Molecular hydrogen and spiltover hydrogen storage on high surface area carbon sorbents

A series of templated carbons with various high surface areas (2033–3798 m²/g) have been prepared using various microporous zeolites as hard templates. Molecular hydrogen storage and spiltover hydrogen storage on these templated carbons were investigated and compared with superactivated carbon AX-21 and other reported porous carbon sorbents at 298 K and 100 atm. Two relationships between the surface areas of these carbons and their hydrogen capacities were obtained. The relationship between molecular hydrogen capacity and surface area showed a 0.23 wt.% H₂/1000 m²/g of carbon sorbent at 298 K and 100 atm, indicating that merely increasing surface areas of the carbon sorbents cannot achieve a significant molecular hydrogen capacity at ambient temperature. Spiltover hydrogen storage was achieved by doping Pt nanoparticles (as dissociative hydrogen source) on these carbons (spiltover hydrogen receptor). Our first result on the relationship between the spiltover hydrogen capacity and surface area showed 0.4 wt.% H₂/1000 m²/g of carbon sorbent at 298 K and 100 atm, which indicated that storage via spillover can lead to an average of 70% enhancement compared to molecular hydrogen storage.     

Misalignment-Induced Bending in Pin-Loaded Tensile-Creep Specimens

In this paper, we have examined the possibility that elastic bending induced by load misalignment can affect creep measurements on pin-loaded tension specimens of silicon nitride (Si₃N₄). We have shown that elastic bending at room temperature can be as great as 42% of the axial strain when clean pins were used but was reduced to ∼3% when lubricated pins were used. Creep tests at the same applied stress and temperature were conducted on two groups of Si₃N₄ test specimens: one group used clean pins, and the other group used lubricated pins. By measuring the shapes of the specimens before and after the creep tests, we have determined that the loading holes were slightly misaligned before the creep tests and that small amounts of bending were induced by the creep tests. Bending occurred both in the gauge section of the specimen and in the transition region between the gauge section and the heads of the specimen (the latter phenomenon is defined as hinge bending). Our study indicated that the secondary creep rate, the hinge bending, and the bending of the gauge section was not dependent on pin lubrication, because the results from the clean and lubricated groups were statistically indistinguishable. Hinge bending was dependent on initial misalignment of the loading holes, whereas bending of the gauge section was independent of such factors.     

Characterization of the surface area of overflow droplets generated by a gas-lift pump under reduced pressure

Water-modelling experiments were carried out to characterize the surface area of overflow droplets generated by a gas-lift pump under reduced pressure as a function of various operating parameters, namely, top pressure, gas flow rate, nozzle submergence, lift ratio and riser diameter. The liquid phase mass transfer coefficient was obtained by applying the penetration theory (Treybal, 1980; Bird et al., 1960) to the overflow generated from the riser. Under reduced pressure, churn-turbulent flow, consisting of distorted bullet-shaped bubbles, was predominant in the flow regime. The increase of liquid circulation rate and flight time and the decrease of droplet size increased the refining rate. Because of the large droplet size, the refining rate of molten metals was smaller than that of water.     

Flexible and mechanical strain resistant large area SERS active substrates

We report a cost effective and facile way to synthesize flexible, uniform, and large area surface enhanced Raman scattering (SERS) substrates using an oblique angle deposition (OAD) technique. The flexible SERS substrates consist of 1 μm long, tilted silver nanocolumnar films deposited on flexible polydimethylsiloxane (PDMS) and polyethylene terephthalate (PET) sheets using OAD. The SERS enhancement activity of these flexible substrates was determined using 10(-5) M trans-1,2-bis(4-pyridyl) ethylene (BPE) Raman probe molecules. The in situ SERS measurements on these flexible substrates under mechanical (tensile/bending) strain conditions were performed. Our results show that flexible SERS substrates can withstand a tensile strain (ε) value as high as 30% without losing SERS performance, whereas the similar bending strain decreases the SERS performance by about 13%. A cyclic tensile loading test on flexible PDMS SERS substrates at a pre-specified tensile strain (ε) value of 10% shows that the SERS intensity remains almost constant for more than 100 cycles. These disposable and flexible SERS substrates can be integrated with biological substances and offer a novel and practical method to facilitate biosensing applications.     

Turbine airfoil degradation in the persian gulf war

Helicopter turbine engines used in the Desert Shield and Desert Storm operations experienced excessive sand ingestion. Fine particles were able to bypass filters and proceed through the combustor or cooling gaspaths. The first-stage turbine vanes were impacted with viscous silicate particles, forming a deposit on the leading-edge root platform and resulting in overheating and oxidation. The chemistry of the raw sand determines that of the ingested powders, the deposits, and the material reactions.     

Matrix Transformation in Boron Containing High-Temperature Co–Re–Cr Alloys

An addition of boron largely increases the ductility in polycrystalline high-temperature Co–Re alloys. Therefore, the effect of boron on the alloy structural characteristics is of high importance for the stability of the matrix at operational temperatures. Volume fractions of ε (hexagonal close-packed—hcp), γ (face-centered cubic—fcc) and σ (Cr₂Re₃ type) phases were measured at ambient and high temperatures (up to 1500 °C) for a boron-containing Co–17Re–23Cr alloy using neutron diffraction. The matrix phase undergoes an allotropic transformation from ε to γ structure at high temperatures, similar to pure cobalt and to the previously investigated, more complex Co–17Re–23Cr–1.2Ta–2.6C alloy. It was determined in this study that the transformation temperature depends on the boron content (0–1000 wt. ppm). Nevertheless, the transformation temperature did not change monotonically with the increase in the boron content but reached a minimum at approximately 200 ppm of boron. A probable reason is the interplay between the amount of boron in the matrix and the amount of σ phase, which binds hcp-stabilizing elements (Cr and Re). Moreover, borides were identified in alloys with high boron content.     

Geometry Dependence of Magnetization Reversal in Nanocomposite Alloys

The geometrical optimization of aligned hard-soft permanent-magnet nanocomposites is investigated by model calculations. Considered criteria are the shapes of the soft and c-axis-aligned hard phases, the packing fraction of the soft phase, and magnetostatic interactions. Taking into account that the energy product is enhanced via the volume fraction of the soft phase, subject to maintaining coercivity, we find that the best structures are soft-magnetic cubes as well as long rods with a square cross section. Comparing embedded soft cubes with embedded soft spheres of the same size, our nucleation-field analysis shows that the volume fraction of the soft phase is enhanced by 91%, with a coercivity reduction of only 25%. Magnetostatic interactions often but not always deteriorate the permanent-magnet performance, as exemplified by the example of MnBi:FeCo bilayers and multilayers.     

Color constancy from invariant wavelength ratios. III: Chromatic adaptation theory,model and tests

A theory of chromatic adaptation is derived from Parts I and II, and presented in terms of relative wavelength, purity, and radiant power, leading directly to a predictive model of corresponding hue, chroma, and lightness. Considering that even simple animals have effective color vision and color constancy, the aim was to develop a simple model of complete adaptation. The model is tested against well‐known data sets for corresponding colors in illuminants D65, D50, and A, and for small and large visual fields, and performs comparably to CIECAM02. Constant hue is predicted from Part I's mechanism of color constancy from invariant wavelength ratios, where constant hues shift wavelength linearly with reciprocal illuminant color temperature. Constant chroma is predicted from constant colorimetric purity. Constant lightness is predicted from chromatic adaptation of spectral sensitivity represented by power ratios of complementary colors (rather than cone responses which lack spectral sharpening). This model is the first of its type and is not formatted for ease of computation. © 2010 Wiley Periodicals, Inc. Col Res Appl, 2010     

Development and Characterization of a Multiplex Assay to Quantify Complement-Fixing Antibodies against Dengue Virus

Antibodies capable of activating the complement system (CS) when bound with antigen are referred to as “complement-fixing antibodies” and are involved in protection against Flaviviruses. A complement-fixing antibody test has been used in the past to measure the ability of dengue virus (DENV)-specific serum antibodies to activate the CS. As originally developed, the test is time-consuming, cumbersome, and has limited sensitivity for DENV diagnosis. Here, we developed and characterized a novel multiplex anti-DENV complement-fixing assay based on the Luminex platform to quantitate serum antibodies against all four serotypes (DENV1-4) that activate the CS based on their ability to fix the complement component 1q (C1q). The assay demonstrated good reproducibility and showed equivalent performance to a DENV microneutralization assay that has been used to determine DENV serostatus. In non-human primates, antibodies produced in response to primary DENV1-4 infection induced C1q fixation on homologous and heterologous serotypes. Inter-serotype cross-reactivity was associated with homology of the envelope protein. Interestingly, the antibodies produced following vaccination against Zika virus fixed C1q on DENV. The anti-DENV complement fixing antibody assay represents an alternative approach to determine the quality of functional antibodies produced following DENV natural infection or vaccination and a biomarker for dengue serostatus, while providing insights about immunological cross-reactivity among different Flaviviruses.     

Preconditioning of AISI 304 stainless steel surfaces in the presence of flavins—Part II: Effect on biofilm formation and microbially influenced corrosion processes

Biofilm formation and microbially influenced corrosion of the iron-reducing microorganism Shewanella putrefaciens were investigated on stainless steel surfaces preconditioned in the absence and presence of flavin molecules by means of XANES (X-ray absorption near-edge structure) analysis and electrochemical methods. The results indicate that biofilm formation was promoted on samples preconditioned in electrolytes containing minute amounts of flavins. On the basis of the XANES results, the corrosion processes are controlled by the iron-rich outer layer of the passive film. Biofilm formation resulted in a cathodic shift of the open circuit potential and a protective effect in terms of pitting corrosion. The samples preconditioned in the absence of flavins have shown delayed pitting and the samples preconditioned in the presence of flavins did not show any pitting in a window of −0.3- to +0.0-V overpotential in the bacterial medium. The results indicate that changes in the passive film chemistry induced by the presence of minute amounts of flavins during a mild anodic polarization can change the susceptibility of stainless steel surfaces to microbially influenced corrosion.