Marangoni forces created by surface plasmon decay

We present optical microfluidic manipulation of silicone oil and glycerol via surface tension driven forces sustained by surface plasmon deexcitation energy. The phonon energy associated with the decaying optically excited surface plasmons in a thin gold foil creates thermal gradients capable of actuating fluid flows. Spectral dependence of the plasmon decay length and control of optical beam characteristics are shown to provide a means for further manipulation.     

Genetic studies of human apolipoproteins: XIV. A simple agarose isoelectric focusing gel method for apolipoprotein E phenotyping

A new and simplified procedure is described for apolipoprotein E (APO E) phenotyping from native plasma or serum samples. Diluted or dialyzed samples are separated on agarose isoelectric focusing gels followed by protein blotting on nitrocellulose membranes. APO E banding patterns are localized immunologically using polyclonal goat anti-APO E antiserum as the primary antibody and rabbit anti-goat IgG conjugated with alkaline phosphatase as the secondary antibody. The method was used in parallel with our previously described polyacrylamide gel system to screen 110 unrelated and healthy US whites. Both gel systems gave identical APO E phenotypes, and allele frequencies were comparable with reported US white values. This simplified method can be used on a large number of population and clinical samples with minimum cost and effort.     

Fabrication of Micro‐ and Nanoscale Polymer Structures by Soft Lithography and Spin Dewetting

In this work, the process of spin dewetting of a polymer solution on a topographically patterned PDMS mold was used for fabrication of micro‐ and nanaoscale polymer structures. Spin coating was used to provide a fast and reproducible coating. This simple technique was capable of producing a wide range of polymer feature geometries from a single microfabricated mold. This experimental study looks at the effects of the original mold feature geometry as well as the polymer solution concentration on the resultant microstructures. Polystyrene and poly(propyl methacrylate) were used as model polymers. Features with film thickness ranging from <100 nm to >5 µm were obtained using this technique. The process was also extended to fabrication of nanoscale features.

     

Domain decomposition algorithms for indefinite weakly singular integral equations: the h and p versions

We extend the approach of Cai and Widlund (Domain decompositionalgorithms for indefinite elliptic problems, SIAM J. Sci. Stat.Comput. 13 (1992), 243-258), which was designed for finite elementdiscretizations, to boundary element discretizations of indefiniteweakly singular integral equations. Both the h and p versionsof the Galerkin approximation are considered. We prove thatthe additive Schwarz method suggested by Cai and Widlund canbe used for this equation as an efficient preconditioner forGMRES, an iterative method of conjugate gradient type. For bothversions, the rates of convergence of this iterative methodare shown to approach 1 only logarithmically as the degreesof freedom tend to infinity.     

Gas chromatographic/mass spectrometric determination of flumioxazin extracted from soil and water

A method was developed for determining flumioxazin in soil and water. Recovery efficiencies for solid-phase extraction (SPE) of flumioxazin from deionized, well, and surface water were between 72 and 77%. SPE was superior to liquid-liquid extraction, using water-hexane and water-chloroform emulsions, which resulted in retrieval efficiencies of 25 and 22%, respectively. However, liquid-liquid extraction with ethyl acetate improved recovery of total flumioxazin to >64%. Extraction from soil samples by direct solvent/soil extraction methods recovered between 18 and 76% of applied flumioxazin, depending on the solvent combination used. However, the use of accelerated solvent extraction techniques resulted in a 106 +/- 8% recovery of flumioxazin from soil. In analysis by capillary gas chromatography with mass selective detection, flumioxazin had a calculated limit of detection of 9 ng/mL with a retention time of 16.66 min.     

Modulation of multiple photon energies by use of surface plasmons

A form of optical modulation at low pulse rates is reported in the case of surface plasmons excited by 1.55-microm photons in a thin gold foil. Several visible-photon energies are shown to be pulsed by the action of the infrared pulses, the effect being maximized when each visible beam also excites surface plasmons. The infrared surface plasmons are implicated as the primary cause of thermally induced changes in the foil. The thermal effects dissipate in sufficiently small times so that operation up to the kilohertz range in pulse repetition frequency is obtained. Unlike direct photothermal phenomena, no phase change is necessary for the effect to be observed.     

On the limitation imposed by gravity on measurements of the critical viscosity of a pure fluid

Measurements of the viscosity of a fluid by means of a parallel plate torsional oscillator are conventionally limited to a plate separation that is much larger than the viscous penetration depth of the fluid contained between the plates. Here we demonstrate that, in principle, useful measurements can be carried out in the opposite regime where the thickness is smaller than the penetration depth. An alternative method, described in the last part of this paper, for alleviating the restriction imposed by the density stratification that results from the earth's gravity, is to use electrostriction, rather than the inertial force, to drive the fluid between the plates.     

Test of the screening approximation (n-1 expansion) for the one-dimensional Ginzburg-Landau field

The screening approximation (n^-1 expansion) has been used to obtain information about phase transitions and critical phenomena in systems of various spatial dimensionalities. In this note, exact results for the Ginzburg-Landau field in one dimension are compared with the screening solution through second order (n^-2).     

What is the Unit?

Mathematicians are sometimes careless about the use of units of linear measure. Specifically, in geometry, it is common to list measurements without a unit. The specific unit selected usually has no effect on the generalizations made. For example, in a right triangle, the Pythagorean Theorem relationship is independent of the selected linear unit. However, the unit of measurement is often of particular importance when a comparison is made between two quantities.     

Friction parameter of an ion near a metal surface

The force on an ion located near a condensed-matter surface determines its Brownian motion along the surface. We have studied the dissipative component of this force using a model in which the ion interacts with a metal while moving parallel with its surface. We recover the known asymptotic form of the force for large separations when only electron-hole excitations are accounted for but find a different form when damping of collective states is included.