Comparing rutting of airfield pavements to simulations using Pavement Analysis Using Nonlinear Damage Approach (PANDA)

This study presents the rutting performance results of full-scale pavement test sections subjected to F-15E and C-17 aircraft wheels at two different temperatures. Pavement structures for the tests were constructed under shelter in the U.S. Army Engineer Research and Development Center's (ERDC) pavement test facility. The full-scale test results are used to validate viscoelastic, viscoplastic and hardening-relaxation constitutive relationships implemented in the Pavement Analysis Using Nonlinear Damage Approach (PANDA) model. PANDA is a mechanistic-based model which incorporates nonlinear viscoelastic, viscoplastic, hardening-relaxation, viscodamage, moisture-induced damage and ageing constitutive relationships. Results of dynamic modulus and different repeated creep-recovery laboratory tests are analysed to extract the parameters associated with viscoelastic, viscoplastic and hardening-relaxation constitutive relationships implemented in PANDA. Once calibrated, PANDA is used to predict the rutting performance observed in full-scale pavement test sections. The simulation results illustrate that PANDA is capable of predicting the rutting of airfield pavements subjected to heavy aircraft wheel loads at intermediate and high temperatures. It is shown that PANDA successfully predicts the effect of shear flow and upheaval at the edges of the wheel. The data from simulation suggested that PANDA, once calibrated, can provide insight into the critical locations of tensile and compressive stresses within the pavement structure. PANDA simulations not only provide a tool for evaluating existing structures, but also can be used in designing more sustainable pavement structures and materials.     

Semi-empirical model for polyelectrolyte intrinsic viscosity as a function of solution ionic strength and polymer molecular weight

Elements of Odijk-Skolnick-Fixman and Yamakawa-Fujii polymer solution theories have been modified to create a new model that correlates flexible coil polyion intrinsic viscosity behavior with solvent and polymer properties. A new dimensionless viscosity is derived and is successfully related to the dimensionless ratio of Debye-Hückel screening length to polyion charge spacing and the degree of polymerization. The model has been applied to intrinsic viscosity data reported in the scientific literature and to data collected in our laboratory, all using sodium chloride solutions ranging in ionic strength. Multiple molecular weight fractions of six compositionally different polyelectrolytes were used to obtain 73 intrinsic viscosity versus ionic strength data points for model analysis. Regression analysis was applied to empirically determine the relationships between the dimensionless groups. The resulting model equation was found statistically adequate in describing the entire data set.     

Gastrin-releasing peptide1-27, unlike bombesin, does not reduce sham feeding in rats

We compared the potencies of systemic administration of bombesin (BN) and its mammalian homologue gastrin-releasing peptide (GRP) to decrease sham feeding in rats. Bombesin (at doses of 8, 16 and 32 micrograms/kg, intraperitoneally) inhibited sham feeding by 37% (p < 0.001), 58% (p < 0.001) and 65% (p < 0.001), respectively, confirming previous results. Gastrin-releasing peptide (16, 32, and 64 micrograms/kg) failed to affect sham feeding. Bombesin (16 micrograms/kg) and gastrin-releasing peptide (32 micrograms/kg) inhibited real feeding by 64% (p < 0.001) and 44% (p < 0.004), respectively. Pregastric food stimulation is not sufficient for the inhibitory action of GRP.     

International stratification and the health of women: an empirical comparison of alternative models of world-system position

Women's health status is investigated in the context of stratification in the world-system. We investigate three alternative conceptualizations of the world-system for their effects on women's health status, using country-level data. The models investigate the effects of world-system position, military expenditures, and health resources on women's health status. Comparison of the alternative conceptualizations of world-system position indicate that a continuous model is only negligibly better than three- or five-block models at explaining women's health status. Regardless of how it is measured, world-system position has dramatic effects on women's health.     

Antioxidant nutrient intake and diabetic retinopathy: the San Luis Valley Diabetes Study

OBJECTIVE: Diabetic retinopathy (DR) is a major cause of visual impairment and blindness in adults. Antioxidant nutrients, such as vitamins C and E and beta-carotene, may be protective of some eye disorders, such as cataract and age-related macular degeneration, but a relationship between these nutrients and DR has yet to be defined. The purpose of this study was to examine the relation between dietary and supplement intakes of vitamins C, E, and beta-carotene and the risk of DR. DESIGN: Both cross-sectional and longitudinal data were collected from participants in the San Luis Valley Diabetes Study, including non-Hispanic white and Hispanic adults in southern Colorado. PARTICIPANTS: A total of 387 participants with type 2 diabetes completed at least 1 complete retinal examination and 24-hour dietary recall (including vitamin supplement use). MAIN OUTCOME MEASURES: Type 2 diabetes was defined according to World Health Organization criteria. DR was assessed by retinal photographs, using the Airlie House criteria to classify DR as none, background, preproliferative, or proliferative. Data for both eyes, from up to three clinic visits per participant, were used for analysis. Ordinal logistic regression analysis was used, taking advantage of multiple clinic visits by individual participants and observations from both eyes, to assess the risk for increased DR severity over time as a function of changes in intake of vitamin C, vitamin E, and beta-carotene. Six categories of intake for each nutrient (first to fourth quintiles and ninth and tenth deciles) were considered to ascertain any potential threshold effect. Analyses accounted for age, duration of diabetes, insulin use, ethnicity, glycated hemoglobin, hypertension, gender, and caloric intake. RESULTS: An increase over time in vitamin C intake from the first to ninth deciles was associated with a risk for increased severity of DR (odds ratio = 2.21, P = 0.01), although excess risk was not observed for the tenth decile or the second through fourth quintiles compared to the first quintile. Increased intake of vitamin E was associated with increased severity of DR among those not taking insulin (odds ratios = 2.69, 2.59, 3.33, 5.65, 3.79; P < 0.02, for an increase over time from the first to the second through fourth quintiles and ninth and tenth deciles, respectively). Among those taking insulin, increased intake of beta-carotene was associated with a risk for severity of DR (odds ratio = 3.31, P = 0.003, and 2.99, P = 0.002, respectively, for the ninth and tenth deciles compared to the first quintile). CONCLUSIONS: No protective effect was observed between antioxidant nutrients and DR. Depending on insulin use, there appeared to be a potential for deleterious effects of nutrient antioxidants. Further research is needed to confirm associations of nutrient antioxidant intake and DR.     

Erfahrungsaustausch und Schadensfälle. Heat exchanger failure through thermal creep stresses

A 4″ ID, 310 SS finned pipe was used as a heat exchanger between an external gas stream at 1660–1740°F and an internal gas stream at 315°F. Failure occurred through multiple circumferential cracks, which found their origin in extensive separations at the grain boundaries on the ID, penetrating as much as 0.150″ (50% of wall thickness). It was found that that the metal temperature ranged from 1200°F at the ID to in excess of 1400°F at the OD. Therefore the ID was exposed to creep stresses at a level of 35 ksi. Since at shutdown the metal could not recover, these creep stresses accumulated at each start-up. Finally system stresses caused the remaining wall thickness to failure. Transposition of the fins from the OD to the ID, or even omission of the OD fins would lower temperatures as well as stress levels sufficiently to prevent this type of failure.     

An InGaP/GaAs Merged HBT-FET (BiFET) Technology and Applications to the Design of Handset Power Amplifiers

The last decade has seen GaAs HBTs emerge as the dominant technology in wireless handset power amplifiers. Modern application requirements and size limitations have driven industry leaders towards the co-integration of depletion mode n-FET and GaAs HBT. The merger of Bipolar and FET, or BiFET, gives an additional degree of freedom in the design of advanced power amplifiers independent of a silicon controller. This paper provides an overview of the various techniques that can be used to join the two device technologies and then shows how a merged epitaxial structure, where an FET is formed in the emitter layers of an HBT, combines functional versatility with the high volume manufacturability needed to supply millions of power amplifiers at low cost. A large-signal model of the FET structure is developed which takes into account the unique physics and geometries of the device, including voltage-dependant parameters and charges on all four electrical terminals. Specific handset applications that can benefit or be enabled by BiFET are presented, such as on-off switching, low voltage bias controllers , Auto-Bias power amplifiers, and bias circuits with low or no voltage reference. When npn-only bias circuitry is limited to low voltage reference levels, HBT power amplifiers with BiFET bias stages are shown to have superior RF performance to their npn-only counterparts.     

Effect of aluminium solids and chlorine on cold water pitting of copper

Both aluminium solids and chlorine are often present in potable water systems, but their effect on copper corrosion and pitting is not well understood. Circumstantial evidence from one system with copper pitting problems suggested that high chlorine residuals and aluminium solids might be contributing factors. To test this hypothesis, a series of experiments were conducted to examine their effect on copper corrosion under stagnant and flow conditions. Although chlorine alone impacted copper corrosion, a synergistic reaction was discovered between chlorine and aluminium solids when exposed to copper. Evidence for this effect was seen in increased chlorine decay rates, increased non-uniform copper corrosion, and rising corrosion potentials during exposure. It is likely this reaction is involved in copper pit initiation.     

Altered feeding responses in mice with targeted disruption of the dopamine-3 receptor gene.

Dopamine signaling has been implicated in the control of food intake and body weight. In particular, dopamine is important in the control of meal size and number and is thought to mediate the response to metabolic deprivation states. In the present experiments, the authors assessed the role of the dopamine-3 receptor (D?R) in the feeding responses to 2-deoxy-D-glucose, mercaptoacetate, and peripheral insulin. All 3 compounds increased food intake in wild-type mice, but the hyperphagic responses were blunted in D?R-/- mice. In other experiments, D?R-/- mice were hyperresponsive to the administration of amylin and leptin relative to wild-type mice. These results support the hypothesis that D?Rs chronically inhibit the effects of adiposity hormones, thereby contributing to a net anabolic state. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Image segmentation using association rule features

A new type of texture feature based on association rules is described. Association rules have been used in applications such as market basket analysis to capture relationships present among items in large data sets. It is shown that association rules can be adapted to capture frequently occurring local structures in images. The frequency of occurrence of these structures can be used to characterize texture. Methods for segmentation of textured images based on association rule features are described. Simulation results using images consisting of man made and natural textures show that association rule features perform well compared to other widely used texture features. Association rule features are used to detect cumulus cloud fields in GOES satellite images and are found to achieve higher accuracy than other statistical texture features for this problem.