possible effects of climate change on ecological functioning of shallow lakes, Lake Loenderveen as a case study

The European Water Framework Directive (WFD) requires all inland and coastal waters to reach "good ecological status" by 2015. The good ecological status of shallow lakes can be characterised by clear water dominated by submerged vegetation. The ecological response of shallow lakes on nutrients largely depends on morphological and hydrological features, such as water depth, retention time, water level fluctuations, bottom type, fetch etc. These features determine the "critical nutrient load" of a lake. When the actual nutrient load of a lake is higher than the critical nutrient load, the ecological quality of this lake will deteriorate, resulting in a turbid state dominated by algae. Climate change might lead to changes in both environmental factors and ecosystem response. This certainly will have an effect on the ecological status. As an illustration the results of a multidiscipline study of a shallow peaty lake (Loenderveen) are presented, including hydrology, geochemistry and ecology. Ground- and surface water flows, nutrient dynamics and ecosystem functioning have been studied culminating in an application of the ecological model of the lake (PCLake). Future scenarios were implemented through changing precipitation, evaporation and temperature. Climate change will lead to higher nutrient loads and lower critical nutrient loads. As a consequence lakes shift easier from clear water to a turbid state.
Hydrological background of the dune slack vegetation in the Kiskunság
Authors: Margóczi Katalin , Szanyi János , Aradi Eszter , Busa-Fekete Bertalan
Published: October 2008

Hydrological background of the dune slack vegetation in the Kiskunság

In the southern Kiskunság the natural vegetation (sand steppe, fen meadow, fen or marsh and alkali vegetation) survived in the dune slack meadows (DSM). The vegetation of these meadows are species rich, and has high natural value. The main goal of this study is to reveal the hydrological backgrounds in order to help conservation of the natural values. Two DSM was investigated (MM and CS site): vegetation was sampled, observation wells were planted, and data of other wells in similar position were used to describe the hydrological background of the vegetation. The characteristic groundwater level of the same vegetation type in the relatively wet 2005 year was higher in MM site, than in the CS site. We suppose, that this is a consequence of the earlier vegetation change because of the strong decrease of groundwater level in the region of MM site. The model of hydraulic flow system showed that the DSMs are situated in hydraulic discharge zones. We suppose, that an upward flow plays an important role in development of alkali vegetation in the CS site. Cross-correlation coefficient between groundwater and previous precipitation indicated a quick infiltration of rainwater into the soil, and a pressure front of the groundwater stream reaching the area of well after 22-23 days after rainfall. The quick and strong regional hydrological changes, especially the decrease of groundwater level would endanger this valuable vegetation, but certain resistance and plasticity of it is rather possible.
How Teachers Respond to Children’s Inquiry
Authors: Engel Susan , Randall Kellie
Published: October 2008

This study examined how teachers respond when children engage in inquiry-based deviations from a planned task. Thirty-one teachers each completed a brief science activity and accompanying worksheet with a student confederate. Teachers were given one of two goals for the study: help the students complete a worksheet or help the students learn more about science. The instructions had a significant effect on the teachers’ responses to students’ deviations. Teachers in the worksheet condition tended to discourage deviation and draw the students back to the task at hand, whereas teachers in the learn more condition were more likely to encourage and expand on the deviation. Apart from their responses to students’ deviations, nearly all teachers were classified as encouraging, suggesting that an articulated goal for the activity has a particular effect on the response to deviations. Implications for the role of teachers in the development of children’s curiosity are considered.
Long-Term Aging Characteristics of Polyphosphoric Acid-Modified Asphalts
Authors: Huang Shin-Che , Turner Thomas F. , Miknis Francis P. , Thomas Kenneth P.
Published: October 2008

An experiment involving three neat asphalts and their mixtures with 1.5 wt % of polyphosphoric acid (105%) was conducted to investigate the effect of polyphosphoric acid (PPA) on the long-term aging characteristics of asphalt binders. Analytical techniques including dynamic shear rheometry, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry, and nuclear magnetic resonance (NMR) spectroscopy were performed on unaged and aged PPA-modified asphalts. Rheological properties of unaged and aged modified asphalts were measured with a dynamic shear rheometer at various temperatures. The concentration of carbonyl-containing compounds present in the various unmodified and PPA-modified binders was determined by FTIR spectrometry. The thermal properties of the unmodified and PPA-modified binder were obtained by using differential scanning calorimetry. The results indicate that PPA-modified asphalts reduce rutting potential by increasing initial stiffness and reduce fatigue or low temperature cracking, or both by improving the low-temperature flow properties. The correlation between rheological properties and chemical properties of unmodified and PPA-modified asphalts is also presented. The results show a linear relationship between physical properties and chemical properties of asphalt binders with respect to oxidative aging. However, addition of PPA to asphalt alters the linear relationship. NMR results showed no new chemical species formed in the asphalt-PPA mixture.
Utilization of Biofuel Coproducts as Performance Enhancers in Asphalt Binder
Authors: McCready Nicolaus S. , Williams R. Christopher
Published: October 2008

Oxidation is the primary cause of long-term aging in asphalt pavements. As a pavement oxidizes, it stiffens and can eventually crack. The use of an antioxidant as a performance enhancer in an asphalt binder could delay aging and thus increase the life of an asphalt pavement. Lignin is a highly available, well-studied antioxidant. A wet-mill ethanol plant produces several coproducts, some containing lignin. The use of coproducts from ethanol production could benefit asphalt pavements while also providing more value to the coproducts. Four lignin-containing coproducts were combined with four asphalt binders in varying amounts to discover the optimum amount of coproduct that would provide the greatest benefit to the asphalt binders. The asphalt-coproduct blends were evaluated according to Superpave® specifications and performance graded on a continuous scale. The data indicate a stiffening effect of the binder caused by the addition of coproduct–the more coproduct added, the greater the stiffening. Binder stiffening benefits the high-temperature properties, while the low-temperature binder properties are negatively affected. However, the low-temperature stiffening effects are small. Instead of acting purely as a filler and shifting the temperature range, the lignin has an overall effect of widening the temperature range of the binders. Testing reveals that the lignin in the coproducts benefits the intermediate-and low-temperature properties of the binders. Oxidative aging products were evaluated and some antioxidant effects were noticed.
Field Aging of Unmodified Asphalt Binder in Three Texas Long-Term Performance Pavements
Authors: Woo Won Jun , Chowdhury Arif , Glover Charles J.
Published: October 2008

Binder hardening in pavements and its impact on pavement durability are becoming better understood. Binders oxidize, harden, and become more susceptible to fatigue and thermal cracking. Data are mounting that binder aging occurs to a significant degree well below the top inch of the pavement, contrary to common belief. Whereas recent data indicate that binders age at constant rates and to a significant depth in pavements, a need exists to obtain the detailed profile for understanding pavement aging as a function of air voids. The extent to which binder oxidation occurs throughout the pavement is an important issue and must be understood and quantified to understand pavement durability better and to design longer-lasting pavements. In this work, two layers in each of three pavements in three Texas districts were evaluated. Pavement measurements included recovered binder properties using a dynamic shear rheometer, size exclusion chromatography, changes in these properties over time due to oxidative aging in the pavement, and pavement total and accessible (interconnected) air voids. Many of the pavement cores were sawed into 0.5-in. layers with the binder and air void properties determined for each layer. These measurements provided an indication of binder aging in Texas pavements and suggest strongly that binders age even inches down into the pavement. It was observed that lower accessible air voids correlated with a lower rate of binder oxidation and hardening.
Mechanical and Performance-Related Properties of Asphalt Mixes Containing Expanded Clay Aggregate
Authors: Losa M. , Leandri P. , Bacci R.
Published: October 2008

The use of artificial aggregates such as expanded clay in the production of asphalt concrete makes it possible to reduce both natural aggregate extraction and the use of nonrenewable raw resources, greatly benefiting the environment. Moreover, the expanded clay production process allows nondangerous waste materials to be reclaimed and thereby avoids the necessity to dispose of them in a landfill or dump–this benefits the environment and also offers economic advantages. This paper reports on the results of laboratory and in situ tests to evaluate the feasibility and advantages of using expanded clay in producing asphalt mixes for use in urban areas to reduce traffic noise. Some experimental low-noise asphalt surfaces were laid, with 15% of expanded clay by weight, and mechanical as well as performance properties were then evaluated. The mechanical characteristics, friction, and acoustic performance, in contrast to results with traditional asphalt surfaces, demonstrated the considerable benefits of using expanded clay in asphalt mixes for surface layers. In particular, the results of friction increase and noise-spectrum reduction are of interest.
Effects of Type and Content of Mineral Filler on Viscosity of Asphalt Mastic and Mixing and Compaction Temperatures of Asphalt Mixture
Authors: Zeng Menglan , Wu Chaofan
Published: October 2008

The mineral filler suspends in asphalt binder and forms asphalt mastic, which coats coarser aggregate particles in asphalt mixture. There are reasons to believe that the viscosity of the asphalt mastic, rather than that of the asphalt binder, should provide pertinent information on the mixing and compaction temperatures of asphalt mixture. Apparent viscosities were tested according to the procedure in ASTM D4402 on various types of asphalt mastics. Analyses of test results show that mastic viscosity is a well-defined linear function of temperature in the coordinates defined in ASTM D2493. The binder type, filler type, and dust-to-binder ratio have significant effects on the relationship between temperature and viscosity. A four-parameters model is appropriate to describe the variation of viscosity with temperature and mineral filler content. With the mastic equiviscous concept, the viscosity ranges are 0.576 ± 0.071 Pa-s and 0.968 ± 0.107 Pa-s for mixing and compaction, respectively, for asphalt mastic of unmodified binder, while for asphalt mastic of modified binder, the ranges are binder specific. The type and content of mineral filler have significant effects on the mixing and compaction temperatures. The dust-to-binder ratio of 0.9 for pulverized limestone is equivalent to 0.75 for portland cement and 0.4 for hydrated lime. For a change of 0.1 in dust-to-binder ratio, the mixing and compaction temperatures vary 3.5°C for pulverized limestone mastics, 4.8°C for portland cement mastic, and 9.3°C for hydrated lime mastic. The modified binder does not exhibit any extraordinary behavior in determining the temperatures using mastic viscosity.
Effect of Ultrafine Particles on Linear Viscoelastic Properties of Mastics and Asphalt Concretes
Authors: Delaporte Brice , Di Benedetto Hervé , Chaverot Pierre , Gauthier Gilles
Published: October 2008

A new type of filler, composed of only ultrafine particles (silica fumes), has been used to design mastics and asphalt concretes. An experimental campaign on mastics and mixtures, performed at the ENTPE/DGCB laboratory, compares the effect of the ultrafine particles to that of “classical” fillers. The linear viscoelastic properties (shear complex modulus G*) of mastics have been measured with a specifically developed device (annular shear rheometer) presented in this paper. The potential for reinforcement of fillers is quantified by the complex reinforcement coefficient RM* introduced in this paper. The results show that the use of the ultrafine particles greatly increases the complex modulus of mastics at high temperature, in comparison to mastics made with classical fillers. In the low-temperature region, the complex modulus is little affected by the filler characteristics. The effect of ultrafine particles has also been analyzed for asphalt concretes, which have been tested using a tension compression test on cylindrical specimens, in the small-strain domain. The analysis reveals that the complex modulus E* is higher for the materials containing ultrafine particles at high temperature, as observed for mastics.
Mechanistic Properties of Hot-Mix Asphalt Mixtures Containing Hydrated Lime
Authors: Mohammad Louay N. , Saadeh Shadi , Kabir Md , Othman Ayman , Cooper Sam
Published: October 2008

Permanent deformation and moisture damage are common distresses found in pavements today. The use of hydrated lime is known to decrease moisture susceptibility, and as a mineral filler it increases the stiffness of the mixture. The objectives of this study were (a) to evaluate the fundamental engineering properties of hot-mix asphalt (HMA) mixtures containing hydrated lime compared with conventional mixtures designed to meet the current Louisiana Superpave® specifications and (b) to evaluate the influence of hydrated lime on the mechanical properties of the resulting HMA mixtures. Nine 19.0-mm Level 2 HMA mixtures were designed and examined. Siliceous limestone aggregates that are commonly used in Louisiana were included in this study. The nine mixtures were divided into three sets; each set contained three mixtures. The first set included three mixtures that are conventional, as control mixtures, containing no hydrated lime and an SB polymer-modified asphalt cement meeting Louisiana specifications for PG 76-22M, PG 70-22M, and a neat PG 64-22. The second set included three mixtures that contained hydrated lime that was incorporated into the aggregate and asphalt cement mixture as slurry. The asphalt cements used were identical to the ones used in the first set, namely PG 76-22M, PG 70-22M, and conventional PG 64-22. The third set included three mixtures that contained hydrated lime that was blended dry with the asphalt cements used in the first and second sets, that is, PG 76-22M, PG 70-22M, and PG 64-22. Mechanistic tests were conducted to define the permanent deformation and endurance life of HMA mixtures with and without hydrated lime. The results indicated that the addition of hydrated lime as a mineral filler improved the permanent deformation characteristics of the asphaltic concrete mixtures. This improvement was particularly apparent at higher testing temperatures with mixes containing polymer-modified asphalt and limestone aggregate.
Evaluation of the Use of Reclaimed Asphalt Pavement in Stone Matrix Asphalt Mixtures
Authors: Watson Donald E. , Vargas-Nordcbeck Adriana , Moore Jason , Jared David , Wu Peter
Published: October 2008

This research evaluated the effect of reclaimed asphalt pavement (RAP) on the combined overall performance of stone matrix asphalt mixtures in Georgia. Four types of RAP were combined at four levels (0%, 10%, 20%, and 30%) with four aggregate sources, with the use of a one-fourth fraction factorial design. Granite materials common to Georgia were used exclusively in this study for both RAP and virgin aggregate. Testing was performed to evaluate the binder effect on resistance to moisture susceptibility, rutting potential, thermal cracking potential, and fatigue life of the recycled mixtures. The following main findings are applicable only to the RAP and virgin aggregates used in this study. Virgin aggregate had a greater effect on Los Angeles abrasion loss and percent flat and elongated particles than did the addition of RAP. Increasing RAP content resulted in higher tensile strengths (conditioned and unconditioned) for moisture susceptibility testing. Up to 20% RAP can be used without significantly affecting performance. Only fatigue life (at high strain levels) decreased significantly with the addition of 30% RAP. Fine-graded RAP reduced virgin binder requirements, which translates into increased economic benefits. However, mixes are stiffer because they have higher aged-to-virgin binder ratios and may be more susceptible to fatigue cracking. Adding up to 30% RAP had little effect on low-temperature performance grade properties, which may indicate that the grade of virgin binder does not have to be adjusted to provide the desired low-temperature binder properties.
Effect of Sasobit and Aspha-Min on Wettability and Adhesion between Asphalt Binders and Aggregates
Authors: Wasiuddin Nazimuddin M. , Zaman Musharraf M. , O'Rear Edgar A.
Published: October 2008

The influence of natural wax in asphalt binders and hot-mix asphalt has been studied for decades, with consideration of both negative and positive effects. Recent advances in warm-mix asphalt (WMA) have spurred interest in the use of commercial waxes such as Sasobit and Asphaltan B as additives in asphalt binders to achieve certain positive effects. Despite a number of previous studies, the effect of Sasobit on wettability and adhesion between asphalt binders and aggregates is not fully understood. Likewise, the effect of water vapor released from Aspha-Min, another WMA additive, at production temperatures is not adequately understood, although such water may negatively influence the behavior of WMA. In the present study, the effect of Sasobit and Aspha-Min on wettability and adhesion was investigated using the surface free energy (SFE) method. Dynamic advancing-wetting contact angles were measured for wettability (coating) and dewetting-receding contact angles were measured to evaluate adhesion. It was observed that Sasobit increases the wettability of asphalt binders over aggregates, as indicated by the change in the spreading coefficient. Conversely, a general trend is that Sasobit reduces the adhesion (free energy of adhesion) between asphalt binders and aggregates. In this study, moisture susceptibility is defined as the amount of spontaneously released free energy due to the breaking of the binder-aggregate bond with water. For PG 64-22, a small or no reduction in moisture susceptibility was observed; for PG 70-28, an increase in moisture susceptibility was observed. In case of the Aspha-Min, the overall SFE results are insignificant.
Forecasting Model for Air Taxi, Commercial Airline, and Automobile Demand in the United States
Authors: Baik Hojong , Trani Antonio A. , Hinze Nicolas , Swingle Howard , Ashiabor Senanu , Seshadri Anand
Published: October 2008

A nationwide model predicts the annual county-to-county person round-trips for air taxi, commercial airline, and automobile at 1-year intervals through 2030. The transportation systems analysis model (TSAM) uses the four-step transportation systems modeling process to calculate trip generation, trip distribution, and mode choice for each county origin-destination pair. Network assignment is formulated for commercial airline and air taxi demand. TSAM classifies trip rates by trip purpose, household income group, and type of metropolitan statistical area from which the round-trip started. A graphical user interface with geographic information systems capability is included in the model. Potential applications of the model are nationwide impact studies of transportation policies and technologies, such as those envisioned with the introduction of extensive air taxi service using very light jets, the next-generation air transportation system, and the introduction of new aerospace technologies.
Are Low-Cost Carriers a Bargain?
Authors: Chang Yu-Chun , Lee Ning
Published: October 2008

Low-cost carriers (LCCs) are now a worldwide phenomenon, and Southeast Asia has a significant number of rapidly growing carriers. Ticket price is the main feature that attracts public and media attention. Although the Southeast Asian LCCs declare that they offer the cheapest tickets, there is no solid evidence that their average prices are indeed the lowest. A study was done to examine whether ticket prices of these LCCs are significantly lower than those of full-service carriers (FSCs) or whether low prices are just an advertising trick. The study first looks at why passengers choose LCCs in this region, and then it collects ticket price data for three Southeast Asian LCCs, AirAsia, Jetstar, and Tiger Airways, and two FSCs, Singapore Airlines and Malaysia Airlines, that are based in the same countries. The differences in ticket prices between LCCs and FSCs are analyzed by applying the t-test. The analysis reveals that the ticket prices of the three LCCs are indeed lower than those of the two FSCs. In general, the disparity between the ticket prices of FSCs and LCCs is about US$0.166 per km. The LCC ticket price can be even lower because of competition in the routes run by both FSCs and LCCs. The study concludes that passengers who travel with LCCs because of lower ticket prices need to book earlier and must be willing to forego a number of services and conveniences.
Cost of Aviation Infrastructure in the United States
Authors: Karlsson Joakim , Odoni Amedeo , Gaudet Megan Brett
Published: October 2008

What portion of the total amount spent annually on commercial air transportation in the United States eventually goes toward paying for infrastructure, including capital, operational, and security-related costs? Previously unavailable data provided by 10 large carriers are used to estimate the amounts paid through various domestic and international taxes and fees as well as the amounts paid directly by the airlines for airport and air traffic management infrastructure. At least 85% of the survey results can be confirmed through publicly available sources. Combined data sources are used to conclude that in 2004, infrastructure-related costs accounted for approximately 15% of the total amount spent by consumers for passenger and cargo air transport. This would make infrastructure-related costs the third largest category in 2004 (with labor first and fuel second). This conclusion contrasts with conventional wisdom: because of incomplete accounting and data fragmentation, the full magnitude of infrastructure-related costs often is not understood, and these costs are treated as relatively minor.
Short-Haul Airline Crew Rostering by Using Inequality-Based Multiobjective Genetic Algorithm
Authors: Jeng Chi-Ruey , Liu Tung-Kuan , Chang Yu-Hern
Published: October 2008

A novel method of inequality-based multiobjective genetic algorithm (MMGA) is presented for solving the airline crew rostering problem. This approach combines a traditional genetic algorithm with a multiobjective optimization method to address multiple objectives at the same time and to explore the optimal solution. With the method of inequalities, the objective can be modified to update different requirements. Therefore, the proposed MMGA approach has the advantages of global exploration and robustness. There are numerous local optima in airline crew rostering problems, so the problem is challenging to evaluate by using genetic algorithm-based approaches. Computational experiments show that the proposed method can obtain better and more robust results than those of manual rosters made by rosterers who have many years of experience. The research objective was to solve the complex airline crew rostering problem by using the MMGA approach and to demonstrate that this method can reduce the solution time. The proposed method is successfully applied to a domestic short-haul airline. It helps managers find a high-quality, feasible roster and reduce crew-related costs in crew rostering applications.
Multifactor Model for Predicting Delays at U.S. Airports
Authors: Xu Ning , Sherry Lance , Laskey Kathryn Blackmond
Published: October 2008

Traffic flow management (TFM), in coordination with airline operation centers, manages the arrival and departure flow of aircraft at the nation's airports on the basis of airport arrival and departure rates for each 15-min segment throughout the day. The management of traffic flow has become so efficient in the United States that approximately 95% of delays now occur at the airports (not while airborne). Inefficiencies in traffic flow occur when nontraffic flow delays (e.g., carrier, turnaround, aircraft swapping, and local weather delays) are superimposed on the traffic flow delays. Researchers have correlated these nontraffic flow delays at airports with sets of causal factors and have created models to predict aggregate delays at airports on the time scale of a day. To be consistent with the way traffic flow is managed, a model of causal factors of delays in 15-min increments would provide the basis for improving the efficiency of TFM. The development of multifactor models for predicting airport delays in 15-min epochs at 34 operational evolution plan airports is described. The models are created by using multivariate adaptive regression splines. The models, generated by using historic individual airport data, exhibit an accuracy of 5.3 min for generated delay across all airports and 2.1 min for absorbed delay across all airports. A summary of the factors that drive the performance of each airport is provided. The implications of these results are discussed.
Statistical Comparison of Passenger Trip Delay and Flight Delay Metrics
Authors: Wang Danyi , Sherry Lance , Xu Ning , Larson Melanie
Published: October 2008

The primary objective of the National Airspace System (NAS) is the transportation of passengers and cargo. Since passenger trip time performance is positively correlated with passenger satisfaction, airfare elasticity, and airline profits, it follows that the evaluation of performance and modernization of the NAS, as well as consumer protection, should be based on passenger trip performance (in addition to airline flight performance). Publicly available regulatory measures of NAS performance, however, are based on flight data and not passenger trip data. Researchers have demonstrated that the trip delays experienced by passengers disrupted by missed connections, canceled flights, and diverted flights are not negligible. Further, research demonstrated that flight delays are a poor proxy for measuring passenger trip delays. A comparative statistical analysis is described between flight delay data and estimated passenger trip delay data for 1 year's worth of flights on the 1,030 single-segment routes between the 35 [airports of FAA's Operational Evolution Partnership (OEP)]. The estimated passenger trip data are derived from publicly available databases and account for delays experienced by passengers on single-segment routes because of canceled flights as well as delayed flights. The statistical analysis indicates that (a) the estimated percentage of on-time passengers is equal to the percentage of on-time flights plus the percentage of canceled flights, (b) the estimated average passenger trip delay is 34 min in excess of the average flight delay, and (c) estimated average passenger trip delay for the worst 5% of delayed passengers is 150 min in excess of the flight delay. The implications of these results for consumers, industry performance measures, and FAA modernization efforts are discussed.
Real-Time Intermodal Substitution
Authors: Zhang Yu , Hansen Mark
Published: October 2008

A strategy for airline recovery from schedule perturbation caused by adverse weather or other temporary events is proposed. Capacity reduction at a hub airport caused by these temporary events is reflected as reduced slots (or later controlled time of arrivals) for airlines from ground delay programs. It is suggested that under severe circumstances legacy airlines with hub-and-spoke networks implement ground transportation into their network to substitute for flights. This strategy is called real-time intermodal substitution (RTIMS). RTIMS is different from air-rail cooperation practiced in Europe in that it is triggered only by a severe demand and supply imbalance at major hub airports and it performs operational integration of airside and ground transportation. Mathematical programming is presented to help airlines make decisions about if and how to delay, canceling flights, or substituting flights with buses. An approximation algorithm is proposed to obtain solutions, avoiding substantial computation time required to solve large-scale nonlinear integer programming. As an evaluation, experimental data are used to compare scenarios with and without tactical intermodal substitution.
Applications of Geographic Information System in Airfield Infrastructure System Management and Maintenance
Authors: Ho Chun-Hsing , Romero Pedro
Published: October 2008

New geographic information system (GIS) applications in airfield infrastructure system management and maintenance are discussed. Aviation activity is steadily increasing, and U.S. airport facilities must provide higher service quality and must increase capacities to accommodate projected aviation growth. In response to the increasing requirements from passengers and airliners, efficiency is the most important factor in airport operations and airfield facilities maintenance. Airport authorities, particularly at large commercial airports, increasingly understand the benefits in using GIS-based programs to plan and manage their airport facilities. An integrated GIS system combined with Geographic Positioning Systems and personal digital assistants provides a powerful tool that helps airport operators and engineers improve regular airfield inspection, management, and reporting processes, resulting in a more efficient airport operation system. GIS applications associated with other tools are introduced, and airport personnel are given several easy-to-learn GIS approaches and techniques. This is intended to help airports improve current airfield facility inspection processes and maintenance mechanisms. An implementation plan achieved at Kaohsiung International Airport in Taiwan was used to demonstrate how an integrated GIS system can help airport operators and engineers receive real-time facilities data, evaluate deterioration rates, and make policy decisions on maintenance and rehabilitation within a short time. This implementation plan is designed on a step-by-step basis that allows airport personnel to easily follow and apply the system to airport practice. Another example carried out at Salt Lake City International Airport (SLC) in Utah was used to show GIS applications in facilitating skid resistance evaluation of runway surfaces. By adding projection data to the airport image, SLC airport maintenance crews can graphically evaluate friction capacities of Runway 16L-34R and investigate potential factors that result in a reduction of skid resistance. Up-to-date GIS application approaches are shown so that airport personnel may develop a suitable GIS system that enables airports to improve their operation systems and increase aviation safety.
Sensitivity Analysis of Engineered Material Arrestor Systems to Aircraft and Arrestor Material Characteristics
Authors: Heymsfield Ernest , Halsey Tyler L.
Published: October 2008

In most aircraft overruns, an aircraft comes to a stop within 1,000 ft (305 m) of the runway threshold. In response, U.S. airfields are required by FAA to have a 1,000-ft runway safety area in addition to the design runway length in case of aircraft overruns. At airfields where space is limited, airport operators need to consider alternative solutions. One solution is for an airport operator to reduce runway length and therefore limit aircraft types landing at their airport. Conversely a more attractive solution is for an airport to implement an engineered material arrestor system (EMAS). An EMAS is a passive system comprising a cementitious type material. Aircraft deceleration occurs because of drag forces that are incurred by the aircraft landing gear as the aircraft passes through and crushes the arrestor material. Parameters significantly influencing a B727 or B747 aircraft's stopping distance as it traverses an EMAS are presented. The computer code, ARRESTOR, developed for FAA, was used to compute the aircraft stopping distances. Five aircraft parameters (mass moment of inertia, weight, wheel friction, reverse thrust, and center of gravity location) for each aircraft type are examined, along with two arrestor material types (low-density concrete and phenolic foam) and three arrestor bed geometries. Each parameter is individually varied to investigate stopping distance sensitivity. Twenty-one overrun simulations were used in the aircraft parameter study, and 100 overrun simulations were used to determine an optimal material compressive strength. Arrestor bed geometry was investigated by using 32 overrun simulations. Study results are summarized in plots and tables.
Comparative Analysis of Regional Airline Industry in Europe and North America and Some Insight into Current Developments
Authors: Dennis Nigel , Smyth Austin , Stevens Ken
Published: October 2008

The regional airline industry in Europe and North America is compared, and through a combination of data analysis and case studies, some of the current changes taking place are investigated. North American regionals are shown to have longer stage lengths, lower unit costs, and higher load factors than their European counterparts. Turboprops remain popular in Europe, but 50-seat jets still dominate in the United States, despite being considered inefficient because of high unit costs and pressure on yields. The bankruptcy of most U.S. legacy carriers has led to renegotiation of contracts for regional flying, with prices being driven down. European regionals face different problems with rail competition, capacity constraints at hub airports, and incursion by low-cost airlines. The differences in the cost structures of BA Connect, British Airways’ former regional arm, and Flybe, operating a new hybrid format, are interpreted, and it is shown that Flybe has much lower labor costs. Alternative business models are then discussed. In the United States, the most popular is the sale of capacity to the majors, whereas in Europe many operate on a quasi-independent franchise basis. It is concluded that European regionals require more action to reduce costs, whereas U.S. regionals will increasingly have to take more of the risk from their major carrier partners. A renewed enthusiasm for turboprops on short sectors is becoming apparent, and the European markets in particular are likely to see a shift to larger aircraft at lower frequency. This puts at risk the schedule convenience and network connections valued by business passengers.
Fly Ash-Calcium Chloride Stabilization in Road Construction
Authors: Saylak Don , Mishra Surendra K. , Mejeoumov Gleb G. , Shon Chang-Seon
Published: October 2008

Both fly ash and calcium chloride have been used in a wide variety of roadway construction applications. Engineering applications of both Class C and Class F fly ashes include portland cement concrete, soil and road base stabilization, flowable fills, grouts, structural fills, and asphalt filler. Until recently, the primary roadway application for calcium chloride has been as a dust-controlling agent on unsurfaced roads. Ongoing research at Texas A&M and Texas Transportation Institute has concluded that when the two are strategically combined within a roadway mix design, their individual mineralogical and physicochemical characteristics interact to further enhance the service performance of the roadway. Although the fines content in the roadbed composition is critical, there is a synergistic effect on the strength generated when calcium chloride is added along with fly ash. This synergistic blending of fly ash and calcium chloride is referred to as “surface-activated stabilization.’'