Short-wave instabilities on a vortex pair of unequal strength circulation ratio

The creation of vortex pairs occurs in a range of industries, including mixing, transport, and plastic moulding. In particular, vortex pairs are observed in the wake of aircraft, and are the cause of a significant hazard in the aviation industry. Instabilities, which grow on vortex pairs, have the potential to lead to enhanced dissipation, thus limiting this safety concern, in addition to enhancing mixing in chemical engineering industries. To date research has mostly considered instabilities growing on a vortex pair where each vortex has the same magnitude of circulation. However, in practice it is unusual to have an equal-strength vortex pair. This investigation is the first to consider the instability modes that may develop on a Lamb–Oseen vortex pair of arbitrary circulation ratio. We find a significant change in the growth rates of all instability modes reported previously for an equal-strength vortex pair. All simulations employ an accurate spectral-element method to discretise the domain coupled with a three-step time splitting scheme. A wide range of instability wavelengths is considered to ensure that all instability modes are captured. By identifying and enhancing the leading instability modes, we are able to enhance the dissipation of the vortex pair.     

Mixed aqueous solutions as dilution media in the determination of residual solvents by static headspace gas chromatography

Static headspace (HS) sampling has been commonly used to test for volatile organic chemicals, usually referred to as residual solvents (RS) in pharmaceuticals. If the sample is not soluble in water, organic solvents are used. However, these seriously reduce the sensitivity in the determination of some RS. Here, mixed aqueous dilution media (a mixture of water and an organic solvent like dimethyl formamide, dimethyl sulfoxide or dimethyl acetamide) were studied as alternative media for static HS-gas chromatographic analysis. Although it has been known that mixed aqueous dilution media can often improve sensitivity for many RS, this study used a systematic approach to investigate phase volumes and the organic content in the HS sampling media. Reference solutions using 18 different class 1, 2 and 3 RS were evaluated. The effect of salt addition was also studied in this work. A significant increase in the peak area was observed for all RS using mixed aqueous dilution media, when compared with organic solvents alone. Matrix effects related to the mixed aqueous dilution media were also investigated and reported. Repeatability and linearity obtained with mixed aqueous dilution media were found to be similar to those observed with pure organic solvents.     

Luminescent lanthanide complexes with liquid crystalline properties

Lewis-base adducts of tris(β -diketonato)lanthanide(III) complexes were prepared, where the β -diketone is para -alkoxy-substituted 1,3-diphenyl-1,3-propanedione. These compounds are the first examples of liquid crystalline lanthanide complexes in which the mesomorphism is introduced via a β -diketonate ligand. Depending on the type of the Lewis base, the metallomesogens exhibit a monotropic smectic A or a monotropic highly ordered smectic phase. Intense photoluminescence was observed for the europium(III) complexes at room temperature.     

GrInvIn in a nutshell

GrInvIn (Graph Invariant Investigator) is a software framework for teaching graph theory and for research in graph theory and graph theoretic chemistry. It enables users to construct graphs, compute invariants (e.g. topological indices in chemistry) and investigate relations between these concepts. The design of GrInvIn emphasizes easy usage and makes use of software engineering techniques that enable the user to easily extend the system (e.g. by adding new topological indices to investigate).     

Reorganizing freshman business mathematics II: authentic assessment in mathematics through professional memos

The first part of this two-part paper (13) described the developmentof a new freshman business mathematics (FBM) course at our college.In this paper, we discuss our assessment tool, the businessmemo, as a venue for students to apply mathematical skills,via mathematical modelling, to realistic business problems.These memos have proven a crucial step in turning our FBM coursearound from a dreaded course with little connection to students’intended careers into a course where students experience thepower of mathematics for solving problems and informing decisions.Comments from students in the course throughout its 6-year historyclearly point to the course's value and importance.     

Immunosensor towards low-cost, rapid diagnosis of tuberculosis

A rapid, accurate tuberculosis diagnostic tool that is compatible with the needs of tuberculosis-endemic settings is a long-sought goal. An immunofluorescence microtip sensor is described that detects Mycobacterium tuberculosis complex cells in sputum in 25 minutes. Concentration mechanisms based on flow circulation and electric field are combined at different scales to concentrate target bacteria in 1 mL samples onto the surfaces of microscale tips. Specificity is conferred by genus-specific antibodies on the microtip surface. Immunofluorescence is then used to detect the captured cells on the microtip. The detection limit in sputum is 200 CFU mL(-1) with a success rate of 96%, which is comparable to PCR.     

Mild and direct conversion of quinoline N-oxides to 2-amidoquinolines with primary amides

[reaction: see text] A simple, one-pot procedure is described for the direct conversion of quinoline N-oxides to alpha-amidoquinolines with primary amides. This methodology is complimentary to the Abramovich reaction, which is limited to the introduction of secondary amides via imidoyl chlorides. Although reaction conditions are quite similar, omission of the base is key for successful reaction with primary amides, which were found not to proceed through the intermediacy of an imidoyl chloride but rather through an acyl isocyanate.     

Building addressable libraries: site selective coumarin synthesis and the "real-time" signaling of antibody-coumarin binding

[reaction: see text] The feasibility of using active semiconductor chips containing addressable arrays of microelectrodes for the "real-time" monitoring of biologically relevant binding events has been demonstrated by detecting the binding of a coumarin substrate by an anticoumarin antibody. The coumarin substrate was synthesized proximal to predetermined electrodes on the chip with the use of a Pd(II) reagent that was itself generated by using the selected electrodes. Once the coumarin was synthesized, its binding to the anticoumarin antibody was detected by monitoring the current associated with a ferrocene-ferrocinium ion redox cycle that was established between the electrodes on the chip and a remote auxiliary electrode.