Investigating the effect of pressure on a vertical two-phase upward flow with a high viscosity liquid

This article presents void fraction and pressure gradient data for sulfur hexafluoride (SF₆) with gas densities of 28 and 45 kg/m³ and oil (with viscosity 35 times that for water) in a 127 mm diameter pipe. The superficial velocities of gas ranged from 0.1 to 3 m/s and those for liquid from 0.1 to 1 m/s, respectively. Measurements of void fraction data were recorded using a capacitance wire mesh sensor (WMS) system, which permits the 3D visualization of the flow patterns. All the data were obtained with a data acquisition frequency of 1,000 Hz. A differential pressure transducer was used to measure the pressure drops along the length of the pipe. The WMS provide time and cross-sectionally resolved data on void fraction and from an analysis of its output, flow patterns were identified using the characteristic signatures of probability density function (PDF) plot of time series of void fraction. The PDF plots showed the single peak shapes associated with bubbly and churn flows but not the twin-peaked shape usually seen in slug flows. This confirms previous work in larger diameter pipes but with less viscous liquids. For the bubble and churn flows investigated, the pressure gradient was observed to decrease with an increase in gas superficial velocity. Nevertheless, there was an insignificant observed effect of pressure on void fraction below certain transitional flow rates, the effect however became significant beyond these values. In the present work, wisps appear to be smaller, which might be due to the different fluid properties of the working fluids employed. In addition, wisps are easily revealed as long as there is a transition between churn and annular flows regardless of the pressure. Experimental data on void fraction and pressure gradient are compared against existing data. Reasonably good agreements were observed from the results of the comparison.     

Premixed hydrogen-air flames interacting with a hydrogen porous wall

A laminar one-dimensional hydrogen-air flame travelling and quenching towards a chemically inert permeable wall (PW) is studied. Hydrogen flows through the wall into the premixed H₂-air. The S3D numerical code with detailed chemistry is used. PW results are compared against results of an impermeable wall (IW), including effects of varying wall mass flux, stoichiometry, inert dilution and unburned-gas and wall temperatures. The maximum reaction heat release rate occurs at the wall in all cases. For rich and stoichiometric mixtures, PW with fuel influx gave a moderate reduction of the quenching (i.e. maximum) wall heat flux compared to IW, whereas for a lean mixture, the increase is considerable. Effects of the fuel influx on the importance of individual elementary reactions and radicals and intermediate species are investigated. The lean PW cases have similarities to much richer IW cases. Both a lower wall temperature and dilution reduce the burned-mixture temperature and, consequently, the wall heat flux.     

Highly Selective Cobalt‐Catalyzed Hydrovinylation of Styrene

Phosphine complexes of cobalt halide salts activated by diethylaluminum chloride are shown to yield highly active catalysts in the hydrovinylation of styrene, with unprecedented high selectivity to the desired product 3‐phenyl‐1‐butene (3P1B). Double‐bond isomerization, a common problem in codimerization reactions, only occurs after full conversion with these catalyst systems, even at elevated temperature. The most active catalysts are based on cobalt halide species combined with either C₁‐ or C₂‐bridged diphosphines, heterodonor P,N or P,O ligands, flexible bidentate phosphine ligands or monodentate phosphine ligands. Kinetic investigations show an order >1 in catalyst, which indicates either the involvement of dinuclear species in the catalytic cycle or partial catalyst decomposition via a bimolecular pathway.     

Classification of different bovine muscles according to sensory characteristics and Warner Bratzler shear force

The aim was to examine how well different beef muscles from Norwegian Red bulls respond to the consumer needs. Ten carcasses were slaughtered at a commercial abbatoir, chilled at 4 °C for 48 h, and 10 muscles excised. After ageing for 9 days at 4 °C, the muscles were subjected to sensory and chemical analyses and classified according to these analyses in 4 quality groups. The results regarding the comparative quality of the muscles were similar to results from other studies on predominantly steers. M. infraspinatus showed superior tenderness, juiciness and colour properties and was the only muscle to be consistent in tenderness with 80% of the samples in the highest sensory quality class. Also M. triceps brachii and M. semimembranosus adductor were reasonably tender and consistent in tenderness. As compared with the studies on steers, the M. biceps femoris and M. vastus lateralis seemed to be less tender in bulls. Results regarding sensory colour intensity, juiciness and taste showed similar findings. The pattern of association between the muscles in this study was highly irregular as the relative muscle quality varied widely, which means that using M. longissimus dorsi as a quality indicator of all muscles in the carcass is questionable.     

Solubility of NiO in Pechini-derived ZrO<Subscript>2</Subscript> examined with SQUID magnetometry

The solubility of NiO in ZrO₂ was studied by X-ray diffraction, TEM, and SQUID magnetometry. Lattice parameter measurements from a similar, established oxide system, NiO−10YSZ, were first used to show that SQUID magnetometry can effectively measure solubility. ZrO₂ specimens with 0, 0.5, 1, 2, 3, and 5 percent by mol NiO were prepared via the Pechini method. The specimens were calcined in air at 500, 600, and 1000 °C. The paramagnetic response of the specimens measured with SQUID magnetometry revealed that up to 5 percent by mol NiO is soluble in ZrO₂ for specimens calcined at 500 and 600 °C. The relatively large solubility compared with NiO−10YSZ occurs due to the very fine grain size (5–10 nm). The fine grain size is also responsible for stabilizing the tetragonal phase of ZrO₂. At the 1000 °C calcination temperature, the ZrO₂ is entirely monoclinic, exhibits larger grains (>45 nm), and only dissolves about 0.5 percent by mol or less NiO. The correlations between grain size, ZrO₂ polytype, and NiO addition are discussed.     

Supramolecular Self-Assembled Ligands in Asymmetric Transition Metal Catalysis

The design of novel chiral ligands is at the core of asymmetric catalysis. The catalytic characteristics of a transition metal catalyst such as activity, selectivity and stability can be fine-tuned by optimization of the steric and electronic properties of the coordinating ligands. In asymmetric transformations, catalyst optimization still relies to a large extent on trial-and-error and educated guesses. New strategies based on combinatorial screening and high-throughput experimentation have been introduced for the design and optimization of new ligands and catalytic systems. Supramolecular bidentate ligands that form by self-assembly of building blocks are particularly suited for this combinatorial approach as the potential number of catalysts grows exponentially with the number of building blocks synthesized. Catalytic systems based on supramolecular interactions have proven to be highly advantageous in creating large ligand libraries for high-throughput screening, which allows optimization of activity and selectivity for a variety of reactions. In this review we describe the progress in this field.     

Antioxidants in Fish Oil Production for Improved Quality

There is an increasing demand for fish oil containing omega-3. By-products (e.g., heads, tails, belly flaps, backbones, and viscera) from fish fillet production are currently utilized for production of fish oil and fish meal for feed but can be a valuable source of omega-3 for human consumption. However, the quality of some oil is not good enough for human consumption due to oxidation during processing. The aim of this work was to decrease oxidation during oil production by adding antioxidants to herring by-products early in the production process. Of several antioxidants the most potent were selected by a fast screening test. Butylated hydroxytoluene, propyl gallate and citric acid were further evaluated on a labaroatory scale and pilot plant production of herring oil. The selected antioxidants resulted in lower total oxidation during processing [up to 71% reduction in TOTOX (2 times the peroxide value plus the anisidine value)]. In addition, higher oil stability was achieved by adding antioxidants during processing (improved stability up to 400%).     

Characterization of Nickel Ions in Nickel‐Doped Yttria‐Stabilized Zirconia

The distribution of Ni²⁺ ions in NiO‐doped 10YSZ powder is examined with Superconducting Quantum Interference Device magnetometry, a technique that is able to distinguish between randomly distributed Ni²⁺ ions in solid solution and ordered Ni²⁺ ions within NiO with high precision. Very high purity powders containing 0.01, 0.1, 0.5, and 1.0 mol% NiO in 10YSZ (all levels below the solid solubility limit of NiO in 10YSZ) were made from acetate precursors and a modified EDTA (ethylenediaminetetraacetic acid)‐citrate synthesis method. The powders were calcined in air at either 873 or 1273 K. The 873 K calcination leads to single phase YSZ particles about 10 nm in diameter, and almost all of the NiO dopant exists in complete solid solution. The 1273 K calcination leads to a larger YSZ particle size (55–95 nm), and also to the formation and/or growth of NiO particles, the amount of which depends on the length of time of calcination. Upon sintering the powders in air (1773 K, 1 h), the NiO dissolves back into 10YSZ. The results demonstrate that particle growth during calcination leads to the exsolution of Ni²⁺ ions to form NiO. This has important implications for the synthesis of NiO‐doped 10YSZ from chemical precursors.     

Rapid prototyping of arrayed microfluidic systems in polystyrene for cell-based assays

Microfluidic cell-based systems have enabled the study of cellular phenomena with improved spatiotemporal control of the microenvironment and at increased throughput. While poly(dimethylsiloxane) (PDMS) has emerged as the most popular material in microfluidics research, it has specific limitations that prevent microfluidic platforms from achieving their full potential. We present here a complete process, ranging from mold design to embossing and bonding, that describes the fabrication of polystyrene (PS) microfluidic devices with similar cost and time expenditures as PDMS-based devices. Emphasis was placed on creating methods that can compete with PDMS fabrication methods in terms of robustness, complexity, and time requirements. To achieve this goal, several improvements were made to remove critical bottlenecks in existing PS embossing methods. First, traditional lithographic techniques were adapted to fabricate bulk epoxy molds capable of resisting high temperatures and pressures. Second, a method was developed to emboss through-holes in a PS layer, enabling creation of large arrays of independent microfluidic systems on a single device without need to manually create access ports. Third, thermal bonding of PS layers was optimized in order to achieve quality bonding over large arrays of microsystems. The choice of materials and methods was validated for biological function in two different cell-based applications to demonstrate the versatility of our streamlined fabrication process.