Evaluation of Laminated Circular Elastomeric Bearings

This paper evaluates the behavior and performance of laminated circular elastomeric bearings and compares them to those of square and rectangular bearings. The study included an experimental evaluation and a nationwide survey of state Department of Transportations on the use and performance of circular bearings and bearings in general in their states. The experimental investigation studied the bearings' behavior in compression, compression and rotation, and compression and shear. Results from this limited study showed that the three bearings have similar stress-strain behavior in compression and they are in agreement with the AASHTO LRFD guide stress–strain curves. In compression and rotation, the AASHTO LRFD substructure moments are slightly less than the measured values for circular bearings and rectangular bearings rotated about their strong axis for a compressive stress of 10.3?MPa (1.5?ksi) and slightly higher than those of rectangular bearings rotated about their weak axis. In compression and shear, the shear stiffness of circular and square bearings is in agreement with theoretical values within the range of design displacements. Results from the survey showed that many states are using circular bearings and more states would consider using them, however no maintenance or monitoring data were available on their short-term and long-term performance.     

Vitek system antimicrobial susceptibility testing of O1, O139, and non-O1 Vibrio cholerae

Vibrio cholerae causes epidemic diarrhea throughout the world. Fluid replacement is the primary therapy for cholera; however, high mortality rates often necessitate the use of antibiotics. V. cholerae, like most bacteria, has developed resistance to some antibiotics. In the early 1990s a new serotype strain, Bengal 0139, began a new wave of cholera epidemics. Bengal isolates showed unique trends in antimicrobial resistance. Many clinical laboratories use automated antibiotic susceptibility testing for V. cholerae. It is important to know if automated susceptibility test results for V. cholerae coincide with reported trends in antibiotic susceptibility. In the present study, we used the Vitek automated susceptibility system to determine the susceptibilities of 79 V. cholerae O1 isolates, 100 O139 isolates, and 112 non-O1 isolates. Vitek susceptibilities for V. cholerae showed a good correlation with preestablished epidemiological data. Although the new O139 serogroup showed a trend of increased resistance to trimethoprim-sulfamethoxazole and nitrofurantoin, it was more susceptible to ampicillin than previous serogroup O1 and non-O1 strains. Regardless of serogroup, > or = 98% of the V. cholerae isolates tested were susceptible to most antibiotics tested by us. It is important to continue susceptibility testing of all new isolates of V. cholerae because of emerging resistant strains. However, V. cholerae remains susceptible to most of the available antibiotics.     

The effect of hydrogen in the mechanism of aluminum-induced crystallization of sputtered amorphous silicon using scanning Auger microanalysis

The metal-induced crystallization (MIC) of hydrogenated sputtered amorphous silicon (a-Si:H) using aluminum has been investigated using X-ray diffraction (XRD) and scanning Auger microanalysis (SAM). Hydrogenated, as well as non-hydrogenated, amorphous silicon (a-Si) films were sputtered on glass substrates, then capped with a thin layer of Al. Following the depositions, the samples were annealed in the temperature range 200 °C to 400 °C for varying periods of time. Crystallization of the samples was confirmed by XRD. Non-hydrogenated films started to crystallize at 350 °C. On the other hand, crystallization of the samples with the highest hydrogen (H₂) content initiated at 225 °C. Thus, the crystallization temperature is affected by the H₂ content of the a-Si. Material structure following annealing was confirmed by SAM. In this paper, a comprehensive model for MIC of a-Si is developed based on these experimental results.     

Magnetocaloric Effect in Sr0.4Ba1.6−x La x FeMoO6

Magnetocaloric effect in half-metallic double perovskite Sr_0.4Ba_1.6?x La _x FeMoO₆ (x = 0, 0.1, 0.2, 0.3) were investigated. It is shown that Sr_0.4Ba_1.6?x La _x FeMoO₆ exhibits the largest magnetic entropy change (ΔS _M ) of 0.086 J/kg K upon 0.2 T magnetic field variation. Furthermore, ΔS _M distribution of the Sr_0.4Ba_1.6?x La _x FeMoO₆ is much more uniform than that of gadolinium. Through these results, polycrystalline samples of Sr_0.4Ba_1.6?x La _x FeMoO₆ have some potential applications for magnetic refrigerants in a wide temperature range, including room temperature.     

Fabrication and Characterization of Undoped and Cobalt-doped ZnO Based UV Photodetector Prepared by RF-sputtering

Undoped and 1 at.% Co-doped ZnO nanostructure based UV photodetectors were successfully fabricated by RF- magnetron sputtering technique with comb like Pt electrodes. Cobalt ions were successfully incorporated into the lattice of the ZnO nanostructure without changing its wurtzite structure. It was indicated that Co-doping can effectively adjust the luminescence properties of the ZnO nanostructure. The undoped and Co-doped ZnO photodetectors were observed to have photosensitivities of 1.44 x 104 % and 8.57 x 102 % and low dark currents of 9.74 x 10-8 A and 1.18 x 10-7 A, respectively.     

Influence of iron doping towards the physicochemical and biological characteristics of hydroxyapatite

Hydroxyapatite (HAP) is the naturally occurring mineral form of calcium apatite and the most studied material as a bone substituent. Considering HAP's inherent properties, this study explored changes in HAP's characteristics from doping with other metals such as Fe. To form pure HAP and Fe-HAP with different amounts of Fe, we used the hydrothermal approach, and the composites that formed were thoroughly analyzed for their crystallinity, surface bonding, morphology, magnetic behavior, mechanical strength, biocompatibility, hemocompatibility, and in vitro cytotoxicity. The powder XRD studies confirmed the samples' crystallinity, and the lowest crystalline size was 19.7 nm in 10Fe-HAP. The FTIR analysis confirmed the formation of HAP by the hydroxyl, phosphate, and carbonate groups. The FESEM demonstrated that the morphology of the pure HAP was rod-shaped, which transformed into spheres after Fe doping. The EDS analysis confirmed the successful formation of HAP and Fe-HAP composites. The magnetic studies indicated the diamagnetic behavior of the pure HAP, while the Fe-doped HAPs had a superparamagnetic nature with saturation magnetizations (M_s) of 2Fe-HAP, 4Fe-HAP, and 10Fe-HAP at 0.0062, 0.0092, and 0.029 emu/g respectively. Assessment of the mechanical properties, biocompatibility, hemocompatibility, and cytotoxicity indicated that the Fe-doped HAPs were superior to the pure HAP, and among the Fe-HAPs, the 10Fe-HAP) had the highest amount of Fe and the best characteristics. The studies also indicated that Ca²⁺ interactions influenced the cells via HAP doping with that of Fe, equally increasing the physicochemical and biological properties.     

The propagation of pressure in a gelled waxy oil pipeline as studied by particle imaging velocimetry

Paraffinic crude oils in pipelines may form waxy gels during flow shutdowns. These gels can be dislodged by applying pressure if the wall shear stress, proportional to the local pressure gradient, exceeds the gel yield stress. The simplest models assume that the axial pressure profile becomes linear immediately after a jump in upstream pressure, but this fails to account for gel time‐dependent rheology or the effect of gel voids on pressure wave propagation. To investigate the former factor, pressure profile and particle imaging velocimetry (PIV) measurements were performed on a model oil gelled under pressure to reduce void formation. After a jump in upstream pressure to a value insufficient to restart flow, the axial pressure profile becomes linear in a two‐step process, with an immediate small rise in downstream pressure followed by a time‐delayed jump. The local downstream gel deformation measured by PIV exhibits similar two‐step time dependence. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Simulation of Magnetocaloric Properties of Antiperovskite Structural Ga1−X Al X CMn3

In this work, low-enhanced magnetic field magnetocaloric effect for Ga_1?X Al _X CMn₃ (X = 0, 0.05, 0.07, 0.12, and 0.15) system near a second-order phase transition from a ferromagnetic to a paramagnetic state is investigated theoretically. It is found that magnetic entropy change distribution is much more uniform than that of gadolinium, which is desirable for an Ericson-cycle magnetic refrigerator. Moreover, the results show that the magnetocaloric effect in this system is tunable by Al doping, which is beneficial for manipulating magnetocaloric refrigeration that occurs in various temperature ranges including room temperature. This makes the Ga_1?X Al _X CMn₃ samples potential candidates for practical applications.