Faceting Behavior of Alumina in the Presence of a Glass

The faceting of alumina interfaces in the presence of a glass affects both grain growth and grain-boundary mobility during liquid-phase sintering. The geometry and movement of facets that form during this sintering process are expected to play an essential role in the development of the final microstructure, in particular, by their influence on the topology of the grain boundaries which ultimately control the properties of Al₂O₃ compacts. A new method for studying the interaction between Al₂O₃ and a glass has been developed. A thin sample of Al₂O₃ suitable for examination in a transmission electron microscope is prepared and examined and then reacted with SiO₂ and CaO via the vapor phase. This experimental approach allows the faceting behavior of glass/Al₂O₃ interfaces to be studied systematically without introducing unnecessary complications during subsequent sample preparation. Faceting occurs almost exclusively on the (0001) and {1 1 02} planes. The interaction between glass and certain structured grain boundaries in alumina has been studied using polycrystalline thin films.     

PREDICTION OF THE FERMENTATION PERFORMANCE OF BREWING YEAST WITH THE ACIDIFICATION POWER TEST

Fermentation performance (defined as the time required, in hours, to attenuate an all malt wort from OG 1040° to 1020°) can be accurately predicted for Saccharomyces cerevisiae NCYC 1681 using the Acidification Power test (r =0.943, p = <0.001: 37 samples). The results obtained with four other yeasts suggest that the test has wide applicability. The test measures the ability of a population of yeast cells to maintain different intracellular and extracellular hydrogen ion concentrations when placed in distilled water. It also measures the change in these concentrations induced by the presence of glucose. The method is reproducible (standard deviation of the mean =0.61 %) and is unaffected by variations of ±11 % of yeast weight in the assay, this makes the Acidification Power test a ‘stand alone’ test, no secondary analyses (such as dry weight determination) are necessary. The test can be performed using common laboratory equipment and can be applied routinely in breweries for yeast selection based on the use of Reject Quality Limits (RQL). In addition, the technique may find application in the evaluation of yeast handling protocols, in the assessment of new or novel yeast strains, and in the assessment of yeast condition prior to acid washing.     

Optical tweezers and optical spanners with Laguerre–Gaussian modes

Abstract

We numerically model the axial trapping forces within optical tweezers arising from Laguerre–Gaussian laser modes. For an 8 μm diameter sphere suspended in water, the higher-order modes produce an axial trapping force several times larger than that of the fundamental. Partial absorption results in a transfer of the orbital angular momentum from the Laguerre–Gaussian mode to the trapped particle. This results in the rotation of the particle by what may be called an optical spanner (wrench). For an absorption coefficient of α = 5700 m^?1 and a laser power of 10 mW, we find that an 8 μm diameter sphere would acquire an angular acceleration of 10 × 10⁴ rad s^?2 and a limiting angular velocity of 0.2 rad s^?1.     

Rare-earth doped optical fibers for temperature sensing

The feasibility of using a variety of rare-earth doped optical fibers for measuring spatially averaged temperatures from ~0 to ~100°C over distances of 10 to 20 m is discussed. Such distributed temperature sensors would be particularly well-suited for building climate control systems and industrial processing applications. The temperature-dependent absorption spectra of 6 MCVD processed fibers containing different concentrations of Nd³⁺, Pr³⁺, and Yb³⁺ rare-earth ions were characterized and used to determine thermally active dopant species, optimal dopant concentrations, and most sensitive operating wavelengths for use as dual wavelength distributed temperature sensors     

Reactive ion etching of waveguide structures in diamond

Waveguide structures were fabricated in both nanocrystalline CVD diamond (NCD) and HPHT type 1b single crystal diamond using photolithography and reactive ion etching. The combination of these techniques allows the patterning of many long photonic structures simultaneously, making it easily scalable. Emphasis has been placed on reducing sidewall roughness to prevent loss due to scattering. In single crystal diamond a peak-to-peak roughness of approximately 10 nm (estimated from SEM images) was achieved for the majority of the structure sidewall.     

Pharmacokinetics of mefloquine combined with artesunate in children with acute falciparum malaria

To study the biologic role of migration inhibitory factor (MIF), a pleiotropic cytokine, we generated a mouse strain lacking MIF by gene targeting in embryonic stem cells. Analysis of the role of MIF during sepsis showed that MIF-/- mice were resistant to the lethal effects of high dose bacterial lipopolysaccharide (LPS), or Staphylococcus aureus enterotoxin B (SEB) with D-galactosamine and had lower plasma levels of tumor necrosis factor alpha (TNF-alpha) than did wild-type mice, but normal levels of interleukin (IL)-6 and IL-10. When stimulated with LPS and interferon gamma, macrophages from MIF-/- mice showed diminished production of TNF-alpha, normal IL-6 and IL-12, and increased production of nitric oxide. MIF-/- animals cleared gram-negative bacteria Pseudomonas aeruginosa instilled into the trachea better than did wild-type mice and had diminished neutrophil accumulation in their bronchoalveolar fluid compared to the wild-type mice. Thioglycollate elicited peritoneal exudates in uninfected MIF-/- mice, but showed normal neutrophil accumulation. Finally, the findings of enhanced resistance to P. aeruginosa and resistance to endotoxin-induced lethal shock suggest that the counteraction or neutralization of MIF may serve as an adjunct therapy in sepsis.     

Pipeline Column Separation Flow Regimes

A generalized set of pipeline column separation equations is presented describing all conventional types of low-pressure regions. These include water hammer zones, distributed vaporous cavitation, vapor cavities, and shocks (that eliminate distributed vaporous cavitation zones). Numerical methods for solving these equations are then considered, leading to a review of three numerical models of column separation. These include the discrete vapor cavity model, the discrete gas cavity model, and the generalized interface vaporous cavitation model. The generalized interface vaporous cavitation model enables direct tracking of actual column separation phenomena (e.g., discrete cavities, vaporous cavitation zones), and consequently, better insight into the transient event. Numerical results from the three column separation models are compared with results of measurements for a number of flow regimes initiated by a rapid closure of a downstream valve in a sloping pipeline laboratory apparatus. Finally, conclusions are drawn about the accuracy of the modeling approaches. A new classification of column separation (active or passive) is proposed based on whether the maximum pressure in a pipeline following column separation results in a short-duration pressure pulse that exceeds the magnitude of the Joukowsky pressure rise for rapid valve closure.     

Valve Design for Extracting Response Functions from Hydraulic Systems Using Pseudorandom Binary Signals

The analysis of the dynamic response of a pressurized water pipeline system is important for the design and also the integrity monitoring of these systems. An efficient method for summarizing the behavior of a pipeline system is through the determination of their system response functions. These functions can be extracted by injecting a pressure signal with a wide bandwidth that persists over the length of a pipeline system. Unlike electrical and mechanical systems, generating such signals in pressurized water systems is difficult. Valves capable of generating a signal against the system back-pressure often lack the necessary maneuverability to ensure the signal is sharp (and hence with high-frequency content) and the generated transient is often large in amplitude, risking damage to the system. A method for generating a small amplitude transient signal with a wide band of frequencies is desirable. This paper presents the design for a side discharge valve for generating a pseudorandom binary sequence of pressure changes that are of a small magnitude in relation to the steady state head of the pipeline. The pseudorandom pressure sequence is used to provide an estimate of the system response function. The continuous form of the signal allows the amplitude of each individual pulse within the signal to be small while maintaining the same signal bandwidth. The valve has been tested experimentally and was found to provide a good match with the theoretical response of the pipeline. The method provides a practical alternative to frequency sweeping using sinusoidal signals or sharp valve closures for the extraction of the response functions. Once determined, the system response function can be utilized to detect system faults such as leaks and blockages.