Adjoint waves in round two-layer shielded waveguide

It is shown that adjoint waves can exist in a round two-layer shielded waveguide. In contrast to the normal waves propagating in guiding electrodynamic structures, the adjoint waves are characterized by a linear dependence of the field on the longitudinal coordinate.     

Effect of Ce and La on microstructure and properties of a 6xxx series type aluminum alloy

The increase in iron content in secondary sources of aluminum has led to an increase in the amount of Fe-bearing intermetallic phases in Al alloys. One of these intermetallics, β-AlFeSi, which is seen as the dominant phase in 6xxx series alloys, reduces bendability of wrought alloys, which in turn, limits their usage in the automotive industry. It is known that small additions of Sr prevent the formation of the β phase and facilitate the precipitation of a less detrimental intermetallic, α-AlFeSi, in as-cast alloys. It is worth investigating whether other elements cause a similar effect. Cerium and lanthanum as the least expensive representatives of rare-earth metals are tried as such elements. It is found that in alloys containing 0.1–0.2 wt.% of lanthanum, the fraction of β particles is pronouncedly less than that in the reference alloy. In addition to this advantage, much smaller grains are seen in the alloy with 0.2 wt.% La. Despite similarities between La and Ce, the latter metal neither modifies the microstructure nor noticeably affects the grain size. Moderate thermo-mechanical processing nullifies the beneficial effect of small La additions resulting in no improvement in the bendability of the alloy.

---

Open, microfluidic flow cell for studies of interfacial processes at gas-liquid interfaces

Interfacial processes involving peripheral proteins depend on the composition and packing density of the interfacial lipid molecules. As a biological membrane model, lipid monolayers at the gas-liquid interface allow independent control of these parameters. However, measuring protein adsorption to monolayers has been difficult. To aid in this and other studies of the interfacial processes, we have developed an open, microfluidic flow cell with which surface physical properties can be controlled and monitored in well-defined lipid monolayers while varying aqueous-phase composition. Using this apparatus, we implement a recently described fluorescence method (Momsen, W. E.; Mizuno, N. K.; Lowe, M. E.; Brockman, H. L. Anal. Biochem. 2005, 346, 139-49) to characterize the adsorption/desorption of glucagon to 1,2-dioleoyl-sn-glycerol monolayers at 27 mN/m. Analysis of the data gives reasonable and self-consistent results for kinetic and thermodynamic constants. Varying the packing density of 1,2-dioleoyl-sn-glycerol does not alter the extent of glucagon adsorption, but comparable measurements with 1-steaoryl-2-oleoyl-sn-glycero-3-phosphocholine show a critical dependence. Because it allows a high degree of control of both lipid monolayer properties and aqueous-phase composition, this microfluidic flow cell should find wide applicability in many areas of research into interfacial processes.