Non-formation of a vacuum state in a standing piston problem

When boundary data is introduced, additional terms are introduced into the weak formulation of the Navier-Stokes conservation law. We examine the example of single standing piston problem. The single piston problem corresponds to a fixed boundary problem.It is intuitively clear when a single piston filled with gas is pulled apart, even though gas becomes sparse in density, a vacuum state is never formed, because of viscosity. To study this rigorously, the Navier-Stokes equations are used to describe the gas's density and velocity, subject to the presence of viscosity. We prove that, given reasonable assumptions on the boundary data, vacuum states cannot form, if they are not present initially.     

A mean field equation as limit of nonlinear diffusions with fractional Laplacian operators

In the limit of a nonlinear diffusion model involving the fractional Laplacian we get a “mean field” equation arising in superconductivity and superfluidity. For this equation, we obtain uniqueness, universal bounds and regularity results. We also show that solutions with finite second moment and radial solutions admit an asymptotic large time limiting profile which is a special self-similar solution: the “elementary vortex patch”.     

The electronic emission spectrum of SiB

The gas phase spectrum of the silicon boride radical has been observed for the first time. Two electronic transitions were observed in emission from a corona excited supersonic expansion source. The D⁴Σ⁻-X⁴Σ⁻ system consists of emission from v′ = 0 to v″ = 0-3, while the A⁴Π-X⁴Σ⁻ system consists of numerous bands with v′ = 0-5 and v″ = 0-11, although only the strong 0-0 and 0-1 bands have been analyzed so far.     

The evaluation of binaural playback systems for virtual sound fields

By means of virtual acoustics technologies the impulse response in a location of a real enclosure can be used to create a virtual room. Also in this virtual space, typically implemented in a dead room, an impulse response can be measured. From both “real” and respective “virtual” impulse response a group of room-acoustical parameters can be calculated. The match of the two groups of indicators mostly depends on the layout of the playback system and on the implemented processing. In this paper a procedure of virtual measurement in a dead room is developed and some typical layouts of playback systems employing two loudspeakers are compared. Based on the consistency of the room-acoustical indicators derived from “real” and “virtual” impulse responses can be investigated. It is shown how the performance depends on the angular separation of loudspeakers and the efficiency of the cross-talk is also tested and discussed. Finally, a set-up which is suitable for psychoacoustics tests is indicated.     

Transport in a shunted surface superlattice with a perpendicular magnetic field

We experimentally investigate the transport through a shunted surface superlattice under the influence of a magnetic field applied perpendicular to the current direction. The current–voltage characteristics of these surface superlattices exhibit a peak which is followed by a wide region of negative differential resistance. The application of a transverse magnetic field has a profound influence on the position and height of this peak. The recorded shifts are compared to the predictions of different superlattice transport theories. Since these theories predict a different dependence on the magnetic field strength, the transport mechanism in the surface superlattice structures can be uniquely determined.     

REGULATORY CONTROLS AND MARKET POWER EXERTION: A STUDY OF THE PACIFIC HALIBUT INDUSTRY

Regulatory controls designed to manage Pacific halibut fisheries are shown to have altered firms' competitive behavior. Managing catch through open access derbies allowed processors to exert monopsony market power at the vessel level during short seasons. As a result, a significant portion of regulatory rents associated with reduced seasons were captured by processors. Results also indicate that processors have not exerted significant market power at the wholesale level.     

Photoelectron spectra of fluorine substituted diazanaphthalenes: “Even cases”

The high resolution He 584 Å photoelectron spectra of three diazanaphthalenes and some of their fluorine derivatives are presented. The qualitative model that is used frequently in the discussion of lone-pair level splittings is examined.     

A variety of lattice-ordered groups containing all representable covers of the abelian variety

A small variety of representable lattice-ordered groups is constructed, which contains all of the representable covers of the abelian variety.     

Polymers used as viscosity index improvers: A comparative study

Ethylene-propylene copolymers and hydrogenated styrene-diene copolymers were used for a comparative study aiming at their application as viscosity index improvers in multigrade engine oils. The variation of viscosity with temperature has been evaluated as a function of the polymer concentrations. The thickening effect of different viscosity index improvers and the dependence of reduced viscosities on temperature were determined. At concentrations lower than 3% (w/w) the viscosity/temperature characteristic suggested the occurrence of polymer coil expansion with temperature for hydrogenated styrene-diene copolymer. The direct dependence of mechanical stability on the copolymer molecular weight was observed.     

Friction force microscopy as an alternative method to probe molecular interactions

Friction force microscopy was applied to study protein-carbohydrate interactions that are important in many cellular recognition processes. The expression and structure of carbohydrates can be investigated using lectins as molecular probes since they recognize different types of sugar molecules. Lectins (concanavalin A and lentil lectin, recognizing mannose-type carbohydrates) were attached to the probing tip and carboxypeptidase Y (possessing complementary carbohydrates) was immobilized on a modified glass surface using microcontact printing. The results obtained from friction force maps and dependencies on the loading rate (measured in a physiological buffer) were divided in two distinct groups. The first group of results obtained for lectin-protein complexes was assigned to molecular recognition events, whereas the other including all control measurements was attributed to nonspecific interaction. All results presented here indicate that friction force microscopy can be successfully employed to study recognition processes.