•Provides models that use only nominal inputs to make reliable property estimates during design phase.•Presents generalized regression framework for developing asphalt property prediction ...models.•Model is verified through statistical comparisons and comparisons with other predictive models.•Application of proposed model for pavement performance prediction is demonstrated.
Dynamic modulus (|E∗|) and phase angle (δ) are necessary for determining the response of asphalt mixtures to in-service traffic and thermal loadings. While a number of |E∗| and δ predictive models have been developed, many of them require lab measured properties (e.g. binder complex modulus). The majority of previous work has focused only on prediction of |E∗|, limited models exist for prediction of δ. This research utilized generalized regression modelling of lab measurements (from 81 asphalt mixtures) to develop and verify prediction models for |E∗| and δ using only nominal asphalt mix properties that are readily available during the initial mixture design and specification process.
This paper presents a generalized framework for determining mechanistically informed layer coefficients (a-values) for asphalt mixtures in the AASHTO empirical pavement design approach. The layer ...coefficients influence the layer thicknesses and consequently the structural capacity of pavements. Therefore, it is critical to determine reliable mechanistically informed a-values. A set of 18 commonly used asphalt mixtures in New Hampshire was selected for investigation including different types of hot mix and cold central plant recycled mixtures that are used as wearing, binder, and base course layers. Laboratory characterization was conducted using the complex modulus, semi-circular bend, and direct tension cyclic fatigue testing methods. The mixtures were evaluated using three performance index parameters: complex modulus rutting index parameter, rate-dependent cracking index parameter, and a new continuum damage parameter (
N
f
at
C
N
f
S
=
100
). The measured field performance of wearing course mixtures in terms of International Roughness Index was used to back-calculate the in situ performance-based layer coefficients (aIRI-values). Using a normal distribution function, the results from performance testing were incorporated with the aIRI-values to develop mechanistically informed mix-specific layer coefficients. In addition, a typical layer coefficient at specific reliability levels for each mix category including hot mix wearing course, hot mix binder and base course as well as cold central plant recycled mix course are proposed for New Hampshire. The recommended a-values are 0.48 for hot mix wearing, 0.41 for hot mixed binder and base, and 0.28 for cold recycled base mixtures; these are approximately 25% higher than the currently used a-values in New Hampshire.
Background
Helicobacter pylori
(
H. pylori
) colonizes human gastric mucosa and is classified as class one carcinogenic bacteria. In this regard, this study aimed to detect major virulence factors in
...H. pylori
strains recovered from gastric biopsy in patients referred to Aras Clinique in Ardabil, northwest of Iran (2019–2021).
Materials and methods
In this descriptive-cross sectional study, 287 dyspeptic patients were included. For bacterial isolation, gastric biopsy specimens (n=287) were taken from gastric antrum, then aseptically were cultured on the selective medium and incubated at 37C in microaerophilic conditions for 3-5 days.
Results
25.18% of all (n = 70) patients were found to be infected with
H. pylori
upon endoscopy. Of them, 9 patients (12.857%) and 2 patients (2.875%) had peptic ulcer disease and gastric cancer respectively. According to the different patterns of virulence factors, 57 virutypes were identified in which
oipA-vacAs1-vacAm2
(3, 4.28% n =) and
oipA-vacAs1-vacAs2-vacAm2
(3, 4.28% n =) were the most common patterns. The simultaneous presence of
vacAS2
,
vacAm2
and
hopQ2
genes was observed in both patients with gastric cancer. OipA (n = 562.5%), VacAs1 (n = 6.75%), VacAs2 (n = 6.75%), and VacAm2 (n = 787.5%) were found to be the most prevalent virulence factor.
Conclusion
According previous studies, it is confirmed that the
cag
PAI gene cluster and
vacA
gene alleles are strongly correlated with gastritis and gastrointestinal tract adenocarcinomas. Our study indicated that 50% of the indigenous strains of
H. pylori
harbor these oncogenic genes and they are hypervirulent.
Depending on the local conditions and structural design of the pavement, multiple asphalt concrete layers including base, intermediate, and wearing courses are used. Typically, the base and ...intermediate layers have larger aggregate sizes and lower total asphalt binder contents as compared with the wearing course. Recently, cold recycled (CR) asphalt mixtures have gained attention as an alternative to the typical base, and to some extent intermediate courses, because of economic and environmental advantages. Challenges with CR include the potential high variability of recycled asphalt pavement (RAP) and lack of knowledge in relation to structural contribution and long-term performance of such layers. This study investigates four different types of CR and four hot mixed plant-produced asphalt mixtures (three intermediate courses and one base course) that are typical mixtures used in New Hampshire. The laboratory performance evaluation is conducted through the resilient modulus (Mr), complex modulus (E*), semi-circular bend and direct tension cyclic fatigue (S-VECD) tests. Pavement performance prediction is carried out using the results from S-VECD approach in the FlexPAVETM software. The test results indicate that the performance of CR is highly affected by the amount of oil distillate percentage in the emulsion as well as the amount of recovered binder in the RAP. While having a relatively lower rutting resistance capability, the CR mixtures maintained an acceptable fatigue performance. As compared with CR mixtures, hot mixed intermediate and base course mixtures indicated better rutting performance while having lower resistance to cracking.
Use of the semi-circular bending (SCB) test has gained popularity for evaluating cracking performance of asphalt mixtures. An Illinois Flexibility Index Test (I-FIT) variant of SCB has shown the ...ability to distinguish mixtures through use of the flexibility index (FI) parameter. While this index has been able to rank the mixtures with respect to performance, a high coefficient of variation (COV) among the replicates has often been observed. Furthermore, parameters such as total fracture energy and FI do not incorporate rate dependency of fracture processes which are very important for viscoelastic materials such as asphalt mixtures at low and intermediate temperatures. In light of these observations, a rate-dependent cracking index (RDCI) is proposed that utilises cumulative fracture work potential and instantaneous power calculated from the I-FIT test to assess impulse of the mixture. Thus, in spirit, this parameter captures the fracture energy and crack velocity of the material; however, these are calculated in a rate-dependent manner. A total of 18 surface course mixtures were analysed using the RDCI and resulted in an average overall reduction of 10.6% in COV as compared to FI while maintaining similar ranking of mixtures. In general, RDCI was able to better discriminate the 18 mixtures as compared to FI. The evaluation of five mixtures at three aging levels showed the robustness of RDCI in capturing effects of aging on fracture behaviour of asphalt mixtures.
The use of quality assurance (QA) processes in highway infrastructure is critical to ensure durable, safe, and economical transportation operations. These processes ensure the desired level of ...quality is maintained throughout manufacturing. Precast and pre-stressed concrete elements are commonly used in highway construction projects, including many bridge elements and drainage components. Owing to their widespread usage, it is necessary to have a comprehensive QA process that includes plant certification, manufacturer’s process and quality control, and agency inspection and acceptance testing. In many cases, one manufacturing plant will serve a region, fabricating a variety of elements for many state departments of transportation (DOTs). Since different state DOTs may have different QA processes in their specifications, the plants need to adjust the fabrication process with respect to these criteria, which results in higher expenses and lower productivity. Furthermore, each agency will need to provide inspection and acceptance testing resources at a fabricator’s location. This study reviews and evaluates the current QA processes for precast and pre-stressed concrete elements used in highway construction in the New England region. Based on a review of current practices, a set of unified QA process recommendations have been developed. This will result in significant financial savings by reducing the number of QA inspectors if the manufacturers for different construction projects around the region follow a unified procedure for maintaining and evaluating the quality of their products. Recommendations for plant/producer prequalification, pre-placement, during placement, and post-placement quality control and agency inspection practices have been developed and are presented.
A variety of approaches are available to design the pavement structures. These approaches are generally divided into two main categories as empirical and mechanistic-empirical (M-E) methods. The most ...widely used empirical method is the AASHTO 1993 design approach which uses material specific coefficients (layer coefficients) to quantify the structural capacity provided by each pavement layer. These coefficients are experimentally developed values from the AASHO road test which was conducted in the early 1960s and are based on statistical regressions. Almost no fundamental or engineering mixture properties or explicit failure criterion were used in their original development. On the other hand, the M-E approaches use fundamental mixture properties such as complex modulus (E* and phase angle) to determine the pavement’s structural response. However, M-E approaches require extensive data for local calibration and as a results, many state agencies are still using the empirical approach. One of the major modifications in the AASHTO 1993 design approach has been to update the layer coefficients (a-value) of the asphalt mixtures using different mechanistic and performance-based measures. The layer coefficients have significant influence in determining the layer thickness which translates into the structural contribution of the layers as well as the long term performance of the pavement and consequently the construction and maintenance costs. Therefore, it is critical to determine reliable a-values that are most relevant to the regional conditions and locally used materials. A set of 18 commonly used mixtures in New Hampshire were selected for performance testing and evaluation of structural contribution in terms of layer coefficients. In order to develop the layer coefficients, comprehensive research was performed on the performance and properties of the mixtures through different mechanistic-based laboratory testing methods. In addition, mixtures from all over the New England region were used to develop and validate three novel performance index parameters for rutting, fatigue and transverse cracking. The developed parameters were incorporated with the field distress data such as International Roughness Index (IRI) in order to develop mechanistically informed layer coefficients for New Hampshire flexible pavement design approach.
One of the most influential variables in determining the performance-based properties of the asphalt mixtures is the specimen fabrication method. This study investigates the impact of specimen ...fabrication methods through a comprehensive study of six test sections constructed in 2011that include a range of RAP contents and two different virgin binders. Complex modulus and fatigue characterisation was conducted on asphalt binders and mixtures. Three specimen fabrication methods were evaluated: specimens compacted from plant sampled loose mix with and without reheating, and specimens fabricated from raw materials in the laboratory. Predicted performance from lab tests were compared to field performance. The mixtures with PG 58-28 binder showed expected trends with increasing RAP content (higher modulus, lower phase angle); however, mixes with PG 52-34 did not. Similar trends were observed for specimens fabricated with plant mix (not reheated), and the specimens fabricated with raw materials in the lab. Binder results and performance prediction using the plant mix agree with the observations in the field.
Eosinophilic gastroenteritis is a rare disease characterized by focal or diffuse eosinophilic infiltration of the gastrointestinal system. The clinical presentation is depending on the involved area ...and its extension into the layers of the gastrointestinal tract. We repor ted a case of eosinophilic gastroenteritis in the setting of cryptogenic cirrhosis which initially appeared as a tumoral obstruction of the 3rd portion of duodenum which is relieved by surgical bypass and two years later presented as eosinophilic ascitis. The patient was treated with corticosteroid with full absorption of ascitis.
Obesity has become a common global problem. Some obese people can be metabolically healthy. Gene-environment interaction can be important in this context. This study aimed to assess the interaction ...between dietary fat quality indices and the Melanocortin 4 receptor (MC4R) gene in metabolically healthy and unhealthy overweight and obese women. This cross-sectional study was conducted on 279 women with overweight and obesity. The definition of metabolically healthy and unhealthy phenotypes was done according to Karelis criteria. Dietary assessment was done using a 147-item validated semi-quantitative food frequency questionnaire and dietary fat quality was assessed by cholesterol-saturated fat index (CSI) and the ratio of omega-6/omega-3 (N6/N3) essential fatty acids. MC4R was genotyped by polymerase chain reaction-restriction fragment length polymorphism technique. A generalized linear model was used to evaluate the interaction between dietary fat quality indices and the MC4R gene in both crude and adjusted models. Study subjects with higher ratio of N6/N3 had higher homeostatic model assessment for insulin resistance (HOMA IR) index (P = 0.03) and other variables showed no difference according to the tertile of CSI and N6/N3. Participants with the C allele of MC4R rs17782313 had lower height (P < 0.001) and higher HOMA index (P = 0.01). We found that the CC genotype of MC4R interacts with the N6/N3 ratio on the metabolically unhealthy phenotype in the crude model (β = 9.94, CI 2.49-17.39, P = 0.009) and even after adjustment for all confounders (β = 9.002, CI 1.15-16.85, P = 0.02, β = - 12.12, CI 2.79-21.46, P = 0.01). The data of this study can justify one inconsistency observed in society, regarding dietary recommendations about metabolic health status. Those with CC genotype, are more likely to have an unhealthy phenotype with an increase in N6/N3 as one fat quality indices than those who do not have CC genotype. We found the interaction of dietary fat quality indices such as N6/N3 and the MC4R gene in metabolically unhealthy overweight and obese women.
